U.S. patent number 3,711,748 [Application Number 05/141,201] was granted by the patent office on 1973-01-16 for electric plug-on circuit breaker with means for assuring tripping of the breaker before unplugging.
This patent grant is currently assigned to Square D Company. Invention is credited to Robert E. Dietz.
United States Patent |
3,711,748 |
Dietz |
January 16, 1973 |
ELECTRIC PLUG-ON CIRCUIT BREAKER WITH MEANS FOR ASSURING TRIPPING
OF THE BREAKER BEFORE UNPLUGGING
Abstract
A molded case electric circuit breaker has plug-on jaws at the
line end arranged to plug onto edge portions of flat bus bars,
stacked in spaced face to face relation, upon movement of the
circuit breaker line and foremost along a fixed path on a mounting
pan to a plugged position, and to disconnect from the bar upon
opposite movement of the circuit breaker along said path. The
breaker has a push-to-test pin accessible through a hole in its
case for movement by an inserted tool to an operating position in
which it rocks a trip bar to circuit breaker tripping position. The
breaker has a safety device comprising a settable element spring
biased so that when released it moves to an operative position
wherein it drives the pin to the pin operating position, and an
element, arranged in fixed position along said path, which
cooperates with the settable element and holds it in an inoperative
position only while the jaws and bus bar are in plugged relation,
and which releases the settable element so that the element is
moved by its spring to the pin operating position prior to
unplugging the jaws from the bus bars as the circuit breaker is
moved in an unplugging direction from its plugged position, and at
all times while the circuit breaker is removed from the pan.
Inventors: |
Dietz; Robert E. (Cedar Rapids,
IA) |
Assignee: |
Square D Company (Park Ridge,
IL)
|
Family
ID: |
22494630 |
Appl.
No.: |
05/141,201 |
Filed: |
May 7, 1971 |
Current U.S.
Class: |
361/673; 335/35;
337/7; 361/825 |
Current CPC
Class: |
H02B
1/056 (20130101) |
Current International
Class: |
H02B
1/056 (20060101); H02B 1/015 (20060101); H02b
001/04 () |
Field of
Search: |
;317/112,119
;335/23,35,173 ;337/7,48 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Tolin; Gerald P.
Claims
Having thus described my invention, I claim:
1. A circuit breaker and safety trip combination, comprising:
a circuit breaker including a casing;
complementary contacts;
an external operating handle for opening and closing the
contacts;
contact jaws for connection to, and disconnection from, bus bars,
concurrently;
means supporting and guiding the circuit breaker for bodily
movement along a predetermined path to a jaw connected position and
to a jaw disconnected position, respectively;
a trip device operative when moved to one position to trip the
circuit breaker;
a normally inactive push-to-test device movable, by a tool
manipulatable from the exterior of the casing, to an active
position, and mechanically connected to the trip device to move the
trip device to its said one position when the push-to-test device
is moved to its said active position;
means to restore the push-to-test device to its inactive condition
when it is unconstrained;
characterized by:
a safety trip mechanism mechanically normally drivingly connected
to the push-to-test device, and disconnectable therefrom, and
operative, when drivingly connected, to move the push-to-test
device to, and to hold the push-to-test device in, its said active
position, and operative, when disconnected, to release the
push-to-test device; and
operator means in fixed position along said path and normally
drivingly disengaged from said safety trip mechanism, and drivingly
engageable with said safety trip mechanism by said bodily movement
of the circuit breaker to its said jaw connected position, and
operative, when so engaged, to disconnect the safety trip mechanism
from the push-to-test device.
2. The structure according to claim 1 wherein the safety trip
mechanism includes:
a movable means connecting the safety trip mechanism to the
push-to-test device;
biasing means normally operative for biasing the movable means from
an inoperative position to an operative position wherein the
movable means operates the push-to-test device to trip the circuit
breaker; and
said operator means is cooperable with the biasing means to render
the biasing means inoperative while the circuit breaker is in its
connected position and to release the biasing means so that it can
operate as the circuit breaker is moved along said path to said
disconnected position.
3. The structure according to claim 2 wherein the push to test
device includes a pin which is drivingly connected to a trip bar of
the circuit breaker, and which is movable endwise in opposite
directions along a given path in one of which directions it moves
to a tripping position wherein it trips the trip bar;
spring means bias the pin in the opposite direction to an
inoperative position; and
said biasing means is a spring which biases the movable means so as
to apply to the pin a force in opposition to, and greater than,
that of the spring means.
4. The structure according to claim 3 wherein the movable means is
movable in opposite directions along a path parallel to the path of
the pin and has a part movable therewith; and
said pin and part have coacting aligned facing shoulders which
engage when said part moved in said one of the directions to a
predetermined position and then, upon continued movement in said
one of said directions, drives the pin to bar tripping
position.
