Abstract:
A composite outsole for a shoe, and a shoe incorporating a composite outsole, are provided. The outsole comprises an inner surface in contact with the shoe upper, and an outer surface in contact with the ground or other walking or running surface. The outsole includes multiple material regions and/or layers having characteristics, such as traction, durability, hardness, etc. The use of multiple materials for fabricating the outsole as an integral structure is designed to provide functional utility in a variety of different environments and when used under different conditions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/575,015, filed May 27, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Typical contemporary outsoles for footwear can be manufactured from a variety of materials of fabrication including natural and synthetic rubber, thermoplastic rubber, and polyvinylchloride. The outsoles fabricated from these materials can be conveniently manufactured using various molding processes including compression molding and injection molding.  
         [0003]     The decision as to the types of materials and material manufacturing processes to use for manufacturing outsoles depends on a number of factors including cost, expected durability, and end use. Shoes designed for running require high anti-abrasive outsole characteristics, suitable traction for running on asphalt, grass, and dirt paths, and sufficient compliance to provide adequate cushioning and resiliency. Work shoes need excellent support and stability characteristics, as well as resistance to water and common chemicals found on the worksite (fuel, oil, etc).  
         [0004]     The shape and size of an outsole is determined by a number of factors including shoe design, shoe type, the fabrication material used, and processing requirements. With compression molded rubber outsoles, the thickness of the outsole is limited to a minimum thickness in order to give the outsole the necessary strength characteristics that allow it to withstand the rigors of the manufacturing process. A compression molded outsole is extracted or “pulled” out of the compression mold after the molding process is complete. An outsole that is too thin would tear as it is removed from the compression mold. Injection molded outsoles have a minimum thickness based on the requirements of the injection mold and the viscosity characteristics of the material being injected into the mold.  
         [0005]     In many cases the minimum geometry requirements of an outsole are dictated by the manufacturing process and not the end use requirements. For instance, a typical compression molded outsole has a base thickness of 4 mm, with a lug thickness of an additional 4 mm. However, it is rare during normal use for the wearer to wear through all 8 mm of rubber. In an effort to save weight and manufacturing costs, the base thickness of the outsole could be reduced. However, this would make manufacturing defects more likely as the outsole is handled during the manufacturing process.  
         [0006]     It is important to note that in order to achieve the best performance properties of the outsole, the chemical composition of the outsole material should be based on the end use requirements. Outsoles that will be used on high abrasive surfaces should have antiabrasive qualities. Outsoles that will be used on slippery surfaces should be constructed from high traction compounds. Outsoles that that will be used as work or duty shoes should be constructed of materials that resist chemicals found in the workplace, and in some cases, resist the build up of electrostatic charges.  
         [0007]     In some cases, this specialization of outsole materials adds significant cost to the outsole. For instance, an outsole that needs to be resistant to fuel spills increases the cost by roughly 25% due to increased material costs. High traction rubbers typically add 20% to the cost of an outsole. Moreover, since the entire component is made from a homogeneous material, compounds that are chosen appropriately for particular end use requirements may fail to deliver optimal performance for other “shoe making” considerations. For instance, compounds that deliver the necessary performance based on the ground/shoe interface may not present the best properties for the outsole/shoe interface. Among other things, this interface requires excellent bonding properties between the outsole and the shoe upper.  
         [0008]     What is desired is an outsole that is designed to perform correctly in its end use, withstand the manufacturing process requirements, and be produced with an efficient cost model. Typically, the outsole material is uniform throughout the component and based primarily on end use specifications. Adjustments to the base thickness of the outsole may be dictated in order to meet the rigors of manufacturing. While this approach works successfully, in many cases it presents a situation where a single material specification, usually designed to meet the outsole to ground surface requirements, dictates the specification for the entire component. An optimized approach to manufacturing this component would utilize separate specifications for the portion of the outsole in contact with the ground as compared to the remainder of the outsole and, in particular, the outsole to shoe surface contact.  
         [0009]     The outsole-to-shoe surface or interface of an outsole has a different set of requirements than the outsole-to-ground surface. Abrasion and traction characteristics are most important for the outsole-to-ground surface. Material hardness and shoe upper bonding performance characteristics should dictate the material for the shoe/outsole surface. What is desired is an outsole that is made of multiple materials/layers that addresses the requirements of each particular layer or surface of the outsole.  
