Abstract:
A flow meter for measuring the volume of fluid flowing through the meter includes an inner cylindrical tube through which the fluid flows and an outer cylindrical tube tending over the inner cylindrical tube. The outer cylindrical tube is radially spaced from the cylindrical inner tube to provide an annular cylindrical space between the inner cylindrical tube and the outer cylindrical tube. A seal between the inner cylindrical tube and the outer cylindrical tube closes the annular cylindrical space adjacent ends of the annular cylindrical space. The inner cylindrical tube further defines at least one opening in a wall of the inner cylindrical tube to balance the fluid pressure in the annular cylindrical space with the pressure in the inner cylindrical tube. A torus wedge flow restriction member is integrally formed within full internal circumference the inner cylindrical tube for restricting the flow of fluid through the inner cylindrical tube and produces a pressure drop in the fluid as it flows past the flow restriction member. The inner cylindrical tube and the outer cylindrical tube in combination further define at least one port for receiving a pressure sensing device to measure the pressure of the fluid flowing through the flow meter.

Description:
BACKGROUND  
       [0001]     The present invention relates to flow meters in general, and in particular to flow meters that employ a wedge-shaped flow restricting element producing a pressure drop within the flow meter to indicate the volume of fluid flowing through the flow meter.  
         [0002]     The use of wedges to create a pressure drop in flow meters for measurement of the volume of fluid passing through a flow meter is known in the art. Wedge-shaped flow meters are described in U.S. Pat. No. 4,237,739 issued on Dec. 9, 1980, U.S. Pat. No. 4,926,698 issued on May 22, 1990, and U.S. Pat. No. 6,672,173. The &#39;739 patent describes a flow meter using a single wedge affixed to the internal wall of the flow meter whereas the &#39;698 patent describes a flow meter having two opposing wedges mounted on opposite sides of the flow meter interior wall. Either arrangement creates an opening within the flow meter having a reduced cross-sectional area in the flow-path of the fluid thereby creating a pressure differential on opposite sides of the wedge or wedges. The pressure differential created on opposite sides of the wedges has a known mathematical relationship to the flow rate of the fluid passing there through, and as long as the cross-sectional area of the opening at the wedge is constant, the fluid flow measurements are very accurate. The &#39;173 patent discloses A flow meter for measuring the volume of fluid flowing through the meter includes an inner cylindrical tube through which the fluid flows and an outer cylindrical tube tending over the inner cylindrical tube. With this meter a flow restriction member is mounted to an inner surface of the inner cylindrical tube for restricting the flow of fluid through the inner cylindrical tube and process a pressure drop in the fluid as it flow past the flow restriction member.  
         [0003]      FIG. 1  shows a typical prior art flow meter  10  shown in cross-section. Flow meter  10  generally comprises a tubular housing  12  having a longitudinal passageway  14  in which a wedge-shaped member  16  is affixed to the inner wall  18  of housing  12  thereby creating at apex  20  of wedge  16  a restricted cross-sectional area represented by dimension D. At least two orts  22  are defined by housing  12 . One of ports  22  is positioned upstream from wedge  16  and the other of ports  22  is positioned downstream from wedge  16 . Ports  22  are in fluid communication with the interior flow through passage  14  thereby permitting the detection of the pressure differential induced by wedge  16  restricting fluid flow through flow meter  10 .  
         [0004]     Nevertheless, fluid flows conditions under which the flow meters are used are variable and tend to change. Specifically, temperature changes and changes in the pressure of the fluid being measured cause the diameter of the passageway through the flow meter to expand and contract. Consequently, the cross-sectional area between the wedge apex and the flow meter wall opposite the wedge does not remain constant. Small changes in the flow meter passageway diameter or the distance between the wedge apex and the wall opposite from the wedge can make substantial changes in the pressure drop of the fluid flowing past the wedge. Consequently, these changes introduce unwanted errors in the calculated volume of fluid flowing through the meter.  
         [0005]     Thus, there is a need within the industry for a torus 360 degree wedge-type flow meter where changes in the pressure and temperature of the fluid being measured by the flow meter will minimally affect the formed internal wedge element. The torus wedge is a significant departure from the traditional orifice plate technology and an enhancement of current wedge technology. The torus wedge flow meter will offer a fluid profile which does not generate fluid phase separation within the flow stream.  
