Technical Field

This invention relates to cooling and dispensing systems for beverages, and in particular to systems having both a pre-cooler for the beverage and a frosted dispensing font of the type known as an "ice tower".

Background of the invention

Traditional coolers for beverages such as alcoholic and non-alcoholic beers, ciders and the like, can take several forms. On popular form is the "shelf cooler" which is generally positioned close to the dispensing point in a bar, i.e. the tap.

In this specification, reference is made to chilling and dispensing beer as an example of the most common cold beverage dispensed in bars, but it is to be understood that the systems being described can equally be used to dispense any other suitable beverage, and it is fully envisaged that such systems are also used for ciders, perries, so-called alcopops (mixtures of spirits and minerals or sodas) and even cold liqueurs and spirits.

In recent years it has become popular to chill the font on which the dispensing tap is mounted and through which the beverage flows. By chilling the exterior of this font to sub-zero temperatures, a layer of ice can be formed from the atmospheric humidity on the outside of the font. When caused to form over the entire outer surface of a portion of the font, the effect is that of a tower of ice. Such fonts are variously known as "ice fonts", "frosted fonts", or most commonly "ice towers". An ice tower serves two purposes. It provides a certain refrigerating effect to the beer just before it is dispensed. The refrigerating effect provided by an ice tower is not usually efficient enough to replace a dedicated cold room or shelf cooler, particularly during busy times when throughput is high. However at quieter times an ice tower will help ensure that beer standing in the dispensing line between the cooler and the tap remains cold.

The second purpose of an ice tower is for its cosmetic and marketing value, i.e. the sight of a beer tap emerging from an ice tower conveys to the customer that the beer is truly cold and refreshing, as well as having novelty value to make the tap stand out from the other products available at a bar.

In conventional shelf coolers, an ice-and-water bath is maintained using a refrigeration circuit and the beverage flows through a coil immersed in the ice-and-water bath. The temperature of the bath is indirectly controlled by controlling the thickness of the ice. A two-prong probe may be immersed in the water with a current passing between the prongs. When ice forms around the probe, the conductivity drops and the compressor is switched off. Alternatively, a mechanical thermostat is employed in which gas within a marrow tube expands or contracts to act on a bellows which mechanically switches the refrigeration circuit on and off.

Such systems cannot be used to create an ice tower, as the low temperatures required to condense frost from the air cannot be reached.

It is therefore necessary to employ a sub-zero fluid, such as a solution of monopropylene glycol in water, and to circulate this fluid within the font to chill the font to a sub-zero temperature (i.e. below zero degrees centigrade). The most straightforward and common approach is to provide two coolers. One cooler is a conventional ice-and-water beer cooler, while the other is used to cool a reservoir of sub-zero fluid (e.g. a 30:70 or 40:60 glycohwater mixture with a freezing point of -25°C to -30°C) which is then circulated by a pump from the reservoir or bath, through the font, and back to the bath. Such systems are inefficient and wasteful, as well as consuming valuable space under the bar.

An alternative approach is shown in Fig. 1 . This system involves two tanks 12,14, both filled with a sub-zero coolant 16, e.g. a 40:60 glycohwater mixture or glycol in tank 12 and water in tank 14. A primary refrigerating circuit comprising a compressor 18, condenser 20 and evaporating coil 22 cools the coolant in tank 12 in known manner. Operation of the compressor (and therefore of the refrigerating circuit) is controlled by a thermostatic switch 24 based on the output of a temperature sensor 26. This refrigerating circuit maintains (or aims to maintain) the volume of coolant 16 in tank 12 at a temperature of -5 ± 1 °C.

Coolant is pumped from this tank to and from the internal channels in a dispensing font (not shown) via pipes 28 so as to cause an ice tower effect to be created on the font surface due to condensation and freezing of ambient moisture. The coolant in tank 12 is used to drive a secondary refrigerating circuit for tank 14. Coolant is pumped by a pump 30 to a coil 32 in tank 14 via a feed pipe 34, and the circuit back to tank 12 is completed via a return pipe 36. Pump 30 is thermostatically controlled by a temperature sensor 31 in tank 14. Coil 32 in tank 14 cools down a glycohwater mixture or water:ice bank within that tank, typically to a temperature of about -2°C- 0°C such that beer pumped through a beer coil (or "python") 38 is chilled as it travels between a keg (not shown) and a dispensing tap mounted on the same chilled font which was fed by the pipes 28 (although there is no reason why the beer tap cannot be on a different font).

