GB2273560A

GB2273560A - Liquid level detection

Info

Publication number: GB2273560A
Application number: GB9325673A
Authority: GB
Inventors: Geoffrey Wood
Original assignee: TECFLO Ltd
Current assignee: TECFLO Ltd
Priority date: 1992-12-15
Filing date: 1993-12-15
Publication date: 1994-06-22
Anticipated expiration: 2013-12-15
Also published as: GB2273560B; GB9226107D0; GB9325673D0

Abstract

A liquid detection apparatus 1 comprising a reservoir 2 formed of a tubular body having end caps 6,7, a photoelectric sensor 19 for determining when the level of liquid in the reservoir 2 falls below a predetermined level, and a support assembly 4 having means 5 for ensuring that the end caps 6, 7 are retained in position against pressure in the reservoir 2. The detection apparatus 1 is advantageously used in a beverage dispensing system, and is operatively associated with an electrical circuit to prevent operation of liquid propelling means when beverage in the reservoir 2 falls below a predetermined value. The photoelectric sensor may comprise a source and detector in a transparent dome which internally reflects light from the source to the detector in the absence of liquid but permits the light to escape through the dome when liquid of similar refractive index is present. <IMAGE>

Description

LIQUID DETECTION APPARATUS The present invention relates to liquid detection apparatus and particularly (but not exclusively) to such apparatus for use in dispensing beverages, e.g. draught beer.

Draught beer is supplied to public houses and bars in barrels or kegs from which the beer is dispensed. One method of dispense involves the use of an electric pump which is used to supply the beer from the barrel to the point of dispense. The electric pump is operated by a switch or the like at the point of dispense, the switch being actuated by the bar person when a glass of beer is to be dispensed. In many cases, a meter is disposed between the pump and the point of dispense so that actuation of the switch causes the pump to operate for a predetermined period of time so as to dispense a metered quantity of liquid, e.g. half a pint.

Dispense systems utilising an electric pump generally also incorporate a liquid detection apparatus in the beer supply line between the barrel and the pump. The liquid detection apparatus incorporates a reservoir which is located in the beer supply line and which is normally maintained full of beer. When the barrel is empty (and therefore requires changing) the reservoir will no longer be full of liquid, and this condition is detected by a detector arrangement incorporated in the apparatus.The liquid detection apparatus is operatively associated with the pump so that the apparatus will prevent further operation of the pump until the barrel has been changed (and the reservoir is once again full). If the dispense system is one which dispenses a metered quantity of beer then the liquid detection apparatus will generally be such that the detection apparatus shuts off the inlet valves to the beer meter so that dispense will continue until the metered quantity present in the beer meter has been delivered to the glass, at which time further operation of the pump is prevented until the barrel has been replaced.

The advantage of the liquid detection system (which is also known as a "fob detector") is that once the barrel has been replaced it is only necessary to bleed gas such as carbon dioxide from the fob detector and that part of the beer line between the barrel and the reservoir.

Fob detectors currently in use in the United Kingdom have a vertically disposed glass reservoir formed in two coaxial halves separated by a perforated plate or the like.

A float is free to move in the upper half of the reservoir down to a position at which it rests on the perforated plate. The float incorporates a magnet which serves to operate a reed switch positioned adjacent the float's lowest possible position. When the barrel is empty, the level of liquid in the reservoir falls as further beer is dispensed until the magnet in the float actuates the reed switch.

The reed switch serves to prevent further operation of the pump via inlet valves to a beer meter, whilst allowing a fully metered quantity of beer to be dispensed, or via solenoid valves on the dispensing apparatus at the bar.

The beer barrel is then changed. The top pressure of the barrel fills the reservoir whilst the operator opens a bleed valve associated with the reservoir to allow gas present therein to be bled off. Once the float in the reservoir has moved away from the reed switch, power to the pump is switched on again.

According to a first aspect of the present invention there is provided liquid detection apparatus comprising a reservoir formed of a one-piece tubular body having a closure arrangement at each end thereof, inlet and outlets to the reservoir, and a photoelectric liquid level sensor for determining when the level of liquid in the reservoir falls below a predetermined level.

An advantage of having the reservoir in one piece is that a simple seal arrangement may be provided at each end (e.g. O-rings around the end caps) to prevent egress of liquid from the reservoir. Therefore the need for a liquid and pressure-tight seal intermediate the ends of the reservoir is avoided.

The closure arrangement at each end of the tubular body may be a removable end cap. The apparatus is preferably associated with a support assembly having means for ensuring that the end caps are retained in position against pressure in the reservoir. The means for resisting movement of the end caps may comprise projections which are provided on the support assembly and which extend through the end caps. Preferably also the end caps are provided with inlet and outlet ports as necessary, and at least one of the caps will be provided with a bleed valve arrangement.

