US2650276A

US2650276A - Circuit breaker

Info

Publication number: US2650276A
Application number: US161493A
Authority: US
Inventors: Harry P Sparkes
Original assignee: Anchor Manufacturing Co
Current assignee: Anchor Manufacturing Co
Priority date: 1950-05-12
Filing date: 1950-05-12
Publication date: 1953-08-25
Anticipated expiration: 1970-08-25

Description

Aug. 25, 1953 H. P, sPARKEs CIRCUIT BREAKER 4 Sheets-Sheet 1 Filed May 12, 1950 y@ W 4f J4 5,? wa m94 H3 jaa' (if f4 jaa /fe .if

L? 2,94 iff F@ [We lai/07 Aug. 25, 1953 H. P. SPARKES 2,650,276

CIRCUIT BREAKER Filed May 12, 1950 4 Sheets-Sheet 2 Aug. 25, 1953 H. P. sPARKEs CIRCUIT BREAKER 4 Sheets-Sheet 3 Filed May 12, 1950 H. P. SPARKES CIRCUIT BREAKER Aug. 25, 1953 4 Sheets-Sheet 4 Filed May 12, 1950 [m6275071 fr? j? m'es /Z y j? mfg/f.

Patented Aug. 25, 1953 UNITED STATES PATENT OFFICE Anchor Manufacturing Company,

Boston,

Mass., a corporation of Massachusetts Application May 12, 1950, Serial No. 161,493

16 Claims.

This invention relates to circuit breakers and more particularly to circuit breakers of the type used in vehicles such as airplanes or in other applications which require that the weight and size of the circuit breaker be kept to a minimum.

With the rapid increase in size and complexity of military and commercial airplanes, there has been a corresponding increase in size and complexity of their electrical supply systems. The electrical loads and number of distribution circuits have greatly increased in number in such modern aircraft requiring control equipment for switching and overload protection which is small in size and light in weight, but which must also be rugged and positive in operation under extreme conditions of temperature and the large forces resulting from acceleration and gravity.

Accordingly the principal objects of this invention are to provide a circuit breaker or solenoid operated switch which is very small and compact in size, which is light in weight, which is dependable and positive in operation, which requires a very low tripping current, which reduces heating and temperature rise to a minimum, which can be mounted adjacent similar circuit breakers without overheating, which has provision for both normally open and normally closed electrical load contacts, which can be tripped and reset manually, which meets the Army and Navy specifications for such type of apparatus, which can be produced by mass production techniques, and which advances the switch art generally.

In a principal aspect the invention contemplates a circuit breaker comprising one or more pairs of electrical load contacts biased in a set or normal position, for example, by a spring. Tripping means for automatically transferring the contacts are provided which include one or more latch pieces carried with or in a block urged by a spring along a path of travel from a latched position to a released position. 'I'he block and latch piece or pieces are restrained in their latched position by the open position of detent means which is moved to a closed position by means including actuating means such as a, solenoid or bimetallic strip to release the block and latch pieces when the electric current through the actuating means exceeds a predetermined value. Preferably the detent means is an armature which is moved from its open position to a closed position wherein it releases the block and latch piece by the magnetic flux induced in a magnetic circuit by a solenoid when the current therethrough exceeds a predetermined value. Lever means interposed in the path of the block are arranged to transfer the contacts from their set position by the travel of the block upon its release by the actuating means. Resetting means are provided for manually returning the block and latch pieces to their latched position and conjointly transferring the contacts.

In a more speciiic aspect the slidable block is carried by two latch pieces, the block and pieces being arranged to slide in parallel relationship upon a portion of the magnetic circuit adjacent the armature. The end of the armature is provided with rollers which contact the ends of the latch pieces respectively when the armature is in the open position thereby to restrain the block and latch pieces in their latched positions. The configuration of the magnetic circuit is made substantially rectangular and the solenoid is wound upon the side or leg thereof opposite the side wherein the armature is hinged or otherwise movakly arranged. The energization of the solenoid induces a magnetic ilux in the magnetic circuit of suiicient magnitude to move the armature to its closed position when the solenoid current exceeds a predetermined value. The magnitude of such current as is required to move the armature to its closed position is determined by the position of an adjustable stop, for example, a threaded pin or screw, which limits the air gap between the armature and the adjacent portions of the magnetic circuit. To reduce to a minimum the force exerted upon the armature by the spring actuating the block, the mechanical advantage gained by the use of one or more levers is employed. For example, respective levers are pivotally attached at an intermediate point on opposite sides of the block so that one end of each lever bears against a respective latch piece. The opposite end of each lever is maintained sta'- ti'onary with respect to the block, for example by pivotally contacting a leaf spring or other member extending from the supporting structure. Greater eiective leverage is obtained by employing a lever, bent for example. at the point of pivotal connection to the block so that the component of restraining force exerted by the armature upon the latch pieces (and therefore upon the block) parallel to the path of travel of the block is relatively effectively greater with respect to the total force exerted by the armature than the parallel component of the force exerted by the spring interposed between acortar@ the block and the casing is with respect to the total spring force.

