US 3509754 A
Description (OCR text may contain errors)
y 5, 1970 J. L; MASSINGILL ETAL METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 8 Sheets-Sheet l 8 Sheets-Sheet 2 y 1970 J. MASSINGILL ETAL METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 JESS L. MASS/NG/LL I! ALD C. GR/ RENKO G5" May 5, 1970 J. MASSINGILL E 3,509,754
- METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 8 Sheets-Sheet 5 INVENTORS JESS L. MASS/NG/LL DONAL D C. GR/GORENKO B@W/HJ Q22 MWJ -IHI I111.
ATTORNEYS May 5, 1970 ,1. L. MASSINGILL ETAL 3,509,754
METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 8 Sheets-Sheet L INVENTORS m m 0 O LKMN mm A 6 Wm@ sum AG M M L d 0 May 5, 1970 J. L. MASSINGILL ET 3,509,754
METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 2 1964 8 Sheets-Sheet 5 5 J rd? r415 I 2000 "uh-:5" 01 "7 moo T M6 mq finullnu ll PM 500 INVENTORS JESS L, MASS/NG/LL ll L0 C. G/Q/GO/PENKO ATTORNEYS J. L. MASSlNGiLL ET AL 3,509,754
METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 May 5, 1970 8 Sheets-Sheet 6 INVENTORS LO. m MM m 6 WW m mg m LC s w 1970 J. 1.. MASSINGILL mm. 3,509,754
METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 8 Sheets-Sheet '7 a a 4 2 4 4 a S awn 2 1 aw 4 m mLO a a M w a W W4M M 4, a 6 m G N 1 k 7. 5 4 N E 6 l S 7 4 O 7 II V a 6 (V O, S G 3 (M6 5 Z 7 4 6 a A Z 3 7 4 DH 4 6 M 2 j 2 6 2 n a f G M 4 .m 7 In a a g 2 .a i u 7 a C 2 a m 7 7 7w u u 3 3 a 4 7 a Z lv w/ 7 m G a E. m I 1 1| y w a mm "a F w m A JM 3 M M r I 6/ d. 7 8 3 1 7 M 0 a0 7 5 7 W I 5 m m 9 a a/ m 2/ a A 4 8 a a M 071 2 7 4/ l M m7 Z: 3; 2 m i 1 w 3 M W 8 M7 a 4 a a 9 a F a a 2 2 m 9 K o 7 a 9 0 3 Y W a d 3 0/ 8 w 6 Z s m 2 am J E m a um I M V 1 W a 7 w m r 4 l 5 7 H 3 m H M 9 w I W m: V ,2 4 g E m 1 Q 5 a in PU- h i I l I fl w 1 F m E B w E a m m .L M 6 4 7 M W A 3 ATTORNEYS y 1970 J. L. MASSINGILL ETAL 3,509,754
METHOD AND APPARATUS FOR DEEP DRAWING METAL Original Filed April 23, 1964 8 Sheets-Sheet 8 JESS L. MASS/NG/LL ALD CGR l GORENKO dimm/ ATTORNEYS United States Patent O 3,509,754 METHOD AND APPARATUS FOR DEEP DRAWING METAL Jess L. Massingill, Cape Coral, Fla., and Donald C. Grigorenko, Columbus, Ohio, assignors to Metal Flo Corporation, Columbus, Ohio, a corporation of Michigan Continuation of application Ser. No. 362,004, Apr. 23,
1964. This application May 28, 1969, Ser. No. 843,882 Int. Cl. B21d 22/28 US. Cl. 72-349 32 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCE This application is a continuation of our application Ser. No. 362,004, filed Apr. 23, 1964, now abandoned.
BACKGROUND OF THE INVENTION The present invention relates to the art of drawing metal and provides ways and means for the economical production of ultra deep drawn metal cans, shells, tubes, and the like, from first operation cup shells, fiat blanks, fiat sheet metal strips, and the like.
In the patented art is found many proposals for effecting the deep drawing of metal wherein the metal being drawn is subjected to a sequence of drawing operations during a single and continuous stroke of the drawing apparatus. US. Pat. Nos. 783,390; 961,131 and 1,720,375, granted in 1905, 1910 and 1929, respectively, are typical of such proposals.
Notwithstanding the numerous patented proposals for the deep drawing of metal by a sequence of operations performed during a single stroke of both mechanical and hydraulic drawing apparatus, such proposals have not experienced any general acceptance in this art. No present commercial use of the many proposals of the above-mentioned type, which appear in the patented art, is known, nor do such proposals appear in engineering handbooks dealing extensively with the art of metal drawing.
A practical commercial process and apparatus for carrying out the process according to the present invention has been provided by performing the drawing operation in a horizontally disposed press in which all the major structural and functional components are supported, adjusted and operated on a rigid, horizontally disposed support structure on which the weight of such components is distributed, as well as shifted, during the cycle of operation of the press.
The rigidity of the press of the present invention is augmented by the telescoping association of the punches which, in addition to forming the metal in the dies, have the further function of serving as pressure pads and pilots during the sequence of the drawing operations. Each punch of each operation of the press is rigidly associated with a vertical plate which is rigidly supported and guided for horizontal movement. As the drawing operations progress, these plates are moved longitudinally in the press and sequentially approach one another to effect a substantial shifting of the structural and functional mass 3,509,754 Patented May 5, 1970 of the press adjacent the area in which the metal shaping is taking place.
To maintain a high degree of rigid parallelism between the punch carrying plates, each plate is carried on a common guide rod system, and the plates are spaced from each other by several systems of spacer elements which are disposed about each punch. The ram pressure of the press is transferred from one punch plate to the next through the spacer elements, whereby the operating pressure of the ram and the reaction of the metal to shaping both tend to effect parallelism between the punch plates.
The draw dies of the press of the present invention are supported and maintained in rigid parallelism and concentricity with the telescoping punches. In each die of each drawing operation, with the exception of the first, the metal being formed is transferred from the previous drawing operation on the punch that performed the previous draw with that particular punch thereafter functioning as a combination pressure pad and pilot for the drawing operation performed by the following punch. Piloting of the Work blank from one punch to the next in each redrawing die tends to promote and maintain a state of concentric association between the dies and punches which contributes to the general rigidity, horizontal alignment and parallelism of the punch and die carrying components of the press.
To prevent as well as to control relative movement between adjacent punch carrying plates, hydraulic means are provided which have a locked state to prevent relative movement, as well as a regulated state for initiating the sequential drawing movement of the punches. The hydraulic means also provides holding pressure for the metal being shaped as Well as holding the plates of the moving plate system together.
Through the horizontal arrangement of the press, the ram of the press is substantially relieved of the dead weight of the punch carrying plates, punches and spacer elements, as well as the components of the hydraulic systems associated therewith. At the same time the horizontal arrangement of the press facilitates set-up operations, inspections of the various operating stages, lubrication of the punches and dies, and cooling of the metal-forming components. It also facilitates the feeding of the stock to the machine and removing of fabricated articles. Any tendency for the horizontal disposition of the punches to cause objectionable drooping with a resulting lack of concentricity of the punches in the draw dies has been avoided by the rigid and telescoping association of the punches, coupled with a departure in accepted practice in metal drawing which provides a high degree of punch hugging by the metal being shaped by a reduction in standard punch and die clearances to a point approaching an interference fit" with the gauge of metal being drawn.
One possible explanation for the unexpected percentage of reduction that may be performed by the present invention in a single stroke of the press, without metal rupture or intermediate anneals, may be contributed to the combination of punch hugging, interference fit" and the piloting action of the punches during the transfer of formed metal from one punch to the next in the draw dies. These functions appear to so uniformly distribute, form and control the metal that stresses on the metal are uniformly distributed with the substantial elimination of localized areas that are less prepared for redrawing than the remaining portions of the formed metal.
When the principles of design discussed in the preceding paragraph are employed in combination with the sequence of drawing operations rigidly performed during a single cycle of operation of the drawing press, the generation of heat and the substantial continuous flowing of the metal throughout the cycle obviously contributes to a substantial extent to the obtaining of greater reductions in blank diameter. However, in order to ob tain the repetitive results of the present invention more is required than merely sequential drawing operations performed during a single and continuous stroke of the press.
Thus, an object of the invention is to provide an improved drawing press for the deep drawing of metal articles wherein a sequence of drawing operations is performed without intermediate annealing through novel and coordinated control of punch movement, through the regulation of the restraining pressures on the metal blank at each drawing operation, and the character of the association of the metal blank with the punch and die structure of each drawing operation.
Another object of the invention is to provide an improved press for the deep drawing of metal articles without annealing wherein rupture of the closed end of the metal blank being drawn is avoided through novel association of the metal blank with the punch and die structures which perform the drawing operations.
A further object is to provide an improved press for the deep drawing of metal articles without annealing wherein the stresses of the drawing operation are uniformly distributed throughout the circumference of the metal blank to permit substantial increases in the percentage of reduction of metal blanks during the drawing operation as compared with standard practices and without experiencing metal rupture.
Still a further object of the invention is to improve the art of deep drawing of metal articles through improved means for the presentation and transfer of the metal blank with respect to the operation carried out in the drawing die.
