Note: Descriptions are shown in the official language in which they were submitted.
CA 02561695 2006-09-29
ARC RESISTANT SWITCHGEAR DOOR AND FRAME ASSEMBLY,
THROUGH THE DOOR RACKING SYSTEM, AND AIR COOLING AND
VENTILATION SYSTEM
FIELD OF THE INVENTION
This invention relates to an arc-resistant switchgear door and frame assembly
and
a "through-the-door" racking system, and an air cooling and ventilation system
for an
arc-resistant switchgear cubicle.
BACKGROUND OF THE INVENTION
Recent safety standards mandate additional personal safety measures be taken
to
protect workers and prevent injury that may be caused by electrical faults in
medium
voltage electrical cabinets. An internal electrical fault in a switchgear
cabinet generates a
large quantity of hot gas and vaporized material, some of which is toxic and
harmful to
workers that may be in or around the cabinet. The electrical fault acts much
like an
explosion and the heat intensity at the centre of the arc can be over 10,000
degrees
Fahrenheit. Such explosions in standard electrical equipment cause a lot of
damage to
the cabinet, including flying parts or superheated particles, and the emission
of hot gases
is harmful to workers.
Known art door securing mechanisms use first and second tabs which are
longitudinally positioned at the sides of the frame and door, respectively.
The first and
second tabs can be vertically translated into an overlapping arrangement when
the door is
swung on its hinges into a secure position. While the overlapping tabs provide
some
resistance to the door being blown off the frame as a result of the force
caused by
explosive gases produced by an arcing fault, the tabs do not "lock" with each
other. The
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tabs are merely aligned in an overlapping arrangement and are susceptible to
bending in
the same direction when a sufficient force is applied to the door.
Another door securing mechanism uses a pin and hole arrangement. A pin is
positioned at the edge of a door and can be fitted into a hole in a plate
provided in a door
casing to lock the door when closed. However, such a securing mechanism is
disadvantageous as the pin is subjected to shearing forces when a
corresponding force is
applied to the face of the door in the event of an electrical fault.
Therefore, there is a need to provide means to contain the electrical fault
safely
and to redirect its force such that it will not harm an operator and also to
minimize the
resulting damage.
There is also a need to enable a user to operate breakers through a door to an
electrical cabinet without having to open the door or expose the user to a
harmful
electrical fault explosion.
A majority of existing switch gear cubicles require that the main breaker
which
connects and disconnects to the main high voltage bus be installed with the
cubicle door
open thereby exposing an operator to a higher risk of injury due to an
inadvertent arcing
event. Thus, a "through-the-door" racking system enables the connection and
disconnection procedure to be completed with the cubicle door closed thereby
enhancing
protection of the operator. The "through-the-door" racking system also
provides a tilting
feature that enables connection and disconnection of a rack end of a racking
shaft to a
breaker. When the racking shaft is connected to a breaker, the breaker can be
pushed or
pulled in or out of position.
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Such a "through-the-door" racking system can either be incorporated in a door
to
a switch gear cabinet, such as the door enhanced securing mechanism described
above,
or can be a retrofit racking system installed in an existing door enabling
breakers to be
modified to allow for the connection or disconnection procedure to be
completed with
the cubicle door closed.
Furthermore, for safety purposes, arc-resistant switchgear cubicles require
that,
under a fault condition, hot gases are prevented from being emitted from the
cubicle.
The most reliable method to ensure that this condition is met is to not have
any air vents
in the various access doors and panels to the cubicle.
As the electrical equipment in the cubicle generates heat, the need for
cooling an
arc-resistant switchgear cubicle has always resulted in a conflict with the
structural
design process. In the past, manufacturers have resolved this problem by
designing
collapsible air vents or incorporating elaborate shrouds which permit cooling
of a
cubicle; however prohibit venting of hot and harmful gases. However, the
applicant has
appreciated that the prior art constructions introduce a weak point in the art-
resistant
capabilities of the cubicle. As a result, the prior art constructions result
in more elaborate
contraptions which require mechanical moving parts.
SUMMARY OF THE INVENTION
The present invention provides an arc resistant door which shuts into a door
casing at an access opening to an electrical cabinet. The door comprises a
reinforced
structure including an internal frame and a skin. The frame and skin design
provides a
reinforced door which is capable of withstanding a great amount of force
without using
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an excessive amount of material. To protect the hinge side of the door from
the force of
an explosion and flying material, an overlapping angle can be provided on the
door
casing and wrapped around part of a hinge side of the casing. In addition,
unique hook
style "gang" operated latches hook themselves into reinforcing pins at a latch
side of the
casing to add additional strength to the frame and resist bending of the door
and/or frame
in the event of an explosion. By providing the unique frame on skin design,
forces are
transferred to the frame rather than the steel skin which is not as strong.
