US 3359751 A
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Dec. 26, 1967 F. STEVENS TWO TEMPERATURE REFRIGERATOR 2 Sheets-Sheet 1 Filed Oct. 14, 1966 5 All]! SOURCE INVENTOR. Fran/r L. Stevens BY K De.2s, 1967 F. L. STEVENS 3,359,751
TWO TEMPERATURE REFRIGERATOR United States Patent 3,359,751 TWO TEMPERATURE REFRIGERATOR Frank L. Stevens, Galesherg, Ill., assignor to Admiral Corporation, Chicago, 111., a corporation of Delaware Filed Oct. 14, 1966, Ser. No. 586,730 8 Claims. (Cl. 62-186) This invention relates in general to refrigerators having two separate refrigerated compartments in side-by-side relationship, and in particular to such refrigerators employing a single evaporator coil for cooling both compartments. More particularly, this invention relates to sideby-side combination refrigerator-freezers employing a single evaporator coil and cooperating temperature responsive means for individually controlling the temperature of each compartment in a manner which precludes excessive compressor running time and abnormally frequent compressor cycling.
Side-by-side combination refrigerator-freezers employing a common vertical dividing wall and separate compartment access doors, have been familiar to the domestic refrigeration industry for many years. However, only recently have such combinations met with consumer acceptance, and now they account for a substantial percentage of the total number of units being manufactured. Major factors leading to such consumer acceptance are the convenience of a separate below freezing compartment adjacent the above freezing compartment, thin wall insulation which allows a greater refrigerated volume in a given space, substantial cost reductions without'sacrificing performance, and decorator acceptance of two doors in sideby-side relationship, rather than the doors being stacked one above the other.
Typical early construction of side-by-side combination refrigerator-freezers comprised separate above freezing and below freezing compartments wherein each compartment had an independent refrigeration system basically comprising a motor-driven compressor, a condenser, restricting means, and an evaporator. Within a short time, due to the expense of two independent refrigeration systems, the components of the second system, except the evaporator, were eliminated. Thus, a single motor-driven compressor and individual evaporators, either with or without circulating fans, were utilized to cool the above freezing and below freezing compartments.
Refrigerators using a single compressor and individual evaporators typically had a single thermostat located in one of the compartments for controlling compressor operation. The thermostat was generally maintained in the above freezing compartment sincein the average home the access door thereto is opened more frequently than the door to the below freezing compartment. Consequently, when the above freezing compartment was opened more than normal, or was left open for an unusually long duration, the compressor operated continuously for long periods to satisfy the thermostat and the below freezing compartment was maintained at a much lower temperature than was desirable. While this was not detrimental from a standpoint of food storage, the unnecessary maintenance of a compartment at such low temperatures resulted in costly refrigerator operation.
This invention obviates many of the difficulties, deficiencies, and inadequacies of prior art side-by-side combination refrigerator-freezers by utilizing a single evaporator coil located in the below freezing compartment. A dual fan system provides air circulation in the below freezer compartment through a major portion of the evaporator, and provides circulation from the above freezing compartment through only an edge portion of the same evaporator. While air from both the above freezing and below freezing compartments circulate through the same evaporator, a bafile is utilized to substantially isolate each air flow, thereby preventing air in the below freezing compartment from commingling with air in the above freezing compartment. In addition, a separate thermostat and fan is provided for each compartment to insure adequate circulation and rapid temperature recovery, and for minimum compressor cycling.
Accordingly, it is the primary object of this invention to provide a side-by-side combination refrigerator-freezer having a single refrigeration system employing a single evaporator coil.
Another object of this invention is to provide a side-byside combination refrigerator-freezer wherein the temperature of each compartment may be individually con trolled by means which preclude lengthy continuous compressor operation or undue compressor cycling.
An additional object of this invention is to provide a side-by-side combination refrigerator-freezer having a thermostatic temperature sensitive element in the below freezing compartment which is located so as to minimize continuous compressor ope-ration and undue compressor cycling by being responsive to the temperatures of the below freezing and above freezing compartments.
