Temperature sensing means for refrigerator

A temperature sensing means for a refrigeration apparatus including sensing means responsive to the temperature within a refrigerated space and to an ambient temperature condition for signalling the temperature condition of the refrigeration apparatus. In the disclosed embodiment, the sensing means is mounted in the access door of the refrigeration apparatus and the temperature sensors are mounted within a single housing. The sensor for sensing the ambient temperature is effectively insulated from the refrigerated space and senses the ambient temperature through a portion of the housing and door. In the illustrated embodiment, the sensing means is used to provide an ambient temperature compensated over-temperature alarm for the refrigeration apparatus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to refrigeration apparatus and in particular to 
means for sensing the temperature within a refrigerated space for the 
purpose of controlling the refrigeration apparatus or for controlling an 
over-temperature indicator. 
2. Description of the Background Art 
In a conventional refrigeration apparatus having a compartment refrigerated 
by suitable refrigerating means, operation of the refrigerating means is 
typically controlled by a sensor which senses the temperature of the 
compartment, to cause refrigeration thereof when the temperature rises to 
a preselected temperature. In one form of such apparatus, the temperature 
sensor is carried by the door of the refrigeration apparatus. 
A problem arises when using a door-mounted temperature sensor in that the 
temperature to which the sensor is exposed and the temperature of the 
refrigerated compartment may increase rapidly toward the ambient 
temperature when the door is opened for a period of time, even though the 
objects being refrigerated within the compartment do not rise in 
temperature as rapidly as the air temperature therein. As a result of the 
temperature sensor in the door being exposed to the relatively higher 
temperature ambient air and compartment air, the sensor output may not be 
reliable for purposes of operating an over-temperature alarm or 
controlling the refrigeration apparatus. 
This condition is aggravated when the refrigeration apparatus is being 
operated in a relatively high ambient temperature. For example, in a 
conventional refrigeration apparatus having an over-temperature alarm and 
a sensor operating at a fixed trip point, it is desirable to set the alarm 
to operate at a sensed temperature of approximately 60.degree. F. The 
60.degree. F. trip point is necessary even though the compartment is 
normally maintained at 34.degree. F.-38.degree. F., in order to prevent 
unnecessary alarm indications from being given as a result of the high 
ambient temperature. Where the refrigeration apparatus is provided in an 
environment of relatively low ambient temperature, the relatively high 
temperature trip point is undesirable. Under such lower ambient 
temperature conditions, it would be desirable to lower the trip point to 
provide a more sensitive operation of the over-temperature indicator. 
A number of refrigeration apparatus controls have been developed over the 
years which are concerned with the problem of controlling the operation of 
the refrigeration apparatus as a function of sensed temperature. 
Illustratively, Raymond J. Ridge, in U.S. Pat. No. 2,148,643, shows a 
refrigerator control having a sensing bulb for sensing the temperature of 
the evaporator and a bimetallic sensing device within a control mechanism 
remote from the sensing bulb and subject to air delivered from the rear of 
the refrigeration apparatus. The control is arranged so that a snap-acting 
mechanism is caused to have its action varied with changes in ambient 
temperature so as to vary the temperature at which the evaporator sensing 
element is effective in controlling the operation of the refrigeration 
apparatus. The apparatus is provided with an access door remotely spaced 
from the sensing elements and switch. 
In U.S. Pat. No. 3,707,851, Robert B. McAshan, Jr. shows a refrigeration 
system having first and second sensing means, such as thermistors. One of 
the thermistors senses the ambient temperature conditions and the other of 
the thermistors senses the temperature of the refrigerant in the 
refrigeration system. 
Ko Toya, in U.S. Pat. No. 3,977,851, shows an automatic electronic 
ice-making control system also utilizing a thermistor as a sensing element 
for terminating an ice-making cycle. A second variable resistance element 
compensates the characteristics of the thermistor in accordance with 
ambient temperature conditions to provide an output signal so as to 
terminate ice-making operation upon production of substantially the same 
quantity of ice independent of the season of the year during which the 
ice-making machine is operative. 
SUMMARY OF THE INVENTION 
The present invention comprehends an improved temperature sensing means for 
a refrigeration apparatus, wherein a pair of temperature sensors is 
carried by an access door to the refrigerated compartment. One of the 
sensors senses the temperature of the refrigerated chamber, or 
compartment, and the other sensor senses the ambient temperature adjacent 
the door. 
