AU635990B2

AU635990B2 - A method of fabricating firearm cartridge cases, and the cartridge case obtained by implementation of such a method

Info

Publication number: AU635990B2
Application number: AU68256/90A
Authority: AU
Inventors: Mette Jensen
Original assignee: GORDON CONSULTING ENG
Current assignee: Gordon Consulting Engineering & Marketing Ltd
Priority date: 1989-12-22
Filing date: 1990-12-19
Publication date: 1993-04-08
Anticipated expiration: 2010-12-19
Also published as: YU241390A; CA2013981A1; CN1023512C; ATE99044T1; BR9006561A; RU2069302C1; IT8903784A0; CA2013981C; DE69005432T2; EP0435830A1; DE69005432D1; AU6825690A; CN1054131A; ES2047306T3; EP0435830B1; IT1235986B

Abstract

The method according to the invention, which allows the manufacture of cartridge cases for firearms of the type having three elements represented by a cylindrical tube (2), a strengthening part (3) which can be arranged in the tube (2) and a base (4) capable of fitting over the tube (2) provides for: the use of a strengthening part (3) obtained from an almost non-deformable material and already provided with at least one end-tooth (31) on the perimeter and protruding from the said part, the use of a base (4) having an open bottom and of different diameters provided for the formation of an annular tapered collar (43) defining a housing (45) in which can be received the anchoring tooth (31) of the strengthening part (3) and one of the ends (21) of the tube (2); and the formation of the case (1) by the insertion of the tube (2) into the base (4) in such a way that it protrudes beyond the portion (41) of smaller diameter of the base (4), by the insertion of the strengthening part (3) firstly into the base (4) and then into the tube (2) in such a way as to fold the respective end portion (21) until contact with the wall of the housing (45) defined by the collar (43) of the base (4) and finally by the folding of the portion of larger diameter (42) of the base (4) in such a way as to bring it into contact with the strengthening part (3). <IMAGE>

Description

635990 S F Ref: 150549 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: 44 4e

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4 4 Name and Address of Applicant: Gordon Consulting Engineering Marketing Limited 100 Chalk Farm Road London NW1 8EH UNITED KINGDOM Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Address for Service: 04 4 4444 4 Complete Specification for the invention entitled: A Method of Fabricating Firearm Cartridge Cases, and the Cartridge Case Obtained by Implementation of Such a Method The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/3

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A METHOD of FABRICATING FIREARM CARTRIDGE CASES, and the CARTRIDGE CASE OBTAINED bv IMPLEMENTATION of SUCH a METHOD ABSTRACT of the DISCLOSURE fig 1 A cartridge case is assembled from three pieces, namely a cylindrical tube, a strengthening piece insertable in the tube, and a base ensheathing the end of the tube occupied by the strengthening 05 piece, utilizing a strengthening piece fashioned in *a substantially non-deformable material with a ready-made radially projecting flange; the base is open at both ends, and formed with stretches of dissimilar diameter interconnected by a flared reduction the internal surface of which creates a seating by which the flange can be accommodated together with one end of the tube. Having inserted the tube through the smaller diameter of the base a ""short way into the larger diameter stretch, the strengthening piece is inserted into the base from the opposite direction, located in the tube, and driven forward such that the end of the tube is splayed and sandwiched between the flange and the seating, whereupon it remains only to crimp the excess part of the larger diameter stretch inwards to lock the strengthening piece in place.

2 BACKGROUND of the INVENTION The invention relates to a method of fabricating three-piece type cartridge cases, and by extension, to the cartridge case obtainable by implementation of such a method.

Cartridge cases, in particular those for guns used in hunting and competition shooting (skeet), are fashioned conventionally by assembling a number of discrete parts consisting but minimally in material of any value, in order to gain economies both in 10 manufacture and ultimately in use, given that such items are generally fired once and discarded.

In the method of fabrication most widely adopted for three-piece cartridge cases, use is made of a tube of plastic or paper material, a cylindrical strengthening piece, also in plastic or paper, and a metal base.

