GB2077432A - Apparatus for determining the depth of beer in a keg - Google Patents

Abstract

Apparatus for determining the depth of beer in a pressurised beer keg includes means 11, 12 for applying beer under pressure and the pressurising gas to opposite sides of a flexible diaphragm 8 and measuring the deflection with a strain gauge 18. A fitting is attached to the top of the keg whereby beer is supplied to chamber 9 via pipe 11 when tap 24 is opened and gas is applied to chamber 10 when valve 12a is opened. The gas pressure is applied to diaphragm 8 via diaphragm 8a and an oil filled chamber 10a. The diaphragm 8 carries rigid plates 14 and is movement is transmitted to a cantilever 15 carrying the strain gauge via link 17. <IMAGE>

Description

SPECIFICATION Apparatus for determining the depth of beer in a keg One kind of beer keg, which, when filled with beer, is pressurised with carbon dioxide, has an opening at its top provided with a self-closing valve and a spear, which is a tube extending downwards into the keg from the valve. Such kegs are subsequently referred to as "kegs of the kind described".

To draw beer from such a keg, a fitting is applied to the opening and carbon dioxide is applied under pressure through the fitting to the space within the keg outside the spear so that the carbon dioxide pressure in this space is maintained and acts on the surface of the beer in the keg. Thus the beer is forced upwards through the spear and out through a duct which extends through the fitting and communicates with the inside of the spear.

Sometimes such kegs are returned by publicans to the brewery in a partly filled state. This happens in particular if the beer has gone off and cannot be sold. If this has happened through no fault of the publican, the publican is credited by the brewery with the value of the beer remaining in the keg. It is therefore necessary to be able to assess the volume of beer remaining in the keg and this may be done by apparatus as described in our Application No. 22545/ 78. The apparatus described in our prior Application operates very satisfactorily, but it is somewhat complex both in construction and operation and can quite easily be damaged when being transported by brewery representatives from Public House to Public House in the course of their duties.

The aim of the present invention is therefore to provide apparatus for determining the depth of beer above the bottom of the spear in a keg of the kind described which is both simpler and more robust than that described in our Application No. 22545/78.

To this end, according to this invention, such apparatus comprises a fitting for attachment to the opening of the keg, the fitting comprising a chamber which is divided by movable partition means into two compartments, a first duct in the fitting communicating with a first one of the compartments and leading, when the fitting is attached to a keg, to the inside of the spear, and a second duct in the fitting communicating with the second compartment and leading to the space, which is filled with carbon dioxide under pressure, outside the spear, a closable valve for venting the first compartment to allow this compartment to be filled with beer from the spear under pressure from the carbon dioxide, and means including an electrical strain gauge to measure the force on the movable partition means caused by the pressure differential between the beer in the first compartment and the carbon dioxide in the second compartment when the valve is closed in order to provide an indication of the level of the surface of the beer in the keg.

The electrical strain gauge may comprise a strain sensor connected to a member which is deflected by movement of the movable partition means the deflection being dependent upon the resultant force acting upon the movable partition means and this sensor may be connected by electrical leads to a meter which may be entirely separate from the fitting which, in operation, is fitted to the keg and which includes the chamber. The apparatus may therefore consist of two very simple parts which are in themselves compact and easily transportable and which are also individually robust.

To use the apparatus, the fitting of the apparatus is fitted to the opening of the keg and the venting valve, which may be in the form of a sample tap, is opened until the first compartment is filled with beer and beer flows from the tap. The tap is then closed. A second valve may be fitted in the second duct and, if the valve is provided, it is then opened to admit carbon dioxide under pressure to the second compartment. A reading is then taken from the strain gauge. The pressure of the beer acting upon one side of the movable partition means is less than the gas pressure acting upon the other side by an amount which is directly dependent upon the mean height of the column of beer between the surface of the beer in the keg and the centre of pressure of the movable partition means.Since the position of the centre of pressure is known, the level of the surface of the beer remaining in the keg will directly affect the reading of the strain gauge, and the meter, to which the sensor of the strain gauge is connected, may be calibrated to provide a direct reading of this height. However in practice conversion tables are necessary to interpret the height from the reading of the meter of the strain gauge because the pressure of the beer will vary according to the specific gravity of the beer.

The movable partition means may comprise two diaphragms between the two compartments, the two diaphragms enclosing between them a third compartment which is filled with liquid so that the carbon dioxide pressure in the second compartment is transmitted through the liquid to the diaphragm bounding the first compartment. Preferably, for constructional simplicity, the diaphragms are arranged in the chamber so that the diaphragm which bounds the first compartment is in a vertical plane when the fitting is attached to the keg and this diaphragm is of such a shape that its centre of pressure is at its geometric centre.

