Electric spot-welding head

Abstract

An electric spot-welding head (10) for a multi-axis industrial robot arm is described, comprising: - a support structure (100) comprising at least one attachment portion (127) for attaching the welding head to the multi-axis industrial robot arm; - a first electrode-holder arm (200) carrying a first welding electrode (202) and connected to said support structure; - a second electrode-holder arm (200) carrying a second welding electrode and connected to said support structure (100); and - an electric transformer (400) configured to apply an electrical voltage to said first and second welding electrodes (202, 302). The electric spot-welding head (10) is characterized in that it comprises particular connection devices (700, 800) to facilitate the electrical and hydraulic connection of the electric transformer (400).

Description

[0001] "Electric spot-welding head"

[0002] ****

[0003] TEXT OF THE DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to an electric spot-welding head for a multi-axis industrial robot arm, in particular of the type comprising:

[0006] - a support structure comprising at least one attachment portion for attaching the welding head to the multi-axis industrial robot arm;

[0007] - a first electrode-holder arm carrying a first welding electrode and connected to said support structure; a second electrode-holder arm carrying a second welding electrode and connected to said support structure; wherein at least said second electrode-holder arm is movable relative to said support structure;

[0008] - an actuator for actuating the movement of the second electrodeholder arm; and

[0009] - an electric transformer configured to apply an electrical voltage to said first and second welding electrodes.

[0010] An electric spot-welding head of the type indicated above usually operates as an end-effector unit of an industrial robot arm and can commonly have two different operational configurations: a first configuration (so-called "fulcrum" type) in which the second electrode-holder arm is movable according to a rotational movement about a rotation axis, and a second configuration (so-called "slide" type) in which the second electrodeholder arm is movable according to a translational movement along a working direction.

[0011] The movement of the second electrode-holder arm is operated to position the respective welding electrode between an open position, in which the welding electrode is further away from the welding electrode carried by the first electrode-holder arm, and a closed position, in which the welding electrodes of the two arms are instead close together.

[0012] During operation of the welding head, the second electrode-holder arm assumes the open position when the welding head is moving to reach the point where it must perform the welding operation, and subsequently assumes the closed position, so that the parts to be welded are clamped between the two welding electrodes.

[0013] Normally, a welding head of the type in question is equipped with a cooling system operating with a cooling fluid that is circulated inside some components of the welding head (among all, the two welding electrodes and the electric transformer can be mentioned here), in order to keep these components at a temperature below a predetermined limit value.

[0014] The production and use of an electric spot-welding head of the type indicated above are subject to a series of technical problems to be addressed.

[0015] First, with reference to its production, it is necessary to guarantee the production of both of the two operational configurations indicated above, fulcrum and slide, and the availability of a warehouse with spare parts for both of the two operational configurations.

[0016] In this regard, it is observed that the welding electrodes and the electrical conductors that electrically connect them to the electric transformer, in particular the element associated with the movable electrode-holder arm, are subject to rapid deterioration over time, so maintenance interventions are usually frequent and the demand for spare parts by users of the head is practically constant.

[0017] Among other things, maintenance interventions usually require the intervention of specialized technicians, since even the simple replacement of parts requires complicated disassembly and assembly operations in which it must finally also be verified that the head has been returned to the predetermined geometric configuration.

[0018] A further complexity arises from the fact that it is necessary to provide welding heads compatible with the different industrial robot arms present on the market, which means that the cooling system of the welding head must be able to be connected to the conduits carried by the robot arm, and that the electric transformer of the head must be able to be connected, both for its electrical power supply and for its control, to the electrical system of the plant in which the robot arm operates.

[0019] Furthermore, depending on the needs of specific applications, different models of electric transformer can be mounted on the welding head, with the necessity, therefore, of adapting each time the parts of the hydraulic circuit and the electrical circuit of the head to the electric transformer used.

[0020] The aforementioned circumstances introduce a high variability of the final configuration of the welding head, which considerably complicates its production and the management of the warehouse of its components. Furthermore, the high variability of the final configuration of the welding head also considerably complicates maintenance interventions, which, in fact, are hardly subject to a standard procedure, but vary significantly from one head to another depending on their configurations.

[0021] In this context, the present invention proposes a new welding head solution which is advantageous compared to known solutions in relation to one or more of the problems highlighted above.

[0022] In general, the present invention relates to an electric spot-welding head according to claim 1 .

[0023] The claims form an integral part of the teaching provided here.

[0024] Further characteristics and advantages of the present invention will be evident from the following description with reference to the attached drawings, provided by way of non-limiting example only, in which: figure 1 represents a first embodiment of the welding head described here;

[0025] - figure 2 illustrates the welding head of figure 1 according to a bottom view;

[0026] - figure 3 illustrates the welding head of figure 1 in a partially exploded view; figure 4 represents a second embodiment of the welding head described here;

[0027] - figures 5A, 5B, 5C, 5D represent a support body of the welding heads of figures 1 and 4, according to an axonometric view, a side view, a rear view and a bottom view, respectively;

[0028] - figure 6 illustrates a connection plate of the welding heads of figures 1 and 4;

[0029] - figures 7 and 8 represent two opposite side views of the welding head of figure 1 ;

[0030] - figures 9 and 10 represent two connection devices of the welding heads of figures 1 and 4;

[0031] - figure 11 represents a connection device of the welding heads of figures 1 and 4;

[0032] - figure 12 represents a connection device of the welding head of figure 1 ;

[0033] - figures 13 and 14 represent two opposite side views of the welding head of figure 4;

[0034] - figure 15 represents a connection device of the welding head of figure 4;

[0035] - figure 16 represents a transformer of the welding heads of figures 1 and 4;

[0036] - figures 17 and 18 represent two orthogonal views of an electrodeholder arm of the welding head of figure 1 .

[0037] In the following description, various specific details are illustrated aimed at an in-depth understanding of the embodiments. The embodiments can be realized without one or more of the specific details, or with other methods, components or materials etc. In other cases, known material structures or operations are not shown or described in detail to avoid obscuring various aspects of the embodiment.

[0038] The references used here are for convenience only and therefore do not define the scope of protection or the scope of the embodiments.