The base appears essentially as a cylinder of which the bottom end is enclosed and enlarged around the periphery by incorporation of a molded rim serving to create an complementary internal seating, and is holed at center to take a cap for detonation of the propellant. The tube, likewise cylindrical, slots into the base until fully abutted with the enclosed bottom, and the peripheral edge o, the inserted end may also be rolled inwards toward its axis, for a reason that will become apparent in due course. The strengthening piece is also cylindrical externally, affording a center hole designed to align coaxially with the hole in the base which accommodates the cap, and is fashioned in a deformable material for a reason that will emerge from the brief outline of the conventional method which follows.

For example, the strengthening piece is inserted into one end of the tube, and this preassembled end then pushed full into the base to the point where contact is made with the enclosed bottom; in the event that the edge of the tube is rolled inwards, as aforementioned, the tube will be inserted into the base, and the strengthening piece then inserted into the tube and located against the rolled edge.

Thereafter, with the three pieces positioned one in relation to the other and correctly held in place,

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a compressive force is applied to the strengthening piece, which under the resultant stress is required tc perform two basic functions: first, to compress the tube against the internal cylindrical surface of the base, and second, to deform the rolled edge of the tube radially in such a way as forces it into the seating created within the molded rim of the base. During such an operation, considerable mechanical stresses are applied to the materials both of the tube, and of the strengthening piece in particular, which can cause irreparable damage if not properly controlled. For example, if too great a force is applied to the strengthening piece, the stretch of the tube inserted into the base may be pinched too tightly and its ability to withstand tensile stress thus weakened, resulting in a loss of strength when the cartridge is fired.

S. This complex and delicate assembly is nonetheless indispensable in order to ensure that the tube does Poe, not separate from the base on detonation of the charge and enter the barrel of the gun, of which the consequences would clearly be hazardous.

P This same assembly procedure serves also to ensure that the base of the cartridge, accommodating the cap and bolstered by the strengthening piece, will 20 afford firm resistance to the firing pin of the gun at the moment when the cap is struck; the requisite properties of rigidity and strength, which can be ensured only where relative movement between the three pieces is disallowed, must be calculated with absolute precision to avoid any risk of irregular initiation and detonation of the charge.

A further aim of the operation in question is to eliminate or at least to minimize the leakages of combustion gas that tend to occur from between the tube and the strengthening piece, which distort the base and thus affect the dimensional structure of the cartridge case.

Numerous instrinsic problems are thus posed in the assembly operation, first among which is the need 9.g 6: 10 for technically complex and high powered machinery, given the requirement for a considerable force to *be generated internally of a restricted space such as that afforded by a cartridge case. Moreover, the part of the machine that engages the strengthening piece and invests it with the compressive force must be of a precise shape, in order to permit of applying the force correctly to ensure a tight .union of the three pieces and obtain the desired ~rigidity of the base.

Neither is it possible to ignore the many external factors adversely affecting the assembly operation and tending to inhibit a firm association between the three pieces. Among such adverse factors are the restrictive dimensions of the seating afforded by the molded rim of the base, the difficulty of bringing about a repeatable and uniform insertion of the tube and strengthening piece materials into the r-ating to provide an efficient anchorage, and the possible tendency of the elastic strengthening material to regain its original shape.

This 'etirb r. ,.ge of factors is aggravated further by the obvious difficulty of verifying with the aid of non-destructive technical or visual means that forcing of the strengthening piece has resulted in o 10 the successful formation of a lip internally of the base seating, this being in effect the one element *4 capable of ensuring a positive connection between the three component pieces.

Accordingly, the object of the present invention is to provide a method of fabricating three-piece type cartridge cases whereby the connection of the three pieces can be maintained secure from assembly right through detonation and discharge without the aid of powerful compressive forces during assembly tending 20 to deform and thus alter the geometry of one or more of the compronent parts of the case.

A further object of the invention is to permit of assembling cartridge cases by adoption of a simple, rational and economic method capable of overcoming the drawbacks mentioned above.