In the illustrated embodiment, the sensing means comprises a portion of a 
sensing and display system carried by the access door of the refrigeration 
apparatus. More specifically, in the illustrated embodiment, the improved 
sensing means operates an over-temperature alarm so as to warn the user of 
the existence of an undesirable temperature condition within the 
refrigerated compartment. 
The invention comprehends providing both sensors within a single housing 
and, in the illustrated embodiment, the housing is mounted within the 
access door. One of the sensors is exposed to the refrigerated air within 
the refrigerated chamber, or compartment, and the other of the sensors is 
in thermal transfer association, through the housing and door, with the 
ambient air adjacent the door. 
The sensing means is arranged so that the trip point produced by the joint 
action of the sensors varies as a function of the sensed ambient 
temperature. Resultingly, the trip point is reduced at low ambient 
temperatures to provide a more sensitive operation of the over-temperature 
indicator. 
The invention thus comprehends the provision of means mounted within the 
refrigeration apparatus for sensing the ambient temperature. 
In the illustrated embodiment, the sensor for sensing the ambient 
temperature is effectively insulated from the refrigerated air within the 
refrigerated compartment by suitable insulation means within the housing. 
The temperature sensing means of the present invention is simple, 
economical of construction, and provides facilitated assembly of the 
refrigeration apparatus, while yet providing an improved temperature 
sensing function.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the exemplary embodiment of the invention as disclosed in the drawing, a 
refrigeration apparatus generally designated 10 illustratively comprises a 
side-by-side refrigerator-freezer housed within a cabinet 11. The 
refrigerator portion of the apparatus defines a refrigerated compartment 
12 defining an access opening 13 selectively closed by a door 14. As seen 
in FIG. 2, the door is defined by an outer panel 15 and is provided with 
suitable insulation 16. 
Mounted in door 14 is an over-temperature indicator device generally 
designated 17 comprising an electronic display similar to that disclosed 
in copending U.S. Letters patent application Ser. No. 255,672, of myself 
and Ralph Tate, Jr., entitled "Door Mounted Electronic Housing Assembly 
For Refrigerator", filed Apr. 20, 1981, the disclosure of which is 
incorporated herein by reference. The indicator device, as seen in FIG. 1, 
includes a display panel 18 similar to the panel disclosed in the 
above-identified application, for providing visual indications to a user 
viewing the front of the refrigeration apparatus which, as disclosed in 
that application, may include an over-temperature indicator indicating an 
undesirably high temperature condition within the refrigerated compartment 
12. Thus, indicator device 17 effectively comprises a means for providing 
a signal for indicating an undesirable temperature condition which may 
result from the failure of the refrigerating means 19 (FIG. 5) provided 
for refrigerating the chamber 12. Such refrigerating means may comprise 
conventional refrigerating means well-known in the art and requires no 
further description herein. 
As discussed briefly above, the temperature of the air within refrigerated 
space 12 tends to rise when the access door 14 is opened to provide user 
access to the refrigerated compartment. Thus, while the indicating means 
17 normally is intended to provide an indication of an over-temperature 
condition within the refrigerated compartment, such as that resulting from 
a failure of the refrigerating means 19 or from an improper temperature 
setting of the temperature control (not shown) for the refrigeration 
apparatus, the indicating means may be caused to provide an indication of 
an over-temperature condition simply as a result of high temperature 
ambient air flowing into the refrigerated compartment, or past the sensing 
means, as during the time the door is opened. To prevent a spurious 
indication of an over-temperature condition from arising due to the 
various effects of a high ambient temperature, the indicating means 17 is 
caused to operate at a trip point which varies as a function of ambient 
temperature. Thus, under high ambient conditions the indicating means 17 
does not provide an indication to the user of an over-temperature 
condition until the sensed temperature within the compartment 12 reaches a 
relatively high temperature such as approximately 60.degree. F., while 
under low ambient conditions an over-temperature indication is provided at 
a lower sensed compartment temperature, such as 45.degree. F. 
A suitable electronic circuit for use in controlling the display panel 18 
is disclosed in my copending U.S. Letters patent application Ser. No. 
255,673, entitled "Electronic Sensing And Strobed Display For 
Refrigerator", filed Apr. 20, 1981. The circuit 20 (FIG. 5) for 
controlling the display 18 may, if desired, comprise a control identical 
to that disclosed in said application Ser. No. 255,673. 
