US 2668345 A
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SHELL MAKING PROCESS Filed July 1 1945 2 Sheet et l INVENTOR GEORGE R. E rE/N BY Feb. 9, 1954 G. R. ECKSTEIN 2,668,345
SHELL MAKING PROCESS Filed July 15, 1945 2 Sheets-Sheet 2 INVENTOR GEORGE R. Ec/rs TE/N Patented Feb. 9, 1954 SHELL MAKING PROCESS George R. Eckstein, Bridgeport, Conn, assignor to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application July 13, 1945, Serial No. 604,777
This invention relates, in general, to the manufacture of ammunition, and, more especially, to an improved method of manufacturing all metal shot shells, and, although the following description refers particularly to the production of an aluminum shot shell, it will be understood that the method has other applications and may be successfully used for producing small arms ammunition components and similar seamless metal tubular articles.
Some efforts have been made heretofore to extrude cartridge cases, but these efforts have not culminated in success due primarily to the persistent separation of body and head on firing. This phenomenon occurs most frequently in shot 2 to prevent the case from elongating as a whole so as to take up bolt set-back or to hold the case firmly in the chamber so as to enable movement of the head relative to the body of the case.
All previously known methods of forming drawn and/or extruded small gauge shot shells have been found inadequate and impractical economically for producing cases having the Wall geometry necessary to prevent head separations.
It is a general object of this invention to provide a method of producing all metal shot shells shells of small diameter (.410) because of the extraction difficulties which they offer and the fact that they have the highest pressure level of any shot shell.
The occurrence of head and body separation is believed to result from a small but appreciable set-back of the bolt in substantially all bolt action commercial guns at the time of firing. One explanation for head separation is that, since the thickness of the wall of a cartridge case or shot shell, and, in particular its powder chamber portion, changes from head to mouth by only a relatively small amount, the entire wall expands substantially simultaneously into gripping engagement with the wall of the barrel chamber. This is sometimes referred to as obturation. The obturation of this relatively large area of the wall of the case effectively holds the entire case from moving rearwardly and the pressure acting on the relatively unsupported head (due to bolt setback) willforce the head rearwardly causing a transverse rupture to occur between the head and the body of the case. A second theoretical explanation is that the obturation of the relatively large area of the wall of the case prevents a uniform overall longitudinal expansion of the case (which,
if permitted, might conceivably take up bolt setback) and again encourages a local stretching of the case such as to cause a transverse rupture.
The present invention has its inception in that the discovery that the separation of the body and head may be effectively prevented by forming "walls of a prescribed geometry such that a proper obturation pattern is obtained. Specifically, it has been found that a case having walls which increase in thickness from the mouth of the case to the base of the head will not be subject ,to head separation. A possible explanation is that because of the variable wall section, a local :obturation is effected which is insufficient either which will not develop head separations on firing. It is a further object of this invention to provide an improved method of producing an aluminum shot shell by extruding a seamless metal tubular case having walls of varying cross section, and then forming a head at one end of the'case. A particular object of this invention is the provision of an improved method of producing an aluminum shot shell by first extruding a seamless metal tube, the walls of which increase in thickness from the base of the tube to its open upper end, inverting a relatively thick wall section at the upper end of the tube to provide material for forming a head, and then heading the tube to form a finished shell.
These and other objects, features and advantages of the invention will be more fully understood upon reference to the following description taken in conjunction with the accompanying drawings, in which:
Fig. 1 is a vertical cross sectional view showing a punch and die assembly adapted to express a slug positioned in the die.
Fig. 2 is a cross sectional view similar to Fig. 1, the parts being in the positions occupied at the end of the extruding operation. V
Fig. 3 is a longitudinal sectional view of the extruded tube.
Fig. 4 is a cross sectional view similar to Fig. 3, but showing the closed end of the tube cut off.
Figs. 5 through 8 are cross sectional views of a die and a punch set used in successive order to invert a portion of the profile of the tube.
Fig. 9 is a longitudinal sectional view of the tube having an inverted profile.
Fig. 10 is a longitudinal sectional view of the completed shot shell.
