Abstract:
A duct detector housing includes a housing cover and a housing body defining a midline between the center of a detector and a printed circuit board within said body. Gas inlet and outlets are off axis of the midline to allow water that collects in conventional housing to drain from the housing. A maintenance mode button associated with a duct detector housing cover that is secured to a housing body of the housing provides a preselected time period during which removal of the cover is independent of a cover removal alarm. A printed circuit board within the housing has dedicated terminal blocks providing grouped connections with each of the groups segregated from another. An improved duct detector terminal has a hole in the terminal adapted to receive a test meter probe therethrough to provide an electrical contact between the wire.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 12/109,860 filed Apr. 25, 2008, the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention in general relates to an air handling detector housing, and in particular to a housing having components facilitating prolonged detector fail safe operation and efficient detector testing. 
     BACKGROUND OF THE INVENTION 
     Air handling duct systems are routinely fitted with air quality detectors such as smoke detectors or carbon monoxide detectors so as to detect an air quality problem and the resulting hazard before the gas is further distributed by the air handling system. Such detectors are routinely placed within a housing receiving inlet sample gas from an air handling system conduit and an outlet exhaust from which air handling system gas is returned to the same or different conduit of the air handling system so as to create a swirling flow pressure differential of air handling system gas around the detector within the housing. Such detectors are periodically tested to assure that a detector properly samples and signals an alarm in response to exposure to a target level of gas or activation of a test circuit. 
     A conventional air handling duct detector housing has a number of limitations that complicate testing and assured operation of a detector contained therein. A representative prior art air handling duct detector housing is provided in  FIG. 1 . A conventional housing has a body including midline inlet I and outlet O apertures along line M-M′ for air to pass therethrough and a cover C that is often transparent that secures to the housing body by way of threaded fasteners F. The housing volume is proportioned and divided to accommodate a given detector D and related printed circuit boards P and electronics needed for coupling to a relay board, providing various normal, alarm, and trouble output signals and the like. The configuration of the air inlet and outlet apertures in communication with an air duct are routinely positioned midline within the housing as shown in  FIG. 1 . When moisture-laden air is conveyed through the air handling system, or alternatively the housing is at a lower temperature than the inlet air, condensation tends to collect within the housing. Under prolonged condensation conditions, water can accumulate in the housing to the midline of the housing resulting in active detector elements for electronic components being submerged in water resulting in emergency service to avoid component failure. Additionally, the seal line at the interface between the housing body and cover, while providing a generally waterproof seal, provides an inadequate bather against vapor and the thermocycling associated with outdoor placement and as such a detector housing of  FIG. 1  is limited to indoor placement. Still another limitation found in a conventional prior art housing is reliance on multiple threaded fasteners to provide a gradual tightening of the cover to the housing body. As a result a loose cover placement will not signal a warning and inhibit proper operation of a detector system. The simultaneous operation of a screwdriver to drive threaded fasteners while holding already removed fasteners, stabilizing the cover all while often balancing on a ladder also leads to inefficient servicing, unpredictable alarm operation and a falling hazard. 
     In view of the limitations found in a conventional prior art housing, there exists a need for an air handling system duct detector housing that is less vulnerable to detector failure through water egress and provides assured repeatability of sealing. There also exists a need for a detector housing that expedites detector testing and servicing and assures proper alarm operation. 
     SUMMARY OF THE INVENTION 
     A duct detector housing includes a housing cover and a housing body defining a midline between the center of a detector and a printed circuit board within the body. The housing body has a gas inlet and a gas outlet in fluid communication therewith. The gas inlet in fluid communication with a gas duct. The gas inlet and the gas outlet are off axis of the midline to allow water that collects in conventional housing to drain from the housing regardless of mounting orientation when the water reaches the level of either the inlet or outlet. 
     A process for testing a detector mounted within a duct housing sampling a forced air duct includes providing a maintenance mode button associated with a duct detector housing cover that is secured to a housing body of the housing and containing the detector therein. The maintenance mode button is activated to provide a preselected time period during which removal of the cover is independent of a cover removal alarm. The cover is then removed, the internal detector tested and the cover replaced without a spurious alarm signal being recorded. 
