US2914311A - Gear quenching apparatus and method - Google Patents

Description

Nov. 24, 1959 Filed Aug. 24, 1956 J. L YARNE I GEAR QUENCHING APPARATUS AND METHOD 6 Shets-Shet 1 @501 @[Q C36] OJQ] QIQI INVENTOR JOHN L. VAR/v5 ATTORNEYS Nov. 24, 1959 J. LQYARNE 2,914,311

' L GEAR QUENCHING APPARATUS AND METHOD Fi1ed AugIj24, 1956 v s Sheets-Sheet 2 Q INVENTOR JOHN A. )ZRNE ATTORNEYS Nov. 24,1959 7 J, L, YARNE I 2,914,311

GEAR QUENCHING APPARATUS AND METHOD Filed Aug. 24, 1956 6 Sheets-Sheet 3 V/AIIIIIIW/A 1%,,

INVENTOR c/OHN L.-}/A RNA-I ATTORNEY 5 1959 J. L. YARNE 2,914,311

GEAR QUENCHING APPARATUS AND METHOD Filed Aug. 24. 1956 s snee ts sh et 4 INVENTOR JOHN L. )QIRNE I BY ATTORNEY5 Nov. 24, 1959 J. L. YARNE GEAR QUENCHING APPARATUS AND METHOD 6 Sheets-Sheet 5 Filed Aug. 24, 1956 v I l I l I I ml lm Q Q g g w ayw ATTORNEYS Nov. 24, 1959 J. L. YARNE 2,914,311

GEAR QUENCHING APPARATUS AND METHOD Filed Aug. 24, 1956 v 6 Sheets-Sheet 6 Q Q INVENTOR JOHN L. XZMNE ATTORNEYS United States Patent GEAR QUENCHING APPARATUS AND METHOD John L. Yarne, Oshkosh, Wis., assignor to Rockwell- Standard Corporation, a corporation of Pennsylvania Application August 24, 1956, Serial No. 606,162

14 Claims. (Cl. 266-6) This invention relates to improvements in processes and apparatus for quenching heat treated gears and like parts and is directed primarily to improvements in the apparatus for, and method of quenching parts which are formed with web and rim portions which are of differing thicknesses.

In the past in quenching helcal gears it has been the general practice to rigidly hold the gear face fiat and the inner bore of the gear web, all of which have been machined to very close tolerances, rigidly to maintain the machined dimensions. With spur and helical gears it has been the practice to hold the gear faces flat and not to restrain the gear web faces. The inner bore of the gear web with this old practice is held rigidly round by an expansible segmented die.

While the need for holding the other machined surfaces rigid during the quenching operation to prevent warping, distortion and tapering is obvious, it has been found impracticable in commercial practice by previously tried methods and apparatus because of the difliculty of consistently maintaining the high degree of accuracy necessary even within tolerance variations in the thicknesses of the web and rim portions of such parts.

These prior practices, permitted warpage, out of fiat, tapering and out of roundness to appear and/or to become magnified during the quenching cycle.

The primary object of this invention is, therefore, to provide a new improved means and method for maintaining gears and like articles both in round and flat as machined during a quenching operation for heat treatment.

Another object is to provide an improved quenching press which utilizes coacting lower and upper die assemblies which are effective to confine both the web and rim portion of gears and like articles to maintain them in there as machined configuration during quenching.

A further object is to provide an improved apparatus for and method of holding the inner bore of a gear rigidly in round by a lower expansible segmented die and upper pilot and the lower face or faces of the gear precisely fiat as machined during quenching.

Another object is to provide an improved apparatus embodying backing means for upper die members which is deformable so as to effect a uniform unit area force balance backing for top die assembly members which is-elfective to-accommodate in tolerance variations in the size of parts being quenched and maintain such parts in there as machined configurat on during quenching.

A further object is to provide an improved apparatus embodying flexible upper die segment backing means which is resistant to heat and impervious to oil.

Another object is to provide an improved apparatus embodying a constrained flexible member functioning in the manner of an incompressible fluid to resist the tendency of multiple gear surfaces to distort and to limit distortion of other integral parts of the gear including gear teeth during quenching.

A further object is to provide an improved quenching apparatus for gears and the like embodying a flexible body held in place in an upper die assembly by multiple annular upper die face members.

