Abstract:
A recess-mounted detector assembly has a housing configured to be recess mounted in an opening of a structure located in a preselected zone. The housing has a base portion bounded by a sidewall portion to define an interior space having an open end. At least one detecting device is mounted in the interior space of the housing and is operable to detect a condition in an airstream in the preselected zone. A cover is configured for removable attachment at the opening of the structure and has at least one aperture therein for allowing an airflow of air from the airstream in the preselected zone into the interior space of the housing. An air inducing device is mounted in the interior space of the housing and is operable to induce the air flow in through the aperture of the cover from the preselected zone and into the interior space to allow the airflow to reach the detecting device to detect the condition in the airstream.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to detector assemblies and, more specifically, to a recessed detector assembly for monitoring confined spaces, such as rooms of a building or home, and detecting the presence of smoke, heat, gas, fire and the like. 
         [0003]    2. Background Information 
         [0004]    There have been proposed various types of detector assemblies which are detachably received into a mounted base installed to a wall or ceiling surface. Such detector assemblies incorporate a detecting device such as a fire or smoke detector that is designed to send an electric alarm signal upon sensing a fire or smoke condition to a central control center through a signal line routed within the ceiling. 
         [0005]    Detecting devices of this type are most commonly attached to inner surfaces of buildings such as walls and ceilings. Since smoke and hot air rise, the detecting devices are preferably matched to the ceiling. One type of such detecting devices is wired into a building&#39;s power supply in a non-interruptable connection. Another type of such detecting devices is battery powered and removably attached to the inner surface of the buildings to allow changing of the battery. Many present building codes require that the devices have dual power sources such as a hard wired connection and a battery for emergency power. In addition, several detectors per floor are required. 
         [0006]    In modern construction, it is generally preferable from an aesthetic viewpoint that internal building surfaces be free of obstructions and protrusions. To accomplish this goal, recessed fixtures have been developed both for new construction and retrofitting. Such fixtures include recessed and indirect lighting appliances and recessed speakers. 
         [0007]    Various assemblies have been proposed for installing a recessed detector device in a ceiling via a housing or junction box so that when installed, the detecting device is hidden from view. However, the structure of such existing assemblies imposes a severe limitation in that wiring operations for the detecting device cannot be done easily due to insufficient interior space afforded to the housing or junction box. As a result, installation and maintenance operations for such existing assemblies have been difficult, time consuming, and expensive to accomplish. Furthermore, such existing ceiling mounted detector assemblies have not been effective in providing adequate detection. 
         [0008]    Accordingly, there is a long-standing need for a recessed detector assembly that provides effective and adequate detection of a fire or smoke condition, that is easy to install and maintain and that, when installed, is completely hidden from view and provides an aesthetic structural appearance. 
       SUMMARY OF THE INVENTION 
       [0009]    It is an object of the present invention to provide a detector assembly that can be recessed in a ceiling, wall or other mounting surface in a building or other structure so that when installed, a cover for the recessed detector assembly is substantially flush with the surface and substantially completely conceals components of the recessed detector assembly so that the appearance of the mounting surface is aesthetically pleasing. 
         [0010]    Another object of the present invention is to provide a recessed detector assembly which is simple in construction and is easy to install and use. 
         [0011]    Another object of the present invention is to provide a recessed detector assembly that provides effective and adequate detection of a fire or smoke condition. 
         [0012]    Another object of the present invention is to provide a recessed detector assembly that improves the detection sensitivity of one or more detection devices of the recessed detector assembly. 
         [0013]    Another object of the present invention is to provide a recessed detector assembly that provides easy access to concealed components of the recessed detector assembly during installation and maintenance thereof. 
         [0014]    Still another object of the present invention is to provide a recessed detector assembly that is adapted for use in a variety of locations. 
         [0015]    Yet another object of the present invention is to provide a recessed detector assembly which is protected from vandalism and is substantially tamper-proof. 
         [0016]    Yet another object of the present invention is to provide a recessed detector assembly which can be used with existing detecting devices for detecting various conditions (e.g., fire, smoke, gas) in the airstream. 
         [0017]    The foregoing and other objects of the present invention are carried out by a recess-mounted detector assembly having a housing configured to be recess mounted in an opening of a structure located in a preselected zone. The housing has a base portion bounded by a sidewall portion to define an interior space having an open end. At least one detecting device is mounted in the interior space of the housing and is operable to detect a condition in an airstream in the preselected zone. A cover is configured for removable attachment at the opening of the structure and has at least one aperture therein for allowing an airflow of air from the airstream in the preselected zone into the interior space of the housing. At least one air inducing device is removably mounted in the interior space of the housing and is operable to induce the air flow in through the aperture of the cover from the preselected zone and into the interior space to allow the airflow to reach the detecting device to detect the condition in the airstream. A filter is preferably disposed between the detecting device and the air inducing device for filtering out impurities from the airflow reaching the detecting device to prevent a false detection by the detecting device of the condition in the airstream in the preselected zone. 
