EP4646309A1 - Spot welding electrode and corresponding spot welding assembly and spot welding device - Google Patents

Spot welding electrode and corresponding spot welding assembly and spot welding device

Info

Publication number
EP4646309A1
EP4646309A1 EP23707158.4A EP23707158A EP4646309A1 EP 4646309 A1 EP4646309 A1 EP 4646309A1 EP 23707158 A EP23707158 A EP 23707158A EP 4646309 A1 EP4646309 A1 EP 4646309A1
Authority
EP
European Patent Office
Prior art keywords
spot welding
electrode
active surface
assemblies
electrodes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23707158.4A
Other languages
German (de)
French (fr)
Inventor
Jonathan DANY
Dominique Duthoo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Areva NP SAS
Original Assignee
Framatome SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Framatome SA filed Critical Framatome SA
Publication of EP4646309A1 publication Critical patent/EP4646309A1/en
Pending legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/10—Spot welding; Stitch welding
    • B23K11/11—Spot welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes
    • B23K11/31—Electrode holders and actuating devices therefor
    • B23K11/312—Electrode holders and actuating devices therefor for several electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/04—Tubular or hollow articles

Definitions

  • the present invention relates to the technical field of spot welding, in particular for spot welding parts of nuclear components, more precisely parts of a structure of a nuclear fuel assembly.
  • a nuclear fuel assembly of a pressurized water reactor comprises a structure and a bundle of fuel rods supported by the structure.
  • the structure comprises a lower nozzle and an upper nozzle spaced along an assembly axis, guide tubes extending longitudinally between the lower nozzle and the upper nozzle, and a plurality of spacer grids distributed between the lower nozzle and the upper nozzle, the guide tubes extending through the spacer grids.
  • the fuel rods are received between the lower nozzle and the upper nozzle extending through the spacer grids which maintains the fuel rods longitudinally along the assembly axis and transversely, the fuel rods being held in transversely spaced relationship.
  • Each spacer grid is for example fastened to each guide tube via at least one pair of tabs of the spacer grid, the two tabs of each pair of tabs contacting opposite sides of the guide tube, each tab having an arched profile matching the outer surface of the guide tube.
  • spot welding gun In order to weld the two tabs of a pair of tabs to a guide tube, it is possible to use a spot welding gun, the spot welding gun having two electrodes each having an active surface of spherical shape, with using the spot welding gun for pressing the active surface of each electrode on a respective tab and to generate an electrical current between the two electrodes such as to spot weld each tab to the guide tube.
  • Imprecise positioning of the electrodes relative to the tabs may lead to unreliable spot welds and/or to a reduction of the lifetime of the electrodes.
  • One of the aims of the invention is to provide a spot welding electrode that eases the positioning of the spot welding electrode during spot welding operations, that allow reducing the superficies of the welded areas with a satisfying mechanical strength, and that can exhibit a long lifetime.
  • the invention proposes a spot welding electrode having an active surface for contact with a part to be welded, wherein the active surface is convex and profiled along a longitudinal axis.
  • a conventional spot welding electrode with a spherical active surface may be difficult to position precisely on a convex surface of a welding part.
  • an electrode having an active surface profiled along a longitudinal axis allows the spot welding electrode to make appropriate contact with a convex surface of a welding part for a plurality of positions of the electrode along the longitudinal axis. This makes the positioning of the electrode easier.
  • that electrode may be orientated with the longitudinal axis making a non-zero angle with the welding part axis such that the active surface of the electrode and the convex surface of the welding part contact each other punctually at a point located along a generatrix of the active surface of the electrode and a generatrix of the convex surface of the welding part.
  • the spot welding electrode comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
  • the active surface is a portion of a cylindrical surface centered on the electrode active surface axis;
  • a radius of curvature of the active surface is comprised between 8 mm and 12 mm;
  • the active surface has a width comprised between 2 mm and 4 mm, the width being taken transversely between two side edges of the active surface parallel to the longitudinal axis.
  • the invention also relates to a spot welding assembly comprising an electrode holder and at least one spot welding electrode as defined above.
  • the spot welding assembly comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
  • each spot welding electrode is attached to the electrode holder in a removable manner for allowing replacement of a used spot welding electrode by a new spot welding electrode ;
  • each spot welding electrode has a mounting portion configured for insertion into a mounting hole of the other;
  • each spot welding electrode has a mounting portion configured for insertion into a mounting hole of the electrode holder;
  • the spot welding assembly comprises two spot welding electrodes;
  • the active surfaces of the two spot welding electrodes are profiled along respective longitudinal axes which are coplanar;
  • each sport welding electrode is a portion of a cylindrical surface
  • the longitudinal axes of the two spot welding electrodes define between them an angle comprised between 60° and 120°, in particular an angle comprised between 80° and 100°.
  • the invention still relates to a spot welding device comprising two spot welding assemblies, one or each spot welding assembly being as defined above, and a spot welding gun configured for supporting the two spot welding assemblies and for generating an electrical current between the two spot welding assemblies while pressing the two spot welding assemblies on parts to be welded together.
  • the spot welding device comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
  • the spot welding gun comprises two support members, each support member being configured for supporting a respective one of the two spot welding assemblies, the two support members being movable between a rest position in which the two spot welding assemblies are moved apart and a welding position in which the two spot welding assemblies are moved closer for welding two parts;
  • the two support members are movable in translation one relative to each other, for example telescopically.
  • FIG. 1 is a diagrammatical side view of a spot welding device comprising two spot welding assemblies
  • FIG. 2 is a perspective view of a spot welding assembly according to one example
  • FIG. 7 is a diagrammatical side view illustrating the contact between an active surface of a spot welding electrode and a convex surface of a welding part.
  • a spot welding device 2 is configured for spot welding parts to be welded or “welding parts” 4, 6 which are placed in contact.
  • the welding parts 4, 6 are preferably electrically conductive.
  • the welding parts are preferably made of metal.
  • the welding parts 4, 6 comprise for example a tube (welding part 6) extending along a tube axis and two tabs (welding parts 4) positioned on the tube at two diametrically opposed positions relative the tube axis.
  • Each tab is for example in the shape of a portion of cylinder extending along a tab axis.
  • the tab axis coincides with the tube axis when the tab is position on the tube.
  • Each welding part 4 provided as a tab has a convex surface 4A.
  • the spot welding device 2 comprises two spot welding assemblies 8, each spot welding assembly 8 comprising an electrode holder 10 and at least one spot welding electrode 12, each spot welding electrode 12 being supported by the electrode holder 10 and comprising an active surface 14 for contacting one of the two welding parts 4, 6.