5. The structure according to claim 3 including means movable from
an inoperative position by effects produced in response to a load
current conducted by a circuit through the circuit breaker to an
operative position in which it trips the bar; and
spring means yieldably holding the last named means in its
inoperative position; and wherein
said pin is connected to the trip bar by said last mentioned means
so that when the pin is moved to its tripping position it operates
said last mentioned means thereby to trip the trip bar.
6. The structure according to claim 1 wherein electroresponsive
means are provided and are operative in response to predetermined
phenomena caused by currents in the circuit break to operate the
trip device;
said electroresponsive means include a member movable relative to
the push-to-test device, by electroresponsive means when the
electroresponsive means are operative, to engage and operate the
trip device; and
said push-to-test device is connected to said member for moving the
member to cause it to engage and trip the trip bar.
7. The structure according to claim 1 further characterized in that
a plurality of bus bars are mounted on the supporting means in
stacked face to face relation to each other with the edges of the
bars facing endwise of the path and aligned with the jaws,
respectively, for connection thereto upon movement of the circuit
breaker to said connected position;
complementary guide means respective to the first mentioned guide
means are carried by the support; and
said safety trip mechanism includes an operator element in fixed
position on the support, and a movable element having a portion
disposed exteriorly of the casing and cooperable with, and moved
by, the operator element as the circuit breaker is moved and guided
along its path to effect said rendering of the safety trip
mechanism operative and inoperative.
8. The structure according to claim 7 wherein said movable element
is movable toward and away from said support, and the operator
element is a cam.
Description
This invention relates to molded case electric circuit breakers
which have plug-on jaws at the line end which, in a connected
position of the circuit breaker, are plugged onto a plurality of
flat bus bars stacked with their faces parallel to a support or
mounting pin, and having a push-to-test device accessible through a
hole in the casing by a tool for tripping the circuit breaker,
combined with a safety trip device so arranged so to trip the
circuit breaker, in event the breaker is not turned off, prior to
the disengagement of the jaws from the bus bars upon movement of
the breaker to a disconnected position, and at all times when the
circuit breaker is in other than connected position.
BACKGROUND OF INVENTION
The electric circuit breaker shown herein for purposes of
illustration is of the basic type disclosed in U.S. Pat., to James
H. Leonard et al., No. 3,341,791, of Sept. 11, 1967, entitled
Electric Circuit Breaker with Improved Operating Mechanism. It is
modified so that it can be plugged onto stacked bus bars, such as
disclosed in U.S. Pat. to G. N. Jorgensen et al., Re. No. 26,737,
of Dec. 9, 1969, entitled Electrical Panelboard, and may be mounted
on a support or mounting pan as disclosed in U.S. Pat. No.
3,346,777, of Oct. 10, 1967, entitled Electric Circuit Breaker and
Mounting Means Therefor.
The circuit breaker of the present invention employs a push-to-test
device having a pin accessible by a tool for tripping the circuit
breaker, broadly as disclosed in U.S. Pat. to B. W. Layton et al.,
No. 3,480,890, of Nov. 25, 1969, entitled Molded-Case Circuit
Breaker with Manual Tripping Means Externally Accessible Only By A
Tool.
As fully disclosed in U.S. Pat. No. 3,341,791, such a circuit
breaker is normally set, and turned OFF and ON while set, by an
exterior operating handle. When set, the circuit breaker is latched
in set position by latches which are releasable, respectively, by
such means as electromagnetic mechanisms responsive to fault
currents, or to sudden severe overloads, or to both, or by thermal
mechanisms responsive to heat produced by long continued, but less
severe, overloads. In many breakers all three latches and
associated mechanisms are incorporated and the electromagnetic and
thermal mechanisms are connected to a single or common rockable
trip bar. The bar is spring biased to rotate about its axis in one
direction to latching position, but, when rotated in the opposite
direction by the one of the electromagnetic or the thermal
mechanisms, releases the latches so that the breaker mechanism is
tripped and its movable contacts are moved to open position.
The latches and mechanisms employed are themselves well known in
the art and their specific structural features form no part of the
present invention. The important features derived from the prior
art and used in the combination of the present invention are (a) a
trip bar which is rockable in one direction to unlatch a circuit
breaker mechanism which thereupon trips the circuit breaker; (b) a
push-to-test trip pin which can be operated from the exterior of
the case by a suitable tool to rock the trip bar into a position to
unlatch the mechanism for tripping; (c) plug-on jaws and associated
bus bars arranged to be engaged edgewise by the jaws; and (d) a
safety device, broadly such as disclosed in French U.S. Pat. No.
