GB2276678A

GB2276678A - Drinks dispensing system

Info

Publication number: GB2276678A
Application number: GB9406344A
Authority: GB
Inventors: Glyn Jones
Original assignee: Stanwell Technic Ltd
Current assignee: Stanwell Technic Ltd
Priority date: 1993-03-30
Filing date: 1994-03-30
Publication date: 1994-10-05
Anticipated expiration: 2014-03-30
Also published as: GB9406344D0; GB9306621D0; GB2276678B

Abstract

A drinks dispensing system for dispensing for example beer from a pressurised container, e.g a barrel (1). The container outlet is connected to a displacement pump which is caused to reciprocate by the supply to the pump of pressurised gas from a gas bottle (7). Exhaust gas from the pump drive (5) is either injected back into the container or re-pressurised by a compressor and injected back to the original source of pressurised gas. The displacement pump (2) may dispense precisely metered quantities of liquid on each stroke so that the pump itself can serve as a metering device. <IMAGE>

Description

DRINKS DISPENSING SYSTEM The present invention relates to drinks dispensing systems, and in particular to systems for dispensing beverages such as beer or carbonated drinks.

The traditional method for delivering beer to a customer in a public house was to use a "beer engine" that was hand pulled, that is a piston and cylinder arrangement operated by pulling on a lever. The amount of effort required to operate a conventional beer engine is significant and furthermore the height to which beer can be lifted is limited.

Hand operated beer engines have in many cases been replaced by electrically driven pumping systems. In such arrangements a centrifugal pump energised by mains electricity is positioned adjacent the barrel from which beer is to be dispensed. The pump is turned on to maintain the pressure in a pipe leading from the pump to a dispensing head mounted on, for example, a bar. The volume of beer dispensed can be determined by the operator manipulating appropriate switches but often a metering device is connected close to the dispensing head so that a predetermined volume of beer is dispensed.

In one known metering device, a reciprocating piston assembly is provided in a cylinder, beer being supplied to each side of the piston assembly in alternate cycles of the device, the beer from the other side of the piston assembly being dispensed. By appropriately dimensioning the piston and cylinder a desired volume of beer can be dispensed on each stroke of the piston assembly.

The known electric pumps are not altogether satisfactory.

Firstly, they are not self-priming and therefore must be carefully located and operated to ensure reliable operation. Secondly, they are not themselves capable of metering a particular volume of beer to be dispensed and therefore where it is desired to dispense metered amounts of beer it is necessary to provide a separate metering apparatus. A third problem associated with the known pumps is that mains voltage must be made available close to the beer barrel. Given the conditions in some cellars this is a significant safety hazard.

Gas driven displacement pumps are known in which a piston assembly reciprocates inside a cylinder. Gas causes the piston assembly to reciprocate. On each stroke of the piston assembly liquid is drawn into one side of that assembly and pumped out of the other side. Gas driven displacement pumps of this type have been used to pump carbonated beverages to a dispensing head. The use of such gas driven displacement pumps has also been proposed for assisting in lifting beer to a hand operated beer engine. The pump is provided merely to reduce the amount of force that the operator has to apply to the hand operated lever. It has also been suggested that gas driven displacement pumps could be used to deliver keg beer to a metering unit mounted on a bar counter.

It is a feature of the gas driven displacement pumps that are currently available that on each stroke of the piston assembly some of the gas used to drive the pump is exhausted to the surrounding atmosphere. Generally, carbon dioxide is used to drive such pumps, the gas being delivered from pressurised bottles. Unfortunately carbon dioxide has a tendency to accumulate close to ground level and since many drinks dispensing systems are installed in cellars there is a risk of a substantial build-up of carbon dioxide in cellars where gas driven displacement pumps are being used. If such pumps are to be used for general dispensing of beer as well as carbonated beverages the accumulation of carbon dioxide could represent a significant safety hazard.

It is an object of the present invention to obviate or mitigate one or more of the problems outlined above.

According to a first aspect of the present invention, there is provided a drinks dispensing system comprising a dispensing head from which liquid is dispensed, a container for liquid to be dispensed, a pipe extending from a lower portion of the container to the dispensing head, a pressurised gas driven displacement pump connected in the pipe between the dispensing head and the container, and a source of pressurised gas connected to the displacement pump, the displacement pump having a reciprocable piston assembly, a gas distribution valve arranged to distribute pressurised gas to the piston assembly so as to cause the piston assembly to reciprocate, and an exhaust outlet to which gas is exhausted from the piston assembly, wherein the exhaust outlet is connected to the container such that the exhaust gas is injected into the container.

