Abstract:
System and method for assembling blow molded parts without the use of separate fasteners, including a tab-and-slot or dovetail mortise and tenon joint that includes a slide-and-lock tab feature. A retention barb on the tab slides along a ramp to engage with a receptacle within the slot. Tabs and slots can have varying widths to create mutual incompatibility with other joint components that are otherwise similarly constructed. An optional stopper on the tab and corresponding notch within the slot can add an additional axis of incompatibility with other joints throughout the assembly. These features prevent incorrect assembly and allow convenient redesigns.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to systems and methods for assembling blow molded parts. More specifically, the invention relates to a system and method of assembling blow molded parts without the use of separate fasteners. 
       BACKGROUND OF THE INVENTION 
       [0002]    The use of blow-molded parts for assembling various sorts of articles is generally well known. 
         [0003]    U.S. Pat. No. 6,557,191 to Bellows (“Bellows”) discloses a bed frame including a headboard, a foot board, a right side rail, and a left side rail. Each side rail has a first member and a corresponding second member. Each of the first and second members can be releasably attached to the headboard and the footboard respectively solely by mating end joint members formed in the first and second members and in the headboard and the foot board. Also, each of the first and second members can be releasably attached to each other solely by mating side joint members formed in the first and second members. The end and side joint members are mated through dovetail joints, pin-in-socket joints, or combinations thereof. The bed frame components can be blow-molded. However, Bellows does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. 
         [0004]    U.S. Pat. No. 7,234,780 to Lipniarski (“Lipniarski I”) discloses a blow-molded braced stool having a seat, legs and a brace having an insertion side and an exit side. The brace has openings for receiving the legs. The seat has indented female connectors on a leg side of the seat. The legs are formed with male connectors. During the assembly, the male connectors on the legs are moved through the openings in the brace and into the female connectors in the seat. Lipniarski I also discloses that different blow-molded structures, such as a table, a bar, a book shelf or a storage surface, can be made using the same female-male connectors. However, Lipniarski I does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. 
         [0005]    U.S. Patent Appl. No. 2010/0044152 to Lipniarski (“Lipniarski II”) discloses a blow-molded ladder assembly including a plurality of molded plastic parts which can be assembled by interfitting connections. The interfitting connections comprise a male interconnection that securely fits inside a female opening. However, Lipniarski II does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. 
         [0006]    U.S. Pat. No. 7,066,553 to Maloney (“Maloney”) discloses a slat furniture structure having a pair of laterally spaced apart supports and slats disposed between the supports. The slats are connected to the supports by a snap fitting connection consisting of resilient U-shaped fingers that fit into recesses in the supports. However, Maloney does not provide any mechanism for ensuring that a particular part can only be connected to a particular counterpart, and does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. Further, Maloney includes delicate barb structures. 
         [0007]    U.S. Pat. No. 6,938,558 to Peres (“Peres”) discloses a two-part blow molded pallet including slats that lock onto support stringers by a sliding, dovetail arrangement. The slats are formed by blow molding and have a plurality of dovetail slots to attach to stringers. However, Peres does not provide any mechanism for ensuring that a particular part can only be connected to a particular counterpart, and does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. In addition, there is no structure to ease the abrupt change in pressure caused by the wedging action of the locking barbs during assembly. 
         [0008]    U.S. Pat. No. 5,417,167 to Sadr (“Sadr”) discloses a plastic pallet with stringers and deck boards made of a thin-walled hollow construction by blow molding or continuous extrusion. The stringers and deck boards can be connected together by interaction between locking barbs and slots and wedge configurations molded into the stringer and deck boards. However, Sadr does not provide any mechanism for ensuring that a particular part can only be connected to a particular counterpart, and does not provide multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. Further, Sadr depends on the opposing force of other components to maintain the connection between two blow molded parts. In addition, there is no structure to ease the abrupt change in pressure caused by the wedging action of the locking barbs during assembly. 
         [0009]    The cited prior art references generally disclose blow-molded assemblies that are connected by various interfitting male-female connectors. However, the references do not disclose a system and method for assembling blow molded parts that provides multiple mechanisms for ensuring mutual incompatibility between joints having otherwise identical structures. In particular, the references do not disclose a system and method which utilizes varied positioning for the slide-locks on female parts and corresponding male parts with different lock barb positions or a stop feature that prevents engagement with any female other than the mate to facilitate error-free assembly of multiple fasteners. 
