FR2475946A1 - Press forming taper noses on sleeves - has twin table with rim notches for single sleeves with punch and sprung matrix at each notch - Google Patents

Abstract

The continuous press forms truncated conical noses on cartridge cases (22) using a vertically reciprocating punch (24) to push a case into an overhead matrix (30) block (26). Individual cases are located by rim recesses (18) of a revolving drum (20). A punch (24) and a matrix block (26) are mounted on the drum at each recess (18). As the drum rotates, a fixed ramped track causes punches (24) to rise in turn and drive the relevent case into the matrix. The punch may be of a round section (32) with an integral tangential bar. The latter is cut away to form shoulders (34) limiting the penetration into the matrix. The punch (24) may make definite contact with the block (26), the latter being mounted on belleville springs (38) which yield under punch impact.

Description

 The present invention relates to continuous stamping machines, and it can be applied more particularly to a shrinking machine capable, by stamping, of causing a shrinking at the end of a hollow cylindrical part such as a munit socket. ion.

 To carry out 11 continuous stamping operation, a barrel is provided comprising at its periphery a plurality of housings regularly distributed in each of which a part to be treated is brought.

A punch and a die block, movable relative to each other in a direction parallel to the axis of the barrel, are arranged one below the other above a part housing. There is provided a punch and a matrix (the latter formed in a matrix block) for each housing and the punches as the dies are integral in rotation with the barrel. They therefore remain at all times in a constant radial position relative to a housing, while they rotate with the barrel.

 A fixed cam system cooperates with the punches (by means of rollers and rods) to make the punches perform an axial reciprocating movement during the rotation of the barrel; during this movement, each workpiece is applied by a punch in the corresponding matrix and shaped as desired according to the shape of the matrix.

 Continuous stamping is thus carried out, the parts being successively introduced into the barrel housings, undergoing the stamping operation during rotation of the barrel, and being extracted at another location.

 In order for the operation to be carried out correctly, it is necessary to provide great precision in the stroke of movement of the punches relative to the dies. This precision can be given by the precision of the layout of the fixed cam and by the punches coming into abutment against the dies.

 Unfortunately, this solution does not prove to be optimal, in particular because even if the cam is precisely machined, the rollers which roll thereon wear out or have manufacturing tolerances such that they are not all identical. In particular, ovalization of the rollers is frequent and does not make it possible to obtain the desired precision over the stroke of the punch.

 In these condltions, tamed given the fact that the punch comes into abutment against the die, an enormous effort of entry risk exerted by the punch on the die if the stroke of the punch is slightly greater than the desired nominal stroke for which one has planned stop. This enormous effort appears if the cam and the matrixing blocks constitute fixed elements with respect to the barrel.

 It is therefore provided according to the invention that the master blocks are mounted in an axially fixed support means with a spring interposed between the block and the support means to establish an elasticity in the axial direction against the force exerted by the punch. when it is applied against the stamping block, stop means being provided on the punch so that the latter comes to abut against the edge of the corresponding stamping block and the movement travel of the punches driven by the dicame system being very slightly greater than the maximum interval between the punch and the die block when the latter is returned by the spring towards the punch.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows and which is given with reference to the accompanying drawings in which
- Figure 1 shows a schematic top view, in section, of a barrel of continuous forging of ammunition casings
- Figure 2 shows a sectional elevation at one of the stamping stations distributed around the periphery of the barrel.

The barrel is generally indicated in FIG. 1 by the reference 10. It has at its periphery a plurality of regularly distributed processing stations, all the stations being able to perform the same operation (in this case an operation for shrinking the end of a round of ammunition), operation which takes place during the rotation of the barrel. The operation is carried out for each of the processing stations 12 in a work area located between a workpiece feed wheel 14 and a workpiece extraction wheel 16 (the entry wheel, the work area, and the extraction wheel succeeding one another in the direction of rotation of the
The wheel 14 for supplying parts is a cell wheel which regularly brings the sleeves, succeeding each other at a step which is the step of distribution of the treatment stations 12 around the barrel 10. The barrel comprises, at an angular position corresponding to that of each of the work stations 12, a cell or part housing 18 capable of receiving a part coming from the feed wheel 14.

