Pressure equalizing check valve

In a water supply system comprising a water supply main conduit serving a plurality of users, a water line connected to the main conduit for serving a water system of one of said plurality of users, the water system of said one user comprising a normally closed system of pipes, and a check valve in said water line for allowing free flow of water from the water supply main conduit into the one user's water system, the check valve comprising:

• a valve body having an upstream side and a downstream side, an internal valve seat, and a pivoted flapper cooperable with the internal valve seat for allowing flow through the conduit in a first direction from the upstream side to the downstream side for delivery of water from the water supply main to the one user's water system, and substantially restricting flow through the conduit in a second direction opposite to the first direction;
• a passage extending through the flapper;
• an auxiliary valve, carried by the flapper and permitting restricted flow, through the passage in the flapper, in said second direction when the flapper is in cooperation with the valve seat for restricting flow, the auxiliary valve being responsive to the flow of water through the passage, and closable in response to flow of water through the passage, in the second direction, at a rate in excess of a predetermined rate, to shut off flow of water through the passage substantially completely, and otherwise permitting restricted flow through the passage;
• whereby, when the flapper is in its flow-restricting position, the auxiliary valve permits slow flow of water through the restricted passage so that the water pressures on both sides of the flapper remain substantially equal, but when the water pressure on the upstream side of the valve drops substantially below the water pressure at downstream side of the valve port, the auxiliary valve closes, thereby substantially completely shutting off flow through the conduit in the second direction.

A valve closure element for use in a check valve for allowing free flow of water from a water supply main conduit into a user's water system, the valve closure element comprising:

• a pivotable flapper cooperable with a valve seat in a valve body for allowing flow through the valve body in a first direction and substantially restricting flow through the valve body in a second direction opposite to the first direction;
• a passage extending through the flapper;
• an auxiliary valve, carried by the flapper and permitting restricted flow, through the passage in the flapper, in said second direction when the flapper is in cooperation with a valve seat for restricting flow, the auxiliary valve being responsive to the flow of water through the passage, and closable in response to flow of water through the passage, in the second direction, at a rate in excess of a predetermined rate, to shut off flow of water through the passage substantially completely, and otherwise permitting restricted flow through the passage;
• whereby, when the flapper is in its flow-restricting position, the auxiliary valve permits slow flow of water through the restricted passage so that the water pressures on both sides of the flapper remain substantially equal, but when the water pressure in the water supply main conduit drops substantially below the water pressure in the user's water system, the auxiliary valve closes, thereby substantially completely shutting off flow through the valve body in the second direction.

A pressure equalizing check valve comprising:

• liquid conduit means comprising a conduit having an inlet and an outlet, the liquid conduit means being closed except for the inlet and outlet;
• first valve means within said conduit, operable, in response to flow of liquid in a first direction through the conduit from the inlet toward the outlet to permit free flow of liquid through the conduit, and in response to flow of liquid in a second direction opposite to the first direction through the conduit from the outlet toward the inlet, at least substantially to retard flow through the conduit in the second direction;
• means providing a restricted passage connecting said inlet and outlet;
• and
• second valve means for permitting slow flow of liquid through the conduit in the second direction, but responsive to flow of liquid through the restricted passage, from the outlet toward the inlet, at a rate in excess of a predetermined rate, to shut off flow of liquid through the conduit in the second direction substantially completely.

A pressure equalizing check valve comprising:

• liquid conduit means comprising a conduit having an inlet and an outlet, the liquid conduit means being closed except for the inlet and outlet;
• first valve means within said conduit, operable, in response to flow of liquid in a first direction through the conduit from the inlet toward the outlet to permit free flow of liquid through the conduit, and in response to flow of liquid in a second direction opposite to the first direction through the conduit from the outlet toward the inlet, at least substantially to retard flow through the conduit in the second direction;
• and
• second valve means for permitting slow flow of liquid through the conduit in the second direction, but responsive to a substantial drop in pressure at said inlet, to shut off flow of liquid through the conduit in the second direction substantially completely.