US2073102A - Circuit breaker - Google Patents

Description

March 9, 1937. c. H. HODGKINS CIRCUIT BREAKER 1933 3 Sheets-Sheet 1 Filed Aug. 4

INVENTOR CHARLES H HODGKINS BY HIS ATTORNEYS Man-ch 9, 1937. C. H. HODGKINS 2,73,102

CIRCUIT BREAKER Filed Aug. 4, 1933 5 Sheets-Sheet 2 INVENTOR CHARLES H. HODGKINS BY HIS ATTORNEYS March 9, 1937. c. H. HODGKIINS CIRCUIT BREAKER 3 Sheets-Shet 3 Filed Aug. 4, 1933 S m .Y s TD m0 mH S E L R A H c U 1 l BY HIS ATTORNEYS Patented Mar. 9, 1937 PATENT orrlcs CIRCUIT BREAKER Charles H. Hodgkins, Fairfield, Conn., assignor to The Bryant Electric Company, Bridgeport, Conn., a corporation of Connecticut Application August 4, 1933, Serial No. 683,673

9 Claims.

This invention relates to circuit breakers. More particularly it relates to automatically operating circuit breakers which are released by the thermal effect of an overload current. The

- invention also relates to arc suppressing means for circuit breakers, and is particularly useful in interrupting alternating currents.

It is an object of this invention to provide an automatic circuit breaker mechanism capable of being housed within a housing of approximately the size of an ordinary screw type fuse plug.

Another object is to provide a circuit breaker of the type just mentioned, in which the contacts may be manually closed and reclosed but can be opened only upon occurrence of an overload current in the device.

Another object is to provide arc extinguishing means useful generally in circuit breakers and adapted particularly to use in a circuit breaker housed in a casing the size of an ordinary fuse plug.

Another object is to provide a circuit breaker capable of attaining the above objects and which 5 will, on overload trip free of the circuit closing means so that it can not be held closed manually.

Another object is to provide a circuit breaker in which the magnetic flux of the overload current is used to assist the opening movement of a bimetallic tripping member.

Another object is to provide a circuit breaker of the type mentioned, with means. to indicate when the contacts are together or separated.

Other objects and advantages of this invention will become apparent as the invention is described in connection with the accompanying drawings.

1 Those features of my invention which are not herein claimed, are claimed in my copending application Ser. No. 706,58; filed January 13,

In the drawings:-

Figure 1 isa midsectional view taken axially, through one form of my invention showing the parts in the position they take after the contacts have been separated by automatic operation or tripping of the circuit breaker mechanism.

Figure 2 is a view corresponding to Figure l but of only the top half of the device, showing the parts in a position intermediate the tripped position of Figure 1 and the closed position of Figure 3. Figure 3 is a view corresponding to Figure 1 but showing the parts in the position they occupy when the contacts are together. I

Figure 4 is a view of the top of the device shown in Figures 1-3.

Figure 5 is a plan view of the device of Figures 1-4 with the cover removed to show the lnterior. 5

Figure 6 is a perspective view of the cover of the device shown in Figure 1.

Figure 7 is a sectional view of another form of the invention, the section being taken axially through the center of the device. The position 10 of the parts after tripping of the mechanism is shown in dotted lines, while the intermediate position of the parts is shown in full lines.

Figure 8 is a view corresponding to Figure 7 but with the parts in circuit-completing posi- 15 tion.

Figure 9 is a midsectional view taken axially through a third form of the invention, showing the parts in tripped position.

Figure 10 is in part an elevation View and in 20 part a midsectional view taken axially through a form of my invention having difierent arc quenching means than that of the other forms.

Figure 11 is a detail view of a locking bar used in the form shown in Figures 7 and 8.

Referring to the drawings Figures 1-6 show an automatically operable circuit breaker mechanism housed; in an insulating casing it of size and shape like that of a conventional screw type fuse plug. Upon the lower end of the casing is 30 mounted a screw shell 12 and a center contact M as in plug type fuses. The center contact I4 is held in position by a screw it which screws into a cylindrical stationary switch contact l8 and holds it Within the casing ill in axial posi- 35 tion at the bottom thereof.

