Lift ignition welding device

Abstract

Welding device for welding a bolt (1) to a workpiece (2) by means of an electric arc according to the lift ignition welding process, comprising - a case (3), - Means of generating a welding current, - a bolt holder (5) attached to the housing (3) for holding the bolt (1), - an electrical conductor arrangement (6) for conducting the welding current, wherein the conductor arrangement (6) has a contact surface area (7) which is designed to be positioned electrically in contact with the workpiece (2), wherein the conductor arrangement (6) is fixedly connected to the housing (3) or is resiliently mounted on the housing (3) or is designed as part of the housing (3), characterized in that the welding device further - a protective gas bell (20) as well as - comprising a magnetic coil (8) or several magnetic coils for generating a transverse magnetic field (9) acting on the arc, wherein the conductor arrangement (6) is designed as part of the protective gas bell (20).

Description

[0001] The invention relates to a welding device for welding a bolt to a workpiece using an electric arc according to the lift-arc welding process.

[0002] In stud welding with lift ignition, according to the state of the art, as in Fig. Figure 7a shows that the welding circuit is closed by a ground cable 100 connected to the workpiece 101 by means of a ground clamp 105 and bolts 102. Therefore, at least one ground cable 100 is attached to the workpiece 101 and connected with a - in Fig. 7a, only vaguely sketched, - the stud welding gun 103 or a stud welding head closes the required welding circuit to form the stud welding process. It is further known that - as in Fig. Figure 7b outlines how better welding results can be achieved by symmetrically applying two corresponding ground connections. However, in practical welding applications, especially with complex component geometries, it is often not possible to establish a symmetrical ground connection as shown in Figure 7b. Fig. 7b outlined, to implement. With a one-sided or asymmetrical ground connection, the arc is controlled by the magnetic field of the welding current, as shown in Fig. 7a, indicated by an arrow, is deflected to one side (blowing effect). This poses a practical problem, as the weld quality of elements welded under blowing effect is significantly reduced.

[0003] Document GB 795 481 A describes a stud welding process under shielding gas. Document DE 27 13 288 A1 describes a stud welding machine. Document DE 26 47 845 A1 describes a stud welding gun with multiple contact surface areas for electrically contacting a workpiece. Document 10 2004 051 389 B4 describes a stud welding process with a transverse magnetic field acting on the arc. Document DE 102 21 387 C1 describes stud welding with an asymmetrically generated magnetic field. Document US 4 182 949 A describes an underwater stud welding machine. Document DE 20 14 189 A describes a stud welding process with a protective collar for electrically contacting a workpiece.

[0004] EP 1 649 962 A1 discloses a stud welding process using a radially symmetrical magnetic field (SRM: stud welding in a radially symmetrical magnetic field). The use of a radially symmetrical magnetic field significantly reduces the undesirable effect of blow-through. This allows for simplified ground clamping on the component. However, even with an asymmetrical ground connection in the SRM process, blow-through can negatively affect the quality of the weld.

[0005] The invention is based on the objective of providing a corresponding improved welding device; in particular, the welding device should enable the achievement of high-quality welded joints with particularly simple handling.

[0006] This problem is solved according to the invention with the subject matter specified in the independent claim. Specific embodiments of the invention are specified in the dependent claims.

[0007] According to the invention, a welding device is provided for welding a stud to a workpiece using an electric arc according to the lift-arc welding process. The welding device comprises a housing, means for generating a welding current, a stud holder mounted on the housing for holding the stud, and an electrical conductor arrangement for conducting the welding current. The conductor arrangement has a contact surface area designed to be electrically contacted on the workpiece. Furthermore, the welding device comprises a magnetic coil or several magnetic coils for generating a transverse magnetic field acting on the electric arc, as well as a shielding gas bell, wherein the conductor arrangement is designed as part of the shielding gas bell. The conductor arrangement is either rigidly connected to the housing, resiliently mounted on the housing, or designed as part of the housing.

[0008] This offers the advantage that clamping a ground connection to the workpiece is not required to set the bolt. This significantly simplifies the handling of the welding device. Furthermore, the conductor arrangement allows for a particularly symmetrical ground connection. This reduces or practically eliminates blow-by, resulting in a particularly high-quality weld.

[0009] As previously described, the welding device has one or more magnetic coils to generate a transverse magnetic field that acts on the arc. This allows a magnetically moving arc to be generated in accordance with the SRM process, enabling the use of a reduced welding current to produce the weld. This reduces the maximum current density of the welding current and thus the risk of damage, particularly to the workpiece or conductor assembly.

