Abstract:
Disclosed is a dock light assembly for illuminating a trailer interior. The dock light assembly may include a cylindrical housing having an illumination source therein, and an optical lens secured to an end of the housing. The optical lens may be configured to provide focused illumination to the trailer interior. A rotationally self-correcting screen device may be positioned between the illumination source and the optical lens. The screen device may be configured to absorb a portion of the focused illumination such that illumination to an upper portion of the trailer interior is reduced. The rotationally self-correcting screen device remains in a horizontal orientation even if the housing is rotated. One benefit of the disclosed dock light assembly is that forklift operators working in the trailer interior are shielded from high intensity light, even though the lower portion of the trailer interior remains brightly lit.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    Reference is made to and this application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/343,159, filed May 31, 2016, entitled “DOCK LIGHT WITH SELF-CORRECTING BEAM”, which application is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Dock lights are used on the loading platform of a warehouse or the like for the purpose of illuminating the interior of a truck backed up to the loading platform. Typically, the light is mounted adjacent to the loading dock of the warehouse undercover to protect the dock light from the elements when not in use. One such dock light is disclosed in commonly owned U.S. Pat. No. 5,709,458 and U.S. Pat. No. 7,686,476, incorporated herein by reference in their entirety, and includes a base portion mounted adjacent the overhead doorway, and a flexible, hollow, self-supporting tube connected to the base. The tube is comprised of a spiral metallic assembly interfitted to provide a self-supporting flexible member. The dock light may include a high intensity halogen bulb, or an array of LED bulbs. In either case, the dock light also includes a fan for drawing air in through louvers in the base portion, with the airflow then passing through the flexible tube to the lamp assembly for purposes of cooling the lamp assembly. 
         [0003]    Although the aforementioned dock light assembly has proven useful and is well-received in the industry, there exists a desire for even brighter illumination within the trailer. However, the high intensity halogen bulbs or LED arrays currently being used are very bright. Further increases in light intensity may not be safe for forklift operators who, when backing out of or otherwise exiting the trailer, are facing directly into the high intensity light. 
       SUMMARY OF THE INVENTION 
       [0004]    Embodiments of the present invention disclose a dock light assembly for illuminating a trailer interior. The dock light assembly includes a main housing comprising a forward end and an opposing rear end, and a lens holder coupled to the forward end of the housing. An optical lens is secured by the lens holder and is configured to provide focused illumination to the trailer interior. The dock light assembly further includes an electronics package including an illumination source secured to a rear portion of the main housing. The dock light assembly further includes a rotationally self-correcting screen device positioned between the illumination source and the optical lens. The screen device is configured to absorb a portion of the focused illumination such that illumination to an upper portion of the trailer interior is reduced. 
         [0005]    In accordance with one aspect of the disclosure, the screen device includes a dense, thin plate having an approximate semi-circular shape, and the rotationally self-correcting feature is characterized by the plate being free to rotate about a center post secured to the main housing such that rotational movement of the housing rotates the post but not the plate. 
         [0006]    In one embodiment, the optical lens is plano-convex. 
         [0007]    In accordance with another aspect of the disclosure, the dock light assembly further includes a heat sink in thermal contact with the electronics package. The heat sink is configured to dissipate heat generated from the light source during operation. 
         [0008]    In one embodiment, the heat sink includes a plurality of thin, radially-extending fins sized for an interference fit within the main housing. 
         [0009]    In accordance with yet another aspect of the disclosure, the screen device includes a sealed volume defining a reservoir, and the rotationally self-correcting feature is characterized by the reservoir being filled to a horizontal level with an opaque fluid, such that rotational movement of the housing does not alter the horizontal level of the fluid. 
         [0010]    In one embodiment, the screen device comprises a ring having a sealed reservoir therein. The ring comprises a forward face and a rear face, each hermetically sealed with an optically clear material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The features described herein can be better understood with reference to the drawings described below. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. 
           [0012]      FIG. 1  schematically illustrates a prior art dock light assembly; 
           [0013]      FIG. 2  depicts a side perspective view of a dock light assembly in accordance with one embodiment of the present invention; 
           [0014]      FIG. 3  schematically depicts a side plan view of a dock light assembly having a plano-convex lens; 
           [0015]      FIG. 4  depicts a side plan view of the dock light assembly shown in  FIG. 3 ; 
           [0016]      FIG. 5  schematically depicts a side plan view of a dock light assembly having a plano-convex lens and a screen device in accordance with one embodiment of the present invention; 
           [0017]      FIG. 6  depicts a side plan view of the dock light assembly shown in  FIG. 5 ; 
           [0018]      FIG. 7  depicts an opposite side perspective view of the dock light assembly shown in  FIG. 2 ; 
           [0019]      FIG. 8  schematically depicts a side plan view of a dock light assembly with plano-convex lens and a screen device in accordance with another embodiment of the present invention; and 
           [0020]      FIG. 9  depicts a front plan view of the screen device shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The present invention is directed to a dock light and more specifically to a high intensity light which is adapted to be mounted inside a warehouse adjacent a door on the loading platform, which is adapted to extend in an adjustable manner outwardly of the warehouse to shine into the interior of a truck backed up to the loading platform. The dock light is designed with a screen device to shade an upper portion of the beam field so as to protect forklift operators from the high intensity light. Because the light assembly is affixed to a flexible tube which allows rotational movement, and the screen device within the lamp assembly should remain substantially horizontal, the screen device is designed to auto-correct for rotational movement. 
