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REFERENCE TO RELATED APPLICATION  
       [0001]    The application claims the benefit of U.S. Provisional Application No. 60/358,788, filed Feb. 22, 2002, the disclosure of which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to a ladder. More particularly, the present invention relates to a convertible ladder that is positionable in a variety of configurations.  
         BACKGROUND OF THE INVENTION  
         [0003]    For some time it has been known that constructing ladders with two sections that are slidably mounted with respect to each other enables the overall length of the extension ladder to be varied depending upon the desired use of the extension ladder. This feature is particularly useful for transporting the ladder to a desired use location.  
           [0004]    Conventional extension ladders do not have the ability to stand up without being leaned against another object. In certain circumstances it is not possible to lean the extension ladder against other objects. To overcome this limitation, Kummerlin et al., U.S. Pat. No. 3,692,143, pivotally attaches two extension ladders together. This ladder retained the benefits of being able to adjust the height of the ladder while adding the benefit that the ladder could remain erect without leaning against other objects.  
           [0005]    Boothe, U.S. Pat. Nos. 4,407,045 and 4,566,150, are both directed to a hinge for an articulating ladder. The hinge includes two hinge plates that are pivotally attached with a central hub. Pivoting of the hinge plates is controlled with a locking handle that extends through apertures in the hinge plates. The locking handle is biased to a locking position where the legs on the locking handle extend into the hinge plate apertures.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is a convertible ladder that includes a first ladder portion, a second ladder portion and an adjustable hinge mechanism. The first ladder portion and the second ladder portion each include a first section and a second section.  
           [0007]    The first and second sections of the first ladder portion are slidably attached to each other. The first and second sections of the second ladder portion are slidably attached to each other. The first sections of the first and second ladder portions are pivotally attached to each other.  
           [0008]    The present invention also includes a fixed hinge mechanism that is attachable to the second sections of the first and second ladder portions to maintain the second sections in an erect position with respect to each other.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a photograph of a convertible ladder of the present invention in a first orientation.  
         [0010]    [0010]FIG. 2 is a photograph of the convertible ladder in a second orientation.  
         [0011]    [0011]FIG. 3 is a photograph of the convertible ladder in a third orientation.  
         [0012]    [0012]FIG. 4 is a photograph of the convertible ladder in a fourth orientation.  
         [0013]    [0013]FIG. 5 is an enlarged view of a lower end of the convertible ladder.  
         [0014]    [0014]FIG. 6 is a photograph of the locking mechanism in an engaged position.  
         [0015]    [0015]FIG. 7 is a photograph of a locking mechanism of the convertible ladder in a disengaged orientation.  
         [0016]    [0016]FIG. 8 is a top view of an adjustable hinge mechanism in an assembled configuration.  
         [0017]    [0017]FIG. 9 is a bottom view of the adjustable hinge mechanism in the assembled configuration.  
         [0018]    [0018]FIG. 10 is a side view of the adjustable hinge mechanism in the assembled configuration.  
         [0019]    [0019]FIG. 11 is a top view of the adjustable hinge mechanism in an unassembled configuration.  
         [0020]    [0020]FIG. 12 is a bottom view of the adjustable hinge mechanism in the unassembled configuration.  
         [0021]    [0021]FIG. 13 is a photograph of the adjustable hinge mechanism in a disengaged orientation.  
         [0022]    [0022]FIG. 14 is a photograph of the adjustable hinge mechanism in an engaged orientation.  
         [0023]    [0023]FIG. 15 is a photograph of the adjustable hinge mechanism in a first position.  
         [0024]    [0024]FIG. 16 is photograph of the adjustable hinge mechanism in a second position.  
         [0025]    [0025]FIG. 17 is a photograph of the adjustable hinge mechanism in a third position.  
         [0026]    [0026]FIG. 18 is a photograph of a static hinge mechanism partially attached to the convertible ladder with the locking mechanism.  
         [0027]    [0027]FIG. 19 is a front view of a fixed hinge mechanism for use with the convertible ladder.  
         [0028]    [0028]FIG. 20 is a top view of the fixed hinge mechanism.  
         [0029]    [0029]FIG. 21 is a side view of the fixed hinge mechanism. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    The present invention is a convertible ladder, as most clearly illustrated at  10  in FIGS.  1 - 4 . The convertible ladder  10  includes a first ladder portion  12  and a second ladder portion  14  that are interconnected with an adjustable hinge mechanism  16 .  