         [0018]    The at least one air inducing device preferably comprises a pair of air inducing devices removably mounted in the interior space of the housing. One of the air inducing devices operates as a primary air inducing device to induce the air flow and the other of the air inducing devices operates as an auxiliary air inducing device operable to induce the air flow when the primary air inducing device becomes non-operational. 
         [0019]    A base plate is pivotally connected to an inner surface of the sidewall portion of the housing. The base plate has a first main surface removably supporting the filter, a second main surface opposite the first main surface and removably supporting the air inducing unit, and an air opening extending from the first main surface to the second main surface and positioned between the filter and the air inducing unit so that the induced air flow passes through the air opening and the filter and reaches the detecting device. 
         [0020]    In another embodiment, a flexible conduit is configured to be connected between the open end of the housing and the opening of the structure for transporting the air flow passing through the aperture of the cover to the interior space of the housing. 
         [0021]    A recess-mounted detector assembly according to yet another embodiment has a housing configured to be recess-mounted in a recessed opening of a structure located in a preselected zone, the housing having a base portion bounded by a sidewall portion to define an interior space having an open end. At least one detecting device is removably mounted to an inside surface of the base portion of the housing for detecting a condition in an airstream in the preselected zone. A cover ring is removably attached to the open end of the housing. The cover ring has an aperture therein for allowing an airflow of air from the airstream in the preselected zone into the interior space of the housing. At least one air inducing device mounted in the interior space of the housing is operable to induce the air flow in through the aperture of the cover ring from the preselected zone and into the interior space to allow the airflow to reach the detecting device to detect the condition in the airstream. A filter is disposed between the detecting device and the air inducing device for filtering out impurities from the airflow reaching the detecting device to prevent a false detection by the detecting device of the condition in the airstream in the preselected zone. 
         [0022]    A base plate is pivotally connected to the inside surface of the sidewall portion of the housing. The base plate has a first main surface removably supporting the filter, a second main surface opposite the first main surface, and a plurality of air openings extending from the first main surface to the second main surface for passage therethrough of the induced air flow to reach the detecting device. A plurality of mounting brackets are removably attached to an inside surface of the sidewall portion of the housing. The mounting brackets separate the interior space of the housing into a plurality of separate and independent compartments, with a first one of the compartments containing the air inducing device. 
         [0023]    The base plate and the base portion of the housing form a compartment that is separate and independent from the plurality of compartments and that contains the detecting device and the filter. Optionally, a light device is disposed in a second one of the plurality of compartments and is removably attached to one of the mounting brackets disposed closer to the cover ring than the other of the plurality of mounting brackets. 
         [0024]    Preferably, the at least one air inducing device comprises a pair of air inducing devices removably attached to different ones of the mounting brackets and disposed in different ones of the plurality of compartments not corresponding to the first compartment. One of the air inducing devices operates as a primary air inducing device to induce the air flow and the other of the air inducing devices operates as auxiliary air inducing device operable to induce the air flow when the primary air inducing device becomes non-operational. The detecting device and the pair of inducing devices are preferably aligned in a vertical direction of the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown. In the drawings: 
           [0026]      FIG. 1A  is a front view of a recessed detector assembly according the present invention as it appears installed in a ceiling; 
           [0027]      FIG. 1B  is a front view of a modified version of the recessed detector assembly shown in  FIG. 1A ; 
           [0028]      FIG. 2  is a partial sectional view of a recessed detector assembly according to a first embodiment of the present invention; 
           [0029]      FIG. 3  is a partial sectional view of the recessed detector assembly shown in  FIG. 2  with the grill removed and the base plate in a pivoted (open) condition; 
           [0030]      FIG. 4  is a partial sectional view of a recessed detector assembly according to a second embodiment of the present invention; and 
           [0031]      FIG. 5  is a partial sectional view of a recessed detector assembly according to a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    While this invention is susceptible of embodiments in many different forms, this specification and the accompanying drawings disclose only some forms as examples of the use of the invention. The invention is not intended to be limited to the embodiments so described, and the scope of the invention will be pointed out in the appended claims. 