  • each spot welding electrode 12 of each spot welding assembly 8 contacts a convex surface 4A of one of the welding parts 4, 6.
  • the welding gun 15 comprises for example two support members 16, each support member 16 being configured for supporting a respective one of the two spot welding assemblies 8, the two support members 16 being movable one relative to the other between a rest position in which the two spot welding assemblies 8 are moved apart and a welding position in which the two spot welding assemblies 8 are moved closer.
  • the rest position is adapted for placing the two spot welding assemblies 8 on both sides of the welding parts 4, 6.
  • the welding position is adapted for clamping the welding parts 4, 6 between the two spot welding assemblies 8.
  • the welding gun 15 is for example configured for moving the two support members 16 in translation along a clamping direction one relative to the other between the rest position and the welding position (see arrow F on Figure 1 ).
  • the two support members 16 are for example mounted telescopically one onto the other such as to be movable in translation one relative to the other between the rest position and the welding position.
  • the spot welding device 2 comprises for example an actuator 18 configured for moving the two support members 16 one relative to the other between the rest position and the welding.
  • the actuator 18 is for example an electrical actuator.
  • the actuator is an hydraulic actuator or a pneumatic actuator.
  • the actuator 18 is for example a linear actuator. In a variant, the actuator 18 is a rotational actuator.
  • a transmission device is optionally provided between the actuator 18 and the support members 16, for example for converting a rotational movement generated by the actuator 18 into a translational movement imparted to at least one of the support members 16.
  • the spot welding device 2 is configured for generating an electrical current between the spot welding electrode(s) 12 of one spot welding assembly 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8.
  • the electrical current circulates through the welding parts 4, 6 with melting the material of the welding parts 4, 6 at the interface(s) between the welding parts 4, 6 and thus welding the welding parts 4, 6 together.
  • the welding parts 4, 6 comprise a tube and two tabs arranged on opposed sides of the tube
  • a mandrel is inserted inside the tube to ease the flow of the electrical current through the tube from one of the tabs to the other.
  • the mandrel is preferably made of metal.
  • the spot welding device 2 comprises a electrical feed unit 20 configured for generating a difference of electrical potential between the spot welding electrode(s) 12 of one spot welding assembly 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8 such as to generate the electrical current when the spot welding electrodes 12 of the welding assemblies 8 are brought in contact with the welding parts 4, 6.
  • the spot welding device 2 preferably comprises an electrical control unit 22 configured for controlling the spot welding device 2 for performing the welding operations, and in particular for controlling the actuator 18 for controlling the movement of the support members 16 and/or controlling the electrical feed unit 20 for feeding electricity to the spot welding electrode(s) 12 of the spot welding assemblies 8.
  • an electrical control unit 22 configured for controlling the spot welding device 2 for performing the welding operations, and in particular for controlling the actuator 18 for controlling the movement of the support members 16 and/or controlling the electrical feed unit 20 for feeding electricity to the spot welding electrode(s) 12 of the spot welding assemblies 8.
  • the spot welding device 2 is for example configured such that the active surface(s) 14 of the spot welding electrode(s) 12 of one spot welding assembly 8 face the active surface(s) 14 of the spot welding electrode(s) 12 of the other spot welding assembly 8 when the spot welding assemblies 8 are mounted on the support members 16.
  • the welding gun 15 supports the spot welding assemblies 8. Welding parts 4, 6 are placed in contact.
  • the welding gun 15 is controlled such that the spot welding assemblies 8 are in the rest position.
  • the welding gun 15 is moved, e.g. by a robotic arm, to position the spot welding assemblies 8 on either sides of the welding parts 4, 6 placed in contact one(s) with the other(s).
  • the welding gun 15 is controlled to move the spot welding assemblies 8 in the welding position such that the spot welding electrodes 12 are in contact with the welding parts 4, 6 and generate an electrical current between the spot welding electrode(s) 12 of one of the spot welding assemblies 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8, through the welding parts 4, 6.
  • the welding gun 15 is then controlled to move the spot welding assemblies 8 back in the rest position.
  • the two spot welding assemblies 8 are similar or identical. Only one spot welding assembly 8 will be described in the following with reference to Figures 2 - 5.
  • the spot welding assembly 8 comprises the electrode holder 10 and at least one spot welding electrode 12 supported by electrode holder 10, each spot welding electrode 12 having an active surface 14 for contacting a welding part 4, 6 (i.e. a part to be welded).
  • Each spot welding electrode 12 is made of an electrically conductive material, preferably a metal.
  • each spot welding electrode 12 is convex and profiled along a longitudinal axis A associated to this spot welding electrode 12.
  • the profiled active surface 14 of each spot welding electrode 12 is made of an infinity of rectilinear lines parallel to the longitudinal axis A passing via the profile of the active surface 14 of said spot welding electrode 12.
  • Each rectilinear line of a profiled surface is named a generatrix.
  • each spot welding electrode 12 has preferably a radius of curvature comprised between 8 mm and 12 mm in each point of the active surface 14, in particular a radius of 10 mm in each point of the active surface 14.
  • each spot welding electrode 12 is advantageously a portion of a cylindrical surface of circular cross-section centered on the longitudinal axis A.
  • each spot welding electrode 12 has a profile that is arc of a circle in view along the longitudinal axis A associated to this spot welding electrode 12.
  • the radius of curvature of the active surface 14 of each spot welding electrode 12 is constant.
  • the radius of curvature of the active surface 14 of each spot welding electrode 12 which is a portion of a cylindrical surface of circular cross-section is preferably comprises between 8 mm and 12 mm and is in particular about 10 mm.
  • each active surface 14 has a width W taken between two side edges of the active surface 14 parallel to the electrode active surface axis A associated to this active surface 14.
  • the width W is preferably comprised between 2 mm and 4 mm.
  • each active surface 14 has a length taken along the longitudinal axis A associated to this active surface 14.
  • the length is preferably comprised between 4 mm and 8 mm, in particular between 5 mm and 7 mm.
  • the spot welding assembly 8 has advantageously two spot welding electrodes 12.
  • the two spot welding electrodes 12 are separate. There is a non-zero distance between the active surfaces 14 of the two spot welding electrodes 12.
  • the two spot welding electrodes 12 are preferably arranged one relative to the other such that the active surfaces 14 of the spot welding electrodes 12 make linear contacts with a same planar surface onto which the two spot welding electrodes 12 are applied simulataneously.
  • the respective longitudinal axes A of the two spot welding electrodes 12 are coplanar.
