US3446107A - Metal forming die elements - Google Patents

Description

May 27, 1969 R. F. Moi/ER METAL FORMING n11: ELEMENTS Sheet Filed Sept. 17, 1965 //vv/v 70/? ROBERT FRANKLIN MOVE? ATTORNEY United States Patent US. Cl. 83658 12 Claims ABSTRACT OF THE DISCLOSURE Die elements fabricated from pre-stressed organic polymers. A bore is provided in a mass of organic material and thereafter a core larger in area than the bore is forced into the bore.

This invention relates to metal forming die elements and more particularly to the punch element and/or the die element, fabricated from a pre-stressed organic polymer.

An object of the present invention is to provide a metal forming punch or die element fabricated from a prestressed organic polymer in cooperation with a metal fabricated element.

Another object of the present invention is to provide an organic polymer punch or die element in pre-stressed condition for cooperative mating with its companion element.

And still another object of the present invention is to provide a mass of an organic polymer in a pre-selected geometric shape and of a preselected durometer condition with a core of organic polymer having a higher durometer condition than the mass, to change and control the comprehensive sensitivity of the surface of the mass through pre-stressing the mass by means of the core and by means of the durometer condition of the core.

In prior art practice metal was formed by being subjected to the action of a steel punch striking the metal blank against the mating steel die.

Recent practice developed the substitution of an oragnic polymer as the die element which cooperated with a metal punch. A defect in this practice has been the lack of detail reproduced in the metal blank by the metal punch. Another drawback in this practice was the extremely limited productive life of the organic polymer die element.

The present invention was developed to overcome these and other inherent deficiencies in the prior practice.

Other objects of the present invention will become apparent in part and be pointed out in part in the following specification and claims.

Referring to the drawings in which similar characters of reference indicate corresponding parts in all the figures:

FIGURE 1 is a perspective view of the machine used to pre-stress the organic polymer.

FIGURE 2 is a vertical cross sectional view taken on line 22 of FIGURE 1.

FIGURE 3 is a perspective view of a block of organic polymer before pre-stressing and for use in a die set. (Core not inserted.)

FIGURE 4 is a fragmentary, cross sectional view illustrating the insertion of a core into block to accomplish pre-stressing of the block.

FIGURE 5 is a fragmentary, cross sectional view, illustrating the core locked in the block by means of the enlarged diameter of the core displacing the softer wall of the bore in the block.

FIGURE 6 is a horizontal cross sectional view taken on line 44 of FIGURE 3 after the block shown in FIGURE 3 is pro-stressed.

FIGURE 7 is a side elevational view of die set with the pre-stressed block of organic polymer in use as a female die member.

3,446,107 Patented May 27, 1969 FIGURE 8 is a horizontal view through the die set taken on line 88 of FIGURE 7.

FIGURE 9 is a side elevational view of a die set wherein a smooth inner and outer surface metal tube is converted into a corrugated tube.

FIGURE 10 is a horizontal view through the die set taken on line 10-10 of FIGURE 9.

FIGURE 11 is a vertical cross sectional view taken on line 11-11 of FIGURE 10.

FIGURE 12 is a view similar to FIGURE 11 showing the organic polymer block, used as a die member, in compressed condition in a die set.

FIGURE 13 is a modified form of organic polymer block used in an embossing machine, schematically illustrated.

Reference is now made to FIGURES 3, 4, 5 and 6 of the drawings wherein is illustrated a die element fabricated from a generic specie of organic polymer material. One such organic polymer material is polyurethane which inherently possesses the physical characteristics of uniform expansion and uniform construction when compressed or when force is removed therefrom.

A polyurethane material having the following physical characteristics provides a satisfactory die block for the purposes which will hereinafter appear:

A durometer reading approximating seventy An elongation potential of approximately six hundred fifty percent (650%) but not less than five hundred percent (500%). A normal elongation of two hundred percent at eighteen pounds per square inch pulling force. A minimum tensile strength of forty-three hundred pounds per square inch. One such polyurethane material is commercially known as Elastacast.

