US3564884A - Deformable die apparatus for tube drawing - Google Patents

Abstract

VARIABLE DIE APPARATUS FOR TUBE DRAWING WHEREIN A DIE RING OF DEFORMABLE MATERIAL, PREFERABLY A STRONG ELASTOMER, IS CIRCUMFERENTIALLY CONFINED AND IS CAUSED TO BE DEFORMED BY FORCE-APPLYING MEANS SO THAT ITS INNER DIAMETER VARIES, SAID FORCE-APPLYING MEANS PREFERABLY BEING HYDRAULICALLY ACTUATED AND OPERATING UPON THE DEFORMABLE DIE RING EXTERNALLY IN ONE FORM OF THE INVENTION AND INTERNALLY IN ANOTHER FORM OF THE INVENTION.

Description

Feb. 23, 1971 w H|N$HAw 3,564,884

DEFORMABLE DIE APPARATUS FOR TUBE DRAWING Filed Aug. 20, 1968 2 Sheets-Sheet 1 fvvs/vrae f JIM/v W II/Mswnw s WM 07 roe/vs Vs.

Feb. 23, 1971 J. w. HINSHAW DEFORMABLE DIE APPARATUS FOR TUBE DRAWING Filed Aug. 20, 1968 2 Sheets-Sheet 2 IN YEN 70A? Jb/wv I4 Ll/Nsunw IOTTOENEr J- United States Patent 3,564,884 DEFORMABLE DIE APPARATUS FOR TUBE DRAWING John W. Hinshaw, Garden Grove, Califi, assignor to Battelle Development Corporation, Columbus, Ohio, a corporation of Delaware Filed Aug. 20, 1968, Ser. No. 753,907 Int. Cl. B21c 3/06 US. Cl 72--57 6 Claims ABSTRACT OF THE DISCLOSURE Variable die apparatus for tube drawing wherein a die ring of deformable material, preferably a strong elastomer, is circumferentially confined and is caused to be deformed by force-applying means so that its inner diameter varies, said force-applying means preferably being hydraulically actuated and operating upon the deformable die ring externally in one form of the invention and internally in another form of the invention.

BACKGROUND OF THE INVENTION In some types of tube drawing operations, as for example in the drawing of cylindrical tubing into a tapered configuration, it is necessary to employ a drawing die which is variable in ID. According to typical prior art practice such a variable drawing die will be composed of a solid metal ring which is sufficiently ductile to allow the ring to expand as it draws the tube down against a tapered mandrel from the small diameter end of the mandrel up to the large diameter end thereof.

A major problem in the use of this and other variable die devices employed in the prior art for tube drawing was that the operator had very little control over the changes in the die shape and size, or in the amount of radially inwardly directed confining force which the die had on the workpiece. A related problem in connection with the use of such prior art variable tube drawing dies was that in general they would only function satisfactorily over a relatively small variation in size.

A still further problem in connection with conventional variable dies for tube drawing is that while such dies could sometimes be made fairly reliable for tube drawing operations wherein the die would expand, as for example when drawing up a taper, they nevertheless were generally ineffective or unreliable where attempts were made to constrict them during a drawing operation, as for example when drawing down a taper.

SUMMARY OF THE INVENTION In view of these and other problems in the art, it is an object of the present invention to provide variable die apparatus for tube drawing which employs as the means operating upon the tube a die ring composed of a material such as an elastomer which is deformable over a much greater range of sizes and shapes than a conventional metal drawing die ring, the apparatus including selectively operable means for deforming the die ring radially inwardly or relaxing the die ring from such deformed condi tion, whereby tubing can be drawn with large variations in its diameter and cross-sectional configuration.

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Another object of the invention is to provide variable die apparatus of the character described for tube drawing wherein the deformable die ring employed therein is composed of a strong material which has good elastic properties, whereby the deformable die ring will elastica ly return to substantially its initial undistorted condition after completion of a tube drawing operation therewith, permitting the deformable die ring to be reused for a number of different tube drawing operations.

