US3460078A - Electrical overload circuit breaker - Google Patents

Description

ug- 5, 1969 H. J. MCcARRlcK ELECTRICAL ovERLCAD CIRCUIT BHEAKER 2 Sheets-Sheet l Filed Sept. 5, 1967 Aug. 5, 1969 H. J. MCCARRICK ELECTRICAL OVERLOAD CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed Sept. 5. 1967 Il l) 3523;

United States Patent Oice 3,460,078 Patented Aug. 5, 1969 ELECTRICAL OVERLOAD CIRCUIT BREAKER Henry J. McCarrick, deceased, late of Middleborough,

Mass., by Mary A. McCarrick, executrix, Middleborough, Mass., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Sept. 5, 1967, Ser. No. 666,236 Int. Cl. H01h 3/60 U.S. Cl. 335-193 5 Claims ABSTRACT OF THE DISCLOSURE A vibration-proof, trip-free, overload circuit breaker having a pair of stationary contacts and a movable bridging contact for making or interrupting an electric circuit. The circuit breaker has a oating contact arm on which the bridging contact is at a head end and a latchable part is at a foot end. A foot latch holds the foot end for manual switch-closing operation. Manual operation is accomplished by means of a toggle mechanism, including resilient means for driving the contact arm into circuitclosing position when the toggle mechanism is manually placed in unbroken or locked position. Said resilient means prevent vibrations from causing unwanted opening of the contacts. An electromagnetically actuated armature, associated with a tripper latch, upon overload controls the foot latch for effecting release of the foot of the contact arm, together with actuation of the circuit breaker to open the contacts and return the toggle to a broken or unlocked position. When the overload ceases, the foot end of the arm is returned to latched position on the foot latch so that when the toggle is returned to locked position the switchtecloses under normal load. A resilient connection interposed between the armature and the tripper latch prevents vibrations from causing unwanted opening of the contacts under normal load.

BACKGROUND OF THE INVENTION The invention pertains to reliable vibration-proof, tripfree overload switching apparatus. Prior-art circuit breakers include those that consist of a toggle linkage assembly connected to a contact-carrying arm, an electromagnetic overload sensing device, an armature actuated by the electromagnet, and a latch interposed in the toggle linkage assembly. The latch is operable by the armature to collapse the assembly by breaking the toggle, to permit the contact-carrying arm to move and separate a pair of contacts for interrupting a circuit. Although such devices have served a purpose, they have not proven entirely satisfactory for some applications because they are not vibration-proof and are diicult to miniaturize, being susceptible to accidental actuation by external shock.

SUMMARY OF THE INVENTION The circuit breaker is composed of a fixed support, a first contact means on the support, and a second contact means carried by a floating contact arm for floating, i.e., pivotal and translating, movement. This carries movable contact means at its head end. Foot latch means engage the other foot end of the arm. A toggle linkage assembly is resiliently connected to the arm for movement from a collapsed, rigid or broken contacts-open position to an uncollapsed or rigid contacts-closed position. The contacts when closed are protected against reopening under vibration by the resilient connection. A tripper latch and an armature responsive to an electrical overload are provided for moving the foot latch out of engagement with the foot of the arm to allow pivoting of the latter so as to effect separation of the contacts under spring action. At this time lthe toggle mechanism moves to unlocked, broken or collapsed position and the switch becomes trip-free. A resilient connection between the armature and the tripper latch is such that vibrations are ineffective to move the tripper latch out of engagement with the foot latch, so that unwanted vibratory tripping and separation of the contacts does not occur. Upon cessation of overload the arm is spring-returned to a position with its foot held by the foot latch and its head holding open the movable contacts. The toggle mechanism may then be moved from its unlocked to its locked position s0 as to reclose the contacts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a side elevation, partly in section, of the circuit breaker in an on or contacts-closed position;

FIG. 2 is a side elevation similar to FIG. l, showing the circuit breaker in an electrically tripped (contactsopen) position;

