US 3557599 A
Abstract available in
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Description (OCR text may contain errors)
Jan. 26, 1 71 I F. cQEIcJKENH RsT 3,557,599
MULTIPLE STATION PLUNGER PRESS Filed A ril 8. 1968 a sheets-s1 1 132 II a Arm/awe J 1971 F. c. EICKENHOR ST 3,557,599
' I MULTIPLE STATION PLUNGER PRESS I Filed April 8. 1968 8 Sheets$heet 2 Jan. 25 1 7 F. c. EICKENHORST 3,557,599
MULTIPLE STATION PLUNGER PRESS Filed April 8, 1968 8 SheetsSheet 3 Illllllll ll'll ArraRA/JV/ WM L 8 Sheets-Sheet 4 F. C. EICKENHORST MULTIPLE STATION PLUNGER PRESS II IIII HE 0 II I j 1 1 win 1 4 E 0'' 'I I :ly if? 0 I'L u Jan. 26, 1971 Filed. April 8, 1968 2 0 m i w H R k 0 U V5 W ma 6 4 2 M n E 3 a w w L p w 6 f I Jan. 26, 1971 F. c. EICKE NHORST 3,557,599
MULTIPLE STATION PLUNGER PRESS 8 Sheets-Sheet 5 Filed April 8. 1968 (9 f awer (am firm/n) (X y q/Wperflrmw) A x. a r 0 5 e a ma 0 5 a m 1 N r f1 4 m m n e f fimmmww 0 0 5M6 0 1 7 61 F 0 F ,9 5;: P 04 F/wye 555%, 52 5;?!
(over 0 O Jan. 26, 1971 F. C(EICKENHORST 3,557,599
' MULTIPLE STATION PLUNGER PRESS Filed April 3. 1968 s Sheets-Sheet e ATTOAAIJX/ Jan. 26, 1971 F. c. EICKENHORST 3,557,599
MULTIPLE STATION PLUNGER PRESS Filed April 8. 1968 s Sheets-Sheet 7 51971 F. C .EICKENH O RST I 3,557,599, MULTIPLE- STATION. PLUNGER ramss 8 Sheets-Sheet 8 Filed A ril as; 1968 United States Patent 3,557,599 MULTIPLE STATION PLUNGER PRESS Franklin C. Eickenhorst, Mason, Ohio, assignor to )ayton Reliable Tool & Mfg. Company, Dayton, Ohio, a
corporation of Ohio Filed Apr. 8, 1968, Ser. No. 719,469 Int. Cl. B213 9/18 US. Cl. 72-404 15 Claims ABSTRACT OF THE DISCLOSURE The equivalent of a row of individual plunger presses for successive stages in the production a finished sheet metal part is incorporated in a multiple-station automatic plunger press that has a lower elongated base structure and a corresponding upper crown structure with the two structures rigidly interconnected at their opposite ends to form a unitary frame. Upper dies at the series of stations are operated by corresponding plungers that are actuated by corresponding cams on an upper cam assembly and the working parts of the corresponding lower dies are operated in the same manner by lower plungers and a lower cam assembly. Precision processing of parts with close control of the dies at rates in the range of 200 to 300 pieces per minute is made possible in part by designing the crown structure and the base structure for deflections of a given maximum which, for example, may be as small as .001" under 15 to 30 ton loading. The base structure is of relatively heavy construction and has a lower natural frequency for adequate energy absorption and for minimum reaction to the die actuating forces. High speed precision processing is made possible in further part by staggering the operating strokes at the various stations in time as may be necessary to avoid simultaneous strokes that would be additive to cause more than the given maximum deflection. Exceptional flexibility with respect to the spacing of the stations, and the size of the workpieces is achieved by providing the plunger press with sets of interchangeable parts including interchangeable cam assemblies and interchangeable guides for the plungers.
BACKGROUND OF THE INVENTION The invention relates in general to a high speed multiple stage apparatus for progressively processing sheet metal parts, for example an apparatus of the general character disclosed in the Fraze Pat. 3,196,817 and, more particularly, relates to a multiple-station cam-operated plunger press of the general type described in an article entitled Part Control is Key to High Speed Production of Drawn Metal Parts in the February 1967 issue of Production, both of which disclosures are hereby incorporated into the present disclosure by reference.
The multiple-station apparatus disclosed in the Fraze patent is a high speed press of heavy construction that fabricates can tops equipped with tear strips and manual pull tabs, the apparatus being capable of operation with high precision. For example, the Fraze apparatus is capable of scoring sheet metal of only .009" thickness to a depth of .006" with precision to leave a residual web along the score line of approximately only .003" thickness. The Fraze apparatus is built to specifications that are dictated by a particular product and is admirably suited for its purpose when the demand for a particular product warrants year around high speed production.
On the other hand, a multiple-station cam-operated press of the character described in the above magazine article is not built around the requirements for the production of a particular article and may be changed over from the fabrication of one product to the fabrication "Ice of a different product. Unfortunately, however, a multiplestation cam-operated press of the character that has been heretofore available commercially is not capable of high speed production With exceedingly precise control of the die operations.
The need to which the present invention is directed is for a multiple stage press that has the speed capability and precision capability of the Fraze apparatus but at the same time is even more flexible than the above mentioned multiple-stage cam-operated press.
A multiple-station cam-operated press of the character described in the above magazine article has a lower elongated base structure and an upper elongated crown structure which are interconnected at their opposite ends to form a unitary open frame that is long enough to accommodate several successive work stations. Each station has cooperative upper and lower dies with the upper dies operated by corresponding plungers which are actuated by corresponding cams on an upp r cam shaft. Parts of the lower dies are operated in the same general manner by suitable lower actuating mechanism. The present invention teaches that certain improvements may be made in the construction of'such a multiple-station cam-operated press to make the press capable of high speed precision die operation and at the same time to make the apparatus flexible for producing a range of widely different products, the flexibility including variable spacing of the row of processing stations.
