Abstract:
A fluid control valve having a spring biased shuttle plunger member which opens or closes fluid flow through a plurality of radially spaced apart fluid passageways disposed between an upstream chamber and downstream chamber in the valve body responsive to a fluid pressure greater than the spring force and any differential pressure between the upstream and downstream chambers to prevent fluid from being supplied at a pressure higher than a desired operating pressure and prevent high dynamic differential pressures, such as a “water hammer” or explosive pressure. Alternatively, in a normally closed embodiment, pilot fluid at a pressure greater than the spring force and any differential pressure in the upstream chamber is utilized to open the valve, which is then closed by the spring force.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to fluid control valves, and more particularly to a fluid control valve having a spring biased shuttle plunger member which opens or closes fluid flow between an upstream and downstream side of the valve body responsive to a fluid pressure greater than the spring force and any differential pressure between the upstream and downstream side to prevent fluid from being supplied at a pressure higher than a desired operating pressure and prevent high dynamic differential pressures, such as a “water hammer” or explosive pressure. 
   2. Background Art 
   Fluid control valves of the on-off type that allow full fluid flow or completely shut off the fluid flow are well known in the art and are available in a wide range of various designs, sizes, pressure capabilities, and modes of operation. Such conventional valves are often identified by the configuration of the main valve components, such as the part that which opens and closes the fluid passage, and are commonly referred to as gate valves, butterfly valves, cock valves, globe valves, ball valves, poppet valves, shuttle valves and stem valves. As the working fluid pressure increases, the selection of suitable on-off valves decreases due to the difficulties in achieving fluid sealing and in operating the moving valve parts. 
   Typically, such valves capable of handling relatively high fluid differential pressures utilize a hardened valve stem, valve needle or valve poppet, usually of circular cross section, which is raised or lowered against a circular fluid passage commonly positioned at the center of a replaceable valve seat constructed of hardened metals. Conventional high-pressure on-off valves require a rotating motion, either manually or automatically, for raising or lowering a valve stem or valve needle. In many applications, such rotary motion is too slow and does not provide the required instant on-off action. In such case, the valve stem or valve needle must slide within the valve cavity to open or close the valve port. 
   Typically, the end of the valve stem which is exposed to the atmosphere is in contact with a source of force that imparts the sliding movement to the valve stem. Such force can be supplied by a human hand or by automatic or powered devices, such as with compressed air, pressurized hydraulic fluid, electricity or the like. Conventional solenoids, pneumatic or hydraulic actuators are also used to supply linear force to move the valve stem. 
   Check valves are also well-known and widely used in fluid systems of various types to permit fluid flow in one direction therethrough while preventing fluid flow in the opposite direction. Such check valves have a variety of different forms, principally ball check valves in which a spherical ball is held by a spring adjacent a seat until opened by fluid pressure overcoming the spring bias, and check valves having generally conical valve members operating in a similar manner as the ball check valve. 
   Dashner, U.S. Pat. No. 4,172,465 discloses a check valve having a semi-spherical valve member movable longitudinally in a generally tubular housing between a closed position engaging a conical valve seat and an open position spaced longitudinally therefrom, the valve member being slidably mounted for such movement on a longitudinally extending support element. The opening in the valve member which receives the support therein has a diameter significantly greater than the diameter of the support element whereby the valve member is pivotal thereon so as to seat properly on the valve seat. The center of the semi-spherical valve member is longitudinally spaced in one direction from the effective center of support thereof at the closed position of the valve member, and is longitudinally spaced in the opposite direction from the effective center of the valve member at the open position of the valve. The valve housing is specially formed to provide a flow path around the valve member which corresponds generally in area to the valve inlet and outlet openings to reduce the pressure loss of the fluid passing through the valve. 
   Muruyama et al, U.S. Pat. No. 5,271,430 discloses A flow rate control valve device for controlling and then supplying fluid under pressure to an actuator such as an hydraulic cylinder or the like which includes a valve body having a drain port kept at a low pressure and a main spool slidably mounted in the valve body to connect or disconnect the drain port with a pressure chamber. Notch grooves are formed on an outer peripheral surface of the main spool. A spring is interposed between the valve body and the main spool to urge the spool to a valve body seat. A pushing device is provided for pushing the main spool against the resilient force of the spring. A plate member is provided on the main spool in the drain port for causing pressurized flow through the notch grooves to flow first in a substantially radial direction of the main spool and subsequently into the drain port so part of the pressurized fluid impinges on the plate member for exerting a force urging the main spool in the direction disengaging the spool from the seat against a force of the spring and a flow force acting between the spool and the seat for at least canceling the flow force. 