         [0010]    What is desired therefore is a system and method for connecting blow molded parts without the use of separate fasteners that addresses these deficiencies. 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, objects of the invention are to provide a system and method for connecting blow molded parts without the use of separate fasteners. Further objects of the invention are to provide a system and method for connecting blow molded parts in such a way as to provide ease of assembly and reliable connections, for preventing incorrect assembly of the parts, as well as facilitating ease of manufacturing, including standardization of joint mechanical properties and simple retooling to facilitate and simplify design changes. Other objects of the invention are to allow parts to be added to the design easily by modifying only the combinations of components within a joint without mechanically redesigning the joint. 
         [0012]    These and other objectives are achieved by providing a slide-lock joint system and method for connecting blow molded parts where a slot having a receptacle is provided on a first part, and a tab having a barb is provided on a second part. A ramp is provided disposed within the slot. The ramp, barb, and receptacle are offset from the side of the slot by an arbitrary distance. When the tab is inserted into the slot, the barb slides up the ramp and engages the receptacle. 
         [0013]    Further objects are achieved by providing a toy assembly comprising blow molded parts assembled using the slide-lock joint system and method. 
         [0014]    These and other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a top view of a female joint element according to aspects of the invention. 
           [0016]      FIG. 2  is a partial side view of a female joint element according to aspects of the invention. 
           [0017]      FIG. 3  is a side view of a male joint element according to aspects of the invention. 
           [0018]      FIG. 4A  is an exploded view of an assembly of a male joint element and a female joint element according to the invention. 
           [0019]      FIG. 4B  is an assembled view of an assembly of the male joint element and female joint element shown in  FIG. 4A  according to the invention. 
           [0020]      FIG. 5  is a view of a blow molded part having two female joint elements according to embodiments of the invention. 
           [0021]      FIG. 6  is a view of a female joint element according to aspects of the invention. 
           [0022]      FIG. 7  is view of a different female joint element according to aspects of the invention. 
           [0023]      FIG. 8  is a view of a male joint according to aspects of the invention. 
           [0024]      FIG. 9  is an exploded view of a toy house according to aspects of the invention. 
           [0025]      FIG. 10  is a flowchart illustrating an example method according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    The present teachings are described more fully hereinafter with reference to the accompanying drawings, in which the present embodiments are shown. The following description is presented for illustrative purposes only and the present teachings should not be limited to these embodiments. For example, it is understood that corners and edges depicted as squared may also be radiused or chamfered without departing from the spirit of the invention. 
         [0027]      FIG. 1  illustrates a view of a female element  1  of a slide-and-lock joint according to aspects of the invention. Female element  1  is disposed on blow molded part  2 . Female element  1  includes a front edge  3 , back edge  4 , left edge  5  and right edge  6 , as well as a bottom surface  7 . Bottom surface  7  is situated at a depth  8  below the outer surface of blow molded part  2 . Bottom surface  7  has a bottom surface width  9  that is equal to the distance between left edge  5  and right edge  6  at bottom surface  7 . Female element  1  has a top opening  10  in a top surface  11  of blow molded part  2 , and a side opening  12  in a side surface  13  of blow molded part  2 . Top opening  10  has a top opening width  14 . The dimensions of female element  1  are such that an area of bottom surface  7  is greater than an area of top opening  10 , and such that female element  1  describes a modified dovetail mortise in general shape, and serves this function mechanically. 
         [0028]    Ramp  15  and receptacle  16  are disposed in bottom surface  7 . Ramp  15  is beveled or tapered and has a ramp width  17 . Receptacle  12  has a receptacle width  18 . Receptacle width  18  can be equal to or related to ramp width  17 . Ramp  15  is disposed in bottom surface  7  such that it extends from front edge  3  toward back edge  4 , gradually shallowing to the depth of bottom surface  7  prior to reaching back edge  4 . Receptacle  16  is aligned with ramp  15  such that the shallow end of ramp  15  is adjacent to receptacle  16 , and such that receptacle  16  is at least partially disposed between ramp  15  and back edge  4 . Receptacle  16  has a depth from the top surface  11  that is deeper than depth  8 . 
