Abstract:
A valve assembly that includes a valve body defining a fluid passage. First and second ends of the fluid passage define first and second ports for fluid flow. A spring and piston are located in the fluid passage. The piston has a travel length extending between first and second positions with a third position located therebetween. The spring biases the piston from the first toward the third position and is located outside the axial piston passage. The piston at least partially defines a first, second and at least one third opening. The first opening defines a variable constriction which increases in size as the piston moves from the first to third positions. The piston end wall defines the second opening and the piston sidewall defines the third openings. Movement of the piston from the third to second position exposes the third openings increasing the area of the second port.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to valves and, more specifically, to a flow regulating valve that regulates the flow of fluid in one direction and allows the generally unregulated flow of fluid in the opposite direction. 
     2. Description of the Related Art 
     In vehicles employing hydraulic systems, it is known to employ valves that limit the flow of the hydraulic fluid through a fluid line leading to a hydraulic actuator such as a hydraulic motor or cylinder to a maximum flow rate. For example, in a combine harvester it is known to use an internal combustion engine to power a hydraulic pump. The hydraulic pump provides hydraulic fluid under pressure to a hydraulic circuit. Each of the driven wheels of the combine harvester may include a separate hydraulic motor that is powered by the hydraulic circuit. Each of the motors may be located in a separate loop in communication with the hydraulic circuit. By reversing the direction of flow through the individual loops with the use of a reversing pump, reversing valve or other suitable means, the rotational direction in which the wheel is driven may also be reversed. 
     In such a loop, it is known to provide two flow regulating valves, one on each side of the hydraulic motor. The flow regulating valves are positioned in the loop such that one of the valves limits the flow of hydraulic fluid through the hydraulic motor, or other hydraulically driven device, to a maximum flow rate in a first direction while the other valve limits the flow to a maximum flow rate in the opposite direction. During operation, while one valve is regulating flow, it is desirable for the other valve in the loop that is not performing a flow regulating function to freely pass the fluid therethrough with a minimal pressure drop and without restricting the flow rate of the fluid. 
     By providing flow regulating valves in each individual hydraulic motor loop, if one of the driven wheels begins slipping, the flow of hydraulic fluid to the slipping wheel will be limited to the maximum flow rate permitted by the valve. Limiting the flow rate of hydraulic fluid to the slipping wheel prevents excess flow of hydraulic fluid to the slipping wheel from depriving the remaining wheels of a sufficient flow of hydraulic fluid as well as preventing the uncontrolled spinning of the slipping wheel which can result in damage to the turf, cropland and/or tire.  FIGS. 1 and 2  illustrate one known example of such a flow-regulating valve. 
     The valve  10  shown in  FIGS. 1 and 2  includes a valve body  12  that receives outlet adapter  14  with an O-ring  15  or other suitable means providing a seal therebetween. Valve body  12  and outlet adapter  14  both include axially extending passages  16  and  18 , respectively, for conveying hydraulic fluid. Valve  10  also includes piston  20 , baffle member  22  and spring  24  which provide for the regulation of fluid flow through the valve. Valve  10  limits the flow of hydraulic fluid to a predetermined design flow rate when hydraulic fluid is flowing through valve  10  in the direction indicated by flow arrows  26  in  FIG. 1 . When hydraulic fluid is flowing in this regulated direction, piston  20  will initially be in the position shown in  FIG. 2  wherein spring  24  biases piston  20  away from baffle  22  to a point where radial flange  28  engages valve body  12 . The flow rate of hydraulic fluid through valve  10  is dependent upon the pressure differential across valve  10 . When the flow of hydraulic fluid through calibrated orifice  30  in the direction indicated in  FIG. 1  increases, the pressure differential acting on piston  20  will also increase. When the pressure differential and resulting force on the piston  20  exceeds the biasing force of spring  24 , piston  20  will be biased towards baffle  22 . As piston  20  moves towards baffle  22 , the annular orifice  32  defined between piston  20  and baffle member  22  decreases in size thereby restricting the flow of fluid through the valve. By properly selecting the spring and valve dimensions, valve  10  may be used to limit the flow of fluid in the direction indicated in  FIG. 1  to a maximum predetermined flow rate. 
