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SePt- 11, 1952
c. |_. JENCKS ETAL
3,053,954 Q
ELECTRIC CIRCUIT BREAKER
Filed April 5, 1961
2 Sheets-Sheet 1
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INVEN TORS
CHARLES L. \JENCKS,
FRANK H.MURPHY
BY
A TTORNEY
Sept- 11, 1962
c. L. JENCKS ETAL
3,053,954
ELECTRIC CIRCUIT BREAKER
Filed April 5, 1961
2 Sheets-Sheet 2
5)
INVENTORS
CHARLES L. dENcKs ,
FRANK H.MuRPHY
BY (EM/4‘.
@4417
A TTOR/VEY
lattes
we
3,653,954
Patented Sept. '11, 1962
1
2
3,053,954
said breaker, and a movable armature adapted to be
attracted to the ?eld piece. Means is further provided
ELECTRIC CHRCUE'I‘ l‘tREAKER
Charles L. lencks, Avon, and Frank H. Murphy, West
Hartford, Conn, assignors to General Electric Com
pany, a corporation of New York
Filed Apr. 5, 1961, Ser. No. 100,960
6 Claims. (Cl. 2tltl—lti6)
for adjusting the position of the armature, the adjusting
means including an elongated supporting shaft having
a knob accessible for rotation from outside the insulat
ing casing. The supporting shaft carries a cam member
which is movable along the shaft, and which is lock
able at a predetermined location on the shaft.
A cam
Our invention relates to electric circuit breakers and
plate or cam follower is provided between the cam mem—
particularly to electric circuit breakers of the type in 10 ber and the armature and includes an elongated cam
cluding a molded insulating casing and current responsive
follower surface on which the cam member is adapted
tripping means provided with means accessible externally
to operate, and a projecting screw adapted to engage
of the main insulating casing for permitting adjustment
the armature.
thereof by the user within predetermined limits.
By means of the apparatus provided, a selected end
Electric circuit breakers of the molded case type 15 point of the adjustment range may be determined by
commonly include current responsive tripping means
adjusting the projecting screw which engages the arma
which is adjustable within predetermined limits by the
ture. The extent of the range, and therefore the other
users. Such circuit breakers are ordinarily of the multi
of the end points of the range, may be adjusted by adjust
pole type, such as three-pole circuit breakers, and an
ing the position of the cam member bodily along the
adjusting knob is provided for each pole, which is acces 20 supporting shaft.
sible through the top wall of the insulating casing for
The invention will be more fully understood from
adjustment within predetermined limits. More recently
the following detailed description, taken in conjunction
such circuit breakers have also been provided, with
means which may be adjusted by the manufacturer be
with the accompanying drawings, and its scope will be
pointed out in the appended claims.
fore complete assembly of the circuit breaker, whereby 25 In the drawings,
the range of adjustment permitted the user may itself
FIGURE 1 is a side elevation view, partially in sec
be varied, so that the needs of the particular user may
tion, of an electric breaker embodying the subject in
be more accurately supplied and whereby the adjustment
Vention;
or “calibration” of the circuit breaker may be more
FIGURE 2 is an end elevation view of a portion of
readily and efficiently performed. Thus, for example,
the current-responsive tripping mechanism of the circuit
breaker of FIGURE 1, taken generally on the line 2-2
of FIGURE 1;
in one form, a circuit breaker is provided including
magnetic tripping means having a magnet and a pivot
ally supported armature. The armature is adjusted by
means of a cam carried by a shaft having a knob acces
sible externally of the insulating casing. A ?rst adjust
ing means is provided which adjusts the tension or
spring ‘force against which the armature must operate
and a second adjustment is provided by which the cam
FIGURE 3 is a fragmentary sectional view of a por
tion of the circuit breaker of FIGURE 1, the section
being taken through the tripping mechanism and show
ing a portion of the latching mechanism;
FIGURE 4 is a view of the current-responsive trip
ping mechanism of one pole of the circuit breaker of
member is bodily shifted with respect to the pivot point
FIGURE 1, as shown in FIGURE 2, but with the adjust
of the armature so that the effective action or mechani 40 ing cam shown in a different adjusted position;
cal advantage of the cam on the armature is varied.