       SUMMARY OF THE INVENTION  
       [0006]     One aspect of the present invention is a flow meter for measuring the volume of fluid flowing through the meter which includes an inner cylindrical tube through which the fluid flows and an outer cylindrical tube tending over the inner cylindrical tube. The outer cylindrical tube is radially spaced from the cylindrical inner tube to provide an annular cylindrical space between the inner cylindrical tube and the outer cylindrical tube. A seal between said inner cylindrical tube and the outer cylindrical tube closes the annular cylindrical space adjacent the ends of the annular cylindrical space. The inner cylindrical tube allows fluid pressure to enter the radial space between the inner cylindrical tube and the outer cylindrical tube through a surface opening opposite the sealed end of the inner cylindrical tube to provide pressure balancing between the pressure in the annular cylindrical space and the pressure in the inner cylindrical  15  tube. A flow restriction member is formed within the internal circumference of the inner cylindrical tube. The flow restricted member is a torus wedge having a full internal 360 degrees circumference V-shaped restriction, which reduces the area available to flow. Each side of the torus wedge has an inclined fluid flow surface to channel the incoming and outgoing fluid flow through the center annulus of the torus wedge. As fluid velocity increases due to contraction of fluid volume at the entrance to the restriction, the kinetic energy of the fluid increases. Thus, a corresponding decrease in static pressure or potential energy of the fluid occurs to preserve conservation of the total energy. The inner cylindrical tube and the outer cylindrical tube in combination further define at least two ports for receiving a pressure sensing device to measure the pressure of the fluid flowing through said flow meter. In an alternative embodiment of the present invention, a torus 360 degree wedge member can be incorporated into the outer cylindrical tube. In this alternative embodiment there is no inner cylindrical tube.  
         [0007]     Another aspect of the present invention is a fluid flow meter for measuring the volume of fluid flowing through a passageway. The meter includes an outer housing having a first internal bore, and a removable inner member telescopically received in the first internal bore. The first internal bore and an outer surface of the inner member in combination define a cannular space therebetween wherein the cannular space is isolated from fluid flowing there through. The inner member has a second internal bore of a first predefined cross-sectional area to accommodate the fluid flow there through and is in pressure equalizing communication with the cannular space. A torus wedge metering structure is formed within the full 360 degree internal circumference of the inner member for measuring the fluid flow there through.  
         [0008]     Yet, another aspect of the invention is a method for measuring the flow of a fluid through a tube. The method comprises the steps of providing an outer housing having an internal bore, and providing a calibrated tubular flow metering device having a torus wedge flow restrictor integrally formed therein. The flow metering device is inserted within the outer housing internal bore in a telescoping fashion to create a cannular space between the outer housing and the metering device. The pressure of the cannular space is equalized with the internal pressure of the flow metering device. The combined outer housing and calibrated tubular flow metering device are coupled in the flow path of a fluid, and the pressure differential on each side of the flow restrictor is then measured.  
         [0009]     These and other advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims and appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a prior art flow meter incorporating an internal wedge to restrict the fluid flow.  
         [0011]      FIG. 2  is a cross-sectional view, shown along a horizontal center line of a fluid flow meter embodying the present invention.  
         [0012]      FIG. 3  is a cross-sectional view of the circular area III of  FIG. 2  taken at the location where the hollow core bolt interfaces with the calibrated tube.  
         [0013]      FIG. 4  is a cross-sectional view of the calibrated tube taken along the horizontal center line.  
         [0014]      FIG. 5  is an alternative embodiment of a cross-sectional view of the calibrated tube taken along the horizontal center line. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]     For purposes of description herein, the terms “upper”, “lower”, “right”, “left”, “rear”, “front”, “vertical”, “horizontal” and derivatives thereof shall relate to the invention as oriented in  FIG. 2 . However, it is to be understood that the invention may assume various alternative orientations and step sequences, unless it is expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.  
