Patent Publication Number: US-2005138847-A1

Title: Protective, orthotic removable insert for footwear

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of U.S. patent application Ser. No. 09/682,732, filed Oct. 11, 2001, entitled PROTECTIVE, ORTHOTIC INSERT FOR FOOTWEAR, which is a continuation-in-part of U.S. patent application Ser. No. 09/687,457, filed Oct. 17, 2000, entitled PUNCTURE RESISTANT ORTHOTIC INSOLE, both under the names of the same inventors. Priority is claimed to this earlier filed U.S. patent Application under 35 United States Code § 120, and the earlier filed applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND  
      1. Field of the Invention  
      This disclosure pertains to shoe inserts, and more particularly to protective shoe inserts that are not integral to a shoe construction.  
      2. Background Information  
      Laborers, technicians, supervisors, project managers and other professionals in industrial and construction industries often work in hazardous environments. Job sites and facilities are generally not open to the public and such facilities are not continually cleaned and made safe of dangerous conditions. As such, shards of glass, shreds of metal and other rigid construction materials, in particular nails, pose a continuing threat of injury to the feet of workers in these environments.  
      To overcome such hazards, it has been proposed, and it is commonly practiced, that the sole of a work boot or safety shoe be integrally constructed of multiple layers of a high tensile strength synthetic or polymeric fibers, such as Kevlar (™) in work boots. U.S. Pat. No. 5,996,225, issued to George Ventura, shows such a technique. Drawbacks, however, to this technique include that it adds cost and complexity to the design of a work boot insole. A similar solution is proposed in U.S. Pat. No. 5,285,583, by Albertus A. W. Alven, of Markdale, Canada, as well in a series of U.S. patents authored by L. P. Frieder et al., for instance U.S. Pat. Nos. 2,803,895, 2,808,663, and 2,920,008. Each of these patents teach that multiple stacked, resin-impregnated, fibrous laminates are needed to prevent penetration by sharp objects.  
      While also an integrally fabricated portion of the protective footwear sole, U.S. Pat. No. 4,271,607, issued to Herbert Funck of Germany, shows that a two-part, yet single-layered, prefabricated steel inlay can be used as a protective shield.  
      Because the metal inlay is integrally molded into the footwear sole, there is the risk that movement and flexing on the integral and flexing will damage the interior lining and sole of the protective footwear. Appreciating this problem, Funck requires a groove and two-part lip molding combination in the forward end (toe end) of the sole to prevent movement, and a cup shaped holder secured to the underside of the steel inlay at the rear end (heel end) to facilitate alignment within the sole assembly. A further drawback is that by incorporating the metal inlay into the sole of the footwear, only about 80% of the bottom surface of a foot is protected by the metal inlay.  
      While either a separate insole insert for footwear, or an integrally molded part at manufacture, U.S. Pat. No. 6,178,664, issued to Robert D. Yant et al., the &#39;664 patent shows another multi-layered metal sheet assembly designed to protect the sole of a shoe from puncture by a sharp object.  
      As is the case with other multi-layered protective layer assemblies, the &#39;664 patent requires an intricate manufacturing process, involving the stamping of multiple metal sheets and spot welding each metal sheet to the next. The end result of the &#39;664 patent is a variable thickness, multi-layered metal sheet assembly.  
     SUMMARY  
      A multi-layer (e.g., three-layer) insert for footwear is provided.  
      In general, in one aspect, a multi-layer protective insert includes a protective layer and one or more layers to provide cushioning and to provide a top contoured surface. For example, a multi-layer protective insert comprises a bottom protective layer; for example, a single steel sheet. The multi-layer protective insert further comprises a middle layer is a cushion layer. The middle layer may be shaped to the contour of the bottom of a foot. The middle layer may further include orthotic supports. The middle layer may be disposed over a bottom protective layer comprising a single steel sheet. The multi-layer protective insert may further comprise a top layer. The top layer may comprise a membrane secured to a middle (e.g., cushion) layer.  
