Note: Descriptions are shown in the official language in which they were submitted.
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:OVEN CONTROL CALIBR~:TION
The present invention reIates to the
calibration of a temperature control device that
regulates the operating temperature of the heating device.
In particular, the present invention relates to the
calibration of a thermostat used for regulating the
operating temperature of an oven.
Oven service repairmen are frequently called
upon by consumers to calibrate the operating temperature
of the consumers' ovens. Commonly, this calibration
involves adjusting a screw to vary the contact pressure
on a Bourdon tube, a diastat, or diaphragm. This
calibration method~has many disadvantages associated
with it one of which is that the calibration screw in
most cases is imbeded in the center of the operating
shaft of the thermostat. This makes access to the
screw dl~ficult and may also result in the shaft weakening.
, ~Of course in smaller diameter shafts the use of a
calibration screw is quite impractical~ Also, another
disadvantage associated with this method of adjusting
the calibration of the oven is that it upsets the~
~ operational point set at the manufacturing sight and
; ~ the control thermostat could fail to work if improperly
adjusted. Lastly, such adjustments in the oven
calibration usually require operating the oven for at
least three cycles(25 to 30 minutes per cycles)in order
to determine the actual temperature of the oven relative
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to that indicated on the control knob. Thus, such a method
of calibration is costly to the consumer in respectof the
time taken by the service repairmen to effect the
calibration.
~nother exis~ing method of calibration is
disclosed in U.S. Patent 3,176,541, issued April 6, 1965,
to Keeling et al. The method of calibration disclosed
in this patent involves rotating a dial relative to the
hub of a control knob attached to the end of an operating
shaft of a thermostat. The dial is secured in a fixed
position by a calibration arm which is secured to the hub
of the knob. The calibration arm is provided with a
tongue which passes through a corresponding slot on the
face of the dial. To calibrate the oven the tongue of the
calibration arm is removed from the slot, and the dial
is rotated relative to the calibration arm and the knob
until another slot in the dial aligns itself with the
tongue. The tongue may then be slipped into this other
slot to complete the calibration of the oven. A
decorative insert is placed over the slots so that they
are not visable. The dial is provided with a temperature
scale which is rotated relative to a reference point on
the faceplate of the oven during the calibration. While
this patent discloses a calibration for an oven that may
be readily adjusted in the field, such an arrangement
tends to be materially expensive in that is uses a number
of different parts for knob and the dial having the
temperature scale.
It is therefore an object of the present invention
to provide a temperature control device which may be
readily calibrated in the fieId by a service repairman
and is relatively ine~pensive in terms of material costs.
Briefly stated, the present invention involves
rotating the temperature control device of a heating means
relative to the wall or faceplate of the heating means to
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effect an adjustment of the calibration.
While the preferred embodiment of the present
invention provides for the rotation of the temperature
control device about an axis defined by the axis of
the operating shaft of the control device, it is
envisaged that the control device may be rotated about
another point as long as the operating shaft passes
through a sloted aperture in the wall oE the heating
means. In the preferred construction, to effect rotation
of the control device about the axis of the operating
shaft two arcuate slots are provided in the faceplate
on either side of the faceplate aperture through which
the operating shaft passes. Fastening means pass through
the slotted apertures and fasten the temperature control
device in a first positioned relation with respect to
the wall. The fastening means may be-loosened to effect
the rotation of the temperature control device. The
length of the slots determines the amount of rotation
which the thermostat control device may undergo, and
therefore the amount of calibration adjustment. In the
preferred ernbodiment of the invention the control knob
and temperature dial are of one piece construction and
are attached to the operating shaft. In the preferred
embodiment the temperature dial covers the fastening
means and the knob is removably attached to the operating
shaft to facilitate access to the fastening means. In an
alternate construction it is envisaged that the temperature
dial would not cover the fastening means, and, therefore,
the knob would not have to be removably attached but could
be fixedly attached to the operating shaft. Also/ in the
preferred construction the arcuate slots are located
proximate to the aperture through which the operating shaft
passes, but such slots do not necessarily have to be
located close to this aperture. Additionally, in the
preferred construction an indicating means in the form
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of a dial is secured to the outside surface of the wall or
faceplate by the fastening means. When the fastening means
are loosened to allow the temperature control device to be
rotated relative to the wall, the dial rotates with the
temperature control device relative to the wall. A reference
point is provided on the wall and indicia are provided on
the dial so that an accurate reading of the calibration,
temperature is visually given to the service repairman
and user.
For a better understanding of the nature and
objects of the present invention, reference may be had
by way of example to the accompanying diagrammatic
drawings in which:
Figure 1 is an exploded perspective view of
the oven control device of the present invention;
Figure 2 is a front view showing the oven
control device mounted to the wall of the oven in a first
positioned relation; and,
Figure 3 is a front view showing the oven
control device mounted to the wall of the oven in a
second positioned relation.
Referring to the figures the preferred embodiment
of the present invention is described. A temperature
control device or thermostat 10 is provided for an oven
(not shown). The thermostat 10 includes an operating
shaft 12 which can be manipulated to adjust the pre-
determined temperature for which the thermostat 10 will
regulate the operating temperature'of the oven. Attached
to the thermostat 10 is a metal bracket 14 which is
attached by means of screws 16 passing through corresponding
apertures in bracket 14. The operating shaft 12 passes
through a central aperture 18 in the bracket 14 and also
passes through a central aperture 20 in the oven or
faceplate 22. Aligned with the central aperture 20 of
the oven wall 22 is a central aperture 24 ofan indicating
means or dial 26. Dial 26 and thermostat 10 are mounted
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normally in a first positioned relation with wall 22
substantially as illustrated in Figure 2. This is
accomplished by a fastening means illustrated by screws
28 passing through mounting apertures 30 of dial 26,
arcuate slots 32 of wall 22, and apertures 34 in the
bracket 14. Attached to the end of the operating shaft
12 is a knob and dial 36. The knob and dial 36 has a
temperature scale 38 marked thereon. The knob 36 has a
hub portion (not illustrated) which is removably attached
to the end of the operating shaft 12.
To effect the calibration of the oven hy a
service repairman, the service repairman first removes
the knob and dial 36 from the end of operating shaft
12. The repairman then loosens screws28, rotates the
indicating dial 26 thereby rotating the thermostat 10
relative to the wall 22 of the oven. As illustrated,
this rotational movement occurs about an axis 40 defined
by the axis of the operating shaft 12. The rotation of
the indicating dial 26 and thermostat 10 is limited by
the length of arcuate slots 32. A reference point 42 is
provided on the wall 22 which point can be compared with
the indicia 44 on the dial 26. For each of the indicia
that the indicating dial 26 is rotated either clock-wise
or counter clockwise, a change in the oven of a temperature
of either plus or minus 5 ~Fwill be effected. The scrPws
28 may then be tightened to mount the thermostat 10 in a
second positioned reIation with respect to the wall 22 as
illustrated, for example, in Figure 3. The knob 36 may
then be re-attached to the end of the operating shaft 12.
The preferred embodiment provides a calibration
method that is readily accomplished by a service repair-
man and is inexpensive in terms of material costs.
It should be understood that alternate
embodiments may be readily apparent to a man skilled in
the art in view of the foregoing description. Accordingly,
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the present invention should only be limited to that
which is claimed in the accompanying claims.
