GB820970A - Improvements in or relating to indicator transmissions - Google Patents

Abstract

820,970. Indicating-apparatus; barometric gauges. SMITH & SONS (ENGLAND) Ltd., S. Nov. 25, 1957 [Dec. 7, 1956], No. 37490/56. Classes 106 (2) and 106 (4). [Also in Group XXIX] Indicating-apparatus comprises a spring blade 27 arranged to move in response to a variable and to engage a fixed abutment 28 so shaped that during one direction of movement a progressively increasing length of resilient blade 27 engages it whereby the stiffness of the spring 27 varies with its deflection in accordance with a given law. Applied to a speed indicator for a boat, pressures S and V+S derived from a pitot head mounted under the boat are applied above and below a flexible, non-resilient diaphragm 19 with a comparatively rigid centre plate 25 supporting the spring blade 27 by means of a boss 26. The centre line of the blade 27 makes line contact with a rib 28 so shaped that the deflection of a pointer 37 will be directly proportional to the speed. For fine adjustments of zero the blade 27 may be adjustably mounted on the boss 26 so as to be movable along a spindle 29 in the transmission or the spindle 29 may be adjustable in length. To avoid errors due to changes in temperature, the chambers above and below the diaphragm 19 communicate with spaces 23, 24 and the volume of the resulting spaces on opposite sides of the diaphragm are arranged to be substantially equal and subject to similar ambient temperature conditions. To enable the pointer 37 to be set to a datum position, a horizontal shaft 30 in the transmission may be carried in a pivoted frame 44 which can be rocked by a crank-pin 47 manipulated by a knob 50.