GB2030499A - Improved punch assembly - Google Patents

Abstract

A punch assembly has an adjustable striker 28 which in use is hit by the ram of a punch machine. The striker is adjustable so as to vary the length of the punch unit. The striker member may be screw-threaded into the punch unit and may be selectively lockable in one of a number of angularly spaced positions by means of a locking screw 20. <IMAGE>

Description

SPECIFICATION Improved punch assembly This invention relates to a punch assembly.

At present punch assemblies have a standard length and are arranged to accommodate the thick- est material to be received by the particular machine.

When punching this material can result in a time loss which can be important, particularly automated machines.

According to the present invention there is provided a punch assembly comprising a movable punch unit including astikermemberwhich in use is hit by the ram of a punch machine, the striker member being adjustable so as to vary the length of the punch unit.

The provision of an adjustable striker member allows its position relative to the ram to be adjusted so as to allow a minimum stroke thereby providing an increased hit rate in automatic machines.

Preferably the striker member is in screw-threaded engagement with the punch unit so as to be adjustable by screwing relative to the punch unit.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevation of a punching tool for forming louvres or the like in accordance with the invention; Figure 2 is an underneath plan view of the tool of Figure 1; Figure 3 is a cross-sectional side elevation of a shear-proof punching tool in accordance with the invention; Figure 4 is a cross-sectional side elevation of an alternative punch assembly in accordance with the invention; and Figure 5 is a cross-section side elevation of a further alternative punch assembly in accordance with the invention.

In Figures 1 and 2 of the drawings tool 1 comprises a movable punch body 2 having a shoulder 3 by means of which the tool is supported in an appropriate holder (not shown). At its upper and the body 2 has an adjustably striker member 4 which is in screw threaded engagement with an aperture 5 in the body 2. Adjustment of the striker member 4 enables the height of the tool relative to the ram of a punch machine (not shown) to be altered to vary the stroke and readily accommodate various thicknesses of workpiece. A locking screw 6 associated with the striker member 4 is engageable with one of four circumferentially spaced grooves in the member 4 to prevent further angular displacement once its position has been set. The locking screw 6 is provided with a spring 7 to provide a back pressure to hold the screw in position.

The lower end of the movable punch body 2 has secured thereto a blade 8 and a former 9. Located between the blade 8 and the former 9 is a block 10 having a working face 11 which is adjustable to alter the depth of louvre formed as explained in more detail in our copending application filed herewith.

The block 10 is a sliding fit between the blade 8 and former 9 and is screw threaded onto a cap screw 12.

The cap screw 12 has a clearance fit through the punch body but its heard engages a surface 13 on the body. The position of the working face 11 is determined by loosening cap screw 12, turning an adjuster 14 until the desired depth of louvre is obtained, and then tightening the cap screw 12 until its head is in engagement with the surface 13. The adjuster 14 has a clearance about the cap screw 12 but is in screw-threaded engagement with the body at15.

The fixed part of the punching tool for forming louvres has a single blade 16 having a cutting edge 17 which is aligned with the cutting edge of blade 8 and radiused forming edge 18 which is aligned with the forming edge of former 9. The blade 16 is held in place, with respect to two adjuster members 19 by cap screws 20 (only one of which members and screws are shown). The adjuster member 19 is in screw-threaded engagement with a plate 20 which is secured to die plate 21 by screws 22.

The protruding part of blade 16 is surrounded by a stripper plate 23 biassed into its extended position, shown in Figure 2 by means of three spring assemblies 24 (only one of which is shown).

In use the striker member 4 is appropriately adjusted and locked in position by locking screw 6 and the other adjustments made as disclosed in our said copending application. The adjustment of the cap screw 12 being effected by inserting an Allen key through the opening 25 in the striker member 4. The workpiece is then positioned below the movable tool on the stripper plate 23 and the movable tool moved downwardly by ram pressure on the striker member 4. As the movable tool meets the fixed blade 16 the stripper plate 23 is moved downwardly against the action of springs 24, a cut is formed in the workplace by the cooperation of the cutting edges and the workpiece opposite the cut is bent into a louvre by cooperation of the forming edges. At the full extent of the stroke the stripper plate is fully retracted and the main part of the workpiece lies on the workbed.

On release of the ram pressure, the movable tool is returned to its position of rest by return springs (not shown) and the stripper plate 23 is automatically returned to its original position by springs 24 thus automatically stripping the fixed blade 16.

Figure 3 of the drawings illustrates the invention combined with a shear-proof punching tool which is shown positioned in a punch station of a rotatable turret, part of which is shown diagrammatically.

