Patent ID: 12240065

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring firstly toFIG.1, a liquid-cooled TIG welding torch is indicated generally at10. The torch is shown in a disassembled state, and three different options of the collet, nozzle, heat isolation spacer and band are shown.

The torch includes a torch body12. The torch body includes an interface section14for attaching the torch to a welding machine. The interface section14includes a cooling liquid inlet16and a cooling liquid outlet18, and a shield gas inlet20. The liquid inlet and outlet16,18and the gas inlet20are all copper tubes. The copper tubes are brazed to a brass body22. The copper tubes and the brass body together form a good electrical conductor, and so can also be used to electrically connect the welding torch to the welding machine, so that voltage can be supplied to the torch to strike an arc and make a weld.

The brass body extends along the neck section24and head26of the torch10. The brass body22is overmoulded with an insulating material, for example silicone rubber. The neck section24includes a location formation28for a moulded handle in the form of an insulated casing (not shown in the drawings). The insulating casing may be rigid plastic and may be, for example, snapped or screwed together over the bottom part of the neck section of the overmoulded brass body22. The insulating casing28extends from the neck section24to form a handle on the welding torch.

The brass body22in the head section26is hollow, i.e. an aperture passes all the way through the brass body22along the line indicated A.

The frontmost part30of the insulated section of the head26of the torch includes a rib32. The backmost section of the uninsulated (exposed brass) part of the head26of the torch includes an external screw thread34.

To assemble the torch, one of the heat isolation spacers36a,36b,36cis screwed onto the screw thread34on the front of the brass body22. One of the collets38a,38b,38cis then passed through the centre of the heat isolation spacer36a,b,c, and through the aperture in the head section26of the brass body22. Each of the collets38a,b,cincludes an external screw thread40a,b,cand this screw thread40a,b,ccorresponds with an internal screw thread44on the front of the back cap42. Therefore, the collet38a,b,c, torch body12and back cap42can all be held together by screwing the internal thread44of the back cap42onto the external thread40a,b,cof the collet38a,b,c.

When the collet is fitted, a band46a,b,ccan be stretched around the frontmost insulated section30of the torch body12. A rib32on the torch body assists with retaining the band46a,b,conto the torch body12, and preferably the band46a,b,calso has one or more internal ribs. A nozzle48a,b,ccan then be fitted over the heat isolation spacer36a,b,c. The nozzle48a,b,cwill be centred and held by the heat isolation spacer36a,b,c. The front part of the band46a,b,cis stretched over a rear section of the nozzle48a,b,c. At least one rib (not visible in the drawing) is provided on the inside of the band46a,b,cwhich assists with gripping of the band around the back part of the ceramic nozzle48a,b,c. In some other embodiments, rib(s) may also be provided around the outside of the back of the nozzle.

Nozzles can be of a variety of shapes, sizes, diameters and lengths to suit specific welding requirements.

FIG.2shows the back cap42in more detail. The back cap is elongate and hollow, so that it can retain the back part of a tungsten rod. It is open at the end facing the torch body12in use (the bottom end inFIG.2). The back cap is made from plastics, and has a brass threaded insert50at the open end. The exterior of the open end is tapered. The taper angle α is preferably 30 degrees.

The tapered front section of the back cap42forms a seal against the silicone overmoulding of the torch body12, when the torch is assembled. The silicone overmoulding of the torch body12for this reason extends substantially behind the brass body22of the head26of the torch. Back caps can be supplied in a variety of lengths and are easily interchangeable on the torch to suit different requirements, for example restricted access to the weld site may require a shorter back cap.

