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The present application is a Divisional of U.S. patent application Ser. No. 12/875,448, filed Sep. 3, 2010, now U.S. Pat. No. 8,499,889. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed to an adjustable work platform and, more specifically, to a heavy duty extendable platform designed to conform to the outer surfaces of a large, irregularly shaped object such as an aircraft. 
     BACKGROUND OF THE INVENTION 
     Maintenance upon large irregularly shaped objects is often difficult because of the cost and difficulty involved in providing safe and reasonably priced work surfaces suited to the outer size and shape of such objects. The variable shapes and sizes of large objects such as aircraft require custom work platforms so that workers can safely reach and work on those objects. Standard scaffolding is designed to facilitate maintenance upon standard rectangular shapes such as brick buildings. Custom scaffolding is known in the art but frequently cost prohibitive given the large variance in the size, shape, and number of objects that must be maintained in a typical setting, such as an airport hanger. To make matters worse, aircraft are subject to tight schedules to remain profitable, so maintenance time must be minimized. What is needed is an adjustable work surface that will accept a range of irregularly sized and shaped large objects quickly, safely, and efficiently. 
     SUMMARY OF THE INVENTION 
     The present invention alleviates many of the problems inherent with prior art work surfaces. The invention provides a novel system and method of use for an adjustable work platform that will accept a range of irregularly sized and shaped large objects quickly, safely, and efficiently. 
     An embodiment of the invention provides an adjustable work platform for carrying heavy loads in a stable manner comprising a fixed platform with a front side and a back side opposite thereto, with a first stringer along the front side comprising defined openings therein, a second stringer along the back side and a multiplicity of I-beam guides spanning between the first stringer and the second stringer, and an adjustable platform extendable from said fixed platform with a slider received by the adjacent I-beam guides and disposed to reversibly extend through one of said openings comprising a toothed member that reversibly engages with the first stringer thereby restricting sliding of said slider, and a back plate attached to the slider to limit the length of extension of said slider through the openings. The toothed member is rotatable about a perpendicular axis to the toothed member. The toothed member is also rotatable about a parallel axis to the toothed member. A back plate on the slider limits the lateral and vertical movement of the slider to provide increased stability of the slider. 
     A novel method of providing a work platform for carrying heavy loads while accessing an irregularly shaped object comprises the steps of providing an adjustable platform as described above, moving a large object to within a predetermined separation distance of the platform, and extending the adjustable platform from the fixed platform, minimizing the separation distance. 
     Another embodiment of the invention provides an adjustable walking surface for carrying heavy loads comprising a substantially horizontal platform having a first stringer disposed parallel to a second stringer and the first stringer and second stringer connecting by two or more I-beam guides that are perpendicularly disposed between the first and second stringer, a slider carried between two or more of the I-beam guides where the slider is operable to extend the horizontal length of the platform by pulling a first distal end of the slider through an opening the second stringer. A back plate is disposed upon a second distal end of the slider, where the back plate allows the slider to ravel horizontally along the lengths of the two or more I-beam guides while simultaneously preventing substantial vertical and lateral movement of the slider. A toothed member is disposed upon the downward facing portion of the slider, which operates to contact the lower vertical surface of the opening in the second stringer where a toothed member rests upon the lower vertical surface while the slider is in an extended position to prevent horizontal movement of said slider by force of gravity acting upon the slider until a greater upward force is applied to the first distal end of the slider followed by a horizontal force to extend or retract the slider. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective top view of an adjustable work platform. 
         FIG. 2  is a perspective bottom view of an adjustable work platform. 
         FIG. 3  is a horizontal view of an interior of an adjustable work platform with a fixed toothed member. 
         FIG. 4  is a horizontal view of an interior of an adjustable work platform with a pivoting toothed member. 
         FIG. 5  is a horizontal view of an interior of an adjustable work platform with a pivoting toothed member and release bar. 
         FIG. 6  is a perspective view of an adjustable work platform in use to perform maintenance on a helicopter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , a top perspective of an adjustable work platform is illustrated. Adjustable work platform  10  includes two stringers  12   a  and  12   b  connected by a series of I-beams  14   a ,  14   b ,  14   c , continuing to  14   n . A multiplicity of sliders  16   a ,  16   b , continuing to  16   n  are disposed between each of the I-beams. Each slider is extendable outward through opening  18  in stringer  12   b . The limit of extension for each slider is reached when a back plate on each slider contacts stop bar  20  or when rubber stop  22  contacts the object to be worked upon. Slider  16   b  includes a set of stability tabs  21   a  and  21   b , which are disposed on every other slider to increase the stability of all sliders once extended. These c-shaped members attach on the side portions of every other slider and provide a channel for each rectangular slider&#39;s extension. 
