Abstract:
A multifunction hydraulic valving apparatus includes a relief valve, a gas purge valve and a bleed valve disposed in a single bore.

Description:
TECHNICAL FIELD 
     The present invention relates generally to valving apparatus, and more particularly, to a multifunction valve for fluids. 
     BACKGROUND ART 
     Valves are frequently used in fluid handling devices, such as metering pumps. In such an environment, a relief valve is often provided to provide a fluid pressure relief function when fluid pressures exceed a maximum value. Further, an automatic air bleed valve separate from the relief valve is also typically provided to allow continuous bleed off of small amounts of air liberated from the working fluid which would otherwise accumulate and be trapped in the working chamber of the pump. Still further, a purge valve may be included to permit rapid purging of relatively large amounts of air from the working chamber. 
     In at least one type of pump design as disclosed in U.S. Pat. No. 5,860,793, the purge valve function is incorporated into the automatic air bleed valve. Specifically, the automatic air bleed valve comprises a ball disposed in a valve body and movable between a lower valve seat and an upper valve seat. A rod is disposed on the top of the ball and is movable therewith. During each discharge stroke of the pump, the ball and rod move upwardly away from the lower seat toward the upper seat. During travel of the ball, a small amount of air and working fluid escape out of the working chamber. Once the ball moves into engagement with the upper seat, further escape of air and working fluid is prevented. On the subsequent suction stroke, the ball moves downwardly back into sealing engagement with the lower seat. The purge function is effected by depressing a pushbutton on the valve, thereby limiting the upward movement of the rod and preventing the ball from reaching the upper seat during the upward travel thereof. Because the ball is not sealed, a larger quantity of air and working fluid can escape from the working chamber. While a purge function can be undertaken in this fashion, the amounts of air that be purged are limited owing to the small clearances between the ball and the valve body. In addition, the pump disclosed in the &#39; 793  patent requires the relief valve in addition to the valve that accomplishes the automatic bleed and purge functions. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a multifunction hydraulic valving apparatus includes a relief valve, a gas purge valve and a bleed valve. The relief valve, the gas purge valve and the bleed valve are disposed in a single bore. The apparatus is preferably, although not necessarily, adapted for use in fluid communication with a pump. 
     Preferably, the bleed valve comprises a ball disposed in a valve chamber and is movable into and out of engagement with a valve seat during suction and discharge strokes of the pump. Also preferably, the purge valve comprises a movable valve element which is manually displaceable away from a sealing position in engagement with a valve seat. Still further in accordance with the preferred embodiment, the relief valve comprises a spring-loaded poppet which is movable in response to an elevated fluid pressure condition away from a sealing surface. 
     The relief valve, the gas purge valve and the bleed valve may have coaxial sealing surfaces and the bleed valve may be disposed within the gas purge valve. In addition, the gas purge valve may be disposed within the relief valve. Still further, the purge valve may comprise a movable valve element and the bleed valve may include a ball movable within a valve chamber disposed in the movable valve element. 
     According to a highly preferred embodiment, the relief valve includes a spring-loaded poppet which is movable in response to an elevated fluid pressure condition, the purge valve comprises a movable valve element disposed in the poppet and the bleed valve includes a ball movable within a valve chamber disposed in the movable valve element. 
     In accordance with another aspect of the present invention, a multifunction hydraulic valving apparatus includes a relief valve, a gas purge valve and a bleed valve all disposed in a single bore. The relief valve, the gas purge valve and the bleed valve have a common center axis and the bleed valve is disposed radially inside the gas purge valve and the gas purge valve is disposed radially inside the relief valve. 
     In accordance with yet another aspect of the present invention, hydraulic apparatus includes a fluid pump and multifunction valving apparatus in fluid communication with the fluid pump and disposed in a single bore in the fluid pump. The valving apparatus includes a relief valve, a gas purge valve and a bleed valve wherein the relief valve, the gas purge valve and the bleed valve have coaxial sealing surfaces. The bleed valve is disposed radially inside the gas purge valve and the gas purge valve is disposed radially inside the relief valve and the relief valve includes a spring-loaded poppet which is movable in response to an elevated fluid pressure condition. The gas purge valve comprises a movable valve element disposed in the poppet and the bleed valve includes a ball movable within a valve chamber disposed in the valve element. 
     Other aspects and advantages of the present invention will become apparent upon consideration of the following drawings and detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 comprises a cross-sectional view of a metering pump incorporating the present invention; 
     FIG. 2 comprises a fragmentary, full sectional view of the metering pump of FIG. 1; 
     FIG. 3 comprises an enlarged, fragmentary, sectional view illustrating the multifunction valve of FIG. 2 in greater detail; and 
     FIG. 4 comprises a sectional view of the multifunction valve taken generally along the lines  4 — 4  of FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, a metering pump  10  is driven by a motor  12  and delivers a controlled quantity of process fluid into a conduit or receptacle (not shown). The metering pump  10  may be of the hydraulically-actuated type, the mechanically-actuated type or the electromagnetically-actuated type. 