Another object of the invention is to provide a novel drawing press in which the ram of the press is preterably horizontally disposed and the punch structure is supported and moved along a horizontally supported, vertically disposed structure with concentricity and alignment of the punch structure being provided by a novel arrangement of telescoping punches and punch carriers.
A still further object is to provide a novel press for performing a sequence of drawing operations during a single stroke of the press in which movement of the ram is transferred to the metal blank through a series of independently supported and independently guided punch carriers, the carriers having common guide and common support structures as well as telescoping and nested association for augmenting parallelism of the punch carriers on their common support structure.
A still further object of the invention is to provide a deep drawing press having a series of punch carriers which are independently supported and relatively movable, the carriers being spaced for both unitary and relative movement, with respect to each other, by the ram of the press through the control of fluid cushions.
A further object of the invention is to provide a press of the design described in the preceding paragraph wherein the fluid cushion structure also functions to control the pressure on the metal blank during each drawing operation.
Another object is to provide a hydraulic deep drawing press in which novel coordination of hydraulic means is provided for controlling punch and pressure pad means during the sequential operation of the metal drawing structure.
BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the present invention are more fully apparent from the following specification and the appended claims:
FIG. 1 is a side elevational view of the press at the start of the down stroke with the hydraulic system diagrammatically shown in dotted outline, and only one of each element of each of the three spacer systems being associated with each of the plates of the moving plate system,
FIG. 2 is a view similar to FIG. 1 and shows the moving plate system at the finish of the down stroke of the press,
FIG. 3 is an enlarged fragmentary portion of the moving plate system of the press, as shown in FIG. 1 but taken from the opposite side, with all of the spacer elements of the three spacer systems shown in place,
FIG. 4 is an enlarged fragmentary portion of the fixed plate system of the press as shown in FIG. 1 taken from the opposite of the press,
FIG. Sis a vertical, cross-sectional view taken on line V-V of FIG. 3 of the moving plate system of the press,
FIGS. 6, 7, and 8 are views similar to FIG. 5 taken on lines VI-VI, VII-VII, and VIHVIII, respectively, of FIG. 3,
FIG. 9 is a vertical, cross-sectional view taken on line IX--IX of FIG. 18 of the fixed plate system of the press,
FIG. 10 is a sectional detail showing the association of a plate and its tension and guide rod,
FIG. 11 is a detail view of the mounting structure for opposite ends of the tension and guide rods,
FIG. 12 is a sectional detail of a fixed spacer element,
FIG. 13 is a sectional detail of the back stroke spacer element,
FIG. 14 is a sectional detail of a hydraulic cushion,
FIG. 15 is a sectional detail showing the association of the telescoping punches with a redrawing die,
FIG. 16 is a fragmentary, elevational view partly shown in broken section showing the relative positions of the plates of the moving and fixed plate systems of the press at the time of the initial drawing operation immediately following the shearing of the work blank,
FIG. 17 is a view similar to FIG. 16 showing the commencement of the first redrawing operation and illustrating the transfer of the work blank from one punch to the next,
FIG. 18 is a view similar to FIG. 16 showing the work blank through the drawing operations and partially through the ironing operation,
FIG. 19 is a diagrammatic view of the valve mechanism associated with certain of the moving plates,
FIG. 20 is a diagrammatic view of the hydraulic systems of the press,
FIG. 21 is a diagrammatic showing of the rogressive forming of the work blank in a modified form of press having five drawing operations and one ironing operation,
FIG. 22 is a diagram view of the pressure pattern of the hydraulic system during the stroke of the press forming the work blank of FIG. 21,
FIG. 23 is an enlargement of a portion of the diagram of FIG. 22 more clearly indicating the pressure impulses,
FIG. 24 is a view similar to FIG. 5 of a modification showing a plurality of telescoping punch sets, and
FIG. 25 illustrates a modified form of support for the moving plates.
The principles of the invention have application to a wide range of metals. In practice it has been found possible to deep draw steel, aluminum and brass on the same tools with equal success with only adjustments in holddown pressures being required in changing from one metal to another. Stainless steel, copper, zinc, as well as some of the recently developed space age metals, are also capable of being drawn with minor changes in tooling and pressure adjustments used for the more ductile metals mentioned above.
BASIC PRESS STRUCTURE When the apparatus for carrying out the improved process of deep metal drawing takes the form of a horizontally disposed hydraulic press, as in the case of the illustrated embodiment of the invention, the basic structure of the press preferably comprises a reinforced concrete base 10 on which a pair of reinforcing and wear plates 12 and 14 are rigidly mounted and constitute the structure referred to in the appended claims as the supporting surfaces. At one end of the base is a reinforced cylinder mounting plate 16, and at the other end is located a reinforced press base plate 18.
Plates 16 and 18 are rigidly mounted in any suitable manner on the reinforcing plateslZ and 14 with their opposed vertical faces 20 and 22 accurately fiat and parallel to each other and accurately disposed at 90 to the plates 12 and 14 which are equally fiat with their upper surfaces preferably disposed in the same plane.
The combination guide rods and tension members 24 are all straight and mutually parallel, and have portions 26 at opposed ends which are mounted in countersunk bores 27 in the faces 20 and 22 with the distance between the end portions 26 of each of the members 24 and the depth of the bores 27 being held the same, within a few thousandths of an inch, to insure that the plates 16 and 18 are parallel to each other as well as perpendicular to the members 24. (See FIG. 10.) To enable the members 24 to function as tension members as well as spacing members, any suitable means may be employed for atfixing the ends 26 of the members 24 to the vertical plates 16 and 18, such as socket brackets 19 in which the ends 26 are received with a close fit, with the ends 26 being tapped to receive the cap screws 21 extending through holes in the plates 16 and 18.
MOVING PLATE SYSTEM The moving plate system of the press may take many forms. One practical arrangement is herein illustrated in which several plates are provided, one for each drawing punch, a ram plate to which the power ram is attached on one side and from which a drawing punch extends from the opposite side, and a plate for the pressure pad and/or a portion of the blanking punch depending on whether presheared blanks or strip or square sheared stock is being run in the press. In the description to follow, the press will be described with a blanking operation being carried on in the press, although it will be understood that circular presheared blanks may be loaded in the press and the blanking operation deleted.
In one sense, the moving plates, mentioned in the preceding paragraph, are supported on the guide rods and tension members 24. More specifically, the ram and punch plate 28, punch plates 30 and 32, and blank and pad plate 34 are all provided with openings 36 in which bushings 37 are inserted, the openings 36 being preferably provided at the four corners of the plates with the members 24 being received within the tushings 37 with a close sliding fit. Clamps 37 hold the bushings 37 in place. (See FIG. 9.)
Each of the plates 28, 30, 32 and 34 is provided at its lower corners with suitable support members 38 capable of sliding or rolling on the reinforcing and wear plates 12 and 14. Preferably, the members 38 are located and removably attached at the lower opposite corners of the aforesaid plates and are adjustably related to their associated plates through the use of shims, and the like, to permit fine vertical regulation to bring about the desired situation in which the members 24 support the plates 28, 30, 32 and 34, and these same plates in another sense support the members 24.
SPACER MEANS FOR THE MOVING PLATE SYSTEM which are imposed between adjacent plates to determine the minimum spacing between such plates on relative approach movement. Another system of spacers is connected between adjacent plates for returning the plates to their relative positions at the conclusion of the back stroke of the press. These spacers will be called back stroke stop spacers. The third system of spacers preferably takes the form of hydraulic cushions which are imposed between adjacent plates 28, 30, 32 and 34 and have two different operation states, a locked state in which they function as a rigid thrust column structure between adjacent plates and a regulated state during which the effective length of the cushion as a spacer is reduced under the control of valving means to permit regulated relative approach movement between adjacent vertical plates.
In the interest of rigidity, augmentation of parallelism, maintenance and accessibility for adjustment, each of the three types of spacers mentioned above is completely independent in structure and functions from the other. However, it is anticipated that two or more of these three systems may be combined into a single system capable of performing the same functions as the three systems described in the preceding paragraph.
To describe each of the three spacer systems in more specific detail and with respect to the illustrated embodiment of the invention, the down" stroke stop spacers in their simplest form may be no more than a block of steel, as indicated at 40, having the vertical faces thereof at opposed ends parallel with each other. Each plate 30, 32 and 34 is provided with a plurality of such blocks preferably equally disposed about the longitudinal axis aa of FIG. 1, only one of such blocks being shown in FIG. 1 associated with each said plate, for purposes of clarity. In practice, the vertical faces of each of the plates 28, 30, 32 and 34 are machined parallel to each other with a high degree of accuracy. As the vertical faces of each of said plates are also parallel to the corresponding opposite faces of adjacent said plates, this arrangement permits all the down stroke stop spacers 40 associated with the same adjacent plates to be of the same identical length. The mounting of the spacers 40 to the vertical face of one of the adjacent pair of plates may be done in any suitable manner, such as by a cap screw 41 located in a horizontal hole in the plate to which the spacer 40 is attached and engaged in a threaded hole in one of the abutment ends of the spacer 40, as shown in FIG. 11. In this manner the vertical face on one end of each spacer 40 may be rigidly clamped to the vertical face of its associated plate, and the opposite end of the spacer 40 presents an abutment surface which is parallel to the surface of the plate with which that end of the spacer 40 engages. The simple attachment arrangement of each spacer 40 to its associated plate also provides for the convenient use of washer-like flat shims of the same thickness to be disposed between the spacer 40 and the face of the plate to change the effective length of each spacer 40 associated with the same plate.
