Welding equipment, in particular for single-sided welding, and a related welding station

Abstract

There is described an item of welding equipment (1), in particular for single-sided welding, comprising: - a welding electrode (2) - a ground electrode (4) - a first robot (6) carried said welding electrode (2) a second robot (8) carrying said ground electrode (4).

Description

[0001] "Welding equipment , in particular for single-sided welding , and a related welding station"

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the Invention

[0004] The present invention refers to welding equipment , in particular to single-sided welding equipment commonly known in the art as single-sided equipment .

[0005] Known Art and General Technical Problem

[0006] The reference technical background of the invention according to the present patent application provides a few examples of single-sided welding heads with substantially fixed electrodes , or in the best of cases with electrodes which may move only axially, and a few examples of single-sided welding heads wherein an electrode has a transverse movement component .

[0007] A technical problem which is common to the known solutions primarily consists in the limited number of j oints on which they can operate .

[0008] As it is commonly known, a single-sided welding head has both electrodes ( a ground electrode and a welding electrode ) placed side by side , so that they are arranged on the same side of the set of sheets to be welded . This enables operating on given types of j oints for which a welding operation by means of a clamp welding head would be unfeasible , albeit with the drawback of having to provide , to a varying extent , an adj ustment to the geometry of the j oint itsel f .

[0009] A first reason of said drawback is due to the fact that in a j oint with two sheets the ground electrode and the active (welding) electrode shall each contact a distinct sheet, in order for the electrical welding process to take place . I f the geometry of the j oint does not allow the centre-to-centre distance o f the electrodes to achieve the necessary positioning, it is practically impossible to weld the j oint .

[0010] In the case of a motor vehicle , moreover, some types of j oints cannot be obtained by means of known single-sided welding heads , because the sheets have a geometric singularity ( a bump, a relief , or else a groove ) which are not compatible with the orientation of the electrodes on the welding head, and / or which would require a substantial modi fication of the sheets to be welded, with the only purpose of being able to position the electrodes of the single-sided welding head in a functionally acceptable fashion .

[0011] Irrespective of possible technologic constraints which may exist regarding the modi fication of some sheet components , it is necessary to consider that the operation may not always be carried out at a sustainable cost , since the modification of some sheet components may easily lead to redesigning the handling equipment of the sheet components themselves , as well as of other line facilities .

[0012] Document EP 3 653 328 Bl shows a partial solution to such a technical problem; however, despite a higher flexibility and a wider range of j oints which may be welded by means of the equipment according to said document , there is still a non-negligible variety of j oints the geometry whereof is intrinsically incompatible with single-sided welding equipment .

[0013] Obj ect of the Invention

[0014] The present invention aims at solving the technical problem described in the foregoing . In detail , the invention aims at providing single-sided welding equipment and a related welding station which are adapted to operate on any kind of j oints , regardless of the geometric constraints it may exhibit .

[0015] Summary of the Invention

[0016] The obj ect of the invention is achieved by means of single-sided welding equipment and by means of a welding station having the features set forth in the claims that follow, which form an integral part of the technical disclosure provided herein in relation to the invention .

[0017] Brief Description of the Figures

[0018] The invention will now be described with reference to the annexed Figures , which are provided purely by way of non-limiting example only and wherein :

[0019] - Figure 1 is a perspective view of an item of welding equipment and of a related welding station according to the invention;

[0020] Figure 2 and Figure 3 respectively show a welding electrode and a ground electrode for an item of welding equipment according to the invention, and

[0021] Figures 4 and 5 show respective operating conditions of the welding equipment and of the related welding station according to embodiments of the invention .

[0022] Detailed Description

[0023] Reference 1 in Figure 1 generally denotes an item of single-sided welding equipment according to the invention, while reference 100 generally denotes a single-sided welding station comprising at least one item of equipment 1 according to the invention .

[0024] In various embodiments , and referring to the Figures 2 , 3 , the equipment 1 comprises a welding electrode 2 , a ground electrode 4 , a first robot 6 carrying the welding electrode 2 and a second robot 8 carrying said ground electrode 4 . In this way, the welding electrode 2 and the ground electrode 4 are movable one with respect to the other by means of each of said first robot 6 and second robot 8 , which are distinct from each other . As can be seen in said Figures , the first robot 6 carries a single welding electrode 2 ( and the electrode 2 only, i . e . it does not carry other electrodes involved in the welding) , and the second robot 8 carries a single ground electrode 4 ( and the electrode 4 only, i . e . it does not carry other electrodes involved in the welding) . Preferably, the electrodes 2 and 4 on board the robots 6 , 8 are moreover electrically supplied by a single trans former, which is an advantage for the manufacturing and the implementation of the equipment .

