Note: Descriptions are shown in the official language in which they were submitted.
7 ~.! 41D-1'J34
DRAWOUT APPARATUS HAVING
IMPROVED TRIP INTERLOCK
Baekground of the Invention
The installation of electrical devices, such as circuit
breakers, in switchboard and panelboard apparatus is generally of
two types. In one type of installation, circuit breakers are
essentially stationarily mounted to structural members or frame of
the switchboard, typically with terminal electrical connection
effected via bolted joints. Alternatively, circuit breakers may
be physically supported solely by the switchboard buswork via these
bolted terminal joints. In such stationary installations, inspec-
tion and maintenance of the eireuit breaker is diffieult and quite
hazardous if attempted while the switehboard is live. In some
situations, the hazards must be assumed, since de-energization of
the switehboard and thus interruption of electrical service to all
of the branch eireuits in the switehboard eannot be tolerated. To
reduee the hazards of working with live switehboards, deviees are
provided with plug-in or stab-type primary diseonneet eontaets whieh
do not require direet eontaet and manipulation to effeet their
eonneetion and diseonneetion with mating disconnect contacts of the
switehboard. Thus, the deviee, e.g., eircuit breaker, can be
plugged in and unplugged from a live switchboard in relative safety.
In higher eurrent applieations, the eireuit breakers are
physieally large and quite heavy, thus rendering the bodily movement
of the eireuit breaker neeessary to eleetrieally eonneet and dis-
eonneet it from the switehboard eumbersome if not impossible, unless
meehanieal assistanee is afforded. Not only does the weight and
bulk of the eireuit breaker become difficult for the eleetrieian to
handle, but, as the eurrent ratings inerease, the eontaet pressures
of the primary diseonneet eontaets beeome extremely diffieult, if
not impossible to overeome. To surmount th~se problems, so-eal ed
-- 1 --
41D-1934
~(~75745;
"drawout" apparatus has been resorted to for both supporting the
circuit breaker and affording mechanical assistance in overcoming
the extreme contact pressures of the disconnect contacts.
Drawout apparatus are typically designed to support the elec-
trical device for racking movement between an extended position well
out of an enclosure compartment and an engaged position within the
compartment where the load current carrying primary disconnect con-
tacts of the device and enclosure are fully engaged. Since electrical
devices, such as circuit breakers for industrial applications, are
typically equipped with a variety of accessorial functions served by
external auxiliary circuits, provisions must be made for making and
breaking these auxiliary circuits as the circuit breaker is moved be-
tween its extended and engaged positions. To this end, so-called
mating secondary disconnect contacts are mounted with the circuit
breaker and the enclosure. These secondary contacts are engaged while
the circuit breaker is in the engaged position and become disengaged
at some point during movement of the breaker out to the disengaged
position. It is common practice to provide a test position for the
circuit breaker intermediate its engaged and extended positions where
the primary contacts are separated but the secondary contacts are
still engaged. In this test position, the accessorial functions can
be thoroughly tested in safety while the breaker is "dead".
During movement between the test and engaged positions, it is
imperative that the circuit breaker internal contacts be open, other-
wise violent arcing will typically occur as the primary contacts
begin engaging while the circuit breaker is moved toward its engaged
position and as the primary contacts begin disengaging and ultimately
separate while the breaker is en route from the engaged to the test
position. Such violent arcing will invariably do considerable
2 --
41D~ 34
1075'74~
damage to the primary contacts and presents an extremely hazardous
situation for both personnel and equipment.
It is accordingly an object of the present invention to
provide drawout apparatus which is equipped with an interlock
operable to insure that the circuit breaker internal contacts are
open while the circuit breaker is being moved between its test and
engaged positions.
An additional object is to provide drawout apparatus of the
above character, wherein the interlock is automatically operable to
permit closure of the breaker contacts while the breaker is in its
test position and its fully engaged position, and to inhibit breaker
contact closure while the circuit breaker is anywhere between these
two positions.
Another object of the invention is to provide drawout
apparatus of the above character wherein with the circuit breaker in
either its test or engaged position and its contacts closed, the
interlock operates to initiate tripping of the circuit breaker
automatically incident to initial movement of the breaker away from
one of these positions toward the other.
A further object is to provide a trip interlock of the above
character which is reliable and fool-proof in operation, and inex-
pensive to manufacture.
Other objects of the present invention will in part be
obvious and in part appear hereinafter.
