Patent Publication Number: US-7896133-B2

Title: Self-elevating platform scaffolding

Description:
FIELD OF THE INVENTION 
     The present invention relates to a scaffolding assembly, and in particular, a scaffolding assembly having a self-elevating work platform. 
     BACKGROUND OF THE INVENTION 
     Scaffolding and elevated work platforms are well known in the construction industry. Scaffolding assemblies having self-elevating work platforms, such as the ones manufactured by Hydro Mobile of L&#39;Assomption, Quebec, are particular useful for moving workers and material to various positions on the building exterior. These scaffolding assemblies include a horizontal work platform suspended between a pair of vertical mast towers, which can be raised and lowered along the mast towers. For ease of explanation, such scaffolding assemblies will be referred to hereinafter simply as a “self-elevating platform scaffolding.” 
     Typically, the work platform is raised and lowered by a “rack and pinion” lift mechanism. Rack and pinion type lift mechanisms use a drive motor mounted under the work platform to turn a pinion, which mates to a vertical rack mounted to the mast tower. In a construction site environment, dirt and debris quickly foul and damage the gear teeth of rack and pinion components. Consequently, rack and pinion type lift mechanisms require frequent maintenance to function properly. The safety and lifting capacity is also a limitation for rack and pinion type lift mechanisms. 
     Other self-elevating platform scaffoldings have a lift mechanism that uses a pair of hydraulic rams to “climb” the mast towers. Hydraulic rams are pivotally connected to the platform adjacent the mast towers and have hooks mounted to the ends of the upwardly extending piston rods, which engage cross members on the mast towers. Each ram operates in alternating succession to raise and lower the platform. The alternating operation of the paired rams creates an inherent intermittent stepping action in a “climbing” type lift mechanism, which presents safety concerns. A lift mechanism that provides a smooth continuous raising and lowering of the movable platforms is needed to provide a safer work environment. 
     SUMMARY OF THE INVENTION 
     The self-elevating platform scaffolding embodying this invention includes a horizontal work platform suspended from a vertical mast tower and a unique lift mechanism mounted to the work platform, which raises and lowers the platform along the length of the tower. The lift mechanism uses a pinion wheel that directly engage a mast tower to raise and lower the work platform along the mast towers. The pinion wheel has a plurality of radially spaced cogs that seat within crescent shaped openings in the mast tower. The lift mechanism is mounted to the work platform adjacent the mast tower such that rotation of the pinion wheel causes the wheel to “walk” up and down the mast tower to raise and lower the platform. The pinion wheel is driven by a hydraulic pump and operated by various hydraulic valves and controls. The hydraulic systems of the lift mechanism ensure safe and reliable operation of the scaffolding apparatus. 
     The lift mechanism allows the pinion wheel to operate in direct contact with the mast tower, thereby eliminating the need for rack sections mounted to the exterior of the towers. The geometric configuration of the pinion wheel is designed so that one cog is always in positive contact with the mast tower. As the pinion wheel turns, each successive cog seats within an adjacent crescent slot in the mast tower with its contact edge bearing against the bottom edge of the tower opening. The lift mechanism allows the work platform to be raised and lowered along the mast tower in a smooth continuous manner for improved safety. The direct connection design of the lift mechanism also allows the entire scaffolding assembly to be very quickly erected and installed. 
     These and other advantages of the present invention will become apparent from the following description of an embodiment of the invention with reference to the accompanying drawings. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is an end elevation view of an embodiment of the self-elevating platform scaffolding of this invention with a cut-away view of the lift mechanism; 
         FIG. 2  is an end elevation view of the scaffolding of  FIG. 1  showing the pinion wheel rotated in one position engaging the mast tower; 
         FIG. 3  is another end elevation view of the scaffolding of  FIG. 1  showing the pinion wheel rotated in second position engaging the mast tower; 
         FIG. 4  is a plan section taken along the line  4 - 4   FIG. 1 ; 
         FIG. 5  is a plan section taken along the line  5 - 5   FIG. 1 ; and 
         FIG. 6  is a simplified end elevation view of the pinion wheel and mast tower showing the pinion wheel rotating to “walk” up the mast tower. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, reference numeral  10  generally identifies a self-elevating platform scaffolding embodying the teaching of this invention. Scaffolding  10  includes a vertical mast tower  20 , movable horizontal work platform  30  suspended from the mast tower and a lift mechanism  40 , which operatively engages the mast tower to allow the platform to be raise and lower the platform vertically along the length of the tower. For simplicity of illustration and description of the construction and operation of scaffolding  10 , a single mast tower is illustrated in the drawings and described herein. Although scaffolding  10  is illustrated as having a work platform suspended from a single mast tower, those of skill in the art will appreciate that the scaffolding may be modified within the scope of this invention to include multiple elevating platforms suspended between multiple mast towers. 
