GB335509A - Improvements in and relating to indicating control means for radio receivers and the like - Google Patents

Abstract

335,509. British Thomson-Houston Co., Ltd., (Assignees of Mapelsden, H. H.). May 29, 1929, [Convention date]. Adjusting wireless apparatus.-A source of light such as a lamp 39 is arranged to project a beam of light through the scale 37 so as to produce an enlarged image of the graduations &c. thereon on a translucent screen 38 spaced from the scale 37. The screen 38 may be of translucent sandblasted amber or brown celluloid, the scale 37 being of white or transparent celluloid blackened except for graduations and indices, or of metal with perforated graduations. The lamp 39 is arranged behind a shield 40 so that its filament is opposite a small orifice 41. Alternatively the lamp may be wholly enclosed in a tubular shield having one end closed by a flat plate in which is a small rectangular or other orifice. The scale 37 is carried by a segmental disc 43, which is also secured to a drum 14 mounted on the shaft 11 of the member to be controlled. The drum 14 is driven, by means of a cord 29, from a driver shaft 17 to which is fixed a knob 18 and a sheave 31. The ends of the cord 29 are passed through a hole 21 in the drum 14, tied together, and attached to the end of a spring 22 to take up any slack. Two springs at an angle may be employed, so as to leave the centre of the drum free for the shaft. The cord 29 is wrapped around the drum 14 in a helix so that it engages and leaves the drum in different planes. The cord passes over an idler pulley 30 and is wrapped about the sheave 31 for a few turns. It is then secured to the sheave, as by passing through a hole 32, and the wrapping is continued. On rotating the knob 18, the cord 29 is wound onto and unwound from the sheave 31 at the same rate, the tension of the cord being thereby maintained constant. In order to provide a stop for the driver shaft 17, a collar 55 is mounted freely thereon and carries an exially extending stud 56 and a radial stud 57. The stud 56 engages a stud 59 carried by the shaft 17, and the stud 57 engages a stud 58 carried by a bracket 19. Two complete rotations of the shaft 17 are thus permitted, and are sufficient to move the scale 37 through 180‹.