WO2004052582A1

WO2004052582A1 - Welding unit for protective gas welding

Info

Publication number: WO2004052582A1
Application number: PCT/SE2003/001897
Authority: WO
Inventors: Michal Ostrowski
Original assignee: Samhall Ab
Priority date: 2002-12-09
Filing date: 2003-12-05
Publication date: 2004-06-24
Also published as: AU2003284821A1; SE0203629D0; SE0203629L; SE524473C2

Abstract

The invention relates to a welding unit intended for protective gas welding of the type that comprises a manually grippable pistol (1) in the form of a long narrow, form-stiff cover, as well as a cable (2) connected to the pistol through which a welding wire and a protective gas may be fed up to nozzles (3) included in the pistol. In the cable, there are also conductors in order to provide the pistol with current. According to the invention, the pistol cover (1) is formed with substantially straight front and rear sections (5, 6), which transform into each other via an arched transition section (7) and extend at an obtuse angle (α) to each other. Said obtuse angle may amount to approximately 130°. The cable (2) is drawn through the rear section (6) as well as the transition section (7) up to a body pipe (not visible) arranged in the front section, to which said nozzles (3) are connected.

Description

WELDING UNIT FOR PROTECTIVE GAS WELDING

Technical Field of the Invention

This invention relates to a welding unit intended for protective gas welding, of the type that comprises a manually grippable pistol in the form of a long narrow, form-stiff cover and a cable connected to the pistol, which cable includes bores for feeding a welding wire to a contact nozzle included in the pistol and a protective gas to a gas nozzle included in the pistol, as well as conductors in order to lead, on one hand, operation current to the contact nozzle with the purpose of melting the welding wire, and, on the other hand, control current to a trigger for controlling the function of the pistol, said nozzles being located along a common geometric axis which extends at an obtuse angle to the cable coming into the pistol.

Prior Art

For protective gas welding or so-called MIG welding, a mobile, most often wheel-carried welding machine as well as a unit connectable to the same of the above-mentioned type are used, i.e. a cable, which at a rear end has a connector that can be connected to the machine, and at a front end a pistol by means of which the real welding operation is carried out. From the machine, the pistol may, via the cable, be supplied with welding wire, protective gas as well as the requisite operation and control current. In order to enable the greatest feasible ergonomy during welding in different practical work situations, it has turned out to be necessary to angle the two nozzles for the wire and the protective gas, respectively, in relation to the rear part of the pistol, which serves as a handle and in which the cable is inserted. More precisely, the angle between the nozzles and the handle part of the pistol should be obtuse and be within the range of 110-135°. In order to provide the desired obtuse angle between the nozzles and the handle part, the nozzles of the pistols of previously known welding units have been manufactured as a separate detail, which is denominated goose-neck by those skilled in the art, and which is composed of two concentric pipe couplings being bent or shaped at an obtuse angle, an outer one of which forms a gas nozzle that at the rear has a union nut, which may be secured to a front male thread on the pistol. To manufacture, in this way, a separate so-called goose-neck having a curved shape is in practice complicated and cost-demanding. Also in other respects, previ- ously known welding pistols of the kind in question are structurally complicated and expensive to produce. A factor that contributes to the same is that the stiff cover, which contains the different components of the pistol, is put together by two mirror-invertedly symmetrical shell parts, which are joined along a central plane, which intersects the trigger for the control of the pistol. Said two shell parts have to be fixed against each other by means of a plurality of screws which are drawn in from the side in different points along the length extension of the pistol. The fact that the divided central plane intersects the trigger, means in practice that the construction of the trigger becomes comparatively complicated and demands considerable time for mounting. Furthermore, in this connection, between the trigger and the surrounding portions of the shell parts, thin gaps arise through which dirt may pene- trate into the interior of the pistol. Another disadvantage of the known pistols is that the cable has to be provided with a deflectable, although stiffening rubber cuff at the rear opening in which the cable is inserted in the pistol, more precisely with the purpose of avoiding abrupt breaks in the part of the cable that connects to the pistol.

Objects and Features of the Invention

The present invention aims at obviating the above- mentioned disadvantages of the previously known welding units and at providing an improved welding unit. Therefore, a primary object of the invention is to provide a welding unit, the pistol of which can be produced by few and structurally simple components. An additional object is to provide a welding unit having a pistol, the different components of which can be oun- ted and connected to the cable in a simple and fast way; all with the purpose of reducing the total cost of the welding unit in its entirety to a minimum. Yet an object of the invention is to provide a welding unit, the gas and contact nozzles of which are structurally simple and can be replaced in a simple and smooth manner. It is also an object to provide a light and ergonomically expedient pistol.