     A duct detector housing includes a housing cover and a housing body having a gas inlet and a gas outlet with the gas inlet in fluid communication with a gas duct and complementary to the cover to form an interface therebetween. The housing encompasses a detector and a printed circuit board within the housing body. The printed circuit board has dedicated terminal blocks providing grouped connections of at least fire alarm connections, detector interconnect connections remote access connections, HVAC connections and inlet power connections with each of the groups segregated from another. 
     An improved duct detector terminal including a wire entering a terminal and a clamping lever that engages the wire through a clamping mechanism has the improvement of a hole in the terminal adapted to receive a test meter probe therethrough to provide an electrical contact between the wire and a test meter without resort to disengaging the wire through operation of the lever. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a prior art detector housing; 
         FIG. 2  is a plan view of an inventive detector housing; 
         FIG. 3  is a partial cutaway view of the housing of  FIG. 2  depicting a single latch binary securement depicted in an open position; 
         FIG. 4  is a perspective magnified view of a slide binary securement apparatus herein; 
         FIG. 5  is a cross-sectional magnified view of a bayonet binary securement operative herein; 
         FIG. 6  is a plan view of the inventive housing of  FIG. 2  with a housing cover hanging tethered to a housing body; 
         FIG. 7A  is an exploded, partial cutaway, perspective view of the housing of  FIG. 2  depicting an inventive cover sealing system; 
         FIG. 7B  is a magnified cross section of an inventive gasket closure in relation to a simultaneously contacting cover lip and housing extending wall surface of  FIG. 7A ; 
         FIG. 8  is a plan view of a housing body of an inventive detector housing in a separated cover and housing relationship with a tether retaining the cover in proximity to the housing; 
         FIGS. 8A-8D  are a schematic of water level management obtained through an inventive housing body of  FIG. 6  regardless of mounting orientation; 
         FIG. 9  is an inventive layout for a duct detector printed circuit board; 
         FIG. 10A  is a perspective view of a conventional prior art node to a wiring terminal; and 
         FIG. 10B  is a perspective view of an inventive node to a wiring terminal including a test meter probe hole. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An inventive duct detector housing provides numerous improvements over the prior art housings as embodied in  FIG. 1  with these improvements alone or in combination rendering more efficient the testing and maintenance of a detector enclosed within such a housing. The aspects of the present invention will be further detailed with respect to the following figures. 
     Referring now to  FIGS. 2-9 , an inventive housing is shown generally at  10 . The housing  10  has a housing body  12  having an inlet  14  and an outlet  16 . The inlet  14  is in fluid communication with an air flow through which air or any other flowing gas enters the housing  10  and into contact with a detector D energized and residing within a detector volume  18 . The detector volume  18  is defined by the cavity formed within the housing body  12  upon mating with a complementary housing cover  20 . The housing body  12  is formed from a variety of materials illustratively including steel, aluminum, thermoset resins, and thermoplastics. Preferably, the housing body  14  is formed of injection moldable thermoplastic such as Bayer Machrolon. The housing body  12  preferably includes a flange  22  adapted to pass a mechanical fastener therethrough so as to secure housing body  12  to a substrate. Typical substrates for mounting an inventive housing  10  are surfaces such as walls and air ducts. While it is conventional to position an inlet and outlet along a midline of the housing body per  FIG. 1 , preferably an inlet  14  and outlet  16  in a housing body  12  according to the present invention are positioned such that at least one of the inlet  14  or outlet  16  is positioned proximal to a bottom edge based on mounting orientation of an inventive housing  10  to a vertical substrate. As a result of at least one of the inlet  14  or outlet  16  being positioned proximal to the bottom edge of the housing  10  as mounted, condensation introduced into the housing detector volume  18  drains back through the bottom edge proximal inlet  14  or outlet  16  so as to preclude condensation water levels rising within the housing detector volume  18  to a level that impairs function or induces malfunction of the detector D housed within the volume  18 . To facilitate joinder of inlet  14  and outlet  16  to tubing in fluid communication with an air duct, the portion of the inlet  14  and outlet  16  within the housing detector chamber  28  are preferably notched and have a securement as detailed in U.S. Pat. No. 7,204,822. More preferably, the inlet  14  and the outlet  16  are positioned diametrically relative to a central detector D so as to maintain conventional convection with the diametrically opposed inlet  14  and outlet  16  each being positioned at an angle of approximately 45 degrees removed from the midline  24  of the detector body  12 . The two possible diametric lines positioning for inlet  14  and outlet  