Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Reexamination Certificate
2000-04-05
2002-07-23
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
C361S120000, C361S124000, C361S129000
Reexamination Certificate
active
06424514
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrical components, in particular a surge voltage protector that is provided with an external short-circuit device.
BACKGROUND INFORMATION
Short-circuit devices of this sort are standard both in two-electrode and in three-electrode surge voltage protectors. Such surge protectors usually have a cylindrical construction, the electrodes being arranged so as to be insulated from one another. The short-circuit devices protect the surge voltage protector in long-term load situations; as a rule, such a short-circuit device contains a constructive element that can melt at higher temperatures, with the aid of which the two electrodes, or the center electrode and one or both end electrodes, can be short-circuited.
For three-electrode protectors, an external short-circuit device is described in U.S. Pat. No. 4,984,125 that is made up of a flexible clip that extends along the axis of the surge voltage protector and is placed onto the center electrode using a clamp. The free ends of the two arms of this spring clip are placed axially rather than radially on the end face of the two end electrodes, with the intermediate connection of an insulating plastic element that is arranged centrically in relation to the respective end electrode and can melt in the case of an overload. The end of each arm of the spring clip is fashioned as a contact bracket that extends diagonally past the plastic spacer element, and that contacts the end surface of the respective end electrode in its edge region in the case of a short circuit.
In addition, there are conventional short-circuit devices that can be used both for two-electrode and for three-electrode surge voltage protectors. These short-circuit devices are likewise made up of a flexible clip having two free ends that are applied axially to the end electrodes. In surge voltage protectors having two electrodes, a fusible insulating film is arranged between the one free end of the flexible short-circuit clip and the associated electrode; in the case of a short circuit this film is punctured by the contact region of the free end of the short-circuit clip. In French Patent No. 2 621 184, this contact region can here be constructed, in the manner of a fork, from two flat contact brackets, provided that the surge voltage protector is provided with axially soldered-on terminal wires. In surge voltage protectors having three electrodes as described in U.S. Pat. No. 5,029,302 and PCT Application No. WO 90/13904, the short-circuit clip contacts the center electrode, and its free ends are applied axially to the end surfaces of the two end electrodes, with intermediate connection of an insulating film that is arranged eccentrically, in the edge region of the respective electrode.
For a two-electrode surge protector, German Patent No. 29 11 110 describes a flexible short-circuit clip whose flexible end is held radially at a distance from the electrode that is to be contacted in case of overload, and whose other end is made up of two fastening tongues that are welded to the edge region of the end face of the other electrode.
In a three-electrode surge voltage protector having a flexible short-circuit clip, as described in U.S. Pat. No. 5,187,634, a specially shaped injection-molded part is provided as an insulating spacer that is placed on the protector in the manner of a saddle and has a stirrup-type piece at both ends. The foot region of the respective stirrup forms the actual spacer for the flexible contact brackets of the spring clip. Each contact bracket is fashioned with two tongues. The two contact tongues have a common base region, are separated from one another by a small slot, are adjacent to the spacer arranged eccentrically to the respective end electrode, and extend radially past the spacer.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a robust short-circuit device that is constructed as simply as possible, is suited for surge voltage protectors having axially welded-on terminal wires, and has a high capacity for carrying alternating current (max. 30 amp/15 min per discharge path).
In order to achieve this object, the present invention provides that the contact brackets release between them the center region of the first electrode, that the spacer is arranged between the common base region of the contact bracets and the end surface of the first electrode, and that the common base region of the contact brackets has a slot in which the insulating spacer is fixed with a retention piece. The retention piece can be fashioned as a short cylindrical support, or also can be formed by an annular recess that is, for example, incorporated in the jacket surface of a cylindrical body.
Such a construction of the short-circuit device enables—independent of whether and how (projecting radially or axially) the terminal wires are connected to the end-face electrodes—contact over a large surface to the end-face electrodes by the forming-out of two contact brackets, which achieve contacting in the edge region of the electrodes without being damaged by molten insulating material. The spacer, which is arranged relatively far away from the contact points, can be fashioned very small; in particular it can be fashioned as a cylindrical body, which constructively facilitates the local fixing of the spacer or spacers.
The short-circuit device constructed according to the present invention is usefully applied for surge voltage protectors having two electrodes, of which the second electrode forms the other end face of the surge voltage protector and is held at a distance from the first electrode by a tube-shaped insulator, in such a way that the short-circuit clip is fashioned symmetrically in the axial direction of the surge voltage protector, and is fixed to the insulator by a bracket. Here the other end of the short-circuit clip can likewise be held at a distance from the second electrode by a spacer; the other end of the short-circuit clip can however also be applied directly to the second electrode.
The application of the short-circuit clip constructed according to the present invention in surge voltage protectors having three electrodes, of which the second electrode forms the other end face of the surge voltage protector and the third electrode is arranged between the first and second electrode and is insulated from these electrodes by a first and second hollow cylindrical insulator, usefully takes place in such a way that the short-circuit clip is likewise of symmetrical construction in the axial direction, and is placed on the third electrode using a bracket.
REFERENCES:
patent: 4362962 (1982-12-01), Lange
patent: 4433354 (1984-02-01), Lange et al.
patent: 4984125 (1991-01-01), Uwano
patent: 5029302 (1991-07-01), Masghati et al.
patent: 5187634 (1993-02-01), Pitsch et al.
patent: 29 11 110 (1980-09-01), None
patent: 2 621 184 (1989-03-01), None
patent: WO 90/13904 (1990-11-01), None
Boy Jürgen
Norbert Krost
Kenyon & Kenyon
Leja Ronald W.
Siemens Aktiengesellschaft
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