[0039] With reference to figures 1 to 4, the illustrated electric spot-welding head - overall indicated by reference number 10 - comprises a support structure 100, on which a first electrode-holder arm 200, carrying a first welding electrode 202, and a second electrode-holder arm 300, carrying a second welding electrode 302, are mounted.

[0040] The first electrode-holder arm 200 is mounted so as to be fixed on the support structure 100, while the second electrode-holder arm 300 is mounted so as to be actuatable in a movement such as to selectively position the respective welding electrode 302 in an open position, in which the welding electrode 302 is further away from the welding electrode 202 carried by the first electrode-holder arm 200, and in a closed position, in which the welding electrode 302 is instead closer to the welding electrode 202 of the first electrode-holder arm 200.

[0041] As is known, during operation of the welding head, the second electrode-holder arm 300 assumes the open position when the welding head is moving to reach the point where the welding operation is to be performed, and subsequently assumes the closed position to clamp the parts to be welded between the two welding electrodes 202, 302.

[0042] The two embodiments of the welding head described here which are illustrated in figures 1 and 4 differ from each other essentially in the type of movement performed by the second electrode-holder arm 300.

[0043] In particular, in the embodiment of figure 1 the second electrodeholder arm 300 is movable according to a rotational movement about a rotation axis I, while in the embodiment of figure 4 the second electrodeholder arm 300 is movable according to a translational movement along a working direction K.

[0044] The welding head 10 further comprises an actuator 60 for actuating the movement of the second electrode-holder arm 300, and an electric transformer 400 for applying an electrical voltage to the two welding electrodes 202, 302.

[0045] In one or more preferred embodiments, as the one illustrated, the actuator 60 is a linear actuator comprising a member 62 movable along an operational axis 60I.

[0046] In one or more preferred embodiments, as the one illustrated, the support structure 100 comprises a support body 102 formed as a single piece and comprising (see figures 5A-5D): a first portion 104, configured for receiving and fixing the first electrode-holder arm 200 to the support body 102; a second portion 106, configured for receiving and fixing the electric transformer 400 to the support body 102; and

[0047] - a third portion 108, configured for receiving and fixing the actuator 60 to the support body 102.

[0048] More particularly, in one or more preferred embodiments, as the one illustrated, the support body 102 comprises a base 110 that extends along a longitudinal reference axis L and from which protrude, along a reference axis T transverse to the reference axis L, on the same side, a pair of appendages 120, parallel to each other and mutually spaced, and a connection portion 130.

[0049] The base 110 has a first end 112, which defines said second portion 106 for receiving and fixing the electric transformer 400 to the support body 102. In one or more preferred embodiments, as the one illustrated, the first end 112 comprises a substantially planar wall 112A provided with a plurality of fixing holes 112B. The same wall 112A also has a central opening 112C, through which the electric transformer 400 is made accessible from the upper side of the base 110; the opening 112C allows, for example, an operator to intervene from the upper side of the base 110 on the transformer 400 or on a component associated therewith.

[0050] In one or more preferred embodiments, as the one illustrated (see figure 6), the support structure 100 comprises a shaped plate 140 via which the electric transformer 400 is fixed to the wall 1 12A.

[0051] In one or more preferred embodiments, as the one illustrated, the shaped plate 140 comprises a first portion 141 , which is fixed to the wall 112A, and a second and a third portion 142, 143, opposite each other, which are oriented transversely to the first portion 141 and between which the electric transformer 400 is received.

[0052] Each of the portions 141 , 142, 143 of the shaped plate 140 is provided with fixing holes, either for fixing the shaped plate 140 to the wall 112A, with reference to portion 141 , or for fixing the electric transformer 400 to the same plate, with reference to the two portions 142, 143.

[0053] Fixing means of known type, for example screws, can be used in cooperation with said fixing holes.

[0054] Preferably, the electric transformer 400 is fixed to each of the two portions 142, 143 via the interposition of at least one damping body 145 (see figure 2), for example an elastic rubber body.

[0055] The damping body 145 performs the dual function of protecting the electric transformer 400 from vibrations to which the support structure 100 is subjected during operation of the welding head, and, on the other hand, of allowing small displacements of the electric transformer 400 relative to the support structure 100 to facilitate the assembly operations of the welding head.

[0056] Returning to the base 110 of the support body 102, it has a second end 116 opposite the first end 112 along the longitudinal reference axis L, which defines said first portion 104 for receiving and fixing the first electrode-holder arm 200 to the support body 102.

[0057] In one or more preferred embodiments, as the one illustrated, the second end 116 comprises a cavity 118 with a U-shaped profile, which is delimited by a bottom 118A and by two opposite lateral walls 118B, 118C, and which receives inside it a proximal portion 204 of the first electrodeholder arm 200.

[0058] The proximal portion 204 rests directly on the bottom 118A, which constitutes a stop defining the correct vertical position of the electrodeholder arm 200 (with reference to the orientation of the welding head shown in the figures).

[0059] In one or more preferred embodiments, as the one illustrated, the proximal portion 204 of the electrode-holder arm 200 has a transverse sectional profile of polygonal shape, preferably rectangular, and the cavity 118 has a U-shaped profile that substantially reproduces part of the polygonal profile of the proximal portion 204 of the tool-holder arm 200.

[0060] In one or more preferred embodiments, as the one illustrated, the proximal portion 204 of the electrode-holder arm 200 has a width slightly smaller than the width of the cavity 118, so that an interstitial space sufficient to facilitate the insertion and removal of said proximal portion, into and from the cavity 118, during the assembly and disassembly operations of the welding head is created.

[0061] In this case, the second end 116 has one or more through holes 116A, preferably threaded, which pass through the lateral wall 118B and open into the cavity 118.

[0062] For the assembly of the electrode-holder arm 200, the holes 116A receive respective pins (not illustrated), preferably threaded, which press the proximal portion 204 against the lateral wall 118C of the cavity 118; in this way, the wall 118C constitutes a stop that defines the correct lateral position of the electrode-holder arm 200.

