WO2004035251A2

WO2004035251A2 - Method and device for removing and/or replacing electrodes of a welding clamp or a welding apparatus

Info

Publication number: WO2004035251A2
Application number: PCT/FR2003/003062
Authority: WO
Inventors: Matthieu Leymarie; Christophe Feron; Daniel Auchecorne
Original assignee: A.M.D.P.
Priority date: 2002-10-17
Filing date: 2003-10-16
Publication date: 2004-04-29
Also published as: FR2845938B1; FR2845938A1; AU2003286226A1; AU2003286226A8; WO2004035251A3; EP1551587A2

Abstract

The invention concerns a method using an electrode replacing station comprising a mobile (T,T') transfer head, whereof the movements are controlled by a processor coupled to the processor of the welding automaton so as to be placed in a theoretical working position marked relative to the theoretical position of the welding electrode to be replaced, as determined by the welding automaton, the transfer (T,T') head including an extractor (E) and a loader (C) capable of being arranged alternately coaxial to a transfer axis fixed relative to the head with an accuracy suitable for replacing the electrode.

Description

METHOD AND DEVICE FOR EXTRACTING AND / OR CHANGING ELECTRODES FROM A WELDING PLIERS OR A WELDING APPARATUS.

The present invention relates to an electrode changer capable of extracting and / or changing the electrodes of a welding gun or a welding device.

It applies in particular, but not exclusively, to the electrodes used in single or multi-point welding devices mounted on a fixed station or on board by robots.

Usually, these devices comprise two arms which are movable with respect to each other and each carrying at one of their ends a conical electrode-holder tip on which an electrode is forcibly engaged by conical fitting.

During welding, the two electrodes which are connected to a source of electrical energy pinch the parts to be welded, so as to generate, inside the zone to be welded, a high intensity electric current locally causing a rise in temperature (by Joule effect) at a level corresponding to the welding temperature.

The electrodes made of a material having a high electrical conductivity (such as copper), each comprise a cylindrical tubular body extended on one side by a tip terminated by a bearing face flat or spherical intended to come to bear on one of the two parts to be welded ("called active face").

The internal diameter of the tubular body is substantially complementary to that of the electrode holder so as to allow a conical engagement by force of the electrode on the support which ensures a joining of the two parts and which guarantees a good conduction of the electric current at the level of the junction.

Usually, the tip has a shape of revolution (for example frustoconical) tapering from the body to the bearing face, so as to converge the current lines towards the areas to be welded and to obtain, at level of these zones, the desired current density to reach the desired welding temperature.

Of course, these shapes are adapted to the nature of the parts that one wishes to weld and are therefore variable from one welding station to another.

It turns out that these electrodes are the seat of intense wear which quickly causes deformations of the nozzle and, in particular, of the bearing face. This wear is notably due to the establishment of electric arcs which form between the electrode and the part and which end up corroding the bearing face, it being understood that the more the electrode is deteriorated, the more arcs are formed , therefore the more intense the corrosion (with risk of deterioration of the parts to be welded) and the poorer the quality of the weld.

To avoid having to replace the electrodes too frequently, devices are used to break in the tips so that they regain their shape with the original precision. In fact, these electrodes can only undergo a limited number of laps beyond which it becomes necessary to replace them.

It turns out that this phase of replacing the electrodes is particularly delicate because it involves extraction of the electrode from its support. In general, the electrode adheres firmly to its support due to the initial force engagement and then to the effects of thermocompression welding exerted during welding. It is therefore often necessary to exert on the used electrode properly oriented impacts to cause it to take off. This is the reason why the automation of this replacement phase is difficult to envisage.

Nevertheless, solutions have already been proposed which make it possible to exert extraction forces on the electrode. In this case, the electrodes are brought one by one to an extraction station. In addition to the fact that these solutions are not always effective, they have the drawback of causing stresses on the welding tongs liable to cause damage either on the tongs or on the mechanism associated with it.

In an attempt to eliminate these drawbacks, the Applicant has already proposed, patent FR No. 97 03807, a method consisting in bringing the electrode carried by an arm of the clamp into an extraction station, then in carrying out the extraction using a wedge-shaped extraction part bearing between the annular face of the electrode and an annular shoulder of the electrode holder. This solution provides for the application of impacts on the extraction part and, simultaneously, of a tensile force on the electrode holders.

This solution is effective. However, it is only suitable for automatic welding machines whose electrode-holder clamps can be brought into the station. extraction and therefore do not apply to fixed or not very mobile welding stations.

Furthermore, an important technical problem which must be resolved in order to be able to carry out the extraction of a used electrode and then the installation of a new electrode results from the fact that these two operations, and more particularly the second, require a precision of the movements of the electrodes and their positioning in the extraction and loading stations, greater than the precision ensured by conventional welding machines. However, it is out of the question to review the design of automatic welding machines to solve the problems relating to the change of electrodes.

The object of the invention is therefore more particularly to provide a method which makes it possible to eliminate these drawbacks and to solve these problems, in a relatively simple, effective manner and which does not call into question the design and programming of automatic welding machines.

To this end, the invention provides a method involving an electrode changing station comprising a movable transfer head, the movements of which are controlled by a processor coupled to the processor of the welding machine so as to be able to be placed in a theoretical working position identified with respect to the theoretical position of the welding electrode that is to be replaced, as determined by the welding machine, the transfer head comprising an extractor and a charger that can be alternately arranged coaxially to a transfer axis fixed relative to the head, and with a precision suitable for carrying out an electrode change.

According to the invention, this method is characterized in that it comprises the following change sequence: - the displacement of the transfer head to bring it into its theoretical working position,

- the installation of the extractor, coaxial with the axis of the electrode (if it is not there beforehand), - the centering of the extractor on the electrode thanks to centering means associated with the extractor so as to obtain a precise alignment of the axis of transfer of the head on the axis of the electrode / electrode holder assembly, this centering causing a displacement of the transfer head,

- the blocking of the position of the transfer head at the end of centering, and the mechanical storage of this position,

- extraction of the electrode by the extractor,

- the positioning of the charger coaxially with the transfer axis, replacing the extractor, thanks to the previously memorized position, - the loading of a new electrode on the electrode holder.

Thanks to these provisions, it is freed from the imprecision of the actual position of the electrode with respect to its theoretical position determined by the automaton, and this, without having to intervene at the automaton.

In fact, centering of the extractor on the electrode may be carried out during the extraction phase. To this end, the extractor may involve a rotary jaw comprising a plurality of jaws arranged radially relative to the axis of rotation of the jaw, these jaws being able to pass from a deployed position, in which they delimit a space in which can engage the electrode, in a tight position in which they come to bear on the electrode by exerting on it a centering action, then clamping so as to be able to transmit an extraction torque to it. Advantageously, during the extraction phase, the machine may also be subjected to an axial force so as to exert on the electrode a helical tearing force.

Two embodiments of an apparatus for implementing the method according to the invention will be described below, by way of non-limiting examples.

A first embodiment of an apparatus will be described below with reference to the accompanying drawings in which:

Figure 1 is a schematic axial section of an electrode and an electrode holder secured to an arm of a welding robot clamp;

Figure 2 is a perspective view of a welding electrode transfer apparatus according to the invention; Figures 3 and 4 are top and side views of the apparatus shown in Figure 2;

Figures 5 and 6 are respectively perspective and side view of the extractor of the transfer device during the engagement phase on an electrode; Figures 7 and 8 are figures similar to Figures 5 and 6 showing the extractor in the release position with angular displacement;

Figure 9 is an axial section of the extractor;

Figures 10, 11, 12 are radial sections of the extractor; FIGS. 13, 14, 15 are views of a jaw for centering and driving the electrodes, comprising a plurality of jaws, respectively in the deployed position (jaws retracted), in the intermediate position and in the clamped position (jaws resting on the electrode);

Figures 16 and 17 are perspective views of the loader respectively in the engagement position and in the release position; Figures 18 and 20 are axial sections of the charger shown in Figures 16 and 17;

Figures 19 and 21 are top views, respectively of sections 18 and 20, of the loader shown in Figures 16 and 17; Figures 22 and 23 are axial sections of the pivoting device of the transfer head with locking control; FIGS. 24a and 24b are respectively an end view and an elevation view of the pivoting mechanism;

Figure 25 is a longitudinal view and an axial section through. reset mechanism; and

FIG. 26 is a partial view of the electrode transfer apparatus, showing the location of the pivoting devices and the reset mechanisms.

A second embodiment of an apparatus will be described below with reference to the accompanying drawings in which:

Figure 27 is a perspective view of a second welding electrode transfer apparatus according to the invention; Figure 28 is a side view of the apparatus shown in Figure 2;

Figures 29 and 30 are side views of the frame of the apparatus equipped with a shaper according to two options;

Figures 31 and 32 are perspective views of the shaper alone;

Figures 33 and 34 are side views of the shaper alone; Figures 35 and 36 are respectively cross sections, along a vertical plane, and longitudinal, along a horizontal plane, of the shaper alone;

Figure 37 is a perspective view of the positioner-blocker mechanism; Figures 38a, 38b, 38c are respectively a longitudinal view, an axial section and a cross section of the positioner-blocker mechanism;

Figures 39a 39b are respectively a longitudinal view and a cross section of the positioner-blocker mechanism;

Figures 40 and 41 are perspective views of the tool holder;

Figures 42, 43, 44 and 45 are cross sections of the tool holder;

Figure 46 is a perspective view of the transfer head; Figure 47 is a top view of the transfer head;

Figures 48, 49 are perspective views of the transfer head housing;

Figure 50 is a side view of the transfer head;

Figure 51 is a longitudinal section of the extractor; Figure 52 is a cross section of the charger;

Figure 53 is a perspective view of the stripped transfer head of the magazine;

Figures 54a, 54b, 55a, 55b, 56a, 56b, 57a, 57b, are top and bottom views of the extraction mechanism; Figures 58 and 59 are cross sections of the charger;

Figure 60 is a cross section of the loader drive mechanism;

Figure 61 is a longitudinal section of the feeder drive mechanism; and Figures 62, 63 are side views of the vertical positioning mechanism of the transfer head.

In this first example, the electrode transfer device according to the invention is intended for extracting and changing the welding electrodes fitted to the welding clamp of a conventional welding robot. As illustrated in FIG. 1, these electrodes 1 comprise a tubular body 2, slightly conical, open on the side of the largest base at the level of the radial face 3 and extended, on the other side, by a nozzle 4 having a profile of revolution stage comprising two successive chamfers 5, 6 ending in a convex shape 7.

This electrode 1 is intended to force-engage the conical end of an electrode holder 8 of the clamp so as to obtain a hold by wedging the electrode 1 on the electrode holder 8.

In the example shown in Figures 2 to 4, the clamp comprises two arms, one of which B1 is fixed relative to the frame of the robot, while the other B2 is mobile. Each of its two arms is terminated by an electrode holder on which an electrode of the above type can engage.

The arm B2 is actuated by a mechanism so as to be able to assume a position opposite the arm Bl, known as the closing arm, in such a way that the electrodes 1 ′, 1 ", as shown in FIG. 4, are arranged coaxially one part relative to the other, at a distance from each other which may for example correspond to the thickness of the parts to be welded, and a position remote from the arm Bl, called the opening, in which the electrodes 1 ′ 1 "are separated from each other. This mechanism is more particularly designed so as to exert opening and closing maneuvers with relatively high forces (extraction, pinching).

In this first example, the electrode transfer device A is secured to the frame of the welding robot by means of a plate P supporting the entire mechanism of the above-mentioned electrode transfer device A, or fixed to the ground and mobile in relation to the welding robot. The electrode transfer device A consists of an electric reduction motor M, the output axis of which drives a first arm 9; the shaft of said gear motor M is disposed along a vertical axis Z, parallel to the vertical plane containing the above arms Bl and B2; the arm 9 is perpendicular to the shaft of the reduction gear motor M and can thus pivot around said vertical axis Z in a horizontal plane. This also applies in a position along a horizontal or inclined axis.

On the end of the arm 9, opposite to that secured to the output shaft of the gear motor M, two structures are pivotally mounted carrying respectively two transfer heads T, T 'assigned to the electrodes carried by the arms. These pivoting assemblies are provided by two lockable pivoting mechanisms essentially comprising a cylindrical shaft 101 and a parallelepiped body 102 as shown in FIG. 22; the pivoting mechanism 10 is arranged such that its shaft 101 is secured to the arm 9 and oriented along an axis X perpendicular to the plane defined by the arm 9 and the axis Z; thus, the parallelepiped body 102 of the pivoting mechanism

10 can pivot around the shaft 101.

A second arm 11, in the shape of an inverted L, is integral with the body 102 of the pivoting mechanism 10, at the level of the upper end of the L; the other end of the L, the lower end, comprises a second pivoting mechanism 12; the second pivoting mechanism 12 essentially comprises a cylindrical shaft 121 and a parallelepiped body 122, as shown in FIG. 23, and is arranged in such a way that its parallelepiped body 122 is integral with the lower end of the second arm

11 and oriented along an axis Y perpendicular to the plane defined by the axes Z and X; thus, the shaft 121 of the pivoting mechanism 12 can pivot in the parallelepiped body 122. The axes X and Y compete at a point O ', O "corresponding to the point materializing the center of the barrel of the above electrodes 1', 1".

