Abstract:
The present disclosure relates to a safety light assembly mountable on a ladder to aid firefighters and other emergency personnel in locating the ladder under adverse visibility conditions such as smoke, darkness, and inclement weather. The light assembly preferably comprises a pair of respective housings each mountable upon one of the outwardly side-facing surfaces of the ladder side members at locations adjacent to the upper end of the ladder. The housings contain respective light sources capable of projecting light in respective opposite outwardly side-facing directions from the ladder while also refracting portions of the light laterally away from the respective outwardly side-facing directions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional App. No. 61/956,317, filed Jun. 4, 2013. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present disclosure relates to a safety light assembly to aid firefighters and other emergency personnel in locating a ladder under adverse visibility conditions such as smoke, darkness, and inclement weather. Such personnel often must locate such a ladder urgently for emergency exit from a building or other structure under such adverse conditions. Previous proposed types of safety lights mountable at or near the top of a ladder have been described in U.S. Pat. Nos. 4,766,525 and 8,167,088. However a problem with such previous proposed types of safety lights is that their directions of light transmission are unduly limited by their mounting positions on the ladder. For example, the light assembly shown in U.S. Pat. No. 4,766,525 transmits light principally in a laterally inward direction from one ladder side member toward an opposing ladder side member, enabling the opposing side member to partially block the inwardly transmitted light while no light is transmitted in an outwardly opposite direction. Alternatively, as shown in U.S. Pat. No. 8,167,088, another previous light assembly directs light principally only in a forward direction from the top of a ladder side member, thereby transmitting little or no light toward either side of the ladder where personnel seeking the ladder are likely to approach. 
         [0003]    The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0004]      FIG. 1  is a front view of the top portion of a ladder equipped with an exemplary light assembly in accordance with the present invention having a pair of respective opposite outwardly facing light sources each enclosed by a respective housing mounted on each top end of the two ladder side members. 
           [0005]      FIG. 2  is a top view of the ladder of  FIG. 1 . 
           [0006]      FIG. 3  is an enlarged outward side view of one of the respective exemplary light source housings of  FIG. 1 . 
           [0007]      FIG. 4  is a detail view of an exemplary light source mounted within the light source housing of  FIG. 3 . 
           [0008]      FIG. 5  is a detail edge view of one exemplary lens and aperture assembly of the light source of  FIG. 4 . 
           [0009]      FIG. 6  is a simplified circuit diagram of an exemplary light source control system usable with the light source of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0010]      FIGS. 1 and 2  show the top of an exemplary aluminum ladder  10  having a spaced pair of elongate side members  12  with respective inwardly-facing surfaces  12   a  interconnected by ladder rungs such as  14 , and with respective outward surfaces  12   b  defining elongate depressions  18  facing in respective opposite side-facing directions  24  and  26 . The top of each such depression  18  has in the past normally been closed by an upwardly rounded cap member (not shown) having leg portions which fit matingly into the top of each depression  18  so a to eliminate any sharp edges at the top of the ladder which might injure hands or arms or catch loose gloves or garments. Alternatively, other types of ladders are possible, now or in the future, not having such depressions  18  but instead, for example, employing cap members which have downwardly-directed sleeves which slip matingly over the tops of the ladder side members. In any case, such mating cap members are removable from the side members and can be replaced by corresponding other mating members if desired, in accordance with the following disclosure. 
         [0011]    In the exemplary structure of  FIGS. 1 and 2 , such cap members are replaced by at least one, but preferably two, housings such as  20 , each containing at least one light source and a battery power source as well as circuitry to be described hereafter for controlling the light source. With reference also to  FIG. 3 , mounting of each housing  20  on the ladder is preferably accomplished by insertably mounting a pair of legs  20   a  of each housing into each depression  18  of the C-shaped side members  12  of the ladder, and fastening each leg  20   a  in place by any suitable means such as rivets or screws through holes such as  20   b  as shown in  FIG. 3 . The legs can be straight or, if desired, L-shaped as shown in  FIG. 3  to rigidify the existing C-shaped side members  12  of the ladder particularly in their topmost areas, which have no rung support, against the risks of bending, twisting or collapsing, while also enabling drainage of moisture away from each housing  20  through a gap  20   c  between the two L-shaped legs  20   a.    
         [0012]    In  FIG. 1 , the ladder  10  with the inserted housings  20  is shown leaning against an exposed elevated surface  22 , such as a roof, or window or door sill, of a building or other structure where firemen or other emergency personnel may urgently need to access the top of the ladder  10  when it is necessary for them to descend. Under conditions of smoke, darkness, fog, precipitation or other visibility-limiting conditions, and especially in cases of urgency, the top of the ladder could often prove to be difficult to locate when it is not known whether the ladder is located toward the right or left side of the personnel seeking to find it. Previous homing lights as described above, which direct light principally forwardly of the ladder, or in only a single lateral direction partially blocked by the ladder structure, do little to alleviate this problem. 
