US 3566450 A
Description (OCR text may contain errors)
Man ch 197 A. s. ROBERTS HIGH PRESSURE CYLINDER AND PRESS STRUCTURE FOR THE CYLINDER 2 Sheet s-Sheet 1 Filed Jan. 25, 1968 ALBERT 5. Roam; q a
mm 2 z March 2, 1971 A. s. ROBERTS 0 HIGH PRESSUREVCYLINDER AND PRESS STRUCTURE FOR THE CYLINDER .Filed Jan. 25, 1968 2 Sheets-Sheet 2 United States Patent 3 566,450 HIGH PRESSURE CYLINDER AND PRESS STRUCTURE FOR THE CYLINDER Albert Samuel Roberts, Rector, Pa., assignor to Kennametal Inc., Latrobe, Pa. Filed Jan. 25, 1968, Ser. No. 700,612 Int. Cl. B290 1/02 US. Cl. 18-34 6 Claims ABSTRACT OF THE DISCLOSURE The invention concerns a high pressure cylinder formed by winding up one or more strips of high tensile strength material to form the cylinder. Closure members are sealingly mounted at the ends of the cylinder so that pressure can be developed in the cylinder. A press in the form of a frame with an opening therein is arranged for receiving the cylinder and its closure members and the opening is of such a size that when pressure is built up in the cylinder, the closure members will be engaged by the press frame and support the closure members against movement out of the ends of the cylinder.
This invention relates to the compacting of granulated or powdered materials and is particularly concerned with a novel apparatus for this purpose embodying a high strength, low cost pressure cylinder.
The compacting of granulated or powdered materials is known and may be carried out by pressing the material between pressing plunger in a die cavity according to well known practices. A large class of workpieces cannot be properly compacted by conventional pressing methods, however, due to the size or configuration of the workpieces and such workpieces are usually compacted by a hydrostatic process. The hydrostatic pressing of powdered materials takes place within a cylinder cavity to which fluid, such as hydraulic fluid, is supplied under pressure with the powdered material to be compacted being contained within a die arrangement inside the cavity. The die arrangement is of flexible rubber-like or elastomeric material so that the powder is subjected to substantially uniform compacting pressure over its entire surface.
The pressures employed in such cylinders may range up to 35,000 pounds per square inch or even higher and the material of the cylinder is thus highly stressed. Here tofore, such cylinders have been made of high quality forgings so that the cost thereof has been extremely high. Furthermore, due to the rather thick-walled sections required, the possibility of flaws in the forging presents itself and this can lead to failure of the cylinder when subjected to high pressure.
With the foregoing in mind, a primary objective of the present invention is the provision of a high pressure cylinder of the nature referred to, and a method of making the cylinder in which the defects which have heretofore been encountered in forged cylinders are eliminated while the cost of the cylinder is substantially reduced.
Another object of the present invention is the provision of a low cost high pressure cylinder of the type especially adapted for use in the hydrostatic pressing of powdered materials in which cylinders of susbtantially any size and proportions can be manufactured.
Another particular object of the present invention is the provision of a novel press structure for receiving a high pressure cylinder according to the present invention.
It is also an object of this invention to provide a simple, low cost press structure for use with a cylinder according to the present invention.
3,566,450 Patented Mar. 2, 1971 These and other objects and advantages of the present invention will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which:
FIG. 1 is a front view, partly broken away, showing a press arrangement and high pressure cylinder according to the present invention;
FIG. 2 is a vertical sectional view indicated by line H- II on FIG. 1
FIG. 3 is a fragmentary plan view showing the manner in which supporting rollers are yieldably mounted on a carriage for the high pressure cylinder;
FIG. 4 is a fragmentary sectional perspective view showing a cylinder according to the present invention;
FIG. 5 is another fragmentary sectional view showing a typical seal arrangement for sealing an end closure member to the cylinder;
FIG. 6 is a view similar to FIG. 5 but shows the cylinder provided with a flexible liner;
FIG. 7 is a view similar to FIG. 6 which shows the use of a sealing sleeve on the inner surface of the cylinder;
FIG. 8 is a somewhat diagramatic fragmentary view showing an arrangement for quickly releasing the pressure from the interior of the cylinder;
FIG. 9 is a plan sectional view showing a typical die mounted in the high pressure cylinder; and
FIG. 10 is a graph showing somewhat schematically certain conditions in the cylinder as pressure is built up therein.
