Socket-outlet

Details Socket-outlet Socket-outlet

1998-12-11

2000-03-14

Jackson, Stephen W.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Ground fault protection

361 56, 361 931, 361115, H02H 300

Patent

active

060381159

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a socket-outlet, in which voltage is connected by a switching circuit, from a supply side to a load side only in response to a designated load. Thus, voltage will be provided at the socket-outlets only when an electrical load is connected. German Patent Application No. U 9 312 528 describes a bus system which directs a switching command to a socket-outlet. In this way, the socket-outlet is usually off-circuit (i.e., without power), and thus that in-circuit (i.e., with power) parts cannot be reached by small children, in inadvertent contact, or by adults, during wallpapering or resulting from an unscrewed cover. A voltage-supplied measuring device includes a D.C. testing circuit which is designed to drive a current across a connectable load for measuring purposes. The D.C. testing circuit is designed to measure the impedance of a connected load using a test voltage that is low with respect to a dangerous voltage. In addition, the device includes an A.C. testing circuit which is designed to measure the impedance of a connected load using a frequency which is at least higher that the line voltage, and at a testing voltage that is lower than a dangerous voltage.
PCT Application No. WO 89/11747 describes a safety device which is switched on between a power supply and a load to be protected. In this device, testing voltages of 5 volts and 9 volts are used for an impedance measurement in order to protect living creatures.


SUMMARY OF THE INVENTION

The present invention is directed to an off-circuit socket-outlet which is independent from external supplied switching commands.
In accordance with the present invention, a voltage supplied measuring device includes a D.C. testing circuit, which is designed to permanently drive a current across a connectible load, the D.C. testing circuit being designed to measure the impedance of a connected load using a test voltage that is low with respect to a possible, dangerous voltage. An alternating current of the measuring device is also provided, the alternating current being at a high frequency, or higher in comparison to the line voltage, and at a low voltage with respect to a possible dangerous voltage. An evaluation circuit, including microprocessors or a CPU, is designed to decide, based on preselected criteria and measuring values supplied by the measuring device, whether the switching contact of the switching device should be connected. A socket-outlet of this type offers should be connected. The evaluation circuit is designed so as not to provide a connection in response to an Impedance 1 of more than 500 Ohms, measured by the D.C. testing circuit, logically ANDed to the relation:
Impedance 2 being determined by the A.C. testing circuit. The prohibited range, in which a connection is not permitted, corresponds to the criteria defined for a human being. The criteria can be adjusted for other living beings. A socket outlet of this type offers current circuit breaker cannot respond because the entire current is flowing back and forth between the monitored conductors. A situation of this type could arise, for example, when a child, insulated from ground, makes contact with the socket-outlet, in the outer conductor and the return conductor, by inserting nails. Heretofore, it has been attempted to avoid endangerments of this type using shutters with mechanical means keeping the socket-outlet closed as long as contact means are not introduced simultaneously into the connecting openings, such as occurs with a plug and its plug contact pins. However, the socket-outlet proposed here is safer than a shutter of that type, which in unfavorable circumstances, in response to certain actions, can be outsmarted. For entry purposes, suitable criteria is described in literature, for example, the book by Gottfried Bieglmeier, Wirkungen des elektrischen Stromes auf Menschen und Nutztiere (The Effects of Electrical Current on Humans and Working Animals).
In practice, it is advantageous if the D.C. testing circuit of the measuring d

REFERENCES:
patent: 4316187 (1982-02-01), Spencer
patent: 5029037 (1991-07-01), Bartelink

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