GB2539412A

GB2539412A - Welding torch

Info

Publication number: GB2539412A
Application number: GB1510439.1A
Authority: GB
Inventors: Parker Tracy
Original assignee: JINAN UNIARC WELDING TECHNOLOGY Ltd; Jinan Uniarc Welding Tech Ltd
Current assignee: JINAN UNIARC WELDING TECHNOLOGY Ltd; Jinan Uniarc Welding Tech Ltd
Priority date: 2015-06-15
Filing date: 2015-06-15
Publication date: 2016-12-21
Anticipated expiration: 2035-06-15
Also published as: GB201510439D0; WO2016203213A3; GB2539412B; WO2016203213A2

Abstract

A welding torch for use in Gas Metal Arc Welding (GMAW) includes a conductor assembly, comprising a conductor tube (Fig 1b; 26) and a conductor core 10 disposed within the tube. A gas flow path is provided through channels 20 in the outer surface of the conductor core 10. The channels are covered by the conductor tube (Fig 1b; 26), the conductor tube and conductor core 10 being made from aluminium, and the conductor assembly is overmoulded with a plastic (Fig 1d; 28), such as polythalamide resin. The core 10 may include a gas inlet at one end 12 and a gas outlet 24 at the other end, the gas inlet being a bore running through the length of the core 10. The gas outlet 24 may be a plurality of apertures. External screw threaded means 12 may be provided to connect to an electricity or gas supply, or wire feed. The core 10 and connection means 12 may be machined from aluminium in a single piece. The welding torch can also include a tip adaptor (Fig 4a; 36) and a welding tip (Fig 5a; 64). The welding tip may have a smooth outer surface (Fig 5a; 66), a screw thread (Fig 5a; 68) for releasable attachment to the welding tip adaptor and a heat sink (Fig 5a; 70). The heat sink may be tapered and include straight lined (Fig 5b & c; 70) helical or spiral (Fig 5a; 70) gas flow channels.

Description

WELDING TORCH

The present invention relates to a welding torch, and in particular a welding torch which is made substantially from aluminium.

BACKGROUND TO THE INVENTION

Gas Metal Arc Welding (GMAW) is one of the most common welding processes which is in industrial use today. A welding torch suitable for use in the GMAW process includes an electrical conductor for supplying current from a power source to strike an arc between the electrode and the workpiece, and a flow path for supplying gas to the weld site. The gas is typically argon, carbon dioxide, or another inert or semi-inert gas or gas mixture for "Metal Inert Gas" (MIG) welding. "Metal Active Gas" (MAG) welding is also known, in which the gas mixture is not inert. For example, the gas mixture may contain oxygen in this process.

In the MIG welding process, the inert gas serves two purposes. Firstly, it provides a shield, protecting the weld site from oxygen and nitrogen in the atmosphere which would otherwise cause defects in the weld. Secondly, the gas acts to cool the welding torch itself, helping to dissipate the generated heat out of the torch so that the torch does not become too hot to safely handle, or damaged by the heat. Welding torches are designed to comply with standards which specify acceptable temperatures at various points on the handle.

Where the MAG welding process is used, the gas mixture is designed to interact with the weld, but still also serves to shield the weld from unwanted atmospheric gases and to improve heat dissipation in the welding torch.

Using a welding torch for a long period can lead to tiredness in the hand and arm muscles. For this reason, a lightweight welding torch is preferred. A lighter torch can allow a welder to work for longer and be more productive, with less risk of tiredness or injury.

Almost all welding torches are made substantially from copper. Copper is preferred because it is a good electrical conductor, and so high currents can be supplied easily to the welding electrode without a great deal of resistive heating in the torch itself. Copper is also a good thermal conductor and therefore heat can be dissipated away from the torch by the welding gas. Copper is also hard enough to make a robust welding torch which is resistant to deformation and damage. However, copper is a relatively dense metal and so known welding torches tend to be fairly heavy.

It is an object of the invention to provide a better welding torch, in particular a welding torch which weighs less but has equivalent performance to known copper welding torches.

The tip of a GMAW welding torch (i.e. the final part which welding wire passes through, which is held adjacent to the workpiece) is usually removably attached to the remaining conductive parts of the torch. Typically, the welding tip is connected to a tip adaptor which in turn connects to the remaining parts of the welding torch. The welding tip is usually made from copper, and has a hollow bore substantially through its centre for the welding wire to pass through in use. When the welding torch is assembled, a nozzle fits over and surrounds the tip. The shield gas passes through the nozzle and around the outside of the tip, cooling the tip.

