The present invention generally relates to devices affixed to the top of a pole—what will be referred to herein as pole top fitters—which are adapted to orient, suspend, and/or otherwise positionally affix one or more objects relative said pole (or relative a target area, for example). More specifically, the present invention relates to the design and operation of pole top fitters as they relate to lighting fixtures; particularly in applications where uplight is to be avoided. Uplight, as it is commonly known in the industry—see, e.g., IES TM-15-11—is generally defined as light projected above a luminaire (assuming a luminaire pointing downwardly), and is later discussed.
A pole top fitter is not a new device or technology; its use has long been established in the art of wide area lighting; see, for example, U.S. Pat. No. 7,500,764 hereby incorporated by reference in its entirety. Pole top fitters provide a foundation for one or more extended armatures—what will be referred to herein as cross-arms—to which one or more lighting fixtures (or other objects) are affixed. As used herein, “lighting fixture” refers generally to a light source, associated housing, associated light directing and/or light redirecting devices, associated electrical connections, and associated devices for attaching to a cross-arm (if any); no distinction has been made between “luminaires” or “lighting fixtures”, and indeed the terms are used interchangeably herein.
Pole top fitters permit a lighting designer to affix multiple luminaires to a single pole, thereby ensuring fewer poles are needed for a given lighting application. As is well known in the art, fewer poles translate to potential cost savings—which for a wide area lighting application (e.g., professional sports field) with poles on the order of several tens of feet tall can be substantial. There is a natural motivation, then, to pack as many fixtures and cross-arms on a pole top fitter as is possible for a given pole, each pole having a loading capacity in accordance with its size, material, processing techniques, mounting height, anticipated wind load for the geographic area, and the like. An overzealous approach to loading a pole top fitter (e.g., producing a greatly unbalanced or eccentric load on a pole to pack in more fixtures)—regardless of whether limitations for a given pole are exceeded—can sometimes result in warpage of the cross-arm or tipping of the pole. For that reason (and perhaps others), sometimes pole top fitters are configured in what will be referred to as a “back-to-back” configuration; namely, lighting fixtures on both sides of the pole and projecting light generally in opposite directions (i.e., forward of the pole and behind the pole). Placing fixtures in a back-to-back configuration on a pole top fitter may permit additional lighting fixtures to be installed on a single pole without bending the pole or warping a cross-arm, but can become problematic when (i) it is undesirable to project light behind a pole or (ii) the positioning of the fixtures on both sides of the pole inadvertently illuminates the pole itself (causing localized glare or otherwise distracting from the intended viewing target).
Returning now to the issue of uplight—the phenomenon of projecting light upwardly of a downwardly-facing lighting fixture can be undesirable for a number of reasons. Generally speaking, any light not directed towards a target area is wasted—lowering the overall efficiency of the lighting system and contributing to sky glow. Sky glow is particularly undesirable in residential areas, areas designated as “dark sky”—see, e.g., www.darksky.org for areas designated as such according to the International Dark-Sky Association—or areas having conservatories, for example. Of course, some lighting applications prefer some degree of uplighting—in particular, aerial sports such as baseball, golf, volleyball, and ski jumping—but in such cases it is desirable for uplighting to be precise and controlled.
In the context of pole top fitters, uplight becomes a concern when a lighting designer attempts to stack multiple rows of lighting fixtures on a pole. The light from a fixture on the top row may strike the housing of a lighting fixture on a lower row and redirect it in a number of directions, producing specular or diffuse reflection depending on environmental conditions, housing material, and the like. This redirected light produces uncontrolled uplight and is undesirable. One solution is to offset lighting fixtures, but this may reduce the fixture count on a pole—which is undesirable. The fixtures could be placed in a back-to-back configuration on the pole top fitter, but this places light behind the pole—which may be undesirable. Additionally, if the fixtures on the back side of a pole in a back-to-back configuration are re-aimed so to attempt to project all light forward of the pole, there is a high likelihood that some of that re-aimed light will strike the pole itself, thereby creating small scale or localized glare—which is undesirable, and may also contribute to uncontrolled uplight. The entire pole top fitter could be angled relative the pole—much like photo finish lighting fixtures for some race tracks—but this configuration is impractical for a large number of fixtures (e.g., because of the risk of pole tipping). The art lacks a solution to providing a large number of fixtures on a pole top fitter in a manner that does not project light behind the pole, does not produce uneven loading, and minimizes uncontrolled uplighting and/or localized glare.
Thus, there is room for improvement in the art.