FIG. 3 is a side elevation similar to FIG. 1, showing the circuit breaker in an off or contacts-open position;

FIG. 4 is a Section on line 4 4 of FIG. l;

FIG. 5 is a section on line 5 5 of FIG. l; and

FIG. 6 is a fragmentary view of certain parts as seen across line 6 6 on FIG. 1.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the present circuit breaker, generally indicated by reference numeral 1, is composed of a housing 3 having an upper tubular barrel 5 and a pair of lower terminal lugs 7 and 9 projecting through suitable apertures in its bottom wall. An inner frame 11 held within the housing (see FIGS. 4 and 5) interiorly supports a circuit breaker mechanism 13. A suitable sealing boot or bellows (not shown) may enclose the open end of the barrel 5 around a toggle switch lever 17 pivoted at pin 21.

The mechanism 13 is comprised of a toggle linkage 15 including the toggle lever 17 and a toggle link 19. The toggle lever 17 is pivotally mounted on a yoke (not shown) in the barrel 5 by the pin 21 and is provided at its upper end with a handle 23 for manual operation. The lower end of the toggle lever 17 is pivoted to the toggle link 19 by a knee pivot pin 25, the latter being biased to the left by a spring 27 for breaking the toggle (see FIG. 3). The lower end of the toggle link 19 is articulated with a oating contact arm 29 by a pin 31 extending through slots 41 in the arm and having reduced end portions 43 and 43 slidafble in and guided by guide slots 45 and 45 in the frame 11. The contact armI 29 includes a pair of elongate parallel side plates 33, 33 interconnected by a movable bridging contact 37 carried by an insulator 39 at what may be called its head end. It also carries a crossbar 35 at the other end, which may be called its foot end. AS above noted, the pivot pin 31 passes through slots 41 in plates 33 and 33 near the center of the contact arm and is provided with reduced- diameter end portions 43 and 43 for engaging the pair of elongate stationary guide slots 45, 45 in the side walls of the frame 11. A spring 47, xed to the center of the pin 31 and engaging the top of the contact arm 29, resiliently pushes the contact arm downward in response to downward pin movement. This prevents any external vibrations from accidentally opening the contacts. A U-shaped contact arm spring 49, consisting of leg portions 51, 51 and web portion 53, engages the contact arm 29 at slot 55 for biasing the contact arm in a counterclockwise, contacts-open direction about pin 31, as viewed in FIG. 1. The lower end 57 of the spring 49 is fixed in a notch 58.

The crossbar or catch 35 at the foot of the arm engages sloping surfaces 67, 67 of a foot latch 59 pivotally mounted an frame 11 at pin 61. The foot latch consists of a pair of parallel legs 63, 63' interconnected at their lower ends by a U-shaped latch -plate 65 (see FIG. 5), and having the inclined contact-arm-engaging surfaces 67, 67'. A return spring 69 resiliently biases the foot latch 59 in a counterclockwise direction about pin 61, as viewed in FIG. 1.

The plate 65 is engaged by a tripper latch 71 at surface 73. The tripper latch 71 is pivotally mounted on a pin 75 together with an armature 77, the latter consisting of a lower leg 79 and a pair of upper counter-balance arms 81 and 81. The tripper latch 71 is biased into engagement with the foot latch 59 by a resilient connection in the fo'rm of a coil spring 83 disposed within a recess 85 formed in the armature leg 79. Any effect of external vibrations on the armature is not transmitted to move the tripper latch 71 from its holding position against the surface 73 at the lower end of the foot latch 59. The armature is biased in a clockwise direction about pin 75 by a return spring 87. The armature 77 is further provided with a plate 89 at the intersection of leg 79 and arms 81, 81', adapted to engage the tripper latch at 91 for rotating the latter about pin 75 to disengage the surface 73 from the foot latch crossplate 65. When actuation of the tripper latch occurs by engagement between the crossbar 89 and surface 91, the spring 83 is compressed. This occurs during the time that the tripper latch releases the foot latch.

