Patent GB-523408-A (GB)
Title: Improvements in and relating to welding apparatus
IPC: B23K11/00
Filed: 1939-01-04
Abstract: 523,408. Welding motor vehicle doors &c. BRIGGS MANUFACTURING CO. Jan. 4, 1939, No. 276. Convention date, May 23, 1938. [Classes 83 (ii) and 83 (iv)] An automatic multiple welding machine, particularly for spot welding the outer to the inner panels of motor vehicle doors, comprises a work carriage moved from a loading station to a position in registration with a number of welders having electrodes arranged in an electric welding circuit, means operated in timed relation to the movement of the carriage for moving the work from the carriage into operative relation with the electrodes, and means controlled by the lastnamed means in timed relation to the movement of the work of the carriage for closing and opening the welding circuit. The work 81 is placed at station 67 between the shoulders 80 of a pair of members 75 on a carriage 66 which is provided with track rollers 72 and is moved by a piston rod 105 carrying a compressed air piston controlled by a needle valve, over a track 69 into a position over a vertically movable platen 83 by which the work is transferred from the carriage into contact with the' electrodes F, F<SP>1</SP>, Fig. 13, of a multiple welding head. The carriage is also provided with a second similar work support 76 having shoulders 96 at one end, which receives the work after welding and transfers it to an unloading station 68. The carriage has side bars 73 engaging the inner sides of the track rods to prevent lateral displacement and dash pots are provided at the ends of the track to cushion the carriage at each. end of its travel. Guide plates 82 are fixed to the track at the loading station to locate the work laterally. The platen is provided with a lifting member 89 in spaced sections so that it may be raised between the side bars of the carriage and of shape corresponding to the contour of the work and having spaced projections 90 to centre the work. The platen is moved vertically by a compressedair piston 85 being guided by stanchions 87 and raises the work into contact first with spring-pressed clamps 91, Fig. 12, and then with the electrodes F, F'. When the work is removed from supports 75 the carriage is returned to loading station so as to receive a new work piece. When welding is completed the platen is lowered and the welded article is received on the supports 76, whereupon the carriage moves forward again, the completed article being pushed by the shoulders 96 over rollers 99 on each side of the track at the unloading station 68, and the new work piece then raised into contact with the electrodes. The welding head consists of a number of groups of electrodes F, F<SP>1</SP>, each group of which is operated successively by hydraulic pressure as controlled by a rotary distributing valve and including two compressed-air operated switches, as described in Specification 523,407. The distributing valve is rotated by a motor M through reducing gear. The fixed electrodes F<SP>1</SP> in the present case are separate from the movable electrodes F and engage the marginal portion of the inner panel Da. The operation is started by a push button switch 111, Fig. 9, arranged at the loading station. This energizes a coil 133 so as to close a relay 112 which is held closed by a latch 121 when the switch 111 is released. A circuit is thus completed through an electromagnetic coil 113 so as to operate a valve 116 to connect the pipe 106 to a supply 117 of compressed air and thus move the carriage from the loading station to place the work over the platen. As the carriage reaches this position it closes a limit switch 122 on the track so as to energize a coil to close relay 123 and thus energize an electromagnetic coil 125 to operate a valve 128. The switch 123 is held closed by a catch 124. The platen is then moved vertically to raise the work to the electrodes. As the platen rises it first releases a limit switch 119 so as to render the push button circuit inoperative and by means of a projection 130 closes a switch 129 on one of the stanchions so as to energize a circuit containing a coil 132 which raises the latch 121 and so releases the relay 112 to reverse the valve 116. The carriage 66 is thus connected to the pipe 107 and is returned to loading position. On further movement of the platen a projection 130<SP>1</SP> closes a switch 136 so as to put in operation the motor M which rotates the distributing valve and thus starts the welding cycle. The motor also rotates a shaft-carrying a contact disc 137. The welding operation is stopped by a projection 138 on the disc opening a switch 139. A second projection 140 on the disc then closes a switch 141 so as to energize a solenoid 143 and thus release the latch 124 so as to de-energize the solenoid 125, whereupon the platen is lowered to place the completed article on the support 76. In order to maintain the platen raised until the support 76 is in position under the electrodes the circuit containing the switch 141 has in series therewith a switch 150, which is secured to the track and is closed by the support 76 when it reaches the required position.