Preferably the member which is deflected by movement of the movable partition means is a cantilever arm which is mounted in the third compartment and upon which the strain sensor is mounted, the arm having at its free end a force transmitting link which is attached to the centre of the diaphragm which bounds the first compartment.

The movement of the diaphragms or other partition means is restricted to a very small magnitude by the stiffness of the cantilever arm, but the diaphragms or other partition means are made freely movable so that the deflection of the cantilever arm is directly dependent upon the force on the diaphragm and hence upon the differential pressure between the pressure of the beer and the pressure of the carbon dioxide.

The partition means may be in the form of a piston or pistons within a cylinder, though this is not very satisfactory because the stickiness of the beer flow ing into the first compartment is liable to cause the piston or pistons to stick and thus gives rise to inaccuracies. It is however necessary for the partition to transmit a force which is directly proportional to the differential pressure and it is for this reason that the partition means preferably consists of freely flexible diaphragms, the diaphragm which bounds the first compartment having a centre part which is made rigid by a stiff plate fixed to one or both sides of the diaphragm and the cantilever arm or other member, the strain of which is measured by the strain gauge, is then connected to the centre of the stiffening the plate or plates by a force transmitting link.

As a further alternative, a resiiiently deflectable diaphragm may be used to bound the first compartment and the diaphragm itself then provides the restoring force acting against the force produced by the differential pressure. In this case, however, part of the resultant force on the diaphragm will be transmitted to the wall of the fitting to which the edge of the diaphragm is fixed and in this case it is necessary to calibrate the meterwhich provides the reading of the strain sensor over the whole of its range of differential pressure varying between a full keg and an empty keg.

The liquid in the third compartment, when this is provided, is preferably silicone oil and when the cantilever arm and the strain gauge are in this compartment, they are fully protected from any contamination.

An example of an apparatus in accordance with the invention is illustrated highly diagrammatically in the accompanying drawings in which: Figure 1 is a side view, partly in section, of a keg of the kind described with the example of the apparatus in accordance with the invention fitted to it; and Figure 2 is a side view, partly in section and to a much larger scale of the main parts of the example of the apparatus in accordance with the invention.

As shown in Figure 1, a beer keg 1 of the kind described has an outlet opening 2 fitted with a self closing valve, which is not shown, and a spear 3. The keg 1 is partly filled with beer 4 up to a level 5.

The apparatus in accordance with the invention comprises a fitting 6 which is fitted to the outlet opening 2 of the keg and a housing 7. As shown in Figure 2, the housing 7 contains a chamber which is divided by partition means formed by a first flexible diaphragm 8 and a second flexible diaphragm 8a into a first compartment 9, a second compartment 10 and a third compartment 10a.

Referring again to Figure 1, the fitting 6 has a first duct 11 leading from the inside of the spear 3 to the first compartment 9. A second duct 12 in the fitting 6 leads through a three-way valve 12a from a gas space 13 outside the spear 3 within the keg 1 to the second compartment 10.

As shown in Figure 2, the diaphragm 8, which is freely flexible, has its periphery clamped between two portions of the housing 7 which are clamped together with the edge of the diaphragm between them by bolts, which are not shown. The whole of the centre portion of the diaphragm 8 is made rigid by plates 14 fixed to its two faces. A cantilever arm or beam 15 is rigidly bolted by a bolt 16 to the inside of the housing 7 and the arm or beam 15 extends vertically downwards and has its free end connected to the plate 14 on the right-hand side of the freely flexible diaphragm 8 by a flexible link 17 which is connected at one end to the arm 15 and at the other end to the plate 14.

An electrical strain gauge sensor 18 is fixed to the arm or beam 15 so that it senses bending strains in the arm or beam 15 in the usual way and the sensor 18 is connected by an electrical lead 19 which leads to an indicator 20 which consists of an electrical power source and a sensitive amplifier and meter in the usual way. The meter 20 has a switch operated by a button 21 and when the button 21 is pressed, a pointer 22 of the meter provides a reading of the strain in the arran or beam 15.

The first compartment 9 has an outlet 23 leading to a.venting valve in the form of a sample tap 24 and the third compartment 10a is sealed and filled with silicone oil.

To measure the surface level 5 of the beer in the keg 1, the fitting 6 is fitted to the outlet opening 2 as shown in Figure 1. Initially the valve 12a vents the compartment 10 and closes the duct 12 below the valve 12a. The sample tap 24 is opened so that the carbon dioxide under pressure in the gas space 13 forces beer up through the spear 3 and the duct 11 into the compartment 9 and thence from the tap 24 where a sample is collected in a mug 25. The tap 24 is then closed and the compartment 9 is at this stage filled with beer. The valve 1 2a is then operated to connect the gas space 13 through the duct 12 to the compartment 10.

