Patent GB-859918-A (GB)
Title: Improvements in or relating to constant speed driven shaft arrangements
IPC: F16D7/02
Filed: 1957-07-12
Abstract: 859,918. Friction clutches. SIEMENS & HALSKE A.G. July 12, 1957 [July 21, 1956], No. 22184/57. Class 80 (2). [Also in Groups XXVI and XXXIV] A constant-speed drive for teleprinters &c. comprises a helical coil spring so controlled by a centrifugal governor that its frictional engagement with a co-operating drum is adjusted to maintain the speed of rotation of a shaft substantially constant. The helical coil spring may be a torque-transmitting clutch element, or alternatively a torque-absorbing brake element (see Groups XXVI and XXXIII). In one form, a driving shaft 1, Figs. 1, 2, is formed with a boss 2 gripped by a helically wound coil spring 3 secured to a driven bush 4 freely rotatable upon the driving shaft. Fast with the driven bush 4 is a flanged sleeve 6 to which is pivoted at 7 a lever 8 carrying a mass 9. The other end of the lever 8 engages the free end 3a of the coil spring 3, and is biased leftwards of Fig. 1 by a tension spring 12 connected to one arm of a two-armed lever 11 having its other end engaged by an adjustably positioned screw 10. When the driving shaft 1 begins to rotate, at first the boss 2 transmits drive through the helically coiled spring 3 to the bush 4 and the sleeve 6. As the speed of rotation of the driving shaft increases, the mass 9 tends to move radially outwards from the axis of the shaft 1 against the bias of the spring 12, and thereby tends to unwind the helically coiled clutch spring 3 from its driving boss 2. Accordingly, slip takes place, and the driven bush 4 &c. rotates at a substantial constant speed independently of fluctuations of the speed of rotation of the driving shaft 1. In a modification, Fig. 3 (not shown), the mass 9-is radially adjustable upon the lever 8 and a spring pawl is arranged to hold the clutch permanently disengaged if the speed or rotation of the driving shaft 1 becomes excessive. In another modification, a driving shaft 20, Fig. 4, is formed with a boss 21 around which is wound a helically coiled clutch spring 22, having one end secured to a rod 23 eccentrically fast upon a driven shaft 24 and its other end secured to a rod 25 fast upon a worm-wheel 26 rotatable relatively to the driven shaft 24. The worm-wheel 26 is connected to the driven shaft 24 by a torque transmitting coil spring 18. The worm-wheel 26 has teeth of square pitch engaging teeth upon a worm 27 which it drives to rotate a simple centrifugal governor having arms 28 which fly out to engage fly-weights 29 with the inside of a stationary brake drum 19. When the shaft 20 is stationary, the coiled clutch spring 22. grips the drum 21 on the driving shaft 20. As the speed of rotation of the driving shaft 20 increases, the worm-wheel 26 drives through the worm 27 to the centrifugal governor, whose fly-weights 29 ultimately engage the brake drum 19 and thus impose a retarding effect upon the worm-wheel. The worm-wheel 26 is thus caused to lag behind the driven shaft 24, the spring coupling 18 permitting such relative rotation between the two parts, so that the clutch coil spring 22 tends to be unwound from the drum 21 and slip then occurs. A constant speed of rotation of the driven shaft 24 is thereby obtained. In another form, a driving shaft 30, Fig. 5, carries a frusto-conical friction clutch member 36 engaged by a co-operating driven clutch ring 37 connected by leaf springs 39 to a spider 38 freely rotatable relatively to a driven shaft 34. Masses 40 are secured to each of the leaf springs 39. Also fast with the driving shaft 30 is a friction cylinder 31, gripped by a surrounding helical coil clutch spring 32 having one end fast on a peg 35 secured to the clutch ring 37 and the other end fast to an arm 33 mounted upon the driven shaft 34. When the driving shaft 30 is stationary, the leaf springs 39 move the clutch ring 37 axially to engage it with the frusto-conical clutch member 36. When the driving shaft 30 begins to rotate, the frusto-conical clutch 36, 37 transmits drive and tightens the helical clutch coil 32 upon its clutch drum 31. As the speed of rotation of the driving shaft 30 increases, centrifugal force acts upon the masses 40 which move radially outwards and draw the clutch ring 37 away from the frusto-conical friction clutch member 36. The masses 40, leaf springs 39 &c., forming a centrifugal governor, then rotate substantially freely of the driving shaft 30 and the driven shaft 34 rotates at a constant speed.