Another object is to provide an improved quenching apparatus for gears and the like embodying an upper die assembly flexible annular body member such as an annular body which is a mixture of a chloroprene polymer and the synthetic rubber product made by polymerization of butadiene, acrylonitrile or styrene having a hardness in the order of 40 durometer.

A further object is an upper die assembly flexible annular body member such as an annular flexible heat and oil resistant shell enclosing a fluid web as a silicone fluid.

Another object'is to provide a quenching press embodyng resiliently compressible annular body members inserted in an upper die assembly for backing individual annular upper die segments.

These and further objects of the present invention will become apparent from the following detailed descrip tion, when considered in connection with the accompanying drawlngs and the appended claims.

In the drawings which illustrate several simple and practical embodiments of the invention:

Figure 1 is a perspective view of a quenching press embodying the present invention;

Figure 2 is a vertical section through the upper and lower die assemblies of the quenching press of Figure 1 showing the dies in their closed position;

Figure 3 is a view similar to Figure 2 showing the die assemblies in their open position;

Figure 4 is a view similar to Figure 2 showing the distribution of quenching fluid during actual quenching;

Figure 5 is a view similar to Figure 2 illustrating a second embodiment of the invention;

Figure 6 is a view similar to Figure 2 illustrating a third embodiment of the invention;

Figure 6A is an enlarged portion of Figure 6; and

Figure 7 is a view similar to Figure 2 illustrating a fourth embodiment of the invention.

Referring now to the drawings and particularly to Figure 1, the quenching press 10 therein illustrated comprises basically a rigid frame structure 12 upon which is mounted a lower die assembly 14 and an upper die assembly 16. The lower die assembly comprises a support plate 18 which is mounted for horizontal translatory movement between the forward gear loading and unloading position as shown in Figure l and a rear operative position coaxially aligned beneath the upper die assembly 16, a plurality of annular gear supporting die rings 20 disposed one within the other to provide a grid-like supporting surface for the lower face of the gear to be quenched, and a plurality of die segments 22 mounted on the base plate 18 for radially outward expanding movement within the bore of the gear to be quenched to engage the bore and to hold it in perfect roundness during the quenching operation. In the structure of Figure 1, the gear to be quenched is a hypoid gear 24 shown mounted upon the supporting annular die rings 20 and in surrounding relation to the radially expansible die segments 22.

The quenching press 10 is an automatically cycling machine. After the gear to be quenched has been placed upon the lower die assembly 14 and the cycle of operation initiated, the lower die assembly is moved to the rear to a position coaxially beneath the upper die assembly 16. This position is illustrated in cross section in Figure 3. The upper die assembly is then lowered under hydraulic pressure to the position shown in Figure 2 to form a fluid tight chamber enveloping the gear to be quenched. This chamber is then flooded with oil, water, or other suitable quenching fluid as illustrated in Figure 4. After the initial flooding of the chamber defined by the upper and lower die assemblies 14 and 16, quenching fluid is continuously introduced into the bottom of the lower die assembly 14 through the passage 26 at a predetermined rate in accordance with the rate of cooling by the gear desired. After cooling of the gear 24 to a temperature in which it may be readily handled, the quenching fluid is exhausted from the chamber defined by the lower and upper die assemblies 14 and 16, the upper die assembly raised under hydraulic pressure to the position shown in Figure 3, and the lower die assembly 14 moved to its position shown in Figure 1 to permit removal of the quenched gear 24 and reloading of the lower die assembly 14 with the next gear to be quenched.

Referring to Figure 2, lower die assembly 14 is provided with a generally hollow base casting 28 formed with an integral apertured transverse web 30 in the top of which is formed a recess 32 in which the plate 18 is received. Plate 18 is formed with spaced apertures 34 adjacent its periphery and a central aperture 36 at its center. The plate 18 is in turn formed with a recess 38 in which is received a plate 40 having a central aperture 42 coaxial with the aperture 36 in base plate 18. Support plate 40 is in turn formed with a cylindrical recess 42 in which are received the lower die rings 20 disposed one within the other. The upper surfaces 44 of the die rings 20 lie in a common plane and are formed with radially extending through slots 46. The slots 46 on each of the rings 20 are circumferentially offset relative to the slots 46 of each adjacent one of the rings 20 so that, as v ewed from above, the slots 46 in the rings 20 form a grid pattern defining a planar support surface pocketed by the recesses 46 through which quenching fluid may circulate beneath the gear 24.