[0025] Referring to Figure 2 , the welding electrode 2 comprises a first electrode body 10 , including a first coupling interface 12 , generally a flange , and a first electrode tip 14 , which is configured to contact a first sheet to be welded . The welding electrode 10 moreover comprises a first linear actuator 16 , configured to move the electrode tip 14 along an axis A16 with respect to the electrode body 10 . In this regard, the electrode tip is carried by a first slider 18 , which is movable along a first axis A10 and is operatively connected to the actuator 16 , and which is guided in its movement along axis A10 by a first straight guide 20 . The coupling with the first robot 6 takes place by means of the coupling interface 12 .

[0026] With reference to Figure 3 , the ground electrode 4 comprises a second electrode body 22 , including a second coupling interface 24 , generally a flange , and a second electrode tip 26 , which is configured to contact a second sheet to be welded with the first sheet , thereby closing the electric circuit ( developing across the metal of the sheets ) which triggers the resistance welding . The ground electrode 4 moreover comprises a second linear actuator 28 , configured to move the electrode tip 26 along a second axis A28 with respect to the electrode body 22 . In this regard, the electrode tip 26 is carried by a second slider 30 , which is movable along the axis A 28 and is operatively connected to the actuator 28 , and which is guided in its movement along the axis A10 by a second straight guide 32 . The coupling to the second robot 8 takes place via the coupling interface 24 . Moreover, as can be seen in Figures 2 , 3 , the first electrode tip 14 has an outer diameter D14 which is smaller than an outer diameter D26 of said second electrode tip 26 . Always referring to Figures 2 , 3 , the electrode tip 14 comprises a first contact end T14 , configured to be applied - by contacting it - onto the first sheet during welding, and the second electrode tip 26 comprises a second contact end T26 , configured to be applied - by contacting it - onto the second sheet during welding . The contact end T14 comprises a first contact surface , having a radius of curvature smaller than a radius of curvature of a second contact surface of the contact end T26 . The latter is preferably implemented in such a way as to be substantially planar and orthogonal to the axis A28 .

[0027] In more detail , with general reference to the Figures 1 and 3 , in preferred embodiments the first robot 6 is an articulated robot , speci fically an anthropomorphic robot , i . e . a robot comprising a robotic arm including a first wrist W6 at the end of the robotic arm, and also the second robot 8 is an articulated robot , speci fically an anthropomorphic robot , i . e . a robot comprising a robotic arm including a first wrist W8 at the end of the robotic arm . The welding electrode 2 is carried by the first wrist W6 , to which it is fixed via the coupling interface 12 in a fashion similar to the coupling of a general tool ( or end ef fector ) , and the ground electrode 4 is carried by the second wrist W8 , to which it is fixed via the coupling interface 24 , again in a fashion simi lar to the coupling of a general tool (or end effector) .

[0028] In the Figures 1, 4, 5, which show preferred embodiments, the robots 6 and 8 are shown as multi-axis (specifically, 6-axis) anthropomorphic robots, which are floor-mounted by means of respective bases 34 (robot 6) and 36 (robot 8) . In the case of an anthropomorphic robot, each base 34, 36 carries a set of articulated elements which define the corresponding robotic arm and which include, in sequence, a shoulder, an elbow, an arm and, at the free end of the arm, the wrist W6 or W8. However, the invention also encompasses embodiments wherein each of the robots 6, 8 is a robot which may be mounted overhead. This means that the general structure of the robot may be kept unvaried with respect to the floor-mounted robots (therefore, it is possible to envisage overhead-mounted articulated, preferably anthropomorphic, robots) ; the only change will regard the fixation fashion, which will be moved overhead with respect to the floor.

[0029] The single-sided welding equipment 1 enables, thanks to the installation of the electrodes 2, 4 on board two mechanically independent robots, achieving a positioning of the electrodes 2, 4 with a number of degrees of freedom which is not available in the case of electrodes installed on a single electrode body, albeit movable one with respect to the other as in the case of the solution according to EP 3 653 328 Bl, wherein the range of positions available for the welding and the ground electrodes is actually limited by the installation thereof on one and the same electrode body. In the case of equipment 1, the relative position of the electrodes 2, 4, and specifically the position of the electrode tips 14, 26 along the axes A16, A28 and the (absolute and relative) inclination of the axes A16, A28 can be varied along the whole movement range available to the robots 6 , 8 ( in addition to the actuators 16 , 28 ) . This enables orienting the electrodes 2 , 4 in space in such a way as to adapt to any configuration of the first and the second sheets that are to be welded . Moreover , the installation of the electrodes 2 , 4 on board the robots 6 , 8 enables varying the center-to-center distance between said electrodes in an enormously greater freedom with respect to the known solutions , wherein the electrodes are installed on a single electrode body, wherein the center-to-center distance is necessarily limited by the mounting on the same electrode body .