   Tavor, U.S. Pat. No. 6,220,272 discloses in-line control valves which include a piston-type valve assembly and a plurality of control chambers controlled via one or more controls ports to provide a normally-open valve that may be closed by controlling the fluid pressure applied to the control port, or a normally-closed valve which may be opened by controlling the fluid pressure applied to the control port. Also described are valves which have a balanced construction and include relatively small actuators for opening and closing the valve. 
   Haeberer et al, U.S. Pat. No. 6,244,253 discloses a pressure control valve for a fuel injection apparatus for internal combustion engines, including a housing with a high-pressure connection and a return connection and including a cup-shaped piston, which is disposed in a housing bore, can be moved axially between a valve seat oriented toward the high-pressure connection and a stop oriented toward the return connection, counter to the spring force of a spring acting in the direction of the valve seat, and has at least one through opening that connects the inside of the cup-shaped piston to the housing bore, and is characterized in that at least one throttle element is disposed upstream and/or downstream of the valve seat in the flow direction of the fuel. 
   Kussel, U.S. Pat. No. 6,263,913 discloses a hydraulic multiway valve having a control piston, which is displaceable against the force of a spring by the plunger of a magnet from its closing position to its opening position. In the closing position, a pressure chamber with a pump connection is closed toward a consumer chamber, and the consumer chamber with a consumer is opened toward a return flow chamber and a reservoir connection. In the opening position, the consumer chamber is closed toward the return flow chamber. The consumer chamber and the return flow chamber are arranged at the opposite ends of the main piston, namely the consumer chamber on the side facing the magnet, and the return flow chamber on the side facing away therefrom. A central channel extends through the main piston and interconnects the consumer chamber and the return flow chamber. A magnet plunger acts upon a plunger piston, which is displaceable in the valve housing in coaxial relationship with the main piston, and which comprises a seat end facing the main piston, through which it closes the central channel, when it contacts the main piston. 
   The present invention is distinguished over the prior art in general, and these patents in particular by a fluid control valve having a spring biased plunger or shuttle member which opens or closes fluid flow through a plurality of radially spaced apart fluid passageways disposed between an upstream chamber and downstream chamber in the valve body responsive to a fluid pressure greater than the spring force and any differential pressure between the upstream and downstream chambers to prevent fluid from being supplied at a pressure higher than a desired operating pressure and prevent high dynamic differential pressures, such as a “water hammer” or explosive pressure. Alternatively, in a normally closed embodiment, pilot fluid at a pressure greater than the spring force and any differential pressure in the upstream chamber is utilized to open the valve. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a fluid control valve that is relatively simple in construction, having few parts and particularly few moving parts. 
   It is another object of this invention to provide a fluid control valve that can serve functions other than simple on-off operations, such as pressure regulation in a fluid system. 
   Another object of this invention is to provide a fluid control valve wherein one or more seal rings on the plunger or shuttle form a fluid tight seal on the sealing surface in the valve body prior to surface-to-surface or metal-to-metal engagement to prevent jamming. 
   A further object of this invention is to provide a fluid control valve having one or more O-ring grooves on the plunger or shuttle configured to reduce the likelihood of the O-ring being swept out of the groove by a fast fluid flow or upon rapid opening of the shuttle. 
   A still further object of this invention is to provide a fluid control valve that is simple in construction, inexpensive to manufacture, and rugged and reliable in operation. 
   Other objects of the invention will become apparent from time to time throughout the specification and claims as hereinafter related. 