Because of the
reinforcing features mentioned herein, the expulsion of hot gasses is limited
by
maintaining a sealed front compartment.
The present invention also provides a racking mechanism to accommodate
operation of various breakers without opening the equipment access door. The
racking
mechanism can be retrofitted to an existing access door. In one aspect, the
racking
mechanism uses a door mounted screw that interfaces with the breaker inside
the cubicle.
Such a mechanism allows a circuit breaker to be changeably withdrawn or
connected to a
live bus while maintaining the Arc-resistant barrier intact. The user is
safely protected
by the door from any flying parts, hot gases and harmful vapours caused by an
explosion.
The present invention also provides an arc-resistant switchgear cubicle which
provides for cooling of the cubicle while maintaining the structural integrity
of the
cubicle to better protect users against harm during a fault condition in the
switchgear
cubicle. The applicant has appreciated that the introduction of insulated
vents, provided
at least at one side of the cubicle, advantageously provides incoming air
which is cooler
than the exhaust air due to the insulation of the vent. Also, by introducing
the cooler air
into a lower portion of the cubicle, the cool air will mix with the hot air in
the cubicle
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and the resulting warmer exhaust air can be vented through a top of the
cubicle. Thus,
the cooling air flow is created by a convection flow of air through the
cubicle.
Furthermore, each section of the cubicle can be isolated from another section
and
multiple air cool vents can be introduced for each section. Each of the intake
vents can
be separated from another intake vent to maintain a maximum flow rate within
each
section of the cubicle.
The features described herein can be altered as to size and material gauge to
accommodate various standard electrical parameters such as voltage class and
interrupting rating and current carrying capacity of various breakers and
individual
specifications.
The features described herein can be incorporated as new equipment in a new
application, and can also be installed with existing equipment in a retrofit
application, for
example to meet new safety standards.
It is an object of this invention to provide means to contain an electrical
fault
safely and to redirect its force to protect an operator and minimize any
resulting damage.
It is a further object of this invention to provide ventilation for an arc-
resistant
switchgear cubicle, which does not require fans or other means to create air
flow, while
maintaining the structural integrity of the cubicle to resist failure during
an arc fault.
In one aspect, the present invention resides in a door for sealing an opening
to an
electrical panel, said door comprising a supporting frame and a door skin
connected to a
side of the supporting frame, the supporting frame comprising: an elongated
hinge side
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member having a top end and a bottom end, an elongated latch side member
having a top
end and a bottom end, a top member having a proximal end and a distal end, the
top
member proximal end being connected to the top end of the hinge side member
and the
top member distal end being connected to the upper end of the latch side
member, and a
bottom member having a proximal end and a distal end, the bottom member
proximal
end being connected to the bottom end of the hinge side member and the bottom
member
distal end being connected to the bottom end of the latch side member, the
door further
comprising a latching mechanism to lock the door to a door casing, the
latching
mechanism comprising at least one latch hook having a latch body and a latch
hook end,
the latch body being connected to a latching mechanism base at a first side of
the latch
hook and connected to a linkage member at a second side of the latch hook at a
position
on the latch body spaced laterally from the attachment to the latching
mechanism base so
that movement of the linkage member in an upward or downward direction causing
the
latch hook to pivot through a plane parallel to a to engage or disengage a pin
provided in
a channel of a door frame, the latching mechanism base being mounted to the
door at or
near the hinge side member with at least one mounting latch plate and a
fastener, and the
door further comprising a door handle having a handle lever and a post
orthogonally
connected thereto, the door handle being mounted on the door skin with the
elongated
post passing through an aperture in the door skin and an aperture in the
latching
mechanism base, the post mating with a hole in a post plate which is connected
to the
linkage member at a position above or below a position of an attachment of the
latch
hook to the linkage member, such that turning the door handle lever moves the
linkage
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member to selectively engage or disengage the at least one latch hook on a
respective at
least one pin of a door case.
In another aspect, the present invention resides in a racking mechanism
mountable to a door comprising: a threaded shaft having a racking end and a
user end,
and a mounting plate, the mounting plate having an aperture with a threaded
hub
positioned there through, the threaded shaft being movable through the hub to
extend the
racking end closer and further from the mounting plate.
