US3195320A

US3195320A - Defrosting device for evaporator

Info

Publication number: US3195320A
Application number: US379501A
Authority: US
Inventors: Kita Shoichi
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd; Sanyo Denki Co Ltd
Priority date: 1963-07-06
Filing date: 1964-07-01
Publication date: 1965-07-20
Anticipated expiration: 1982-07-20

Description

July 20, 1965 SHOICHI KlTA DEFROSTING DEVICE FOR EVAPORATOR Filed July 1, 1964 3 Sheets-Sheet 1 m a N m owm W. .l M 0 y 1965- SHOICHI KlTA 3,195,320

' .DEFROSTING DEVICE FOR EVAPQRATOR Filed July 1, 1964 5 Sheets-Sheet 2 FIG.4

IN VENTOR Sf/O/CH/ K/734 July 20, I965 sHOlCHl KITA 3,195,320

DEFROSTING DEVICE FOR EVAPORATOR Filed July 1, 1964 3 Sheets-Sheet 3 so 3 36 2a Ill/l FIG. 6 INVENTOR 7 56 0/05 MIA United States Patent 3,195,320 DEFROSTING DEVICE FOR EVAPORATOR Shoichi Kita, Ota-shi, Gunma-lren, Japan, assignor to Sanyo Denki Kabushiki Kaisha, Osaka-fir, Japan, a corporation of Japan Filed July 1, 1964, Ser. No. 379,501 Claims priority, application Japan, July 6, 1963 (utility model), 3s/5e,s27; Sept. 23, 1963 (utility model), 38/ 72,003; Oct. 17, 1963 (utility model), 33/78,442

8 Claims. (Cl. 62-276) This invention relates to a defrosting device for evaporators for use in refrigerators and the like, and especially to a defrosting device for evaporators made by a method which is known as Roll-Bond method of US. Patent No. 2,690,002 according to the method of which a coolant passageway for flowing the coolant therethrough and an electric heater wire passageway for containing an electric heater wire therein are formed in an evaporator which is made of a double metal plate, and the electrical heater wire is made to operate in order to melt the frost adhered to the evaporator.

The conventional defrosting devices for evaporators used in refrigerators can be classified in general into three classes, (1) Off-Cycle System, (2) Hot-Gas System, and (3) Electric-Heater System. The off-cycle system in which the coolant circuit is made forcibly non-operative for a predetermined time, is most inexpensive, but it has the fatal disadvantage that a long time is necessary for the defrosting. On the other hand, the hot-gas system, in which a high temperature high pressure gas from a coolant compressor is caused to directly flow into an evaporator by-passing a condenser and capillary tube, has an advantage of a short defrosting time, but, at the same time, it has the disadvantage that as the exterior temperature drops in winter the temperature of the coolant gas which is sent out from the compressor becomes lower compared to that of summer time, and, accordingly, the defrosting time becomes longer. Now, the last mentioned electric heater system can provide good defrosting in both summer and winter, and it is often employed in the conventional refrigerators.

The electric heater element of the electric heater system is a so-called sheath heater which is so made that an electrical resistive body consisting for example of Nichrorne wire is insulated with a heatproof electrically insulating substance such as magnesium oxide so that the Wire does not alter due to the humidity within the re frigerator, and the insulated wire is installed in a metal tubing. A heater element such as the above is bent in a sinuous shape and is welded to the side wall of an evaporator, and, therefore, its processing is not efiicient, and the product can but become expensive.

Now, Roll-Bond method, that is a method of making double metal plate which is shown in US. Patent No. 2,690,002 entitled Method of Making Hollow Sheet Metal Fabrications Having a Plurality of Interconnected Passageways, has enabled the formation of the various desirable coolant pasageways for use in the evaporators of refrigerators. In addition, there has become available a Method of Inserting an Electrically Resistive Heater Element Into a Hollow Structure of Japanese Patent No. 403,815 according to the method of which a desired coolant passageway and another passageway which is independent from the former are formed in an evaporator which is made of a double metal plate, and a nickelchromium-iron alloy wire coated with an insulating silicon rubber is inserted into the latter passageway. Because of the above mentioned new idea, it is expected that a provision for evaporator having more eflicient and inexpensive electrical heater wire compared to the con- 3,195,320 Patented July 20, 1965 ventional one in which an electrical heater element comprising a metal tubing is welded to the evaporator will become feasible.

