Note: Descriptions are shown in the official language in which they were submitted.
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COMPACT THREE-POLE CIRCUIT BREAKER
BACKGROUND OF THE INVENTION
The present invention relates to a three-pole, ~olded case
circuit breaker of modular construction and compact physical size.
Heretofore, typical circuit protection for three phase elec- ;
trical distribution circuits utilized in light industrial, commer-
cial and institutional applications has been provided by three-pole
- molded case circuit breakers of the wire-in, wlr~ou~ variety.
- These circuit breakers would normally be installed in circuit
breaker load centers containing banks of single-pole, plug-in
circuit breakers forbranch circuit protec~ion. Since the ~ypical
three-pole circuit breaker, in addition to being nonplug-in, is
wider than the combined width of three single-pole branch breakers,
special provisions must be made to physically mount the three-pole
bxeaker within the load center. Thus, the load centers must be
specially designed to the customer's specifications to accept
`` specified numbers of three-pole and single-pole breakers. Typically,,~ ~ the electrical connections between the three-pole breaker and the -;
~r Tch breaker line buses are pxe-wired by the manufacturer. Under
~` th~se circumstances, the load center is relatively inflexible in
terms of the applications it can accommodate. That is J if the
- customer's el~ectrical requirements should change in the future,
thè existing load center may not be conducive to the changed require-
. ~
`~ ments. This is particularly true if an additional three-pole
breaker is required.
It is accordingly an ob~ect of the present invention tv
` provide a three-pola circuit breaker of compact modular construction.
A further ob~ect is to provide a three-pole circuit breaker
of the above character which requires no special mo-~nting provislons
for its installation in a standard plug-~n circuit breaker load
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center.
Another object ls to provide a ~hree~pole circu~t breaker of
the above cha~acter which is comparable ln width to ~he combined
; widths of ~hree, standard single-pole branch circuit breakers.
Yet another object is to provide a three-pole circuit breaker
- o~ the above character which is equipped with line terminal s~abs
enabling the installation of the breaker in any load center space
normally occupied by three side-by-side branch circuit breakers.
A still further object is to provide a three-pole circuit
breaker of the above character having improved current carrying and
current interrupting capacities.
An additional object of the present invention is to provide
a three-pole circuit breaker of the above character which is effi-
; cient in design, inexpensive to manufacture and reliable in opera-
, 15 tion.
Other objects o the invention will in part be obvious and
~n part appear hereinafter.
` ? S~ARY OF THE INV~NTION
In accordance with ~he present invention, there is pro~ided
a compact three-pole circuit breaker having a molded case of a
width comparable to the combined widths of three single-pole branch
~`. circuit breakers and line terminal s~abs situated to accommodate
installation in a plug-in circuit breaker load center at any loca-
tion normally occupied by three side-by-side branch breakers. The`. 25 three-pole circuit breaker utilizes two identical operating mechan-
isms in controllably articulating a movable contact arm situated in
each o~ three pole chambers provided in the breaker case. The two
operating mechanisms occupy positions intermPdiate adjacent pole
chambers and are ganged together for concerted manual operation by
30 an external handle tie and internal coupling elements operatively
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interconnecting the three contact arms and the operating mechanism~.
Trip units, one in each pole chamher, independently act on an inter-
nal common trip bar ~o sim~ltaneously trip bo~h operating mechanisms
and thus effect concerted opening movement o the three co~tact arms
in.quick break fashion under the urgence of mechanism springs,
; supplemented by helper springs .
The invention accordingly comprises the features of construc-
: tion and arrangement of parts which will be exemplified in the con-struction hereinafter set forth, and the scope of the invention will
be indicated in the claims.