[0063] In an alternative embodiment, the U-shaped profile of the cavity 118 instead precisely reproduces the external polygonal profile of the proximal portion 204, so that, between this and the cavity 118, a shape coupling is realized capable of determining the correct positioning of the electrodeholder arm 200 in a plane orthogonal to the working direction K.

[0064] In one or more preferred embodiments, as the one illustrated (see figures 2 and 4), the support structure 100 further comprises a clamping body 119 which is disposed against two abutment edges 117 made on the second end 1 16 on opposite sides of the cavity 118, and which clamps the first electrode-holder arm 200 inside the cavity 118 preventing its removal.

[0065] The clamping body 119 and the abutment edges 117 are both provided with fixing holes to be fixed together via fixing means of known type, for example screws.

[0066] It can now be observed that the cavity 118 of the support body 102 and the proximal portion 204 of the electrode-holder arm 200 are configured to determine a correct positioning of the arm 200 on the support body 102 simply by effect of their mutual coupling, without the need for any adjustment.

[0067] The electrode-holder arm 200 is then fixed to the body 102 through the simple application of the clamping body 119.

[0068] It will therefore be understood how, thanks to this mounting method, the assembly operations of the welding head are greatly simplified.

[0069] In one or more preferred embodiments, as the one illustrated, the base 110 is also provided with a lateral opening 111 at an intermediate region thereof between the two ends 112, 116, which is configured to make the electric transformer 400 and / or one or more components associated therewith accessible from the upper side of the same base. The opening 111 allows, for example, an operator to intervene from the upper side of the base 110 on the transformer 400 or on a component associated therewith.

[0070] Returning to the support body 102 (see figures 5A-5D), the pair of appendages 120 defines said third portion 108 for receiving and fixing the actuator 60.

[0071] The two appendages 120 have essentially identical configuration, so reference will be made below to only one of the two appendages.

[0072] In one or more preferred embodiments, as the one illustrated, the appendage 120 comprises two distinct formations 121 , 122 for fixing the actuator 60, which are positioned at different distances from the base 110 of the support body 102 along the transverse reference axis T; in particular, in the illustrated example, the fixing formation 121 is closer to the base 110 than the fixing formation 122.

[0073] In one or more preferred embodiments, as the one illustrated, each of the two fixing formations 121 , 122 comprises a central opening 123 of larger diameter and a plurality of fixing holes 124 of smaller diameter that surround the central opening 123.

[0074] The actuator 60 can be fixed to the pair of appendages 120 via the selective use of the formations 121 or the formations 122 and with the aid of fixing flanges 125, which support the actuator 60 on opposite sides and engage the central openings 123, while being simultaneously fixed to the appendages 120 via fixing means, for example screws, which engage the fixing holes 124.

[0075] Now making a comparison between figures 1 and 4, it can be noted that, in the embodiment of figure 4, the actuator 60 is fixed to the appendages 120 via the formations 121 , so as to assume an orientation such that its operational axis 60I is parallel to the longitudinal axis L of the support body 102 and aligned with the working direction K; on the other hand, in the embodiment of figure 1 , the actuator 60 is fixed to the appendages 120 via the formations 122, so as to assume an orientation such that its operational axis 60I is instead inclined relative to the longitudinal axis L.

[0076] Furthermore, with specific reference to the embodiment of figure 4, the two fixing formations 121 , 122 can be advantageously exploited to realize the welding head 10 in at least two different sizes, which are distinguished from each other by the distance subtended between the two electrode-holder arms 200 and 300 along the direction T; as known to the person skilled in the art, the space made available by this distance is intended to receive, during operation of the head, parts of the two components that are subjected to a welding operation by the head itself.

[0077] In an alternative embodiment, the appendage 120 can instead comprise a single formation for fixing the actuator 60, which is used for assembling the head according to both the "fulcrum" and "slide" configurations.

[0078] In one or more preferred embodiments, as the one illustrated, the appendage 120 further comprises an attachment portion 127 for fixing the welding head 10 to the multi-axis industrial robot arm. As is known, the attachment portion 127 can, for example, comprise a planar wall 127A provided with a central opening 127B and a plurality of fixing holes 127C distributed around the central opening 127B. The fixing of the welding head 10 through the attachment portion 127 can occur either directly or indirectly, via brackets or adapters.

[0079] The person skilled in the art will observe that the provision of an attachment portion 127 on each of the appendages 120 offers great versatility to the welding head, which can in fact be used indifferently for applications that involve mounting the head from the right side, or from the left side, or even from both sides.

[0080] In this regard, it is further observed that the welding head 10 has a mechanical structure (intended as an assembly defined at least by: the support body 100, the two electrode-holder arms 200 and 300 and their respective members for their connection to the support body 100, and the actuator 60) that is substantially symmetrical with respect to a longitudinal plane parallel to the reference axes T and L, and passing through the point of contact of the ends of the two electrodes 202, 302.

[0081] This allows the robot arm to which the welding head 10 is coupled to be actuated according to the same driving algorithms regardless of which side of the head (whether its right side, or its left side) the robot arm is fixed to.

[0082] In one or more preferred embodiments, as the one illustrated, the pair of appendages 120 is located substantially at the second end 116 of the base 110, or in any case closer to that end than the connection portion 130, and, correspondingly, the connection portion 130 is located substantially at the first end 112 of the base 110, or in any case closer to that end than the two appendages 120.

[0083] In this way, the connection portion 130 faces towards the front end of the welding head 10 (i.e., towards the welding electrodes 202, 302), while the appendages 120 face towards the opposite rear end.

[0084] In one or more preferred embodiments, as those illustrated, the connection portion 130 is configured for connection to the support body 102, indifferently, of an oscillating lever 160 which is rotatable about the rotation axis I and by which the second electrode-holder arm 300 is carried, in the embodiment of figure 2, or of a bracket 150, fixed, for supporting the second electrode-holder arm 300 movable along the working direction K, in the embodiment of figure 4.

[0085] In one or more preferred embodiments, as those illustrated, the connection portion 130 is provided with a connection formation 131 comprising a central opening 133 and a series of fixing holes 134 arranged around the central opening 133.

