GB2212784A

GB2212784A - Metered beverage dispensing apparatus

Info

Publication number: GB2212784A
Application number: GB8827468A
Authority: GB
Inventors: Brian Glover
Original assignee: GRUNDY
Current assignee: GRUNDY
Priority date: 1987-11-30
Filing date: 1988-11-24
Publication date: 1989-08-02
Anticipated expiration: 2008-11-24
Also published as: GB8727947D0; GB2212784B; GB8827468D0

Abstract

In a metered beverage dispense system a pressure sensing switch (8) is located in the line (5) closely adjacent the outlet of the meter (4) and this switch is arranged so that it detects the point at which a rapid and significant fall in pressure occurs adjacent the meter outlet. This pressure drop results from the metering ball seating firmly to close the outlet of the meter and provides a positive and reliable signal of the end of the dispense stroke. As soon as the pressure drop occurs the switch operates to cut the electrical supply (7) to the tap (6) thereby instantly shutting off the outlet and maintaining pressure within the line (5). <IMAGE>

Description

TITLE Metered Beveraae Dispensing Apparatus This invention relates to metered beverage dispensing apparatus such apparatus being used, as example, for the dispensing of a metered volume of beverage such as beer. In such an apparatus the beverage from a container passes into a metering device which feeds the counter dispense tap at a remote location. Operation of the dispense tap causes a defined volume of the beverage to pass from the container to the dispense tap whereafter the dispense tap and metering unit are shut down.The metering device may comprise a unit as described in GB 1591881 and in this system a coiled tube is used to define the volume of beverage with a ball moving through the tube along with the flow of liquid the terminal position of the ball being sensed by opto-electronic means to close the dispense tap. Other systems may be used for example a piston moving in a cylinder.

With such metering devices it is essential to make provision for a delay between the metering operating element such as the ball reaching the end of its stroke and the dispense valve at the tap closing. It will be appreciated that with a considerable length of tubing between the metering device and the dispense tap (10 metres being typical), if the dispense tap is closed at the instant the metering device reaches the end of its stroke then there is the possibility of a short measure being dispensed.

In order to keep a carbonated beverage in good condition whilst in the line between the metering unit, normally located in the cellar, and the bar dispense tap, the line must be maintained under pressure to prevent dissolved carbon dioxide from breaking out of solution and forming bubbles along the length of the line. Bubbles severely restrict the rate of dispensing and create troublesome froth or fob within the line and during the dispense operation. In the known system the metering device shuts off the flow abruptly but the mass of moving liquid beverage within the pipe continues and causes cavitation at the meter outlet. This causes carbon dioxide to break out of solution and it is only after this has occurred that the solenoid operated dispense tap closes.The beverage in the line will now be under no applied pressure and further quantities of carbon dioxide escape from the liquid to form bubbles until a state of pressure equilibrium occurs within the line preventing further gas from breaking out of solution. This equilibrium can take several minutes.

One method is known for solving this problem utilising a hydraulic reservoir of the beverage at the meter outlet but such a method can reduce the accuracy of the dispensed volume.

This invention seeks to provide an arrangement wherein the line pressure between the meter and dispense tap is substantially maintained at the end of a dispense operation thereby preserving the condition of the beverage within the line.

According to this invention there is provided in a beverage dispense system including a volume metering device, a line pressure sensing means positioned close to the meter outlet, the pressure sensing means being associated with a switch to cause the bar dispense tap to close following a significant pressure drop in the line at or near the meter outlet.

With the arrangement according to the invention the dispense tap is no longer directly under the control of the metering device, that is the tap is not closed directly on the metering device signalling the end of the meter stroke (or shortly thereafter following a preset time delay) but is determined by the criteria of the pressure in the line close to the meter outlet falling significantly. This pressure drop signifies that the meter has completed dispense of the correct volume and by closing the bar dispense tap at this instant cavitation within the pipeline is substantially prevented and the line pressure maintained to ensure that the beverage therein is kept in good condition.

In a typical embodiment the pressure sensing switch operates within a few milliseconds following the termination of the metered dispense to close the dispense tap. In practice, this action may produce a water hammer behind the dispense tap causing a reflected pressure wave to travel backwards and forwards along the line. This reflected pressure wave may cause the pressure switch to re-operate and according to a further feature of the invention, means are provided to effectively de-bounce the operation of the pressure switch by causing same to become inoperative for a predetermined period of time whereby the switch will ignore any reflected pressure waves until the line has settled down to a near steady pressure.

The invention is further described by reference to an example shown in the accompanying drawings.

In the dravings:- Figure 1 shows schematically an arrangement according to the invention, and Figure 2 shows the circuit of a means providing de bounce of the pressure sensing switch.

