Note: Descriptions are shown in the official language in which they were submitted.
~ 9D-HR-14534
BACKGROUND OF THE INVENTION
Household refrigerators generally comprise
an outer metal case and at least one inner Liner insul-
ated from the case and defining a refrigerated food
storage compartment. Due to leakage through the insul-
ating means separating t.he outer metal case from the
liner or due to refrigerated air leakage past the door
sealing means, portions of the outer metal case adjac-
ent the access opening to the storage compartment tend
L0 to fall below the dew point of the surrounding atmos-
phere causing the accumulation of moisture in these
areas. To prevent such condensation, suitable heating
means such as an electric resistance heater, generally
known as anti-sweat heater, have been provided to main-
tain the temperature of the case area adjacent the
access openings sufficiently warm so that such condensa-
tion does not readily occur. The heating means general-
ly employed has been a low wattage electrical resist-
ance heater connected directly across the power supply
lines so as to be continuously energized regardless
of whether the refrigerating means for cooling the
storage compartment is operating or not. This kind
of arrangement, however, can use electrical energy
unnecessarilyO
Various alternative arrangements to reduce
the electric power consumption of the anti-sweat heat-
ers have been used in the past. For instance, U.S.
Patent 3,939,666, L.T. Bashark, issued February 24, 1976,
discloses an electrical control circuit that, when the
refrigeration system is not in defrost and there is a
high humidity condition, the mullion heater utilizes
full power and the stile heater utilizes half ~lectrical
9D-HR-1~534
power. In the case of low humidity and, again, the
regrigerating system is not in defrost, the mullion
heater utilizes half electrical power and the stile
heater uses no electrical power. When the refriger-
ating system is in a defrost condition, both the mullion
and stile heaters are "off". This arrangement, however,
controls power to the heaters by means of a humidity
sensor. It does not control the electrical power to
the anti-sweat heaters responsive to the compressor
operation which is an important aspect of the present
invention. When the compressor of the refrigeration
system is "on", there is inherently produced more cold
air leakage from the refrigerated compartment than
when it is "off". However, there is still some reduced
amount of cold air leakage that will produce condensation
when the compressor is "off".
U.S. Patent 2,135,091 issued November 1938 to
Newill discloses energization of the anti-sweat heaters
at full electrical power either only when the compressor
of the refrigerating system is operating or all the
time when the system is operating.
There is also a prior art arrangement that
utilizes a manually operated switch for half electrical
power, full electrical power, or no electrical
power for the anti-sweat heaters which selection
must be made by the user of the refrigerator.
It is desirable in a household refrigerator,
to have the anti-sweat heaters automatically con-
trolled during operation of the refrigeration system
so that when the compressor is "on", full electrical
power will be supplied to the anti-sweat heaters and
when the compressor is "off", only half electrical power
-- 2 --
9D~ 453
will be supplied to the anti-sweat heaters. By my
invention, there is provided a refrigerator, including
anti-sweat heaters, having a control circuit which will
accomplish these desirable results.
SUMMARY OF THE INVENTION
.
According to one aspect of my invention,
there is provided a refrigerator comprising a cabinet
including a storage compartment and electrical anti-
sweat heater means for warming a portion of the cabinet,
refrigerating means including a compressor and an
evaporator for cooLing the compartment, and tempera-
ture sensing means to energize the compressor at one
predetermined temperature and de-energize the compressor
at a second lower temperature. There is also provided
automatic switch means associated with the temperature
sensing means to apply full electrical power to the
electrical anti-sweat heating means when the compressor
is energized and apply half electrical power to the
electrical anti-sweat heating means when the compressor
is not energized.
BRIEF DESCRIPTION OF THE DRAWINGS
_
Figure 1 is a side-elevational cross-
sectional view of a household refrigerator including
one embodiment of the anti-sweat heater control circuit
of the present invention.
Figure 2 is an electrical circuit diagram
of a refrigerator control system according to the prior
ar~.
Figure 3 is an electrical circuit diagram
of a refrigerator control system according to one embodi-
ment of the present invention.
