Electric heating – Metal heating – For bonding with pressure
Patent
1997-02-14
2000-01-04
Shaw, Clifford C.
Electric heating
Metal heating
For bonding with pressure
219 99, B23K 920
Patent
active
060112344
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a device and the use of a device for welding together at least two parts, using an arc welding or resistance welding procedure, in particular an arc pressure welding procedure, in which a first part remains stationary and a second part, held in a holding device, can be moved backwards and forwards relative to this first part by means of an actuating device in a welding head, and in which the second part can be aligned relative to the first part by means of a positioning drive (manipulator) for positioning the welding head.
A device of this kind, by means of which arc pressure welding can be carried out, is already known. This latter process is used, for example, in the field of automotive engineering or automobile body assembly. In this process, a small part, for example, is welded to a larger part, and in particular a bolt is welded to a part of an automobile body. The second part is precisely aligned in relation to the first part, and this can be done by means of a known type of positioning drive (manipulator). The actuator then causes the second part to move relative to the first part, for example by executing a feed motion, possibly after first lifting up the second part. In the case of resistance fusion welding, the fusion between the two parts is generated by electrical resistance. In the case of resistance pressure welding, as the current flows through, the electrical resistance in the weld zone generates the heat necessary for the welding process. The bonding of the points to be connected is achieved by pressing the parts together. This type of welding includes, for example, also spot welding and projection welding. In the case of arc welding, an electric arc burns between the two parts, one of which is usually a welding electrode which melts during the welding process.
In the case of arc pressure welding, an electric arc is struck between the first and second parts, both of which melt at the faces in contact with the ends of the arc. Then, the second part is moved relatively rapidly towards the first part so that the two weld puddles are united. With the hardening of the combined weld puddles, the two parts become welded together. Whatever the case, the important factor here is the relative movement of the first and second parts, one of which as a rule remains stationary while the other part is moved towards it, and this feed motion may be preceded by movement in the opposite direction. The latter motion may be dispensed with if, due to its special shape, the part being fed is shortened by being partially melted away before the general strong melting of both parts commences.
In a known device used for arc pressure welding, the second part is approached to within a predetermined distance from the first part; this can easily be accomplished using either a supporting foot or a tripod. The second part, e.g. a bolt held in a welding head, which is to be welded to the first part, is exactly positioned relative to the first or base part, e.g. a car body. In this process a usually pneumatically operated carriage moves the actual welding stroke mechanism, carrying the bolt to be welded, towards the first, stationary part. The force with which the bolt is pressed against the base part when the two parts are being welded together is not freely adjustable, unless the system is mechanically converted. The supporting foot requires a free space of about 30 mm around the bolt to be welded, and no disruptive contours may be present in this space.
The welding process is initiated by triggering a preliminary welding current. Using a lifting device, usually a solenoid, and while the preliminary welding current is still being applied, the bolt is raised against a return-action device, in particular a return spring, until a fixed stop is reached. Here again, unless the system is mechanically converted, the welding stroke length can be adjusted only once.
The preliminary welding current which is applied generates a weak electric arc. The main welding current is triggered once the ma
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patent: 5252802 (1993-10-01), Raycher
patent: 5317123 (1994-05-01), Ito
patent: 5406044 (1995-04-01), Killian et al.
patent: 5662820 (1997-09-01), Schwiete et al.
Claussen Carsten M.
Ilch Hartmut
Kirchner Eduard
Kang Gregory B.
Nath Gary M.
Shaw Clifford C.
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