         [0033]    For the purposes of this application, the term “detecting device” means a device which detects one or more prescribed conditions of the atmosphere in the vicinity of the device, such as, without limitation, smoke, fire, heat, temperature, gases and particulate matter, and upon such detection produces a signal such as an audible and/or visual alarm. In some circumstances such a detecting device may also activate other equipment to extinguish the fire detected such as sprinklers or extinguishers. Common names of such detecting devices include smoke detector, fire alarm, thermal sensor, ionization detector, carbon monoxide detector, photoelectric detector, activator and the like. 
         [0034]    It is understood that the recessed detector assembly of the present invention is adapted for use in a variety of locations and structures, including residential, commercial, and industrial buildings and transportation vehicles. For example, the recessed detector assembly is suitable for mounting to the fuselage of an aircraft for detecting a fire or smoke condition in the aircraft. 
         [0035]    Although the recessed detector assembly of the present invention is shown and described mounted to a ceiling, it is understood that the recessed detector assembly can be mounted to other structures, including walls, columns and cabinets, and with various types of surfaces (e.g., flat and non-flat surfaces). 
         [0036]    Certain terminology is used in the following description for convenience only and is not intended to be limiting. The words front, rear, upper, lower, behind, horizontal, and outwardly designate directions in the drawing to which reference is made. Such terminology includes the words above specifically mentioned and words of similar import. 
         [0037]    Referring now to the drawings in detail, wherein like numerals are used to indicate like elements throughout, there is shown in  FIGS. 1A-1B  and  2 - 5  embodiments of a recessed detector assembly, generally designated at  10 , according to the present invention.  FIGS. 1A-1B  are front views of two examples of the recessed detector assembly  10  as they appear installed in a mounting surface, such as a ceiling C. It will be appreciated that, when installed in the ceiling C, the detector assembly  10  is completely hidden from view with the exception of a removable cover  35 , provided with apertures or perforations  35   a , which is substantially flush with the surface of the ceiling C and is intended to substantially completely conceal the remaining structure and other components of the detector assembly  10 , including one or more detection devices that are mounted inside of the detector assembly as further described below. Because the detector assembly  10  is recessed, and the removable cover  35  is flush with the ceiling C, the appearance of the ceiling C is aesthetically pleasing. 
         [0038]    A first embodiment of the detector assembly  10  according to the present invention is shown in  FIGS. 2-3  which are sectional views of the detector assembly  10  installed in a ceiling C.  FIG. 2  shows the state of the detector assembly  10  during use, and  FIG. 3  shows a state of the detector assembly in which the cover  35  has been removed and a base plate  25  is pivoted downwardly, as further described below, to enable access to the interior of the detector assembly  10 , such as during repair or maintenance of the detector assembly  10 . It will be appreciated that the detector assembly  10  is configured to be installed in an opening in the ceiling C, rather than attached to the exterior surface of the ceiling C. 
         [0039]    As shown in  FIGS. 2-3 , the detector assembly  10  comprises a housing or container  12  composed of plastic or other non-metallic material. The housing  12  has a closed rear (base) portion  13  bounded by a sidewall portion  14  that terminates at its front end in an outwardly extending flange  15  for attachment of the detector assembly  10  to the ceiling C. The front portion of the housing  12  is open. A movable support portion  38  is provided at the inner surface of the sidewall portion  14  (i.e., on the left side of the sidewall  14  as shown in  FIGS. 2-3 ) for supporting a base plate  25  as further described below. The rear portion  13  and sidewall portion  14  form an interior space  12   a  of the housing  12 . 
         [0040]    To the inside surface of the rear portion  13  are mounted two or more detecting devices, such as a smoke detector  18  and a heat detector  20 . Though not shown, a gas detector (e.g., carbon monoxide detector), or a fire detector may also be mounted in the housing  12 , or any combination of these or other detectors may be used. The detectors  18 ,  20 , etc. are preferably removably mounted to the inside surface of the rear portion  13  so that they may be serviced, replaced or exchanged with other detectors. The smoke detector  18  and the heat detector  20  are hard-wired to a controller (not shown) through wiring  22  that extends through a grommet  23  in the sidewall portion  14  of the housing. Alternatively, a battery can be used to power the detectors or the battery can be provided for back up purposes. While two detectors  18 ,  20  are shown in this embodiment, it will be understood that number of detectors may be one (as shown in the embodiment of  FIG. 4 , for example) or more than two. 