The specific structure of the back stroke stop spacers for locating each plate 30, 32 and 34 relative to each other, as well as relative to the plate 28, at the conclusion of the back stroke of the press, may take many and varied forms. Such spacers are indicated at 42 and they are of a design that does not interfere with the relative movement of the vertical plates with respect to each other during the down stroke of the press, yet on the back stroke of the press the spacers 42 act as the means for returning the plates 30, 32 and 34 in definite relationship to each other on the return of the ram plate 24 at the conclusion of the back" stroke of the press.
In the illustrated form, each spacer 42 comprises a rod 44 fixedly attached in any suitable manner at one end to a plate of the moving plate system of the press and having a free sliding fit in a bushing 46 carried on and aligned with opening 48 in an adjacent plate. Abutment head 50, preferably adjustable by use of shims between head 50 and rod 44, is attached to the opposite end of the rod 44.
When adjacent plates approach each other on the down stroke of the press, the rod 44 will slide through the bushing 46 in opening 48 with relative movement taking place between the head 50 and the outer face of the bushing 46. On the back stroke of the press, movement of the ram plate 28 will provide the necessary relative movement for the head 50 to be engaged by the outer face of the bushing 46. On such engagement between the opposed faces of the bushing 46 and head 50, the rod 44 will be tensioned and the movement of one plate will be progressively transferred to the next adjacent plate.
The spacers 42, associated with adjacent plates of the moving plate system, are preferably equally disposed about the longitudinal axis a-a of FIG. 1, as in the case of the spacers 40. Each spacer 42 associated with each pair of adjacent plates is preferably of substantially the same effective length so as to complement the parallelism of the plates 30, 32 and 34.
By having the rods 44 of equal effective length and parallel to the guide rods and tension members 24, as well as to each other, and having the abutting faces of the bushings 46 and heads 50' parallel to each other and to the faces of the moving plates, movement of the plates 30, 32 and 34 by the ram plate 28 on the back stroke of the press is accomplished without disturbing the parallelism of the components of the press. It will be appreciated that flexible cables or chains of the proper lengths may be attached between adjacent members of the moving plate system of the press which would perform a function similar to that attributed to the rods 44 and associated structure as above described, except for the guide pin effect of the rods 44.
HYDRAULIC CUSHIONS The third spacer system of the press is more complex as to both structure and function than the systems of the spacers 40 and 42. Because of this fact, the hydraulic cushions which characterize the spacer means of the third system, although all are similar in function and construction (as in the case of spacers 40 and 42) each set of cushions associated with each of the plates 28, 30 and 32 will be identified and described through the use of separate reference characters.
In general, each cushion comprises a cylinder which is fixedly mounted on its associated plate of the moving plate system and functions as an integral part thereof. As a functional part of each cylinder, a piston is provided which extends into the cylinder as well as out of the cylinder. That portion of the piston which projects from the cylinder performs the function of a thrust member of adjustable length which spaces the plates of the moving plate system as well as controls their relative sequential movement in an approaching direction on the down stroke of the press. The cylinders of the set of hydraulic cushions associated with each of the above-mentioned plates are preferably equally distributed about the longitudinal axis aa, as in the case of the spacers 40 and 42.
In specific detail, one set of hydraulic cushions 52 is mounted on the plate 28, another set of cushions 54 is mounted on the plate 30, and a third set of cushions 56 is mounted on the plate 32. Each set of cushions 52, 54 and 56 comprises cylinders 58, 60 and 62, and pistons 64, 66 and 68, respectively. It will be noted that the cushions of each set are the same as to length, and that each set of cushions is different from the other as to length. The difference in length of the cushions is determined by the necessary spacing of the plates of the moving plate system when that system is being advanced by the ram as a thrust column of constant length. As will be hereinafter described in more detail, hydraulic fluid is admitted to the cylinders 56, 60 and 62 to act on the ends of the pistons 64, 66 and 68, respectively, to extend the pistons 64, 66 and 68 to their extended positions, which positions are preferably determined by the effective lengths of the spacers 42. Thus, fluid pressure in the cushions 52, 54 and 56 acts to 8 place the rods 44 of spacers 42 under tension by acting to separate plates 28, 30, 32 and 34.
When the hydraulic fluid is trapped in the cushions 52, 54 and 56 by suitable valve means, the pistons thereof will function as relatively solid thrust columns disposed between the plates 28, 30, 32 and 34. By regulating the flow of fluid from the cushions by suitable valve means, the cushions will collapse and the effective length of the pistons 64, 66 and 68 will be reduced to permit the plates of the moving plate system to approach each other.
It should be understood that the ram pressure of the press is impressed on the metal forming tools of the press through the hydraulic cushions 52, 54 and 56. When the cushion 56 has collapsed to the point at which the spacers 40 on plate 34 abut the plate 32, the limit of relative approach movement between the plates 32 and 34 has been reached. Likewise, when the cushion 54 has collapsed to a point at which the spacers 40 on plate 32 abut the plate 30, the limit of relative approach movement between the plates 32 and 30 has been reached. A similar situation exists when the collapse of the cushion 52 permits the spacers 40 on the plate 30 to engage the plate 28. On sequential collapsing of the cushions 52, 54 and 56, the working load being applied to the metal forming tools will be transferred by the locked cushions and the collapsing cushions will hold the plates ahead in the moving plate system together when they have reached their position of complete approach, which position is determined by the spacers 40 being engaged by adjacent plates. The further function of the cushions 52, S4 and 56 will be described in connection with the function of the punches of the plates of the moving plate system as pressure pads.
TELESCOPING PUNCHES Each of the plates 28, 30 and 32 supports a tubular punch 70, 72 and 74, respectively, the punches being nested one within the other with a close sliding fit. As the punches will normally be of tool steel, to avoid a galling, that may be experienced with a steel-to-steel fit, nonferrous bushings 75 are preferably employed between the punches.
The amount of reduction in the diameter of the work blank between drawing operations is such that the tubular punches 70, 72 and 74 have suflicient wall thickness to make them structurally rigid. They are rigidly connected to their respective plates of the moving plate system in any suitable manner with their longitudinal axes being common to the axis a-a of FIG. 1. As shown each punch 70, 72 and 74 has a series of tapped holes 76 at its inner end for receiving screws 77 for attaching the punches to the plates. The plates 30, 32 and 34 have openings 78 concentric with the punches to permit the telescoping assembly of the punches to extend through the plates with clearance, as well as permitting the plates to have relative approach movement.
When the press is at the end of its back stroke and in the position from which the down stroke is initiated, the forward ends 80, 82 and 84 of the punches 72 and 74, respectively, are preferably disposed in the slightly stepped position shown in FIG. 4. This arrangement permits a slight amount of creeping of the punches relative to each other without the tendency to crown the bottom of the metal article being obviated. The stepped arrangement of the punches has the further advantage of providing a slight amount of lag in the sequential functioning of the punches so as to make the timing of the punch movement less critical.
FIXED PLATE SYSTEM The number of plates in the fixed plate system and the tools mounted on the plates thereof will usually be determined by the number of plates in the moving plate system and the article that is to be formed by a single continuous stroke of the press. If blanking is to take place in the press, then the first fixed plate will mount the blanking operation as well as the first draw. The following fixed plates may be tooled for a redrawing or ironing operation or a combination thereof. If the metal article being formed is to have a detailed bottom, then the innermost punch of the telescoping punch assembly will be shaped on its outer end to perform the detailing operation in cooperation with a detailing die carried by the last fixed plate, or the base plate 18, as may be desired. Preferably, the base plate 18 is apertured to enable the same to carry a drawing or ironing die, as well as a stripper mechanism where detailing of the bottom of the formed article is not to be performed.
In the illustrated form of the invention, the fixed plate system of the press comprises the plates 86, 88, 90 and 92, all having clearance holes 94 therein of different sizes with their centers located on the axis a--a of FIG. 1. The fixed plates are of rigid construction and are provided with holes 36 at their four corners with bushings 37 to receive the guide and tension members 24 with a close sliding fit so as to permit adjustment of the fixed plates along the members 24. As in the case of the plates of the moving plate system, rigidity, parallelism and concentric alignment is important. To that end the vertical faces of each plate 86, 88, 90 and 92 are parallel to each other, as well as to the faces of the other fixed plates. Located between each of the plates 86, 88, 90 and 92 and between the plate 92 and the base plate 18 are sets of spacers 98 equally distributed about the axis a-a of FIG. 1. The spacers 98 have a length which depends on the necessary spacing of the plates to form the metal article and they usually are of increasing length in the direction of the down stroke of the press. However, the spacers 98 of each set are preferably of the same length so as to hold the plates 86, 88, 90 and 92. parallel with the ends of the spacers 98 abutting the opposite vertical surfaces of adjacent plates. Cap screws 100 may be employed to connect the plates 18, 86, 88, 90 and 92 into a rigid complex of parallel plates horizontally aligned on the members 24, as well as being vertically supported from the supporting surface of the base of the press through adjustable leveling screws 101.
