US2183637A

US2183637A - Production of tubular metal cases

Info

Publication number: US2183637A
Authority: US
Publication date: 1939-12-19
Anticipated expiration: 1956-12-19

Description

Dec. 19, 1939. o. BIGINELLI 2,183,637 PRODUCTION OF TUBULAR METAL CASES SUCH AS CARTRIDGE CASES Filed June 23, 1937 4 Sheets-Sheet 1 Fig.1 Fig.2 Fig.5 Fig.4

INVENTOR ORESTE BIGINELL/ B A ATTORNEYS 0. BIGINELLI Dec. 19, 1939.

PRODUCTiON OF TUBULAR METAL CASES SUCH AS CARTRIDGE CASES Filed June 23, 1937 4 Sheets-Sheet 2 I u I f 1 INVENTOR L4 L 5 E U KR a m T T 5 A E 7 mm o. BIGINELLI- 2,133,637

PRODUCTION OF TUBULAR METAL CASES SUCH AS CARTRIDGE CASES Dec. 19, 1939.

Filed June 23, 1937 4 Sheets-Sheet 3 Dec. 19, 1939. o. BIGINELL] 2,183,637

PRODUCTION OF TUBULAR METAL CASES SUCH AS CARTRIDGE CASES Filed June 23, 1937 4 Sheets-Sheet 4 ATTORNEYS Patented Dec. 19, 1939 UNITED STATES PATENT OFFICE Oreste Biginelli, Clermont-Ferrand, France Application June 23, 1937, Serial No. 149,856 In France August 1, 1936 2 Claims.

This invention relates to the production of tubular metal cases such as cartridge cases. In the common method of manufacturing military cartridge cases or the like the initial blank consists of a metal disc of diameter considerably greater than the ultimate diameter of the case and of thickness corresponding substantially to that of the base of the finished case. This blank is formed into the case by a series of stamping l operations with intermediate annealing operations. In the first stamping operation the blank is formed into a small cup and the subsequent stamping operations are numerous.

A disadvantage of this known process is due to if; the necessity for using blanks of very exact dimensions. Thus, as the blanks are usually cut off from a sheet, the latterhas to be carefully made and the blanks have a high cost price. The cost price is further increased on account of the waste metal left over after the blanks have been cut out. A further disadvantage is due to the number of stamping operations that are necessary and of consequent annealing operations. An object of the present invention is to provide a method in which these disadvantages are eliminated.

According to the present invention, a metal case such as a military cartridge case is formed from a solid piece or" metal by extruding a tubular extension from the solid piece so as to provide a case consisting of a tube closed at one end. Conveniently, the solid metal piece may be inserted into a heated die and, after being heated to a predetermined temperature, sub- 35 jected to pressure which causes part of the metal to flow between the wall of the die and a core constituted by a member which takes part in exerting the pressure on the metal. The said member is constituted by a punch and this may 40 co-operate with a counter-punch arranged so that at the end of extrusion the space left between the punch and counter-punch is filled with metal which constitutes the base of the case.

The cross section of the initial metal piece is usually circular and its length is determined by the quantity of metal necessary for forming the case. The metal piece is inserted into a bore in the die, the diameter of the bore corresponding to that or the metal piece with a little clearance to allow it to be inserted easily. The metal piece may be heated prior to its introduction into the die or it may be inserted cold. In the latter case time has to be allowed for the metal to become sufficiently plastic and then, under the action of pressure, the tubular part of the case is extruded. When a punch and counter-punch are used the relative movement between these is stopped when the punch is at a predetermined distance from the counter-punch, that is, when the initial section has been fashioned into a case 5 comprising both a base in the form of the space left between the punch and the counter-punch, and a tubular part.

If the base of the case obtained in the initial operation is not of the required shape, the case is subjected to a further operation in which the base of the case is forced to undergo a change in shape by a process similar to that of the first operation, i.e. between a punch and counterpunch formed in accordance with the shape of the base required and acting inside a heated die. Further, if the cross section of the wall of the tubular part of the case is not of the required form after the extrusion, the tubular part may be subjected to one or more drawing operations for the purpose of causing the wall to become, for example, tapered in cross section. A large number of drawing operations is never necessary because a case with long thin walls is obtained by the extrusion operation.

