Abstract:
In a method of forming an article of footwear, a shell is formed between at least two die portions. The shell has a flash line defined proximate an interface of the die portions and along a perimeter of the shell. The method may include coupling a component directly to the shell so that the flash line is at least in part disposed proximate or below an upper edge of the component, with the component selected from the group consisting of a midsole and an outsole. The flash line may be positioned to coincide with an edge of a ridge on the shell.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates generally to methods and apparatuses for forming shells for articles of footwear. In particular, the present invention relates to methods and apparatuses for molding shells such that the flash line is positioned along a perimeter of the shell.  
         BACKGROUND OF THE INVENTION  
         [0002]    Footwear manufacturing operations involve a multi-step procedure in which an upper, comprising an assembly of various components used to cover and support the top of the foot, is coupled to a sole. Outdoor multi-purpose boots, in particular, are typically constructed by assembling an outsole, a molded shell, an insole, and an upper. The molded shell is often formed by injecting a polyurethane or other suitable polymer into an appropriately shaped mold, where the polymer cures into a solid shell. Use of polymers such as polyurethane permits the manufacture of a shell that provides waterproofing, resiliency, and resistance to damage.  
           [0003]    Prior art shells have been molded using a pair of mold faces which together form a cavity that defines the outer shape of the shell. During molding of a shell, the mold faces are joined and molding material is introduced into the cavity. Typically, some of the molding material escapes along the interface of the mold faces. This creates a feature that is commonly known as a flash line or parting line—a raised line on the surface of a molding. The flash line is generally undesirable, as it may detract from the aesthetic and/or functional qualities of the shell. Additional finishing operations may be required to remove the excess material so that it does not remain on the final product in a prominent location. In order to “hide” the flash line, some shell designs incorporate ribs or other protrusions and molded geometries coinciding with the location of the flash line. For example, the rib may be molded along the longitudinal axis of the shell, at the location where the mold faces were joined during injection molding.  
           [0004]    As shown in FIGS. 1 and 2, a prior art polyurethane shell  8  may be produced using cooperating halves of a split metal die assembly  10 . A left die half  12  mates with a right die half  14  to create a cavity  16  in a desired outer shell shape. Die halves  12 ,  14  are configured and dimensioned such that each die half defines either the lateral portion  12 ′ of shell  8  or the medial portion  14 ′ of shell  8 . A last or inner mold portion  18  is disposed between die halves  12 ,  14  in cavity  16 , thereby creating a desired inner shell shape. Cavity  16  of die assembly  10  is in communication with runners  20  ending in gates  22 , through which polyurethane flows for injection into cavity  16 . After polyurethane is injected into and fills cavity  16  in the space defined between die halves  12 ,  14  and inner mold portion  18 , sprues may be created integrally with the shell as a remnant of the molding process.  
           [0005]    As shown in FIG. 2, a flash line  24  is disposed along the longitudinal axis  26  of shell  8 . Flash line  24 , for example, is generally in the form of a protrusion extending above the adjacent surface  28  of lateral portion  12 ′ and adjacent surface  30  of medial portion  14 ′. Because of the mating of die halves  12 ,  14 , flash line  24  is disposed in both the toe region  32  and the heel region  34  of shell  8 . Especially proximate toe region  32 , flash line  24  provides a stiffened region of shell  8  proximate longitudinal axis  26 , which may adversely impact performance of shell  8  by limiting flexure when disposed around a foot of a user.  
