Thermal measuring and testing – Thermal calibration system
Reexamination Certificate
1999-05-11
2001-01-09
Bennett, G. Bradley (Department: 2859)
Thermal measuring and testing
Thermal calibration system
C374S003000
Reexamination Certificate
active
06170983
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the calibration of stem thermometers. Examples of applications in which such thermometers are used are cooking, laboratory work, or testing, though the thermometers can be used to measure any suitable medium.
BACKGROUND OF THE INVENTION
Stem thermometers have a stem that can be inserted into a medium to measure its temperature. One popular use for stem thermometers is monitoring cooking food, especially meat. Throughout the specification, this use will serve as an example, even though the invention can be used to calibrate thermometers applied to many other purposes.
In cooking, a dial and a pointer of a stem thermometer indicate the temperature of the interior of the food. These thermometers need to be calibrated occasionally to ensure accurate temperature measurement and, in the case of food monitoring, optimum cooking of the food. An improperly adjusted or off-calibration thermometer can cause serious problems. In the case of meat cooking, undercooking can result in serious illness, while overcooking shrinks the meat and alters the flavor, making the meat less palatable.
Stem thermometers used in restaurants are sometimes calibrated by comparison with each other, which can lead to error if the comparison standard thermometer is off calibration. Testing laboratories calibrate thermometers with special equipment that is too expensive and cumbersome for restaurant use, though smaller and portable calibrators are available. Use of these calibrators involves holding the thermometer stem in thermal communication with a heat sink raised to a calibration temperature and using a wrench to turn an adjuster on the back of the thermometer to bring the dial and pointer into calibration.
DESCRIPTION OF THE RELATED PRIOR ART
U.S. Pat. No. 4,749,281 to Nunes discloses a universal thermometer movement that can be used in a variety of thermometer housings, indicators, and scales. This device is related to thermometers of the type calibrated by the instant invention. One embodiment of the movement comprises a coil support, a casing, a bimetallic coil, an arbor, and an attachment point to which an end of the coil is attached. A socket receives the arbor, the outer end of the socket being threaded to receive washers and a nut such that the socket can be tightened into place within a central aperture. Rotation of the coil support relative to the casing calibrates the thermometer movement. However, the patent does not disclose any way to determine the amount of relative rotation to impart to the movement to achieve proper calibration.
U.S. Pat. No. 1,694,164 to Crosthwait, Jr. discloses a method and apparatus for setting or adjusting thermostats of the type used in thermostatic steam traps. The specification of Crosthwait implies that the method and apparatus are used only in the assembly and installation of the thermostat. A casing forms a steam space and is closed by a top or cap having a flange that screws into the casing. The thermostatic member is a disk that expands when heated, usually as a result of the expansion of a fluid contained within the disk. A stud extends from one surface of the disk and screws into a socket projecting from the top to hold the thermostat in place in the trap. The thermostat is adjusted by screwing the stud into or out of the socket via a nut, thereby moving the disk in relation to the top.
The method and apparatus of Crosthwait require the use of three devices and many steps to calibrate thermostats. First, the thermostat alone is measured by one device that fills the thermostat with compressed air to simulate the fluid later placed in the thermostat. Then, a second device measures the change in the thermostat size as a result of mounting it in the trap top and filling it with fluid. Finally, a third device is used to adjust the thermostat after it is in the trap top. The specification does not suggest that this adjustment could be performed at the site where the thermostat is used to calibrate the thermostat after a period of use, nor does it provide for easy, one-step calibration.
U.S. Pat. No. 4,079,618 to King discloses a dry well for a temperature calibration system of the general type contemplated for use with the invention. An electronically controlled heat sink is provided into which a thermometer or temperature probe is inserted for calibration. After selecting a test temperature, the user inserts the component to be tested into a receptacle in the calibrator to heat the component to the test temperature. However, while this device is called a “calibration system,” it only allows a user to test the accuracy of a thermometer. To calibrate the thermometer, the user must insert a wrench behind the thermometer head to engage and hold the thermometer adjuster. While holding the adjuster in position, the operator must rotate the thermometer head to adjust the reading. The operation can be awkward and inconvenient.
U.S. Pat. No. 4,901,257 to Chang et al. discloses another temperature calibration system. The system includes a temperature well that holds the probe to be calibrated and is very similar to the device disclosed in U.S. Pat. No. 4,079,618 to King. The temperature of the well is controlled by an electronic control system. While the device includes components that allow it to calibrate itself, there are no provisions for the calibration of the temperature probe other than a display of the temperature of the well, which can then be compared with the temperature probe readout. Thus, as with King above, the thermometer must be calibrated with an awkward and inconvenient process of inserting a wrench behind the thermometer head and holding the adjuster in place while rotating the head until the thermometer shows no significant discrepancy in its reading.
U.S. Pat. No. 4,819,249 to Ekstrom et al. discloses a device for determining the accuracy of a thermally activated instrument, such as a thermometer or temperature probe. An enclosure holds the instrument to be tested and heats the instrument using electric current. An external electric controller controls the temperature of the enclosure. Again, this device only allows the user to test the accuracy of the instrument. Calibration must be performed in a manner similar to that used in the King and Chang et al. devices, making calibration an inconvenient and awkward process.
U.S. Pat. No. 5,678,923 to Germanow et al., the disclosure of which is hereby incorporated by reference, discloses a thermometer calibrator that is similar to the instant invention. The Germanow et al. device has a socket into which the stem of a thermometer is inserted, the socket being shaped to hold the adjuster or adjustment nut of the thermometer in place while the thermometer head is rotated to calibrate the thermometer. The Germanow et al. calibrator allows for calibration of thermometers that have different sized nuts. However, as seen in FIGS.
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, this is achieved using an external adapter plate screwed onto the outside of the casing, the plate having an opening configured to hold nuts narrower than those the socket can handle. This can be inconvenient and time consuming if a batch of thermometers of different adjuster sizes is being calibrated, requiring the adapter to be put on and removed repeatedly.
SUMMARY OF THE INVENTION
The inventive thermometer calibrator allows calibration of thermometers using adjustment nuts of different sizes without having to attach an adapter plate to the outside of the housing over the calibration socket. Instead, the calibration socket is staggered, having a larger opening at an outer level, and one or more smaller openings at respective inner levels, the openings getting smaller the farther into the casing they are. The outermost, largest opening can be formed in the housing while the inner, smaller openings can be formed in a block held in the socket or even held by the outermost opening itself. This provides a way for the inner openings to be changed by changing the block held in the socket or in the outermost opening. The user can thus con
Germanow Andrew C.
Marsh Robert I.
Bennett G. Bradley
Eugene Stephens & Associates
Germanow-Simon Corporation
Verbitsky Gail
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