US2754758A - Primer chamber for a cartridge case - Google Patents

Description

July 17, 1956 R. w. TAFEL ,7

PRIMER CHAMBER FOR A CARTRIDGE CASE Filed July 8, 1952 Z1 29 FIG. IA

, r35 7 mww '1 I I 7 1a g 19 INVENTOR. ROBERT W. TAFEL ATTORNEYS:

different from that used for the cartridge case.

PRIMER CHAMBER FOR A CARTRIDGE CASE Robert W. Tafel, Drexel Hill, Pa.

Application July 8, 1952, Serial No. 297,797

4 Claims. (Cl. 102-44) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and usedby or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to a cartridge case and more particularly to an improved structure for an aluminum cartridge case which will minimize primer leaks and erosion of material about the primer pocket.

In cartridge cases made from material such as aluminum, considerable difficulty has been experienced with leaks and erosion of the material about the primer pocket and base when the cartridge is fired. This is particularly bad from a ballistic standpoint and frequently this condition is so serious that the case material is burned out to the extent that it endangers the gunner.

Although several preventive measures have been proposed heretofore which have proved more or less successful, none of these measures are as efficient as would be desirable. For example, one of the measures makes use of an insert or liner within the primer pocket which is of a harder material than the aluminum used for the case. This assembly has been successful in materially reducing erosion of the metal immediately adjecnt to the primer. However, leaks and erosion of metal still occur between the insert and the case material forming the pocket for the insert.

Therefore, it is a primary object of the present invention to provide an improved structure for a cartridge case which utilizes a separate insert to line the primer pocket.

It is also an object of the present invention to provide an improved structure for a cartridge case which is highly etficient in preventing erosion of the case about the primer pocket.

It is a further object of the present invention to provide an improved structure for a cartridge case which will be eflective in preventing leaks about the primer pocket.

Still further is an object of the present invention to provide an improved structure for the primer pocket in a cartridge case which will effectively seal the pocket against escape of gases.

Another object of the present invention is to provide an improved structure for a cartridge case which is simple and easy to construct and which is highly efficient for its intended purpose.

In accordance with the present invention, the head end of a cartridge case is provided with a cup-shaped insert for receiving a primer, the insert comprising a material A double lip seal is provided for the insert by portions of the case engaging the insert at points about the open end thereof and within the flash hole in the base in a manner to prevent escape of gases between the insert and the material of the case providing the insert pocket.

The novel features of the present invention, as well as additional objects and advantages thereof, will be better understood from the following detailed description when read in connection with the accompanying drawing, in which:

p 2,754,75 Patented July 17, 1956 Fig. 1 is a view, in section, of an apparatus for forming a cartridge case in accordance with the present invention, the parts being shown preparatory to pressing;

Fig. 1A is a view similar to Fig. 1 but showing an intermediate step in the pressing operation;

Fig. 1B is another view similar to Fig. 1 but showing the cartridge case provided with a primer insert, the view being taken after withdrawal of the heading punch; and

Fig. 2 is a side view, partly in section, of a finished cartridge provided with a primer insert in accordance with the present invention.

Referring more particularly to the drawing, a single, preferred embodiment of the present invention is'illustrated using similar reference characters to designate corresponding parts throughout.

The invention is shown applied to a cartridge 1 of conventional design which comprises a cylindrical shell, case, or main body portion 3 having one end 5 open to receive a bullet 7 and the opposite or head end 9 thereof closed.

The case 3 comprises a walled enclosure made from a suitable metal but particularly aluminum, or the like, the characteristics of which are such as to be susceptible to the aforementioned difliculties. The interior of the case 3 is divided into two chambers 11, 13 by a portion 15 of the head end which forms an internal partition wall. The one chamber 11 is utilized to store a powder or explosive charge and the other chamber 13, located within the head 9, is provided for receiving a primer 17.

The head end 9 of the case is provided with a centrally disposed opening 19 which extends axially inwardly and expands within the head end to form the primer receiving chamber 13. In order to minimize erosion of the case material about the primer 17 as well as to prevent gas leaks, an insert 21 is utilized to line the primer receiving chamber. Inasmuch as the insert is made from a material, preferably steel, harder than the material of the cartridge case, it is not as readily susceptible to the aforementioned difliculties of the softer case material. The insert 21 comprises a cup-shaped member having one end 23 thereof open and directed outwardly in alignment with the end wall opening 19. The opposite or base end 27 of the insert is provided with or more vents or openings 29 which serve as flash holes for passage of the primer flash. Both the internal diameter of the insert 21 and the diameter of the end wall opening 19 at the outer end thereof are substantially equal to the outside diameter of the primer 17.

The internal partition Wall 15 of the case is provided with at least one opening 25 which connects the head end chamber 13 with the powder charge chamber 11. The openings 29 in the base of the insert correspond in number with and are aligned with the internal partition wall openings. These aligned openings 25, 29 serve as flash holes through which the flash from a primer passes to ignite the powder charge in a manner well known in the art.

