Abstract:
A step ladder includes rigidified left and right legs and step units between the legs. Each rigidified leg includes a web interconnecting first and second tubular members. Each step unit includes a hollow step including an internal rigidifying partition wall and step mounts for coupling the hollow step to the legs.

Description:
BACKGROUND AND SUMMARY 
   The present disclosure relates to a ladder, and particularly to a collapsible ladder. More particularly, the present disclosure relates to a collapsible ladder including steps mounted on a frame. 
   Ladders have a frame and one or more steps that people use for elevation when reaching for objects, painting walls, or any everyday task where extra elevation would be helpful. Ladders are often foldable for ease of storage when the ladder is not being used. 
   According to the present disclosure, a step ladder includes left and right legs and several step units located in fixed positions between the legs. In an illustrative embodiment, each leg includes spaced-apart first and second tubular members and a web located between and coupled to the first and second tubular members so as to provide a rigidified leg. 
   Each step unit includes a hollow step, a left step mount for coupling a left end of the hollow step to the left leg, and a right step mount for coupling a right end of the hollow step to the right leg. The hollow step includes a horizontal top wall providing a step tread and a U-shaped base wall coupled to the horizontal top wall to form a hollow interior region therebetween. In an illustrative embodiment, the hollow step also includes a partition wall extending through the hollow interior region from the horizontal top wall to the U-shaped base wall to provide the step with a rigidified B-shaped cross-sectional shape. Each step mount has one side that is configured to mate with the first and second tubular members and to be coupled to the web located between those tubular members and an opposite side that is configured to mate with a distal end of the hollow step. 
   Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The detailed description particularly refers to the accompanying figures in which: 
       FIG. 1  is a perspective view of a step ladder in accordance with the present disclosure in an opened position showing an inclined front frame comprising left and right “double-tube” legs, three hollow step units coupled to the left and right double-tube legs of the inclined front frame, and an inclined rear frame comprising smaller left and right double-tube legs; 
       FIG. 2  is an exploded perspective view of some of the components included in the step ladder of  FIG. 1  showing that each hollow step unit includes a step provided with a “B-shaped” cross-section and a pair of step mounts for coupling ends of each B-shaped step to the left and right double-tube legs; 
       FIG. 3  is a sectional view taken along line  3 — 3  of  FIG. 1  showing a cross-sectional shape of each of the four double-tube legs included in the step ladder of  FIG. 1  wherein each leg comprises first and second tubular members and a web interconnecting the first and second tubular members; 
       FIG. 4  is a perspective view of a portion of the front right double-tube leg, a portion of the middle B-shaped step, and a step mount adapted to be anchored to the front right double-tube leg and configured to receive a right end of the middle B-shaped step to support the step on the leg; 
       FIG. 4   a  is an enlarged perspective view of the step mount shown in  FIG. 4  from a different point of view; 
       FIG. 5  is a section taken along line  5 — 5  of  FIG. 4  showing a partition wall shared by horizontal tubular members cooperating to form the middle B-shaped step and formed to include a pair of fastener-receiving bores; 
       FIG. 6  is a side elevation view of the step mount of  FIG. 4  anchored in place on the portion of the front right double-tube leg of  FIG. 4 ; 
       FIG. 7  is a section taken along line  7 — 7  of  FIG. 1  showing a step mount located between the front right double-tube leg and the B-shaped step coupled to that step mount; 
       FIG. 8  is a section taken along line  8 — 8  of  FIG. 7  showing fasteners arranged to anchor the step mount shown in  FIG. 7  to the front right double-tube leg and engagement of the step mount with its companion B-shaped step; and 
       FIG. 9  is a section taken along line  9 — 9  of  FIG. 1  showing a portion of the carrying handle mounted on the front right double-tube leg. 
   

   DETAILED DESCRIPTION 
   As shown in  FIG. 1 , step ladder  10  includes a frame  12 , several step units  14  mounted on the frame  12 , a top platform step  16 , a fixed tray  18 , and a movable tray  20  located between top platform step  16  and fixed tray  18 . Frame  12  includes a front set of left and right legs  21 ,  22  and a rear set of left and right legs  23 ,  24 . In the illustrated embodiment, step ladder  10  is collapsible and includes a pair of front legs  21 ,  22  and a pair of rear legs  23 ,  24 . It is within the scope of this disclosure to provide a step ladder (not shown) omitting rear legs  23 ,  24 , stretcher bars  45 , platform  16 , and movable tray  18 . 