In another aspect, the present invention resides in a racking mechanism
mountable to a door comprising: a threaded shaft having a racking end and a
user end,
the racking end having a socket adapter connected thereto and the user end
having a
socket adapted to connect with a wrench; a first mounting plate having at
least one
mounting hole and a second mounting plate having at least one mounting hole,
the first
and second mounting plates being hingedly connected; a hollow cylindrical hub
support
is fixed to the first mounting plate and a hub hole is formed through the
first mounting
plate so that the hub support is accessible at both ends and provides a hollow
cylindrical
channel; and a cylindrical hub having a threaded core is threadably movable on
the
threaded shaft and the hub is securable within the hollow cylindrical channel
of the hub
support.
In a further aspect, the present invention resides in a door for sealing an
opening
to an electrical panel, said door comprising a supporting frame and a door
skin connected
to a side of the supporting frame, the supporting frame comprising: an
elongated hinge
side member having a top end and a bottom end, an elongated latch side member
having
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a top end and a bottom end, a top member having a proximal end and a distal
end, the top
member proximal end being connected to the top end of the hinge side member
and the
top member distal end being connected to the upper end of the latch side
member, and a
bottom member having a proximal end and a distal end, the bottom member
proximal
end being connected to the bottom end of the hinge side member and the bottom
member
distal end being connected to the bottom end of the latch side member, the
door further
comprising a latching mechanism to lock the door to a door casing, the
latching
mechanism comprising at least one latch hook having a latch body and a latch
hook end,
the latch body being connected to a latching mechanism base at a first side of
the latch
hook and connected to a linkage member at a second side of the latch hook at a
position
on the latch body spaced laterally from an attachment to the latching
mechanism base so
that movement of the linkage member in an upward or downward direction causing
the
latch hook to pivot through a plane parallel to a to engage or disengage a pin
provided in
a channel of a door frame, the latching mechanism base being mounted to the
door at or
near the hinge side member with at least one mounting latch plate and a
fastener, and the
door further comprising a door handle having a handle lever and a post
orthogonally
connected thereto, the door handle being mounted on the door skin with the
elongated
post passing through an aperture in the door skin and an aperture in the
latching
mechanism base, the post mating with a hole in a post plate which is connected
to the
linkage member at a position above or below a position of an attachment of the
latch
hook to the linkage member, such that turning the door handle lever moves the
linkage
member to selectively engage or disengage the at least one latch hook on a
respective at
least one pin of the door case, the door further having a threaded aperture
through which
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a racking mechanism is positioned, the racking mechanism comprising a threaded
shaft
having a racking end and a user end, the racking end having a socket adapter
connected
thereto.
In a further aspect, the present invention resides in an air cooling system
for an
arc-resistant switchgear cubicle, wherein: at least one insulated ventilation
shaft is
positioned longitudinally at a side of the cubicle, the at least one insulated
ventilation
shaft having an inlet at an upper end and an outlet at a lower end; at least
one blow vent
is provided at a top of the cubicle; and whereby cold air is drawn into the
cubicle through
the inlet of the at least one insulated ventilation shaft and enters the
cubicle through the
outlet, and warm air is exhausted from the cubicle through the at least one
blow vent, the
flow of air being generated by convection current.
In yet a further aspect, the present invention resides in an air cooling
system for
an arc-resistant switchgear cubicle having three sections formed by vertically
disposed
walls within the cubicle, wherein: each section has two insulated ventilation
shafts, each
shaft being positioned longitudinally at each side wall of the section, each
insulated
ventilation shaft having an inlet at an upper end and an outlet at a lower
end; one blow
vent is provided at a top surface of the section; and whereby cold air is
drawn into each
cubicle section through the inlets of the insulated ventilation shafts and
enters the cubicle
section through the outlets, and warm air is exhausted from each cubicle
section through
the blow vent, the flow of air being generated by convection current.
Further and other features of the invention will be apparent to those skilled
in the
art from the following detailed description of the embodiments thereof.
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BRIEF DESCRIPTION OF THE DRAWINGS
Reference may now be had to the following detailed description taken together
with the accompanying drawings in which:
Figure 1 shows a door and frame design of the present invention;
Figure 2 shows the door shown in Figure 1;
Figure 3 shows the frame shown in Figure 1;
Figure 4 shows the latching mechanism of the present invention;
Figure 5 shows an exploded view of the latching mechanism shown in Figure 4;
Figure 6 shows a latch hook of the latching mechanism of the present
invention;
Figure 7 shows a racking mechanism of the present invention;
Figure 8 shows a racking mechanism mounting plate with a hinge in perspective
view;
Figure 9 shows the racking mechanism mounting plate of Figure 8 from a top
view;
Figure 10 shows a racking mechanism including a threaded shaft and mounting
plate in exploded view;
Figure 11 shows the racking mechanism of Figure 10 with the threaded shaft
fitted with the mounting plate shown in perspective from a back side of the
mounting
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plate; and
Figure 12 shows a racking mechanism of Figure 11 in perspective view from a
front side of the mounting plate.
