EP0005084B1

EP0005084B1 - Apparatus for drawing and ironing containers

Info

Publication number: EP0005084B1
Application number: EP19790300714
Authority: EP
Inventors: Edward G. Maeder
Original assignee: National Can Corp; American National Can Co
Current assignee: Rexam Beverage Can Co; National Can Corp
Priority date: 1978-04-26
Filing date: 1979-04-26
Publication date: 1985-07-31
Also published as: DE2967489D1; EP0005084A1

Description

Technical Field

The present invention relates generally to can making machines and more specifically to an improved floating arrangement for various components of a drawing and ironing machine.
In the formation of a "two-piece" container, it has been customary to utilize a plurality of die assemblies that cooperate with a punch for converting circular metal discs into finished containers which have a sidewall and an integral end wall. One of these processes consists of originally drawing a circular metal disc into a cup utilizing what is commonly referred to as a cupping machine. The cup is then transferred to a bodymaker wherein the cup is converted into the finished container. In one process, which is being used commercially, the preformed cup is first redrawn to a smaller diameter and larger height and then is substantially simultaneously converted to an ironed container wherein the sidewall thickness is reduced in one or more steps. One type of such commercial machine is produced by Ragsdale Bros., Inc. and is identified as a Model CR-24 canwall drawing and ironing press. Normally the material for such containers is either aluminum or tinplate.
In such a process, a punch normally cooperates with a plurality of ironing dies and the stroke of the punch is fairly long in order to produce conventional 340 to 455 cm³ (12 and 16 ounce) containers. The length of the stroke of the punch for the bodymaker or press has heretofore created substantial problems in producing a satisfactory container which has a uniform wall thickness in the sidewall thereof. One of the problems encountered has been in maintaining all of the elements in very accurate alignment with respect to each other in order to produce a finished container which has a uniform wall thickness around the entire perimeter thereof and also the entire length thereof.

Background Prior Art

In order to alleviate some of the problems in maintaining accurate alignment between the various dies and the punch, several proposals for producing floating ironing dies have been proposed. For example, British Patent No. 724,251 published February 16, 1955 discloses a method of supporting ironing dies that will accommodate movement of the dies with respect to the punch but will also provide a self-centering feature which theoretically will reposition the die to a predetermined position whenever all external forces have been removed.
The particular arrangement for accomplishing the self-centering and floating feature in the assembly disclosed in the British patent consists of cooperating inclined surfaces between the ironing die and its support mechanism with a biasing mechanism which will automatically center the ironing dies with respect to a predetermined axis whenever external forces are removed. The biasing mechanism in this patent has been illustrated as either consisting of an elastomeric member or rubber ring which produces a centering action between an ironing die and a cooperating support. Alternatively, the centering means in the disclosed patent also shows the use of springs that cooperate with the ironing die and the support to center the ironing die with respect to a predetermined axis. However, such arrangement has not been too successful in accurately returning the ironing die to a centered position after being moved away from the centered position.
These problems have been overcome by the present invention according to which in a drawing and ironing machine including a frame having a redraw die assembly, at least one ironing assembly and a stripper assembly, arranged in series and each having an opening to define a path with a punch movable along said path through said openings, the redraw die assembly including a redraw ring defining said opening and resilient centering means between said frame and said ring, there is also provided a said centering means including a plurality of circumferentially-spaced biasing means producing radial forces on said ring at circumferentially-spaced locations, each of said biasing means being independently biased to a first position when said ring is in a centered position, at least some and less than all of said biasing means moving from said first position to accommodate radial movement of said ring with respect to said path.
By means of the invention, when the redraw ring is moved off-center, centering forces will be applied to the redraw ring by those biasing means which have been moved from the said first position but these forces will not be opposed by forces from the biasing means which have not moved. Thus the effective centering force is maximised and is fully operative until centering has been completely effected. Moreover, the redraw ring is returned to the required central position even if the force applied by each biasing means is not identical to that of each of the other biasing means.
An additional problem that has been encountered in the formation of two-piece drawn and ironed containers has been encountered when the cup is initially formed and then is redrawn just prior to the ironing of the sidewall. In a redraw operation just prior to the ironing of the sidewalls of the cups, it is customary to hold the cup through what may be termed a cup holder sleeve in an accurate position with respect to the redraw ring just prior to the punch entering into the cup and forcing the cup through the redraw ring. It has been found that, under certain conditions, the cup holder sleeve is not accurately centered, while applying uniform hold-down pressure on the cup to hold the cup in a fixed position with respect to the redraw ring. This will produce an uneven redrawn cup which can produce a tear-off of the longer end either in the redraw state or in subsequent ironing stages.
It has also been determined that if the cup holder sleeve face does not apply a uniform pressure to the cup it may wrinkle in selected areas during the redraw application.
Preferably, therefore, the drawing and ironing machine includes a cup holder sleeve positioned ahead of said redraw die assembly in the movement of the punch through said redraw die assembly and having an axial bore for receiving said punch, and a sleeve support assembly for said cup holder sleeve, the sleeve support assembly including a support having an opening therein generally aligned with said opening in said redraw die assembly and having a circumferential recess extending from the periphery thereof, a movable support element having a peripheral portion received in said recess and cooperating with one end of said cup holder sleeve, and biasing means between said support element normally maintaining said support element centered with respect to said opening in said support and accommodating radial movement of said one end of said cup holder sleeve and said support element with respect to said support.
By this means, the previously mentioned problems of the cup holder sleeve not being accurately centered are overcome. A further problem which may occur with the cup holder sleeve is that the longitudinal axis of its bore may diverge at a slight angle from the axis of the path of the punch and according to a preferred feature of the invention this problem is overcome by additional means having confronting arcuate surfaces between said support and said cup holder sleeve to accommodate tilting of said axis of said bore with respect to said path. Preferably, free relative movement of the confronting arcuate surfaces is assured by at least one of the said surfaces having a continuous recess therein and providing for supplying lubricant to said recess.
The base of a can is often shaped by a domer and it is important that this too is centered. Accordingly, the drawing and ironing machine preferably includes a domer assembly which includes a support having a recess with the base of the recess defining a support surface, a carrier element received in said recess and having a cooperating surface, a domer element on said carrier element, means for supplying a bearing fluid between said surfaces, and biasing means between said support and carrier element normally maintaining said surfaces in a predetermined position with respect to each other and accommodating movement of said carrier element in all radial directions within said recess.

