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

Abstract

System and method for indirect resistance welding of a sealing plate to an anchor plate. The present invention relates to an indirect resistance welding system (S1) of a sealing plate (1) of a tank intended to contain liquefied gas, to an anchor plate (22) disposed partially under the sealing plate (1), comprising: - a pair of electrodes and a current generator adapted to be connected to the electrodes (41, 42); - a support (5) adapted to hold the electrodes relative to each other; - means for positioning the support (5) against the sealing plate (1), adapted to position a first electrode (41) above the sealing plate (1) and a second electrode (42) above the free portion of the anchor plate (22); and - at least one actuator (9) adapted to press the first electrode (41) against the sealing plate (1) and the second electrode (42) on the free portion of the anchoring plate (22). (Figure 3)

Description

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

[0001] The present invention relates to the field of tanks for gases in a liquid state, for example liquefied natural gas (LNG), particularly for maritime or river transport or for an onshore reservoir. More specifically, the invention relates to a welding system for a sealing plate adapted for such a tank, and an associated welding process.

[0002] Liquefied gas tanks have a capacity of several thousand cubic meters of liquid gas each, or even several tens of thousands of cubic meters. Liquefied gas transport vessels have holds specifically designed to contain these tanks, their holds often being divided into several tanks. Such a tank can also be constructed outside a ship for onshore storage of natural gas in liquid form.

[0003] The gas is kept inside the tank in a liquid state, for example at -163°C (degrees Celsius) for LNG, at atmospheric pressure. Therefore, the tank must be leak-proof and thermally insulated. Consequently, 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 together, each sealing plate forming part of the tank's sealing membrane.

[0004] The walls of the tank further 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 sealing membrane, called a secondary sealing membrane, by example made of thin sheet metal

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

[0008] The primary waterproofing membrane is fixed to the primary insulation layer by welding the waterproofing sheets to anchoring plates, which are integral with the primary insulation layer and which can, in particular, be riveted to the wooden frames of the primary insulation layer. These anchoring plates form a grid pattern across all the frames but do not completely cover them.

[0009] Currently, as shown [Fig. 1], the fixing welds 3 of a plate Sealing 1 on an anchor plate 22 are carried out 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 weld 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 advantageously form a grid and allow the absorption of deformations of the tank due to 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 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 frame. The third axis A3 of this orthonormal frame extends orthogonally to the principal extension plane of the sealing plate 1.

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

[0013] As shown in [Fig. 1], the sealing plate 1 is fixed using six 20 mm (millimeter) long welds between the two corrugations 12 and 14, spaced 20 mm apart, which allows the sealing plate 1 to be fixed between the two corrugations 12 and 14 over a distance of at least 220 mm. For reference, the peak-to-peak distance dl between corrugations 12 and 14 is 340 mm, which allows for some deformation.

[0014] The lap welds 3 are operational and allow for visual verification of the welds performed. However, this process is carried out manually, which makes attaching the tank sealing plates to the anchor plates of the primary insulation layer very time-consuming. Automating these welds 3 with a TIG welding process would require very complex and expensive equipment, particularly for automatic and precise tracking of the edge 15 of the sealing plate 1. Positioning the rail on which an automatic TIG welding machine would be placed would also be very time-consuming.

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

[0016] To this end, the invention proposes an indirect resistance welding system for a sealing plate of a tank intended to contain liquefied gas, on a plate anchoring system positioned partially 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 suitable for connection to the electrodes, - a support capable of holding the electrodes of 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 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 create a weld point located under the membrane electrode, with a diameter of up to 5 mm, between the sealing plate and the anchoring plate. This weld point is created by applying a current of several kiloamperes between the electrodes. This change in welding technique compared to the prior art makes it possible to quickly attach the sealing plate to the anchoring plate by, for example, making only four weld points between two corrugations of the sealing plate, between the latter and the anchoring plate. These weld points can be made more quickly by an operator than lap welds, as they are point welds and do not require very precise positioning of the welds relative to the edge of the sealing plate.

