Electrical component with a safety release

Details Electrical component with a safety release Electrical component with a safety release

1999-10-25

2001-11-27

Easthom, Karl D. (Department: 2832)

Electrical resistors

Resistance value responsive to a condition

Current and/or voltage

C337S031000, C337S405000, C361S104000, C361S131000

Reexamination Certificate

active

06323750

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention is directed to an electrical component, particularly a varistor, that is installed in a plastic cup and has at least two electrical connecting leads, lead wires or lines, and whereby a fuse formed by a solder metal is arranged in at least one connecting line or lead, said fuse disconnecting the component from a current source given overload, whereby the solder metal bridges a separating point arranged in the lead and the lead is charged with a prestressed spring that removes the lead from the parting location given response of the fuse.
DE 42 41 311 C1 discloses such a component.
For example, DE 25 31 438 C3 also discloses that an interspace between cathode terminal and cathode contacting in a tantalum electrolyte capacitor is bridged by a metal alloy that melts given overload or incorrect polarization. The capacitor therein is surrounded with a plastic envelope that also encloses the fuse location.
A proper functioning of the fuse, however, assumes that the molten solder can escape, so that a reliable interruption of the current is assured. Since this can only ensue when the envelope bursts (crack formation), the molten solder continues to conduct the current until the envelope bursts without an interruption of the power thereby occurring.
In order to overcome these difficulties, it is therefore disclosed in EP 0 110 134 B1 that the melt fuse is surrounded by a layer of a wax-like substance whose thickness is dimensioned such that the molten metal alloy in case of a short can form molten beads in the molten wax, so that an interruption of the current can occur in time.
The described safety devices, however, assume that the component itself and the connecting wires are fixed in the plastic envelope since there would otherwise be the risk that, despite the melting of the fuse, the connecting wire would again come into contact with the component, so that a renewed current conduction could ensue.
SUMMARY OF THE INVENTION
An object of the present invention is to specify a safety release in a component of the species initially cited that allows a dependable disconnection from a power source and has an improved service life of the solder location.
This object is inventively achieved in that the lead is pinched, squeezed or flattened to a thickness of 0.2 through 0.5 mm.
The following advantages are achieved by this embodiment:
a) The lead wire receives a defined bending location.
b) The bending force is drastically reduced and a separation is still possible even with forces of approximately 0.5 N. The “flowing” which is known given soft solder under mechanical tensile stress is thus reduced and the service life of the solder location is improved.
c) The enlargement of the surface due to the pinching also effects an increased heat elimination compared to the unadulterated wire surface, the temperature stress of the parting location is thereby reduced when soldering the overall component in.
For better separation, a plastic part can be additionally arranged at the spring in the region of the fuse in a known way (DD 122 757 A), so that the protective function is improved by inserting this plastic part into the soft solder location. On the one hand, an accelerated triggering is assured because the force acts directly on the solder bead and, on the other hand, the penetrating plastic part lengthens the insulating path between the wires without deflecting these.
It is also advantageous when an additional signal line is arranged at the component, whereby a signal lamp is connected between signal and connecting line.
On the other hand, it is also possible to arrange a signal flag at the terminal side, so that the response of the thermal fuse can also be recognized through a window in the plastic cup.
The invention is explained in greater detail below with reference to the following exemplary embodiments.


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patent: 25 31 438 (1978-07-01), None
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patent: G 93 19 287.8 (1994-03-01), None
patent: 42 41 311 A1 (1994-06-01), None
patent: 42 41 311 C2 (1995-06-01), None
patent: 0 110 134 (1988-01-01), None
Caddock Brochure, 1973.

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