The shaft 121 of the pivoting mechanism 12, pivoting in the tubular body 122, is integral with a flange 13, C-shaped; the above-mentioned shaft 121 is perpendicular to the amount of the C representing the above-mentioned flange 13.

A cylindrical shaft 14 is made integral with the flange 13, passing right through it perpendicularly to the two wings of its C shape, defining an axis Δ of rotation; thus, the shaft 14, parallel to the upright of the C representing the above-mentioned flange 13, is perpendicular to the Y axis and can pivot in a plane normal to said Y axis.

The transfer head T has a shape close to a V, and is articulated around the cylindrical shaft 14, located perpendicular to the plane defined by said V shape, at the base of said V. At each end of said shape in V are located respectively the extractor and the welding electrode charger.

Thus, the transfer head T has four degrees of freedom defined by the four axes of rotation Z, X, Y, Δ; the two axes Z and Δ make it possible to bring either the extractor or the charger of said head in a coaxial position relative to the axis of the electrode 1 "; the axes X and Y define an approach sphere relative to the actual position of said 1 "electrode.

An assembly, comprising the elements 10 ′, 11 ′, 12 ′, 13 ′, 14 ′ and the corresponding axes X ′, Y ′, Δ ′, arranged head to tail relative to the assembly constituted by the elements 10, 11, 12, 13, 14 and the corresponding axes X, Y, Δ, secured to the arm 9, with an opposite end to that secured to the outlet axis of the gear motor M, constitutes the support for the transfer head T '. Thus, the transfer head T 'has four degrees of freedom defined by the four axes of rotation Z, X', Y ', Δ'; the two axes Z and Δ 'make it possible to bring either the extractor or the charger of said head in a coaxial position relative to the axis of the electrode l'; the axes X 'and Y' define an approach sphere relative to the real position of said electrode 1 '.

In the example shown in Figures 5 to 8, the transfer head T comprises a body 15, V-shaped, articulated around the cylindrical shaft 14, which is located at the base of said V; the aforesaid body 15 supports, at the two ends of its V-shape, an extractor E whose main axis Δl, in the rest position of said extractor, is collinear with the axis of rotation Δ of the transfer head T and a loader C whose main axis Δ3 is also collinear with the axis of rotation Δ of the transfer head T.

The extractor E which will be described in more detail later, essentially consists of a housing 16 supporting an extraction device 17 and a reduction gear motor 18; the extraction device 17 of the extractor E is arranged coaxially with the main axis Δl of said extractor; the gear motor 18 is arranged coaxially to an axis Δ2; the two axes Δl, Δ2 are collinear with the axis of rotation Δ of the transfer head T, said extractor E being in the rest position. The housing 16 of the extractor E is integral with the body 15 of the transfer head T by means of a cylindrical shaft 19, arranged in the end of the corresponding branch of the V shape of said head, so that the axis Δ0 of the cylindrical axis 19 is perpendicular to the plane defined by the axes Δ, Δl; thus, the housing 16 can slightly pivot around the cylindrical shaft 19, between a rest position corresponding to the collinearity of the two axes Δ, Δl, and a slightly oblique position, called extraction. The charger C which will be described in more detail later, essentially consists of a housing 20 supporting a barrel 21 and of a geared motor drive 22; the barrel 21 of the charger C is arranged coaxially with the main axis Δ3 of said charger; the gear motor 22 is arranged coaxially with an axis Δ4; the two axes Δ3, Δ4 are collinear with the axis of rotation Δ of the transfer head T. The housing 20 of the charger C is integral with the body 15 of the transfer head T at the end of the corresponding branch of the V shape of said head.

In the example shown in Figures 5 to 8, the transfer head T comprises a lifting device L, pivotally mounted around the shaft 14 of said transfer head T; the lifting device L comprises a plate 23, pivotally mounted on the shaft 14 at its lower end, beyond the flange 13, so that it can pivot around the cylindrical shaft 14 and not translate vertically along said cylindrical shaft 14 by means of shoulders not shown. Said plate 23 comprises a gear motor 24 actuating a bevel gear 25, which actuates a helical screw 26 whose axis is collinear with the axis Δ of the transfer head T; said helical screw 26 bears on the lower surface of the body 15 of the transfer head T and its upward and downward movement caused by the gear motor 24, makes it possible to move the assembly of the transfer head along the axis Δ defined by the cylindrical shaft 14.

Thus, the downward movement of the transfer head T allows the approach of the extractor E around the electrode; the upward movement of said transfer head T, preceded by the clamping operation of the electrode described in more detail later, allows the extraction of the electrode. In the same way, the downward movement of the transfer head T allows the charger C to approach the level of the electrode support, allowing the electrode to be changed; the upward movement of said transfer head T allows the magazine C to be released. Of course, the change operation electrode will be preceded by a rotational movement of said transfer head around its shaft 14, so as to bring the charger C in the position identical to that previously occupied by the extractor E.

In the example shown in Figures 9 to 15, the extractor E consists of a housing 16 supporting an extraction device 17 and a reduction gear motor 18; said housing 16 is integral with the transfer head T via the cylindrical shaft 19; the extraction device 17 of the extractor E is arranged coaxially with the main axis Δl of said extractor; the gear motor 18 is arranged coaxially with the axis Δ2; the two axes Δl, Δ2 are perpendicular to the upper external surface of the housing 16; the gear motor 18 is disposed below the housing 16, integral with said housing, and its drive shaft comprises in the upper part a pinion (not shown), which pinion drives a toothed crown 29 disposed in the middle zone of said housing 16; said toothed ring 29 drives a shaft 30, crossing vertically right through said housing 17 and its axis Δl ', collinear with the two axes Δl, Δ2, is located in the plane containing the axes Δl, Δ, closer to Δl axis than the Δ axis; said shaft 30 drives, at its upper part, close to the external face of the housing 16, a second toothed ring 31, which drives the extraction device 17; a cover 28 closes off the upper face of the housing 16, essentially at the level of said ring gear 31.

In the example shown in FIGS. 13 to 15, the extraction device 17 consists of a crown 32 comprising a plurality of teeth on its external periphery and a plurality of teeth on its internal periphery, the plurality of external teeth being in drive relation with said second ring gear 31; a plurality of jaws, five of which are shown in FIGS. 13 to 15, are arranged inside said ring 32, each pivoting around axes parallel to said axis Δl, said axes being located on a circumference of diameter between 70% and 90% of the original diameter said plurality of internal teeth; jaws 33 a to 33 e, pivoting about their respective axes 33 a 'to 33 e' each have a part in an arc of a circle concentric with their axis of rotation and a gripping part; said part in an arc, with an opening of between 100 ° and 180 °, comprises a plurality of teeth meshing with the opposite part of the plurality of internal teeth of said crown 32; the grip part has a slightly rounded tip.

Thus, during the clockwise rotation of said crown 32, by means of there toothed ring 31, of the axis 30 and of the pinion secured to the shaft of the reduction gear motor 18, the jaws 33 a to 33 e are rotated, also clockwise, around their respective axes 33 a 'to 33 e'; the extraction device 17 passes from the deployed position (jaws retracted) to a tight position (jaw resting on the electrode).

In the same way, during the rotation in the counterclockwise direction of said crown 32, by means of the toothed crown 31, of the axis 30 and of the pinion integral with the shaft of the reduction gear motor 18, the jaws 33 a to 33 e are rotated, also counterclockwise, around their respective axes 33 a 'to 33 e'; the extraction device 17 passes from the clamped position (jaws resting on the electrode) to the deployed position (jaws retracted).

The transfer head T, having its four degrees of freedom described above, will be driven by a self-centering movement of the extraction device 17 relative to the electrode during the rotation in a clockwise direction. said crown 32, gradually making the axis Δl coincide with the main axis of the electrode, as shown in FIGS. 13, 14, 15.

In the example shown in FIGS. 9 to 12, the extractor E comprises a drum 34, integral with the cylindrical shaft 30, in the middle zone of said cylindrical shaft 30, below the ring gear 29; the aforesaid drum 34 comprises on its periphery a plurality of ferromagnetic pads positioned opposite a plurality of electromagnetic angular position sensors 35a to 35c, integral with the housing 16, and arranged radially on said housing 16. The extractor E further comprises a disc 36, integral with the cylindrical shaft 30, below said drum 34, close to the underside of the housing 16; the aforesaid disc 36 comprises, in an angular sector between 90 ° and 130 °, a cylindrical zone surrounded on one side by a slight bell-shaped protuberance and on the opposite side, a hook oriented towards said cylindrical zone of the disc 36. The extractor E further comprises a piston 38, disposed radially to the aforesaid disc 36, along an axis contained in the plane defined by the axes Δ, Δl, Δl ', facing the peripheral surface of the aforementioned disc 34, passing through the housing 16 in the opposite direction to that of the extraction device 17; said piston 38 comprises at its internal end, opposite the disc 36, a pin 37 whose axis is collinear with the axis Δl ', and at its external end, a pin 39, whose axis is orthogonal to that of the pin 37; thus, the aforesaid disc 36, driven, clockwise, by the reduction motor 18, by means of its drive pinion, the toothed ring 29 and the cylindrical shaft 30, is present:

- in the so-called "locking" position when the hook is inserted on the pin 37, then

in the so-called “progressive clamping” position of the jaws during the rotation of the cylindrical zone, then in the so-called “tilting” position during the extraction of the piston 38 under the effect of the thrust of the protuberance of the disc 36 on the internal face of piston 38.

Thus, the so-called “locking” position makes it possible to keep the jaws retracted in the deployed position of the extraction device 17, in order to avoid possible contact of said jaws with the electrode during the positioning of the extractor E around the electrode; the so-called “progressive clamping” position of said jaws makes it possible to pass from the deployed position to the clamped position. To this end, an index i (FIG. 9) urged by a friction mechanism firstly ensures that the ring 33 for supporting the jaws is prevented from rotating. When the resistive torque exerted on this crown exceeds a predetermined threshold, the index i disappears to release the crown 33 which can then rotate in synchronism with the crown 32 with, however, a tightening hold due to the torque generated by the friction forces ; the third step called "tilting" allows said housing 16 to tilt slightly around the cylindrical shaft 19, the pin 39 being received in a recess, not shown, located in the body 15 of the transfer head T.

In the example shown in Figures 16 to 21, the charger C consists of a housing 20 supporting a barrel 21 and a reduction gear motor 22; the barrel 21 of the charger C is arranged coaxially with the main axis Δ3 of said charger and comprises a plurality of lids intended to receive the electrodes; the gear motor 22 is arranged coaxially with the axis Δ4; the two axes Δ3, Δ4 are collinear with the axis of rotation Δ of the transfer head T. The housing 20 of the charger C is secured to the body 15 of the transfer head T via a tenon / mortise connection at the end of the corresponding branch of the V-shape of said head. The gear motor 22 is disposed below the housing 20, integral with said housing, and its drive axis comprises in the upper part a disc 40 disposed between the upper wall of the housing 20 and the barrel 21. The barrel 21 is pivotally mounted around a shaft 41, which is integral with the housing 20 and is coaxial with the axis Δ3; a disc 42, of outside diameter less than the outside diameter of the barrel, is pivotally mounted around the shaft 41 and is arranged below said barrel 21; the disc 42 is made integral with the barrel 21 by two threaded screws 43, arranged axially. The disc 42 consists of a plurality of branches of a number equivalent to that of the plurality of lids situated on the barrel and intended to receive the electrodes; each branch, of equal length, widens from the center to the edge of the disc and forms a double plurality of points on the outer periphery of said disc; each branch is separated from the adjacent branches by a slot of equivalent shape and having two parallel edges; the end of each branch has a circular notch connecting the two points of the periphery of the disc 42; the set of branches represents a Maltese cross, the number of branches of which is equivalent to the number of electrodes placed on said barrel 21. The above-mentioned disc 40 has on its upper face, facing the above-mentioned disc 42, a on the one hand, a first tenon of cross section in a half-moon and, on the other hand, diametrically opposite, a tenon of circular section; the first tenon is intended to be housed in the notches of the branches of the disc 42; the second stud is intended to be housed in the slots separating said branches from the disc 42; thus, during a 360 ° rotation of the disc 40 around the axis Δ4, the first tenon then the second tenon drive the disc 42 in rotation around the axis Δ3 by a sector of angle equivalent to that of 'a branch and a slot of the aforesaid disc 42.

The angular displacement of the disc 42 is transmitted to the barrel 21 and thus makes it possible to position the electrode opposite the corresponding housing of the electrode holder.

As indicated above, each electrode comprises a tubular body 2 extended by a nozzle 4 having a stage revolution profile which comprises a chamfer 5 for connection between said tubular body 2 and said nozzle 4; an O-ring 46 is arranged around the electrode on said tubular body 2, near said chamfer 5, and makes it possible to maintain the electrode in a vertical position in the cover of barrel 21; the final positioning of the electrode in the corresponding housing of the electrode holder, that is to say the fitting, is carried out by a closing movement of the welding device. As indicated above, the transfer head T comprises an elevation device L, pivotally mounted around the shaft 14 of said transfer head T. Thus, the downward movement of the transfer head T allows the loader to engage and placing the electrode on the electrode holder; the upward movement of said transfer head allows the release of the charger C.

