Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Reexamination Certificate
1999-03-04
2002-09-03
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
C337S183000, C337S195000, C337S405000, C337S407000, C307S010700, C307S131000, C180S279000, C361S057000, C361S087000, C361S104000, C361S211000
Reexamination Certificate
active
06445276
ABSTRACT:
BACKGROUND OF THE INVENTION
The subject invention is directed to the art of electrical fuses and, more particularly, to an electrical fuse that is particularly adapted for use in motor vehicle applications.
Electrical fuses of the general type under consideration are commonly used in the automotive technical field. In particular, cut-out type fuses are currently employed in many applications. Cut-out fuses are adapted to interrupt a current supplied to one or more succeeding or downstream electrical consumers by melting a fusible zone when the current exceeds the nominal rated current of the fuse.
One disadvantage of cut-out fuses, however, is that they require a high intensity of current, typically significantly above the nominal current, to flow for a relatively long period of time before the fuse melts. As a consequence, cable carrying power between the fuse and electrical consumers succeeding or downstream of the fuse must be appropriately over-dimensioned or oversized in order to avoid over-current conditions and cable fires which have the potential of endangering the motor vehicle.
In addition to the above, other problems associated with electrical fuses of the type presently available include arcing phenomenon generated by the fuses when they melt and open the circuit. The arcing can have an interfering electromagnetic effect on the motor vehicle.
Yet another problem associated with meltable fuses is that they require a method or structure for screening off the fuse in order to prevent molten metal droplets produced from the melted portion of the fuse from migrating into other electrical components or circuits where they can cause shorting or other electrical damage.
In contrast thereto, it is a primary object of the present invention to provide an electrical fuse that is particularly adapted for use in motor vehicle applications that requires practically no over-dimensioning of the succeeding or downstream electrical cables and which does not generate any electrical arcing or sparks when the current is interrupted.
SUMMARY OF THE INVENTION
The subject invention provides an electrical fuse apparatus that overcomes the above-noted problems and results in a device that interrupts electrical current without producing undesirable electric arcing or molten metal droplets that are found to be damaging in motor vehicles. Further, for all practical purposes, the subject fuse apparatus enables the use of electrical cables that are precisely sized to carry only the electrical currents that are anticipated to be required by the electrical consumers rather than oversized for carrying excess current that has been the practice in the past.
In particular, and in accordance with one aspect of the invention, there is provided a fuse apparatus for selectively interrupting a load current flowing between a pair of associated conductor leads. The fuse apparatus includes at least two spaced apart electrically conductive contact elements, a fuse element, and an electrically conductive connection material. The at least two spaced apart electrically conductive contact elements are each operatively connected with the associated electrical conductor leads. The electrically conductive connection material selectively holds the fuse element across the at least two contact elements to allow a load current to flow between the pair of associated conductor leads. In accordance with the preferred embodiment of the present invention, the connection material is adapted to electrically disconnect the fuse element from the spaced apart electrically conductive contact elements when a temperature of the connection material exceeds a predetermined threshold temperature.
In accordance with a more limited aspect of the invention, the electrically conductive connection material has an intrinsic electrical transition resistance characteristic whereby the connection material develops a temperature in proportion to an intensity of current flowing therethrough.
By connecting the fuse element to the pair of spaced apart electrically conductive contact elements using a meltable electrically conductive connection material, the connection material melts and thus separates the fuse element from the contact elements before the fuse element proper has an opportunity to possibly melt and scatter molten metal or generate electrical arcing interference. Preferably, the fuse element is a cut-out fuse of the type commonly available in the art and described above.
In accordance with a still further aspect of the invention, the electrically conductive connection material disposed between the fuse element and the pair of contact elements becomes soft at elevated temperatures and melts when its temperature exceeds a predetermined temperature. In that manner, the fuse element is separated from the contact elements without arcing or molten droplets being formed. Preferably, the predetermined temperature is reached when the current flowing through the connection material surpasses the rated current of the fuse. Overall, this results in the benefit of a substantially lower amount of heat needed for triggering the fuse. That is, the subject fuse reacts to small increases in power surpassing the rated current of the fuse. In that regard, the subject invention is more sensitive to currents that are only slightly above the rated current of the system. Thus, the drawbacks of the melting process at high temperatures typically found in fuses in the past are avoided.
In accordance with yet a still further aspect of the invention, the connection between the fuse element and the contact elements is established by means of soldering. In this manner, interruption of the load current by separation of the fuse element from the contact elements is readily obtained when the solder melts. Preferably, in accordance with the present invention, this takes place at temperatures of approximately 180°. Accordingly, any danger of producing arcing which is promoted in prior art cut-out fuses by the occurrence of high temperatures, is practically non-existent in the present invention.
According to one embodiment of the invention, the fuse element is acted upon by the force of a resilient spring element, independent of the position of the fuse, so that during the melting or softening of the connection between the fuse element and the contact elements, the fuse element is lifted or separated from the contact elements, thus interrupting the flow of load current through the fuse system.
In accordance with yet another aspect of the invention, in one embodiment, the fuse apparatus is provided with an additional heating portion. The heating portion is included to obtain an interruption in the flow of current to the electrical power consumer in the presence of a given or varying nominal current. More particularly, the heating is performed so that the immediate environment of the connections is heated between the safety element and the contact elements. In the preferred mode, heating takes place by generation of an additional current through the fuse element and through the one or several contact elements. The additional current utilized for heating, is superimposed on the load current supplied to the succeeding or downstream electrical power consumers.
For generating the additional heating current, the power consuming device can be dimensioned in such a manner that with any direct connection with a battery using the fuse, a theoretically inadmissible high current would result. More particularly, the excess current that is used for heating is discharged via a resistor which is preferably connected with one of the connection contacts or to the fuse element itself. The discharge current and heat generated thereby is preferably dissipated using a mass such as a heat sink, for example. The resistance value of the bleeder resistor through which the additional heating current flows, is used to control the temperature of the connections between the fuse element and the contact elements during normal fuse operation. Accordingly, the rated current of the fuse is established by me
Bornhorst Dieter
Jüngst Joachim
Korherr Joachim
Schön Uwe
Fay Sharpe Fagan Minnich & McKee LLP
TRW Automotive Electronics & Components GmbH & Co. KG
Vortman Anatoly
LandOfFree
Electrical fuse for use in motor vehicles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrical fuse for use in motor vehicles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrical fuse for use in motor vehicles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2849856