ELECTRODE HOLDER

Abstract

The present disclosure concerns an electrode holder (100, 200) for electrical discharge machining, the electrode holder (100) comprising: a frame (103) having a first end (104) and an opposing second end (105); and a cartridge (110, 200) moveably mounted to the frame (103) and having a resilient sealing member (201) with a series of holes (308) each configured to receive a first end of one of a plurality of tubular electrodes (102, 301), the cartridge (110, 200) having an inlet for receiving a pressurised supply of dielectric fluid for transmission to each of the tubular electrodes (102, 301), wherein a cross-section of the resilient sealing member (201) in a plane parallel to a longitudinal direction of the tubular electrodes (102, 301) has a narrow central portion (305) between broader outer portions (306, 307).

Claims

1. An electrode holder for electrical discharge machining, the electrode holder comprising: a frame having a first end and an opposing second end; and a cartridge moveably mounted to the frame and having a resilient sealing member with a series of holes each configured to receive a first end of one of a plurality of tubular electrodes, the cartridge having an inlet for receiving a pressurised supply of dielectric fluid for transmission to each of the tubular electrodes, wherein a cross-section of the resilient sealing member in a plane parallel to a longitudinal direction of the tubular electrodes has a narrow central portion between broader outer portions.

2. The electrode holder of claim 1 wherein the resilient sealing member is positioned within a recess in an outer housing of the cartridge, the recess having a slot extending through to an outer face of the outer housing, the slot having a width narrower than a width of the resilient sealing member.

3. The electrode holder of claim 2 wherein the cartridge comprises an inner housing defining an internal volume, the inner housing comprising a protrusion configured to fit into the recess to provide a compressive force on the resilient sealing member in a direction parallel to the longitudinal direction of the tubular electrodes.

4. The electrode holder of claim 3 wherein the cartridge comprises a biasing element arranged to bias the inner housing against the outer housing to provide the compressive force against the resilient sealing member.

5. The electrode holder of claim 3 wherein the cartridge comprises a fastener arrangement comprising a plurality of bolts and corresponding holes connecting the inner and outer housings together.

6. The electrode holder of claim 1 wherein the cartridge is suspended from the second end of the frame by a pulley spring configured to provide a biasing force towards the second end of the frame that is greater than a weight of the cartridge.

7. The electrode holder of claim 1 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

8. The electrode holder of claim 2 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

9. The electrode holder of claim 3 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

10. An electrode holder for electrical discharge machining, the electrode holder comprising: a frame having a first end and an opposing second end; and a cartridge moveably mounted to the frame and having a resilient sealing member with a series of holes each configured to receive a first end of one of a plurality of tubular electrodes, the cartridge having an inlet for receiving a pressurised supply of dielectric fluid for transmission to each of the tubular electrodes, wherein a cross-section of the resilient sealing member in a plane parallel to a longitudinal direction of the tubular electrodes has a narrow central portion between broader outer portions, wherein the resilient sealing member is positioned within a recess in an outer housing of the cartridge, the recess having a slot extending through to an outer face of the outer housing, the slot having a width narrower than a width of the resilient sealing member, wherein the cartridge comprises an inner housing defining an internal volume, the inner housing comprising a protrusion configured to fit into the recess to provide a compressive force on the resilient sealing member in a direction parallel to the longitudinal direction of the tubular electrodes. wherein the cartridge is suspended from the second end of the frame by a pulley spring configured to provide a biasing force towards the second end of the frame that is greater than a weight of the cartridge.

11. The electrode holder of claim 10 wherein the cartridge comprises a biasing element arranged to bias the inner housing against the outer housing to provide the compressive force against the resilient sealing member.

12. The electrode holder of claim 11 wherein the cartridge comprises a fastener arrangement comprising a plurality of bolts and corresponding holes connecting the inner and outer housings together.

13. The electrode holder of any claim 10 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

14. The electrode holder of any claim 11 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

15. The electrode holder of any claim 12 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

16. The electrode holder of any claim 13 further comprising: a first electrode chuck fixed to the first end of the frame and configured to hold the plurality of tubular electrodes in parallel and at a fixed separation from each other; and a second electrode chuck mounted to the frame and configured to clamp the plurality of tubular electrodes in parallel and at the fixed separation from each other, the second electrode chuck being moveable relative to the frame along the longitudinal direction of the tubular electrodes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0021] FIG. 1 is a schematic diagram of an example electrode holder with tubular electrodes in place;

[0022] FIG. 2 is sectional view of a portion of a cartridge for holding multiple tubular electrodes;

[0023] FIG. 3 is a partial schematic sectional view of the cartridge with a tubular electrode in place within the sealing member; and

[0024] FIG. 4 is a partial schematic sectional view of the cartridge with a tubular electrode in place within the sealing member, with a force applied to cause the sealing member to provide a seal against the tubular electrode.

DETAILED DESCRIPTION

[0025] FIG. 1 illustrates an example electrode holder 100, holding a plurality of electrodes 102 in place. In the example illustrated, five electrodes are held in place by the holder 100. Other numbers of electrodes may be held using the same principle, limited only by the practical size limit of the frame and the available power for machining.