In the example shown in FIGS. 22 to 24, the pivoting mechanisms 10 and 12 comprise a cylindrical shaft, respectively 101 and 121, which can slide and pivot in the bore of a body of parallelepiped shape, respectively 102 and 122; the two mechanisms being of equivalent structure, we will limit ourselves to the example shown in FIGS. 22 and 24.

The cylindrical shaft 101 passes right through the parallelepipedic body 102 and is supported in the above body by two ball bushings 103 and 104, respectively disposed at the end of the said body near the end of the cylindrical shaft 101 integral with the arm 9, and close to a blocking device B.

In the example shown in FIG. 22, the locking device comprises a support cup 105, a locking washer 106, a support washer

107, a locking screw 108 and an end flange 109 of the above-mentioned parallelepiped body 102.

The body 102 comprises, on the side of the blocking device, an annular recess arranged coaxially with the axis X of said body; the above-mentioned recess contains the support cup 105, the locking washer 106 and the support washer 107.

The . support cup 105, of inverted L-shaped section, secured by its external face to the body 102, bears on the internal face of the recess and is freely traversed by the cylindrical shaft 101. The locking washer 106, in the form of a cup having a concavity facing the adjacent end of the body 102, is also crossed freely by the cylindrical shaft 101; its external face, of cylindrical shape, coaxial with the axis X, bears freely on the internal surface of the support cup 105.

The support washer 107, of rectangular section, is also freely traversed by the cylindrical axis 101; its external face, of cylindrical shape, coaxial with the axis X, bears freely on the internal surface of the recess of the body 102, at a distance from the support cup 105 greater than the displacement of the locking screw 108. The locking screw 108 comprises a sleeve, externally threaded and a cylindrical shoulder, coaxial with the axis X, allowing the gripping of the locking screw; the cylindrical internal surface of the threaded sleeve bears freely on the shaft 101; the threaded cylindrical outer surface is screwed into the end flange 109 of the body 102; the end of the threaded sleeve, opposite the gripping shoulder, bears on the support washer 107.

The end flange 109, of cross section equivalent to the body 102, is integral with the aforesaid body by a fixing means not shown, and comprises, coaxially with the axis X, a threaded surface, complementary to the threaded sleeve of the locking screw 108.

Thus, a rotational movement of the locking screw 108, clockwise (the thread being said to the right), causes the translation of the aforesaid screw taking support on the support washer 107 which, in turn, takes support on the locking washer 106, causing its radial deformation; this radial deformation has the effect of reducing the inside diameter and increasing the outside diameter of the said locking washer 106, causing the shaft 101 and the support cup 105 to join together and, consequently, the joining of the shaft 101 and the body 102. The counterclockwise reverse movement of the locking screw 108 causes the shaft 101 and the body 102 to become detached. In the example shown in Figures 24a and 24b, a disc 110 is integral with the end of the shaft 101 opposite to that concerned by the locking device B; the aforesaid disc 110 comprises on an area of its peripheral surface an arm, of the same thickness as the cylindrical part of the disc 110, arranged radially and comprising a cylindrical orifice, crossing the thickness of the arm and whose axis is parallel to the body X axis 102; this orifice is the housing of a stud secured to a reset mechanism which will be described below. Thus, the arm of the disc 110, integral with the shaft 101, pivots about the axis X and translates along said axis X, as a function of the relative movement between the shaft 101 and the body 102 of the pivoting mechanism with locking 10. It is the same for the arm of the disc 130, integral with the shaft 121 of the pivoting mechanism with blocking 12. A reset mechanism RZ, which will be described below, is reproduced in four copies, at a rate two reset mechanisms by pivoting device with lock; in fact, each pivoting device has, as indicated above, two degrees of freedom, namely: a rotational movement around the axis of the body of the pivoting device and a translational movement along the above-mentioned axis; thus, each degree of freedom is associated with a reset mechanism.

In the example shown in FIG. 25, the reset mechanism RZ, referenced 200, comprises a tubular part comprising two cylindrical sleeves of the same diameter 201 and 202, integral with one another by a third sleeve 203, of short length, of the same outside diameter and having a smaller inside diameter than that of the above sleeves

201 and 202; the assembly is coaxial with a main axis Δ5; two cylindrical ends 204 and 205 are respectively fixed to the sleeves 201 and

202 at their free end; each of the aforesaid ends 204 and 205 consists of a cylindrical sleeve whose internal surface is integral with the external surface of said cylindrical sleeves 201 and 202, and of a wall normal to the main axis Δ5; the end piece 204 has, at its wall normal to the main axis Δ5, a cylindrical orifice with a diameter less than the inside diameter of said central sleeve 203; a cylindrical shaft 206, sliding freely in the orifice of the wall of the end piece 204, penetrates the assembly consisting of the three sleeves 201, 202, 203, and comprises, near the internal end, a shoulder of equivalent length the length of the sleeve 203, and sliding freely in the inner cylindrical part of said sleeve 203; on either side of the shoulder of the cylindrical shaft 206, two other cylindrical sleeves 207, 208 with a length close to a third of that of the sleeves 201, 202, slide freely on the cylindrical shaft 206 and on the cylindrical part sleeves 201, 202 respectively; said sleeves 207, 208, positioned on either side of the shoulder of the cylindrical shaft 206, form, with said sleeves 201, 202 and said end pieces 204, 205, two cylindrical cavities 209, 210; each of said cavities 209, 210 contains a helical spring designed to be in slight compression, respectively 211 and 212; two flanges 213, 214 are secured respectively to the outer free end of the cylindrical shaft 206 and to the outer free wall of the end piece 205; said flanges 213, 214 constitute the fixing points of the reset mechanism. Thus, a displacement of the cylindrical shaft 206, caused by an external force, along the axis Δ5, causes additional compression of one of the two helical springs concerned; the external force ceasing, the cylindrical shaft returns to its initial position, its shoulder being in facing with the sleeve 203.

As indicated above, the pivoting devices with blocking 10, 12 each comprise two reset mechanisms corresponding to the two degrees of freedom that said pivoting devices with blocking 10, 12. In the example shown in FIG. 26, the second arm 11, in the shape of an inverted L, comprises at the upper end of the L, the pivoting device

10, and at the lower end of the L, the pivoting device 12; the cylindrical shaft 101 of the pivoting device 10 is coaxial with the axis X and integral with the first arm 9; the cylindrical shaft 121 of the pivoting device 12 is coaxial with the axis Y and integral with the flange 13 of the transfer head T.

The arm of the disc 110, integral with the shaft 101 of the pivoting device 10 comprises two tenons, one of which is coaxial with the shaft 101 and the other of which is perpendicular to said shaft 101; likewise, the arm 210, integral with the shaft

121 of the pivoting device 12, comprises two tenons, one of which is coaxial with the shaft 121 and the other of which is perpendicular to said shaft 121.

Thus, the pivoting device 10 comprises two reset mechanisms 200a, 200b; similarly, the pivoting device 12 comprises two reset mechanisms 200c, 200d.

The flange 213a of the reset mechanism 200a is integral with the first tenon of the arm of the disc 110 of the pivoting device 10.

The flange 214a of the reset mechanism 200a is secured to the vertical upright of the inverted L of the arm 11. The flange 213b of the reset mechanism 200b is secured to the second tenon of the arm of the disc 110 of the pivoting device 10.

The flange 214b of the reset mechanism 200b is integral with the body 102 of the pivoting device 10.

The flange 213c of the reset mechanism 200c is integral with the first tenon of the arm of the disc 130 of the pivoting device 12.

The flange 214c of the reset mechanism 200c is integral with the horizontal upright of the inverted L of the arm 11.

The flange 213d of the reset mechanism 200d is secured to the second tenon of the arm of the disc 130 of the pivoting device 12. The flange 214d of the reset mechanism 200d is secured to the body 122 of the pivoting device 12. Thus, the rotation of the arm 11 around the axis X and its translation along said axis X, relative to the first arm 9 on the one hand, and the rotation of the flange 13 around the axis Y and its translation along said Y axis, relative to the second arm 11 on the other hand, are automatically compensated, in the absence of blocking of the two pivoting devices 10, 12, by the four reset mechanisms 200a, 200b, 200c, 200d.

Thus, according to the first example described above, the electrode change sequence is as follows:

displacement of the transfer head T to bring it into its theoretical working position by pivoting of the arm 9 around the axis Z actuated by the gear motor M,

- installation of the extractor E, the transfer axis Δl coaxially with the axis of the electrode (if it is not there before),

- centering of the extractor E on the electrode thanks to the extraction device 17 associated with the extractor E so as to obtain a precise alignment of the transfer axis Δl of the transfer head T on the axis of l 'electrode / electrode holder assembly, this centering causing a displacement of the transfer head T,

blocking of the position of the transfer head at the end of centering by means of the locking screws 108, 128, respectively of the pivoting devices 10, 12,

- Extraction of the electrode by the extractor E by a rotational movement around the transfer axis Δl actuated by the gear motor 18, a translational movement along said axis Δl actuated by the gear motor 24 and a tilting movement of the extractor E around the axis Δ0 actuated by the gear motor 18, - insertion of the charger C by rotation of the transfer head T around the axis Δ, replacing the extractor E,

- rotation of the barrel 21 actuated by the gear motor 22 to allow the positioning of the new electrode relative to the electrode holder, - lowering of the charger C by translation actuated by the gear motor

24,

- change of a new electrode on the electrode holder,

- mounting of the transfer head T actuated by the gear motor 24,

- Return to the initial position of the transfer head T by pivoting the shaft 9 around the axis Z actuated by the reduction motor M.

Of course, the same operations, described above, will be carried out in the same way on the second electrode by means of the transfer head T ', simultaneously, that is to say that the operation on both electrodes at the same time.

In a second example, the electrode transfer device according to the invention is also intended for extracting and changing the welding electrodes fitted to the welding clamp of a conventional welding robot.

In the example shown in Figures 27 and 28, the clamp comprises two arms, one of which B1 is fixed relative to the frame of the robot, while the other B2 is mobile. Each of its two arms is terminated by an electrode holder on which an electrode of the abovementioned type can be engaged, that is to say one secured to the electrode holder of arm B 1, and one "secured to the electrode holder of arm B2.

In this second example, the electrode transfer device A is not secured to the frame of the welding robot; it rests on the ground, in the immediate vicinity of the welding robot. Furthermore, in the same way as the first example, the electrode transfer device which will be described, allows the two electrodes associated with the electrode holders of the two arms of the welding gun to be changed, by tilting the second arm after the replacement of the electrode of the electrode holder of the first arm.

The electrode transfer apparatus A comprises a column I of rectangular section, the main axis Z of which is vertical and parallel to the vertical plane containing the above arms Bl and B2.

Column I is secured, at its lower end, to a base S resting on the ground, and comprises three sub-assemblies:

- a CO shaper secured to the upper end of column I,

- a tool holder PO secured to the CO shaper, - a transfer head T, secured to the tool holder PO.

Furthermore, column I supports, opposite the welding robot, a tank BA for receiving used electrodes, and on the side opposite to said welding robot, an electronic unit BE containing the various command and control members of the welding machine. transfer of electrodes A.

Unlike the first example described above, this second example only has a single transfer head T making it possible to extract and replace the used welding electrodes on the two aforementioned arms Bl, B2, according to a process which will be described later.

The transfer head T comprises an extractor E and a charger C, substantially identical to those described according to the first example; the said transfer head T is integral with a tool holder PO, allowing a displacement of the transfer head T along two orthogonal axes Δl and Δ2, respectively the axis of translation, perpendicular to the plane defined by the two arms Bl, B2, and the axis of engagement / disengagement, perpendicular to the axis Δl, and contained in a plane parallel to the plane defined by the two arms Bl, B2.

The PO tool holder is integral with the CO conformator, allowing the PO tool holder to:

- move along an axis Δ3, perpendicular to the above axes Δl, Δ2,

- pivot around an axis Δ4, parallel to the axis of translation Δl, located at the welding electrode,

- move along an axis Δ5, parallel to the axis of translation Δl, - pivot around the axis Δ3.

All of said translations, along the axes Δl, Δ2, Δ3, Δ5, and said rotations, around the axes Δ3, Δ4, allows the extractor E to position itself precisely around the used electrode, extract it, then use the charger C to replace the used electrode with a new electrode in the precise position where the used electrode was previously located.

In the example shown in Figures 29 to 36, the CO shaper includes a central shaft CO whose axis is the above axis Δ3; said central shaft COi comprises at one of its ends a flange C0 ₂ , in the form of a disc, making it possible to. secure the above-mentioned tool holder PO to the central shaft COi; moreover, it is pivotally mounted and slidable in a parallelepipedic body C0 ₃ , by means of two bearings or bearings C0 ₄ , C0 ₅ , arranged at each end of said body C0 ₃ ; thus, the aforesaid central shaft COi can pivot around its axis Δ3 and move along said axis Δ3.

The parallelepiped body C0 ₃ comprises two ribs of the same thickness, and of width close to that of said body C0 ₃ , located symmetrically on either side of the body C0 ₃ , in a plane perpendicular to the axis Δ3, which plane is located approximately the first third of the length of the body C0 ₃ , close to the flange C0 ₂ . In each of said ribs are mounted two shafts C0 ₆ , C0 ₇ , whose respective axes are mutually parallel and perpendicular to the axis Δ3; the aforesaid shafts C0 ₆ , C0 ₇ are mounted to pivot and slide in their respective ribs by means of bearings, respectively C0 ₆₁ , C0 ₆₂ , C0 ₇₁ , C0 ₇₂ ; moreover, the shafts C0 ₆ , C0 ₇ emerge on either side of the width of their respective ribs.