Summary of the Invention
In accordance with the present invention, there is provided
drawout apparatus for racking a circuit breaker into and out of a
compartment in an electrical enclosure. The circuit breaker and the
enclosure are equipped with mating primary and secondary disconnect
contacts. The circuit breaker is mounted on a carriage which is
41D-1934
~075~7~
supported on opposed rail assemblies for movement between an
extended position well out of the compartment and an engaged
position within the compartment where the primary and secondary
contacts are engaged. An intermediate test position is established
where the primary contacts are disengaged, while the secondary
contacts remain engaged. The carriage is manually movable on the
rails between the disengaged and the test positions, however, due
to the extreme contact pressures of the primary contacts, a rack-
ing mechanism is utilized to propel the circuit breaker and carriage
between the test and engaged positions.
The drawout apparatus further includes an interlock uniquely
constructed in accordance with the present invention to insure that
during movement of the circuit breaker between its test and engaged
positions the breaker internal contacts are open, since it is
during this segment of the racking movement that the primary, load
current carrying disconnect contacts are engaging and disengaging.
Since this segment of the racking movement is handled by the racking
mechanism, the interlock is equipped to operate automatically off
the racking mechanism to preclude closure of the circuit breaker
contacts while it is positioned anywhere between its test and en-
gaged positions. Moreover, the interlock of the present invention
is equipped to initiate tripping of the circuit breaker contacts
should the circuit breaker contacts be closed while it is being moved
away from its engaged position toward its test position. Since it
is desirable th.at the circuit breaker be capable of being closed
while in its test position so as to permit thorough testing of the
accessorial functions with which the breaker is equipped, the
interlock of the present invention enables closure of the breaker
contacts while the breaker is in its test position as well as in its
engaged position. However, the interlock operates automatically to
41~A-1934
75'74t~
trip the circuit breaker as it is moved away from its test
position toward its engaged position. Under these circum-
stances, it is seen that the possibility of even inadvertent-
ly engaging or disengaging the primary disconnect contacts
while the circuit breaker internal contacts are closed is
absolutely precluded.
The invention accordingly comprises the features of
construction, combination of elements, and arrangement of
parts which will be exemplified in the construction here-
inafter set forth, and the scope of the invention will be
indicated in the claims.
For a better understanding of the nature and objects
of the invention, reference should be had to the following
detailed description taken in connection with the ac-
companying drawings, in which:
FIGURE 1 is a front perspective view of a circuit breaker
mounted in a switchboard compartment by a drawout apparatus
embodyin~ the present invention;
FIGURE 2 is an enlarged, fragmentary perspective view
of a portion of the drawout apparatus of FIGURE l;
FIGURE 3 is a fragmentary perspective view of the portion
of the drawout apparatus of FIGURE 2 with the circuit breaker
in a drawn out or extended position;
FIGURE 4 is a fragmentary perspective view of that
portion of the drawout apparatus of FI~URE 1 mounted by the
switchboard;
FIGURE 5 is a front elevational view of that portion of
the drawout apparatus seen in FIGURE 4:
FIGURE 6 is a plan view of the drawout apparatus portion
seen in FIGURE 5;
FIGURE 7 is an end elevational view of the drawout
apparatus portion of FIGURE S;
41DA-1934
~75 7~r?
FIGURE 8 is a fragmentary, somewhat diagrammatic, front
elevational view of a portion of FIGURE 5, to illustrate the
action of the gate controlling movements of the circuit breaker
between its test and disengaged positions;
FIGURE 9 is a front elevational view of the circuit
breaker carriage utilized in the drawout apparatus of
FIGURE l;
FIGURE 10 is a side elevational view of the carriage
of FIGURE 9;
FIGURE 11 is fragmentary view of a portion of FIGURE
10 illustrating the action of the racking mechanism;
FIGURE 12 is an enlarged side view of the crank shaft
mounted by the carriage of FIGURE 9;
FIGURE 13 is a fragmentary perspective view of one of
the telescoping rail assemblies in the drawout apparatus
of FIGURE 1, shown in its fully extended condition;
FIGURE 14 is a fragmentary perspective view of a rail
assembly in its fully compacted condition.
FIGURE 15 is a fragmentary, perspective view of a portion
of FIGURE 1, illustrating the locking feature for locking
the circuit breaker in either its disengaged or test positions;
FIGURE 16 is an end view of a circuit breaker interlock
operating off the crank shaft of FIGURE 12;
FIGURE 17, 18 and 19 are a series of side views of a
position indicator utilized in the drawout apparatus of
FIGURE l;
FIGURE 20 is a front view of the position indicator in
its condition illustrated in FIGURE 1~3;
FIGURE 21 is a plan view of the position indicia bearing
label utilized in the position indicator of FIGURES 17~ 18
and 19;
FIGURE 22 is an exploded, somewhat diagrammatic end view
~ 757~ 41DA-1934
of circuit breaker-switchboard secondary contacts utilized
in the drawout apparatus o~ FIGURE l;
FIGURE 23 is a plan view of the secondary contacts of
FIGURE 22 in their engaged positions; and
FIGURES 24, 25 and 26 are diagrammatic views of the
circuit breaker in its various positions relative to the
switchboard primary disconnect contacts as accommodated by
the drawout apparatus of FIGURE 1
Corresponding reference numerals refer to like parts
throughout the several views of the drawings.