The use of a photoelectric liquid level sensor comprising a light source and a light detector avoids the need for any moving parts in the apparatus.

Preferably the photoelectric sensor arrangement comprises a light source and a light detector within a cover which is such that (i) when the cover is not immersed in liquid, light from the source is totally internally reflected from the cover boundary to the detector, and (ii) when the sensor is so immersed, there is a change in the refractive index at the boundary between the cover and the surroundings which allows light to escape from the sensor arrangement thus changing the signal received by the light detector.

Preferably the light source is an LED and the light detector is an optical Schmitt trigger.

The liquid level sensor is, of course, primarily intended for use in a beverage dispensing system and therefore according to a second aspect of the present invention there is provided a beverage dispensing system comprising a dispense outlet, an electrical circuit associated with liquid propelling means for dispensing beverage from a supply thereof to the outlet, and a liquid detection apparatus in accordance with the first aspect of the invention, the liquid detection apparatus being operatively associated with the electrical circuit to prevent dispense of beverage when a predetermined condition has been met.

The predetermined condition may be when beverage in the reservoir falls below a predetermined value or may be when beverage present in a beverage meter has been dispensed.

The liquid propelling means may be an electric pump or may comprise a gas supply connected to the beverage barrel to force beverage under pressure along the supply lines.

The electrical circuit may be operatively associated with inlet valves on a beer meter. When the liquid level sensor detects that level of liquid present in the reservoir has fallen below a predetermined level, the electrical circuit prevents operation of the beer meter but only after a metered quantity of beer has been dispensed.

Several beer meters may be connected to one beer barrel, and hence to one reservoir.

Alternatively, the electrical circuit may be associated with valves on the dispenser at the bar.

Closure of the valves thus effectively cuts the supply of beer off, as no further beer may be drawn through the dispenser.

The use of the preferred photoelectric sensor is an important development in its own right and leads to a third aspect of the present invention according to which there is provided a beverage dispense system comprising a dispense outlet, an electrical circuit associated with liquid propelling means for dispensing beverage from a supply thereof to the outlet, and a liquid detection apparatus including a reservoir and a liquid level sensor for determining when the level of liquid in the reservoir falls below a predetermined level, the liquid detection apparatus being operatively associated with the electrical circuit to prevent dispense of beverage when a predetermined condition has been met, wherein the liquid level sensor is a photoelectric sensor arrangement which incorporates a light source and a light detector within a cover which is such that (i) when the cover is not immersed in liquid, light from the source is totally internally reflected from the cover boundary to the detector, and (ii) when the sensor is so immersed, there is a change in the refractive index at the boundary between the cover and the surroundings which allows light to escape from the sensor arrangement thus changing the signal received by the light detector.

According to a fourth aspect of the present invention there is provided a method of dispensing beer which comprises using a photoelectric sensor to monitor the level of beer in a reservoir and prevent dispense of beer when a predetermined condition has been met.

The predetermined condition may be when beer in the reservoir falls below a predetermined value or may be when beer present in a beer meter has been dispensed.

The invention will be further described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a part sectional side view of a liquid detection apparatus; Fig. 2 is a front view of the apparatus illustrated in Fig. 1; and Fig. 3 is an end elevation in the direction of arrow III of Fig.2.

Referring to the drawings there is illustrated a liquid detection apparatus 1 comprising a cylindrical reservoir 2 mounted on the lid 3 of a back box 4 by means of studs 5 secured to the lid 3 and passing through end caps 6, 7 of the reservoir 2.

Each end cap 6 and 7 is approximately cylindrical but is stepped as at 8 so as to form two sections of sightly different diameter. The narrower diameter section locates within the end of reservoir 2 whereas the wider diameter section projects therefrom. Extending diametrically through the wider section of each of the end caps 6 and 7 is a respective bore 9 in which the stud 5 is accommodated.

A nut 10 is secured to the free, threaded end of stud 5 so as to retain the end cap 6 or 7 (and thereby the reservoir 2) in position. The studs 5 also serve to prevent displacement of the end caps 6, 7 by pressure generated within reservoir 2.

The narrower diameter section of each end cap 6, 7 is formed with two axially spaced circumferential grooves 11 in which are accommodated O-ring seals 12 to prevent egress of liquid from the reservoir. A further circumferential groove 13 is provided in the wider section of each end cap which is received in cradle formations 14 provided on the lid 3 to assist in location of the reservoir 2.

The end cap 6 (i.e. the upper cap illustrated in Fig.

1) differs from cap 7 in that the former is provided with an inlet port 15 and a bleed valve port 16, whereas the latter is simply provided with an outlet port 17.