     In  FIG. 2 , the flow of hydraulic fluid through valve  10  is in the opposite return flow direction as indicated by flow arrows  27 . When fluid is flowing in this return direction, there is no fluid flow force to counteract the biasing force of spring  24  and annular orifice  32  maintains a constant size regardless of the flow rate or pressure differential of the hydraulic fluid. Consequently, valve  10  does not positively control the flow rate of the hydraulic fluid through the valve in the return direction and flow is limited by the size of the metering orifice  30 . In other words, the valve does not regulate the flow of fluid through the valve when the fluid is flowing in the direction indicated by arrows  27  in  FIG. 2  but rather the limited size of metering orifice  30  restricts the flow of fluid through the valve resulting in a pressure drop across the valve and undesirable power losses and heating of the fluid. 
     Another example of a known flow compensating valve assembly is shown in U.S. Pat. No. 5,320,135. The valve assembly disclosed in this patent may be used with hydraulic cylinders found in hydraulic platform lifts. The compensator valve  1  includes a valve body  10  receiving a sleeve  12  having an upper portion  16  and a lower portion  18 . A piston  20  is sliding received within sleeve  12  and, as best seen in  FIGS. 3–6 , a spring  30  is provided between the bottom end  19  of the lower sleeve portion  18  and the top end wall  21  of piston  20 . Piston  20  includes an axial main port  22  and a pair of relief ports  23   a  and  23   b  on its side wall periphery portion. In operation, as shown in  FIG. 3 , when hydraulic fluid is traveling from the pump to the hydraulic cylinder from borehole  44  to bore  41 , as shown by the arrows, hydraulic fluid travels around and between the lower sleeve portion  18  and the inner wall portion  54  of the valve body  10  and into sleeve  12  through ports  15   a  and  15   b.  As shown, during this condition, piston  20  is forced toward bore hole  41  thereby causing relief ports  23   a  and  23   b  to be placed in communication with the relief region  56  of sleeve  12 . Thus, flow is provided through side relief ports  23   a  and  23   b  as well as through the axial main port  22 . When the flow direction is reversed, with fluid flowing from the hydraulic cylinder to the pump, and there is little or no back pressure as depicted in  FIG. 4 , spring  30  maintains the piston  20  in the fully extended position thereby allowing flow through the ports  23   a  and  23   b.  When the flow from the hydraulic cylinder to the motor is increased, as depicted in  FIG. 5 , piston  20  acts against the spring  30  and travels into sleeve  12  thereby closing off the fluid relief ports  23   a  and  23   b  such that flow occurs only through the main axial port  22 . As the hydraulic fluid pressure further increases as shown in  FIG. 6 , the piston exerts yet a greater force against spring  30  traveling further into the sleeve  12  so as to partially block outlet ports  15   a  and  15   b.    
     While the valve assembly disclosed in U.S. Pat. No. 5,320,135 may effectively regulate the flow of hydraulic fluid for the hydraulic cylinder of a hydraulic lift, it is not without shortcomings. If such a valve assembly were to be used to limit the flow of hydraulic fluid to a hydraulic motor by placing the valve in a hydraulic motor loop circuit, as shown in  FIGS. 4–6  of U.S. Pat. No. 5,320,135, the fluid flow would initially have to overcome the resistance of spring  30  before the valve is moved from the condition shown in  FIG. 4  to that shown in  FIG. 5 . This could result in a relatively rough transition wherein the fluid flow initially increases rapidly while the valve was in the condition of  FIG. 4  and then rapidly decreases as the valve is moved to the condition shown in  FIG. 5  wherein ports  23   a  and  23   b  are closed. The flow rate could then resume its increase until the valve begins to close ports  15   a  and  15   b  as depicted in  FIG. 6 . While this may be acceptable for the operation of a hydraulic lift, such a transition could result in the rough and unacceptable operation of a hydraulic motor driven wheel. This rough transition would likely be particularly evident when the direction of fluid flow to such a hydraulic motor was reversed and fluid flow was initially being increased. 
     An improved valve assembly is desired which may be used to efficiently regulate the flow of fluid in one direction to a hydraulic device without rapid or rough transitions and, in the other direction, allow unregulated fluid flow with minimal restriction thereby minimizing power losses and heating of the fluid. 
     SUMMARY OF THE INVENTION 
     The present invention provides a flow regulating valve that regulates the flow rate of a fluid through the valve in one direction and allows return fluid to efficiently flow through the valve in the opposite direction. 
