Chamberless wide area duct smoke detector

A detector assembly for a duct of a heating ventilation and air conditioning system includes an outer housing having at least one through hole formed therein, an inner sampling support receivable within a hollow interior of the outer housing, and at least one detector mounted to the inner sampling support. The at least one detector is axially aligned with the at least one through hole when the inner sampling support is installed within the hollow interior of the outer housing. The at least one detector is operable to sample air within the duct to detect a hazardous condition.

BACKGROUND

Exemplary embodiments pertain to the art of indoor air quality sensors, smoke sensors, and more particularly to chamberless smoke and indoor air quality sensors for use in a duct of a heating, ventilation, and air conditioning system.

Detection systems are often installed in office buildings, airports, sports venues, retail stores and the like to identify smoke or chemicals for early warning of a threat event. As examples, systems may be designed to identify trace amounts of smoke particles as an early warning of a fire, trace amounts of target chemicals as an early warning of toxicity in an environment, or minute amounts of airborne substances.

Detectors for sensing one or more conditions within a duct of a heating, ventilation, and air conditioning system are typically mounted to a flange or other component and/or the outside of an air duct and include a sampling pipe which extends laterally into the duct from the exterior. The air within the duct flows into inlets formed in the sampling pipe to a smoke sensor, located in a housing outside of the duct. The air is then returned to the interior of the duct via an output flow pipe.

The sampling pipes used to direct air from inside the duct to a smoke detector have different lengths and different hole spacings based on the size of the duct. In addition, dust may accumulate within the chamber of the smoke detector resulting in false alarms and frequent maintenance. Maintenance of a duct detector is typically a time consuming procedure having limited effectiveness. As a result, maintenance of a duct detector often entails replacement of the detector.

BRIEF DESCRIPTION

According to an embodiment, a detector assembly for a duct of a heating ventilation and air conditioning system includes an outer housing having at least one through hole formed therein, an inner sampling support receivable within a hollow interior of the outer housing, and at least one detector mounted to the inner sampling support. The at least one detector is axially aligned with the at least one through hole when the inner sampling support is installed within the hollow interior of the outer housing. The at least one detector is operable to sample air within the duct to detect a hazardous condition.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector is an optical detector including at least one light source and at least one light detecting device.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner sampling support further comprises: a tube body and a flange mounted to an end of the tube body.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector is mounted to an exterior surface of the tube body.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector is at least partially embedded within the tube body.

In addition to one or more of the features described above, or as an alternative, in further embodiments the tube body further comprises a plurality of segments connected together, each of the segments including at least one detector.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner sampling support includes one or more positioning flanges to limit at least one of vertical and lateral movement of the inner sampling support when installed within the hollow interior of the outer housing.

In addition to one or more of the features described above, or as an alternative, in further embodiments the outer housing further comprises a body defining the hollow interior and a flange located at a first end of the body.

In addition to one or more of the features described above, or as an alternative, in further embodiments the outer housing further comprises at least one cleaning mechanism mounted within the hollow interior of the body in axial alignment with the at least one detector.

In addition to one or more of the features described above, or as an alternative, in further embodiments when the inner sampling support is installed within the hollow interior of the outer housing, the inner sampling support is rotatable about an axis such that the at least one cleaning mechanism engages the at least one detector.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising an actuation mechanism coupled to the inner sampling support, wherein the actuation mechanism is operable to rotate the inner sampling support about the axis.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector includes one or more light sources, one or more light sensing device, and a processing device operably coupled to the one or more light sources and the one or more light sensing device.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector assembly includes a first detector and a second detector spaced along an axis of the inner sampling support.

In addition to one or more of the features described above, or as an alternative, in further embodiments a processing device of the first detector is also a processing device of the second detector.

According to another embodiment, a heating ventilation and air condition system includes a duct having a hollow interior and at least one detector assembly mounted to the duct. The at least one detector assembly includes an outer housing having at least one through hole formed therein, an inner sampling support mounted within the outer housing, and at least one detector mounted to the inner sampling support. The at least one detector is arranged in fluid communication with the hollow interior of the duct and is operable to detect a hazardous condition within the hollow interior of the duct.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector assembly includes a plurality of detector assemblies mounted at intervals over an axial length of the duct.