Referring to the drawings, paratus comprises a die l5 having a die aperture indicated generally at it and comprising a conical bottom I! preferably roughened as shown to insure optimum performance, slightly tapered side walls 18 and rounded shoulders it which join the tapered side walls 18 to the base the extruding apof a substantially cylindrical counterbore 20 in the upper end of the die aperture. The specific geometry of the die aperture is particularly suited for extruding the .410 shot shell. It will be understood, however, that modifications thereof are included within the scope of this invention for extrudiiig shells of other sizes.-
The aluminum Sing 22 from which the extruded tube is formed is preferably stamped or coined to have a shape conforming substantially to the profile of the die aperture, all edges of the slug being smooth and rounded. A conical recess 24 is shown in the top of the slug to facilitate longitudinal alignment of the axes of the punch and slug. The recess 24 may also be used as a pocket for holding a lubricant.
The punch 25 is provided with a conical nose 25, the base of which comprises a narrow substantially cylindrical land 26 of slightly greater diameter than that of the shank porticn of the punch and joinedthereto by a skirt 2} having outw r y tan ri w t -an e of h t being substantially 3 in the embodiment shown. Thepunch and die assembly are suitably mounted a r sso e i wel known n h a and which need not beillustrated or described here since it forms no part of the invention.
As the b nch Zimq c nw t e d 15, the metal of the slug is mgved both radially and upwa d y .i qihe s ce. e ihs Pu ch n zfian i e ll i e scua erb r l t i m n gw lhgme i b ni sae ce re e to as reverse eatrusion initially, the width of the swe ten s n themes a Q QKl 3 of the die remains substantially constant and the extruded flangejil formed therebetweeh comprises s taf tia lly cylindrical profile as shown in Figs.
is restricted so that the cross section of the wall a relatively thick wall section having a sub- V Hot-rever as the land approaches the ounded shoulder l9 of the die, the flow of metal of the extruded tube is decreased forming the tapered portion 33 at the based the flange 31?.
,The small radius'of the shoulder it produces a relatively abrupt reduction in thickness of the extruded metal and thereafter as the land 25 ,moves down below the shoulder IQ of the die,
the cross sectionof the wall of the tube being feixtrllded decreases in thicknessmore slowly corresponding substantially to theftaper oi the wall 18 of the die aperture. The completely extruded tube is shown at '28 in Fig. 3. The bottom'o'f the tube is closed by an integral conical cap 35. It will be noted that the inside diameteroi the tube is substantially constant throughout its length,
and that the outside diameter increases steadily from the closed end of the tube to its open upper end. This external taper matches exactly the taper of the .410 shot shell chamber and constitutes the external taper of the finished shell.
The next step in forming the shell is to cut off the conical cap 34. This operation and the subsequentprocess of inverting the profile of the enlarged wall section or flangeiiil are done at successive stations of a horizontal dial press of a Well known type. Theicap cut oil is preferably accomplished by a rapidly rotating saw mounted on the press.
Following cut off, the tapered tube 35, see Fig.
:4, is forced through a die by a plurality of punches of diilerent sizes, as illustrated in Figs. 5, 6, 7 and 8 so as to transfer the profile of the external flange 3!! onto the inside of the tube, this process being termed profile inversion. To this end, the tube is inserted with its small end first into a die 36, the aperture of which comprises a bore 31 having a taper corresponding substantially to the taper of the outer wall of the tube; and a countersink 31 constituting a relatively steep tapered surface. Initially, a punch 38 having a frusto-conical nose 39, the base diameter of which corresponds substantially to the major diameter of the countersink 31' is adapted to force the flange portion 38 of the tube into the countersink 31 thereby moving the metal of the flange inwardly radially to the extent "shown in Fig. 5.
Following this, the punch 38 is withdrawn from the die 36 and a second punch 40 is entered into the die to push the tube further into the bore 31. Theproi'lle of the nose of the punch 48 is substantially identical to that of the punch 38, but is of smaller base diameter. This second step brings more metal of the flange 30 to the inside of the case, as shown in Fig. 6. The final working step is shown in Figs. 7 and 8, in which a third punch 22 of still smaller diameter but having a similar nose profile completes the process of pushing the tube 35 through the die, the result or whichis to force all of the metal of the flange 35 to the inside of the tube. The profile of the resulting restriction in the tube cornprises a substantially cylindrical section 54 and a relatively abrupt taper 45, and, in these respects, is substantially thereverse of the original profile or" the fiangieor heavy external wall section of the tube. The outside profile 0f thissection of the tube has been made substantially cylindrical as indicated at 46 in Fig. 9.
The particular profile inversion die and pdnch assemblies shown in Figs. 4 through '7 are "for forming the .410 "aluminum shot shell and to this end the punches '38, 40 and 42 are substantially 0.625 inch, 0.525 inch and 0.450 inch in 'd'lafineti respectively. Moreover, for optimum performance, the angle of the frusto-conicalrio'se of fe'ac'h punch is substantially 33 which is considered critical for the extrusion of aluminum.
