Abstract:
A cable suspension system for linear lighting fixtures simplifies installation procedures by providing a simple leveling adjustment compensation for weight imbalance about a longitudinal axis of the lighting fixture. A suspension cable is fixed in a bore of a cable fitting, with the cable fitting being mounted to a bracket which pivots relative to the fixture. The pivot axis is parallel to the longitudinal axis of the fixture. The angle of the bracket is adjusted relative to the fixture is adjusted such that the fixture as a whole hangs horizontally level.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to cable suspended lighting assemblies and more particularly to a system for leveling a linear lighting fixture about its longitudinal fixture axis. 
     2. Antecedents of the Invention 
     A popular installation for linear lighting assemblies has been the suspension of lighting fixtures from braided steel cables. A linear fixture was supported by a pair of braided steel cables, the upper ends of which were anchored to a ceiling support and the lower ends of which were locked in a bore of a cable anchor. The cable anchors were positioned in registration with the longitudinal axis of the fixture, equidistantly spaced from the ends of the fixture. The cable anchors included a spring loaded locking clamp for adjustment of the effective length of the cable so that the fixture could be horizontally leveled along its longitudinal axis. 
     In addition to wiring and fixture costs, a significant factor in the total cost of lighting was the installation. While leveling the fixture along its longitudinal axis was relatively simple, the more difficult task was leveling the fixture about its longitudinal axis. Weight imbalances due to ballasts, sockets, related wiring, brackets and mechanical components carried within the fixture resulted in moments about the longitudinal axis of the fixture which were required to be balanced in order to hang the fixture in a horizontal plane. 
     Previous techniques for leveling a cable suspended fixture about its longitudinal axis included the installation and positioning of counterbalance weights within the fixture housing. Such task was labor intensive and time consuming, with workers standing on scaffolding or ladders. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a leveling system for a linear lighting assembly suspended from cables. The cables hang substantially vertically from a ceiling anchor with each cable being received within the bore of a cable anchor attached to the fixture. 
     The cable anchor is secured to a bracket which pivots about an axis parallel to the longitudinal axis of the fixture. The bracket may be carried in an assembly strut which joins elongate side extrusions of the fixture. 
     The strut comprises an open channel having parallel side walls and a bottom. A bracket pivot extends through the side walls of the strut. Positioned between the strut bottom and the underside of the bracket on one side of the pivot is a compression spring while a screw extends through the bracket on the other side of the pivot and bears against the bottom of the strut. Rotation of the screw varies the plane of the cable anchor bracket relative to a reference plane of the fixture to horizontally level the reference plane and compensate for fixture weight imbalance. 
     From the foregoing compendium, it should be appreciated that it is an aspect of the present invention to provide a leveling system for a cable suspended lighting fixture of the general character described which is not subject to the disadvantages of the antecedents of the invention aforementioned. 
     It is a feature of the present invention to provide a method of leveling a cable suspended lighting fixture of the general character described which is simple to practice. 
     A consideration of the present invention is to provide a method of leveling a cable suspended lighting fixture of the general character described which reduces installation labor costs. 
     Another aspect of the present invention is to provide a leveling system for a cable suspended lighting fixture of the general character described which is relatively low in cost and suitable for economical mass production fabrication. 
     An additional feature of the present invention is to provide a leveling system for a cable suspended lighting fixture of the general character described whereby a reference plane extending through the fixture is horizontally leveled in the presence of a weight imbalance about the longitudinal axis of the fixture by varying the angle of an adjustment bracket. 
     A further consideration of the present invention is to provide a leveling system for a cable suspended lighting fixture of the general character described whereby the lighting fixture may be leveled about its longitudinal axis utilizing an adjustment screw. 
     Yet a further aspect of the present invention is to provide a leveling system for a cable suspended lighting fixture of the general character described which compensates for a weight imbalance varying the position of one portion of the fixture relative to a reference plane of the fixture. 