~ 9D-HR-14534
DESCRIPTION OF THE PREFERRED EMBODIMENT
_ .
Wlth reference to Figure 1 of the drawing,
there is ilLustrated a refrigerator cabinet including
an outer case 1, an upper inner liner 2 defining a
freezer storage compartment, and a lower inner liner
3 defininy a fresh food storage compartment. The
forward edges of both liners are spaced from the
forward edges of the case and these spaces are bridged
by heat insuLating breaker strips 4 while the spaces
L0 between the liners and the outer case are fiLled with
suitable insulating material 5. The access openings
to the freezer and fresh food compariments are respec-
tively closed by gasketed doors 6 and 7.
Refrigeration for the two compartments is
provided by an evaporator 8 positioned in the parti-
tion between the two compartments which forms part
of the refrigeration system including an electric
motor driven compressor 9 and a condenser 10. A fan
11 rearwardly from evaporator 8 provides means for
circulating air from the two compartments over the
evaporator 8 and back into the compartments.
A thermostatic control means generally
indicated by the numeral 34 including a temperature
sensing means or thermostat 48, is provided for aut-
omatically controlling the operation of the compressor
~ to maintain the temperature within the fresh food
compartment within a controlled range. Also, in
accordance with the usual practice, this thermostatic
control means c~n be manually adjusted for the desired
temperature in the fresh food compartment and also it
can be moved to an "off" position whereby the compressor
9 is de-energi~ed .regardless of the temperatures within
~ 9D HR-14534
the cabinet.
Evaporator 8 operates at temperatures below
freezing and for the purpose of periodically removing
accumulated frost from the evaporator surfaces, there
is provided a defrost heater 16 which is periodically
energized by operation of a timer 17.
The control circuitry and components for
controlling the normal and defrost operation of a prior
art refrigerator is illustrated in Figure 2 of the
drawing. A conventional power plug 18 supplies L and
N supply conductors 20 and 22, and has a connection
24 to ground the frame of the refrigera~or. The refrig-
eration system includes a compressor motor 26 and an
evaporator fan motor 28 connected in parallel. The
refrigeration system further includes a condenser fan
and motor 30 for forced-air cooling of the condenser 10.
For controlled operation of the refrigeration
system, the compressor and evaporator fan motors 26
and 28 are connected to the L supply conductor 20
through a defrost control 32 and through the thermo-
static control means 34 for controlllng the interior
temperature of the refrigerator. The compressor,
evaporator fan and condenser fan motors 26, 28, and
30 each have return electrical connections to the N
supply conductor 22.
The defrost control 32 includes a cam-operated,
single-pole double-throw switch 36 operated through a
- link 38 by a defrost control cam 40 driven by a timing
motor 42. When the defrost control switch 36 and the
cam 40 are in the cooling position shown, the compressor
and evaporator fan motors 26 and 28 are connected
through the switch terminals 44 and 46 and through
9D-HR-14534
;3~0t~
the thermostatic control means 34 to the L supply
conductor 20.
The particular thermostatic control means 34
includes a temperature sensing means or thermostat 48
which is a conventional hydraulic type normally employ-
ed in refrigerators, and includes a remote temperature-
sensing bulb, represented by an eLement 50, at the end
of a small-diameter tube. The thermostat 48 has a
range of adjustment for the normal fresh food compart-
ment temperature which setting is normally between
33F to 43F, with 38F being a nominal setting. It
will be understood that the temperature sensing means
48 operates independently of the defrost control timer
32.
