US3187402A - Metal cartridge manufacture - Google Patents

Description

June 1955 A. J. DUFFIELD 3,

METAL CARTRIDGE MANUFACTURE Filed March 18, 1963 2 Sheets-Sheet l [JG I z? INVENTOR ALBERT J DUFF/5L0 June 1965 A. J. DUFFIELD 3,187,402

METAL CARTRIDGE MANUFACTURE Filed March 18, 1963 2 Sheets-Sheet 2 I g If 4- x 6 I6 FIG-3 W FIG 2 INVENTOR.

ALBERTJ DUFF/[L0 A TTORNEV United States Patent Mathieson Chemical Corporation, a corporation of Virginia Filed Mar. 18, 1963, Ser. No. 265,783 8 Claims. (CI. 29-13) g This invention relates to a method of preparing metal blanks and hollow shells closed at one end for fabrication of articles such as Cartridge cases, and specifically relates to a novel method for fabrication of such tubular products at least initially and sometimes largely by impact extrudmg.

I One object of the invention is to produce an improved closed-end tubular product adapted to be finished to a cartridge case with a superior head structure.

Another object is the fabrication of such tubular bodies in an economical manner comprising an impact extrusion modification eliminating the need for a rolling, blanking with the accompanying waste, and either eliminating or reducing the great multiplicity of drawing and annealing operations heretofore employed in conventionalmethods of making tubular bodies such as shells closed at one end, from rolled sheet metal.

Another object is to avoid in metal shell making the H uneven mechanical properties found in hollow metallic bodies produced byj'extrusion either in a direction counter,- current to the direction of pressing intoa blank'placed in a mold according to prior methods suchas those described in various US. patents such .as No. 172,333, grantedto Meigs; No. 457,767,1granted to Bradley; and No; 1,024,- 840, granted to Ehrhardt; or .in the direction of pressing as in the Hooker process, U.S. 922,985.

Other objects and advantages in method, product, and

apparatus will beapparent from a description of a specific embodiment illustrated in the accompanying 'drawings in which:

FIG. 1 is an elevational view partly in cross section of apparatus for impactextrusion in a press by which the invention may be practiced, and showing a blank in cross section in position in the apparatus; H

FIG. 2 is a sectional and enlarged viewthroughlthe cupped blank produced as an intermediate product'iri the apparatus of FIG. 1;

FIG. 3 is an elevational view partly 'in cross section showing the apparatus in a subsequent stage of operation shown with the final extruded product ready forejection and subsequent operations such as trimming, annealing, and final drawing, heading and mouth trimming; and

FIG. 4 is a fragmentary view of a cartridge case shown in cross section at the head and of the case made in accordance with this invention. 7

Metallic cartridge cases are usually manufactured from rolled strip and the finished cartridge case in being drawn fromsuch stockhas the same grain size in the head as that of the rolled stock. Grain refinement for strength here does not occur because of the relatively small working subsequently performed in this area in comparison with which the grain in the tubular wall is considerably finer. Another disadvantage of using blanks from rolled sheets is the high percentage-of waste resulting from the necessity of cutting out the blanks, usually round one s.

'Moreoventhere is a tendency to draw the metal irregula'rly because of oriented graining in the direction of rolling. Production from such cut blanks by direct extrusion in reverse, i.e. up the punch, still produces unfavorable differences in grain structure resulting in a tendency to separation of the head from the tube wall. 'In an efiort to improve the processing, blanks have been cast or sheared rorn cast bars and then subjected to drawing or extruding,

and sometimes the blank has been subjected to a flattening 1 L stationary 3,187,402 Patented June 8, 1965 P ICC known as pancaking before drawing or extruding, but disadvantages have persisted such as the many low reduction. and intermediate handling steps needed in processing by drawing and also the inability to make the head structure more like that of the cartridge tube wall in processing either by drawing or extrusion.

