GB1208417A - Vacuum-operable units for use with ignition distributors - Google Patents

Abstract

1,208,417. 417. Timing ignition. JOSEPH LUCAS (INDUSTRIES) Ltd. Nov.1, 1967 [Nov.14, 1966], No.50875/66. Heading F1B A vacuum operable unit for use with a distribution includes a casing 1920, a diaphriam 23 dividing the casing into first and second chambers 21, 22 a plunger 26 slidably received in the first chamber 21, the plunger being secured at one end to the diaphram and extending at its other end from the first chamber for connection to the distributer so that axial movement of the plunger varies the ignition timing of the distributer, first and second conduits 41, 37 communicating with the first and second chambers respectively, first resilient means 36 within the second chamber for resisting movement of the diaphram in a direction to reduce the volume of the second chamber and sealing means 28 acting between the wall of the first chamber and the plunger to seal the first chamber while allowing relative movement between the plunger and the wall of the first chamber Second resilient means within the first chamber acts on the disphram to resist reduction of the volume of the first chamber, the diaphram being urged under the influence of the first and second resilient means to a rest position corresponding to the normal zero advance position of the distributer with which the unit is to be associated. The application to the second chamber of the varying pressure at the air inlet side of the throttle valve of the engine, during normal running of the engine, serves to control the normal ignition advance of the distributer from and retard to the zero advance position. The application of the reduced pressure at the inlet manifold of the engine, during over-run or idling conditions, to the first chamber serves to control retardation of the ignition timing of the distribution from the normal zero advance position.