GB2326528A

GB2326528A - A magnetic holding device

Info

Publication number: GB2326528A
Application number: GB9811793A
Authority: GB
Inventors: Graham Thorpe
Original assignee: Eclipse Magnetics Ltd
Current assignee: Eclipse Magnetics Ltd
Priority date: 1997-06-05
Filing date: 1998-06-02
Publication date: 1998-12-23
Anticipated expiration: 2018-06-02
Also published as: GB2326528A8; GB9711627D0; GB2326528B; GB9811793D0; GB2326528A9

Description

A Magnetic holding Device The invention relates to a magnetic holding device such as a magnetic chuck or work holder in particular used on machine tools for machining of flat plate work pieces and in particular using pole members to provide the desired support for the work piece during machining.

In the field of magnetic work pieces for holding work pieces on machine tools there is a problem of holding the work piece without causing any distortion while the piece is being machined. The work piece must be located in the correct position and not move or bend during the machining process.

This is particularly a problem for irregularly shaped work pieces and is solved by the use of pole pieces which may extend away from the magnetic holding device towards the work piece to engage the work piece in an irregular manner corresponding to the surface of the work piece. Such a magnetic holding device is disclosed in US patent 4837540. The pole pieces are extendible and may have inclined surfaces to correspond to the work piece. Similarly the work piece may be clamped to the magnetic holding device to prevent movement or bending of the work piece during machining. Such known devices whilst essential for fixing the work pieces are a hindrance to the machining process in particular for work pieces which are required to be machined on the sides. To carry out such machining it is necessary to remove and replace the clamps or remove and relocate the pole extension supports. This process is very time consuming and leads to a long total machining time for the work piece concerned.

It is therefore an objective of the invention to provide a magnetic holding device which can hold a work piece which require machining on at least one of its the sides in a single operation without the need to relocate any pole pieces or clamps.

It is a further objective of the invention to provide a magnetic holding device which provides easy access for a milling or other machine tool to the work piece for the complete machining operation.

According to the invention there is a provided a magnetic work holding device comprising in combination; a magnetically activatable and deactivatable holding surface comprising pole pieces of different polarities and comprising pole extension members arranged on the pole pieces of said holding surface, characterised in that the pole extension members are arranged in a configuration that corresponds approximately to the desired shape of the work piece.

Preferably the pole pieces are of the same thickness and width but of differing length and are removably attached to the holding surface by removable fixing means such as screws, so that the arrangement of the pole extension members can be altered to accommodate different final desired shape of the work piece.

According to the invention there is a provided a magnetic work holding device comprising in combination; a magnetically activatable and deactivatable holding surface comprising pole pieces of different polarities and comprising pole extension members arranged on the pole pieces of said holding surface, characterised in that at least one datum bar is provided on the holding device and removably attached there to by suitable removable fixing means such as screws. Preferably there is a side datum bar and end datum bar to provide a datum for a flat plate-like work piece in the two axes of the plane of the work piece.

According to the invention the datum bars comprise datum pins which are removably located in holes on the datum bars. The datum bars are arranged such that they do not protrude above the plane of the holding surface whereas the datum pins do protrude above the plane of the holding surface and engage the work piece to locate it in the desired position on the magnetic holding device. The datum pins are removable after the work piece is located on the holding device to permit the machine tool to access the sides portions of the work piece.

The datum pins are preferably circular and located in circular holes on the datum bars. The datum pins may however be located directly in corresponding holes in the holding surface.

The preferred embodiment of the invention will now be described in more detail with reference to the drawing in which: figure 1 is a schematic arrangement of the holding device of the invention, and figure 2 is an enlarged view showing the datum bar of the holding device offigure 1.

Referring to figure 1 there is shown a magnetic work holding device 1 comprising in combination; a magnetically activatable and deactivatable holding surface ; comprising pole pieces of different polarities and comprising pole extension members 3 arranged on the pole pieces of said holding surface 2. The pole pieces are arranged in a configuration that corresponds approximately to the shape of the work piece 5 which may either be the shape after the machining process if the machining process is to be an operation which changes the shape of the work piece or essentially the same shape as the work piece before the machining operation if the operation is to providing a finishing operation such as a bevel to the side edges of the work piece. The work piece is shown as a plate with an irregular shape which required the edges to be bevelled to provide the desired edge finish. The shaped will typically have been cut out by a cutting operation which leaves a relatively rough finish.