FIGURE 5 is a fragmentary View of the adjusting
Such a construction is shown for example in application
mechanism similar to FIGURE 4, but with the adjust
Serial No. 62,184, ?led October 12, 1960, by K. W. Klein
ing cam in a different bodily adjusted position;
and D. B. Powell, and assigned to the same assignee as
FIGURE 6 is an exploded perspective view of the
45 magnetic tripping mechanism of one pole of the circuit
the present invention.
While the construction disclosed in the abovemen
breaker of FIGURE 1, and
tioned application is quite satisfactory for certain types
FIGURE 7 is a fragmentary perspective view of a por
vand sizes of electric circuit breakers, it is not readily
tion of the tripping mechanism showing particularly the
adaptable to the more rigid space requirements of cer
ambient temperature compensating means.
tain other circuit breakers, and it is not readily usable 50
In the drawings, the invention is shown as embodied
in circuit breakers where it is not feasible to provide
in an electric circuit breaker having a molded insulating
adjusting means for adjusting the tension of the arma
casing including a base 10 and a cover 11. The base 10
ture bias spring.
and the cover 11 are each provided with integral barrier
It is an object of the present invention to provide
portions forming three elongated pole chambers extending
an electric circuit breaker of the type including adjust 55 from end to end of the casing.
able tripping means which is more compact than types
For convenience, FIGURE 1 is taken generally on a
previously available.
line through the central pole chamber, excepting that the
It is another object of the present invention to pro
trip unit, to be described is shown in full.
vide an electric circuit breaker including adjustable trip
A plurality of line terminals 12, one for each pole
ping means wherein adjustment is permitted over a 60 chamber are supported on line terminal straps 13 at one
predetermined range and wherein the maximum and
end of the base 10. Each of the line terminal straps 13
minimum of such range may be independently set, and
is attached to the base by suitable means such as by a
which adjustment is nevertheless simple and inexpensive.
In accordance with the invention in one form, an
electric circiut breaker is provided including a molded
insulating casing having at least one pair of separable
'contacts and operating mechanism for operating the
contacts, the operating mechanism including a member
releasable to cause automatic opening of the contacts.
screw 14. Each of the line terminal straps 13 carries a
line contact 15 at the inner end thereof. A movable con
tact is provided mounted on a contact carrier member
16 which in turn is pivotally supported on a contact
arm 17 by a pivot pin 18. The movable contact carrier
16 is connected, by means of a ?exible electrical conduc
tor 19 to the current responsive tripping assembly 20 to
The circuit breaker also includes automatic tripping 70 be described. The current is carried through the tripping
means comprising a relatively stationary magnetic ?eld
assembly 20 by means of a conductor 20A, having termi
piece adapted to be energized by current passing through
nal portions- 203 and 20C. (See FIGURE 3.) The
3,053,954.
£1
current path is then completed from the trip unit 20 to’
to move to collapsed position and the movable contact
a load terminal strap 21 which supports a load terminal
connector 22. The load terminal strap 21 is ?xedly at
tached to the base 10 by means of screw 23.
members 17 to move to open circuit position, even though
the handle 38 is retained in the “on” position.
As previously described, the current carrying parts just
described are repeated in each of the three pole chambers
of the circuit breaker.
For the purpose of providing simultaneous operation
of the contact member of each of the pole chambers,
Following such a “tripping” operation, the parts may
e returned to their original condition by moving the
handle 38 to the left, during which movement a depend
ing portion 39a of the handle support 39 engages the
releasable member 29 and rotates it counterclockwise
until the latch projection 31 becomes reengaged with the
the contact arms 17 are each ?xedly attached to a con 10 latch member 32.
The construction and operation of the trip unit 20
tact cross arm 24.
The contact arm 17 of the center pole is pivotally sup
ported on a pivot pin 17A carried by the mechanism side
will be described with particular reference to FIGURES
3 through 6. The current responsive tripping mechanism
is contained within a separate insulating enclosure which
supported on the extending portions of the contact cross 15 is removable as such from the main circuit breaker en
frames 25.
