Resistance welding apparatus having a fixed electrode and a movable electrode between a working position and two distinct rest positions

Abstract

TITLE: Welding apparatus comprising an arm with a moving electrode. The invention relates to a resistance welding apparatus comprising a clamp (1) for supporting an arm having a first part (1A) supporting a fixed electrode (2) and a second part (1B) supporting a moving electrode (3), the electrodes (2, 3) being designed to carry an electric current and to grip metal elements for welding, the moving electrode (3) being configured to move between a working position (P0) in which the electrodes (2, 3) grip the metal elements to be welded and two open positions allowing the metal elements to be inserted between the electrodes (2, 3) arranged opposite each other. Abstract figure: [Fig. 1]

Description

Title of the invention: Resistance welding apparatus having a fixed electrode and a movable electrode between a working position and two distinct rest positions Scope of the invention

[0001] The field of the invention is that of resistance welding devices.

[0002] The invention relates more particularly to such devices comprising a clamp for supporting an arm consisting of a first part supporting a fixed electrode and a second part supporting a moving electrode. Prior art and its drawbacks

[0003] Resistance welding devices have a means of generating very high electric currents which pass through electrodes via electrical contacts contained in each of them. The electrodes are configured to grip materials, in particular metallic elements, in order to weld them, notably by creating a weld point.

[0004] During the welding process, the passage of very high currents between the electrodes heats the materials due to the greater electrical resistance of the materials compared to the electrodes. For example, the very high currents passing through the electrodes range from 1,000 A to 15,000 Amperes.

[0005] Spot welding apparatus with a block comprising a clamp for supporting an arm, for example C-shaped, having a first part supporting a fixed electrode and a second part supporting a moving electrode. Current welding apparatus include an actuator, for example containing a pneumatic cylinder. The use of such a pneumatic cylinder makes it possible to control and impart a linear movement to the moving electrode. This linear movement allows, in a first direction, the moving electrode to be brought closer to the fixed electrode in order to clamp the materials to be welded in a working position, the clamp being then in a closed position, and in a second direction opposite to the first, the moving electrode to be moved away from the fixed electrode in order to release these materials, the clamp moving from the closed position to an open position.

[0006] When the clamp is open, locking means block the mobile electrode in a rest position away from its working position.

[0007] Conventionally, the linear movement of the mobile electrode from the rest position to the working position is initiated after activation of a control button configured to pressurize a chamber of the pneumatic cylinder.

[0008] Once the weld point has been made, the moving electrode is configured to move from the working position to the rest position after deactivation of the control button for example, so as to induce a vacuum in the chamber of the pneumatic cylinder which was then under overpressure.

[0009] One drawback of these resistance welding devices is that the distance between the working position and the rest position of the moving electrode is fixed. In particular, this distance is predefined and optimized according to the geometries and thicknesses of the materials to be welded.

[0010] To overcome this drawback, resistance welding apparatus exist in which it is possible to increase this distance by manually manipulating the moving electrode of the clamp to move it further away from the fixed electrode, i.e., by retracting the moving electrode. For example, means for locking the moving electrode in the rest position may include a clamping means, such as a clamping ring, against which the moving electrode is locked and cannot move further away from the fixed electrode. In particular, the clamping means is designed, on the one hand, to be manually tightened onto the second part of the arm in order to hold the moving electrode in its rest position.On the other hand, following manual loosening of the clamping means, it is possible to act directly on the moving electrode, and in particular to move it further away from the fixed electrode before manually tightening it to hold the moving electrode in a new resting position.

[0011] However, with such a clamping device, it is necessary for an operator to manually intervene on the moving electrode to change its resting position. Furthermore, the clamping efficiency of such a clamping device inevitably degrades over time, particularly with repeated clamping and loosening cycles. Objectives of the invention

[0012] The present invention proposes a welding apparatus with a linear motion arm for a spot welding clamp with "C" motion.

