Cooling device for refrigerator

A cooling device for a refrigerator comprising a plurality of cooling tubes, each of the cooling tubes being formed by helically winding a thermally conductive metal pipe having radial spine fins over the entire periphery thereof, being substantially in parallel to the axis of helix thereof and being connected together through a bent connection portion, to provide a continuous refrigerant passageway.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a cooling device for refrigerators, and 
more particularly to a cooling device which is provided in the cold air 
circulation channel of a refrigerator of the forced circulation type 
wherein cold air is forcedly circulated by a fan to cool a refrigerator 
compartment or freezer compartment. 
2. Description of the Prior Art 
Cooling devices for refrigerators of the forced circulation type must 
efficiently cool the air to be forcedly circulated by a fan. These devices 
usually comprise a finned tube. 
Already known as such tubes are one comprising a tube and plate fins 
attached to the tube transversely thereof and arranged longitudinally of 
the tube at equal spacing as disclosed in U.S. Pat. No. 3,252,292, and one 
comprising a tube and radial spine fines helically wound around the tube 
as disclosed in U.S. Pat. No. 3,022,049. 
For use in refrigerators with improved cooling efficiency, another cooling 
device is known which comprises a finned tube helically bent into a 
tubular form as disclosed in U.S. Pat. No. 3,766,679. The fins in this 
case are radial spine fins but are provided only inside the tubular body. 
SUMMARY OF THE INVENTION 
The present invention provides a cooling device for refrigerators which 
comprises a plurality of cooling tubes, each of the tubes being formed by 
helically winding a thermally conductive metal pipe having radial spine 
fins over the entire periphery thereof, being substantially in parallel to 
the axis of helix thereof and being connected together through a bent 
connection portion, to provide a continuous refrigerant passageway. 
The invention further provides a cooling device of the type described 
wherein each of the cooling tubes has a through bore defined by the tips 
of spine fins thereon and coaxial with the helix thereof, and a defrosting 
electric pipe heater is inserted in the bore in pressing contact with the 
fin tips. 
The cooling device of the present invention for use in refrigerators has 
the structural feature that radial spine fins are provided over the entire 
periphery of a pipe which is wound helically. Because of this feature, the 
present device has a greatly reduced size and yet achieves a high heat 
exchange efficiency, thereby permitting the refrigerator to have a cold 
air circulation channel of reduced size and consequently giving a reduced 
overall size to the refrigerator without altering the sizes of the 
refrigerator compartment and the freezer compartment. 
Another important feature of the present cooling device is that the device 
having the foregoing structural feature can be produced by a novel method 
as will be described later. 
Further making use of the structural feature of the cooling device of the 
invention, a defrosting electric pipe heater is inserted in the spine fin 
pipe coaxially of its helix in pressing contact with fin tips, whereby an 
increased defrosting efficiency can be achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First, the present invention will be described with reference to the 
embodiment shown in FIGS. 1 to 3. Indicated at 1 is the main body of a 
refrigerator having an inner case 2 and an outer case 3, with an expanded 
heat insulator 4 filled in the space therebetween. The interior of the 
main body 1 is separated by a partition 5 to provide a freezer compartment 
6 in the upper portion and a refrigerator compartment 7 in the lower 
portion. The freezer compartment 6 and the refrigerator compartment 7 have 
doors 8 and 9, respectively, for openably closing their front openings. 
The refrigerator has a cooling device 10 disposed above a frost water 
receptacle 11 within the partition 5, an electric fan 12 disposed in the 
rear of the cooling device for forcedly circulating cold air through the 
two compartments 6 and 7, a compressor 13 disposed in a machine chamber 14 
at a lower rear portion of the main body 1, and an evaporator tray 15 
provided above the compressor 13 for evaporating the water resulting from 
defrosting, utilizing the heat released from the compressor 13. The 
compressor 13, a condenser 17, a capillary tube 18 serving as an expansion 
valve, the cooling device 10 serving as an evaporator and the compressor 
13 are interconnected in a loop form in the order mentioned by a 
refrigerating cycle 16 incorporating a refrigerant. Cold air is circulated 
through the refrigerator compartment 7 and the freezer compartment 6 
through a cold air circulation channel 19. 
The cooling device 10 has the following construction. Tubes (or pipes) 11a, 
12a of copper or like material having high thermal conductivity are 
provided, over the entire periphery thereof, with radial spine fins 11b, 
12b of aluminum material to form spine fin tubes 10', 10", which are 
helically wound into a tubular form. The spine fin tube 10' is positioned 
upstream (the flow of cold air is indicated by arrows A in FIG. 1) from 
the other spine fin tube 10" in parallel therewith and in opposite 
relation thereto in respect of the direction of helix. The tubes 10', 10" 
are interconnected by a pipe 13c of the same material as the tubes 11a, 
12a. Thus, the cold obtained by evaporation of the refrigerant is 
delivered to air through the spine fins on the entire peripheral surfaces 
of the tubes. Moreover, since air flows through the cooling device 10 in 
bent streams as indicated by arrows B1 and B2, air effectively comes into 
contact with the fin tubes to be fully cooled by the device. 
