Electromagnetically actuatable pressure modulator

Claim 1

Hydraulic braking apparatus for a wheelsupported land vehicle; said apparatus including: operator actuated first means for generating hydraulic pressure in said apparatus; hydraulically operated second means for exerting pressure to stop rotation of a wheel means; third means defining a passage for communicating hydraulic pressure from said first means to said second means, said passage including an expandable chamber having an inlet for fluid flow between said chamber and said first means; said second means communicating with said chamber independently of said inlet; a valve and first biasing means urging said valve in a direction to close said inlet; a moveable section partially defining said chamber, and second biasing means for urging said movable section in a first direction to reduce the volume of said chamber and toward operative engagement with said valve to operate same in a direction to open said inlet; fourth means to generate an opposing force that acts against force produced by said second biasing means; said fourth means including an electromagnet with a movable armature; a force transmitting mechanical device interposed between said armature and said movable section; said mechanical device being operatiavely constructed to transform a non-linear force/displacement characteristic of said armature into movement of said movable section in said second direction with a generallly linear force/displacement characteristic; a control means operatively connected to said fourth means to activate and deactivate same under predetermined conditions of deceleration for wheel means that is to be stopped by said second means; said fourth means when activated generating said opposing force thereby permitting pressure within said chamber to operate said movable section in a second direction, opposite to said first direction; operation of said movable section in said second direction serving to expand said chamber and move said movable section away from operative engagement with said valve permitting the latter to close said inlet and isolate said chamber from said first means to limit pressure applied to said second means.