BLANKING, DRAWING, IRONING AND DETAILING DIES When a circular blank is to be punched from strip stock or square cut stock S, a blanking punch 102 in the form of a flat ring is mounted on one face of the plate 34 in any suitable manner. The blanking die 104 is mounted on the opposite face of the fixed plate 86 and takes the form of an annulus which presents a shearing edge to the blank punch 102. The first draw die 106 is nested within the blanking die 104. A flat vertical face 108 on the drawing die 106 provides a hold down surface with which the fiat surface 109 of the blanking punch 102 co-acts as a pressure pad to control the marginal portion of the sheared blank B during the first draw operation. In all of the following redrawing operations, the telescoping punches of the press perform the function of pressure pads on the progressively drawn work blank B.
Plates 88 and 90 are shown with redraw dies 110 and 112, respectively, while the plate 92 has an ironing die 114 on one side and a stripper mechanism 116 on the opposite side. A die 118 is shown mounted on the inside surface of the base plate 18 for detailing the bottom of a metal article being formed. It will be understood that the work blank will be carried through the redrawing die 112 and the ironing die 114 on the punch 70 mounted on the moving plate 28. Also, the punch 70 will detail the bottom of the work blank in the die 118 at the end of its down stroke, and the completed work blank will be stripped off the punch 70 by the mechanism 116 on the back stroke of the press.
The punch 74 mounted on the moving plate 32 will continue through the drawing die 106 to its fully approached position relative to the redrawing die 110, at
which position the end 84 will perform the function of a pressure pad in conjunction with the face 111 of the die 110. When the travel of the punch 74 is arrested by spacer 40 on plate 34, the punch 72 on the moving plate 30* will draw the work blank in the redrawing die and continue to its fully approached position relative to the redrawing die 112, in which position the end 82 of the punch 72 will perform the function of a pressure pad.
CONTROL OF PRESSURES AND STRESSES ON WORK BLANK The present invention is primarily concerned with the deep drawing of metal articles without annealing in which the ratio of height to diameter of the work blank at the conclusion of the drawing operation, performed during a single continuous stroke of the press, is substantially greater than has been heretofore performed in commercial practice. A ratio of height to diameter exceeding 4 to 1 and up to 8 to 1 has been obtained under practical commercial operating conditions. When one or more ironing operations are performed in the press following the last redrawing operation, the ratio of height to diameter of the work blank may readily be in the order of 8 to 1 through 15 to 1. Thus, it will be appreciated that the telescoping punches will of necessity be of extreme length in order to perform the drawing, ironing and stripping operations in the fixed plate area of the press. This is especially true where the diameter of the finished metal article exceeds six inches.
Due to the heat generated by the drawing and ironing operation performed by a single and continuous stroke of the press, thermal expansion of the punches Will take place which will affect the performance of the press. When the press has been out of operation for any substantial length of time and the temperature of the telescoping punches has returned to substantially room temperature, adjustment of the spacers of the press at that time to correctly locate the ends of the punches relative to the drawing dies will result in an improper adjustment when the punches are brought up to the temperature at which the punches obtain during prolonged operation of the press. To avoid this situation, an elongated fully enclosed thermostatically controlled electrical resistant heating unit 120 is shown located within the innermost punch 70 of the assembly of the telescoping punches. The unit 120 is shown connected to an electrical outlet 122 for convenient attachment to a source of electrical energy when the press is not in operation. In this manner the punches are maintained at a temperature corresponding to the operating temperature and start-up adjustments are avoided.
According to the invention the work blank B in all drawing operations is preferably drawn over a relative gradual radius 124 with minimum clearance being provided between the drawing die and the punch, as compared to standard practice, to cause the Work blank to have an inside diameter, very close to the outside diameter of the punch, preferably, to the point of punch hugging. In practicing the invention, it has been found that the clearance 126 between the drawing die and the punch in each drawing operation may be the same and good results are obtained when this clearance is in the order of 60-70 percent of the clearance recommended by standard handbook practice with light gauge material. For example, whereas standard practice may call for a clearance at 126 of 2.3 times the thickness of the stock being drawn, according to the present invention the clearance used is, preferably, in the order of 2.2 times the thickness of the stock.
Whereas it has been thepractice heretofore to increase the clearance 126 in subsequent redrawing operations because of the tendency of the work blank to thicken at the top during each following drawing operation, the objects of the present invention are best obtained by maintaining substantially the same clearance 126 in all subsequent redrawing operations, and effecting at least a slight amount of ironing action on the top area of the work blank in each drawing operation.
The ironing operation, mentioned in the preceding paragraph, at the top of the work blank, results from the fact that the reduction in clearance over standard practice provides an interference fit between the punch and drawing die and the thickened top portion of the Work blank.
During the sequence of drawing operations being carried out in accordance with the present invention by a single continuous stroke of the press, the top area. of the work blank that is ironed will be greater in each successive drawing operation.
As will be more fully discussed hereinafter, the process of the present invention results in what appears to be a reduction in the amount and/ or the rate of work and strain hardening of the work blank in obtaining the same reduction in blank diameter heretofore experienced under generally accepted commercial practice. Under the practice of the present invention, in addition to the apparent lower rate of work or strain hardening, a high degree of uniformity of work hardening is maintained circumferentially of the work blank with the avoidance of overworked localized areas which would have a tendency to initiate metal rupture in following redrawing operations, or would necessitate annealing of the Work blank before performing secondary operations on the work blank B after removing the same from the press. In the following paragraphs the structural factors which are believed to contribute to the circumferential uniformity of the work or strain hardening of the work blank are reviewed:
The initial movement of the moving plate system along the guide and tension members 24 rigidly couples the same to the rigid mass of the fixed plate system through the medium of the guide pins 128 on the moving plate 34 entering the bushings 130 in the fixed plate 86 with a close tolerance sliding fit. As the drawing operations are being carried out in sequence in the press, the mass of the moving plate system is becoming more compact as it moves toward the area in which the drawing operations are being carried out. This increase in compactness is due to the relative approaching movement of adjacent moving plates under the control of the hydraulic cushions and has the effect of augmenting the rigidity, parallelism, and concentricity of the components of the moving plate system.
The telescoping association of the punches of the press, coupled with the rigid parallelism of the moving plate system which supports the punches, results in the punches being concentrically presented to the drawing dies with a high degree of accuracy. This concentric relation between the punches and the dies is maintained throughout the several drawing operations performed in the press during a single continuous stroke thereof. As a result, excellent control of the metal of the work blank becomes a possibility when this relationship is combined with the movement of the work blank from one punch, with pilot action, through the drawing die and back on the next punch. This factor plus a tendency toward punch hugging of the work blank and the ironing of the top area of the work blank in each drawing operation, all seems to contribute to the circumferential uniformity of the work or strain hardening of the work blank.
With highly polished drawing dies in a process having the structural and functional features described above, total reduction of blank size in the order of 80% has been successfully carried out during a single continuous stroke of the press under conditions of commercial practice with out metal rupture, and at the conclusion of the drawing operations effecting such a high reduction, the metal of the work blank is still capable of withstanding forming operations on the open end of the work blank, such as a beadingoperation, without first annealing. Also, it has been possible in the practice of the present invention to have successive reductions in the redrawing operations,
each in the order of 25% to 30% in lieu of the practice of carrying out reductions in redrawing on a severe sliding scale such as 25%, 15% and 10%.
In the light of the results obtained by the present in vention, it is practical to have a reduction in the first drawing die 1% in the order of 40% and to perform redrawing in each of the drawing dies 110 and 112 with reductions in the order of 25%. Using three redrawing dies, this practice will give a total reduction in blank sizes without annealing of approximately and if four redrawing operations are used, the total reduction may be in excess of These results may be compared with standard practice giving total reduction possible under conditions of commercial practice in the order of 55% before annealing.
Another area of departure of the process herein disclosed over standard practice relates to the speed of drawing the metal in the press. Whereas, heretofore conventional practice has indicated speeds in the orderof 45 feet to 70 feet per minute, excellent results have been obtained according to the invention with drawing speeds in the order of feet per minute.
RATE OF WORK OR STRAIN HARDENING It appears that in the process of metal forming as carried out in accordance with the present invention the rate of work hardening is materially reduced over the rate that is experienced when the same work blank is processed over the same tools but with an interruption between each operation in lieu of all the operations being carried out during a single continuous stroke of the press.
In an effort to establish the reduction in the rate of work hardening, numerous microphotographs have been taken of work blanks which have been sheared and drawn from the same strip of stock as produced at the milhSome of these work blanks were drawn in a press constructed and operated accordingto the invention by being completely for-med by a single continuous uninterrupted down stroke of the press. Other work blanks were formed by interrupting the down stroke of the same press after the first drawing operation and then thereafter completing the following drawing operations. Some of these blanks were removed from the press following the first drawing operation and were then transferred to conventional drawing tools to complete the drawing operations, the reductions of the conventional drawing tools corresponding to those of the omitted drawing operations in the press of the invention, whereby the total amount of deformation of the metal would be substantially the same in the articles completely formed in the press of the invention as in the articles partially formed in such a press and then completed on conventional tooling.
The remaining workability of the work blanks processed according to the present invention, as compared to the work blanks finished on conventional tooling, clearly suggests a lower rate of work hardening. However, the comparison of grain structure in microphotographs has failed to fully account for the substantial increases in remaining workability of the work blank and the substantial increase in total reductions that can be obtained in commercial practice by following the teaching of the present invention.