Brief Description of Several Views of Drawings

Fig. 1 schematically illustrates a fragmentary sectional view of a drawing and ironing machine into which the present invention can be incorporated;
Fig. 2 is an enlarged plan view of the cup holder sleeve support with portions thereof broken for purpose of clarity;
Fig. 3 is a fragmentary sectional view, as viewed along line 3-3 of Fig. 2;
Fig. 4 is a fragmentary sectional view, as viewed along line 4-4 of Fig. 2;
Fig. 5 is an enlarged fragmentary sectional view similar to Fig. 3 showing the details of the redraw and ironing die assemblies;
Fig. 6 is an enlarged fragmentary sectional view similar to Fig. 3 showing the details of the stripper assembly;
Fig. 7 is an enlarged fragmentary plan view, as viewed along line 7-7 of Fig. 5, showing part of the redraw assembly; and,
Fig. 8 is an enlarged fragmentary sectional view similar to Fig. 3 showing the details of the domer assembly.

Detailed Description

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention.
Fig. 1 of the drawings schematically illustrates selected portions of a bodymaker 10 used for converting a cup 12 into a finished container 14. Bodymaker 10 includes a cup holder sleeve 20 which has an axial bore 22 therein through which a punch 24 is adapted to be moved. Punch 24 is axially aligned with path P and is movable along path P which has a plurality of die assemblies in a support 30. The first die assembly consists of a redraw ring assembly 26 and the other die assemblies are ironing ring assemblies 28.
Before the stroke of punch 24 and cup holder sleeve 20 is initiated, a cup 12 is generally aligned with redraw ring 26 through a cup locating mechanism (not shown) and cup holder sleeve 20 is then moved axially generally to the position illustrated in Fig. 1 to hold the cup 12 in a fixed position with respect to redraw ring 26. Punch 24 is then moved axially through bore 22 to force the cup initially through the redraw ring 26 wherein the cup diameter is decreased and the cup height is increased and subsequently through the ironing rings 28 which cooperate with the peripheral surface of punch 24 to reduce the sidewall thickness of cup 12. After the cup has been passed through the respective rings, the lower end of the punch, which is generally dome-shape in cross- section, cooperates with domer 34 to reform the bottom wall of the cup and produce a finished container. During the return stroke of punch 24, stripper assembly 32 engages the upper free edge of finished container 14to strip the container from the punch. _;
As was indicated above, one of the problems encountered in producing satisfactory containers utilizing a process described above, is to maintain accurate alignment of all of the various parts at all times. Any misalignment of any of the elements by even as little as 0.00254mm (one ten- thousandths of an inch) will result in having a finished container which has a sidewall of uneven thickness. One of the most critical initial areas in the above described process is to make sure that the cup is accurately positioned with respect to the redraw ring and uniform hold-down pressure is applied to the cup before the drawing and ironing process is initiated.
For practical considerations, a clearance must be maintained between the periphery of punch 24 and the inner surface of cup holder sleeve 20. Therefore, the punch cannot be utilized for aligning the cup holder sleeve with respect to the axis of the punch which is presumed to be aligned with the center of the opening in redraw ring 26. Therefore, in cases of jams, the large unsymmetrical forces that are developed in the system may force the cup holder sleeve out of alignment with the axis of punch 24 and redraw ring 26. The result may be that the sleeve remains permanently misaligned after after a jam and may become exaggerated during subsequent jams.
According to one aspect of the present invention, cup holder sleeve 20 is mounted for universal movement with respect to the path P to facilitate tilting and radial movement during a jam while still remaining aligned after a jam.
As most clearly illustrated in Fig. 3, cup holder sleeve 20 is supported in a cup holder sleeve support 40 which consists of first and second members 42 and 44 which have cooperating threads 46 to be assembled with respect to each other, for a purpose that will be described later. Support 40 has a substantial circular opening 48 therein which is aligned with the circular opening 50 that is defined in the redraw ring 26 and the centers of these openings are located along the path P of punch 24. Members 42 and 44 cooperate with each other to define a recess 52 extending from the periphery of opening 48 and recess 52 has a shoulder 54 which extends substantially radially from the axis of opening 48. A support element or cup holder sleeve support member 60 has a peripheral portion 62 which is received into recess 52 and also has a contiguous cooperating surface 64 which is in engagement with shoulder surface 54. Support element 60 also has a circular aperture 66, therein, which is generally of the same size as bore 22 in cup holder sleeve 20.
