Patent ID: 7389791

Claim:
Backflow prevention device ( 1 , 1 ′), comprising a mounting housing ( 2 ) that can be inserted into a fluid conduit ( 3 ), and having at least one sealing ring ( 4 ) that is held in an annular groove ( 5 ) provided on an outer circumference of the mounting housing ( 2 ) and that provides a seal between the mounting housing ( 2 ) and the fluid conduit ( 3 ), wherein when the backflow prevention device ( 1 , 1 ′) is closed and a fluid volume is sealed at a flow outlet side, the sealing ring ( 4 ) can be shifted axially in the groove against a restoring force from a sealing position into a leakage position in order to compensate pressure, and in the annular groove ( 5 ) an annular guide segment ( 9 ), encompassed by the sealing ring ( 4 ), is provided that tapers against an inflow direction (Pf 1 ) of the backflow prevention device ( 1 , 1 ′) which does not contact the sealing ring in the sealing position.