| 摘要 |
The present invention relates to a nut positioning pin disposed on a lower electrode for the projection welding of a nut. The present invention increases cooling and positioning accuracy, prevents entrance of sputtering particles, and increases 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 (m) for preventing the entrance of sputtering particles, a coupling block (28) and a magnetic shield, which comprises a magnetic member for preventing a magnetic detecting element from being affected by an external magnetic field. The present invention accurately guides cooling water and the coupling rod in the electrode holder and prevents sputtering particles from entering the electrode holder, and prevents a detector from being adversely influenced by an external magnetic field for increased detecting accuracy.
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