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

Abstract

System and method for indirect resistance welding of a sealing plate to an anchor plate The present invention relates to a system (S1) for indirect resistance welding of a sealing plate (1) of a tank intended to contain liquefied gas, on an anchor plate (22) arranged partly under the sealing plate (1), comprising: - a pair of electrodes and a current generator capable of being connected to the electrodes (41, 42) - a support (5) capable of holding the electrodes relative to each other, - means for positioning the support (5) against the sealing plate (1), capable of positioning a first (41) of the electrodes above the sealing plate (1) and a second (42) of the electrodes above the free portion of the anchor 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) on the free portion of the anchor plate (22). (Figure 3)

Description

Title of the invention: System and method for indirect resistance welding of a sealing plate to an anchor plate

[0001] The present invention relates to the field of liquid gas tanks, for example liquefied natural gas (LNG), in particular for maritime or river transport or for a land tank. More specifically, the invention relates to a system for welding a sealing plate suitable for such a tank, and an associated welding method.

[0002] Liquid gas tanks have a capacity of several thousand cubic meters of liquid gas each, or even several tens of thousands of cubic meters of liquid gas. Liquefied gas transport ships have holds specifically designed to contain these tanks, their holds often being partitioned into several tanks. Such a tank can also be made outside a ship for land-based storage of liquid natural gas.

[0003] The gas is kept inside the tank in the liquid state, for example at -163°C (degree Celsius) for LNG, at atmospheric pressure. The tank must therefore be sealed and thermally insulated. Therefore, the internal surface of such a tank is covered with a sealing membrane, generally made of an assembly of metal sealing plates (typically stainless steel plates) welded to each other, each sealing plate being a part of the tank's sealing membrane.

[0004] The walls of the tank also comprise, successively under the sealing membrane intended to be in contact with the liquefied gas, this sealing membrane being called the primary sealing membrane:

[0005] - a primary insulation layer, for example made with wooden boxes filled with reinforced polyurethane foam,

[0006] - another waterproofing membrane, called a secondary waterproofing membrane, by example in thin sheet metal,

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

[0008] The primary waterproofing membrane is fixed to the primary insulation layer by welding the waterproofing plates to anchor plates, integral with the primary insulation layer, which may in particular be riveted to the wooden boxes of the primary insulation layer. These anchor plates form a grid pattern across all the boxes but do not cover them entirely.

[0009] Currently, as shown [Fig.l], the fixing welds 3 of a plate sealing 1 on an anchor plate 22 are produced manually by a welding process using the heat of an electric arc, this process being called TIG (from the English “Tungsten Inert Gas”).

[0010] The welds 3 are made in a lap on an edge 15 of the sealing plate 1, located between two waves 12, 14 of the sealing plate 1. These waves correspond to ribs on the sealing plate 1, which can participate in advantageously forming a grid and making it possible to absorb the deformations of the tank due to the thermal variations thereof.

[0011] The edge 15 of the sealing plate 1 extends parallel to the direction of a first axis Al of an orthonormal reference frame (Al, A2, A3), the waves 12, 14 extending orthogonally to this first axis Al while being parallel to the direction of a second axis A2 of this orthonormal reference frame. The third axis A3 of this orthonormal reference frame extends orthogonally to the main extension plane of the sealing plate 1.

[0012] The anchoring plate 22 is located between the two waves 12, 14, being fixed by rivets 24 to a wooden box here not visible of the primary insulation layer, the box also being located between these two waves 12, 14. Other anchoring plates 21 and 23 are located on either side of the anchoring plate 22, being fixed to other wooden boxes of the primary insulation layer by other rivets 24.

[0013] As visible in [Fig.l], the fixing of the sealing plate 1 uses 6 welds of 20 mm (millimeters) in length between the two waves 12, 14, spaced 20 mm apart, which makes it possible to fix the sealing plate 1 between the two waves 12, 14 over at least 220 mm. As an indication, the distance dl peak to peak between the waves 12 and 14 is 340 mm, which leaves a margin for their deformation.

[0014] The production of the 3-lap welds is operational and allows a visual check of the welds carried out. However, this production is carried out manually, which makes the fixing of the sealing plates of the tank on the anchor plates of the primary insulation layer very long. A process of automating these welds 3 with a TIG welding process would require very complex and expensive equipment, in particular for automatic and precise tracking of the edge 15 of the sealing plate 1. The positioning of the rail on which an automatic TIG welding machine would be placed would require a lot of time in particular.

[0015] The present invention aims to remedy at least in part the aforementioned drawbacks by providing in particular a welding system and a welding method which make it possible to accelerate the welding of the sealing plates of a tank to the anchoring plates of the tank, in a simple and inexpensive manner, while guaranteeing good welding quality.

[0016] To this end, the invention proposes a system for indirect resistance welding of a sealing plate of a tank intended to contain liquefied gas, on a plate anchoring plate arranged partly under the sealing plate so as to leave a free portion of the anchoring plate outside the sealing plate, an edge of the sealing plate separating the sealing plate from the free portion of the anchoring plate, the welding system comprising: - at least one pair of electrodes and a current generator capable of being connected to the electrodes, - a support capable of holding the electrodes of the at least one pair of electrodes relative to each other, - 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 said at least one pair of electrodes, called the membrane electrode, above the sealing plate and another electrode of said at least one pair of electrodes, called the anchoring electrode, above the free portion of the anchoring plate, and - at least one actuator for each pair of electrodes, capable of pressing the membrane electrode onto the sealing plate and the anchoring electrode onto the free portion of the anchoring plate.

[0017] The use of an indirect resistance welding system makes it possible to produce a welding point arranged under the membrane electrode, with a diameter of up to 5 mm, between the sealing plate and the anchor plate. This welding point is carried out by applying a current of several kiloamperes between the electrodes. This change in welding technique compared to the prior art makes it possible to fix the sealing plate to the anchor plate quickly by carrying out, for example, only four welding points between two waves of the sealing plate, between the latter and the anchor plate. These welding points can be carried out more quickly by an operator than lap welds, being punctual and not requiring very precise positioning of the welds relative to the edge of the sealing plate.

[0018] The welding system according to the invention is capable of positioning the membrane electrode and the anchoring electrode on either side of an edge of the sealing plate arranged on the anchoring plate, allowing the membrane electrode to be positioned on the sealing plate at a point which is also above the part of the anchoring plate located under the sealing plate, and 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.

[0019] The support makes it possible to maintain a predefined 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:

[0020] - sufficiently short to allow the sealing plate to be welded to the anchor plate by heating created by the Joule effect between these two plates, due to the resistance created by the interface between the plates on the path of the current flowing through the electrodes,

[0021] - and sufficiently large to avoid the creation of an electric arc. In fact, a such an electric arc generates projections and apparent defects which are not acceptable.

[0022] Furthermore, the electrode located on the sealing plate must also not be too close to the edge, otherwise excessive heating of the sealing plate at this location will be generated, which will cause local deformation and degradation of the welding point obtained.

[0023] The electrodes are for example each approximately 8 mm apart from the edge of the sealing plate, their respective distances from this edge preferably being between 5 mm and 15 mm.

[0024] In an embodiment with several pairs of electrodes, the support makes it possible to keep the electrodes of the different pairs of electrodes at a distance from each other.

[0025] This support is for example a simple electrode holder, allowing its manual movement at several points on the sealing plate not located above a rivet of the anchoring plate.

[0026] The current generator of the welding system according to the invention is preferably remote from the support, so as not to require its movement at the same time as the movement of the support to carry out several welding points. For example, the current generator is arranged on a carriage and connected to the electrodes fixed to the support, by metal conductors, which can take the form of large copper metal braids, given the amperage used.

[0027] The at least one actuator is for example secured to the support. According to an optional characteristic of the invention, the support comprises at least one upright on which the fixed part of the at least one actuator is secured. This is for example a jack, the electrodes being secured to the extension tube of the jack.

