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BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to scaffolds and more particularly to an adjustable height scaffold with a work platform for use in hanging sheetrock. 
   2. Description of the Related Art 
   When hanging sheet rock it is often necessary to reach elevated areas of a wall that are out of reach of the worker while standing on the floor. Many different devices are in existence that can aid a worker hang sheet rock at heights greater than that of the worker. Common devices include lifts and scaffold devices for elevating the worker while hanging sheet rock. The following patent documents disclose devices for lifting a worker. 
   French Patent number 2 624 173 published on Jun. 9, 1989 discloses a climbing platform-scaffolding forming an independent unit. The climbing scaffolding comprises at least one vertical mast that is supported against a vertical wall. The mast serves as an anchor for a cable that allows a platform to slide vertically up and down the cable. The platform also provides handrails to protect the workers that are positioned on the platform. 
   U.S. Pat. No. 6,446,752 issued on Sep. 10, 2002 to Philippe, M. J., discloses a scaffolding assembly. The invention is a bracing assembly for supporting an upright structure. The scaffolding assembly comprises a horizontal platform that is supported by a pair of vertical supports. A bracing assembly, comprising two angled braces, is secured to the vertical supports to prevent them from collapsing. The scaffolding further provides a guide rail on the platform. 
   U.S. Pat. No. 6,109,390 issued on Aug. 29, 2000 to Giannopoulos, J. discloses a motorized scaffolding truck. The scaffolding truck provides a horizontal support frame that is adapted for supporting scaffolding and ladders. A vertical steering mast is secured to the horizontal support frame for steering the motorized truck. A plurality of wheels is secured to the bottom of the support frame. A motor, for driving the plurality of wheels, is mounted on the support frame. Once the scaffolding is supported on the truck, the truck allows the scaffolding to be easily repositioned by driving it from one position to the next. 
   U.S. Pat. No. 6,076,621 issued on Jun. 20, 2000 to Horn, G. H. discloses a mobile work platform. The work platform comprises a base portion housing a motor and gear box for driving the mobile platform. A plurality of wheels is mounted to the underside of the base. A pair of ladders is mounted to, and extends upward from, the top of the base. The ladders support a horizontally disposed work platform that includes a plurality of guard rails disposed around it. The mobile platform also provides a control system for regulating the speed and direction of travel of the platform. 
   U.S. Pat. No. 4,967,733 issued on Nov. 6, 1990 to Rousseau, Y. J. discloses a lifting carriage. The lifting carriage comprises a base member having a plurality of wheels disposed along its underside. A motor for driving the wheels is mounted to the base. A rectangular frame, having four corner posts, for supporting a horizontal platform is disposed on top of the base. A motor and chain assembly powers the platform to move vertically along the four corner posts. 
   U.S. Pat. No. 4,886,139 issued on Dec. 12, 1989 to Dupont et al. discloses a mobile scaffold with a power operated platform elevation. The scaffold includes a base mounted on a set of wheels for repositioning of the scaffold. A pair of masts is mounted to the base and supports a horizontal platform. The height of the masts may be increased by the addition of a mast extension. The mast extension is powered by a motor mounted to the base of the scaffold. 
   U.S. Pat. No. 3,548,970 issued on Dec. 22, 1970 to Hutchens, Sr., R. W. discloses a scaffolding and material handling system. The invention is a vertically extendible scaffolding assembly in which the scaffolding is supported by vertically moveable carriages that are connected to vertical frame members. The material handling portion of the assembly comprises a vertical chain conveyor system for lifting materials from a lower level to an upper level for subsequent movement by a horizontal conveyor at the upper work level. 
   U.S. Pat. No. 4,598,794 issued on Jul. 8, 1986 to Anderson, C. E., U.S. Pat. No. 4,453,619 issued on Jun. 12, 1984 to Bierman, J. H., U.S. Pat. No. 3,851,854 issued on Dec. 3, 1974 to Roybal, F. V., U.S. Pat. No. 3,825,095 issued on Jul. 23, 1974 to Clark, A. L., U.S. Pat. No. 2,857,212 issued on Oct. 21, 1958 to Everitt, R., U.S. Pat. No. 2,573,575 issued on Oct. 30, 1951 to Keroson, G. E., U.S. Pat. No. 2,072,354 issued on Mar. 2, 1937 to Biebel, J. P., U.S. Pat. No. 1,736,501 issued on Nov. 19, 1929 to Macklem, J. J., U.S. Pat. No. 1,432,040 issued on Oct. 17, 1922 to Schuler, E., U.S. Pat. No. 902,949 issued on Nov. 31, 1908 to Dibler, J. M., and U.S. Patent Application number 2002/0096394 published on Jul. 25, 2002 for Chick, M. C. each disclose general scaffolding assemblies. 
