Device for removing an electrode cap from an electrode shank

Abstract

The present invention relates to an electrode cap tripping device, which comprises at least one tripping device (1) rotatably supported around a tool rotation axis and equipped with clamping means (2, 3) for fixing an electrode cap to be removed, and which has a combination of a clamping means (2) having a straight tooth arrangement and a clamping means (3) having a helical tooth arrangement.

Description

[Technical field]

[0001] The present invention relates to an apparatus for removing an electrode cap from an electrode shank in a resistance spot welding process. [Background technology]

[0002] Spot welding is often used to join metal sheets and strips, particularly in the automotive industry where this method is used for the construction of car bodies on automated production lines.

[0003] Typically, a number of welding robots are used here to connect the body sheet metal parts to one another by spot welding, which are equipped with welding guns, the electrode shanks of which are each fitted with a spot welding electrode, a so-called electrode cap.

[0004] The welding gun is brought close to the positioned metal sheets to be welded together. The precise positioning of the welding gun with respect to the metal sheets to be welded as well as their arrangement relative to one another is nowadays automated and computer-aided. In such automated production lines, the welding process is timed as quickly as possible and takes place without interruption.

[0005] This exposes the electrode caps in particular to high wear, since their contact surfaces come into contact with the respective body sheet metal components to be welded. During the welding process, the current between the electrodes flows through the mutually contacting body sheet metal components to be welded. This causes changes in the contact surfaces of the electrode caps in the weld-affected areas of the electrode caps.

[0006] Frequently, burnt bumps, or pick-ups, form at the edges of the contact surface, which, due to the increase in the contact surface, cause changes in the welding conditions. In order not to have to counter these changes by uneconomical adaptation of the current intensity, the electrode cap is reworked by milling periodically and depending on the load on the electrode cap and the resulting wear.

[0007] For this purpose, milling devices are arranged so that the welding gun of the welding robot can reach said milling devices and the electrode caps are engaged with the respectively installed milling devices. These electrode cap milling devices are usually formed from a tool support which has at least one milling tool rotatably supported therein about a tool rotation axis and a drive for said milling tool.

[0008] In many cases, the electrodes working together in one welding gun wear to the same or similar extent, so that these electrodes must be periodically and simultaneously post-machined by milling. After multiple post-machining operations have been performed, material removal from the electrode cap has been such that the electrode cap must be replaced. For this, the worn electrode cap is pulled off from the electrode shank.

[0009] When the electrode cap is pulled off from the welding electrode shank, the electrode cap is firmly clamped with the clamping jaws on its cylindrical circumference, and then the electrode cap is rotated about its axis or about the axis of the welding electrode shank, which is held non-rotatably, and the electrode cap is pulled off from the welding electrode shank in the axial direction of the welding electrode shank.

[0010] Manual tripping personnel are known for this purpose, but such manual tripping personnel should not be deployed on automated production lines because they endanger the workforce.

[0011] A device for pulling off an electrode cap is known, for example, from German Utility Model No. 20209401. This describes a device for pulling off an electrode cap, in which the electrode cap is placed on the electrode shank with a small distance from the abutment flange of the electrode shank, whereby a groove-like free space running in the circumferential direction is created between the abutment flange and the end of the electrode cap facing the abutment flange, into which a wedge-shaped section that thickens tangentially in the direction of the width of the free space engages.

[0012] From German Utility Model No. 88 08 586 a device is known in which an electrode cap is pulled off from an electrode cap shank by means of a lever structure.

[0013] Also known is a tripping device arranged on a tool support, which has a tripping tool supported for rotation about the tool rotation axis and a drive for the tripping tool. The electrode cap is fixed by clamping jaws arranged on the tripping tool. The electrode cap is then rotated about its axis or about the axis of a welding electrode shank, which is held non-rotatably, so that the electrode cap is pulled off from the welding electrode shank in the axial direction of the welding electrode shank.

[0014] Another known solution consists in that the electrode cap is not pulled off from the electrode shank, but rather the electrode shank is pulled off from the rotating cap by opening the welding gun, in which case the cap is also fixed by means of clamping jaws, in which case the cap is rotated about its axis or about the axis of the welding electrode shank which is held non-rotatably, and when the gun is opened the electrode shank is pulled off from the electrode cap.