[0013] The welding apparatus has a mechanism allowing, on the one hand, for moving the moving electrode between the clamping position, i.e. the working position, and the rest position, and on the other hand, for moving the moving electrode from the first rest position to a withdrawal position located at a distance from the working position greater than the distance separating the working position from the rest position.

[0014] Furthermore, the movement of the mobile electrode between its rest position and its retraction position is carried out without manual manipulation of the mobile electrode. Description of the invention

[0015] To this end, the invention relates to a resistance welding apparatus comprising a clamp for supporting an arm having a first part supporting a fixed electrode and a second part supporting a moving electrode, the electrodes being intended to carry an electric current and to grip metallic elements for welding them, the moving electrode being configured to move between: - a working position in which the electrodes grip the metal parts to be welded, - a first opening position allowing the insertion, between the electrodes arranged opposite each other, of the metal elements to be welded, in which the moving electrode is in a first rest position and located at a first distance from the fixed electrode, - a second opening position allowing the insertion, between the electrodes arranged opposite each other, of the metal elements to be welded in which the moving electrode is in a second rest position and located at a second distance from the fixed electrode, greater than the first distance,

[0016] the welding apparatus comprising means for locking the moving electrode in the first rest position and actuating means intended to act on the locking means to allow the movement of the moving electrode towards the second rest position under the effect of return means.

[0017] The combined presence of the locking means, the actuating means, and the return means makes it easy to allow the movement of the moving electrode from the first rest position to the second rest position. In particular, the return means ensure the automatic movement of the moving electrode from the first rest position to the second rest position without manual intervention on the moving electrode, but by acting on an actuating button configured to activate the actuating means.

[0018] Furthermore, allowing the clamp to be opened further makes it possible to insert, between the two electrodes, metallic elements, for example automotive body panels, with thicknesses greater than the distance separating the working position of the mobile electrode from its first rest position in which it is mechanically locked if no external force is applied to the actuation means.

[0019] Furthermore, when the metal elements to be welded include an obstacle, for example when the sheets for the manufacture of automobile bodies include a body element defined by a thickness greater than the distance separating the working position of the first rest position, it is thus possible to bypass it to perform a weld at a precise point located on the other side of the obstacle.

[0020] Advantageously, the invention comprises the following features, taken alone or in combination: - the resistance welding apparatus includes a jack rod on which the moving electrode is mounted to be driven in translation, the jack rod being integral with the return means configured to bring the moving electrode from the working position to the first rest position, then to the second rest position when this movement is permitted; this makes it easier to move the moving electrode while having a simple mechanism to implement;This also allows for a single-acting cylinder which includes a single chamber capable of being pressurized, on the one hand, to move the electrode from the second rest position to the first rest position, and from the first rest position to the working position, and on the other hand, to be depressurized to, in combination with the return means, move the electrode from the working position to the first rest position, and from the first rest position to the second rest position; - the locking means include a locking latch provided with a locking finger configured to cooperate with a stop formed on the outer surface of the cylinder rod; this allows for easy-to-implement locking means with the locking latch which guarantees the translational locking of the cylinder from the first rest position to the second rest position when it cooperates with the stop; - the locking latch is mounted pivoting around an axis of rotation between a locking position in which the locking finger cooperates with the stop and a release position in which the movement of the mobile electrode towards the second rest position is allowed; this allows for a mechanism for allowing the movement of the mobile electrode that is simple to implement; - the actuation means include a release lever configured to actuate the pivoting of the locking latch; this allows manual switching between the locking position and the release position. Brief description of the figures

[0021] Other features and advantages of the invention will now become apparent in greater detail in the following description of illustrative and non-limiting embodiments, with reference to the accompanying figures which represent:

[0022] [Fig-1]: [Fig.1] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a first rest position;

[0023] [Fig.2]: [Fig.2] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a working position;

[0024] [Fig.3]: [Fig.3] presents a schematic cross-sectional view of a clamp of a welding apparatus comprising a movable electrode according to an example embodiment, the movable electrode being in a second rest position;

