Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1980-10-14
1982-06-08
Moose, Jr., Harry E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361129, H02H 322
Patent
active
043342574
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an overvoltage protection device for wires of the kind mentioned in the preamble of the following independent claim.
DESCRIPTION OF PRIOR ART
Overvoltage protection devices are known in which overvoltage arresters for separate wires for discharging overvoltage on a wire to ground are placed in separate boxes. An example of such an overvoltage protection device is described in the Swedish published patent application No. 361387. The separate overvoltage arresters in question both in the known overvoltage protection device and in the overvoltage protection device according to the invention are of the gas filled discharge tube type described in the Swedish published patent application No. 360507. A disadvantage of the known overvoltage protection device is that the exchange of separate overvoltage arresters is rather cumbersome since they are somewhat inaccessible and that in a telephone exchange a large number of them are present.
Furthermore overvoltage protection devices are known in which a number of overvoltage arresters are enclosed in a cassette. This is intended to be inserted in a space in the overvoltage protection device proper such that springs in the latter or in the cassette connect the overvoltage arresters to one wire each. When a fault, for example a shortcircuit, is suspected in some of the overvoltage arresters in the cassette, it is removed and replaced by a cassette with faultless overvoltage arresters. The overvoltage arresters in the removed cassette are then tested in a laboratory, often all of them simultaneously, and the overvoltage arrester found to be defective is replaced by a new one. A disadvantage of the cassette being designed in this way is that, if one of the overvoltage arresters is shortcircuited, and this is the most common reason for removing the cassette, when the cassette is being drawn out the shortcircuited overvoltage arrester on its way out shortcircuits several wires to earth for a short period of time. This results in disturbances on the shortcircuited wire which can be especially annoying if some of the wires are utilized for data transmission. Another disadvantage is that the exchange of an overvoltage arrester in the cassette can be as difficult as the exchange in an overvoltage protection device having overvoltage arresters in separate boxes.
SUMMARY OF THE INVENTION
The overvoltage protection device according to the invention is intended to offer a solution to the problem of providing overvoltage arresters forming part of the overvoltage protection device which are enclosed in a detachable cassette and which are easy to exchange in the cassette, and of ensuring that the cassette is easy to reach in the overvoltage protection device while annoying shortcircuits when exchanging the cassette are prevented.
An overvoltage protection device according to the present invention is characterized in a manner which appears from the characterizing part of the following independent claim.
With the overvoltage protection device according to the invention a solution of the posed technical problem is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of a overvoltage protection device according to the invention is described below with reference to the following drawings, in which:
FIG. 1 shows an overvoltage protection device in a closed condition;
FIG. 2 shows a cross section through the overvoltage protection device;
FIG. 3 shows the overvoltage protection device in an open condition;
FIG. 4 shows a top view of a holder;
FIG. 5 shows a longitudinal section of the holder;
FIG. 6 shows an end view of the holder;
FIG. 7 shows a top view of a cassette;
FIG. 8 shows a longitudinal section of the cassette;
FIG. 9 shows a side view of a lock; and
FIG. 10 shows a top view of the lock.
PREFERRED EMBODIMENT
The overvoltage protection device according to the invention, as appears from FIG. 1 and FIG. 2 comprises a holder 1 of sheet metal and a terminal block 2 of an insulating material which is fastened in t
REFERENCES:
patent: 2507363 (1950-05-01), Baker
patent: 3917982 (1975-11-01), George et al.
patent: 4146755 (1979-03-01), Causse
Ekdahl Per A. A.
Moller Fred L.
Moose Jr. Harry E.
Telefonaktiebolaget L M Ericsson
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