US3013399A

US3013399A - Refrigerating apparatus

Info

Publication number: US3013399A
Application number: US836999A
Authority: US
Inventors: Edward C Simmons; Roy R Smith
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1959-08-31
Filing date: 1959-08-31
Publication date: 1961-12-19
Anticipated expiration: 1978-12-19

Description

Dec. 19, 1961 Filed Aug. 31, 1959 E. C. SIMMONS EI'AL REFRIGERATING APPARATUS 2 Sheets-Sheet '1 I2 46 w n INVENTORS Edward 0. Simmons BY Roy R. Smith The/r Attorney Dec. 19, 1961 E. c. SIMMONS EI'AL 3,013,399

REFRIGERATING APPARATUS Filed Aug. 31, 1959 2 Sheets-Sheet 2 INVENTORS F 2 Edward C. .Slmmons BY Roy R. Smith United States Patent 3,013,39? REFRIGERAIING APPARATU Edward C. Simmons and Roy R. Smith, Dayton, Ohio, assignors to General Motors (Jorporation, Detroit, Mich., a corporation of Deiawar'e Filed Aug. 31, 1959, Ser. No. 836,999 3 tJlaims. (Cl. 62-151) This invention relates to refrigerating apparatus and more particularly to an improved arrangement for controlling the defrosting of the evaporator.

It is a well known fact that the. rate at which frost forms on the evaporator of a refrigerator varies from day to day depending upon the ambient wet and dry bulb temperatures, the type of products placed in a refrigerator, the number and length of door openings, and similar factors. Consequently, conventional defrost control systems operated by a clock or by the number of door openings do not cause defrosting to take place in accordance with actual defrost requirements.

It is an object of this invention to provide an improved defrost control arrangement which automatically compensates for variations in many of the factors which vary the frequency at which defrosting should take place.

Another object'of this invention is to provide a defrost control arrangement having improved reliability.

Still another object of this invention is to provide an automatic timing device which eliminates the need for use of mechanical timers such as clocks and the like which tend to become noisy and which are otherwise unreliable or unsatisfactory.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic view showing a preferred embodiment of the invention; and

FIGURE 2 is a schematic view showing a modified embodiment of the invention.

Referring now to FIGURE 1 of the drawings wherein a preferred embodiment of the invention has been shown, reference numeral designates a conventional insulated freezer cabinet having a freezer compartment 12 and a compressor compartment 14 provided therein. The compartment 12 is provided with the usual type of access door 16 and is adapted to be cooled by means of a con; ventional evaporator 18. The evaporator 18 is connected in series refrigerant fiow relationship with a conventional motor compressor unit 20, a condenser unit 22 and a pressure reducing device 24. A thermostat 25, which is arranged to respond to refrigeration requirements in the compartment 12, serves to cycle the compressor 20 so as to maintain the desired freezer compartment temperature.

During normal operation of the refrigerating system, frost will accumulate on the evaporator 18 and as the result thereof, it becomes necessary to remove period] cally this frost. For purposes of illustration, there is shown an arrangement in which this is done by means of on electric heater 26 arranged in thermal exchange relationship with the evaporator 18. For purposes of illustrating the invention, the evaporator 18 has been shown disposed directly within the food storage compartment 12, Whereas it could be located in any other suitable location, such as in a duct communicating with the food storage compartment. Likewise, the heating coil 26 has been shown arranged adjacent the lower edge of the evapora or 18 whereas this coil could be arranged so as to be in contact with a major portion of the evaporator 18 or in thermal exchange relationship with a liquid reservoir formed as a part of the evaporator in accordance with well known defrost principles.

The control for the defrost heater 26 includes a hermetically sealed receptacle 28 which may be made of glass or any other suitable material. The receptacle 23 is provided with an upper portion 30 which is arranged in thermal exchange relationship with the contents of the frozen food storage compartment 12 and a lower portion 32 which is arranged in thermal exchange relationship with the machinery compartment wherein the compressor and/or condenser 22 are located. A body of Water or similar liquid 34 is provided in the receptacle 28.

During normal operation of the refrigerator, the upper end of the receptacle 28 will be subjected to below freezing temperatures and the lower end thereof will be subjected to temperatures considerably above the freezing temperature of water with the result that water disposed within the receptacle will tend to be vaporized by the heat surrounding the lower end of the receptacle and most of the resulting Water vapor will accumulate as frost on the inner wall surfaces of the upper end of the receptacle 28. The size of the receptacle and the quantity of water disposed therein are preferably designed so as to require approximately twenty-four hours for the evaporation of the water to take place under average temperature and refrigerator usage.

Power is supplied to the defrost heater 26 from the main power source 36. Thus, a first conductor 38 connects the one side of the heater 26 to the one side of the power source and a second conductor 40 serves to connect the other side of the heater to the other side of the power line through a pair of

thermostatic switches

42 and 45. The thermostatic switch 42 is a conventional defrost limiter switch which serves to open the circuit v to the defrost heater when the temperature of the evaporator indicates that all of the frost, which previously accumulated on the evaporator,'has been melted.

