Patent Publication Number: US-2011072685-A1

Title: Integral insole with multiple areas of different resiliency and method of making the insole

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional Application No. 61/245,701 filed Sep. 25, 2009. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to insoles for shoes that are inserted in a shoe on top of a built-in insole or would replace a removable insole of the shoe. 
     2. Background Art 
     Shoes are generally constructed to include a sole and a built-in insole that is either cemented onto the sole of the shoe, or is removable. Insoles are inserted into shoes on top of the built-in insole or may replace the removable insole to provide additional cushioning and support in the shoe. Persons who may benefit from inserts may include runners, athletes, diabetics, and the like. 
     Generally, insoles are formed in one piece of either foam or an elastomeric material. One example of a foam material commonly used in the manufacture of insoles is ethylene vinyl acetate (EVA) foam that uses air pockets formed in situ in the material to create a cushioning effect. One problem with this type of material is that the EVA foam lacks durability and breaks down with each step. Multiple piece insoles have also been developed that provide cushioning areas formed of different compositions. 
     The above problem and other problems are addressed by Applicants as summarized below. 
     SUMMARY OF THE INVENTION 
     An insole is disclosed that includes a plurality of different areas to provide stable support and increased resiliency in localized areas of the insole. 
     The insole includes a body portion that is molded from a mixture of polyurethane and granulated cork. The body portion defines a metatarsal opening that extends completely through the body portion. A soft medical grade silicone insert is assembled to the metatarsal opening to provide resiliency and comfort for the metatarsal portion of a wearer&#39;s foot. The body portion constrains and stabilizes the silicone insert. A heel area referred to as the heel pod is molded from an elastomer material below a heel area of the body portion. The heel pod does not extend through the body portion, but is attached in a layered arrangement. A fabric cover layer is bonded to the top surface of the body portion and is cut away when the metatarsal opening is cut into the body portion. An interchangeable or removable arch support may be attached to the body portion to permit the insole to be adapted for use by persons having various foot arch heights. 
     According to another aspect of the disclosure, an insole for a shoe is provided that comprises a body that is configured to fit within the shoe that defines a heel recess that extends partially through the body in a heel area and a metatarsal opening that extends completely through the body in a metatarsal area. A heel insert is secured in the heel recess and a metatarsal insert secured in the metatarsal opening. 
     According to another aspect of the disclosure, an insole for a shoe is provided that comprises a body having a bottom surface and a top surface defining a thickness. The body defines a heel recess that extends from the bottom surface and partially towards the top surface in a heel area. A metatarsal opening extends completely through the body in a metatarsal area. The metatarsal opening includes a metatarsal shoulder defined outboard the opening that has a depth less than the thickness of the body. A heel insert is secured to the heel recess, and a metatarsal insert is secured to the metatarsal opening and metatarsal shoulder. 
     According to other aspects of the disclosure, the body of the insole has a hardness of between 25 and 35 on the Shore A scale and the inserts have a hardness of less than 10 on the shore A scale. More specifically, the body of the insole may has a hardness of 30 on the Shore A scale and the inserts may have a hardness of 5 on the Shore A scale. The body of the insole may be formed of a mixture of polyurethane and cork particles. The inserts may be formed of medical grade silicone. 
     According to another aspect of the disclosure, the insole may further comprise an arch support attachment that is assembled to a lower surface of the body between the heel area and the metatarsal area. The arch support attachment may have a first surface feature and the body may have a second surface feature that cooperate to secure the arch support attachment to the body. The first surface feature may be a rib and the second surface feature may be a groove defined on a lower surface of the body. 
     According to further aspects that relate to the metatarsal opening, a metatarsal wall may be at least partially defined about the periphery of the metatarsal opening. The metatarsal opening wall extends from a top surface of the body to a bottom surface of the body. The metatarsal insert is adhered to the metatarsal opening wall. The metatarsal opening includes a metatarsal area shoulder defined outboard of the metatarsal opening that has a depth that is less than the thickness of the body in the metatarsal area. The metatarsal insert includes a step extending outwardly from the periphery of the metatarsal insert that is configured to adhere to the metatarsal area shoulder. 
     The heel recess includes a heel area shoulder defined outboard of a base area of the recess, that has a depth that is less than the depth of the base area. The heel recess extends from a bottom surface of the body and partially towards a top surface of the body. 
     The insole also may include a fabric layer that defines a cut-out portion and that is secured to the body with the cut-out portion being aligned with the metatarsal opening. The fabric layer may include a bamboo fiber. The fabric is adhered to a top surface of the body. 
     The insole may be a supplemental insole for a shoe that has an integral insole that is configured to fit within the shoe on top of an integral insole. Alternatively, the insole the shoe may have a removable insole and the insert may be configured to fit within the shoe to replace the removable insole. 
