GB660695A - Improvements in shaft control devices comprising arresting discs provided on a shaftand pawls actuated by a selecting member - Google Patents

Abstract

660,695. Positive and friction clutches; stopping in predetermined positions. PHILIPS ELECTRICAL, Ltd. March 16, 1949 [March 19, 1948], No. 7231/49. Class 80 (ii) [Also in Group XL (c)] A shaft control device for bringing a member, for example the rotor 32 of a radio tuning condenser, into any one of a number of predetermined positions comprises a system of arresting discs, spring-loaded pawls and a pawl-selector shaft 30, and has a setting of the selector shaft in which the member is completely freed for manual control thereof. The arresting discs 2-6 are adjustably held on the shaft 1 of the rotor 32 by friction discs 8 fixed to the shaft, each arresting disc having a peripheral recess 7 engageable by one of the pawls 17-21. The pawl 22 is actuated when manual control is desired and co-operates with a coupling element 10 connectting the shaft 1 to a gear wheel 9 driven, through a slipping clutch 13, by a motor 14. The other ends of the pawls 17-22 co-operate with discs 23-28 secured to the pawl selector shaft 30, each disc having a peripheral recess 29 and the arrangement being such that the recesses are relatively displaced symmetrically about the shaft 30. Upon turning of the shaft 30 to the required setting, one of the pawls, all of which are pivoted on a shaft 16, is actuated by its spring 31 to enter its recess 29 and the motor 14 then drives the shaft 1 until the actuated pawl enters its recess 7 to stop the shaft, thereby causing the clutch 13 to slip. The coupling element 10 (Fig: 2) is formed with projections 52, 53 and is pivoted at 51 to the gear 9. A spring 56 engages a pin 54 in the element normally to hold the projection 53 in driving engagement with a projection 57 on a bush 11 secured to the shaft 1. Upon actuation of the pawl 22, the projection 52 engages the pawl and the element 10 is rotated about the pin 51, to disengage the parts 53, 57 and stop the wheel 9 upon the engagement of the pin 54 with the edge of an aperture 55 in the wheel. The shaft 1 may then be manually operated. In an alternative form of coupling between the wheel 9 and shaft 1, a flexible band secured at one end to the wheel surrounds a cylindrical bush on the shaft and carries at its other end a projection engageable by the pawl 22. The two ends are connected by a spring so that normally the bush is gripped by the band, but upon actuation of the pawl 22 the band is opened to release the shaft 1 and the projection engages a pin on the wheel 9 to stop its rotation. Specification 634,781 is referred to.