Applicant has utilized these natural characteristics and modified them in the following manner.

The die block, generally indicated by reference numeral 10, is preferably, in one embodiment, rectangular in shape and provided with an axial opening 11. The axial opening or bore 11 is approximately fifty percent (50%) in diameter to the width of the die block. Opposite ends of axial bore 11 are provided with countersunk areas 12.

A core 13 is inserted into opening 11 in order to prestress die block 10. Die block 10 is pre-stressed to create a desired degree of comprehensive sensitivity in the outside surfaces 10A, 10B, 10C, 10D of die block 10.

It has been found that a core fabricated from wood, iron, steel or other non-compressible material defeats the object sought in prc-stressing die block 10, namely, controlling the degree of compressive sensitivity in the body of die block 10.

In pre-stressing die block 10, the outside surface of the core 13 provides a supporting surface for the surface of the axial opening 11. The supporting surface of the core 13 must be harder or more rigid than the material of the die body 10 in order to support and sustain the prestressed condition of the die body 10. In addition, the supporting surfaces of the core 13 must be yielding or elastic to react to a blow struck on the surfaces 10A, 10B, 10C and 10D. A material found satisfactory when combined with a material having the physical characteristics outlined above is an organic polymer having similar physical characteristics as stated for the die block 10 with the exception that the durometer reading would be in the range of ninety and the diameter of the core 13 would be approximately twelve percent (12%) greater than the diameter of the bore 11. In this manner the core 13 would pre-stress die block 10 and provide a yielding supporting surface for the axial opening 11.

The ratio of the area of the bore 11 to the area of the mass 10 will vary according to the phyiscal characteristics of the organic polymer selected. With the physical characteristics specified above (representing Elastacast) the bore 11 approximates fifty percent of the mass area of die block 10.

The diameter of the core 13 is larger than the diameter of the bore 11 in order to provide a pre-stressed condition in the mass or die block 10. The ratio of enlargement of the diameter of the core 13 to the bore 11 controls the degree of compressible sensitivity in the mass or body of die block 10. This may be rephased as the degree of compressible sensitivity in faces A, 10B, 10C and 10D.

Another factor governing the compressible sensitivity in die block 10 is the relation of the durometer characteristics of the core 13 to the mass. In the illustration the core has a durometer reading of (90) ninety and the die block has a durometer reading of (70) seventy. To provide a greater degree of compressible sensitivity in the die block 10, the die block would be fabricated from an organic polymr having a durometer reading of sixty (60) or fifty (50).

The usual method of producing a die block 10 fabricated of an organic polymer is by molding. A wide range in the physical characteristics of organic polymers is commercially available but none duplicate the physical compressible characteristics provided by pre-stressing.

FIGURES 1 and 2 illustrate a machine for producing a pre-stressed condition in die block 10.

The machine, generally indicated by reference numeral 15, comprises a frame having side walls 16, 17 held in spaced relation by means of front brackets 18, 19 and rear brackets 20, 21. Angle iron feet 22, 23 are fastened to side walls 16, 17, respectively. A bottom platform 25 provided with a central opening 26 is fastened on oppo site sides to front bracket 18 and rear bracket 20. A top platform 27 provided on opposite sides with blocks 28, 29 is fastened on opposite sides through blocks 28, 29 to front bracket 19 and rear bracket 21. Two pneumatic cylinders 30, 31 are fastened on one end to top platform 27 and on the other end to a flange 32 on the opposite end.

A piston head 33, provided with a piston stem 34, is slidably mounted in pneumatic cylinder with piston stem 34 slidably mounted in flange 32 which is provided with a bore for that purpose. Similarly, a piston head 37, provided with a piston stem 38, is slidably mounted in pneumatic cylinder 31 with piston stem 38 slidably mounted in flange 32 having a bore for that purpose. A shelf 40 is fastened to the ends of piston stems 34, 38.