Figure 13 shows an arc-resistant cubicle in perspective view;
Figure 14 shows the arc-resistant cubicle of Figure 13 from a front view; and
Figure 15 shows the arc-resistant cubicle of Figure 13 from a top view section
through line A-A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in the preferred construction in Figure 1, a door 2 is connected to a
door case 4 by hinges 6. The door case 4 is suitable for positioning at an
entrance to an
electrical panel or circuit breaker cabinet, not shown. The door 2 is movable
between
open and closed positions, the closed position being shown in Figure 1. When
in the
closed position, the door 2 seals the entrance to the electrical panel from
the area
surrounding the entrance from any gas or vapour exiting therefrom.
The door 2 has an internal door frame comprised of an elongated tubular metal
hinge side member 8 having a top end 10 and a bottom end 12 for vertical
positioning at
a hinge side of the door 2. A similar elongated tubular metal latch side
member 14 has a
top end 16 and a bottom end 18 for vertical positioning at a latch side of the
door 2.
A tubular elongated metal top member 20 having a proximal end 22 and a distal
end 24. The top member 20 is positioned horizontally along a top of the door 2
with the
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top member proximal end 22 welded to the top end 10 of the hinge side member
8, and
the top member distal end 24 welded to the top end 16 of the latch side member
14. A
tubular elongated metal bottom member 26 has a proximal end 28 and a distal
end 30
and is positioned horizontally along the bottom of the door 2. The bottom
member
proximal end 28 is welded to the bottom end 12 of the hinge side member 8, and
the
bottom member distal end 30 is welded to the bottom end 18 of the latch side
member
14.
While the connections of the ends metal hinge side member 8, latch side member
14, top member 20 and bottom member 26 are preferably formed with mitre cuts
and are
connected by weld joints, it is appreciated that other suitable means of
connecting these
members would also be suitable, for example corner brackets. Also, the metal
hinge side
member 8, latch side member 14, top member 20 and bottom member 26 are
preferably
made of steel.
A door skin 32 forming a covering is connected at an outer side of the hinge
side
member 8, latch side member 14, top member 20 and bottom member 26 to provide
a
covering for the door 2. The door skin 32 is shown more clearly on the door 2
in Figure
2. Preferably, the door skin 32 is a metal sheet or plate and is made of
steel.
The dimensions of the door 2 depend on the size of the arc-resistant
switchgear
cabinet which varies depending on the voltage and current rating. In a
conventional
embodiment, the door 2 has a width between 29 to 48 inches and a height
between 40
and 90 inches.
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As shown in Figure 1, the door 2 is hingedly attached to the door case 4 so as
to
move between open and closed positions. The door case 4 is shown in Figure 3
and is
comprised of elongated metal channel members which are welded together. An
elongated casing top channel 34 is provided at a top of the door case 4. The
casing top
channel 34 has a proximal end 34 and a distal end 36. An elongated casing
hinge side
channel member 40 extends vertically at a hinge side of the door case 4 and
has an upper
end 42 and a lower end 44. Similarly, an elongated casing latch side channel
member 46
extends vertically at a latch side of the door case 4 and has an upper end 48
and a lower
end 50.
The door case 4 is formed by connecting the proximal end 36 of the casing top
channel member 34 to the upper end of the casing hinge side channel member 40.
The
distal end 38 of the casing top channel member 34 is connected to the upper
end 48 of
the casing latch side channel member 46. Preferably, the proximal end 36 and
distal end
38 and upper ends 42 and 48 are formed with mitre cuts and weld joints
although it is
appreciated that other suitable fastening means could be used.
The door 2 is connected to the door case 4 by three hinges 6A, 6B and 6C which
are welded to the casing hinge side channel member at intervals spaced along a
vertical
length thereo~ The hinges 6A, 6B and 6C are also welded to the door hinge side
member 8.
As shown in Figure 3, three pins 52A, 52B and 53C are positioned horizontally
in
the casing latch side channel member 46 and spaced at a vertical distance from
one
another. A latching mechanism 54 is provided on the door 2 and has three latch
hooks
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56A, 56B and 56C which engage the three pins 52A, 52B and 52C, respectively
when
the door 2 is locked.
