WO1997049519A1

WO1997049519A1 - Quick change welding electrode

Info

Publication number: WO1997049519A1
Application number: PCT/US1997/010199
Authority: WO
Inventors: Joseph Harry Krenz; Timothy John Haynie; Erik Waelchli
Original assignee: Hess Engineering, Inc.
Priority date: 1996-06-26
Filing date: 1997-06-17
Publication date: 1997-12-31

Abstract

An electric resistance welding apparatus (10) includes a welding electrode (12) mounted on an electrode holder (14). The electrode (12) includes a pair of intersecting surfaces (18, 20) forming a welding edge (22) at which welding takes place. The surfaces (18, 22) must be resurfaced periodically to maintain the welding edge (22). The electrode holder (14) includes an obliquely extending surface (24) which supports the electrode (12) such that the electrode (12) may be moved along the surface (24) to compensate for the material removed from the welding surface edge (22). Bolts (32, 34) are installed between the electrode (12) and the electrode holder (14) to maintain the welding edge (22) in the welding position. The electrode holder (14) is mounted on an electrode support (16) by a clamping mechanism (36). When the electrode (12) is to be changed the electrode (12) is communicated with a vacuum source thereby pulling the coolant out of the electrode (12) to permit quick electrode (12) changeover. A nozzle (98) permanently mounted on the electrode holder (14) is oriented along one of the surfaces (18) so that a blast of air blows debris away from the welding edge (22).

Description

QUICK CHANGE WELDING ELECTRODE

This application claims domestic priority based upon U.S. Provisional Patent Application Serial No. 60/020,584, filed June 26, 1996. This invention relates to a welding mechanism and electrode holder.

Many production processes require that strips of sheet material be welded or forged together along their edges. Many of these products, such as wheel rims, are commonly manufactured in large quantities, requiring automated welding/forging equipment. Resistance welding techniques used in such high-volume production are well known to those skilled in the art. Such electrical resistance welding techniques involve passing electrical current through an electrode to effect welding. A typical prior art arrangement is illustrated in German Published Patent Application DE4107984A1, published September 17, 1992. However, the edge of the electrode at which welding or forging takes place wears quickly, so that the electrode must be removed and a rebuilt or new electrode installed at frequent intervals. Since no production takes place while the electrode is being replaced, it is necessary that the electrode be removed and replaced as quickly as possible so that production interruptions are minimized.

It is also desirable that the electrode holder be able to accommodate rebuilt electrodes. It is common to refurbish and rebuild the electrode by removing a small amount of material from the sides of the electrode defining the welding edge. Of course, removal of this material changes the shape of the electrode slightly, so that the holder must be modified to accommodate the rebuilt electrode, while maintaining the welding edge in the proper position to effect high-production welding.

Since electricity is being passed through the edge to effect welding, the electrode and the electrode holder are heated, and this heat must be removed by pumping water through the electrode holder. However, when the electrode is changed, the electrode holder and the electrode are removed from the clamping mechanism. Accordingly, the water or other coolant must be drained or evacuated from the electrode holder. In prior art apparatus, a significant time was required to 97/49519 PC17US97/10199

drain water from the electrode holder, thus resulting in additional production delays.

It is also common practice in high production welding to remove flash and other debris from the area around the welding edge by using a blast of air from an air nozzle. Accordingly, it is common practice to provide an air blast nozzle to clean the electrode, which must be mounted in close proximity to the electrode. Accordingly, the known air blast nozzles must be removed to effect an electrode changeover.

According to the present invention, a welding electrode is mounted in a holder which is retained on an electrode support by a spring actuated, hydraulically released locking plunger. During production, the electrode holder and electrode are held in place by a spring, thus assuring that the electrode will be properly retained, and hydraulic pressure need only be applied when the electrode holder is removed. Furthermore, the present invention provides a vacuum system for quickly evacuating water or other coolant from the electrode holder just prior to electrode changeover. Accordingly, the coolant is quickly removed from the apparatus, further reducing production delays which were inherent in prior art mechanisms. Still further, the electrode holder of the present invention provides a pair of cooperating surfaces, one of which is sloped, that locates and supports the welding electrode in the electrode holder. Accordingly, removal of material during rebuilding of the electrode is accommodated by placing shims of increasing thickness between the electrode and the electrode holder to thereby maintain the welding edge in its proper position. Still further, an integral permanent air blast nozzle which need not be changed or removed when the electrode is changed, is mounted on the mechanism and directed toward the welding electrode.

