Patent Application
20050134468
1. Field of the Invention
The present invention relates to optical smoke detectors and, more specifically, to the detection chamber of an optical smoke detector and the cleaning thereof.
2. Description of the Related Art
Smoke detectors that employ optical sensors to detect the presence of smoke in a detection chamber are known in the art. Optical sensors operate based upon principles of scattered light absorption. Typically, a light emitting diode (LED) transmits light into a detection chamber where it is absorbed by a labyrinth structure. When smoke, due to a fire, is present in the air entering the detection chamber, the smoke particles scatter the light generated by the LED. A photodiode is used to measure the amount of light scattered by the particles and, when the quantity of scattered light exceeds a predetermined threshold, an alarm signal is generated. Detectors that combine thermal and/or chemical sensors with an optical sensor are also known in the art.
When employing an optical smoke detector, the accumulation of dust particles or other particulate matter within the detection chamber can have a detrimental impact on the performance of the smoke detector. The accumulation of such particulate matter in the detection chamber requires the eventual cleaning or replacement of the detection chamber to maintain the smoke detector in proper working order. The cleaning of a conventional optical smoke detector typically requires the disassembly of the detector to expose and gain direct access to the detection chamber. After gaining access to the detection chamber, clean air, such as from a container of clean pressurized air, may be used to clean the chamber. The disassembly and subsequent reassembly of the optical smoke detector can result in damage to various component parts of the detector which typically includes a printed circuit board. Disassembly and handling of the smoke detector and detection chamber can also leave oil from the hand of the maintenance personnel on surfaces within the detection chamber which could reflect light and interfere with the performance of the smoke detector. Although it is also known to disassemble and replace the detection chamber and then reassemble the smoke detector to provide the smoke detector with a clean detection chamber this too may result in the damage of various component parts of the detector and increases the cost of maintaining the detectors by increasing the quantity of required replacement parts.
An optical smoke detector having an improved design that facilitates the cleaning of the detection chamber of the smoke detector is desirable.
The present invention provides an optical smoke detector that includes a cleaning port that provides for the rapid and convenient cleaning of the detection chamber of the smoke detector without requiring the disassembly of the smoke detector.
The invention comprises, in one form thereof, an optical smoke detector for detecting the presence of particulates in an air sample and which is cleanable with the use of a supply of clean air introduced through an air nozzle. The smoke detector includes a detection chamber defining an enclosure for the air sample and at least one opening in fluid communication with the detection chamber wherein the air sample is introducible and dischargeable from the detection chamber through the at least one opening. A cleaning port defines a passageway to the detection chamber from a first position external to the optical smoke detector and a valve member seals the cleaning port with a substantially air-tight seal. The valve member is accessible from the first position external to the smoke detector and is openable, permitting the passage of air through the cleaning port into the discharge chamber.
The present invention comprises, in another form thereof, an optical smoke detector for detecting the presence of particulates in an air sample and which is cleanable with the use of a supply of clean air introduced through an air nozzle. The smoke detector includes a detection chamber defining an enclosure for the air sample, a plurality of openings are in fluid communication with the detection chamber wherein, during operation of the smoke detector in a detection mode, the air sample is introduced into the detection chamber through at least one of the plurality of openings and discharged from the detection chamber through another one of the plurality of openings solely by ambient air movement. A cleaning port defines a passageway to the detection chamber from a first position external to the smoke detector. A resilient valve member seals the cleaning port with a substantially air-tight seal. The valve member is accessible from the first position external to the smoke detector and is openable, permitting the passage of air through the cleaning port into the detection chamber, by engaging the valve member with the air nozzle.
In some embodiments of the invention, the detection chamber is defined by a chamber member having an end wall and a sidewall extending substantially transverse to the first end surface and circumscribing the detection chamber. The sidewall also engages a base member that defines a surface of the detection chamber opposite the end wall. The sidewall also includes a plurality of circumferentially spaced openings through which the air sample enters and exits the detection chamber. Additionally, the passageway defined by the cleaning port may extend through the surface of the detection chamber defined by the base member.
The valve may take various forms including one wherein it has a distal first end and a proximal second end, the first end being disposed more distally from the detection chamber than the second end. The first end of the valve defines a bore hole and the second end defines a sealing member providing a substantially air tight seal within the cleaning port. The sealing member defines a central passage extending from the bore hole through the second end wherein the central passage is closed in the absence of an external force and is openable to permit the passage of air when an air nozzle is introduced into the bore hole and clean air is introduced into the valve through the air nozzle.