SUMMARY QOF THE INVENTION There is disclosed herein a method of fabricating a firearm cartridge case, the case comprising: a cylindrical tube, a substantially non-deformable strengthening piece located in one end of the tube, the strengthening piece comprising an annular tapered flange having a maximum diameter not less than the external diameter of the tube, and a base located about said strengthening piece and said one end of the tube, the method comprising: in forming said base, providing a hollow metal piece having open end portions, the first end portion having an internal diameter substantially equal to the external diameter of said tube and the internal diameter of the other second end portion having an internal diameter substantially equal to said maximum diameter of said flange, said first and second end portions being connected by a tapered portion having a taper substantially following the shape of said annular tapered flange, inserting the tube into the first end portion of the base such that an end of the tube resides alongside said tapered portion of the base, inserting the strengthening piece into the base via said second end .portion such that said annular tapered flange engages said end of the 2 tube and deforms the same into close contact with said tapered portion of o 25 the base, and ~rolling, crimping or otherwise folding said second end portion of the base into contact with the strengthening piece.

*...BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: -fig 1 illustrates the three pieces of a cartridge case according to the invention, In axial section, seen in readiness for assembly by implementation of the method disclosed; RLF/ .2561 8 -figs are further axial sections of the three pieces of fig 1, seen during successive steps of the method disclosed; -fig 5 illustrates a different embodiment of the cartidge case of fig 4, seen in axial section; -figs illustrate three different embodiments of the strengthening piece shown in fig 1.

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DESCRIPTION of the PREFERRED EMBODIMENTS o OSS S Referring now to the drawings, the method according to the present invention permits of fabricating a cartridge case, denoted 1 in its entirety, embodied in three component parts: a cylindrical tube 2, a strengthening piece 3 insertable into the tube, and a base 4.

The method disclosed consists first and foremost in fashioning a basically cylindrical strengthening piece 3 from essentially non-deformable material, of shape such at least as to exhibit a peripheral lip, or flange, denoted 31, which in the example illustrated exhibits a maximum diameter 3d greater than the maximum diameter 2d of the tube, and is flared in relation to the cylindrical surface of the component.

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0* 6e 0*SS Needless to say, the strengthening piece 3 will be non-deformable not in any absolute sense, but only insofar as no deformation occurs during the steps of the method disclosed. Also, reference to the strengthening piece 3 of a cartridge case according to the invention vs being non-deformable permits conveniently of drawing a clear distinction with the corresponding component in a conventional cartridge case, of which the drastic deformation undergone during assembly is such as to alter both its geometry and its mechanical properties; whereas the application of a strong compressive force is intended conventionally to enhance rigidity of the flat bottom of the base, this very notion places a marked limitation on the number of profiles that can be adopted for the strengthening piece, which in the finished cartridge is positioned in direct contact with the propellant.

The method according to the invention comprises the further expedient of adopting a base 4 embodied with two coaxial stretches 41 and 42 of dissimilar internal diameter 41d and 42d, respectively, of which the smaller diameter 41d is substantially equal to the external diameter 2d of the tube 2, and the larger diameter 42d is substantially equal *000 0 00 0 2 to the maximum diameter 3d of the flange 31 of the strengthening piece 3. The two coaxial stretches 41 and 42 are interconnected by a stretch 43 serving to create a peripheral rip, matched in profile with the flared flange 31 of the strengthening piece 3, internally of which a complementary seating 45 is afforded of dimensions such as to accommodate the flange 31 and one end 21 of the tube 2: together.

Utilizing a strengthening piece 3 and a base 4 10 embodied thus, the method disclosed comprises the following steps: -insertion of the tube 2 into the base 4 to the e a.

o point where the inserted end 21 projects beyond the level, denoted 44, at which the smaller diameter stretch 41 of the base 4 merges with the rim 43, by a distance 1 not less than the axial dimension of the peripheral flange 31 (fig 2); -insertion of the strengthening piece 3 into the base 4 and into the projecting end 21 of the tube 2 in such a way that the projecting end 21 is splayed and driven into 'contact with the internal wall of the seating 45 (fig 3); -folding of the larger diameter stretch 42 of the base 4 in toward center to the point where contact is made with the strengthening piece 3 (fig 4).

