GAS-COOLED WELDING TORCH

Description

[0001] The present invention relates to a welding torch for gas shielded welding having the features of the preamble of patent claim 1.

[0002] Such welding torches are well-known in the art. They are used primarily in metal inert gas welding (MIG) and metal active gas welding (MAG), but can also be used in tungsten inert gas welding (TIG). They can be used both in automated welding, often mounted on welding robot systems, and in manual welding, in which case they are used in conjunction with appropriate handheld welding equipment.

[0003] The high temperatures generated at the welding point during the welding process are also transferred to the welding torch. The resulting heat energy input to the welding torch must be dissipated by suitable cooling, not least to protect and preserve the welding torch and its individual components. In the prior art, this is generally achieved using two possible cooling media: liquid cooling and gas cooling. Systems are also known that operate with a mixture of both liquid and gaseous cooling media. If cooling is carried out using a gaseous medium, the shielding gas used in the process, be it an inert gas or an active gas involved in the welding process, can be used for this purpose, for example as disclosed in US 2018 / 0304395 A1 (which discloses the preamble of claim 1), GB 2539412 A, or DE 602 24 140 T2.As the supplied shielding gas flows around the heat-stressed elements of the welding torch, it absorbs the heat energy introduced there and dissipates it as it flows toward the weld. In the front area of ​​the welding torch, this occurs by the shielding gas flowing around the outer surface of the contact tip. To enhance the cooling effect, particularly long contact tips are also used in the front or front section.

[0004] While a liquid coolant generally has the advantage of having a higher heat capacity and thus a better cooling effect, such a liquid coolant also has problems and disadvantages. On the one hand, in addition to the supply of welding current and shielding gas, a coolant supply and return line must be provided as additional components in the media supply of the corresponding welding device or automatic welding machine. Furthermore, a liquid coolant inside the welding torch can only be brought very close to the elements that are particularly thermally stressed, such as the contact tip that serves to contact a welding electrode, e.g. a fed-in welding wire, to a limited extent, meaning that cooling cannot take place directly at the location where the thermal input is particularly high.Finally, the supply of an additional, liquid, cooling medium to the weld area carries the risk that, in the event of a leak, this cooling medium could escape and thus cause damage and weld defects. Escaping cooling water, for example, can lead to an electrical jump in the welding current to the area surrounding the weld; the workpiece to be welded is usually rendered unusable by contact with escaping coolant such as water. In contrast, gas cooling, particularly cooling with the shielding gas that is already in use, has the advantage that no additional medium needs to be supplied and that a seal towards the weld is not necessary, since the shielding gas is designed to escape and flow there anyway, i.e., is supplied to the weld anyway. Accordingly, gas-cooled welding torches are widely used in the state of the art.To support the cooling effect, liquid cooling is often used in addition, which can cool areas of the welding torch that are further back, so that additional energy can be dissipated and thus prevent the contact tip and other components of the welding torch from having to grow further in size at higher currents, which in turn would impair the ergonomics and usability of the welding torch.

[0005] However, the problem with gas-cooled welding torches, as already explained above, is that the cooling performance of a cooling gas is lower than that of a cooling liquid due to its lower heat capacity and thus lower thermal energy absorption capacity. Accordingly, special efforts must be made to ensure adequate cooling of the welding torch, especially of the components subject to high thermal stress, such as the contact tip and the contact tip holder.

[0006] The object of the present invention is to achieve an improvement in this endeavour, in particular to achieve improved cooling of the contact tip and the contact tip holder.

[0007] This object is achieved according to the invention by a welding torch for gas shielded welding having the features of patent claim 1. Advantageous embodiments of such a welding torch according to the invention are proposed in the dependent claims 2 to 13.

[0008] According to the invention, a welding torch for gas shielded welding initially has a rear connection to a media supply, which in any case comprises a supply of shielding gas and a supply of welding current.

[0009] This media guide can also contain additional media lines, for example a supply and return line for a cooling liquid if additional liquid cooling of the welding torch is provided, or a welding wire feed for a welding wire used as a consumable electrode. The welding torch according to the invention also has a welding-side front end. It has an electrically contacted and electrically conductive contact tip holder for applying the welding current, in which a contact tip made of an electrically conductive material, such as copper, is detachably arranged. The contact tip is in electrically conductive contact with the contact tip holder, so that the supplied welding current is passed on to the contact tip via the contact tip holder.