     As seen in FIG. 2, the pump  10  is preferably of the hydraulically-actuated type and includes a liquid end  14  which is separated from a displacement chamber  16  by a diaphragm  18  and a mechanically actuated refill valve  20 . A piston or plunger  22  is disposed in the displacement chamber  16  and is reciprocated therein by a drive assembly  24 . In operation, reciprocation of the plunger  22  in the displacement chamber  16  results in reciprocating movement of the diaphragm  18  during suction and discharge strokes of the pump  10 . During each suction stroke, process fluid is drawn through one or more check valves  27  into a diaphragm head chamber  26 . During each discharge stroke, process fluid is discharged from the diaphragm head chamber  26  through one or more additional check valves  25 . During normal operation, a small amount of working fluid (e.g., oil) escapes from the displacement chamber  16  into a reservoir  28  in the drive assembly  24  through a multifunction valve  30  and through a clearance between the plunger  22  and a sleeve  31 . Eventually, the quantity of working fluid in the displacement chamber  16  is reduced to an extent which causes the diaphragm to contact and open the valve  20  during one or more suction strokes of the pump. Opening of the valve  20  causes working fluid to flow from the reservoir  28  through a spring-loaded check valve  32  and the valve  20  into the displacement chamber  16 . Eventually, sufficient make-up working fluid is supplied to the displacement chamber  16  to prevent further actuation of the valve  20  during subsequent suction strokes. In this fashion, the amount of working fluid in the displacement chamber  16  is maintained at a level sufficient to ensure continued proper operation of the pump  10 . 
     Referring now to FIG. 3, the multifunction valve  30  accomplishes an automatic air bleed function, a gas purge function and a relief function utilizing components disposed in a bore  40  formed in a top portion of a housing  42  of the displacement chamber  16 . Because the multifunction valve  30  is located above the displacement chamber  16 , any gas that might come out of solution from the working fluid migrates to the base of the valve  30  through passages  44  and  46 . 
     AIR BLEED VALVE DESIGN 
     The air bleed function is accomplished by an air bleed valve  50 , which includes a first valve element in the form of a ball  52 . The ball  52  is movable in a valve chamber or recess  54  formed in a second valve element  56 . The valve chamber  54  is defined in part by first and second sealing surfaces or valve seats  58 ,  60 , respectively. The first valve seat  58  is carried by an O-ring seal  59  which is retained by a retainer  61  held in place by an interference or friction fit inside the second valve element  56 . 
     During operation of the pump  10 , the ball  52  travels back and forth between the first and second valve seats  58 ,  60  and allows air and working fluid to escape from the displacement chamber  16 . Specifically, during each discharge stroke of the pump  10 , the pressure in the displacement chamber  16  rises, causing the pressure on the lower end of the ball  52  also to rise. The pressure on the upper end of the ball  52  remains at substantially atmospheric pressure and hence a pressure differential is created across the ball  52  which, in turn, causes the ball  52  to move toward the second valve seat  60 . During this travel of the ball  52 , a small amount of working fluid (approximately one drop per stroke) escapes from the displacement chamber  16  around the ball  52  into the bore  40 . Escaping with this working fluid is any gas which may have accumulated in the passage  46 . The level of working fluid in the bore  40  rises during subsequent strokes until such level reaches an exit port  62 . Thereafter, the working fluid flows in a drop-by-drop fashion through passages  63  and  65  to the reservoir  28 . A sight glass  64  is provided to allow an operator of the pump to visually observe this escape of working fluid, thus providing assurance of proper pump operation. 
     During each discharge stroke, once the ball  52  has moved into sealing engagement with the second valve seat  60 , further escape of working fluid and gas past the ball  52  is prevented. In addition, the second valve element  56  is biased by a spring  66  upwardly to cause a conical portion  68  thereof to sealingly engage a third sealing surface or valve seat  70  carried by an upper portion  72  of a poppet body  74 . This sealing engagement prevents further escape of working fluid and gas from the displacement chamber  16 . 
     As the plunger  22  begins a suction stroke, a reverse pressure differential is created across the ball  52 , in turn causing the ball  52  to be quickly pulled downwardly into engagement with the first valve seat  58  and preventing working fluid from being drawn back into the displacement chamber  16 . 
     PURGE VALVE DESIGN 
     In the event that a blockage occurs in the pump supply line, a vacuum pressure condition is created in the hydraulic working fluid during the suction stroke. This vacuum condition allows for a relatively large volume of gas to be liberated from solution. This gas pocket then accumulates under the valve  30 . When the supply line is reopened, the flow rate of the pump  10  is severely compromised by the presence of this gas volume. The performance of the pump  10  could be slowly restored through the gradual release of gas through the air bleed valve  50  described above. However, the operator of the pump typically prefers to quickly restore the pump back to normal operation. Thus, a purge valve  80  allows for a quick release(purge) of a large volume of accumulated gas from the hydraulic system. 