[0015] From DE 10 2014209 828 A1 a removal tool for removing an electrode cap from a cap support of a spot welding electrode is known, which has a tool body (24) rotatable about a rotation axis (A) during a removal operation and with an electrode cap receiving opening (56) open in the direction of the rotation axis (A) for receiving the electrode cap, a first set of clamping jaws (26) for clamping engagement on an electrode cap (20) positioned in the electrode cap receiving opening (56) at least when the tool body (24) rotates about the rotation axis (A) in a first rotation direction (R1) and a second set of clamping jaws (28) for clamping engagement on an electrode cap (22) positioned in the electrode cap receiving opening (56) at least when the tool body (24) rotates about the rotation axis (A) in a second rotation direction (R2) opposite to the first rotation direction (R1).

[0016] Known interchangeable head types according to the known prior art are primarily equipped with either jaws with straight teeth or jaws with helical teeth, where three jaws are usually used. This type of construction has the advantage that the tool or workpiece to be fastened can be well centered.

[0017] However, a disadvantage of the variant with jaws having exclusively straight toothed teeth is that when the electrode cap is removed from the gun shank, there is no or only little fixation against axial movement, and therefore, after the removal process, uncontrolled and premature loss of the electrode cap may occur.

[0018] In the modified interchangeable head variants with jaws that exclusively have helical toothing, this problem does not occur. With helical toothing, the gun shank is protected by a screw thread effect when removing the electrode cap, because the cap is pushed axially and thus away from the electrode shank by the oblique engagement of the toothing when biting into the base material. Thus, the electrode cap is quickly moved away from its seat during the interchangeable head rotation, so that less / shorter friction occurs between the contact surface of the electrode cap cone and the corresponding shank, and thus the electrode cap is fixed against axial movements.

[0019] This ensures a secure hold of the electrode cap being removed, but has the disadvantage that it increases the rotation angle required for the two-part process of gripping the electrode cap and initiating the rotational movement, reducing the effective rotation angle during the "removal phase". Summary of the Invention [Problem to be solved by the invention]

[0020] The object of the present invention is to improve a tripping device of the above-mentioned type in such a way that the disadvantages of the solutions known hitherto are avoided as far as possible and, in particular, process reliability is guaranteed. [Means for solving the problem]

[0021] According to the invention, this problem is solved by the device according to claim 1 and by claim 2. In the following, the device according to the invention is explained in more detail on the basis of the drawings and the following examples. [Brief description of the drawings]

[0022] [Figure 1] 1A and 1B are a perspective view and a cross-sectional plan view showing a tripping device 1 according to the present invention in an assembled and ready-to-use state. [Diagram 2]FIG. 2 shows a clamping means 2 with straight teeth 4 as well as a clamping means 3 with helical teeth 5, which are to be combined with one another and which are used. [Diagram 3] FIG. 2 is an exploded view of the tripping device 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The electrode cap tripping device according to the invention comprises at least one tripping device 1 which is supported rotatably about the tool rotation axis and which is provided with clamping means 2, 3 for fixing the electrode cap to be removed.

[0024] The electrode cap removal device according to the invention has a combination of clamping means 2 with straight teeth and clamping means 3 with helical teeth. In the inventive use of a mixed implementation with at least one clamping means 2 with straight teeth, this mixed implementation supports an earlier initiation of the rotational movement for the electrode cap to be removed.

[0025] The use of at least one clamping means 3 with helical toothing ensures a sufficient form-fit by biting into the copper material and thus security against uncontrolled removal of the cap / loss of the removed cap.

[0026] Thus, the combination of tooth types allows for process reliable removal, retention and placement of the electrode cap in the desired position.

[0027] In a particular configuration of the solution according to the invention, it is possible to select these clamping means such that the clamping means used are clamping means 2 or alternatively clamping means 3.

[0028] It has proved to be particularly advantageous in the use of the solution according to the invention that the solution according to the invention can also be used in tripping devices that are already in use, where the same clamping means previously used can be modified in such a way that at least one clamping means is replaced by a clamping means of another embodiment.

Claims

1. A device for pulling off an electrode cap from an electrode shank, comprising at least one pull-off device (1) rotatably supported about a tool rotation axis and equipped with clamping means (2, 3) for fixing the electrode cap to be pulled off, the device having a combination of clamping means (2) with straight teeth and clamping means (3) with helical teeth.

2. The present invention relates to a tripping device that is formed from at least one tripping device (1) that is rotatably supported about a tool rotation axis and that is provided with clamping means (2, 3) for fixing an electrode cap to be removed, and uses a combination of a clamping means (2) having a straight tooth arrangement and a clamping means (3) having a helical tooth arrangement.

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