Abstract:
A welding device for operating in exiguous spaces, in particular for butt-joint welding parts, e.g. tubes, includes a rotor equipped wih an orbiting welding-torch and connected to a driven motor through a flexible transmission member. A control and feed device communicates with the rotor and the torch through the flexible transmission member.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a welding device for operating in exiguous spaces, in particular for butt-joint welding parts, e.g. tubes. 
     Some apparatuses are already known, of the type comprising a module equipped with all mechanical and electrical components adapted to rotate about the parts to be welded together. 
     Such module includes the mechanisms for moving the electric torch and those for advancing the filler-metal, are feed and control circuits as well as circuits for controlling the angular position of the torch. The welding operations can be remotely controlled by means of a programmer. 
     Usually, the module is divided into two parts so as to allow the mounting and withdrawal thereof with respect to the parts to be welded together. 
     Such apparatuses are perfectly suitable for welding great lengths of heavy tubes with diameters of at least 50 millimeters. However, they require a large free space in the immediate vicinity of the welding area. 
     There also exist apparatuses of smaller volumes, capable of being introduced into a limited space and permitting the butt-joint welding of parts without the use of a filler metal, in particular tubes with an outer diameter of at least about 5 millimeters. 
     Such apparatuses are in the form of a portable tool provided with an openable rotor capable of being mounted about the parts to be welded. The rotor is driven by a crown-gear which, in its turn, can be divided into two parts. An electric torch is placed inside one of the rotor jaws. 
     In view of the reduced thickness of the rotor, it is not possible to introduce a filler-metal pouring device or an auxiliary fluid, so that such apparatuses can exclusively be used for the metal-to-metal fusion welding of the parts involved. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to obviate the above drawbacks. 
     More specifically, the present invention relates to a welding device for operating in exiguous spaces, in particular for butt-joint welding parts, e.g. tubes, such device including a rotor equipped with an orbiting welding-torch or electrode and a mechanism for the remote control of the rotor. The device specifically includes: 
     a control device connected to a driven rotor equipped with an orbiting welding torch through flexible transmission member, 
     a feed device supported by the control device and communicating with the rotor and the torch through the flexible transmission member. 
     This combination of features makes it possible to extend the present field of application of automatic welding by increasing the distance between the torch and the feed and control devices. 
     According to a preferred embodiment, the flexible transmission member comprise a connecting member, the stroke of which, in a direction parallel to the longitudinal axis thereof, is at least equal to its full wound length about the entire periphery of the rotor. 
     Within the ambit of the above embodiment, the means for rotating the driven rotor are connected to the inlet end of the connecting member, the parallel ducts of which are distributed between the control and feed devices. 
     According to a most preferred embodiment, the control device comprises a drum adapted to wind the connecting member, such drum being driven by a crown-gear in mesh with a motor provided with a speed-reducing device. 
     According to a variant, the control device comprises a carriage for transferring the connecting member, such carriage being movable along slide-ways via a translation motor provided with a speed reducer in mesh with a rack. 
     According to the invention, the feed device comprises connections necessary for operating the torch, such connections passing through parallel ducts of the connecting member and comprising at least a fluid-circuit and a filler-metal wire. In addition, such connections comprise at least an electrically-conductive cable for the torch. 
     In order to make it possible to adjust the electric arc during a welding operation, the control device comprises, on the one hand, connections necessary for operating the torch passing through the connecting member ducts, and, on the other hand, among such connections, at least one control cable connected to a rocking-lever articulated to the rotor, supporting the torch as well as the extremity of one of the ducts for the filler-metal. 
     Another object of the invention is to design the connecting member with a cross section in compliance with the conditions of of the particular device in use. To this end, the connecting member cross-section should be selected either from various quadrangular shapes, or from the group comprising circles, ellipses and related curves. 
     According to another preferred embodiment, it is contemplated to control the angular position of the torch by means of coding marks that, for any given advance of the connecting member, take account of the length changes due to the helical winding of the member about the rotor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features of the invention will appear from the following description given merely by way of example, with respect to the accompanying drawings, in which: 
     FIG. 1 is a view in elevation, partially in cross-section, of a preferred embodiment of the invention; 
     FIG. 2 is a plan view, in cross-section, of the embodiment of FIG. 1; 
     FIG. 3 is a perspective view of details of FIGS. 1 and 2; 
     FIG. 4 is a perspective view of a modified embodiment of the invention; 
     FIG. 5 is a side view of features relating to the winding of a connecting member according to the invention; 
     FIG. 6 is a perspective view illustrating in more detail the construction of the connecting member; and 
     FIG. 7 is a perspective view illustrating the connecting member coding-marks. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     According to a preferred embodiment shown in FIGS. 1 and 2, the device comprises a head 1, equipped with a rotor 2, adapted to rotate about a bearing 3 fixed to a support 4. 