According to the invention, at least the primary object is attained by the features defined in the characteriz- ing clause of claim 1. Preferred embodiments of the invention are furthermore defined in the dependent claims .

Additional Elucidation of Prior Art

In US 6225599, an example is shown of a gas welding pistol according to previously known technique. In this case, the pistol includes an expensive so-called goose-neck of the type that has an angled shape in order to provide the requisite obtuse angle between the gas nozzle and the handle of the pistol.

Brief Description of the Appended Drawings

In the drawings Fig 1 is a side view of a pistol included in a welding unit according to the invention, a short distance of a cable included in the welding unit also being shown,

Fig 2 is a planar view from above of the pistol and the cable according to fig 1, Fig 3 is a perspective view of only the pistol seen obliquely from behind, Fig 4 is a perspective view of the pistol seen obliquely from the front, Fig 5 is a perspective exploded view showing different components included in the pistol, above all two shell parts that together form a pistol cover as well as the cable of the welding unit,

Fig 6 is a perspective view of an outer shell part, Fig 7 is a perspective view of an inner shell part, Fig 8 is a longitudinal section through the pistol, and Fig 9 is an enlarged cross-section A-A in fig 2.

Detailed Description of a Preferred Embodiment of the Invention

In figs 1 and 2, a welding unit is visualised, which includes on one hand a manually grippable pistol generally designated 1, and on the other hand a cable 2, which is merely shown partially. In said cable 2, bores or ducts are included in a conventional way for feeding a welding wire to a contact nozzle included in the pistol 1 as well as a protective gas to a gas nozzle 3. Furthermore, two different types of conductors are included in the cable in order to lead operation current to the contact nozzle with the purpose of melting the welding wire, as well as control current to a trigger 4 for controlling the function of the pistol. The pistol 1 consists of a generally long narrow, form-stiff cover, the construction of which is described in detail below, reference being made to figs 3-8. However, it should already now be pointed out that a substantial feature of the pistol cover 1 is that the same has been formed with substantially straight front and rear sections 5, 6, which transform into each other via an arched transition section 7. The sections 5, 6 extend at an obtuse angle α to each other. In the example, said angle α amounts to approximately 130°. Said angle α may, per se, vary, but should in practice be within the range of 110-135°.

In figs 5-8 is seen how the pistol cover 1 is compo- sed of two long narrow and cross-section-wise curved shell parts 8, 9, which are substantially of uniform width and mutually joined along longitudinal pairs of edges or edge surfaces 10 and 11, respectively, being pressed against each other. Characteristic of the cover according to the invention is that one of the shell parts, viz. the shell part 8, is in the form of a back-like outer piece, the edge surfaces of which are partially concavely curved in the area 10', while the second shell part 9 is in the form of an inner piece, the edge surfaces 11 of which are partially convexly curved in the area 11'. The two front portions 5A, 5B of the shell parts 8, 9 consist of straight, semi-cylindrical wall portions. In an analogous way, the two rear wall portions 6A, 6B, which together form the rear section 6 of the composed pistol cover, are substantially semi-cylindrical and approximately straight. At two arched thickenings or bulgings 12A, 12B, the front wall portions 5A, 5B transform into archedly curved transition wall portions 7A and 7B, respectively, which in turn transform into the rear wall portions 6A, 6B approximately at the reference designation 13. In the composed state of the cover 1, the two thickenings 12A, 12B form a continuous, front stopper ring 12 for a hand, which seizes the pistol.

On the inside of the front wall portion 5A, two arched, mutually parallel beads 14A are formed. Analogous beads 14B are formed on the inside of the wall portion 5B. When the shell parts 8, 9 are put together, the pairs of beads define a ring-shaped seat, which in fig 8 is designated 14.

On the inside of the rear wall portions 6A, 6B, sets of comparatively thin ribs 16A, 16B are formed, which extend axially, i.e., in the longitudinal direction of the pistol cover. The front ends of said ribs are connected to transverse flanges 17A, 17B, while the rear ends are located in the area of the rear ends of the shell parts. Said rear ends are formed with thickened ring formations 18A, 18B, which together form a rear stopper ring 18 for the hand that seizes the pistol. As is seen in fig 6, two inwardly opening recesses 19 in which malelike projections 20 may be received formed on the inside of the rear ring formation 18B of the inner piece 9 are formed in the thickened ring formation 18A. In the thickening 12A of the outer shell part 8, holes 21 are formed for screws 22 (see fig 5), which may be inserted via non-threaded bores 23 in the corresponding thickening 12B of the inner shell part 9.

