GB2347541A

GB2347541A - Smoke detector for a duct

Info

Publication number: GB2347541A
Application number: GB0005398A
Authority: GB
Inventors: Edward J Thorp; James F Wiemeyer; George A Schoenfelder; Lee D Tice
Original assignee: Pittway Corp
Current assignee: Pittway Corp
Priority date: 1999-03-04
Filing date: 2000-03-06
Publication date: 2000-09-06
Also published as: CA2299919A1; GB0005398D0

Abstract

A smoke detector (10) for mounting to an air duct has a housing (12) from which extend inflow (20) and outflow (22) sampling tubes. A sensor (28) is located in the housing between the tubes, and an aspirator (24) such as a centrifugal blower is carried within the housing adjacent to a proximal end of the inflow tube such that 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 sensor such that a constant sensitivity is achieved regardless of the velocity of air flow in the duct.

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 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.

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.

Summarv of the Invention: A duct detector has ahousing 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.

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 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. Altemately, 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.

Numerus 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.

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 ; 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 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.

Detailed Description of the Preferred Embodiments : Wile 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 principes of the invention and is not intended to limit the invention to the specific embodiments illustrated.

Figs. I 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. I and 2, region 14 is associated with 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 I on either a continuous or an intermittent basis. The duct D might be incorporated into a building or other region to which air is being supplie, 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 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 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 an output or outflow port 24b from which outflowing ambient atmosphere 32b is injected into a fire sensor 28.

Sensor 28 incorporates an internal sensing region 28a and can be implemented as a photoelectric-type or an ioliization-typé 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.

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 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 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 assigne 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 10-1 and 10-2, each of which includes a form of the channel 40 but without the aspirator 24. In the 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 22 thereby producing an inflow of ambient atmosphere from duct D through tube 20, through channel 40 and into sensor 28. Qutflow 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 e 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 43 a and b formed around sensor 28 which extend channel 42 therearound and 43a-1, 43b-l 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 confine by channel mçrnbers 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 me duct detector 1-5. Detector 10-5 has an opening 50-1 to align with the hole in the duct hall.

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 reverse in the duct detector. Altemately, opening D-1 could be large enough to receive fan 24'. In this case, the fan 24'could be carried on the outside of f housing 50.

From the foregoing, it will be observe 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 apparats 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 scope of the claims.

Claims

CLAIMS:

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 directe 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 detectcr as in daim 1 ar 2 Oein the Vr Fibits a sXrkially 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 any preceding claim wherein the aspirator is carried within the housing.

5. A detector as in claims 1 to 3 wherein the aspirator is carried by the housing.

6. A detector as in claim 1 to 3 wherein the aspirator is carried outside of the housing and in flow communication with the internal sensing region.

7. A detector as in any preceding claim wherein the aspirator establishes a flow of air through the sensing region that is substantially independent of the velocity of air in the duct.

8. A detector as in any preceding claim wherein the housing is elongated with the tubes spaced therealong.

9. A detector as in any preceding claim wherein the aspirator comprises a rotary air mover located in the housing.

10. A detector as in claim 9 wherein the air mover is located adjacent to the fluid inflow tube.

11. A detector as in claim 9 or 10 wherein the air mover comprises a centrifugal blower with an input port adjacent to the fluid inflow tube.

12. A detector as in any prceding claim wherein the aspirator comprises a centrifugal blower with an input port adjacent to the fluid inflow tube.

13. A detector as in claim 11 or 12 wherein the blower of the aspirator has an output port adjacent to the sensing region.

14. A detector as in any preceding claim which includes a fire sensor wherein the sensing region is positioned within tie fire sensor.

15. A detector as inj any preceding claimkwhich includes a substantially closed flow channel which extends at least in part between a prokimal end of the one tte arI a selected pcrtof the sersing regrn.

16. A detector as in claim 14 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 af = awsr is located in the closed flow channel.

13. A detector as in claim 16 or 17 which includes a second, outlfow sample tube displaced from the one sample tube with the fire sensor therebetween.

19. Adetector as in claimk 16, 17 or 18, whereinj the housing includes a removeable cover, which, when coupled to the housing, substantially closes the flow drennel wherein a portion of the flow channel is formed in the cover.

20. A detector as in any preceding claimk wherein the aspirator creates a pmwe 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 any of claims 21 to 27 wherein the channel is substanbally closed therealong with spaced apart, open ends.

29. A detector as in claim 14 or any claim appended thereto or claim 22 or any claim appended thereto, wherein the fire sensor is one of a photoelectric-type, an ionizationtype sensor and a gas sensor.

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 claimk 30 or 31 which includes a fe S3Ecr c3zied within the housing and in flow communication with the internal flow path.

33. A detector as in any of claims 30 to 32 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 any cf claims 30 to 33 e indues an aspicatnr closed by the housing.

35. A detector as in claim 34 wherein the aspirator is located in one of the channes.

36. A detector as in claims 1 to 20 and 30 to 35 dedn the adratcr establishes a sensitivity for the detector substantially independent of the velocity

a n ti et.

37. 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 extemal atmospheric Howrates.

38. A detector as in claim 37 which includes an aspirator.

39. A detector as in claim 37 cr 38 n the sr is ooLnL=d to an output of the flow path.

40. A detector as in ary cf cuirs 37 to 39 wherein the aspirator is carried by the housing.

41. A detector as in any cf dajrns 37 to 39 Oin ths aspit is carried outside of the thoushing and in flow comunication with the internal sensing region.

42. 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.

43. A detector as in claim 42 wherein the aspirator is attached to the housing.

44. A detector as in claim 41 cr 42 which includes an output flow port for returning ambient air frcm the sensor to the duct.

45. A duct type smoke detector substantially as hereinbefore described with reference to, and as shown in any of Figures 1 and 2, 3 to 8 and 10 of the accompanying drawings.