For engagement with the stationary contact 18 a cylindrical movablecontact 20 is mounted upon one end of a reciprocative contact carrier 22. The lower end of this carrier is cylindrical and 40 is adapted to slide within an axial passage formed by the registering central openings in an annular insulating support 24, an annular arc quenching ring 26 of magnetic material such as iron (whose function will be hereinafter de- 45 scribed) seated upon the support 24, and an in- .sulating washer 28 seated upon the arc ring 26.

The are ring 2% has a circular flange or neck 2i extending axially away from the contacts and fitting snugly into a complementary recess in 50 the bottom of the washer 28. The washer 28 also has a circular neck or flange 29 extending axially away from the contacts and forming a guide for the lower end of a helical coil spring 38 which presses against the upper face of the washer 28. The upper end of the spring 30 encircles and is guided by a cylindrical enlargement 220 on the movable contact carrier 22. The upper end of the spring 30 presses against the under face of the head 22h of the movable contact carrier, which. head constitutes a further enlargement of the contact carrier and is of the same overall diameter as the overall diameters of the arc ring support 24, are ring 26, and washer 28, all being slightly lessin diameter than the diameter of the bore Illb (see Figure 5) in the lower part of the casing I0, whereby all said parts may he slipped into position and the contact carrier may slide within the bore as pressure is exerted to overcome the tension of the spring 30 which normally tends to separate the contacts I8 and 20.

To prevent the carrier 22, washer 28, are ring 26 and support 24 from rotating within the. bore Iflb a rib I01- is formed in the wall of the bore and a complementary recess for the rib is formed in the periphery of each of the above listed members.

The mechanism for moving the contact 20 into engagement with contact I3 and for holding it in such engagement until occurrence of an overload, will now be described.

' Projecting symmetrically from the upper surface of the carrier 22, away from the contacts are spaced parallel arms 22a, and situated between said arms is an insulating block 40 of width approximately equal to the spacing of the arms 22a. The block 40 is held between said arms by a pin 42 passing transversely through it and having ends extending into identical elongated vertical slots 22s in the arms 22a. Thus the block 40 is permitted limited movement between the arms in a direction axially of the device. The block is normally pressed away from the head 22h of the carrier 22 by a strong compression coil spring 44. For the purpose of housing this spring 44 the upper surface of the carrier 22 and the lower surface of the block 40 are provided with coaxial bores of suificient diameter to accommodate the spring. -Preferably the bore in the carrier is enlarged at its top and the block 40 is provided with a hollow cylindrical extension or collar which'slides within the enlarged portion of said bore to guide the axial movement of the block.

The block 40 acts also as a support for a latch 46 which is mounted piyotally upon the pin 42 and within a slot cut in the top of the block in a plane perpendicular to the pin. The latch 46 extends approximately equally on opposite sides of the pin. One end of the latch has formed on it a shoulder 46s, which is adapted to engage with a thermo-bar 48. This end of the latch also has'a lateral extension 466 to engage with an actuating earn as will be presently described. The other end of the latch is turned up slightly and is adapted to be engaged by the actuating cam as will be described.

The thermo-bar 48 is made of united strips of metal having difierent coefficients of expansion. The bar is secured at its lower end to the inside wall of the casing ID near the bottom by a rivet 49 which passes through the wall and is connected to the screw shell I2.

To the top of the thermo-bar 48 is attached a conductor 5| which is also connected to the contact carrier 22 so that current entering the device through shell I2 passes through the thermo-bar 48, conductor 5|, carrier 22 to contact 20 and leaves the device through contact I8 and center socket contact IS.