   The above noted objects and other objects of the invention are accomplished by a fluid control valve having a spring biased plunger or shuttle member which opens or closes fluid flow through a plurality of radially spaced apart fluid passageways disposed between an upstream chamber and downstream chamber in the valve body responsive to a fluid pressure greater than the spring force and any differential pressure between the upstream and downstream chambers to prevent fluid from being supplied at a pressure higher than a desired operating pressure and prevent high dynamic differential pressures, such as a “water hammer” or explosive pressure. Alternatively, in a normally closed embodiment, pilot fluid at a pressure greater than the spring force and any differential pressure in the upstream chamber is utilized to open the valve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal cross section through a normally closed embodiment of the fluid control valve in accordance with the present invention, wherein the valve body and main body portion of the shuttle are tapered at an acute angle with respect to the longitudinal axis of the valve body to provide a conical sealing surface arrangement. 
       FIG. 1A  is a transverse cross section through the valve assembly taken along line  1 A— 1 A of  FIG. 1 . 
       FIG. 1B  is a partial cross section of the sealing surface of the valve body of the embodiment of  FIG. 1 . 
       FIG. 2  is a partial cross sectional view showing an enlarged detail of an undercut wedge-shaped O-ring seal groove. 
       FIG. 3  is a longitudinal cross section through a first alternate embodiment of the normally closed fluid control valve in accordance with the present invention. 
       FIG. 3A  is a longitudinal cross section through a second alternate embodiment of the normally closed fluid control valve having a secondary return spring arrangement. 
       FIG. 4  is a longitudinal cross section through a normally open embodiment of the fluid control valve in accordance with the present invention. 
       FIG. 5  is a partial longitudinal cross sectional view, showing somewhat schematically, a modification of the fluid control valve wherein the valve body and main body portion of the shuttle have sealing surface arrangement generally parallel to the longitudinal axis of the valve body. 
       FIG. 6  is a partial longitudinal cross sectional view, showing somewhat schematically, another modification of the fluid control valve wherein the valve body and main body portion of the shuttle have sealing surface arrangement generally perpendicular to the longitudinal axis of the valve body. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 ,  1 A and  1 B of the drawings by numerals of reference, there is shown a preferred normally closed embodiment of the fluid control valve  10 . The fluid control valve  10  includes a valve body  11  having a longitudinal axis A, a generally cylindrical upstream chamber  12  extending inwardly from an upstream end  13  and a generally cylindrical downstream chamber  14  extending inwardly from a downstream end  15 . For purposes of illustration, the upstream end  13  is shown on the right-hand side of the valve body  11 , and downstream end  15  is shown on the left-hand side. The body  11  has an interior wall  16  with an upstream side  16 U and a downstream side  16 D disposed perpendicular to the longitudinal axis A. The upstream chamber  12  terminates at the upstream side  16 U of the interior wall  16 , and the downstream chamber  14  terminates at the downstream side  16 D. The upstream end of the upstream chamber  12  and the downstream end of the downstream chamber  14  are each sealingly enclosed by a respective end closure, such as an O-ring sealed end plate or flange  17  to allow easy disassembly and service of the valve. A reduced diameter central bore  18  extends through the interior wall  16  coaxial with the longitudinal axis A, and a plurality of fluid passageway bores  19  extend through the interior wall in circumferential radially spaced relation to the central bore. 
   The valve  10  is provided with at least one fluid inlet  20  in fluid communication with the upstream chamber  12 , and at least one fluid outlet  19  in fluid communication with the downstream chamber  14 . For purposes of example, in  FIG. 1  the fluid inlet  20  and fluid outlet  21  are shown extending through the end flanges  17 . However, it should be understood that the fluid inlet and outlets  20  and  21  may extend through the side wall  11 A of the valve body  11 . It should also be understood that the fluid inlet and outlets  20  and  21  may be threaded for receiving threaded fluid inlet and outlet pipe connections. Preferably, the fluid passageways  19  are of a sufficient number and are sized to provide a total cross-sectional flow area to equal to, or exceeding, the cross-sectional flow area of the inlet and outlet connections. 
   The valve assembly includes a shuttle member  22  having a main body portion  23  with a flat bottom surface  23 A of sufficient diameter to engage the downstream side  16 D of the interior wall  16  and cover the passageway bores  19 , and a smaller diameter cylindrical stem portion  24  extending from the bottom surface and slidably through the central bore  18 . In the normally closed embodiment of  FIG. 1 , the main body portion  23  of the shuttle  22  is disposed in the downstream chamber  14  and its stem portion  24  is slidably received in the central bore  18  facing the downstream end  15 . A central reduced diameter boss  35  protrudes a short distance from the main body portion  23  opposite the stem portion  24 . 