For a better understanding of the nature and objec~s of the
-- invention, re~erence should be had to the following detailed des-
`~ cription taken in conjunction with the accompanying drawings, in
; which:
FIGURE 1 is a perspective view of a three-pole, molded case
~ circuit breaker constructed in accordance with the present inven- :
`~ tion;
^`` FIGURE 2 is a plan view of the circuit breaker of FIGURE 1
` with the case cover removed;
.; 20 FIGURE 3 is an exploded, perspective view of a portion o
the current path through each pole of the circuit breaker of
FIGURE l;
FIGURE 4 is a side elevational view of the current path
through each pole of the circuit breakèr of FIGURE l;
FIGURE S is a ~ragmentary, side elevational view of a por-
tion of the breaker pole current path seen in FIGURES 3 and 4, with
the contacts engaged;
FIGURE 6 is a side elevational view, partially broken away,
o one of the breaker operating mechanisms utillzed ln the circuit
breaker of FIGURE l,and depicted in its open circuit condition;
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~ FIGURE 7 is a slde elevational view o~ the breaker operating
mechanism seen ln FIGURE 6, but depicted in it~ closed circuit con- 1
dition; and
FIGURE 8 is an exploded perspective view of a portion of the
~5 circuit breaker o FIGURE 1, illustratlng the lnternal coupling s
between the two breaker operating mechanisms.
~ike reference numerals refer to like parts throughout the
;` several views of the drawings.
` DETAILED DESCRIPTION 1,
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.`~0 Referrin~ now to the drawings, the multi-pole circuit breaker
of the present invention, generally indicated at 10 in FIGURE 1, is
housed in a molded insulative case consisting of a base 12 and a
. cover 14 secured together by screws, not shown. Top surface of
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cover 14 is provided with a raised escutcheon 14a in which are pro '.
.:
L5 vided a pair of openings 14b accommodating the protrusion of a pair
of manual operating handles 16. A handle tie 18, together with a
pin 19, gangs the operating handles together such that they are
pivoted in concert durin~ manual operation of the circuit breaker. "
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; A lever 18a, pivotally mounted to handle tie 18, may be swung up-
. 20 wardly and grasped by the operator to achieve enhanced mechanical
advantage while toggling the operating handles. `;
Turning to FIGURE 2~ it is seen that base 12 of the breaker ~,
case is struc~ured to provide three, side-by-side, longitudinally
elongated pole chambers 10a, 10b and 10c defined in part by base
sidewalls 12a and intermediate, upstanding b~se partiti.ons 12b and
12c. The intermediate partitions 12b, together with the base
: sidewalls provide arc chambers 20 at corresponding one ends of the
three pole chambers, each arc chamber accommodating an arc chute,
generally indicated at 20a. In the longitudinal gaps between par- `
titions 12b and 12c, there is accommodated a pair o~ identical
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breaker operating mechanisms, eachgenerally indicated at 22. It is
seen that one of theqe operating mechanisms is po~ltioned between
- left pole chamber lOa and cen~er pole chamber lOb, while the other
operating mechanism is positioned between cen~er of pole chamber lOb
,5 and right pole chamber lOc. Operating in each breaker pole chamber .-
is a movable contact arm 24 whose upper end (in the orientation seen
in FIGURE 2) extends into its associated arc chamber 20. A movable
contact 26 is brazed to the upper end o each contact arm for move-
ment therewith between open circuit and closed circuit positions ;
` lO with respect to an associated fixed or stationary contact situated
in each arc chamber. .
Turning to FIGURE 4, each fixed contact 28 is mounted atopone end of a separate line strap 30 whose other end is connected
via a braid 32 to a female stab connector 34 exposed in an opening !.
`15 12d provided in the floor 12e of breaker case 12. These female stab
connectors accommodate male stab connectors of a plug-in circuit
breaker load cen~er pursuant to both electrically and physically
installing circuit breaker lO therein. These stab connectors, one
situated in each breaker pole chamber, are positioned on, for
~0 example, one inch centers, thereby enabling circuit breaker 10,
whose case is then three inches wide, to plug on~o three consecutive,
aligned load center stabs in the manner of three, side-by-side, one ;
inch, single-pole branch circuit breakers.
