Spot welding tongs with a balancing unit comprising a curved connector element

The present invention includes a tong base body, two tong arms, and one correction unit configured to movably connect one of the tong arms to the tong base body and convert rotational motion into linear motion. With respect to spot welded tongs with tongs correction, including. The correction unit is composed of a drive device and a connector element, and the connector element is eccentrically and movably fixed to an eccentric disk fixed to the drive device.

This type of spot weld tongs is known, for example, from International Application No. 02/078892 (WO 02/078892 A1). In the patent application, the correction operation is achieved through the drive device coupled to the connector element via the eccentric tappet by converting the rotational movement of the drive device into the longitudinal movement of the connector element.

A spot welded tong with a correction unit can be obtained from German Patent Application Publication No. 103 44 056 (DE 103 44 056 A1). In the patent application, the correction drive is coupled to the joint lever of the weld tongs via an eccentric drive. The spot weld tongs are further configured to be removed by the latter (eccentric drive), where a separate correction drive is replaced by simple and mechanical means.

Correction units that convert rotational motion into linear motion by threads are known in the prior art. For example, from German Utility Model Application Publication No. 202 14 970 (DE 202 14 970 U1), robot welding tongs including correction devices are known. In the utility model application, the spindle is driven by an electric motor. In addition, the linear motion obtained from it is used for the tong arm of the welding tong as a motion to maintain equilibrium. Since the spindle in that case is self-locking, the compensation unit is configured to include elastic elements such as springs to allow suspension of compensation movement.

However, it is disadvantageous that such a configuration of the correction unit requires an additional elastic element for the suspension of the correction operation. This includes high structural and maintenance costs. Moreover, such spindle drives are associated with many thermal problems. Many thermal problems are due to the high friction loss caused by the spindle drive.

An object of the present invention is to provide a spot welded tong with tong compensation. The correction unit converts the rotary motion of the electric motor into a linear motion (that is, a correction motion) of the tong arm in a simple manner. The drawbacks of the prior art are avoided or at least reduced.

An object of the present invention is achieved by the connector element being configured to be curved in the end region. Such a configuration of the connector element of the compensating unit ensures that the rotational motion of the drive unit is optimally converted to linear motion. It has the advantage that the conversion of rotational motion into linear motion is achieved by the crank structure. Therefore, it is equally desirable that the structure is simple, non-complex, and easy to maintain.

Preferably, the configuration of the correction unit according to the invention as defined in claims 2 to 6 interferes with the automatic locking operation of the correction unit so that no additional element with elastic action is required.

The measurement, where the drive is preferably located on the base of the tongs or on one of the tong arms, provides flexible placement options for the drive or compensation unit, respectively. provide.

Preferably, the measuring element provided on the connector element ensures that accurate and force-related control is achieved for a precisely defined compensating force.

The present invention will be described in detail with reference to the attached schematic diagram.

FIG. 1 shows a spot weld tong 1 for resistance welding of the workpiece 2. The spot weld tongs 1 are preferably operated by a robot. The fixing is realized by the robot flange 3 attached to the end of the tong base body 4. At the other end of the tong base body 4, the pins 5 form a rotation axis with respect to the entire spot weld tong 1, and around that rotation axis, the tong arms 6 and further the tong arms 7 are pivoted by the pivot arms 8, 9. It is configured to be rotatably attached to pin 5. Between the pin 5 and the robot flange 3, the tong arms 6 and 7 are connected to each other by the main drive device 10. In this way, the so-called X-shaped spot weld tongs 1 are formed. In the front area of the tong arms 6 and 7, especially at their front ends, the electrode holders 11 and 12 are arranged to hold the electrodes 13 and 14, respectively.

During the welding process, the workpiece 2 to be welded is located between the electrodes 13, 14 and the workpiece is composed of, for example, two components 15, 16. To perform the welding procedure, the spot weld tongs 1 must first be positioned by the robot. For this purpose, the spot weld tongs 1 are in the open state according to FIG. 1, i.e. in the starting position or the original position. In FIGS. 2-4, the individual operating steps of the spot weld tongs 1 are shown up to the realization of a resistance welding operation.

The tong arms 6,7 must be fully opened before the robot can position the spot weld tongs 1 at the weld position with the previously fixed components 15,16. This is achieved by the main drive 10. The main drive 10 moves the tong arms 6 and 7 in exactly the opposite way. The tong arms 6,7 open, taking into account the shape of components 15,16, the tolerances of components 15,16, and the positioning accuracy of the robot.

