US3319128A - Electric circuit utilizing an adjustable and resettable fuse - Google Patents

Description

y 9, 1967 0. K. NILSSEN 3,319,128 I ELECTRIC CIRCUIT UTILIZING AN ADJUSTABLE AND RESETTABLE FUSE Filed Nov. 19, 1964 FEE-=4.

OLE K. NILSSEN lNVENTOR ATTOR/V VS United States Patent 3,319,128 ELECTRIC CIRCUIT UTILIZING AN ADJUSTABLE AND RESETTABLE FUSE Ole K. Nilssen, Livonia, Mich., assignor to Ford Motor Company, Dearhorn, Mich., a corporation of Delaware Filed Nov. 19, 1964, Ser. No. 412,367 8 Claims. (Cl. 317-54) This invention relates to an electric circuit in which there is employed a reliable and inexpensive electromagnetic fuse that may be both adjustable and resettable.

In automotive vehicles and other applications, there is need for an electrical circuit in which a reliable and inexpensive fuse that is both adjustable and resettable can readily be employed. This invention provides such an electrical circuit and fuse.

In the invention, a magnetic reed relay or switch is employed that has a pair of reeds positioned in series with the power source and the load to be supplied by this source. A winding connected in series with the power source and the load is positioned around the reeds. A permanent magnet axially polarized in the direction of the reeds is also positioned around the reeds and the magnetomotive force of this permanent magnet is opposite to the magnetomotive force furnished by the current that flows through the Winding from the power source.

The permanent magnet provides a magnetic bias on the reeds so that once the reeds are closed they will remain closed. If, however, the current flowing through the winding reaches a predetermined level at which the magnet-emotive force of the permanent magnet is reduced to the point where the magnetomotive force on the reeds is no longer large enough to maintain the reeds in the closed position, the reeds will then open and the circuit to the load will be broken.

The reeds may be reclosed by shifting the permanent magnet in a direction toward the junction position of the reeds to increase the magnetomotive force on the reeds to the point where they will again be closed.

To adjust the current level at which the reeds open, the permanent magnet may be moved in an axial direction to adjust the magnetomotive force on the reeds that tend to keep them closed, or the winding which supplies the subtractive magnetomotive force bias may be moved in an axial direction.

To initially close the reeds of the magnetic switch or relay, the permanent magnet may be momentarily moved into such a position that the magnetic bias or magnetometive force is large enough to close the reeds. It must thereafter be returned to the proper position, however, to provide the correct fusing action. It is also possible to provide an extra winding around the magnetic relay or switch in which current is momentarily applied so as to increase the magnetic bias or magnetomotive force sufficiently to close the reeds. This winding may also be energized to reset the magnetic reed switch.

To open the magnetic reed relay or switch, short of drawing too much load current, the permanent magnet may be shifted axially momentarily in a direction to decrease the magnetomotive force applied to the reeds by this magnet, or current could be applied to the extra winding previously described so as to decrease the magnetic bias or magnetomotive force on the reeds.

An object of the present invention is the provision of an electric circuit which includes a simple and reliable fuse element that may be adjustable and resettable.

Another object of the invention is the provision of an electric circuit that includes a simple and reliable fuse element that may also be adjustable and resettable.

Other objects and attendant advantages of the present invention may be more readily realized as the specification 3,319,128 Patented May 9, 1967 is considered in connection with the attached drawings in which:

FIGURE 1 is a circuit diagram of one embodiment of the invention, and

FIGURE 2 is a circuit diagram of another embodiment of the invention.

Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown in FIGURE 1 a source of electrical energy or battery 10 having its positive terminal 11 connected through lead 12 to one reed 13 of a magnetic reed relay or switch 14. The other reed 15 of the magnetic reed relay or switch 14 is connected through lead 16 to one terminal of a winding or electromagnetic means 17. The other terminal of the winding or electromagnetic means 17 is connected through lead 18 to a load 21. The load in turn is connected through lead 22 to the negative terminal 23 of the battery or source of electrical energy 10. A switch 20 may be positioned in the lead 12 to control the energization of the load 21.

The magnetic reed relay or switch 14 is of standard construction in which the reeds 13 and 15 will close upon the application of a predetermined magnetomotive force. The magnetic reed relay or switch 14 has hysteresis characteristics in which the magnetomotive force required to keep the reeds closed after they have once been closed is less than the force required for closing.