In another aspect a rocking toggle member is bent at its midpoint so that the ends thereof, one or both of which are provided with movable contacts, form an obtuse angle. The rocking member is pivotally supported at its midpoint preferably being provided with notches which engage the bifurcated end of a strap which being made of conducting material provides an electrical path to the moving contacts. A toggle arrangement including a biasing spring is provided for maintaining the rocking member at either end of its path of travel so that the movable contacts upon the ends thereof are alternatively maintained in either an open position or in engagement with corresponding stationary contacts carried by the support. The toggle arrangement comprises a hollow actuator which also acts as a manual lreset lever for returning the block and latch pieces to their latched position which actuator is pivotally attached to the casing or cover therefor immediately above'the pivot point of the rocking member and has telescoping therein a member such as a pin. The 'rounded lower end of the pin is held against the rocking member by a spring thereby to maintain the rocking member at either end of its path of travel so that the contacts are biased in either an open or .closed position as the case may be. The actuator is also providecLwith one or more extensions interposed in the path of the block so that the movement of the block upon its release by the armature transfers the contacts from the set or on position.

These and other objects and aspects will be apparent from the following description of an illustrative specific embodiment. of the invention referring to drawings in which: i

Fig. 1 is a top view of one embodiment of the invention with cover partially broken away;

Fig. 2 is a bottom view showing the terminal block;

Fig. 3 is a sectional View online 3 3 of Fig. l;

Fig. 4 is a sectional view on line 4-4 of Fig. 3;

Fig. 5 is a sectional View on line 5-5 of Fig. 3;

Fig. 6 is a fragmentary sectional view on line 6-6 of Fig. 5 showing the movable block and latch pieces in the latched position;

Fig. 7 is a similar view to that shown in Fig. 6 with the movable block in elevation moved to the released position;

Fig. 8 is an isometric view showing the details of the coverplate;

Fig. 9 is an isometric view of the conducting straps comprising the electrical circuit;

Fig. 10 is an isometric view of the armature and block and latch assembly; and

f Fig. l1 is a partial elevation view in section showing a second configuration wherein the contacts are free tripping.

Referring particularly to Figs. 2 and 3 of the drawings, the circuit breaker illustrated comprises a terminal block lll, preferably molded of an insulating plastic material, upon which block are supported the magnetic and electric circuitsy and the tripping mechanism as will be described in detail hereinafter. The bottom of the block Il) is provided with a serrated barrier l2 (Fig. 2) molded integrally therewith to form a plurality of recesses wherein are located the heads of screws for terminals tI-t5 which are used to connect the circuit breaker with the leads from its external load and control circuits (not shown). Each of the terminals tI-t consists of an insert having a threaded axial recess to receive the correlated screw for securing the lug (not shown) of a connecting conductor. The outer surface of the inserts are preferably knurled so that they can be securely molded into the block I8.

The upper end of the insert i4 (Fig. 9) for the terminal t2 is slotted to accommodate 'a strap I6 of a conducting material, theA strap being silver soldered o'r otherwise secured in the slot in the insert in an offset position so that the strap is located centrically with respect to the width of the block it. A second conducting strap I8 extends directly upwardly at one corner of the block i9 from the insert 20 of the terminal t3, the strap preferably being formed as an integral part of the insert. The insert 22 of the terminal tl has silver soldered thereto a conducting strap 24 which laterally' extends to the opposite corner of the block i9 being cut away as at 26 so that it avoids the terminal t5.

To complete the electrical circuit from terminal tl to the movable contacts, the strap 24 has attached to its upwardly projecting end the lower end of a conducting strap 28. The ends of the

straps

24 and 28 are lapped and fastened together by means of a ilat headed screw 30. The strap 28 is bent at a right angle at an intermediate point so that a lateral portion thereof extends obliquely inwardly to a central position as is best shownin Fig. 4. The centricaly located end 32 of the strap 23 is stepped upwardly and bifurcated, as is shown in Fig. 9, having two upwardly projecting fingers 34 which respectively engage notches in the upturned lips 33 (Fig. 3) located at the midposition of a bent rocking toggle member or arm 40 carrying the movable contacts si and s2 at its respective ends.

