US2539813A - Refrigerating apparatus and method - Google Patents

Description

7 Filed Sept. 27, 1946 2 Sheets-Sheet 1 Jan. 30, 1951 1.. E. CARSON v 2,539,813

REFRIGERATING APPARATUS AND METHOD I INVENTOR. l E E (V/197a Z. (ar a BY W W Jan. 30, 1951 E. CARSON REFRIGERATING APPARATUS AND METHOD 2 Sheets-Sheet 2 Filed Sept. 27, 1946 INVENTOR. [aw/awn? Z. (0/50/7 Patented Jan. 30, 1951 FUNITEJD srATEs PATENT O FIC p I 2,539,813 REFRIGERATING APPARATUS METHOD Lawrence E. Carson, Alhambra, Calif.

Application September 27, 1946, Serial No. 699,797

1 Claim. (-Cl. 62102) The present invention relates to a refrigerating apparatus and methods, and more particularly to apparatus and methods for accomplishing the defrosting of low temperature refrigerating apparatus.

It has been conventional practice in commercial refrigerating apparatus designed to store food stuffs and the like at temperatures above the freezing point, to employ what is known as an automatic defrosting cycle. This arrangement effects defrosting of the refrigeration coils automatically during each off cycle of the refrigeration unit by providing controlling means which initiate operation of the refrigerating unit only when the temperature of the refrigerating coil itself reaches a level substantially above the freezing point, and terminate operation of the refrigerating unit when the coil reaches a temperature corresponding to the desired temperature of the storage space, usually 32 F. to 34 F.; thecoil temperatureitself being-substantially lower than thisfigur'e and therefore low enough to cause frosting of the coil. This arrangement has numerous advantages, among which are the minimization of the control devices required and the prevention of the building up of a more than thin film of frost upon the refrigerating coils. Since only thin films of frost areformed, the heat transfer fins carried by the refrigeration coils may be spaced apart a minimum distance to increase the effective heat transfer area and the efficiency of heat'exchange process. Close fin spacing is not possible in those installations where comparatively thick formations of frost are allowed to buildup, because of an inabilityto automatically defrostina manner similar to the'methods used with coils operating in appliances maintained abov'ifreezing.

This method-of accomplishing defrosting, however, has not previouslybeen applied to refrigerators designed for storing ,food stufis and the like at the low temperaturesbelow freezing, becausethe melting of the frost covering the coils obviously can be achieved only when the temperature of the coils rises above the freezing point. It has therefore been necessary in connection with the defrosting of the refrigerating units employed in such lowtemperature refrigerators to employ relatively complicated arrangements such as the use of time-controlled def-rosting devices, employingv coil heating devices of I very high output, limiting their operation to short periods of time to avoid overheating in the storage space, or to emplo complex control devices iorlreversing the refrigerating cycle so as to effect condensation within the refrigerating coil.

The principal object of the present invention is to make possible the employment in low temperature refrigerators of a defrosting means and method, similar to that above described, as previously used only in connection with the refrigerators designed for storing food stuffs and the like at temperatures above the freezing point.

A further object of the invention is to prevent the raising of the temperature of the storage compartment during defrosting of the refrigeration coils- A further and more specific object of the invention is make possible the automatic selective operation of the refrigerating apparatus in either a defrosting cycle or a normal refrigeratioficycle depending upon the extent of frost or ice formation upon the refrigeration coils.

A further object of the invention is to facilitate the removal from the storage compartment of water resulting from the defrosting operation.

The foregoing together with the other objects and advantages of the invention are preferably accomplished by providing ahood-like member extending above and at the sides of the refrigerating coils in such a way as to effectively prevent the passage of heated air by convection from the neighborhood of the refrigerating coils to the food storage space while leaving an open space below the level of the coils for the circulation of cold air either by convection or forced draft. In order to accelerate defrosting, heat- ,ing means which may be of relatively low thermal output are disposed within this hood-like'memher and control devices are provided for causing the heating means to warm the air within the hood-like member whenever the operation of the refrigerating unit terminates, thus melting any ice or frost accumulation from the coils.

During such defrosting the hood-like member prevents the passage of the warmed air within the hood to the storage compartment.

