US3488610A - Circuit breaker with improved thermalmagnetic tripping mechanism - Google Patents

Circuit breaker with improved thermalmagnetic tripping mechanism Download PDF

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Publication number
US3488610A
US3488610A US669435A US3488610DA US3488610A US 3488610 A US3488610 A US 3488610A US 669435 A US669435 A US 669435A US 3488610D A US3488610D A US 3488610DA US 3488610 A US3488610 A US 3488610A
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United States
Prior art keywords
cradle
pivot
casing
latch
magnet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US669435A
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English (en)
Inventor
David B Powell
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General Electric Co
Original Assignee
General Electric Co
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Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
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Publication of US3488610A publication Critical patent/US3488610A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
    • H01H71/10—Operating or release mechanisms
    • H01H71/12—Automatic release mechanisms with or without manual release
    • H01H71/40—Combined electrothermal and electromagnetic mechanisms
    • H01H71/405—Combined electrothermal and electromagnetic mechanisms in which a bimetal forms the inductor for the electromagnetic mechanism
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
    • H01H71/10—Operating or release mechanisms
    • H01H71/12—Automatic release mechanisms with or without manual release
    • H01H71/14—Electrothermal mechanisms
    • H01H71/16—Electrothermal mechanisms with bimetal element
    • H01H71/162—Electrothermal mechanisms with bimetal element with compensation for ambient temperature