         [0022]      FIG. 1  depicts a prior art dock light assembly  10  having a high intensity halogen bulb. The dock light assembly  10  includes a base portion  12  mounted to an interior wall  14  of a loading dock, a hollow, flexible tube  16  connected to the base portion  12 , and a lamp assembly  18  having a halogen bulb. In operation, loading dock personnel adjust the flexible tube  16  to properly illuminate the trailer interior  20 . Although the lamp assembly  18  provides adequate illumination, the light field  22  is omni-directional, meaning light beams are emitted equally in all directions. Thus, when a forklift operator turns around to back out of the trailer interior  20 , the operator faces directly into the light beam. 
         [0023]    Referring to  FIG. 2 , wherein like numerals indicate like elements in  FIG. 1 , a dock light assembly  110  is shown according to one embodiment of the invention. The dock light assembly  110  includes a main housing  124 , which may be a thin-walled cylinder and formed of a thermally conductive material, such as aluminum. The housing  124  may include a locking feature  126  to secure the internal components of the lamp assembly. In one example, the outer surface of the main housing  124  defines an annular groove  126 , which may be formed into the thin-walled housing. The indented groove  126  on the outer surface forms a corresponding annular raised ridge on the inner surface of the housing  124 , which may be utilized to secure internal components. 
         [0024]    The dock light assembly  110  further includes a ring-shaped lens holder  128  on a forward end  130  of the assembly, the forward end being defined as the beam-emitting end. The lens holder  128  secures an optical lens  132  which, in the illustrated embodiment, is a plano-convex lens having the flat side oriented towards the light source. In this configuration, light emitted from a source within the housing  124  converges in front of the lens at the lens focal point  134  ( FIG. 3 ), then diverges to illuminate the trailer, as shown in  FIG. 3 . 
         [0025]    Other types of optical lens are anticipated within the scope of the present invention. For example, the optical lens may be a projector type, having a polyellipsoidal reflector and condenser lens. This listing is exemplary in nature and not intended to be limiting. 
         [0026]    Structural support for the lens holder  128  may be provided by a plurality of stiffener legs  136  secured to the outer diameter of the lens holder  128 . The stiffener legs  136  may be integral with the lens holder  128  or fasten thereto. The stiffener legs  136  may define a capture feature  138  to engage the locking feature  126  on the housing  124 . In one example, the outer diameter of the stiffener legs  136  may be sized for a slight interference fit with the annular raised ridge  126  on the inner surface of the housing  124 . The axial length of the legs  136  may be dictated by optical considerations. For example, a particular combination of light source and lens may require a specific axial separation or distance between the two to properly converge the light field  122  at a focal point  134  that results in a desirable illumination in the trailer interior  120 . 
         [0027]    An electronics package  140  may be disposed within the opposing rear end  142  of the housing  124 . The electronics package  140  may comprise a printed circuit board, and may be secured to the stiffener legs  136  to complete a frame-like structure. The electronics package  140  may include, as illustrated, an LED array  144  to provide the illumination source. In alternate embodiments, the electronics package  140  may include a halogen bulb, for example. 
         [0028]    A heat sink  146  may be in thermal contact with the electronics package  140  to dissipate the heat generated from the light source during operation. In one embodiment, the heat sink  146  comprises a plurality of thin, radially-extending metallic fins. In one example, the heat sink fins  146  are sized for a slight interference fit within the housing  124 . In this manner, heat dissipated off the fins may be conducted into the housing  124 . In one embodiment, the forward end  130  of the heat sink  146  defines a planar surface to which the electronics package  140  may be directly mounted. In another embodiment, some of the outer edges of the fins define an aperture  148  suitable for mounting provisions to secure the stiffener legs  136  with bolts, for example. 