         [0031]    The convertible ladder  10  is convertible between four different configurations. In a first configuration, the convertible ladder  10  is an extension ladder, as most clearly illustrated in FIG. 1. In a second configuration, the convertible ladder  10  is an upright standing, 2-sided step ladder, as most clearly illustrated in FIG. 2. In a third configuration, the convertible ladder  10  separates into two ladder portions  10   a,    10   b  that may be used independently or with a scaffold  20 , as most clearly illustrated in FIG. 3. In a fourth configuration, the convertible ladder  10  is adjusted so that the first ladder portion  12  and the second ladder portion  14  have different lengths to facilitate using the convertible ladder on uneven surfaces such as stairs  22 , as most clearly illustrated in FIG. 4.  
         [0032]    As a result of the various configurations in which the convertible ladder  10  may be positioned, the convertible ladder  10  of the present invention takes the place of several different prior art ladders. The convertible ladder  10  thereby reduces the number of ladders that a person must own to do a variety of tasks.  
         [0033]    The first ladder portion  12  and the second ladder portion  14  each include a first section  30  and a second section  32  that are slidably attached together, as most clearly illustrated in FIG. 1. The first section  30  includes a pair of first side rails  34  and a plurality of first rungs  36  that are mounted to extend between the first side rails  34  at selected intervals. The first side rails  34  preferably have a rectangularly shaped configuration. A person of ordinary skill in the art will appreciate that the size of the first side rails  34  and the first rungs  36  is selected based upon the intended use of the convertible ladder  10 .  
         [0034]    The second section  32  includes a pair of second side rails  40  and a plurality of second rungs  42  that are mounted to extend between the second side rails  40  at selected intervals. The second side rails  40  preferably have a C-shaped configuration that permits the first side rails  34  to at least partially seat with the second side rails  40 . A person of ordinary skill in the art will appreciate that the size of the second side rails  40  and the second rungs  42  is selected based upon the intended use of the convertible ladder  10 .  
         [0035]    The second section  32  also preferably includes a Y-shaped brace  44  proximate a lower end thereof, as illustrated in FIGS. 2 and 5. Lower ends  45  of the brace  44  are attached to the front and back of each C-shaped side rail  40 . The upper end  47  of the brace  44  is attached to the lowest rung  42 . The brace  44  thereby enhances the ability of the ends of the second sections  32  to resist deformation when forces are applied thereto.  
         [0036]    The second section  32  further preferably includes at least one brace  46  that extends between the second side rails  40  opposite the rungs  42 , as illustrated in FIG. 2. Preferably one of the braces  46  is located proximate a lower end of the second section  32  and one of the braces  46  is located proximate an upper end of the second section  32 . The at least one brace  46  further enhances the structural rigidity of the second section  32 .  
         [0037]    Proximate lower ends of the second side rails  40 , feet  48  are attached thereto, as illustrated in FIGS. 2 and 5. The feet  48  enhance the ability of the convertible ladder  10  to remain in a stationary position. The feet  48  are preferably removably attached to the second side rails  40  with a bolt. The bolt enables the feet  48  to be readily replaced when damaged.  
         [0038]    The lower ends of the second side rails  40  are flared apart from each other so that a distance between the second side rails  40  proximate the lower end is greater than a distance between the second side rails  40  proximate the upper end. Using this configuration enhances the lateral stability of the convertible ladder  10 .  
         [0039]    The second sections  32  each have a pair of locking mechanisms  51 . The locking mechanisms  51  are attached to the second side rails  40  proximate an upper end thereof. The locking mechanism  51  preferably includes a lock handle  53 . The lock handle  53  is movable between in an engaged position and a disengaged position. The lock handle  53  is preferably biased to the engaged position. When in the engaged position, the lock handle  53  engages the first section  30  and thereby maintains the first section  30  in a fixed position with respect to the second section  32 , as illustrated in FIG. 6. When in the disengaged position, the lock handle  53  permits the first section  30  to slide with respect to the second section  32 , as illustrated in FIG. 7.  
         [0040]    The adjustable hinge mechanism  16  includes a handle  50 , a first hinge plate  52  and a second hinge plate  54 , as most clearly illustrated in FIGS.  8 - 11 . The first hinge plate  52  is pivotally mounted with respect to the second hinge plate  54 .  
         [0041]    The first hinge plate  52  and the second hinge plate  54  each include a pivot aperture  56  formed therein. The pivot apertures  56  are aligned when the first hinge plate  52  is pivotally attached to the second hinge plate  54 .  
         [0042]    The first hinge plate  52  has a pair of first positioning apertures  60  formed therein, as most clearly illustrated in FIG. 11. The first positioning apertures  60  are located on opposite sides of the pivot aperture  56 .  
