US2073103A - Circuit breaker - Google Patents

Description

March 9, 1937. c. H. HODGKINS 2,073,103

CIRCUIT BREAKER Original Filed Aug. 4; 195:5 s Sheets-Sheet 1 CHARLES H. HODGKINS March 9, 1937. c. H. HODGKIINS cmcun BBEAKER Original Filed Au 4, 1933 3 Sheets-Sheet 2 amvemioz CHARLES H. HODGKINS A flfl'oznu s Mam]! 1937. c. H. HODGKINS 2,073,103

cmcum BREAKER Original Filed Aug. 4, 1933 SSheets-Sheet s [=5=1.1E1 CHARLES H. HODGKINS Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Charles H. Hodgkins, Fairfield, Coma, assignor to The Bryant Electric Company, Bridgeport, (John, a corporation of Connecticut Original application August 4, 1933, Serial No. 683,673. Divided and this application January 13, 1934, Serial No. 706,564

44 Claims.

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 simple and compact contact-operating mechanism useful generally in circuit breakers and adapted particularly to use in a circuit breaker housed in a casing approximately the size of the most common size of screw-type fuse plug.

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

Another object isto provide a circuit breaker in which the magnetic flux of the overload cur rent 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.

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

This application is a division of my co-pending application Serial No. 683,673, filed August 4, 1933, entitled Circuit breakers in which is claimed the arc extinguishing features of-my invention.

In the drawings:

Figure 1 is a 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 1 but -ofon1y the top half of the device, showing the parts in a position intermediate the tripped showing the parts in the position they occupy when the contacts are together.

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

Figure 5 is a plan view of the form of my invention shown in Figure 9 with the cover removed to show the interior.

Figure 6 isa perspective view of the cover of the device shown in Figure 1. Figure 7 is a sectional view of another form of 5 the invention, the section being taken axially through the center of the device. The position of the parts after tripping of the mechanism is shownin 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 position.

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 part a mi'dsectional view taken axially through a form of my invention having different are 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 Ill of size and shape like that of a conventional screw type 25 fuse plug. Upon the lower end of the casing is mounted a screw shell l2 and a center contact it as in plug type fuses. The center contact I! is held in position by a screw it which screws into a cylindrical stationary switch contact I8 and holds it within the casing ill in axial position at the bottom thereof.

For engagement with the stationary contact I 8 a cylindrical movable contact 20 is mounted upon one end of a reciprocative contact carrier 22. The lower end of this carrier is cylindrical and 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 0 (whose function will be hereinafter described) seated upon' the support 24, and an insulating washer 28 seated upon the arc ring 26. The are ring 26 has a circular flange or neck 21 extending axially away from the contacts and fitting snugly into a complementary recess in 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 30 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 22c 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, whichliead 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 less in diameter than the diameter of the bore lob (see Figure 5) in the lower part of the casing l6, 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 thespring 36 which normally tends to sep arate the contacts l8 and 26.

To prevent the carrier 22, washer 28, are ring 26 and support 24 from rotating within the bore I 8b 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. With this arrangement the insulating casing I is itself the frame of the circuit breaker which supports and guides the part of the operating mechanism so that a separate frame of metal is not required. This makes the device more compact and less expensive to manufacture.

The mechanism for moving the contact 20 into engagement with contact l8 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 46 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 suflicient 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 46 acts also as a support for a latch 46 which is mounted pivotally 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 46c to engage with an actuating cam as will be presently described. The other end of th latch is turned up slightly and is adapted to be engaged by the actuating cam as will be described. The movable contact 20 is thus pivotally carried by the member 46 adjacent the mid-point thereof. The member 46 does not have any fixed pivot point, but as will be more fully described later, pivots about one end or the other, so that it acts as a floating lever arm.

The thermo-bar 48 is made of united strips of metal having different coeflicients of expansion. The bar is secured at its lower end to the inside wall of the casing H) near the bottom by a rivet 49 which passes through the wall and is connected to the screw shell l2.

