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PRIORITY 
     This application claims the benefit of the priority of U.S. provisional application 61/622,664, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention generally relates to the field of electro-mechanical equipment and more particularly to means for supporting said equipment for use in residential and/or commercial garages or work bays with overhead doors. Typically in such spaces electrical power is not readily available except around the perimeter of the space, yet much of the work that takes place in these locations is not near the perimeter. For example, automotive repair work is performed on the vehicle wherever it is parked in the garage bay. Similarly, lighting is often poor in garages that were designed primarily for automobile storage. 
     In some commercial garages or work bays, special accommodations have been designed into the structure to provide electrical and other utilities away from the perimeter of the space. Electrical power, for example, may be available using a ceiling mounted, retractable extension cord device, the extension cord being electrified from junction boxes distributed where needed on the ceiling. Similarly, by advanced planning, some commercial garages have ceiling mounted light fixtures distributed above the expected work spaces. 
     In other commercial garages, these amenities may not be available, particularly if the garage was not originally designed to serve as a work space. Similarly, nearly all residential garages lack these amenities, again because they were not originally designed to be work spaces. 
     An additional obstacle in providing electrical or mechanical amenities in a garage or work bay is the most common vehicle access door in these spaces—the overhead, roll-up door. By definition, an overhead roll-up door will, when in the open position, intercept the space between the ceiling and the work space below. Thus, no permanent, ceiling mounted device can be installed above the work space unless the device can fit entirely above the raised roll-up door. 
     Furthermore, in retrofit applications, permanent ceiling mounted devices often require expensive renovation work or, at a minimum, the service of licensed tradespeople. 
     There is, therefore, a need for an easily installed means of providing electrical or mechanical utilities in existing work spaces. 
     SUMMARY OF THE INVENTION 
     The present invention comprises an apparatus for providing electrical utilities to support lighting and electrically powered equipment in pre-existing workspaces, the workspace having an overhead roll-up door. That is, workspaces like residential garages having roll-up, overhead doors rather than swing open doors for, typically, vehicular access. 
     In one instance the apparatus is a trolley, the trolley being a platform to support or carry items and/or to carry electrical utilities from the location of a fixed outlet to a designated location where the electricity is needed. The trolley generally has four wheels or rollers, wherein rollers are a common term for wheels designed to ride in overhead garage door tracks. The four rollers are generally located near the corners of the trolley. In one instance, the rollers are designed to ride in the tracks of a pre-existing, roll-up door such as is used for vehicular access to a garage. In some embodiments the trolley may have only one roller on each of two parallel sides. 
     In another instance the trolley comprises skid blocks to replace the rollers, the skid blocks being designed to ride in the same existing overhead roll-up door tracks. 
     In one instance the trolley is approximately the width of the garage door, and has two rollers in the door&#39;s left hand track and two rollers in the door&#39;s right hand track. 
     In another instance, the trolley is disposed between two roll-up overhead doors of a double door garage. In this instance the trolley has its two left hand rollers in the right hand track of one door and its two right hand rollers in the left hand track of the adjacent door. 
     In some embodiments the trolley comprises a flat platform while in other embodiments the trolley additionally comprises one or more sidewalls, forming a tray- or pan-like structure. In other embodiments the trolley further comprises an enclosing plate that completes a box structure. 
     In some embodiments the trolley comprises only sidewalls, with no platform, in which embodiments the electrical utilities are transported by the sidewalls. 
     In some instances the trolley comprises an electrical power cord. One end of the power cord is equipped with an approved electrical plug compatible with local electrical codes. The other end of the cord may terminate in a so-called power strip, which typically provides a number of standard electrical outlets compatible with local electrical codes. In other instances this second end of the electrical power cord may be “hard-wired” to one or more pieces of electrical equipment. 
     In some instances the trolley comprises one or more electric light fixtures. 
     The above and other features of the invention, including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The foregoing and other objects, features and advantages of the invention will become apparent from the following description in conjunction with the accompanying drawings, in which reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. In the drawings: 
         FIG. 1  illustrates schematically an exemplary installation of a trolley; 
         FIG. 2  is an illustration of an embodiment of an overhead door equipment trolley; 
         FIG. 3  is a detail illustration of a roller set and supply/distribution box; 
         FIG. 4  illustrates a commercially available roller/axle combination; 
         FIG. 5  illustrates schematically a second exemplary installation of a trolley; and 
         FIG. 6  is an illustration of a second embodiment of an overhead door equipment trolley. 
