System and method for indirect resistance welding of sealing plate to anchor plate

Abstract

The invention relates to a system (S1) for indirect resistance welding of a sealing plate (1) of a tank configured to contain liquefied gas to an anchoring plate (22) arranged partially below the sealing plate (1), comprising:-a pair of electrodes and a current generator adapted to be connected to said electrodes (41, 42); -supports (5) capable of holding the electrodes relative to each other; -positioning means for positioning the support (5) against the sealing plate (1), capable of positioning a first of the electrodes (41) above the sealing plate (1) and a second of the electrodes (42) above a free portion of the anchoring plate (22); and-at least one actuator (9) capable of pressing the first electrode (41) against the sealing plate (1) and the second electrode (42) against the free portion of the anchor plate (22).

Description

Technical Field

[0001] The present invention relates to the field of tanks for liquid gases, such as liquefied natural gas (LNG), in particular for marine or river transport or for use in shore containers. More specifically, the present invention relates to a welding system for welding sealing plates suitable for such tanks, and to a related welding method. Background Art

[0002] Liquefied gas tanks each hold thousands, even tens of thousands, of cubic meters of liquefied gas. Ships transporting liquefied gas have cargo holds specially equipped to accommodate these tanks, and their cargo holds are often divided into several tanks. These tanks can also be built externally on ships for shore storage of liquefied natural gas.

[0003] Gas is held in a liquid state within a tank, for example, LNG, at -163°C (-163°C) at atmospheric pressure. Therefore, the tank must be watertight and thermally insulated. Consequently, the inner surface of such a tank is covered with a sealing membrane, typically made from an assembly of welded metal sealing plates (usually stainless steel), each of which forms part of the tank's sealing membrane.

[0004] The wall of the tank also comprises, in succession, below a sealing membrane configured to be in contact with the liquefied gas (this sealing membrane is called the primary sealing membrane):

[0005] - primary insulation, for example using a wooden shell filled with reinforced polyurethane foam,

[0006] - another sealing membrane, called secondary sealing membrane, made for example of thin sheet metal,

[0007] - A secondary thermal insulation layer, for example also made of a wooden shell filled with reinforced polyurethane foam.

[0008] The primary sealing membrane is attached to the primary insulation by welding sealing plates to anchor plates which are fixed to the primary insulation and can be riveted to the wooden shell of the primary insulation. These anchor plates form a grid around all the shells but do not completely cover them.

[0009] Currently, if Figure 1 As shown, the weld 3 attaching the sealing plate 1 to the anchor plate 22 is made manually by a welding method using arc heat, a method known as TIG (Tungsten Inert Gas).

[0010] The weld 3 is fillet welded to the edge 15 of the sealing plate 1 between its two corrugations 12, 14. These corrugations correspond to ribs on the sealing plate 1 which advantageously help to form the grid and allow for deformations of the tank due to its thermal variations.

[0011] The edge 15 of the sealing plate 1 extends parallel to a first axis A1 of a standard orthogonal reference system (A1, A2, A3). The corrugations 12 and 14 extend orthogonally to the first axis A1 and parallel to a second axis A2 of the standard orthogonal reference system. A third axis A3 of the orthogonal reference system extends orthogonally to the main extension plane of the sealing plate 1.

[0012] An anchor plate 22 is located between the two corrugations 12, 14 and is attached by rivets 24 to a wooden shell, here not visible from the primary insulation, which is also located between the two corrugations 12, 14. Further anchor plates 21 and 23 are located on either side of the anchor plate 22 and are attached by further rivets 24 to the other wooden shell of the primary insulation.

[0013] As in Figure 1 As can be seen in FIG, the sealing plate 1 is attached using six 20 mm (millimeters) long welds spaced 20 mm apart between the two corrugations 12, 14, allowing the sealing plate 1 to be attached over at least 220 mm between the two corrugations 12, 14. As an indication, the peak-to-peak distance d1 between the corrugations 12 and 14 is 340 mm, which leaves an allowance for their deformation.

[0014] The performance of fillet welds 3 is operational and allows for visual verification of the welds performed. However, this execution is manual, which means that it takes a long time to attach the tank's sealing plate to the anchor plate of the primary insulation layer. Automating these welds 3 using the TIG welding method would require very complex and expensive equipment, particularly for the automatic and precise tracking of the edges 15 of the sealing plate 1. In particular, positioning the rails on which the automated TIG welding machine would be placed would require a significant amount of time. Summary of the Invention

[0015] The object of the present invention is to remedy at least some of the above-mentioned drawbacks by, in particular, providing a welding system and a welding method which allow to accelerate the welding of the sealing plate of the tank to the anchoring plate of the tank in a simple and inexpensive manner while guaranteeing a good weld quality.

[0016] To this end, the present invention proposes a system for indirectly resistance welding a sealing plate of a tank configured to contain liquefied gas to an anchor plate, the anchor plate being partially arranged below the sealing plate so as to leave a free portion of the anchor plate outside the sealing plate, the sealing plate being separated from the free portion of the anchor plate by an edge of the sealing plate, the welding system comprising:

[0017] at least one pair of electrodes and a current generator adapted to be connected to said electrodes,

[0018] a support capable of holding electrodes of the at least one pair of electrodes relative to each other,

[0019] Positioning means for positioning the support against the sealing plate, capable of positioning the electrodes of the at least one pair of electrodes on either side of the edge by positioning one electrode of the at least one pair of electrodes, called the membrane electrode, above the sealing plate and the other electrode of the at least one pair of electrodes, called the anchor electrode, above the free portion of the anchor plate, and

[0020] At least one actuator for each pair of electrodes, which is capable of pressing the membrane electrode against the sealing plate and the anchor electrode against the free portion of the anchor plate.

[0021] By using an indirect resistance welding system, welds up to 5 mm in diameter can be produced between the sealing plate and the anchor plate beneath the membrane electrode. These welds are made by applying a current of several thousand amperes between the electrodes. Compared to existing techniques, this change in welding technology means that the sealing plate can be quickly attached to the anchor plate, for example, by welding only four welds between the two corrugations of the sealing plate and between the sealing plate and the anchor plate. These welds can be performed more quickly by the operator than fillet welds because they are spot welds and do not require very precise positioning of the weld seam relative to the edge of the sealing plate.

[0022] The welding system according to the present invention is capable of positioning the membrane electrode and the anchoring electrode on either side of the edge of a sealing plate arranged on the anchoring plate, allowing the membrane electrode to be positioned at a point on the sealing plate that is also above the portion of the anchoring plate that is located below the sealing plate, and allowing the anchoring electrode to be positioned on the anchoring plate so as to allow an indirect resistance welding point between the sealing plate and the anchoring plate.

[0023] The supports allow maintaining a predetermined distance between the electrodes so that when they are positioned by the positioning means, their respective distances from the edge of the sealing plate are:

[0024] short enough to allow the sealing plate to be welded to the anchor plate by heating produced by the Joule effect between these two plates due to the resistance created by the interface between the plates in the path of the current flowing through the electrodes,

[0025] and be large enough to prevent arcing which would create unacceptable protrusions and visible defects.

[0026] The electrodes located on the sealing plate must also not be too close to the edge, otherwise the sealing plate would overheat at this point, leading to local deformation and damage to the weld obtained.

[0027] For example, the electrodes are each approximately 8 mm relative to the edge of the sealing plate, their respective distances from this edge being preferably between 5 mm and 15 mm.

[0028] In embodiments with several pairs of electrodes, the support keeps the electrodes of different pairs at a distance from each other.

[0029] The support is, for example, a simple electrode holder allowing it to be moved manually to several points on the sealing plate that are not above the rivets on the anchoring plate.

[0030] The current generator of the welding system according to the invention is preferably located remote from the support so that it does not have to be moved simultaneously with the movement of the support in order to perform multiple welds. For example, the current generator is placed on a cart and is connected to the electrodes attached to the support via a metal conductor in the form of a large copper braid, taking into account the amperage used.

[0031] For example, the at least one actuator is fixed to a support. According to an optional feature of the invention, the support comprises at least one column, to which a stationary portion of the at least one actuator is fixed. For example, this is a column, wherein the electrode is fixed to an extension tube of the column.

[0032] The welding system according to the present invention comprises, for example, an electrode holder in which the electrode is held stationary, the electrode holder being fixed to the at least one actuator. When the at least one actuator is in the shape of a cylinder, the electrode holder is attached, for example, to an extension tube of the cylinder.