To the top of the thermo-bar 48 is attached a conductor which is also connected to the contact carrier 22 so that current entering the device through shell l2 passes through the-thermobar 48, conductor 5|, carrier 22to. contact 28 and leaves the device through contact l8 and center socket contact I6. It should be noted that the movable contact 26, carrier 22, and'the floating lever arm 46 are all electrically at the same potential as the movable upper end of the bimetallic member 48 so that it is not necessary to provide insulation therebetween.

, Themanual means for moving the contact 20 into engagement with contact l8 comprises a cover 50 for the casing In, 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 56 as shown in Figure 6. The cams are oppositely inclined thus bringing their peaks at the same side of the cover. One cam, I80, 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 are depressed 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 160 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 assembly is 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 l8, 2|]. 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 I62 until the parts are in the position of Figure l. 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. To re-engage the contacts l8 and 20 the cover will be rotated clockwise whereby the I02 to slide over and press down the other end of the latch, while the latched end is held in engagement 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 oi the pivot 42 and its block 40 the spring 44 (being stronger than spring will not be compressed but will cause the carrier 22 and block to move as a-unit to compress spring 30. At the end of the travel of carrier 22 when the contacts II and 20 engage any further movement downward oi 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 Gil in the side of the casing l0 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 64 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 12 is cut away at the lower end of the passage 60 in order that the locking bar 62 may be slid downward to 'remove its end from recess 64. But this can only be done when the device has been removed from the fuse socket. For facilitating the removal of the bar, a nub'or thumb piece 66 is provided on its lower end and normally fits in the lower spiral of the screw shell. 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 10 extending through the center of the cover, is provided. This button is supported upon a spiral 0 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 12 is fully expanded and the contacts I8 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 i 8 and 20 separate, the carrier 22 and block 40 are pushed toward the cover by main spring 3|] 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 I3 inside the cover to prevent the button from being pushed through the cover by the spring I2.

To prevent the button 10 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 15 passes through the button and has its ends extending beyond the sides of the button within the countersink. When the ends oi the pin 15 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 01' the button will be limited when the top of the button is flush with the top of the cover. 7

The functions oi! the three springs 30, 44 and 12 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 or the carrier 22 and contact 20 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 motion connection between the indicating button Ill and the block 40 so that actuation of the indicator will not result in movement of the contact 20.

In Figures 7 and 8, I have shown another form 01' means to lock the cover to prevent the device from being used as a switch. This locking means is automatic. The device is the same as that shown in Figures 1 to 3 except that the passage 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 locking 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 86 of Figures 7 and 8 is like the latch 36 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 82 when the conbut at the same time the latch is pivoted to bring.

the finger 81 down a distance suflicient to remove the locking bar from 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 1. 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 the omission of the locking means is exactly the same as the forms previously descr bed.

which the whole of my invention must be crowded the maximum contact separation is comparatively magnetic material such as iron through which the movable contact passes and through which the .arc incipient upon contact separation is drawn.

The internal diameter of the ring 26 is slightly greater than the diameter 01 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 I8. 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, without the benefit of this invention.

Even better results are obtainable with the form of invention shown in Figure 10. In'this form the contact operating mechanism is the same as that previously described. But the casing III] of the device is formed with an annular interior shoulder I I2 upon which rests the arc quenching iron ring I26 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 I I8, within which neck the movable contact I20 slides. The stationary contact H8 is a thick disc lying upon the bottom of the casing III) 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 I26, 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 I22 of less height or thickness than the height or thickness of the contact IIB. This ring I22 cooperates with the ring I26 to produce a powerful arc quenching effect so that with a small contact separation heavy currents may be interrupted. This are quenching feature is claimed in my copending application Serial No. 683,673 filed August 4th, 1933 of which the present application is a division.

In each of the forms shown the contact carrier 28 forms a comparatively close fit with, 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 reduces the pressure on the casing and other parts of the device.

