Abstract:
A molded plastic wheel includes a seamless annular body that is integrally molded from a first material exhibiting a first density and includes a hollow hub having an axle bore and hollow spokes that radially extend from the hub to a hollow box defined by planar first and second side wall surfaces, which extend from the spokes substantially orthogonal to a tread surface that lies parallel to the axle bore. Cavities of the hub, the spokes, and the box communicate with each other. A tread piece having a channel shape with first and second side pieces projects substantially orthogonal to a connecting tread band. The tread piece is separately molded from a second material exhibiting a second density different from the first material. The tread piece is stretch fitted over the box such that the tread band overlies the tread surface and the side pieces abut the side wall surfaces.

Description:
RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part of U.S. patent application Ser. No. 09/090,618 filed Jun. 4, 1998. 
     
    
     
         [0002]    BACKGROUND OF THE INVENTION  
           [0003]    The present invention relates to plastic wheels and, in particular, to a blow molded wheel having spring biased axle retainer and a fitted tread piece.  
           [0004]    Varieties of pneumatic and composite wheels have been developed that include integral axle retainers. Sonic available composite wheels include an injection-molded hub that supports a molded rubber tread piece at a flanged rim. The tread piece is separately attached to the hub, such as by stretching. A spring-biased pill is molded into the hub and the pin projects into the bore of an axle support. With the attachment of the wheel to an axle having a mating annular recess, the pin depresses and expands into the recess to permanently secure the wheel to the axle. The pin otherwise is not exposed to facilitate detachment of the wheel.  
           [0005]    An all plastic wheel can provide a cost-effective alternative. However, all plastic wheels are generally not available that include an integral retainer. A blow-molded wheel that does include a retainer is shown at U.S. Pat. No. 5,368,371. The retainer consists of annular tabs that extend into an axle bore and that mount to a grooved recess at a mating axle. The strength of the tabs can limit the type of applications to which such wheels are placed. The tabs are also prone to damage, if the wheels are removed.  
           [0006]    The present invention was developed to provide an improved blow-molded plastic wheel having an integral axle retainer. The wheel provides an externally accessible, spring biased retainer pin that is inserted into a blow-molded wheel. The retainer pill can mount in a discrete housing that is fitted to the wheel or a cavity formed into the wheel. In a preferred construction, the retainer pin radially projects from a pin retainer sleeve that is fitted to an axle sleeve. A bore and adjoining cavity at the wheel support the axle sleeve to provide a load-bearing surface for the axle and align the pin to the axle. The wheel also includes a tread surface that can be molded as part of the wheel or that can be separately attached to the wheel.  
         SUMMARY OF THE INVENTION  
         [0007]    It is accordingly a primary object of the invention to provide a blow-molded wheel with an integral axle retainer.  
           [0008]    It is a further object of the invention to provide a wheel having an axle retainer that indexes to a separately molded wheel and includes a pin and axle sleeve that extend transverse to one another.  
           [0009]    It is a further object of the invention to provide a wheel with an axle retainer pin that can be released from the axle after mounting.  
           [0010]    It is a further object of the invention to provide a retainer that can be mounted to the wheel prior to final cure.  
           [0011]    Several of the foregoing objects, advantages and distinctions of the invention are obtained in a presently preferred blow-molded wheel. The wheel is blow molded in conventional fashion and includes a cavity at one of the spokes that is shaped to accept a spring biased retainer. The cavity opens to an axle bore at the wheel. The retainer is set into the cavity immediately upon the wheel being withdrawn from the mold, while the plastic is warm. The plastic shrinks around the retainer as it cools and permanently secures the retainer to the wheel.  
           [0012]    The retainer includes a pin sleeve that supports a spring within a longitudinal bore. The spring biases the retainer pin to project into a longitudinal bore of an axle sleeve. The axle sleeve concentrically mounts within the axle bore. The bore of the axle sleeve acts as a bushing and provides a load-bearing surface for the axle. The bore of the axle sleeve extends transverse to the bore of the pin sleeve. An opening is provided through the walls of the pin sleeve to permit release of the pin from the axle.  
           [0013]    Still other objects, advantages, distinctions and constructions of the invention will become more apparent from the following description with respect to the appended drawings. Similar components and assemblies are referred to in the various drawings with similar alphanumeric reference characters. The description should not be literally construed in limitation of the invention. Rather, the invention should be interpreted within the broad scope of the further appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a perspective view shown in exploded assembly to a wheel constructed with a releasable axle retainer assembly.  