         [0041]    The base plate  25  is composed of plastic or other non-metallic material and has opposite first and second ends  25   a ,  25   b . The base plate  25  is pivotally connected at the first end  25   a  to the inner surface of the sidewall portion  14  (i.e., the right sidewall portion  14  as shown in  FIGS. 2-3 ) by means of a hinge  26  or the like. The second end  25   b  of the base plate  25  is configured to generally rest and be supported by the movable support portion  38  of the housing  12  so that the base plate is maintained in the position shown in  FIG. 2 . The sidewall portion  14  is provided with the support portion  38  which is preferably in the form of a cut-out that is bent inwardly to form a ledge on which the second end  25   b  of the base plate  25  rests. 
         [0042]    To pivot the base plate  25  downwardly (i.e., to an open position) from its normal (i.e., closed) position shown in  FIG. 2 , the cut-out  38  is simply pushed outwardly so that the distal end of the base plate  25  clears the ledge. Similarly, to return the base plate  25  to its normal position, the base plate  25  is pivoted upwardly until the second end  25   b  thereof pushes the ledge outwardly, after which the cut-out  38  flexes inwardly to again engage the underside of the base plate  25 . It will be appreciated that structures other than the cut-out  38  are suitable for supporting the second end  25   b  of the base plate  25  without departing from the spirit and scope of the invention. 
         [0043]    The removable cover  35  is removably attached to the open front portion of the housing  12 . The cover  35  is formed of plastic or other non-metallic material and is provided with the apertures or perforations  35   a  to permit the flow of air through the cover into the interior of the housing  12 . By way of example, the cover may have an upstanding flexible annular rim  36  that can be snap-fit into the front opening of the housing  12 . As shown in  FIGS. 1A-1B  and  2 , when the cover  35  is mounted in place, it lies flush with the ceiling C thereby creating an aesthetically pleasing appearance. The cover  35  may have any desired shape and color to match the decor of the room. A grill-like cover or any other similar device is suitable as the cover  35 , and the apertures or perforations  35   a  are dimensioned to keep foreign objects from entering the interior of the housing  12  while allowing the passage of air flow therethrough.  FIG. 1A  shows an example of the grill-like cover  35  in which the apertures  35   a  are circular-shaped.  FIG. 1B  shows another example of the grill-like cover  35  in which the apertures  35   a  are in the form of horizontal slits. Other forms of the apertures (e.g., vertical slits; non-circular apertures) are also suitable for the grill-like cover  35 . 
         [0044]    A pair of low-voltage fans  28 ,  28  are powered by respective fan motors (not shown) and are removably attached to the front face of the base plate  25  by screws  24  or the like. The base plate  25  is provided with air openings  29 ,  29  located behind the fans  28 ,  28 , and the housing  12  is provided with air openings  30  in the rear portion  13 . The fans  28 ,  28  are also hard-wired to the controller through wiring (not shown) for connection to an external source of electrical power (not shown). Preferably, a battery back-up power supply is provided for powering the fans  28 ,  28  (and the detectors) in the event of an electrical power failure. Alternatively, a battery can be used to power the fans instead of being hard-wired. 
         [0045]    The fans  28 ,  28  are preferably low-volume fans capable of creating a flow of air (denoted by arrows in  FIG. 2 ) through the housing  12  by pulling ambient air from the zone corresponding to the location of the ceiling C in which the detector assembly  10  is mounted and into the housing  12  via the apertures or perforations  35   a  of the cover  35  which functions as an air intake grill. Thus each of the fans  28  corresponds to a device defining means for inducing an air flow inwardly through the intake grill  35  into the housing  12 . By mounting the detectors  18 ,  20  to the inner surface of the rear portion  13  of the housing  12  provided with the air openings  30 , the airflow generated by the fans  28 ,  28  is directed toward the detectors  18 ,  20 , thereby reducing the time required for the fans  28 ,  28  to detect combustion products, including hot fluids (e.g., gas, smoke). 
         [0046]    Each of the fans  28 ,  28  is preferably coupled to a relay (not shown) which will shut-off the fan when at least one of the detectors is activated (e.g., triggering the activation of an audible alarm) by the detection of a corresponding combustion product. This will prevent circulation of the combustion product (e.g., gas, smoke) by the fan after detection by the detectors. Each of the fans  28 ,  28  is also preferably coupled to a flow sensor (not shown) which senses the presence of airflow through the housing  12  and thereby determines if an adequate flowrate is created by the fan. It will be appreciated that only one of the fans  28  is required to be driven to achieve the purpose and objectives of the invention described herein. The other of the fans  28  is an auxiliary fan which will be activated automatically by the controller should the driven fan become non-operational. 
         [0047]    An air filter  32  is removably connected, such as by clips, to the rear face of the base plate  25 . The purpose of the air filter  32  is to filter out impurities (e.g., non-smoke impurities) from the flow of air or airstream generated by the fans  28 ,  28  and entering the housing  12 . The filtered impurities may be substances that provide a false detection of a specific combustion product (e.g., gas, smoke) to be detected by the detectors. 