The toggle arm 49 'is pivoted on the fingers 34 with a rocking motion by means which will be described hereinafter so that the movable contacts si and s2 at the ends thereof are alternatively brought into electrical engagement with stationary contacts s3 and s4 respectively. The stationary contact s3 is secured to one end of a conducting 'strap 42 (Fig. 9) which is bent normally at an intermediate point so that the opposite end thereof lies adjacent the upwardly extending end of the strap i8, the straps being fastened together by means of a flat headed screw 44. The stationary contact s4 is similarly carried by a strap 46 which connects with the strap I6 extending from the terminal insert i4 as has been described heretofore, by means of the at headed screw 43. A mica arc shield 49 having apertures for the stationary contacts ls3 and s4 is laid upon the top of the conducting straps 42 and 46 thereby to separate the contacts from the remaining gliemesnts of the. circuit breaker as is shown in From the foregoing, it will be evident that upon the positioning of the toggle arm 40, as is shown in Fig. 3 so that the contacts s2 and s4 are in engagement, completes an electrical circuit from terminal tl to terminal t2; and conversely the positioning of the toggle arm so that the contacts sl and s3 are in engagement completes an electrical circuit from terminal tl to terminal t3. The above-mentioned positioning of the 'toggle arm 40 may be accomplished manually by means of an actuator 50 which actuator also carries the spring means for biasing the toggle arm in either of its extreme positions as will be described below. As is best shown in Fig. 3, the actuator 5U Surrounding the opposite end of the tube 5| is a sleeve 53 having a pair of oppositely disposed trunnions 54 (see also Fig. l), journaled in recesses in the top of a casing 55 which mounts on top of the terminal block I8 to enclose the remaining elements of the circuit breaker. The trunnions 54 are held in the casing recesses by a cover 58 which is attached to the casing by means of screws 51 engaging inserts in the top of the casing 55. Telescopingly arranged within the tube 5| is a member such as the pin 58 the upper end of which is contacted by a spring 58 compressed within the tube recess. The lower end of the pin 58 is spherically shaped and bears against the toggle member 48 thereby biasing such member in either of its extreme limits of travel.

Provision is also made for tripping the contacts of the circuit breaker automatically. To this end, the actuatorl 58 has extending from the lower end thereof two arms 88 which are formed integrally and bent at right angles to a. central portion 82 having an aperture so that it can be pressed over the tube 5| beneath the trunnion sleeve 53. With the actuator in a rst position as shown in Fig. 3, the arms 88 bear against the end of a slidable trigger block 85. As is best shown in Fig. 10, the central portion of the block 85 is provided with a circular aperture 84 wherein is enclosed a trigger spring 88 (Fig. 3) one end of which bears against the bottom of the recess. The other end of the spring 68 seats in a recess in a separator or insert 68 which separates the conducting straps 48 and |8 from the low reluctance elements of a magnetic circuit as will be described in detail below.

The block 85 is restrained by a detent member so that it cannot move the actuator arms 88 and thus rock the toggle arm 48. The detent member is also the armature 18 of the above mentioned magnetic circuit. The end of the armature 18 is provided with two rollers 12 which bear against the respective upturned ends 14 of two latch pieces 15 to restrain the trigger block 85 in its latched position shown in Fig. 3. As is best shown in Fig. 10, the bottom of the trigger block 85 has two longitudinally disposed grooves 18 whose depth is slightly more than the thickness of the latch pieces 15 so that the pieces extend slightly below the block. Similar grooves `are provided in the front face of the block 85 to accommodate the upturned ends 14. The top of the block 85 is provided with a protruding boss 11 whose upper wedge-shaped portion, when the block is in the latched position shown in Fig. 6, engages the beveled under surface of the strap 48 thereby to insure that all elements are in exact position so that an accurate calibration can be secured which will permit the circuit breaker to repeat at temperatures varying over a very wide range and without requiring close manufacturing limits.

To reduce the restraining force exerted by the armature 18 to a minimum, two bent levers such as the angular displaced dogs 88 are pivotally attached to the block 85 by means of pills' 18 (Fig. 3) so that the dogs can rotate in deepslots 82 (Fig. 10) in the rear o! the block. The lower end or tail 8| of each dog 88 engages'al rectangular notch cut in the side of the corresponding latch piece 15, the tails being prevented from leaving the notches by the upturned projections 84 respectively. A finger 88 at the opposite end of each dog 88 engages a mating nnger 88 (Fig. 3) extending downwardly from a respective cantilever spring 88 one end o1' which is inserted in a slot in the plastic insert 88 so that the tip of the ilnger 88 acts as a fulcrum for the dog 88 whereby a. mechanical advantage of as great a value as 8 may be readily obtained. An additional mechanical advantage is obtained by angularly displacing the dog 88 at the pin 18 so that a ratio of approximately 2:1 exists between the cosine of the .angle formed by the vector of the force exerted by the trigger spring 88 and a line normal to the lever arm extending from the point of vcontact between the