These and other advantages of the present invention will become apparent from the description, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view taken through the clamp mechanism, electrode holder, electrode and electrode support of a welding mechanism made pursuant to the teachings of the present invention; Figure 2 is a partial cross-sectional view taken substantially along lines 2-2 of Figure 1 ; and

Figure 3 is a schematic illustration of the cooled evacuation system used in the present invention. Referring now to the drawings, a high volume electrical resistance welding assembly is generally indicated by the numeral 10 and includes a welding electrode 12 mounted in an electrode holder 14 which in turn is supported on an electrode support generally indicated by the numeral 16. The electrode 12 includes an upper surface 18 and a side surface 20 which meet at an edge 22. Welding takes place at the abutting part surfaces by passing electricity through the surface 18. Both the electrode 12 and the electrode holder 14 may be, for example, several inches long and are mated with other electrodes to effect welding of materials passed between the electrodes. Since forging takes place at the edge 22, this edge wears relatively quickly, so that the electrode 12 must be removed and a new or rebuilt electrode installed on holder 14. Because the electrode 12 is a wear item, it is common to rebuild the electrode 12 by removing material from the surfaces 18 and 20 to provide a sharp edge 22 to assure proper forging. Of course, if material is removed from surfaces 18 and 20, the electrode 12 must be shifted upwardly and to the right viewing Figure 1 to maintain the welding edge in the proper position. In order to permit adjustment of the edge 22 to compensate for rebuilding, a tapered supporting surface 24 is provided on the electrode holder 14 to support the electrode 12. A shim or shims 26 are installed between vertical edge 28 on the electrode 12 and vertical edge 30 on the electrode holder 14. The shims 26 may be of varying sizes, so that when the electrode 12 is rebuilt, the electrode may be shifted upwardly along the tapered surface 24 by installing a thicker shim 26. Accordingly, the position of the welding edge 22 is maintained, even though the electrode 12 may be rebuilt a number of times.

The electrode 12 is secured to the holder 14 by bolts 32, 34, which extend through oversized bores 33, 35 in electrode holder 14. Accordingly, when replacement of the electrode 12 is necessary, the electrode 12 is removed with its holder 14 by release of a clamping mechanism which will be described hereinafter, and a new holder and electrode assembly is installed so that production can immediately resume. The electrode 12 can then be dismantled from the holder and rebuilt offline in a toolshop.

