EP0251793B1

EP0251793B1 - Improved liquid dispensing arrangement

Info

Publication number: EP0251793B1
Application number: EP87305855A
Authority: EP
Inventors: Phillip Morgan
Original assignee: Pektron Ltd
Current assignee: PEKTRON GROUP LIMITED
Priority date: 1986-07-02
Filing date: 1987-07-01
Publication date: 1992-07-01
Anticipated expiration: 2007-07-01
Also published as: ATE77803T1; GB2193704A; GB8715467D0; DE3780093T2; GB8616106D0; EP0251793A1; DE3780093D1; GB2193704B

Abstract

A beer dispensing arrangement comprises electronic control circuitry (56) having in circuit reed switches (42) and a Hall effect sensor (54), the circuitry (56) also having in circuit a beer pump (24) for moving beer from a supply to dispensing taps (30,32). The reed switches (42) are operated by a magnet in a float (34) while the sensor (54) detects movement of a magnet (52) controlled by a pressure sensitive diaphragm (48). During dispense, with the float (34) being sensed in its uppermost position, the sensor (54) reacts to the pressure in the line and the control circuitry (56) operates by way of the sensor (54) to automatically control the pump (24) and maintain pressure in the line at a desired operating level. Regardless therefore of the condition of either tap (30,32), the arrangement provides a substantially constant rate of dispense.

Description

This invention is concerned with improvements in or relating to an arrangement for dispensing liquid, particularly carbonated beverages such as beer, under pressure from a container, for example to dispense in locations in a bar.
In GB-A-1545447, a dispensing arrangement provides for automatic control of the speed of the pump motor in accordance with a change in liquid pressure from a pre-set dispense pressure in the line between the supply and the dispensing tap when the latter is opened. Such control is effected by the action of a pressure switch together with the flow switch which senses liquid flow in the line. When the tap is closed, the flow switch switches off the pump with the line substantially at the dispense pressure. It is an object of the invention to provide an arrangement which provides advantages in relation to such a dispensing arrangement.
According to the present invention there is provided an arrangement for dispensing liquid under pressure from a supply, said arrangement, for moving the liquid in a line between the supply and dispensing means comprising a pump pressure sensitive means and liquid flow sensing means in the line between the pump and the dispensing means and electrical control circuitry operable to switch on the pump in accordance with a reduction in pressure in the line sensed by the pressure sensitive means the control circuitry including means operable by the pressure sensitive means when there is no liquid flow sensed by the liquid flow sensing means to provide a variable output signal proportional to pressure in the line, whereby to automatically and continuously vary the speed of the pump during dispense so as to maintain the pressure in the line at a desired operating level and thus provide a substantially constant rate of dispense, but, when there is no liquid flow sensed by the liquid flow sensing means the control circuitry is operable to drive the pump to cause the pressure in the line to reach a pre-set level above the desired operating pressure level before switching off the pump the control circuitry further being operable to switch off the pump after a pre-set time delay when there is no liquid flow sensed by the liquid flow sensing means and the pressure in the line does not reach the pre-set level, this being indicative of no liquid in the line.
Preferably the control circuitry includes drive means for the pump whereby control of the pump can be effected by automatic adjustment of the spped of the pump. The pump speed may be adjusted by means of phase angle control.
The operating level at which the pressure in the line is maintained may be pre-selected, and may be set by means of a manually adjustable potentiometer included in the control circuitry.
An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Fig. 1 is a schematic view in part section of a liquid dispensing arrangement according to the invention; and
Fig. 2 is a graph showing pressure in the line during operation.