     Bearing 3, support 4 and rotor 2 have a common bore 5 in conformity with the diameters of parts 6 to be butt-welded. A radial slot 7 in bearing 3 and in support 4, together with one jaw 2a of rotor 2 make it possible to introduce head 1 about parts 6. FIG. 1 represents jaw 2a as being open, as it appears when head 1 is being introduced or withdrawn. 
     In the embodiment shown in the drawings, in order to provide the normal rotation of rotor 2 in spite of radial slot 7, pressure rollers 8a, 8b applied against the cylindrical periphery 2b of the rotor are provided. 
     An arc-welding torch or electrode 10 and indexable guiding member 11 for filler-metal 12 are mounted at the extremity of a rocking lever 15, articulated to a pivot 15a integral with one side of the rotor (see also FIG. 3). 
     Rocking lever 15 is brought into abutment by means of a spring 15b and it is driven by a control cable 16, the operation of which will be described later on. 
     According to the invention, a tense connecting member 17 contains the required elements for maintaining the electric arc and, if necessary, allows fluids to flow and contains control member for positioning the torch. 
     To this end, one inlet extremity 17a of member 17 is connected to feed and control means to be described later on, whereas one outlet extremity 17b is fixed to the periphery of rotor 2. 
     In a preferred embodiment, tense connecting member 17 is in the form of a strip of rectangular cross-section containing ducts such as 17c, 17d, 17e . . .17n (FIG. 6), parallel with the longitudinal axis of the strip. 
     Ducts 17c to 17n, at outlet extremity 17b, are extended by end conduits 24a, 24b, 24c . . .24n, (FIG. 3 and 4) respectively through which filler-metal 12, control cable 16 and electrical lead 25 reach torch 10. Such end conduits can be constituted either by members linked to the above ducts, or by extensions of sheaths mounted in the ducts. 
     In FIG. 6 there is shown a tense connecting member 17 of rectangular cross-section capable of allowing a satisfactory winding of the strip and an easy distribution of the ducts. 
     Without departing from the scope of the invention, both other quadrangular shapes and cross-sections in the form of circles, ellipses or combinations of such curves can be adopted. 
     Preferently, tense connecting member 17 is made from an electrically non-conductive and heat-resistant material. 
     Torch 10 is insulated from the bulk of the device by appropriately mounting support 10a on rocking-lever 15, e.g. by means of an electrically non-conductive ceramic member. 
     FIGS. 1 to 3 illustrate feed means 18 and control means 20 adapted to co-operate through the winding of tense connecting member 17. 
     In this instance, extremity 17a is wound about a transfer means, namely a drum 18a, the rotation of which is controlled, e.g., by means of speed reducer 19a driven by a motor 19. 
     One face of drum 18a is provided with driving rollers 18c, 18d, actuated by a motor (not shown) comprising a speed reducer. In the vicinity of such face is placed a filler-metal magazine constituted by a spool 18b co-axial with drum 182 and capable of rotating independently of the latter. 
     Whenever rollers 18c, 18d drive filler-metal 12, the latter causes the spool to rotate so as to be unwound with respect to drum 18a. Such movement causes filler-metal 12 to be pushed along its respective duct (e.g. 17), whatever the drum angular position may be. 
     Filler-metal 12, which can be a wire or a tape, passes through end conduit 24a (FIG. 3), and then issues from the extremity of guide-member 11, in the vicinity of torch 10. 
     Current is fed to torch 10 through a brush 25a adapted to rub against a conductive ring 25b (a portion of which is shown in FIGS. 1 and 2), integral with drum 18a and coaxial with the latter. Ring 25b is insulated with respect to drum 18a and connected to lead 25, the latter being adapted to feed torch 10 after having passed through duct 17e (FIG. 6). 
     In addition, fluids (e.g. a gas, air or coolant water) can flow through ducts such as 17n after having been injected into member 17 through extremity 17a thereof. In such case, flexible fittings and/or rotary sealing joints (not shown) provide the necessary connections with circuits outside the device as described. 
