Check valve having variable opening-force threshold

A valve assembly for use in a fluid system having fluid flow therethrough, said valve assembly comprising:

• a mounting member having a front surface, a rear surface and a passage therethrough, said mounting member positionable within the fluid system;
• a flapper pivotably carried by said mounting member, said flapper having a front surface and a rear surface, said flapper having an open position and a closed position, wherein said flapper blocks fluid flow through said passage of said mounting member when said flapper is in said closed position;
• a cam member defining a cam surface carried by said rear surface of said flapper, said cam member having a hump formed thereon;
• a follower carried by said mounting member, said follower dimensioned to engage said cam member and slide thereon, wherein the fluid flow must be at a predetermined minimum pressure on said front surface of said flapper to allow said follower to initially overcome said hump of said cam member thus allowing said flapper to pivot to said open position;
• and
• wherein said follower is a wheel having a recessed area, and wherein said cam surface engages within said recessed area.

A fluid flow check valve for placement within a fluid flow conduit, comprising in combination:

• a valve seat adapted to be placeable in a fixed position relative to the fluid flow conduit;
• said valve seat at least partially surrounding a passage for fluid flow through said valve seat;
• a flapper adapted to be placeable in at least two positions relative to said valve seat including a closed position and an open position;
• said closed position of said flapper at least partially abutting said valve seat and at least partially blocking said passage;
• said open position of said flapper providing less blockage of said passage than said closed position;
• a closure arm, said closure arm adapted to move between at least two closure arm positions, wherein said closure arm and said flapper pivot in a common rotational direction when opening and closing;
• said closure arm maintaining contact with said flapper;
• said closure arm maintaining exertion of a closure force on said flapper urging said flapper toward said closed position of said flapper;
• and
• said closure force of said closure arm upon said flapper being greater when said flapper is in said closed position than when said flapper is in said open position.

A fluid flow check valve for a placement within a fluid flow conduit, comprising in combination:

• a valve seat adapted to be placeable in a fixed position relative to the fluid flow conduit;
• said valve seat at least partially surrounding a passage for fluid flow through said valve seat;
• a flapper adapted to be placeable in at least two positions relative to said valve seat including a closed position and an open position;
• said closed position of said flapper at least partially abutting said valve seat and at least partially blocking said passage;
• said open position of said flapper providing less blockage of said passage than said closed position;
• a closure arm, said closure arm adapted to move between at least two closure arm positions;
• said closure arm maintaining contact with said flapper;
• said closure arm maintaining exertion of a closure force on said flapper urging said flapper toward said closed position of said flapper;
• said closure force of said closure arm upon said flapper being greater when said flapper is in said closed position than when said flapper is in said open position;
• wherein said closure arm has a pivot end pivotably attachable relative to said valve seat and a flapper contact end at which said closure arm maintains contact with said flapper;
• wherein said closure arm is biased toward a position with said flapper contact end of said closure arm forced against said flapper;
• wherein said flapper contact end of said closure arm contacts said flapper at a non-linear cam interface such that said closure force of said closure arm against said flapper has a non-linear relationship with a position of said flapper between said open position and said closed position;
• wherein said cam interface includes a follower on said closure arm flapper contact end and a non-linear surface on said flapper against which said follower contacts;
• wherein said follower includes a wheel, said wheel rotating relative to said flapper contact end of said closure arm;
• and
• wherein said wheel is lobed in a non-circular fashion.

A fluid check valve comprising in combination:

• an elongate hollow conduit body;
• a valve seat fixed to said conduit body, said seat having a passage therethrough, said seat at least partially surrounding said passage;
• a flapper movably attached to said conduit body;
• said flapper having an open position primarily spaced from contact with said valve seat and at least partially allowing fluid flow through said passage;
• said flapper having a closed position allowing less fluid flow through said passage than said open position;
• a closure element within said conduit and biased toward contact with said flapper both when said flapper is in said open position and said closed position, wherein said closure element and said flapper pivot in a common rotational direction when opening and closing;
• said closure element exerting a closing force on said flapper;
• and
• said closing force greater when said flapper is in said closed position than when said flapper is in said open position.

A fluid flow check valve for placement within a fluid flow conduit, comprising in combination:

• a valve seat adapted to be placeable in a fixed position relative to the fluid flow conduit;
• said valve seat at least partially surrounding a passage for fluid flow through said valve seat;
• a flapper adapted to be placeable in at least two positions relative to said valve seat including a closed position and an open position;
• said closed position of said flapper at least partially abutting said valve seat and at least partially blocking said passage;
• said open position of said flapper providing less blockage of said passage than said closed position;
• a closure arm, said closure arm adapted to move between at least two closure arm positions;
• said closure arm maintaining contact with said flapper;
• said closure arm having a pivot end pivotably attachable relative to said valve seat and a flapper contact end at which said closure arm maintains contact with said flapper;
• said closure arm being biased toward a position with said flapper contact end of said closure arm forced against said flapper;
• said closure arm maintaining exertion of a closure force on said flapper urging said flapper toward said closed position of said flapper;
• and
• said flapper contact end of said closure arm contacts said flapper at a non-linear cam interface such that said closure force of said closure arm against said flapper has a non-linear relationship with a position of said flapper between said open and said closed position;
• said cam inteface including a follower on said closure arm flapper contact end and a non-linear surface on said flapper against which said follower contacts;
• and
• said closure force of said closure arm upon said flapper being greater when said flapper is in said closed position than when said flapper is in said open position.