Abstract:
A flow meter includes a cylindrical flow chamber having an axis and an internal cylindrical wall. Axially spaced about opposite ends of the flow chamber are an inlet and an outlet. Both the inlet and outlet are oriented generally tangential with respect to the interior cylindrical wall. Rotatively mounted about the axis of the chamber is a rotor but wherein the rotor is mounted within the chamber between the inlet and outlet. Fluid entering the chamber via the inlet tends to spiral around the axis of the chamber and generally moves axially in the process to where the fluid engages and turns the rotor but wherein the fluid continues to move axially through the chamber to where the fluid exits the outlet.

Description:
FIELD OF THE INVENTION 
   The present invention relates to flow meters, and more particularly to a flow meter having a cylindrical chamber and wherein the fluid being measured moves axially through the flow chamber. 
   BACKGROUND OF THE INVENTION 
   Conventional turbine flow meters utilize a rotor for measuring the flow rate of a fluid. These conventional turbine designs utilize a rotor that is aligned to the flow path of the fluid being measured. That is, the general direction of the entering flow is aligned with the axis of the rotor. Such rotors have blades that are generally positioned angularly to the flow path. As the velocity of the fluid increases, the rotor will rotate. The speed of rotation of the rotor is proportional to the velocity of the fluid passing across the rotor. 
   It is quite difficult to mechanically measure fluid flow at low fluid velocities with conventional turbine flow meters. One of the problems in precisely measuring low flow rates with a mechanical device is that the flow meter must overcome the effects of friction and inertia. That is, the velocity of the fluid being measured must be sufficient to overcome the effects of friction and inertia in order for the flow meter to properly function and to measure relatively low flow rates. 
   Therefore, there has been and continues to be a need for a turbine type flow meter that will precisely measure low flow rates. 
   SUMMARY OF THE INVENTION 
   A flow meter is provided that includes a housing and a cylindrical flow chamber including a cylindrical inner wall and opposed end portions. An inlet is formed at one end portion of the chamber for directing fluid into the chamber. An outlet is formed at the other end portion of the chamber for directing fluid from the chamber. The chamber includes an axis and wherein the inlet and outlet are axially spaced and disposed about opposite end portions of the chamber. A rotor is rotatively mounted about the vertical axis of the chamber and axially spaced between the inlet and outlet such that the inlet, outlet and rotor lie in separate traverse planes. The chamber, inlet, outlet and rotor are arranged such that the fluid entering the chamber at the inlet is constrained to move axially through the chamber past the rotor and then onto the outlet where the fluid exits the chamber. 
   In one embodiment, the flow meter comprises a housing and a cylindrical flow chamber disposed within the housing and having an interior cylindrical wall. A rotor is rotatively mounted within the flow chamber. An inlet is formed in the housing and opened to the chamber for directing fluid into the chamber. Likewise an outlet is formed in the housing and opened to the chamber for directing fluid from the chamber. The inlet and outlet are axially spaced with respect to the flow chamber, and the rotor is rotatively mounted between the inlet and the outlet, but axially spaced from both the inlet and the outlet. The inlet is oriented with respect to the interior wall of the chamber such that the fluid directed into the chamber via the inlet is directed generally tangential to the interior wall of the chamber. The orientation of the inlet with respect to the rotor and interior wall of the chamber results in fluid flow directed into the chamber spiraling around the interior wall and engaging and turning the rotor prior to being directed out the outlet. 
   In addition, the present invention entails a method of measuring fluid flow by directing fluid through an inlet into a cylindrical flow chamber having an axis and a cylindrical interior wall such that the fluid entering the chamber is directed in a direction generally tangential to the interior wall. Once in the flow chamber, the fluid moves from the inlet axially through the chamber and at least some of the fluid tends to spiral around the axis. As the fluid moves axially through the chamber the fluid engages the rotor causing the rotor to rotate. After engaging the rotor, the fluid continues to move through the chamber to where the fluid is directed out an outlet. 
   Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrative of such invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a vertical cross sectional view of the flow meter illustrating the inlet, outlet and the rotor and the relationship between the inlet, outlet and rotor. 
       FIG. 2  is a transverse sectional view of the flow meter showing the relationship of the inlet to the flow chamber. 
