GB2051352A - Measuring apparatus for measurement of liquid flow rates - Google Patents

Abstract

Apparatus for the measurement of quantity and/or speed of throughflow of liquid comprises a rotary body drivable by a stream of liquid, the rotary body being arranged in a housing section of a duct for the liquid. A light barrier contactlessly records the rotation of the rotary body by reflection or transmission of emitted light and delivers pulses to an evaluating circuit which converts the pulses into electrical signals indicative of flow rate.

Description

SPECIFICATION Measuring apparatus for measurement of liquid flow rates The present invention relates to measuring apparatus for measurement of quantity and/or speed of throughflow of liquids.

As is known, clothes washing machines, dish washing machines and the like are connected directely to the water mains generally by means of a hose. It is also known that machines of that kind are provided with program switching mechanisms which co-operate with a system, consisting of pressure monitors and magnetic valves, for blocking the water supply in order to meter the quantity of water in dependence on individual programmed operations, such as washing and final rinsing. The direct connection of the machine to the water main can have the consequence of water damage in the vicinity of the machine if the connecting hose bursts when the machine is operating without supervision, if a hose joint loosens, or if, for example due to a defective pressure monitor, the vavle does not interrupt the water supply to the machine.

In German (Federal Republic) patent specification No. 2 335 195 there is disclosed a safety device for monitoring the water circuit in washing machines, dish rinsing machines and the like, the device consisting of an impeller wheel arranged in a water supply duct to the machine and drivable by the pressure of the water flowing to the machine. By means of a gear, the impeller effects closure of a water feed valve as soon as the quantity of the water running to the machine has reached a predetermined amount to which the safety device was set.

There is, however, a need for apparatus which is suitable for measurement of the quantity and/or speed of throughflow of flowing liquids and in which rotary motion taken up by a rotary body in a stream of liquid is transmitted contactlessly to a measuring equipment.

According to the present invention there is provided measuring apparatus for measurement of liquid flow rates, comprising a rotary body mountable in a liquid flow path to be rotationally driven by liquid flowing along the path, detecting means to detect the rotational speed of the rotary body by pulses generated in response to modulation of a light beam by the rotary body on rotation thereof, and convertor means responsive to the pulses to generate electrical signals indicative of the flow rate.

In apparatus embodying the invention, apart from the rotary body which comes into contact with the liquid to be measured, the components of the apparatus are not fixed to any particular material and the apparatus is suitable for measurement in any desired liquid.

In a preferred embodiment of the invention, the apparatus comprises an apertured rotary body, for example an impeller wheel, which is so arranged either directly in a liquid duct or in an interposed housing as to substantially fill the cross-section of the duct. In both executions, the liquid in passing the impeller wheel sets this into a rotary motion and thereby reproduces the speed of flow or the quantity of throughflow of the liquid in the speed of rotary motion of the impeller wheel.

This rotary motion is detected contactlessly through a light barrier either by periodic interruption of a light beam or by periodic reflection of the beam. For this purpose, the rotary body is either surrounded by transparent material, for example a housing of PLEXIGLAS (Trade Mark), or else located in a housing with at least one window of light-impermeable material, preferably two oppositely disposed lightpermeable windows.

The windows are positioned in such a manner that the transmission of a light beam therebetween is shaded or interrupted by the rotating impeller wheel. In the case of reflection, however, one light-permeable window suffices. It is, however, important that reflective sections of the rotary body, or reflective segments of a segmented disc provided on the rotary body, have a sufficiently different reflective behaviour relative to the liquid to be measured. In addition, in order to enable the individual segments to be resolved separately, the spacing between the window and the segments or the window and the light barrier must be sufficiently small. This arrangement is particularly significant for cloudy, lightimpermeable liquids.The light barrier can consist of a luminescent diode serving as a transmitter and a corresponding photo-sensitive component, for example a photo-diode or a photo-transistor, serving as a receiver. The wavelength emitted by the luminescent diode is, for example, in the near infrared range of about 900 nanometres.

The advantage of the apparatus according to the said embodiment are that the rotary body and, with the exception of the transparent window, also the housing are not restricted to the use of a particular material or class of material, as is the case of, for example, the inductive method, which requires a rotary body of magnetic material.

Consequently, there are no restrictions to be observed in respect of the chemical properties of the liquid to be measured, as the constituent material of the rotary body can take account of the properties of the liquid to be measured.

Furthermore, the resolution of the measurement values can be increased by precise segmenting of the rotary body into individual segments or chambers, which does not place high demands on the constructional tolerances of the measuring equipment in order to achieve satisfactory operation. The limit on the accuracy of the resolution is not imposed by the optical evaluation, but by the geometry of the rotary body itself, as it must be ensured that the segment chambers are large enough to permit complete filling and emptying by the measured liquid. In the dimensioning of the chambers, attention must be given to achieving an acceptable measurement result in light of the likely measurement error due to, for example, a proportion of the liquid which passes between the housing or duct wall and the outer impeller wheel edges and thereby bypasses the impeller wheel.

