Patent Publication Number: US-6220391-B1

Title: Scaffolding structure

Description:
This is a continuation-in-part of application Ser. No. 09/094,784, filed Jun. 15, 1998, abandoned which is a continuation-in-part of application Ser. No. 08/811,379, filed Mar. 4, 1997, U.S. Pat. No. 5,810,114 issued Sep. 22, 1998. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of scaffolding. More specifically, this invention relates to an improved scaffolding system which may be more quickly and efficiently raised and which provides greater utility than conventional scaffolding systems. 
     BACKGROUND 
     In the field of construction and maintenance of structures, scaffolding is typically required in order to place workers and materials at elevated work areas. The scaffolding is vertically erected alongside the building and may include several levels, as dictated by the heights which must be reached, with each level serving as a platform for support of workers and materials. When work is completed, the scaffolding is removed or disassembled as it is no longer needed. 
     Scaffolding is by definition a temporary structure, and many forms of prefabricated scaffolding are available to provide a reusable scaffolding system for scaffolding users. A type of prefabricated scaffolding commonly used in construction of buildings, for example, includes end frames having two support columns with a horizontal cross-bar connecting the two scaffolding columns at the upper ends of the columns. Walk boards, typically in the form of wooden planks, are simply laid across the horizontal cross-bars of adjacent end frames so that one end of a plank rests upon the cross-bar of one end frame with the other end of the plank resting on the cross-bar of an adjacent end frame. Successive ones of the end frames are connected to one another by cross-bracing each support column of each end frame to corresponding support columns of adjacent end frames. Planks are typically longer than the distance from end frame to end frame so the plank overlaps the end frame to some degree. 
     Several undesirable consequences result from this approach. For example, a scaffolding structure as described above exhibits limited utility since the cross-braces on the working side of the scaffolding (i.e., the side which faces the building under construction) represent an obstacle which inhibits access to the building by workers. To avoid the cross-braces, workers often remove them and thereby compromise the structural integrity of the scaffolding in order to improve access to the building. The necessary placement of workers and materials at the same level of the scaffolding structure further restricts the worker&#39;s ability to move freely about, creating an additional hazardous condition for the worker and others. 
     Scaffolding of the type described above is also structurally unstable when workers and materials are placed at higher levels of the scaffolding structure. Forces exerted at upper levels of the structure, such as the effect of wind, movement of workers and materials, and the like, can easily exceed the scaffolding&#39;s limits, causing it to topple. To prevent such an occurrence, it is common practice to secure the scaffolding by chain or rope to the building itself whenever possible. 
     Another difficulty with the use of conventional scaffolding structures is that they are difficult and hazardous to ascend and descend. Truss members used for adding structural strength between the columns and cross-bar are often used by workers for climbing the scaffolding. However, these truss members are load-bearing members of the scaffolding end frame and are not designed to meet applicable industry standards (including OSHA standards) for climbing apparatus. Overlapped planks are also a safety hazard since workers can trip over the ends of the planks or upend a plank by stepping on the overhang. 
     Still another problem arising from the use of conventional scaffolding is most prevalent in higher scaffolding where electrical tools are required. In such instances, electrical lines are extended from the ground to the level at which electrical power is required. However, dangling electrical lines tend to be pulled downward by the effects of gravity and other forces, resulting in an inconvenience to the worker and a hazard to equipment and other workers at lower levels. 
     The following list of U.S. Patents represent scaffolding types which are typical of the art. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 U.S. Pat. No. 
                 Inventor(s) 
                 Issue Date 
               
               
                   
                   
               
             
            
               
                   
                 2,305,563 
                 R. A. Uecker, et al. 
                 Dec. 15, 1942 
               
               
                   
                 2,449,069 
                 H. A. Harrison 
                 Sep. 14, 1948 
               
               
                   
                 2,555,782 
                 R. G. Brownstein 
                 Jun 5, 1951 
               
               
                   
                 3,726,362 
                 J. D. Puckett 
                 Apr 10, 1973 
               
               
                   
                 4,391,348 
                 R. L. Rieland 
                 Jul 5, 1983 
               
               
                   
                 4,430,839 
                 G. Buffers 
                 Feb 14, 1984 
               
               
                   
                 4,891,926 
                 D. Alenbaugh 
                 Jan 9, 1990 
               
               
                   
