BACKGROUND OF THE INVENTION 
       [0001]    This disclosure generally relates to valves, and more particularly, to contaminant resistant pressure regulating valves. 
         [0002]    Some known valves incorporate matched diameter components with metering edges to resist buildup of contaminants that may be present in fluid passed through the valves. However, pressure and fluid flow forces may drive contaminants into clearances between the matched diameter components. Over time, such contaminants may accumulate in these sensitive clearances, which may bind the valves in the open or closed position, for example. 
         [0003]    When the valves are open and flowing, the contaminants in the fluid stream may be directed into these clearances by fluid momentum and pressure deltas (i.e., pressure differences over a portion of the valves). When the valves are closed, the pressure deltas continue to drive contaminants into clearances such as diametrical clearances between a piston and a sleeve. In addition, the valves may include a metering edge that includes non-flowing areas, which may allow contaminants to remain in those non-flowing areas and build up over time. Accordingly, it is desirable to provide a self-cleaning, contamination resistant valve. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one aspect, a pressure regulating valve assembly is provided. The valve assembly includes a housing having a fluid inlet and a fluid outlet, a sleeve positioned within the housing, and a spool at least partially positioned within the sleeve. The spool includes an outer surface having a shoulder, and the spool is configured to translate within the sleeve between a closed position and an open position. The valve assembly further includes a cap coupled to the sleeve and surrounding at least a portion of the spool, and the cap includes an inner surface with a flange extending therefrom. In the closed position the spool shoulder abuts against the cap flange to define a sealed metering edge. In the open position the spool shoulder is spaced from the cap flange to unseal the metering edge and define a metering window to facilitate fluid flow therethrough to the fluid outlet. 
         [0005]    In another aspect, a pressure regulating valve assembly is provided. The valve assembly includes a housing having a fluid inlet, a first fluid outlet, and a second fluid outlet, a sleeve positioned within the housing, the sleeve including a window formed therethrough, and a spool at least partially positioned within the sleeve. The spool includes a downstream end and an upstream end, the upstream end including an outer surface having a shoulder, and the downstream end having an axially extending fluid channel and at least one fluid outlet formed therein. The spool is configured to translate within the sleeve between a closed position and an open position. The valve assembly further includes a cap coupled to the sleeve and surrounding at least a portion of the spool, the cap having an inner surface with a flange extending therefrom. The spool shoulder is configured to abut against the cap flange to define a sealed metering edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0007]      FIG. 1  is a cross-sectional view of a valve assembly in a closed position; 
           [0008]      FIG. 2  is a cross-sectional view of the valve assembly shown in  FIG. 1  in an open position; 
           [0009]      FIG. 3  is an enlarged view of the valve assembly shown in  FIG. 1  and taken on section  3 ; and 
           [0010]      FIG. 4  is an enlarged view of the valve assembly shown in  FIG. 2  and taken on section  4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    Described herein is a pressure regulating valve having self-cleaning, contaminant resistant features. The valve includes a cap and a translating spool. In a closed position, the spool abuts against the cap to create a sealed metering edge. In an open position, a 360° metering edge or window is defined between the spool and the cap and facilitates preventing contaminates from being trapped proximate the metering edge. A downstream intermediate area between the spool and the cap and an outlet window formed in the cap are each formed larger than an inlet window formed in the spool. The larger downstream intermediate area and outlet window create a zero pressure restriction that facilitates preventing contaminant buildup between the spool and other valve components. 
         [0012]      FIGS. 1 and 2  illustrate a cartridge or valve assembly  10  that generally includes a housing  12 , a sleeve  14 , a spool  16 , a cap  18 , and a closure  20 .  FIG. 1  illustrates valve assembly  10  in a closed position, and  FIG. 2  illustrates valve assembly  10  in an open position. 
         [0013]    Housing  12  includes a fluid inlet  22 , a main fluid outlet  24 , and a secondary fluid outlet  26 . A fluid  100  flows from fluid inlet  22  to fluid outlets  24 ,  26 , as is described herein in more detail. Fluid inlet  22 , main fluid outlet  24 , and secondary outlet  26  are each configured to be coupled to plumbing ( 104 ,  106 ,  108 ) of a pressure regulated system (e.g., a dual vane fuel pump). In one embodiment, assembly  10  is a self-contained cartridge that may be inserted directly into the pressure regulated system (not shown). 
         [0014]    Sleeve  14  is positioned within housing  12  and includes a first end  28 , a second end  30 , and an inner wall  31  defining a spool cavity  32 . First end  28  includes a threaded outer surface  34 , and second end  30  includes a window  36  formed therein. Window  36  defines a downstream variable restrictor  38  to restrict fluid flow to secondary fluid outlet  26 . 
         [0015]    Spool  16  is movably positioned within sleeve spool cavity  32  such that spool  16  translates between the closed position ( FIG. 1 ) and the open position ( FIG. 2 ). Spool  16  is biased in the closed position by a biasing mechanism  40  (e.g., a spring). Spool  16  includes a large piston or upstream end  42  and a small piston or downstream end  44 . Upstream end  42  includes a cylindrical wall  46  and a cylindrical wall  48  extending therefrom. Cylindrical wall  46  defines a bore  50  therein, and cylindrical wall  48  defines an inlet area  52  therein to receive fluid flow  100  from housing inlet  22 . Cylindrical wall  48  includes inlet windows  54  formed therethrough to facilitate supplying fluid  100  to housing main fluid outlet  24  when valve assembly  10  is in the open position. 
