Method of calibrating a knob for use with an adjustable control device and a knob calibrated thereby

A method of calibrating an adjustable control device using a knob assembly with adjustable temperature scale. A knob and a bezel that bears the temperature scale are assembled and the temperature scale is calibrated without physically changing any internals within the adjustable control device. The knob and bezel are secured to the adjustable control device so that the knob and bezel assembly can transmit an input load from a user through to the adjustable control device and so that the bezel can be rotated relative to the knob which remains fixed to an input shaft of the control for calibration purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a knob assembly that interfaces with an adjustable control device that controls a variable. In particular, the present disclosure in a preferred embodiment relates to a calibratable oven knob that interfaces with an adjustable control thermostat.

2. Description of Related Art

Traditional oven and griddle assemblies are manufactured with a removable knob that fits over a valve stem of a thermostatic control. The knob is typically splined or keyed to the stem so that force applied to the knob by the end user can be transmitted through to the control to affect the output temperature of a cooking appliance. Examples of common thermostatic controls include the FDO control and the BJWA control available from Invensys. Some controls, such as the FDO control and the BJWA control, provide manufacturer backed means of field calibration that allow a service technician to make a manual adjustment and change the calibration of the thermostat by some amount. In the case of the FDO and BJWA controls, this adjustment is typically ±10 degrees Fahrenheit. It is common for the service technician to have to remove the knob before such an adjustment can be made.

However, not all thermostat controls provide a capability for a field calibration as desired by the end consumer. Therefore, there is a need to provide an alternate manner of calibration without impacting on the warranty of the thermostat control.

SUMMARY OF THE INVENTION

The present disclosure provides a calibratable knob and temperature scale that can be accurately and positively aligned during assembly with an adjustable control device.

A method of the present disclosure calibrates a knob and a temperature scale with an adjustable control that controls heating of a cooking appliance. The method comprises securing the knob and the temperature scale to a rotatable element of the adjustable control device so that moving the knob also moves the temperature scale and the rotatable element. The knob, and temperature scale, is set to a predetermined temperature. The resulting temperature of the cooking appliance is measured. When the measured temperature reaches a steady state temperature, it is determined if the steady state temperature is equal to the predetermined temperature selected. If the steady state temperature is not equal to the predetermined temperature, the knob and temperature scale is moved to heat or cool the cooking appliance until the steady temperature is equal to the predetermined temperature. One of the knob and temperature scale is moved relative to the other to the predetermined temperature on the temperature scale.

In one embodiment of the method of the present disclosure, the knob and temperature scale are moved by an amount about equal to a difference between the steady state temperature and the predetermined temperature to heat or cool the cooking appliance.

In another embodiment of the method of the present disclosure, the method further comprises loosening the temperature scale relative to the knob before moving one of them; and securing the knob and the temperature scale to one another after the one of them is moved.

In another embodiment of the method of the present disclosure, the method further comprises an indicator that is fixed relative to the knob and the temperature scale and the adjustable control device.

In another embodiment of the method of the present disclosure, the indicator is located on the adjustable control device.

In another embodiment of the method of the present disclosure, the temperature scale has an amount of angular rotation in a range from about 10 degrees to about 30 degrees.

In another embodiment of the method of the present disclosure, the temperature scale is located on an annular disk that is rotatable relative to the knob when loosened and rotatable with the knob when secured to the knob.

In another embodiment of the method of the present disclosure, the method further comprises turning the cooking appliance on so that the adjustable control device controls a heating system of the cooking appliance to heat and cool the cooking appliance.

A knob assembly of the present disclosure comprises a knob that comprises a handle portion and a hub portion. The hub portion comprises a control element receiving socket at an outer end of the knob capable of transmitting an applied load. The handle portion comprises a cylindrical base and an indented blade portion capable of receiving the applied load. A member is coupled to the knob. A temperature scale is located on a surface of the member. One of the member and knob is movable relative to the another.

In one embodiment of the knob assembly of the present disclosure, the member is an annular disc.

In another embodiment of the knob assembly of the present disclosure, at least one curvilinear slot faces the outer end and at least one screw extends through the curvilinear slot to lock and unlock the annular disc to the knob. The annular disc when unlocked is rotatable with respect to the knob in an angular range determined by a size of the curvilinear slot.

In another embodiment of the knob assembly of the present disclosure, at least one additional curvilinear slot faces the outer end and at least one additional screw extends through the additional curvilinear slot. The one screw and the additional screw lock and unlock the annular disc to the knob.

In another embodiment of the knob assembly of the present disclosure, the surface of the annular disc comprises a bezel.

In another embodiment of the knob assembly of the present disclosure. the handle portion is manufactured from phenolic.

In another embodiment of the knob assembly of the present disclosure, the bezel is manufactured from cast aluminum.

In another embodiment of the knob assembly of the present disclosure. the control element is a force transmitting element of an adjustable control device, further comprising a set screw that positively locks the knob to the control element of the adjustable control device.

In another embodiment of the knob assembly of the present disclosure, the control element comprises a knob that is locked to a rotatable stem of the adjustable control device.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1, a calibratable knob assembly12is shown attached to an adjustable control device14. Adjustable control device14controls a variable such as temperature, pressure, humidity, flow or other variable. By way of example and completeness of description, adjustable control device14will be described herein for the application of controlling a temperature of a stove, oven, griddle, or other cooking appliance.

In the illustrated embodiment, adjustable control device14is connected to a cooking appliance16. Cooking appliance16comprises a heating system18and cook chamber22. In particular, adjustable control device14is connected to heating system18to heat and cool cook chamber22.

