U.S. patent number 3,633,374 [Application Number 05/009,152] was granted by the patent office on 1972-01-11 for refrigerator with self-regulating heaters.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to James A. Canter.
United States Patent |
3,633,374 |
Canter |
January 11, 1972 |
REFRIGERATOR WITH SELF-REGULATING HEATERS
Abstract
In the preferred form a refrigerator is provided with positive
temperature coefficient thermistors acting either as heaters alone
or in series with a small electric heater for preventing
condensation of moisture adjacent the door openings and for
evaporating melted frost and also to prevent freezing of the water
delivery means of the icemaker provided in the refrigerator as well
as preventing freezing of defrost water in the drainage means or
the evaporator and to control the heating temperature of the butter
compartment to maintain the butter at proper spreading consistency,
and to heat the fluid motor of the control switch to assure control
in accordance with the temperature of the thermosensitive
element.
Inventors: |
Canter; James A. (Englewood,
OH) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
21735888 |
Appl.
No.: |
05/009,152 |
Filed: |
February 6, 1970 |
Current U.S.
Class: |
62/156; 62/202;
62/377; 62/275; 219/505 |
Current CPC
Class: |
F25D
21/14 (20130101); F25D 17/065 (20130101); F25C
1/25 (20180101); F25D 23/123 (20130101); F25D
11/02 (20130101); F25D 21/002 (20130101); G05D
23/2401 (20130101); F25D 21/04 (20130101); F25C
2400/10 (20130101); F25D 2400/04 (20130101) |
Current International
Class: |
F25D
21/00 (20060101); F25C 1/22 (20060101); F25D
17/06 (20060101); F25D 11/02 (20060101); F25D
21/04 (20060101); F25D 21/14 (20060101); F25D
23/12 (20060101); G05D 23/24 (20060101); G05D
23/20 (20060101); F25d 021/06 () |
Field of
Search: |
;62/202,275,276,377,156
;165/30,26,27 ;219/505,504 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Perlin; Meyer
Assistant Examiner: Capossela; Ronald C.
Claims
I claim:
1. A refrigerator including a cabinet having below freezing and
above freezing compartments to be kept cool, insulated partition
means separating said compartments including a mullion exposed to
the outside air, refrigerating means including an evaporator for
cooling said compartments respectively to below and above freezing
temperatures and incidentally accumulating frost upon said
evaporator, means for periodically defrosting said evaporator,
drainage means for disposing of the defrost water from said
evaporator, an icemaker in said below freezing compartment provided
with water delivery means for delivering water thereto, said
cabinet being provided with a butter compartment for cooling butter
preferably at a slightly higher temperature than the temperature in
the above freezing compartment, wherein the invention comprises
self-controlling positive temperature coefficient thermistor
heaters associated with said butter compartment and said drainage
means and said water delivery means and said icemaker and said
mullion each of said thermistor heaters connected across the
refrigerator power supply conductors so as to be continually
energized, said thermistor heaters operative for supplying a small
amount of heat in said locations at low temperatures to prevent
freezing of the water in said drainage means and said water
delivery means and to prevent the condensation of the water vapor
upon said mullion and to maintain said butter compartment at
temperatures the desired amount above the temperatures of said
above freezing compartment.
2. A refrigerator including a cabinet having a below freezing
compartment, refrigerating means for cooling said compartment to
below freezing temperatures, an icemaker in said below freezing
compartment provided with water delivery means for delivering water
thereto, wherein the improvement comprises a positive temperature
coefficient thermistor heater connected across the refrigerator
power supply conductors so as to be continually energized, said
thermistor heater in heat transfer with said water delivery means
for said icemaker, said thermistor heater connected in parallel
circuit with the icemaker thereby causing a sharply reduced lower
current when said thermistor heater rises to temperatures to and
above a range of 40.degree. to 50.degree. F., said thermistor
heater operative for supplying a small amount of heat thereto at
low temperatures to prevent the freezing of water in said water
delivery means.
3. A refrigerator including a compartment to be kept cool,
refrigerating means including an evaporator for cooling said
compartment, means for periodically defrosting said evaporator,
drainage means for disposing of the defrost water from said
evaporator, wherein the improvement comprises a positive
temperature coefficient thermistor heater connected across the
refrigerator power supply conductors so as to be continually
energized, said thermistor heater in heat transfer with said
drainage means for supplying a small amount of heat in said
location at low temperatures to prevent the freezing of the water
in said drainage means.