  • the respective longitudinal axes A of the two spot welding electrodes 12 define a non-zero angle between them.
  • the angle between the longitudinal axes A of the two spot welding electrodes 12 is preferably comprised between 60° and 120°, in particular between 80° and 100°, more in particular between 85° and 95°.
  • the angle between the longitudinal axes A of the two spot welding electrodes 12 is 88°.
  • the angle between the coplanar longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 is taken in view along a direction perpendicular to the plane defined by the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12.
  • the two spot welding electrodes 12 are preferably arranged one relative to the other such that the active surfaces 14 of the two spot welding electrodes 12 make a linear contact with a same planar surface parallel to the plane defined by the coplanar longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12.
  • the active surface 14 of each spot welding electrode 12 is a portion of a cylindrical surface of circular cross-section, the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 are coplanar, the active surfaces 14 of the spot welding electrodes 12 have the same radius of curvature, and, preferably, the longitudinal axes A of the active surfaces 14 of two spot welding electrodes 12 define a non-zero angle between them.
  • the two spot welding electrodes 12 are preferably symmetrical with respect to a median plan P extending between the two spot welding electrodes 12.
  • the spot welding assembly 8 is preferably symmetrical with respect to the median plan P.
  • the electrode holder 10 is configured for supporting each spot welding electrode 12 and for fastening the electrode holder on a spot welding device 2, in particular on a support member 14 of a spot welding device 2.
  • the electrode holder 10 is for example provided with a fastening hole 24 configured for receiving a fastening member, such as a screw, for fastening the electrode holder 10 to a spot welding device 2, in particular to a support member 14 of a spot welding device 2.
  • a fastening member such as a screw
  • the electrode holder 10 comprises for example a holder body 26 configured for mounting the electrode holder 10 on a spot welding device 2, in particular on a support member 14 of a spot welding device 2, and two arms 28, each arm 28 extending from the holder body 26 and supporting a respective spot welding electrode 12.
  • Each arm 28 has for example a proximal end connected to the holder body 26 and a distal end supporting the corresponding spot welding electrode 12.
  • the electrode holder 10 has for example a “Y” shape, the holder body 26 defining the leg of the “Y” and each arm 26 defining a respective branch of the “Y” shape.
  • the fastening hole 24 is for example provided through the holder body 26.
  • the spot welding gun 15 is preferably configured such that when the spot welding assemblies 8 are mounted on the spot welding gun 15, a plan defined by the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 of one or each spot welding assembly 8 is substantially perpendicular to a pressing direction along which the spot welding assemblies 8 are pressed on the welding parts 4, 6.
  • the spot welding gun 15 comprises support members 16 movable in translation one relative to the other
  • the spot welding gun 15 is configured such the plan defined by the longitudinal axes A of the two spot welding electrodes 12 of one or each spot welding assembly 8 is perpendicular to the direction of translation of the support members 16 one relative to the other.
  • the electrode holder 10 is preferably electrically conductive.
  • the electrode holder 10 is for example made of an electrically conductive material, preferably a metal.
  • each spot welding electrode 12 is electrically connected to the electrical feed unit 20 via the electrode holder 10.
  • At least one or each spot welding electrode 12 of the spot welding assembly 8 is made integrally in one single piece of material with the electrode holder 10.
  • a spot welding assembly 8 is configured such that each spot welding electrode 12 is removably mounted on the electrode holder 10.
  • the spot welding assembly 8 comprises a mounting assembly for mounting each spot welding electrode 12 on the electrode holder 10 in a removable manner.
  • the mounting assembly is for example configured for mounting at least one or each spot welding electrode 12 individually on the electrode holder 10 and/or for mounting at least two spot welding electrodes 12 jointly on the electrode holder 10, said two spot welding electrodes 12 being preferably made unitary in a single piece of material.
  • the spot welding electrodes 12 are separate and the mounting assembly is for configured for mounting each spot welding electrode 12 individually on the electrode holder 10.
  • at least two spot welding electrodes 12 are made unitary in a single piece of material and the mounting assembly is for configured for mounting the spot welding electrode 12 jointly on the electrode holder 10.
  • the mounting assembly comprises for example at least one mounting hole extending along a mounting axis and at least one mounting portion, each mounting portion being configured for insertion into a corresponding mounting hole, each mounting hole being provided one of the electrode holder 10 and a spot welding electrode 12, the corresponding mounting portion being provided on the other.
  • Each mounting hole is for example conical and the corresponding mounting portion is of a conical shape complementary to that of the mounting hole. With such a configuration, the mounting portion inserted into the mounting hole can stick inside the mounting hole sufficiently during welding operations such that no additional retaining device is necessary.
  • Each conical mounting hole defines a tapered seat.
  • the mounting assembly is configured such that each spot welding electrode 12 is mounted on the electrode holder 10 along a mounting axis with being indexed angularly and/or locked in rotation relative to the electrode holder 10 about this mounting axis.
  • At least one mounting hole has a non-circular cross-section and the corresponding mounting portion has a corresponding non-circular cross-section.
  • At least one mounting hole has an elliptical cross-section, the corresponding mounting portion having a corresponding elliptical cross-section and/or at least one mounting hole has a flat and the corresponding mounting portion has a corresponding flat.
  • At least one or each spot welding electrode 12 is mounted on the electrode holder 10 via two distinct mounting holes and two corresponding mounting portions.
  • the two mounting holes are provided on the electrode holder 10, the two mounting portions being provided on the spot welding electrode 12, or the two mounting holes are provided on the spot welding electrode 12, the two mounting portions being provided on the electrode holder 10, or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrode 12.
  • the mounting assembly comprises two mounting holes and two corresponding mounting portions for each spot welding electrode 12 mounted individually onto the electrode holder 10.
  • the two mounting holes are for example provided on the electrode holder 10, the two mounting portion being provided on the spot welding electrode 12 mounted individually onto the electrode holder 10, or the two mounting holes are for example provided on the spot welding electrode 12 mounted individually onto the electrode holder 10, the two mounting portions being provided on the electrode holder 10 or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrode 12 mounted individually onto the electrode holder 10.
  • the mounting assembly comprises two mounting holes and two corresponding mounting portions.
  • the two mounting holes are for example provided on the electrode holder 10, the two mounting portion being provided on the spot welding electrodes 12 mounted jointly onto the electrode holder 10, or the two mounting holes are for example provided on the two spot welding electrode 12 mounted jointly onto the electrode holder 10, the two mounting portions being provided on the electrode holder 10 or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrodes 12 mounted jointly onto the electrode holder 10.
