Spot welding gun and related spot welding method

Abstract

The spot welding gun (12) comprises a frame (18) and a movable group (20) movable within the frame (18) along a welding direction (W-W ') and comprising:-an outer unit (28) comprising a proximal electrode (34) and an outer actuation flange (38); an inner unit (30) comprising a distal electrode (44) and an inner actuation flange (48); a clamping actuator (32) connected to the inner actuating flange (48) and the outer actuating flange (38); the gun (12) comprises a clamping actuator (30) configured for displacing said flanges (38, 48) to displace the proximal electrode (34) relative to the distal electrode (44) in the welding direction (W-W '), the gun (12) comprising a compensation actuator (21) arranged between the frame (18) and the movable group (20), the compensation actuator (21) being configured to apply a biasing force to compensate for the weight of the movable group (20) according to the orientation of the welding direction (W-W').

Description

Technical Field

[0001] The present invention relates to a spot welding gun. The present invention also relates to a spot welding method implemented by such a spot welding gun. Background Art

[0002] In the field of nuclear power plant construction, and for example for a pressurized water reactor nuclear power plant, it is crucial to ensure the correct welding of the components to be welded. These components are, for example, the structural components of the fuel element cage. Therefore, ensuring the controlled and reliable welding of such components is crucial for ensuring the durability and safety of these cages and more generally of the entire reactor including such cages.

[0003] To weld such components, it is known to use a spot welding gun mounted on a robotic arm. The spot welding gun relies on resistance welding to weld the components together. Such a gun generally includes opposing electrodes that are intended to generate a current that conducts in the components to be welded. In particular, the components to be welded are arranged between the opposing electrodes such that they are resistively heated by the current generated between the electrodes, thereby causing local welding of the components.

[0004] The electrodes of these components are generally mounted on units that can move relative to each other. The movement of such units is intended, for example, to press the electrodes around the components to be welded to ensure the correct welding of the components. However, if the units are directly controlled from the robotic arm or the frame of the gun, the accuracy of the robotic arm is insufficient to allow for the correct centering of the components to be welded between the electrodes, or in other words, between the units that move relative to each other.

[0005] To address this shortcoming, a spot welding gun has been proposed that includes a frame and a movable group that can move within the frame, the movable group itself including units that can move relative to each other, the units including electrodes.

[0006] Such a spot welding gun is particularly advantageous because the entire movable group can move within the frame relative to the components to be welded. This ensures the "automatic centering" of the group relative to the components to be welded. In particular, since the entire movable group can move within the frame, the interaction of the electrodes on one side of the components to be welded can cause the displacement of the entire movable group until the opposing electrodes are pressed around the components to be welded.

[0007] However, such a spot welding gun is not entirely satisfactory. In particular, and since the entire movable group can move relative to the frame, the weight of the movable group is not supported by the robotic arm unless the movable group abuts against the part of the frame within which the movable group can move. Therefore, the weight of the movable group is generally supported by the components to be welded through the electrodes. This results in strain in the components to be welded and also in an imbalance in the welding forces between the opposing electrodes. This results in poor welding quality.

[0008] Therefore, the object of the present invention is to provide a spot welding gun for improving welding quality. Summary of the Invention

[0009] To this end, the subject of the present invention relates to a spot welding gun for a welding robot arm, the spot welding gun comprising a frame and a movable group capable of moving along the welding direction within the frame, the movable group comprising:

[0010] - An external unit, which includes:

[0011] + A proximal electrode,

[0012] + A guiding element that extends along an elongation axis parallel to the welding direction, the proximal electrode being attached to the guiding element, and

[0013] + An external actuating flange attached to the guiding element,

[0014] - An internal unit, which includes:

[0015] + A distal electrode,

[0016] + A guided element that extends along the elongation axis and is capable of translational movement along the welding direction within the guiding element, the distal electrode being attached to the guided element,

[0017] + An internal actuating flange attached to the guided element,

[0018] - A clamping actuator that defines a clamping actuation axis parallel to the welding direction, the clamping actuator being connected to the internal actuating flange and the external actuating flange and being configured to displace the flanges to displace the proximal electrode relative to the distal electrode along the welding direction,

[0019] The spot welding gun further includes a compensation actuator disposed between the frame and the movable group, the compensation actuator being configured to apply a biasing force according to the orientation of the welding direction to compensate for the weight of the movable group.

[0020] The use of the movable group and the compensation actuator configured to apply a biasing force to compensate for the weight of the movable group is particularly advantageous because it allows the electrodes to be placed at the center of the component to be welded while preventing any unbalanced forces on the electrodes or induced strains in the component to be welded. This results in high-quality welding.