' Preferably, though not necessarily, additional control means may be provided for preventing the operation of the heating means in the event the coil temperature is not suflicient'ly below the. temperature of the storage compartmenttoim dicate the necessity for defrosting, and where forced draft circulation of refrigerated air is provided for it is desirable, though not essential, to provide means for delaying the initiation of operation of the air circulating means until a suflicient period after the resumption of the operation of the refrigerating unit to permit adequate cooling of the air within the hood-like member previously heated for the purpose of defrosting.

Other objects and advantages of the invention will be apparent from -the following description taken in conjunction with the drawings forming part of this specification, and in which:

Figure 1 is a ghost view in side elevation of a low temperature refrigerator embodying the invention;

Figure 2 is a view in section taken along the lines 2-2 of Figure 1;

Figured is a viewin section, partly broken I away, taken along lines 3-3 of Figure 1.

Figure 4 is a view in isometric perspective of the hooded coil housing of the refrigerator; and

Figure 5 is a diagrammatic illustration of the electrical system utilized for the automatic control of the refrigerator.

Referring to the drawings for more specific details of the invention, the refrigerator is comprised of a storage assembly, a duct assembly, and a hooded coil housing, indicated generally at I0, I2 and I4, respectively. Each wall of the storage assembly is comprised of an inner shell I6, an outer shell I8, and a substantial thickness of insulating material l8, such as glass wool. therebetween. An insulating partition wall is shown as dividing the assembly into two compartments 22 and 24, access to the former being had through a door 26, located in the top of the assembly and pivotably secured thereto by hinges 21, while access to the latter compartment is had through a door 28 in the front wall of the as"embly. The compartment 24 is adapted to serve as an auxiliary chamber and is not a necessary element of the embodiment of the invention.

The floor of the compartment 22 is multi-level, comprising a raised surface 30 and a lower surface 32, said latter surface being adapted to sup port a leg-supported wire tray 34 for a purpose hereinafter described, so that the upper surface of the tray is at the level of floor surface 80.

The rear wall of the storage assembly adjacent the upper compartment 22 contains a pair of spaced apart vertical ducts 38 and 38, duct 38 having an inlet 40 communicating with the chamber 22 above the floor surface 30 and an outlet 42 communicating with the duct assembly I2, and duct 38 having an outlet 44 communicating with the chamber 22 adjacent the floor surface 32 and an inlet 48 communicating with the duct assembly I2.

The duct assembly I2 comprises insulation walls similar in type to those of the storage assembly I0 and is secured to the storage assembly so that the outlet 42 of duct 36 and the inlet 46 of duct 88 are in communication respective, with spaced apart vertical ducts 48 and 50 within the duct assembly I2. The duct 48 has an outlet 52 and the duct 50 has an inlet 54, both the outlet 52 and the inlet 54 being provided with inwardly extending flanges, as shown.

The hooded coil housing I4, shown in greatest detail in Figure 4, constitutes a fixed means.

having no movable elements such as doors, dampers or thexlike, adapted to inhibit the passage of air from the coil to the storage compartment through the passages connecting the coil with the said-compartment. In the illustrated e'mbodiment this housing is rectangular in form 4 at 88, comprising headers", a bank of tubes I2. and a plurality of spaced apart parallel fins I4. A metal drainage tray I8 having a pipe drain I8 underlies the coil assembly 88. A vertical inner wall 80 and a horizontal inner wall 82, extending from the front wall 84 and terminating a substantial distance forwardly of the rear wall 88 deflne an air inlet duct having a Supported by the wall ifi iorwardly and below" the coil assembly 68 is a rotary blower 88 adapted to be driven by a motor located within a housing 80 supported on the outside of the housing I4 on the side wall 56. The blower comprises an inlet 92, a blower fan, not shown, and an outlet duct 94 communicating with a flanged outlet 96 of the housing I4.

The hooded coil housing I4 is secured to the duct assembly I2 so that the flanged inlet 84 and the flanged outlet 96 of the housing are received, respectively, by the flanged outlet 52 of the duct 48 and the flanged inlet 54 of the duct 50.

