GB2290738A - Extraction of press tool bushes - Google Patents

Abstract

A pierce bush 12 is mounted directly in a bore 14 in the lower casting 10 of a press. Grooves 36 and 38 in the bush and the casting define a hole 40 in which a locating dowel 42 is inserted to prevent the bush from rotating in the casting. Cooperating formations 48, 50 on the bush and dowel engage each other so that the bush can be extracted from the casting 10 by pulling the dowel out with a dowel extractor. <IMAGE>

Description

Extraction of Press Tool Bushes The present invention relates to press tools, and in particular to tools which are designed to punch or pierce holes through sheet material such as steel vehicle bcdy panels.

Press tools of this type generally have a lower support member, usually a large casting, which supports one or more bushes. Each bush defines a bore which is aligned with a punch on the upper part of the press tool. The sheet material is supported on the support member and punch is brought downwards through the sheet material and into the bore in the bush, thereby punching a hole through the sheet material. Generally, until recently, the bushes were supported in steel blocks which were attached to the lower casting of the press. These blocks were relatively small and could easily be removed from the casting to replace the bushes if they became damaged. However it nas become more common to have the bushes let directly into bores in the casting. This has the disadvantage that it 15 hard to extract the bushes if they become damaged.A large force is required to remove the bushes, and it can usually only be done by removing the whole lower casting from the press and pushing the bushes out from below.

Accordingly the present invention provides apparatus for piercing holes through sheet material, the apparatus tool including a support member, a bush let into the support member, the bush and the support member having grooves therein which cooperate to define a hole, anci a locating member adapted to be inserted in the hole, the locating member and the bush having cooperating formations thereon whereby correct movement of the locating member will cause the bush to be lifted out of the support member.

This arrangement allows the bush to be extracted from the support member without the need to remove the support member from the press.

The formations may comprise a cooperating projection and cut-out which engage such that pulling the locating member out of the hole will cause the bush to be lifted out of the support member.

The grooves in the bush may define a bore which extends along the full length of the bush and has threads formed in it, and the apparatus may further comprise an externally threaded member which is adapted to be screwed through the threaded bore to lift the bush and locating member out of the support member.

Alternatively the formations may comprise a projection on the bush and a helical groove in the locating member which engage such that rotation of the locating member ifli the hole lift the bush out of the support member.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a section through a press tool cording to a first embodiment =f the invention, Figure 2 is a view on line II - II of Figure 1, Figure 3 is a section through a press tool according to a second embodiment of the invention, and Figure 4 is a section through a press tool according to a third embodiment of the invention.

Referring to Figures 1 and 2, a press tool comprises a cast support member 10 with a plurality of bushes ;2 (only one of which is shown) let into bores 14 in its upper surface 16. Each bore 14 has an upper section 18 which is just wide enough for the bush ;2 to fit into it, and a narrower lower section 20 which allows the punched material to drop out of the tool. The shoulder 22 between the two sections 18, 20 of the bore supports the bush 12, the upper end 24 of which is flush with the upper surface 16 of the support member. The bush 12 is circular in cross section and has a central bore 26 which Is aiso in two sections, an upper narrower one 28 and a lower wider one 30.A punch 32 is mounted on the upper part 34 of fle press and is aligned with the upper bore 28 in the bush so that when the upper part of the press is brought downwards the punch 32 passes through the sheet material and into the upper bore 28 in the bush to punch a hole through the sheet material.

Because the bush 12 is circular n cross sectIon nerve is a possibility that it might rOtate in the support member 10. In order to prevent this, grooves 36 anus 38 are formed in the bush and the support member. The grooves are semi-circular in cross section and cooperate to define a hole 40 parallel to the axis of the bush. A locating dowel 42 in the hole 40 prevents the bush 12 from rotating. The dowel 42 has a threaded bore 44 in its top end 46 to enable it to be extracted using a threaded dowel extractor.

Cooperating formations, comprising a projection 48 in the groove 35 in the bush and a cut-out 50 in the dowel 42, engage each other so that when the dowel is pulled upwards the bush is lifted out of the support member 10.

Using this arrangement, if one of the bushes 12 needs to be replaced it can be lifted quickly out of the support member, and a replacement bush inserted together with the dowel 42.

Referring to Figure 3, the second embodiment is similar to the first and corresponding features are indicated by the same reference numerals. The only difference is that the threaded bore 44 in the dowel extends through the entire length of the dowel. A bolt 52 is used to extract the dowel by inserting it into the threaded bore 44 and turning It. The boit 52 passes through the dowel 42 and bottoms out on the shoulder 22. Further turning lifts th; dowel and the bush out of the support member 10.

Referring to Figure 4 the third embodiment IS also similar to the first and second embodiments with orresponding features Indicated ba trite same reference numerals. The differenc- in thIs embodiment is that the locating member comprises a screw 54 which Is threaded on the outside and the protection 48 t tne bush engages with the thread on the screw. The screw 54 also has a slot 56 in the top to enable it to be rotated. To extract the bush 12 the screw 54 is rotated and the projection 48 on the bush runs up the thread on the screw thereby lifting the bush out of the support member.

Claims (7)

1. Apparatus for piercing holes through sheet material, the apparatus including a support member, a bush let into the support member, the bush and the support member having grooves therein which cooperate to define a hole, and a locating member adapted to be inserted in the hole, the locating member and the bush having cooperating formations thereon whereby correct movement of the locating member will cause the bush to be lifted out of the support member.

2. Apparatus according to claim 1 wherein the formations comprise a cooperating projection and cut-out which engage such that pulling the locating member out of the hole will cause the bush to be lifted out of the supporting member.

3. Apparatus according to claim 2 wherein the grooves in the bush define a bore which extends along the full length of the bush and has threads formed in it.

II

4. Apparatus according to claim 3 further comprising an externally threaded member which is adapted to be screwed through the tnreaded bore to lift the bush and locating member ou of the srt member.

5. Apparatus according to claim 1 wherein the formations comprise a prsJecticn on the bush and a thread on the locating member which engage such that rotation of the locating member in the hole lifts the bush out of the supporting member.

6. Apparatus according to any foregoing claim wherein the support member has a plurality of bushes let into it.

7. Apparatus substantially as hereinbefore described with reference to Figures 1 and 2, Figure 3 or Figure 4 of the accompanying drawings.