[0028] The welding system according to the invention comprises, for example, electrode holders in which the electrodes are held fixed, the electrode holders being secured to said at least one actuator. When said at least one actuator takes the form of a jack, the electrode holders are, for example, fixed to the extension tube of the jack.

[0029] According to an optional characteristic of the welding system according to the invention, the latter comprises two actuators for each pair of electrodes, a first ac- donor capable of pressing the membrane electrode onto the sealing plate with a first pressing force, and a second actuator capable of pressing the anchoring electrode onto the free portion of the anchoring plate with a second pressing force.

[0030] It should be noted that in this application, the term "plating force", exerted by an actuator via an electrode, refers to the contact force resulting from the pressure exerted by the electrode on the surface of the anchoring or sealing plate on which the electrode is pressed by the actuator. The recovery of force applied to the electrodes can be carried out by an operator or by a machine which maintains the welding system.

[0031] This feature makes it possible to bring the sealing plate into contact with the anchoring plate more reliably at the welding point, and therefore to ensure good welding quality. According to an optional feature of the invention, the second plating force has a lower value than that of the first plating force. The first plating force, expressed in kilograms of force, corresponds for example to a force approximately equal to 4 kilograms, and the second plating force corresponds for example to a force approximately equal to 2 kilograms respectively. These values ​​are given here for information purposes only, without being limiting of the invention. For example, much higher plating forces can be applied, in particular if the force is taken up by a machine.

[0032] According to an optional characteristic of the welding system according to the invention, the membrane electrode comprises a contact surface with the sealing plate strictly smaller than a contact surface of the anchoring electrode with the free portion of the anchoring plate.

[0033] This contact surface determines the current flow section between each electrode and the plate against which the electrode is pressed. For example, the membrane and anchoring electrodes are cylindrical and are pressed by one of their bases onto the sealing or anchoring plate. The membrane electrode then has a circular section of, for example, between 7 and 9 mm and preferably 8 mm, while the anchoring electrode has a circular section of, for example, between 11 and 13 mm and preferably 12 mm.

[0034] In another example, the membrane and anchor electrodes have a right prism shape of polygonal cross-section, the polygonal cross-section of the membrane electrode being smaller than the polygonal cross-section of the anchor electrode.

[0035] In yet another example, when the electrodes take the form of wheels configured to roll on the plates, of the same diameter, their contact surfaces with the plates are portions of their lateral surfaces, of lengths the dimensions of the wheel orthogonal to their radii, and the length of the portion of the lateral surface of the membrane electrode is smaller than the length of the portion of the lateral surface of the anchor electrode. In this example the lateral surfaces of the wheels preferably have flats, the actuators being activated when one of the flats of each electrode is in contact with the sealing plate or the anchor plate, in order to ensure a sufficient contact surface to pass the current.

[0036] In one embodiment of the invention, the positioning means comprise at least one stop secured to the support and capable of being pressed against the edge of the sealing plate, or against a wave of the sealing plate. The positioning means comprise, for example, two stops secured to the support and capable of being pressed against the edge of the sealing plate, or one or more stops capable of being pressed against a wave of the sealing plate, the bottom being parallel to the edge of the sealing plate. The electrodes are then preferably arranged on the support, between the two stops.More preferably, the dimension of the support parallel to the edge of the sealing plate, and between two consecutive waves of the sealing plate, when the stop or stops are pressed against this edge, is strictly less than the distance between these two consecutive waves between which the support is partly installed, so as to be able to slightly move the support parallel to the edge of the sealing plate, to position the electrodes outside the riveted locations of the anchoring plate.

[0037] The welding system according to the invention optionally comprises several pairs of electrodes arranged between the two stops. It comprises, for example, as many pairs of electrodes as there are welding points to be made between the two stops, the number of welding points to be made preferably corresponding to the number of welding points to be made between two consecutive waves of the anchor plate. Thus, an operator can make all the welding points between two consecutive waves without moving the support of the welding system according to the invention. The pairs of electrodes are spaced from each other by a distance greater than or equal to a predetermined minimum distance making it possible to avoid the formation of parasitic current paths when making a welding point. This predetermined minimum distance is, for example, between 30 mm and 60 mm and is preferably equal to or approximately equal to 50 mm.

[0038] In one embodiment of the invention, the support comprises two rails capable of being positioned on either side of the edge of the sealing plate and parallel to said edge, and means for moving the electrodes of each pair of electrodes, mounted to move in translation on the two rails. By "parallel to said edge" is meant substantially parallel to said edge, that is to say to a tolerance of a few degrees. The rails of the support are capable of being positioned on either side of the edge of the sealing plate and parallel to said edge, that is to say that in a configuration of placing the support on the sealing and anchoring plates to weld them, the rails are positioned on either side of the edge and parallel to it.

[0039] The displacement means comprise, for example, uprights fixed to slide on the rails, the uprights being secured to the fixed parts of one or more actuators themselves secured to the electrodes by their movable parts. The rails and the displacement means allow, for example, the electrodes to move between two stops arranged at the longitudinal ends of the support and capable of pressing the latter against the edge of the sealing plate.

[0040] The displacement means comprise for example at least one axle arranged orthogonally to the rails, the electrodes of each pair of electrodes taking the form of wheels mounted on the at least one axle. This axle is for example fixed to the movable part of the at least one actuator, and is for example connected to a rotary motor. When the electrodes are each pressed with a distinct pressing force, each electrode is mounted on a separate axle, fixed to the movable part of a separate actuator. Each axle is then for example connected to a rotary motor. One of the axles supporting an electrode is for example fixed to an extension tube of a jack secured to one of the uprights fixed sliding on one of the rails, the other of the axles supporting another electrode being fixed to an extension tube of another jack secured to the other of the uprights fixed sliding on the other of the rails.

[0041] In another example, the displacement means comprise at least one axle arranged orthogonally to the rails as well as a first hub mounted on the at least one axle and on which the membrane electrode is arranged, the displacement means further comprising a second hub mounted on the at least one axle and on which the anchoring electrode is arranged, each pair of electrodes being configured such that the membrane electrode is able to be in contact with the sealing plate at the same time as the anchoring electrode is able to be in contact with the free portion of the anchoring plate. The displacement means comprise for example a rotary motor mechanically connected to the axle, and at least one rack cooperating with the axle, the rack being formed on one of the rails.When one axle per hub is used, the means of movement include, for example, one rack per rail, and one rotary motor per axle or the same rotary motor for both axles.

[0042] In another example, the indirect resistance welding system according to the invention comprises several pairs of electrodes and the displacement means comprise at least one axle arranged orthogonally to the rails as well as a first hub mounted on the at least one axle, the membrane electrodes of the pairs of electrodes being distributed angularly around the first hub, the displacement means further comprising a second hub mounted on the at least one axle, the anchoring electrodes of the pairs of electrodes being angularly distributed around the second hub, the pairs of electrodes being configured such that the membrane electrode of one of the pairs of electrodes is able to be in contact with the sealing plate at the same time as the anchoring electrode of said pair of electrodes is able to be in contact with the free portion of the anchoring plate. The membrane electrodes form, for example, radii angularly distributed around the first hub, and the anchoring electrodes form, for example, radii angularly distributed around the second hub.

[0043] By "orthogonally to the rails" is meant substantially orthogonally to the rails, that is to say to a tolerance of a few degrees.

[0044] As in the previous example, the at least one axle is for example fixed to the movable part of the at least one actuator. In addition, when the membrane and anchor electrodes are pressed with distinct pressing forces, each hub is mounted on a separate axle fixed to the movable part of a separate actuator. One of the axles supporting one of the hubs is for example fixed to an extension tube of a jack secured to one of the uprights fixed sliding on one of the rails, the other of the axles supporting the other of the hubs being fixed to an extension tube of another jack secured to the other of the uprights fixed sliding on the other of the rails.