     Maintenance personnel can use the adjustable work platform sliders to create a suitably shaped work surface first by pulling a large irregularly shaped object, such as a helicopter, into a work bay with the adjustable work platform  10  disposed on one or more sides of the helicopter as illustrated in  FIG. 6 . When the helicopter is placed in the center of work platform  10 , maintenance personnel then extend each of the sliders  16   a  to  16   n  outward by lifting the distal end of each slider and pulling outward to extend each slider through opening  18  until rubber stop  22  contacts the side of the helicopter. The weight of individual sliders, combined with a toothed member  24  illustrated in  FIG. 2 , holds each slider safely in place along the irregularly shaped outer surface of the helicopter. In this manner, adjustable platform  10  fills the gaps along the outer surface of the helicopter so that a safe and easily adjustable work surface is provided for maintenance on the helicopter. 
     Referring now  FIG. 2 , adjustable work platform  10  is shown from a bottom perspective view. Back plate  26  and stop bar  20  are illustrated in more detail. The maximum length of extension of sliders  16   a  to  16   n  is limited when back plate  26  contacts stop bar  20 . Normally sliders  16   a  to  16   n  do not reach their maximum extended length, however, because rubber stop  22  is designed to contact the outer surface of the large irregularly shaped object. 
     As discussed with respect to  FIG. 1 , sliders  16   a  to  16   n  are positioned around the outer surface of an irregularly shaped object in the following manner. Once the object is placed adjacent to adjustable work platform  10 , an operator extends each of the sliders  16   a  to  16   n  outward by lifting the distal end of each slider upward and pulling outward to extend each slider through opening  18  until rubber stop  22  contacts the side of the object. Once the desired length of extension of each slider is reached, the operator simply lowers the distal end of the slider so that toothed member  24  then contacts the lower surface of opening  18  on stringer  12   b . The rigidity of stringer  12   b , which is generally made of metal, combined with the shape and rigidity of the toothed member  24 , which is also generally also made of metal, causes slider  16  to remain safely in place by force of its own weight. 
     Back plate  26  has several purposes. First, it provides a stop mechanism by limiting maximum travel of each slider to stop bar  20  as described above. Second, it provides additional stability by keeping the inner end of each slider firmly placed between each I-beam  14   a  to  14   n . As discussed further with respect to  FIG. 3 , back plate  26  prevents unwanted lateral and vertical movement of each slider by completely filling the inner space between I-beams  14   a  to  14   n . In this manner, the slider is allowed only minimal vertical travel on the distal end containing rubber stop  22 , so that the toothed member pivots perpendicular to its own axis when an operator lifts the end to extend or retract a slider. 
     Thus an operator may easily and safely vary the length of extension of each slider  16   a  to  16   n  by lifting upward on the end of each slider where rubber stop  22  is located and then pulling horizontally outward to increase the length of extension of slider or pushing horizontally inward to decrease the length of extension of slider. Once the user has selected a desired length of extension the user then lowers the distal end of the slider, which then allows toothed member  24  to contact and engage with the lower edge of opening  18 , thereby firmly holding the slider in place. 
     Referring now to  FIG. 3 , the above operation of each slider is more clearly illustrated looking directly down the length of sliders  30   a  and  30   b  disposed within I-beams  32   a ,  32   b , and  32   c . Slider  30   a  on the left has been lifted by an operator to its upward position where it can be retracted or extended, whereas slider  30   b  on the right is in the locked lower position held firmly in place by contact of toothed member  34   b  on edge  36   b , which represents the lower edge of opening  18  from  FIGS. 1 and 2 . Toothed members  34   a  and  34   b  are located on the bottom of t-shaped members  33   a  and  33   b , which attach to the center of sliders  30   a  and  30   b  and project downward. 
     Vertical and lateral movement of slider  30   a  and  30   b  is limited by use of back plates  31   a  and  31   b  because the back plates fill the interior spaces between I-beams  32   a ,  32   b , and  32   c , as indicated by the shaded portions of  FIG. 3 . In other words, back plates  31   a  and  31   b  are sized to fill the entire space between I-beams  32   a ,  32   b  and  32   c  so that sliders  30   a  and  30   b  are held firmly in an upright position without any side-to-side or up and down movement. Although the embodiments of  FIGS. 4 and 5  would include a back plate, none is shown so that the other components in  FIGS. 4 and 5  can be more clearly illustrated. 
