Patent Publication Number: US-2006005424-A1

Title: Bonding of an upper and a shell in a shoe

Description:
TECHNICAL FIELD  
      This disclosure relates generally to shoes and more particularly to bonding of an upper and a shell in a shoe.  
     BACKGROUND  
      Shoes provide an important barrier between our feet and the physical world. In many circumstances, such as cold-weather environments, a waterproof shoe is desirable. However, the consumer market for shoes is a highly competitive market, in which buyers demand low prices. Thus, additional shoe features, such as waterproofing, will not lead to commercial success, unless those features can be provided affordably. Because making shoes is a labor-intensive activity, costs are most effectively contained by minimizing the amount of labor needed to add new features to shoes.  
     SUMMARY  
      According to one method, a shoe shell is attached to a shoe upper by molding. The upper is placed on a mold core, which includes a portion resembling a foot and a portion on which the upper fits. A flap provided on the upper extends along at least a portion of a bottom rim of the upper and has opposing interior and exterior sides. A mold is provided around the mold core and the flap so as to define a cavity between the mold and the mold core. The flap extends into the cavity so that both the interior and exterior sides of the flap are exposed within the cavity. A shell material is introduced into the cavity so as to mold the shell material directly around the mold core portion resembling a foot and to cohere the shell material to both the interior and exterior sides of the flap.  
      According to another method, a shoe shell is attached to a shoe upper without stitching. The upper has opposing interior and exterior sides and a bottom periphery rim for attachment to the shell. The shell has a top periphery rim, which coheres to portions of both the interior and exterior sides of the upper in proximity to the bottom periphery rim of the upper.  
      A shoe may be made in accordance with either method described in the preceding paragraphs. Regardless of its method of manufacture, a shoe comprises an upper and a shell. The upper has opposing interior and exterior sides and a bottom rim. The shell has an upper rim, which coheres to at least portions of both the interior and exterior sides of the upper in proximity to the bottom rim of the upper, without stitching of the upper to the shell. As used herein, the term “shoe” encompasses all types of footwear, including, for example, boots. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a shoe upper on a mold core, according to one embodiment.  
       FIG. 2  is a side cross-section view of a mold being placed around a portion of the shoe upper and mold core of  FIG. 1 .  
       FIG. 3  is a partial cross-section view of a shoe shell formed within the mold of  FIG. 2 .  
       FIG. 4  is the shoe of  FIG. 3  in the process of being removed from the surrounding mold.  
       FIG. 5  is cross-section view of toe portion of the shoe, mold core, and mold of  FIG. 3 , taken along line  5 - 5  of  FIG. 3 .  
       FIG. 6  is an enlarged cross-section view of a bond between the upper and shell of the shoe of  FIG. 3 , according to a first embodiment.  
       FIG. 7  is an enlarged cross-section view of a bond between the upper and shell of the shoe of  FIG. 3 , according to a second embodiment. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
      With reference to the above-listed drawings, this section describes particular embodiments and their detailed construction and operation. As one skilled in the art will appreciate, certain embodiments may be capable of achieving certain advantages over the known prior art, including some or all of the following: (1) attachment of a shoe shell to an upper without stitching; (2) a waterproof interface between a shoe shell and an upper; (3) simpler and less expensive construction; and (4) greater design freedom by relaxing restrictions on permissible curves and angles imposed by a stitching allowance. These and other advantages of various embodiments will be apparent upon reading the following.  
       FIGS. 1-4  illustrate steps of a method for assembling a shoe according to one embodiment. Generally, that method comprises placing a shoe upper on a mold core, placing a mold around portions of the upper and mold core, molding a shell material between the mold and the mold core to form a shell cohered to the upper, and removing the mold and mold core after the shell material has solidified in the form of the shell.  
      As shown in  FIG. 1 , the first step of the method is to place a shoe upper  100  on a mold core  110 . The mold core  110  comprises a top portion  120  generally resembling an ankle and a bottom portion  130  generally resembling a foot. The ankle-like top portion  120  and the foot-like bottom portion  130  may be separate or integral. Although the mold core  110  is preferably solid, that need not be the case; the mold core  110  may be an inflatable bladder, for example. The mold core  110  is preferably formed of metal, such as stainless steel, which can be exposed to high-temperature molding materials without significant deformation or deterioration.  