         [0048]    In a modification to the first embodiment, instead of connection to the base plate  25 , the air filter  32  may be positioned so as to rest directly on an inside surface (i.e., the surface facing the interior of the housing  12 ) of the cover  35 . In yet a further modification, a separate air filter  32  may be associated with each of the detectors, such as by mounting the air filters directly on air intake surfaces of the respective detectors. These modified configurations would also achieve filtering out of the impurities from the airstream prior to the airstream being detected by the detectors. 
         [0049]    During use, the detectors  18  and  20  and the fans  28 ,  28  are electrically connected to the controller. One of the fans  28  is driven to gently draw air (denoted by arrows in  FIG. 2 ) upwardly through the perforations  35   a  in the cover  35  into the housing  12  and through the air opening  29  to circulate around the detectors  18  and  20 . The circulating air then exits the housing  12  through the air openings  30 . Should an abnormal level of a combustion product (e.g., gas, smoke) be detected, the appropriate detector will be activated and an audible alarm generated. The controller will also notify a central office of the detected abnormality. Should the driven fan become non-operational, the other fan  28  will be activated automatically by the controller. 
         [0050]    In order to service, replace or exchange the detectors  18  and  20 , or to service or replace the fans  28 ,  28 , the cover  35  is removed after which the base plate  25  is pivoted downwardly as described above and shown in  FIG. 3 . This enables ready access to the detectors  18  and  20 . In addition, this enables the air filter  32  to be cleaned and/or replaced and enables ready access to the fans  28 ,  28 . 
         [0051]    It will be appreciated that the ready access to the detectors  18  and  20 , fans  28 ,  28 , and filter  32  described above is greatly facilitated by the compartmentalized structure of the detector assembly  10  of the present invention. More specifically, when in the normal (i.e., closed) position shown in  FIG. 2 , the base plate  25  divides the interior space  12   a  of the housing  12  into an upper (first) compartment  40  and a lower (second) compartment  50 . The upper compartment  40  contains or houses the filter  32  and the detectors  18 ,  20 . The lower compartment  50  contains or houses the fans  28 ,  28  and includes the open front portion of the housing  12  which is closed by the cover  35 . By this compartmentalized construction, access to the interior space  12   a  of the detector assembly  10  is facilitated. For example, since the fans  28 ,  28  in the lower compartment  50  can be accessed by simply removing the cover  35  and without the necessity of pivoting the base plate  25 , damage to the detectors  18 ,  20  is prevented when replacing or maintaining the fans  28 ,  28 . Furthermore, access to the detectors  18 ,  20  in the upper compartment  40  is accomplished by simply pivoting the base plate  25  as described above. 
         [0052]      FIG. 4  shows a second embodiment of the recessed detector assembly  10  according to the present invention that is configured to be installed (i.e., recessed) in an opening in a wall or ceiling C as described above for the first embodiment in  FIGS. 2-3 . The material and general structure of the housing  12  in the second embodiment is the same as described above for the first embodiment, with the same reference numerals being used to designate similar structure, and structural differences in the housing  12  and other components between the first and second embodiments are as set forth below. 
         [0053]    In the second embodiment, the housing  12  has a compartmentalized construction with five compartments denoted with reference numerals  60 - 100 , and is configured for supporting a single detector  110  which may be a smoke detector, a heat detector, a gas detector (e.g., carbon monoxide detector), a fire detector or the like as described above for the first embodiment. The detector  110  is mounted to the inside surface of the rear portion  13  of the housing  12 . It is understood, however, that the housing  12  of the second embodiment may be configured to support two or more of these types of detectors. The detector assembly  10  of the second embodiment also includes an air filter  32 , and two (first and second) low-voltage fans  28 ,  28  which are hard-wired to a controller (not shown) through wirings  22  that extend through a grommet  23  in the sidewall portion  14  of the housing  12 . The construction and features of the filter  32  and fans  28 ,  28  are as described above for the recessed detector assembly  10  of the first embodiment. 
         [0054]    In the second embodiment, the filter  32  is removably connected, such as by clips, to the rear face of a base plate  25  provided with air openings  29  and which otherwise has the same construction as the base plate  25  described above with respect to the first embodiment shown in  FIGS. 2-3 . The base plate  25  is also pivotally connected to the inner surface of the sidewall portion  14  of the housing  12  by means of a hinge  26  or the like and rests on a ledge  38  of the sidewall portion  14  as described above for the first embodiment of  FIGS. 2-3 . 