Referring to Fig. 1 of the drawings, a pump control unit comprises a body 10 having a substantially cylindrical cross section defining a through bore 12 and preferably formed of a moulded plastics material. The body 10 has at one end thereof a flange 16 by means of which an internally threaded securing nut 18 is retained on the body 10. The latter is arranged to be connected at said one end by means of the nut 18 to a delivery pipe 20 from a beer cask or barrel (not shown), an electrically operated pump 24 being operatively connected with the pipe 20. At its other end the body 10 has an outlet connection 26 connected by means of a delivery pipe 28 having two branches to respective dispensing taps 30, 32.
In the bore 12 there is located a control member or a float 34 comprising a magnet inserted into a slug preferably of hollow plastics material and sealed with a close-fitting plug. The bore 12 is stepped to define a shoulder 36 which limits movement of the float 34 in an upward direction as viewed in Fig. 1, when beer is flowing and at the lower end of the bore 12 there is provided a retaining bar 38 to retain the float 34 captive in the bore 12. A housing 40, preferably formed of a plastics material, is positioned with one side adjacent to the body 10. A pair of magnetic reed switches 42 are located in the housing 40 at said one side to be positioned close to an upper end of the bore 12, such that when flow of beer in the bore 12 occurs, the float 34 is moved to an upper postion in the bore 12, as shown by dotted lines, alongside the reed switches 42. The affect of the magnet within the float 34 causes the reed switches 42 to move from a normally open to a closed position, thereby enabling flow to be detected.
A through aperture 44 is provided in a wall of the body 10 and is aligned with a through aperture 46 in the closely adjacent wall of the housing 40. Between the body 10 and the housing 40 a diaphragm 48 is located to cover the aligned apertures 44, 46. A spring loaded pressure button 50 in the housing 40 is biassed against the diaphragm 48 such that any change in pressure of beer in the bore 12 results in a lateral movement of the diaphragm 48 and consequently movement of the pressure button 50 against the spring bias. The pressure button 50 has attached thereto a magnet 52 which is associated with a Hall effect sensor 54, the latter being capable of detecting any movement in the magnet 52 and thus in the pressure button 50 due to the pressure in the bore 12. The sensor 54 gives a variable voltage and analogue output according to the position of the pressure button 50, which is proportional to the pressure within the bore 12, whereby the pressure can be sensed.
Electronic control circuitry 56 has, in circuit, the reed switches 42 and the sensor 54 and is also in circuit with the electric pump 24. A manually adjustable potentiometer 58 included in the circuitry 56 is adjustable from externally of the housing 40, and a manual override button 60 is also in circuit with the circuitry 56 and is accessible from externally of the housing 40.
When the taps 30, 32 are closed and there is no flow of beer in the line, the system pressure is high and is at a level (P) predetermined by the control circuitry 56 (see Fig. 2). This level (P) can be factory set and can be nominally set at 50 PSI (3.515 kg/sq.cm). When the tap 30 is opened the system pressure falls below the level (P) and this fall is detected by the pressure sensor 54 due to movement of the diaphragm 48 and the pressure button 50. While there is no flow in the line the control circuitry 56 causes the beer pump 24 to run at full speed. The flow which is subsequently created in the bore 12 raises the float 34 alongside the reed switches 42. The closure of the latter causes the control circuitry to adjust the speed of the beer pump 24 by means of phase angle control until the pressure detected within the bore 12 corresponds to an operating pressure setting C selected by the user by way of the pressure setting potentiometer 58. The control circuitry 56 therefore switches to a constant pressure mode, the system pressure selected by the user determining the speed of dispense at the bar tap 30.
If the tap 32 is then also opened, the system pressure will fall again. The control circuitry 56 is then arranged to automatically adjust the speed of the beer pump 24 until the pressure within the bore 12 once again corresponds to the setting C on the potentiometer 58. In this way the circuitry 56 by means of a closed loop feedback system varies the speed of the beer pump 24 so as to maintain constant pressure in the line, despite anything which may occur so as to otherwise affect the system pressure during dispense. Similarly, when the tap 32 is closed again with the tap 30 still open, the circuitry 56 will operate to maintain the pressure within the system constant at setting C.
When both taps 30, 32 are closed the flow of beer in the line will cease. The fall of the float 34 will close the reed switches 42 to enable the control circuitry 56 to detect that flow has ceased. The circuitry 56 is arranged to then cause the beer pump 24 to run again at full speed, thus causing the system pressure to rise rapidly until the pressure reaches the relatively high preset value (P). When the level (P) is reached the sensor 54, together with the closure of the reed switches 42, causes the circuitry 56 to switch off the beer pump 24. The beer line is then again ready for further dispense.
When the circuitry 56 causes the beer pump 24 to run at full speed, i.e. if flow ceases in the bore 12 causing closure of the reed switches 42, if after a preset time period, for example of 30 seconds, either flow is not sensed by the reed switches 42 as a result of a tap being opened, or the pressure does not reach the preset level (P) if the beer taps are closed, the circuitry 56 operates to switch off the beer pump 24, on the assumption that the beer supply has run out. The manual override button 60 enables this delay period to be restarted when attaching a new barrel or installing the equipment.
There is therefore provided an arrangement wherein, during dispense, the flow rate can be automatically maintained substantially constant, even if a plurality of beer taps fed from a single electric pump had opened simultaneously. Installation and set up are very simple and the arrangement has only one control which requires adjustment by the user, i.e. the pressure setting potentiometer to determine the dispense pressure and therefore the speed of dispense. In between dispenses the line pressure is maintained at a relatively high preset level to help stop breakout of carbon dioxide in very gassy beers. The switching off of the beer pump after the time delay in the event that the beer supply runs out prevents excessive pump wear due to dry running.
It will be appreciated that the closed loop system can be used in any beverage dispense installation so to automatically maintain line pressure and thus flow rate at a substantially constant value during dispense.
Various modifications may be made without departing from the invention. For example control of the pump may be by other than speed control, and the configuration of certain of the components may differ from that described and shown, provided the components function in the required manner.

