CN115533358A

CN115533358A - Welding machine

Info

Publication number: CN115533358A
Application number: CN202210757192.5A
Authority: CN
Inventors: M.比登巴赫; N.劳雷恩
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2021-06-30
Filing date: 2022-06-29
Publication date: 2022-12-30
Also published as: JP2023008934A; KR20230004316A; FR3124753B1; FR3124753A1

Abstract

The invention relates to a welding machine (1) configured to be moved along at least two parts to be welded, the welding machine (1) comprising at least one drive wheel (20) for moving the welding machine (1) relative to the parts to be welded, at least one actuator (22) capable of rotating the drive wheel (20), and at least one welding wheel (26) capable of welding the parts to be welded by rolling against the at least one part to be welded, wherein the welding wheel (26) is free to rotate relative to the drive wheel (20).

Description

Welding machine

Technical Field

The field of the invention is welders comprising electrodes in the form of welding wheels for welding together parts to be welded.

Background

Current welders include a drive wheel and a weld wheel for welding the parts to be welded together, and an actuator capable of rotating the drive wheel and the weld wheel along the parts to be welded. More specifically, the actuator is capable of rotating the welding wheel and the drive wheel at the same rotational speed such that the welding machine moves along the parts to be welded while performing the welding action.

One problem with such welders is, among other things, that when welding the parts to be welded, the welding wheels wear, and in particular lose the constituent material located at the periphery, i.e. in the vicinity of the contact area with the parts to be welded. In other words, as the welder moves forward, and thus as the parts to be welded are welded, the diameter of the welding wheel decreases. Thus, the reduction in the diameter of the welding wheel results in a significant difference in tangential velocity between the welding wheel and the drive wheel.

This difference in tangential velocity between the welding wheel and the driving wheel can lead to a slipping phenomenon, whereby the welding wheel slips along the parts to be welded. This sliding of the welding wheel along the parts to be welded creates sealing problems due to the fact that the welding is carried out in the vicinity of the sliding area. Furthermore, when using a welding machine, the slipping problem of the welding wheel requires regular replacement.

Disclosure of Invention

The object of the present invention is therefore to overcome the above mentioned problems by devising a welding machine in which the difference in tangential speed between the driving wheel and the welding wheel due to the wear of said welding wheel does not affect the welding quality of the parts to be welded and which requires a longer time for replacing said welding wheel.

The invention therefore relates to a welder configured to move along at least two parts to be welded, the welder comprising at least one drive wheel for moving the welder relative to the parts to be welded, at least one actuator capable of rotating the drive wheel and at least one welding wheel capable of welding the parts to be welded by rolling against at least one of the parts to be welded, the welder being characterized in that the welding wheel is free to rotate relative to the drive wheel.

The welder according to the invention can be used, for example, to weld two parts to be welded of a sealing film forming part of the wall of a tank for storing and/or transporting cryogenic products such as liquefied natural gas. More specifically, the welding machine allows to weld the raised edges of two adjacent parts, called first part to be welded and second part to be welded, in order to form a sealing membrane of the wall of the tank for storing and/or transporting the cryogenic product. To this end, the welding machine comprises at least a driving wheel which, with an actuator, ensures that the welding machine moves along the part to be welded in a linear welding direction, also referred to as the direction of travel of the welding machine. The actuator may be, for example, a hydraulic, pneumatic or even mechanical actuator. Preferably, the actuator within the scope of the present invention is an electric actuator.

The welding wheel allows welding by contact with one of the parts to be welded. More specifically, when welding parts to be welded, movement of the welder relative to the parts to be welded rotates a welding wheel against one of the parts to be welded, and a current through the welding wheel allows a weld to be formed on the parts to be welded. More specifically, the welding wheel is rotated by the actuator independently of the rotation of the drive wheel.

According to one feature of the invention, the welding wheel is rotated by contacting the welding wheel to one of the parts to be welded as the welder moves.