  • electrode holder 10 has a respective mounting hole 30 for each spot welding electrode 12 and each spot welding electrode 12 comprises a mounting portion 32 configured for insertion into the corresponding mounting hole 30.
  • Each mounting hole 30 extends for example along a mounting axis B with being conical and the mounting portion of each spot welding electrode 12 is of a conical shape complementary to that of the mounting hole 30.
  • each mounting hole 30 has a hole flat 30A and the corresponding mounting portion 32 has a portion flat 32A.
  • Removable spot welding electrodes 12 make it possible to replace a used spot welding electrode 12 of the spot welding assembly 8 without replacing the entire spot welding assembly 8.
  • the electrode holder 10 When the electrode holder 10 supports a plurality of spot welding electrodes 12, the electrode holder 10 is reusable with a plurality of sets of spot welding electrodes 12, with replacing a worn set of spot welding electrodes 12 by new spot welding electrodes 12.
  • the invention is not limited to the examples and variants described above. Other examples and variants may be contemplated.
  • the spot welding assembly 8 may comprises one single spot welding electrode 12.
  • the unique spot welding electrode 12 may be formed integrally in one single piece of material with the electrode holder 10 or removably mounted on the electrode holder 10.
  • a spot welding assembly 8 may comprises more than two spot welding electrodes 12 supported by the electrode holder 10.
  • the spot welding assembly 8 comprises at least one spot welding electrode 12 supported by the electrode holder 10, and in particular one spot welding electrode 12, two spot welding electrodes 12 or more than two spot welding electrodes 12.
  • each spot welding assembly has spot welding electrodes 12 each having an active surface 14 which is profiled.
  • a spot welding assembly 8 comprises a spot welding electrode 12 having an active surface 14 that is convex and profiled, in particular an active surface 14 that is a portion of a cylindrical surface, preferably a portion of a cylindrical surface of circular cross-section, and another spot welding electrode having an active surface that is a portion of a spherical surface.
  • the spot welding device 2 comprises two spot welding assemblies 8 each comprising at least one a spot welding electrode 12 having an active surface 14 which is profiled.
  • a spot welding device 2 comprises one spot welding assembly 8 having a spot welding electrode 12 having an active surface 14 that is convex and profiled, in particular an active surface 14 that is a portion of a cylindrical surface, preferably a portion of a cylindrical surface of circular cross-section, and another spot welding assembly comprising at least one spot welding electrode, each spot welding electrode of the other spot welding assembly having an active surface that is a portion of a spherical surface.
  • a spot welding electrode 12 having an active surface 14 that is profiled along longitudinal axis A renders the positioning of the spot welding electrode 12 relative to a convex surface 4A of a welding part 4 easier for making a contact point M that is precisely located on the welding part 4.
  • the position of the contacting point M on the convex surface 4 can remain the same even if the position of the spot welding electrode 12 along the electrode axis A is changed.
  • the lifetime of the spot welding electrode 12 can be increased.
  • a spot welding assembly 8 provided with an electrode holder 10 removably holding at least one spot welding electrode 12 make it possible to replace a used spot welding electrode 12 with a new spot welding electrode 12and reusing the electrode holder 10, which is more economical.
  • the spot welding electrode 12, the spot welding assembly 8 comprising the spot welding electrode 12 or a spot welding device 2 comprising a spot welding assembly 8 can be used in particular in the nuclear technical field, for example for welding metal parts of a structure of a nuclear fuel assembly.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Resistance Welding (AREA)

Abstract

The spot welding electrode has an active surface (14) for contact with a part to be welded (4, 6), wherein the active surface (14) is convex and profiled along a longitudinal axis (A).

Description

Spot welding electrode and corresponding spot welding assembly and spot welding device
The present invention relates to the technical field of spot welding, in particular for spot welding parts of nuclear components, more precisely parts of a structure of a nuclear fuel assembly.
In the domain of nuclear power plants, it is critical to ensure a proper welding of parts that needs to be welded, such as to ensure a controlled and reliable welding which is critical for durability and safety.
A nuclear fuel assembly of a pressurized water reactor comprises a structure and a bundle of fuel rods supported by the structure.
The structure comprises a lower nozzle and an upper nozzle spaced along an assembly axis, guide tubes extending longitudinally between the lower nozzle and the upper nozzle, and a plurality of spacer grids distributed between the lower nozzle and the upper nozzle, the guide tubes extending through the spacer grids.
The fuel rods are received between the lower nozzle and the upper nozzle extending through the spacer grids which maintains the fuel rods longitudinally along the assembly axis and transversely, the fuel rods being held in transversely spaced relationship.
Each spacer grid is for example fastened to each guide tube via at least one pair of tabs of the spacer grid, the two tabs of each pair of tabs contacting opposite sides of the guide tube, each tab having an arched profile matching the outer surface of the guide tube.
In order to weld the two tabs of a pair of tabs to a guide tube, it is possible to use a spot welding gun, the spot welding gun having two electrodes each having an active surface of spherical shape, with using the spot welding gun for pressing the active surface of each electrode on a respective tab and to generate an electrical current between the two electrodes such as to spot weld each tab to the guide tube.
However, it is necessary to position the electrodes very precisely on the tabs to ensure the generation of controlled and reliable welding spots between the tabs and the guide tube. Imprecise positioning of the electrodes relative to the tabs may lead to unreliable spot welds and/or to a reduction of the lifetime of the electrodes.
One of the aims of the invention is to provide a spot welding electrode that eases the positioning of the spot welding electrode during spot welding operations, that allow reducing the superficies of the welded areas with a satisfying mechanical strength, and that can exhibit a long lifetime. To this end, the invention proposes a spot welding electrode having an active surface for contact with a part to be welded, wherein the active surface is convex and profiled along a longitudinal axis.
A conventional spot welding electrode with a spherical active surface may be difficult to position precisely on a convex surface of a welding part.
The provision of an electrode having an active surface profiled along a longitudinal axis allows the spot welding electrode to make appropriate contact with a convex surface of a welding part for a plurality of positions of the electrode along the longitudinal axis. This makes the positioning of the electrode easier.
In particular, when the convex surface of the welding part is profiled along a welding part axis, that electrode may be orientated with the longitudinal axis making a non-zero angle with the welding part axis such that the active surface of the electrode and the convex surface of the welding part contact each other punctually at a point located along a generatrix of the active surface of the electrode and a generatrix of the convex surface of the welding part.
In specific embodiments, the spot welding electrode comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
- the active surface is a portion of a cylindrical surface centered on the electrode active surface axis;
- a radius of curvature of the active surface is comprised between 8 mm and 12 mm;
- the active surface has a width comprised between 2 mm and 4 mm, the width being taken transversely between two side edges of the active surface parallel to the longitudinal axis.
