GB2408706A

GB2408706A - A die assembly

Info

Publication number: GB2408706A
Application number: GB0328101A
Authority: GB
Inventors: Christopher Rose
Original assignee: WILSON TOOL INTERNAT Ltd
Current assignee: WILSON TOOL INTERNAT Ltd
Priority date: 2003-12-04
Filing date: 2003-12-04
Publication date: 2005-06-08
Also published as: GB0328101D0

Abstract

A die assembly 10 comprising a holding member 11, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part 12 carried by the holding member and moveable relative thereto so as to retract during a forming operation and extend thereafter to strip a formed workpiece off the forming part 14, wherein movement of the stripping part relative to the holding member causes movement of the forming part in the opposite direction relative to the holding member. The forming part 14 includes rack gear formations 17 facing the rack gear formations 15. Pinion gear wheels 16 are provided which engage the facing rack gear formations.

Description

Title: A Die Assembly.

Description of Invention

The present invention relates to a die assembly, which may be used in effecting a forming operation on a workpiece. More particularly, the present invention relates to a die assembly comprising a holding member, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part which is also carried by the holding member and is moveable relative thereto. The movement of the stripping part relative to the holding member enables it to retract during a forming operation leaving the forming part protruding so that it can fulfil its function, and to extend after the forming operation to strip a formed workpiece off the forming part.

A die assembly according to the present invention has been devised for use in effecting an operation such as the forming of louvres, vents or other formations in sheet metal, although it is to be understood that it may have other applications, for example in cutting sheet metal possibly as part of a forming operation. The die assembly forms a first part of a die set which may be fitted to a press, conventionally with the die assembly fitted to a machine table of the press and a complementary second part of the die set attached to a mechanically- or hydraulically- operated forming ram.

It is conventional to use a press with a two-part die set in performing forming operations on sheet metal. The press typically includes a machine table with clamps to hold the sheet metal to be formed in position over a first part of the die set, while a second part of the die set is attached to a mechanically or hydraulically operated forming ram, which is positioned above the first part of the die set. The first part of a typical die set has a holding member which is adapted to be held in place in the machine table, a forming part, and a spring biased stripping part surrounding the forming part, the spring biasing of the stripping part biasing it to an extended position. The stripping part has an opening through which the forming part extends, and when downwards pressure is applied to the stripping part it moves downwards, exposing the forming part. The second part of the die set has a formation complementary to the forming part of the first part.

In use, the sheet metal to be formed is clamped to the machine table, with the part which is to be formed positioned above the first part of the die set.

The forming ram is then forced down onto the sheet metal. The pressure of the ram causes the stripping part to move downwards, exposing the forming part.

The sheet metal takes on the shape of the forming part and of a complementary formation in the second part of the die set. The ram is then moved back upwards, removing the pressure on the stripping part, which extends under the influence of its biasing springs, stripping the formed workplace off the forming part.

Although this is generally an effective method of forming sheet metals, the utility of conventional presses is limited by the space available between the forming ram and the upper surface of the first part of the die set, which limits the depth of formations that can be made in the sheet metal. To make deeper formations, a different machine with a larger gap between the forming ram and the upper surface of the first part of the die set would be required, which is uneconomical. It would be useful to provide a die set capable of making deeper formations in the sheet metal without requiring a larger gap between the forming ram and the upper surface of the first part of the die set. It is an object of the present invention to provide such a die set.

According to a first aspect of the present invention, there is provided a die assembly comprising a holding member, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part carried by the holding member and moveable relative thereto so as to retract during a forming operation and extend thereafter to strip a formed workpiece off the forming part, wherein movement of the stripping part relative to the holding member causes movement of the forming part in the opposite direction relative to the holding member.

The relative movement of the forming part and the stripping part in opposite directions allows deeper formations than those made by a conventional die to be made in the workpiece, without increasing the height of the forming part.

