GB2192989A

GB2192989A - Measuring the level of beverage in a keg

Info

Publication number: GB2192989A
Application number: GB08717181A
Authority: GB
Inventors: Stephen Leslie Russ Wellington
Original assignee: Bass PLC
Current assignee: Bass PLC
Priority date: 1986-07-26
Filing date: 1987-07-21
Publication date: 1988-01-27
Also published as: GB2192989B; GB8717181D0; GB8618276D0

Abstract

A standard beer keg (1) has a spear (6) with a top fitment (7) and a tube (8) which is open at the bottom. Valves in the top fitment can be opened by a coupler having a carbon dioxide inlet leading to the headspace (9) and a beer outlet leading from the tube (8). The invention provides apparatus for measuring the volume of beer in such a keg and includes a coupler (12) connected to flexible pipes (13 and 14). A branch (17) from one pipe (13) is connected to a carbon dioxide cylinder or a pump (not shown). In use the pressurized gas enters the tube (8) rather than the headspace (9) which is connected to the other pipe (14). The pipes are also connected to opposite sides of a pressure-measuring device such as a manometer (15). Gas is forced into the tube (8) until it is heard to bubble from the bottom. The depth of beer in the keg is then proportional to the pressure difference between the headspace and the interior of the tube and is measured by the pressure-measuring device. <IMAGE>

Description

SPECIFICATION Measuring the level of beverage in a keg This invention relates to the measurement of the level of beverage in a keg. The invention is particularly concerned with kegs of the kind (hereinafter referred to as the kind specified) comprising a container having a spear attached to it, the spear incorporating a top fitment with a tube depending from it, the tube having a port at or near the bottom thereof, and the arrangement being such that in normal use beverage leaves the container by way of the port, the tube and the top fitment, while gas such as carbon dioxide can be introduced under pressure into the headspace of the container.

It is customary for beer and other beverages such as cider to be stored in kegs, and there is often a requirement to measure the quantity of beverage in a keg; for example it may be necessary to measure the total quantity of beer present in a group of kegs in a cellar.

Standard kegs currently in use in the trade have capacities of 11 gallons, 1 8 gallons, 22 gallons and 36 gallons (50 1, 81.81 1 100 1 and 163.7 I respectively).

Various methods have been proposed to determine the volume of beer in a keg, but in general they have either been difficult to carry out accurately or involved the use of relatively expensive equipment.

An object of the present invention is to provide a method of enabling this to be done and which can be carried out relatively simply and reliably using equipment that need not be expensive.

From a first aspect the present invention consists in a method of measuring the level of beverage in a keg of the kind specified, in which method a pressure-measuring device is connected between the headspace of the container and the tube of the spear, introducing gas into the tube until gas can escape through the port, and using the pressure-measuring device to measure the difference in pressure between the gas in the headspace and the gas in the tube, that pressure difference being proportional to the depth of the port below the level of beverage in the container, and thus to measure the level of the beverage in the container.

The method may be used to provide a reading of the level of the beverage in the container or to provide a reading of some other, related value such as the volume of the beverage remaining in the container. In this connection it is to be understood that the present invention includes within its scope not only methods which give rise to a reading or numerical value of the level of beverage in a keg but also methods which give rise to a reading or value of a variable, such as volume or weight, that is a function of the level of beverage in a keg.

From a second aspect the present invention consists in apparatus for use in carrying out a method in accordance with the first aspect of the present invention and comprising a pressure-measuring device capable of measuring the difference in pressure between first and second connections thereof and a coupling releasably connectable to a keg of the kind specified in such a manner as to enable the headspace of the container to communicate through the coupling to the first connection of the pressure-measuring device and to enable said tube to communicate through the coupling to the second connection of the pressure-measuring device and to a source of gas, whereby the pressure-measuring device can be used to measure difference in pressure between the gas in the headspace and the gas in the tube.