      In general, in another aspect, a metatarsal support region may be integrated with an intermediate layer such as a cushion layer. In another aspect, an intermediate layer such as a cushion layer may further be characterized by a lip that extends upwardly and outwardly relative to the protective layer (e.g., a single steel sheet).  
      In general, in another aspect, a method for making the same is also provided. The method may comprise forming a cushion layer that provides orthotic support for a foot. The method may further comprise attaching a membrane to a top surface of the cushion layer and trimming the membrane to match a perimeter of the top surface of the cushion layer. The method may further comprise forming a protective layer by stamping a single metal sheet from stainless spring steel, stainless steel shim stock, 301 full hard stainless steel, or the like. The protective layer may have a top surface configured to receive a bottom surface of the cushion layer, and a bottom surface configured to engage a top surface of an interior cavity of the footwear.  
      In general, in another aspect, the method may further include applying bonding material to the top surface of the metal sheet; and placing the metal sheet into a mold for the cushion layer. The cushion layer may be formed directly over the metal sheet. In other aspect, the method may include pre-processing (e.g., brushing) the top surface of the metal sheet prior to placing the placing the metal sheet into the mold for the cushion layer. In still another aspect, the method may include other processing (e.g., deburring) of the metal sheet prior to placing the metal sheet into a mold for the cushion layer.  
      In general, in another aspect, an insert may include a puncture-resistant layer and a cushion layer. The puncture-resistant layer may have a bottom surface shaped and sized to engage an inner bottom surface of the footwear. The cushion layer may have a first surface portion shaped to a contour complementary to a bottom of a foot contour. The cushion layer may be adjacent to the upper surface and the outer perimeter of the puncture-resistant layer, and may include a lip that extends upwardly from a region proximate to a bottom surface of the puncture-resistant layer and outwardly relative to the puncture-resistant layer.  
      In general, in another aspect, a method of forming an insert may comprise providing a form including a recess shaped and sized to form a portion of the footwear insert; the form further including a positioner shaped and sized to receive a protective insert portion having a top surface and a perimeter surface. The method may further comprise providing a complementary recess having a footward surface shaped and sized to engage a bottom of a foot. The method may further comprise positioning the protective insert portion in the positioner.  
      The method may further comprise forming a mold region comprising the recess and the complementary recess and introducing a material into the mold region. The material may form a support region of the insert, and may be proximate to the top surface and the perimeter surface of the protective insert portion.  
      These and other features and advantages will become more apparent upon reading the following detailed description and upon reference to the accompanying figures. 
    
    
     DESCRIPTION OF DRAWINGS  
      The description is aided by way of the following figures, in which like reference numerals on different figures refer to the same or equivalent elements as in other figures.  
       FIG. 1  is a top view of an implementation of a protective insert.  
       FIG. 2  is a bottom view of the protective insert of  FIG. 1 .  
       FIGS. 3 and 4  are side views of the protective insert of  FIG. 1 .  
       FIG. 5  is a cross-sectional view of the protective insert of  FIG. 1 .  
       FIG. 6  is a cross-sectional view of another implementation of a protective insert.  
       FIGS. 7A and 7B  show an implementation of a system for forming a protective insert. 
    
    
      Like reference symbols in the various drawings indicate like elements.  
     DETAILED DESCRIPTION  
      The current inventors recognized that a number of benefits may be provided by a multi-layer protective insert for footwear. For example, the systems and techniques described herein may provide a cost-effective insert that is both protective and supportive.  
      In some implementations, the insert is a protective, orthotic insert comprising three layers. A bottom layer comprises a substantially puncture-resistant layer, such as a single sheet of stainless steel. A middle layer comprises a cushion layer, for instance made of polyurethane, neoprene, PVC foam, EVA, or the like, configured to support the heel and arch of the wearer&#39;s foot. A top layer may protect the cushion layer from substantial contact with an inserted foot. For example, the top layer may comprise a membrane, such as a skin (for example open cell polyurethane), cloth, and/or another synthetic material. The top layer may also discourage unsightly discoloration and unpleasant odor.  