         [0029]    As illustrated in  FIGS. 3-4 , the LED array  144  emits a light field  122  that passes through the plano-convex optical lens  132 , converges at the focal point  134 , and diverges therebeyond to illuminate the trailer interior  120 . Although the configuration provides a better focused illumination, it does not necessarily solve the problem of the beam shining in the eyes of a forklift operator. Referring back to  FIG. 2 , in one embodiment of the invention the problem is solved by placing a screen device  150  in the dock light assembly  110 . The screen device  150  is placed within the illumination path between the light source and the optical lens  132  to shade an upper portion of the beam field  122  so as to protect forklift operator&#39;s eyes from the high intensity light. As illustrated in  FIGS. 5-6 , blocking the bottom portion of the illumination path has the effect of shading the upper portion of the trailer interior  120 . 
         [0030]    The flexible tube portion  116  of the dock light assembly  110  permits an operator to adjust the lamp assembly over a fairly wide vertical and horizontal range. The flexible nature of the tube also permits the operator to rotate the lamp which, under prior art circumstances, had no deleterious effect on the light beam since the housing is round and the beam was omni-directional. However, a dock light assembly  110  having a screen device  150  secured to the housing  124  (as illustrated in  FIG. 5 ) could present a problem: the horizontal upper surface of the plate  150  would rotate with the housing  124 , and thus rotate the shaded portion projected into the trailer, which could negate the benefits of the screen device. 
         [0031]    To solve this problem, a screen device  150  is disclosed that self-corrects for rotational movement. In the embodiment shown in  FIG. 2 , the screen device  150  is a dense, thin plate having an approximate semi-circular shape. In one example, the plate is formed of steel. The upper portion of the plate may be horizontal (or slightly angled within 15°) to provide a line of demarcation in the shaded region projected into the trailer interior  120 . The screen device  150  may include a thru-hole of sufficient diameter to allow a generous clearance for a post  152  or threaded rod to pass through. In the illustrated embodiment, a threaded bolt  152  is used. The thru-hole in the plate should be located near the top horizontal surface. 
         [0032]    To assemble the rotationally self-correcting screen device  150 , the threaded bolt  152  is passed through the hole in the plate, and the plate is pushed along the shank up to the bolt head  154 . A nut  156  is next run up the threaded bolt  152 , and stopped several thread turns away from engaging the plate. In this manner, the plate may rotate freely about the bolt, but it is captured axially between the bolt head  154  and nut  156 . The bolt  152  may next be threaded into a corresponding tapped hole in the heat sink  146 , for example, along the centerline of the housing  124  and optical lens  132 . 
         [0033]    The dense nature of the screen plate  150 , coupled with its center of gravity being well below the bolt hole, and its freedom to rotate, permits the force of gravity to keep the plate in a horizontal orientation. Any rotation of the main housing  124  will have no effect on the screen plate  150 . Although the bolt  152  will rotate with the housing  124 , the plate self-corrects to remain horizontal. 
         [0034]    Turning now to  FIGS. 8-9 , in another embodiment of the invention a screen device  250  may comprise a sealed volume of opaque fluid, such as ink. In one embodiment, the screen device  250  may include a thin ring  258  approximately ⅛″ to ¼″ thick, having an outer diameter approximately equal to that of the lens holder or stiffener legs, and an inner diameter no less than the optical lens  232 . The forward and rear faces of the ring  258  may be hermetically sealed with an optically clear material  260  such as glass or acrylic, thereby providing an internal volume within the thickness (T) of the ring  258 . An opaque fluid  262  may be injected into the internal volume, to a height sufficient to provide the desired screen or shading effect. Any rotation of the main housing  224 , indicated by arrows in  FIG. 9 , will have no effect on the function of the screen device  250  because the opaque fluid  262  self-corrects to remain horizontal. In one example, the opaque fluid  262  may comprise a dark fluid to absorb virtually all light passing through it. In another example, the opaque fluid  262  may comprise a mixture having a dark fluid in suspension with a lighter fluid. The ratio of dark fluid to light fluid may be varied to achieve a “dimming effect” within the trailer interior, rather than a complete blockage of light. In yet another example, the opaque fluid  262  may comprise a mixture having a graduated opacity, in which the light-absorbing properties vary from top to bottom, side-to-side, or a combination of the two. A fluid  262  having a graduated opacity may provide illumination in the trailer with a gradual transition to darkness, which operators may find easier on their vision. 
         [0035]    While the present invention has been described with reference to a number of specific embodiments, it will be understood that the true spirit and scope of the invention should be determined only with respect to claims that can be supported by the present specification. Further, while in numerous cases herein wherein systems and apparatuses and methods are described as having a certain number of elements it will be understood that such systems, apparatuses and methods can be practiced with fewer than the mentioned certain number of elements. Also, while a number of particular embodiments have been described, it will be understood that features and aspects that have been described with reference to each particular embodiment can be used with each remaining particularly described embodiment.