   Many of the inventions disclosed above provide scaffolds that are secured directly to the wall that the user is working on. These are not advantageous to someone hanging sheet rock because they can not be moved easily and since they are secured to the wall they do not leave room to mount the sheet rock. Other patents disclose free standing lifts with platforms. The platforms discussed above are not advantageous to workers hanging sheet rock because the platforms do not provide sufficient room to support the worker, to support sheet rock materials and for the worker to move freely to hang the sheet rock. A worker using these platforms would have to lower the platform every time more sheet rock material was needed. Therefore, what is needed is a height adjustable workstation that may be easily moved while the worker is positioned on the platform. What is also needed is a height adjustable workstation that provides sufficient room for a worker, sheet rock material, waste material and still leave enough room for the worker to cut and mount the sheet rock material. 
   None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus an adjustable height workhorse solving the aforementioned problems is desired. 
   SUMMARY OF THE INVENTION 
   The adjustable height workhorse of the present invention is a height adjustable workspace for allowing a worker to easily hang sheet rock on walls at elevated heights. The adjustable height workhorse provides a work platform supported by a frame assembly having a plurality of vertically disposed posts and a plurality of horizontally disposed height adjustment bars. The support frame is positioned on the top surface of a base board. A plurality of wheels is disposed underneath of the base board. 
   The wheels allow the workhorse to be repositioned along the work area while the worker is located on the platform. The workhorse may be repositioned manually by the worker or automatically by a motor. 
   The plurality of height adjustment bars is mounted on either side of the support frame. The bars are positioned at varying heights so that the worker may adjust the height of the platform according to his height and needs. Each of the posts on the frame are equipped with post securing pins that are adapted to secure a second set of posts on top of the support frame. The second set of posts may be added to the support frame to increase the height of the workhorse if needed. 
   The platform is horizontally disposed across the support frame and is supported by the height adjusting bars. The platform is of suitable size to support a worker and the worker&#39;s sheet rock material while providing enough room for the worker to operate. One side of the platform extends sufficiently beyond the support frame to provide a storage space for the worker&#39;s waste materials. A plurality of restraint beams is disposed along the top surface of the platform. The restraint beams secure the sheet rock material and waste material in place while they are resting on the platform. 
   Accordingly, it is a principal object of the invention to provide a height adjustable workstation that may be easily moved while the worker is positioned on the platform. 
   It is another object of the invention to provide a height adjustable workstation with sufficient room for a worker, sheet rock material, waste material and still leave enough room for the worker to cut and mount the sheet rock material. 
   It is a further object of the invention to provide a height adjustable workstation that can support a work platform at varying heights to easily accommodate the needs of the user. 
   It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
   These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental, perspective view of an adjustable height workhorse according to the present invention. 
       FIG. 2  is a front view of the frame of the adjustable height workhorse. 
       FIG. 3  is a side view of the frame of the adjustable height workhorse. 
       FIG. 4  is a rear view of the frame of the adjustable height workhorse. 
       FIG. 5  is a top perspective view of the platform of the adjustable height workhorse. 
       FIG. 6  is a bottom view of the platform of the adjustable height workhorse. 
       FIG. 7  is an exploded perspective view of a second embodiment of the present invention. 
       FIG. 8  is front view of a third embodiment of the present invention. 
   

   Similar reference characters denote corresponding features consistently throughout the attached drawings. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is a workhorse that provides a workstation whose height may be adjusted to aid workers in installing sheetrock.  FIG. 1  is an environmental, perspective view of an adjustable height workhorse  10  according to a preferred embodiment of the present invention. The workhorse comprises a support frame  20 , a work platform  30 , a base board  40 , wheel assemblies  50  and a plurality of braces  60 . The platform  30  provides a workspace that supports the worker W and his sheetrock materials M. The platform  30  also provides an area outside of the support frame  20  for storing waste material WM. The base board  40  provides an area underneath of the platform  30  where the worker W may store his tools. 
   The support frame  20  comprises a plurality of posts  70 , a plurality of height adjusting rails  90  and a plurality of support crossbars. The platform  30  is horizontally disposed across the support frame  20  and is supported on either side of the frame  20  by one of the plurality of height adjusting rails  90 .  FIG. 2  depicts a front view of the support frame  20  with the platform  30  removed from the workhorse  10 . The frame  20  includes a top cross bar  22  and two angled cross bars  24 ,  26 . The top cross bar  22  and the angled crossbars  24 ,  26  are disposed along the rear of the support frame  20 . The cross bars act as protective supports that prevent the worker W or the material M from falling off of the workhorse  10 . 