     An exemplary method of making the insole is summarized below. A clam shell injection mold having an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity may be used to manufacture the insole. A segment of fabric is pinned or otherwise attached to the upper portion of the mold spanning the upper mold cavity. An elastomeric material is injected into the heel pod forming portion of the lower mold cavity in the lower portion of the clam shell injection mold. A two-part reactive resin system is mixed with a quantity of granulated cork particles to form a body composition mixture. The body composition mixture is injected into the lower mold cavity and onto the elastomer in the heel pod portion. A molded interface is created between the heel pod elastomer and the body mixture composition above the heel pod. As the body composition mixture is injected, a metatarsal opening area is molded in the lower mold cavity. The segment of fabric is secured by laminate bonding to the top surface of the body portion. The metatarsal opening area and the fabric bonded to that area is trimmed to finish the metatarsal opening. A metatarsal insert is molded in the shape of the metatarsal opening in a separate molding operation. The metatarsal insert is then assembled to and bonded, or adhered, to the metatarsal opening. 
     According to another aspect of the method of making an insole, the method may be performed in an injection mold in which a first part and a second part of a reactive resin system is mixed with a quantity of cork particles to form a body mixture. The body mixture is injected into the injection mold and a body portion of the insole is molded to include a heel recess and a metatarsal opening area. A heel insert is molded from silicone in the shape of the heel recess. A metatarsal insert is molded from silicone in the shape of the metatarsal opening. The heel insert and metatarsal insert are attached to the heel recess and the metatarsal opening, respectively. 
     According to other aspects of the method, during the step of molding of the body portion a base and a heel wall are formed about the heel recess and a metatarsal wall is formed about the metatarsal opening. In addition, during the step of molding of the body portion, the heel insert is bonded to the base and the heel wall and during the step of attaching the metatarsal insert, the metatarsal insert is bonded to the metatarsal wall. 
     The method may be practiced in the injection mold that has an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity. The method may further comprise attaching a segment of fabric to the upper mold cavity wherein the segment of fabric is bonded to a top surface of the body portion. In addition, the segment of fabric may be trimmed to define an opening corresponding to the metatarsal opening in the body portion. 
     These and other aspects of the insole and method of making the insole developed by Applicants will be better understood in view of the attached drawings and the following detailed description of the illustrated embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of the bottom of a insole having multiple areas of different resiliency; 
         FIG. 2  is a top plan view of the insole shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along the line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a bottom plan view of the insole without an arch support attached; 
         FIG. 5  is a bottom plan view of the insole with an arch support attached to the arch support cavity of the insole; 
         FIG. 6  is a perspective view of a small arch support insert; and 
         FIG. 7  is a perspective view of a large arch support insert. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring to  FIG. 1 , a insole  10  is illustrated with its component parts separated from the insole  10 . Insole  10  includes a body portion  12  that is formed of a mixture of polyurethane and granulated cork particles. It should be understood that the body portion may be formed from another mixture of material that offers similar resiliency and strength characteristics. The body portion  12  in the illustrated exemplary embodiment is made from a polyurethane foam or elastomer having a hardness in the range of 20 to 50 on the Shore A scale. More specifically, the hardness range may be between 25 and 36 on the Shore A scale with the optimum hardness believed to be about 30 on the Shore A scale. The polyurethane foam is a two-part polyurethane including polyol and isocyanate and a blowing agent that are blended with granulated cork particles that increase the hardness of the mixture after curing. The granulated cork particles are preferably 14/30 mesh granulated cork. The hardness of body portion  12  can be controlled by increasing the amount of cork added to the mixture. The cork is preferably 20% by weight of the mixture. The mixture is blended and then pumped to a mix head that injects the mixture into the mold. 
     The granulated cork particles have a honeycomb arrangement of cells that comprise complex fatty acids that are filled with compressed air-like gas. The granulated cork particles may be compressed to about half of their depth without losing flexibility. The cork particles also provide the unique ability to be compressed in one direction without increasing size in another direction. When the granulated cork particles are mixed with polyurethane, the cured mixture may be cut, shaped or shaved to the desired dimensions. In this way, the body portion  12  that is made from the cured mixture of polyurethane and granulated cork particles may be shaped to provide a customized insert that is adapted to the dimensions of a user&#39;s foot and to fit into a shoe. 
     The polyurethane base in the body portion  12  offers resiliency that provides energy return when compressed. Polyurethane is durable and resists permanent deformation after repeated compression to offer a user many years of comfort and support. 