The tip usually has a substantially flat base, and an externally screw-threaded shaft which extends away from the flat base for screwing into a corresponding internal thread on the tip adaptor. The flat base abuts a corresponding face on the tip adaptor which is also substantially flat. Electricity is conducted through the abutting flat face and screw, into the tip.

This known design of welding tip is almost universal, but has various problems. Firstly, if there is any damage to either of the flat faces, then the faces will not be in contact over the whole area of the face, and electrical conductivity in the joint will be poor. In particular, the thread on the welding tip is prone to damage due to heat, and a damaged thread can lead to a poor joint. Even with undamaged faces, the conductance through the welding torch is often limited by the joint at the tip. Secondly, it is difficult to efficiently cool the tip. Gas flows around the outer surface of the tip, between the tip and the nozzle, but there is a limited surface area over which the gas may flow at this point. The flow of gas when it leaves the nozzle needs to be smooth and directed at the workpiece, so that it performs effectively as a shield, and so the tip must be smooth, which reduces surface area and reduces cooling efficiency.

It is a further object of the invention to provide a welding tip which is more readily cooled and provides a better electrical connection.

STATEMENT OF INVENTION

According to a first aspect of the present invention, there is provided a welding torch suitable for use in Gas Metal Arc Welding (GMAW), the welding torch including a conductor assembly, the conductor assembly comprising a conductor tube and a conductor core disposed within the tube and a gas flow path being provided through the conductor assembly, the gas flow path including channels in the outer surface of the conductor core and the channels being substantially covered by the conductor tube, the conductor tube and conductor core being made substantially from aluminium, and the conductor assembly being overmoulded with a plastics material.

It has previously been thought that aluminium is not a suitable material for producing a high-performance welding torch because its electrical and thermal conductivity is lower than copper, and because it is an inherently soft material which is prone to deformation and damage. However, these problems are overcome in the present invention by overmoulding the conductor assembly with plastics. This adds strength and allows an aluminium torch to be produced which has a useful life comparable with known copper torches. The overmoulded construction also allows the thickness of the conductor assembly, in particular the wall thickness of the conductor tube, to be increased significantly in comparison with known copper welding torches, to provide similar performance in terms of electrical and thermal conductivity. This is because the plastics overmoulding provides a reliable insulator around the whole conductor assembly, whereas in known devices an insulator needs to be provided around the conductor core. In the present invention, the conductor tube adds to the overall bulk of the conductor assembly, ensuring a good electrically conductive path.

The use of aluminium to form the conductor assembly in the welding torch of the invention is highly advantageous in terms of providing a lightweight torch. Aluminium is around three times less dense than copper, and a difference of a few hundred grams can be realised in a welding torch according to the invention as compared with known copper welding torches. This difference in mass provides for a welding torch which is more comfortable and less tiring to use. Although more material has to be used to achieve equivalent conductance, an aluminium welding torch can provide a weight saving of around 60%, which is highly significant.

In terms of the power-to-weight ratio (KW output divided by mass in kg), one embodiment of a torch according to the invention can achieve a ratio of 4.58 KW/kg. Known copper welding torches generally achieve a power-to-weight ratio of around 2.75 -2.90 KW/kg.

The plastics overmoulding may be a polyphthalamide resin, or another engineering polymer with suitable properties.

The wall thickness of the conductor tube may be at least 1.6mm, preferably at least 2mm and more preferably at least 2.5mm. It is found that a wall thickness of between around 2.5mm and 3mm provides good conductance. The exterior diameter of the conductor tube may be greater than 18mm.

The aluminium conductor core may include a gas inlet at a first end and a gas outlet at a second end. The gas inlet may be via a bore running substantially through the whole length of the conductor core, and the gas outlet may be in the form of a plurality of outlets which surround the bore at the second end. The inlet may be connected to the channels on the outer surface of the core via inlet channels close to the first end, and the outlets may be connected to the channels on the outer surface of the core via outlet channels close to the second end. Connection means may be provided at the first end for connecting with an electricity supply, gas supply, and / or wire feed, and connection means may be provided at the second end for attaching a welding tip, typically via a tip adaptor. Preferably the connection means are external screw threads, as is well known in the art, so that the welding torch of the invention is compatible with existing equipment. However, the connection means at either end are preferably provided integrally with the conductor core, the whole core including the connection means being machined from aluminium in a single piece. Existing copper welding torches are typically formed by brazing inlet and outlet parts with connection means onto either end of the conductor core, but with aluminium it is found more effective to machine the whole conductor core, including the inlet and outlet parts, from one piece.