The pitch of helix P1 of the spine tube 10' in the upstream position is 
larger than the pitch of helix P2 of the spine tube 10" in the downstream 
position. (For example, P1= and P2=41 mm). Accordingly frosting occurs 
uniformly over the entire device to preclude uneven flow of cold air, 
whereby an increased cooling efficiency can be achieved by the device. 
The fins 11b, 12b are attached to the tubes 11a, 12a (for example, 9.0 mm 
in outside diameter and 8.0 mm in inside diameter) by the following 
method. First, a thin aluminum strip (24.0 mm in width and 0.2 mm in 
thickness) is bent into a channel form having elongated opposed pieces 
(11.0 mm in length) and an interconnecting portion (2.0 mm in length) of 
the opposed pieces, and incisions are formed in the opposed pieces at a 
small spacing (0.8 mm) to provide spines. The bent strip formed with the 
spine fins is then wound around the tube, with the outer surface of the 
interconnecting portion in intimate contact with the surface of the tube 
(see, for example, U.S. Pat. No. 3,134,166). 
The spine fin tube thus obtained is helically wound by the method to be 
described below with reference to FIGS. 4 (a) and (b). 
A jig 29 for helically bending a spine fin tube 26 has an outside diameter 
d2 (8.0 mm) slightly smaller than the inside diameter d1 (9.0 mm) of the 
tube 26 by an amount for forming a suitable clearance. The jig extends 
substantially straight and has a forward end 29a which has a curve 
(indicated by an arrow a) corresponding to the curve of the helix and a 
twist (indicated by an arrow b) corresponding to the pitch P of helix. The 
straight portion of the jig 29 is inserted through the tube 26, and a 
fixing jig 30 is then secured to the exposed portion 29b of the jig 29 to 
thereby fixedly support the jig 29. A feeding member 31 is thereafter 
sliding moved on the jig 29 in the direction of arrow c by a feeder (not 
shown). Consequently the tube 26 is pushed forwardly of the jig 29 by the 
feeding member 31. When the tube 26 passes over the forward end 29a of the 
jig 29, the tube is helically bent in conformity with the curve (of arrow 
a) and, at the same time, bent inconformity with the twist (of arrow b) so 
as to have the pitch P. Thus the tube is helically bent as desired. 
In this way, the spine fin tube can be easily formed into a helix without 
causing damage to the spine fins on its entire peripheral surface, by 
utilizing the internal space of the tube, i.e. by inserting the jig 
through the tube. 
When a spine fin tube is to be helically wound, it is usually necessary to 
apply an external force thereto, but the spine fins, which have very low 
rigidity, then inevitably become deformed, failing to perform the 
comtemplated function. To avoid this problem, it was therefore necessary 
to provided spine fins limitedly on a portion of the surface of the tube 
as is the case with the cooling device disclosed in the aforementioned 
U.S. Pat. No. 3,766,976. However, the problem has been overcome by the 
forming method of the invention wherein the internal space of the tube is 
utilized. 
The embodiment shown in FIGS. 5 and 6 will now be described. 
The cooling device 100, like the one shown in FIGS. 1 to 3, is provided in 
a suitable portion of the cold air circulation channel. However, the 
second embodiment differs from the first in that it has a defrosting 
electric pipe heater. A spine fin tube 120 is made of copper, aluminum or 
like metal having relatively high thermal conductivity and is in the form 
of a helix having a pitch P and an inside diameter D1 as specified. A pipe 
heater 123 comprises a heater wire 124 covered with an insulator and 
inserted in a metal pipe 125, which is completely sealed off at its 
opposite ends with rubber or like elastic member 126. The outside diameter 
D2 (9.0 mm) of the heater is slightly larger than the inside diameter D1 
(8.0 mm) of the helix, i.e. through bore, of the spine fin tube 120. The 
pipe heater 123, as inserted in the interior of the helix of the tube 120, 
is resiliently supported by spine fins 122. The metal pipe 125 of the 
heater 123 is made of copper, aluminum or like material having high 
thermal conductivity. Accordingly the heat of the metal pipe 125 rapidly 
diffuses through the spine fins 122. The present embodiment has the same 
dimensions as the embodiment of FIG. 1. Indicated at 127 in FIG. 5 is a 
portion for interconnecting two opposed tubes. The connecting portion has 
no spine fins. This renders the metal pipe 125 easily insertable through 
the two tubes in the direction of arrow shown. Indicated at 128 is a flat 
pipe portion which is suitable for mounting a defrosting sensor thermostat 
thereon. 
Because the heat of the pipe heater rapidaly diffuses through a large 
number of spine fins in contact with the heater, the surface of the heater 
is maintained at a low temperature close to frost thawing temperature to 
prevent generation of steam and preclude undesired rise of the internal 
temperature of the refrigerator which is equipped with the present device. 
The pipe heater, which is supported by the spine fins, does not require a 
specific support or the like. This assures a simple construction. 
The cooling device 10 shown in FIGS. 1 to 3 can be provided with a pipe 
heater such as the one shown in FIGS. 5 and 6 (in the position indicated 
in a broken line H in FIG. 2). 
Irrespective of the presence or absence of the pipe heater, the spine fin 
tubes of FIGS. 1 to 3 can be identical in the direction and pitch of the 
helix.