   According to the preferred embodiment of the workhorse  10  the frame  20  comprises four posts  70 . Two posts  70  are disposed on either end of the base board  40 . Each of the four posts  70  is disposed on the top surface  42  of the base  40 . Each post comprises a top  74 , a bottom  72 , an exterior surface  78  and a post securing pin  76 . The post securing pins  76  are disposed in a hole  77  located in the center of the top  74  of each post  70 . The hole  77  allows the securing pins  76  to extend a distance into the post  70 . 
   As shown in  FIG. 4  the top cross bar  22  extends across the rear of the support frame  20  and is secured to the exterior surface  78  of the two rear posts  70 . Each of the two angled cross bars  24 ,  26  extend diagonally across the rear of the frame  20  from the top  74  of one of the posts  70  to the bottom  72  of one of the posts  70 . The two angled cross bars  24 ,  26  are secured to one another at their point of intersection by a fastener  28  (shown in FIG.  2 ). 
   The height adjusting rails  90  are disposed on either side of the support frame  20 . According to the preferred embodiment of the present invention there are three height adjusting rails  90  positioned on each side of the support frame  20 . Each of the rails  90  is mounted across two adjacent posts  70  (as shown in FIG.  1 ). Each of the rails  90  is mounted evenly with a corresponding rail  90  on the opposite end of the support frame  20 , i.e. rails  91  and  92 . Each corresponding set of even rails  90  allows the platform  30  to be positioned at a set height. The first set of rails  91 ,  92  is positioned near the bottom of the frame  20 . The second set of rails  93 ,  94  is positioned near the middle of the frame  20 . The third set of rails  95 ,  96  is positioned near the top of the frame  20 . 
     FIG. 1  shows a single worker W supported on the workhorse  10 . The platform  30  is large enough, however, to support two workers on the workhorse  10  at the same time. In the instance where there is a significant difference in the height of the two workers, the position of the platform  30  may be adjusted to compensate for the height difference. The platform  30  may be positioned on an incline so that the taller of the two workers may stand on the lower portion of the platform, while the shorter worker may stand on the higher portion of the platform. For example, a first end of the platform  30  may be positioned on rail  91  while a second end of the platform  30  is positioned higher on rail  94 . 
   A plurality of threaded fasteners  100  is disposed along the exterior surface  78  of the two front posts  70 . Each threaded fastener  100  extends out of the post  70  and has a securing device  102  releasably secured to it. The threaded fasteners  100  are adapted to releasably secure a guard rail  80  to the two front posts  70 . The guard rail  80  prevents the worker W from falling off of the workhorse  10  while hanging sheet rock. The guard rail  80  may be repositioned at varying heights on the posts  70  consistent with the height of the platform  30 . 
   The wheel assemblies  50  are disposed on the bottom surface  44  of the base board  40 . The wheel assemblies  50  allow the worker W to move the workhorse  10  along a workspace. Each wheel assembly  50  is positioned directly underneath one of the posts  70 . The wheel assemblies  50  each comprise a wheel  52 , a wheel mount  54  and a locking lever  56 . The wheel mount  54  is secured to the wheel  52  at its axis and mounts the wheel  52  to the bottom surface  44  of the baseboard  40 . The wheel mount  54  is preferably a caster that allows the wheels to be pivoted in different directions. The locking lever locks the wheels  52  to prevent the workhorse  10  from moving. The wheel assembly  50  further comprises a lock rod  58  (shown in  FIG. 1 ) that allows the worker W to unlock/lock the wheels  52  while standing on the platform  30 . The locking rods  58  are secured to one end of the locking levers  56  and extend upward towards the platform  30 . The worker W can pull up or push down on the locking rod  58  to move the locking lever  56  from a locked to an unlocked position and from an unlocked to a locked position. 
   The workhorse  10  also provides a plurality of support braces  60  ( FIGS. 1 ,  3  and  4 ). The braces  60  extended on a slope, outward from the rear of the workhorse  10 . When the braces  60  are in place they prevent the workhorse  10  from tipping over. According to the preferred embodiments of the present invention the workhorse  10  provides three braces  60 ; two sides braces  61 ,  63  and a center brace  62 . 
   Each of the braces  60  comprises an elongate body having a top end  64  and a bottom end  65 . Each brace  60  has a brace wheel  66  mounted to its bottom end  65  by a brace wheel mount  68 . The brace wheel mount  68  secures the brace wheel  66  to the brace  60  and locks the wheel  66  to prevent it from rolling. The wheel mount  68  locks the brace wheels  66  in place so that they only roll side to side and not front to back. Each of the braces  60  has a mounting projection  69  that extends from the top end  64  of the brace  60 . Each mounting projection  69  is adapted to releasably engage one of a plurality of mounting hooks  28  secured to the workhorse  10 . A plurality of threaded brace fasteners  67  more firmly secures the braces to the workhorse  10 . As shown in  FIG. 4 , the side braces  61 ,  63  are secured to the two rear posts  70 . The center brace  62  is secured to the top cross bar  22  of the workhorse  10 . 