A fixture comprising an upper plate 41 and lower plate 42 which are held in spaced relation by means of rods 43, 44 is fastened to shelf 40 by means of the threads on a slide bar 45. Slide bar 45 is slidably mounted in flange 32 and top platform 27.

A mass of organic polymer material, illustrated as a rectangular die block 10 provided with an axial bore 11 having countersunk areas 12, is placed upon bottom platform 25. A rod provided with an enlarged head 51 is slidably mounted in bottom platform 25. Head 51 is passed through axial bore 11. Rod 50 is fastened in lower plate 42. Enlarged head 51 is slightly larger in diameter than the diameter of a core 13, so that core 13 will easily slide into axial bore 11 through the path provided by enlarged head 51. A core 13 is placed between the top of enlarged head 51 and upper plate 41. Piston heads 33, 37 are actuated in a manner well known to the pneumatic arts. Actuation of piston heads 33, 37, simultaneously forces core 13 into axial bore 11 as lower plate 42 pulls rode 50 and enlarged head 51 downwardly through axial bore 11.

One of the physical characteristics of an organic polymer is that its compressibility is so negligible as to be disregardable in its use as a die block. Its non-compressibility is the essence of its superiority as a die set memher.

The enlarged diameter of core 13 forces the wall of axial bore 11 to be displaced. That displacement will be in the direction of the countersunk areas 12, so that the insertion of core 13 into bore 11 causes the mass of die block 10 to shift and fill the space provided by countersunk areas 12. In this manner, as seen in FIGURE 5, the ends of the core 13 are locked in bore 11 in the fashion of a rivet. The top and bottom of die block 10 are smooth, horizontal and parallel. In other words the excess material created by the displacement of material in the wall of axial bore 11 caused by the enlarged diameter of core 13 is removed by countersinking the ends of bore 11 before the core 13 is inserted into the axial bore 11.

The insertion of the enlarged core 13 into the bore 11 increases the outside dimension of die block 10 radially, because the organic polymer material is non-compressible.

FIGURES 7 thru 13 illustrate three practical applications in the use of a pre-stressed die block 10.

FIGURES 7 and 8 illustrate a punch and die set. A punch and die set is an assembly consisting of an upper member called the punch holder and a lower member called the die holder. The under surface of the punch holder and the upper surface of the die holder are those on which the punch and die sections of a finished punch press tool are mounted. In use the die holder is clamped to the bed of the punch press, while the upwardly extending punch holder shank is fastened in the clamping hole provided therefor in the sliding punch press ram. The tool is actuated by the reciprocating motion of the ram. Mating guide posts and bushings of an assembled die set assist in maintaining tool alignment during die setting and the operation of the tool in the punch press.

These guide posts and bushings are employed in maintaining the punch and die details in true alignment during ram-produced reciprocatory movement of the punch and punch holder relative to the die and die holder. In conventional constructions, the posts are of plain cylindrical formation and are carried by and depend rigidly in relatively spaced order form die holders.

The life of the punches and dies and the accuracy of the work accomplished are directly affected by the accuracy of alignment of the respective moving parts of the punch and die set, and more particularly by the manner in which this alignment is retained over a long period of time.

In the past the bushings and the mating guide posts upon which the bushings slide or reciprocate were ordinarily tightly forced into holes drilled into the punch holder and die holder, respectively. Of course, any alignment thus obtained is dependent upon the accuracy with which the holes into which the parts to be forced have been drilled. It is well known that by the use of ordinary drills, it is hard to provide holes of any reasonable degree of accuracy, and that such holes can be obtained only by either separately reaming or boring the walls of the holes, with the consequent risk of inaccuracy in the separate holes. It was also necessary to grind the guide pins and the mating bushings on centers and arbors, respectively, to insure absolute concentricity of the outside diameter of the guide pin and the outside diameter of the mating bushings. These many and varied manufacturing operations causes inaccuracies in relative alignment of the guide posts and bushing holes in the holders as well as in the center distance between these holes. A range of less than several thousandths of an inch was not ordinarily or easily or economically obtained. This was especially true because of the methods of assembling the guide posts and bushings in their respective plates.