         FIG. 7  illustrates an electrical light fixture installed on an overhead door equipment trolley. 
         FIG. 8  illustrates the use of skid blocks on an overhead door equipment trolley. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a top view of an embodiment of an overhead door equipment trolley  10  as it would be typically installed in a workspace having two roll-up, overhead doors  910 . Two individual trolleys  10  are shown in this exemplary installation, one for each of the two workspaces. In this embodiment, trolley  10  comprises a support platform  100  to which various pieces of electrical or non-electrical equipment may be attached. Each trolley  10  further comprises two roller sets  200 , one attached to a left side  110  of support platform  100  and one attached to a right side  112  of support platform  100 , where left and right are arbitrarily defined as viewed from the access door. Trolley  10  is designed to be supported by two existing tracks  920  provided for the roll-up overhead door. 
     The three-dimensional outline of trolley  10  typically comprises a generally low rectangular shape comprising a height, a width, and a depth. When trolley  10  is intended to be installed in a garage or other workspace that has an roll-up overhead access door  910 , the width, “W”, of trolley  10  is the lengthwise dimension of the two sides of the rectangle parallel to access door  910 , the depth, “D”, of trolley  10  is the lengthwise dimension of the two sides parallel to the tracks  920  on which the roll-up overhead door rolls up, and the height of trolley  10  is the remaining (vertical) dimension. For clarity, the depth sides of trolley  10  are the left side  110  and right side  112  and the width sides of trolley  10  are what would conventionally be called the front and back sides, the front being closest to the access door. Typically, the width of trolley  10  is greater than its depth and the height is significantly less than either of the other two dimensions. 
     Typically, as shown in  FIG. 2 , trolley  10  also comprises one or more side walls  120 , in which embodiment trolley  10  has a tray- or pan-like structure, and often further comprises an enclosing plate (not illustrated), in which embodiment trolley  10  is box-like. Note that side walls  120  may extend upwardly or downwardly from support platform  100 . Generally, side walls  120  are attached to support platform  100  along one edge  122  and the enclosing plate, if used, is attached to one or more side wall  120 , that attachment being along an edge  124  running parallel to edge  122 . In one embodiment, side walls  120  extend upwardly from support plate  100 , so the enclosing plate is a top. In that embodiment (not illustrated), trolley  10  is box-like, which makes cleaning easier. 
     In other embodiments, trolley  10  does not include support platform  100  and instead, comprises the side walls  120 , each joined to the adjacent sidewalls along their respective edges  126 , edges  126  being generally perpendicular to edges  122  and  124 . In yet other embodiments, trolley  10  comprises one or more sections of support platform  100 , wherein the sections do not extend over the full length of trolley  10 . 
     The attachments between support platform  100 , side walls  120 , and enclosing plate  130 , if present, may be made by any well known attaching or joining technique appropriate to the material selected for manufacture of the trolley, including but not limited to screws, nails, welding, or gluing. 
     As shown in  FIG. 2 , trolley  10  further comprises two or more roller sets  200 , wherein a roller  210  is a wheel designed to match a track. Rollers  210  are preferably designed to operate in industry-standard tracks used in the roll-up overhead garage door industry. As shown in  FIG. 3 , roller set  200  comprise at least one roller  210 , said roller attached to an axle  220 , the axle attached, directly or indirectly, to a side of trolley  10 . Roller/axle combined units, as illustrated for example in  FIG. 4 , are available as standard parts in the overhead door industry. One or both of the axle attachments is a rotary attachment; that is, at one or more attachment the axle is allowed to rotate, preferably with low friction, relative to the mating part while being constrained in the axial direction. This axial constraint does not need to be absolute; the axial constraint is only required to keep the axle from falling out of the rotary attachment. Generally the rotary attachment is a ball bearing or oil impregnated bushing although a dry sleeve (i.e., a hole) may be used. 
     In some embodiments, as shown in  FIG. 2  and  FIG. 3 , roller set  200  further comprises a bracket  230 . Bracket  230  forms the interface between axle  220  and support platform  100 . In other embodiments axle  220  is attached directly to trolley  10 , typically to a side wall  120 . Several components comprising roller set  200  are available commercially from manufacturers of overhead door components, distributed at retail by many vendors such as Overhead Garage Door Store, PO Box 2814, Oregon City, Oreg. 97045. 
