US2394883A - Metal working - Google Patents

Description

Feb. 12', 1946. E. G. 'WHEPPLE METAL WORKING Filed Dec. 23', 1944 INVENTOR.

. E RNEST G. WHIPPLE BY AGENT a Patented Feb. 12, 1946 UNITED STATES PATENT OFFICE METAL WORKING Ernest G. Whipple, Stratford, Conn., assignor to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application December 23, 1944, Serial No. 569,585

' Claims. (01. 2205-45 This invention relates to metal drawing, and more especially,'to a drawing and cutoff die assembly for forming drawn metal cases of predetermined length such as used in themanufacture of small arms ammunitioncomponents.

In general, drawn metal cases and particularly brass cartridge cases are manufactured from a blank by cutting the blank and then forming an elongated case from the cup by successive drawing and trimming operations. The common practice is to trim the drawn cases to length after drawing. This method requires much handling of the individual cases, and, to avoid this, efforts have been made to draw a case and then cut off the drawn. case to a predetermined length in a single draw. To this end, the draw punch is provided with a shoulder or shearing'edge which is moved into cooperative association with the wall of the draw die aperture following the drawing of the case to pinch off the upper end thereof. A scrap ring is thus formed which usually encircles the draw punch and heretofore has been removed from the punch by a suitable stripper mounted above and independently of the draw die assembly. However, draw and cutoff operations as practiced have produced a large percentage of imperfectly drawn cases and it has been discovered that this was due primarily to the lack of adequate guide means for guiding the workpieces into the draw die, this function being performed usually by the workpiece feeding means operable between the die assembly and the scrap ring stripper. v

A feature of the present invention is the discovery that for positively guiding workpieces into the draw die, guide means must be provided comprising a substantially integral part of the draw die assembly and that for efiicient operation the scrap ringstripper should be mounted in the die assembly between the draw die and the guide means. A die assembly is, however, for all practical purposes, limited in height to the distance between the bed plate of the press on which it is mounted and the workpiece feeding means located immediately above the die assembly.

An object of the present invention is,'therefore, the provision, in a die assembly of predetermined height, of guide means for guiding a workpiece into the draw die and a stripper for removing scrap material from the draw and cutoff punch. A further object is to provide a draw die assembly with an improved device for stripping scrap material from the draw and cutoil punch, and means for removing the scrap material from the draw die assembly. A still further object is to provide an improved stripper for metal drawing apparatus.

These and other objects, features and advantages of the invention will be more particularly described in the specification, having reference to the drawing in which:

. Fig. 1 is a side elevation in section of the draw die assembly including a fragmentary portion of a draw and cutoff punch.

Fig. 2 is a fragmentary plan view, partly in section, in the direction of arrows 2-2 of Fig. 1 showing the die assembly mounted in a die slide.

Fig. 3 is a plan view, partly broken away, of the improved stripper.

Fig. 4 is an exploded view of the stripper shown in Fig. 3 not including the stripper fingers.

Fig. 5 is a plan view of one of the stripper fingers. r

Fig. 6 is a cross sectionon line 6-6 of Fig. 5 of one of the stripper fingers.

The improved draw and cutoff die assembly of this invention is adapted for use on a draw press of any well known type comprising a bed plate, a reciprocating gate mounted above the plate adapted to carry a draw punch, feed means mounted'on the bed plate for feeding workpieces I to the draw station, and a die slide mounted on the bed plate for supporting a draw die assembly, the slide being adapted to hold the die assembly in position beneath the feed means and in axial alignment with a workpiece supporting aperture thereof and the draw punch.

Referring to the drawing, the die assembly of the present invention is indicated generally at H) in Figs. 1 and 2 and is shown supported in an aperture l I in the end of a die slide l2. The latter is mounted on a member 13 corresponding to the bed plate of a draw pres's,the die slide being locked or otherwise secured thereto by clamps or other fastening means (not shown).

Supported in axial alignment with the die aperture M of the draw die assembly H] by means of a reciprocable gate (not shown) is a punch l5, the latter having a tapered nose portion for drawing a workpiece, which may be a cup or partially drawn case, through the land ll; of a suitable draw die I! of the'die assembly l0. Adjacent the upper end of the nose portion of the punch i5 is a shoulder IB comprising a sharp shearing edge adapted, at the end of the draw stroke, to out off a portion of the upper end of the draw piece by pinching the metal thereof between the adjacent wall of the draw dieaperture l 4 and the sharp shoulder 18. The length of the trimmed draw piece is, of course, determinable being a measure of the distance between the shoulder l8 of the punch and end thereof.

