Abstract:
A fine control gas valve is disclosed. The valve has a tee having first and second tee runs co-axially aligned on a longitudinal axis, and a tee branch oriented non-parallel to the longitudinal axis. A rotatable hand operator member cooperates with a threaded member and a sleeve to enable a valve to be adjustably positioned within the tee. Indicia on the valve may be used to help a user understand how a fluid flow through the valve will be affected by adjustments made by the rotatable hand operator member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/088,000, filed on Apr. 15, 2011. The entire disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to gas flow control valves used in both pressurized and vacuum applications. 
       BACKGROUND 
       [0003]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0004]    Gate and globe valves used for controlling flow of fluids in a gaseous state are typically functional only for on-off control of flow because they do not permit fine flow control of compressible fluids and commonly provide little control of flow immediately upon opening of the valve disc. Gas control valves used for throttling flow commonly have elongated valve discs typically in a conical or tapering shape to permit incremental changes in flow rate. These valves are acceptable for controlling flow at mid and high flow ranges, but may not provide acceptable flow control immediately upon opening the valve disc because the geometry of the valve disc is constant and may therefore permit spiked flow rates at low inlet pressure. Known fine control or throttling valve designs are also commonly created from cast or forged body components, include finely machined ports and valve discs to achieve fine flow control, and are therefore expensive to tool and to construct. 
       SUMMARY 
       [0005]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0006]    In one aspect the present disclosure relates to a fine control gas valve. The valve may comprise a tee having first and second tee runs co-axially aligned on a longitudinal axis, and a tee branch oriented non-parallel to the longitudinal axis. A hand operator member may be configured to be engaged with one or more fingers and rotated. A sleeve may be fixedly secured to the first tee run, the sleeve having a threaded bore coaxially aligned with an axial center of the first tee run, and configured to telescopically engage with the hand operator member as the hand operator member is rotated. A valve assembly may be partially received in the first tee run and have a valve disc connected to a threaded drive screw. The threaded drive screw may be threadably engaged in the threaded bore of the sleeve and is operably coupled to the hand operator member. In this manner rotational movement of the hand operator member causes a corresponding rotational movement of the drive screw through the sleeve, and concurrent longitudinal movement of the valve disc within the first tee run. The second tee run may be configured to accept a section of an external piping such that the external piping is disposed generally coaxial with an axial center of the first tee run. The valve disc may be moveable from a first position in which the valve disc prevents flow of a fluid from the second tee run into the tee branch, to a second position in which the valve disc permits flow through the second tee run into the tee branch. The gas valve may include markings that become visible or obscured depending on the telescopic positioning of the handle operator member relative to the sleeve. The markings are useable to help a user understand how flow of the fluid through the gas valve will be affected by axial positioning of the valve disc within the first tee run. 
         [0007]    In another aspect the present disclosure is directed to a fine control gas valve having a tee. The tee has first and second tee runs co-axially aligned along a longitudinal axis, and a tee branch oriented non-parallel to the longitudinal axis. A sleeve is included which has a threaded bore axially aligned with the longitudinal axis, and which is coupled to the first tee run. A valve disc is positioned within the first tee run and is connected to a drive screw. The drive screw is threadably engaged within the threaded bore of the sleeve. A hand operator member is engaged with the drive screw such that rotational movement of the hand operator member threadably advances or retracts the drive screw towards or away from the second tee run. The drive screw is longitudinally moved by axial rotation of the drive screw. The hand operator member and the sleeve are telescopically coupled, with one of the hand operator member and the sleeve including indicia thereon, the indicia being covered up or revealed depending on whether the hand operator member is rotated in clockwise or counterclockwise directions. This aids a user in adjusting a flow of a fluid through the second tee run into the tee branch. The valve disc also has a flange which helps to form a seal for seating the valve disc within the tee to block a flow of the fluid from the second tee run to the tee branch. 