     To provide a leveling system for a cable suspended lighting fixture of the general character described which reduces the necessity for field installation of counterbalance weights is a further feature of the present invention. 
     Further aspects, features and considerations in part will be obvious and in part will be pointed out hereinafter. 
     With these ends in view, the invention finds embodiment in the various combinations of elements, arrangements of parts and series of steps by which the aforesaid aspects, features and considerations and certain other aspects, features and considerations are attained, all with reference to the accompanying drawings and the scope of which will be more particularly pointed out and indicated in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings in which is shown one of the various possible exemplary embodiments of the invention, 
     FIG. 1 is a fragmentary perspective view of a cable suspended linear lighting fixture having a leveling system construed in accordance with and embodying the present invention. 
     FIG. 2 comprises an enlarged scale exploded perspective view of the leveling system of the present invention and showing a fixture assembly strut, a cable anchor and an anchor bracket which is adjustably pivotable relative to the fixture. 
     FIG. 3 is an enlarged scale sectional view through the lighting fixture and a ceiling support, the same being taken substantially along the plane  3 — 3  of FIG.  1  and illustrating some typical operating components of the fixture and showing the fixture as initially hung with a weight imbalance. 
     FIG. 4 is an enlarged scale sectional view through the lighting fixture, identical to that of FIG. 3 yet illustrating the fixture after adjustment of the anchor bracket to level the fixture. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in detail to the drawings, the reference numeral  10  denotes generally a linear lighting fixture illustrated without lighting components in FIG.  1 . It should be understood that the fixture is merely exemplary and that the leveling system of the present invention is equally suited for employment in lighting fixtures of other types and configurations. 
     The fixture  10  comprises a housing frame formed of a pair of extrusions  12 ,  14  which are joined together at their ends by a pair of end caps  16 , only one of which is illustrated. The extrusions are additionally maintained in spaced apart relationship by at least two assembly struts  18 , equidistantly spaced from the end caps  16 . The upper surface of the fixture lies in a reference plane  15 . 
     The extrusions  12 ,  14  generally include a plurality of internal channels which are employed for the purpose of mounting the assembly struts  18 , as by screws  20 , as well as lighting fixture components such as sockets employed to mount a lighting tube  22 , to mount ballasts  24  and to carry associated wiring. The extrusion channels are also employed, in a conventional manner, for factory or field mounting of a course adjustment counterbalance weight  26 , if necessary, and to mount light reflectors  28 , which overly the ballasts, as well as a light diffuser  30 . 
     The fixture  10  is suspended by at least two braided steel cables  32 , each of which extends along a generally vertical axis  33 . Each cable  32  is received, at its upper end, in an upper cable anchor  34 , mounted in a utility box  36 . The anchor  34  is secured to a suitable fixed ceiling member through a rod  38 . A canopy  40 , which lies against an exposed ceiling surface, is employed to conceal the upper mounting assembly. 
     Pursuant to the invention, a leveling system  42  is provided for quickly and precisely leveling the suspended fixture  10  about a longitudinal axis  44  of the fixture. It should be understood that the longitudinal axis  44  does not generally coincide with the center of gravity of the fixture. 
     The leveling system  42  includes cable anchor  46  having a bore  47  extending along an axis  49  for receiving the cable  32 . The cable anchor  46  is of conventional configuration, e.g. Part No. 100015, available from Linear Lighting Corp., Long Island City, N.Y. Adjustment of the effective length of the cable is accomplished by releasing a spring loaded internal clamp of the cable anchor  46 . Such adjustment is done at an initial stage of the fixture installation for assuring that the fixture is hung from the specified height and also for assuring that the fixture is horizontally level along the longitudinal axis  44 . 
     The cable anchor  46  is secured in a bracket  48  which is carried within a central span  50  of the strut  18 . The central span  50  includes a pair of parallel side walls  52 ,  54  and a bottom  56 . The bottom  56  extends upwardly adjacent the ends of the side walls and thereafter extends in opposite directions as a contoured mounting flange  58 , having a slot  60  which receives the mounting screw  20 . 