It would also be taken into account that the robot requires a starting point or reference point so that the tong arms 6, 7 are brought to the welded position of workpiece 2 in a non-contact manner while open. .. The reference point is defined, for example, on the contact surface between the component 16 and the electrode 14. The tong arm 7 to which the electrode 14 is attached is coupled to the tong base body 4 by the correction unit 17 so that the contact surface of the electrode 14 actually contains the reference point. By properly operating the correction unit 17 achieved by the controller of the spot weld tongs 1, the contact surface of the tongs arm 7 or electrode 14 is kept above the reference point. It is ensured that the spot weld tongs 1 are maintained in the same place at any possible weld position.

In this way, the correction unit 17 constantly holds the spot weld tongs 1, or tong arms 6, 7 in the same position, especially during the robot positioning procedure. In this way, the robot can easily and particularly non-contactly position the spot weld tongs 1 and the tong arms 6, 7 at the desired weld positions of the components 15, 16.

During the positioning procedure, the reference point or contact surface of the electrode 14 is positioned at a defined distance below the weld position of the components 15, 16 as is apparent from FIG. 2, for example 2 cm. At the welding site, the electrodes 13 and 14 are positioned so as to substantially normally extend to the components 15 and 16 to be welded to each other. After positioning is complete, the robot sends a message to the tongs controller, resulting in resistance welding. The tong arms 6 and 7 are moved towards each other to perform a resistance welding operation at the weld sites of components 15 and 16. In doing so, there are various options for controlling the correction unit 17.

According to FIG. 3, resistance welding is performed, for example, by the correction unit 17 with the tong arm 7 until the electrode 14 comes into contact with the component 16 by a predetermined force determined by the force sensor or by the evaluation of the motor current of the correction unit 17. And the electrode 14 is moved to the component 16. Proper control of the correction unit 17 keeps the tong arm 7 in this position until the end of the welding procedure. After this, as is apparent from FIG. 4, the main drive 10 attaches the tong arm 6 and the electrode 13 to the component 15 until the required and predetermined pressure is applied to the components 15 and 16 between the electrodes 13 and 14. Move. As a result, a given current supplied by the welding equipment is guided through electrodes 13, 14 to perform resistance welding of components 15, 16.

Similarly, a resistance welding operation occurs so that the tong arm 6 is moved to the component 15 by the main drive 10 up to a distance between the electrode 14 and the component 16, eg, a predetermined distance substantially corresponding to 2 cm. It is possible. As a result, the correction unit 17 is inactive or, for example, preferably switched from a predetermined closing angle of the spot weld tongs 1 without current. Thereby, the tong arms 6 and 7 are positioned in the center of the workpiece 2 and the main drive 10 applies a predetermined pressure required for performing resistance welding. This type of movement allows the tong arms 6 or 7 engaged by the correction unit 17 to move freely to ensure automatic abutment of electrodes 13, 14 on components 15, 16. That is achieved by the removal of the correction unit 17.

In a further variant for performing resistance welding, control of the correction unit 17 is achieved such that the latter is powered, for example, at a predetermined current. The level of current is chosen so that the spot weld tongs 1 are maintained in their positions while they are mobile to the extent of their limits. Thereby, the suspension of the correction operation can prevent any deformation of the workpiece 2 or the components 15, 16. As described above, the tong arms 6 and 7 are again positioned in the center of the workpiece 2 and the main drive 10 applies a predetermined pressure required for performing resistance welding.

Upon completion of the resistance welding operation, the spot weld tongs 1 or tong arms 6 and 7 are returned to their starting positions, as shown in FIG. Further, as shown in FIG. 1, it is possible to return the spot welding tong 1 to its original position. Further, the spot weld tongs 1 can move the components 15 and 16 to the next weld position after being returned, as shown in FIG. 1 or 2.

In the correction unit 17 according to the present invention for performing the described modification of resistance welding, the correction unit 17 is composed of a drive device 18 and a connector element 19 eccentrically arranged on the drive device 18. It is configured in. In this way, the connector element 19 converts the rotational motion of the drive device 18 into a linear motion of the tong arm 6 or 7. The suspension required for the correction operation of the correction unit 17 is achieved by proper control of the drive unit 18. And a simple structure of the correction unit 17 that minimizes the maintenance cost is provided.

The setup of the correction unit 17 according to the present invention is clear from FIG. 6 and 7 show correction units 17 at different positions for performing correction operations.

The drive unit 18 of the correction unit 17 substantially comprises an electric motor 20 and gears 21, preferably planetary gears. The drive device 18 and particularly the electric motor 20 rotate by a shaft 22. The rotational motion is converted into linear motion by the connector element 19. For this purpose, the eccentric disc 23 is fixedly attached to the shaft 22. The eccentric disc 23 is fixed to the shaft 22 via a recess 24 provided in its center so that it can rotate with the help of a fixing means 25 formed by, for example, a screw and a disc. In this way, the eccentric disk 23 rotates along the shaft 22. Further, the lever 26 is arranged on the eccentric disc 23. The lever comprises a hole 27 for fixing the connector element 19. Placing the hole 27 eccentrically on the eccentric disk 23 means that the connector element 19 fixed to the hole 27 of the correction operation converts the rotational motion of the eccentric disk 23 into a linear motion.