SUMMARY OF THE INVENTION The problem of attaining a production rate higher than 200 pieces per minute, for example a production rate of 300 or more pieces per minute, with high loading, for example with 20 to 30 tons loading on the crown structure and 10 to 20 tons loading on the base structure and with close control of the die movements relative to the workpieces, for example control within a given maximum tolerance, say a maximum tolerance of .001" or less, is met in part by employing a crown structure in the form of a beam with a section of high modulus to provide a deflection of the crown on the order of magnitude of .0003 to .0005 with maximum per linear foot in response to the highest load that is contemplated at any of the multiple stations.
The problem is met in further part by making the base structure of heavy construction to absorb the reactions to the die operations and by designing the base structure to have a natural frequency well below the r.p.m. of the upper cam shaft.
Finally, the problem is met in still further part by operating at least some of the upper cams out of phase with each other to avoid synchronous die operation at any group of the stations wherein the synchronous loads imposed at the group of stations would result in a deflection of the crown structure in excess of the given tolerance. Preferably the arrangement is such that no two die reaction forces that occur simultaneously provide a total reaction force in excess of the reaction force at the station where the loading is maximum. In one practice of the invention where the reaction force at the station of maximum loading would result in greater than the permitted combined deflection of the crown and base structures if the loading were in the central longitudinal region of the press, care is taken to locate the station of maximum loading well away from the longitudinal center of the press.
In a typical operating cycle for a conventional tenstation cam-operated press, all of the working strokes occur simultaneously and the cycle is divided into the following four parts in terms of degrees of rotation of the cam shaft: a first period of for forward movement of the transfer bar; a second period of 60 for simultaneous work strokes of the dies; a third period of 120 for return movement of the transfer bar; and a fourth period of 60 for simultaneous return of the dies to their starting positions. In the preferred embodiment of the present invention, the ten work strokes are 2 apart and therefore, the fourth period is extended from 60 to 80 to permit sequential return of the dies to their starting positions and to permit this extension of the fourth period, the return movement of the transfer bar is speeded up to reduce the extent of the third period from 120 to 100.
Spacing the peak loads at the various stations 2 apart not only minimizes the deflections of the crown structure to make high accuracy possible at high rates of production but also spreads the work load by 20 of rotation of the cam shaft. Consequently the maximum input torque on the cam shaft is greatly reduced with corresponding substantial reduction in the power required to actuate the press. This concept also makes it possible to reduce the mass of the parts of the press mechanism.
With reference to the problem of providing flexibility with respect to the number of the stations and the spacing of the stations, it is to be noted that the plungers actuated by the cams operate in vertical guideways and the spacing of the guideways and earns is in accord with the desired spacing of the stations. In this regard the preferred practice of the invention is characterized by the concept of providing sets of interchangeable press parts to permit choice in the spacing of the stations. For this purpose a set of interchangeable guide members is used wherein the different guide members provide guideways of different spacing. Thus three guide members may have their guideways spaced center-to-center at three inches, four inches, and five inches respectively. In the preferred practice of the invention a set of similar interchangeable guide members is provided for the lower plungers that actuate the lower dies at the various stations.
Within the scope of the invention, various solutions may be found for varying the spacing of the actuating cams to match the spacings determined by the various interchangeable guide members. One solution is to use split cams that may be loosened to permit shifting of the cams along a cam shaft for the purpose of changing the spacing of the cams to match the spacing of the guideways in the different interchangeable guide members.
Another solution is to provide a set of interchangeable cam assemblies. Each of the interchangeable cam assemblies may comprise a frame carrying bearings for a cam shaft with cams spaced apart on the cam shaft by a particular distance to match the spacing of the guideways of a corresponding guide member. In the preferred practiee of the invention, the upper cam shaft carries a special cam for reciprocating the transfer bar that carries the workpieces from station-to-station. Each cam assembly of the set of cam assemblies may have such a special cam designed for the particular magnitude of reciprocation of the transfer bar that is required for a particular spacing of the stations.
Another aspect of the flexibility of the new multiple station press is the concept of changing over from the processing of one product at a series of stations to the processing of another product at the same stations with no change in spacing of the stations, the change over being accomplished by simply substituting one cam as sembly for another cam assembly where the essential difference is solely in the plunger actions at the different stations. Where two products are produced periodically, interchangeable specialized cam assemblies of this character may be kept on hand for periodic use.
An important feature of the invention is that the camactuated plungers are designed for such stale reciprocation that dies may be mounted thereon at positions substantially offset from the axes of the plungers, theoffset being as much as three inches in one embodiment of the invention. For example, where the plungers are spaced apart five inches center-to-center by the guideways of a particular guide member, die holders of nearly five inch width may be mounted on the working ends of the plungers, and dies may be mounted on the die holders as far from the axes of the corresponding plungers as the width of the die holders permit. As will be explained, this concept makes it possible to vary the spacing of the successive dies, i.e. the spacing of the successive stations without corresponding change in the spacing of the plungers. Thus the dies on a row of five die holders approximately five inches wide that are mounted on plungers that are spaced five inches center-to-center, makes it possible at one extreme to space the five dies four and one half inches apart or at the other extreme to space the five dies six inches apart. In a ten station press such an arrangement permits two production rows of five dies each served by a common transfer bar.
The use of relatively wide die holders with radially offset dies as made practical by the exceptional stability of the plungers not only permits flexibility in the spacing of the successive stations, as explained above, but also makes possible a dual multiple-station press with a pair of (lies on each die holder to provide two parallel production lines by means of a single set of die holders on a single set of plungers actuated by a single set of cams. Preferably the two dies of each pair are equally spaced from the axis of the corresponding plunger in opposite radial directions so that the reactions to the die operations are balanced with respect to the plunger. With the single cam shaft operating at 200 to 350 r.p.m., from 400 to 700 parts are produced per minute.
The required degree of stability in the reciprocating plungers is difficult .to achieve for two reasons. In the first place a rotating cam necessarily exerts non-radial thrusts against a cooperating follower and if the follower is on the trailing end of a die-carrying plunger such thrusts tend to tilt the plunger relative to its guideway. -In the second place, stable reciprocation of a plunger requires a guideway of adequate length and therefore the vertical distance between the overhead cam shaft and the level of the processing zone must be used to full advantage.
