APPARATUS AND METHOD FOR CONTINUOUS WIRE FEED WELDING

Field of the invention

The present invention relates to an apparatus and a method for continuous wire feed welding. More particularly, the invention relates to a welding apparatus and method which provide for drawing and exhausting welding fumes inside the welding torch and the torch feeding cable.

State of the art

Different kinds of torches for welding in inert gas protected atmosphere (MIGMAG), or wire feed welding, are known at present, which torches are equipped with orifices for drawing the welding fumes arranged on the torch itself, whereby use of external drawing hoods for extracting the welding fumes from the working stations is dispensed with. An example of such torches id disclosed in document US 3 798 409

(Troyer et al.). The body of such torch is cooled by the flow of the fumes and the other atmospheric gas being drawn.

It has been realised that, by reducing the weight and the external size of the known welding torches, a throughput increase could be generally achieved. A lighter torch and/or a lighter feeding cable would be less tiring for the operator in charge of welding, thereby allowing the operator to perform the welding operations for longer periods without pauses. Less cumbersome torch and/or feeding cable would be handier: more particularly, a thinner nozzle and a thinner torch spout would allow performing welds in restricted spaces or in spaces that are otherwise difficult to be accessed.

It is an object of the present invention to provide a wire feed welding torch and the relevant feeding cable, which are improved with respect to the prior art torches and feeding cables, especially as far as the weight, the size and the handiness of the torch and/or its feeding cable are concerned.

Summary of the invention

The above object is achieved, according to a first aspect of the invention, by means of a continuous wire feed welding apparatus having the features as claimed in claim 1. According to a second aspect of the invention, the above object is achieved by means of a continuous wire feed welding apparatus having the features as claimed in claim 17.

According Io a third aspect of the invention, the above object is achieved by means of a connector for mechanically and fluidically connecting a torch for continuous wire

feed welding with a torch cable, having the features as claimed in claim 21.

According to a fourth aspect of the invention, the above object is achieved by means of an apparatus for continuous wire feed welding having the features as claimed in claim 24. According to a fifth aspect of the invention, the above object is achieved by means of a method for continuous wire feed welding having the features as claimed in claim 28.

The flow of liquid coolant allows a stronger cooling of the welding spout and the torch cable than that allowed by a flow of gaseous coolant and, for the same amperage required, electrical conductors are required for the welding power supply that in the whole are smaller and lighter. Thus, for the same welding current, a lighter, handier and less cumbersome assembly of a welding torch and a torch cable is sufficient, resulting in a lower operator's fatigue, especially if the operator is to perform welding operations for a great part of the working day.

The reduced sizes of the power supply conductors allow employing, for the same amperage required for welding, a torch having a nozzle and a spout with smaller diameter, which allows performing welds in spaces that are more restricted or anyway difficult to be accessed.

The reduced sizes of the power supply conductors moreover result in the availability of a greater section for the passage of the conduits exhausting the fumes being drawn, allowing also in this respect a reduction in the weight and the sizes of the assembly of the torch and the torch cable.

Further advantages attainable by means of the invention will become more apparent, to the skilled in the art, from the following detailed description of some specific embodiments, given by way of non limiting examples with reference to the accompanying schematic drawings. List of the Figures

FIG. 1 is an overall view of a welding torch and the torch cable feeding it, according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view of the welding spout of the torch shown in FIG. 1, according to section plane A-A;

FIG. 3 is a sectional view, according to a longitudinal section plane, of the welding nozzle of the torch shown in FIG. 1;

FIG. 3 A is a longitudinal sectional view of an alternative component for building the inverting connector of the torch shown in FIG. 1;

FIG. 4 is a perspective cross-sectional view of the torch cable shown in FIG. 1, according to section plane C-C;

FIG. 5 is a sectional view, according to a longitudinal section plane, of the welding nozzle of a welding torch according to a second embodiment of the present invention; FIG. 6 is a perspective view of some components of the welding nozzle shown in

FIG. 5, in disassembled condition;

FIG. 7 is a sectional view, according to a longitudinal section plane, of the welding nozzle and spout of a welding torch according to a third embodiment of the present invention; FIG. 8 is a cross-sectional view of the welding spout of the torch shown in FIG. 7, according to section plane B-B;

FIG. 9 is a side view of a half shell of the handle of the torch shown in FIG. 1 ;

FIG. 10 is a side view, partly in cross section, of the connector connecting the torch and the torch cable shown in FIG. 1; FIG. 11 is a side view, partly in cross section, of a connector for connecting a torch and a torch cable according to the prior art;