In addition to one or more of the features described above, or as an alternative, in further embodiments wherein the at least one detector further comprises a plurality of detectors mounted at intervals over an axial length of the inner sampling support.

In addition to one or more of the features described above, or as an alternative, in further embodiments the inner sampling support further comprises a plurality of segments connected together and each of the plurality of segments including at least one detector.

In addition to one or more of the features described above, or as an alternative, in further embodiments the duct further comprises a sidewall and the outer housing further comprises a flange, the flange being mounted to the sidewall to attach the at least one detector assembly to the sidewall.

In addition to one or more of the features described above, or as an alternative, in further embodiments the at least one detector assembly extends within the hollow interior of the duct perpendicular to an axial length of the duct.

DETAILED DESCRIPTION

With reference now toFIG. 1, an example of a duct20of a heating, ventilation, and air conditioning (HVAC) system is illustrated. As shown, one or more detector assemblies30are mounted to the duct20. Each detector assembly30is operable to sample an area within the interior22(seeFIG. 2) of the duct20to determine if particles representative of a hazardous condition are present. In the illustrated, non-limiting embodiment, a plurality of detector assemblies30, for example three detector assemblies, are mounted at intervals spaced along the axial length L of the duct20. However, it should be understood that a duct20having any number of detector assemblies30coupled thereto is within the scope of the disclosure. The total number of detector assemblies30will typically vary based on the overall length L of the duct20and the maximum allowable spacing between detector assemblies30as dictated by one or more building codes or regulations.

As best shown inFIG. 2, each of the detector assemblies30is affixed to a sidewall24of the duct20and extends from the sidewall24into the interior22of the duct20, perpendicular to the axial length L of the duct20. In the illustrated, non-limiting embodiment, the detector assemblies30are affixed to an exterior surface26of the sidewall24, and extend through an opening28formed therein. However, embodiments where the detector assembly30is mounted to an interior surface29of the sidewall24are also contemplated herein. In addition, embodiments where a detector assembly30extends parallel to the axial length L of the duct20are also contemplated herein. In such embodiments, one or more detector assemblies30may be spaced over a width W of the duct20.

With reference now toFIGS. 3-5, an example of a detector assembly30suitable for use within a duct20is illustrated in more detail. The detector assembly30generally includes an outer cover41, outer housing32(FIG. 4), an inner sampling support34(FIG. 4) receivable within the outer housing32, and one or more detectors36. The outer cover41may contain one or more visual indicators such as an LED43, an indicating light ring45, a local display47, or any combination thereof. The outer housing32includes a conduit-like body38having a generally hollow interior40(FIG. 4). In the illustrated, non-limiting embodiment, the body38of the outer housing32is generally cylindrical in shape; however, it should be understood that a body38having any suitable configuration, such as a rectangular shape for example, is also within the scope of the disclosure. The hollow interior40may have a shape complementary to the exterior of the body38, or alternatively, may have a contour distinct from the shape of the body38.

One or more one through holes42are formed in the sidewall of the body38. The total number of through holes42formed in the body38will depend on the overall length of the body38and the total number of detectors36associated with the detector assembly30. In the illustrated, non-limiting embodiment, a mounting flange44is located at a first end46of the body38of the outer housing32. The mounting flange44may be integrally formed with the body38, or alternatively, may be affixed to the first end46via adhesive, fasteners, or any other suitable coupling mechanism. The flange44may be used to mount the outer housing32to the sidewall24of the duct20. For example, as shown inFIG. 2, the mounting flange44may abut the exterior surface26of the sidewall24such that the body38of the outer housing32extends into the interior22of duct20. However, other methods of mounting the outer housing32in fluid communication with the interior22of the duct20are contemplated herein. For example, the body38of the outer housing32may be mounted to the duct20via a simple temper fit, friction fit, a tightening nut, adhesive or any other suitable mechanism.