[0010] Preferably, the conductor arrangement extends at least partially inside and / or outside the magnetic coil. This makes the conductor arrangement particularly suitable as part of a protective gas bell.

[0011] Preferably, the contact surface area has a ring shape extending around a longitudinal axis defined by the bolt holder. This allows for a particularly symmetrical welding current flow. In the SRM process, this ensures that the current takes the shortest path during the arc's rotation phase at every deflection angle. Furthermore, the design is preferably such that the contact surface area—viewed in a cross-section perpendicular to the longitudinal axis—extends to cover the projection of the magnet coil(s), particularly to form a magnetic air gap. This is especially advantageous with regard to achieving a particularly symmetrical magnetic field generated by the magnet coil(s).

[0012] Alternatively, the contact surface area can be provided with at least two, preferably three, contact surface areas extending within an annular region that runs around the longitudinal axis. This has the advantage that a suitably symmetrical contact can be achieved particularly easily, even in the case of small irregularities on the surface of the workpiece.

[0013] Preferably, the design is such that the conductor arrangement is resiliently mounted parallel to a longitudinal axis defined by the bolt holder relative to the housing. This is advantageous with regard to establishing a reliable and uniform electrical contact between the conductor arrangement and the workpiece, particularly in the case of an uneven workpiece surface.

[0014] Preferably, the design is such that the contact surface areas are each arranged to be resiliently movable relative to the housing, independently of one another. This makes it particularly suitable for compensating for a certain degree of misalignment of the welding device with respect to the workpiece surface.

[0015] Preferably, the welding device further comprises a control unit for controlling the welding current, the design of which is such that the control unit releases the welding current depending on a pressure acting between the conductor arrangement and the housing. This makes it possible, in particular, to prevent the welding process from being initiated if the welding device presses against the workpiece surface with a contact force that is below a certain suitable minimum value. It also makes it possible to interrupt a welding process if the contact force decreases during the welding process so that it falls below the minimum value, for example, if the welding device is accidentally lifted from the workpiece surface.This prevents, in particular, the formation of an arc between the conductor assembly and the workpiece in the event of the welding device lifting off during a welding process, and thus prevents damage to the conductor assembly and / or the workpiece.

[0016] Preferably, the welding device further comprises several pressure sensing elements connected to the control unit for detecting pressures between each of the contact surface portions and the housing. The design is preferably such that the control unit can only switch on the welding current if each of the pressures exceeds a certain minimum value. This ensures that a welding process can only be initiated or released if all contact surface portions are pressed sufficiently against the workpiece. This results in particularly reliable symmetrical contact. Furthermore, the design is preferably such that the control unit switches off the welding current as soon as one of the pressures falls below the specified minimum value. This allows for a suitable safety shutdown.

[0017] Preferably, the welding device further includes a measuring arrangement connected to the control unit for measuring the electrical resistance between the workpiece and the conductor arrangement. This ensures that a welding process can only be initiated if the contact resistance is sufficiently low. Excessive contact resistance can be caused, for example, by corrosion or residues on the workpiece. Furthermore, preferably, the design is such that the control unit switches off the welding current as soon as the electrical resistance exceeds a certain minimum value. This also provides a suitable safety shutdown.

[0018] Preferably, the welding device further comprises a ground wire and a supply wire for conducting the welding current, both mechanically connected to the housing, with the ground wire and the supply wire being mechanically connected to each other. This is advantageous with regard to the handling of the welding device, as it eliminates the need for a separate ground cable.

[0019] Preferably, the welding device also has one or more release buttons for a two-hand control.

[0020] The invention will be explained in more detail below with reference to an exemplary embodiment and the drawings. The drawings show: Fig. 1 a sketch of an embodiment of a welding device in which the conductor arrangement is designed as part of a shielding gas bell, Fig. 2a an embodiment according to the invention in which the conductor arrangement is formed in conjunction with an SRM magnetic field coil, Fig. 2b an embodiment according to the invention with improved electrical contact area, Fig. 3a to 3c Sketches of different possible configurations of the conductor arrangement, each showing the path of the welding current, Fig. 4 a sketch of the electrical contact area, viewed normal to the longitudinal axis of the bolt holder, Fig. 5 a sketch of an alternative design with three contact surface area proportions, Fig. 6a to 6c Sketches of designs with spring elements acting between the housing and the conductor arrangement, and Fig. 7a and Fig. 7b Sketches of a welding device with a mass connection to the workpiece according to the state of the art.