Definitions

  • a circuit breaker is constructed to have a highly eflective thermal-magnetic tripping mechanism which is adaptable to devices of small width wherein an elongated latch member has its lower end portion latchingly engaged with one end of the cradle and an elongated magnet member has a generally U-shaped field portion opening toward and spaced from the lower end portion of the latch member.
  • a bimetallic strip pivoially mounted at its upper end extends through the field portion of the magnet member for generation of a magnetic field therein and, upon deflection as a result of a sustained short circuit current, will pivot the latch member away from the cradle to effect release thereof.
  • the upper end portions of the latch and magnet members are pivotally connected for relative movement therebetwen and ar pivotally supported in the casing for pivotal movement relative to the cradle about a common pivot for simultaneous pivoting thereof.
  • Another object is to provide such a circuit breaker construction wherein use of a common trip member is readily accomodated and possible damage thereby to the thermalmagnetic means is precluded.
  • Still another object is to provide a thermal-magnetic means for a circuit breaker which is readily adapted to facile calibration and in which operation is not highly sensitive to minor deviations in tolerance or calibration.
  • the casing has a releasable cradle pivotably mounted at one end therein and an elongated latch member having its lower end portion latchingly engaged with the free end of the cradle.
  • An elongated magnet member in the casing has a generally U-shaped field portion adjacent its lower end opening towards and spaced from the lower end portion of the latch member.
  • Means in the casing provide a pivotal connection between the upper end portions of the latch and magnet members for relative movement therebetween and pivotally support the upper end portions of the latch and magnet members for pivotal movement about a common pivot for simultaneous pivoting thereof relative to the free end of the crade.
  • Biasing means pivot the lower end portion of the latch member toward the free end of the cradle so as to encourage latching engagement therebetween, and a bimetallic strip pivotally mounted at one end extends through the field portion of the magnet member to generate a magnetic field therein upon passage of current therethrough.
  • the bimetallic strip is deflectable by a sustained short circuit current of relatively low magnitude flowing therethrough to pivot the latch member against the pressure of the biasing means away from the free end of the cradle, thereby releasing the cradle and tripping the breaker.
  • a magnetic field will be generated in the field portion of the magnet member which is of sufiicient magnitude to pivot the latch member about the pivot between the latch and magnet members and towards the field portion, thereby effecting release of the cradle and tripping of the breaker.
  • This arrangement permits the latch member to pivot towards the magnet member about the pivot therebetween when a common trip member is employed and thus precludes damage which might result from the use of a stationary magnet member or a structure in which the bimetallic strip carries the field piece and closely coupled to the latch member to effect tripping thereof.
  • FIGURE 1 is a side elevational view of an electric circuit breaker embodying the present invention with one side of the insulating casing removed to show internal construction;
  • FIGURE 2 is a sectional view of the circuit breaker of FIGURE 1 generally along the line 2-2 thereof;
  • FIGURE 3 is a fragmentary, partially diagrammatical view showing the operating mechanism in the on condition
  • FIGURE 4 is a similar view showing the operating mechanism in the t ipped condition
  • FIGURE 5 is a fragmentary sectional view thereof on a greatly enlarged scale illustrating the tripping mechanism
  • FIGURE 6 is an exploded view of the thermal-magnetic tripping mechanism of the circuit breaker of FIG- URE 1;
  • FIGURE 7 is a fragmentary elevational view of an alternate embodiment of thermal-magnetic trip construction
  • FIGURE 8 is a view similar to FIGURE 7 drawing in phantom line the displacement of the main bimetallic strip provided by the ambient bimetallic strip;
  • FIGURE 9 is a perspective view of the magnet-ambient bimetallic member subassembly of FIGURE 7.
  • an electric circuit breaker embodying the present invention has a molded insulating casing provided by a pair of interfitting sections generally designated by the numerals 10, 12 which are secured together by fasteners (not shown) seated in the apertures 14 therein.
  • Each of the sections has a complex interior surface configuration providing ribs, shoulders, apertures and recesses as will be described more fully hereinafter in connection with the various parts of the operating mechanism.
  • a movable contact 24 is carried by the lower end of the contact arm generally designated by the numeral 26 for movement into and from electrical engagement with the stationary contact 22.
  • the contact arm 26 is fabricated from sheet metal to minimize thickness of the breaker and has a laterally extending finger 28 at its upper end which is pivotably mounted in the aperture 30 of the operating handle generally designated by the numeral 32.
  • the upper portion 34 of the contact arm 26 is generally planar and extends adjacent the sidewall 36 of the casing section 12 and to the side of the operating handle 32. At its center is an offsetting portion 38 with a pair of apertures 40 therein and extending transversely of the casing below the operating handle 32.
  • the lower portion 42 of the contact arm 26 is generally L-shaped with its vertical portion extending generally planar adjacent the sidewall 44 of the casing section and its horizontal portion carrying the movable contact 24.
  • a tension spring 46 Engaged at one end in the apertures 40 of the contact arm 26 is a tension spring 46 which has its-other end engaged in a notch or recess 48 in the upper edge of the cradle generally designated by the numeral 50.
  • the spring 46 applies biasing pressure on the contact arm 26 toward the handle 32 and cradle 50 which ensures rapid snap action into open or closed contact position as it pivots about the handle 32.
  • the cradle 50 is a relatively thin member disposed between the operating handle 32 and the sidewall 44 of the casing 10. It has a generally inverted U-shaped configuration with a pair of legs 70, 72 and a center portion 74 having the notch 48 in its upper edge into which the spring 46 is hooked.
  • the forward leg 70 has a generally circular end portion 76 which is pivotably retained in cooperatively configured recesses 78 formed in the sidewalls 36, 44 of the casing sections 10, 12 so that the cradle 50 may pivot thereabout.
  • a spacing boss 80 is provided on the sidewall 44 of casing section 10 which extends through an elongated slot 82 in the cradle rear leg 72. As the cradle 50 pivots about the end portion 76, the boss 80 will slide freely within the slot 82 thereof.
  • the cradle front leg 70 has a laterally inwardly extending tab 84 at its front edge which is adapted to be engaged by the depending portion 68 of the operating handle 32 when it is moved to the OE position shown in FIGURE 1 so as to produce pivoting of the cradle 50 from the tripped condition shown in FIGURE 4.
  • the further pivoting of the handle 32 in the clockwise direction past the off position lifts the cradle 50 into the latched condition.