                 5,388,661 
                 R. Hood, Jr. 
                 Feb 14, 1995 
               
               
                   
                 5,400,870 
                 S. Inoue 
                 Mar 28, 1995 
               
               
                   
                 5,412,913 
                 H. F. Daniels, et al. 
                 May 9, 1995 
               
               
                   
                   
               
            
           
         
       
     
     None of these scaffold structures solve the problems discussed above. 
     What is needed, therefore, is an easily assembled scaffolding structure which enhances the placement, access, movement, and safety of workers and materials at elevated work areas. 
     SUMMARY 
     With regard to the foregoing and other objects, the invention in one aspect provides a scaffolding end frame having a forward scaffolding column, a center scaffolding column nonremovably attached to the forward column, and a rearward scaffolding column nonremovably attached to the center column. Each of the columns lie in a common plane and are of unibody construction with a lower end in opposed relation to an upper end. The upper and lower ends of each column include means for connecting the column to an upper or lower end of a corresponding column of a further end frame so that the end frames can be vertically stacked to form a multi-level scaffolding structure. 
     Preferably, the forward, center, and rearward columns are substantially parallel to each other. Also preferably, each scaffolding column is substantially the same length. 
     The end frame may also include a board support member nonremovably attached to the forward scaffolding column and the center scaffolding column. A board support member may also be attached to the center scaffolding column and the rearward scaffolding column. The board support members are configured to receive and support a substantially planar scaffolding board. Board support members may also be provided at different heights as measured from the lower ends of the columns. 
     A ladder may be attached to one or more of the end frames to assist workers in ascending and descending the scaffolding structure. In a preferred embodiment, the ladder is substantially non-load bearing such that the absence of the ladder imposes substantially no effect to the structural integrity of the first end frame. The ladder is also preferably constructed to meet applicable industry standards, such as OSHA. 
     Electrical power may be provided to the end frame by including an electrical carrier attached to one of the scaffolding columns. An electrical conduit disposed within the column provides electrical continuity between a power source and the electrical outlet. 
     The present invention also provides a scaffolding structure having first and second end frames with each end frame having an upper end and a lower end. Each end frame includes forward, center, and rearward columns having substantially the same length. A walk board having opposed ends interconnects the two end end frames at a first distance from the lower ends of the end frames. A work board having opposed ends also interconnects the two end frames, but at a second distance from the lower ends of the end frames with the second distance being greater than the first distance. Means are provided for cross-bracing the first end frame relative to the second end frame. Vertical stacking of like end frames is preferably accomplished by providing a plurality of receptors in the upper and lower ends of the end frames which receive a plurality of studs interconnecting with other like end frames. 
     In a preferred embodiment, cross-bracing may be provided by a cross-brace having opposed ends with one end of the cross-brace attached to the rearward scaffolding column of the first end frame and the other end of the cross-brace attached to the rearward scaffolding column of the second end frame. 
     Each end frame also preferably includes a walk board support nonremovably attaching the forward and center columns and a work board support nonremovably attaching the center and rearward columns, as described above. The walk board support is configured to receive an end of the walk board so that the ends of the walk board may be joined with their respective walk board support members of the two end frames at said first distance from the lower ends of the end frames. Similarly, the work board support is configured to receive an end of the work board so that the ends of the work board may be joined with their respective walk board support members of the two end frames at said second distance from the lower ends of the ends frames. Stiffener plates may be attached to the ends of each walk board and work board to reduce board flexure and to provide a wear-resistant interface between the board and its support member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features, aspects and advantages of the present invention will now be discussed in the following detailed description and appended claims considered in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of a section of scaffolding constructed in accordance with the present invention; 