     The means for controlling the position of torch 10 are illustrated in FIGS. 1 to 3. In this embodiment, control cable 16 slides freely in duct 17d or in an intermediate sheath immobilized in such duct. 
     One end of cable 16 is connected to rocking lever 15, whereas its other end passing through extremity 17a is fixed to a swing-piece 20c, actuated by a draw rod 20d connected to rotor 20b of a swinging jack 20a, e.g. of the electrical type, 
     All these control parts are housed in drum 18a. The movements of the rotor of jack 20a controlled by outer regulating means that do not form part of the present invention, cause cable 16 to slide in both directions with respect to the longitudinal axis of member 17. 
     Thus, rocking lever 15 will oscillate about its pivot 15a and bring torch 10 to its various positions dictated by the welding process (i.e. contact with the parts to be welded, initiation and maintenance of the electric arc). 
     Indexable guide-member 11 mounted on rocking lever 15 makes it possible to bring filler-metal 12 in close proximity to torch 10 and to orientate the same so as to achieve a very good fusion in the arc area. 
     In FIG. 4 are shown feed means 18 and control means 20 co-operating via rectilinear transfer means, namely a carriage 28 adapted to slide along guiding members 30a, 30b. According to this variant, inlet end 17a of member 17 is integral with carriage 28 and can thereby have imparted a rectilinear movement. 
     Guiding members 30a, 30b are integral with a support 31 (which is the equivalent of support 4 in FIG. 1) comprising bearing 3 of head 1, on the one hand, and with a gripping handle 34, on the other hand. 
     Carriage 28 supports spool 18b containing filler-metal 12, rollers 18c, 18d and their motor for causing filler-metal 12 to advance, jack 20a and also a translation motor 32. The latter actuates a speed-reducing device 32a in mesh with a rack 30c integral with guiding member 30a. 
     The device according to the invention operates as follows: jaw 2a is opened, so that parts 6 to be butt-welded can be introduced into common bore 5 of rotor 2, bearing 3 and support 4. 
     In the course of this operation, connecting member 17 is not yet wound about the periphery 2b of the rotor, and is fully located on drum 18a (as in FIGS. 1 and 2), or at a retracted position with carriage 28 pushed towards the extremities of guiding members 30a, 30b (arrow D in FIGS. 1 and 4). 
     Then support 4 is fixed, as in the above example, by outer means that do not form part of the invention, in order to cause the axes of parts 6 and of rotor 2 to coincide. 
     The operator then rotates the rotor manually so as to wind member 17 on the periphery 2b (FIGS. 1, 4 and 5, arrow E). Drum 18a of carriage 28 follow the course imparted by inlet end 17a (rotary or rectilinear translation). 
     When the torch has rotated by at least one turn with respect to its initial position (FIG. 5, arrow E), drum 18a, or carriage 28 is put in motion, drum 18a by motor 19 and the speed reducing device 19a thereof, and carriage 28 by motor 32, the speed reducing device 32a thereof and rack 30c. Connecting member 17 is therefore caused to unwind in the opposite direction (FIGS. 1, 4, 5, arrow D). At the same time, electric current is applied to torch 10 and filler-metal 12 is driven by rollers 18c, 18d, into its respective duct 17c. Rollers 18c,18d are actuated by motor 18e, in the case of FIG. 4. Control cable 16 is either pulled or pushed by swinging jack 20a so as to change the position of torch 10 with respect to parts 6 and to ensure a steady operation of the electric arc. 
     The welding operation is finished as soon as torch 10 has reresumed its initial position (FIG. 1, arrow D), and it is then possible to open jaw 2a and to remove the device. 
     Without departing from the invention, tense connecting member 17 might be wound about rotor 2 in such manner that, during the unwinding thereof, the torch rotates by more than one turn about parts 6 to be welded. 
     In order to make it possible to control the welding steps, the invention additionally provides coding marks for member 17, making it possible to determine the angular position of torch 10, allowing for the change of length of member 17 resulting from the helical winding thereof about rotor 2. 
     FIG. 7 shows grouped, with a view to simplification, various coding marks consisting, e.g., of notches 36 or bores 37 or of magnetic prints 38 spaced along connecting-member 17. 
     Such coding marks (36,37,38) move past a fixed sensing-device that does not form part of the invention, so as to provide, as mentioned above, information related to the torch angular position and, if desired, to the speed thereof.