Patent ID: 7527073

Claim:
Backflow preventer ( 1 ), which can be inserted into a gas or liquid line ( 2 ), comprising a closing body ( 3 ) embodied as a hollow body open on a drainage side, which limits a passage channel ( 5 ) between the closing body and a central closing body counterpart ( 4 ), the closing body ( 3 ) being displaceable by a flow medium flowing through the passage channel ( 5 ) in a flow direction (Pf 1 ) from a closed position, contacting the closing body counterpart ( 4 ) in a sealing manner, into an open position against a restoring force of an elasticity and/or a stability of the closing body, the closing body ( 3 ), in an unstressed closed position, initially contacts only a partial or edge region ( 6 ) of the closing body counterpart ( 4 ) with a partial region embodied as a sealing lip ( 12 ) of the closing body and can additionally be pressed against the closing body counterpart ( 4 ) with a partial region of a longitudinal extension thereof under a pressure of the fluid flowing against the flow direction (Pf 1 ), opening a downstream buffer volume for back flowing fluid, the closing body ( 3 ) is located at a fixed position, at a peripheral edge ( 10 ) thereof, relative to the closing body counterpart ( 4 ) in the backflow preventer in the gas or liquid line, and the central closing body counterpart ( 4 ) is connected to a through flow plate ( 7 ).