GB1573901A

GB1573901A - Refrigerated chest and a method of defrosting it

Info

Publication number: GB1573901A
Application number: GB2025/78A
Authority: GB
Original assignee: Electrolux AB
Current assignee: Electrolux AB
Priority date: 1977-02-01
Filing date: 1978-01-18
Publication date: 1980-08-28
Also published as: FI64239C; AU509659B2; NO780360L; FR2378482B1; NO143954C; IT7847857A0; AU3281378A; DK23378A; JPS53124369A; ES469581A1; ES466507A1; NO143954B; FI64239B; FI780277A; IT1102264B; DE2804008A1; DK150124B; FR2378482A1

Description

(54) A REFRIGERATED CHEST AND A METHOD OF DEFROSTING IT (71) We, AKTIEBOLAGET ELECTROLUX, a Swedish joint stock company, of Luxbacken 1, S--105 45 Stockholm, Sweden, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of defrosting at least one cooling element in a refrigerated chest for cooled or frozen items, the chest having a channel for air which is caused to circulate about a storage space for the items, through the cooling element in the channel, and over an open side of the space.

To cool such a chest, circulating air is used whose content of moisture will gradually settle and form frost on the cooling element. To maintain its cooling effect the element must be defrosted at regular intervals. For this purpose for example an electric heater has been used which is placed close to the cooling element. The compressor is shut off and heat energy is supplied to the heater. A circulating fan is kept in operation so that circulation of air continues. In this way comparatively rapid defrosting is achieved, but at the same time considerable energy has to be supplied and an expensive assembly of the heater and its connecting wires is required. Instead of supplying electric energy it has been proposed to use heat from the ambient atmosphere around the chest.For this purpose special air channels have been provided in the chest for supplying warm ambient air and discharging the air cooled by the cooling element so that there will be no air circulation. Thus, not only additional air channels are required but a system of movable flaps or other guides is needed, which have to be adjusted before and after defrosting so that the desired air passages are obtained. Also these defrosting arrangements involve increased cost for the chest and, further, they add to the risk of operation disturbance and require increased supervision.

An object of the invention is to provide for defrosting of a refrigerated chest by simple and reliable means, without significant increase of cost and rated input.

According to this invention there is provided a method of defrosting a cooling element in a refrigerated chest, the chest having a storage space for items which are to be kept cooled or frozen, the sapce having an open side, a channel for circulation of air about the space in one direction during normal operation, and a cooling element in the channel, wherein, for defrosting, i) the cooling element is deactivated; ii) air is caused to flow in the channel in a direction opposite to its direction of flow during normal operation; iii) air cooled by the cooling element is caused by means of a guide to flow from the channel in a direction away from the space; iv) ambient air is drawn in at the location where air is blow out during normal operation; and v) during defrosting a greater quantity of air per unit time is circulated than during normal operation.

The invention also includes a refrigerated chest comprising: a storage space for items which are to be kept cooled or frozen, the space having an open side; a channel and air circulating means for circulation of air about the space in one direction during normal operation; a cooling element in the channel; means for reversing the direction of air flow; and a guide in that opening of the channel into which air is drawn during normal operation, the guide on defrosting and discharge of air from the channel directing the air flow away from the space, air to the channel being drawn in during defrosting from the ambient atmosphere outside the chest, and wherein during defrosting the circulating means operates with a larger quantity of air than during normal operation.

The invention will now be described by way of example with reference to the drawings, of which Figure 1 is a vertical cross section of one embodiment of display freezer chest, and Figure 2 a like section of another embodiment.

The freezer chest shown in Figure 1 has two end walls 10, a front wall 11, a rear wall 12 and a bottom 13, all these parts being heat insulated. The freezer chest stands with feet 14, 15 on a floor 16 and it is placed in a shop in such a way that customers pass it on the right-hand side as viewed in Figure 1.

Therefore the wall 11 is low but has a top part 17 of heat insulating glass so that the items in the freezer chest are easily seen. In the freezer chest is an open-topped box of metal sheets 18, 19, 20 for frozen items 21 of merchandise.

The box is designed and placed relative to the freezer chest walls so that an air channel 22 is formed between the box and the walls 11, 12 and bottom 13. Under the box the air channel 22 has a fan 24, operated by a motor 23, and a cooling element 25. The latter can be of known type and thus details thereof are not shown. The cooling element comprises pipe coils with fins and is con nected to known cooling apparatus, in which refrigerant is circulated through the coils.

The bottom of the air channel 22 is inclined towards an outlet 26 for water formed on defrosting of the cooling element 25. The bottom outlet 26 is in use con nected to a drain system.