According to one aspect of the invention, cup holder support element 60 and cup holder sleeve 20 are normally centered with respect to opening 48 through centering means which will now be described. In the illustrated embodiment, the centering means consists of four circumferentially spaced biasing means 70 that are equally spaced from each other around the perimeter of the substantially circular support 40. The respective biasing means 70 are spaced approximately 90 degrees from each other and produce equal forces around the perimeter of support element 60 to maintain the support element in a centered position with respect to the circular support 40 more particularly opening 48. The respective biasing means 70 are identical in construction and only one will be described in connection with Figs. 2 and 3.
Each biasing means 70 consists of a spring 72 that has one end received into a cup 74 which has an annular shoulder 76 cooperating with an enlarged portion 78 of a radial opening in support 40. The opposite end of spring 70 engages the inner surface of a support ring 80 which forms part of support 40. The springs 72 are selected so as to produce an equal force and cup 74 is designed so that the inner surface thereof is in engagement with the periphery of support element 60 as illustrated in Figs. 2 and 3.
The cups 74 are all accurately dimensioned so that when the shoulders 76 engage with support 40, the free ends of the cups are on a common circle which has a diameter that is equal to the peripheral diameter of the support element 60. However, if external forces are applied to cup holder sleeve 20 which may result from a misfed cup or a defective cup, the springs will accommodate radial movement to prevent permanent misalignment between opening 48 and redraw ring 26. When the external forces are removed the springs which are compressed will return the sleeve to a centered position. The centering means or biasing spring 70 will, therefore, always accurately position support element 60 in a centered position with respect to opening 48 which is accurately centered with opening 50.
According to a further aspect of the invention, the axis of bore 22 of cup holder sleeve 20 can also be tilted with respect to the path P if there is a misfed cup to apply a uniform hold-down pressure at all times. For this purpose, support element 60 has an arcuate or spherical segment 90 on the lower surface thereof surrounding aperture 66 and the concave surface segment 90 cooperates with'a convex surface segment 92 defined on an enlarged portion 100 on the upper end of cupper sleeve 20. The cooperating surface segments 90 and 92 will accommodate movement of the lower free end of cup holder sleeve 20 to allow the cup holder sleeve to assume an angular position wherein the axis of bore 22 is axially aligned with the axis of punch 24. The centers of spherical surface segments 90 and 92 are located at a point 95 which is located on path P.
Flat surfaces 54 and 64 and spherical surfaces 90 and 92 are normally held in engagement with each other through biasing means that cooperate with support 40 and cupper sleeve 20, as well as support element 60. For this purpose, enlarged portion 100 of cup holder sleeve 20 is received into recess 52 and spring biased tabs 102 are received in recesses 103 and cooperate with the lower surface of enlarged portion 100 for biasing the various surfaces into engagement with each other. More specifically, each tab (there being four equally spaced around the perimeter of support 40) has a cup 104 secured thereto as by welding and a hold-down spring 106 is telescoped into the cup. Cup 104 is received in an opening 108 in member 42 and one end of the spring engages the surface on member 44 which forms part of support 40.
The base of each recess 103 in member 42 defines an accurate space between the tab and surface 54 and such spacing will be maintained even when the spring forces for the respective springs are different.
Thus, each tab 102 is biased into the position illustrated in Fig. 3 wherein the axis of aperture 66 and the axis of bore 22 are aligned with the axes of openings 48 and 50. However, should there be a need for having the cup holder sleeve 20 tilted with respect to the path P of punch 24, the tabs will allow a certain amount of tilting movement of the sleeve 20 with respect to support element 60.
According to a further aspect of the invention, the various surfaces which are moved relative to each other are continuously lubricated through lubricating means which will now be described. The lubricating means is most clearly illustrated in Fig. 4 and consists of an opening 110 in member 42 which has a threaded exterior portion 111 to which a source of pressurized lubricant may be connected. The inner end of opening or bore 110 is in communication with a continuous circumferential recess 112 that is defined in shoulder surface 54 of member 42. The recess 112 extends around the entire perimeter of surface 54 and is also in communication with a second continuous recess 120 in surface 90 through one or more small openings 122. Therefore, a continuous flow of fluid from a source (not shown) through opening 110 will provide a constant supply of lubricant between the relatively movable surfaces of the cup holder sleeve assembly. This arrangement substantially reduces the frictional forces that must be overcome when the various elements have to be moved with respect to each other. Of course, the continuous supply of lubricant to these relatively movable surfaces will also substantially reduce the wear of the overall assembly.