     FIG. 2A illustrates an end elevation view of the scaffolding section shown in FIG. 
     FIG. 2B illustrates an end elevation view of an alternate embodiment of a scaffolding end frame in accordance with the invention; 
     FIG. 3 is a top plan view of an end frame for use with the scaffolding section shown in FIG. 1; 
     FIG. 4 is a top plan view of a corner walk board and work board for a scaffolding structure in accordance with the invention; 
     FIG. 5 is a front elevation view of a handrail for use with the scaffolding section shown in FIG. 1; 
     FIG. 6 is an end elevation view showing the connection of the handrail of FIG. 5 to an end frame; 
     FIG. 7 is a functional block diagram of a multi-section scaffolding structure in accordance with the invention; 
     FIG. 8 is a cross-sectional view of the walk board support shown in FIG. 3 taken along line A—A; 
     FIG. 9 is an elevated sectional view of a walk board joined with a walk board support; 
     FIG. 10 is a perspective view of an alternate embodiment of a scaffolding section constructed in accordance with the present invention; and 
     FIG. 11 is a side sectional view of a walk board, stiffener plate, and walk board support in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference now to the drawings in which like reference characters designate like or similar parts throughout the several views, FIG. 1 illustrates a section of an improved scaffolding  10  incorporating various features of the present invention. The improved scaffolding  10  is designed to include an integrated walk board  74  used to join successive pairs of end frames  12  such that problems typically associated with walk boards are avoided, with end frames  12  being constructed such that workers may freely walk between successive sections thereof along either of two walk-through areas of the scaffolding  10 . Moreover, in a preferred embodiment of the present invention, a work board  82  is provided at an elevated location with respect to the walk board  74 . Electrical power is provided to alleviate problems associated with dangling electric cords. Due to the configuration of the improved scaffolding  10 , assembly and disassembly thereof is accomplished with greater efficiency when compared to the assembly and disassembly of prior art scaffolding. 
     The walk board  74  and work board  82  are each fabricated from a rigid material, preferably aluminum, with structural reinforcement included on the underside of the boards  74 ,  82  as needed. In an alternate embodiment, the walk board  74  and work board  82  are fabricated from a wooden plank or a plurality of wooden planks. The walk board  74  and work board  82  may be fabricated from other suitable materials as well, including plastic. 
     When raised or assembled, each section of the improved scaffolding  10  of the present invention includes a pair of end frames  12 , a walk board  74 , a work board  82 , and handrail  52 . Each end frame  12  is configured to be common to successive scaffolding sections. FIG. 1 illustrates, in perspective view, one section of the improved scaffolding  10  of the present invention. 
     As illustrated in FIG. 2A, each end frame  12  includes three compressive load bearing structural members, or columns, including a center column  14 , a forward column  20 , and a rearward column  22 . The columns  14 ,  20 ,  22  are nonremovably attached to each other and combine to produce scaffolding having a walk-through area defined by that area bounded by the walk board  74 , the forward column  20 , and the center column  14  and a second walk-through area defined by that area bounded by the work board  72 , the center column  14 , and the rearward column  22 . Although the center, forward, and rearward columns  14 ,  20 ,  22  exhibit square or rectangular cross-sectional dimensions for the embodiments shown in FIGS. 1-6, it will be understood that these columns, as well as other structural members of the scaffolding  10 , may have a cross-sectional dimension which is circular, triangular, hexagonal, or other. Also, each column  14 ,  20 ,  22  is preferably fabricated as a continuous single column (unibody construction) to enhance and simply assembly of the scaffolding structure. 
     A walk board support  24  is mounted between the center and forward columns  14 ,  20 , at the lower ends thereof. A work board support  30  is mounted between the center and rearward columns  14 ,  22  at an elevation above the walk board support  24 . In the illustrated embodiment, the work board support  30  is disposed proximate the middle of the center and rearward columns  14 ,  22 . In a preferred embodiment, the walk board and work board supports  24 ,  30  are permanently mounted between the respective forward, center and rearward columns  20 ,  14 ,  22 . However, it will be understood that the walk board and work board supports  24 ,  30  may be adjustable in height, thus enabling the disposition of the walk board  74  and work board  82  to be variable. 