It will be appreciated that the actuator ensures that the drive wheel rotates, allowing the welding machine to move relative to the parts to be welded, said movement of the welding machine facilitating the rotation of the welding wheel when said wheel is in contact with at least one of the parts to be welded.

According to one feature of the invention, the welding machine comprises at least two driving wheels and two actuators, separate from each other, each driving wheel being driven by one of the actuators.

A front end and a rear end of the welder are defined, which are opposite to each other in a direction of travel of the welder. According to one example of the invention, one drive wheel may be located at the front end of the welder and another drive wheel may be located at the rear end of the welder. Furthermore, according to another example of the present invention, the at least two drive wheels may both be provided at a front end or a rear end of the welder.

According to one feature of the invention, one of the drive wheels is rotated by one of the actuators at a first rotational speed and the other drive wheel is rotated by the other actuator at a second rotational speed, the first and second rotational speeds being different from one another. Alternatively, the first rotational speed and the second rotational speed of the drive wheel are identical to each other.

According to one example of the present invention, one of the drive wheels (e.g., the drive wheel at the front end of the welder) is rotated by one of the actuators at a first speed that is higher than a second speed of rotation of the other drive wheel, e.g., the other drive wheel at the rear end of the welder, under the influence of the other actuator. In this example, one drive wheel at the front end of the welder and another drive wheel at the rear end of the welder are speed regulated.

Another possibility covered by the present invention consists in the fact that one driving wheel, for example the driving wheel located at the front end of the welding machine, is rotated by one of the actuators at a determined speed, while the other driving wheel, for example the driving wheel located at the rear end of the welding machine, is controlled on the basis of the torque of the other actuator. In this example, the drive wheel at the front end of the welder and the other drive wheel at the rear end of the welder are torque regulated.

Both configurations advantageously allow the raised edges of the parts to be welded, disposed between the drive wheels, to be tensioned, subsequently facilitating welding of the parts to be welded by the welding wheels. The second configuration allows sensing of the sliding of the actuator to ensure that the parts to be welded are under tension. The second configuration is also more reliable.

According to an alternative of the invention, the welding machine comprises at least two drive wheels separate from each other and comprising an actuator, the two drive wheels being rotated by the actuator common to the two drive wheels.

In this alternative of the invention, the drive wheels may be located at the front or rear end of the welder and may be rotated by the same actuator. According to another alternative of the invention, one drive wheel may be arranged at the front end of the welder and another drive wheel may be arranged at the rear end of the welder, the drive wheels being rotated by the same actuator.

According to one feature of the invention, the welding wheel is arranged on the welding machine between one drive wheel and the other drive wheel in the longitudinal direction of said welding machine.

It should be understood that the longitudinal direction of the welder corresponds to its direction of travel, i.e. to the welding direction. It should be appreciated that this feature applies when at least one of the drive wheels is disposed at the front end of the welder and the other drive wheel is disposed at the rear end of the welder.

According to a feature of the invention, at least one of the welding wheel and the driving wheel of the welding machine is arranged in the same plane. According to a preferred embodiment, the welding wheel is arranged in a common plane with all driving wheels of the welding machine.

Alternatively, the welding wheel is arranged in a plane separate from the plane in which the drive wheel of the welding machine extends. According to one example of the invention, each drive wheel may be arranged in a plane intersecting a plane in which a welding wheel of the welder extends to increase the holding force of the welder against the parts to be welded.

According to one feature of the invention, the welding machine comprises at least one pressing member for pressing said at least one welding wheel against one of the parts to be welded.

The pressing part may for example take the form of a cylinder capable of pressing the at least one welding wheel against one of the parts to be welded. This pressing part then compensates for any play between one of the parts to be welded and the welding wheel, which play is caused by wear of the welding wheel when welding the parts to be welded. According to other examples of the invention, the pressing member may take the form of a piston or even an elastic spring.

According to a feature of the invention, the welder may comprise at least one member for pressing the driving wheel. In this configuration, the purpose of the part for pressing the driving wheel is to open and close on the part to be welded, in order to ensure, on the one hand, that the welding machine is locked in place on said part to be welded, and, on the other hand, that the driving wheel is pressed against the part to be welded, thereby ensuring the movement of the welding machine.