Part of the solution taught by the present invention is to divorce the follower completely from the plunger by placing the follower on a laterally extending pivoted arm so that the lateral thrust of the cam against the follower is borne by the pivoted arm and is directed towards or away from the pivot of the arm. Since the pivoted arm recriprocates the follower along an arcuate path, the pivoted arm is operatively connected to the plunger by a suitable link that oscillates with reciprocation of the plunger.
This approach poses further problems. In the first place the thrust of the oscillating link is at least slightly out of alignment with the axis of the plunger and if the oscillating link is connected to the end of the plunger the thrust of the link tends to tilt the plunger. In the second place, with the oscillating link connected to the trailing end of the plunger, the vertical space occupied by the link severely shortens the vertical dimension that is available for the plunger guideway.
These further problems are solved by using a hollow plunger and by extending the link into the interior of the hollow plunger with the link pivotally connected to the plunger in the region of its longitudinal center or center of gravity. With the link inside the hollow plunger and with nearly the Whole length of the link coextensive with the upper half of the plunger, the presence of the link necessitates substantially no reduction in the vertical dimension that is available for the plunger guideway. It is also to be noted that directing the thrust of the link against the center of gravity of the plunger avoids the creation of any tilting moment whatsoever. The side thrust against the plunger is minimized by a low angle of divergence of the link which is made possible by providing a relatively long link and since the side thrust is directed to the longitudinal center of the plunger there is an ample extent of the plunger guideway in the opposite longitudinal directions from the center of thrust.
An important feature of the invention relates to the wear between a plunger and the guideway in which the plunger slides. The problem is to minimize the wear and to simplify the replacement of worn parts. The problem is complicated by the necessity of preventing even the slightest rotation of the plunger on which the die is mounted. In the prevalent type of cam-operated plunger press, rotation of a plunger is prevented by employing a plunger of non-circular cross-sectional configuration in a guideway of similar cross-sectional configuration. For example, a plunger of square cross-sectional configuration is commonly mounted in a similar guideway and usually a diagonal of the square cross section is in the plane of whatever side thrust is exerted on the plunger by the cam follower. Such an arrangement not only results in aggravated wear at at least one corner of the square cross section but also increases the cost of replacing worn parts.
The present invention meets this situation by employing cylindrical plungers, in cylindrical guideways and by relying on the above mentioned pivoted arm to prevent rotation of the plunger. To carry out this concept both the pivotal connection between the above mentioned link and the plunger and the pivotal connection between the link and the pivoted arm are designed to eliminate any freedom for relative rotation between the interconnected parts. The cylindrical plungers wear less than plungers of square cross-sectional configuration and, of course, the elimination of tilting moments on the cylindrical plungers further reduces wear. -In addition, the invention provides removable liner sleeves for the guideways which sleeves may be conveniently and inexpensively replaced when worn.
In a cam-operated press the upper cam shaft not only has cams to carry out the working strokes of the plungers but also has associated cams to lift or return the plungers to their upper starting positions. It is common practice to provide a lifter arm that overhangs a lifter cam for cooperation therewith, the lifter arm being rigidly mounted on a vertical slide member that is connected to the upper end of the plunger by a horizontal yoke. One disadvantage of such an arrangement is that it requires head room above the lifter cam and another disadvantage is the necessity of providing structure to guide the vertical slide member.
The present invention not only avoids these disadvantages but also greatly simplifies the lifter mechanism itself. In the new construction, the previously mentioned pivoted arm that carries the follower creating the work stroke of the plunger is one arm of a bell crank and the second arm of the bell crank extends upward to hold the lift follower against the rearward side of the corresponding lift cam. Thus with the bell crank arm connected to the hollow plunger by the previously mentioned oscillating link, the bell crank not only moves the plunger downward on its work stroke but also lifts the plunger back to its starting position. Preferably the bell crank is preloaded by flexure of one of its two arms to result in constant pressure by the two followers against the two cams respectively for close control of the plunger with no backlash.
The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings:
BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustrative FIG. 1 is a simplified diagrammatic perspective view with parts broken away and parts omitted to show the general organization of the presently preferred embodiment of the invention;
FIG. 2 is a somewhat schematic longitudinal view showing the crown structure, the upper and lower cam shafts and the reciprocative transfer bar removing workpieces from station to station;
FIG. 3 is a transverse section as indicated along the line 3-3 of FIG. 2 showing the lower part of the structure including the two bolster plates which are shown in plan;
FIG. 4 is a fragmentary vertical section taken along the line 44 of FIG. 2 showing how one of the upper plungers 36 is actuated by cams on the cam shaft by means of a bell crank;
.FIG. 5 is a fragmentary section taken as indicated by the angular line 55 of FIG. 4 showing how the bell cranks are operatively connected to the upper plungers;
FIG. 6 is a fragmentary section taken as indicated by the angular line 6-6 of FIG. 5;
FIG. 7 is a fragmentary section taken as indicated by the line 7-7 of FIG. 4, the view showing the construction of the bell cranks;
FIG. 8 is a view similar to FIG. 4 showing how a plunger is actuated by cams on the lower cam shaft by means of a bell crank;
FIG. 9 is a diagrammatic view showing by way of 7 example workpieces and operations thereon at the various stages of the press;
FIG. 9a is a perspective view of a container, the top of which is progressively fabricated at the successive stations;
FIG. 10 is a fragmentary plan view of the transfer bar that advances the workpieces from station to station;
FIG. 11 is a sectional view of the die set for forming the bubble or boss in the workpiece at station B in FIG. 9, the view further showing how the lower die is mounted on a bolster plate with the moving parts of the lower die actuated by a corresponding lower plunger;
FIG. 12 is a fragmentary elevational view showing how two pairs of cooperating dies may be used at each station to provide a dual press having two parallel rows of dies for two simultaneous production lines;
FIG. 13. is a diagram showing how the upper plungers may be equipped with die holders carrying corresponding dies with greater spacing between the dies than the spacing between the plungers;
FIG. 14 is a view similar to FIG. 13 showing how dies may be mounted on the same die holders with the spacing between the successive dies substantially less than the spacing between the plungers; and
FIG. 15 is a diagram representing the operating cycle of the presently preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The multiple-station press has a, heavy frame which includes: a longitudinal base 20; a bed plate 22 spaced above the base and supported thereon by two opposite end blocks 24; an upper longitudinal crown structure, generally designated 25, which is supported at each of its opposite ends by a pair of spaced legs 26 that extend upward from the bed plate 22; and four tubular tie rods 28 at the four corners of the frame, respectively, that interconnect the crown structure and the base, the four tie rods being preloaded in tension to make the frame rigid. As indicated in FIG. 1, the crown structure 25 has two heavy vertical longitudinal steel side plates 30 which form a longitudinal beam having a section of high modulus to minimize deflection of the beam in reaction to die operating forces. The longitudinal plates 30' are interconnected by spaced heavy transverse vertical steel plates 32 which serve to transfer the reaction forces to the longitudinal side plates. In addition the upper side of the crown structure is formed by a top plate 34 to which the four tie rods 28 are connected.