16  are denoted in  FIGS. 2  as  26  and  26 ′. Although the figures depict the inlet  14  and outlet  16  as being along line  26 , it is appreciated that they are equally well positioned along line  26 ′ to provide an equivalent diametric position with at least one of the inlet  14  or outlet  16  able to act as a drain of condensate regardless of whether an inventive housing  10  is mounted horizontally per  FIGS. 8A and 8B , an inverted horizontal mounting per  FIG. 8  or a vertical mounting of an inventive housing  10  per  FIGS. 8C and 8D . The ability of inventive housing  10  having diametrically positioned inlet  14  and outlet  16  that are offset from midline  24  by an angle of between 30 and 60 degrees and preferably about 45 degrees to function as a condensate drain is depicted schematically in  FIG. 2 . While the housing body  12  is depicted with a rectilinear housing detector chamber  28 , it is appreciated that a variety of other shapes are also amenable to the condensation drain aspects associated with placement of an inlet  14  or outlet  16  along a bottom edge relative to mounting position. These other shapes illustratively include circular, square, triangular and other regular and nonregular polygonal shapes. 
     The housing body  12  is optionally divided into a housing detector chamber  28  and a printed circuit board (PCB) chamber  30  that are physically isolated yet provide electrical communication therebetween. A printed circuit board (PCB)  32  is secured to the housing body  12  by way of anchor posts  34  extending into the PCB chamber  30 . The advantage of physical isolation between housing detector chamber  28  and PCB chamber  30  is to isolate the electronics on PCB  32  from particulate and condensation associated with gas flow introduced by way of inlet  14 . It is appreciated that a single chamber housing is readily provided and protection of PCB  32  provided by way of PCB  32  encapsulation. Preferably, the housing body  12  has one or more preformed apertures  36  or a thin-walled region  38  that upon dislodgement defines an aperture. An aperture  36  or a thin-walled region  38  is intended to provide a site for joinder of an electrical wire coupling  40 . 
     Intermediate between the cover  20  and the housing body  12  is a gasket. As depicted with respect to prior art  FIG. 1 , a circular, square or rectilinear cross section gasket G is press fit between a groove adapted to receive the gasket and a flat surface associated with the inner surface of a cover and housing body face. Unfortunately, such as gasket tends to be thin pinched by uneven pressure associated with fastener pressure urging the cover into contact with the gasket and the housing body thereby resulting in an unreliable seal. Additionally, single point of contact seals as well as fluid ingress by way of fastener holes precludes outdoor placement of such a prior art housing. In a preferred embodiment, an inventive gasket  42  having at least one lateral contact point  43  between a cover lip  52  encompassing an extending wall  44  of the housing body  12 . The gasket  42  secures to an extending wall bounding one or both of the housing detector chamber  28  and the PCB chamber  30  in  FIG. 7A . The extending wall  44  projects upward relative to housing body surface  46  as depicted in  FIGS. 7A and 7B . The gasket  44  is adhesively secured to the extending wall  44  such that at least one protrusion from the gasket  42  extends outward relative to the extending wall  44  to form contact points  43  and preferably multiple contact points  43 . More preferably, the gasket  42  has a top cap portion  48 . Most preferably, the top cap portion  48  overhangs the extending wall  44  so as to overlie one of the housing detector chamber  28  or PCB chamber  30 . The nature of the inventive gasket is best shown with regard to the magnified outset cross-sectional image provided in  FIG. 7B . A cover  20  engaging an inventive gasket  42  has a cover lip  52  adapted to encompass the extending wall  44  with a degree of clearance such that the protrusions  46  are laterally compressed therebetween. The cover lip  52  intersects a covering surface  54  of the cover  20  and simultaneously compresses a top cap portion  48  of gasket  42 , if portion  48  is present. Preferably, the cover  20  has an inner lip  56  adapted to engage an overhang portion  50  of the gasket  42 , if present. In contrast to prior art gasket sealing schemes per prior art  FIG. 1 , an inventive sealing system involving a cover  20 , housing body  12  and a gasket  42  preferably provides multiple contact points  43 . With securement of a gasket  42  to an extending wall  44  with a conventional adhesive such as an acrylic adhesive, five separate gasket seal points are provided as depicted in  FIG. 7B  with three contacts associated with protrusions  46 , one with top cap protrusion  48  and one with overhang portion  50 . Such a gasket renders an inventive housing suitable for outdoor placement. An inventive gasket  42  requires a degree of compressibility difficult to achieve with a conventional solid neoprene gasket such as G of  FIG. 1 . Preferably, an inventive gasket is an expanded elastomer such as neoprene, latex, natural rubber, or other appropriate compounds either in singular or mixed compounds present as either an open-celled or closed-celled foam sponge. Preferably, the gasket  42  is a closed-cell foam so as to preclude water intercalation by way of gasket porosity. 
