WO2008119980A1

WO2008119980A1 - Method for controlling a beverage dispenser

Info

Publication number: WO2008119980A1
Application number: PCT/GB2008/001130
Authority: WO
Inventors: Douglas P. Goulet; Balaji Maniam
Original assignee: Imi Vision Limited
Priority date: 2007-03-29
Filing date: 2008-03-28
Publication date: 2008-10-09
Also published as: GB0706084D0

Abstract

A method of controlling a frozen beverage dispenser having a plurality of refrigerated beverage barrels (4) cooled by a refrigeration circuit (2) having a common compressor (14) is disclosed. The refrigerant is supplied to the circuit of a first beverage barrel to cause a partially frozen beverage to form therein. The ice fraction of the beverage of each subsequent beverage barrel is compared to a predetermined value when the ice fraction of the beverage of the barrel being cooled reaches a maximum value. If the ice fraction of the beverage in any subsequent beverage barrel is below the predetermined value, the flow of the refrigerant is switched from the refrigerant circuit of the barrel being cooled to the refrigerant circuit of a subsequent beverage barrel containing beverage having an ice fraction below the predetermined level until the ice fraction of the beverage of all of said beverage barrels is above the predetermined value. The compressor (14) is switched off when the ice fraction of all of the beverage barrels is above the predetermined value and is switched on to supply refrigerant to a beverage barrel when the ice fraction of the beverage falls below a minimum value that is less than the predetermined value.

Description

METHOD FOR CONTROLLING A BEVERAGE DISPENSER

This invention relates to a method of controlling the distribution of refrigerant to the beverage barrels of a frozen beverage machine.

Frozen beverage machines are well known in the art and typically comprise a barrel in which the product is frozen by means of a scraped surface heat exchanger to form a partially frozen slush beverage. The barrels are refrigerated by means of a standard refrigeration circuit comprising a compressor, evaporator and condenser, the evaporator encircling the barrel.

A number of systems are known having a plurality of barrels, some of which have one refrigeration system for each barrel and some of which have one refrigeration system, with multiple evaporators, for all of the barrels.

Systems which have one system control the refrigeration in a number of ways. One way is that when switched on the refrigeration system refrigerates all the barrels and when turned off the refrigeration system does not refrigerate any barrels. This is not a satisfactory system as the product consistency, largely dependent on the percentage of ice, the ice fraction, in the beverage cannot be maintained constant as there is no individual control of the various barrels.

An alternative system monitors the product within each barrel, either by monitoring the temperature or the ice content, and turns on the refrigeration system and opens valves to enable the refrigerant to be supplied to the requisite barrel as and when needed. This provides a good system that enables a good control of the product consistency. However as the three barrels are controlled independently the compressor is started up and shut down repeatedly and is only on for short periods at any one time. This cyclic operation has a detrimental effect on the life of the compressors and compressor failure is a common complaint in systems operated in this way. The present invention attempts to mitigate these problems.

According to the present invention there is provided a method of controlling a frozen beverage dispenser having a plurality of refrigerated beverage barrels cooled by a refrigeration circuit having a common compressor, comprising the steps of:

a) supplying refrigerant to the circuit of a first beverage barrel to cause a partially frozen beverage to form therein;

b) monitoring the ice fraction of the beverage within each of the first and at least one subsequent beverage barrel;

c) comparing the ice fraction of the beverage of the at least one subsequent beverage barrel to a predetermined value when the ice fraction of the beverage of the barrel being cooled reaches a maximum value;

d) switching the flow of the refrigerant from the refrigerant circuit of the barrel being cooled to the refrigerant circuit of a subsequent beverage barrel containing beverage having an ice fraction below the predetermined level when the ice fraction of the beverage in any subsequent beverage barrel is below said predetermined value; and

e) switching off the compressor when the ice fraction of the beverage within all the beverage barrels is above the predetermined value.

Preferably, when the beverage dispenser has three or more beverage barrels then, prior to step turning the compressor off, the method further comprises repeating steps c) and d) until the ice content of all of said beverage barrels is above a predetermined value.