[0018] The welding system according to the invention is suitable for positioning the membrane electrode and the anchor electrode on either side of an edge of the sealing plate disposed on the anchor plate, allowing the positioning of the membrane electrode on the sealing plate at a point which is also above the part of the anchor plate located below the sealing plate, and the positioning of the anchor electrode on the anchor plate, so as to allow an indirect resistance weld point between the sealing plate and the anchor 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 shall be:

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

[0021] - and sufficiently large to prevent the creation of an electric arc. Indeed, a Such an electric arc generates projections and apparent defects that 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 is generated at that point, which causes local deformation and degradation of the weld point obtained.

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

[0024] In an embodiment with several pairs of electrodes, the support allows the electrodes of the different pairs of electrodes to be kept at a distance from each other.

[0025] This support is for example a simple electrode holder, allowing its manual movement to 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 located away from the support, so as not to require its movement along with the support to perform several weld points. For example, the current generator is mounted on a trolley and connected to the electrodes fixed to the support by metallic conductors, which may take the form of thick copper braids, given the amperage used.

[0027] At least one actuator is, for example, attached to the support. According to an optional feature of the invention, the support comprises at least one post to which the fixed part of at least one actuator is attached. This actuator is, for example, a cylinder, with the electrodes attached to the cylinder's extension tube.

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

[0029] According to an optional feature of the welding system according to the invention, it comprises two actuators for each pair of electrodes, the first of which is 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 anchor electrode onto the free portion of the anchor plate with a second pressing force.

[0030] It should be noted that in this application, the term "plate 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 to which the electrode is pressed by the actuator. The transfer of force applied to the electrodes can be carried out by an operator or by a machine that maintains the welding system.

[0031] This feature allows for more secure contact between the sealing plate and the anchoring plate at the weld point, thus ensuring good weld quality. According to an optional feature of the invention, the second clamping force has a lower value than the first clamping force. The first clamping force, expressed in kilograms-force, corresponds, for example, to a force of approximately 4 kilograms, and the second clamping force corresponds, for example, to a force of approximately 2 kilograms. These values ​​are given here by way of example only and are not intended to limit the invention. For example, much higher clamping forces can be applied, particularly if the force is transferred by a machine.

[0032] According to an optional feature of the welding system according to the invention, the membrane electrode has a contact surface with the sealing plate that is strictly smaller than a contact surface of the anchor electrode with the free portion of the anchor plate.

[0033] This contact surface determines the cross-sectional area through which the current passes between each electrode and the plate against which the electrode is pressed. For example, the membrane and anchor electrodes are cylindrical and are pressed by one of their bases against the sealing or anchoring plate. The membrane electrode then has a circular cross-section of, for example, between 7 and 9 mm² and preferably 8 mm², while the anchor electrode has a circular cross-section of, for example, between 11 and 13 mm² and preferably 12 mm².

[0034] In another example, the membrane and anchor electrodes have a right prism shape with a 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 plates of the same diameter, their contact surfaces with the plates are portions of their lateral surfaces, of lengths the dimensions of the wheel orthogonally to their radii, and the length of the portion of the The lateral surface area of ​​the membrane electrode is smaller than the length of the portion of the lateral surface area of ​​the anchor electrode. In this example, the lateral surfaces of the wheels preferably have flats, with 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 area for current flow.

[0036] In one embodiment of the invention, the positioning means comprise at least one stop fixed to the support and adapted to be pressed against the edge of the sealing plate, or against a corrugation of the sealing plate. The positioning means comprise, for example, two stops fixed to the support and adapted to be pressed against the edge of the sealing plate, or one or more stops adapted to be pressed against a corrugation of the sealing plate, Fonde being parallel to the edge of the sealing plate. The electrodes are then preferably arranged on the support, between the two stops.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(s) 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 move the support slightly parallel to the edge of the sealing plate, to position the electrodes outside riveted locations of the anchor plate.

[0037] The welding system according to the invention may optionally comprise several pairs of electrodes arranged between the two stops. For example, it may comprise as many pairs of electrodes as there are weld points to be made between the two stops, the number of weld points to be made preferably corresponding to the number of weld points to be made between two consecutive waves of the anchor plate. Thus, an operator can make all the weld 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 to prevent the formation of parasitic current paths when making a weld 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 adaptable to be 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 movably in translation on the two rails. By "parallel to said edge" is meant substantially parallel to said edge, that is to say, within a tolerance of a few degrees. The rails of the support are adaptable to be 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 setting up the support on the sealing plates and anchoring them to weld them, the rails are positioned on either side of the edge and parallel to it.

