Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
  • B21K21/00—Making hollow articles not covered by a single preceding sub-group
  • B21K21/04—Shaping thin-walled hollow articles, e.g. cartridges
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/02—Making uncoated products
  • B21C23/20—Making uncoated products by backward extrusion
  • B21C23/205—Making products of generally elongated shape
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B33/00—Manufacture of ammunition; Dismantling of ammunition; Apparatus therefor

Definitions

• the invention relates to a method of forming a closed end metal tube according to claim 1.
• Brass cases for firearm cartridges are conventionally made in numerous steps and on successive machines.
• cases are formed from brass strip stock that is cupped and then drawn in multiple stages. Annealing steps between the drawing stages are ordinarily required, especially where relatively long cases, such as rifle cases, are being manufactured.
• the strip stock method produces a high scrap ratio, requires energy for annealing, is slow and prone to dimensional variability, and occupies considerable floor space.
• 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.
• a long cartridge case blank is achieved that can be finish drawn to a tube wall thickness that heretofore required annealing between conventional drawing processes.
• 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.
• An object of the present invention is to overcome the disadvantages of the prior art. It is further an object of the present invention to create an enhanced method of forming a closed end metal tube. In particular, less stress is placed on the tooling of the forming machine using the enhanced method.
• the object is achieved by a method of forming a closed end metal tube comprising cutting a blank from a solid round metal wire, backward extruding an axial hole in the blank to produce a hollow sidewall with a thickness, and reducing the sidewall thickness by using a Modified Hooker extrusion.
• 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 or in other words to form elongated hollow parts made from solid metal wire. 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.
• a "Hooker Extrusion” is defined as: The forward extrusion of the outside diameter of a hollow part with a mandrel used to maintain the inside diameter of the extruded part.
• 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.
• tool life is improved and a smaller and faster cold forming machine can be used.
• the outer diameter of the sidewall may stay confined during the Modified Hooker extrusion.
• the tooling life is further improved in said forming method.
• the elongated hollow part is machined by a tool, e.g. a punch, wherein the tool is inserted into the axial hole of the elongated hollow part and is designed to produce a wall thickness that is less than the wall thickness of the hollow part after backward extrusion.
• the tool is only inserted into the axial hole by a first moving distance so that the area below the tool in the hollow part comprises the thicker wall thickness on the sidewall.
• a succession of Modified Hooker extrusions are performed on the sidewall.
• the workpiece is formed smoothly, while the external diameter of the part is maintained.
• the tool is inserted into the axial hole of the elongated hollow part and is designed to produce a wall thickness that is less than the wall thickness of the hollow part after the first Modified Hooker extrusion.
• the tool is only inserted into the axial hole by a second moving distance so that the area below the tool in the hollow part comprises the thicker wall thickness on the sidewall.
• the second moving distance is less than the first moving distance of the first Modified Hooker extrusion.
• the forming part is finish drawn to the final sidewall thickness of the desired part.
• the part can be finish drawn to the final sidewall thickness of the desired part on a smaller forming machine compared to the known method.
• the method is performed on a single forming machine.
• the estimated total forming load is reduced by 50% and the energy consumption is reduced by 40% compared to previously multiple backward extrusion processes.
• Positional indications such as “above”, “below”, “right” or “left” are in each case related to the corresponding embodiments and are not to be understood as restrictive.
• Indications such as “first”, “second”, or “further” are in each case related to the corresponding device and are not to be understood as restrictive or enumeration.
• the invention also encompasses individual features shown in the figures, even if they are shown there in connection with other features and/or are not mentioned above. Further, the term “comprising” and derivatives thereof do not exclude other elements or steps. Likewise, the indefinite article “a” or “one” and derivatives thereof do not exclude a plurality. The functions of multiple features recited in the claims may be performed by a single unit. The terms “substantially”, “approximately”, “about” and the like in connection with a characteristic or a value define, in particular, also exactly the characteristic or exactly the value. All reference signs in the claims are not to be understood as limiting the scope of the claims.
• a cartridge case has a tapered inside diameter associated with a tube wall thickness that reduces away from a cartridge head towards the open end.
• the forming steps illustrated in FIG. 1 are typically done on a multi-station cold forming machine.
• a blank 10 is cut off from a solid round metal wire fed to the forming machine 20 (step 0).
• the blank 10 is squared up by a first tool (step 1), and at a second station 25 of the forming machine 20 the blank 10 is backward extruded by a second tool with an inside diameter (iD) reduced from what was previously done, thereby reducing tool loads (step 2).
• the required forming load to produce a backward extruded hole 11 decreases as the reduction in area decreases.
• the backward extruded hole 11 comprises a minimum hole diameter and therefore the sidewall thickness D0 at its maximum.
• the backward extrusion results in a hole 11 that is minimal while the earlier process requires a hole that is maximal to form a mouth of the blank.
• the backward extruded blank 10 as shown in FIG. 1 is subjected to a first Modified Hooker extrusion at the next station (step 3) and a second Modified Hooker extrusion at the following station (step 4).
• Said first Modified Hooker extrusion leads to an initial decrease in the wall thickness of the sidewall 12 compared to the wall thickness after said backward extruding process.
• the outer diameter aD of the sidewall 12 stays confined during the Modified Hooker extrusion.
• a second Modified Hooker extrusion leads to a further decrease in the wall thickness of the sidewall 12 compared to the wall thickness after said first Modified Hooker extrusion process.
• the outer diameter aD of the sidewall 12 stays confined during the Modified Hooker extrusion.
• FIG. 2 illustrates the start of a Modified Hooker extrusion 30
• FIG. 3 illustrates the completion of a Modified Hooker extrusion.
• a punch 32 exerts a force on the semi-finished cartridge and forms the semi-finished cartridge into shape along a first moving distance 13 in the axial hole 11 with an initial decrease in the wall thickness of the sidewall 12 from a sidewall thickness D0 to a decreased sidewall thickness D1. It is seen from FIGS.
• a further Modified Hooker extrusion will further reduce the sidewall thickness to the sidewall thickness D2 along a second moving distance 14 (see FIG. 1 , step 4).
• 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 - see FIG 1 , step 5.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• General Engineering & Computer Science (AREA)
• Metal Extraction Processes (AREA)
• Forging (AREA)
• Extrusion Of Metal (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=95900107

Family Applications (1)

Country Status (6)

Citations (3)

Family Cites Families (11)

• 2024
  • 2024-06-11 US US18/739,604 patent/US20250375805A1/en active Pending
• 2025
  • 2025-05-14 CA CA3273840A patent/CA3273840A1/en active Pending
  • 2025-05-19 IL IL321016A patent/IL321016A/en unknown
  • 2025-06-05 MX MX2025006541A patent/MX2025006541A/es unknown
  • 2025-06-07 EP EP25181528.8A patent/EP4663318A1/de active Pending
  • 2025-06-09 CN CN202510762076.6A patent/CN121104552A/zh active Pending

Patent Citations (4)

Also Published As

Similar Documents

Legal Events