[0021] Fig. Figure 1 shows a cross-sectional sketch of an embodiment of a welding device. In this figure, Fig. Figure 1 shows only a front end section of the welding device. The welding device could be, in particular, a welding gun or a welding head.

[0022] The welding device is designed to join a bolt 1 to a workpiece 2 by means of an electric arc according to the principle of lift-arc welding. Here, "bolt" is generally understood to mean a bolt-like welding element suitable for lift-arc welding, such as a threaded bolt, a pin, or a bushing.

[0023] The welding device has a housing 3, the front end of which is in Fig. 1 is only schematically indicated. The "front end area" of the housing 3 refers to the area of ​​the housing 3 that points towards the workpiece 2 during the welding process.

[0024] Furthermore, the welding device includes means for generating a welding current for the welding process; these means can be, as in Fig. 1 schematically indicated, comprising a welding power source 30.

[0025] Furthermore, the welding device has a bolt holder 5, mounted on the housing 3, for holding the bolt 1. The bolt holder 5 can, in particular, be connected to a movement device for carrying out the welding process according to the principle of lift-arc welding, as is known per se from the prior art.

[0026] The welding device further comprises in particular a control device for controlling the welding power source 30 and the movement device, wherein the control device is in particular designed to trigger the welding process by appropriately controlling the welding power source 30 and the movement device.

[0027] Furthermore, the welding device comprises an electrical conductor arrangement 6 for conducting the welding current, wherein the conductor arrangement 6 has a contact surface area 7 designed to electrically contact the workpiece 2 for the welding process. Accordingly, it is provided that, for the welding process, the conductor arrangement 6 with its contact surface area 7 is brought into contact with the workpiece 2, or pressed against the workpiece 2 with a contact pressure, such that a suitable electrically conductive connection for the flow of the welding current during the welding process is established between these two parts 6 and 2. Naturally, the bolt holder 5 and the conductor arrangement 6 are not directly electrically connected to each other.

[0028] As in Fig. As indicated in Figure 1, the bolt holder 5 can accordingly be electrically connected via a first electrical conductor 31 to a first pole, for example the negative pole of the welding power source 30, and the conductor arrangement 6 can be connected via a second electrical conductor 32 to a second pole, for example the positive pole of the welding power source 30. Naturally, a switch, push button, or the like can be provided in the first electrical conductor 31 and / or in the second electrical conductor 32.

[0029] The conductor arrangement 6 is either rigidly connected to the housing 3, spring-mounted to the housing 3, or designed as part of the housing 3. For example, it can be, as in Fig. 1 is sketched as part of a shielding gas bell 20 of the welding device. In this way, handling during welding is made easier, because – compared to the prior art mentioned above – the need to clamp a ground clamp to the workpiece 2 before the actual welding process is eliminated.

[0030] Furthermore, the aforementioned ladder arrangement 6 improves the conditions for the welding process, as it allows the mass connection to be designed in a particularly suitable symmetrical manner, which is especially advantageous with regard to the blowing effect.

[0031] The protective gas bell 20 and the conductor arrangement 6 can be designed as a closed ring with respect to a longitudinal axis L defined by the bolt holder 5. In this way, the contact surface area 7 can also be designed as a circle or rotationally symmetrical with respect to the longitudinal axis L or the bolt holder 5. This allows for a particularly symmetrical mass connection, which is especially advantageous with regard to the blow-out effect.

[0032] The design can be such that the contact surface area 7 is located relatively close to the bolt holder 5, thus providing a "local ground connection". For example, the radial distance a between the bolt holder 5 and the conductor arrangement 6, with respect to the longitudinal axis L of the bolt holder 5, can be less than three times or twice the radial extent r of the bolt 1, preferably less than the radial extent r. This is advantageous with regard to the symmetry of the electric field conditions.

[0033] However, due to the generally relatively high currents used in stud welding, a ground connection – as in Fig. As outlined in Figure 1, the shielding gas bell 20 is not always without its problems. For example, due to a one-sided arc, the current can concentrate in an area with better contact – despite the symmetrical design – leading to an increased current density in that area. This poses a risk of damaging the workpiece 2 and / or the shielding gas bell 20 or the conductor arrangement 6.

