CA2299919A1 - Duct detector - Google Patents

Duct detector Download PDF

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Publication number
CA2299919A1
CA2299919A1 CA002299919A CA2299919A CA2299919A1 CA 2299919 A1 CA2299919 A1 CA 2299919A1 CA 002299919 A CA002299919 A CA 002299919A CA 2299919 A CA2299919 A CA 2299919A CA 2299919 A1 CA2299919 A1 CA 2299919A1
Authority
CA
Canada
Prior art keywords
detector
housing
flow
aspirator
duct
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002299919A
Other languages
French (fr)
Inventor
George A. Schoenfelder
Lee D. Tice
James F. Wiemeyer
Edward J. Thorp
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pittway Corp
Original Assignee
Pittway Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Pittway Corp filed Critical Pittway Corp
Publication of CA2299919A1 publication Critical patent/CA2299919A1/en
Abandoned legal-status Critical Current

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Classifications

    • GPHYSICS
    • G08SIGNALLING
    • G08BSIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00Fire alarms; Alarms responsive to explosion
    • G08B17/10Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • GPHYSICS
    • G08SIGNALLING
    • G08BSIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00Fire alarms; Alarms responsive to explosion
    • G08B17/10Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113Constructional details

Abstract

A duct-type smoke detector has an elongated housing from which extend inflow and outflow sampling tubes. A fire sensor is located in the housing between the tubes. An aspirator, such as a centrifugal blower is carried within the housing adjacent to a proximal end of the inflow tube. A flow output from the blower is directed toward the sensor. A closed channel can extend between a proximal end of the inflow tube and the fire sensor. The aspirator can be located in the channel.

Description

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 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 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 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 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 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 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 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.

Claims (45)

