Patent ID: 7681584

Claim:
A system disconnector for physically disconnecting an upstream liquid system with an upstream inlet pressure from a downstream liquid system with a downstream pressure, said upstream and downstream pressures defining a pressure difference, the system disconnector comprising: an outlet valve, said outlet valve being adapted to open and close depending on said pressure difference between the upstream and the downstream liquid system; an upstream backflow preventer; a downstream backflow preventer; and an outlet valve body in the form of a piston arranged between said upstream and downstream backflow preventers, said outlet valve body moving in an opening and a closing direction; wherein a space is defined upstream of said upstream backflow preventer, said space being exposed to said inlet pressure of said upstream liquid system; a medium pressure space is defined between said outlet valve body and said downstream backflow preventer, said medium pressure space being exposed to a medium pressure; a space is defined downstream of said downstream backflow preventer, said space being exposed to said outlet pressure of said downstream liquid system; a biasing spring is provided acting in said opening direction of said outlet valve body; and said pressure difference at said outlet valve body between said inlet pressure and said medium pressure counteracts said biasing spring; and wherein an actuating member is provided, said actuating member limiting said medium pressure space; said actuating member has an upstream and a downstream side, said upstream side being exposed to said inlet pressure and said downstream side being exposed to said medium pressure; and two stops are provided, said actuating member being adapted to move between said two stops against the power of a spring.