         [0016]    Spool downstream end  44  includes an axially extending fluid channel  56  that extends between bore  50  and fluid outlets  58  formed in downstream end  44 . Fluid outlets  58  are fluidly coupled to downstream variable restrictor  38  when valve assembly  10  is in the open position, and fluid is prevented from entering restrictor  38  via fluid outlets  58  when valve assembly  10  is in the closed position. 
         [0017]    A fixed orifice  60  is oriented within spool bore  50  and includes an inlet end  62  and a restrictor outlet end  64  fluidly coupled to fluid channel  56 . A screen or fine filter  66  is coupled to fixed orifice inlet end  62  to facilitate filtering particulates or contaminants out of fluid flow  100  passing therethrough from spool inlet area  52 . 
         [0018]    Cap  18  is generally cylindrical and includes a first end  68 , a second end  70 , and an inner wall  72  defining an aperture  74 . Inner wall  72  includes a threaded portion  76  on second end  70  such that second end  70  is coupled to sleeve  14  by threading onto sleeve threaded surface  34 . However, cap  18  may be coupled to sleeve  14  by any suitable fastening or coupling method (e.g., via welding). Cap first end  68  may include a screen or coarse filter  78  to facilitate filtering particulates or contaminants out of fluid flow  100  passing therethrough from housing fluid inlet  22  to spool inlet area  52 . 
         [0019]    Cap  18  includes outlet windows  80  formed therethrough to fluidly couple spool inlet area  52  and housing main fluid outlet  24  when valve assembly  10  is in the open position. When cap  18  is coupled to sleeve  14 , an intermediate cavity  82  is defined between spool cylindrical wall  48  and cap inner wall  72 . Intermediate cavity  82  receives fluid  100  flowing through spool inlet windows  54 . 
         [0020]    Cap outlet windows  80  and/or intermediate cavity  82  each have an area and/or volume that is larger than the respective area and/or volume of spool inlet windows  54  to create a low pressure area downstream of spool inlet windows  54 . The low pressure area facilitates supplying fluid flow  100  directly to housing main fluid outlet  24  through inlet windows  54 , intermediate cavity  82 , and cap outlet windows  80 , and facilitates preventing fluid flow  100  from entering a clearance  84  defined between spool  16  and sleeve inner wall  31 . As such, contaminants contained in fluid  100  are prevented from being deposited within clearance  84 . 
         [0021]    Closure  20  is positioned within housing  12  and includes an inner wall  86  defining a bore  88  that receives a portion of sleeve  14 . Closure  20  also includes outlet windows  90  formed therethrough to enable fluid  100  to flow from spool fluid outlets  58 , through downstream variable restrictor  38 , and to housing secondary fluid outlet  26 . 
         [0022]    In one embodiment, valve assembly  10  includes a fluid modulating circuit  102 , which is defined by and includes serial flow through filter  66 , fixed orifice  60 , spool fluid channel  56 , spool fluid outlets  58 , downstream variable restrictor  38 , closure outlet windows  90 , and housing secondary fluid outlet  26 , as is described herein in more detail. 
         [0023]      FIGS. 3 and 4  illustrate relative positioning between spool  16  and cap  18  in the open and closed positions of valve assembly  10 .  FIG. 3  illustrates valve assembly  10  in the closed position, and  FIG. 4  illustrates valve assembly  10  in the open position. As shown in more detail, spool cylindrical wall  46  includes a tapered shoulder  92  and cap inner wall  72  includes a flange  94 . 
         [0024]    In the closed position ( FIG. 3 ), spool shoulder portion  92  abuts against flange  94  to create a sealed metering edge  96 , which facilitates preventing flow of fluid  100  to housing main fluid outlet  24 . In the exemplary embodiment, spool  16  and cap  18  are fabricated from metal such that there is a metal-to-metal contact seal formed therebetween. However, spool  16  and cap  18  may be fabricated from any suitable material that enables valve assembly  10  to function as described herein. 
         [0025]    In the open position ( FIG. 4 ), spool shoulder portion  92  and flange  94  are separated to create a clearance or metering window  98  therebetween such that metering edge  96  is unsealed and facilitates flow of fluid  100  through spool inlet windows  54  to housing main fluid outlet  24 . In the illustrated embodiment, metering window  98  is a 360° circumferential window formed between spool  16  and cap  18 , and the 360° window facilitates eliminating non-flowing areas that may trap contaminants proximate metering edge  96 . 
         [0026]    In operation, fluid  100  flows from an inlet conduit  104 , through housing fluid inlet  22 , and passes through filter  78  where relatively large contaminants or particles contained in fluid  100  are separated therefrom. Fluid  100  subsequently flows into spool inlet area  54 . 
