US3512111A

US3512111A - Speedy operative circuit protector

Info

Publication number: US3512111A
Application number: US733889A
Authority: US
Inventors: Hajime Goto
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-12-29
Filing date: 1968-06-03
Publication date: 1970-05-12
Anticipated expiration: 1987-05-12

Description

May 12, 1970 HAJIMEIGOTO SPEEDY OPERATIVE CIRCUIT PROTECTOR 3 Sheets-Sheet 1 Filed June 5, 1968 F/GZ FIG. 1

6 x 12 w EU N: a Q Sm x2 h M Q q H 9 5 9 2 V INVENTOR A fMV k1 1i;

ATTORNEY Mayglz, 0 HAJIMEGOTO 3,512,111

SPEEDY OPERATIVE CIRCUIT PROTECTOR Filed June 3, 1968 I 3 Sheets-Sheet 2 3 1 S N -HPM-HCO/'l 7 w 1 a s f /v 6 3 F IG. 8 9 ON A T T 5 i E E 7 5 E i I f 1 H4 H7 H5 H6 H3 H5 *H/Hmw-Hco/l) F IG. 9

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ATTORNEY y 1 HAJIME'GOTO 1 3,512,111

SPEEDY OPERAIIVE CIRCUIT PROTECTOR Filed June 5, 1968 3 Sheets-Sheet 5 FIG. 11

0.0'0/ 0'.0/ I r c.

P-P 4/ ON 42 E Lpupl OFF INVENT OR ATTORNEY United States Patent 0 Int. Cl. Htllh 1/66, 51/22 US. Cl. 335-153 3 Claims ABSTRACT OF THE DISCLOSURE A circuit protector device wherein a two contact switch of magnetic material is disposed in a container which is surrounded by a coil in series with the switch. A permanent magnet is disposed in the vicinity of the switch, and, when moved towards the switch acts to close the contact. This permits a current to flow through the switch and through the coil. The direction of current flow and the BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a switch useful as a rapid circuit protector and more particularly to a rapid circuit protector useful against an excess current in an electric circuit.

Since semiconductor circuits or integrated circuits generally use weak currents, these circuits are defective from the standpoint of an over current flow especially in cases where a valve circuit i.e., vacuum tube arrangement has been employed in the past. Because of this over-current flow defect, there are many cases where semi-conductor circuits or integrated circuits cannot be employed owing to the fact that they cannot be provided with a proper, reliable rapid operative circuit protector.

Description of the prior art subjected to an over current. However, it has proven to I be considerable trouble to change the protective semiconductor unit ever time it blows.

The arrangement of the protective unit of the present invention will eliminate such difliculty.

Summary of the invention Broadly stated, the present invention contemplates using a magnet to close a two contact switch allowing an electric current to flow therethrough. With the flow of current, a weak magnetic field is created around the switch also by the current flow. Even though counter to the magnets field, the Withdrawal of the magnet still will not open the switch. In series with the switch is a coil which also acquires a magnetic field with current flow therethrough. This coil magnetic field also acts on the switch but is insufiicient to upset the combination of the magnetic field caused by the flowing current as well as the "ice magnetic field of the withdrawn magnet. However, a large surge of current through the coil will increase the mag netic field in the coil and open up the switch.

The objects and advantages of the invention will become more readily apparent to persons skilled in the art from the following detailed specification and annexed drawings.

Brief description of the drawings FIG. 1 is an elevated cross-sectional view of the device contemplated herein;

FIG. 2 is an elevated cross-sectional side view of the device shown in FIG. 1;

FIG. 3 is a back view of the device contemplated herein;

FIG. 4 is a plane view of the device contemplated herein;

FIG. 5 is a view of the device shown in FIG. 1 from the under side thereof;

FIG. 6 is a cross-sectional view of the bottom of the drum contemplated herein;

FIG. 7 is a connection schematic and block diagram of the electric circuit of the device contemplated herein;

FIG. 8 is an illustration of an operating circuit;

FIG. 9 is a graphic illustration of the operation of the device contemplated herein;

FIG. 10 is simplified explanation of the operation of a switch arrangement contemplated herein;

FIG. 11 illustrates in graphic form a curve of the breaking point in a semiconductor circuit;

FIG. 12 is a block circuit diagram of the use of the protective device herein contemplated in a circuit; and,

FIG. 13 is a graphic explanation of an operating circuit employing the device herein contemplated while using A-C current.