         [0029]    Receptacle width  18  and ramp width  17  are both less than bottom surface width  9 . An offset distance  19  is defined between left edge  5  and ramp  15 . Offset distance  19 , ramp width  17 , and receptacle width  18  can be varied among several instantiations of female element  1  either disposed on blow molded part  2  or disposed on other parts of an overall assembly of blow molded parts (not shown) while maintaining all other dimensions of female element  1 . This can have the advantage of ensuring exclusive compatibility with a specific male counterpart (not shown) while maintaining substantially the same or similar mechanical characteristics of the dovetail joint among the various instantiations (not shown). 
         [0030]      FIG. 2  illustrates a view of female element  1 . Maximum ramp depth  20  is measured below bottom surface  7 . Undercut depth  21  is the distance between right edge  6 ′ measured at bottom surface  7 , and right edge  6 ″ measured at top surface  11 . Undercut  22  is disposed in right edge  6  and an analogous undercut  23  is disposed in left edge  5 . 
         [0031]      FIG. 3  illustrates a view of a male element  24  of a slide-and-lock joint according to aspects of the invention. Male element  24  is a counterpart to female element  1  ( FIGS. 1 and 2 ). Male element  24  extends from a second blow molded part  25  and includes a front edge  28  back edge  27  left edge  29  and right edge  30 , as well as a bottom surface  26 . Bottom width  31  is measured from left edge  29  to right edge  30  at bottom surface  26 . A top surface (not shown) has an area less than that of bottom surface  26 . A top width (not shown) measured from left edge  29  to right edge  30  at the top surface (not shown) that is less than bottom width  31 , such that the difference in width forms protrusions  33  and  34 , and such that male element  24  describes a modified dovetail tenon in general shape, and serves this function mechanically. 
         [0032]    Protrusions  33  and  34  complement undercuts  22  and  23  of female element  1  ( FIGS. 1 and 2 ) in shape. 
         [0033]    Locking barb  32  is disposed on bottom surface  26  such that it complements the corresponding receptacle  16  ( FIG. 1 ) of female element  1  ( FIGS. 1 and 2 ) in location and dimensions. In various embodiments, locking barb  32  may be beveled or tapered to complement ramp  15  ( FIG. 1 ) and/or to facilitate easy assembly with female element  1  ( FIGS. 1 and 2 ). 
         [0034]      FIGS. 4A  and B illustrate an exploded view and an assembled view of an example assembly of blow molded parts according to the invention. To connect blow molded parts  2  and  25 , male element  24  is inserted into female element  1  such that protrusions  33  and  34  engage with undercuts  22  and  23 , and such that locking barb  32  ( FIGS. 1-3 ) engages with ramp  11 . As male element  24  is inserted into female element  1 , the gradual shallowing of ramp  15  exerts pressure on locking barb  32  such that these components undergo a substantially elastic deformation. When male element  24  has been inserted to a depth where locking barb  32  ( FIG. 3 ) can engage with receptacle  16  ( FIGS. 1-2 ), locking barb  32  ( FIG. 3 ) snaps into engagement. Optionally, this abrupt engagement provides tactile and/or auditory feedback, confirming proper assembly of the joint (not shown). The resulting combination of engagements between the surfaces of the male and female elements when assembled can firmly but removably assemble blow molded parts  2  and  25  one to the other. 
         [0035]      FIG. 5  illustrates a blow molded part  35  having two female joint elements  36 ,  37  according to embodiments of the invention, each including an offset distance  38 ,  39 , and each substantially similar to the female element  1  as described with respect to  FIGS. 1 and 2 . Female joint element  36  differs from female joint element  37  only in that offset distance  38  is different than offset distance  39 , such that a corresponding male joint element for each (not shown) is incompatible with the other. In this way, female joint elements  36  and  37  retain substantially the same mechanical properties while ensuring mutual incompatibility. This can have the advantages of ensuring proper assembly and simplifying design and manufacture. 
         [0036]      FIGS. 6 and 7  are detail views of female joint elements  36  and  37  showing mutually incompatible offset distances  38  and  39 . It should be understood that other variations in the dimensions and alignments of the ramp and receptacle elements can also be used to ensure mutual incompatibility (not shown). 
         [0037]      FIG. 8  illustrates a top view of a male element  40  of a slide-and-lock joint according to another embodiment of the invention. Male element  40  is similar to male element  24  (described above with respect to  FIG. 3 ) except that male element  40  includes stopper  41 . Stopper  41  is disposed on and raised from a bottom surface  42 . Stopper  41  is shaped and positioned on bottom surface  42  in such a way as to prevent full insertion of male element  40  into an otherwise corresponding female element (not shown) that does not contain a complimentary notch feature (not shown) which would allow stopper  41  to pass. When it is blocked, stopper  41  prevents engagement of locking barb  43 , and thus prevents improper assembly of blow molded part  44 . 