[0034] To reduce this risk, it is advantageously provided that – as in Fig. 2a, as sketched, the welding device also includes a magnetic coil 8 for generating a transverse magnetic field 9 acting on the arc, for example, as is known per se from the aforementioned document EP 1 649 962 A1. This makes the welding device suitable for an SRM process. By using a correspondingly magnetically moved arc, conditions are created that are advantageous with regard to the effect of the conductor arrangement 6 according to the invention, because the required welding current can be reduced by more than 50%. This reduces the maximum possible current density and thus decreases the susceptibility to damage.

[0035] Instead of or in addition to the magnetic coil 8, several magnetic coils may be provided.

[0036] The combination of the magnetic coil 8 and the conductor arrangement 6 is hereinafter also referred to as the “SRM unit”. In order to minimize the electrical contact resistance between the SRM unit and the workpiece 2, it is preferably provided that the conductor arrangement 6 – as shown in Fig. 2b is sketched – to be designed with a material having high electrical conductivity in the contact area between the SRM unit and the workpiece 2. Here, "contact area" refers to a portion of the conductor arrangement 6 that is located in front of a plane oriented perpendicular to the longitudinal axis L, which defines a front boundary of the magnetic coil 8 or coils; in other words, a front end region of the conductor arrangement 6 that extends in front of the magnetic coil 8 or coils. When the welding device is positioned in contact with the workpiece 2 as intended for the welding process, this contact area is thus located between the magnetic coil 8 or coils on the one hand and the workpiece 2 on the other.

[0037] This contact area is preferably made of a non-magnetically conductive material. This creates a so-called magnetic air gap, which, when welding on a magnetically conductive base material (steel), has a positive influence on the SRM process in practice, as it prevents the magnetic field generated by the magnet coil 8 from concentrating at a point with particularly good contact. In particular, this ensures that small irregularities on the surface of the workpiece 2, which could otherwise lead to uneven contact, have virtually no negative effect on the symmetrical formation of the magnetic field. Alternatively, the contact area 7 can also be coated with a highly electrically conductive material.

[0038] In the Fig. Figures 3a to 3c show different embodiments of the ground connection or the conductor arrangement 6, and the resulting current waveforms 4 of the welding current are indicated by thick arrows. In the case of the Fig. In the embodiment sketched in 3a, the conductor arrangement 6 extends predominantly within the magnetic coil 8, in which Fig. 3b outlined version predominantly outside the magnetic coil 8 and in the Fig. The embodiment sketched in 3c is shown both inside and out. In each case, the contact surface area 7 is preferably designed such that, viewed in a cross-section perpendicular to the longitudinal axis L, it extends over the projection of the magnetic coil 8. This is advantageous with regard to the formation of the aforementioned magnetic air gap.

[0039] The time-averaged current flow of the welding current resulting from the SRM process in conjunction with a ground supply symmetrically integrated into the SRM unit by the conductor arrangement 6 is in Fig. Figure 4 is shown schematically, which depicts a representation in a plane perpendicular to the longitudinal axis L. In the Fig. In the embodiment shown in Figure 4, the ground contact is uniformly distributed around the circumference. The contact area 7 thus has a circular ring shape that extends symmetrically around the longitudinal axis L. With this design, the current can flow along the shortest path during the arc's rotation phase at any deflection angle.

[0040] Fig. Figure 5 shows, in an analogous representation, an alternative, preferred variant in which the contact surface area 7 has at least two, preferably three, and in particular exactly three contact surface area portions 10, which extend within an annular area around the longitudinal axis L. Preferably, these contact surface area portions 10 are uniformly distributed over the annular area, i.e., in the case of exactly three contact surface area portions 10, each defining a 120° angle with respect to the longitudinal axis L. In particular, it can be provided that the contact surface area portions 10 extend further forward with respect to the annular area, so that separately raised contact points are formed which, when contacted with the workpiece 2, constitute the only contact points.This promotes symmetrical contact even with small irregularities on the surface of the workpiece 2, because the risk of the welding device tilting when contacting the workpiece 2 is particularly low due to this design. The welding current is distributed evenly across the three contact area portions 10 during the welding process.

[0041] As exemplified in the Fig. 6a and Fig. As sketched in 6b, the design is further preferably such that the conductor arrangement 6 is resiliently mounted parallel to the longitudinal axis L relative to the housing 3. For this purpose, the welding device can in particular have at least one spring element 21, for example in the form of a compression spring acting parallel to the longitudinal axis L, which, for example, as in the Fig. 6a and Fig. 6b indicated - is arranged acting between the magnetic coil 8 and the conductor arrangement 6.