A frame C0 ₈ , of rectangular shape and thickness close to that of the above-mentioned ribs, surrounds the above-mentioned body C0 ₃ at the level of the said ribs and is integral with the two shafts C0 ₆ , C0 ₇ , at the level of their emerging parts, while leaving sufficient play; thus, this clearance allows the assembly consisting of the body C0 ₃ and the central shaft COi to move in the frame COg along the above axis Δ5.

The above-mentioned shafts C0 ₆ , C0 ₇ emerge in their turn from the frame C0 ₈ on either side of said frame COg so as to be able to slide in two curved grooves situated in two walls C0 ₉ , CO ₁₀ ; the above walls C0 ₉ , COι ₀ are arranged in a vertical plane, on either side of said frame C0 ₈ , and integral with a horizontal sole CO _n , itself integral with the above-mentioned column I, at its the top part.

The two ribs, located in the COg frame each form an arc, the center of which is at point O corresponding to the point materializing the center of the barrel of the above electrodes 1 ', 1 ".

Thus, the axis Δ3 of the central shaft COi can pivot around the point O in a vertical plane, the axis Δ5 of translation of said axis Δ3 of the central shaft COi describing a cylindrical surface whose axis is horizontal and passes by point O. In other words, the central shaft COi can pivot around its axis Δ3, translate along said axis Δ3 and translate perpendicular to said axis Δ3 in a plane passing through the aforesaid axis Δ4, which plane can pivot around said axis Δ4, the above axis Δ4 passing through the above point O.

The frame C0 ₈ comprises, at the lower level, a rib extending downward, which is crossed by a shaft C0 ₁₂ whose axis Δ6 is parallel to the axes of the above trees C0 ₆ , C0 ₇ ; this COι ₂ shaft, rotatably mounted in the above rib of the frame C0 ₈ , emerges on either side of said rib; each of the two ends of the shaft CO ₂ is pivotally mounted in a flange CO ₃ , H-shaped; said ends of the shaft COι ₂ pass through the two upper arms of the H and are held by two screws secured to the shaft COι ₂ .

The other two lower arms of the H are crossed by a shaft C0 ₁₄ whose axis Δ7 is parallel to the axis Δ6; the aforesaid shaft CO] ₄ is pivotally mounted in an arm C0 ₁₅ ; the ends of the shaft C0 ₁₄ pass through the two lower arms of the H and are held by two screws secured to the shaft C0 ₁₄ .

The aforesaid arm COι ₅ , articulated at one of its ends by means of the shaft COι, is also articulated at the other end by means of a shaft COι ₆ whose axis Δ8 is parallel to the axis Δ7; the above-mentioned shaft C0 ₁₆ is pivotally mounted in the two branches of a C-shaped COπ base, integral with the sole COn; the ends of the shaft C0 ₁₆ cross the two branches of the C and are held by two screws integral with the shaft COι ₆ .

Thus, the flange COι ₃ , in the form of H, associated with the two shafts COι ₂ , CO], the arm CO ₁₅ , associated with the two shafts COι ₄ , COι ₆ , the base C0 ₁₇ , secured to the sole CO] _ls allow the CO _g frame to be held laterally.

The crew surrounding the central shaft COi consisting of the coφs C0 ₃ , the frame CO _s , the flange COι ₃ , the arm COι ₅ , and the shafts C0 ₆ , C0 ₇ , COι ₂ , COι ₄ , represents a certain mass, to which must be added the representative masses of the tool holder PO and of the transfer head T, the center of gravity of the assembly lying in a plane close to that defined by the sole COπ.

So as to maintain the assembly: mobile assembly of the CO shaper, tool holder PO and transfer head T, in equilibrium, that is to say to maintain the axis Δ3 passing through the point O corresponding to the point materializing the center of the barrel of the electrode, almost horizontal, two antagonistic systems act simultaneously. on said set.

A first connection system between the frame C0 ₈ and the column I or the associated sole COn, will exert an almost vertical force from bottom to top, the amplitude of which is close to the mass of the above-mentioned assembly. A second connection system between the COg frame and the walls C0 ₉ , COι ₀ , will exert two opposing forces.

Thus, the association of these two systems will keep the above mentioned in balance while ensuring a certain rigidity due to the presence of opposing forces.

The first system, as shown in Figures 29, 30, can take two forms:

- a first option (figure 29) comprising a counterweight associated with a cable and a return pulley pivotally mounted at the level of the sole

COn, the cable being secured, at one of its ends, to a guided sliding arm, itself secured to the frame C0 ₈ , and at the other end of the above against weight,

- a second option (Figure 30) comprising a gas spring secured, at one of its ends, to a fixing flange itself secured to the column I, and at the other end of a fixing flange itself secured to the frame C0 ₈ .

The second system, as shown in Figures 31, 33, 34, comprises two air springs COι ₈ , CO ₁₉ , exerting an almost vertical force, one from top to bottom and the other from bottom to top in bearing, on the one hand, on the walls C0 ₉ , CO ₁₀ and, on the other hand, on the frame C0 ₈ .

In fact, the gas spring C0 ₁₈ is integral, at its upper articulation with the frame C0 ₈ , and at its lower articulation with the wall CO ₉ . The gas spring CO ₁₉ is integral, at its lower articulation of the frame C0 ₈ , and at its upper articulation of the wall

The central shaft COi, associated with its mobile equipment previously described, can pivot around its axis Δ3, translate along said axis Δ3 and translate peφendicululaire to said axis Δ3 in a plane passing through the aforesaid axis Δ4, which plane can pivot around said axis Δ4, the aforesaid axis Δ4 passing through the above point O. Thus, four degrees of freedom are associated with said central shaft COi.

Furthermore, during the electrode change sequence, which will be described later, the extractor E is positioned precisely around the used electrode and consequently defines the positioning of the transfer head T; the corresponding position of the transfer head T must be kept to allow precise positioning of the charger C, when changing a new electrode.

In order to allow positioning of the transfer head T, each degree of freedom of the central shaft COi must be associated with a positioner-blocker mechanism PB. In the example shown in FIGS. 37, 38, 39, the positioner-blocker mechanism PB, referenced 300, comprises a tubular part comprising two cylindrical sleeves of the same diameter 301 and 302, integral with one another by a third sleeve 303, of short length, coming to cover one of the ends of each of the sleeves 301, 302, and having a smaller internal diameter than that of the sleeves 301 and 302; the assembly is coaxial with a main axis Δ0; two cylindrical ends 304 and 305 are respectively secured to sleeves 301 and 302 at their free end; each of the aforesaid ends 304 and 305 consists of a cylindrical sleeve whose internal surface is integral with the external surface of said cylindrical sleeves 301 and 302, and of a wall normal to the main axis Δ0; the end piece 304 comprises at its wall normal to the main axis Δ0 a cylindrical orifice with a diameter less than the inside diameter of said central sleeve + 303; a cylindrical shaft 306, sliding freely in the orifice of the wall of the end piece 304, penetrates the assembly consisting of the three sleeves 301, 302, 303, and comprises, near the internal end, a shoulder of equivalent length to the internal length of the sleeve 303, and sliding freely in the inner cylindrical part of said sleeve 303; on either side of the shoulder of the cylindrical shaft 306, two other cylindrical sleeves 307, 308 of a length close to a third of that of the sleeves 301, 302, slide freely on the cylindrical shaft 306 and on the cylindrical part sleeves 301, 302 respectively; said sleeves 307, 308, positioned on either side of the shoulder of the cylindrical shaft 306, form with said sleeves 301, 302 and said end caps 304, 305, two cylindrical cavities 309, 310; each of said cavities 309, 310 contains a helical spring designed to be in slight compression, respectively 311 and 312; a flange 313 is secured to the free external end of the cylindrical shaft 306 and constitutes a first point of attachment of the positioner-blocker mechanism PB. All of the elements referenced 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313 constitute the positioner part of the positioner-blocker mechanism PB.

Associated with the end piece 304, a housing of parallelepiped shape 314 is crossed by the free end of the cylindrical shaft 306; at the level of the cavity of said casing 314, surrounding the cylindrical shaft 306, two plates 315, 316, of rectangular shape, are arranged substantially peφendicular to the shaft 306 which passes through them; these two plates 315, 316, are pierced with a cylindrical orifice whose internal diameter is slightly greater than the external diameter of the shaft 306; said plates 315, 316 are arranged one opposite the other and each comprise, one facing the other, a blind hole for accommodating a compression spring 317, thus tending to separate the two plates 315 , 316 from each other. Opposite said blind holes, relative to the axis Δ0 of the shaft 306, two pins 318, 319, respectively associated with the plates 315, 316, whose main axis is peφendicular to the axis Δ0, are integral with the casing 314; thus, the two plates 315, 316 are kept pivoting one opposite the other and, being subjected to a spacing due to the presence of the compression spring 317, will make it possible to block the shaft 306 relative to the casing 314 .

A metal cable under sheath 320 is secured at one of its ends to the plate 315; disposed parallel to the axis Δ0, it passes through a metal tube 321, itself integral with the end piece 304 and pressing, at one of its ends, on the plate 316. Thus, a tensile force applied to the cable 320, relative to the casing 314, allows the plate 315 to be brought closer to the plate 316, so as to arrange them substantially parallel, which, consequently, frees the shaft 306 in translation.

All of the elements referenced 314, 315, 316, 317, 318, 319, 320, 321 constitute the blocking part of the positioner-blocker mechanism PB. Furthermore, the positioner-blocker mechanism PB comprises a stirrup 322, U-shaped, the axis of articulation ΔO ', crossing the two branches of the U, is peφendicular to the axis ΔO; this stirrup 322 is associated with the positioner-blocker mechanism PB, at the casing 314, by means of two shoulder screws 323, 324, integral with the casing 314, allowing said stirrup 322 to pivot freely around the axis ΔO '; a third shouldered screw 325, secured to the base of the U, is arranged so that its axis ΔO "is peφendicular to the plane defined by the axes ΔO and ΔO '.

All of the elements referenced 322, 323, 324, 325 constitute the second attachment point of the positioner-blocker mechanism PB.

Four positioner-blocker mechanisms PB1, PB2, PB3, PB4, are associated with the four degrees of freedom of the central shaft COi; more precisely, the fourth mechanism PB4 only includes the blocking part.

In fact, the central shaft COi comprises at its free end, opposite to that associated with the circular flange COi, a finger CO ₂₀ , secured at one of its ends, to the central shaft COi, and arranged peφendicular to the axis Δ3; at the other free end, the CO ₂₀ finger comprises a pin whose axis is parallel to the aforesaid CO ₂₀ finger; this pin determines the fixing point of two positioner-blocker mechanisms PB1, PB2, by means of their respective flange 313.

The positioner-blocker mechanism PB1 is arranged so that its main axis Δ0 is peφendicular to the axis Δ3 of the central shaft COj; the upper fixing point, as indicated above, is integral with the pin ₂₀ CO pin; the lower fixing point, at its shoulder screw 325, is located on a base C0 ₂ ι, itself secured to the coφs C0 ₃ ; thus, the PB1 positioner-blocker mechanism positions and blocks the central shaft COi in rotation around its axis Δ3, that is to say according to its first degree of freedom.

The positioner-blocker mechanism PB2 is arranged so that its main axis ΔO is parallel to the axis Δ3 of the central shaft COi; the upper fixing point, as indicated above, is integral with the pin ₂₀ CO pin; the lower fixing point, at the level of its shoulder screw 325, is integral with the coφs C0 ₃ ; thus, the positioner-blocker mechanism PB2 positions and blocks the central shaft COi in translation along its axis Δ3, that is to say according to its second degree of freedom.

The positioner-blocker mechanism PB3 is arranged so that its main axis ΔO is peφendicular to the respective main axes of the positioner-blocker mechanisms PB1, PB2; it is therefore peφendicular to the axis Δ3 of the central shaft COi; the upper fixing point, at its flange 313 is integral with the COg frame; the lower fixing point, at the level of its shoulder screw 325, is integral with the coφs C0 ₃ ; thus, the positioner-blocker mechanism PB3 positions and blocks the central shaft COi in translation along the axis Δ5, that is to say according to its third degree of freedom.

The PB4 positioner-blocker mechanism only includes the blocker part; it is arranged so that its main axis Δ0 is substantially parallel to the main axis Δ0 of the positioner-blocker mechanism PB 1; the upper fixing point, at its flange 313 is integral with a spacer C0 ₂ connecting the two walls C0 ₉ , COι ₀ , at their upper part, parallel to the sole COn; the lower fixing point, at the level of its shoulder screw 325, is integral with the frame C0 ₈ ; thus, the positioner-blocker mechanism PB4 blocks the central shaft COi in rotation around the point O, corresponding to the point materializing the center of the barrel of the electrode, that is to say according to its fourth degree of freedom. Furthermore, the above blocker part is associated with the two gas springs C0 ₁₈ , COι ₉ , previously described, in order to constitute the positioner-blocker mechanism PB4.

