WO2004076983A1

WO2004076983A1 - Flow meter

Info

Publication number: WO2004076983A1
Application number: PCT/AU2004/000235
Authority: WO
Inventors: Lance Trigwell Gardiner
Original assignee: Beverage Technologies Pty Ltd
Priority date: 2003-02-25
Filing date: 2004-02-25
Publication date: 2004-09-10
Also published as: AU2003900822A0

Abstract

A fluid flow meter (10) has two vanes (36, 38) moving through a chamber (26) along with the fluid for which the flow rate is to be measured. The vanes (36, 38) divide the flow into discrete volumes (64, 66) in order for the volume of fluid moving through the chamber to be determined. The vanes (36, 38) each rotate and move about a central axis whilst being constrained by a guide (48) rotating about an axis offset from the central axis.

Description

TITLE

"FLOW METER"

FIELD OF THE INVENTION The present invention relates to a flow meter.

BACKGROUND TO THE INVENTION

It is known to require a meter which can accurately measure the volume of fluid passing through a fluid conduit.

A known type of flow meter operates by measuring the velocity of fluid flow in one direction of a conduit, and calculates the volume flow rate of the fluid by multiplying the fluid velocity by the cross sectional area of the conduit at the point at which the velocity is measured. This method of measuring the rate of fluid flow is inherently inaccurate, as it assumes an ideal condition where flow conditions are constant throughout the cross section of the conduit.

The known method is particularly unsuitable for use with compressible fluids, such as liquids containing dissolved carbon dioxide. Where such fluids are used, the action of the fluid against the flow meter alters the properties of the fluid, and thus the rate measured is not truly representative of the fluid as a whole.

The known method is also unsuitable for use with fluids having rheological properties which alter when the fluid is subjected to shear. The present invention attempts to overcome at least in part some of the aforementioned disadvantages of previous flow meters.

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention there is provided a flow meter including a chamber through which fluid passes, characterised in that the chamber has an inlet and an outlet, the flow meter having at least one vane which is moveable within the chamber, the vane having a chamber engaging portion ^"wherein the chamber engaging portion divides the chamber into a leading region located between the chamber engaging portion and the outlet, and a following region located between the chamber engaging portion and the inlet, the chamber engaging portion having a first position wherein the chamber engaging portion substantially prevents the flow of fluid between the leading region and the following region, and a second position wherein the chamber engaging portion permits the flow of fluid between the following region and the outlet, the chamber engaging portion being moveable at least partially through the chamber away from the inlet and towards the outlet whilst remaining in the first position.

Advantageously, the present invention provides for the accurate measurement of fluid volume passing through the flow meter, without relying on a calculation based on fluid property assumptions. Also advantageously, the present invention provides for the integration of flow meter components into the fluid flow, thus minimising disturbance to the flow. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a side view of a flow meter in accordance with the present invention; Figure 2 is a cross sectional plan view of the flow meter of Figure 1, taken through line A-A;

Figure 3 is a cross sectional elevation view of the flow meter of Figure 1, taken though line C-C; and

Figure 4 is a cross sectional plan view through a lower housing of the flow meter of Figure 1, taken through line B-B..

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the Figures, there is shown a flow meter 10 having an upper housing 12, a lower housing 14 and a inner housing 16. The inner housing 16 has a front face 18, a rear face 20, a first side face 22 and a second side face 24.

A curved chamber 26 is located within the flow meter 10. The chamber 26 has an inlet 28 located on the front face 18 of the inner housing 16, adjacent the first side face 22. The chamber 26 has an outlet 30 located on the second side face 24 of the inner housing 16, adjacent the rear face 20. The chamber 26 is arranged so that, in use, fluid entering the inlet 28 can flow through the chamber 26 and exit at the outlet 30.

The lower housing 14 includes a substantially central, circular recess 32 oriented towards the upper housing 12. A control disc 34 is located within the recess 32, and arranged to rotate within the recess 32 about an axis substantially perpendicular to the control disc 34.

The flow meter 10 includes a first vane 36 and a second vane 38. Each of the first vane 36 and the second vane 38 are substantially elongate, with an upper edge 40 and a lower edge 42. The upper edge 40 is substantially level with a lower surface 13 of the upper housing 12 which partially defines the chamber 26. The lower edge 42 is substantially level with an upper surface 35 of the control disc 34. A pin 44 is located centrally of the lower edge 42 of each vane 36, 34, and extends downwardly from the vane 36, 38. The control disc 34 includes two pin receiving apertures 46, located in opposed positions approximately two thirds of the distance between a central point and an outer edge of the control disc 34, as seen in figure 3. In use, the pins 44 of the first and second vanes 36, 38 are located within pin receiving apertures 46, and first and second vanes 36, 38 are thus each able to rotate relative to the control disc 34 about an axis substantially parallel to the axis of rotation of the control disc 34.