   As shown in  FIGS. 2 and 3 , each front leg  21  and  22  includes first and second tubular members  26 ,  28  and a web  27  located between and coupled to first and second tubular members  26 ,  28  so as to rigidify front legs  26 ,  28 . Also, each rear leg  23  and  24  includes third and fourth tubular members  126 ,  128  and a web  127  located between and coupled to third and fourth tubular members  126 ,  128  to rigidify rear legs  23 ,  24 . 
   Each of step units  14  includes a step  30  and a pair of step mounts  31 ,  32 . Each of step mounts  31 ,  32  is configured to mate with one end of a step  30  and first and second tubular members  26 ,  28  of the leg  21  or  22  associated with the step mount. Fasteners  33  are used to anchor each step mount  31 ,  32  to one of the legs  21  or  22  to support the step  30  mated with the step mounts  31 ,  32  in a horizontally extending fixed position between left and right legs  21 ,  22 . 
   As suggested in  FIGS. 2 ,  4 , and  5 , each step  30  is hollow and includes a horizontal top wall  34  providing a step tread  36 , a U-shaped base  38  coupled to horizontal top wall  34  to form a hollow region  40  therebetween, and a partition wall  42 . As shown best in  FIG. 5 , partition wall  42  extends from horizontal top wall  34  to U-shaped base wall  38  and substantially bisects hollow interior region  40  to provide step  30  with a rigidified, substantially B-shaped cross-sectional shape. It is within the scope of this disclosure to provide a step  30  omitting partition wall  42 . 
   Each step mount  31 ,  32  is adapted to mate with one end of hollow step  30  and a portion of either leg  21  or leg  22  as suggested in  FIGS. 1 ,  2 , and  4 . As suggested in  FIGS. 4–6 , an inner portion  35  of each step mount  31 ,  32  is formed to include means for receiving and mating with an end  37  of step  30 . An outer portion  39  of each step mount  31 ,  32  is formed to include means for mating with web  27  and portions of first and second tubular members  26 ,  28  on either side of web  27  to allow fasteners  33  to pass through apertures  41  formed in web  27  and into bores  43  formed in partition wall  42  to anchor step  30  in a fixed position relative to said first and second tubular members  26 ,  28  and web  27 . 
   As shown in  FIGS. 1 and 2 , frame  12  includes a front frame portion  13  and a rear frame portion  15  mounted for movement relative to front frame portion  13  between an expanded position (shown in  FIG. 1 ) supporting front frame portion  13  in an inclined position and a collapsed position (not shown) lying alongside front frame portion  13 . Front frame portion  13  includes left and right legs  21 ,  22  and leg end caps  44 . Rear frame portion  15  includes left and right legs  23 ,  24 , stretcher bars  45  interconnecting rear left and right legs  23 ,  24  and leg end caps  46 . Rear frame portion  15  further includes pivot mounts  47  anchored in fixed positions on front left and right legs  21 ,  22  and coupled by means of pivot pins  48  to upper ends of rear left and right legs  23 ,  24  to support rear frame portion  15  for pivotable movement about pivot axis  49  relative to front frame portion  13 . 
   A carrier lock  190  is coupled to front and rear right legs  22 ,  24  in the manner suggested in  FIGS. 2 and 9  to provide means for aligning and locking legs  22 ,  24  upon movement of legs  22 ,  24  to a side-by-side collapsed position (not shown). Carrier lock  190  also provides handle means for carrying the collapsed ladder  10 . Carrier lock  190  includes a pivot support mount  191  coupled to front right leg  22  using a fastener  133  as shown in  FIG. 9  and a handle  192  mounted for pivotable movement of pivot support mount  191 . Carrier lock  190  further includes an alignment bracket  193  coupled to rear right leg  24  and adapted to mate with pivot support mount  191  upon movement of front and right rear legs  22 ,  24  to the side-by-side collapsed position. 