[0039] The means of movement include, for example, fixed uprights sliding on rails, the uprights being attached to the fixed parts of one or more actuators which are themselves attached to the electrodes by their moving parts. The rails and the means of movement allow, for example, the electrodes to move between two stops located at the longitudinal ends of the support and capable of pressing the support against the edge of the sealing plate.

[0040] The means of movement 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 at least one axle. This axle is, for example, fixed to the moving part of 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 moving 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 cylinder attached to one of the fixed uprights sliding on one of the rails, the other axle supporting another electrode being fixed to an extension tube of another cylinder attached to the other fixed upright sliding on the other rail.

[0041] In another example, the means of movement comprise at least one axle arranged orthogonally to the rails and a first hub mounted on at least one axle and on which the membrane electrode is arranged. The means of movement further comprise a second hub mounted on at least one axle and on which the anchoring electrode is arranged. Each pair of electrodes is 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 means of movement 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 transport include, for example, a rack per rail, and a 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 means of movement comprises at least one axle arranged orthogonally to the rails as well as a first hub mounted on at least one axle, the membrane electrodes of the pairs of electrodes being distributed angularly around the first hub, the means of movement further comprising a second hub mounted on at least one axle, The anchoring electrodes of the electrode pairs are distributed angularly around the second hub, and the electrode pairs are configured such that the membrane electrode of one of the electrode pairs is able to contact the sealing plate at the same time as the anchoring electrode of said electrode pair is able to contact the free portion of the anchoring plate. For example, the membrane electrodes form radii distributed angularly around the first hub, and the anchoring electrodes form radii distributed angularly around the second hub.

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

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

[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 specifically, considering the axial direction defined by the axle, an electrode pair is defined with a membrane electrode and an anchor electrode that are aligned with each other.

[0046] Furthermore, according to an optional feature of the indirect resistance welding system according to the invention, it comprises gripping means attached to the support. These gripping means facilitate the positioning of the support against the sealing plate, and the effort to be exerted on the support by an operator to counteract the clamping force(s) exerted by at least one actuator.

[0047] The indirect resistance welding system according to the invention optionally comprises a trolley 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 trolley 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 trolley carries, for example, in addition to the current generator, a source of fluid for supplying the hydraulic cylinders, connected by fluid connections to the hydraulic cylinders. Furthermore, the trolley preferably transports control means for the robotic arm, cylinders and current generator.

[0048] The invention also relates to an indirect resistance welding process, using an indirect resistance welding system according to the invention, and comprising the steps of: - positioning of the membrane electrode above the sealing plate and of the anchor electrode above the free portion of the anchor plate, using the positioning means, - activation of 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 uses the current generator of course.

[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 anchor electrode onto the free portion of the anchor plate with a second pressing force, the activation step preferably includes pressing the membrane electrode onto the sealing plate with the first force and pressing the anchor electrode onto the free portion of the anchor 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 suitable for 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 movably 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 activation and current sending steps, the welding process according to the invention further comprising a step of moving the electrodes along the rails, intercalated between a current sending step and an activation step of at least one actuator.

[0052] The displacement step allows the electrodes 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 prevents the creation of parasitic current paths during a current delivery step.

[0053] Alternatively, when the indirect resistance welding system comprises a row of electrode pairs arranged on the support, the positioning step comprises positioning each membrane electrode of the electrode pairs above the sealing plate and each anchor electrode of the pairs electrodes above the free portion of the anchor plate, and the welding process according to the invention comprises as many current delivery steps as there are pairs of electrodes, each current delivery step being spaced a predetermined minimum time apart and each supplying a single pair of electrodes. The longitudinal section of the row here refers to a cross-section of the row along its length.

