GB2050910A

GB2050910A - Improvements in and relating to punch assemblies

Info

Publication number: GB2050910A
Application number: GB7921634A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-06-21
Filing date: 1979-06-21
Publication date: 1981-01-14

Abstract

A spring cassette (1) for a punch assembly for use in punching machines comprises a housing (4) open at both ends and in which an axially compressible spring (6) is retained, the spring defining a central bore (8) for a punch (2) which has an enlarged head (10) dimensionally larger than the bore (8) and by which the punch engages the spring (6). <IMAGE>

Description

SPECIFICATION Improvements in and relating to punch assemblies The present invention relates to improvements in and relating to punch assemblies for use in punching machines for making perforations in sheet material.

Punch assemblies generally comprise a punch which is received in a punch guide through which the punch is movable axially to effect punching, and a spring associated with the punch for returning the punch to its initial position after a punching operation, the spring generally being retained between an enlarged head on the punch and the punch guide. In such assemblies the spring is generally permanently associated with the punch so that when a punch needs to be changed, either because it has become defective or because a different sized punch is required, the entirely assembly has to be changed.

Because the components of the assembly are permanently associated, when any one component becomes defective the entire assembly has to be rejected. This increases the cost of the operation and essentially arises because each punch is provided with its own spring.

Additionally if a punching machine is used for punching different types of sheet material different spring pressures may be required with the same punches. When each punch is permanently associated with its spring, this means that a range of identical punches is required provided with different springs.

It is known to provide a punch assembly in which the punch is in two parts, one part of the punch being permanently associated with a spring and the other part including the operative end of the punch.

When it is required to change the punch, only the other part of the punch has to be changed, however the entire assembly has to be removed from the machine and the two parts of the punch disconnected. Additionally, the punch must be in two parts and this may be disadvantageous when punching very hard or difficult sheet materials, for example of manganese or titanium.

According to one aspect of the present invention, there is provided a spring cassette for a punch assembly for use in a punching machine, the spring cassette comprising a tubular housing which is open at both ends, and an axially compressible spring means received and retained axially within the housing and defining an axial bore for receiving a punch.

According to another aspect of the present invention there is provided a punch assembly comprising a spring cassette as described above and a punch, the punch extending through the axial bore in the spring means and having an enlarged head at that end opposite the punching end which is larger than the bore so that it bears on the spring.

The assembly may include a punch guide having a bore therethrough which that portion of the punch extending beyond the spring cassette extends, the exterior dimensions of the guide being smaller than the internal dimensions of the adjacent end of the cassette housing so that the housing can telescope over the guide.

According to a further aspect of the present invention there is provided a punch assembly comprising a punch and a guide therefore having a bore in which the punch is received, wherein the punch includes a non-circular portion received in an orientating member so as to be angularly fast therewith, the member having a projection extending parallel to the axis of the punch and which is received in a selected one of a plurality of bores in the guide for orientating the punch relative to the guide.

The guide is provided with means for preventing relative angular movement between the guide and the part of the punching machine in which the g#uide is received and these means may comprise a radially extending projection which is received in a slot in the part.

The invention will be more fully understood from the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an axial section through an embodiment of a punch assembly according to the present invention and comprising an embodiment of a spring cassette according to the present invention: Figure 2 is an axial section to another embodiment of a punch assembly according to the present invention and including the spring cassette of Figure 1; Figure 3 is an axial section through a further embodiment of a punch assembly according to the present invention and including the spring cassette of Figure 1; Figure 4 is a section on the line IV-IV of Figure 3; and Figure 5 is a section on the line V-V of Figure 3.

The punch assembly shown in Figure 1 comprises a spring cassette 1, a punch 2 and a punch guide 3.

The spring cassette 1 comprises a tubular housing 4which, as shown, has a circular section but could have another, e.g. polygonal, section as required.

The housing is open at both ends and at the lower end has an inwardly extending flange 5 provided by any suitable means; e.g. machining, which may extend continuously or intermittently around the lower end of the housing. An axially compressible spring 6 is received within the housing and is retained at the lower end of the housing by the flange 5 and at the upper end of the housing by a second inwardly directed flange 7 which, as shown, is provided by a circlip but may be provided by other suitable means.

The spring 6 may for example be a helical spring or, as shown, an assembly of disc springs and the spring 6 may be pre-tensioned when assembled with the housing 4.

The spring 6 provides an axial bore 8 through which the punch 2 is inserted. The body of the punch 2 may be in a single piece or, as shown, two pieces connected by a threaded element, and has at one end the operative punching end 9 and at the other end an enlarged head 10. The head 10 is dimension aliylarger than the bore 8 while the rest of the body of the punch 2 is smaller than the bore 8 so that the punch can be inserted through the spring cassette and is retained relative to the cassette by the head 10.

The part of the punch 2 below the spring cassette 1 is received in the punch guide 3 which is, in use, received in a bore 11 in a plate 12 of a punching machine and rests on the plate 12 by a step 13 provided thereon. The upper end of the guide 3 is dimensionally smaller than the internal dimensions of the flange Sat the lower end of the cassette housing 4 so that the housing 4 can be telescoped over the guide.

In operation, a ram engages the head 10 of the punch to force the punch through the material to be perforated. During this operation the spring 6 is compressed and then returns to its initial condition when the ram is withdrawn. Because the cassette housing 4 can telescope over the upper end of the guide 3, the diameter of the ram may exceed the external diameter of the housing 4 without affecting operation of the punch assembly, so long of course as there is sufficient clearance below the end of the housing 4 to permit its movement with the ram.