According to the present invention, the redraw die assembly 26 is mounted in support 30 in a manner that allows radial movement of the assembly with respect to the normal path of movement P of punch 24 to allow the assembly to be moved to a centered position with respect to the axis A of punch 24, should the punch be offset from the path P.
As illustrated in Fig. 5, redraw die assembly 26 includes a support 230 which supports a redraw ring 232 that has a circular opening 234. Support 230 has a lower flat surface 236 which extends perpendicular to path P and is in extended engagement with a flat surface 238 that is defined in frame structure 225. The periphery of support 230 is preferably circular, and centering means 240 cooperate with the periphery of support 230 to normally maintain support 230 and ring 232 centered with respect to path P. The centering means 240 consists of an annular ring 242 which is held in a fixed position on frame 225 and has a plurality of circumferentially spaced spring assemblies 244 associated therewith. Preferably, at least four such spring assemblies 244 are circumferentially equally spaced around the perimeter of support 230 and each spring assembly 244 includes a plunger 246 reciprocated in an opening 247 extending into the inner surface of ring 242. Plunger 246 has an enlarged flange 248 located in a cup 250 with a spring 252 also located in cup 250 which biases plunger 246 into engagement with the periphery of support 230. Normally, all plungers 246 are biased to a position illustrated in Fig. 5 wherein the flange 248 of each plunger 246 is in engagement with a surface of ring 242 around opening 247. This arrangement defines an extremely accurate centered position of the opening 234 with respect to path P. However, should there be any misalignment between the axis of the punch and path P, one or more of the springs 252 will be compressed and support 230 moves radially of path P to allow the axis of opening 234 to be aligned with the axis of the punch. During such radial movement, only a selected number, less than all, of the springs 252 are compressed, while the remaining springs located located on the side opposite the direction of movement of support 230 will remain in their prestressed condition illustrated in Fig. 5. This arrangement insures that there is no resistance to having the die ring moved to a centered position with respect to path P after a cup has been forced through redraw ring 232 by punch 24. This arrangement also eliminates the possibility of having the redraw assembly off-center with respect to path P because of varying forces applied by the respective springs.
According to another aspect of the invention, a fluid bearing is interposed between cooperating surfaces 236 and 238 to reduce the friction forces that must be overcome to allow radial movement of support 230 with respect to path P. For this purpose, support surface 236 has one or more annular recesses 260 defined therein and recesses 260 are in communication with a bore 262 which is defined in frame 225. A supply of pressurized fluid, such as air, is connected to the inlet end of bore 262 and is delivered to the respective annular recesses 260. Since the only exit from recesses 260 is along the surfaces 236 and 238, the fluid will act as a bearing surface to tend to separate these surfaces when external forces are applied to the redraw die assembly which will assist in allowing the opening 234 to move to a predetermined centered position with respect to punch 24.
According to a further aspect of the invention, the redraw die assembly also includes a centered mechanism for centering the cup 12 with respect to redraw ring 232 prior to having the punch enter the cup. This centering mechanism consists of a nesting ring 266 that has an opening 268 which is larger than opening 234. Nesting ring 266 is held in a fixed position with respect to redraw ring 232 through a support ring 270 which is held in a fixed position with respect to support 230 by screws 272 and thus forms a part of support 230. The diameter of opening 268 is substantially equal to the peripheral diameter of cup 12 as it is received by the redraw die assembly and is larger than the diameter of opening 234 so that a portion of the surface of ring 232 is exposed.
