Fuse Blowing Detector

The present invention relates generally to a device for detecting whether any one of a number of fuses in an electrical system has blown out.

A machine, such as an automobile, which incorporates a large number of electrical devices, such as ignition loads, radio sets, various different lamps, etc., requires a relatively large number of fuses for protecting the loads from excessive current, and for guarding against fire and so on caused by short circuits. Various devices have been proposed for detecting whether any of thses fuses have been blown out. For example, a fuse blowing detector such as shown in FIG. 1 of the accompanying drawings has been suggested. In this device, an automobile has an electric system which includes loads L1, L2, L3 fed from a battery 1 through an accessory switch SW1, loads L4 and L5 fed through an ignition switch SW2, and loads L6 and L7 fed directly from the battery. These loads L1-L7 are fused by fuses F1-F7 respectively. Several switches are shown as controlling supply of power to some of the loads, such as S1, S3, S4, and S6. The fuse blowing detector shown in FIG. 1 includes wires to each of the junctions between a fuse and its load, and a slidable changeover switch 2 which has a plurality of fixed contact points 2a connected to the other ends of these wires. The slidable contact 2b is capable of contacting each of these fixed contacts, by the movement of a slide lever 3 and an indicator lamp 4 having one terminal connected to the slidable contact 2b and an other terminal to the earth of the vehicle.

In operation, the ignition switch SW2 and the accessory switch SW1 are closed, and the slide lever 3 is moved to and fro. If all the fuses are intact, the lamp 4 is lighted each time slidable contact 2b and a fixed engage 2a contact. However, if any one of the fuses is blown, contact between slide lever 3 and the corresponding fixed contact, does not cause lamp 4 to light, thereby signalling blowing of the fuse.

This detector, however, has certain disadvantages because the use of a mechanical part, such as the slide lever 3, makes the detector prone to malfunctions. Another disadvantage is that the number of movements of the slide lever 3 for each test sequence is equal to the number of fuses. Further, use of only one lamp has made it difficult to know which fuse is defective.

Therefore, it is an object of the present invention to provide a device for detecting the blowing of any of a plurality of fuses, which allows the easy detection of which of the fuses is blown.

It is a further object of the present invention to provide a device of the above mentioned sort which is not liable to mechanical malfunction, and thus is of high reliability, and which is compact.

According to the present invention, a first terminal of an electrical source is connected to first terminals of a plurality of fuses, having second terminals of fuses connected to the first terminals of the same number of loads. The other terminals of the loads are connected to the other terminal of the electrical source, whereby the loads are supplied with electrical power via their respective fuses. A device for detecting the blowing of any one of the fuses comprises, for each fuse, a light emitting element, having one terminal connected to the second terminal of the fuse. A common switch for all of the light emitting elements has one terminal connected to all the other terminals of all the light emitting elements. The other terminal of the switch is connected to the other terminal of the electrical source.

According to a particular feature of the present invention, the light emitting elements are light emitting diodes. The polarities of the source and the diodes is such that, if the switch is closed, and a fuse is intact, the corresponding diode is lit.

Other objects, features, and advantages of the present invention will become more clear from the following description of several preferred embodiments of the present invention, when taken in conjunction with the accompanying drawings, which, however, are given for illustration only. None of the particular features of any of the embodiments described, or of the drawings, are to be taken as in any way limitative of the present invention, whose scope, as well as the extent of protection sought to be afforded by Letters Patent, is to be delimited solely by the accompanying claims. In the drawings:

FIG. 1 is a diagram of a prior art fuse blowing detector, associated with an electrical circuit of an automobile, as described supra.

FIG. 2 is a diagram, similar to FIG. 1, of a preferred embodiment of the present invention;

FIG. 3 is a perspective view of a block, in which fuses and light emitting elements are arranged together in an easily visible view, and an easily operable fixed switch;

FIG. 4 is a view, similar to FIG. 3, of another embodiment of the present invention, wherein a cover is shown as removed; and

FIG. 5 is a perspective exploded view of an automobile fuse device in which the present invention is applied.

In the various figures, similar parts are denoted by the same reference numbers, and detailed repetitive descriptions are omitted for the sake of brevity.