     FIG. 5  is a top perspective view of the platform  30 . The platform  30  provides a sturdy workspace that may hold the worker W and his sheet rock material M. According to the preferred embodiments, the platform  30  comprises a generally rectangular, flat top board  32  and a plurality of rails  35  disposed along the bottom surface of the top board  32 . The preferred embodiment of the platform  30  comprises three rails  35  that define two openings  36  that extend along the entire length of the platform  30 . 
   The platform  30  further comprises a plurality of mounting slots  37  (also shown in  FIG. 6 ) that define generally rectangular openings that extend through the rails  35  from the front surface  34  of the platform across the entire width of the platform  30 . The mounting slots  37  are adapted for releasably engaging the height adjustment bars  90  that support the platform  30 . According to the preferred embodiment of the present invention the platform has a set of mounting slots  37  disposed on either side of the platform  30 . Each set comprises two slots  37 . The multiple slots  37  in each set allow the position of the platform  30  on the frame  20  to be adjusted. 
   A plurality of restraint beams is disposed along the top surface of the top board  32 . According to the preferred embodiments there are two side restraints  131 ,  132  and a center restraint  130 . The restraints are generally rectangular, elongate beams that are disposed along the surface of the platform  30 . The restraints are secured to the platform  30  by a plurality of restraint fasteners  134 , which are preferably threaded fasteners such as screws. The restraints prevent the sheetrock material M from sliding off of the platform  30  while the worker W is working. The center restraint  130  holds the material M in place on the platform  30  by securing the material M against the rear of the support frame  20 . The side restraints  131 ,  132  allow the worker W to store waste material along the sides of the support frame  20  while the worker W remains on the platform  30 . 
   If the worker W needs to further increase the height of the platform  30  then an additional support frame  200  may be secured to the top of the support frame  20 . The second support frame  200  comprises a plurality of posts  202 , a plurality of height adjusting bars  206  and a plurality of cross bars  207 ,  208 . The individual elements of the second support frame  200  are generally equivalent to the elements of the support frame  20 . The second support frame  200  further comprises a frame connector hole  204  disposed on the bottom surface of each of its posts  202 . The connector hole  204  is adapted to engage the post securing pins  76  of the support frame  20  to releasably engage the second support frame  200  to the support frame  20 . An additional set of braces  60  may also be used to aid in supporting the second frame  200 . 
   The workhorse  10  may be easily moved by the worker W while he is either on or off of the workhorse  10 . The workhorse W is easily moved by releasing the wheel lock and then manually pushing the workhorse  10 . The wheels  52  may roll forward, backward and side to side to reposition the workhorse  10  in any direction.  FIG. 8  depicts a front view of a second embodiment of the present invention. The embodiment depicted in  FIG. 8  provides a motor  140  for automatically repositioning the workhorse  10 . The motor  140  is disposed on the top surface  42  of the base board  40 . The motor  140  provides power to the wheels  52  to move the workhorse  10 . The worker W may optionally be supplied with a remote control for the motor  140  to activate and control the motor  140  while positioned on the elevated platform  30 . 
   The support frame  20 , including the posts  70 , the cross bars  22 ,  24 ,  26 , the height adjusting bars  90  and the guard rail  80  are all made from a light metal pipe similar to the material used in conventional scaffolds. Preferred embodiments of the present invention will be made from materials including, but not limited to, light steal and aluminum. The baseboard  40  and the top board  32  of the platform  30  are preferably made from plywood. The rails  35  underneath the platform  30  are preferably made from aluminium as well, but any suitable strong, light material may also be used. 
   It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Summary:
The adjustable height workhorse is a height adjustable workspace for allowing a worker to easily hang sheet rock on walls at elevated heights. The workhorse provides a platform supported by a frame having a plurality of vertical posts and a plurality of horizontal height adjustment bars. The frame is positioned on a base board. A plurality of wheels is disposed underneath of the base board. The wheels allow the workhorse to be repositioned while the worker is on the platform. The height adjustment bars are mounted on either side of the frame. The bars are positioned at varying heights so that the worker may adjust the height of the platform. The platform is disposed across the frame and is supported by the height adjusting bars. The platform is of suitable size to support a worker and the worker&#39;s sheet rock material while providing enough room for the worker to operate.