Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Reexamination Certificate
2001-06-08
2004-12-07
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
C361S044000
Reexamination Certificate
active
06829124
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an error detection circuit interrupter device that includes a detection circuit for determining whether an error has occurred in an exterior circuit and includes an interrupter device for stopping current flow to the exterior circuit when an error has been detected. More particularly, the invention relates to a GFCI that has a reset device which utilizes a test current to actuate a bistable latching relay and reset the tripped GFCI - thus testing the functionality of the GFCI and resetting the GFCI simultaneously. Furthermore, the invention relates to a ground fault circuit interrupter device (GFCI) with a fail safe mode, wherein the GFCI is incapable of being reset after a trip if any of its key electrical components malfunction or are not working.
2. Description of the Related Art
Fault or error detection devices are well known in the art to provide additional safety for electrical components. A specific type of fault or error detection device is known as a GFCI device. In operation, a GFCI type device supplies electricity to an exterior circuit and opens an outlet circuit when a ground fault occurs in the exterior circuit, i.e., when a portion of a circuit that is plugged into the outlet becomes grounded. For example, if a hair dryer is negligently dropped into a bathtub, electricity may flow from the hair dryer circuit to ground through the bathtub water. A person might be part of the current path to ground. An electrical outlet provided with a GFCI device would detect such a ground fault and, almost instantaneously, open the outlet circuit to prevent current from flowing from the hair dryer circuit to ground. Although the GFCI device is described above as being associated with an outlet, the typical GFCI device can be associated with other different types of electrical junctures.
Conventional GFCI devices include a detection circuit that compares the current leaving the outlet circuit to the current returning to the outlet circuit. When there is a pre-set differential between the leaving and returning outlet currents, the GFCI opens the outlet circuit and indicates that a ground fault has occurred. The detection circuit can be constructed in a number of different ways, including providing a differential transformer for sensing the imbalance in the current flow. In addition, there are many different structures that have conventionally been used to open the circuit once the ground fault has been detected. For example, some conventional GFCI devices use a trip coil to open the outlet circuit. A test and reset button are also typically provided on the GFCI device for testing whether the device is functioning properly and for resetting the device after testing or after the device has been tripped. Conventional GFCI devices are often complicated structures that require sophisticated manufacturing processes to ensure that they work properly and safely. Conventional GFCI devices, as well as the GFCI device in U.S. application Ser. No. 09/251,427, do not have a structure for ensuring that the GFCI device cannot be reset when one or more key electrical components, such as the transformer, integrated circuit (IC), solenoid, and solenoid controlling devices are not operable. For example, for the GFCI device of application Ser. No. 09/251,427, if the GFCI unit trips because of a ground fault, the unit can be manually reset by depressing the reset button. If one of the key electrical components is damaged due to the ground fault or by any other means, the GFCI can still be reset so that electricity would be provided to the electrical outlet. In this case however, the GFCI will no longer be able to detect another ground fault and thus will no longer be able to stop current flow to the exterior circuit. Several other drawbacks also exist in other conventional GFCI devices, including high manufacturing cost, poor reliability, poor endurance, potential safety concerns due to excessive heat generation and/or poor reliability, and general aesthetic and ergonomic drawbacks.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fault/error detection device that is economic to manufacture, requires as few parts as possible and operates at a high level of reliability. Another object of the present invention is to provide a GFCI device that is capable of being reset after a trip only if the GFCI circuit is operational. Another object of the invention is to provide a GFCI device that is incapable of being reset if any of the key electrical components become inoperable. Another object of the invention is to provide a GFCI device that is simple to manufacture and includes as few parts as possible while also providing the structural stability necessary for the device to be tested on a regular basis. Another object of the invention is to provide a GFCI device that includes a test light indicator that will indicate when the GFCI device has been tripped, whether the GFCI device is wired correctly.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the GFCI device includes a switch connected to a current sensing device. The current sensing device is capable of determining whether the outflow of current is different from inflow, and upon sensing a difference between outflow current and inflow current (sensing a possible ground fault), outputting an electrical signal to a bistable latching relay trip mechanism which then opens the main switch and prevents current from flowing through the GFCI. The device includes a reset switch that sets up a test condition for the GFCI device. If the reset switch is activated and test conditions indicate that the GFCI is functioning properly, an electrical signal is provided to the bistable latching relay switch which then closes the main switch and permits current to pass through the GFCI.
In accordance with another aspect of the invention, a GFCI device with a fail safe mode prevents restoration of current flow through a first circuit when a component of the GFCI device is malfunctioning or otherwise inoperable. The ground fault circuit interrupter device can include a housing, a substructure located in the housing, a ground fault detector located on the substructure and capable of detecting whether a ground fault has occurred in the first circuit, a current path structure located on the substructure and having a first end terminating at an input connector and a second end terminating at an output connector. The current path structure preferably includes a single electrical splice. A pair of contact points can be located in the current path structure and displaceable from each other to open the current path structure and cause current to stop flowing in the first circuit when the ground fault detector detects that a ground fault has occurred. The means for displacing the contact points can include a latch biased towards a predetermined position by a hairspring at one end and an armature within a solenoid at another end, where displacement of the armature in a predetermined direction causes displacement of the latch to ultimately allow displacement of the contact points.
In accordance with another aspect of the invention, the GFCI device can include a thermally activated part that, upon being heated by an overheated solenoid coil, moves into a position to block the ability for the GFCI device to be reset. The GFCI reset ability can be blocked by preventing normal movement of the latch or preventing normal movement of the armature. The overheated solenoid is an indication that the GFCI device is malfunctioning and therefore should not be permitted to be reset. The thermally activated part can be, for example, a thermocouple connected to an electrical switching device that moves a locking mechanism into contact with either the latch or the armature when a predetermined “solenoid overheating” temperature is sensed by the thermocouple.
It is to be understood that both the foregoing general description and the
Gallas Gunter A.
Leopold Howard S.
Benenson Boris
Cooper Wiring Devices, Inc.
Jackson Stephen W.
Ostrager Chong Flaherty & Broitman P,C
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