Detailed description Generally speaking the present invention contemplates a circuit protector device wherein a two contact switch of magnetic material is disposed in a container which is surrounded by a coil which is in series with the switch. A permanent magnet is disposed in the vicinity of the switch, and, when moved towards the switch acts to close the contacts. With the closing of the contacts, a current flows through the switch and through the coil. The coil is so wound as to produce a magnetic field counter to that of the permanent magnet. However, the flow of current through the contacts also causes a magnetic field to flow which is counter to the magnetic field of the permanent magnet. Nevertheless, when the magnet is withdrawn away from the contacts a certain distance, the contacts remain closed, the field strength of the magnet about balancing the counter field strength of the coil and switch. Means are provided for adjusting the positions of the magnet and coil to set the field strength at desired levels so as to open the switch contacts at predetermined overload conditions.

A two contact switch is employed as the key switch component. The switch consists of a glass tube or envelope 2 in which is disposed a switch unit formed of two contact pieces 1 of permalloy, a magnetic alloy of nickel and iron having a high permeability and, an inert gas. The switch tube 2 is sealed and, the switch contacts at the end of the permalloy switch unit 4 are closed by means of the attractive force of a magnet or the energizing of a coil wound on the outer surface of the switch tube.

Considering a prior art type reed relay first, only the coil and the switch when the coil, wound on outer surface of the switch tube is energized, and the energizing electric current is increased from zero upwards, the intensity of the magnetic field around the coil is increased and rises up to a value H as shown in FIG. 9. The contact of the switch is closed, and is kept closed by the electric current further increasing so as to make H more intense. If on the other hand there is a decrease in the electric current until the intensity of the magnetic field comes down to H the contact do not open but are opened at less intense magnetic field value of H This value H is less than the magnetic field value which existed when the contact was closed. Accordingly, between magnetic field values H and H there exists a kind of stable area wherein the contact remains in the closed state. The circuit protector arrangement herein contemplated makes advantage use of this situation.

The basic circuit configuration contemplated is shown in FIG. 7. Here, a coil 3 is connected, in series with a switch 4 in a circuit. The two terminals shown, are to be disregarded for the moment for a clearer understanding of the invention. There is provided a permanent magnet 5 next to switch 4.

When the switch circuit protector is interposed between an electric circuit to be protected and a source of D-C current, the switch is acted upon differently, first by the magnetizing force caused by DC current flow I flowing in the coil 3 and second, by the permanent magnet 5. Both of these magnetic fields have an influence on the stable area hereinbefore mentioned with respect to the understood stability of the switch 4. This may be better understood by a study of FIG. 8. To enable the circuit protector i.e., by having it act on the electric circuit, it is necessary to first close the contact. To do this it is necessary to create a magnetic force H, which will influence the switch, of a value exceeding or equal to H The permanent magnet 5 should be brought close enough to the switch 4 to accomplish this. When the switch contacts are closed the current flow is in a direction to counter the intensity of magnetic field caused by the permanent magnet 5. This will lower the field value to H This is sufficient to keep the contacts closed owing to the proximity of permanent magnet 5 to the switch 4.

Thus, it is impossible to open the contacts or to keep them open even though there is a current larger than H.,, the switch will open. However, in this case, the operative point is too deep and it takes too long to open the switch.