The invention also relates to a spot welding assembly comprising an electrode holder and at least one spot welding electrode as defined above.
In specific embodiments, the spot welding assembly comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
- each spot welding electrode is attached to the electrode holder in a removable manner for allowing replacement of a used spot welding electrode by a new spot welding electrode ;
- one of the electrode holder and each spot welding electrode has a mounting portion configured for insertion into a mounting hole of the other;
- each spot welding electrode has a mounting portion configured for insertion into a mounting hole of the electrode holder; - the spot welding assembly comprises two spot welding electrodes;
- the active surfaces of the two spot welding electrodes are profiled along respective longitudinal axes which are coplanar;
- the active surface of each sport welding electrode is a portion of a cylindrical surface;
- the active surfaces of the spot welding electrodes have the same radius of curvature;
- the longitudinal axes of the active surfaces of two spot welding electrodes define a non-zero angle between them;
- the longitudinal axes of the two spot welding electrodes define between them an angle comprised between 60° and 120°, in particular an angle comprised between 80° and 100°.
The invention still relates to a spot welding device comprising two spot welding assemblies, one or each spot welding assembly being as defined above, and a spot welding gun configured for supporting the two spot welding assemblies and for generating an electrical current between the two spot welding assemblies while pressing the two spot welding assemblies on parts to be welded together.
In specific embodiments, the spot welding device comprises one or several of the following optional features, taken individually or according to any technically feasible combination:
- the spot welding gun comprises two support members, each support member being configured for supporting a respective one of the two spot welding assemblies, the two support members being movable between a rest position in which the two spot welding assemblies are moved apart and a welding position in which the two spot welding assemblies are moved closer for welding two parts;
- the two support members are movable in translation one relative to each other, for example telescopically.
The invention and its advantages will be better understood upon reading the following description which is given solely by way of non-limiting example and with reference to the appended drawings, in which:
- Figure 1 is a diagrammatical side view of a spot welding device comprising two spot welding assemblies;
- Figure 2 is a perspective view of a spot welding assembly according to one example;
- Figure 3 is a front view of the spot welding assembly of Figure 2; - Figure 4 and 5 are sides view of the spot welding assembly of Figure 2 taken along two different view directions illustrated respectively by arrows V4 and V5 on Figure 3;
- Figure 6 is a perspective view of a spot welding assembly according to another example;
- Figure 7 is a diagrammatical side view illustrating the contact between an active surface of a spot welding electrode and a convex surface of a welding part.
As illustrated on Figure 1 , a spot welding device 2 is configured for spot welding parts to be welded or “welding parts” 4, 6 which are placed in contact. The welding parts 4, 6 are preferably electrically conductive. The welding parts are preferably made of metal.
As illustrated on Figure 1 , the welding parts 4, 6 comprise for example a tube (welding part 6) extending along a tube axis and two tabs (welding parts 4) positioned on the tube at two diametrically opposed positions relative the tube axis.
Each tab is for example in the shape of a portion of cylinder extending along a tab axis. The tab axis coincides with the tube axis when the tab is position on the tube.
Each welding part 4 provided as a tab has a convex surface 4A.
The spot welding device 2 comprises two spot welding assemblies 8, each spot welding assembly 8 comprising an electrode holder 10 and at least one spot welding electrode 12, each spot welding electrode 12 being supported by the electrode holder 10 and comprising an active surface 14 for contacting one of the two welding parts 4, 6.
The spot welding device 2 comprises a welding gun 15 supporting the two spot welding assemblies 8 and configured for pressing the two spot welding assemblies 8 on the welding parts 4, 6, each spot welding assembly 8 being in contact with a respective one of the welding parts 4, 6 via the active surface 14 of each spot welding electrode 12 of said spot welding assembly 8.
Preferably, the active surface 14 of each spot welding electrode 12 of each spot welding assembly 8 contacts a convex surface 4A of one of the welding parts 4, 6.
The welding gun 15 comprises for example two support members 16, each support member 16 being configured for supporting a respective one of the two spot welding assemblies 8, the two support members 16 being movable one relative to the other between a rest position in which the two spot welding assemblies 8 are moved apart and a welding position in which the two spot welding assemblies 8 are moved closer.
The rest position is adapted for placing the two spot welding assemblies 8 on both sides of the welding parts 4, 6. The welding position is adapted for clamping the welding parts 4, 6 between the two spot welding assemblies 8. The welding gun 15 is for example configured for moving the two support members 16 in translation along a clamping direction one relative to the other between the rest position and the welding position (see arrow F on Figure 1 ).
The two support members 16 are for example mounted telescopically one onto the other such as to be movable in translation one relative to the other between the rest position and the welding position.
The spot welding device 2 comprises for example an actuator 18 configured for moving the two support members 16 one relative to the other between the rest position and the welding.
The actuator 18 is for example an electrical actuator. In a variant, the actuator is an hydraulic actuator or a pneumatic actuator.
The actuator 18 is for example a linear actuator. In a variant, the actuator 18 is a rotational actuator.
A transmission device is optionally provided between the actuator 18 and the support members 16, for example for converting a rotational movement generated by the actuator 18 into a translational movement imparted to at least one of the support members 16.
The spot welding device 2 is configured for generating an electrical current between the spot welding electrode(s) 12 of one spot welding assembly 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8.
Upon generating such a current when the spot welding assemblies 8 are clamping the welding parts 4, 6, the electrical current circulates through the welding parts 4, 6 with melting the material of the welding parts 4, 6 at the interface(s) between the welding parts 4, 6 and thus welding the welding parts 4, 6 together.
Optionally, when the welding parts 4, 6 comprise a tube and two tabs arranged on opposed sides of the tube, a mandrel is inserted inside the tube to ease the flow of the electrical current through the tube from one of the tabs to the other. The mandrel is preferably made of metal.
The spot welding device 2 comprises a electrical feed unit 20 configured for generating a difference of electrical potential between the spot welding electrode(s) 12 of one spot welding assembly 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8 such as to generate the electrical current when the spot welding electrodes 12 of the welding assemblies 8 are brought in contact with the welding parts 4, 6.
The spot welding device 2 preferably comprises an electrical control unit 22 configured for controlling the spot welding device 2 for performing the welding operations, and in particular for controlling the actuator 18 for controlling the movement of the support members 16 and/or controlling the electrical feed unit 20 for feeding electricity to the spot welding electrode(s) 12 of the spot welding assemblies 8.