According to the present invention a circular disc, rectangular slug, or the like suitable blank 1 of cast or hot extruded and annealed metal of sufficiently coarse grain structure is directly subjected to impact by a ram to first produce a reverse extrusion of an outside diameter, i.e. transverse. dimensions, substantially that of the relatively thick blank, and the resulting extruded shallow cup 2 is then subjected to a forward extrusion driving the metal severely reduced cold by at least about 50 percent in the bottom 3 of the cup through an impact extrusion die of the Hooker type to produce a shell 4 of reduced diameter or dimensions having a tubular wall 6 of desired length and reduction in wall thickness from the annular walls 5 of the extruded cup. As a result the metal in both the side 6 and the base 7 of the shell is worked to a reduction of at least from about 45 percent'to about 55 percent, producing a grain of desired structure with orientation extending longitudinally in the side and transversely in in both the side 6 and base 7 was'found to have a remarkable uniformity of worked grain structure, involving a considerable improvement in the base as well as the tubular Wall. By anneal is meant the conventional recrystallization annealing heat treatment of metals, such as copper, aluminum, and their alloys, which must have been previously cold worked at a temperature not'in the'excess of the recrystallization temperature above which upon annealing, a new refined grain structure .may occur, provided the metal has been deformed to a reduction while cold. (See Metals Handbook, 7th Edition, pp. 259-263.)

'In lieuof a relatively thin and medium grained blank sheared out of rolled sheet =metal, disc 1, shown placed in'the press of FIG. 1, is relatively thick and coarse grained in the range of grain size from about 0150mm. to about 6.5 mm. It may be, for example, a die-cast slug of brass of coarse grain of from about 0.6 mm. to about 0.8 min, or a disc cut from a cast rod of brass of very coarse grain larger than 1.0 mm., or a disc cut from extruded and annealed brass rod of from 0.150 mm. to 0.3

mm. grain size. 7 j

With the pressforming cavity closed at the bottom by :plunger21, press ram 30 is first lowered to extrude the blank Ito the intermediate product 2, after which plunger 21 is released and ram 30 is lowered again to rc-extrude the intermediate product to the final extruded shell 4,-ex-

eluding scrap ring 8 which severed by any suitable trimming device. a

First, the blank-is placed in cylindrical die carried ina stationary die holder 12 and mounted on lower supporting die block 1 3,by any suitable means as bolts 14.

Die 11 rests on a supporting ring 15 also carried by the die block 13. Ring 15 has a central opening Die 11 has a die bore 17 aligned with the smaller ring opening 16; mounted in the bore 17 is a die bushing .18 resting adjacent ring IS'and'haVing a squeeze surface 19 forming the entry to an extrusion constriction formed in i the bushing.

Depending upon whether a round or polygonal tube isto be produced, cylindricaldie bore '17 is made either circular, square, rectangular, hexagonal, or of other appropriate transverse dimensions; and disc 1 is of a comparable shape to be received slideably in die bore 17 as shown in FIG. 1.

At the bottom, plunger 21 is reciprocably mounted in the larger ring opening 36 so that the end 22 of the plunger 21 may extend up into die bushing 18 where the plunger end 22 forms a die bottom at the constriction 20 in the stage shown in FIG. 1 and also forms a knockout after the stage shown in FIG. 3. The plunger is supported as shown by any means such as cam shaft 23 having a lobe 24 upon which the plunger roller 25 follows. Die bottom support is provided when roller 25 is at the high point 26 of the cam lobe.

At this position of the die bottom, ram 30, carried by the upper press block 31, is lowered into the die bore 17 against disc 1. Ram 30 comprises a shank 32, and a tapered forming end or nose 33, between which there is an outwardly projecting flange or collar 34 having a guide fit in bore 17. The bottom of the collar 34 has a beveled annular squeeze surface 35 somewhat flatter than the bevel of the die squeeze surface 19, which facilitates extrusion of the metal in the later stage shown in FIG. 3.

With the parts positioned as shown in FIG. 1, when ram 30 is lowered the disc is cupped to the special shape shown in FIG. 2, by compression in bore 17 between the die bottom formed by bushing surface 19 and fixed plunger end 22 as the nose 33 presses into the metal of the disc.