       FIG. 1  is a top view of a protective insert  100 , according to some implementations. The insert  100  includes a forward end (the toe end)  116 , and a rear end (the heel end)  120 . A thin top layer comprising a cloth-like material  104  is directly seen from this view as it resides over a middle layer  108 . The top layer  104  may be constructed of Cambrelle+ (™), which is commercially available from the Faytex Corporation in Weymouth, Mass. Of the materials used by the inventors, this material provided a beneficial mix of characteristics, including substantial prevention of discoloration and odor, moisture wicking, and reduction of friction with the foot.  
      As viewed from the top, a number of features (not necessarily attributable to the top layer  104 ) are visible. For instance, a lip  132  rises up around the outer perimeter of the insert  100 . The lip  132  projects outwardly, slightly away from the interior portion of the insert  100 , to keep the inserted foot centered on top of the insert, and to further provide horizontal support for the insert  100  when it is inserted into footwear, such as a tennis shoe, work boot, a dress shoe, or the like. This keeps the insert snug into the footwear and reduces lateral or back and forth motion.  
      According to some implementations, lip  132  need not completely surround the perimeter of the insert  100 . For example, there may be no upwardly extending lip region in the vicinity of the toe end  116  of the insert  100 .  
      In addition to lip  132 , also visible in  FIG. 1  is an arch support  128 , which also rises up with respect to bottom layer  112 . In the implementation shown in  FIG. 1 , the top surface  104  reaches its peak height at approximately the crest of the lip region over the arch support  128 .  
       FIG. 1  also shows heel support  124 , which may have a bulbous shape that rises upwardly with respect to the lowest portions of the top layer  104  at the heel end  120  of the insert  100 . In  FIG. 1 , the lip  132  is thicker (horizontally) and deeper (vertically) at the heel end  120  of the insert than in most other regions, excepting the arch support  128 .  
      According to some implementations, an optional metatarsal support region  136  is also included in insert  100 . The metatarsal support region  136  may be integrally molded from the middle layer (discussed below). In another implementation, the metatarsal region  136  may be partially or fully built up after manufacture; for instance, by creating a pocket beneath the top layer  104  in which an orthotic cushion can be inserted or received.  
      According to some implementations, a pocket for the metatarsal support  136  is formed by a cut into the top ( 104 ) and middle ( 108 ) layers of the insert  100 , which runs parallel with a line formed between the toe ( 116 ) and heel ( 120 ) ends of the insert  100 . Alternatively, the metatarsal support  136  can be a separate element that is disposed over and bonded to the bottom layer  112  before the middle layer  108  is added.  
       FIG. 2  shows a bottom view of the insert  100 . The bottom layer  112  is prominent in this view, but also visible is the middle layer  108 , and more particularly the lip  132  and arch support  128 .  
      In some implementations, the bottom layer  112  comprises a single layer stainless steel shim stock, stainless spring steel, or 301 full hard stainless steel of an appropriate thickness. For example, thicknesses between about 0.020 and about 0.025 inches may be used. Of the materials used by the inventors, the properties of steel were preferred to other materials (e.g., Kevlar (™) and other synthetic materials). However, synthetic or other materials may be used.  
      Steel (e.g., at least some of the types of steel noted above) may exhibit a number of beneficial characteristics. Steel may be highly puncture resistant, as well as largely impervious to the pH of the foot. As a result, systems and techniques provided herein may have additional advantages over some available inserts. Some available multi-layered designs run a greater risk of water and sweat finding their way into the spaces between the layers. With time, the water may cause deterioration, such as rust and mold, of protective layers, if not the entire shoe sole. Since some available designs are integrally molded or embedded into the sole, they are not readily inspectable. As a result, fatigue deterioration may go unnoticed, which may increase the risk of injury to the foot.  
      According to some implementations, a thickness of the protective layer may be selected so that the protective layer returns to substantially the same shape, even with repeated use. The protective layer may thus be said to exhibit the characteristic of “memory.” By memory we mean that the bottom layer  112  tends to return to its constructed position and returns some kinetic energy to the wearer as the layer  112  bends and is then released by walking action.  