[0030] This enables establishing the contact with the sheets - while respecting the functional constraints due to the need of implementing an electric circuit between the tips 14 and 26 , so as to perform resistance welding - even in positions remote from each other, thereby enabling, for example , bypassing a geometric constraint which would be unsurmountable with the known configurations o f single-sided welding equipment . In other words , whereas the welding electrode is still positioned at the area where the welding spot shall be obtained, the ground electrode may also be positioned in an area which is remote from the welding spot but free from any obstacle , provided that the electric circuit defined between the welding electrode 2 and the ground electrode 4 ( electrically) enables performing the welding .

[0031] Referring to the Figures 1 , 4 , 5 , by means of the equipment 1 it is possible to implement a single-sided welding station 100 for any application which involves the welding of a first sheet with a second sheet , wherein the station 100 generally comprises :

[0032] - a work area WA, configured to receive a set of sheets to be welded; in the preferred embodiment shown in Figure 1 , the work area WA comprises an assembly line AL for motor vehicle bodies V, which in turn includes a fixed path 102 along which assembly supports ( so-called "pallets" ) 104 are adapted to move , wherein the set of sheets comprises a plurality of body sheets of a motor vehicle ; at least one item of single-sided welding equipment 1 , wherein the first robot 6 and the second robot 8 are configured to position, respectively, the welding electrode 2 and the ground electrode 4 at the work area for welding the set of sheets .

[0033] This of fers various possibilities to install the robots 6 , 8 . A first possibil ity corresponds to an arrangement of the first robot 6 and of the second robot 8 on the same side of the work area WA. This also includes configurations which - with reference to the line AL - provide an item of welding equipment 1 for each side of the area WA, astride the line AL ( Figure 1 ) •

[0034] A second possibility, which is not shown in the Figures as it i s immediately evident , envisages the installation of the first robot 6 and of the second robot 8 on opposite sides of the work area WA. This means that it is possible to have the welding electrode 2 carried by the robot 6 on one side of the area WA, and the ground electrode 4 carried by the robot 8 on an opposite side of the area WA. In stations 100 which do not contemplate the continuous movement of the sets of sheets ( as is the case in the assembly line AL ) it is moreover possible to arrange the robots 6 , 8 on adj acent / consecutive sides of the area WA.

[0035] Finally, it is possible to have a single robot 8 carrying a single ground electrode , and two robots 6 each carrying a respective welding electrode 2 , which are arranged on opposite sides of the area WA ( astride the line AL, with reference to Figure 1 ; Figure 1 shows a condition of rest of the welding equipment 1 ) . Thereby it is possible to perform two welding operations in two di f ferent locations by using a single ground electrode , therefore further limiting the ef fect of possible constraints or geometric singularities on the welding .

[0036] As can be seen especially in the Figures 4 and 5 , the equipment 1 may operate in conditions of singlesided welding which are unpracticable for any known single-sided welding equipment , such as a condition which involves the positioning of the electrodes 2 , 4 astride a pillar "B" 106 of the body V ( Figure 4 ) , in order to perform a welding operation at an area which is behind the surface of the pillar 106 , or else a condition which involves the execution of a welding operation at a longitudinal rail 108 of the body V ( Figure 5 ) , which is an area having a complex geometry which poses many limitations to the positioning of the electrodes 2 , 4 . The flexibility of the welding equipment 1 is so high that it may even be used to perform welding operations with a two-sided configuration of the electrodes , in areas wherein such a configuration may be simpler compared to the s inglesided configuration, without necessarily implying a coaxial positioning of the tips 14 , 26 .

[0037] On an operational level , the invention therefore also defines a method for operating a welding station 100 , comprising : positioning a temporarily assembled set of sheets at the work area WA; an example may be a set of sheets for a vehicle body, which sheets are prepositioned by means of so-called tacking devices before welding; actuating the first robot 6 , to bring the welding electrode 2 into contact with the first sheet of the set , actuating the second robot 8 , to bring the ground electrode 4 into contact with the second sheet of the set , which in turn is arranged in a relationship of electric conduction with the first sheet , supplying an electric current between the welding electrode and the ground electrode across the first sheet and the second sheet , to obtain a welded j oint between the first sheet and the second sheet .

[0038] Moreover, in view of the considerations about the connection of the electrodes 2 , 4 to a single trans former, supplying an electric current to the welding electrode 2 and to the ground electrode 4 across the first sheet and the second sheet comprises supplying the electric current by means of said single trans former .

[0039] Of course , the implementation details and the embodiments may amply vary with respect to what has been described and illustrated, without departing from the extent of the present invention as defined by the annexed claims .

Claims

CLAIMS1. Welding equipment (1) , in particular for single-sided welding, comprising:- a welding electrode (2)- a ground electrode (4) a first robot (6) carrying said welding electrode (2) a second robot (8) carrying said ground electrode ( 4 ) .