[0021] According to a specific embodiment of the present invention, the spot welding gun further includes one or more of the following features considered independently or in any technically possible combination:

[0022] - The compensation actuator is connected to the frame and one of the external unit and the internal unit;

[0023] - The frame includes a transverse flange located between an outer actuation flange and an inner actuation flange, and the movable group defines:

[0024] - A stationary configuration in which the transverse flange is pressed between the inner actuation flange and the outer actuation flange, and in which the movable group is fixed within the frame,

[0025] - A movable configuration in which at least one of the inner actuation flange and the outer actuation flange is spaced apart from the transverse flange, and in which the movable group is capable of moving along the welding direction,

[0026] By actuating a clamping actuator to displace the inner actuation flange relative to the outer actuation flange, the movable group can be reconfigured between the stationary configuration and the movable configuration;

[0027] - The compensation actuator is actuated to apply a biasing force to compensate for the weight of the movable group only when the movable group is in the movable configuration;

[0028] - The frame includes two guiding tracks parallel to the welding direction, and the guiding tracks are configured to guide the movable group along the welding direction within the frame;

[0029] - One of the internal unit and the external unit includes at least one plastic spacer, and the spacer is configured to guide a guided element within a guiding element;

[0030] - The clamping actuator includes a flat cylinder;

[0031] - The distance between the clamping actuation axis and the elongation axis is less than 50 mm;

[0032] - The movable group further includes a force sensor that defines a sensor axis and is configured to measure the welding force applied between the electrodes. The force sensor is connected to the clamping actuator, and the sensor axis is aligned with the clamping actuation axis;

[0033] - The spot welding gun includes a welding control module that is connected to the force sensor and the electrodes, and is configured to activate the electrodes for welding only when the force measurement value of the force sensor reaches a predetermined threshold; and

[0034] - Wherein the spot welding gun includes a compensation control module that is configured to detect the gravitational field to determine the orientation of the welding direction and control the compensation actuator according to the determined orientation.

[0035] According to some embodiments, the present invention also relates to a spot welding method implemented by the spot welding gun as described above, wherein the method includes the following steps:

[0036] - Providing a spot welding gun and at least one component to be welded;

[0037] - Shift the spot welding gun so that the electrode face of the spot welding gun faces at least one component to be welded;

[0038] - Actuate the clamping actuator to shift the electrodes relative to each other along the welding direction; and

[0039] - Depending on the orientation of the welding direction, actuate the compensation actuator to apply a biasing force to compensate for the weight of the movable group of the spot welding gun.

[0040] In some embodiments, the present invention also relates to a spot welding gun of a welding robot arm, which includes a frame and a movable group that can move within the frame along the welding direction. The movable group includes:

[0041] - An external unit, which includes:

[0042] + A proximal electrode,

[0043] + A guiding element that extends along an elongation axis parallel to the welding direction, and the proximal electrode is attached to the guiding element, and

[0044] + An external actuation flange that is attached to the guiding element,

[0045] - An internal unit, which includes:

[0046] + A distal electrode,

[0047] + A guided element that extends along the elongation axis and can translate along the welding direction within the guiding element, and the distal electrode is attached to the guided element,

[0048] + An internal actuation flange that is attached to the guided element,

[0049] - A clamping actuator that defines a clamping actuation axis parallel to the welding direction. The clamping actuator is connected to the internal actuation flange and the external actuation flange, and is configured to shift the flanges to shift the proximal electrode relative to the distal electrode along the welding direction,

[0050] The spot welding gun includes a clamping actuator stopper that is configured to limit the actuation of the clamping actuator so that the distance between the internal actuation flange and the external actuation flange is limited to a predetermined value. The spot welding gun also includes an abort module that is configured to command welding abort when the distance between the internal actuation flange and the external actuation flange exceeds the predetermined value.

[0051] According to a specific embodiment of the present invention, the predetermined value is lower than the distance between the internal actuation flange and the external actuation flange, and this distance corresponds to the configuration of the movable group where the electrodes are in contact.

[0052] According to some embodiments, the present invention also relates to a spot welding method implemented by the spot welding gun as described above, wherein the method comprises the following steps:

[0053] - Providing a spot welding gun and at least one component to be welded;

[0054] - Shifting the spot welding gun such that the electrode face of the spot welding gun faces at least one component to be welded;

[0055] - Actuating a clamping actuator to shift the electrodes relative to each other along the welding direction; and

[0056] - Limiting the actuation of the clamping actuator by a clamping actuation stopper and then aborting the welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Other features and advantages of the present invention will become apparent from the following detailed description given by way of indication and not limitation with reference to the accompanying drawings, in which:

[0058] - Figure 1 is a schematic top view of a robotic arm including a spot welding device according to the present invention, wherein the movable group of the welding device is in an active configuration;

[0059] - Figure 2 is Figure 1 a schematic side view of the spot welding device; and

[0060] - Figure 3 is a view of the spot welding device as Figure 1 wherein the movable group of the welding device is in a stationary configuration. DETAILED DESCRIPTION

[0061] In the following description, the terms "distal" and "proximal" are understood with respect to the position on the spot welding gun relative to the position of the spot welding gun held, for example, by a robotic arm. A distal element is, for example, further away from the element holding the spot welding gun than a proximal element.

[0062] Referring to Figure 1 , the robotic arm 10 includes a spot welding gun 12.

[0063] The robotic arm 10 is, for example, a 6-axis robotic arm, and the spot welding gun 12 is arranged at the end 14 of the robotic arm 10. It can be understood that the spot welding gun 12 is, for example, mounted on the tool port of the robotic arm 10 on the robotic arm 10 such that the robotic arm 10 includes the spot welding gun 12 (not shown).

[0064] The spot welding gun 12 is preferably configured to weld components 16 of a nuclear power plant (e.g., a pressurized water reactor of a nuclear power plant).