     The invention comprises, in one form thereof, a valve assembly including a valve body defining a fluid passage extending through the valve body. The fluid passage has a first end and an opposite second end wherein the first end defines a first port through which fluid is communicated to and from the fluid passage and the second end defines a second port through which fluid is communicated to and from the fluid passage. A biasing element and a valve member are also provided. The valve member is moveably disposed within the fluid passage within the valve body and has a travel length extending from a first position relative to the valve body to a second position relative to the valve body. The biasing element biases the valve member along the travel length from the first position toward a third position disposed between the first and second positions. The valve member at least partially defines a variable first opening (e.g., variable annular opening  98 ), a second opening (e.g., metered orifice  62 ) and at least one third opening (e.g., openings  64 ). The first opening defines a variable constriction in the fluid passage between the first and second ends and has a size which progressively increases as the valve member moves from the first position toward the third position. The second opening and the at least one third opening define the second port wherein, when the valve member is disposed between the first position and the third position, the second port is defined substantially solely by the second opening and, when the valve member is in the second position, the second port is defined by both the second opening and the at least one third opening. The valve member defines a passage extending from the second port to the first opening and the biasing element is located outside the valve member passage. Fluid flow through the fluid passage in a first direction from the second end toward the first end exerts pressure upon the valve member and biases the valve member toward the first position. Fluid flow through the fluid passage in a second direction from the first end toward the second end exerts pressure upon the valve member and biases the valve member toward the second position. 
     The invention comprises, in another form thereof, a valve assembly including a valve body defining a fluid passage extending through the valve body. The fluid passage has a first end and an opposite second end. The first end defines a first port through which fluid is communicated to and from the fluid passage and the second end defines a second port through which fluid is communicated to and from the fluid passage. A biasing element and a valve member are also provided. The valve member is moveably disposed within the fluid passage within the valve body and has a travel length extending from a first position relative to the valve body to a second position relative to the valve body. The valve member further defines a third position along the travel length wherein the third position is disposed between the first and second positions. The valve member at least partially defines a variable first opening and the second port. The first opening defines a variable constriction in the fluid passage between the first and second ends and has a size that progressively increases as the valve member moves from the first position toward the third position. The second port is variably sized wherein the second port defines a first area providing fluid communication with the fluid passage when the valve member is in the third position and defines a second area providing fluid communication with the fluid passage when the valve member is in the second position with the second area being greater than the first area. The travel length includes a biased travel portion between the first and third positions wherein the biasing element biases the valve member from the first position towards the third position and an unbiased travel portion between the third position and the second position wherein the valve member is unbiased with respect to the biasing element. Fluid flow through the fluid passage in a first direction from the second end toward the first end exerts pressure upon the valve member and biases the valve member toward the first position. Fluid flow through the fluid passage in a second direction from the first end toward the second end exerts pressure upon the valve member and biases the valve member toward the second position. 
     The invention comprises, in yet another form thereof, a valve assembly including a valve body defining a fluid passage extending through the valve body. The fluid passage has a first end and an opposite second end. The first end defines a first port through which fluid is communicated to and from the fluid passage and the second end defines a second port through which fluid is communicated to and from the fluid passage. A spring is disposed within the fluid passage and is engageable with the valve body. A piston is moveably disposed within the fluid passage and is operably couplable with the spring. The piston has a travel length extending from a first position in the fluid passage to a second position in the fluid passage. The piston also defines a third position along the travel length wherein the third position is disposed between the first and second positions. The piston has a substantially cylindrical sidewall defining an axially extending passage through the piston and an end wall disposed at a first axial end of the piston. The piston at least partially defines a first opening, a second opening and at least one third opening. The first opening is in communication with the axial piston passage and is disposed at a second axial end of the piston opposite the first axial end. The first opening defines a variable constriction in the fluid passage between the first and second ends and has a size which progressively increases as the piston moves from the first position toward the third position. The end wall of the piston defines a second opening in communication with the axial piston passage and the piston sidewall defines at least one third opening proximate the end wall. When the piston is disposed between the first and third positions, the second port is defined substantially solely by the second opening and, when said piston is in the second position, the second port is defined by both the second opening and the at least one third opening. The spring is located outside the axial piston passage. Fluid flow through the fluid passage in a first direction from the second end toward the first end exerts pressure upon the piston and biases the piston toward the first position. Fluid flow through the fluid passage in a second direction from the first end toward the second end exerts pressure upon the piston and biases the piston toward the second position. 