     Mast towers  20  are formed from a series of stacked, box-type mast sections. Mast sections are connected end to end to form a continuous vertical column. Each mast section is constructed from four corner rails and covered by an outer skin of heavy gage sheet metal. As shown, mast tower  20  has four flat vertical faces. Each face has a plurality of semi-circular openings  21  vertically orientated and evenly spaced in succession along the length of the mast towers. Each opening  21  is defined by a horizontal bottom edge  22  and an arcuate upper edge  24 . Openings  21  are equally spaced with approximately 9.8175 inches between adjacent bottom edges  22 . 
     Work platform  30  includes an upper deck  32  supported by a sub-frame  34  constructed of various metal beams, braces and cross members. Mast towers  20  extend through work platform  30  and are shiftably seated between side members  36  and cross members  38  of sub-frame  34 . To facilitate movement along the mast towers  20 , work platform  30  is movably coupled to the mast towers using various rollers and carriage assembles, which allow the work platform to move freely and uniformly up and down the mast towers without binding or twisting. For simplicity of description and illustration only, these rollers and carriage assemblies are not described herein, but are understood to be well known in the art. 
     Lift mechanisms  40  includes a rotating pinion wheel  50  driven by a hydraulic pump motor  60 . Pinion wheel  50  operatively engages mast tower  20  to raise and lower platform  30 . Pinion wheel  50  is rotatably mounted between two support members  42  mounted to sub-frame  34  of platform  30 . As shown, pinion wheel  50  rotates on an axis perpendicular to the longitudinal axis of both platform  30  and mast tower  20 . A pinion gear  46  is mounted to one side face of pinion wheel  50 . Pinion wheel  50  and pinion gear  46  turns on a center shaft  44  journaled between various bearings and bushings. Pump motor  60  turns a drive gear  48 , which meshes with pinion gear  46  to turn pinion wheel  50 . 
     Pump motor  60  is powered by an internal combustion engine (not shown) and actuated by a system of valves and controls (not shown). This type of hydraulic system is well known in the arts. While illustrated and described as being driven by a hydraulic system, the pinion wheel can be driven by any conventional power system. Ideally, the hydraulic system should allow platform  30  to be safely locked in position as well as, being raised and lowered along mast tower  20 . It should be noted that lift mechanism  40  may be modified to include multiple pinion wheels, with one or more pinion wheels operatively engaging each mast tower to raise or lower the platform. Each pinion wheel being driven by its own pump motor, but powered and controlled as part of an integrated hydraulic system. For simplicity of explanation and illustration only, lift mechanism  40  is shown and described herein using only a single pinion wheel operating on a single mast tower. The lift mechanism should also allow redundant back up systems and controls for safe operation of the scaffold. 
     Pinion wheel  50  directly engages mast tower  20  to raise and lower platform  30  as the wheel turns and moves vertically over the length of the mast tower. Pinion wheel  50  has a plurality of circular cogs  52  (eight cogs are illustrated in the drawings), which extend radially from the outer edge of the pinion wheel. Cogs  52  are configured to extend into openings  21  in mast tower  20 . Each cog  52  has a contact edge  53 , which runs from the apex of the cog to the junction between the cogs and outer edge of pinion wheel  50 . A pair of curved shoes  54  are welded to both sides of cogs  52  to reinforce the cogs and provide a larger contact face for the contact edges of the cogs. Shoes  54  abut and extend around the outer edge of cogs  52 . Pinion wheel  50  has a radius of approximately 12.5 inches to the edge between cogs  52 . Cogs  52  have a radius of approximately 2.5 inches and the center of each cog is located approximately 13.5 inches from the center axis of pinion wheel  50 . 
     As shown in  FIG. 6 , the rotation of pinion wheel  50  causes the wheel to “walk” up and down mast tower  20  to raise and lower platform  30 . The geometric configuration of pinion wheel  50  is designed so that at least one cog  52  is always in positive contact with mast tower  20  as the pinion wheel “walks” up and down the mast tower. As pinion wheel  50  turns, each successive cog  52  is seated within an adjacent crescent opening  21  in masts  30  with the contact edge  53  bearing against bottom edge  22  of opening  21 . The circular configuration of the cog  52  allows the point of contact between the cog and bottom edge  22  to move along the contact edge  53  as pinion wheel  50  walks up and down along mast tower  20 . The geometric configuration of pinion wheel  50  ensures that a single cog is contacting the mast tower over approximately 48° of the pinion wheel&#39;s rotation. Each cog  52  bears against the bottom edge of the opening alone for approximately six degrees of rotation (illustrated as rotation between α 1  and α 2  in  FIG. 6 ), before an adjacent cog comes into engagement with the bottom edge of an adjacent opening. Two adjacent cogs  52  are contacting mast tower  20  over approximately 312° of rotation. Consequently, 85 percent of the time, the weight of platform  30  is supported by pinion wheel  50  engaging mast tower  20  at two separate contact points. As a result of this pinion wheel configuration, pinion wheel  50  “walks” smoothly up and down mast tower  20  without any slippage as adjacent cogs  52  move into and out of contact with the mast tower. 
     The embodiment of the present invention herein described and illustrated is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is presented to explain the invention so that others skilled in the art might utilize its teachings. The embodiment of the present invention may be modified within the scope of the following