The ten upper dies 35 at the ten stations respectively are mounted on ten corresponding upper plungers 36 by means of corresponding die holders 37 and the ten plungers reciprocate in vertical guideways 38 in an upper longitudinal guide member 40 that is of angular cross section as shown in FIG. 4. The opposite ends of the upper guide member 40 are removably attached to the frame of the press and for this purpose the opposite ends of the guide member may be anchored to corresponding boxlike support structures 42 (FIG. 4), each of which extends between a pair of legs 26 and is anchored to the legs.
The ten lower dies 43 are mounted on lower die holders 44 on a pair of heavy bolster plates 45 that are positioned end-to-end and rest on the bed plate 22, the bed plate having a large opening 46 to expose the major portions of the lower surfaces of the bolster plates. The working parts of each of the lower dies 43 are operatively connected to a corresponding lower plunger 48 as indicated diagrammatically by a dotted line 50 in FIG. 1 and the lower plungers are slidingly mounted in corresponding guideways 52 in a lower longitudinal guide member 54 that is similar in construction to the upper guide member 40. The opposite ends of the lower guide member 54 may be releasably anchored to the previously mentioned end blocks 24 of the frame structure.
Each of the upper plungers 36 is controlled by a corresponding upper bell crank, generally designated 55, which in turn is controlled by a pair of cams on a cam shaft 56 of an upper cam assembly that is generally designated 58. The upper cam assembly 58 includes a pair of parallel longitudinal bars 60 which are interconnected by spaced depending heavy plates 62 in which the cam shaft 56 is journallel by suitable bearings (not shown). It is contemplated that the upper cam assembly will be releasably mounted on the underside of the crown structure 25 and for this purpose, as indicated in FIG. 4, the underside of the crown structure may be provided with a pair of flanged parallel rails 64 which form a longitudinal track on which the cam assembly may be releasably mounted.
As best shown in FIG. 2, each of the pairs of .cams for controlling an upper plunger 36 comprises a power cam 65 to carry out the downward working stroke of the plunger and a lift cam 66 to return the plungerto its starting position, the two cams being portions of a single cam body.
As shown in FIG. 7, the ten upper bell cranks 55 are mounted by pairs on five short shafts 68 that are positioned end-to-end in axial alignment, the five shafts being fixedly supported by spaced brackets 69. As shown in FIG. 4, each of the bell cranks 55 has a first forwardly extending arm 70 that carries a follower 72 in the form of a roller to cooperate with the corresponding power cam 65 and the bell crank has a second upwardly extending arm 74 carrying a follower in the form of a roller 75 for cooperation with the corresponding lift cam 66.
Preferably, but not necessarily, each of the two arms 70 and 74 of a bell crank is independently rotatable about the corresponding short shaft 68. For this purpose, as shown in FIG. 6, each of the second arms 74 of a bell crank may have an integral hub portion by means of which it is rotatably mounted on the corresponding shaft 68 and the first arm 70 of the bell crank may have a hub portion 82 that is rotatably mounted on the corresponding hub portion 80.
Each bell crank 55 is preferably preloaded in flexure to maintain its two followers 72 and 75 in continuous pressure contact with the corresponding cams 65 and 66. For this purpose, each of the second bell crank arms 74 may be formed with a web 84 and a cap screw 85 extending through the web may be threaded into an adjacent portion of the corresponding first bell crank arm 70. It is apparent that tightening the cap screw 85 stresses the two arms in fiexure for the desired continuous pressure 8 of the followers 72 and 75 against the corresponding cams 65 and 66.
As shown in FIGS. 4 and 5, each of the plungers 36 is slidingly mounted in the corresponding guideway 38 by means of upper and lower liner sleeves 86 which may be readily replaced when worn. As heretofore stated, the plungers 36 are hollow to permit each plunger to be operatively connected to the arm 70 of the corresponding bell crank by means of a link 88 that extends downward into the interior of the plunger for pivotal connection to the plunger at the longitudinal mid point or center of gravity of the plunger.
Since each plunger 36 carries a corresponding upper die 35 on the die holder 37 and the upper die must be of constant orientation, some provision must be made to keep each plunger from rotating in its guideway. For this purpose, a diametrical wrist pin 90 of the plunger pivotally connects the plunger to the corresponding link 88 in a manner that prevents rotation of the plunger on its axis relative to the link and, in turn, the upper end of the link is pivotally connected to the corresponding bell crank arm 70 in a manner that prevents rotation of the link on its axis relative to the bell crank arm. I
As shown in FIGS 4 and 5, the upper end of each link 88 may be connected to the corresponding bell crank arm 70 by means of a cross pin that has an intermediate portion 94 of noncircular configuration for fixed engagement by the upper end of the link and has two opposite end portions 95 that are journalled in the outer end of the corresponding bell crank arm 70. As indicated in FIG. 4, the intermediate portion 94 of each cross pin may be substantially square in cross section to fit into a substantially square socket in the upper end of the link 88, the socket being split to yield as may be necessary for admission of the cross pin. A cap screw 96 extending through one side of the socket at the upper end of the link is threaded into the cross pin as shown in FIG. 4 to pull the cross pin tight against one side of the socket. The one side of the socket and the intermediate portion of the cross pin are shaped and dimensioned for wedging engagement of the noncircular portion of the cross pin with the side of the socket to make the cross pin rigid relative to the upper end of the link and thus prevent even the slightest rotation of the link on its axis relative to the bell crank arm 70.