It is, therefore, an object of thisinvention to provide a defrosting device for an evaporator in which two passageways are formed in a double metal plate and a complete terminating treatment is applied to both end portions of the heater wire passageway into which the electrical heater wire is inserted by fluid pressure.

Another object of this invention is to provide a defrosting device for an evaporator in which a coolant passageway and a heater wire passageway into which an electrical heater wire is inserted are provided in the evaporator which is made of double metal plates, the connecting point of said electrical heater wire and a power source lead wire is electrically insulated with a certainty, and a terminating treatment is applied thereto so that mechanical force is not applied to the electrical heater wire.

A further object of this invention is to provide a de frosting device for an evaporator which has a coolant pas- I sageway and a heater wire passageway in which an electrical heater wire is inserted, wherein both end portions of the heater wire passageway are completely hermetically sealed, and, thereby, the electrical heater wire is completely protected from the humidity within the refrigerator.

A still further object of this invention is to provide a defrosting device for an evaporator which has a coolant passageway and a heater wire passageway in which an electrical heater wire is inserted, wherein the electrical insulation of the connecting portion of the electrical heater wire and the power source lead wire and the sealing of both end portions of said heater wire passageway are done with hermetic capshaving resiliency, and, thereby, a good insulation and hermetic sealing effect are obtained with a simple processing and with inexpensive materials.

It has been publicly known, because of the presence of said Japanese Patent No. 403,815, to form a defrosting device by inserting an electrical heater wire in an evaporator which has a coolant passageway and a heater wire passageway. On the other hand, in the case of employment of such device, as a defrosting device for an evaporator in a refrigerator, that an electrical heater wire consisting of a Nichrome wire to which a silicon rubber insulating coating is applied is inserted into the above mentioned heater wire passageway, it is necessary to make it a hermetically sealed structure at both end portions of the heater wire passageway because of the following reason: humidity within a refrigerator penetrates into said passageway, and repeated freezing and melting in accordance with cooling and heating, and, as particularly the passageway is sinuous, the moisture condenses and be comes water drops at the time of heating and remains within the passageway in said state. Furthermore, because of vapor pressure difference due to the temperature difference more humidity enters, at the time of cooling it freezes, and accumulation of moisture thus occurs. At the time of freezing, the stored water component expands in volume resulting in a deterioration and impairment in the insulating coating of the electrical heater wire, and, therefore, it is necessary to cut off said passageway from the open air and to make it a hermetically sealed structure.

On the other hand, the connection of the electrical heater wire and the power source lead wire should be preferably done within said passageway in the evaporator because of the disadvantage, otherwise, that in case the electrical heater wire extends to the exterior of the evaporator the insulating coating will be deteriorated due to the a above mentioned reason by the adhesion of humidity within the refrigerator, and that because of the presence of the humidity an electrolytic corrosion may be caused between the heater wire and a terminal of the power source lead wire.

Furthermore, the insulating coating material of the electrical heater wire is required to be such that it does not alter at a high temperature. In the case of silicon rubber, when heating and cooling are repeated in the presence of humidity it deteriorates to a large extent, and in the case of glass fiber, for example, electrical insulation cannot be maintained because of the adhesion of water component.

In an evaporator having a coolant passageway and a heater wire passageway in which an electrical heater Wire is inserted in accordance with this invention, a hermetic cap having a hollow portion opening at an end and extending to the center portion of the cap and a through aperture extending from said hollow portion to the other end of the cap is utilized, the connecting portion of said heater wire and said power source lead Wire is positioned in said hollow portion, the assemblage is inserted into and fixed to an opening of said heater wire passagewa and, thereby, a well protected defrosting device for an evaporator can be obtained.