[0045] The electrode pairs formed by the membrane and anchor electrodes are for example configured on the hubs such that each membrane electrode is angularly arranged on the first hub at the same level as an anchor electrode on the second hub. More particularly, considering the axial direction defined by the axle, a pair of electrodes is defined with a membrane electrode and an anchor electrode that are aligned with each other.

[0046] Furthermore, according to an optional characteristic of the indirect resistance welding system according to the invention, the latter comprises gripping means secured to the support. These gripping means facilitate the positioning of the support against the sealing plate, and the force to be exerted on the support by an operator, to counter the pressing force(s) exerted by the at least one actuator.

[0047] The indirect resistance welding system according to the invention optionally comprises a carriage on which is mounted a robotic arm capable of cooperating with the gripping means. Thus the force to be exerted on the support is provided by the robotic arm. The carriage also carries, for example, the current generator, connected by conductors to the various electrodes, and preferably also supplying the various actuators when these are electric cylinders. In the case where these actuators are hydraulic cylinders, the carriage carries, for example, in addition to the current generator, a source of liquid for supplying the hydraulic cylinders, connected by fluid connections to the hydraulic cylinders. In addition, the carriage preferably carries means of controlling the robotic arm, the cylinders and the current generator.

[0048] The invention also relates to a method of indirect resistance welding, using an indirect resistance welding system according to the invention, and comprising steps of: - positioning the membrane electrode above the sealing plate and the anchoring electrode above the free portion of the anchoring plate, using the positioning means, - activation of the at least one actuator until the membrane electrode is pressed against the sealing plate and the anchoring electrode against the free portion of the anchoring plate, and - sending current to the electrodes.

[0049] Sending current of course uses the current generator.

[0050] When the indirect resistance welding system comprises two actuators, including a first actuator capable of pressing the membrane electrode onto the sealing plate with a first pressing force, and a second actuator capable of pressing the anchoring electrode onto the free portion of the anchoring plate with a second pressing force, the activation step preferably comprises pressing the membrane electrode onto the sealing plate with the first force and pressing the anchoring electrode onto the free portion of the anchoring plate with the second force, the first force being strictly greater than the second force.

[0051] When the indirect resistance welding system comprises two rails capable of being positioned on either side of the edge of the sealing plate and parallel to said edge, and means for moving the electrodes of the pair of electrodes, mounted mobile in translation on the two rails, the positioning step comprises the positioning of the rails on either side of the edge of the sealing plate, and is followed by several steps of activation and sending of current, the welding method according to the invention further comprising a step of moving the electrodes along the rails, interposed between a step of sending current and a step of activating the at least one actuator.

[0052] The displacement step makes it possible to move the electrodes 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 makes it possible to avoid the creation of parasitic current paths during a current sending step.

[0053] Alternatively, when the indirect resistance welding system comprises a row of pairs of electrodes arranged on the support, the positioning step comprises positioning each membrane electrode of the pairs of electrodes above the sealing plate and each anchoring electrode of the pairs of electrodes 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 pairs of electrodes, the current sending steps each being spaced apart by a predetermined minimum duration and each supplying a single pair of electrodes. The longitudinal section of the row here designates a section of the row along the length thereof.

[0054] In this alternative embodiment of the invention, the welding points are preferably carried out consecutively by each pair of electrodes of the row of pairs of electrodes, in a direction of travel of this row, that is to say that the welding points are made one behind the other along the edge of the sealing plate. Thus the steps of sending current in the electrodes are less likely to cause parasitic current paths. In addition, the predetermined duration between each step of sending current also makes it possible to avoid the creation of parasitic current paths. It is for example between 300 and 400 ms and preferably equal or approximately equal to 350 ms (milliseconds).

[0055] Furthermore, in this alternative embodiment of the invention, the actuator(s) of each pair of electrodes are preferably activated separately from the actuators of the other pairs of electrodes, before the step of sending current into the pair of electrodes, which avoids having to apply too much force to the support to counteract the plating forces exerted on the electrodes.

[0056] The welding method according to the invention, in its various embodiments, has advantages similar to those of the welding system according to the invention.

[0057] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0058] [Fig. 1], already described in relation to the prior art, represents a portion of sealing plate welded to an anchor plate,

[0059] [Fig.2] illustrates the principle of indirect resistance welding used in the invention to weld a sealing plate to an anchor plate,

[0060] [Fig.3] is a perspective view of an indirect resistance welding system according to the invention, in a first embodiment of the invention, the system being positioned against an edge of a sealing plate, above the latter and an anchoring plate,

[0061] [Fig.4] is a side view of the indirect resistance welding system of the [Fig.3],

[0062] [Fig.5] is a top view of the indirect resistance welding system of the [Fig.3],

[0063] [Fig.6] is a perspective view of an indirect resistance welding system according to the invention, in a second embodiment of the invention, the system being positioned against an edge of a sealing plate, above the latter and an anchoring plate,

[0064] [Fig.7] is a perspective view of an indirect resistance welding system according to the invention, in a third embodiment of the invention, the system being positioned against an edge of a sealing plate, above the latter and an anchoring plate,

[0065] [Fig.8] is a perspective view of an indirect resistance welding system according to the invention, in a fourth embodiment of the invention, the system being positioned against an edge of a sealing plate, above the latter and an anchoring plate,

[0066] [Fig.9] is a perspective view of an indirect resistance welding system according to the invention, in a fifth embodiment of the invention, the system being positioned against an edge of a sealing plate, above the latter and an anchoring plate,

[0067] [Fig. 10] is a perspective view of an indirect resistance welding system according to the invention, comprising the indirect resistance welding system of the second embodiment of the invention, as well as a robotic arm capable of pressing this indirect welding system against a sealing plate,

[0068] [Fig. 11] represents steps of an indirect resistance welding method according to the invention, using the indirect resistance welding system of the first, third or fourth embodiment of the invention, and

[0069] [Fig. 12] represents steps of an indirect resistance welding method according to the invention, using the indirect resistance welding system of the second embodiment of the invention.

[0070] [Fig. 2] schematically represents an embodiment of a welding point 30 by an indirect resistance welding system according to the invention. This comprises an electrode 41 called the membrane electrode, and an electrode 42 called the anchoring electrode, each connected to a different terminal of a current generator (not shown).

[0071] The indirect resistance welding system according to the invention makes it possible to press the membrane electrode 41 against the sealing plate 1, in the vicinity of the edge 15 of the sealing plate separating the part of the anchoring plate 22 arranged under the sealing plate 1 from the free portion of the anchoring plate 22, not covered by the sealing plate. The anchoring plate 22 is riveted to a box 40.

[0072] For information purposes, the thickness of the sealing plate 1 is 1.2 mm and that of the anchoring plate 22 is 2 mm.

[0073] The indirect resistance welding system also allows for plating the anchoring electrode 42 against the free portion of the anchoring plate 22, in the vicinity of the edge 15 of the sealing plate.

[0074] The current generator allows the sending of a current I passing through the electrodes 41, 42, and between the electrodes 41, 42. The path of the current I between the electrodes 41, 42 passes through the sealing plate 1 and through the anchoring plate 22 passing through a point located under the sealing plate 1, at the right angle of the membrane electrode, at the interface with the anchoring plate 22. Of course the direction of the current between the electrodes 41, 42 is not important. The electrical resistance at this point is significant and causes, by Joule effect, during the passage of the current I, a fusion of material forming a welding point 30, which is therefore located under the sealing plate 1.

[0075] The electrodes 41 and 42 are each separated from the edge 15 by a distance approximately equal to 8 mm, for example 7.5 mm. It should be noted, however, that the distance from the membrane electrode 41 to the edge 15 is not necessarily identical to the distance from the anchoring electrode 42 to the edge 15.

