US2698521A - Refrigerating apparatus, incluiding defrosting means - Google Patents

Description

Jan. 4, 1955 L. J. MANN 2,698,521

REFRIGERATING APPARATUS, INCLUDING DEFROSTING MEANS Filed Jan. 4, 1952 United States Patent '0 REFRIGERATING APPARATUS, INCLUDING DEFROSTING MEANS Leonard 3. Mann, Dayton, Ohio, 'assigrior to General Motors Corporation, Dayton, Ohio, a corporation of Deiaware Application January 4, 1952, Sei'ial No. 254,935

4-Claims. =(CL' 62 4) This invention relates to refrigerating apparatus and more particularly to a system for defrosting evaporate-rs.

Various systems have 'been devised for defrosting evaporators automatically but there has alwaysbeenditfi culty in causing this'defrosting to take place uniformly. Particularly it has been foundthat, adjacent the inlet and outlet connections of certain 'evaporators and the connections themselves, there has been difficulty in removing the frost from these portions and keeping the frost removed. If the'defrosting cycle were lengthened, then refrigerator would'become too warm before all portions were completely defrosted.

It is an object of my'invention'to provide'an additional supply of heat adjacent 'the portion which is most dinicult to defrost.

It is another object of my invention to seal-range the refrigerator that the heat absorption by the evaporator is greatest adjacent the refrigerant'supply and return con nections.

It is another-object of my invention to apply the condenser of a secondary refrigerant circuit to that portion of the evaporator and also to the adjacent portions of ;he refrigerant conduit where it is ditficult 'to remove the rost.

It is another object of my invention to provide an upright rectangular type of evaporator having the refrigerant connections adjacent the upper corner with a vertical condenser tube of which the lower portion is in heat exchange relation with that corner'of 'the plate and the upper portion of which is inh'eat exchange relation with the conduits.

It is another object of my invention 'to applyto a refrigerator having a separate insulated freezing 'cor'npartment and a food compartment provided with an upright rectangular refrigerant plate, asecondary refrigerant circuit for cooling portions of the food compartment which has a vertical condenser located adjacent an upper corner of the refrigerated plate where the refrigerantsupply and return conduits to it are located.

These Objects are obtained by providing in the food cornpartment a vertical refrigerant plate having supply and return connections at an upper corner extending from the primary or freezing evaporator. A secondary refrigerant circuit having its evaporator located beneath the bottom of the food compartment 'has avertie'al tunnlar condenser with its lower portion in direct Contact with the end portion of the refrigerated plate and its extreme upper portion clamped in heat exchange relation with the supply and return conduits. The "system operates upon a defrosting cycle according "to the temperature of the diagonally opposite, corner of the refrigerated plate. By this arrangement, the freezing evaporator is kept at all times at a'low temperature "and'the refrigerated plate in the food compartment provides proper temperature and humidity conditions and defrosting both of the plate and the supply connections is obtained every cycle.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing:

The figure is a vertical sectional view of a two-compartment refrigerator embodying one form of my invention.

Referring now to the drawing, there is provided an outer hermetically sealed sheet metal shell 20 enclosing the cabinet. The joints of this shell are sealed. There is of the cabinet in the form of a box-'shapedfmetal ed11- tainer having its front side open. Beneath the freezing compartment container 32 there is'provided a'foodco'rnpartment container 38 in the form of 'a'box-shapedini'et'al inner'containeror liner, also having its front side open. The front edges of the box- shaped container 32 and 38 are connected by breaker strips of heat insulating rn'ate'rial "with the frontwall'of the outer shell 20 as is oil'stomary in the art. The freezing compartment container 32 and the food compartment'container 38 are preferably closed by separate front doors (-not shown). The spaces between these containers 32 and 38 and the walls of the outer shell are filled with insulation such as "thineralor glass wool enclosed'in sealed bags of somesuitahle material such as polyethylene.

The freezing compartment container 32 is provided with smooth surfaced inner walls so that any snow or frost accumulating thereon can be readily scraped or brushed off. The freezing compartment container 32 is cooled by the evaporating stage of a prnn'ary refrigcrating system which includes a sealed motor compressor unit which delivers compressed refrigerant to a condenser 52, both of which are located in amachinejcoinpartment 161 beneath the partition wall 24 of the cabinet 20. The motor compressor unit50 is 'preferably'o'f tlie high side type shown in the Rataiczak Patent 2,377,965, issued June 12, 1945.