The stripping part may surround the forming part such that when the stripping part moves the forming part moves in the opposite direction through an opening in the stripping part.

The stripping part may be biased towards an extended position in which the forming part substantially does not extend beyond the stripping part.

The stripping part and the forming part may be connected mechanically, such that movement of one of the stripping part or the forming part causes 1 S movement of the other in the opposite direction.

The distances by which the stripping part and forming part move in opposite directions may bear a predetermined relationship to one another; they may be equal or possibly unequal.

The stripping part and the forming part may each include at least one rack gear formation, the or the respective rack gear formations being engaged by a or a respective pinion.

With this arrangement, the movement of the stripping part may conveniently cause movement of the forming part in the opposite direction by an equal distance, relative to the holding member. However it would be possible to incorporate gears to change the effective gear ratio between the stripping and forming parts, to move them by unequal distances.

According to a second aspect of the present invention, there is provided a die set comprising a first part of the kind described above and a second part having a formation complementary to the forming part of the die assembly.

According to a third aspect of the present invention, there is provided a method of carrying out a forming operation on a workpiece by using a die set having first and second complementary parts between which the workpiece is formed, the first part of the die set being a die assembly comprising a holding member, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part carried by the holding member and moveable relative thereto so as to retract during a forming operation and extend thereafter to strip a formed workpiece off the forming part, the method comprising the steps of: (i) positioning the workpiece between the first and second parts of the die set; (ii) effecting relative movement between the first and second parts of the die set towards one another to engage the workpiece therebetween and cause said retraction of the stripping part relative to the holding member; (iii) causing movement of the forming part in the opposite direction to the retracting stripping part, relative to the holding member, to form the workpiece, and (iv) effecting relative movement of the first and second parts of the die set away from one another to cause or permit extension of the stripping part and movement of the forming part in the opposite direction relative to the holding member, to strip the formed workpiece off the forming part.

The forming part and the stripping part may move an equal distance, relative to the holding member.

Specific and non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 shows a die assembly according to the present invention, with the forming part concealed by the stripping part.

FIGURE 2 shows a die assembly according to the present invention, with the stripping part retracted and the forming part extended.

FIGURE 3 shows a punch press including a die assembly according to the present invention.

Referring first to Figure 1, there is shown a die assembly 10, which forms a first part of a die set, having a holding member in the form of a retaining ring 11 to secure it to a punch press, and a stripping part 12 surrounding a forming part 14. An opening 13 is provided in the stripping part 12 through which the forming part 14 can move. The stripping part 12 is spring-biased towards the position shown, in which the forming part 14 substantially does not extend beyond the stripping part 12, in conventional manner, and includes rack gear formations 15. The forming part 14 includes rack gear formations 17 facing the rack gear formations 15. The rack formations 17 may be components separate from and secured to the forming part 14, enabling replacement of the latter if required without having to replace the racks. Pinion gear wheels 16 are provided which engage the facing rack gear formations 17 on the forming part 14 and the rack gear formations 15 of the stripping part 12, such that movement_of the stripping part 12 causes movement of the forming part 14 in the opposite direction by an equal distance, relative to the retaining ring 11.

Turning next to Figure 2, there is shown a die assembly 10, which forms a first part of a die set, in an 'operational' position in which the forming part 14 extends beyond the upper surface of the stripping part 12. In this position, the stripping part 12 has retracted against the action of its biasing springs. This movement causes the rack gear formations 15 on the stripping part 12 to move downwards, thus causing the pinion gear wheels 16 to rotate, which in turn causes the rack gear formations 17 of the forming part 14 to move upwards, raising the forming part 14.

Referring now to Figure 3, there is shown a press 20 including a die assembly 10, which forms a first part of a die set, and a second part 24 of a die set according to the present invention. The punch press 20 has a machine table 21 with clamps 22 to hold a workplace to be formed. A die holder 23 is provided, in which the die assembly 10 is received. Located above the die holder 23 is a mechanically- or hydraulically-operated ram 26, to which is attached a second part 24 of a die set having a receiving formation 25 which corresponds to the forming part 14 of the first part 10 ofthe die set.

