Abstract:
A unitized check valve assembly comprises: a valve body having a bore therethrough, the bore having an inlet and an outlet, a valve disk engaging said body at said outlet, a valve retainer engaging the body and surrounding the valve disk and the outlet; a first biasing member in compression between the body and the valve retainer; and a second biasing member in compression between the body and the valve disk. The flow passage between the valve seat and the valve is continuous around the circumference of the valve. In a preferred embodiment, the valve body and the valve disk each have a mating surface, the mating surfaces define an interface therebetween, and the interface comprises a portion of a spherical surface.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention generally relates to check valves used in pumping operations. More specifically, the invention relates to a check valve for pumping applications that includes a spherically profiled valve seat, a spherically profiled valve member, a replaceable spherically or conically profiled sealing member, a secondary means for maintaining the assembly as a unit, and a fluid outlet passageway that is unrestricted about the periphery of the sealing member. 
     BACKGROUND OF THE INVENTION 
     Check valves are devices that allow fluid to flow through a passageway in one direction but block flow in the reverse direction. They are used in a variety of applications. One of the many industrial applications for check valves is in reciprocating pump assemblies. Reciprocating pumps are used by field workers in various operations to pressurize a slurry mixture of solids and liquids and transfer fluids and mixtures from one station to another. 
     For example, reciprocating pumps are used in drilling operations to pressurize a slurry mixture of solids and liquids known as drilling mud to the bottom of a hole drilled into the earth. The pressurized mud is used to lubricate and cool a downhole drill bit as well as to carry loosened sediment and rock cuttings back to the surface. At the surface, the cuttings and sediment are removed from the returning drilling mud for examination and the filtered drilling mud is able to be reused. In many cases, highly abrasive particles are present in the fluids that are being pumped through the system. Because of these highly abrasive components, valves and seals of reciprocating pumps must be designed to resist harsh abrasion, while maintaining positive sealing action and withstanding high operating pressures. 
     A schematic diagram of a check valve supported reciprocating pump is shown in FIG.  1 . In a pump of this type, a piston  21  reciprocates within a cylinder  20  in the direction shown by arrow  24 . Check valves  22  are utilized at inlets  25  and outlets  26  of the cylinder  20  to restrict the flow of fluid to one direction. At fluid inlet  25 , a check valve  22  is placed and oriented so that it only allows inward flow. At outlet  25 , another check valve  26  is located so that it that only allows outward flow. The use of check valves  22  at pump inlets  25  and outlets  26  enables the pump to function in a much simpler fashion that does not require a timing or driving means to open and close the inlet  25  and outlet  26  valves at the appropriate times. Check valves  22  are often spring loaded so that at times of low or zero flow pressure, they are automatically shut. Effective check  410  valves  22  for pumping applications are also designed so that pressure in the back-flow direction contributes to the strength of the sealing mechanism. 
     For pump applications that utilize multiple check valves, it is preferred that all check valves be of the same design to ensure that the inlet and outlet flow characteristics of the pump are similar. Additionally, identical check valves allow the pump operator to carry fewer replacement parts, since he or she only has to carry parts for one type of valve. In many applications, it is further preferred that the check valves be unitized, or self-contained. A damaged unitized check valve can be easily removed from the pump assembly and replaced with minimal tooling and effort. Once the unitized check valve has been removed from the pump device, it can be disassembled and repaired if possible. By replacing check valves as units, expensive delays in operations can be minimized. 
     FIG. 2 shows a prior art unitized check valve that is typical of those used in reciprocating pump assemblies. The prior art check valve assembly  80  includes a valve body  81 , a seal member  82 , a biasing spring  83 , and a spring retainer  84 . The seal member  82  has a conical seal face  88  and guide legs  85  that facilitate the alignment within the valve body  81 . The valve body  81  has a corresponding conical valve seat  87 , and inner diameter  89 , and rotary retaining tabs  90  for engaging the spring retainer  84 . The spring retainer  84  has rotary retaining hooks  91  and fluid flow passageways  86 . The rotary retaining hooks  91  of the spring retainer  84  correspond with the rotary retaining tabs  90  of the valve body  81  to form what is commonly referred to as a bayonet connector. 