       FIG. 5  shows a cross-sectional view of insert  100 , while  FIGS. 3 and 4  depict side views. In each of the figures, the proportions of the insert assembly are exaggerated for the purpose of illustration. The actual dimensions in these drawings, as well in  FIGS. 1 and 2 , are not to scale.  
      According to some implementations, middle layer  108  structurally forms the orthotic characteristic of the insert  100 . According to some implementations, the middle layer conforms to U.S. military specifications for orthotic inserts. Commercially available, pre-manufactured units may also be used, such as the Mid-Pro Mold Thick-toe, from ATP Manufacturing LLC, in North Smithfield, R.I. When a pre-manufactured middle layer  108  is employed, for instance the Mid-Pro Mold, it may be affixed to the bottom layer. For example, it may be glued to the bottom layer  108  with an adhesive contact cement that is specifically chemical formulated to bond closed cell polyurethane to steel. For instance, part no. E-2150, a commercially available contact cement, is available from Worth Industries, in Nasoun, N.H. can be employed.  
       FIG. 5 , shows a cross sectional view of section  5 - 5 , which is a view toward the heel side  120  of the insert  100 . The three layers of the illustrative implementation of the protective, orthotic shoe insert  100  are plainly visible: a bottom layer, middle layer and top layer. For example, a single stainless steel sheet, which forms the bottom layer  112 , a molded polyurethane layer, which forms the middle layer  108 , which is shaped to the contour of the bottom of a foot and disposed over the bottom layer  112 , and an air and water permeable membrane, which forms the top layer  104 .  
      In the illustrated implementation, the perimeter of the bottom surface of the molded polyurethane layer (middle layer  108 ), and the perimeter of the top surface of the single stainless steel sheet (bottom layer  112 ), are roughly equal. In other implementations, the perimeter of the stainless steel sheet is less than the perimeter of the bottom surface of the polyurethane layer. Note how the lip  132  slopes in an outwardly direction from the bottom layer  112 .  
      According to some implementations, the insert  100  is formed by the following processes. First, a single stainless steel sheet is stamped from stainless steel shim stock, for example 301 stainless steel full hard. The stamped single stainless steel sheet may have a thickness between 0.020 and 0.025 inches. According to some implementations, the stainless steel sheet can be manually or automatically inspected and/or processed to remove any sharp burrs or imperfections. For example, it may be deburred and then polished.  
      Next, the stainless steel sheet is inserted into a mold, where a polyurethane orthotic insole is formed over the top surface of the stainless steel sheet. The two layered insert is then allowed to cure. If desired, a Cambrelle (™) membrane is disposed over the top surface of the polyurethane. In some implementations, the top surface of the stainless steel sheet is mechanically or chemically etched and a bonding material sprayed on the top surface before the polyurethane is formed over top surface of the stainless steel sheet in the mold.  
      After the layers of the orthotic insole are formed, the orthotic insole can be trimmed to remove any excess materials or imperfections along the perimeter (for example about lip  132 ).  
      Note that it is possible that a two level cushion layer can be constructed of polyurethane to form the cushion layer and the membrane. For instance, an open cell polyurethane can be used to create the cushion layer, after the steel sheet is inserted into the mold, and a second polyurethane layer, for instance a closed cell polyurethane layer, can be molded directly over the open cell polyurethane layer. This process of forming the top layer may be referred to as a “skinning” process.  
      Furthermore, if the metatarsal support  136  is not integrally molded with the middle layer  108 , the desired mechanical or structural attachment means can be made after the three primary layers of the insert  100  are formed. It is also possible to manufacture an insert as described above without a lip region, such as an executive model, that slides into a dress shoe and does not provide the support described above with reference to the figures. In such an embodiment, a two or three layer insert, preferably a two layer insert, is the desired end product.  