Claims

1. An arrangement for dispensing liquid under pressure from a supply, said arrangement, for moving the liquid in a line between the supply and dispensing means (30, 32), comprising a pump (24), pressure sensitive means (48, 52) and liquid flow sensing means (34, 42) in the line between the pump (24) and the dispensing means (30, 32), and electrical control circuitry (56) operable to switch on the pump (24) in accordance with a reduction in pressure in the line sensed by the pressure sensitive means (48, 52), the control circuitry (56) including means operable by the pressure sensitive means (48, 52), when there is liquid flow sensed by the liquid flow sensing means (34, 42), to provide a variable output signal proportional to pressure in the line, whereby to automatically and continuously vary the speed of the pump (24) during dispense so as to maintain the pressure in the line at a desired operating level and thus provide a substantially constant rate of dispense, but, when there is no liquid flow sensed by the liquid flow sensing means (34, 42), the control circuitry (56) is operable to drive the pump (24) to cause the pressure in the line to reach a pre-set level above the desired operating pressure level before switching off the pump (24), the control circuitry (56) further being operable to switch off the pump (24) after a pre-set time delay when there is no liquid flow sensed by the liquid flow sensing means (34, 42) and the pressure in the line does not reach the pre-set level, this being indicative of no liquid in the line.

2. An arrangement according to claim 1, characterised in that the control circuitry (56) includes drive means for the pump (24) whereby control of the pump (24) can be effected by automatic adjustment of the speed of the pump (24).

3. An arrangement according to claim 2, characterised in that the pump speed is adjusted by means of phase angle control.

4. An arrangement according to any of the preceding claims, characterised by means (58) for pre-selecting the operating level at which the pressure in the line is maintained.

5. An arrangement according to claim 4, characterised in that the pre-selection means (58) comprises a manually adjustable potentiometer included in the control circuitry (56).

6. An arrangement according to any of the preceding claims, characterised in that the pressure sensitive means comprises a member (50) carrying a magnet (52) and the means associated with the pressure sensitive means comprises a sensor (54) in the control circuitry for detecting movement of the magnet (52).