The manner in which the moving parts of the lower dies 43 are actuated by the corresponding lower plungers 48 may be understood by reference to FIG. 11 where a lower die, generally designated 43a, cooperates with a corresponding upper die, generally designated 35a, to carry out a forming operation at station E in FIG. 9 where a bubble or boss 98 is formed in a blank 100. The lower die 43a has a cylindrical die cavity 102 to cooperate with a male element 104 of the upper die 35a for the purpose of forming the bubble or boss 98. A pressure pad 105 which surrounds the male die element 104 is urged downward by a set of coil springs 106 to cooperate with the lower die 43a to place the workpiece under light pressure as the two dies approach each other. The portion 108 of the lower die 43a that provides the die cavity 102 is supported by three rods 110 that extend upward from the corresponding lower plunger 48 through corresponding bores 112 in the bolster plate 45, the upper plungers 36 and the lower plungers 48 cooperating to open and close the pairs of dies.
As may be seen in FIG. 8, each of the lower plungers 48 and its associated actuating mechanism is similar in construction to a previously described upper plunger 36 and its associated actuating mechanism, but preferably the lower plungers are scaled down to approximately half size. Each of the lower plungers 48 reciprocates in two liner sleeves 86a in the corresponding guideway 52 and each lower plunger is connected in the previously described manner to a corresponding link 88a which in turn is pivotally connected to a first arm 70a of a lower bell crank a that has a second arm 74a, the two arms being independently rotatable on a common shaft 68a as heretofore described.
In the previously described manner, each lower plunger 48 is controlled by a pair of integral cams a and 66a on a lower cam shaft 56a, a follower 72a on the bell crank arm a cooperating with the cam 65a and a follower 75a on the bell crank arm 74a cooperating with the cam 66a. As indicated in FIG. 2, the lower cam shaft 56a is incorporated in a lower cam assembly 58a which is similar to the previously described upper cam assembly 58a and which is removably mounted on the base 20 of the press.
The manner in which the upper cam shaft 56 and the lower cam shaft 56a are driven in synchronism may be understood by reference to FIGS. 1 and 2. An upper motor on a supporting bracket 116 has a drive shaft 118 carrying a sheave 120 which is connected by a belt 122 with a sheave 124 on the upper cam shaft 56. A gear 125 on the upper cam shaft 56 meshes with a gear 126 on a countershaft 128 and a sprocket 130 on the countershaft is connected by a link belt 13-2 with a sprocket 134 on a lower countershaft 135. Finally, a gear 136 on the lower countershaft meshes with a gear 138 on the lower cam shaft 56a.
The workpieces in process are moved to the successive stations of the press by a reciprocative transfer bar which is generally indicated at 140 in FIG. 1. The transfer bar 140 which is suitably slidingly supported for longitudinal reciprocation comprises two longitudinal side bars 142 interconnected by transverse end bars 144 and is operatively connected by a link 145 to the lower arm of a lever 146 that is mounted on a suitable pivot means 148. The upper arm of the lever 146 is actuated by continuous shoulder means formed on the outer circumference of a special cam 152 on the end of the upper cam shaft 56.
In the construction shown, the shoulder means on the special cam 152 comprises the opposite side surfaces of a continuous circumferential rib 154 and the upper arm of the lever 146 is provided with a pair of spaced followers 155 which straddle the continuous rib for cooperation with the opposite continuous shoulders thereof. The continuous rib 154 is of suitable undulating configuration to cause the desired periodic reciprocation of the lever 146 to operate the transfer bar 140 in timed relation to the operation of the upper and lower plungers 36 and 48. As indicated in FIG. 10, the transfer bar 140 is provided in a well known manner with pairs of elements 156 which are mounted on the side bars 142, respectively, to pick up the Workpieces at the various stations of the press.
For the purpose of the present disclosure it is not necessary to describe specifically how successive operations may be performed on workpieces at the various stations. By way of example, however, FIG. 9 indicates in a general way the various stages in the production of a particular product in the form of a top wall of a rectangular metal container for a granular product. At the first station A shown in FIG. 9, strip stock 158 is advanced periodically to permit successive blanks 159 to be punched out of the stock. One pair of the transfer bar elements 156 is adapted to move blanks 159 from the first station A to the second station B where a bubble or boss 160 is formed as heretofore described. A second pair of the transfer bar elements 156 moves the workpieces to the third station C and other pairs of the transfer bar elements engage the workpieces at the different stages to transfer the workpieces from station to station.
At the third'station C the bubble or boss 160 is converted into a hollow rivet 160a and at station D certain holes are punched in the workpiece. Strip stock 161 is fed laterally to station E, the strip back stock being used to provide a small closure member 162 which is to be pivotally mounted on the hollow rivet 160a. The workpieces with the closure members thereon are flanged at station F, embossed at station G and curled at the edges at station H.
10 At station I means detects whether or not a closure member 162 is attached to the workpiece and at station I where the finished workpieces are unloaded, the defective workpieces are automatically discarded. It is to be understood, of course, that stations I and I may be employed to carry out punch-press operations on workpieces, it being a feature of the invention that all ten of the stations may be die-operating stations.