As indicated previously, each positioner-blocker mechanism PB1, PB2, PB3, PB4, comprises a metallic cable under sheath making it possible to unlock the corresponding shaft by pulling on said cable. These pulls will be performed automatically at the transfer head T, and will be described later.

The above transfer head is integral with the central shaft Cθ _! through the PO tool holder; it essentially consists of a so-called motorized "XY" table allowing the transfer head to move along the two orthogonal axes referenced Δl, Δ2.

The tool holder PO, as shown in FIGS. 40, 41, essentially comprises two orthogonal C-shaped cradles; a first cradle, integral with the central shaft COi belonging to the CO shaper, whose main axis Δ2 is located in a plane containing the axis Δ3 of the central shaft CO _l5 which first cradle supports and drives a second cradle whose l main axis Δl is peφendicular to the plane defined by the above axes

Δ2, Δ3.

The above second cradle supports and drives the transfer head T.

Since the central shaft COi can pivot around its axis Δ3, the axis Δ2 of the first cradle may not be vertical and the axis Δl of the second cradle may not be horizontal.

Furthermore, the central shaft COi is integral with the first cradle at its upper part; this arrangement makes it possible to obtain a pendulum effect of the tool holder assembly PO around the central shaft COi. Each of the aforementioned cradles, in the form of a C, comprises a driving mother screw whose axis corresponds to the main axis of said cradle, and two guide columns, of circular section, whose axes are parallel to said main axis of the cradle. The lead screw is kept pivoting in the cradle at the level of the two branches of the C; the two guide columns are secured to the cradle also at the level of the two branches of the C. Each of the mother screws is secured to one of its ends of a pulley, which is driven, by means of a belt, by an electric motor, which is secured to the cradle by means of a plate. At its other end, the lead screw is in connection with an angular position sensor also integral with the corresponding cradle.

Each of the mother screws drives a threaded nut in shape correspondence with the threads of the mother screw; a first nut of the first cradle drives the second cradle; a second nut of the second cradle drives the transfer head T. The drive of the second cradle or of the transfer head by the corresponding nut comprises a mechanism making it possible to obtain a certain elasticity, on either side of a equilibrium position, along the main axis of the corresponding cradle. Said mechanism makes it possible to position the mobile element of the cradle in abutment on either side of the movement of said mobile element.

In the example shown in FIGS. 40, 41, the first cradle P0 ₂₀ o, in the form of C, secured to the central shaft COi of the conformator CO by means of the circular flange C0 ₂ , comprises: - a screw mother PO ₂₀ ι, the axis of which is collinear with the main axis Δ2 of the cradle P0 ₂₀ o, pivotally mounted at the level of the two branches of the C, - two guide columns P0 ₂ o, PO ₂₀₃ , whose axes respectively Δ2 ', Δ2 "are parallel to the main axis Δ2, mounted integral with the two branches of the C, - a toothed pulley PO ₂₀ , mounted integral with the mother screw PO ₂₀ ι, at the upper end of said mother screw PO ₂₀ ι, a PO ₂₀ electric motor, the main axis Δ2 '"of which is parallel to the axis Δ2, mounted integral with a plate PO ₂₀₈ , which is integral with the upper branch of the C of the cradle P0 ₂₀ o,

a second toothed pulley PO ₂₀₅ , secured to the shaft of the electric motor PO ₂₀₇ , driving the pulley PO ₂₀₄ by means of a toothed belt PO ₂₀₆ ,

- An angular position sensor PO ₂₀₉ , the shaft of which is driven by the lead screw PO ₂₀ ι at its lower end, the coφs of said sensor PO ₂₀ ι being integral with the lower branch of the C of the cradle P0 ₂₀ o.

The second cradle P0 ₁₀ o, driven by the lead screw PO ₂₀ ι and guided by the guide columns P0 ₂ o ₂ , P0 ₂ o ₃ of the first cradle, comprises:

- a lead screw PO ₁₀₁ , whose axis is collinear with the main axis Δl of the POioo cradle, pivotally mounted at the two branches of the C, - two guide columns POι ₀₂ , POι ₀₃ , whose axes respectively

Δl ', Δl "are parallel to the main axis Δl, mounted integral with the two branches of the C,

- a notched pulley POι ₀₄ , mounted integral with the mother screw POioi, at a first end of said mother screw POioi, - an electric motor PO ₁₀ , whose main axis Δl '"is parallel to the axis Δl , mounted integral with a plate POι ₀₈ , which is integral with the corresponding branch of the C of the POioo cradle,

a second toothed pulley POι ₀₅ , secured to the shaft of the electric motor POι ₀ , driving the pulley PO ₁₀₄ by means of a toothed belt POι ₀₆ ,

- an angular position sensor POι ₀₉ , the shaft of which is driven by the POioi mother screw at the second end, the coφs of said PO ιoι sensor being integral with the corresponding branch of the C of the cradle

POioo- In the example shown in Figure 42, the first cradle is shown in cross section along the plane defined by the axes Δ2, Δ3; in the example shown in Figure 43, the first cradle is shown in cross section along the plane containing the axis Δ2 and peφendicular to the axis Δ3.

The PO ₂₀ ι lead screw is pivotally mounted:

- On the one hand, in the upper branch of the C of the cradle P0 ₂₀ o, by means of a bearing P0 ₂ n associated with a socket PO ₂ ι ₀ supporting at the free end of the mother screw PO ₂₀ ι the PO ₂₀₄ toothed pulley; moreover, the bearing P0 ₂ n is maintained in the cradle P0 ₂₀ o by means of a circlip P0 ₂ ι ₂ ,

- on the other hand, in the lower branch of C of the cradle P0 ₂ oo, by means of a bearing P0 ₂ , the corresponding free end of the mother screw PO ₂₀ ι being secured to the sensor shaft angular position PO ₂₀₉ -

The lead screw PO ₂₀ ι drives a threaded nut P0 ₂ ι, of partially circular section, which nut P0 ₂ ι ₄ slides freely in a cylindrical cavity P0 ₂ i ₅ , concentric with the axis Δ2; the cylindrical cavity P0 ₂ ι ₅ passes right through the POioo cradle at the level of the wall connecting the two branches of the C.

The aforementioned nut P0 _i4 is not directly integral with the POioo cradle, as indicated above, a mechanism makes it possible to associate said nut P0 ₂ ι with a degree of freedom along the axis Δ2. Indeed, the nut P0 ₂ ι ₄ is positioned between two rings P0 ₂ ι ₆ , P0 ₂ ι ₇ , of circular section, of length close to that of the nut P0 ₂ ι, and sliding freely in the cylindrical cavity P0 _{2 to} ₅ .

The above cylindrical cavity P0 ₂ ι ₅ is limited, at each of its ends, by two flanges P0 ₂ ι ₈ , P0 ₂ ι ₉ , integral with the cradle POioo, respectively at the upper level and at the lower level of said cradle POioo- The spaces in the cylindrical cavity P0 ₂ ι ₅ defined, on the one hand, by the ring P0 _2i6 and the flange P0 ₂ ι ₈ and, on the other hand, by the ring P0 ₂ ι ₇ and the flange P0 ₂₁₉ , respectively contain the springs PO ₂₂₀ and P0 ₂₂₁ , which springs P0 ₂₂ o and P0 ₂₂ ι are mounted in compression.

The admissible travel, along the axis Δ2, by the nut P0 _{2! 4} , is defined by two stops consisting of two plates P0 ₂₂ , P0 ₂₂₃ , housed in a recess P0 ₂₂₄ , and integral with the cradle POioo-

The P0 ₂₂₄ recess, of parallelepiped shape is located in the central part of the POioo cradle, the opening facing the POioi screw, its depth being slightly less than that of the deepest generator of the cylindrical cavity P0 ₂ ι ₅ , the width being close to three times the diameter of the mother screw POioi, and its length, along the axis Δ2, slightly less than the length equivalent to the sum of the lengths of the nut P0 _2i4 and the two rings P0 ₂ ι ₆ , P0 ₂ ι ₇ .

The rectangular plates P0 ₂₂₂ , P0 ₂₂₃ are located in the bottom of the abutment P0 ₂₂ , on either side of the nut P0 ₂ ι ₄ , and integral with the cradle POioo- In addition, the two rings P0 ₂ ι ₆ , P0 _2i7 , have a shoulder of smaller diameter than that of the cylindrical cavity P0 ₂ ι ₅ , on the side of their bearing face with the nut P0 ₂ ι ₄ . Thus, the abovementioned rectangular plates P0 _{2 2} , P0 ₂₂₃ have, at each of their ends, lugs coming to bear on the abovementioned shoulders of the two rings P0 ₂ ι ₆ , P0 _{2! 7} . On the other hand, the nut P0 ₂ ι ₄ has two flats, symmetrical with respect to the axis Δ2, located in a plane parallel to the plane defined by the axes Δ2, Δ3. Thus, the two rectangular plates P0 ₂₂₂ , P0 ₂₂₃ bear on the above-mentioned flats of the nut P0 _2J4 . The length of these bearing surfaces being greater than the length of the nut P0 ₂₁₄ , it can thus move on either side of the point of equilibrium by a distance equal to half the difference in length between the bearing faces of the two plates P0 ₂₂₂ , P0 ₂₂₃ , and the length of the nut P0 ₂ ι.

Finally, PO _202a , PO ₂ 02b, PO _203a , PO ₂₀₃ b ball rings, integral with the POioo cradle, allow the movement of said cradle along the guide columns, respectively PO ₂₀₂ , PO ₂₀₃ , integral with the cradle P0 ₂ oo -

In the example shown in Figure 44, the second cradle is shown in cross section along the plane containing the axis Δl and peφendicular to the axis Δ2; in the example shown in Figure 45a, the second cradle is shown in cross section along the plane containing the axis Δl and peφendicular to the axis Δ3; in the example shown in Figure 45b, the second cradle is shown in cross section along the plane containing the axis Δ3 and peφendicular to the axis Δl.

The POioi lead screw is pivotally mounted:

- On the one hand, in a branch of the C of the POioo cradle, by means of a PO bearing associated with a POn ₀ socket supporting at the free end of the POioi screw, the POι ₀ toothed pulley; moreover, the POm bearing is held in the POioo cradle by means of a POπ ₂ circlip,

- on the other hand, in the other branch of the C of the POioo cradle, by means of a POn ₃ bearing, the corresponding free end of the POioi lead screw being secured to the shaft of the angular position sensor PO ₁₀₉ .

The mother screw PO ₁₀₁ drives a threaded nut POn ₄ , of circular section; the aforesaid nut POn is not directly integral with the casing Ca of the transfer head T, as indicated above; a mechanism makes it possible to associate with said nut POπ a degree of freedom along the axis Δl. Indeed, the nut POιι is positioned between two rings POn ₆ , POn ₇ , of section circular, of length close to that of the nut POn ₄ , and sliding freely in a cylindrical cavity POn ₅ , concentric with the axis Δl.

A crew POn ₈ of the nut POn ₄ , of parallelepiped shape is maintained in a cavity in shape correspondence with said crew co POs POπg, in the housing Ca of the transfer head T. Said crew coφs POn ₈ includes:

- the cylindrical cavity POn ₅ , crossing right through the crew coφs, whose main axis is Δl, - a rectangular cavity PO _i20 forming a central light in the thickness of said crew co dudits whose main axis Δl l is perpendicular to the Δl axis and parallel to the Δ3 axis,

- Two cavities of oblong section POι ₂ ι _a , PO _i2 i _b , whose common axis Δ12 is peφendicular to the plane defined by the axes Δl, Δl l, and whose length is greater than the length of the nut POn.

Thus, the two rings POu ₆ , PO _n7 , located on either side of the nut POn ₄ , each have, on the side opposite their bearing face with said nut POn ₄ , a circular recess making it possible to accommodate a spring. Two flanges POn _9a , POn _9b , secured to the crew POn ₈ , each comprising a cylindrical orifice with a diameter slightly greater than the diameter of the mother screw POioi, seal the coaxial cavity POn ₅ and constitute a stop for each spring.

Two springs POι ₂₆ , POι ₂₇ , mounted in compression are thus held in the two cavities, located on either side of the nut POn ₄ , consisting of the cylindrical cavity POn ₅ and respectively, of the ring POπ ₆ and of the POn flange _9a , and POn ring ₇ and POn flange _9b .

The nut POπ is held between two half-moons POι _22a , POι ₂₂ , of width equal to a circular shoulder located on the periphery of said nut PO ₁₁₄ , internal diameter equal to the external diameter of said shoulder of the nut PO n ₄ and of external diameter slightly less than the thickness of the crew coφs POπ; said half-moons P0 _122a , POι _22b , are integral with the nut POn ₄ by two clamping screws not shown.

Two shoulder screws POι _23a , POι _23b , are screwed into the half-moons, respectively POι _22a , PO _mb along the axis Δ12; said shoulder screws POι _23a , POι _23b each maintain a ball bearing and a spacer, respectively POι _24a , POι _25a , and POι _24b , POι _25b ; the outside diameter of said ball bearings POι _24a , POι _24b is slightly less than the width of the oblong section of the above cavities POι ₂ ι _a , POi ₂ i _b -

Thus, the nut POn ₄ can move on either side of the point of equilibrium by a distance equal to half the difference between the length of the oblong section of the above cavities POι ₂ ι _a , PO _J i _b , and the outside diameters of the above ball bearings POι _24a , POι _24b .