The contact arms for the two outer poles are
closure, this removable assembly being referred to for
arm 24.
convenience as a “trip unit” 20. The enclosure of the
The movable contact member 16 for each of the poles
is pivotally supported on the contact arm 17 by means
trip unit as includes a ?rst portion 45 and a second por
of a pivot pin 18 as previously described. For the pur
tion 46. A latch mechanism supporting frame 47 is rigid
pose of providing contact pressure, a compression spring 20 ly attached to the outer face of the ?rst portion by suitable
26 is provided between the movable contacts 16’ and
means such as by rivets 48. A pivot pin 49‘ is rigidly
the forward projecting portion of the contact arm 17.
supported between the opposed side portions of the frame
The spring 26 is retained in place by a projecting stud 27
47. The primary latch member 32 is pivotally and slid
carried by the contact member 16 and also by a generally
ably supported on the pivot pin 1-19 and is biased in a
cup-shaped retainer 28 carried by the forward end of 25 counterclockwise direction by means of spring 50. A
the contact arm 17.
An operating mechanism is provided for the purpose
of operating the movable contacts 16' between open and
secondary latch member 51 is also pivotally supported on
the frame 47 by pivot pins 52.. The secondary latch mem
contacts in the closed circuit position, whereby to permit
automatic opening upon the occurrence of predetermined
ber 51 carries a roller 53, and the primary latch mem
ber 32 has an engagement with the roller 53 such that
the primary latch 32 when loaded by the releasable mem
ber 29, biases the secondary latch 51 for rotation in a
current conditions, in a manner to be described.
clockwise direction as viewed.
closed circuit position and for releasably restraining the
The
operating mechanism, which is positioned Within the cen
The secondary latch 51 is restrained from rotating in
tral pole chamber, includes a pair of opposed side plates
a clockwise direction by reason of its engagement with
25, which serve to support the mechanism, including the 35 a secondary latch retaining member 54 which is rigidly
pins 17A and 18 previously described. The operating
carried by a trip bar 55, see FIGURE 3.
mechanism also includes a releasable support member 2?‘
In operation therefore, rotation of the trip bar 55 in
which is pivotally supported on a pivot pin 34} extending
a clockwise direction as viewed in FIGURE 3, moves
between the opposed side plates 25. The member 29
the secondary latch retaining member 54 out of the path
has a projecting latch portion 31 releasably held by a 40 of movement of the secondary latch 51 and permits the
latch member 32 which is movable to cause release of the
member 29 in a manner to be described.
The releas
able member 29 serves to support the normally stationary
pivot pin 33 which pivotally supports a pair of upper
toggle links 34 (only one shown) which are connected
by a knee pivot pin 35 to a pair of lower toggle links 36‘.
The lower toggle links 36 extend through slots 37 in the
contact arm 17 and are connected by pivot pin 18 to the
contact arm 17. A manually engageable handle member
38 is supported on a metallic handle support member 39‘,
which in turn is pivotally supported in the insulating
casing on a pivot pin 40.
A tension spring 4-1 is connected between the central
portion of the handle 38 and the toggle knee pivot pin 35.
secondary latch 51 to move in a clockwise direction, which
in turn permits the primary latch 32 to rotate in a clock
wise direction, releasing the releasable member 29.
For the purpose of causing rotation of the trip bar 55
in response to overload current conditions, a bimetallic
strip is provided, which is mounted on a return-bent por
tion 26D of the main current conductor 20A extending
through the trip unit at that particular pole. This return
bent portion 20D ‘acts as a heater to produce heat which
causes de?ection of the bimetallic strip 56. The bimetal~
lic strip 56 is mounted on the heater portion 20D‘ by suit
able means such as by rivets 58.
The bimetallic strip 56 acts on, the trip bar 55 through
engagement with a calibrating screw 59‘, carried by a
When the handle is in the “on” position as shown in
second strip of bimetallic material 60, which is rigidly
FIGURE 1, the tension spring All acts on the pivot pin
supported at its opposite end on the trip bar 55‘, so that
35 in such a way as to maintain the toggle links 34, 36
the end thereof carrying the calibrating sscrew 59‘ is free
in a straightened condition, holding the movable con
to move as the strip 60 de?ects. The strip 60 functions
tact member 16’ against the stationary contact member
to provide “ambient compensation,” since when the am
15. When the handle 38 is moved to the left to the “off” 60 bient temperature increases, the bimetallic strip 60‘ de
position, the tension spring 41 passes across the line of
?ects in the same direction that the main bimetallic strip
centers of the pivot pins 35 and 33 and causes the pivot
56 de?ects, thereby producing no relative movement be
pin 35 to move to the left, collapsing the toggle links
tween them, and therefore no change in calibration of
34-36, and moving the movable contact arm 17 to open
the circuit breaker.
circuit position.