Referring first to FIGURE 1, the invention is embodied
in a drawout mechanism for facilitating racking movement of
a large, industrial type circuit breaker 20 into and out
of a cubicle or compartment of an electrical enclosure or
switchboard 22. m e circuit breaker is mounted by a carriage,
generally indicated at 24, which in turn is supported for
racking movement by opposed telescoping rail assemblies,
generally indicated at 26 and mounted to the compartment
sidewalls The rail assemblies accommodate racking movement
of the circuit breaker between withdrawn or extended position
to a retracted or "engaged" position (FIGURE 26), wherein -
the breaker-switchboard load current carrying primary dis- -
connect contacts 27 are engaged. In an intermediate circuit
breaker position, commonly referred to as the "test" position
(FIGURE 25), the primary contacts are disengaged, while
circuit breaker-switchboard secondary contacts, generally
indicated at 28 in FIGURE 1, remain engaged to permit
operational testing of the various accessorial of auxiliary
functions embodied in the circuit breaker. Intermediate the
extended and test positions is a so-called "disengaged"
position (FIGURE 24) wherein both the primary and se~~ondary
contacts are disengaged. These engaged, test and disengaged
41DA-1934
1(~757~
positions are displayed frontally to the operator of the
drawout mechanism by an indicated at 30. Racking movement
of the circuit breaker between its extended and test positions
is readily effected manually through the convenience of the
rail asse~lies 26. However, due to the extreme contact
pressure built into the primary disconnect contacts 27 required
for cool xunning joints at higher current ratings, racking
movement between the test and engaged positions is effected
by operation of a racking mechanism, generally indicated at
32 in FIGURE 1.
The carriage consists of a pair of spaced sideplates
34 rigidly interconnected across the top by a tie strap
35 and across the back by a pair of stringers 36. Bolts
37 threaded into the base of circuit breaker 20 clamp the
stringers to the circuit breaker case affix the circuit
breaker to the carriage A horizontally elongated bracket
38 is affixed to each sideplate 34 for the purpose of mount-
ing front and rear carriage support pins 39. As will be
seen, these pins are received in slots provided in the
inner rails of each rail assembly in mounting the circuit
breaker-carriage assembly thereon. As seen in FIGURE 10,
mounting plate 40, affixed to the right carriage sideplate
34, is formed with a turned out front flange 40a which ro-
tatably mounts a lead screw 42 included in racking mechanism
32 A collar 43 fitted on lead screw 42 cooperates with -~
the lead screw head 42a to prevent axial movement thereof.
A slide plate 44 is provided with a horizontally elongated
slot 44a through which a bolt 46 extends; the end of this
bolt being threaded into the adjacent carriage sideplate.
A bracket 47 is affixed to this slide plate and captures a
traveling nut 48 through which lead screw 42 is threaded.
It is thus seen that slide plate 44 is free to reciprocate
~ ~5745 41DA_1934
horizontally as the lead screw is rotated in opposite
directions via a suitable tool, for example, a conventional
socket wrench.
Racking mechanism 32 further includes a crank shaft
50 (FIGURES 9 and 12) extending across the back of the
circuit breaker and journalled adjacent its ends in carriage
sideplates 34 Affixed to each end of this shaft beyond
the sideplates is a crank arm 52. The right crank arm carries
an inwardly extending pin 54 which is received in a vertic-
ally elongated slot 44b in slide plate 44. It is thus seen
that reciprocation of slide plate 44 by lead screw 42 swings
the right crank arm 52 through an arc via pin 54, and like-
wise the left crank arm via interconnecting shaft 50. The
crank arms mount outwardly extending crank pins 56 which,
as will be described, operate on stationary cam surfaces to
achieve racking movement between the test and engaged positions
via operation of the racking mechanism 32 Also mounted by
the crank arms are actuating pins 58 which, as will be de-
scribed, trip latches as the circuit breaker is moved -
between the test and disengaged positions such as to re-
position gates controlling entry to and egress from the test
position.
The rail assemblies are mounted to the compartment side-
walls by mounting pans 60, each of which, in turn, mount two
sets of vertically opposed rollers 62. An intermediate rail
64 is provided with upper and lower flanges 64a, which are
received in the peripheral grooves of rollers 62 pursuant
to rollably mounting the intermediate rails to the mounting
pans 60 Each intermediate rail mounts a series of rollers
66 (FIGURE 14) having grooved peripheries for receiving
upper and lower rail members 68 affixed to an inner rail 70.