FIG. 12 is a side view of the front part of a half shell of the handle of the torch shown in FIG. 1, with the trigger and the relevant microswitch assembled;

FIG. 13 is a perspective view of the trigger shown in FIG. 12; FIG. 14 is a side view of a half shell of a handle of a welding torch according to the prior art;

FIGS. 15 and 16 are a longitudinal sectional view and a front view, respectively, of the securing wing nut of the torch shown in FIG. 1;

FIG. 17 is a side view, partly in cross section, of the torch shown in FIG. 1, with the wing nut assembled. Detailed description

FIGS. 1 to 4 refer to a first embodiment of a welding apparatus according to the present invention.

Such an apparatus includes a torch for wire feed welding, generally denoted 1, and a feeding cable 3, also referred to as "torch cable" (FIG. 4).

Torch 1 includes a casing 5, for instance of plastics, defining a handle 7 that can be gripped by an operator during welding.

Torch 1 further includes a welding spout 9, which juts out from casing 5 and through which a plurality of conduits longitudinally extend, which conduits are shown in FIG. 2

and described hereinafter.

Spout 9 has, in its innermost portion, a conduit, conventionally referred to as "gas conduit" 11, which extends along the spout and through which there are fed: - the melting wire electrode 13, to be consumed during welding; and - the shielding gas that must isolate wire electrode 13 from atmospheric oxygen during welding.

Gas conduit 11 is formed within an elongated body 15, which in turn is inserted into an inner tube 20 so as to define two longitudinal conduits 17, 19, separated in liquid-tight manner from each other and from the outside environment. The assembly of inner tube 20 and elongated body 15 is conventionally referred to hereinafter as "torch body tube" 21

(FIGS. 2, 3).

Cooling liquid, for instance water, directed towards welding nozzle 27 secured at one end of spout 9 flows along one of conduits 17, 19; cooling liquid returning from welding nozzle 27 flows instead along the other conduit 19 or 17, respectively. Torch body tube 21 is surrounded by an annular cavity 23 inside which flow the welding fumes and other atmospheric gases sucked by the welding nozzle. Annular cavity 23 is separated from the outside environment by means of outer tube 25. Longitudinal separating body 15 and tubes 21 and 25 can be made for instance of copper or another metal. Typically, tube 25 is made of brass. Welding nozzle 27 is shown in greater detail in FIG. 3. It includes a first tubular component 29, conventionally referred to as nozzle cap, which is screwed onto a drawing element 31. Drawing element 31 is secured onto outer tube 25 and it defines, on its sides, a plurality of drawing orifices 33, for instance three drawing orifices. Such orifices are formed in sections of drawing conduits which preferably have inclined axes diverging from the axis of nozzle 27, and preferably such orifices are arranged with radial symmetry with respect to the axis of nozzle 27. Clearly, in other embodiments, even one drawing orifice 33 only could be provided, which could even be shaped as an annular slot wholly surrounding the nozzle sides.

Drawing element 31 internally houses, in suitable seats, two insulating bushes 35, 37. Wire-guiding tip 39, formed by two elements 39A and 39B, is secured inside insulating bush 35. Wire electrode 13 is fed inside wire-guiding tip 39. Reference numerals 39C in FIG. 3, as well as reference numerals 39C in FIG. 5, denote outlet holes for the shielding gas.

Wire 13 receives the power supply from torch cable 3 through torch body tube 21,

which is wholly electrified during welding. Thus, bushes 35, 37 have the function of electrically insulating torch body tube 21 from the rest of torch 1.

Inverting connector 40 is inserted in drawing element 31 and insulating bush 37.

Such a connector 40, with frusto-conical or generally flared shape so as to reduce inlet turbulence of the fumes and the other gases being drawn, is formed of an inner body 4OA and a bush 4OB mounted and braze-welded onto body 4OA. The assembly of connector 40 is welded or brazed onto one end of inner tube 21 of the spout, and it internally defines one or more cavities 41, conventionally referred to as "inverting cavities" 41, which receive the cooling liquid coming from coolant delivery conduit 17 and invert the flow direction of the liquid, sending it to coolant return conduit 19 (FIG. 3).

In order to increase the cooling efficiency, coolant delivery conduit 17 and return conduit 19 in the torch body tube are directly connected to coolant deliver}.' and return conduits 17C and 19C, respectively, in torch cable 3 (FIG. 4).