When it is required to replace the punch during operation of the punching machine, it is merely necessary to remove the punch and if desired the cassette from the guide 3 and replace it by a new punch. The arrangement of the springs is not affected by this operation because the spring is retained independently by the housing 4. To change the spring cassette, for example where a different spring pressure is required, it is merely necessary to remove both the punch and the spring cassette, assemble the punch with a new spring cassette and reinsert the punch into the punch holder.

It may be necessary to provide two or more guides to accommodate a range of different diameter punches. For example the guide shown in Figure 1 may be that for punches having diameters between 1.25 and 2.5 cm (" to 1"). For smaller diameter punches, the guide 23 shown in Figure 2 may be used. This guide differs from that shown in Figure 3 in that the axial bore 24 in which the punch 22 is received has a reduced diameter towards its lower end. The upper part of the tool 22 is dimensionally the same as that shown in Figure 1 so that the same spring cassette 1 can be used.

Figures 3 to 5 show an embodiment according to the invention for a punch assembly in which the punch 32 is shaped and has therefore to be orientated relative to the plate 12 and therefore relative to the corresponding die against which the punch acts.

As shown in Figures 3 to 5, orientation of the punch is obtained by orientating the guide 33 relative to the plate 12 and the punch 32 relative to the guide 33.

The guide 33 is orientated relative to the plate 12 as shown by providing the guide 33 with a radial projection 34 in the form of a pin, which engages in a slot 35 in the plate 12. Orientation of the punch 32 relative to the guide 33 is obtained by an orientating member 36 which is positioned between the guide 33 and the spring cassette 1. In this region, the punch is provided with a part 32a of non circular section. As shown part 32a is circular with two diametrically opposed flats 32b machined in it. The member 36, which is in the form of a disc, is provided with a slot 37 in which part 32a is received to be angularly fast with the disc 36. The disc 36 is also provided with a downwardly extending projection 38, as shown in the form of a pin, which is received in a bore 39 in the guide 33.To permit variable orientation of the punch relative to the guide 33, the guide 33 may be provided with a plurality of bores 39 in any one of which the pin 38 may be received, depending on the required orientation of the punch.

The above described means for orientating the punch relative to the guide has particular advantages in that it is a simple and cheap matter to produce holes, e.g. by drilling, in components as compared with the cost of, for example, making slots which are required in conventional means for orientating the punch and the guide.

In assembling the above described punch assembly, the punch 32 is inserted into the spring cassette 1 and the disc 36 is then radially slid onto the part 32a of the punch. Thereafter the assembly is inserted into the guide 33 and the pin 38 located in the correct bore 39. Disassembly of the punch and the spring cassette is obtained simply by reversing the above operations.

Claims

1. A spring cassette for a punch assembly for use in a punching machine, the spring cassette comprising a tubular housing which is open at both ends, and an axially compressible spring means received and axially retained within the housing and defining an axial bore for receiving a punch.

2. A spring cassette as claimed in claim 1, wherein the spring means comprises a helical spring.

3. A spring cassette as claimed in claim 1, wherein the spring means comprises an assembly of disc springs.

4. A spring cassette as claimed in any one of the preceding claims, wherein the housing includes radially inwardly projecting flange means at each end for retaining the spring means therein.

5. A spring cassette substantially as herein described with reference to the accompanying drawings.

6. A punch assembly comprising a spring cassette as claimed in any one of the preceding claims, and a punch adapted to be received in the punch and extend through the axial bore in the spring cassette, the punch having an enlarged head at that end opposite the punching end which is larger than the bore such that, in use, the head bears on the spring means of the cassette.

7. A punch assembly as claimed in claim 6, including a punch guide having a bore therethrough through which that portion of the punch extending beyond the spring cassette extends, the guide being dimensioned so that, in use, the end thereof adjacent the cassette housing is telescopically receivable within the cassette housing.

8. A punch assembly as claimed in claim 7, wherein, in use, the end of the punch guide adjacent the cassette housing bears directly on the spring means.

9. A punch assembly as claimed in claim 6, wherein the punch is orientatable relative to the punch guide, the punch includes a non-circular portion which is, in use, received in an orientating member so as to be angularly fast therewith, the orientating member having a projection extending parallel to the axis of the punch and the punch guide having a plurality of bores corresponding to the projection and in a selected one of which the projection is, in use, receivable.

10. A punch assembly as claimed in claim 9, wherein the orientating member is, in use, arranged between the cassette and the punch guide, bears on the spring means of the cassette and is telescopically receivable within the cassette housing.

11. A punch assembly as claimed in either claim 9 or claim 10, wherein the orientating member is in the form of a disc having a radial slot in which the non-circular portion of the punch is received.

12. A punch assembly as claimed in any one of claims 9 to 11, wherein the punch guide is provided with a radially extending projection for engagement in a slot in the punching machine.

13. A punch assembly comprising a punch, a guide therefor having a bore in which the punch is received and orientating means for orientating the punch relative to the guide, the orientating means comprising an orientating member in which, in use, the punch is received so as to be angularly fast therewith, the orientating member having a projection extending parallel to the axis of the punch and the punch guide having a plurality of bores corresponding to the projection and in a selected one of which the projection is, in use, receivable.

14. A punch assembly as claimed in claim 13, wherein the orientating member is in the form of a disc and is, in use, arranged at that end of the guide remote from the punching end of the punch, the orientating member having a radial slot in which a non-circular portion of the punch is received.

15. A punch assembly as claimed in either claim 13 or claim 14, wherein the punch guide is provided with a radially extending projection for engagement in a slot in the punching machine.

16. A punch assembly substantially as herein described with reference to the accompanying drawings.