The ~ixed contact end of each load line strap 30, as seen in
FIGURES 3-5, is resiliently supportPd with respect to floor 12e of
~he breaker case via an intervening hairpin spring 35. As seen in
FIGURE 5, with contact arms 24 in their closed circuit positions
`` bringing the movable contacts 26 into electrical contacting engage-
ment with their associated fixed contacts 28, springs 35 are com-
pressed ~o supply upwardly directed spring forces efective in
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insuring adequate and uniform con~.act pres,t~ures. In additlon, ;;
springs 35 serve to compensate ~or variations in the closed circui~ ,~
positions of the contact arms 24 due to manuacturing tolerances.
Also afixed to the fixed contact end o each line strap 30 is a
steel arc runner 36 serving ~o direct an arc struck be~ween the
.
- fixed and movable contacts during a circuit interruption out into
the assoclated arc chutes 20a for efficien~ arc extinction. It
will be no~ed that the upper surface of the arc runner is flush with
the upper surface of fixed contact 28 so as to promote smooth run-
~10 ning of an arc out onto the arc runner surface. The folded back
configuration of the arc runners provid~s double thickness arc run-
ner segments to withstand ~he eroding effects of successive circuit
interruptions.
Referring jointly to FIGURES 2, 3 and 4, the end o each
contact arm 24 remote from lts movable contact end is electrically
connected via a braid 38 to a heater 40 included in a separate trip
unit, generally indicated at 42 and accommodated in each breaker ~,
pole chamber. Each heater is constructed as an integrally formed
conductor having an upright body 40a from which extends a pair of
laterally spaced, curved arms 40b terminating in a common path 40c
to which the end of braid 38 is brazed~ Welded to the lower termin-
al portion of upright heater body for vertical extension in proxi~
mate, ~hermally cou~led relation ~hereto is a bi metal 44. It will
be noted that heater arms 40b straddle bi-metal 44 in accommodating
its vertical extent, and together pro,vide sufficient conduetive
metal cross-section in thestringent lateral confines of each pol~
chamber. Moreover, welding the braid 38 to the common termination
of arms 40b rather than to the lower termination o~ heater body 40a
at the location where bi-metal 44 i8 also welded obviates the need
- 30 for specialized tri-metal welding ~echniques. The internal breaker
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circuit for each breaker pole i~ terminated by an L-shaped load
strap 46, the vertical portion of which is welded at its upper
termination to the upper t~rminal portion of i~8 associated heater
-. body 40a, while the horizontal load strap portion is bolted to the
~- 5 breaker case floor in electrical connection with a wire lug 48 seen
in FIGURE 2.
Each trip unit further includes a U-shaped magnetic field
`i piece 50 mounted in partially embracing relation to heater body 40a.
Flux developed in each ~ield piece in response to current flowing
.-10 through its associated heater body 40a acts on an associated arma-
ture 5~ e~uipped with opposed laterally extending ear~ 52a received .,
in opposed notches S3 formed in the rims of the case sidewalls 12a
and intermediate partitions 12c, as the case may be, pursuant to
pivotally mounting each armature in their respective pole chambers ,`
(FIGURE 2). A torsion spring 53a provides the requisite armature
bias in opposition to the magnetic attraction by its associated ,
~ield piece 50, while a depending finger 52b engages an abutment
~not shown) provided in the ase 12 pursuant to establishing an
appropriate air gap between the associated armatures and field .
pieces.