[0010] The welding torch further comprises a gas distributor, which serves to evenly distribute the shielding gas, particularly circumferentially, and, typically in conjunction with a gas nozzle of the welding torch, to direct the shielding gas toward the front end of the welding torch. The shielding gas then typically exits the front end of the welding torch in the form of a shielding gas column surrounding the weld.

[0011] A front end of the contact tip arranged in the contact tip holder is guided to the front end of the welding torch. A rear section of the contact tip rests in a receiving opening of the contact tip holder. The rear section of the contact tip has a region tapering towards a rear end of the contact tip, and the receiving opening in the contact tip holder has a surface section shaped complementarily to the tapered region of the contact tip. The region tapering towards the rear end of the contact tip can be shaped to taper discontinuously, e.g., stair-like or stepped. In one possible embodiment, it tapers continuously, e.g., parabolically or conically, with a conical shape being particularly preferred in this case.The tapered region of the contact tip and the complementarily shaped surface section are shaped to complement each other in such a way that the contact tip inserted into the receiving opening, with its tapered region, is in close mechanical and electrical contact with the complementarily shaped surface section of the receiving opening. If the contact tip is tapered conically in the tapered region, the complementarily shaped surface section therefore has a conical shape complementary to the conical shape of the contact tip region.

[0012] The contact tip in such welding torches is typically a wearing part that must be replaced regularly. Despite all efforts to cool it, it is subject to high thermal stress and carries high electrical currents. Accordingly, after a number of welding cycles, it wears out and must be replaced. Therefore, this contact tip is detachably located in the contact tip holder and is usually designed so that it can be easily removed from the contact tip holder and replaced with a fresh contact tip inserted and removably secured into the contact tip holder.In the welding torch according to the invention, the tapered shape of the tapered region of the contact tip in its rear section, with which the contact tip lies in the receiving opening of the contact tip receptacle, provides, on the one hand, good mechanical and electrical contact, since the contact tip with its tapered region, which can be a cone, for example, can be pressed into the complementarily shaped, e.g., complementarily conical, receiving opening and thus can be brought into intimate contact. On the other hand, it particularly facilitates the release of the contact tip, since such a shape is less likely to jam in the event of possible thermally induced deformation when the contact tip is to be released.

[0013] The special feature of the welding torch according to the invention is that at least one channel-like recess is formed in the complementarily shaped surface section of the receiving opening, through which a gas guide channel is formed between the contact tip holder and the contact tip. This gas guide channel is connected, on the one hand, to the supply of shielding gas from the media supply and, on the other hand, to the gas distributor. During operation of the welding torch, the supplied shielding gas is guided through this gas guide channel, which can in particular be formed exclusively by a channel-like opening formed in the complementarily shaped surface section of the receiving opening, before flowing further to the gas distributor and from there being guided towards the welding point, where it escapes to form the shielding gas column.As a result of this measure, the shielding gas in the rear area of ​​the contact tip, which in the known art is usually firmly held in the opening of the contact tip holder and does not experience any separate cooling by the shielding gas, is in intimate contact with the material of the contact tip and can thus absorb and dissipate the heat energy transferred there. As it flows further, the shielding gas then also sweeps over a front section of the contact tip, which is located towards the front end of the welding torch, and also leads to a cooling effect there. Accordingly, this solution according to the invention achieves an improved cooling effect of the gas-cooled contact tip, since the contact tip is swept over by the shielding gas serving as the cooling medium over a wider area of ​​its axial extent, and is in intimate contact with the shielding gas.The current transfer to the contact tip, which also takes place in the tapered region in which the at least one gas guide channel is formed, is not impaired by the interruption of the contact surface formed by the at least one gas guide channel, in particular since it can still be dimensioned sufficiently large. Outside the at least one gas guide channel, contact surfaces extending both in the longitudinal direction of the contact tip and in its circumferential direction are formed with sufficient area, which on the one hand ensure mechanical hold and on the other hand in particular the transfer of the required welding current to the contact tip. It should be emphasized at this point that the gas guide channel formed is neither limited in its orientation relative to a longitudinal axis nor in its cross-sectional shape. It can run in the longitudinal direction of the contact tip or at an angle to it, e.g. in a spiral shape.A branched profile is also conceivable. It can also have a square or rounded cross-section, e.g., rectangular, triangular, polygonal, (partially) circular, or even (partially) elliptical, or similar. The only important thing is that this gas guide channel directs the shielding gas flowing from the gas supply toward the gas distributor in such a way that it cools the contact tip in particular, but possibly also other components that it passes by.

