Abstract:
A metering valve for controlling the flow rate of a fluid has a substantially rigid housing having an internal cylindrical wall defining a cavity. The cavity has a first opening at one end and a spaced second opening in the cylindrical wall. A substantially rigid valve element that fits closely within the cavity has an internal bore extending axially from a first end toward a second end. A metering aperture penetrates the valve element wall between the outer surface of the valve element and the valve element bore. Moving the valve element within the housing cavity to a first position places a portion of the second opening within the cavity&#39;s second opening at a first position to allow a first rate of fluid flow between the first chamber and the second chamber. Moving the valve element to a second position places the metering aperture at a second position different from the first position to allow a second rate of fluid flow between the first and second chambers. The flow has an axial flow vector within the valve element bore and a radial flow vector through the metering aperture.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Valves for control of fluid flow have a variety of designs. Many include both flow rate and shutoff functions. For example, the common residential water faucet typically has a threaded stem controlling the position of a valve element, usually including a rubber washer for sealing flow of water. Rotating the stem with the handle in one direction presses the valve element&#39;s washer against a seat to shut off water flow. Rotating the stem in the opposite direction lifts the washer from the seat and allows control of the flow rate. 
         [0002]    Ball and gate valves are other types of valves that combine flow control and shutoff functions. 
         [0003]    Each of these valves has advantages and disadvantages. Threaded stem valves require a multi-turn rotary actuator but give quite precise flow control and secure shutoff. As any homeowner knows however, the sealing washers on these valves require regular replacement. Ball and gate valves can be operated with a rotary actuator but provide relatively coarse flow control. 
         [0004]    A valve operable by a short stroke linear actuator and that has relatively precise flow control has many advantages. Such a valve that can also provide secure shutoff is even more desirable. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    A metering valve for controlling the flow rate of a fluid has a housing having an internal cylindrical wall defining a cavity. The cavity has a first opening at one end and a spaced second opening in the cylindrical wall and comprising a flow space. The flow space is defined at least in part by an edge. 
         [0006]    A substantially rigid valve element has an outer surface that fits closely within the cavity to oppose leakage between the cavity and the valve element. The valve element has an internal bore extending axially from a first end toward a second end and with the valve element outer surface, defining a wall. A metering aperture penetrates the valve element wall between the outer surface of the valve element and the valve element bore. 
         [0007]    The valve element can be shifted within the housing cavity to a first position placing a portion of the flow space edge within the metering gap at a first position to align a portion of the metering aperture with a portion of the flow space to allow a first rate of fluid flow between the first chamber and the second chamber. Sliding the valve element to a second position places the metering aperture at a second position different from the first position to allow a second rate of fluid flow between the first and second chambers. The flow has an axial flow vector within the valve element bore and a radial flow vector through the metering aperture. 
         [0008]    The flow space edge may be between the first and second openings, or one of the openings itself may form the edge. 
         [0009]    In one embodiment, the valve the valve element has a sealing element engaging a passage opening when the valve element is in a third position, to close off the passage opening, and thereby close the valve to fluid flow. 
         [0010]    In another embodiment, the valve element includes a diaphragm having a center sealingly attached to an end of the valve element and a periphery sealingly attached to the housing. The diaphragm defines a portion of the chamber to prevent fluid flow from the valve except through one of the ports, or to prevent flow between the ports except through the valve itself. 
         [0011]    Still other embodiments have various shapes for the metering aperture. Some of these metering apertures may comprise a series of adjacent holes or gaps in the valve element wall. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a perspective view of a control element of a valve. 
           [0013]      FIG. 2  is a cross section view of the control element of the valve. 
           [0014]      FIGS. 3 and 4  are cross section view of the valve with the control element in closed and open positions respectively. 
           [0015]      FIGS. 5 and 6  show a cross section view of a commercial embodiment of a valve incorporating the invention in closed and in partially opened states. 
           [0016]      FIG. 7  is a cross section view of a first alternative embodiment of the valve shown in  FIGS. 5 and 6 . 
           [0017]      FIG. 8  is a perspective view of a first alternative to the embodiment of the valve element shown in  FIG. 1 . 
           [0018]      FIG. 9  is a perspective view of a second alternative to the embodiment of the valve element shown in  FIG. 1 . 
           [0019]      FIG. 10  is a perspective view of a third alternative to the embodiment of the valve element shown in  FIG. 1 . 
           [0020]      FIG. 11  is a cross section view of a fourth alternative embodiment similar to the valve element shown in  FIG. 1 . 
