Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Reexamination Certificate
1998-10-09
2001-07-10
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
C374S179000, C374S208000
Reexamination Certificate
active
06257758
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a surface temperature sensor, and more particularly to a sensor having a thermally conducting surface supported by a coiled temperature sensing element.
BACKGROUND OF THE INVENTION
Surface temperature sensors are known in the art; contact-type surface temperature sensors are designed to make contact with a surface in order to measure the temperature of the surface. For example, U.S. Pat. No. 4,859,081 describes one type of surface temperature sensor which includes a thin plate spring with a thermocouple junction on a central portion thereof. The plate spring is fixed at both of its ends to a support member so that the plate spring projects semicircularly in side elevation to form a temperature sensing portion. The plate spring and the thermocouple junction are brought into contact with the surface to be measured and are pressed against the surface to flatten slightly the semicircular portion of the plate spring. As a result, part of the plate spring and the thermocouple junction are engaged closely in press contact with the surface to be measured.
GB Application No. 932,260 (Pearce) relates to another type of surface temperature sensor having a thermocouple ring supported by an insulated disk which in turn is supported by a coil consisting of one of the two thermocouple materials. The sensor is pressed against a surface to be measured, whereby the thermocouple ring makes direct contact to the surface. The thermocouple ring and the insulated disk arrangement is capable of travel in a direction perpendicular to the surface due to the coil. The amount of travel is limited by an outer casing which surrounds the thermocouple ring.
Another type of surface temperature sensor is disclosed in U.S. Pat. No. 4,454,370 (Voznick) which shows a pair of side-by-side elongated coils that come into contact with one another at their ends to form a thermocouple junction. The surface temperature sensor further includes a protective sleeve supported by a coil which engages the surface to be measured prior to the thermocouple junction in order to ensure a safe rate of contact and thereby protect the thermocouple from damage. Once in contact with the surface, the thermocouple junction is further operable to move in a direction perpendicular to the surface via its secondary coils to make a direct press contact with the surface.
There are several drawbacks associated with the conventional contact-type surface temperature sensors enumerated above. In each of the above sensors, the thermocouple junction makes contact directly with the surface to be measured. When using conventional lap joints for thermocouples, wherein one of the thermocouple materials overlap the other to form the thermocouple junction, the lap joint prevents the junction from uniformly contacting the surface to be measured, thereby introducing a measurement error. Alternatively, when using a conventional butt joint to form the thermocouple junction, sputtering, flash, etc. can produce a buildup at the joint or a nonuniformity, such as a burr, may form on the surface and prevent the thermocouple junction from uniformly engaging the surface to be measured. Such direct contact of the thermocouple junction to the surface to be measured results in substantial thermal contact resistance. Any such contact resistance is in series with other thermal resistance and undesirably reduces the heat transfer between the surface to be measured and the sensor.
Another drawback associated with conventional surface temperature sensors is the use of an electrical insulating layer between the thermocouple junction and the junction holding apparatus. The insulating layer, although electrically insulating, contains a substantial thermal mass and thereby provides a thermal loading effect on the thermocouple junction, thereby resulting in thermal measurement error and a slow response time which thus requires contact with the surface to be measured to be maintained for an undesirably long period of time to ensure an accurate thermal measurement.
Yet another disadvantage associated with the conventional contact-type surface temperature sensors is the excessive thermal loading due to the travel stop. Such prior art protection includes semicircular housing walls which substantially encircle the thermocouple junction. The housing walls limit the distance the resilient thermocouple junction can be deflected when pressed against a large surface. The housing walls come in contact with the surface to be measured and, due to the substantial thermal mass of the housing walls, may modify the surface temperature. Therefore such prior art designs are undesirable because the housing walls may cause measurement error.
In view of the above shortcomings associated with convention contact-type surface temperature sensors, there is a need in the art for a rugged surface temperature sensor which reduces heat transfer errors and provides for miniaturization.
SUMMARY OF THE INVENTION
The present invention relates to a contact-type surface temperature sensor for measuring the temperature of a surface. The sensor includes a thermally conductive surface contact member which engages a surface to be measured. The contact member is supported by a coil having thermal sensing elements therein which form a thermocouple junction. The sensor of the present invention, by incorporating the thermal sensing elements within the coil, allows for the miniaturization of the sensor.
Use of the thermally conductive contact member serves to help protect the thermocouple junction and eliminates a need for prior art protective housings, thus reducing the thermal loading of the sensor and reducing measurement errors associated therewith. In addition, since the sensor does not incorporate an insulative disk, but rather is supported primarily or entirely by the coil, measurement error due to thermal loading and heat transfer is further reduced over the prior art.
According to one aspect of the present invention, the thermally conductive surface contact member is stepped or recessed, respectively, along a bottom surface thereof to facilitate the engagement of the coil to the surface contact member. Consequently, the coil can be secured to the contact member for improved ruggedness. In addition, the gradual exit of the coil from the contact member reduces heat transfer errors due to thermal shunting. Since thermal shunting is a function of the thermal gradient at the sensor, the gradual exit of the coil isolates the thermal shunting from the thermocouple junction by causing the thermal gradient to exist along the coil at a distance away from the thermocouple junction.
According to another aspect of the present invention, the sensor includes a base portion to which the coil attaches. The base portion includes a support member, about which one or more turns of the coil may attach, which provides additional support to the coil for improved ruggedness and durability. The support member may further include an over travel protection member extending from the support member toward the contact member. The over travel protection member advantageously protects the sensor even in instances where a small object or surface is to be measured in contrast to prior art sensors which only provide protection as a travel stop in instances where the object to be measured is larger than the sensor diameter.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
REFERENCES:
patent: 2288510 (1942-06-01), Branno
Claud S. Gordon Company
Guadalupe Yaritza
Gutierrez Diego
Renner , Otto, Boisselle & Sklar, LLP
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