   As indicated in dashed line, the central bore  18  may be provided with in an oil-impregnated bearing  26  to reduce sliding friction of the shuttle stem  24 . Alternatively, the surface of either of the central bore  18  or the shuttle stem  24  may be provided with circumferentially spaced teeth or splines to lower sliding friction, and the central bore may be provided with a wiper to inhibit entry of solids or grime. 
   The main body portion  23  of the shuttle  22  may be of several different configurations, each corresponding to a sealing surface configuration formed in the valve body as described hereinafter. 
   In the normally closed embodiment of  FIG. 1 , the downstream chamber  14  of the valve body  11  has a conical sealing surface  27  extending from the downstream side  16 D of the interior wall  16  toward the downstream end  15  at an angle “B” with respect to the longitudinal axis A of the valve body, and the main body portion  23  of the shuttle  22  has a conical outer periphery  28  extending from its flat bottom surface  23 A at substantially the same angle as the sealing surface  27 . 
   In a preferred embodiment, the conical sealing surface  27  of the valve body and the main body portion  23  of the shuttle  22  are tapered at an acute angle of from about 2° to about 15° with respect to the longitudinal axis A of the valve body, however, the sealing angle may vary depending upon the end use of the valve, and may range anywhere between 0° to 90°, as described hereinafter. 
   At least one O-ring groove  29  is formed on the outer periphery  28  of the main body portion  23  of the shuttle  22 , and an elastomeric seal ring is received in each ring groove. Two O-ring grooves  29  are shown in the illustrated example of the shuttle  22  having a conical outer periphery. 
   Referring additionally to  FIG. 2 , in a preferred embodiment, each seal ring groove  29  is a generally wedge-shaped circumferential groove, which in transverse cross section, has a flat bottom surface  29 A and opposed converging sides  29 B extending outwardly therefrom in opposed angular relation. 
   A compression spring  31  disposed in the downstream chamber  14  having one end surrounding the raised boss  25  is engaged on the main body portion  23  of the shuttle  22  and its opposed end is engaged on a snap ring  32  provided in the downstream chamber of the valve body  11 . The O-ring seals  30  of the shuttle  22  are normally maintained in a sealing relation on the sealing surface  27  of the valve body by the spring force of the compression spring  31 , thereby closing off fluid flow through the fluid passageways  19 . Fluid flow from the upstream side  13  to the downstream side  15  must overcome the spring force, and any excess differential pressure on the downstream side of the shuttle. Backflow of fluid attempted from the downstream side  15  to the upstream side  13  only makes the seal tighter. 
   The angled sealing surface  27  of the valve body  11  and the angled outer periphery  28  of the main body portion  23  of the shuttle  22  are correlated such that in the closed position, the flat bottom surface  23 A of the shuttle engages the downstream side  16 D of the interior wall  16  and each seal ring  30  engages the sealing surface  27  and forms a fluid tight seal between the outer periphery of the shuttle and the sealing surface prior to surface-to-surface or metal-to-metal engagement of the outer periphery on the sealing surface to prevent jamming of the outer periphery on the sealing surface. 
   The shuttle  22  is maintained in a normally closed position with its flat bottom surface  23 A engaged on the downstream side  16 D of the interior wall  16  and covering the passageway bores  19  and its seal rings  30  preventing fluid flow of a pressure less than the spring force of the compression spring  31  and any differential pressure in the downstream chamber  14  through the fluid passageway bores between the upstream chamber  12  and the downstream chamber. 
   Fluid flow through the fluid inlet  21  into the upstream chamber  12  and the passageway bores  19  of a pressure exceeding the spring force and any differential pressure in the downstream chamber  14  impinges the flat bottom surface  23 A of the shuttle  22  to move the main body portion  23  away from the downstream side  16 D of the interior wall  16  to an open position, and flows through the fluid passageway bores  19 , around the main body portion  23 , into the downstream chamber  14 , and exits through the fluid outlet  21 . 