It is therefore an object of the present invention to provide a new and improved punch and die set structure which is not subject to the limitations, difiiculties and costs of manufacture above discussed, and wherein alignment is more radily achieved between the male member, the punch, and the female member, the die. It is a further object of the present invention to provide an improved product as a result of the mating of the punch and die, with a strip of metal to be worked, located therebetween.

Referring to FIGURES 7 and 8 of the drawings, reference numeral 60 designates the punch holder provided with a shank 61, and 62 designates the die holder, said parts being movably positioned with respect to each other by guide pins 63, 64, carried by the die holder 62. Said guide pins 63, 64, being coaxial with and slidable within bushings 65, 66, respectively, carried by the punch holder 60.

A steel collar 67 having a chamber 68 is fastened to die holder 62, as by welding. Chamber 68 is of a shape to accommodate die block 10 in a manner wherein the walls of chamber 68 engage to support the sides 10B, 10C and 10D and ends of die block 10, when slight pressure is exerted upon side 10A of die block 10. The core 13 in die block 10, in the example of use illustrated in FIGURES 7 and 8 lies in a horizontal plane parallel to die holder 62.

A punch of preselected configuration is fastened to punch holder 60, in conventional manner, by use of dowel pins and screws (not shown). A strip of metal 71 to be worked and therefore termed a work strip, is placed upon die block 10. The ram of the press will force punch 70 against work strip 71 and into die block 10, Where, due to the previously described physical characteristics of die block 10, a female die will momentarily be formed. In this manner the conventional female die and all of the attenuating manufacturing difficulties are totally eliminated. It is apparent that with each stroke of the press the punch creates a new female die element which confroms exactly to the configuration of the male punch element. Wear on the punch is mininized. The configuration of the work piece is sharp and exact. The work done by the punch may be stamping, forming, drawing, severing or any other conventional function performed by a punch in a conventional die set. The sensitivity of compression of the die block 10 to the stroke of the punch 70 was previously described. The fact that the organic polymer from which the die block is fabricated is noncompressible but is displaceable, permits the contour of the punch 70 to be reproduced in the die block 10 with the work piece sandwiched there between. The functions performed by the punch with die block 10 include shearing.

In the illustration shown in FIGURES 7 and 8, a variation in the gage or thickness in the work piece 71 is of no consequence, due to the pre-stressed die block 10. However, where a metal punch is mated with a metal die to accommodate a work piece of a preselected gage; any large variation in the gage of the work piece would result in a broken punch.

Reference is now made to FIGURES 9, 10, 11 and 12 wherein a new concept, function, construction and result are performed in a punch and die set. Punch holder 60A, shank 61A die holder 62A, guide pins 63A, 64A and bushings 65A, 66A are constructed identical to and function as described with reference to FIGURES 7 and 8. A steel collar 67A provided with a chamber 68A is embedded at 67B in die holder 62A and is welded thereto, so as to withstand the strain thereon as will presently appear.

Chamber wall 68A may be provided with a preselected configuration illustrated as convoluted. A die block 10A, similar to die block 10, with the exception that is is round rather than square in horizontal cross-section, (compare FIGURE 6 with FIGURE 10).

Core 13A is located in a position at right angles or verticle to die holder 62A, because the compressive force to be applied will compress die block 10A in a manner to expand die block 10A radially to core 13A.

A metal tube 73 is placed in the chamber between the outside diameter of die block 10A and the convoluted chamber wall 68A.

A punch 70A in the preselected configuration of a disk having an outside diameter, approximately equal to or slightly smaller than (see FIGURE 12) the outside diameter of die block 10A, is fastened to punch holder 60A by means of screws 74.

Reciprocating movement of the press will force punch 70A into die block 10A thereby uniformly expanding die block 10A radially, thereby forcing tube 73 into convolutions of chamber wall 68A to produce a corrugated contoured tube.