[0025] [Fig.4]: [Fig.4] presents a schematic cross-sectional view centered on the means for locking the moving electrode of a clamp of a welding device according to an example embodiment, the locking means being in a position blocking the movement of the moving electrode from the first rest position to the second rest position;

[0026] [Fig.5] : [Fig.5] presents a schematic cross-sectional view centered on the means for locking the moving electrode of a clamp of a welding device according to an example embodiment, the locking means being in a position allowing the movement of the moving electrode from the first rest position to the second rest position;

[0027] [Fig.6]: [Fig.6] presents a front view of the moving electrode of a welding apparatus according to an example embodiment, in which the locking means are in a position blocking the movement of the moving electrode from the first rest position to the second rest position;

[0028] [Fig.7]: [Fig.7] presents a front view of the moving electrode of a welding apparatus according to an exemplary embodiment, in which the locking means are in a position allowing movement of the moving electrode between the first rest position and the second rest position. Detailed description

[0029] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0030] The invention relates to a resistance welding apparatus for welding metallic elements together.

[0031] For example, the metallic elements may take the form of sheets intended for use in the manufacture of automobile bodies.

[0032] As illustrated in Figures 1 to 3, the welding apparatus comprises a clamp 1. The clamp 1 has an arm with two parts located opposite each other. A first part IA terminates in a fixed electrode 2 and a second part IB terminates in a movable electrode 3.

[0033] Preferably, the arm and gripper assembly 1 is held by an operator or attached to the end of a robotic arm. The fixed electrode 2 and the moving electrode 3 are designed to carry an electric current to weld the metal elements clamped between the fixed electrode 2 and the moving electrode 3, creating a weld point. This electric current passes through the two electrodes 2 and 3 via, in particular, electrical contacts contained within each of them.

[0034] Preferably, the movable electrode 3 is mounted on a cylinder rod 4. The cylinder is, in one embodiment, a single-acting cylinder defined by a predefined stroke length.

[0035] Preferably, the cylinder rod 4 is inserted into a cylinder in which it slides. The cylinder rod 4 then carries the movable electrode 3 at one end and a piston sliding in the cylinder at its opposite end. The movement of the movable electrode 3 is then achieved by the forward and backward movements of the cylinder.

[0036] Preferably, a cylinder chamber is located on the sliding piston side. The forward and backward movements of the cylinder are then initiated by alternately applying fluid pressure and fluid vacuum to the cylinder chamber. For example, the fluid pressure in the cylinder chamber is generated by pressurizing a pneumatic fluid, such as compressed air, while the fluid vacuum is created by removing a volume of compressed air from the cylinder chamber.

[0037] In this way, the mobile electrode 3 is driven in translation by the cylinder rod 4 in a first direction along a longitudinal axis X and in a second direction, opposite to the first direction along the longitudinal axis X. Thus, the cylinder rod 4, on the one hand, advances in the first direction, when the cylinder chamber is put under fluidic overpressure, so that the mobile electrode 3 and the fixed electrode 2 grip the metal elements, and on the other hand, recoils in the second direction, when the cylinder chamber is put under fluidic overpressure, to free the mobile electrode 3 from the metal elements and move it away from the fixed electrode 2 after possible completion of the weld point.

[0038] According to the invention, for the translational drive of the cylinder rod 4 in the second direction, the rod is attached to return means configured to disengage the movable electrode 3 from the metallic elements when the cylinder chamber is subjected to fluidic depressurization. In particular, the return means make it possible to guarantee the translational displacement of the cylinder rod 4 in the second direction when the cylinder chamber is placed under fluidic depression.

[0039] In one embodiment, the return means include a return spring 41 integral with the sliding piston. Preferably, the return spring 41 is a tension spring. In particular, the sliding piston is mounted on the return spring 41 which, when the return spring 41 is relaxed, exerts a restoring force on the cylinder rod 4 so that the rod moves in the second direction when the cylinder chamber is subjected to fluid vacuum.