     An additional problem associated with conventional housings such as those of prior art  FIG. 1 , through resort to multiple mechanical fasteners to secure a cover to a housing body since integrity of the seal between cover and housing body is suspect owing to variables such as differential torque applied to fasteners, stripped fastener threads, and a missing fastener. Additionally, a technician standing on a ladder using one hand to position a cover by using the other hand to attempt to secure fasteners represents not only an installation and maintenance inefficiency but also a safety hazard. In order to overcome the limitations associated with multiple threaded fasteners used to secure a cover in place, an inventive housing  10  preferably resorts to a binary securement mechanism  60 . The binary securement mechanism is distinguished over the prior art in having definitive “open” and “closed” positions that preclude the graded tightening of a threaded fattener. The binary mode securement mechanism  60  is depicted as a pivoting latch  61  in  FIGS. 2 ,  3 ,  6  and  7 ; a sliding latch  61 ′ as depicted in  FIG. 4 ; and a bayonet latch  61 ″ in  FIG. 5 . The binary mode securement mechanism  60  provides ease of cover securement while assuring seal integrity regardless of whether an inventive gasket  42  or a conventional gasket G is present at the interface between the cover  20  and the housing body  12 . The latch  61 - 61 ″ is typically formed of materials such as those from which the housing body  12  is formed and includes a hook engagement portion  62 ,  62 ′ or a pin  63  and a handle portion  64 - 64 ″. The latch  61  is pivotally secured to the cover  20  about a pivot pin portion  66  of the cover  20  of  FIG. 3 . The latch  61 ′ is mounted to track  59  to slide laterally in the cover  20 ′ of  FIG. 4 . Preferably, the hook engagement portion  62  or  62 ′ has a first notch  68  or  68 ′ in a complementary position relative to a catch  70  or  70 ′. The latch  61 ″ of  FIG. 5  press fits against cover  20 ″ in response to a pin  63  engaging a groove  65  in a socket  67  adapted to receive cylindrical base  69  of the latch  61 ″ with rotation of the handle portion  64 ″. The groove  65  has a discontinuous closed portion  71  that assures a binary closed position. Preferably, a spring-loaded plate  73  ejects the base  69  to an “open” position when in a position other than the pin  63  engaging groove closed portion  71 . 
     The common feature of binary mode securement mechanism  60  reproducible assurance that the latch  61 - 61 ″ is either “open” or “closed.” Preferably, the binary mode securement mechanism  60  is located intermediate between a housing detector chamber  28  and a PCB chamber  30  so as to assure a generally uniform circumferential pressure applied to a gasket  42  or G upon sealing of a cover  20 - 20 ″ to a housing body  12 - 12 ″. More preferably, a second notch  76  or  76 ′ is provided that is complementary to a cover stay  78 ,  78 ′ or  78 ′ integral with the cover  20  or  20 ′ such that the second notch  76  or  76 ′ upon engagement of the cover stay  78  or  78 ″holds the binary mode securement mechanism  60  in an “open” position. It is appreciated that first notch  68  is readily placed on surface  72  while catch  70  is readily placed onto hook engagement portion  62  forming an inverted complementary pair of notch and catch. Likewise second notch  76  or  76 ′ and cover stay  78  or  78 ′ are readily inverted as to placement on hook engagement portion  62  or  62 ′ and cover  20  or  20 ′ to form an equivalent latch retention position. Still more preferably, an indent  80  is provided in the cover  20  adjacent to the handle portion  64  of the latch  61  when in a closed position. An indent  80  is provided to facilitate operation of the latch  61 . Preferably, cover removal button  82  is provided to communicate to the cover removal switch  84  on a printed circuit board  32 . The cover removal switch  84 - 84 ″ sends an electrical signal based on whether the cover removal button  82 - 82 ″ is depressed by the handle  64 - 64 ″ or free of contact with the latch  61 - 61 ″. Preferably, when a cover removal button  82  is present, the button is positioned in the cover  20 - 20 ″ so as to be depressed when the handle portion  64 - 64 ″ in a fully closed position. Alternatively, a cover removal button  82  is provided in an underlying relationship relative to mode binary securement mechanism surface  72  or  72 ′ or plate  73  such that the hook engagement portion  62  or  62 ′ or base  69  likewise depresses a cover removal button  82  when the mode binary securement mechanism  60  is in a closed position. It is appreciated that covers  20 ′ and  20 ″ as well as complementary housings  12 ′ and  12 ″ are identical to cover  20  and housing  12 , respectively, with the exception of differences in securement mechanism  60  and description of other inventive attributes are equally operative therewith. 
