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Патент USA US2406325

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Aug. 27, 1946.
2,406,325
lH. D. DORFMAN
CIRCUIT INTERRUPTER
Filed April 29, 1942>
77
37
95
Insel/a fio/1
7
BY
.
A TORNEY
`
'
Patented Aug. 27, 1946
2,406,325
vUNITED STATES PATENT OFFICE'
2,406,325
CIRCUIT IN TERRUPTER
Hiller D. Dorfman, Forest Hills, Pa., assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application April 29, 1942, Serial No. 440,934
11 Claims.
1
This invention relates to circuit interrupters
of the type having a thermally responsive trip
element of bimetallic material for causing auto
matic opening of the interrupter in response to
(Cl. 20D-116)
2
wherein the bimetal deflects laterally when
heated by persistent low overloads to trip the
circuit breaker after a time delay and in which
excessive current ñowing in opposite directions
through the bimetal element and its support
An object of the invention isto provide a cir
members generates an electromagnetic force to
cuit breaker having an improved thermal trip
instantaneously trip the breaker on heavy over
device wherein a bimetal trip element is mounted
loads.
at each end of resilient support members which
Another object of the invention is to provide
flex in response to defiection of the bimetal ele 10
a circuit breaker with an improved trip device
ment to effect tripping of the breaker.
wherein a thermal element in the form ora
Another object of the invention is to provide
loop is supported at each end while relative move
a circuit breaker having an improved- thermal
ment therebetween is permitted.
trip device comprising a generally U-shaped bi
Another object o1" the invention is to provide
metal element having both legs supported on
a circuit breaker with an improved thermal trip
resilient support members which are adapted to
means comprising a bimetallic loop with the dis
be ilexed, when the bimetal deflects, and to dis
tance between the sides thereof variable upon
place the bimetal element to effect tripping of the
change of temperature, and means supporting
breaker.
each end of said bimetallic element while per
Another object of the invention is to provide
mitting relative movement therebetween.
a circuit breaker having an improved thermal
Another object of the invention is to provide
trip device comprising a generally U-shaped fbi
an improved circuit breaker comprising a mem_
metal element adapted when heated to move the
ber biased to eiîect opening of the breaker with
legls thereof relative to each lother, the legs of
an improved trip means comprising a U-shaped
the bimetal being mounted on resilient support
bimetal element having the distance between its
members which bend when the bimetal element
sides variable upon change of temperature for
deiiects and causes movement of the bimetal
restraining and releasing the biased member, and
bodily to eiiect tripping of the breaker.
means supporting each end of the bimetal ele
Another object of the invention is to provide
ment to oppose release of the biased member
a circuit breaker having an improved thermal 30 in responseto sudden shocks.
trip device comprising an arcuate bimetal ele
Another object `of the invention is to provide
ment the ends of which are disposed to deflect
a circuit breaker with a novel thermal trip de
outwardly when heated, the ends of the bimetal
vice which is simple in construction, reliable and
element being mounted on resilient support mem
efficient in oper-ation and inexpensive to manu
bers arranged to flex upon deñection of the bi
facture.
metal element to effect tripping of the breaker.
The novel features that are considered char
Another objectl of the invention is to provide
acteristic of the invention are set forth in par
a circuit breaker having an improved trip device
ticular in the appended claims. The invention
including a U-shaped bimetal element having its
itself, however, both as to structure and oper
ends mounted cn substantially parallel resilient 40 ation, together with .additional objects and ad~
support members, the bimetal element being dis
vantages thereof, will be best understood from
posed to deflect laterally when-heated to eiïect
the following description of several embodiments
tripping of the breaker.
thereof when read in conjunction with the ac
Another object of the invention is to provide a
companying drawing, in which:
circuit breaker with a novel trip device wherein 45
Figure 1 is a vertical section view of a circuit
excessive current ilowing in opposite directions
breaker .embodying an improved current respon
through the parallel legs of a U-shaped Ibimetal
sive bimetallic control device constructed in ac
and the resilient support members for the legs
cordance with the invention.
of the bimetal produces an electromagnetic force
Figs. 2 and 3 are fragmentary sectional views
to instantaneously trip the breaker on heavy 50
predetermined conditions.
overloads.
Another object of the invention is to provide
showing modifications of the improved current
responsive bimeta-llic control device.
The Ycircuit breaker illustrated in Fig. 1, with
the exception of the trip device, is substantially
prising a U-shaped bimetal element having its
the same as that disclosed in Patent 1,802,758,
legs supported on resilientl support members 55 issued
to H. D. Dorfman on April 28, 1931, and
a circuit breaker with a novel trip device com
2,406,323
El
assigned to the assignee of this invention, for
which reason only a brief description of the
structure of the circuit breaker will be given
herein. For the details of construction refer
ence may be had to the above referred to patent.
