Blown fuse indicator

• US 4,691,197 A
• Filed: 06/24/1985
• Issued: 09/01/1987
• Est. Priority Date: 06/24/1985
• Status: Expired due to Fees

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Schmerda, Richard F., Damiano, Michael A.
• Primary Examiner(s): Rowland, James L.
• Assistant Examiner(s): Hofsass, Jeffery A.
• Application Number:
  US06/748,106
• Time in Patent Office: 799 Days
• Field of Search: 340/638, 340/639, 340/641, 340/642, 340/644, 340/652, 340/815.12-815.19, 307/252 N, 315/129, 315/130, 315/135, 323/327, 337/79, 337/241, 337/242, 337/265, 337/266, 337/332, 337/376, 335/6, 335/17, 361/41, 361/104
• US Class Current: 340/638
• CPC Class Codes: H01H 85/32 Indicating lamp structurally associated with the protective device
• CPC Class Codes: H02H 3/046 Signalling the blowing of a fuse detecting non functioning of a lamp H05B47/20

Abstract

A solid state switching circuit for energizing a lamp (L) is connected around a fuse (12) across an AC supply for detecting a voltage differential at the opposite sides of a blown fuse and applying that differential across the control (g) and switching (c) electrodes of the solid state switch (SCR) to render the same conductive. Current limiting resistors (RL1 and RL2) are placed in the ends of wire conductors which are to be connected at opposite sides of the fuse, thereby to limit current flowing in the conductors over the entire length of the conductor, minimizing electrical shock hazard upon damage to the conductor.

Claims

1. A blown fuse indicator comprising, in combination:

a power supply source;

an indicator;

a solid state switching device having a pair of switching terminals and a control terminal, said switching terminals being connected in circuit with said indicator across said source;

a control circuit for said solid state switching device comprising;

a voltage divider connected across said source, said voltage divider having two parts with a junction there between connected to said control terminal, one of said parts comprising two parallel branches; and

a fuse connected in one of said branches effective when it opens to interrupt said one branch for raising the voltage at said junction to render said solid state switching device conductive to energize said indicator to indicate the open state of said fuse.

2. The blown fuse indicator defined in claim 1 wherein at least a portion of the other of said branches is in series circuit with said switching terminals for limiting current in said indicator circuit.

3. The blown fuse indicator defined in claim 1 wherein said one branch comprises a test switch effective when opened for raising said voltage at said junction to render said solid state switching device conductive to energize said indicator for indicating operability of said blown fuse indicator.

4. The blown fuse indicator defined in claim 1 wherein said branches each comprise current limiting impedance means for limiting current in said indicator circuit and said control circuit.

5. The blown fuse indicator defined in claim 4 wherein said current limiting impedance means are connected immediately adjacent respective opposite terminals of said fuse.

6. The blown fuse indicator defined in claim 1 wherein the other of said branches comprises an impedance connected across said control terminal and a switching terminal of said solid state switching device for bypassing current from said control terminal circuit.

7. A blown fuse indicator for enclosed fusible electrical apparatus comprising, in combination:

a power supply source;

an enclosure containing electrical apparatus and at least one fuse, said fuse being connected in circuit with said power supply source;

indicator lamp means mounted on said enclosure remote from said fuse comprising an individual lamp visible to the exterior of said enclosure for each fuse, and solid state switching means for each lamp responsive to a voltage differential at opposite sides of a blown fuse for effecting energization of a respective lamp; and

means for providing said voltage differential comprising;

pairs of wire conductors for each fuse, said conductors connected at one end to said lamp means and having a second end extending within said enclosure to opposite sides of a respective fuse, and

an impedance connected to each said conductor at said second end thereof and to a respective opposite said of said fuse immediately adjacent said fuse, said impedance limiting current in said conductor to a value safe for human contact.

8. The blown fuse indicator defined in claim 7 wherein said solid state switching means comprises:

a solid state switch having a pair of switching terminals and a control terminal, said switching terminals being connected in circuit with said lamp across said source; and

said means for providing said voltage differential at opposite sides of a blown fuse comprises a voltage divider connected across said source, said voltage divider comprising two parts with a junction therebetween connected to said control terminal, one of said parts comprising two parallel branches, and each branch comprising a respective one of said current limiting impedances.

9. The blown fuse indicator defined in claim 8 wherein said switching terminals and said lamp are in series circuit with at least a current limiting impedance portion of one of said branches.

10. The blown fuse indicator defined in claim 9 wherein the other of said branches comprises a test switch effective when opened for raising the voltage at said junction for simulating said voltage differential and rendering said solid state switch conductive for energizing said lamp.

