Patent GB-1111421-A (GB)
Title: Electrical resistance welders
IPC: B23K11/10
Filed: 1965-07-09
Abstract: 1,111,421. Welding by pressure. TEXAS INSTRUMENTS Inc. 9 July, 1965 [10 July, 1964], No. 29310/65. Heading B3R. An electrical resistance welder includes a movable electrode and apparatus for controlling the force with which the electrode is pressed against a workpiece during welding the apparatus comprising means for driving the electrode into engagement with the workpiece to produce a reaction force, means for opposing the reaction force with another force, electrically controlled means for adjusting the other force to a pre-determined value and means responsive to an overbalancing of the other force by the reaction force to prevent the means for driving the electrode from increasing the reaction force. A lower arm 11 and an upper bracket 15 extend from a housing 13, the bracket 15 having an upper member 17 and a lower member 19 connected at the outer end by a post 21 on which is slidable a sleeve 23 on a weld head 25. A rotary turret 99 is provided on the head 25 and carries a pair of parallel electrodes 101 having tips 10 with parallel sides and an electrode 103 for vertical spot welding while a rotary turret 97 on the arm 11 has a flat insulating facing 105 and an electrode 107 for vertical spot welding. Angular faces 109 are provided on the turrets to receive pincer electrodes. The sleeve 23 has an inwardly projecting arm 27 with a tongue 29 extending into a groove 31 in a platform 33 on the member 19 and the platform carries an extension 35 over the arm 27. Vertical guide posts 37 are fixed on the extension 35 on which is slidable the casing of a motor 39 having a threaded drive shaft 43 engaging a threaded opening in the arm 27. A lever 49 is pivoted to the member 17 and has a lug 51 engaging the top of the casing of the motor 39, contact between the lug and casing being maintained by a spring 53 connected to the remote end of the lever 49 and to a vertically movable scanner carrier 55. A switch 50 is provided to engage the lever 49. A screw 57 is threaded in an opening in the carrier 55 and carries at its lower end a pinion 59 and at its upper end a pinion 61, the pinion 59 meshing with a gear 71 on a motor 75 secured to die member 19 and the pinion 61 meshing with an indicating dial 69. The scanner carrier 55 has an arm 79 with a tongue 81 movable in a groove 83 in a wall 85 in the platform 33 and a block 91 on the wall 85 carries fixed scanner contacts traversed by a scanner contact 95 on the carrier 55. A programming card reader is provided in the housing 13 to read the mechanical force to be applied to the work and the energy to be employed and when such a card is inserted in the reader circuits are prepared including a certain one of the fixed scanner contacts. The insertion of a card causes the motor 75 to be actuated to drive the screw 57 and move the carrier 55 to advance over the fixed contacts until the selected one is reached. The motor 75 is then de-energized and braked electrodynamically and the spring 53 is correctly tensioned. A foot or hand switch is closed by the operator and the motor 39 is actuated to drive down the head 25 to bring the electrodes into contact with the work. The reaction force then moves the motor 39 up the posts 37 and when the reaction force overcomes the loading on the lever 49 the lever moves upwardly and operates switch 50. The motor 39 is thereby reversed and the required amount of energy is fed through the electrode.. The energy is derived from a bank of capacitors discharging through a transformer. The motor 39 then returns to its lowermost position and draws the weld head away from the work.