GB2339549A

GB2339549A - Welding tool

Info

Publication number: GB2339549A
Application number: GB9815128A
Authority: GB
Inventors: Dale Matthew Goulding
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-07-14
Filing date: 1998-07-14
Publication date: 2000-02-02
Also published as: GB9815128D0

Description

2339549 Welding Tool The present invention relates to an improved welding

tool, with particular, but not exclusive use, for spot welding from within a tubular member.

In particular it is not currently practicable to spot weld from within a tubular member. This is because it is difficult to locate and to brace a welding electrode within a tubular member. It is necessary to brace the electrode against the inside of the tube to generate a reaction force in order assist the process of spot welding. It is even more difficult to locate and to brace the welding electrode accurately. These difficulties are further increased if the tubular member is not straight, but is curved, kinked or otherwise diverted from a straight path. It will be understood that the tool has application in other confined spaces and in other locations to which access is difficult using current welding tools.

According to a first aspect of the present invention a welding tool comprises a welding head including a welding electrode characterised in that the welding tool also comprises locating means to urge the welding electrode away from a first surface located behind the welding electrode.

This has the advantage that the welding electrode is urged towards and into contact with a second surface in front of the welding electrode. In a tubular member, the first and second surfaces will comprise opposite sides of the tubular member.

Preferably, the locating means comprises an extendible member located at the rear of the welding head.

More preferably, the extendible member comprises an inflatable sack. Alternatively, the extendible member comprises a reciprocating member, such as a 5 plunger.

According to a second aspect of the invention, a welding tool comprises a welding head incorporating a welding electrode characterised in that the welding head is carried on an elongate carrier member.

Preferably, the elongate carrier member comprises a plurality of mutually adjustable members. More preferably, at least one adjustable member may be driven between a first position with respect to an adjacent adjustable member and a second position with respect to the adjacent adjustable member. Conveniently the relative positions of the adjustable members with respect to one another is monitored and controlled by an electronic control apparatus.

Alternatively, the elongate carrier member is preformed to a shape suitable to provide access to a desired location. The desired location may for example be within a curved tubular member.

The invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure I illustrates diagramatically a section of a tube showing a welding tool according to a first embodiment of the present invention in an operative position; Figure 2 illustrates diagramatically a section of a tube showing a welding tool according to a second embodiment of the present invention in an operative position; and Figure 3 illustrates diagramatically a section of a tube showing a welding tool according to the present invention incorporating an elongate carrier member.

Referring first to Figure I there is shown a tubular member 10 with a welding tool 20 in an operative position. The tubular member 10 has a first wall 12 and second wall 14 which are oppositely disposed to one another.

The welding tool 20 comprises an electrode 22 disposed on a head 24 of the welding tool located at a remote end of a carrier member 26. At the rear of the welding tool head 24 there is located a reciprocating plunger 30. The plunger is moveable between a first retracted position and a second extended position shown.

The plunger comprises a reciprocating piston 32. One end of the piston works within a bore (not shown) in the welding tool head, the other end 34 is attached to a pad 36.

In use, the welding tool head 24 with the plunger 30 in the first retracted position is introduced into the tubular member 10 until the welding tool head has reached the region of the tubular member 10 at which the spot weld is to be made. The plunger is then actuated to move to the second extended position in which the pad 36 abuts an inner surface 16 of the first wall 12 of the tubular member 10. The welding electrode on the opposite side of the welding tool head is then urged into contact with an inner surface 18 of the second wall 14 of the tubular member 10.

The plunger is provided with a stroke sufficiently long that in attempting fully to move to the extended position the plunger provides a back pressure on the welding electrode 22. This back pressure acts to held the welding tool in position. Once the electrode 22 of the welding tool 20 is in position a complimentary welding electrode can be placed into position outside of the tubular member., A spot welding operation can then be performed at this location.

Referring now to Figure 2 there is shown a tubular member 110 with a welding tool 120 according to a second embodiment of the invention in an operative position. The tubular member 110 has a first wall 112 and second wall 114 which are oppositely disposed to one another.

The welding tool 120 comprises an electrode 122 disposed on a head 124 of the welding tool located at a remote end of a carrier member 126. At the rear of the welding tool head 124 there is located an inflatable sack 130. The sack 130 is moveable between a first deflated position and a second inflated position shown.

In use, the welding tool head 124 with the sack 130 in the first deflated position is introduced into the tubular member 110 until the welding tool head has reached the region of the tubular member 110 at which the spot weld is to be made. The sack 130 is then actuated to inflate to the second inflated position in which a portion of the inflated sack abuts an inner surface 116 of the first wall 112 of the tubular member 110. The welding electrode on the opposite side of the welding tool head is then urged into contact with an inner surface 118 of the second wall 114 of the tubular member I 10.

The sack is able to inflate to a degree sufficient to provide a back pressure on the welding electrode 122. This back pressure acts to hold the welding tool in position.

Once the electrode 122 of the welding tool 120 is in position a complimentary welding electrode can be placed into position outside of the tubular member. A spot welding operation can then be performed at this location.

Referring to Figure 3, there is shown a tubular member 210 having a first bend 212 and a second bend 214. A welding tool 220 is shown within the tubular member 210. The desired position of- the welding tool head is shown in ghost. A welding tool having no inherent rigidity can be fed into the tubular member 210 until the tool reaches the desired position and the locating means are actuated to brace an electrode against an inner surface of the tubular member.

However, there is an inherent danger that such a tool may become twisted and so a user would not know at what point to place a complimentary electrode. In any case such a tool would not be capable adequately to deal with any upward bends in the tubular member.

In those cases where the bends are not too tight or disposed in opposite directions, the electrode may be carrier on an elongate carrier member of fixed shape. The elongate carrier member may be jiggled along the tubular member into position and the locating means are actuated to brace an electrode against an inner surface of the tubular member.

However, in such a construction there is a risk that the welding electrode may become damaged by the journey to the welding region.

In a preferred embodiment, an elongate carrier member 226 comprises a plurality of mutually adjustable members. At least one adjustable member may be driven between a first position with respect to an adjacent adjustable member and a second position with respect to the adjacent adjustable member. The elongate carrier member 226 is thus able to snake along the tubular member 210 to the desired position.

Conveniently the relative positions of the adjustable members with respect to one another are monitored and controlled by an electronic control apparatus. The electronic control apparatus may also be used to control the welding operation.

Claims

1. A welding tool comprising a welding head incorporating a welding electrode is characterised in that the welding tool also comprises locating means to urge the welding electrode away from a first surface located behind the welding electrode.

2. A welding tool according to claim 1, characterised in that the locating means comprises an extendible member located at the rear of the welding head.

3. A welding tool according to claim 2, characterised in that the extendible member comprises an inflatable sack.

4. A welding tool according to claim 2, characterised in that the extendible member comprises a reciprocating member.

5. A welding tool according to any previous claim, characterised in that the welding head is carried on an elongate carrier member.

6. A welding tool according to claim 5, characterised in that the elongate carrier member comprises a plurality of mutually adjustable members.

7. A welding tool according to claim 6, characterised in that at least one adjustable member may be driven between a first position with respect to an adjacent adjustable member and a second position with respect to the adjacent adjustable member.

8. A tool according to claim 7, characterised in that relative positions of the adjustable members with respect to one another are monitored and controlled by an electronic control apparatus.

9. A welding tool according to claim 5, characterised in that the Iongate carrier member is preformed to a shape suitable to provide access to a desired location.

10. A welding tool substantially as described herein with reference to and as illustrated in the accompanying drawings.