As is clear from FIGS. 6 and 7, the eccentric disc 23 and the lever 26<u style="single">Range of rotation 28</u>(Eg 90 °) would be useful for the correction operation substantially. Preferably,<u style="single">Range of rotation 28</u>Is between the 270 ° position of the lever 23, that is, the lower end position 29 vertically below the recess 24, and the 360 ° position of the lever 26, that is, the upper end position 30 in the horizontal direction of the recess 24. To allow the connector element 19 to convert this rotational motion into linear motion, the former is rotatably fixed to the shaft 22 by, for example, a fixing means 25 formed by a screw and a disc. It is configured in. Therefore, the eccentric disk 23 rotates with respect to the shaft 22.

Further, the lever 26 is arranged on the eccentric disc 23. The lever 26 includes a hole 27 for fixing to the connector element 19.

Placing the hole 27 on the eccentric disc 23 translates the rotation of the eccentric disc 23 into a linear motion, for example, via a connector element 19 fixed to the hole 27 in the correction operation.

As is clear from FIGS. 6 and 7, the eccentric disc 23 and the lever 26<u style="single">Range of rotation 28</u>(Eg 90 °) would be useful for the correction operation substantially. Preferably,<u style="single">Range of rotation 28</u>Is between the 270 ° position of the lever 23, that is, the lower end position 29 vertically below the recess 24, and the 360 ° position of the lever 26, that is, the upper end position 30 in the horizontal direction of the recess 24. The former is configured to allow the connector element 19 to convert this rotational motion into linear motion. Thus, the connector element 19 has two shapes.

The end region secured to the lever 26 is curved to substantially match the eccentric disc 23. A hole 31 is provided in the end region fixed to the lever 26.

The hole 31 serves to rotatably fix the connector element 19 to the hole 27 of the lever 26 via the pin 32. For this purpose, the curved end region of the connector element 19 includes a recess formed corresponding to the lever 26.

Thus, the curved end region of the connector element 19 encloses the lever 26. The end region of the connector element 19, located opposite the curved end region, is configured as the web 33.

The web 33 serves, for example, as a movable attachment to the tong base body 4. Preferably, the movable attachment of the web 33 is realized with the help of eyebolts 34 or connecting rods detachably connected to the web 33, for example by threads.

The threads also make it possible to adjust the distance. To secure the eyebolt 34 to the web 33, the web 33 is provided with an internal thread. In female threads, the nut 35 is further used for fixing as a so-called counter nut.

Due to this configuration of the correction unit 17, the rotational movement of the drive device 18 and the eccentric disk 23 fixed to the shaft 22 is linearly moved via the connector element 19 rotatably attached and fixed to the lever 26. It becomes possible to convert to.

For this purpose, the drive unit 18 is attached, for example, to the tong arm 7. Further, the eyebolt 34 connected to the web 33 of the connector element 19 is fixed to the tong base body 4.

Similarly, the drive device 18 may be fixed to the tong arm 6. Alternatively, the eyebolt 34 may be fixed to one of the tong arms 6 and 7, and the drive device 18 may be correspondingly fixed to the tong base body 4. This will guarantee the required correction operation regardless of the placement of the correction unit 17.

The correction operation of the tong arm 7 is achieved by raising or lowering the drive device 18. It is attached to the longitudinal axis of the tong arm 7.

Thus, the eyebolt 34 constitutes a stationary but rotatable pivot for the correction unit 17.

Raising and lowering the tong arms 6 and 7 by the correction unit 17 achieves the power consumption of the motor 20 as low as possible. Adjustment of the correction unit 17 is necessary. The minimum consumption of power for motor 20 is<u style="single">Range of rotation 28</u>Is effectively provided at. Therefore, the rotational movement of the motor 20 and the lever 26 for the correction operation (that is, from the reference point to the contact with the component 16) is<u style="single">Range of rotation 28</u>It is preferable to occur within.

The reference point is required by the robot for positioning the spot weld tongs 1. As is already known, the reference point constitutes, for example, the contact surface of the electrode 14.

The position of the tong arm 7 is obtained from the reference point. The drive unit 18 is fixed to the tong arm 7 via, for example, an angle bracket 36 composed of several parts.

From this, the length for the connector element 19 is obtained. The length of the connector element 19 is adjusted by the thread of the eyebolt 34 and the female thread provided in the web 33, respectively.

The exact length is adjusted when the curved end region of the connector element 19 is secured to the lever 26 in the region of the upper end position 30 on the lever 26.

