GB1151775A - Resistance Welding Equipment. - Google Patents

Abstract

1,151,775. Resistance welding. RUBERY' OWEN & CO. Ltd. 1 Nov., 1967 [5 Aug., 1966], No. 35284/66. Heading B3R. An electrode supporting mechanism for electric resistance welders comprises a firststage fluid pressure ram for bringing the electrode up to the work and a second-stage fluid pressure ram for applying squeezing pressure to the electrode for the welding operation wherein both rams are sequentially controlled through a single common four-way valve 20, and in which the supply of pressure fluid from the four-way valve to the end 11 of the first stage ram which causes an advance of the electrode towards the work passes through a changeover valve 21 which, when moved to a changed-over condition, cuts that end of the first-stage ram off from the four-way valve and admits to that end pressure fluid at a pressure higher than that available at the four-way valve, or which is at least enough to produce a greater force on the piston 1 of the first-stage ram than the maximum opposing force that can be applied to the other side of that piston from pressure fluid passing through the four-way valve. The first-stage ram comprising piston 1 and cylinder 16 has a low pressure inlet 15 to chamber 13 supplied directly from the four-way valve 20, and an inlet 12 to chamber 11 supplied through the change-over valve 21 from the fourway valve 20. The change-over valve is also directly connected to a source of high-pressure fluid from which the four-way valve is also fed via a pressure-reducing valve 22. The secondstage ram comprises a piston 7 and cylinder 2 formed by the hollow piston-rod of the first-stage ram. A passage 14 links the chamber 13 with the chamber 10 of the second-stage ram such that these chambers are always so interconnected irrespective of the positions of the rams. The chamber 9 of the second-stage ram is fed from the four-way valve via an inlet 5 and a bored piston-rod 3 attached to the piston 1 and opening into the chamber 9. In a modification (Fig. 2, not shown), the piston-rod 3 passes through piston 1 and is attached to piston 7. A pressure-switch 23 initiates the supply of current and welding cycle timing upon a predetermined pressure being attained in chamber 9. Three different modes of operation are described according to the settings of a wafer-switch and the use of a foot-pedal (T). The four-way valve 20 and change-over valve 21 may be solenoid operated.