         [0015]    [0015]FIG. 2 is a perspective view shown in partial cutaway to a blow-molded wheel having a tread piece mounted over the wheel and fitted with an axle retainer assembly.  
         [0016]    [0016]FIG. 3 is a partial section view through the axle and retainer of FIG. 1, when mounted together.  
         [0017]    [0017]FIG. 4 is a front view of the retainer.  
         [0018]    [0018]FIG. 5 is a rear view of the retainer.  
         [0019]    [0019]FIG. 6 is a rear view of a retainer wherein the external surface is formed to enhance attachment to the blow-molded wheel.  
         [0020]    [0020]FIG. 7 is a front view of a blow-molded wheel and a retainer assembly shown in exploded assembly.  
         [0021]    [0021]FIG. 8 is a rear view of the blow-molded wheel of FIG. 7.  
         [0022]    [0022]FIG. 9 is a front view of a blow-molded wheel and wherein a retainer assembly is formed to extend from the tread support surface.  
         [0023]    [0023]FIG. 10 is a rear view of the blow-molded wheel of FIG. 9.  
         [0024]    [0024]FIG. 11 is a front view of a blow-molded wheel and wherein a retainer assembly is formed to extend from the tread support surface.  
         [0025]    [0025]FIG. 12 is a rear view of the blow-molded wheel of FIG. 9.  
         [0026]    [0026]FIG. 13 is a front view of a blow-molded wheel and wherein a retainer sleeve extends from a raised web that lies parallel to a plane at the parting line of the wheel and with a groove at the box.  
         [0027]    [0027]FIG. 14 is a rear view of the blow-molded wheel of FIG. 13.  
         [0028]    [0028]FIG. 15 is a front view of a blow-molded wheel and wherein a retainer sleeve having a two-stage bore extends from a raised web that lies parallel to a plane at the parting line of the wheel.  
         [0029]    [0029]FIG. 16 is a rear view of the blow-molded wheel of FIG. 15.  
         [0030]    [0030]FIG. 17 is a front view of a blow-molded wheel and wherein a retainer sleeve having a two-stage bore extends from a raised web that lies parallel to a plane at the parting line of the wheel and between interrupted adjoining spokes.  
         [0031]    [0031]FIG. 18 is a rear view of the blow-molded wheel of FIG. 17.  
         [0032]    [0032]FIG. 19 is a front view of a blow-molded wheel and wherein a retainer sleeve is formed to extend from the hub at an acute angle relative to a plane at the parting line of the wheel.  
         [0033]    [0033]FIG. 20 is a rear view of the blow-molded wheel of FIG. 19.  
         [0034]    [0034]FIG. 21 is a front view of a blow-molded wheel and wherein a retainer sleeve is formed to extend at an acute angle relative to a plane at the parting line of the wheel from a raised platform at the web.  
         [0035]    [0035]FIG. 22 is a rear view of the blow-molded wheel of FIG. 21.  
         [0036]    [0036]FIG. 23 is a cross section view through a wheel having a raised parting line that mounts to an aligned groove at a mating tread piece. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    Referring to FIGS. 1, 2 and  3 , views are shown to improved wheels  2  and  3  that are fitted with an axle retainer assembly  4 . The wheels  2  and  3  are constructed from blow-molded plastic wheels  6  and  7 . The wheels  6  and  7  each include a cavity  8  that receives an axle retainer assembly  4 . A double-ended pin  10  of the assembly  4  aligns with and mounts to an annular groove  12  of an axle  14 , reference FIG. 3.  
         [0038]    The wheels  6  and  7  are blow-molded in conventional fashion and provide a hub  16  and from which a number of spokes  18  and intermediate flat webs  19  radiate to an annular box or rim  20 . The wheel  6  includes a number of lugged treads  22 . The treads  22  are molded into a surface  24  that engages the ground. A raised band  26  projects around the circumference of the wheel  6  and above the treads  22  at the center of the tread surface  24 . A parting line defined by the molding operation extends around the center of the band  26 . An accessory trim piece or whitewall  28  can be attached to an annular groove  30  that is formed into one or both exposed side wall faces of the box  20 .  