[0014] Advantageously, the welding torch according to the invention can be provided so that electrical contacting of the contact tip in the rear section occurs exclusively via a circumferential surface of the contact tip in the tapered region, which surface bears against the complementarily shaped surface section of the receiving opening. Transmission of the welding current via the circumferential surface is possible with a sufficiently large contact area, so that, in particular, a rear end of the contact tip does not have to abut or rest against an electrically conductive part. However, such a design does not preclude current transmission in another section of the contact tip, e.g., in a connecting section.In particular, according to a further advantageous embodiment of the welding torch according to the invention, a rear end face of the contact tip arranged and secured in the contact tip receptacle can be exposed without contact with another element. In particular, this also prevents the rear end face of the contact tip from becoming stuck during use against such an otherwise required contact surface in the contact tip receptacle or an adjacent part, which in turn makes it difficult, or in the worst case, even impossible, to remove the contact tip from the welding torch to replace a worn contact tip with a fresh one.

[0015] For a further improved cooling effect, it can be provided that not just one gas guide channel is formed, but that at least two, in particular several, advantageously four, gas guide channels are present, each formed by channel-like recesses formed in the complementarily shaped surface section of the receiving opening between the contact tip receptacle and the contact tip, wherein the gas guide channels are each connected on the one hand to the supply of protective gas from the media supply and on the other hand to the gas distributor. In this way, protective gas is guided over a larger contact surface along the rear section of the contact tip and contributes to the cooling of the contact tip and possibly other parts swept by the protective gas in this section. The two or more gas guide channels formed in this way can in particular be distributed at uniform angular intervals along a circumference of the contact tip.This ensures that the cooling effect is distributed symmetrically around the circumference, and areas of sufficient size are left between the gas guide channels in which the contact tip with its tapered area is in close mechanical and, above all, electrical contact with the complementarily shaped surface section of the receiving opening for a safe and sufficient transfer of the welding current to the contact tip.

[0016] Advantageously, the gas guide channel(s) formed by the channel-like recess(es) is / are designed with a cross-section that tapers toward the front end of the contact tip. This provides improved guidance of the shielding gas used as a cooling medium at this point, with improved flow-dynamic properties.

[0017] According to the invention, the welding torch according to the invention is provided with a gas outlet bore which transverses the contact tip receptacle and opens into the at least one gas guide channel, and through which shielding gas can be transferred from the gas guide channel to an inner side of the gas distributor. If multiple gas guide channels are provided, such a gas outlet bore is preferably provided for each of the gas guide channels, wherein these gas outlet bores are preferably arranged in the same axial position, relative to a longitudinal axis of the welding torch or the contact tip, and distributed radially along the circumference. During operation, the shielding gas, after having swept over the rear section of the contact tip and created a cooling effect there, can be introduced into the gas distributor through these gas outlet bores, from where it is distributed circumferentially and passed on towards the front end of the welding torch.

[0018] The gas distributor of the welding torch according to the invention has, according to the invention, gas passage openings which cross the latter and are distributed along a circumference of the gas distributor for guiding the shielding gas from the inside of the gas distributor to an outside of the gas distributor and for forwarding the shielding gas to the front end of the welding torch, which gas passage openings can in particular also be arranged in a same position viewed along the longitudinal axis but distributed radially along the circumference, wherein then, according to the invention, the gas outlet bore(s) is / are located closer to the front end of the gas distributor in the axial direction than the gas passage openings. As a result of this measure, the gas emerging from the gas outlet opening(s) mustThe shielding gas exiting the gas outlet openings initially flows back in the gas distributor in the opposite direction to its original flow direction before exiting through the gas passage openings and then flowing in the opposite direction toward the front end of the welding torch. This measure extends the distance covered by the gas with a cooling effect and improves the homogenization of the shielding gas flow, thus resulting in an improved flow pattern of the shielding gas when it exits the front end of the welding torch.

