GB2274642A

GB2274642A - Liquid metering system

Info

Publication number: GB2274642A
Application number: GB9401878A
Authority: GB
Inventors: Sammy James Engineer; George Philip Tarling
Original assignee: Whitbread PLC; Whitbread and Co Ltd
Current assignee: Whitbread PLC; Whitbread and Co Ltd
Priority date: 1993-02-02
Filing date: 1994-02-01
Publication date: 1994-08-03
Anticipated expiration: 2014-02-01
Also published as: GB9301966D0; GB2274642B; GB9401878D0

Abstract

A liquid metering system for dispensing a predetermined volume of beverage, such as beer, comprises a supply of beverage (1), a pipe line (2) connecting the supply to a beverage dispensing outlet (3), a flow meter (4) in the pipe line (2) for monitoring the flow of the beverage through the pipe line (2), a valve (5) in the pipe line (2) operable to interrupt the flow, and a controller (6) connected to the flow meter (4) and to the valve (5) to monitor the flow rate and to operate the valve (5). The controller (6) enables the valve (5) to be open only when the flow rate is within a pre-determined range, and interrupts the flow when a pre-determined quantity of beverage has been dispensed. <IMAGE>

Description

LIOUID DETERING SYSTEM The present invention is a liquid metering system for dispensing a pre-determined volume of beverage, such as beer, and more particularly for a system including a flow meter.

Conventionally, a fixed displacement system is used to dispense a pre-determined volume of beer. Such systems usually include a piston which is driven backwards and forwards along a cylinder. On movement of the piston, a pre-determined volume, drawn from a beverage supply, is driven out of a dispensing nozzle. This system ensures that the volume of beer dispensed during each movement of the piston is the same. This system is disadvantageous in that its overall size is large, and it is difficult to clean.

A system using a flow meter to monitor the flow of beer through a pipe as it is dispensed would be preferable in that the cost would be lower, the overall volume of the system be reduced, and that it would be easier to keep clean. However, systems using flow meters have so far been unable to obtain the statutory approval under Weights and Measures legislation due to their unreliability under all dispensing conditions. To meet the approval standards, it is necessary to dispense a precise volume of beer, and with previous proposals including flow meters, this has not been possible.

According to the present invention, a beverage dispensing system comprises a supply of beverage, a pipe line connecting the supply to a beverage dispensing outlet, a flow meter in the pipe line for monitoring the flow of the beverage through the pipe line, a valve in the pipe line operable to interrupt the flow, and a controller connected to the flow meter and to the valve to monitor the flow rate and to operate the valve, enabling the valve to be open only when the flow rate is within a pre-determined range, and to interrupt the flow when a pre-determined quantity of beverage has been dispensed.

The present invention is advantageous over fixed displacement systems as it is cheaper to manufacture, has a smaller overall volume, and is easier to clean.

Further, the system is accurate under all conditions in which beverage may be dispensed and is therefore able to obtain the required statutory approval.

Preferably, the pre-determined range of flow rate in which the valve may be open is the range in which the output of the flow meter is directly proportional to the flow rate. A flow meter may include a turbine which is rotated by the flow of beverage.

When beverage is initially to be dispensed, the valve is preferably opened by the controller in response to a start up signal which over-rides other inputs to the controller during the period before an accurate flow rate can be obtained. The start up signal may be provided from a switch.

Preferably, the flow meter outputs a series of pulses, the rate of which is proportional to the flow rate in the pre-determined range. In this case the volume of beverage dispensed is calculated from the product of the number of output pulses of the flow meter, and the volume per pulse as determined for the system. The pre-determined volume dispensed by the system is typically half a pint.

A specific example of the present invention will be described with respect to the accompanying drawings, in which:- Figure 1 is a schematic diagram of the liquid metering system; and Figure 2 is a graph showing the performance of a turbine type flow meter with respect to flow rate.

The liquid metering system according to the present invention is used to dispense a pre-determined quantity of beer from a keg 1 through a dispensing outlet 3, such as a tap.