According to one feature of the invention, the welding machine comprises a first welding wheel and a second welding wheel opposite to each other in a transverse direction of the welding machine.

More specifically, the transverse direction of the welder is perpendicular to the longitudinal direction of said welder. Thus, it can be appreciated that the first and second welding wheels are disposed on opposite sides of the part to be welded. More specifically, the first welding wheel is configured to face a first raised edge of a first part to be welded and the second welding wheel is configured to face a second raised edge of a second part to be welded. This therefore allows a more reliable weld to be formed between the first part to be welded and the second part to be welded, thereby enhancing the seal therebetween.

According to an alternative of the invention, the first welding wheel and the second welding wheel rotate while the welding machine is moving, the welding machine comprising at least one component for synchronizing the rotation of the first welding wheel with the rotation of the second welding wheel.

According to one feature of the invention, the first welding wheel and the second welding wheel rotate at the same tangential speed as the welding machine moves.

According to an alternative feature, each welding wheel has a different diameter from each other, the tangential speeds of the first and second welding wheels being different from each other.

According to one feature of the invention, the welding machine is able to weld at least two raised edges of two parts to be welded forming a sealing membrane of a portion of a tank for storing and/or transporting low-temperature products. More specifically, the tank may be a tank for storing and/or transporting liquefied natural gas. It should also be understood that the two welded parts are the aforementioned first part to be welded and second part to be welded.

Drawings

Further features, details and advantages of the invention will become more apparent from the description provided below by way of illustration with reference to the accompanying drawings in which:

figure 1 is a general perspective view of a tank for storing and/or transporting cryogenic products, comprising at least two parts to be welded forming part of a sealing membrane of the tank;

FIG. 2 is a perspective view of a welding machine according to the present invention capable of welding the raised edges of two parts to be welded;

FIG. 3 is a partial side view of the welder of FIG. 2 including at least one drive wheel and at least one weld wheel;

FIG. 4 is a schematic view of the welder of FIG. 2 according to a first embodiment;

FIG. 5 is a schematic illustration of the welder of FIG. 2 according to a second embodiment;

FIG. 6 is a schematic view of the welder of FIG. 2 according to a third embodiment.

Detailed Description

It should be noted, at the outset, that although the drawings disclose in detail embodiments of the invention, these drawings may clearly serve to better define the invention, if applicable. It should also be noted that the figures disclose only embodiments of the invention. Finally, like reference numerals refer to like elements throughout the several views of the drawings.

Fig. 2 shows a welding machine 1 configured to be moved along at least two parts to be welded 2, each part to be welded comprising at least one raised edge 4. More specifically, the parts to be welded 2 form part of a sealing membrane 6 of a wall 7 of a tank 8 for storing and/or transporting cryogenic products (for example liquefied natural gas).

The welding machine 1 then allows to weld the first raised edge 4a of the first part to be welded 2a and the second raised edge 4b of the second part to be welded 2b, respectively, which parts are adjacent. Preferably, the welding is performed by means of anchoring wings anchored to the insulation belonging to the wall 7 of the tank 8 and arranged between two adjacent raised edges. Such welding of the first part to be welded 2a and the second part to be welded 2b forms a weld bead 10 on the first projecting edge 4a and the second projecting edge 4b, the weld bead 10 extending along the welding axis S, as shown in fig. 3. The weld seam 10 formed between two parts to be welded 2 allows in particular to provide a seal between said parts to be welded 2, thus facilitating the sealing of the diaphragm 6 forming part of the wall 7 of the tank 8 for storing and/or transporting the cryogenic product.