[0086] With reference to the embodiment of figure 1 , in one or more preferred embodiments, as the one illustrated, the lever 160 comprises two parallel and opposed arms 162, which are disposed on opposite sides of the connection portion 130 and are connected in an articulated manner to said portion, about the rotation axis I, via an articulation pin 135 (see figure 3) inserted inside the central opening 133 of the connection portion 130.

[0087] At its end opposite the rotation axis I, the lever 160 is further connected in an articulated manner, about a rotation axis 11 parallel to the rotation axis I, to the movable member 62 of the actuator 60 received between the appendages 120 of the support body 102.

[0088] In one or more preferred embodiments, as the one illustrated (see figure 3), the lever 160 comprises a first lever body 161 , which comprises the two arms 162 and a cavity 161 A with a U-shaped profile facing in a direction opposite to the arms 162 and delimited by a bottom 161 B and by two opposite lateral walls 161 C.

[0089] A proximal portion 304 of the second electrode-holder arm 300 is received in the cavity 161 A.

[0090] Preferably, the proximal portion 304 of the second electrode-holder arm 300 has a transverse sectional profile of polygonal shape, preferably rectangular. At the same time, the cavity 161 A of the lever body 161 has in transverse section a U-shaped profile that reproduces part of the polygonal profile of the portion 304 of the electrode-holder arm 300 so that a shape coupling is realized between the cavity 161 A and the portion 304 received therein.

[0091] In one or more preferred embodiments, as the one illustrated, the lever 160 further comprises a second lever body 162, which is disposed against the first lever body 161 so as to close the cavity 161 A from above and clamp the electrode-holder arm 300 inside the same cavity to prevent its removal.

[0092] Finally, the second lever body 162 is connected in an articulated manner to the movable member 62 of the actuator 60 about the rotation axis 11.

[0093] Both of the two lever bodies 161 , 162 are provided with fixing holes to be fixed together via fixing means of known type, for example screws.

[0094] It will be evident to the person skilled in the art that this mounting method of the second electrode-holder arm 300 allows obtaining the same advantages discussed above with reference to the mounting method of the first electrode-holder arm 200 on the support body 102.

[0095] Still with reference to the embodiment of figure 1 , it will be noted that the two electrode-holder arms 200, 300 are preferably identical to each other, thus facilitating the management of the warehouse of components of the welding head described here

[0096] With reference now to the embodiment of figure 4, in one or more preferred embodiments, as the one illustrated, the bracket 150 comprises two parallel and opposed arms 152, which engage the two opposite faces 132A, 132B of the connection portion 130 and are provided, at their respective proximal ends, with fixing holes arranged so as to coincide with the fixing holes 134 of the connection portion 130.

[0097] Fixing means of known type, for example screws, can engage said fixing holes to fix the bracket 150 to the connection portion 130.

[0098] In one or more preferred embodiments, as the one illustrated, the end 154 of the bracket 150 has an internal cylindrical opening 154B which is engaged by a cylindrical portion 304 of the second electrode-holder arm 300, realizing a linear joint that allows the electrode-holder arm 300 to move along the working direction K.

[0099] The bracket 150 can be made as a single piece or as an assembly of a plurality of distinct components, for example represented by the two arms 152 and the end 154.

[0100] In view of the above, it therefore appears evident how the welding head described here can be easily set up, indifferently, in the configuration of Figure 1 and in the configuration of Figure 4, using a same basic structure common to the two configurations; in this regard, the support body 102 constitutes a reference for the precise positioning of all the other components of the head that eliminates the need to adjust the positions of these components individually.

[0101] In particular, it can be observed how the connection portion 130 is advantageously capable of realizing both the fixing of the bracket 150 to the support structure 100, and the articulated connection of the lever 160 to the support structure 100, guaranteeing, in the first case, the sliding of the electrode-holder arm 300 along the predetermined working direction L, and in the second case, the rotation of the electrode-holder arm 300 about the predetermined rotation axis I.

[0102] In one or more preferred embodiments, as the one illustrated, the electric transformer 400 comprises two output poles 403, 404 which are electrically connected to the two electrode-holder arms 200, 300, respectively, via a first electrical conductor element 501 and via a second electrical conductor element 502.

[0103] As is known, the electrical conductor element 502 is preferably flexible, so as to be able to accommodate the displacement of the electrodeholder arm 300 between the open position and the closed position; for example, the electrical conductor element 502 is formed by a plurality of overlapping lamellae made of electrically conductive material.

[0104] On the other hand, the electrical conductor element 501 can be formed by a rigid body made of electrically conductive material.

[0105] The welding head 10 comprises a cooling system for cooling, during welding operations, the following group of components or a related subgroup: the electric transformer 400, the two electrode-holder arms 200, 300, the two welding electrodes 202, 302, and the two electrical conductor elements 501 , 502.

[0106] In general, said cooling system comprises a hydraulic line which is configured to transport a cooling fluid inside or in proximity to said components so as to place them in a condition of thermal exchange with said cooling fluid, in order to keep the same components at a temperature below a predefined limit.

[0107] With reference to the electric transformer 400, this comprises an inlet 401 for introducing the cooling fluid inside the electric transformer, and an outlet 402 through which the cooling fluid exits the electric transformer.

[0108] In one or more preferred embodiments, as the one illustrated, the welding head 10 comprises at least one interface module through which its cooling system can be connected, in a simple and rapid manner, to a first external conduit for supplying the cooling fluid to the welding head, and to a second external conduit for removing the cooling fluid after it has been heated following the passage through the welding head; the two external conduits can for example be part of the fittings of the industrial robot arm on which the welding head is fixed.

[0109] Said at least one interface module is not part of the electric transformer 400, but is instead a separate module which, preferably, is mounted on the shaped plate 140 described above.

[0110] In particular, in one or more preferred embodiments, as the one illustrated (see figures 7, 8, 13 and 14) the welding head 10 comprises a first interface module 601 for connecting the welding head to the external conduit for supplying the cooling fluid, and a second interface module 602 for connecting the welding head to the external conduit for transporting the heated cooling fluid.

[0111] In one or more preferred embodiments, as the one illustrated (see figures 7, 8, 13 and 14), the two interface modules 601 , 602 are both carried by the plate 140 and, in particular, are respectively fixed to the outer sides of the two portions 142, 143, so as to protrude on opposite sides of the electric transformer 400.