Referring firstly to Figure 1 of the drawings, a generally conventional beverage dispense system is shown, this comprising a supply 1 from a suitable container (not shown) feeding a pump means 2 supplying the beverage along the line 3 to a metering device 4. This metering device may comprise a coiled length of stainless steel tubing with a ball free to move therealong by the flow of liquid and with sensing means at each end of the tube to optically sense when the ball reaches the end of its stroke. Solenoid valve means are provided in such a meter so that the flow direction of the beer along the metering tube is switched over at the end of one dispense operation so that a second dispense operation may be effected using reverse flow through the tube.The ball in the tube is detected by a photoelectric means and furthermore when it reaches the end of the tube it seats to close off the outlet to define the end of the measured dispense volume. The dispensed beverage passes along line 5 which may be of a considerable length (10 metres being typical) to a bar dispense tap 6 which incorporates a solenoid operated valve controlled via electrical line 7. In this system, pressing the solenoid valve control 6 signals the beverage meter and pump which then causes the predetermined volume of beverage to be passed along the line 5. At the end of the dispense operation the solenoid valve 6 is closed by interruption of the electrical supply but this cannot be effected instantly the ball is detected by the photoelectric means.A short delay must be allowed in order to ensure that the ball moving within the metering tube has seated finally to shut off the supply and this short delay causes the pressure in the line 5 to normally fall due to the moving mass of beverage which may still flow due to the tap 6 being open.

To avoid this problem and in accordance with the invention a pressure sensing switch 8 is located in the line 5 closely adjacent the outlet of the meter 4 and this switch is arranged so that it detects the point at which a rapid and significant fall in pressure occurs adjacent the meter outlet. This pressure drop results from the metering ball seating firmly to close the outlet of the meter and provides a positive and reliable signal of the end of the dispense stroke. As soon as the pressure drop occurs the switch operates to cut the electrical supply 7 to the tap 6 thereby instantly shutting off the outlet and maintaining pressure within the line 5.

It has been found that the sudden shutting of the dispense tap 6 causes a reflected pressure wave to transit the length of the tube for several oscillations and in order to prevent spurious tripping of the pressure switch, circuit means as shown in Figure 2 is provided.

Referring to Figure 2 of the drawings the circuit is powered from AC present on line 7 which is used to open the tap solenoid valve 6. Power is fed via rectifier RA with associated smoothing capacitor C1. Power is only present on line 7 during the normal dispense operation and when this is initiated capacitor C3 is charged up by R2 via PS1 which is operated by pressure switch 8. PS1 is in the position shown whilst normal dispense pressure exists in line 5. The solenoid valve 6 is energised by line 7 through normally closed relay contacts RLA which are associated with relay RL1. In this condition and during the dispensing operation transistor TRt is switched off.At the end of the dispensing operation the ball in the meter 4 will seat against the end stop thus closing the line and this will cause a rapid and significant pressure change to occur close to the meter outlet. This change is detected by the switch 8 causing PS1 to change over whereby capacitor C3 discharges through R4 to C2 and through R3 to switch on TR1 thus immediately pulling in RL1 and opening contacts RLA. The tap solenoid valve 6 then closes. The charge in C2 maintains TR1 switched on and RL1 remains energised until the meter 4 shuts down after a time delay and in accordance with its normal operation. At this point the power supply on line 7 is cut off and C2 discharges through the base of TR1 regardless of the position of switch PS1. The circuit will then be ready for the next dispense operation.In the circuit shown any pressure fluctuations which might occur at the beginning of the dispensing operation will be ignored because C3 will not have had sufficient time to charge up via R2 until well into the dispensing process. An additional feature of the circuit is that as it is energised by the meter output it cannot interfere with the volume of beer dispensed as any failure in the circuit will simply result in contacts RLA being maintained closed and the meter will operate in the hitherto -customary manner.

This invention thus provides a device which responds to a sudden pressure drop at the meter output which is used as a signal to rapidly close the solenoid tap valve at the bar to thereby reduce transient vacuum damage to the beverage within the line and to provide a residual line pressure which prevents degassing of the beverage between dispense operations.

A-preferred feature of the device is a provision of a signal discrimination circuit which serves to ignore unwanted pressure signals on the line so that they do not cause operation of the solenoid tap valve.

In addition the invention enables the ending of the stroke of the meter to be sensed by a pressure signal to thereby provide instantaneous operation as against known systems which detect the end of the dispense stroke by indirect means relying on mechanical movement essentially requiring a settling period to ensure the full amount of liquid is dispensed.

The sensing at the end of the meter stroke may be by means of a pressure switch, one or more limit switches, proximity switches or optical sensors.

Claims

1. A beverage dispense system including a volume metering device, a line pressure sensing means positioned close to the meter outlet, the pressure sensing means being associated with.a switch to cause the bar dispense tap to close following a significant pressure drop in the line at or near the meter outlet.

2. A beverage dispense system according to Claim 1, wherein means are provided to effectively de-bounce the operation of the pressure switch by causing same to become inoperative for a predetermined period of time whereby the switch will ignore any reflected pressure waves until the line has settled down to a near steady pressure.

3. A beverage dispense system according to Claim 1 or 2, wherein the pressure sensing means operates on a pressure drop which is both significant and rapid.

4. A beverage dispense system as described herein and exemplified with reference to the drawings.