         [0016]     Turning to the drawings, FIGS.  2  to  4  show a flow meter  30 , which is one of the preferred embodiments of the present invention, and illustrates its various components. A preferred embodiment of flow meter  30 , as shown in  FIG. 2 , comprises a housing  31  which receives therein an inner member  80 . Inner member  80  has a central bore  82  through which a fluid flows in a direction indicated by arrow “A”. Although the fluid in  FIG. 2  is shown as flowing in direction “A”, this is for illustration purposes only, and those skilled in the art will recognize that the various possible embodiments permit accurate metering of fluid flowing in either direction through flow meter  30 . Flow meter  30  can be installed in either a ‘forward’ or ‘reverse’ orientation with no effect on the accuracy or operation of the flow meter. A flow restrictor  97  is formed internally within the inner wall of inner member  80  and forms part of a metering structure. First and second port connections  47  and  49  respectively are equidistantly spaced from flow restrictor  97 . First port connection  47  is positioned upstream from flow restrictor  97  and second port connection  49  is positioned downstream from flow restrictor  97 .  
         [0017]     As illustrated in  FIG. 2 , housing  31  generally comprises a tubular body  32  having a flange  33  at a first end  34  thereof and a second flange  35  at a second end  37 . First and second flanges  33  and  35  have a plurality of attach holes  36  to affix flow meter  30  within a pipeline. Second end  37  is configured in a manner to mate with a tube or a pipe in a fluid transmission system (not shown), and can take on a variety of configurations dependent on the requirements of the fluid transmission system. Housing  31  has an internal bore  42  extending longitudinally therethrough and has a central longitudinal axis  44 . Peripheral lip  43  extends radially into internal bore  42  at second end  37  to define a bore opening at second end  37  that is smaller in diameter than bore  42 . Peripheral lip  43  has an internal chamfer  39  which substantially faces inwardly from the opening to internal bore  42  at second end  37 .  
         [0018]     First end  34  of housing  31  has a circular recess  38  machined therein and further includes at least two alignment pins  40  embedded within flange  33  and extending into recess  38 . Alignment pins  40  are precision located in a predefined pattern for engagement and positioning of a first end of inner member  80  as further described below.  
         [0019]     Flow meter  30  has a vertical center line generally shown by dashed line  45 . First and second port connections  47  and  49  respectively are positioned equidistant from centerline  45 . Port connections  47  and  49 , in the preferred embodiment, are connections that are commercially available and well known in the art. Port connections  47  and  49  are affixed to tubular body  32  by welding to a top portion thereof. Each of port connections  47  and  49  have a vertical bore  51  extending therethrough and are in fluidic communication with internal bore  42 . An upper portion  52  of central bore  51  in port connections  47  and  49  are internally threaded while a lower portion  53  is a smooth non-threaded bore and generally of smaller diameter than upper portion  52 . Each of port connections  47  and  49  receive therein a hollow core bolt  55 .  
         [0020]     Referring also to  FIG. 3 , each hollow core bolt  55  has an upper threaded shank portion  59  and a lower non-threaded shank portion  61 . Each bolt  55  is threaded into each of port connections  47  and  49  to a desired depth wherein lower non-threaded shank portion  61  extends into internal bore  42  in a sealing manner with inner member  80  as further described below. Bolts  55  are retained in their vertical position within port connections  47  and  49  by lock nuts  56  engaging a portion of upper threaded shank  59  and bearing against a top of port connections  47  and  49 . Bolts  55  also have a head  58  which extends above lock nuts  56 . A central bore  57  extends the length of bolt  55  to provide fluid communication with housing internal bore  42 . Head  58  further includes a threaded bore  60  for receiving a pressure gauge or a pressure transmission tube for connection to a pressure gauge. Smooth non-threaded shank portion  61  of bolt  55  includes a groove  62  therearound. Groove  62  retains a first O-ring  66  to create a pressure seal between lower smooth portion  53  of central bore  51  in port connections  47  and  49  and lower unthreaded shank  61  of bolt  55 . Bottom  63  of bolt  55  defines a second circular groove  64  therein which retains a second O-ring  68  for sealing engagement with inner member  80  as further described below.  