The solution of Fig. 1 is less bulky than two separate coolers, and there is some economy of construction, with only a single compressor and condenser being required. In practice, however, problems have been found.

Firstly, the use of a glycol/water mixture to cool the beer is satisfactory when flow rates are low, but at busy times, such as when several litres of beer are poured continuously from the tap, the transfer of heat from the beer in coil 38 to the coolant 16 in tank 14 can overwhelm the refrigerating capacity of the system. The coolant in the coil 32 heats up and as it returns to tank 12, the volume of coolant in that tank heats up also, with the result that the ice tower may be melted due to high beer flow through the cooler python coil. While one can attempt to overcome this problem by turning down the thermostat 26 in tank 12, this has the result that the font is chilled to a sufficiently low temperature that beer freezes inside it at quieter times when flow is low or non-existent.

It has also been found that the dual tank system is inefficient and that the compressor is continuously switching on and off due to complex interaction and load balancing between the primary refrigerating circuit and the secondary refrigerating circuit, and due to the strong influence played by the beer flowing through the second tank 14.

It is not possible to simply place the beer coil into the same glycol-filled tank as is used to drive the ice tower circuit because this would exacerbate the problem of the warming effect of the beer on the coolant used in the font. Cooling the coolant further would also run the risk of the beer freezing in the coil.

A further problem with systems of this kind, in which glycol/water is used as a coolant system, is that the tank through which the beer passes is kept at a sub-zero temperature. Cleaning of beer lines requires passing a cleaning solution (primarily water) through the line and leaving it sit in the line for a period of time. If part of the beer line is kept below 0°C, then the coolant will freeze. Therefore, glycol-based coolers, and in particular those which must be operated at a sub-zero temperature due to the requirements of an ice tower, are generally flushed through with warm water for a period of time until the coil is no longer in danger of freezing, or they are switched off for a period before the cleaning operation begins. Disclosure of the Invention

There is provided a cooler which forms a bank of frozen, sub-zero coolant on a heat exchanger inside a tank containing coolant also in liquid form, where a beverage coil is immersed in the liquid coolant for routing and chilling a beverage, and where the liquid coolant is used as a reservoir for a coolant circuit to a font to provide an ice tower.

In contrast to known ice bank type coolers which detect the formation of ice and thereby control the temperature indirectly, this cooler employs a liquid temperature probe to ensure the liquid coolant is kept at the required temperature, with the ice bank being permitted to form out to the point of the probe. This provides a single tank solution which achieves the cooling of beer and the chilling of a font which can only be achieved in conventional systems using two tanks. Conventional single tank solutions can only either chill the font or cool the beverage.

Preferably, said coolant has a freezing point of between 0 and 1 °C above the freezing point of the beverage being dispensed. In this way, the tank can hold a bank of frozen coolant on the heat exchanger, and generally this will surround a volume of slightly warmer coolant which is just at or slightly above the freezing point of the beverage.

Preferably, said heat exchanger forms part of a refrigeration circuit which circulates refrigerant through a refrigeration cycle.

More preferably, said refrigerating circuit comprises a compressor, a first heat exchanger located outside the reservoir and adapted in normal operation to receive compressed, hot refrigerant and to disperse heat to the atmosphere, and a second heat exchanger located in the reservoir and adapted in normal operation to receive cooled refrigerant and to absorb heat from coolant in the reservoir.

Preferably, said tank is in the form of an insulated bath, and said heat exchanger is located adjacent a sidewall of the bath. The cooler preferably further comprises an agitator pump to agitate the liquid sub-zero coolant against the frozen coolant bank. Further, preferably, pumping means are provided to pump the subzero fluid through said coolant circuit to a font.