The shear-proof punching tool of Figure 3 comprises a punch assembly 26, a punch holder 27 and a striker member 28. The punch assembly 26 and the punch holder 27 are joined together by a screw 29 and are together axially movable relative to the stripping guide 32'. A spring assembly 30, which comprises a spring retainer 31 secured to the punch holder 27, a spring support 32 abutting the stripping guide 32' and coil springs 33, serves to bias the movable parts of the tool into the retracted position shown. The striker member 28 is in screw-threaded engagement with the spring retainer 31 and has a central aperture through which the screw 29 passes.

The punch assembly 4 which is disclosed in more detail in our copending application No. 40182/78 to which reference is directed consists of a square punch 34 having a groove 35 formed in each corner.

Each groove 35 slidably receives a punch finger 36 and the fingers 36 are held in position by a punch retainer 37. All the fingers 36 have an associated spring 38 which biasses the respective finger into an extended position as shown and its extended movement is limited by a shoulder 39 on the finger which engages the punch retainer 37. The punch 34 and associated punch fingers 36 are slidable relative to a stripper plate 40 which is removably secured to the stationary stripping guide 32' by means of screws 41.

The striker member 28 is adjustably mounted on the spring retainer 31 by means of a timing screw 42 which is engageable with any one of four arcuate grooves in the striker member 28 to lock the member 28 into position at a particular height. This adjust mentfacility means that the position of the striker member 28 relative to the punch ram (not shown) can be adjusted so as to allow a minimum stroke thereby providing an increased hit rate in automatic punching machines.

In operation the desired punch and corresponding stripper is selected and then the striker member is adjusted to a desired setting depending upon the material being punched. The fingers of the shearproof punch pass into the die corners and locate the punch against lateral and angular displacement before any punching actually takes place.

Figure 4 of the drawings illustrates a further punching assembly incorporating the adjustable striker of the present invention In this embodiment a punch 42 is slidably received in a punch guide 43.

The punch 42 has an axial screw-threaded bore 44 which receives a screw 45 releasably securing the punch 42 to a punch cap 46. The punch cap 46 has an externally screw-threaded portion 47 which is releasably secured to a punch head by engagement in an externally screw-threaded cylindrical extension 48 of a return spring retainer 49. The return-spring retainer 49 has a central opening 50 which receives the striker member 51 and both the spring retainer 49 and the striker 51 have an axial bore 52therethrough to allow the screw 45 to be released when the punch is to be changed. The punch 42, and the punch head formed by spring retainer 49, punch cap 46 and striker 51 together form an axially moveable punch unit of the assembly.

As seen from Figure 4 the striker 51 is adjustably recieved in the spring retainer 49 and has a grub screw 52' which is engageable with one of a number of indentations 53 (only one of which is shown) in the bottom surface of the opening 50. This adjustment facility means that the position of the striker member 51 relative to the punch ram (not shown) can be adjusted so as to allow a minimum stroke for varying thicknesses of material to be punched.

Alternatively, the striker 51 may be locked in position by means of arcuate grooves in the edge of the striker member.

In the alternative embodiment of Figure 5 the punching assembly is similar to that shown in Figure 4 except that the cylindrical extension is replaced by a separate sleeve 54: the punch cap 46 having an externally screw-threaded portion engaging in the internally screw-threaded sleeve. The other end of the sleeve 54 recieves the striker 51. The striker 51 has an axial bore 55 therethrough aligned with the sleeve 54 to allow the screw 45 to be released when the punch is to be changed. The axial bore 55 is smaller than the axial bore 12 of the first embodiment. The embodiments of Figures 4 and 5 are disclosed in more detail in out co-pending application No. 45265/78 to which reference is directed.

Claims (5)

1. A punch assembly comprising a movable punch unit including a striker memberwhicn in use is hit by the ram of a punch machine, the striker member being adjustable so as to vary the length of the punch unit.

2. A punch assembly according to claim 1 wherein the striker member is in screw-threaded engagment with the punch unit so as to be adjustable by screwing relative to the punch unit.

3. A punch assembly according to claim 2 wherein the striker member is selectively lockable within one of a number of angularly spaced positions.

4. A punch assembly according to claim 3 wherein the striker member is selectively lockable by means of a locking screw the head of which is engageable with one of a plurality of circumferentially spaced grooves about the striker member.

5. A punch assembly according to any one of the preceding claims wherein the striker member has an axial bore to permit access to within the punch unit for adjustment for punch replacement.