. To properly fix the operative point of the circuit protector, the permanent magnet 5 has to be placed a little further away from switch 4 to decrease the magnetic force acting thereon, so as to draw this magnetic force nearer to H i.e., to about the operative point 6 corresponding to magnetic force H Under these conditions, when an electric current of from about 1.5 to about 1.8 times the rated current flows, the instantaneous magnetic force becomes less than H and the contacts are opened. Then, the magnetic force produced by coil 3 goes to zero, and the operative point moves to point 7 changing the magnetic force to H which in this case, should be smaller than H By making use of this arrangement the switch whose operation has just been described is used as a circuit protector.

In a circuit overload breakdown test, as illustrated in FIG. 11, the horizontal coordinate shows the time during which an abnormal over current is flowing, and the vertical coordinate shows the value of said current. The curve so obtained illustrates that the shorter the flowing time of an over current, the stronger is the circuit resistance against breakdown against the over current.

In carrying out the foregoing concepts into practice, the construction shown in FIGS. 1 to 6- is advantageous. In these figures there is shown a circuit protector arrangement having a switch 4 for controlling a main electric current. A permanent magnet 5 is disposed, adjacent to the switch 4. The switch is contained in a sealed tube surrounded by a coil 3 so disposed with respect to the permanent magnet 5 as to define as near as possible the lower field value of the stabilized field hereinabove described with respect to switch 4. In order to close the contact 1 of the switch 4 there is provided a hand button which will place the permanent magnet 5 close to the contact which are to be set or reset. Coil 3 is connected in series to the switch 4 over which is created the magnetic field caused by the coil. In the example shown the arangement is set for a D-C current. Coil 3 which is connected in series to said lead switch 4. The value of the magnetic field around the coil is normally less than that of the permanent magnet -5.

The device is housed in a frame 8 having a U-shape. In the side plates 9 of U-shaped frame 8 there is an aperture 10 for inserting a first screw rod 11. Screw rod 11 has a first insulating block 12 mounted thereon. Between the insulating block 12 and one side of one plate 9 there is provided a spring 13. The spring is mounted towards the head of screw rod .11. The head 14 of the screw rod is disposed outside of the plate 9 and can be turned by a screw drive so that the first insulating block 12 can be moved up and back within frame 8.

On the opposite sides of plate 9 are

other apertures

15 and 16 for inserting a second screw rod into the one 15 and the other 16 aperture and for a push button 20, mounted on the outer end of rod 17. Mounted on second rod 17 is a second insulating block 18. Also on screw rod 17 on the side of aperture 15 between second insulation block 18 and side plate 9 is a spring 19. Thus, on one end of second rod 17 is spring 19 while on the other end is a push button 20.

Insulating block 18 can be moved against the reaction of spring 19 by pushing the button 20' by hand and returns to its former position by releasing the button.

Mounted in the center of U-shaped frame 8 is an elongated hollow insulated tube 21 which is fixed to the center of frame 8, i.e., to opposed plates 9 of the frame 8. Permalloy switch 4 is disposed in tube 21, and, around tube 21 and over the contact points of switch 4 is wound an insulated wire coil 3. Coil 3 is electrically in series with switch 4. Thus the lead lines of the switch 4 pass through apertures at both ends of tube 21 and the inner lead of the switch acts as the inner lead of the coil. This inner lead of switch and coil is held on the upper portion of first insulating block 12. In other words, one end of coil 3 is connected to the lead wire of switch 4. The other lead wire end 23 of coil 3, together with the other lead wire 24 of the switch 4, are connected to the power line terminals of the device. The other lead wire end 23 of the coil passes through first insulating block 12. Both leads 23 and 24 then pass out of an eyelet 31 (see FIG. 2) of the device.

Affixed to second insulating block 18 is a permanent magnet 5, which is disposed so as to provide a magnetic field over switch 4. By turning the head 25 of screw rod 17 with a screwdriver, permanent magnet 5 can be moved slightly for controlling the location of the magnetic force field H By pushing button 20 by a hand, magnet 5 is moved nearer to the contact points of the switch 4 for increasing the magnetic field so as to close the contacts. In this way, the circuit protector device can be set or reset.