[0026] The holder 100 comprises a frame 103 having a first end 104 and an opposing second end 105. Fixed to the first end 103 is a first electrode chuck 106. The chuck 106 is configured to hold, i.e. to clamp in place, the electrodes 102, maintaining the electrodes 102 in parallel arrangement and at a fixed separation from each other but allowing the electrodes 102 to slide back and forth through the chuck 106. An optional nosepiece 107 is attached to the front of the first electrode chuck 106, through which the electrodes 102 pass. The nosepiece 107 may be shaped to match the contour of the piece to be machined, for example to match the curved contour of the side of a turbine blade.

[0027] A second electrode chuck 108 is mounted to the frame 103 and is configured to clamp the electrodes 102 in parallel and at the same fixed separation as defined by the first electrode chuck 106. The second electrode chuck 108 is moveable relative to the frame 103, as indicated by arrow 109, such that the second electrode chuck 108 may move in a longitudinal direction of the electrodes 102. With the second electrode chuck 108 clamping the electrodes 102, movement of the second electrode chuck 108 towards the first end 104 of the frame 103 causes the electrodes to extend further from the first electrode chuck 106, and through the nosepiece 107 if used.

[0028] A cartridge 110 is mounted to the frame 103 such that it can also move relative to the frame in the same direction as the second electrode chuck 108. The cartridge 110 has a series of holes (not shown), each hole being configured to receive one of the electrodes 102. The series of holes is arranged in the same fixed separation as for the first and second electrode chucks 106, 108, so that the electrodes 102 are held in parallel between the cartridge 110 and the first electrode chuck 106.

[0029] The cartridge 110 comprises an inlet (not shown in FIG. 1) for receiving a pressurised supply of dielectric fluid for transmission to each of the electrodes 102. An internal volume of the cartridge 110 connects the inlet to each of the electrodes 102.

[0030] The cartridge 110 shown in FIG. 1 is suspended from the second end 105 of the frame 103 by a pulley spring 111. This arrangement allows the cartridge 110 to move freely relative to the frame 103 in the same direction as the second electrode chuck 108, with the frame 103 vertically oriented, while maintaining tension in the electrodes 102 to prevent buckling of the electrodes 102. The pulley spring 111 may be configured to counteract at least the weight of the cartridge 110.

[0031] During operation, as the pressurised dielectric fluid supply is provided to the cartridge 110 and thereby to the electrodes 102, the second electrode chuck 108 is moved towards the first electrode chuck 106 as the electrodes 102 machine holes in the workpiece. The electrodes 102 move in parallel into the workpiece as the second electrode chuck 108 is moved until the machining operation is completed or until the second electrode chuck 108 reaches the first electrode chuck 106. The electrodes 102 can then be withdrawn from the workpiece by moving the second electrode chuck 108 away from the first electrode chuck 106. To allow the electrodes 102 to be further extended, the second electrode chuck 108 can be unclamped from the electrodes 102 and moved further away from the first electrode chuck 106. After clamping the second electrode chuck 108 again on the electrodes 102, a further machining operation can be done.

[0032] FIG. 2 illustrates in partial sectional view an example of a cartridge 200 in which a resilient sealing member 201 provides a seal against multiple electrodes (not shown) passing through an outer housing 202 of the cartridge 200 into an internal volume 203 through which a pressurised dielectric fluid is provided. The resilient sealing member 201 is disposed in a recess 204 of the outer housing 202, the recess 204 having a slot 205 extending through to an outer surface 206 of the outer housing 202. The slot 205 has a width 207 that is narrower than a width 208 of the resilient sealing member 201. The slot 205 allows the electrodes (not shown in FIG. 2) to pass through from the outer surface 206 of the outer housing 202 to the internal volume 203 and allows the resilient sealing member 201 to be compressed to form an effective seal against the electrodes.

[0033] FIGS. 3 and 4 are schematic diagrams showing in further detail how the resilient sealing member 201 may provide a seal against multiple tubular electrodes, one of which 301 is illustrated passing through a hole 308 in the sealing member 201. FIG. 3 shows the sealing member 201 prior to being compressed, and FIG. 4 following compression by a force 401 acting in a direction parallel to the longitudinal axis 302 of the tubular electrode 301. The force 401 acts on a protrusion 303 of an inner housing 304 within which is defined the internal volume 203 of the cartridge 200. The protrusion 303 fits within the recess 204, preferably with a sliding fit, and acts on the sealing member 201 to compress the sealing member 201 along the longitudinal axis 302.

[0034] The cross-sectional shape of the sealing member 201, having a narrower central portion 305 between broader outer portions 306, 307, allows the sealing member 201 to compress further than a sealing member of uniform section, which results in an improved fluid seal being formed against the tubular electrode 301 by deformation of the elastomeric material under the uniaxial force 401 provided via the protrusion 303 on the inner housing 304. This is because more of the uniaxial force on the sealing member 201 is transmitted to the broader portion 306 that is further away from the protrusion 303, rather than being reduced due to frictional forces against the wall of the recess 204. As a result, either an improved seal can be obtained for the same applied force, or the same seal obtained with a reduced applied force.

[0035] The axial force 401 may for example be provided by a biasing element, such as a spring 209 (shown in FIG. 2), loaded against the inner housing 304, or may alternatively be provided by a fastener arrangement of the type described in GB2550592A, for example comprising a plurality of bolts and corresponding holes connecting the inner and outer housings 304, 202 together.

[0036] Other components of the electrode holder, and the EDM apparatus in general, may be similar to those described in GB255092A.

[0037] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.