US2178336A - Refrigerator defroster - Google Patents

Description

139., c. M. CHAPMAN REFRIGERATOR DEFROSTER Filed Sept. 13, 1937 INVENTOR.

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Patented Oct. 31, 1939 2.11am aarnmam'roa nsmos'rmi Clifford M. Chapman, lmiianapolll M, assign or of two-thirdsto Bil-ell B.

one-third to And: Storm. both of Indianapolis, Ind.

Application September 18, 198?, Serial No. 183,544

30laiml.

This invention relates to a defrosting device for refrigerator units which is particularly adaptable to mechanical refrigerators of the household type. In order that such refrigerators may I be operated at the maximum efliciency, it is necessary to remove the frost on the refrigerating unit at periodic intervals. This is generally accomplished by stopping the refrigerating action and permitting the temperature within the re- 10 frigerator to rise above the freezing point for a sufficient length of time to melt the frost from the unit. The time consumed in defrosting the refrigerator by this method is relatively great since the temperature of the whole interior must 15 be raised. This increase in temperature is also objectionable since it defeats the very purpose of the refrigerator.

Attempts have been made to defrost a refrigerator by electrical means by the use of a resisgo tance heating unit placed in position to supply heat to the refrigerating unit. Such methods reduce the time required for defrosting and prevent an undue increase in temperature of the refrigerator. One object of the present invention is to provide an electrical means for defrosting the cooling unit of a. refrigerator in the shortest time with the smallest rise in temperature of the refrigerator as a whole. This is accomplished by placing the heating element in such position that transmitted by direct conduction to the heat transfer surfaces of the cooling unit on which the frost collects.

Another object of the invention is to provide 35 means for mounting the defrosting elements in such manner that they may be quickly assembled as an accessory in a refrigerator already in use and may be attached to various types and sizes of refrigerating units without mechanical change. Other objects and features of the invention will be understood from the accompanying drawing and the following description and claims,

Fig. 1 is a sectional view through the upper portion of a household refrigerator showing the 48 cooling unit in side elevation with a defrosting unit attached thereto. Fig. 2 is a perspective view of a portion of the defrosting unit.

In the form of the invention shown by way of illustration in the drawing, there is illustrated 50 the upper portion of a refrigerator l having the usual door II and cooling unit l2 suitably mounted therein. The cooling unit herein shown is provided with a manifold l3 having connected thereto a plurality of refrigerant conductors I4 55 which pass down the side of the unit across the all, or nearly all of the heat generated therein isbottom and upwardly to a similar manifold on the opposite side not shown. The refrigerant conductors Il may be supplied with refrigerant at a low temperature inany well known manner and serve as the principal heat transfer surface 5 of the cooling unit. They are-normally in direct conductive relation with the walls of the unit I2 proper.

Beneath the unit I2 there is provided an electrical resistance heating element of a common form enclosed in a U-shaped metallic tube It. Said tube is held in position beneath the unit by a supporting cross piece It having adjustable hooks ll secured to its ends. A tension spring I. is secured to the hooks l1 and passes over the unit l2. A metallic plate I9 is preferably interposed between the U-shaped tube l5 and the lower portion of the refrigerant, conductors it. The resistance element within the tube i5 is supplied with electricity by conductors passing through an insulated cable 20 to a switch 2| which is in turn connected by a cable 22 to any suitable source of electric current. The switch 2i is provided with' ajbutton 22 by means of which the current tothe heating element may be manually turned on. The switch is provided with a thermostat bellows 23 connected by a tube 24 to a thermostat bulb 25. The bulb 25 is placed in contact with the walls of the cooling unit and the bellows 23 operates the switch in a well known manner to turn off the heating current when the temperature at the bulb 25 rises sufficiently above the melting point to melt the frost on the unit.

By means of. this construction, the defrosting of the refrigerator may be accomplished in a rapid and efllcient manner with a minimum of attention from the housewife. It is only necessary for the housewife to operate the switch 2i without disturbing the action of the refrigerating unit. The heat from the resistance element within the tube 15 is largely transmitted by direct conduction to the plate i9 and distributed by said plate by direct conduction to the refrigerant conductors l5 and thence to the walls of the unit. The heat radiated from the tube I5 and the plate I!) to the interior of the ice box as a whole is a very small percentage of the heat generated, since these surfaces prior to defrosting are generally at a low temperature and are themselves covered with 60 frost due to their direct conductive relation with the refrigerant conductors It. The temperature of the heat transfer surfaces can be raised very rapidly and as soon as this temperature has increased to a point at which the frost will be melted,

the heat is automatically turned oil without attention from the housewife.

The resilient mounting of the heating unit beneath the cooling unit provides that it may be quickly attached to almost any size of the'cooling unit and, therefore, does not need to be designed to fit a particular refrigerator. It may be installed by unskilled labor and may easily be installed in refrigerators already in service. The switch 2|, of course, may be supported by any suitable means anywhere within the refrigerator.

While the foregoing specification describes in detail a preferred form of the invention, the various elements thereof may be variedby those skilled in the art without departing from the scope of the invention as defined in the appended claims.

The invention claimed is:

1. In combination with the cooling unit of a refrigerator, a plate of heat conducting material engaging at least a portion of the heat transfer surface of said cooling unit, an electrical resistance heating unit engaging the opposite face of said plate, an elongated tension spring passing about said cooling unit, and means attached to the ends of said spring for supporting said heating unit in contact with said plate, and said plate in contact with said cooling unit.

2. In a refrigerator having a cooling unit with refrigerant conductors arranged about the outside thereof, the combination of a plate of heat conducting material engaging at least a part of the outer surfaces of said refrigerant conductors,

-an electrical resistance heating unit engaging the opposite face of said plate, an elongated tension spring passing about said cooling unit, and means attached to the ends of said spring for supporting said heating unit in contact with said plate, and said plate in contact with said cooling unit.

3. In combination with the cooling unit of a refrigerator, an electrical resistance heating element, heat transfer means interposed between said element and at least a portion of the heat transfer surface of said cooling unit, an elongated tension spring passing about said cooling unit, and means attached to the ends of said spring for supporting said heating element and said heat transfer means in heat transfer relation to said cooling unit.

CLIFFORD M. CHAPMAN.

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