To provide a magnetic bias or magnetomotive force for closing the reeds 13 and 15, a permanent magnet 24 that may take the form of a ceramic cylindrical permanent magnet polarized in an axial direction, is positioned over the reed relay or switch 14. This permanent magnet 24 engages the cylindrical housing of the reed relay or switch in a snug fit and is movable axially on the housing against the friction force developed between the housing and the magnet.

The winding 17 is wound on the magnetic reed relay or switch 14 in a direction such that current through it will create a magnetomotive force that opposes the magnetomotive force of the permanent magnet 24.

In the operation of the circuit shown in FIGURE 1, the permanent magnet 24 is shifted axially'upon the housing of the magnetic reed relay or switch 14 toward the junction of the two reeds 13 and 15. When the magnetomotive force across the open reeds 13 and 15 becomes large enough, the reeds will close and the permanent magnet 24 is shifted back to the position on the housing to provide proper fusing action. This position must be such that when the current through the winding 17 or electromagnetic means becomes large enough to open the reeds, that the magnetomotive force on the reeds supplied by the permanent magnet 24 is not sufficiently large to reclose the reeds 13 and 15 when the current through the winding 17 or electromagnetic means is interrupted.

It can be readily appreciated that the permanent magnet 24 may be shifted axially to adjust the current level at which the reeds 13 and 15 open. Also to open the reeds 13 and 15 short of drawing too much current through the load 21 or opening the switch 20, the permanent magnet 24 may be shifted momentarily to the left in FIG- URE 1.

It can be readily appreciated that when current through the load 21 rises to a certain predetermined level in which the magnetomotive force of the winding 17 reduces the m-agnetomotive force applied by the permanent magnet 24 on the reeds 13 and 15 to a predetermined level, that the reeds 13 and 15 will open, thereby interrupting current to the load 21. Thereafter, the reeds may again be closed and the fuse reset by shifting the permanent magnet momentarily toward the junction point of the reeds 13 land 15, or to the right as viewed in FIGURE 1.

Another embodiment of the invention is shown in FIG- URE 2. This embodiment of the invention is similar to the embodiment shown in FIGURE 1 except that an additional winding or electromagnetic means 26 is positioned about the magnetic reed relay or switch 14, and the permanent magnet 24 is of the rubber based type. The purpose of the extra winding 26 is to provide extra magnetomotive force on the reeds 13 and 15 to close them initially and for reclosing them after opening due to overload conditions rather than shifting the permanent magnet 24 as was done in FIGURE 1.

To provide this additional magnetomotive force, a push button switch 31 has one terminal connected through lead 32 to the lead 12 and the positive terminal 11 of battery 10. The other terminal of the push button switch 31 is connected through lead 33 to one terminal of the winding 26. The other terminal of the winding 26 is returned through lead 34 and lead 22 to the negative terminal 23 of the battery 10. The winding is wound such that the energization of this winding through the actuation of push button switch 31 supplies a magnetomotive force in the same direction as of that supplied by the permanent magnet 24; and if the reeds 13 and 15 are initially open, the pushing of this push button switch will close them. The pushing of the push button switch 31 will also provide a means for resetting the magnetic reed relay or switch 14 should it open due to an overload condition in which current through the load 21 and winding 17 exceeds a predetermined level.

It can be readily appreciated that the operation of this circuit is very similar to that shown in FIGURE 1. Depression of the push button switch 31 will close the reeds 13 and 15. An overload condition in which current through the winding 17 exceeds a predetermined level will cause the reeds 13 and 15 to open, thereby interrupting current through the load 21. The magnetomotive force applied by the permanent magnet 24 will be insufiicient to close the reeds 13 and 15. The pushing of the push button switch 31, however, will reset the reeds 13 and 15 into the closed position to provide the resetting of the switch or relay mechanism.

In the circuit shown in FIGURE 2 as Well as the circuit shown in FIGURE 1, the permanent magnet 24 may be shifted axially to adjust the initial magnetic bias or magnetomotive force to be applied on the reeds 13 and 15.

The present invention thus provides in an electric circuit a simple and reliable magnetic reed relay or switch that may be employed as a fusing element in the circuit. Means are provided to reset the magnetic reed relay or switch element should it open due to an overload condition and to provide an initial setting or adjustment.

It is to be understood that this invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I- claim:

1. An electric circuit comprising, a source of electrical energy, a load, a magnetic reed switch having a pair of reeds and a winding surrounding said reeds, circuit means coupling said source of electrical energy, said pair of reeds, said winding and said load in series, and a cylindrical permanent magnet surrounding said reeds and polarized in an axial direction, said cylindrical permanent magnet having sufficient magnetomotive force to close said reeds, said winding being wound to produce a magnetomotive force in the opposite direction from said permanent magnet when current flows therethrough whereby said reeds will open interrupting current to said load when said current produces a predetermined magnetomotive force.