To provide internal common tripping o~ t~e two breaker oper-
ating mechanisms 22 in response to an overcurrent condition in any
one of the breaker poles, as sensed by the associated trip unit 42, :,
there is provided a common trip bar 54 positioned to span the three
pole chambers in proxima~e relation to each o~ the trip units. As
best seen in FIGURE 2 and 8, a ~itting 55 is riveted to each end of
the trip bar to provide a laterally extending ear 55a which is
received i~ opposed notches 55b formed in the rim of each case slde- .
wall 12a pursuan~ to pivotally mounting ~he common tr~p bar. The
common trip bar i~ ~urther provided wi~h a ~paced array o upwardly
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~ extending protuberances 54a respectlvely situated above each pole
`~ ~hamber in confronting rela~ion with the ~rlp unit 42 thereln. The
~`- common trip bar carries a pair of latch members 56 at location~
intermediate adjacent pole chambers ~or dependence into cavi~ies 57
provided in intermediate base partitions 12c. Each latch element
is provided with a lanced latch shoulder 56a servin~ to latchably
engage the tip 58a of a trigger ~8 extending into the respective
cavities 57 from the two operating mechanisms 22. Depending leaf
`~ springs 59 carried by the trip bar 54 act against an end wall in
each intermediate partition cavity 57 to bias the trip bar into a
pivotal position accommodating latching engagement of the latch
~-` shoulder~ 56a with the respec~ive operating mechanism trigger 58
pursuant to releaseably detaining the two operating mechanisms in ,-
their reset or untripped conditions.
In the event o~ current of overload proportions flows through
any one of the breaker poles, the bi-metal 44 of the trip unit 42
~ituated in that particular pole chamber is indirectly heated by the
current flowing through the heater body 40a. The bi-metal 44 begins
to flex, causing the tip of a calibrating screw 44a threaded through
a tapped pole in the upper end thereof, to engage the confronting ~;
one o~ the protuberances 54a, causing trip bar 54 to pivot in a l;
direction leading to the ultimate disengagement o~ the latch e~ement
shoulders 56a ~rom ~he two operating mechanism ~riggers 58. As will
be described below, upon unl~atching of the operating mechanism
triggers, they pivot downwardly away from the common trip bar to
defeat internal operating mechanism latches pursuant ~o achievin~
circuit interruption in all three breaker poles in quick break
fashion.
To e~fect magnet~c tripping of the breaker in response to
the flow of current o$ heAvy overload and short circuit proportions
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through any one of the breaker poles, each armature 52 is provided
with an upwardly extending finger 52c which is situated to engage
the confronting one of the trip bar protuberances 5ga as the arma-
ture is attracted to its ac-tuated position by the flux generated in
its associated field piece 50. This armature engagement induces
pivotal movement of the trip bar in a direction to unlatch and trip
both operating mechanisms 22. To prevent single phasing of one or
two poles of breaker 10, the upper end of each latch element 56 is
connected to the associated operating mechanism trigger 58 by a
spring 60. Consequently, should one of the operating mechanism
triggers unlatch before the other one, its tripping movement is
communicated to common trip bar 54 via spring 60, thereby insuring
pivotal movement of the common trip bar completely to its unlatching
position well displaced from latching engagement with the other
operating mechanism trigger. Thus, the possibility of one operating
mechanism tripping without the other is precluded.
The two breaker operating mechanism 22 are identical to each
other and constructed essentially in the manner disclosed and claimed
in commonly assigned U.S. Pat. 3,786,382 - Powell dated Jan/15/1974.
As thus seen in FIGURES 6, 7 and 8, each operating mechanism includes a
frame consisting of spaced metallic sideplates 61 rigidly inter-
connected by a J-shaped connecting member 62 via suitable means, such
as staking. Also s-taked to the sides of the operating mechanism
frame are insulative panels 63 which serve as interphase barriers
for adjacent pole chambers. Along the upper edge of each frame
sideplate there is provided a semi-circular projection 61a which serve
to mount a transverse pin 64 on which operating handle 16 is pivotally
mounted. Handle 16 is provided with a depending portion 16a
which serves to carry a transverse pin 66 to which the upper
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" ends of a pair o~ upper toggle links 68 are pivotally mounted.
. Frame sideplates are provided with arcuate S10~8 61b ~hrough which ,,
the ends of pin 66 move during pivotal manipulation of operating
~, handle 16. Handle 16 is provide~ with a een~rally located, longitu~: 5 dinally extending slot (not shown) for accommodating trigger 58 which `'
is p~votally mounted by handle pin 64. The ~rigger is provided with
an arcuat~ slot (not shown) so as to avoid interference with toggle
pin 66.