     A metatarsal insert  16  is preferably made from silicone and is formed in an arcuate, or boomerang, shape to conform to the metatarsal and outer arch portion of a user&#39;s foot. The metatarsal insert  16  extends from the top to the bottom surface of the insert  10 . The metatarsal insert  16  may be made of medical grade liquid silicone rubber. The hardness of the insert may range from 1 to 25 on the Shore A scale. More specifically, the silicone rubber may have a hardness of 1-9 on the Shore A scale and most preferably has a hardness of about 5 on the Shore A scale. 
     The inserts are intended to replicate the hardness of the natural fatty tissue on a young person&#39;s foot that sometimes diminishes with age. The silicone provides superior rebound resilience so that the metatarsal insert  16  returns to its original shape after compression. The silicone absorbs shock and displaces the energy away from the point of impact. The body portion  12  constrains the periphery of the metatarsal insert  16 . The functional characteristics of the medical grade silicone are believed to offer more comfortable support of the metatarsal portion of a person&#39;s foot. The medical grade silicone is also less likely to cause irritation to the wearer&#39;s skin. 
     A heel pod  18  is preferably formed of an elastomer, such as polyurethane or silicone. The heel pod  18  may be made from polyurethane elastomer having a hardness in the range of 5 to 50 on the Shore A scale. More specifically, the hardness range may be between 5 and 25 on the Shore A scale with the optimum hardness being about 10 on the Shore A scale. The heel pod  18  may be made of an elastomer such as liquid polyurethane (non-foamed). 
     The heel pod  18  is provided below the rear part of the body portion  12 . The cured polyurethane and cork mixture provides a durable heel landing area that benefits from a softer feel provided by the elastomer forming the heel pod  18 . The insole  10  is preferably convex in shape to form a heel receiving area for a user&#39;s foot. The heel cup area cradles the heel of a user&#39;s foot aligning the natural shock absorbing pad under the heel bone of a user&#39;s foot with the heel pad  18 . Optimal padding, including the natural shock absorbing pad and the insole should be at least 14 mm in depth to correctly pad and stabilize the heel during the striking phase of the human step. 
     A removable or replaceable arch support  20  is also shown in  FIG. 1 . 
     The removable arch support is preferably made of the same material as the body portion  12 . That is, a cured polyurethane and granulated cork mixture. The functionality of the insole  12  may be improved by providing customized arch supports. Different arch supports may be provided to accommodate different heights and lengths of the arch of a user&#39;s foot. Arch supports must be easily assembled to the body portion  12  and secured by a durable securing mechanism. The arch support may be attached or adhered to the base of the insole in various ways. The preferred connection mechanism will be described with reference to  FIGS. 4-7  below. Ideally, the arch support  20  is configured to conform, as closely as possible, to the natural arch of a user&#39;s foot. 
     A cover  22  is shown below the body portion  12  in  FIG. 1 , but it should be understood that the cover  22  is on the top of the insole  10  in use. The cover  22  extends across the full length and width of the insole  10  and is bonded or otherwise adhered to the upper surface of the body portion  12 . The cover  22  may be a fabric selected to absorb and evaporate moisture quickly. The cover may be made of a moisture managing fabric that may be made of about 75% polyester and about 25% natural bamboo fibers. Bamboo or other similar natural material is preferred because of its natural anti-bacterial and anti-fungal properties that naturally neutralize odors. The fabric cover  22  must be flexible to allow it to conform and remain adhered to the different parts of the insole  10 . A binder may be laminated to the fabric cover  22  to promote adhesion and sealing. The binder fabric may also function to prevent the polyurethane mixture from penetrating through the fabric cover  22  during manufacture or use. 
     A metatarsal opening  24  is provided in the body portion  12  within which the metatarsal insert  16  is received. The metatarsal opening  24  is arcuate, or “boomerang” shaped, and receives the metatarsal insert  16 . An overhanging flange  26 , or first step, is provided around the periphery of the metatarsal opening  24  and a second step  30  may be provided around the metatarsal opening  24  and adjacent to the overhanging flange  26 , or first step. The cover  22  may have a cut-out portion aligned with the metatarsal opening  24 . 
     The metatarsal insert  16  has a full thickness portion  34  comprising the portion that is inboard of the flange  26 . The reduced thickness portion  36  of metatarsal insert  16  is received by the flange  26  and step  30 . The reduced thickness portion may have one or two steps depending upon the configuration of the metatarsal opening  24 . The reduced thickness portion  36  is bonded by an adhesive or solvent to the body portion  12  in the area of the first and second steps  26  and  30 . 
