Check valve having pivoting link

A check valve for a backflow preventer, the check valve comprising:

• a housing having a fluid flow channel therethrough;
• a valve seat;
• a clapper movable between a closed position and a fully open position, the clapper positioned against the valve seat and inhibiting fluid flow past the valve seat while the clapper is in the closed position, the clapper spaced apart from the valve seat and permitting fluid flow past the valve seat while the clapper is in the fully open position;
• a biasing member for biasing the clapper toward the closed position;
• and
• a pivot link pivotable about a pivot axis that is fixed relative to the valve seat, the pivot link transmitting an effective biasing force from the biasing member to the clapper, the effective biasing force that is transmitted to the clapper while the clapper is in the closed position being greater than the effective biasing force transmitted to the clapper while the clapper is in the fully open position.

A check valve comprising:

• a housing having a fluid flow channel therethrough;
• a valve seat;
• a clapper movable between a closed position and a fully open position, the clapper positioned against the valve seat and inhibiting fluid flow past the valve seat while the clapper is in the closed position, the clapper spaced apart from the valve seat and permitting fluid flow past the valve seat while the clapper is in the fully open position;
• and
• a pivot link pivotable about a pivot axis, the pivot link including,
• a first arm coupled to the clapper,
• a second arm coupled to a biasing member, the second arm proximate a wall of the housing, and
• an elongated rod rigidly connecting the first arm to the second arm, the elongated rod offset from the pivot axis of the pivot link,
• wherein the pivot link transmits a biasing force from the biasing member to the clapper, an effective biasing force that is transmitted to the clapper while the clapper is in the closed position being greater than an effective biasing force transmitted to the clapper while the clapper is in the fully open position.