[0065] The component 16, also referred to hereinafter as the "component to be welded", is, for example, a component of a fuel element holder of a pressurized water reactor.

[0066] As will be presented in more detail later, the spot welding gun 12 is configured to weld the components 16 by spot welding (i.e., by local resistance welding of the components 16). The spot welding gun 12 relies on the Joule heating of the components 16 to be welded to weld these components together.

[0067] As Figures 1 to 3 shown, the spot welding gun 12 includes a frame 18 and a movable group 20. As will be disclosed in more detail hereinafter, the movable group 20 can move within the frame 18 along the welding direction W-W'.

[0068] As will be presented later, the spot welding gun 12 further includes a compensation actuator 21 connecting the frame 18 and the movable group 20.

[0069] Referring Figures 1 to 3 , the frame 18 includes, for example, a body 22, a lateral flange 24 and includes, for example, two guide rails 26.

[0070] The frame 18 is, for example, substantially flat and defines a frame plane P-P. In other words, as viewed from Figure 1 it can be seen that the width W of the frame 18 is, for example, substantially greater than the thickness T of the frame 18, which thickness is visible from the Figure 2 covering area of the frame 18 shown by the dashed line above.

[0071] As viewed from Figure 1 it can be seen that the body 22 is, for example, at least partially arranged around the movable group 20. In particular, the body, for example, defines an internal volume 27 in which the movable group 27 can move.

[0072] As Figures 1 to 3 shown, the body 22, for example, extends along the welding direction W-W'.

[0073] The lateral flange 24 extends laterally within the body 22. The lateral flange 24, for example, extends in the body 22 perpendicular to the welding direction W-W'. As Figure 1 and Figure 3 shown, the lateral flange 24 connects, for example, opposite walls of the body 22.

[0074] As Figure 1 shown, the guide rails 26 are parallel to the welding direction W-W'. The guide rails 26, for example, are connected to opposite walls of the body 22.

[0075] As Figures 1 to 3 shown, the guide rails, for example, extend through the lateral flange 24.

[0076] Each guide rail 26 includes, for example, a rod having a diameter between 5 mm and 20 mm and, for example, being 10 mm.

[0077] The distance D1 between the guide rails includes, for example, values between 20 mm and 100 mm, for example between 40 mm and 80 mm, and is, for example, 58 mm.

[0078] The guide rails 26 together define, for example, a rail plane R-R that is substantially parallel to the frame plane P-P.

[0079] As will be presented in more detail later, the guide rails 26 are configured to guide the movable group 20 along the welding direction W-W'.

[0080] As Figures 1 to 3 shown, the movable group 20 includes an outer unit 28, an inner unit 30, and a clamping actuator 32. The movable group 20 also includes, for example, a force sensor 33.

[0081] As Figures 1 to 3 shown, the outer unit 28 includes a proximal electrode 34, a guide element 36, and an outer actuating flange 38.

[0082] The guide element 36 extends along an elongation axis E-E' that is parallel to the welding direction W-W'.

[0083] The guide element 36 is, for example, translatable relative to the frame 18 along the welding direction W-W'. The guide element 36 is, for example, movable through an orifice (not labeled) in the body 22.

[0084] The guide element 36 is, for example, tubular and has, for example, a circular cross-section.

[0085] The ratio of the length of the guide element 36 measured along the elongation axis E-E' to the width of the guide element 36 measured transversely to the elongation axis is, for example, greater than 5.

[0086] As Figures 1 to 3 shown, the proximal electrode 34 is attached to the guide element 36, for example, at the distal end (not labeled) of the guide element 36. For example, the outer unit 28 includes an electrode port 42 that connects the proximal electrode 34 to the guide element 36, and the electrode port 42 extends radially relative to the elongation axis E-E'.

[0087] In a specific embodiment, the term proximal electrode 34 should be understood as a set of proximal electrodes 34, for example, two proximal electrodes 34.

[0088] As Figures 1 to 3 shown, the outer actuating flange 38 is attached to the guide element 36, for example, opposite the proximal electrode 34. As Figures 1 to 3 shown, the outer actuating flange 38 is attached to the guide element 36, for example, at the proximal end (not labeled) of the guide element 36.

[0089] In an embodiment not shown, the outer actuation flange 38 and the guiding element 36 are integral, for example.

[0090] The outer actuation flange 38 preferably extends radially with respect to the elongation axis E-E'.

[0091] As can be seen from Figure 1 and Figure 2 the outer actuation flange 38 extends transversely within the frame 18, for example.

[0092] The outer actuation flange 38 includes, for example, two guiding orifices 51 which are configured to cooperate with the guiding tracks 26 and to guide the displacement of the external unit 28 within the frame 18 along the welding direction W-W'.

[0093] As Figures 1 to 3 shown, the internal unit 30 includes a distal electrode 44, a guided element 46 and an inner actuation flange 48.

[0094] The guided element 46 extends along the elongation axis E-E'. The guided element 46 is, for example, concentric with the guiding element 36.

[0095] The guided element 46 is, for example, tubular and has, for example, a circular cross-section.

[0096] The ratio of the length of the guided element 46 measured along the elongation axis E-E' to the width of the guided element 46 measured transversely to the elongation axis is, for example, greater than 5.