     An advantage of the present invention is that it minimizes the restriction and enhances the return flow of fluid through the valve and thereby reduces power losses and the heat generated by the flow of return fluid through the valve in the unregulated direction. Additionally, by removing the spring from the interior of the piston, the calibration orifice of the piston may be enlarged thereby reducing the pressure drop experienced by fluid flowing through the calibration orifice and enhancing the operation of the valve for fluid flow in both the regulated and unregulated flow directions. The regulation of the fluid flow through the valve assembly in the regulated flow direction is also relatively smooth without abrupt transitions as the flow rate changes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a cross sectional view of a conventional flow regulating valve. 
         FIG. 2  is another cross sectional view of the conventional flow regulating valve of  FIG. 1 . 
         FIG. 3  is an exploded view of a valve in accordance with the present invention. 
         FIG. 4  is a cross sectional view of the valve of  FIG. 3  wherein fluid is flowing in the regulated direction at less than the maximum flow rate. 
         FIG. 5  is another cross sectional view of the valve of  FIG. 3  wherein fluid is flowing in the regulated direction at the maximum flow rate. 
         FIG. 6  is another cross sectional view of the valve of  FIG. 3  wherein fluid is flowing in the unregulated direction. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A valve assembly  40  in accordance with the present invention is shown in an exploded view in  FIG. 3 . Valve assembly  40  includes a valve body  42  having a passageway defined by three axially aligned cylindrical bore sections  44 ,  46 ,  48  of differing diameters. In the illustrated embodiment, valve member  50  takes the form of a piston  50  reciprocatingly disposed in valve body  42 . Piston  50  includes a cylindrical sidewall  52  that defines interior passage  54  extending from first axial end  56  of piston  50  to the opposite second axial end  58  of piston  50 . An endwall  60  is located at first axial end  56  and includes a metering orifice  62 . A plurality of circumferentially spaced openings  64  are located in sidewall  52  proximate first axial end  56 . Second axial end  58  of piston  50  is open, i.e., it does not include an endwall or otherwise define a restriction within axial passage  54 . The radially outer surface of sidewall  52  at second axial end  58  forms a tapered surface  66  which cooperates with baffle member  78 . Piston  50  also includes a radially outwardly extending flange  68 . 
     A coupling member  70 , which takes the form of a washer in the illustrated embodiment, is located between flange  68  and biasing element  76 . Washer  70  includes a planar annular element  72  having a lip  74  located at its outer circumference. In the illustrated embodiment, biasing element  76  is a helical spring and the portion of spring  76  which directly engages washer  70  is seated within lip  74  to maintain the proper engagement of spring  76  with washer  70  during operation of valve  40 . 
     A baffle member  78  is also shown in  FIG. 3  and includes a cylindrical sidewall  80  having a first end  82 . First end  82  of baffle  78  cooperates with second axial end  58  and tapered surface  66  to define a variable opening  98 . A radially projecting flange  84  is used in the securement of baffle  78  within valve  40 . An interior partition  86  extends across the interior space of the baffle and includes a bleed hole  88 . Circumferentially spaced openings  90  are located in sidewall  80  with partition  86  being located between first end  82  and openings  90 . 
     Baffle  78  is fixed within valve assembly  40  between adapter body  92  and valve body  42 . Baffle  78  is fixed in place by spring  76  which biases radial flange  84  into engagement with adapter body  92 . Alternative methods of securing baffle  78  may also be employed. Such alternative retaining means for preventing baffle member  78  from moving toward piston  50  during reverse flow conditions could include a snap ring seated in an annular groove in cylindrical bore  48 , a radially inwardly projecting annular lip in bore  48 , or a step in bore  48  that would engage radial flange  84 . Dashed lines  48   a  in  FIG. 3  illustrate schematically represent such an alternative retaining means that could be formed by a snap ring or annular lip. The function of baffle  78  might also be incorporated into another component part of valve assembly  40  such as adaptor body  92  or valve body  42 . For example, baffle  78  could be integrally formed with adaptor body  92 . Adapter body  92  includes an interior fluid passage  94  that is in fluid communication with bore  48  to thereby form a fluid passage  100  extending through valve assembly  40  between first port  102  and second port  104 . An O-ring  96  is used to provide a seal between adapter body  92  and valve body  42 . Other suitable means for providing a seal may also be employed. 