Preferably, a temperature probe is positioned at the interface between said frozen coolant bank and said liquid sub-zero coolant.

Further, preferably, an electronic control device is connected to the temperature probe, and provides thermostatic control of the temperature of the liquid sub-zero coolant and the thickness of the frozen bank of coolant.

Further preferably, the thermostatic control is set to maintain a temperature of between -4.5 and -2.5°C, more preferably about -3.5°C with a differential of about +/- 0.5°C. Most preferably, the thermostat is set with a differential of about 0.5°C such that the refrigeration circuit is activated 0.5°C above a set point and deactivated at the set point. The set point will be chosen according to the coolant freezing point and the beverage freezing point to ensure a sufficient ice bank.

Preferably said coolant is a freezing point depressant comprising a mixture of glycol and water, mixed to provide a glycol concentration of 10%.

In another aspect there is provided a cooler for beverages, the cooler having a reservoir for holding a volume of sub-zero coolant and a refrigerating circuit which is set to operate at or below zero degrees Celsius, where the refrigerating circuit has a compressor, a first heat exchanger located outside the reservoir and adapted in normal operation to receive compressed, hot refrigerant and to disperse heat to the atmosphere, and a second heat exchanger located in the reservoir and adapted in normal operation to receive cooled refrigerant and to absorb heat from coolant in the reservoir, the circuit also comprising a divert valve operable in a cleaning mode of operation to divert hot refrigerant into said second heat exchanger to thereby actively heat the coolant in the reservoir.

Brief Description of the Drawings

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a schematic view of a known cooler for chilling an ice font and chilling beer; and

Fig. 2 is a schematic view of a single tank cooler for chilling an ice font and chilling beer. Detailed Description of Preferred Embodiments

In Fig. 2 there is indicated generally at 40 a beer cooler having a complete refrigeration system that includes a compressor 42, a condenser 44 and evaporator 46 all interconnected by fluid delivery conduits 48 for delivering refrigerant through the system. A fan 50 directs air at the condenser 44 to improve efficiency.

An insulated bath 52 holds the evaporator at the side of the walls of the bath. Also within the bath is a product (beverage) coil 54, in the form known as a "python" with an inlet 58 and outlet 56 for the product to pass through. There may be a plurality of product coils.

An agitator pump 60 is provided to agitate the liquid subzero coolant 62 against a frozen coolant bank 64 which forms in the vicinity of the evaporator coils 46 around the walls of the tank 52. This pump also pumps the subzero fluid within the bath to the dispensing font (not shown) creating an ice tower effect. The font is supplied with subzero coolant from the bath via an outlet 66, and returns via an inlet 68.

An ice bank control device 70 such as a probe, is positioned between the interface of the frozen and liquid sub-zero coolant. An electronic control device 72 is connected to the probe, and is set at -3.5°C with a differential of +/- 0.5°C to control the temperature of the subzero fluid 62 and the thickness of the frozen bank of coolant 64. The coolant used is the freezing point depressant sold by Innserve (Tadcaster, North Yorkshire, UK) under the trade mark InnCool, but mixed to provide a glycol concentration of 10% rather than the 7%-8% recommended by the manufacturer.

A defrost switch 74 bypasses the normal electronic control device 72 of the refrigerated cooler, turning on the compressor 42. A defrost light indicator 76 indicates that the cooler is in defrost mode. The defrost switch 74 controls a solenoid 78 to activate a diverter valve to reverse the heat transfer direction of the refrigerated system, heating the evaporator 46. Thus, when in cleaning or defrost mode, the bath 52 can be quickly heated, by the circulation of hot gas from the compressor 42, to above the freezing point of the cleaning solution, without the necessity of flushing the system with warm water or waiting for an extended period of time for the system to defrost.

By diverting hot refrigerant directly through the evaporator in the tank, and actively heating the bath, a cleaning solution passed through the beverage coil does not freeze. By avoiding a passive defrost one can thereby speed up the cleaning cycle. The invention is not limited to the specific embodiments which may be modified without departing from the scope of the claimed invention.