The present invention, however, comprehends an improved temperature sensing 
means generally designated 21 which includes a pair of temperature 
sensors, including sensor 22 for sensing the temperature of the 
refrigerated air within compartment 12, and sensor 23 for sensing the 
ambient air temperature. The temperature sensing means 21 provides an 
output signal to the display circuit 20 which, as described below, is a 
function of the temperature sensed by both sensors and, thus, provides an 
improved functioning of the indicating means 17, permitting the 
compartment trip point temperature to be adjusted in accordance with the 
ambient temperature condition so as to provide improved sensitivity in the 
over-temperature indicating control. 
As shown in FIGS. 2 and 3, the temperature sensors are mounted in a single 
housing 24 which, in turn, is mounted within the door 14. The housing 
includes an upper rear portion 25 which carries the sensor 22. Sensor 22 
is disposed so as to be in heat transfer association with the air within 
the compartment 12. The specific manner in which sensor 22 communicates 
with the compartment air and the details of using such a sensor for 
controlling an over-temperature indication are disclosed in the 
above-identified applications. 
With reference to FIG. 3, housing 24 includes a front portion 26 defined by 
a front wall 27. A circuit board 28 is spaced inwardly of the front wall 
27 to define a space 29 therebetween. As shown, sensor 23 is mounted to 
the lower portion of a circuit board 28, in heat transfer association with 
the air within space 29. More specifically, sensor 23 is located adjacent 
a portion of housing wall 27 which directly contacts the outer door panel 
15 at a point which is spaced from display panel 18 and directly exposed 
to the ambient temperature. Thermal insulation 30 is provided within the 
housing, positioned rearwardly of circuit board 28 so as to effectively 
define a wall which insulates sensor 23 from the temperature conditions 
within the refrigerated compartment 12. With this arrangement, the 
temperature of sensor 23 tracks the ambient temperature adjacent the outer 
door panel 15 quite closely. The panel 15 remains substantially at ambient 
temperature, and the temperature response of sensor 23 is largely due to 
the contacting of panel 15 by housing wall 27 and the proximity of sensor 
23 to the panel 15, coupled with the effect of insulation 30. 
As indicated above, temperature sensing means 21 provides a coordination of 
the signal sensed by sensors 22 and 23 so as to provide an improved signal 
to the display cirucit 20 associated with the refrigeration apparatus 19 
and indicating means 17. 
The coordinated action of the sensors is graphically illustrated in FIG. 4. 
As shown in FIG. 4, the circuitry associated directly with sensor 22 
provides a signal at a compartment temperature trip pont 32, such as 
60.degree. F., irrespective of changes in the ambient temperature. 
Additional circuitry within the temperature sensing means 21 is arranged 
so as to cause the trip point to be varied as a function of the ambient 
temperature sensed by sensor 23. As illustrated in FIG. 4, the temperature 
sensing means 21 is arranged to provide a signal at the 60.degree. F. trip 
point sensed by sensor 22 when the ambient temperature sensed by sensor 23 
is approximately 80.degree. F. or more. However, as the ambient 
temperature decreases below 80.degree. F., the trip point is 
correspondingly lowered as a result of the operation of sensor 23 and its 
associated circuitry so that at lower ambient temperature conditions, 
indicating means 17 may indicate an over-temperature condition at 
compartment temperatures below 60.degree. F. 
The coordination of the sensors 22 and 23 may be effected by suitable 
circuitry, and as discussed above, in the illustrated embodiment, the 
temperature sensing means 21 is utilized to provide an improved, ambient 
compensated over-temperature signal. More specifically, as shown in FIG. 
5, thermistor 22 is connected from a power supply lead L1 to a lead 34. 
The sensor thermistor 22 may comprise a thermistor having 20 Kohms 
resistance at approximately 25.degree. C. Lead 34 is connected to the 
noninverting terminal of a comparator 36. The output 37 of the comparator 
is connected through a diode 38 to a lead 39, which supplies the output of 
sensing means 21 to the control 20. Lead 39 is connected through a fixed 
resistor 40 to ground, resistor 40 illustratively being a 15 Kohm 
resistor. Resistor 40 maintains lead 39 normally at ground potential. 
A resistor 41 is connected between input 35 and output 37 of the 
comparator, and in the illustrated embodiment, resistor 41 comprises a 6.8 
megohm resistor. A 1 Kohm resistor 42 is connected bewteen power supply 
lead L1 and output 37. 
The inverting input 43 is connected to power supply lead L1 through a 30.5 
Kohm resistor 44 and to ground through a 30.5 Kohm resistor 45 in parallel 
with a 0.022 microfarad capacitor 46. Lead 34 is connected to ground 
through a 30.5 Kohm resistor 47 and a 0.022 microfarad capacitor 48 in 
parallel therewith. 