Connecting the exhaust outlet to the container from which liquid is being dispensed ensures that no gas leaks into the local environment. Since the volume of gas exhaust is a function of the volume of liquid dispensed, there is no risk of the pressure in the container rising so high as to prevent operation of the pump.

The gas source may be connected to the container through a pressure reducing valve, the exhaust outlet being connected to a pipe extending between the pressure reducing valve and the container.

Such an arrangement is suitable for maintaining a top pressure on the content of the container.

The pump displacement may be precisely limited such that on each stroke of the piston a predetermined fraction of a desired volume to be dispensed is delivered to the dispensing head. The total volume dispensed during a single dispensing operation can be controlled by selecting the total number of strokes of the piston assembly. The dispensing head may comprise a switch which when actuated opens the control valve to supply pressurised gas to the pump, and a counter arranged to count the strokes of the pump and to close the control valve after a preselected number of strokes of the piston assembly.

According to a second aspect of the present invention, there is provided a drinks dispensing system comprising a dispensing head, and means for pumping liquid to the dispensing head and metering the volume of drink dispensed, wherein the pumping and metering means comprise a displacement pump having a reciprocable piston assembly which displaces a predetermined volume of liquid on each stroke, and means for controlling the pump such that in the course of each dispensing operation the piston assembly executes one or more complete strokes.

With such an arrangement desired pumping and metering characteristics can be achieved using a single economic apparatus.

According to a third aspect of the present invention there is provided a drinks dispensing system comprising a dispensing head from which liquid is dispensed, a container for liquid to be dispensed, a pipe extending from a lower portion of the container to the dispensing head, a pressurised gas driven displacement pump connected in the pipe between the dispensing head and the container, and a source of pressurised gas connected to the displacement pump, the displacement pump having a reciprocable piston assembly, a gas distribution valve arranged to distribute pressurised gas to the piston assembly so as to cause the piston assembly to reciprocate, and an exhaust outlet to which gas is exhausted from the piston assembly, wherein the exhaust outlet is connected through a compressor to the gas source such that the exhaust gas is injected back into the source.

Such an arrangement can be used in circumstances where there is no convenient container to receive the exhausted gas other than the original source of the pressurised gas. For example, where a gas driven pump is used to assist in the lifting of beer to a hand operated pump, the exhaust gas cannot be returned to the barrel from which beer is being lifted as that barrel is not sealed. A simple compressor is however sufficient to inject the exhaust gas back into for example pressurised gas bottles.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 is a schematic representation of a first embodiment of the present invention; Fig. 2 is a schematic representation of a second embodiment of the present invention; Figs. 3 and 4 illustrate the detailed structure of a displacement pump which can be used in accordance with the present invention; and Figs. 5 and 6 illustrate the outward appearance of the pump illustrated in Figs. 3 and 4.

Referring to Fig. 1, the basic components of a dispensing system in accordance with one embodiment of the present invention are illustrated. A barrel 1 of for example beer is connected to a gas driven pump 2 the output of which is passed through a metering unit 3 to a dispensing head 4. The pump 2 has a reciprocating piston assembly, the assembly being reciprocated by a pump drive 5 that in turn is driven by pressurised gas delivered from a pump drive pressure control valve 6. Pressurised gas is supplied from a pressurised gas bottle 7 to a further control valve 8 which applies a predetermined gas pressure to the surface of liquid within the barrel.

The gas bottle also supplies pressurised gas to the control valve 6.

Typically the pressure above the liquid in the barrel (the top pressure) will be of the order of 10 psi if the contained liquid is beer and 20 psi if the contained liquid is lager. The control valve 8 can be simply adjusted to provide the appropriate top pressure desired.

The pressure delivered to the pump drive 5 is significantly above the output pressure of the valve 8 and accordingly gas exhausted from the pump drive 5 is at a sufficiently high pressure to enable it to be injected into the pipe 9 which links the control valve 8 and the barrel 1. Accordingly any gas exhausted from the pump drive 5 is not released into the atmosphere but is rather injected into the container 1.

