Abstract:
An apparatus includes a mounting base and a compatible electrical unit removably carried on the base. The base carries a transducer and a sensor external to the unit. The transducer emits radiant energy toward the unit. The sensor receives radiant energy modulated by the unit. A local control unit can store the received, modulated radiant energy as a base-line profile. Subsequently, additional profiles can be generated and compared to the stored base-line to determine is a spatial characteristic of the electrical unit has changed.

Description:
FIELD 
     The invention pertains to electrical units such as ambient condition detectors. More particularly, the invention pertains to such detectors which incorporate circuitry to detect obstruction of flow of local ambient atmosphere. 
     BACKGROUND 
     Smoke detectors have been recognized as useful and effective devices in providing warnings of smoke in the adjacent, local ambient atmosphere. In the presence of smoke, such devices can emit an audible, alarm indication. 
     Where detector inflow ports have been accidentally or intentionally obstructed, the devices may not work as intended. At times, smoke detectors have been, or might be intentionally obstructed to prevent detection of smoke from cigarettes in offices, dormitories, or hotels. During new construction, or during renovations, dust covers used to protect detectors from contamination might be unintentionally left in place after initial installation, or, after the renovation has been completed. 
     There is a need to minimize any likelihood that one or more detectors of an alarm, or monitoring system, might not function properly due to the presence of an obstruction which blocks inflow of local ambient atmosphere into the respective detector or detectors. Preferably such functionality would be readily installable in existing monitoring systems, and would not compromise normal functioning of the respective detector(s). It would also be desirable if blockage indicating audible, visible or electrical indicia could be provided on a per detector basis to facilitate identification and correction of the problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an electrical unit which embodies the present invention; 
         FIG. 2  is a flow diagram of a method in accordance with the invention; 
         FIG. 3  another flow diagram which illustrates additional aspects of a method in accordance with the invention; 
         FIG. 4  is a top plan view of a smoke detector which embodies the invention; and 
         FIG. 5  is a sectional view taken along plane  5 - 5  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     In one aspect of the invention, an ultrasonic emitter and receiver can be positioned on a housing or base of an electrical unit, such as a smoke detector, such that a portion of the unit, such as a sensing chamber, lies between them. The emitter can be energized when the unit is functioning properly and is not improperly obstructed in any way. The receiver responds to received ultrasonic energy. The received energy represents a profile of the unit in the absence of any obstructions. 
     In the presence of an obstruction, the characteristics of the energy incident on the receiver due to path changes, absorption, reflections diffractions or the like will vary from the profile of the unit in the absence of any obstructions. The differences between the two profiles can be detected and obstruction indicating indicia can be generated locally, or transmitted to a remote control center or unit. 
       FIG. 1  illustrates a system  10  which embodies the invention. System  10  can include a regional monitoring and alarm system generally indicated at  12 . System  12  can include control circuits, or control unit,  14  which could be implemented with one or more programmable processors and associated control software. 
     Unit  14  is coupled via a wired or wireless medium  16   a ,  16   b  to a plurality  18  of ambient condition detectors such as smoke detectors, gas detectors, fire detectors, intrusion detectors, and the like all without limitation for the purpose of providing real-time monitoring of various conditions in a region R. Examples of such monitoring systems have been disclosed in U.S. Pat. No. 5,483,222 to Tice entitled “Multiple Sensor Apparatus and Method” which issued on Jan. 9, 1996 and U.S. Pat. No. 6,163,263 to Tice et al. entitled “Circuitry for Electrical Device in Multi-Device Communications System which issued on Dec. 19, 2000. Both the &#39;222 and &#39;263 patents are assigned to the Assignee hereof and are hereby incorporated by reference herein. 
     A representative one of the detectors  20  which is coupled to unit  14  has an associated mounting base  22 . Base  22  can be used to releasibly attach detector  20  to a mounting surface S in the region R. Those of skill in the art will understand that with use of the base  22  a variety of detectors, output modules or output appliances can easily be coupled to system  14 . All such units come within the spirit and scope of the invention. 
     Base  22  carries an ultrasonic emitter  26  and a receiver  28 . The emitter  26  and receiver  28  are positioned on the base  22  with detector, or other electrical unit,  20  located therebetween. Ultrasonic energy from emitter  26  is spatially modulated by the presence of detector  20  prior to being sensed at receiver  28 . 