A further object of the invention is to provide variable die apparatus of the character described for tube drawing wherein the deformable die ring which operates upon the tube is circumferentially confined and is caused to be deformed for variation of its ID by hydraulically actuated means which affords the operator wide latitude in controlling the ID of the deformable die ring and in the amount of constricting force of the deformable die ring against the tube that is being drawn.

A still further object of the invention is to provide variable die apparatus of the character described wherein the die ring of deformable material is circumferentially confined and is varied in ID by axial compression of the ring between opposed surfaces on members which are adjustable relative to each other in the axial direction, preferably by hydraulically actuated means.

Another object is to provide variable die apparatus of the character described wherein the deformable die ring which operates directly upon the tubing that is being drawn is hydraulically actuated for variation of the ID thereof and the amount of force applied by the ring against the tubing by application of hydraulic pressure to the inside of the deformable die ring and release of such pressure therefrom.

An additional object of the invention is to provide variable die apparatus of the character described for tube drawing wherein the die ring is composed principally of a deformable material such as a strong e astomer, but also includes an expansible spring metal core which tends to retain the initial cross-sectional shape of the die ring as the die ring contracts or expands circumferentially and hence radially.

Further objects and advantages of the present invention will appear during the course of the following part of this specification, wherein the details of construction and mode of operation of several preferred embodiments are described with reference to the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial section illustrating assembled deformable die apparatus according to the invention with the parts thereof in their unactuated condition and the deformable die ring in its relaxed condition.

FIG. 2 is a fragmentary axial section similar to FIG. 1, but illustrating the apparatus in an actuated condition, with the deformable die ring deformed and squeezed inwardly, the apparatus having been employed to draw down a taper.

FIG. 3 is a cross-sectional view taken on the line 33 in FIG. 2.

FIG. 4 is a side elevational view, partly in axial section, of the deformable die ring of FIGS. 1 and 2 separated from the remainder of the apparatus and in its relaxed condition.

FIG. is a side elevational view, partly in axial section, similar to FIG. 4, but illustrating a second form of deformable die ring which includes an expansible, split spring metal ring molded therein to increase the crosssectional rigidity of the deformable die ring.

FIG. 6 is an axial sectional view similar to FIG. 2, but illustrating the apparatus after it has been employed to draw back up a taper on the same tube, the apparatus still being slightly actuated :but approaching return to its condition of repose.

FIG. 7 is an axial section, partly in elevation, illustrating variable die apparatus similar to that shown in FIGS. 1 to 6, but wherein the deformable die ring is of generally hexagonal shape, and is in the process of applying a taper of hexagonal cross-section to an initial cylindrical tube.

FIG. 8 is a cross-sectional view taken on the line 8-8 in FIG. 7.

FIG. 9 is a perspective view of the piston portion of the apparatus shown in FIGS. 7 and 8, with the hexagonal die ring of deformable material shown in phantom in axially exploded relationship relative to the piston.

FIG. 10 is an axial sectional view showing still another form of die ring according to the invention disposed in its die holder seat, this form of ring defining a hollow annulus therein for receiving hydraulic fluid under pressure to cause radial deformation thereof.

DETAILED DESCRIPTION Referring at first to FIGS. 1 to 4 of the drawings, the deformable die apparatus which is illustrated in these figures employs a die ring 10 composed of a plastic material which is resiliently deformable. The hardness of the deformable die material will vary according to the strength and thickness of the wall of the tubing that is being drawn, and according to the configuration to which the tubing is being drawn. However, where the apparatus is to be employed for drawing most types of metal tubing, it is preferred that the deformable die ring 10 be composed of an elastomer material which has the characteristics of being generally rigid and tough, but deformable or distortable upon the application of substantial unbalanced forces thereto. A material which has been found particularly suitable for use as a deformable die ring in drawing tapered copper and aluminum tubes is Elastacast polyurethane produced b Acushnet Process Company. It is to be understood, however, that the present invention is not limited to the use of any particular resilient deformable material for the deformable die ring 10, and that a variety of different materials will be suitable for different tube drawing applications.

