GB721389A - Improvements in or relating to fly-back mechanisms - Google Patents

Abstract

721,389. Converting rotary into reciprocating or oscillatory motion. MILLEDGE, S. Z., and FRENCHAY PRODUCTS, Ltd. July 30, 1953 [May 16, 1952], No. 12479/52. Classes 80 (1) and 80 (3). A mechanism which provides a reciprocatory or oscillatory movement of a carriage from a continuous rotary movement is particularly applicable to the scanning of a series of cam members in the selecting mechanism of a multi-channel radio tuning apparatus. As shown in Figs. 1 and 4, a carriage 13 carrying a follower 12 cooperating with a series of cam discs 11 on a tuning condenser spindle 10 is guided for reciprocatory movement along a rotating screw 14 and a guide rod 27. Connection between the thread of screw 14 and the carriage 13 is provided by a toothed wheel 24, Fig. 4, which is mounted upon a spindle 23 on the carriage 13 which spindle carries an arm 25 having a projecting pin 26 thereon. The carriage 13 is biased by a spring 22 towards the right and from the position shown it will be moved freely by the spring since the pin 26 has disengaged from the guide 27 and the toothed wheel 24 is free to rotate and rolls along the screw 14 as a rack. When the carriage 13 reaches the right hand position against a boss 29 the pin 26 has made approximately one complete revolution to come into contact again with the guide rod 27. The free rotation of wheel 24 is thereby prevented and the carriage 13 moves to the left as a nut on the screw 14. On the carriage reaching its extreme left hand position the pin 26 disengages again to allow return movement of the carriage to the right again under the action of spring 22. A modified arrangement for obtaining an oscillatory motion is shown in Fig. 5, the driven carriage comprising an arm 36 rotatable about the axis of a driving sun gear 33. A planet wheel 37 rotatably mounted on the arm 36 engages the sun gear 33 and carries an arm 38 with a projecting pin 39 which co-operates with a segmental guide disc 41. When the sun gear 33 is driven continuously anti-clockwise the arm 36 is alternately driven anti-clockwise with the pin 39 engaging the guide 41 and clockwise under the action of a return spring 43 when the pin 39 disengages from the guide 41 to allow the pinion 37 to roll freely backwards on the sun gear 33. In both arrangements the return movements may be effected by gravity instead of springs and the toothed wheel 24 or 37 may be acted upon by a brake or detent which is operated by limit stops adjustable to vary the length or angle of stroke.