Abstract:
A first plastic component and a second plastic component are joined together by an expansive joint system on the first plastic component and a driving joint system on the second plastic component. The expansive joint system has two expansive units while the driving joint system has corresponding driving units. When the driving units simultaneously expand the respective expansive units to a predetermined point, the expansive units contract to their original position and securely lock onto portions of the second plastic component.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed toward an interlocking mechanism for plastic materials. 
       BACKGROUND OF THE INVENTION 
       [0002]    Confer Plastics, Inc., the assignee, has been manufacturing plastic products for more than 30 years. It has obtained a few patents directed to how to interconnect plastic materials together. One of those patents is U.S. Pat. No. 6,190,600. In view of Confer&#39;s experience in the plastic industry and obtaining patents, Confer is familiar with various methods to interconnect plastic pieces together. 
         [0003]    The conventional method to interconnect plastic pieces together is to have a tongue and groove system with an additional interlocking device. That additional interlocking device includes screws. Screws and conventional metallic interconnecting components however deteriorate the integrity of the plastic material. As such screws and other metallic interconnecting components are to be avoided as the additional interlocking device. 
         [0004]    To address that problem, the additional interlocking device has included an additional male component interlocking with an additional female component wherein the male component is incorporated in the original tongue system and the additional female component is incorporated in the original groove system. 
         [0005]    An example of the tongue and groove system with additional male and female components is found in Confer Plastics&#39; Leisure Accents step ladder. The Leisure Accents step ladder, as illustrated in  FIGS. 1 to 4 , has at least two identical side walls  10  (two are illustrated by broken lines in  FIG. 1  and one is shown in  FIGS. 2 ,  3 , and  4 ), a interconnect base board  20   a , a terminal base board  20   b  (see  FIGS. 1 ,  2 , and  3 ), an interlocking step  40   a  and a terminal step  40   b  (shown at  FIGS. 3 and 4 ). Each side step side wall  10  has a first riser section  12   a  for the interconnect base board  20   a , a second riser section  12   b  for the terminal base board  20   b , a first tread section  14   a  for the interlocking step  40   a , and a second tread section  14   b  for the terminal step  40   b . Each riser section  12  has a tongue section  16   a  and each tread section  14  also has a tongue section  16   b . The tongue section  16   a ,  16   b  extends the length or at least the majority of the length of the respective section. At a predetermined position (can be a different position for each riser section  12  and tread section  14 ) on the tongue section  16   a  has at least one male component  18   a , and the tongue section  16   b  has at least one male component  18   b . The male component  18   a,b  is hour glassed shape or variations thereof as illustrated in  FIGS. 2 and 3 . 
         [0006]    Each base board  20  has an exposed surface  22 , an opposite surface  24 , a proximal end  26  (closest to the ground) and a distal end  28 . As illustrated in  FIG. 3 , the base board&#39;s  20  opposite surface  24  has a groove section  30  and a female component  32  that respectively receive the riser&#39;s tongue section  16   a  and male component  18   a . In particular the female component  32  has a rib area  34  that conforms to the narrow section of the male component&#39;s  18   a  hour-glass shaped area. As illustrated at  FIG. 2 , the exposed surface  22  on the interconnect base board  20   a  has a notch  36  that extends adjacent and parallel to the base board&#39;s  20  proximal end  26  length. 
         [0007]    The step  40  has, as illustrated at  FIGS. 2 ,  3 , and  4 , a stepped on surface  42 , an opposite surface  44 , an exposed end  46  and an unexposed end  48 . At the unexposed end  48  on the interlocking step  40   a  is a protrusion  50 . The notch  36  receives the protrusion  50 . 
         [0008]    Reverting to  FIGS. 3  and/or  4 , the step  40  on the opposite surface  44  has a groove section  52  and a female component  54  that respectively receive the riser&#39;s tongue section  16   b  and male component  18   b . In particular the female component  54  has a rib area  56  that conforms to the narrow section of the male component&#39;s  18   b  hour-glass shaped area. 