[0097] As can be seen from Figures 1 to 3 the guided element 46 is, for example, longer than the guiding element 36.

[0098] The guided element 46 can move translationally within the guiding element 36 along the welding direction W-W'.

[0099] As can be seen from the dashed line in Figures 1 to 3 the guided element 46 can, for example, move along the welding direction W-W' through the transverse flange 24 and the outer actuation flange 38, for example through orifices (not shown) of the transverse flange 24 and the outer actuation flange 38. The guided element 46 can also move through the body 22, for example.

[0100] As Figures 1 to 3 shown, the distal electrode 44 is attached to the guided element 46, for example, at the distal end (not marked) of the guided element 46. For example, the internal unit 30 includes an electrode port 50 which connects the distal electrode 44 to the guided element 46 and which extends radially with respect to the elongation axis E-E'.

[0101] In a specific embodiment, the term distal electrode 44 should be understood as a set of distal electrodes 44, for example two distal electrodes 44.

[0102] As Figures 1 to 3 shown, the inner actuation flange 48 is attached to the guided element 46, for example opposite the distal electrode 44. As Figures 1 to 3 shown, the inner actuation flange 48 is attached to the guided element 46, for example at the proximal end portion (not labeled) of the guided element 46.

[0103] In an embodiment not shown, the inner actuation flange 48 and the guided element 46 are integral, for example.

[0104] The inner actuation flange 48 preferably extends radially with respect to the elongation axis E-E'.

[0105] As can be seen from Figure 1 and Figure 2 the inner actuation flange 48 extends transversely within the frame 18, for example.

[0106] The inner actuation flange 48 includes, for example, two guide apertures 43 which are configured to cooperate with the guide tracks 26 and to guide the displacement of the inner unit 30 within the frame 18 along the welding direction W-W'.

[0107] As Figures 1 to 3 shown, the flanges 38, 48 can move, for example, on opposite sides of the transverse flange 24. In other words, the transverse flange 24 is arranged between the outer actuation flange 38 and the inner actuation flange 48.

[0108] As can be seen from Figures 1 to 3 one of the inner unit 28 and the outer unit 30 includes at least one plastic spacer 52 which is configured to guide the guided element 46 within the guide element 36.

[0109] The plastic spacer 52 is, for example, a known spacer under the trade name IGLUDUR W300.

[0110] The spacer 52 is attached, for example, to the inner face 54 of the guide element 36 and is configured to guide the guided element 46 within the guide element 36. In an alternative, the spacer 52 is attached to the outer face 56 of the guided element 46 and is configured to be guided by the guide element 36.

[0111] The clamping actuator 32 defines a clamping actuation axis C-C' parallel to the welding axis W-W'. For example, the clamping actuator 32 includes a cylinder 58 and an actuating element 60 which can move relative to the cylinder 58 along the clamping actuation axis C-C'. The actuating element 60 extends, for example, along the clamping actuation axis C-C'.

[0112] The clamping actuator 32 is, for example, a pneumatic or hydraulic actuator.

[0113] The clamping actuator 32 is, for example, an actuator known as a "flat cylinder", i.e., an actuator including a cylinder 58 that is flat. The cylinder 58 is, for example, a prismatic cylinder, such as a parallelepiped cylinder.

[0114] The actuator 32 is flat, for example, along a plane parallel to the frame plane P-P.

[0115] The distance D2 between the actuation axis and the elongation axis is, for example, less than 50 mm and, for example, equal to 33 mm.

[0116] The clamping actuator 32 is connected, for example, to the internal unit 28 and the external unit 30. In particular, the clamping actuator 32 is connected to the inner actuation flange 48 and the outer actuation flange 38.

[0117] For example, and as will be disclosed in more detail later, the clamping actuator 32 is connected, for example, to one of the inner actuation flange 48 and the outer actuation flange 38 via a force sensor 33.

[0118] In Figures 1 to 3 the example shown, the cylinder 58 is fastened to the outer actuation flange 38, and the actuation element 60 is fastened to the inner actuation flange 48 via a force sensor 33.

[0119] The clamping actuator 32 is configured to displace the internal unit 28 relative to the external unit 30. The clamping actuator 32 is particularly configured to displace the flanges 38, 48 to which it is connected, so as to displace the proximal electrode 34 relative to the distal electrode 44 along the welding direction W-W'.

[0120] Thus, the clamping actuator 32 is configured to displace the electrodes 34, 44 relative to the parts 16 to be welded, in particular to weld these parts 16.

[0121] The movable group 20 particularly defines Figure 3 the stationary configuration shown and Figure 1 the movable configuration shown.

[0122] By actuating the clamping actuator 32 to displace the internal unit 30 relative to the external unit 28 and, in particular, to displace the inner flange 48 relative to the outer flange 38, the movable group 20 can be particularly reconfigured between the stationary configuration and the movable configuration.

[0123] In the stationary configuration, and as Figure 3 shown, the lateral flange 24 is pressed between the inner actuation flange 48 and the outer actuation flange 38. In other words, the distance D3 between the inner flange 48 and the outer flange 38 along the welding direction W-W' is substantially equal to the width of the lateral flange 24 along the welding direction W-W'.

