Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
2002-03-18
2004-02-10
Paik, Sang Y. (Department: 3742)
Electric heating
Heating devices
Combined with diverse-type art device
C219S211000, C219S528000, C219S529000, C219S549000
Reexamination Certificate
active
06689989
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electric blankets, and in particular, to an electric blanket incorporating an improved structure for heating the electric blanket and preventing the overheating of the same.
BACKGROUND AND SUMMARY OF THE INVENTION
In colder climates, electric blankets are often used to keep individuals warm. Typically, an electric blanket includes first and second sheets of cloth material having a heating structure captured therebetween. The heating structure includes a heating core wire connectable to an electrical power source through a controller. The controller allows a user to vary the magnitude of the electrical power provided to the heating core wire, and hence, to control the heat dissipated by the heating core wire and the temperature of the electric blanket.
The heating core wire is contained in an insulation sheath that is protected by a woven screen. In normal use, an electric blanket should be spread out over a large surface area, such as a bed, in order for the whole surface to dissipate the heat generated by the heating core wire. It can be appreciated that the maximum temperature reached by the heating core wire must be below the melting point of the insulation. However, the risk of an electric blanket overheating may be significant in those situations when the heating core wire is electrically coupled to the electrical power source and the electric blanket is folded onto itself so as to prevent the heat generated by the heating core wire to escape. In such a situation, a first layer of the folded electric blanket may heat an adjacent layer (and vice versa) to such point as to cause the electric blanket to reach a temperature that is capable of starting a fire. It is noted, however, that the insulation about the heating core wire must melt before the cloth layers of the electric blanket begin to char and a fire starts.
In order to prevent the possibility of a fire starting due to the overheating of the electric blanket, most electric blankets incorporate a protective fuse circuit. The protective fuse circuit is usually connected to the woven screen. If the heater core wire overheats, the insulation softens and melts such that the heater core wire engages the woven screen causing a short circuit. The protective fuse circuit disconnects the heating coil wire from the electrical power source in response to the short circuit.
By way of example, it is contemplated that the protective fuse circuit include series resistor-diode combinations connected to corresponding ends of the woven screen. The resistors of the resistor-diode combinations are positioned adjacent a thermal fuse. In response to a short circuit between the heating core wire and the woven screen anywhere along the length of the heating core wire, current will flow through the resistor-diode combinations so as to heat the resistors. The thermal fuse is actuated by the dissipation of heat in the resistors so as to disconnect the heating coil wire from the electrical power source. It is noted that the conductive directions of the diodes of the resistor-diode combinations are opposed in order to prevent current flow through the protective fuse circuit unless there is a short circuit between the heating core wire and the woven screen. While functional for their intended purpose, these prior heating structures used in the electric blankets are relatively expensive. As such, it would be highly desirable to provide an electric blanket that utilizes less expensive components than prior electric blankets.
For electric blankets to be used on double beds, an additional design criteria must be considered. More specifically, multiple users of a single electric blanket may desire the electric blanket to be set to different temperatures. As such, electric blankets are often provided with independent heater structures and controllers for each side of the electric blanket. It can be appreciated that this type of arrangement requires a separate power outlet for each side of the electric blanket and/or additional pairs of wires directed to the heating structures for each side of the electric blanket. Therefore, it would be highly desirable to provide an electric blanket that uses a minimum number of wires and that has a single power outlet, but still allows for the independent control of the temperatures for each side of the electric blanket.
Therefore, it is a primary object and feature of the present invention to provide an electric blanket that utilizes a minimum number of wires and a less expensive components than prior electric blankets.
It is a further object and feature of the present invention to provide an electric blanket that allows for the independent control of the temperatures for each side of the electric blanket and that utilizes a single power outlet.
It is a still further object and feature of the present invention to provide an electric blanket that is simple and inexpensive to manufacture.
In accordance with the present invention, an electric blanket is provided. The electric blanket includes a first core wire having first and second ends. A second core wire is positioned adjacent the first core wire. The second core wire engages the first core wire in response to a predetermined temperature. A cutout is operatively connected to the first end of the first core wire. The cutout is movable between a first connected state wherein the cutout electrically couples the first end of the first core wire to a variable power source and the second disconnected state wherein the cutout disconnects the first end of the first core from the variable power source. A monitoring circuit is operatively connected to the second core wire. The monitoring circuit moves the cutout between the connected state and the disconnected state in response to engagement of the second core wire and the first core wire.
The first and second core wires are wrapped in insulation. The insulation melts in response to exposure to a predetermined temperature. The second core wire has first and second ends. The monitoring circuit includes a first resistor and diode combination interconnecting the first end of the second core wire and a neutral point. The monitoring circuit further includes a second resistor and diode combination interconnecting the second end of the second core wire and the first end of the first core wire. The first and second resistor and diode combinations are interconnected in series. The diodes of the resistor and diode combinations have predetermined conductive directions and the conductive directions of the diodes of the resistor and diode combinations are opposed. It is contemplated to position the cutout in close proximity to the resistors of the first and second resistor and diode combinations.
The electric blanket may also include a third core wire positioned adjacent the second core wire. The third core wire has a first end operatively connected to the second end of the first core wire and a second end operatively connected to a neutral point. The monitoring circuit moves the cutout between the connected state and the disconnected state in response to engagement of the second core wire and the third core wire. The cutout may include a thermal fuse.
In accordance with a further aspect of the present invention, an electric blanket is provided. The electric blanket includes a first heater having a first heating wire, a second heating wire and a monitoring wire. The first heating wire has a first end and a second end. The second heating wire has a first end operatively connected to the second end of the first heating wire and a second end operatively connected to a first neutral point. The monitoring wire is positioned between the first and second heating wires. The monitoring wire is engageable with the first and second heating wires in response to a predetermined temperature. A cutout is operatively connected to the first end of the first heating wire. The cutout is movable between the first connected state wherein the cutout electrically couples the first end of the heating wi
Cheng Kin Sang
Crawford John
Irwin, Sr. Harold W.
Boyle Fredrickson Newholm Stein & Gratz S.C.
Dahbour Fadi H.
Paik Sang Y.
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