Electric heating – Heating devices – Combined with pressure application means
Reexamination Certificate
1997-04-25
2001-10-23
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with pressure application means
C219S251000, C307S116000, C340S635000
Reexamination Certificate
active
06307182
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electric appliances having an automatic power interrupting device and, in particular, to electric appliances having a proximity sensor to detect use and non-use of the appliance.
BACKGROUND OF THE INVENTION
Conventional electric pressing irons have been used for many years to press articles of clothing and various textiles. Such irons include a soleplate having a heating element connected to a source of electrical power which heats the soleplate to a sufficient temperature to press the articles of clothing.
A number of problems exist with conventional electric pressing irons, however, in that the iron is prone to scorch clothing, cause fires, or cause burns to a person who inadvertently contacts the heated soleplate of the iron. For example, when the attention of a user of the iron is directed away from the iron, the heated soleplate may be left in a horizontal position and in direct contact with an article of clothing. As such, the article of clothing may be scorched by the iron, or, more seriously, the heated soleplate may cause the article of clothing to ignite into flames, potentially creating a fire in the household. Moreover, when an iron is left unattended in a vertical position, a person, commonly a child, may contact the heated soleplate of the iron, typically causing severe burns to the person. Thus, a need has existed to provide an automatic power interrupting device which disconnects the heating element from the source of electrical power upon the detection of non-use of the iron. One attempt to address the above-noted problem has been to provide motion sensitive switches which disconnect the heating element from the source of electrical power when no movement of the iron is detected. A disadvantage exists, however, in that vibrations caused by sources other than a user of the iron, such as nearby machinery or human activity, may cause motion sensitive switches to detect movement, thus resulting in an unattended iron being heated.
Another attempt to address the above-noted problem has been to provide touch sensitive switches which disconnect the heating element from the source of electrical power when no direct contact is detected between the hand of a user and a conductive sensor on the handle of the iron. A disadvantage exists, however, in that if there is not sufficient isolation between the conductive sensor and the source of electrical power, there is a potential for a dangerous shock to the user who is in direct electrical contact with the conductive sensor.
Another attempt to address the above-noted problem has been to provide user proximity switches which employ a proximity sensor located within the handle of the iron to detect AC power line frequencies picked up by the body of a user and capacitively coupled from the hand of the user to the proximity sensor. Such switches disconnect the heating element from the source of electrical power when no AC power line frequencies are detected. A disadvantage exists, however, in that objects other than the hand of a user placed near the handle of the iron may pick up AC power line frequencies and couple them to the proximity sensor, thus resulting in an unattended iron being heated. In addition to the above-noted disadvantages, a further problem exists in that the automatic power interrupting devices of such electric pressing irons do not automatically reconnect the heating element to the source of electrical power upon the detection of use of the iron. As such, the user must manually reconnect the heating element to the source of electrical power after a period of non-use of the iron, such as by turning the iron off and back on again, or by depressing a manual reset switch.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an electric appliance, such as a pressing iron, which detects non-use of the appliance without relying on the detection of movement of the appliance.
It is another object of the present invention to provide an electric appliance, such as a pressing iron, which detects non-use of the appliance without relying on the detection of direct contact between the body of a user and a conductive sensor located on an outside surface of the appliance.
It is another object of the present invention to provide an electric appliance, such as a pressing iron, which detects non-use of the appliance without relying on the detection of AC power line frequencies capacitively coupled from the body of a user to a proximity sensor located within the appliance.
It is a further object of the present invention to provide an electric appliance, such as a pressing iron, which automatically connects the appliance to the source of electrical power upon the detection of use of the appliance.
In a preferred embodiment, an electric pressing iron according to the present invention includes a soleplate having a heating element operatively connected to a source of electrical power which heats the soleplate to a desired temperature.
The iron also includes a power control circuit having a user proximity circuit for detecting the proximity of the hand of a user to the handle of the iron, a conventional orientation circuit for detecting the position of the iron, and a switching circuit controlled by the user proximity circuit and the orientation circuit for automatically connecting and disconnecting the heating element to and from the source of electrical power.
The user proximity circuit of the power control circuit includes a proximity sensor, a signal generator for periodically charging the proximity sensor to a predetermined voltage level, and a signal detector for determining the amount of time required to charge the proximity sensor to such predetermined voltage level, the amount of time being directly related to the capacitance of the proximity sensor. The proximity sensor consists of a conductive sheet located within the handle of the iron, such that when the hand of a user is in proximity to the handle of the iron, the conductive sheet functions as the first plate of a capacitor, the user functions as the second plate of the capacitor, and the handle of the iron functions as the dielectric of the capacitor. Thus, when the hand of a user is in proximity to the handle of the iron, the capacitance of the proximity sensor is increased and the amount of time required to charge the proximity sensor to the predetermined voltage level is increased, thereby allowing the user proximity circuit to detect that the hand of the user is in proximity to the handle of the iron. Conversely, when the hand of a user is not in proximity to the handle of the iron, the capacitance of the proximity sensor is decreased and the amount of time required to charge the proximity sensor to the predetermined voltage level is decreased, thereby allowing the user proximity circuit to detect that the hand of the user is not in proximity to the handle of the iron. As such, the electric pressing iron in the preferred embodiment detects non-use, as well as use, of the iron by detecting the capacitance of the proximity sensor.
As is known in the art, the conventional orientation circuit of the power control circuit detects whether the iron is in a substantially horizontal position or a substantially vertical position.
As previously stated, the switching circuit of the power control circuit is controlled by the user proximity circuit and the conventional orientation circuit. In use, when the hand of a user is in proximity to the handle of the iron and the iron is in a horizontal position, the switching circuit automatically connects the heating element to the source of electrical power. When the user's hand is not in proximity to the handle of the iron and the iron is in a horizontal position, the switching circuit automatically disconnects the heating element from the source of electrical power. When the iron is in a vertical position, the switching circuit automatically disconnects the heating element from the source of electrical power after a predetermine
Sonnenschein Nath & Rosenthal
Toastmaster Inc.
Van Quang
Walberg Teresa
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