SAFETY ELECTRICAL OUTLET WITH LOGIC CONTROL CIRCUIT
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention
[0002] The present invention relates to a logic control device that can be integrated into any double or single household or commercial electrical outlet. It controls the outlet and transforms it into a safe and "smart" outlet. The device can also be integrated into an extension cord, adapter or placed over an outlet as a cover plate. The logic circuit in the smart outlet instantly senses the state and condition of itself and the physical and electrical changes that occur.
[0003] 2. Description of the Related Art
[0004] Every year thousands of people are killed or injured by accidents and fires caused by faulty electrical devices or appliances causing electrical shock. Many protective devices are being implemented to protect young children from accidentally accessing an electrical outlet, causing injuries due to electrical shock. Modern appliances that are more prone to cause accidents are equipped with ground fault protection. Such ground fault circuitry interrupters either interrupt the power until the electric circuit is restored to normal, for example, by manually resetting an electromechanical breaker. Some circuits automatically power-up when normal power resumes. Conveniently, such ground fault circuit interrupters are wired, for example directly into the tool, device or appliance, or it is molded into the cord designated for the tool or device line. Ground fault interrupters are developed to sense minute imbalances in a circuit by current leakage to ground.
[0005] Standard electrical built-in outlets either in the home or in an industrial setting, may be also equipped with a ground fault circuit interrupter, a GFCI. Such GFCI devices provide a test and reset function which both work together so that a tripped GFCI cannot be reset if the GFCI circuit no longer provides ground fault protection. The test button can still be operated in the event of an open neutral condition even though the GFCI circuit is no longer powered. A built-in line load reversal feature also prevents the GFCI from resetting if the load and the conditions are mistakenly reversed. The GFCI receptacle face will be live, but there will be no power delivered to devices downstream, indicating a load reversal.
[0006] An intelligent circuit interrupt system is disclosed, for example, in U.S. Pat. No. 6,111,733 in which an intelligent circuit is electrically connected between an AC source and a load for interrupting a flow of AC from the source to the load upon detection of an interrupt condition. A circuit interrupter electrically connected to phase and neutral terminals of the AC source defines the interrupt condition. A relay switch with a relay coil and phase and neutral contacts is included such that line and load ends of the phase contact are electrically connected, respectively, between the interrupt means load side phase port and a phase terminal of the load. Line and load ends of the neutral contact are electrically connected, respectively, between the interrupt neutral port and a neutral terminal of the load. The relay coil is electrically coupled between load sides of said phase and neutral contacts for controlling the contacts in response to the interrupt signal. An open-contact miswiring detector
(OCMD) is electrically connected to one of the phase and neutral contacts for detecting a miswiring condition when the contacts are in an open state, and a closed-contact miswiring detector (CCMD) is electrically connected to the OCMD and to one of the neutral and phase contacts for detecting a miswiring condition when the contacts are in a closed state. A timing signal generator generates system timing signals. A test circuit electrically coupled to the interrupt means and the timing signal generator tests the interrupt means operability. An alarm circuit is electrically responsive to the test circuit, the timing signal generator, the OCMD and the CCMD for communicating an open-contact miswiring condition, a closed-contact miswiring condition, an operational failure condition, and a need for external testing condition. A power supply is electrically connected between the load ends of the phase and neutral contacts, and to the timing signal generator.
[0007] Thus, there is continuous need for an electrical outlet having additional safety features to protect against hazards inherent with standard outlets, such as fire hazards due to overheating, insertion of improper objects into the outlet and current overload. In addition, there is a need to provide an outlet which is capable of detecting whether a load is present.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide an outlet connected to an intelligent circuit, making the outlet a logically controlled device. The intelligent circuit is mounted inside or alongside a standard electrical codeapproved outlet box, such that the outlet itself can be installed in the same or similar manner as any outlet is installed. The outlet with the intelligent circuit is preferably a wall mount single or double outlet box and creates thereby a "smart outlet." Thus, existing industry standard outletrelated functions are maintained. The smart outlet does not alter normal operation of any appliance or device, and does not change or modify the normal flow of electricity or any of its characteristic. It operates at the rated voltage, amperage and frequency, for example, at 120Vac and 10 Amp for residential use, or at 240Vac, 15 Amp for commercial use, either at 50 or 60 Hz. The smart outlet of the present invention allows normal operation of any device or appliance plugged to the outlet directly or through an extension cord. It can be used with any standard on/off, a remote control unit or any other switching device.
[0009] Generally, power supplies from household or industrial outlets deliver power as soon as the device or appliance is plugged in or, power is always present and uninterrupted at the outlet, power or extension cord and appliance or device, except for an interruption within or at this device, yet in general all devices and appliances remain fully or partially powered, in particular power and extension cords. When a smart outlet is used and the electrical plug of an electrical device or appliance is properly inserted, the device is initially always turned off. The logic circuit will sense this condition and the power will remain off, i.e., the smart outlet will not provide any power to the device or appliance. Only when the power switch of the device or appliance is turned on and the circuit is electrically completed, can the device or the appliance draw power and operate. Thus, if a bulb in a lamp is unscrewed while the lamp switch is on, one may touch the contacts inside the
socket and not experience an electrical shock. The smart outlet is designed such that it will shut off the power, when the circuit is interrupted (for example, the bulb is unscrewed or has burned out). The power will remain off until the electrical circuit is re-established, and the electrical device or appliance is turned on again.