A further object of this invention is to provide a frost free side-by-side combination refrigerator-freezer having counter-flow air movements through a single evaporator coil for more advantageous frost accumulation and subsequent defrosting of the above freezing section of said evaporator coil, and for more natural circulation through the below freezing section thereof.
It is also an object of this invention to provide a single evaporator coil for a two temperature refrigerator wherein said evaporator coil is void of heat exchange fins in the section thereof having the greatest exposure to moisture, thereby precluding the possibility of a rapid accumulation of frost from causing blockage of air movement therethrough.
Other objects of this invention will become apparent upon an examination of the following description taken in conjunction with the accompanying drawings wherein:
FIG. 1 is a three dimensional front view of a side-byside combination refrigerator-freezer in which the invention is incorporated, having its access doors in an open position.
FIG. 2 is a skeleton view of a side-by-side combination refrigerator-freezer showing the location of the single evaporator, the two fans, and the air flow pattern for each compartment.
FIG. 3 is an enlarged elevation view taken along line 3-3 of FIG. 2, showing in detail the single evaporator, the location of the fans, and the location of the thermostat sensing bulb in the below freezing compartment.
FIG. 4 is a schematic drawing of an electrical system for a side-by-side combination refrigerator-freezer incorporating the invention.
Turning to consideration of the drawings and in particular to FIG. 1, there is shown an automatic defrosting, side-by-side combination refrigerator-freezer which includes a cabinet 10 comprising side walls 12 and 14, a rear wall 15 extending between the side walls, and a common vertical dividing wall 16 dividing the cabinet into a below freezing compartment 18 and an above freezing compartment 20, each of which has its own access door 22 and 24, respectively. The below freezing compartment includes a motor driven fan 26 for circulating air therein and a thermostat 27 having a control knob 28 for controlling the compartment interior temperature. The above freezing compartment is equipped with a separate thermostat 30 having a control knob 32 and a sensing element 34 for sensing the interior temperature thereof.
Referring now to FIGS. 2 and 3, a rectangular evaporator, generally referred to by reference numeral 40, is mounted on the upper half of rear wall 15, parallel thereto. The evaporator is fabricated in a manner wellknown to those familiar with the domestic refrigeration art and basically is of the fin and tube construction. Evaporator tubing 42 is formed into a coil having a serpentinelike configuration, the straight portions of which are bonded to a series of vertical fins 44 for good heat transfer thereto and increased heat transfer surface area. A vertical baffle 46 located adjacent one end of the straight tubing portion (best seen in FIG. 3) divides the evaporator into two evaporator passages, a first passage 48, and a second passage 50.
First evaporator passage 48 comprises the straight portions of tubing 42 and vertical fins 44, and functions to cool below freezing compartment 18. Evaporator passage 50 primarily comprises U shaped end loops 51 of the serpentine coil which are void of heat transferring fins. The end loops function to absorb heat from the air circulating through passage 50 from the above freezing compartment, in a manner to be explained below.
The evaporator also includes a defrost heater 45 which is merely a resistance wire in contact with the fins and tubing for periodically melting frost accumulations.
The evaporator is the cooling element of the refrigeration system which also includes a motor-driven compressor 52, a condenser 55 and a capillary tube 57, or other suitable refrigerant restricting means. Operation of the refrigeration system comprising compressing, cooling, expanding, and evaporating the refrigerant gas contained in the system, is well-known by those in the art and need not be described in detail.
Air in the below freezing compartment circulates in a substantially rectangular pattern as indicated by the broad cross-hatched arrows of FIG. 2. The pattern is established by below freezing compartment fan 26 which forces air into the top of first evaporator passage 48, and into heat transfer relationship with tubing 42 and fins 44. The cooled air is discharged through the bottom of the evaporator passage, and into the below freezing compartment. The pattern of air flow in this compartment is assisted by natural convection, that is, the cold air seeks a lower level through the evaporator, and the warm air tends to rise.