FIG. 12 shows how each upper plunger 36 and the corresponding lower plunger 48 may actuate respectively an upper pair of dies and a lower pair of dies to provide two simultaneous production lines at the ten stations of the press. The die holder 37 on the upper plunger 36 carries two spaced upper dies 35b which preferably are at equal and opposite distances from the axis of the plunger for balanced reaction on the plunger. In like manner a cooperating lower die holder 44 on a bolster plate 45 has two spaced lower dies 43 actuated by corresponding rods 110 that extend upwardly from the corresponding lower plunger 48 (not shown). The two pairs of cooperating dies at each station form two parallel rows of cooperating dies which operate simultaneously to double the production of the multiple-station press. A dual transfer bar advances the twin workpieces from station to station.
As heretofore explained, the provision of a relatively long vertical guideway for each of the plungers 36 and the connection of the corresponding link 88 with the longitudinal center or center of gravity of the plunger results in exceptional stability of the plunger as it reciprocates in its guideway. Since the exceptional stability of the reciprocations upper plungers makes it possible to mount the upper dies at positions offset from the upper plungers, it is practical to vary the spacing of the successive stations independently of the spacing of the upper plungers. By way of example, FIG. 13 shows five successive die holders 37 on five successive upper plungers 36 with the plungers spaced apart five inches center to center and with the die holders nearly five inches wide. In FIG. 13 five upper dies 350 are positioned on the five die holders at six inch spacing. In FIG. 14, however, the five upper dies 35c are spaced apart by only four and one quarter inches. Where only five operations are required on a workpiece, a ten station press may have two series of five dies each arranged as shown in FIG. 13 or in FIG. 14 with strip material fed to both series of dies and with the finished product discharged at two stations of the press. If there are two dies spaced apart on each die holder as shown in FIG. 12, four production lines may be provided by the two series of stations for even greater press capacity of the press.
It is apparent from FIGS. 13 and 14 that the spacing of the five dies on the five die holders may be any selected spacing within the range of four and one quarter to six inches. If an upper guide member with guideways at four inch spacing is substituted for the guide member having the guideways spaced at five inches and corresponding substitution is of one cam assembly for another, the upper plungers being spaced at four inches center to center may be provided with die holders of nearly four inch width to permit the spacing of dies on the five die holders to be varied within the range of three and one quarter to four and one half inches. In like manner, substituting a different guide member and a different cam assembly to reduce the spacing of the upper plungers to three inches permits the use of a third set of a die holders of nearly three inches width to permit the five dies to be spaced apart at any selected spacing within the range of two and three quarters to three and one quarter inches. Thus with three sets of interchangeable parts, the dies at the five stations may be varied in spacing from two and three quarter inches to six inches.
FIG. 15 is a diagram which provides a comparison between the conventional cycle of operation of a multiple-station punch press and the operating cycle of the present invention. The upper curve represents the simultaneous movement of the dies at the multiple stations of a conventional punch press and the upper set of arrows represent the two opposite movements of the transfer bar that are synchronized with the movement of the dies.
The operating cycle of a conventional multiple-station punch press carried out by 360 of rotation of the cam shaft is divided into four stages as follows: A first stage of rotation of the cam shaft in which the upper dies are at upper retracted positions as indicated by the horizontal line 172 while the previously mentioned transfer bar makes its forward index movement as indicated by the arrow 174 to advance all of the workpieces by one station; a second stage of 60 of rotation of the cam shaft in which the upper dies make their simultaneous downward work strokes as indicated by the inclined line 175 while the transfer bar dwells as indicated by the line 176; a third stage in which the dies are at lower positions as indicated by the horizontal line 178 while the empty transfer bar makes its return index movement to its starting position as indicated by the arrow 180; and, finally, a fourth stage of the last 60 in which the upper dies retract to their upper positions simultaneously as indicated by the inclined line 182 while the transfer bar dwells as indicated by the line 184.
The cycle of operation taught by the present invention is indicated by the lower half of the diagram. The first stage of 120 is identical with the first stage of a conventional operating cycle, all of the upper dies being at upper retracted positions as indicated by the horizontal line 185 while the transfer bar 40 makes its forward index movement as indicated by the arrow 186; a second stage of 80 rotation instead of 60 rotation of the cam shaft during which the ten dies at the ten stations initiate their downward work strokes in timed sequence as indicated by the ten downwardly inclined lines 188 while the transfer bar remains stationary as indicated by the line 188; a third stage of 100 rotation of the cam shaft instead of 120 rotation during which the dies are at lower positions as indicated by the horizontal line 190 while the empty return bar makes its return index movement to its starting position as indicated by the arrow 192; and, finally a fourth stage identical with the fourth stage of a conventional punch press in which all of the dies are retracted upwardly simultaneously to their starting positions as indicated by the inclined line 194 while the transfer bar remains stationary as indicated by the line 195 to receive the workpieces that are released by the retracting dies.
Since the ten dies initiate their work strokes in timed sequence, the ten peak loads created by the ten work strokes also occur in timed sequence to prevent any peak load from being added to another peak load. Thus the maximum reaction force to which the structure of the punch press is subjected is limited to reaction force created by a single work stroke. It has been found that initiating the ten work strokes at a time spacing of approximately two degrees of rotation of the cam shaft provides adequate separation of the peak loads and therefore the points in time at which the work strokes are initiated are distributed over a period of 20 of rotation of the cam shaft. To carry out such a sequential operation in the second stage without the necessity of speeding up the down strokes of the dies, it is necessary to increase the duration of the second stage by 20, the duration of the second stage being 80 of rotation of the cam shaft instead of 60 of rotation as in a conventional multiplestation punch press.
To compensate for the increased duration for the second stage, the duration of the third stage is correspondingly reduced, the third stage extending over 100 of rotation of the cam shaft instead of extending over 120 as in the conventional multiple-station punch press. Since the transfer bar must carry out its return index movement in a period of 100 of rotation of the cam shaft instead of a period of 120 of rotation, the return movement of 12' the transfer bar is carried out at correspondingly higher velocity than the forward index movement.