According to a second aspect of the invention, there is provided a welding tip for use in a Gas Metal Arc Welding (GMAW) welding torch, the tip comprising an end section having a substantially smooth outer surface, an externally screw-threaded shaft extending behind the end section for releasably attaching the welding tip to a tip adaptor on a welding torch, and a heat sink section extending behind the screw-threaded shaft, for providing an electrical connection between the welding tip and the tip adaptor and for providing a heat-conducting path between the welding tip and the tip adaptor. The screw-threaded shaft may of course also form an electrically conductive connection. Indeed, it is envisaged that the entire welding tip will usually be made in one piece from a conductive material.

The heat sink section behind the screw thread allows for extra cooling and electrical conductance to the welding tip.

The heat sink section is tapered, that is, the heat sink section has a larger diameter adjacent the screw threaded shaft and a smaller diameter distant from the screw threaded shaft.

The tapered heat sink section, if used with a correspondingly tapered tip adaptor, is highly advantageous because the tapered heat sink section of the welding tip forms a tapered plug which fits in a tapered socket of the tip adaptor. The tapered fitting ensures good thermal and electrical conductivity by providing a large contact surface area, even when the surface of either part is damaged or uneven. Furthermore, the inner surface of the tapered socket of the tip adaptor is less likely to become damaged because it is protected. The outer surface of the tapered plug of the welding tip remains exposed when the welding tip is disassembled, but a welding tip is usually considered a consumable part in any case, and so damage is not such a serious issue.

When assembling the tip into the tip adaptor, the welding tip may be tightened onto the tip adaptor by rotating the welding tip to tighten the screw thread. As this is done, the tapered heat sink plug of the welding tip will push into the corresponding tapered socket on the tip adaptor, until the outer wall of the tip is pushing firmly against the inner wall of the tip adaptor, forming a highly conductive interface between the two parts.

A further advantage of the tapered heat sink section is that it ensures that the welding tip is centred with respect to the tip adaptor, when assembled. It also ensures that the physical connection is firm in that the welding tip will not move with respect to the tip adaptor in use.

The heat sink section of the welding tip may include gas flow channels for allowing a cooling gas to cool the tip when attached to the tip adaptor. In one embodiment, the gas flow channels run longitudinally and in substantially straight lines along an exterior wall of the heat sink section. In another embodiment, gas flow channels are spiral or helical, around and along the heat sink section of the tip.

According to a third aspect of the invention, a welding torch is provided which includes a welding tip, a tip adaptor, a diffuser surrounding the tip adaptor and a nozzle. A gas flow path is provided which passes through channels in the tip adaptor, through outlet apertures in the tip adaptor at a point adjacent the screw-threaded shaft of the welding tip, and then reverses and flows towards the back of the welding torch, between the tip adaptor and the diffuser. The gas then flows through the outer wall of the diffuser, and reverses direction again, flowing forwards between the nozzle and the diffuser, and out of the torch towards the workpiece being welded.

The welding tip may be a welding tip in accordance with the second aspect of the invention, and in this case the gas flow path may include channels in the heat sink section of the welding tip. The channels in the welding tip may be provided in the flow path between the channels in the tip adaptor and the part of the flow path between the tip adaptor and the diffuser.

It will be understood that "forwards" means towards the workpiece, out of the welding torch, and "backwards" is the opposite direction, "into" the welding torch.

The reversing of gas flow in and around the welding tip and tip adaptor creates multiple cooling paths, increasing heat dissipation in the front-end parts where large amounts of heat are prone to build up.

The diffuser may be made from a thermoplastic material, and also serves to protect the metal parts of the welding torch from 'spatter' of weld material.

According to a fourth aspect of the present invention, there is provided a welding torch which includes a conducting assembly for conducting electricity between a cable and a welding tip, and for connecting the welding tip to a gas supply, a handle fitted over at least part of the conducting assembly, for substantially covering the part of the conducting assembly, and an thermally insulating spacer provided between the conducting assembly and the handle, for creating a thermal break in the form of an air gap between the conducting assembly and the handle.

