Line-protection device with integrated cutoff

Details Line-protection device with integrated cutoff Line-protection device with integrated cutoff

1999-05-24

2001-02-13

Ballato, Josie (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

High voltage dissipation

C361S124000, C361S103000

Reexamination Certificate

active

06188559

ABSTRACT:

The invention relates to a line-protection device of the type referred to as having “integrated cutoff”, serving to protect equipment connected to a low-current line in the event that an electrical fault occurs on the line, as is conventional in telecommunications systems.
BACKGROUND OF THE INVENTION
Such devices are commonly used at cable heads or at telephone distribution frames, in particular for protecting user telephone sets against any voltage surges that might be transmitted by the transmission links that enable the sets to be connected to remote centralizing telecommunications equipment. Such protection is achieved conventionally by interrupting electrical continuity along the two wires of a link, and by grounding the wires in the device, when said device is active.
Document FR-A-2560458 describes a protection device triggered by a lightning arrester overheating. A grounding spring is maintained cocked and not in contact by an insulating fuse pellet. The lightning arrester being heated to above a determined temperature value causes the pellet to melt, at least partially, and causes the spring to perform grounding. Unfortunately, because of the structure of the device, and in particular because of the position of the pellet relative to the lightning arrester that controls it, it is not possible to obtain a response that is as quick and reliable as is necessary.
Document FR-A-2659204 describes a protection device which is also triggered by a pellet melting due to a lightning arrester overheating. However, in that case, the pellet is in direct thermal contact with the lightning arrester, which makes it possible for the response speed characteristics of the device to be better controlled. Unfortunately, as indicated in that document, it is possible, under certain conditions, for the pellet to be softened only, and the response of the device is then not necessarily identical to that obtained when the lightning arrester overheating leads to total and rapid melting.
OBJECTS AND SUMMARY OF THE INVENTION
The invention thus proposes an integrated-cutoff protection device that is of simple structure, and that offers high reliability and high speeds of response, in particular under lower limit conditions for the triggering voltage.
The protection device of the invention comprises:
a three-pole lightning arrester provided with two line electrodes and one ground electrode;
conductor means which define two line input terminals, two line output terminals, and a ground terminal, and which provide respective links between the line electrodes of the lightning arrester and respective ones of the input terminals, between the ground electrode of the lightning arrester and the ground terminal, and between the line input terminals and the line output terminals;
switch means having conductive blades in which each blade connects one of the input terminals to a respective one of the output terminals when it is in a first position, and is resiliently returned against a grounding piece connected to the ground terminal when it is in a second position, whereupon it interrupts the link hitherto established between an input terminal and an output terminal; and
trigger means comprising a trigger fuse piece which is thermally connected to the lightning arrester and which maintains the blades in their first position until a heating limit temperature is reached above which the piece melts and enables the blades to be resiliently returned to their second position;
wherein the trigger means are constituted by a trigger piece which is made up of a recessed central body bearing against the lightning arrester, and of blade-retaining members positioned on either side of the central body so as to secure said trigger piece to each of the blades.


REFERENCES:
patent: 4876626 (1989-10-01), Kaczmarek
patent: 4901188 (1990-02-01), Gilberts
patent: 2 560 458 A1 (1985-08-01), None
patent: 2 659 504 A1 (1991-09-01), None

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