65
For the purpose of limiting the effect of the ambient
When the handle 38 is in the “on” position as shown
compensating bimetallic strip 6%, there is provided an ad
in FIGURE 1, and the latch member 32 is moved, in a
justable carrier stud 61 which is threadedly engaged in
manner to be described, so as to release the latch projec
the trip bar 55 and is locked with respect thereto by a
tion 31 of the releasable member 29, the releasable
lock nut 62. The stud 61 carries a pair of ?anges 63 and
member 29 moves under the action of the spring 41 in
64 which act as tops to limit the de?ection of the am
a clockwise direction. As the member 29 moves in a
bient compensating bimetallic strip 60 in each direction.
clockwise direction, the pivot pin 33 moves upwardly
In addition to the means just described for providing
and at the same time across the line of action of the
time-delayed tripping action, there is provided, in accord
spring 41, thereby reversing its direction of pull on the
ance with the present invention “instantaneous acting”
knee pivot pin 35, and permitting the toggle links 34-456 75 adjustable tripping means, together with means whereby
5
3,053,954
the user may adjust the current level required to actuate
such tripping means, within a predetermined selected
range.
In accordance with the invention, there is provided at
each pole of the circuit breaker of FIGURE 1, a rela
tively stationary magnetic ?eld piece 66 (see FIGURE
2) which is rigidly attached to the base of the trip unit
by suitable means such as by rivets 67. Each of the ?eld
6
When the cam member 81 is rotated to its maximum
position, as shown in {FIGURE 4, the cam plate 74 is ro
tated clockwise so that the projecting screw 78 depresses
the armature 68 to reduce the air gap and to thereby
lower the setting at which the magnetic trip. will operate.
The position of the parts as indicated in the FIGURE
2 represents the maximum air gap setting. As previously
mentioned, in this setting the cam follower surface of the
portion '77 extends parallel to the shaft '82. ‘It will now
pieces 66 is generally U-shaped and is ‘arranged so that the
conductor 20A passing through the trip unit at each pole, 10 be observed that the position of the armature 68 may be
adjusted without rotating the cam plate 74, by loosening
passes through the U of the corresponding magnetic ?eld
the lock nuts 79 and adjusting the projecting screw 78.
piece 66. For the purpose of actuating the trip bar, a
When the cam 81 is turned to the position in which
movable armature 68 is provided which is ?xedly attached
the armature is depressed the maximum amount, as shown
to a supporting shaft 69 by suitable means such ‘as by set
screw 70. The shaft 69 is supported for vertical sliding 15 in FIGURE 4, the position of the cam plate 74, and
therefore of the armature 68, may be further adjusted by
movement by engagement in a hole 66A in the bight por
adjusting the vertical position of the cam member 81 on
tion of the magnetic ?eld piece 66 and in a hole in a sup
the shaft 82. This may be accomplished by loosening
port ‘and guide bracket 71 which is supported on the heater
the lock nut $3 and by rotating the shaft 82. When the
portion by the same rivets 5% which mount the bimetallic
strip. A compression spring 72 is provided which acts 20 desired setting has been achieved, the insulating knob 86
is pushed onto the enlarged portion 84 of the shaft 82 in
between the support 71 and a projecting ?ange '73 on the
shaft 69, so as always to urge the shaft 69 in an upward
a proper position so that the arrow 87 points to a pre
point and extent of such range. For this purpose a cam
meet certain predetermined requirements: (1) the shaft
determined “high” marking on the circuit breaker casing.
direction.
While the various adjusting means may be utilized in
An adjustable stop is also provided for the armature
68, together with means for adjusting said stop through 25 a number of ways, the following procedure has been
found to be desirable in calibrating a circuit breaker to
a predetermined range, and for ‘determining the starting
plate 74 is provided which is pivotally supported on a
82 is rotated to the position in which the cam follower
surface of the portion 77 extends parallel to the shaft 82
(the maximum gap position ‘as shown in ‘FIGURE 2);
30
piece 66. The cam plate 74 includes a projecting cam
(2) the device is tested by passing current through it to
follower portion 77 for a purpose to be described. The
pivot pin 75, carried by an upstanding portion of the ?eld
cam plate 74 also carries an adjusting screw 78‘ which
is threadedly engaged therein and which is locked with
respect thereto by the lock nut 79. The cam plate 74 is
biased at all times in a counterclockwise direction by
means of a spring St).
