Pressure limiting pneumatic valve for commercial vehicle brakes - has spring biased piston with poppet valve and unloading valve element built into end sections

摘要

A pneumatic pressure limiting valve has a main poppet stage (17) that controls the flow from a supply (14) to a load (16). The poppet is formed in a cylindrical piston (4) that is subjected to a spring force on one side and pneumatic pressure on the other. A second valve stage (38) is formed at the end of the piston and has a section (12) that locates against a seal (40) set into the read. A small piston (31) provides a safety relief function. When the pressure limit is reached the main poppet closes. Unloading is provided by the small piston valve. ADVANTAGE - As soon as it leaves its normal position, the piston immediately changes over to the closing position of the first seat valve, the effective surface of the piston part additionally coming into operation. Undesired intermediate positions of the piston in the closing path are avoided. Upon return of the piston to the normal position, the safety valve is used without hindrance to change the effective surface of the piston part without exerting pressure. The piston is then ready for the next accelerated switching movement.