The latching mechanism is shown in Figures 4 and 5. The latch hooks 56A, 56B
and 56C are mounted on a latching mechanism base 58 which is a rectangular
plate
which has, at one edge, a strip of the base 58 which is bent orthogonal to a
plane of the
base 58. The strip has slots 60A, 60B and 60C through which the respective
latch hooks
56A, 56B and 56C are positioned.
One latch hook 56 is shown in Figure 6. The latch hook 56 is formed from a
plate of metal and has a latch body 62 at one end and a latch hook end 64 at
an opposite
end. The latch body 62 has a latch hook mounting hole 66, for mounting the
latch hook
56 to the base 58. The latch body 62 also has a link bar mounting hole 68
beside the
latch hook mounting hole 66 at a position closer to the latch hook end 64.
As shown in the exploded view in Figure 5, Latch hook 56A is pivotably
attached
to the latching mechanism base 58 by a latch hook bolt 70 which is passed
through a
latch hook hole 72 punched or drilled through the base 58. The latch hook 56A
is
positioned with the latch hook end 64 passed through slot 60A and is pivotably
attached
to the base 58 by passing the latch hook bolt 72 through the latch hook
mounting hole 68
on the latch hook body 62 and screwing a threaded latch hook nut 74 thereon.
By the
pivotal mounting of the latch hook 56A on the latching mechanism base 58 and
with the
latch hook end 64A positioned through slot 60A, the latch hook 56A can pivot
through
the slot in a direction of arrow 76 shown in Figure 4. The direction of travel
of the latch
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hook 56A is through a plane orthogonal to a longitudinal axis A-A of pin 52A.
Thus, the
latch hook 56A can selectively engage and disengage pin 52A.
Each of latch hooks 56B and 56C are pivotally attached to the base 58 as has
been described with reference to latch hook 56A.
As shown on Figure 5, the latch hooks 56A, 56B and 56C are also connected to a
link bar 78. The link bar 78 is an elongated metal bar having three link bar
holes 80A,
80B and 80C drilled there through. The link bar holes 80A, 80B and 80C are
drilled at a
spacing selected in-line with the link bar mounting holes of the respective
latch hooks
56A, 56B and 56C.
The attachment of the link bar 78 should be done before the attachment of the
latch hooks 56A, 56B and 56C are attached to the base 58. The attachment of
the link
bar 78 will be described with respect to latch hook 56A. A link bar bolt 82 is
passed
through the link bar mounting hole 68 from a side of the latch hook 56A that
will be
facing the base 58 when the latching mechanism 54 is assembled. The link bar
bolt 82 is
then passed through the link bar hole 80A of the latch body 62 and a threaded
link bar
nut 84 is fastened thereon.
As shown in Figure 4, moving the link bar 78 in a direction of a longitudinal
axis
B-B, the latch hooks 56A, 56B and 56C are moved through the respective slots
60A, 60B
and 60C selectively engaging the respective pins 52A, 52B and 52C.
A door handle 86 is provided to move the link bar 78. As shown in Figure 5,
the
door handle has a lever 88, which can be gripped by a user, and a handle post
90 which is
CA 02561695 2006-09-29
rotated corresponding to a rotation of the lever 88. The handle post 90 has a
square
cross-sectional shape.
As shown in Figure 2, the door handle 86 is mounted to the door skin 32 using
three mounting bolts 92 fastened through holes in a handle mounting plate 96.
Three flat
washers 94 are placed between the head of the respective mounting bolts 92 and
the
handle mounting plate 96.
When the door handle 86 is mounted on the door skin 32, the handle post 90
projects through a handle post aperture 98 on the latching mechanism base 58.
The
handle post 90 projects through a post hole 100 on a handle post plate 102 at
a side of the
latching mechanism base 58 opposite to the door skin 32. The post hole 100 has
a square
shape corresponding to the square cross-sectional shape of the handle post 90.
Thus, the
handle post 90 mates with and engages the post hole 100, such that rotation of
the post
90 causes the handle post plate 102 to rotate.
The post plate 102 is also connected to the link bar 78 using a link bar bolt
82P
fitted through a link bar hole and a link bar nut 84P, in a similar manner as
the latch
hooks 56A, 56B and 56C are fixed, as shown in Figure 5.
Before mounting the door handle 86, the latching mechanism base 58 is attached
to the door 2 using three door mounting latch plates 104A, 104B and 104C. The
door
mounting latch plates 104A, 104B and 104C are positioned on a side of the door
skin 32
at a side opposite to a side which the latching mechanism base 58 is to be
attached.
