Patent GB-939951-A (GB)
Title: Improvements relating to booster-assisted hydraulic systems
IPC: F15B3/00
Filed: 1960-04-21
Abstract: 939,951. Welding by pressure. C. R. BATES. July 21, 1961 [April 21, 1960], No. 13943/60. Class 83 (4). [Also in Group XXIX] A fluid actuated system for controlling the movement of the electrode of a spot-welding machine operating an hydraulic riveter or the ram of a deep-drawing press, comprises a double-acting master cylinder 5, Fig. 1, which delivers fluid under pressure to a double-acting slave cylinder 6 and is actuated by a booster 1 driven by a further fluid-pressure system. The booster has a diaphragm or piston 2 connected by a rod 3 to the piston 4 of the master cylinder and pneumatic fluid is supplied through a filter F, regulator P, surge tank S and lubricator L to a solenoid-operated valve V which directs the fluid above or below the piston 2 to actuate the master cylinder and move the piston of the slave cylinder which, as described, is connected to the electrode of the spot-welding machine. The ratio of the areas of the piston and rod of the master cylinder is the same as that for the piston and rod of the slave cylinder. A source of hydraulic pressure is connected by check valve 7 to the hydraulic circuit to replenish losses caused by leakage. In another embodiment, the booster has two diaphragms or pistons and pneumatic pressure selectively supplied to the upper and lower surfaces of the pistons under the control of a pair of solenoid-operated valves moves the piston of the master cylinder so that the slave piston moves in one direction with a full stroke, then in the reverse direction with a short stroke, and finally returns to its original position along the same two-directional path, the arrangement being suitable for spotwelding workpieces of re-entrant shape, such as channel-section beams. In a further embodiment having three valves V3, V4, V5, Fig. 7, in the position shown, valve V3 connects a tank T1 of hydraulic fluid to a pneumatic pressure source, and valve V4 connects the tank to the slave cylinder 6 which is thereby filled with fluid. The space above the piston 4 of the master cylinder is connected to a tank T2 and the valve V3 connects the tank to atmosphere, fluid in the tank passing through an annular recess 17 and around piston 4 when in its upper position to fill cylinder 5. When the valve V4 is operated to disconnect the slave cylinder from the tank, pneumatic pressure applied above piston 2 upon operation of the valves V3, V5 actuates the master and slave cylinders. Further operation of the valves returns the pistons 2, 4 to their upper position, the pistons of the slave cylinder being fully returned by the fluid from tank T1. The booster for use in the circuit wherein the slave piston is returned a short distance after its full stroke may comprise two pistons 2, 8, Figs. 5 and 6, piston 8 having a hollow rod 10 through which air can be directed to the space between the pistons and on which is a nut 13 limiting the stroke of piston 8. Piston 2 has a rod 3 connected to the piston 4 of the master cylinder 5 and in the upper position of piston 4, a liquid pressure source is connected by passage 14, groove 15 and passage 16 to the space above the piston and by annular recess 17 to the space below the piston so that the cylinder is filled with liquid.