Thus, as the cup holder sleeve enters cup 12 and moves towards redraw die assembly 26, the nesting ring 266 aids in centering the center of the cup with respect to the center of redraw ring 232 before punch 14 enters sleeve 20. This movement is in part assured by the fact that the lower peripheral end of cup 12 normally has a radiused portion 274 and the radiused portion will aid in guiding the periphery of cup 12 into opening 268 of centering ring 266. Of course, if there is axial misalignment between the center of openings 268 and 234 with respect to the center or axis of cup 12, biasing means 240 will allow the entire die assembly to move radially with respect to path P. The diameter of bore 22 in sleeve 20 is slightly larger than the diameter of punch 14 so that redraw die assembly 26 and sleeve 20 with cup 12 clamped between them can move radially and the center of opening 234 will align with the axis of punch 14.
According to a further aspect of the invention, the nesting ring 266 also incorporates means for supplying lubricant between the exposed surface of redraw ring 232, which initially supports the cup and the adjacent surface of cup 12. As most clearly illustrated in Fig. 7, the lower surface of support ring 270 has an annular recess 280 defined therein and recess 280 is closed by a surface of support 230 to produce a channel. The channel is in communication with the periphery of support 230 through openings 282. A pressurized lubricant is supplied to openings 282 through an opening 284 in frame 225. Annular recess or channel 280 is in communication with opening 268 through a plurality of non-radial recesses 288 in one surface of nesting ring 266 and recesses 288 are circumferentially spaced around the perimeter of opening 268. The recesses are closed by adjacent surfaces of support 230 and redraw ring 232 to produce flow paths. As illustrated in Fig. 7, all of the recesses or flow paths are generally linear and the axes of the flow paths are radially offset from the center of opening 268 in nesting ring 266. This arrangement insures that there is non-radial flow of the fluid from channel 280 through flow paths 288 into opening 268. Also, the radiused peripheral lower edge 274 of cup 12 (Fig. 5) will cooperate with the upper exposed surface of redraw ring 232 and the annular inner surface of opening 268 to produce a small channel for lubricant flow around the perimeter of the cup to all areas of the exposed surface of redraw ring 232.
Thus, the lubricant that is received into annular recess 280 flows through the respective recesses 288 into the channel created by the radius portion 274 and results in a circumferential flow of the lubricant within the channel during the redraw operation. Stated another way, the non-radial recesses or slots 288 distribute the lubricant, which also acts as a coolant, in a vortex pattern across the redraw die surface during the redraw operation. The lubricant also cleans and cools the redraw die surface after the cup has been redrawn.
Each of the ironing assemblies 28 is generally identical in construction and again provides a floating arrangement for the ironing ring to accommodate radial movement of the ironing ring with respect to the path P and thereby insure more uniform wall thickness of the finished container. The details of one ironing assembly are illustrated in Fig. 5 and include an ironing die 300 that has a land 302 which cooperates with the peripheral surface of the punch 24 to reduce the sidewall thickness of a cup as it passes through the ironing die 300. Ironing die 300 is supported in a circular support 304 which has a recess 306 for receiving and supporting die 300. In the illustrated embodiment, the ironing die assembly also has a locator die 310 supported on a circular plate 312 which acts as a guide for the cup as it leaves the ironing die 300. Support 302 and plate 312 have a peripheral band 314 engaging the peripheral surfaces thereof so that the ironing die and locator die 300 and 310 move as a unit when external forces are applied thereto.
The lower surface 320 of support 312 is in sliding contact with a radail surface 322 defined on a support structure 324 for the ironing die. Likewise, the upper surface 326 of upper ironing die support 302 is in sliding contact with a radial surface 328 that is also part of the support 324. The entire ironing die assembly 28 is again maintained in a predetermined position by a plurality of centering means 330 that are circumferentially spaced around the peripheral surface of ring or band 314 and are carried by support 324. Each centering means or spring assembly includes a cup 332 that has a base thereof in juxtaposed relation to the peripheral surface of band 314 and has a radially extending flange 334 at the opposite open end thereof. A spring 336 is telescoped into the cup and the outer end thereof engages a cover portion 338 that is removably secured to support 324 through suitable retaining means 340.
Again, preferably there are four such spring assemblies 330 equally spaced at 90 degrees around the perimeter of band 314 and are dimensioned such that when flanges 334 engage adjacent shoulders defined on the support 324 the ironing land 304 is accurately centered with respect to the path of punch 24. However, if the center of the opening defined by land 304 is slightly offset with respect to the axis of the punch 24, at least some, but not all, of the spring assemblies will be compressed and allow radial movement of the entire die assembly 28 to center the land opening with respect to the punch and insure a uniform wall thickness for the finished container.