4. A refrigerator including a cabinet having a compartment to be
kept cool, refrigerating means for cooling said compartment to
suitable refrigerating temperatures, said cabinet also being
provided with a butter compartment for storage of butter, wherein
the improvement comprises a self-controlled positive temperature
coefficient thermistor heater connected across the refrigerator
power supply conductors so as to be continually energized, said
thermistor heater in heat transfer with said butter compartment
providing a sharp drop in current flow as the temperature rises to
and above the range of about 45.degree. to 55.degree. F. to
maintain said butter compartment at temperatures a desired amount
above the temperature normally maintained in said refrigerating
compartment.
5. A refrigerator including a cabinet having a compartment to be
kept cool, refrigerating means for cooling said compartment and
incidentally cooling surfaces of the cabinet around the door of the
compartment exposed to the outside air, wherein the improvement
comprises a positive temperature coefficient thermistor heater in
heat transfer with said portion of said surfaces of said cabinet
around the door exposed to outside air said thermistor heater
connected across the refrigerator supply conductors so as to be
continually energized, said thermistor heater operative for
supplying a small amount of heat thereto at low temperatures to
prevent the condensation of moisture upon said exposed surfaces
while reducing the current flow in said thermistor heater at
outside air temperatures above approximately 90.degree. F. to
prevent overheating of said cabinet surfaces.
6. A refrigerator including a cabinet having a compartment to be
kept cool, refrigerating means for cooling said compartment, a
thermostatic switch having an operating fluid motor in the form of
a bellows and a thermosensitive bulb in the form of a long closed
tube connected thereto containing a volatile liquid for controlling
said refrigerating means, wherein the improvement comprises
positive temperature coefficient thermistor heater connected across
the refrigerator supply conductors so as to be continually
energized, said thermistor heater in heat transfer with said fluid
motor bellows to maintain said bellows at temperatures slightly
higher than said thermosensitive tubing, said thermistor heater
reducing its heating effect when its temperature rises to the range
of 50.degree. to 60.degree. F. for ensuring that the thermostatic
switch and the refrigerator means are continuously controlled in
accordance with the temperature of the thermosensitive tubing.
Description
This invention relates to refrigerators normally provided with
small electrical heaters in certain locations to prevent certain
objectionable effects of excessive cooling and other
conditions.
In household refrigerators it has been customary to provide small
electric heaters adjacent the door openings to prevent condensation
of moisture and also to provide small electric heaters adjacent the
discharge spout of the water delivery means of the ice maker and a
small electric heater in the drainage system of an evaporator and a
small electric heater associated with the butter compartment to
keep the butter at a desired temperature above the normal
refrigerating temperature of the food compartment. In certain
arrangements it is desirable to provide a small heater for the
fluid motor of the control switch to assure control by the
thermistor element. Also, heaters are provided to prevent
refreezing and the accumulation of melted frost. This slight amount
of heat is wasteful when it is not needed since it adds to the
amount of heat which must be removed by the operation of the
refrigerating apparatus and also adds to the electrical energy used
by the refrigerator.
It is an object of this invention to provide a simple inexpensive
reliable means which will reduce or eliminate such electrical
heating when it is not needed, especially when the environment
temperatures are sufficiently high to make such heating
unnecessary, particularly when the demand for refrigeration is high
and there may be difficulty in maintaining low refrigerating
temperature in the refrigerated compartments.
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:
FIG. 1 is a fragmentary side sectional view of a household
refrigerator embodying one form of my invention;
FIG. 2 is an enlarged sectional view of the dividing wall shown in
FIG. 1 taken along the line 2--2 of FIG. 3;
FIG. 3 is a horizontal sectional view taken along the lines 3--3 of
FIG. 1; and
FIG. 4 is a wiring diagram of the refrigerator.
Referring now more particularly to FIG. 1, there is shown a
refrigerator cabinet 120 provided with an upper below freezing
compartment 142 and a lower above freezing compartment 144. These
compartments are separated by an insulated horizontal dividing
means which includes a lower sheet metal wall 146 having a high
front portion 148 and a low rear portion 450 with an inclined
portion 152 in between. The top member 193 of the dividing means is
provided with a series of air entrances 191 which connect with the
air passages 159 in the front insulation piece 245 and with the
evaporator chamber 153. The evaporator compartment 153 is also
surrounded by an insulation piece 158 having a passage 229
providing communication with the air entrances 151 from the above
freezing compartment 144 to the evaporator chamber 153.