Finally, ball rings POι _02a , POι ₀₂ b, POι _{0 a} , POι ₀ b, integral with the casing

Ca of the transfer head T, allow the displacement of said coφs along the guide columns, respectively POι ₀₂ , POι ₀₃ , integral with the cradle

POioo-

In the example shown in FIGS. 46, 47, the transfer head T comprises four sub-assemblies: - an extractor E, intended to allow the transfer head T to be positioned around the electrode to be extracted, then to extract it by pinching said electrode followed by a rotational movement, - a charger C, intended, after displacement of the transfer head T, to replace the extractor E, to place the new electrode on the holder electrode, - a motorized group Mo, intended to drive the extractor E in rotation, to activate and deactivate the positioner-blockers,

- A mechanism Me, intended to drive the charger C in rotation associated with the movement of the transfer head T during its movement from the "charger position" to the "extractor position".

The aforesaid transfer head T consists of a housing Ca, of complex shape, essentially parallelepiped, associated with two plates Pex, Pmo, respectively "extractor plate" and "motor plate". In the example shown in FIGS. 48, 49, the casing Ca includes a number of bearing surfaces, flat and cylindrical, making it possible to position and secure the following sub-assemblies:

- the crew cost POng of the tool holder PO, oriented along the axis Δl,

the ball rings POι _02a , POι _02b , POι _03a , POι ₀₃ , for guiding the columns POι ₀₂ , POι ₀₃ , whose main axes, respectively Δl ',

Δl ", define with the Δl axis a so-called reference plane II assumed to be vertical,

the motor plate Pmo, secured to the casing Ca along a vertical bearing face peφendicular to the reference plane π and disposed at one end of said casing Ca, supporting a motor whose main axis Δ9 is parallel to the reference plane U, and a transmission by pulleys and toothed belts,

a lead screw, driven by the above transmission, the main axis Δ10 of which is parallel to the reference plane π, associated with a rack concentric with said lead screw,

- a shaft, pinion, ball bearing, cam, extractor drive assembly, the main axis Δ6 of which is perpendicular to the axis Δl and parallel to the reference plane π, said assembly being associated with the said rack , - the Pex extractor plate, secured to the casing Ca along a horizontal support face peφendicular to the reference plane π and disposed at the other end of the housing Ca, supporting the crown of the electrode extractor, whose main axis Δ7 is parallel to the axis Δ6,

- a shaft, pinion, loader plate assembly, the main axis Δ8 of which is parallel to the axis Δ6, and disposed close to the aforesaid Pmo motor stage, - a shaft, pinion, drum, ratchet, drive of the above-mentioned drive assembly loader plate, whose main axis Δl l is parallel to the axis Δ6, and disposed close to the axis Δ8,

- a drive rack of the previous assembly, whose main axis Δ12 is parallel to the reference plane II.

In the example shown in FIG. 50, the transfer head T comprises, as indicated above, the motor plate Pmo comprising:

- a Ti motor, not shown in FIG. 50, secured to the above-mentioned plate on the opposite side, - a first toothed pulley T ₂ , secured to the motor shaft Ti whose main axis is Δ9,

a second toothed pulley T ₃ , integral with the same shaft whose main axis is Δ13, of a third pulley T ₄ ,

a fourth pulley T ₅ , integral with a shaft T _{] 0} , not shown in FIG. 50,

a first belt T ₆ for driving the above pulleys T ₂ , T ₃ ,

a second belt T ₇ for driving the above pulleys T ₄ , T ₅ ,

- a mechanism T ₈ making it possible to tension the above-mentioned belts T ₆ , T ₇ simultaneously, - a friction mechanism T ₉ , or torque limiter, making the above-mentioned pulley T ₅ integral with the shaft Tι ₀ .

Furthermore, the pulleys T ₂ , T ₄ , are of diameters smaller than those of the pulleys T ₃ , T ₅ , so as to reduce the angular rotation speed of the shaft Tι ₀ relative to that of the motor shaft Ti and thus to increase the torque transmitted by said shaft Tι ₀ . In the example shown in FIG. 51, the above-mentioned motorized group Mo comprising the plate Pmo, the motor Ti, the pulleys T ₂ , T ₃ , T ₄ , T ₅ , the belts T ₆ , T ₇ , drives the shaft Tι ₀ of the extractor sub-assembly E by means of the friction mechanism T ₉ . In fact, the shaft T ₁₀ comprises, over approximately a quarter of its length, a cylindrical surface supporting a bush Tu, integral with the shaft T ₁₀ ; the aforesaid bush Tu is made integral with the pulley T ₅ by means of the friction mechanism T ₉ , bearing on the pulley T ₅ by means of another bush Tι ₂ , in two parts enclosing said pulley T ₅ . The cylindrical bearing of the shaft Tι ₀ also supports two ball bearings Tι ₃ , Tι ₄ , integral with the casing Ca of the transfer head T; thus, the Tio shaft is pivotally mounted in said housing Ca.

The Tι ₀ shaft also comprises, over approximately three quarters of its length, a threaded part, constituting a lead screw. This threaded part drives a rack Tι ₅ , of cylindrical section whose main axis is collinear with the axis Δ10, the bore of said rack T ₁₅ being threaded in accordance with the shape of the threaded part of the shaft Tι ₀ . The rack Tι ₅ has two parallel flats, arranged over its entire length, symmetrical with respect to the axis Δ10, the two flats being parallel to the so-called reference plane π.

One of the above-mentioned flats has a series of straight teeth, the other flap constitutes a guide bearing in rotation, the rack T _{] 5 being} able to slide in the housing Ca by means of two guide rings Tι ₆ , Tι ₇ , integral with the housing Ca , located at the opposite end to that of the cylindrical bearing of the shaft T ₁₀ . A guide roller Tι ₈ , located between the above rings T _i6 , T ₁₇ , whose axis Δ14 is parallel to the plane called reference II and perpendicular to the axis Δ10 of the rack Tι ₅ , is supported on the flat constituting the anti-rotation guide range.

Thus, a rotational movement of the shaft Tι ₀ , around the axis Δ10, causes a translational movement of the rack Tι ₅ , along said axis Δ10; which translational movement of the rack T ₁₅ causes a rotational movement of a pinion Tι ₉ , secured to a shaft T ₂₀ , whose main axis is the axis Δ6, previously defined, the teeth of said pinion ι ₉ being conformity of form with the abovementioned series of straight teeth of the rack T ₁₅ .

In the example shown in FIG. 52, the drive assembly of the extractor E, whose main axis Δ6 is peφendicular to the axis Δl and parallel to the so-called reference plane II, said assembly being associated with the the aforementioned rack Tι ₅ , includes: - the Pex plate, defined above, secured to the housing Ca,

- two Pexa, Pexb plates, located on either side of the Pex plate, around a bore, located in the Pex plate, whose axis is Δ7, previously defined,

- the shaft T ₂₀ , the main axis of which is collinear with the axis Δ6, pivotally mounted by means of two ball bearings T ₂₁ , T ₂₂ , integral with the casing Ca, and located approximately in the central part of said tree T ₂₀ ; furthermore, said shaft T ₂₀ has a shoulder in excess thickness close to the upper bearing T ₂₂ ,

the drive pinion Tι ₉ , integral with the shaft T ₂₀ , at the level of the lower part of said shaft T ₂₀ ,

- A shaft T ₂₃ , the main axis of which is collinear with the axis Δ6, is integral with the aforesaid shaft T ₂₀ at its lower end, and drives an angular position sensor T ₂₄ , the stator of which is integral with the casing Ca, - a pinion T ₂₅ , the main axis of which is collinear with the axis Δ6, mounted clamped between two lower and upper coaxial rings, respectively T ₂₆ , T ₂₇ ,

two lower and upper coaxial friction washers, respectively T _25a , T _25b , mounted respectively between the ring T ₂₆ and the pinion T ₂₅ , and between the ring T ₂₇ and the pinion T ₂₅ , . - a tightening nut T ₂₈ , mounted on a threaded part, in shape correspondence, located at the upper end of the shaft T ₂₀ ,

- a set of washers, having a certain radial elasticity, located between the tightening nut T ₂₈ and the upper coaxial ring T ₂₇ , - a third ball bearing T ₃₀ , located on the abovementioned shoulder of the shaft T ₂₀ ,

- A cam T ₃ ι, pivotally mounted around the shaft T ₂₀ , by means of the aforesaid ball bearing T ₃₀ .

Thus, the two coaxial rings T ₂₆ , T ₂₇ , integral with the shaft T ₂₀ in rotation, and being able to slide freely on said shaft T ₂₀ , secure the pinion T ₂₅ of the shaft T ₂₀ by means of two washers coaxial friction T _25a , T _25b , thanks to the tightening carried out by the nut T ₂₈ pressing on the ring T ₂ via the set of washers T ₂₉ , the ring T ₂₆ being supported on the abovementioned shoulder in extra thickness of the shaft T ₂₀ .

Furthermore, a pin, not shown, whose main axis is parallel to the axis Δ6, integral with the coaxial ring T ₂₆ , rotates the cam T ₃ ι.

Consequently, during the rotation of the shaft T ₂₀ , causing the blocking of the electrode extraction mechanism, by means of the pinion T ₂₅ , said coaxial friction washers T _25a , T _25b make it possible to ensure , by friction effect, the partial rotation of the cam T ₃ ι.

The electrode extraction mechanism is identical in all respects to the mechanism described above, concerning the first example of an electrode transfer device according to the invention, said extraction mechanism being coaxial with the axis Δ7, housed in the above bore of the Pex plate and maintained between the two lower and upper plates, respectively Pexa, Pexb.

In the example shown in FIG. 53, the extractor E comprises, in addition to the elements described above, an articulated arm T ₃₂ , oscillating around a shaft T ₃₃ , the central axis Δ15 of which is parallel to the axes Δ6, Δ7 and situated at the top of an isosceles triangle whose base is defined by said axes Δ6, Δ7; this swing arm T ₃₂ is actuated, in its central part, by the cam T _3i ; it has at one end, close to its axis of articulation Δ15, a locking lug oriented towards the extractor, and at its other end a hinge shaft T ₃₄ making it possible to drive, in horizontal translation, a shoe T ₃₅ , which drives, via four cannons T _{36aι b,, d,} the four sheathed cables which actuate the four positioner-blockers PB1, PB2, PB3, PB4.

Thus, the articulated arm T ₃₂ controls, via the cam T ₃₁ , on the one hand, the extractor in the clamping position and, on the other hand, the blocking or unblocking of said positioner-blockers, depending on the angular position of said cam T ₃₁ .

In the example shown in Figures 54, 55, 56, 57, the extractor E is shown in top view (Figures 54a, 55a, 56a, 57a) and in bottom view (Figures 54b, 55b, 56b, 57b ). Note that part of the pinion T ₂₅ is cut away so as to indicate the shape of the cam T _3J in the vicinity of the articulated arm T ₃₂ .

Two locking pins T ₃₉ , T ₄₀ , located in the corner opposite to the shaft T ₃₄ of the Pex plate, are arranged on either side of the extractor; both are urged each by a compression spring, not shown, so as to be in contact, respectively, with the upper part T ₃₈ ι and with the lower part T ₃₈₂ , of the jaw support crown T ₃₈ .

The aforesaid jaw support crown T ₃₈ comprises five jaws T _38a , T _38b , T _38c , T ₃ g _d , T _38e , not shown, articulated respectively around the shafts T _{38a '} , T _38b' , T _38c >, T _38c i _' , T _38e >. A toothed crown T ₃₇ , concentric with the jaw support crown T ₃₈ , is driven by the pinion T ₂₅ , and in turn, drives the toothed parts of said clamping jaws T _38a , T _38b , T _38c , T _38d , T _38th .

This assembly is identical to that described above under the first example of an electrode transfer device.

FIGS. 54 to 57 represent the four stages concerning the blocking of the electrode in the extractor and the rotation of said electrode so as to separate it from its electrode holder.

During the first step, the cam T ₃ ι pushes the articulated arm T ₃₂ , so that:

on the one hand, the lug of said arm is inserted into a notch in the lower part T ₃₈₂ of the jaw support ring T ₃₈ , blocking in rotation the jaw support ring T ₃₈ ,

- On the other hand, the shaft T ₃₄ drives the shoe so as to pull on the cables of the four positioner-blockers, causing the unlocking of said positioner-blockers.

During this first step, the pinion T ₂₅ rotates counterclockwise, the toothed crown T ₃₇ rotates clockwise, which, by reaction effect due to the presence of said jaws, tends to rotate the support crown jaws T ₃₈ counterclockwise; moreover, said jaw support ring T ₃₈ is locked in rotation, on the one hand, by the lug T ₃₉ at the level of the upper part T ₃₈₁ and, on the other hand, by the lug of the arm T ₃₂ at level of the lower part T ₃₈₂ .

Note that the directions of rotation, clockwise / anti-clockwise, are defined for the top views.

The blocking of the jaw support crown T ₃₈ and simultaneously the rotation of the toothed crown T ₃₇ have the effect of rotating the five jaws T _38a , T _38b , T _38c , T _38d , T _38e which thus come into contact with the electrode; this step is the second.

