US2388370A

US2388370A - Primer pocket

Info

Publication number: US2388370A
Application number: US510755A
Authority: US
Inventors: Samuel A Snell
Original assignee: Ryerson and Haynes Inc
Current assignee: Ryerson and Haynes Inc
Priority date: 1943-11-18
Filing date: 1943-11-18
Publication date: 1945-11-06
Anticipated expiration: 1962-11-06

Description

5. A. SNELL PRIMER POCKET Nov. 6, 1945.

Filed Nov. 18, 1945 Emma F7. ENELL'H Patented Nov. 6, 1945 Samuel A. Snell, Jackson, Mich., assignor to Ryerson & Haynes, Inc., Jackson, Mich., a corporation of Michigan Application November 18, 1943, Serial No. 510,755

2 Claims.

The present invention relates to the method of forming primer pockets and flash holes for cartridge cases, the method having particular application to cartridge cases Where the primer extends part way into the head of the case and communicates with the inside of the case through a flash hole, as in fifty caliber and twenty millimeter ammunition.

Heretofore two methods have been generally used in forming primer pockets for cartridge cases. One method involves drilling and reaming, which has not proven entirely satisfactory due to the low rate of production and the high percentage of rejections. Another method employs a coining operation in which the metal displaced by the coining punch is forced outwardly and increases the outside diameter of the head of the cartridge case in proportion to the amount of the metal displaced by the coining punch. This method puts an extremely heavy load on the coining tool with the result that the tools have a relatively short life and causing frequent stoppage to replace worn and broken tools which slows down production'materially.

According to the present invention a new method is provided wherein that part of the metal displaced by the first indenting or roughing punch is permitted to flow into the surrounding part of the head, increasing the outside diameter in the usual manner. The next step is to punch or drill a hole through the head of the casing removing a volume of metal approximately equal to or slightly in excess of the volume of metal displaced by the final tool, and causing the metal displaced by the final tool to flow inwardly practically closing the hole. The next and final step is to punch or drill the collapsed hole to the proper dimensions for the flash hole.

Thus one of the objects of the present invention is to provide a method for increasing tool life and production in connection with the forming of primer pockets and flash holes for cartridge cases.

A further object is to provide a method wherein steps are provided of a character which facilitate the flow of metal and formation of primer pockets and flash holes in cartridge cases in a manner which will result in increased tool life.

These and other objects and advantages residing in the present invention will more clearly appear from a consideration of the following matter.

In the drawing wherein one manner of carrying out the principles of the present invention is disclosed,

Fig. 1 is a cross-sectional view through a cartridge case showing the first coining step of the head,

Fig. 2 is a view similar to Fig. 1 showing a piercing or drilling operation in the region of the flash hole,

Fig. 3 is a view similar to Fig. 1 showing the second coining operation providing the finished primer pocket, and

Fig. 4 is a view similar to Fig. 1 showing the final steps of completing the flash hole.

The preferred sequence of operation for carrying out the method of the present invention is illustrated in the drawing where, in Fig. 1, the cartridge case Ill, having a head I2, is shown with a, generally cone-shaped depression l4 formed by a coining or punching operation using an indenting or roughing punch. The formation of the depression M in the head I2 will cause certain metal to flow in the head l2 outwardly and upwardly, slightly increasing both the diameter and thickness of the head I2. The next operation is to provide the hole I6 in the region of the flash hole, either by piercing or drilling operations. 'The third step in my improved method is illustrated in Fig. 3, wherein a suitable punch has brought the primer pocket [8 into finished form by enlarging the generally conical depression I 4 shown in Fig. l. The enlargement of the depression I4 into the finished primer pocket I8 results in a flow of metal inwardly restricting or reducing the hole Hi to an irregular opening 20 shown in Fig. 3. The final operation in the formation of the primer pocket and flash hole is illustrated in Fig. 4, and consists in piercing or drilling the flash 1 hole 22 to its final form.

The operations above described may be advantageously carried out and performed successfully in a punch press equipped with a dial feed, producing a finished primer pocket and flash hole at each stroke of the press.

It has been foundin practice that by performing the above outlined sequence of operations that the tool life has been materially increased and breakage of tools reduced to a minimum. This has been accomplished primarily through the sequence of operations which facilitates the fiow of metal and provides some place for the metal to flow with greater ease than has been heretofore possible in accordance with standard practices.

What I desire to secure by Letters Patent and claim is:

1. The method of forming primer pockets for cartridge cases comprising the steps of forming a substantially cone-shape depression partly through the head of the cartridge case to permit displaced metal to flow outwardly into the head of the case and leave a solid body of metal between the bottom of the depression and the inside of the cartridge case, connecting the bottom of the cone-shaped depression to the inside of the cartridge case by a hole, shaping the coneshaped depression by pressure to a substantially 2. A method of forming primer pockets for cartridge cases comprising the steps of forming a depression in the head of the cartridge case by causing the metal to flow outwardly, providing an opening between said depression and the interior of the cartridge case, shaping said depression intothe final form of the primer pocket by causing'the metal to flow inwardly into said opening, and thereafter shaping said opening to cylindrical depression, permitting the displaced 10 the final dimension of the flash hole.

metal to flow into the hole, and then enlarging the hole to form a flash hole between the primer pocket and th inside of the cartridge case.

SAMUEL A. SNELL.