         [0039]    The blow-molded wheel  3  of FIG. 2 is substantially the same as the wheel  2 , except a separately molded tread piece  5  is mounted to the box  20 . A smooth, recessed surface  7  of the box  20  includes a flange  9  and to which the tread piece  5  is aligned. The tread piece  5  is molded from an ethylene methyl acrylate (EMA) copolymer, although an EEA, EVA or LLDPE material, among other materials could be used. A number of lugged treads  11  are molded into the tread piece  5 . The tread piece  5  is stretch fitted over the wheel  7  while warm. The density of the tread piece  5  is selected to provide a durable, Ion-wearing surface. The tread piece  5  also minimizes rolling sounds of the wheel  3  over certain surfaces and which sounds otherwise can be magnified due to the hollow cavity at the wheel  3 .  
         [0040]    Returning attention to FIG. 1, the cavity  8  is molded into one of the spokes  18 . The cavity  8  opens at one end into an axle bore  29 . An opposite end provides a closed wall  33 . A housing  31  of the assembly  4  includes a pin sleeve  32  that mounts within the cavity  8 . The pin  10  is supported within a bore  34  of the pin sleeve  32  and is biased to permit reciprocating movement in conjunction with a spring  36 . The pin  10  projects through an aperture  38  of the bore  34 , reference FIG. 3, and into a longitudinal bore  40  of an axle sleeve  42  that extends transverse to the pin sleeve  32 . The spring  36  abuts an end of the recess  33  at an open end of the pin sleeve  32 .  
         [0041]    The bore  40  separately accepts the axle  14 . The bore  40  provides a load-bearing surface for the axle  14 . A cover  46  closes the end of the housing  31  and bole  40 . The housing  31  is retained to the wheel  6  at the pin and axle sleeves  32  and  42 . The transverse orientation of the pin and axle sleeves  32  and  42  to one another assures that the retainer assembly  4  does not loosen and rotate with the wheel  6 . The retainer housing  31  can be bonded to the wheel  6 . Presently it is secured through the shrinkage of the wheel material. If required, retention can be enhanced by forming the external walls of the retainer to include shaped surfaces such as described below in relation to FIGS. 6 and 7.  
         [0042]    With additional attention to FIGS. 3 and 4, an aperture  48  extends through a side wall of the axle sleeve  32  and is exposed at the wheel  6  to permit access to the pin  10 . By inserting a tool through the aperture  48 , a shoulder  47  of the pin  10  can be engaged and the pin  10  can be depressed to release one of a pair of ends  49  from the axle  14 . The aperture  48  can be flashed over, such as in FIG. 2, when molding the housing  31  to prevent casual access to the pin  10 .  
         [0043]    Depending upon the application, the wheels  6  and  7  can be molded from a variety of types of plastic. The type of plastic and density of material can be varied to a particular application and the load and wear specifications for a particular wheel. The configuration and size of the wheels  6  and  7  can also be varied. The wheels  6  and  7  are presently molded from a high-density polyethylene material and each is constructed to a 12-inch diameter. A variety of other known materials can be used to equal advantage.  
         [0044]    The retainer housing  31  is molded from a material that is compatible to the wheel material. An HDPE material is presently used. Depending on the application, however, the housing  31  can be constructed from a variety of other materials including various metals and plastics. The pin  10  is constructed from metal. Various other materials can be used provided they are able to withstand anticipated wear at the axle  14 .  
         [0045]    After extracting the wheel  6  from its mold and while the plastic is warm, the retainer assembly  4  is fitted to the cavity  8  and the bore  31 . As the wheel  6  cools, the material shrinks around the axle sleeves  32  and  42  to permanently mount the retainer assembly  4  to the wheel  6 . Although not presently required, retention might be enhanced by shaping the external surfaces of the sleeves  32  and  42  to grip mating surfaces of the wheels  6  and  7 . For example and with additional attention to FIG. 6, a flat surface  50  and/or raised projections  52  and/or one or more recesses can be provided. Presently, a recessed groove  54  is included. The groove  54  separately aids in the extraction of the retainer housing  31  from an injection mold. The raised projections  52  can be formed as annular ribs or knurling.  
         [0046]    [0046]FIGS. 7 and 8 depict a front and rear view to a wheel  60  that is fitted with a retainer housing  62 . The housing  62  supports a retainer pin and spring at a pin sleeve  63  in a fashion similar to the retainer assembly  4 . A bore  65  (shown in dashed line) through an axle sleeve  67  supports an axle  14 . A groove  64  extends around the exterior of the housing  62 . Separately formed into the housing  62  are a groove  66  and raised projection  68  that extend approximately one-half the circumference of the housing  62 . Also shown in dashed line is a raised band  70  that can be included or not and that can have a rounded exposed surface, like an O&#39;ring, or a wedge or ramped shape. Appropriate provisioning of the exterior surface of the housing  62  with grooves  64 ,  66  and/or projections  68  and  70  facilitates retention of the housing in the wheel  60 .  
