GB514481A - Improvements in means of adjusting rotatable control spindles - Google Patents

Abstract

514,481. Wireless receiving sets. COLE, Ltd., E. K., and SHACKELL, A. April 8, 1938, Nos. 10750 and 16811. [Class 37] [Also in Group XXIV] A coarse and fine tuning adjustment comprises an epicyclic friction gear between the control knob 14 and the spindle 2 of the variable tuning-element 1, wherein fine tuning is obtained by rotation of the knob in either direction until a member 15 on the knob strikes an abutment 16 connected to the reaction member 7 of the gear, whereafter the entire gear rotates to give a direct drive for coarse tuning. The gear comprises a reaction member constituted by a cup 7 mounted freely on the shaft 2 and normally prevented from rotation by frictional engagement with a fibre washer 6 on the condenser end plate 3. A differential assembly 9 is secured to the spindle 2 and comprises two dished wheels 12, the hubs 11 of which frictionally engage the lip of the cup 7 while the wheel edges are in frictional engagement with a sleeve 4, to which the knob 14 is attached and which rotates on the spindle 2. Thus rotation of the knob rotates the discs 12 in opposite directions, and the assembly 9 rotates, together with the tuning spindle 2, at a much reduced speed, by means of the hubs 11 which travel round the rim of the cup 7. When the member 15 on the knob 14 strikes projection 16 on the cup 7, the friction between cup 7 and fibre washer 6 is overcome and the entire gear rotates as a direct drive. The only unbalanced reaction in the gear is that due to the axial pressure of the members 11 on the cup 7, and this reaction provides the necessary frictional engagement between the cup 7 and washer 6. The contact between members 15 and 16 may be used electrically to mute the receiver while tuning, or to disable the A.F.C. circuits.