fingers

88 and 88 and the center of the pin 18 and the cosine of the angle formed by the vector of the restraining force exerted upon the end 8| of the dog'by the associated latch piece 15 and a line normal to the lever arm extending from the point oi contact between the ilngers 88 and 88 and the point of contact of the dog end 8| and the associated latch piece 15. that is, the component of the restraining force acting parallel to the path of travel of the block exerted by the rollers 12 of the armature 18 upon the upturned ends 14 of the latch pieces 15 and the front face of the block 85 is relatively approximately twice as eiective with respect to the total force exerted by the armature as the parallel component of the force exerted b v the spring 88 is to the total' rtripping occurs the above described relation between the vectors of the forces reverses and the ratio is reduced from 2:1 to 1:1 by a slight forward motion of the block, a feature which de creases the trip time and aids in positive action of the device.

The required magnetic force for closing the armature is further reduced by beveling the front face 0f the latch piece ends 14 against which the rollers 12 bear so that a slight movement of the armature 18 brings it past the dead center point whereupon the force of the trigger spring 88 aids rather than hinders the closing thereof.

Upon the closing of the armature 18 by magnetic ilux induced in the magnetic circuit as will be described in detail below, the latch pieces 15 are no longer restrained so that they are slid along the top of a portion of the magnetic circuit adjacent the armature to the position shown in Fig. '1. The tripping spring 88 also moves the block 85 and the actuator arms 88 until the side of the arms opposite the block come into contact with the top portion of a second plastic separator or insert 84 for separating the components of the magnetic and electrical circuits.

The above mentioned magnetic circuit of which the armature 18 is one element also includes two inverted L-shaped

straps

88 and 98 of a low magnetic reluctance material, for example mild steel. The lower end of the vertical leg of the strap 88 is provided with two projecting protuberances such as the flngers |88 which extend into respective recesses in the terminal block I8. Similar fingers are also provided upon the end of the corresponding leg of the strap 88. As is best shown in Fig. 10. the end lateral leg of the strap 88 is bifurcated having two iingers or tines |82 between which is pivotally supported the armature 18.- The pivotal connection or hinge consists of a pin |83 which extends through assauts aligned apertures near the ends of the tines to shield 49 is set in place over the stationary conengage a transverse aperture positioned near the longitudinal midpoint of the armature. amature 10 is statically and dynamically balanced thereby substantially overcoming the eiiects of vibration,.shock, gravity and acceleration.

The movement of the armature towards its closed position is limited by a stop piece E04 of a low reluctance material which is attached beneath the lateral leg of the strap 95 by means of two at headed screws |05. The top and one end of the stop piece |04 are grooved to receive the amature biasing spring 92 mentioned above. A shim |06 of brass or other high reluctance material is interposed between the stop piece |06 and the strap 96 so that the armature does not freeze in the closed position when it is in contact with the stop piece as is shown in Fig. 7.

The movement of the armature 'i0 in the opposite direction to its open position is limited by a stop such as the head of an adjustment screw |08 (Figs. 3 and 10') which is contacted by the beveled end 09 of the armature opposite the rollers 12. The screw |08 threadingly engages an aperture in the magnetic circuit strap 98 and is locked in position by means of a circular checknut H (Fig. 3). From the above it will be evident that rotating of the screw M19 will either raise or lower the head of the screw with 'respect to the strap 98 and therefore with respect to the pivot point of the armature l0. It will be further evident that the raising of the screw |08, decreases the air gap between the stop piece |04 and end of the armature'l, so that the magnetic ux required to close the armature against the force of the biasing spring 92 is decreased;l

and conversely lowering the screw increases the air gap so that the magnetic flux required to close the armature is increased. To facilitate rotating the screw H08, both the end of the screw body and the corresponding end of the checknut ||0 are provided with transverse slots vfor a screw driver or other adjusting tool'. A circular aperture provided in the mica arc shield i9 and the conducting strap recessed as at M2 (Fig. 9) so that the screw driver can be inserted in the slots by removal of the cover plate 57i.

'Ihe magnetic circuit is completed by a core piece I i4 which extends between the vertical legs of the

straps

96 and 98 being secured thereto by means of the screws H6. The core piece H4 is circular in cross section to accommodate a plastic spool ||8 whereuponis wound the solenoid L for inducing the magnetic iiux in the magnetic circuit. vThe solenoid L comprises a plurality of turns of an insulated conductor, the respective ends of which are connected by soldering to lugs |20 on-the ends of the inserts of terminals t4 and t5.