The lower portions of the die segments 22 form a segmented cylinder received within the cylindrical aperture 48 through the innermost one of the die segments 20 and are provided with radially outwardly projecting portions 50 terminating in segmental cylindrical surfaces 52 provided with axially extending slots therein 54. Segments 22 coact to define a upwardly opening frusto-conical recess 56 into which the frusto-conical end portion 58 of the plunger or pilot 60 of the upper die assembly 16 is received when the upper die assembly 16 is lowered to a position shown in Figure 2. The downward movement of the plunger 60 from the position shown in Figure 3, through the mating engagement between the frusto-conical portion 58 of pilot 60 and frusto-conical recess 56 produces a wedging action which wedges the die segments 22 radially outward to expand them into rigid engagement with the bore 62 of the gear 24 to hold the bore 62 in perfect cylindrical form as machined during the quenching operation.

The upper die assembly comprises a main hydraulicall ly actuated backing plate or ram 64, and annular plate 66 received within a piloting recess 68 formed in the backing plate 64, a support plate 70 piloted within a cylindrical recess 72 in the plate 66 affixed thereto by suitably circumferentially spaced bolts 74. The backing plate 64 is formed with a central hydraulic cylinder 76 into which hydraulic fluid is introduced automatically and selectively through a duct (not shown) and in which is axially slidably received a piston 78 integral with the pilot 60. The piston 78 is retained within the bore 76 of the member 64 by a retainer ring 80 received within a cylindrical recess 82 formed in the end wall of recess 68 coaxially with the cylinder 76. Retainer 80, plate 66, and support plate 70 are formed respectively with through apertures 84, 86, and 88 through which the pilot 60 projects for free vertical relative movement therethrough. Plate 66 and retainer 80 are affixed to the backing plate 64 by suitable means not shown.

Support member 70 is formed with an annular recess 90 defined by an outer cylindrical wall 92, an inner cylin;

drical wall 94 coaxial with wall 92, and an end wall 96 normal to the axis of cylindrical walls 92 and 94. A pair of annular die rings 98 and 100 are received in juxtaposition within the recess for independent axial sliding movement therein. Die rings 98 and are formed respectively with aligned through apertures 102 and 104 which are elongated in the axial direction of rings 98 and 100 and through which project a retainer bolt 106 which extends through an aligned piloting aperture 108 in the outer annular wall 110 of support member 70 through the apertures 102 and 104 and is threadedly received in a threaded hole 112 in the inner annular wall 114 of the support member 70. The bolts 108 extend radially relative to the axis of the die rings 98 and 100 and are located at symmetrically spaced positions about that axis. The diameter of the shank of the bolt 106 is sufficiently smaller than the larger dimension of the elongated apertures 102 and 104 to permit free axial movement of the rings 98 and 100 within the recess 90 over a limited distance between the positions in which the opposite end walls of the apertures 102 and 104 abut the adjacent sides of the bolt 108.

An annular flexible deformable backing ring 116 is received within the recess 90 against the end wall 96 above the rings 98 and 100 to provide a flexible backing support for those rings which is effective to equalize the axial forces applied to rings 98 and 100.

The die ring 100 terminates in a planar end face 118 normal to the axis of ring 100 which is formed with a plurality of symmetrically circumferentially spaced radially extending through slots 120 to permit circulation of oil therethrough. The end face 118 abuts the top planar surface of web 122 of the gear 24 when the upper die assembly is lowered to the position shown in Figure 2 from the open position shown in Figure 3 and is effective to maintain the web 122 of the gear 24 firmly biased against the top surface 44 of the supporting die rings 20 and maintain the web 122 perfectly flat in its machined condition during the quenching operation. The outer die ring 98 terminates in a concave frusto-conical face 124 having an apex angle complementary to the apex angle of the frusto-conical profile of the outer faces of teeth 126 on the hypoid or bevel gear 24 and, with the upper die assembly in the position of Figure 2, firmly abuts the outer faces of the teeth 126 to hold the outer portion of the gear 24 firmly against the surface 44 of the lower die rings 20. The upper die rings 98 and 100 are axially movable independently and thus can compensate for in tolerance variations in the thickness of the web 122 and the thickness of the outer rim portion of the gear 24 and the differential contraction, if any, of the web and outer rim portion during the quenching operation and maintains such web and outer rim portion firmly in there as machined condition during the entire quenching operation.