11 The length 1 of the inserted end 21 of the tube 2 may vary from the minimum shown in fig 4, in which case the flange 31 of the strengthening piece 3 registers in direct contact with the inside wall of the larger diameter stretch 42 of the base 4, up to a maximum that exceeds the axial dimension of the flange 31, measured parallel to its generators, in such a way that the tube projects into the largkr diameter stretch 42 to the point of enveloping the 10 flange 31 entirely (see fig In this instance, the outer diameter 3d of ,he peripheral flange 31 e* will be substantially equivalent to the internal 0* diameter 42d of the relative stretch of the base 4, minus twice the thicknsss s of the tube 2.

It will be apparent immediately that the method disclosed hinges on the adoption of a strengthening piece that is preformed, and can be assembled with .other components to create a rigid fabricated whole by exploiting an established geometry that remains 20 unaltered throughout the assembly procedure.

Expressed in other terms, the stability of the fit between tube 2, strengthening piece 3 and base 4 is ensured by a geometrical shape that is discernible and verifiable prior to assembly and remains stable right through to completion of the assembly steps.

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Accordingly, the machine used to lock together the three components, namely the tube 2, st ingthening piece 3 and base 4, will be a simple and economical item of equipment when compared with the machines currently in use; thus, the costs of manufacturing cartridge cases can be cut drastically by virtue of the substantially smaller capital outlay, and the significant savings in expenditure on labor, raw materials and maintenance of the equipment. In the case of conventional equipment currently in use, in effect, where one has considerable forces unleashed in confined spaces such as that encompassed by a cartridge tube, servicing of the higher precision machines (presses in particular) is essentially an on-going process. As to the consumption of raw materials, this is undoubtedly reduced by adoption of the method disclosed, inasmuch as the base 4 is of open design rather than enclosed as in prior art embodiments. What is more, the method disclosed permits of eliminating the operation of roll-edging one end of the tube 2 in order to improve the fit between the three components.

As illustrated in fig 4, a typical cartridge case 1 obtained by implementation of the method disclosed will be seen to consist in a tube 2, an open-ended

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00005 base 4 ensheathing the tube, and a strengthening piece 3 that is embodied with a radially projecting peripheral flange 31 and inserted into the tube.

Given that the strengthening piece 3 is not subject to appreciable deformation during assembly, it can be embodied with the geometrical shape best able to ensure that the cartridge case 1 is as functional and ballistically effective as possible.

For example, 38 denotes the part of the piece 3 in contact with the propellant, which might be cupped as illustrated in the drawings; this part could be embodied with projections 33 disposed peripherally about an axial hole 32 in the strengthening piece 3 which serves to accommodate a detonation cap Such projections 33 have the function of ensuring that the propellant powder, which is subsequently )acked into the cup 38, does not smother the fire issuing from the cap 5 seated in the hole 32, and might be embodied as a plurality of fins radiating from the hole; in positive terms, the fins serve to increase the propagation front of the ilame thrown by the cap The axial hole 3 in the strengthening piece 3 might be embodied in a variety of ways in order to enable the accommodation.of different types of cap 5; the hole 32 could incorporate a rigid element 34, for example, serving as the anvil for a conventional "Berdan" type cap (fig 7).

In a further embodiment, the strengthening piece 3 could exhibit a peripheral groove 35, and created between the groove 35 and the cup 38, a web 37 that is able to flex in the face of thrust generated by the detonating powder. In.this type of embodiment, the flexibility of the web 37 remains compatible 10 with the essentially non-deformable characteristic of the strengthening piece 3 described earlier. In effect, the web 37 undergoes no deformation during

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assembly of the three components of the cartridge case, even as a result of such forces as may be generated in the course of the procedure, though deformation is indeed envisaged thereafter, when the cartridge is discharged and becomes subject to forces infinitely greater in absolute terms than

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those attributable to the steps of the method as 20 described above.

Fig 8 illustrates an embodiment of particular interest as regards the question of saving on raw materials. More exactly, the strengthening piece 3 is relieved of material at points 36 on the side accommodated by the larger diameter stretch 42 of 9* 9 .e 9 9 .9 9* the base, and in the case in question, simply by sinking a number of blind holes. Such an expedient is made possible by virtue of the fact that the piece is not subject to any deforming stress worthy of note during assembly of the cartridge case 1, and being thus able to retain its shape unaffected, can be embodied with any given geometry provided that the peripheral flange 31 is included.

