Abstract:
A visual alarm indicating output device includes a plurality of light sources arranged in a circular pattern about a centerline. Each of the sources is oriented so that respective light output is directed to a common, cylindrical Fresnel lens. The lens is symmetrical about the centerline. The sources are pulsed from a common current supply.

Description:
FIELD 
       [0001]    The application pertains to alarm indicating visual output devices. More particularly, the application pertains to such output devices which project non-oriented, omni-directional three hundred sixty degree light output relative to a center line of the device. 
       BACKGROUND 
       [0002]    The main drivers within the Visual Alarm Devices sector of the Fire/Life safety industry revolve around the usual commercial factors of cost, device installation time, power consumption, and overall output performance characteristics. In this regard, there can be added installation costs associated with the installation and adjustment of the field of light emitted from alarm indicating visual output devices. 
         [0003]    EN54-23 is a new European Standard supporting the manufacture and use of VAD&#39;s (Visual Alarm Devices) for or within an emergency evacuation system. Prior to the new standard, VAD type devices had no minimum or maximum output requirements that needed to be met. The new standard is in general for the European market a game changer for the evacuation industry. Now there are minimum light output requirements vs. the amount of power through a flashed pulse which are to be available from the evacuation system. 
         [0004]    The new EN54:23 Standard requires manufacturers to develop visual beacons that are capable of delivering set values of light coverage volumes at controlled intensity parameters. To reduce power consumption the standard allows devices to save wasted light distribution and allows for orientated device installation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  illustrates aspects of a system, in accordance herewith, with a selected alarm indicating audible/visual output device installed in a region being monitored; 
           [0006]      FIG. 2  is a side sectional view of portions of the output device of  FIG. 1 ; 
           [0007]      FIG. 3  is a top planar view of a light emitting diode array usable in the output device of  FIG. 2 ; 
           [0008]      FIG. 4  is a sectional view of a portion of a lens of the output device of  FIG. 2 ; 
           [0009]      FIG. 5A  is a bottom view of the lens of  FIG. 2 ; 
           [0010]      FIG. 5B  is a side, sectional view of the lens of  FIG. 2 ; 
           [0011]      FIG. 6A  is a bottom view of an alternate form of the type of lens as in  FIG. 2 ; 
           [0012]      FIG. 6B  is a side sectional view of the lens of  FIG. 6A ; 
           [0013]      FIG. 6C  is an enlarged side sectional view of a portion of the lenses of  FIGS. 5A and 6A ; 
           [0014]      FIG. 7A  is a side sectional view of the output device of  FIG. 1  illustrating additional details thereof; 
           [0015]      FIG. 7B  is a top planar view of the lenses of  FIGS. 5A ,  5 B; 
           [0016]      FIG. 7C  is a top planar view of the lens of  FIGS. 6A ,  6 B; 
           [0017]      FIG. 8A  illustrates an exemplary 360 degree light output profile from an output device as in  FIG. 1 ; and 
           [0018]      FIG. 8B  illustrates an exemplary 90 degree light output profile. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    While disclosed embodiments can take many different forms, specific embodiments hereof 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 hereof, as well as the best mode of practicing same, and is not intended to limit the claims hereof to the specific embodiment illustrated. 
         [0020]    In embodiments hereof, an advantageous solution is provided to the requirements of the EN54:23 Standard. This solution enables the installer to install the device on the wall, or ceiling, without the need to orientate the device for desired light coverage. A single Fresnel type lens, symmetrical about a centerline can be used to distribute the output light in accordance herewith. 
         [0021]    In one aspect hereof, light is distributed through one hundred eighty degrees relative to a plane parallel to a printed circuit board that carries an array of light emitting diodes, the alpha plane. Light is also distributed through three hundred sixty degrees relative to the axis of symmetry (perpendicular to the alpha plane), in the rotational orientation plane, the beta plane. The array of light emitting diodes is positioned between the lens and the printed circuit board and driven with a switch mode power supply. 
         [0022]    In another aspect hereof, a degree of power loss is accepted to provide for a non-orientated installation. The installer merely needs to establish an appropriate location for the device and mount it at that location. No time or effort are needed, beyond the mounting and connecting process, to provide the desired omni-directional light output pattern to satisfy the requirements of EN54:23. 