The welding machine 1 shown in particular in fig. 2 and 3 has a substantially parallelepiped shape and extends in a main direction of elongation P parallel to the longitudinal direction L of the welding machine 1. The welding machine 1 comprises in particular a front end 12 and a rear end 14 opposite to each other in the longitudinal direction L of the welding machine 1. It should also be understood that the concept of front/back of the welder 1 refers to the direction of travel a of said welder 1, which is parallel to the welding axis S and the longitudinal direction L of said welder 1. Furthermore, the welding machine 1 comprises an upper surface 16 and a lower surface 18 opposite to each other in a vertical direction V of the welding machine 1 perpendicular to its longitudinal direction L, the lower surface 18 being the surface of the welding machine 1 facing the parts 2 to be welded.

The welding machine 1 according to the invention comprises at least one driving wheel 20 and at least one actuator 22, the driving wheel 20 being intended to move the welding machine 1 relative to the part 2 to be welded, the actuator 22 being able to rotate said at least one driving wheel 20, as shown in figures 4 to 6.

More specifically, the drive wheel 20 is arranged on the lower surface 18 of the welding machine 1 such that it is in contact with at least one of the parts 2 to be welded. The rotation of the driving wheel 20 performed by the actuator 22 therefore allows said driving wheel 20, which is arranged in contact with one of the parts 2 to be welded, to produce a movement of the welding machine 1 along the parts 2 to be welded with a rectilinear translational movement parallel to the direction of travel a of said welding machine 1. More specifically, the driving wheel 20 is in contact with one of the raised edges 4 of one of the parts 2 to be welded. According to an example of the invention, as shown in fig. 4 to 6, the welder 1 comprises four driving wheels 20.

Then a first pair of drive wheels 20a arranged at the front end 12 of the welder 1 and a second pair of drive wheels 20b arranged at the rear end 14 of the welder 1 are defined.

Then, each of the first pair 20a of driving wheels 20 is opposite to each other in a transverse direction T of the welding machine 1, which is perpendicular to its longitudinal direction L and to the vertical direction V. It will be appreciated that each of the first pair 20a of drive wheels 20 is configured to be disposed on either side of a raised edge of a part to be welded. More specifically, according to the example of the present invention shown in fig. 2 to 6, the first front drive wheel 201 of the first pair 20a of drive wheels 20 is disposed facing the first projecting edge 4a of the first part to be welded 2a, and the second front drive wheel 202 of the first pair 20a of drive wheels 20 is disposed facing the second projecting edge 4b of the second part to be welded 2 b.

The welding machine 1 comprises at least one pressing element 24 arranged between the driving wheels 20 of the first pair 20a of driving wheels 20. The pressing member 24 particularly allows the driving wheel 20 of the first pair 20a of driving wheels 20 to be pressed against the member to be welded, more particularly against the projecting edge. More specifically, the purpose of the pressing member 24 is to move the first front drive wheel 201 and the second front drive wheel 202 away from and toward the first projecting edge of the first part to be welded and the second projecting edge of the second part to be welded, respectively. This therefore allows the welding machine 1 to be placed on the raised edge and also ensures that the drive wheel 20 is pressed against the raised edge in order to lock the welding machine 1 in position relative to the parts to be welded. It will be appreciated that the pressing of the first pair 20a of drive wheels 20 against the raised edges of the parts to be welded helps to ensure movement of the welder 1 during rotation of said drive wheels 20 of the first pair 20a of drive wheels 20.

Furthermore, the pressing member 24 ensures that the welding machine 1 is held against the parts to be welded when said welding machine 1 is stationary, i.e. when the driving wheel 20 is not rotated by said at least one actuator 22. According to an example of the invention, the pressing member 24 may take the form of a piston or a cylinder or a spring. It will be appreciated that, in order to remove the welding machine 1 from the parts to be welded, the driving wheel 20 is removed from the parts to be welded, in particular by stopping the operation of pressing the parts 24.

According to one feature of the invention, the first front drive wheel 201 and the second front drive wheel 202 of the first pair 20a of drive wheels 20 are arranged in a common plane L, T, hereinafter referred to as plane R.

According to an alternative of the invention, not shown, each of the first front drive wheel and the second front drive wheel of the first pair of drive wheels extends in a plane intersecting the main longitudinal and transversal plane in which the welder extends. In this way, the holding force of the welder with respect to the parts to be welded is increased.