[0033] According to an optional feature of the welding system of the invention, it comprises two actuators for each pair of electrodes, comprising a first actuator capable of pressing the membrane electrode against the sealing plate with a first pressing force, and a second actuator capable of pressing the anchor electrode against the free part of the anchor plate with a second pressing force.

[0034] It should be noted that, in the present application, the term "pressing force" applied by the actuator via the electrode refers to the contact force generated by the pressure exerted by the electrode on the surface of the anchoring or sealing plate, to which the electrode is pressed by the actuator. The force pickup applied to the electrode can be performed by an operator or by a machine maintaining the welding system.

[0035] This feature allows the sealing plate to more firmly contact the anchor plate at the level of the weld point, thereby ensuring good weld quality. According to an optional feature of the present invention, the second pressing force has a lower value than the first pressing force. The first pressing force, expressed in kilograms-force, corresponds, for example, to a force of approximately 4 kilograms, and the second pressing force corresponds, for example, to a force of approximately 2 kilograms. These values ​​are provided here by way of indication and are not intended to limit the present invention. For example, much higher pressing forces may be applied, particularly if force pickup is performed by a machine.

[0036] According to an optional feature of the welding system according to the invention, the membrane electrode comprises a contact surface with the sealing plate which is strictly smaller than a contact surface of the anchor electrode with the free portion of the anchor plate.

[0037] This contact surface determines the cross-section for the current flow between each electrode and the plate against which it is pressed. For example, the membrane and anchor electrodes are cylindrical and are pressed against the sealing or anchor plate via one of their bases. The membrane electrode then has a circular cross-section of, for example, between 7 and 9 mm, preferably 8 mm, while the anchor electrode has a circular cross-section of, for example, between 11 and 13 mm, preferably 12 mm.

[0038] In another example, the membrane electrode and the anchor electrode have shapes resembling right prisms with polygonal cross-sections, the polygonal cross-section of the membrane electrode being smaller than the polygonal cross-section of the anchor electrode.

[0039] In yet another example, when the electrodes are in the form of wheels having the same diameter configured to roll on the plates, their contact surfaces with the plates are portions of their lateral surfaces, the length of the contact surface being a dimension of the wheel perpendicular to its radius, and the length of the portion of the lateral surface of the membrane electrode being shorter than the length of the portion of the lateral surface of the anchor electrode. In this example, the lateral surface of the wheel preferably includes a flat portion, and when one of the flat portions of each electrode contacts the sealing plate or the anchor plate, the actuator is activated to ensure sufficient contact surface for current flow.

[0040] In one embodiment of the invention, the positioning means comprise at least one stop element which is fixed to the support element and which can be pressed against an edge of the sealing plate or against a corrugation of the sealing plate.

[0041] When the stopper is configured to abut against the edge of the sealing plate, the stopper comprises, for example, a lower surface located at the same level as the end of the anchoring electrode, which end is configured to contact the anchoring plate in a direction parallel to the direction of the current flowing in the anchoring electrode when a weld is produced by the welding system according to the present invention. Thus, the stopper can be used to position the electrode on either side of the edge of a sealing plate of any thickness.

[0042] When the stopper is configured to abut against the corrugations of the sealing plate, the stopper includes, for example, a lower surface located at the same level as the end of the membrane electrode, which is configured to contact the sealing plate in a direction parallel to the direction of current flow in the membrane electrode when a weld is produced using the welding system according to the present invention. Thus, the stopper can be used regardless of the height of the corrugations on the membrane, which typically include corrugations of varying heights.

[0043] For example, the support comprises a frame defining an opening, the stop forming an extension of a lower portion of the support capable of coming into contact with one or the other of the sealing plate or the anchoring plate without blocking the opening in the frame.

[0044] The positioning means comprise, for example, two stops fixed to the support and capable of pressing against the edge of the sealing plate, or one or more stops capable of pressing against a corrugated portion of the sealing plate, the corrugated portion being parallel to the edge of the sealing plate. The electrode is then preferably arranged on the support between the two stops.

[0045] Even more preferably, the dimension of the support parallel to this edge of the sealing plate and comprised between two consecutive corrugations of the sealing plate is strictly smaller than the distance between these two consecutive corrugations between which the mounting support is partially mounted, when the stop or stops are pressed against this edge, so as to enable a slight movement of the support parallel to the edge of the sealing plate in order to position the electrode outside the riveted position of the anchoring plate.

[0046] The welding system may include multiple electrode pairs arranged between the two stoppers. For example, it may include as many electrode pairs as welds to be formed between the two stoppers, preferably corresponding to the number of welds to be formed between two consecutive corrugations of the anchor plate. This allows the operator to perform all welds between two consecutive corrugations without moving the support member of the welding system according to the present invention. The electrode pairs are spaced apart by a distance greater than or equal to a predetermined minimum distance to prevent the formation of parasitic current paths when producing the welds. This predetermined minimum distance is, for example, between 30 mm and 60 mm, and is preferably equal to or approximately equal to 50 mm.

[0047] In one embodiment of the invention, the support comprises two rails that can be positioned on either side of the edge of the sealing plate and parallel to said edge, and a moving device for moving the electrodes of each pair of electrodes, the moving device being mounted so as to move in translation on the two rails. "Parallel to said edge" means substantially parallel to said edge, i.e., within a tolerance of a few degrees. The rails of the support can be positioned on either side of the edge of the sealing plate and parallel to said edge, i.e., in a configuration in which the support is placed on the sealing plate and the anchor plate for welding them, the rails are positioned on either side of the edge and parallel to the edge.

[0048] The movement means comprise, for example, a stud attached in a sliding manner to a rail, the stud being fixed to the fixed part of one or more actuators, which themselves are fixed to the electrode by their mobile part. The rail and the movement means allow the electrode to be moved, for example, between two stops arranged at the longitudinal ends of the support and capable of pressing it against the edge of the sealing plate.

[0049] The moving device includes, for example, at least one axis arranged orthogonally to the track, and the electrodes in each pair of electrodes are in the shape of a wheel mounted on the at least one axis. The axis is attached to the moving part of the at least one actuator, for example, and is connected to a rotary motor. In the case where each electrode is pressed with a separate pressing force, each electrode is mounted on a separate axis attached to the moving part of a separate actuator. Then, for example, each axis is connected to a rotary motor. For example, one of the axes supporting the electrodes is attached to an extension tube of a column, the extension tube of the column is fixed to one of the columns attached to one of the tracks in a sliding manner, and the other axis supporting the other electrode is attached to an extension tube of the other column, the extension tube of the other column is fixed to another column attached to the other track in a sliding manner.

[0050] In another example, the moving device includes at least one shaft arranged orthogonally to the track and a first hub mounted on the at least one shaft and having the membrane electrode arranged thereon, the moving device also includes a second hub mounted on the at least one shaft and having the anchor electrode arranged thereon, each pair of electrodes being configured so that the membrane electrode can contact the sealing plate while the anchor electrode can contact the free portion of the anchor plate. The moving device includes, for example, a rotary motor mechanically connected to the shaft and at least one rack engaged with the shaft, the rack being formed on one of the tracks. When one shaft is used for each hub, the moving device includes, for example, one rack per track and one rotary motor per shaft, or the same rotary motor is used for both shafts.

[0051] In another example, an indirect resistance welding system according to the present invention includes a plurality of electrode pairs, and a moving device includes at least one shaft arranged orthogonally to a track and a first hub mounted on the at least one shaft, wherein the membrane electrodes of the electrode pairs are angularly distributed around the first hub, and the moving device further includes a second hub mounted on the at least one shaft, wherein the anchor electrodes of the electrode pairs are angularly distributed around the second hub, and wherein the electrode pairs are configured such that the membrane electrode of one of the electrode pairs can contact the sealing plate while the anchor electrode of the electrode pair can contact the free portion of the anchor plate. The membrane electrodes, for example, form radii angularly distributed around the first hub, and the anchor electrodes, for example, form radii angularly distributed around the second hub.

[0052] "Orthogonal to the track" means substantially orthogonal to the track, ie within a tolerance of a few degrees.

