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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    The present invention relates generally to ladders in general and in particular to a method and apparatus for permitting a user to climb a vertical column. 
         [0003]    2. Description of Related Art 
         [0004]    Ladders are a common implement use for enabling a user to reach heights not otherwise accessible to them. Conventional ladders however, have several disadvantages their use. In particular, the rungs of the ladder may be prone to becoming slippery in wet or adverse conditions or when the user has limited grip available from their shoes. This difficulty may be exacerbated on worksites in which the user is required to walk through mud and or dirt prior to using the ladder. The potential risks associated with a user&#39;s foot slipping off of a ladder rung include death or serious injury from the resulting fall. 
         [0005]    Landers conventionally fall into one of two configurations, a leaning ladder or an A-frame ladder. A-frame ladders typically have two sides forming in a frame so as to be self-supporting in the location which they are placed. Conversely, a leaning or extension ladder includes a single elongate element having rungs therealong which may be leaned against a structure to support it. In each of these classes of ladders, the main climbing portion of the ladder is angled so as to enable the user to climb without fear or risk of falling backwards off the ladder. A disadvantage of such angle is that the ladder requires a larger ground area in order to permit a sufficiently wide base for the ladder to climb to higher heights. Additionally, leaning ladders also suffer from the disadvantage of requiring a firm surface against which to lean in order to be operated. This may be difficulty in locations where the object to be reached is suspended above the user with limited surrounding rigid objects. 
       SUMMARY OF THE INVENTION 
       [0006]    According to a first embodiment of the present invention there is disclosed a climbing apparatus comprising a base, an upright member extending vertically upwardly from the base and having first and second sides and first and second carriages slidably locatable along the first and second side of the upright member. The apparatus further comprises a foot support associated with each of the first and second carriages, the carriages being rotatable supported by the carriage; and an upright engaging member extending from each foot support to selectably engage the upright when the foot support is rotated to a first orientation and to disengage from the column when the foot support is rotated to a second orientation. 
         [0007]    The upright may include front and rear surfaces. The front surface may include a plurality of horizontal projections extending therefrom adapted to engage the upright engaging members of the foot supports. The horizontal projections may comprise lips having horizontal top surfaces. 
         [0008]    The first and second sides of the upright may include tracks therein. The tracks may comprise c-shaped openings. The first and second carriages may include rollers locatable within the tracks of the upright. The tracks may include lips extending towards each other to contain the rollers of the carriages therein. 
         [0009]    The first orientation may be a lowermost position. The second orientation may be a raised position such that the upright engaging member is rotated away from the upright. The upright engaging members may comprise posts extending towards each other from the food supports. 
         [0010]    The foot support may include a planar foot platform. The foot support may include a heal cup adapted to surround a heel of a user&#39;s foot to retain the foot upon the foot platform. The heal cup may be slidably supported by the foot platform and biased towards the upright. The foot support may include a top member adapted to extend over the foot to retain the food upon the foot platform. The top member may include an open side. The foot support may be pivotable about a pivot located above the foot platform. 
         [0011]    At least one of the carriages may include a post extending substantially therefrom to a support tray. The apparatus may further comprise a waist strap extending from the post adapted to surround a torso of a user. 
         [0012]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    In drawings which illustrate embodiments of the invention wherein similar characters of reference denote corresponding parts in each view, 
           [0014]      FIG. 1  is a perspective view of a ladder according to a first embodiment of the present invention. 
           [0015]      FIG. 2  is an exploded view of the carriage and ladder assembly of the ladder of  FIG. 1 . 
           [0016]      FIG. 3  is a cross-sectional view of the upright and carriage of the ladder of  FIG. 1 . 
           [0017]      FIG. 4  is a side view of one of the foot supports of the ladder of  FIG. 1  at a first position. 
           [0018]      FIG. 5  is a side view of one of the foot supports of the ladder of  FIG. 1  at a second position. 
           [0019]      FIG. 6  is a detailed perspective view of the bottom portion of the ladder of  FIG. 1 . 
           [0020]      FIG. 7  is a bottom plan view of the ladder of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Referring to  FIG. 1 , a ladder according to a first embodiment of the invention is shown generally at  10 . The ladder  10  is formed of a base  12  having an upright member  40  extending substantially vertically therefrom. A pair of foot supports  80  are supported by a pair of longitudinally slidable carriages  60  to a plurality of locations along the upright to support the feet of a user (not shown). 
         [0022]    With reference to  FIG. 6 , the base is formed of a bottom cap  14  secured to the bottom end of the upright  40 . The bottom cap  14  includes a pivot arm  16  extending therefrom pivotally supporting a base bracket  18 . As illustrated in  FIG. 6 , the base bracket  18  includes locking arms  20  extending therefrom and may be rotated in a direction generally indicated at  122  into engagement against the bottom cap  14  such that the locking arms  20  are located to either side thereof. Thereafter a pin  26  may be passed through bores  22  in the locking arms and a corresponding bore in the bottom cap  14  to secure the base bracket  18  thereto. 
         [0023]    The base bracket  18  pivotally supports first, second, third and fourth arms  30   a ,  30   b ,  30   c  and  30   d  therefrom which may be rotated about parallel axes to be arranged to extend substantially radially from the upright. As illustrated in  FIG. 7 , the arms  30   a ,  30   b ,  30   c  and  30   d  may be rotated in directions generally indicated at  124  so as to spread the arms around the upright  40 . The arms may include flexible connectors, such as cables  32  chains or the like therebetween sized to fix the arms at desired orientations from the base to provide sufficient stability to the apparatus. In particular, one of the cables  33  between one set of the arms  30   a  and  30   b  may extend from the first arm and include a hook  34  at a distal end thereof adapted to engage upon a corresponding loop on the fourth arm. In such a manner the arms may be folded to be parallel for storage as illustrated in  FIG. 6  or extended to support the upright as illustrated in  FIG. 7 . 