The deformable die ring 10 includes generally flat, parallel side surfaces 12', a generally cylindrical annular outer surface 14, and an inner annular surface 16 which is rounded in cross-section.

The deformable die ring 10 is supported in a die holder sleeve 18 having an annular body portion 20, a generally flat or radially oriented annular shoulder 22 against which one of the side surfaces 12 of die ring 10 seats, and a generally cylindrical skirt portion 24 which is preferably slightly greater in axial dimension from the shoulder 22 than the thickness of the die ring 10 between its side surfaces 12. Thus, the deformable die ring 10 in its relaxed condition as shown in FIGS. 4 and 1 fits entirely within the cylindrical skirt portion 24 of the die holder sleeve 18, being slightly recessed inwardly from the outer end of the skirt 24, and seating flush against the shoulder portion 22 of die holder sleeve 18.

The die holder sleeve 18 is mounted inside a 'hydraulic cylinder generally designated 26, and including a cylindrical barrel 28 within which the sleeve 18 is fitted. The cylinder 26 has an end plate 30 on one end thereof against which the body portion of the die holder sleeve 18 4 abuts, the end plate including a cylindrical flange threadedly connecting the end plate 30 to the barrel 28. The end plate 30 has a central aperture 34 therethrough which is axially aligned with, and substantially the same size as, the passage through the body portion 20 of die holder sleeve 18.

The cylinder'barrel 28 is provided with an in-turned end flange 36 at its other end, the flange 36 defining a circular aperature 38 that is somewhat larger in diameter than the aperture 34 in end plate 30.

A piston 40 is slidably engageable within the cylinder barrel 28, and is integrally formed on the inner end of a hollow piston rod 42 which extends out through the aperture 38 defined by the cylinder end flange 36. A pair of T sealing rings 44 on the piston provide a fluid-tight seal between the piston and cylinder barrel, and the fluid-tight seal within the cylinder between the piston and cylinder end flange 36 is completed by a further sealing ring 46 in the cylinder end flange aperture 38.

Hydraulic fluid is introducible through fluid line 48 from a suitable fluid pressure source (not shown) and through port 50 into the annular cylinder chamber 52 behind piston 40 to drive the piston to the right as illustrated in FIGS. 1 and 2. The piston includes an annular pressure face 54 which is engageable against the exposed side surface 12 of the deformable die ring 10 as the piston is forced to the right in FIGS. 1 and 2, to compress the die ring 10 in the axial direction and thereby force the rounded inner die surface 16 to constrict from its position of repose as illustrated in FIG. 1 to a substantially constricted position as illustrated in FIG. 2. It will be noted that the annular pressure face 54 on the piston is slightly frusto-conical in configuration. This angle on the pressure face 54 causes the inner peripheral edge of the face 54 to first contact the deformable die ring 10 adjacent the rounded inner working surface 16 of the die ring. Then, as the inclined pressure face 54 compresses the deformable die ring 10 it tends to lock the die ring material in its operative position and to direct the displaced ring material substantailly entirely radially inwardly as best illustrated in FIG. 2.

It will be apparent that the greater the hydraulic pressure applied in the cylinder chamber 52, the tighter the piston will axially squeeze the deformable die ring 10, and the greater the radially inwardly directed deformation of the die ring 10 will be. Conversely, by allowing the hydraulic pressure to bleed out of cylinder chamber 52 through port 50 and conduit 48, the resiliency of the deformable die ring 10 will cause the die ring to resume its original, relaxed shape as illustrated in FIGS. 1 and 4, the die ring moving the piston 40 back to the left as it thus resumes its initial configuration. Accordingly, the fluid pressure source connected to fluid conduit 48 is adapted to supply fluid over a Wide range of pressures 'as required for any particular forming operation, and is also provided with bleeder valve means to allow selective reduction of the pressure from the cylinder when desired.