     Properly sized back plates  31   a  and  31   b  allow substantial movement of sliders  30   a  and  30   b  in one direction only, which is inward and outward along the interior surfaces of I-beams  32   a ,  32   b , and  32   c . For added stability, back plates  31   a  and  31   b  also contain a lower lip  37   a  and  37   b  along their lower edges designed to fit between the bottom edges of I-beams  32   a ,  32   b , and  32   c . It is important to note that, while back plates  31   a  and  31   b  prevent vertical movement of the inner portion of each slider (the distal end opposite rubber stop  22 ), each back plate also allows the small and necessary vertical movement of the outer end of each slider (distal end with rubber stop  22 ) needed to lift the distal end of each slider to extend or retract the slider. In this manner, each slider is allowed minimal but sufficient vertical travel on the distal end containing rubber stop  22 , so that toothed members  34   a  and  34   b  pivot perpendicular to their own axis when an operator lifts the end of a slider to extend or retract that slider. 
     While slider  30   a  is shown in the lifted position to allow its extension or retraction, slider  30   b  is shown in the resting position where movement of the slider is prevented. As slider  30   b  is lowered by an operator into the position shown, toothed member  34   b  engages the lower edge  36   b  of the opening of the stringer indicated by the dashed line. As both toothed member  34   b  and lower edge  36   b  are both generally made of rigid metal, contact between the two prevents further horizontal extension or retraction of slider  30   b . The weight of slider  30   b  is generally sufficient to maintain the necessary contact between  34   b  and  36   b  so that movement of the slider is prevented. 
     Referring now to  FIG. 4 , an alternate embodiment of the toothed member is illustrated, wherein the toothed member pivots about its parallel axis and is held in place by a pivoting socket and compressible spring. I-beams  42   a ,  42   b , and  42   c  hold sliders  40   a  and  40   b  in place. Slider  40   a  is shown with the pivoting toothed member  44   a  at rest and held in place by spring  48   a . T-shaped member  45   a  contains a pivoting socket  47   a  designed to receive toothed member  44   a  and to allow toothed member  44   a  to pivot so that the toothed member is rotatable about its parallel axis. This differs from the fixed-toothed member  33   a  shown in  FIG. 3 , which rotates about a perpendicular axis to engage and disengage. 
     Slider  40   b  is illustrated with pivoting toothed member  44   b  rotated into an unlocked position, whereby spring  48   h  is compressed. Toothed member  44   b  may be rotated from locked to unlocked in a number of ways. In one embodiment, an operator may simply reach under the edge of rubber stop  22  (shown in  FIGS. 1 and 2 ) and apply upward lateral pressure on toothed member  44   b  to compress spring  48   b  and rotate toothed member  44   b  about its parallel axis into the retracted position as shown. In this manner toothed member  44   b  no longer contacts edge  46   b  so that slider  40   b  is free to be extended or retracted as desired. 
     Referring now to  FIG. 5 , another embodiment is illustrated for engaging a pivoting toothed member. Operator handle  51   a  is inserted into opening  53   a  and placed in its operating position so that distal end  59   a  is in contact with a side portion of toothed member  54   a . The operator may then twist the handle  51   b  as shown on the right so that distal end  59   b  contacts the edge of  54   b , thereby pivoting toothed member  54   b  so that it rotates about its parallel axis. This movement unlocks slider  50   b  by preventing contact of toothed member  54   b  with edge  56   b  so that an operator is then free to extend or retract slider  50   b  in normal use. 
     Once slider  50   b  is extended or retracted into a desired position, the operator then twists the handle  51   b  in the opposite direction to return the toothed member to its resting position, as indicated by  54   a . Compression springs  58   a  and  58   b  resist the rotation of toothed members  54   a  and  54   b  to force toothed members  54   a  and  54   b  back into a vertical position, as illustrated by  54   a , once the operator twists the handle back to its original position, as indicated by  51   a.    
     Referring to  FIG. 6 , an embodiment of the invention in use is illustrated to provide a three-sided adjustable work platform  100  for maintenance on a helicopter. Work platform  100  comprises two primary sections—fixed platform  110  and adjustable platform  120 . Fixed platform  110  holds the various sliders described above. Once helicopter  115  is rolled into position at the center of work platform  100 , those sliders are extended to form the adjustable platform  120  around the irregular outer surface of helicopter  115  as illustrated in  FIG. 6 . In this manner, a safe, inexpensive, and quickly established adjustable work surface is provided to facilitate maintenance on the helicopter. 
     These illustrated examples are offered by way of illustration of the invention&#39;s versatility and not meant to limit the invention in any way. The present invention may be embodied in other specific forms without departing from its spirit of essential characteristics. The described embodiments are to be considered in all respects only illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and scope of equivalency of the claims are to be embraced within their scope.

Summary:
An adjustable work platform comprises a fixed platform carrying a multiplicity of adjustable members designed to slide out of the fixed platform to variable lengths as needed. A large irregularly shaped object, such as an aircraft, may be driven into the interior of the platform with the adjustable members retracted. Once in place, the adjustable members are extended to form a heavy duty work platform conforming to the irregular shape of the exterior of the object.