     To enhance stability of the end frame  12 , brace members  36  are provided to extend between the rearward column  22  and the work board support  30  and between the work board support  30  and the center column  14  in order to form triangular configurations between the respective members. In the illustrated embodiment, the brace members  36  are permanently secured. However, it will be seen that in an embodiment as discussed above, wherein the work board support is adjustable, the brace members  36  are adjustable as well. It will further be seen that the brace members  36  may be disposed in similar fashion below the walk board support  24  in addition to or in lieu of the illustrated brace members  36 . 
     Each of the lower and upper ends of the forward, center and rearward columns  20 ,  14 ,  22  defines an integral receptor  38  configured to closely receive a stud  40 , which is integral with or inserted into the upper end of corresponding columns  20 ,  14 ,  22  of a further end frame  12 . Accordingly, end frames  12  are stackable in an end to end fashion in order to accomplish multi-level scaffolding. As a safety precaution, locking pins may be provided for preventing the studs  40  from becoming dislodged from the receptors  38 . 
     Electrical outlets  42  are preferably provided at each end of the center column  14  for powering electrical equipment. In the embodiment shown in FIG. 1, wiring  44  is disposed within the center column  14 , with a pair of outlets  42  disposed at each end of the center column  14 . A jumper  46  which includes an electrical cord having oppositely disposed male ends is provided for establishing electrical continuity between successive pairs of end frames  12 . When the bottom end frame  12  is connected to a power source, and jumpers  46  are attached between the end frames  12 , an outlet  42  disposed at each of the upper and lower ends of each end frame  12  is provided with electricity. 
     An end handrail  48  is secured between the upper ends of the forward and center columns  20 ,  14 . In a preferred embodiment, the end handrail  48  is removably mounted in a conventional manner such that it may be placed only at the ends of each run of scaffolding  10 . By providing the end handrail  48  only at the ends of a run of scaffolding  10 , movement between each section of scaffolding  10  is unencumbered. However, it will be seen that the handrail  48  may be permanently mounted to each end frame  12  in a conventional manner. 
     A ladder  50  is carried by the end frame  12 , preferably on the forward side of the center column  14  such that a worker ascending or descending the ladder  50  may easily access the walk board  24  or work board  30  at the desired scaffold level. Alternatively, the ladder  50  is attached to the forward column  20  or the rearward column  22 . In a preferred embodiment, the ladder  50  is permanently mounted on the end frame. However, as in the above instances, the ladder may be removable if desired. As illustrated in FIG. 2B, the ladder  50  in an alternate embodiment includes a first ladder portion  50 A carried on the rearward side  18  of the center column  14  below the work board support  30 , a second ladder portion  50 B carried on the forward side  16  of the center column  14  above the first ladder portion  50 A, and a third ladder portion  50 C on the rearward side  18  of the center column  14  above the second ladder portion  50 B. While some degree of stiffness may be added to the center column  14  by the presence of the ladder  50 ,  50 A-C, the ladder  50 ,  50 A-C is considered to be non-loading bearing in the sense that the absence of the ladder imposes substantially no effect to the structural integrity of the end frame. Instead, the only significant loading carried by the ladder  50 ,  50 A-C are loads imparted to the ladder  50 ,  50 A-C when the ladder  50 ,  50 A-C is in use by a worker. 
     FIG. 7 illustrates in block diagram form a multi-section scaffolding structure  100  in accordance with the invention. The particular scaffolding structure of FIG. 7 includes five sections of scaffolding on each of two levels  102 ,  104  where each section  102   a-e ,  104   a-e  of the structure  100  is constructed and raised in accordance with the section of scaffolding  10  shown in FIG.  1 . At each level of the structure, contiguous sections of scaffolding  10  share a common walk board support  24  and a common work board support  30 . In a preferred embodiment, the end frames  12  for all intermediate sections  102   b-d ,  104   b-d  of the structure  100  do not include a ladder  50  since a ladder  50  at these sections of scaffolding would tend to serve as an obstruction to movement of workers and materials between successive sections of scaffolding. If desired, however, all end frames  12  of the structure  100  may include ladders. 
