Neck-forming Apparatus For Cartridge Shells

Abstract

A neck is formed on a cup-shaped cartridge shell blank in an axially movable tubular die whose cavity tapers at one end. A tubular mandrel and an ejector pin slidable in the mandrel enter the cavity through the tapering end, and a driver moves axially into and out of the other end. A lost-motion coupling connects the driven ejector pin with the mandrel. A neck is formed on a blank while the blank is pushed by the driver over the stationary mandrel in the tapering die end. The driver moves with the ejector pin to discharge the finished cartridge shell.

Description

This invention relates to the forming of a neck on a tubular blank, and will be described hereinafter with reference to the forming of a neck on an otherwise finished cartridge shell.

It is common practice to form a neck on a cartridge shell blank between a mandrel and a suitable tapering die in whose cavity the mandrel is arranged. As far as the known devices are capable of giving the cartridge neck a precisely predetermined inner and outer configuration, they are either complex in their design and correspondingly costly to build and to maintain in good working order, or they are capable of operating at a low output rate only. Less costly and faster known machines may be capable of precisely shaping the outer face of a cartridge shell or the inner face, but not both.

The primary object of the invention is the provision of apparatus for forming the neck of a cartridge shell or like tubular blank which is capable of reproducing a desired internal and external configuration with high precision at a high output rate, yet is simple and rugged in its construction, and therefore inexpensive to build and to maintain.

The apparatus of the invention permits the neck of a cartridge shell to be formed between a stationary mandrel and a stationary die while the blank is forced through the annular gap between the die and mandrel, and the apparatus is kept simple by the provision of a guide arrangement which guides the die during a limited axial movement on the supporting machine structure, and by coupling the mandrel to the driven ejector pin by a lost-motion coupling for joint axial movement.

Other features, additional objects and many of the attendant advantages of this invention will readily be appreciated from the following detailed description of a preferred embodiment when considered in connection with the appended drawing in which:

FIG. 1 shows a neck-forming apparatus of the invention in elevational section; and

FIGS. 2 to 4 illustrate the apparatus of FIG. 1 in sequential other operating positions.

The drawing shows only as much of an otherwise conventional, cam-operated power press as is necessary for an understanding of the invention.

Referring initially to FIG. 1, there is seen a heavy-walled tubular die 1 whose cavity has a longer and wider axial front section of circular cross section, a narrower, short, cylindrical rear section, and an intermediate conical section axially connecting the two cylindrical sections. The die 1 is axially slidably received in a conforming cylindrical bore of a guide sleeve 2 normally fixed in the stationary supporting structure 11 of the press.

Axial movement of the die 1 on the support 11 in a forward direction is limited by an internal flange 3 which bounds an opening 5 at the front end of the guide sleeve 2 aligned with the die cavity, and in the rearward direction by a cover 6 which is also normally fixed on the support 11 and assists in guiding the die 1. Several, circumferentially distributed, blind bores 4 in an annular radial face 19 of the cover 6 hold helical compression springs 7 which bias the die 1 toward the flange 5 (FIGS. 3 to 5).

A central bore in the cover 6 aligned with the axis of the die 1 slidably receives a tubular mandrel 10. In the position shown in FIG. 1, the mandrel partly extends into the cylindrical front portion of the die cavity, and the forward terminal portion of the mandrel 10 has an annular, radially enlarged sizing portion 12 received in the conical section of the die cavity. An annular notch 13 near the rear end of the mandrel 10 is engaged by two diametrically opposite U-shaped detents 14 radially slidable in recesses of the cover 6 and biased into locking engagement with the notch 13 by helical compression springs 18.

The reduced front portion 8 of an ejector pin 15 is slidably received in the bore of the mandrel 10 and connected with the mandrel by a lost-motion coupling. Rearward axial movement of the pin 15 relative to the mandrel 10 is limited by abutting engagement of an enlarged head 9 on the free front end of the pin portion 8 against the front end of the mandrel. During forward movement of the pin 15 from the position of FIG. 1, a conical face of the pin 15 at the rear end of the pin portion 8 abuttingly engages the rear end of the mandrel 10. The ejector pin 15 is moved longitudinally by a nonillustrated cam driven by the main drive shaft of the press in a known manner, not shown.

The pin 15 is longitudinally or axially aligned with the cylindrical ram or driver 17 of the press which is also cam-operated in the nonillustrated conventional manner referred to above, and thus is synchronized with the ejector pin 15. The driver 17 moves into and out of the opening 5 in each cycle of press operation.

In the position of the apparatus illustrated in FIG. 1, the driver 17 has pushed a tubular, bottomed cartridge-shell blank 16 into the die cavity, through the opening 5, and frictional engagement of the blank with the inner die wall has moved the die 1 against the restraint of the springs 7 to the fixed face 19 of the cover 6.