At the end of a certain angle of rotation of the pinion T ₂₅ and consequently of the cam T ₃₁ , the latter releases the thrust on the articulated arm T ₃₂ , thus releasing the lug of said arm on the lower part T ₃₈₂ , as well as the traction on the four cables of the positioner-blockers; thus, during the third stage:

- the positioner-blockers are locked in their respective position, - the crowns T ₇ , T ₃₈ are driven clockwise,

- the electrode is also driven clockwise and separates from its electrode holder.

At the end of a rotation of the assembly T ₂₅ , T ₃₇ , T ₃₈ by approximately 180 degrees, the lower lug T ₄₀ engages in a notch located in the lower part T ₃ g ₂ ; which has the effect, during the fourth step, of blocking the rotation of the jaw support crown T ₃₈ and of maintaining the electrode between the five clamping jaws.

The reverse rotation of the pinion T ₂₅ , following the reversal of the direction of rotation of the motor T frees the electrode from the clamping jaws and returns to the initial position corresponding to the above first step.

In the example shown in Figures 58, 59, 60, 61, the charger C consists of a barrel T ₄ ι whose main axis is the axis Δ8; said barrel T _4J comprises a plurality of lids intended to receive the electrodes; unlike the barrel, referenced 21, of the first example of an electrode transfer apparatus, said barrel T ₄₁ comprises lids which can alternately receive electrodes, the tubular part of which is sometimes oriented upwards, sometimes oriented downwards; a metal ring elastic, not shown, keeps the electrodes in the lids.

A shaft T ₂ , pivotally mounted in the casing Ca, makes the above-mentioned barrel T ₄ ι integral with a disc T ₄₄ which, by means of a nut T ₄₃ , is screwed at the level of the upper part of said shaft T ₄₂ .

The disk T ₄₂ is identical to that described in the first example under the reference 42; it includes, identically, a plurality of branches of a number equivalent to that of the plurality of lids situated on the barrel, all of these said branches representing a Maltese cross.

A disc T ₄₅ , the main axis of which is Δl l, comprises, in the manner previously described under the reference 40, a first tenon of section in a half-moon T ₄₆ (ex 44) and a second tenon of circular section T ₇ (ex 45).

The above-mentioned disc T ₄₅ is secured to a shaft T ₄₉ , which is secured to a disc T ₅₀ , the assembly being coaxial with the axis Δl 1.

The 360 degree rotation of this assembly around the axis Δl l, the first tenon T ₄₆ then the second tenon T ₄₇ drive the disc T ₄₄ in rotation around the axis Δ8 by a sector of angle equivalent to that a branch and a disc slot T ₄₄ .

The angular displacement of the disc T ₄₄ is transmitted to the barrel T ₄ ι and thus makes it possible to position the electrode opposite the corresponding housing of the electrode holder.

The 360 degree rotational drive of the assembly T ₄₅ , T ₄₈ , T ₅₀ is carried out by means of a rack T ₅₂ , the main axis of which is Δ12; the aforementioned rack T ₅₂ drives in rotation, during its longitudinal displacement, a free-rotating equipment around the shaft T ₄₈ , namely: a pinion T ₄₉ , in connection with the above rack T ₅₂ and a drum T ₅ ι, integral with the above pinion T ₄₉ .

The drum T ₅ ι comprises a ratchet T ₅₄ whose axis of rotation Δl l "is parallel to the axis Δl l, which ratchet is in shape correspondence with a notch made on the peripheral surface of the disk T ₅₀ ; during the rotation of the drum T ₅₁ , driven by the translation of the rack T ₅₂ , the ratchet T ₅ in turn drives the disc T ₅₀ and therefore the disc T _45. The backward movement of the rack T ₅₂ does not cause the disc T ₅₀ , given the non-reversibility of the ratchet T ₅ and the presence of a second ratchet T ₅₃ in correspondence of shape with a notch on the peripheral surface of the disc T ₄₅ , which ratchet T ₅₃ has its axis of rotation Δl parallel to the axis Δl l.

The round-trip movements of the above rack T ₅₂ are carried out during the movements of the transfer head T; in fact, the rack, passing right through the casing Ca, protrudes by a length corresponding to the plurality of teeth necessary to rotate the above pinion T ₄₉ by 360 °; thus, each time the transfer head T is brought into abutment during its movement along the axis Δl, the rack T ₅₂ is introduced towards the inside of the casing Ca; the 360-degree rotational movement of the assembly described above is carried out at the end of translation of the transfer head T, from its loading position to its extraction position.

Finally, a detector for the presence of electrodes T ₅₅ is positioned on the casing Ca so as to generate an optical beam which will be reflected by the electrode in the event of its presence, or by a reflector situated beyond the barrel T ₄₁ , in the absence of an electrode in said barrel T ₄₁ .

Advantageously, a mechanism will be provided for verifying the operation of the extractor by means of the absence of an electrode on the electrode holder as well as the loading of the new electrode by the presence of the latter on the holder. -electrode. In the example shown in FIGS. 62, 63, a mechanism, associated with the transfer head T and the tool holder PO, makes it possible, during the phase of extraction of the electrode from its electrode holder, to limit the stroke, along the axis Δ2, of said transfer head T, on either side of the middle position.

Indeed, a finger T ₅₅ , integral with the cradle P0 ₂₀ o, is positioned in the center of one of the external faces of said cradle P0 ₂ oo, and oriented in the direction of the transfer head T. In addition, two pawls T _56a , T ₅₆ , pivotally mounted around their shaft, respectively T _57a , T _57b , which are integral with the flange POn _9b of the POφ crew ₁₈ and their axis, respectively Δ16a, Δ16b, is parallel to the axis

LLE.

The above-mentioned pawls T _56a , T ₅₆ , are arranged head to tail, on either side of the axis Δl, at a distance equal to the width of the above-mentioned finger T ₅₅ , and are each actuated by a spring, not shown. , so that their respective bearing surface is peφendicular to the so-called reference plane π.

Thus, during the translation of the transfer head T from the high stop position, defined by the cradle P0 ₀ o, in the direction of the middle position, the finger T ₅₅ causes the lower pawl T ₅₆ to tilt by a neighboring angle 45 degrees counterclockwise, allowing passage to the transfer head T; the finger T ₅₅ , arriving in the middle position, comes into abutment low against the bearing surface of the upper pawl T _56a .

Similarly, during the translation of the transfer head T from the bottom stop position, defined by the cradle P0 ₂₀ o, in the direction of the middle position, the finger T ₅₅ causes the upper pawl T _56a to tilt by an angle close to 45 degrees clockwise, allowing passage to the transfer head T; the finger T ₅₅ , arriving in the middle position, comes into high abutment against the bearing surface of the lower pawl T _56b . The mechanism described above makes it possible, in the extraction position of the transfer head T, to limit the stroke of said transfer head T to approximately half the stroke defined by the cradle P0 ₂₀ o along the axis Δ2, on either side of the middle position.

Thus, according to the second example described above, the sequence for changing the electrodes is as follows:

- displacement of the transfer head T to bring it into its position. theoretical work by horizontal translation actuated by the motor

POιo and vertical upwards, in high stop, actuated by the motor ^• P0 ₂ o,

- translation downwards of the transfer head T to bring it into abutment on the upper pawl T _56a , actuated by the motor PO ₂₀₇ , - installation of the extractor E, the transfer axis passing through the point O of the bottom electrode (if it is not there before),

- centering of the extractor E on the bottom electrode and simultaneously maintaining in traction the cables of the positioner-blockers, actuated by the motor Ti, so as to obtain a precise alignment of the transfer axis of the transfer head T on the axis of the bottom electrode / electrode holder assembly, this centering causing a displacement of the transfer head T,

- release of the cables from the positioner-blockers at the end of centering and blocking of the position of the transfer head T, actuated by the motor

- extraction of the bottom electrode by the extractor E by a rotational movement around the transfer axis, actuated by the motor Ti,

- upward translation, in high stop, of the transfer head T, actuated by the motor P0 ₂ o ₇ , - positioning of the charger C by horizontal translation of the transfer head T, actuated by the motor POι ₀₇ , - translation downwards of the transfer head T to bring the new electrode located on the charger C to the stop, on the electrode holder, and maintaining the pressure of the new electrode on the electrode holder for a few seconds, actuated by the PO ₂₀₇ motor, - upward translation, in high stop, of the transfer head T, actuated by the PO ₂₀₇ motor,

- horizontal translation of the transfer head T at mid-stroke between the two extreme positions of positioning of the extractor E and of the charger C, actuated by the motor POι ₀ , - control by the above-mentioned verification mechanism of the presence and / or absence of electrode on the electrode holder, change of electrode from the bottom on the electrode holder of the arm Bl, and the presence of the electrode to be changed on the electrode holder of the arm B2,

- control by the sensor T ₅₅ of the presence of electrodes on the cylinder T ₄ ι, - translation downwards, in bottom stop, of the transfer head T, actuated by the motor PO ₂₀₇ , simultaneously tilting of the arm B2 of the clamp of the welding robot, so as to bring the axis of the electrode holder of the above-mentioned arm B2 approximately in vertical position, and simultaneously reverse rotation of the extractor E actuated by the motor Ti, thus releasing the old electrode from the bottom ,

- horizontal translation of the transfer head T, actuated by the motor POι ₀₇ to bring it into the extractor position, simultaneously displacement of the rack T ₅₂ causing the rotation of the barrel T _4J to allow the positioning of a new electrode relative to the electrode holder, and simultaneously return to the initial position of the extractor E actuated by the motor Ti,

- upward translation of the transfer head T to bring it into abutment on the lower pawl T ₅₆ , actuated by the motor PO ₂₀₇ ,

- installation of the extractor E, the transfer axis passing through the point O of the top electrode (if it is not there before), - centering of the extractor E on the upper electrode and simultaneously maintaining in traction the cables of the positioner-blockers, actuated by the motor T _l5 so as to obtain a precise alignment of the transfer axis of the transfer head T on the axis of the upper electrode / electrode holder assembly, this centering causing a displacement of the transfer head T,

- extraction of the top electrode by the extractor E by a rotational movement around the transfer axis, actuated by the motor T _i5

- translation downwards, at the bottom stop, of the transfer head T, actuated by the motor PO ₂₀ ,

- introduction of the charger C by horizontal translation of the transfer head T, actuated by the POιo motor,

- upward translation of the transfer head T to bring the new electrode located on the charger C to the stop, on the electrode holder, and maintaining the pressure of the new electrode on the electrode holder for a few seconds, actuated by the PO ₂₀₇ motor, - translation downwards, at the bottom stop, of the transfer head T, actuated by the PO ₂₀₇ motor,

- horizontal translation of the transfer head T at mid-stroke between the two extreme positions of installation of the extractor E and of the charger C, actuated by the motor POι ₀₇ , - control by the sensor T ₅₅ of the replacement of the old top electrode by a new electrode, by the absence of an electrode on the T ₄ barrel ι-

Thanks to these arrangements, the imprecision of the actual position of the electrode with respect to its theoretical position determined by the welding device is overcome. An important advantage of the two solutions described above is that all the operating sequences can be fully automated and that, on the other hand, the use of electric actuators is widespread.

Claims

1- Method for extracting and / or changing the electrodes of an electrode holder of a welding gun or a welding device, by means of a device comprising a movable transfer head comprising an extractor and an electrode charger along a transfer axis, characterized in that it comprises the following change sequence:

- the displacement of the transfer head to bring it into its theoretical working position,

- the installation of the extractor, coaxial with the axis of the electrode (if it is not there before),

- centering of the extractor on the electrode thanks to centering means associated with the extractor so as to obtain a precise alignment of the transfer axis of the head on the axis of the electrode / holder assembly electrode, this centering causing a displacement of the transfer head,

- the extraction of the electrode by the extractor, - the positioning of the charger coaxially with the transfer axis, replacing the extractor, thanks to the previously memorized position,

- the loading of a new electrode on the electrode holder.

2- A method according to claim 1, characterized in that the change sequence is carried out simultaneously on the two electrodes of the welding device.

3- Device for implementing the method according to one of claims 1 and 2, this device involving a movable transfer head comprising an extractor and an electrode charger along a transfer axis, characterized in that it comprises:

- means allowing the transfer head to be moved to bring it into its theoretical working position, - means allowing the extraction of the extractor, coaxial with the axis of the electrode (if there is not not found before),

centering means associated with the extractor so as to obtain a precise alignment of the axis of transfer of the head on the axis of the electrode / electrode holder assembly, this centering causing a displacement of the transfer head ,

means for blocking the position of the transfer head at the end of centering, and means for mechanically memorizing this position,

- an extractor to extract the electrode,

- means for positioning the charger coaxially with the transfer axis, replacing the extractor, thanks to the previously memorized position.

- Device according to claim 3, characterized in that it involves an electrode transfer device (A) comprising an electric reduction motor (M) whose output shaft drives a first arm (9), the shaft of said gear motor (M) being arranged along a vertical axis (Z), parallel to the vertical plane containing the arms (Bl) and (B2) of the above-mentioned welding tongs of the spot welding apparatus, said arm (9) being peφendicular to the shaft of the reduction motor (M) and thus able to pivot around said vertical axis (Z) in a horizontal plane.

