WELDING TONGS

Abstract

Welding tongs (1), especially X-welding tongs (1) for resistance spot welding, with a first tong arm (11), a second tong arm (12), and a drive unit (2) comprising a motor (4) and a gearing (6) for rotating the first tong arm (11) relative to the second tong arm (12) about an axis of rotation (14) of the welding tongs (1), wherein the motor (4) and the gearing (6) are arranged coaxially and the second tong arm (12) is fastened to the housing in an abutment plane (29), which is situated on the motor side of an outer driven bearing plane of the drive unit (2).

Claims

1. Welding tongs, comprising a first tong arm, a second tong arm, and a drive unit comprising a motor and a gearing for rotating the first tong arm relative to the second tong arm secured on a housing of the drive unit about an axis of rotation of the welding tongs, wherein the motor and the gearing are arranged coaxially in the axis of rotation, and wherein the second tong arm is fastened to the housing in an abutment plane, which is situated on the motor side of an outer driven bearing plane of the drive unit.

2. Welding tongs according to claim 1, wherein the housing comprises a flange arranged between a motor housing portion of the housing and a gearing housing portion of the housing, on which the second tong arm is secured.

3. Welding tongs according to claim 1, wherein the first tong arm is mounted by at least one driven bearing of the gearing situated in the driven bearing plane and able to turn about the axis of rotation.

4. Welding tongs according to claim 1, wherein the first tong arm has a step in the direction of the axis of rotation.

5. Welding tongs according to claim 4, wherein the step of the first tong arm forms an offset, so that at least one of a working point and a work plane of the welding tongs lies on the motor side of a fastening plane of the first tong arm.

6. Welding tongs according to claim 1, wherein the second tong arm is configured without a step.

7. Welding tongs according to claim 1, wherein the gearing comprises a first gearing stage and a second gearing stage.

8. Welding tongs according to claim 7, wherein the first gearing stage is configured as a planetary prestage.

9. Welding tongs according to claim 7, wherein the second gearing stage comprises a cam disk for the driving of radially movable teeth and an internal ring gear.

10. Welding tongs according to claim 9, wherein the internal ring gear is situated between the outer driven bearing plane of an outer driven bearing and an inner driven bearing plane of an inner driven bearing of the gearing.

11. Welding tongs according to claim 1, wherein at least one of the working point of the welding tongs and the abutment plane lies on the motor side of an inner driven bearing plane perpendicular to the axis of rotation and extending through an inner driven bearing of the gearing.

12. Welding tongs according to claim 5, wherein the distance from the work plane to the abutment plane is less than 40% of the length of the drive unit.

13. Use of the welding tongs according to claim 1 for the welding of sheet metal.

14. Welding tongs according to claim 1, wherein the welding tongs are X-welding tongs for resistance spot welding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows a schematic top view of a sample embodiment of welding tongs;

[0030] FIG. 2 shows the welding tongs of FIG. 1 in a schematic side view;

[0031] FIG. 3 shows a schematic cross sectional drawing through the welding tongs of FIGS. 1 and 2.

DESCRIPTION OF SAMPLE EMBODIMENTS

[0032] In the following, typical sample embodiments shall be described, where the same reference numbers are used sometimes for the same or similar parts, sometimes also for several different embodiments. Basically, the application is not confined to the different embodiments, but instead the scope is defined by the claims. Sometimes individual parts are explained only in connection with one figure, and insofar as these parts are represented in other figures they are not necessarily described once again.

[0033] FIG. 1 shows a sample embodiment of welding tongs 1 in a schematic top view. The welding tongs 1 of FIG. 1 are so-called X-welding tongs for resistance spot welding especially of sheet metal, such as flat steel for automotive manufacturing. The welding tongs 1 comprise a drive unit 2, having a motor 4 and a gearing 6. The motor 4 and the gearing 6 are indicated only schematically by a broken line, as they are arranged inside a common housing 8. The common housing 8 is two pieces, comprising for example in embodiments (see FIG. 3) a motor housing portion and a gearing housing portion, with a flange arranged between the motor housing portion and the gearing housing portion.

[0034] The motor and the gearing need not necessarily be arranged exclusively in the respective housing portions, it may also occur in embodiments that parts of the motor or of the gearing also protrude into the other respective housing portion.

[0035] The welding tongs 1 comprise a first tong arm 11 and a second tong arm 12. The first tong arm 11 is connected to a driven element of the gearing 6, so that with the drive unit 2 the first tong arm 11 can be turned about an axis of rotation 14 of the welding tongs 1. The motor 4 and the gearing 6 are arranged coaxially to each other. Furthermore, the motor 4 and the gearing 6 are also arranged coaxially to the axis of rotation 14 of the welding tongs 1, so that an extremely compact design results.

[0036] The second tong arm 12 is fixed to the housing 8 of the drive unit 2, so that the second tong arm 12 remains stationary in regard to a system of coordinates of the drive unit 2. The second tong arm 12 is secured to the flange 9, and the abutment plane 29 is defined at the boundary surface between the flange 9 and the tong arm.

[0037] With the second tong arm, a bracket is formed as a single piece or seperately in typical embodiments, making possible a fastening of the welding tongs to a robot. In other typical embodiments, the second tong arm is fastened directly to a bracket. In other typical embodiments, the second tong arm is not fastened to the bracket, but instead an additional flange may be provided on the housing, for example, in order to fasten the welding tongs to a bracket.