Referring toFIG. 4, the inner sampling support34includes a tube body50having an axial length generally equal to, or shorter than the axial length of the body38of the outer housing32. As shown, the tube body50may be cylindrical in shape; however, other shapes are also within the scope of the disclosure. An outer flange52is positioned at the first end54of the tube body50. The outer flange52has at least one dimension that is larger than a diameter of the hollow interior40of the body38of the outer housing32. As a result, when the inner sampling support34is installed relative to the outer housing32, a surface of the outer flange52abuts a corresponding surface of the mounting flange44. Further, when the inner sampling support34is mounted within the outer housing32, the inner sampling support34and the outer housing32may be arranged generally concentrically about an axis X defined by the body38of the outer housing32. However, in other embodiments, the inner sampling support34and the outer housing32may not be concentric with one another. For example, in an embodiment, the inner sampling support34and the outer housing32are not mounted concentrically when cam-type operation is intended. The phrase “cam-type operation” as used herein is intended to include embodiments where the axis defined by the inner sampling support34is offset from the axis of the outer housing32or where the contour (i.e. the radius) of either the inner sampling support34or the outer housing32varies about the circumference thereof. In such embodiments, rotation of the inner sampling support34is non-uniform relative to outer housing32.

The positioning of the inner sampling tube34and the contour of the outside of the body38of the outer housing32may be oriented to achieve a nearly continuous surface along the outer housing32. Simulations of the velocity contours around a cylindrical-shaped tube in the duct for both low velocity (100 ft3/min) and high velocity (4000 ft3/min) air flows have been performed. These simulations indicate that self-cleaning of the detector assembly30, to be described in more detail below, is most efficient when the detectors36are appropriately positioned relative to the direction of the airflow through the duct20. In an embodiment, the detectors36are mounted at angular position between 45° and 85° relative to the airflow direction in order to maximize the self-cleaning effect. At these angular positions, the air velocity at the surface of the outer housing32is the greatest. Accordingly, the contour of the outer housing32can be modified to have a non-circular cross-section, e.g. oval or airfoil shape, to increase the airflow velocity at specific locations on the outer housing32, where the detectors36would be located, to increase cleaning efficiency.

With continued reference toFIG. 4, one or more positioning flanges56extend radially outwardly from an exterior surface of a portion of the tube body50receivable within the hollow interior40of the body38of the outer housing32. As shown, these positioning flanges56may be arranged in pairs extending in radially opposite directions at a location of the tube body50. However, embodiments where only a single positioning flange56, or more than two positioning flanges56are arranged at an axial location of the tube body50are also within the scope of the disclosure. Each positioning flange56is sized to engage a corresponding surface (not shown) defining the hollow interior40of the body38, thereby limiting vertical and lateral movement of the inner sampling support34within the outer housing32. In the illustrated, non-limiting embodiment, the tube body50includes a first pair of positioning flanges56arranged near a midpoint of the axial length of the tube body50, and a second pair of positioning flanges56adjacent a second end58of the tube body50. The total number of positioning flanges56may vary based on a length of the inner sampling support34and the number of detectors36associated with the detector assembly30.

As previously noted, one or more detectors36are associated with the detector assembly30, such as mounted to or embedded within the tube body50of the inner sampling support34. The term “detector” as used herein may include, but is not limited to, smoke detectors or indoor air quality sensors that are capable of detecting small amounts of particulate (e.g. smoke particles, dust, steam, or other particulates), chemicals, and/or biological agents. Example types of detectors may include ionization detectors, photoelectric aspirating detectors, photoelectric chamber or chamber-less detectors, and combinations thereof.

In the illustrated, non-limiting embodiment shown inFIGS. 3-5, the detector assembly30includes two detectors36spaced apart from one another over the axial length of tube body50of the inner sampling support34. Each detector36is positioned at an axial length of the tube body50such that when the inner sampling support34is installed within the hollow interior40of the body38of the outer housing32, the detector36is aligned with a corresponding through hole42formed in the outer housing32. As a result, each detector36is arranged in fluid communication with the area of the duct20surrounding the outer housing32. Although two detectors36are shown, in should be understood that embodiments having only a single detector36, or alternatively, embodiments having more than two detectors36are also within the scope of the disclosure. In embodiments of the detector assembly30including a plurality of detectors36, the detectors may, but need not have substantially similar configurations to each other. Further, a detector assembly30may include a plurality of modules or segments connected together such as via a fastening mechanism, for example interlocking threads, fasteners, or adhesive. Each segment of the detector assembly30may have a predefined length and a number of detectors36associated therewith. As a result, various segments may be combined to achieve a detector assembly30having a desired configuration.

