GB278793A - Improvements in and relating to variable electric condensers - Google Patents

Abstract

278,793. Hall, A., and Ferranti, Ltd. July 8, 1926. Wireless tuning-apparatus, adjustment devices for.-A variable condenser operated by reduction gearing has indicating means associated with the operating member and further indicating means associated with the movable element of the condenser, so that a direct and a magnified indication. of movement in the position of the latter is obtained throughout its range, the two indicating means being coaxial. One construction is shown in elevation in Fig. 1 and in section on the line A-A in Fig. 3. The spindle c of the movable element of the condenser carries a toothed wheel d which meshes with a pinion e rigid with an intermediate toothed wheel f. mounted on a fixed spindle h. Engaging with the wheel d is a driving-pinion g fast with a spindle o, to the upper end of which is attached the operating-knob r. Coaxial with the spindle o is a sleeve i carrying a crank m which engages a pin n on the toothed wheel d fixed to the condenser spindle c. The sleeve j carries a pointer which indicates on a fixed dial p the position of the moving element of the condenser. The knob r carries a second pointer which gives a magnified indication on the same dial. In order to prevent backlash a gear wheel may be formed of two identical gear-wheel elements 2, 3, Fig. 5, having between them a spring 4 which tends to cause relative rotation. The element 2 is fixed to the driving or driven sleeve 6<a>, the element 3 being free to rotate thereon. An alternative means of preventing backlash is shown in Fig. 6, in which the intermediate wheel unit comprising wheels 7, 8 is mounted on an eccentric pin 9, which may he rotated and locked in position by a screw 10 so as to throw the wheel 8 closer into mesh with the pinion 11. The wheel 7 has its teeth cut at an angle to the axis and is thrust axially by a spring 13. In a modification the condenser spindle is actuated by means of epicyclic gear at its lower end, the spindle being bored axially to take the operating-spindle. The upper end of the condenser spindle carries the direct indicating pointer.