         [0008]    In still another aspect the present disclosure makes use of a fine control gas valve. The valve may comprise a tee having opposed first and second tee runs axially aligned along a common longitudinal axis, and a tee branch extending non-parallel to the common longitudinal axis. A sleeve is fixedly secured to one end of the first tee run, the sleeve having a threaded bore axially aligned with the longitudinal axis. A hand operator member is included which is adapted to be grasped with two or more fingers of a hand and rotated. The hand operator member is telescopically engaged with the sleeve to move longitudinally into and out from the sleeve as the hand operator member is rotated. A generally conically shaped valve disc is disposed in the first tee run, with the valve disc being fixedly connected to a threaded drive screw by a pin, and longitudinally moved within the first tee run by rotation of the threaded drive screw. The threaded drive screw is further engaged within the sleeve. Indicia is included which is operably associated with the hand operator member such that rotational movement of the hand operator member cooperates with the indicia to cover or reveal portions of the indicia. This helps a user to determine how fluid flow from the second tee run to the branch tee will be affected. 
         [0009]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0010]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0011]      FIG. 1  is a top perspective view of a fine control gas valve of the present disclosure; 
           [0012]      FIG. 2  is a front elevational view of the valve of  FIG. 1 ; 
           [0013]      FIG. 3  is a cross sectional left side elevational view taken at section  3  of  FIG. 2 ; 
           [0014]      FIG. 4  is a front elevational view of a valve assembly of the present disclosure; 
           [0015]      FIG. 5  is a right side elevational view of the fine control gas valve of  FIG. 1 ; 
           [0016]      FIG. 6  is a left side elevational view of the fine control gas valve of  FIG. 1 ; 
           [0017]      FIG. 7  is a first end elevational view of the fine control gas valve; 
           [0018]      FIG. 8  is a second end elevational view of the fine control gas valve; 
           [0019]      FIG. 9  is a top perspective view of a valve disc of the present disclosure; 
           [0020]      FIG. 10  is a top plan view of the valve disc of  FIG. 9 ; 
           [0021]      FIG. 11  is a cross sectional side elevational view taken at section  11  of  FIG. 10 ; 
           [0022]      FIG. 12  is a front elevational view of the valve disc of  FIG. 9 ; 
           [0023]      FIG. 13  is a rear elevational view of the valve disc of  FIG. 9 ; 
           [0024]      FIG. 14  is graph of open turns versus flow rate for an exemplary 2 inch fine control gas valve of the present disclosure. 
       
    
    
       [0025]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0026]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0027]    Referring to  FIG. 1 , a fine control gas valve  10  includes a valve assembly  12  connected to a tee  14 . Tee  14  can be a commercially available polymeric material tee made for example from industry standard schedule  80  polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (CPVC) material tees. An inlet pipe  16  is oppositely disposed about tee  14  with respect to valve assembly  12  which is connected to a source of fluid such as a gas, including methane, air, carbon monoxide, carbon dioxide, and the like. 
         [0028]    According to several embodiments, valve assembly  12  includes a tubular-shaped cover sleeve  18  of a polymeric material having a hand operator  20  connected to cover sleeve  18  such that rotation of hand operator  20  also co-axially rotates cover sleeve  18  with respect to a valve longitudinal axis  22 . Hand operator  20  is connected to a drive screw which is shown and described in detail in reference to  FIG. 3 , therefore rotation of hand operator  20  and cover sleeve  18  also longitudinally displaces cover sleeve  18  in a valve closing direction “A” or a valve opening direction “B”. This longitudinal displacement acts to either cover or expose an indicator sleeve  24  which is fixedly connected to a flanged connector  26 . Flanged connector  26  is in turn fixedly (non-rotatably) connected to tee  14  using a plurality of connector fasteners  28  inserted through both a wall of a first tee run  30  and material of flanged connector  26  such that flanged connector  26  and indicator sleeve  24  are non-rotationally connected to first tee run  30  of tee  14 . Flanged connector  26  and indicator sleeve  24  therefore do not rotate with respect to the valve longitudinal axis  22  when hand operator  20  is rotated. 
         [0029]    To provide a visual indication of an opened/closed or intermediate position of valve assembly  12 , indicator sleeve  24  includes at least one and according to several embodiments a plurality of valve position indicators  36  applied, stamped, labeled or embossed thereon. Valve position indicators  36  will be described in greater detail in reference to  FIG. 2 . 
         [0030]    Tee  14  includes a tee body  38  having a second tee run  40  oppositely directed and co-axially aligned on valve longitudinal axis  22  with respect to first tee run  30 . A tee branch  42  is oriented substantially perpendicular with respect to valve longitudinal axis  22 . The inlet pipe  16  which is received in second tee run  40  can include a pipe connection end  44 . According to several embodiments pipe connection end  44  can be a plurality of threads or similar connection means such as braising rings, O-rings, or an adhesive applied to create the connection, or the like. Fine control gas valve  10  is therefore not limited by the design or type of pipe connection end  44  provided. 
