Refrigerator

A refrigerator has a first cooling device i.e. a direct cooling evaporator and a second cooling device i.e. an indirect cooling device to cool a circulating air in a refrigerator box, in which a cold storage member is attached to the direct cooling evaporator whereby when the indirect cooling evaporator is heated for defrosting, the temperature rise of the direct cooling evaporator due to a refrigerant gas flowed from the indirect cooling evaporator back into the direct cooling evaporator is prevented.

BACKGROUND OF THE INVENTION 
This invention relates to a refrigerator equipped with a direct cooling 
evaporator and indirect cooling evaporator. 
A refrigerator of this type equipped with an indirect cooling evaporator is 
known as a fan cooling type refrigerator in which air in the refrigerator 
box including a refrigerating chamber and a freezing chamber, which is 
circulated by a fan is cooled by the evaporator to cause storage food to 
be cooled. This type of the refrigerator has an advantage of producing no 
deposited frost on the wall of the freezing chamber and a disadvantage of 
requiring a longer time of making ice or freezing the food. A refrigerator 
has recently been developed in which in addition to the indirect cooling 
evaporator a direct cooling evaporator is disposed in that freezing 
chamber portion facing a fan blow outlet for cooling air and the 
ice-making and the freezing are made for a brief period of time with an 
ice tray or a freezing food arranged on, or in contact with, the direct 
cooling evaporator. 
In this case, the freezing cycle is such that part of a refrigerant 
entering into the direct cooling evaporator from a condenser through a 
capillary tube is evaporated there and the remaining refrigerant is sent 
through the next capillary tube into the indirect cooling evaporator where 
it is all evaporated, permitting a return of it to a compressor. A 
temperature during the cooling operation of the indirect cooling 
evaporator is set lower than the temperature of the direct cooling 
evaporator and deposited frost is produced only on the indirect cooling 
evaporator. Since the evaporator only is heated by providing a defrost 
heater etc., it is possible to prevent a temperature rise of the direct 
cooling evaporator and thus the ice tray and frozen food arranged on, or 
in contact with, the evaporator. 
It has, however, been found that, since during the defrosting operation the 
compressor is usually stopped and thus the refrigerant circulation is 
stopped, part of the refrigerant gas in the indirect cooling evaporator 
which is raised in its temperature is flowed back into the preceding stage 
direct cooling evaporator through the capillary tube or heat conduction 
etc. through the tube wall is also involved, causing the direct cooling 
evaporator and thus ice cubes in the ice tray and frozen food to rise in 
their temperature and causing them to be melted or thawed with the 
resultant deterioration. 
SUMMARY OF THE INVENTION 
It is accordingly the object of this invention to provide a refrigerator 
which can suppress a temperature rise in a direct cooling evaporator when 
the defrosting of an indirect cooling evaporator is effected and can 
prevent a bad effect, such as melting or deteriorating thawing, on ice 
cubes in an ice tray and frozen food. 
According to this invention there is provided a refrigerator comprising a 
refrigerator box partitioned into a freeizing chamber, refrigerating 
chamber and cooling chamber communicating with these chambers; a first 
cooling device disposed within the freezing chamber; a fan device disposed 
in the cooling chamber to permit circulation of air in the freezing and 
refrigerating chambers i.e. air in the refrigerator box; a second cooling 
device provided in the cooling chamber for cooling the circulating air, 
communicating with the first cooling device and set such that a 
temperature during the cooling operation is lower than that of the first 
cooling device; a heating means for defrosting which is provided on the 
second cooling device only; and a cold storage means provided on the first 
cooling device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
This invention will now be explained below by referring to the accompanying 
drawings. 
In FIG. 1, reference numeral 1 shows a refrigerator box partitioned into a 
freezing chamber and refrigerating chamber; 2, a door for the 
refrigerating chamber which has a grip 2a; 3, an upper door for the 
freezing chamber which has a grip 3a; and 4, a lower door for the freezing 
chamber which has a grip 4a. In FIG. 2, reference numeral 5 shows the 
freezing chamber in the box which confronts both the doors 3, 4 for the 
freezing chamber. A partition wall 6 is disposed at the rear side of the 
freezing chamber with a predetermined spacing kept relative to the wall 
surface of the freezing chamber. A cooling chamber 9 is provided with an 
air inlet 7 at the lower side and an air outlet 8 at the upper side 
thereof and communicates with a duct section. A second cooling device i.e. 