       FIG. 3  is a transverse sectional view of the flow meter showing the relationship of the outlet to the flow chamber. 
       FIG. 4  is another vertical sectional view of the flow meter, but illustrating a flow-sensing element connected to the housing of the flow meter. 
       FIG. 5  is a fragmentary perspective view illustrating components of the flow meter. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With further reference to the drawings the present invention is shown therein and indicated generally by the numeral  10 . Flow meter  10  comprises a housing indicated generally by the numeral  12 . Housing  12  includes a top  14 , a bottom  16 , and sidewall  18 . Housing  12  can be constructed of various materials but it is contemplated that in one embodiment the flow meter  10  would be constructed of stainless steel. 
   A central bore is formed in the housing  12 . The central bore includes opposed threaded portions. Secured into both of the opposed threaded portions of the bore is a threaded plug  20 . When the threaded plug  20  is securely screwed into the threaded bore, a fluid tight or sealed relationship is established between each threaded plug  20  and the housing  12 . 
   A flow chamber  30  is formed within the housing  12 . In particular, flow chamber  30  is a generally cylindrical chamber that is formed by the central bore formed in the housing  12  and the two threaded plugs  20 . Flow chamber  30  includes an interior cylindrical wall  30 A. Thus, the bounds the flow chamber  30  is formed by the interior wall  30 A, which forms a part of the bore of the housing  12 , and the threaded plugs  20 . 
   Formed in the wall structure of the housing is a fluid inlet  32 . This is illustrated in  FIGS. 1 and 2  of the drawings. Fluid inlet  32  extends from the outer wall  18  of the housing  12 , through the wall structure of the housing and to the interior wall  30 A of the flow chamber. Fluid inlet  32  is particularly oriented with respect to the flow chamber  30  such that it extends in generally tangential relationship to the interior wall  30 A. See  FIG. 2 . That is, as will be described subsequently herein, fluid being directed into the flow chamber  30  via the fluid inlet  32  will enter the flow chamber in a direction that is generally tangential to the interior wall  30 A that lies adjacent the fluid inlet  32 . 
   Likewise there is provided a fluid outlet  34 . Note in  FIG. 1  where the fluid outlet  34  is axially spaced from the fluid inlet  32 . That is, for purposes of reference, it is said that the flow chamber  30  includes an axis that is referred to by the numeral  31 . Thus, again as viewed in  FIG. 1 , the fluid outlet  34  is axially spaced from the fluid inlet  32 . Like the fluid inlet  32 , the outlet  34  is oriented with respect to the flow chamber  30  such that it extends in a generally tangential relationship with respect to the adjacent interior cylindrical wall  30 A. That is, as seen in  FIG. 3 , outlet  34  is positioned with respect to the interior wall  30 A such that it extends in a direction that is generally tangential to the adjacent interior wall  30 A. 
   Each threaded plug  20  includes an inner end portion or shoulder  36  that projects into the flow chamber  30 . Each shoulder includes a face that includes a seat or bore  38  formed therein. As will be appreciated from subsequent portions of this disclosure, the seat or bore  38  is adapted to receive a shaft that will in turn support a rotating rotor. 
   Rotatively mounted between the shoulders  36  of the respective plugs  20  is a rotor  40 . Rotor  40  includes a series of blades that extend outwardly therefrom. Although the rotor  40  may be constructed of various materials, it is contemplated that in one embodiment, that the rotor would be constructed of magnetic steel in order to be compatible with a conventional magnetic sensor/counter. As noted above, the opposed shoulders  36  of the threaded plugs  20  are designed to hold, retain and generally support a shaft. As seen in the drawings, a shaft  42  extends through the rotor  40  and into the opposed seats  38  formed in the shoulders  36  of the threaded plugs  20 . Rotor  40  is bearinged on the shaft  42 . The bearing, in conventional fashion, can be accomplished with ball bearings or a bushing. It should also be noted that the seats  38  formed in the shoulders  36  of the threaded plugs  20  may permit the shaft  42  to move or float up and down therein. As seen in  FIGS. 1 ,  4  and  5 , rotor  40  is positioned between the shoulders  36  such that there is a relative small space between the top and bottom of the rotor  40  and the adjacent faces of the shoulders  36 . It is desirable that the top and bottom portions of the rotor  40  do not engage and drag against the face of the shoulders  36 . To minimize the potential for drag and consequently friction, each face of each shoulder  36  can be provided with a thin annular ring that extends outwardly from the face. This would assure that the entire surface of the face of the shoulders  36  is not engaged by the rotor but that at most the only engagement that would occur would be between a portion of the rotor  40  and the annular rings. 