      The upper  100  may be any material suitable for a shoe upper, such as natural leather, synthetic leather, a textile, or the like. The upper  100  is preferably waterproof, as the interface between it and a shell (not shown in  FIG. 1 ) below the upper  100  can be made waterproof, as explained below. Examples of waterproof materials suitable for the upper  100  include waterproof leather and textiles with a waterproof membrane or coating, such as, for example, an expanded polytetraflouroethylene membrane commonly sold under the trademarks GORETEX® and EVENT®, or a polyurethane coating. In one form, the upper  100  is a two-ply material of textile on the exterior side and a waterproof membrane or coating on the interior side (although the waterproof layer can be on the exterior side, if desired).  
      The upper  100  has two opposing sides: an interior side  140  and an exterior side  150 . Along the bottom of the upper  100  is a bottom periphery rim  160 . The interior side  140  generally fits snugly against the mold core  110 , except along the bottom periphery rim  160 , which may be more loosely disposed on the mold core  110 . Optionally, jigs, pins, pegs, pinchers and wipers, or the like (not shown) can be fitted between the mold core  110  and the interior side  140  of the upper  100  in the vicinity of the bottom periphery rim  160  to separate the upper  100  from the mold core  110  along the bottom periphery rim  160  or portions thereof. Alternatively or additionally, the bottom periphery rim  160  is or comprises a flap of the upper  100 . As will be described in greater detail below, that flap is an area of attachment of the upper to a shell (not shown in  FIG. 1 ), which goes around the bottom portion of the mold core  110 . The flap may be a stitch flange (although it is not attached by stitching) provided on the interior side  140  of the upper  100  and may extend downward about 8 millimeters (mm), for example.  
      A next step is shown in  FIG. 2 , which is a side cross-section view of a mold  200  being placed around a portion of the shoe upper  100  and the mold core  110 . In most cases the mold  200  comprises two pieces, such as a front mold piece  210  and a rear mold piece  220 , as shown in  FIG. 2 . Other arrangements for a two-piece mold are possible, e.g., top and bottom pieces, left and right side pieces, etc. Although a two-piece mold offers the advantage of being separable while minimizing the number of joints between pieces, a mold can be formed with three or more pieces. As shown, the front mold piece  210  is moved over the toe portion of the mold core  110  and the rear mold piece  220  is moved over the heel portion of the mold core  110  until mating surfaces  230  abut and preferably engage in a more-or-less sealing contact. Ideally, the mating surfaces  230  are built with sufficient precision to fit together and seal against each other. The mating surfaces may have complementary tongue-in-groove or other surface features to enhance their seal.  
      When the front mold piece  210  and the rear mold piece  220  contact, they define an interior chamber, in which is typically disposed the mold core  110 , or a portion thereof, clad with the upper  100 . The interior cavity is defined by an interior wall  240  of the mold  200 . A bottom portion of the interior chamber is slightly larger than the foot-like bottom portion  130  of the mold core  110 . Thus, when the mold  200  is fully engaged around the mold core  110 , there is a cavity or space between the interior wall  240  of the mold  200  and the mold core  110 . It is in that cavity where the shell will be formed, as described in further detail below.  
      Along the interior wall  240  is a ridge  250  positioned to contact and press against the upper  100  somewhat above the flap or bottom periphery rim  160  of the upper  100  when the mold  200  is fully engaged around the mold core  110  clad with the upper  100 . The ridge  250  functions to dam the flow of the shell material and retain the shell material in place when it is injection molded, as explained in more detail below. In some cases, it may be helpful to apply an upward force to the mold core  110  and a downward force to the mold  200  to aid in pinching the upper  100  between the mold  200  and the mold core  110  above the flap. (Directional terms, such as “upward” and “downward” are used herein consistently with the orientation of the drawings, to facilitate ready understanding; however, the use of directional terms should not be construed to imply that any particular directional orientation is required; the mold core  110 , the upper  100 , and the mold  200 , for example, may be oriented upside down, sideways, or in any other spatial direction during the manufacturing method; moreover, the directional orientation may change from stage to stage of manufacture.) Alternatively, a gasket or dam may be useful at the external interface between the upper  100  and the mold  200 . The mold  200  also preferably has one or more sprues, runners, or flow ports  260  through which shell material can be inserted to form the shell. The number and placement of the flow ports  260  are not critical. The mold  200  is typically made of a metal, such as steel, capable of withstanding the heat associated with an injection molding process.  