An evaporator cover 54 overlays the front of evaporator 40 and includes a protective grill 56 in front of fan 26 to preclude accidental interference therewith. The below freezing compartment thermostat 27 includes a temperature sensing bulb 58 secured in intimate contact with the back surface of evaporator cover 54, opposite and slightly above evaporator passage 48, and directly beneath fan 26. Thermostat 27 controls operation of freezer compartment fan 26 and compressor 52, i.e. the refrigeration system.
While fan 26 and compressor 52 are idle, sensing bulb 58 primarily senses the interior temperature of the below freezing compartment by conduction through the evaporator cover, although, as the evaporator absorbs heat from the above freezing compartment in a manner to be explained below, sensing bulb 58 may also be influenced by conduction through the evaporator tubing. During operation of fan 26, the relatively warm air at the top of the below freezing compartment passes directly over bulb 58 before being cooled, thus the thermostat is only actuated when the compartment is thoroughly cooled. This provides longer continuous compressor running time and less compressor cycling, with improved operating efiiciency.
The above freezing compartment is cooled by passing air from it through second evaporator passage 50 containing end loops 51, which will be recalled are void of fins. To accomplish this, a diagonal duct 60 is provided within the confines of vertical dividing wall 16. Duct so has an inlet 62 at the bottom of the above freezing compartment, and an outlet 64 at the bottom of the second evaporator passage in the below freezing compartment. The duct provides a conduit for moving air from the above freezing compartment into the second evaporator passage. After passing through the second evaporator passage and being cooled by the evaporator end loops, the air is returned to the above freezing compartment via a second duct 66 having its inlet 68 at the top of the second evaporator passage and having its outlet '70 connected to an opening 74 provided through vertical dividing wall 16.
A fan 72 is mounted in opening 74 for establishing the air pattern in the above freezing compartment. This pattern comprises moving air from the above freezing compartment upwardly through duct 60, evaporator passage 50 and duct 66, then returning it to the original compartment through opening 74. The cold air slowly migrates to the bottom of the above freezing compartment to be drawn upwardly again through duct 60. This air fiow pattern can be clearly seen in FIG. 2 and is represented by the narrow solid arrows shown therein.
The air in the above freezing compartment typically has a high relative humidity due to the nature of the foods usually stored therein. As the air from this compartment circulates through second evaporator passage 50, frost will accumulate on the evaporator end loops which typically are maintained at a temperature of about -10 F. During initial cooling of the above freezing compartment, when the relative humidity is very high, the frost build-up can be so severe as to cause a substantial restriction of the passage if the evaporator were contructed in a conventional manner. This is obviated by eliminating the heat transfer fins from the evaporator end loops which prevents a frost accumulation on closely adjacent surfaces. While some loss may be detected in the quantity of heat transferred between the evaporator and the air from the fresh food compartment, this can be compensated for in various ways such as by providing more pronounced end loops or a greater air flow through the passage.
Moist air from the above freezing compartment enters the bottom of the second evaporator passage and immediately condenses and freezes on the lower evaporator end loops. Consequently, the greatest quantity of frost will accumulate in this area. Frost accumulation on the lower evaporator end loops, rather than on the loops near the top, is advantageous during the defrost phase since the frost loosened by the defrost heaters can drop unobstructed to the drip trough 80, where it may be melted by suitable electrical resistance heaters, not shown.
Operation of fan 72 is controlled by thermostat 30 (FIG. 1) located in above freezing compartment 20. Sensing bulb 34 for the thermostat is situated in the above freezing compartment, directly in the air stream flowing through opening 74 from the second evaporator passage. The sole function of thermostat 30 is to control operation of fan 72, and its operation is completely independent of compressor 52 and fan 26.
Thermostat 27 for the below freezing compartment, having its temperature sensing bulb 58 secured to the rear surface of evaporator cover 54, which as explained above, controls simultaneous operation of fan 26 and compressor 52, is also influenced by operation of above freezing compartment fan 72. This influence is exerted by relatively Warm air from the above freezing compartment moving through evaporator passage 50, warming the end loops which vaporizes the refrigerant contained therein. The vaporized refrigerant expands and flows through the evaporator tubing, especially through the passes at the top, radiating heat to sensing bulb 58 which actuates the thermostat and turns on the compressor and fan 26.