     The check valve is assembled by placing seal member  82  into valve body  81 , placing biasing spring  83  on top of seal member  82 , placing the spring retainer  84  over spring  83  and compressing spring  83  until spring retainer  84  meets valve body  81 , and engaging the bayonet connectors by turning retainer  84  clockwise with respect to valve body  81 . Once assembled, seal member  82  is free to move up and down within the assembly while the guide legs  85  assure that when in the down position, the seal face  88  of the seal member  82  aligns properly with the valve seat  87 . The valve design allows flow from valve body  81  through retainer  84  but prevents the fluid from flowing from retainer  84  through the valve body  81 . The biasing spring  83  acts both to shut the valve during situations of low pressure and to maintain the tension required to keep the bayonet connection engaged. 
     It is preferred that all components of a reciprocating pump be designed so that the flow of the working fluid is as unrestricted as possible. Obstructions to fluid flow in the pump assembly can create fluid turbulence which increases the flow resistance of the fluid. By reducing flow resistance, a pump&#39;s efficiency, or ratio of work output to work input, can be increased. Increasing the efficiency of the pumping device reduces the costs of operation. In addition, because of the aforementioned abrasive particles existent in fluids, if prior art check valves are installed in solids laden pumping applications, they would experience a tremendous amount of erosion wear and fail prematurely. Hence, an effective check valve design for reciprocating pump applications should be able to withstand abrasive elements and maintain a tight seal. 
     The guide leg design of the prior art unitized check valve blocks the free flow of fluid from the valve body to the spring retainer and can cause undesirable turbulence. Also, the prior art design check valve includes a single biasing spring to compress the sealing member against the valve seat and to maintain the bayonet connection between the valve body and the spring retainer. In the event of failure or weakening of this biasing spring, the prior art valve can come apart during operation and damage the surrounding pump components. In order to prolong pump life and minimize operating costs, an alternative to the prior art design is desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a unitized check valve that includes a spherical valve seat geometry, a free flowing design, a field replaceable valve seal, and an independent assembly maintenance device. The spherical geometry offers an improvement over traditional conical geometry by allowing the valve to function without precise alignment of its components. By eliminating the need for guidance members of traditional designs, disruptions to fluid flow within the valve and induced flow turbulence can be minimized. 
     The invention also incorporates a replaceable seal element about the seal disk that is able to withstand the particulate abrasion that occurs in some reciprocating pump applications. When the elastomeric seal element finally does wear to ineffectiveness, the element can be quickly replaced in the field, allowing the valve to be inexpensively repaired and returned to use. 
     In one preferred embodiment the assembly maintenance device is a wave spring compression element. The assembly maintenance device acts independently of the valve disc biasing device to maintain the unity of the check valve assembly in the event of failure or weakening of the main valve biasing spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of a reciprocating pump apparatus that utilizes inlet and outlet check valves; 
     FIG. 2 is an exploded drawing of a typical prior art unitized check valve; 
     FIG. 2 b  is a perspective view of the device of FIG. 2 a  in its assembled state; 
     FIG. 3 is an exploded drawing of a unitized check valve in accordance with the present invention; 
     FIG. 4 is an assembly drawing of the unitized check valve of FIG. 3; 
     FIG. 5 is a section view of the valve body of the unitized check valve of FIG. 3; 
     FIG. 6 is a section view of the seal disk of a the unitized check valve of FIG. 3; 
     FIG. 7 is a section view of the replaceable seal member of the unitized check valve of FIG. 3; and 
     FIG. 8 is a section view of the outlet shroud of the unitized check valve of FIG. 3; 
     FIG. 9 is an assembly drawing of the unitized check valve without seal device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Initially referring to FIGS. 3 and 4, a unitized check valve assembly  10  in accordance with the present invention, includes an outlet shroud  11 , a biasing spring  12 , a valve  18 , a wave spring  15 , and a valve body  16 . According to a preferred embodiment, valve  18  comprises a valve sealing disk  13  and a replaceable seal device  14 . 
