Patent GB-738154-A (GB)
Title: Improvements in or relating to resistance welding apparatus
Inventor: COOKE FRANK ARTHUR
IPC: B23K11/10
Filed: 1951-09-20
Abstract: 738,154. Welding by pressure. ROLLS-ROYCE, Ltd. Dec. 18, 1952 [Sept. 20, 19511, No. 22110/51. Class 83 (4). In stitch welding apparatus comprising roller electrodes and a piston and cylinder device supplied with pressure fluid through a first valve means to apply pressure between the electrodes, there is provided an indexing ratchet device operated by a second piston and cylinder device supplied with pressure fluid through a second valve means to partake alternately of idle and indexing travel in opposite senses and thus to effect stop by step rotation or at least one electrode and control means for the valve means and welding current supply such that the idle travel occurs while current is flowing and the indexing travel occurs after current is cut off. In one embodiment an arm 13, Fig. 1, supports a cylinder 30 having a piston 31 whose rod 33 carries an upper electrode 14. The lower electrode 12 is secured to a sleeve 15 rotatable on an aim 11 and carrying a ratchet wheel 16 around which a spider 17 carrying pawls 18 is rotatably mounted. An arm 19 on the spider is connected to a rod 20, Fig. 2, of a differential piston 21 in a cylinder 22 one side 23 of which is connected to a pressure source through pipe 25 and the other larger side 24 of which is connected to the pressure source or to atmosphere by a valve 27 operated by a solenoid 28. The upper side 34 of cylinder 30 is connected to a pressure source and the lower side is connected to a higher pressure source through pipe 37 or to atmosphere by valves 38 and 42 controlled by solenoids 39 and 43. The latter solenoid is operated by the closing of contacts 44 when the electrodes are separated. At the start of a welding operation solenoids 39, 43 are de-energized, the lower side of cylinder 30 is connected to atmosphere and the electrodes 12, 14 are pressed together. The solenoid 28 is de-energized and the end 24 of the cylinder 22 is connected to atmosphere. The operator's foot switch is pressed to simultaneously supply current to the electrodes and to energize solenoid 28 to allow pressure fluid in space 24 and thus to move the spider in its idle movement. A timing device cuts off the current after 16 cycles and a further timer de-energizes the solenoid 28 at the same time to vent the space 24 to atmosphere. The indexing movement of the spider tends to take place but pressure between the electrodes prevents it. The solenoid 39 is energized by a timer after a further 4 cycles to allow pressure fluid in the lower side of the cylinder 30 to relieve the pressure on the electrodes and allow the indexing movement to take place. After a further 10 cycles the solenoid 39 is de-energized by a further timer, the lower side of the cylinder 30 is vented to atmosphere and the electrodes are again under full pressure. Another timer after a further 0-8 cycles re-establishes welding current and re-energizes solenoid 28 to repeat the process. A modified form of the means controlling the movement of the upper electrode 14 is shown in Fig. 4. The space above the piston 31 is connected to a pressure source and from this source a pipe is connected to one end of a cylinder 62 for a differential piston valve 63. The space below the piston 31 is connected via a space 61 in the cylinder to a pipe 65 and atmosphere or to a pipe 66 and a highpressure source by a valve 67 controlled by a solenoid 68 corresponding to solenoid 39. The other end of the cylinder 62 is connected to atmosphere through a restrictor or a highpressure source by a hand valve 72. During welding the valve 67 connects to atmosphere and when the solenoid 68 is energized highpressure fluid flows to relieve the electrode pressure. To raise the electrode 14 the hand valve is connected to the high-pressure source to move the valve 63 to the right to connect the source via a passage 77 in the valve 63 with the cylinder 30. Specification 679,739 is referred to.