[0054] In this alternative embodiment of the invention, the weld points are preferably made consecutively by each pair of electrodes in the row of electrode pairs, in the direction of travel along this row; that is, the weld points are made one after the other along the edge of the sealing plate. Thus, the current-sending steps in the electrodes are less likely to cause parasitic current paths. Furthermore, the predetermined time between each current-sending step also helps to prevent the creation of parasitic current paths. For example, it is between 300 and 400 ms and preferably equal to 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 on the support to counteract the clamping forces exerted on the electrodes.

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

[0057] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0058] [Fig. 1], already described in relation to the prior art, represents a portion of a sealing plate welded clinker-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 is positioned against an edge of a sealing plate, above it 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 is positioned against an edge of a sealing plate, above it 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 is positioned against an edge of a sealing plate, above it 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 is positioned against an edge of a sealing plate, above it 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 is positioned against an edge of a sealing plate, above it 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 process 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 process according to the invention, using the indirect resistance welding system of the second embodiment of the invention.

[0070] Figure 2 schematically represents an implementation of a weld point 30 by an indirect resistance welding system according to the invention. This system comprises an electrode 41, referred to as the membrane electrode, and an electrode 42, referred to as 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 allows the membrane electrode 41 to be pressed against the sealing plate 1, near the edge 15 of the sealing plate separating the portion of the anchoring plate 22 located 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 housing 40.

[0072] For guidance 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 a current I to be sent through electrodes 41, 42, and between electrodes 41, 42. The path of the current I between electrodes 41, 42 passes through the sealing plate 1 and the anchoring plate 22, passing through a point located under the sealing plate 1, directly above the membrane electrode, at the interface with the anchoring plate 22. The direction of the current between electrodes 41, 42 is irrelevant. The electrical resistance at this point is significant and, due to Joule heating, causes the current I to melt material, forming a weld point 30, which is therefore located under the sealing plate 1.

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

[0076] Alternatively, the membrane electrode 41 and the anchoring electrode 42 are each distanced from the edge 15 by a distance of less than 8 mm, for example by a distance of 6 mm, but greater than 5 mm, or are each distanced from the edge 15 by a distance greater than 8 mm, for example by 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 anchor plate 22 and the sealing plate 1 at the weld point 30 to be sufficiently large to allow the creation of this weld 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 includes 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 are designed, in particular, to ensure 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 illustrated example, the positioning means include 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 stopping 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 on 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 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 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 includes a first upright 55 extending orthogonally to the rectangular frame 53, being fixed sliding 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 taking in a pincer one of the edges of the rail 532.

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

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

[0085] The membrane electrode 41 is cylindrical with a circular cross-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, i.e. it is intended to be in contact with the sealing plate 1.

[0086] The anchor electrode 42 is cylindrical with a circular cross-section approximately 12 mm in diameter. The circular end of the anchor electrode 42, which extends from the side of the rectangular frame 53 associated with the stops 51, 52, forms a contact surface of the anchor electrode 42 with the anchor plate 22, i.e., it is intended to be in contact with 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 (along 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, along a direction orthogonal to the rectangular frame 53, is therefore 1.2 mm.

[0088] A first handle 81 is fixed to the ends of a first of the short edges of the rectangular frame 53 and a second handle 82 is fixed 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 Figures 3 to 5, i.e. by aligning the long edges of the rectangular frame 53 along the first axis Al parallel to the edge 15 of the sealing plate 1, so that the edge 15 is found 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 being on top of the sealing plate 1 and the anchoring electrode 42 being on top of the anchoring plate 22.

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

[0091] - against the free portion of the anchor plate 22, parallel to the third axis A3 that is to say 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 to say orthogonally to the edge of the sealing plate 1.

[0093] As shown [Fig.4], the indirect resistance welding system SI includes 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 positioned correctly orthogonally to the third axis A3.

[0094] When the stopping 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 the desired and easily reproducible distance, here about 8 mm, from the edge 15 of the sealing plate.

[0095] A portion of the rectangular frame 53 is then located between the waves 12 and 14 of the sealing plate 1, without abutting another wave 16 of the sealing plate 1, which is far from the edge 15 and orthogonally joined to the waves 12 and 14. This portion of the The rectangular frame 53 is strictly smaller than the distance between the waves 12 and 14, by at least the dimension of a rivet 24, so that the rectangular frame 53 can be moved 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 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, for example, to three kilograms. The electrodes are then able to be supplied with current so as to form a weld point 30 between the sealing plate 1 and the anchoring plate 22.