[0019] In addition to the gas outlet bore(s), one or more gas inlet bore(s) are provided according to the invention, which cross(es) the contact tip receptacle in a position which is further away from the front end of the welding torch in the axial direction compared to a position of the gas outlet bore(s) and open(s) into the gas guide channel(s) for transferring inflowing shielding gas into the gas guide channel(s). Such a gas inlet bore(s) are preferably provided when a gas supply from the rear

[0020] Connection to the media supply is made by the welding torch in a radially outward position.

[0021] Advantageously, the welding torch according to the invention can be provided with the tapered region of the contact tip extending to its rear end. With such a configuration, there is no further, for example, cylindrically shaped section of the contact tip, which, if it rests in a correspondingly shaped receptacle, could lead to the problems of blocking or jamming described above when a worn contact tip is to be removed from the contact tip receptacle and replaced with a fresh contact tip.

[0022] However, it may be possible, and in a currently preferred embodiment, this is also practiced, for the contact tip to have a cylindrical portion in its rear section located in front of the tapered region, as seen from its front end. This portion is spaced apart, in particular, from a wall of the receiving opening surrounding this portion, so that a gap is left and this cylindrical portion cannot lead to jamming as described above due to deformation, particularly thermal deformation.

[0023] For releasable securing in the contact tip receptacle, the contact tip of the welding torch according to the invention can, in particular, have a thread in a securing section adjoining the rear section in the direction of the front end. With this thread, the contact tip can be screwed tight into a counter-thread and thus pressed into the contact tip receptacle, in particular with the tapered region of the rear section forced into the receiving opening of the contact tip receptacle. However, other securing methods are also conceivable, e.g., a type of bayonet connection.

[0024] In the welding torch according to the invention, in particular in one embodiment variant, the gas distributor can be placed onto the contact tip holder and detachably connected to it, in particular by screwing. In this case, it can also be advantageously provided that the contact tip is detachably secured to the gas distributor and projects with its rear section into the receiving opening of the contact tip holder. In particular, if the contact tip has a thread in the fixing section as described above, it can be screwed into an internal thread formed on the gas distributor. In this case, the gas distributor is then closed in particular by the contact tip screwed into it at a front end pointing towards the front end of the welding torch, in particular in such a gas-tight manner that the shielding gas cannot escape there.

[0025] As an alternative to designing the contact tip with a region that tapers continuously, in particular conically, toward its rear end, this region can also be formed in a stepped manner, as already mentioned above. In this case, it can also be provided, in particular, that the surface section of the receiving opening provided in the contact tip receptacle, which surface section is shaped complementarily to the thus tapered region of the contact tip, is shaped in a continuously tapered manner, specifically such that at least one transverse channel is formed in at least one section in which the tapered region has a step. This transverse channel runs essentially along the circumferential direction of the contact tip.With such a design, the tapered region is not continuous over the length of the tapered region in those sections where physical contact is maintained between the tapered region and the receptacle, but at least one transverse channel is formed; multiple transverse channels can also be formed. A further cooling effect can be achieved in these by the gas flowing through. This can be further improved if the at least one gas guide channel is circumferentially offset in sections where it opens into the transverse channel. The flowing gas is then forced to follow a flow path in the transverse channel that follows the circumference of the contact tip.

[0026] The contact tip has a front section facing a welding point when the contact tip is installed, a fastening section adjoining the front section at the rear, and a rear section adjoining the fastening section at the rear. The fastening section, which can in particular have a thread but can also generally have other fastening structures, such as protruding projections of a bayonet connection or the like, allows the contact tip to be secured in a contact tip receptacle with a corresponding counterstructure. The rear section of the contact tip also serves to secure the contact tip in the contact tip receptacle of a welding torch.