The circuit breaker is assembled by rst mounting the `elements of the magnetic circuit on the top of the terminal block l0 with the iingers |00 engaging the recesses in the block. The `separa'tors 68 and 94 are then inserted respectively between the magnetic circuit strap 96 and the conducting strap I6 and the magnetic strap 98 and the conducting straps I8 and 24. The tripping block 65` and associated parts are assembled on thetop of the magnetic circuit strap 96 and secured in place by attaching the conducting strap 46` to the strap I6 by means of f the screw'48"which also lockstthe spacer 68 in place. The other spacer`p94 is secured in an analogous manner by attachingthestraps 28 and 42 to the straps 24 and I9 respectively. The mica tacts s3 and fc4 before the outer casing 55 is set in andslid overthe parts assembled as described above. '.'iii'e casing 55 is secured in place by two oppsed screws 22 which extend through clearance holes in the casing to engage threaded apertures in the oppositesides of the separator 68. The toggle arm is placed on the fingers 34 at the end: oi the conducting strap 28 and the trunnions 54 of the actuator 50 placed in the journal recesses in the top of the casing 55. The trunnions 54 are held in place by the cover plate l'which is secured by the screws |51. The above described relay is connected to its external circuits in the conventional manner, the terminals tI-t3 connecting to the circuit to be controlled; the solenoid L being connected in the same or a separate control circuit by the terminals t4 and t5. With the actuator handle 52 moved to the set position shown in Fig. 3, the contacts s2 and s4 are closed and the contacts sl and s3 are in the open positions. vThe movement of the actuator to the set position also causes the arms to force the trigger block 65 into lthe position shown in Fig. 6, wherein the block is latched by the armature 'l0 as'described heretofore. The contacts can be transferred so that contacts 82 and s4 are open and s| and s3 are vclosed by rocking the toggle member 40 by movement of the actuator 50 to its opposite position from that shown in Fig. 3. Such movement may be accomplished manually by means of the handle 52 whereupon the trigger block is still restrained by the armature 'i0 as is shown in Fig. 6. The automatic movement of the actuator 50 results from the forcing of the block against the arms 60 by the action of the spring 66, when the block is released by the armature 10 upon the iiow of a current through the solenoidL of a suilicient magnitude so that the resultingfiux in the magnetic circuit overcomes the biasing action of the spring 92. The position of the various tripping elements after being automatically tripped is shown in Fig. 7. The circuit breaker is reset by manual movement of the actuator 50 to the set position as described above.

The second embodiment of the circuit breaker shown. in Fig. 11 is analogous inmost respects to the above described embodiment, its similar parts being identied by the same indicia with the exception of its toggle member 40a and actuator arms 60a which are altered so that it trips free. In the embodiment of Fig. 11 the contacts s2 and s4 are replaced by a iinger 4| which is riveted to the underside of the right hand end of the toggle member 40a so that the hooked end of the finger is in the path of travel of the trigger block 65. The obtuse angle at which the toggle member 4| is bent is such that the actuator 50 is moved to a vertical position as the contacts sl and s3 are opened by the iinger as the actuator is contacted by the trigger block 65 upon the release thereof by the armature 10.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall Withinthe scope of the'appendecl claims.

I claim:

l. A circuit breaker comprising at least one` pair of electrical contacts one of `which is .movable'; means for biasing the movable one of said contactsina set position; tripping means including a slidably arranged block, a spring-for urging theblocl; along a path of travel from a latched position to a released position, and lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from their set position upon the movement of the block to its released position; detent meansV for restraining the block in its latched position including a lever arrangement pivotally attached to the block with one end bearing against a relatively stationary portion of the circuit breaker to act as a fulcrum whereby the force exerted by the detent means against the block to overcome the force of the spring is reduced; magnetic means including a solenoid for releasing the detent means so that the block is moved along its path of travel by the spring to transfer the contacts when the current through the solenoid exceeds a predetermined value; and resetting means for returning the block to its latched position and conjointly transferring the contacts to their set position.

2. A circuit breaker comprising at least one pair of electrical contacts one of which is mov able; meansincluding a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including a latch piece slidably arranged with respect' to the magnetic circuit to move along a p'ath of travel from a latched position wherein the latch piece is restrained by the armature in its open position to a released position, a block carried by said latch piece, and a spring bearing against said block to urge conjointly the block and latch piece to the released position; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon the release of the latch piece by the movement of the armature to its closed position; and resetting means for returning the block and latch piece to their latched position and conjointly transferring the contacts to their set position.