In the area between two stiffening transverse flanges 24, 25, the inner shell part 9 is formed with a downwardly bulging cap portion 26 in which there is an opening being closed by the trigger 4, which, when being pushed in, may actuate an electric connector 28. Not only the two shell parts 8, 9, but also the trigger 4 (see fig 5) may be made from a stiff plastic. In doing so, the detail that forms the trigger 4 may be applied in the opening in the cap portion 26 and be connected to the same along the edges thereof by means of a dense, flexible film, which is heat-sealed against the shell part 9. It is also feasible to utilize a plastic moulding technique where the trigger 4 and the shell part 9 are integrally moulded, the movability of the trigger being obtained by the fact that the same - entirely or partly - is formed from a plastic which is softer than the plastic in the shell part. In fig 9 is shown how the edge surfaces of the shell parts 8, 9, which are to be pressed against each other, advantageously may be formed with ridges 31, 32 (not shown in figs 5-7) overlapping each other, which form tight joints between the two shell parts. In fig 9 is also seen that the cable 2 in a conventional way includes an inner pipe, which defines a bore 33 through which a welding wire and a protective gas, respectively may be fed up to the pistol. Furthermore, a heavy conductor 34 is included in the cable in order to provide the pis- tol with power current, as well as two finer conductors 35 for control current to a connector 28, which in figs 5 and 6 is shown mounted on a supporting plate 29, which is fixed between the free edges of two side pieces 30 protruding from the inside of the shell part 8. Reference is now made to fig 5, which shows how the cable 2 is connected to a body pipe 36 via a connection cuff 37. In the front end of the pipe 36, a contact nozzle 38 is detachably mounted through which a welding wire may pass during melting of the same. At a distance from the cuff 37, a number of radial holes 39 are arranged through which a protective gas can pass. On the body pipe 36, a cage 40 having a thickened collar 41 may be applied. Along the envelope surface of the cage, a number of elastically compliant or resilient rings 42 are arranged, which are anchored in grooves in the envelope surface of the cage and have the purpose of being pressed against the inside of the pipe 3 serving as a gas nozzle. In this connection, it should be mentioned that the detachable retention of the gas nozzle pipe 3 in the cage 40 may also be provided in other arbitrary ways, e.g. by means of a single continuous screw spring.

The ribs 16A, 16B in the two sets of ribs at the rear ends of the shell parts 8, 9 are partially arched in order to define together a space 27 widening in the backward direction, as is best seen in fig 8. The front portions of the ribs clamp the cable when the shell parts are put together. However, in the space 27 widening backwards, the cable may be deflected in order to accommodate itself to different working positions for the pistol without being broken in an abrupt way. In this way, the need is eliminated for a particular rubber cuff in order to support the cable at the entrance in the pistol.

The assembly of the welding unit according to the invention is carried out in the following way: In a first step, the body pipe 36 is connected to the cable 2 via the cuff 37. In practice, the body pipe 36 is made from an electrically conducting material, such as copper. When assembling, it is ensured that the conductor 33 in the cable 2 is brought into contact with the body pipe. Furthermore, the conductors 35 for the control current are brought out from the cable and are connected to the connector 28 on the supporting plate 29. Furthermore, the cage 40 is pressed on to the outside of the body pipe 36, more precisely by being pushed inwards towards the cuff 37 so that the holes 39 are freely exposed in the area in front of the cage. The cage may be fixed to the body pipe only by press fit, although it is also feasible to use particular fixing members, e.g., radial screws in the collar 41. After this, the contact nozzle 38 is mounted, preferably by being screwed with a male thread in a female thread on the inside of the free end of the body pipe 36.

In the next step, the two shell parts 8, 9 are put together in order to form the pistol cover 1. To start with, the cable 2 together with the body pipe 36 are put into the shell part 8, the collar 41 on the cage 40 being applied in the space between the transverse flanges 14A, and the deflectable cable being located in the space between the side pieces 30. The supporting plate 29 for the connector 28 is snapped-on between said side pieces 30 in the position illustrated in fig 6. After this, the shell part 9 is mounted. This is carried out by the projections 20 being brought into engagement with the recesses 19, and then the screws 22 are tightened in the screw holes 21. In doing so, the pairs of projections and recesses form a rear male/female coupling, which together with the two single screws 22 is the single means which is needed in order to hold together the two shell parts to an integrated, stiff cover. In a final step, the gas nozzle pipe 3 is applied to the cage 42 by the simple measure of slipping-on the pipe on the cage, the snap rings 42 clamping the pipe. As is seen in figs 1-4, the pistol cover is formed with two grip-facilitating knurlings 43, 44, which in the example consist of a plurality of transverse ridges. More precisely, a first knurling 43 extends in the backward direction from the trigger 4 on the inside of the rear section 6 of the cover. In other words, the knurling 43 is formed on the inner shell part 9. The second knurling 44 extends in the main along the arched transition section 7 of the cover and is turned outwards. In other words, the knurling 44 is formed on the outer shell part 8.