From the foregoing description of FIG. 15 it is apparent that the invention teaches that the maximum reaction load imposed on the structure of the punch press and the maximum applied torque of power input required for operation of the cam shaft may both be reduced by the following steps: increasing the velocity of the return index movement of the transfer means in the third stage relative to the velocity of the forward index movement of the transfer bar in the first stage; correspondingly decreasing the duration of the third stage; correspondingly increasing the duration of the second stage of the operating cycle wherein the work strokes of the dies occur; and carrying out the peak load portions of the work strokes of the several dies in timed sequence in the second stage of the operating cycle as permitted by the increased duration of the second stage.
A feature of the preferred practice of the invention is that the region of all of the moving parts above the upper plungers 36 is sealed off from the region of the die operation to prevent themigration or gravitation of foreign particles and lubricant into the region of the workpieces that are in process. Such a provision has special utility when the workpieces are parts of containers for food products.
For the purpose of sealing off the upper working parts, FIG. 4 shows two opposite longitudinal wall members 96 and 98 which form a trough, the bottom surface of the trough being the upper surface of the upper longitudinal guide member 40. This trough is the lower portion of an upper sealed chamber that encloses the upper cam assembly 58 together with the bellcranks 55 that cooperate with the cams on the cam shaft. This sealed chamber is preferably maintained under an air pressure of approximately 20 psi. and for that purpose is in communication with a suitable source of compressed air (not shown) and is provided with a relief valve 200 that opens in the event that the air pressure in the chamber rises excessively.
As indicated in FIG. 4, the means for sealing off the upper moving parts further includes a plurality of bellows-like elastomeric sleeves 202 corresponding to the plurality of upper plungers 36, the lower end of each sleeve being attached in a fluid-like manner to the flange of the corresponding upper liner cylinder 86 and the upper end of the sleeve being attached to the outer end of the arm 70 of the corresponding bellcrank. As indicated at 204 an extension of the sleeve 202 extends over the pivotal connection between the bellcrank arm 70 and the link 88 that actuates the corresponding upper plunger 36. Lubricant may be either dripped onto the working parts in the sealed chamber or may be sprayed onto the working parts. The lubricant tends to accummulate at the bottom of the described trough and may be drained periodically by opening a drain port 205 at one end of the trough.
My description of the selected embodiment of the invention will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.
1. In an automatic plunger press of the character described having an elongated lower base structure and a corresponding elongated upper crown structure interconnected to form an unitary frame to accommodate a linear series of stations, for example ten stations, for successive operation on workpieces that are moved to the stations sequentially by transfer means, wherein each station has cooperative upper and lower dies with the working parts of the upper dies operated by corresponding upper plungers that are actuated by corresponding upper cams on an upper cam shaft and with the working parts of the lower dies operated by a lower mechanism,
the improvement to permit production to be carried out at a rate substantially higher than 200 pieces per minute, for example approximately 300 pieces per minute with high loading, for example a loading of twenty to thirty tons on the crown structure and a loading of twenty to thirty tons on the base structure, with exceedingly close control of the movements of the parts of the upper dies relative to the Workpieces with a given tolerance of relative movement, for example a given tolerance of approximately .001, comprising:
the crown structure being a beam with a section of high modulus and the base structure being of high rigidity to provide a minimum deflection of the crown structure at any one station no greater than the given tolerance in response to the load imposed by the processing of a workpiece at that station;
each of the upper cams being out of phase with all of the other upper cams to avoid synchronous die operations at any group of stations wherein the load imposed at the group of stations would result in a deflection of the crown structure in excess of the given tolerance; and
the base structure being of heavy construction to absorb the reactions to the die operations and to have a natural frequency substantially lower than the frequency of the revolutions of the upper cam shaft.
2. An improvement as set forth in claim 1 in which the upper crown structure comprises an elongated boxlike beam with a plurality of plate-like elements in planes substantially perpendicular to the longitudinal axis of the beam.
3. In an apparatus of the character described, the combination of:
a rotary cam;
a hollow plunger carrying a die on its leading end;
guide means forming a guideway slidingly embracing the plunger; pivoted arm extending adjacent the trailing end of the plunger;
a follower on the pivoted arm cooperative with the rotary cam to oscillate the pivoted arm; a link operatively connecting the pivoted arm with the hollow plunger, said link being pivotally connected to the arm and extending generally longitudinally of the plunger into the interior of the plunger and being pivotally connected to the plunger inside the plunger centrally of the length of the plunger; and
a sleeve connected at one end to said pivoted arm and connected at the other end to said guide means to prevent lubricant and other foreign matter from migrating from the region of said other end of the plunger along the plunger to the region of the die means,
said sleeve being axially expansible to accommodate the oscillation of the pivoted arm relative to the guide means.
4. In an automatic plunger press of the character described of elongated configuration having a frame including a lower base structure and an upper cro'wn structure with cooperating upper and lower dies at a plurality of longitudinally spaced stations, wherein the upper dies are operated by corresponding upper plungers actuated by corresponding cams on an upper cam shaft with the plungers mounted in longitudinally spaced guideways, the improvement comprising:
a set of guide members for mounting interchangeably on said frame, said guide members forming said guideways for the plungers with the guideways at different spacing on the different guide members to permit the plunger press to be changed over from one production run with said stations at a given longitudinal spacing to a second production run with said stations at a different longitudinal spacing.
5. An improvement as set forth in claim 4 which includes a set of cam assemblies corresponding to said set of guide members for mounting interchangeably on the underside of said crown structure,
each of said cam assemblies including a cam shaft with cams thereon to actuate said upper plungers,
the spacing of the cams on the cam shaft of the different cam assemblies matching the spacing of the guideways on the corresponding guide members of the set of guide members.
