GB2071340A

GB2071340A - Fluid flow meter

Info

Publication number: GB2071340A
Application number: GB8106996A
Authority: GB
Original assignee: University of Exeter
Current assignee: University of Exeter
Priority date: 1980-03-07
Filing date: 1981-03-05
Publication date: 1981-09-16

Abstract

Fluid such as petrol flows around a circular passage 10 from a tangential inlet 12 to an outlet 14. A spherical indicator 18 which is of only slightly less cross-section than the passage is constrained to be driven around the passage at the same rate as the fluid. Its motion is detected by a magnetic transducer 20 or an optical transducer 28, and the pulses produced are counted by a device 26 and which indicates total flow or flow rate. <IMAGE>

Description

SPECIFICATION Fluid flow meter This invention relates to a fluid flow meter.

According to the invention there is provided a fluid flow meter comprising an endless passage defining a circuit for fluid, an inlet and outlet for the fluid to and from the passage, arranged so that the fluid passes in one direction around the passage from the inlet to the outlet, and an indicator element which is constrained to move around the circuit defined by the passage and which in use is driven around the circuit by fluid flowing in the passage, whereby the rate at which the indicator element passes around the circuit provides a measure of the fluid flow rate.

Preferably the cross-section of the indicator element is not substantially less than the crosssection of the passage so that the indicator element is driven at substantially the same rate as the fluid.

Preferably the inlet is substantially tangential to the passage, in order to cause fluid to flow in one direction around the passage and not the opposite direction. The outlet is preferably adjacent the inlet in the opposite direction to the direction of flow around the passage. The passage preferably defines a circular path for the fluid and indicator element.

Preferably a transducer is provided which produces a signal relating to the rate of circulation of the indicator. For example, the indicator may be of magnetic material and a magnetic transducer may be arranged adjacent the passage so that when the indicator passes the transducer, the transducer produces a pulse. Alternatively, an optical transducer may be used, and passage of the indicator past the optical transducer may block light reaching the transducer, or reflect light to the transducer, so as to produce a pulse. In either case, the output of the transducer is suitably connected to a counter which counts the pulses and provides a visual display relating to the flow rate.

A fluid flow meter according to the invention will now be described by way of example, with reference to the accompanying drawings in which: Fig. 1 is a schematic diagram of the flow meter, and Fig. 2 is a cross-section of the line Il-Il in Fig. 1.

An endless tube 10 provides a circular passage for fluid such as petrol. An inlet 1 2 for fluid is arranged tangentially to the circular passage, and an outlet 14 leads fluid radially inwardly to a central sink 1 6. Because it is entering tangentially in the inlet 12, the fluid prefers to flow in the direction of arrow A around the circular passage.

The outlet 14 is provided adjacent the inlet 12 on the circuit around the passage 10, but in the direction from the inlet 12 which is opposite the arrow A. Thus, the fluid has to travel substantially around the entire circuit of the passage 10 in order to get from the inlet to the outlet.

A spherical indicator element 1 8 is provided in the passage 10, and is a loose fit therein. The diameters of the inlet 12 and outlet 14 are less than that of the indicator element 18, so that the indicator 1 8 is constrained to travel around the circular path defined by the passage 10. The indicator element 1 8 is only slightly smaller than the cross-section of the tube 10, so that it is displaced by the fluid as it passes around the circuit and travels at substantially the same rate as the fluid. If the indicator 10 were smaller, although its rate of motion would still be related to the rate of flow of fluid the relationship might be less accurate. The indicator 18 should be of a density similar to the fluid being used for best results.

When the fluid leaves the tube 10 at the outlet 14, the indicator 18 continues to travel around the tube 10. It would be possible to obtain a measure of the flow rate merely by observing the rate of revolution of the indicator 1 8 around the circular tube 10. In the preferred arrangement, however, a transducer is provided adjacent one portion of the tube 10. In the drawing there is shown schematically a magnetic transducer in the form of a coil 20, and the indicator element 1 8 contains a magnetic material.The coil 20 is energised by conventional control circuitry 22 which sends a pulse via wires 24 to a counter 26 every time the magnetic field of the coil 20 is disturbed by the passing of the indicator 1 8. The counter 26 can provide a straightforward indication of the number of revolutions the indicator 18 has made around the passage 10 (which will be proportional to the volume of fluid which has passed), or it can incorporate a timer and be calibrated to provide a direct read-out of the flow rate.

An alternative transducer, shown in dotted lines in the drawing, would be an optical transducer such as a light dependent resistor or a photodiode 28 which receives light from a source 30 through the tube 10, which light is blocked every time the indicator 18 passes. When this happens a pulse shaping circuit 32 provides a pulse to the counter 26, which acts as before. The tube 10 should be of a transparent material such as glass or Perspex (Registered Trade Mark) acrylic plastics material, or have a transparent window in the region of the transducer 28.

Instead of light from a source 30 being blocked by the indicator 1 8 as it passes, the indicator 18 could be coloured white or a bright colour, and reflect light onto the optical transducer 28 as it passes so as to produce a pulse.

The coil 20 or optical transducer 28 can be placed in proximity to the tube 10 anywhere around the circuit defined thereby.

A particularly preferred construction can be seen from Fig. 2. The passage 10 is formed from two co-operating semi-circular cross-section grooves in mating faces 34 of two translucent nylon blocks 36. The inlet 12 and outlet 14 are also semi-circular grooves in the face 34, and for ease of manufacture they and the sink 1 6 are provided in one only of the blocks 36. An optical transducer 28 and source 30 are affixed to the respective blocks 36, above and below the passage 10. For best results the transducer 28 should be sensitive to infra-red radiation (to which nylon is more transparent). The source 30 may be an infra-red light emitting diode.

Claims

1. A fluid flow meter comprising an endless passage defining a circuit for fluid, an inlet and an outlet for the fluid to and from the passage, arranged so that fluid passes in one direction around the passage from the inlet to the outlet, and an indicator element which is constrained to move around the circuit defined by the passage and which in use is driven around the circuit by fluid flowing in the passage, whereby the rate at which the indicator element passes around the circuit provides a measure of the fluid flow rate.

2. A fluid flow meter according to claim 1 wherein the cross-section of the indicator element is not substantially less than the cross section of the passage so that the indicator element is driven at substantially the same rate as the fluid.

3. A fluid flow meter according to claim 1 or claim 2 wherein the inlet is substantially tangential to the passage.

4. A fluid flow meter according to any one of the preceding claims wherein the outlet is adjacent the inlet in the opposite direction to the direction of flow around the passage.

5. A fluid flow meter according to any one of the preceding claims wherein the passsage defines a circular path for the fluid and indicator element.

6. A fluid flow meter according to any one of the preceding claims wherein the indicator element is spherical.

7. A fluid flow meter according to any one of the preceding claims having a transducer which produces a signal relating to the rate of circulation of the indicator.

8. A fluid flow meter according to claim 7 wherein the indicator element is of magnetic material and the transducer is a magnetic transducer arranged adjacent the passage so that when the indicator element passes the transducer.

the transducer produces a pulse.

9. A fluid flow meter according to claim 7 wherein the transducer is an optical transducer, and passage of the indicator element past the transducer blocks light reaching the transducer, or reflects light to the transducer, so as to produce a pulse.

10. A fluid flow meter according to claim 7, 8 or 9 having a counter connected to the output of the transducer, and arranged to count pulses therefrom and provide a visual display related to the flow rate.

11. A fluid flow meter substantially as described herein with reference to the drawings.