Three sets of mounting latch plate bolts 106A, 106B and 106C, each having lock
washers 108A, 108B and 108C thereon, are positioned through three respective
pairs of
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mounting apertures 112A, 112B and 112C on the latching mechanism base 58. The
latching mechanism base 58 is positioned at the door skin 32 and holes, not
shown, are
drilled through the door skin 32, at locations corresponding to the mounting
apertures
112A, 112B and 112C. The three sets of mounting latch plate bolts 106A, 106B
and
106C are positioned through the holes in the door skin 32 and through
corresponding
pairs of mounting latch plate holes 114A, 114B and 114C in the three door
mounting
latch plates 104A, 104B and 104C, which are positioned at the opposite side of
the door
skin 32. Three sets of threaded mounting latch plate nuts 110A, 110B and 110C
are
screwed onto the respective mounting latch plate bolts 106A, 106B and 106C, to
secure
the latching mechanism to the inside of the latch edge of the door 2.
Thus, when a user turns the door handle lever 88, the door handle post 90
rotates
to, in turn, rotate the handle post plate 102 to move the link bar 78 up or
down through
axis B-B. This movement of the link bar 78 causes each of the latch hooks 56A,
56B
and 56C to rotate to selectively engage or disengage the respective pins 52A,
52B and
52C. Thus the door 2 can be locked, where the latch hooks 56A, 56B and 56C
engage or
hook around the respective pins 52A, 52B and 52C, and unlocked, where the
latch hooks
56A, 56B and 56C disengage or are unhooked from the respective pins 52A, 52B
and
52C.
As shown on Figure 2, the door handle lever 88 has a lever locking tab 116
with
an aperture there through. A corresponding mounting plate locking tab 118 is
provided
on the mounting plate, so that, when the door handle lever 88 is
perpendicular, and the
latch hooks 56A, 56B and 56C are engaged with corresponding Pins 52A, 52B and
52C,
the apertures of the respective tabs 116 and 118 are aligned. The alignment of
the
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apertures of the tabs 116 and 118, enables a lock, not shown, can be placed
through the
apertures to secure the door 2 from access unless the lock is removed.
As shown in Figure 1, to enhance the structural integrity of the door 2, cross
brace bars 120A, 120B and 120C are welded horizontally between the door hinge
side
member 8 and the door latch side member 14. The cross brace bars 120A, 120B
and
120C are spaced from each other at longitudinal intervals of the door hinge
side member
8 and the door latch side member 14 to provide additional strength to the
frame of the
door 2.
Also shown in Figure 1, an overlapping angle 122 is wrapped around the casing
hinge side channel member 40. The overlapping angle is preferably steel to
create an
overlap with the casing hinge side channel member 40 to provide additional
structural
strength to the hinge side of the door casing 4.
As shown in Figure 2, the door skin 32 has a generally square aperture 150.
The
aperture 150 can be covered with a Plexiglas sheet 152 so that the inside of a
cabinet can
be visible by a user from the outside, but a seal can be maintained at the
door 2. The
Plexiglas sheet 152 is mounted to the door skin 32 using an upper window clamp
154
and a lower window clamp 156. The upper and lower window clamps 154 and 156
are
formed by bending sheet metal steel plates to have a z-shaped profile. By
fastening the
upper and lower window clamps 154 and 156, respectively, to an inside of the
door skin
32 horizontally at an upper and lower edge of the aperture 150, the Plexiglas
sheet 152
can be slidably inserted between the upper and lower window clamps 154 and
156,
respectively, to cover the aperture 150.
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Shown in Figure 7 is a screw raking mechanism 200. The screw racking
mechanism 200 has a threaded shaft 202 screwed through a hub 204 having
corresponding threads. The threaded end 202 has a racking end 206 with a
socket
adapter 208, preferably one-half inch, fixed thereto. The socket adapter 208
can be fitted
with ratchet sockets of various sizes, not shown, to activate and deactivate
various types
of breakers.
The diameter and length of the threaded shaft 202 varies depending on the size
and weight of the breaker, which can be between 300 and 40001bs. The diameter
of the
threaded shaft can range from 2 inches to 3 inches in a conventional
embodiment. In a
conventional embodiment, the length of the threaded shaft 202 is equal to the
distance
between the switchgear door to the breaker plus 12 inches. In a typical
embodiment, the
distance between the door and breaker is between 7 inches and 20 inches.