The spot welding device 2 is for example configured such that the active surface(s) 14 of the spot welding electrode(s) 12 of one spot welding assembly 8 face the active surface(s) 14 of the spot welding electrode(s) 12 of the other spot welding assembly 8 when the spot welding assemblies 8 are mounted on the support members 16.
Preferably, the active surface 14 of each spot welding electrode 12 of one spot welding assembly 8 faces the active surface 14 of a respective spot welding electrode 12 of the other spot welding assembly 8.
In the welding position of the support members 16, the active surface 14 of each spot welding electrode 12 of one spot welding assembly 8 and the active surface 14 of the corresponding spot welding electrode 12 of the other sport welding assembly 8 are in register.
In operation, the welding gun 15 supports the spot welding assemblies 8. Welding parts 4, 6 are placed in contact.
The welding gun 15 is controlled such that the spot welding assemblies 8 are in the rest position. The welding gun 15 is moved, e.g. by a robotic arm, to position the spot welding assemblies 8 on either sides of the welding parts 4, 6 placed in contact one(s) with the other(s).
The welding gun 15 is controlled to move the spot welding assemblies 8 in the welding position such that the spot welding electrodes 12 are in contact with the welding parts 4, 6 and generate an electrical current between the spot welding electrode(s) 12 of one of the spot welding assemblies 8 and the spot welding electrode(s) 12 of the other spot welding assembly 8, through the welding parts 4, 6.
The welding gun 15 is then controlled to move the spot welding assemblies 8 back in the rest position.
The two spot welding assemblies 8 are similar or identical. Only one spot welding assembly 8 will be described in the following with reference to Figures 2 - 5.
As illustrated on Figure 2 - 5, the spot welding assembly 8 comprises the electrode holder 10 and at least one spot welding electrode 12 supported by electrode holder 10, each spot welding electrode 12 having an active surface 14 for contacting a welding part 4, 6 (i.e. a part to be welded).
Each spot welding electrode 12 is made of an electrically conductive material, preferably a metal.
The active surface 14 of each spot welding electrode 12 is convex and profiled along a longitudinal axis A associated to this spot welding electrode 12. The profiled active surface 14 of each spot welding electrode 12 is made of an infinity of rectilinear lines parallel to the longitudinal axis A passing via the profile of the active surface 14 of said spot welding electrode 12. Each rectilinear line of a profiled surface is named a generatrix.
The active surface 14 of each spot welding electrode 12 has preferably a radius of curvature comprised between 8 mm and 12 mm in each point of the active surface 14, in particular a radius of 10 mm in each point of the active surface 14.
The active surface 14 of each spot welding electrode 12 is advantageously a portion of a cylindrical surface of circular cross-section centered on the longitudinal axis A.
In other words, the active surface 14 of each spot welding electrode 12 has a profile that is arc of a circle in view along the longitudinal axis A associated to this spot welding electrode 12.
In such case, the radius of curvature of the active surface 14 of each spot welding electrode 12 is constant.
Preferably, the radius of curvature of the active surface 14 of each spot welding electrode 12 which is a portion of a cylindrical surface of circular cross-section is preferably comprises between 8 mm and 12 mm and is in particular about 10 mm.
Preferably, each active surface 14 has a width W taken between two side edges of the active surface 14 parallel to the electrode active surface axis A associated to this active surface 14. The width W is preferably comprised between 2 mm and 4 mm.
Preferably, each active surface 14 has a length taken along the longitudinal axis A associated to this active surface 14. The length is preferably comprised between 4 mm and 8 mm, in particular between 5 mm and 7 mm.
As illustrated on Figures 2 - 5, the spot welding assembly 8 has advantageously two spot welding electrodes 12.
The two spot welding electrodes 12 are separate. There is a non-zero distance between the active surfaces 14 of the two spot welding electrodes 12.
The two spot welding electrodes 12 are preferably arranged one relative to the other such that the active surfaces 14 of the spot welding electrodes 12 make linear contacts with a same planar surface onto which the two spot welding electrodes 12 are applied simulataneously.
Preferably, the respective longitudinal axes A of the two spot welding electrodes 12 are coplanar.
Preferably, the respective longitudinal axes A of the two spot welding electrodes 12 define a non-zero angle between them. In such case, the angle between the longitudinal axes A of the two spot welding electrodes 12 is preferably comprised between 60° and 120°, in particular between 80° and 100°, more in particular between 85° and 95°. In a preferred example, the angle between the longitudinal axes A of the two spot welding electrodes 12 is 88°.
The angle between the coplanar longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 is taken in view along a direction perpendicular to the plane defined by the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12.
The two spot welding electrodes 12 are preferably arranged one relative to the other such that the active surfaces 14 of the two spot welding electrodes 12 make a linear contact with a same planar surface parallel to the plane defined by the coplanar longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12.
In a preferred example, as illustrated on Figures 2 - 5, the active surface 14 of each spot welding electrode 12 is a portion of a cylindrical surface of circular cross-section, the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 are coplanar, the active surfaces 14 of the spot welding electrodes 12 have the same radius of curvature, and, preferably, the longitudinal axes A of the active surfaces 14 of two spot welding electrodes 12 define a non-zero angle between them.
The two spot welding electrodes 12 are preferably symmetrical with respect to a median plan P extending between the two spot welding electrodes 12.
The spot welding assembly 8 is preferably symmetrical with respect to the median plan P.
The electrode holder 10 is configured for supporting each spot welding electrode 12 and for fastening the electrode holder on a spot welding device 2, in particular on a support member 14 of a spot welding device 2.
The electrode holder 10 is for example provided with a fastening hole 24 configured for receiving a fastening member, such as a screw, for fastening the electrode holder 10 to a spot welding device 2, in particular to a support member 14 of a spot welding device 2.
The electrode holder 10 comprises for example a holder body 26 configured for mounting the electrode holder 10 on a spot welding device 2, in particular on a support member 14 of a spot welding device 2, and two arms 28, each arm 28 extending from the holder body 26 and supporting a respective spot welding electrode 12.
Each arm 28 has for example a proximal end connected to the holder body 26 and a distal end supporting the corresponding spot welding electrode 12.
The electrode holder 10 has for example a “Y” shape, the holder body 26 defining the leg of the “Y” and each arm 26 defining a respective branch of the “Y” shape. When provided, the fastening hole 24 is for example provided through the holder body 26.
The spot welding gun 15 is preferably configured such that when the spot welding assemblies 8 are mounted on the spot welding gun 15, a plan defined by the longitudinal axes A of the active surfaces 14 of the two spot welding electrodes 12 of one or each spot welding assembly 8 is substantially perpendicular to a pressing direction along which the spot welding assemblies 8 are pressed on the welding parts 4, 6.