[0040] Preferably, the translational drive of the cylinder rod 4 in the first direction is engaged when an operator continuously presses a control button to actuate the supply of compressed air to the cylinder chamber in order to put it under fluidic overpressure.

[0041] Preferably, the second-direction translation of the cylinder rod 4 is engaged when the operator releases the control button to create a fluid vacuum in the cylinder chamber. This allows the cylinder rod 4, under the effect of the return spring 41, to retract along the entire stroke length of the cylinder if this movement is permitted, i.e., if the cylinder rod is not blocked in any position in the meantime.

[0042] It should be noted that the assembly including the cylinder is designed to stabilize the position of the moving electrode 3 when the electrodes are either in contact with each other or in contact with the metal elements to be welded.

[0043] In [Fig.1] the clamp 1 is shown open in a first open position. In particular, the movable electrode 3 is here in a first rest position PI, in which it is possible to insert the metal parts to be welded between the fixed electrode 2 and the movable electrode 3, which are then positioned opposite each other.

[0044] The mobile electrode 3 is then located at a first distance DI from the fixed electrode 2.

[0045] The mobile electrode 3 can no longer move away from the fixed electrode 2. Indeed, this The distance is blocked by locking means which will be described later. Preferably, the first distance DI is less than the stroke length of the cylinder.

[0046] Figure 2 shows the clamp 1 closed. The movable electrode 3 is shown here in a working position PO, in which it is possible to perform the weld on the metal parts. The movable electrode 3 moves from the first rest position PI to the working position PO when the clamp 1 is closed, that is, when the cylinder chamber is pressurized so that the cylinder rod 4 advances. The movable electrode 3 then approaches the fixed electrode 2 to stabilize in the working position PO.

[0047] It should be noted that the moving electrode 3 also moves from the working position PO, shown in [Fig. 2], to the first resting position PI, shown in [Fig. 1], when the opening of the clamp 1 is engaged. In particular, during this movement, the rod 4 of the cylinder retracts until the locking means are engaged.

[0048] After acting on the locking means to unlock them, via actuation means that will be described later, the mobile electrode 3 moves from the first rest position PI to a second rest position P2 shown in [Fig. 3]. This movement is enabled by an operator when an over-opening of the clamp 1 is desired in order to open it further.

[0049] In particular, [Fig. 3] represents the clamp 1 open in the second open position. In the second open position, it is possible to insert, between the fixed electrode 2 and the moving electrode 3, which are then positioned opposite each other, metal elements to be welded, defined by a thickness greater than the metal elements that could be inserted through the clamp 1 when the moving electrode 3 was in the first rest position PI.

[0050] It should be noted that in the second open position, the mobile electrode 3 is therefore located at a second distance D2 from the fixed electrode 2 which is greater than the first distance Dl.

[0051] Thus, when the cylinder chamber is depressurized in order to retract the cylinder rod 4 under the effect of the return spring 41 attached to the sliding piston, the moving electrode 3 moves from the working position PO to the first rest position PI, then to the second rest position P2 when this movement is allowed, that is to say when the cylinder rod 4 is not blocked by the blocking means.

[0052] Figures 4 and 5 represent in particular an example of an embodiment of the locking means. In particular, [Fig.4] represents the locking means in a locking position, i.e. in a blocked position, while [Fig.5] represents the locking means in an unlocking position, i.e. in a position where the cylinder rod 4 is released.

[0053] In particular, the locking means here comprise a longitudinal groove 6 formed on the outer surface of the cylinder rod 4 and along its longitudinal axis X. Preferably, the longitudinal groove 6 is a keyway.

[0054] The locking means further comprise a locking latch 5 provided with a locking finger configured to fit into the longitudinal groove 6 and make a sliding connection with it.

[0055] In particular, the groove 6 has a wall transverse to the longitudinal axis X forming a stop 61 in contact with a locking surface 51 of the locking finger. Preferably, the locking surface 51 of the locking finger is a flat surface.