FIG.3shows the heat isolation spacers36a,b. Each of the heat isolation spacers is made from stainless steel, and each is substantially in the form of a tapered elongate shell which is wide towards the rear (towards the top of theFIG.3drawings) and narrower towards the front. Longitudinal slots52extend from the front of each heat isolation spacer, along for example two thirds of the length of the heat isolation spacer. The slots are equally spaced around the circumference of the heat isolation spacer, for example five slots may be provided spaced by 72 degrees. The stainless steel leaves defined by the slots form leaf springs, and so when the nozzle48a,b,cis pushed onto the front of the heat isolation spacer36a,b,cthe leaves will deform inwardly, but push outwardly onto the inside surface of the nozzle48,a,b,c, holding the nozzle in place on the heat isolation spacer. Each of the heat isolation spacers36a,bincludes an internal screw thread54, near the rear end of the heat isolation spacer. The internal screw thread54corresponds with the screw thread (34,FIG.1) on the brass body22of the head26of the torch, so that the heat isolation spacer may be screwed onto the brass body22. The heat isolation spacer is designed to provide a thermal break between the nozzle and the body22, thus preventing heat generated from the welding process from being transmitted to the body22.

FIG.4shows the collet38cin more detail. The collet comprises a rear attachment section56, a central heat sink section58and a front grip section60. The rear attachment section56includes the external screw thread40cwhich corresponds with the internal screw thread on the threaded insert (50,FIG.2) of the back cap (42,FIGS.1,2). Also, a longitudinal slot62extends from the rear of the collet38c, cutting through the screw thread and terminating in front of the screw thread40c. A rib64is provided at the end of the screw thread, and the slot62passes also through the rib64. The rib64provides a shoulder to limit how far the collet38ccan be screwed into the back cap (42).

The slot corresponds to the position of a pin which extends from the inside wall of the hollow brass body of the torch head (26). As the collet38cis passed through the aperture in the brass body, the pin slides into the slot62. The pin and slot62prevent rotation of the collet38cwith respect to the brass body (22). This ensures that the collet38ccan be tightened onto the back cap (42) simply by holding the torch (for example by its handle) and rotating the back cap (42).

The heat sink section58of the collet38cincludes spines65, and channels61running between the spines65. In use, shield gas passes through the channels61on its way from the gas inlet (20) and out of the front of the nozzle (48c). This assists with cooling the torch.

The front grip section60of the collet38cis the part which grips the tungsten rod when the collet38cis closed. A tapered section66is provided, which is wider towards the front of the collet38cand narrower towards the rear. In use, the tapered section66passes into the front of the aperture in the brass body (22) of the head (26) of the torch. As the collet38cis drawn backwards by tightening the screw thread40conto the back cap42, wider and wider parts of the tapered section66are drawn into the aperture in the brass body (22) of the head (26). This closes the jaws of the collet38cto retain the tungsten rod. Preferably, the front opening of the aperture in the brass body (22) is internally tapered to match the taper66of the collet38c. The jaws will therefore move from fully open to fully closed on very slight movement of the collet38cfrom an open position where the front edge of the tapered section66is just in line with the opening of the body (22) of the head (26), to a closed position where the front edge of the tapered section66is recessed within the opening of the body (22) of the head (26) by for example 0.5 mm. In front of the front edge of the tapered section66, an undercut68is provided. The undercut68, together with longitudinal slots70through the tapered section66, provide gas flow channels to allow shield gas to flow from the channels61of the heat sink section58, through the front of the collet38cand out of the nozzle.

FIGS.5aand5bshow an alternative collet38b. The collet38bagain has an attachment section56and a heat sink section58. These parts are substantially identical to those of the collet38cinFIG.4. The grip section60likewise includes a tapered section66, an undercut68and longitudinal slots70. However, this alternative collet38bis provided with an integrated gas lens72. The gas lens72is of a known type—a series of meshes provided in the path of the shield gas serves to direct the shield gas, ensuring more uniform flow and better welding performance. The gas lens72is integrated into the collet. This is done by providing circumferential slots around the jaws of the collet. Internal rings on the gas lens assembly72are retained in the circumferential slots. This allows the gas lens to be fitted around the jaws of the collet, which means there no increase in the length of the torch when fitted with a gas lens. This allows the advantages of the gas lens to be realised without making the torch long and cumbersome.

FIG.6shows the welding torch ofFIG.1, when fully assembled. Parts of the torch are cut away so that gas and liquid flows can be seen.

The band46cis seen fitted inFIG.6, providing a gas-tight seal between the nozzle and the torch body. The band46cis shown in cross-section, and internal ribs on the band are visible, both where the band46ccontacts the torch body and where the band contacts the nozzle48c.