It should be appreciated that the availability of the remaining workability of the work blank at the conclusion of the drawing and ironing operations is of great commercial importance when secondary operations are to be formed on the metal article. This available workability enables such operations to be performed directly on removing the article from the draw press and without the necessity of subjecting the same to an annealing operation.
13 CONTROL SYSTEM FOR HYDRAULIC CUSHIONS It will be appreciated that with the sets of hydraulic cushions 52, 54 and 56 mounted on and moving with the plates 28, 30 and 32 of the moving plate system of the press, the supply of hydraulic fluid to and from the cushions and the control of hydraulic fluid pressure in the cushions during unitary as well as relative movement of such plates should be carried out, if possible, without resorting to an involved hydraulic system which would materially increase the cost of the press and its maintenance. The quantity of hydraulic fluid required in large size presses of the type contemplated by the present invention and the rapidity with which the fluid must be transferred relative to the cushions during the operation of the press, without overheating or foaming of the fluid, aggaravtes the problem.
First, it should be noted that the hydraulic system for the fiow of fluid to and from the supply and the control of the hydraulic cushions is separate and distinct from the hydraulic system that may be employed to actuate the ram on the down and back strokes of the press. This is true, although the forces exerted by the ram on the moving plate system create the working pressure in the hydraulic cushions.
Preferably, the hydraulic fluid employed in the hydraulic cushions 52, 54 and 56 is transferred between the cylinders 62 and the supply 132 through large size flexible hose lines 134 which are attached at one end to the valve structure of the moving plates 28, 30, 32 and 34 and at their opposite ends to one or more suitable supply tanks. These lines are supplied and supported in such a manner as to avoid abrasion as their ends attached to the plates travel back and forth during the operation of the press.
To eliminate as much piping and external manifolding as possible, each of the moving plates 28, 30, 32 and 34 has passages 136 and they each act as a manifold for delivery of hydraulic fluid to the set of cushions associated with each of these plates. Mounted on top of each of the ported plates is a hydraulic manifold 138 for the hydraulic connection of the passages 136 of the plates with a main control valve 140. Plates 30 and 32 carry pressure switching valves 142 on their sides. Each of the mentioned valves has a manually actuated knob 144 for effecting pressure changes. In the operation of the press of the present invention, it is usually only necessary to make adjustments in pressures through manipulation of the knobs 144 in changing from one material to another of the same gauge. Aluminum, brass and steel articles, for example, fabricated from stock of the same gauge have been successfully drawn over the same dies by merely changing the operating pressures of the hydraulic cushions 52, 54 and 56 associated with the moving plates of the moving plate system.
Each of the passages 136 of the plates of the moving plate system has a connection with the longitudinally extending passage 148 in each piston 68 of each hydraulic cushion. The outer end of each piston 68 has a sealed connection with the passage 136 in the plate to enable hydraulic fluid to flow to and from the cylinder 62 through the passage 148 in the piston 68. When the fluid is trapped or locked in the cylinder 62 by the valve 142, each cylinder 62 and each piston 68 will collectively function as a thrust column of fixed length between adjacent plates of the moving plate system. When the valve 140 is triggered by the pressure switching valve 142, as will hereinafter be described in more detail, the fluid is metered from the cylinder 62 through the passages 148 and 136 and the piston and hydraulic cushion collectively defined by the cylinder 62 and piston 68 will collapse under controlled conditions to enable adjacent plates of the moving plate system to approach each other.
14 SWITCHING VALVE FUNCTION In order to more fully describe the function of the switching valves 142, let it be assumed that the hydraulic pressure system for operating the ram 150 is capable of exerting 50 tons of force on the ram 150, which force is in turn directed through the semirigid connection 152 to the plate 28. The main valve 140 under the conditions assumed would be adjusted to maintain in excess of 50 tons of force, or a pressure such that each of the four hydraulic cushions associated with each of the plates 28, 30 and 32 is capable of exerting back pressure in excess of 12.5 tons.
At this point it should be noted that preferably the main control valve 140 of the plate 34 does not have a switching valve 142 connected to it. Instead, it is a self-contained pressure regulating valve and functions to maintain a constant pressure in the cushions of the set of cushions 56 disposed between the plates 32 and 34 sufiicient only to hold the sheared work blank B from wrinkling while the first drawing operation is being performed.
Let it be assumed that the valve 140 of plate 34 is set at a pressure at which the set of four cushions 56 will exert a total of 15 tons of hold-down pressure available in the pressure pad structure in the first drawing operation. This 15 tons of pressure is constant and it will be maintained through the entire first drawing operation. When the 15 tons of hold-down pressure is substracted from the 50 tons of available force of the ram 150, the remaining 35 tons is available for the first drawing operation with the ram 150 delivering only the amount of force resisting its down stroke movement. It will be understood that a constant back pressure in the order of 20 to pounds per square inch is imposed on the hydraulic fluid supply 132 which keeps the hydraulic cushion full of fluid and the valves of the hydraulic system of the hydraulic cushions in a working condition. When the hydraulic cushions are full of fluid and such fluid is locked or trapped therein, it causes each of the hydraulic cushions 52, 54 and 56 of the set located between the plates 28, 30, 32 and 34 to function as a thrust column of fixed length until the movement of the plate 34 is arrested and the pressure of the ram 150 on the moving plate system overcomes the pressure setting of the valve on the plate 34, thereby causing the fluid trapped in the set of cushions 56 to be expelled therefrom permitting the plate 32 to approach the plate 34.
As the moving plate system is advanced as a unit by the ram at the start of the down stroke of the press, the guide pins 128 on the plate 34 enter the bushings 130 on the plate 86 to rigidly couple the plate 34 to the plate 86 just before the blanking punch 102 engages the strip stock S and forces the stock S against the cutting edge of the blanking punch 102. The cutting edge of the blanking punch 102 must have enough shear angle on it to allow the strip stock S to be blanked with a force less than 15 tons, otherwise the set of cushions 56 will start to collapse and the work blank will be engaged by the punch 74 before the work blank B is completely sheared and the face 109 of the blanking punch is in a position to function as a pressure pad.
Assuming the plates 34 and 86 have approached each other to complete the shearing of the work blank B from the strip stock S and the face 109 of the blanking punch 102 carried on plate 34 is exerting 15 tons of pressure on the marginal portion of the work blank B sheared from the strip stock S, the spacers 40 located between the plates 34 and 86 have become effective and have limited the approach movement of the plate 34 toward the plate 86. By so doing, the spacers 40 have stopped the plate 34 in a position spacing the face 109 of the blanking punch 102 from the face 108 of the first drawing die 106 on the plate 86 a distance approximating the thickness of the strip stock from which the work blank B has been sheared. This function of the spacers 40 provides stop arrested blank-holding for the workpiece or blank.
With the unitary movement of the moving plate system having advanced all the plates 28, 30, 32 and 34 to the point at which the spacers 40, between the plates 34 and 86, have arrested further down stroke movement of the plate 34, the set of cushions 56 which has been spacing the plates 32 and 34 will start to collapse under the force being exerted by the ram 150 which is in excess of the 15 tons of pressure pad action being exerted on the spacers 40 between the plates 34 and 86. This pressure reacts against any tendency for the marginal portions of the sheared work blank B to wrinkle and thicken during the first drawing operation. Under the influence of such pressure the face 109 of the blanking punch 102 provides pressure blank-holding for the workpiece or blank.
As the set of cushions 56 collapses, hydraulic fluid in the cylinders 62 will be forced out through the longitudinal passages 148 in the pistons 68 into the passage 136 of the plate 34 and through the control valve 140 to the supply 132, the flow of fluid between the valve 140 and the supply 132 being against the supply pressure created by the air pressure of 400 pounds per square inch upon the hydraulic fluid in the supply 132.
With the initial collapsing movement of the cushions 56, the plate 32 and its associated drawing punch 74 will be advanced to move the punch 74 into contact with the sheared work blank B imposed on the face 108 of the drawing die 106 carried on the fixed plate 86 of the fixed plate system. With the unitary movement of the moving plate system now confined to the plates 28, and 32, the continued down stroke of the ram 150 will start the first drawing operation by advancing the punch 74 through the drawing die 106 of the plate 86.
In FIG. 16 the relative positions of the plates 32, 34 and 86 is shown with the first drawing operation partially complete. The extent that the plate 32 has approached the plate 34 is indicated by the distance the head 50 of the back stroke spacer 42 has been projected from the face of the bushing 46 supported on the vertical face of the plate 32. It is also to be noted that the pressure switching valve 142 carried on the plate 32 is approaching its actuator 154 on the plate 34.
FIG. 17 shows the relative position of the plates 32, 34 and 86 after the completion of the first drawing operation and at the start of the first redrawing operation in the drawing die 110 carried on plate 88. The spacers 40, between the plates 32 and 34, are new active to limit the down stroke approach of the plates 32 and 34, the collapse of the cushions 56 having terminated, and the pressure switching valve 142 having engaged its actuator 154 on the plate 34 to unlock the fluid in the set of cushions 54 spacing the plates 30 and 32. Collapsing action of the cushions 54 will initiate the first redrawing operation as the down" stroke of the moving plate system, now confined to the plates 28 and 30, continues.