The pole piece extensions are arranged to correspond to the shape of the work piece so that the milling machine can gain access to the entire perimeter of the work piece to provide the desired bevel finish over the complete perimeter in a single operation.

The pole pieces are of the same thickness and width but of differing length and are removably attached to the holding surface by removable fixing means 6 such as screws, so that the arrangement of the pole pieces 3 can be altered to accommodate different final desired shape of the work piece 5.

Two datum bars 7, 8 are provided on the holding device 1 and removably attached there to by suitable removable fixing means 9 such as screws.

The side datum bar 8 and end datum bar 7 provide the datum for the work piece 5 in the two axes of the plane of the work piece 5 so that the bevelling operation can be automated to follow the predetermined profile of the work piece.

The datum bars 7, 8 comprise datum pins 10 which are removably located in holes 11 on the datum bars 7, 8. The datum bars 7, 8 are arranged such that they do not protrude above the plane of the holding surface 2 whereas the datum pins 10 do protrude above the plane ofthe holding surface 2 and are engaged against the work piece 5 to locate it in the desired position on the magnetic holding device 1. The datum pins 10 are then removed, after the work piece 5 is located on the holding device and the holding device has been activated to retain the work piece on the holding surface, to permit the machine tool to access the sides portions of the work piece 5.

The datum pins 10 are circular and located in circular holes 11 on the datum bars 7, 8. It will be appreciated however that they may be of any convenient cross section. The datum pins may alternatively be located directly in corresponding holes in the holding surface 2.

Claims

1. According to the invention there is a provided a magnetic work holding device 1 comprising in combination; a magnetically activatable and deactivatable holding surface 2 for holding a work piece 5 comprising pole pieces of different polarities and comprising a plurality of pole extension members 3 arranged on the pole pieces of said holding surface 2, characterised in that the pole extension members 3 are arranged in a configuration that corresponds approximately to the shape of the work piece 5 and permitting access to the entire perimeter of the work piece in a single operation without relocating the work piece on the holding surface 2.

2. A magnetic holding device according to claim 1 characterised in that the pole extension members 3 are of the same thickness and width but of differing length.

3. A magnetic holding device according to claim 1 characterised in that the pole extension members 3 are of the same thickness but of differing width.

4. A magnetic holding device according to claim 1 characterised in that the pole extension members 3 are removably attached to the holding surface by removable fixing means 6 such as screws.

5. A magnetic work holding device 1 comprising in combination; a magnetically activatable and deactivatable holding surface 2 comprising pole pieces of different polarities and comprising pole extension members 3 arranged on the pole pieces of said holding surface, characterised in that at least one datum member 7, 8, 10.

6. A magnetic holding device according to claim 5 characterised in that the datum member is a datum bar 7, 8 removably attached to the holding device 1 by removable fixing means 9 such as screws.

7. A magnetic holding device according to claim 5 characterised in that the datum member comprises a side datum bar 8 and end datum bar 7 to provide a datum for a flat plate like work piece 5 in the two axes of the plane of the work piece 5.

8. A magnetic holding device according to claim 6 characterised in that the datum bars 7, 8 comprise datum pins 10 which are removably located in holes 11 on the datum bars 7, 8.

9. A magnetic holding device according to claim 6 characterised in that the datum bars 7, 8 are arranged such that they do not protrude above the plane of the holding surface 2.

10. A magnetic holding device according to claim 6 characterised in that the datum member includes a datum pin 10.

11. A magnetic holding device according to claim 10 characterised in that the datum pins 10 protrude above the plane of the holding surface 2 and are engaged against the work piece 5 to locate it in the desired position on the magnetic holding device 1.

12. A magnetic holding device according to claim 5 characterised in that the datum pins 10 are removable after the work piece 5 is located on the holding device to permit the machine tool to access the sides portions of the work piece 5.

13. A magnetic holding device according to claim 10 characterised in that the datum pins 10 are circular and located in corresponding circular holes 11 on the datum bars 7, 8.

14. A magnetic holding device according to claim 5 characterised in that the datum pins are located directly in corresponding holes in the holding surface 2.