GB2282223A

GB2282223A - Flow measuring apparatus

Info

Publication number: GB2282223A
Application number: GB9319562A
Authority: GB
Inventors: Cyril Ward Nugent
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-09-22
Filing date: 1993-09-22
Publication date: 1995-03-29
Also published as: GB9319562D0

Abstract

Flow measuring apparatus (10, fig. 1 not shown) particularly for use in fluid flow measurement in a drinks dispensing machine, comprises a flow passage (11) on which are mounted a pair of oppositely directed receiver/transmitter devices 12. In use the receiver/transmitter devices can switch between modes or both devices can transmit bursts of an oscillating signal simultaneously and then to receive the signal emitted by the other device. The rate of fluid flow is determined from the phase difference of the received signals by the control circuit (13) and can be displayed at window an output. The control circuit comprises window circuits 21, a schmitt trigger 22 and an exclusive OR gate 23. <IMAGE>

Description

FLOW MEASURING APPARATUS This invention relates to apparatus for measuring flow of substances particularly although not exclusively to measuring flow of fluids through dispense pipes.

When drinks are dispensed in a bar or other establishment, it is necessary to maintain an accurate control over the flow-of fluids through the dispense pipes, especially if more than one constituent is being mixed to form the drink.

It is an object of the present invention to provide an improved flow measuring apparatus which will allow flow rates to be measured in a particularly simple and accurate manner.

Thus, and in accordance with the present invention therefore, there is provided flow measuring apparatus comprising a flow passage through which a substance can flow, at least two transmitters to transmit an oscillating signal respectively in opposite directions in said passage, at least two receivers disposed spaced from said transmitters to receive said signals transmitted from said transmitters and phase difference calculating means operable to calculate a phase difference between transmitted signals received at said receiver and to produce an output indication of the flow velocity of the substance through the pipes from said phase difference.

With this arrangement it is possible to monitor flow velocities of substances in flow passages in a particularly simple and accurate manner.

Preferably each said transmitter and receiver are formed as a single transmitter/receiver device switchable so as to operate as a transmitter or receiver.

Preferably said oscillating signal comprises an ultrasonic wave which may be at a frequency of 2MHz. If desired, a packet or small burst of ultrasonic waves may be used.

The receivers and transmitters or receiver/ transmitter units are interconnected so that operation thereof. can be achieved simultaneously. Preferably the receivers/transmitters comprise crystal oscillators which can be driven at any desired frequency. For example, the crystal oscillators can be driven at a frequency to produce an oscillating signal having a frequency 2MHz.

If desired, or as appropriate, the transmitter can be driven so as to produce packets, bursts or pulses of oscillating signals at an appropriate frequency.

The flow passage and/or transmitters and/or receivers can be encapsulated with a plastics material for protection purposes.

The invention will now be described further by way of example only and with reference to the accompanying drawings of which: Fig. 1 shows a plan view of one form of flow measuring apparatus according to the present invention; and Fig. 2 shows a diagrammatic representation of one form of circuit for producing an output indicative of the flow velocity of a substance through the flow passage.

Referring now to the drawings, there is shown in Fig. 1 flow measuring apparatus 10 for -measuring the flow of fluid through a dispense pipe.

The apparatus comprises a flow passage 11 of generally U-shaped form, a pair of transmitter/receiver devices 12 and control circuitry 13. All of the components of the measuring apparatus are encapsulated in a block of plastics material 14 to provide protection to the apparatus and in particular the control circuitry 13 and flow passage 11.

The flow passage 11 is generally of inverted U-shape form and comprises an inlet part 16 and an outlet part 17 linked by a flow measuring part 18. The flow measuring part 18 is generally straight and extends parallel to a longitudinal axis of the block but laterally spaced therefrom. The pair of transmitter/receivers 12 are mounted adjacent respective ends of the flow measuring part 18 of the flow passage and are directed inwardly along the flow measuring part in generally opposite directions.

The transmitter/receiver devices 12 comprise crystal oscillators which are switchable between transmit and receive modes under the control of the control circuitry 13. The devices 12 are mounted relative to the flow passage 11 in a manner whereby oscillating signals produced by the devices 12 when in transmit mode can be directed generally along a longitudinal axis of the flow passage in opposite directions.

The control circuitry 13 can conveniently be mounted on a printed circuit board (PCB) which can be incorporated in the block between arms 16, 17 of the flow passage 11. The control circuitry is shown more clearly in Fig. 2 and comprises a pair of window circuits 21 of conventional form, a conventional Schmitt trigger circuit 22 and a gate circuit 23 which acts to produce a d.c.

output voltage indicative of the flow velocity of the fluid in the flow passage.