[0027] This contact tip is advantageously characterized in that the ratio of an outer surface formed by the contact tip in the tapered region to a radius of the contact tip in the rear section where the tapered region with the larger radius begins, i.e. at a base of the tapered region, is at least 35 mm, preferably at least 40 mm, in particular at least 43 mm. The fact that a ratio is provided here with a length specification in mm and is not dimensionless stems from the fact that a ratio of an area to a length is specified. This value is particularly high compared to contact tips known from the prior art that have tapered regions in their rear sections. Known contact tips of this type generally have a ratio of these values ​​in the range of around 20 mm, in exceptional cases up to 30 mm.This can be explained by the fact that the contact tips, which are consumables and often have to be replaced and are typically made from the comparatively expensive material copper, are manufactured in the rear area, which contributes to the actual welding process in known welding torches only through the welding current transfer that takes place there, in order to reduce material costs in this area, using as little material as possible, i.e. they are short and therefore with a small external surface of a tapered section. The surface area of ​​this tapered area in relation to the radius at its base is essentially determined by the contact area required for sufficient current transfer. For the present welding torch, however, part of the external surface of the contact tip in this tapered area is deliberately excluded from current transfer in order to form the gas guide channel(s).which serves or serve to dissipate heat. In order to, on the one hand, continue to have sufficient surface area for current transfer, and on the other hand to maintain a sufficient surface exposed in the gas guide channel(s) in this area for heat dissipation to the shielding gas flowing past there, the tapered area of ​​the rear section of the contact tip is designed with an enlarged surface and is typically also elongated. For this reason, ratios of the surface area of ​​the tapered section to the radius at the base of the tapered section of at least 35 mm, preferably at least 40 mm, in particular at least 43 mm and more have proven particularly suitable for fulfilling the dual purpose of this tapered section, namely current transfer and providing a heat-dissipating surface.The higher material usage required for this can be more than compensated by the improved cooling in the welding torch according to the invention and by the resulting extended service life of the contact tip.

[0028] Furthermore, in the welding torch according to the invention, it can be provided that the contact tip has a central bore for passing through and electrically contacting a welding wire supplied via the media supply in a manner which is customary and known for such contact tips.

[0029] A front end, or front section, of the contact tip of the welding torch according to the invention, with which it protrudes and projects toward the front end of the welding torch, can in principle be provided with a different shape, for example, cylindrical. In a current design variant, a similarly tapered, in particular conical, shape is preferably selected, with the contact tip in this section tapering toward the front end of the welding torch.

[0030] Further advantages and features of the welding torch according to the invention described here will become clearer to those skilled in the art based on the following description of possible design variants of exemplary embodiments with reference to the attached figures. Figure 1 is an exploded view of an embodiment of the front section of a welding torch according to the invention; Figure 2 is a contact tip of the welding torch according to the invention Figure 1 ; Figure 3 a contact tip holder of the welding torch according to the invention from Figure 1 in a view obliquely from the front; Figure 4 the contact tip holder from Figure 3 in a side view; Figure 5 in a partially cut-away side view the arrangement of the contact tip in the contact tip holder in the welding torch according to the invention according to Figure 1 Figure 6 the arrangement of the contact tip in the contact tip holder as in Figure 5 in a partially cutaway isometric view; Figure 7 shows a gas distributor of the welding torch according to the invention from Figure 1; Figure 8 shows the gas distributor according to Figure 7in a longitudinal section; Figure 9 in a partially sectioned view of the front section of the welding torch according to the invention Figure 1 with flow lines drawn to illustrate the protective gas flow; and Figure 10 an enlarged view of a section of Figure 9 to illustrate the flow path of the shielding gas in the area of ​​the rear section of the contact tip and the gas distributor.

[0031] The figures referenced below to explain the exemplary embodiment of a welding torch according to the invention shown here show schematic representations of the essential elements of a welding torch according to the invention, wherein identical elements are provided with identical reference numerals. The following description is to be understood as a description of only one possible exemplary embodiment; there are further embodiments of a welding torch according to the invention that are not explained in more detail here and that will be readily apparent to a person skilled in the art from the above general description of the invention and from the following patent claims. In this respect, the following description of the exemplary embodiment should in particular not be understood as limiting the scope and significance of the invention, which is disclosed in the claims.

[0032] In Figure 1First, an exploded view of a welding torch 1 according to the invention is shown in its front section. The rear section of the welding torch 1, facing away from the welding point, corresponds in design to that of usual and conventional welding torches and is therefore not shown or explained in detail here. A media supply is connected to a rear end of the rear section of the welding torch 1, through which welding media, in particular shielding gas, welding current and welding wire, and possibly also coolant, are supplied. Additional control and supply lines can also be connected there.

