Stud-welding circuit with a plurality of outputs

A stud welding machine features several welding outputs for welding tools with different polarity for various welding operations. The polarity of at least one welding output is reversible.

This is a continuation of application PCT/DE90/00599 filed on Aug. 3, 1990. 
The invention concerns a stud welding machine with several welding outputs 
for welding tools with different polarity for various welding operations. 
A stud welding machine exists which supports several welding outputs, four, 
for example, that do not possess a different polarity. The disadvantage, 
therefore, lies in the necessity of changing connections of the welding 
cables. Such controllers are not optimally suited for the application in 
connection with robotically-operated welding tools or the like in transfer 
lines. 
The invention is based on the creation of a controller which makes it 
possible that the polarity of the welding outputs will adjust itself 
according to given welding operations at the time. 
Since the polarity of all welding outputs can be reversed, the controller 
is therefore able to adjust to different welding operations without 
changing the connections of the welding cables. Especially when the 
reversing of the polarity of the welding outputs is controllable, for 
example, through a program or remote control, is such stud welding machine 
excellently suited for employment in connection with robot-operated stud 
welding tools in transfer lines. 
Further developments of the invention are demonstrated in the following 
claims. 
The invention is subsequently further explained with reference to a drawing 
of a demonstrated execution example.

The stud welding machine features a direct current source 1, where the 
positive pole is connected via line 2 with a conductor 3. Four 
controllable electronic switches in the form of silicon controlled 
rectifiers or thyristors 4, 5, 6, and 7, for example, are connected with 
their ends to this conductor. The cathode connections of these thyristors 
are connected with plug connections 8 of the welding outputs AG1, AG2, 
AG3, and AG4. These welding outputs are generally fashioned of special 
sockets. Should the control electrodes 9 be applied to voltage via 
non-represented switches, which are located at the controller for hand 
operation or on the welding tool for remote control, the thyristors are 
switched to a transmission state. Through this the plug connections 8 
receive positive potential. 
As illustrated at the welding output AG1 the welding tool is connected in 
such a fashion that the stud to be welded 10 shows positive potential for 
a certain welding operation. 
The negative pole of the direct current source 1 is connected via a line 11 
to a conductor 12. The cathodes of the controllable electronic switches in 
the form of silicon controlled rectifiers or thyristors 13, 14, 15, and 16 
are connected to this conductor 12. The anodes of these thyristors are 
connected via plug connectors 17 of the welding outputs AG1, AG2, AG3, and 
AG4. The workpiece 18 is connected to the plug connector 17 of the welding 
output AG1, to which the stud 10 is to be butt-welded. The workpiece 18 is 
grounded, as usual. 
Preferably the stud welding machine is equipped in such a way that all four 
welding outputs are only temporarily successively usable. To this end a 
non-represented controller is built-in, which only switches a welding 
output on each time its respective welding tool establishes the electrical 
circuit to the welding current first. 
Furthermore, the negative pole of the direct current source 1 is connected 
via a line 20 to a conductor 21. The controllable electronic switches in 
the form of silicon controlled rectifiers or thyristors 22, 23, 24, and 25 
are connected with their cathodes to this conductor 21. The anodes of 
these thyristors are connected with the plug connectors 8. Their 
controlled electrodes 9 are on the other hand accessed just like those of 
the thyristors 4, 5, 6, and 7. 
Furthermore, the positive pole of the direct current source 1 is connected 
via a line 26 to a conductor 27. The anodes of controllable electronic 
switches in the form of silicon controlled rectifiers or thyristors 28, 
29, 30, and 31 are connected to this conductor. The cathodes are connected 
to the plug connectors 17. 
The control electrodes 9 are connected here too in similar fashion like 
those of the other thyristors with corresponding switches at the 
controller or on the welding tool. 
Through this illustrated circuit, each of the welding outputs AG1, AG2, 
AG3, and AG4 with their plug connectors 6 and 17 can be poled in such a 
way, depending on which thyristors are switched into transmission state, 
that when the plug connector 8 is positive, plug connector 17 is negative 
or when plug connector 8 is negative, then the plug connector 17 is 
positive. 
The welding outputs AG1 through AG4 can thus be poled alternately from case 
to case according to the welding operations at hand. Such demands are 
especially made should such a controller be implemented for robot welding 
or for transfer lines. The switching on of thyristors can therefore occur 
via pre-programmed operating elements.