It is in connection with the first redrawing operation that the drawing punch 74 of the first drawing operation takes on the dual function of a pilot and a pressure pad for the following drawing operation. This dual function has been described in detail heretofore in regard to that shown in FIG. 15. To function properly as a pressure pad, the end 84 of the punch 74 must be maintained a proper distance from the face 111 of the first redrawing die 110. It is one of the functions of the spacers located between the plates 32 and 34 to provide such spacing. As the length of the spacers 40, between the plates 32 and 34, is determined without regard to the longitudinal thermal expansion of the punch 74, pinching of the work blank may result of a magnitude that will cause rupture of the work blank during the first redrawing operation. It is for this reason that it may be found desirable, as herein proposed, to maintain the telescoping punch assembly at a controlled temperature at all times to avoid start-up adjustment or metal rupture from thermal expansion when operating temperatures have been reached in a production run.
CLEARANCE HOLES IN MOVING PLATE SYSTEM As heretofore mentioned, for the sake of clarity, in FIGS. 1 and 2 only one spacer element of each of the three spacer systems for the moving plate system has been illustrated. However, in FIGS. 3, 4, 15, 17 and 18 such spacer elements are all shown in the actual number used in the press and as they appear in side elevation.
In FIGS. 5, 6, 7 and 8 these cross-sectional views are taken on the sectional lines of FIG. 3 so that the spacer elements omitted in FIGS. 1 and 2 all appear in FIGS. 5, 6, 7, 8, 16, 17 and 18.
Of the elements of the three spacer systems shown in FIGS. 12, 13 and 14, only the spacer elements of FIGS. 13 and 14 necessitate that the plates 28 and 30 of the moving plate system be provided with clearance holes in order to permit the plates 28 and 30 to move from the position of FIG. 1 to the position of FIG. 2 on the down stroke of the press.
In FIG. 7 is shown clearance holes 50 for the heads 50 of the spacers 42 attached to the plate 32. Also, in FIG. 7 is shown the clearance holes 56 in the plate 30 to permit passage of cylinder 62 of the cushions 56 mounted on the plate 32. FIG. 8 shows the clearance holes 54' in the plate 28 for the passage of the cylinders 60 of the cushions 54 mounted on the plate 30.
FIGS. 5, 6 and 7 indicate the distribution on the plates 30, 32 and 34 of the spacer elements of the three systems illustrated in FIGS. 12, 13 and 14. The elements are shown as being used in sets of four associated with each of the plates 30, 32 and 34. Preferably, they are as equally distributed as possible about the axis aai and in this manner assist in maintaining parallelism of the plates 28, 30, 32 and 34. Obviously, the number of spacer elements in each set may be varied as may their location on the plates.
MULTIPLE SETS OF TOOLS The design of the press of the present invention lends itself to unlimited enlargement of the plates carrying the dies and punches Where it is desired to produce more than one drawn article during each stroke of the press. For example, to adapt the press to the economical manufacture of inexpensive seamless cans for use in the packaging of food and beverages, a great many sets of telescoping punches could be mounted on the plates of the moving plate system of the press with corresponding sets of dies located in the fixed plate system of the press. In lieu of the plate 28, for example, carrying only one punch 70, it could carry a great many punches, the number depending on the size of the can to be drawn and the practical and economical limitation on the size of the press.
FIG. 24 illustrates a modified form of the invention in which three sets of telescoping punches are shown installed in the press in lieu of the single set of telescoping punches employed in the form of the invention of FIG. 1. FIG. 24 is a cross-sectional view corresponding substantially to FIG. 5. It Will be noted that the sets of punches each comprises punch '72 and 74, and that these sets are grouped around the central axis of the plate 34 in lieu of being located concentric with the axis in the manner of the single set of telescoping punches of FIG. 5. The primed reference characters of FIG. 24 indicate the same parts designated in FIG. 5 with corresponding unprimed reference characters.
THEORIES OF THE INVENTION In order to provide a possible explanation for the unexpected results obtained in the commercial practice of the present invention in the production of metallic articles fabricated from sheet metal by a single continuous uninterrupted stroke of the press, such articles have been fully investigated through the use of microphotographs, by residual stress analysis, and determination of mechanical properties.
For the purpose of making comparison between articles fabricated by employing the invention and articles fabricated in accordance with well established commercial practices heretofore employed, every possible precaution has been taken to obtain substantially identical test blanks. Such blanks have been drawn on substantially identical tooling, one set of tooling being employed in a press constructed according to the invention and another set of tooling being used in conventional drawing press apparatus.
In analyzing the results obtained in comparative tests, metal rupture, metal splitting, degree of work hardening, remaining workability of the drawn article and uniformity of mechanical properties have all been factors of principle importance for consideration from a commercial point of view.
As heretofore stated, the studies that have been made in regard to comparative tests have indicated that there has been a reduction in the degree of work hardening (in terms of remaining workability) in the fabrication of metallic articles in accordance with the principles of the present invention, as compared with the amount of work hardening that is experienced when metallic articles are subjected to the same amount of metal deformation when carried out in accordance with existing conventional practices.
Investigation as to residual stresses appears to indicate that the press and process of the present invention tends to minimize the accumulation of residual stresses of a nature detrimental to deep-drawing of metallic articles.
Example No. 1
This test was conducted on sheet metal blanks certified by the metal producer as being substantially identical in all respects. The blank size was 12.25, the stock thickness .045, the material 1008 low carbon draw quality steel, and the finished can had an outside diameter of 4 and a height of 8 /4". The first draw die, first redraw die and second redraw die and radii of A1, A and /2", respectively, while the corresponding punches had diameters of 6.73", 4.82" and 3.91", respectively.
Sample D.-Blanks according to the preceding paragraph were placed in a press constructed according to the invention and having a set of nested punches consisting of the three punches indicated above. The cans were formed with one continuous uninterrupted stroke of the press, the speed of the stroke being approximately 50 feet per minute. Punch and die clearances and all other constructional and functional features of the present invention, as heretofore set forth in this specification, were observed in this test. The drawn articles resulting from the test showed no splitting or metal rupture and were otherwise completely satisfactory as to finish, lack of surface defects and other qualities required of drawn metallic articles for commercial purposes.
Sample D31.-The procedure set forth under Sample D was modified by stopping the press at the completion of the first draw and removing the can from the first draw punch. Eighteen hours later the can in the same condition as it was when it was removed from the punch was installed on the first draw punch and the down stroke of the press was continued to complete the first and second redrawing operations. In every case splitting of the can was experienced at the top of the can, the splits occurring, for the most part, in the valley between the eating on the upper edge of the can and generally taking place at the time of stripping of the can from the punch, indicating excessive work hardening with a resulting brittleness that would not withstand the action of the jaws of the conventional stripping mechanism.
Example No. 2
The conditions were the same as set forth in Example No. 1, except the material being tested was low carbon aluminum killed steel in lieu of drawing quality steel.
Sample K21.Procedure was the same as in Sample D of Example No. 1 with the same result, namely, no splitting or metal rupture.
Sample K29.Procedure was the same as in regard to Sample D31 of Example No. 1 with the same result, namely splitting of the can was experienced.
Example No. 3
The conditions were the same as set forth in Example No. 1 except the material was commercial quality low carbon steel.
Sample C.Procedure was the same as in the case of Sample D of Example No. l with the same result, namely, no splitting or metal rupture.
Sample C27.Procedure was the same as in Sample D31 of Example No. 1, with the same result, namely, splitting of the can.
Example No. 4
A test was run on a press constructed and operated in accordance with the invention, the press being one used in regular commercial production. In this press the moving plate system comprises a set of five telescoping punches having diameters of 14", 10.7", 8.5, 6.5" and 5.2 for carrying out the first draw, four redraws and an ironing operation, all performed within approximately seven seconds during a 91" continuous uninterrupted down stroke of the press.
The drawing dies carried in the fixed plate system of the press had clearance with the punches which followed the principles of the invention with the radius of the first drawing die being A" and the radii of the following four redrawing dies being FIG. 21 of the drawing depicts the work blanks as they are run in this particular test, while FIGS. 22 and 23 indicate the pressure pattern obtained with the tooling and material used in this test.
The material used was Alcoa aluminum alloy 3003-0 (dead soft) in the form of 19" presheared circles of .040 stock. In the ironing operation which followed the fourth redraw and took place on the 5.2" diameter punch, the wall of the can was ironed from a thickness of approximately .040" to a finished wall thickness of .027". The finished can had an outside diameter of 5.25" and a height of 22".
All cans run during this test were without rupture or splitting, and they had an excellent finish free from defects of all kinds. On removing the cans from the press, the tops of the cans were slightly trimmed in an amount required to remove the caring at the upper edge of the can, and the workability at the trimmed line was such that a A diameter outside bead was provided in the top of the can, as a secondary operation, by forming the trimmed top edge through 270 without effecting rupture or cracking of the metal at any point, without annealing.
As taken from the press, the cans were tested to determine the dimensions and mechanical properties. The locations on the cans where the dimensions and mechanical properties were determined in making up the following tabulation appear in the lowermost illustration of FIG. 21. Typical tabulation of dimensions and mechanical properties of such cans follows:
Percent elongation Wall Location on can Tensile Yield in 2" thickness The tensile and yield determinations are given in the above in thousandths of pounds per square inch.