Preferably there are at least three ice fraction values used in the control method, the maximum required value and a minimum required value which define the envelope in which the beverage is within its specification, and the predetermined value, which is between the minimum and the maximum value.

Instead of switching the compressor and refrigeration on and off for each barrel based only on maximum and minimum ice fraction values, as is standard practice with conventional dispensers, in the present method whenever the compressor is running and the ice fraction of the beverage in the barrel it is refrigerating reaches a maximum value the control system compares the ice fraction of the beverage in the other barrels to the predetermined value and if it is below the predetermined value then instead of turning the compressor off, as in conventional control systems, the flow of refrigerant is switched to that barrels.

Once the compressor is turned off it will not turn on again until the ice fraction of one of the barrels falls below its minimum required value.

The result of this control strategy is that the compressor will only turn off if the ice fraction of the beverage in all of the barrels is above the predetermined value. This causes longer compressor on times and longer compressor off times at a greater time interval than in conventional control systems thereby reducing cycle rate of the compressor and increasing its life.

The predetermined value may be up to the maximum required value but is preferably lower to prevent constant short time interval switching of the refrigerant flow between all of the barrels.

In one preferred method, where the dispenser has three or more barrels and in step d) the ice fraction of the beverage in two or more barrels is below the predetermined value, the refrigerant supply is switched to the refrigeration circuit of the barrel having the lowest ice fraction In an alternative preferred method where the dispenser has three or more barrels and in step d) the ice fraction of the beverage in two or more barrels is below the predetermined value the refrigerant supply is switched to the refrigeration circuit of the barrels containing beverage with an ice fraction below the predetermined value in a sequential order.

Preferably the method of monitoring the ice fraction of the product in the barrels comprises directly measuring the ice fraction. Alternatively the method of monitoring the ice content comprises monitoring the viscosity of the beverage, said viscosity being directly related to the ice fraction.

In a preferred embodiment of the invention the beverage barrels comprise: a refrigerated cylindrical outer wall; an impeller means located substantially on the central axis to rotate the beverage within the barrel; and a cage, positioned adjacent the barrel wall, which is rotated by means of fluid coupling with the impeller via the beverage. The viscosity of the beverage is then monitored by measuring the rotation speed of the cage in the barrel. As the ice fraction increases the beverage becomes more viscous and the speed of rotation of the cage reduces, therefore measuring the speed of the rotation of the cage gives a signal indicative of the ice fraction.

Preferably, during initial start up when none of the barrels contain any ice fraction, the refrigerant is supplied to all of said beverage barrels until the ice fraction of at least one of said beverage barrels reaches the required value.

Preferably any of the plurality of barrels can be excluded from the control system. In this way a single barrel can be taken off line, for example to flush the barrel out between changing flavors, whilst the other barrels continue to freeze and dispense beverage.

In one preferred arrangement, if the ice fraction of any barrel goes below its minimum value then, providing the beverage in the other barrels has an ice fraction between its minimum and maximum values, refrigeration will immediately be switched to the barrel having an ice fraction below its minimum value. This enables the control system to break out of its mode of operation and switch refrigeration from one barrel to another before the predetermined value of ice fraction is achieved in the barrel it is refrigerating. This prevents the ice fraction of beverage in any of the barrels from falling below the minimum required value and therefore maintains the quality of the dispensed beverage.

Specific embodiments of the invention will now be described, by way of example, with reference to the drawings in which:

Figure 1 is a diagram of a beverage dispenser having a control system according to the invention.

Figure 2 is a diagram of a refrigerated beverage barrel having a cage used to determine the ice fraction of the beverage within the barrel.

Referring to Figures 1 and 2, a refrigerating circuit of a machine for producing and dispensing iced beverages, generally denoted by 2 is shown. The machine comprises a plurality of beverage-containing barrels 4, each provided with an evaporator 6 for a refrigerating circuit. Advantageously, the evaporator is of a type provided with a coiled tube in thermal contact with the outer surface of the barrels 4. Also provided within the barrel is a central impeller 8 driven by a motor 10 at 1000 to 2000 rpm. Also within the barrel 4 is a cage 12 which rotates freely within the barrel. A dispensing valve 32 is at one end of the barrel and allows for frozen beverage to be dispensed therefrom.