[0076] Alternatively, the membrane electrode 41 and the anchoring electrode 42 are each spaced from the edge 15 by a distance less than 8 mm, for example a distance of 6 mm, but greater than 5 mm, or are each spaced from the edge 15 by a distance greater than 8 mm, for example a distance of 12 mm, but less than 15 mm.

[0077] These minimum and maximum distances make it possible to avoid the formation of an electric arc with the edge 15 when sending a current I by the current generator into the electrodes, while allowing the current I passing through the anchoring plate 22 and the sealing plate 1 at the welding point 30 to be sufficiently large to allow the creation of this welding point 30.

[0078] According to a first embodiment of the invention shown in Figures 3 to 5, an indirect resistance welding system SI according to the invention comprises a support 5 forming a rectangular frame 53 delimiting an opening 530. This indirect resistance welding system SI comprises the same electrodes 41, 42 as that of [Fig.2], and comprises a current generator connected in the same way to these electrodes.

[0079] The support 5 comprises means for positioning the support 5 relative to the sealing plate 1, and more particularly means for positioning the support 5 against the edge 15 of the sealing plate 1. These positioning means have in particular the function of ensuring a reliable position of the support 5 and therefore of the electrodes 41, 42 relative to the sealing plate 1 and the anchoring plate 22. These positioning means may in particular take the form of at least one stop, intended to come into contact with the edge 15 of the sealing plate. In the example illustrated, the positioning means comprise a first stop 51 and a second stop 52.

[0080] Under a middle part of the two short edges of the rectangular frame 53, the first stop 51 and the second stop 52 (visible [Fig.4]) are fixed, the stop surfaces of which are coplanar and parallel to the two long edges of the rectangular frame 53. The stops 51 and 52 extend on either side of the rectangular frame 53 without protruding from the side of the opening 530 of the rectangular frame 53.

[0081] 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 of substantially U-shaped section, the branches of the U extending parallel to the main extension plane of the rectangular frame 53. The rails 532, 534 extend on one side of the rectangular frame 53 which is opposite the side of the projecting frame from which the stops 51, 52 extend.

[0082] The support 5 also comprises a first upright 55 extending orthogonally to the rectangular frame 53, being slidably fixed in the first of the rails 532, the first upright 55 being cut at one of its ends so as to form a slide 550 therein gripping one of the edges of the rail 532.

[0083] Similarly, the support 5 comprises a second upright 57 extending orthogonally to the rectangular frame 53, being slidably fixed in the second of the rails 534, the second upright being cut at one of its ends so as to form a slide therein gripping one of the edges of the rail 534.

[0084] An actuator 9 is arranged between the uprights 55, 57 and is secured there by its fixed part. The actuator 9 is, in this embodiment of the invention, an electric or hydraulic cylinder whose outer tube is secured to the uprights 55, 57. Two electrode holders 61, 62 are fixed to the extension tube of the actuator 9 and respectively hold longitudinally one of the electrodes 41, 42 orthogonally to the main extension plane of the rectangular frame 53. The first electrode holder 61 holds the membrane electrode 41 by being fixed to the extension tube on the side of the first upright 55 while the second electrode holder 62 holds the anchoring electrode 42, by being fixed to the extension tube on the side of the second upright 57. The electrodes 41, 42 are arranged partly in the opening 530 of the rectangular frame 53.

[0085] The membrane electrode 41 is cylindrical with a circular section approximately 8 mm in diameter. The circular end of the membrane electrode 41, which extends from the side of the rectangular frame 53 associated with the stops 51, 52, forms a contact surface of the membrane electrode 41 with the sealing plate 1, that is to say it is intended to be in contact with the sealing plate 1.

[0086] The anchoring electrode 42 is cylindrical with a circular section approximately 12 mm in diameter. The circular end of the anchoring electrode 42, which extends from the side of the rectangular frame 53 associated with the stops 51, 52, forms a contact surface of the anchoring electrode 42 with the anchoring plate 22, that is to say it is intended to be in contact with the anchor plate 22.

[0087] The electrodes 41, 42 are here of the same height but their attachment to the extension tube of the actuator 9 offsets them longitudinally from each other (in the direction of the axis A3 when the support 5 is positioned on the sealing and anchoring plates), 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 anchoring electrode 42 with the anchoring plate 22. This longitudinal offset, in a direction orthogonal to the rectangular frame 53, is therefore 1.2 mm.

[0088] A first handle 81 is attached to the ends of a first of the short edges of the rectangular frame 53 and a second handle 82 is attached to the ends of a second of the short edges of the rectangular frame 53.

[0089] These handles 81, 82 allow an operator to install the indirect resistance welding system SI on the sealing plates 1 and anchoring plates 22 as shown in FIGS. 3 to 5, that is to say by aligning the long edges 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 in the opening 530 of the rectangular frame 53. This alignment is carried out so that the electrodes are on either side of the edge 15 of the sealing plate, with the membrane electrode 41 located above the sealing plate 1 and the anchoring electrode 42 located above the anchoring plate 22.

[0090] The first and second stops 51, 52 allow the operator to press the support 5 on the one hand:

[0091] - against the free portion of the anchoring plate 22, parallel to the third axis A3 that is, orthogonally to the principal extension planes of plates 1, 22, and

[0092] - against the edge 15 of the sealing plate 1, parallel to the second axis A2 that is, orthogonally to the edge of the sealing plate 1.

[0093] As shown [Fig.4], the indirect resistance welding system SI comprises a wedge 54 fixed under the first rail 532 of the support 5 and allowing the rectangular frame 53 and in particular the rails of the support 5 to be correctly positioned, orthogonally to the third axis A3.

[0094] 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 anchoring electrode 42 are each located at the desired and easily reproducible distance, here approximately 8 mm, from the edge 15 of the sealing plate.

[0095] A part of the rectangular frame 53 is then located between the waves 12 and 14 of the sealing plate 1, without abutting against another wave 16 of the sealing plate 1, distant from the edge 15 and orthogonally joining the waves 12 and 14. This part of the rectangular frame 53 is of a dimension strictly smaller than the distance between the waves 12 and 14, by at least the dimension of a rivet 24, so as to be able to move the rectangular frame 53 along the edge 15 to avoid positioning the electrodes 41, 42 above such a rivet 24. It should be noted that in an alternative embodiment, the first and second stops 51, 53 coming against the edge 15, are replaced by one or more stops coming against the wave 16 parallel to the edge 15.

[0096] The actuator 9 is then able to press the membrane electrode 41 onto the sealing plate 1 and the anchoring electrode 42 onto the free portion 22 of the anchoring plate, with the same pressing force corresponding for example to three kilograms. Then the electrodes are able to be supplied with current so as to form a welding point 30 between the sealing plate 1 and the anchoring plate 22.

[0097] Once the welding point has been made and the actuator 9 deactivated, the rails 532, 534 and the slides of the uprights 55, 57 allow an operator to move the electrodes 41, 42 in the opening 530 of the rectangular frame 53 of the support 5, by a minimum distance of approximately 40 mm, before making a new welding point. The opening 530 of 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 4 to 6 welding points 30 to be made between the sealing plate 1 and the anchoring plate 22, without moving the rectangular frame 53.

[0098] As a variant of this first embodiment of the invention, each electrode 41, 42 is fixed to a separate actuator, which makes it possible to apply a greater force to the membrane electrode 41 than to the anchoring electrode 42.

[0099] A second embodiment of the invention is now described in relation to [Fig. 6], in which an indirect resistance welding system S2 comprises elements common to those of the indirect resistance welding system SI of the first embodiment of the invention, these common elements being referenced identically.