         [0021]      FIG. 4  illustrates inner member  80  which generally comprises inner cylindrical tube  81  having a flange  86  at a first end  85 . Flange  86  is generally circular in configuration and is sized to be received within circular recess  38  at first end  34  of housing  31 . Flange  86  includes alignment pin holes  88  therein in a precision pattern coincident with the pattern of alignment pins  40  in recess  38  of housing  31 . Inner cylindrical tube  81  has an inner wall  83  which defines an internal bore  82  extending longitudinally therethrough. Bore  82  has a central longitudinal axis illustrated by dash line  84 . Inner cylindrical tube  81  has a pressure equalization hole  90  extending therethrough permitting fluidic communication between internal bore  82  and an exterior of inner cylindrical tube  81 . Inner member  80  has a second end  92  which has an external chamfer  94  at second end  37  of housing  31 . Chamfer  94  is angularly oriented substantially equal to internal chamfer  39  for engagement therewith. Inner member  80  has a vertical center line shown by dash line  96 . Vertical center line  96  of inner member  80  and vertical center line  45  of housing  31  are substantially coincident when inner member  80  is received into housing  31 . A flow restrictor  97  is integrally formed within the inner wall  83  of cylindrical tube  81 . In the preferred embodiment, flow restrictor  97  is a 360 degree torus wedge  98  having opposing first and second wedge member  100  and  102  respectively. Wedge member  100  and  102  have substantially a full internal V-shaped circumference and are adjoined at circular vertex  406  to form flow constrictor member  99 .  
         [0022]     Wedge member  100  and  102  each are respectively defined by circular base ( 400 ,  401 ) and adjoining circular vertex ( 406 ). Both base  400  and  401  have a diameter coincident to the diameter of inner cylindrical tube  81 . Along the circumference of base  400  and  401 , internal wall  83  uniformly inclines inwardly and converges into the circumference of vertex  406  to form constrictor member  99 . The inclined V-shaped inner wall of wedge member  100  and  102  reduces the area available to flow through constrictor member  99 , but the inclined V-shaped inner wall also channels the incoming and outgoing flow through constrictor member  99 .  
         [0023]     The diameter of circular vertex  406  smaller than diameter of base  400  and  401 , thereby restricting the fluid flow through internal bore  82 . However, in the preferred embodiment, the diameter of circular vertex  406  can be any diameter necessary to create the differential use for measurement. Constrictor member  99  is formed within inner wall  83  cylindrical tube  81  such that the central radius of constrictor member  99  is substantially perpendicular to both longitudinal axis  84  and, the diameter of constrictor member  99  is coincident with vertical axis  96 . Torus Wedge  98  is retained to housing  31  by fastener  104  thereby rendering torus wedge  98  removable and readily replaceable with a torus wedge of different dimensions or configuration.  
         [0024]     The angular inclined depth between adjoining wedge members  100  and  102  as taken along vertical center line  96  perpendicular to axis  84  ranges between 45 and 90 degrees. Those knowledgeable in the art will also realize that opposing wedges  98  can also be utilized to provide the desired flow restriction with substantially the same results as a single wedge as disclosed in the prior art. Each combined wedge  98  and tube  81  can be precalibrated for use in any housing  31  without requiring recalibration of the tube-wedge combination. However, those skilled in the art will also recognize that the replacement of a wedge  98  in a specific tube  81  will require recalibration of the wedge-tube combination.  
         [0025]     Cylindrical tube  81  further includes circular recesses  105  at a top portion thereof. Recesses  105  are equally spaced about center line  96  and upon receipt of inner member  80  within housing  31  are in vertical registration with central bores  51  of port connections  47  and  49 . Recesses  105  have a circular land  108  and a pressure port  106  extending through land  108  to internal bore  82 .  
         [0026]      FIG. 5  illustrates another aspect of the present invention wherein the torus wedge is incorporated into outer member  380 . Outer member  380  which generally comprises inner cylindrical tube  381  having a flange  333  at a first end  334  thereof and a second flange  335  at a second end  337 . First and second flanges  333  and  335  have a plurality of attach holes  336  to affix outer member  380  within a pipeline. Inner cylindrical tube  381  has an inner wall  383  which defines an internal bore  382  extending longitudinally therethrough. Bore  382  has a central longitudinal axis illustrated by dash line  384 . Outer member  380  has a vertical center line shown by dash line  396 . A flow restrictor  97  is integrally formed within the inner wall  383  of cylindrical tube  381 . In the preferred embodiment, flow restrictor  97  is a 360 degree torus wedge  98  having opposing first and second wedge member  100  and  102  respectively. Wedge member  100  and  102  have substantially a full internal V-shaped circumference and are adjoined at circular vertex  406  to form flow constrictor member  99 .  