         [0009]    The base board  20  is installed onto the side wall  10  first by applying a force over the base board&#39;s female component  32  so the female component  32  receives the male component  18   a . The protrusion  50  is then inserted into the notch  36  to ensure the proper alignment between (a) the base board and the step and (b) the step and the riser. Once the step is properly aligned, a force is applied to the step&#39;s female component  54  to receive the male component  18   b.    
         [0010]    A problem with the current Leisure Accents step ladder is the step can be displaced when excess weight is applied to the steps. In particular when excess and abnormal pressure is applied to the step&#39;s exposed end  46 , the step could be dislodged. This is a problem to be avoided. 
       SUMMARY OF THE INVENTION 
       [0011]    A first plastic component and a second plastic component are joined together by an expansive joint system on the first plastic component and a driving joint system on the second plastic component. The expansive joint system has two expansive units while the driving joint system has corresponding driving units. When the driving units simultaneously expand the respective expansive units to a predetermined point, the expansive units contract to their original position and securely lock onto portions of the second plastic component. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0012]      FIG. 1  illustrates a front view of a prior art step ladder side walls (illustrated by solid and dashed lines), steps and base boards. 
           [0013]      FIG. 2  illustrates a side view of  FIG. 1  taken from arrow  2 . 
           [0014]      FIG. 3  illustrates a view of  FIG. 1  taken along the lines  3 - 3 . 
           [0015]      FIG. 4  illustrates a cross-sectional view of  FIG. 2  taken along the lines  4 - 4  or lines  5 - 5 . 
           [0016]      FIG. 5  illustrates a front view of the current invention&#39;s side walls and steps. 
           [0017]      FIG. 6  illustrates a view of  FIG. 5  taken along the lines  6 - 6 . 
           [0018]      FIG. 7  illustrates a view of  FIG. 5  taken along the lines  7 - 7 . 
           [0019]      FIG. 8  illustrates a view of the  FIG. 6  taken along the lines  8 - 8  without the step. 
           [0020]      FIG. 9  illustrates a view of  FIG. 6  taken along the lines  8 - 8  with a portion of the step. 
           [0021]      FIG. 10  illustrates a view of  FIG. 9  taken along lines A-A. 
           [0022]      FIG. 11  illustrates  FIG. 10  without the side wall. 
           [0023]      FIG. 12  illustrates  FIG. 9  without the side wall. 
           [0024]      FIG. 13  illustrates a cross-section of  FIG. 6  taken along the lines  13 - 13 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The present invention is directed to a secure interconnection between two plastic blow-molded unitary components. To understand the nuances of this invention we will first describe each element illustrated in  FIGS. 5 to 13 . 
         [0026]      FIG. 5  illustrates front side view of an open step ladder system  100 . The open step ladder system  100  has a first side wall  110 , a second side wall  120 , a first step  130  and a second step  140 . The first side wall  110  and the second side wall  120  are identical. Likewise, the first step  130  and the second step  140  are identical. The side walls and the steps are blow-molded plastic materials and each component is a single unitary device. 
       Side Wall 
       [0027]      FIG. 6  illustrates a side view of  FIG. 5  taken along the lines  6 - 6 . In  FIG. 6 , each side wall  110 ,  120  is illustrated having a first riser  150 , a second riser  152 , a first tread  154 , a second tread  156 , a narrow section  158 , a wide section  159 , a base  151 , and a back support  153 . 
       A. Riser Area 
       [0028]    Each riser  150 ,  152  have defined areas. Those defined areas are the proximal end  160 —the area closest to the ground—and the distal end  162 —the area furthest from the ground. The risers  150 ,  152  illustrated in  FIG. 5 to 13  are in the open step ladder embodiment. Moreover, the risers are shaped in a conventional riser manner. In the open step ladder embodiment illustrated in  FIGS. 5 to 13 , the risers  150 ,  152  have no grooves, tongues, male components, or female components. 
       B. Tread Area 
       [0029]    Each tread area  154 ,  156  have defined areas as well. The areas illustrated in  FIG. 6  are a first transition area  164 , a first locking area  166   a , a step receiving area  168 , a second locking area  166   b , and a second transition area  170  or a termination area  172  The termination area  172  is the location wherein there are no further risers to go up. Looking at  FIGS. 7  (a cross section of  FIG. 5  taken along the lines  7 - 7 ) and  8  (a top view of  FIG. 6  along the lines  8 - 8  without the step), each tread area  154 ,  156  has a protuberance guide area  174  that extends from portions of the step receiving area  168 . 
         [0030]    The locking areas  166   a,b  have distinct areas. Those areas include an expansion angled lip  176 , a locking upper lip  178  and a receiving lip  180 . Those areas are best illustrated in  FIG. 10 . 
       Step 
       [0031]      FIGS. 5 ,  6 ,  7 ,  9 ,  10 ,  11 ,  12 , and  13  illustrate the steps  130 ,  140  from different angles and perspectives. The steps  130 ,  140  each have distinct areas. Those areas are a top surface  200 , a bottom surface  202 , a back section  204  (area closest to the side wall&#39;s back support  153 ), a front section  206  (best seen at  FIGS. 5 ,  9 ,  10 , and  11 ), a first interconnect area  208   a  (see  FIGS. 9 ,  10  and  11 ), a second interconnect area  208   b  (only shown at  FIG. 5 ) and a channel area  216  (shown at  FIGS. 7 ,  12  and  13 ). First interconnect area  208   a  and second interconnect area  208   b  are identical and are the areas that interconnect to the respective side walls—first interconnect area  208   a  mates with the first side wall  110  and the second interconnect area  208   b  mates with the second side wall  120 . Please recall the first side wall  110  and the second side wall  120  are identical. Likewise, the first step  130  and the second step  140  are identical. 
         [0032]    As illustrated in greater detail at  FIGS. 11 and 12 , each interconnect area  208  has a first driving expansion area  210  positioned toward the front section  206 , a second driving expansion area  211  positioned toward the back section  204 , a first locking lower lip  212   a , a second locking lower lip  212   b , a first step receiving area  214   a , and a second step receiving area  214   b.    
         [0033]    The first driving expansion area  210  has a first conical shaped area  230  separated from a second conical shaped area  232  by an angled sloped area  234 . The first driving expansion area  210  extends from the bottom surface  202  to the first locking lower lip  212   a —a middle level positioned immediately below the expansion angled lip  176 —a third level—when the first interconnect area  208  connects to the first and second locking areas. The first locking lower lip is positioned at the middle level and positioned over portions of the first driving expansion area. The first step receiving area extends from the second locking lower lip to the top surface. 
         [0034]    The second driving expansion area  211  has a convex surface that slopes from the bottom surface to the middle level. The second locking lower lip is positioned at the middle level and positioned over portions of the second driving expansion area. The second step receiving area extends from the second locking lower lip to the top surface. 
         [0035]    The top section  200  can have furrows  201 . The furrows increase friction to the steps and direct liquids off the top surface  200 . 
       Combination of Step and Side Wall 
       [0036]    Now that we identified the areas of the step ladder system  100 , we can describe the system in greater detail. 
         [0037]    The side wall has the narrow section  158  and the wide section  159  as best illustrated at  FIG. 13 . The wide section is positioned at and near the perimeter of the side wall. The wide section  159  includes the areas commonly referred to as the first riser  150 , the second riser  152 , the first tread  154 , the second tread  156 , the base  151 , and the back support  153 . In particular, the wide section ranges from 0.25 to 3 inches wide, and 0.25 to 3 inches into the interior of the side wall from the perimeter. The remaining portion of the side wall is a narrow section  158  to save space and material. 
         [0038]    When the step ladder  100  is used, the back support  153  contacts or is positioned near an object. The object is something or is a portion of something that is not within the normal reach of the user. As such the step ladder  100  is utilized. Likewise the base  151  is positioned against the ground, flooring and/or support near the object. 
         [0039]    The user is expected to climb the step ladder  100  by positioning at least one of their feet on a step  120 ,  140 . In some cases the user may even position one of their feet on the first transition area  164  and the second transition area  170 . 