     Optionally, a removable baffle  37  designed to insert within the housing detector chamber  28  serves to overlie the detector D and overlie at least one of inlet  14  or outlet  16  is provided to modify air circulation within the housing detector chamber  28  based on the performance characteristics of the detector D and the velocity of gas entering housing  10  by way of the inlet  14 . An alarm test of detector D is optionally provided by inclusion of an elastomeric test port in the cover  20  as detailed in U.S. Pat. No. 6,741,181. 
     In a preferred embodiment, a cover  20  has exposed thereon a maintenance mode button  90 , a test/reset button  92  and indicator lights indicative of pilot mode  94 , trouble mode  96  and alarm mode  98 . Preferably, the lights  94 ,  96 ,  98  are light emitting diodes (LEDs). An inventive housing  10  with the provision of buttons  80 ,  92 ,  94  and indicator lights  94 ,  96 ,  98  allows an installer, a service technician or an inspector of an inventive housing  10  to readily access sequence of operations for either indoor or outdoor units. In contrast to conventional detector test protocols initiated by removal of a cover, an inventive detector housing  10  eliminates dual trouble signals when trouble and alarm testing are performed on detectors associated with monitoring smoke alarm systems. As a result of the ability to initiate maintenance or test/reset detector associated electronics without cover removal, alarm cover removal switch  84  is not triggered in the process thereby simplifying system testing readout and test protocols. 
     By way of example, operation of an inventive detector housing  10  in a maintenance mode is provided. The detector D and associated housing  10  in normal mode is indicated by operating power on, the cover  20  in place and pilot light  94  illuminated steady, preferably color coded as green; trouble indicator  96 , preferably a yellow LED off; and alarm indicator  98  off, preferably in a red LED, as well as the trouble and test/reset buttons in normal inactive states  92  and  94 . Depressing the maintenance button on the cover  20 , housing body  12 , or remote from the housing  10  activates a maintenance mode switch causing the pilot indicator light  94  to begin to flash which confirms maintenance mode initiation. A remote button is typically associated with a master control unit monitoring multiple detectors in multiple housings  10 . Once maintenance mode button  92  has been pushed, the detector D goes into approximately a three minute timed test/maintenance mode where the front cover  20  can be removed for internal testing trouble and alarm functions of the detector D itself. Specific problems associated with the detector D which are tested for include proper placement of a detector head and an alarm caused by smoke testing of the detector head. During this three minute timed test, the position of the cover  20  does not affect the status of the detector housing  10 . It is appreciated that this three minute timed test/maintenance mode is readily preselected to be a longer or shorter interval and is also well suited for troubleshooting minor wiring or electrical problems. While pilot light  94  is flashing, the trouble light  96  and alarm light  98  follow the actions as performed on the detector D itself. The alarm and trouble contacts on the printed circuit board P will also follow these actions as performed on the detector D for proper system integration testing. Upon proper replacement of the cover  20 , the maintenance mode is automatically canceled but housing  10  reverts to normal operational status where failure of the cover  20  to be properly placed and the latch  60  closed to depress button  82  immediately causes a trouble condition. During the maintenance mode timing sequence optionally additional testing and maintenance time can be provided in three minute increments with a momentary repeated depression of the maintenance mode switch on the printed circuit board P that was previously engaged by depressing maintenance button  90 . With depression of the maintenance mode switch, additional three minute increments of maintenance time are provided. In the event the maintenance mode switch is not activated to provide an additional three minute increment of operational time, the pilot indicator light  94  extinguishes and the trouble indicator  96  illuminates and the trouble contacts transfer immediately upon opening binary mode securement mechanism  60  and/or subsequent removal of the cover  20 . A representative test sequence procedure includes: (1) Push maintenance mode button  