   Referring now to  FIG. 3 , there is shown a second embodiment  10 A of the normally closed fluid control valve, wherein the sealing surface is in the upstream chamber and the valve is opened by a piston controlled by a pilot fluid. The components described previously are assigned the same numerals of reference, but their detailed description will not be repeated again to avoid repetition. As with the previously described embodiment, the upstream end of the upstream chamber  12  and the downstream end of the downstream chamber  14  are each sealingly enclosed by a respective end closure, such as an O-ring sealed end plate or flange  17  to allow easy disassembly and service of the valve. A reduced diameter central bore  18  extends through the interior wall  16  coaxial with the longitudinal axis A, and a plurality of fluid passageway bores  19  extend through the interior wall in circumferential radially spaced relation to the central bore. 
   In this embodiment, the valve  10 A is provided with at least one fluid inlet  20  in fluid communication with the upstream chamber  12 , and at least one fluid outlet  21  in fluid communication with the downstream chamber  14 , and a pilot fluid inlet  33  and outlet  34  in fluid communication with the downstream chamber for introducing a pilot fluid thereinto. For purposes of example, in  FIG. 3  the fluid outlet  21  and pilot fluid inlet and outlets  33  and  34  are shown extending through the side wall  11 A of the valve body  11 . It should be understood that the fluid inlet  20  and outlet  21  and pilot fluid inlet  33  and outlet  34  may be threaded for receiving threaded connections. 
   In the normally closed embodiment of  FIG. 3 , the main body portion  23  of the shuttle  22  is disposed in the upstream chamber  12  and its stem portion  24  is slidably received through the central bore  18  facing the downstream end  15 , and a generally cylindrical piston member  35  is slidably and sealingly disposed in the downstream chamber  14 . The piston member  35  has a downstream side  35 D and an upstream side  35 U disposed perpendicular to the longitudinal axis A of the valve body, and the piston member is movable between the pilot fluid inlet and outlets  33 ,  34  and the fluid outlet  21 . The upstream side  35 U of the piston member is connected with the downstream end of the stem  24  of the shuttle  22  to move therewith. In this embodiment, the flat bottom surface  23 A of the shuttle  22  is configured to engage the upstream side  16 U of the interior wall  16  and cover the passageway bores  19 . 
   In the embodiment of  FIG. 3 , the upstream chamber  12  of the valve body  11  has a conical sealing surface  27  extending from the upstream side  16 U of the interior wall  16  toward the upstream end  13  at an angle B with respect to the longitudinal axis A of the valve body, and the main body portion  23  of the shuttle  22  has a conical outer periphery  28  extending from its flat bottom surface  23 A at substantially the same angle as the sealing surface. 
   A compression spring  31  disposed in the upstream chamber  12  having one end surrounding the raised boss  25  of the shuttle  22  is engaged on the main body portion  23  of the shuttle and its opposed end is engaged on a snap ring  32  provided in the upstream chamber of the valve body  11 . The O-ring seals  30  of the shuttle  22  are normally maintained in a sealing relation on the sealing surface  27  of the valve body  11  by the spring force of the compression spring  31 , thereby normally closing off fluid flow through the fluid passageways  19 . 
   In this embodiment, pilot fluid (gas or liquid) at a pressure greater than the spring force of the spring  31  and any differential pressure in the upstream chamber  12  is introduced into the downstream chamber  14  between the enclosed end of the valve body and the downstream side  35 D of the piston  35  to move the piston and the stem  24  of the shuttle  22  toward the downstream side  16 D of the interior wall  16  and move the main body portion  23  of the shuttle away from the upstream side  16 U of the interior wall  16  to an open position, whereby fluid flows through the fluid inlet  20  into the upstream chamber  12 , around the main body portion  23 , through the passageway bores  19  into the downstream chamber  14  between the interior wall downstream side  16 D and the upstream side  35 U of the piston, and exits through the fluid outlet  21 . Upon releasing the pilot fluid pressure, the shuttle  22  is returned by the compression spring  31  to its normally closed position. 
   Alternatively, as shown in  FIG. 3A , a second compression spring  31 A may be installed between the upstream side  35 U of the piston  35  and downstream side  16 D of the interior wall  16 , in which case, pilot fluid at a pressure greater than the combined spring force and any differential pressure in the upstream chamber  12  is introduced into the downstream chamber  14  between the enclosed end of the valve body and the downstream side  13 D of the piston  35  to move the piston and the stem  24  of the shuttle  22  toward the downstream side  16 D of the interior wall  16  and move the main body portion  23  of the shuttle  22  away from the upstream side  16 U of the interior wall to an open position, and upon releasing the pilot fluid pressure, the shuttle is returned by the compression springs  31 ,  31 A to its normally closed position. 