The circuit breaker, as illustrated in Fig. 1,
comprises a base 1, and a cover 9 of molded
insulating material, end terminals I I, a stationary
Contact I3, a movable contact I5, operating mech
anism indicated generally at I1, a current re
4
straight strip of material and is formed to sub
stantially the shape shown in Fig. 1 with the
high expansion side facing the latch member.
When the bimetal element is heated a predeter
mined amount in response to abnormal current
traversing the circuit of the breaker, the legs oi'
the bimetal element move inwardly toward each
other flexing the resilient supports 63 and 65
which results in moving the bimetal bodily to
the position shown in dotted lines in Fig. l.
When this occurs, the spring 55 moves the latch
member 41 in a counterclockwise or unlatching
direction disengaging the latch 53 from the cra
dle 31. This allows the overcenter springs 43
left hand terminal II, through the current re
to rotate the cradle 31 in a clockwise direction
sponsive trip device I9, a' conducting strip 23
during which rotation the line of action of the
through a flexible shunt conductor 23, a resilient
springs 43 is changed to cause collapse of the
Contact arm 21, the movable contact I5, the
toggle 39-4I and opening oi the contacts in a
stationary contact I3, and a conducting strip 25
manner well known in the art.
to the right-hand terminal I I.
'
Before the contacts may be closed, it is nec
The movable contact I5 is secured to the re 20
essary to reset the cradle 31 to its latched posi
silient contact arm 21 which is secured by means
sponsive trip device indicated generally at I3
and an arc extinguisher 2 I.
The circuit for the breaker extends from the
tion. This is accomplished by rotating the oper
ating lever 33 in a counterclockwise direction by
means of the operating handle
During this
of a pivot pin 33 on a U-shaped main frame 3l.
The operating mechanism I1 comprises a U 25 movement, the extension 4S engages and rotates
of rivets or other suitable means to a channel
shaped frame 29 pivotally supported by means
shaped operating lever 33 having an operating
the cradle 31 in the same direction to reengage
the latch portion 45 of the cradle with the latch
handle 35 of molded insulating material secured
59 on the latch member 41. The contacts can
theretoy a cradle 31, a toggle comprising a pair
now be closed by moving the handle 35 and the
of toggle links 39 and 4I and a pair of overcenter
springs 43 (only one being shown). The operat 30 operating lever 33 to their extreme right hand
positions, which movement changes the line of
ing lever 33 is pivotally mounted on pivot pins
action of the overcenter spring 43, so as to
34 on the sides of the frame 3l, and the cradle
straighten the toggle 35i-«4I and thus eiîect clos
31 is pivoted on a pin 38 also supported in the
ing of the contacts with a snap action.
frame 3I. One end of the toggle link 39 is piv
The breaker may be opened manually by mov
otally connected to the cradle 31 by a pin 40, 35
ing the handle 35 toward the left during which
and the toggle link 4I is pivotally connected to
movement the line of action of the springs 43 is
the free end of the channel shaped-member 29
moved to the left of the pivot pin 43. The springs
by means of a pin 42. The toggle links 39 and
thus exert a force on the toggle 39~4I 'in a di
4I are pivotally connected together by a knee
rection to cause its collapse which results in
The
overcenter
springs
43
are
ten-`
40
pivot pin 44.
movement of the movable contact I5 with a snap
sioned between the knee pin 44 of the toggle 39--action to the open position. The contacts are
4I and the outer end of the operating lever 33.
closed in the previously described manner.
The cradle 31 is provided with a latch portion 45
The short bimetal element 6I (Fig. l) provides
with which a pivoted latch member 41 is adapted
to cooperate to releasably restrain the cradle 31 45 a low electrical resistance and is particularly
adapted for use where currents of higher rating,
in the position shown. The operating member
for instance, above '10 amperes are to be con
33 is provided with an extension 49 which is
trolled by the breaker. In such circumstances
adapted to cooperate with the cradle in order to
it is desirable that the resilient supports 63 and
reset the cradle after the breaker has been
tripped.
-
The trip device I9 includes the latch member
41 which is pivotally mounted by means of a
pivot pin 5I supported in a bracket 53 formed
on the conducting strip 2B. The latch member
41 is biased in unlatching direction by a spring
55 having one end connected to the latch mem
ber and the other end hooked to a spring clipl
51 secured to an upturned portion of the strip 2D.
50 65 be made of low resistance material such aS
bronze or copper.