[0097] Once the weld 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 within the opening 530 of the rectangular frame 53 of the support 5, a minimum distance of approximately 40 mm, before making another weld 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) for at least twenty centimeters so as to allow 4 to 6 weld points 30 to be made between the sealing plate 1 and the anchoring plate 22, without moving the rectangular frame 53.

[0098] In 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 on the membrane electrode 41 than on 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 identically referenced.

[0100] The indirect resistance welding system S2 comprises a support 5b having a rectangular plate 53b in which four openings 530b are arranged at regular intervals along the length of the rectangular plate 53b. The indirect resistance welding system S2 also comprises four pairs pl, p2, p3, p4 of electrodes 41 and 42, these four pairs being arranged in a row in the support 5b. Each pair of electrodes pl to p4 passes partially through a separate opening 530b in the rectangular plate 53b. The indirect resistance welding system S2 also comprises switching means for connecting each pair of electrodes pl 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 in this second embodiment are 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 to the rectangular plate 53b of the support 5b and extending orthogonally thereto.

[0102] Similarly, the anchoring electrode 42 of each pair of electrodes pl 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 on the rectangular plate 53b of the support 5b and extending orthogonally to it.

[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 cut along the length of the rectangular plate 53b. In other words, all the membrane electrodes 41 are located on one side of the rectangular plate 53b along the length of this rectangular plate 53b, and all the anchoring electrodes 42 are located on the other side of the rectangular plate 53b with respect to this same side.

[0105] Similar to the first embodiment, the support 5b includes 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 mid-portion of two short edges of the rectangular plate 53b, the stopping surfaces of the stops 51b and 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 in 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, forming here the positioning means mentioned above, allow the support 5b to be pressed against the edge 15 of the sealing plate 1 and the free portion of the anchoring plate 22 in a manner similar to support 5 is pressed against 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 allows each membrane electrode 41 to be placed above the sealing plate 1 and each anchor electrode 42 above the anchoring plate 22, so that each is placed at a desired and easily reproducible distance, about 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 along 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 pl to p4 of electrodes are capable of pressing the membrane electrode 41 onto the sealing plate 1 and the anchor electrode 42 onto the free portion 22 of the anchor plate, with a pressing force of approximately 4 kilograms for the membrane electrode 41 and a pressing force of approximately 2 kilograms for the anchor electrode 42. These values ​​are given for guidance purposes only. This pressing is carried out electrode by electrode pair, as the weld points are being made. Indeed, the current I is also sent successively to each pair of electrodes pl to p4 to avoid current leakage, poor current distribution, and the need for an excessive current.

[0112] In other words, when a pair of electrodes is pressed against the plates to make a weld 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 it is pressed against the plates.

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

[0114] In 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 described now 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 includes means for positioning the support against the edge 15 of the sealing plate. The positioning means include 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 has a foot forming the first stop 51c, and one end of a second of the two short edges of the rectangular frame 53c has 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 stopping 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 includes a first upright 55c extending orthogonally to the rectangular frame 53c, being fixed sliding 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 taking in a pincer 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 fixed to slide within the second of the rails 534c, the second upright 57c being cut at one of its ends so as to form a slide that clamps one of the edges of the second rail 534c. The uprights 55c and 57c are held apart from each other and within the first and second rails 532c, 534c, by a crossbar 56 connecting the ends of the uprights 55c, 57c opposite to 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 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 fixed 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 fixed to the ends of the first short edge of the rectangular frame 53c, and a second handle 82c is fixed 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], i.e., 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 located 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 51, 52c allow the operator to press the support 5c against the support on the one hand:

[0128] - against the free portion of the anchor plate 22, orthogonally to the planes main extension of 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 includes a wedge 54c fixed under the first rail 532c of the support 5c and allowing the rectangular frame 53c to be held orthogonally to the third axis A3.