2. An electric circuit comprising, a source of electrical energy, a load, a magnetic reed switch having a housing, a pair of reeds mounted in said housing, a winding positioned on said housing about said reeds, circuit means coupling said source of electrical energy, said pair of reeds, said winding and said load in series, a cylindrical permanent magnet slidably mounted on said housing and having sufficient magnetomotive force to close said reeds, said winding being wound to produce a magnetomotive force in the opposite direction from said permanent magnet when current fiows therethrough whereby said reeds will open interrupting current to said load when said current produces a predetermined magnetomotive force.

3. An electric circuit comprising, a source of electrical energy, a load, a magnetic reed switch having a housing, a pair of reeds mounted in said housing, a permanent magnet means positioned adjacent said housing and producing sufiicient magnetomotive force to close said reeds, an electromagnetic means, means for connecting said electromagnetic means in series with said source of electrical energy, said pair of reeds and said load, said electromagnetic means producing a magnetomotive force in a direction to oppose the magnetomotive force of said permanent magnet whereby said reeds will open interrupting current to said load when said current produces a predetermined magnetomotive force.

4. An electric circuit comprising, a source of electrical energy, a load, a magnetic reed switch having a cylindrical housing, a pair of reeds positioned in said housing and extending in a generally axial direction with respect to said housing, a cylindrical permanent magnet means polarized in an axial direction positioned around said housing at one end thereof, said cylindrical permanent magnet means having sufficient magnetomotive force and being positioned to close said reeds, an electromagnetic means positioned about said housing at the other end thereof, said electromagnetic means being connected in series with said source of electrical energy, said reeds and said load, said electromagnetic means being wound to produce a magnetomotive force that opposes the magnetomotive force produced by said permanent magnet means as current flows from said source of electrical energy through said load, said electromagnetic means producing sufficient magnetomotive force to cause said reeds to open when the current therethrough reaches a predetermined value.

5. The electrical circuit of claim 4 in which said cylindrical permanent magnet means is axially movable along ,said cylindrical housing to enable said reeds to be either opened or closed.

6. The electrical circuit of claim 4 in which said electromagnetic means is axially movable along said cylindrical housing.

7. The electrical circuit of claim 4 in which both said cylindrical permanent magnet and said electromagnetic means are axially movable along said cylindrical hous- 8. The electrical circuit of claim 4 in which a second electromagnetic means is positioned about said cylindrical housing and in which means are .provided for temporarily coupling said winding in circuit with said source of electrical energy to produce a magnetomotive force in the same direction as said cylindrical permanent magnet.

References Cited by the Examiner UNITED STATES PATENTS 2,509,590 5/1950 Galt 317-154 X 2,923,791 2/1960 Cor-bitt et al. 335-153 3,204,059 8/1965 Saaty 335l53,

FOREIGN PATENTS 81,023 8/1958 Italy.

MILTON O. HIRSHFIELD, Primary Examiner.

R. V. LUPO, Assistant Examiner.

Claims (1)

1. AN ELECTRIC CIRCUIT COMPRISING, A SOURCE OF ELECTRICAL ENERGY, A LOAD, A MAGNETIC REED SWITCH HAVING A PAIR OF REEDS AND A WINDING SURROUNDING SAID REEDS, CIRCUIT MEANS COUPLING SAID SOURCE OF ELECTRICAL ENERGY, SAID PAIR OF REEDS, SAID WINDING AND SAID LOAD IN SERIES, AND A CYLINDRICAL PERMANENT MAGNET SURROUNDING SAID REEDS AND POLARIZED IN AND AXIAL DIRECTION, SAID CYLINDRICAL PERMANENT MAGNET HAVING SUFFICIENT MAGNETOMOTIVE FORCE TO CLOSE SAID REEDS, SAID WINDING BEING WOUND TO PRODUCE A MAGNETOMOTIVE FORCE IN THE OPPOSITE DIRECTION FROM SAID PERMANENT MAGNET WHEN CURRENT FLOWS THERETHROUGH WHEREBY SAID REEDS WILL OPEN INTERRUPTING CURRENT TO SAID LOAD WHEN SAID CURRENT PRODUCES A PREDETERMINED MAGNETOMOTIVE FORCE.

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