     When a button  82  on top of a manually displaceable actuator in the form of a stem  84  is depressed against an upward force exerted by a spring  85 , a bottom surface  86  of the stem  84  contacts a top surface  88  of the second valve element  56 . When the force applied to the button  82  and stem  84  exceeds the upward force exerted by the spring  66 , the second valve element  56  is displaced downwardly such that the conical portion  68  no longer is in sealing engagement with the third valve seat  70  carried by the upper portion  72  of the poppet body  74 . As seen in FIG. 4, the second valve element  56  may be machined from hexagonal bar. A sliding fit exists between points  89  of the hexagonal bar and an inner circular cylindrical surface  90  of the upper portion  72  of the poppet body  74 . Flat surfaces  92  of the hexagonal bar allow for passage of gas and working fluid. As the contact is removed between the conical portion  68  and the third valve seat  70 , working fluid then escapes up along the flat surfaces  92  of the hexagonal bar and out of an opening between the second valve element  56  and the third valve seat  70 . The clearances are designed to permit a large release of working fluid and gas. Thus, the gas is quickly purged to restore the pump to normal flow rates and operation. 
     If desired, the second valve element  56  may be fabricated from circular cylindrical bar having an outer diameter less than the diameter of the inner circular cylindrical surface  90  of the upper portion  72  of the poppet body  74  such that an annular clearance for the passage of gas and working fluid is provided. 
     RELIEF VALVE DESIGN 
     The poppet body  74  includes the upper portion  72  described above and a lower portion  100  joined together in any suitable fashion, such as by an interference fit. A conical surface  101  of the lower portion  100  is urged by a spring  102  into contact with a fourth sealing surface or valve seat  104  located just above the passage  46 . The force exerted by the spring  102  is controlled by the amount of spring compression, which is determined by the location of an adjustment stem  106 . The spring  102  is captured between the upper portion  72  of the poppet body  74  and a washer  108  which abuts a shoulder  110  of the adjustment stem  106 . A threaded portion  112  of the adjustment stem  106  is threaded into a cap  114  and the latter is threaded into the bore  40 . An O-ring  115  seals the bore  40 . The position of the washer  108  is adjusted by turning a top hexagonally-shaped portion  116  of the adjustment stem  106 . Clockwise rotation of the adjustment stem  106  (when looking down on the valve  30 ) causes downward movement of the washer  108  which increases the compression on the spring  102  and, in turn, the spring force. Counterclockwise rotation of the adjustment stem  106  conversely decreases the compression of the spring  102  and the applied spring force. A lock nut  117  is tightened down on the cap  114  to maintain the position of the adjustment stem  106 . An O-ring seal  118  abuts a shoulder  119  and prevents working fluid from entering an annular space between the stem  84  and the adjustment stem  106 . 
     Relief of pressure in the displacement chamber  16  occurs when the fluid pressure on the bottom of the poppet body  74  is high enough to overcome the spring force exerted on the top of the poppet body  74 . As seen in FIG. 4, the upper portion  72  of the poppet body  74  is machined from hexagonal bar and includes points  120  that have a sliding fit within a circular cylindrical surface  122  defining the bore  40 . Once the fluid pressure overcomes the force of the spring  102  and lifts the conical surface  101  out of contact with the fourth valve seat  104 , working fluid then escapes through clearances between flat surfaces  124  of the upper portion  72  and the surface  122 . Released oil then flows out of the exit port  62  and into the reservoir  28 . 
     If desired, the upper portion  72  of the poppet body  74  may be formed from circular cylindrical stock and may have an outer diameter less than the diameter of the circular cylindrical surface  122  to form an annular clearance for the passage of oil or other working fluid. 
     When the fluid pressure drops to a level where the fluid force on the bottom of the poppet body  74  is less than the spring force on the top, the poppet body  74  is then displaced downward until sealing contact of the conical surface  101  with the fourth valve seat  104  is restored. The points  120  of the upper portion  72  provide guidance while the poppet body  74  is in motion. To protect the pump components against damage from an overpressure condition, the operator may be advised to set the relief valve at 15% over the nominal operating pressure. The sight glass  64  allows the operator to see when the pump is in a relief condition. This visual indication of relief may aid in pump diagnostics and setting of the relief valve. 
     A cover  130  may be threaded onto the cap  114  and an O-ring  132  may be provided for sealing purposes, if desired. 
     From the foregoing, it can be seen that the first through fourth sealing surface are preferably coaxial (i.e., they have a common center axis). Also, the air bleed valve is preferably disposed radially inside the purge valve and the purge valve is preferably disposed radially inside the relief valve. This arrangement of elements advantageously results in a compact overall size. 
     Numerous modifications to the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is presented for the purpose of enabling those skilled in the art to make and use the invention and to teach the best mode of carrying out same. The exclusive rights of all modifications which come within the scope of the appended claims are reserved.