         [0038]    The addition of stopper  41  provides an additional axis of variability among various joints of an assembly (not shown) which can have the advantage of further helping to ensure exclusive compatibility with a specific male counterpart (not shown) while maintaining the mechanical characteristics of the dovetail joint among the various instantiations (not shown). This can have the advantages of further ensuring proper assembly and further simplifying design and manufacture. 
         [0039]      FIG. 9  illustrates a toy house  900 , which is an example assembly of blow-molded plastic parts according to aspects of the invention. 
         [0040]    Toy house  900  is an assembly of blow molded part  902  and blow molded part  904 . Blow molded part  902  comprises female joint elements  906 ,  914 ,  910 . Blow molded part  904  comprises male joint elements  908 ,  916 ,  912 . 
         [0041]    To assemble blow molded part  902  with blow molded part  904 , male joint elements  908 ,  916 ,  912  are inserted into female joint elements  906 ,  914 ,  910 , respectively. These male and female joint elements assemble in substantially the same manner described with respect to  FIGS. 4A and 4B . Each male joint element  908 ,  916 ,  912  is compatible only with its corresponding female joint element  906 ,  914 ,  910 , respectively. 
         [0042]    Female joint elements  906 ,  914 ,  910  each have a structure substantially similar to female element  1  ( FIG. 1 ), female joint element  36  ( FIGS. 5 and 6 ), or female joint element  37  ( FIGS. 5 and 7 ). Each of female joint elements  906 ,  914 ,  910  has an offset similar to offset  38  or  39  ( FIGS. 5 ,  6 ,  7 ) which is different from the offset of each other female joint element  906 ,  914 ,  910 . 
         [0043]    Similarly, male joint elements  908 ,  916 ,  912  each have a structure substantially similar to male element  24  ( FIG. 3 ) or male element  40  ( FIG. 8 ). Each of male joint elements  908 ,  916 ,  912  has a locking barb similar to locking barb  32  ( FIG. 3 ) which complements only the offset of the corresponding female joint element  906 ,  914 ,  910 . 
         [0044]    The incompatibility among each of the joints has the advantage of ensuring that blow molded part  902  and blow molded part  904  can only be assembled in the correct orientation, preventing improper assembly of the toy house while permitting each joint to retain substantially the same mechanical properties. 
         [0045]      FIG. 10  is a flowchart illustrating a method  1000  according to the invention. 
         [0046]    In a step  1002 , a first blow molded part and a second blow molded part are provided. 
         [0047]    In a step  1004 , a slot is provided on the first blow molded part. The slot has a receptacle and a ramp disposed within the slot, the ramp extending and shallowing from the insertion point toward the receptacle, the slot having at least one slide engagement recess. 
         [0048]    In a step  1006 , a tab is provided on the second blow molded part. The tab has a barb and at least one slide engagement protrusion. 
         [0049]    In an optional step  1008 , the ramp is of a lesser width than the slot, and the barb is of a width corresponding to the width of the ramp, wherein the ramp is disposed at a ramp offset from a side of the slot, and the barb is disposed at a barb offset from a side of the tab corresponding to the ramp offset. 
         [0050]    In an optional step  1010 , a stopper is provided on the tab, and a notch is provided within the slot, the stopper having a stopper width and a stopper offset from a side of the tab, and the notch having a notch width corresponding to the stopper width and a notch offset from a side of the slot corresponding to the stopper offset, the stopper preventing full insertion of the tab into another slot that is not provided with a notch having a width and offset that are complimentary to the stopper. 
         [0051]    In a step  1012 , the tab is inserted into the slot such that the slide engagement protrusions engage the slide engagement recesses and the barb begins to engage the ramp, sliding up the ramp toward the receptacle, the barb finally engaging with the receptacle, retaining the tab within the slot. 
         [0052]    It should be clear that the invention can be practiced with all manner of objects and structures which can be assembled from blow-molded plastic parts such as boxes, containers, tables, chairs, packages, carrying cases, enclosures, wheels, toys, and the like. 
         [0053]    Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many modifications and variations will be ascertainable to those of skill in the art.