A,lower toggle link 70, of U-shaped cross-section is pivotally
connected to the two upper toggle links 68 by a knee pin 72 (FIGURE
6). The lower end of toggle link 70 carries a ~ransverse rod 74
which extends well beyond both sides of the mechanism frame through ',
kidney-shaped slots 63a formed in the insula~ive panels 63. To in-
sulatively, mechanically couple the movable contact arms 24 to the
operating mechanisms 22, a grommet 76 of insulative material is pro- ,,,
vided with opposed, centrally located blind holes 76a into which the
ends of rod 74 are inserted pursuant to mounting a separate grommet ~' '
to each end of this rod. Each grommet is provided with a hub 76b
which is received in a hole 24a provided in each movable contac~ arm
24, while an integral grommet flange 76c provides the requisi~e ~ ,
spacing between the operating mechanism frame and the contact arms
to each side thereof. As best seen in FIGU~E 8, the grommet mount-
ing the c,enter pole contact arm accommodates the insertion from ,'
` opposite sides of the rods 74 rom the two operating mechanisms 22
'~ 25 into its blind central hole~ 76a to achieve effective ganging of the
`~ three movable contact arn~s. The grommet located intermediate the , '
two operating mechanisms has an insulative washer 77 fitted on its
step-down hub portion 76d so a~ to cooperate wlth ~he grommet flange
76c in centrally locating the cen~er pole con~act arm with respec~
to the two operating mechanisms.
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A8 disclosed in greater detail in the above~noted patent No
- ~ 3,786,382/ the opera~ing mechanism ~o~gle is normally maintained in "-
an essentially straightened conditlon whereby pivotal movement of
. - the operating handle.16 is communicated to the movable contact arms
. 5 24.pursuant to articulating them between their open and closed cir ~.
cuit positions. However, when ~he operating mechaniii~ims are tripped
by the ac~ion of any one o trip units 42 is releasing triggers 58, i'
the ability of the toggle in each operatin~ mechanism to maintain
its straightened conditior: is defeated, enabling the movable contact .:
arms to jointly move to their open circuit positions independently
of the operating handles. To this end, as seen in FIGURE 6 herein,
a latch 78 is pivo~ally mounted adjacent its lower end on rod 74 and .
carries adjacent its upper end laterally extending ears 78a which are
adapted to engage latch shoulders 68a formed adjacent the lower ends
o~ the two upper toggle links 68. A torsion spring 79 carried on .
knee pin 72 ac~s on latch 78 to normally bias it in a counterclock- .
~ise pivotal direction seen in FIGURE 6, thereby urging the latch
.ears 78a into positions of latching engagement with their associated
latch shoulders 68a. It is thus seen that, as long aisi this latching
" 20 engagement is maintained, relevant pivotal movement of the two toggle ~.
links about their knee pin 72 is restrained, and the toggle is thus
.. maintained in its illustrated subs~antially s~raightened condition. -
Under these circumstances, with pivotal movement of handles 16 in
the counterclockwise direction from their posi~ions in FIGURE 6 to
their positions seen in FIGURE 7, the movable contac~ arms 24 ganged
to rods 74 are jointly rocked downwardly, generally about pins 24b
extending from each side of each contact arm and caught in opposed
notches 80 formed in interior-portions of base 12 located in ~ach
pole chamber. When, durin~ this downward movement of the contact
. 30 arms 24 ~heir movable contact 26 engage their assdiciated stationary ;
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contacts 28, the ulcrums ~or the rocklng mo~ion of the contact arms
shift to the point of contact engagement, and the opposite ends of
the contact arms move downwardly, ducking pins 24b toward the bottoms
of notches 80 at the conclusion of contact closure articulation of
S - the operating mechanisms. During downward movement of the c~ntact~
arms leading to circuit breaker closure, a compression spring 82
located in each operating mechanism and acting between J-shaped
frame member 62 and rods 74 is loaded preparatory to powering an
opening movement of the operating mechanisms and contact arms in
quick break fashion. Also serving in this capacity are outboard
helper springs 84, seen in FIGURES 2 and 3, having their one ends
hooked on portions of base 12 and their other ends hoaked on the
left and right pole movable contact arms. To manually open circuit
breaker lO1 the handles are toggled in the clockwise direction back
to the position o~ FIGURE 6, thereby lifting the straightened toggle
and the contact arms are rocked upwardly to open circuit positions
` under the urgence of springs 82, 84.
