Patent GB-683792-A (GB)
Title: Improvements in or relating to automatic overload release clutch mechanism
IPC: F16D45/00
Filed: 1951-01-11
Abstract: 683,792. Overload release clutches. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Jan. 11, 1951 [Jan. 14, 1950], No. 812/51. Class 80 (ii). A fixed shaft 2, Fig. 1, has mounted rotatably and axially slidably thereon a reversing sleeve 5 carrying rotatable driving and driven gears 3, 4 connected by disengageable, resilient, lostmotion means, operative in both directions of rotation. A lost motion connection transmits drive from the gear 3 to a toothed intermediate member 14, engaged by a pawl 12 on a pawl shaft 10 in an auxiliary member 8 slidably keyed to the reversing sleeve 5. A pin 29 on the auxiliary member 8 engages recesses in two spring-interconnected discs 6, 7, Fig. 4, also having two other recesses engaged by a pin 26 on the driven gear 4. The pawl shaft 10 passes through a slot 11, Fig. 3a, in the driven gear 4, the end of the pawl 12 having a pin 18 engaging with cam grooves in a spring mounted plate 19 on the said driven gear, the interconnection being such that on overload the relative movement between the driven gear 4 and the auxiliary member 8 causes the pawl 12 to be lifted out of engagement with the teeth on the intermediate member 14. Driving connection between the gears 3, 4 is thus interrupted. The reversing sleeve 5 is axially movable with respect to the driving gear 3 by spring-urged balls 53, 54, Fig. 5, co-operating, as shown, with flanges 49, 50 on the sleeve, or by other means, so that reversal of the direction of rotation of the driving gear moves the reversing sleeve either to the left or to the right in Fig. 1. A toothed flange 38 on the reversing sleeve may thus be engaged in the manner of a claw coupling with one or other of two members 39, 40 each connected by freewheel means (as shown, ball in recess means) to a rotatable drum 41. The senses of rotation of these two freewheels are opposed to each other, and whichever is operative prevents the driven gear 4 being rotated backward by an overload. A switch member 44 is integral with the drum 41 and on overload of the mechanism engages with one or other of two switches 46, according to the direction of rotation, these switches controlling the driving means to reverse the direction of rotation or stop the prime mover, or alternatively to give a warning signal. In normal operating conditions, the reversing sleeve 5 is engaged through the flange 38 with one or other of the toothed coupling members 39, 40. On overload, the pawl 12 disengages the drive between gears 3, 4, as already described, and the tension of the springs between the discs, 6, 7 drives the drum 41 backwards through a limited travel by means of the appropriate freewheel until one of the switches 46 is engaged, further backward rotation then being prevented by the said switch. The drive between the gears 3, 4 can be re-engaged by removing the overload or alternatively by reversing the direction of rotation of the input gear. In one modified form of the invention, not shown, driving and driven gears are interconnected by means similar to those described above, but the reversing member, although axially slidable, is non-rotatable on its supporting shaft. Reverse rotation of the auxiliary member, when the drive is disengaged, is prevented by an additional pawl on the pawl shaft engaging a dish-shaped member normally restrained from rotation by its spring-urged engagement through a claw coupling with the non- rotatable reversing sleeve. Ball means serve to move the reversing sleeve axially, and disengage the claw coupling, on reversal of the direction of rotation of the input gear. In a further modification, not shown, an additional pawl on the pawl shaft engages with a fixed toothed wheel to prevent reverse rotation of the driven part when the clutch is overloaded, a cam on the end of the pawl shaft co-operating with cam grooves in a rotatable member, coupled by means of axially directed pins to the slidable member of .a claw coupling, to thereby control the pawls. The other member of the claw coupling is integral with the driven gear. The axially slidable reversing member co-operates with the claw coupling to momentarily disengage it on reversal of the direction of rotation of the input gear. The claw couplings may alternatively be replaced by magnetic _ couplings. The device is particularly applicable to machine tools.