[0053] As in the previous example, the at least one shaft is attached to the moving part of the at least one actuator. Furthermore, in a case where the membrane and anchoring electrode are pressed with separate pressing forces, each hub is mounted on a separate shaft attached to the moving part of a separate actuator. For example, one shaft supporting one of the hubs in the shaft is attached to an extension tube of a cylinder, which is fixed to one of the uprights slidably attached to one of the rails, and the other shaft supporting the other hub in the shaft is attached to an extension tube of another cylinder, which is fixed to another upright slidably attached to another rail.

[0054] The electrode pair formed by the membrane electrode and the anchor electrode is, for example, arranged on the hubs such that each membrane electrode is arranged on a first hub at an angle to the same level as the anchor electrode on the second hub. More specifically, with respect to the axial direction defined by the shaft, an electrode pair is defined as having the membrane electrode and the anchor electrode aligned with each other.

[0055] An optional feature of the indirect resistance welding system is that it includes clamping means fixed to the support member. These clamping means facilitate positioning of the support member against the sealing plate and the application of a force by an operator on the support member to resist the one or more pressing forces applied by the at least one actuator.

[0056] The indirect resistance welding system according to the present invention may include a cart on which is mounted a robotic arm capable of cooperating with the clamping device. In this way, the force to be applied to the support is provided by the robotic arm. For example, the cart also carries a current generator, which is connected to the various electrodes via conductors and, preferably, also supplies the various actuators when these are electric cylinders. If these actuators are hydraulic cylinders, in addition to the current generator, the cart also carries a liquid source for supplying the hydraulic cylinders, which is connected to the hydraulic cylinders via fluid connections. Furthermore, the cart preferably carries the means for controlling the robotic arm, the cylinders, and the current generator.

[0057] The present invention also relates to a method for indirect resistance welding, which uses the indirect resistance welding system according to the present invention and comprises the following steps:

[0058] positioning the membrane electrode above the sealing plate and the anchor electrode above the free portion of the anchor plate by pressing the positioning means against a portion of the sealing plate,

[0059] activating the at least one actuator until the membrane electrode is pressed against the sealing plate and the anchor electrode is pressed against the free portion of the anchor plate, and

[0060] An electric current is sent to the electrodes.

[0061] Sending current naturally uses a current generator.

[0062] When the indirect resistance welding system comprises two actuators, including a first actuator capable of pressing the membrane electrode against the sealing plate with a first pressing force, and a second actuator capable of pressing the anchoring electrode against the free part of the anchoring plate with a second pressing force, the activation step preferably comprises pressing the membrane electrode against the sealing plate with a first force and pressing the anchoring electrode against the free part of the anchoring plate with a second force, the first force being strictly greater than the second force.

[0063] When the indirect resistance welding system comprises two rails positionable on either side of an edge of the sealing plate and parallel to said edge, and moving means for moving the electrodes of the electrode pair, said moving means being mounted so that they can be moved in translation on the two rails,

[0064] The positioning step comprises positioning the track on either side of the edge of the sealing plate, and is followed by a plurality of steps of activating and sending current, the welding method according to the invention also comprising a step of moving the electrode along the track, which step is between the step of sending current and the step of activating at least one actuator.

[0065] The displacement step allows the electrode to be moved by at least a predetermined minimum distance, for example between 30 mm and 60 mm, and preferably equal to or approximately equal to 50 mm. This minimum distance allows preventing the creation of parasitic current paths during the current sending step.

[0066] Alternatively, when the indirect resistance welding system comprises a row of electrode pairs arranged on a support, the positioning step comprises positioning each membrane electrode of the electrode pair above the sealing plate and positioning each anchor electrode of the electrode pair above the free portion of the anchor plate, and the welding method according to the invention comprises as many current sending steps as there are electrode pairs, the current sending steps being each spaced apart by a predetermined minimum duration and each supplying a single electrode pair. A longitudinal section of a row is here understood to mean a section of the row along its length.

[0067] In this alternative embodiment of the present invention, welds are preferably formed sequentially by each electrode pair in a row, in one direction of travel of the row. That is, welds are formed one after another along the edge of the sealing plate. This means that the steps involved in sending current to the electrodes are less likely to cause parasitic current paths. Furthermore, the predetermined time between each current sending step prevents the creation of parasitic current paths. This time is, for example, between 300 and 400 ms, and is preferably equal to or approximately equal to 350 ms (milliseconds).

[0068] Furthermore, in this alternative embodiment of the invention, prior to the step of sending current to the electrode pairs, one or more actuators of each electrode pair are preferably enabled separately from the actuators of other pairs of electrodes, which avoids having to apply too much force to the support to offset the pressing force applied to the electrodes.

[0069] In its various embodiments, the welding method according to the invention offers advantages similar to those of the welding system according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Other characteristics and advantages of the invention will emerge more clearly on reading the following description on the one hand and on reference to a number of exemplary embodiments given in an indicative and non-limiting manner in the accompanying schematic drawings on the other hand, in which:

[0071] [ Figure 1 ] has been described in relation to the prior art, showing portions of the sealing plate fillet welded to the anchor plate,

[0072] [ Figure 2 ] shows the principle of indirect resistance welding used in the present invention to weld the sealing plate to the anchor plate,

[0073] [ Figure 3 ] is a perspective view of an indirect resistance welding system according to the present invention, in a first embodiment of the present invention, the system being positioned against an edge of a sealing plate, above the sealing plate and the anchor plate,

[0074] [ Figure 4 ]yes Figure 3 A side view of an indirect resistance welding system is shown.

[0075] [ Figure 5 ]yes Figure 3 A top view of the indirect resistance welding system is shown.

[0076] [ Figure 6 ] is a perspective view of an indirect resistance welding system according to the present invention, in a second embodiment of the present invention, positioned against an edge of a sealing plate, above the sealing plate and the anchor plate,

[0077] [ Figure 7 ] is a perspective view of an indirect resistance welding system according to the present invention, in a third embodiment of the present invention, positioned against an edge of a sealing plate, above the sealing plate and the anchor plate,

[0078] [ Figure 8 ] is a perspective view of an indirect resistance welding system according to the present invention, in a fourth embodiment of the present invention, positioned against an edge of a sealing plate, above the sealing plate and the anchor plate,

[0079] [ Figure 9] is a perspective view of an indirect resistance welding system according to the present invention, in a fifth embodiment of the present invention, positioned against an edge of a sealing plate, above the sealing plate and the anchor plate,

[0080] [ Figure 10 ] is a perspective view of an indirect resistance welding system according to the present invention, including an indirect resistance welding system according to a second embodiment of the present invention, and a robot arm capable of pressing the indirect resistance welding system against a sealing plate,

[0081] [ Figure 11 ] represents a step in an indirect resistance welding method according to the present invention, which uses the indirect resistance welding system according to the first, third or fourth embodiment of the present invention, and

[0082] [ Figure 12 ] shows steps in an indirect resistance welding method according to the present invention, which uses an indirect resistance welding system according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0083] Figure 2 A weld 30 produced by an indirect resistance welding system according to the invention is schematically shown. This comprises an electrode 41 called a membrane electrode and an electrode 42 called an anchor electrode, each connected to a different terminal of a current generator (not shown).

[0084] The indirect resistance welding system according to the present invention allows the membrane electrode 41 to be pressed against the sealing plate 1 near its edge 15, which separates the portion of the anchor plate 22 located below the sealing plate 1 from the free portion of the anchor plate 22 not covered by the sealing plate. The anchor plate 22 is riveted to the shell 40.

[0085] As a guide, the thickness of the sealing plate 1 is 1.2 mm and the thickness of the anchoring plate 22 is 2 mm.

[0086] The indirect resistance welding system also allows the anchor electrode 42 to be pressed against the free portion of the anchor plate 22 near the edge 15 of the sealing plate.

[0087] The current generator allows a current I to be sent through and between the electrodes 41, 42. The current path I between the electrodes 41, 42 passes through the sealing plate 1 and through the anchor plate 22, passing through a point located below the sealing plate 1, in line with the membrane electrode, and at the interface with the anchor plate 22. Of course, the direction of the current between the electrodes 41, 42 is irrelevant. The resistance at this point is high, and as a result of the Joule effect when the current I passes, the material melts to form the weld point 30, which is therefore located below the sealing plate 1.

[0088] Electrodes 41 and 42 are each separated from edge 15 by a distance of approximately 8 mm, for example 7.5 mm. However, it should be noted that the distance from membrane electrode 41 to edge 15 is not necessarily the same as the distance from anchor electrode 42 to edge 15.