[0100] The indirect resistance welding system S2 comprises a support 5b comprising a rectangular plate 53b in which are arranged four openings 530b arranged at regular distances from each other along the length of the rectangular plate 53b. The indirect resistance welding system S2 also comprises four pairs p1, p2, p3, p4 of electrodes 41 and 42, these four pairs being arranged in a row in the support 5b. Each pair of electrodes p1 to p4 partly passes through a separate opening 530b of the rectangular plate 53b. The indirect resistance welding system S2 also comprises switching means capable of connecting each pair of electrodes p1 to p4 to a current generator.

[0101] In this second embodiment of the invention, each membrane electrode 41 or anchoring electrode 42 of a pair of electrodes pl to p4 is actuated by a first separate actuator 91 or respectively a second separate actuator 92, which are in this second embodiment, hydraulic or electric cylinders. In particular, the membrane electrode 41 of each pair of electrodes pl to p4 is fixed by its electrode holder 61, to the extension tube of a first actuator 91, this first actuator 91 being secured by its outer tube to a first upright 55b fixed on the rectangular plate 53b of the support 5b and extending orthogonally thereto.

[0102] Similarly, the anchoring electrode 42 of each pair of electrodes p1 to p4 is fixed by its electrode holder 62, to the extension tube 920 of a second actuator 92, this second actuator 92 being secured by its outer tube to a second upright 57b fixed to the rectangular plate 53b of the support 5b and extending orthogonally thereto.

[0103] The electrode holders 61, 62 longitudinally hold the electrodes 41, 42 respectively, orthogonally to the main extension plane of the rectangular plate 53b of the support 5b.

[0104] The arrangement of the electrodes 41, 42 in the support 5b is such that a longitudinal section of the rectangular plate 53b separates each membrane electrode 41 from each anchoring electrode 42. This longitudinal section corresponds to a median section along the length of the rectangular plate 53b. In other words, all the membrane electrodes 41 are located on the same side of the rectangular plate 53b along the length of this rectangular plate 53b, and said all the anchoring electrodes 42 are located on the other side of the rectangular plate 53b relative to this same side.

[0105] Similar to the first embodiment, the support 5b comprises means for positioning the support against the edge 15 of the sealing plate. The positioning means here comprise a first stop 51b and a second stop 52b arranged under a middle portion of two short edges of the rectangular plate 53b, the stop surfaces of the stops 51b, 52b being coplanar and parallel to the long edges of the rectangular plate 53b. The stops 51b and 52b extend on either side of the rectangular plate 53b without obstructing the openings 530b of the rectangular plate 53b.

[0106] Furthermore, a first handle 81b is fixed to the ends of a first of the short edges of the rectangular plate 53b and a second handle 82b is fixed to the ends of a second of the short edges of the rectangular plate 53b.

[0107] The first and second stops 51b, 52b, here forming the positioning means previously mentioned, make it possible to press the support 5b against the edge 15 of the sealing plate 1 and the free portion of the anchoring plate 22 in a manner similar to plating of the support 5 by the first and second stops 51, 52 of the first embodiment.

[0108] The support 5b also includes a wedge, not shown, allowing the rectangular plate 53b to be held orthogonally to the direction of the axis A3.

[0109] This positioning makes it possible to place each membrane electrode 41 above the sealing plate 1 and each anchoring electrode 42 above the anchoring plate 22, so that they are each placed at a desired and easily reproducible distance, approximately 8 mm from the edge 15 of the sealing plate 1.

[0110] Unlike the first embodiment of the invention, in this second embodiment, the electrodes 41, 42 are not movable over a part of the length of the rectangular plate 53b of the support 5b. In addition, their respective contact surfaces with the sealing plate 1 or the anchoring plate 22 can be fixed to the extension tubes of the actuators 91, 92, at the same level orthogonally to the main extension plane of the rectangular plate 53b, when the extension tubes are retracted, since these extension tubes can move independently of each other.

[0111] The actuators 91 and 92 of each pair p1 to p4 of electrodes are capable of pressing the membrane electrode 41 onto the sealing plate 1 and the anchoring electrode 42 onto the free portion 22 of the anchoring plate, with a pressing force of approximately 4 kilograms for the membrane electrode 41 and a pressing force of approximately 2 kilograms for the anchoring electrode 42. These values ​​are given for information purposes only. This pressing is carried out pair of electrodes by pair of electrodes, as the welding points are made. Indeed, the current I is also sent successively into each pair of electrodes p1 to p4 so as not to generate current leaks, poor current distribution and require too high a current.

[0112] In other words, when a pair of electrodes is pressed against the plates to produce a welding point, the other pairs of electrodes are raised, that is to say arranged at a distance from the plates, and the current I is sent successively into each pair of electrodes only when the latter is pressed against the plates.

[0113] The openings 530b are for example 50 mm apart from each other, so as to make four welding points 30 distributed over a significant length along the edge 15 of the sealing plate 1.

[0114] As a variant of 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.

[0115] According to a third embodiment of the invention now described in relation to [Fig.7], an indirect resistance welding system S3 comprises a support 5c forming a rectangular frame 53c delimiting an opening 530c.

[0116] Similar to the first embodiment, the support 5c comprises 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.

[0117] One end of a first of the two short edges of the rectangular frame 53c comprises a foot forming the first stop 51c, and one end of a second of the two short edges of the rectangular frame 53c comprises a foot forming the second stop 52c, the stops 51c and 52c being arranged on the side of the same long edge of the rectangular frame 53c. The stop surfaces of the first and second stops 51c, 52c are coplanar and parallel to the two long edges of the rectangular frame 53c. The stops 51c and 52c extend under the rectangular frame 53c without obstructing the opening 530c of the rectangular frame 53c.

[0118] Each long edge of the rectangular frame 53c is extended orthogonally to the rectangular frame 53c by a first rail 532c or a second rail 534c identical to the rails 532 and 534 of the first embodiment of the invention.

[0119] The support 5c also comprises a first upright 55c extending orthogonally to the rectangular frame 53c, being slidably fixed in the first of the rails 532c, the first upright 55c being cut at one of its ends so as to form a slide 550c therein gripping one of the edges of the first rail 532c.

[0120] Similarly, the support 5c comprises a second upright 57c extending orthogonally to the rectangular frame 53c, being slidably fixed in the second of the rails 534c, the second upright 57c being cut at one of its ends so as to form a slide therein gripping one of the edges of the second rail 534c. The uprights 55c and 57c are held at a distance from each other and in the first and second rails 532c, 534c, by a transverse bar 56 connecting the ends of the uprights 55c, 57c opposite the ends of the uprights forming slides.

[0121] Indeed, unlike the first embodiment of the invention, in this third embodiment of the invention, the indirect resistance welding system S3 comprises a first actuator 91c and a second actuator 92c, secured by their fixed parts to the respective uprights 55c, 57c. The actuators 91c, 92c are, in this exemplary embodiment of the invention, hydraulic or electric cylinders.

[0122] The first actuator 91c is secured by its extension tube to a first axle on which a first hub 63 is rotatably mounted, and the second actuator 92c is secured by its extension tube to a second axle on which a second hub 64 is rotatably mounted. The first hub 63 and the second hub 64 are therefore electrode holders.

[0123] Membrane electrodes 41c, of the same shape as the electrodes 41 of the first embodiment, are secured to the first hub so as to form spokes, or radial branches, regularly and angularly distributed around the first hub.

[0124] Similarly, anchoring electrodes 42c, of the same shape as the electrodes 42 of the first embodiment, are secured to the second hub so as to form spokes, or radial branches, regularly and angularly distributed around the second hub.

[0125] Furthermore, a first handle 81c is attached to the ends of the first short edge of the rectangular frame 53c, and a second handle 82c is attached to the ends of the second short edge of the rectangular frame 53c.