     In some embodiments, roller set  200  comprises a single roller/axle/bracket whilst in other embodiments, such as illustrated in  FIGS. 2 and 3 , a roller set  200  comprises two or more rollers  210  each individually mounted on axles  220 . The two or more axles may be attached to support platform by a single bracket  230  or they may attached with two individual brackets  230  or they may be attached without a bracket directly to a sidewall  120 . 
     In some embodiments, roller set  200  comprises skid blocks  270  as substitutions for rollers  210 . As illustrated in  FIG. 8 , skid blocks are preferably shaped to match the cross-section of the track on which trolley  10  is intended to ride. In the exemplary embodiment of  FIG. 8 , skid blocks  270  comprise a U-shaped channel wherein the essentially semi-cylindrical bottom  272  of the “U” has a radius comparable with the external radius of a standard overhead roll-up door roller  210 , shown in  FIG. 4 . In other embodiments skid block  270  may be a solid block with a similar lower edge radius. Preferably the skid blocks are manufactured from a low friction, low wearing material, for example, polished steel, which will allow trolley  10  to move forward and backward in the overhead door track without significant resistance. Skid blocks  270  are attached to the trolley, typically, with a fixed skid block arm  274 , such that semi-cylindrical bottoms  272  ride in the existing overhead door track. In some embodiments block arm  274  is attached to the end of support platform  100  with a bracket  231 . Skid block arm  274  is preferably rigid in the front-back direction but may have springiness in the up-down direction. 
     It may be noted that in  FIGS. 1 ,  2  and  3 , rollers  210  are disposed to project outwardly from the right  112  and left  110  sides of trolley  10 . This orientation is based on the design decision that the illustrated trolley should be positioned between the tracks  920  of roll-up overhead door  910 . As will be described below in conjunction with  FIG. 5 , rollers  210  are sometimes disposed to point inwardly towards the center of trolley  10 , such as when the trolley is supported by the adjacent tracks of adjacent overhead doors. Further, hybrid versions of trolley  10  are possible, whereby, for example, the trolley is supported by the left hand tracks of two adjacent overhead doors. In such hybrid versions one set of rollers are disposed to project outwardly while the other set of rollers are disposed to project inwardly. 
     As illustrated, for example, in  FIG. 3 , some embodiments of trolley  10  further comprise an electrical supply/distribution junction box  300 . Supply/distribution box  300  is disposed at any convenient location in or on trolley  10 . Box  300  comprises an electrical input and one or more electrical outputs. Typically, the electrical input comprises a multi-conductor electric supply cord  310  where the cord is compatible with local building and electrical codes and is configured to be compatible with a user&#39;s electrical service. For example, most residential units in the United States have 15 ampere or 20 ampere service at 110-120 VAC. Supply cord  310  is configured with a locally compatible plug, for example, in the US, a National Electrical Manufacturers Association (NEMA) standard 5-15P or 5-20P plug. 
     Supply cord  310  may enter supply/distribution box  300  from any convenient direction (top, side, or bottom) at the designer&#39;s discretion. In some embodiments supply cord may be self-coiling, as illustrated, to minimize interference with activities below trolley  10 . Self-coiling power cords are readily available; for example, a 20 foot, 3-conductor, coiled cord, part number NCV183, is available from CABLEscience, 9211 Greenleaf Ave., Santa Fe Springs, Calif. 90670. 
     The output from supply/distribution box  300  may take several forms depending on whether trolley  10  is to be delivered to a user as a fully factory-configured unit or as an end-user configurable unit. In one embodiment, illustrated in the partial bottom view in  FIG. 7 , the output of supply/distribution box  300  comprises code approved electrical wiring  320 A to supply current to an illumination fixture  400 . In this exemplary embodiment fixture  400  is substantially a fluorescent “work light” comprising two linear fluorescent tubes  410 . In another embodiment the output of supply/distribution box  300  is one or more pairs of electrical “pig-tail” wires  320  to which one or more pieces of electrical equipment may be hard-wired. In another embodiment, not illustrated, the output of box  300  comprises an electrical power strip, into which pieces of electrical equipment may be plugged. In yet other embodiments, box  300  itself is configured with one or more standard electrical receptacles such as NEMA 5-15R receptacles or with an electrical socket for other electrical devices, for example, a light bulb. 