An electric heater 44 which is connected to the power source 36 at all times serves to apply auxiliary heat to the lower end of the receptacle 2% so as to facilitate evaporation of the Water therein. So long as any appreciable amount of water remains in the lower end of the receptacle 28, the heat 44 is incapable of providing enough heat to cause the thermostat 45 to close the circuit at 46 to initiate operation of the defrost heater 26 but once the water in the receptacle 28 has been vaporized andm-igrated to the upper end of the tube in the form of frost, the lower end of the tube and the thermostat 45 will rather quickly become heated to a temperature high enough to initiate operation of the defrost heater 26. It will be noted that the bimetallic thermostat 45 includes a double set of contact-s so that when the upper end of the thermostat moves from the left to the right, as viewed in FIGURE 1 of the drawings, it opens the circuit to the motor compressorvunit at 48 and closes the circuit to the defrost heater 26.. During approximately twenty-four hours of the day under average temperature and refrigeration usage conditions, the thermostat 45 will maintain the circuit at 4 8 closed'so as to provide for operation of the compressor 20 at all times when the thermostat ,45 calls for refrigeration. Once the thermostat 45 opens the circuit to the motor compressor unit 20 and closes the circuit to the defrost heater 26, the accumulated frost on the evaporator 18 will melt and this will occasion an increase in the temperature within the compartment 12 with the result that the frost accumulated in the upper end of the receptacle 28 will also melt and will begin to refill the lower end of the receptacle 28. The direct of the frost melting in the receptacle 28 is to cause the lower end of the receptacle 28 to cool off. A small heater 27 is provided for supply- 3 ing heat to the thermostat 45 during the defrost period to prevent premature restarting of the compressor prior to complete defrosting of the evaporator 18. The upper end of the receptacle 28 is larger than the lower end thereof so as to prevent the frost from sliding down the sides of the receptacle when it first begins to melt.

Referring now to FIGURE 2 of the drawing wherein a modified type of control arrangement has been shown, the same reference numerals have been used to designate parts which are identical or similar in construction and function to the correspondingly numbered parts shown in FIGURE 1. The construction shown in FIGURE 2 of the drawings differs from the construction shown in F IGURE 1 primarily in that the sealed receptacle 28 serves to house a float 50 which controls a switch 52 disposed within the receptacle 28. The movable contactor of the switch 52 is at all times electrically connected to a conductor 54 carried by the float. The lower end of the conductor 54 extends into a body of mercury 56 provided in the lower end of the receptacle 28. A lead wire 58 which is connected to the source of power 36 extends through the wall of the receptacle 28 into the body of mercury 56, as shown. A quantity of water 34 is provided in the receptacle 2S and is adapted periodically to be at least partially vaporized so as to cause the float 50 to close the switch 52 at spaced intervals of time depending on the length of time for the water 34 to vaporize and migrate to the cold surfaces adjacent the upper end of the receptacle 28.

Closing of the switch 52 causes energization of a solenoid coil 68 which, when energized, serves to raise the double pole, double throw, switch arm or bar 62. This upward movement of the switch bar 62 serves to break the circuit to the compressor motor 20 and make a circuit to the defrost heater 26. An auxiliary contact bar 64 which is also actuated by the solenoid 60 serves to close a holding circuit 66 whereby the solenoid 60 will remain energized irrespective of the position of the float operated switch 52 until the defrost limiter switch 42 opens the circuit to the solenoid 60. The defrost limiter switch 42 will remain closed until the temperature of the evaporator 18 exceeds 36 F. at which time it will open the circuit including the solenoid 60 and the defrost heater 26. Upon deenergization of the solenoid 60, the motor control switch 62 will close the circuit leading to the compressor motor with the result that the compressor motor will operate whenever the thermostatic switch 7 6 calls for refrigeration. The switch 70 is preferably located in the food compartment so as to cause operation of the compressor whenever refrigeration is required. The type and location of the freezer compartment temperature regulating switch 70 is broadly immaterial as any conventional refrigerant cycling control can be used.

The arrangement of the heater 36 in each of the circuits is preferably such that it will supply heat directly to the evaporator 18 and will also assist in heating the upper end of the receptacle 28 by radiation, convection and if necessary by direct conduction. The size and location of the heater 26 will, of course, vary with different size freezer compartments. It is also within the purview of this invention to place a portion of the heater 26 or an auxiliary heater directly on the upper end of the receptacle 23 when the construction and relative location of the parts is such that the main defrost heater 26 is incapable of melting the frost in the upper end of the receptacle 23 in the desired time.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In combination, a refrigerator cabinet having a food storage compartment therein, an evaporator for cooling said food storage compartment, refrigerant liquefying means supplying liquid refrigerant to said evaporator, means for defrosting said evaporator, control means for said defrosting means comprising a fluid receptacle having one portion arranged in thermal exchange relationship with said food storage compartment so as to condense and freeze moisture on the inner walls thereof and having another portion arranged in thermal exchange relationship with said refrigerant liquefying means so as to be heated thereby, and means responsive to a predetermined change in fluid level within said receptacle for initiating operation of said means for defrosting said evaporator.

2. In combination, means forming an insulated food storage compartment, an evaporator in thermal exchange relationship to air for said compartment, a refrigerant liquefying means supplying liquid refrigerant to said evaporator, means for defrosting said evaporator, and control means for said defrosting means comprising a receptacle having its upper portion arranged in thermal exchange relationship with said food storage compartment, a quantity of liquid in said receptacle, means for applying heat to said liquid so as to vaporize at least a portion thereof, and cans responsive to the vaporization of a predetermined quantity of said liquid for initiating defrosting of said evaporator.

3. In combination, means forming an insulated food storage compartment, an evaporator arranged to cool the contents of said compartment, a refrigerant liquefying means for supplying liquid refrigerant to said evaporator, means for defrosting said evaporator, control means for said defrosting means comprising a fluid receptacle having a first portion arranged in thermal exchange relationship with said food storage compartment and having a second portion arranged in thermal exchange relationship with a relatively warm zone whereby fluid therein vaporizes and migrates to said first portion, and means responsive to a given change in the liquid level in said second portion for controlling said means for defrosting said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 2,155,262 Fiene Apr. 18, 1939 2,303,182 Tobey Nov. 24, 1942 2,324,647 Ray July 20, 1943 2,524,813 Lathrop Oct. 10, 1950 2,570,451 Hottenroth Oct. 9, 1951 2,735,272 Lange Feb. 21, 1956