     As will be noted from an observation of FIG. 2, the bracket  48  includes a central raised platform  62  which includes a threaded bore  64  into which is received a matingly threaded mounting skirt  66  of the cable anchor  46 . The platform  62  lies in a plane  65 , with the bore axis  49  being perpendicular to the plane  65 . 
     FIG. 3 illustrates the fixture  10  as hung with the plane  65  of the platform  62  parallel to the plane  15  of the fixture. The left side of the fixture  10  is heavier than the right side, perhaps due to field installed internal wiring. Such weight imbalance results in a counterclockwise moment imbalance. As a result, the fixture  10  is not horizontally level. 
     It should be noted that the portion of the cable  32  received in the bore  47  of the cable anchor  46  is at an angle other than vertical such that a portion of the cable  32  adjacent the cable anchor  46  is slightly curved, bowed or bent with an equilibrium state reached when the reference plane  15  is sloped. 
     In accordance with the invention, the bracket  48  is adjustable relative to the fixture  10  to horizontally level the reference plane  15  without adding counterbalance weights to the fixture  10 . 
     By way of example, a configuration for the bracket  48  which facilitates such adjustment includes a pair of end panels  68 ,  70  which extend from opposite ends of the central platform  62 . The bracket  48  additionally includes a pair of side panels  72  which extend from the end panel  68  and a pair of side panels  74 , which extend from the end panel  70 . 
     Portions of the side panels  72 ,  74  overlap one another as can be seen in FIG.  2 . The outer side panels  72  are dimensioned such that the bracket  48  can be received between the side walls  52 ,  54  of the strut  18 . A transverse bore  76  extends through the overlapped portions of the side panels  72 ,  74 , with the bore  76  being registered with a coaxial bore  78  in the side walls  52 ,  54  of the strut  18 . 
     A pin, screw or screws  82  extend through the coaxial bores  76 ,  78  such that the bracket  48  is capable of pivotal movement about a common bore axis  80 , which is parallel to the longitudinal axis  44  of the lighting fixture  10 . 
     A tongue  84  extends downwardly from the panel  68 . The tongue  84  serves as a seat for a helical coil compression spring  86 ; the bottom of the spring  86  is seated over a screw  88  which extends upwardly through a threaded aperture in the bottom  56  of the strut  18 . 
     An adjustment screw  90  extends through a U-nut or J-nut clip  92  which is secured around an aperture formed in the end panel  70 . The bottom of the screw  90  is seated in a depression or well  94  formed in the bottom  56 . 
     It will be appreciated that the spring  86  urges the bracket  48  in a counterclockwise direction, as viewed in FIG. 2, about the axis  80 , with the angular position of the central platform  62  being adjusted and held fast through rotation of the adjustment screw  90 . 
     By adjustment of the plane  65  of the bracket central platform  62  to other than parallel to the reference plane  15  of the lighting fixture, e.g. to the angle illustrated in FIG. 4, the fixture  10  may be leveled such that the reference plane  15  is horizontal. In the adjusted FIG. 4 position, the portion of the cable  32  received in the bore  47  of the cable anchor  46  is at the angle relative to the upper vertical portion of the cable axis  33 . That is the axis  49  of the bore  47  of the cable anchor  46  is not vertical. This results in the cable being correctively curved or bowed or bent adjacent the cable anchor. It is believed that resistance to such corrective bending of the cable  32  generates a clockwise moment as viewed in FIG. 4, to compensate for the unequal weight distribution of components within the fixture such that an equilibrium state is reached, similar to that in FIG.  3 . Adjustment of the bracket  48  relative to the fixture  10  levels the reference plane  15 . 
     Thus it will be seen that there is provided a leveling system for a suspended lighting fixture which achieves the various aspects, features and considerations of the present invention and which is well suited to meet the conditions of practical usage.