A portion 31 of the interal wall 15 surrounding each flash hole opening 25 extends into the insert opening aligned therewith to an extent no greater than the thickness of the insert base 27 thereby to provide a lip which serves to effect a seal between the insert and the internal wall. A second lip for effecting a seal against leaks between the insert and the case material is provided by a portion 33 of the case head end surrounding the central opening 19 extending over or beyond the periphery of the insert open end but not beyond the inner edge of the open end. Thus, the insert is provided with a double lip seal which is highly effective in preventing the escape of gases between the insert and the case. Should any gases succeed in escaping between the insert and the case, they must follow a long circuitous path thereby minimizing further detrimental etfects. In addition thereto,

As shown in the drawings, the structure lends itself to Y a simple pressing operation to dispose the insert within the head end of the case. Briefly, an apparatus comprising a heading press 35 of conventional design and consisting of a heading die 37, a heading punch 39, and a heading stem 41 is used. A vented insert 21 is placed on an end of the heading punch 39 in the manner shownin Fig. 1. A prepocketed drawpiece v43 of metal, such as aluminum, is disposed within the heading die 37 and supported or reinforced with a heading stem 41 inserted into the drawpiece pocket intended for the powder chamber 11. The end of the drawpiece adjacent to the other pocket is then headed by pressing the heading punch against the drawpiece and die, in the manner shown in Fig. 1A, so that the insert 21 is disposed Within the pocket. The pressing of the drawpiece coins the aluminum into each insert vent or flash hole opening 29 and also over the peripheral edge of the open end 23 of the insert. With this arrangement, it will be recognized that the insert becomes securely fastened or locked within the pocket of the case and is in such close fitting relation therewith as to make the assembly practically leak-proof. Once the drawpiece assembly is removed from the heading press, the aluminum within the insert flash hole 29 is then drilled to provide a connecting passageway between the primer chamber within the insert and the powder chamber. The flash hole should, however, be of such size as to leave a portion of the aluminum as a liner for the insert flash hole.

in order to insure a tight fit for the lip seal about the open end of the insert, it is suggested that the heading punch 39 be provided with an annular embossing ring (not shown) located in radial, spaced relation to and about the pocketing punch end 45 around which the insert is disposed 7 prior to insertion within the case. The function of such an embossing ring will facilitate coining of the metal about the open end of the insert to provide a tighter seal between the case and the insert.

From the foregoing description, it will be recognized by persons skilled in the art that the present invention provides a double lip seal for a primer insert used with cartridge cases of relatively soft material such as aluminum. Because of its simple structure it is readily adapted to a simple manufacturing operation and is highly efficient for the intended purpose. 7

Although there has been shown and described but a single, preferred embodiment of the'present invention, it will also be recognized by persons skilled in the art that changes and modifications are possible within the spirit of the invention. For example, when the occasion warrants it, more than one flash hole may be provided to connect the primer pocket with the powder chamber. Other changes of similar scope will, nodoubt, readily suggest themselves. Therefore, it is desired that the embodiment of the present invention described herein shall be considered merely as illustrative and not as limiting its scope.

I claim:

1. In a cartridge having a case comprising a walled enclosure defining a powder chamber, one end ofsaid case comprising a head end, said head end having a centrally disposed opening extending inwardly thereof and expanding within said head end to form a pocket, at least one other opening in said head end connecting said pocket with said powder chamber, an insert comprising a cupshaped member disposed within said pocket for receiving a primer, said insert having at least one opening in the base thereof, each said insert opening being aligned with said head end other opening and a portion of said head end defining each said other opening extending into said insert opening aligned therewith.

2. In a cartridge having 'a case comprising a walled enclosure defining a powder chamber, one end of said case comprising a head end, said head end having a centrally disposed opening extending inwardly thereof and expanding Within said head end to form a pocket, at least one other opening in said head end connecting said pocket with said powder chamber, an insert comprising a cup-shaped member disposed within said pocket for receiving a primer, said insert having at least one opening in the base thereof, each said insert opening being aligned with said head end other opening, a first portion of said head end defining each said other opening extending into said insert base opening aligned therewith and a secondportionof said head end defining said centralopening extending over said insert open end substantially to the inner edge of said open end.

3. In a cartridge having a case comprising a walled enclosure, one portion of said case comprising an internal wall dividing the interior into a first chamber for receiving a powder charge and a second chamber for receiving a primer, another portion of said case comprising an outer end wall adjacent to said second chamber, said outer end wall being provided with an opening communicating with said second chamber, said-internal wall being provided with at least one opening connecting both said chambers, an insert disposed within said second chamber, said insert comprising a cup-shaped member disposed with the open end'thercof directed outwardly and aligned with said end wall opening, said insert being provided with at least one opening in the base thereof, each of said insert openings being aligned with a separate one of'said internal wall openings and a portion of said internal wall extending into each said insert base opening.

4. In a cartridge having acase comprising a walled enclosure, one portion of saidcase comprising an internal wall dividing the interior into a first chamber for receiving a powder charge and a second chamber for receiving a primer, another portionof said case comprising an outer end wall adjacent to said second chamber, said outer end wall being provided with an opening communicating with said second chamber, said internal wall being provided with at least one, opening connecting both said-chambers, an insert disposedwithin said second chamber, said insert comprising a cup-shaped member disposed with the open end thereof directed outwardly and aligned with said end wall opening, said insert being providedwith at least one opening in the base thereof, each of said insert openings being aligned with a separate one of said internal wall openings, a portion of said outer end wall extending over said open end of said insert substantially to the inner edge of said open end and a portion of said internal wall 1 extending into each said insert base opening.

References Cited in the file of this patent UNITED STATES PATENTS

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