90  momentarily and confirm mode activation by flashing pilot light optionally alternating with trouble indicator LED 96. (2) Unlatch latch  60  and remove cover  20 . Preferably, a tether  100  as shown in  FIG. 6  maintains the cover  20  in proximity to the housing body  12  after removal. (3) The head of the detector D is twisted out to verify proper unit and system trouble response. (4) The head of the detector D is twisted back into place to verify proper unit and system trouble restoral. (5) A smoke test for the detector D is used to provide proper unit and alarm response. (6) With the clearing of any residual smoke from the detector head and with momentary depression of the test/reset button  92 , proper unit and system alarm restoral is confirmed. (7) The cover  20  is replaced and secured by pressing the latch handle portion  64  to a closed mode and in the process depressing a cover removal button  82 , if present. 
     Preferably, while an inventive housing  10  is in maintenance mode, the flash rate of the pilot indicator light  94  begins flashing at a rate that increases as the timed maintenance mode period approaches within thirty seconds of preselected time sequence completion, or any other preselected window of time test completion. In the event that the maintenance mode button  90  is activated by mistake, maintenance mode button  92  is optionally depressed within a preselected amount of time within the initial depression such as for example ten seconds to cancel the maintenance mode request. An additional optional mode is that if the maintenance mode button  90  is activated and the binary mode securement mechanism  60  is not released within a preselected amount of time such as for example twenty seconds, the timed test/maintenance mode is terminated and the housing  10  is returned to normal mode as indicated by pilot indicator light  94  being continually green. It is appreciated that the lights  94 ,  96 ,  98  are mounted on an underlying printed circuit board P and visible through the cover  20  such that removal of cover  20  does not limit operational status information from installer or a service provider or an inspector during removal of the cover  20 . 
     Referring now to  FIG. 10 , an inventive layout for a printed circuit board for inclusion in an inventive housing  10  is provided generally at  212 . The printed circuit board  212  in contrast to a conventional PCB P segregates wire connection blocks based on individual specialists who may access an inventive housing  10 . Specifically, terminal blocks are associated with fire alarm connections  202 , HVAC connections  204 , detector interconnect connectors  206 , remote accessory connections  208  and input power connections  210  on PCB  212 . With the provision of dedicated terminal blocks based on specialty, an individual accessing a PCB  212  for a specific purpose concentrates their energy on a collected set of connections related to their purpose instead of the same number of connections scattered across the surface of PCB  212 . Preferably, indicia as to the nature of the terminal blocks  214  is provided on the board  212 . More preferably, the dedicated terminal blocks  202 - 210  of PCB  212  are color coordinated. 
     Referring now to  FIG. 11A , a conventional prior art terminal as used on PCB P is shown inclusive of a wire W entering the terminal T. A clamping lever L allows for selective securement or release of the wire W and the terminal T. The testing of terminal T and wire W currently requires the latch L to be operated to disengage the wire W. 
       FIG. 11B  shows an improved inventive terminal  300  that represents an improvement over the prior art terminal depicted in  FIG. 11A  on the basis of providing a test meter probe hole  302  providing electrical continuity testing of the wire W without resort to operating the clamping lever L. Like numerals and letters are used to designate like components detailed above with respect to prior art  FIG. 11A . With the provision of hole  302 , the time of testing is reduced as well as the prospect of damaging by over stripping resulting in shock and short danger the contact between a wire W and a terminal T associated with unclamping and repeatedly clamping wire W with resort to lever L. 
     Patent documents and publications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. These documents and publications are incorporated herein by reference to the same extent as if each individual document or publication was specifically and individually incorporated herein by reference. 
     The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.