       FIG. 3  shows a partial cross-section view of a shoe shell  300  formed within the mold  200 , around the mold core  110 , and attached to the upper  100 . The shell  300  is preferably formed by injecting a shell material into the flow ports  260 . Preferably, the shell material  300  is a deformable or flowable material that can be hardened. An example of one such material is a thermoplastic material, such as, thermoplastic resin (TPR), thermoplastic urethane (TPU), thermoplastic elastomer (TPE), or the like. If necessary, the shell material is heated to a liquid state and then flowed or injected through the flow ports  260 , from which it fills the cavity between the interior wall  240  of the mold  200  and the mold core  110 . There the shell material  300  is allowed to cool and solidify. During that process, the shell material  300  coheres to both sides of the upper  100  along its bottom periphery rim  160 , both sides of which are exposed in the cavity. That cohering is described in greater detail below with reference to  FIGS. 6 and 7 .  
      Other types of flowable or deformable material may not require heating to flow. For example, some materials cure or harden upon mixing (e.g., two-part foams, resins, or epoxies), heating, exposure to ultraviolet light, or other environmental conditions. Such materials may be used as the shell material  300 .  
      Although  FIGS. 2 and 3  show that the shell material  300  is added after the mold  200  has been placed around the mold core  110 , that need not be the order of operations. In some cases, it may be possible to coat either the interior wall  240  of the mold  200  or the sides of the mold core  110  with the shell material before attaching the mold  200  around the mold core  110 . It is also possible to provide reinforcement fibers in the cavity between the mold core  110  and the mold  200 , in order to augment the structural strength of the resulting shell  300 .  
       FIG. 4  depicts a resulting shoe  400  as the front and rear mold pieces  210  and  220  dissociate from each other and uncover the shoe  400  on the mold core  110 . The shoe  400  may undergo additional processing before it becomes a finished product. For example, an outsole  310  (indicated by phantom lines in  FIG. 3 ) may be attached to the bottom side of the shoe  400  underneath the shell  300 , and an insole (not shown) may be placed inside and along the bottom of the shoe  400 . The shoe  400  can be removed from the mold core  110  by unlacing (or otherwise unfastening) the shoe  400  and then lifting the mold core  110  out of the shoe  400 , or by pulling the shoe  400  from the mold core  110 , just as a person would typically remove his foot from a shoe. If the shell  300  has flashing where the front and rear mold pieces  210  and  220  meet, as might happen when they do not seal together with sufficient tightness and precision, then that flashing can be trimmed after removal of the mold  200  is removed from around the shoe  400 .  
       FIG. 5  is a cross-section view of toe portion of the shoe  400 , mold core  110 , and mold  200 , taken along line  5 - 5  of  FIG. 3 . Between the mold  200  and the mold core  110  are the upper  100  and the shell  300 . This view shows that the shell  300  contacts both the interior side  140  and the exterior side  150  of the upper  100  along the bottom periphery rim  160  of the upper  100 . In other words, the shell  300  can be said to define a channel along its top periphery rim, in which the bottom periphery rim  160  of the upper  100  is disposed.  