As soon as punch 70A is withdrawn from die block 10A, the die block 10A will return to initial pre-pressed position shown in FIGURE 11.

The reason die block 10A is able to perform the function of forcing tube 73 into convolutions 68A is the non-compressibility of the organic polymer controlled as to the extent of resilient sensitivity through pre-stressing so as to expand uniformly or simultaneously throughout its outer surface as contrasted to a rubber block which expands from the ends toward the middle. The uniform expansion of die block 10A, simultaneously engaging tube 73 along its entire length prevents rupture of the walls of tube 73, a condition which prevails when a die block engages the tube 73 progressively from the ends toward the middle of the tube 73 if pre-stressing is absent or rubber is used as die block material.

Reference is now made to FIGURE 13 wherein is illustrated schematically mechanism for embossing metal foil. A cylinder provided with the male component of a rotating die is rotatively mounted upon a shaft 81. A die block 10B cylindrical in contour is pressed against cylinder 80 by means of pressure rolls 82, 83, mounted, respectively, upon shafts 84, 85.

In the past cylinder 10B would be provided with the female mating component to male component 80. Applicant substitutes a cylinder die iblock 10B of a prestressed organic polymer with a smooth outer surface for the embossed female mating die component of the prior art. In this manner applicant eliminates the complicated and expensive procedure of producing a mating female die for a male die component and at the same time is able to provide sharper impressions on metal foil 88 passing between cylinders 80 and 10B.

Cylinder 80 is a driven troll. Cylinder 10B and pressure rolls 82, 83 are idler rolls rotated through cylinder 10Bs engagement with cylinder 80.

Having shown and described preferred embodiments of the present invention by Way of example, it should be realized that structural changes could be made and other examples given without departing from either the spirit or scope of this invention.

What I claim is:

1. The method of pre-stressing a metal forming die element mass of organic polymer material of pre-selected hardness, comprising the steps of providing an axial longitudinal passageway in said mass, pre-stressing the outside surface of the mass by forcing a core of a diameter greater than the diameter of said axial longitudinal passageway and of a hardness greater than said mass into said axial longitudinal passageway to fill said axial longitudinal passageway in order to produce a pre-selected sensitivity to compressive resistance on the outside surface of the mass.

2. A metal forming die element comprising a mass fabricated of an organic polymer material having an axial longitudinal passageway of pre-selected area, a core larger in area than said pre-selected area of said axial longitudinel passageway, said core contained within said axial longitudinal passageway, said core being of a density greater than the density of said mass to provide a pre-stressed condition in said mass to produce a pre-selected sensitivity to compressive resistance on the outside surface of the mass.

3. A die block adapted to resist the compressive forces of a punch consisting of a mass of material of preselected geometric shape and fabricated from an organic polymer, an axial opening of preselected area provided in said die block, a core larger in area than the area of said axial opening and contained within said axial opening and fabricated from an organic polymer having a density greater than the density of the first mentioned organic polymer to provide a pre-stressed condition in said die block and a preselected sensitivity to the compressive forces of a punch.

4. A device to resist compressive forces comprising a mass of material, of preselected geometric shape, fabricated from an organic polymer, an axial bore in said mass having an area approximately equal to one half the area of the entire mass, a core approximately ten percent larger than said axial bore and fabricated from an organic polymer having a hardness approximately twelve percent greater than the hardness of the first mentioned organic polymer, said core contained within said axial bore to provide a pre-stressed condition in said mass with a pre-selected sensitivity to compressive resistance in said mass.

5. A claim as recited in claim 4 wherein counterbored areas are provided at opposite ends of said axial bore in said mass and said core displaces said mass to fill out said counterbores and provide locking means in said mass for opposite ends of said core.