Referring now toFIG. 6, an example of a detector36is illustrated in more detail. As shown, the detector36is an optical detector that uses light to evaluate an adjacent area, hereinafter referred to as a “monitored space” for the presence of one or more conditions. In this example, the monitored space is a portion of the interior22of a duct20(Shown inFIG. 2), such as of an HVAC system for example. When the light encounters an object, such as a smoke particle, or gas molecule for example, the light is scattered and/or absorbed due to a difference in the refractive index of the particle compared to the surrounding medium (air). Observing any changes in the incident light can provide information about the monitored space including determining the presence of a condition or event.

Each detector36includes one or more light sources60and one or more light sensing devices62and a processing device64. In an embodiment, the one or more light sources60include a first light source60aand a second light source60b. The light sources60a,60bmay include a light emitting diode (LED) or laser operable to emit a light beam at a wavelength or over a range of wavelengths into the monitored space. In an embodiment, the first light source60amay emit light having a wavelength characteristic of infrared light and the second light source60bmay emit light have a wavelength characteristic of blue visible light. In such embodiments, the infrared light may be used in the detection and false alarm discrimination of smoke. Similarly, the blue visible light may be used in the false alarm discrimination of smoke. Additionally, in some embodiments, the combination of infrared light and visible light may be used to determine the size of particles at or near the detector36within the monitored space.

The one or more light sensing devices62may include photodiodes, bipolar phototransistors, photosensitive field-effect transistors, photodetectors, and the like. Although only a single light sensing device62is shownFIGS. 3-6, in other embodiments, the detector36may include a plurality of light sensing devices62, such as two, three, four, or any number of light sensing devices. The light sensing device62is operable to emit sensor signals in response to interaction of a light beam emitted by a light source60of the detector36with one or more particles in the monitored space. The light sensing device62generates a signal in response to receiving scattered light resulting from the interaction between the emitted light beam and a particle. The signals generated are proportional to the intensity of the scattered light received by the light sensing device62.

With reference again toFIG. 5and continued reference toFIG. 6, in the illustrated, non-limiting embodiment, a plurality of channels66are formed in the tube body50, and each of the at least one light source60and at least one light sensing device62is mounted within a respective channel66. However, in other embodiments, a single channel66may be formed in the tube body50, and the one or more light sources60and/or the one or more light sensing devices62of a detector36may be mounted within the channel66. The at least one light source60is mounted such that light is emitted therefrom radially outwardly, toward the monitored space. Similarly, each of the one or more light sensing devices62is positioned such that the portion of the at least one light sensing device62configured to receive a light signal is also facing the monitored space.

The light emitted from each of the light sources60defines an emitter cone increasing in diameter away from the surface of the detector assembly30. In embodiments including a plurality of light sources60, the emitter cones formed by each light source60may be oriented at any angle to one another. Any suitable angle between the emitter cones is within the scope of the disclosure. The at least one light sensing device62similarly defines a receiving cone associated therewith. The volume where each emitter cone overlaps with the receiving cone is defined as a sensing volume. For example a first sensing volume is defined between the first emitter cone and the receiving cone and a second sensing volume is defined between the second emitter cone and the receiving cone. The one or more light sensing devices62are configured to measure signals from the one or more light sources60within each sensing volume. In an embodiment, the one or more light sources60, and the one or more light sensing devices62may be packaged into a pre-formed assembly or module. In such embodiments, each module may be easily mountable as a whole to the inner sampling support34(shown inFIG. 4).

A processing device64, such as a printed circuit board containing signal conditioning circuits (not shown), analog to digital conversion circuits (not shown), microprocessor (not shown) and memory (not shown), is arranged in electrical communication with the detectors36, and specifically with at least one light source60and the at least one light sensing device62. In an embodiment, best shown inFIGS. 4 and 5, the one or more detectors36are connected with one or more wires31a,31bterminated with one or more connectors33a,33b. The connectors33a,33bare in turn attached to at least one processing electronics device64. Furthermore, the processing electronics device64may be powered by an internal battery (not shown) or externally, for example, by a fire panel70(FIG. 3) or other suitable source of electrical energy.

The purpose of the processing electronics device64is to supply power and control the operation of the detectors36, and to process the signals from the detectors36. In an embodiment, the processing device64is configured to control operation of the at least one light source60with regard to Off/On, varying light intensity (power or energy density), varying light wavelength, and/or varying pulse frequency. As an example, the processing device64may be used to alter a wavelength of the light beam emitted by a light source60in a controlled manner. Moreover, at each wavelength, the light intensity and/or pulse frequency can be varied in a controlled manner.

