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This application is a division of application Ser. No. 11/033,092, filed Jan. 10, 2005, now U.S. Pat. No. 7,322,555. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a sliding door system for freight elevator landings and, more particularly, to a door suspension system that is easily and quickly installed and adjusted. 
     PRIOR ART 
     Horizontal sliding doors for freight elevator landings are typically suspended from overhead tracks. Building codes and good workmanship dictate that the door panels have a limited clearance with the sill plate at the landing floor. Achieving a certain working clearance without exceeding specified limits can be tedious and time-consuming. Typically, a door system is installed by attaching various hardware components to the existing building. Relevant parts of the building are ordinarily of masonry construction and by the nature of such construction, are neither perfectly flat nor regular in hardness and finish. These physical conditions make it difficult for even a skilled installer to initially mount system hardware in a precise location. Prior art arrangements for adjusting the door panels vertically have been less than ideal, requiring, for example, individual adjustment of each door with eccentric roller mounts or use of spacers. Eccentric roller mounts give a non-linear response to adjustment and can throw a panel out of plumb each time one of a pair of rollers is adjusted. Use of spacers, known in the art, is typically troublesome from both a manufacturing standpoint and an installer&#39;s perspective. Where door panels in prior art arrangements are individually vertically adjusted, the time required to set all of the panels will ordinarily be proportional to the number of door panels being installed. 
     SUMMARY OF THE INVENTION 
     The invention relates to an improved system for suspending horizontal sliding door panels at freight elevator landings that reduces installation time and effort while, at the same time, being simple and economical to manufacture. The system has a vertical adjustment arrangement that facilitates the original installation of the overhead track for the door panels and, additionally, serves to provide for the final vertical adjustment of the door panels. The arrangement, moreover, preferably, uses a screw to raise or lower the track components and door panels with relative ease and with linear, stepless precision. 
     In the preferred embodiment, the invention includes a plurality of wall mounted brackets that suspend overhead tracks for the sliding door panels. The brackets are situated along the header over the landing opening. The brackets are each initially attached to the wall with an anchor bolt that, besides securing the bracket to the wall, serves as a vertically fixed peg or platform on which the bracket can be jacked up or down. The bracket assembly has a vertically slotted leg and an apertured block which together are assembled on an exposed portion of the installed wall anchor. A jacking screw carried in a threaded hole in the bracket body bears against the block enabling this screw to raise or lower the bracket relative to the anchor with the vertical slot accommodating this motion. Several identical or similar brackets are installed in the same manner along the entrance header to collectively support the tracks from which the door panels are suspended. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a somewhat schematic fragmentary elevational view of a freight elevator landing door assembly as seen from the shaft; 
         FIG. 2  is a perspective view of the tracks and supporting brackets of the door assembly; 
         FIG. 3  is a perspective view of a typical track mounting bracket and portions of tracks; 
         FIG. 4  is a cross-sectional view of a typical bracket taken in the plane  4 - 4  indicated in  FIG. 3 ; and 
         FIG. 5  is a fragmentary cross-sectional view of the door assembly taken in the plane  4 - 4  indicated in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to  FIG. 1 , there is shown, from the shaft side, a freight elevator landing door installation  10  including a set of four horizontal sliding door panels  11  in a closed position. The door panels  11  protect an opening to the elevator shaft at a landing. The panels  11  are suspended from overhead tracks  13  in a generally conventional manner. Each panel  11  has a pair of associated traction rollers  14  that roll on a horizontal surface  23  ( FIG. 5 ) of a respective track  13 . The rollers  14  of each panel are mounted on a bracket  16  ( FIG. 5 ), a separate bracket being associated with each panel  11 . Preferably, each bracket  16  ( FIG. 5 ) is bolted to the top edge of a respective panel  11 . The door panels  11  in the illustrated case are in pairs, two associated with the left (as viewed in the figures) and two associated with the right. The panels  11  of each pair are in staggered vertical planes with the outer panels adjacent the plane of the shaft or building wall, designated  17 , and the central panels spaced from the wall slightly more than the thickness of the outer panels. The panels  11  can be identical or nearly identical in construction, as desired. 
     With reference to  FIG. 5 , the bottoms of the door panels  11  are guided by gibs  18 . Preferably, a pair of gibs is associated with each panel. The gibs  18 , which are bolted to the panels to enable their replacement, are received in and slide along respective slots  19  in a sill assembly  21 . 
     The illustrated suspension tracks  13  are fabricated from steel stock into a J-shape with the hook end including a rectangular tube  22  or an equivalent form to provide the horizontal roller support surface  23 . The tracks  13  ( FIG. 4 ) are secured to the underside surfaces  24  of a plurality of bracket assemblies  26  spaced along the header, designated  27  ( FIG. 1 ) of the opening  12  ( FIG. 5 ). 
     The bracket assemblies  26  ( FIG. 4 ) can be identical (with the exception that the central bracket can have a double set of track mounting slots). A main body  28  of the bracket assembly  26  can be made, preferably, of a single sheet of steel bent and welded into the illustrated shape. The main body includes a vertical leg  31  and a horizontal leg  32 . The lateral edges of the legs  31 ,  32  are interconnected by triangular gussets  33 . The top of the bracket  28  has a horizontal web  34  and a downwardly extending reinforcing flange  36 . The web  34  is integral with the vertical leg  31  and the downwardly extending flange is integral with the web. The web  34  and flange  36 , preferably, are welded at their lateral edges to the gussets  33 . A boss  37  is welded or otherwise fixed at a hole  38  in the web  34  centered between the gussets and has a vertical internally threaded bore  39 . A jacking screw  41  in the form of a threaded machine bolt, is assembled in the threaded boss  37 . A vertical slot  42  in the vertical bracket leg  31  is centered between the gussets  33  and a round hole  43  is formed through the vertical bracket leg on a common vertical center line with the slot. Thus, preferably, the slot  42  and hole  43  are symmetrically disposed about a vertical plane perpendicular to the vertical bracket leg  31  and passing through the axis of the jacking screw  41 . 