         [0055]    The recessed detector assembly  10  of the second embodiment includes a low-voltage light unit  120 , such as an LED light unit, that is mounted in the housing  12  forwardly (i.e., in a direction towards the front portion of the housing  12 ) of the fans  28 ,  28 . The low-voltage light unit  120  is also hard-wired to the controller through wiring  22 . It will be appreciated that the low-voltage light unit  120  is an optional feature for the recessed detector assembly  10  and that the purposes and advantages of the invention described herein are achieved with or without the incorporation of the low-voltage light unit  120 . 
         [0056]    The fans  28 ,  28  and light unit  120  are mounted in the housing  12  via mounting brackets  150 ,  160 ,  170  which are in the form of elongated mounting bars. The fans  28 ,  28  and the light unit  120  are removably attached to front faces of the mounting brackets  150 - 170 , respectively, by screws or other removable fastener. In this embodiment, each of the mounting brackets  150 ,  160 ,  170  is removably connected to a seat or ledge  14   a  formed on the inner surface of the sidewall portion  14  by screws or the like. It is understood, however, that other forms of connection are suitable for removably connecting the mounting brackets  150 ,  160 ,  170  to the sidewall portion  14 . For example, opposite end portions of each of the mounting brackets  150 ,  160 ,  170  may be clipped into respective holes formed in the sidewall portion  14 . It is understood that the air filter  32  may be alternatively positioned so as to rest directly on the mounting bracket  170 , or multiple air filters  32  may be positioned so as to rest on the respective mounting brackets  150 - 170 . Likewise, a separate air filter  32  may be associated with each of the detectors, such as by mounting the air filters directly on air intake surfaces of the respective detectors, as described above with respect to the first embodiment of the detector assembly. 
         [0057]    In the second embodiment shown in  FIG. 4  only one mounting bracket is used to removably mount each of the fans  28 ,  28  and the light device  120  to the sidewall portion  14  of the housing  12 . In a modification to the second embodiment, a second (i.e., an additional mounting bracket) mounting bracket is used to removably mount each of these components to the sidewall portion  14 . More specifically, for each of these components, the second mounting bracket is connected to the sidewall portion  14  in spaced-apart, coplanar relation to the other corresponding mounting bracket. For example, in  FIG. 4  the second mounting bracket for each component would be positioned directly behind (i.e., in the direction into the page of  FIG. 4 ) the corresponding mounting bracket shown. The second mounting bracket for each of the components would be removably connected to a corresponding seat or ledge formed on the inner surface of the sidewall portion  14  in the same manner as shown in  FIG. 4  for the mounting brackets  150 ,  160 ,  170 . 
         [0058]    A cover ring  180  is removably attached to the open front end of the housing  12 . The cover ring is composed of plastic or other non-metallic material and, by way of example, has upstanding flexible portions  182  that can be snap-fit into the front opening of the housing  12 . The cover ring  180  has an opening  184  which is disposed generally directly below the light device  120  when the cover ring  180  is attached to the housing  12  as shown in  FIG. 4 . Thus, when installed in an opening in a wall or ceiling, the cover ring  180  will substantially completely conceal (i.e., when viewing the installed recessed detector assembly directly into the opening  184  of the cover ring  180 ) the components (e.g., mounting brackets, fans, filter, detector) mounted inside of the housing  12 , except for the light device  120  which is disposed generally directly above the opening  184  of the cover ring  180 . Since generally only the light device  120  can be viewed through the opening  184  of the cover ring  180 , the recessed detector assembly  10  creates the appearance of a light fixture. Furthermore, when the cover ring  180  is mounted in place, it lies flush with the ceiling or wall. It will be appreciated that this structural configuration creates an aesthetically pleasing appearance for the recessed detector assembly  10 . 
         [0059]    During use of the recessed detector assembly according to the second embodiment, the detector  110 , the fans  28 ,  28 , and the light device  120  are electrically connected to the controller. One of the fans  28  is driven to gently draw air (denoted by arrows in  FIG. 4 ) upwardly through the opening  184  of the cover ring  180  into the housing, around the mounting brackets  150 ,  160 ,  170 , through air openings  29  of the base plate  25  and through the filter  32  to circulate around the detector  110 . The circulating air then exits the housing  12  through the air openings  30 . Should an abnormal level of a combustion product (e.g., gas, smoke) be detected, the detector  110  will be activated and an audible alarm generated. The controller will also notify a central office of the detected abnormality. Should the driven fan become non-operational, the other fan  28  will be activated automatically by the controller. 