The pressure-measuring device may be of any suitable form and may comprise a manometer of which one limb communicates with the gas in the tube and the other limb communicates with the headspace of the container. The liquid in the manometer may be water or it may be some other liquid such as mercury. There is preferably provided valve means, which, when closed, prevents the escape of liquid from the manometer. Alternatively the pressure-measuring device may comprise a chamber divided by a flexible diaphragm into two portions, one of which communicates with the gas in the tube and the other of which communicates with the headspace of the container, the distortion of the diaphragm being dependent on the pressure difference, and the distortion of the diaphragm being detected and providing a measure of the pressure difference.

A widely-used kind of spear comprises a tube which is open at the bottom (the opening constituting the port referred to above) and has a top fitment provided with an inlet communicating with the headspace and an outlet communicating with the interior of the tube, the top fitment incorporating self-closing valves for the inlet and outlet. In normal use, when the spear is fitted to a keg, the tube extends to a location close to the bottom of the keg and the inlet and outlet valves are closed. When the beer or other beverage in the keg is to be withdrawn, a coupling is fitted to the top fitment. The coupling is connected to two flexible pipes, the first one of which leads from a supply of carbon dioxide under pressure and the second of which leads to a dispense point.Connection of the coupling to the top fitment automatically opens the inlet and outlet valves, thereby enabling carbon dioxide from the first pipe to enter the headspace within the keg and enabling the beer or other beverage to pass up the tube in the keg and along the second pipe to the dispense point.

In carrying out the method of the present invention it is convenient to employ a pressure-measuring device connected to a coupling similar to the coupling described but provided with passageways leading from the coupling to the pressure-measuring device Moreover, that passageway communicating with the the interior of the tube of the spear is preferably connected or capable of connection to a source of gas which can be introduced into the tube. It is normally necessary for the gas to be pressurized, and the necessary pressure may be derived from a container or containers containing gas under pressure.

For example it may be derived from a cylinder containing carbon dioxide or nitrogen or a mixture of carbon dioxide and nitrogen under pressure. The cylinder may also be used to supply pressurized gas for introduction into the headspace of the container when beer or other carbonated beverage is to be dispensed.

Alternatively the necessary pressure may be derived from- the operation of a pump. The pump may be manually operable and may, for example, comprise a cylinder containing a reciprocable piston. Alternatively the pump may be power-operated and may, for example, comprise an electrically powered rotary pump such as a centrifugal pump or a peristaltic pump. The inlet of the pump may be connected to atmosphere or to a source of inert gas such as carbon dioxide or nitrogen or a mixture of those gases. In a preferred arrangement, however, the inlet to the pump is in communication with the gas in the headspace.

In each form of apparatus the connection between the coupling and the pressure-measuring device is preferably flexible. This enables the pressure-measuring device and its associated parts to be placed in a suitable position when the coupling has been connected to the top fitment of a keg.

The apparatus is preferably portable.

Examples of the present invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 is a section through a beer keg of the kind specified, Figure 2 is an elevation of apparatus embodying the present invention for use in measuring the level of beer in the keg shown in Figure 1, Figure 3 is an elevation of a form of apparatus embodying the present invention alternative to that shown in Figure 2, part of the apparatus being shown in section, Figure 4 is an elevation of a further alternative form of apparatus embodying the present invention, part of which is shown in section, and Figure 5 is an elevation of a further alternative form of apparatus embodying the present invention, part of which is shown in section.

For clarity of disclosure each of the Figures is of simplified, somewhat diagrammatic form.

In Figure 1 there is shown a beer keg 1 of a well-known kind comprising a cylindrical container or drum 2 with domed ends 3 and provided with chines 4. A hole in the middle of the upper end is surrounded by an upstanding neck 5 of which the bore is internally screw-threaded. A spear 6 is fitted to the keg. The spear consists of a top fitment 7 with a depending tube 8 which extends to a location near the bottom of the keg and is open at its lower end. The top fitment is externally screw-threaded and engages the thread in the neck 5 of the keg. The top fitment has an inlet communicating with the headspace 9 in the keg and an outlet communicating with the upper end of the tube 8.