         [0031]    Referring to  FIG. 2 , hand operator  20  is fixed with respect to cover sleeve  18  using an operator retention pin  46  such as a spring pin. Any axial rotation of hand operator  20  therefore also co-rotates cover sleeve  18 . As cover sleeve  18  axially rotates it also axially displaces in either of the valve closing direction “A” or valve opening direction “B” such that a sleeve end face  50  of cover sleeve  18  approaches or extends away from flanged connector  26 . The valve position indicator  36  can include a plurality of position indicator values  48  each corresponding to one of the valve position indicators  36 , which according to several embodiments are line segments or slots. The position indicator values  48  can start for example at a value of 1 and successively increase to a maximum value, which according to several embodiments indicates a maximum extended position of cover sleeve  18  with respect to flanged connector  26  and therefore a fully open condition of fine control gas valve  10 . When sleeve end face  50  either closely approaches or contacts flanged connector  26 , a valve closed condition is reached which can be visually indicated using a valve closed position indicator  52 . The valve closed condition does not require sleeve end face  50  to contact flanged connector  26 . 
         [0032]    According to several embodiments, each of the valve position indicators  36  and position indicator values  48  represent a 360 degree axial rotation of a drive screw  54  which is threadably connected to flanged connector  26 . In other embodiments, each of the valve position indicators  36  and position indicator values  48  may represent less or more than a 360 degree axial rotation of drive screw  54  due to the thread pitch of drive screw  54 . Drive screw  54  is connected to hand operator  20 , and is also connected at an opposite end to a valve disc  56  using a disc connecting pin  58  such as a spring pin. Rotation of hand operator  20  therefore not only co-rotates cover sleeve  18  but further co-rotates each of drive screw  54  and valve disc  56 . Axial rotation of drive screw  54  also causes longitudinal displacement of valve disc  56  based on a thread pitch of drive screw  54 . As valve disc  56  displaces in the valve opening direction “B” a disc flow control surface  60  of valve disc  56  permits controlled flow of a fluid such as a gas present in inlet pipe  16  to exit through tee branch  42 . 
         [0033]    According to several embodiments, drive screw  54  includes an acme thread which can include a thread pitch preselected such that each valve position indicator  36  and position indicator value  48  corresponds to a single complete revolution of drive screw  54 . Valve position indicator  36  and position indicator value  48  provide visual indication to the valve operator of a quantity of turns opened or closed by rotation of hand operator  20 . By use of a graph such as shown in  FIG. 14 , the operator can set a flow rate of fine control gas valve  10  based on the quantity of turns of hand operator  20  and drive screw  54 . 
         [0034]    Referring to  FIG. 3 , operator retention pin  46  also extends through a drive screw first end  62  in addition to extending through hand operator  20  and cover sleeve  18 , such that rotation of hand operator  20  co-rotates both cover sleeve  18  and drive screw  54 . According to several embodiments, drive screw  54  includes a drive screw unthreaded portion  64  which is slidably received against a sleeve inner wall  66  of indicator sleeve  24 . A seal member  68  such as an O-ring or D-ring can be positioned between unthreaded portion  64  of drive screw  54  and sleeve inner wall  66  of indicator sleeve  24  to provide a fluid containment boundary. 
         [0035]    A sleeve outer wall  70  of indicator sleeve  24  is circular and is spaced from cover sleeve  18  to provide clearance for rotation of cover sleeve  18  about a perimeter of sleeve outer wall  70 . Drive screw  54  further includes a threaded portion  72  which is partially positioned within a clearance bore  74  of indicator sleeve  24  and is threadably engaged with a threaded bore  76  created in a cylindrical body portion  78  of indicator sleeve  24 . Clearance bore  74  therefore provides an unthreaded length for axial displacement of drive screw  54  allowing axial displacement of valve disc  56  to open and close control gas valve  10 . 