Example No. 5
This test was run on a press constructed and operated in accordance with the invention, the press being one used in regular commercial production. The set of five telescoping punches had diameters of 14", 10.7", 8.5, 6.5" and 4.5 with the first draw die having a radius of A", the first, second, and third redraw dies each having a radius of and the fourth redraw die having a radius of :43".
The material for this test was the same as in Example No. 4 except the thickness of the stock was .050 and the ironing operation performed on the 4.5" punch following the fourth redraw operation, reducing the wall of the finished can to .040".
The 23 diameter presheared circles of 3003- aluminum alloy (dead soft) were placed in the press and drawn and ironed in one continuous uninterrupted down stroke of the press to produce finished cans having diameters of 4.58" and heights of 38". The total reduction in the five draw operation was in excess of 80%. It will be noted that the ratio of diameter to height in the cans thus produced was approximately 1 to- 8. Cans produced in this test contained no ruptures or splits of any kind and possessed the same high finish, excellent surface quality and available workability set forth in respect to Example No. 4. The speed of the down stroke of the press was approximately 70 feet per minute, and the punch to die clearance followed the principles of the invention heretofore described.
Example No. 6
This test was conducted under the same conditions as Example No. 4, using the same punches and dies, the only departure residing in the substitution of Alcoa aluminum alloy 3003-H19 (full hard) for the aluminum alloy 3003-0 (dead soft). The results obtained in this test were the same as those set forth in Example No. 4 in respect to lack of rupture or splitting. If anything, the finish was even better and the workability, after the removal of the can from the press, without annealing, permitted the rolling of the same bead mentioned in Example No. 4 with the same excellent results. These results with full hard material were completely unexpected and are unexplainable when viewed in the light of existing commercial practices. Upon checking the mechanical properties of cans produced under this test from 3003-H19 aluminum alloy, it was found that the bottom of the can, as indicated in FIG. 21, had maintained its full hardness and the wall of the can was above full hard. A tabulation of the mechanical properties of a typical can run in this test as determined by the Aluminum Company of America follows:
Yield Tensile Elongation Top:
Across grain 28. 4 30. 4. 0 With grain 29. 7 33. 5 4. 0 Across grain- 7. 5 30. 2 4. 0 With grain 30. 0 33. 3 4. 0 Across grain 26. 4 30. t) 4. 0 With grain 28. 3 31. 8 4. 0 B ottom:
Across grain 25. 7 29. 5 4. 5 With grain 28. 0 29. 2 4. 5
2.0 Example No. 7
In an attempt to determine the upper limits of the.
improvement in workability of drawn and ironed metallic articles processed in accordance with the invention, the tooling used on the press in running example No. 5 was modified to permit the use of sheet material of .100" thickness. This was accomplished by using the same punches as set forth in Example No. 5 and substituting larger dies in the first draw and following four redraw operations. The ironing die of Example No. 5 was enlarged to reduce the wall of the article to .60" and a second ironing die was added to reduce the wall of the finished article to .040".
As in the case of Example No. 5, the material being drawn and ironed was 3003-0 (dead soft) aluminum alloy, and the diameter of the Work blank in the fiat sheet was 23". Without removing the work blank from the telescoping punch assembly and without annealing or resorting to any other form of conventional means heretofore employed for restoring workability following work hardening, it was possible to draw and iron the 23" diameter work blank into a finished can having an inside diameter of 4.5 and an over-all length of 66" without metal rupture or splitting of any kind. The quality of the finish and lack of surface defects was equal to that noted in regard to Example No. 5. The speed of the stroke of the press and the radii of the dies were as indicated in Example No. 5.
A can formed as described in the preceding paragraph was cut lengthwise and Rockwell readings taken on the 30-T Scale with a load of 30kg. using a ball. Starting 4" from the bottom of the can, readings were taken at 4" intervals with the final being taken 2" from the open top of the can. The readings were as follows: 26, 28, 27.5, 27.5, 28.5, 29, 30, 29, 30, 28, 28, 29.5, 30, 30, 30 and 31.
Whereas, in Example No. 5 the ratio of diameter to height of the drawn and ironed can was approximately 1 to 8, in Example No. 7 this ratio was increased to approximately 1 to 15 without metal rupture or splitting and with the article after being drawn and ironed possessing remaining workability to a degree clearly indicating that the upper limits of workability of the material processed in accordance with the invention, as set forth in Example No. 7, had not been reached.
HYDRAULIC SYSTEM OF THE RAM While it is anticipated that means other than fluid pressure may be employed to actuate the ram 150, in the commercial form of the invention the ram is a direct extension of the piston 156 located in the cylinder 158, the length of which determines the maximum stroke of the ram 150. Preferably, the fluid pressure that is directed against the piston 156 on the clown stroke of the press is of a pulsating character, whereby the ram 150 and the plates of the moving plate system transfer high frequency fluid impulses to the telescoping punches throughout the down stroke of the press.
In practice, the fluid pressure for effecting the down" stroke of the press throughout movement of the ram 150 may be provided by means of pumps 160 and 162 of the axial piston type, in which one or more axial pistons provide positive displacement of fluid each revolution of the pump. In such pumps, each piston will provide a pressure impulse on each rotation. Pumps of this kind, such as manufactured by Dennison Engineering Division, when supercharged, as by pump 164, are designed to be operated in the order of 1800 r.p.m. Usually, such pumps have a plurality of axial pistons, with the ones used on the presses of the present invention having seven axial pistons and being capable of delivering 5,000 p.s.i. at 50 g.p.m. and 100 g.p.m., respectively. To analyze the pressure pattern during the down stroke of the press, shown in FIGS. 22 and 23, a high speed electronic analyzer was used, manufactured by the Aeroquip Corportion of Jackson, Mich, and sold under the trademark Hydrauliscope. This apparatus translates the output of a pressure pickup to vertical deflection on a cathode-ray oscilloscope. To obtain the pressure pattern of FIGS. 22 and 23, the pressure pickup was subjected to the fluid pressure acting on the piston 156 of the ram 150. FIG. 23 is a reproduction of the curve traced on the screen of the cathode-ray tube during a complete down stroke of the press when tooled to produce the drawn and ironed article depicted in the sequence of steps of FIG. 21 and described under Example No. 4.
Referring to FIG. 22, the down stroke of the press Was completed in seven seconds. The pressure pattern indicates the pressure peak d of the first draw to be approximately 1900 pounds per square inch acting against the ram 150. The first redraw pressure peak rd indicates a similar maximum pressure. It will be noted that both of the pressure peaks of the first draw and the first redraw took place within the first second of operation of the press. This indicates a relatively shallow first drawing operation, and this fact is confirmed by referring to FIG. 21 wherein the sheet metal strip S is reduced to form the work blank B. Between the pressure peak rd of approximately 1900 pounds per square inch of the first redraw operation and the pressure peak rd2 of approximately 1750 pounds per square inch of the second redraw operation, a greater time interval is indicated than between the pressure peaks d and rd. This indicates a lengthening of the article which is taking place during the first redraw operation, and this is apparent by referring to the form of the work blank B1 of FIG. 21.
FIG. 22 indicates that the pressure peaks M2 and rd3 of the second and third redraw operations, respectively, took place at approximately 1750 pounds per square inch, while the pressure peak rd4 of the fourth redraw operation took place at approximately 1400 pounds per square inch. The time interval between each of the adjacent maximum pressure peaks of the redrawing operations is shown as progressively increasing, indicating the progressive lengthening of the article, bearing in mind that it is desirable to delay the start of one drawing operation until the previous one has been completed. Also, it is desirable to avoid delaying the following drawing operation once the previous drawing operation has been completed, as to do otherwise would of necessity extend the length of the press unnecessarily. In FIG. 21 the work blank B has taken the form of B1, B2, B3 and B4 at the conclusion of the first, second, third and fourth redraw operations, respectively.
The ironing operation in the press of the invention is indicated at i in the pressure pattern of FIG. 22 and takes place at approximately 750 pounds per square inch. At the completion of the ironing operation, the pressure drops to approximately 500 ounds per square inch as indicated at e, with a maximum pressure peak of the entire down cycle of the press approximately 2450 pounds per square inch at the time the bottom of the article is detailed at the end of the down stroke. The work blank B following the ironing operation has taken the form B of FIG. 21.
In both FIGS. 22 and 23 between the pressure peaks pressure impulses 166 have been indicated. In these figures no attempt has been made to depict the frequency of these impulses, although the same can be determined with electronic analyzer apparatus mentioned above. In tests that have been conducted on the presses of the present invention using the pumps of the type above described, the impulses of a frequency in the order of 60 cycles per second or more Were present, and were indicated on the pressure pattern in the form of a band having a width depicting amplitudes covering a pressure range in the order of 200 pounds.
Referring to FIG. 23, it will be understood that this is an enlargement of the upper left hand corner of FIG. 22. The frequency of the pressure impulses making up the wide band of the traced pressure pattern during the sweep of the down stroke of the press is determined by the design of the pumps employed in the hydraulic system for actuating the ram and the speed at which the pumps are driven. These impulses are transferred to the ram 150 and hence to the plates and punches of the moving plate system of the press, the transfer of the impulses between adjacent plates being through the hydraulic cushions, as well as through the nested arrangement of the punches.