[0124] In the stationary configuration, the movable group 20 is fixed within the frame, and the inner actuation flange 38 and the outer actuation flange 38 cooperate on both sides of the transverse flange 24 to hold the movable group 20 in a fixed position on the track 26.

[0125] In the active configuration, and as Figure 1 and Figure 2 shown, at least one of the inner actuation flange 48 and the outer actuation flange 38 is spaced apart from the transverse flange 24. In other words, the distance D3 along the welding direction W-W' between the inner flange 48 and the outer flange 38 is greater than the width of the transverse flange 24 along the welding direction W-W'.

[0126] In the active configuration, the movable group 20 can move along the welding direction W-W'. In particular, the movable group 20 can move along the track 26 between a position where one of the inner flange 48 and the outer flange 38 abuts against the transverse flange 24 and another position where the other of the inner actuation flange 48 and the outer actuation flange 38 abuts against the transverse flange 24.

[0127] The force sensor 33 is configured to measure the force applied between the distal electrode 44 and the proximal electrode 34. To this end, the force sensor 33 is connected, for example, to the external unit 28 and the internal unit 30. In particular, and as Figures 1 to 3 shown, the force sensor 33 is connected to the external unit 28 and the internal unit 30, for example, by the clamping actuator 32.

[0128] The force sensor 33 is arranged, for example, between the clamping actuator 32 attached to one of the internal unit 30 and the external unit 28 and the other of the internal unit 30 and the external unit 28. Thus, the force sensor 33 is configured to measure the acting force applied by the clamping actuator 32 on the internal unit 30 and the external unit 28, and is thus configured to measure the force applied between the electrodes 34, 44. As can be seen above, each electrode is connected to the corresponding actuation flange 38, 48.

[0129] As Figures 1 to 3 shown, the force sensor defines a sensor axis S-S', and the force sensor is configured to measure the force along this sensor axis. The sensor axis S-S' and the clamping actuation axis C-C' are, for example, aligned. The force sensor 33 is, for example, configured to measure only the acting force applied by the clamping actuator 32 along the clamping axis C-C'.

[0130] As Figures 1 to 3 shown, the compensation actuator 21 is arranged between the frame 18 and the movable group 16 to connect the frame 18 and the movable group 20.

[0131] The compensation actuator 21 is connected, for example, to the frame 18 and one of the external unit 28 and the internal unit 30. In Figures 1 to 3In the example, the compensation actuator 21 connects the frame 18 and the external unit 28, and more specifically, connects the frame 18 and the external actuating flange 38.

[0132] The compensation actuator 21 includes, for example, a cylinder 62 and an actuating element 64. In Figures 1 to 3 the example, the cylinder 62 is connected to the lateral flange 24, and the actuating element 64 is connected to the frame 18.

[0133] The compensation actuator 21 is, for example, a pneumatic or hydraulic actuator.

[0134] The compensation actuator 21 is configured to apply a biasing force according to the orientation of the welding direction W-W' to compensate for the weight of the movable group 20. In accordance with the orientation of the welding direction W-W', it can be understood that the biasing force depends on the orientation of the welding direction W-W' relative to the environment in which the spot welding gun 12 operates, in particular relative to the gravitational field in the environment in which the spot welding gun 12 operates.

[0135] In a specific embodiment, and as will be presented in more detail later, the compensation actuator 21 is actuated to apply a biasing force to compensate for the weight of the movable group 20 only when the movable group 20 is in the active configuration. In particular, and since the movable group 20 is fixed within the frame 18 when the movable group 20 is in its stationary configuration, no biasing force is required to compensate for the weight of the movable group 20.

[0136] As can be seen from Figure 1 and Figure 3 the spot welding gun includes, for example, a compensation control module 66 and / or a welding control module 68.

[0137] The compensation control module 66 is configured to detect the gravitational field to detect the orientation of the welding direction W-W'. For this purpose, the compensation control module 66 includes a gravity sensor (not shown), or is connected to a gravity sensor (not shown).

[0138] The compensation control module 66 is further configured to control the compensation actuator 21 according to the determined orientation. For example, the control module 66 is provided with the mass information of the movable group 20 and is configured to control the compensation actuator 21 according to the determined orientation and the mass of the provided actuator.

[0139] As an example, based on Figures 1 to 3The spot welding gun 12 shown, if the spot welding gun 12 is horizontal, that is, if the welding direction is horizontal, or in other words perpendicular to the ambient gravitational field, the compensation control module 66 controls the compensation actuator 21 such that the compensation actuator 21 does not exert any force between the frame 18 and the movable group 20. If the spot welding gun 12 is vertical with its distal end upward, the compensation control module 66 controls the compensation actuator 21 such that the compensation actuator 21 pulls the movable group 20 upward relative to the frame 18 by applying a force equal to and opposite to the weight of the movable group 20 to the movable group 20. If the spot welding gun 12 is vertical with its distal end downward, the compensation control module 66 controls the compensation actuator 21 such that the compensation actuator 21 pushes the movable group 20 upward relative to the frame 18 by applying a force equal to and opposite to the weight of the movable group 20 to the movable group 20.

[0140] It should be understood that the control module 66 controls the compensation actuator 21 such that regardless of the orientation of the welding direction W-W', the force exerted by the actuator 21 compensates for the weight of the movable group 20, and in some cases, the component of the weight is supported by the frame 18 (e.g., the track 26).