It is thus seen that the intermediate rail rides on sta-
. .
41DA-]934
~O'~S745
tionary rollers 62, while the inner r~il 70 rides on rollers
66 carried by the intermediate rail, as the two rails of
each rail assembly move telescopically in racking the circuit
breaker in and out
To limit rail travel, a tab 72 (FIGURES 4 and 5) is
affixed to the inner end of each intermediate rail 64. The
end 72a of this tab lying behind the intermediate rails
engages a stop 73 lanced from the mounting pan 60 to limit
outward travel of the intermediate rails. As best seen in
FIGURE 13, tab 74 turned out from the inner end of each
inner rail 70 engages a stop 75 struck from a plate 76
mounted by each intermediate rail 64 to limit outward travel
of the inner rails. As a safety measure, tabs 78 depending
from the inner ends of inner rails 70 encounter pins 79
carried at the inner ends of elongated rail latch members
80 also affixed to mounting pans 60 to limit outward travel
of the rails should any of the normal stops fail During
compaction of the rails, tab 74 encounters tab 72 such that
the inner and intermediate rails move together to their
fully compacted conditions bottomed against the compartment
rear wall.
Adjacent its inner end, each inner rail 70 is provided
with a vertical slot 81 in which is accommodated a rail
stop latch 82 ~FIGURES 13 and 14). Each latch is mounted
to its inner rail by opposed brac~ets 83~ and is biased up_
wardly in its slot 81 by a spring 84 The upper end portion
82a of each latch 82 is bent inward, while the lower end
portion 82b is bent outward. As seen in FIGURE 13, the
lower portions 82b serve as stops, which~ with the latches
82 elevated by springs 84, engage the front edges 80a of
rail latch members 80 to lock the rails 64, 70 in their
fully extended conditions. Similarly, with the rails fully
compacted, as seen in FI~URE 14, and the latches 82 elevated,
-- 10 --
~)7S~ 41DA-1934
the latch stops 82b engage the rear edges 8ob of rail latch
members 80 to prevent outward travel of the rails. With
the rails latched in their fully extended conditions, inner
rails 70 are held stationary to thus facilitate mounting of
the circuit breaker-carriage assembly with the headed carriage
pins 39 received in upwardly opening notches 85 formed in the
inner rails. In so mounting the circuit breaker, a rear-
ward extention 38a of each bracket 38 (FIGURE 10~ engages the
turned-in upper end portions 82a of latches 82, automatically
depressing same to drop their lower stop portions 82b below
rail latch members 80 and thus free the rail for compaction
It is thus seen that as long as the circuit breaker-
carriage assembly is mounted on the rail assemblies 26,
latches 82 are automatically disabled, freeing the rail
assemblies to accommodate racking movement. However, with
the circuit breaker-carriage assembly dismounted, these
latches are effective to lock the rail assemblies in either
their fully extended or fully compacted conditions; the
latter being a convenience during shipment of the switch-
board sans the circuit breaker-carriage assembly.
It will also be noted that with the rail assemblies
fully extended, the circuit breaker-carriage assembly, while
supported by the inner rails, may be swung over on the two
forward pins 39 to an inverted orientation, thereby facilita-
ting inspection and maintenance of the circuit breaker
; and switchboard primary contacts. This releases latches
82 to lock the rail assemblies in their fully extended
conditions. To permit inverting the circuit breaker in
the first instance, the rails must be fully extended to
retract an elongated latching flange 76a formed with plate
76 carried by each intermediate rail 64. It is seen that,
as the rails are compacted, these latching flanges im-
41DA-1934
~0~574~
mediately ride over the heads of the two rear carriage pins
39 in notches 85 and ultimately the two forward pins to lock
the circuit breaker-carriage assembly on the rails in a
highly stable manner.
That portion of the racking mechanism carried by
carriage 24, namely the racking screw 42, slide plate 44,
crank arms 52, crank pins 56, etc., has already been des-
cribed in conjunction with FIGURE~ 9-12. The remaining,
stationary portion of the racking mechanism is carried by
mounting pans 60 (FIGURES 4-8) affixed to the compartment
sidewalls. ~o each mounting pan there is mounted a plate
90 having formed therein a double acting cam slot 92 ex-
tending from an upwardly directed opening downwardly and
somewhat rearwardly ~he crank pins 56 operate in these
cam slots; acting on the forward edges 92a thereof to
draw the circuit breaker from the test position inwardly
to the engaged position and acting on the rearward edges
92b thereof to draw the circuit breaker back to the test
position. q~is action is ~mplemented by the rotation of
the racking mechanism lead screw 42 in one direction to
swing the crank pins downwardly in slots 92 and draw the
circuit breaker into the engaged position and by rotation
of the racking screw in the opposite direction to swing the
crank pins upwardly in the slots to back the circuit breaker
off to the test position Guide plates 93, affixed to
mounting pans 60 and extending forwardly of the cam slot,
have laterally flared frontal portions 93a positioned to
engaged the crank pins 56 and correct any lateral mis-
alignment of the circuit breaker-carriage assembly as it
approaches the test position
Entry and exit of the crank pins 56 relative to slots
92 and thus movement of the circuit breaXer between the test
1~7~7~ 41DA-193~
position and the disengaged position is controlled by a
gate 94 pivotally mounted at 95 to each plate 90, As best
seen in FIGURE 7, depending link 96, affixed to each gate
by pins 97, terminates in an offset tab 96a which is
engaged in a vertically elongated slot 98a formed in the
inner end portion of an elongated gate operator arm 98.
The outer end of each arm terminates in a handle 98b ac-
cessible to an operator at the front corners of the com-
partment, It is seen that pulling the arms 98 outward pivots
the gates upward to permit the crank pins 56 to move into
positions immediately above the openings into cam slots 92
as the circuit breaker is manually shoved into the test
position from the disengaged position; the test position
- being determined by abutment of the crank pins against the
upper terminal portion of cam surface 92b, Similarly, with
the gates pivoted upward, the crank pins are free to move
away from the slot openings, thus permitting the circuit
breaker to be manually pulled out from the test position
into the disengaged position,
In order that the gates 94 need not be manually held
open to permit entry and egress of the crank pins 56, gate
actuating arms 98 are equipped with latches to sustain their
extended position. Each such latch comprises an elongated
latch plate 100 pivotally mounted on a post 102 laterally
outstanding from each mounting pan 60, The posts pass
through elongated slots 98c in arms 98 and thus also serve
to slidingly mount the arms. Additional mounting support
for the arms is afforded by brackets 104 affixed to the
mounting pans with one bracket fastener extending through a
second elongated slot 98d in each arm. Each arm 98 carries
a pin 106 which operates in a T-shaped slot 108 formed in
latch plate 100, A spring 110 is connected between a tab
_ 13 -
574t':
41DA-1934
lOOa offset Erom latch plate and pin 106 to bias the latch
plates to rotation about post 102 ~counter-clockwise in the
case of the one latch plate shown in FIGURE 5. It is seen
that when the arms 98 are pulled out to open gate 94, the
pins 106 move forward in their associated latch plate slots
108. When the arms are pulled out to their full extent,
springs 110 can then rotate the latch plates and the pins
106 enter the upper extensions 108a of slots 108 to latch
up the arms in their extended positions.
To automatically release the arms 98 once the crank
pins have entered or left the cam slots 92, the latch plates
are provided with rearward extensions 112, each carrying an
upwardly facing nose 112a. When the latch plates are cocked
to latch the arms in their extended positions, the noses
ll~a are elevated into positions where they are engaged by
the gate actuating pins 58 carried by the crank arms 52 as
the circuit breaker makes its final approach into the test
position and as the circuit breaker exits the test position
into the disengaged position (FIGURE 8). It is seen that
this engagement by pins 58 rotates the latch plates to
remove the pins 106 from upward slot extensions 108a to
unlatch the arms which are then retracted by springs 110,
closing gates 94 l~e slots 108 are provided with non-
latching, downward slot extensions 108b to accommodate latch
plate overtravel in response to actuating pin engagement,
as may be o¢casioned by manul'acturing tolerances. As a
backup for the automatic unlatching of arms 98 and closure
of gates 94, a lever 111, accessible at each front cover
of the compartment~ is pivotally mounted at lla to each pan
60. ~he inner ends of these levers are situated to engage
and rotate the latch plates 100 in directions to move pins
10~ out of slot extensions 108a and thus unlatch arms 98
_ 14 --
., ~ . . .
~) 75 74~ 41DA_1934
A stop 11~ outstanding from each pan 60 maintains the levers
poised in operative relation with the latch plates.
It is often desirable to lock the circuit breaker in
various positions so as to prevent unauthorized operation of
the drawout apparatus. To serve this purpose, a locking slide
113~ as best seen in FIGURE 15, is mounted by fasteners 114
received in vertically elongated slots 114a formed in the
right carriage sideplate 34. This slide is provided with an
offset lower portion designed to deny access to the racking
screw head 42a when the slide is in its lower position. In
this position apertures in the locking slide and the flange
40a line up, such as to receive the hasp of a padlock 115,
seen in phantom. musly padlocked, the locking slide cannot
be raised to permit fitting a socket wrench on the racking
screw, and thus the racking mechanism cannot be operated.
It is desired that padlocking be permitted only with
respect to the test and disengaged positions, and to this
end the slide 113 is provided with a laterally extending
flange 113a which drops into notches 116a or 116b formed in
the upper edge oE the right gate operator arm 98 when the
circuit breaker is in the disengaged and test positions, re-
spectively. A bracket 117, affixed to mounting pan 60, has
notches which line up with notches 116a, 116b when the arm
98 is in its retracted, gate closure position. As thus seen,
with the circuit breaker in its disengaged position, slide
113 can be dropped down to obstruct the racking screw head,
and concurrently flange 113a enters the aligned notches 116a
in arm 98 and bracket 117 to prevent both manual movement of
the circuit breaXer and pulling of the arm to open the right
gate 94 In the test position, the flange 113a drops into
the notches 116b to pre~ent movement in either direction away
from the test position
4ID~-1934
~0'75'74~
The position indicator assembly includes an arm 120
pivotally mounted at 122 to a bracket 123 affixed to the
left carriage sideplate 34. The forward portion of arm 120
is laterally offset from bracket 123 and terminates in a bent
back flag 124 to which is affixed a label 124a (FIGURE 21)
bearing the words "engaged", "test" and "disengaged", one
above the other. The laterally turned front end portion
123a of bracket 123 is provided with a window 123b im-
mediately in front of flag 124 (FIGURE 20), Affixed to the
back of bracket portion 123a is a plate 125 having an aperture
125a exposing one vertical segment of label 124a. A flange
126 turned back from the side edge of flag 124 opposite the
termination of arm 120 carries an upper stop 126a and a lower
stop 126b which engage a stop pin 127 carried by bracket 123
to determine the limits of pivotal movement of the indicator
arm, The arm is biased downward in the clockwise direction
by a spring 128 anchored at one end to a post 129 carried
by bracket 123,
The bottom edge of arm 120 is machined to provide a step
cam having a series of straight segments 120a-130e connected
by sharply angled segments 131, Operating against this step
cam is a stationary indicator actuator 132 constituted by a
- laterally turned flange carried by bracket 104 ~FIGURES 4-6)
affixed to mounting pan 60, It is thus seen that as the
circuit breaker is moved in and out, the indicator arm 120
is variously angularly positioned depending on which step
cam segment 130a-130e is riding on actuator 132, By cor-
relating the positioning of the indicia on the label 124a
affixed to flag 124 with these cam segments, the position of
the circuit breaker can be read through the aperture 125a in
plate 125, Thus, when cam segment 130a is riding on actuator
132, the word "engaged" is visible in aperture 125a. As the
_ 16 -
.: .
1-~7574~ ~lDI~-1934
circuit breaker is withdraw~ by operation of the racking
mechanism 32, cam segment 130b rides onto actuator 132 and
arm 120 is pivoted downward an increment by spring 128 to
remove the word "engaged" from in back of aperture 125a.
By virtue of the sharply angled transition cam segment 131
the change in indication is rather abrupt ~hile cam segment
130b is riding on actuator 132, the primary disconnect con-
tacts are engaged, but not fully so, and therefore the in-
dicator can not properly display the word "test" in aperture
125a. To do so would create a false and extremely hazardous
situation. On the other hand, to continue displaying the
word "engaged" while the primary contacts are not fully
engaged is equally hazardous, since the current carrying
capacity of partially engaged primary contacts is under-
standably greatly diminished. Accordingly, during the
transitionary movement between the engaged and test positions
while the primary contacts are progressively disengaging,
arm 120 is angularly positioned by cam segment 130b to align
in aperture 125a the blank segment of label 124a between the
words "engaged" and "test". Thus, the operator is advised
that the circuit breaker is in neither the test nor the engaged
position, but rather at some point in between.
Continued withdrawal by the racking mechanism ultimately
separates the primary contacts, and, when crank pins 56 clear
cam slots 92, cam segment 130c will have riden down on actu-
ator 132. Arm 120 abruptly drops down an increment to dis-
play the word "test" in aperture 125a. The circuit breaker is
now in the test position, wherein the switchboard-circuit
breaker secondary contacts are still engaged, but their
primary contacts are completely disengaged. Consequently
the circuit breaker is no longer live and the various ac-
cessorial functions served by these secondary contacts can be
_ 17 --
"
1~ 7574~ ~lDA-1934
operationally tested in complete safety
Upon manual withdrawal of the circuit breaker from the
test position, cam segment 130d rides onto actuator 132 and
arm 120 abruptly drops down an increment to display the word
"disengaged" in aperture 125a The operator is thus advised
that the circuit breaker is in the disengaged position with
both the primary and secondary contacts disengaged. Continued
manual withdrawal brings the circuit breaker into the ex-
tended position and cam segment 130e rides onto actuator 132.