While it is a theory of the present invention that the high frequency impulses imparted to the metal-forming components of the press constitute one of many factors contributing to the unexpected results flowing from the present invention, acceptable commercial results have nevertheless been obtained during experiments when an accumulator was attached to the hydraulic system of the ram in a deliberate effort to reduce the magnitude of such impulses.
Those skilled in the art will appreciate that by studying and comparing pressure patterns as depicted in FIG. 22 taken with different materials being run in the press and under different conditions of regulation, that the pressure patterns so obtained and compared will be useful in adjusting and operating the press of the invention in commercial use.
To determine the extent the pressure impulses on the ram 150 were transferred to the press structure closely associated with the punches, the pressure pickup of the electronic analyzer above mentioned was shifted to the fluid system of the hydraulic cushions 56 of the plate 34. The pressure patterns taken at this location were very similar to those shown in FIGS. 22 and 23, and the width of the pressure pattern traced clearly indicated the existence of impulses 166 of approximately the same frequency and magnitude as those determined when the pickup Was located in the hydraulic pressure system of the ram 150.
When the press of the invention was operated without any material being drawn or ironed, under conditions of operation otherwise the same as prevailed when the pressure patterns of FIGS. 22 and 23 were obtained with material being drawn and ironed in the press, it was found that the maximum pressure peaks traced were only slightly lower. On the average, the maximum pressure peaks of the pressure pattern covering the full sweep of the down stroke of the press, without material being formed, was less than pounds below the maximum pressure peaks when the material was being deformed.
The low load yield of the metal of the work lblank B to the drawing and ironing operations, as indicated in the preceding paragraph, is deemed to indicate a softening of the metal by two phenomena having cumulative effects and which offer a possible explanation for the unusual results flowing from the present invention as manifested, for instance, in the aforesaid Examples 6 and 7.
One phenomenon that may contribute to the apparent low load yield of the metal of the work blank B in the press of the invention relates to the effect of softening produced by high frequency vibration. Where metal being drawn has been subjected to the effects of a macrosonic vibrator, one explanation for the softening effect is that the grain boundaries absorb sufficient energy through in elastic scattering of ultrasonic waves that the scattering atoms approach melting temperatures within milliseconds with the stress required to cause their mobility being suddenly reduced. It is a claim of this invention that the pressure impulses produced by the pumps supplying the fluid pressure for actuating the ram are functioning in a comparable manner.
The other phenomenon, also deemed to contribuite to the low stress yielding of the metal to deformation, pertains to the step of carrying out the deformation of the metal of the work blank B during a single, continuous and uninterrupted rapid stroke of the press without appreciable dissipation of the internally generated heat between the acts of deformation.
It appears that the advantages of combining high frequency pulsation of the tooling of a deep-drawing press with sequential deformation of the metal taking place in one rapid, continuous uninterrupted stroke of the press has not been heretofore contemplated, or the improvements resulting therefrom anticipated.
Always, it should be understood, as heretofore mentioned in regard to many of the departures of the present invention over previous processes and apparatus, that many factors contribute to the improvements flowing from the invention. For example, it has been established that the piloting of the work blank B from one punch to the other during the redraw operations is extremely important particularly in regard to the forming of high-strength alloys. To give full recognition to this fact, the reduction taking place in the first draw die is preferably less than heretofore considered good practice. This departure from standard practice has been taken in order to increase the amount of reductions that take place following the first drawing operation during the redraw operations, at which time the work blank is transferred from one punch to the next.
In the operation of the particular press of the invention on which the pressure patterns of FIGS. 22 and 23 were taken, a 400 horsepower electric motor Was used to drive two axial piston-type pumps having capacities of 50 and 100 g.p.m. at 5,000 psi. at 1750 r.p.m. The fluid pressure thus provided was directed into a cylinder having a 6" ID and against the piston directly connected to the ram of the press.
By substituting a gear pump of 150 g.p.m., but of lower pressure capacity, for the pumps mentioned in the preceding paragraph, the cost of the hydraulic pressure system of the ram may be materially reduced. However, in making this substitution, some of the benefits of the high frequency vibrations of the fluid pressure system produced by axial piston pumps may be sacrificed. In such event, the use of transducer means for effecting vibrations, acting directly on either or both of the hydraulic systems of the press, is anticipated to effect a low load yield of the work blank B to deformation in the press. For example, hydraulic vibrators of the type presently used commercially to test the fatigue of materials may be coupled with the press to impart vibrations as high as 500 cycles per second as compared with the pressure impulses in the order of 200 cycles per second that are obtainable with one or more axial piston-type pumps having seven pistons and operating at 1750 rpm. Such a pump is described in US. Pat. 2,608,158.
For a more detailed explanation of the eflects of macrosound upon metal, reference may be had to an article entitled, Ultrasonic; An Aid to Metal Forming? appearing in the April 1964, issue of Metal Process, page 97, published by the American Association of Metals, Mt. Morris, Ill. This article deals with the effect of high frequency vibration in producing in metal a low load yield to deformation without affecting such mechanical properties as ductility. Thus, the results of the present invention are not anticipated.
HYDRAULIC SYSTEM OF MOVING PLATES It will be observed from a study of FIGS. 5, 6 and 7 that the locations of the passages 136 do not follow a definite pattern but are dependent to a great extent on the location of transverse clearance holes in the plates 30, 32 and 34. As a result, it may be necessary in practice to drill two or more intersecting holes in the plates and then plug the ends of some of such holes in order to provide a connecting fluid passage 136 between one edge of the plate and a passage 148 of a hydraulic cushion. Also, it is not always possible to have all of the passages 136 exit from the same edge in plates 30, 32 and 34. In FIG. this has been possible, while in FIGS. 6 and 7 two outside connections 168 are shown carried on the vertical edges of plate 32 and connecting the passage 136 between the two lower hydraulic cushions and the manifold 138 at the upper edge of the plate.
The manifold 138 of the valve 140 and its associated valve body 170 carried on each of the plates 30, 32 and 34 may correspond in general construction and function to that disclosed in US. Pat. 2,938,718, issued to F. M. Williamson. As there is no switching valve associated with the plate 34, the valve 149 on that plate may correspond substantially to that shown in U.S. Pat. 2,938,- 718. However, on plates 30 and 32, which both carry a switching valve 142, the valve 140 is so adjusted'as to operate under the control of the switch valve 142. Such an arrangement is diagrammatically shown in FIG. 19.
Referring to FIG. 19, the manifold 138 on top of the plate 32 connects with the passage 136, which in turn extends to and communicates with the passage 148 of the hydraulic cushions associated with the plate 32. The valve body 170 of the valve 140 is mounted on the manifold 138, and has a bore 172 which aligns with the port 174 in the manifold 138 in communication with the passage 136. A sleeve 176 is disposed in the bore 172 and it is provided with teardrop-shaped ports 1'78 opening into an annular passage 180, which in turn communicates with the passage 182 connected to the hydraulic fluid supply 132 through the flexible lines 134. An unloading valve 184 is disposed in the sleeve 176 with a spring 186 being provided to hold it to its seat in a position closing the ports 178. The small port 188 in the valve 184 communicates the fiuid pressure of the hydraulic cushions created by the ram of the press to the switch valve 142 through the port 190 and passage 192.
Switching valve 142 has a spool Valve 194 with a plunger 196 at one end which is adapted to engage the adjustable abutment 154 of the adjacent plate 34 to shift the valve 194 to the left against the tension of the spring 196 from the position shown in which the valve 194 is blocking the passage 192 to lock the fluid in the hydraulic cushions 54 and, thus, prevent approaching movement of the adjacent plates 32 and 34. When the valve 194 is shifted to the left, the passage 192 is brought into register with the annular passage 198 and fluid pressure flow takes place through the port 200 into passage 292 and, hence, to the port 204. The valve 206 operates to close the port 204, with the amount of fluid pressure required to lift the valve 206 from its seat being determined by the tension of the spring 208.
The knob 144 may be actuated to vary the tension of the spring 208 of the switching valve 142. Lifting of the valve 206 from its seat in the port 264 will enable the flow of fluid in passage 136 to raise the unloading valve 184,
opening the ports 178, to return the fluid trapped in the hydraulic cushions 56 to the supply 132 as the cushions start to collapse and the plates 32 and 34 are able to approach each other. Adjustment of the tension on the spring 208 by the knob 144 will determine the resistance to collapsing being provided by the fluid in the hydraulic cushions 54. When the unloading valve 184 is under the control of a switch valve 142, the valve 210 may be used to trigger the unloading valve 184 under conditions exceeding the regulation of the valve 142 such as overload. In practice, the tension of the spring 212 of the valve will be greater than the tension of the spring 208 of the regulating valve 206.
To enable the fluid returning to the supply 132 to be handled rapidly and with relatively small lines, two passages 182 are preferably provided in the valve body for that purpose. It will be understood that the fluid pressure supply 132 is under constant pressure as the result of air pressure applied to the surface. This pressure is suflicient to return the fluid to the hydraulic cushions 54 and to maintain the valve mechanism in Working condition. This pressure is in the order of 20-100 pounds and returns the fluid past the ball valve 214 to the passage 136 leading to the hydraulic cushions 54. This fluid is also directed through the passages 216 to react against the spool valve 194 when in the position shown.
The flexible hose lines 134 are disposed above the press