           [0021]      FIG. 12  is perspective view of a fifth alternative embodiment similar to the valve element shown in  FIG. 1 . 
           [0022]      FIG. 13  is a cross section view of the valve element shown in  FIG. 12 . 
           [0023]      FIG. 14  is a cross section view of an alternative embodiment of the valve element shown in  FIGS. 12 and 13 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]      FIGS. 1 and 2  show a first embodiment of a substantially rigid valve element  15  suitable for use in a valve unit  10  embodying the invention to allow precise control of fluid flow rate. Valve element  15  has first and second end surfaces  20  and  27  aligned along an axis, and a generally cylindrical outer surface  19  extending between end surfaces  20  and  27 . In a typical embodiment, surface  19  is circularly cylindrical. Valve element  15  has a bore  23  extending axially from the first end surface  20  to the second end surface  27 . Bore  23  and surface  19  define between them a tubular wall  17 . 
         [0025]    An aperture or slot  18  in wall  17  extends axially for a selected distance between and spaced from end surfaces  20  and  27 . Aperture  18  extends radially between the outer surface  19  and bore  23  to allow fluid to flow between bore  23  and areas surrounding surface  19 . “Axially” for these features of valve element  15  has the conventional meaning of extending along the axis  22  of the cylindrical outer surface  19 . Aperture  18  should form a passage large enough to allow the maximum desired amount of fluid flow. While a single aperture  18  is shown in  FIGS. 1-4 , multiple apertures are also possible and will be disclosed below. 
         [0026]    The cross section view in  FIGS. 3 and 4  shows valve unit  10  with valve element  15  incorporated.  FIG. 3  shows valve  10  when closed, and  FIG. 4  shows valve  15  when partially open. 
         [0027]    The valve unit  10  has a generally rigid housing  37  with a cylindrical bore or cavity  21  shown partially occupied in  FIGS. 3 and 4  by a valve element  15  whose dimensions are compatible with housing  37 . Cavity  21  is defined by a wall  33  having an annular inner surface  34 , and which forms a part of housing  37 . Cavity  21  will usually have a circularly cylindrical cross section, but other cylindrical cross sections may be advantageous for some applications. The open end of cavity  21  forms a first port  41  serving in this embodiment as an inlet port. 
         [0028]    Valve unit  10  has an inlet chamber generally designated at  43 . An outlet chamber of valve unit  10  is generally designated at  44 . A wall  49  of which only a small portion is shown, physically separates an inlet chamber shown at  43  and an outlet chamber shown at  44  so that no fluid can flow between them except through cavity  21  and valve element  15 . 
         [0029]    In the valve unit  10  embodiment, outer surface  19  of valve element  15  fits closely within cavity  21  and can slide within cavity  21  to any of a variety of axial positions as shown by the double-ended arrow. “Fits closely” means that the outer surface  19  has a shape and dimensions that forms a sealing interface with the inner surface  34  allowing a little fluid at most to leak between surfaces  19  and  34 . The surfaces  19  and  34  may fit so tightly with each other that no fluid leakage occurs. Alternatively, the design may incorporate sealing elements such as O-rings between surfaces  19  and  34  to oppose or prevent fluid leakage. A surface  19  in designs using such sealing elements also is considered to “fit closely” within cavity  21 . 
         [0030]    In another embodiment, surfaces  19  and  34  may be deliberately formed with a small gap between them to allow flow or leakage of some fluid between surfaces  19  and  34 . Such a gap provides a limited flow of fluid through valve  10  regardless of the position of valve element  15 , and will be discussed in more detail later. 
         [0031]    An opening or window  30  spaced from the open end of cavity  21  penetrates annular wall  33  to cavity  21 . Opening  30  extends through wall  33  to allow flow through wall  33  from cavity  21 . Opening  30  has an edge or corner  29  at one axial extreme. The external opening  30  forms in this embodiment, a second port  42  serving as an outlet port. Opening  30  should extend axially for a predetermined distance and have an angular width sufficient to allow the maximum desired amount of fluid flow. In this embodiment, aperture  18  should be held in substantial angular alignment with opening  30 . 
         [0032]      FIG. 4  indicates fluid flow by an arrow  36  entering bore  23  axially from first port  41 . As can be seen, the direction of fluid flow then changes approximately 90° to radial flow. Port  41  is shown as the inlet port in this embodiment, but in fact either of port  41  or port  42  may serve as the inlet port with the other serving as the outlet port. 