Depending upon the size of the evaporator and mutual positional relation of a coolant passageway and a heater wire passageway, the hermetic cap may, instead of being fixed in the opening of the heater wire passageway of the evaporator, be fixed in the opening of a connecting tubing made of a metal and having a proper length and being connected with said opening of the heater wire passageway. In the examples of embodiment of this invention which will be explained hereinafter, a connecting tube is connected to the evaporator due to the convenience in processing since the evaporator is of a small capacity and the hermetic cap is fixed with a pressing mold.

Other objects and features of this invention will be more clearly understood by the explanation made hereinafter referring to the drawings in which:

FIGURE 1 is an explanatory schematic diagram of a coolant circuit and an electrical circuit of a refrigerator,

FIGURE 2 is a developed plan view of an evaporator having a coolant passageway and a heater wire passagey,

FIGURE 3 is diagram of a perspective view of the evaporator of FIGURE 2 bent into its final form,

FIGURE 4 is a sectional diagram on the plane of line 4-4 of FIGURE 3 showing the connection of an electrical heater Wire and a power source lead wire within a connecting tubing which is connected to an opening of a heater wire passageway of an evaporator,

FIGURE 5 is a diagram showing the mode of the device of assembling FIGURE 4, and

FIGURE 6 is a sectional diagram of a power source lead wire which is hermetically sealed and located in a. portion of a side wall of a refrigerator.

In FIGURE 1, there are shown a coolant circuit and an electrical circuit of a refrigerator which has a defrosting device for an evaporator in accordance with this invention. The coolant circuit comprises a motor driven compressor 1, a condenser 2, a capillary tube 3 and an evaporator 4, connected in series, the circuit being arranged so that the motor driven compressor 1 is operated and stopped by a temperature adjuster 5 which performs a switching operation in response to the temperature of the evaporator 4. Due to the operation of the coolant circuit the evaporator 4 is cooled, the humidity in a storage chamber 6 becomes frost and adheres thereto, and the cooling efficiency of the evaporator 4 is thereby lowered. Now, an electrical heater wire '7 which is inserted into the evaporator 4 is automatically energized by a proper defrosting starting device in order to remove the frost.

The above mentioned defrosting starting device starts the defrosting action once a day, for example, by means of an electric clock device 8 as is shown in the drawing, but

all

reverse contact point 14 which are controlled by energization of the coil It). The electrical heater wire 7 is connected with a power source in series with the parallel connection of the positive contact points 11 and 13 and the series connection of the coil It a bimetallic switch 15 for terminating the defrosting action and a manual switch 16 for voluntarily stopping the defrosting is connected in parallel with the electrical-heater wire 7. The reverse contact point 14 is connected to the power source in series with the temperature adjuster 5 and the motor driven compressor 1. V

The evaporator 4 shown in FIGURES 2 and 3 is made of a double metal plate which is made by a method known as Roll-Bond method. The process of Roll-Bond method is such that a stop weld material is interposed between two metal sheets, a heat and a pressure are applied thereto in order to bond the metal sheets together at the pertions where said stop weld material is not interposed, the interior passageway formed by said stop weld material is expanded by liquid pressure, and a complicated passageway is forrned therein. The evaporator 4 is formed in a U shape by being bent as shown in FIGURE 3. The evaporator 4- has a coolant passageway 24 which comprises liquid storing portions 19, 19 (FIG. 2)

portions

18, 18 of which are welded and most portions of which are expanded in both wing vertical portions17, 17,

flow passageways

21, 21 in a horizontal portion 20 for connecting said liquid storing portions, a narrow portion 22 of the flow passageway at one corner of the horizontal portion Ztl, and an opening 23, and a heater wire passageway 25 which traverses the upper part of one vertical portion 17, then comes down to the horizontal portion 20 and extends in a sinuous curve therethrough, then goes up to the other vertical portion 17 and traverses its upper part, and which as a wholeis parallel with said coolant passageway 24.

An inlet tube 46 having a built-in capillary tube 3 is connected with an opening 23 of said coolant passageway, and the capillary tube 3 is enlarged only after it goes through said narrow portion 22. A coolant in a liquid state entering through the capillary tube 3 flows through the liquid storing portion 19 in the'vertical portron 17, the flow passageway 21 in the horizontal portion 20, and the liquid storing portion 19 of the vertical portron 17 of the other side. The coolant absorbs heat and 1s gasified to cool the evaporator 4, and then flows to the motor driven compressor 1 through the tube 46.