In this manner, according to the present invention, both the body of torch 1 and cable 3 feeding the torch are cooled by a flow of cooling liquid, capable of ensuring a stronger cooling than that attainable by means of a flow of drawn gases, for instance as disclosed in document US 3 798409 (Troyer et al.) mentioned above.

Preferably, the cooling liquid, which can be for instance water or another aqueous solution, is made to circulate within torch 1 and cable 3 by means of a pump 10 (FIG. 1) or other equivalent device capable of producing a forced circulation of the coolant.

FIG. 4 is a cross-sectional view of torch feeding cable 3. In the present exemplary embodiment, the cable is formed by a bundle of tubes and cables arranged side by side:

- tube 12C, internally defining gas conduit HC allowing the flow of the shielding gas towards torch 1; - tubes 15C and 18C, internally defining conduits 17C and 19C which are the conduits for the delivery of the cooling liquid towards torch 1 and the return from the torch, respectively;

- tube 14C, inside which wire electrode 1 is made to advance for reaching torch 1.

Inside cavity 17C of tube 15C there is further housed an internally hollow conducting plait 43, which supplies torch body tube 21 with electric power and which is immersed in the cooling liquid. In other embodiments plait 43 can be replaced by different kinds of sheaths or conductors for power supply.

The bundle of tubes 12C, 14C, ϊ5C, 18C is enclosed within an external tubular sheath 25C, and the welding fumes and the other atmospheric gases being drawn flow in

the hollow spaces between such a sheath and said tubes. Tubes 12C, 14C, 15C, 18C and sheath 25C may be for instance made of suitably flexible PVC.

Welding wire 13 enters torch body tube 21 at a suitable intermediate section of such tube and receives the power supply from torch body 21 mainly due to the contact with element 39A.

Thus, using a torch cable 3 and a torch body tube 21 that are both cooled by a liquid coolant allows, for the same amperage, using a set of power supply conductors having a smaller overall section than in case of a torch body tube and/or a torch cable that are not cooled or are cooled by a gaseous coolant. Therefore, on the one side, cooling by means of a liquid allows utilising a torch cable 3 which has a smaller diameter, or anyway is less cumbersome and lighter, thereby making the torch handier and making the welding manual labour less tiring; on the other hand, smaller power supply conductors, for the same external size of cable 3, leave a greater section 23C available for the passage of the fumes being drawn, thereby allowing drawing a higher flow rate. For the same welding currents required, this allows employing thinner and less cumbersome welding nozzles and torches, capable of performing welds in more restricted spaces or in spaces that generally are more difficult to be accessed.

By way of indication, thanks to the above teachings, the cross-sectional sizes of welding nozzle 27 and welding spout 9 could be reduced by about 60%. Moreover, the higher flow rate of the fumes being drawn increases the cooling of torch 1.

FIG. 3A shows an alternative component for building the aforementioned inverting connector. Component 40' is braze-welded onto inner tube 20.

FIGS. 5 and 6 relate to a second embodiment of the present invention. In such an embodiment, a nozzle cap 29' with substantially tubular shape, of a kind known per se, is secured onto the outer tube of the torch spout by means of a drawing element 31' that is equipped, on its sides, with a plurality of drawing orifices 33'. In the present example, the sides of drawing element 31' have a substantially frusto-conical shape, or generally they have cross sectional sizes decreasing towards the spout end. Also in this embodiment wire electrode 13, the shielding inert gas and a cooling liquid are fed to the welding torch through a feeding cable, which is also cooled by the cooling liquid and can be for instance the same cable 3 as shown in FIGS. 1 and 2. In the embodiment shown in FIG. 5 wire electrode 13, the shielding inert gas and the cooling liquid from cable 3 are fed to welding nozzle 27' through the corresponding internal conduits of a torch body tube 21', of which

the cross sectional size can be substantially the same as that of tube 21 shown in FIG. 2. Torch body tube 21' reaches drawing element 31'and runs over the whole length thereof, extending beyond drawing orifices 33'. The downstream end of element 31' has screwed thereon wire-guiding tip 39', which is formed of the two elements 39A' and 39B ¹ and from which wire electrode can come out.