In «the modification illustrated in Fig. 2, the
arcuate bimetal element B1 is considerably longer
to provide greater electrical resistance which is
necessary for lower currents, for instance fifty
amperes or less. In this modiiication, the high
expansion side of the bimetal 61 is one the inside
of the arc. Support members 69 and 1I of re
silient conducting material are secured to the
A latch 59 mounted on the free end of the latch
member 41 but suitably insulated therefrom co 60 ends of the bimetal by welding, brazing, or by
other suitable means. The resilient support
operates with the latch portion 45 of the cradle
member 69 is secured by means of a screw 13 to
31. The latch member 41 is normally restrained
the inner end of the left hand circuit breaker
in latching position against the bias of the spring
terminal I I, and the resilient support member 1I
55 by a U-shaped bimetallic element 6I (Fig. 1).
is similarly secured by means of a screw 15 to
Each leg of the bimetal element El is secured by
the upper end of the conductor strip 20 which
welding or by other suitable means to resilient
in this case is extended upwardly a greater dis
support members 63 and 65 of conducting mate
tance than in Fig. l.
rial. The resilient members are secured one to
When the bimetal element 51 (Fig. 2) is heated
the inner end of the terminal II, and the other
to the upturned end of the conducting strip 2B 70 a predetermined amount by overload .currents
traversing the circuit controlled by the' breaker,
by means of screws 66. The bimetal element 6I
it tends to straighten itself. This causes the re
is insulated from the latch member 41 by means
silient support members 69 and 1I to flex ano.
of a strip 91 of insulating material secured to
the parts assume the shape substantially as shown
the latch member.
The bimetal element 6I is constructed from'aï' 75 by dotted lines (Fig. 2) , the bimetal moving away
2,406,325
5
6
from the latch member 4l' permitting the spring
ed in a manner to effect tripping of the breakerI
after a time delay on persistent overloads of low
value and substantially instantaneously on sud
den heavy overloads or short circuits. The bi
metal element of each of the modifications illus
55 to disengage the latch from the cradle 31. In
the Fig. 2 embodiment of the invention, the sup
port members iid and li for the bimetal element
for lower current ratings may serve as heater
elements for the bimetal by constructing them
of suitable resistance material.
According to the modified embodiment of the
invention illustrated in Fig. 3, the bimetallic trip
element T! is U-shaped and the legs thereof are
suitably secured to resilient support members 19
and Si. The support member T9 is secured by
trated may be made from a flat strip of bimetallic
means of a screw 8i? to a conducting strip S3 eX
material and is, therefore, inexpensive to manu
facture.
Having described several embodiments of the
invention in accordance with the patent statutes,
it is to be understood that various changes and
modifications may be made therein without de
parting from some of the essential features of
tending downwardly from the terminal il, and
the invention. It is, therefore, desired that the
the support member 3l is secured by means of a
screw 85 to the formed end of the conductor 2%.
language of the appended claims be given as rea;
sonably broad interpretation as the prior art per
mits.
The high expansion side of the bimetal element
il is on the inside and when the bimetal is heated
a predetermined amount in response to overload
I claim as my invention:
1. A circuit breaker comprising relatively mov
currents below a predetermined value, the legs 20 able contacts, operating mechanism for said con
tacts, a trip device including a generally U-shaped
of the bimetal element spread apart or separate,
current responsive bimetal element disposed to
:flexing the resilient support members 'E9 and di.
deñect when heated a predetermined amount, and
lThis spreading action is utilized to operate a latch
resilient support means for independently sup
member di te reiease the breaker mechanism.
porting both ends of said bimetal element, said
The
pivot iatch
pin 8E lever
mounted
El isin pivotally
a pair of brackets
supported
'Si (only
on
support means iiexing when the bimetal deiiects
to cause an operation of the operating mechanism
one being shown) secured to the base 'i of the
to open the contacts.
breaker by screws @3. The upper end of the latch
2. A circuit breaker comprising separable con
lever S1 carries a latch Sb which is insulated from
the latch lever and cooperates With the latch end 30 tacts, operating mechanism including a member
releasable to cause opening of the contacts, latch
45 of the cradle 3l to releasably restrain the op~
means for releasably restraining said member, a
erating mechanism il' in closed circuit position.
trip device comprising a bimetal element disposed
The latch lever 8l is biased in latching direction
to deflect when heated a predetermined amount
by means of a spring Si coiled about the pin 3S
and having one end bearing against the brackets 35 by excessive current, and a plurality of resiiient
support means for supporting both ends of the bi
9i and the other end bearing against the upper
metal element and for connecting said bimetal
end of the latch lever. The lower arm of the
element in the circuit of the breaker, said support
latch lever 87 carries an insulating button 9i) with
means flexing when the bimetal deflects a prede
which the thermal element cooperates to operate
termined amount to effect release of said re
the latch lever. The spreading movement of the
leasable member.
support member 'i9 may be limited in one direc
3. A circuit breaker comprising separable con
tion by a stop member lei of insulating material
tacts, operating mechanism for said contacts in
secured to the conductor SES.