           [0006]    In view of the prior art shell and manufacturing technique therefor, there exists a need for an improved shell and manufacturing method. In particular, there exists a need for shells molded such that the flash line is positioned along a perimeter thereof, instead of along the longitudinal axis, so that flexure proximate the axis is not hindered by the flash line. There also exists a need for a method of manufacturing shells which obviates the need for performing extensive finishing operations on the outer surface of the shell that is exposed in the finished boot.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention relates to a method of forming an article of footwear including: forming a shell between at least two die portions, the shell having a flash line defined proximate an interface of the die portions and along a perimeter thereof. The method may further include coupling a component directly to the shell so that the flash line is at least in part disposed proximate or below an upper edge of the component, with the component selected from the group consisting of a midsole and outsole. In addition, the method may include: coupling a midsole to a lower portion of the shell; disposing a shank between the midsole and shell; coupling an outsole to a lower portion of the midsole; disposing an insole inside the shell; disposing at least one cushion between the insole and shell, wherein the at least one cushion comprises a cushion disposed proximate a heel region of the shell and a cushion disposed proximate a forefoot region of the shell; and coupling an upper to an upper portion of the shell. Furthermore, the method may include bonding a component directly to the shell, with the component selected from the group consisting of a midsole and an outsole. The component and shell may be adhesively bonded to each other. An inner mold portion may be disposed in a cavity between the die portions when the shell is formed.  
           [0008]    The flash line may extend substantially around the perimeter of the shell, and may coincide with at least a portion of an edge of a ridge on the shell, wherein the ridge may be disposed proximate a heel end of the shell. The flash line may be disposed along a sidewall of the shell and define a first surface above the flash line and a second surface below the flash line, wherein the first and second surfaces have different texturing. At least one rib may be disposed on the shell transverse to the flash line. Also, a top portion of the shell may be substantially smooth proximate a central longitudinal axis of the shell.  
           [0009]    The shell may be formed of a polyurethane and formed by injection molding. Indicia may be disposed on the shell, and may be integrally formed therewith.  
           [0010]    Each die portion may define one of the group consisting of substantially the entirety of an upper portion of the shell and substantially the entirety of a lower portion of the shell. In some methods, the die portion defining the upper portion of the shell may be disposed above the die portion defining the lower portion of the shell. In other methods, the die portions may be disposed in side by side relation such that the die portion defining the upper portion of the shell may be disposed adjacent the die portion defining the lower portion of the shell, each die portion having a toe end and a heel end with the toe ends of the die portions being disposed above the heel ends of the die portions.  
           [0011]    The invention also relates to a method of forming an article of footwear including: forming a shell between at least two cooperating die portions defining a cavity, the shell having a parting line defined proximate an interface of the die portions and extending around a perimeter thereof, and coupling a lower portion of the shell to a component selected from the group consisting of a midsole and an outsole. The component may be coupled to the shell so that the parting line is at least in part disposed proximate or below an upper edge of the component. The parting line may coincide with an edge of a ridge on the shell. The method may further include: forming sprues only proximate an outside bottom portion of the shell; substantially removing the sprues from the shell; coupling an upper portion of the shell to an upper; and disposing an inner mold portion between the cooperating die portions in the cavity defined therebetween while the shell is formed. The shell may be formed by injecting polymer through a plurality of runners each communicating with the cavity proximate a bottom face of the die portion that defines the lower portion of the shell.  
           [0012]    One of the at least two cooperating die portions may define a lower portion of the shell. Each die portion may define one of the group consisting of substantially the entirety of an upper portion of the shell and substantially the entirety of a lower portion of he shell. In some methods, the die portions may be disposed in side by side relation, each die portion having a toe end and a heel end with the toe ends of the die portions being disposed above the heel ends of the die portions. The cooperating die portions may be provided with portions that mate in male-female relation when the die portions are aligned with respect to each other. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    Preferred features of the present invention are disclosed in the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and wherein:  
         [0014]    [0014]FIG. 1 shows a perspective view of a prior art split metal die assembly with an inner mold portion;  
         [0015]    [0015]FIG. 2 shows a top view of a prior art shell formed with the split metal die assembly of FIG. 1;  
         [0016]    [0016]FIG. 3 shows an exploded perspective view of an exemplary boot construction according to the present invention;  
         [0017]    [0017]FIG. 4 shows a partial cross-sectional side view of an exemplary disengaged split metal die assembly with an inner mold portion according to the present invention;  
         [0018]    [0018]FIG. 5 shows a partial cross-sectional side view of the exemplary split metal die assembly of FIG. 4 in an engaged position;  
         [0019]    [0019]FIG. 6 shows a lateral side view of the exemplary shell of FIG. 3;  
         [0020]    [0020]FIG. 7 shows a medial side view of the exemplary shell of FIG. 3;  
         [0021]    [0021]FIG. 8 shows a top view of the exemplary shell of FIG. 3; and  
         [0022]    [0022]FIG. 9 shows a perspective view of the midsole and shell of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]    Referring to FIG. 3, an exemplary boot construction according to the present invention is shown. Boot  110  includes an outsole  112 , midsole  114 , shank  116 , and shell  118 . Heel cushion  120  and forefoot cushion  122  may be disposed between an insole  124  and shell  118 . An upper  126  also is provided, and optionally may include lacing  128 . Preferably, shank  116  is disposed in a recess  114   a  in midsole  114 , while cushions  120 ,  122  are disposed in recesses in insole  124 .  