[0042] This makes it possible to establish a particularly suitable electrical contact between the conductor arrangement 6 and the workpiece 2. In particular, this allows – similarly to the method described in Fig. The design shown in 5 achieves a particularly uniform contact in the case of an uneven surface of the workpiece 2.

[0043] Furthermore, advantageously, in such a spring-mounted embodiment of the conductor element 6, the welding device comprises a pressure sensing element for detecting the pressure prevailing between the conductor arrangement 6 and the housing 3 or the magnetic coil 8, wherein the design is such that the control device releases the welding process depending on the pressure detected by the pressure sensing element. In particular, the design can be such that the welding process can only be released or triggered by the control device if the detected pressure exceeds a certain predetermined minimum value.

[0044] In this way, it is particularly important to prevent the welding process from being carried out if the contact pressure exerted by the welding device on the workpiece 2 is insufficiently low. In particular, this ensures that the spring force generated by the at least one spring element 21 must be overcome before the welding process is initiated. For example, it can be provided that the spring force – as in Fig. 6b indicated - up to a stop element 28 that is fixed in position relative to the housing 3 must be overcome before the welding process can be initiated.

[0045] As in Fig. As indicated in 6c, in the case of an embodiment with several contact surface area portions 10, the design is such that the contact surface area portions 10 are each arranged to be resiliently movable relative to the housing 3 or to the magnetic coil 8 independently of each other, in particular by several corresponding spring elements 24.

[0046] If multiple contact surface area portions 10 are provided, the welding device preferably has several corresponding pressure sensing elements connected to the control unit for detecting pressures between each of the contact surface area portions 10 and the housing 3 or the magnetic coil 8. The design is preferably such that the welding process can only be enabled by the control unit if each of these detected pressures exceeds a certain corresponding minimum value.

[0047] A suitable "spring-loaded ground connection" ensures that the welding process can only be enabled or triggered when proper contact is established between the conductor arrangement 6 and the workpiece 2, with sufficient contact pressure. For evaluation purposes, a switch 22 can be used, or – in the version according to Fig. 6c - several switches 23 can be provided accordingly.

[0048] The spring-loaded mass feed makes it possible, in particular, to compensate for any misalignment of the welding device by the at least one spring element 21 or the spring elements 24. This is especially advantageous in the case of a welding gun.

[0049] It is also possible to design the device such that the welding current is switched off by the control unit as soon as any of the pressures falls below a specified minimum value. This ensures, in particular, that the welding process is interrupted as soon as the welding device is accidentally lifted from the workpiece 2 during the welding process. This measure prevents an arc from forming between the contact surface area 7 and the workpiece 2 when the welding device is lifted during the welding process, and thus prevents damage to the workpiece 2 and / or the conductor assembly 6. In this way, a safety shutdown can be implemented.

[0050] This safety shutdown and welding release can also be implemented using spring-loaded, movable tripod rods equipped with switches, to which the combined magnetic field / shielding gas unit is attached, or using force sensors to measure the axial contact force.

[0051] Furthermore, the described design ensures that an uncontrolled triggering of a welding process is prevented. For example, when reloading a bolt, a short circuit could occur if the bolt accidentally bridges the gap between the bolt holder 5 and the conductor assembly 6. A short circuit would, in principle, activate the welding process, and the welding process could also be unintentionally started manually by accidentally pressing a trigger button on the welding device. Accordingly, the design – as described above – is preferably such that the welding process can only be released or triggered after applying a corresponding force parallel to the longitudinal axis L, i.e., in the "axial direction".

[0052] Furthermore, the welding device can advantageously include a measuring arrangement connected to the control unit for measuring the electrical resistance between the workpiece 2 and the conductor arrangement 6. In particular, it can be provided that this measuring arrangement determines the resistance indirectly by measuring the electrical voltage. This voltage increases as soon as a contact is broken.

[0053] This ensures that the welding process can only be enabled or initiated once a sufficiently low contact resistance has been established between the conductor arrangement 6 and the workpiece 2. This prevents a welding process from being initiated if the contact resistance is too high. Such an increased contact resistance can occur, for example, due to corrosion or residues on the workpiece 2. In particular, the design can also be such that the control unit switches off the welding current as soon as the electrical resistance exceeds a certain minimum value. This also serves as a safety shutdown mechanism.