In particular, when the spot welding gun 15 comprises support members 16 movable in translation one relative to the other, the spot welding gun 15 is configured such the plan defined by the longitudinal axes A of the two spot welding electrodes 12 of one or each spot welding assembly 8 is perpendicular to the direction of translation of the support members 16 one relative to the other.
The electrode holder 10 is preferably electrically conductive. The electrode holder 10 is for example made of an electrically conductive material, preferably a metal.
The electrically conductive electrode holder 10 is advantageously in electrical contact with each spot welding electrode 12 held by the electrode holder 10.
When the electrode holder 10 is mounted on the spot welding gun 15, each spot welding electrode 12 is electrically connected to the electrical feed unit 20 via the electrode holder 10.
As illustrated on Figures 2 - 5, at least one or each spot welding electrode 12 of the spot welding assembly 8 is made integrally in one single piece of material with the electrode holder 10.
In such case, when a spot welding electrode 12 is worn away, it is necessary to replace the entire used spot welding assembly 8 with new spot welding assembly 8.
As illustrated on Figure 6, in a variant, a spot welding assembly 8 is configured such that each spot welding electrode 12 is removably mounted on the electrode holder 10.
In one example, the spot welding assembly 8 comprises a mounting assembly for mounting each spot welding electrode 12 on the electrode holder 10 in a removable manner.
The mounting assembly is for example configured for mounting at least one or each spot welding electrode 12 individually on the electrode holder 10 and/or for mounting at least two spot welding electrodes 12 jointly on the electrode holder 10, said two spot welding electrodes 12 being preferably made unitary in a single piece of material.
In one example, the spot welding electrodes 12 are separate and the mounting assembly is for configured for mounting each spot welding electrode 12 individually on the electrode holder 10. In another example, at least two spot welding electrodes 12 are made unitary in a single piece of material and the mounting assembly is for configured for mounting the spot welding electrode 12 jointly on the electrode holder 10.
The mounting assembly comprises for example at least one mounting hole extending along a mounting axis and at least one mounting portion, each mounting portion being configured for insertion into a corresponding mounting hole, each mounting hole being provided one of the electrode holder 10 and a spot welding electrode 12, the corresponding mounting portion being provided on the other.
Each mounting hole is for example conical and the corresponding mounting portion is of a conical shape complementary to that of the mounting hole. With such a configuration, the mounting portion inserted into the mounting hole can stick inside the mounting hole sufficiently during welding operations such that no additional retaining device is necessary. Each conical mounting hole defines a tapered seat.
Advantageously, the mounting assembly is configured such that each spot welding electrode 12 is mounted on the electrode holder 10 along a mounting axis with being indexed angularly and/or locked in rotation relative to the electrode holder 10 about this mounting axis.
In one example, at least one mounting hole has a non-circular cross-section and the corresponding mounting portion has a corresponding non-circular cross-section.
For example, at least one mounting hole has an elliptical cross-section, the corresponding mounting portion having a corresponding elliptical cross-section and/or at least one mounting hole has a flat and the corresponding mounting portion has a corresponding flat.
Optionally or alternatively, at least one or each spot welding electrode 12 is mounted on the electrode holder 10 via two distinct mounting holes and two corresponding mounting portions.
The provision of two mounting holes and two corresponding mounting portions provide angular indexation and/or rotation locking.
In such case, the two mounting holes are provided on the electrode holder 10, the two mounting portions being provided on the spot welding electrode 12, or the two mounting holes are provided on the spot welding electrode 12, the two mounting portions being provided on the electrode holder 10, or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrode 12. In one example, the mounting assembly comprises two mounting holes and two corresponding mounting portions for each spot welding electrode 12 mounted individually onto the electrode holder 10.
In such case, the two mounting holes are for example provided on the electrode holder 10, the two mounting portion being provided on the spot welding electrode 12 mounted individually onto the electrode holder 10, or the two mounting holes are for example provided on the spot welding electrode 12 mounted individually onto the electrode holder 10, the two mounting portions being provided on the electrode holder 10 or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrode 12 mounted individually onto the electrode holder 10.
In one example, for two spot welding electrodes 12 are made unitary in a single piece of material and mounted jointly on the electrode holder 10, the mounting assembly comprises two mounting holes and two corresponding mounting portions.
In such case the two mounting holes are for example provided on the electrode holder 10, the two mounting portion being provided on the spot welding electrodes 12 mounted jointly onto the electrode holder 10, or the two mounting holes are for example provided on the two spot welding electrode 12 mounted jointly onto the electrode holder 10, the two mounting portions being provided on the electrode holder 10 or one mounting hole and one mounting portion are provided on the electrode holder 10, the corresponding mounting portion and mounting hole portion being provided on the spot welding electrodes 12 mounted jointly onto the electrode holder 10.
In a particular example, electrode holder 10 has a respective mounting hole 30 for each spot welding electrode 12 and each spot welding electrode 12 comprises a mounting portion 32 configured for insertion into the corresponding mounting hole 30.
Each mounting hole 30 extends for example along a mounting axis B with being conical and the mounting portion of each spot welding electrode 12 is of a conical shape complementary to that of the mounting hole 30.
Optionally, each mounting hole 30 has a hole flat 30A and the corresponding mounting portion 32 has a portion flat 32A.
Removable spot welding electrodes 12 make it possible to replace a used spot welding electrode 12 of the spot welding assembly 8 without replacing the entire spot welding assembly 8.
When the electrode holder 10 supports a plurality of spot welding electrodes 12, the electrode holder 10 is reusable with a plurality of sets of spot welding electrodes 12, with replacing a worn set of spot welding electrodes 12 by new spot welding electrodes 12. The invention is not limited to the examples and variants described above. Other examples and variants may be contemplated.
The spot welding assembly 8 may comprises one single spot welding electrode 12. The unique spot welding electrode 12 may be formed integrally in one single piece of material with the electrode holder 10 or removably mounted on the electrode holder 10.
A spot welding assembly 8 may comprises more than two spot welding electrodes 12 supported by the electrode holder 10.
In a general manner, the spot welding assembly 8 comprises at least one spot welding electrode 12 supported by the electrode holder 10, and in particular one spot welding electrode 12, two spot welding electrodes 12 or more than two spot welding electrodes 12.
In the example of Figures 1 - 5, each spot welding assembly has spot welding electrodes 12 each having an active surface 14 which is profiled.