     The shape and physical characteristics of detector  20 , or any other electrical unit carried on base  22 , will produce a unique modulation, hence a profile that can be associated with the unit  20 . Varying the shape of detector  20 , for example by covering it with a plastic bag, will produce a different modulation and a different profile. This difference can be locally detected and used to produce obstruction indicia or trouble indicators. 
     Base  22  also carries emitter drive circuits  26 - 1  coupled to the emitter  26 . Receiver amplifier and detection circuitry  28 - 1 , carried on base  22  is coupled to receiver  28 . Local controller  30 , which could include a programmable processor  30   a , and associated control software  30   b , can be in bidirectional communication and coupled to circuits  26 - 1  and  28 - 1 . 
     Controller  30  can in turn activate emitter  26  and obtain, via receiver  28  an ultrasonic profile of detector  20 . Controller  30  can store and analyze that profile, including comparing it to previously received profiles of detector  20  to determine if operation of detector  20  has been impaired by an obstruction. Controller  30  can generate local audible and/or visual indicia indicative of an obstruction. Alternately, controller  30  can communicate such indicia, via medium  16   b , to unit  14  for follow-up action or maintenance. 
     It will be understood that circuitry illustrated on base  22  is exemplary only. Alternates to the ultrasonic emitter  26  and receiver  28  come within the spirit and scope of the invention. It will also be understood that the nature of the electrical unit  20  is not a limitation of the invention. Further, some or all of the units  18  can include a base, such as base  22  which can be used to monitor conditions of an associated electrical unit without departing from the spirit and scope of the invention. 
       FIG. 2  is a flow diagram of a process  100  in accordance with the invention. Process  100  establishes an expected profile of detector or electrical unit  20 , mounted on base  22 , when in a first state. 
     Where the detector  20  is exhibiting a first state, unobstructed for example, as at  102 , emitter  26  can be activated, as at  104 . Responsive to activating emitter  26 , a profile of unit  20  can be sensed at receiver  28 , as at  106 . The received pattern or profile can be stored by controller  30 , for subsequent use, as at  108 . Normal operation can then continue. 
       FIG. 3  is a flow diagram of a process  200  also in accordance with the invention. Process  200  establishes a current profile of detector or electrical unit  20  mounted on base  22  to determine if it continues to exhibit the first state. 
     Emitter  26  can be pulsed or activated, as at  202  where the control circuits generate a time sequential sequence of indicators. A sound pattern sensed at receiver  28 , as at  204 , can be stored, as at  208  by the controller  30 . Controller  30  can compare a previously established profile, as at  108  of process  100 , to a current profile as at  210 , to determine if an obstruction is present. In the event of a detected difference, indicating a change in status of unit  20 , controller  30  can generate local audible or visible indicia there of, or communicate same to control circuits  14  for inspection or maintenance, as at  212 . Controller  30  can continue carrying out other functions as previously established. 
       FIG. 4  and  FIG. 5  illustrate a smoke detector  20 ′ mounted on a base  22 . Radiant energy  40 , illustrated pictorially only, emitter by transducer  26  is angled toward the smoke entry area of the detector  20 ′. At least a portion of the ultrasonic energy will pass through the detector&#39;s smoke chamber and be sensed, in spatially modulated form by receiver  28 . As noted above, each type of electrical unit or detector mounted on a base, such as base  22 , can be expected to produce its own profile in both unobstructed and obstructed states. 
     Those of skill in the art will understand that the unobstructed profile could be sensed and factory programmed, at time of manufacture for example, into each unit for subsequent use. Such pre-stored profiles could be transmitted to an adjacent base, where a base is used, when the unit or detector is mounted in the field. 
     In another aspect of the invention, embodiments hereof do not require a base. In such embodiments, an emitter and sensor of obstruction sensing radiant energy for example, could be mounted on the respective unit or detector. In yet another embodiment, one of the transducers could be mounted inside the unit or detector, such as in a sensing chamber of a smoke detector. In such embodiments, it may not be necessary to make a comparison to an unobstructed profile. In another embodiment, an ultrasonic emitter could be mounted in a detector and an ultrasonic sensor mounted outside of the detector. Only one need be mounted on the detector. The other could be mounted on an adjacent base. 
     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.