In use, the workpiece, such as a suitable piece of sheet metal, to be formed is placed on the machine table 21 and held in place with the clamps 22, with the part which is to be formed being positioned above the die assembly 10.

The second part 24 of the die set is then forced downwards by moving the ram 26 downwards. The second part 24 of the die set comes into engagement with the workpiece to be formed, and the pressure of the ram 26 causes the stripping part 12 of the die assembly 10 to retract, causing the forming part 14 to extend, as previously described. Under the force exerted by the ram 26, the workplace takes on the shape of the forming part 14 of the die assembly 10 and the corresponding receiving formation 25 of the second part 24 of the die set. The ram 26 is then moved upwards, causing the second part 24 of the die set to move out of engagement with the formed workpiece. As the pressure of the ram 26 is released, the stripping part 12 of the die assembly 10 moves upwards under the influence of its biasing springs. This in turn causes the forming part 14 to move downwards, thus stripping the formed workpiece off the forming part 14.

As will be understood by those skilled in the relevant art, the present invention constitutes an advance over prior art constructions. The provision of a die assembly wherein movement of the stripping part causes movement of the forming part in the opposite direction extends the utility of existing presses, enabling them to be used to effect deeper forming operations than was previously possible.

In the present specification "comprises" means "includes or consists of'' and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A die assembly comprising a holding member, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part carried by the holding member and moveable relative thereto so as to retract during a forming operation and extend thereafter to strip a formed workplace off the forming part, wherein movement of the stripping part relative to the holding member causes movement of the forming part in the opposite direction relative to the holding member.

2. A die assembly according to claim 1 wherein the stripping part surrounds the forming part such that when the stripping part moves the forming part moves in the opposite direction through an opening in the stripping part.

3. A die assembly according to claim 1 or claim 2 wherein the stripping part is biased towards an extended position in which the forming part substantially does not extend beyond the stripping part.

4. A die assembly according to any one of the preceding claims in which the stripping part and the forming part are connected mechanically, such that movement of one of the stripping part or the forming part causes movement of the other in the opposite direction.

5. A die assembly according to claim 4 wherein the stripping part and the forming part each include at least one rack gear formation, the or the respective rack gear formations being engaged by a or a respective pinion.

6. A die assembly according to any one of the preceding claims wherein the distances by which the stripping part and forming part move in opposite directions bear a predetermined relationship to one another.

7. A die assembly according to claim 6 wherein the movement of the stripping part causes movement of the forming part in the opposite direction by an equal distance, relative to the holding member.

8. A die assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. A die set comprising a first part according to any one of the preceding claims and a second part having a formation complementary to the forming part of the die assembly.

10. A method of carrying out a forming operation on a workplace by using a die set having first and second complementary parts between which the workpiece is formed, the first part of the die set being a die assembly comprising a holding member, a forming part carried by the holding member so as to be operable on a workpiece, and a stripping part carried by the holding member and moveable relative thereto so as to retract during a forming operation and extend thereafter to strip a formed workplace off the forming part, the method comprising the steps of: (i) positioning the workpiece between the first and second parts of the die set; (ii) effecting relative movement between the first and second parts of the die set towards one another to engage the workpiece therebetween and cause said redaction of the stripping part relative to the holding member; (iii) causing movement of the forming part in the opposite direction to the retracting stripping part, relative to the holding member, to form the workpiece; and (iv) effecting relative movement of the first and second parts of the die set away from one another to cause or permit extension of the stripping part and movement of the forming part in the opposite direction relative to the holding member, to strip the formed workplace off the forming part.

11. A method according to claim 10 wherein the forming part and the stripping move an equal distance, relative to the holding member.

12. A method substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 3. Any novel feature or novel combination of features described herein andlor in the accompanying drawings.