The annular ring 116 is a body of incompressible yet flexible heat and oil resistant material and is fully confined radially between the cylindrical walls 92 and 94 and axially between the end wall 96 and the opposed upper end faces of the annular die rings 98 and 100. The annular ring 116, which is preferably formed of a mixture of a chloroprene polymer and the synthetic rubber product made by polymerization of butadiene, acrylonitrile or styrene having a hardness of 40 durometer, llexibly balances the downward force of the backing plate or ram 64 between the inner and outer die rings 98 and 100 allowing for dimensional differences between gears and yet clamping each gear in alignment while still in its hot plastic state and throughout quenching. The deformation of ring 116 is analogous to the deformation of a body of incompressible fluid similarly fully confined.

The ram 64 is provided with a cylindrical hood 130 fixed to the periphery thereof in fluid tight relation and which, when lowered to the position shown in Figure 2, is effective at its lower edge to form a fluid tight seal at the base 28 to thus form a chamber 132 enveloping the gear 24 and the upper and lower dies 98, 100, 20 and 22 and into which quenching fluid such as oil or water is introduced to efiect the quenching of the gear 24. The ram 64 and the plate 66 are formed with aligned fluid passages 134 and 136 at a plurality of spaced point to permit discharge of the quenching fluid from the chamber 132. During the quenching operation, referrlng to Figure 4, quenching fluid is introduced through the opening 26 into the chamber 132 and passes out through the apertures 134 in the ram 64, apertures 134 b e1ng connected by suitable means not shown to a receiving reservoir. Figure 4 illustrates the manner in which the chamber 132 is completely flooded with quenching fluid. The control of the rate of flow of quenching fluid to and from chamber 132 is the same as in the prior conventional practice with quenching presses of this type.

The raising and lowering of ram 64 is effected by hydraulic actuation of ram 64 by hydraulic actuating means (not shown). The piston 78 is hydraulically independent of the actuating means for ram 64, so that the two pistons (that acting on ram 64 and piston 78) can exert d fferent degrees of pressure to compensate for any variatlons 1n the metals behavior during quenching.

Figure 5 illustrates an improved quenching press embodying die rings adapted to support a spur gear having either helical or straight teeth or a similar flat article. As in the previous embodiment, the embodiment of Figure 5 includes an upper ram 150 having a tubular hood 152 which coacts with a die assembly support plate 154 an annular bottom recess 208 defined by the inner cylinand its mount to form a fluid tight quenching chamber 156 into which quenching fluid is introduced through apertures 158 and 168 in plate 154 and from which it is exhausted through aperture 162 in ram 150 and aligned aperture 164 in a plate 166 fixed to the ram 150. A plurality of lower die rings 168a to 16811 are received in nested relationship one within the other within the recess 170 in the top surface of the support plate 154 and supported by the end wall 172 or recess 170. The upper surface 174 of the rings 168a to 168k are each formed with a plurality of equiangularly disposed radially extending through slots 176 which in assembly are clrcumferentially offset relative to the slots 176 of the adjacent one of the rings 168a to 168k to provide a firm continuous support surface while permitting free circulation of quenching fluid through the slots 176 beneath the supporting surface 174. The innermost one of the die rings 168a supports a plurality of radially movable die segments 180 each of which is formed with axially extending exterior surface slots 182 to permit the free circulation of quenching fluid through the bore of the gear to be quenched.

The radially movable die segments 180 are shifted radially outward to their expanded position in firm engagement with the bore 184 of the web 186 of the gear 188 by the downward movement of the pilot 190 mounted on the ram 150 and independently hydraulically actuated in a manner identical with the structure previously described in reference to Figures 2 to 4 by the wedging action of its convex frusto conical end portion 192 with the complementarily concave frusto conical recess defined by the segmental frusto conical surfaces 194 of the die segments 180.