     As will be discussed in more detail below, the lower end of the rearward column  22  defines a through opening  54  for mounting a handrail  52  on intermediate layers of scaffolding  10 . A through opening  54  is also defined at the upper end of the rearward column  22  for mounting a support brace  62  associated with a handrail  52  mounted to the intermediate runs of scaffolding  10 , or for mounting a handrail  52  on the top run of scaffolding  10 . A receptor  56  is defined a distance below the upper through opening  54  for mounting a support brace  62  associated with the handrail  52  on the top run of scaffolding  10 . The spacing between the upper through opening  54  and the receptor  56  is equal to the spacing between the lower through opening  54  on a first end frame  12  and the upper through opening  54  on a second end frame  12  disposed immediately below the first. An upper through opening  54  and a receptor  56  are also defined by the upper end of the forward column  20  for mounting a handrail  52  on each run of scaffolding  10 . 
     An eyelet, preferably an eye bolt  72 , is provided at the upper end of each center column  14  for receipt of a safety cable. The safety cable is threaded through each eye bolt  72  along a run of scaffolding  10 . Workers are then tethered to the safety cable in a conventional manner. By disposing the eye bolt  72  at an upper end of the center column  14 , the worker wearing a harness tethered to the safety line is less likely to become entangled. 
     The walk board  74  and the work board  82  are each constructed in similar fashion to each other. In the illustrated embodiment, each includes a frame  76 ,  84  constructed from tubular steel and a support surface  78 ,  86  fabricated from a selected grating material. A toe board  90 , best illustrated in FIG. 4, is provided for attachment to the rearward side of the work board  82 , thus providing a means for preventing items from being pushed off of the work board  82 . As illustrated in FIG. 4, the toe board  90  is mounted on the work board  82  in a conventional manner such as by clamping. A handrail may also be mounted to the work board using the clamps  92  shown to mount the toe board  90 . 
     FIG. 3 is a top plan view of an end frame  12  in accordance with the invention showing the walk board support  24  and the work board support  30 , and FIG. 8 is a cross-sectional view of the walk board support  24  shown in FIG. 3 taken along cross-section line A—A, it being understood that a cross-section of the work board support  30  is similar to or the same as the cross-sectional view of the walk board support  24  shown in FIG.  8 . As can be seen, each walk board and work board support  24 ,  30  is provided with two horizontal support members  94 ,  94 ′,  96 ,  96 ′ separated by a raised vertical support member  26 ,  32 , thereby forming a T-shaped cross-sectional dimension as shown in FIG.  8 . The ends of the boards are supported by the horizontal support members  94 ,  94 ′,  96 ,  96 ′ and the length of the vertical support members  26 ,  32  is preferably the same as or slightly less than the thickness of the boards so that when the boards are positioned end to end in the board support  24 ,  30  the board ends are flush with respect to one another and provide a safe, smooth walking surface with no overlap of the board ends. A plurality of receptors  28 ,  34  are provided in each horizontal support member  94 ,  94 ′,  96 ,  96 ′ for receiving mounting studs  80 ,  88  (FIG. 9) carried at the ends of each walk board  74  and work board  82  so that the board  74 ,  82  remains fixed with respect to the horizontal support member  94 ,  94 ′,  96 ,  96 ′. 
     In a preferred embodiment, the mounting studs  80 ,  88  extend from a stiffener plate  98  (shown in FIGS. 9 and 11) attached to the underside of both ends of the walk board  74  and the work board  82 . The stiffener plate  98  is particularly advantageous for use with wooden boards  74 ,  82  and is easily attached thereto with wood screws  99 ,  99 ′ or other suitable fastener. The stiffener plate  98 , which is preferably constructed from a stiff, durable, corrosion-resistant material such as aluminum, helps to distribute load forces exerted on the ends of the boards  74 ,  82 , reduces flexing of the boards  74 ,  82 , and provides a hard, durable, wear-resistant surface contact with the board supports  24 ,  30 . The stiffener plate also includes a corrugation  97  to enhance stiffness. 
     From the above-described construction, it can be seen that assembly and disassembly of the improved scaffolding  10  of the present invention is performed quickly and efficiently. 
     Although several methods may be followed to assemble the improved scaffolding  10 , one preferred method is to secure one end of a walk board  74  to a walk board support  24  of one end frame  12 . Then the other end of the walk board  74  is secured to the walk board support  24  of a second end frame  12 . A work board  82  is then secured at either end to the respective work board supports  30  of the two end frames  12 . Locking pins  68  are put in place where required. Handrail  48 ,  52  is then mounted as required. As described above, multi-level scaffolding is raised by vertical stacking of end frames through use of studs  40  received in the receptors  38  at the ends of each end frame  12 . 
