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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to commercial painting scaffolding for painting or otherwise servicing the elevated sides of a cylindrical tank or like structure. More particularly, the invention relates to scaffolding that is supported on the top of a cylindrical tank and is driven around the tank by a remotely controlled drive mechanism.  
         BRIEF SUMMARY OF THE INVENTION  
         [0002]    In accordance with the present invention, a movable scaffolding for painting or otherwise servicing the sides of a cylindrical tank or like structure comprises a remote controlled, powered, truck that is positioned adjacent a peripheral edge of the tank, a tether that connects the truck to the tank and constrains the truck to movement in a circular path around the vertical axis of the tank, and a vertically raisable platform attached to an outer side of the truck for vertical movement along outer sides of the tank.  
           [0003]    In one aspect of the invention, the truck comprises a radially oriented beam, with at least one and preferably two longitudinally spaced wheels rotatably mounted on radially oriented axles. The tether is operatively connected with an inner end of the beam, while the platform is operatively connected with an outer end of the beam  
           [0004]    These and other features, objects, and benefits of the invention will be recognized by one having ordinary skill in the art and by those who practice the invention, from the specification, the claims, and the drawing figures.  
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0005]    [0005]FIG. 1 is a perspective view of a painting scaffold with truck of the invention, shown relative to a tank structure;  
         [0006]    [0006]FIG. 2 is an enlarged perspective view of the truck;  
         [0007]    [0007]FIG. 3 is an enlarged elevational view thereof, taken along line III-III of FIG. 1;  
         [0008]    [0008]FIG. 4 is a partial cross-sectional view thereof, taken along line IV-IV of FIG. 3; and  
         [0009]    [0009]FIG. 5 is the view of FIG. 1, showing a non-driven truck towed by a driven truck with the two trucks suspending a large scaffold platform. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]    A preferred embodiment of a painting scaffold with truck of the invention is generally shown in the drawing figures. The major components of the invention are a powered truck  10 , a truck tether  12 , and a scaffold platform or basket  14 .  
         [0011]    The truck  10  has a beam  20  that extends along a beam axis between a first beam end  22  and an opposing second beam end  24  (FIG. 1). Tie pads  26  are preferably provided at each of the opposing ends  22  and  24 , although other fastening devices may be substituted as will be understood by one having ordinary skill in the art (FIGS. 1 and 2). The beam  20  may be constructed of any suitable structural material by any method appropriate to the material selected. Metal, wood, and plastic may be successfully used for the beam  20 , for example. An about 108 inch (2743 mm) length of two inch (51 mm) square, standard strength, mild steel tubing has been found to work well for the beam, for example.  
         [0012]    The beam  20  may be strengthened from sagging with tension straps  30  (FIG. 2). The straps  30  maybe constructed of lengths of about two inch (51 mm) by about quarter inch (6 mm) mild steel that extend between the opposing ends  22  and  24  of the beam. The straps  30  are spaced about 10 inches (254 mm) above the beam  20  at an about mid-point of the beam by another length  32  of two inch (51 mm) square, standard strength, mild steel tubing. One having ordinary skill in the art will understand that cables or rods may be used instead of the straps  30 , for example. Further the beam  20  may be constructed without need of further strengthening, although this would tend to an unduly heavy beam.  
         [0013]    A carriage portion is constructed under the beam  20 . A main carriage member  40  is connected by an array of secondary stringers  42  and  44  (FIG. 4). The main carriage member  40  is preferably an about thirty inch (762 mm) length of one inch (25 mm) square, standard strength, mild steel tubing. Two secondary stringers  42  may be about twenty-one inch (533 mm) lengths of one inch (25 mm) square, standard strength, mild steel tubing, that extend from opposing ends of the member  40  to meet at opposing sides of the beam  20 , at about the mid-point of the beam  20 . Four secondary stringers  44  may be lengths of standard strength one inch (25 mm) angle iron. Two of the four secondary stringers  44  extend from the opposing ends of the member  40  toward the first end  22  of the beam  20 , and meet at opposing sides of the beam  20  at a point about two thirds of the length of the beam  20  from the stand off  32  to the end  22 . The other two of the four secondary stringers  44  extend symmetrically from the opposing ends of the member  40  toward the second end  24  of the beam  20 , and meet at opposing sides of the beam  20  at a point about two thirds of the length of the beam  20  from the stand off  32  to the end  24 .  
         [0014]    Wheels are mounted to the carriage with a pair of generally U-shaped wheel brackets  46 , which may be fabricated of quarter inch (6 mm) thick, two inch (51 mm) wide mild steel. The wheel brackets  46  are preferably connected at the opposing ends of the main carriage member  40  and aligned with each other in a downward opening orientation (FIGS.  1 - 4 ). The legs of each bracket  46  are drilled to receive a wheel axle  50 , which may be provided as a half inch (13 mm) bolt, for example. The axles  50  are preferably parallel with one another. A wheel  52  is provided on each axle  50 . Ten inch (254 mm) diameter steel wheels with a molded on two and a half inch (64 mm) polyurethane tread have been found to perform well.  