   The blades projecting from the rotor  40  can be oriented in any number of configurations. It may be preferred to orient the blades such that they extend generally perpendicular to the direction of fluid flow through the flow chamber  30 . As will become apparent from subsequent portions of the disclosure, because it is contemplated that the fluid flow would follow a spiral path around the axis  31  of the flow chamber  30 , the blades would be accordingly angled to result in the fluid flow generally contacting the blades generally perpendicularly. 
   Flow meter  10  would be provided with a conventional flow sensor mechanism. Details of such a flow sensor mechanism is not dealt with herein because such is not material per se to the present invention and further because flow sensors for use in conjunction with flow meters are well known and appreciated by those skilled in the art. However, as illustrated in  FIG. 4 , a portion of a flow sensor mechanism is screwed into the housing  12  of the flow meter  10  and this portion of a conventional flow sensor mechanism is referred to generally by the numeral  44 . As noted before, numerous types of conventional flow sensors or counters can be utilized. Typically flow meters of this type utilize a magnetic sensor or counter which essentially counts the revolutions of the rotor  40  as fluid moves through the flow chamber  30 . In addition to magnetic sensing devices, a variety of other commonly employed actuator-sensor technologies are also available which can effectively and efficiently perform the same function. Optical encoders, for example, are commonly utilized to perform tasks similar to those performed by magnetic sensors or counters. 
   Turning to  FIG. 5 , it is seen that the fluid inlet  32  is axially spaced with respect to the fluid outlet  34 . In addition, rotor  40  is positioned between the inlet  32  and the outlet  34 . In this particular embodiment, the inlet  32 , rotor  40  and outlet  34  lie in separate transverse planes relative to the axis  31  of the flow chamber  30 . Because of the tangential orientation of the inlet  32  and outlet  34  with respect to the interior wall  30 A of the flow chamber  30 , it is postulated that a substantial portion of the fluid flow passing through the chamber  30  will do so by moving in a spiral path or configuration. That is, it is believed that the fluid entering through inlet  32  into the chamber  30 , as illustrated in  FIG. 5 , will tend to spiral around the interior cylindrical wall  30 A. As the fluid flow spirals around the interior wall  30 A that the fluid will also move axially from inlet  32  past the rotor  40  and out the outlet  34 . It is believed that as the fluid enters the chamber  30  from the inlet  32  that initially the fluid will not engage the rotor  40 . But as the fluid spirals and moves axially through the chamber  30 , that the fluid will come into contact with the rotor  40  and turn the rotor. It is believed that the fluid will engage the rotor for a full 360° and thereafter continue to move axially towards the outlet  34  where the fluid is discharged from the chamber. 
   It is contemplated that the flow meter  10  of the present invention may perform better when vertically oriented such as shown in  FIG. 1 . By vertical orientation, it is meant that the axis  31  of the flow chamber  30  is oriented in a vertical position and the inlet  32  is disposed below the outlet  34 . If the flow meter is oriented horizontally, the fluid may initially have to have sufficient energy to “climb” the interior wall and that may have an adverse effect on the accuracy of the flow meter  10  at very low flow rates. 
   The flow meter  10  of the present invention may accurately measure liquids, for example, at a rate of 0.01 gal/min. to 1 gal/min. This yields an effective turn down ratio of 100. 
   The present invention is designed to precisely measure relatively low flow rates. It is believed that the design and particularly the orientation of the inlet and outlet with respect to the rotor  40  and the cylindrical chamber  30  will minimize the adverse effects of friction and inertia when measuring these low flows. 
   Reference is made to U.S. Pat. No. 5,992,230 which describes a turbine type flow meter. The disclosure of U.S. Pat. No. 5,992,230 is expressly incorporated by reference. 
   The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and the essential characteristics of the invention. The present embodiments are therefore to be construed in all aspects as illustrative and not restrictive and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.