A die ring or supplemental backing ring 168 surrounds the die segments 180 above the die ring 168b and is supported by die ring 168b through a shim 196 interposed therebetween. The upper surface of the die ring 168j is formed with equi-angularly disposed radially extending top surface slots 198 which permit free circulation of quenching fluid beneath the web 186 of the gear 188 which is supported by the top surface 200 of die ring A support member 202 received in a recess 204 of the plate 166 affixed thereto by screws 206 is formed with drical wall 210 of an outer annular portion 212, the outer cylindrical surface 214 of inner annular wall portion 216 and an end wall 218 which is normal to the common axis of the surfaces 210 and 214. A pair of die rings 220 and 222 are received in axial sliding engagement in the recess 208 and are retained therein independently by retainer screws 224 and 226 engaging axially elongated slots 228 and 230 formed respectively in the inner wall of inner die'ring 220 and the outer wall of outer die ring 222 to permit free axial movement of die rings 220 and 222 over a limited distance independently of one another. A flexible backing ring 232 of the same form as the ring 116 of the embodiment of Figure 2 is received within the recess 204 between the end wall 218 and the die rings 220 and 222 in fully confined relation. The lower face 234 of the inner die ring 220 is a planar surface normal to the axis of die ring 220 which abuts the top face of the web 186 of the gear 188 and which is formed with a plurality of radially extending surface slots 236 to permit the free circulation of quenchng fluid over the top surface of the web 186 of the gear 188. Similarly, the bottom surface 238 of the die ring 222 is planar and normal to the axis of the die ring 222 to abut the top surface of the rim portion of the gear 188 to firmly hold the rim portion against the die rings 168d, e and 1 during the quenching operation. Surface slots 240 are formed through the bottom surface 238 of outer die ring 222 to permit free circulation of quenching fluid over the rim of the gear 188 in the same manner as in the other die rings.

As in the previous embodiment of the invention the die rings 2 20 and 222 are firmly biased against the web and rim of the gear 188 under the force equalizing action of the ring 32 which accommodates for the in tolerance variations in the dimensions of the web and rim of the gear 183 and both the rim and web of the gear 188 are maintained in there as machined condition during the quenching operation without warpage and contraction of the gear during quenching is accommodated while maintaining the gear firmly confined.

Referring to Figure 6, the embodiment therein illustrated is with but one exception structurally identical with the embodiment illustrated in Figure 5, the corresponding parts having been assigned like reference numerals.

. The distinction between the embodiment of Figure 5 and embodiment of Figure 6 is in the structure of the backing ring 232 which, as is most clearly illustrated in Figure 6A, comprises a heat and oil resistance flexible annular shell 250, such as the 40 durometer hardness mixture of a chloroprene polymer and the synthetic rubber product made by polymerization of butadiene, acrylonitrile or styrene previously referred to, which forms a sealed annular chamber 252 in which is confined a body of incompressible fluid 254 which completely fills chamher 252. The fluid 254 within the chamber 252 is preferably one of the silicone fluids. The force equalizing action of the ring 232' containing the incompressible fluid 254 is substantially identical with that of the ring 232 of the embodiment of Figure 5.

A further embodiment of the invention is illustrated in Figure 7. With the exception of the structure of the support member 202' and the components mounted thereon, the structure of the quenching press is identical with that which has been described in detail with reference to Figure 5, like reference numerals having been assigned to the corresponding parts in Figure 7 and no further detailed description of the identical structure being considered necessary.

The upper die support member 202' is formed with three concentric annular wall portions 260, 262 and 264 which define a pair of concentric annular recesses 266 and 268. Recess 266 is defined by an inner annular wall 270 and an outer annular wall 272 concentric with wall 270 and an end wall 274 normal to the common axis of 270 and 272. Similarly, recess 268 is defined by an outer wall 276, an inner annular wall 278 concentric with wall 276 and an end wall 280 normal to the common axis of walls 276 and 278. An outer annular die ring 282 is axially slidably received within the recess 266, the limits of its axial movement therein being defined by the engagement of a stop screw 284 with an axially elongated slot 286 formed in the exterior periphery surface of ring 282. A flexible resilient compressible annular backing ring 288 is confined within the recess 266 against the end wall 274 thereof by the die ring 282. Similarly the inner die ring 299 is axially slidably received within the recess 268, its limits of movement being defined by the engagement between a stop screw 292 and an axially elongated slot 294 formed in the inner annular surface of the ring 298. A flexible resilient compressible annular backing ring 296 is confined within the recess 268 in abutment with the end wall 280 by the die ring 290. Die rings 282 and 298 are formed with symmetrically circumferentially arranged radially extending slots 298 and 308 respectively in their end surfaces 302 and 304 which, respectively, abut the top surface of the rim of the gear 188 and the top surface of the web 186 of the gear 188. Slots 298 and 300 permit free quenching fluid circulation over these surfaces as in the previous embodiments. The provision of independent rings 288 and 296 for the outer and inner die rings 282 and 290 provides sufficient take up for each of these die rings to maintain alignment of the respective die engaged portions of the gear 188 no matter how much the dimensions of the various gear portions may vary from gear to gear within even extremely wide manufacturing tolerances.