[0038] In other typical embodiments, the first tong arm may also be fastened on or to a bracket, so that the overall drive unit with the second tong arm rotates about the first tong arm when the drive unit is activated. This is encompassed by the phrasing that the first tong arm rotates.

[0039] In preferred embodiments, the motor is connected directly to the gearing, especially preferably a driven shaft of the motor engages with the gearing or with a first gearing stage of the gearing. The gearing or a first gearing stage of the gearing are therefore preferably configured as a coaxial gearing.

[0040] The first tong arm is typically connected directly or indirectly in a torque-proof manner to a driven element of the gearing, such as a tooth carrier or a planet carrier. This means, in particular, that no further gearing, toothed wheels or toothed belts are interposed in between.

[0041] The first tong arm 11 of the welding tongs 1 has a first step 21 in the direction of the axis of rotation 14 in the direction of the motor 4. In this way, a work plane 25 of the welding tongs 1 is displaced relative to a first fastening plane 27 of the first tong arm 11 in the direction of the motor 4 along the axis of rotation 14.

[0042] The second tong arm 12 has no step, i.e., it is step-less. Since the second tong arm 12 is fastened to the centrally positioned flange 9, the second tong arm 12 needs no step. This increases the rigidity and reduces the required design space. The abutment plane 29 substantially coincides with the work plane 25. Substantially can mean, for example, that the distance between the work plane 25, in which the working point (not shown) lies, and the abutment plane 29 is less than the thickness of the second tong arm 12. In this application, further examples of an interpretation of substantially coincides are given in other places.

[0043] In FIG. 2, the welding tongs 1 of FIG. 1 is shown schematically in a side view. For the description of the individual parts, reference is made to the description for FIG. 1. In FIG. 2 there are additionally shown a first electrode 31 and a second electrode 32. The first electrode 31 is fastened on the first tong arm 11 and the second electrode 32 on the second tong arm 12. The tip of the second electrode 32 here forms the working point of the welding tongs 1, wherein the work plane 25 (FIG. 1) runs through the tips of the electrodes 31 and 32 and lies in the plane of movement of the electrode 31. The electrode 31 can perform a rotary movement about the axis of rotation 14, when it is driven by the drive unit 2 (FIG. 1).

[0044] FIG. 3 shows schematically a cross sectional view of the drive unit 2 with parts of the welding tongs 1. Once again, reference is made to the descriptions of FIGS. 1 and 2 for the description of many parts, axes, and planes which are also represented in FIG. 3.

[0045] The gearing is represented in more detail in FIG. 3 than in FIG. 1, but also heavily schematically. The gearing comprises a planetary gearing as the first gearing stage 6.1 and a galaxy gearing as the second gearing stage 6.2.

[0046] The sun wheel (not shown) of the planetary gearing is fastened on the motor driven shaft 36 of the motor 4. The motor driven shaft 36 thus also forms the input shaft of the first gearing stage 6.1 as a single piece.

[0047] The galaxy gearing has an inner situated cam disk (not shown), which is arranged on a shaft connected to the power takeoff of the planetary gearing.

[0048] The cam disk has two bulges, which ensure that radially movable teeth 38 come into engagement with an internal ring gear 40. The internal ring gear 40 is arranged between two driven bearings 42 and 44 of the gearing 6. An outer driven bearing 42 is arranged on the side of the internal ring gear 40 facing away from the motor, and an inner driven bearing 44 is arranged on the motor side of the internal ring gear 40.

[0049] The layout of the second gearing stage 6.2 can be found in greater detail for example in the aforementioned DE 10 2015 105 525 A1, wherein a tooth carrier 46 serves as the driven element, receiving the radially movable teeth 38. The first tong arm 11 is secured directly to the driven element, which comprises the tooth carrier 46. In this way, the first tong arm 11 is mounted by the driven bearings 42 and 44. The work plane 25 of the welding tongs 1 lies through the step 21 on the motor side of both the driven bearing plane of the outer driven bearing 42 and on the motor side of the driven bearing plane of the inner driven bearing 44.

[0050] The invention is not confined to the above described sample embodiments, for example, the second arm may be fixed to any desired side of the drive unit. Instead, the scope of the invention is defined by the claims.

REFERENCE NUMBERS

[0051] Welding tongs [0052] Drive unit [0053] Motor [0054] Gearing [0055] 6.1 First gearing stage (planetary gearing/planetary prestage) [0056] 6.2 Second gearing stage (galaxy gearing) [0057] 8 Housing [0058] 8.1 Motor housing portion [0059] 8.2 Gearing housing portion [0060] 9 Flange [0061] 11 First tong arm [0062] 12 Second tong arm [0063] 14 Axis of rotation [0064] 21 First step [0065] 25 Work plane [0066] 27 First fastening plane [0067] 29 Abutment plane [0068] 31 First electrode [0069] 32 Second electrode [0070] 36 Motor driven shaft [0071] 38 Teeth [0072] 40 Internal ring gear [0073] 42 Outer driven bearing [0074] 44 Inner driven bearing [0075] 46 Tooth carrier