The method disclosed provides a facility not found in prior art cartridge case manufacture, namely, of selecting the' geometry of the strengthening piece 3 according to the features it may be sought to build into the cartridge case; the strengthening piece 3 thus plays an active role in fabrication, given that a variation in its shape has material bearing on the performance of the finished cartridge.

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Claims

1. A method of fabricating a firearm cartridge case, the case comprising: a cylindrical tube, a substantially. non-deformable strengthening piece located in one end of the tube, the strengthening piece comprising an annular tapered flange having a maximum diameter not less than the external diameter of the tube, and a base located about said strengthening piece and said one end of the tube, the method comprising: in forming said base, providing a hollow metal piece having open end portions, the first end portion having an internal diameter substantially equal to the external diameter of said tube and the i; 15 internal diameter of the other second end portion having an internal diameter substantially equal to said maximum diameter of said flange, said first and second end portions being connected by a tapered portion having a taper substantially following the shape of said annular tapered flange, 20 iriserting the tube into the first end portion of the base such that an end of the tube resides alongside said tapered portion of the base, inserting the strengthening piece into the base via,. said second end portion such that said annular tapered flange engages sad end of the tube and deforms the same into close contact with said tapered portion of 25 the base, and rolling, crimping or otherwise folding said second end portion of the base into contact with the strengthening piece.

2. The method of claim 1, wherein the maximum external diameter of the flange is substantially equal to the greatest internal diameter of the base minus twice the thickness of the tube.

3. The method of claim 1, wherein the inserted end of the tube projects beyond the level at which the smaller diameter portion of the base merges with the tapered portion, by a distance less than the length of said tapered portion.

4. The method of claim 3, wherein the strengthening piece is inserted into the base and the tube, no farther than a bottom face of the strengthening piece. p 7I 5. The method of claim 3, wherein the strengthening piece is RLF/02561 17 fully inserted into the base and the tube, beyond the strengthening piece by a distance such as enables its compression and retention between a folded edge of the larger diameter portion of the base and the bottom face of the strengthening piece.

6. A three-piece cartridge case, obtained by the implementation of the method of any one of the preceding claims.

7. The cartridge case of claim 6, wherein the strengthening piece comprises an axial hole serving to accommodate a detonation cap, and is provided at the emergence of the hole onto a surface offered directly to propellant powder in the case with a plurality of projections of which the purpose is to prevent powder packed into the tube from smothering a flame generated by the cap.

8. The cartridge case of claim 7, wherein the projections provided at the emergence of the axial hole onto the surface of the strengthening piece offered to the propellant powder are embodied as a plurality of fins radiating from the hole.

9. The cartridge case of claim 7, wherein the shape of the axial hole in the strengthening piece is matched to the shape of the accommodated cap.

10. The cartridge case of claim 9, wherein a given proportion of the axial hole of the strengthening piece is occupied by a coaxial element serving as an anvil for a cap accommodated by the remaining proportion of the hole.

11. The cartridge case of claim 6, wherein shape and geometry of 25 the strengthening piece are selected to the end of maximizing ballistic performance and intrinsic safety of the cartridge, without any restriction attributable to assembly requirements.

12. The cartridge case of claim 6, 'herein shape and geometry of the strengthening piece are selected, without any restriction attributable to assembly requirements, in such a manner that at least the part farthest inside the tube is rendered axially flexible in the face of thrust generated by propellant powder in combustion. •13. The cartridge case of claim 12, wherein the strengthening piece exhibits a peripheral groove isolated from propellant by a web of thickness such as to enable flexing movement in the face of thrust generated by the propellant in combustion.

14. 'The cartridge case of claim 6, wherein a face of the strengthening piece not in contact with propellant is relieved of .A material by the formation of at least one concavity or indentation. '/LMM/2561 18 A method of fabricating a firearm cartridge case, the method being substantially as hereinbefore described with reference to the accompanying drawings.

16. A firearm cartridge case substantially as hereinbefore described with reference to the accompanying drawings. DATED this EIGHTH day of FEBRUARY 1993 Gordon Consulting Engineering Marketing Limited Patent Attorneys for the Applicant SPRUSON FERGUSON e. S o RLF/LMM 2561