[0131] When the stopping 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 anchor electrodes 42c are each located at a desired and easily reproducible distance, here about 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 brings each membrane electrode 41c and an anchor electrode 42c successively into alignment with the sealing plates 1 and anchoring plates 22. Then the actuators 91c, 92c press this membrane electrode 41c against the sealing plate 1. at the same time as they press the anchor electrode 42c against the anchor plate 22. These two electrodes 41c, 42c pressed at the same time form a pair of electrodes capable of making a weld point 30, by sending the current I into this pair of electrodes 41c, 42c thus pressed.

[0133] The hubs 63, 64 have the same number of membrane electrodes 41c and anchoring electrodes 42c, respectively, which is six in this case, forming six pairs of electrodes 41c, 42c. The indirect resistance welding system S3 also includes switching means for successively connecting each pair of electrodes 41c, 42c to a current generator. In an alternative embodiment, however, the hubs have only two, three, four, or five pairs of electrodes.

[0134] The actuators 91c, 92c are capable of exerting clamping 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 against the anchoring plate 22 respectively. 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 weld 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 described now in relation to [Fig.8], an indirect resistance welding system S4 has 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 includes 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 respectively secured.

[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 and 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 and rotatably mounted. The first actuator 91c is capable of exerting a first clamping force of approximately 4 kilograms on the membrane electrode 41d, and the second actuator 92c is capable of exerting a second clamping force of approximately 2 kilograms on the anchoring electrode 42d. These values ​​are again given for illustrative purposes only.

[0139] The membrane and anchoring electrodes 41d, 42d are of the same diameter, but the membrane electrode 41d is thinner than that of the electrode anchoring electrode 42d, for example, the membrane electrode 41d is 8 mm thick and the anchoring electrode 42d is 12 mm 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 high current between each electrode and the sealing plate 1 or anchoring plate 22 to which it is applied.

[0140] When the stopping 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 about 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 the first and second pressing force respectively against the sealing plate 1 or the anchoring plate 22, and when the uprights 55c, 57c are moved along the rail, weld points 30 are able to be made 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 plate 22 between two activations is less than their default height just after the positioning of the support 5c.

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

[0143] In particular, the indirect resistance welding system S2b comprises a pair of electrodes 41, 42 of the same shape as those of one of the pairs of electrodes pl 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 an indirect resistance weld to be made from 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 cut in the sealing plate 1.

[0145] The support 5d comprises a plate 53d having an opening 530d through 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, parallel to within a tolerance of a few degrees, while being held at a distance from these plates by means of a stop 5 Id forming a first foot of the plate 53d, and to a wedge 54d forming a second foot of plate 53d. The stop 51d and the wedge 54d are fixed to distinct ends of plate 53d.

[0146] The stop 5Id forms a portion of a hollow cylinder extending orthogonally to the plate 53d and whose free end has a semi-circular stopping surface complementary to at least a first part of the circular edge 15b of the sealing plate 1. Thus the stop 51d is able to position 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 allows the fixed parts of the actuators 91, 92 to be separated from their moving parts to which the electrode holders 61, 62 are attached. Thus the moving 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 with respect 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 thus are 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 S2b welding system 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 attached to the support 5d on either side of it to facilitate gripping the welding system S2b.

[0149] When the welding system S2b is in position on the sealing plates 1 and anchoring plate 22, the stop 5Id is positioned against the first part of the circular edge 15b of the sealing plate 1 by resting in the circular cutout of the sealing plate 1, and 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 that is not in contact with the stop 51d. This second part of the circular edge 15b is diametrically opposite 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 about 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 clamping force on the membrane electrode 41, and the second actuator 92 is able to exert a second clamping force on the anchoring electrode 42. According to the examples As previously mentioned, the first plate force can be in the order of 4 kilograms while the second plate force is in the order of 2 kilograms, these values ​​being to be considered as indicative and not limiting.

[0151] Thus, when the actuators 91, 92 press the electrodes 41, 42 with respectively the first and second pressing force against the sealing plate 1 or the anchoring plate 22, a weld point 30 is able to be made by sending the current I into the electrodes 41, 42. Then other weld points 30 are able to be made on the sealing plate 1 along the perimeter of its circular cut, by first moving the electrodes 41, 42 away respectively from the sealing plates 1 and anchoring plate 22, 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 includes a stopping surface suitable for cooperating with other types of cutouts 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 clamping force on the support 5b of the indirect resistance welding system S2, making it possible to counteract the inverse support reactions of the clamping forces exerted by the actuators 91, 92 during the making of a weld point.