Both the inlet and outlet are normally closed by spring-loaded valve means. At the upper end of the top fitment is a flange 10 of noncircular outline to which a coupling (not shown) can be releasably attached.

The coupling is connected to two flexible pipes, the first leading to a cylinder containing carbon dioxide under pressure and the second leading to a dispense tap at a bar. When the coupling is attached to the top fitment 7, a lever on the coupling can be operated to open the valve means in the top fitment. When the valve means is open, carbon dioxide from the cylinder can enter the headspace 9 through the inlet in the top fitment while beer 11 from the keg can pass to the dispense tap by way of the tube 8, the outlet in the top fitment and the second pipe.

The apparatus shown in Figure 2 comprises a coupling 12 similar to the coupling described above. Two flexible pipes 13 and 14 lead from the coupling and are connected to opposite limbs of a manometer 15 comprising a glass or other transparent U-tube containing a quantity of water or other liquid 16. The pipe 13 has a branch 17. In use the coupling 12 is connected to the top fitment 7, the branch 17 is connected to the carbon dioxide cylinder and the lever (not shown) is operated to open the valve means in the top fitment. Carbon dioxide from the cylinder enters the pipe 13 and, by way of the coupling 12 and the outlet in the top fitment, enters the tube 8. Meanwhile the headspace 9 is connected, by way of the outlet in the top fitment, to the pipe 14. The flow of carbon dioxide from the cylinder is controlled by a manually-operable valve (not shown) which may conveniently be incorporated in or mounted on the coupling. The user manipulates the valve in such a manner that carbon dioxide is introduced into the tube 8 in such a quantity and at such a pressure that the gas bubbles slowly from the open lower end of the tube 8. The occurrence of this bubbling can normally be heard quite readily by the operator. When the gas pressure in the pipe 13 is just sufficient to cause bubbles to leave the lower end of the tube 8, the pressure exceeds the gas pressure in the headspace and in the pipe 14 by an amount equal to the product of the density of the beer and the vertical distance between the lower end of the tube 8 and the surface of the beer in the keg.Consequently the pressure applied to one limb of the manometer 15 exceeds the pressure applied to the other limb thereof by the same amount. As the density of the beer 11 in the keg is known, the height of the beer-level above the lower end of the tube 8 can be calculated from the reading of the manometer. If desired the manometer may be calibrated to provide readings of that height. Alternatively, as the volume of beer present in the keg is a function of that height, the manometer may be calibrated to provide readings of the volume of beer remaining in the keg. In a further alternative, tables may be provided appropriate for beers of different densities to enable the height or volume of a known kind of beer to be assessed from a manometer reading.

It will be appreciated that in carrying out this invention the carbon dioxide is introduced through the coupling 12 into the tube 8 and that this contrasts with the normal use of a coupling, which serves to enable carbon dioxide to be introduced into the headspace 9.

In the method of using the apparatus described above, the operator must listen for the occurrence of bubbles issuing from the lower end of the tube 8. This may not always be necessary, as an operator may well be able to tell when bubbles occur merely by watching the level of the liquid in the manometer. As carbon dioxide is progressively introduced into the tube, the level of beer in the tube will progressively fall, and the manometer reading will progressively increase. When bubbles issue from the tube a steady rate has been reached so that there is no further change in the manometer reading. This cessation of change may itself provide the operator with an indication that gas is issuing from the lower end of the tube 8.

Figures 3 and 4 show other forms of apparatus, either of which can be used in place of the apparatus shown in Figure 2. Each includes a connector with flexible pipes connected to it, and as these are of the same construction and have similar functions to the corresponding parts shown in Figure 1 they have been given the same reference numerals.