The evaporators 6 are connected with one and the same compressor 14 by means of solenoid valves 16 for selective connection and shut off of the evaporators 6 to and from the refrigerating circuit respectively.

The refrigerating circuit comprises known elements for these types of circuits, such as a condenser 18 having forced ventilation circuit 20, a capillary tube 22, a filter 24. An accumulator 26 of appropriate volume may be also present for collecting the outputs of all evaporators 6 and connect them to the compressor 14.

The machine 2 comprises a control system 28 comprising a microcontroller. The control system 28 receives signals from the barrel indicative of the viscosity of the beverage within the barrel. As the viscosity is related to the ice fraction of the beverage the signal can be used in the control system 28 to maintain ice fraction of the beverage within a desired range. The signals are received from a Hall Effect sensor which registers the passing of a magnet attached to one end of the cage 12. As the cage 12 is driven by the impeller 8 via a fluid coupling through the beverage, a change in viscosity associated with an increase or decrease in the ice fraction of the beverage will cause the speed of rotation of the cage 12 to decrease or increase respectively.

In use on start up the motor 10 rotates the impellers 8 which cause beverage within the barrels 4 to rotate. The rotating fluid forms a hydraulic coupling to the cage 12 which in turn also starts to rotate within the barrel. As the cage 12 rotates the magnets in the end of it pass the Hall Effect sensor and a signal is generated. In the start up condition when the beverage within the barrels is liquid refrigerant is supplied to the evaporators of the barrels via the refrigeration system. Preferably during start up refrigerant will be supplied to all of the barrels simultaneously. As the refrigerant passes through the evaporators it cools the barrel and beverage starts to freeze on the inside of the barrel. The rotating cage 12 harvests the ice off the walls and the cage 12 and impellers 8 mix the ice with the beverage to produce a substantially homogeneous mixture. The ice fraction of the beverage will continue to increase as more beverage is frozen and mixed with the liquid beverage until it reaches a maximum value of required ice fraction desired in a dispensed beverage, typically in the region of 40-45%, although obviously this is a matter of preference in consistency of the dispensed drink. The ice fraction is measured indirectly by monitoring the speed of rotation of the cage 12 as described above. When the maximum value is reached in a barrel 4 the control system 28 sends a close signal to the valve 16 controlling the flow of refrigerant to that particular barrel thereby shutting off its refrigerant flow. The impeller 8 continues to be rotated by the motor 10. The other valves 16 remain open until such time as the maximum value of ice fraction is reached in all the barrels.

When the barrel 4 being supplied with refrigerant reaches the maximum value of ice fraction the control system 28 monitors the ice fraction of the other barrels 4 and, if they are below a predetermined value which is between the maximum value and a minimum value of required ice fraction, signals are sent to the valves 16 by the control system 28 to switch the flow of refrigerant to the barrel 4 having an ice fraction below the predetermined value. If more than one barrel 4 has an ice fraction below the predetermined value then the flow of refrigerant will be switched to the barrel 4 having the lowest ice fraction. This process is repeated until all of the barrels 4 have an ice fraction that is above the predetermined value. When the beverage in a barrel 4 being supplied with refrigerant reaches the maximum value of ice fraction, and all the other barrels 4 have an ice fraction above the predetermined value then the compressor 14 is switched off. The motors 10 continue to rotate the impellers 8 in the barrels 4 and the control system 28 continues to monitor the ice fraction of the beverage. Over time the barrel 4 will absorb heat from the atmosphere and the rotation of the impeller 8 will impart a small amount of energy into the beverage. In addition beverages may be dispensed from the barrel 4 and replaced with unfrozen beverage. The result being that over time the ice fraction within the barrels 4 will drop. When the control system 28 detects that the ice fraction in any of the barrels 4 has fallen below a minimum value of required ice fraction then the compressor 14 is started and the valves 16 operated to supply refrigerant to the required barrel. Once the ice fraction of that barrel 4 reaches the maximum value the above process of looking at the ice fraction in the other barrels and if necessary switching the flow of refrigerant thereto is repeated. Due to the frequency and shortness of the duty cycle beverage machines of the type described herein are particularly susceptible to compressor failure. By this method of control the compressor 14 has longer runtimes and a lower duty cycle which greatly extends the life of the compressor providing a more robust system. If, while supplying refrigerant to a barrel 4, at any point in the above process the ice fraction of beverage in a different barrel falls below the minimum value then the control system 28 operates the valves 16 to supply refrigerant to that barrel. This may be done simultaneously with supplying refrigerant to the barrel initially being refrigerated or supply of the refrigerant may be completely switched to the barrel with an ice fraction below the minimum value, either way the purpose being that during normal operation the ice fraction of beverage in the barrels should not be allowed to fall below minimum value without immediately being refrigerated.