[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 SI, S2b, S3 or S4 according to the invention.

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

[0156] We now describe in relation to [Fig. 11], a 100 indirect resistance welding process, using the indirect resistance welding system SI, S3 or S4 in possible combination with the trolley and robotic arm 83 of the indirect resistance welding system S5.

[0157] A first step 102 of the indirect resistance welding process 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 wedge 54 or 54c against the sealing plate 1. Following this positioning 102, the first or first electrodes 41, 41c, 41d are positioned above the sealing plate 1 and the second or second electrodes 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 holding 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 next step 104 of the indirect resistance welding process 100 is the activation of the actuator(s) 9, 91c, 92c. For the indirect resistance welding system S3, only the electrodes 41c, 42c whose contact surface is located opposite the sealing plate 1 and the anchoring plate 22, respectively, are considered here. In this step 104, the actuators 9, 91c, 92c are activated until they exert a first clamping force on the membrane electrode 41, 41c, 41d on the sealing plate 1 and a second clamping force on the anchoring electrode 42, 42c, 42d on the anchoring plate 22.

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

[0161] Conversely, the first actuator 91 of the indirect resistance welding system S3 or S4 exerts a first clamping force of 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 clamping force of approximately 2 kilograms on the anchor electrode 42c or the anchor electrode 42d. These values ​​are given for guidance purposes only; other values ​​may be used for the clamping forces.

[0162] The next step 106 of the indirect resistance welding process 100 is the application of a current I of several kiloamperes to the electrodes 41, 42, 41c, 42c, 41d, 42d, so as to form a weld point 30 between the sealing plate 1 and the anchoring plate 22. For the indirect resistance welding system S3, only the electrodes 41c, 42c whose contact surface is opposite the sealing plate 1 and the anchoring plate 22, respectively, are considered here. Following the application of the current in step 106, the current I is switched off, and the actuators 9, 91, 92 are deactivated so as not to press the electrodes 41, 42, 41c, 42c, 41d, 42d against the plate. sealing plate 1 or anchor plate 22.

[0163] Then the next step 108 is a test verifying whether all the weld points 30 to be made 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 actuators 9, 91, 92 and the sending of current I are computer controlled. If, at the end of test 108, it is confirmed that all the required weld points 30 have been completed (branch Y), then the indirect resistance welding process 100 is terminated.

[0164] If, on the contrary, at the end of test 108, it is found that not all the weld points 30 to be made have been carried out (branch N), then the next 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 position to make a new weld point 30, separated from the previous weld 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 time between two weld points 30 of at least 350ms, the indirect resistance welding process 100 continues by returning to the activation step 104 of the actuators 9, 91, 92, until the test in step 108 becomes positive.

[0166] We now describe in relation to [Fig. 12], an indirect resistance welding process 200, using the indirect resistance welding system S2 in possible combination with the trolley and robotic arm 83 of the indirect resistance welding system S5.

[0167] A first step 202 of the indirect resistance welding process 200 is the positioning of each membrane electrode 41 of the electrode pairs pl to p4 above the sealing plate 1 and of each anchor electrode 42 of the electrode pairs pl to p4 above the free portion of the anchor plate 22, by pressing the first and second stops 51b, 52b against the edge 15 of the sealing plate 1, and the support wedge 5b against the sealing plate 1. Following 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 welding of the points is performed by a computer program, during this first step 202, this program initializes an electrode pair number to 1 to designate the first pair of electrodes pl.

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

[0169] The next step 206 of the indirect resistance welding process 200 is the sending of a current I of several kiloamperes into the electrodes 41, 42 of the first pair pl of electrodes, so as to form a first weld point 30 between the sealing plate 1 and the anchoring plate 22. At the end of this current sending step 206, the current I is cut off, and the actuators 91, 92 are deactivated so as not to press the electrodes 41, 42 of the first pair of electrodes pl against the sealing plate 1 or the anchoring plate 22.

