Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02299919 2000-06-OS
DUCT DETECTOR
This application claims the benefit of United States Provisional Application
Serial No. 60/123,081, filed March 4, 1999 and entitled Aspirated Duct
Detector,
and United States Provisional Application Serial No. 60/156,834, filed
September
30, 1999 and entitled Duct Detector With Shroud.
Field of the Invention:
The invention pertains to smoke detectors. More particularly, the invention
l0 pertains to duct-type smoke detectors.
Background of the Invention:
Duct mounted smoke detectors are known. Such detectors usually mount on
or attach to the outside of an air duct, a conduit for flow of air which is
being
distributed in a region such as in a building. Duct detectors are often
included in a
building or region monitoring system. They provide information as to airborne
contents of the duct.
Known duct detectors incorporate a sampling tube which extends laterally
into the duct from the detector which is mounted outside of the duct. The
sampling
tube contains holes that face into the air stream.
2o The air stream flows into the tube, through an internal volume which
includes a smoke sensor and out of the housing back into the duct via an
output
flow tube. The sensor may be of the ionization or the photoelectric type.
Known
detectors are often rated in an air speed range from 500 feet per minute to
4000 feet
per minute.
Summary of the Invention:
A duct detector has a housing which defines an interior region. At least one
sampling tube extends substantially perpendicular to the housing. When mounted
on a duct, the housing is positioned adjacent to the exterior of the duct and
the
sampling tube extends into the duct and is exposed to the air flow therein.
3o A fire sensor, which defines an internal sensing region, is positioned in
the
interior region of the housing. In one aspect of the invention, a closed
channel
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extends between a proximal end of the sampling tube and the sensor. The closed
channel forces substantially all of the incoming ambient atmosphere to pass
through
the sensing chamber of the sensor.
In another aspect of the invention, an aspirator, for example a centrifugal
blower, can be carried outside of or incorporated into the internal region of
the
housing. The aspirator draws in airborne particulate matter present in the
duct, via
the sampling tube, thereby providing increased quantities of fire indicating
particulate matter for the sensor.
In yet another aspect of the invention, the aspirator can be incorporated into
1 o the closed channel thereby forcing the airborne particulate matter being
drawn into
the channel thereby directly into the smoke sensor. In this instance, as is
the case
with the unaspirated channel, the incoming airborne gases and/or particulate
matter
is/are unable to spread into the remainder of the internal region of the
housing until
it has passed through the sensing region.
In yet another aspect of the invention, the sensor can be implemented as at
least one of a photoelectric smoke sensor, an ionization-type smoke sensor or
a gas
sensor. The housing can be closed with a removable cover.
A portion of the channel can be molded into the housing. The remainder of
the channel can be molded into the cover. Attaching the cover to the housing
forms
the closed channel between the sampling tube where the smoke flows into the
detector and the sensor. Alternately, the entire channel can be molded into
one of
the housing or the cover.
In yet another aspect, an aspirated duct detector incorporates an inflow port
and an outflow port. An aspirator can be located within or adjacent to the
housing
of the detector.
Numerous other advantages and features of the present invention will
become readily apparent from the following detailed description of the
invention
and the embodiments thereof, from the claims and from the accompanying
drawings.
3o Brief Description of the Drawings:
Fig. 1 is a perspective view of a detector in accordance with the present
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invention with the cover removed;
Fig. 2 is a sectional view taken along plane 2-2 of Fig. 1;
Fig. 3 is a fragmentary perspective view of an alternate form of detector in
accordance with the present invention with the cover removed;
Fig. 4 is a perspective fragmentary view of yet another alternate
embodiment of a detector in accordance with the present invention with the
cover
removed;
Fig. 5 is a perspective fragmentary view of yet another embodiment of the
detector in accordance with the present invention with the cover removed;
1o Fig. 6 is a perspective fragmentary view of yet another embodiment of the
detector in accordance with the present invention with the cover removed;
Fig. 7 is a perspective fragmentary view of yet another embodiment of the
detector in accordance with the present invention with the cover removed;
Fig. 8 is a perspective fragmentary view of yet another embodiment of the
15 detector in accordance with the present invention with the cover removed;
Fig. 9 illustrates a graph illustrating sensitivity versus duct air velocity
of
detectors in accordance with the present invention; and,
Fig. 10 illustrates yet another embodiment of a detector in accordance with
the invention.