3. A circuit breaker comprising at least one pair of electrical contacts one of which is movable; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including two latch pieces arranged to slide in parallel relationship on-a portion of the magnetic circuit, a block carried by the latch pieces, a spring urging the block and latch pieces along a path of travel from a latched position wherein the block and latch pieces are retrained by the armature in its open position to a released position; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon the release of the block and latch pieces by the movement of the armature to its closed a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including a usA position; and resetting means for returning the pair of electrical contacts one of which is mov- I able; an enclosing casing; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open t0 latch piece arranged to slide on a portion of the magnetic circuit, a block carried by the latch pieceL a spring interposed between the casing and one end of the block for urging the block and latch piece along a path of travel from a latched position wherein the block and latch piece are restrained by the armature in its open position to a released position and a lever pivotally attached at an intermediate pointl to the block so that one end thereof bears against the latch piece, the opposite end of the lever being maintained stationary with respect to the block to act as a fulcrum thereby reducing the force exerted upon the armature by the action of the spring; lever means interposed in the path ofthe block and connected with said movable contact to transfer the contacts from a set position upon the release of the block and latch piece by the movement of the armature to its closed position; and resetting means for returning'the block and latch piece to their latched position and conjointly transferring the contacts to their set position.

5. A circuit breaker comprising at least one pair of electrical contacts one of which is movable; an enclosing casing; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including two latch pieces arranged to slide in parallel relationship on a portion of the magnetic circuit, a block carried by the latch pieces, a spring interposed between the casing and one end of the block for urging the block and latch pieces along a path of travel from a latched position wherein the block and latch pieces are restrained by the armature in its open position to a released position, and two levers each pivotally attached at an intermediate point to a respective side of the,

block so that one end thereof bears against respective latch pieces, the opposite end of each lever being maintained stationary with respect to the block to act as a fulcrum thereby reducing the force exerted upon the armature by the action of the spring; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon the release of the block and latch pieces by the movement of the armature to its closed position; and resetting means for returning the block end latch pieces to their latched position and conjointly transferring the contacts to their set position.

6. A circuit breaker comprising, at least one pair of electrical contacts one of which is movable; an enclosing casing; meansicludlng a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a. closed position when the solenoid currentexceeds a predetermined value; tripping means for the movable one of said contacts including a latch piece arranged to slide on a portion of the magnetic circuit, a block carried by the latch piece, a spring interposed between the casing and one Vend of the block for urging the block and latch piece along a path of travel from a latched position wherein the blockand latch piece are restrained by the armature in its open position l1 to a released position, and a lever pivotally attached at an intermediate point to the block so that one vend thereof bears against the latch piece, the opposite end of the lever being maintained stationary with respect to the block to 5 act as a fulcrum thereby reducing the force exerted upon the armature by the action of the spring, the lever being bent at its point of attachment to the block so that the effective com-'Wi ponent oi' the restraining force exerted parallel 10 to the path of travel of the block by the armature is relatively greater than the parallel effective component o1' the force exerted by the spring; lever means interposed inthe path of the block and connected with said movable contact to transfer the contacts from a. set position upon the release of the block and latch piece by the movement of the armature to its closed position; and resetting means for returning the block and latch piece to their latched position and conjointly transferring the contacts to their set position. v

7. A circuit breaker comprising at least one pair of electrical contacts one of which is mova-v ble; an enclosing casing; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic ilux therein to move the armature from an ,open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of s ald contacts including two latch pieces arranged to slide in parallel relationship on a portion of the magnetic circuit, a block carried by the latch pieces, a spring interposed between the casing and one end of the block for urging the block and latch pieces along 'a path of travel from a latched position wherein the block and latchpieces are restrained by the armature in its open position to a released position, and two levers each pivotally attached 40 at an intermediate point to a respective side of the block so that one end thereof bears against a respective latch piece, the opposite end of each lever being maintained stationary with respect to the block to act as a fulcrum thereby reducing the force exerted upon the armature by the action of the spring, the levers being bent at their point of attachment to the block so that the effective component of the restraining force exerted parallel to the path of travel of the block by the armature is relatively greater with respect to the total force exerted by the armature than the parallel eective component of the total force exerted by the springs; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon the release of the block and latch pieces by the movement of the armature to its closed position; and resetting means for returning the block and latch pieces to their latched position and conjointly transferring the contacts to their set position.

8. A circuit breaker comprising at least one pair of electrical contacts one of which is movable; a magnetic circuit of low reluctance mate--A rial formed into an essentially rectangular configuration, one of the sides thereof having a hinged portion acting as an armature, a spring biasing the armature in an open position, and 'a solenoid Wound about a second side of the magnetic circuit for inducing a magnetic flux therein to move the armature from the open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including a latch piece slidably arranged with respect to the 12 magnetic circuit, a block carried by the latch piece, a spring conjointly urging the block and latch piece along a path of travel from a latched position wherein the block and latch piece are restrained by thev armature in its open lposition to a released position; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon the release of the block and latch piece by the movement of the armature to its closed position; and resetting means for returning the block and latch piece to their latched position and conjointly transferring the contacts to their set position.