As the driver 17 moves farther inward of the die cavity in engagement with the outer bottom wall of the blank 16, as shown in FIG. 2, a reduced neck is formed on the open end of the blank 16. The outer configuration of the neck is determined by the shape of the conical and narrower cylindrical walls of the die cavity, and the wall thickness of the cartridge shell neck is precisely determined by the spacing of the stationary sizing portion 12 from the stationary walls of the die 1 while the blank is forced over the sizing portion 12 by the driver 17.

The driver 17 is thereafter withdrawn, the die 1 is moved by the springs 7 against the flange 3, and the ejector pin 15 moves forward (FIG. 3) to engage the inner bottom wall of the blank 13. Because the neck of the blank is resiliently retained by the sizing portion 12, the blank is stretched axially and contracts radially until the neck portion of the finished cartridge shell expands resiliently to slip over the sizing portion 12. Approximately simultaneously, the conical face of the ejector pin 15 cammingly dislodges the detents 14 from the notch 13 and thereafter abuts against the rear end of the mandrel 10 so that the pin 15, the mandrel 10, and the cartridge shell 16 move forward jointly into the position of FIG. 4 in which the cartridge shell 16 is fully exposed outside the cavity of the die 1 and may be removed by hand or by a nonillustrated automatic device.

During the subsequent rearward movement of the ejector pin 15, the head 9 on the front portion 8 of the pin engages the front end of the mandrel 10 to couple the mandrel to the pin and shifts the mandrel rearward into a position in which the head 9 still partly projects from the opening 5 to facilitate insertion of the next blank 16 whereupon the condition seen in FIG. 1 is restored and another neck-forming cycle begins after the mandrel 10 is axially secured by the spring-loaded detents 14.

While the apparatus of the invention has been described hereinabove with reference to the forming of necks on cartridge shells, other applications for the manufacture of similarly shaped containers will readily come to mind.

Cartridge shells have been produced on the illustrated apparatus from brass and mild steel to precisely reproducible shapes at high production rates, and the apparatus has performed satisfactorily over extended production runs. We are not aware of known apparatus of comparable simplicity that would permit a taper and an adjacent reduced cylindrical section to be formed on a cartridge shell neck with similar precision of outer and inner dimensions.

Claims

What is claimed is:

1. In apparatus for forming a neck on a tubular blank including a support, a die mounted on said support and formed with a cavity having an axis and tapering at one axial end, a driver member mounted on said support for axial movement into and out of said cavity through the other axial end thereof, a mandrel member in said tapering end of said cavity, an ejector member axially movable in said cavity, and drive means for axially moving said driver member and said ejector member in timed sequence, the improvement which comprises:

a. guide means guiding said die for limited axial movement on said support;

b. lost-motion coupling means coupling said mandrel member to said ejector member for joint axial movement;

1. said mandrel member being formed with an axial passage receiving said ejector member;

c. releasable detent means on said support for axially securing said mandrel member; and

d. cam means on said ejector member for releasing said detent means in response to an axial movement of said ejector member.

2. In an apparatus as set forth in claim 1, said mandrel member and said ejector member each having respective end portions adjacent and remote from said driver member, the adjacent end portion of said mandrel member being radially enlarged, and the remote end portion of said mandrel member being formed with a recess, said detent means including a detent member on said support, and yieldably resilient means biasing said detent member inward of said recess when the detent member and said recess are radially aligned.

3. In an apparatus as set forth in claim 2, said cam means including a cam face on said remote end portion of said ejector member engageable with said detent member when said ejector member moves toward said driver member.

4. In an apparatus as set forth in claim 3, said cam face being substantially conical about said axis and being abuttingly engageable with said mandrel member as an element of said coupling means.

5. In an apparatus for forming a neck on a tubular blank including a support, a die mounted on said support and formed with a cavity having an axis and tapering at one axial end, a driver member mounted on said support for axial movement into and out of said cavity through the other axial end thereof, a mandrel member in said tapering end of said cavity, an ejector member axially movable in said cavity, and drive means for axially moving said driver member and said ejector member in timed sequence, the improvement which comprises:

a. guide means guiding said die for limited axial movement on said support,

1. said mandrel being formed with an axial passage receiving said ejector member; and

b. lost-motion coupling means coupling said mandrel member to said ejector member for joint axial movement,

1. said coupling means including an enlarged head on said ejector member in said cavity and outside said passage,

2. said head being dimensioned for engagement with an end face of said mandrel member.

6. In an apparatus as set forth in claim 5, said guide means including a guide member formed with a bore, said die being axially movable in said bore, and an internal flange on said guide member projecting into said bore and limiting the axial movement of said die.

7. In an apparatus as set forth in claim 6, yieldably resilient means biasing said die axially in said bore toward said flange and toward said driver member.

8. In an apparatus as set forth in claim 7, said yieldably resilient means including a plurality of spring members circumferentially distributed about said axis and each interposed between said support and said die.