It will be appreciated that each feature of the first front drive wheel 201 and the second front drive wheel 202 of the first pair 20a of drive wheels 20 applies mutatis mutandis to the second pair 20b of drive wheels 20, in particular the first rear drive wheel 203 and the second rear drive wheel 204 of the second pair 20b of drive wheels 20, located at the rear end 14 of the welder 1.

Therefore, according to an example of the present invention, the first pressing member 24a is provided between the first front driving wheel 201 and the second front driving wheel 202 in the first pair 20a of driving wheels 20, and the second pressing member 24b is provided between the first rear driving wheel 203 and the second rear driving wheel 204 in the second pair 20b of driving wheels 20.

Furthermore, advantageously, the driving wheel 20 of the second pair 20b of driving wheels 20 extends in the plane R together with the first pair 20a of driving wheels 20. According to an alternative of the invention, not shown, the driving wheels of the second pair of driving wheels extend in a plane different from the plane in which the first pair of driving wheels extend.

As previously mentioned, the welder 1 comprises at least one actuator 22 ensuring the rotation of the driving wheel 20, which may take the form of a hydraulic, pneumatic or even a mechanical actuator 22. Preferably, the actuator 22 according to the invention is an electric motor. It will then be appreciated that the actuator 22 facilitates moving the welding machine 1 along the part 2 to be welded in the direction of travel a of said welding machine 1.

According to a first example of the invention, as shown in fig. 4, a first actuator 22a rotates a first pair 20a of drive wheels 20 and a second actuator 22b rotates a second pair 20b of drive wheels 20. More specifically, the drive wheel 20 of the first pair 20a of drive wheels 20 is rotated by a first actuator 22a at a first rotational speed and the drive wheel 20 of the second pair 20b of drive wheels 20 is rotated by a second actuator 22b at a second rotational speed.

According to one embodiment, a first rotational speed of the drive wheel 20 of the first pair 20a of drive wheels 20 and a second rotational speed of the drive wheel 20 of the second pair 20b of drive wheels 20 are different from each other. More specifically, a first rotational speed of the first pair 20a of drive wheels 20 is higher than a second rotational speed of the second pair 20b of drive wheels 20. The advantage of this feature is that it allows the raised edges of the parts to be welded disposed between the drive wheels 20 of the first 20a and second 20b pairs of drive wheels 20 to be tensioned, thereby facilitating welding by the at least one welding wheel 26 of the welder 1.

Alternatively, the first rotational speed of the first pair 20a of drive wheels 20 is the same as the second rotational speed of the second pair 20b of drive wheels 20.

According to a second embodiment of the invention, as shown in fig. 5, the welder 1 may comprise four actuators 22 separated from each other, each actuator 22 being able to rotate one of the four driving wheels 20 of the welder 1. Thus, it will be appreciated that the first front drive wheel 201 of the first pair 20a of drive wheels 20 may rotate at a rotational speed equal to or different from the rotational speed of the second front drive wheel 202 of the first pair 20a of drive wheels 20. Similarly, the first rear drive wheel 203 of the second pair 20b of drive wheels may rotate at a rotational speed equal to or different than the rotational speed of the second rear drive wheel 204 of the second pair 20b of drive wheels.

An advantage of this configuration of the welding machine 1 is that it allows a more precise adaptation of the rotational speed of each driving wheel 20 of the welding machine 1 independently of the other driving wheels 20. This allows for more efficient tensioning of the raised edges of the two parts to be welded to facilitate their welding by the welding wheel 26, thereby allowing for a more reliable weld to be obtained between the two parts. Furthermore, this configuration of the welder 1 allows the actuator 22 to be free of bearings, thus reducing weight and reducing the footprint of the welder 1.