As a result in the cup the metal in the bottom 3 is subjected to a compressive working of about 50 percent and a side wall extrusion is produced up between the die bore 17 and the ram nose 33. Here, for example, a brass disc having a weight of about 290-300 grains, a diameter of about 0.750 of an inch and a thickness of about 0.320 of an inch is reshaped at 3 to a thickness of about 0.160 of an inch and a height at 5 of about half of an inch varying in radial thickness from about 0.150 of an inch adjacent bevel 9 to about 0.170 of an inch adjacent bevel 10.

Ram 30 is put in readiness for the next operation as soon as cam shaft 23 has turned counterclockwise sufficiently to align plunger 21 and its roller 25 first with the cam downgrade 27 and then with the low area 28. While the cam moves in this way to free plunger 21, ram 30 is lowered further into the same die so that after cupping by reverse extrusion, a forward extrusion may take place. Both operations occur consecutively in a single stroke or pass of the press by taking advantage of the extreme Working of the metal accomplished in cup 2 as nose 33 and collar 34 advance against the metal.

Acting upon the work heated cup formed, ram squeeze surface 35 presses down against the beveled edge 9 of the cup the bottom of which at bevel is thereby pressed against the die entry and squeeze surface 19 causing the metal to extrude forward through the open die bottom between the lateral surface of the tube wall former nose 33 and the die bushing constriction as collar 34 approaches bushing 18 for coaction between the apparatus and cup 2. Because of the conical shape of nose 33 the thickness of the metal produced as shown in FIG. 3 in the side wall 6 adjacent the bottom 7 will be slightly more than the thickness of the metal in the side wall adjacent the scrap ring 8 left at the end of the forward extrusion operation. In the example illustrated in FIG. 3, the cup having a diameter of about 0.750 of an inch was extruded through a constriction at 20 having a diameter of about 0.525 of an inch. As the tube product 4 is formed, plunger 21 is driven down by the extrusion until the roller rests on the cam shaft low area 28. 1

Further counterclockwise movement of cam shaft 23 brings the cam rise 29 into contact with roller 25 for lifting plunger 21 to effect an ejection of the tube product 4 as ram is lifted by upper press block 31, completing a cycle.

Although both cupping and forming takes place by extrusion consecutively in a single pass of the press, which mounts blocks 13 and 31 and the cam shaft 23, it will be appreciated that the apparatus may be modified to permit ejection of the intermediate cup product 2. In this event, the intermediate cup blank must be subjected to an intermediate anneal, where desired, to cleaning, and lubrication prior to reinsertion and further extrusion as shown in FIG. 3. This permits practice of the invention in two stages involving two independent strokes of the press.

By conducting the operation at a suitable speed, the sequence of operation is preferably conducted in a single pass of the press involving reverse extrusion, followed by forward extrusion.

A brass shell product 4 produced according to this invention has its base 7 produced from the compressively reduced central portion 3 of the cup blank and both this and the wall 6 of the extruded piece can both be annealed to about a 0.35-0.40 mm. grain size, a remarkable uniformity of grain refinement. A comparable tube product made from rolled strip stock has a much coarser grain in the base, usually about the same as in the rolled stock because of the little additional working occurring in this area.

The tubular product formed is especially suited for making a metal cartridge case 40, the improved head of which is shown in FIG. 4 after further fabrication. By remaining finishing steps involving trimming off the scrap ring, annealing, washing, drawing, followed by indenting, heading, and piercing, case 40 is produced having not only a strong finished side wall 41 but also a strengthened head structure at a web 42 adjacent the primer pocket 43 and flash hole 44.

The present method produces a superior cartridge case and is quicker and less productive of scrap. A significant cartridge case improvement and great saving in cost are made possible, even where an annealing operation is interposed between the cup extrusion and the shell extrusion.

This method makes possible further economy of production from use of various direct cast slugs of substantially uniform weight, size, shape, and composition, not only of the disc type shown in FIG. 1, for example, but also of the drop cast pellet type disclosed in US. Patent No. 2,919,471, granted January 5, 1960.