         [0024]    In an exemplary preferred embodiment, outsole  112  is formed of carbon rubber, while midsole  114  is formed of molded ethyl vinyl acetate foam. Shank  116  may be formed of a thermoplastic polyurethane, while upper  126  may be formed of leather, fabric textiles, foam and other suitable insulation. The various polymer components may be coupled to each other with an adhesive or other bonding agent, while upper  126  may be coupled to shell  118 , for example, using stitching proximate the lower edge of leather portion  130  of upper  126 .  
         [0025]    Turning to FIGS. 4 and 5, an exemplary split metal die assembly  132  according to the present invention is shown. A first die portion  134  mates with a cooperating second die portion  136  to create a cavity  138  in a desired outer shell shape. In one preferred embodiment, die portions  134 ,  136  are formed of steel and configured and dimensioned such that each die portion defines either an upper portion  134 ′ of shell  118  or a lower portion  136 ′ of shell  118 . A last or inner mold portion  140  is disposed between die portions  134 ,  136  in cavity  138 , thereby creating a desired inner shell shape. Cavity  138  of die assembly  132  is in communication with runners  142  ending in gates  144 , through which polyurethane flows for injection into cavity  138 . After polyurethane is injected into and fills cavity  138  in the space defined between die portions  134 ,  136  and inner mold portion  140 , sprues may be created integrally with the shell as a remnant of the molding process. In one preferred embodiment, runners  142  only communicate with cavity  138  proximate bottom face  139  of die portion  136  defining lower portion  136 ′ of shell  118 . Thus, sprues are only created during the molding process proximate the outside, bottom portion of shell  118 . Sprues therefore may be removed without meticulous finishing operations, and artifacts thereof are hidden from view by another component of boot  110  such as midsole  114 . Preferably, shell  118  is formed of an injectable thermoplastic polyurethane which cures to form a generally flexible body. In one embodiment, a TPU is used with a durometer (hardness) of 80±3 on the Shore A scale. In alternate embodiments, shell  118  is formed of another synthetic material.  
         [0026]    Shell  118  may be molded to include indicia  118 ′ on the outer surface thereof. In one embodiment, indicia  118 ′, such as a logo or other feature, are molded on either a lateral or medial side of shell  118 . By consistently molding indicia  118 ′ on a lateral or medial side of shell  118 , the indicia  118 ′ may serve to indicate whether the shell  118  is configured and dimensioned for use with a left or right foot. In other words, indicia  118 ′ may assist in identifying whether shell  118  should be used in the manufacture of a boot for a left foot or a right foot.  
         [0027]    Die portions  134 ,  136  may be provided with portions that mate in male-female relation when die portions  134 ,  136  are aligned with respect to each other. At least one of die portions  134 ,  136  may be provided with alignment features, such as alignment posts  146 . Recessed regions  148  are provided in the die portion  134 ,  136  opposing each post  146  and aligned therewith, such that movement of die portions  134 ,  136  toward each other in the direction of arrows A permits each post  146  to mate with a corresponding recessed region  148 .  