- Device according to claim 4, characterized in that the electrode transfer device (A) comprises at the end of the arm (9), opposite to that secured to the output shaft of the reduction motor (M), a first biocable pivoting mechanism (10), comprising a cylindrical shaft

(101) and a parallelepipedic shell (102), the pivoting mechanism (10) being arranged so that its shaft (101) is integral with the arm (9) and oriented along an axis (X) peφendicular to the plane defined by the arm (9) and the axis (Z), the parallelepiped coφs (102) of the pivoting mechanism (10) which can pivot around the shaft (101).

- Device according to claim 4, characterized in that the electrode transfer device (A) comprises a second arm (11), in the shape of an inverted L, secured to the coφs (102) of the pivoting mechanism (10), at the upper end of the L, the other end of the L, the lower end, comprising a second mechanism. pivot (12) comprising a cylindrical shaft (121) and a parallelepipedic shell (122), said second pivoting mechanism (12) being arranged in such a way that its parallelepipedal shell (122) is integral with the lower end of the second arm (11) and oriented along an axis (Y) peφendicular to the plane defined by the axes (Z) and (X), the shaft (121) of the pivoting mechanism (12), which can pivot in the parallelepipedic shell (122), is integral with a flange (13), C-shaped, the above shaft (121) being peφendicular to the amount of C representing the above flange (13).

- Device according to claim 4, characterized in that the electrode transfer device (A) comprises a cylindrical shaft (14) made integral with the flange (13), by traversing it right through peφendicular to the two wings of its C-shape, defining an axis (Δ) of rotation, the shaft (14), parallel to the amount of C representing the above-mentioned flange (13), is perpendicular to the axis (Y) and can pivot in a normal plane said axis (Y).

- Device according to claim 4, characterized in that the electrode transfer device (A) comprises a transfer head (T) having a coφs (15), V-shaped, articulated around the cylindrical shaft ( 14), which being located at the base of said V, the above coφs (15) supporting at both ends of its V shape, an extractor (E) whose main axis (Δl), in the rest position of said extractor, is collinear with the axis of rotation (Δ) of the transfer head (T) and a charger (C) whose main axis (Δ3) is also collinear with the axis of rotation (Δ) of the transfer head (T).

- Device according to claim 8, characterized in that the extractor (E) comprises a housing (16) supporting an extraction device (17) and a drive reduction motor (18), the extraction device (17 ) of the extractor (E) being arranged coaxially to the main axis (Δl) of said extractor, the gear motor (18) being arranged coaxially to an axis

(Δ2), the two axes (Δl, Δ2) being collinear with the axis of rotation (Δ) of the transfer head (T), said extractor (E) being in the rest position, the housing (16) of the the extractor (E) is integral with the coφs (15) of the transfer head (T) by means of a cylindrical shaft (19), disposed in the end of the corresponding branch of the V shape of said head, so that the axis (ΔO) of the cylindrical axis (19) is perpendicular to the plane defined by the axes (Δ, Δl), the housing (16) can slightly pivot around the cylindrical shaft (19), between a rest position corresponding to the collinearity of the two axes (Δ, Δl) and a slightly oblique position, called the extraction position.

0-Device according to claim 8, characterized in that the charger (C) comprises a housing (20) supporting a change device (21) and a drive reduction motor (22), the barrel (21) of the charger ( C) being arranged coaxially to the main axis (Δ3) of said loader, the gear motor (22) being arranged coaxially to an axis (Δ4), the two axes (Δ3, Δ4) being collinear with the axis of rotation (Δ ) of the transfer head (T), the casing (20) of the charger (C) is integral with the case (15) of the transfer head (T) at the end of the corresponding branch of the V-shape of said head. -A device according to claim 8, characterized in that the transfer head (T) comprises a lifting device (L), pivotally mounted around the shaft (14) of said transfer head (T), the device d elevation (L) comprising a plate (23), pivotally mounted on the shaft (14) at its lower end, beyond the flange (13), so that it can pivot around the cylindrical shaft (14) and not translate vertically along said cylindrical shaft (14) by means of shoulders, said plate (23) comprising a reduction gear (24) actuating a bevel gear (25), which actuates a helical screw ( 26) whose axis is collinear with the axis (Δ) of the transfer head (T), said helical screw (26) resting on the lower surface of the coφs (15) of the fransfer head (T) and its upward and downward movement caused by the reduction motor (24) allows the entire transfer head to be displaced along the axis (Δ) defined by the cylindrical shaft (14).

- Device according to claim 9, characterized in that the gear motor (18) of the extractor (E), disposed below the housing (16), integral with said housing (16), comprises a drive shaft actuating in the upper part a pinion, which pinion driving a toothed crown (29) disposed in the middle zone of said housing (16), said toothed crown (29) driving a shaft (30), passing vertically right through said housing (16) and its axis (ΔT), collinear with the two axes (Δl, Δ2), is located in the plane containing the axes (Δl, Δ), closer to the axis (Δl) than to the axis (Δ), said shaft (30) driving, at its upper part, close to the external face of the housing (16), a second toothed ring (31), which drives the extraction device (17).

-A device according to claim 12, characterized in that the extraction device (17) consists of a crown (32) comprising a plurality of teeth on its outer periphery and a plurality of teeth on its internal periphery, the plurality of external teeth being in drive relation with said second toothed crown (31), and a plurality of jaws (33 a to 33 e) arranged inside said crown (32), pivoting each around an axis collinear with said axis (Δl), which axis being situated on a circumference of diameter between 70% and 90% of the pitch diameter of said plurality of internal teeth, the jaws (33 a to 33 e), pivoting around their respective axes (33 a 'to 33 e'), each have a part in an arc of a circle concentric with their axis of rotation and a gripping part, said part in an arc of a circle, with an opening of between 100 ° and 180 °, comprises a plurality of teeth meshing with the facing part of the plurality of internal teeth of said crown (32), the gripping part comprising a slightly domed end.

- Device according to claim 3, characterized in that it involves an electrode transfer device (A) comprising:

- a transfer head (T) comprising an extractor (E) and a charger (C),

- a tool holder (PO) supporting the said transfer head (T),

- a conformator (CO) associated with the above-mentioned tool holder (PO).

- Device according to claim 14, characterized in that the said transfer head (T), integral with the tool holder (PO), moves along two orthogonal axes (Δl) and (Δ2), respectively the axis of translation, peφendicular to the plane defined by the two arms (B1), (B2), and the axis of engagement / release, peφendicular to the axis (Δl) and contained in a plane parallel to the plane defined by the two arms (B 1 ), (B2).

- Device according to claim 14, characterized in that the aforesaid tool holder (PO), integral with the shaper (CO):

- moves along an axis (Δ3), peφendicular to the above axes (Δl), (Δ2), - pivots around an axis (Δ4), parallel to the axis of translation (Δl), located at the welding electrode, - moves along an axis (Δ5), parallel to the axis of translation (Δl),

- pivots around the axis (Δ3).

-A device according to claim 14, characterized in that the conformator (CO) comprises:

- a central shaft (COi), whose axis is the above axis (Δ3); said central shaft (COi), comprising at one of its ends a flange (C0 ₂ ), in the form of a disc, making it possible to secure the abovementioned tool holder (PO) to the central shaft (COi); said central shaft (COi) being pivotally mounted and sliding in a parallelepipedic coφs (C0 ₃₎ , by means of two bearings or bearings (C0 ₄ ), (C0 ₅ ), arranged at each end of said coφs (C0 ₃ ),

- the parallelepiped coφs (C0 ₃ ) comprising two ribs of the same thickness, and of width close to that of said coφs (C0 ₃ ), located symmetrically on either side of the coφs (C0 ₃ ), in a plane peφendicular to axis (Δ3), which plane is located approximately at the first third of the length of the cost (C0 ₃ ), close to the flange (C0 ₂ ),

- two trees (C0 ₆ ), (C0 ₇ ), the respective axes of which are parallel to each other and peicendicular to the axis (Δ3); the aforesaid shafts (C0 ₆ ), (C0 ₇ ), being mounted pivoting and sliding in their respective ribs by means of bearings, respectively (C0 ₆ ι), (C0 ₆₂ ), (C0 ₇ ι), (C0 ₇₂ ) and emerging from either side of the width of their respective ribs,

- A frame (COg), of rectangular shape and thickness close to that of the above-mentioned ribs, surrounding the above-mentioned coφs (C03) at the level of the said ribs, being integral with the two shafts (C0 ₆ ), (C0 ₇ ), at the level of their emerging parts, while leaving sufficient play,

- the above trees (C0 ₆ ), (C0 ₇ ) emerging in turn from the frame (C0 ₈ ) on either side of said frame (C0 ₈ ) so as to be able to slide in two curved grooves located in two walls (C0 ₉ ), (COι ₀ ); the above walls (COg, CO ₁₀ ) being arranged in a vertical plane, on the and other of said frame (C0 ₈ ), and integral with a horizontal sole (COn),

- the above-mentioned ribs, located in the frame (C0 ₈ ) each forming an arc, the center of which is at point (O) corresponding to the point materializing the center of the barrel of the above-mentioned electrodes,

- four positioner-blocker mechanisms (PB1), (PB2), (PB3), (PB4) making it possible to position and block the above-mentioned central shaft (COi), when the latter moves along an axis (Δ3), peφendicular to the above axes (Δl), (Δ2), pivots around an axis (Δ4), parallel to the translation axis (Δl), located at the welding electrode, moves along an axis

(Δ5), parallel to the axis of translation (Δl), and pivots around the axis (Δ3).

-A device according to claim 17, characterized in that the positioner-blocker mechanism (PB) comprises: - a part called the positioner,

- a so-called blocker part,

- a so-called stirrup part.

- Device according to claim 18, characterized in that the so-called positioner part of the positioner-blocker mechanism (PB) comprises:

- A tubular part comprising two cylindrical sleeves of the same diameter (301), (302), integral with one another by a third sleeve (303), of short length, coming to cover one of the ends of each of the sleeves (301 ), (302), and having a smaller internal diameter than that of the sleeves (301), (302),

- two cylindrical ends (304), (305) respectively secured to the sleeves (301), (302) at their free end; each of the above-mentioned end pieces (304), (305) consisting of a cylindrical sleeve whose inner surface is integral with the outer surface of said cylindrical sleeves (301), (302), and of a wall normal to the main axis (Δ0); the end piece (304) comprising at its normal wall to the main axis (ΔO) a cylindrical orifice with a diameter less than the inside diameter of said central sleeve (303);

- A cylindrical shaft (306), sliding freely in the orifice of the wall of the nozzle (304), penetrating the assembly consisting of the three sleeves (301), (302), (303), and comprising, close from the internal end, a shoulder of length equivalent to the internal length of the sleeve (303), and sliding freely in the internal cylindrical part of said sleeve (303);

- two cylindrical sleeves (307), (308) of a length close to a third of that of the sleeves (301), (302), on either side of the shoulder of the cylindrical shaft (306), sliding freely on the cylindrical shaft (306) and on the cylindrical part of the sleeves respectively (301), (302); said sleeves (307), (308), positioned on either side of the shoulder of the cylindrical shaft (306), forming with said sleeves (301), (302) and said end pieces (304), (305 ), two cylindrical cavities

(309), (310); each of said cavities (309), (310) containing a helical spring designed to be in slight compression, respectively (311), (312);

- A flange (313) secured to the free outer end of the cylindrical shaft (306) and constituting a first point of attachment of the positioner-blocker mechanism (PB).

- Device according to claim 18, characterized in that the so-called blocker part of the positioner-blocker mechanism (PB) comprises: - a housing of parallelepipedal shape (314) crossed by the free end of the cylindrical shaft (306), associated at the end piece (304);

- Two plates (315), (316), of rectangular shape, arranged substantially peφendicular to the shaft (306) which passes through them, at the level of the cavity of said casing (314), surrounding the cylindrical shaft; these two plates (315), (316) being pierced with a cylindrical orifice whose internal diameter is slightly greater than the external diameter of the tree (306); said plates (315), (316) being arranged one opposite the other and each comprising, one facing the other, a blind hole for accommodating a compression spring (317), thus tending to separate the two plates (315), (316), from one another. - two pins (318), (319), respectively associated with the pads

(315), (316), whose main axis is peφendicular to the axis (ΔO), integral with the casing (314); the two plates (315), (316) being pivotally held one opposite the other and being subjected to a spacing due to the presence of the compression spring (317), making it possible to block the shaft (306) relative to the housing (314).

- A metallic cable in sheath (320) integral, at one of its ends, with the plate (315); disposed parallel to the axis (Δ0), and passing through a metal tube (321), itself secured to the end piece (304) and pressing, at one of its ends, on the plate (316).

21 -A device according to claim 18, characterized in that the so-called stirrup part of the positioner-blocker mechanism (PB) comprises:

- a stirrup (322), U-shaped, whose axis of articulation (Δ0 '), crossing the two branches of the U, is peφendicular to the axis (Δ0); this stirrup (322) being associated with the positioner-blocker mechanism PB, at the casing (314), by means of two shoulder screws (323), (324), integral with the casing (314), allowing said stirrup (322) ) pivot freely around the axis (Δ0 ');

- A third shouldered screw (325), integral with the base of the U, arranged so that its axis (Δ0 ") is peφendicular to the plane defined by the axes

(Δ0) and (Δ0 ') and constituting the second attachment point of the positioner-blocker mechanism (PB).