GB2262364A - Refrigerated units for the display of goods - Google Patents

Abstract

A refrigerated unit (1) for the display of goods comprising a cool compartment (3); a refrigeration unit operable to maintain the cool compartment (3) at a predetermined temperature; and a controller (20), the controller (20) being operable repeatedly to interrupt the operation of the refrigeration unit (2) for a second interval, if, after a first interval, the temperature of the cool compartment (3) is above said predetermined temperature. The evaporator (10) is disposed at the top of the cool compartment. <IMAGE>

Description

REFRIGERATED UNITS The present invention relates to refrigerated units and a method for controlling the same, and more particularly, although not exclusively, to such units in the form of refrigerated showcases.

Refrigerated showcases are used to display goods, such as dairy produce for example, which need to be kept below normal ambient temperature. Items required for purchase can be removed from the showcase and the latter is restocked from time to time. Such units normally comprise a refrigeration unit and a display compartment cooled by the refrigeration unit.

Prior art refrigerated showcases are as a result of their compressors being driven continuously when the temperature of their internal cool compartment exceeds that desired, prone to layers of frost forming on the exterior surface of the evaporator. This frost formation is highly undesirable as it progressively impairs the efficiency of the refrigeration unit as the thickness of the frost layer increases.

In known refrigerated showcase units the standard method of cooling the display compartment is to blow air upwardly into the cool compartment. This is inefficient, because the cold air produced at the evaporator has a greater density than the rest of the air in the display compartment and, therefore, has a propensity to sink to the bottom of the cool compartment. Since the evaporator is connventionally situated at the bottom of the display compartment energy must be expended in keeping the top of the display compartment sufficiently cold.

Accordingly, it is an object of the present invention to provide a more efficient refrigerated unit.

In one aspect the present invention provides a refrigerated unit comprising a cool compartment; a refrigeration unit operable to maintain the the cool compartment at a predetermined temperature; and a controller, the controller being operable repeatedly to interrupt the operation of the refrigeration unit for a second interval, if, after a first interval, the temperature of the cool compartment is above said predetermined temperature.

Preferably the controller is further operable, when the temperature inside the cool compartment is not greater than the predetermined temperature, to interrupt unconditionally the operation of the refrigeration unit.

To this end, the controller preferably further includes a temperature sensor for sensing the temperature of the cool compartment; a user-adjustable temperature setter to select said predetermined temperature within the cool compartment; and comparison means responsive to the temperature sensor and the temperature setter to provide an output indicative of the difference between the actual and predetermined temperatures and to deactivate the refrigeration unit when the temperature in the cool compartment substantially equals the predetermined temperature.

The temperature sensor, the temperature setter and the comparison means may coveniently be embodied as a conventional thermostat.

The controller may further comprise resettable timing means operable to provide the first and second intervals and the timing means may comprise a first timer operable to provide the first interval, and a second timer operable to provide the second interval. The first and second timers may be arranged to reset each other on timing out.

In another aspect the present invention provides a method of controlling a refrigerated unit comprising a cool compartment and a refrigeration unit operable to maintain the cool compartment at a predetermined temperature, the method involving repeatedly performing the steps of interrupting the operation of the refrigeration unit for a second interval if, after a first interval, the temperature of the cool compartment is above said temperature.

The first and second intervals may both be conveniently selected to be of constant duration.

In a still further aspect the invention provides a refrigerated unit comprising a cool compartment and a refrigeration unit wherein the evaporator of the refrigeration unit is disposed at the top of the cool compartment.

Exemplary embodiments of the invention will hereinafter be described with reference to the accompanying drawings, in which Figure 1 shows a schematic view of the physical layout of a refrigerated showcase according to the present invention; Figure 2 shows a schematic perpsective view of a refrigerated showcase in accordance with the present invention, which exemplifies the air flow within the cooled cool compartment; Figure 3 is a block diagram of a controller shown in Figure 1; and Figure 4 shows a schematic exemplary graph of temperature versus time for the showcase depicted in Figure 1 and controlled in accordance with the present invention.