[0033] In the Figure 1The structure of the front end of the welding torch 1 can be seen with a contact tip holder 2, a contact tip 3, a gas distributor 4 and a gas nozzle 5. In the assembled state of the welding torch 1, the gas distributor 4 is placed on the contact tip holder 2 and connected to it in a fixed position, screwed in the embodiment shown, and the contact tip 3 is attached to the gas distributor 4 and rests with a rear end in the contact tip holder 2. The gas nozzle 5 is slipped over this arrangement and attached to a base body 6 of the welding torch 1, screwed here.

[0034] The individual in Figure 1 Components shown are in the Figures 2 to 4 and 7 and 8 are shown again in isolation. Figure 2shows the contact tip 3. This has a front section 7, which faces the welding point during operation, a fixing section 8 adjoining the front section 7 in the direction of a rear end, in which in this embodiment an external thread is formed, and a rear section 9 adjoining the fixing section 8. This rear section 9 is divided into a cylindrical area 10 directly adjacent to the fixing section 8 and a area 11 tapering conically from this area 10 towards the rear end. A bore 13 opens at a rear end 12, which is guided longitudinally through the contact tip and exits at its front end (cf. Figure 9). In the front section 7, flattened areas 14 are provided at radially opposite positions, which serve as a tool attachment for attaching a tool for securing or releasing the contact tip 3 in or from the gas distributor 4. According to the invention, in the contact tip 3, the ratio of the outer surface formed in the tapered area to a radius of the contact tip 3 in the rear section 9 where the tapered area 11 with the larger radius begins, i.e. at a base B of the tapered area 11, is at least 35 mm, preferably at least 40 mm, in particular at least 43 mm. This ratio is therefore given with a dimension in mm, since here an area (measured in mm 2< ) is related to a distance, the radius (measured in mm). The contact tip 3 is formed from an electrically conductive material, in particular from copper.

[0035] Figures 3 and4show the contact tip receptacle 2. This is provided with an external thread 15, which is pierced by recesses 16 extending in the axial direction and evenly distributed along the circumference. From a front end, a recess 17 is introduced into the contact tip receptacle 2, which has circumferential, conical surface sections 18 shaped complementarily to the conically tapered section 11 of the contact tip 3. Between these surface sections 18, recesses or notches 19 extend radially outwards into the material of the contact tip receptacle 2, which in this embodiment extend in the longitudinal direction of the contact tip receptacle 2. In the region of the recesses 16, gas inlet bores 20 are led through the wall of the contact tip receptacle 2 into the recess 17 extending into its interior, and which open into the recesses 19.Gas outlet bores 21 pass through the wall of the contact tip holder 2 at positions of the recesses 19 further facing the front end of the contact tip holder 2 in the axial direction.

[0036] Figures 5 and 6show the fit of the rear section 9 of the contact tip 3 in the recess 17 of the contact tip receptacle 2. In particular, it is illustrated there that when the contact tip 3 is properly seated in the contact tip receptacle 2, the contact tip 3, with its conically tapered region 11, rests in close contact with the surface sections 18, so that mechanical contact is maintained there and a firm fit of the contact tip 3 in the contact tip receptacle 2 is ensured. In the sections in which the recesses 19 are made in the contact tip receptacle 2, gas guide channels are formed between the conical surface of the contact tip 3 in the region 11 and the contact tip receptacle 2. The gas inlet bores 20 and the gas outlet bores 21 open into these gas guide channels.During operation, the contact tip holder 2, which is also made of a conductive material, in particular copper, is electrically connected to the welding current supply line, i.e. is electrically contacted. As a result, electrical contact is established between the contact tip 3 and the surface sections 18 via the surface contact of the lateral surface sections of the contact tip 3 in the conically tapered region 11, so that welding current can be applied to it during operation. Due to the comparatively large surface area of ​​the surface sections 18, electrical contact is made over a large total area, ensuring a good electrical transition at this point. The front end 12 of the contact tip 3 is exposed and does not come into contact with the contact tip holder 2 or other parts.