[0112] The two interface modules 601 , 602 comprise respective hydraulic connectors 601 A, 602A for connection to the two external conduits indicated above.

[0113] In an alternative embodiment (not illustrated), the two interface modules 601 and 602 can on the contrary be integrated together into a single module.

[0114] The welding head 10 further comprises a third interface module 605 for connecting the electric transformer 400 to an external electrical cable for transmitting control signals from an external control unit, for example the same control unit that commands the robot arm, to the electric transformer 400, and vice versa.

[0115] Similarly to the two interface modules 601 , 602, the interface module 605 is not part of the electric transformer 400, but instead constitutes a separate component, which preferably is mounted on the shaped plate 140; for example, as in the illustrated example, the interface module 605 is disposed on a rear appendage 144 of the plate 140, transverse to each of the portions 141 , 142, 143, so as to position itself on the rear end of the welding head 10.

[0116] The interface module 605 comprises an electrical connector for connection to the external electrical cable, and a communication unit (not illustrated) which is configured to receive the electrical control signals coming from the external control unit and transmit them to the electric transformer 400, and vice versa.

[0117] In view of the above, the interface modules 601 , 602 and 605 therefore constitute the means for the electrical and hydraulic connection of the welding head with the robot arm and the plant in which it operates.

[0118] Thanks to the fact that these modules are made as distinct and separate components from the other components of the welding head, in particular from the electric transformer, it is possible to set up the welding head in a simple and rapid manner for the different possible applications, simply by installing interface modules 601 , 602, 605 suitable for operating in the specific application, while otherwise maintaining a configuration common to all the different applications.

[0119] In particular, as modules 601 , 602, interface modules equipped with hydraulic connectors 601 A, 602A compatible with the hydraulic connectors associated with the two external conduits carried by the robot arm will be adopted; similarly, as module 605, an interface module equipped with an electrical connector compatible with the electrical connector associated with the electrical cable present in the external plant will be adopted, and furthermore equipped with a communication unit configured to operate with the specific communication protocol used by the control unit of said plant.

[0120] In one or more preferred embodiments, as the one illustrated (see figures 7, 8, 13 and 14), the welding head 10 further comprises a first connection device 700, which carries a first end 502A of the second electrical conductor element 502 and is coupleable in a removable manner to the electric transformer 400 so as to electrically connect the second output pole 404 of the electric transformer 400 to the second electrical conductor element 502 and so as to place the inlet 401 of the electric transformer 400 in fluid communication with the hydraulic line of the cooling system.

[0121] Furthermore, the welding head 10 comprises a second connection device 800, which carries a first end 501 A of the first electrical conductor element 501 and is coupleable in a removable manner to the electric transformer 400 so as to electrically connect the first output pole 403 of the electric transformer to the first electrical conductor element 501 and so as to place the outlet 402 of the electric transformer 400 in fluid communication with the hydraulic line of the cooling system.

[0122] In one or more preferred embodiments, as the one illustrated (see figure 9), the first connection device 700 comprises an electrical connector (not illustrated) configured to couple to the second output pole 404 of the electric transformer 400, a first hydraulic connector 702 configured to couple to the inlet 401 of the electric transformer 400, and a second hydraulic connector 703 configured to couple to an end 901 A of a conduit 901 of the hydraulic line of the cooling system which, at its opposite end 901 B, is connected to the interface module 601 .

[0123] The two hydraulic connectors 702, 703 are placed in fluid communication, inside the connection device, so that the cooling fluid entering the device through connector 703 can exit the same device through connector 702.

[0124] Preferably, the connection device 700 comprises a hollow body on which said hydraulic connectors are defined, and which is configured to place said connectors in mutual fluid communication.

[0125] Preferably, the connection device 700 is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with the end 502A of the second electrical conductor element 502; for example, said hollow body comprises one or more thermally conductive parts, or appendages, that come into contact with the end 502A.

[0126] On the other hand, in one or more preferred embodiments, as the one illustrated (see figure 10), the second connection device 800 comprises an electrical connector (not illustrated) configured to couple to the first output pole 403 of the electric transformer 400, a first hydraulic connector 802 configured to couple to the outlet 402 of the electric transformer 400, a second hydraulic connector 803 configured to couple to an end 902A of a conduit 902 of the hydraulic line of the cooling system that supplies the cooling fluid to the first welding electrode 202, and a third hydraulic connector 804 configured to couple to an end 903A of a conduit 903 of the hydraulic line of the cooling system that supplies the cooling fluid to the second welding electrode 302. The three hydraulic connectors 802, 803, 804 are placed, inside the device 800, in fluid communication so that the cooling fluid entering the device through connector 802 can exit the same device through the two connectors 803, 804.

[0127] Preferably, the connection device 800 comprises a hollow body on which said hydraulic connectors are defined and which is configured to place said connectors in mutual fluid communication. Preferably, the connection device 800 is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with the end 501 A of the first electrical conductor element 501 ; for example, said hollow body comprises one or more thermally conductive parts, or appendages, that come into contact with the end 501 A.

[0128] The two connection devices 700, 800 therefore perform the function of connecting, in a simple and rapid manner (without the use of tools), the electric transformer 400 simultaneously to the electrical circuit of the welding head and to the hydraulic line of the cooling system.

[0129] It is now noted that there are different models of electric transformers for electric spot-welding heads on the market, which differ from each other - besides other aspects - in the conformation of their respective electrical output poles and / or in the conformation of the inlet and outlet for the cooling fluid.

[0130] In welding heads according to the prior art, the choice of one type of transformer over another considerably influences the construction and assembly of the welding head, since, depending on the transformer model used, both the hydraulic line and the electrical circuit of the welding head vary.

[0131] Conversely, in the solution described here, thanks to the two connection devices 700 and 800, the use of one model of electric transformer over another simply implies the adoption of connection devices 700, 800 compatible with the model of the electric transformer used, i.e. , provided with electrical and hydraulic connectors capable of connecting to the connectors of the latter.