determine the amount of current required to cause the
armature to pull in; if this amount of current is found‘ to
be too high, the adjusting screw 7 8 is turned inwardly to
reduce the air gap; if the amount of current required to
produce pull-in is found to be too low the adjusting
screw 78 is backed off to increase the air gap; thus any
For the purpose of adjusting the position of the cam
desired pull-in point may be achieved with the cam 81
plate 74', there is provided an adjusting cam 81, which
at its “high or maximum” setting; (3) the shaft 82 is
is threadedly carried by ‘a shaft 82. The shaft 82 has its
rotated so that the cam 81 is in the position in which
40
lower end journalled in an opening in the inturned por
the cam 81 has rotated the cam plate 74 the maximum
tion of the extension 76 of the ?eld piece 66, and has its
amount (as shown for example in FIGURE 4); the de~
upper end journalled in an opening in the top wall of the
vice is tested at this setting and if it is found that the cur
insulating casing of the trip unit. The cam member 81
rent required to cause the armature to pull in at this set
is normally locked against movement with respect to the
ing
is higher than the amount which is desired, then the
45
shaft 82 by suitable means such as by \a lock nut 83‘.
The upper end of the shaft 82 is provided with an en
larged portion 84 which provides a shoulder portion over
lying a portion of a washer 85 which in turn overlies the
outer surface 45A of the casing portion 45. The portion
lock nut 83 is loosened and the cam member 81 is held
from rotating while the shaft 82 is turned. This causes
the cam 81 to move downwardly on the shaft 82, thereby
producing a greater de?ection of the cam plate 74, as
shown for example in FIGURE 5. If on the other hand
84 also carries a control knob 86, with an indicating arrow 50 it is found that at the “low” setting the current required
87 thereon, for a purpose to be described.
to cause the armature to pull-in is too low, then the lock
In order to provide a frictional retaining force to main
nut 83 is loosened and the shaft 82 is rotated in a direc
tain the knob 86 ‘and shaft 82 in any predetermined pre
tion to cause the cam 81 to move ‘upwardly on the shaft
set position, there is provided a retaining washer 8S, hav
82, thereby producing lesser de?ection of cam plate 74
ing depending downwardly pointing teeth or projections 55 at this setting.
thereon whereby it may be moved upwardly on the shaft
82 but cannot move downwardly thereon. A compres
It is to be noted that all adjustment is performed before
the customer’s adjusting knob 86 is mounted. When the
sion spring member in the form of a spring washer 39 is
adjusting knob 86 is mounted, it is inserted on the en
provided on the shaft 82 between the washer 88 and the
larged portion 84 of the shaft 82 with the arrow 87 ex
inner surface 45B of the insulating casing portion 45. 60 actly in alignment with the “high” or “low” marking on
When the parts are assembled, the spring member 39 is
the upper surface of the circuit breaker cover '11.
trapped with a predetermined force between the retain
The shaft 69 has a headed portion 69a which is adapted
ing washer 88 and the inner surface 45B of the insulat
to engage a washer 69b over-lying an extending portion of
ing casing, whereby the spring member 89 exerts a down
the trip bar 55. When the armature 68 is drawn toward
ward force on the washer 88 and on the shaft 82, main 65 the magnet 66, therefore, the shaft 69 moves downwardly
taining the shaft 82 in frictionally retained engagement
and the head 69a engages the washer 69b and rotates the
against unintentional rotation at all times.
trip bar 55 to cause tripping.
Referring particularly to FIGURE 2, it will be observed
While there has been shown and described only one
that when the cam 81 is turned to a position in which the
embodiment of the invention, it will be readily apparent
lowest point thereof is in engagement with the cam fol 70 that many modi?cations thereof may be made, and we
lower portion 77, the cam ‘follower portion 77 extends
therefore intend, by the appended claims, to cover all
substantially parallel to the shaft 82. This position rep
such modi?cations as fall within the true spirit and scope
resents the extreme counterclockwise portion of the cam
of the invention.
"plate 74 and therefore the highest position of the screw
What we claim as new and desire to secure by Letters
78 and of the armature 68.