an indirect cooling evaporator 10 is located at the lower portion of the 
cooling chamber 9. A fan device 13 which forces the cooled air circulation 
in the refrigrator box is located at the upper section of the cooling 
chamber 9 and comprises a motor 11 and blade 12. Reference numeral 14 
shows a first cooling device i.e. a direct cooling evaporator disposed in 
upper and lower stages at that upper area of the freezing chamber 5 which 
confronts the air outlet 8 and upper door 3. Reference numeral 15 shows a 
plurality of shelves disposed in the middle area of the freezing chamber 
5; 16, an article receptacle; 17, a dew tray disposed below the indirect 
cooling evaporator 10; 18, an evaporating tray disposed outside the 
refrigerator box and communicating with the dew tray 17 through a 
communicating means, not shown; and 36, a compressor located in a machine 
chamber which is positioned outside the refrigerator box 1 such that it is 
located at the lower side of the box. As shown in FIG. 3 the direct 
cooling evaporator is formed by causing an evaporator, i.e. a refrigerant 
path 20, comprised of a metal tube such as an aluminium tube to be 
meanderingly arranged on the lower surface of a metal plate downturned at 
their side edges 19a, 19b, for example, a heat transfer plate 19 made of 
aluminium. To the lower side of the resultant structure is attached a cold 
storage member 22 which is obtained by sealing a cold storage agent 22' 
(for example, an agent containing as a main constituent element an 
electrolytic solution such as KCl to which a gelling agent is added and 
having a temperature of -11.degree. to -12.degree., a melting latent 
freezing heat of 70 Kcal/kg.deg. and a coefficient of expansion of about 7 
to 8%) into a non-rigid vinyl chloride flat bag 21 which is incorporated 
with nylon fibers. The resultant structure is covered by a cover 23 from 
below to permit the member 22 to be intimately contacted with the lower 
surface of the heat transfer plate 19 and the lower surface of the tube 20 
on the lower surface of the plate 19, as shown in FIG. 4. The cover 23 is 
fixed by rivets to the heat transfer plate 19 by downturning the side edge 
portions into substantially U-shaped configurations with the top surface 
and outer side wall surfaces of the substantially inverted U-shaped 
sections abutted against the lower surface and lower side surfaces of the 
heat transfer plate 19. The direct cooling evaporator 14 is mounted by 
below-mentioned fitting means on the freezing chamber 5 with the cold 
storage member 22 sandwiched between the heat transfer plate 19 and the 
cover 23. As shown in FIG. 5, inverted L-shaped cutout mounting portions 
25 are provided at the rear portions of the side surfaces 19a, 19b of the 
heat transfer plate 19 and side surfaces 23a, 23b of the cover 23, and 
inverted U-shaped cutout mounting portions 26 are provided at the front 
portions of the side surfaces 19a, 19b of the heat transfer plate 19 and 
side surfaces 23a, 23b of the cover 23. First, the openings of the 
mounting portions 25 are aligned with supporting pins 27 projected from 
the side wall surfaces of the upper portion of the freezing chamber 5 with 
the evaporator inclined from the front side toward the rear side. Then, 
the evaporator is moved relative to the pins so as to describe an L-shaped 
configuration in a direction indicated by an arrow A in FIG. 6 to permit 
the pins to be fitted into the openings of the mounting portions 25. After 
the evaporator is brought back to the horizontal state, the mounting 
portions 26 are caused to confront the support pins 28 projected from the 
side surfaces of the upper portion of the freezing chamber 5 and then the 
evaporator is lowered in a direction as indicated by B in FIG. 7 to permit 
the supporting pins 28 to be fitted in the openings of the mounting 
portions 26. In this way, the evaporator 14 is mounted on the upper 
portion of the freezing chamber 5. In FIG. 8, reference numeral 29 shows a 
front frame with the front surface 29a inclined toward the front side. 
U-shaped cutout mounting portions 30 provided in the inner end portions of 
the side surfaces 29b of the front frame 29 are made to confront the 
supporting pins 28 and then the front frame 29 is moved in a direction as 
indicated by an arrow C in FIG. 8 to permit the supporting pins 28 to be 
fitted in the mounting portions 30. At this time, a hook 31 provided on 
the rear edge of the upper surface of the front frame is engaged with a 
hook hole 32 provided in the front edge portion of the upper surface of 
the heat transfer plate 19. By so doing, the front frame 29 is mounted on 
the heat transfer plate and at the same time the direct cooling evaporator 
14 is prevented from being detached from the chamber wall. The supporting 
pins 27, 28 have stepped portions as shown in FIG. 9 whereby a clearance g 
of, for example, about 15 mm for passage of the cooling air is defined 
between each end of the direct cooling evaporator 14 and the wall surface 
of the freezing chamber 5. Likewise, a clearance is defined between the 
front frame 29 and the inner surface of the upper door 3 and between the 
rear frame 33 in FIG. 5 and the front wall of the partition plate 6. The 
rear frame 33 is mounted by causing a hook 34 provided on each inner side 
surface of the rear frame 33 to be engaged with a hook hole 35 provided on 
the rear portion of each side surface (19a, 19b) of the heat transfer 
plate 19. 
FIG. 10 shows a freezing cycle. In FIG. 10, reference numeral 36 shows a 
compressor whose outlet is connected to a condenser 37. The condenser 37 
is connected to a first capillary tube 38 which in turn is connected to 
the direct cooling evaporator 14. The evaporator 14 is connected through a 
second capillary tube 39 to the in direct cooling evaporator 10. The 
evaporator 10 is connected to the suction inlet of the compressor 36. In 
this way, the freezing cycle 41 is completed. A defrosting device 40 is 
attached to the indirect cooling evaporator 10 only. In the freezing cycle 
41, the second capillary tube 39 connected to the direct cooling 
evaporator 14 is connected to the intake port of the indirect cooling 
evaporator 10, the intake port being located at the bottom of the 
evaporator 10, as shown in FIG. 11. 