Referring toFIGS. 1 and 4, calibratable knob assembly12is mounted on the end of a rotatable member70of adjustable control device14. In a preferred embodiment, the rotatable member comprises a rotatable shaft or stem controlling a gas valve, thermostat or an electrical rheostat that controls the temperature of cooking appliance16. For example, adjustable control device14is a model 630 modulating thermostat available from SIT La Precise S.p.A. of Padova, Italy.

Calibratable knob assembly12comprises a knob10and an annular member or disc15that form a two-piece assembly. Knob10comprises a handle portion20and a hub portion25(FIG. 2). Hub portion25comprises a control shaft receiving socket30at its outer end. Handle portion20comprises a cylindrical base35, an indented blade portion40and an axially facing annular rim45surrounding cylindrical base35. Handle portion20is manufactured from any suitable material, an example of which is phenolic. Annular member15is manufactured from any suitable material, for example a metal such as aluminum or any suitable plastic. Annular member15comprises a suitable surface that bears a temperature scale50. The surface may be flat, inclined or other shape dependent on human viewing desirability. In the illustrated embodiment, annular member15has an inclined surface and is sometimes referred to herein as bezel15.

Temperature scale50comprises a secondary piece that can be attached to bezel15using an adhesive. In other exemplary embodiments, temperature scale50is molded as an integral part of bezel15, printed directly on the surface of bezel15, or secured to bezel15using any other method known presently or in the future by one skilled in the art. As shown inFIG. 2, at least two curvilinear slots80are disposed in the rear of bezel15in alignment with mating screw holes (not shown) disposed in the rear of knob10. Bezel15with temperature scale50is assembled, secured or locked to knob10with one or more screws55via curvilinear slots80. Temperature scale50can be configured to display any desired temperature range in either degrees Celsius and/or degrees Fahrenheit. Knob10comprises an optional center indicator strip60and an “OFF and PILOT” indicator strip65. “OFF and PILOT” indicator strip65is in one fixed position on bezel15. Indicator strip65may also show only the word “PILOT” to suit specific applications.

Referring toFIG. 4, adjustable control device14has a knob75that is attached to a rotatable shaft or stem70of adjustable control device14. The rear of calibratable knob assembly12, seen clearly inFIG. 2, has a complimentary or mating configuration to a knob75of adjustable control device14. Knob10has an internal female hub that is splined and mates with the externally splined profile of control knob75of adjustable control device14. To this end, knob socket30of knob10comprises a plurality of spline ribs that mate with a like plurality of spline grooves on knob75. Referring toFIGS. 2-4, a tapped hole100is located in a rim105of knob10to be in alignment with a pilot hole110in knob75. Knob10is secured to knob75with a set screw (not shown) via tapped hole100and pilot hole110. This allows an operator to rotate knob75by rotating knob10. This allows calibratable knob assembly12and knob75to be securely attached and properly aligned with one another.

During the calibration process, bezel15is secured to knob10using screws55. Screws55pass through curvilinear slots80and screw into mating screw holes (not shown) in knob10. When screws55are loosened, bezel15and temperature scale50can be rotated about ±10 rotational degrees or in a range of 20 degrees of rotation which is equivalent to about ±17° Fahrenheit (or a range of 34°) on temperature scale50for this application. The exact amount of rotation and corresponding calibration shift may vary depending on the particular application.

Referring toFIGS. 1,4and5, knob10and bezel15are secured to one another. The oven is turned on and knob assembly12is turned to a predetermined calibration temperature, typically 400° F. In this embodiment, the reference marker is circle120on adjustable control device14inFIG. 1. That is, the 400° F. position on temperature scale50is now aligned with circle120. Oven temperature readings are taken with a probe. If the oven temperature at steady state is 400° F., knob assembly12is calibrated. If the probe reading is 405° F., knob assembly12is rotated counterclockwise to indicate approximately 395° F. to cool the oven by 5° F. When the temperature probe reading is 400° F., bezel15is loosened and rotated clockwise to indicate 400° F. Bezel15is then secured to knob10with screws55. Through this method, the adjustable control device in this embodiment is calibrated. In other embodiments the reference marker can be located in another stationary place on the cooking appliance or on the knob itself.

The data below in Table 1 supports the finding that knob assembly5of the present disclosure is calibratable with adjustable control device70and ±10 rotational degrees is equivalent to about ±17 temperature degrees F. The table data was obtained as follows. Bezel15was loosened, positioned at the mid point of its rotational range and then secured to knob10. Knob assembly12is then set to each of the temperatures listed in the column labeled Nominal SIT Dial Marking. The recorded oven temperatures are listed in the right hand column labeled Oven Temperature in average conditions. For each of the temperatures 250, 300, 350, 400, 450 and 500° F., three temperature readings are taken. For example, the procedure at the 400° F. nominal first set knob assembly12to 400° F. The recorded temperature was 400° F. Bezel15was loosened, rotated counterclockwise to its angular extreme and then secured to knob10. Knob assembly12was then positioned to 400° F. The recorded temperature was 385° F. Then bezel15was again loosened, rotated clockwise to its other angular extreme and then secured to knob10. Knob assembly12was then positioned to 400° F. The recorded temperature was 415.5° F. This demonstrates that bezel15has a temperature adjustment range of about 30° F. The same procedure was performed at each of the other temperatures 250, 300, 350, 450 and 500° F.

In an alternate embodiment, a linear temperature indicator could be tied via a linkage to the rotational motion of the adjustable control device. In this embodiment, the knob and linear temperature scale is arranged for relative motion for calibration purposes.

The embodiments of the present disclosure having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present embodiments as defined in the appended claims.