Patent GB-1002279-A (GB)
Title: Improvements in and relating to motion changing mechanisms
IPC: F16H29/22
Filed: 1962-03-09
Abstract: 1,002,279. Variable speed ratchet gearing; cams. C. F. PRINS. March 9, 1962 [March 14, 1961], No. 9140/62. Headings F2D, F2K, F2Q and F2U. The throw of a compound eccentric 12-13, Fig. 1, oscillating a follower 14 is controlled by centrifugal weights so that as the speed of the driving shaft 11 increases the two elements 12-13 of the eccentric are relatively rotated to increase the throw to a maximum which may be limited by an adjustable stop. As shown, the driving shaft 11 has fixed thereto two opposed eccentrics 12 each carrying an eccentrically bored element 13 engaged by a forked follower 14, the two followers oscillating in anti-phase and acting through friction ratchet gearing comprising metal straps 27 to rotate an output shaft 23 at a variable speed. Each compound eccentric 12-13 is controlled by a respective centrifugal system comprising weights or links 18, 19 pivoted together at 20 and pivoted to arms 16, 17 respectively fixed to the shaft 11 and the element 13. The two centrifugal systems are coupled by a slotted bar 22 on the shaft 11 receiving the two pivot pins 20. As the speed of shaft 11 increases, the throw of the eccentrics and hence the speed of output shaft 23 increases from zero to an adjustable maximum determined by the engagement of a stop 24 on the element 13 with a stop 25 on a boss 26 which is adjustably fixed on the shaft 11. On overload of the shaft 23 the centrifugal systems allow the throw of the two eccentrics to decrease-if necessary to zero-as shaft 11 continues to rotate. In a modification allowing the maximum throw, and hence the speed of an output shaft, to be adjusted during drive, a driving shaft 43, Fig. 5, carries two compound eccentrics 44-45 controlled by a common centrifugal system 50, the maximum eccentricity being limited by a stop 80 engaging a stop 81 on a boss 83 corresponding to the boss 26 in Fig. 1. Stops 85, 86 interengage when the eccentricity is zero. The boss 83 is fast with a cage 92 coupled for rotation with the shaft 43 by the arms of a spider 89 engaging a helically-splined portion of the shaft, the spider being mounted in a bearing in a threaded ring 100 engaging an internal thread on a rotatably adjustable housing 93. Hence adjustment of housing 93 moves the spider 89 along the helically-splined portion and thereby effects relative rotation between the boss 83 and shaft 43. The centrifugal adjustment of each element 45 is effected by U-shaped weights 64 moving radially between the spokes 62, Fig. 6, of a flywheel 59 loosely mounted on a boss 53 of the shaft 43. A chain 86 adjustably secured at one end to the boss 53 passes over pins 71 on the weights and under pins 70 on the flywheel spokes, the chain lying between the axiallyspaced parts of the flywheel 59 and having its free end secured to a pin 70 so that the flywheel rotates with the shaft. As the weights 64 move outwards the chain causes relative rotation between the flywheel 59 and boss 53, this being conveyed to both elements 45 through shoes 67 on arms 55 of the elements, the shoes engaging slots in side plates 56 of the flywheel. The movements of the weights 64 are coordinated by two freely rotatable washers 77 having slanted guides, Fig. 7 (not shown), through which pass the pins 71 of the weights, the ends of pins 71 engaging radial guides 72 in the plates 56. Each compound eccentric 44-45, Fig. 3, acts through a bearing 47, follower 46 and pivot 48 to oscillate a friction ratchet comprising a strap 35 which is articulated at 36 and held at 37, the strap embracing the output boss 39. The strap has adjustment means 41 and spring return means 42. The two compound eccentrics thus act on the single output shaft to produce continuous rotation at a speed which increases from zero to a maximum which may be varied during rotation by adjustment of housing 93. As previously the speed ratio is automatically reduced on overload. In a further construction. Fig. 10 (not shown) the stop 81 is secured on the shaft 43 by clamping means which can only be adjusted when the shaft is stationary.