20 Detailed Description of the Preferred Embodiments:
While this invention is susceptible of embodiment in many different forms,
there are shown in the drawing and will be described herein in detail specific
embodiments thereof with the understanding that the present disclosure is to
be
considered as an exemplification of the principles of the invention and is not
25 intended to limit the invention to the specific embodiments illustrated.
Figs. 1 and 2 illustrate different views of a detector 10 in accordance with
the present invention. The detector 10 includes an elongated housing 12 which
in a
disclosed embodiment defines an internal region 14 and a displaced internal
region
16. In the disclosed embodiments of Figs. 1 and 2, region 14 is associated
with
3o fluid flow. Region 16 is associated with control circuitry and connectivity
to the
detector 10. It will be understood that the housing 12 could be formed as two
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separate housings, one including the region 14 and a second including the
region 16
without departing from the spirit and scope of the present invention.
As disclosed, the detector 10 is a duct-type detector intended to be mounted
on an airflow conduit or duct D. Air flows through the duct D in a direction D
1 on
s either a continuous or an intermittent basis. The duct D might be
incorporated into
a building or other region to which air is being supplied, such as in a
heating/air
conditioning system.
Extending laterally from the housing 12 are first and second tubes 20, 22.
Tube 20 has associated therewith a plurality of input ports 20a, 20b ... 20n
which
to receive an inflow of air in the duct D to be monitored by the detector 10.
As is clear from Figs. 1 and 2, the tubes 20, 22 extend through holes in the
duct D into the interior thereof so as to be exposed to the airflow therein.
Inflowing
air indicated generally at 30a, b flows through inflow or sampling tube 20,
through
filter 22 and into an aspirator 24 which has a central input port indicated
generally
15 at 24a.
The aspirator 24 could be implemented as a centrifugal blower or other type
of electrically driven air mover without departing from the spirit and scope
of the
present invention. The blower 24 has amoutput or outflow port 24b from which
outflowing ambient atmosphere 32b is injected into a fire sensor 28.
2o Sensor 28 incorporates an internal sensing region 28a and can be
implemented as a photoelectric-type or an ionization-type smoke sensor. It
could
also be a gas sensor. The details of such sensors would be understood by those
of
skill in the art and are not limitations of the present invention. The sensor
28 in the
detector 10 is surrounded by cylindrical screen or filter 28b.
25 The inflowing ambient air 32b from aspirator 24 passes through sensing
region 28a which in turn results in an electrical signal indicative of smoke
density
or gas level therein in an electrical control element 40 as would be
understood by
those of skill in the art. Outflowing ambient air 32c flows from sensing
region 28a
into internal region 14 of housing 12 and into output filter 23b, through
output tube
30 22 and via output ports 22a, b .. n back into duct D.
As is illustrated in Figs. 1 and 2, the inflowing ambient atmosphere 32a is
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drawn into aspirator 24, ejected from aspirator 24 into sensing region 28a of
sensor
28. Outflow 32c from sensor 28 exits housing 12 via outflow tube 22. The
aspirator 24 could be located adjacent to inflow tube 20, shown, or adjacent
to
outflow tube 22.
An internal channel or shroud 40 indicated with sections 40a and 40b
provides a closed flow region when cover 12a is attached to housing 12. The
channel 40 confines inflowing ambient atmosphere 32a to a region in the
vicinity of
aspirator 24 which in turn ejects it into sensor 28, outside of channel 40.
Fig. 9 illustrates a graph 100 which illustrates sensitivity of detector 10
(with a smoke sensor) vs. velocity of air flow in the duct D. As illustrated
in Fig.