[0132] The two connection devices 700 and 800 can advantageously be identical to each other, so as to reduce the number of (distinct) components of the head. Returning to the description of the electrical circuit of the welding head, in one or more preferred embodiments, as the one illustrated (see figures 7, 8, 13 and 14), the end 501 B of the first electrical conductor element 501 , opposite the end 501 A connected to the electric transformer 400, is carried by a connection device 720 which electrically connects it to the first electrode-holder arm 200.

[0133] Similarly, the end 502B of the second electrical conductor element 502, opposite the end 502A connected to the electric transformer 400, is carried by a connection device 820 or 820' which electrically connects it to the second electrode-holder arm 300.

[0134] As will be seen in greater detail below, the two embodiments of figures 1 and 4 have respective connection devices 820, 820' which differ from each other due to the different configuration of the electrode-holder arms 200, 300 to which they are associated.

[0135] In one or more preferred embodiments, as the one illustrated (see figure 11 ), the connection device 720 comprises an electrical contact portion 721 , preferably having a planar conformation and placed in contact with the first electrode-holder arm 200 to electrically connect the latter to the end 501 B of the first electrical conductor element 501 .

[0136] In one or more preferred embodiments, as the one illustrated, the connection device 720 further comprises a first hydraulic connector 722, to which the end 902B of the conduit 902 is connected, which is connected, at its opposite end 902A, to the connection device 800, and a second hydraulic connector 723, to which a conduit 904 is connected that transports the cooling fluid to the first welding electrode 202.

[0137] The two hydraulic connectors 722, 723 are placed in fluid communication, inside the connection device, so that the cooling fluid entering the device through connector 722 can exit the same device through connector 723. Preferably, the connection device 700 comprises a hollow body on which said hydraulic connectors are defined and which is configured to place said connectors in mutual fluid communication. Preferably, the connection device is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with the end 501 B of the first electrical conductor element 501 and / or with the first electrode-holder arm 200; for example, said hollow body comprises thermally conductive parts, or appendages, that come into contact with the end 501 B and / or with the first electrode-holder arm 200.

[0138] Note that, in the operation of mounting the electrode-holder arm 200, the contact portion 721 of the connection device 720 can be used as a stop against which to place the electrode-holder arm 200 to identify its correct longitudinal position along the reference axis L.

[0139] In one or more preferred embodiments, as the one illustrated (see figure 12), the connection device 820 - which is used in the embodiment of figure 1 - comprises an electrical contact portion 821 , preferably having a planar conformation and placed in contact with the second electrode-holder arm 200 to electrically connect the latter to the end 502B of the second electrical conductor element 502.

[0140] In one or more preferred embodiments, as the one illustrated, the connection device 820 further comprises a first hydraulic connector 822, to which the end 903B of the conduit 903 is connected, which is connected, at its opposite end 903A, to the connection device 800, and a second hydraulic connector 823, to which a conduit 906 is connected that transports the cooling fluid to the second welding electrode 302.

[0141] The two hydraulic connectors 822, 823 are placed in fluid communication, inside the connection device, so that the cooling fluid entering the device through connector 822 can exit the same device through connector 823.

[0142] Preferably, the connection device 820 comprises a hollow body on which said hydraulic connectors are defined, and which is configured to place said connectors in mutual fluid communication. Preferably, the connection device 820 is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with the end 502B of the second electrical conductor element 502 and / or with the second electrode-holder arm 300; for example, said hollow body comprises thermally conductive parts, or appendages, that come into contact with the end 502B and / or with the second electrode-holder arm 300.

[0143] In one or more preferred embodiments, as the one illustrated, the two welding electrodes 202, 302 are both provided with an internal hydraulic circuit for the circulation of the cooling fluid, which is configured to place the respective electrode in a condition of thermal exchange with the circulating cooling fluid, and to whose inlet the conduit 904 or 905 is connected that supplies the cooling fluid to the electrode itself.

[0144] From the outlets of the internal hydraulic circuits of the two welding electrodes 202, 302, respective conduits 905, 907 start, which transport the now-heated cooling fluid up to the interface module 602.

[0145] With specific reference to the embodiment of figure 4 (see also figures 13, 14 and 15), the connection device 820' comprises an electrical contact portion 82T having a semi-annular conformation which receives the second electrode-holder arm 300 by engaging with it according to a sliding contact on a substantially cylindrical or semi-cylindrical area, to electrically connect the end 502B of the second electrical conductor element 502 to the second electrode-holder arm 300.

[0146] Furthermore, the connection device 820' comprises two hydraulic fittings 821 'B (only one of which is visible in figure 5) disposed in a position opposite to the electrical contact portion 821 ' and configured to hydraulically connect respectively to an inlet and an outlet (not visible) of an internal hydraulic circuit of the second arm, for the circulation of the cooling fluid, which extends up to the welding electrode 302.

[0147] In one or more preferred embodiments, as the one illustrated, the connection device 820' further comprises a hydraulic connector 822' to which the end 903B of the conduit 903 is connected, and which is in turn in fluid communication with the hydraulic connector 821 'B connected to the inlet of the internal hydraulic circuit of the second electrode-holder arm 300.

[0148] The connection device 820' comprises, finally, a hydraulic connector 823' to which a conduit 909 is connected, which transports the now-heated cooling fluid up to the interface module 602, and which is in turn in fluid communication with the hydraulic connector 821 'B connected to the outlet of the internal hydraulic circuit of the second electrode-holder arm 300.

[0149] Preferably, the connection device 820' comprises a hollow body on which said hydraulic connectors are defined and which is configured to place these connectors in mutual fluid communication as indicated above. Preferably, the connection device 820' is configured to place the cooling fluid, through which said hollow body is traversed, in a condition of thermal exchange with the end 502B of the second electrical conductor element 502; for example, said hollow body comprises one or more thermally conductive parts, or appendages, which are brought into contact with the end 502B.

[0150] Preferably, the various hydraulic and / or electrical connectors of the connection devices 700, 800, 720, 820, 820' described above are connectable according to a quick-attachment mode, for example by snap- fit, so as to facilitate and make faster the assembly and disassembly operations of the welding head.

