Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02373527 2002-02-19
1
TITLE OF THE INVENTION:
A Circuit Breaker Panel For Hazardous Environments
FIELD OF THE INVENTION
The present invention relates to a circuit breaker panel
for hazardous environments and, more particularly, Class 1,
Division 2 environments.
BACKGROUND OF THE INVENTION
In North America, hazardous environments fall into
different categories. Class 1 Division 1 covers hazardous
environments in which a hazard, such as an explosive gas, is
continuously or frequently present. Class 1 Division 2 covers
hazardous environments in which the hazard potentially can be,
but is only rarely, present. An arbitrary threshold level has
been established of less than 10 hours a year, which serves as
the dividing line between Division 1 and Division 2.
In Division 1 environments, circuit breaker panels are
used which have explosion proof housings made from cast
aluminum with specific tolerances engineered to contain any
explosion. A flange is provided around an access opening to
the housing. A closure door is secured by dozens of bolts to
the flange, in order to prevent the closure door from being
blown off the housing by the explosion. The width of the
flange is selected so that any hot gases escaping past the
flange have cooled sufficiently to avoid igniting gases in the
outside environment by the time they exit the housing. The
weight of these explosion proof housings vary with their size,
but in all cases they weigh hundreds of pounds and a support
structure must be provided that can support such weight. In
view of this approach North American Division 1 circuit breaker
panels are expensive and cumbersome to access.
Europe has adopted similar categories to Division 1 and
Division 2, which are termed "Zone 1" and "Zone 2" . Their Zone
1 standards are more stringent. Each electrical component must
CA 02373527 2002-02-19
2
have its own self contained explosion proof casing. These
explosion proof electrical components are placed into carbon
impregnated enclosures which can be grounded. They use
multiple housings which are assembled in a modular fashion.
The European Zone 1 circuit breaker panels are even more
expensive than those used in North America. European Zone 2
installations use the same circuit breaker panels as are used
for Zone 1.
In an effort to address the above described problems with
expense and access, there has been a movement to use two panels
in tandem in North American Division 2 environments . One panel
has a housing which is not explosion proof and the other panel
has an explosion proof housing. Only those circuit breakers
and other electrical components which may cause arcing or
sparking during the course of their operation, are placed into
the explosion proof housing. Providing two housings reduces
access problems, as only circuit breakers and other arcing and
sparking electrical components must be isolated within the
explosion proof housing. It does not, of course, reduce the
size and space requirements as two housings are used.
Although using one explosion proof panel and one panel
that is not explosion proof has reduced expense and access
problems, the industry is still looking for a better approach
to Division 2 circuit breaker panels.
SUL~B~1A,RY OF THI: INY~NTION
What is required is an alternative circuit breaker panel
for Division 2 hazardous environments.
According to the present invention there is provided an
circuit breaker panel for hazardous environments and, in
particular, Class 1, Division 2 environments. The circuit
breaker panel includes a housing having an internal cavity and
an access opening through which the internal cavity is
accessed. A closure door covers the access opening of the
CA 02373527 2002-02-19
3
housing. The closure door is held in a closed positioned
solely by one or more latches. This permits rapid access to
be obtained to the internal cavity through the access opening.
Electrical components are positioned within the internal cavity
of the housing, some of the electrical components being circuit
breakers. Each of the circuit breakers and all other arcing
and sparking electrical components are enclosed in its own self
contained explosion proof casing.
The circuit breaker panel, as described above, meets the
safety requirements for Class 1 Division 2, while dramatically
reducing costs and enhancing ease of access. The housing is
not explosion proof and, as such, is light weight. This makes
the cost of manufacture less and also results in savings for
the support structure required to mount the housing. The
closure door can either be hinged and latched or can be made
removable and latched. The use of latches dramatically
enhances ease of access. There is no need to separate
electrical components by placing circuit breakers and all other
arcing and sparking components into an explosion proof housing
and all other electrical components into a housing that is not
explosion proof ; as the circuit breakers and the arcing and
sparking components are, themselves, explosion proof.
BRIEF DESCRIPTION OF TIDE DRAWINGS
These and other features of the invention will become more
apparent from the following description in which reference is
made to the appended drawings, the drawings are for the purpose
of illustration only and are not intended to in any way limit
the scope of the invention to the particular embodiment or
embodiments shown, wherein:
FIGURE 1 is a perspective view of a circuit breaker panel
for hazardous environments constructed in accordance with the
teachings of the present invention.
FIGURE 2 is a front elevation view, in section, of the
circuit breaker panel illustrated in FIGURE 1.
FIGURE 3 is a top plan view of the circuit breaker panel
CA 02373527 2002-02-19
4
illustrated in FIGURE 1.
FIGURE 4 is a side elevation view, in section, of the
circuit breaker panel illustrated in FIGURE 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, a circuit breaker panel for
hazardous environments generally identified by reference
numeral 10, will now be described with reference to FIGURES 1
through 4.
Structure and Relationship of Parts:
Referring to FIGURE l, there is provided a circuit breaker
panel 10 that includes a rectangular housing 12. Housing 12
is preferably made from metal or fibreglass. Referring to
FIGURE 3, housing 12 has an internal cavity 14 and an access
opening 16 through which internal cavity 14 is accessed. A
closure door 18 covers access opening 16 of housing 12.
Referring to FIGURE l, closure door 18 has a first side edge
and a second side edge 22. Closure door 18 is pivotally
20 mounted to housing 12 for pivotal movement between an open
position and a closed position by hinges 24 that are positioned
along first side edge 20.
Referring to FIGURE 4, a latch 26 is positioned along
second side edge 22. Closure door 18 is held in the closed
positioned solely by latch 26, whereby rapid access is obtained
to internal cavity 14 through access opening 16. Referring to
FIGURE 3, electrical components 28 are positioned within
internal cavity 14 of housing 12. Referring to FIGURE 2, some
of electrical components 28 are circuit breakers 30. Each of
the circuit breakers 30 and all other arcing and sparking
electrical components is enclosed in its own self contained
explosion proof casing 32. Referring to FIGURE 3, a power
distribution bus or block 38 is positioned between circuit
breakers 30. Referring to FIGURE 4, housing 12 has mounting
tabs 34 for mounting circuit breaker panel 10 to a surface 36.
CA 02373527 2002-02-19
Operation:
The use and operation of circuit breaker panel for
hazardous environments generally identified by reference
numeral 10, will now be described with reference to FIGURES 1
5 through 4. Referring to FIGURE 1, circuit breaker panel 10 is
provided as described above. When access to electrical
components 28 is required, closure door 18 is unlatched from
housing 12, and pivoted to the open position. Electrical
components 28, including circuit breakers 30 contained within
l0 housing 12 can then be accessed through access opening 16 of
housing 12. When access is not required, closure door 18 is
pivoted to the closed position, and latch 26 is activated to
maintain closure door 18 in the closed position. In the event
of an explosion within housing 12, an explosion within one of
circuit breakers 30 will be contained within their own
explosion proof casing 32 within housing 12.
Variations:
Instead of a latch, relatively rapid access may still be
maintained by having four or six screws securing closure door
18 in the closed position.
In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items following the word
are included, but items not specifically mentioned are not
excluded. A reference to an element by the indefinite article
"a" does not exclude the possibility that more than one of the
element is present, unless the context clearly requires that
there be one and only one of the elements.
It will be apparent to one skilled in the art that
modifications may be made to the illustrated embodiment without
departing from the spirit and scope of the invention as
hereinafter defined in the Claims.