[0141] The welding control module 68 is connected, for example, to a power source (not shown) and is configured to supply power to the electrodes 34, 44.

[0142] The welding control module 68 is connected, for example, to the force sensor 33 and the electrodes 34, 44.

[0143] The welding control module 68 is configured, for example, to activate the electrodes 34, 44 for welding, or in other words supply power to the electrodes 34, 44 from the power source, only when the force measurement value of the force sensor 33 reaches or in other words is higher than a predetermined threshold.

[0144] The welding control module 68 is also connected, for example, to a hydraulic or pneumatic power source (not shown) to control the clamping actuator 32, for example, according to instructions provided by a human-machine interface (not shown).

[0145] For example, the welding control module 68 is configured to activate the electrodes 34, 44 for welding only when the force measurement value of the force sensor 33 reaches a force equal to a preset value of the force at each of the electrodes 34, 44.

[0146] For example, the spot welding gun 12 includes an information processing unit, which includes a memory associated with a processor (not shown), for example.

[0147] In such an example, the compensation control module 66 and the welding control module 68 are each generated, for example, in the form of software executable by a processor. The memory is capable of storing weight compensation software configured to detect the gravitational field to determine the orientation of the welding direction W-W' and to control the compensation actuator based on the determined orientation. Then, the memory is also capable of storing welding control software configured to activate the electrodes 34, 44 for welding only when the force measurement value of the force sensor 33 reaches a predetermined threshold.

[0148] The processor of the information processing unit is then capable of executing acquisition software, filtering software, and command software.

[0149] In a variant (not shown), the compensation control module 66 and the welding control module 68 are each generated in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or in the form of an application-specific integrated circuit, such as an ASIC (Application-Specific Integrated Circuit), or in the form of any combination of ASIC, FPGA, and / or software.

[0150] In another variant (not shown), the compensation control module 66 and the welding control module 68 are each implemented as an analog signal processing device.

[0151] When the processing component is made in the form of one or several software programs (i.e., in the form of a computer program), it can also be stored on a computer-readable medium (not shown). The computer-readable medium is, for example, a medium suitable for storing electronic instructions and capable of being coupled to the bus of a computer system. By way of example, the readable medium is an optical disc, a magneto-optical disc, a ROM memory, a RAM memory, any type of non-volatile memory (e.g., EPROM, EEPROM, FLASH, NVRAM), a magnetic card, or an optical card. The computer program including the software instructions is then stored on the readable medium.

[0152] According to another aspect of the present invention, and as Figures 1 to 3 presented in the spot welding gun 12 shown, the spot welding gun 12 includes a clamping actuator stopper 70 and an abort module 72.

[0153] In Figures 1 to 3 the example shown, the spot welding gun 12 including the clamping actuator stopper 70 and the abort module 72 includes the aforementioned features. In other embodiments, the spot welding gun 12 including the clamping actuator stopper 70 and the abort module 72 does not include all of the previously described features, for example, does not include the compensation actuator 21.

[0154] As Figures 1 to 3As schematically shown, the actuator stop 70 is configured to limit the actuation of the clamping actuator 32 such that the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 is limited to a predetermined value.

[0155] For example, the actuator stop 70 is an adjustable stop such that the predetermined value can be adjusted by the user of the spot welding gun 12.

[0156] The predetermined value is, for example, lower than the distance D3 between the inner actuation flange 48 and the outer actuation flange 38, which distance D3 corresponds to the configuration of the movable group 20 in which the electrodes 34, 44 are in contact.

[0157] In a specific embodiment, the predetermined value is, for example, equal to the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 corresponding to the configuration of the movable group 20 in which the electrodes 34, 44 are in contact.

[0158] Alternatively, the predetermined value is, for example, equal to the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 corresponding to the configuration of the movable group 20 in which the electrodes 34, 44 are spaced less than 5 mm apart.

[0159] The abort module 72 is configured to command a welding abort when the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 exceeds the predetermined value. To this end, the abort module 72 is, for example, connected to the actuator stop 70.

[0160] For example, the abort module 72 is connected to the electrodes 34, 44 and / or connected to the welding control module 68 to prevent the electrodes 34, 44 from being powered when the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 exceeds the predetermined value.

[0161] Furthermore, the abort module 72 is, for example, connected to the clamping actuator 32 and / or connected to the welding control module 68 to deactivate the actuator 32, for example to bring the movable group 20 into a stationary configuration, when the distance D3 between the inner actuation flange 48 and the outer actuation flange 38 exceeds the predetermined value.

[0162] For example, and as presented above, the spot welding gun 12 includes an information processing unit that includes, for example, a memory associated with a processor (not shown).

[0163] In such an example, the abort module 72 has, for example, a similar form to the compensation control module 66 and the welding control module 68 and is, for example, generated in the form of software executable by the processor.

[0164] In one variant (not shown), the abort module 72 is produced in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or in the form of an application specific integrated circuit, such as an ASIC (Application Specific Integrated Circuit), or in any combination of ASIC, FPGA and / or software.

[0165] In another variant (not shown), and similar to the compensation control module 66 and the welding control module 68, the abort module 72 is implemented as an analog signal processing device.