[0089] Alternatively, the membrane electrode 41 and the anchor electrode 42 are each less than 8 mm, such as 6 mm, but greater than 5 mm from the edge 15 , or are each greater than 8 mm, such as 12 mm, but less than 15 mm from the edge 15 .

[0090] These minimum and maximum distances prevent arcing with the edge 15 while allowing the current I passing through the anchoring plate 22 and the sealing plate 1 to be sufficiently high at the level of the weld 30 to produce it when the current I is sent by the current generator to the electrodes.

[0091] according to Figures 3 to 5 In the first embodiment of the present invention shown, the indirect resistance welding system S1 according to the present invention comprises a support 5 forming a rectangular frame 53 defining an opening 530. The indirect resistance welding system S1 comprises a support 5 forming a rectangular frame 53 defining an opening 530. Figure 2 The present invention relates to a device for producing a current generator comprising the same electrodes 41, 42 in the embodiment of the present invention and including a current generator connected to these electrodes in the same manner.

[0092] The support 5 comprises positioning means for positioning the support 5 relative to the sealing plate 1, and more particularly positioning means for positioning the support 5 against the edge 15 of the sealing plate 1. The function of these positioning means is to ensure that the support 5, and therefore the electrodes 41, 42, are reliably positioned relative to the sealing plate 1 and the anchoring plate 22. These positioning means may in particular take the form of at least one stopper configured to come into contact with the edge 15 of the sealing plate. In the example shown, the positioning means comprise a first stopper 51 and a second stopper 52.

[0093] The first stopper 51 and the second stopper 52 (at Figure 4 The stoppers 51 and 52 are attached below the middle portions of the two short edges of the rectangular frame 53, with their stop surfaces being coplanar and parallel to the two long edges of the rectangular frame 53. The stoppers 51 and 52 extend on either side of the rectangular frame 53 without protruding beyond the sides of the opening 530 of the rectangular frame 53.

[0094] Each long edge of the rectangular frame 53 is extended orthogonally to the rectangular frame 53 by a rail 532, 534 in the form of a slide with a substantially U-shaped cross section, the arms of the U extending parallel to the main extension plane of the rectangular frame 53. The rails 532, 534 extend from the side of the rectangular frame 53 opposite to the side from which the stops 51, 52 of the protruding frame extend.

[0095] The support 5 also includes a first column 55 extending orthogonally to the rectangular frame 53, the first column 55 being attached so as to slide in a first track of the tracks 532, the first column 55 being cut off at one of its ends so as to form a slider 550 that grips one of the edges of the track 532.

[0096] Similarly, the support 5 comprises a second upright 57 extending orthogonally to the rectangular frame 53 , the second upright 57 being attached so as to slide in a second track 534 in the track 534 , the second upright being cut off at one of its ends so as to form a slider that grips one of the edges of the track 534 .

[0097] Actuator 9 is arranged between columns 55 and 57 and fixed to columns 55 and 57 via its fixing portion. In this embodiment of the present invention, actuator 9 is an electric cylinder or a hydraulic cylinder, the outer tube of which is fixed to columns 55 and 57. Two electrode holders 61 and 62 are attached to the extension tube of actuator 9 and each holds one of electrodes 41 and 42 in a longitudinal direction perpendicular to the main extension plane of rectangular frame 53. The first electrode holder 61 holds membrane electrode 41 via the extension tube attached to the side of first column 55, while the second electrode holder 62 holds anchor electrode 42 via the extension tube attached to the side of second column 57. Electrodes 41 and 42 are partially arranged in opening 530 of rectangular frame 53.

[0098] The membrane electrode 41 is cylindrical with a circular cross-section of approximately 8 mm in diameter. The circular end of the membrane electrode 41 extending on the side of the rectangular frame 53 associated with the stoppers 51 and 52 forms the contact surface of the membrane electrode 41 with the sealing plate 1, that is, it is configured to contact the sealing plate 1.

[0099] The anchor electrode 42 is cylindrical and has a circular cross-section with a diameter of approximately 12 mm. The circular end of the anchor electrode 42 extending on the side of the rectangular frame 53 associated with the stoppers 51, 52 forms the contact surface of the anchor electrode 42 with the anchor plate 22, that is, it is configured to contact the anchor plate 22.

[0100] The electrodes 41, 42 here have the same height, but their attachment to the actuator extension tube 9 causes them to be offset longitudinally (in the direction of the axis A3 when the support 5 is positioned on the sealing plate and the anchor plate) relative to each other by the thickness of the sealing plate 1, so that the contact surface of the membrane electrode 41 with the sealing plate 1 is closer to the opening 530 than the contact surface of the anchor electrode 42 with the anchor plate 22. This longitudinal offset, in a direction orthogonal to the rectangular frame 53, is therefore 1.2 mm.

[0101] The first handle 81 is attached to an end portion of a first short side among the short sides of the rectangular frame 53 , and the second handle 82 is attached to an end portion of a second short side among the short sides of the rectangular frame 53 .

[0102] These handles 81, 82 allow the operator to install the indirect resistance welding system S1 on the sealing plate 1 and the anchor plate 22, as shown in FIG. Figures 3 to 5 As shown, that is, by aligning the long sides of the rectangular frame 53 along the first axis A1 parallel to the edge 15 of the sealing plate 1 so that the edge 15 is located in the opening 530 of the rectangular frame 53. This alignment is performed so that the electrodes are located on either side of the edge 15 of the sealing plate, with the membrane electrode 41 located above the sealing plate 1 and the anchor electrode 42 located above the anchor plate 22.

[0103] The first stop 51 and the second stop 52 allow the operator to press the support 5 into position as follows:

[0104] parallel to the third axis A3, ie orthogonal to the main extension plane of the plates 1 , 22, against the free part of the anchoring plate 22, and

[0105] The tabs, parallel to the second axis A2 , ie orthogonal to the sealing plate 1 , bear against the edge 15 of the sealing plate 1 .

[0106] like Figure 4 As shown, the indirect resistance welding system S1 comprises a wedge 54 attached below a first rail 532 of the support 5 , allowing the rectangular frame 53 , in particular the rail of the support 5 , to be positioned orthogonally to the third axis A3 .

[0107] When the stop surfaces of the first and second stops 51 , 52 are pressed against the edge 15 of the sealing plate, the membrane electrode 41 and the anchor electrode 42 are each located at a desired and easily reproducible distance from the edge 15 of the sealing plate, here approximately 8 mm.

[0108] A portion of the rectangular frame 53 is then located between the corrugations 12 and 14 of the sealing plate 1 without abutting against the other corrugation 16 of the sealing plate 1, away from the edge 15 and orthogonally joining the corrugations 12 and 14. This portion of the rectangular frame 53 is strictly smaller than the distance between the corrugations 12 and 14 by at least the size of the rivet 24, so that the rectangular frame 53 can be moved along the edge 15 to avoid positioning the electrodes 41, 42 above such rivets 24. It should be noted that in an alternative embodiment, the first stop 51 and the second stop 53 abutting against the edge 15 are replaced by one or more stops abutting against the corrugation 16 parallel to the edge 15.

[0109] The actuator 9 can then press the membrane electrode 41 against the sealing plate 1 and the anchoring electrode 42 against the free portion 22 of the anchoring plate with the same pressing force corresponding to, for example, 3 kg. An electric current can then be supplied to the electrodes to form the weld 30 between the sealing plate 1 and the anchoring plate 22.

[0110] Once a weld has been made and the actuator 9 is deactivated, the rails 532, 534 and the sliders of the uprights 55, 57 allow the operator to move the electrodes 41, 42 a minimum distance of approximately 40 mm in the opening 530 of the rectangular frame 53 of the support 5, before making a new weld. The opening 530 in the rectangular frame 53 extends, for example, longitudinally (along the length of the frame and parallel to the axis A1 when the support 5 is positioned on the sealing and anchoring plates) over at least twenty centimeters, so as to allow the making of 4 to 6 welds 30 between the sealing plate 1 and the anchoring plate 22 without moving the rectangular frame 53.

[0111] As an alternative to this first embodiment of the invention, each electrode 41 , 42 is attached to a separate actuator, which allows applying a greater force to the membrane electrode 41 than to the anchor electrode 42 .