Following profile inversion, the tube is transferred to a conventional-case heading machine which embodies a heading die the bore of which has a taper equal tothe external taper of the tube, the die being fixed-ly supported in ak'ial alignment with and between the workpiece engaging ends are horizontally mounted reciprocable punch and -hunter. The tube is inserted into the heading die with the invertedprofile end of the tube opposite the hunter. The punchis then moved into the opposite end of thetub'e until the end of the punch engages the restriction 43 formed therein by the metal of the in verted profile and thereafter the he'adingbunter is moved forcefullyin'toengagement with theadjacent open end of the 'tube'causing the metal which constitutes the inverted profile'to flow inwardly substantially radially around the primer pocket-forming nib of the hunter and to form a solid head having a primer pocketf4 1, flash hole ligand an extraction rim "49. It will be noted that themetal is relatively free to fiowinwardly radially because offth'e -"centralaperture ol-the inverted pro le and hence? theh eadingoperation which increases'in width from its *junctionwitu the substantially cylindrical internal walls of the case to the base of the head is formed on the inside of the case.
The case or shell formed by the above described process has, therefore, walls which increase in thickness from the mouth of the shell to its base. Moreover, the taper is relatively complex. Forthe .410 aluminum shot shell this taper is exemplified by a wall thickness of substantially 0.035 inch at the junction of the base of the shell and its wall, a wall thickness of substantially 0.019 inch within one-half an inch of the base formed by the tapered exterior wall and the tapered interior wall of the case and thereafter a gradual external taper to a wall thickness of substantially 0.010 inch at the mouth of the shell. It should be emphasized that the final external taper of the major portion of the shell is formed during the extrusion operation and that during the heading operation a similar taper is impressed on the headed section of the shell so that a fully tapered shell is formed without a conventional tapering operation.
This specific taper provides an optimum obturation pattern for the .410 shot shell such that head separation is virtually eliminated, and, al though the process has been described with relation to the use of aluminum, it will be under stood that other metals and alloys of aluminum may be used.
What is claimed is:
1. A method of producing a cartridge case having walls of a predetermined geometry such as to preclude head separations on firing comprising the steps of extruding a thin walled tube having a heavy externally flanged wall section at one end, then completely inverting the profile of said externally flanged wall section by radially swaging same to provide a heavy flange on the inside of said tube, partially closing said one end and then heading said tube by deforming said heavy flanged section.
2. A method of producing a cartridge case hav ing walls of a predetermined geometry such as to preclude head separations on firing comprising the steps of extruding a tube having tapered walls and a heavy externally flanged wall section at the upper end of said tube, then completely inverting the profile of said heavy externally flanged wall section by radially swaging same to provide a heavy flange on the inside of said tube partially closing said upper end, and then heading said tube by deforming said heavy flanged section.
3. A method of producing in successive operations a metal shot shell comprising the steps of extruding a tube having a relatively thin wall of constant internal diameter and an external taper corresponding to the final taper of a finished shell and a heavy externally flanged wall section at the upper end of said relatively thin wall, completely inverting the profile of said flanged wall section by radially swaging same to transfer said heavy wall section to the inside of said tube and partially close said up er end then radially supporting said tube and axially contracting said inverted profile heavy wall sec tion to impress an external taper on said tube adjacent said heavy wall section corresponding to and blending with the external taper of said rel atively thin wall.
4. A method of producing in successive operations a metal shot shell comprising the steps of extruding a tube having a relatively thin wall of constant internal diameter and an external taper corresponding to the final taper of a fin i'shed shell and a heavy externally flanged wall section at the upper end of said relatively thin wall, completely inverting the profile of said flanged wall section by radially swaging same to transfer said heavy wall section to the inside of said tube and partially close said upper end, then radially supporting said tube both externally and internally at predetermined contour limits and axially contracting said heavy wall section simultaneously to impress an external taper on said tube adjacent said heavy wall section corresponding to and blending with the external taper of said relatively thin wall and to form a solid head on said tube having a primer pocket, a flash hole and an extracting rim.
GEORGE R. ECKSTEIN.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,162,183 Mixsell Nov. 30, 1915 1,212,120 Steedman Jan. 9, 1917 2,079,102 Biginelli May 4, 1937 2,104,222 Decker Jan. 4, 1938