From the foregoing it is apparent that there are hereby provided new processes and proved apparatuses for maintaining alignment of heat treated gears during quenching. It provides new improved upper die assemblies for quenching processes. It provides backing means for multiple upper dies which are of heat and oil resistant relatively incompressible material and yet flexible so as to effect unit area force balance backing for the multiple top dies. It provides solid flexible annular members and also flexible shell fluid filled annular members either of which may be used to back up a multiple upper die or dies of a quenching press. It also provides an upper quenching press die assembly with multiple dies each of which is individually backed by a resiliently compressible material.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a quenching press for articles having a web and a rim of differing thicknesses, opposed relatively movable upper and lower die assemblies adapted when in closed position to axially and independently confine the rim and web of such article to prevent distortion thereof during quenching while permitting the free circulation of quenching fluid over such article, one of said die assemblies having radially separate rigid relatively axially movable annular elements for engaging respectively the rim and web of the article disposed between the die assemblies, and flexible force transmitting means backing said elements for permitting such slight relative axial displacement between said elements as to enable both of said elements to engage said article With sufficient axial force to prevent said distortion.

2. In a quenching press for articles having a web and rim of differing thicknesses, opposed relatively movable upper and lower die assemblies adapted when in closed position to axially confine the rim and web of such article with sufficient force to prevent distortion thereof during quenching while permitting the free circulation of quenching fluid over such article, said upper die assembly comprising inner and outer independently axially movable annular dies adapted to engage the upper surfaces of the article web and rim respectively and flexible force transmitting backing means for at least one of said dies effective to compensate for tolerance variations in the thickness of said web and rim in different articles held in said press.

3. The combination defined in claim 2 wherein said flexible backing means comprises a confined deformable ring individual to each of said dies.

4. The combination defined in claim 2, wherein said flexible backing means comprises a single deformable annulus common to both of said annular dies.

5. In a quenching press for articles having a web and rim of different thicknesses, opposed relatively movable upper and lower die assemblies adapted when in closed position to axially confine the rim and web of such article to prevent distortion thereof during quenching while permitting the free circulation of quenching fluid over such article, at least one of said die assemblies comprising inner and outer independently axially movable rigid dies adapted respectively to engage the corresponding surfaces of the article web and rim respectively, and flexible force transmitting backing means for said dies effective to compensate for tolerance variations in the thicknesses of said web and rim of different articles held in the press, said flexible backing means comprising a deformable substantially incompressible confined ring common to both of said dies operative to substantially equalize the forces exerted by said dies on an article to be quenched.

6. The combination defined in claim 5 wherein said ring is a unitary body of synthetic rubber having a hardness in the order of 40 durometer.

7. The combination defined in claim 4 wherein said ring is an integral body of synthetic rubber material composed essentially of a mixture of chloroprene polymer and the polymerization product of butadiene, acrylonitrile or styrene or mixtures thereof.

8. The combination defined in claim 5 wherein said ring is an annular flexible heat and oil resistant shell and a body of liquid confined within the said shell.

9. The combination defined in claim 8 wherein the confined liquid is a silicone.

10. In a quenching apparatus for a gear or like article having rim and web portions of different axial thickness, upper and lower die assemblies adapted to be brought together to hold said article between them, one of said die assemblies having at least two radially separate rigid annular article engaging members mounted thereon so as to be capable of relative axial displacement, and flexible force transmitting means in the mounting for said members permitting said relative displacement but maintaining operative engagement of said members with the article held between said die assemblies.

11. In the apparatus defined in claim 10, said lastnamed means comprising an annulus of heat resistant synthetic rubber backing both said members in said one die assembly.

12. In the apparatus defined in claim 10, said lastnamed means comprising separate rings of heat resistant synthetic rubber independently backing said members in said one die assembly.

13. In the apparatus defined in claim 10, said lastnamed means comprising an annulus of heat resistant synthetic rubber backing at least one of said members insaid one die assembly.

14. In the apparatus defined in claim 10, said lastsembly.

References Cited in the file of this patent UNITED STATES PATENTS Lehmann July 1, 1924 10 White Nov. 10, 1925 Joksch June 4, 1929 Bauer Jan. 17, 1950 Vickers June 12, 1951 Doyle Dec. 15, 1953

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