: To defeat the restraint maintaining the toggle in its
straightened condition, latch 78 is provided with an upwardly
extending tab 78b which is poised in a position to be struck by a
nose 58b carried by trigger 58 when the latter is released from
: . ,.
latch shoulder 56a pursuant to`trippingthe operating mechanisms 22. ,
Tripping movement of triggers 58 is powered by individual springs -
86 connected between each trigger and its associated mechanism frame
member 62. It is seen rom FIGURE 6 that upon unlatching of the
triggers, springs 86 propel their triggers in a counterclockwise
direction bringing the trigger nose 58b into striking engagement
` with latch tab 78b, causing latch ears 78a to disengage latch
shoulders 68a. The toggle of each operating mechanism is thus freed
to buckle under the urgence of springs 82 and 84, and the contact
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arms 24 are abruptly rocked upwardly to their open circuit positions,
; all as more clearly disclosed in the above-noted patent With the
- operating mechanisms tripped, a handle sprlng (not shown~ biases the
two operating handles 16 to an intermediate, trip indicating position.
To reset the operating mechanisms, the operating handles are pivoted
. to their clockwisemost positions seen in FIGURE 6, lifting their
n triggers 58 upwardly into positions of latching engagement with their
; respective latch shoulders 56a and, at the same time, straightening
the toggle to bring the latch ears 78a back into latching engagement
with latch shoulders 68a. With the toggle now held in its straight-
ened condition, the breaker can be reclosed.
It will be noted that each operating mechanism 22 is opera-
- tively positioned independently of cover 14 by various grooves 87
(FIGURE 2) and ridges 88 (FIGURE 8) ~ormed in portions of base 12,
and secured by a screw 89 extending through a hole 12f in base floor
12e and threaded into a tapped bore 6~a provided in swagged-up por-
tion of frame member 62. This swa~ged-up portion serves to position-
ally locate the lower end of mechanism spring 82. By virtue of this
construction, together with the pivotal mounting of the armatures 52
and common trip bar 54 in the base 12, it is seen that circuit
breaker 10 is operational with cover 14 removed to facilitate trouble
shooting.
As an additional feature o~ the present invention, the ends
of the contact arms 24 extend into their respective arc chambers 20
through vertically elongated slots provided in a pair of barriers
90 and 92, seen in FIGURES 2 and 3. Barriers 92, closest to the
arc chambers are formed of bone fiber which ablate water vapor in
the presence of arcing; this water vapor assisting in moving the
arcs out into the arc chutes 20a. The other barriers 90 are formed
of a rigid, high temperature melamine and are engaged along their
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` `~ upper edges by the cover to press down on the load straps 30 situa-
j: ~ ted therebeneath to preset the open circuit positions of the station-
5-~ ary contacts 28 and the lnitial loading o springs ~5 (FIGURES 4 and
.' S)'
S . It will thus be seen that the objec~s set ~orth above, among
those made apparent in the preceding description, are efficiently
attained and, since certain changes may be made in the above con-
struction without departing from the scope of the invention, it is
intended that all matter contained in the above description or shown
.... .
` 10 in the accompanying drawings shall be interpreted as illustrative
and not in a limiting sense.
~aving described our invention, what we claim as new and
desire to secure by Letters Patent is:
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