[0056] Preferably, the locking latch 5 is integral with the actuation means described later. The actuation means are configured to lower the locking latch 5 so as to move from the locked position as illustrated in [Fig. 4], towards the release position as illustrated in [Fig.5] when a force is exerted on them (the force being represented by an arrow in [Fig.5]).

[0057] In particular, the actuation means are configured to hold, when not actuated, the locking latch 5 raised so that the locking finger is flush with a sliding surface of the groove 6 when the groove is opposite the locking finger. In this way, the stop 61 moves translationally along the longitudinal axis X while the locking finger is kept in contact with the sliding surface of the groove 6 when the movable electrode 3 moves between the working position PO and the first rest position PI. Thus, when the locking surface 51 of the locking finger is in contact with the stop 61, the movement of the movable electrode 3 from the first rest position PI to the second rest position P2 is blocked.

[0058] To allow the rearward movement of the cylinder rod 4 in order to move the movable electrode 3 from the first rest position PI to the second rest position P2, an operator exerts a force on the actuation means to lower the locking latch 5 in order to remove the locking finger from the groove 6. This prevents the locking surface 51 of the locking finger from contacting the stop 61.

[0059] According to one embodiment, the locking latch 5 is oblong in shape and therefore has two ends. Thus, to raise and lower it, its first end is mounted to pivot about an axis of rotation 9 formed by a pivot joint connecting the first end of the locking latch 5 and the second part of the arm.

[0060] The second end of the locking latch 5 is connected to the actuation means which, according to an embodiment illustrated in Figures 6 and 7, comprise a slide 7, a release lever 10 preferably terminating in a release finger 11, and a retaining spring configured to hold the locking latch 5 in the raised position when the release lever 10 is not actuated. It should be noted that the release finger 11 may be in the form of any type of actuation button.

[0061] Preferably, the slide 7 is oblong in shape and thus has two ends. The slide 7 also has an opening through which the movable electrode 3 is inserted to allow its translational movement between the various positions mentioned above. One end of the slide 7 is connected to the second end of the locking latch 5, for example via a connecting element 8, which is either an integral part of the slide 7 or the locking latch 5, or a separate element. Here, the connecting element 8 is an extension of the first end of the slide that fits into the second end of the locking latch 5 in order to create a movable connection between the locking latch 5 and the slide 7.

[0062] According to one embodiment, the unlocking handle 10 comprises a rod having a first end and a second end, the ends being inclined relative to each other at an angle of inclination, for example, greater than 90°. Preferably, the first end of the rod is inserted into a second end of the slide 7, and the second end of the rod terminates in the unlocking finger 11. The rod is pivotally mounted about a pivot joint 12 made, preferably, at the angle of inclination, so as to set the slide 7 in motion.

[0063] The slide 7 is in particular configured to move in translation along a direction substantially transverse to the longitudinal axis X between the blocking position and the release position of the blocking means.

[0064] In particular, when the slide 7 is in a raised position as illustrated in Figures 4 and 6, the locking finger of the locking latch 5 is inserted into the groove 6. The movable electrode 3 is then locked in the first rest position PL. When the slide 7 is in a lowered position as illustrated in Figures 5 and 7, the locking finger is withdrawn from the groove 6. In this situation, a portion of the first end of the slide 7 and / or a portion of the second end of the latch 5, and possibly also the connecting element 8, are housed in a suitable recess 81 formed in the second part IB of the gripper arm 1. The movable electrode 3 is then brought into the second rest position P2.The slide 7 moves from its raised position to its lowered position when, preferably, the operator manually releases the locking means by exerting, for example, a force on the release finger 11. The slide 7 moves from its lowered position to its raised position by the application of a force by a return element. The slide 7 is held in its raised position by the force applied by the return element when no force is directly exerted on the release finger 11.