In the apparatus shown in Figure 3, the manometer 15 has been replaced by a modified form of manometer. comprising a closed vessel 18 containing a quantity of water or other liquid, and having a headspace connected to the pipe 13. A tube made of glass or other transparent material extends through the top of the vessel 18; its lower end is adjacent to the bottom of the vessel and its upper end is connected to the pipe 14. As the capacity of the vessel 18 is considerably greater than the capacity of the tube 19, there are only negligible variations in liquid level in the vessel 18 when the level of liquid varies in the tube 19.

The height of the liquid in the tube 19 therefore-provides an adequately accurate value of the liquid level in the keg, without it being necessary to determine the level of liquid in the vessel 18.

In the apparatus shown in Figure 4, the manometer is replaced by a device comprising a closed chamber 20 containing a flexible diaphragm 21 which divides the interior of the chamber into two portions which do not communicate with each other. One portion is connected to the pipe 13 and the other portion to the pipe 14. A transducer 22 has electrical properties that vary with the deformation of the diaphragm. Those variations are reflected in the readings of an electrical meter 23. If desired the readings may be stored in RAMs or the like constituting part of an electronic unit under the control of a microprocessor forming part of that unit.

Figure 5 shows a form of apparatus which largely resembles that shown in Figure 3, so corresponding parts have been given the same reference numerals. No coupling has been illustrated, but it is to be understood that a coupling similar to the coupling 12 is connected to the pipes 13 and 14. Portions of those pipes adjacent to the coupling are flexible to enable the remainder of the apparatus to be placed in any suitable position relative to a keg when, in use, the coupling has been connected to the top fitment of the keg.

A lower part of the vessel 18 and the bottom end of the tube 19 are connected by a short transverse duct, but this arrangement functions in exactly the same manner as that shown in Figure 3. A scale rod 20 extends alongside the tube 19 and bears a scale calibrated to provide a direct reading of the volume of beer remaining in a keg. In a convenient arrangement the scale rod 20 is of square cross-section and is so mounted that it can be rotated about its longitudinal axis so that any one of its four longitudinally extensive faces can be brought into use at will. Each face carries a different scale, each scale being appropriate for a different one of the four standard keg capacities referred to above.

The pipe 13 is provided with an on/off valve 21, the pipe 14 is provided with an on/off valve 22, and the branch 17 is provided with an on/off valve 23. The three valves 21, 22 and 23 operate in unison.

When the apparatus is in use they are open but when the apparatus is not in use they can be closed to prevent the escape of the liquid 16 from the manometer or the ingress of liquid from outside. The three valves may be biased to their closed positions, it then being necessary to hold them open manually when a reading is to be taken.

The branch 17 may be adapted for connection to a source of carbon dioxide under pres sure, as with each of the forms of apparatus shown in Figures 2 to 4, but in a preferred arrangement, as illustrated, the branch 17 is connected to the outlet of a gas pump 24.

The pump may be manually operable and comprise a cylinder containing a reciprocable piston. Preferably, however, the pump is power-operated. It may conveniently be electrically operated, in which case it may be controlled by a switch coupled to the valves 21, 22 and 23 so as to be operative only when those valves are open. The power-operated pump may be a rotary pump such as a centrifugal pump or a peristaltic pump. The inlet of the pump may be connected to atmosphere, or it could even be connected to a source of carbon dioxide at substantially atmospheric pressure. In a preferred arrangement, however, as illustrated, the inlet 25 of the pump 24 is connected to the pipe 14 so that in use it receives gas from the headspace and from the glass tube 19.The advantage of that arrangement is that the apparatus is entirely self-contained and that no air is drawn into the apparatus or pumped into the beer when the apparatus is in use.

In each of the forms of apparatus illustrated in Figures 2 to 5, all the components except the coupling 12 and the flexible pipes leading to it are preferably mounted on a common support or stand. The apparatus is then read ily portable. The apparatus shown in Figure 5 may, for example be mounted on a stand of generally pyramidal shape, an upward projection containing the glass tube 19 and the scale rod 20. A handle projects from the front of the stand. When depressed it opens the valves and causes the pump-motor to be switched on. When released it returns to its initial position, causing the valves to close and the motor to be switched off.