During normal operation of the freezer chest the fan 24 operates in a direction such that air, as shown by the full-line arrows 27, is drawn into the channel 22 on the upper right-hand side of the Figure and downwards to the fan, through the latter and the cooling element 25 to pass upwards between the rear wall 12 and the box 18, 19, 20, whence the air is forced out through guides 28 on the upper left-hand side of the Figure in a horizontal direction over the items in the box. The air is directed by the guides as indicated towards the air intake of the channel to the right in the Figure.

Even -if the guides 28 are of suitable form and the quantity and velocity of the air are well balanced, one cannot avoid some mixing-in of warm, moist ambient air. Since this moisture will successively settle on the cooling element in the form of frost, the element has to be defrosted. This is effected partly by causing the air to flow through the channel 22 in a direction opposite to the normal operation direction, and partly by interrupting the circulation and taking in warm, ambient air through the guides 28, while the air cooled by the cooling element forces the exhaust air by way of guides 29, 30 at the opposite end of the channel in a direction away from the items 21 and away from the normal path of circulation, so that the air will not flow back to the guides 28 and no circulation of cold air will occur.

The ambient warm air has a considerably higher temperature than the cooling element 25 and thus it can be used for defrosting. However, its heat content is limited and it is not sufficient if defrosting is to be effected rapidly. Therefore the freezer chest in accordance with the invention is so designed that the quantity of air conveyed per unit of time on defrosting is larger than the quantity of air circulated during normal operation. It is suitable to design the device so as to circulate a larger quantity on defrosting, and preferably a quantity which is two to four times larger per unit of time.

To obtain reversal of the flow direction of the air on defrosting, as shown by dashed arrows 31, the motor 23 of tht fan 24 is controllable so that the fan can operate in either direction of rotation. To obtain the intended increase of the conveyed air quantity it is also possible to arrange the motor to operate at a higher speed on defrosting than on normal operation. Simultaneously or alternatively the fan can be designed to operate with a larger capacity of air on defrosting than during normal operation.

If the freezer chest is elongate, several fans with motors can be arranged in the air channel. Cooling is carried out by one cooling element suited to the length of the chest, or by several cooling elements. In Figure 2 a freezer chest is shown which has two separate storage spaces for items in two boxes 32, 33; between these boxes is a partly common, vertical air channel 34. The freezer chest has two end walls 35, one of which is seen, and two long walls 36, 37 designed so as to make the contents accessible to view by customers from both sides.

The freezer chest also has a bottom 38 and feet 14, 15 and stands on a floor 16. During normal operation air is taken in at the top of the central channel 34, as indicated by the solid arrows 39, and drawn downwards by fans 41 operated by motors 40 and common for a continued channel 42 to the left and a continued channel 43 to the right in the Figure; only one fan and one motor is seen in this Figure. In the channel 42 the air passes through a cooling element 44 and in the channel 43 through a cooling element 45 and then moves upwards through channel parts 46, 47 to be blown out through guides 28 on each side. The air is blown out in the horizontal direction over the items 21 and towards a central line above the inlet to the central channel 34, where it is drawn in to circulate again both ways.

On defrosting, the flow direction of the air is reversed in the channels and cold air is blown out through the central channel 34 as shown by the dashed arrows 48. Thus air drawn in at the guides 28 on both sides is not cold but warm ambient air, as indicated by the dashed arrows 49. Guides 50 at the upper opening of the channel 34 direct the air flowing out on defrosting upwards and away from the normal circulation paths.

Also the freezer chest shown in Figure 2 has a bottom which is inclined and designed so that water formed on defrosting is collected for draining.

A large quantity of air can be obtained by operating the fans at high speed. A lower fan speed can be obtained by voltage reducing means in the supply wires of the motors, for example by a transformer or a thyristor control.

Because of the high flow velocity of the air there will be no parallel flow over the surface of the items and thus quite a lot of warm ambient air is drawn in and can be used for defrosting. When the air velocity is reduced, the flow returns to normal circulation.

Formation of frost on the cooling elements in a freezer display chest can vary, for example depending on the ambient climate. To ensure that frost is removed from the elements during defrosting, the flow direction of the air can be reversed to the normal direction towards the end of the defrosting while keeping the cooling elements shut off and maintaining the large air quantity per unit of time during a short period. This ensures that water formed during defrosting is dried before the normal operation starts again. For this purpose the control means of the freezer chest can have a retarding device, for example a relay, to change the time at which the speed of the fan motors is reduced and the cooling compressor is started after defrosting.