Each spot welding assembly 8 having two spot welding electrodes does not necessarily comprises two spot welding electrodes 12 having active surfaces 14 which is profiled.
In another example, a spot welding assembly 8 comprises a spot welding electrode 12 having an active surface 14 that is convex and profiled, in particular an active surface 14 that is a portion of a cylindrical surface, preferably a portion of a cylindrical surface of circular cross-section, and another spot welding electrode having an active surface that is a portion of a spherical surface.
Similarly, in the example of Figures 1 - 5, the spot welding device 2 comprises two spot welding assemblies 8 each comprising at least one a spot welding electrode 12 having an active surface 14 which is profiled.
In another example, a spot welding device 2 comprises one spot welding assembly 8 having a spot welding electrode 12 having an active surface 14 that is convex and profiled, in particular an active surface 14 that is a portion of a cylindrical surface, preferably a portion of a cylindrical surface of circular cross-section, and another spot welding assembly comprising at least one spot welding electrode, each spot welding electrode of the other spot welding assembly having an active surface that is a portion of a spherical surface.
As illustrated on a Figure 7, a spot welding electrode 12 having an active surface 14 that is profiled along longitudinal axis A renders the positioning of the spot welding electrode 12 relative to a convex surface 4A of a welding part 4 easier for making a contact point M that is precisely located on the welding part 4. As a matter of fact, the position of the contacting point M on the convex surface 4 can remain the same even if the position of the spot welding electrode 12 along the electrode axis A is changed.
In particular, when the convex surface 4A is profiled along a welding part axis B, the spot welding electrode 12 can be orientated such that the longitudinal axis A and the welding part axis B make a non-zero angle between them whereby the active surface 14 and the convex surface 4A will come into contact at a contacting point M of the convex surface 4 which remains the same even if the spot welding electrode 12 is moved along the longitudinal axis A relative to the welding part 4.
Besides, if the spot welding electrode 12 perform welding operations repetitively making a contacting point M which his precise on the welding parts 4 but which varies on the active surface 14 of the spot welding electrode 12 from one welding operation to the other, the lifetime of the spot welding electrode 12 can be increased.
Owing to the invention, a spot welding electrode 12 has a convex active surface 14 that is profiled along a longitudinal axis A makes the positioning of the spot welding electrode 12 easier and enables increased lifetime of the spot welding electrode 12.
Besides, a spot welding assembly 8 provided with an electrode holder 10 removably holding at least one spot welding electrode 12 make it possible to replace a used spot welding electrode 12 with a new spot welding electrode 12and reusing the electrode holder 10, which is more economical.
The spot welding electrode 12, the spot welding assembly 8 comprising the spot welding electrode 12 or a spot welding device 2 comprising a spot welding assembly 8 can be used in particular in the nuclear technical field, for example for welding metal parts of a structure of a nuclear fuel assembly.
It can be used on various other technical domain for welding together metal parts of any kind. It can for example be used on the automotive industry for welding parts of the structure of an automotive vehicle.

Claims

1. Spot welding electrode having an active surface (14) for contact with a part to be welded (4, 6), wherein the active surface (14) is convex and profiled along a longitudinal axis (A).
2. Spot welding electrode according to claim 1 , wherein the active surface (14) is a portion of a cylindrical surface centered on the electrode active surface axis (A).
3. Spot welding electrode according to claim 1 or 2, wherein a radius (R) of curvature of the active surface (14) is comprised between 8 mm and 12 mm.
4. Spot welding electrode according to any one of the preceding claims, wherein the active surface (14) has a width comprised between 2 mm and 4 mm, the width being taken transversely between two side edges of the active surface (14) parallel to the longitudinal axis (A).
5. Spot welding assembly according to any one of the preceding claims, comprising an electrode holder (10) and at least one spot welding electrode (12) according to any one of the preceding claims.
6. Spot welding assembly according to claim 5, wherein each spot welding electrode (12) is attached to the electrode holder (10) in a removable manner for allowing replacement of a used spot welding electrode (12) by a new spot welding electrode (12).
7. Spot welding assembly according to claim 5 or 6, wherein one of the electrode holder (10) and each spot welding electrode (12) has a mounting portion (32) configured for insertion into a mounting hole (30) of the other.
8. Spot welding assembly according to any one of claims 5 - 7, wherein each spot welding electrode (12) has a mounting portion (32) configured for insertion into a mounting hole (30) of the electrode holder (10).
9. Spot welding assembly according to any one claims 5 - 8, comprising two spot welding electrodes (12).
10. Spot welding assembly according to claim 9, wherein the active surfaces (14) of the two spot welding electrodes (12) are profiled along respective longitudinal axes (A) which are coplanar.
11. Spot welding assembly according to claim 9 or 10, wherein the longitudinal axes (A) of the two spot welding electrodes (12) define a non-zero angle between them.
12. Spot welding assembly according to any one of claims 9 - 1 1 , wherein the longitudinal axes (A) of the two spot welding electrodes (12) define between them an angle comprised between 60° and 120°, in particular an angle comprised between 80° and 100°.
13. Spot welding device comprising two spot welding assemblies (8), one or each spot welding assembly being according to any one of claims 5 - 12, and a spot welding gun (15) configured for supporting the two spot welding assemblies (8) and for generating an electrical current between the two spot welding assemblies (8) while pressing the two spot welding assemblies (8) on parts (4, 6) to be welded together.
14. Spot welding device according to claim 13, wherein the spot welding gun (15) comprises two support members (16), each support member (16) being configured for supporting a respective one of the two spot welding assemblies (8), the two support members (16) being movable between a rest position in which the two spot welding assemblies (8) are moved apart and a welding position in which the two spot welding assemblies (8) are moved closer for welding two parts (4, 6).
15. Spot welding device according to claim 14, wherein the two support members (16) are movable in translation one relative to each other, for example telescopically.
EP23707158.4A 2023-01-05 2023-01-05 Spot welding electrode and corresponding spot welding assembly and spot welding device Pending EP4646309A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IB2023/000021 WO2024147025A1 (en) 2023-01-05 2023-01-05 Spot welding electrode and corresponding spot welding assembly and spot welding device

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CA2310025A1 (en) * 1997-08-14 1999-02-25 Magna Ihv Gesellschaft Fur Innenhochdruckverfahren Mbh Assembling electroconductive parts by electric current heating
DE19805196A1 (en) * 1998-02-10 1999-08-12 Herbert Hess Resistance welding electrode arrangement
US8785807B2 (en) * 2011-03-17 2014-07-22 GM Global Technology Operations LLC Welding electrode and method of forming a resistance spot weld joint

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