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Publication numberUS3726105 A
Publication typeGrant
Publication dateApr 10, 1973
Filing dateMar 8, 1971
Priority dateMar 6, 1970
Also published asCA929254A1, DE2010717A1
Publication numberUS 3726105 A, US 3726105A, US-A-3726105, US3726105 A, US3726105A
InventorsAuracher R
Original AssigneeCanfield Co Gmbh H O
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Control arrangement for automatically defrosting a refrigerator
US 3726105 A
Abstract
A control arrangement for automatically defrosting a refrigerator in which a normally open bi-metal switch is arranged in the circuit of the motor driving the compressor of the refrigerator. The bi-metal switch closes upon heating thereof by a resistor arranged adjacent thereto. The resistor is arranged in a control circuit in series with a normally straight bi-metal strip arranged adjacent the evaporator of the refrigerator to sense the temperature of the evaporator and the bi-metal strip curves to close the control circuit upon sensing of a temperature of about between 3 DEG -5 DEG C to thereby energize the resistor and cause closing of the bi-metal switch. An elongated permanent magnet cooperates with the bi-metal strip to expedite closing of the latter.
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Description  (OCR text may contain errors)

Waited States Fatent Auracher CONTROL ARRANGENENT FOR AUTOMATICALLY DEFROSTING A REFRIGERATOR Robert Auracher, Stuttgart-Stammheim, Germany Europaische 11.0. Canfield Co., GmbH, Gartenberg/Off., Germany Filed: Mar. 8, 1971 Appl. No.: 121,928

Inventor:

Assignee:

Foreign Application Priority Data Mar. 6, 1970 Germany ..P 20 10 717.9

US. Cl. ..62/ 156, 62/80, 62/202,

62/208 Int. Cl ..F25d 21/06 Field of Search ..62/80, 156, 202, 62/208, 209

References Cited UNITED STATES PATENTS [0/1956 Shaw ..62/202 Primary ExaminerWilliam J. Wye Attorney-Michael S. Striker ABSTRACT A control arrangement for automatically defrosting a refrigerator in which a normally open bi-metal switch is arranged in the circuit of the motor driving the compressor of the refrigerator. The bi-metal switch closes upon heating thereof by a resistor arranged adjacent thereto. The resistor is arranged in a control circuit in series with a normally straight bi-metal strip arranged adjacent the evaporator of the refrigerator to sense the temperature of the evaporator and the bi-metal strip curves to close the control circuit upon sensing of a temperature of about between 35C to thereby energize the resistor and cause closing of the bi-rnetal switch. An elongated permanent magnet cooperates with the bi-metal strip to expedite closing of the latter.

7 Clains, 2 Drawing Figures COMM/V567? CGMWESSZZ? ram/e PATENTEUAPR1 0% 3,726,105

SHEET 1 OF 2 FIG] INVI-LN'IOR: none/1r 1402401 5/1 CONTROL ARRANGEMENT FOR AUTOMATICALLY DEFROSTING A REFRIGERATOR BACKGROUND OF THE INVENTION The present invention relates to a control arrangement for automatically defrosting of refrigerators.

In modern refrigerators there are two evaporators provided, namely an evaporator for the main compartment of the refrigerator and an evaporator for the freezer compartment.

In order to prevent accumulation of ice on the evaporator of the main compartment, the letter is provided with a heater which defrosts this evaporator during the time it is not in operation. Nevertheless, when the time periods during which the evaporator is not in operation are too short it is possible that ice will accumulate on the evaporator of the main compartment.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome this disadvantage of refrigerators known in the art and to positively prevent accumulation of ice on the evaporator in the main compartment of the refrigerator.

With this object in view the present invention mainly comprises a control arrangement for automatically defrosting a refrigerator which as usual comprises an evaporator for cooling the main compartment of the refrigerator, a compressor connected to this evaporator and an electric motor for driving the compressor, and the control arrangement of the present invention comprises an electrical circuit for energizing the motor, normally open bi-metal switch means in this circuit constructed to close the circuit upon heating of this bimetal switch to a first predetermined temperature, resistor means adjacent the bi-metal switch for heating, during passage of current therethrough, the bi-metal switch to close the latter, control circuit means connected to the resistor, and second normally open bimetal switch means arranged adjacent the main evaporator and sensing the temperature of the latter in which this bi-metal switch means is constructed to close upon sensing a second predetermined temperature to thereby energize the resistor.