     Referring to  FIGS. 2 and 3 , the insole  10  is shown as it appears after molding and trimming, but prior to assembly of the metatarsal insert  16 . A fragmentary portion of the cover  22  is shown in  FIG. 2 . The cover  22  includes a plurality of vent holes  38  in the area located below a user&#39;s foot arch. The heel pod  18  is shown as it is secured to the body portion  12 . A rear edge  40  of the heel portion is an arcuate area that conforms to the shape of the body portion  12  on the rear edge of the body portion. An arcuate groove  42  is provided between the front of the heel pod  18  and the portions of the body portion  12  located in front of the heel pod  18 . A heel cup  44 , as best shown in  FIG. 3 , is provided in the body portion above the heel pod  18 . The heel cup  44  is concave in shape and curved to conform to the user&#39;s foot. A molded interface  46  is provided between the heel pod  18  and body portion  12 . The heel pod  18  is initially formed by injecting elastomeric material into an injection mold to form the heel pod  18 . Subsequently, the polyurethane and granulated cork mixture is injected into the mold. The polyurethane and cork mixture of the body portion  12  bonds to the heel pod  18  to secure the body portion  12  and heel pod  18  together. 
     Referring to  FIGS. 4 and 5 , the fully assembled insole  10  is shown. In  FIG. 4 , no arch support  20  is provided. In  FIG. 5 , a small arch support is shown assembled to the insole  10 . Referring to  FIG. 4 , an arch support cavity  48  is shown between the metatarsal insert  16  and the heel pod  18 . 
     Referring to  FIGS. 6 and 7 , two different sized arch supports  20  are shown. A small arch support  20 ′ is shown in  FIG. 6  and a large arch support  20 ″ is shown in  FIG. 7 . 
     Referring to  FIGS. 4-7 , the arch supports  20 ′,  20 ″ have a convex upper surface  50  that is received in a face-to-face relationship in the arch support cavity  48 . A plurality of transverse ribs  52  and a longitudinal rib  54  are formed on the convex upper surface  50 . The ribs,  52  and  54 , are received in an interference fit in a plurality of transverse grooves  56  and a longitudinal groove  58  formed in the arch support cavity  48 . In the illustrated embodiment, the ribs are provided on the convex upper surface  50  of the arch support  20 , but the ribs could be provided in the arch support cavity  48  with the grooves being provided in the convex upper surface  50  of the arch support  20 . The ribs and grooves interlock to prevent the arch support  20  from shifting either in a lateral or a longitudinal direction. It should be understood that as used herein, the terms “lateral” and “longitudinal” are not to be construed in their strict directional sense, but indicate that they extend generally in the lateral or longitudinal direction, as illustrated. The arch support  20  may also be secured by means of an adhesive or glue to the arch support cavity  48 , either with or without the intersecting ribs and grooves. 
     The process used to manufacture the insole  10  is an injection molding process that is performed using a clam shell type of injection mold. The clam shell injection mold includes an upper portion that defines an upper mold cavity and a lower portion that defines a lower mold cavity. The cover material fabric is pinned to the upper portion of the mold and spans the upper mold cavity. A sheet of thermo-formed plastic with embedded releasing agent is used to conform to the overall shape and defines the heel pod  18 , arch area  48  and metatarsal opening  24  shape. The thermo-formed plastic with embedded releasing agent is inserted into the lower mold cavity of the lower portion of the mold. The thermo-formed plastic with embedded releasing agent is used to reduce tooling costs and increase mold life. The process could be performed without the use of the thermo-formed plastic form by molding directly on the lower mold cavity. 
     The injection mold is then closed and an elastomeric material that is preferably not foamed is injected into the heel pod forming portion of the thermo-formed plastic with embedded releasing agent or lower mold cavity. Next, the two-part polyurethane foam including 20% by weight granulated cork particles is blended and then injected into the mix head that mixes the material before injection into the mold. The mixture is injected into the lower mold cavity and onto the elastomer that was previously injected into the heel pod portion. The body composition mixture and elastomer of the heel pod are bonded together in the course of the molding process with a molded interface being created between the heel pod elastomer and the body mixture composition. The mold or thermo-formed plastic with embedded releasing agent sheet generally define the shape of the metatarsal opening during the molding process to reduce waste of the body mixture composition. The mold defines flange areas that extend about the metatarsal opening area  24 . The flange area may have one or more steps  26 ,  30  to which the metatarsal insert is later adhered. The cover fabric is laminated to the top surface of the body portion  12  during the molding process. 
     After at least partially curing, the clam shell mold is opened and the body portion  12 , heel cup  18 , cover  22  and thermo-formed plastic with embedded releasing agent are removed from the mold. The metatarsal opening  24  is formed by cutting the molded body composition mixture and adhered cover fabric  22  in a die cutting operation. After the metatarsal opening  24  is formed in the body portion  12 , the metatarsal insert  16  is assembled to the metatarsal opening  24  and bonded or otherwise adhered to the flange  26  that may also include the second step  30 . The finished insert may be decorated with a heat transfer logo or the like. 
     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.