The at least one welding wheel 26 of the welding machine is able to weld the first raised edge 4a of the first part to be welded 2a and the second raised edge 4b of the second part to be welded 2b, respectively, forming the weld seam 10, as previously described in fig. 2 and 3. To perform the welding action, the welding wheel 26 is intended to be traversed by an electric current when the welder 1 is operating. According to a feature of the invention, the welding wheel 26 is free to rotate with respect to said at least one driving wheel 20 of the welding machine 1. More specifically, according to an example of the invention, the welding wheel 16 is free to rotate relative to each drive wheel 20 of the first 20a and second 20b pairs of drive wheels 20.

Then, when the welding machine 1 is moved by direct contact of said welding wheel 26 against one of the parts to be welded, more specifically against one of the raised edges of one of the parts to be welded, the welding wheel 26 is rotated. It will thus be appreciated that the actuator 22 of the drive wheel 20 of the welder 1 has no direct effect on the rotation of the welding wheel 26. In other words, the rotation of the welding wheel 26 depends on the one hand on its contact with one of the parts to be welded and on the other hand on the movement of the welder 1 along the parts to be welded, which movement is generated by the drive wheel 20 and the actuator 22 of the welder.

When using the welding machine 1, the rotation of the welding wheel 26 against one of the parts to be welded produces a loss of material on the periphery of said welding wheel 26, i.e. in the contact area 28 of the welding wheel 26 with one of the parts 2 to be welded, the loss of material at the contact area 28 being a function of the material of the welding wheel 26 and the temperature of the contact area 28 when the welding machine 1 is operated. It will be appreciated that the contact region 28 thus forms an effective surface of the welding wheel 26. Furthermore, as shown in FIG. 3, material loss at the periphery of the welding wheel 26 tends to gradually decrease the diameter D of the welding wheel 26. In order to compensate for the loss of material of the welding wheel 26 when using the welding machine 1, said welding machine comprises a third pressing element 24c for the welding wheel 26. The third pressing member 24c ensures contact between the welding wheel 26 and one of the raised edges of one of the parts to be welded, regardless of the diameter of said welding wheel 26. It can therefore be understood that the third pressing member 24c allows the gap between the welding wheel 26 and one of the parts to be welded, which is caused by the peripheral wear of the welding wheel 26 when the welder 1 is operating, to be adjusted according to the wear, allowing the weld to be produced by the effective resistance of the parts to be welded.

As shown in the example of the present invention, the welding wheel 26 is disposed longitudinally on the welder 1 between one drive wheel 20 of the first pair 20a of drive wheels 20 and one drive wheel 20 of the second pair 20b of drive wheels 20 disposed facing each other in the longitudinal direction L of the welder 1. Furthermore, the welding wheel is arranged in the plane R together with the driving wheel 20 of the first pair 20a of driving wheels 20 and the driving wheel 20 of the second pair 20b of driving wheels 20, the welding wheel being arranged between these two driving wheels.

Alternatively, according to a not shown example of the invention, the welding wheels are arranged on the welding machine in a longitudinal and transverse plane which is different from at least one of the planes along which at least one of the driving wheels of the welding machine extends.

According to the illustrated example of the invention, the welding machine 1 comprises a first welding wheel 26a and a second welding wheel 26b, in accordance with the characteristics of the at least one welding wheel 26 described above. The first welding wheel 26a and the second welding wheel 26b are opposite to each other in the transverse direction T of the welding machine 1. In other words, the first welding wheel 26a and the second welding wheel 26b are opposite to each other so that they grip the parts to be welded, in particular the two raised edges of the two parts to be welded. More specifically, the first welding wheel 26a is disposed to face a first projecting edge of a first part to be welded, and the second welding wheel 26b is disposed to face a second projecting edge of a second part to be welded.

It will be understood that the third pressing member 24c of the welding machine 1 is arranged between the first welding wheel 26a and the second welding wheel 26b to ensure that said welding wheels 26a, 26b are pressed against the raised edges of the parts to be welded. Thus, a sealing weld is provided between two parts to be welded, in particular between their raised edges, despite the loss of material of the welding wheels 26a, 26b during their use.