     A rectangular block  46 , preferably of steel, is proportioned to slide vertically between the gussets  33  and includes a central hole that aligns with the slot  42 . The block  46  has a thickness sufficient when in contact or near contact with the vertical bracket leg  31  to extend under the jacking screw  41  and, ideally, completely under its diameter to provide a full bearing surface for the end face of the screw. The horizontal bracket leg  32  has a series of slots  47 , each slot overlying a respective one of the tracks  13 . The illustrated brackets  16  are arranged to support three tracks corresponding to a six-panel door. For illustrative purposes, the third track is shown in phantom ( FIG. 3 ). 
     The door installation  10  ( FIG. 1 ) can be initiated by mounting a sill assembly  21  at the shaft wall  17  at the level of the landing floor with appropriate masonry anchor bolts or other accepted technique. Thereafter, a bracket assembly  26  can be mounted on the shaft wall  17  centered above the door opening a specified distance above the sill assembly  21 . This is accomplished by first drilling a hole in the header area  27  of the wall  17  sized to work with a specified anchor bolt. Thereafter, with an anchor bolt  51  positioned in the drilled hole, designated  52 , the bracket body  28 , block  46 , washers  53  and nut  54  are assembled on the anchor bolt  51  as shown in  FIG. 4 . With the first bracket assembly  26  installed, the remaining bracket assemblies  26  can be similarly installed. A recommended procedure to accomplish this task is to use the tracks  13  with factory-installed upstanding threaded studs  55  to laterally locate the remaining bracket assemblies  16 . A first stud  55  is inserted into the proper slot  47  in the central bracket body  28 . The central bracket assembly  28  can be provided with a double set of slots  47  to receive respective studs  55  at the ends of left and right sections of the tracks  13 . The tracks  13  are preliminarily leveled and temporarily held in place with suitable clamps and/or props. Other bracket assemblies  26  are positioned so that appropriate studs  55  are received in their respective slots  47 . Holes  52  are drilled in the shaft wall header  27  at the center of the slots  42  of the additional bracket assemblies  26  and these bracket assemblies are provisionally installed as described for the center bracket assembly. A track spacer plate  56  has holes for receiving and locating the studs  55 , and therefore locating the tracks  13  in a desired spacing relative to one another. A spacer plate is associated with each bracket  26 . Nuts  57  are assembled on upstanding track studs  55  to fasten the tracks  13  to the brackets  26 . The slots  47  permit the tracks  13  to be adjusted horizontally towards and away from the shaft wall  17  as required. 
     In the illustrated arrangement, as described above, each door panel  11  has an associated hanger or bracket  16  on which is assembled a pair of traction rollers  14 . The hangers or brackets  16  are installed with the rollers on the track support surfaces  23 . With the hangers  16  located on appropriate tracks  13 , the door panels  11  can be bolted onto the hangers. For example, bolts (not shown), assembled vertically through holes in horizontal webs of the hangers  16  can be turned into threaded holes in the upper edges of the door panels  11  to secure the door panels to the hangers. With each door panel  11  secured to a respective hanger  16 , the panels are suspended overhead from the tracks  13 . 
     The bracket assemblies  26  afford a convenient, accurate and fast way of adjusting a gap  61  ( FIG. 5 ) between the bottom of the door panels  11  and the sill  21  to meet building code requirements and assure smooth opening and closing operation of the door panels. With the nuts  54  slightly loose on the studs of the anchor bolts  51 , the jack screws  41  can be rotated in either direction as needed to raise or lower the tracks  13  and, therefore, the door panels  11 . The jack screws  41  bear against the top surface of their respective blocks  46  thereby transferring the weight of the tracks  13  and door panels  11  to the anchor bolt  51  while allowing the respective bracket assemblies  26  to move vertically within limits of the slots  42 . One or more bracket assemblies  26  are adjusted as necessary. The adjustment mechanism afforded by the jack screw  41  has the desirable characteristic of being linear, lifting or lowering the door panels  11  a distance directly proportional to the angle through which a screw is turned. All of the door panels  11  are adjusted at the same time rather than being adjusted one at a time. When the door panels have been properly adjusted, each of the bracket assemblies  26  can be locked in position by drilling a hole in the building wall header  27  using the hole  43  as a pilot. Thereafter, an anchor bolt  63 , shown in phantom in  FIG. 4 , is positioned through the bracket hole  43  into the drilled hole. A nut  64  on this second anchor  63  can then be tightened for additional securement of the bracket assembly  26 . Additionally, the nut  54  associated with the first anchor bolt  51  is fully tightened at this time. 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.

Summary:
A method and apparatus for adjustably mounting tracks that suspend horizontal sliding doors at a freight elevator landing. The apparatus comprises a plurality of brackets adapted to be mounted in the shaft on the header above the landing opening. The brackets are each secured to the header with anchor bolts. Each anchor bolt is set in the header but initially allows vertical movement of the bracket. An adjusting screw, carried on each bracket, is arranged to easily and precisely move the bracket up or down relative to the anchor bolt as needed to position the tracks and, therefore, the door panels at a proper height. Once adjusted such that a specified gap is established between the lower edges of the door panels and the threshold, each anchor bolt can be tightened to fix its respective bracket in its adjusted position.