End openings

26, 26 of the heater wire passageway 25 are provided at the upper side of each of the vertical 7

portions

17, 17, and connecting

tubes

27, 27 made of a metal are connected with both said

end opening portrons

26, 26. A flexible electrical heater wire 7 is inserted through the connecting tube. The electrical heater wire 7 is so made that a resistive body consisting of a IIrChrome wire is helically Wound on a core body which is made of a glass fiber and is shaped with a silicon varnish, and the coil is electrically insulated with a silicon rubber. In accordance with the method of the above mentioned Japanese patent, the electrical heater wire 7 1s inserted into a connecting tube 27 which is connected with one of the end openings 26 of said passageway 25, and by flowing therein a pulsating current of'a high pressure air the electrical heater wire 7 is made to go through such a bent heater wire passageway;

The sectional diagrams of FIGURES 4 and 5 illustrate the structure and the process of assembling of the defrost: ing device of evaporator of this invention.

The connecting tube 27 having a proper length is brazed to the end opening 26 of the heater wire passageway of the evaporator 4, and said electrical heater wire 7 is so inserted therein by fluid pressure that the proper length of each end portion extends to the outside. A power source lead wire 28 having a normal vinyl insulating coating is connected by a cylindrical terminal 29 to the end of the electrical heater wire 7 by being pressed by a press-bonding device 30, whereby a connected portion 37 is formed. A soft vinyl insulating tube 31 is placed to enclose the connection 37. The power source lead wire 28 is inserted through the through aperture 36 of a hermetic cap 32 and the connection 37 covered by the tube 31 is positioned in the hollow portion or cavity of the cap 32. The cap 32 is then pushed into the enlarged outer end of the tube 27 until a shoulder 33 of the cap 32 abuts against the end of the connecting tube 27. Thus the cylindrical body 39 of the cap 32 is positioned within the connecting tube 27 except for the head portion 34. The structure thus far defined is then located between the pressing molds 3838 and pressure is applied to form a groove in the tube 27 and of course in the cap 32, this groove lying substantially midway between the cavity 35 and the end of the cap. The cap 32 is thus fastened in position.

After this a protective cylinder made of thermocontacting synthetic resin is placed over the structure described covering a part of the connecting tube 27, the head 34 of cap 32 and a part of the power source lead wire 23. After the cylinder 50 has been positioned, heat is applied thereto causing the cylinder to contract in diameter and adhere tightly to the surfaces of the portions mentioned. FIGURE 4 shows the connection as completed while FIGURE 5 shows the various steps in forming the connection or joint.

A suitable material for the protective cylinder 50 is that known as Hishi Tube which is a tube of material of the vinyl chloride family sold by Mitsubishi Jushi KK. of Japan.

The sectional diagram of FIGURE 6 shows the power source lead wire 28 which is contained within a wall body 41 consisting of an outer box 42, an inner box 43 and a heat insulating material 44 and which is to be connected with the relay 9 and the switch 16 shown in FIGURE 1. In case the power source lead wire is a stranded wire, the vinyl insulating coating is peeled oh, and a bonding agent 45 consisting of a silicon resin having an osmosis is coated thereon in order to prevent humidity from flowing in through the gap of the strand.

Even though this invention is explained in connection with the above mentioned exemplary embodiment it is apparent that various modifications in details can be easily made by experts in the art, and such modifications shall be regarded as within the range of this invention.

What is claimed is:

1. A defrosting device for an evaporator, comprising a coolant passageway having an embossed portion which is distributed substantially uniformly on a surface of a plate, an electrical heater wire passageway having an embossed portion which is distributed substantially uniformly on said surface of said plate substantially parallel to said coolant passageway, a flexible electrical heater wire inserted by fluid pressure into said electrical heater wire passageway, and resilient caps hermetically fixed to each of the open ends of said electrical heater wire passageway, said caps each having a hollow portion which opens at one end and extends to the center portion of said cap and a through aperture which extends from said hollow portion to the other end of said cap, a power source lead wire extending through said through aperture and being connected with said electrical heater wire, and said connected portion being positioned within said hollow portion.