An electromagnet 93 is mounted in the lower end of housing 3 adjacent the armature leg 79. The electromagnet 93 is composed of an electrical coil, indicated diagrammatically at 95, a core 97 and a pair of pole pieces 99 and 100. The coil 95 is connected in series with the terminal 7 and a first xed contact 101 through conductor 103 (see FIG. 4). A second xed contact 105 is electrically connected to terminal lug 9 by a conductor 107. Thus, when the bridging contact 37 engages the fixed contacts 101 and 105, an electrical circuit connected lbetween terminals 7 and 9 is completed through the electromagnet-coil 95. This is best seen in FIG. 6. An abutment or back-stop 109 is formed on housing 3 against which the insulator 39 bears when the breaker is in the trip and Off positions.

The core 97 may be comprised of a conventional timedelay tube (not shown) having a spring-loaded movable iron core and a silicone fluid therein. The core normally remains outside the coil center and the spring is calibrated such that no movement occurs until a predetermined current trip value is reached in the coil. The core is then attracted into the coil against the s pring and its speed is governed by the damping action of the iluid. As the core approaches the coil center, the reluctance of the magnetic circuit is reduced until a sutlcient value of flux is reached, when the breaker will trip. If the magnitude of coil trip current becomes great enough (usually between 300% and 400% of normal rating) the breaker will trip independent of the movable core position within the coil. Thus, upon extreme overload the breaker will exhibit no time delay but will trip instantaneously.

Operation is as follows:

When the toggle lever 17 is in the on position illustrated in FIG. l, the contact arm 29 is maintained in a contacts-closed position against the opposing forces of contact arm spring 49 and toggle spring 27 by the latching action of the rigid or unbroken toggle assembly 15 pressing down through spring 47 on the center portion of the arm with holding reactions at the latch surface 67 and at contacts 101 and 105. The resiliency of spring 47 in the toggle train mechanism prevents ordinary vibration from causing the toggle to break from the FIG. 1 to the FIG. 3 position. Such break occurs, however, when lever 17 is manually thrown from the FIG. 1 to the FIG. 3 position.

When a predetermined value of trip current is reached or exceeded in coil 95, armature leg 79 is sufficiently magnetically attracted to pole piece 99 to rotate about pin 75 against the opposing force of return spring 87 and seat itself against the pole piece. As armature 79 rotates, spring 83 is lirst compressed. Spring 83 thus iirst holds the tripper latch in holding position on the surface 73 of the foot latch 59 but in due time part 89 strikes the tripper latch at 91, rotating the catch surface 73 out of engagement with surface 65. This permits free clockwise rotation of foot latch 59 about pin 61 under the inuence of the downward force exerted by the contact arm crossbar 35 at surfaces 67, 67'. This downward force is produced by the combined forces of contact arm spring 49 and spring 47. Thus, foot latch 59 rotates clockwise sufciently to release contact arm 29 and permit its free counterclockwise rotation about pin 31 under the influence of spring 49 to separate bridging contact 37 from fixed contacts 101 and 105 and interrupt the electrical continuity between terminals 7 land 9. The instantaneous position of the circuit breaker parts in this position is illustrated in FIG. 2. It should be noted that the pin 31 has remained stationary in guide slots 45, 45' and the toggle linkage 15 has remained rigid throughout the above-described operation.