Unnecessary compressor cycling attributed to cooling the above freezing compartment is prevented in a novel manner. The sensing bulb for thermostat 27 is positioned at the top of the evaporator, which is the last portion to be warmed. Thus, the temperature of the entire evaporator must be increased before heat is radiated to the sensing bulb for actuating thermostat 27. Under normal operating conditions, fan 72 may cycle on and off several times before the entire evaporator is heated sufiiciently to actuate thermostat 27 since the specific heat of the evaporator section in passage 48 is large'compared to the heat'absonbed in cooling the above freezing compartment.
Turning now to FIG. 4, a schematic diagram of the compressor and fans for the two temperature refrigerator described, is shown. An A.C. source supplies power to motor-driven compressor 52 and the parallelly connected fan motor 26, which operate simultaneously. A snap action electric switch, having contacts 29, serially couples the source to the compressor and fan for controlling energization thereof. The switch is actuated by thermostat 27 mounted in the above freezing compartment which, as will be recalled, has its sensing element 58 secured tothe back side of evaporator cover 54. The AC. source is also connected to fan motor 72 which is controlled by a second snap action switch 31. This switch is actuated by thermostat 30, which has its sensing element 34 in the above freezing compartment.
A defrost timer 84 is provided to insure adequate defrost of evaporator 40 as specified time intervals during the day. This timer energizes defrost heater 45 which rapidly heats the evaporator and melts any frost accumulation. Water from the evaporator drips into a drain trough 80 and is piped to a convenient receptacle for disposal, such as a moisture evaporating pan, not shown.
In operation, the side-by-side combination refrigeratorfreezer is designed to operate as follows. The below freezing compartment thermostat closes electrical contacts 29, energizing fan 26 and the compressor, at approximately +8 F. They operate continuously until the temperature of the \below freezing compartment reaches approximately +2 F. During this time, above freezing compartment fan 72 may or may not be operating, depending upon the temper-anire of that compartment. This fan only operates responsive to thermostat 30 Which is preferably adjusted to close electrical contacts 31 at a temperature of +36 F. and open them at +31 F., and of course is capable of operating while the compressor is off. Fan 72 moves air through evaporator passage 50 and into the above freezing compartment, thereby reducing its temperature until bulb 34 senses that the compartment is satisfied. Thermostat 30 then opens contacts 31, tie-energizing the fan. Eventually, heat conducted to evaporator end loops 42 will be sensed by thermostat sensing bulb 58 thereby initiating operation of fan 26 and the compressor.
It should be noted that during the entire operation of either or both fans, air passing from the above freezing compartment through the second evaporator passage is entirely segregated from air passing through the first evaporator passage, by bafile 46. This complete segregation eliminates the possibility of an extremely cold quantity of air being conducted into the above freezing compartment, such as exists in many prior art two-temperature refrigerators. In addition, a localized high temperature area in the below freezing compartment is prevented by eliminating the entrance of relatively warm air from the above freezing compartment.
What has been described is a side-by-side combination refrigerator-freezer having a single evaporator with segregated air passages and independent, thermostatically operated fans for providing circulation through each compartment. Operation of the refrigeration system is controlled by a thermostat having a sensing bulb in one compartment, which is sensitive to the temperature of both compartments.
It is obvious that upon study by those skilled in the art, the disclosed invention may he altered or modified both in physical appearance and construction without departing from its inventive concept. Therefore, the scope of protection to be given this invention should not be limited by the embodiment described above, but should be determined by the essential descriptions thereof which appear in the appended claims.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A refrigerator comprising: an insulated cabinet; an insulated vertical wall dividing said cabinet into a below freezing compartment and an above freezing compartment, each of said compartments having an access opening thereto and movable doors for opening and closing said access openings; a refrigeration system, including an evaporator vertically mounted on a rear wall of said below freezing compartment; said evaporator including a serpentine like refrigerant conduit having U shaped end loops, and a vertical evaporator partition positioned perpendicular to said rear wall dividing said evaporator into a first evaporator passage comprising a major portion of said refrigerant conduit and a second evaporator passage comprising said end loops; means forming an air passage in said vertical wall having an inlet communicating with said above freezing compartment and an outlet adjacent said. evaporator in said below freezing compartment; and fan means for only circulating air in said below freezing compartment through said first evapor'ator passage and only circulating air from said above freezing compartment through said air passage, through said second evaporator passage, and back to said above freezing compartment.