The valve may also take a form wherein it has a substantially cylindrical central section with first and second opposite ends with the first and second ends respectively defining first and second radially outwardly extending flanges. The first and second flanges define first and second diameters respectively with the central section of the valve being positioned in an aperture having a third diameter. Each of the first and second diameters are greater than the third diameter whereby the valve is secured in the aperture. The smoke detector may be adapted for mounting on a support structure, such as a wall or ceiling, with the cleaning port positioned to face the support structure when the smoke detector is mounted on the support structure.
The present invention comprises, in yet another form thereof, a method of cleaning an optical smoke detector that detects the presence of particulates in an air sample. The method includes providing the smoke detector with a detection chamber for enclosing the air sample and a cleaning port defining a passageway to the detection chamber from a first position external to the smoke detector. The method also includes controlling the passage of air through the cleaning port with a valve member, the valve member sealing the cleaning port with a substantially air-tight seal during operation of the smoke detector in a detection mode, and opening the valve and introducing clean air into the detection chamber through the cleaning port to flush particulates from the detection chamber. The method may also include deactivating the smoke detector prior to opening the valve and introducing clean air into the detection chamber.
An advantage of the present invention is that it does not require the disassembly of the smoke detector when flushing smoke particles and other particulate matter from the detection chamber. Because the smoke detector does not have to be disassembled and reassembled during cleaning, the probability of damaging the smoke detector during cleaning of the detector is reduced. Additionally, the time required by the maintenance personnel during the routine cleaning of the smoke detector is reduced thereby facilitating the reduction of the cost of facility maintenance in a building employing smoke detectors in accordance with the present invention.
The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed.
In accordance with the present invention, an optical smoke detector 20 is shown in
A printed circuit board 32 is secured to mounting plate 28. Printed circuit board 32 includes a light emitting diode 34 and a photosensor 36. Printed circuit board 32 also has an assembly 38 that includes two conductive members extending outwardly from the printed circuit board. Assembly 38 has a thermal sensor located on its distal end.
Base member 26 is also secured to mounting plate 28 and is positioned over printed circuit board 32 with assembly 38 extending through slot 40. Two depressions 42, 44 are formed in base member 26. Depressions 42, 44 are aligned and slant downwardly as they extend away from each other towards their respective outermost ends 43, 45. Outer ends 43, 45 define openings which are respectively aligned with photodiode 34 and photosensor 36 when base member 26 is secured to mounting plate 28. Also shown in
Chamber member 24 includes an upper chamber wall 56 and a sidewall 58. Sidewall 58 takes the general form of a conical section defining a progressively larger radius as it projects from end wall 56, however, the angle between walls 56 and 58 is such that sidewall 58 remains substantially transverse to end wall 56. A plurality of vertically extending elongate openings 60 are circumferentially spaced about sidewall 58 and are separated by vertically extending ribs 59. Chamber member 24 is engaged with surface 52 of base member 26 to define a detection chamber 62. Assembly 38 extends along the outer surfaces of sidewall 58 and end wall 56 with the distal end of assembly 38 being disposed within guard member 64 on outer housing 22. Outer housing 22 also includes a substantially transparent indicator 66. Indicator 66 extends toward printed circuit board 32 and allows a light emitting diode located on printed circuit board 32 to be used to communicate the status of smoke detector 20 to technicians or maintenance personnel. Outer housing 22 also includes openings 68 to communicate air between chamber 62 and a position external to smoke detector 20. After positioning base member 26 and chamber member 24 on mounting plate 28, mounting plate 28 and outer housing 22 are assembled together to form smoke detector 20. To secure mounting plate 28 and outer housing 22, the outer radial edge 70 of mounting plate 28 is snap fit to outer housing 22 as best seen in
As seen in
The operation of smoke detector 20 will now be discussed. Sidewall 58 together with the interior surface 82 of end wall 56 and surface 52 of base member 26 define detection chamber 62. Sidewall 58 circumscribes detection chamber 62 with surface 52 being positioned opposite end wall 56. Depressions 42, 44 are located within detection chamber 62 whereby light emitted from LED 34 enters chamber 62 and sensor 36 measures the quantity of light reflected by smoke and similar particulate matter within chamber 62. Opening 50 is also located in chamber 62 as discussed below. Smoke detector 20 is configured to inhibit other sources of light from reaching sensor 36. The interior of chamber member 24 is illustrated in
When the quantity of reflected light reaching sensor 36 exceeds a threshold value, presumably because of the presence of a smoke particles in chamber 62, smoke detector 20 generates an alarm signal. This use of a light emitting source and sensor for measuring reflected light within a discharge chamber to detect the presence of smoke in the ambient air is well known to those having ordinary skill in the art. For example, smoke detectors commercially available from Bosch Security Systems, Inc., having a place of business in Fairport, N.Y., under the MAGIC.SENS brand name such as the O 300 Optical Smoke Detector and O 400 LSN Optical Smoke Detector are used to detect the presence of smoke using similar techniques and these products may be modified for use with the present invention by adding a cleaning port as described below.
