Method for welding a bolt onto a workpiece and a bolt-welding device

Method as defined in any of the preceding claims, characterized in that the level of the force can be varied.

Method as defined in any of the preceding claims, characterized in that the force is applied at least when the drive shaft (11) is slanted relative to the horizontal plane.

Method as defined in any of the preceding claims, characterized in that a position measuring system (7) is used for detecting the adjustment range of the drive shaft (11) and that said position measuring system (7) is used for detecting the position of the drive shaft (11) relative to the horizontal plane.

Method as defined in any of the preceding claims, characterized in that the force is connected when the drive shaft (11) moves in the direction toward a predetermined target position.

Method as defined in any of the preceding claims, characterized in that the force is connected and fixing the drive shaft (11) in position when the welding tool provided with the drive shaft (11) is moved relative to the work piece.

Method as defined in any of the preceding claims, characterized in that the force is a clamping force generated between the drive shaft (11) and the housing (3).

Method as defined in any of the preceding claims, characterized in that the force is applied by a hydraulic, pneumatic or electric drive.

Method as defined in any of the preceding claims, characterized in that the force is applied to the drive shaft (11) opposite the forward direction (V) of the linear drive (5).

Method as defined in any of the preceding claims, characterized in that the force is apportioned relative to the forward direction (V) of the linear drive (5) such that is performs a dampening function when the drive shaft (11) is moved to a target position.

Bolt-welding device, especially for performing the method defined in any of the preceding claims, having at least one drive shaft (11) connected to the bolt (19) to be welded, at least one linear drive (5) acting in axial direction with at least one coil (9), where the drive shaft (11) can be moved by the linear drive (5), characterized by a switchable device provided on the drive shaft (11) or the housing (3) and engaging on the housing (3) or the drive shaft (11) when connected and applying a force to the drive shaft (11) which exerts a resistance against a displacement of the drive shaft (11) at least in forward direction (V).

Bolt-welding device as defined in any of the preceding claims, characterized in that the device is a clamping device (51) acting transversely to the drive shaft (11).

Bolt-welding device as defined in any of the preceding claims, characterized in that the device is a dampening device acting in forward direction (V) and/or in an opposite direction (R).

Bolt-welding device as defined in any of the preceding claims, characterized in that the device can apply a force which can hold the drive shaft (11) fixed in a desired position in any position of the drive shaft (11) relative to the horizontal plane.

Bolt-welding device as defined in any of the preceding claims, characterized in that the device is a hydraulic or pneumatic piston-cylinder unit (29;

• 53).

Bolt-welding device as defined in any of the preceding claims, characterized by a control unit (23) controlling the coil (9) and the device.

Bolt-welding device as defined in any of the preceding claims, characterized in that the drive shaft is part of the linear drive (5), that it projects into the coil (9) and that it is provided with at least one permanent magnet (13).