It will be understood that the conducting assembly may also be covered by electrical insulators, for example the conducting assembly may be overmoulded with plastics in accordance with the first aspect of the invention. However, providing a spacer which creates an air gap between the conducting assembly and the handle substantially reduces transfer of heat into the handle, which leads to a cooler handle which is safer and more

comfortable in use.

The spacer may include locating elements for locating the handle over the conducting assembly, and the spacer may be slidable over a portion of the outer surface of the conducting assembly.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, preferred embodiments will now be described with reference to the accompanying drawings, in which: Figure la is a perspective view of an aluminium conductor core, forming part of a welding 15 torch; Figure lb is a perspective view of an aluminium conductor tube, forming part of a welding torch; Figure lc is a perspective view of a conductor assembly comprising the conductor core of Figure la and the conductor tube of Figure lb; Figure ld is a perspective view of the conductor assembly of Figure lc, overmoulded with plastics; Figure le is a perspective view of the conductor assembly of Figure ld, with an insulating spacer fitted; Figure 2 is a cross section of the front end of a welding torch according to aspects of the invention; Figure 3 is an exploded view of a welding torch including the conductor assembly of Figure le, a tip adaptor, a welding tip, a diffuser and a nozzle; Figure 4a is a cross section through a tip adaptor, part of the welding torch shown in Figure 3; Figure 4b is a side view of the tip adaptor of Figure 4a, part of the welding torch shown in Figure 3; Figure 5a is a side view of a welding tip according to an aspect of the invention, and part of the welding torch of Figure 3; Figure 5b is a side view of an alternative embodiment of a welding tip according to an aspect of the invention; Figure 5c is a side view of a third embodiment of a welding tip according to an aspect of the invention; Figure 5d is a side view of a fourth embodiment of a welding tip according to an aspect of the invention; and Figure 6 is a side view of a nozzle forming part of the welding torch of Figure 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring firstly to Figure la, a conductor core is indicated at 10. The conductor core is machined from a single piece of aluminium. The conductor core has an attachment means in the form of an external screw thread at a first end 12, for attachment to a cable and gas supply of a welding machine, and attachment means in the form of an external screw thread at a second end 14, for attachment to a tip adapter and subsequently a welding tip.

The conductor core 10 is substantially hollow, having a continuous bore 16 passing longitudinally through the centre of the core 10.

Gas flow channels 20 extend longitudinally along the outer surface of a major part of the conductor core. The gas flow channels 20 communicate with the central bore 16 via apertures 22 close to the first end 12 of the conductor core. A flange 18 extends around the base of the screw thread at the second end, and the channels continue through the flange and emerge at outlet apertures 24 at the second end 14 of the core.

Figure lb shows a conductor tube 26, which fits over the conductor core 10, covering the part of the core 10 between the flange 18 and the base of the screw thread at the first end 12. In particular, the conductor tube covers the entire extent of the gas flow channels 20.

In use, when the conducting core 10 is connected to a gas supply and the conductor tube 26 is fitted over the core 10, gas flows into the central bore 16 at the first end 12, radially out through the apertures 22 and into the channels 20 which run along the outer surface of the core 10, between the core 10 and the tube 26. The gas then flows through the flange 18, and out of the outlet apertures 24 which surround the central bore 16 at the second end 14 of the core 10.

Figure lc shows the conductor tube 26 fitted over the conductor core 10 to form a conductor assembly. The conductor assembly is bent into a swan-neck shape as illustrated in the drawing, and the tube 26 is then permanently attached to the core 10 by brazing or welding at the points labelled W. Figure ld shows the conductor assembly of Figure lc, overmoulded with an engineering polymer. In this embodiment, a polyphthalamide resin is used.

The plastics overmoulding is indicated at 28, and adds strength and rigidity to the aluminium conductor assembly. Furthermore, the overmoulding 28 insulates the entire conductor assembly from the handle (not shown). This means that all of the metal parts (i.e. the core 10 and the tube 26) can be used to conduct electricity from the power supply in the welding machine, which is connected at the first end 12, to the welding tip which is connected at the second end 14. This ensures good conductance in the connection, despite the relatively low conductivity of aluminium as compared with copper.