       FIG. 4  illustrates valve assembly  40  with fluid flowing in a first direction from the second end  105  of fluid passage  100  to the first end  103  of fluid passage  100  as indicated by flow arrows  106 . The flow direction illustrated in  FIG. 4  is the regulated flow direction of valve assembly  40 . As shown in  FIG. 4 , the flow path of fluid through fluid passage  100  of valve assembly  40  begins with fluid entering passage  100  through second port  104 . When piston  50  is in the position shown in  FIG. 4 , the second port is defined solely by an opening  62  which forms a metered orifice. Fluid enters axial passage  54  through second port  104  and subsequently passes through variable opening  98  to enter bore section  48  where it passes through and around spring  76  before entering openings  90  in baffle  78 . After passing through baffle  78 , the fluid enters passage  94  in outlet adapter  92  and then exits valve assembly  40  through first port  102 . 
       FIG. 4  illustrates the condition wherein the fluid flow and pressure differential on opposite sides of piston  50  is not sufficient to overcome the biasing force of spring  76 . In this condition, spring  76  biases washer  70  into engagement with end face  47  of bore  48  in valve body  42 . Relief bore  46  is configured to allow flange  68  to be received therein and prevent the entry of washer  70 . In the illustrated embodiment, this is accomplished by using a circular washer  70  having a diameter greater than cylindrical bore  46 , however, other geometric shapes may also be employed. When fluid is flowing in the direction indicated by flow lines  106 , a pressure differential between different points in the fluid path will exist and will generate forces acting upon piston  50 , primarily the pressure differential on either side of orifice  62  which acts upon end wall  60 , and will bias piston  50  to the position shown in  FIG. 4 . At relatively low flow rates, the force acting on piston  50  generated by the pressure differential will be relatively low and be unable to overcome the biasing force of spring  76 . 
       FIG. 5  illustrates valve assembly  40  with fluid flowing in the same direction as shown in  FIG. 4  but wherein the pressure differential on opposite sides of piston  50  is higher. In the condition illustrated in  FIG. 5 , the force acting on piston  50  generated by the pressure differential is large enough to compress spring  76  and bias piston  50  toward baffle member  78 . As piston  50  is biased towards baffle  78 , annular opening  98  becomes progressively smaller and thereby acts to restrict the flow of fluid through fluid passage  100 . Generally, a higher pressure differential would result in a higher flow rate through a given fluid passage. However, due to the variable constriction in fluid passage  100  defined by variable opening  98 , opening  98  acts to constrict the flow of fluid through passage  100  and thereby counteracts the flow increasing effects of an increasing pressure differential. At a sufficiently high pressure differential, opening  98  may be completely closed with tapered surface  66  engaging baffle end  82 . If opening  98  is completely closed, a small quantity of fluid may still pass through bleed hole  88  and allow some fluid to be conveyed through fluid passage  100 . Thus, the operable coupling of spring  76  with piston  50  provides a restriction, i.e., opening  98 , that varies in response to the pressure differential of the fluid on opposite sides of the restriction and thereby provides a flow compensating mechanism which limits the flow rate of fluid through valve assembly  40  to a maximum value. The precise value of the maximum flow rate will be determined not only by the dimensions of opening  62 , the spring force of spring  76  and the configuration of variable opening  98 , but also by the properties of the fluid flowing through the valve assembly as will be recognized by those having ordinary skill in the art. 