2. A defrosting device for an evaporator, comprising a coolant passageway having an embossed portion which is distributed substantially uniformly on a surface of a plate, an electrical heater wire passageway having an embossed portion which is distributed substantially uniformly on said surface of said plate substantially parallel to said coolant passageway, connecting tubes which are connected with each of both ends of said electrical heater wire passageway, a flexible and electrically insulated electrical heater wire which is inserted by fluid pressure into said connecting tube and said electrical heater wire passageway, and resilient hermetic caps which are hermetically fixed to the openings of each of said connecting tubes, each of said hermetic caps having a hollow portion which opens at one end and extends to the center portion of said hermetic cap and a through aperture which extends from said hollow portion to the other end of said hermetic cap, a power source lead wire extending through said through aperture and being connected with said electrical heater wire, and said connected portion being positioned within said hollow portion.

3. A defrosting device for an evaporator, comprising a coolant passageway having an embossed portion which is distributed substantially uniformly on a surface of a plate, an electrical heater wire passageway having an embossed portion which is distributed substantially uniformly on said surface of said plate substantially parallel to said coolant passageway, a connecting tube connected to each end of said electrical heater wire passageway, 21 flexible and electrically insulated electrical heater wire which is inserted by a pulsating current of a high pressure air into said connecting tubes and said electrical heater Wire passageway, and an hermetic cap fixed to the opening of each said connecting tube and having a hollow portion which opens at one end and extends to the center portion of said hermetic cap and a through aperture which extends from said hollow portion to the other end of said hermetic cap, a power source lead wire extending through said through aperture and connected with said electrical lead wire, said connected portion being positioned within said hollow portion and electrically insulated, and said connecting tube being squeezed at the portion around said through aperture so that said hermetic cap is hermetically fixed to said connecting tube.

4. An evaporator according to claim 1, characterized in that said hermetic cap is inserted in the open end of said heater wire passageway, and a portion of said passageway together with said hermetic cap is deformed by pressure to retain said cap in said passageway.

5. A defrosting device for an evaporator according to claim 2, characterized in that a protecting cylinder made of a heat-shrinkable synthetic resin is tightly fixed to the outer surface of said connecting tube and the outer surface of said power source lead wire covering the junction.

6. A defrosting device for an evaporator according to claim 1, characterized in that said power source lead wire has a stranded core wire, a part of the coating of said lead wire is peeled off, and an osmotic bonding agent is coated on said peeled portion.

7. A refrigerator having an outer wall consisting of an insulating material and comprising an evaporator according to claim 6, wherein the portion of said peeled core wire on which said osmotic bonding agent is coated is positioned in the interior of said wall.

8. In a refrigerator defrosting device of the type in which an electrical heating wire is positioned in a passageway in an evaporator structure and in tubes aligned with the ends of said passageway and extending outwardly from each end, said heating wire being electrically insulated from the passage walls while heat conductively related thereto, in combination, means for connecting the heater wire to power source lead wires, said connecting means comprising a metallic member crimped about the bared ends of each power source lead and a respective end of the heater wire, a sleeve of flexible insulated material extending about said crimped metallic member, a cap having an enlarged head, a cavity in said cap, an

a,1a5,a2o I i si aperture'extending from said cavity to an end of said 7 References Cited by the Examiner cap, said crimped metallic connector lying in said cavity and said power source lead Wire extending through said UNITED STATES PATENTS aperture, said cap extending into said respective tube with 2,431,308 11/47 Cole 174--152 said head abutting the end of said tube, a peripheral 5 2,75 8,150 8/56 Zargarpur 62-276 groove f rmed in said tube and said cap adjacent said head 1 2 399 57 p i -52 27 and a cover of moisture "impermeable material tightly fitting over said tube cap and a portion of said power WILLIAM WYE, Primary Examiner. source lead adjacent said cap.