Also assisting in the initial contact separation is the additional compression of the spring 44 incident to the continued movement of the carrier 22 by the cam I02 after the contacts I8 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 44, 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 repellant eifect depends on the proximity of the conductors and the current value. For conductors close together the repellant eifect may become very great for high current values such as are developed upon overload.

Eifective 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 I2 (see Fig. 1) is through the rivet 49 up bimetallic strip 48, through conductor 5|, carrier 22 to contacts 20, I8, and IS. The current path is therefore substantially U-shaped, forming in effect two parallel conductors of which the bimetallic member is one, and the members 22, 20,

I8, I6 are the other. Current flows in opposite direction in these paths (which, due to the compactness of the device, are close together) so that upon a severe overload a considerable force is exerted upon the bimetallic bar 48, in a direction to cause release of the latch 46.

It will be understood that during normal current fiow the electro dynamic effect upon the bimetallic member is negligible but upon a very heavy overload when the current value becomes a multiple of its normal value, the electro dynamic efiect is very powerful and is effective to accelerate the movement of the bimetallic member into position to release the latch 46. Thus on slight overloads the bending of the bimetallic member due to increase in temperature will cause the tripping of the breaker but on very great overloads the bending effect will be assisted by the electro dynamic effect and the latter may be so great, if the overload he suddenly applied, that it will accelerate the tripping of the breaker.

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.

My invention is especially useful in interrupting alternating currents but may also beused 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.

I claim:

l. A circuitbreaker comprising an insulating casing, a rotatable cover, a single set of stationary and movable switch contacts within said casing, said switch contacts completing the circuit upon coming into engagement and breaking the circuit upon their separation, screw shell and center contacts outside said casing and connected to said stationary and movable contacts, mechanism for separating said switch contacts with a snap motion, and a cam formed on said cover for causing said. mechanism to bring said contacts into engagement.

2, A circuit breaker comprising an insulating casing, a rotatable cover, a single set of stationary, and. movable switch contacts within said casing, said switch contacts completing the circuit upon coming into engagement and breaking the circuit upon ther separation, screw shell and center contacts outside said casing and connected to said stationary and movable contacts,

mechanism for separating said switch contacts with a snap motion, and a cam formed on said cover for causing said mechanism to bring said contacts into engagement, and means holding said contacts in engagement, said holding means being releasable by the thermal effect of an overload current in the device.

3. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable switch contacts within said casing, screw shell and center contacts outside' said casing and connected to said stationary and movable contacts, mechanism for separating said switch contacts with a snap motion, and means holding said contacts in engagement, said meansincluding a bimetallic member responsive to the thermal effect of an overload current in the device, and means on said cover and rotatable therewith in one direction to reset said holding means and in the other direction to cause said mechanism to bring said switch contacts into engagement.

4. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable switch contacts within said casing. screw shell and center contacts outside said casing, and connected to said stationary and movable contacts, mechanismfor separating said switch contacts with a snap motion, and means holding said contacts in engagement, said means including a bimetallic member responsive to the thermal effect of an oveload current in the device, and means on said cover and rotatable therewith in one direction to reset said holding means and in the other direction to cause said mechanism to bring said switch contacts into engagement, and means preventing the rotation of said cover while the switch contacts are engaged.

5. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable switch contacts within said casing, screw shell and center contacts outside said casing and connected to said stationary and movable contacts, mechanism for separating said switch contacts with a snap motion, and means holding said contacts in engagement, said means including a bimetallic member responsive to the thermal eifect of an overload current in the device, and means on said cover and rotatable therewith in one direction to reset said holding means and in the other direction to cause said mechanism to bring said switch contacts into engagement, and means operating automatically upon movement of said contacts into engagement to prevent rotation of said cover until said contacts have been separated by overload.

6. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable switch contacts within said casing, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, screw shell and center contacts outside said casing and connected to said stationary and movable contacts, mechanism for separating said switch contacts with a snap motion, and means on said cover for causing said mechanism to bring said switch contacts into engagement, and indicating means projectible from the cover upon separation of said switch contacts and retractible by engagement of said switch contacts.

7. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable contacts within said casing, screw shell and center contacts outside said casing and connected to said stationary and movable contacts, mechanism. for separating said switch contacts with a snap motion, and means holding said switch contacts in engagement, said means including a bimetallic member responsive to the thermal effect of an shell and center contacts mounted thereon, fixed and movable switch contacts mounted therein, means for moving said movable contact with a snap motion, a pivotally mounted bodily movable latch, a thermally responsive element engageable by said latch, and a rotatable cover for said casing. cam means on said cover for moving said latch to cause setting of said latch and engagement of said switch contacts.

9. A circuit breaker comprising a casing, screw shell and center contacts mounted on said casing, separable switch contacts within said casing connected to said screw shell and center contacts, means to separate said switch contacts with a snap motion to break the circuit upon the occurrence of an overload, latch means for moving said switch contacts into engagement, current responsive means for releasing said latch upon overload, a cover capable of rotation in one direction to set said latch and in the other direction to cause engagement of the contacts which break the circuit on overload.

10. A circuit breaker comprising a casing. screw shell and center contacts mounted on said casing, separable switch contacts within said casing connected to said screw shell and center contacts, means to separate said switch contacts with a snap motion, latch means for moving said switch contacts into engagement, current responsive means for releasing said latch upon overload, a cover capable of rotation in one direction to set said latch and in the other direction to cause engagement of the switch contacts, and locking means engageable with the cover when said switch contacts are engaged, to prevent rotation of said cover.

11. A circuit breaker comprising a casing, screw shell and center contacts mounted on said casing, separable switch contacts within said casing connected to said screw shell and center contacts, means to separate said switch contacts with a snap motion, latch means fo'r moving said switch contacts into engagement, current. responsive means for releasing said latch upon overload, a cover capable of rotation in one direction to set said latch and in the other direction to cause engagement of the switch contacts, and locking means engageable with the cover when said switch contacts are engaged, to prevent rotation of said cover, said locking means operating automatically upon rotation of said cover to cause engagement of the switch contacts. J

12. In a circuit interrupter. a pair of relatively movable contacts, one of said contacts when in closed-circuit position being biased to move to open-circuit position, an actuating lever connected at a point intermediate its ends to said contact, operating means for normally supporting said lever adjacent one end, and current responsive means for normally supporting said lever adjacent its other end, said current responsive means removing its support. and causing said movable contact to open the circuit upon the occurrence of predetermined current conditions irrespective of the support of said operating means, and said operating means including means movable to first restore the support of said current responsive means and to thereafter return said movable contact to closed-circuit position.

13. In a circuit interrupter, an insulating casing having a bottom and side walls, a fixed contact I contact carrier in closed position against the bias of said spring, said bimetallic member releasing said lever under predetermined conditions and causing said contact carrier to move to open position, and said operating means ineluding means movable to first return one end oi said lever into engagement with said bimetallic member and to thereafter actuate the other end oi said lever to move said contact carrier to closed position.

14. In a circuit interrupter, a hollow plug of insulating material, a contact shell surrounding said plug and a centercontact on the outside of the bottom of said plug for electrically connecting the circuit interrupter in the circuit, a pair of separable contacts positioned within said plug, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, one of said separable contacts being fixedly mounted on the bottom of the plug and electrically connected through the bottom of the plug directly to said center contact and the other of said separable contacts being movable into and out of engagement with said fixed contact to open and close the circuit, means for biasing said movable contact to open-circuit position, means for retaining said movable contact in closed-circuit position against said bias, said retaining means being releasable in response to the occurrence of predetermined electrical conditions, and manually operable means for returning said movable contact to closed circuit position.