A refrigerated unit in the form of a refrigerated showcase, generally denoted 1, has two compartments, an upper cool display compartment 3 and a lower compartment 4.

The boundary between the upper compartment 3 and the lower compartment 4 is defined by the display floor 6, the display floor preferably having an array of orifices formed therein. An evaporator 10 of conventional finned tube construction having a high pressure inlet and a low pressure outlet is disposed at the top of the cool compartment 3 together with an expansion valve 12, also of conventional construction. A drainage duct 5 is disposed immediately beneath the evaporator 10. The drainage duct 5 is provided with two drain tubes 8 at opposite longitudinal ends thereof (one shown) which extend from the drainage duct 5 into a drip tray 7 which is disposed in the lower compartment 4. The drainage duct 5 and the draining tubes 8 are depicted into dotted rotation for the sake of clarity.The high pressure inlet of the evaporator 10 is connected to a conduit 17, via expansion valve 12, and the low pressure outlet is connected directly to conduit 18, both conduits 17 and 18 respectively extending from the evaporator 10 down the rear portion of the cool compartment 3 into the lower compartment 4. On entering the lower compartment 4, conduits 17 and 18 connect to a condenser 16 and a compressor 14, respectively. An intermediate conduit 19 is provided between the compressor 14 and the condenser 16, whereby the evaporator 10, the compressor 14 and the condenser 16 constitute a conventional refrigeration unit 2. The compressor 14 is driven by a motor 15. The refrigerated showcase 1 is further provided with a fan 23 (as best shown in Figure 2), driven by a fan motor 25 and mounted adjacent the evaporator 10.The compressor motor 15 and the fan motor 25 are both controlled by a controller 20 which is hereinafter described with particular reference to Figure 3.

The controller 20 includes a temperature sensor 21, mounted at the top of the rear wall of the cool compartment 3, for measuring the temperature within the cool compartment 3, and more specifically the temperature of the air at the air-flow input of the fan 23; a user-adjustable temperature setter 27 to select the desired temperature within the cool compartment 3; a resettable timing means 30 for providing, after it has been reset, an activation signal indicative of a first selectable interval after said reset, and a deactivation signal indicative of a second selectable interval after the end of the said first interval.

The activation and deactivation signals may be provided by timing means 30 in the form of two coupled timers (not shown), the first of which provides an activation signal indicative of the first interval, and the second of which is reset by the first timer when the latter times out and provides a deactivation signal indicative of the second interval. The first timer is reset when the second timer times out and so on. The timing-out of each timer may be detected by a pulse generator (differentiator) to effect the resetting of the other timer Alternatively, the activation and de-activation signals may be provided by timing means 30 in the form a single timer (not shown) having one digital binary output in the form of, for example, a mark portion (HIGH) representing the activation signal, the space portion (LOW) representing the deactivation signal.

The controller 20 also includes comparison means 29 responsive to the temperature sensor 21 and the temperature setter 27 to provide an output indicative of whether the temperature inside the cool compartment 3 is less than that desired. In use the controller 20 is operable, when the comparison means 29 output indicates that temperature inside the cool compartment 3 is not greater than the selected temperature, to interrupt the operation the compressor 14 irrespective of the output signal of the timing means 30, the controller 20 being further operable, when the comparison means 29 output indicates that the temperature in the cool compartment 3 is greater than the selected temperature, to activate or deactivate the compressor 14 solely in accordance with the output of the timing means 30.

In this embodiment of the invention the comparison means 29, the temperature setter means 27, and the timing means 30 may be implemented on a single timer board 24.

The temperature sensor 21 communicates with the timer board 24 via temperature readout means 22, which also serves to provide a visual indication of the actual temperature in the cool compartment 3.

In another embodiment of the invention (not shown), the temperature sensor 21, the temperature setter 27 and the comparison means 29 are embodied as a conventional thermostat.

