GB575522A - Improvements in torque limiting means for torque transmitting mechanism - Google Patents

Abstract

575,522. Overload release clutches. SINCLAIR, H. March 8, 1944, No. 4331. [Class 80 (ii)] [Also in Group XXIX] An overload release clutch adapted to maintain full engagement between the clutch members up to a critical value of the torque transmitted and then to give substantially instantaneous release, comprises dogs 54 on a flange 55 of a driven shaft 51 which engage dogs 58 on a helical toothed gear 53 mounted for rotation upon shaft 51 and engaging a gear 52 fixed on a driving shaft 50. Owing to the helical teeth on the gears 62, 53, the transmission of torque tends to move gear 53 to the left to disengage the dogs 58, 54 and gear 52, together with its shaft 50, to the right against a piston member 77. The axial movement of gear 53 is prevented, however, until an abutment ring 59, which is provided with teeth 60 co-operating with teeth 62 on a fixed ring member 63, is rotated to bring the teeth 60 and 62 out of line. The rotation of the ring 59 is effected by a spring 64, Fig. 7, but a catch lever 68 engaging a tooth 71 normally restrains such operation. The piston member 77 is subjected to fluid pressure from a'conduit 79, controlled by a restriction 81 and an exhaust port 82, which opposes movement of the gear 52 due to normal torque, but on the torque reaching a predetermined critical value, the gear moves the piston to the right to close the exhaust port 82 by a valve 83 with a resulting build-up of pressure in the piston chamber. This pressure is transmitted through conduit 90 to a bellows 91, Fig. 8, which operates the and 95 of catch lever 68 which results in the catch releasing the ring 59 which is rotated by spring 64 to allow axial movement of the gear 53 to disengage the dogs 58, 54. To reset the clutch, either the driving shaft 50 must be rocked backwards through a small angle, or the driven shaft 51 moved forward, which allows reverse-facing ratchet pawls 96 on the flange 55 to engage the teeth 58 of gear 53 and to slide the gear to the right to re-engage the dogs 58, 54. At the same time a resetting lever 99 must be actuated to engage a tooth 100 on, and move ring 59 back, to engage with the catch-lever 68 again, the gear 52 and piston 77 having been returned to their normal positions by the pressure of the fluid behind the piston. In another arrangement, the clutch is made double-acting to operate in either direction of rotation and the tripping operation is carried out electrically from a reversible driving motor. At the critical value of current corresponding to the critical torque, a relay is energized to operate, through a solenoid, the abutment ring which allows axial movement of one of the clutch members under the torque to disengage