The manual means for movingthe contact 20 into engagement with contact I8 comprises a cover 50 for the casing III, which cover is provided on its lower surface with a circular shoulder 52 engaging the inside edge of the top of the casing to guide rotative movement of the cover on the casing. The cover is provided on its top surface with four equally spaced radially extending ribs 54 to be gripped by the fingers of the operator when he is manipulating the cover to cause engagement of the contacts. The cover is held upon the casing by a ring 56 lying lightly upon it and secured to the casing by two legs 56a bent down from the periphery of the ring in diametrically opposed positions and screwed to the side wall of the casing near the top.

To move the latch 46 as the cover is rotated two approximately concentric circular cams are formed upon the bottom surface of the cover 50 as shown in Figure 6. The cams are oppositely inclined thus bringing their peaks at the same side of the cover. One cam, I00, serves to depress the latching end of the latch 46 while the other cam I02 serves to depress the other end of the latch. The ends aredepressed alternately due to the high points of the cams being on the same side of the center of the cover. To prevent rotation of the cover past the point where the ends of the latch are depressed the maximum amount two lugs 53 separated approximately are formed on the underside of the cover and engage with a cooperating lug 55 on the inside wall of the casing ID at the top thereof. Thus the cover is permitted approximately 160 of rotation upon the casing.

From the foregoing, the operation of the device may now be understood. The device after assemblyis screwed into a fuse socket and, if the contacts are engaged as shown in Figure 3 the circuit through the device will be complete. If an overload occurs the thermo-bar 48 will be heated and will bend away from the latch nose 46s allowing the spring 30 to raise the contact carrier 22 and separate the contacts I8, 2IJ.v

During this operation the latch 46 rotates about its mounting pin 42 and pivots about the point of contact of the end of the latch with cam I02 until the parts are in the position of Figure 1. The spring 44 is stronger than the spring 30 so that as the contacts separate, the pressure of the spring 44 will not be overcome but will cause the block 40 to move upward with the carrier 22 as a unit. Figure 1 may be called the tripped position. cover will be rotated clockwise whereby the cam I00 will slide over and press down the nose 46s into engagement with the thermo-bar. same time the other end of the latch moves up as shown in Figure 2. Now, the cover must be rotated counterclockwise causing the cam I02 to slide over and press down the other end of the latch, while the latched end is"- held in engage ment with the thermo-bar. During this movement the pivot 42 Will be moved down a distance at least as great as the separation of the contacts, in order to cause engagement of the contacts as shown in Figure 3. During this downward movement of the pivot 42 and its block 40 To re-engage the contacts I8 and 20 the At the the spring 44 (being stronger than spring 30) will Y not be compressed but will cause the carrier 22 and block 40 to move as a unit to compress further movement downward of block 40 will be accommodated by compression of spring 44.

In order that the device may not be opened manually, I have provided a passage 60 in the side of the casing l running parallel to the axis of the casing and in this passage there is a looking bar 62 which is adapted to slide in the passage upward until the end of the bar enters a recess t4 that is formed in the underside of the cover in position to register with the passage 60 when the cover is in position to cause engagement of the contacts (Figure 3). The end of the screw shell 62 is cut away at the lower end of the passage 50 in order that the locking bar 62 may be slid downward to remove its end from recess t4. But this can only be done when the device has been removed from the fuse socket. For facilitating the removal of the bar, a nubor thumb piece 66 is provided on its lower end and normally fits in the lower spiral of the screw shell. This nub can be grasped by ones fingers since enough of it is outside the screw shell for that purpose. The device can not be screwed into the fuse socket when the bar 62 is not entirely within the passage 60. Hence the device must be reset and locked before it can be replaced in a socket to complete a circuit, and when replaced the device can not be operated as a switch.

In order to indicate the condition of the contacts, indicating means comprising a button extending through the center of the cover, is provided. This button is supported upon a spiral spring 12 which is seated upon the top of the block 40 and is attached to the enlarged head of a pin 14 whose shank is moulded in the button. When the spring 72 is fully expanded and the contacts l8 and 20 are in engagement the top of the button is flush with the top of the cover as in Figure 3. But when the contacts l8 and 20 separate the carrier 22 and block 40 are pushed toward the cover by main spring 30 and the button is caused to move outwardly of the cover by the pressure of button spring 12 as shown in Figure l. The button is provided with a flange 13 inside the cover to prevent the button from being pushed through the cover by the spring 12.