The evaporator compartment 153 includes an evaporator 24 which is
supported upon the drain pan 12. It is supplied with liquid
refrigerant from the compressor 452 and a condenser (not shown)
through the capillary tube restrictor 19 extending within the
suction conduit 20 provided with a loop 22 connecting with the
combined entrance and exit of the evaporator 24. A fan motor 13 is
provided with a side inlet centrifugal fan 91 at the rear which
draws air through the inlets 191 and 151 into the evaporator
chamber 153 and through the evaporator 24 and discharges the air
upwardly through the duct 184 and the discharge opening 186 into
the below freezing compartment 142 while a reduced amount of air is
discharged downwardly through the duct 188 and the discharge
opening 190 into the above freezing compartment 144.
The below freezing compartment 142 is provided with an ice maker
310 which may include a twistable rotatable flexible tray 312
rotatably supported on a frame 314. The tray 312 is filled once
each cycle through a water delivery conduit 316 extending through
the insulation in the top wall 124 to the discharge spout 318 which
delivers the water to the front of the tray 312. This icemaker for
example may be similar to the icemaker shown in U.S. Pat. No.
3,308,631 issued Mar. 14, 1967. The refrigerator is also provided
with an upper door 242 for closing the below freezing compartment
142 and a lower door 244 closing the above freezing compartment
144. This door 244 is provided with a butter compartment 145 for
keeping a small supply of butter for table purposes.
In FIGS. 2 and 3 there is shown a light socket 410 provided with a
light bulb 412 which is controlled by a door switch 414 operated by
a plunger 416 adapted to be engaged by the lower door 244 to open
the door switch 414 to extinguish the lamp 412 when the door 244 is
in the closed position. There is also provided a thermostatic
switch 418 including an operating bellows 420 and a thermostat bulb
422 extending therefrom beneath the sheet metal wall 146 in order
to make the switch responsive to the temperature in the compartment
144. A small electric heater 424 is wrapped around the casing of
the bellows 420 to provide a small amount of heat to ensure that
the operating temperatures of the switch 418 are controlled by the
temperature of the thermostat bulb 422 rather than being controlled
by the temperature of the casing of the bellows or fluid motor
420.
According to my invention, to limit the heating of the casing of
the bellows 420, I provide a positive temperature coefficient
thermistor 426 in series circuit with the heater 424 and the
conductors 428 and 430 connected across the conductors 436, 438.
This positive temperature coefficient thermistor 426 preferably
sharply reduces the heating effect of the heater 424 and its own
heating effect at temperatures between and above about 50.degree.
to 60.degree. F. If desired, the electric heater 424 may be omitted
and both the heating and controlling functions are embodied in the
positive temperature coefficient thermistor 426. The thermistor 426
thereby reduces the heating effect in either form when its
temperature rises to 50.degree.- 60.degree. F. This protects the
refrigerator from excessive current flow in the event that the
applied voltage is high or the environment temperature is high and
thereby limits the heating effect and the current used. This also
limits the amount of heat which is delivered to the above freezing
compartment 144 so that a minimum of refrigeration is required to
offset this introduction of heat.
The refrigeration of the compartments 142 and 144 also frequently
causes the cooling of the exposed surfaces 156 of the cabinet
around the doors 244 and 242 below the point at which water vapor
will condense thereon. This causes objectionable sweating around
the doors. For this reason, it has been customary to provide small
electric heaters 432 around such door openings. According to my
invention, I provide a positive temperature coefficient thermistor
434 in series with the heaters 432 and the conductors 436 and 438
connected across the supply conductors 116, 117 to limit the
heating effect of the heaters 432. Preferably this thermistor 434
will sharply reduce the current flow between and above the range of
90.degree. to 100.degree. F. This will prevent overheating of such
surfaces and reduce the amount of refrigeration which is required
to counteract such heating.
The evaporator 24 is provided with a radiant defrosting heater 37
for defrosting the evaporator. As shown in the wiring diagram FIG.