[0166] A spot welding method implemented by the spot welding gun as described above will now be presented.

[0167] In the providing step, a spot welding gun 12 and at least one component 16 to be welded are provided as described above.

[0168] In the shifting step, the spot welding gun 12 is shifted such that the electrodes 34, 44 of the spot welding gun 12 face at least one component 16 to be welded. For example, the spot welding gun is shifted such that the spot welding gun 12 faces opposite faces of at least one component 16 to be welded.

[0169] The spot welding gun 12 is shifted, for example, by a robotic arm 10 to which the spot welding gun 12 is mounted.

[0170] In the first actuation step, the clamping actuator 32 is actuated to shift the proximal electrode 34 relative to the distal electrode 44 along the welding direction W-W'. For example, in the first actuation step, the clamping actuator 32 is actuated to reconfigure the movable group 20 from a rest configuration to an active configuration, and the inner actuation flange 48 and the outer actuation flange 38 are pushed away from each other by the clamping actuator 32, thus bringing the electrodes 34, 44 closer to each other.

[0171] In a second actuation step, which occurs, for example, in parallel with the first actuation step, the compensation actuator 21 is actuated.

[0172] The compensation actuator 21 is actuated, in particular according to the orientation of the welding direction W-W', to apply a biasing force to compensate for the weight of the movable group 20 of the spot welding gun 12.

[0173] Furthermore, in an alternative to the second actuation step, or in addition to the second actuation step for the Figures 1 to 3 shown spot welding gun, the spot welding method includes a limiting step.

[0174] In the limiting step, the clamping actuator stop 70 limits the actuation of the clamping actuator 32, and subsequently the welding is aborted, for example, by the abort module 72.

[0175] In particular, the actuator stop 70 limits the distance D3 between the inner actuator flange 48 and the outer actuator flange 38 to a predetermined value. If the distance D3 between the inner actuator flange and the outer actuator flange exceeds the predetermined value, or if, for example, the actuator stop 70 limits the distance D3 between the inner actuator flange 48 and the outer actuator flange 38 to a predetermined value, the abort module 72 commands, for example, a welding abort.

[0176] As can be understood from the above description, the use of the compensation actuator 21 is particularly beneficial for improving the welding quality.

[0177] The use of the compensation actuator connecting the connecting frame 18 to one of the external unit 28 and the internal unit 30 is particularly beneficial for simplifying the weight compensation mechanism.

[0178] The movable group defining the stationary configuration and the movable configuration is particularly beneficial for ensuring the centering of the electrodes 34, 44 while reducing the energy requirement for compensating the weight of the movable group, especially when the biasing force is applied only when the movable group 20 is in its movable configuration.

[0179] The use of the parallel guide tracks 26 allows an inter-track space that can be used to reduce the thickness of the spot welding gun 12.

[0180] The plastic spacer 52 is particularly advantageous because such a spacer 52 allows reducing the friction between the external unit 28 and the internal unit 30, thereby further improving the clamping accuracy and the welding quality.

[0181] The use of the flat cylinder 58, the limited distance D2 between the actuation axis C-C' and the elongation axis E-E', and the use of the sensor axis S-S' aligned with the actuation axis C-C' allow better control of the clamping between the electrodes 34, 44.

[0182] The condition activation of the electrodes 34, 44 according to the force measurement values ensures the correct welding of the components 16 to be welded.

[0183] The use of the clamping actuator stop 70 and the abort module 72 as described above is particularly advantageous because it allows the detection of missing electrodes 34, 44 and thus prevents any defective welding and hazards associated with the missing electrodes 34, 44.

Claims

1. A spot welding gun (12) of a welding robot arm (10), which includes a frame (18) and a movable group (20) that can move along the welding direction (W-W') within the frame (18), and the movable group (20) comprises: - An external unit (28), which includes: + A proximal electrode (34), + A guiding element (36) that extends along an elongation axis (E-E') parallel to the welding direction (W-W'), the proximal electrode (34) being attached to the guiding element (36), and + An external actuation flange (38) attached to the guiding element (36), - An internal unit (30), which includes: + A distal electrode (44), + A guided element (46) that extends along the elongation axis (E-E') and can translate along the welding direction (W-W') within the guiding element (34), the distal electrode (44) being attached to the guided element (46), + An internal actuation flange (48) attached to the guided element (46), - A clamping actuator (32) that defines a clamping actuation axis (C-C') parallel to the welding direction (W-W'), the clamping actuator (32) being connected to the internal actuation flange (48) and the external actuation flange (38), and being configured to displace the flanges (38, 48) to displace the proximal electrode (34) along the welding direction (W-W') relative to the distal electrode (44), The spot welding gun further includes a compensation actuator (21) disposed between the frame (18) and the movable group (20), and the compensation actuator (21) is configured to apply a biasing force according to the orientation of the welding direction (W-W') to compensate for the weight of the movable group (20).

2. The spot welding gun (12) according to claim 1, wherein the compensation actuator (21) connects the frame (18) and one of the external unit (28) and the internal unit (30).