With reference to cap 6, the inlet port 15 is situated near the edge of the cap and is angled as shown in its lower region so that beer (passing through port 15) is introduced generally tangentially into reservoir 2 to avoid the build-up of excessive froth, and also so that on cleaning of the device any cleaning fluid will spiral around the reservoir and creates a whirlpool effect to clean as much of the inner surface of the reservoir as possible.

The outlet port 17 in cap 7 serves, of course, to allow beer to exit from the reservoir 2.

The wall of reservoir 2 is provided with a threaded aperture 18 positioned approximately 3/4 of the way up the reservoir. Accommodated in the aperture 18 is a liquid sensor 19 provided with a nut 20 to assist in screwing the sensor 19 in position. Sensor 19 comprises an LED and an optical Schmitt trigger sealed into the base of a light transparent plastics dome. Such a sensor may, for example, be a solid state liquid level sensor as supplied by Honeywell. The sensor 19 works by bouncing light emitted from the LED off the plastics dome so that the light is detected by the optical Schmitt trigger. If the sensor is not immersed in liquid, there is complete internal reflection of the light and a signal of a particular value is provided as an output from the detector 19.Conversely, if the detector 19 is immersed in liquid, then the refractive index at the boundary between the dome and the surroundings is changed (as compared to the condition where no liquid is present) and light escapes into the liquid.

Thus, less light is received by the optical Schmitt trigger such that the detector 19 provides a different signal.

A lead 21 extends from the sensor as shown. This lead is normally hidden from view by a cover plate 22 which extends between (and is located on) the studs 5.

Electrical circuitry (not shown) associated with the detector 19 is housed within the box 4 which is provided at one end with a socket (not shown) to which the lead 21 may be connected.

In use, the illustrated liquid detection apparatus will be mounted on a wall (or other suitable surface) by screws or the like which pass through the rear side of box 4. The illustrated detector apparatus is positioned so that the reservoir 2 is vertical. The inlet port 15 is connected to the supply side of the beer line whereas the outlet 17 is connected to the dispense side. Beer enters the reservoir 2 via the inlet port 16 under the influence of the top pressure in the barrel. Owing to the configuration of the inlet port, beer entering the reservoir spirals around the surface of the reservoir ensuring that froth does not build up in the reservoir.

Simultaneously with the filling of the reservoir, bleed valve 16 is opened to allow gas such as carbon dioxide to escape from the reservoir. When the reservoir is full, beer may be dispensed.

Whilst the reservoir 2 remains full of liquid, the detector 19 allows operation of the electric pump so that beer may continue to be dispensed. However, when the barrel is empty, further dispensing of beer is stopped. If the reservoir is connected to a beer meter (not shown) the detector 19 shuts off the inlet valves to the beer meter, preventing further liquid being drawn into the meter. Any beer remaining in the meter unit may still be dispensed.

It will be appreciated that the positioning of the sensor 19 about 3/4 of the way up the reservoir 2 means that there is sufficient beer remaining in the reservoir (as the level has fallen below sensor 19) to complete the re-filling of a beer meter with a metered quantity of beer. Thus, when the liquid falls below the level of sensor 19 there is always enough liquid remaining in the system so that any metered amount of beer which has been requested may be completed, even when several beer meters are connected to one barrel. If the reservoir is not connected to a beer meter, the detector 19 shuts off solenoid valves provided at the dispensing outlets at the bar. This prevents further beer being drawn from a pump or under pressure along the supply lines.

It will be appreciated that the illustrated embodiment has a number of important advantages. In particular, the illustrated apparatus is of simple construction which is easy to produce and also to dismantle for the purposes of cleaning and repair. Furthermore the use of the photoelectric detector arrangement avoids the need for the reservoir to be formed in two halves and the complications associated therewith.

It is possible to mount the liquid detection apparatus horizontally. In this case, it is necessary to alter the positions of the sensor and the inlet and outlet ports. A horizontally mounted device is useful for, for example, cider, where a smaller reservoir than that used for beer would be employed (typically because there will be fewer cider dispensers at a bar, often with smaller barrels being used). The horizontal meter may not generally be used with beer meters, as, for example, beer meters are not used for cider, and so the dispensing of liquid already present in such a meter is not required. Thus, a horizontal meter may only need to be able to immediately cut off the supply of beverage.

Claims

1. Liquid detection apparatus comprising a reservoir formed of a one-piece tubular body having a closure arrangement at each end thereof, inlet and outlets to the reservoir, and a photoelectric liquid level sensor for determining when the level of liquid in the reservoir falls below a predetermined level.

2. Apparatus as claimed in claim 1 wherein the closure arrangement at each end of the body is a removable end cap.

3. Apparatus as claimed in claim 2 associated with a support assembly having means for ensuring that the end caps are retained in position against pressure in the reservoir.

4. Apparatus as claimed in claim 3 wherein the means for resisting movement of the end caps comprise projections which are provided on the support means and which extend through the end caps.