         [0043]    The second hinge plate  54  preferably has three pair of second positioning apertures  62  formed therein (two pairs are shown in phantom and one pair is aligned with the first positioning apertures  60 ). The second positioning apertures  62  are located on opposite sides of the pivot aperture  56  so that each pair of second positioning apertures  62  may be selectively aligned with the first positioning apertures  60 .  
         [0044]    A hub  70  extends through the pivot apertures  56  to pivotally attach the first hinge plate  52  to the second hinge plate  54 , as illustrated in FIGS. 11 and 12. Proximate a first end of the hub  70  an outwardly extending flange  72  is provided. A channel  73  is provided at an intermediate location on the hub  70 . A locking clip  74  seats in the channel  73  to retain the first hinge portion  52  and the second hinge portion  54  on the hub  70 .  
         [0045]    The hub  70  has a bore  76  extending therethrough. The bore  76  is adapted to receive a hinge shaft  78 . The hinge shaft  78  has a first shaft section  80  and a second shaft section  82  that are substantially adjacent to each other. The second shaft section  82  has a diameter that is smaller than the first shaft section  80  so as to define a shoulder  84 .  
         [0046]    The first shaft section  80  has at least one recess  85  formed therein that is adapted to receive an outwardly biased ball bearing (not shown). The ball bearing is adapted to engage a corresponding recess  87  formed in the hub  70 . Seating of the ball bearing in the recess  87  maintains the adjustable hinge mechanism  16  in the disengaged position so that the hinge plates  52 ,  54  may be pivoted with respect to each other. Once the hinge plates  52 ,  54  are positioned at a desired orientation, a modest force on the handle  50  causes the adjustable hinge mechanism  16  to return to the engaged position.  
         [0047]    A diameter of the hub bore  76  is approximately the same as the diameter of the first shaft section  82 . The hub  70  also preferably includes an end plate  88  proximate the second end. The end plate  88  has an aperture formed therein. A diameter of the end plate aperture is approximately the same as a diameter of the second shaft section  82 .  
         [0048]    A safety sleeve  86  extends at least a portion of the second shaft section  82 . The safety sleeve  86  is preferably fabricated from a material with a color that contrasts from a color of the other portions of the convertible ladder  10  so that the safety sleeve  86  is readily visible when exposed. A person of ordinary skill in the art will appreciate that, as an alternative to placing a safety sleeve  86  over the second shaft section  82 , the safety sleeve  86  may be formed by applying paint to the second shaft section  82 .  
         [0049]    When in the disengaged position, as illustrated in FIG. 13, the safety sleeve  86  is visible on either side of the convertible ladder  10 . When in the engaged position, as illustrated in FIG. 14, the safety sleeve  86  is not visible on either side of the convertible ladder  10 . The safety sleeve  86  thereby indicates to the person that the person should not step on the convertible ladder  10 , as the adjustable hinge mechanism  16  is not in the engaged position.  
         [0050]    The handle  50  has a first portion  100  and a second portion  102  that are attached on opposite sides of the hinge shaft  78 , as illustrated in FIGS.  8 - 10 . The first portion  100  preferably has a substantially elongated shape with a pair of locking pins  104  extending therefrom. The locking pins  104  are preferably selected with a width that is approximately the same as the diameter of the first positioning apertures  60  and the second positioning apertures  62 .  
         [0051]    Moving the first portion  100  towards the first hinge plate  52  causes the locking pins  104  to extend through the first positioning apertures  60  and the second positioning apertures  62  to thereby maintain the first hinge plate  52  in a rotational position with respect to the second hinge plate  54 .  
         [0052]    The adjustable hinge mechanism  16  preferably includes a spring  110  that biases the first portion  100  towards the first hinge plate  52  to maintain the adjustable hinge mechanism  16  in a locked position. Urging the second portion  102  towards the first hinge plate  52  causes the locking pins  104  to be withdrawn from the first positioning apertures  60  and the second positioning apertures  62  to thereby permit the first hinge plate  52  to rotate with respect to the second hinge plate  54 .  
         [0053]    The second portion  102  preferably has a substantially cylindrical shape that includes a top section  112  and a side section  114  that extends from the top section  112 . The top section  112  provides a substantially flat surface that is depressed for urging the adjustable hinge mechanism  16  from the engaged position to the disengaged position. The side section  114  extends towards the first hinge section  52  and thereby reduces the potential for a person&#39;s fingers to become pinched between the second portion  102  and the first hinge section  52 .  