     To establish continuous scaffolding  10  around corners of structures, a corner walk board  74 A and a comer work board  82 A are provided, as shown in FIG.  4 . Each corner walk board  74 A and corner work board  82 A defines first and second ends disposed at a right angle with respect to each other. Each end, however, is configured to be substantially similar to the respective ends of the walk board  74  and work board  82  shown in FIG.  1 . Although not shown, the corner walk board  74 A and work board  82 A may be adjustable to accommodate for varied spacing of the straight runs of scaffolding to which they attach. Adjustment of the length of the corner walk board  74 A and corner work board  82 A is accomplished by constructing each to include two telescoping members. 
     FIG. 5 illustrates the handrail  52  mounted at the upper end of the top run of scaffolding  10  on the rearward columns  22 , at the lower end of each intermediate run of scaffolding  10  on the rearward columns  22 , and at the upper end of each run of scaffolding  10  on the forward columns  20 . The support braces  62  are pivotally mounted at one end on the handrail  52  as shown. A locking pin  68  (FIG. 6) is carried by the free end of each mounting brace  62  for being received with either the upper through opening defined by the rearward column  22  or the receptor  56  defined by either of the rearward or forward columns  22 ,  20 , depending upon the disposition of the handrail  52 . When the handrail  52  is not in use, the locking pin  64  carried by the mounting brace  62  free end may be received within a receptor  66  defined proximate the middle of the handrail  52 . 
     As can be more clearly seen in FIG. 6, the handrail  52  defines a mounting stud  58  configured to be closely received within either of the through openings  54  defined by the rearward column  22  upper and lower ends and the forward column  20  upper end. A pin receptor  60  is defined at the distal end of the handrail mounting stud  58 . The pin receptor  60  is disposed such that when the handrail mounting stud  58  is received within a through opening  54 , a locking pin  68  is received with the pin receptor  60 , and the mounting brace locking pin  64  is received within a through opening  54  or receptor  56 , the mounting brace  62  is tensioned to bias the handrail  52  away from the end frame  12 . In so doing, movement of the handrail  52  with respect to the end frames  12  is inhibited. 
     The mounting stud locking pin  68  is equipped with a securement device  70  for permanently securing the locking pin  68  to the end frame  12 . In the illustrated embodiment, one end of a cable is mounted on the end frame  12 , such as by welding, with the other end of the cable being secured to the locking pin  68 . It will be seen that other embodiments of the securement device  70  may be incorporated as well. By providing a securement device  70  such as that described, it will be seen that the locking pins  68  will not get lost, which is the tendency in a conventional scaffolding system. 
     FIG. 10 shows an alternate embodiment of a dual walk-through section of scaffolding  10  in accordance with the invention which includes a walk board  114 , a work board  116 , end frames  118 ,  118 ′, a handrail  111 , rearward column cross-bracing  112 ,  112 ′, and center column cross-bracing  117 ,  117 ′. In this embodiment, the side handrail  52  of FIG. 1 is eliminated and a standard handrail  111  commonly used in conventional scaffolding is employed when needed. Cross-braces  112 ,  112 ′,  117 ,  117 ′, which are provided to enhance structural stability and integrity, are also standard cross-braces commonly used in conventional scaffolding. The handrail  111  and cross-braces  112 ,  112 ′,  117 ,  117 ′ each include through openings at their opposed ends. The through openings of the handrail  111  and cross-braces  112 ,  112 ′ are received by studs  146  attached to the rearward columns  124 ,  124 ′. The through openings of cross-braces  117 ,  117 ′ are received by studs  146  attached to the center columns  122 ,  122 ′. Eyelets  148 ,  148 ′ are provided to receive a safety cable or rope. 
     The extent to which cross-bracing is needed for scaffolding constructed in accordance with the invention depends upon the amount of loading imposed on the structure, including loading resulting from the weight of workers and materials, multi-level stacking of scaffolding, wind, and other forces. Generally, the greater the loading the greater the need for cross-bracing. Under moderate loading conditions, a single conventional type cross-brace at each section of scaffolding  10  may provide sufficient cross-bracing to prevent collapse of the scaffolding  110 . In a preferred embodiment, two cross-braces  112 ,  112 ′ connected to the rearward columns  124 ,  124 ′ and two cross-braces  117 ,  117 ′ connected to the center columns  148 ,  148 ′ provide ample cross-bracing for normal loading conditions. Thus, there are no cross-braces connected to the forward columns  120 ,  120 ′ on the working side of the scaffolding  10  to restrict a worker&#39;s access to the work area. If desired, however, cross-braces may be attached between the forward columns  120 ,  120 ′. 
