GB1032112A - Improvements relating to mechanisms for deriving accelerated angular displacement from subtantially continuous rotation - Google Patents

Abstract

1,032,112. Intermittent toothed gearing. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. March 5, 1963 [March 13, 1962], No. 9616/62. Heading F2Q. [Also in Division H2] In a mechanism providing rapid intermittent rotation of a Geneva star-wheel 2, particularly for rotation of a transformer tap changer, a roller 15 driving the star-wheel is carried by an operating member 3 which is driven, as by a geared-down electric motor 8, through a first lost-motion coupling comprising a driving arm 33 and driven arms 31, 32, a shaft 4 coaxially arranged within the member 3, and a second lost-motion coupling comprising a crank arm 5 of the shaft 4 and shoulders 21, 22 on the member 3, and a spring assembly connected to the crank arm 5 provides a snap-action drive which overruns that of the motor 8 and rapidly rotates the operating member only during its star-wheel rotating movement. The star-wheel 2 comprises slots 16 to receive the roller 15 and locking recesses to engage an operating member cylindrical portion 19 having the usual cut-away 17. The spring assembly comprises a pivoted cylinder 13, a piston 25 having a rod 12 pivoted on a pin 11 of the crank arm 5, and a spring 14 between the piston 25 and a collar 26 which has free movement on the rod limited by a rod abutment 27 so that the spring is pre-stressed. A hole 28 is bored in the cylinder so that when the latter is immersed in oil the piston and cylinder act as a dashpot. From top dead centre of the crank pin 11 (Fig. 2) the piston-rod movement is initially free until the collar 26 abuts the bottom end of the cylinder. The spring is then compressed until the pin 11 reaches bottom dead centre after which the spring expands and rapidly upwardly returns the crank pin. The second lost-motion coupling enables the mechanism to be used in either direction of rotation. In operation, from the starting position shown, as the motor 8 rotates, say in an anticlockwise direction, the arm 33 abuts the arm 31 to rotate the shaft 4. The rod 12 moves out of the cylinder and eventually the crank arm 5 abuts the shoulder 21 to rotate the operating member 3. The driving roller 15 enters a slot 16 at bottom dead centre of the pin 11 and spring expansion causes rapid rotation of the operating member 3 and the star wheel 2, overrun of the motor being permitted by the first lost motion coupling 33, 31, 32. Immediately the roller 15 emerges from the slot 16 the abutment 27 engages the collar 26 so that no further movement is provided by the spring and the arms 33, 32 abut at this instant. No further rotation of the operating member occurs until the arm 33 catches up with the arm 31 at completion of the cycle. The main drive by the motor 8 ensures full rotation of the star-wheel 2 in the event of spring drive failure.