         [0013]    In accordance with the present disclosure, therefore, a significantly more effective solution is accomplished by equipping each housing  20 , or any other suitable alternative light source-mounting structure, with a light source capable not only of projecting its light in a respective side-facing direction such as  24  and/or  26  as shown in  FIGS. 1 and 2 , but also capable of diverging a major portion of its light in multiple angular directions laterally surrounding the respective side-facing direction  24  or  26  so as to project the light in a generally conically expanding shape as exemplified by the broadly spread divergent directions  28   a,  b and  30   a,  b shown in  FIGS. 1 and 2 . 
         [0014]      FIG. 5  exemplifies a preferred type of a single light source  32  usable herein. However, although in some applications it may be the only light source within each housing  20 , it is preferably used in multiples within each housing  20  as will be explained hereafter. The exemplary light source  32  preferably includes an LED  34  (light-emitting diode) mounted on a circuit board  36  which controls the LED. The LED preferably emits light either at an adjustable pulse rate or at a steady state, as selected and downloaded to a microprocessor ( FIG. 6 ) on the circuit board  36 . The light is preferably emitted from the LED through a hemispherical lens  34   a  and then transported through an integral minimal-loss light pipe portion of a thin-walled diverging lens  38  whose exterior curved lens surface  38   a  preferably encompasses approximately  60  degrees and is recessed slightly within the outside of an aperture plate  40  of the housing  20 , so as to protect the lens  38  from damage. To maximize the lateral divergence of the light emitted from the lens surface  38   a,  the aperture  42  is beveled (chamfered) laterally outwardly by about  50  degrees or more from the respective side-facing direction such as  26  to maximize the desired expanding light cone. The lens  38  is cored to create a thin-walled divergent lens primarily because, if it were to be a solid piece, the injection molding process would increase the risk of creating bubbles within the lens, thereby causing optic distortion in the lens. The center of the LED  34  is aligned horizontally with the center of the lens  38 . The foregoing factors all contribute to minimizing the loss of light intensity between the LED and the ambient conditions outside the lens. 
         [0015]    The color of the light emitted by the LED  34  is preferably blue because, when observed, it radiates a soothing psychological effect which is a factor in calming the nerves of personnel at risk. The color blue is a result of the LED radiating at a dominant wavelength of  465  nm. The color blue is also preferable because, in the desired laterally angular directions where maximum light intensity is desired in accordance with this disclosure, the luminous intensity of the blue LED light is greater than that of other lights such as a comparable white LED light. If the LED pulsates, the LED preferably comes on abruptly at high intensity and then dims gradually to zero intensity over the remainder of the cycle. 
         [0016]    As mentioned above, multiple light sources similar to light source  32  are preferred within each housing  20 . At least two substantially identical light sources, each having a respective LED  34  mounted on the circuit board  36 , preferably cooperate with a unitary molded resin lens assembly  44  mounted on the circuit board  36  as shown in  FIG. 4 . Such two light sources both preferably project blue light through two identical laterally adjacent respective lenses such as  38  and  39  and respective beveled apertures  42  and  43  in the aperture plate  40 , as needed to fulfill desired light intensity requirements by combined simultaneous emissions from the multiple light sources. An additional light source, projecting preferably red pulsed light through an identical lens  46  and beveled aperture  47  as shown in  FIG. 3 , can optionally be used to signal a low battery. 
         [0017]    The resin composition of the unitary molded lens assembly  44  may be polycarbonate, or any other suitable lens material. The polycarbonate material is clear and highly resistive to breakage and scratching. When installed in a housing such as  20 , the lens material is preferably under no deflective load, and sits directly on the face of the circuit board  36 . A trench (not shown) containing an O-ring may be formed in the bottom side of the lens assembly encircling the multiple lenses so that, when the circuit board is attached through screw holes such as  48  in the lens assembly to the housing  20 , a seal is created between the lens assembly and the circuit board to minimize light leakage. 
         [0018]      FIG. 6  shows an exemplary simplified operating circuit usable in controlling the foregoing light source system. Actuation and deactivation of the system can be by remote control from an RF transmitter  50 . No manual control switch on the ladder itself is recommended because it would often be in an awkward position for the user, or would require the user to divert attention from other tasks. The signal from the transmitter could be programmed so as to activate as many or as few light sources as the user wishes, subject to distance limitations of the system. 
         [0019]    Alternatively, or in combination with the remote control, actuation and deactivation could be controlled automatically by a tilt sensor switch  52  which activates the system preferably when the ladder is at or beyond a predetermined tilt angle such as  45  degrees regardless of which end of the ladder is lifted. Such tilt sensor switches are shown, for example, in U.S. Pat. No. 7,045,724 or US patent application publication No. 20120325629, which are incorporated herein by reference. 
         [0020]    The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.