The beverage dispenser also incorporates a user interface 30 by which the operator can choose to manually isolate particular barrels 4 from the refrigeration control system by turning off the supply of refrigerant to the barrels 4 by means of valve 16. In addition the impeller 8 for the same barrel may be manually switched off. By this method one barrel can be taken off line for example, for flushing out between having different flavored beverages therein.

The system as described herein may be used for creating and dispensing frozen un- carbonated beverages or frozen carbonated beverages.

Alternative embodiments of the invention will be apparent to those skilled in the art, for example alternative methods of monitoring beverage viscosity such as measuring torque on the motor driving the impeller, and while this control method is described in relation to a specific design of beverage barrel it is equally applicable to any of the current known designs of frozen beverage dispensers, and such alternatives are within the scope of the invention

Claims

1 A method of controlling a frozen beverage dispenser having a plurality of refrigerated beverage barrels cooled by a refrigeration circuit having a common compressor, comprising the steps of:

2 The method according to claim 1 wherein, prior to switching off the compressor, the method further comprises repeating steps c) and d) until the ice fraction of the beverage of all of said beverage barrels is above the predetermined value.

3 The method according to claim 1 or claim 2 further comprising the step of: f) starting the compressor and supplying refrigerant to a beverage barrel when the ice fraction of said beverage falls below a minimum value, that minimum value being less than the predetermined value.

4 The method according to claim 3 wherein the minimum value and the maximum value define the range for which a dispensed beverage is at the required consistency.

5 The method according to any of the preceding claims wherein the predetermined value for ice fraction is below the maximum required value.

6 The method according to any of the preceding claims wherein, in step d), the refrigerant supply is switched to the refrigeration circuit of the barrel having the lowest ice fraction.

7 The method according to any one of claims 1 to 5 wherein, in step d), the refrigerant supply is switched to the refrigeration circuit of the barrels containing beverage with an ice fraction below the predetermined value in a sequential order.

8 The method according to any of the preceding claims wherein the means of monitoring the ice fraction comprises directly measuring the ice fraction.

9 The method according to any one of claims 1 to 8 wherein the means of monitoring the ice fraction comprises monitoring the viscosity of the beverage, said viscosity being directly related to the ice fraction.

10 The method according to any of the preceding claims wherein the beverage barrels comprise: a refrigerated cylindrical outer wall; an impeller located on the central axis to rotate the beverage within the barrel; and a cage, positioned adjacent the barrel wall, which is rotated by means of fluid coupling with the impeller via the beverage. 11 The method according to claim 9 and claim 10 wherein the viscosity of the beverage is monitored by measuring the rotation speed of the cage in the barrel.

12 The method according to any of the preceding claims wherein, during initial start up, when the beverage in the barrels has little or no ice content, the refrigerant is supplied to all of said beverage barrels until the ice fraction of at least one of said beverage barrels reaches the required set ice value.

13 The method according to any of the preceding claims wherein any of the plurality of barrels can be excluded from the control system.

14 The method according to any of the preceding claims wherein if the ice fraction of any barrel goes below its minimum value then, providing the beverage in the other barrels has an ice fraction between its minimum and maximum values, refrigeration will immediately be switched to the barrel having an ice fraction below its minimum value.