The wiring circuit of Figure 5 shows the manner m which the actuating mechanism or the refrigerator is operably interconnected to provide for a fully automatic cycle of operation. In Figure 5, the compressor motor 98, adapted to circulate a suitable refrigerant through the coil assembly 88, is connected across electrical power lines I00 and I02, while, in shunt therewith, is a motor I04, located within the houing and adapted to drive the fan of blower 88, and a thermostat switch I06. A heater element I08 is connected from line I00 to a pole of a main thermostat switch' IIO. The switches I08 and H0 are shown in position for positive low temperature operation of the refrigerator. When the compressor motor 88 and the blower motor More in operation, air at a temperature of 0-13 F.-is.recirculated between the hooded coil housing I4 and the storage compartment 22 in the following manner: The air, after passing over the coil assembly 68, passes into the blower inlet 92, along the blower duct 94, upwardly through duct 50 in assembly I2, downwardly through duct 38 in assembly I0, and through the outlet 44 in compartment 22 to pass upwardly through the raised wire tray 34 and contact the stored articles thereon. The air at a temperature of 0-13 F. passes out of compartment 22 through the duct inlet 40, upwardly through duct 38, downwardly through duct 48, and through the duct 84 in the housing I4 to the coil assembly 68. The dotted arrows of Figure 1 indicate the path of air from the blower 88 to the compartment 22 while the solid arrows indicate the path of the air in passing from the compartment 22 to the blower 88.

As the aforedescribed operation continues, heat from the circulating air is being continuously given up to the refrigerant within the coil assembly 88 to lower the temperature of the circulating air, and frost is being continuously formed on the coil assembly in this process.

When the temperature of the circulating air has dropped to a lower limit value, as for example 0 F., the main thermostatic switch 0, located within the housing I4, automatically reverses to disconnect the compressor motor 88 and the blower motor I04 frm the power source and to connect heater element I08, also located within the housing I4 adjacent the coil assembly 88, to said source. When the air in the vicinity of the coil assembly reaches a temperature of approxi- The air within the upper ortion of housing I4 is continually heated by the eater element 338 until it reaches a temperature of approximately 38 F. in order to completely defrost the coil assembly 68. As the temperature of the air rises and the defrosting operation continues, water falls from the coil asembly 68, collects in the tray I6, and passes therefrom through the drainpipe 18 to a location, not shown, outside of the housing I4.

It will be noted that the warm air, of a temperature approaching 38 F., within the housing I4, is prevented from entering the storage com partment 22 or from causing any substantial temperature raising effect in said compartment by virtue of the warm air trap provided by the housing I4 above the blower 88, and the fact that the Warm air will have to extend downwardly at least to the inlet 92 of the blower in order to pass into the vertical duct 50. If the blower is so constructed that the air may not freely pass through the blower 88 ino duct 50 when the blower fan is not in operation, then the warm air will have 1 to extend downwardly to the duct 84 in order to pass into the vertical duct 48. Thus the arrangement is such that either a blower which does not materialy restrict or one which does substantially restrict the pasage in which it is disposed may be used, and the hood may be placed within the upper part of the refrigerating compartment itself and used either with or without a blower ifdesired. Thus, there will be relatively little heat transfer due to convection between the housing i4 and the ducts 48 and 50. There will be heat transfer by way of conduction, however, between the warm air at 38 F. in the upper portion of the housing It and the cold air in ducts 48 and 50,

but as the air in these ducts is raised in temper-' ature it will rise to be trapped in the upper pore tion of ducts 36 and 38, and will be prevented from perature of 0 F. and is well within the desired operating range of 0-13 F.

When the temperature of the air ,within the housing It reaches 38 F., the main thermostat switch H0 again automatically reverses to disconnect the heater element I08 and actuate the compressor motor 98. It is to be noted that the thermostat switch I06 is in the open position and the blower motor I04 is not in operation. The temperature of the air within the housing I4 drops under the cooling action of the rei'riz crant within the coil assembly 68, and, when the temperature oi the air has dropped from 38 F. to approximately 13" F., the thermostat switch I06 closes to actuate the blower motor I04 to cause circulation of the air between the housing I4 and the storage compartment 22 along the closed path heretofore described. When the air again reaches a temperature of 0 F., the automatic sequence of defrosting is repeated.

While the preferred embodiment of the invention has been shown and described, it is understood that the structure shown is susceptible of modification within the scope of the appended claim.

What I claim as new and desire to secure by Letters Patent is:

Refrigerating apparatus comprising a storage compartment, a hooded housing spaced therefrom, a refrigerating coil in the housing, an air duct connecting the hooded housing and the storage compartment, and an air return duct connecting said compartment and housing, said duct-s extending upwardly from the housing at points substantially beneath the level of the coil and being reversed in direction to extend downwardly to points adjacent the lower portion of the compartment.

LAWRENCE E. CARSON.

REFERENCES CITED The following references are of record in the file of this patent:

Clerc May 25, 1943

Images