GB723036A - Torque responsive stud tightening machine - Google Patents

Abstract

723,036. Screwing-up nuts &c. FARMER, H. E. April 28, 1952 [May 17, 1951], No. 10639/52. Class 83 (3). A machine for tightening screwed fasteners, particularly for tightening the cap screws of engine bearings in pairs with selected equal torque, comprises a pair of spindles 78 carrying sockets 80, a differential mechanism 54 for dividing the torque supplied by an electric motor equally between the two spindles and an electronic control system for disconnecting an electromagnetic clutch 28 (not shown), in the motor drive and for retracting the spindles when the torque on the screws reaches the selected value. The drive from the clutch is connected by a worm shaft 30 and stub shaft 52 to the spider 54 of the differential gear and pinions 56 journalled in the spider mesh both with a pinion 62 on an inner shaft 64 and a pinion 58 on an outer tubular shaft 60. The shafts 60, 64, separately drive shafts 66, 68, in which the socket spindles 78 are splined for reciprocable movement by a pair of hydraulic rams 86 controlled by a solenoid-operated valve 98 (not shown). On closing a starter pushbutton, with the driving motor already run. ning, relays are operated to engage the clutch 28, disengage a brake 136 (not shown), on shaft 30 and, after a delay which allows the differential to run up to operating speed, set the hydraulic valve so that the spindles are lowered to engage the sockets with the cap screws. The differential then divides the torque from the shaft 30 equally between the spindles so that when the input on one spindle is half the desired torque, the spindle stops, while the other spindle continues to rotate until its input also reaches half the torque. A valve supplied with adjustable bias from a pair of rectifier valves is fitted in the control system and one of the leads of the driving motor is in circuit, through a transformer. with the bias circuit so that when the current consumption of the motor corresponds to the desired torque, the bias is overcome and the valve then conducts current to operate the relays and thus disconnect the clutch 28, apply the brake 136 so that the momentum of the differential does not cause over-tightening, and change over the hydraulic valve so that the spindles 78 are withdrawn upwards. Reference has been directed by the Comptroller to Specification 687,616.