GB2044425A - Freezer chest - Google Patents

Abstract

A freezer chest with a chilled food compartment closable by a cover, has a refrigerating unit comprising an evaporator (9), a compressor (21), capillary tube 36, a condenser (24) and auxiliary evaporator which is (19) constructed as a closed container and connected to the outflow side of the evaporator (9). The evaporator (19) has a lower trough (40) for collecting liquid refrigerant which is evaporated by an electrical heating system 18 and an upper connector (42) to the suction side of the compressor (21). The condenser (24) and the capillary tube (36) are by-passed by a line 25 for defrosting the evaporator by a timing device controlling a valve 23. <IMAGE>

Description

SPECIFICATION Freezer chest The invention relates to a freezer chest with a chilled food compartment, whose cooling chamber can be closed and with a refrigerating unit comprising an evaporator, a steam dome, a compressor and a condenser, whose evaporator has pipe coils arranged in the cooling chamber and whose steam dome constructed as a closed container is connected to the outflow side of the evaporator and has a trough at the bottom for collecting liquid cooling agents and above which exits a connecting piece connected to the suction side of the compressor and whose compressor can be connected on the pressure side, with the interposing of the condenser to a capillary tube issuing at the inflow side to the evaporator.

In the case of freezer chests of this type it may happen that part of the cooling agent flows out in liquid form from the evaporator and this increases in inverse proportion to the cooling demand in the cooling chamber. This liquid cooling medium must not reach the compressor, because it would disturb the operation thereof and is therefore collected in the steam dome trough and from there can only reach the compressor in the form of steam.

In refrigerating equipment an ice layer can form on the evaporator which must be thawed in order to maintain the chilling function. British Patent 1 395 083 discloses a refrigerator which has two separate cooling chambers, whereof the first is cooled to very low temperatures by an inflow-side portion of the pipe coil of the evaporator, whilst the second is cooled to less low temperatures by an outflow side-portion of the pipe coil. The cooling medium is controlled by a continuously readjusted throttle valve arranged on the inflow side of the evaporator as a function of the cooling demand, so that there is no steam dome.For defrosting purposes by a by-pass line bridges the condenser and the throttle valve and a second throttle valve is connected between the two portions of the pipe coils of the evaporator and an electrical heating system located in the second cooling chamber is switched on. The second cooling chamber is heated by this heating system and any ice there is thawed and the cooling medium in the outflow side portion is warmed.

This warmed cooling agent driven by the compressor, travels via the by-pass line to the inflow side portion where it brings about the necessary defrosting.

The problem of the present invention is to so further develop a freezer chest of the type defined hereinbefore that defrosting can take place with minimum additional expenditure and effort and as far as possible with no interruption to the cooling operation.

The invention is characterized in that a by-pass line is provided by means of which the pressure side of the compressor can be directly connected to the inflow side of the evaporator, whilst bridging the condenser and the capillary tube and that an electrical heating system is provided for the steam dome and acts directly on the liquid cooling medium in the trough.

According to the invention the heating necessary for defrosting purposes acts directly on the liquid cooling medium and from there directly on the iced-up coils of the evaporator. Thus, heating action on the cooling chamber and on frozen food is largely avoided and the defrosting process can be rapidly performed. Both of these factors contribute to keeping the interruption to cooling, which is unavoidable during the defrosting process to a minimum.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings wherein show: Fig. 1 partly broken away a freezer chest according to the invention, Fig. 2 a circuit diagram for the freezer chest according to fig. 1, Fig. 3 the steam dome of fig. 1 in cross section, Fig. 4 the section IV of fig. 3.

In the drawings 1 is the chilled food compartment comprising an aluminium chilling vat 16 surrounding a cooling chamber 3 and said vat contains two aluminium partitions 13, 14, surrounded by an insulating cover 2 and sealable by means of a cover 35, which can be fitted and which is also made of insulating material. The evaporator 9 has a pipe coil 10, comprising three portions 11, 1 2 1 5. The inflow side portion 11 is located in the bottom 8 of cooling trough 16, the central portion 12 is located in the two partitions 1 3, 14 and the outflow side portion 1 5 is located in the outer walls 4, 5 6, 7 of trough 1 6.

The steam dome 1 9 is positioned below the chilled food compartment 1 is connected to the discharge 1 7 of pipe coil 10. The steam dome 19 is constructed as a closed container and has a trough 40 at the bottom for collecting liquid cooling medium 41. Above trough 40 a connecting piece 42 issues from steam dome 1 9 and by means of a line 20 it is connected to the suction side of a compressor 21, so that only cooling medium in steam form can reach the compressor. Within the trough 40 there is a tubular electrical heating system 43 which, in the manner of an emersion heating system, is emersed in the liquid cooling medium 40 which may be contained within trough 40, and it is provided with an overheating protections means, which.is not shown in the drawing.The pressure side of the compressor 21 is connected to a threeway valve 23 which can be switched over by an electrical actuating element 22, whereby to one outlet of the valve is connected condenser 24 and to its other outlet is connected a by-pass line 25.

Condenser 24 is in the blowing area of a blower 27 which can be driven by an electric motor 26 and is connected by means of a drier 34 to a capillary tube 36 issuing into the pipe coil 10 at the inflow end 29 and specifically together with the by-pass line 25.

Reference numeral 32 designates an automatic device which can be controlled by a time switch 33 and in turn the automatic device controls the electrical heating system 43, the actuating element 22, electric motor 26 and compressor 21.