[0037] The Figures 7 and 8show the gas distributor 4. Here it can be seen that it has an internal thread 22 and 23 in the area of ​​its two longitudinal ends. With the internal thread 22, the gas distributor 4 is connected to the Figure 3 visible external thread 15 of the contact tip holder 2. The contact tip 3 is screwed into the internal thread 23 with the external thread formed in the fastening section 8 and is thus pressed with the rear section 9, in particular with the conically tapered area 11, into the receiving opening 17 of the contact tip holder 2, so that the intimate contact between the conically tapered area 11 and the surface section 18, as described above, is created and ensured (see also Fig. 9). It should be emphasized here that the cylindrical area 10 in the rear section 9 of the contact tip 3 is arranged at a distance from the surrounding inner wall of the contact tip receptacle 2, so that there is no contact between the contact tip receptacle 2 and the contact tip 3. The gas distributor 4 has, in a conventional manner, radially distributed gas passage openings 24 located in the same longitudinal position, which serve for the outlet of the protective gas flowing therethrough.

[0038] The gas flow in the welding torch according to the invention is in the Figures 9 and 10 The shielding gas S, which is supplied in the usual way via the media supply and is illustrated here by dashed lines, initially flows along the recesses 16 (see Figures 5 and 6) along the outside of the rear end of the contact tip holder 2 and then enters through the gas inlet openings 20 into the gas guide channels formed by the recesses 19. The shielding gas flows along the rear section 9 (see also Figures 5 and 6 ) of the contact tip 3, in particular along its conically shaped area 11, and provides a cooling effect. The shielding gas S flows further into the gas guide channels, which narrow in cross-section, and reaches the gas outlet openings 21, where it leaves the interior of the contact tip holder 2 and enters a space formed between the gas distributor 4 and the contact tip holder 2. In particular in Figure 10It can be clearly seen that the gas outlet openings 21, viewed in the longitudinal direction, are located in a position in front of the position of the gas passage openings 24 of the gas distributor 4, so that the shielding gas is deflected at this point and must initially flow backwards, counter to the forward direction, before it exits the gas distributor 4 through the gas passage openings 24 and flows further along the outside of the gas distributor 4 inside the gas nozzle 5, then flows along the front section 7 of the contact tip 3 and finally leaves the gas nozzle 5 at the front end of the welding torch 1 facing the welding point in a columnar manner surrounding the welding wire emerging there.

[0039] Through the, in Figure 10As already mentioned, the gas flow shown in an enlarged manner results in a clear and noticeably improved cooling effect of the contact tip 3. In particular, the contact tip 3 in the welding torch according to the invention can be cooled much better, which results in an improved service life of the contact tip.

[0040] A cooling effect, which in turn also allows the Figure 10 recognize, the protective gas achieves on its as in Figure 10 shown path also with regard to the gas distributor 4.

[0041] The above description of the exemplary embodiment has once again made clear the advantages and features of the invention disclosed and claimed herein. The following claims define and characterize this invention in its general scope. List of reference symbols

[0042] 1Welding torch 2Contact tip holder 3Contact tip 4Gas distributor 5Gas nozzle 6Base body 7Front section 8Fixing section 9Rear section 10Cylindrical section 11Conically tapered section 12Front end 13Bore 14Flat 15External thread 16Recess 17Recess / receiving opening 18Surface section 19Recess 20Gas inlet hole 21Gas outlet hole 22Internal thread 23Internal thread 24Gas passage opening BBase SProtective gas

Claims

1. A welding torch (1) for gas-shielded arc welding with a rear connection to a media supply comprising at least a supply of shielding gas (S) and a supply line for welding current and with a welding-side front end, wherein the welding torch (1) has an electrically contacted and electrically conductive contact tip holder (2) for application of the welding current and a contact tip (3) which is detachably arranged in the contact tip holder (2), is in electrically conductive contact with the contact tip holder (2) and is formed from an electrically conductive material, as well as a gas distributor (4) for distributing and supplying the shielding gas (S) in the direction of the front end of the welding torch (1), wherein a front end of the contact tip (3) is guided to the front end of the welding torch (1) and a rear section (9) of the contact tip (3) rests in a receiving opening (17) of the contact tip holder (2), wherein the rear section (9) of the contact tip (3) has a region (11) which tapers, in particular continuously, preferably conically, towards a rear end (12) of the contact tip (3), and the receiving opening (17) in the contact tip receptacle (2) has a surface section (18) which is shaped in such a complementary manner to the tapering region (11) of the contact tip (3), that the contact tip (3) with the tapering region (11) is in close mechanical and electrical contact with the complementary shaped surface section (18), characterised by at least one channel-like recess (19) formed in the complementarily shaped surface section (18) of the receiving opening (17), through which a gas guide channel is formed between the contact tip receptacle (2) and the contact tip (3), which channel is connected on the one hand to the supply of shielding gas (S) from the media supply and on the other hand to the gas distributor (4), by at least one gas outlet bore (21) which crosses the contact tip receptacle (2), gas outlet bore (21) opening into the at least one gas guide channel for transferring shielding gas (S) from the gas guide channel to an inner side of the gas distributor (4), through the gas distributor (4), gas passage openings (24) distributed along a circumference of the gas distributor (4) for guiding the shielding gas (S) from the inside of the gas distributor (4) to an outside of the gas distributor (4) for conveying the shielding gas (S) to the front end of the welding torch (1), wherein the gas outlet bore (21) is located closer to the front end of the gas distributor (4) than the gas passage openings (24) when viewed in an axial direction, and by at least one gas inlet bore (20), which crosses the contact tip holder (2) in a position further away from the front end of the welding torch (1) in the axial direction compared with a position of the gas outlet bores (21) and opens into the gas guide channel for the transfer of inflowing shielding gas (S) into the gas guide channel.