1,183,823, of Feb. 2, 1959, but arranged so that it assures that
the circuit breaker is tripped before it is disconnected from the
bus bars and before it is connected to the bars.
SUMMARY OF THE INVENTION
The present invention is directed primarily to the foregoing
features combined with each other and with an additional feature
which causes the push-to-test pin to be operated by the safety
device so as to trip the circuit breaker prior to unplugging of the
plug-on jaws from the bus bars, and to hold the push-to-test pin in
tripping position while the circuit breaker is disconnected from
its mounting pan.
Various specific objects and advantages of the present invention
will become apparent from the following description wherein
references is made to the drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a perspective view of an electrical panel board and a
plurality of circuit breakers of the present invention mounted
thereon, certain parts being omitted for clearness in
illustration;
FIG. 2 is a perspective view of part of a circuit breaker of the
present invention, part of the case of the circuit breaker and
other mechanism being omitted, to show the relation of the
push-to-test pin and associated safety device;
FIG. 3 is an enlarged fragmentary sectional view taken generally
along the line 3'3 of FIG. 1, parts thereof being shown in section
for clearness in illustration, and showing the circuit breaker in
the untripped position and connected to the power side of a
circuit;
FIG. 4 is a view similar to FIG. 3 showing the circuit breaker in
tripped condition, with the exterior operating handle in the
tripped position, during disconnection of the circuit breaker from
the power source; and
FIG. 5 is a view similar to FIG. 3 showing a like circuit breaker,
but employing stab terminals for connecting it to load terminal
conductors.
Referring to the drawings, a plurality of circuit breakers are
shown mounted on an electrical panelboard, indicated generally at
1, including a mounting pan 2 carrying a stack, indicated generally
at 3, of elongated insulators and a plurality of flat bus bars. The
bus bars 4 are interleaved between a rear insulator 5, two
intermediate insulators 6, and a front insulator 7. Mounted on the
mounting pan 2 are three relatively large three pole molded case
circuit breakers 10 which, if desired, may be interspersed with
relatively small single pole molded circuit breakers 12 and with
blank fillers 13.
For purposes of illustration herein, only one of the three pole
circuit breakers 10 is described in detail.
Referring to FIGS. 2 through 4, the circuit breaker 10 has a two
piece case 11 of molded material which, at its line end, is
connected to a shroud 16 of insulating material. Terminal straps 18
are provided, one for each pole of the three pole circuit breaker.
The straps 18 are connected through circuit breaker contacts (not
shown) to pairs of plug-in jaws 20, 21, and 22, respectively, which
are disposed at the line or power end of the circuit breaker and
are adapted to be plugged onto the front edges of the bus bars 4,
respectively.
For purposes of illustration, only one strap 18 is shown herein.
The strap 18 is associated with a magnetic release mechanism 23
which includes a magnetic core 24 of U-shaped structure having
upturned marginal flanges 25. The strap 18 extends between the
marginal flanges of core 25 so that currents through the strap
produce flux in the core 24.
A common trip bar 28 is spring biased, clockwise in FIGS. 2 and 3,
to rock to latching position with respect to the circuit breaker
mechanisms and so remains while the circuit breaker is in the
untripped condition so long as the currents through the strap 18
are within a normal operating range. The bar 28 is moved
counter-clockwise by electromagnetic mechanism to trip the circuit
breaker in response to a fault current, or a temporary surge of
lesser current beyond normal through the strap 18.
As mentioned, and as disclosed in U.S. Pat. No. 3,341,791, it is
customary to provide in circuit breakers latches which are operated
to release by thermo-responsive mechanism which becomes heated by
long sustained overload currents through the strap 18 insufficient
to cause the magnetic release mechanisms to operate, and thereby
rocks the bar 28 to tripping position. Rocking of the bar
counterclockwise against the bias of its spring by any one of the
latch operating mechanisms will trip the circuit breaker. The
specific latching mechanism and their operating mechanisms form no
part of the invention and, accordingly, only an electromagnetic
release mechanism is discussed herein specifically.
The electromagnetic release mechanism illustrated in FIGS. 1 - 4
includes an armature 30 which is in magnetically attractive
relation to the flanges 25 of the core 24. The armature 30 is
biased, upwardly in FIG. 3, by a biasing spring 31 which is
connected to a suitable bracket 32 in the casing. The spring 31 is
of such force that it retains the armature 30 in raised position,
as illustrated in FIG. 3, against any magnetic attraction due to
flux in the core 26 caused by currents in the strap 18 within the
normal operating range of the circuit breaker. The armature is
drawn downwardly against the force of the spring 31 by flux
generated by currents in excess of the normal currents. The
armature 30 is carried on an upright rod 33 which, at its upper end
has a cap portion 34 which extends through a hole in an arm 35 of
the bracket 32 and is guided thereby for vertical
reciprocation.