Sensor 23 comprises a thermistor having a 20 Kohm resistance at 
approximately 25.degree. C., and has a resistor 49 in parallel therewith. 
Thermistor 23 is connected to ground through a resistor 50 in parallel 
with a 0.022 microfarad capacitor 51. The thermistor 23 is further 
connected to the inverting input 52 of a second comparator 53, and 
thermistor 22 is connected via lead 34 to a noninverting input 54 thereof. 
A 6.8 megohm resistor 55 is connected between the noninverting input 54 
and output 56 of the comparator 53. The output is connected through a 1 
Kohm resistor 57 to power supply lead L1, and to a second diode 58. Diodes 
38 and 58 comprise an OR gate which is connected to lead 39, as shown in 
FIG. 5, to complete the control circuitry. 
The sensing means 21 functions so as to provide a high output signal at a 
compartment temperature trip point which varies with the ambient 
temperature, as shown by curve 33 in FIG. 4. This high output signal 
corresponds to an over-temperature condition. Thus, whenever the sensor 22 
senses a predetermined high temperature condition within the chamber 12, 
such as over 60.degree. F., comparator 36 toggles and forces the output 
signal on lead 39 high so as to provide a signal to the control 20 for 
indicating the over-temperature condition. However, as discussed above, 
comparator 53 is also coupled to the lead 39 and toggles as a function of 
the temperature sensed by both thermistor 22 and thermistor 23, so as to 
lower the compartment temperature at which the signal on lead 39 changes 
state as a direct function of the ambient temperature sensed by sensor 23. 
In the illustrated embodiment, the component valves have been chosen such 
that comparator 53 controls the output on lead 39 below a preselected 
ambient temperture, such as 80.degree. F., while comparator 36 controls 
the output for ambient temperatures above 80.degree. F., as illustrated in 
FIG. 4. Thus, while comparator 36 goes high when sensor 22 senses a 
compartment temperature of 60.degree. F. or more, comparator 53 provides 
an adjusting signal providing the desired lowering of the compartment 
temperature trip point in correspondence with a lowering of the ambient 
temperature, so as to cause the indicator 18 to display an 
over-temperature condition at correspondingly lower compartment 
temperatures, thereby providing improved sensitivity in the 
over-temperature indicating means. 
If desired, a third comparator 63 can be connected in circuit with 
comparators 36 and 53, as shown by the dashed line connections in FIG. 5, 
and arranged to pull line 39 high for sensed compartment temperatures 
below 45.degree. F. By way of example, resistors 59, 60 and 61 may have 
values of 46 Kohm, 30 Kohm and 6.8 megohm, respectively, and capacitor 62 
may have a value of 0.022 microfarad. Comparator 63, as well as 
comparators 36 and 53, may comprise a type LM 339 comparator. This 
arrangement alters the circuit output on lead 39 as shown by the broken 
line in FIG. 4, to provide a fixed minimum trip point temperature for very 
low ambient temperature conditions. 
Thus, as shown, the present invention comprehends an improved temperature 
sensing means for use in a refrigeration apparatus wherein it is desired 
to provide a signal indicating an over-temperature condition of the 
apparatus. The invention comprehends providing means for adjusting the 
temperature trip point so as to lower that trip point as a function of the 
ambient temperature surrounding the refrigeration apparatus. 
Further, the improved temperature sensing means comprehends providing a 
refrigeration apparatus with a single, self-contained housing which houses 
a temperature sensor for the refrigerated compartment and an ambient 
temperature sensor. In the illustrated embodiment, the housing is mounted 
within the door for controlling access to the refrigerated chamber through 
the access opening thereto. 
In the illustrated embodiment, the sensor for sensing the ambient 
temperature is mounted in an insulated portion of the housing so as to be 
responsive to the ambient temperature adjacent the door. As further 
disclosed in the illustrated embodiment, the ambient temperature sensor 
senses the ambient temperature through a portion of the housing and door, 
yet can be effectively sealed within the housing in the refrigeration 
apparatus. 
While the embodiment of the invention illustrated herein is particularly 
adapted for use with an over-temperature indicating means, it will be 
appreciated that the invention can also be utilized in association with 
the temperature control means for a refrigeration apparatus. 
The foregoing disclosure of specific embodiments is illustrative of the 
broad inventive concepts comprehended by the invention.