GB1312435A - Impact wrench with torque control means - Google Patents

Abstract

1312435 Impact wrench ATLAS COPCO AB 20 April 1971 [24 April 1970] 10174/71 Heading B3N An impact wrench having torque control means consisting of the addition of incremental displacements which occur at each impact operates as follows. The wrench is connected to a compressed air supply and throttle valve 62 depressed so that reversing valve 61 is pressurized as is the case with passages 87, 59. From passage 59 air enters cylinder 60 actuating servo piston 57 to bring the clutch halves 52, 51 of clutch shaft 30 into frictional engagement. Pressure fluid then passes through passage 87 and the bore 80 past cut-off 32 and thence to the passage 88 and to the motor inlet. The screw rotates until it has been driven against a workpiece whereupon anvil 23 stops and the rotary impact motor starts impacting. Prior to each impact the inertia member is in a state of rapid rotation and when the anvil 29 at impact causes the rotor to stop, the inertia body 28 will continue its rotation performing, by reason of the oblique grooves 34, 36, and cam balls 35, an axial rearwardly directed stroke for each impact delivered. Thus piston 37 is firstly displaced freely rearwardly and thereafter returned under the bias of spring 38 entraining adding shaft 29. Uni-directional angular movements of adding shaft 29 are transmitted directly to clutch shaft 30 and via clutch halves 52, 51 to the gear 50. As a result of each reciprocation, inertia body 28 and adding shaft 29 sum up the length of displacement by unidirectional rotation and turning of gear 50, the rotation of the latter being transmitted via gear rim 63 to the drum portion 31. The turning motion forces pin 70 of setting drum 31 to leave the tooth as the increment lengths of the displacements generate turning movement of the adding shaft 29 and the setting drum 31, the pin 77 will be successfully displaced towards arm 90. After a sufficient number of impacts pin 77 hits arm 90, lever 84 is unlatched and the motor cut-off is released so that it can fall into the middle portion of the bore 80, thus closing the air supply to the motor inlet. On release of throttle valve 62 and the release of pressure in passage 87, closing bias against piston 79 disappears and spring 81 returns the cut-off to an open position. Relief of passage 59 relieves servo piston 57 and annular springs 58 displace axial pin 56 away from cross-pin 53. This allows spring 55 to move pin 53 and clutch half 52 away from clutch half 51, the gear 50 thus becoming released for free rotation on clutch shaft 30. This allows tensioned spring 67 to return the setting drum 31 back to the start position. The initial setting of pin 77 is controlled by locking-plate 71. In an electrically driven wrench the cut-off would preferably be by a conventional solenoid-actuated switch.