What is claimed is:

1. The method of making a metal shell product closed at its base comprising (a) placing into a round die one at a time substantially uniform round blanks of metal received therein in centered relationship and having a coarse grain in the range from about 0.150 mm. to about 6.5 111111., (b) pressing each said blank by .a ram having a reduced end former centrally in the closed end of said round die receiving said blank and former and thereby compress ing the center while simultaneously reverse extruding the marginal edge of said blank to form in said die a cup of said metal having a central bottom compressively cold worked in said die to a reduction of about 50 percent to produce a substantial length of cylindrical wall integral with the margin of said bottom, and then (c) pressing said wall lengthwise in said die to subject said margin and wall to a forward extruding around said former and through a reduced die aperture, thereby providing said shell product having a worked tubular section elongated by said pressing of said wall to at least a final increased length and reduced thickness integral with said compressed bottom forming said base, said section worked for grain refinement by said extruding and said base worked for grain refinement by said reduction, substantially equal to the refinement in said section.

-2. The method of making a metal shell product closed at its base comprising (a) placing into a die one at a time substantially uniform metal blanks slidably fitting in said die and having a relatively coarse recrystallized grain structure, (b) pressing each said blank centrally in one direction toward the closed end of said die receiving said blank in centered relationship for reducing the center and simultaneously extruding the marginal edge of each blank to form said blank to a cup of said metal having a central bottom reduced in thickness in said die by a cold reduction of at least about 50 percent and a cylindrical wall extruded reversely of said direction to a length integral with the margin of said bottom, and (c) with said cup in a die having a reduced aperture relative to said cylindrical wall, pressing said wall lengthwise in said direction to subject said margin and wall to a forward extruding through said reduced aperture thereby providing said shell product having a tubular section worked for grain refinement by said extruding and elongated to increased length and reduced thickness integral with said reduced bottom forming said base worked by said reduction for grain refinement substantially equal to said refinement of said section upon subsequent annealing.

3. The method of making a cartridge case from a metal shell product closed at its base comprising (a) placing into a die a disc of brass having a coarse grain size relative to that of the worked metal and comparable to that of the cast metal and having a diameter not more than the diameter of said die, (b) pressing said disc cold into the closed end of said die of said diameter with a ram of smaller diameter adapted to compress the central portion of said disc by a reduction of at least about 50 percent in thickness to a reduced bottom and simultaneously extrude back the marginal edge portion of said disc to a wall of substantially about the same thickness as said bottom and integral with the margin of said reduced bottom to form a shallow cup, and subsequently (c) pressing the wall to extrude said wall and margin with said ram forwardly through a reduced aperture of a die, thereby providing said shell product of elongated shape having a tubular section worked to increased length and reduced thickness for grain vrefinement and integral with said reduced bottom forming said base, said base worked by said reduction for about the same grain refinement upon annealing, and having opposite said base a residual ring adapted for severance from said Wall for finishing said product to the shape of said case including a strengthened head from the grain refined metal at said base.

4. The method of making a cartridge case from a metal shell product closed at its base comprising (a) placing in an axially extending die a blank of 70:30 brass having a relatively coarse grain size of from about 0.150 mm. to about 6.5 mm. and transverse dimensions adapting said blank to slideably fit into said die in centered relationship, (12) axially pressing said disc col-d with a ram into the closed end of said die of substantially the same diameter as said ram having an end former of smaller diameter adapted to compress the central portion of said blank to a reduction of at least about 50 percent and simultaneously extrude back the marginal edge portion of said blank in substantially about the same diameter for forming a cup with a reduced central bottom integral with a round cylindrical wall, and subsequently (c) pressing the wall to extrude a substantial part of said wall forwardly and drive said bottom end part through a reduced diameter aperture of a die over said end former of smaller diameter, thereby providing said shell product of elongated shape having a a tubular section worked to increased length and reduced thickness for grain refinement of said section integral with said bottom forming said base, said base worked by said reduction for about the same refinement, and having opposite said base a residual ring of said brass adapted for severance from said wall, said refinement being in the range of from about 0.030 mm. to about 0.050 mm. grain size upon annealing of said product.