The electrode 12 and holder 14 are mounted on the support 16 by a clamping mechanism generally indicated by the numeral 36. Two or more clamping mechanisms 36 may be spaced along the length of the electrode support 16. When the electrode support 14 is installed on a surface 38 of the support 16, a stepped bore generally indicated by the numeral 40 in the electrode holder 14 is substantially coaxial with bore 42 in the electrode support 16. Bore 40 is stepped to define a smaller diameter portion 44, a larger diameter portion 46, and a portion 48 of intermediate diameter. One end 50 of a stem generally indicated by the numeral 52 is mounted in portion 44 of bore 40, and the opposite end 54 of the stem 52 is mounted in support member 56. The outer circumferential surface of the end portion 50 of stem 52 is undercut to provide an undercut surface 58 of the stem 52. A ramp 60 connects the undercut surface 58 with outside surface 78 of the stem 52. Stem 52 is further provided with an axially extending passage 62 which communicates water or other appropriate cooling fluid from an inlet fitting 64 to a transverse passage 66 which extends through the electrode holder 14 at a point adjacent the electrode 12. Water is discharged from the passage 66 through a discharge fitting (not shown) adjacent the end of the holder 14 opposite the end upon which the mechanism 36 is mounted. Accordingly, water or other coolant can be pumped through the electrode holder 14 during production to carry away heat generated by the welding operation. Clamping mechanism 36 further includes a stepped piston 68 having a larger diameter portion 70 and a smaller diameter portion 72 with a shoulder 74 therebetween. Piston 68 further includes a bore 76 which is slidably supported on the outer circumferential surface 78 of the stem 52. Circumferentially spaced, radially extending apertures 80 are provided in the piston 68 adjacent the end 82 thereof. Hardened metal spheres 84 are received in each of the apertures 80. A compression spring 86 circumscribes smaller diameter portion 72 of piston 68 and yieldably urges the piston to the left viewing Figure 1. Hydraulic pressure is selectively communicated through fitting 88 to chamber 90 where it acts on the end surface 92 of the piston 68, such that hydraulic pressure in the chamber 90 urges the piston to the right viewing Figure 1 , in opposition to the force exerted by the spring 86. A circumferentially extending insert 94 is secured within larger diameter portion 46 of the bore 40 in electrode holder 14 at a point adjacent the end 82 of the piston 68. The insert 94 includes larger and smaller diameter portions with a ramp 96 extending therebetween. The ramp 96 engages the spheres 84 when the spheres are urged up the ramp 60 and onto the outer cirumferential surface 78 of the stem 52. The spring 86 urges the piston 68 into the position illustrated in Figure 1, in which the spheres 84 rest on the outer surface 78 of stem 52, so that a portion of the outer surface of the spheres 84 also engage the ramp 96 of the insert 94. Since the insert 94 is fixed to the electrode holder 14, the electrode holder 14, and therefore the electrode 12, are locked in place on the electrode support 16 by the spring 86 urging the piston 68 to the left viewing

Figure 1. When the electrode holder 14 is to be removed for replacement of the electrode 12, hydraulic pressure is admitted into chamber 90 where it acts on surface 92 of the piston 68, thereby urging the latter to the right viewing Figure 1 in opposition to the spring 86. As the piston 68 is urged to the right, the spheres drop down the ramp 60 and rest on the undercut portion 58 of the stem 52. The difference in the diameter between the undercut portion 58 and the outer circumferential surface 78 of stem 52 is sufficient to cause the spheres 84 to clear the smaller diameter surface of insert 94, thereby permitting the holder 14 to be removed by sliding the holder 14 across the apertures 82. The process is reversed when the electrode holder 14 is reinstalled on the holder 16.

As discussed above, it is desirable to periodically clean the area around the edge 22 by blasting air across the upper surface 18 through an air blast nozzle, which is removed to affect an electrode change over. According to the present invention, a permanent nozzle is mounted on the electrode assembly which need not be changed when the electrode is changed. Accordingly, a nozzle assembly generally indicated by the numeral 98 includes a pair of shaped members 100, 102 which extends substantially parallel with the electrode 12 and project above the electrode holders. The members 100, 102 cooperate with one another to define an air chamber 104 which is communicated to passage 110, which is in turn communicated to an exterior air supply (not shown). Dividers 106 are spaced along the chamber 104 to divide the nozzle into sections. The members 100, 102 are connected to the support 56 by screws 108 extending through the members 100, 102 and into the support 56. The upper surface 1 10 of the member 102 may be contoured to form a converging flow path with the member 100 to thereby form the nozzle which is used to blast across and clear surface 18. As also discussed above, it is necessary to remove water or other coolant from the electrode holder 14 before the latter is removed for electrode changeover. For this reason, the evacuation system generally indicated schematically at 112 in Figure 3 is provided. This system 112 can be used to evacuate multiple electrode holders 14 as indicated in Figure 3. Flow into the passage 114, which communicates with the fitting 64, is controlled by a two position solenoid control valve generally indicated by the numeral 1 16. During normal operation, in which coolant flow is being communicated to the electrode holder 14, the solenoid valve 116 is shifted from the position in Figure 3 to a position in which the valve 116 connects the line 114 to the output of a coolant system circulating pump generally indicated by the numeral 118. The inlet of the pump 118 is connected to a water reservoir 120, in which water or other appropriate cooling liquid is stored. The reservoir 120 is vented by vent 122, such that the volume of air above the water level in the reservoir 120 is always vented to atmosphere. As long as the outlet of the pump 118 is connected to line 114, the valve 116 shuts off line 124 which is connected to a vacuum tank 126. Water that has been circulated through the electrode holders 14 through the line 114 passes through a conventional one-way check valve 128, through a venturi 130, and back to the coolant tank 120. The passage of the water or other coolant through the venturi 130 draws a vacuum in vacuum tank 126 through the one way check valve 132. The vent 122 is connected through the air volume of coolant tank 120 through a pressure line 134 and check valve 136 to the coolant outlet from the electrode holders, at a point between the check valve 128 and the electrode holder.