Again, in order to reduce friction and accommodate this radial movement, a fluid bearing is interposed between surfaces 320 and 322 and consists of annular recesses 346 that are in communication with an air supply through one or more openings 348.
While only one such die assembly has been disclosed, it will be appreciated that in most instances more than one ironing die assembly will be used so that a sidewall of a cup will be reduced in thickness in stages to increase the overall efficiency of the system.
According to a further aspect of the present invention, stripper assembly 32 is also designed to accommodate radial movement of the assembly with respect to path P during a drawing and ironing operation. The stripper assembly 32 is illustrated in greater detail in Fig. 6 and includes a stripper support element 410 that has an enlarged portion 412 received into a recess 414 defined in support 425. A plurality of pivoted jaws 416 are located around the perimeter of path P and the lower edges of jaws 416 cooperate to define an opening 418 through which the finished container and punch 24 pass during the last part of the stroke of a drawing and ironing process. The respective jaws or segments 416 are held in a predetermined position through a resilient support member 422 and support ring 423 as well as an elastomeric member 424 as illustrated in Fig. 6. The jaws are biased to a position wherein the opening 418 is slightly smaller than the peripheral diameter of the finished container which passes therethrough. Thus, as the container and punch pass through opening 418, the lower edges of pivoted jaws 416 are moved outwardly slightly to accommodate the movement of the container therethrough. However, after the upper free edge of the container moves beyond the lower edge of the pivoted jaws 416, the jaws will move inwardly into the path of return movement of the upper free end of the container.
Stripper assembly 32 is again held in a centered position with respect to path P through biasing means 430 which can be identical to the biasing or centering means 240 described above. Thus, should for any reason, the axes of punch 24 with the finished container on it be offset somewhat from the path P during the downward movement of the punch and container, the biasing means 430 will again accommodate radial movement of the entire stripper assembly with respect to path P to insure that there is no substantial interference between the container and the stripper jaws. Again, support 410 and frame 425 have flat radially extending cooperating surfaces that accommodate such radial movement. This arrangement insures that all of the jaws are located in the same position with respect to the periphery of the punch. This insures that the jaws which engage the free edge will engage across the entire width of the edge for more reliable stripping and less damage to the free edge.
As illustrated in Fig. 6, the lower surface of enlarged portion 412 has a flat annular surface 432 which is supported on an annular flat surface 434 that is defined in frame structure 425. Frame structure 425 also has an upper annular surface 436 which cooperates with flat upper surface 438 of support member 410.
It has been found that the use of the floating redraw ring and stripper in combination with the plurality of floating ironing assemblies and the floating redraw assembly substantially increases the productivity of a bodymaker of this type and produces containers that have a better finished appearance and have a uniform wall thickness throughout the entire diameter of each container as well as throughout the length thereof.
As was indicated above, one of the problems in producing satisfactory containers utilizing a process such as that described above, is to maintain extremely accurate alignment between the axis of punch 14 and the center or axis of domer assembly 34. Any misalignment of these two elements with respect to each other by even a small increment will result in a defect in the end wall of the container which in turn will impair the strength of the container.
According to the present invention, the domer assembly 34 is constructed in such a fashion that the domer element which forms part of the assembly can readily be moved in any direction radially of the axis or path P to move into a position in exact alignment with the center of punch 24 should the punch be offset from the path for any reason. For this purpose, domer assembly 34 (Fig. 8) consists of a support 530 which may be accurately positioned with respect to the remainder of the frame structure of the bodymaker 10 and is supported on a cushion such as air, for axial movement (not shown). Support 530 has a recess or opening 532 extending from the upper surface 534 and recess 532 has an enlarged portion 536 and a reduced portion 538 with a generally flat bottom wall or surface 540 defined in the reduced portion 538. The center of circular opening 532 is accurately positioned and centered with respect to path P.