A substantial advantage of the welding unit according to the invention is that the pistol included in the unit can be made of a few simple components, which may be assembled in a simple and fast way in connection with the final assembly; all while guaranteeing that the requisite obtuse angle between the gas nozzle and the handle part of the pistol is integrated in the pistol. As a gas nozzle, a simple, straight pipe may be used instead of the expensive so-called goose-necks that have been required in previously known welding pistols. Another advantage is that the gas nozzle and the contact nozzle may, if required, be replaced in a fast and simple way, these two components, thanks to the constructive simplicity thereof, being inexpensive. Furthermore, the work of mounting together the pistol and the cable becomes extraordinarily cost effective as a consequence of the fact that the number of working operations is small. Thus, the principal working operation merely consists of tightening two single screws. Furthermore, the completed pistol is ergonomically expedient, among other things, as a consequence of the two axially spaced-apart knurlings on the inside and the outside, respectively, of the pistol cover.

Thus, the hand may, in a grip-facilitating safe way, be applied not only in the area behind the manoeuvre trigger 4, but also considerably farther forward along the cover. In difficult work situations, the hand may accordingly be applied all the way up to the front stopper ring 12.

Feasible Modifications of the Invention

The invention is not limited solely to the embodiment described above and shown in the drawings. Thus, it is, for instance, feasible to use other connecting elements than screws, e.g., rivets, snap elements or the like, for the mutual fixation of the two shell parts in the pistol cover. It is also feasible to permanently unite the two shell parts with each other, e.g., by means of welding, such as ultrasonic welding.

Claims

1. Welding unit for protective gas welding, comprising a manually grippable pistol in the form of a long narrow, stiff cover (1) and a cable (2) connected to the pistol, which cable includes a bore (33) for feeding a welding wire to a contact nozzle (38) included in the pistol and a protective gas to a gas nozzle (3) included in the pistol, as well as conductors (34, 35) for leading, on one hand, operation current to the contact nozzle with the purpose of melting the welding wire, and, on the other hand, control current to a trigger (4) for controlling the function of the pistol, said nozzles (3, 38) being located concentrically along a geometric axis that extends at an obtuse angle (α) to the cable coming into the pistol, c h a r a c t e r i z e d in that the pistol cover (1) is formed with substantially straight front and rear sections (5, 6) , which transform into each other via an arched transition section (7) and extend in said obtuse angle (o;) to each other, and that the cable (2) is drawn through the rear section (6) as well as the transition section (7) up to a body pipe

(36) arranged in the front section (5), to which body pipe said nozzles (3, 38) are detachably connected.

2. Welding unit according to claim 1, c h a r a c t e r i z e d in that the body pipe (36) is centred and fixed in the front cover section (5) by means of an outer cage (40) having a collar (41), which is located in a ring-shaped seat (14) in the interior of the cover, a pipe coupling (3) serving as a gas nozzle being applied to the envelope surface of the cage (40) .

3. Welding unit according to claim 1 or 2, the cover being composed of two long narrow, cross-section-wise curved shell parts

(8, 9) , which are mutually joined along longitudinal pairs of edges (10, 11) pressed against each other, c h a r a c t e r- i z e d in that one of the shell parts (8) is in the form of a back-like outer piece having two partially concavely curved edge surfaces (10'), while the second shell part (9) is in the form of an inner piece having two partially convexly curved edge surfaces (11') to be pressed against the concavely curved edge surfaces (10') of the outer piece.

4. Welding unit according to claim 3, c h a r a c t e r i z e d in that the trigger (4) is included only in the inner piece (9) of the cover and is placed in the area of the arched transition section (7) between the front and rear sections (5, 6).

5. Welding unit according to claim 3 or 4, c h a r a c t e r- i z e d in that a grip-facilitating first knurling (43) extends backwards from the trigger (4) on an inside of the rear section (6) of the cover, and a second knurling (44) extends along the outside of the arched transition section (7) of the cover.

6. Welding unit according to any one of claims 3-5, c h a r- a c t e r i z e d in that the two shell parts (8, 9) are interconnected via a male/female coupling (19, 20) at the rear end of the pistol, as well as via a screw joint or the like (22) at the front end of the pistol.

7. Welding unit according to any one of claims 3-6, c h a r- a c t e r i z e d in that the two individual shell parts (8, 9) at the rear have sets of internal, longitudinal ribs^' (16A, 16B) , which are at least partially arched in order to define together a space (27) , widening in the backward direction, in which the cable (2) is deflectable.