2. The combination as set forth in claim 1 including additionally: a duct extending from one end of said second evaporator passage to an opening through and defined by said vertical dividing wall; said air passage formed in said vertical dividing wall having its inlet adjacent the bottom of said above freezing compartment and its outlet adjacent the remaining end of said second evaporator passage; and wherein said fan means comprise a first fan mounted in said below freezing compartment for moving air therein, and a second fan mounted in said opening for moving air from said above freezing compartment through said passage in the vertical well, through said second evaporator passage, and through said duct, thereby returning it to said above freezing compartment, and means controlling operation of said fans responsive to the respective temperatures of said compartments.
3. The combination as set forth in claim 2 wherein the refrigerant conduit in said first evaporator passage includes a plurality of spaced apart fins for rapid heat transfer from the air circulating therethrough, said fins being subject to only minor frost accumulation thereon due to a normally low moisture content in said below freezing compartment; and wherein said end loops are void of fins thereby precluding the occurrence of excessive frost resulting from a fortuitously abnormal moisture condition in said second compartment causing a rapid frost accumulation thereon and consequent blockage of said second evaporator passage; and heater means in heat transfer relationship with said evaporator for periodic defrosting thereof.
4. The combination as set forth in claim 3 wherein the air from said above freezing compartment circulates upwardly through said second evaporator passage thereby concentrating a fortuitous ice formation at the lower end thereof for simplified defrosting; and wherein the air in said below freezing compartment is circulated downwardly through said said first evaporator passage thereby taking advantage of natural air convection.
5. The combination as set forth in claim 4 wherein said first fan and said refrigeration system operate simultaneously responsive to the con-joint temperatures of said below freezing compartment and of said evaporator, and wherein said second fan operates responsive to the interior temperature of said above freezing compartment.
6. The combination as set forth in claim 5 including additionally: an evaporator cover substantially parallel to said rear wall for enclosing the front of said refrigerant conduit and having one surface thereof exposed to the interior of said below freezing compartment; and wherein said means controlling operation of said fans comprise two thermostats; a first of said thermostats controlling operation of said first fan and having a temperature sensing bulb secured to said evaporator cover adjacent the major portion of said refrigerant conduit primarily sensing the temperature of said below freezing compartment by conduction through said evaporator cover, said bulb also sensing a temperature change of said refrigerant conduit caused by heat exchange from air circulating through said second passage; and a second of said thermostats having a separate temperature sensing bulb located in said above freezing compartment controlling operation of said second fan, whereby the temperature of said compartments may be maintained at separate and substantially independently regulated levels.
7. The combination as set forth in claim 6 wherein the temperature sensing bulb of said first thermostat is located in the air stream of said first evaporator passage, adja cent its upper end, for maximum exposure to warm air from said below freezing compartment during operation of said first fan and said compressor, whereby said sensing bulb accurately portrays the temperature condition existing within said below freezing compartment and said thermostat allows said compressor to operate continuously until the below freezing compartment is thoroughly cooled, eliminating unnecessary frequent cycling thereof.
8. The combination as set forth in claim 7 wherein the specific heat of the major portion of said refrigerant conduit is relatively large and the quantity of heat transferred to the air circulated past said end loops by said second fan is relatively small, the temperature of said evaporator thereby slowly increasing, further eliminating frequent compressor cycling.
References Cited UNITED STATES PATENTS 2,812,642 11/1957 Jacobs 62-186 2,815,649 12/1957 Angelus 62-419 3,027,732 4/1962 Mann 62-419 3,122,899 3/ 1964 Constantini 62-419 3,232,071 2/1966 Wallenbrock 62-419 WILLIAM J. WYE, Primary Examiner.