The die assembly l includes a stripper 19 which, in the present embodiment, is of the type shown and described more fully in the Newell patent, No. 2,345,357, April 4, 19%. The stripper is supported in axial alignment with the draw die I! by a holder 20 and is adapted in a well known manner to engage the trimmed edge of the draw piece as the punch I6 begins its upward stroke to strip the draw piece off of the punch. superposed on the draw die and stripper assembly is a cylindrical spacer block 22 which is adapted to make a snug fit in the die slide aperture H and has a U-shaped radiall extending slot 23 cut through its wall, the width of the slot being greater than the diameter of the draw die aperture l4 as shown in Figs. 1 and 2. The closed end 23 of the U-shaped slot is provided with a counterbore- 24 to receive the draw die: It, The spacer block 22 is secured against rotation in the die slide 12 by a suitable key 22 and is relatively thick as shown so that the inner closed 2'3 of the slot defines a chamber of. appre ciable size, A relatively small aperture 25' is shown extending radially through. the wall of the spacer" block: 22v in substantially axial alignment with its slot 23: and is adapted: to provide access to the chamber 23' so that an air hose 2d secured in the hole 25 ma deliver air under relatively high pressure to the chamber: 23'

The upper end or the chamber 23 is shown with a coun-terbor'e- 21 which is adapted to provide a seat for supporting a scrap ring stripper 28.

The stripper 28 is designed to remove the scrap ring or cutoff portion of the draw piece which encircles the draw punch and to hold the scrap ring back in the chamber 23' as the punch moves upwardly out of the die assembly. As shown in Figs. 3, 4 and 5, the" scrap ring stripper is made extremely thin so as to allow the use of a guide member as an. element of the die assembly for guiding the draw punch and workpiece into the draw die as hereinafter described; and; to enable the stripper to be mounted between. the draw die and the guide member without exceeding the permissible height of the die assembly.

The scrap ring stripper 28: comprises, in. general, three apertured disks or plates of quarter hard: cold rolled steel held together by rivets 29 in a rigid laminated structure; The upper and lower plates are identical and are indicated in the: drawing by the numeral 3a each having a central aperture 32 and four countersunk rivet holes: 35 spaced substantially 90 apart.

The middle plate 34'- has' four noncountersunk rivet holes 3'5 adapted, to line up with the rivet holes of the top and bottom plates 30; and a central aperture 331.. The latter is substantially diamond-shaped, as shownv in Figs. 2 and 3,. its two converging substantially straight sides 3'! blend-ingat adjacent ends into an arcuate recess 38.. Similarly, the two opposite converging sides 39 blend into an arcuate recess 49. A substanti-a'l-ly rectangular tongue; 42 is formed at the intersection of the adjacent ends of each respective pair of sides 3-! and. 39 and projects radially into the central aperture 35,, Supported within the diamond-shaped aperture 36 by the respective recesses 38 and M! and tongues 42 are a pair of resilient members 43, see Fig. 3, hereinafter referred to as stripper members. As shown in Fig. 5, each stripper member comprises a steel wire which, in the embodiment shown, comprises No. 17 gauge music wire, bent to provide an armate head 44 and a pair of outwardly diverging fingers 45 having shoes 45 at the end thereof. The head 44 of each stripper member is adapted to seat in its respective arcuate recess or seat 38 and 40 of the intermediate plate 34 while the shoes 46- of the fingers 45 bear against adjacent sides of the respective tongues 42, the inherent resiliency of the fingers being sufficient to firmly hold the shoes 46 against the sides of the tongues 42 and the heads 44 of the members in their respective seats. As shown, each shoe 46 is relatively short so as to provide clearance space be tween its end and a wall 4'! at the base of and extending at substantially right angles to the adjacent tongue 42. The shoes 46 are thus free to move laterally.

Normally, the resilient fingers 45 of the stripper members extend inwardly beyond the circumference of the central: aperture 32 of th stri per forming, in. effect, four chords equally spaced about the aperture 32. However, as the drawing punchmoves a workpiece through the stripper aperture, the resilient fingers 45 are engaged and forced outwardlyandinasmuch a the shoes 46 are free to move laterally, the resilient fingers offer relatively little resistance thus minimizing any tendency to scratch or mar the workpiece. The fingers 45 do, however", engage the surface of the punch closely, and, consequently as the punch begins to move upwardly following draw and cutoff, the fingers engage the top edge of the scrap ring which encircles the punch and. holds it back while the punch continues its upward movement, thereby stripping the Scrap ring off of the punch. and holding it in the chamber 23'. The stripping members 43 are formed from wire which is substantially round in cross section. It has been found, however, that the efficacy of the stripper fingers 45'may be enhanced by grinding or otherwise forming a flat surface on. the underside of the wire, as shown in Fig. 6, so as to form relatively sharp edges 45 thereon for engagin the scrap ring.

