Abstract:
A smoke detector has a geometry that locates a sensor or sensors at or near a boundary layer of smoke movement thus facilitating smoke entry into the sensor and/or sensors. The sensors are mounted so as to protrude from the bottom of a cover instead of into the cover of the detector.

Description:
This application claims the benefit of the earlier filing date of Provisional Application Ser. No. 60/165,874, filed Nov. 16, 1999. 
    
    
     FIELD OF THE INVENTION 
     This invention pertains to ambient type sensors such as photoelectric and ionization smoke detectors. More particularly, the invention pertains to structures for locating the respective sensor/sensors with an orientation that facilitates the ingress of smoke into the sensors 
     BACKGROUND OF THE INVENTION 
     Known smoke detector designs mount the respective sensor inside a housing or on top of the housing. Both ionization and photoelectric sensors have been located inside housings having complicated vents and baffling designs in order to promote the ingress of smoke. Smoke detectors having sensors mounted inside the cover of the detector may have barriers such as the p-horn, battery, or other electrical components that interfere with smoke detection due to interference with smoke flow. 
     FIGS. 1A-1C illustrate relevant aspects of a prior art smoke detector  10 . The detector  10  includes a base  12  intended to be attached to a ceiling C. A cover  14  is carried on the base  12 . A plurality of openings indicated generally at  16  provide smoke pathways into and out of the cover  14 . 
     In the detector  10 , a printed circuit board  20  is carried adjacent to the mounting base  12 . The printed circuit board  20  in turn carries an ambient condition sensor, such as a smoke sensor  22 , an audible output device such as a horn or the like  24 , and a power supply such as a battery  26 . Other electrical or electronic components generally indicated at  28 , are conventionally carried by the printed circuit board  20  often on the same side as are sensor  22 , horn  24  and battery  26 . 
     The configuration illustrated in FIGS. 1A,  1 B and  1 C results in convoluted and tortuous smoke flow paths in and out of openings  16  and into cover  14 . Placing the sensor  22  on the printed circuit board as in FIGS. 1A,  1 B and  1 C directs the sensor  22  into the internal volume of the cover  14  away from smoke flow adjacent ceiling C. To compensate for placement of the sensor  22 , known detectors have included vents and baffles for the purpose of promoting smoke flow to and from the respective sensor. 
     It would be desirable from a cost and design manufacturing perspective to be able to eliminate known vents, baffles and flanges. Preferably such reduced complexity might promote improved flow into and out of the respective housings. 
     SUMMARY OF THE INVENTION 
     The invention takes advantage of both the laminar and turbulent nature of smoke flow. Often smoke detectors are ceiling mounted. The sensor or sensors are arranged within the detector so as to be located near the respective mounting surface, such as near or on the ceiling. 
     The sensors are carried adjacent to a mounting surface of the detector as opposed to being mounted in the cover as in prior art smoke detectors. The design hereof displaces the sensor/sensors away from electronic components and closer to the mounting surface such as the ceiling. An air sampling gap exposes the sensor/sensors to air and smoke adjacent to the ceiling. 
     One or more sensors (ionization or photoelectric) may be carried adjacent to the mounting member for the detector. The present invention promotes omni-directional ingress of smoke into the detector. 
     Unlike the prior art, this invention eliminates the need for complicated venting geometries and complex baffling designs. This follows since the sensors are located adjacent to the mounting surface so as to promote direct ingress and egress of airborne smoke, and thus improved directionality. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A,  1 B and  1 C taken together are various views of a prior art smoke detector; 
     FIG. 2A is a side elevational view of a detector in accordance with the present invention; 
     FIG. 2B is a top plan view of the detector of FIG. 2A taken along plane  2 A— 2 A; 
     FIG. 2C is a side sectional view of the detector of FIG. 2A taken along plane  2 C— 2 C; 
     FIG. 3A is a side elevational view of a dual sensor detector in accordance with the present invention; 
     FIG. 3B is a view taken along plane  3 B— 3 B of FIG. 3A; and 
     FIG. 3C is a side sectional view taken along plane  3 C— 3 C of FIG.  3 B. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     FIGS. 2A,  2 B,  2 C illustrate various views of a detector  30  in accordance with the present invention. The detector  30  includes a housing generally indicated at  32  having a base  32   a  which is intended to be attached to a mounting surface such as a ceiling C. The housing  32  includes a cover  32   b  coupled to the base  32   a.    