   As shown in  FIG. 3 , first tubular member  26  of front left leg  21  includes first side wall  51 , second side wall  52 , third side wall  53 , and fourth side wall  54 . Second side wall  52  includes a short wall portion  55  and a long wall portion  56 . These four side walls  51 ,  52 ,  53   54  cooperate to form an interior region  57  therebetween. Likewise, first tubular member  26  of front right leg  22  includes first side wall  51 , second side wall  152 , third side wall  153 , fourth side wall  154 , short wall portion  155 , long wall portion  156 , and interior region  157 . In the illustrated embodiment, the fist tubular members  26  of front left and right legs  21 ,  22  are mirror images of one another. 
   As shown in  FIG. 3 , second tubular member  28  of front left leg  21  includes first side wall  61 , second side wall  62 , third side wall  63 , and fourth side wall  64 . Second side wall  62  includes a short wall portion  65  and a long wall portion  66 . These four side walls  61 ,  62 ,  63 ,  64  cooperate to form an interior region  67  therebetween. Likewise, second tubular member  28  of front right leg  22  includes first side wall  161 , second side wall  162 , third side wall  163 , fourth side wall  164 , short wall portion  165 , long wall portion  166 , and interior region  167 . In the illustrated embodiment, the second tubular members  28  of front left and right legs  21 ,  22  are mirror images of one another. 
   In this disclosure, each of the rear left and right legs  23 ,  24  includes a pair of “tubular members.” To promote clarity and to draw a distinction between the first and second tubular members included in each of the front left and right legs  21 ,  22 , one of the tubular members in each of the rear left and right legs  23 ,  24  will be identified as a “third” tubular member and the other of the tubular members in each of the rear left and right legs  23 ,  24  will be identified as a “fourth” tubular member. 
   As shown in  FIG. 3 , third tubular member  126  of rear left leg  23  includes first side wall  71 , second side wall  72 , third side wall  73 , and fourth side wall  74 . Second side wall  72  includes a short wall portion  75  and a long wall portion  76 . These four walls  71 ,  72 ,  73 ,  74  cooperate to form interior region  77  therebetween. Likewise, third tubular member  126  of rear right leg  24  includes first side wall  171 , second side wall  172 , third side wall  173 , fourth side wall  174 , short wall portion  175 , long wall portion  176 , and interior region  177 . In the illustrated embodiment, the third tubular members  126  of rear left and right legs  23 ,  24  are mirror images of one another. 
   As shown in  FIG. 3 , fourth tubular member  128  of rear left leg  23  includes first side wall  81 , second side wall  82 , third side wall  83 , and fourth side wall  84 . Second side wall  82  includes short wall portion  85  and long wall portion  86 . These four walls  81 ,  82 ,  83 ,  84  cooperate to form interior region  87  therebetween. Likewise, fourth tubular members  128  of right rear leg  24  includes first side wall  181 , second side wall  182 , third side wall  183 , fourth side wall  184 , short wall portion  185 , long wall portion  186 , and interior region  187 . In the illustrated embodiment, the fourth tubular members  128  of rear left and right legs  23 ,  24  are mirror images of one another. 
   As suggested in  FIG. 3 , first side walls  51 ,  61  of first and second tubular members  26 ,  28  of front left leg  21  lie in coextensive relation with a first reference plane  101 . Third side walls  53 ,  63  lie in coextensive relation with a second reference plane  102  that is oriented to cooperate with first reference plane  101  to define a first acute included angle  91  therebetween. In practice, these side walls may have a somewhat conical or arcuate shape. As used herein, “coextensive” means “having substantially the same spatial scope or boundaries” so that, e.g., both a flat side wall  51  or a slightly conical or arcuate side wall  51  could be said to lie in coextensive relation with reference to plane  101 . Web  27  is arranged to lie closer to first reference plane  101  than to second reference plane  102  to lie in offset relation to a central reference plane  100  bisecting second side walls  56 ,  66  of first and second tubular members  26 ,  28  of front left leg  21 . 