The cooling liquid from delivery conduit 17C in cable 3 flows through the whole of drawing element 31' and reaches the end thereof, onto which nozzle cap 29' is secured, by flowing along delivery conduit 17' that is fed from delivery conduit 17C in torch cable 3. Approximately at the end of drawing element 31', the flow of cooling liquid is deflected into return conduit 19' of torch body tube 21', through which the liquid can then flow to return conduit 19C in torch cable 3. That is, also in this embodiment, both torch cable 3 and the whole of the torch body are cooled by means of a forced circulation of cooling liquid, whereby the aforesaid advantages of reduction of the weight and size thereof, convenience of use and increase in the flow rate of the fumes being drawn are achieved. Reference numeral 40' denotes a bush with frusto-conical or generally flared shape, so as to reduce turbulences of the fumes and the other gases being drawn by the torch. Bush 40' is welded onto torch body tube 21' and is equipped with a throughhole through which torch body tube 21 ' can run.

The section of torch body tube 21' downstream bush 40' in inserted in three electrically insulating bushes 35', 36', 37' having a similar electrical function to insulating members 35, 37 in the embodiment shown in FIG. 3. Advantageously bush 36', which when mounted is interposed between bushes 35' and 37', has a tubular shape, substantially cylindrical and without flanges or other radial projections. Such a shape allows manufacturing bushes 36' with different lengths, and hence welding torches with nozzles of different lengths, while keeping the equipment costs relatively limited.

Always referring to the embodiment of FIGS. 5, 6, nozzle cap 29' is secured, for use, onto male end 44 of the drawing element by means of a leaf spring 45, known per se (FIG. 6). In the present embodiment, male end 44 is not threaded. To allow upstream end of cap 29' to be narrowed because of the pressure of spring 45, and possibly to radially expand, longitudinal cuts 47, also known per se, are made on the sides of such an end.

Tubular caps 29, 29' and wire-guiding tips 39, 39' are considered, by people working in the field, as "expendable materials" since, apart from the wire electrodes, they are the parts of a welding plant that are subjected io the quickest wear and to the highest replacement rates because of the high temperatures they are exposed to. The companies

working in the welding field consume great amounts and have relatively great stocks thereof. Correspondingly, the shapes and sizes of the tubular caps and the wire-guiding tips are relatively standardised.

Advantageously, therefore, non-threaded male end 44 is substantially cylindrical, with a diameter of about 20 ± 4 mm and more preferably about 20 ± 0,5 mm.

The constructional features employed in the embodiment of FIGS. 5, 6 allow manufacturing wire feed welding plants using standard or generally already commercially available tubular caps and wire-guiding tips, even if the torch body and the torch cable are cooled by a forced circulation of liquid coolant and a system for drawing welding fumes internal to the same torch is provided. That is, the constructional features employed in the embodiment of FIGS. 5, 6 allow a company working in the welding field to pass from a conventional welding system to a system with fume drawing and liquid-cooled torch cable and body without heavy losses of capitals due to the impossibility of using stocks of previously purchased expendable materials. With the welding torch structure shown in FIGS. 5, 6, the manufacturer can easily change the length of the welding nozzle, i.e. without incurring in heavy expenses for preparing different lengths. The simple cylindrical shape, lacking radial projections, of intermediate insulating bush 36' contributes among other things to this.

FIGS. 7 and 8 relate to a third embodiment of the present invention, where welding torch 1 " is equipped with a drawing element 31 " on which a nozzle cap 29" is mounted.

Torch 1" is fed by a torch cable 3 of the kind shown in FIG. 4, cooled by a forced flow of liquid coolant.

FIG. 8 shows a cross sectional view, taken according to section plane B - B ₅ of spout

9" of torch 1". Unlike the embodiment shown in FIGS. 1, 2, in spout 9" two conduits 17D, 19D for the delivery and the return, respectively, of the cooling liquid externally extend along torch body tube 21". In the present embodiment, conduits 17D, 19D are located at diametrically opposite positions with respect to the centre of spout 9".

Still in the present embodiment, cooling liquid delivery and return conduits 17", 19" extending inside torch body tube 21" do not extend beyond fume drawing orifices 33", but they end about at the level of such orifices, where they are fmidically connected together.

On the contrary, delivery and return conduits 17D, 19D external to torch body tube 21" extend beyond drawing orifices 33". Actually, conduits 17D, 19D reach an annular cavity 44', tightly sealed with respect to ihe outside environment and located between the male end of drawing element 31" and the female seat of nozzle cap 29" inserted onto said