In the operation of the prior art circuitry
shown in Figure 2, thus far described, the thermostat
48 i5 enabled to cycle the compressor motor 26, the
evaporator fan motor 28 and the condenser fan motor
30 as required to maintain the temperature ln the
refrigerated compartments. Each time the enabled
thermostat 48 closes, power is supplied through contact
49 along conductor 52 to the defrost controL timing
motor 42 to rotate the defrost control cam 40. In
order to initiate automatic defrosting operations,
the timing of motor speed and cam arrangement are such
that after every 5 1/2 hours of timing motor running
time, the cam 40 switches the defrost control switch
36 to the lower position, de-energizing the compressor
and evaporator fan motors 26 and 28, and energizing a
defrost heater 54. The defrost control switch 36
remains in the lower position for a period of approxim-
ately 30 minutes. The N re~urn for the defrost heater
' 9D-HR-14534
0~
54 is connected through a defrost-terminating bimetallic
switch 56 which is adjusted to open at approximately
50F. Under normal frost loading conditions, the
evaporator is completely defrosted and the bimetallic
switch 56 opens within the 30-minute defrost duration
period determined by the defrost control cam 40 and
the defrost control timing motor 42.
While the particular defrost control 32
illustrated is an electro-mechanical device, it will
L0 be apparent that various other timing means may be
employed. For example, an electronic timer may be
used, using either RC or digital counter timing elem-
ents. Depending upon the precise timer employed, a
different means for interrupting the timer may be
appropriate, and not necessarily a simple interrup-
tion of power.
The refrigerator control circuit further
includes a conventional anti-sweat heater 58, which
serves to prevent condensation forming on the visible
outer portions of the refrigerator cabinet. The anti-
sweat heater is energized through a manually operated
power saver switch 60 and a conductor 62 when the
switch is in its closed position as shown in the draw-
ing The anti-sweat heater 58 is de-energized when
the power saver switch 60 is manually opened. N
return conductor 64 for the anti-sweat heater 58 is
connected through the defrost terminating switch 56
to the N power source conductor 22 to prevent the
heater 58 from operating during those periods when
the evaporator temperature exceeds 50F during defrost
operations.
Referring now to Figure 3, there is shown a
~~ ~ 9D-HR-14534
schematic diagram of a refrigerator control circuit
according to the preferred embodiment of the invention.
The circuit of F'igure 3 d~~rs from ~he circuit of
Figure 2 as will be dlscussed below. It will be app-
reciated that the clrcui~ of Figure 3 remains unchang-
ed in other respects and a complete description thereof
is not repeated.
The modification to the prior art control
circuit shown in Figure 2 involves the thermostatic
control means 34 which has added thereto a second
contact 66 plus a rectifier or diode 70 located in
the circuit between contact 66 and the anti-sweat
heater 58. The conventional manually operated power
saver switch 60 may or may not be in the circuit for
the purposes of this invention. However, in the
preferred embodiment, a power saver switch 60 is shown
in both the prior art circuit and in the preferred
embodiment circuit of Figure 3. When the power saver
switch 60 is open, there is no power applied to the
an~i-sweat heater 58. Assuming, however, that the
power saver switch 60 is closed and the thermostat
48 is closed, the compressor and the evaporator and
condenser fans will be energized. Full electrical
power will be supplied from L conductor 20 through
contact 66, conductor 69 to the anti-sweat heater 58
then through return conductor 64, bimetallic switch
56 to the N conductor 22. The full electrical power
is desirable at this time in the refrigeration cycle
as sweating is more prone to occur on the cabinet
surfaces which are to be protected by the anti-sweat
heater 58 due to cold air leakage. Assuming that the
power saver switch 60 is closed but that the thermostatic
9D-HR-14534
3~
control 48 is open, contacts 49 and 66 wilL also be
open and the compressor and the evaporator and con-
denser fans are not energized. Half electrical power
will flow from L conductor 20 through the power saver
switch 60 and conductor 71 through diode 70 to the
anti-sweat heater 58 and back to the N conductor 22
via return conductor 64 and bimetallic switch 56. Thus,
with this arrangement, the anti-sweat heater will
automatically be subjected to full electrical power
when the refrigerating system is operating and the
compressor is energized and only half power when the
compressor is not energized.
While the preferred embodiment of the inven-
tion has been illustrated and described herein, it is
realized that numerous modifications and changes will
occur to those skilled in the art. It is therefore
to be understood that the appended claims are intended
to cover all such modifications and changes as fall
within the true spirit and scope of the invention.