Referring to the drawings somewhat more in detail, FIGS. 1 and 2 show a press structure generally indicated at 10 and which is made up of a plurality of rectangular plates 12 having rectangular openings 14 therein and with spacer members 16 interposed between plates 12 at the ends thereof. Bolts or other securing means indicated at 18 clamp plates 12 and spacers 16 fixedly together, thereby forming a simple, low cost, but, nevertheless, high strength press frame. As will be seen in the drawings, there may be a bearing plate 20 provided at the top of the press opening and a further bearing plate 22 provided at the bottom of the press opening. These bearing plates efficiently transmit pressing forces to the press plates 12 for an etficient realization of the structural strength of plates 12.
The lower bearing plate 22, and which may be considered to be the bed of the press, has tracks 24 that receive the rollers 26 of a carriage 28. Rollers 26 are mounted on the ends of shafts 30 which are connected to the carriages by centrally located blocks 32. The arrangement is such that the bottom of the carriage is normally sup ported above the top of plate 22 so that the carriage and any load mounted thereon can be rolled into and out of the press. However, when pressing force is exerted downwardly on carriage 28, shafts 30 will yield and the carriage will be pushed downwardly into load transmitting engagement with plate 22.
Carriage 28 is adapted for receiving the lower closure member 34 of high pressure cylinder 36 which also has an upper closure member 38.
A passage 40 extends from the interior of cylinder 36 through lower closure member 34 to a flexible conduit 42 which leads through a check valve 44 to the discharge side of a pump 46 which has its suction side connected to a reservoir 48. A normally closed pilot operated valve 50 is connected between reservoir 48 and the down stream side of check valve 44 for releasing pressure from cylinder 46.
The carriage 28 is adapted for being rolled out of the press on external tracks 52 for loading and unloading fluid motor consisting of a cylinder 54 connected to the press frame and having reciprocably mounted therein 3 a double acting ram 56 which is connected with the carriage is employed for moving the carriage into and out of the press.
Reciprocation of ram 56 in cylinder 54 to move the carriage into and out of the press frame is accomplished by shifting of the four-way valve 58 connected between opposite ends of cylinder 54, the discharge side of a pump 60 and reservoir 48.
In operation, when pump 46 is Operated to develop pressure within cylinder 36, upper closure member 48 will be pushed upwardly against upper plate 20, which may be considered to be the head of the press, while closure member 34 is pushed downwardly thereby to cause carriage 28 to move downwardly and engage plate 22. A clearance on the order of A1" or even less is suflicient between carriage 28 and plate 22 and between closure member 38 and plate so that only a relatively small amount of fluid is needed after the cylinder is filled to commence to build up pressure in the cylinder and which pressure will, of course, be carried by the press frame.
The closure members have seals thereon as at 62 to prevent the escape of fluid from the cylinder and to permit the building up of pressure therein. As mentioned previously, the cavity in the cylinder is, in one way or the other, provided with powdered material to be compacted contained within a die cavity of suitable shape so that the pressure build up in the cylinder effects the compacting of the powdered material.
Cylinder 36, which is a particular novel feature of the present invention is made, as will be seen in FIG. 4, by tightly winding a strip 64 of material, preferably a thinly rolled good grade of steel, to form a cylinder of desired internal and external diameters. Several advantages are obtained by rolling up a strip in this manner. In the first place, the thin strip of material, and which may only be .004 or .005 inch in thickness or more is less likely to contain flaws than a forging made to the same dimensions as the cylinder. Furthermore, should the strip contain one or more flaws, the influence thereof is more localized than would be the case of a flaw in a forging. Also, cylinders rolled up from strip material are much more inexpensive than cylinders machined out of heavy forgings. Ordinary techniques can be employed for Winding the strip about a mandrel while maintaining the strip under tension to keep the convolutions in face to face engagement so that the construction of the cylinder is much less time consuming than if it were made by forging and machining procedures.