[0126] These handles 81c, 82c allow an operator to install the indirect resistance welding system S3 on the sealing plates 1 and anchoring plates 22 as shown in [Fig.7], that is to say by aligning the long edges of the rectangular frame 53c parallel to the edge 15 of the sealing plate 1, so that the edge 15 is in the opening 530c of the rectangular frame 53c. This alignment is carried out so that the membrane electrodes 41c are located above the sealing plate 1 and the anchoring electrodes 42c are located above the anchoring plate 22.

[0127] The first and second stops 51c, 52c allow the operator to press the support 5c on the one hand:

[0128] - against the free portion of the anchoring plate 22, orthogonally to the planes main extension plates 1, 22, and

[0129] - against the edge 15 of the sealing plate 1, orthogonally to the edge of the sealing plate 1.

[0130] As shown [Fig.7], the indirect resistance welding system S3 also comprises a wedge 54c fixed under the first rail 532c of the support 5c and making it possible to hold the rectangular frame 53c orthogonally to the third axis A3.

[0131] When the stop surfaces of the first and second stops 51c, 52c are pressed against the edge 15 of the sealing plate, the membrane electrodes 41c and the anchoring electrodes 42c are each located at a desired and easily reproducible distance, here approximately 8 mm, from the edge 15 of the sealing plate 1.

[0132] When the uprights 55c, 57c slide along the rails 532c and 534c, the synchronous movement of the first and second hubs 63, 64 makes it possible to bring each membrane electrode 41c successively opposite the sealing plate 1 and anchoring plate 22, at the same time as an anchoring electrode 42c. Then the actuators 91c, 92c press this membrane electrode 41c against the sealing plate 1 in at the same time as they press the anchoring electrode 42c against the anchoring plate 22. These two electrodes 41c, 42c pressed at the same time form a pair of electrodes capable of carrying out a welding point 30, by sending the current I into this pair of electrodes 41c, 42c thus pressed.

[0133] The hubs 63, 64 comprise the same number of membrane electrodes 41c and anchor electrodes 42c, which is here six, forming six pairs of electrodes 41c, 42c. The indirect resistance welding system S3 also comprises switching means capable of successively connecting each of the pairs of electrodes 41c, 42c to a current generator. In an alternative embodiment, however, the hubs comprise two, three, four or five pairs of electrodes only.

[0134] The actuators 91c, 92c are capable of exerting plating forces of 4 kilograms and 2 kilograms respectively on the electrodes 41c, 42c, when their respective contact surfaces are arranged against the sealing plate 1 and respectively against the anchoring plate 22. Of course, these values ​​are given only as an indication, other values ​​may be used.

[0135] This third embodiment therefore makes it possible to make six welding points in the opening 530c of the rectangular frame 53c of the support 5c, without moving the rectangular frame 53c.

[0136] According to a fourth embodiment of the invention now described in relation to [Fig.8], an indirect resistance welding system S4 comprises many elements in common with the indirect resistance welding system S3 of the third embodiment of the invention, referenced in the same way.

[0137] In particular, the indirect resistance welding system S4 comprises the same support 5c of the third embodiment, comprising the stops 51c, 52c, the wedge 54c, the rails 532c, 534c and the uprights 55c, 57c on which the fixed parts of the first actuator 91c and the second actuator 92c are secured respectively.

[0138] Unlike the third embodiment of the invention, in the indirect resistance welding system S4, the first actuator 91c is secured by its extension tube to a first axle on which a wheel-shaped membrane electrode 41d is directly rotatably mounted, and the second actuator 92c is secured by its extension tube to a second axle on which a wheel-shaped anchoring electrode 42d is directly rotatably mounted. The first actuator 91c is capable of exerting a first plating force of approximately 4 kilograms on the membrane electrode 41d, and the second actuator 92c is capable of exerting a second plating force of approximately 2 kilograms on the anchoring electrode 42d. These values ​​are again given for information purposes only.

[0139] The membrane and anchor electrodes 41d, 42d are of the same diameter, but the membrane electrode 41d is of smaller thickness than that of the electrode anchoring electrode 42d, for example the membrane electrode 41d is 8mm thick and the anchoring electrode 42d is 12mm thick. The wheels formed by the membrane and anchoring electrodes 41d, 42d have flats allowing a sufficiently large contact surface for the passage of a strong current between each electrode and the sealing plate 1 or anchoring plate 22 on which it is applied.

[0140] 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 anchoring electrode 42d are each located at the desired and easily reproducible distance, here approximately 8 mm, from the edge 15 of the sealing plate 1. In addition, the rails 532c, 534c are arranged on either side of the edge 15 of the sealing plate 1, being parallel to it.

[0141] Thus when the actuators 91c, 92c press the electrodes 41d, 42d with respectively the first and second pressing force against the sealing plate 1 or the anchoring plate 22, and when the uprights 55c, 57c are moved along the rail, welding points 30 are able to be produced by sending the current I into the electrodes 41d, 42d at regular intervals, along the sealing plate 1. To accelerate the welding process, the height of the actuators 91c, 92c relative to the sealing plates 1 or anchoring plates 22 between two activations, is smaller than their default height just after the positioning of the support 5c.

[0142] According to a fifth embodiment of the invention now described in relation to [Fig.9], an indirect resistance welding system S2b comprises many elements in common with the indirect resistance welding system S2 of the second embodiment of the invention, and referenced in the same way.

[0143] In particular, the indirect resistance welding system S2b comprises a pair of electrodes 41, 42 of the same shapes as those of one of the pairs of electrodes p1 to p4 of the second embodiment. These electrodes 41, 42 are fixed by electrode holders 61, 62 identical to those of the second embodiment, on actuators 91, 92 identical to those of the second embodiment.

[0144] This fifth embodiment differs from what has been previously described in that the actuators 91, 92 are fixed on a support 5d allowing indirect resistance welding of the sealing plate 1 to the anchoring plate 22, at a circular edge 15b of the sealing plate 1, this circular edge 15b being for example formed by a circular cutout in the sealing plate 1.

[0145] The support 5d comprises a plate 53d comprising an opening 530d in which the extension tubes 920 of the actuators 91, 92 extend. The plate 53d is intended to be positioned substantially parallel to the sealing plates 1 and anchoring plates 22, that is to say parallel to a tolerance of almost a few degrees, while being kept at a distance from these plates thanks to a stop 5 Id forming a first foot of the plate 53d, and to a shim 54d forming a second foot of the plate 53d. The stop 51d and the shim 54d are fixed to separate ends of the plate 53d.

[0146] The stop 51d forms a portion of hollow cylinder extending orthogonally to the plate 53d and the free end of which comprises a semi-circular stop surface complementary to at least a first part of the circular edge 15b of the sealing plate 1. Thus the stop 51d is capable of positioning the support 5d against the circular edge 15b of a circular cutout in the sealing plate 1.

[0147] The opening 530d in the plate 53d makes it possible to separate the fixed parts of the actuators 91, 92 from their movable parts to which the electrode holders 61, 62 are fixed. Thus the movable parts of the actuators 91, 92, the electrode holders 61, 62 and the electrodes 41, 42 are arranged in the space delimited by the plate 53d, the stop 51d and the wedge 54d, while the fixed parts of the actuators 91, 92 are located on the other side of the plate relative to the stop 51d and the wedge 54d. The fixed parts of the actuators 91, 92 rest on either side of the opening 530d and are able to slide towards each other, their extension tubes being able to follow this movement through the opening 530d, and therefore being able to adjust their respective positions on the plate 53d. This arrangement makes it possible to adjust the distance between the electrodes 41, 42.It is understood that the welding system S2b comprises a single pair of electrodes, and means for adjusting the distance between the membrane electrode 41 and the anchoring electrode 22.

[0148] Finally, handles 81d and 82d are secured to the support 5d on either side of the latter to facilitate gripping of the welding system S2b.