4 the heater 37 is connected to one of the alternate terminals of a
double throw switch 440 which is normally closed to energize the
compressor motor 442 and the fan motor 13 through the thermostat
switch 418. Periodically the timer motor 444 operates the double
throw switch 440 to the alternate position energizing the defrost
heater 37 and deenergizing the compressor motor 442 and the fan
motor 13 to melt the frost from the evaporator 24. The water
resulting from the melted frost flows into the drain pan 12 and the
drainage system 237 to the backwall 534 of the compartment 144
where it flows down the backwall to a drain 470 in the bottom wall
of the inner liner 134. Beneath the drain 470, the melted frost is
collected in a pan 472. Under most circumstances the normal
circulation of air is sufficient to evaporate the melted frost in
the pan 472. However, under conditions of high atmospheric humidity
the evaporation may be insufficient to prevent the accumulation of
the melted frost. A nickel chromium electric wire heater 474 is
embedded in epoxy material 476 and placed in the bottom of the pan
472 for heating and evaporating the melted frost water collected
therein. The epoxy material includes an upwardly extending stem or
pipe 479 which may enclose one or more of the lead-in wires for the
heater 474. The drainage system 237 is also provided with a small
heater 446 to prevent freezing of the defrost water in the drainage
system 237 to prevent it from clogging.
According to another feature of my invention, a positive
temperature coefficient thermistor 448 is connected in series with
the heater 446 across the supply conductors 116, 117 to limit the
current and the heat output in the heater 446. Preferably, the
thermistor 448 provides a marked drop in current flow between and
above the temperature range of 40.degree. to 50.degree. F. so as to
limit the amount of heat provided when the temperature is high
enough that freezing will not take place in the drainage system. If
desired, the thermistor 448 may be of sufficient heat output to
provide sufficient heat to the drainage system 237 without the use
of the heater 446.
According to an additional feature of my invention, a positive
temperature coefficient thermistor 478 is embedded in the epoxy 476
and connected in series with the heater 474 across the supply
conductors 116, 117. This positive temperature coefficient
thermistor 478 preferably has the characteristic of producing a
sharp drop in current flow above the range of about 90.degree. to
100.degree. F. However, positive temperature coefficient
thermistors with other temperature ranges such as 140.degree. to
150.degree. F. may be used if desired. The temperature range
selected preferably should supply current to the heater 474
whenever the melted frost water is present in sufficient amounts to
keep the heater 474 and the thermistor 478 cooled below the
switching temperature of the thermistor 478. The thermistor 478
will prevent heating when there is no water present. The heater may
have a rating of 2 watts for example. The heater 474 may be omitted
if the thermistor 478 has a sufficient heat output to evaporate the
water from the pan 472.
The icemaker 310 includes a motor 452 which turns and twists the
tray 212 at the proper time and controls the switches 454, 456
which respectively control its operation and also the operation of
the solenoid valve 458 which controls the flow of water through the
supply conduit 316 to the discharge nozzle 318. The discharge
nozzle 318 is provided with a small electric heater 460 of a rating
of about 2 watts to prevent freezing of the water therein.
According to another aspect of my invention, the positive
temperature coefficient thermistor 462 is connected in series with
this small electric heater in parallel circuit with the icemaker to
limit its heat output. Preferably, this thermistor causes a sharply
reduced lower current when the thermistor 462 rises to temperatures
to and above a range of 40.degree. to 50.degree. F. This
arrangement provides sufficient heat to prevent freezing of the
water and yet minimizes the heat supplied and the current used
sufficient to prevent the freezing. This likewise limits and
reduces the amount of heat which must be removed by the
refrigeration system and also reduces the amount of electrical
energy consumed. If desired, the heater 460 may be omitted and
sufficient heat output is then provided by the thermistor 462.
The butter compartment 145 in the door 244 is also provided with a
small electric heater 464 of about 2 watts rating which may be
connected in series with a switch 466 to provide a sufficient
amount of heat to raise the temperature above the temperature of
the above freezing compartment 144 so that butter is sufficiently
soft to spread. According to another aspect of my invention, a
positive temperature coefficient thermistor 468 is connected in
series with the heater 464 and the switch 466 across the supply
conductors 116, 117 to limit the heating so as to prevent
overheating when the compartment 144 and the door 244 are warmer
than normal and also during periods of high voltage. Preferably,
the thermistor 468 provides a sharp drop in current flow as the
temperature rises to and above the range of about 45.degree. to
55.degree. F. If desired the thermistor 468 may be provided a
sufficiently high heat output so that heater 464 may be
omitted.
The thermistors also prevent excessive heat output which may result
from abnormally high supply voltages. Preferably, these positive
temperature coefficient thermistors are of barium titanate made
with rare earth doping materials and of such composition that they
reduce the current flow within the temperature ranges
suggested.
While the embodiments of the invention as herein disclosed
constitute preferred forms, it is to be understood that other forms
might be adopted.
* * * * *