   In the embodiments described above that incorporate a pilot fluid, the diameter of the piston  35  may be sized so as to allow movement by the same fluid pressure as the pressure of the fluid being controlled. Thus, in some installations, a portion of the fluid being controlled may be utilized as the pilot fluid. 
   Referring now to  FIG. 4 , there is shown a preferred normally open embodiment of the fluid control valve  10 C. The components described previously are assigned the same numerals of reference, but their detailed description will not be repeated again to avoid repetition. As with the previously described embodiments, the upstream end of the upstream chamber  12  and the downstream end of the downstream chamber  14  are each sealingly enclosed by a respective end closure, such as an O-ring sealed end plate or flange  17  to allow easy disassembly and service of the valve. A reduced diameter central bore  18  extends through the interior wall  16  coaxial with the longitudinal axis A, and a plurality of fluid passageway bores  19  extend through the interior wall in circumferential radially spaced relation to the central bore. 
   In this embodiment, the valve  10 C is provided with at least one fluid inlet  20  in fluid communication with the upstream chamber  12 , and at least one fluid outlet  21  in fluid communication with the downstream chamber  14 , and at least one vent port  36  in fluid communication with the downstream chamber for venting fluid pressure therefrom. For purposes of example, in  FIG. 4  the fluid outlet  21  and vent port(s)  36  are shown extending through the side wall  11 A of the valve body  11 . It should be understood that the fluid inlet  20  and outlet  21  and the vent port(s)  36  may be threaded for receiving threaded connections. 
   In the normally open embodiment of  FIG. 4 , the main body portion  23  of the shuttle  22  is disposed in the upstream chamber  12  and its stem portion  24  is slidably received through the central bore  18  facing the downstream end  13 , and a generally cylindrical piston member  35  is slidably and sealingly disposed in the downstream chamber  14 . The piston member  35  has a downstream side  35 D and an upstream side  35 U disposed perpendicular to the longitudinal axis A of the valve body, and the piston member is movable between the vent port(s)  36  and the fluid outlet  21 . The upstream side  35 U of the piston  35  may be connected with, or free-floating to engage, the downstream end of the stem  24  of the shuttle  22  to move therewith, and has a reduced diameter stop surface  35 A engageable with the downstream side  26 D of the interior wall  16  radially inward of the fluid passageway bores  19  to prevent the piston from passing over or covering the fluid outlet  21 . 
   In the embodiment of  FIG. 4 , the upstream chamber  12  of the valve body  11  has a conical sealing surface  27  extending from the upstream side  16 U of the interior wall  16  toward the upstream end  13  at an angle B with respect to the longitudinal axis A of the valve body, and the main body portion  23  of the shuttle  22  has a conical outer periphery  28  extending from its flat bottom surface  23 A at substantially the same angle as the sealing surface, and the flat bottom surface of the shuttle is configured to engage the upstream side  16 U of the interior wall  16  and cover the passageway bores  19  when the valve is in a closed position. 
   A first compression spring  31  disposed in the upstream chamber  12  having one end surrounding the raised boss  25  of the shuttle  22  is engaged on the main body portion  23  of the shuttle and its opposed end is engaged on a snap ring  32  provided in the upstream chamber of the valve body  11 . 
   A second compression spring  31 A is disposed in the downstream chamber  14  and has one end engaged on the downstream end closure  17  and its opposed end engaged on the downstream side  35 D of the piston  35  to normally urge the stop surface  35 A of the piston into engagement with the downstream side  16 D of the interior wall  16  with the flat bottom surface  23 A of the shuttle  22  disposed a distance away from the fluid passageway bores  19 . In this arrangement, the O-ring seals  30  of the shuttle  22  are normally maintained away from the sealing surface  27  of the valve body by the spring force of the second compression spring  31 A, thereby allowing fluid flow through the fluid passageways  19 . 
