Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With bimetallic element
Reexamination Certificate
1998-12-19
2001-02-06
Picard, Leo P. (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With bimetallic element
C337S033000, C337S318000, C337S365000
Reexamination Certificate
active
06184768
ABSTRACT:
FIELD OF THE PRESENT INVENTION
The present invention relates to a kind of actuator, and more particular to a thermal actuator which comprises a thermal detector and an actuator unit electrically connected together in parallel manner, wherein the actuator unit can automatically provide an actuating action once the temperature of a predetermined surrounding zone is detected overheat or over-cold by the thermal detector. It is a universal device adapted to the overheat or over-cold of various apparatus and appliances, such as an electrical circuit breaker, a motor, a refrigerator, a freezing storage, a coffee maker, a heater, a computer, and etc.
BACKGROUND OF THE PRESENT INVENTION
Most electrical appliances break down because of overheating. Overheating of an appliance or a circuit frequently causes fire or electrical shock. In order to provide a kind of protection, most houseware appliances install a fuse or a thermo cut off to prevent the overheating of the electrical wires. However, both the fuse and the thermo cut off are one time use only and can not be reset to use again. In other words, once the fuse or the thermo cut off is functioned to cut off the electric circuit, it must be replaced by a new one before the electrical appliances can function again. For the building circuitry, the bi-metal type breaker is the most common device installed in the control panel to prevent the overheating of the electrical wiring.
In other words, those conventional thermal protectors are substantially the electrical current protection to prevent overheating of the electrical wiring. However, the surrounding around the electrical appliance has nothing to protect against overheated or over-cold. For example, a pot of a coffer maker may also be overheated if there is no more coffee therein. It will also create danger of fire or breaking down situation. A halogen floor lamp would generate a great amount of heat therearound that has a high risk of burning stuff like the curtain around.
The surge protector is the most common MOV (metal oxide varistors) utilized in various electrical appliances. However, due to the fluctuation of the voltage, it may easily generate great amount of heat and may also result in explosion.
Moreover, it is well known that the CPU of a computer generates heat during operation. If the heat around the CPU accumulates to a certain extent, the CPU will be malfunctioned. Also, a heater is an appliance for generating heat. However, the user can only control the heat by setting the power output or the timer control. It is relatively expensive and difficult to control the heater according to the actual temperature around the heater.
In fact, every electrical appliance that generates heat needs a thermal guard to prevent the surrounding being overheated or over-cold. It would be a remarkable matter if there is an inexpensive device that can cut the circuit or switch off the appliance if the surrounding thereof is too hot. It not only can prolong the service life of the appliance, but also can help the user to avoid unreasonable hazard or damages.
Moreover, it would be a more advance concept to have a thermal actuator, which can easily connect with the electrical circuit of an electrical appliance without affecting the original circuit or sharing its voltage power. Besides, how to connect more than one set of thermal actuators or more than one thermal detectors thereof becomes another important and practical problem pending to be solved.
SUMMARY OF THE PRESENT INVENTION
It is thus a main object of the present invention to provide a thermal actuator adapted to provide an actuating action to break a circuit or to switch off the appliance when the temperature of a predetermined surrounding zone is higher than a safe temperature, wherein the thermal actuator comprises at least a thermal detector and at least an actuator unit electrically connected in parallel manner with the electrical circuit of the appliance.
A further object of the present invention is to provide a thermal actuator which is a universal device adapted for installing to most kinds of electrical circuitry or appliances.
Another object of the present invention is to provide a thermal actuator which can be repeatedly reset to use after the circuit is broken.
Yet another object of the present invention is to provide a thermal actuator adapted to employ with a surge protector, wherein the thermal actuator can prevent the surge protector from dangerous conditions by breaking the circuit urgently before it is overheating.
Yet another object of the present invention is to provide a thermal actuator which has a relatively economic structure and is easy to install.
Still another object of the present invention is to provide a thermal actuator which may comprises more than one thermal detectors parallelly connected with an actuator unit.
Accordingly, in order to accomplish the above objects, the present invention provides a thermal actuator which comprises at least a thermal detector for breaking a current flowing therethrough when a temperature therearound reaches a predetermined temperature, at least an actuator unit, and a connecting circuit for electrically connecting the thermal detector in parallel with the actuator unit.
The thermal detector comprises a first contact member made of electrical conducting material, a second contact member made of thermostatic metal and an insulating connector connected between a connecting end of the second contact member and the first contact member. The second contact member has a contact end normally pressed against and remained in contact with the first contact member. The contact end of the second contact member would bend away from the first contact member so as to render the first and second contact members becoming uncontacted when the temperature around the thermal detector reaches a predetermined temperature. However, when the temperature around the thermal detector cools down to normal, the first and second contact members will automatically reset to the contact condition again.
The actuator unit comprises an actuating piece made of thermostatic metal strip, a conducting terminal piece connected to the actuating piece, an insulating sleeve covering a portion of the actuating piece, and an electrical heat wire wrapping around the insulating sleeve which has one end connected to the actuating piece.
The connecting circuit comprises an input terminal, an output terminal, a first connecting wire electrically connected the thermal detector between the input and output terminals, and a second connecting wire which is extended between the input and output terminals in parallel with the first connecting wire so as to electrically connect the actuator unit between the input and out put terminals.
When the second contact member is normally remained in contact with the first contact member, more than 50% of a main current input at the input terminal of the connecting circuit flows through the thermal detector and less than 50% of the main current flows through the actuator unit. However, when the second contact member bends to uncontact with the first contact member due to overheated or over-cold temperature around the thermal detector, 100% of the main current flows to the actuator unit. The heat wire wrapped the actuating piece generates heat to increase the temperature around the actuating piece. When the temperature around the actuating piece increases to a predetermined extent, the actuating piece bends so as to provide an actuating action. If the actuator unit is installed close to a switch or a breaker, the actuating action of the actuating piece can activate the switch to turn off or the jumper of the breaker to cut the electric supply.
REFERENCES:
patent: 1996720 (1935-04-01), Getchell
patent: 2302924 (1942-11-01), Valverde
patent: 2605339 (1952-07-01), Connolly
patent: 2635156 (1953-04-01), Welter
patent: 2763750 (1956-09-01), Adams et al.
patent: 3066206 (1962-11-01), Dales
patent: 3087146 (1963-04-01), Boudouris
patent: 3107281 (1963-10-01), Tufts
patent: 3258647 (1966-06-
Chan Raymond Y.
David & Raymond
Picard Leo P.
Vortman Anatoly
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