The invention is not limited to the embodiments described but can be modified within the scope of the claims. For example, although the drawings show freezer chests for frozen items, the invention is applicable also to chests for cooled items.

WHAT WE CLAIM IS: 1. A method of defrosting a cooling element in a refrigerated chest, the chest having a storage space for items which are to be kept cooled or frozen, the space having an open side, a channel for circulation of air about the space in one direction during normal operation, and a cooling element in the channel, wherein, for defrosting, i) the cooling element is deactivated; ii) air is caused to flow in the channel in a direction opposite to its direction of flow during normal operation; iii) air cooled by the cooling element is caused by means of a guide to flow from the channel in a direction away from the space; iv) ambient air is drawn in at the location where air is blown out during normal operation; and v) during defrosting, a greater quantity of air per unit time is circulated than during normal operation.

2. A method according to claim 1 wherein the quantity is two to four times greater.

3. A method according to claim 2 wherein, towards the end of defrosting the air flow direction is reversed with the cooling element deactivated while maintaining the large quantity of air per unit of time for a short time, after which the air quantity is reduced to that of normal operation.

4. A refrigerated chest comprising:- a storage space for items which are to be kept cooled or frozen, the space having an open side; a channel and air circulating means for circulation of air about the space in one direction during normal operation; a cooling element in the channel; means for reversing the direction of air flow; and a guide in that opening of the channel into which air is drawn during normal operation, the guide on defrosting and discharge of air from the channel directing the air flow away from the space, air to the channel being drawn in during defrosting from the ambient atmosphere outside the chest, and wherein during defrosting the circulating means operates with a larger quantity of air than during normal operation.

5. A chest according to claim 4 wherein the circulating means is a fan driven by a motor operable at two different speeds.

6. A chest according to claim 5 wherein the direction of rotation of the fan is reversible.

7. A chest according to claim 5 or claim 6 wherein the motor is operable at higher speed during defrosting.

8. A chest according to any of claims 5 to 7 comprising retarding means to change the time at which the speed of the motor is reduced and the cooling element is started after defrosting.

9. A chest according to claim 8 wherein the retarding means is a relay.

10. A method of defrosting a cooling element in a refrigerated chest, substantially as herein described with reference to the drawings.

11. A refrigerated chest constructed and arranged substantially as herein described and shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. On defrosting, the flow direction of the air is reversed in the channels and cold air is blown out through the central channel 34 as shown by the dashed arrows 48. Thus air drawn in at the guides 28 on both sides is not cold but warm ambient air, as indicated by the dashed arrows 49. Guides 50 at the upper opening of the channel 34 direct the air flowing out on defrosting upwards and away from the normal circulation paths. Also the freezer chest shown in Figure 2 has a bottom which is inclined and designed so that water formed on defrosting is collected for draining. A large quantity of air can be obtained by operating the fans at high speed. A lower fan speed can be obtained by voltage reducing means in the supply wires of the motors, for example by a transformer or a thyristor control. Because of the high flow velocity of the air there will be no parallel flow over the surface of the items and thus quite a lot of warm ambient air is drawn in and can be used for defrosting. When the air velocity is reduced, the flow returns to normal circulation. Formation of frost on the cooling elements in a freezer display chest can vary, for example depending on the ambient climate. To ensure that frost is removed from the elements during defrosting, the flow direction of the air can be reversed to the normal direction towards the end of the defrosting while keeping the cooling elements shut off and maintaining the large air quantity per unit of time during a short period. This ensures that water formed during defrosting is dried before the normal operation starts again. For this purpose the control means of the freezer chest can have a retarding device, for example a relay, to change the time at which the speed of the fan motors is reduced and the cooling compressor is started after defrosting. The invention is not limited to the embodiments described but can be modified within the scope of the claims. For example, although the drawings show freezer chests for frozen items, the invention is applicable also to chests for cooled items. WHAT WE CLAIM IS:

1. A method of defrosting a cooling element in a refrigerated chest, the chest having a storage space for items which are to be kept cooled or frozen, the space having an open side, a channel for circulation of air about the space in one direction during normal operation, and a cooling element in the channel, wherein, for defrosting, i) the cooling element is deactivated; ii) air is caused to flow in the channel in a direction opposite to its direction of flow during normal operation; iii) air cooled by the cooling element is caused by means of a guide to flow from the channel in a direction away from the space; iv) ambient air is drawn in at the location where air is blown out during normal operation; and v) during defrosting, a greater quantity of air per unit time is circulated than during normal operation.

9. A chest according to claim 8 wherein the retarding means is a relay.