9, as a result of incorporating aspirator 24 in combination with channel 40 as
illustrated in Figs. 1 and 2, the detector 10 exhibits a substantially
constant
sensitivity from a relatively low velocity less than 50 feet per minute
through a
significantly higher velocity of 1000 feet per minute. Hence, even during
intervals
where the air in the duct D is moving very slowly, the detector 10 maintains
substantially the same sensitivity to smoke as it does at higher velocities in
excess
of 800 feet per minute. Similar constant sensitivity can be expected with duct
air
velocities up to, at least 4000 feet/minute.
Figs. 3 and 4 illustrate alternate embodiments 10' and 10". In the
2o embodiment of Fig. 3, detector 10' is illustrated having a channel 40'
formed
completely in the cover 12a'. Other elements detector 10' which correspond to
elements of detector 10 have been assigned the same identification numerals.
In
Fig. 4 in the detector 10", a channel 40" is formed completely in the housing
12".
In this embodiment, none of the channel 40" is molded into the cover 12a'.
It will also be understood that in addition to using a variety of aspiration
units, corresponding to the aspirated 24, it is within the scope and spirit of
the
present invention to use a variety of smoke or gas sensors 28.
Figs. 5 and 6 illustrate alternate embodiments of detectors 10-l and 10-2,
each of which includes a form of the channel 40 but without the aspirator 24.
In the
3o detector 10-1, the channel 40 is formed with portion 40a molded in housing
12.
Portion 40b is formed in the cover 12a. In this embodiment, when the cover 12a
is
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attached to the housing 12, the channel segments 40a, 40b provide a closed
inflow
channel 40 between a proximal end of sampling tube 20 and sensing chamber 28.
Movement of air in the duct D produces a pressure differential between the
proximal end of the sampling tube 20 and the proximal end of the outflow tube
22
thereby producing an inflow of ambient atmosphere from duct D through tube 20,
through channel 40 and into sensor 28. Outflow from sensor 28 is through
outflow
tube 22 back into duct D.
Fig. 6 illustrates housing 12" which incorporates channel 40" therein. None
of the channel 40" is formed in the housing 12".
Fig. 9 includes a graph 102 illustrating sensitivity of detectors such as 10-1
and 10-2 as a function of duct air velocity. In the absence of aspirator 24,
the
detectors 10-1 and 10-2 exhibit substantially constant sensitivity between 300
feet
per minute and 1000 feet per minute.
Figs. 7 and 8 illustrate two additional embodiments, detectors 10-3 and 10-
4, respectively. With respect to Fig. 7, detector 10-3 incorporates aspiration
unit 24
in combination with sensor 28. An extended channel 42 has inflow channel
regions
42a-1, 42a-2 formed respectively in the housing 12-1 and cover 12a-1.
Additionally, detector 10-3 incorporates extensions 43a and b formed around
sensor
28 which extend channel 42 therearound and 43a-1, 43b-1 in the cover so as to
limit
outflow from sensor 28 to an outflow region indicated generally at 46.
In the embodiment of the detector 10-4 in Fig. 8, channel extension
members 43a and 43b' also enclose the proximal end of outflow tube 22 on the
outflow side of sensor 28. Hence, ambient atmosphere which is injected via
aspirator 24 into sensing chamber 28a of sensor 28 flows via outflow region
46' of
sensor 28 and is confined by channel members 43a and 43b' to them flow out the
proximal end of outflow tube 22.
Fig. 10 illustrates another embodiment 10-5. A fan 24' is mounted inside
the duct D' with an opening D-1 in the duct wall to allow air flow to the duct
detector 1-5. Detector 10-5 has an opening 50-1 to align with the hole in the
duct
3o wall.
The fan 24' forces air to flow through the duct detector which contains the
CA 02299919 2000-06-OS
sensing region 28a . The fan direction can be reversed and the air flow
direction
will be reversed in the duct detector. Alternately, opening D-1 could be large
enough to receive fan 24'. In this case, the fan 24' could be carried on the
outside of
housing 50.
From the foregoing, it will be observed that numerous variations and
modifications may be effected without departing from the spirit and scope of
the
invention. It is to be understood that no limitation with respect to the
specific
apparatus illustrated herein is intended or should be inferred. It is, of
course,
intended to cover by the appended claims all such modifications as fall within
the
Io scope of the claims.