The operation of the refrigerator will now be explained below. 
During the cooling operation, a refrigerant supplied under pressure from 
the compressor 36 is supplied through the condenser 37 and the first 
capillary tube 38 to the direct cooling evaporator 14 where part of it is 
evaporated, and the remaining part of the refrigerant is supplied through 
the second capillary tube 39 to the indirect cooling evaporator 10 where 
it is all evaporated and returned to the compressor 36, repeating this 
operation. By this cooling operation, the indirect cooling evaporator 10 
is cooled at a temperature lower than the direct cooling evaporator 14 by 
preferably more than 5.degree. C. Since during the cooling operation the 
fan device 13 is driven, air in the freezing chamber 5 is sucked from the 
air inlet 7 into the cooling chamber 9 and sent out from the air outlet 8 
through the duct section into the freezing chamber 5. In this way, a 
circulating path as indicated by an arrow D in FIG. 2 is followed. Thus, 
the air is cooled and chilled by the indirect cooling evaporator 10 in the 
cooling chamber 9, causing the cooling of frozen food on the shelf 15 at 
the middle portion of the freezing chamber or storage articles in the 
receptacle at the lower portion of the freezing chamber. Water in the ice 
tray and the frozen food which are placed on or in contact with the direct 
cooling evaporator 14 is directly cooled by the evaporator 14 and 
indirectly cooled, like the other storage food, upon receiving the cooling 
air which is blown off from the air outlet 8. With the further cooling 
operation, the cold storage member 22 in contact with the lower surface of 
the heat transfer plate 19 of the direct cooling evaporator 14 is cooled 
by the refrigerant path 20 and stores a cooling energy. Frost is deposited 
on the indirect cooling evaporator 10 lower in temperature than the 
temperature of the direct cooling evaporator 14. Even if frost should be 
deposited on the direct cooling evaporator 14, it is transferred to the 
indirect cooling evaporator 14 by a sublimation phenomenon and air blowing 
of the fan device 13. 
At the defrosting operation which is effected a predetermined time after a 
timer (not shown) is set, the compressor 36 is stopped and, instead, the 
defrosting heater or device 40 is turned ON, heating the indirect cooling 
evaporator 10 to cause the frost concentratedly deposited on the 
evaporator 10 to be melted away. The refrigerant gas in the indirect 
cooling evaporator 10 is raised in its temperature due to the heat 
generation of the defrosting heater 40 and some of it is flowed back into 
the direct cooling evaporator 14 through the second capillary tube 39, but 
it is cooled by the cooling energy stored in the cold storage member 22 
which is intimately contacted with the heat transfer plate 19 of the 
direct cooling evaporator 14 as mentioned above, and suppresses the 
temperature rise in the direct cooling evaporator 14. Experiments were 
conducted in connection with a change in the temperature rise of each 
evaporator during the defrosting operation, under the conditions that 
under control at no load (100 V 60 Hz) the defrosting cycle occurred once 
per 12 hours of the compressor operation integrating time and the 
defrosting time was 15 to 20 minutes (in FIG. 12, the bimetal regaining 
temperature: 15.degree. C., the defrosting time: 18 minutes) from the 
starting of the turn-ON of the timer to the regaining of the bimetal. The 
results of the experiments are as shown in FIG. 12 in which a relation of 
the temperature of the conventional direct cooling evaporator 14 { as 
indicated by the broken line (X)} with no cold storage member 22 to the 
temperature of the direct cooling evaporator 14 {as indicated by solid 
line (Y)} with a cold storage member 22 (the embodiment of this invention) 
is shown. As the cold storage member 22 use is made of a flexible 
container in the form of a package or bag containing 0.7 Kg of a cold 
storage agent obtained by adding a gelling agent, etc. to a KCl solution 
as mentioned above. The package is attached to the direct cooling 
evaporator 14. In FIG. 12, Y' shows the surface temperature of the direct 
cooling evaporator 14 and Z shows a variation in the temperature of the 
indirect cooling evaporator 10. 
As evident from FIG. 12, with the starting of defrosting of the defrosting 
heater 40 the temperature X of the direct cooling evaporator with no cold 
storage member rises from the minus to the plus region (5.degree. C.). On 
the other hand, the direct cooling evaporator 14 with the cold storage 
member 22 (this invention) is such that the surface temperature Y' can be 
controlled to a lower temperature of about -7.degree. C. at the portion of 
the heat transfer plate 19 in contact with the cooling path 20 and that 
the temperature Y of the evaporator 14 can be controlled to a lower 
temperature of about -15.degree. C. at the middle section of the cold 
storage member 22. Thus, the defrosting of the indirect cooling evaporator 
10 can be performed without involving the melting or degenerative thawing 
of ice cubes in the ice tray or the frozen food.