Patent ID: 6019452
Filing Date: 2000-02-01
Classification: B41J

Abstract:
An ink jet apparatus comprising a pump for generating a pressure change used for sucking ink from a discharge port for discharging ink through a cap for covering the discharge port, said pump havinga cylinder,a piston shaft including an abutment surface, said piston shaft being reciprocally movable in said cylinder, anda cylindrical piston in said cylinder, reciprocally movable in said cylinder by contact with the abutment surface of said piston shaft, for forming a closed suction chamber in said cylinder by closely contacting an inner wall of said cylinder and said piston shaft when said piston shaft moves from an upper dead center to a lower dead center of said cylinder,wherein said inner wall of said cylinder is in close contact with an outer wall of said piston, and wherein a sealing rib is provided on at least one of a close contact surface of said piston against the abutment surface of said piston shaft and the abutment surface of said piston shaft, said sealing rib thereby providing close contact between said piston shaft and said piston when said piston shaft moves from the upper dead center to the lower dead center of said cylinder, wherein said pressure change is generated in said suction chamber as said piston shaft moves from the upper dead center to the lower dead center of said cylinder, and wherein close contact between said piston shaft and said piston is released when said piston shaft moves from the lower dead center to the upper dead center, thereby opening a gap between said piston shaft and said piston, the gap forming a route for expelling waste ink sucked in said suction chamber.