It is desirable at times to trip the trip bar 28 for testing the
circuit breaker, and, for this purpose, the circuit breaker is
provided with a push-to-test pin 36.
The push-to-test pin 36 is mounted for vertical reciprocation in a
bracket 37 and with its upper end reciprocable in and guided by a
passage 38 in one wall of the circuit breaker case 11. The pin 36
is biased upwardly to an extended position by a spring 39
interposed between a shoulder 40 and the rod and the bracket 37. In
its extended position, the upper end of the pin 36 is near the top
surface of the case 11 and it is accessible through the passage 38
by a suitable tool so that it can be depressed against the force of
the biasing spring 39. The lower end of the pin 36 normally rests
on the upper end of the cap portion 34 of the rod 33. If it is
desired to trip the circuit breaker to test it, the push-to-test
pin 36 is depressed, thus depressing the armature 30 the same as
though it were drawn downwardly by the armature 30 and magnetic
flux in the core 24, thereby causing the cap portion 34 to engage
the trip bar 28 and rock it counterclockwise in FIGS. 2 and 3,
against the bias of its spring, to a position for tripping the
circuit breaker.
As mentioned, in installing or connecting the circuit breaker to
the bus bars, it is desirable that the circuit breaker be supported
on the pan 2 and then moved from its initial position along a
predetermined path toward the bus bars so as to effect engagement
of the various pairs of plug-on jaws 20, 21, and 22 with their
associated bus bars 4. For this purpose, a suitable bracket 44 is
provided on the load end of the case 11 and is adapted to be
received in a suitable opening or slot 45 in the pan 2. The bracket
is arranged to guide the load end of the circuit breaker as the
circuit breaker is moved toward the bus bars, line end foremost,
and is provided with a retaining screw 46 so as to retain the
circuit breaker in position after the push-on jaws have engaged the
bus bars 4. The rear insulator 5 is provided with grooves 47,
extending transversely of the bus bars. Suitable ribs 48 on the
rear or lower surface of the shroud 16 are received in and guided
by the grooves 47. Generally the mating grooves and ribs are
arranged one rib and one associated groove near each outer lateral
limit of the circuit breaker case. In order to install the circuit
breaker on the panel, it is placed in position such that the rear
end of the bracket 44 can pass readily through the opening or slot
45, in which position the plug-on jaws are spaced transversely of
and out of contact with their associated bus bars 4. At the same
time, the ribs 48 are engaged at their outer ends with the outer
portions of the grooves 47. With this alignment of the ribs 48 and
grooves 47, the circuit breaker is pushed toward the bus bars so as
to cause the plug-on jaws to engage their associated bus bars 4,
and drawn away from the bus bars to disengage the jaws from the
associated bus bars.
There is relatively little danger of any arcing or deleterious
effects upon movement of the jaws into connected relation to the
bus bars, whether the breaker is tripped or untripped, or OFF or
ON. However, there is grave danger in disconnecting the plug-on
jaws from the bus bars with the circuit breaker closed,
particularly if a load is connected to the load side terminals of
the circuit breaker. It is desirable, therefore, if an attempt is
made to connect or disconnect the jaws from the bus bars, that the
circuit breaker be tripped before connection or disconnection. For
this purpose, a safety trip mechanism is provided.
The safety trip mechanism comprises a push rod 50 which at its
lower end extends through a hole in the rear or bottom of the case
11 of the circuit breaker, and is mounted within the case 11 for
vertical reciprocation. At its upper end, the rod 50 carries a
transversely extending yoke 51 which has spaced arms 52 between
which the push-to-test pin 36 passes. A suitable E-ring or locking
washer 53 is provided on the pin 36 and is adapted to be engaged
and pushed downwardly by the yoke arms 52 as the rod 50 is moved
downwardly, thus, in effect, pushing the push to trip pin 36
downwardly so that the cap portion 34 of the magnetic armature rod
33 is pushed downwardly to tripping position. The rod 50 is
normally biased downwardly by a spring 55. For operatively
connecting the spring 55 to the rod 50, a finger 56 is mounted on,
and extends upwardly from, the yoke 51 and has a shoulder 57 spaced
from its upper end. The spring 55 is interposed between the
shoulder 57 and an inverted socket 58 in the front or top wall of
the case 11. The spring 55 is such strength that when the rod 50 is
free to move downwardly the spring 55 can push downwardly on the
lock washer 53 and drive the pin 36 downwardly against the combined
forces of its spring 39 and the biasing force of the armature
spring 31, thus causing the common trip bar 28 to trip the circuit
breaker in the same manner as it would be tripped by the
push-to-test pin. Thus, with the circuit breaker disconnected from
the panel, the safety device assures that the circuit breaker is
tripped as the rod 50 is then free and is moved downwardly and held
extended by its spring 55.
