Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-07-25
2002-09-03
Buiz, Michael Powell (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S529000, C251S337000
Reexamination Certificate
active
06443184
ABSTRACT:
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
This invention relates to a type of valve known as a “backflow preventer check valve.” These types of check valves are well known and are widely used to control backflow of fluids carrying undesirable contaminants into a fluid supply. These valves have evolved to become highly specialized in their function and operation, and are similar in that they all contain spring-loaded members which are biased towards the valve-closed position until fluid pressure acting on the checking members forces the valves open. Although the invention of the present application may be used in any suitable environment in which the flow of liquids must be controlled, the invention is preferably intended for use on a backflow preventer, which is a well-known device commonly used to protect potable water supplies from pollutants originating from downstream sources. A typical backflow preventer has two spring-loaded check valves positioned in conventional serial combination within a vessel body for preventing backflow of a fluid.
Many prior art spring-loaded check valves are of a poppet type, and include checking members whose movement is linear and remains in the fluid path. The pressure required to open such check valves is established by regulation and provides a minimum degree of protection against reverse flow. To provide some degree of protection, the springs in spring-loaded check valves provide a static differential pressure drop and corresponding static energy while the check valves are in a closed, or “no flow,” condition. The pressure and corresponding energy required to open these check valves is provided by the fluid and is created at the source by, for example, a pump. As fluid flows through the valve, both the differential pressure drop and corresponding energy change from static to dynamic. The total dynamic energy of the fluid in motion through the check valves is reduced by friction within the pipes and other obstacles (including the checking members) which remain disposed directly in the fluid path within the fluid conduit system. Once it increases beyond a certain amount, this loss of dynamic energy, also known as “headloss,” is no longer beneficial. Unfortunately, due to the position and linear movement of the springs within typical spring-loaded check valves, as headloss increases, fluid pressure decreases. This results in reduced fluid flow.
The invention of the present application addresses the problem of uncontrolled headloss by providing a poppet-type check valve which includes radially-loaded springs. Unlike a typical spring-loaded check valve, which has a spring loaded along the horizontal axis of a corresponding valve stem, the check valve of the present invention includes three springs, each of which is loaded within the check valve in radial relation to the other springs such that one end of the spring is attached to, and the other end extends outwardly from, the valve stem. By taking advantage of radial placement and careful angling in relation to the stem, the radially loaded springs included in the invention of the present application maintain a force on the poppet which is adequate to keep the poppet closed during static, “no-flow” conditions, yet decreases as fluid flow increases through the check valve. Positioning the springs in this manner reduces head loss, and preserves both fluid pressure and flow.
SUMMARY OF THE INVENTION
Therefore, it is an object of the invention to provide a radially loaded, poppet-type check valve which reduces “head loss.”
It is another object of the invention to provide a poppet-type check valve having springs positioned to allow spring loading to decrease as the check valve opens.
It is another object of the invention to provide a poppet-type check valve which provides a static differential pressure drop for providing protection against reverse fluid flow.
It is another object of the invention to provide a poppet-type check valve that allows the resultant force of the springs acting on the poppet to be adequate when the check valve is closed in a static, “no-flow” condition, and then to decrease as fluid flow increases and the check valve opens.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a poppet-type check valve for controlling fluid flow including a valve housing having an interior and first and second ports therein communicating with the interior of the valve housing for permitting fluid flow from an upstream side to a downstream side thereof. At least one valve assembly is disposed within the interior of the valve housing for controlling fluid flow therethrough. The valve assembly includes a valve seat positioned in the interior of the valve housing, and a seal retainer positioned in the interior of the valve housing downstream from the valve seat and mounted on a stem. The seal retainer and the stem are axially moveable away from the valve seat in response to fluid flow in a downstream direction, axially moveable toward the valve seat in response to fluid flow in an upstream direction, and in sealing engagement against the valve seat in the absence of fluid flow. A plurality of springs are pivotally mounted in the interior of the valve housing and interconnect the valve housing and stem for normally maintaining the seal retainer in sealing engagement with the valve seat in the absence of fluid flow. The springs are positioned in radial opposition to one another and extend outwardly from the stem in the downstream direction to cause the seal retainer to move away from the valve seat in response to fluid flow in the downstream direction, thereby increasing the force of the stem on the springs and causing the springs to pivot and compress to produce a diminishing resultant spring load on the stem.
According to one preferred embodiment of the invention, a poppet-type check valve for controlling fluid flow is disclosed, comprising a valve housing having an interior and first and second ports therein communicating with the interior of the valve housing for permitting fluid flow from an upstream side to a downstream side thereof. At least one valve assembly is disposed within the interior of the valve housing for controlling fluid flow therethrough. The valve assembly includes a valve seat positioned in the interior of the valve housing, a stem guide mounted on a downstream side of the valve seat, and a seal retainer mounted on an upstream end of a stem which extends downstream from the valve seat and through the stem guide. The seal retainer and the stem are axially moveable away from the valve seat in response to fluid flow in a downstream direction, axially movable toward the valve seat in response to fluid flow in an upstream direction, and in sealing engagement against the valve seat in the absence of fluid flow. The valve assembly also includes a plurality of springs pivotally mounted in the interior of the valve housing. The springs interconnect the stem and the stem guide downstream from the seal retainer for normally maintaining the seal retainer in sealing engagement with the valve seat in the absence of fluid flow. The springs are positioned in radial opposition to one another and extend outwardly from the stem in the downstream direction to cause the seal retainer to move away from the valve seat in response to fluid flow in the downstream direction, thereby increasing the force of the stem on the springs and causing the springs to pivot and compress to produce a diminishing resultant spring load on the stem.
According to another preferred embodiment of the invention, a poppet-type check valve for controlling fluid flow is disclosed, comprising a valve housing having an interior and first and second ports therein communicating with the interior of the valve housing for permitting fluid flow from an upstream side to a downstream side thereof. At least one valve assembly is disposed within the interior of the valve housing for controlling the fluid flow therethrough. The valve assembly includes a valve sea
Adams, Schwartz & Evans P.A.
Buiz Michael Powell
Conbraco Industries, Inc.
Schoenfeld Meredith H.
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