The condenser 52 delivers liquid refrigerant through a capillary tube restrictor '54 to the inlet connection of serpentine tubing 57 applied to the rear wallof the container'SZ'and loops 58, 59 and 60 applied to'the teens-y shelves at one side of the;container 32. From the loop 60 the refrigerant passes into sections 61 of'evapo'ra'tor tubing which extend in heat'exchange relation with the top, bottom and sides ofthe container 32.

7 After passing through a liquid trap at the endof the tubing 61, the refrigerant is conducted through a supply conduit 72-to a vertical rectangular refrigerated plate type evaporator Q0 spaced from, but fastened to, the rear wall of the food compartment container 38 within and near the top of the food compartment. The refrigerated plate 90 has a minimum of mass and low hold-over capacity. It is provided with 'a refrigerant passage 91 which extends'along the "edges of the refrigerated plate evaporator 99 having its inlet '89 connected to the supply conduit "2 and its outlet 87 connected to the return conduit 94 adjacent the upper left-hand corner of the plate 90 as shown in the figure. The return conduit 34 connects to an accumulator tank 96 located along the upper rear edge of the freezing compartment container 32. The suction conduit 125 extends from this accumulator tank 96 to the suction inlet of the compressor 58.

The operation of the motor-compressor unit 50 is controlled by a snap-acting thermostat switch 89 connected in series with the supply conductor 81 of the motorcompressor unit 50. This switch is set to operate upon a defrosting cycle and has its thermo-sensitive element 378 clamped to the lower right-hand corner of the refrigerated plate 9i? in substantially direct heat exchange relation with the refrigerant passage 95. The thermosensitvie element 370 is located upon the plate with respect to the refrigerant passage 91 at such a location which will provide a control of the amount'of liquid rejfrigerant in the passage 91 during the operating period thesy'stem to provide the desired average temperature for the interior of the food compartment 81. The switch '84 is set so that it will not close until the rtempera'tur'e of the thermo-sensitive element reaches a defrosting tern; perature such as 34 to 36 degrees Fahrenheit. The switch '30 is set to open at a s'utficiently low temperature below freezing, such as 0 to 10 degrees Fahrenheit, which will assure adequate cooling for the food compartment 38.

The freezing compartment container 32 is sufficiently isolated thermally from the food compartment 38 and the refrigerated plate 90 and the refrigerated plate 90, in general, defrosts sufiiciently rapid that the food compartment container 32 and its contents remain at a low sub-freezing temperature at all times. However, ditliculty was encountered in defrosting the upper corner of the refrigerated plate 90 adjacent the inlet and outlet 89 and 87 and the adjacent portions of the refrigerant sup ply and return connections 72 and 94. On these surfaces frost would not melt completely during the idle period of the refrigerating system and, consequently the frost and ice would build up and accumulate until a large mass was obtained. This made it necessary to shut down the entire refrigerating system and to remove and store, in another cold place, the contents of the freezing compartment container 32.

At the bottom of the food compartment container 38 there are provided two ventilated vegetable drawers 127 and 129 which provide a moist cold atmosphere/ To keep these drawers 127 and 129 at a sufiiciently low temperature, there is provided a secondary refrigerant circuit including an evaporating portion 131 in the insulation space immediately beneath the bottom of the food compartment container 38. The condenser of the secondary circuit has been located in various points in other refrigerators. For example, the condenser has been located in heat exchange relation with the freezing container 32. It has been placed on the rear wall of the food compartment container 38 adjacent the plate 90. It has also been placed in heat exchange relation with the central portion of the plate 90. These locations were not ideal.

