Long Cartridge Case

The invention relates to the formation of elongated hollow parts made from solid metal wire.

U.S. Patent Nos. 10,495,430 and 11,333,473 disclose a method of making long cartridge cases that involves multiple backward extrusions of an initially solid cylindrical blank. The high forces involved, at times, can cause poor tool life, leaving a need for a tube forming process that places less stress on the tooling.

The invention requires only one backward extrusion which is less severe than in the prior art process to form a hollow part suitable for use in making a long cartridge case. Additional backward extrusions are avoided by using one or more modified successive Hooker extrusions to obtain a desired wall thickness in the workpiece which can be a preform for a long cartridge having a length greater than 2-1/2 times its diameter.

The Modified Hooker extrusions are varied from conventional Hooker extrusion practice. With a conventional Hooker Extrusion, the internal diameter of the part is maintained. Here, the Modified Hooker extrusions maintain the external diameter of the part.

By reducing the total forming load and energy, tool life is improved and a smaller and faster cold forming machine can be used.

The forming steps illustrated inare typically done on a multi-station cold forming machine. A blankis cut off from a solid round metal wire fed to the forming machine. At a first station the blankis squared up, and at a second station the blankis backward extruded with an inside diameter reduced from what was previously done, thereby reducing tool loads. The required forming load to produce a backward extruded hole decreases as the reduction in area decreases. Here the backward extrusion results in a hole that is minimal while the earlier process requires a hole that is maximal to form a mouth of the blank.

The backward extruded blankas shown in, is subjected to a first Modified Hooker extrusion at the next station and a second Modified Hooker extrusion at the following station.illustrates the start of a Modified Hooker extrusion, andillustrates the completion of a Modified Hooker extrusion. It is seen fromthat only the sidewall of the blankis extruded so that the reduction in area is relatively small. The estimated total forming load is reduced by 50% and the energy consumption is reduced by 40% compared to previously multiple backward extrusion processes. The part can be finish drawn to the final sidewall thickness of the desired part on the same forming machine as the previous forming steps are performed.

It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.