[0054] Preferably, the welding device further comprises a ground wire mechanically connected to the housing 3 and a supply wire for conducting the welding current, both mechanically connected to the housing 3, wherein the ground wire and the supply wire are mechanically connected to each other. Accordingly, the ground wire is preferably electrically connected to the conductor arrangement 6. In particular, the ground wire can extend from the welding power source 30 to the welding device in a single bundle with the supply wire. This greatly simplifies handling, as it eliminates the need for a separate ground cable.

[0055] Preferably, the welding device also includes one or more release buttons for two-hand operation. Two-hand operation with an additional release button on the welding device is advantageous with regard to safety during operation and enables a sufficiently high level of safety, even without a spring-loaded ground contact.

[0056] The described radial grounding system represents a process improvement, particularly in magnetically driven arc welding. Here, the arc can execute the desired magnetically excited movement under especially favorable ground symmetry conditions. Due to the symmetrical grounding, the weld circle has a constant length, regardless of the arc's position. The elimination of a separate ground connection significantly simplifies handling. The welding device according to the invention, with its consistently defined ground connection, enables particularly uniform conditions and thus reproducible welding results.

Claims

[1] Welding device for welding a bolt (1) to a workpiece (2) by means of an electric arc according to the lift ignition welding process, comprising - a case (3), - Means of generating a welding current, - a bolt holder (5) attached to the housing (3) for holding the bolt (1), - an electrical conductor arrangement (6) for conducting the welding current, wherein the conductor arrangement (6) has a contact surface area (7) which is designed to be positioned electrically contacting the workpiece (2), wherein the conductor arrangement (6) is fixedly connected to the housing (3) or is resiliently mounted on the housing (3) or is designed as part of the housing (3), characterized by that the welding device further - a protective gas bell (20) as well as - comprising a magnetic coil (8) or several magnetic coils for generating a transverse magnetic field (9) acting on the arc, wherein the conductor arrangement (6) is designed as part of the protective gas bell (20). [2] Welding device according to claim 1, wherein the conductor arrangement (6) extends at least partially inside the magnet coil (8) and / or outside the magnet coil (8). [3] Welding device according to claim 1 or 2, wherein the contact surface area (7) has a ring shape extending around a longitudinal axis (L) defined by the bolt holder (5). [4] Welding device according to claim 3, wherein the design is such that the contact surface area (7) - viewed in a cross-section normal to the longitudinal axis (L) - extends to cover the projection of the magnet coil (8) or the magnet coils. [5] Welding device according to claim 1 or 2, wherein the contact surface area (7) has at least two contact surface area portions (10) which extend within an annular area which extends around a longitudinal axis (L) defined by the bolt holder (5). [6] Welding device according to one of the preceding claims, wherein the design is such that the ladder arrangement (6) is resiliently mounted parallel to a longitudinal axis (L) defined by the bolt holder (5) relative to the housing (3). [7] Welding device according to claim 5, in which the design is such that the ladder arrangement (6) is resiliently mounted parallel to a longitudinal axis (L) defined by the bolt holder (5) relative to the housing (3), wherein the contact surface area portions (10) are each arranged to be resiliently movable relative to the housing (3) independently of each other. [8] Welding device according to claim 6 or 7, further comprising - a control device for controlling the welding current, wherein the design is such that the welding current is released by the control device depending on a pressure acting between the conductor arrangement (6) and the housing (3). [9] Welding device according to claim 7, further comprising - a control device for controlling the welding current, wherein the design is such that the welding current is released by the control device depending on a pressure acting between the conductor arrangement (6) and the housing (3), and - several pressure sensing elements connected to the control unit for detecting pressures between each of the contact surface area parts (10) and the housing (3). [10] Welding device according to claim 9, wherein the design is such that the welding current can only be switched on by the control device if each of the pressures exceeds a certain minimum value. [11] Welding device according to claim 10, wherein the design is such that the welding current is switched off by the control device as soon as one of the pressures falls below the specified minimum value. [12] Welding device according to any one of claims 8 to 11, further comprising - a measuring arrangement connected to the control device for measuring an electrical resistance existing between the workpiece (2) and the conductor arrangement (6). [13] Welding device according to claim 12, wherein the design is such that the welding current is switched off by the control device as soon as the electrical resistance exceeds a certain minimum value. [14] Welding apparatus according to one of the preceding claims, further comprising - a ground wire mechanically connected to the housing (3) and a supply wire mechanically connected to the housing (3) for conducting the welding current, wherein the ground wire and the supply wire are mechanically connected to each other. [15] Welding apparatus according to one of the preceding claims, further comprising - one or more release buttons for a two-hand control.

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