Patent ID: 6543474
Filing Date: 2003-04-08
Classification: F16K,Y10T

Abstract:
A pressure equalizing check valve comprising:a liquid conduit having an inlet port and an outlet port, the liquid conduit being closed except for the inlet and outlet ports; a main valve seat within said liquid conduit; a main valve closure element within said conduit, the main valve closure element being movable, in response to flow of liquid in a first direction through the conduit from the inlet port toward the outlet port, to an open position in which it is out of contact with the seat and permits 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 port toward the inlet port, to a closed position in which it is in contact with the seat, and at least substantially retards flow through the conduit in the second direction; a restricted passage connecting the inlet port to the outlet port at least when the main valve closure element is in its closed position; an auxiliary valve controlling flow through the restricted passage when the main valve closure element is in its closed position, the auxiliary valve comprising an auxiliary valve closure element and an auxiliary seat, the auxiliary valve closure element being normally held away from the auxiliary seat and engageable with said auxiliary seat in response to flow of liquid through the restricted passage, from the outlet port toward the inlet port, at a rate in excess of a predetermined rate, to shut off flow of liquid through said auxiliary passage substantially completely; whereby, when the main valve closure element is in said closed position, the auxiliary valve permits slow flow of liquid through the restricted passage so that the liquid pressure at the outlet port is held at a level substantially equal to the liquid pressure at the inlet port, but when the liquid pressure at the inlet port drops substantially below the liquid pressure at the outlet port, the auxiliary valve closes, thereby substantially completely shutting off flow through the conduit in the second direction.