Warning device for dual circuit hydraulic brake systems

Claim 1

A pressure differential warning device for dual circuit brake systems of the type comprising two pistons arranged in a closed cylinder with the pressure chambers formed between the outside piston surfaces and the cylinder end walls respectively connected to the separate brake circuits and means responsive to the movement of the pistons for generating a signal when a pressure difference across the pistons causes the pistons to move toward one end of the cylinder, the warning device characterized in that the facing ends of the pistons are tapered toward each other to provide cam surfaces and by a cam follower spring biased against the cam surfaces, a normally open switch having a contact movable with the cam follower and adapted to be closed when the cam follower is moved beyond a predetermined position, and an electric signalling device adapted to be actuated by closing of the contacts, said cam follower holding said two pistons in a spaced relation with respect to each other when they are in their rest position while upon an equal increase in pressure in the separate brake circuits there results a movement of the two pistons an equal amount toward each other until the facing ends of the pistons abut each other and the cam follower is moved by the cam surfaces to a position less than the predetermined position.