To provide satisfactory operation of the system and complete defrosting of all refrigerated surfaces in the food compartment 38 every cycle, I provide a long vertical tubular condenser 137. The upper third of this condenser 137 I clamp by means of the clamp 138 to the supply and return connections 72 and 94 nearest the inlet and outlet 89 and 87 on the back side of the plate 90. The lower two-thirds of the condenser 137 is also clamped in direct heat exchange relation with the upper left-hand corner of the refrigerated plate evaporator 90 in vertical position directly between the inlet 89 and the outlet 87 as shown in the drawing. This condenser 137 is connected by supply and return conduits 133 and 135 with the secondary evaporator 131 as shown in the drawing. Accordingly, the secondary refrigerant circuit provides an added source of heat for the upper left-hand corner of the refrigerated plate 90 and the adjacent portions of the supply and return conduits 72 and 94 which in prior arrangements defrosted more slowly than the remainder of the plate 90, thereby hastening the defrosting of this portion of the refrigerated plate 90 during each cycle period of the compressor. In this way, adequate refrigeration is provided for the secondary circuit and at the same time defrosting of all refrigerated surfaces in the food compartment 38 is assured every cycle, thereby overcoming the previously encountered difficulty of the accumulation of frost upon this portion of the refrigera1te9d4plate 90 and the supply and return connections 72 an While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as will come within the scope of the claims which follow.

What is claimed is as follows:

1. Refrigerating apparatus including an above f eezing food compartment and a below freezing compartment, a thermal heat transfer barrier between said compartments, a refrigerant liquefying means, a freezing evaporating means in heat exchange relation with said below freezing compartment and having its inlet connected to an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to an outlet of said freezing evaporating means, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, a secondary refrigerant circuit having an evaporating portion in heat exchange relation with a portion of said food compartment and a condensing portion in heat exchange relation with the portion of the food compartment evaporating means nearest the refrigerant inlet and means responsive to the temperature of the food compartment evaporating means for cyclically controlling the supply of refrigerant to said an outlet of said liquefying means, a food compartment,

evaporating means in heat exchange relation with said food compartment and having its inlet connected to an outlet of said freezing evaporating means, means for returning evaporated refrigerant from said freezing and food compartment evaporating means to said liquefying means, a secondary refrigerant circuit having an evaporating portion in heat exchange relation with the lower portion of said food compartment and an upright condensing portion having a portion in heat exchange with the refrigerant inlet connection to said food compartment evaporating means and a portion in heat exchange relation with an adjacent portion of the food compartment evaporating means and means responsive to the temperature of the food compartment evaporating means for cyclically controlling the supply of refrigerant to said food compartment evaporating means so as to vary the temperature thereof below and above freezing during each cycle so as to defrost said food compartment evaporating means once each cycle.

3. Refrigerating apparatus including an insulated refrigerator cabinet containing a first low temperature compartment and a second higher temperature compartment, a first evaporator in said first compartment, an upright plate type refrigerant evaporator located in direct heat exchange relation with air in said second compartment, refrigerant supply and return conduits connected to said plate type evaporator, refrigerant liquefying means connected to supply liquid refrigerant to said evaporators in series, a secondary refrigerant circuit including an evaporating means in heat exchange relation with a portion of said compartment and a condensing means in heat exchange relation with the portion of said plate evaporator nearest the refrigerant supply conduit, and means responsive to the temperature of said plate evaporator for cyclically controlling the supply of refrigerant to said plate type evaporator so as to vary the temperature thereof below and above freezing during each cycle so as to defrost said plate evaporator once each cycle.

4. Refrigerating apparatus including an insulated cabinet having a food storage compartment therein, an upright plate type rectangular refrigerant evaporator adjacent to but spaced from the rear wall of said compartment and having a refrigerant passage extending along the edges thereof with the inlet and outlet located adjacent an upper corner thereof, supply and suction conducits connecting to said inlet and 'outlet, refrigerant liquefying means connecting to said conduits, a secondary refrigerant circuit including a condensing means in heat exchange relationtwith the upper corner of said plate evaporator ad acent said inlet and outlet, and in heat exchange relation with the portion of said conduits ad- References Cited in the file of this patent UNITED STATES PATENTS 2,282,342 Preble May 12, 1942 2,301,313 Money- Nov. 10, 19-42 2,484,588 Richard Oct. 11, 1949 2,491,105. Gaugler Dec. 13, 1949 2,561,305 Limpert July 17, 1951

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