Patent GB-639640-A (GB)
Title: Improvements in screw driving machines
IPC: B23P19/06
Filed: 1948-04-02
Abstract: 639,640. Screw-driving machines. THOMSON MANUFACTURING CO., J. L. April 2, 1948, No. 9370. Convention date, April 4, 1947. [Class 83 (iii)] [Also in Group XXIV] A screw-driving machine comprises a base 1, a post 2 mounted on the base, a bracket 5 adjustably secured to the post, a carriage 16 actuated along vertical guideways 14 in the bracket 5 by a fluid-pressure piston and cylinder 22 carried by the bracket, a motor 32 attached to, and controlled by the position of, the carriage for driving a screw-driver 44 which depends from the motor 32, and means for delivering screws 47 one by one beneath the screw-driver. The bracket 5, Fig. 4, is vertically adjustable on the post 2 by screw-and-nut means 3,8 and is locked in adjusted position by bolts 7. The carriage 16 is guided by inturned ends 15 on the guideways 14, which are formed on a channel-shaped extension 12 of the bracket 5, and the motor 32 is clamped to the carriage by a strap 31. A rearward extension 17 on the carriage is connected to the lower end of a vertical piston-rod 20, the piston of which operates in the cylinder 22 and is moved to raise or lower the carriage 5 by supplying pressure-fluid to the corresponding end of the cylinder 22. When the carriage descends, it releases a spring-loaded bell-crank switch 151, Fig. 1, and thereby energizes the motor 32 to rotate the top part 78, Fig. 5, of an overload.-clutch, the other part 77 of which is normally urged into engagement therewith by a spring 76. This part 77 is keyed to a spindle 70 which carries an adjustable bearing-nut 71 for the spring 76 and is supported in a bearing 67 on an extension 34 of the motor casing. Clutch teeth 66 on the lower end of the spindle 70 co-operate with corresponding clutch teeth 65 on a shaft 41 ; the two parts 65, 66 are normally spaced apart by a spring 81 acting on an extension spindle 80 integral with the shaft 41. The screw-driver 44 is held by a spring- pressed ball 48 in a socket in the shaft 41 and is slidably and rotatably mounted in a sleeve 52 carried from the extension 34. Screws are fed one by one from a ratchet-operated device 101, Fig. 1, down a shoot 103 and past a separator 104 permitting the passage of one screw at a time into a slot 105 formed between a pair of grippers 106 which are held together by L- shaped springs .108 secured to a block 112. This block is slidable from an upper position, in which it receives a screw, to a lower position, in which the screw is just above the level of the work, on a rod 113 fixed in the end 121 of a side plate 122 carried by the bracket 5. The end 115 of a shaft 114, which is adjustably secured by a set-screw 120 to the end 121, serves as a stop to limit downward movement of the block 112 caused by the downwardly-moving carriage 16 engaging a spring-pressed pin 131 carried by the block; the spring 132 of the pin 131 bears on the block 112 and causes downward movement of the block against the action of a return spring 125 connected between the block and the plate 122. When the block 112 is at the top of its travel, the grippers 106 receive a screw from the shoot 103, the device 101 and selector 104 being adapted to function automatically as the carriage is actuated by linkage 1020, 1041, 1043, 102, Fig. 1. As the carriage is lowered, the screw-driver is rotated by frictional contact between the spindles 70, 80 and locates itself in the slot in the screw; if desired, a spring-pressed plunger 137, Fig. 7 forming part of a work support 136, locates a nut 135 beneath the work-piece W. Continued lowering of the carriage 16 engages the clutch parts 65, 66 and rotates the screw-driver 44 to feed the screw 47. When the screw-driver encounters excessive resistance, the spring 76 allows the overload clutch 77, 78 to slip. The operator then operates the fluid-pressure valve to raise the carriage 16, cause the spring 81 to disengage the clutch 65, 66, and allow the spring 76 to re-engage the clutch 77, 78. The motor 32 is stopped when the carriage contacts the switch 151.