To prevent the button ID from being pushed into the casing until it engages block 40 and then continuing its inward movement carrying with it carrier 22 and contact 20 until contact I8 is engaged, the aperture in which the button slides is countersunk from the outside of the cover and a diametrical pin passes through the button and has its ends extending beyond the sides of the button-within the countersink. When the ends of the pin I5 engage the bottom of the countersink the inward travel of the button is halted and it therefore can not be used as a switch operating means. Preferably the inward travel of the button will be limited when the top of the button is flush with the top of the cover.

The functions of the three springs 30, 44 and 72 may now be understood. Main spring 30 serves to separate the contacts when the circuit breaker is tripped. Auxiliary spring 44 provides lost motion to take care of what might amount to overtravel of the carrier 22 and contact if spring connection 44 were not provided. It also presses the movable contact 20 closely against the stationary contact. Button spring 12 provides a lost motionconnection between the indicating button 10 and the block 40 so that actuation of the indicator will not result in movement of the contact 20.

In Figures '1 and 8, I have shown another form is automatic.

of means to lock the cover to prevent the device from being used as a switch. This locking means The device is the same as that shown in Figures 1 to 3 except that the passage 80 in which the locking bar 82 works is shorter than the corresponding passage 60 in Figures 1 to 3 and is closed at the bottom end. The locking bar 82 differs from looking bar 62 previously described, in that bar 82 is slotted longitudinally from its upper end as at 83 and its lower end is of reduced width. The lower end fits within and is surrounded by a coil spring 84 whose lower end presses against the bottom of the passage 80 and whose upper end presses against shoulders 85 of the locking bar formed by the reduction of the lower end of the bar. See Figure 11.

The latch 56 of Figures 7 and 8 is like the latch 56 of Figures 1 to 3 as to its latching end but its other end has finger 81 in extension thereof and adapted to engage in the bottom of the slot 83 of the locking bar 32 when the contacts i8-2D are engaged and also adapted to press against the bottom of the slot 83 and force down the locking bar against the action of the spring 84, when the latch is released upon overload as is shown in dotted lines in Figure 7. In that position the mounting pin 42 for the latch has moved up by an amount at least as great as the contacts separation (from the'Figure 8 position) but at the same time the latch has pivoted to bring its finger 81 down a distance as great as the upward movement of the pivot plus the depth of the recess 64 in the cover.

During the rotation of the cover 50 clockwise to reengage the latch with the thermo-bar i. e. into the full line position of Figure 7, the looking bar 82 is held down by its top sliding along the under surface of the cover 50. Upon rotation of the cover counterclockwise to engage the contacts i. e. into the position of Figure 8, the spring 84 will snap the locking bar into recess 64 as soon as it comes in register with the recess 80, thereby locking the cover and preventing its rotation until the contacts have been separated by the operation of the device due to an overload.

In Figure 9, I have shown a further modification in which the cover 50 is not locked and may be rotated at will to operate the device as a switch. The construction of this form, except for I the omission of the locking means is exactly the same as the forms previously described.

By reason of the limited space available into which the whole of my invention must be crowded the maximum contact separation is comparatively small. Itis therefore important that arcing between the contacts be reduced to a minimum and the arc quenched or suppressed as soon as possible after contact separation. A very effective means for this purpose I have found to be a ring 26 of magnetic material such as iron through which the movable contact passes and through which the arc incipient upon contact separation is drawn.v The internal diameter of the ring 26 is slightly greater than the diameter of the contact 20 so that contact will not touch but will be insulated by an air gap from the ring. It should be observed'that the ring is placed above the stationary contact l8. Repeated tests under conditions of extreme overloads have shown that currents may be interrupted by this invention, far in excess of what has heretofore been possible in prior devices.