       FIG. 6  shows a cross-sectional view of another implementation of an insert  600 . Insert  600  includes a protective layer  612  and a formed layer  608 . As above, protective layer  612  includes a material that is puncture resistant: for example, a metal (e.g., steel) or other (e.g., synthetic or ceramic) puncture resistant material. Rather than being adjacent to only a top surface of protective layer  612  (as illustrated in  FIG. 5 ), formed layer  608  is adjacent to both the top surface and outer perimeter formed layer  608  extends from a bottom  613  of insert  608 . Insert  600  further includes a lip  632 . Rather than extending from the top of protective layer  612 , lip  632  extends upward and outward from a bottom  613  of insert  608 .  
       FIGS. 7A and 7B  show perspective and cross sectional views of a system  740  that may be used to form an insert such as insert  600  of  FIG. 6 . System  740  may be a molding system such as an injection molding system.  
      System  740  may include a form  750 , with a recess  751  shaped and sized for forming insert  600 . A positioner  752  may be located in recess  751  to position protective layer  612  in recess  751 . System  740  may also include a complementary recess  760  shaped and sized so that formed layer  608  can be molded onto protective layer  612 .  
      Form  750  and/or positioner  752  may comprise, for example, iron or steel, and may be coated with a material such as Teflon (™). Positioner  752  may be a thin ring shaped and sized to fit protective layer  612 , so that when material for forming layer  608  is introduced into system  740 , the material is substantially prevented from flowing under the bottom of protective layer  612 . Although positioner  752  is shown as separate from form  750 , in some implementations, positioner  752  may be integrated with form  750 . Although the height of positioner  752  is shown as shorter than the thickness of protective layer  612  in  FIG. 7B , it may be either greater than, or the same as, the thickness of protective layer  612 .  
      An insert may be formed using a system such as system  740  of  FIG. 7  as follows. Protective layer  612  may be provided. For example, protective layer  612  may be formed by stamping stainless steel shim stock, as described above. Protective layer  612  may be formed in other ways; for example, it may be separately molded. Protective layer  612  may be positioned in positioner  752  of form  750 . In some implementations, at least one of form  750 , positioner  752 , and protective layer  612  may be held in place in system  740 ; for example, using one or more magnets.  
      A mold region comprising recess  751  and complementary recess  760  may be formed by bringing portion  742  and portion  743  of system  740  together. A material for forming formed layer  608  may then be provided to the mold region (e.g., injected into the mold region). The material flows around positioner  752 , which substantially prevents material from flowing under protective layer  612 . Thus, after forming, formed layer  608  of insert  600  is adjacent not only to a top surface  635  of protective layer  612 , but also a perimeter surface  639  of protective layer  612 , as shown in  FIG. 6  (there is initially likely to be a slight gap between the perimeter surface  639  of the protective layer and adjacent walls of the formed layer  608 ). The insert may be removed from the mold and further processed.  
      By making the insert  100  a separately added feature of a shoe, rather than integrating the protective qualities into the manufacture of the shoe, a number of benefits may be obtained. For example, an insert as described herein may achieve a greater surface area of protection of the foot than available systems. For example, in some implementations, the stainless steel sheet covers in excess of 90% of the bottom of a foot residing above the insert.  
      Additionally, implementations incorporating single layer stainless steel sheet is less costly to manufacture, and achieves a good balance between puncture resistance and comfort of use. Inserts according to implementations described herein may be used in any footwear, although they may be particularly beneficial for some uses. For example, our solution has considerable advantages for those who work in construction and industrial industries, or in environments where the risk of material puncturing a foot is high. We note that our invention is especially advantageous for diabetics, for whom a nail or other injury to the foot can prove fatal.  
      A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, different puncture resistant materials may be used for the protective layer. Different materials may be used for the formed layer as well. Additionally, the protective layer may be formed in other ways than those described herein.  
      Although the protective layer is referred to as a “bottom” layer in some implementations, it need not be the layer directly contacting the interior surface of the footwear upon insertion. For example, the bottom of the insert may be at least partially coated or covered with some material in some implementations. Similarly, a “top” layer need not be positioned at the very top of the insert. These terms are used to describe the positions of the layers in the exemplary embodiments illustrated. Accordingly, other implementations are within the scope of the following claims.