The processing device64typically includes a memory (not shown) capable of storing executable instructions. The executable instructions may be stored or organized in any manner and at any level of abstraction, such as in connection with one or more applications, processor, or routines, to analyze the signals detected by the plurality of sensors to make alarm decisions after preset threshold levels are reached according to the method described herein. In embodiments where the detector assembly30includes a plurality of detectors36, a single processing device64may be connected to the light source60and light sensing device62of multiple detectors36. Alternatively, a distinct processing device64may be associated with each detector36.

In an embodiment, the processing electronics device may be operable to communicate the processed data to another element of the detection system20, such as an indicator device for example. Examples of an indicator device include, but are not limited to, a local LED indicator43, a local indicator light ring45, a local display47, and/or a remote display72(FIG. 3) associated with the fire panel70, and/or other suitable remote displays or indicators (not shown). The information displayed may indicate a safe condition of a duct, for example by illuminating the LED indicator43or the indicator light ring45with a first color, such as green. Alternatively, the information displayed may be indicative of alarm or unsafe condition. In such instances, the LED indicator43or the indicator light ring45may be illuminated with a second color, for example red. Similarly, the information on the local or the remote display47,72may indicate the type of particles that have been detected. In an embodiment, a text message identifying the type of particles observed, such as ‘SMOKE’ or ‘PARTICULATES’ may be displayed. Further, in some embodiments, a concentration levels of the particles detected may also be displayed.

Referring now toFIG. 7, a method100of operating a detector36of the detector assembly30to monitor air quality and/or detect particles indicative of a hazardous condition, such as a fire for example, is illustrated. At block102, the processing device64communicates with at least one light source60such that light is transmitted therefrom, for example in an ultraviolet, infrared, or blue visible spectrum. The transmitted light is scattered by any airborne particles in the path of the transmitted light. The scattered light is received at one or more of the light sensing devices62of the detector36at block104. At block106, the processing device64is utilized to analyze the scattered light received at the light sensing devices62for the presence of one or more particles, such as smoke, gas, or other contaminants for example. In an embodiment, upon determining that one or more hazardous particles are present, the processing device64may transmit a signal to a building management system, fire panel70, and/or an input/output devices such as local LED indicator43, local light ring45, local display47and/or other remote devices to indicate the presence of the hazardous particles, and in some embodiments, the type of particle detected, as shown at block108.

In an embodiment, best shown inFIG. 8, a cleaning mechanism80may be mounted to an interior surface of the body38of the outer housing32in axial alignment with each detector36of the detector assembly30. The cleaning mechanism80may include a cloth-like material, bristles, or any other suitable mechanism configured to remove dust or debris from a surface via engagement with the surface. When the inner sampling support34is installed within the hollow interior40(FIG. 4) of the body38of the outer housing32, the inner sampling support34may be rotatable about a central axis X of the inner sampling support34and outer housing32. By rotating the inner sampling support34in a first direction about the axis X, the one or more detectors36are moved into engagement with the cleaning mechanism80. Accordingly, as the inner sampling support34rotates about the axis X relative to the outer housing32, the one or more light sources60and light sensing devices62of a detector36engage the cleaning mechanism80such that dust or other debris accumulated on the light sources60and light sensing devices62is removed. This rotation of the inner sampling support34may be performed manually, or alternatively, may be driven by an actuator M, for example in response to a signal from the processing device64. In an embodiment, the actuator M may initiate a cleaning operation (i.e. rotation of the inner sampling support34) in response to detection of a dust particle by the detector36. Alternatively, the actuator M may be controlled to automatically perform a cleaning operation on a schedule, such as a predefined number of hours, days, weeks, or months for example.

A detector assembly30as illustrated and described herein has a reduced likelihood of false alarms due to dust accumulation and condensation. Existing systems monitor a flow of air through the duct to determine whether one or more conditions is present. Because the detector assembly30is operable to detect a hazardous condition based on the presence of particles within the duct, rather than an airflow through the duct, the need to monitor and verify a pressure within the system is eliminated. Further, the detector assembly30may be formed by connecting multiple segments, each having a predefined length and number of detectors36associated therewith. As a result, the segments of a detector assembly30do not need to be uniquely fabricated for each application.