         [0033]      FIGS. 3 and 4  show valve element  15  in two different positions within cavity  21 . Positioning aperture  18  with respect to edge  29  to form an overlap relation with opening  30  as shown in  FIG. 4  creates an orifice at  38  through which fluid can flow. The size of this orifice  38  can be varied by changing the axial position of valve element  15  within cavity  21 . The two-headed arrows in  FIGS. 3 and 4  indicate that valve element  15  can shift axially within cavity  21  to control or alter the fraction of aperture  18  occluded by facing wall  34 . The size of the orifice  38  formed by the overlap of gap  30  and metering aperture  18  controls the flow rate of fluid through valve  10 . 
         [0034]      FIGS. 3 and 4  do not show the positioning mechanism for valve element  15 . A variety of positioning means are possible. For example, a mechanical link may be attached to valve element  15  at the second end surface  27  and project rightwardly through an aperture (not shown) in housing  37  to outside of housing  37 . A seal mechanism between the mechanical link and housing  37  opposes fluid leaks from cavity  21 . A linear actuator or other control may apply force to valve element  15  through this link to position valve element  15  in any desired position and control fluid flow with precision and repeatability. 
         [0035]    The position of valve element  15  shown in  FIG. 3  corresponds to closing valve  10 . In structures where the seal created between valve element  15  and passage  21  is adequate to prevent any fluid leakage, the position of valve element  15  in  FIG. 3  is adequate by itself to allow shutoff of fluid flow. 
         [0036]      FIGS. 5 and 6  show a flow control valve  10 ′ that forms a variant of the flow control valve  10 . Reference numbers for components and features of valve  10 ′ in  FIGS. 5-7  that are analogous to various components and features of valve  10  have similar numeric portions. 
         [0037]    Valve  10 ′ includes a rigid housing  37 ′ having first and second ports  41 ′ and  42 ′. Fluid flows into one of ports  41 ′ and  42 ′ and flows out of the other. Arrows in  FIG. 5  show one path of fluid flow. 
         [0038]    Housing  37 ′ has an inlet chamber  54  in fluid communication with port  41 ′ and an outlet chamber  55  in fluid communication with port  42 ′. Outlet chamber  55  is defined in part by walls of housing  37 ′, partly by a cap  59 , and partly by a diaphragm  50 . Cap  59  attaches to a top surface of housing  37 ′ by means not shown but which are simple for someone with skill in these arts to devise. Diaphragm  50  is peripherally attached to a top surface of cap  59 . The attachments between cap  59  and housing  37 ′ and between diaphragm  50  and housing  37 ′ seals against escape of any fluid within chamber  55 . Alternatives for attaching diaphragm  50  to cap  59  are possible and easy for someone with skill in the art to devise. 
         [0039]    Housing  37 ′ also has an internal cavity  21 ′ that connects chamber  54  with chamber  55 . Cavity  21 ′ should be cylindrical and typically will be circularly cylindrical. An annular edge  29 ′ defines the upper end of cavity  21 ′. A sealing surface  53  is radially outboard of edge  29 ′. 
         [0040]    The rigid valve element  15 ′ in  FIGS. 5 and 6  is functionally similar to valve element  15  shown in  FIGS. 1-4 , with a bore  23 ′ and an aperture  18 ′ such as a slot providing fluid communication from bore  23  to the area exterior to valve element  15 ′. In the embodiment of  FIGS. 5 and 6 , a portion of valve element  15 ′ is external to cavity  21 ′, and bore  23 ′ extends only to this external portion of valve element  15 ′. 
         [0041]    Valve element  15 ′ has an enlarged shoulder section  65  with a surface in facing relation to a seat  53  forming a part of the housing  37 ′ internal structure. A sealing element comprising portions of shoulder section  65  and seat  53  or alternatively, an O-ring  62 , may form a part of shoulder section  65  to provide for secure valve shutoff. 
         [0042]    Diaphragm  50  is attached to the upper surface of valve element  15 ′ and to a projection  56  carried on valve element  15 ′. Again, the attachment between diaphragm  50  and projection  56  resists leakage of fluid in chamber  55 . Diaphragm  56  flexes to allow axial translation of valve element  15 ′. Projection  56  may attach to an actuator that axially positions valve element  15 ′. 