The line 10 in Fig. 1 indicates an electrical control signal line which is used to control the metering unit 3. The metering unit 3 can for example be a displacement piston type device two strokes of which dispense one pint of beer. Thus, once the operator indicates by pressing an appropriate switch (not shown) on the dispensing head that beer is to be dispensed the metering unit will deliver the appropriate amount of beer. As beer is dispensed the pressure applied by the pump drive 5 maintains the appropriate pressure in the supply line to the dispensing head 4.

Referring now to Fig. 2, this shows a similar arrangement to that of Fig. 1 but which relies upon the pump 2 to perform some of the functions of the metering unit 3 of Fig. 1. In the arrangement of Fig.

2, the displacement pump 2 is itself used as a metering device, each stroke of the pump 2 being arranged to deliver a predetermined fraction of a desired final delivery volume. In the case of the device illustrated in subsequent drawings the stroke of the pump piston has been limited such that each stroke of the piston delivers 1/6 of one pint of liquid. Accordingly, by arranging for the pump to perform three strokes, half a pint of liquid will be dispensed.

The precise volume dispensed is controlled by a dispense controller 11 which in turn controls a pump drive on/off valve 12.

When a switch (not shown) on the dispensing head 4 is depressed, a signal is transmitted on line 10 to the dispense controller 11 which opens the valve 12. Drive gas pressure is then delivered to the pump drive 5 and the pump starts to operate. The operation of the pump drive is monitored, for example by providing a position detector on a reciprocating shaft of the pump so as to deliver an output on line 13 to the controller 11. The controller simply counts the number of strokes completed by the pump and closes the valve 12 once the required number of strokes has been counted.

As in the case of the embodiment of Fig. 1, in the embodiment of Fig. 2 exhaust gas is injected back into the line 9 extending between the top pressure control valve 8 and the barrel 1. Thus no gas is released into the atmosphere. The arrangement of Fig. 2 has the additional benefit of course of not requiring a separate metering unit, the pump 2 doubling as both a pump and metering unit.

Referring now to Fig. 3 this shows the basic structure of the displacement pump used in for example systems of the type described in Figs. 1 and 2. The pump comprises a pair of substantially identical sections each comprising an outer housing or end cap 14, an inner housing 15, a diaphragm 16, a piston 17 which runs in a respective cylinder defined by the adjacent housing parts, and a pair of one way valves 18. Liquid to be pumped is introduced through inlet 19, is drawn into the spaces defined between the end caps 14 and the pistons 17 during motions of the pistons away from the end caps, and is pumped out through an outlet 20 during the movement of the pistons towards the end caps.The pistons are mounted on a shaft 21 and reciprocate such that as the shaft moves in one direction fluid is drawn into the space adjacent one piston and pumped out from the space adjacent the other piston and vice versa. A disc 22 is mounted on the shaft 21 and provides for the interaction between the basic pump structure and a reversing valve assembly 23. As will be described hereinafter, a reversing valve restraining bracket 24 is also mounted on the pump housings adjacent the shaft 21.

Fig. 4 shows the reversing valve assembly in greater detail. A spool 25 reciprocates within a valve body 26. With the spool 25 in one extreme position compressed air supplied to the pump assembly is delivered to the chamber defined between one pump casing component 15 and the adjacent diaphragm 16, the other space being connected to atmosphere, whereas with the spool 25 in its other extreme position the situation is reversed. Thus, so long as pressurised gas is supplied to the reversing valve assembly the piston assembly generally described in Fig. 3 reciprocates periodically.

The arrangement of Figs. 3 and 4, with the exception of component 24, is entirely conventional. A displacement pump of this type is freely available in the United Kingdom under the trade name "LANCER". The reversing valve restraining bracket 24 of Fig. 3 is provided simply to enable the adjustment of the volume of liquid delivered by the pump on each stroke of the piston.

The volume of liquid delivered on each stroke is primarily a function of the diameter and length of stroke of the pistons.

Experience has shown, however, that in the case of the illustrated pump the volume delivered cannot be precisely predetermined by reference only to the diameter and nominal stroke of the piston. It has proved highly advantageous to provide a mechanism for precisely limiting the maximum stroke of the two pistons and such an arrangement is illustrated by the photographic representations set out in Figs. 5 and 6.