15. In a circuit interrupter, a hollow plug of insulating material, a contact shell surrounding said plug and a center contact on the outside of the bottom of said plug for electrically connecting the circuit interrupter in the circuit, a pair of separable contacts positioned within said plug, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, one of said separable contacts being fixedly mounted on the bottom of the plug and electrically connected through the bottom of the plug directly to said center contact and the other of said separable contacts being slidable axially of the plug into and out of engagement with said fixed contact to open and close the circuit, means for biasing said movable contact to open-circuit position, releasable retaining means for holding said movable contact in closed-circuit position against said bias including a bimetallic element extending along the side wall of the plug and having one end rigidly mounted on said plug and electrically connected to said contact shell and having its other end electrically connected to said movable contact, manually operable means for returning said movable contact to closed circuit position after release thereof, and said releasable means causing opening of the circuit upon the occurrence of predetermined electrical condition irrespective of the position in which said manually operable means is held.

16. A circuit breaker comprising actuating means, a lever pivoted at a point intermediate its ends and acted upon at one end by said actuating means, current responsive means engaging said lever at its other end, movable contact carrying means connected with said lever at its pivot point, a fixed contact, and a movable contact engageable with said fixed contact by pivotal movement of said lever about its current responsive end when said actuating means is operated, means biasing said movable contact away from said fixed contact and causing separation of said contacts when said current responsive means disengages said lever.

1'7. A circuit breaker comprising actuating means, a lever pivoted at a point intermediate its ends and acted upon at one end by said actuating means, current responsive means engaging said lever at its other end, movable contact carrying means connected with said lever at its pivot point, a fixed contact. and a movable contact engageable with said fixed contact by pivotal movement of said lever about its current responsive end when said actuating means is operated, means biasing said movable contact away from said fixed contact and causing separation of said contacts when said current responsive means disengage's said lever, and means causing re-engagement of said lever with current responsive means before said actuating means is again operated for contact engagement.

18. In a circuit breaker, a pair of relatively movable contacts, means urging said contacts apart, a movable contact carrier, a lever pivotally connected at a point intermediate its ends to said carrier, operating means engaging one end of said lever and current responsive means engaging the other end and cooperating to hold said contacts engaged under normal conditions or to cause contact separation upon abnormal conditions, said current responsive means operating independently of said operating means whereby said operating means may not be continuously operated to hold the contacts together during an excess current condition.

19. A circuit breaker comprising an insulating casing, a movable operating member mounted sponsive means for actuating said operating mechanism on overload, said current responsive means being independent of said operating member whereby said contacts may not be held closed on overload, and contact means for engaging complementary contact means on a panel-whereby said breaker may be mounted on a panel, and means preventing the movement of said operating member to separate said switch contacts while the breaker is mounted on a panel.

20. A circuit breaker comprising an insulating casing, a movable operating, member mounted thereon, switch contacts, operating mechanism, current responsive means for actuating said operating mechanism on overload, said current responsive means being independent of said operating member whereby said contacts may not be held closed on overload, and contact means for engaging complementary contact means on a panel whereby said breaker may be mounted on a panel, and means automatically locking said operating member while said switch contacts remain in closed circuit position.

21. A circuit breaker comprising an insulating casing, a movable operating member mounted thereon, switch contacts, operating mechanism, current responsive means for actuating said operating mechanism on overload, said current responsive means being independent of said operating member whereby said contacts may not be held closed on overload, and contact means for engaging complementary contact means on a panel whereby said breaker may be mounted on a panel, and means locking said operating member against movement while said switch contacts casing, screw shell and central contacts on said casing, a single set of separable switch contacts within. said casing, means tending to separate said; contacts, operating mechanism for moving said switch contacts into engagement, current responsive means operable on overload to cause contact separation, and an operating member movable in one direction to move said contacts into engagement and movable in the other direction to disengage said contacts, said current responsive means operating independently of said operating member whereby said contacts may not be held together during an excess current condition.

23. A circuit breaker comprising separable contacts, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, latching means to hold said contacts together, a member bendable in response to the thermal effect of an overload current through said device to release saidlatching means, and said parts being arranged to create a concentration of electro-magnetic flux lines between said bendable member and the other current carrying parts of said device and tending to move said member in direction to release said latching means upon overload.