9. A circuit breaker comprising at least one pair of electrical contacts one of which is movable; a magnetic circuit of low reluctance material formed into an essentially rectangular conguration, one of the sides thereof having a hinged portion acting as an armature, a spring urging the armature so as to increase the air gap between the armature and the adjacent portions of the magnetic circuit, an adjustable stop for limiting the movement of the armature thereby determining its open position, and a. solenoid wound about an opposed side of the magnetic circuit for inducing a magnetic flux therein to move the armature from the open to a closed position when the solenoid current exceeds a value determined by the adjustment of the stop; tripping means for the movable one of lsaid contacts including a latch piece slidably arranged with respect to the magnetic circuit, a block carried by the latch piece, a spring conjointly urging the block and latch piece along a path of travel from a latched position wherein the block and latch piece are restrained by the armature in its open position to a released position; lever means interposed in the path of the block and connected with said movable contact to transfer the contacts from a set position upon therelea-se of the block and latch piece by the movement of the armature to its closed position; and resetting means for returning the block and latch piece to their latched position and conjointly transferring the contacts to Itheir set position.

10. A circuit breaker comprising at least one pair of electrical contacts one of which is movable; means including a low reluctance magnetic circuit having a hinged portion forming an armature and a solenoid for inducing a magnetic ilux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means `for the movable one of said contacts including a latch piece slidably arranged with respect to the magnetic circuit, a block carried by the latch piece, a spring conjointly urging the block and latch piece along a path of travel from a latched position to a released position, a roller carried by the armature and contacting the latch piece in the open .position of the armature thereby to restrain the block and latch piece in' the latched position; lever means interposed in the path oi' the'block and connected with said movable contact to transfer the contacts from aset position upon the release of the block and latch piece by the movement of the armature to its closed position; and resetting means for returning the block and latch piece to their latched position and conjointly transferring the contacts to their set position.

11. A circuit breaker comprising at least one pair of electrical contacts one of which is mov- 13 able; means including a, low reluctance magnetic circuit having a hinged portion forming an armature provided'with rollers on one end thereof, and a. solenoid for inducing a magnetic ux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including two latch pieces arranged to slide in parallel relationship on a portion of the magnetic circuit adjacent the end of the armature carrying the rollers, each of the latch pieces having a shoulder at one end thereof, a block carried by the latch pieces, a spring conjointly urging the block and latch piece along a path of travel from a latched position to a released position, the rollers carried by the armature contacting the respective shoulders of the latch pieces in the open position of the armature thereby to restrain the block and latch pieces in the latched position, the surfaces of shoulders being chamfered so that the force exerted by the spring assists the magnetic flux in moving the armature to its closed position; lever-means interposed in/ the path of the block and connected with said movable contact to transfer the contacts from a' set position upon the release of the block and latch pieces by the movement of the armature to its closed position; and resetting means for returning the block and latch pieces to their latched position and conjointly transferring the 'contacts to their set position.

l2. A circuit breaker comprising an enclosing casing having an open end, a terminal block closing said end, two pair of electrical contacts positioned at the opposite ends of the casing,

each pair including a stationary contact and a movable contact, two conducting straps each carrying a stationary contact and extending respectively along the inner surfaces oi opposed walls of the casing to lthe terminal block, a rocking member carrying the movable contacts at the respective ends thereof, a third conducting strap extending along one of the casing walls from the terminal block and having an end upon which is pivotally mounted the rocking member so that the movable contacts can be selectively transferred to make electrical contact with a corresponding stationary contact; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the -solenoid current exceeds a predetermined value; spacers inserted between the conducting straps and the magnetic circuit so that the straps and magnetic circuit are held in position by the casing; tripping means for the movable one of said contacts including a latch piece arranged to slide along a portion of the magnetic circuit adjacent the armature, a movable block carried by the latch piece, a spring conjointly urging the movable block and latch piece along a path of travel from a latched position wherein the movable block and latch piece are restrained by the armature in its open position to a released position; lever means interposed in the path of the movable block and connected with said movable contact to transfer the contacts upon the release of the movable block and latch piece by the movement of the armature to its closed position; and resetting means for returning the movableV block and latch piece to their latched position and conjointly retransferring the contacts.