The scrap ring which is stripped. off of the draw and cutoff punch by the stripper fingers is de posited in the chamber 23 and is adapted to be removed therefrom by an air blast provided by the hose 2%. To this end, an aperture 48' is provided in the wall of the die slide H (see Fig. 2) in alignment with the radial slot 23- and chamber 23 of the spacer block 22 to permit the scrap rings to be blown out of the chamber and die slide assembly.

The final. element of the die assembly is a guide ring 49 which has a snug fit in the aperture H of thedie slide [2 and seats ontop of the spacer block 22 and the countersunk stripper- 2-3 formmg, in effect, an integral part of the die assembly. The guide ring 49 is provided with an accurately dimensioned guide aperture 50 in axialalignrnent with; the draw die aperture l4 and: the apertures of the. twostrippers l9 and 28. By making the guide ring a substantially integral part of the die assembly, the guide aperture 50 constitutes means for positively aligning the workpiece and draw punch with the draw die and strippers as the workpiece and punch move downwardly therethreugh. Thus irrespective of the type or feed means used to deliver the workpieces to the die assembly, the workpieces will always-be properly aligned with thedraw die during draw and cutoff.

What is claimed is:

1. Apparatus for drawing metal comprising a die slide; a die assembly mounted in said die slide, said die assembly comprising a draw die, a guide member and a spacer block having an aperture, said spacer block being arranged between said die and said guide member so that its aperture is in substantially axial alignment with the draw die and guide; a reciprocable punch for drawing a workpiece through said die, said punch being guided by said guide member in axial alignment with said die and includin means thereon arranged to cut off the upper end of the drawn workpiece; a stripper forming a part of said die assembly and arranged to strip the drawn workpiece from said punch; and a second stripper secured between said die and said guide,

said second stripper being arranged to remove the cutoff portion of the workpiece from said punch during its upward stroke and to hold the cutoff portion in the aperture of the spacer block.

2. Apparatus for drawing metal comprising a die slide; a die assembly mounted in said die slide, said die assemby comprising a draw die, a guide member and a spacer block having an aperture, said spacer block being arranged between said die and said guide member so that its aperture is in substantially axial alignment with the draw die and guide; a reciprocable punch for drawing a workpiece through said die, said punch being guided by said guide member in axial alignment with said die and including means thereon arranged to cut off the upper end of the drawn workpiece; a stripper forming a part of said die assembly and arranged to strip the drawn workpiece from said punch; a second stripper secured between said die and said guide, said second stripper being arranged to remove the cutoff portion of the workpiece from said punch during its upward stroke and to hold the cutoff portion in the aperture of the spacer block; and means to remove said cutoff portion from said aperture.

3. A die assembly for metal drawing and cutofi apparatus comprising a draw die; a guide member for guiding a workpiece into said die; a spacer block separating said die and said guide the draw and cutoii punch, said stripper com prising a base plate having a central aperture;

resilient stripping elements on said base plate, each element comprising an eye having a pair a of straight diverging arms, the outer end of each arm being free and the portion intermediate its outer end and said eye being arranged to eX- tend beyond the edge of said aperture; a recessed member fixed to said base p a 0 hold aid St ipping elements in their properly oriented position; and an apertured cover plate on said recessed member arranged to be secured to said base plate to hold said resilient stripping elements thereon.

5. In a die assembly for metal drawing and cutoff, a stripper for removing scrap material from the draw and cutoff punch, said stripper comrising a base plate having a central aperture; resilient stripping elements on said base plate, each element comprising an eye having a pair of straight diverging arms, the outer end of each arm being free and the portion intermediate its outer end and said eye being arranged to extend beyond the edge of said aperture; an intermediate plate on said base plate, said intermediate plate having a central aperture provided with diametrically opposite recesses to receive each of said eyes and diametrically opposite tongues arranged to abut the free ends of said arms to hold said eyes in said recesses and to insure the proper orientation of said stripping elements; and an apertured cover plate on said intermediate plate arranged to be secured to said base plate to hold said resilient stripping elements thereon.

ERNEST G. WHIPPLE.

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