Advantages arising from the invention are as follows:

(1) The dimension of the initial metal piece does not have to be very accurate, a small error in the diameter or length of the piece appearing simply as a small variation in the length of the extruded tubular part.

(2) Very small waste of metal when the metal pieces are cut from a long bar, this waste being negligible in comparison with that in the aforementioned usual process in which blanks are cut out of a sheet.

(3) Considerable reduction in the number of steps necessary for the formation of the case, the extrusion of the tubular part giving, in a single operation, an elongated form of case which, if produced by stamping, would require in its production a large number of stamping and annealing operations.

A machine for carrying the method according to the invention into effect may be furnished with a die formed with a cylindrical bore and a punch and counter-punch arranged to move axially in the bore, the counter-punch being arranged to act as an abutment, while the punch, 50 the diameter of which is less than the bore, acts as a core around which the metal is extruded by axial pressure applied as a result of relative movement between the punch and counter- Punch. Conveniently, the punch may be formed with a conical head of which the base is slightly wider than the body of the punch and the tip is coaxial with the body of the punch, the base of the conical head being rounded so as to provide a surface around which the metal can flow as it is extruded.

In order that the invention may be clearly understood and readily carried into effect, a method and apparatus in accordance therewith will now be described by way of example with reference to the accompanying drawings in which:

Figures 1 to 4 are transverse cross sections showing difierent phases in the manufacture of a cartridge case, Figure 1 showing an initial cylindrical blank, Figure 2 showing the shape of the case obtained after the cylindrical wall has been extruded, Figure 3 showing the shape of the case after the shape of the base has been modified, and Figure 4 showing the shape of the finished case.

Figures-5, 6 and '7 show a diagrammatic cross section of apparatus, in various phases of its operation, for producing acase as shown in Figure 2.

Figure 8 shows a detail of apparatus for producing a case as shown in Figure 3.

Referring to Figures 5, 6 and '7, supports t and 5 form parts of the framework of a press. A die 6, formed with a. projection i, screwed into the support e, is made of heat-resisting steel capable of resisting the temperature to which the work is subjected. The work consists initially of a short metal piece of cylindrical cross section which fits into a corresponding bore 8,

formed in the die 8. The diameter of the bore 8 is from to millimetres greater that that of the work. The latter is heated while in the die by means of a heating system surrounding the die and consisting, for example, of an electrical resistance 9, which is represented diagrammatically in the figures and is surrounded by a heat-insulating jacket Hi. When the work has been heated sufiiciently for it to become plastic it is subjected to pressure between a punch l l and a counter-punch 18, the wall thickness of the die being sufficient to resist, without deformation, theinternal pressure to which it is subjected.

The punch ii is formed at one end with a conical head I2, the base of which is rounded and provides a flange it. The diameter of this flange is equal to the internal diameter of the tubular wall to be extruded. Behind the head 22 the punch comprises a cylindrical part it of diameter very slightly less than that of the flange i3 and of length slightly greater than that of the tubular wall to be extruded. A further cylindrical part 55 is disposed behind the part M and is of diameter equal to that of the flange l3. The punch is formed behind the part l5 with a third cylindrical part which provides a flat shoulder It at right angles to the axis of the punch.

The punch H is moved longitudinally when the press is operated, and is shown in its outermost position in Figure 5. In this position the flange i3 is supported by a sleeve II in which the flange 93 fits with light friction.

The diameter of, the counter-punch i8, which is cylindrical, is less by several tenths of a millimetre than that of the bore 8, except at the end is which fits withlight friction in thisbore.