   Second side walls  56 ,  66  of first and second tubular members  26 ,  28  of front left leg  21  are coupled to web  27  located between those first and second tubular members  26 ,  28  as shown in  FIG. 3 . Short wall portion  55  is arranged to interconnect web  27  and first side wall  51  while short wall portion  65  is arranged to interconnect web  27  and first side wall  61 . Short wall portions  55 ,  65  are arranged to lie in confronting relation to one another and are separated by a first distance  58 . Long wall portion  56  is arranged to interconnect web  27  and third side wall  53  while long wall portion  66  is arranged to interconnect web  27  and third side wall  63 . The relatively longer long wall portions  56 ,  66  are arranged to lie in confronting relation to one another and are separated by a second distance  59  that is greater than first distance  58 . 
   As shown in  FIG. 3 , first side walls  151 ,  161  of first and second tubular members  26 ,  28  of front right leg  22  lie in coextensive relation with a third reference plane  103  that lies in spaced-apart parallel relation to first reference plane  101 . Third side walls  153 ,  163  lie in coextensive relation with a fourth reference plane  104  that is oriented to cooperate with third reference plane  103  to define a second acute included angle  92  therebetween. In practice, these side walls may have a somewhat conical shape. First acute included angle  91  is substantially equivalent to second acute included angle  92 . Fourth reference plane  104  is oriented to cooperate with second reference plane  102  to define a third acute included angle  93  therebetween. 
   Second side walls  156 ,  166  of front right leg  22  are coupled to web  27  as shown in  FIG. 3 . Short wall portion  155  is arranged to interconnect web  27  and first side wall  151  while short wall portion  165  is arranged to interconnect web  27  and first side wall  161 . Short wall portions  155 ,  165  are arranged to lie in confronting relation to one another and are separated by first distance  58 . Long wall portion  156  is arranged to interconnect web  27  and third side wall  153  while long wall portion  166  is arranged to interconnect web  27  and third side wall  163 . The relatively longer long wall portions  156 ,  166  are arranged to lie in confronting relation to one another and are separated by second distance  59 . 
   Each of the first, second, third, and fourth tubular members  26 ,  28 ,  126 ,  128  has a different size and cross-sectional shape in the embodiment illustrated in  FIG. 3 . Interior region  57  of first tubular member  26  has a volume that is less than the volume of interior region  67  of second tubular member  28  yet greater than the volumes of interior regions  77 ,  87  of third and fourth tubular members  126 ,  128 . Interior region  77  of third tubular member  26  has a volume that is greater than the volume of interior region  87  of fourth tubular member  128 .  FIG. 3  is a scaled drawing and shows relative sizes, shapes, and walls of all tubular members accurately in accordance with a presently preferred embodiment. 
   Continuing to refer to  FIG. 3 , it will be seen that first side walls  51 ,  61 ,  71 ,  81  of first, second, third, and fourth tubular members  26 ,  28 ,  126 ,  128  of front and rear left legs  21 ,  23  lie in coextensive relation with first reference plane  101 . Third side walls  73 ,  83  lie in coextensive relation with a fifth reference plane  105  that is oriented to cooperate with first reference plane  101  to define a third acute included angle  94  therebetween and to cooperate with second reference plane  102  to define an obtuse included angle  95  therebetween. Each of webs  27 ,  127  of front and rear left legs  21  and  23  is oriented to lie in coextensive relation with a sixth reference plane  106  and each of webs  27 ,  127  of front and rear right legs  22 ,  24  is oriented to lie in coextensive relation with a seventh reference plane  107  as also shown in  FIG. 3 . Sixth reference plane  106  is oriented to lie in offset relation to central reference plane  100  as shown in  FIG. 3 . Seventh reference plane  107  is oriented to lie in offset relation to a central reference plane  108  bisecting second side walls  156 ,  66 ,  176 ,  186  of first, second, third, and fourth tubular members  26 ,  28 ,  126 ,  128  of front and rear right legs  22 ,  24  as shown in  FIG. 3 . 