Even better results are obtainable with the form of the invention shown in Figure 10. In this form the contact operating mechanism is the same as that previously described. But the casing ill] of the device is formed with an annular interior shoulder I I2 upon which rests the arc quenching iron ring l26 upon which, in turn rests the insulating member or washer I28. The member I28 as in the construction previously described, has a neck or collar projecting away from the fixed contact H8, within which neck the movable contact I20 slides. The stationary contact H8 is a thick disc lying upon the bottom of the casing H and secured there by a screw H6 which screws into the bottom of the contact from the outside of the casing. The inner edge of the ring i215, facing the stationary contact may be beveled as shown.

Held in the bottom of the casing around the contact H8 is a second iron are quenching ring 522 of less height or thickness than the height or thickness of the contact MB. This ring 22 cooperates with the ring I26 to produce a powerful arc quenching efiect so that with a small contact separation heavy currents may be interrupted.

In each of the forms shown the contact carrier 28 forms a comparatively close fit within the side walls or well in the bottom of the casing I0. Upon contact separation the heat of the arc heats and tends to expand'the gases, thereby creating an appreciable force upon the walls of the contact chamber and the contact carrier 22 causing the carrier to move away from the stationary contact more rapidly than the spring 30 could move it. The movement of the carrier away from the fixed contact increases the space in which the heat gases may expand and thus rier 22 by the cam I02 after the contacts l8 and 20 have become engaged. This additional compressive movement is small in comparison to the maximum possible from such a spring but since the spring is powerful, a small compressive movement is of consequence.

It will be observed therefore that three forces may act upon contact separation, namely spring 84, spring 30 and the force of the expanding arc gases.

It is a well known principle of-electro-dynamics that a pair of parallel conductors carrying current flowing in opposite directions repel each other or, in other words, tend to move apart. The repellent effect depends on the proximity of the conductors and the current value. For conductors close together the repellent effect may become very great for high current values such as are developed upon overload.

Efiective use of this phenomenon is made in the various forms of the present invention for it will be noted that the current path from the screw shell l2 (see Fig. 1) is through the rivet 49 up bimetallic strip 48, through conductor carrier 22 to contacts 20, I8 and lb. The current tion to cause release of the latch 46.

It will be understood that during normal curcelerate the movement of the bimetallic member Thus on into position to release the latch 46. slight overloads the bending of the bimetallic member due to increase in temperature will cause the tripping of the breakerbut on very great overloads the bending eiiect will be assisted by the electrodynamic efiect and the latter may hey so much greater and, if the overload be suddenly applied, it may act so much quicker than the bending that the breaker will be tripped practically entirely due to the electrodynamic efiect.

Thus I have provided a circuit breaker in which thermal as well as electrodynamic effects are utilized to accomplish rapid tripping of the circuit breaker mechanism.

The electrodynamic effect of the parallel conductors also acts to advantage in another relation in my circuit breaker, namely, it causes movement ,of the are from the center or other point on the contacts where it strikes into the arc quenching rings, and causes the arc to move around to various points on the rings and contacts. By moving the arc to various cool surfaces on the rings and contacts it is quenched quickly.

My invention is especially useful in interrupting alternating currents but may also be used in direct current work.

Many changes within the scope of my invention will occur to those skilled in the art, therefore I do not limit myself to the specific forms shown. 1

I claim:

1. A device for making and breaking electric circuits repeatedly, comprising stationary and movable contacts and magnetic arc-suppressing means surrounding the path of movement of said contacts, whereby an arc incipient upon the contact separation is drawn along said path through said means, and additional cooperating arc-suppressing means surrounding said stationary contact in position removed from the arc path.

2. A device for making and breaking electric circuits repeatedly, comprising stationary and movable contacts and metallic arc suppressing means surrounding the path of movement of said contacts, whereby an arc incipient upon the contact separation is drawn along said path through said means, and additional cooperating arc-suppressing means surrounding said stationary contact in position removed from the arc path, both of said are suppressing means being formed of iron.