According to one feature of the invention, which is not shown, the welding machine comprises a cooling system for cooling at least one of the welding wheels. More specifically, each of the first and second welding wheels is cooled by a cooling system of the welder, which cooling system comprises active cooling by circulating a fluid within the welding wheels. This allows limiting any heating of the welding wheel when welding the parts to be welded. Furthermore, the drive wheels of the second pair of drive wheels, which are located downstream of the welding wheel in the direction of travel of the welding machine, i.e. in contact with the weld seam formed by said welding wheel, may be cooled by a cooling system in a similar manner as the welding wheel.

According to the example of the invention shown in fig. 6, the welding machine 1 comprises at least one synchronization member 30 for synchronizing the rotation of the first welding wheel 26a with the rotation of the second welding wheel 26b. In other words, the welder 1 includes a synchronizing member 30 that allows the first welding wheel 26a and the second welding wheel 26b to rotate synchronously at the same rotational speed as the welder 1 moves. In other words, the synchronization member rotationally links the first 26a and second 26b welding wheels, the initial rotation being transmitted by the movement of the machine and the contact of at least one of the two welding wheels 26a, 26b.

The invention as described above, however, should not be limited to the specifically described and illustrated devices and configurations, but is equally applicable to any equivalent devices or configurations and any combination of such devices or configurations.

Claims

1. A welding machine (1) configured to move along at least two parts to be welded (2, 2a, 2b), said welding machine (1) comprising at least one driving wheel (20) for moving the welding machine (1) with respect to the parts to be welded (2, 2a, 2b), at least one actuator (22) capable of rotating the driving wheel (20) and at least one welding wheel (26) capable of welding the component to be welded (2, 2a, 2b) by rolling against at least one of the parts to be welded (2, 2a, 2b), said welding machine (1) being characterized in that the welding wheel (26) is free to rotate with respect to the driving wheel (20), said welding machine (1) comprising at least two driving wheels (20) and two actuators (22) separated from each other, each driving wheel (20) being driven by one of the actuators (22).

2. Welding machine (1) according to claim 1, wherein the welding wheel (26) is rotated when the welding machine (1) is moved by bringing the welding wheel (26) into contact against one of the parts (2, 2a, 2b) to be welded.

3. Welding machine (1) according to claim 2, wherein one of said drive wheels (20) is rotated by one of said actuators (22) at a first rotational speed, while the other drive wheel (20) is rotated by the other actuator (22) at a second rotational speed, said first and second rotational speeds being different from each other.

4. Welding machine (1) according to any of the claims 1-2, wherein one of the driving wheels (20) is rotated by one of the actuators (22) at a determined speed, while the other driving wheel (20) is controlled based on the torque of the other actuator.

5. Welding machine (1) according to any one of claims 1 to 4, wherein the welding wheels (26) are arranged on the welding machine (1) between one of the driving wheels (20) and the other driving wheel (20) in the longitudinal direction (L) of the welding machine (1).

6. Welding machine (1) according to any one of the preceding claims, comprising at least one pressing member (24 c) for pressing at least one welding wheel (26) against one of the parts to be welded (2, 2a, 2b).

7. Welding machine (1) according to any of the previous claims, comprising a first welding wheel (26 a) and a second welding wheel (26 b) opposite each other in a transverse direction (T) of the welding machine (1).

8. Welder (1) according to claim 7, wherein the first welding wheel (26 a) and the second welding wheel (26 b) rotate when the welder (1) is moving, the welder (1) comprising at least one synchronizing means (30) for synchronizing the rotation of the first welding wheel (26 a) with the rotation of the second welding wheel (26 b).

9. The welding machine (1) according to any of the claims 7 or 8, wherein the first welding wheel (26 a) and the second welding wheel (26 b) rotate at the same rotational speed when the welding machine (1) is moving.

10. Welding machine (1) according to any one of the previous claims, capable of welding at least two raised edges (4) of two parts to be welded (2, 2a, 2b) of a sealing membrane (6) forming part of a tank (8) for storing and/or transporting cryogenic products.