The upper housing 12 includes a substantially circular recess 50 oriented towards the lower housing 14. The centre of the recess 50 is offset from the centre of the upper housing 12, and is not aligned with the centre of the control disc 34. The flow meter 10 further includes a guiding rotor 48. The guiding rotor 48 is substantially cylindrical in shape, with a radius substantially similar to a radius of the recess 50 and extends between the upper housing 12 and the lower housing 14. An upper portion of the guiding rotor 48 is located within the recess 50 of the upper housing 12. The guiding rotor 48 is arranged to rotate about an axis passing through the centre of the recess 50, the axis of rotation being substantially parallel to the axis of rotation of the control disc 34 and the first and second vanes 36, 38. The guiding rotor 48 has a first slot 52 and a second slot 54. The first and second slots 52, 54 each extend through a diameter of the guiding rotor 48, and are substantially disposed at right angles to each other.

The first and second slots 52, 54 each extend from a lower edge of the guiding rotor 48 adjacent the lower housing 14 and the upper surface 35 the control disc 34 to the level of the upper edge 40 of the first and second vanes 36, 38. The first and second slots 52, 54 are sized to allow the respective first and second vanes 3^*6,38 to slide within the respective first and second slots 52,54 diametrically through the guiding rotor 48. It will be appreciated that the components are sized so as to provide a very small clearance between the vanes 36, 38 and slots 52, 54, thus minimising the possibility of back flow of fluid through the slots 52, 54. The chamber 26 has an inner portion 58 which is bounded by an inner wall 60 of the inner housing 16, the lower surface 13 of the upper housing 12, an upper portion 15 of the lower housing 14, a portion of the upper surface 35 the control disc 34, and a portion of the guiding rotor 48. The inner wall 60 is curved in a partially elliptical shape.

During operation, the first and second vanes 36, 38 are constrained to move in a particular path by the geometry of the control disc 34, and the guiding rotor 48. Rotation of the control disc 34 causes the receiving apertures 46 and the pins 44 to revolve about the axis of the control disc 34. This in turn causes the first and second vanes 36, 38 to revolve about the axis of the control disc 34. The action of the vanes within the guiding rotor 48 causes the guiding rotor 48 to rotate about its own axis.

The location of the first and second vanes 36, 38 within the first and second slots 52, 54 of the guiding rotor 48 constrains the first and second vanes 36, 38 to be aligned at all times in a radial direction relative to the guiding rotor 48. The offset between the axis of the control disc 34 and the axis of the guiding rotor 48 means that the distance between the axis of the guiding rotor 48 and the axis of the pins 44 is constantly changing. Outer portions of the first and second vanes 36, 38 are thus caused to move inwardly and outwardly of the chamber 26 as the control disc 34 rotates.

The inner wall 60 is shaped such that it substantially follows the curve defined by the outer edge of the first vane 36 during a portion of the rotation of the control disc 34. The first vane 36 and the second vane 38 each have a chamber engaging portion 62 extending into the chamber 26 during a portion of the rotation of the control disc 34. It will be appreciated that the size of the chamber engaging portion 62 will vary during revolution of the vane 36, 38. It will be understood that the location of the chamber engaging portion 62 will switch from one end of the vane 36, 38 to the other during alternate passes of the vane 36, 38 through the inner portion 58 of the chamber 26. When the vane 36, 38 is extending into the chamber 26, it has the effect of dividing the chamber 26 into a leading region 64 and a following region 66. This is shown in Figure 1 in relation to the first vane 36. The leading region 64 is the portion of the chamber 26 between the chamber engaging portion 62 and the outlet 30, and the following region is the portion of the chamber 26 between the chamber engaging portion 62 and the inlet 28.

The chamber engaging portion 62 has a first position when the first vane 36 extends into the inner portion 58 of the chamber 26. It will be appreciated that the outer edge of the first vane 62 is adjacent the inner wall 60 of the inner housing 12 when in the first position. As a result, fluid can not flow past the chamber engaging portion 62 between the leading region 64 and the following region 66.