male seat. Through annular cavity 44', delivery conduit 17D feeds return conduit 19D. The operation of the cooling circuit of welding torch 1" is as follows. The cooling liquid from delivery conduit 17C in torch cable 3 successively flows to delivery conduit 17" and then, upon inversion of the flow direction, to return conduit 19" in torch body tube. Upon attaining U bend 49, the cooling liquid inverts again the flow direction and flows to delivery conduit 17D located externally of torch body tube 21", thereby flowing again towards the welding nozzle. Upon attaining annular cavity 44', the liquid flows to return conduit 19D, through which it then reaches return conduit 19C in torch cable 3. That is, in the embodiment of FIGS. 7, 8, the portion of the welding nozzle downstream drawing orifices 33" is cooled by a flow of cooling liquid that is not internal to the torch body tube or anyway to the wire-guiding tip but external thereto, whereas the portion of torch body tube 21" upstream the drawing orifices is cooled by a coolant flow internal to the torch body tube itself. The suitable cooling of nozzle cap 29" and drawing element 31" by means of a liquid coolant reduces the risk that, due to the high temperatures attained during welding, the shielding gas catches fire when contacting nozzle cap 29", thereby compromising the protection of the melting bath from the external atmosphere. This kind of welding torch with a double cooling obtained in this manner is therefore suitable for carrying out, with a particularly high safety level, welds having no blowholes or other defects caused by the contact of the melting bath with atmospheric oxygen, for instance for welding components made of aluminium or other light alloys.

Advantageously, drawing orifices 33, 33', 33" are arranged at a distance substantially equal to or greater than 4 cm from the end of welding nozzle 27, 27', 27", respectively, wherein such distance DB is measured from the edge of the free end of nozzle cap 29, or generally from the edge of nozzle mouth 30, to the closest edge of orifices 33, 33', 33" (FIG. 3). More preferably, distance DB is substantially equal to or greater than 4 cm. Still more preferably, distance DB is 4 to 8 cm. Still more preferably, distance DB is 5 to 7 cm. Indeed, it has been realised that, in this manner, and taking into account that wire electrode 13 generally projects by about 1 cm from nozzle mouth 30 (length LF in FIG. 3), it is possible to draw the fumes developed in the welding region without an early suction of the shielding gas delivered by nozzle 27, that is, without damaging the gaseous barrier protecting the wire electrode from atmospheric oxygen during welding. The above values of distance DB have proven particularly optimum for such a purpose.

FIGS. 9, 10, 12, 13, 15 - 17 relate to a possible embodiment of a handle that may be used for instance but not necessarily for a wire feed welding torch according to the invention.

Handle 7, with elongated shape,- extends between welding spout 9 and the head of feeding cable 3, internally encloses external tube 25 and is connected to cable 3 through connector 100 shown in FIG. 10.

Such a connector 100 includes an outer sleeve 102, which is preferably but not necessarily made of plastics, and an inner sleeve 104, which advantageously is made of metal, e.g. steel. In the present exemplary embodiment, outer sleeve 102 has an outer thread 106 in order it can be secured to a correspondingly threaded end of feeding cable 3.

An edge of inner sleeve 104 is equipped with a flange 105.

The main body of handle 7 is made of two half shells 107, which are preferably but not necessarily made of plastics (FIG. 9). In the present exemplary embodiment, the surface separating half shells 107 longitudinally extends over the assembled handle 7. A suitable half-circular groove 108 is formed in the rear portion of each half shell

107. Connector 100 is secured to handle 7 by bringing half shells 107 close to each other so that flange 105 is retained in half-circular seats 108. Half shells 107 can subsequently be permanently closed e.g. by means of screws (not shown), which are inserted into suitable seats 109 in the half shells. Advantageously, during normal use, flange 105 is constantly held between half shells 107, so that it can be neither axially extracted nor rotated about itself relative to the half shells.

Advantageously, while the welding torch is being used, inner sleeve 104 can rotate about itself within outer sleeve 102. Since no relative sliding occurs between the feeding cable and inner sleeve 104, to which outer sheath 25C is secured, and since the surface of relative sliding between sleeves 102 and 104 is much greater than prior art flange 112, connector 100 practically does not become worn, not it wears cable 3 or handle 7.

On the contrary, in prior art connector 108, securing flange 112, being secured to the thread for the fastening to the feeding tube, was necessarily to rotate relative to the torch handle, with a resulting wear of the torch and of connector 108 itself.

Thus, connector 100 has a longer operating life than the prior art connectors, and it considerably increases the operating life of the rest of the welding torch, in particular of the handle thereof.

End 111 of inner sleeve 104 opposite to that equipped with flange 105 is slightly flared towards the outside, thereby preventing outer sleeve 102 from coming off.

Moreover, inner sleeve 104, being made of metal, can have a smaller thickness than if it was made of plastics; thus, inner sleeve 104 may have a greater internal diameter for the same external diameter, and thus it can internally house a feeding cable 3 with greater cross-sectional size.