         [0036]    Cylindrical body portion  78  also includes a seal member  80  such as an O-ring or D-ring which provides a fluid boundary between a perimeter surface of cylindrical body portion  78  and the inner body wall of first tee run  30 . Cylindrical body portion  78  is slidably inserted into first tee run  30  until flanged connector  26  contacts a run end face  82  of first tee run  30 . A body portion end face  83  of cylindrical body portion  78  creates a positive stop for travel of valve disc  56  in the valve opening direction “B”. At this time, each of the connector fasteners  28  are installed such that a threaded shank  84  of each connector fastener  28  is slidably inserted through an aperture  85  created through a wall of the first tee run  30  to threadably engage in one of a plurality of blind body apertures  86  created in cylindrical body portion  78 . Fine control gas valves  10  can be used for example by connecting a vacuum line (not shown) such as a tube, hose, or pipe to tee branch  42  to draw gas in inlet pipe  16  out through tee branch  42  with valve disc  56  in the valve open condition. The position of seal members  80  and  68  are therefore selected to prevent fluid within tee  14  from escaping through any of the apertures  85  or past sleeve inner wall  66  for pressurized operation, or from atmospheric air being drawn into tee  14  through apertures  85 , at run end face  82 , or into clearance bore  74  if a partial vacuum is present in tee  14 . 
         [0037]    A drive screw second end  88  of drive screw  54  is connected to valve disc  56  using a disc connecting pin  58  such that axial rotation of drive screw  54  also co-rotates valve disc  56 . A disc seating diameter “C” of valve disc  56  is substantially equal to or less than a sealing diameter “D” of an inlet pipe insertion portion  90  of inlet pipe  16 . Inlet pipe insertion portion  90  of inlet pipe  16  is received in second tee run  40  and connected thereto using an inlet pipe connection joint  92 . Inlet pipe connection joint  92  can be a threaded connection, an adhesively bonded connection, or similar mechanical joint providing a fluid-tight boundary between inlet pipe insertion portion  90  and second tee run  40 . 
         [0038]    Inlet pipe insertion portion  90  is inserted into second tee run  40  until a first portion  94   a  of a pipe end face/seat surface  94  contacts a shoulder  95  integrally formed in material of second tee run  40  and extending inwardly from second tee run  40  such that shoulder  95  provides a known and predetermined position for contact by pipe end face/seat surface  94 . Direct contact between a disc flange  96  of valve disc  56  with a second portion  94   b  of pipe end face/seat surface  94  defines a closed condition of control gas valve  10 . First and second portions  94   a ,  94   b  of pipe end face/seat surface  94  are co-planar with respect to each other. In the valve open condition shown, fluid at a valve inlet port  98  and inlet pipe  16  flows past the disc flow control surface  60  of valve disc  56  and exits control gas valve  10  via a valve outlet port  100  defined by tee branch  42 . The valve open condition is reached by rotation of hand operator  20  causing longitudinal displacement of valve disc  56  away from contact with pipe end face/seat surface  94  in the valve opening direction “B”. 
         [0039]    Referring to  FIG. 4  and again to  FIG. 3 , flanged connector  26  includes a first flange contact face which is oriented toward cover sleeve  18 . The sleeve end face  50  of cover sleeve  18  can contact the first flange contact face  102  in the valve closed condition, or cover sleeve  18  can be sized such that sleeve end face  50  approaches but does not contact first flange contact face  102  in the valve closed condition therefore retaining visibility of valve closed position indicator  52  for observation by the operator. A parallel second flange contact face  104  is located on an opposite side of flanged connector  26  with respect to first flange contact face  102 . Second flange contact face  104  directly contacts run end face  82  when cylindrical body portion  78  is fully received within first tee run  30 . Cylindrical body portion  78  can further include a seal member receiving slot  106  extending around a perimeter wall of cylindrical body portion  78  receiving seal member  80 . As previously noted, seal member  80  provides the fluid-tight boundary for cylindrical body portion  78 , therefore an additional seal member is not required between second flange contact face  104  and run end face  82 . 
         [0040]    Valve disc  56  includes a disc connection portion  108  which directly receives the disc connecting pin  58  to connect valve disc  56  to drive screw  54 . Positioned opposite to the disc connection portion  108  is a disc free end  110  which according to several embodiments is a planar surface oriented parallel to disc flange  96 . The disc flow control surface  60  extends from disc flange  96  toward disc free end  110  initially defining a disc columnar portion  112  which is oriented substantially perpendicular to disc flange  96 . A disc curved portion  114  tangentially transitions from disc columnar portion  112  and extends in a continuously curving, and therefore continuously reducing diameter from disc seating diameter “C” to an outer diameter of disc free end  110 . An opposed pair of disc slots are created on disc flow control surface  60  having a first disc slot  116  visible in this view and a second disc slot which will be shown and described in better detail in reference to  FIG. 13 . The first disc slot  116  is generally pie-shaped having a narrow first end starting in the disc columnar portion  112  and a wide second end extending into the disc curved portion  114 . A disc flange seat contact surface  118  is also created on a disc flow control surface  60  side of disc flange  96 . With further reference to  FIGS. 3 and 4 , when disc flange seat contact surface  118  contacts the pipe end face/seat surface  94  the valve closed condition is defined. 