       FIG. 6  illustrates valve assembly  40  with fluid flowing in a direction reverse to that depicted in  FIGS. 4 and 5  as indicated by flow arrows  108  and sometimes referred to as the unregulated direction. When fluid flows in the direction depicted in  FIG. 6 , if piston  50  is initially in the position shown in  FIG. 5 , it will be biased by spring  76  into the position shown in  FIG. 4 . At this position, a radial outer portion  73  of coupling member  70  engages endface  47  to limit the travel of the coupling member, e.g., washer  70 . Piston  50  will then be biased to the position shown in  FIG. 6  due to the pressure differential and forces imparted to piston  50  by the fluid impinging upon piston  50 , primarily upon end wall  60 , as the fluid flows through valve assembly  40 . The travel of piston  50  will be stopped at the position shown in  FIG. 6  due to the engagement of flange  68  with end face or ledge  67  between cylindrical passage sections  46  and  44 . Thus, piston  50  has a length of travel from a first position  50   a  depicted in  FIG. 5  to a second position  50   b  depicted in  FIG. 6  which has a biased portion and an unbiased portion with respect to spring  76 . Piston  50  also has a third position  50   c,  depicted in  FIG. 5 , between the first and second positions  50   a,    50   b.  When piston  50  is located between the first position  50   a  and third position  50   c,  spring  76  exerts a biasing force on piston  50  urging it towards the third position  50   c,  thus, that portion of the travel length of piston  50  between positions  50   a  and  50   c  is a biased portion. When piston  50  is located between positions  50   c  and  50   b,  piston  50  is unbiased with respect to spring  76 . As described above, however, piston  50  is biased by the flow of fluid either toward or away from baffle  78  when it is between positions  50   c  and  50   b.    
     When piston  50  is between positions  50   a  and  50   c  shown in  FIGS. 5 and 4  respectively, second port  104  is defined solely by metering orifice  62  which has a fixed area for the communication of fluid therethrough. As piston  50  moves from position  50   c  to position  50   b  shown in  FIG. 6 , first end  56  of piston  50  is projected beyond cylindrical section  43  of valve body  42  exposing openings  64  in sidewall  52 . As openings  64  are exposed, the area of second port  104  is effectively enlarged enhancing the outflow of fluid from fluid passage  100 . In the illustrated embodiment, variable opening  98  is also enlarged as piston  50  moves from position  50   c  ( FIG. 4 ) to position  50   b  ( FIG. 6 ) and increases the gap between baffle end  82  and piston end  58 . It is not necessary for opening  98  to vary in area when piston  50  is between positions  50   c  and  50   b  because valve assembly  40  is not performing a flow regulating function when fluid flow positions piston  50  between  50   c  and  50   b.  The continued enlargement of opening  98 , however, whereby opening  98  has its largest area when piston  50  is in position  50   b,  does advantageously enhance the flow of fluid through valve assembly  40  in the reverse or unregulated direction depicted in  FIG. 6 . 
     When the valve assembly is in the condition shown in  FIG. 6  and the flow of fluid is reversed, piston  50  will initially be in the position shown in  FIG. 6 , however, since piston  50  is unbiased by spring  76  in this position, piston  50  will move to the position shown in  FIG. 4  almost immediately upon the reversal of fluid flow due to the forces acting on piston  50  caused by the flow of fluid through valve assembly  40  and the flow rate will not be subject to a later rough transition caused by the closure of openings  64 . Thus, by providing a piston  50  with a travel length having a portion unbiased by spring  76 , the flow of fluid through valve  40  in the direction shown in  FIG. 4  almost immediately closes openings  64  and allows the flow rate of the hydraulic fluid to be smoothly regulated. 
     It is also noted that the efficient flow of fluid through valve assembly  40  is enhanced by the use of a large diameter spring that is located radially outwardly of cylindrical sidewall  52  of piston  50 . By providing a spring  76  having a diameter  77  that is larger than the diameter  51  of piston  50  and locating spring  76  outside of the axial passage of the piston, opening  62  in end wall  60  can be made larger because end wall  60  no longer must engage spring  76 . The use of a larger metering orifice  62  facilitates the efficient conveyance of fluid through valve assembly  40  in both directions. By more efficiently conveying fluid through valve assembly  40 , the fluid will experience a smaller pressure loss and generate less heat as it passes through orifice  62  and valve assembly  40 . 
     Also seen in  FIGS. 3–6  is an O-ring  110  located on cylindrical section  43 . O-ring  110  is used to provide a seal between valve body  42  and the structure to which valve body  42  is secured. In a typical installation, valve body  42  would be threaded into the port of a cast iron valve body. Similarly, O-ring  112  located on adapter body  92  is used to provide a seal between adapter body  112  and a fluid conduit or other fluid conveyance structure. In a typical installation, adaptor body  92  would be placed in communication with a fluid conduit, e.g., a hose or tube, leading to a hydraulic motor. 
     While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.