Assuming, however, that the circuit breaker is placed on the wall
of the mounting pan 2 in position to be moved into connected
relation to the bus bars, it is desirable that the breaker remain
in tripped position until the plug-on jaws have made firm contact
with their associated bus bars. For this purpose, a cam 60 is
provided, and is arranged to lie in the path of the lower end of
the rod 50 as the circuit breaker is moved to and from final
contact position with respect to the bus bars. The cam 60 is
contoured so that, assuming that the push-on jaws are in contact
with the bus bars, the cam holds the rod 50 in raised position
against the force of the spring 55, and constrains it from
operating the push-to-test pin. If the circuit breaker is moved to
the left from the position shown in FIG. 3 to and beyond the
position shown in FIG. 4, the lower end of the rod 50, starting
from the position in FIG. 3 at the crest of the cam 60, in which it
holds the spring 55 fully compressed so that the springs 31 and 39
can hold the push-to-test pin 38 in its raised extended position
with the circuit breaker mechanism untripped, will begin riding
down the cam 60. As the circuit breaker is moved farther to the
left from the position illustrated in FIG. 4, the lower end of the
rod 50 travels down the left side of the cam 60 allowing the spring
55 to extend and, through the medium of the yoke 52 and washer 53,
to drive the pin 36, and thereby the cap portion 34 and rod 33
downwardly against the common trip bar 28 so as to rock it
counterclockwise in FIG. 3 to tripping position. This occurs before
the circuit breaker has been moved to the left from the position in
FIG. 4 in which the plug-on jaws disconnect from their respective
bus bars 4. Accordingly, the tripped position, illustrated in FIG.
4, occurs before the breaking of contact between the jaws and the
bus bars.
On the other hand, in moving the circuit breaker toward connected
position, the rod remains in the position illustrated in FIG. 4, in
which it has caused the circuit breaker to be tripped, until the
push on jaws are connected with the bus bars 4, whereupon continued
movement to the right to final connected position, the rod is again
lifted by the cam 60 so that it does not drive the push-to-test pin
36 to operating position. Thereby the trip bar remains in tripping
position until after the contact with the bus bars is effected.
Thereafter, of course, the circuit breaker can be set in the
untripped position, with the operating handle 61 thereof in the ON
or OFF position, and with the various latching mechanisms holding
the movable contacts in closed position.
In FIG. 5 a similar circuit breaker is shown in the position
illustrated in FIG. 3. In this particular circuit breaker, the load
side contacts are carried in a separate housing 62 mounted on the
front or upper face of a portion of a mounting pan 63, which
corresponds to the pan 2. Mounted in the housing 62 is a conductor
64 secured in place by a bolt 64a and carrying a terminal connector
65 for receiving the end of an exterior load conductor.
The conductor 63 is provided with contact jaws 66 which are open to
the left in FIG. 5. The housing 62 is provided with a cover 67,
having an elongated slot 68 therein. A stab terminal 69 is
connected to the load bar 70 of the circuit breaker, corresponding
to the load bar 18 therefore described, and is connected to the
housing of the breaker 70 by a suitable screw or bolt 71. The stab
terminal extends rearwardly or downwardly and is insertable through
the slot 68 when the breaker is lowered into position on the pan
and housing 62 preparatory to sliding it toward the bus bars into
connected position with the bus bars 4.
The slot is sufficiently long so that when the breaker is lowered
in place, the stab terminal passes endwise through the slot 68 and
lies in a position to the left of the jaws 66 so that upon movement
of the circuit breaker to the right to connected position, the stab
terminal engages resiliently between the jaws 66. The width of the
slot 68 is such that the stab terminal, by engaging the sides
thereof, acts as a forward guide in much the same manner as the
bracket 44 heretofore described.
In this form of the invention, if desired, a suitable bracket 73
may be provided and arranged as is the bracket 62 in the co-pending
application of Wilhelm T. Hackenbroch, Ser. No. 2,149, filed Jan.
12, 1970, for cooperation with a suitable rack disclosed at 60 in
the application, for the purpose of prying the circuit breaker from
the unconnected position to the connected position, as illustrated
in FIG. 4, should the frictional resistance to such movement so
require.
* * * * *