         [0041]    Referring to  FIG. 5 , according to several embodiments the valve position indicator  36  can be repeated in multiple areas or zones about the circumference of indicator sleeve  24 . For example, a first valve position indicator  36   a  and a second valve position indicator  36   b  can be oriented at approximately 120 degree intervals with respect to each other about the perimeter of indicator sleeve  24 . 
         [0042]    Referring to  FIG. 6  and again to  FIG. 5 , a third valve position indicator  36   c  can also be provided which is oriented at approximately 120 degrees with respect to the other valve position indicators such as second valve position indicator  36   b  only partially shown. One of the valve position indicators  36   a ,  36   b ,  36   c  will therefore be visible to an operator of control gas valve  10  regardless of the orientation of control gas valve  10  in its system installed orientation. 
         [0043]    Referring to  FIG. 7  and again to  FIG. 1 , hand operator  20  can include a plurality of raised grip members  120  to assist in manual rotation of hand operator  20 . In addition to the directional arrow  34  provided with indicator ring  32 , an open indicator  122  can also be provided signifying the rotation of hand operator  20  in the direction of directional arrow  34  operates to open flow control gas valve  10 . According to several embodiments a wrench engagement slot  124  is provided in indicator ring  32  which has a square or rectangular shape. The purpose for wrench engagement slot  124  is to receive a wrench (not shown) which can be used to provide additional torque for rotation of hand operator  20 , or if access is limited for hand contact with hand operator  20 . The geometry or shape of wrench engagement slot  124  can also be varied from that shown and can include other geometric shapes such as a star shape, a hexagon shape, or other geometric shapes matching the geometry of tools used for this purpose including allen wrenches. 
         [0044]    Referring to  FIG. 8 , as previously noted valve disc  56  includes two disc slots including first disc slot  116  and an oppositely positioned second disc slot  126 . When fine control gas valve  10  is positioned in the valve closed condition, valve disc  56  contacts the disc flange/seat contact surface  118  such that fluid flow through either of the first or second disc slots  116 ,  126  is precluded. First and second disc slots  116 ,  126  are provided to initially increase a flow area of disc flow control surface  60  when valve disc  56  is initially moved away from contact with disc flange/seat contact surface  118 . The pie-shaped flow areas of first and second disc slots  116 ,  126  gradually increase the fluid flow area and therefore the fluid flow rate after initially opening valve disc  56 . This creates a flatter initial valve flow curve which is shown and described in better detail in reference to  FIG. 14 . 
         [0045]    Referring to  FIG. 9 , valve disc  56  additionally includes first and second pin receiving apertures  128   a ,  128   b  which are both co-axially aligned on a pin/aperture longitudinal axis  130  extending through disc connection portion  108 . The first disc slot  116  as well as the second disc slot  126  (not visible in this view) each include a slot side wall  132  which initially begins in the disc columnar portion  112  and ends at a side wall tangent point  134  positioned along the disc curved portion  114 . A length and height of slot side wall  132  affect the initial flow area and flow response of valve disc  56  upon opening of the control gas valve. 
         [0046]    Referring to  FIG. 10 , each of the disc flange  96  and the disc connection portion  108  are circular in shape and are coaxially aligned with respect to a disc longitudinal axis  136 . A disc flange diameter “E” defines the largest diameter of disc flange  96  and thereby defines a space envelope required for valve disc  56  to be received within tee  14  of fine control gas valve  10 . 
         [0047]    Referring to  FIG. 11  and again to  FIG. 3 , each of the first and second pin receiving apertures  128   a ,  128   b  have a common pin receiving aperture diameter “G” which is sized to slidably receive and frictionally engage disc connecting pin  58 . A bore  137  is coaxially aligned on disc longitudinal axis  136  and is sized to slidably receive the drive screw second end  88 . The slot side wall  132 ,  132 ′ of each of the first and second disc slots  116 ,  126  are substantially identical and each have a side wall height “F” which when varied changes the location of side wall tangent point  134  thereby increasing or decreasing a fluid flow area of first and second disc slots  116 ,  126  and therefore increases or decreases a fluid flow rate through the first and second disc slots  116 ,  126 . 