         [0023]      FIG. 1  illustrates a system  10  which includes an alarm/monitoring control unit or panel,  12  which is coupled via medium  14  to a plurality of substantially identical visual, or audible/visual output devices  16  which are used to alert individuals in a region R being monitored as to the presence of an alarm indicating condition. Those of skill will understand that the system  10  could be coupled to a plurality of ambient condition detectors scattered throughout the region R. Further, the medium  14  could be a wireless medium or a wired medium implemented, for example, with an electric cable. 
         [0024]    Exemplary audible/visual output device  20  could correspond to the members of the plurality  16 . As those of skill will understand a discussion of the unit  20  is applicable to other members of the plurality  16  and they do not need to be separately discussed. 
         [0025]    Unit  20  can be mounted on a surface S of a wall in the region R at a preferred installation height on the order of 2.4 meters above the floor on the region R. Unit  20  includes a mounting base  22  which can be attached to the surface S. A lens/electronics assembly  24  can be releasibly carried by the base  22 . For example assembly  24  can engage the base with a snap-fit arrangement, a friction fit or a twist-lock configuration all without limitation. 
         [0026]    The assembly  24  can communicate, via the base  22  and medium  14 , with the control unit  12 . The medium  14  can provide electrical energy to activate the units  16 ,  20 . Alternately, the unit  16 ,  20  can receive instructions or commands via the medium  14  and a local supply can be provided to energize the units  16 ,  20 . 
         [0027]    The exterior surface of the unit  20  is symmetrical with respect to an axis A. The assembly  24  can carry an optical lens  30  implemented as a Fresnel ring array  32 . Additional details of the array  32  are illustrated in  FIG. 4 , detail  32   a . Lens  30  is symmetrical with respect to axis A. 
         [0028]    The lens  30  also carries a printed circuit board  34 . The printed circuit board is preferably arranged so as to be on the order of 18.5 mm from the exterior tip of the lens  30 . 
         [0029]    A light emitting diode array  36  is arranged on printed circuit board  34  in a circular pattern about the axis A. Control and drive current circuits  38  are also carried on assembly  24 , coupled to the array  36 , and, via wiring  40  to the medium  14  and the control unit  12 . The array  36  has a diameter preferably on the order of 30 mm. 
         [0030]    The circuits  38  provide drive current to the light emitting diodes which, in response thereto, emit light pulses that are transmitted via lens  30  into the region R in accordance with a predetermined pattern. For example, drive currents of 200 mA can be provided to each string of four diodes. This current can be in the form of square wave pulses, with a maximum amplitude of one amp, and with a duration of 66 mSec. 
         [0031]      FIGS. 5A and 5B  illustrate bottom and side views of the lens  30 . The snap fit features  30   a  can be used to attach the lens  30  to the base  22 . 
         [0032]      FIGS. 6A ,  6 B illustrate an alternate lens configuration  50 . Lens  50  has a surround  50   a  which can slidably engage an alternate to the base  22  as would be understood by those of skill in the art. As illustrated in  FIG. 6C , the lens  30  and the lens  50  are identical in their optical characteristics. Both include the same Fresnel array design. 
         [0033]      FIGS. 7A ,  7 B respectively illustrate the alpha plane and the beta plane relative to the lens  30 .  FIG. 7C  illustrates the beta plane for the lens  50 . 
         [0034]      FIG. 8A  illustrates an intensity profile of visible light output from a device  20 , as in  FIG. 1 . The light is emitted for the full three hundred sixty degrees of revolution about the device axis A which produces the desired radiant distribution.  FIG. 8B  illustrates an exemplary ninety degree output profile extending from the axis of symmetry A. 
         [0035]    In summary, in accordance with embodiments hereof, a circular LED array is positioned at a predetermined distance from and generally parallel to an optical Fresnel lens. This configuration overcomes the need to specify the rotational position of the product on a mounting surface. Once the correct installation height is achieved it is not necessary to align any light output elements (in this case LED&#39;s) to any given instance relative to the horizontal floor. 
         [0036]    The combination of the light emitting diodes, arranged in a circle with a selected diameter, a Fresnel ring array of the polycarbonate lens and the predetermined distance of the emission surfaces of the light emitting diodes to each of the Fresnel rings allows light propagated from those diodes to be refracted in a proportional manner from the diode array to a diverse spectrum of viewing angles relative to the device when installed. This is achieved in the main by the incident angles of each of the Fresnel ring faces and the intrinsic relationship of each ring to its neighbor and the family of rings as a whole. 
         [0037]    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. 
         [0038]    Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments.