Note: Descriptions are shown in the official language in which they were submitted.
41DA-3025
iO'~2163
Drawout apparatus are well known expedients for
facilitating the installation and removal of physically large
electrical devices, such as switches and circuit breakers,
with respect to switchboards and panelboards. The device is
provided with plug-in or stab-type disconnect primary contacts
which mate in electrical interconnection with complementary
switchboard primary disconnect contacts incident to racking
movement of the device to its innermost, engaged position,
thereby making the electrical joints requisite to electrically
connecting the device into the switchboard. -
In higher current applications, the devices become
quite large and heavy, thus rendering the bodily movement of
the devices necessary to electrically connect and disconnect
them from the switchboard extremely cumbersome without structure
supporting the device in its racking movement. ~oreover, as
current ratings increase, the requisite high contact pressures
embodied in the primary disconnect contacts become extremely
difficult, if not impossible, to overcome without mechanical
assistance. Thus, drawout apparatus for accommodating these
larger electrical devices typically include not only provisions
for supporting the device during racking movement, but also
various camming or levering mechanisms operating to mechanically
assist the racking movement of the device at least during that
segment of travel necessary to engage anddisengage the device-
switchboard primary disconnect contacts.
The principle limitation to the utilization of drawout
apparatus is the ability of the plug-in primary terminal joints
to carry the increasingly higher currents called for in many
applications. These joints are sources of heat which can
contribute to an intolerable high temperature condition within
the switchboard. Consequently, bolted terminal joints must be
resorted to, and, as a result, the signal advantage in drawout
~1 ~
10~Z163 4lDA-3025
installations of being able to connect and disconnect a device
from a live switchboard without having to operate directly on
the primary terminal joint is lost.
It is accordingly an object of the present invention
to provide improved drawout apparatus capable of racking circuit
; breakers of large size and weight into and out of an electrical
enclosure.
A further object of the present invention is to provide
drawout apparatus of the above character adapted to support a
lQ circuit breaker for racking movement between extended and engaged
positions with respect to primary terminals of an electrical
switchboard.
Yet another object of the present invention is to
provide drawout apparatus of the above character which includes
provisions for effecting cool running electrical joints between
the circuit breaker and switchboard primary terminals.
An additional object is to provide drawout apparatus
of the above character which includes circuit breaker tripping
means operating automatically to insure that the breaker is
tripped and cannot be closed until the breaker-switchboard
joints are fully perfected.
A still further object of the invention is to provide
drawout apparatus of the above character which includes display
apparatus for indicati~g the circuit breaker position relative
~ to the switchboard and the fact that the terminal joints have
; been perfected.
Still another object of the present invention is to
provide a drawout apparatus of the above character, which is
inexpensive to manufacture, efficient in design, rugged in
construction, safe and reliable in operation.
Other objects of the invention will in part be
obvious and in part appear hereinafter.
- 2 -
` 10'7~16~ 4lDA-3025
In accordance with the present invention, there is
provided drawout apparatus for racking relatively large, heavy
duty circuit breakers into and out of a switchboard compartment
and having provision for effecting plural cool running joints
between the breaker primary terminals and the switchboard
primary terminals. These terminal joints are effected
substantially concurrently in relative safety, even while the
switchboard is live. Generally stated, the drawout apparatus
of the invention includes a carriage on which the circuit
, 10 breaker is mounted. The carriage, in turn, is supported on
opposed, telescoping rails mounted to the electrical switch-
board. The rails accommodate facile movement of the circuit
breaker-carriage assembly from a fully extended position to a
test position just short of inter-engagement of connectors
affixed to the circuit breaker and switchboard primary load
current carrying terminals. Between the test position and the
engaged position, racking movement of the circuit breaker-
carriage assembly is mechanically assisted by a racking mechanism
lead screw which affords ample mechanical advantage while
2Q precisely positioning the circuit breaker with its primary
terminal connectors in joint-making relation with the
switchboard primary terminal connectors.
The drawout apparatus further includes manually
operable means; effective while the circuit breaker is in the
- engaged position, to achieve forceful clamping pressures on
lapped contact elements of associated circuit breaker and
switchboard primary terminal connectors, such as to achieve
cool running joints in the manner of bolted joints. More
specifically, the drawout apparatus includes a joint clamping
mechanism utilizing a second, clamping screw which is torqued
at the front of the carriage by the operator to develop equal
and oppositely directed forces on the lapped contact elements
lOq~163 41D~-3025
of associated breaker-switchboard terminal connectors, thereby
pressing same in secure electrical interconnection.
A trip interlock is controlled from the racking
mechanism to enable the circuit breaker to be closed while in
the test position and controlled by the clamping mechanism to
permit circuit breaker closure after the terminal joints have
been clamped. For all other situations, the trip interlock
operates automatically to maintain the circuit breaker tripped
and thus incapable of closure. Also included in the drawout
apparatus is indicating means for indicating the position of
the circuit breaker relative to the switchboard and the clamped
condition of the breaker-switchboard primary joints.
The invention accordingly comprises the features
of construction and arrangement of parts which will be exemplified
in the construction hereinafter set forth, and the scope of
the invention will be indicated in the claims.
- For a fuller understanding of the nature and objects
of the invention, reference should be had to the following
detailed description, taken in connection with the accompanying
drawings, in which:
FIGURE 1 is a front perspective view of a switch-
board compartment equipped with circuit breaker drawout apparatus
embodying the present invention;
FIGU~E 2 is a rear perspective view of the drawout
apparatus of FIGURE l;
FIGURES 3 and 4 are side elevational views of a
circuit breaker carriage utilized in the drawout apparatus
of FIGURE 1, these figures portraying the operation of a racking
mechanism included in the drawout apparatus;
FIGURE 5 is a fragmentary perspective view of a
portion of the drawout apparatus of FIGURE 1 mounted by the
switchboard;
~ Z163 41DA-3025
FIGURE 6 is a fragmentary, somewhat diagramatic, side
elevational view of a portion of FIGURE 5, illustrating the
action of a gate in controlling the racking movement of the
circuit breaker-carriage assem~ly between its test and dis-
engaged position;
.~
FIGURE 7 is a fragmentary, perspective view of a
`. portion of a joint clamping mechanism incorporated in the
drawout apparatus o.. FIGURE l;
FIGURE 8 is an isometric view of the back wall of
the switchboard cubical accommodating the drawout apparatus of
FIGURE l;
. FIGURE 9 is an exploded, perspecti`ve view of a
portion of the joint clamping mechanism of FIGURE 7;
` FIGURE 10 is a fragmentary, perspective view of a
: portion of the joint clamping mechanism of FIGURE 7 depicted
in its joint clamping condition;
- FIGURE 11 is a fragmentary, plan view, partially
broken away, of a portion of the joint clamping mechanism of
FIGURE 7;
.. 20 FIGURE 12 is a plan view, partially broken away, of
- a ~ortion of the joint clamping mechanism of FIGURE 7, depicted
in its joint clamping condition;
; FIGURE 13 is an exploded, perspective view of a portion
of an access control assembly incorporated in the drawout
apparatus of .IGURE l;
- FIGURE 1~ is a perspective view of a portion of the
access control assembly of FIGURE 13, illustrating different
relative positions of the various parts;
FIGURE 15 is a fragmentary, perspective view of
the access control assembly of FIGURE 13, illustrating the
relative positions of the various parts assumed when the
circuit breaker-carriage assembly arrives at its engaged position;
10~163 41DA-3025
FIGURES 16 through 19 are a series of perspective
views of the access control assembly in its various conditions
to control access to the racking and joint clamping mechanisms;
FIGUR~ 20 through 23 are a series of side elevational
views illustrating the operation of a position indicator
assembly utilized in the drawout apparatus of FIGURE l;
FIGURE 24 is a front elevational view of the position
indicator apparatus of FIGURES 20 through 23;
FIGURES 25 is a plan view of a position indicia
bearing label displayed by the position indicator apparatus of
FIGURES 20 through 23;
FIGURES 26 and 27 are plan views, partially broken
away, of a portion of the drawout apparatus of FIGURE 1
illustrating the manner in which a trip interlock assembly and
the position indicator assembly of FIGURES 20 through 23 are
controlled by the joint clamping mechanism of FIGURE 7;
FIGURES 28 and 29 are sectional views of the trip
interlock assembly of FIGURES 26 and 27, illustrating the
manner in which the trip interlock assembly is controlled by
the racking mechanism of 3 and 4; and
FIGURE 3a is an exploded, fragmentary perspective
view of a portion of the trip interlock assembly of FIGURES 26
and 27.
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 apparatus for facilitating racking
movement of a large, industrial-type circuit ~reaker 2Q into
and out of a cubical or compartment of an electrical enclosure
or switchboard 22. The circuit breaker is mounted by a
carriage, generally indicated at 24, which in turn is supported
for racking movement by opposed telescoping rail assemblies,
-- 6 --
.
10~163 41DA-3025
generally indicated at 26 and mounted to the compartment
sidewalls 22a. The rail assemblies are preferably constructed
in the manner disclosed in the commonly assigned, Canadian
application Serial No. 249,917, filed April 9, 1976, Ericson
et al. These rail assemblies accommodate racking movement
of circuit breaker 20 between a withdrawn or extended position
and a retrated or "engaged" position, wherein the breaker-
switchboard load current carrying primary contact terminals
are in engageable relation, ready to be made into cool running
joints by a clamping mechanism generally indicated at 27. As
disclosed in the above-noted Canadian application, the rail
assemblies accommodate positioning of the circuit breaker in
; an intermediate position, commonly referred to as the "test"
position, wherein the primary contact terminals are disengaged,
while circuit breaker-switchboard secondary contacts remain
engaged to permit operational testing of various accessorial or
~ auxiliary functions embodied in the circuit breaker. Inter-
- mediate the extended and test positions is a so-called
"disengaged" position wherein both the primary and secondary
contacts are disengaged. These engaged, test and disengaged
; positions of the circuit breaker are displayed frontally to
the operator of the drawout apparatus by an indicator assemhly,
generally indicated herein at 30 in FIGURE 1. Racking movement
of the circuit breaker between its extended and test positions
is readily effected manually through the convenience of the
rail assemblies 26. However, in order to achieve precise
positioning of the circuit breaker in its engaged and test
positions, racking movement therebetween is effected by
operation of a racking mechanism, generally indicated at 32 in
3Q FIGURE 1.
Carriage 24, as seen in FIGURES 1 and 2, includes
a pair of spaced sideplates 34 interconnected across the back
iO~Z163 41DA-3025
by a series of horizontal stringers 36. Bolts 37 clamp
laterally extending flanges 20a, integral with the circuit
breaker base, to the carriage stringers 36 pursuant to affixing
` the circuit breaker to the carriage. As best seen in FIGURE 3,
a horizontally elongated bracket 38 is affixed to each sideplate
34 for the purpose of mounting front and rear carriage support
pins 39. As disclosed in the above-noted Canadian application,
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 FIGURES 3 and 4 herein,
a mounting plate 40, affixed to the right carriage sideplate
34, is formed with a turned out frontal flange 40a which
serves to rotatably mount a lead screw 42 included in racking
mechanism 32. A collar 43, fitted on lead screw 42 behind
flange 40a, cooperates with the lead screw head to preclude
axial movement of the lead screw. A slideplate 44 is provided
with a longitudinally elongated slot 44a which receives a
laterally outstanding pin 46 carried by mounting plate 40.
A bracket 47 is affixed to slideplate 44 and captures a
travelling nut 48 through which lead screw 42 is threaded.
It is seen that slideplate 44 is thusly mounted to reciprocate
horizontally as the lead screw is rotated in opposite
directions via a suitable tool, such as a conventional socket
wrench.
Racking mechanism 32 further includes a crank
shaft 50 ~FIGURE 2~ extending across the back of the circuit
breaker and journaled adjacent its ends in carriage sideplates
34. To the ends of the crank shaft are affixed right and
left crank arms 52. The right crank arm as seen in FIGURES
3~ 3 and 4, carries an inwardly extending pin 54 which is received
in a vertically elongated slot 44b in slideplate 44. It is
thus seen that reciprocation of slideplate 44 by rotation of
-- 8 --
41DA-3025
107Z163
lead screw 42 swings the right crank arm 52 through an arc
centered about the crank shaft axis via the pin 54 and
; slot 44b interconnection. Thus, rotation of the lead screw
42 in a direction to move the slide to the left from its
position in FIGURE 3 to its position in FIGURE 4 swings the
right crank arm 52 in the clockwise direction. Crank shaft
50 is thus also rotated in the clockwise direction, and the
left crank arm affixed to its other end is swung through a
corresponding arc. The crank arms mount outwardly extending
lQ crank pins 56 which, as described in detail in the above-noted
Canadïan application, operate on stationary cam surfaces to
achieve racking movement of the circuit breaker-carriage
assembly between the test and engaged positions via operation
of rack;ng mechanism 32.
Each rail assembly, as seen in FIGURE 5, includes
two sets of vertically opposed rollers 62 which are mounted
to the compartment sidewall 22a. These rollers serve to
movably mount an intermediate rail 64 which, in turn, mounts
a series of rollers 66. These rollers, in turn, movably
2Q mount an inner rail 70. It is thus seen that the intermediate
rail rides on stationary rollers 62, while the inner rail 70
; rides on rollers 66 carried by the intermediate rail, thus
accommodating telescopic movement of the two rails of each
rail assembly in and out. To mount carriage 24 to the rail
assemblies, each inner rail 70 is provided with front and rear
upwardly opening notches 72 which receive the carriage support
pins 39 (FIGURE 3~.
As disclosed in the above-noted Canadian Application
Serial No. 249,917, the rail assemblies 26 include provisions
for limiting the telescopic movements of the intermediate
and inner rails, locking the carriage in its supported
position on the rail assemblies, and latching means for latching
iO72163 41DA-3025
the rail assemblies in their extended and compacted conditions
in the absence of the circuit breaker carriage. Also, the rail
assemblies are structured such that the circuit breaker-
carriage assembly may be swung over on the two forward carriage
support pins 39 to an inverted orientation, thereby facilitating
inspection and maintenance of the circuit breaker and switch-
board primary contact terminals.
That portion of the racking mechanism 32 carried by
carriage 24, namely the racking screw 42, slideplate 44,
crank arms 52, crank pins 56, etc. have already been described
in connection with FIGURES 3 and 4. The remaining, stationary
portion of the racking mechanism is supported by each compartment
sidewall 22a. Thus, as seen in FIGURE 5 and as described in
detail in the above-noted Canadian application, a plate 90,
affixed to each compartment sidewall, is provided with a double-
acting cam slot 92 extending from an upwardly directed mouth
downwardly and somewhat rearwardly. Crank pins 56 (FIGURES
3 and 4) operate in these cam slots as illustrated in FIGURE 6;
acting on the forward edges thereof to draw the circuit
breaker-carriage assembly from the test position inwardly to
engaged position and acting on the rearward edges thereof to
draw the assembly back to the test position. This action is
implemented by 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 in the opposite direction to swing the crank
pins upwardly in the slots to back the circuit breaker off
to the test position.
Entry and exit of the crank pins 56 from their
associated cam slots 92 are controlled by pivotally mounted
gates 94. Positioning of each gate 94 is manually controlled
by a separate, elongated gate operator arm 98 extending to
-- 10 --
-- . ~
:
` 41DA-3025
iO'72163
the front side edge of the switchboard compartment. As
described more clearly in the above-noted Canadian application,
arms 98 are pulled out in order to pivot the gates 94 to
their open position seen in FIGURE S and in phantom in FIGURE 6.
Latches 100 are provided to hold the operator arms in their
pulled out positions against the bias of return springs 101,
such as to sustain the gates in their open positions and
thus accommodate movement of the crank pins 56 into the mouths
of cam slots 92 as the circuit breaker-carriage assembly is
manually pushed in from the disengaged position to the test
position. Latches 100 also sustain the gates in their open
; positions to accommodate exiting of the crank pins 56
as the circuit breaker-carriage assembly is manually pulled
away from the test po8ition into the disengaged position. The
latches laO are also equipped to automatically release the
arma 98 for retraction by springs 101 to close the gates 94
once t~e crank pins 56 have either entered or left the mouth
of cam slots 92. To this end, the latches 100 are provided
with rearward extensions 112. When the latches are positioned
to latch the arms 98 in their pulled out positions, the
extensions are elevated into positions where they are engaged
by a gate actuating pin 58 ~FIGURES 3 and 4) carried by each
crank 52 as the circuit breaker-carriage assembly makes its
final approach into the test position and as the assembly
exits the test position enroute to the disengaged position.
This engagement unlatches the latches to release the arms,
and the gates close, all as more clearly described in the
above-noted Canadian application Serial No. 249,917.
- To prevent undesirable rocking and skewing of
the circuit breaker-carriage assembly during its racking
movement, a longitudinally elongated guide channel, generally
indicated at 114 in FIGURES 3 and 4, is affixed to each
i~7~3 41DA-3025
carriage sideplate 34. Each guide channel consists of
vertically spaced, laterally extending flanges 116a and 116b.
The channel 118 defined by these flanges is bottomed by a
series of spaced posts 120. As seen in FIGURE 5, a
longitudinally elongated guide flange 122 is mounted to each
compartment sidewall 22a. Guide flange 122 is made up of two
flange halves between which are captured a series of rollers
124. During racking movement of the circuit breaker-carriage
assembly, guide flange 122 is received in the guide channel
118 with rollers 124 rolling against the upper and lower
channel defining flanges 116a, 116b to prevent rocking
motion of the circuit breaker-carriage assembly during
racking movement without adding noticeably to the required
racking force. Posts 120 situated in the bottoms of the
guide channels 118 engage the free edges of guide flanges
122 so as to inhibit appreciable skewing motion of the circuit
breaker-carriage assembly during racking movement.
Returning to FIGURES 1 and 2, circuit breaker 20
is provided with massive line terminal straps 130 extending
2Q upwardly from the breaker case and a plurality of downwardly
extending load terminal straps 132. To each line terminal
strap there is clamped in electrical connection, by means of
bolts 131, a separate stab connector 134 (FIGURE 2). Similarly,
bolts 131 secure individual stab connectors 134 to each of
the load straps 132. As will be seen, the line stab connectors
are ganged together to provide a line connector stack
assembly 135, while the load stab connectors are ganged together
to provide a load connector stack assembly 137; both assemblies
being included in the joint clamping mechanism 27. As best
seen in FIGURE 7, each stab connector 134 comprises a base
134a which is provided with tapped bores into which the bolts
131 are threaded pursuant to clamping the connector in
~ 41DA-3025
. ` iO7:~163
` electrical connection with its associated terminal strap.
Integrally formed with connector base 134a are a plurality
of parallel spaced contact fingers 134b. As seen in FIGURE
8, the switchboard 22 is equipped with line and load receiver
connectors 136 respectively electrically connected to line
; and load bus (not shown). These switchboard line and load
receiver connectors are similarly provided with a series of
~ parallel spaced contact fingers 136a. Returning to FIGURF
; 7, when the circuit breaker-carriage assembly is in the
la engaged position, the contact fingers of the associated
circuit breaker stab connectors and switchboard receiver
connectors interleave. The spacings between the contact
fingers of the associated stab and receiver connectors are such
that they slide freely relative to each other in assuming
their interleaved relationships. Preferably, the line and
load stab connectors are individually secured to elongated
insulative bars 139 affixed to the carriage stringers 36 as
best seen in FIGURE 2, and thus the line and load connector
stack assemblies may be supported as completed assemblies
20 by the carriage 34, independently of the circuit breaker
terminal straps.
- Referring jointly to FIGURES 7 and 9 through 12, the
contact fingers 134b of each of the identically constructed
line and load connector stack assemblies 135, 137 are
provided with transversely registered apertures 134c through
which extends an elongated clamping rod 140 (FIGURE 11~. An
insulating sleeve 142 encompasses the clamping rod 140 so
as to electrically insulate the rod from the individual
contact fingers. Centrally apertured insulator blocks 144
30 are loosely fitted on clamping rod 140 to take up the space
between adjacent stab connectors 134. Similar, centrally
apertured insulator blocks 144 are loosely received on each
- 13 -
iO7Z163 4lDA-3025
end portion of clamping rod 140 beyond the outboard stab
connectors 134. The left end of clamping rod 140 passes
through a central opening in a U-shaped clamping plate 146
and terminates in a threaded portion accommodating a nut
148. Captured on the left end of clamping shaft 140 inter-
mediate nut 148 and clamping plate 146 are a series of four
Belleville washers 140. A sheet 151 of insulation is
interposed between clamping plate 146 and the left most
insulator block 144 so as to increase the over surface
lQ clearance between the outboard connector and the metal part
therebyond.
The right end of clamping rod 14Q of each connector
stack assembly passes through another U-shaped clamping
plate 146, an insulative sheet 151, and a series of four
Belleville washers, terminating in a tongue 152 having
formed therein a rectangular opening 152a, as best seen in
FIGURE 9. A U-shaped clamping element 154 is formed having
an aperture 154a in its bight portion 154b through which the
; right end clamping rod 14Q freely passes. The legs 154c of
2Q clamping element 154 are spaced apart sufficiently to receive
therebetween tongue 152 at the right end of clamping rod 14Q.
Rectangular openings 154d are provided in the clamping element
legs 154c in opposed relation with rectangular opening 152a
in tongue 152.
As best seen in FIGURE 2, a vertically oriented
clamping shaft 160, also included in the joint clamping
mechanism 27, is journaled for axial rotation by brackets 162
affixed to the upper and lower carriage stringers 36.
The upper and lower terminal portions of this clamping shaft
3Q are provided with opposed flats 160a (FIGURE 9~, with these
terminal portions extending through the rectangular openings
in the clamping element 154 and tongue 152 of both line and
- 14 -
" ` lO~Z163
41DA-3025
load connector stack assemblies 135, 137. In the quiescent
condition of joint clamping mechanism 27, clamping shaft 160
is angularly oriented as seen in FIGURE 7, such that the
flats 160a at its terminal end portions are arranged
perpendicular to the axis of clamping rod 140. Thus, these
flats engage the outer edges of the rectangular openings 152a
in tongues 152 and the inner edges of rectangular openings
154d in clamping elements 154.
Still considering the joint clamping mechanism 27,
a bracket 170 is attached to the inner side of the right carri-
age sideplate 34, as seen in FIGURE 11. The forward portion
of this bracket is laterally turned to provide a flange 170a
for rotably mounting a lead screw 172. A collar 174 fitted to
` lead screw 172 behind flange 170a prevents axial movement
of the lead screw. A sideplate 176 is mounted for
reciprocating movement by a bracket mounted pin 177 received
in a longitudinally elongated slot 176a visible in FIGURE 16.
~, The slideplate captures a travelling nut 178 through which
lead screw 172 is threaded. A transversely elongated slot
176b formed in slideplate 176 receives a pin 18Q carried at
the free end of a crank arm 182 affixed at its other end of
clamping s~aft 16Q, as ~est seen in FIGURE 9. It is thus
seen that rotation of clamping screw 172 via a suitable
tool, such as a socket wrench, reciprocates slide 176, which
in turn, via crank arm 182, rotates clamping shaft 160.
~ith the contact fingers of the switchboard
receiver connectors and the line and load connector stack
assemblies interleaved, rotation of the clamping shaft 16Q
swings the rounded portions of its shaft terminations into
` 30 engagement with the opposed edges of the rectangular openings
in the tongues 152 and clamping elements 154 of both stack
assemblies. As a result, tongues 152 are cammed to the
- 15 -
10'~63 41DA-3025
`~ `
cammed to the right as seen in FIGURE lO, pulling with it
- clamping rod 140 and thereby loading the Belleville washers
150 at the left ends of both the line and load connector stack
; assemblies. At the same time, clamping elements 154 are cammed
` to the left as seen in FIGURE 10 to load the Belleville
washers 150 at the right ends of the line and load connector
stack assemblies. These Belleville washers at each end of
the joint stack assembly develop oppositely directed clamping
forces effective to clamp the interleaved contact fingers of
lQ the circuit breaker stab and switchboard receiver connectors
in secure electrical connection.
While the joint clamping mechanism together with
its line and laod connector stack assemblies are disclosed
as being mounted by the carriage, it will be appreciated
that this mechanism could be mounted instead by the switchboard.
Preferably, the stab connectors 134 are each provided with
one more contact finger 134b than is provided in each of the
receiver connectors 136, as illustrated herein, and con-
sequently the stab contact fingers can effectively define
all of the slots into which the receiver contact fingers
136-a are inserted.
It will be appreciated that the disclosed joint
clamping mechanism offers-numerous advantages. The designed
differential in the effective diameters of the clamping shaft
- flats 160a versus the rounded portions of the shaft
terminations is operative to impart a predetermined and
very-repeatahle loading or compression of the sets of
~elleville washers at each end of both stack assemhlies.
Thus, the clamping forces devleoped by the opposed sets
of spring washers are equally predetermined and repeatable.
Since these clamping forces are essentially equal and
oppositely directed, there is no significant resultant forces
- 16 -
41DA-3025
10'~163
acting on the connector stack assemblies. Joint clamping
s forces of as much as 3,000 pounds have been achieved utilizing
, the disclosed joint clamping mechanism. The nuts 148, threaded
on the ends of the clamping rods 140, are turned to readily
establish the desired clamp force magnitude. While Belleville
washers are illustrated herein, it will be understood that
other forms of joint clamping force generating springs may
be utilized. Also to be noted is the fact that the disclosed
joint clamping mechanism affords the opportunity to perfect
high current carrying primary terminal joints from the front
of the switchboard in complete safety even while the switch-
board line receiver connectors are live. Moreover, all
phases of both the line and load primary terminal joints
are perfected concurrently in convenient fashion, with the
joints having all the attributes of bolted joints. While
the joint clamping mechanism is herein disclosed in its
application to effecting electrical joints between a
switchboard and an electrical device, it will be appreciated
that the teachings may be readily applied to the making of
high current carrying electrical joints in general, such as
between busway sections and between busway and busway plugs.
As a safety measure, it is deemed appropriate to
interlock the operations of the racking mechanism 32 and
the joint clamping mechanism 27, depending upon the position
of the circuit breaker-carriage assembly. That is, it is
very important that the clamping screw 172 not be rotated
to exert clamping pressures on the line and load connector
stack assemblies until the circuit breaker is in its engaged
position with the contact fingers of the stab and receiver
connectors fully interleaved. It will be appreciated that
permanent deformation of the circuit breaker stab connector
fingers could well result if clamping pressure is exerted
107~163 41DA-3025
absent the interleaved switchboard receiver contact fingers.
Also, interleaving of the contact fingers could not be
achieved as the circuit breaker is racked into its engaged
position if the connector stack assemblies were pre-clamped,
and attempts to do so would damage the racking mechanism 32.
By the same token, attempts to rack the circuit breaker-
carriage assembly away from its engaged pos-ition without first
unclamping the joint stack assemblies could also damage the
racking mechanism.
lQ To this end, an access control assembly, generally
indicated at 179 in FIGURES 1 and 16 through 19, is provided
to include a first access control plate 180 having vertically
; elongated slots 180a through which are received pins 181
- pursuant to vertically reciprocatively mounting the plate
to the inner side of the righ* carriage sideplate 34 as best
seen in FIGURES 13 through 15. This access control plate
further includes an offset and upwardly extending barrier
180b which, with the plate in its elevated position, partially
overlies the head of clamping screw 172, thus denying access - -
thereto. Riveted to access control plate 180 is a faceplate --
182, which is provided with a lower offset tab 182a to --
serve as a handle for manually vertically positioning the
access control assembly 179. A second access control plate
184 is mounted by a pivot pin 185 between the first access
control plate 180 and faceplate 182. The second access
control plate 184 is provided with an offset and depending
barrier 184a which is adapted to control access to the head
of racking screw 42, depending upon the vertical position of -
the access control assembly and the angular position of
the second access control plate. A spacer rivet 186 extending
between faceplate 182 and access control plate 180 through
an elongated slot 184b in the second access control plate
- 18 -
10'7~163 41DA-3025
:
184 (FIGURE 17) holds these plates in spaced relation to
` accommodate plate 184. A clamping screw 187 is adjusted to
squeeze the two outer plates together so as to exert a light
frictional drag on the pivotal movement of the second access
control plate and thus discourage spurious pivotal movement
of access control plate 184 during vertical reciprocation
of the access control assembly 179.
From the description thus far, it is seen that
while the second access control plate 184 is in its counter-
clockwise most pivotal position seen in FIGURE 16, its barrier
184a is in position to deny access to the racking or drawout
screw 42 while the access control assembly 179 is in its
depressed position. However, barrier 180b is then ducked
away from the head of clamping screw 172 such as to afford
access thereto. When the access control assembly is in its
elevated position seen in FIGURE 19, barrier 180b is in
position to deny access to clamping screw 172, while barrier
element 184a is elevated away from the head of racking screw
42 to admit access thereto. With the access control assembly
in its elevated position and the control plate 184 pivoted
to its clockwise-most position as illustrated in FIGURE 17,
access to both racking screw 42 clamping screw 172 is denied.
In this condition, aperture 182b in faceplate 182, aperture
184d in control plate 184, and aperture 180c in control plate
18a LFIGURE 13~ are in registry to receive the hasp of a
padlock 188.
To interlockingly regulate the movement of the
access control assembly according to the circuit breaker-
carriage assembly position, a slide 190 is mounted to the
3a underside of the lower guide channel flange 116b (FIGURES
3, 4 and 13 through 15) for limited fore and aft movement.
A spring 192, operating between a turned down tab l90a at
-- 19 --
41DA-3025
iO~Z163
.
the rear end of slide 190 and a post 193 depending from
guide channel flange 116b, biases the slide to its rearward
position. An arm 194 adjustably mounted to the underside
of guide flange 122 (FIGUR~ 5 and 13), carries a laterally
extending tab 194a which is positioned to engage a turned down
tab 190a, shifting slide 190 to its forward position as the
circuit breaker-carriage assembly is racked to its engaged
position. The forward end of arm 194 is turned up to provide
a convenient handle for adjusting the mounting position of the
arm such that slide 190 is shifted sufficiently forward upon
arrival of the circuit breaker-carriage assembly in its
engaged position to register a notch 190b formed therein with
a laterally turned tab 180d carried by access control plate
180. A tab 190c depending from slide 190 just forward of notch
190b, prevents access control plate tab 180d from getting caught
under the slide. Once the appropriate position of arm 194 is
established, it is immovably clamped to the underside of guide
flange 122. It is seen from FIGURE 13, that until slideplate
190 is shifted to its forward position by engagement with arm
tab 194a upon arrival of the circuit breaker in its engaged
position, notch 190b is out of registry with tab 180d, and
access control assembly 179 cannot, under this circumstance,
be shifted downwardly to afford access to clamping screw 172.
As an additional precautionary measure, a flange 196
is riveted to the racking screw slideplate 44, as seen in
FIGURES 3, 4, 15 and 15. The upper elongated edge 196a of
this flange is positioned in underlying relation to access
control plate tab 180d, such as to prevent downward movement of
the access control assembly until the racking mechanism has
been operated to draw the circuit breaker-carriage assembly into
the engaged position. Once in the engaged position, flange 196
has moved completely forward of the access control plate tab
- 20 -
. .
` 10'~163 41DA-3025
- 180d, as seen in FIGURES 4 and 15, thus clearing tab 180d tomove downwardly through notch l90b and beyond the back edge of
flange 196. These two separate, but functionally related
interlocking porivisions are seen to prevent inadvertant,
untoward operation of the joint clamping mechanism, both while
the circuit breaker-carriage assembly is mounted or dismounted
with respect to the rail assemblies 26.
With the circuit breaker-carriage assembly in its
engaged position and the access control assembly freed to be
shifted downwardly to access the clamping screw while, at the
same time, denying access to the racking screw, clamping
operation of the connector stack assemblies then may proceed.
As the clamping mechanism slideplate 176 is drawn forwardly by
rotation of clamping screw 172, it moves over an upstanding
- tab 180e carried by access control plate 180 (FIGURES 15 and
` 16) so as to prevent elevation of the access control assembly
during the time that clamping pressures are being exerted on
the connector stack assemblies, and consequently, access to
the racking screw 42 is, under this circumstance, denied.
It is preferred that the access control assembly can
only be locked by padlock 188 when the circuit breaker-carriage
assembly is in either its test or engaged positions. To this
end, the pivotal access control plate 184 is provided with a
laterally extending tab 184c whichis received in one of two
sets of notches 200a and 200b formed in the upper edges of
both the right gate control arm 98 and a bracket 202 supporting
same, as seen in FIGURES 5, 16 and 17. These notches are
positioned such that the set 200a is aligned with tab 184c when
the circuit breaker-carriage assembly is in its test position
and the set 200b is aligned with the tab when the assembly is
in its disengaged position. For the engaged position of the
assembly, tab 184c is not registerable with either of these
:101~2163 4lDA-3025
- notch sets, and consequently access control plate 184 cannot
be pivoted sufficiently clockwise to align its hasp aperture
184d with the hasp apertures in the faceplate and access control
plate 180 such as to permit padlocking. However, with tab
184c lodged in either of the notches sets 200a, 200b and the
padlock applied, racking movement of the circuit breaker-
carriage assembly and operation of the gate control arm
are both precluded, and the access control assembly is locked
in the condition denying access to both lead screws 42 and
172.
The present drawout apparatus includes position
indicating apparatus similar to that disclosed and claimed
in the commonly assigned, Canadian application, Serial
No. 248,381, filed March 17, 1976, Ericson et al. In the
drawout apparatus of this Canadian application, there were
only three significant circuit breaker-carriage positions,
namely, the disengaged, test and engaged positions. In the
instant drawout apparatus, there is an additional position,
which is in actuality a condition, namely, the ~oint clamped
position. In terms of circuit breaker-carriage assem~ly
position, the engaged and clamped positions are the same. me
clamped position pertains when the circuit breaker stack
connector assemblies are clamped in electrical connection with
the switchboard receiver connectors. Accordingly, the posi*ion
indicating apparatus 30 of the present drawout apparatus is
structured so as to indicate not only the disengaged, test and
engaged positions of the circuit breaker-carriage assembly,
but also the clamped condition of the circuit breaker-switch-
board primary contact terminals.
To this end, the position indicator assembly 30
includes, as seen in FIGURES 20 through 23, an arm 21Q
pivotally mounted at 212 to a bracket 213 affixed to the
- 22 -
41DA-3025
iO'~163
left carriage sideplate 34. The forward portion of arm 210
is laterally offset away from bracket 213 and terminates in a
bent back flag 214 to which is affixed label 214a (FIGURE 25)
bearing the words "Disengaged, "Test", "Engaged" and "clamped",
one below the other. A laterally turned front end portion
213a of bracket 213 is provided with a rectangular opening
213b (FIGURE 24) behind which is affixed a mask 215 having a
window 215a in which the label indicia is separately displayed.
A flange 216 turned back from the side edge of flag 214
opposite its junction with arm 210 carries an upper stop 216a
and a lower stop 216b which engage a stop pin 217 carried by
bracket 213 to determined the limits of pivotal movement of
indicator arm 210, as best seen in FIGURE 20. The arm is biased
downwardly in the clockwise direction by a spring 220 anchored
to a post 221 carried by bracket 213.
As disclosed in the above-noted Canadian application
Serial No. 248,381, the bottom edge of indicator arm 210 is
machined to provide a step cam having a series of straight cam
segments 210a, 210b, 210c and 210d interconnected by sharply
angled cam segments 210e. Operating against this step cam is
a stationary indicator actuator 222 fixedly mounted by the
compartment sidewall. It is thus seen that as the circuit
breaker-carriage assembly is moved in and out, the indicator
arm 120 is variously angularly positioned depending upon which
step cam segment is riding on actuator 222. By correlating
the positioning of the indicia on the label 214a affixed to
flag 214 with these cam segments, the position of the circuit
breaker-carriage assembly can be read through the window 215a in
mask 215. Thus, when cam segment 210a is riding on actuator
222 (FIGURE 23), the word "disengaged" is visible in window 215a.
As the circuit breaker-carriage assembly is pushed into the test
position, cam segment 210b rides onto actuator 222 and arm 210
- 23 -
:10'~163 4lDA-3025
is pivoted upwardly to index the word "test" into registry
with window 215a. By virtue of the sharply angled transistion
cam segment 210e the change in position indication is rather
abrupt, occurring essentially upon arrival of the circuit
breaker-carriage assembly at its test position. From the
test position, the circuit breaker-carriage assembly is drawn
toward the engaged position by the racking mechanism 32. Cam
segment 210c then rides onto actuator 222, and the indicator
arm 210 is pivoted upwardly to register the blank space
between the words "test" and "engage" in window 215a. This
blank indication advises the operator that the circuit
breaker-carriage assembly is in neither the test position nor
the engaged position, but is in transient therebetween. Upon
arrival at the engaged position, cam segment 210d rides onto
actuator 222, pivoting arm 210 upwardly still another increment
to register the word "engaged" in window 215a. Though in the
engaged position, the circuit breaker must not be turned on
until the switchboard-circuit breaker primary contact terminals
are clamped in electrical interconnection by operation of
joint clamping mechanism 27.
In order to indicate achievement of the clamped
condition, the fact of completed operation of the clamping
joint clamping mechanism must be communicated to the indicator
assembly. To this end, a slide 230, elongated to extend
substantially the full width of the carriage 24, is mounted
by one of the rear carriage stringers 36, as seen in FIGURE 2.
More specifically, and as best seen in FIGURES 26 and 27,
slide 230 is formed having a series of longitudinally elongated
slots 230a in which are received pins 232 carried by the slide
- 30 supporting stringer 36. This mounting affords limited
longitudinal movement of the slide against the force of a
spring 236 normally biasing the slide to its right-most
- 24 -
iO~163 4lDA-3025
position seen in FIGURE 27. The left end of this slide seen
in FIGURES 26 and 27 mounts a bracket 234 carrying an arm
234a. An adjusting screw 235 threaded through a laterally
turned flange portion 234b of bracket 234 bears against arm
234a to adjust its positioning so as to bear against the
periphery of clamping shaft 160 when the slide is in its
right-most position. Clamping shaft 160 is provided with a
bolt 238 extending diametrically through the clamping shaft
at an elevation aligned with arm 234a of bracket 234. Upon
operation of the joint clamping mechanism to perfect the
circuit breaker-switchboard primary contact terminals, clamping
shaft 16Q is rotated, bringing the head of the bolt around
into engagement with arm 234a, as seen in FIGURE 26, thereby
shifting slide 23Q to its left-most position at the conclusion
of the joint clamping operation.
An arm 240 is pivotally mounted at 240a to the slide
mounting stringer 36 adjacent the right end of the slide 230
seen in FIGURES 26 and 27 and is provided at one end with an
elongated slot 240b in which is received a pin 242 carried by the
2Q slide. It is thus seen that the lateral shifting of the slide
position produces pivotal movement of arm 240. The other
end of arm 24Q from post 242 carries a laterally extending
tab 240c which extends through an opening 243 ïn the adjacent
carriage sideplate 34. A wire link 244 is hooked at one Qnd
to tab 24Qc of arm 24Q and extends through an aperture in a
bracket 246 carried by indicator arm 21Q, as seen in FIGURES
20 through 23. The free end of link 244 is threaded to receive
nuts 248 which are adjustably positioned to established the
appropriate length of link 244. In comparing FIGURES 2Q and 21,
it is seen that with the circuit breaker-carriage assem~ly in
the engaged position and its primary contact terminal joints
with the switchboard still to be clamped, cam surface 210d is
- 25 -
107~63 41DA-3025
riding on actuator 222. Upon actuation of the clamping
mechanism to its completed joint clamping condition, the
bolt head 238 carried by shaft 160 shifts slide 230 to the
left as seen in FIGURE 26, pivoting arm 240 in a direction
to draw the link 244 to the left as seen in FIGURE 20, thereby
lifting indicator arm 210 upwardly off of actuator 222 sufficient-
ly to register the word "clamped" in window 215a. As the joint
clamping mechanism is operated to relax the joint clamping
pressure, clamping shaft 160 rotates to swing the head of bolt
238 away from arm 234a, and slide 230 is returned to the right
by its spring 236. Arm 240 is thus pivoted in the opposite
direction to shift link 244 to the right as seen in FIGURE 21,
permitting arm 210 to drop back down onto actuator 222 under
the bias of spring 220, thereby again registering the term
"engaged" in window 215a.
In addition to the safety interlocking features
provided by the access control assembly 179 operating to control
access to the joint clamping mechanism 27 and the racking
mechanism 32 depending upon the position of the circuit
breaker-carriage assembly, the instant drawout apparatus also
includes circuit breaker trip interlocking provisions similar ;
to that disclosed and claimed in the commonly assigned,
Canadian application, Serial No. 267,440 filed December 8, 1976,
Ericson et al. In this Canadian application, the trip interlock
functioned to automatically enable closure of the circuit
breaker while in either its test or engaged positions and to
automatically trip the circuit breaker, should it be in its
ON condition, during initial racking movement from the test
position toward the engaged position and from the engaged
position toward the test position. Thus the trip interlock
functions to insure that the circuit breaker contacts are
open during racking movement between the test and engaged
- 26 -
` 41DA-3025
iOqZ163
positions, so as to preclude the possibility of load current
flowing through the plug-in primary disconnect contacts while
they are in the process of being engaged and disengaged. In
the case of the drawout apparatus disclosed in the present
application, circuit breaker trip interlocking, insofar as the
test position is concerned, is performed in the manner described
in the above-noted Canadian application. However, to defeat
the trip interlock upon arrival of the circuit breaker-carriage
~ assembly ati~S engaged position, as was done in the drawout
; 10 apparatus of the Canadian application, would create a hazardous
situation, since inadvertent closure of the circuit breaker
contacts before the circuit breaker-switchboard primary contact
terminals have been clamped could have disastrous consequences.
~` Accordingly, as described below, the trip interlock
of the instant drawout apparatus is conditioned by the racking
mechanism to permit closure of the circuit breaker contacts
while in the test position and to trip the circuit breaker
should its contacts be left closed as racking movement is
initiated from the test position toward the engaged position.
2Q Once ïn the engaged position, the trip interlock is controlled
by the joint clamping mechanism such as to prevent closure of
the circuit breaker contacts until the circuit breaker-switch-
board primary contact terminals have been completely clamped
in electrical interconnection and to trip the circuit breaker
should its contacts be closed during initial operation of the
joint clamping mechanism toward relaxing the joint clamping
pressure.
A trip interlock, generally indicated at 250 in
FIGURES 2, 26 and 27, includes a bracket 252 affixed by suitable
3Q means (not shown~ to the same rear carriage stringer which
mounts slide 230. This bracket mounts a plunger 254 which
is normally biased rearwardly in FIGURE 27 or to the left in
- 27 -
10~163 4lDA-3025
FIGURE 28 by a spring 256. The outer end of plunger 254 is
necked down for engagement with an elongated lever 250
pivotally mounted at 259 to bracket 252. The spring 256 is
thus effective through plunger 254, to bias the free, right
end of lever 258 rearwardly away from circuit breaker 20, as
seen in FIGURE 27. The inner end of plunger 254 carries a
cam follower plate 260 having a crooked end 260a which is
urged by spring 256 into engagement with the periphery of
crank shaft 50, as best seen in FIGURE 28.
An extension 258a of lever 258 is engaged under the
head of a screw 262 adjustably threaded into the end of a plunger
264 which is suitably slideably mounted for protrusion through
the circuit breaker case into controlling engagement with a
circuit breaker tripping element 266. A spring 268 acting
between the lever extension arm 258a and plunger 264 accommodates
any over travel of the lever 258 in operating the circuit
breaker tripping element 266, as occasioned by manufacturing
tolerances.
To operate trip interlock 250 off the racking
mechanism 32, a bolt 269, mounted transversely through crank shaft
50, is so positioned that its head engages the crooked end
260a of cam follower plate 260 thereby depressing plunger 254
when the racking mechanism accommodates the circuit breaker-
carriage assembly to its test posi~ion. Depression of plunger
254 pivots lever 258 toward the circuit breaker forcing plunger
264 inwardly, or to the right as seen in FIGURE 29, thereby
depressing the tripping element 266 to enable closure of the
circuit breaker contacts. As the racking mechanism is operated
to move the circuit breaker-carriage assembly away from the
3Q test position toward the engaged position, the head of bolt 269
carried by crank shaft 50 swings away from cam follower plate
260, and spring 256 returns lever 258 and plunger 264 to
- 28 -
i~q2163 41DA-3025
their positions shown in FIGURE 28. Tripping element 266
is thus released and the circuit breaker is automatically
tripped and cannot be reset and closed.
The above described construction and operation of
trip interlock 250 are similar to that disclosed in the above-
noted Canadian application. However, instead of mounting a
second transverse bolt in the crank shaft to actuate the trip
interlock upon arrival of the circuit breaker-carriage assembly
at its engaged position, the instant trip interlock utilizes
lQ a second lever 270 which is operated by slide 230 moving in
response to operation of the joint clamping mechanism 27.
Thus, as seen in FIGURES 26 and 27, lever 270 is pivotally
mounted by a pin 272 affixed to rear carriage stringer 36
through a longitudinally elongated slot 273 in slide 230.
A spring 274 normally biases lever 270 in the counterclockwise
direction as seen in FIGU~ES 26 and 27. A wire link 276
interconnects the free end of lever 270 and slide 230 to
translate longitudinal movement of the slide into pivotal
movement of the lever.
The free end of lever 270 carries an actuating
tab 278 poised to engaged and depress plunger 254 when lever
270 is pivoted in the clockwise direction by link 276 in
response to the slide 230 being shifted to the left as seen
in FIGURE 26 by the clamping shaft mounted bolt head 238 upon
completion of the joint clamping operation. Depression of
plunger 254 pivots lever 258 inwardly to achieve depression of
plunger 264, which, in turn, depresses tripping element 266
to enable operation of the circuit breaker to its ON condition.
As the joint clamping mechanism 27 is operated preparatory to
relaxing the joint clamping pressure, bolt head 238 releases
slide 230, which is returned to the right by its spring 236.
Link 276 thus releases the free end of lever 270, and spring
- 29 -
: `-` 41DA-3025
iO~2163
274 pivots this lever around in the counterclockwise direction,
releasing plunger 254. Its return spring 256 then acting
through lever 258, retracts plunger 264, releasing the tripping
element 266. The circuit breaker is thus automatically
tripped, as well as being disabled from being reset and turned
on until the joint clamp pressure is fully relaxed and the
circuit breaker-carriage assembly backed out to the test
position.
It will thus be seen that the objects set forth.
above, among those made apparent in the preceding description,
are efficiently attained and, since certain changes may be
made in the above construction without department 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 .
- 30 -