         [0048]    Referring to  FIG. 12  and again to  FIG. 3 , each of first and second disc slots  116 ,  126  (second disc slot  126  is clearly visible in  FIG. 13 ) are substantially pie-shaped and include a narrow width first end  138  positioned in disc columnar portion  112 . The width of first and second disc slots  116 ,  126  continuously increases to a wide width second end  139  which defines a slot end arc tangentially interfacing with disc curved portion  114 . This continuous increase in width of first and second disc slots  116 ,  126  provides a continuously increasing flow area for fluid passing along disc curved portion  114  as valve disc  56  moves away from a seated position defining the closed condition. The portion of first and second disc slots  116 ,  126  having the smallest width and area is located in disc columnar portion  112  whose diameter “D” is substantially equal to the inner diameter inlet pipe  16 . Therefore, initial fluid flow past valve disc  56  will be through the narrow width first end  138 . Flow gradually increases in a finely controllable manner through tee branch  42  as valve disc  56  opens due to an increased flow area created by the increasing exposed area of first and second disc slots  116 ,  126  as wider width second end  139  moves with respect to pipe end face/seat surface  94 . Valve flow rate thereafter continues to increase due to a continuously increasing flow area due to disc curved portion  114  continuously decreasing in diameter as it transitions away from pipe end face/seat surface  94  and disc columnar portion  112 . 
         [0049]    A total disc length “H” of valve disc  56  includes a flange thickness “J” of disc flange  96 , a height or length of disc connection portion  108 , and a flow control surface length “K” of disc flow control surface  60 . A flow control surface radius of curvature “L” of disc curved portion  114  is determined from a tangent point at the junction between disc columnar portion  112  and disc curved portion  114 , located at a radius end point location dimension “M” with respect to a reference line which is parallel to the disc longitudinal axis  136 . A columnar portion length “N” and a slot radius locating dimension “P” are both determined with respect to the disc flange seat contact surface  118 . The following dimensions are provided for exemplary purposes defining an exemplary embodiment of a two-inch valve disc  56 . According to several embodiments, total disc length “H” can be 5.71 cm (2.25 in), flange thickness “J” can be 0.63 cm (0.25 in), flow control surface length “K” can be 3.81 cm (1.50 in), flow control surface radius of curvature “L” can be 3.81 cm (1.50 in), radius end point location dimension “M” can be 1.35 cm (0.53 in), columnar portion length “N” can be 0.64 cm (0.25 in), and slot radius locating dimension “P” can be 0.32 cm (0.126 in). These dimensions apply with respect to a two-inch valve disc  56  having a sealing diameter “D” of 4.93 cm (1.940 in). Any of these dimensions can be changed at the discretion of the manufacturer to modify the flow results identified in the flow curve shown and described in reference to  FIG. 14 . 
         [0050]    Referring to  FIG. 13 , second disc slot  126  is oppositely directed with respect to first disc slot  116  and is therefore substantially a mirror image of first disc slot  116 . Each of the first and second disc slots  116 ,  126  include a first side wall edge  140  and a second side wall edge  142  which are oriented at an angle α with respect to each other. According to several embodiments for a two-inch valve disc  56  angle α is approximately 30 degrees. The second side wall edge  142  is located at a second slot wall location dimension “Q” with respect to a reference line oriented parallel to disc longitudinal axis  136 . A slot end radius “R” for each of the first and second disc slots  116 ,  126  is located with respect to a slot radius locating dimension “P”. According to several embodiments with respect to the exemplary two-inch valve disc  56 , slot radius locating dimension “P” is approximately 0.48 cm (0.189 in), second slot wall locating dimension “Q” is 0.16 cm (0.063 in), and slot end radius “R” is 0.16 cm (0.063 in). 