6. An improvement as set forth in claim 4 which includes:
pluralities of die holders, the pluralities corresponding respectively to the guide members of the set of guide members, the die holders of each plurality being removably attachable to the leading ends of the respective plungers,
the die holders of each plurality being relatively wide with adjacent edges of the die holders of each plurality relatively close together when mounted on the plungers, the die holders being relatively narrow where the plungers are closely spaced and being relatively wide where the plungers are relatively widely spaced,
said guide members slidingly supporting the; plungers with sufficient stability to permit each die to be mounted on the die holders at positions thereon as far offset from the axis of the corresponding plungers as the width of the die holder permits,
whereby employing any given guide member with the corresponding plurality of die holders on the plungers permits dies to be mounted on the respective die holders at various uniform spacing between the dies, including at one extreme a spacing substantially less than the width of the die holders and at the other extreme a spacing substantially greater than the width of the die' 'holders.
7. In an automatic plunger press of the character described of elongated configuration having a frame including a lower base structure and an upper crown structure with cooperating upper and lower dies at a plurality of longitudinally spaced stations, wherein the upper dies are operated by corresponding upper plungers actuated by corresponding cams on an upper cam shaft with the plungers actuated by corresponding cams on an upper cam shaft with the plungers mounted in longitudinally spaced guideways, the improvement comprising:
each of the plungers carrying a pair of dies oppositely offset from its axis, the pairs of dies on the plungers forming two parallel rows of stations to provide two parallel production lines for operation simultaneously by the plungers.
8. An improvement as set forth in claim 7 in which the dies carried by each plunger are at diametrically opposite equal distances from its axis for balanced reaction forces on the plunger.
9. In an automatic plunger press of the character described of elongated configuration having a frame including a lower base structure and an upper crown structure with cooperating upper and lower dies at a plurality of longitudinally spaced stations, wherein the upper dies are operated by corresponding upper plungers actuated by corresponding cams on an upper cam shaft with the plungers mounted in longitudinally spaced guideways, the improvement comprising:
each of said plungers being stabilized in its guideway to withstand die reaction forces created at points substantially offset from the axis of the plunger;
die holders mounted on the leading ends of the respective plungers, said die holders being substantially as wide as the spacing of the plungers with the confronting edges of the successive die holders close together; and
dies mounted on the respective die holders,
said dies being uniformly spaced apart with the space between the dies substantially different from the spacing of the plungers, the width of the die holders and the stabilization of the plunger permitting the dies at one extreme to be spaced apart substantially less than the plungers measured center to center and at the other extreme to be spaced apart more than the plungers.
10. An improvement as set forth in claim 9 in which each of said plungers is of hollow construction;
in which a pivoted arm extends adjacent the trailing end of the plunger;
in which a follower on the pivoted arm cooperates with the corresponding cam to oscillate the pivoted arm; and
in which a link operatively connects the pivoted arm with the hollow plunger, said link being pivotally connected to the arm and extending generally longitudinally of the plunger into the interior of the plunger and being pivotally connected to the plunger inside the plunger centrally of the length of the plunger.
11. An improvement as set forth in claim 9 in which the guideways of the plungers are formed in a guide member that is removably mounted on the press;
in which interchangeable, guide members are provided with differently spaced guideways; and which includes sets of die holders of widths corresponding to the spacing of the guideways of the different guide members, whereby interchanging the guideways and the die holders makes possible a wide range of variation in the spacing of the stations.
12. In a four stage method of operation of a punch press of the character described having several stations, for example ten stations, wherein the corresponding dies at the stations are at retracted starting positions during the first stage of the operating cycle while transfer means indexes forwardly to advance workpieces by one station; wherein the transfer means dwells during the second stage of the operating cycle while the dies advance to carry,
out their work strokes; wherein the dies are at their advanced positions during the third stage of the operating cycle while the transfer means carries out its return index movement; and wherein the transfer means dwells during the fourth stage while the dies retract to their stationary positions,
the improvement to reduce the maximum load on the punch press structure in reaction to the several work strokes and to reduce the maximum rate of power input required to carry out the work strokes, comprising: increasing the velocity of the return index movement of the transfer means relative to the velocity of the forward index movement; correspondingly decreasing the duration of the third stage of the operating cycle wherein the return index movement of the transfer means occurs; correspondingly increasing the duration of the second stage of the operating cycle wherein the dies advance over a time interval which is at least approximately the time interval by which the duration of the second stage of the operating cycle is increased.
14. An improvement as set forth in claim 12 in which the velocity of the work strokes is substantially unchanged and in which the moments of initiation of the work strokes of the several dies are distributed over a time interval which is at least approximately the time interval by which the duration of the second stage of the operating cycle is increased,
15. In a multiple-station punch press of the character described wherein upper and lower dies at each station have a range of relative movement towards each other to change the form of a workpiece at the station, the combination of:
upper cams at the various stations rotatable in unison;
guided hollow plungers corresponding to said upper cams;
upper die holders at the various stations mounted on said hollow plungers respectively;
a set of followers corresponding to said upper cams;
a set of links corresponding to the set of followers, each of said links operatively connecting the corresponding follower to the corresponding plunger, each of said links being pivotally connected to the plunger interiorly thereof at a point intermediate the length of the plunger;
lower cams at the various stations rotatable in unison in the timed relation to the upper cams; and
lower die holders at the various stations carrying the lower dies, said lower die holders being operable for upward work strokes by the corresponding lower cams,
whereby the range of relative movement of the upper 'and lower dies towards each other at a station may be the sum of the upward and downward work strokes at the station,
and whereby; if desired, the upward and downward work strokes at a station may overlap in time to result in a higher rate of relative movement of the upper and lower dies towards each other than can be provided by either the upper cams alone or the lower cams alone,
and whereby the workpiece at a work station may be subjected to both downward impact force and upward impact force and, if desired, the downward and upward impact forces maybe applied simultaneously to result in a combined impact force on a workpiece greater than either impact force alone.
References Cited UNITED STATES PATENTS 1,977,549 10/1934 Glasner -292 2,183,287 12/1939 Candee 72-404 3,094,091 6/1963 Peccerill 10029.2 3,199,358 8/1965 Bradlee 74-53 3,358,591 12/1967 Bradlee -5 100-257 JOHN F. CAMPBELL, Primary Examiner G. P. CROSBY, Assistant Examiner U.S. Cl. X.R.