Patent GB-980677-A (GB)
Title: Improvements relating to mechanisms for driving an output shaft
Inventor: WILKINS JOHN THOMAS
IPC: F16H27/04
Filed: 1960-01-29
Abstract: 980,677. Springs. ENGLISH ELECTRIC CO. Ltd. Jan. 27, 1961 [Jan. 29, 1960], No. 3325/60. Heading F2S. [Also in Division H2] Mechanism for producing repeated rotation of an output shaft in alternate senses between two latching positions of the output shaft as a result of continued rotation of an input shaft in either direction comprises resilient driving means connected to drive the output shaft, charging means for the resilient driving means and operated by the input shaft, first and second latching means for holding the output shaft in the two latching positions, and means operated by the input shaft for releasing the first latching means when the shaft is in one latching position and the resilient driving means is charged, the arrangement being such that the resilient driving means then drives the output shaft to the other latching position, where it engages with the second matching means. The input shaft 79, Fig. 2, which is driven in an anticlockwise direction by an electric motor or hand turning gear (not shown), turns a shaft 10 in a clockwise direction by means of arms 78, 178 and a Geneva wheel 77. Shaft 10 is connected through a crank 80 and connecting rod 81 to a pair of arms 76 loosely mounted on the output shaft 11. A cylinder 60 pivotally attached by pins 75 to the arms 76 contains a spring 64 which is connected through a piston 63 and a lost-motion connection 67, 68 to a piston rod 65 which in turn is connected to a crank pin 74 for driving the output shaft 11. Initially, spring 64 is in compression and tends to cause shaft 11 to rotate, rotation being prevented by the engagement of a latch face 128, Fig. 1, of a latch arm 19 with a face 44 on a latch block 43 carried by the shaft 11. The latch arm 19 is pivotally coupled to a compression spring unit 32 which is mounted on a pivot pin 36. When shaft 10 is rotated, a wheel 12 carried by the shaft acts through pin 13, slotted link 14 and pin 20 to rotate a toggle link 18 in an anticlockwise direction, whereby the latch arm 19 passes over a dead centre with respect to the link 18. This allows the spring 64 to begin to rotate the output shaft 11 in an anticlockwise direction. As the shaft 11 turns and the latch arm 19 moves downwards, a roller 30 contacts the straight face of a cam plate 40 and rides on to a part-circular face 41, thereby disengaging the latch face 128 from the face 44. Meanwhile, a pin 20 moves along the slot 16 in the link 14 until the toggle link 18 is buffered by an hydraulic stop 38, as shown in Fig. 4. The shaft 11 accelerates until the piston 63 reaches the end of its stroke and thereafter the high inertia of the system (a flywheel, not shown, is mounted on the shaft 11) keeps the shaft 11 moving at substantially constant velocity (the corresponding movement of the piston rod 65 being permitted by the lost-motion connection 67, 68). Movement of the piston 63 towards the end of its stroke is damped hydraulically by means of a plunger 73 and orifice 72. Towards the end of the rotation of the shaft 11, a roller 31 carried by a further latch arm 22 rides off the circular face 41 of the cam 40 on to the flat face 42 as shown in Fig. 4, allowing a further pivoted compression spring unit 33 to urge the arm 22 towards the latch block 43. Meanwhile, the lost motion at 67, 68 has been taken up and the spring 64 is compressed again, whereupon the shaft 11 decelerates to rest and then begins to turn in the opposite direction, finally being arrested by the engagement of a latch face 129 on arm 22 with a face 45 on latch block 43. After turning through 180 degrees, the arms 78, 178 engage the Geneva wheel 77 a second time, thereby tilting the arms 76 in a clockwise direction. The resultant relative movement between the piston 63 and the cylinder 60 compresses the spring 64 in readiness for a reverse operation of the shaft 11. When the input shaft 79 is subsequently turned in the same direction as before, it produces a reverse rotation of the output shaft 11, whereby the latter returns in a clockwise direction from the position shown in Fig. 4 to that shown in Fig. 1. As a safety measure, a further Geneva wheel 84 is operated by the arms 78, 178. An eccentric 110, Fig. 3, secured to the wheel 84 turns a sector gear 113 freely mounted on the shaft 79, whereby a pinion 114 mounted coaxially with the output shaft 11 turns through 260 degrees in each direction, normally following the output shaft 11 as the latter turns through 240 degrees in each direction without engagement of keys 115 and 116. If, say, spring 64 fails, the keys 115 and 116 engage and the pinion 114 turns the output shaft 11 to a position 5 degrees short of the normal latching position, latching then occurring at a secondary face 46 or 47. An indicator (not shown) indicates failure to achieve the normal rotation. The output shaft 11 operates the divertor switches of an on-load transformer tap-changer. For this purpose, four cranks 150, Fig. 7, spaced 80 degrees apart are driven from the output shaft 11 through gearing of unity ratio. Each crank 150 is coupled by a connecting rod 152 to a moving contact 153 pivoted at 155 and co-operating with a spring-loaded fixed contact 156 which is pivotally mounted at 157.