     Referring now to FIG. 5, valve body  16  includes a spherically profiled valve seat  56 , rotary bayonet connector tabs  52 , a load face  54  and a fluid inlet  58 . The profile of the spherical valve seat  56  can be described as the surface of intersection between the valve body  16  and an imaginary sphere  55  that includes a radius  57  and a center point  53  that lies on the center axis  59  of valve body  16 . 
     Referring now to FIGS. 6 and 7, valve disk  13  preferably includes an outer diameter  38 , a disk surface  34 , an annular shoulder  40 , a seal diameter  33 , and a biasing spring seat  32 . The disk surface  34  is preferably spherical in profile and corresponds to the geometry of the valve seat  56  portion of the valve body of FIG. 5. A cutaway  36  is located at the bottom of the valve disk  13  and is for the purpose of reducing the overall weight of the disk. The seal pocket  39  defined between the outer diameter  38  and the seal diameter  33  is adapted to receive replaceable seal  14 . 
     Referring now to FIG. 7, seal  14  includes a seal outer diameter  46 , an annular seal surface  42 , an annular v-notch  47  and an inner seal member  48  having an inner seal lip  49 . Seal  14  is preferably constructed to have a smaller inside diameter than the outside seal diameter  33  of seal disk  13 . The seal  14  is installed on valve disk  13  by stretching it over shoulder  40  until it rests within seal pocket  39 . Because the relaxed diameter of lip  49  is less than seal diameter  33 , seal member  48  is stretched and v-notice section  47  is compressed. This causes the inner seal lip  49  to press firmly against the seal diameter  33  thereby forming a fluid-tight seal between valve disk  13  and seal  14 . 
     Like disk surface  34  of valve disk  13 , seal surface  42  of seal  14  is preferably spherical in profile and also corresponds to the geometry of the valve seat  56 . Because of its elasmeric characteristics, seal surface  42  of seal  14  can also be conical. Once installed about valve disk  13 , seal surface  42  and disk surface  34  form the primary means to prevent reverse flow of the working fluid from the valve outlets  64  through the inlet  58 . Because it is removable from valve disk  13 , seal  14  can be easily replaced as it becomes worn, thus allowing a longer working life for valve disk  13 . 
     It will be understood that seal  14  can be omitted from the present design as shown in FIG. 9, if desired. Valve disk  13  itself can be made of an elastomer, if desired, or from any other material that is adapted to withstand the fluid flow, so long as it is capable of forming a seal with valve seat  56 . 
     Referring now to FIG. 8, outlet shroud  11  includes valve outlet cutaways  64  located about the periphery and rotary bayonet connector hooks  68  corresponding to the bayonet connector tabs  52  of valve seat  16 . A disk stop  62  is included inside the outlet shroud to prevent displacement of the valve disk  13  beyond a specified maximum distance from valve seat  52 . 
     Referring again to FIGS. 3 and 4, biasing spring  12  and wave spring  15  can be described. Biasing spring  12  is a simple coil spring that, when compressed, acts to maintain a load between the outlet shroud  11  and the valve disk  13 . Although an embodiment comprising a simple coiled metal spring with circular cross-section is shown, alternative embodiments of the invention include any suitable biasing means, including those of non-metallic composition or non-circular cross-section. Additionally, an alternative embodiment of the invention can include a biasing member manufactured of a viscous elastic material, for example a soft rubber or elastomer, that provides a damping effect to the valve disk in addition to any spring effects of traditional spring devices. 