The piston is provided with an annular recess immediately radially outwardly of the pressure face 54 thereon to accommodate the outer edge portion of the die holder skirt 24 as best shown in FIG. 2. By this means, the outer peripheral edge of the deformable die ring 10 is substantially completely circumferentially confined during the time that the piston 40 is applying axial compression to the die ring 10.

FIG. 2 illustrates a tube drawing operation wherein an initially cylindrical tube 58 is supported at one end by an end plug 60 and clamped at that end between jaws 62 to secure that end of the tube against axial movement, and the tube 58 is then moved axially to the right while hydraulic fluid pressure is increased in the cylinder chamber 52 so that the piston gradually squeezes the deformable die ring 10 radially inwardly to apply a taper 64 to the tube 58. Drawing down the taper as illustrated in FIG. 2 can be accomplished by the present invention without requiring that the taper be drawn over a tapered mandrel. Drawing down a taper is very difficult to accomplish with conventional variable drawing dies, while it is relatively easy to accomplish with the present invention.

FIG. illustrates a second form of deformable die ring a which is the same as die ring 10 except for the inclusion within the resilient plastic material of an expansible, split spring metal ring 66 having a generally circular overall cross-sectional shape. This metal ring 66 assists the deformable die ring 10a to retain the desired curvature of its rounded inner working surface 16a as the die ring is being compressed axially and thereby deformed radially inwardly.

FIG. 6 shows the deformable die apparatus of FIGS. 1 to 4 with the tube 58 drawn further therethrough in such a way as to draw back a taper after reaching a point 68 along the tube 58 of desired minimum diameter. As the portion 64 of the tube was being drawn through the deformable die ring 10, increasing pressure was supplied to the cylinder chamber 52 to progressively constrict the deformable die ring 10 about the tube so as to progressively constrict the tube 58 down to the point 68 of minimum diameter. Then, as tube 58 continued to be drawn to the right through the deformable die ring 10 as illustrated in FIGS. 2 and 6, the hydraulic pressure in cylinder chamber 52 was gradually reduced to allow gradual enlargement of the inner working surface 16 of the deformable die ring and consequent gradual enlargement of the tube 58, so as to produce the reverse tapered portion 72 of the tube 58. This reverse tapered portion 72 is almost completed in FIG. 2, and the net result is that the tube 58 has been formed into the shape of a venturi tube,

With the present invention tubes may be drawn either down or up a taper, or may be drawn into abruptly or gradually stepped configurations of different diameters, or may be otherwise shaped without requiring the use of mandrels within the tube. However, if desired, a mandrel may be employed to assure the operator of an accurate formed tube configuration, or to simplify the control required by the operator. For illustrative purposes a tapered mandrel 74 has been shown in the reverse tapered portion 72 of tube 58 in FIG. 6.

FIGS. 7 to 9 illustrate an alternative form of the invention which is adapted to draw tubing into a cross- Sectional shape other than round, in this case a hexagonal shape. In this form of the invention the die ring 10b is hexagonal both in OD and ID, as best shown in solid lines in FIG. 8 and in phantom in FIG. 9. Otherwise, the die ring 10b is the same as die ring 10 of FIGS. 1 to 4 and 6. Although the ID of the die ring may be provided in an cut-of-round shape while leaving the OD round, it is preferred to provide the OD in substantially the same outof-round configuration as the ID to prevent distortion of the ID as the die ring is squeezed axially and the OD correspondingly contracted to a smaller size.

The apparatus of FIGS. 7 to 9 employs the same cylinder 26 as the apparatus of FIGS. 1 to 3 and 6, but the die holder sleeve 18b is modified so that the skirt portion 24b thereof has an ID complementary to the OD of the die ring 10b, in this case hexagonal. Similarly, the piston 40b is modified from the piston 40 of FIGS. 1 to 3 and 6 by providing the pressure face 54b thereof with outer dimensions which conform with those of the die ring 10b, in this case hexagonal. Accordingly, the inner axially oriented wall of recess 56b is of hexagonal shape.