In use, the flow measuring apparatus 10 is connected in the dispense pipe of a fluid to be dispensed to allow the fluid to flow from the inlet 24 to the outlet 26 of the apparatus. With fluid flowing through the flow passage 11, a burst of oscillating signals are emitted by the devices 12 for a predetermined period of time. It will be appreciated that given the location and orientation of the devices, when the oscillating signals are emitted, the signal from one device 12 travels generally parallel to and in the same direction as the fluid in a flow measuring part 18 of the flow passage 11 and the signal from the other device 12 travels in a direction opposite to the direction of the flow of fluid in the flow measuring part 18. Thus, the oscillating signals travelling in each direction have a phase shift imposed upon them by the effects of the fluid flow velocity in the passage 11, the effect being in the opposite sense on each signal. Whilst the oscillating signals are passing along the passage, the switching circuit 27 switches the mode of the devices 12 into receive mode in order that the oscillating signals as modified by the flow of fluid in the passage can be received. The signals received by the devices at each end of the flow measuring part 18 of the passage 11 are passed through a conventional window circuit 21 which separates out the received signals from the effects of static flow, turbulence, etc. The separated received signals are then squared by passage through a conventional Schmitt trigger circuit 22 to provide a suitable input for a gate circuit 23. The gate circuit comprises an EXOR (exclusive OR) gate (not shown) which compares the phase difference between the respective signals received by the two devices 12 and produces an output d.c. signal via a resistive load (not shown) indicative of the phase difference and hence the velocity of flow in the flow passage.

Since it is thought that frequencies of oscillating signals of the order of 2MHz will be used, it is possible to use a microprocessor based switching circuit or arrange for the switching of the devices 12 between the two modes by a computer to allow high speed switching.

Furthermore, if desired, microprocessor based or computer based circuit can be used to process the received signals in lieu of, or additionally to, the window circuits 21.

In this case the computer based circuit can identify and remove any noise or other unwanted addition to the received signal to produce a more accurate output.

It is envisaged that the flow measuring apparatus of the present invention will find particular application in the control of fluid flow in dispense pipes for the dispensing of mixer drinks in which commonly a number of dispense pipes are provided for a number of constituents which are mixed to provide the finished drink. In these types of arrangement it is necessary to keep a very accurate control of the dispensing of fluid through the dispense pipes to ensure accurate mixing of the constituents and the present invention enables this to be done simply and accurately. The invention can however be used in any situation where accurate dispensing of fluids is required, e.g. measuring chemicals for mixing bag prescriptions, control of dyestuff flow and intensive care dosing.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims

1. A flow measuring apparatus comprising a flow passage through which a substance can flow, at least two transmitters to transmit an oscillating signal respectively in opposite directions in said passage, at least two receivers disposed spaced from said transmitters to receive said signals transmitted from said transmitters and phase difference calculating means operable to calculate a phase difference between transmitted signals received at said receiver and to produce an output indication of the flow velocity of the substance through the pipes from said phase difference.

2. Flow measuring apparatus according to claim 1 wherein each said transmitter and receiver re formed as a single transmitter/receiver device switchable so as to operate respectively as a transmitter or receiver.

3. Flow measuring apparatus according to claim 1 or claim 2 wherein said oscillating signal comprises an ultrasonic signal.

4. Flow measuring apparatus according to claim 3 wherein the ultrasonic signal is transmitted at a frequency of substantially 2MHz.

5. Flow measuring apparatus according to any one of claims 1 to 4 wherein the oscillating signal is transmitted in short packets or bursts of a predetermined length.

6. Flow measuring apparatus according to any one of claims 1 to 5 wherein the transmitters comprise crystal oscillators which can be driven at any desired frequency.

7. Flow measuring apparatus according to any one of claims 1 to 6 wherein the receivers and transmitters are interconnected in order that operation thereof can be achieved simultaneously.

8. Flow measuring apparatus according to any one of claims 2 to 6 wherein when the transmitters and receivers are formed as a pair of receiver/transmitter devices, the switching of said devices to operate respectively as a receiver or transmitter can be achieved simultaneously.

9. Flow measuring apparatus according to any one of claims 1 to 8 wherein said flow passage is generally Ushaped with a respective receiver and/or transmitter disposed respectively at opposite ends of a flow measuring part of the flow passage.

10. Flow measuring apparatus according to claim 8 wherein switching of said devices is performed by a high speed switching arrangement, e.g. microprocessor or computer controlled switching.

11. Flow measuring apparatus according to any one of claims 1 to 10 wherein the control circuitry includes a further circuit to filter out any noise signals or other audible signals from the received signals.

12. Flow measuring device substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the drawings.

13. A flow measuring apparatus according to claim 1 when used in a drinks dispensing apparatus.