         [0047]    [0047]FIGS. 9 through 12 show wheels  90  and  92  that are molded with integral retainer sleeves  94  and  96 . Such a construction avoids the necessity of fitting a separate retainer housing to a finished wheel. The sleeves, however, require additional plastic and can increase the complexity of the mold and/or molding difficulty.  
         [0048]    The sleeves  94  and  96  extend from the hub  16  to the box  20  of the wheels  90  and  92  along webs  98  and  100 . The webs  98  and  100  arc vertically offset from the other webs  19 . The sleeve  96  exhibits a larger outer diameter than the sleeve  94  and tapers inward slightly as it extends to the box  20 . The sleeves  94  and  96  include longitudinal bores  95  and  97  that receive an appropriate retainer pin and spring. The bores  95  and  97  are accessed by drilling aligned holes  101  and  103  through the periphery of the box  20  and hub  16 . The drilling operation is typically performed after molding the wheels  90  and  92 . The tread piece  5  and/or a plug (not shown) cover and/or fill the holes  101  and  103 .  
         [0049]    [0049]FIGS. 13 through 18 depict front and rear views of wheels  102 ,  104  and  106  that include retainer sleeves  108 ,  110  and  112  that are molded to avoid having to drill holes through the box  20  to facilitate mounting an axle retainer pin and/or spring. The retainer sleeves  108 ,  110  and  112  are molded into webs  114 ,  116  and  118  that are elevated above the webs  19  between the other spokes  18 . The elevation of the webs  114 ,  116  and  118  is determined relative to the necessary boring operations. The web  118  also includes a slight recess  119  that is visible at FIG. 18.  
         [0050]    Aligned grooves  120 ,  122  and  124  are molded into the box  20  of the wheels  102 ,  104  and  106  to facilitate forming the bores  126 ,  128  and  130  of the retainer sleeves  108 ,  110  and  112 . The grooves  120 ,  122  and  124  are shown exposed, although are normally substantially covered by the tread piece  15 . The bores  128  and  130  are formed with two differing internal diameters that define an internal shoulder that limits the movement of the retainer pin. Upon fitting an appropriate retainer pin and bias spring mechanism into the retainer sleeves  94 ,  96 ,  108 ,  110  and  112 , an end cap is secured to the sleeves. A threaded end cap is typically used, although a variety of other plugs can be substituted, provided they securely retain the retainer pin in the pin sleeve.  
         [0051]    Two other alternative wheels  132  and  134  are shown at FIGS. 19 through 22. The wheels  132  and  134  include retainer sleeves  136  and  138  that extend at acute angles relative to a plane that contains the parting line of each wheel. The sleeves extend along webs  140  and  142 . The web  140  extends from the hub  16  at a continuous slope. The web  142 , in contrast, provides an elevated interior portion  144  that is raised above an outer portion  146 . Bores  148  and  150  extend through the sleeves  136  and  138 . Upon drilling the sleeves, fitting appropriate retainer pins and springs, a threaded end cap  152  is secured to each sleeve.  
         [0052]    [0052]FIG. 23 lastly depicts a cross section view to the mounting of an alternative tread piece  160  to a blow-molded wheel  162 . The wheel  162  is essentially similar to the wheel  3 , except that it includes a raised projection  164  at the parting line of the wheel  162 . The wheel  162  can be adapted to include any of the foregoing axle retainers or not, as desired.  
         [0053]    The projection  162  mounts within a slot  166  molded into the tread piece  160 . The mating of the slot  166  to the projection  164  stabilizes the tread piece  160  against lateral slippage and minimizes possible tread separation. In most instances, the annular flanges  9  are sufficient to prevent tread separation.  
         [0054]    Although a single, continuous projection  162  is shown, multiple adjacent projections  162  can be provided at the periphery of the blow-molded wheel  162 . The projections  162  can also be constructed to be discontinuous. The projections can exhibit rounded, ramped, or other contour shapes, when viewed in side profile, such as the projections  52  and  68 .  
         [0055]    While the invention has been described with respect to a preferred construction and considered improvements or alternatives thereto, still other constructions may be suggested to those skilled in the art. Although certain features are also shown at particular wheels, it is also to be appreciated the features can be included alone or in other combinations in other of the disclosed wheels. The foregoing description should therefore be construed to include all those embodiments within the spirit and scope of the following claims.