         [0051]    Referring to  FIG. 14 , a graph  144  provides a first axis  146  delineating a quantity of complete open turns of an exemplary 2 inch drive screw  54  of control gas valve  10  versus a similar sized 2 inch commercial gate valve. A second axis  148  delineates a flow rate in cubic feet per minute of control gas valve  10  versus the similar sized commercial gate valve at each of the various open turn positions. A flow rate per open turn curve  150  demonstrates that fine control gas valve  10  provides a more linear flow curve with respect to the number of open turns of control gas valve  10  compared to a flow rate per open turn curve  152  for the comparably sized two-inch gate valve. Fine control gas (FCG) valve  10  provides improved flow rate control particularly between 1 and 4 open turns compared to the 2 inch gate valve, providing the user greater capability to throttle gas or fluid flow at lower flow rates. By direct comparison, fine control gas valve  10  provides throttling flow control over a 22 CFM range varying from 1 open turn (approximately 8 CFM) to 4 open turns (approximately 30 CFM). In contrast, the 2 inch gate valve provides substantially no throttling capability, ranging approximately 127 CFM between 1 open turn (approximately 8 CFM) and 4 open turns (approximately 135 CFM). One advantage of control gas valve  10  is therefore provided in the ability to finely control the flow rate at a lower open turn range of the valve when used in compressible gas service. 
         [0052]    With continuing reference to  FIGS. 1-13 , fine flow control valve  10  can be operated as follows. With the valve disc  56  initially in a valve closed condition, disc flange seat contact surface  118  of disc flange  96  is in contact with second portion  94   b  of pipe end face/seat surface  94 , and disc columnar portion  112  is substantially in sliding contact with the sealing diameter “D” portion of inlet pipe insertion portion  90 . Upon rotation of hand operator  20  in a counterclockwise opening direction indicated by directional arrow  34 , drive screw  54  axially rotates such that threaded portion  72  engaged with threaded bore  76  causes a corresponding longitudinal displacement of valve disc  56  in the valve opening direction “B”. This results in disc flange seat contact surface  118  of disc flange  96  displacing away from contact with second portion  94   b  of pipe end face/seat surface  94 . Valve disc  56  displaces in the valve opening direction “B” until the narrow width first end  138  of both first and second disc slots  116 ,  126  passes second portion  94   b  of pipe end face/seat surface  94 , creating a fluid flow path for a fluid (such as a gas) in valve inlet port  98  to escape past disc columnar portion  112  and second portion  94   b  of pipe end face/seat surface  94  via a path through first and second disc slots  116 ,  126  an out through the narrow width first end  138  and exiting through valve outlet port  100 . 
         [0053]    With increasing longitudinal displacement of valve disc  56  in the valve opening direction “B”, a rate of discharge flow increases gradually as more of the width (and therefore more of an area) of first and second disc slots  116 ,  126  is exposed with respect to second portion  94   b  of pipe end face/seat surface  94 . When the tangential junction between disc columnar portion  112  and the disc curved portion  114  passes second portion  94   b  of pipe end face/seat surface  94 , the curvature of disc curved portion  114  plus the increasing width (and therefore the area) of first and second disc slots  116 ,  126  permits substantially greater discharge flow through valve outlet port  100 . The effect of first and second disc slots  116 ,  126  on valve flow rate is diminished substantially to zero after wider width second ends  139  pass second portion  94   b  of pipe end face/seat surface  94  during valve disc travel in the valve opening direction “B”. Valve discharge flow rate thereafter continues to increase as the diameter of disc curved portion  114  continues to decrease with respect to sealing diameter “D” during valve disc travel in the valve opening direction “B”. Valve disc  56  can be continually longitudinally displaced until disc flange  96  contacts body portion end face  83  of cylindrical body portion  78  of indicator sleeve  24  establishing the valve fully open condition. Fine flow control valve  10  can then be returned from the valve open condition to the valve closed condition, or any operating position therebetween, by an opposite (clockwise) rotation of hand operator  20 . 
         [0054]    The position of valve disc  56  is indirectly visually indicated by the position of sleeve end face  50  of cover sleeve  18  with respect to any of the individual ones of the valve position indicators  36  and position indicator values  48 . The operator can consult one of a plurality of graphs  144 , an example of one presented in  FIG. 14 , to set a position of fine control gas valve  10  for a desired flow rate based on a predetermined number of valve turns. Multiple versions of graphs  144  can be provided, for example to define operating conditions for different types of gases, different gas pressures, gas temperature/density differences, valve size, and the like. 
         [0055]    Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
         [0056]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0057]    When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0058]    Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
         [0059]    Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0060]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.