11. A blown fuse indicator for enclosed fusible electrical apparatus comprising, in combination:

an indicator housing mounted on an enclosure for said apparatus;

individual lamp means for each fuse of said apparatus mounted in said housing and visible to the exterior of said enclosure;

solid state switching means in said housing for energizing a respective lamp in response to a blown fuse;

control means in said housing for controlling said solid state switching means;

a first member of a separable plug-in electrical connector affixed to said housing and electrically connected to said control means; and

a current limiting wiring harness comprising;

a pair of wire conductors for each fuse of said apparatus;

a second member of said separable plug-in electrical connector being electrically connected to respective first ends of said wire conductors, said second member being cooperably connected to said first member;

impedances individually connected to respective second ends of said wire conductors for limiting current in said wire conductors to values safe for human contact; and

connector means attached to said impedance for electrical connection thereof immediately adjacent opposite sides of respective ones of said fuses.

12. The blown fuse indicator defined in claim 11 wherein said current limiting impedance means comprises an electrical resistor connected in each said conductor.

13. The blown fuse indicator defined in claim 12 wherein said connector means comprise a wiring connector element connected to said resistor.

14. The blown fuse indicator defined in claim 13 wherein said connector elements of a respective pair of said wire conductors are connected on respective opposite electrical sides of said fuses outside of a main current carrying path of said apparatus.

15. The blown fuse indicator defined in claim 11 wherein said housing comprises a window in an exterior surface disposed over said lamps and having indicia thereon relating each lamp with a respective fuse.

16. The blown fuse indicator defined in claim 15 wherein a pushbutton switch actuator extends through said exterior surface of said housing, said actuator being depressible to operate switch contacts for simultaneouly testing operability of said lamps and said solid state switching means.

17. The blown fuse indicator defined in claim 11 wherein said current limiting impedance means limit current in said conductors to 6 milliamps.

18. An open circuit indicator comprising, in combination:

a power supply source;

an indicator;

a solid state switching device having a pair of switching terminals and a control terminal, said switching terminals being connected in circuit with said indicator across said source;

a control circuit for said solid state switching device comprising;

a voltage divider connected across said source, said voltage divider having two parts with a junction there between connected to said control terminal, one of said parts comprising two parallel branches; and

circuit interrupter means connected in one of said branches effective in an open state to interrupt said one branch for raising the voltage at said junction to render said solid state switching device conductive to energize said indicator to indicate the open state of said circuit interrupter means.

19. The open circuit indicator defined in claim 18 wherein at least a portion of the other of said branches is in series circuit with said switching terminals for limiting current in said indicator circuit.

20. The open circuit indicator defined in claim 18 wherein said one branch comprises a test switch effective when opened for raising said voltage at said junction to render said solid state switching device conductive to energize said indicator for indicating operability of said open circuit indicator.

21. The open circuit indicator defined in claim 18 wherein said branches each comprise current limiting impedance means for limiting current in said indicator circuit and said control circuit.

22. The open circuit indicator defined in claim 21 wherein said current limiting impedance means are connected immediately adjacent respective opposite terminals of said circuit interrupter means.

23. The open circuit indicator defined in claim 18 wherein the other of said branches comprises an impedance connected across said control terminal and a switching terminal of said solid state switching device for bypassing current from said control terminal circuit.

24. An open circuit indicator for energizing signaling means whenever a power supply circuit is open comprising, in combination:

conductor means connected to a power supply;

interrupter means connected in said conductor means for interrupting one side of said supply;

a solid state switch having a pair of switching terminals and a control terminal, said switching terminals being connected to said conductor means across said supply at the supply side of said interrupter means;

signaling means connected in series with said switching terminals;

control means for said solid state switch connected to said control terminal and connected to said conductor means across said supply at an output side of said interrupter means for providing a voltage differential at opposite sides of an open interrupter means for rendering said solid state switch conducting and energizing said signaling means, said control means comprising impedances connected immediately adjacent said interrupter means at opposite sides thereof and wire conductors extending between said impedances and said solid state switch, said impedances limiting current in said wire conductors to values safe for human contact.

25. The open circuit indicator defined in claim 24 wherein said control means for providing a voltage differential at opposite sides of an open interrupter means comprises a voltage divider connected across said source, said voltage divider comprising two parts with a junction therebetween connected to said control terminal, one of said parts comprising two parallel branches, and each branch comprising a respective one of said current limiting impedances.

26. The open circuit indicator defined in claim 25 wherein said switching terminals and said signaling means are in series circuit with at least a current limiting impedance portion of one of said branches.

27. The open circuit indicator defined in claim 26 wherein the other of said branches comprises a test switch effective when opened for raising the voltage at said junction for simulating said voltage differential and rendering said solid state switch conductive for energizing said signaling means.