   Hollow steps  30  are shown, for example, in  FIGS. 1 ,  2 ,  4 ,  5 ,  7 , and  8 . As shown best in  FIG. 5 , a rear portion  110  of U-shaped base wall  38  is positioned to lie in spaced-apart parallel relation to partition wall  42 . Rear portion  110  is coupled to a rear edge  112  of horizontal top wall  36  and cooperates with wall  36  to define an acute included angle  114  therebetween. A front portion  116  of U-shaped base wall  38  is coupled to a front edge  118  of horizontal top wall  36  to define an acute included angle  120  therebetween. Front and rear portions  116 ,  110  of U-shaped base wall  38  are arranged to diverge in a direction toward horizontal top wall  36  a shown, for example, in  FIG. 5 . In the illustrated embodiment, U-shaped base wall  38  further includes a center portion  122  interconnecting front and rear portions  116 ,  110  and mating with partition wall  42 . Center portion  122  is somewhat curved in cross-section and has a concave surface facing toward horizontal top wall  36  as shown in  FIG. 5 . 
   Each step mount  31 ,  32  includes a first plate  130 , a second plate  132 , and a mount anchor  134  positioned to lie between first and second plates  130 ,  132  as suggested in  FIGS. 4 ,  4   a , and  6 . When the step mount  31 ,  32  is mounted on a leg  21  or  22 , first plate  130  is arranged to abut a companion first tubular member  26 , second plate  132  is arranged to abut a companion second tubular member  28 , and mount anchor  134  is positioned to extend into an anchor-receiving channel  136  defined by the companion first and second tubular members  26 ,  28  and the web  27  located between the companion first and second tubular members  26 ,  28  as suggested in  FIGS. 4 ,  6 , and  7 . 
   As suggested in  FIGS. 4 and 4   a , each step mount  31 ,  32  further includes a mount flange  138  positioned to lie in spaced-apart relation to mount anchor  134  to locate at least a portion of first plate  130  therebetween. Mount flange  138 , first plate  130 , and mount anchor  134  cooperate to define a first tube channel  140  for receiving a portion of the first tubular member  26  associated with the selected step mount  31  or  32  therein as shown best in  FIG. 7 . The mount anchor  134  and second plate  132  of each step mount  31 ,  32  are oriented relative to one another to define a second tube channel  142  for receiving a portion of the second tubular member  28  associated with the selected step mount  31  or  32  therein as also shown best in  FIG. 7 . 
   As shown best in  FIGS. 7 and 8 , anchor mount  134  is arranged to abut web  27 . Web  27  is formed to include fastener-receiving apertures  144  and anchor mount  134  is formed to include fastener-receiving apertures  41 . Fasteners  33  are arranged to extend through these apertures  41 ,  144  and into bores  43  formed in partition wall  42  of hollow step  30  (to provide means for mating with a distal portion of fasteners  33 ) to anchor step  30  and its companion step mount  31  or  32  in a fixed position on the companion leg  21  or  22 . 
   Anchor mount  134  extends away from first and second plates  130 ,  132  in a first direction  146  as suggested in  FIGS. 4 and 4   a . Each step mount  31 ,  32  also includes a rim  148  that extends away from first and second plates  130 ,  132  in an opposite second direction  146 ′ as suggested in  FIG. 4  to define chamber means for receiving one end of the step  30  associated with the step mount  31  or  32  so that the step mount is located in a fixed position on the step  30 . Partition wall  42  of step  30  is arranged to extend along and in alignment with the mount anchor  134  of each step mount  31 ,  32  coupled to such step  30  as suggested in  FIGS. 2 and 4 . 
   As shown in  FIG. 9 , pivot support mount  191  of carrier lock  190  includes a base  194  having a first base portion  195  arranged to abut third side wall  163  of second tubular member  28  of front right leg  22  and a second base portion  196  arranged to abut third side wall  153  of first tubular member  26  of front right leg  22 . Base  194  also includes a mount anchor  197  positioned to lie between first and second base portions  195 ,  196  and to extend into an anchor-receiving channel  136  defined by the companion first and second tubular members  26 ,  28  and the web  27  located between the companion first and second tubular members  26 ,  28  as suggested in  FIG. 9 . Mount anchor  197  and base  194  are formed to include a fastener-receiving passageway  198  as shown in  FIG. 9  and this passageway  198  is aligned with a fastener-receiving aperture  144  formed in web  27  so that fastener  133  can pass therethrough and anchor base  194  in a fixed position relative to front right leg  22  as shown in  FIG. 9 . Handle  192  is mounted to pivot about pivot axis  199  relative to pivot support mount  191  as suggested in  FIG. 9 .