It is known that metal rolled out in the form of a thin strip is capable of developing higher strength than metal in the form of a large block, such as a forging, so that by making the cylinder according to the present invention, a stronger cylinder can be produced of a given size than can be made by forging and machining procedures.
Still further, it will be evident that it becomes a simple matter to make cylinders of any size and proportions according to the present invention and even to modify the cylinders after manufacture much more simply than can be done by forging.
In FIG. 4 the strip 64 at its inner end 66 may be bevelled, depending on the thickness of the strip and the edge 66, furthermore, may be sealed as by the rubberlike or plastic seal strip 68.
At its outer edge 70, strip 64 is secured to itself as by adhesive tapes 72 although welding or brazing or cementing, as by epoxy resin, is possible. Also, the entire cylinder can be banded after it is wound up and this also has proved to be a satisfactory manner of holding the cylinder together.
The ends of the cylinder may or may not be provided with plates or end rings secured thereto and it has been found satisfactory to employ the cylinders without end plates provided the seals on the closure members are sufficiently flexible to form a good seal completely about the periphery of the cylinder. It is usually the case that the seals are eflicient enough to seal the cylinder even at the inner end 66 of strip 64 so that the invention can be practiced either with or without end members on the cylinders.
In FIG. 5 cylinder is provided with a closure mber 82 and a seal is established between the closure member and the cylinder by providing a reduced diameter portion 84 on the inner end of the closure member on which is mounted an upper wedge member 86 and a lower wedge member 88. The lower end of plunger wedge member 88 is concave and fits an O ring 90 disposed between reduced diameter portion 84 and the inside of cylinder 80. A snap ring 92 holds the seal in place on the closure member. When pressure is built up in the cylinder below the seal, the seal will form itself into tight sealing relation with the closure member on the inside of the cylinder.
In FIG. 6 a cylinder is provided with an end mem ber at end ring 102 having a cylindrical portion 104 extending telescopically into the adjacent end of the cylinder. Closure member 106 telescopically engages portion 104 and is sealed thereto by sealing ring 108.
Cylinder 100 in FIG. 6 is provided with a flexible baglike element 110 which defines an annular chamber 112 with the cylinder. The ends of baglike member 110 are turned backwardly against the inside of the cylinder as at 114 and are held in sealing engagement with the cylinder, as by expansion spring ring means 116.
A passage 118 in end plate 102 is adapted for connection to a source of fluid under pressure, and leads to a tubular element 120 extending into the end of baglike member 110. With the arrangement of FIG. 6, the space inside baglike member 110 in cylinder 100 does not receive any liquid and thus can itself be charged with dry material to be compacted, or may have placed therein a resilient die having a cavity containing the material to be compacted. The compacting fluid is confined to the annular space 112 and this permits the manufacture of larger workpieces than when the pressure fluid is supplied to the entire inside of the cylinder and likewise permits compacting to be done with a smaller quantity of fluid.
In FIG. 7 a similar arrangement to that of (FIG. 6 is illustrated except that, in addition to a baglike element in cylinder 1 32, there is also a sealing sleeve 134 covering the inner surface of the cylinder. While the convolutions of the cylinder are normally pressed tightly against each other when pressure is developed on the inside of the cylinder so that fluid will not leak along the inner face of the convolutions of the strip from which the cylinder is made, the provision of the sealing sleeve 134 absolutely prevents any such leakage of fluid which might occur if for any reason the convolutions of the cylinder become somewhat loosened.
FIG. 8 shows a manner in which pressure can be released relatively quickly from the space around a baglike member 136 in a cylinder 138. The annular chamber 140 surrounding the baglike member has pressure fluid supplied thereto via a passage 142 and by a non-illustrated pumping means. Also connected with passage 142 is a cylinder 144 having a plunger 146 reciprocable therein. Plunger 146 is connected to a substantially larger piston 148 which is, in turn, reciprocally mounted in a cylinder 150. A four-way reversing valve 152 is connected to opposite ends of cylinder 150 and is supplied with fluid under pressure by a pump 154. When valve 152 is in one position, piston 148 and plunger 146 are held in the position in which they are illustrated in FIG. 8, with piston 148 being of such a size that plunger 146 will be held stationary at the maximum pressure developed in passage 142. When the supply of pressure fluid to conduit 142 is interrupted, the pressure in annular chamber 140 can be reduced quite suddenly by shifting valve 152 to drive piston 148 and plunger 146 leftwardly from their FIG. 8 position. The described arrangement permits rapid decompression of the cylinder and thus more rapid cycling of the press.