[0112] Now about Figure 6 A second embodiment of the present invention is described in which an indirect resistance welding system S2 includes elements common to the indirect resistance welding system S1 of the first embodiment of the present invention, these common elements being numbered identically.

[0113] Indirect resistance welding system S2 includes a support member 5b, which includes a rectangular plate 53b with four openings 530b arranged at regular intervals along the length of rectangular plate 53b. Indirect resistance welding system S2 also includes four pairs of electrodes 41 and 42, p1, p2, p3, and p4, arranged in a row within support member 5b. Each pair of electrodes p1 to p4 partially extends through a separate opening 530b in rectangular plate 53b. Indirect resistance welding system S2 also includes a switching device capable of connecting each pair of electrodes p1 to p4 to a current generator.

[0114] In this second embodiment of the present invention, each membrane electrode 41 or anchor electrode 42 of a pair of electrodes p1 to p4 is actuated by a separate first actuator 91 or, respectively, a separate second actuator 92, which in this second embodiment is a hydraulic cylinder or an electric cylinder. Specifically, the membrane electrode 41 of each pair of electrodes p1 to p4 is attached via its electrode holder 61 to the extension tube of the first actuator 91, which is fixed via its outer tube to the first upright 55b, which is attached to the rectangular plate 53b of the support 5b and extends orthogonally thereto.

[0115] Similarly, the anchoring electrode 42 of each pair of electrodes p1 to p4 is attached via its electrode holder 62 to the extension tube 920 of the second actuator 92, which is fixed via its outer tube to the second upright 57b attached to the rectangular plate 53b of the support 5b and extends orthogonally thereto.

[0116] The electrode holders 61 and 62 longitudinally hold the respective electrodes 41 and 42 orthogonally to the main extension plane of the rectangular plate 53 b of the support 5 b.

[0117] The electrodes 41 and 42 are arranged in the support 5b such that a longitudinal section of the rectangular plate 53b separates each membrane electrode 41 from each anchor electrode 42. This longitudinal section corresponds to a central cut along the length of the rectangular plate 53b. In other words, all membrane electrodes 41 are on the same side of the rectangular plate 53b along its length, and all anchor electrodes 42 are on the other side of the rectangular plate 53b relative to this same side.

[0118] In a manner similar to the first embodiment, the support member 5b includes positioning means for positioning the support member against the edge 15 of the sealing plate. The positioning means include a first stopper 51b and a second stopper 52b arranged below the middle portion of the two short edges of the rectangular plate 53b. The stopper surfaces of the stoppers 51b and 52b are coplanar and parallel to the long edges of the rectangular plate 53b. The stoppers 51b and 52b extend on either side of the rectangular plate 53b without blocking the opening 530b in the rectangular plate 53b.

[0119] Furthermore, a first handle 81 b is attached to an end portion of a first short side among the short sides of the rectangular plate 53 b , and a second handle 82 b is attached to an end portion of a second short side among the short sides of the rectangular plate 53 b .

[0120] The first and second stops 51b, 52b forming the above-mentioned positioning means allow the support 5b to be pressed against the edge 15 of the sealing plate 1 and the free part of the anchoring plate 22 in a similar manner to the first and second stops 51, 52 of the first embodiment.

[0121] The support 5 b also comprises a wedge (not shown) which allows the rectangular plate 53 b to be retained in a direction orthogonal to the axis A3 .

[0122] This positioning allows each membrane electrode 41 to be positioned above the sealing plate 1 and each anchor electrode 42 to be positioned above the anchor plate 22 so that they are each positioned at a desired and easily reproducible distance of approximately 8 mm from the edge 15 of the sealing plate 1 .

[0123] In contrast to the first embodiment of the present invention, in this second embodiment, the electrodes 41, 42 may not move along a portion of the length of the rectangular plate 53b of the support 5b. Furthermore, when the extension tubes are retracted, their respective contact surfaces with the sealing plate 1 or the anchor plate 22 may be attached to the extension tubes of the actuators 91, 92 at the same level, orthogonal to the main extension plane of the rectangular plate 53b, because these extension tubes can move independently of each other.

[0124] The actuators 91 and 92 of each pair of electrodes p1 to p4 are capable of pressing the membrane electrode 41 against the sealing plate 1 and the anchor electrode 42 against the free portion 22 of the anchor plate, with a pressing force of approximately 4 kg for the membrane electrode 41 and approximately 2 kg for the anchor electrode 42. These values ​​are provided for informational purposes only. When creating a weld, this pressing is performed on a pair-by-pair basis. Current I is also supplied sequentially to each pair of electrodes p1 to p4 to avoid current leakage, poor current distribution, or the need for excessively high currents.

[0125] In other words, when one pair of electrodes is pressed against the plates to create a weld, the other pairs of electrodes are elevated, ie placed at a distance from the plates, and current I is sent successively to each pair of electrodes only while it is pressed against the plates.

[0126] The openings 530 b are spaced apart by 50 mm, for example, so that four welding points 30 are carried out, which are distributed over a considerable length along the edge 15 of the sealing plate 1 .

[0127] As an alternative to this second embodiment of the invention, the support 5b comprises more or less than four pairs of electrodes, for example only one pair of electrodes or six pairs of electrodes.

[0128] According to the current Figure 7 A third embodiment of the present invention is described, indirect resistance welding system S3 includes a support 5c forming a rectangular frame 53c defining an opening 530c.

[0129] In a similar manner to the first embodiment, the support 5c comprises positioning means for positioning the support against the edge 15 of the sealing plate. The positioning means comprise a first stop 51c and a second stop 52c.

[0130] One end of the first of the two short sides of the rectangular frame 53c includes a foot portion forming a first stopper 51c, and one end of the second of the two short sides of the rectangular frame 53c includes a foot portion forming a second stopper 52c. The stoppers 51c and 52c are arranged on the same side of the long side of the rectangular frame 53c. The stopper surfaces of the first and second stoppers 51c and 52c are coplanar and parallel to the two long edges of the rectangular frame 53c. The stoppers 51c and 52c extend below the rectangular frame 53c without obstructing the opening 530c of the rectangular frame 53c.

[0131] Each long side of the rectangular frame 53c extends orthogonally to the rectangular frame 53c through a first rail 532c or a second rail 534c that is the same as the rails 532 and 534 of the first embodiment of the present invention.

[0132] The support member 5c also includes a first column 55c extending orthogonally to the rectangular frame 53c, the first column 55c being attached so as to slide in a first track of the tracks 532c, the first column 55c being cut off at one of its ends so as to form a slider 550c that clamps one of the edges of the first track 532c.

[0133] Similarly, support member 5c includes a second upright 57c extending perpendicular to rectangular frame 53c. Second upright 57c is attached so as to slide in a second of rails 534c. Second upright 57c is cut away at one of its ends to form a slider that grips one of the edges of second rail 534c. Uprights 55c and 57c are held at a distance from each other and in first rail 532c and second rail 534c by crossbar 56, which connects the ends of uprights 55c and 57c opposite to the ends of the uprights forming the slider.

[0134] Unlike the first embodiment of the present invention, in this third embodiment of the present invention, the indirect resistance welding system S3 includes a first actuator 91c and a second actuator 92c, which are fixed to the corresponding columns 55c and 57c via their fixing parts. In this example, the actuators 91c and 92c are hydraulic cylinders or electric cylinders.

[0135] The first actuator 91c is fixed to the first shaft via its extension tube, on which the first hub 63 is rotatably mounted, and the second actuator 92c is fixed to the second shaft via its extension tube, on which the second hub 64 is rotatably mounted. The first hub 63 and the second hub 64 are thus electrode holders.

[0136] A membrane electrode 41 c having the same shape as the electrode 41 of the first embodiment is fixed to the first hub so as to form radial or radial branches regularly and angularly distributed around the first hub.

[0137] Similarly, an anchoring electrode 42 c having the same shape as the electrode 42 of the first embodiment is fixed to the second hub so as to form radial or radial branches regularly and angularly distributed around the second hub.

[0138] Furthermore, a first handle 81 c is attached to an end portion of a first short side of the rectangular frame 53 c , and a second handle 82 c is attached to an end portion of a second short side of the rectangular frame 53 c .