Figs. 5 and 6 are views from slightly different angles of a pump in accordance with Figs. 3 and 4 mounted immediately above a junction box provided to enable the performance of the pump to be monitored in the manner outlined with reference to Figs. 2. Reference numerals 19, 20 and 24 as used in Fig. 6 correspond to the components carrying those reference numerals in Fig. 3. An exhaust gas outlet 25 may be connected as indicated in Figs. 1 and 2 to a top pressure pipe inlet to a liquid container. Pressurised gas is supplied to the unit through an inlet 26 which enters the pump housing at the rear of the unit as illustrated in Figs. 5 and 6. The screws 27 and 28 are supported on the bracket 24 so as to extend into the path of the ring 22 which is shown in Fig. 3 and is fixed to the reciprocating shaft 21. The ends of the bolts 27 and 28 lying in the path of the ring 22 define cam surfaces such that by rotation of the bolts 27 and 28 the position at which the travel of the shaft 21 is arrested can be adjusted. Bolts which are partially visible in Fig. 5 beneath the bracket 24 enable the bolts 27 and 28 to be locked in any desired position. Thus the travel of the shaft 21 and hence the volume of liquid dispensed from the pump can be precisely determined. The ring 22 also acts upon the reversing valve assembly to control the distribution of gas to the main pump component and accordingly it is necessary to ensure that the ring 22 travels sufficiently far for the reversing mechanism to switch over.There is sufficient inertia in the system, however, to ensure that this is achieved whilst still giving some leeway to adjust the final resting point of the shaft 21 before it is driven in reverse as a result of the reversal of the supply of pressurised gas to the assembly.

Thus, by appropriate adjustment of the position of the bolts 27 and 28, the amount of liquid dispensed by the pump on each stroke can be closely controlled so that for example one half pint cf liquid is dispensed as a result of three strokes (one and a half reciprocations) of the shaft and piston assembly. All that is therefore required to use the pump as an accurate metering device is to be able to ensure that during any one dispensing operation the shaft and piston assembly starts at one extreme position, performs a predetermined number of strokes and finishes at either the original position or at the opposite extreme position.

Claims

1. A drinks dispensing system comprising a dispensing head from which liquid is dispensed, a container for liquid to be dispensed, a pipe extending from a lower portion of the container to the dispensing head, a pressurised gas driven displacement pump connected in the pipe between the dispensing head and the container, and a source of pressurised gas connected to the displacement pump, the displacement pump having a reciprocable piston assembly, a gas distribution valve arranged to distribute pressurised gas to the piston assembly so as to cause the piston assembly to reciprocate, and an exhaust outlet to which gas is exhausted from the piston assembly, wherein the exhaust outlet is connected to the container such that the exhaust gas is injected into the container.

2. A drinks dispensing system according to claim 1, wherein the gas source is connected to the container via a pressure reducing valve, and the exhaust outlet is connected to a pipe extending between the pressure reducing valve and the container.

3. A drinks dispensing system according to claim 1 or 2, wherein the pump displacement is determined such that on each stroke of the piston a predetermined fraction of a desired dispense volume is delivered to the dispensing head, and means are provided to control the volume dispensed by selectively controlling the total number of strokes of the piston assembly.

4. A drinks dispensing system according to claim 3, wherein the dispensing head comprises a switch which when actuated opens a control valve to supply pressurised gas to the pump, and means are provided to count the strokes of the piston assembly and to close the control valve after a preselected number of strokes of the piston assembly.

5. A drinks dispensing system comprising a dispensing head, and means for pumping liquid to the dispensing head and metering the volume of drink dispensed, wherein the pumping and metering means comprise a displacement pump having a reciprocable piston assembly which displaces a predetermined volume of liquid on each stroke, and means for controlling the pump such that in the course of each dispensing operation the piston assembly executes one or more complete strokes.

6. A drinks dispensing system comprising a dispensing head from which liquid is dispensed, a container for liquid to be dispensed, a pipe extending from a lower portion of the container to the dispensing head, a pressurised gas driven displacement pump connected in the pipe between the dispensing head and the container, and a source of pressurised gas connected to the displacement pump, the displacement pump having a reciprocable piston assembly, a gas distribution valve arranged to distribute pressurised gas to the piston assembly so as to cause the piston assembly to reciprocate, and an exhaust outlet to which gas is exhausted from the piston assembly, wherein the exhaust outlet is connected through a compressor to the gas source such that the exhaust gas is injected back into the source.

7. A drinks dispensing system substantially as hereinbefore described with reference to any one or more of the accompanying drawings.