The counterclockwise rotation of contact arm 29 about pin 31 removes the forces of contact arm spring 49 and spring 47 from toggle link 19, thus permitting toggle assembly 15 to collapse under the influence of toggle return spring 27 to the otf" position of the breaker illustrated in FIG. 3. This is further assisted by the clockwise torque generated by the force of spring 49 acting about the point of contact between insulator 39 and the abutment 109 of housing 3. When the toggle assembly 15 collapses to the left, spring 49 reacting against abutment 109 causes the contact arm to slide or translate upwardly in slots 45, 45 from its FIG. i2 to its FIG. 3 position wherein crossbar 35 is again supported on foot latch surface 67. Electrical continuity within coil is interrupted because of the separation of contacts 37 and 101 and 105, thereby permitting armature 77 to return to its normal position under the influence of return spring 87. This removes the force exerted by armature 77 against tripper latch surface 91. Since the downward force exerted by the contact 'arm against foot latch surface 67 is removed, and since the contact arm is permitted to assume its normal off position by the collapse of toggle assembly 15, foot latch 59 is free to rotate counterclockwise about foot latch pin 61 under the influence of return spring 69 to its normal position. As this occurs, tripper latch 71 is free to rotate clockwise under the inuence of spring 83 and return to its normal latching engagement with the foot latch at surfaces 73 and 65. The circuit breaker thus automatically resets itself upon electrical tripping from the intermediate FIG. 2 trip position to the FIG. 3 olf position. It may then be manually actuated to the FIG. 1 on position by merely pivoting the toggle lever 17 toward the left. This will cause the toggle link pin 25 to pass to the right of a line drawn between pins 21 and 31 and will force the contact arm 29 down in slots 45, 45 and the movable bridging contact 37 into engagement with the fixed contacts 101 and 105. The contact arm slot 41 and spring 47 provide a lost-motion interconnection with the pin 31 to insure positive engagement of contacts 37, 101 and 105.

Since lever 17 is in latching engagement with contact arm 2.9 through link 19 and pins 25 and "31 when in the on position, merely moving lever 17 to either its on or ofi position results in a switching action of movable bridge contact 37 with stationary contacts 101 and 105. It can also be seen that the circuit breaker provides tripfree action in that mechanically maintaining toggle lever 17 in its on position will not interfere with electrical tripping of contact arm 29 since operation of the latter is independent of toggle 17, as set forth above. It should be noted, however, that lever 27 must be permitted to return to its oil position before movable bridge contact 37 and fixed contacts 101 and 105 may be reclosed. Thus, the circuit breaker is Vibration-proof and provides snapacting tripping, with trip-free operation, and readily lends itself to miniaturization.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A circuit breaker comprising a pair of fixed contacts, a movable contact arm having a slot therein, a bridging contact carried at one end of said contact arm for engaging and disengaging said fixed contacts to complete or interrupt an electrical circuit connected therebetween, a toggle lever, a `toggle link pivotally mounted at one end of said lever, a pivot pin passing through said slot and an aperture in said link and engaging a pair of stationary guide slots, said lever and link being movable from a rigid contacts-closed position to a collapsed contacts-opened position, first lost-motion resilient means biasing said bridging and fixed contacts together, second resilient means biasing said link toward a collapsed position, third resilient means biasing said arm for pivotal movement about said pin toward a contacts-open position and translatory movement in said guide slots, a pivotally mounted foot latch having a contact arm engaging surface, the other end of said arm engaging said surface when in a contactsopen and contacts-closed position and disengaging said surface when in an intermediate trip position, a pivotal tripper latch normally engaging said foot latch for maintaining said surface in engagement with said contact arm a pivotal armature for moving said tripper latch out of engagement with said foot latch, and an electromagnet for pivoting said armature in response to an electrical overload, said electromagnet being connected in series with said fixed contacts.

2. A circuit breaker as in claim 1 wherein said contact arm is composed of a pair of spaced parallel arms interconnected by said bridging contact at said one end and a crossbar at said other end, and said foot latch comprises a pair of spaced parallel arms having inclined contactarm-engaging surfaces, said latch arms being mounted between said contact arms for engagement by said crossbar at said inclined surfaces.