The operation of the refrigerated unit 1 will be hereinafter described. Assuming the showcase 1 is empty and at room temperature and is now required to be filled with goods, for example dairy produce, soft cheese or cold meats, which have to be maintained at a predetermined temperature, the showcase 1 is opened using doors and or flaps in the casing (not shown) and loaded with the required goods.The required temperature within the cool compartment 3 is then set using the temperature setter 27 and the refrigeration unit 2 switched on, whereby the normal refrigeration cycle will take place, ie the compressor 14 will compress the refrigerant and apply it under pressure; in the form of "hot" gas, to the condenser 16 which condenses the gaseous refrigerant into a "warm" liquid which is then passed to the expansion valve 12 and thence to the evaporator 10 and finally back to the compressor 14. As this cycle repeats, the temperature within the cool compartment 3 will reduce and without the present invention, the normal operation would be for the compressor 14 to operate continuously until such time as the temperature within the cool compartment 3 reaches the selected value.

With the compressor 14 operating continuously, frost begins to form on the fins of the evaporator 10 in growing amounts and in so doing, the efficiency of the refrigeration unit 2 decreases. In accordance with the present invention, the operation of the refrigeration unit 2 is interrupted after a predetermined period of time from being rendered operative, this period of time depending on the size of showcase but may be for example, of the order of 15 minutes. Both this period, the activation period (ie 15 minutes), and the deactivation period (typically approximately 1 minute) are set into the timing means 30.

With particular reference to Figure 4, when the refrigeration unit 2 is first switched on, see point A, the timing means 30 is reset. After the predetermined first period of operation, the activation period of 15 minutes (point B), the refrigeration unit 2 is rendered inoperative irrespective of the fact that the temperature of the cool compartment 3 is not yet at the selected temperature. The melting of the frost is promoted at this point by the occurance of a 'thermal syphon' in the refrigeration unit 2.This 'thermal syphon' occurs because as the compressor 14 is inoperative, the refrigerant in the conduit 17 is under less pressure than during the first interval, and hence as the refrigerant flows into the evaporator 10, via expansion valve 12, little or no expansion of the refrigerant occurs, thereby producing a reduced temperature drop in the refrigerant which serves to melt the frost on the evaporator 10 andsresults in a temperature increase in the cool compartment 3. The melting frost is collected by the drainage ducts 5 and passes down the drainage tubes 8 into the drip tray 7. The disposition of the drip tray 7 with respect to the condenser 16 and the conduit 17 is such that cold water in the drip tray 7 serves to aid the cooling of the refrigerant in the condensor 16. This temperature rise is depicted by the line BC.After having been interrupted for the deactivation period of 1 minute, the refrigeration unit 2 is rendered operative again.

If the cool compartment 3 is still not at the required temperature after the elapse of the first period of time, then again the refrigeration unit 2 will be interrupted and so on until the cool temperature is at the required temperature at which time the controller 20 will serve to switch off the refrigeration unit 2 regardless of the output of the timimg means 30 (point E). With normal use of the refrigerated showcase 1, the required temperature within the cool compartment 3 will not normally rise dramatically due to the dispensing of goods therefrom and replacing them but when it does depart from the required temperature, the controller 20 will switch back in the refrigeration unit 2 while at the same time resetting the timing means 30.The refrigeration unit 2 will probably only operate for a few minutes in order to bring the temperature back to that required. Therefore, provided the temperature within the cool compartment 3 is brought back to the desired temperature prior to the first period of time (eg 15 minutes) elapsing, then the timing means 30 will not time-out. These minor fluctuations in the temperature within the cool compartment 3 are illustrated by F and G. However, if the door or flap of the showcase is left open, for example, and/or the showcase is replenished and/or further loaded with goods at room temperature, then a rise in the temperature of the cool compartment 3 is to be expected, this is shown as point H.

In an effort to return the temperature of the cool compartment 3 to the selected temperature, the refrigeration unit 2 may well normally operate for longer than the first predetermined period of time, whereupon the timing means 30 will time-out and the refrigeration unit 2 will be interrupted as already explained. This situation is illustated by the line HI.