Referring to FIG. 2, there is shown a circuit diagram of a preferred embodiment of the present invention, associated with an electrical circuit powered by a DC source 1, typically an automobile battery having a grounded negative terminal and a positive terminal. The terminals of source 1 are connected via plural fuses F1-F7 to plural parallel loads L1-L7. The condition of fuses F1-F7 is detected by light emitting elements D1-D7. The number of light emitting elements D1-D7, preferably light emitting diodes, is equal to the number of fuses F1-F7. The anodes of diodes D1-D7 are respectively connected to junction points between fuses F1-F7 and shunt loads L1-L7. The cathodes of all the light emitting diodes D1-D7 are connected together to a common junction, connected via switch 5 to the ground terminal of source 1, i.e., the terminal of source 1 which is not connected to fuses F1-F7. If the polarity of battery 1 is opposite to that shown, the polarity of diodes D1-D7 is reversed so, that, if a fuse is intact, and switch 5 is closed, the corresponding diode is lit.

Thus, in operation, in response to closure of switch 5 the diodes corresponding to intact fuses are lit. If any particular fuse is blown, its corresponding diode is not lit.

FIG. 3 is a perspective view of an embodiment of the present invention in which diodes D1-D7 and fuses F1-F7 are arranged in one-to-one correspondence with one another. Diodes D1-D7 and fuses F1-F7 are easily visible in block 6 which carries switch 6 so that the switch can be easily operated.

FIG. 4 is an exploded perspective view of another embodiment, wherein the switch 5' is a normally closed switch that is usually open circuited by engagement with a face of the cover 7 that contacts the portion of block 6 from which switch 5' extends. When, however, cover 7 is removed from block 6, switch 5' is automatically closed so light-emitting diodes D1-D7 automatically show which fuses F1-F7, if any, are blown. Alternatively, block 6 may be part of an automobile instrument panel having a cover 7.

In FIG. 5 is shown a particular type of automobile fuse device to which the present invention is applied. The fuse device includes a housing 8a made of transparent electrically insulating resin material. In housing 8a are two spaced electrically conducting terminal strips 8b and 8c, which are normally electrically connected by a fuse F, which bridges a gap between the strips. If fuse F blows, strips 8b and 8c are electrically insulated from each other. Strips 8b and 8c espectively include ends 8b1 and 8c1 which fit into elongated rectangular openings 8a1 and 8a2 at the top of housing 8a. Strips 8b and 8c have shoulders 8b2 and 8c2 that abut on corresponding shoulders in housing 8a. The top of housing 8a includes elongated rectangular opening 8a3 into which is fitted end tab 8d1 of a third electrically conducting auxiliary terminal strip8d, end tab 8d1 extends from shoulder 8d2 of strip 8d. The top of housing 8a includes a circular groove 8e between openings 8a2 and 8a3, whereby diode D and its connecting wires are held in situ between interior strip 8c and strip 8d at the outside of the housing. The lower ends of the terminal strips 8b, 8c and 8d are plugged into female plugs (not shown), for easy replacement. Strip 8b is connected to battery 1; strip 8c is connected to load L for a particular branch energized by battery 1; and strip 8d is connected, along with all the other strips 8d', 8d", etc., of the other similar fuse devices, to resistor Ro and switch 5 for testing the fuses F. Thus, as described supra, closing of switch 5 completes a circuit which shows immediately which of fuses F1-F7 is blown, because the diode associated with the branch is not lit.

To indicate the correct direction for insertion of the terminal strips 8b, 8c, 8d into the housing 8a, housing 8 is formed asymmetrically, or marked in some way.

The illustrated embodiment is suitable for applications in which the entire fuse elment for a branch, including housing 8 and the diode D for the particular branch, is discarded when the fuse for the branch is blown out, and a new fuse element replaces the discarded element is used.

In the above embodiments the use of light emitting diodes has been described. However, this is not essential. Small lamps may be used instead of the diodes. In this case the protective resistor Ro shown in FIGS. 2 and 5 may be omitted. If lamps are used instead of diodes, problems may occur with reverse flow of current. However, in any event when switch 5 is closed the invention operates as specified. If these reverse flow problems are severe, rectifying diodes may be provided in series with the lamps to eliminate the problems, as will be obvious to one skilled in the art, based upon the foregoing disclosure.

Although the present invention has been shown and described in terms of several preferred embodiments thereof, the exact details of any particular embodiment are subject to various modifications, changes and/or omissions, by a person of ordinary skill in the art, depending upon the foregoing disclosure, without departing from the scope or the spirit of the present invention. Therefore it is desired that the aforesaid scope, as well as the breadth of the protection granted, should be defined, not by any of these purely fortuitous details of the shown embodiments, or of the drawings, but solely by the appended claims, which follows.