3. A vibration-proof and trip-free circuit breaker com prising at least one fixed contact on a support, a floating contact arm carrying a movable contact at a head end thereof, said movable contact being engageable and disengageable with the fixed contact, a foot latch for holding a foot end of the arm, a toggle linkage movable from an unlocked to a locked position thereof, said linkage having a resilient driving connection with said arm between the head and foot of the arm, whereby the toggle linkage when moved to locked position drives the foot of .the arm against said foot latch and drives the movable contact against the fixed contact at the head of the arm, spring means reacting from said support against the arm to drive it to open the contacts when the toggle mechanism is unlocked, an overload electromagnet having an armature, a tripper latch for holding the foot latch to support or release'said foot end -of the arm, said armature upon actuation operating the tripper latch to release the foot latch and said foot of the arm, whereby the contacts open and the toggle linkage returns to unlocked position, and a resilient connection between the armature and the tripper latch for biasing the tripper latch into poistion firmly holding the foot latch against release of the foot of the arm under vibration until the tripper latch is actuated by the armature to drive the trigger latch to release the foot latch.

4. A vibration-proof and trip-free circuit breaker comprising a fixed support, a pair of contacts carried by said support, an electromagnet on the support having an armature .movable on the support, a circuit to be controlled serially including said contacts and the electromagnet, a floating contact arm including a conductive bridging means at a first end thereof for connecting and disconnecting said contacts, said arm being movable in translation and rotation, an abutment on the support for engagement by said first end of the contact arm when the contacts are opened, a spring-biased foot latch for supporting a second end of the contact arm, a reactive spring means reacting from the support for biasing said arm toward engagement of its first end with the abutment while opening the contacts and t-o be held at its second end by said foot latch, means including a tripper latch for the foot latch, said tripper latch -being resiliently connected with and responsive to motion of the armature upon electrical overload to release said foot latch so as to release said second end of the arm for downward movement, a toggle linkage including a toggle lever pivoted to the support, a toggle link pivoted to the toggle lever, said toggle link having a pivotal and translatory lost-motion resilient connection with said contact arm and a sliding connection with said support, toggle spring means biasing the toggle linkage from a locked to a collapsed position, said toggle linkage adapted when locked to hold said first end of the contact arm in a contacts-closed position while the second end of the contact arm is supported by said latch, said second end of the contact arm being moved downwardly when said foot latch is released by said armature-operated tripper latch, so that said reactive spring means may first drive said first end of the contact arm against said abutment into a contacts-open position and secondly drive the second end of the contact arm back into position to be held by said foot latch.

5. A circuit breaker comprising, a fixed support, a first guide slot therein and a pair of fixed contacts and a fixed back-stop carried thereby,

a floating contact arm having a movable head end, a movable foot end, a second guide slot in and between the ends of the arm, and a bridging contact on said movable head end,

a -toggle mechanism including a toggle arm pivoted to the support and a toggle link pivoted to the toggle arm, means projecting from the toggle link and movable in said first and second slots,

a foot latch having a holding portion for said foot end of the contact arm, a tripper latch having a first position for latching the foot latch in position to hold the foot end of the arm on said holding portion, said trip per latch in a second position thereof releasing the foo-t latch to permit movement of the foot end of the arm from said holding portion,

a first spring reacting between said projecting means and said contact arm to bias the head end of the oating arm towards engagement between said contacts and holding its foot end against said holding portion on the foot latch, said spring also maintain- `ing the toggle in unbroken position when the contacts are engaged and said foot end is supported,

electrically responsive overload means for actuating the tripper latch to release the foot latch thereby to release the foot end of the arm,

a second spring reacting between the support and the oating arm to bias the head end of the arm toward said stop to separate the bridging contacts from the fixed contacts and to bias its foot end toward said holding portion of the foot latch after the tripper latch is actuated,

a third spring for biasing the toggle toward broken position after tripping has occurred,

and a fourth spring for returning the foot latch to be held in latched position by the tripper latch, in which latched position the foot end 0f said arm is supported on said holding portion of the foot latch and the head end of the arm is held in position by the second spring against the backstop with the bridging contact separated from the fixed contacts.

References Cited UNITED STATES PATENTS 2,607,867 8/ 1952 Platz 335-24 2,932,706 4/ 1960 Bodenschatz 335-46 3,242,286 3/ 1966 Heilman 335-46 15 BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner

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