The overmoulding 28 includes an integrally-formed substantially square location element 30. The integral location element 30 is substantially in the form of a pair of spaced-apart square planar elements 30a, 30b which are joined by reinforcing walls 32. Between the planar elements 30a, 30b and the reinforcing walls 32, gaps are defined which form sockets for corresponding protrusions on a handle (not shown).

A locator element 34 is also provided which fits over the overmoulding 28 near the first end 12 of the conductor assembly. The locator element 34 includes raised sections 36 which form air gaps between the locator element 34 and the overmoulding 28. The air gaps form a thermal break and reduce the amount of heat transfer into the handle. The raised sections 36 also aid in locating a handle over the overmoulded conductor assembly, enabling a tight-fitting handle which will not move around on the conductor assembly.

Figure le shows the overmoulded conductor assembly with the locator element 34 fitted.

Referring now to Figure 2 and Figure 3, the front end of a welding torch is shown in cross section and in an exploded view, respectively. The front end of the welding torch includes the second end 14 of the conductor assembly described above, and further includes a tip adaptor 36, a welding tip 38, a diffuser 40 and a nozzle 42. As indicated by the arrows (»)) in Figure 2, gas flows out of the outlet apertures 24 in the second end 14 of the conducting core 10, into channels 44 in the tip adaptor. The gas then flows between the tip adaptor 36 and the welding tip 38, through channels 46 in the outer surface of a back part of the welding tip 38. The gas is then guided radially outwards through outlet channels 48 in the walls of the tip adaptor, where it changes direction and flows backwards (i.e. substantially upwards and right in Figure 2), between the diffuser 40 and the tip adaptor 36. Finally, the gas flows out of the diffuser through radial apertures 50, reverses direction again and flows forwards (downwards and left in Figure 2, out of the welding torch) between the diffuser 40 and the nozzle 42, and around the outside of the front part of the welding tip 38.

In the cross-section of Figure 2, only two inlet apertures 44, two outlet apertures 48 and two diffuser apertures 50 are visible. However, it will be appreciated that apertures are in fact disposed at intervals around the entire curved outer surface of the tip adaptor and the diffuser, so that there is substantially even flow around the whole periphery of the front end of the welding torch.

With reference to Figure 3, note that a retaining ring 52 is provided, as well as an insulator 54. The tip adaptor 36 and welding tip 38 need to be in electrical contact with the conductor assembly 10, but the nozzle 42 must be insulated from the electrical supply. The diffuser 40 is made from an insulating thermoplastic material.

Figures 4a and 4b show the tip adaptor 36 in more detail. The tip adaptor 36 includes a fluted socket 56 for receiving a back section of a welding tip, and an internal screw thread 58 for attaching and retaining the welding tip. The tip adaptor 36 further includes an external screw thread 60 for connecting the nozzle, a further internal screw thread 62 for connecting to the conductor assembly, and a further external screw thread 61 for connecting the diffuser.

The tip adaptor 36 also includes a chamfered flange 63 which sits behind the external thread 60 for attaching the nozzle. When the nozzle is attached, the chamfered flange 63 mates with a corresponding internal chamfer in the nozzle. This ensures that the nozzle sits completely concentrically around the tip adaptor when installed. In the same way, the tapered plug on the welding tip and corresponding tapered socket 56 on the tip adaptor ensure that the welding tip is centred with respect to the tip adaptor.

Figures 5a and 5b show alternative embodiments of a welding tip 64, 64'. Each welding tip 64, 64' includes a tip section 66, 66' having a smooth outer surface, an externally screw-threaded shaft 68, 68' and a heat sink section 70, 70' extending behind the shaft 68, 68'. The heat sink section 70, 70' in each case is fluted to conform with the fluted socket 56 in the tip adaptor. In other words, the heat sink section has a wider diameter adjacent to the threaded shaft 68, 68' than it does at its distal end. The heat sink section 70, 70' includes gas flow channels on its outer surface. In the embodiment of Figure 5a, the gas flow channels 72 spiral around the outer surface of the fluted heat sink section. In the embodiment of Figure 5b, the channels 72' run in substantially straight lines along the surface of the heat sink section, each channel 72' taking the shortest path along the surface between the distal end of the heat sink section and the screw threaded shaft 68'.