     The cover  32   b  substantially defines an internal region  34 . The region  34  is open to the ambient atmosphere via slots, ports or openings generally indicated at  36  located adjacent to the base  32   a . The openings or slots  36  are disposed around the housing  32 . 
     The housing  32  carries an ambient condition sensor  40 , which could be a smoke sensor, with a portion thereof positioned adjacent to the base  32   a . The sensor  40  could be carried within the region  34  by a planar mounting element  42 . Element  42  could be implemented as one or more printed circuit boards. 
     The element  42  carries an audible output device  46  and a power supply, for example a replaceable battery  48 , on a side  42   a  displaced from a side  42   b  upon which the sensor  40  is mounted. Other electronic components  50 , for example control circuitry, as would be understood by those of skill in the art could be carried on the side  42   a  interconnected with audible output device  46  and battery  48 . Electrical connections to sensor  40  could be made using plated through holes or vias in the board  42  or other known methods as would be understood by those of skill in the art. 
     The configuration of detector  30  is particularly advantageous in that sensor  40  has input/output openings  40   a ,  40   b  which are in an ambient atmospheric flow pattern indicated generally at F 1  and F 2  through openings  36 . In this regard, the position of other components  46 ,  48  and  50  on side  42   a  of the board or element  42  has located those components out of the ambient flow stream, F 1 , F 2 . 
     An inflow and outflow F 1 , F 2  of ambient atmosphere, which could carry fire indicating smoke, is able to flow unimpeded into and out of sensor  40  in a symmetrical fashion relative to the housing  32 . No special vanes or deflecting elements are required to cause inflow or outflowing ambient, smoke carrying, atmosphere to flow into openings  40   a ,  40   b  of sensor  40  since those openings and the associated portions of sensor  40  are located directly in the flow path. 
     It will be understood that the sensor  40  could be implemented as an ionization-type or photoelectric-type smoke sensor without departing from the spirit and scope of the present invention. Other types of smoke sensors or gas sensors if desired could also be used without departing from the spirit and scope of the present invention. Preferably sensor  40  would be symmetrically located on a center line L of housing  32 . 
     FIGS. 3A,  3 B and  3 C illustrate various views of a dual sensor detector  60  in accordance with the present invention. Detector  60  includes a housing generally indicated at  62  which has a base  62   a  intended to be mounted to a surface such as a ceiling C. Additionally, housing  62  includes a cover  62   b  which substantially defines an internal region  64 . A plurality of openings, generally indicated at  66 , provides for an inflow and outflow of ambient atmosphere which could include airborne smoke which has accumulated adjacent to ceiling C. 
     Detector  30  includes first and second ambient condition sensors  70   a  and  70   b . By way of example, and not limitation, sensor  70   a  could be implemented as an ionization-type smoke sensor. Sensor  70   b  could be implemented as a photoelectric-type smoke sensor. One of the sensors could be a gas sensor. 
     The sensors  70   a ,  70   b  are mounted on a printed circuit board  72   a  carried in housing  62 . The printed circuit board  72   a  and the sensors  70   a, b  are oriented such that inflow and outflow ports of the respective sensors are located adjacent the ports or openings  66  to promote a direct inflow and outflow of ambient atmosphere including airborne smoke therein. 
     For exemplary purposes, a second printed circuit board  72   b  can be mounted adjacent to the circuit board  72   a  and carry additional components such as audible output device, a piezo electric horn, control circuitry and a power supply which could include a replaceable battery. These respective components would be carried on printed circuit board  72   b  and oriented so as to not impinge upon or alter the ingress and egress of airborne ambient, such as airborne smoke, through openings  66 . As illustrated in FIG. 3B, ingress and egress of airborne ambient can occur symmetrically relative to housing  62  and impinge upon the sensors  70   a, b  without obstruction from or deflection due to other components in the detector. 
     It will be understood that the choice of sensors  70   a, b  is exemplary. Other choices such as smoke and gas sensors could also be used without departing from the spirit and scope of the present invention. It will also be understood a variety of mounting arrangements could be implemented with base  62   a  without departing from the spirit and scope of the present invention. 
     The cover of the sensor may include a myriad of designs since adding vents, holes, etc. will not affect the sensor/sensors behavior in the detection of airborne smoke particulates, gas, etc. 
     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.