GB708567A - Improvements in or relating to change-speed gearing for gramophones - Google Patents

Abstract

708,567. Change-speed gear. CHAPMAN, C. T. Dec. 13, 1951, No. 29224/51. class 80 (2) Change-speed means for a gramophone, of the type in which an idler disc 9, Fig. 2, carried by a displaceable spring-loaded member 6 provides a friction drive between a vertically disposed driving shaft 10 and the rim of the turntable (not shown), comprises a two-part stepped friction wheel assembly 14, 16 mounted upon the driving shaft for rotation therewith, manually operable means 23, 24 for displacing relatively the two components of the said friction wheel assembly to bring a selected friction surface into driving engagement with said disc, and detent means for locating the components in each of their several relative positions. The stepped friction wheel comprises an inner sleeve 14, Fig. 5, secured to the driving shaft 10 by a set screw 15 and a surrounding axially slidable but relatively non-rotatable body member 16 provided with the stepped portions 19, 19a, a rodlike extension 18 of the sleeve 14 passing through the apex of the body to provide a third driving surface 19b, and detent means for locating the body 16 axially consisting of a ball 20 (or alternatively a pin) urged inwards by a surrounding spring circlip 21 to engage in one of three recesses 22 in the sleeve. The body 16 is displaced axially by a pin 25 on a crank 24 engaging a groove 26 therein, the crank 24 being attached to a rotatable spindle 23 mounted in a bearing piece 28 provided with separate detent means, Fig. 3 (not shown), which can retain the pin 25 free from the sides of the groove 26 once the velocity ratio has been selected. The crank mechanism 25 &c. may be replaced by cam or equivalent means to produce the axial displacement of the body 16.