The illustrated smoke detector 20 relies upon the ambient air currents to introduce air into and discharge air from detection chamber 62 while smoke detector 20 is activated and in a detection mode actively monitoring the air sample within detection chamber 62. In other words, the illustrated embodiment does not include any means for actively pumping the air being monitored through the detection chamber. In contrast, aspirator-type smoke detectors include means for pumping air into a detection chamber and will oftentimes include a filter for removing larger particulates from the air being pumped into the detection chamber.
It is desirable for the air sample contained within detection chamber 62 to have the same concentration of smoke particles as the ambient air in the environment being monitored by the smoke detector 20 to allow for the accurate monitoring of the air. Over prolonged periods of time, however, dust particles and other particulate matter may accumulate in detection chamber 62 of the smoke detector. This unwanted accumulation of particulates in detection chamber 62 can elevate the reflected light values measured by sensor 36. This elevated level of reflected light effectively lowers the particulate concentration in the ambient air that will trigger an alarm event and increases the possibility of a false alarm. For commercial smoke alarm installations, false alarms have the potential to unnecessarily cause the evacuation of a building and are highly undesirable. It is also possible for particulate matter to accumulate in chamber 62 in a manner that partially blocks the light emitted by LED 34. This can possibly increase the quantity of smoke in the air that is required to generate an alarm signal and is also undesirable.
To prevent the excessive accumulation particulate matter, detection chamber 62 may be periodically cleaned to remove accumulated particulate matter. In accordance with the present invention, smoke detector 20 has a cleaning port 86 that defines a passageway extending from an external surface of mounting plate 28 to detection chamber 62. In the illustrated embodiment, cleaning port 84 is defined by aperture 54 in mounting plate 28 and opening 50 in base member 26. A valve member 90 controls the passage of air through cleaning port 86.
Valve 90 is shown in
As best seen in
The illustrated valve 90 is manufactured using a silicone rubber SHORE 45A. This provides a resilient and flexible valve member that can be easily inserted into aperture 54. After removing nozzle 104 from valve 90, the material used to form seal member 100 returns to its original configuration closing passage 102, i.e., the material used to form valve 90 is resilient. Although a specific embodiment of a valve is illustrated herein, alternative valve members may also be used with the present invention to seal cleaning port 86 to control the flow of air into chamber 62. For example, the cleaning port might have a threaded end that receives a complimentary threaded cap whereby the threaded cap forms a valve member and is easily removed, i.e., opened, to provide access to the detection chamber for cleaning purposes.
With reference to
Initially, smoke detector 20 is removed from mounting base 30. Dismounting of smoke detector 20 serves two purposes, it exposes cleaning port 86 and also deactivates smoke detector 20 by disconnecting electrical contacts 72 from contacts 74. It is advantageous to deactivate smoke detector 20 because of the likelihood of inaccurate readings during the cleaning process and the potential to cause a false alarm. By positioning cleaning port 86 so that it faces mounting base 30 when detector 20 is mounted and thereby requiring the removal of detector 20 from mounting base 30 to expose cleaning port 86, the deactivation of smoke detector 20 prior to cleaning can be assured.
After exposing cleaning port 86, the nozzle 104 of a pressurized air canister 106 is inserted into bore hole 98 of valve 90 and air is discharged from canister 106 as shown in
Although the cleaning process did involve removing and reinstallation of smoke detector 20 on mounting base 30, it did not require the opening of the housing enclosure defined by mounting plate 28 and outer housing 22 and, thus, neither printed circuit board 32 nor the interior of detection chamber 62 were exposed or subject to direct manual handling by the individual performing the cleaning process. By avoiding the exposure of printed circuit board 32 and the interior surfaces of chamber 62 during the cleaning process, i.e., by not disassembling smoke detector 20, the possibility of the individual cleaning the detector inadvertently damaging the smoke detector is substantially reduced.
While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.