Each part to undergo 11 necking operation is therefore brought into a cell 18, it rotates with the barrel and enters the work area where the processing station corresponding to this cell performs its necking operation while it turns in the area working with the barrel to which it is attached. At the exit from the working area, the extraction wheel 16 collects the parts having undergone the shrinking operation; the extraction wheel 16 is provided for this purpose with extraction cells distributed at the same time as the cells of the barrel so as to evacuate from the barrel each of the parts which has undergone the treatment.

 In Figure 2, we see the detail of a stamping station 12 of the barrel, taken in section, in a radial direction passing through this station.

 The barrel body, which rotates around a vertical axis, is designated by the reference 20. We see a cell 18 for receiving an ammunition shell.

A socket 22 is visible in the figure, not in the cell 18 but above the latter because the machine is shown in a step where the socket 22 has been pushed back by a punch 24 towards a stamping block 26. It will therefore be understood that FIG. 2 represents a particular phase during the processing of a part and therefore that the section of FIG. 2 is situated in a radial direction inside the work area shown in FIG. 1.

 the treatment station seen in section in FIG. -2, essentially comprises a stamping block 26 integral in rotation with the barrel by means not shown, and a punch 24 also integral in rotation with the barrel and displaceable in axial translation ( parallel to the axis of the barrel), for example by being driven by a connecting rod 28 capable of moving itself axially thanks to a roller (not shown), placed at its lower end, roller which rolls on a fixed circular cam path, that is to say, not rotating with the barrel (cam path not shown).

 The stamping block 26 of each treatment station comprises an opening 30 located just above the punch 24 and in the axis thereof, this opening being intended to receive a bush 22 pushed axially by the punch 24. The shape interior of the opening 30 machined in the die block 26 corresponds to the final shape which it is desired to give to the socket (which penetrates in the form of a blank in the block 26). In the example shown, this involves giving a constricted shape at the end of the bushing and the opening 30 of the die block 26 is machined with a reduction in diameter at the end to achieve this constriction.

 The cross section of the punch 24 (which has the function of pushing the sleeve 22 into the die block) is shown in Figure 2 it is a central surface 32 sufficient to ensure uniform support over the entire lower surface of the sleeve 22, this surface being extended by lateral wings 34 which are intended to serve as a stop so that the punch 24 cannot penetrate into the opening 30 of the die-stamping block but, on the contrary, comes at the end of its movement of mounted under the action of the cam, abut against the edges of the die block.

 Each matrix block 26. Of a treatment station 12 is mounted inside a support 36 fixed relative to the barrel (that is to say integral both in rotation and in axial displacement), and it is provided according to the invention that the stamping block 26 is mounted with a certain axial elasticity with respect to the support 36. In this way, there is no risk of causing dangerous forces when the punch 24 abuts against the stamping block , effort which would appear in the eventuality where the matrix block would be fixed and where the fixed cam path would cause the punch to rise slightly above the level of the matrix block 26. With a certain axial elasticity between the matrix block 26 and its support 36, a slightly too large stroke of the punch 24 has the effect of pushing back the stamping block 26 without exerting on the fixed support 36 or on the punch 24 forces greater than the elastic force present between the block and its support fixed 36.

 More specifically, the die block 26 is mounted inside a bore axially drilled in the support 36, the bore opening in the direction of the punch 24. A spring, in the form of a stack of Belleville washers 38, is housed at the bottom of the bore and the die block 26 bears against this stack of washers. The spring thus formed is prestressed in the axial direction by means of a nut 40 which tightens the die block 26 towards the bottom of the bore of the support 36. 'nut 40 prevents the die die block 26 from coming out of the support 36 and performs the preload of the spring38 to a determined value (intermediate between the force necessary for the execution of the stamping operation of the sleeve 22 and the forces which it is not desired to exceed on the punch 24 and the frame of the barrel.