[0139] These handles 81c, 82c allow the operator to install the indirect resistance welding system S3 on the sealing plate 1 and the anchor plate 22, as shown in FIG. Figure 7As shown, this is done by aligning the long sides of rectangular frame 53c parallel to edge 15 of sealing plate 1 so that edge 15 is located in opening 530c of rectangular frame 53c. This alignment is performed so that membrane electrode 41c is above sealing plate 1 and anchor electrode 42c is above anchor plate 22.

[0140] The first and second stoppers 51c, 52c allow, on the one hand, the operator to press the support 5c:

[0141] - a free portion resting against the anchoring plate 22 orthogonally to the main extension plane of the plates 1 , 22 , and

[0142] - Abutting against the edge 15 of the sealing plate 1 orthogonally to the tabs of the sealing plate 1 .

[0143] like Figure 7 As shown, the indirect resistance welding system S3 further comprises a wedge 54c attached below the first rail 532c of the support 5c allowing the rectangular frame 53c to be maintained orthogonal to the third axis A3.

[0144] When the stop surfaces of the first and second stops 51c , 52c are pressed against the edge 15 of the sealing plate, the membrane electrode 41c and the anchor electrode 42c are each located at a desired and easily reproducible distance from the edge 15 of the sealing plate 1 , in this case approximately 8 mm.

[0145] As the posts 55c, 57c slide along the rails 532c, 534c, the synchronized movement of the first hub 63 and the second hub 64 allows each membrane electrode 41c and the anchor electrode 42c to be simultaneously and successively opposed to the sealing plate 1 and the anchor plate 22. The actuators 91c, 92c then press the membrane electrode 41c against the sealing plate 1 while they press the anchor electrode 42c against the anchor plate 22. The two electrodes 41c, 42c pressed simultaneously form a pair of electrodes capable of performing the weld 30 by sending a current I to the pair of electrodes 41c, 42c pressed thereby.

[0146] The hubs 63, 64 each include the same number of membrane electrodes 41c and anchor electrodes 42c, which in this case are six, forming six pairs of electrodes 41c, 42c. The indirect resistance welding system S3 also includes a switching device capable of sequentially connecting each of the pairs of electrodes 41c, 42c to a current generator. Alternatively, however, the hubs may include only two, three, four, or five pairs of electrodes.

[0147] The actuators 91c, 92c are capable of exerting a pressing force of 4 kg and 2 kg on the electrodes 41c, 42c, respectively, when their respective contact surfaces are placed against the sealing plate 1 and against the anchoring plate 22. Of course, these values ​​are given only as a guide, as other values ​​may be used.

[0148] Therefore, this third embodiment allows six welding points to be performed in the opening 530c of the rectangular frame 53c of the support 5c without moving the rectangular frame 53c.

[0149] According to the current Figure 8 The fourth embodiment of the present invention, an indirect resistance welding system S4, is described as including many elements in common with the indirect resistance welding system S3 of the third embodiment of the present invention, and is referenced in the same manner.

[0150] In particular, the indirect resistance welding system S4 includes the same support member 5c as the third embodiment, which includes stoppers 51c, 52c, a wedge member 54c, rails 532c, 534c and columns 55c, 57c, and the fixed portions of the first actuator 91c and the second actuator 92c are fixed to the columns 55c, 57c, respectively.

[0151] In contrast to the third embodiment of the present invention, in indirect resistance welding system S4, a first actuator 91c is fixed to the first shaft via its extension tube, a membrane electrode 41d shaped like a wheel is directly mounted on the first shaft for rotation, and a second actuator 92c is fixed to the second shaft via its extension tube, an anchor electrode 42d shaped like a wheel is directly mounted on the second shaft for rotation. The first actuator 91c is capable of applying a first pressing force of approximately 4 kg to the membrane electrode 41d, and the second actuator 92c is capable of applying a second pressing force of approximately 2 kg to the anchor electrode 42d. Again, these values ​​are provided for guidance only.

[0152] The membrane and anchor electrodes 41d, 42d have the same diameter, but the membrane electrode 41d is thinner than the anchor electrode 42d, for example, the membrane electrode 41d is 8 mm thick and the anchor electrode 42d is 12 mm thick. The wheel formed by the membrane and anchor electrodes 41d, 42d has a flat portion that provides a sufficiently large contact surface for high current to pass between each electrode and the sealing plate 1 or anchor plate 22 to which it is applied.

[0153] When the stop surfaces of the first and second stops 51c, 52c are pressed against the edge 15 of the sealing plate 1, the membrane electrode 41d and the anchor electrode 42d are each located at a desired and easily reproducible distance, here approximately 8 mm, from the edge 15 of the sealing plate 1. Rails 532c, 534c are also arranged on either side of the edge 15 of the sealing plate 1, parallel thereto.

[0154] Thus, when the actuators 91c, 92c press the electrodes 41d, 42d against the sealing plate 1 or the anchor plate 22 with a first and a second pressing force, respectively, and when the posts 55c, 57c move along the track, welding points 30 can be produced at regular intervals along the sealing plate 1 by sending a current I to the electrodes 41d, 42d. To accelerate the welding process, the height of the actuators 91c, 92c relative to the sealing plate 1 or the anchor plate 22 is reduced between two actuations relative to its default height immediately after the positioning of the support 5c.

[0155] According to the current Figure 9 The fifth embodiment of the present invention, indirect resistance welding system S2b, is described as including many elements in common with the indirect resistance welding system S2 of the second embodiment of the present invention and is referenced in the same manner.

[0156] Specifically, the indirect resistance welding system S2b includes a pair of electrodes 41, 42 having the same shape as one of the electrode pairs p1 to p4 of the second embodiment. These electrodes (41, 42) are attached to actuators (91, 92) similar to those used in the second embodiment via electrode holders (61, 62) similar to those used in the second embodiment.

[0157] This fifth embodiment differs from the previously described embodiments in that the actuators 91 , 92 are attached to a support 5 d which allows indirect resistance welding of the sealing plate 1 to the anchoring plate 22 at the level of a circular edge 15 b of the sealing plate 1 , formed, for example, by a circular cutout in the sealing plate 1 .

[0158] Support member 5d includes a plate 53d having an opening 530d into which extension tubes 920 of actuators 91 and 92 extend. Plate 53d is configured to be positioned substantially parallel to sealing plate 1 and anchor plate 22, i.e., within a tolerance of a few degrees, while being maintained at a distance from these plates by a stopper 51d forming a first foot of plate 53d and a wedge 54d forming a second foot of plate 53d. Stopper 51d and wedge 54d are attached to separate ends of plate 53d.

[0159] The stop 51d forms part of a hollow cylinder extending orthogonally to the plate 53d, the free end of which comprises a semicircular stop surface complementary to at least a first portion of the circular edge 15b of the sealing plate 1. The stop 51d is thus able to position the support 5d against the circular edge 15b of the circular cutout in the sealing plate 1.

[0160] Opening 530d in plate 53d allows the fixed portion of actuators 91 and 92 to be separated from their movable portion, to which electrode holders 61 and 62 are attached. Thus, actuators 91 and 92, electrode holders 61 and 62, and the movable portion of electrodes 41 and 42 are arranged in the space defined by plate 53d, stopper 51d, and wedge 54d, while the fixed portion of actuators 91 and 92 is located on the other side of the plate relative to stopper 51d and wedge 54d. The fixed portions of actuators 91 and 92 rest on either side of opening 530d and can slide toward each other, with their extension tubes able to follow this movement through opening 530d and thus adjust their respective positions on plate 53d. This arrangement allows the distance between electrodes 41 and 42 to be adjusted. It will be appreciated that welding system S2b includes a single pair of electrodes and means for adjusting the distance between membrane electrode 41 and anchor electrode 22.

[0161] Finally, handles 81d and 82d are fixed to the support 5d on either side to make it easier to grip the welding system S2b.

[0162] When welding system S2b is in place on sealing plate 1 and anchor plate 22, stopper 51d is positioned against the first portion of circular edge 15b of sealing plate 1, and thus on anchor plate 22, by being placed in the circular cutout of sealing plate 1, while wedge 54d is placed on sealing plate 1. Anchor electrode 42 is then positioned above anchor plate 22, in the circular cutout of sealing plate 1, while membrane electrode 41 is positioned above sealing plate 1, opposite membrane electrode 41 relative to a second portion of circular edge 15b that is not in contact with stopper 51d. This second portion of circular edge 15b is diametrically opposed to the first portion of circular edge 15b. Membrane electrode 41 and anchor electrode 42 are then each positioned at a desired and easily reproducible distance from the second portion of circular edge 15b of sealing plate 1, in this case approximately 8 mm.

