Backflow preventing valve construction

In a backflow preventing valve having a body with an inlet passage for connection to a source of fluid, an intermediate chamber fluidly connected to said inlet passage via an inlet check valve, an outlet passage fluidly connected to said intermediate chamber via an outlet check valve for connection to a receiver of fluid, an exhaust valve connected to said inlet passage and to said intermediate chamber which vents fluid in said intermediate chamber to the atmosphere when the pressure of fluid in said intermediate chamber is equal to the pressure of said fluid in said inlet passage, the improvement in each check valve comprising:

• valve port means;
• valve seat means for movement between open and closed positions relative to said port means, said seat means including a frustoconical surface and an axial cavity;
• valve closing means, for urging said seat member to a valve closed position, said closing means including:
• stationary shaft means for sliding engagement with said axial cavity;
• roller means for rolling engagement with said frustoconical surface;
• arm means, for positioning said roller means against said seat means;
• and
• spring means for biasing said roller means against said frustoconical surface, whereby:
• (i) said outlet check valve seat means is urged to said valve closed position by said outlet valve spring means when the fluid pressure in said intermediate chamber is less than the fluid pressure in said outlet passage plus the biasing force provided by said outlet valve spring means and applied to said seat means by said roller means, and
• (ii) said inlet valve seat means is urged to said valve closed position by said inlet check valve spring means when the fluid pressure in said inlet passage is less than the fluid pressure in said intermediate chamber plus the biasing force of said inlet check valve spring means.

In a backflow preventing valve having a body with an inlet passage for connection to a source of fluid, and an intermediate chamber fluidly connected to said inlet passage, an exhaust valve connected to said inlet passage and to said intermediate chamber which vents fluid in said intermediate chamber to the atmosphere when the pressure of fluid in said intermediate chamber is equal to the pressure of said fluid in said inlet passage, said exhaust valve comprising:

• a valve body communicating with said intermediate chamber and with said atmosphere;
• means for sensing the fluid pressure in said inlet passage;
• means for sensing the fluid pressure in said intermediate chamber;
• means, communicating with both of said sensing means, for comparing the fluid pressures in said inlet passage and displacement from said intermediate chamber resulting from large reductions in said inlet passage pressure;
• and
• balanced valve means, movably mounted to said valve body and resiliently coupled to said comparing means, for providing an opening from said intermediate chamber to said atmosphere only when said intermediate chamber fluid pressure is equal to said inlet passage fluid gressure, whereby said comparing means maintains said valve means in a valve closed position during said reductions in said inlet passage pressure.

An exhaust valve for a backflow preventing valve having a body with an inlet passage for connection to a source of fluid, and an intermediate chamber fluidly connected to the inlet passage, said exhaust valve being connected to said inlet passage and to said intermediate chamber to vent fluid in said intermediate chamber to the atmosphere when the pressure of the fluid in said intermediate chamber is greater than the pressure of said fluid in said inlet passage, said exhaust valve resisting said venting of said fluid for transitory flucuations in said inlet passage pressure and comprising:

• valve body means including a diaphragm cavity communicating with said inlet passage and with said intermediate chamber and an exhaust port communicating with the atmosphere;
• diaphragm means, resiliently attached to said valve body means for movement within said diaphragm cavity and having diaphragm portions separately communicating with said inlet passage and with said intermediate chamber;
• means, resiliently attached to said body means for opening said exhaust port to the atmosphere;
• and
• biasing means, positioned between said diaphragm means and said opening means and between said opening means and said valve body means, for supporting said opening means in a balanced manner, whereby:
• (i) as said inlet passage pressure increases, said diaphragm means moves toward said opening means and said biasing means resiliently transfers said movement to said opening means to position said opening means to close said exhaust port, and
• (ii) as said intermediate chamber pressure increases, said diaphragm means moves away from said opening means, thereby allowing said biasing means to position said opening means to open said exhaust port, said biasing means resiliently resisting said opening of said exhaust port for transistory changes in said inlet passage pressure.