         [0027]    With valve assembly  10  in the closed position ( FIGS. 1 and 3 ), tapered shoulder  92  is seated against cap flange  94  such that metering edge  96  is sealed and facilitates preventing fluid flow  100  into intermediate cavity  82  and thus housing main fluid outlet  24 . Fluid  100  may flow into spool fluid channel  56  of modulating circuit  102  via filter  66  and fixed orifice  60 . However, in the closed position, spool fluid outlets  58  abut against sleeve inner wall  31 , thereby facilitating preventing fluid  100  from flowing into downstream variable restrictor  38  and thus housing secondary fluid outlet  26 . 
         [0028]    Valve assembly  10  is moved to the open position ( FIGS. 2 and 4 ) when the fluid pressure on spool  16  exceeds the designed biasing force of biasing mechanism  40 . As such, spool  16  is translated within sleeve  14  toward closure  20  and into the open position. During the translation of spool  16 , tapered shoulder  92  is separated from cap flange  94 , which unseals metering edge  96  and forms the 360° metering window  98  between spool  16  and cap  18 . With metering edge  96  unsealed, fluid  100  freely flows into intermediate cavity  82  while removing or self-cleaning any contaminates that have built up on spool  16  and/or cap  18  near metering edge  96 . Fluid  100  subsequently flows through cap outlet windows  80  to housing main fluid outlet  24  and into a main outlet conduit  106  coupled to housing  12 . 
         [0029]    Because intermediate cavity  82  and outlet windows  80  have a larger area and/or volume than spool inlet windows  54 , the resulting lower pressure of the larger area and/or volume directs fluid  100  to main fluid outlet  24  rather than into clearance  84 . Accordingly, the pressure on both sides of spool upstream end  42  is directed to the same pressure source to minimize any delta pressure across the interface between the inner diameter of sleeve first end  28  and the outer diameter of spool  16 , which facilitates preventing fluid  100  and any contaminants flowing into sensitive clearance  84  by pressure deltas. 
         [0030]    In addition to flow through metering window  98 , fluid  100  may be directed through modulating circuit  102  when valve assembly  10  is in the open position. As such, a portion of fluid  100  flows through fine filter  66  where relatively fine contaminants or particles contained in fluid  100  are separated therefrom. Fluid  100  subsequently flows through restrictor  64  of fixed orifice  60  and into fluid channel  56 . Due to translation of spool  16 , fluid outlets  58  are now fluidly coupled to downstream variable restrictor  38 . Higher pressure fluid  100  then flows to restrictor  38  while removing or self-cleaning any contaminants that have built up in the fluid interface between spool end  44  and sleeve end  30  and/or between spool downstream end cavity  32  and fluid outlet  58 . Fluid  100  subsequently flows through closure outlet windows  90  to housing secondary fluid outlet  26  and into a secondary outlet conduit  108  coupled to housing  12 . Conduit  108  may then be fluidly coupled to main outlet conduit  106 . 
         [0031]    As such, modulating circuit  102  modulates pressure in valve assembly  10  as valve assembly  10  moves to the open position. Circuit  102  modulates the pressure of fluid  100  flowing therethrough to vary the force balance across spool  16 . This, in turn, controls the pressure drop across valve assembly  10 . As valve assembly  10  moves more to the full-open position, the window size defined between downstream variable restrictor  38  and fluid outlets  58  increases, and the larger window opening results in a decreased pressure drop across valve assembly  10 . Alternatively, valve assembly  10  may not include modulating circuit  102 . 
         [0032]    A method of assembling valve cartridge assembly  10  includes providing housing  12  having sleeve  14 , and providing spool  16 . Fixed orifice  60  and filter  66  are threaded into spool bore  50 , and biasing mechanism  40  and spool  16  are subsequently assembled into sleeve  14 . Cap  18  is threaded onto spool  16 . Cartridge  10  may then be calibrated as a sub-assembly. Once the desired performance is achieved, cartridge  10  may be assembled into a main assembly (not shown) for use. 
         [0033]    Described herein are systems and methods for preventing or reducing fluid contaminant buildup in pressure regulator valves. The valve assembly includes a metering edge between a spool and cap that is sealed when the valve assembly is in the closed position and defines a 360° metering window when the valve assembly is in the open position. A relatively large cavity and cap outlet window downstream of a spool inlet window prevents fluid flow into sensitive clearances between the spool and other components. Accordingly, the metering edge reduces or prevents fluid contaminant buildup in the closed position and self-cleans buildup near the metering edge when the valve assembly is open. 
         [0034]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
In one aspect, a pressure regulating valve assembly is provided. The valve assembly includes a housing having a fluid inlet and a fluid outlet, a sleeve positioned within the housing, and a spool at least partially positioned within the sleeve. The spool includes an outer surface having a shoulder, and the spool is configured to translate within the sleeve between a closed position and an open position. The valve assembly further includes a cap coupled to the sleeve and surrounding at least a portion of the spool, and the cap includes an inner surface with a flange extending therefrom. In the closed position the spool shoulder abuts against the cap flange to define a sealed metering edge. In the open position the spool shoulder is spaced from the cap flange to unseal the metering edge and define a metering window to facilitate fluid flow therethrough to the fluid outlet.