75 Patent of the United States is:
3,053,95a
1. An electric circuit breaker comprising at least one
pair of relatively movable contacts, operating mechanisms
for operating said movable contacts between open and
closed circuit positions, said operating mechanism includ
ing a member releasable to cause automatic opening of
said contacts, current responsive means for causing the re
lease of said releasable member upon the occurrence of
for moving said contacts between open and closed circuit
positions, said operating mechanism including a member
releasable to cause automatic opening of said contacts,
current-responsive means for causing release of said re
leasable member upon the occurrence of predetermined
current conditions, said current-responsive means com
prising a relatively stationary magnet, an armature sup
ported for movement relative to said stationary magnet,
predetermined current conditions, said current-responsive
an electrical conductor disposed to energize said magnet
means comprising a relatively stationary magnet, an arma
ture movable with respect to said stationary magnet, an 10 upon the passage of curent therethrough, biasing means
electrical conductor including at least a portion passing
between said magnet and said armature, biasing means
biasing said armature away from said magnet, adjustable
biasing said armature away from said magnet, adjust
able stop means for adjustably positoning said armature,
said adjustable stop means including a pivotally supported
stop means for limiting the movement of said armature
away from said magnet said adjustable stop means com
prising a cam plate including an elongated cam follower
portion and a projection adapted to engage said armature,
an elongated shaft, a cam member carried by said shaft
and disposed and arranged to engage said cam follower
surface whereby rotation of said cam member moves said
cam plate and causes said cam plate to engage said arma
ture to move said armature with respect to said magnet,
cam plate, a projection carried by said cam plate and
disposed and arranged to engage said armature, said cam
plate including an elongated cam follower surface, an
said cam member being axially adjustable along said
elongated shaft extending generally parallel to said cam
follower surface in at least one possible adjusted position
of said cam plate, said shaft having a threaded portion, a
cam member threadedly supported on said threaded por
tion of said shaft, whereby rotation of said supporting
shaft while said cam member is restrained from rotation
causes movement of said cam member axially along said
shaft, and means for locking said cam member against
25 rotation on said supporting shaft.
said cam follower surface.
I
5. An electric circuit breaker as set forth in claim 3,
2. An electric circuit breaker comprising at least one
said circuit breaker also including insulating means en
pair of relatively movable contacts, operating mechanism
closing said current-responsive means, an aperture in said
for operating said contacts between open and closed cir
insulating enclosing means, said supporting shaft includ
cuit positions, said operating mechanism including a mem
ber releasable to cause automatic opening of said con 30 ing an end portion projecting through said aperture, and
an insulating control knob mounted on said projecting
tacts, current-responsive means for causing release of said
end portion of said shaft to permit operation of said shaft
releasable member upon the occurrence of predetermined
from outside said insulating enclosure.
current conditions, said current-responsive means includ
6. An electric circuit breaker as set forth in claim 3,
ing a relatively stationary magnet, an armature movably
said circuit breaker including insulating means enclosing
supported with relation to said magnet, means biasing said
said current-responsive means, an aperture in said in
armature away from said magnet, adjustable stop means
sulating enclosure means, said supporting shaft including
for limiting the movement of said armature away from
an end portion projecting through said aperture, a washer
said magnet comprising a pivotaliy supported cam plate,
on said shaft overlying the outer surface of said enclosure
said cam plate including a cam follower portion, an elon
gated operating shaft extending parallel to said cam fol 40 means, an enlargement on said shaft overlying said
shaft, to vary the mechanical advantage of said cam on
lower surface in at least one adjusted positon of said cam
washer, a compression spring member on said shaft ad
plate, a cam member carried by said elongated shaft and
jacent the inner surface of said enclosure, abutment means
carried by said shaft within said enclosure, said compres
sion spring member being compressed between said inner
face whereby rotation of said cam member causes pivotal
movement of said cam plate to Vary the adjusted posi 45 surface of said enclosure and said abutment to frictionally
retain said shaft against rotation.
tion of said armature, and means for adjustably position
disposed and arranged to engage said cam follower sur
ing said cam member at selected positions axially along
said supporting shaftv
3. An electric circuit breaker as set forth in claim 2,
wherein said cam plate also includes an adjusting screw 50
engaging said armature, and means for locking said ad
justing screw with respect to said cam plate.
4. An electric circuit breaker comprising at least one
pair of relatively movable contacts, operating mechanism
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,508,178
2,586,326
2,673,264
Lindstrom et al ________ __ May 16, 1950
Grissinger et al ________ .d Feb. 19, 1952
Cole ________________ __ Mar. 23, 1954
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