24. A circuit breaker comprising separable contacts, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, latching means to hold said contacts together, a member bendable in response to the thermal eilect of an overload current through said device to release said latching means, and said parts being arranged to form a pair of proximate current paths with current flowing in opposite directions therein, said bendable member being one ot'said paths and said latching means being the other of said paths, whereby a concentration of electromagnetic flux lines is created tending to move said bendable member in direction to release said latching means upon overload.

25. A circuit breaker comprising an insulating casing of substantially the size and shape of a common screw type plug fuse casing, a rotatable cover on said casing, fixed and movable contacts in said casing, mechanism in said casing. operable by rotation of said cover to cause engagement of said contacts and operable by reversed rotation of the cover to cause disengagement of said contacts, and means in said casing for holding said contacts in engagement but responsive to the thermal effect of an overload current to release said holding means, said mechanism and said means cooperating to prevent said contacts being held in engaged position by said cover during continuance of overload current. v

26. A circuit breaker comprising an insulating casing of substantially the size andshape of a common screw type plug fuse casing, a rotatable cover on said casing, fixed and movable contacts in said casing, mechanism in said casing operable by rotation of said cover to cause engagement oi said contacts and operable by reversed rotation of the cover to cause disengagement of said contacts, and means in said casing for holding said contacts in engagement but responsive to the thermal eflect oi. an overload current to release said holding means and a resilient lost motion connection between said movable contact and said cover, said mechanism and said means cooperating to prevent said contacts being held in engaged position by saidcover during continuance of overload current.

27. A circuit breaker comprising an insulating casing, a rotatable cover, stationary and movable switch contacts within said casing which complete the circuit through the breaker at the moment of their engagement, screw shell and center contacts outside said casing and connected to said stationary and movable contacts, mechanism for separating said switch contacts with a snap motion, and means on said cover for causing said mechanism to bring said switch contacts into engagement and causing, upon reversal of rotation of the cover, said mechanism to disengage said contacts, and indicating means projectable from the cover upon separation of said switch contacts and retractable by engagement of said switch contacts.

28. A circuitbreaker comprising separable'contacts, means causing said contacts to complete the circuit through the breaker at the moment of their engagement, latching means to hold said contacts together, a member bendable in response to the thermal effect of an overload current through said device to release said latching means, and said parts being arranged to create a concentration of electro-magnetic flux lines between said bendable member and the other current carrying parts of said device and tending to move said member in a direction to release said latching means upon overload, and means preventing said contacts from being held closed manually during occurrence of an overload.

29. A circuit breaker comprising fixed and movable contacts. a manually movable member for moving said contacts into and out of engagement, at floating actuating lever between said manual member and said movable contact and having a pivotal connection with said manual member, a member bendable in response to the efiect of an overload current to release said actuating lever, said bendable member acting as a support for said actuating lever whereby said actuating lever pivots about its point of engagement with I said bendable member during manual engagement and disengagement 01' said contacts, said actuating member rotating about said point of pivotal engagement with said manually opering its movement whereby the use of a separate switch frame is made unnecessary.

30. A circuit breaker comprising fixed and movable contacts, a manually movable member for moving said contacts into and out of engagement, a floating actuating lever between said manual member and said movable contact and having a pivotal connection with said manual member, a member bendable in response to the effect of an overload current to release said actuating lever and pivotally supporting said actuating member for movement about one end during manual operation of the switch but releasing said actuating member on overload for pivoting about an axis spaced from said end, and an insulating casing formed. and constructed to provide a meansi'or supporting said manually movable member and guiding its movement whereby the use of a separate switch frame is made unnecessary. 31. A circuit breaker comprising fixed and movable contacts, a manually movable member for spring means acting on said lever between said pivotal supporting means.