[0163] The first actuator 91 can then exert a first pressing force on the membrane electrode 41, and the second actuator 92 can exert a second pressing force on the anchor electrode 42. According to the example given above, the first pressing force can be of the order of 4 kg, while the second pressing force is of the order of 2 kg, these values ​​being considered indicative and not limiting.

[0164] Thus, when actuators 91, 92 press electrodes 41, 42 against sealing plate 1 or anchor plate 22 with first and second pressing forces, respectively, weld points 30 can be created by sending current I to electrodes 41, 42. Additional weld points 30 can then be created on sealing plate 1 along the periphery of the circular cutout in sealing plate 1 by first moving electrodes 41, 42 away from sealing plate 1 and anchor plate 22, respectively, and then repositioning support member 5d (support member 5d is guided in rotation by stopper 51d that moves against circular edge 15b of sealing plate 1).

[0165] Alternatively, in this fifth embodiment, the stop 51 d has a different shape and comprises a stop surface capable of cooperating with other types of cutouts in the sealing plate 1 .

[0166] Figure 10 An indirect resistance welding system S5 according to the present invention is now shown, which comprises the indirect resistance welding system S2 according to the present invention, and a robot arm 83 capable of exerting a pressing force on the support 5 b of the indirect resistance welding system S2, allowing an opposing supporting reaction force to resist the pressing force applied by the actuators 91, 92 during the production of the weld.

[0167] In an alternative embodiment, the indirect resistance welding system S5 does not include the indirect resistance welding system S2 according to the present invention, but rather includes the indirect resistance welding system S1 , S2b , S3 , or S4 according to the present invention.

[0168] The robot arm 83 is attached to a housing 84 comprising several pieces of equipment, which is transported on a mobile cart of the indirect resistance welding system S5. The housing 84 includes, for example, a current generator for supplying the electrodes 41, 42, means for controlling the robot arm 83, the current generator and the actuators 91, 92, and possibly a source of liquid for supplying the actuators when the actuators are hydraulic cylinders.

[0169] Now refer to Figure 11 , describes an indirect resistance welding method 100 using an indirect resistance welding system S1 , S3 or S4 , possibly in combination with a cart and robot arm 83 of an indirect resistance welding system S5 .

[0170] The first step 102 of the indirect resistance welding method 100 is to position the rails 532, 534 or 532c, 534c on either side of the edge 15 of the sealing plate 1 by pressing the supporting positioning means 5, 5c (i.e., the first and second stops 51, 52 or 51c, 52c) against the edge 15 of the sealing plate 1 and the wedge 54 or 54c against the sealing plate 1. After this positioning 102, the first electrode or electrodes 41, 41c, 41d are positioned above the sealing plate 1 and the second electrode or electrodes 42, 42c, 42d are positioned above the free portion of the anchor plate 22, each electrode being at a desired distance from the edge 15 of the sealing plate 1.

[0171] During this first step 102 , if the electrode 41 , 41c , 41d , 42 , 42c , 42d is opposite the rivet, the position of the support 5 , 5c can be adjusted along the edge 15 by holding the stop 51 , 52 or 51c , 52c against this edge 15 .

[0172] The next step 104 of the indirect resistance welding method 100 is the activation of the actuator or actuators 9, 91c, 92c. For the indirect resistance welding system S3, only the electrodes 41c, 42c are considered here, whose contact surfaces are opposite the sealing plate 1 and the anchor plate 22, respectively. In this step 104, the actuators 9, 91c, 92c are activated until a first pressing force is applied to press the membrane electrodes 41, 41c, 41d against the sealing plate 1 and a second pressing force is applied to press the anchor electrodes 42, 42c, 42d against the anchor plate 22.

[0173] When using actuator 9 of indirect resistance welding system S1 , the first pressing force is equal to the second pressing force and corresponds to, for example, 3 kg. Other values ​​may of course be used, in particular depending on the mechanism of force pickup on the support.

[0174] On the other hand, the first actuator 91 of the indirect resistance welding system S3 or S4 applies a first pressing force equal to approximately 4 kilograms to the membrane electrode 41c or the membrane electrode 41d, and the second actuator 92 of the indirect resistance welding system S3 or S4 applies a second pressing force equal to approximately 2 kilograms to the anchor electrode 42c or the anchor electrode 42d. These values ​​are given only as a guide, as other values ​​may be used for the pressing force.

[0175] The next step 106 in the indirect resistance welding method 100 is to send a current I of several thousand amperes through the electrodes 41, 42, 41c, 42c, 41d, 42d to form the weld 30 between the sealing plate 1 and the anchor plate 22. For the indirect resistance welding system S3, only the electrodes 41c, 42c are considered here, whose contact surfaces are opposite the sealing plate 1 and the anchor plate 22, respectively. At the end of the current sending step 106, the current I is turned off and the actuators 9, 91, 92 are deactivated so that the electrodes 41, 42, 41c, 42c, 41d, 42d are no longer pressed against the sealing plate 1 or the anchor plate 22.

[0176] The next step 108 is a test to check whether all welds 30 to be performed along rails 532, 534, 532c, 534c have been completed. If the movement of uprights 55, 57, 55c, 57c, the activation of actuators 9, 91, 92, and the delivery of current I are controlled by a computer, this test can be visual or supervised by a program. If, at the end of test 108, it is confirmed that all welds 30 to be performed have been completed (branch Y), the indirect resistance welding method 100 is terminated.

[0177] If, on the other hand, at the end of the test 108 it is found that not all the welds 30 to be performed have been completed (branch N), the next step is a step 110 of moving the electrodes 41, 42, 41c, 42c, 41d, 42d along the tracks 532, 534, 532c, 534c until they are in a position to perform a new weld 30 separated from the previous welds 30 by at least a predetermined distance, for example equal to 40 mm.

[0178] At the end of the shifting step 110 , allowing a minimum time of at least 350 ms between two weld points 30 , the indirect resistance welding method 100 continues back to the step 104 of activating the actuators 9 , 91 , 92 until the test of step 108 becomes positive.

[0179] Now refer to Figure 12 , describes an indirect resistance welding method 200 using an indirect resistance welding system S2, possibly in combination with a cart and robotic arm 83 of an indirect resistance welding system S5.

[0180] The first step 202 of the indirect resistance welding method 200 is to position each membrane electrode 41 of the electrode pairs p1 to p4 above the sealing plate 1 and each anchor electrode 42 of the electrode pairs p1 to p4 above the free portion of the anchor plate 22 by pressing the first stopper 51b and the second stopper 52b against the edge 15 of the sealing plate 1 and pressing the wedge of the support 5b against the sealing plate 1. After this positioning 202, each pair of electrodes p1 to p4 41, 42 is positioned at a desired distance from the edge 15 of the sealing plate 1. When the successive generation of weld points is performed by a computer program, during this first step 202, the program initializes the electrode pair number to 1, designating the first electrode pair p1.

[0181] The next step 204 in the indirect resistance welding method 200 is to activate the actuators 91, 92 to which the electrodes 41, 42 of the first pair of electrodes p1 are attached. In this step 204, these actuators 91, 92 are activated until a first pressing force of approximately 4 kg is applied to the sealing plate 1 by the membrane electrode 41 and a second pressing force of approximately 2 kg is applied to the anchor plate 22 by the anchor electrode 42, these values ​​being given for informational purposes only.

[0182] The next step 206 in the indirect resistance welding method 200 is to send a current I of several thousand amperes through the electrodes 41, 42 of the first electrode pair p1 in order to form the first weld 30 between the sealing plate 1 and the anchor plate 22. At the end of this step 206 of sending current, the current I is switched off and the actuators 91, 92 are deactivated so that the electrodes 41, 42 of the first electrode pair p1 are no longer pressed against the sealing plate 1 or the anchor plate 22.

[0183] The next step 208 is then a test to check whether all welds 30 to be performed without moving the support 5b have been completed. If the activation of the actuators 9, 91, 92 and the delivery of the current I are controlled by a computer, this test can be visual or supervised by a program. If, at the end of the test 208, it is confirmed that all welds 30 to be performed have been completed (branch Y), the indirect resistance welding method 200 ends.