[0065] In one embodiment, the release lever rod 10 is mounted on the retaining spring, which is preferably a compression spring. Thus, the pressure of the retaining spring, when the retaining spring is compressed, exerts a force on the slide 7, naturally raising it and thus opposing its movement from its raised position to its lowered position. This keeps the locking finger of the locking latch 5 in the groove 6, thereby preventing the rearward movement of the cylinder rod 4 when no force is exerted on the release finger 11.

[0066] Preferably, the unlocking lever 10 is connected to the second part IB of the gripper arm 1 by the pivot joint 12. Thus, the slide 7 moves from its raised position to its lowered position when the operator exerts a force of rotation on the release finger 11. For example, the rotational force that the operator must exert on the release finger 11 to unlock the locking means is a counterclockwise force. It should be noted that the release finger 11 then moves naturally, via the force exerted by the retaining spring, clockwise to return to its equilibrium position, i.e., its position when the slide 7 is in its raised position.

[0067] It should be noted that when the unlocking finger 11 is in its equilibrium position, the locking and actuation means are sufficiently rigid so as not to deform.

[0068] It is further indicated that the gripper 1 has a means of gripping and handling such as a handle 13, possibly removable, fixed to the second part IB of the arm of the gripper 1.

[0069] The clamp 1 described above has the advantage of being able to open in two opening positions: an opening position corresponding to the first rest position PI of the mobile electrode 3, and an over-opening position corresponding to the second rest position P2 of the mobile electrode 3.

[0070] This allows the clamp 1 to be adapted to thicknesses of metal elements greater than the distance separating the electrodes 2, 3 in the first rest position PI, but also to simplify the positioning of the electrodes on either side of metal elements to be welded when access to these elements is reduced and difficult.

[0071] According to the invention, it is possible to carry out this over-opening without manually manipulating either of the electrodes or using a pneumatic circuit.

[0072] Although the present invention has been described with reference to the particular embodiments illustrated, it is not limited by these embodiments but only by the appended claims. It should be noted that changes or modifications may be made by those skilled in the art.

Claims

Demands

1. A resistance welding apparatus comprising a clamp (1) for supporting an arm having a first part (IA) supporting a fixed electrode (2) and a second part (IB) supporting a moving electrode (3), the electrodes (2, 3) being designed to carry an electric current and to grip metal elements for welding, the moving electrode (3) being configured to move between: - a working position (PO) in which the electrodes (2, 3) grip the metal elements to be welded, - a first opening position allowing the insertion, between the electrodes (2, 3) arranged opposite each other, of the metal elements to be welded in which the moving electrode (3) is in a first rest position (PI) and located at a first distance (Dl) from the fixed electrode (2), - a second opening position allowing the insertion, between the electrodes (2, 3) arranged opposite each other,the metal parts to be welded in which the moving electrode (3) is in a second rest position (P2) and located at a second distance (D2) from the fixed electrode (2), greater than the first distance (D1), the welding apparatus comprising means for locking the moving electrode (3) in the first rest position (PI) and actuating means intended to act on the locking means to allow the movement of the moving electrode (3) towards the second rest position (P2) under the effect of return means.

2. Resistance welding apparatus according to claim 1, comprising a cylinder rod (4) on which the movable electrode (3) is mounted to be driven in translation, the cylinder rod (4) being integral with the return means configured to return the movable electrode (3) from the working position (PO) to the first rest position (PI), then to the second rest position (P2) when this movement is permitted.

3. Resistance welding apparatus according to claim 2, wherein the locking means comprise a locking latch (5) provided with a locking finger configured to cooperate with a stop (61) formed on the outer surface of the cylinder rod (4).

4. Resistance welding apparatus according to claim 3, wherein the locking latch (5) is mounted pivotally about an axis of rotation (9) between a locking position in which the locking finger cooperates with the stop (61) and a release position in which movement of the movable electrode (3) towards the second rest position (P2) is permitted.

5. Resistance welding apparatus according to claim 4, wherein the actuation means comprise a release handle (10) configured to actuate the pivoting of the locking latch (5).

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