3. A device for making and breaking electric circuits repeatedly, comprising stationary and movable contacts, and arc-suppressing means comprising an iron ring surrounding the path of movement of said movable contact and positioned in a plane above the stationary contact, and an,iron ring surrounding the stationary contact and positioned below the plane of the upper face of 'said stationary contact.

4. A device'for making and breaking electric circuits repeatedly, comprising separable contacts, means for mounting said device in a conventional .plug type fuse socket, conducting means encircuited between one-of said contacts and said socket-engaging means, the path of said conducting means being arranged to create a concentration of lines of magnetic flux on one side of the arc path between said contacts, and arc-suppressing means comprising a magnetic ring surrounding the path of movement of said contacts, the arc, incipient upon contact separation, being drawn along said path of movement and being moved against said ring by the action of said magnetic flux lines.

5. A device for making and breaking electric circuits repeatedly, comprising separable contacts, means for mounting said device in a conventional plug type fuse socket, conducting means encircuited between one of said contacts and said socket-engaging means, the path of said conducting means being reversed upon itself to form parallel current paths with the current flowing in opposite directions therein creating a concentration of magnetic flux lines at one side of the arc path between said contacts, and arcsuppressing means comprising a. magnetic ring surrounding the path of movement of said contacts, the arc, incipient upon contact separation, being drawn along said path of movement and being moved against said ring by the action of said magnetic flux lines.

6. A device for making and breaking electric circuits repeatedly, comprising separable contacts, means for mounting said device in a conventional plug type fuse socket, conducting means encircuited between one of said contacts and said socket-engaging means, the path of said conducting means being arranged to create a concentration of lines of magnetic flux on one side of the arc path between said contacts, and magnetic arc-suppressing means surrounding the path of movement of said contacts, whereby an arc incipient upon the contact separation is drawn along said path of movement through said are suppressing means and is drawn against said are suppressing means by the action of said magnetic flux lines, and additional cooperating arc suppressing means surrounding said stationary contact in position removed from the arc path but in position to be engaged by the are when moved under the action of said flux lines.

7. A device for making and breaking electric circuits repeatedly, comprising separable contacts, terminals for connecting said device in an electric circuit, conducting means encircuited between one of said contacts and one of said terminals, the path of said conducting means being arranged to create a concentration of lines of magnetic flux on one side of the arc path between said contacts, and arc-suppressing means comprising a magnetic ring surrounding the path of movement of said contacts, the arc, incipient upon contact separation, being drawn along said path of movement and being moved against said ring by the action of said magnetic flux lines.

8. A device for making and breaking electric circuits repeatedly, comprising separable contacts, terminals for connecting said device in an electric circuit, conducting means encircuited between one of said contacts and one of said terminals, the path of said conducting means being reversed upon itself to form parallel current paths with the current flowing in opposite directions therein creating a concentration of magnetic flux lines at one side of the arc path between said contacts, and arc-suppressing means comprising a magnetic ring surrounding the path of movement of said contacts, the arc, incipient upon contact separation, being drawn along said path of movement and being moved against said ring by the action of said magnetic flux lines.

9. A device for making and breaking electric circuits repeatedly, comprising separable contacts, terminals for connecting said device in an electric circuit, conducting means encircuited between one of said contacts and one of said terminals, the path of said conducting means being arranged to create a concentration of lines of magnetic flux on one side of the arc path between said contacts, and magnetic arc-suppressing means surrounding the path of movement of said contacts, whereby an arc incipient upon the contact separation is drawn along said path of movement through said arc-suppressing means and is drawn against said arc-suppressing means by the action of said magnetic flux lines, and additional cooperating arc-suppressing means surrounding said stationary contact in position removed from the arc path but in position to be engaged by the arc when moved under the action of said flux lines.

CHARLES H. HODGKINS.

Images