     Trolley  10  may be embodied to be field adjustable in length to better fit specific overhead door installations. In one embodiment, side rails  120  comprise two or more overlapping segments, for example, segments  120 A and  120 B as illustrated in  FIG. 3 . Trolley length is adjusted by increasing or decreasing the overlap between said segments. Side segments used to form an adjustable length trolley, such as segments  120 A and  120 B are preferably pre-drilled/machined with a series of slots  126  and/or holes  128  wherein nuts, bolts, and washers (not shown) can be used to secure the overlapping segments at the desired length. Support platform  100  may also be adjusted in length by segmentation. In the exemplary embodiments illustrated in  FIGS. 2 and 3 , support platform  100  comprises three segments  100 A,  100 B, and  100 C. In one embodiment the sum of the lengths of these platform segments is the shortest length obtainable for trolley  10 . When the length of the trolley is adjusted to be longer, gaps are allowed to exist between the three segments. In another embodiment the sum of the lengths of the segments is the maximum length obtainable for trolley  10 . When the length is adjusted to be shorter, the length of at least one of the segments, preferably the center segment, is reduced, generally by sawing. In yet other embodiments, central segment  100 C may be left out altogether, as illustrated in  FIG. 7  where central segment  100 C has been replaced with fluorescent fixture  400 . 
       FIG. 5  schematically illustrates a trolley  10  as it would be typically installed in a dual overhead door workspace when it is desirable to share one trolley between the two spaces behind the two access doors.  FIG. 6  illustrates one example of this “shared” embodiment, wherein trolley  10  rides on one track from each of the two overhead doors. In this embodiment, roller sets  200  are disposed on opposing sides of, and generally equally spaced from, a central line C of trolley  10 , where central line C is parallel to a front-to-back axis and runs through an estimated center of mass. This preferred roller disposition maintains substantially equal weight on each roller set. Note that the roller sets  200  of the embodiment in  FIG. 6  are disposed at the outer edges of support platform  100  but other embodiments it may be desirable to extend support platform  100  beyond the limit of one or both tracks, as is suggested in  FIG. 5 . In an embodiment where support platform  100  has been so extended, it is preferable that support platform be extended substantially symmetrically to maintain central line C between roller sets  200 . 
     As was mentioned above and illustrated in  FIG. 6 , in trolley embodiments that are disposed to ride on tracks from adjacent overhead doors, rollers  210  are typically disposed to point inwardly towards the center of trolley  10 . 
     In a typical installation, trolley  10  is disposed on the horizontal portions of the left and right tracks of a roll-up overhead access door (or, alternatively, on a pair of tracks from adjacent doors). With the access door in the closed (“down”) position, trolley  10  may be moved forward (toward the access door) or backward in the tracks, thereby positioning any equipment mounted thereon, for example, a light fixture, at any desired location within the range of the horizontal track sections. In some embodiments a “leash” of some design may be attached to trolley  10  to make positioning of trolley possible without the need to reach up to the typical six-foot-plus height at which the trolley typically rides. In those embodiments in which trolley  10  comprises an electrical supply/distribution box  300 , supply cord  310  will typically be plugged into a wall or ceiling mounted receptacle. Generally supply cord  310  can connected to the receptacle via a route that allows cord  310  to be left plugged in full-time. In some installations the receptacle is wall mounted, in which installation a power switching mechanism can be installed at the receptacle to power and depower the trolley. In other installations, such as those with a ceiling mounted receptacle, it may be desirable to mount a switch on the bottom of trolley  10  to turn power on and off. 
     When the roll-up overhead is opened to allow access to the workspace, the upper edge of the door contacts the front edge of trolley  10  and pushes trolley  10  backward along the tracks without damage to either door or trolley. In some instances it may be desirable to added a compliant bumper material along the front edge of trolley  10 . 
     While various embodiments of the innovation have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the innovation as defined by the appended claims. For example, virtually any object or piece of equipment may be attached or integrated onto support platform  100 , whether or not said object or piece of equipment is electrically powered.

Summary:
A trolley for supporting equipment on an overhead door using the existing track for the overhead door is described. The invention may be used to allow utility items such as lighting, electrical outlets, and safety devices to be mounted conveniently and efficiently.