The hub 204 is fixed at an aperture through a racking mechanism mounting plate
210. At an opposite side of the mounting plate 210, a hollow cylindrical hub
support 212
is provided such that the threaded shaft 202 is screwed through the hub 204,
and the hub
is fitted in the hub support 212, so that the threaded shaft 202 extends
through both sides
of the plate 210.
The racking mechanism mounting plate 210 can be fixed to the door 2, although
not shown, to provide "thru-the-door" racking so that a user can operate
various breakers
from outside an electrical cabinet. In a more preferred form, the threaded
racking bar
202 can be screwed through a threaded hole in the door 2 as a more simplified
construction,
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CA 02561695 2006-09-29
Figure 8 shows a racking mechanism mounting plate 210 which comprises a first
plate portion 214 and a second plate portion 216 connected by a hinge 218. The
hinge
218 enables manipulation of the first plate portion 214 with respect to the
second plate
portion 216 to adjust an angle of axis A-A extending through a centre axis of
the hub
support 212.
The mounting plate 210 can be fixed to a door of an electrical cabinet using
fastening means, for example screws or bolts (not shown), which are positioned
through
the first and second pairs of mounting holes 220 and 222, on the respective
first and
second mounting plates 214 and 216. To enable the tilting of the first
mounting plate
214 by the hinge 218, the fasteners used to fix the first mounting plate 214
to the door
through mounting holes 220 can be loosened. Preferably, wing nuts are fastened
on bolts
positioned through the first pair of mounting holes 220 so that a user can
selectively
loosen and tighten the first mounting plate 214. By loosening the fasteners
securing the
first mounting plate 214, the first mounting plate 214 and therefore hub 204
and threaded
shaft 202 can be selectively tilted from a substantially horizontal plane
towards a vertical
plane. While the required degree of tilting of the threaded shaft 202 to
selectively
connect and disconnect a breaker varies depending on the size of breaker and
distance
from the door to the breaker. In a conventional embodiment, the degree of
tilting is
preferably 15 degrees at a minimum.
Figure 9 shows the mounting plate of Figure 8 in top view. As shown in both of
Figures 8 and 9, the hub support 212 is provided with two hub positioning nuts
224 fixed
to the sides of the hub support 212. As shown in Figure 8, two hub support
holes 226 are
formed at the same location as the hub mounting nuts 224. As shown in Figure
9, a hub
CA 02561695 2006-09-29
hole 213 is formed on the first plate portion 214 so that the hollow
cylindrical hub
support 212 is accessible at both ends thereof.
As can be seen in the exploded view in Figure 10, two hub mounting screws 228
can be threadably secured in the respective hub mounting nuts 224 to be
positioned
within respective hub holes 230 formed on the sides of the hub 204, to thereby
secure the
hub 204 within the hub support 212.
As can be envisaged from Figure 10, to assemble the screw racking mechanism
200, the hub 204 is threaded onto the threaded shaft 202 and the cylindrical
hub 204 is
positioned within the cylindrical channel of the hub support 212. Hub mounting
screws
228 are screwed into hub mounting nuts 224 to engage within hub holes 230 of
the hub
204.
The threaded shaft 202 can then be threadably moved within the hub 204 by a
user, for example using a wrench or a speed wrench (not shown) which is
inserted into a
socket 232 at a user end 234 of the threaded shaft 202.
Figure 11 shows the screw racking mechanism 200 in perspective view from a
back side of the racking mechanism mounting plate 210. As shown in Figure 11,
the
racking end 206 has a custom socket 236 fitted thereto.
Figure 12 shows the screw racking mechanism 200 assembled and in perspective
view.
Figure 13 shows an arc-resistant switchgear cubicle 302 which houses
electrical
equipment (not shown). The arc-resistant switchgear cubicle 302 has a planar
top
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CA 02561695 2006-09-29
surface 304, a planar side surface 306 and a planar front surface 308. A
second planar
side surface, a planar bottom surface and a planar back surface are not shown,
but exist
to provide an enclosed cubicle.
As shown, the front surface 308 has three access doors 310A, 310B and 310C
which can be opened to access the interior of the arc-resistant switchgear
cubicle. The
doors 310A, 310B and 310C can be designed as the aforementioned door 2 and all
of its
features and locking assembly, in a preferred embodiment.