[0149] When the welding system S2b is in position on the sealing plate 1 and anchoring plate 22, the stop 51d is positioned against the first part of the circular edge 15b of the sealing plate 1 by being placed in the circular cutout of the sealing plate 1, therefore on the anchoring plate 22, while the shim 54d is placed on the sealing plate 1. The anchoring electrode 42 is then positioned above the anchoring plate 22, in the circular cutout of the sealing plate 1, while the membrane electrode 41 is positioned above the sealing plate 1, opposite the membrane electrode 41 with respect to a second part of the circular edge 15b which is not in contact with the stop 51d. This second part of the circular edge 15b is diametrically opposite to the first part of the circular edge 15b.The membrane electrode 41 and the anchoring electrode 42 are then each located at the desired and easily reproducible distance, here approximately 8 mm, from the second part of the circular edge 15b of the sealing plate 1.

[0150] The first actuator 91 is then able to exert a first plating force on the membrane electrode 41, and the second actuator 92 is able to exert a second plating force on the anchoring electrode 42. In accordance with the examples previously mentioned, the first plate force can be of the order of 4 kilograms while the second plating force is of the order of 2 kilograms, these values ​​being considered as an indication and not as a limitation.

[0151] Thus, when the actuators 91, 92 press the electrodes 41, 42 with the first and second pressing forces respectively against the sealing plate 1 or the anchoring plate 22, a welding point 30 can be produced by sending the current I into the electrodes 41, 42. Then other welding points 30 can be produced on the sealing plate 1 along the periphery of its circular cutout, by first moving the electrodes 41, 42 away from the sealing plate 1 and anchoring plate 22 respectively, then by repositioning the support 5d, the latter being guided in rotation by the stop 51d moving against the circular edge 15b of the sealing plate 1.

[0152] In variants of this fifth embodiment, the stop 5 Id is of a different shape, and comprises a stop surface capable of cooperating with other types of cutout in the sealing plate 1.

[0153] [Fig. 10] now illustrates an indirect resistance welding system S5 according to the invention, comprising the indirect resistance welding system S2 according to the invention, as well as a robotic arm 83 capable of exerting a pressing force on the support 5b of the indirect resistance welding system S2, making it possible to counteract the inverse support reactions of the pressing forces exerted by the actuators 91, 92 when producing a welding spot.

[0154] In an alternative embodiment, the indirect resistance welding system S5 comprises not the indirect resistance welding system S2 according to the invention, but the indirect resistance welding system S1, S2b, S3 or S4 according to the invention.

[0155] The robotic arm 83 is fixed to a casing 84 comprising several pieces of equipment, the casing 84 being transported on a mobile carriage of the indirect resistance welding system S5. The casing 84 comprises, for example, the current generator supplying the electrodes 41, 42, the means for controlling the robotic arm 83, the current generator and the actuators 91, 92, as well as possibly a source of liquid for supplying the actuators when these are hydraulic cylinders.

[0156] A method of indirect resistance welding 100 is now described in relation to [Fig. 11], using the indirect resistance welding system S1, S3 or S4 in possible combination with the carriage and the robotic arm 83 of the indirect resistance welding system S5.

[0157] A first step 102 of the indirect resistance welding method 100 is the positioning of the rails 532, 534 or 532c, 534c on either side of the edge 15 of the sealing plate 1, by pressing the positioning means of the support 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 shim 54 or 54c on the sealing plate 1. At the end of this positioning 102, the first electrode(s) 41, 41c, 41d are positioned above the sealing plate 1 and the second electrode(s) 42, 42c, 42d are positioned above the free portion of the anchoring plate 22, each at the desired distance from the edge 15 of the sealing plate 1.

[0158] During this first step 102, the position of the support 5, 5c is optionally adjusted along the edge 15, by maintaining the stops 51, 52 or 51c, 52c against this edge 15, if the electrodes 41, 41c, 41d, 42, 42c, 42d are opposite a rivet.

[0159] The following step 104 of the indirect resistance welding method 100 is the activation of the actuator(s) 9, 91c, 92c. Considered here, with regard to the indirect resistance welding system S3, are only the electrodes 41c, 42c whose contact surface is located opposite the sealing plate 1 and respectively the anchoring plate 22. In this step 104, the actuators 9, 91c, 92c are activated until they exert a first force for pressing the membrane electrode 41, 41c, 41d onto the sealing plate 1 and a second force for pressing the anchoring electrode 42, 42c, 42d onto the anchoring plate 22.

[0160] When the actuator 9 of the indirect resistance welding system SI is used, the first plating force is equal to the second plating force and corresponds for example to 3 kilograms. Other values ​​can of course be used and depend in particular on the force recovery mechanism on the support.

[0161] On the other hand, the first actuator 91 of the indirect resistance welding system S3 or S4 exerts a first plating force equal to approximately 4 kilograms on the membrane electrode 41c or the membrane electrode 41d, and the second actuator 92 of the indirect resistance welding system S3 or S4 exerts a second plating force equal to approximately 2 kilograms on the anchor electrode 42c or the anchor electrode 42d. These values ​​are given for information purposes only, other values ​​may be used for the plating forces.

[0162] The following step 106 of the indirect resistance welding method 100 is the sending of the current I of several kiloamperes into the electrodes 41, 42, 41c, 42c, 41d, 42d, so as to form a welding point 30 between the sealing plate 1 and the anchoring plate 22. Here, with regard to the indirect resistance welding system S3, only the electrodes 41c, 42c whose contact surface is located opposite the sealing plate 1 and respectively the anchoring plate 22 are considered. At the end of the current sending step 106, the current I is cut off, and the actuators 9, 91, 92 are deactivated so as to no longer press the electrodes 41, 42, 41c, 42c, 41d, 42d against the sealing plate 1 or the anchor plate 22.

[0163] Then the next step 108 is a test verifying whether all the welding points 30 to be carried out along the rails 532, 534, 532c, 534c have been carried out. This test can be visual or supervised by a program if the movement of the uprights 55, 57, 55c, 57c, the activation of the actuators 9, 91, 92 and the sending of the current I are controlled by computer. If at the end of the test 108, it is confirmed that all the welding points 30 to be carried out have been carried out (branch Y), then the indirect resistance welding process 100 ends.

[0164] If, on the contrary, at the end of the test 108, it is found that not all the welding points 30 to be made have been made (branch N), then the following step is a step 110 of moving the electrodes 41, 42, 41c, 42c, 41d, 42d along the rails 532, 534, 532c, 534c until they are in a position to make a new welding point 30, separated from the previous welding point 30 by at least a predetermined distance, for example equal to 40 mm.

[0165] At the end of the displacement step 110, allowing a minimum duration between two welding points 30 of at least 350 ms, the indirect resistance welding method 100 continues by returning to the step 104 of activation of the actuators 9, 91, 92, until the test at the step 108 becomes positive.

[0166] A method of indirect resistance welding 200 is now described in relation to [Fig. 12], using the indirect resistance welding system S2 in possible combination with the carriage and the robotic arm 83 of the indirect resistance welding system S5.

[0167] A first step 202 of the indirect resistance welding method 200 is the positioning of each membrane electrode 41 of the pairs of electrodes pl to p4 above the sealing plate 1 and of each anchoring electrode 42 of the pairs of electrodes pl to p4 above the free portion of the anchoring plate 22, by placing the first and second stops 51b, 52b against the edge 15 of the sealing plate 1, and the support shim 5b on the sealing plate 1. At the end of this positioning 202, the electrodes 41, 42 of each pair pl to p4 are each positioned at the desired distance from the edge 15 of the sealing plate 1. When the successive production of the welding points is carried out by a computer program, during this first step 202, this program initializes an electrode pair number to 1 to designate the first pair of pl electrodes.