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

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

[0172] At the end of this waiting step 210 of a predetermined duration, the indirect resistance welding process 200 continues by returning to a step 204 of activation of 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 finding 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 just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the features of different variants or embodiments of the invention can be combined to carry out the invention, provided that these variants or embodiments are not incompatible with each other.

Claims

Demands

1. An indirect resistance welding system (SI, S2, S3, S4, S5) for a sealing plate (1) of a tank intended to contain liquefied gas, to an anchoring plate (22) disposed partially 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 suitable for connection to the electrodes (41, 42, 41c, 42c, 41d, 42d), - a support (5, 5b, 5c) suitable for holding the electrodes of at least one pair electrodes relative to each other, - means for positioning the support (5, 5b, 5c) against the sealing plate (1), suitable for positioning the electrodes of at least one pair of electrodes on either side of the edge (15),by positioning one electrode of said at least one pair of electrodes, referred to as the membrane electrode (41, 41c, 41d), above the sealing plate (1) and another electrode of said at least one pair of electrodes, referred to as the 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, of which 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 anchor electrode (42, 42c, 42d) onto the free portion of the anchor plate (22) with a second pressing force.

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

4. Indirect resistance welding system (SI, S2, S3, S4, S5) according to any one of claims 1 to 3, wherein the positioning means comprise at least one stop (51, 51b, 51c, 52, 52b, 52c) attached 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 (SI, S3, S4) according to any one of claims 1 to 4, wherein the support (5, 5b, 5c) comprises two rails (532, 532c, 534, 534c) suitable for 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 movably in translation on the two rails (532, 532c, 534, 534c).

6. Indirect resistance welding system (S4) according to claim 5, wherein the means of movement 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 at least one axle.

7. Indirect resistance welding system (S3) according to claim 5, wherein the means of movement comprise at least one axle arranged orthogonally to the rails (532c, 534c) and a first hub (63) mounted on at least one axle and on which the membrane electrode (41c) is arranged, the means of movement further comprising a second hub (64) mounted on 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. An indirect resistance welding system (S3) according to claim 5, comprising several pairs of electrodes and wherein the means of movement comprise at least one axle arranged orthogonally to the rails (532c, 534c) and a first hub (63) mounted on at least one axle, and wherein the membrane electrodes (41c) of the electrode pairs are distributed angularly around the first hub (63), the means of movement further comprising a second hub (64) mounted on 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. Indirect resistance welding method (100, 200) using an indirect resistance welding system (SI, S2, S3, S4, S5) according to any one of claims 1 to 8, comprising the steps of: - positioning (102, 202) the membrane electrode (41, 41c, 41d) above the sealing plate (1) and the anchor electrode (42, 42c, 42d) above the free portion of the anchor plate (22), using the positioning means, - activating (104, 204) 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) on the free portion of the anchor plate (22), and - sending current (106, 206) into the electrodes (41, 41c, 41d, 42, 42c, 42d).

10. Indirect resistance welding method (100, 200) according to claim 9 in combination with claim 2, wherein 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 anchor electrode (42, 42c, 42d) on the free portion of the anchor plate (22) with the second force, the first force being strictly greater than the second force.

11. Indirect resistance welding method (100) according to claim 9 or 10, in combination with claim 5, wherein the positioning step (102) comprises the positioning of 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 the electrodes along the rails (532, 532c, 534, 534c), interposed between a current sending step (106) and an activation step (104) of at least one actuator (9, 91, 92, 91c, 92c).

12. Indirect resistance welding method (200) according to claim 9 or 10, wherein the indirect resistance welding system (S2, S5) resistor comprising a row of electrode pairs (p1, p2, p3, p4) arranged on the support (5b), the positioning step (202) includes the positioning of each membrane electrode (41) of the electrode pairs (pl, p2, p3, p4) above the sealing plate (1) and of each anchor electrode (42) of the electrode pairs (pl, p2, p3, p4) above the free portion of the anchor plate (22), and the welding process (200) includes as many current sending steps (206) as there are electrode pairs (pl, p2, p3, p4), the current sending steps (206) being spaced apart by a predetermined minimum duration and each supplying a single electrode pair (pl, p2, p3, p4).

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