FIG. 9 shows a typical die arrangement for use in any of the FIGS. 6, 7 and 8 modifications. In FIG. 9 cylinder 160 has a cavity 162 and a baglike element 164 therein defining an annular chamber 166. Inside bag 164 is a rubber-like filler sleeve 168 and inside filler sleeve 168 is a die consisting of four rubber-like segments [170 with a divided plate 172 extending between two of the segments. A pair of cavities 174 is thereby defined into which powder material is introduced for being compacted when fluid pressure is built up in chamber 166.
In respect of a high pressure cylinder according to the present invention, when pressure is developed therein, the edge of the innermost convolution is sealed to the inside of the cylinder, either by a flexible liner sleeve or by some other sealing means so that as pressure is built up in the cylinder the fluid is prevented from getting between the convolutions of the cylinder. As the pressure rises in the cylinder, the convolutions slip on each other somewhat and the cylinder will expand as to inside diameter while substantially no change occurs in the outside diameter. Further, the pressing together of the convolutions enhances the seal at the end of the innermost convolution.
As the internal pressure rises in the cylinder, the laminar stress is high in the inside of the cylinder and gradually reduces toward the outside diameter of the cylinder. Inasmuch as the convolutions are pressed tightly against each other, even though the strip forming the cylinder is smooth, friction is developed between adjacent convolutions due to the radial pressure acting on the sealed coiled surfaces. The tensile stress and the friction locking of the convolutions to each other increases substantially in direct proportion to the internal pressure developed in the cylinder. The aforementioned friction lock of the convolutions with each other tends to localize the influence of any faults in the strip from which the cylinder is made up.
I urthermore, due to the friction lock referred to, the cylinder could be made from more than one strip. The separate strips could be overlapped or interleaved at the outer end of the inner strip and the inner end of the outer strip and ultimate strength of the cylinder would not be decreased for the reason that it was made from more than one strip. The possibility of making the cylinder from more than one strip introduces the possibility of providing the cylinder with integral lift eyes or the like by utilizing a second strip having lift eyes thereon and winding the second strip together with a first strip.
A cylinder constructed according to the present invention, as explained above, will expand and contract as to internal diameter as the pressure varies in the cylinder. This breathing effect is different than What is encountered with solid cylinders, such as are made from forgings, and the conditions under which the material of the cylinder operates are substantially different. When stn'p metal, such as steel, is rolled out in a thin strip, the crystals of the metal become somewhat oriented in the direction of the length of the strip and this imparts considerably higher strength per unit area to such a strip in the direction of its length than will be the case of a like metal in unrolled condition. When such a strip is now wound up to form a cylinder, it will be evident that the strip is disposed in such a manner as to take maximum advantage of its strength characteristics. This is a particularly important feature of the present invention because, as mentioned previously, a much stronger cylinder can be made from the same weight of material than can be made by machining the cylinder out of a solid block.
The variation of conditions in the cylinder as pressure is built up therein is somewhat schematically illustrated in FIG. 10. In FIG. the line marked A designates a change in pressure in the cylinder from zero to a predetermined maximum.
The innermost end of the strip is sealed to the next convolution of the cylinder with a predetermined presealing stress and the sealing force at this edge is then indicated by line B. The sealing force is always in excess of the pressure in the cylinder so that no leakage of fluid to the space between the convolutions can take place.
The line marked C indicates the tensile stress developed in the strip while the line marked D shows how the friction locking of the adjacent convolutions with each other also rises as pressure is built up therein.
It will be understood that the change in internal diameter of the cylinder does not change so much that the end seals on the cylinder become ineffective. The seal shown in FIG. 5, for example, is of such a nature that it will accommodate the expansion which is encountered in the cylinder without losing its effectiveness.
It will be understood, also, that the present invention is susceptible of modification to adapt it to particular circumstances and such modifications that come within the scope of the attached claims are considered to be within the purview of the present invention.