Domer assembly 34 also includes a support element or member 542 which has an enlarged portion 544 received into enlarged portion 536 of recess 532 and a reduced portion 546 with reduced portion 546 having a bottom surface 548 which is in extended egagement with bottom wall or surface 540 for recess 532. Recess 532 and carrier element 542 are both circular in cross section and carrier element 542 is smaller in dimension than the recess 532, as will be described later.
The remainder of domer assembly 34 consists of a domer element or tool 550 which is supported in an opening 552 in carrier element 542 and is secured thereto by a bolt 554. The threaded bolt or stud 554 extends through an opening 556 in carrier element 552 and is threaded into an opening in the domer element 550 so that the carrier element 542 and domer element 550 move as a unit in a radial direction with respect to path P.
The domer assembly also includes biasing means 560 between support 530 and carrier element 542. Biasing means 560 consists of four or more circumferentially equally spaced spring assemblies that each consist of a spring 562 having one end received into a cup 564 which is reciprocated in a bore 566 in carrier element 542 and the opposite end received into a reduced portion 566. The inner end of each cup 564 is received into the enlarged portion of bore 566 and is biased into engagement with the sidewall of the reduced portion 538 of recess 532. Thus, the four or more spring assemblies will always maintain the domer assembly, particularly domer element 550, in a predetermined position with respect to the axis or path P. However, should the axis of punch 24 be slightly offset from the path P, the various spring assemblies will allow carrier element 542 and domer element 550 to move radially with respect to the punch and to accurately align itself with the axis of the punch to produce a satisfactory finished container having a reformed end wall of any particular configuration.
According to another aspect of the invention, domer assembly 526 also includes prestressing means cooperating with the respective spring assemblies for insuring that the domer element 550 is always moved to a same exact centered position with respect to path P when the external forces are removed. For this purpose, a circular or annular ring 570 extends around and is spaced from the periphery of the reduced portion 546 of support carrier 542 and cooperates with the respective spring assemblies to maintain all of the springs in a certain prestressed condition at all times. Ring 570 is accurately positioned with respect to carrier element 542 by a cooperating offset portion 572 and a recess 574 respectively defined on the ring 570 and carrier element 542. Ring 570 is releasably secured to carrier element 542 through a plurality of threaded studs 576.
With this arrangement, the various springs 562 and cups 564 can be positioned into openings 566 and ring 570 can then be telescoped to the position illustrated in Fig. 8 and secured to carrier element 542 through bolts or studs 572. The outer free edge of each of the cups, which is generally spherically shaped, thus cooperates partially with the inner surface of ring 570 to maintain all of the springs in a prestressed condition, regardless of variations in spring force. If there is a need for the carrier element to move radially with respect to path P, only a certain number of spring assemblies, less than all, are further compressed, while the remainder of the spring assemblies remain in the same prestressed condition. Thus, when an external force is removed, after the carrier assembly has been moved off its normally centered position, there is no interference by certain springs preventing the carrier element 542 and domer 550 from moving to the predetermined centered position.
According to a further aspect of the invention, domer assembly 526 also includes fluid means for supplying a bearing fluid between surfaces 540 and 548 of carrier element 542 and support 530. This fluid supply consists of a bore 580 extending through support 530 and in communication at its inner end with an annular recess or opening 582 that extends from surface 540. A pressurized fluid supply, such as air, is attached to the outer end of bore 580 and supplies a constant flow of air to annular recess 582 which must then flow between bearing surfaces 540 and 548 which results in a fluid bearing between the surfaces. Such arrangement reduces the frictional forces encountered when carrier element 542 is attempted to be moved radially of path P.
The carrier element 542 is releasably retained in recess 532 by a cap 590 secured to support 530 by screws 592.
It should be noted that while not specifically shown, lubricating means could also be provided between surfaces 432, 434, 436, and 438 of stripper assembly 32, if desired.
In summary, having all the components, except the punch, that come into contact with the cup during the drawing and ironing process movable radially will result in a finished container having a more uniform wall thickness and will minimize tool damage in case of jams.

