Patent ID: 6875946
Filing Date: 2005-04-05
Classification: B23K

Abstract:
1. A device for welding, comprising: a tubular electrode holder, a lower electrode coupled to an upper end of the electrode holder and having a though hole defined centrally therein, an air cylinder coupled to a lower end of said electrode holder by a coupling block, a coupling rod disposed in a tube of said electrode holder and vertically movable when said air cylinder is operated, a positioning pin disposed on an upper portion of the coupling rod and having a tip end movable into and out of the through hole in said lower electrode when the coupling rod is vertically moved, an air blowing mechanism adapted to deliver air into an upper portion of the tube from a lower portion of said electrode holder, wherein said coupling block comprises a magnetic member, an insulation is provided between the electrode holder and the air cylinder, wherein said air cylinder has a cylinder rod with magnetic graduations, and said air cylinder has a magnetic detecting element adapted to detect said magnetic graduations and an amplifier adapted to amplify a signal from said magnetic detecting elements, wherein a magnetic shielding member covers and magnetically shields the cylinder rod with the magnetic graduations, the magnetic detecting element, and the amplifier, and wherein said magnetic member and said coupling block, or said coupling shaft is disposed such that the magnetic flux density in the vicinity of the magnetic graduations on the cylinder rod, the magnetic detecting element, and the amplifier is suppressed to 500 gauss or less.