Arm 120 drops down another increment to display a blank label - -
segment in aperture 125a. By inspection of the circuit breaker
position, the operator can not confuse this blank designation
with the blank designation displayed in the transition
between the test and engaged positions.
In the fully extended position, cam segment 130e rides
off the actuator 132, however, stop 126a engages pin 127 to
inhibit further downward movement of arm 120. The trailing
edge of cam segment 130e is chamfered, as indicated at 130f,
such that the actuator 132 will readily pick up the step cam
as the circuit breaker is racked in from the fully extended
position It will be appreciated that the indicator as-
sembly operates in reverse fashion from that described above
as the circuit breaker is racked into the compartment through
the disengaged and test positions to the engaged position.
It will also be appreciated that the indicator arm could be
mounted by the switchboard and the actuator by the circuit
breaker carriage and achieve comparable, unambiguous position
indication.
To insure safe operation of the drawout apparatus of the
present invention, a trip interlock, operation off the racking
mechanism 32, automatically trips the circuit breaker to an
open circuit condition during initial movement of the circuit
~ ~S7~5 41DA-1934
breaker away from its engaged position. The trip interlock
is structured, once the circuit breaker has reached its
test position~ to permit resetting and reclosure of the
circuit breaker in order that the various accessorial
functions can be fully tested Since the primary contacts
are disengaged while the circuit breaker is in its test
position, reclosure of the circuit breaker contacts can be
effected in relative safety.
Referring to FIGURE 16, a U-shaped bracket 142, affixed
to one of the carriage stringers 36, mounts a plunger 144.
A spring 145 acting on a pin 146 extending transversely
through plunger 144 biases this plunger upward as seen in
FIGURE 16. me upper end of plunger 144 is necked down for
engagement with an elongated lever 148 pivotally mounted at
149 to block 150 affixed to bracket 142. Spring 145 is thus
effective, through plunger 144, to elevate the free, right
end of lever 148 The lower end of plunger 144 carries a
cam follower plate 150 having a crooked end 150a which is
urged by spring 145 into engagement with the periphery of
shaft 50 interconnecting the right and left crank arms 52
(FIGURES 9-12).
The free end of lever 148 is engaged under the head of
a screw 152 adjustably threaded into the end of a plunger
154 slideably mounted in an aperture in the other carriage
stringer 36 and in an aperture provided in a secondary
bracket 156 affixed to this stringer. A compression spring
157 mounted on screw 152 operates between lever 148 and the
upper end of plunger 154. ~he lower end of this plunger acts
on the end of still another plunger 158 mounted within the
circuit breaker case. A spring 159 acts on the flanged upper
end of plunger 158 to normally bias it upwardly as seen in
FIGURE 16. m e lower headed end of plunger 158 engages a
-- 19 _
,,
~075~5 4lDA-1934
latch member 160 included in the circuit breaker operating
mechanism. Spring 159, in normally urging the plunger 158
upwardly, causes the headed lower end of this plunger to
pick up latch 160, tripping the circuit breaker in the first
instance and, once tripped, to prevent reclosure of the
circuit breaker internal contacts. Thus, the circuit breaker
contacts can only be closed as long as plunger 158 is de-
pressed by plunger 154, such as to release latch 160, where-
upon the circuit breaker operating mechanism can be reset
and the contacts closed.
To operate the trip interlock 140 off the racking
mechanism 32, a pair of headed screws 161 and 162 are threaded
transversely through shaft 50. The angular locations of
these screws are such that their heads depress cam plate 150
when the racking mechanism is operated to position the circuit
breaker in either the engaged or test positions It is seen
that when the head of either screw 161 or 162 engages the
follower end portion 150a of cam plate 150, plunger 144 is
depressed, causing lever 148 to pivo~ downwardly. The free
end of this lever acting on spring 157 overpowers spring 159
to depress both plungers 154 and 158 to release the circuit
breaker latch member 160. The presence of spring 157 ac-
commodates any overtravel of lever 148 occasioned by man-
ufacturing tolerances With the latch thus released, circuit
breaker 20 can be closed. Upon operation of the racking
mechanism, the conse~uent rotation of shaft 50 to rack the
circuit breaker from the test position toward the engaged
position or vice versa, the head of one of the screws 161,
162, as the case may be, releases the cam plate, whereupon ~-
spring 145 pushes plunger 15~ upward, raising the free end
of lever 148. Spring 159 pushes plungers 154 and 158 up-
wardly, and latch 60 is thus picked up to trip the circuit
_ 20 -
107S 7~5 41DA-1934
breaker 20. By virtue of this construction, the trip in-
terlock 140 is capable of insuring that the circuit breaker
is open during engagement and disengagement of the primary
contacts. It will be appreciated that should the primary
contacts begin engaging or disengaging while the circuit
breaker is closed, arcing and consequent damage to the
primary contacts can result Trip interlock 140 insures
that this cannot happen, even inadvertently It will also
be appreciated that during transitionary movement between
the test position and the fully engaged position, the
circuit breaker is not only open, but is prevented from being
closed by trip interlock 140.