13. A circuit breaker comprising an enclosing 14 casing having an open end, a terminal block closing said end, two pair of electrical contacts positioned at the opposite ends of the casing. each pair including a stationary contact and a mov able contact.l two conducting straps each carrying a stationary contact at one end thereof respectively, the other end. of each connecting with the terminal block, a rocking member carrying the movable contacts at the respective ends thereof, a third conducting strap connecting with the terminal block and having an end upon which is pivotally mounted the rocking member so that the movable contacts can be selectively transferred to make electrical contact with a corresponding stationary contact; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including a latch piece arranged to slide along a. portion of the magnetic circuit adjacent the armature, a

' movable block carried by the latch piece, a spring conjointly urging the movable block and latch piece along a path of travel from a latched position wherein the movable block and latch piece are restrained by the arm-ature in its open position to a released position, lever means interposed in the path of the movable block and connected with said movable contact to transfer, the contacts upon the release of the movable block and latch piece by the movement of the armature to its closed position; and resetting means for returning the movable block and latch piece to their latched position and conjointly retransferring the contacts.

14. A circuit breaker comprising an enclosed casing having an open end, a terminal block closing said end, two pair of electrical contacts positioned at the opposite ends of the casing, each pair including a stationary contact and a movable contact, twc conducting straps each carrying a stationary contact at one end thereof respectively, the other end of each connecting with the terminal block, a rocking member bent and notched at its midpoint so that the ends form an obtuse angle, each end carrying a movable contact, a third conducting strap connecting with the terminal block and having a bifurcated end which engages the notches of the rocking member so that the movable contacts can be selectively transferred to make electrical contact with a corresponding stationary contact; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; tripping means for the movable one of said contacts including a latch piece arranged to slide along a portion of the magnetic circuit adjacent the armature, a movable block carried by the latch piece, a spring conjointly urging the movable block and latch piece along a path of travel from a latched position wherein the movable block and latch piece are restrained bythe armature in its open position to a releasedY position, lever means interposed in the path of the movable block and connected with said movable contact to transfer the contacts upon the release of the movable block and latch piece by the movement of the armature to its closed position; and resetting means for returning the movable block and latch piece to their latched position and conjointly transferring the contacts.

l5. A circuit breaker comprising a pair ofI electrical contactsincluding a stationary and a movv make contact with the stationary contact, a hollow actuator pivotally attached to the casing immediately above the. point of attachment of the rocking member, a spring loaded telescoping member extending from the actuator to contact the rocking member forming a toggle whereby the contacts are biased in both theopen and closed positions; meansv including a low reluctance magnetic circuit having an armature and a solenoid fr inducing a magnetic flux therein to move the armature from an open toa closed position when the solenoid current exceeds a predetermined value; automatic tripping means for the contacts including a. latch piece slidably arranged with respect to the magnetic circuit, a block carried by the latch piece, a spring con- Jointly urging the block and latch piece along a path of travel from a latched position wherein the block and latch piece are restrained by the armature in its open position to a released position, a finger extending from said actuator so that it is interposed in the path of the block thus transferring the contacts upon the release ofthe block and latch piece by the movement of the armature to its closed position; said actuator having a handle portion for manually returning the block and latch piece to their latched position and conjointly transferring the contacts.

16. A circuit breaker comprising a pair of electrical contacts including a stationary and a movable contact; a rocking member carrying the movable contact at one end thereof, said member being bent at itsl midpoint so that the ends form an obtuse Iangle, means for pivotally supporting the rocking member at its midpoint so that the movable contact can be selectively transferred to A 16 mediately above the point of attachment of the rocking' member, a spring loaded telescoping member extending from the actuator to contact .the rocking member forming a toggle whereby the contacts can be biased in the closed position; means including a low reluctance magnetic circuit having an armature and a solenoid for inducing a magnetic flux therein to move the armature from an open to a closed position when the solenoid current exceeds a predetermined value; automatic tripping means for the contacts including a latch piece' slidably arranged with respect to the magnetie'circuit, a block carried by the latch piece, a spring conjointly urging the block and latch piece along a path of travel from a latched position wherein the block and latch piece are restrained by the armaturein its open position to a released position, a finger attached to the opposite'end of the rocking member from the movable contact and extending from said member so that it is interposed in the path of the block thus opening the contacts upon the release of the block and latch piece by the movement of the armature to its closed position; said actuator havinga handle portion and two fingers which contact the end of the block as the handle portion is manually moved to return the block andv latch piece to their latched position and conjointly to close the contacts.

HARRY P. SPARKES.

References Cited in the le of this patent UNITED STATES PATENTS Number i Name Date 997,759 'Denny July 11, 1911 1,950,225 Burton Mar. 6, 1934 1,974,488 Geraghty Sept. 25, 1934 2,027,538 Krieger Jan. 14, 1936 2,091,108 Sengebusch Aug. 24, 1937 2,171,267 Doty Aug. 29, 1939 2,253,400 Shoemaker et al. Aug. 1, 1941 2,502,537 Speck Apr. 4, 1950 FOREIGN PATENTS Number Country Date 315,121 Germany Oct. 25, 1919