Backflow preventer

Claim 2

A backflow preventer comprising: a housing having an inlet passage and an outlet passage; a generally annular diaphragm having an outer peripheral region fixed to said housing between the inlet and outlet passages and having a central opening bounded by an inner region; said diaphragm being flexible and resilient for movement downstream from a relaxed position in response to pressurization of the inlet passage; a valve seat surrounding the outlet passage radially between the diaphragm outer and inner regions and spaced downstream from the diaphragm in its relaxed position; a vent passage radially outside said valve seat and communicating across said valve seat with said outlet passage in the relaxed position of said diaphragm; a check member disposed on the upstream side of said diaphragm and having a valve surface engageable with said inner region; and spaced stop means for permitting limited movement of said check member between an upstream position wherein the valve surface engages said inner region in the relaxed position of the diaphragm and a downstream position wherein said diaphragm engages said valve seat and said valve surface remains in engagement with said inner region; the portion of said diaphragm radially inside said valve seat being movable further downstream to permit flow through said central opening.

Claim 3

The backflow preventer of claim 1, said inner region including a circular inner edge wall of said diaphragm, and said valve surface being defined on a projecting portion of said check member.

Claim 4

The backflow preventer of claim 2, said projecting portion comprising a spherical segment.

Claim 5

The backflow preventer of claim 2, said check member including flow passage means radially outside of said valve surface.

Claim 6

The backflow preventer of claim 4, said check member including peripheral skirt means confined for limited movement between said stop means.

Claim 7

The backflow preventer of claim 5, said stop means including an upstream stop surface formed on said housing, and a downstream stop surface formed on the upstream side of said diaphragm adjacent said outer region.

Claim 8

The backflow preventer of claim 5, said skirt means being continuous and said flow passage means comprising a circular array of openings.

Claim 9

The backflow preventer of claim 5, said skirt means including discrete segments, arms joining said segments to said valve surface, and said flow passage means including openings between said arms.

Claim 10

The backflow preventer of claim 1, said housing including inlet and outlet members attached to one another, said diaphragm being peripherally clamped between said members.

Claim 11

A backflow preventer comprising in combination: a body defining an upstream liquid flow passage and a downstream liquid flow passage; a valve seat surrounding said downstream passage; a flexible resilient member separating said upstream passage from said valve seat and downstream passage; vent passage means in said body disposed radially outside of said valve seat on the downstream side of said resilient member; said resilient member including a periphery fixed to said body, a sealing surface radially inside said periphery adapted to engage said valve seat to close said vent passage means upon downstream deflection of said resilient member, and a central aperture through said resilient member radially inside of said sealing surface; and the improvement comprising: a check valve member mounted in said upstream passage for movement together with said flexible member in a limited range of movement between an upstream position and a downstream position in which said flexible member engages said valve seat, and a valve surface on said check valve member engageable with the upstream side of said flexible member to close said central aperture throughout said range of movement, said flexible member being movable downstream beyond said downstream position of said check valve member to open said central aperture for flow between said upstream and downstream passages.

Claim 12

A backflow preventer comprising in combination: a body defining an upstream liquid flow passage and a downstream liquid flow passage; a valve seat surrounding said downstream passage; a flexible resilient member separating said upstream passage from said valve seat and downstream passage; vent passage means in said body disposed radially outside of said valve seat on the downstream side of said resilient member; said resilient member including a periphery fixed to said body, a sealing surface radially inside said periphery adapted to engage said valve seat to close said vent passage means upon downstream deflection of said resilient member, and a central aperture through said resilient member radially inside of said sealing surface; and the improvement comprising: a check valve member mounted in said upstream passage for movement together with said flexible member in a limited range of movement between an upstream position and a downstream position in which said flexible member engages said valve seat, and a valve surface on said check valve member engageable with the upstream side of said flexible member to close said central aperture throughout said range of movement, said flexible member being movable downstream beyond said downstream position of said check valve member to open said central aperture for flow between said upstream and downstream passages.