2. Equipment (1) according to claim 1, wherein said welding electrode (2) and said ground electrode (4) are movable one with respect to the other by means of each of said first robot (6) and second robot (8) .

3. Equipment (1) according to claim 1 or claim 2, wherein said first robot (6) is an articulated robot comprising a first robotic arm including a first wrist (W6) , and said second robot (8) is an articulated robot comprising a second robotic arm including a second wrist (W8) , wherein said welding electrode (2) is carried by said first wrist (W6) and said ground electrode (4) is carried by said second wrist (W8) .

4. Equipment (1) according to claim 3, wherein each of said first robot (6) and second robot (8) is, alternatively,- a floor-mountable robot (34, 36) ,- an overhead-mountable robot.

5. Equipment (1) according to any of the preceding claims, wherein: the welding electrode (2) comprises a first electrode body (10) including a first coupling interface (12) for coupling to said first robot (6) , and a first electrode tip (14) configured to contact a first sheet to be welded, the first electrode tip (14) being movable with respect to said first electrode body (10) , in particular along a first axis (A16) ,the ground electrode (4) comprises a second electrode body (22) including a second coupling interface (24) for coupling to said second robot (6) , and a second electrode tip (26) configured to contact a second sheet to be welded with the first sheet, the second electrode tip (26) being movable with respect to said second electrode body (22) , in particular along a second axis (A28) .

6. Equipment (1) according to any of the claims 1 to 4, wherein: the welding electrode (2) comprises a first electrode body (10) including a first coupling interface (12) for coupling to said first robot (6) , and a first electrode tip (14) configured to contact a first sheet to be welded, the welding electrode (2) moreover comprising a first linear actuator (16) configured to move the electrode tip (14) along a first axis (A16) with respect to the first electrode body (10) , the ground electrode (4) comprises a second electrode body (22) including a second coupling interface (24) for coupling to said second robot (6) , and a second electrode tip (26) configured to contact a second sheet to be welded with the first sheet, the ground electrode (4) moreover comprising a second linear actuator (28) configured to move the second electrode tip (26) along a second axis (A28) with respect to the second electrode body (22) .

7. Welding equipment (1) according to any of the preceding claims, wherein:- the first robot (6) carries a single welding electrode (2)- the second robot (8) carries a single ground electrode ( 4 ) .

8. Welding equipment (1) according to any of theclaims 5 to 7, wherein: said first electrode tip (14) has an outer diameter (D14) smaller than an outer diameter (D26) of said second electrode tip (26) ,- the first electrode tip (14) comprises a first contact end (T14) comprising a first contact surface, configured to be applied onto a first sheet during a welding operation,- the second electrode tip (26) comprises a first contact end (T26) comprising a second contact surface, configured to be applied onto a second sheet to be welded with the first sheet, during welding, the first contact surface having a radius of curvature smaller than a radius of curvature of the second contact surface.

9. A welding station (100) , in particular for single-sided welding, comprising:- a work area (WA) configured to receive a set of sheets to be welded at least one item of welding equipment (1) according to any of the preceding claims, wherein the first robot (6) and the second robot (8) are configured to respectively position the welding electrode (2) and the ground electrode (4) at the work area (WA) for welding said set of sheets.

10. A welding station (100) according to claim 9, wherein the first robot (6) and the second robot (8) are positioned on one and the same side of said work area (WA) .

11. A welding station (100) according to claim 9, wherein the first robot (6) and the second robot (8) are positioned on opposite sides of said work area (WA) .

12. A welding station (100) according to any of the claims 9 to 11, wherein the work area (WA)comprises an assembly line (AL) for motor vehicle bodies (V) , and wherein the set of sheets comprises a plurality of sheets of a motor vehicle body.

13. A welding station (100) according to any of the claims 9 to 12, wherein the welding electrode (2) carried by the first robot (6) and the ground electrode carried by the second robot (8) are electrically connected to a single transformer.

14. A method for operating a welding station (100) according to any of the claims 9 to 13, comprising: positioning a temporarily assembled set of sheets at the work area (WA) , actuating the first robot (6) to bring the welding electrode (2) into contact with a first sheet of the set, actuating the second robot (8) to bring the ground electrode (4) into contact with a second sheet of the set, which in turn is arranged in a relationship of electric conduction with said first sheet, supplying an electric current between said welding electrode (2) and said ground electrode (4) across the first sheet and the second sheet, in order to obtain a welded joint between the first sheet and the second sheet.

15. A method according to claim 14, wherein said supplying an electric current between said welding electrode (2) and said ground electrode (4) across the first sheet and the second sheet comprises supplying said electric current by means of a single transformer.

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