cluding a member biased to cause opening of the
When the U-shaped bimetal element 11 is
heated a predetermined amount in response to 45 contacts, a latch for releasably restraining said
member, said latch being biased in unlatching
persistent overloads, it flexes and moves its legs
direction, a trip device comprising a generally
away from each other as indicated by dotted
U-shaped bimetal element for restraining the
lines in Fig. 3. This spreading action rotates the
latch in latching position, and resilient support
latch lever 8l counterclockwise to release the
cradle 3l and cause opening of the contacts after 50 means for resiliently supporting both legs of said
a time delay in the previously described manner.
bimetal element, said bimetal element deilecting
when heated a predetermined amount by exces
On overloads above the predetermined value or
sive current in the circuit of the breaker, and
on short circuits, the magnetic repelling force
said resilient support means flexing when the ele
generated by the heavy current flowing in oppo
ment deflects to cause the latch to release the
site directions through the support members 19
said member of the operating mechanism for an
and Si and the legs of the bimetal element 1l is
opening operation.
sufficient to cause iieXing of the legs of the bi
4. A circuit breaker comprising relatively mov
metal element and the support members to sub
able contacts, operating mechanism including a
stantially instantaneously operate the latch lever
Si to trip the breaker.
60 member biased to cause opening of said contacts,
It will be seen from the foregoing description
trip means for releasing said member, `said trip
means comprising a generally U~shaped bimetal
that there is provided an improved thermal trip
element disposed to deflect in a direction to move
device for a circuit breaker which comprises a U
its ends toward each other, and resilient sup
shaped bimetal element having both legs thereof
mounted on resilient support members. This 65 port members for supporting both ends of said
bimetal element, said resilient 'support members
construction, while reliable in operation in re
ilexing when the bimetal deflects for moving the
sponse to overload currents, is sufficiently rigid
bimetal to cause release of the operating mecha
to oppose tripping of the breaker in response to
msm.
physical shocks or jars. By selecting the ma
5. A circuit breaker comprising relatively mov
terial for the support members from a group of 70
able contacts, operating mechanism including a
materials having various resistance characteris
tics, it is obvious that the tripping characteristic
member biased to cause opening of said contacts,
of the breaker may be suited to various current
and trip means for releasing said members, said
ratings. Another advantage of the invention re
trip means comprising a generally U-shaped
sides in the provision of a bimetal element mount 75 bimetal element disposed to deñect in a direc
2,406,325
7
8
tion to separate its ends. resilient support mem
bers for supporting both ends of said bimetal ele
ment, said resilient support members flexing
perature and having a portion intermediate the
ends of the loop movable upon a predetermined
change in temperature to effect operation of said
When the bimetal deñects for moving the bimetal
to cause release of the operating mechanism.
6. The invention according -to claim 1 charac
operating mechanism, and means for supporting
each end of said bimetal element while permit
terized by the fact that the resilient support
members comprise heater elements for heating
ting relative movement therebetween.
10. A circuit breaker comprising relatively
movable contacts, operating mechanism for Isaid
the bimetal element.
contacts including a member biased to cause
7. In a circuit breaker, the combination of a 10 opening of said contacts, trip means comprising
releasable operating mechanism for the breaker,
a U-shaped bimetal element having the distance
between the sides of the U variable upon change
of temperature, said bimetal element acting at
a point intermediate its ends to normally restrain
said biased member and being operable when
heated a predetermined amount to release said
being physically disposed substantially parallel to
biased member to effect opening of said contacts,
each other and being electrically disposed in
and means supporting each end of said bimetal
series relation with each other in the circuit
element to oppose release of said biased member
of the breaker and being responsive to overload
in response to sudden shocks or jarring forces.
currents to operate the latch member.
11. In a circuit breaker comprising relatively
8. In a circuit breaker, releasable operating
movable contacts, operating mechanism for said
mechanism for the breaker, a pivoted latch
contacts including a member biased to eii‘ect
member operable t-o release the operating mem
opening of said contacts, latch means restrain
ber, a trip device including a bimetal element
ing said biased member against operation, a trip
heated in response to the current of the circuit,
device for effecting operation of said latch means
and resilient support members for resiliently
comprising a U-shaped bimetal element having
supporting both ends of said bimetal element,
the distance between its ends variable upon
said support members iiexing when the bimetal
change of temperature, said bimetal element be
element deflects to physically displace the bimetal
ing operable when heated a predetermined
element and thereby cause operation of the
amount to effect release of said biased member
latch.
and opening of said contacts, and means sup
9. A circuit breaker comprising relatively mov
porting each end of said bimetal element to op
able contacts, operating mechanism for said con
pose operation of said latch in -response to sud
tacts, a trip device comprising a bimetal element 35 den shocks.
in the form of a loop with the distance between
HILLER D. DORFMAN.
the sides thereof variable upon change of tem
a latch member for releasably restraining the
operating mechanism, a U-shaped thermal ele
ment having both legs thereof supported on re
silient support members, the legs of the ther
mal element and said resilient support members
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