Also shown are three insulated ventilation shafts 312A, 312B and 312C. The
insulated ventilation shafts 312A, 312B and 312C are preferably insulated with
a rigid
insulation such as dense styrofoam insulation panels adhered to an outside
surface of the
ventilation shafts using adhesive or other suitable mechanical fasteners. The
three
insulated ventilation shafts 312A, 312B and 312C have respective inlets 314A,
314B and
314C, and respective outlets 316A, 316B and 316C. The inlets 314A, 314B and
314C
are provided at a top of the insulated ventilation shafts 312A, 312B and 312C,
and are
shown as being positioned at the top surface 304 of the arc-resistant
switchgear cubicle
302. The outlets 316A, 316B and 316C are provided at a lower end of the
insulated
ventilation shafts 312A, 312B and 312C, as shown.
To cool the arc-resistant switchgear cubicle 302, cooling air is drawn in
through
the inlets 314A, 314B and 314C, flows through the insulated ventilation shafts
312A,
312B and 312C, as indicated by arrows 318A, 318B and 318C, and then enters the
arc-
resistant switchgear cubicle 2 through the outlets 316A, 316B and 316C.
Because the
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ventilation shafts 312A, 312B and 312C are insulated, the cooling air remains
cool while
being drawn through the insulated ventilation shafts 312A, 312B and 312C.
After entering the arc-resistant switchgear cubicle 302, the cooling air mixes
with
the hot air inside the arc-resistant switchgear cubicle 302 to provide cool
air to the arc-
resistant switchgear cubicle 302. Hot air is generated by the electrical parts
(not shown).
The mixing of cooling air generates warm exhaust air flows upwards through the
arc-
resistant switchgear cubicle 302, to exit the arc-resistant switchgear cubicle
302 via
respective blow vents 320A, 320B and 320C positioned at the top surface 304 of
the arc-
resistant switchgear cubicle 302.
The cooling air flow is established by convection currents and therefore there
is
no requirement for a fan or other means to direct the air flow. Because the
cooling air
enters into the insulated ventilation shafts 312A, 312B and 312C to be
introduced into
the interior of the arc-resistant switchgear cubicle 302, at a bottom thereof,
the mixing of
the cooling air with warm air inside the arc-resistant switchgear cubicle 302,
generates
warmer air which, by its nature, flows upwards to exit the arc-resistant
switchgear
cubicle 302 through blow vents 320A, 320B and 320C.
Figure 14 shows the arc-resistant cubicle 302 of Figure 13 however an
additional
insulated ventilation shaft 312'A is shown as longitudinally extending along a
side of the
cubicle 302 opposite the surface 306. Thus, two insulated ventilation shafts
312A and
312'A are provided with inlets 314A and 314'A and outlets 316A and 316'A,
respectively. Each of the insulated ventilation shafts 312A and 312'A has
insulation
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322A and 322'A provided longitudinally along each of the insulated ventilation
shafts
312A and 312'A, as shown.
Figure 14 illustrates the flow of cooling air into and through the cubicle
302. As
shown by the arrows, the cooling air enters the ventilation shafts 312A and
312'A
through inlets 314A and 314'A, respectively. The cooling air travels
downwardly
through the insulated ventilation shafts 312A and 312'A and enters into the
cubicle 302
through the outlets 316A and 316'A. The cooling air then mixes with the warm
air in the
cubicle 302 in the mixing zone generally indicated as 324. The mixed cooling
air with
the warm air inside the cubicle 302 generates warmer exhaust air which travels
upwardly
through the interior of the cubicle 302 and exits from the top of the cubicle
302 through
the blow vent 320A.
The flow of air is established by the convection current created by the rising
warmer air which in turn draws the cooler cooling air into the cubicle 302.
Figure 15 is a sectional view of the cubicle 302 through section A-A shown in
Figure 14. As shown in Figure 15, three compartments are provided within the
cubicle
302, being a first compartment 326, a second compartment 328 and a third
compartment
330. Each of the compartments 326, 328 and 330 is separated from the adjacent
compartment so as to form segregated independent sections. As shown, the
insulated
ventilation ducts 312A and 312'A are provided to cool the first compartment
section 26,
insulated ventilation ducts 312B and 312'B are provided to cool the second
compartn-tent
section 328 and insulated ventilation ducts 312C and 312'C are provided to
cool the third
compartment section 330.
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Although this disclosure has described and illustrated certain preferred
embodiments of the invention, it is also to be understood that the invention
is not
restricted to these particular embodiments rather, the invention includes all
embodiments
which are functional, or mechanical equivalents of the specific embodiments
and features
that have been described and illustrated herein.
It will be understood that, although various features of the invention have
been
described with respect to one or another of the embodiments of the invention,
the various
features and embodiments of the invention may be combined or used in
conjunction with
other features and embodiments of the invention as described and illustrated
herein.