32. A circuit breaker comprising fixed and movable contacts, a manually movable member for moving said contacts into engagement, a floating actuating lever between said manual member and said movable contact, means providing a pivotal support for pivotal movement of said lever during manual operation of said contacts into engagement, means providing a pivotal support for pivotal movement of said lever during overload operation of said contacts, said firstnamed means including a member movable in response to overload current to release said lever for pivoting about said overload-operation pivot, spring means urging said lever into engagement with both said pivotal supporting means, said spring means acting on said lever between said pivotal supporting means, and said manually movable member being actuable to return' said lever into engagement with said manual-operation pivotal supporting means prior to return of said contacts into engagement after their release by action of overload current.

33. A circuitbreaker comprising fixed and movable contacts, a manually movable member for causing movement of said contacts into engagement, a floating actuating lever between said manual member and said movable contact, two points about which said lever may pivot, said lever pivoting about one point during manual operation and about the other point during overload operation of said movable contact, spring means between said pivot points urging said lever against said points, a member movable in response to overload currents to remove the support of one of said pivot points and permit pivoting of said lever about said other point.

34. A circuit breaker comprising fixed and movable contacts, a manually movable member for moving said contacts into and out of engagement, a floating actuating lever between said manual member and said movable contact, a member bendable in response to overload currents for causing said movable contact to disengage said fixed contact, said bendable member affording pivotal support for said lever during manual operation of said contacts, and said manually movable member affording a, pivotal support for said lever during operation of said contacts on overload, and spring means between said bendable member and said manually movable member urging said lever against said members.

35. In a circuit breaker, a pair of contacts, one of said contacts being movable to open and close the circuit, a lever arm movable to actuate said movable contact, a spring applying a biasing force tending to move said lever arm when said movable contact is in closed circuit position, a thermally responsive element engaging and normally latching one end of said lever arm against movement due to the bias of said spring, and a man- .ually operable member comprising a cam of inmovement by said spring, said bimetallic member providing a pivot point for said floating arm at its point 01 engagement therewith about which said floating arm is rotatable to normally open and close the circuit, a manually operable member comprising a cam of insulating material upon movement of which the force exerted thereby is appliedto said floating arm at a point to rotate it against the bias of said spring about its end engaging said bimetallic member, and said bimetallic member being movable upon the occurrence of an abnormal condition to release the end of said floating arm and cause it to rotate under the bias of said spring about the point at which the force exerted by said cam of in sulating material is normally applied thereto and thereby move said movable contact to open-circuit position.

37. In a circuit breaker, a pair of con-tacts, one of said contacts being movable to open and close the circuit, actuating means for said movable contact electrically at the potential of the movable contact and including a lever arm, a spring applying a biasing force tending to move said lever arm, a bimetallic member fixedly mounted at one end and having a movable latch portion adjacent its other end normally engaging and latching one end of said lever arm against movement by said spring, said bimetallic member being electrically connected in the circuit adjacent its fixedly mounted end and having a flexible shunt connected thereto adjacent its movable end, said flexible shunt completing the circuit from the movable end of the bimetallic member to said movable contact whereby'said movable contact, said actuating means and said movable latch portion of the bimetallic member are all at the same potential making it unneces- I sary to provide insulation therebetween, and a manually operable member of insulating material having a cam surface thereon for moving said actuating means for the movable contact.

38. In a circuit breaker, a pair of contacts, one of said contacts being movable to open and close the circuit, a floating arm carrying said movable contact, a spring applying a biasing force tending to move said floating arm and said movable contact, a bimetallic member fixedly mounted at one end and movable at its other end, the movable end of said bimetallic member normally engaging and supporting one end of said floating arm and providing a pivot point about which it is rotatable to normally open and close the circuit, means electrically connecting the fixed end of the bimetallic member in the circuit, a flexible shunt connected to a point on the bimetallic member adjacent its movable end and complet- I ing-the circuit to said movable contact whereby said movable end of the bimetallic member, said floating arm and the movable contact carried thereby are electrically at the same potential making it unnecessary to haveinsulat ion therebetween, a manually operable member comprising a cam of insulating material upon movement of which the force exerted thereby is applied to said floating arm at a point to rotate it against the bias oi said spring about its and engaging said bimetallic member, and said bimetallic member being mo abIe upon the occurrence of an ab- I 8 normal condition to release the end of said floating arm and cause it to rotate under the bias of said spring about the point at which the force exerted by said cam of insulating material is normally applied thereto and thereby move said movable contact to open-circuit position.

