Dual brake system fault detection device

Claim 1

A fault detecting device for a vehicle dual brake system having brake actuating means, a front brake system including a front master cylinder and front wheel cylinders, a rear brake system including a rear master cylinder and rear wheel cylinders, conduit means operatively connecting said master cylinders to apply braking fluid pressure to said wheel cylinders to brake said vehicle in response to operation of said actuating means, and regulating valve means provided in said rear brake system for regulating the braking fluid pressure applied in said rear wheel cylinders, said fault detection device comprising an alarm circuit including signal means for providing an indication of a fault in said system upon actuation of said circuit, first and second pressure-sensitive switches each operatively associated with said alarm circuit and adapted to be switched between a circuit activating condition and a circuit deactivating condition in response to pressure applied thereto, said first pressure-sensitive switch being connected to sense pressure in said rear master cylinder and to switch to said circuit-activating condition when said rear master cylinder pressure reaches a predetermined level, said second pressure-sensitive switch being connected to sense a difference between master cylinder pressure and wheel cylinder pressure and switch to said circuit deactivating condition when the sensed difference reaches a predetermined level, said alarm circuit being operative to generate a fault-indicating signal when both said switches are in the circuit-activating condition.