In robotic welding technology, there are used welding tongs with replaceable welding caps. The wear of the welding caps can be noticeably retarded by a good cooling. For this purpose cooling systems are provided which include cooling lines. In the cooling lines water is used as a cooling agent, to which glycol and further additives have been added, for instance. During replacement of the welding caps the cooling line is automatically sealed up in the region of the welding caps in order to prevent any escape of the pressurized cooling agent. As it is not possible to immediately seal up the cooling line despite the use of quick-acting stop valves, an undesired squirting of cooling agent will occur due to the pressure which continues to be present in the sealed-up portion of the cooling line.
European Patent Application EP 0 433 586 A shows a device for cooling welding caps of a welding apparatus comprising an exhaust system. Part of the cooling line is shut and completely discharged. This technique is disadvantageous because upon refill it is unavoidable that undesired air gets into the cooling line.
It is an object of the invention to provide a device for cooling welding caps, which avoids a loss of cooling agent to a large extent.