Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With longitudinally expansible solid element
Reexamination Certificate
2003-02-21
2004-08-24
Gutierrez, Diego (Department: 2859)
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With longitudinally expansible solid element
C374S208000
Reexamination Certificate
active
06781505
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the priority of Austrian Patent Application, Serial No. A 279/2002, filed Feb. 25, 2002, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates, in general, to a temperature sensor of a type including a sensor tube and a sensor rod, which is arranged in the sensor tube and has a thermal expansion coefficient that differs from a thermal expansion coefficient of the sensor tube.
In typical temperature sensors, the sensor rod has one end, which is supported in the area of the free end of the sensor tube, and another end, which forms the actuating element of a switching contact assembly and is surrounded at least partially by an insulating member. The sensor tube with the accommodated sensor rod is guided through an opening of the insulating member, with a support plate being provided in the area of the opening and either directly connected to the sensor tube, supported at the opening, or connected to a tubular insert, placed in the opening and supporting the sensor tube. Conventionally, the tubular insert of the sensor tube has been screwed to the support plate in the opening of the insulating member, or these components have been connected to one another through riveting or interlacing. As a consequence, gaps are formed that allow access to the interior of the insulating member, which houses the switching contact assembly. Thus, particles may penetrate from outside and adversely affect the switching behavior of the switching contact assembly.
Temperature sensors are also known in which one end of the sensor rod is a supported by end piece in the area of the free end of the sensor tube, and the other end of the sensor rod is configured as actuating element of a switching contact assembly. Temperature sensors, which trigger actuation of a switching contact as a result of different thermal expansion coefficients of their components, have proven their ruggedness in practice. As they are manufactured on a large scale, temperature sensors should be as reliable as possible and cost-efficient. While implementation of a smallest possible size and a smallest possible material consumption is desired, the production should also result in temperature sensors that are still reliable in operation to ensure a proper actuation of the switching contact system. The active length available for contact actuation and affected by the thermal elongation, as the temperature sensor is heated, should therefore be as long as possible in relation to the overall length of the temperature sensor.
European Pat. No. EP 0 476 304 A describes a temperature sensor with an end piece for the sensor tube, whereby the sensor tube extends into the end piece so that a significant portion of the length of the sensor tube is lost for the active length of the temperature sensor.
It would therefore be desirable and advantageous to provide an improved temperature sensor which obviates prior art shortcomings and which is constructed to seal the insulating member with the switching contact assembly in the area of the opening for the sensor tube in a dust-tight manner against the ambient environment.
It would also be desirable and advantageous to provide an improved temperature sensor which is simple in structure and cost-efficient to manufacture, while realizing a rapid, permanent and play-free securement of the sensor tube or combination of sensor tube and tubular insert.
It would also be desirable and advantageous to provide an improved temperature sensor which is so constructed as to afford a greatest possible active length.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a temperature sensor includes a sensor tube, a sensor rod received in the sensor tube and having a thermal expansion coefficient, which differs from a thermal expansion coefficient of the sensor tube, with the sensor rod having one end, which is supported by a free end of the sensor tube, and another end, which forms an actuating element of a switching contact assembly, an insulating member constructed to at least partly surround the switching contact assembly and having an opening for passage of the sensor tube with accommodated sensor rod, a support plate mounted to the insulating member in the area of the opening and connected at least indirectly to the sensor tube by a welding process such that an opening-surrounding wall portion of the insulating member is held in place.
According to another feature of the present invention, the support plate may be welded directly to the sensor tube so that the opening-surrounding wall portion of the insulating member is held between the support plate and the sensor tube. As an alternative, the support plate may be welded to a tubular insert, placed into the opening for support of the sensor tube, so that the opening-surrounding wall portion of the insulating member is held between the support plate and the tubular insert. In either case, through application of a welding process, the support plate can be connected to the sensor tube or the tubular insert for the sensor tube in such a manner that no dust particles can penetrate from outside into the interior of the insulating member. The welding process represents also a cost-efficient and rapid method to connect the respective components and to secure the components to be connected in place. Of course, the sensor tube should be made of metal, when the support plate is directly welded to the sensor tube. Examples of suitable metal include high temperature-resistant metal, such as a CrNi alloy.
Suitably, the support plate is configured for attachment of the temperature sensor to a desired device. According to another feature of the present invention, the support plate may have a bore for allowing attachment of the temperature sensor to a heating element.
According to another feature of the present invention, the tubular insert may have an outer diameter, which is smaller than a diameter of the opening of the insulation member, and an inner diameter, which is greater than a diameter of the sensor tube, wherein the tubular insert has one end configured as a flange. The tubular insert with flange enables a solid seat of the sensor tube and the provision of a stable support of the sensor tube in relation to the insulating member.
According to another feature of the present invention, the support plate may have an opening for passage of the sensor tube, wherein welding bosses are arranged in an abutting joint area of the support plate and the tubular insert. In this way, a sufficiently stable and permanent welding connection can be implemented.
According to another feature of the present invention, the sensor tube may have a flanged shoulder for support upon the insulating member in the area of the opening, or for support upon the tubular insert, thereby realizing a cost-efficient support which is easy to make.
A stable seat of the sensor tube may also be realized, when the sensor tube has in the area of the opening of the insulating member a diameter which is greater than a diameter of a sensor tube portion projecting into the insulating member. By widening the end of the sensor tube in this manner, the bending moment, required for a flexure, is increased.
According to another aspect of the present invention, a temperature sensor includes a sensor tube having a free end, a sensor rod received in the interior of the sensor tube and having a thermal expansion coefficient which differs from a thermal expansion coefficient of the sensor tube, with the sensor rod having one end, which is supported by an end piece in the area of the free end of the sensor tube, and another end, which forms an actuating element of a switching contact assembly, wherein the end piece has a configuration of a tubular cap which is permanently placed over the free end of the sensor tube, wherein the one end of the sensor rod is supported against an inner side of the tubular cap, which inner side confronts the inte
Electrovac, Fabrikation elektrotechnischer Spezialartikel Gesell
Feiereisen Henry M.
Gutierrez Diego
Pruchnic Jr. Stanley J.
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