[0168] The next step 204 of the indirect resistance welding method 200 is the activation of the actuators 91, 92 on which the electrodes 41, 42 of the first pair p1 of electrodes are fixed. In this step 204, these actuators 91, 92 are activated until they exert a first plating force of approximately 4 kilograms of the membrane electrode 41 on the sealing plate 1 and a second plating force of approximately 2 kilograms of the anchoring electrode 42 on the anchoring plate 22, these values ​​being given for information purposes only.

[0169] The next step 206 of the indirect resistance welding method 200 is the sending of the current I of several kiloamperes into the electrodes 41, 42 of the first pair pl of electrodes, so as to form a first welding point 30 between the sealing plate 1 and the anchoring plate 22. At the end of this step 206 of sending current, the current I is cut, and the actuators 91, 92 deactivated so as to no longer press the electrodes 41, 42 of the first pair of electrodes pl against the sealing plate 1 or the anchoring plate 22.

[0170] Then the next step 208 is a test verifying whether all the welding points 30 to be carried out without moving the support 5b have been carried out. This test can be visual or supervised by a program if the activation of the actuators 9, 91, 92 and the sending of the current I are controlled by a computer. If at the end of the test 208, it is confirmed that all the welding points 30 to be carried out have been carried out (branch Y), then the indirect resistance welding process 200 ends.

[0171] If, on the contrary, at the end of test 208, it is found that not all the welding points 30 to be carried out have been carried out (branch N), then the next step is a step 210 of waiting for a predetermined duration, set at 350 ms in this embodiment of the invention, then of incrementing, when the successive production of the welding points is carried out by a computer program, the number of the pair of electrodes. During the first passage through step 210 of waiting for a predetermined duration, this number is incremented to two, designating the second pair of electrodes p2 to be considered for the following steps.

[0172] At the end of this step 210 of waiting for a predetermined duration, the indirect resistance welding process 200 continues by returning to a step 204 of activating the actuators 91, 92 applied to the second pair of electrodes p2, followed by a new step 206 of sending current into this second pair of electrodes p2, then a new test step 208, and so on until the sending of current into the pair of electrodes p4 and the observation of the end of the indirect resistance welding process 200 during a final test step 208.

[0173] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of different variants or different embodiments of the invention can be combined to achieve the invention, insofar as these variants or embodiments are not incompatible with each other.

Claims

Claims

1. Indirect resistance welding system (SI, S2, S3, S4, S5) of a sealing plate (1) of a tank intended to contain liquefied gas, on an anchoring plate (22) arranged partly under the sealing plate (1) so as to leave a free portion of the anchoring plate (22) outside the sealing plate (1), an edge (15) of the sealing plate (1) separating the sealing plate (1) from the free portion of the anchoring plate (22), the welding system (SI, S2, S3, S4, S5) comprising: - at least one pair of electrodes and a current generator capable of being connected to the 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, - 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 an electrode of said at least one pair of electrodes, called membrane electrode (41, 41c, 41d), above the sealing plate (1) and another electrode of said at least one pair of electrodes, called anchoring electrode (42, 42c, 42d), above the free portion of the anchoring plate (22), and - at least one actuator (9, 91, 92, 91c, 92c) for each pair of electrodes, capable of pressing the membrane electrode (41, 41c, 41d) onto the sealing plate (1) and the anchoring electrode (42, 42c, 42d) onto the free portion of the anchoring plate (22).,

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

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

4. Indirect resistance welding system (S1, S2, S3, S4, S5) according to any one of claims 1 to 3, in which the positioning means comprise at least one stop (51, 51b, 51c, 52, 52b, 52c) secured to the support (5, 5b, 5c) and capable of being pressed against the edge (15) of the sealing plate (1), or against a wave (12, 14, 16) of the sealing plate (1).

5. Indirect resistance welding system (S1, S3, S4) according to any one of claims 1 to 4, in which the support (5, 5b, 5c) comprises two rails (532, 532c, 534, 534c) capable of being positioned on either side of the edge (15) of the sealing plate (1) and parallel to said edge, and means for moving the electrodes (41, 42, 41c, 42c, 41d, 42d) of each pair of electrodes, mounted movable in translation on the two rails (532, 532c, 534, 534c).

6. Indirect resistance welding system (S4) according to claim 5, wherein the displacement means comprise at least one axle arranged orthogonally to the rails (532c, 534c), the electrodes (41d, 42d) of each pair of electrodes taking the form of wheels mounted on the at least one axle.

7. Indirect resistance welding system (S3) according to claim 5, wherein the displacement means comprise at least one axle arranged orthogonally to the rails (532c, 534c) as well as a first hub (63) mounted on the at least one axle and on which the membrane electrode (41c) is arranged, the displacement means further comprising a second hub (64) mounted on the at least one axle and on which the anchoring electrode (42c) is arranged, each pair of electrodes being configured such that the membrane electrode (41c) is able to be in contact with the sealing plate (1) at the same time as the anchoring electrode (42c) is able to be in contact with the free portion of the anchoring plate (22).

8. Indirect resistance welding system (S3) according to claim 5, comprising several pairs of electrodes and in which the displacement means comprise at least one axle arranged orthogonally to the rails (532c, 534c) as well as a first hub (63) mounted on the at least one axle and in which the membrane electrodes (41c) of the pairs of electrodes are distributed angularly around the first hub (63), the displacement means further comprising a second hub (64) mounted on the at least one axle and in which the anchoring electrodes (42c) of the pairs of electrodes are distributed angularly around the second hub (64), the pairs of electrodes being configured such that the membrane electrode (41c) of one of the pairs of electrodes is able to be in contact with the sealing plate (1) at the same time as the anchoring electrode (42c) of said pair of electrodes is able to be in contact with the free portion of the anchoring plate (22).

9. Method for indirect resistance welding (100, 200), using an indirect resistance welding system (S1, S2, S3, S4, S5) according to any one of claims 1 to 8, comprising steps of: - positioning (102, 202) the membrane electrode (41, 41c, 41d) above the sealing plate (1) and the anchoring electrode (42, 42c, 42d) above the free portion of the anchoring plate (22), using the positioning means, - 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 anchoring electrode (42, 42c, 42d) is pressed against the free portion of the anchoring plate (22), 42c, 42d) on the free portion of the anchor plate (22), and - sending current (106, 206) into the electrodes (41, 41c, 41d, 42, 42c, 42d).

10. Method of indirect resistance welding (100, 200) according to claim 9 in combination with claim 2, in which the activation step (104, 204) comprises the plating of the membrane electrode (41, 41c, 41d) on the sealing plate (1) with the first force and the plating of the anchoring electrode (42, 42c, 42d) on the free portion of the anchoring plate (22) with the second force, the first force being strictly greater than the second force.

11. Method for indirect resistance welding (100) according to claim 9 or 10, in combination with claim 5, in which the positioning step (102) comprises positioning the rails (532, 532c, 534, 534c) on either side of the edge (15) of the sealing plate (1), and is followed by several activation (104) and current sending (106) steps, the welding method (100) further comprising a step of moving (110) the electrodes along the rails (532, 532c, 534, 534c), interposed between a current sending step (106) and a step of activating (104) the at least one actuator (9, 91, 92, 91c, 92c).

12. Method of indirect resistance welding (200) according to claim 9 or 10, in which the indirect resistance welding system (S2, S5) is resistance comprising a row of pairs of electrodes (pl, p2, p3, p4) arranged on the support (5b), the positioning step (202) comprises the positioning of each membrane electrode (41) of the pairs of electrodes (pl, p2, p3, p4) above the sealing plate (1) and of each anchoring electrode (42) of the pairs of electrodes (pl, 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 pairs of electrodes (pl, p2, p3, p4), the current sending steps (206) each being spaced apart by a predetermined minimum duration and each supplying a single pair of electrodes (pl, p2, p3, p4).

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