         [0015]    The truck  10  may be propelled with an about half horse power electric motor  60 , for example. The motor  60  may be mounted on the main carriage member  40  and a chain drive may interconnect the motor  60  with one of the wheels  52 . More particularly, the chain drive may include an eleven tooth drive pinion  62  on the motor shaft, a sixty tooth plate sprocket  64  on the one wheel  52 , and a no.  35  chain  66  engaging the pinion  62  and sprocket  64  (FIG. 4). A standard forward and reverse electric circuit  70  may be operatively connected with the motor  60 . The circuit  70  may include a control box  74  and a pendant control  72 . The control  72  is preferably connected with the control box  74  by a cable  76  that is routed along the beam  20 , from the control  70  toward the second end  24  of the beam. The cable  76  preferably has a length that allows the pendent control  72  to hang below the second end  24  a sufficient distance that it is conveniently accessible by a user in the work basket  14  when in the uppermost position. Thus, a user in the work basket  14  may manipulate forward, reverse, and stop modes of the drive  70 , and movement of the truck  10 , by actuation of the control  72 .  
         [0016]    Because of a pendulum effect upon the basket  14 , the truck is most preferably driven only when the basket  14  is suspended near the beam  20 , not away from the beam. If for only this safety issue, the pendant control  72  may hang down from the end  24  of the beam  20 , only so far as it is accessible when the basket  14  is suspended in an upper most position under the beam. The control  72  does not need to travel with the basket  14 .  
         [0017]    The truck  10  is anchored at the first end  22  by the tether  12  to an anchor  80 . The anchor  80  will commonly be a man hole access to a tank  82  that is to be painted, or the like. The tether  12  may include a choker cable  84  that loops around the anchor  80 ; a leash  86  that extends between the truck tie pad  26  at end  22  and the choker  84 ; and a block  88  that interconnects the leash and choker. Lengths of a common half inch (13 mm) wire rope may be used for the choker  84  and the leash  86 , although one having ordinary skill in the art will know that other cable or rope devices may also be used with good effect. At the opposing or second end  24  of the beam  20 , the scaffold platform or basket  14  is attached to the tie pad  26  and suspended under the truck  10 . The platform  14  may be any of numerous commercially available work baskets or the like. The inventor has used a commonly known Spider™ basket, for example.  
         [0018]    In use, the truck  10  and tether  12  may be located on top of a tank  82  or other structure that is to be painted. The choker  84  is secured about a structurally sound and generally centrally located anchor  80 , including a man hole combing, for example. The block  88  and leash  86  are connected between the choker and the tie pad  26  at the first end  22  of the truck  10 . A lift cable  92  extends from the work basket  14  and is connected with the second end  24  of the truck  10 , as will be understood by one having ordinary skill in the art. The truck is positioned adjacent an edge or slope knuckle  90  with the wheels generally parallel with a tangent to an outer arc of the tank  82  (FIGS. 1 and 3). So positioned, the first end  22  of the beam  20  extends back toward the anchor  80 , while the second end  24  extends outward beyond a cylindrical side of the tank  82 . Users may then winch the work platform  14  up to an upper most position and manipulate the control  72  to relocate the truck and the work platform rotationally about the tank.  
         [0019]    In a first alternative embodiment, a second, non-powered truck  100  may be coupled by a tow line  102  with the first truck  10 . Now, an extra large work platform by be suspended under both the trucks  10  and  100 . When rotational relocation is desired, the platform  114  is lifted to its highest or upper most position and the truck  10  is driven by manipulation of controller  72  to pull the second truck  100 .  
         [0020]    It will be understood by one having ordinary skill in the art and by those who practice the invention, that various modifications and improvements may be made without departing from the spirit of the disclosed concept. Various relational terms, including left, right, front, back, top, and bottom, for example, are used in the detailed description of the invention and in the claims only to convey relative positioning of various elements of the claimed invention. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.

Summary:
A movable scaffolding for painting or otherwise servicing the sides of a cylindrical tank or like structure comprises a remote controlled, powered truck that is positioned adjacent a peripheral edge of the tank and directed for circular movement around the tank. A tether connects the truck to the tank and constrains the truck to movement in a circular path around the vertical axis of the tank. A vertically raisable platform is attached to an outer side of the truck for vertical movement along outer sides of the tank. In one aspect of the invention, the truck comprises a radially oriented beam, with at least one and preferably two longitudinally spaced wheels rotatably mounted on radially oriented axles. The tether is operatively connected with an inner end of the beam, while the platform is operatively connected with an outer end of the beam