The chamber engaging portion 62 has a second position where the vane 36, 38 is not extending into the inner portion 58 of the chamber 26. This can be seen in Figure 1 in relation to the second vane 38. It will be appreciated that when in the second position fluid can flow past the outer edge of the chamber engaging portion 62. The inner wall 60 extends through an angle of about 90 degrees. Where this angle is exactly 90 degrees, as in the preferred embodiment shown in the drawings, the chamber engaging portion 62 of the first vane 36 enters the first position at the samp point of revolution as the chamber engaging portion 62 of the second vane 38 leaves the first position. One of the vanes 36, 38 is thus in the first position at all times. In an alternative embodiment, there is an overlap period of rotation where both the vanes 36, 38 are in the first position. The flow meter 10 further includes a motion detecting means 70. The motion detecting means 70 is arranged to measure the number of revolutions or partial revolutions of the control disc 34. In a preferred embodiment the sensor 70 is an optical sensor, however it will be appreciated that other sensors such as a hall effect sensor may be used. It is considered preferable to use a sensor 70 which allows the fluid flow to be measured from outside a sealed flow meter 10, thus reducing the risk of contamination of the fluid.

In use, the flow meter 10 is placed in a fluid flow path, with fluid arranged to enter the flow meter 10 at the inlet 28 and exit the flow meter 10 at the outlet 30. The fluid acts against the chamber engaging portion 62 of the first and second vanes 36, 38, causing the vanes 36, 38 to drive revolution of the control disc 34 and the guiding rotor 48. At the moment when one of the first and second vanes 36, 38 is moving into the first position, and the other vane 38, 36 is moving into the second position, the inner portion 58 of the chamber 26 is momentarily enclosed between the respective chamber engaging portions 62 of the first and second vanes 36, 38, a portion of the guiding rotor 48 and the inner wall 60. The volume of this enclosed portion 58 is fixed by the geometry of the flow meter 10. This situation will be repeated four times during each revolution of the control disc 34. It will be appreciated that all fluid which passes through the inner portion 58 of the chamber 26 will be enclosed in this manner once, and only once. The volume of fluid which passes through the flow meter 10 during each revolution of the control disc 34 will thus be equal to four times the volume of the. enclosed portion. The motion detecting means 70 acts as a counter to measure the number of revolutions or partial revolutions of the control disc 34. The total volume of fluid passing through the flow meter can thus be readily ascertained. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A flow meter including a chamber through which fluid passes, .the chamber having an inlet and an outlet, the flow meter having at least one vane which is moveable within the chamber, the vane having a chamber engaging portion wherein the chamber engaging portion divides the chamber into a leading region located between the chamber engaging portion and the outlet, and a following region located between the chamber engaging portion and the entrance, the chamber engaging portion having a first position, wherein the chamber engaging portion substantially prevents the flow of fluid between the leading region and the following region, and a second position, wherein the chamber engaging portion permits the flow of fluid between the following region and the outlet, the chamber engaging portion being moveable at least partially through the chamber away from the inlet and towards the outlet whilst remaining in the first position.

2. A flow meter as claimed in claim 1, characterised in that the flow meter includes means for constraining the at least one vane to move in a particular path.

3. A flow meter as claimed in claim 2, characterised in that the flow meter includes a control disc, the at least one vane being receivable within the control disc and being able to rotate relative to the control disc about a vane axis.

4. A flow meter as claimed in claim 3, characterised in that the control disc is rotatable about a central axis thereof.

5. A flow meter as claimed in claim 4, characterised in that the vane axis is parallel to, and displaced from, the central axis of the control disc.

6. A flow meter as claimed in claim 4 or claim 5, characterised in that the means for constraining the movement of the at least one vane comprises a guiding rotor, the guiding rotor being rotatable about an axis substantially parallel to, and displaced from, that of the control disc.

7. A flow meter as claimed in claim 6, characterised in that the guiding rotor includes at least one slot through which the at least one vane is constrained to move.

8. A flow meter as claimed in claim 7, characterised in that the at least one slot defines a diameter of the guiding rotor.

9. A flow meter as claimed any of the preceding claims, characterised in that the flow meter includes a first vane and a second vane.

10. A flow meter as claimed in claim 9, characterised in that when one of the first and second vanes is in the first position the other of the first and second vanes is in the second position

11. A flow meter as claimed in claim 9, characterised in that the flow meter has a state when both the first vane and the second vane are in the first position.

12. A flow meter as claimed in claim 7 and claim 9, characterised in that the guiding rotor includes two slots, the two slots being arranged substantially at right angles.