~he secondary contacts consists of a plurality of circuit
breaker secondary contact strips fixedly mounted to the
carriage 24, which engage a complementary plurality of
secondary contact strips floatingly mounted by the compart-
ment sidewall. These secondary contact strips are suf-
ficently elongated in the direction of racking movement of
the circuit breaker to insure contact engagement while the
circuit breaker is in either its engaged or test position.
As best seen in FIGURES 3 and 23, the circuit breaker
secondary contact strips, indicated at 170, are mounted in
front and rear vertical arrays by terminal blocks 172a and
172b, respectively. These terminal blocks are mounted between
upper and lower frame members 174 affixed to the carriage
sideplate 34 As seen in FIGURE 23~ each contact strip 170
is secured adjacent its forward end portion to its respective
terminal block 172a, 172b by rivets (not shown). Screw 173
serves as a binding head screw for making connection with
auxiliary circuit leads (not shown~. The rearward extension
of each contact strip is offset such as to lie in spaced re-
lation to its mounting terminal block to thus provide, by
~07S7~ 41DA-1934
virtue of the inherent resiliency of the strip material,
an essentially free floating contact engaging segment 170a.
The switchboard secondary contact strips, indicated at
175 in FIGURES 22 and 23, are mounted in front and rear
vertical arrays to terminal blocks 176a and 176b, respectively.
The orientations of the switchboard secondary contact strips
are reversed relative to the circuit breaker contact strips
170 in that rivets (not shown) clamp the rearward portions
of the strips to their respective terminal blocks Thus,
the forward extensions of contact strips 175 are offset in
spaced relation to their mounting terminal blocks to provide
essentially free floating segments 175a for engagement with
the corresponding segments 170a of the circuit breaker
secondary contact strips As best seen in FIGURE 23, the
front and rear vertical arrays of circuit breaker contact
strips 170 are laterally offset, while the front and rear
- vertical arrays of switchboard contact strips 175 are later-
ally offset in complementary fashion so as to prevent
spurious contact engagement between the rear vertical array
of circuit brea]cer contact strips and the forward array of
switchboard contact strips during racking movement of the
circuit breaker.
The switchboard terminal blocks 176a, 176b are mounted
in laterally offset relation in a shell 178. This shell,
in turn, is slideably mounted on front and rear bolts 180
laterally outstanding from a bracket 181 affixed to the
compartment sidewall Bolts 180 pass through clearance
holes in the shell base and carry compression springs 182
acting to bias the shell against mounting bracket 181. It
is thus seen that the switchboard secondary contacts are
mounted in an essentially free floating manner with respect
to the compartment sidewall.
- 22 -
1~7~74~ 41DA_1934
The upper and lower sidewalls 183 of shell 178 extend
laterally well beyond the switchboard secondary contact
strips 175 and terminate in opposed upper and lower, horizont-
ally elongated guideways 185. The forward end portion of
each of these guideways, specifically the outer sidewall
or flange thereof, is flared away from the compartment
sidewall, as indicated at 185a. The upper and lower mount-
ing plates 174 for the circuit breaker secondary contacts
each carry a series of in-line locating posts 187 which, as
the circuit breaker is moved in from its extended position,
engage the flared entries 185a of the upper and lower guide-
ways 185, thereby camming the switchboard secondary contacts
away from the compartment sidewall The locating pins 187
are positioned relative to the circuit breaker secondary
contacts and the guideways 185 are positioned relative to
the switchboard secondary contacts such that, as the locat-
ing pins slide into the guidew~ys, the switchboard secondary
contacts are forcibly aligned for electrical contacting
engagement with the circuit breaker secondary contacts
as the carriage is moved into the test position and on to
the engaged position. It is obvious that the circuit breaker
secondary contacts can be mounted by the circuit breaker
itself, rather than the carriage, and that the circuit
breaker secondary contacts can be floatably mounted, rather
than the switchboard secondary contacts as herein disclosed.
It will thus be seen that the objects set forth above,
amon~ those made apparent in the preceding de6cription, are
efficiently attained and, since certain changes may be made
in the above construction without departing from the scope
of the invention, it is intended that all matter contained
in the above description or shown in the accompanying drawings
shall be interpreted as illustrative and not in a limiting sense.
_ 23 -