Figure 5c shows a further alternative embodiment of a welding tip 64". In this embodiment, the channels 72" run in substantially straight lines along the outer surface of the heat sink section 70", along a part of the heat sink section 70" which has substantially constant width. The channels 72" are therefore substantially parallel with each other and with a longitudinal axis of the welding tip 64". The part of the heat sink section 70" behind the channels 72" is tapered, reducing in width towards the distal end of the heat sink section 70".

Figure 5d shows a further alternative embodiment of a welding tip 64". In this embodiment, there are no channels but nevertheless a tapered heat sink section 70"' is 30 provided.

Figure 6 shows a cross-section of the nozzle 42. The nozzle includes a threaded insert 74 which is crimped into the nozzle shell. The threaded insert 74 includes an internal screw thread which corresponds with the external screw thread 60 on the tip adaptor. The threaded insert 74 is insulated from the nozzle 42 by insulators 76, 78, so that when the welding torch is assembled the nozzle is insulated from the tip adaptor, and therefore is insulated from the power supply of the welding machine.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims

CLAIMS1. A welding torch suitable for use in Gas Metal Arc Welding (GMAW), the welding torch including a conductor assembly, the conductor assembly comprising a conductor tube and a conductor core disposed within the tube, and a gas flow path being provided through the conductor assembly, the gas flow path including channels in the outer surface of the conductor core and the channels being substantially covered by the conductor tube, the conductor tube and conductor core being made substantially from aluminium, and the conductor assembly being overmoulded with a plastics material.
2. A welding torch as claimed in claim 1, in which the plastics material is a polyphthalamide resin.
3. A welding torch as claimed in claim 1 or claim 2, in which the wall thickness of the conductor tube is at least 1.6mm.
4. A welding torch as claimed in claim 3, in which the wall thickness of the conductor tube is at least 2mm.
5. A welding torch as claimed in claim 4, in which the wall thickness of the conductor tube is at least 2.5mm.
6. A welding torch as claimed in any of claims 3 to 5, in which the wall thickness of the conductor tube is less than 3mm.
7. A welding torch as claimed in any of the preceding claims, in which the exterior diameter of the conductor tube is greater than 18mm.
8. A welding torch as claimed in any of the preceding claims, in which the conductor core includes a gas inlet at a first end and a gas outlet at a second end.
9. A welding torch as claimed in claim 8, in which the gas inlet is via a bore which runs substantially through the whole length of the conductor core.
10. A welding torch as claimed in claim 9, in which the gas outlet is in the form of a plurality of apertures surrounding the bore at the second end.
11. A welding torch as claimed in claim 9 or claim 10, in which a flow path is provided between the gas inlet and the channels in the outer surface of the conductor core via inlet channels through the wall of the conductor core, close to the first end.
12. A welding torch as claimed in claim 8, in which connection means are provided at the first end of the conductor core for connecting with an electricity supply, gas supply, and / or wire feed, and connection means are provided at the second end for attaching a welding tip.
13. A welding torch as claimed in claim 12, in which the connection means are screw threads.
14. A welding torch as claimed in claim 13, in which the screw threads are external screw threads.
15. A welding torch as claimed in any of claims 12 to 14, in which the whole conductor core, including the connection means at either end, is machined from aluminium in a single piece.
16. A welding torch as claimed in any of the preceding claims, in combination with a tip adaptor connected with the outlet at the second end of the conductor core, and a welding tip connected to the tip adaptor.
17. A welding torch as claimed in claim 16, in which the welding tip includes an end section having a substantially smooth outer surface, an externally screw-threaded shaft extending behind the end section for releasably attaching the welding tip to the tip adaptor, and a heat sink section extending behind the screw-threaded shaft, for providing an electrical connection between the welding tip and the tip adaptor and for providing a heat-conducting path between the welding tip and the tip adaptor.
18. A welding torch as claimed in claim 17, in which the heat sink section is tapered, the heat sink section having a larger diameter adjacent the screw threaded shaft and a smaller diameter distant form the screw threaded shaft.
19. A welding torch as claimed in claim 17 or claim 18, in which the heat sink section of the welding tip includes gas flow channels for allowing a cooling gas to cool the tip when attached to the tip adaptor.
20. A welding torch as claimed in claim 19, in which the gas flow channels run in substantially straight lines, longitudinally along the outer surface of the heat sink section of the tip adaptor.