A flow meter 4 is included in the pipe line 2 linking the keg 1 and the dispensing outlet 3. The flow meter 4 is a turbine 8 or paddle-wheel which is rotated as beer flows along the pipe line 2. The rate of rotation of the turbine 8 is related to the flow rate of the beer along the pipe line 2. When the flow rate is very low, the turbine 8 will not rotate due to fluid slippage. This results in an incorrect calculation of the volume of beer dispensed, and therefore too large a volume will be dispensed. If the flow rate is too high, fast friction effects on the turbine 8 will prevent the turbine 8 from rotating correctly, and again too large a volume of beer will be dispensed. In the intermediate range, as shown in Figure 2, the output of the turbine 8 is linearly related to the flow of the beverage through the pipe line 2.

As beer flows along the pipe line 2, the turbine 8 is rotated, and produces an output pulse every time the turbine rotates through a pre-determined angle. When the flow rate of beer through the pipe line 2 is within the pre-determined range, each rotation of the turbine will correspond to a particular volume of beer. This volume may be determined for a particular system by experimentation.

The number of output pulses from the turbine 8 is counted by the controller 6, and the volume dispensed calculated as the product of pulses and volume per pulse.

The controller 6 also monitors the flow rate by monitoring the rate at which output pulses are received from the turbine 8. If the flow rate exceeds the upper threshold of acceptable flow rate, or is below the lower threshold, then the controller 6 causes the valve 5 in the pipe line 2 to close, thereby preventing any further dispensing of the beverage.

By ensuring that beer may only be dispensed when the flow rate is in the pre-determined range, it is ensured that the volume of beverage dispensed is accurately known.

After the pre-determined quantity of beverage has been dispensed, the controller 6 closes the valve 5 in the pipe line 2 to prevent any more beverage from being dispensed.

When a request to dispense the beverage is initially made, the valve 5 is in the closed state, and therefore there is no flow of beverage along the pipe line 2. The controller 6 includes an over-ride to allow the valve 5 to open for a short time immediately after a request is made to dispense beverage, irrespective of the flow rate.

After this pre-determined period, the control of the valve 5 is returned to the normal control determined by the flow rate and the volume of beverage dispensed.

When the valve 5 is closed due to the flow rate falling outside the pre-determined range, the valve 5 remains closed for a time-out period, typically for two minutes. The flow rate may have fallen outside the predetermined range as the beer supply has been exhausted, or as the propellant which dispenses the beverage, for example a gas supply or mechanical pump, has failed. The beer supply and propellant should be checked by the operator in this period while the valve 5 is closed. The beer dispensed immediately prior to the closing of the valve is discarded, and the dispensing cycle re-started after the time-out period.

When initially setting up the system, the pressure of the propellant is adjusted so that the flow rate is normally within the pre-determined range.

The flow meter 4 may be any form of flow meter, and is not limited to a turbine flow meter.

Claims

1. A beverage dispensing system comprising a supply of beverage, a pipe line connecting the supply to a beverage dispensing outlet, a flow meter in the pipe line for monitoring the flow of the beverage through the pipe line, a valve in the pipe line operable to interrupt the flow, and a controller connected to the flow meter and to the valve to monitor the flow rate and to operate the valve, enabling the valve to be open only when the flow rate is within a pre-determined range, and to interrupt the flow when a pre-determined quantity of beverage has been dispensed.

2. A beverage dispensing system according to claim 1, in which the pre-determined range of flow rate in which the valve may be open is the range in which the output of the flow meter is directly proportional to the actual flow rate.

3. A beverage dispensing system according to claims 1 or 2, in which the flow meter includes a turbine which is rotated by the flow of the beverage.

4. A beverage dispensing system according to any of the preceding claims, in which the valve is opened by the controller in response to a start-up signal which overrides other inputs to the controller during the period before an accurate flow rate is obtained.

5. A beverage dispensing system according to claim 5, in which the start-up signal is provided from a switch.

6. A beverage dispensing system according to any of the preceding claims, in which the flow meter outputs a series of pulses, the rate of which is proportional to the flow rate in the pre-determined range.

7. A beverage dispensing system according to claim 7, in which the volume dispensed is calculated from the product of the number of pulses output by the flow meter and the volume per pulse for the system.

8. A beverage dispensing system according to any of the preceding claims, in which the pre-determined quantity of beverage dispensed is half a pint.

9. A beverage dispensing system substantially as described with reference to the accompanying drawings.