Patent ID: 7968815

Claim:
A resistance spot welder comprising: a first plate; a second plate rotatably connected to the first plate through a shaft, and driven on the shaft by an actuator; gun arms, removably fixed on and electrically insulated with the first and second plates, respectively; electrode tips, confronting each other, and fixed on the gun arms, respectively; a cylindrical collar, inserted concentrically on the shaft, and being shorter than the shaft; a first bearing, including a first bearing portion adapted to be slid on the shaft; and a second bearing, including a second bearing portion adapted to be slid on the shaft, wherein a clearance for reserving a lubricating medium is formed near a central position of the shaft, the first plate includes a pair of plates which confront each other and are arranged in a first direction with a predetermined space therebetween, the actuator and a welding transformer are arranged in the predetermined space in a second direction perpendicular to the first direction, the first bearing is inserted between the shaft and the collar and includes a first flange portion radially rising on the first bearing portion, the second bearing includes a second flange portion radially rising on the second bearing portion, the first flange portion and the second flange portion are arranged concentrically on the shaft and held in contact with each other, the first plate is integrally fixed on the second bearing and the second plate is integrally fixed on the collar, and the clearance is formed near a central position between the shaft and the collar.