Failure warning switch for dual circuit braking system - has double piston between circuits which is moved by differential pressure when one circuit fails

摘要

The warning switch for a vehicle twin circuit braking system has two connections (15,16) for the two sections of the braking circuit. The two connections are at the inlet ends of two cylinders (11,14) containing pistons (12,13) which meet at a central point (19) when the pressure is equal in the two sections. Above the central point is located a plunger (22) with a diaphragm (32) resting on it. When one circuit section fails, so that there is no pressure in that half, pressure in the other half pushes the two pistons sideways so that a sloping part (20,21) lifts the plunger. This raises the diaphragm and a collar (31) on which it is mounted, against the force of a spring (33) and enables contacts (34) mounted on the diaphragm to close a warning circuit. The cover (26) over the spring can be returned manually to re-open the switch contacts.