In the extruding operation the punch H and counter-punch l8 first take up their outermost positions, as shown in Figure 5. The work in.

the form of the short solid piece, of circular cross section, shown in Figure 1 is then inserted into the bore 8 so as to occupy the position shown at 20 in Figure 5. Then, after enough delay to enable the work to reach a predetermined temperature at which it becomes sufficiently plastic, the punch II is caused to move from the position of Figure 5 to that of Figure 6. During this movement the counter-punch i8 is rigidly buttressed so that it cannot yield as a result of the force due to the action of the punch H. As the latter moves to the position of Figure 6 with the cylindrical part l5 sliding in the sleeve II, the head [2 becomes embedded into the metal and the metal displaced by the head is forced to extrude through the annular space between the surface of the bore 8 and the flange l3 of the punch ll. As soon as the latter reaches the position of Figure 6 it is stopped, this position being determined by the engagement of the shoulder it with a corresponding surface on the support 5.

Thus, as Figure 6 indicates, a case in the shape of that shown in Figure 2 is obtained, the base 22 of the case being moulded to fit exactly the space between the head H? of the punch and the end of the counter-punch.

Figure '7 shows how the case 2i, after formation, is ejected from the die. From this figure it will be seen that the punch 52 is returned to its outermost position. As it is returned to this position it withdraws the case from the bore 8. After leaving this bore the end of the case 2i abuts against the sleeve i'l so that, during the continued movement of the punch ii, the latter is withdrawn from the case. In the event of the case not being withdrawn from the bore 8 by the punch ii, the counter-punch I8 is moved to the position of Figure 7 so as to eject the case 2 i this movement taking place after the punch H has reached the position of Figure '7.

In the arrangement shown in the accompanying drawings and described above, the extrusion of the metal is effected by the action of the punch H being moved relatively to the stationary assembly constituted by the counter-punch l8 and the die 6. It will be appreciated, however, that the same result can be obtained by an analogous arrangement in which a member similar to the counter-punch i8 is moved relatively to a star,

' used, such as those employing gas burners, hot

circulating gases, and so forth. The work can be heated prior to insertion into the die, in

which case no delay prior to the mechanical working of the metal is necessary.

Figure 8 shows an arrangement in which the form of the base of the case shown in Figure 2 can be modified so that the case takes the form shown in Figure 3. The arrangement of Figure 8 is analogous to that of Figures 5 to 7, the only difference being in the shapes of the ends of the punch and counter-punch. The heated die 23 is identical to the die 6.

Figure 8 shows the punch 2s and counterpunch 25 in their innermost positions, the base of the case exactly filling the space left between their ends. It will be seen that a small projection 28 on the counter-punch 25 forms a cavity 2 for a percussion cap, while the inner face i of the base of the case is flat and merges gently into the tubular wall.

The cartridge case is caused to take its final form shown in Figure 4 by one or more drawing operations in which the cross section or the tubular Wall 3 is caused to become tapered What i claim and desire to secure by Letters Patent of the United States is:

1. The method of forming a metallic case from a solid piece of metal by reverse extrusion, said method comprising in combination, the steps of placing said piece of metal in contact with a heated body to heat said piece until it becomes plastic, and then subjecting the middle portion of the heated piece of metal to pressure to cause the edge portions thereof to flow in a direction opposite to that of said pressure and to form a tubular member, such as a cartridge case, and then removing said tubular member from contact with said body while the latter is heated.

2. A device for forming a metallic case from a solid piece of metal by reverse extrusion, said device comprising, in combination, a heat transmitting die having a cylindrical bore formed therein, heating means surrounding said die, whereby a piece of metal inserted into said bore is heated until it becomes plastic, a counterpunch movable within said bore and serving as an abutment for the piece of metal, another die situated at a distance from the first mentioned die, and a punch having a conical head, an ad-- jacent cylindrical portion having a diameter which is somewhat smaller than the largest diameter of said conical head, and a shoulder portion adapted to engage the second-mentioned die, said punch being carried by the secondmentioned die and. being movable within said bore to press axially against said piece of metal and cause a portion of the heated metal to flow around the walls of the punch and into the space between the two dies to form a tubular member, such as a cartridge case.

ORESTE BIGINELLI.