         [0028]    Although die portions  134 ,  136  are shown with upper portion  134 ′ of shell  118  formed above lower portion  136 ′ of shell  118 , other orientations are within the scope of the present invention. For example, in a preferred exemplary embodiment, upper portion  134 ′ of shell  118  instead may be formed to the left or right of lower portion  136 ′ of shell  118 , as long as cavity  138  is created when die portions  134 ,  136  mate. Thus, die portions  134 ,  136  are disposed in side by side relation such that die portion  134  defining upper portion  134 ′ of shell  118  is disposed adjacent die portion  136  defining lower portion  136 ′ of shell  118 , each die portion  134 ,  136  having a toe end T and a heel end H with the toe ends T of die portions  134 ,  136  disposed above the heel ends H of die portions  134 ,  136 . In another embodiment, upper portion  134 ′ may be formed below lower portion  136 ′.  
         [0029]    Die portions  134 ,  136  mate and form an interface disposed proximate a perimetral portion of cavity  138 . Thus, in one preferred embodiment, the interface is formed proximate one or more perimetral features to be molded in shell  118 , such as a ridge, recess, or transition between surface textures or patterns.  
         [0030]    Referring to FIGS.  6  to  8 , an exemplary preferred shell  118  includes a toe end  150 , a heel end  152 , and lateral and medial sidewalls  154 ,  156 , respectively, disposed therebetween. Because of the positioning of die portions  134 ,  136  to form upper and lower portions  134 ′,  136 ′, respectively, of shell  118 , a flash line  158  is formed at the interface of die portions  134 ,  136  along an outer perimeter  160  of shell  118 . In the exemplary preferred embodiment, flash line  158  coincides with an edge of ridge  162  along length L 1  of shell  118  proximate heel end  152 . Flash line  158  continues along lateral and medial sidewalls  154 ,  156  along length L 2  of shell  118  defining surfaces  164 ,  166  adjacent flash line  158 . The surface texturing on surfaces  164 ,  166  may be different, thus permitting flash line  158  to define a transition therebetween.  
         [0031]    Advantageously, flash line  158  is substantially disposed remote from longitudinal axis  168  of shell  118 . Thus, top portion  170  may be formed as a smooth surface without a feature such as a rib proximate axis  168  to hide a flash line. In addition, no flash line extends from the top edge  172  to the bottom edge  174  of heel end  152 . Thus, shell  118  is configured such that flexure proximate axis  168  is not hindered by a flash line. Moreover, the stiffness of shell  118 , particularly at top portion  170  proximate axis  168 , may be selected as a function of design parameters without accounting for the presence of a flash line.  
         [0032]    As shown in FIG. 8, flash line  158  extends around the periphery of shell  118 . In addition, midsole  114  has an upper edge  176 . In a preferred exemplary embodiment of boot  110 , when shell  118  is coupled to midsole  114 , the flash line  158  is disposed proximate upper edge  176 . Thus, flash line  158  is hidden from view by midsole  114  and/or blends with upper edge  176  in an aesthetic manner. In an alternate embodiment, flash line  158  is hidden from view below upper edge  176  of midsole  114  when shell  118  is coupled to midsole  114 .  
         [0033]    While various descriptions of the present invention are described above, it should be understood that the various features can be used singly or in any combination thereof. For example, while flash line  158  is described as being disposed proximate or below an upper edge  176  of midsole  114  when shell  118  is coupled to midsole  114 , the flash line  158  may alternatively be disposed above upper edge  176 . In addition, shell  118  may be coupled to another component of a boot  110 ; for example, lower portion  136 ′ of shell  118  may be coupled directly to an outsole  112 , with flash line  158  being disposed proximate or below an upper edge of outsole  112 . Thus, the present invention is not to be limited to only the specifically preferred embodiments depicted in the drawings.  
         [0034]    Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. For example, if desired, one or more ribs or other surface features may be provided along the longitudinal axis  168  of shell  118 , in addition to a flash line  158  running around a perimeter of shell  118  and disposed transverse to the rib. Such a rib may confer desired rigidity. Ribs may also be provided for added reinforcement in regions of localized stress concentrations. Also, molding techniques other than injection molding may be used, and in some embodiments, flash line  158  may be disposed along only a portion of the perimeter of shell  118 . Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein are within the scope and spirit of the present invention and are to be included as further embodiments. The scope of the present invention is accordingly defined as set forth in the appended claims.