         [0040]    The first transition area is positioned from the riser&#39;s distal end  162  to the tread area&#39;s first locking area  166   a . In view of the cases that the user may use the first transition area, first transition area portions adjacent to the step  164   a  and the step&#39;s top surface  200  should be in approximately the same plane. At the same time, the first transition area closest to the riser  166   b  is equivalent to the step&#39;s front section  206 . In particular the first transition area, closest to the riser and the step&#39;s front section, is convex shaped and slopes toward the ground. The sloped edge is commonly used to indicate to most users that the step area is terminating. 
         [0041]    The second transition area is positioned from the riser&#39;s proximal end  160  to the tread area&#39;s second locking area  166   b . The second transition area is a gradually concave-sloped section that transitions into the second riser section. 
         [0042]    The second driving expansion area is applied through a force to the second expansion angled lip. When a force is applied to the second driving expansion area onto the second expansion angled lip, the second expansion angled lip uniformly moves away from the first wall. In contrast, when a force is applied to the first driving expansion area onto the first expansion angled lip, the first expansion angled lip that contacts the conical shaped areas of the first driving expansion area move further away from the second wall than the section of the first expansion angled lip that contacts the angled slope area—a non-uniform force. The non-uniform force application and the uniform force application are normally applied simultaneously to the side wall. Applying both types of forces simultaneously decreases the stress applied upon the side wall and the step. Decreasing the stress means there is a decreased chance of breaking the blow molded plastic material. This stress relief is necessary because when the two plastic materials are joined together it is almost impossible to separate the plastic materials without excessive force (sledge hammer or equivalent) which could damage the plastic materials. 
         [0043]    As the expansion angled lip  176  contracts to and remains in its original position, the side wall&#39;s locking upper lip  178  is positioned over the step&#39;s locking lower lip  208 . When the locking upper lip  178  is positioned over the step&#39;s locking lower lip  208 , the step is unable to be removed from the side wall without excessive force. By excessive force, we mean a sledge hammer or equivalent thereof. 
         [0044]    The step&#39;s locking lower lip  208  and the side wall&#39;s locking upper lip  178  are mirror images of each other. The step&#39;s locking lower lip  208  is a planar surface parallel to the top surface  200  that extends from the expansion area  206  in to the direction of the bottom surface  202 . 
         [0045]    Preferably when the locking upper lip  178  is positioned over the step&#39;s locking lower lip  208 , the locking upper lip  178  contacts the step&#39;s receiving area. The step wall receiving area extends from the step&#39;s locking lower lip  208  to the top surface  200 . The step&#39;s receiving area is positioned opposite the expansion angled lip  176  when the step is properly positioned in the side wall. 
         [0046]    To ensure the step is properly positioned in the step wall, the step&#39;s channel area  216  is positioned over the protuberance guide area  174 . The channel area  216  has a trapezoidal shape or equivalent thereof, the wider section of the channel area  216  is at the step&#39;s bottom surface while the narrower section is toward the top surface  200 . These embodiments are clearly illustrated in  FIGS. 12 and 13 . The protuberance guide area  174  is inserted into the channel area  216  and therefore has the same or similar shape except it protrudes from the step receiving area  168 . 
         [0047]    Obviously, alternative embodiments of the protuberance guide area and groove can be utilized. For example, the step can have the protuberance guide area and the side wall have the channel area. Or the first side wall can have the channel area and the second side wall can have the protuberance guide area; and the step&#39;s first interconnect area can have a protuberance guide area and the second interconnect area can have the channel area. 
       Other Alternative Embodiments 
       [0048]    The risers can be closed. By closed, we mean base boards, without notches, are attached to the risers in the same or similar manner as disclosed in Confer&#39;s Leisure Accents product and/or the present interconnection system. 
         [0049]    While the present invention has been described and illustrated in conjunction with a number of specific embodiments, those skilled in the art will appreciate that variations and modifications may be made without departing from the principles of the invention as herein illustrated, described and claimed. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as only illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.