6. A device to resist compressive forces comprising a mass of material of preselected geometric shape, and fabricated from an organic polymer having a durometer reading approximating seventy, an elongation potential of approximately six hundred fifty percent an elongation of two hundred percent at eighteen hundred pounds per square inch pulling force, a minimum tensile strength of fortythree hundred pounds per square inch and an axial bore comprising approximately fifty percent of the area of the mass, a core approximately twelve percent larger in area than the area of said axial bore and contained within said axial bore and fabricated from an organic polymer having a durometer reading approximately ninety, an elongation potential of two hundred percent at eighteen hundred pounds per square inch pulling force, and a minimum tensile strength of forty-three hundred pounds per square inch, to provide a pre-stressed condition in said mass of material.

7. A punch and die set comprising a punch holder provided with bushings, a die holder provided with guide pins coaxially aligned with said bushings for relative sliding movement therebetween, a punch means fastening said punch to said punch holder, a collar having a chamber of preselected contour, means fastening said collar to said die holder, a mass of material of preselected contour to mate with the preselected contour of said chamber and located and supported in said chamber, and fabricated of an organic polymer, an axial bore of preselected area provided in said mass, a core larger in area than the preselected area of said axial bore and contained within said bore, said core being of a density greater than the density of said mass to provide a pre-stressed condition in said mass and a mating die for said punch with a preselected sensitivity to the compressive forces of the punch.

8. A punch and die set comprising a punch holder provided with a plurality of bushings, a die holder provided with a plurality of guide pins coaxially aligned with said plurality of bushings for relative sliding movement therebetween, a punch, means fastening said punch to said punch holder, a collar having a chamber of preselected contour, means fastening said collar to said die holder, a mass of material of preselected geometric shape to mate with the preselected contour of said chamber and located within said chamber, and fabricated from an organic polymer, an axial bore in said mass having an area approximately equal to one half the area of the entire mass, a core approximately ten percent larger than said axial bore and fabricated from an organic polymer having a hardness approximately twelve percent greater than the hardness of the first mentioned organic polymer, said core contained within said axial bore to provide a pre-ssressed condition in said mass with a preselected sensitivity for the compressive resistance to the action of said punch.

9. A claim as defined in claim 8 wherein said core lies in a plane perpendicular to the axis of the reciprocating movement of said punch.

10. A claim as defined in claim 9 wherein said core lies in a plane parallel to the axis of the reciprocating movement of said punch.

11. A punch and die set comprising a punch holder provided with a plurality of bushings, a die holder provided with a plurality of mating guide pins for relative sliding movement with said plurality of bushings, a punch, means fastening said punch to said punch holder, a circular collar having an inner wall of preselected contour forming a chamber, means fastening said collar to said die holder, a cylinder fabricated from an organic polymer and provided with an axial bore having an area approximately equal to one half the area of the cylinder, a core approximately twelve percent larger in area than the area of said axial bore to radially increase the diameter of said cylinder, said core fabricated from an organic polymer having a durometer reading approximately thirty percent greater than a durometer reading of said first mentioned organic polymer, means fastening said cylinder to said die holder centrally located in relation to said inner wall and within said chamber, one end of said cylinder and said core engageable with said punch whereby engagement of said punch in compressive action on said cylinder and core uniformly expands the outside surface of said cylinder toward said inner wall.

12. The method of pre-stressing a mass of organic polymer material comprising the steps of forming the mass into a pre-selected geometric shape, providing an axial longitudinal passageway in said shape of an area equal to one half the entire area of the shape, providing a core of organic polymer material of a density of said first mentioned organic polymer material and of an area approximately twelve percent greater than the area of said axial longitudinal passageway, providing said core with a mating contour to the contour of said axial longitudinal passageway, forcing said core into said axial longitudinal passageway to radially increase the size of said shape, whereby said shape becomes pre-stressed and acquires a prese-' lected sensitivity to compressive forces.

References Cited UNITED STATES PATENTS 2,572,215 10/1951 Swart. 2,948,773 8/ 1960 Hawes. 2,966,872 1/1961 Schmocker 72-55 3,153,697 10/l964 Faulkner 269229 X JAMES M. MEISTER, Primary Examiner.

U.S. Cl. X.R.

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