2. A welding torch (1) according to claim 1, characterised in that electrical contacting of the contact tip (3) in the rear section (9) takes place exclusively via a lateral surface of the contact tip (3) in the tapered region (11), which lies against the complementarily shaped surface section (18) of the receiving opening (17).

3. A welding torch (1) according to one of the preceding claims, characterised in that there are at least two, in particular four, channel-like recesses (19), each formed in the complementarily shaped surface section (18) of the receiving opening (17), which each form a gas guide channel between the contact tip receiver (2) and the contact tip (3), which is connected in each case on the one hand to the supply of shielding gas (S) from the media supply and on the other hand to the gas distributor (4) .

4. A welding torch (1) according to claim 3, characterised in that the recesses (19) forming the gas guide channels are arranged distributed along a circumference of the contact tip (3) with uniform angular spacing.

5. A welding torch (1) according to one of the preceding claims, characterised in that the gas guide channel or gas guide channels formed by the channel-like recess or recesses (19) have a cross-section which narrows towards the front end of the contact tip (3).

6. A welding torch (1) according to one of the preceding claims, characterised by a gas inlet bore (20) which crosses the contact tip holder (2) in a position further away from the front end of the welding torch (1) in the axial direction compared with a position of the gas outlet bore (21) and opens into the at least one gas guide channel for transferring inflowing shielding gas (S) into the gas guide channel.

7. A welding torch (1) according to one of the preceding claims, characterised in that the tapered region (11) of the contact tip (3) extends to a rear end of the contact tip (3).

8. A welding torch (1) according to one of the preceding claims, characterised in that the contact tip (3) has in its rear section (9) a cylindrical region (10) located in front of the tapering region (11) as seen from its front end.

9. A welding torch (1) according to one of the preceding claims, characterised in that the contact tip (3) has a thread in a fixing section (8) adjoining the rear section (9) in the direction of the front end.

10. A welding torch (1) according to one of the preceding claims, characterised in that the gas distributor (4) is placed on the contact tip holder (2) and is detachably connected thereto, in particular screwed.

11. A welding torch (1) according to claim 10, characterised in that the contact tip (3) is detachably fixed to the gas distributor (4) and projects with the rear section (9) into the receiving opening (17) of the contact tip holder (2).

12. A welding torch (1) according to one of the preceding claims, characterised in that the region (11) tapering towards the rear end (12) of the contact tip (3) is formed in a stepped manner and in that the surface section (18) of the receiving opening (17) provided in the contact tip receptacle (z) and complementarily shaped to the tapering region (11) of the contact tip (3) is continuously tapered, so that at least one transverse channel is formed in at least one section in which the tapering region (11) has a step.

13. A welding torch (1) according to one of the preceding claims, characterised in that the contact tip (3) has a front section (7) pointing in the direction of the front end of the welding torch (1) and towards a welding point and a fastening section (8) adjoining the front section (7) at the rear, the fastening section (8) being adjoined at the rear by the rear section (9), wherein the ratio of an outer surface formed by the contact tip (3) in the tapered region (11) to a radius of the contact tip in the rear section (9) at the point where the tapered region (11) with the larger radius is located is at least 35 mm, preferably at least 40 mm, in particular at least 43 mm.