The condenser 24 is constructed as the base of the freezer chest on which is placed the chilled food compartment 1. The base contains in addition to steam dome 19, compressor 21, blower 27, three-way valve 23 and defrosting tray 31 which is open at the top and which is positioned below a defrosting water drain 30 located at the lowest point of bottom 8.

During freezing the by-pass line 25 is switched off and the condenser 24 is connected to the pressure side of compressor 21, heating system 43 is switched off, the electric motor 26 of blower 27 is switched on and compressor 21 is operating.

The cooling medium in the pipe coil system evaporates in evaporator 9 and cools the frozen food in the cooling chamber 3 and then passes to steam dome 1 9. Any residual moisture on the cooling medium is deposited there and collect in trought 40 whilst the gaseous cooling medium is sucked in by compressor 21 where it is compressed and passes to condenser 24 where it is cooled and liquefied. The now liquid cooling medium is injected through capitlary tube 36 into pipe coil 10 of the evaporator.

When the time switch 33 has reached the defrosting time automatic device 32 switches to defrost for a period of time preset in time switch 33. Automatic device 32 then switches over the three-way valve 23 by means of actuating members 22 during defrosting so that condenser 24 is disconnected from compressor 21 and instead the by-pass line 25 is connected.

Furthermore electric motor 26 is stopped and heating system 43 is switched on. Compressor 21 remains switched on. These parts maintain this switching state throughout the defrosting period.

As a result of the running compressor the cooling medium is kept circulating and flows through bypass line 25 passed condenser 24 and capillary tube 36. The heating system 43 acts like an emersion heater and heats the liquid cooling medium in the steam dome so that it evaporates.

The gaseous cooling medium is sucked in by compressor 24 compressed, forced as a heating gas via by-pass line 25 into pipe coil 10 and brings about the sought defrosting of evaporator 9.

In normal cooling operation it is not absolutely necessary to have a line section in bottom 8. This section 11 is, however, particularly important during defrosting, because the water resulting from the falling of the ice flows down to the bottom 8 and it must be ensured that it does not freeze in there and can instead flow away. For this reason the section 11 placed in bottom 8 is arranged on the inflow side, so that the thawing action is most intense in this bottom area. The defrosting water then flows out through the drain 30 drips into the defrosting tray 31 and from there flows via an underlying evaporating dish 37, through which passes the hot line section 38 which evaporates the defrosting water in the next few hours, so that it is taken up by the ambient external air.

On completion of the defrosting of the bottom, partitions 13, 14 and the outer walls 4, 5, 6 and 7 are defrosted. When the defrosting time is at an end the automatic defrosting device switches off the heating system 43 again, switches on electric motor 26 and returns the three-way valve 23 to its initial position in which the by-pass line 25 is switched off and instead the line branch is again connected to condenser 24 and capillary tube 26.

The compressor continues running and the system now operates on the freezing basis. Instead of controlling the automatic device with a time switch in time-dependent manner it is also possible, optionally also additionally, to provide for control purposes one or more sensing bulbs.

Experience has shown that in the case of a freezer chest having a capacity of up to about 8000 litres and set to a freezing temperature of 20a C, a single defrosting operation lasting approximately 20 minutes is sufficient. If the freezer chest is a chest in which products are offered for sale to customers, then it is opened during the selling periods, i.e. during the day, but overnight it is appropriately covered by the cover 35 shown in broken-away form in fig. 1.

Advantageously the defrosting period is at night when the chest is closed by cover 35. Under these conditions the heating on the surface of the frozen product is limited to less than 2OC during the defrosting phase.

The invention can also be used with other refrigerating equipment for example equipment in which the evaporators comprise pipes providing with cooling fins, which are located within the cooling chamber.

Claims (9)

1. A freezer chest with a chilled food compartment, whose cooling chamber can be closed and with a refrigerating unit comprising an evaporator, a steam dome, a compressor and a condenser, whose evaporator has pipe coils arranged in the cooling chamber and whose steam dome constructed as a closed container is connected to the outflow side of the evaporator and has a trough at the bottom for collecting liquid cooling agents and above which exits a connecting piece connected to the suction side of the compressor and whose compressor can be connected on the pressure side, with interposing of the condenser to a capillary tube issuing at the inflow side to the evaporator, characterized in that a by-pass line 25 is provided by means of which the pressure side of the compressor 21 can be directly connected to the inflow side 29 of the evaporator 9 whilst bridging the condenser 24 and the capillary tube 36 and that an electrical heating system 18 is provided for the steam dome 1 9 and acts directly on the liquid cooling medium in the trough 40.

2. Freezer chest according to claim 1, characterized in that the heating system 1 8 is arranged within the trough 40 in the manner of an emersion heating system.

3. Freezer chest according to claim 1, characterized by an automatic defrosting device 32 which, during defrosting, switches on by-pass line 25 via a valve arrangement 23 and the electrical heating system 1 8.

4. Freezer chest according to claim 3, characterized in that during defrosting the automatic defrosting device 32 switches off a blower 27 provided for condenser 24.

5. Freezer chest according to any one of the preceding claims, characterized in that the cooling chamber 3 is lined by metal walls 4, 5, 6, 7, within which is laid a portion 1 5 of pipe coil 10.

6. Freezer chest according to one of the preceding claims, characterized in that the cooling chamber 3 has a metal bottom 8 in which is laid a portion 11 of the pipe coil 10.

7. Freezer chest according to claim 6, characterized in that a portion 1 5 of pipe coil 1.0 located on the inflow side is laid in bottom 8.

8. Freezer chest according to one of the preceding claims, characterized by a defrosting water drain 30 below the chilled food compartment 1 which issues into a defrosting water collecting tray 31 which is open at the top.

9. A freezer chest substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.