         [0060]    In order to service, replace, exchange and/or clean the filter  32  and/or the detector  110 , or to service or replace the fans  28 ,  28 , the cover ring  180  is removed after which the mounting bracket  170  is disconnected from the sidewall portion  14  of the housing to provide access to the fan  28  directly above the light device  120 . To access the other fan  28  and the base plate  25 , the brackets  160  and  170  are sequentially disconnected from the sidewall portion  14 . To access the filter  32 , the base plate  25  is pivoted downwardly as described above and shown for the first embodiment of  FIG. 3 . This also enables ready access to the detector  110 . 
         [0061]    It will be appreciated that the ready access to the detector  110 , filter  32  and fans  28 ,  28  described above is greatly facilitated by the compartmentalized structure of the detector assembly  10  according to the second embodiment. More specifically, when in the normal (i.e., closed) position shown in  FIG. 4 : the cover ring  180 , mounting bracket  170  and sidewall portion  14  form the first compartment  60  containing the light device  120 ; the mounting brackets  160 ,  170  and sidewall portion  14  form the second compartment  70  containing the first fan  28 ; the mounting brackets  150 ,  160  and sidewall portion  14  form the third compartment  80  containing the second fan  28 ; the base plate  25 , mounting bracket  150  and sidewall portion  14  form the fourth compartment  90 ; and the rear portion of the housing  13  and base plate  25  form the fifth compartment  100  containing the filter  32  and the detector  110 . By this compartmentalized construction, access to the interior space  12   a  of the detector assembly  10  for maintenance and/or repair of the light device  120 , fans  28 ,  28 , filter  32  and detector  110  is facilitated. 
         [0062]      FIG. 5  shows a third embodiment of the recessed detector assembly  10  according to the present invention that is configured to be installed (i.e., recessed) in an opening in a wall or ceiling C as described above for the first embodiment in  FIGS. 2-3 . All of the components of the recessed detector  10  in the third embodiment are the same as those described above for the first embodiment of  FIGS. 2-3 , except for the provision of a flexible duct or conduit  200  as described below. 
         [0063]    In the third embodiment, the flexible conduit  200  of the recessed detector assembly  10 , which is made of a plastic or other non-metallic material, is removably connected by screws or other removable fastener to the housing  12  and the ceiling C. More specifically, an upper portion of the conduit  200  is connected to the outwardly extending flange  15  of the ceiling C, and a lower portion of the conduit  200  is connected to the ceiling C. The cover  35  is snap-fit into an opening C 1  of the ceiling C so that the conduit  200  extends between the cover  35  and the housing  12 . 
         [0064]    The recessed detector assembly  10  of the third embodiment is particularly adapted for use in locations which lack sufficient space directly near the opening of the wall or ceiling of the structure in which the detector assembly is to be mounted. With the conduit  200 , this configuration permits detection of a condition (e.g., fire, smoke, etc.) in the airstream of a particular zone with limited space in the wall or ceiling while permitting the housing  12  with the detectors  18 ,  20  and fans  28 ,  28  to be mounted at a location in the ceiling or wall which can accommodate the same. 
         [0065]    For example, the third embodiment of the recessed detector assembly is well adapted for installation to the fuselage above the ceiling of the passenger and/or cargo compartment of various types of aircraft. Due to the limited space in-the ceiling of an aircraft fuselage, the housing  12  containing the fans  28 ,  28 , filter  32 , and detectors  18 ,  20  is mounted in the ceiling at a first location of the fuselage which can accommodate the housing  12 . The cover  35  is mounted into an opening of the ceiling at a second location of the fuselage with limited space which corresponds to the zone for which detection of the condition of the airstream is desired. The conduit  200 , which is connected between the housing  12  and the cover  35 , provides a means for transporting air (e.g., denoted by arrows in  FIG. 5 ) which is drawn by the fans  28 ,  28  upwardly through the openings  35   a  of the cover  35  (at the second location of the fuselage) into the housing  12  (at the first location of the fuselage). It will be appreciated that since the fans  28 ,  28  provide a means for inducing an air flow in through the intake grill  35  into the housing  12  via the conduit  200 , there is no need to couple the housing and/or the conduit  200  to the aircraft vent system or the like for the purpose of directing a flow of air to the detectors  18 ,  20 . 
         [0066]    In a modification to the third embodiment, instead of connection to the base plate  25 , the air filter  32  may be positioned so as to rest directly on an inside surface (i.e., the surface facing the interior of the housing  12 ) of the cover  35 . In yet a further modification, a separate air filter  32  may be associated with each of the detectors, such as by mounting the air filters directly on air intake surfaces of the respective detectors. These modified configurations would also achieve filtering out of the impurities from the airstream prior to the airstream being detected by the detectors. 
