Abstract:
A dual channel aspiring smoke detector includes ultrasonic flow sensors associated with each channel. The detector can make determinations of smoke levels associated with respective channels as well as rates of flow through each channel. Respective alarm or trouble indicators can be output in response to determined smoke levels as well as determined flow rate. The detector can be used as a stand alone device or part of a fire alarm system.

Description:
FIELD 
       [0001]    The invention pertains to aspirated smoke detectors. More particularly, the invention pertains to such detectors which include ultrasonic flow sensors. 
       BACKGROUND 
       [0002]    Aspirating smoke detectors draw air from a protected area using a network of sampling pipes. The sampled air is then passed through one or two smoke sensors. Smoke levels can be evaluated locally or transmitted to a displaced system control unit for alarm determination. 
         [0003]    In known aspirating detectors, a fan is used to draw the sampled air into the unit and for providing the sampled air to the smoke sensor or sensors. Detectors can be operated as stand alone devices or as an element in a fire alarm system. Local relays can be provided to provide fault indicators or to activate one or more alarm devices such as sounders or strobes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is an overall configuration diagram including a detector in accordance with the invention; 
           [0005]      FIG. 2  is an isometric view of the detector of  FIG. 1 ; 
           [0006]      FIGS. 3A ,  3 B are views of the detector of  FIG. 2  with the front cover removed to illustrate internal details; 
           [0007]      FIG. 4  is an overall all block diagram of the detector of  FIG. 1 ; 
           [0008]      FIG. 5  illustrates aspects of the ultrasonic transducers of the detector of  FIG. 1 ; 
           [0009]      FIG. 6  is a flow diagram illustrating aspects of operation of the detector of  FIG. 1 ; and 
           [0010]      FIGS. 7A ,  7 B illustrate information presentable on a display of the detector of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, as well as the best mode of practicing same, and is not intended to limit the invention to the specific embodiment illustrated. 
         [0012]      FIG. 1  is a diagram of a detector  10 , which embodies the invention coupled to a plurality of atmospheric flow pipes such as P 1 A, P 1 B, P 2 A, P 2 B. Each of the pipes includes a plurality of inflow ports, or holes, such as HA 1  . . . HA 4  and HA 5  associated with pipe P 1 A. 
         [0013]    The flow pipes each terminate at an outflow opening and are connected to a cabinet  12  of detector  10 . Smoke S, from a fire F in a region R being monitored can be drawn into an adjacent flow pipe, such as P 2 B, through an opening such as HB 4 . 
         [0014]    Aspirators, or fans, F 1 , F 2  carried by cabinet or housing  12  draw ambient air, or fluid, through respective pipes such as P 1 A, P 1 B, P 2 A or P 2 B and into respective flow channels such as  16   a, b  (best seen in  FIG. 3A ) in cabinet  12 . Ambient air drawn through detector  10  exits from two outflow ports, Outflow 1  and Outflow 2 . 
         [0015]    Detector  10  also includes a user interface device  14  which includes a display  14   a  and user inputs  14   b , both carried by housing  12  and optional filters F 1 , F 2  (best seen in  FIG. 3   a ). Housing  12  also carries local control circuits  18  coupled to sensors S 1 , S 2 . 
         [0016]    Housing  12  also carries ultrasonic transducers  20   a,b  associated with flow channel  16   a  and  22   a,b  associated with channel  16   b . The transducers are supported in the housing  12  on a printed circuit board  24  which also carries the control circuits  18  and the interface device  14 . The transducers  20   a,b  and  22   a,b  are each transmitters and receivers and establish air flow speed n the channels  16   a,b  by comparing transit time for each channel in both directions relative to air flow. The difference in transit times is indicative of speed of air flow in the respective channel. 
         [0017]      FIG. 4  illustrates added details of detector  10 . Outputs from smoke sensors S 1 , S 2  and ultrasonic sensors  20   a,b  and  22   a,b  are coupled to the control circuits  18  on the printed circuit board  24 . The control circuits  18  can be implemented at least in part with a programmable processor  18   a  and associated pre-stored control circuitry  18   b . The processor  18   a  and control software  18   b  can evaluate outputs from smoke sensors S 1 , S. Sensors S 1 , S 2  can make pre-alarm and alarm determinations, as would be understood by those of skill in the art. Alternately, smoke level signals can be coupled to the control circuits  18  for the purpose of making such determinations. 
         [0018]    The control circuits  18  can also emit outputs  30 , trouble signals indicative of conditions that need to be addressed at the detector  10 . One form of output device is a relay. Other outputs include sounder, audible alarm devices, output signals  32  as well as pre-alarm or alarm indicating outputs  34  for channels  16   a,b  if desired. 
         [0019]      FIG. 6  illustrates aspects of a method  100  in accordance with the invention. Air samples are acquired via pipes P 1 A, P 2 A for example as at  102 . Those samples are evaluated, as at  104  to establish the presence of one or more alarm conditions. Responsive to an established alarm condition, an alarm indicating output to an output device or a displaced alarm system can be emitted as at  106 . In the absence of an alarm condition, air flow rate in the channels  16   a,b  can be established as at  108 . Where the established flow rate(s) are outside of expected range(s) a trouble output can be generated, as at  112 . 
         [0020]      FIGS. 7A and 7B  illustrate various output displays available on the output device  14   a .  FIG. 7A  illustrates smoke levels in each channel, OBS 1 , OBS 2 . Channel  1  is showing that smoke level has reached pre-alarm level three with an alarm to be issued at level seven. 
         [0021]      FIG. 7B  illustrates two different pre-alarm and alarm levels, dependent on day/night sensitivity. Channel one,  16   a  has a day alarm at level seven and a night alarm at level six. Channel two  16   b , has a day alarm at level nine and a night alarm at level six. 
         [0022]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.