     Wave spring  15  is preferably manufactured from a flat metal ribbon of generally rectangular cross-section that is formed into a circular ring. Around the circumference of this ring  15 , the ribbon material is upset into the sinusoidal geometry shown in FIG.  4 . Because of its sinusoidal configuration, appears to be “wave” shaped when viewed from the side. The wave spring  15  is equivalent in function to a typical coiled wire compression spring, but is dramatically reduced in height. The wave spring  15  is preferable to other styles of compact compression springs because of its simplicity of operation, its ease of assembly, and its ability to reliably provide a compression load that is not too high or too low. 
     The unitized check valve shown in FIGS. 3 and 4 is assembled by placing valve disk  13  with assembled seal  14  on top of valve seat  56  portion of valve body  16 . Wave spring  5  is then installed over the bayonet retaining tabs  52  and seated on the load face  54  of the valve body  16 . Biasing spring  12  is placed into spring seat  32  of valve disk  13  and outlet shroud  11  is placed over biasing spring  12 . To complete the assembly, outlet shroud  11  is forced toward valve body  16 , compressing both biasing spring  12  and wave spring  15 . While both springs  12  and  15  are compressed, outlet shroud  11  is rotated until the bayonet connector hooks  68  are aligned with their counterpart tabs  52  on valve body  16 . Once the tabs  52  and hooks  68  are aligned, springs  12  and  15  can be further compressed until outlet shroud  11  can be rotated to engage the bayonet connection. 
     Following assembly, the unit check valve can be placed into operation. The valve is designed to “open” and allow fluid passage when the force of the working fluid in the positive flow direction  60  exceeds the compressive load of biasing spring  12  that maintains valve  18  against the valve seat  56 . If flow pressure decreases or reverses direction, the biasing spring will act to close the valve  18  against the valve seat  56  and prevent reverse fluid flow. 
     The disk stop  62  is included in the geometry of the outlet shroud  16  to prevent displacement of the valve disk  13  beyond a predetermined maximum allowable displacement. Excessive displacement of the valve disk  13  may cause the disk to become stuck or reversed within the outlet shroud. A stuck or reversed valve disk  13  will prevent the valve assembly  10  from functioning properly. Disk stop  62  prevents such excessive displacement. 
     Wave spring  15  serves to maintain the bayonet connection and to prevent undesired disassembly of check valve  10  during operation. In unitized check valves without assembly maintenance springs  15 , the main biasing spring  12  acts as the only means securing the bayonet connector. In the event of biasing spring  12  failure or weakening, the bayonet connector can come apart during use, with serious consequences. Since the wave spring  15  of the present invention is not cycled with the opening and closing of the valve, it does not experience the fatigue experienced by conventional biasing springs  12  and can maintain the unity of the check valve  10  long after other components fail. 
     The spherical valve seat  56  and spherical seal surfaces  34  and  42  are preferred because they allow positive sealing without requiring precise alignment of the mating components. Prior art systems that utilize conical sealing surface geometries require alignment devices to ensure that the valve seats and seals effectively. Because the invention does not require precise alignment of valve disk  13  with valve body  16 , no alignment devices is required. By removing the need for alignment guides, the flow through the apparatus is unobstructed, making the valve assembly  10  of the present invention less flow restrictive than prior designs. 
     Finally, since the primary sealing device  14  of the check valve  10  is replaceable, the lifetime of the valve assembly can be extended well beyond the lifetime of traditional valves by simply replacing worn seals. The replaceable seal design enjoys an advantage over its predecessors because of the range of materials that may be selected for seal  14 . Depending on the composition of the fluid being flowed through the check valves, seal materials can be selected to maximize performance and durability for specific applications. 
     Although some aspects of the present invention are described with particular reference to a unitized check valve used with reciprocating pumps, it will be recognized that features thereof may be used or adopted to use in other applications and that the present invention can be used advantageously in any reciprocating pump application. While the preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. For example, the relative dimensions of various parts, the materials from which the components are made and other parameters can be varied. 
     The embodiments described herein are exemplary only, and are not limiting. Many variations and modifications of the invention and the principles disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims that follow, that scope including all equivalents of the subject matter of the claims.