[0151] As visible in figures 7 and 8, the conduits 904, 905, 906 and 907 extend until they reach the welding electrodes, running inside and along the arms 200 and 300, through a respective internal passage 207 or 307 made in each of the two arms.

[0152] Preferably, at the proximal ends 204, 304 of the arms 200, 300, to reach said internal passage starting from the connection devices 720, 820, these conduits are received inside respective grooves 90, which are made on the flank of the same proximal ends and extend longitudinally along the longitudinal direction of these ends, from a region of the start of the internal passage 207 or 307, and until they open onto the end face 204A or 304A of the respective arm intended to be placed in contact with the electrical contact portion 721 or 821 of the electrical connection device 720 or 820.

[0153] With particular reference to figures 17 and 18, in one or more preferred embodiments, as the one illustrated, the grooves 90 have a transverse section defining a circular arc profile extending over an angular interval greater than 180° and are open towards the outside, on the flank of the arm, with a narrow opening 90A, so as to prevent the respective conduit from exiting through this opening.

[0154] The Applicant has been able to verify that the provision of said grooves 90, instead of through holes made completely inside the proximal ends, offers the dual advantage of not significantly altering the electrical characteristics of the electrode-holder arm, in particular the value of its electrical resistance, and at the same time of retaining the conduits more effectively without, however, subjecting them to more intense wear phenomena, caused by the relative sliding of the conduits relative to the arms by which they are carried.

[0155] In the welding head according to the configuration of figures 13 and 14, the electrode-holder arm 200 can include the same grooves 90 described above.

[0156] In view of the aforementioned advantages, more generally the following invention can therefore be identified:

[0157] 1 . An electrode-holder arm (200; 300) for an electric spot-welding head comprising:

[0158] - a distal end, on which a welding electrode (202; 302) is carried;

[0159] - a proximal end (204; 304) configured to realize a connection of the electrode-holder arm to a support structure of the welding head, wherein said proximal end (204; 304) comprises an electrical contact face (204A, 304A) configured to be placed in contact with an electrical contact portion (721 ) of a connection device (720) of the welding head;

[0160] - a first internal passage (207; 307) extending from the proximal end to the distal end and configured to receive one or more conduits (904, 905; 906 and 907) for supplying a cooling fluid to the welding electrode; wherein on the proximal end (204; 304) one or more grooves (90) open towards the outside of the arm are made, which extend longitudinally along said proximal end, from said internal passage until they open onto said electrical contact face (204; 304), and which are configured to receive, each, a respective conduit of said one or more conduits for supplying a cooling fluid to the welding electrode, in a condition in which said respective conduit is completely contained inside said groove, so as not to protrude beyond the transverse footprint of the proximal end (204; 304).

[0161] 2. The electrode-holder arm according to point 1 , wherein each groove (90) of said one or more grooves (90) has a transverse section defining a circular arc profile extending over an angular interval greater than 180° and is open to the outside, preferably on a flank of the proximal end, with a narrow opening (90A), so as to prevent the respective conduit from exiting the groove (90) through this narrow opening (90A).

[0162] Naturally, the principle of the invention remaining the same, the details of construction and the embodiments may vary, even significantly, with respect to what has been illustrated here by way of non-limiting example only, without thereby departing from the scope of the invention, as defined by the attached claims.

Claims

CLAIMS1. Electric spot-welding head (10) for a multi-axis industrial robot arm, comprising:- a support structure (100) comprising at least one attachment portion (127) for attaching the welding head to the multi-axis industrial robot arm;- a first electrode-holder arm (200) carrying a first welding electrode (202) and connected to said support structure;- a second electrode-holder arm (200) carrying a second welding electrode and connected to said support structure (100); wherein at least said second electrode-holder arm (300) is actuatable via an actuator in a movement relative to said support structure between an open position in which the second welding electrode (302) carried by the second electrode-holder arm is further away from the first welding electrode (202) carried by the first electrode-holder arm (200) and a closed position in which the second welding electrode carried by the second electrode-holder arm is closer to the first welding electrode carried by the first electrodeholder arm,- an electric transformer (400) configured to apply an electrical voltage to said first and second welding electrodes (202, 302);- a first electrical conductor element (501 ), which electrically connects the electric transformer (400) to the first electrode-holder arm (200),- a second electrical conductor element (502), preferably flexible, which electrically connects the electric transformer (400) to the second electrode-holder arm (200),- a cooling system for cooling the following group of components or a related subgroup: said electric transformer, said first welding electrode, said second welding electrode, said first electrical conductor element, said second electrical conductor element, wherein said cooling system comprises a hydraulic line for transporting a cooling fluid and wherein said electric transformer (400) comprises:- a first output pole which is electrically connected to said first electrode-holder arm via said first electrical conductor element;- - a second output pole which is electrically connected to said secondelectrode-holder arm via said second electrical conductor element;- an inlet through which the cooling fluid transported by said hydraulic line of said cooling system is introduced inside the transformer; and- an outlet through which the cooling fluid exits from said transformer and returns inside said hydraulic line; said electric spot-welding head comprising: a first connection device (700), which carries a first end (502A) of said second electrical conductor element (502) and is electrically connected to said first end, wherein said first connection device (700) is removably coupleable to said electric transformer (400) so as to electrically connect said second output pole of said transformer to said first end (502A) of said second electrical conductor element and to place in fluid communication said inlet of said transformer with said hydraulic line of said cooling system; and a second connection device (800), which carries a first end (501 A) of said first electrical conductor element (501 ) and is electrically connected to said first end, wherein said second connection device (800) is removably coupleable to said electric transformer (400) so as to electrically connect said first output pole of said electric transformer to said first end (501 A) of said first electrical conductor element (501 ) and to place in fluid communication said outlet of said electric transformer with said hydraulic line of said cooling system.

2. Electric spot-welding head according to claim 1 , wherein said first connection device (700) comprises an electrical connector configured to couple to said first output pole of said electric transformer, a first hydraulic connector (702) configured to couple to said inlet of said transformer, and a second hydraulic connector (703) configured to couple to an end of a conduit (901 ) for supplying the cooling fluid to said electric transformer (400), wherein the two hydraulic connectors (702, 703) are placed in fluid communication, inside the connection device (700), so that the cooling fluid entering the device through the second connector (703), can exit the same device through the first connector (702).