At the back of the torch body, a pin63is visible. The pin63corresponds with the slot (62) in the collet38c, to prevent the collet38cfrom rotating with respect to the torch body when it is fully inserted into the aperture in the torch body. Also clear fromFIG.6is the extent of the silicone overmoulding behind the brass body22of the torch head26. The silicone overmoulding extends behind the brass body22by almost the extent of the tapered section of the back cap42. With the back cap42fully tightened onto the collet38c, the tapered section of the back cap42forms a gas-tight seal with the silicone overmoulding of the torch head26, preventing any leaking of shield gas out of the back of the torch.

The front section of the brass body22of the torch is also shown in cross-section, and the tapered entrance which corresponds to the tapered section66of the collet38cis visible.

The flow of inert shield gas through the welding torch10is indicated by arrows. From the end of the inlet tube20at the top of the neck (to the left ofFIG.6), shield gas flows in the channels (61) of the collet38c, between the collet38cand the inside wall of the brass body of the torch head26. The gas then flows through the slots (70) in the jaws of the collet38c, and then out of the small gap between the collet38cand the front edge of the brass body22, at the very front of the undercut (68) in the collet38c. The gas is then directed towards the workpiece by the nozzle48c.

The brass body22of the head26of the torch10has a hollow wall. This forms a liquid-filled jacket which allows cooling liquid to pass from liquid inlet16, into the hollow wall of the brass body, and then out of the liquid outlet18. The liquid jacket is indicated at74.

The heat isolation spacer36cis shown installed on the torch with the thread54screwed onto the brass torch body22. It is apparent from the cross section inFIG.6that the heat isolation spacer36is only in contact with the brass body at the thread54, and just to the rear of the thread. The parts of the heat isolation spacer36cwhich are forward of the thread54are spaced from the brass body22. This reduces heat transfer from the nozzle into the brass body. It will also be noted that the small part of the brass body which is in contact with the heat isolation spacer is substantially centrally disposed relative to the hollow wall section, which is cooled by liquid. These features increase the time for which welding can be carried out before the handle of the torch becomes hot.

FIG.7shows the gas-cooled version of the torch ofFIG.6. Again, arrows show the flow of gas through the torch. The gas flow is identical to that in the torch ofFIG.6, passing through the channels in the collet38b, and then out of the front, directed by the nozzle. The gas-lens version of the collet38bis fitted inFIG.7, but equally the collet38cwithout the gas lens could be fitted to the gas-cooled torch10′.

The construction of the brass body22of the torch10′ is again almost identical to that of torch10. The brass body22still has a hollow wall, although no liquid flows within the cavity. Instead, the hollow cavity75in the brass body22forms a thermal break, insulating the outside of the brass body from the inside. This reduces heat transfer from the nozzle48b, which is closest to the hot workpiece, into the brass body22and then to the handle of the torch10′. Again, the heat isolation spacer36bis only in contact with the brass body22over a very small area, and the area of contact is substantially central on the extent of the hollow thermal break75.

The torches10,10′ retain the nozzle48a,b,cusing the heat isolation spacer to grip the nozzle from the inside. The nozzles48a,b,ctherefore do not require manufacture with a screw thread, which increases possible manufacturing tolerances, reduces cost, and improves durability. The collet38a,b,cwill also last longer than in similar known torches, because it is not subject to twisting forces when tightened. The twisting from rotation of the back cap42is resisted very close to the back cap42longitudinally, by the pin63in the slot62.

The gas seal at the back of the torch10,10′ is also more reliable and longer lasting than in known designs. The tapered front section of the back cap42, which seals against the silicone overmoulding behind the back of the brass body22, provides a high-quality seal.

Finally, the torch10,10′ has excellent thermal performance compared with known designs. The nozzle is joined to the body of the torch via a heat isolation spacer36a,b,c. The heat isolation spacer is made from stainless steel which has lower thermal conductivity than brass or copper, and the area of contact between the heat isolation spacer and the brass body is very small. Furthermore, where the heat isolation spacer does contact the brass body, there is either a thermal break or liquid cooling channel, limiting the heat that is transferred into the handle of the torch.

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.