         [0067]    The remaining features and operation of the recessed detector assembly  10  according to the third embodiment are the same as described above for the first embodiment of  FIGS. 2-3 . It will be understood that the recessed detector assembly  10  according to the third embodiment is also adapted for use in connection with transportation devices other than aircraft, such as various types of spacecraft, trains, buses and other forms of transportation. 
         [0068]    In each of the foregoing embodiments of the recessed detector assembly, the wirings of the detectors, fans and light unit extend from the interior of the housing through an opening formed in the sidewall portion of the housing via a grommet and are wired to the corresponding alarm, power and relay controllers. In a preferred modification to these embodiments, the grommet may be replaced with a splice box or the like that is mounted on the sidewall portion of the housing to facilitate connection (i.e., plug-in) and disconnection (i.e., to and from the corresponding alarm, power and relay controllers) of the detectors, fans and light unit from the interior of the housing. By way of example, the splice box may be in the form of a telephone-type plate mounted on the sidewall portion of the housing and provided with connection screws on opposite surfaces of the plate (i.e., the surfaces facing the respective interior and exterior of the housing) for connection thereto of the detector, fan and light unit wirings and wirings from the plate to the corresponding alarm, power and relay controllers. By this construction, the splice box allows for quick connection and disconnection of the detector, fan and light unit wirings (i.e., from the corresponding alarm, power and relay controllers) from the interior of the housing during installation and maintenance of the detector assembly. 
         [0069]    It is understood that other forms of the splice box are suitable for achieving the quick connect and disconnect feature of the detector, fan and light unit wirings from the corresponding alarm, power and relay controllers. For example, instead of connection screws, the opposite surfaces of telephone-type plate may be provided with connection jacks, and the wirings for the detector, fan and light unit and the corresponding alarm, power and relay controllers may be provided with connection clips for quick connection/disconnection to the corresponding connection jacks of the plate. It is also understood that, in addition to or alternative to the splice box, and for the purpose of achieving the foregoing quick connect and disconnect feature, the ends of the wirings that connect to the corresponding detector, fan and light unit may also be provided with a quick connect/disconnect connector (e.g., pin, screw, or clip connector) so that these components may be quickly connected and disconnected from the corresponding alarm, power and relay controllers directly from these components and from the interior of the housing. 
         [0070]    Thus the present invention provides a recessed detector assembly that can be recessed in a ceiling, wall or other mounting surface in a building, transportation vehicle, or other structure so that when installed, a cover for the recessed detector assembly is substantially flush with the mounting surface and substantially completely conceals components (e.g., detectors, filter, fans) of the recessed detector assembly so that the appearance of the mounting surface is aesthetically pleasing. The structure of the recessed detector assembly provides easy access to the concealed components during installation and maintenance thereof, such as the pivotal base plate that can be pivoted downwardly to enable access to the air filter and detector(s) (first-third embodiments) and the fans (first and third embodiments) for removal, maintenance and/or repair of the same. 
         [0071]    The recessed detector assemblies of the present invention is simple in construction and is easy to install and use, can be used with existing detectors (e.g., smoke, gas, fire detectors), is adapted for use in a variety of locations (e.g., including locations with limited space), and provides effective and adequate detection of various conditions (e.g., fire, gas, smoke) in the airstream of the zone desired to be detected by the detectors. 
         [0072]    Moreover, the recessed detector assemblies according to the present invention are substantially tamper-proof. In this regard, the recessed detector assemblies of the first ( FIGS. 2-3 ) and third ( FIG. 5 ) embodiments include the cover  35  as shown in  FIGS. 1A  or  1 B which substantially completely conceals the fans  28 ,  28  and detectors  18 ,  20  that may invite tampering (e.g., the cover  35  creates the appearance that the recessed detector assembly is only a ventilation duct). The recessed detector assembly of the second ( FIG. 4 ) embodiment includes the cover ring  180  which also substantially completely conceals the fans  28 ,  28  and detector  110  that may invite tampering (e.g., the cover ring  180  only permits the light device  120  to be viewed, thereby creating the appearance that the recessed detector assembly is merely a light fixture, such as a high hat-type light fixture). Thus the recessed detector assemblies according to the present invention are substantially protected from vandalism. 
         [0073]    From the foregoing description, it can be seen that the present invention comprises an improved recessed detector assembly. It will be appreciated by those skilled in the art that obvious changes can be made to the embodiments described in the foregoing description without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover all obvious modifications thereof which are within the scope and the spirit of the invention as defined by the appended claims.