5. Apparatus as claimed in claim 2 or 3 wherein the end caps are provided with inlet and outlet ports as necessary.

6. Apparatus as claimed in claim 5 wherein the end cap provided with the inlet port is further provided with a bleed valve arrangement.

7. Apparatus as claimed in any one of claims 1 to 4 wherein the photoelectric liquid level sensor is a photoelectric arrangement comprising a light source and a light detector.

8. Apparatus as claimed in claim 7 wherein the photoelectric sensor arrangement comprises a light source and a light detector within a cover which is such that (i) when the cover is not immersed in liquid, light from the source is totally internally reflected from the cover boundary to the detector, and (ii) when the sensor is so immersed, there is a change in the refractive index at the boundary between the cover and the surroundings which allows light to escape from the sensor arrangement thus changing the signal received by the light detector.

9. Apparatus as claimed in claim 8 wherein the light source is an LED and the light detector is an optical Schmitt trigger.

10. A beverage dispense system comprising a dispense outlet, an electrical circuit associated with liquid propelling means for dispensing beverage from a supply thereof to the outlet, and a liquid detection apparatus in accordance with any one of claims 1 to 9, the liquid detection apparatus being operatively associated with the electrical circuit to prevent operation of the liquid propelling means when a predetermined condition has been met.

11 A beverage dispense system as claimed in claim 10, wherein the predetermined condition is when the amount of beverage in the reservoir falls below a predetermined value.

12. A beverage dispense system as claimed in claim 10, wherein the predetermined condition is when beverage present in a beverage meter has been dispensed.

13. A beverage dispense system as claimed any of claims 10 to 12, wherein the liquid propelling means is an electric pump.

14. A beverage dispense system as claimed in any of claims 10 to 12, wherein the liquid propelling means comprises a supply of gas to force beverage along the supply lines under pressure.

15. A beverage dispense system as claimed in any of claims 10 to 14, wherein the electrical circuit is operatively associated with inlet valves provided on a beverage meter in the supply lines.

16. A beverage dispense system as claimed in any of claims 10 to 14, wherein the electrical circuit is operatively associated with valves provided on the dispense outlet.

17. A beverage dispense system comprising a dispense outlet, an electrical circuit associated with liquid propelling means for dispensing beverage from a supply thereof to the outlet, and a liquid detection apparatus including a reservoir and a liquid level sensor for determining when the level of liquid in the reservoir falls below a predetermined level, the liquid detection apparatus being operatively associated with the electrical circuit to prevent operation of the liquid propelling means when a predetermined condition is met, wherein the liquid level sensor is a photoelectric sensor arrangement which incorporates a light source and a light detector within a cover which is such that (i) when the cover is not immersed in liquid, light from the source is totally internally reflected from the cover boundary to the detector, and (ii) when the sensor is so immersed, there is a change in the refractive index at the boundary between the cover and the surroundings which allows light to escape from the sensor arrangement thus changing the signal received by the light detector.

18. A beverage dispense system as claimed in claim 17, wherein the predetermined condition is when beverage in the reservoir falls below a predetermined value.

19. A beverage dispense system as claimed in claim 17, wherein the predetermined condition is when beverage present in a beverage meter has been dispensed.

20. Apparatus as claimed in any of claims 17 to 19, wherein the light source is an LED and the light detector is an optical Schmitt trigger.

21. A beverage dispense system as claimed in any of claims 17 to 19, wherein the liquid propelling means is an electric pump.

22. A beverage dispense system as claimed in any of claims 17 or 20, wherein the liquid propelling means comprises a supply of gas to force beverage along the supply lines under pressure.

23. A beverage dispense system as claimed in any of claims 17 to 22, wherein the electrical circuit is operatively associated with inlet valves provided on a beverage meter in the supply lines.

24. A beverage dispense system as claimed in any of claims 17 to 22, wherein the electrical circuit is operatively associated with valves provided on the dispense outlet.

25. A method of dispensing beer which comprises using a photoelectric sensor to monitor the level of beer in a reservoir and prevent dispense of beer when a predetermined condition has been met.

26. A method as claimed in claim 25, wherein the predetermined condition is when beer in the reservoir falls below a predetermined value.

27. A method as claimed in claim 25, wherein the predetermined condition is when beer present in a beer meter has been dispensed.

28. Liquid detection apparatus comprising a reservoir formed of a tubular body having an end cap for each end thereof, a liquid level sensor for determining when the level of liquid in the reservoir falls below a predetermined level, and a support assembly having means for ensuring that the end caps are retained in position against pressure in the reservoir.

29. Liquid detection apparatus substantially as hereinbefore described with reference to the accompanying drawings.

30. A method of dispensing beer substantially as hereinbefore described with reference to the accompanying drawings.