  • the cradle 50 When the cradle 50 is released from the latch 90, it rotates clockwise as viewed in FIGURE 1, carrying the upper end of the spring 46 across the line of centers of the spring anchor point 26a on contact member 26 and pivot 28 on handle 32. This causes the spring 26 to rotate the contact arm 26 toward open condition.
  • the toggle system comprising handle pivot 32a, contact arm pivot 28, and spring anchor point 26a collapses by movement of the mid-point 28 to the left as viewed, rotating the handle clockwise.
  • the clockwise rotation of the handle 32 is limited by its engagement with tab 84 of the cradle 50.
  • a second laterally inwardly extending tab 86 is provided on the rear edge of the front leg 70 at a point spaced downwardly from the tab 84 so that it will strike the contact arm 26 upon tripping of the breaker in the event that the stationary contact 22 and movable contact 24 are fused together by a short circuit current and thus break them apart.
  • the rear leg 72 of the cradle 50 has a latch portion 88 at its lower end providing a shoulder or edge which is latched or engaged with a tab 90 adjacent the lower end of the latch member generally designated by the numeral 92 in the normal operating or untripped condition of the breaker.
  • the upper end portion of the latch member 92 has laterally extending shoulder portions 94a, 94b with rearwardly extending arms 96a, 96b at the lower end thereof, and the shoulder portion 94a seats in the recess 98 in the sidewall 44 of the casing section 10.
  • the arms 96a, 96b slidably seat on a downwardly sloping shoulder 100 of the recess 98 in the sidewall 44 of the casing section 10.
  • the magnet member 112 is fabricated from a magnetically susceptible metal and has a field portion 114 of generally U-shaped cross section opening toward the latch member 92 adjacent the lower end thereof and an arm portion 116 extending upwardly from one leg of the field portion 114 along the sidewall 36 of the casing section 10 with the finger 110 at the upper end thereof.
  • a gen erally U-shaped hook element 118 of non-magnetic metal extends forwardly from the other leg of the field portion 114 and engages the lower end of the latch member 92 in the normal operating condition.
  • a common tripping member generally designated by the numeral 158, is of elongated nature and has ears adjacent the upper end thereof which pivotally seat in recesses 162 in the sidewalls 36, 44 of the casing sections 12, 10. At its lower end it has a transversely extending bar 164 adapted to bear against the latch member 92 upon pivoting thereof in the counterclockwise direction so as to effect release of the cradle 50 in the event of pivoting thereof by action of another breaker through a trip interlock (not shown) seated in the slot 166 therein.
  • a relatively short ambient bimetallic strip generally designated by the numeral 170 is secured at its upper end to the field portion 114 of the magnet member 112 at the point A by welding or the like to provide a point about which it may pivot.
  • the lower end portion 172 is offset towards the bimetallic strip 120 and will normally bear thereagainst and will flex away therefrom as a result of temperature changes.
  • the hook element 118 on the magnet member 112 establishes the magnetic gap accurately and it remains constant whether the circuit breaker is cold or hot.
  • the latch portion 88 of the latch member 92 may have a projection thereon extending towards the cradle 50 and limiting the amount of surface contact between the tab 90 and the latched end of the releasable cradle 50 so as to minimize the amount of pivoting of the latch member required to effect tripping of the breaker.
  • Such an arrangement is particularly desirable with breakers of low current rating when they are cold to increase their sensitivity.
  • the operating mechanism of the illustrated embodiment is optimum from the standpoint of competence, and ease of construction and assembly, it will be appreciated that the thermal-magnetic tripping mechanism of the present invention may be utilized with other more conventional types of operating mechanism. It will also be appreciated that other more conventional means for effecting calibration of the bimetallic strip can be employed such as a screw acting directly upon the upper end portion of the terminal strap and bimetallic strip to shift the pivot point thereof.
  • circuit breaker of the present invention provides a thermal-magnetic tripping mechanism readily adapted to relatively small widths while still affording highly effective means for handling substantial circuit currents.
  • the interrelation of the parts permits a minimization of parts and the size of the assembly while affording optimum coaction therebetween.
  • the several parts can be readily fabricated and easily assembled rapidly and with minimum likelihood of improper assembly.
  • an elongated magnet member having a generally U-shaped field portion adjacent its lower end opening towards and spaced from said lower end portion of said latch member;
  • a bimetallic strip fixedly mounted at one end and extending through said field portion to generate a magnetic field therein upon passage of current therethrough, said bimetallic strip being defiectable by a sustained short circuit current of relatively low magnitude flowing therethrough to pivot said latch member and said magnet member about said common pivot in a direction so as to move said lower portions of said latch member and said magnet member away from said cradle against the pressure of the biasing means and thereby to release said cradle, said bimetallic strip upon passage of a sudden relatively high short circuit current flowing therethrough generating a magnetic field in said field portion of said magnet member of suflicient magnitude to pivot said latch member relative to said magnet member in a direction towards said field portion and thereby to release said cradle.
  • circuit breaker in accordance with claim 1 wherein said circuit breaker includes means pivotally inter-connecting said latch member and said magnet member, and wherein the common pivot for said magnet and latch members relative to said casing is spaced toward the upper ends thereof from said inter-connection so as to provide a scissors-type action therebetween by said biasing means tending to move the lower ends of said magnet and latch members apart.
  • said pivotal supporting means includes a shoulder on the casing providing a pivot point and bearing surface for one of the members and a second shoulder on the casing providing sliding support for the other member to provide pivotal movement about a common pivot provided by said pivot point.
  • circuit breaker in accordance with claim 1 wherein there is provided a common trip member pivotally mounted in said casing and pivotable against said latch member to effect release of said cradle, said latch member being pivotable towards said magnet member about said pivotal supporting means.
  • said pivotal supporting means includes a laterally extending arm portion at the upper end portion of said magnet member and a shoulder on the latch member pivotably seated thereon, said casing providing a first angularly disposed shoulder supporting said arm portion thereon and a second angularly disposed shoulder spaced above said first shoulder and against which said upper end portion of said magnet member bears in response to the pressure of said biasing means to provide said common pivot therefor.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Breakers (AREA)
US669435A 1967-09-21 1967-09-21 Circuit breaker with improved thermalmagnetic tripping mechanism Expired - Lifetime US3488610A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US66943567A 1967-09-21 1967-09-21