 It is then expected that the stroke of the punch 24, stroke given by the fixed cam path around the barrel, is such that the punch 24 tends to exceed the normal position of rest of the base of the die block 26, the excess stroke being a few millimeters at most. During the operation of the machine, when a processing station is located at the level of the workpiece feed wheel 14, the punch 24 is located below the cell 18 of the barrel, that is to say in the completely low position so as not to hinder the introduction of a part to be treated into the cell 18. During the rotation of the barrel, the punch 24 rises gradually by lifting the bush 22, this rise being effected under the action of the fixed circular cam. Continuing to rise, the punch 24 causes the bushing 22 to penetrate into the opening 30 of the stamping block corresponding to this punch. During this penetration, the bushing undergoes a constriction at its end, constriction which is made possible by force exerted by the punch 24 in the vertical direction. During this phase, the die block remains stationary in its initial position, because the force of the return springs 38 is greater than the force exerted by the punch during the necking operation.

 When the punch 24 comes almost to the end of its travel, it abuts against the edges of the opening of the die blocks 26, and, as the punch 24 is driven by the rolling of a roller on a fixed cam, it then exerts on the stamping block a force sufficient to push the stamping block 26 against the spring 38 until the stroke of the punch is completed (for example it can be provided that the punch continues its stroke upwards two millimeters after coming into abutment against the die block).

 Thus, within the limit of a clearance corresponding to this excess travel, the same precision of penetration of the bushing 22 will always be obtained in the opening of the matrix block, without however exerting prohibitive forces on the fixed or rotating parts. with the barrel.

 The shape of the section of the punch 24, chosen such that the sockets can be supported completely from below and such that the wings allow the punch to come into abutment against the stamping block, has been drawn in FIG. 2; it allows the punch to penetrate vertically into the cells 18, by lifting the sockets; the wings are also provided so as not to hinder the vertical movement of the punch, that is to say in particular it is preferable that they extend tangentially to the barrel inside the cells, and also it is preferable that they extend sufficiently close to the barrel so as not to be obstructed possibly by the guard ramps provided around the barrel to prevent the parts from leaving laterally from the cells (example ramps 40 in FIG. 1).

  The choice of Belleville washers for the spring 38 is particularly advantageous in the case of a continuous necking station such as that which is visible in FIG. 2, in fact the Belleville washers leave a central free space allowing the passage of a calibration punch 42 intended to penetrate through the upper part of the sleeve to internally calibrate the constricted part, and incidentally to cause the sleeve to take off and descend after the constriction operation. The calibrating punch 42 is actuated in the same way as the punch 24 by a fixed cam system and a roller rolling on this cam.

Claims (7)

RVENDI CAT IONS  1. Forging machine, in particular machine for shrinking hollow cylindrical parts, operating continuously, characterized in that it comprises a barrel carrying at its periphery regularly spaced housings capable of receiving each a workpiece, a series of punches movable parallel to the axis of the barrel, and rotating with the barrel, each punch being placed in the axis of a respective housing, a series of matrix blocks rotating with the barrel and each placed in the axis of a housing respective and of a respective punch, a fixed cam system for axially moving the punches during their rotation with the barrel, support means axially fixed on the barrel for supporting the master blocks, and a spring interposed between each master block and the support means for establishing an elasticity against the force exerted by the punch when it is applied against the die block, goal means ée being provided on the punch so that it comes to abut against the edge of the corresponding matrix block and the displacement travel of the punches driven by the cam system being very slightly greater than the maximum interval existing between the punch and the block forging when it is returned by the spring in the direction of the punch.  2. Continuous stamping machine according to claim 1, characterized in that the stamping blocks have a cylindrical outer shape and that the support means comprise corresponding bores facing the punches in which the blocks are slidably mounted, a spring being placed at the bottom of each bore.  3. Continuous stamping machine according to one of claims 1 and 2, characterized in that the stamping blocks comprise an opening for inserting the pieces and that the punches comprise at least at their ends portions projecting laterally to constitute an end surface wider than the opening and thus allow the punches to abut against the master blocks.  4. Forging machine according to claim 3, characterized in that the punches comprise at least at their end protrusions disposed substantially tangentially to the barrel, radially outside the housings thereof to allow the axial displacement of the punches in housing.  5. Forging machine according to claim 4, characterized in that the projections extend radially relative to the barrel substantially not or barely further than the parts contained in the housings.  6. Forging machine according to one of claims 1 to 5, characterized in that the force of each spring is greater than the force necessary to effect the forging of a part.  7. Forging machine according to one of claims 1 to 6, characterized in that the springs are Belleville washers.