Therefore, in order to secure the hole 31 to the hole 27, the eccentric disc 23 is fixed to the shaft 22 or positioned by proper control of the motor 20.

As for the reference point, as is clear from FIG. 6, the position of the lever 26 is close to, for example, the upper end position 30.

The position of the lever 26 is<u style="single">Range of rotation 28</u>Being in the central region of is equally feasible for the reference point.

Upon completion of the correction operation, that is, the position of the lever 26, as shown in FIG. 7, so that the component 16 is in contact with the contact surface of the electrode 14.<u style="single">Range of rotation 28</u>It is reduced to the central area of.

<u style="single">Range of rotation 28</u>The position of the lever 26 near the lower end position 29 of is also obtained after the correction operation as a function of the position of the lever 26 with respect to the reference point.

After adjusting the correction unit 17, that is, the lever 26<u style="single">Range of rotation 28</u>Resistance welding is feasible when moving in.

With the above adjustments, the reference point will be defined and will be known for robot control.

In other words, the controller of the robot is associated with the controller of the spot welding tong 1 and the correction unit 17 (that is, the tong controller) and the controller of the welding device.

The robot can then position the spot weld tongs 1 at the weld positions of the components 15 and 16 for resistance welding.

After this, the drive unit 18 and the electric motor 20 are added, as is clear from FIG.<u style="single">Range of rotation 28</u>The lever 26 moves in the direction of the lower end position 29 inside, and is first controlled to perform the correction operation.

Since the web 33 of the connector element 19 is stationary and fixed to the tong base body 4 via the eyebolt 34 and the drive device 18, the tong arm 7 and the electrode 14 are the component 16 as shown in FIG. Moved to.

The correction operation according to FIG. 3 is also achieved in that the tong arm 7 applies to the component 16 by a predetermined force. For this purpose, a force measuring sensor or strain gauge is provided, for example, in the area of the web 33.

And once a given force is reached, this will signal the tong controller.

It is also possible to perform a correction operation so that the curved end regions of the connector element 19 are adjacent on the eccentric disk 23.

This is achieved in that the connector element 19 moves to the eccentric disk 23 during the correction operation.

The screw is provided, for example, above the lever 26 or on the connector element 19 so that the abutment of the connector element 19 on the eccentric disk 23 occurs in a predetermined manner.

The rotation of the screw allows for adjustment of the abutment and thus the position of the electrode 14.

Then, the resistance welding can be performed by the main driving device 10 closing the tong arms 6 and 7 by a predetermined welding force.

As already shown in FIG. 4, the tong arm 7 is opened by the main drive 10 after the completion of the resistance welding operation of the components 15 and 16. After this, the contact surface between the lever 26 and the electrode 14 is repositioned and held on the reference point by proper control of the drive device 18.

Then, the robot can position the spot welding tongs 1 at the next welding position in order to perform each resistance welding operation.

Such configuration of the correction unit 17 and its positioning or adjustment on the spot weld tongs 1<u style="single">Range of rotation 28</u>It results in a short distance for the correction action within.

Therefore, the minimum expenditure of force with respect to the drive device 18 is obtained.

The power consumption for the motor 20 can be further minimized by using the gear 21.

In this case, the drive device 18 is configured so that the rotational movement of the electric motor 18 is converted by the gear 21 and the eccentric disk 23 is rotated by the gear 21.

However, the reduced power consumption for the motor 20 to perform the correction operation will ensure a minimum of heat load on the motor 20.

Thus, the life of the motor 20 and the overall drive 18 will be increased.

The correction unit 17 according to the present invention with respect to the spot welded tongs 1 is used in any of the configurations of the spot welded tongs 1. And, for example, C-shaped spot welded tongs 1 or C-spot welded tongs.

Therefore, it is feasible to adapt the shape of the connector element 19 to allow the correction unit 17 to be used in different spot weld tong embodiments.

The connector element 19 is, for example, a web shape, and thus the shape of the eccentric disk 23 is adapted.

<figref num="1">It is a simplified schematic diagram which illustrates the spot welding tongs at the starting position including the correction unit which concerns on this invention.</figref><figref num="2">The spot weld tongs according to FIG. 1 positioned on the workpiece are shown.</figref><figref num="3">The spot weld tong according to FIG. 1 in which the tong arm is in contact with the workpiece is shown.</figref><figref num="4">The spot welding tongs according to FIG. 1 during resistance welding are shown.</figref><figref num="5">The structure of the correction unit according to the present invention is schematically shown.</figref><figref num="6">The correction unit according to FIG. 5 at the position of the correction operation is shown.</figref><figref num="7">The correction unit according to FIG. 5 at another position of the correction operation is shown.</figref>