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US3488610A true US3488610A (en) 1970-01-06

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US669435A Expired - Lifetime US3488610A (en) 1967-09-21 1967-09-21 Circuit breaker with improved thermalmagnetic tripping mechanism

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US (1) US3488610A (enrdf_load_stackoverflow)
GB (1) GB1227806A (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4276457A (en) * 1979-07-30 1981-06-30 Gould Inc. Circuit breaker having planar cradle with edge portions providing relatching and contact kicker functions
US4479101A (en) * 1982-07-02 1984-10-23 Siemens-Allis, Inc. Circuit breaker with self-adjusting armature
US4546337A (en) * 1983-09-02 1985-10-08 Eaton Corporation Residential circuit breaker with one piece slot motor
US4546336A (en) * 1983-09-02 1985-10-08 Eaton Corporation Residential circuit breaker with combination slot motor and arc chute
US4549153A (en) * 1983-09-02 1985-10-22 Eaton Corporation Residential circuit breaker with slot motor
US4868529A (en) * 1988-08-24 1989-09-19 Siemens Energy & Automation, Inc. Circuit breaker armature latch with control leg
US4929919A (en) * 1988-06-27 1990-05-29 Eaton Corporation Twin unit circuit breaker with improved magnet structure

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2902560A (en) * 1955-05-18 1959-09-01 Square D Co Circuit breaker
US3401363A (en) * 1966-11-10 1968-09-10 Square D Co Multipole circuit breaker with trip indicator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2902560A (en) * 1955-05-18 1959-09-01 Square D Co Circuit breaker
US3401363A (en) * 1966-11-10 1968-09-10 Square D Co Multipole circuit breaker with trip indicator

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4276457A (en) * 1979-07-30 1981-06-30 Gould Inc. Circuit breaker having planar cradle with edge portions providing relatching and contact kicker functions
US4479101A (en) * 1982-07-02 1984-10-23 Siemens-Allis, Inc. Circuit breaker with self-adjusting armature
US4546337A (en) * 1983-09-02 1985-10-08 Eaton Corporation Residential circuit breaker with one piece slot motor
US4546336A (en) * 1983-09-02 1985-10-08 Eaton Corporation Residential circuit breaker with combination slot motor and arc chute
US4549153A (en) * 1983-09-02 1985-10-22 Eaton Corporation Residential circuit breaker with slot motor
US4929919A (en) * 1988-06-27 1990-05-29 Eaton Corporation Twin unit circuit breaker with improved magnet structure
US4868529A (en) * 1988-08-24 1989-09-19 Siemens Energy & Automation, Inc. Circuit breaker armature latch with control leg

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GB1227806A (enrdf_load_stackoverflow) 1971-04-07

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