When an electrode changeover is to be effected, the coolant lines are first evacuated of coolant by operating the valve 1 16 to move the latter to the position illustrated in Figure 3, connecting the line 114 and the vacuum in tank 126 through the line 124. Accordingly, vacuum in tank 126 draws coolant out of the electrode holders 14 by drawing air form the vent 122 through the line 134 and the check valve 136, through the electrode holders, and into the line 114. Accordingly, coolant is withdrawn from the coolant passages within the electrode holders quickly. Electrode changeover can then take place by operating the clamp mechanism 36 to release the electrode holder 14. After electrode changeover has been effected and production is to begin, the valve 116 is again shifted to connect the outlet of pump 118 to the line 114. Accordingly, production interruption is minimized, since the vacuum generated by the passage of water through the venturi 130 quickly evacuates the tank 126, maintaining a state of readiness for the next electrode changeover.

Claims

WHAT IS CLAIMED:

1. Welding assembly comprising an electrode having an surfaces joining at a welding edge at which welding takes place when said electrode is mounted to maintain the welding edge in a welding position, said welding edge wearing during welding and requiring periodic refurbishing by removing material from said surfaces to thereby provide a renewed welding edge, an electrode holder for supporting said electrode in said welding position, and adjustable fastening means for securing said electrode to the electrode holder in multiple positions whereby said electrode may be moved from one of said positions to another of said positions in response to removal of material from said surfaces to maintain said welding edge in said welding position.

2. Welding assembly as claimed in claim 1, wherein said assembly includes an electrode holder support, and clamping means for releasably securing said electrode holder to said electrode holder support.

3. Welding assembly as claimed in claim 1 , wherein said adjustable fastening means includes a pair of mounting edges on said electrode assembly and a pair of supporting edges on said electrode holder engaging a corresponding mounting edge to thereby support said electrode on the electrode holder, one of said mounting edges and its corresponding supporting edge extending obliquely whereby said electrode may be moved along said one mounting edge and its corresponding supporting edge to maintain said welding edge in said welding position compensating for material removed from said surfaces.

4. Welding assembly as claimed in claim 3, wherein said fastening means includes a pair of fasteners, each of said fasteners extending through one of said mounting and supporting edges to secure the electrode to said electrode holder, said fasteners extending through bores in said electrode holder to engage said electrode, the cross section of said bores being substantially greater than the cross section of said fasteners whereby said electrode may be moved relative to said fasteners as the electrode is moved from one of said positions to another position.

5. Welding assembly as claimed in claim 4, wherein at least one shim is installed between the other mounting edge and its corresponding supporting edge.

6. Welding assembly comprising an electrode, and electrode holder releasably secured to said electrode, said electrode holder being mounted on an electrode holder support, clamping means for releasably securing said electrode holder to said electrode holder support, said clamping means including a piston slidably mounted in said electrode holder support, camming means responsive to movement of the piston to a latched position to engage said electrode holder to thereby lock the electrode holder on the electrode holder support, said camming means being responsive to movement of the piston away from said latched position to disengage said electrode holder from said electrode holder support, a spring yieldably urging said piston to said latched position, said piston being moved away form said latched position in opposition to said spring by fluid pressure communicated to a fluid pressure responsive face of said piston whereby said electrode holder is retained on said electrode holder support by the force of said spring and is released for removal from said electrode holder support by fluid pressure.