The main components of the circuit protector device constructed as hereinbefore described is contained in a housing 26. Button 20 projects out of the housing. The housing forms a single unit with the frame 8 and frame insulating plate 28 'by the use of dowel-like projections 27 located on the outer sides of plates 9 of the base frame 8. These dowel-like projections fit into holes 29 of the insulating plate 28. The projections 30 formed on the housing 26 are bent so as to secure insulation plate 28 to complete the package.

Insulating plate 28 is also held by means of eyelets 31 serving the double purpose of acting as holding means and as passages for circuit lead 23 of the coil 3 and for the lead 24 of the switch 4. These leads are pulled out through holes of the eyelet 3.

The housing 26 is provided with two

apertures

33, 34, one of which 33 is for controlling the relationship between switch 4 and the coil 3 by moving the latter together with the insulating plate 12 which holds the both ends of the coil 3. Screw rod 11 is turned by using a screwdriver inserted at aperture 33. The other aperture 34 is for controlling the magnetic field H; of the circuit protector by turning screw rod 17 with a screwdriver which is inserted at hole 34.

Since button 20 is pushed in and out for set or reset, and screw rod 11 extends out from base frame 8, the diameter of aperture 33 should be large enough to pass the top head 25 f screw rod 17 through it. The numeral 35 in FIG. 4 indicates a fixed portion of the circuit protector located in housing 26. The device operates as follows:

As shown in FIG. 12, the circuit protector device 36 is connected between an electric source 37 of a D-C current and the semiconductor circuit 38 to be protected. The circuit is designed for a rated current I. Button 20 is pushed so that the permanent magnet approaches the contacts of the switch 4 increasing the magnetic field around the switch to close the contacts of the switch 4 so that current I is fed to the semiconductor circuit to be protected. The magnetic field force acting on the contacts at this time, will be increased from H, to H (see FIG. 8).

After the contacts have been closed, a magnetic field is formed by the action of current I flowing in the circuit. This field is opposite to the field caused by the permanent magnet 5 and decreases the magnetic field acting upon the contacts, but the magnetic field of the permanent magnet 5 is still sufficiently large to keep the contacts closed. This magnetic field is labeled as H which corresponds to point 39 in FIG. 8.

Upon releasing button the permanent magnet 5 returns to its former position by the action of spring 19, and the magnetic field acting on the contacts labeled H corresponding to point 6. The device is now prepared against an abnormally large electric current, and the circuit protector device is all set to work.

Point 6 corresponding to magnetic field H is controlled by turning screw rod 17. This point depends on the construction of the device taking into consideration, the magnetizing force of the permanent magnet 5 and the ampere turn of coil 3.

It is possible to control this magnetizing force minutely for the purpose of defining the breaking point of the electric circuit.

By properly turning screw rod 17, an operative point can be selected for the highest speed and it is also possible to correct the contacting pressure of the contacts which causes distortion in the flexibility of the contacts 1 of the switch 4 or, by distortion of magnetic reluctance of the unit. Thus it is possible to manufacture circuit protector devices having distortion peculiarities and these can then be corrected by adjustment.

As described above, when a magnetic field H acts on the contacts of the switch 4, if a current of from about 1.5 to about 1.8 times the rated current is sent through the circuit protector, the magnetic field of the coil 3 will be increased. Since the magnetic field H equals the permanent magnetic field less the coil field, or H: (H -H coil). When the field decreases below point H the contacts of switch 4 will open and the operative point of the switch will be moved to point 7. Thus, an over current in the electric circuit of the semiconductor to be protected is cut in an instant.

When it is necessary to reset the electric circuit, by pushing the button 20, it can be done like the setting of the circuit.

Although the arrangement hereinbefore described relates to a circuit protector for a D-C current system, the system can also be used for an A-C current.