In the use of the apparatus, quantity measurement is based on the association of a predetermined number of light beam interruptions with a particular liquid volume, and flow speed measurement is based on association of a predetermined number of light beam interruptions with a particular time interval.

The apparatus is, inter alia, usuable for the control of washing and rinsing operations in automatic washing machines. In this case, the impeller wheel may have a height of about 10 millimetres and a diameter of about 20 millimetres and consist of six segments. The impeller wheel is incorporated in a housing of PLEXIGLAS with water feed and drainage into the water supply of the automatic washing machine.

A light barrier mounted externally of the housing is arranged with a transmitter and receiver disposed opposite each other on either side of the housing.

Water flowing to the washing machine has a throughflow speed of about 10 to 20 litres per minute and sets the impeller wheel into a rotary motion so that 800 interruptions of a transmitted light beam are generated for each litre of water that has flowed in. This number of 800 pulses per litre is electronically divided by 8 so that 100 pulses per litre of water are obtained, which corresponds to a result of 10 millilitres of water, the result being displayed at a display.

Apparatus embodying the invention is not, however, restricted to use in domestic machines.

It can, for example, be used for petrol quantity measurement at the filling point of a petrol station.

It is advantageous that the petrol flow quantity can be increased substantially with optoelectronic apparatus embodying the invention. A higher resolution, for example of 1 millilitre, could be provided by subdivision of the impeller wheel into, for example, eight chambers or by mounting of a more highly divided segment disc on the impeller wheel. In that case, an evaluation of the rotary motion of the impeller wheel by a reflected light beam is advantageous.

Claims (14)

1. Measuring apparatus for measurement of liquid flow rates, comprising a rotary body mountable in a liquid flow path to be rotationally driven by liquid flowing along the path, detecting means to detect the rotational speed of the rotary body by pulses generated in response to modulation of a light beam by the rotary body on rotation thereof, and convertor means responsive to the pulses to generate electrical signals indicative of the flow rate.

2. Measuring apparatus as claimed in claim 1, wherein the rotary body is arranged in a housing which comprises light-permeable material for the passage of the light beam therethrough.

3. Measuring apparatus as claimed in claim 2, wherein the housing is made from transparent material.

4. Measuring apparatus as claimed in claim 2, wherein the housing includes at least one window made of light-permeable material.

5. Measuring apparatus as claimed in any one of the preceding claims, wherein at least part of the rotary body is divided into a plurality of zones adapted to produce changes in the light beam.

6. Measuring apparatus as claimed in claim 5, wherein the zones include light-reflective surfaces which differ between the zones and which have reflective characteristics different from those of a liquid to be measured.

7. Measuring apparatus as claimed in either claim 5 or claim 6, wherein the rotary body comprises at least one vane defining chambers associated with the body, the zones being defined by the chambers.

8. Measuring apparatus as claimed in claim 7, wherein the rotary body is provided with perforated discs arranged in the chambers to provide additional definition of the zones.

9. Measuring apparatus as claimed in either claim 5 or claim 6, wherein the rotary body comprises an element divided into a plurality of segments, the zones being defined by the segments.

10. Measuring apparatus claimed in claim 9, wherein the rotary body comprises means defining chambers associated with the body, the chambers being different to the segments.

11. Measuring apparatus as claimed in any one of claims 5 to 10, the detecting means being arranged closely adjacent to said zones.

12. Measuring apparatus as claimed in claim 4 or any one of claims 5 to 11 when read with claim 4, the detecting means being arranged closely adjacent to said window.

13. Measuring apparatus as claimed in any one of the preceding claims, the detecting means comprising a luminescent diode for transmitting infrared light and a photosensitive element for receiving such light.

14. Measuring apparatus as claimed in claim 13, wherein the photo-sensitive element comprises a photo-diode or a photo-transistor.

1 5. Measuring apparatus as claimed in any one of the preceding claims, the detecting means comprising a light transmitter for transmitting a light beam and a light receiver so arranged in opposition to the transmitter as to to receive such light beam.

1 6. Measuring apparatus as claimed in any one of claims 1 to 14, the detecting means comprising a light transmitter for transmitting a light beam to be reflected by the rotary body and a light receiver so arranged adjacent to the transmitter as to receive such reflected light beam.

1 7. Measuring apparatus as claimed in claim 1,the converter means being adapted to provide digital electrical signals.

1 8. Measuring apparatus as claimed in claim 1, the convertor means comprising evaluating means for comparing the frequency of the pulses with predetermined frequencies representative of given flow rates.

1 9. Measuring apparatus for measurement of liquid flow rates, the apparatus being substantially as hereinbefore described.