3. The spot welding gun (12) according to claim 1 or 2, wherein the frame (18) includes a transverse flange (24) located between the external actuation flange (38) and the internal actuation flange (48), and the movable group (20) defines: - A stationary configuration, in which the transverse flange (24) is pressed between the internal actuation flange (48) and the external actuation flange (38), and in the stationary configuration, the movable group (20) is fixed within the frame (18), - A movable configuration, in which at least one of the internal actuation flange (48) and the external actuation flange (38) is spaced apart from the transverse flange (24), and in the movable configuration, the movable group (20) can move along the welding direction (W-W'), By actuating the clamping actuator (32) to displace the inner actuating flange (48) relative to the outer actuating flange (38), the movable group (20) can be reconfigured between the stationary configuration and the active configuration.

4. The spot welding gun (12) according to claim 3, wherein the compensation actuator is actuated to apply a biasing force to compensate for the weight of the movable group only when the movable group is in the active configuration.

5. The spot welding gun (12) according to any one of the preceding claims, wherein the frame (18) includes two guide rails (26) parallel to the welding direction (W-W'), and the guide rails (26) are configured to guide the movable group (20) along the welding direction (W-W') within the frame (18).

6. The spot welding gun (12) according to any one of the preceding claims, wherein one of the internal unit (30) and the external unit (28) includes at least one plastic spacer (52), and the spacer (52) is configured to guide the guided element (46) within the guiding element (36).

7. The spot welding gun (12) according to any one of the preceding claims, wherein the clamping actuator (32) includes a flat cylinder (58).

8. The spot welding gun (12) according to any one of the preceding claims, wherein the distance (D2) between the clamping actuation axis (C-C') and the elongation axis (E-E') is less than 50 mm.

9. The spot welding gun (12) according to any one of the preceding claims, wherein the movable group (20) further includes a force sensor (33), the force sensor (33) defines a sensor axis (S-S') and is configured to measure the welding force applied between the electrodes (34, 44), the force sensor (33) is connected to the clamping actuator (32), and the sensor axis (S-S') is aligned with the clamping actuation axis (C-C').

10. The spot welding gun (12) according to claim 9, wherein the spot welding gun (12) includes a welding control module (68), the welding control module (68) is connected to the force sensor (33) and the electrodes (34, 44), and is configured to activate the electrodes (34, 44) for welding only when the force measurement value of the force sensor (33) reaches a predetermined threshold.

11. The spot welding gun (12) according to any one of the preceding claims, wherein the spot welding gun (12) includes a compensation control module (66), the compensation control module (66) is configured to detect the gravitational field to determine the orientation of the welding direction (W-W') and control the compensation actuator (21) according to the determined orientation.

12. A spot welding method implemented by the spot welding gun (12) according to any one of claims 1 to 11, wherein the method comprises the following steps: - providing the spot welding gun (12) and at least one component to be welded (16); - Shift the spot welding gun (12) so that the electrodes (34, 44) of the spot welding gun face the at least one component (16) to be welded; - Actuate the clamping actuator (32) to displace the electrodes (34, 44) relative to each other along the welding direction (W-W'); And - Depending on the orientation of the welding direction (W-W'), actuate the compensation actuator (21) to apply a biasing force to compensate for the weight of the movable group (20) of the spot welding gun (12).

13. A spot welding gun (12) of a welding robot (10), comprising a frame (18) and a movable group (20) movable within the frame (18) along a welding direction (W-W'), the movable group (20) Comprises: - An external unit (28), which includes: + A proximal electrode (34), + A guiding element (36) that extends along an elongation axis (E-E') parallel to the welding direction (W-W'), the proximal electrode (34) being attached to the guiding element (36), and + An external actuation flange (38) attached to the guiding element (36), - An internal unit (30), which includes: + A distal electrode (44), + A guided element (46) that extends along the elongation axis (E-E') and is translatable along the welding direction (W-W') within the guiding element (34), the distal electrode (44) being attached to the guided element (46), + An internal actuation flange (48) attached to the guided element (46), - A clamping actuator (32) that defines a clamping actuation axis (C-C') parallel to the welding direction (W-W'), the clamping actuator (32) being connected to the internal actuation flange (48) and the external actuation flange (38) and configured to displace the flanges (38, 48) to displace the proximal electrode (34) relative to the distal electrode (44) along the welding direction (W-W'), The spot welding gun includes a clamping actuator stopper configured to limit the actuation of the clamping actuator such that the distance between the internal actuation flange and the external actuation flange is limited to a predetermined value, and the spot welding gun further includes an abort module configured to command welding to abort when the distance between the internal actuation flange and the external actuation flange exceeds the predetermined value.

14. The spot welding gun (12) according to claim 13, wherein the predetermined value is lower than the distance (D3) between the internal actuation flange (48) and the external actuation flange (38), the distance (D3) corresponding to the configuration of the movable group (20) in which the electrodes (34, 44) are in contact.

15. A spot welding method implemented by the spot welding gun (12) according to claim 13 or 14, wherein the method Comprises the following steps: - Provide the spot welding gun (12) and at least one component (16) to be welded; - Shift the spot welding gun (12) such that the electrodes (34, 44) of the spot welding gun (12) face the at least one component (16) to be welded; - Actuate the clamping actuator (32) to displace the electrodes (34, 44) relative to each other along the welding direction (W-W'); and - Limit the actuation of the clamping actuator (32) by the clamping actuation stopper (70) and subsequently abort the welding.

Images