Retraction mechanism

摘要

The invention relates to a retraction mechanism (7) for an electrical contact (9), the retraction mechanism characterized by comprising a drive shaft (20) with an external thread arranged to ratably drive the retraction mechanism, the drive shaft being supported by a frame (6) in a fixed position relative to the frame; a threaded collar (1008) with an internal thread arranged to engage with the outer thread of the drive shaft, the threaded collar being arranged to be moved along the drive shaft by rotation of the drive shaft and means (1000, 1009,1010) to lock the position of the threaded collar with respect to the frame.