The mean pressure of the beer in the compartment 9 is less than the carbon dioxide pressure in the compartment 10 by an amount which is dependent upon the heighth (see Figure 1) between the surface 5 of the beer and the centre of pressure acting on the diaphragm 8 which corresponds with the point of attachment of the link 17. This pressure differential exerts a force through the oil in the compartment 10a towards the left as shown in Figure 2 upon the diaphragm 8, the force being equal to the mean pressure differential multiplied by the total area of the diaphragm 8.As the movement of the diaphragm 8 towards the left is restricted by the arm 15 acting through the link 17, and the edge portion of the diaphragm 8 is freely flexible, the whole of the differential pressure acting on the diaphragm 8 is transmitted through the link 17 to the cantilever arm or beam 15 which is accordingly bent in a clockwise direction as seen in Figure 2. This bending strain is measured by the strain gauge sensor 18 and the strain is directly dependent upon the heighth and, of course, the specific gravity of the beer 4, but this is known and is a constant. In consequence when the button 21 is pressed, a pointer 22 gives a reading which is directly indicative of the height hand the level 5 can then immediately be determined from previousiy plotted graphs or tables.

The sample collected in the mug 25 may also be tasted to determine whether or not the beer is saleable and, if it is not, an experienced taster may also be able to determined the cause of the beer having gone off.

When the fitting 6 is first fitted to the outlet opening 2 of the keg and the compartment 10 is vented through the valve 12a, beer flows into the compartment 9 through a non-return valve 26 having a closure member 27. This applies a large unbalanced pressure towards the right, as seen in Figure 2, on the diaphragm 8. To prevent this pressure causing damage to the diaphragm 8, a rigid stop ring 29 is provided and this is contacted by the plate 14. When the fitting 6 is removed again, the beer pressure in the compartment 9 is allowed to decay only slowly through a bleed passage 28 through the closure member 27.

The apparatus in accordance with the invention, and in particular the example illustrated is so compact and simple to use that it is of great value not only for brewery representatives needing to determine the amounts of beer remaining in kegs with the value of which the publican is to be credited, but is also extremely valuable for publicans themselves for stocktaking and other purposes. The apparatus enables stocktaking to be carried out without removing the spear and dipping the keg, which was a practice sometimes resorted to, but generally considered unsatisfactory by brewers because of the possibility of contamination.

Claims (9)

1. Apparatus for determining the depth of beer above the bottom of the spear in a keg of a kind described, the apparatus comprising a fitting for attachment to the opening of the keg, the fitting comprising a chamber which is divided by movable partition means into two compartments, a first duct in the fitting communicating with a first one of the compartments and leading, when the fitting is attached to a keg, to the inside of the spear, and a second duct in the fitting communicating with the second compartment and leading to the space, which is filled with carbon dioxide under pressure, outside the spear, a closable valve for venting the first compartment to allow this compartment to be filled with beer from the spear under pressure from the carbon dioxide, and means including an electrical strain gauge to measure the force on the movable partition means caused by the pressure differential between the beer in the first compartment and the carbon dioxide in the second compartment when the valve is closed in order to provide an indication of the level of the surface of the beer in the keg.

2. Apparatus according to Claim 1, in which the electrical strain gauge comprises a strain sensor connected to a member which is deflected by movement of the movable partition means, the deflection being dependent upon the resultant force acting upon the diaphragm or other partition.

3. Apparatus according to Claim 2, in which the sensor is connected by electrical leads to a meter which is separate from the fitting which includes the chamber.

4. Apparatus according to any one of the preceding Claims, in which the closable valve for venting the first compartment is in the form of a sample tap.

5. Apparatus according to any one of the preced ing Claims, in which the movable partition means comprises two diaphragms between the two com partments, the two diaphragms enclosing between them a third compartment which is filled with liquid so that the carbon dioxide pressure in the second compartment is transmitted through the liquid to the diaphragm bounding the first compartment.

6. Apparatus according to Claim 5, in which the diaphragms are arranged in the chamber so that the diaphragm which bounds the first compartment is in a vertical plane when the fitting is attached to the keg and this diaphragm is of such a shape that its centre of pressure is at its geometric centre.

7. Apparatus according to Claim 6 when depen dent on Claim 2, in which the member which is deflected by movement of the movable partition means is a cantilever arm which is mounted in its third compartment and upon whiich the strain sensor is mounted, the arm having at is free end a force transmitting link which is attached to the centre of the diaphragm which bounds the first compart ment.

8. Apparatus according to any one of Claims 5 to 7, in which the diaphragm which bounds the first compartment is a freely flexible diaphragm having a centre part which is made rigid by a stiff plate, or plates fixed to one or both sides of the diaphragm and the cantilever arm or other member, the strain of which is measured by the strain gauge, is connected - by a flexible link to the centre of the stiffening plate or plates.

9. Apparatus according to Claim 1, substantially as described with reference to the accompanying drawings.