3. Welding head according to claim 2, wherein said first connection device (700) comprises a hollow body on which said first and secondhydraulic connectors (702, 703) are defined, and which is configured to place said hydraulic connectors in mutual fluid communication.

4. Welding head according to claim 3, wherein said first connection device (700) is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with said first end (502A) of the second electrical conductor element (502), preferably said hollow body comprising one or more thermally conductive parts, or appendages, which are brought into contact with said first end (502A) of said second electrical conductor element (502).

5. Electric spot-welding head according to any one of the preceding claims, wherein said second connection device (800) comprises an electrical connector configured to couple to said second output pole of said electric transformer (400), a first hydraulic connector (802) configured to couple to said outlet of said electric transformer (400), a second hydraulic connector (803) configured to couple to an end of a conduit (902) of said hydraulic line for supplying the cooling fluid to the first welding electrode (202), and a third hydraulic connector (804) configured to couple to an end of a conduit (903) of said hydraulic line for supplying the cooling fluid to the second welding electrode (300), wherein said hydraulic connectors (802, 803, 804) are placed, inside the connection device (800), in fluid communication, so that the cooling fluid entering the device through the first hydraulic connector (802), can exit the same device through the second and the third hydraulic connector (803, 804).

6. Welding head according to claim 5, wherein said second connection device (800) comprises a hollow body on which said, first, second and third, hydraulic connectors (802, 803, 804) are defined, and which is configured to place said hydraulic connectors in mutual fluid communication.

7. Welding head according to claim 6, wherein said second connection device (800) is configured to place the cooling fluid through which said hollow body is traversed in a condition of thermal exchange with said first end (501 A) of the first electrical conductor element (501 ), preferably said hollow body comprising one or more thermally conductive parts, or appendages, which are brought into contact with said first end (501 A) of said first electrical conductor element (501 ).

8. Welding head according to any one of the preceding claims, further comprising, at least one interface module (601 , 602) for connecting the hydraulic line of the cooling system of the electric spot-welding head to a first external conduit for supplying the cooling fluid to the welding head, and to a second external conduit for removing the cooling fluid after it has been heated following the passage through the welding head, wherein said at least one interface module (601 , 602) is not part of said electric transformer (400) and comprises at least a first hydraulic connector (601 A) for connection to the first external conduit, and at least a second hydraulic connector (602A) for connection to the second external conduit.

9. Welding head according to claim 8, comprising:- a first interface module (601 ) for connecting the hydraulic line of the cooling system of the electric spot-welding head to the first external conduit, said first interface module comprising said first hydraulic connector (601 A); wherein said first interface module (601 ) is not part of said electric transformer (400) and is hydraulically connected, via a conduit (901 ) of said hydraulic line, to said first connection device (700),- a second interface module (602) for connecting the hydraulic line of the cooling system of the electric spot-welding head to the second external conduit, said second interface module (602) comprising said second hydraulic connector (602A); wherein said second interface module (601 ) is not part of said electric transformer (400) and is connected to two conduits (905, 907) of said hydraulic line which are configured to transport the cooling fluid exiting from said first and second welding electrodes (202, 302).

10. Welding head according to any one of the preceding claims, comprising an interface module (605) for connecting an external electrical cable for transmitting control signals from a control unit of the robot arm to the electric transformer, and vice versa, wherein said interface module (605) is not part of said electric transformer and is electrically connected thereto, and wherein said interface module (605) comprises a communication unit configured to receive the electrical control signals from the control unit of the robot arm and to transmit them to said electric transformer (440), andvice versa, wherein said interface module (605) has at least one electrical connector (605A) for connection to the external electrical cable.

11. Welding head according to any one of claims 8 to 10, wherein said electric transformer (400) is fixed to said support structure (100) via a shaped plate (140) fixed to a rear end (112) of said support structure (100), on a front end (116) of said support structure (100) said first electrodeholder arm (200) being received; wherein said shaped plate (140) comprises a first portion (141 ) fixed to said rear end (112), and a second and a third opposite portion (142, 143), which are oriented transversely to said first portion and between which said electric transformer is received, wherein said electric transformer is fixed to each of said second and third portion of said shaped plate via the interposition of at least one damping body (145), and wherein said at least one interface module and / or said interface module (601 , 602, 605) are fixed to said shaped plate (140).

12. Welding head according to claim 11 , wherein said first and second interface module (601 , 602) are mounted respectively on the second and third portion (142, 143) of the shaped plate (140) so as to be arranged on opposite sides with respect to said electric transformer (400), and wherein said interface module (605) is mounted on a rear appendage of said shaped plate (140) so as to be arranged at the rear end of the welding head.

13. Welding head according to any one of the preceding claims, wherein at least one of said first and second electrode-holder arm (200, 300) comprises:- a distal end, on which a welding electrode (202; 302) is carried;- a proximal end (204; 304) configured to realize a connection of the electrode-holder arm to a support structure of the welding head, wherein said proximal end (204; 304) comprises an electrical contact face (204A, 304A) configured to be placed in contact with an electrical contact portion (721 ) of a connection device (720) of the welding head;- a first internal passage (207; 307) extending from the proximal end to the distal end and configured to receive one or more conduits (904, 905;906 and 907) of said hydraulic line of said cooling system; wherein on the proximal end (204; 304) one or more grooves (90) open towards the outside of the arm are made, which extend longitudinally along said proximal end, from said internal passage until opening onto said electrical contact face (204; 304), and which are configured to receive, each, a respective conduit of said one or more conduits for supplying a cooling fluid to the welding electrode, in a condition in which said respective conduit is completely contained inside said groove, so as not to protrude beyond the transverse footprint of the proximal end (204; 304).

14. Welding head according to claim 13, wherein each groove (90) of said one or more grooves (90) has a transverse section defining a circular arc profile extending over an angular interval greater than 180° and is open to the outside, preferably on a flank of the proximal end, with a restricted opening (90A), so as to prevent the respective conduit from exiting the groove (90) through said restricted opening (90A).

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