- 39. In a circuit breaker, a casingof insulating material, a pair of cooperating contacts one of which is movable to open and close the circuit,

released by said current responsive means, anda handle member for normally moving said movable contact between open and closed circuit positions. 40. In a circuit breaker, a casing of insulating material, a pair of cooperating contacts one of which is movable to open and close the circuit, actuating means for said movable contact, said actuating means being supported and guided during movement by the insulating material of the casing, said actuating means including a floating bar connected at one point to said movable contact, current responsive means in latching engagement with said floating bar at another point, means for biasing said floating bar to carry said movable contact to open-circuit position when released by said current responsive means, a handle member for normally moving said movable contact between open and closed circuit positions, said movable contact being movable to open-circuit position when released by said current responsive means irrespective of the position of said'handle member, and said handle member being movable to return said floating bar to position when it is latched by said current responsive means.

41. In a circuit breaker, a casing of insulating material, a pair 01' cooperating contacts one of which is movable to open and close the circuit, actuating means for said movable contact, said casing of insulating'material forming the frame of the circuit breaker and supporting and guiding the actuating means during its movement, said actuating means including a floating bar connected at one point to said movable contact, a current responsive latch normally holding said floating bar at another point, biasing means for to causing said floating bar to carry said movable contact to open-circuit position when released by said current responsive latch, and a handle member ior normally moving said movable contact between open and closed-circuit positions. so 42. In a circuit breaker, easing of insulating material, a pair 0! cooperating contacts one of which is movable to open and close the circuit. actuating meansfor said movable contact. said casing of insulating material forming the frame or the circuit breaker and supporting and guiding the actuating means during its movement,

said actuating means including a floating bar.

connected at one point to said movable contact, a current responsive latch normally holding said floating bar at another point, biasing means for causing said floating bar to carry said movable contact to open-circuit position when released by said current responsive latch, and a handle member of insulating material having a cam surface formed of the insulating material for operating said actuating means to normally move the movable contact between open and closedcircuit positions, and said movable contact being movable to open circuit position upon the release of said floating bar by the current responsive latch irrespective of the position in which the handle member may be held.

43. In a circuit breaker, a casing of insulating material, a pair of cooperating contacts one of which is movable, to open and close the circuit, actuating means for said movable contact, said actuating means including a movable bar and a slidable member, said movable bar being connected at one point to the movable contact and being normally movable about another point as a pivot, said casing of insulating material forming the frame of the circuit. breaker and having means formed therein for guiding the movement of said slidable member, a current responsive latch normally holding one point of said actuating means, a spring for moving said movable contact to open-circuit positionupon the release of the actuating means by said current responsive latch, a handle member for normally moving said movable contact between open and closed-circuit positions, and said movable contact being movable to open-circuit position upon release of said actuating means by said current responsive latch irrespective of the position in which said handle member may be held.

44. A circuit breaker comprising flxed and movable contacts, a manually movable member for causing movement of said contacts into engagement, a floating actuating lever between said manual member and said movable contact, two points about which said lever may pivot, said lever pivoting about one pivot point during manual operation and about the other point during overload operation of said movable contact, spring means between said pivot points urging said lever to rotate in opposite directions about said points, a member movable in response to overload currents to remove the support of one of said pivot points and permit pivoting of said lever about said other point and thereby carry said movable contact out of engagement with the flxed contact, said movement in response to overload currents taking place irrespective of the position in which said manual member may be held, and said manual member being movable to return said lever to position where it is again supported at said point where support was removed.

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