21. A welding torch as claimed in claim 20, in which the gas flow channels are spiral or helical, around and along the heat sink section of the tip.
22. A welding torch as claimed in any of claims 16 to 21, further including a diffuser substantially surrounding the tip adaptor, and a nozzle substantially surrounding the welding tip and the tip adaptor.
23. A welding torch as claimed in claim 22, in which a gas flow path is provided which passes through channels in the tip adaptor, through outlet apertures in the tip adaptor adjacent the screw-thread shaft of the welding tip, and then reverses and flows towards the back of the welding torch, between the tip adaptor and the diffuser, the through the outer wall of the diffuser and reverses direction again, flowing forwards between the nozzle and the diffuser and out of the torch towards the workpiece being welded.
24. A welding torch as claimed in claim 23, when dependent on claim 19, in which the gas flow path further includes the channels in the heat sink section of the welding tip.
25. A welding torch as claimed in any of claims 22 to 24, in which the diffuser is made from a thermoplastic material.
26. A welding tip for use in a Gas Metal Arc Welding (GMAW) welding torch, the tip comprising an end section having a substantially smooth outer surface, an externally screw-threaded shaft extending behind the end section for releasably attaching the welding tip to a tip adaptor on a welding torch, and a heat sink section extending behind the screw-threaded shaft, for providing an electrical connection between the welding tip and the tip adaptor and for providing a heat-conducting path between the welding tip and the tip adaptor, in which the heat sink section is tapered, having a larger diameter adjacent the screw threaded shaft and a smaller diameter distant from the screw-threaded shaft.
27. A welding tip as claimed in claim 26, in which the heat sink section includes gas flow channels for allowing a cooling gas to cool the tip when attached to the tip adaptor.
28. A welding tip as claimed in claim 27, in which the gas flow channels are substantially straight and run substantially longitudinally along the surface of the heat sink section of the welding tip.
29. A welding tip as claimed in claim 27, in which the gas flow channels spiral around and along the heat sink section of the welding tip.
30. A welding torch suitable for use in Gas Metal Arc Welding (GMAW), the welding torch including a welding tip, a tip adaptor, a diffuser substantially surrounding the tip adaptor and a nozzle substantially surrounding the welding tip and the tip adaptor, a gas flow path being provided through channels in the tip adaptor, through outlet apertures in the tip adaptor adjacent the screw threaded shaft of the welding tip, and then reversing direction and guiding flow towards the back of the welding torch, between the tip adaptor and the diffuser, and then reversing direction again and guiding flow forwards between the nozzle and the diffuser, and out of the torch towards the workpiece being welded.
31. A welding torch as claimed in claim 30, in which the welding tip is a welding tip as claimed in any of claims 27 to 29, and in which the gas flow path through the welding torch includes channels in the heat sink section of the welding tip.
32. A welding torch as claimed in claim 31, in which the channels in the heat sink section of the welding tip form a part of the flow path between the channels in the tip adaptor and the part of the flow path between the tip adaptor and the diffuser.
33. A welding torch as claimed in any of claims 30 to 32, in which the diffuser is made from a thermoplastic material.
34. A welding torch including a conducting assembly for conducting electricity between a cable and a welding tip and for connecting the welding tip to a gas supply, a handle fitted over at least part of the conducting assembly for substantially covering the part of the conducting assembly, and a thermally insulating spacer provided between the conducting assembly and the handle for creating a thermal break in the form of an air gap between the conducting assembly and the handle.
35. A welding torch as claimed in claim 34, in which the spacer is slidable over and covers a portion of the outer surface of the conducting assembly.
36. A welding torch as claimed in claim 34 or claim 35, in which the spacer includes locating elements for locating the handle over the conducting assembly.
37. A tip adaptor for use with a GMAW (Gas Metal Arc Welding) welding torch, the tip adaptor including a tapered socket for receiving a tapered plug of a welding tip, an external thread for connecting a nozzle, and a chamfered flange behind the external thread for bearing against the nozzle and for centring the nozzle with respect to the tip adaptor.
38. A welding torch substantially as described herein, with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.
39. A welding tip substantially as described herein, with reference to and as illustrated in Figures 5a, 5b, 5c and 5d of the accompanying drawings.
40. A tip adaptor substantially as described herein, with reference to and as illustrated in Figures 4a and 4b of the accompanying drawings.