         [0024]    Turning now to  FIGS. 1 and 2 , the upright  40  comprises an elongate member having first and second sides,  42  and  44 , respectively and front and rear surfaces,  46  and  48 , respectively. The first and second sides  42  and  44  include elongate channels  50  therein adapted to receive the carriages as will be more fully described below. The front surface  46  includes a plurality of protrusions  52  extending therefrom. As illustrated in  FIGS. 1 and 2 , the protrusions  52  may comprises substantially rectangular shelves having planar top surfaces  54 . 
         [0025]    Turning now to  FIG. 3 , a cross sectional view of the upright is shown in which the channels  50  located within each of the first and second sides  42  and  44  thereof. As illustrated, the channels  50  may comprise substantially c-shaped channels having retaining panels  56  extending from the sides thereof to retain the carriage therein as will be more fully described below. 
         [0026]    Each carriage  60  comprises a base panel  62  having front and rear surfaces,  64  and  66 , respectively. The rear surface  66  supports a plurality of rollers  68  on roller pins  70  extending therefrom. The front surface  64  includes a foot support pin  72  extending therefrom. As illustrated, the carriage  60  may include three rollers  68  although it will be appreciated that more or less may also be utilized. The rollers  68  are sized and spaced apart by a distance sufficient to be located within the channel  50  such that the retaining panels  56  surround the rollers  68  to keep them within the channel  50 . The roller pins  70  have a length selected to space the rollers  68  apart from the rear surface 
         [0027]    The foot support  80  comprises a planar foot supporting platform  82  extending between front and rear ends,  84  and  86 , respectively. The front end of the platform  82  includes an upright panel  88  extending therefrom to a top distal end  90 . The top distal end includes a sleeve  92  adapted to receive the foot support pin  72  therein. In such a manner the foot support  80  may be pivotally supported about the foot support pin  72 . The foot support  80  includes an upright engaging body  94  extending from a side surface proximate to the upright at a position selected to be in front of the upright as illustrated in  FIG. 4 . The upright engaging body  94  is sized to correspond to the top surfaces  54  of the protrusions  52  so as to be engageable thereon. Optionally, as illustrated in  FIGS. 4 and 5 , the platform  82  may also include a rear stop bar  96  extending towards the same side as the upright engaging body and positioned to be located to the rear of the upright  40 . 
         [0028]    The platform  82  includes a top band  98  having an open side, generally indicated at  100  extending above the platform which is positioned to extend over the foot of a user located on the platform and thereby to retain the user&#39;s foot upon the platform when in use. Additionally, the platform also includes a rear heal cup  102  extending upwardly from the rear edge  84  of the platform  82 . The heal cup  102  includes a cup portion  104  sized and shaped to correspond to a users&#39; heal and an upright portion  106  spacing the cup portion  104  above the platform. Optionally, the heal cup  102  may include a base portion  108  slidably located within or below the platform  82  and biased towards the front edge  86  of the platform to retain the user&#39;s foot therein. As illustrated in  FIGS. 4 and 5 , the platform  82  may include a toe wall  110  located such that the user&#39;s foot may be located between the toe wall  110  and the heal cup  102 . 
         [0029]    In operation as illustrated in  FIGS. 4 and 5 , a user&#39;s foot may be located on the platform  82  between the toe wall  110  and heal cup  102  such that the top band  98  is located thereover. In the resting position with the user&#39;s weight upon the platform  82 , the platform will be rotated down until upright engaging body  94  engaged against the front surface  46  of the upright  40 . Thereafter the user&#39;s weight will move the upright engaging body  94  onto the top surface  54  of the next protrusion  52 . When the user wishes to climb, they may lift their foot thereby rotating the platform  82  in an upward direction generally indicated at  120  so as to disengage the upright engaging body  94  wherein the rear stop bar  96  engages the rear surface  48  of the upright preventing further rotation. Continued upward movement of the user&#39;s foot will thereafter lift the foot support  80  and carriage  60  upward until a sufficient foot height has been reached. Once the user thereafter presses their foot back down, the platform  82  will be rotated back to the orientation shown in  FIG. 4  and the upright engaging body  94  engaged upon a higher protrusion  52 . In such a manner, the user may then climb the upright without lifting their foot off of the platform and thereby reducing the risk of slips or the like. 
         [0030]    Optionally, as illustrated in  FIG. 1 , one or more of the carriages may include a post  140  extending therefrom adapted to have a tray  142  or the like located thereon. Additionally, the safety belts or the like may be secured around the user to the post to prevent accidental falls or the like. Additionally, as illustrated in  FIG. 1 , the legs may include rollers at the distal ends thereof as are commonly known to enable easy repositioning of the apparatus. 
         [0031]    While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Summary:
A climbing apparatus comprising a base, an upright member extending vertically upwardly from the base and having first and second sides and first and second carriages slidably locatable along the first and second side of the upright member. The apparatus further comprises a foot support associated with each of the first and second carriages, the carriages being rotatable supported by the carriage; and an upright engaging member extending from each foot support to selectably engage the upright when the foot support is rotated to a first orientation and to disengage from the column when the foot support is rotated to a second orientation.