[0010] Thus, only a properly operating electrical device or appliance may be powered up with the device of the present invention. If the electrical circuit is interrupted or overloaded, a fault is detected and the logic circuit of the smart outlet shuts the power to the connected device or appliance off.
[0011] The smart outlet is designed to continually monitors any or all of the designed functions, such as it monitors proper and full plug insertion, load presence, current load on the outlet and it senses the outlet temperature.
[0012] Accordingly, it is an important object of this invention to monitor whether the blades of the plug are fully and correctly inserted into the slotted openings of the socket, before the outlet provides power. This aspect is of particular importance to promote child safety, because children are known to be attracted to inserting a variety of foreign objects such as bobby pins, metal nails or needles, which may cause disastrous injuries to children. Thus, the smart outlet monitors the acceptance of a properly and fully (completely) inserted plug with standard, acceptable prongs, in good mechanical conditions.
[0013] In one embodiment, it is contemplated to utilize a radiation source, such as a light source, for example, an LED, which is positioned inside the socket assembly and within a light conducting means. For example, the light conducting means channel may extend through the outlet perpendicularly to the slotted plug openings for the outlet contacts. At each end of the light conducting channel, a photo sensor is positioned. The photo sensors may be cadmium- sulphide photo cells, photo diodes or photo transistors. When the blades of the plug are fully inserted into the slotted openings of the socket, the blades interrupt the radiation stream in the radiation conducting channels and the illumination of the photo sensors is interrupted. The photo sensors are connected to a logic circuit that controls power to the outlet. While radiation, or specifically, light is emitted from the radiation source, specifically, the diodes, impinges on the photo sensors, no power is provided to the outlet contacts. Preferably, the circuitry includes logic means, such as an "AND" gate and/or appropriate software in a micro controller to sense that both photosensor are simultaneously substantially light blocked or un-illuminated which indicates a correct insertion. This insures that both blades are fully inserted into the outlet contacts. When both photo sensors are simultaneously blocked, the software will permit a relay in the circuit to close. Power can only reach the outlet contacts when the relay is closed. Thus, a broken plug, or a single wire, clip or other invalid object will not cause electric power to be applied to the outlet.
[0014] It can easily be appreciated that the invention also contemplates to utilize as a radiation source a non-visible light LED i.e., ultra-violet radiation.
[0015] It is yet another object of the present invention to provide a current overload sensor. This feature addresses the problems of overloading outlets with too many appliances or
devices, which causes overheating and potential fire. The load current is measured by the voltage drop across a resistor positioned in the current path. This voltage drop is then amplified by a gain block, typically an op amp, integrated by a network, and then tested for magnitude by a comparator. If a current overload occurs, the output of the comparator will go high, thus signaling that event to the micro controller. This will engage a software routine to turn off a relay, and thus removing the line voltage from the socket. An indicator light will be turned on at this point, such as a red LED, showing that an overload has occurred.
[0016] Another aspect of the invention is to provide sensing the load presence and current load on the outlet. The monitoring of the load presence makes it possible to only allow power to be present when a load is drawing a specified minimum amount of current. That is, a device or appliance which is turned off, will not draw current and thus, no voltage will be applied. This will also eliminate a major cause for electric shocks. The invention makes it possible to detect even a very small load, such as the load of an electric clock which draws only a few milliamperes. This feature is also particularly important as a child safety feature, because, as discussed above in conjunction with the monitoring of proper plug insertion, a child might insert a proper plug, having cut, open or raw wires extending from the plug, that is, the plug is not attached to any device. In such instance, the circuitry will not allow power to go to the outlet and, thus, the plug will not be under power.
[0017] Further, the invention provides for monitoring the temperature in the outlet. Changes in the temperature are observed. If the temperature deviates or exceeds a safe operating temperature, no power is provided to the outlet. This feature alone eliminates one of the major causes of electrical fires, since overheating of electrical outlets is one of a major fire hazards. Overheating is often caused by a defective plug, that is, a plug which is either physically damaged, rusty, or corroded. Rust, corrosion or dirt on the plug blades causes a high electrical resistance to exist between the blades of the plug and the outlet contacts. This high resistance causes a power loss and will raise the temperature of the outlet structure. Ultimately, the combustion temperature of the wall material or the insulation on the wiring may be reached, and a fire will occur. In order to prevent such overheating, the present invention provides a temperature sensing means which interrupts the power supply to the device or appliance if the sensed temperature raises above a set temperature. Good electrical practice dictates that the outlet temperature should not rise higher than about 70° C. to 80° C, depending on the local code. However, this threshold can be set for any code mandated, or safe operating temperature.
[0018] One embodiment for monitoring the outlet temperature utilizes a thermistor, but any other device for sensing temperature may be used. The thermistor is preferably placed in close physical contact with the plastic body of the outlet structure, so that the thermistor temperature is approximately equal to the outlet temperature. The electrical resistance of a thermistor varies inversely as a function of its temperature. By means of well known electronic circuitry, preferably a comparator or a Schmitt trigger, the electrical resistance of the thermistor and hence its temperature, can be compared with an accurate internal reference.
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