5, Apparatus for making a metal shell product closed at its base and adapted for metal grain refinement in said base as well as in its tubular section integral with the base comprising an extrusion die having a bore for receiving a metal blank, fitting in centered relationship in said bore; said die having adjacent one end of said bore an extrusion bushing provided with an annular stationary constriction and a beveled squeeze surface leading from said bore to said constriction; plunger means moveable relative to said die to form in said bore at said constriction a die closure; a ram adapted to slideably fit in and close said bore opposite said die closure, said ram having a reduced leading end providing a metal former adapted for first pressing said blank centrally in said die against said die closure tor centrally reducing said blank to a thinned bottom of worked metal and reversely extruding a substantially cylindrical wall of metal up between said die and former; means for imparting relative movement between said ram and closed die to effect said first pressing and reverse extrusion, said ram having a second squeeze surface annularly surrounding said former; and means for withdrawing said plunger from said constriction to provide thereat a reduced die aperture and to further move said ram former into said aperture and said second squeeze surface against said wall for pressing said wall to eliect a forward extrusion between said constriction and former, thereby providing said shell product having said tubular section worked to increased length and reduced thickness integral with said base formed from said bottom worked for grain refinement by said first pressing and subsequent annealing.

6. The method of making a shell product closed at its base comprising (a) placing into a die a blank of metal adapted to be received in centered relationship and having a coarse grain relative to the worked metal and comparable to that of the cast metal, 8

(b) pressing aid blank centrally into the closed end of said die and thereby reducing the thickness of the blank centrally by a cold reduction and simultaneously reverse extruding the blank marginally to form a cup of said metal in said die having respectively a central bot-tom worked to a reduced thickness and also having integral with said bottom a cylindrical wall worked to a substantial length, and I (c) pressing said wall lengthwise in a die for forward extruding metal in said length about a central former and through a reduced die aperture thereby providing said product having a tubular section elongated by pressing of said wall to at least final length and reduced thickness of said section integral with said bottom forming said base, said base by said reduction and said section by said reverse and forward extruding being worked for more nearly equal grain refinement upon annealing .to recrystallize the metal in said base as well as in said section.

7. The method of claim 6- wherein the pressings are such that the base and tubular section are worked to a reduction of at least from about 45 percent to about 55 percent for refinement in the base substantially equal to the refinement in the tubular section.

8. The method of claim 6 wherein the bottom is reduced in thickness by a reduction 'of about 50 percent.

References Cited by the Examiner UNITED STATES PATENTS 1,925,823 9/33 Singer 291.3 X 2,805,466 9/57 Lyon 29'1.3 2,840,884 7/58 Biginelli 29-l.3

FOREIGN PATENTS 507,071 11/54 Belgium.

5,014 4/92 Great Britain. 627,697 8/49 Great Britain. 834,626 5/60 Great Britain.

RCHARD H. EANES, IR., Primary Examiner.

Claims (1)

1. THIS METHOD OF MAKING A METAL SHELL PRODUCT CLOSED AT ITS BASE COMPRISING (A) PLACING INTO A ROUND DIE ONE AT A TIME SUBSTANTIALLY UNIFORM ROUND BLANKS OF METAL RECEIVED THEREIN IN CENTERED RELATIONSHIP AND HAVING A COARSE GRAIN IN THE RANGE FROM ABOUT 0.150 MM. TO ABOUT 6.5 MM., (B) PRESSING EACH SAID BLANK BY A RAM HAVING A REDUCED END FORMER CENTRALLY IN THE CLOSED END OF SAID ROUND DIE RECEIVING SAID BLANK AND FORMER AND THEREBY COMPRESSING THE CENTER WHILE SIMULTANEOUSLY REVERSE EXTRUDING THE MARGINAL EDGE OF SAID BLANK TO FORM IN SAID DIE A CUP OF SAID METAL HAVING A CENTRAL BOTTOM COMPRESSIVEDLY COLD WORKED IN SAID DIE TO A REDUCTION OF ABOUT 50 PERCENT TO PRODUCE A SUBSTANTIAL LENGTH OF CYLINDRICAL WALL INTEGRAL WITH THE MARGIN OF SAID BOTTOM, AND THEN (C) PRESSING SAID

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