1. A duct detector comprising:
a housing mountable to an air flow duct wherein the housing includes an internal sensing region;
at least one port carried by the housing and exposed to air flow in the duct when the housing is attached to the duct wherein a flow path in the port is in fluid flow communication with the internal sensing region; and an aspirator whereby a flow of fluid is directed into the sensing region.
2. A detector as in claim 1 which includes two tubes, one tube provides an inflow of fluid, the other provides an outflow of fluid, wherein, when the housing is mounted to the duct, an enhanced flow of air from the duct is present in the sensing region.
3. A detector as in claim 1 wherein the detector exhibits a substantially constant sensitivity in the presence of air flow rates incident on the one tube in a range extending from less than 100 to at least 1000 feet/minute.
4. A detector as in claim 1 wherein the aspirator is carried within the housing.
5. A detector as in claim 2 wherein the aspirator establishes a flow of air through the sensing region that is substantially independent of the velocity of air in the duct.
6. A detector as in claim 5 wherein the housing is elongated with the tubes spaced therealong.
7. A detector as in claim 6 wherein the aspirator comprises a rotary air mover located in the housing.
8. A detector as in claim 7 wherein the air mover is located adjacent to the fluid inflow tube.
9. A detector as in claim 8 wherein the air mover comprises a centrifugal blower with an input port adjacent to the fluid inflow tube.
10. A detector as in claim 9 wherein the blower has an output port adjacent to the sensing region.
11. A detector as in claim 1 wherein the aspirator comprises a centrifugal blower with an input port adjacent to the fluid inflow tube.
12. A detector as in claim 11 wherein the blower has an output port adjacent to the sensing region.
13. A detector as in claim 12 which includes a fire sensor wherein the sensing region is positioned within the fire sensor.
14. A detector as in claim 13 wherein the fire sensor comprises at least one of a photo-electric smoke sensor, an ion-type smoke sensor and a gas sensor.
15. A detector as in claim 1 which includes a substantially closed flow channel which extends at least in part between a proximal end of the one tube and a selected portion of the sensing region.
16. A detector as in claim 13 which includes a substantially closed flow channel which extends between a proximal end of the one tube and a portion of the fire sensor.
17. A detector as in claim 16 wherein the blower is located in the closed flow channel.
18. A detector as in claim 16 which includes a second, outflow sample tube displaced from the one sample tube with the fire sensor therebetween.
19. A detector as in claim 16 wherein the housing includes a removable cover which, when coupled to the housing, substantially closes the flow channel wherein a portion of the flow channel is formed in the cover.
20. A detector as in claim 1 wherein the aspirator creates a pressure differential between the flow path of the tube and the internal sensing region.
21. A duct detector comprising:
an elongated hollow housing from which extends at least one fluid flow tube; and a channel formed within the housing wherein the channel is in flow communication with a proximal end of the tube and an internal region of the housing.
22. A detector as in claim 21 which includes a fire sensor carried within the housing adjacent to an end of the channel displaced from the proximal end of the tube.
23. A detector as in claim 22 which includes a second, output tube which extends from the housing with the sensor positioned between the tubes.
24. A detector as in claim 23 wherein the channel provides an internal flow path in the housing between the one flow tube and the sensor with a larger flow path provided between the sensor and the second tube.
25. A detector as in claim 23 which includes an aspirator coupled to the channel.
26. A detector as in claim 25 wherein the aspirator is carried within the channel.
27. A detector as in claim 23 wherein the housing is closed with a removable cover and wherein a portion of the channel is formed in the cover.
28. A detector as in claim 26 wherein the fire sensor is one of a photoelectric-type, an ionization-type sensor and a gas sensor.
29. A detector as in claim 21 wherein the channel is substantially closed therealong with spaced apart, open ends.
30. A detector comprising:
a housing which defines an internal region and which includes an isolating internal flow path in part of the region;
an aspirator coupled to the flow path;
an input port for ambient atmosphere wherein the input port is coupled to the flow path, and, a displaced, separate output flow port for outflow of fluid in the housing wherein the output flow port is coupled to a greater volume within the housing than is contained within the internal flow path.
31. A detector as in claim 30 wherein the housing is elongated with the ports are displaced axially therealong and wherein the housing is closed, at least in part, by a removable cover wherein a portion of the internal flow path is formed in the cover.
32. A detector as in claim 30 which includes a fire sensor carried within the housing and in flow communication with the internal flow path.
33. A detector as in claim 22 which includes a second channel formed within the housing and having an input end adjacent to the fire sensor and an output end adjacent to an output port of the housing.
34. A detector as in claim 33 which includes an aspirator carried by the housing.
35. A detector as in claim 34 wherein the aspirator is located in one of the channels.
36. A detector as in claim 1 wherein the aspirator establishes a sensitivity for the detector substantially independent of the velocity of air in the duct.
37. A detector as in claim 30 wherein the aspirator establishes a sensitivity for the detector substantially independent of the velocity of air in the duct.
38. A detector comprising:
a housing which includes a flow isolating internal flow path;
an input port for ambient atmosphere wherein the input port is coupled to the flow path, and, a displaced, separate output flow port for outflow of fluid from the housing; and a sensor carried, in the housing in the flow path wherein the detector exhibits a substantially constant performance parameter in the presence of varying external atmospheric flow rates.
39. A detector as in claim 38 which includes an aspirator.
40. A detector as in claim 38 wherein the sensor is coupled to an output of the flow path.
41. A detector as in claim 1 wherein the aspirator is carried by the housing.
42. A detector as in claim 2 wherein the aspirator is carried outside of the housing and in flow communication with the internal sensing region.
43. A duct detector comprising:
a housing which carries a sensor wherein the housing includes an attachment element for attaching the housing to an air containing duct, at least an input port, adapted for sealingly interfacing to an opening in the duct; and an aspirator associated with the housing for providing a flow of ambient air, from the duct to the sensor.
44. A detector as in claim 43 wherein the aspirator is attached to the housing.
45. A detector as in claim 44 which includes an output flow port for returning ambient air from the sensor to the duct.
CA002299919A 1999-03-04 2000-03-03 Duct detector Abandoned CA2299919A1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US12308199P 1999-03-04 1999-03-04
US60/123,081 1999-03-04
US15683499P 1999-09-30 1999-09-30
US60/156,834 1999-09-30
US51805300A 2000-03-02 2000-03-02
US09/518,053 2000-03-02

Publications (1)

Publication Number Publication Date
CA2299919A1 true CA2299919A1 (en) 2000-09-04

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
CA002299919A Abandoned CA2299919A1 (en) 1999-03-04 2000-03-03 Duct detector

Country Status (2)

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CA (1) CA2299919A1 (en)
GB (1) GB2347541A (en)

Cited By (1)

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TWI499365B (en) * 2008-03-31 2015-09-01 Nohmi Bosai Ltd Electrical machines and smoke sensors

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Publication number Publication date
GB0005398D0 (en) 2000-04-26
GB2347541A (en) 2000-09-06

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