7. Welding assembly as claimed in claim 6, wherein said electrode has surfaces joining at a welding edge at which welding takes place when said electrode is mounted to maintain the welding edge in a welding position, said welding edge wearing during welding and requiring periodic refurbishing by removing material from said surfaces to thereby provide a renewed welding edge, and adjustable fastening means for securing said electrode to the electrode holder in multiple positions whereby said electrode may be moved from one of said positions to another of said positions in response to removal of material from said surfaces to maintain said welding edge in said welding position.

8. Welding assembly as claimed in claim 7, wherein said adjustable fastening means includes a pair of mounting edges on said electrode assembly and a pair of supporting edges on said electrode holder engaging a corresponding mounting edge to thereby support said electrode on the electrode holder, one of said mounting edges and its corresponding supporting edge extending obliquely whereby said electrode may be moved along said one mounting edge and its corresponding supporting edge to maintain said welding edge in said welding position compensating for material removed from said surfaces.

9. Welding assembly as claimed in claim 6, wherein said camming means includes camming members movable with said piston and an insert carried by said electrode holder, said camming members engaging said insert to latch said electrode holder and disengaging from said insert to release said electrode holder.

10. Welding assembly as claimed in claim 9 , wherein said camming members are spheres, said insert receiving said spheres when the piston is moved to the latched position, said spheres disengaging from said insert when the piston is moved away from the latched position.

1 1. Welding assembly as claimed in claim 10, wherein said piston is slidably mounted on a stem mounted within said electrode holder support, said spheres being retained in apertures extending through said piston and engaging said stem, said stem having a ramp surface moving said spheres from a lowered position in which the spheres are disengaged from said insert to a raised position in which the spheres engage said insert as the piston is moved into and away from the latched position.

12. Welding assembly as claimed in claim 6, wherein said piston is slidably mounted on a stem, said stem having a camming surface for operating said camming means as said piston moves between said engaged and released positions.

13. System for supplying liquid coolant to a welding electrode of a welding assembly and for evacuating said coolant from the electrodes when the electrodes are to be changed comprising a reservoir for storing coolant, a pump for taking coolant from said reservoir and pumping the coolant to said electrode, a return line for returning coolant from said electrode to said reservoir, means for causing a reduced pressure level to be drawn in a vacuum tank that is less than atmospheric pressure, and a selectively actuated valve switchable from a normal position communicating said pump to the electrode to an evacuating position closing communication between the pump and the electrode and opening communication between the electrode and the vacuum tank.

14. System for supplying liquid coolant as claimed in claim 13, wherein said means for causing a reduced pressure level is a venturi in said return line communicated to said vacuum tank, said venturi being responsive to coolant communicated through the return line to reduce the pressure in the vacuum tank to a level below atmospheric pressure.

15. System for supplying liquid coolant as claimed in claim 14, wherein a vent line communicates the electrode to atmosphere when the valve is in the evacuating position.

16. System for supplying liquid coolant as claimed in claim 15, wherein said vent line includes a check valve permitting air to communicate through the vent line to the electrode when the selectively actuated valve is in the evacuating position but preventing coolant from communicating through the vent line when the electively actuated valve is in the normal position.

17. Welding assembly comprising an electrode having intersecting surfaces joining at a welding edge, at which welding takes place when said electrode is mounted to maintain the welding edge in a welding position, an electrode holder for supporting said electrode in said welding position, and adjustable fastening means for securing said electrode to the electrode holder, an electrode holder support, clamping means for releasably securing said electrode holder to said electrode holder support, and a nozzle mounted on said electrode holder support for directing blasts of air along one of said surfaces to thereby remove debris from said welding edge.

18. Welding assembly as claimed in claim 17, wherein said nozzle extends along said one surface substantially parallel to said welding edge.

19. Welding assembly as claimed in claim 18, wherein said nozzle projects above said one surface.