In other words, the aforementioned second bi-metal switch means are connected to the evaporator of the main compartment of the refrigerator and senses the temperature of this evaporator. The second bi-metal switch closes when for instance a temperature of 3 5C is reached and closing of this second bi-metal switch means energizes the resistor. When however the temperature sensed is for instance under 0C, or at another value for which the second bi-metal switch is constructed, then the aforementioned resistor is not switched on, that is, the contacts of the first mentioned bi-metal switch in the main circuit of the refrigerator remain spaced from each other and the evaporator is not operated. However, if current passes through the resistor then the bi-metal springs of the first-mentioned bi-metal switch means are heated in a known manner and the contacts close, that is, the machine operates as long until the desired temperature in the main compartment is reached. Thereafter, the aforementioned described cycle is repeated.

An additional feature according to the present invention is the arrangement of a magnet strip adjacent to the bi-metal strip of the above-mentioned second bimetal switch means. This magnet strip is arranged at a distance from the bi-metal strip of the second bi-metal switch means in such a manner that the magnet strip will not influence the operation of the bi-metal strip of the second bi-metal switch means when this bi-metal strip is in substantially straight condition. In other words, the magnet will become active only when the bimetal strip with its contact at one end thereof slightly curves toward the fixed contact arranged opposite the contact on the bi-metal strip. The movement into the closed position of the two contacts will then occur suddenly with a snap action since the bi-metal strip tends to move towards the closing position and this movement is supported by the attraction force of the magnet.

Preferably, a permanent magnet is used for this purpose and especially a flexible magnet known per se.

The bi-metal strip of the second bi-metal switch means is constructed to close at a predetermined temperature. This predetermined temperature is preferably between 3 5C above zero, but evidently this switch may be constructed to close also at other temperatures.

According to the method of the present invention, the temperature of the main evaporator of the refrigerator is constantly sensed and the motor of the compressor for feeding refrigerant into the main evaporator is only energized if the sensed temperature is above a predetermined temperature and this predetermined temperature is preferably in the region of 5C above zero.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of the control arrangement of the present invention; and

FIG. 2 schematically illustrates the control arrangement connected to a refrigerator.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, the control arrangement of the present invention comprises a first bi-metal switch including the bi-metal springs 2 and 2a of which the bimetal spring 20 carries a movable contact 7 opposite of which a stationary contact 7a is arranged, and this bimetal switch is arranged in the circuit of a motor M which drives the compressor for furnishing a refrigerant to the main evaporator of the refrigerator. This bi-metal switch is normally open and the contacts 7 are closed only when this bi-metal switch is heated up to a first predetermined temperature. A resistor l is arranged adjacent to the springs of the mentioned bimetal switch and the resistor R is connected in series with a second bi-metal switch comprising a bi-metal strip 3 carrying at one end thereof a movable contact 4 arranged spaced from and opposite a fixed contact 5. This second bi-metal switch is connected to the main evaporator of the refrigerator, and senses the temperature of this main evaporator. An elongated permanent magnet 6 is arranged substantially parallel and spaced from the bi-metal strip 3.

The above-described control operate as follows:

As long as the temperature of the main evaporator sensed by the bi-metal strip 3 will be below a predetermined temperature, for instance below C above zero, the bi-metal strip 3 will stay in substantially straight condition so that the contacts 4 and 5 will be separated from each other. When the temperature sensed by the bi-metal strip 3 rises above the above-mentioned temperature, the bi-metal strip 3 will curve so that the contact 4 carried at one end thereof will move toward the stationary contact 5 and this movement will, after the curving has started, be supported by the attraction of the magnet 6 and therewith accelerated so that the contacts 4 and 5 will close suddenly to thereby energize the resistor 1 which in turn will heat up the springs 2 and 2a of the main bi-metal switch closing thereby the contacts 7 and 7a thereof to energize the motor of the compressor which furnishes refrigerant to the main evaporator. The temperature of the main evaporator will thereby be lowered which in turn will cause reopening of the contacts 4 and 5. When the resistor l is not energized the main bi-metal switch will stay in the position as shown in FIG. 2 to energize thereby the evaporator heater or defroster so that the evaporator is defrosted while the compressor motor is at standstill.