What is claimed is:
1. A cylinder member especially adapted for use under high pressure and comprising a strip of high tensile strength material formed into a coil so as to define a cylinder :bore, the convolutions of the coil being in face to face engagement with adjacent convolutions, said coil being open on the ends for sealingly receiving closure members, means retaining at least the outermost end of said strip in place against the outer surface of the cylinder, said convolutions being free of interconnection except for the connection of at least one of the innermost and outermost ends of said strip to the opposite end of the respective convolutions, end rings on the ends of said cylinder, each said ring having a disc-like outer part engaging the respective end of the cylinder and a tubular inner part telescopically engaging the adjacent end of the cylinder bore, end closure members for the cylinder bore telescopically and sealingly engaging said inner parts of said end rings, and passage means extending through at least one of said end rings for fluid communication with said cylinder bore.
2. A high pressure cylinder member comprising a strip of high tensile strength material in the form of metal formed into a coil so as to define a cylinder bore, the convolutions of the coil being in face to face engagement with adjacent convolutions, the innermost one of said convolutions forming the radial limits of said cylinder bore, said coil being open on the ends for sealingly receiving closure members, means retaining at least the outermost end of said strip in place against the outer surface of the coil, said convolutions being free of interconnection between the innermost and outermost ends of said strip, a sealing element sealingly connecting the entire length of innermost end of said strip to the inner surface of said cylinder bore, closure members telescopically engaging opposite ends of said cylinder bore, means sealing said closure members to said cylinder bore, and at least one of said closure members includes passage means extending therethrough for effecting fluid communication with said cylinder bore, said sealing means and closure members being operable when disposed in the ends of said cylinder bore to confine high pressure therein.
3. A cylinder according to claim 1 which includes a flexible bag element in said cylinder bore extending between the opposed ends of said tubular inner parts of said end rings and sealed to the cylinder bore at the ends, said bag element defining an annular space in said cylinder bore surrounding said bag element, said passage means extending through at least one end of said bag element and into said annular space.
4. A cylinder according to claim 3 which includes a sealing sleeve closely fitted in said cylinder bore and extending from end to end thereof and forming the outer wall of said annular space.
5. A cylinder according to claim 1 which includes a first fluid cylinder connected to said passage means, a plunger reciprocable in said first fluid cylinder, a second fluid cylinder substantially larger in diameter than said first fluid cylinder, a double acting piston in said second fluid cylinder connected to said plunger, and means for reversibly supplying fluid under pressure to said second fluid cylinder to reciprocate said piston therein and thereby reciprocate said plunger in said first fluid cylinder to cause fluid exchange between said first fluid cylinder and said annular space.
6. A cylinder according to claim 2 which includes a first fluid cylinder connected to said passage means, a plunger reciprocable in said first fluid cylinder, a second fluid cylinder substantially larger in diameter than said first fluid cylinder, a double acting piston in said second fluid cylinder connected to said plunger, and means for reversibly supplying fluid under pressure to said second fluid cylinder to reciprocate said piston therein thereby to reciprocate said plunger in said first fluid cylinder so as to cause fluid exchange between said first fluid cylinder and said cylinder bore.
References Cited UNITED STATES PATENTS 350,344 10/ 1886 Caldwell 20659F 1,912,388 6/1933 Slovin 206-59F 2,883,045 4/ 1959 Abramson 20659F 3,131,725 5/ 1964 Chyle 220-3X 2,104,884 1/1968 Quarnstrom 29'476.5X 2,273,736 2/1942 Raymond et al. 29446 X 2,337,247 12/ 1943 Kepler 29446X 2,367,525 1/1945 Renpel 18l6E 3,133,346 5/1964 Allen 29476.5X 3,134,350 5/1964 Danly et a1 18 l6EX 3,241,188 3/1966 Febbo et al. 18-HPD 3,346,922 10/ 1967 Brayman et a1. 18HPD FOREIGN PATENTS 295823 5 1965 Netherlands 1'8I-EPD CHARLES W. LANHAM, Primary Examiner J. E. ROETHEL, Assistant Examiner US. Cl. X.R. 18l6