       FIGS. 6 and 7  are exploded diagrams of two illustrative bonds between the upper  100  and the shell  300  of the shoe  400 . In  FIG. 6 , the upper  100  is a simple one-ply material, such as a leather, which may be treated (e.g., buffed) to remove oils that might interfere with its bonding to the shell  300 . The shell  300 , when injected in a molten state coheres to the surface of the upper  100  everywhere they are allowed to contact (i.e., on both the interior side  140  and the exterior side  150  in the vicinity of the bottom periphery rim  160  of the upper  100 ). Such cohering can result from the physical interconnections between the upper  100  and the shell  300 . For example, in the vicinity of the bottom periphery rim  160  the upper  100  may have a roughened surface texture (not shown), which enhances the ability of the shell  300  to intermesh with and grip the surface of the upper  100 . As another example, in the vicinity of the bottom periphery rim  160  the upper  100  may be a fibrous, porous, or woven material, to which the shell  300  can bond by interspersing among or into fibers, pores, or woven strands (not shown). As yet another example, the upper  100  may comprise perforations (not shown) extending from the interior side  140  to the exterior side  150  along some or all of the bottom periphery rim  160 , such that the shell  300  can form in those perforations. In those cases, injecting the shell material  300  in a molten state under sufficiently high pressure can cause the shell material  300  to permeate and interlock with any perforations, fibers, pores, woven strands, or roughened surface features on the upper  100 .  
      In  FIG. 7 , the upper  100  is a two-ply material of a waterproof membrane  100 A on the interior side  140  and a textile  100 B on the exterior side  150 . As shown in  FIG. 7 , the upper  100  is folded upon itself. That has two effects. First, it exposes the waterproof membrane  100 A on both sides of the upper  100 . Second, it creates a bulge on the exterior side  150  of the upper  100 . In the areas where the shell  300  contacts the textile  100 B during hot injection molding, the shell  300  coheres to the textile  100 B, typically by flowing into and subsequently solidifying in or around the pores, woven strands, and/or fibers in the textile  100 A. In the areas where the shell  300  contacts the waterproof membrane  100 A, the cohering is more like a weld, as the hot shell material melts the waterproof membrane  100 A, the two molten materials partially mix, and then solidify bonded together. Moreover, if the fold is in the other direction such that the bulge forms on the interior side, then the heat of the molten shell  300  can melt the waterproof membrane  100 A to itself in the interior portion of the fold, so as to retain the upper  100  in its folded position. (Note that the fold can be held in place initially with some minimal adhesive or stitching, which can be easily accomplished as part of the construction of the upper  100 .)  
      The bulge in the upper  100  shown in  FIG. 7  can further increase the strength of the bond between the upper  100  and the shell  300 . The bulge provides a ledge that resists lateral movement of the cohered surfaces of the shell  300  and the upper  100  across each other over that ledge (i.e., movement of the shell to the right and/or the upper to the left, as shown in  FIG. 7 ). The bulge also deflects lateral forces acting upon the portion where the shell  300  and the upper  100 B cohere above the bulge. Although  FIG. 7  shows one form of a bulge formed by a fold in the upper  100 , bulges of any type, formed by any means, on either or both sides of the upper  100 , are also possible.  
      Note that although  FIG. 7  illustrates a folded two-ply material as the upper  100 , it is possible to use any number of layers of materials as a multi-layer laminate upper  100 , without or without folds, and with or without a waterproof membrane, which could be in any arbitrary layer.  
      As  FIGS. 6 and 7  make clear, the shell  300  can be attached to the upper  100  in a waterproof interface without stitching of the shell  300  to the upper  100 . The absence of a stitched attachment reduces the labor and material costs associated with making the shoe  400 . Stitching also tends to defeat waterproofing, as threads can act as wicks to transport moisture from one side of a stitched barrier to the other side, unless additional, costly measures are taken to seal and isolate the stitching from possible moisture sources. The shoe  400  avoids those problems. When the upper  100  is a waterproof material, the shoe  400  is a simple-to-construct, waterproof shoe.  
      The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations can be made to the details of the above-described embodiments without departing from the underlying principles of the invention. For example, just a portion of the shell may be formed and attached to the upper in the manner described above, so as to permit modular shoe designs and constructions. The scope of the invention should therefore be determined only by the following claims, and their equivalents, in which all terms are to be understood in their broadest reasonable sense unless otherwise indicated.