The significance of the latter advantage becomes more apparent from a comparison with prior art connector 108, shown in FIG. 11 : the non-threaded end that is inserted in the torch handle, being wholly made of plastics, must have a minimum wall thickness SR' not lower than about 2.5 mm. On the contrary, inner sleeve 104, being made of metal, is sufficiently robust even if its wall thickness SR is 0.6 - 0.8 mm. Thus, for the same external diameter (DR = DR ¹ = 35 -ram), inner sleeve 104 may have an inner diameter exceeding by 3.4 - 3.8 mm that of end 110 of connector 108, this corresponding to an increase of the feed-through section by about 24 - 27% with respect to the section of prior art connector 108:

Outer sleeve 102 made of plastics makes connector 100 lighter.

Advantageously, inner sleeve 104 has substantially the shape of a tube with constant internal cross-section, so that it does not include narrower regions that uselessly restrict the cross-section of the conduits Funning along feeding cable 3, in particular the cross- section of conduit 23C drawing the welding fumes.

Turning back to the description of handle 7, the latter is equipped, in its front part, with an actuating lever, or trigger, 114 (FIGS. 12, 13). By pressing trigger 14, a microswitch 116, for instance of the type manufactured by company OMRON. is operated, which in turn controls the flow of the different materials through cable 3, i.e. the flow of wire electrode 13, the shielding gas, the water or other cooling fluid and the welding fumes being drawn.

Advantageously, trigger 114 has a seat 118 arranged to accommodate microswitch 116.

If microswitch 116 has a rectangular, or generally an elongated shape as in the present exemplary embodiment, it is advantageously longitudinally secured to one or both half shells 107.

Advantageously moreover microswitch 116 is secured to one of half shells 107 so thai it is at least partially received again within seat 118 when trigger 114 is pressed. Advantageously, seat 118 is arranged to accommodate at least 0.1 times the volume of

microswitch 116. More preferably, seat 118 is arranged to accommodate at least one third of the volume of microswitch 116.

In this manner it is possible to considerably reduce the size of microswitch 116 in a direction transversal to the axis of handle 7, and to increase the space available inside handle 7 for the passage of outer tube 25 of the torch body. Actually, as shown in FIG. 14, prior art handles 120 had a narrowing 122 in the channel where metal tube 124 of the torch body passes, in correspondence of seat 126 accommodating the microswitch. Eliminating narrowing 122 allows housing in the torch drawing conduits with greater cross-sectional sizes, thereby increasing the maximum flow rate of the fumes being drawn for the same external size. In this respect it is to be noted that in torch 1 and feeding cable 3 the conduit for drawing the welding fumes has a considerably greater cross-sectional size than the conduits where the wire electrode, the cooling water and the shielding gas pass.

Moreover the front portion of prior art handles 120 was relatively squat and bulky. The above reduction of the size of microswitch 116 allows eliminating or at least considerably reducing narrowing 122 and reducing the external size of the front portion of the handle, thereby enabling the torch to access welding regions located in more restricted spaces and generally making the torch handier. In this respect, the front portion of the handle may have- a more slender and taping shape, as shown in FIGS. 9 and 12. Also trigger 114 can be made of plastics.

FIGS. 15 to 17 relate to a component, herein referred to as "securing wing nut 130", enabling the torch body to be firmly secured to handle 7. Securing wing nut 130 has a substantially tubular shape and is equipped with a pair of side wings 134. Inner tube 20 of the torch body is made to pass through central throughhole 134 of the wing nut and braze- welded thereon (FIG. 17). To this end, wing nut 130 is advantageously made of brass, like tube 25. When the torch is assembled, the free ends of side wings 134 are each inserted into a seat 136 formed on half shells 107 of the handle (FIG. 9).

FIG. 17 show the arrangement of wing nut 130 in a welding torch according to the invention. Outer tube 25 is inserted over a short length into the half shells and then it ends, whereas inner tube 20 extends through handle 7 over a greater length. Welding fumes being drawn, after having flown through the whole of outer tube 25, are subsequently contained by the shell of the handle itself.

Thanks to its ihroughhole 134 and its wings 132, wing nut 130 on the one hand can be precisely locked relative to handle 7, and on the other hand it allows letting the cooling

water flow therethrough with a relatively simple construction.

The exemplary embodiments described above can undergo several changes and modifications without departing from the scope of the present invention.

The examples and the lists of possible modifications in the present application are to be intended as non-exhaustive lists.