         [0027]     Wedge member  100  and  102  each are respectively defined by circular base ( 400 ,  401 ) and adjoining circular vertex ( 402 ). Both base  400  and  401  have a diameter coincident to the diameter of inner cylindrical tube  381 . Along the circumference of base  400  and  401 , internal wall  383  uniformly inclines inwardly and converges into the circumference of vertex  406  to form constrictor member  99 . The inclined V-shaped inner wall of wedge member  100  and  102  reduces the area available to flow through constrictor member  99 , but the inclined V-shaped inner wall also channels the incoming and outgoing flow through constrictor member  99 .  
         [0028]     The diameter of circular vertex  406  is smaller than diameter of base  400  and  401 , thereby restricting the fluid flow through internal bore  82 . Constrictor member  99  is formed within inner wall  383  of cylindrical tube  381  such that the central radius of constrictor member  99  is substantially perpendicular to both longitudinal axis  384  and, the diameter of constrictor member  99  is coincident with vertical axis  396 .  
         [0029]     The angular inclined depth between adjoining wedge members  100  and  102  as taken along vertical center line  396  perpendicular to axis  384  ranges between 45 and 90 degrees. Those knowledgeable in the art will also realize that opposing wedges  100  and  102  can also be utilized to provide the desired flow restriction with substantially the same results as a single wedge as disclosed in the prior art. In use, each combined wedge  98  and cylindrical tube  381  must be pre-calibrated.  
         [0030]     In use, referring to  FIGS. 1-4 , a housing  31  is selected for insertion in a fluid line to measure the fluid flow therethrough. An inner member  80  comprising a specific 360 degree wedge  98  and tube  81  configuration is selected based upon the type of fluid to be measured and the flow rate to be measured thereby. Inner member  80  is telescopically inserted into first end  34  of housing  31  and aligned so that alignment pins  40  in circular recess  38  are received in alignment pin holes  88  of flange  86 . Engagement of pins  40  in holes  88  substantially centers first end  85  with respect to bore  42 . Upon full insertion chamfer  94  at second end  92  of inner member  80  is received by internal chamfer  39  of housing  31 . The tapered surfaces of chamfers  39  and  94  interacts such to center second end  92  inner cylindrical tube  81  within internal bore  82  of housing  31 . Flange  86  of inner member  80  is sealed against circular recess  38  and inner cylindrical tube  81  is centered along its length within internal bore  42  of housing  31 .  
         [0031]     Since, the outer diameter of inner cylindrical tube  81  is smaller than bore  42 , a space  110  is defined by the outer diameter of tube  81  and inner bore  42  of housing  31 . Space  110  is sealed from internal bore  82  of inner member  80  except for pressure equalization hole  90  which permits the fluid pressure within space  110  to be equalized with the pressure of the fluid flowing through internal bore  82 . However, because space  110  is otherwise sealed from internal bore  82 , there is no fluid flow therethrough. After inner member  80  is received and centered within internal bore  42 , hollow core bolts  55  are inserted in first and second port connections  47  and  49 . Bolts  55  are threaded down until first O-ring  66  seals the upper portion of bore  51  from the fluid pressure in space  110 . Further, bottom  63  of bolt  55  bears against circular land  108  of inner cylindrical tube  81  such that second O-ring  68  seals space  110  from internal bore  82 . Lock nuts  56  are used to secure bolts  55  within port connections  47  and  49  to maintain the pressure seals created by O-rings  66  and  68 . Pressure gauges or fluid pressure  55  transmission lines (not shown) can be coupled with threaded bore  60  in head  58  of bolt  55  such that when a fluid flows through bore  82 , the pressure differential between pressure port  106  at port connection  47  upstream from flow restrictor  97  can be compared with the pressure at pressure port  106  of port connection  49  downstream from flow restrictor  97  in a manner well known in the art to determine the fluid flow rate therethrough. The preferred embodiment permits the measurement of fluid flow in a bi-directional manner with out loss of metering accuracy in either direction.  
         [0032]     Those skilled in the art will recognize that different flow restrictor sizes, shapes and configurations can be utilized to optimize the fluid flow metering performance of meter  30 , and that different quantities of pressure sensing ports can also be utilized as alternate embodiments. Further, in addition to the foregoing description, those skilled in the art will readily appreciate that other modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims expressly state otherwise.