Claims

1. A drawing and ironing machine including a frame (30) having a redraw die assembly (26), at least one ironing assembly (28) and a stripper assembly (32), arranged in series and each having an opening to define a path (P) with a punch (24) movable along said path through said openings, the redraw die assembly (26) including a redraw ring (232) defining said opening and resilient centering means (240) between said frame and said ring, characterized by said centering means (240) including a plurality of circumferentially-spaced biasing means (246, 252) producing radial forces on said ring at circumferentially-spaced locations, each of said biasing means being independently biased to a first position when said ring is in a centered position, at least some and less than all of said biasing means moving from said first position to accommodate radial movement of said ring with respect to said path (P).

2. A drawing and ironing machine as defined in Claim 1, in which said redraw ring (232) is carried by a support (230), and the support (230) and the frame (30) have cooperating surfaces (236, 238) extending radially of said path (P) further characterized by means (260, 262) for introducing a fluid between said cooperating surfaces (236, 238).

3. A drawing and ironing machine as defined in Claim 1 or Claim 2 in which the ironing assembly includes an ironing ring (300) carried by a support (304, 312), and which includes resilient centering means between said frame (30) and said support (304, 312), said centering means (330) including a plurality of circumferentially-spaced biasing means (332, 336) producing radial forces on said ironing ring at circumferentially-spaced locations, each of said biasing means (332, 336) being independently biased to a first position when said ironing ring is in a centered position, at least some and less than all of said biasing means (332, 336) moving from said first position to accommodate radial movement of said ironing ring with respect to said path (P).

4. A drawing and ironing machine as defined in Claim 3 in which the support (304, 312) and the frame (30) have cooperating surfaces (320, 322) extending radially of said path (P) further characterized by means (346, 348) for introducing a fluid between said cooperating surfaces (320, 322).

5. A drawing and ironing machine as defined in Claim 1, in which the stripper assembly includes a stripper ring (412) carried by a support (410) and having a plurality of stripping jaws (146) pivoted thereon, and which includes resilient centering means between said frame (30) and said support (410), said centering means including a plurality of circumferentially-spaced biasing means (430) producing radial forces on said stripper ring at circumferentially spaced locations, each of said biasing means (430) being independently biased to a first position when said stripper ring is in a centered position, at least some and less than all of said biasing means (430) moving from said first position to accommodate radial movement of said stripper ring with respect to said path (P).

6. A drawing and ironing machine as defined in any one of Claims 1-5, and including a domer assembly spaced from said stripper assembly, further characterized by said domer assembly including a support (530) having a recess (532) with the base of the recess defining a support surface (540), a carrier element (542) received in said recess and having a cooperating surface (548), a domer element (550) on said carrier element, means (580, 582) for supplying a bearing fluid between said surfaces, and biasing means (560) between said support and carrier element normally maintaining said surfaces in a predetermined position with respect to each other and accommodating movement of said carrier element in all directions within said recess.

7. A drawing and ironing machine as defined in any one of Claims 1-6 and including a cup holder sleeve (20) positioned ahead of said redraw die assembly in the movement of the punch through said redraw die assembly and having an axial bore (22) for receiving said punch, and a sleeve support assembly for said cup holder sleeve, characterized by said sleeve support assembly including a support (40) having an opening (48) therein generally aligned with said opening in said redraw assembly and having a circumferential recess (52) extending from the periphery thereof, a movable support element (60) having a peripheral portion (62) received in said recess (52) and cooperating with one end of said cup holder sleeve, and biasing means (70) between said support (40) and said support element (60) normally maintaining said support element centered with respect to said opening in said support (40) and accommodating radial movement of said one end of said cup holder sleeve and said support element (60) with respect to said support (40).

8. A drawing and ironing machine as defined in Claim 7, further characterized by additional means (90, 92, 102-108) between said support element (60) and said cup holder sleeve (20) accommodating tilting of said axis of said bore (22) with respect to said path (P).

9. A drawing and ironing assembly as defined in Claim 8, further characterized by said additional means including confronting arcuate surfaces (90, 92) between said support element (60) and said cup holder sleeve (20) with at least one of said surfaces having a continuous recess (120) therein and lubricating means (110, 112, 122) for supplying lubricant to said recess.

10. A drawing and ironing machine as defined in any one of Claims 1-9, characterized by said biasing means (246, 252, 332, 336, 430, 560) including four circumferentially spaced spring assemblies each including a plunger having a shoulder with a spring normally biasing said shoulder into engagement with a stop defining said centered position.