   In the normally open embodiment, the shuttle  22  is maintained by the second compression spring  31 A in a normally open position with its flat bottom surface disposed a distance away from the interior wall  16  and passageway bores  19 , and fluid of a pressure less than the spring force of the sprig  31 A flows through the fluid inlet  20  into the upstream chamber  12 , around the main body portion  23  of the shuttle  22 , through the passageway bores  19  into the downstream chamber  14  between the interior wall  16  and the upstream side  35 U of the piston  35 , and exits through the fluid outlet  21 . The first spring  31  maintains the shuttle  22  centered, and prevents wobbling. 
   Fluid at a pressure greater than the spring force of the spring  31 A and any differential pressure in the downstream chamber  14  moves the shuttle member to a closed position with its flat bottom surface  23 A engaged on the upstream side  16 U of the interior wall  16  and covering the passageway bores  19  and the O-ring seals  30  in fluid sealing relation on the sealing surface  27  to prevent fluid flow through the fluid passageway bores into the downstream chamber  14 . Upon the fluid pressure in the upstream chamber  12  falling below the spring force of the spring  31 A, the shuttle  22  is returned by the compression spring  31 A to its normally open position. 
   The sealing surface  27  of the valve body  11  and the main body portion  23  of the shuttle  22  have been shown and described in the embodiments above as being tapered at an acute angle, however, it should be understood that the sealing angle may range anywhere between 0° to 90°. 
   For example,  FIG. 5  shows, somewhat schematically, a valve sealing arrangement wherein either the upstream chamber  12  or downstream chamber  14  (depending upon whether the main body portion of the shuttle  22  is disposed in the upstream or downstream chamber) has a cylindrical sealing surface  27 A extending from the interior wall  16  that is substantially parallel with the longitudinal axis A of the valve body  11 , and the main body portion  23 A of the shuttle  22  has a cylindrical outer periphery  28 A extending from its flat bottom surface  23 A; thus forming a sealing surface having approximately a 0° sealing angle with respect to the longitudinal axis. 
     FIG. 6  shows, somewhat schematically, a valve sealing arrangement wherein either the upstream side  16 U or downstream side  16 D of the interior wall  16  (depending upon whether the main body portion of the shuttle  22  is disposed in the upstream chamber  12  or downstream chamber  14 ) has a flat sealing surface  27 B surrounding the fluid passageway bores  19  radially outward therefrom that is substantially perpendicular to the longitudinal axis A of the valve body  11 , and the flat bottom surface  23 A of the shuttle  22  has a seal ring groove  29  formed therein disposed radially outward from the fluid passageway bores  19  which receives an O-ring  30  to surround them when engaged on the sealing surface; thus forming approximately a 90° sealing angle with respect to the longitudinal axis. 
   The seal angle of the sealing surface depends upon the end use of the valve. When the angle is approximately a 90° sealing angle with respect to the longitudinal axis, (perpendicular) there would be no jamming of the shuttle, but the sealing properties may be reduced, particularly in instances where there is a low differential pressure across the seal. When the angle is approximately a 0° sealing angle with respect to the longitudinal axis (parallel), there is little possibility of jamming, but the seal life is reduced due to O-ring wear. When the seal angle is an angle less than 90°, but large there may be jamming, however, a good leakproof seal remains even with O-ring wear. When the seal angle is large enough to avoid jamming, the minimum differential pressure must be large enough to compress the O-ring(s). Thus, a preferred seal angle must strike a balance between the O-ring wear and the ability to seal at low differential pressures. 
   For the extreme case, where the valve is subject to very high differential pressure or very high dynamic differential pressure, as in a “water hammer” or explosive pressure, the seal angle should be great enough to provide good sealing at low differential pressure, over a range of O-ring wear, but small enough to prevent jamming. The wedge-shaped O-ring groove reduces the likelihood of the O-ring being swept out of the groove by a fast fluid flow. 
   The wedge-shaped O-ring groove  29  having tapered sides  29 B that converge angularly inward and upward from the bottom  29 A of the groove reduces the tendency for the O-ring  30  of the shuttle to be sucked out upon rapid opening of the shuttle. It should be understood, that the elastomeric O-ring seal element  30  may have a round or clover leaf transverse cross sectional configuration. 
   While this invention has been described fully and completely with special emphasis upon preferred embodiments, it should be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.