Patent ID: 7431048

Claim:
Backflow preventer ( 1 ), comprising an insert housing ( 2 ) with a housing interior ( 5 ) in which a valve member ( 6 ) is located which contacts a valve seat ( 7 ) in a closed position thereof and which can be moved against a restoring force from the closed position into an open position, wherein the housing interior ( 5 ) has, in a movement zone of the valve member ( 6 ), an interior section (A), which has a greater open cross section relative to an outer periphery of the valve member, wherein for play-free guidance of the valve member ( 6 ) there is a spring-elastic valve member guide ( 9 ) having at least two spring arms ( 10 ) formed on an inner portion of the insert housing ( 2 ) between which the valve member slides, the spring arms arranged with free spring arm ends thereof in a region of the valve seat ( 7 ), the spring arms are substantially parallel to a movement direction of the valve member ( 6 ) and contact at least one of the housing inner wall or the valve member ( 6 ), the spring-elastic valve member guide ( 9 ) being effective between the valve member ( 6 ) and a housing inner wall surrounding the interior section (A).