| 摘要 |
The present invention relates to a nut positioning pin disposed on a lower electrode for the projection welding of a nut, and an object of the present invention is to increase cooling and positioning accuracy, prevent the entrance of sputtering particles, and increase the detecting accuracy. The present invention comprises an electrode holder (2) of a double-tube structure having a cooling water passage, a guide ring (13) for guiding a coupling rod (7) for vertical movement, an air passage means (m) for preventing the entrance of sputtering particles, a coupling block (28) and a magnetic shield which comprise a magnetic member for preventing a magnetic detecting element from being affected by an external magnetic field. <??>The present invention is capable of accurately guiding cooling water and the coupling rod in the electrode holder and preventing sputtering particles from entering the electrode holder, and of preventing a detector from being adversely influenced by an external magnetic field for increased detecting accuracy. <IMAGE>
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