         [0054]    Using the three pairs of second positioning apertures  62  enables the first hinge plate  52  to be locked at three different angular positions with respect to the second hinge plate  54 . In a first orientation of the adjustable hinge mechanism  16 , the first ladder portion  12  is positioned adjacent to the second ladder portion  14  for storage or transportation, as most clearly illustrated in FIG. 15. In a second orientation of the adjustable hinge mechanism  16 , the first ladder portion  12  is oriented at an angle with respect to the second ladder portion  14  for use as a step ladder, as most clearly illustrated in FIG. 16. In a third orientation of the adjustable hinge mechanism  16 , the first ladder portion  12  is parallel to and aligned with the second ladder portion  14  for use as an extension ladder, as most clearly illustrated in FIG. 17. A person of ordinary skill in the art will appreciate that varying the number of second positioning apertures  62  allows the number of angular orientations to be varied.  
         [0055]    Two of the static hinge mechanisms  140  are preferably attached to one of the second sections  32 , as illustrated in FIG. 18. Another second section  32  is then aligned with the static hinge mechanism  140  to assemble the erect step ladder.  
         [0056]    The convertible ladder  10  also includes a fixed hinge mechanism  140  is most clearly illustrated in FIGS.  19 - 21 . The fixed hinge mechanism  140  includes a first plate  142  and a second plate  144  that are attached together in a spaced-apart configuration.  
         [0057]    The first plate  142  and the second plate  144  each preferably have a generally U-shaped configuration. An angle α between hinge legs  146  is less than 90 degrees, preferably between 20 and 50 degrees and most preferably about 35 degrees. A person of ordinary skill in the art will appreciate that the angle α is selected based upon the desired use conditions such as the weight that is to be placed on the second sections  32 .  
         [0058]    A length of the hinge legs  146  is selected so that the hinge legs  146  extend sufficiently into the second sections  32  to prevent the second sections  32  from rotating with respect to each other.  
         [0059]    Proximate the end of the hinge legs  146 , each of the hinge legs  146  has an aperture  148  formed therein. The aperture  148  is adapted to receive either the lock handle  53  to thereby retain the fixed hinge mechanism  140  in a fixed position with respect to the second sections  32 .  
         [0060]    Positioned between the first plate  142  and the second plate  144  is an intermediate plate  145 . The intermediate plate  145  maintains the first plate  142  and the second plate  144  in a spaced apart relationship. The intermediate plate  145  also limits the extent to which the second sections  32  can be inserted into the fixed hinge mechanism  140 .  
         [0061]    The first plate  142 , the second plate  144  and the intermediate plate  145  are attached to each other with a plurality of reinforcing members  150 . The number and size of the reinforcing members  150  is selected based upon the anticipated load that is to be placed on the convertible ladder  10 . A spacer is also provided to maintain the first plate  142  and the second plate  144  at a desired position with respect to each other. A stop is further provided on the fixed hinge mechanism  140  to limit a distance that the fixed hinge mechanism  140  may be inserted into the second sections  32 .  
         [0062]    The components of the convertible ladder  10  are preferably fabricated from a lightweight aluminum material. However, a person of ordinary skill in the art will appreciate that it is possible to fabricate the convertible ladder  10  from alternate materials such as steel and fiberglass using the concepts of the present invention.  
         [0063]    Since the fixed hinge mechanism  140  is not used in three of the four configurations of the convertible ladder  10 , there is the potential that the fixed hinge mechanism  140  will be misplaced when not in use. To minimize the potential of the fixed hinge mechanism  140  being lost, the fixed hinge mechanism  140  is preferably stored in a case  160 . The case  160  is preferably injection molded plastic and includes a handle. The case may also be used to store other items such as instructions on the use of the convertible ladder  10 .  
         [0064]    It is contemplated that features disclosed in this application, as well as those described in the above applications incorporated by reference, can be mixed and matched to suit particular circumstances. Various other modifications and changes will be apparent to those of ordinary skill.

Summary:
A ladder having a first ladder section, a second ladder section, an adjustable hinge mechanism, and an engagement indicator. The adjustable hinge mechanism is mounted with respect to the first ladder and the second ladder so that the adjustable hinge mechanism is moveable between an engaged position and a disengaged position. When in the engaged position, the adjustable hinge mechanism retains the first ladder section in a stationary orientation with respect to the second ladder section. When in the disengaged position, the adjustable hinge mechanism permits the first ladder section to pivot with respect to the second ladder section. The engagement indicator is mounted on the adjustable hinge mechanism. The engagement indicator is visible when the adjustable hinge mechanism is in the disengage position. The engagement indicator is not visible when the adjustable hinge mechanism is in the engaged position.