Throughout the foregoing description- of the present invention there are many circum stances of a kind in which the functioning of the method or apparatus depends on the fact that the pressure af a confined volume of gas is constant as between one location and another. It must be understood, however, that if desired it is possible to sub-divide such a volume of gas into two or morse parts sepa rated by a barrier which is free to move and which is such as to introduce no pressure dif ference between the parts. Such a barrier could be provided, for example, by flexible bellows or by a freely-floating piston in a cyl inder. The use of such an arrangement would, of course, remain within the scope of the pre sent invention.

Claims

1. A method of measuring the level of be verage in a keg of the kind specified, in which method a pressure-measuring device is con nected between the headspace of the con tainer and the tube of the spear, introducing gas into the tube until gas can escape through the port, and using the pressure-measuring device to measure the difference in pressure between the gas in the headspace and the gas in the tube, that pressure difference being proportional to the depth of the port below the level of beverage in the container, and thus to measure the level of the beverage in the container.

2. A method according to claim 1 in which the pressure-measuring device comprises a manometer of which one limb communicates with gas in the tube and the other limb communicates with the headspace of the container.

3. A method according to claim 1 in which the pressure-measuring device comprises a chamber divided by a flexible diaphragm into two portions, one of which communicates with the gas in the tube and the other of which communicates with the headspace of the container, the distortion of the diaphragm being dependent on the pressure difference, and the distortion of the diaphragm being detected and providing a measure of the pressure difference.

4. A method according to any one of claims 1 to 3 in which the gas introduced into the tube is under pressure and the necessary pressure is derived from a container or containers containing gas under pressure.

5. A method according to any one of claims 1 to 3 in which the gas introduced into the tube is under pressure and the necessary pressure is derived from the operation of a pump.

6. A method according to claim 5 in which the inlet of the pump is in communication with the gas in the headspace.

7. A method of measuring the level of beverage in a keg of the kind specified, substantially as hereinbefore described with reference to Figure 1 and any one of Figures 2 to 5 of the accompanying drawings.

8. Apparatus for use in carrying out a method in accordance with claim 1, comprising a pressure-measuring device capable of measuring the difference in pressure between first and second connections thereof and a coupling releasably connectable to a keg of the kind specified in such a manner as to enable the headspace of the container to communicate through the coupling to the first connection of the pressure-measuring device and to enable said tube to communicate through the coupling to the second connection of the pressure-measuring device and to a source of gas, whereby the pressure-measuring device can be used to measure difference in pressure between the gas in the headspace and the gas in the tube.

9. Apparatus according to claim 8 in which the pressure-measuring device comprises a manometer of which one limb communicates with gas in the tube and the other limb com municates with the headspace of the container.

10. Apparatus according to claim 9 in which there is valve means which, when closed, prevents the escape of liquid from the manometer.

11. Apparatus according to claim 8 in which the pressure-measuring device comprises a chamber divided by a flexible diaphragm into two portions, one of which communicates with the gas in the tube and the other of which communicates with the headspace of the container, the arrangement being such that distortion of the diaphragm is dependent on the pressure difference and can be detected to provide a measure of the pressure difference.

12. Apparatus according to any one of claims 8 to 11 in which there is a pump operative to create a pressure for introducing the gas into the tube.

13. Apparatus according to claim 12 in which the pump is manually operable.

14. Apparatus according to claim 12 in which the pump is power-operated.

15. Apparatus according to any one of claims 12 to 14 in which the inlet to the pump is in communication with the first connection of the pressure-measuring device.

16. Apparatus according to any one of claims 8 to 15 in which the connection between the coupling and the pressure-measuring device is flexible.

17. Apparatus according to any one of claims 8 to 16 which is portable.

18. Apparatus for use in measuring the level of beverage in a keg of the kind specified, substantially as hereinbefore described with reference to any one of Figures 2 to 5 of the accompanying drawings.