It is bedause the refrigeration unit 2 is virtually always operating at maximum efficiency because frosting of the evaporator is not permitted to any great extent, then the overall period of time in which a showcase 1 is brought to its required temperature from ambient temperature is very significantly reduced even though one might expect it to be increased having regard to the fact that the operation of the refrigeration unit 2 is interrupted.

Accordingly, the present invention affords a significant adavance in the art and can be applied to any refrigerated unit and not just to refrigerated showcases in connection with which it has primarily been discussed. It will be appreciated that while the conduits 17,18 and the drainage tubes 8 have been depicted as intruding significantly into the main volume of the cool compartment 3, in practice, they are by reason of obvious aesthetic considerations likely to be hidden behind a partition (not shown) towards the back of the cool compartment 3 or actually fed outside the cool compartment 3 itself before entering the lower compartment 4.

The efficiency of operation is further improved due to the disposition of the evaporator 10 at the top of the cool compartment 3. The disposition of the the temperature sensor at the fan inlet ensures that the temperature within the main body of the cool compartment 3 is always less than that measured to ensure thereby that sensitive foods comply with the relevant food regulations.

The following table indicates the reduction in time for different sizes of showcase which are controlled in accordance with the present invention, to bring the cool compartment to 3 degrees C from different ambient temperatures in comparison to showcases, the refrigeration units of which, are driven in a conventional continuous manner.

Size Start Final Inter- Cont Temp. Temp. I rupted inous Runn- Runn ing ing (mins) (mins) 700mm x 620mm x 330mm 280C 30C 32 75 700mm x 620mm x 330mm 200C 30C 20 60 1100mm x 620mm x 330mm 280C 30C 35 100 1100mm x 620mm x 330mm 200C 30C 25 70 1400mm x 620mm x 330mm 280C 30C 40 140 1400mm x 620mm x 330mm 200C 30C 30 90

Claims (11)

1. Claims 1. A refrigerated unit comprising a cool compartment; a refrigeration unit operable to maintain the cool compartment at a predetermined temperature; and a controller, the controller being operable repeatedly to interrupt the operation of the refrigeration unit for a second interval, if, after a first interval, the temperature of the cool compartment is above said predetermined temperature.
2. 2. A refrigerated unit as in claim 1, wherein the controller is further operable, when the temperature inside the cool compartment is not greater than the predetermined temperature, to interrupt unconditionally the operation of the refrigeration unit.
3. 3. A refrigerated unit as in any preceding claim, wherein the controller includes : a temperature sensor for measuring the temperature of the cool compartment; a useradjustable temperature setter to select said predetermined temperature within the cool compartment; and comparison means responsive to the temperature sensor and the temperature setter to provide an output indicative of the difference between the actual and predetermined temperatures and to deactivate the refrigeration unit when the temperature in the cool compartment substantially equals the predetermined temperature.
4. 4. A refrigerated unit as in claim 3, wherein the controller further comprises resettable timing means operable to provide the first and second intervals.
5. 5. A refrigerated unit as in claim 4, wherein the timing means comprises a first timer operable to provide the first interval, and a second timer operable to provide the second interval and the first and second timers are arranged to reset each other on timing out.
6. 6. A method of controlling a refrigerated unit comprising a cool compartment and a refrigeration unit operable to maintain the cool compartment at a predetermined temperature, the method involving repeatedly performing the steps of interrupting the operation of the refrigeration unit for a second interval if, after a first interval, the temperature of the cool compartment is above said temperature.
7. 7. A method of controlling a refrigeration unit as in claim 6, wherein the first and second intervals are both selected to be of constant duration.
8. 8. A refrigerated unit as in claims 3,4 or 5, wherein the temperature sensor, the temperature setter and the comparison means are embodied as a thermostat.
9. 9. A refrigerated unit wherein the evaporator is disposed at the top of the cool compartment.
10. 10. A refrigerated showcase constructed, arranged and adapted to operate substantially as described with reference to figure leof the drawings.
11. 11. A method of controlling a refrigerated unit substantially as described with reference to Figures 1-4 of the drawings.