The magnet 6 is arranged at such a distance from the bi-metal strip 3 and exerts such a force on the latter so as not to prevent the reopening of the contacts 4 and 5. Evidently, the bi-metal strip 3 has a strip portion which is magnetizable by the magnet 6.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of control arrangements for automatically defrosting of refrigerators differing from the types described above.

While the invention has been illustrated and described as embodied in a control arrangement for automatically defrosting of a refrigerator, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the prevent invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning arrangement will and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. Control arrangement for a refrigerator including an evaporator for cooling the main compartment of the refrigerator and a compressor motor, said control arrangement comprisin an electric circuit for energizing the motor; first norma ly open bi-metal switch means in said circuit constructed to close said circuit upon heating of said bi-metal switch means to a first predetermined temperature; resistor means adjacent said himetal switch means for heating, during passage of current therethrough, said first bi-metal switch means to close the latter; and control circuit means connected to said resistor and comprising a second normally open bimetal switch means arranged adjacent the evaporator and sensing the temperature of said evaporator, said second bi-metal switch means being constructed to close when the temperature of said evaporator sensed by said second bi-metal switch means reaches a second predetermined temperature to thereby energize said resistor to heat said first bi-metal switch to said first predetermined temperature so as to close said first bimetal switch means.

2. A control arrangement as defined in claim 1, wherein said first bi-metal switch means comprises two bi-metal springs and wherein said second bi-metal switch means comprises a bi-metal strip carrying at one end a movable contact and a fixed contact normally spaced from said movable contact.

3. A control arrangement as defined in claim 2, and including magnet means cooperating with said bi-metal strip for expediting closing of the latter.

4. A control arrangement as defined in claim 3, wherein said magnet means is a permanent magnet.

5. A control arrangement as defined in claim 4, wherein said bi-metal strip is normally in a substantially straight position and bends with said one end thereof toward said fixed contact upon sensing said second predetermined temperature and wherein said permanent magnet is in the form of a magnet strip extending substantially parallel to said bi-metal strip and spaced therefrom a distance such so as not to cause closing of said second bi-metal switch means when said bi-metal strip thereof is in said straight condition.

6. A control arrangement as defined in claim 1, wherein said second bi-metal switch means is constructed to close at a temperature of about 5C above zero.

'7. Control arrangement as defined in claim 1, wherein said control arrangement further comprises heating means for heating said evaporator to said second predetermined temperature to thereby defrost said evaporator, said heating means being connected to said first bi-metal switch means to be actuated when said first bi-metal switch means is in open position.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2765630 *Jun 17, 1955Oct 9, 1956Borg WarnerRefrigerator air temperature control device
US3105364 *Apr 24, 1961Oct 1, 1963Gen Motors CorpRefrigerating apparatus with defrost means
US3134238 *Aug 31, 1960May 26, 1964Controls Co Of AmericaDefrost control responsive to frost accumulation
US3138006 *Apr 30, 1962Jun 23, 1964Gen Motors CorpRefrigerating apparatus including defrost means
US3174297 *Dec 24, 1962Mar 23, 1965Gen Motors CorpRefrigerating apparatus with defrost control means
US3228204 *Jul 3, 1963Jan 11, 1966Controls Co Of AmericaRefrigeration control for defrosting
US3525222 *Jun 11, 1968Aug 25, 1970Schuller PeterElectric temperature regulator
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3834618 *Feb 11, 1974Sep 10, 1974Keens LTemperature setback control
US4530217 *Apr 19, 1983Jul 23, 1985Indesit Industrial Elettrodometici Italiana S.P.A.Defrosting device for a refrigerator
US4741169 *Aug 6, 1987May 3, 1988Whirlpool CorporationIce maker safety control
US8794026Apr 18, 2008Aug 5, 2014Whirlpool CorporationSecondary cooling apparatus and method for a refrigerator
Classifications
U.S. Classification62/156, 62/208, 62/202, 62/80
International ClassificationF25D21/00
Cooperative ClassificationF25D21/002
European ClassificationF25D21/00A