     In an alternate embodiment, conventional type cross-braces  112 ,  112 ′ connecting the rearward columns  124 ,  124 ′ and conventional type cross-braces  117 ,  117 ′ connecting the center columns  122 ,  122 ′ are eliminated and cross-bracing of the scaffolding  110  is provided by cross-bracing members connected to the walk board  114  and work board  116  and one or more of the end frame columns  120 ,  120 ′,  122 ,  122 ′,  124 ,  124 ′. For example, four cross-bracing members may be connected between the walk board  114  and the forward and center columns  120 ,  120 ′,  122 ,  122 ′, and four cross-bracing members may be connected between the work board  116  and the center and rearward columns  122 ,  122 ′,  124 ,  124 ′. 
     As described above with regard to FIGS. 1,  2 A, and  2 B, electrical power may be provided to the end frames of the scaffolding  110 . Also, as previously described, receptors  140  formed in the lower ends of the columns  120 ,  120 ′  122 ,  122 ′,  124 ,  124 ′ are sized to closely receive a stud  142  carried by or inserted in the upper ends of corresponding columns  120 ,  120 ′  122 ,  122 ′,  124 ,  124 ′ so that end frames  118 ,  118  can be stacked to achieve a multi-level scaffolding structure. If desired, locking pins  144  or similar locking devices may be used to inhibit or prevent the studs  142  from becoming dislodged from the receptors  38 . At each level of the structure, contiguous sections of scaffolding  110  share a common walk board support  126 ,  126 ′ and a common work board support  128 ,  128 ′. 
     Each end frame  118 ,  118 ′ includes a forward column  120 ,  120 ′, a center column  122 ,  122 ′, and a rearward column  124 ,  124 ′. Walk board supports  126 ,  126 ′ are employed to interconnect the forward column  120 ,  120 ′ with the center column  122 ,  122 ′ and to support opposed ends of the walk board  114 . Work board supports  128 ,  128 ′ are employed to interconnect the center column  122 ,  122 ′ with the rearward column  124 ,  124 ′ at an elevated position with respect to the position of the walk board support  126 ,  126 ′ so that when the work board  116  is attached to the work board supports  128 ,  128 ′ and the walk board  114  is attached to the walk board supports  126 ,  126 ′ in the manner described above with regard to FIGS. 8,  9 , and  11 , the work board  116  is maintained at an elevation above the walk board  114 . Keepers  130  are provided at the ends of the walk board  114  and work board  116  to inhibit vertical displacement of the boards  114 ,  116 , as may occur during high-level wind updrafts. 
     A ladder  132 ,  132 ′ configured as shown, is attached to the center columns  122 ,  122 ′ of each each frame  118 ,  118 ′. As previously described with respect to the ladders  50 ,  50 A-C of FIGS. 1 and 2B, the ladder  132  of FIG. 10 is preferably non-load bearing and carries significant loads only when in use by a worker. The ladder  132  is permanently attached to the center column  122 ,  122 ′ in a preferred embodiment but may be detachable if desired. The ladder  132  of FIG. 10 also meets applicable industry standards including OSHA standards. 
     From the foregoing description, it will be recognized that a scaffolding system offering significant advantages over the prior art has been provided. Among these advantages are a three-column structural support configuration which provides enhanced stability and load distribution and dual walk-through work areas, special structural support members for support of walk boards and work boards to reduce or eliminate hazards associated with unsecured and overlapped boards, an integral, non-load bearing ladder which meets applicable OSHA standards, a walk board level and a work board level which is elevated with respect to the walk board level to optimize positioning and accessibility of workers and materials, and elimination of cross braces on the working side of the scaffolding to enhance accessiblity to work areas. The scaffolding is also designed to enable workers to easily and safely move between successive sections of the scaffolding. Electrical power provisions are integrated with the scaffolding structure to alleviate problems and hazards associated with dangling electrical cords. Due to the configuration of the scaffolding system, assembly and disassembly thereof is accomplished with greater efficiency when compared to the assembly and disassembly of prior art scaffolding. 
     It is contemplated, and will be apparent to those skilled in the art from the foregoing specification, drawings, and examples that modifications and/or changes may be made in the embodiments of the invention. Accordingly, it is expressly intended that the foregoing are illustrative of preferred embodiments only, not limiting thereto, and that the true spirit and scope of the present invention be determined by reference to the appended claims.