         [0043]    The lower portion of valve element  15 ′ has a cross section that matches the cross section of cavity  21 ′ and fits closely into cavity  21 ′. Valve element  15 ′ can shift axially within cavity  21 ′. The edge  29 ′ defines one end of the portion of aperture  18 ′ through which fluid can flow. As with the valve of  FIGS. 3 and 4 , the distance that aperture  18 ′ extends past edge  29 ′ of cavity  21 ′ determines the area of aperture  18 ′ through which fluid can flow. When valve element  15 ′ is shifted downwards as far as possible, O-ring  65  seals against seat  53  to oppose all fluid flow through valve  10 ′. 
         [0044]      FIG. 7  shows a version of valve  10 ′ where O-rings  68  seal chamber  55 , replacing the function of diaphragm  50 . 
         [0045]      FIG. 8  shows a valve element  15   a  that can substitute for valve element  15  in  FIGS. 1 and 2 . Valve element  15   a  has an aperture  18   a  with a cross section substantially in the form of a trapezoid. As more and more of aperture  18   a  is exposed, a proportionately larger orifice forms that allows proportionately greater fluid flow. 
         [0046]      FIGS. 9 and 10  also show valve elements that can substitute for valve element  15  in  FIGS. 3 and 4 .  FIG. 9  shows a valve element  15   b  for use in a housing  37  as shown in  FIGS. 3 and 4 . Valve element  15   b  has two adjacent rows of small holes at  71  and  72  penetrating the annular wall of valve element  15   b  and that collectively comprise an aperture  18   b . These holes provide fluid communication between bore  23  and the area external to valve element  15   b . In a preferred embodiment, individual holes at  71  and  72  may be elliptical in cross section as shown with their major axes aligned with the axis of valve element  15   b . The individual holes forming the row at  71  may be axially staggered with respect to the individual holes forming the row at  72 . This design for aperture  18   b  may result in a flow rate that does not smoothly increase as more holes in the rows at  71  and  72  are exposed within gap  30 . 
         [0047]      FIG. 10  shows still another valve element  15   e  for use in the housing shown in  FIGS. 3 and 4 . Aperture  18   e  is similar to aperture  18   a  in valve element  15   a  of  FIG. 8 . However, the side walls  92  defining aperture  18   e  are slightly curved, so that a relatively small amount of area for fluid flow is exposed when a portion of the narrow (left) end of aperture  18   e  is within gap  30 . The curved walls  92  of aperture  18   e  then create an area for fluid flow that, with leftward axial displacement of valve element  15   e  within bore  21  of housing  37 , increases more rapidly than proportionally to the axial movement of element  15   e.    
         [0048]    In  FIG. 10 , end wall  89  in aperture  18   e  is shown as concave relative to the inside of the aperture  18   e . Wall  89  may be blended with walls  92 . When so blended, this feature avoids any corners in the aperture  18   e  that may induce cavitation or turbulence. 
         [0049]      FIG. 11  shows a valve  10   f  as another version of valve  10  with a valve element  15   f  in bore  21 . Valve element  15   f  has a feature  90  in the nature of a slot or chamfer intersecting the first end and the outer surface  19  thereof. Feature  90  provides for fluid flow as shown at  91  when aperture  18  is completely outside gap  30 . In some circumstances a small amount of fluid flow at all times may be desirable, and feature  90  provides for such flow. 
         [0050]      FIGS. 12 and 13  show a further version of a valve element  15   g  designed to axially slide in the bore  21  of housing  37 , see  FIGS. 3 and 4 . Valve element  15   g  has a slot  18   g  with a number of bridges  90  transversely mounted across the width of slot  18   g  and defining a number of adjacent openings  91  between adjacent bridges  90  or between a bridge  90  and an end of slot  18   g . The outer surface of each bridge  90  may be recessed from the extension of the valve element outer surface  15   g.    
         [0051]    Valve element  15   g  operates in a manner similar to that of valve element  15 . The transverse bridges  90  improve the structural integrity of slots  18   g  and provide different flow rate characteristics as a function of element  15   g  position. 
         [0052]      FIG. 14  shows further variations in the design of individual bridges  90   a  across a slot  18   h . Bridges  90   a  have a non-rectangular cross section, shown as triangular in  FIG. 14 . A tapered or triangular cross section of bridges  90   a  may reduce turbulence of flow directed inwardly through slots  18   h  to bore  23 . 
         [0053]      FIG. 14  also shows a bridge  90   b  that has a cross section larger than that of bridges  90   a . Low flow conditions maximize the pressure drop across slot  18   h . A larger cross section can resist this greater pressure more effectively to prevent failure of bridge  90   b  under high pressure drops.