[0184] On the other hand, if at the end of test 208 it is found that not all welds 30 to be performed have been completed (branch N), the next step is step 210, in which, when the successive formation of welds is executed by the computer program, a predetermined duration is waited, which in this embodiment of the invention is set to 350 ms, and then the number of electrode pairs is incremented. During the first elapse of the predetermined duration of wait step 210, this number is increased to 2, designating the second pair of electrodes p2 to be considered for the subsequent step.

[0185] At the end of this waiting step 210 of a predetermined duration, the indirect resistance welding method 200 continues by returning to step 204 of enabling the actuators 91, 92 applied to the second pair of electrodes p2, followed by a new step 206 of sending current to this second pair of electrodes p2, then a new test step 208, and so on, until current is sent to the electrode pair p4 and the end of the indirect resistance welding method 200 is established in a final test step 208.

[0186] Of course, the present invention is not limited to the above examples and many modifications may be made to these examples without departing from the scope of the present invention. In particular, the features of different variants or different embodiments of the present invention may be combined to implement the present invention, as long as these variants or these embodiments are not mutually incompatible.

Claims

1. A welding system (S1, S2, S3, S4, S5) for indirectly resistance welding a sealing plate (1) of a tank configured to contain liquefied gas to an anchor plate (22), the anchor plate (22) being partially arranged below the sealing plate (1) so as to leave a free portion of the anchor plate (22) outside the sealing plate (1), the edge (15) of the sealing plate (1) separating the sealing plate (1) from the free portion of the anchor plate (22), the welding system (S1, S2, S3, S4, S5) comprising: at least one pair of electrodes and a current generator adapted to be connected to said electrodes (41, 42, 41c, 42c, 41d, 42d), a support (5, 5b, 5c) capable of holding the electrodes of the at least one pair of electrodes relative to each other, Positioning means for positioning the support (5, 5b, 5c) against the sealing plate (1), capable of positioning the electrodes of the at least one pair of electrodes on either side of the edge (15) by positioning one electrode of the at least one pair of electrodes, called the membrane electrode (41, 41c, 41d), above the sealing plate (1) and the other electrode of the at least one pair of electrodes, called the anchor electrode (42, 42c, 42d), above the free portion of the anchor plate (22), and At least one actuator (9, 91, 92, 91c, 92c) for each pair of electrodes is capable of pressing the membrane electrode (41, 41c, 41d) against the sealing plate (1) and the anchor electrode (42, 42c, 42d) against the free part of the anchor plate (22).

2. The indirect resistance welding system (S2, S3, S4, S5) according to claim 1, comprising two actuators (91, 92, 91c, 92c) for each pair of electrodes, comprising a first actuator (91, 91c) capable of pressing the membrane electrode (41, 41c, 41d) against the sealing plate (1) with a first pressing force, and a second actuator (92, 92c) capable of pressing the anchor electrode (42, 42c, 42d) against the free part of the anchor plate (22) with a second pressing force.

3. The indirect resistance welding system (S1, S2, S3, S4, S5) according to claim 1 or 2, wherein: The membrane electrode (41, 41c, 41d) comprises a contact surface with the sealing plate (1), which is strictly smaller than the contact surface of the anchoring electrode (42, 42c, 42d) with the free part of the anchoring plate (22).

4. The indirect resistance welding system (S1, S2, S3, S4, S5) according to any one of claims 1 to 3, wherein: The positioning device comprises at least one stopper (51, 51b, 51c, 52, 52b, 52c) fixed to the support member (5, 5b, 5c) and capable of pressing against an edge (15) of the sealing plate (1) or against a corrugated portion (12, 14, 16) of the sealing plate (1).

5. The indirect resistance welding system (S1, S2, S3, S4, S5) according to claim 4, wherein: The support member (5, 5b, 5c) comprises a frame (53, 53b, 53c, 53d) defining an opening (530, 530b, 530c, 530d), the stop member (51, 51b, 51c, 52, 52b, 52c) forming an extension of the lower part of the support member (5, 5b, 5c), the extension being capable of coming into contact with one or the other of the sealing plate (1) or the anchoring plate (22) without blocking the opening in the frame (53, 53b, 53c, 53d).

6. The indirect resistance welding system (S1, S3, S4) according to any one of claims 1 to 5, wherein: The support (5, 5b, 5c) comprises two rails (532, 532c, 534, 534c), the two rails being positionable on either side of an edge (15) of the sealing plate (1) and parallel to the edge, and a moving device for moving the electrodes (41, 42, 41c, 42c, 41d, 42d) of each pair of electrodes, the moving device being mounted for translational movement on the two rails (532, 532c, 534, 534c).

7. The indirect resistance welding system (S4) according to claim 6, wherein: The movement means comprises at least one shaft arranged orthogonally to the track (532c, 534c), the electrodes (41d, 42d) of each pair of electrodes being in the shape of a wheel mounted on the at least one shaft.

8. The indirect resistance welding system (S3) according to claim 6, wherein: The moving device includes at least one axis arranged orthogonally to the track (532c, 534c) and a first hub (63) mounted on the at least one axis, the membrane electrode (41c) is arranged on the first hub, and the moving device also includes a second hub (64) mounted on the at least one axis, the anchoring electrode (42c) is arranged on the second hub (64), and each pair of electrodes is configured so that the membrane electrode (41c) can contact the sealing plate (1) while the anchoring electrode (42c) can contact the free part of the anchoring plate (22).

9. The indirect resistance welding system (S3) according to claim 6, comprising a plurality of electrode pairs, and wherein, The moving device comprises at least one axis arranged orthogonally to the track (532c, 534c) and a first hub (63) mounted on the at least one axis, wherein the membrane electrode (41c) of the electrode pair is angularly distributed around the first hub (63), the moving device further comprises a second hub (64) mounted on the at least one axis, wherein the anchoring electrodes (42c) of the electrode pair are angularly distributed around the second hub (64), the electrode pairs being configured such that the membrane electrode (41c) of one of the electrode pairs can contact the sealing plate (1) at the same time as the anchoring electrode (42c) of the electrode pair can contact the free portion of the anchoring plate (22).

10. A method for performing indirect resistance welding (100, 200) using the indirect resistance welding system (S1, S2, S3, S4, S5) according to any one of claims 1 to 9, comprising the following steps: Positioning (102, 202) the membrane electrode (41, 41c, 41d) above the sealing plate (1) and positioning the anchor electrode (42, 42c, 42d) above the free portion of the anchor plate (22) by pressing the positioning device against a portion of the sealing plate (1), activating (104, 204) the at least one actuator (9, 91, 92, 91c, 92c) until the membrane electrode (41, 41c, 41d) is pressed against the sealing plate (1) and the anchor electrode (42, 42c, 42d) is pressed against the free portion of the anchor plate (22), and A current (106, 206) is sent to the electrodes (41, 41c, 41d, 42, 42c, 42d).

11. The indirect resistance welding method (100, 200) according to claim 10 in combination with claim 2, wherein: The activation step (104, 204) comprises pressing the membrane electrode (41, 41c, 41d) against the sealing plate (1) with a first force and pressing the anchor electrode (42, 42c, 42d) against the free portion of the anchor plate (22) with a second force, the first force being strictly greater than the second force.

12. The indirect resistance welding method (100) according to claim 10 or 11 in combination with claim 6, wherein: The positioning step (102) includes positioning the track (532, 532c, 534, 534c) on either side of the edge (15) of the sealing plate (1), and is followed by a plurality of steps of activating (104) and sending current (106), the welding method (100) further comprising a step (110) of moving the electrode along the track (532, 532c, 534, 534c), which step is between the step of sending current (106) and the step (104) of activating the at least one actuator (9, 91, 92, 91c, 92c).

13. The indirect resistance welding method (200) according to claim 10 or 11, wherein: The indirect resistance welding system (S2, S5) comprises a row of electrode pairs (p1, p2, p3, p4) arranged on the support (5b), The positioning step (202) comprises positioning each membrane electrode (41) of the electrode pair (p1, p2, p3, p4) above the sealing plate (1) and positioning each anchoring electrode (42) of the electrode pair (p1, p2, p3, p4) above the free portion of the anchoring plate (22), and the welding method (200) comprises as many current sending steps (206) as there are electrode pairs (p1, p2, p3, p4), the current sending steps (206) each being spaced apart by a predetermined minimum duration and each supplying a single electrode pair (p1, p2, p3, p4).

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