FIGS. 7 and 8 illustrate drawing an initially cylindrical tube 58b with the apparatus of FIGS. 7 to 9 so as to produce a tapered portion 64b thereof having a hexagonal cross-section. This operation is illustrated in FIG. 7 as being performed in the same manner as the tapering with a circular form in FIG. 2, by drawing down the taper while gradually building up the hydraulic pressure in cylinder chamber 52 so as to progressively constrict the hexagonal die ring 10b.

It will be apparent from FIGS. 7 to 9 and from the foregoing description of the apparatus there illustrated that the deformable die ring may be provided in a variety of circumferential shapes to draw tubing into a corresponding variety of circumferential shapes, all within the scope of the present invention.

FIG. 10 illustrates another form of the invention wherein the deformable die ring 10c is similar to the deformable die ring 10 in overall configuration and composition, but differs by being hollow, having a torus-shaped annular recess 76 therein which communicates through a fluid conduit 78 with a variable source (not shown) of fluid pressure. The conduit 78 may extend through the body of die holder sleeve 180 which is otherwise similar to the die holder sleeve 18 of FIGS. 1, 2 and 6, and thence through a suitable accommodation in the cylinder end plate.

If desired, the hollow deformable die ring may be employed in the same apparatus as the deformable die ring 10, which apparatus is shown in FIGS. 1 to 3 and 6, but will permit added operator control by the direct application of fluid pressure within the die ring 100 or release of fluid pressure therefrom. Alternatively, the hollow deformable die ring 100 may be employed in die holder apparatus not otherwise adjustable, as for example in apparatus similar to that shown in FIGS. 1 to 3 and 6 but wherein the piston pressure face 54 is fixedly positioned relative to the die holder sleeve 18c. In such case, the entire control will be accomplished by adjustment of the fluid pressure within the torus-shaped annular recess 76 in the die ring 100.

While it is contemplated that the deformable die ring of the present invention will, in many tube drawing operations, be deformed by hydraulic actuating means radially inwardly during the drawing operation, it is to be understood that the deformable die ring of the invention is equally applicable to use where it is initially constricted, as by hydraulic actuating means, and then is gradually relaxed by release of the hydraulic pressure actuating means so as to be allowed to radially expand. It will be apparent from the accompanying drawings and the foregoing description that one of the basic advantages of the present invention is the fact that a wide latitude of control is permitted over the ID of the deformable die ring during operation.

While the instant invention has been shown and described herein in what are conceived tobe the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein, but is to be accorded the full scope of the appended claims.

I claim:

1. In tube drawing mechanism of the type having a drawing die through which a tube is adapted to be drawn, a die holder, and drive means engageable with the tube for applying axial movement of the tube relative to the die holder so as to drive the tube through the die, the combination with said mechanism of variable die apparatus which comprises a die ring composed of resiliently deformable material and having a generally radially inwardly directed working surface, support means forming a part of said die holder peripherally confining said die ring and partially confining the ring in the axial direction, and selectively operable means that is operable independently of said drive means for deforming the die ring so as to vary the size of said inner working surface.

2. Variable die apparatus as defined in claim 1, wherein said die ring is composed of a generally rigid but elastically deformable plastic material.

3. Variable die apparatus as defined in claim 1, wherein said die ring has an expansible annular spring metal core member embodied therein.

4. Variable die apparatus as defined in claim 1, wherein said means for deforming the die ring comprises an annular hydraulic chamber defined within said deformable die ring, and conduit means connected to the die ring and communicating with said chamber for introducing hydraulic pressure therein.

5. Variable die apparatus as defined in claim 1, wherein said working surface has an out-of-round circumferential shape, and the outer periphery of the die ring has a similar, complementary out-of-round circumferential shape.

6. Apparatus as defined in claim 1, wherein said radially inwardly directed working surface of the die is inwardly convexly rounded in axial cross section.

References Cited UNITED STATES PATENTS RICHARD J. HERBST, Primary Examiner U.S. Cl. X.R.

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