In case the electric source has a sinusoidal output of 50 or 60 Hertz, the magnetic field produced by the coil 3 is also an alternating field, of 50 or 60 cycles per second.

Considering these conditions, each operative point can be set, as illustrated in FIG. 13. Assuring that when the magnetic field acting on switch 4 reaches a value of to H the contacts are closed, but when the magnetic field reaches a value of H the contacts are opened at the same time, assuming that, when the permanent magnet 5 is in position in accordance with the reaction of the spring 19, the operative point would be on a point 40 corresponding to magnetic field H acting on the switch 4, the point 40 will be moved to the right, by letting the permanent magnet 5 draw nearer to the contacts. By pushing button 20 the operative point is moved to location 41, and the magnetic field value becomes H Then the magnetic field of the coil 3 can be expressed as Hm sin (wt-i-O). To this is added the force of the permanent magnet, the magnetic field acting on the contacts of the switch 4.

The magnetic field can be mathematically described as Hpm-l-Hm sin (wt-H1), (assuming W=0t1rf, where f is the frequency of the source); 0=initial phase; Hm=maximum value of the magnetic field of the coil, and Hpm the value of the magnetic field of the permanent magnet.

The contacts will be closed by pushing button 20. Then upon releasing the button 20, the button returns to its former position by the action of the spring 19 so that the magnetic field oscillates around point 42 until the minimum peak wave value between plus peak and minus peak of the magnetic field produced by the coil 3, becomes less than H so that the contacts are opened, namely, when Hm is opposed by the field strength of a high wave of current flowing in the coil 3. When an abnormally large current flows, the value of the magnetic field of coil 3 will increase so that the contacts of the switch 4 are opened at once, making the instantaneous value (Hpnv-Hm) of the magnetic field Hpm+Hm sin (wt+0) which acts upon the switch 4, less than the field value H The necessary switching time of the lead switch is less than one millisecond, so that if the frequency of the electric source is of 50 Hertz a half cycle corresponds 10 milliseconds which is enough to open the contacts.

Thus the device is useful when an A-C current is the electric source. Similarly the device is adjusted by turning screw rod 17 to control the magnetic field. Acting on the contacts of the switch 4 and by using the permanent magnet 5 properly to shorten the operating time.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. A circuit tion:

(a) a frame (8);

(b) a tube (21) held in said frame;

(c) a two contact switch (4) inside said tube (21) said switch (4) being made of magnetic material;

(d) a coil (3) wound around said tube, in series with said switch;

(e) a rod (17) disposed adjacent said tube, held by said frame;

(f) a permanent magnet (5) mounted on said rod disposed in the vicinity of said envelope;

(g) means (20) for moving said permanent magnet towards and away from said switch;

(h) said means comprising a push button (20) on the end of said rod (17); and,

(i) a spring (19) coiled around said rod to restore said magnet to its original position, whereby, when said permanent magnet is moved towards the switch,

protector device comprising in combinasaid switch contacts close permitting a current flow so as to 'be able to move said coil along said tube (21) through the switch and coil, the winding of the coil for adjusting the magnetic field of the coil.

being such as to produce a magnetic field counter to 3. A device as claimed in claim 2 wherein said first that of the permanent magnet, the fiow of current and second rods are screw rods including a screw head through the contacts also causing a magnetic field and can be turned by turning said heads so as to laterally around the switch so that the movement of said permove said magnet (5) and said insulation block (12) manent magnet away from said switch to its original with respect to said switch (4). i position will not cause the switch to open since the field strength of the magnet about balances the coun- References Cited ter field strength of the coil, but an overcurrent flow- 10 UNITED STATES PATENTS ing through the coil opens up the switch contacts.

2. A device as claimed in claim 1 including a second rod (11) mounted between said frame disposed adjacent BERNARD GILHEANY Primary Examiner said tube (21), an insulation block (12) mounted thereon, the end wires of said coil (3) passing therethrough 15 VALL, JR., Assistant Examiner 3,319,128 5/1967 Nilssen 335-153X