         [0010]     While it is common practice to construct an outsole with multiple colors for design aesthetics, the use of multiple materials for functional and manufacturing reasons has not been addressed by footwear manufacturers. Accordingly, it is desirable to provide an outsole fabricated from multiple materials designed for use in different environments and under different conditions. It is also desirable to provide an outsole that is optimized for performance and that can be produced more economically than a conventional outsole.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention relates to a composite outsole for a shoe, and a shoe incorporating the composite outsole. The shoe can be any manner of footwear, such as dress and casual shoes, loafers, hiking shoes and boots, athletic shoes including sneakers, running shoes, trail running shoes and the like, workboots, boat shoes, sandals, moccasins, etc. The outsole comprises at least two components including an inner surface in contact with the shoe upper, and an outer surface in contact with the ground or other walking or running surface.  
         [0012]     The outer surface of the outsole is constructed of materials that enhance performance to ground contact. Materials with high anti-abrasion and high traction are most desirable for the outer surface. Preferably, the outer surface is fabricated from materials designed to match the performance characteristics of the specific surfaces that the shoe will be used on. For instance, basketball shoes should use outer surface materials with high traction scores when tested on wooden surfaces. Rock climbing shoes should have high traction values on rock surfaces and abrasion characteristics that resist abrasion from rock. As explained in more detail herein, the outer surface of the outsole need not be a homogeneous material, and materials having different properties and characteristics can be included within the outer surface to optimize overall performance and to minimize costs.  
         [0013]     The inner surface of the outsole is joined or otherwise affixed to the shoe&#39;s upper by a suitable bonding agent (cement). The material on the inner surface of the outsole can be matched to the performance necessary to meet specific needs. In most cases, a less expensive material, such as an inexpensive grade of rubber, can be used on the inner surface of the outsole. This less expensive material should have the ability to adhere well to typical shoe upper materials, such as leather, fabric and synthetic leather.  
         [0014]     The outsole components can be fabricated by compression molding, injection molding, open pouring, painting, dipping and skim coating. Typical materials of fabrication include natural and synthetic rubbers, polyvinylchloride (“PVC”) and polyurethane (“PU”).  
         [0015]     In accordance with one embodiment of the present invention, an article of footwear is provided. The article of footwear comprises an upper and an outsole. The upper includes first and second sections. The first section is adapted to receive a foot and the second section is positioned beneath the foot. The outsole includes first and second surfaces in a unitary structure. The first surface comprises a first material adapted to contact a ground surface. The second surface comprises a second material joined to the second section of the upper. The second material is selected to include a qualitative characteristic different than a qualitative characteristic of the first material.  
         [0016]     In one alternative, the second material is selected to have a high degree of adhesion to the second section of the upper. In this case, the first material preferably has a greater traction coefficient than the second material. Optionally, the second material is less than about 1 mm thick.  
         [0017]     In another alternative, the first material includes first and second regions. The first region has a physical property selected from a first set of qualitative characteristics. The second region has a physical property selected from a second set of qualitative characteristics. The first set is different than the second set. In this case, the first region preferably has a greater traction coefficient than the second region. Optionally, the first region provides greater abrasion resistance than the second region. In another example, the first region provides greater cushioning than the second region. In a further example, the first region provides greater liquid resistance than the second region. In yet another example, the first region provides greater electrostatic discharge resistance than the second region.  
         [0018]     In accordance with another embodiment of the present invention, an outsole for use in an article of footwear is provided. The outsole comprises first and second surfaces in a unitary structure. The first surface comprises a first material adapted to contact a ground surface. The second surface comprises a second material joined to an upper of the article of footwear. The second material is selected to include a qualitative characteristic different than a qualitative characteristic of the first material.  
         [0019]     In one alternative, the first material includes first and second regions. The first region is selected to include a qualitative characteristic different than a qualitative characteristic of the second region. In this case, the first region is preferably completely surrounded by the second region. In another alternative, the first material is at least about 3 mm thick and the second material is less than about 1 mm thick.  
         [0020]     In accordance with yet another embodiment of the present invention, a method of fabricating an outsole of an article of footwear is provided. The method comprises forming a first layer of material having a first surface for connection to an upper portion of the article of footwear. The first material layer is selected based upon a first qualitative characteristic. The method also comprises applying a second layer of material to the first layer. The second material layer is selected based upon a second qualitative characteristic different than the first qualitative characteristic of the first material layer.  
         [0021]     In one alternative, applying the second layer comprises a process selected from the group consisting of compression molding, injection molding, open pouring, and painting. In another alternative, applying the second layer comprises skim coating the second layer onto the first layer. In a further alternative, applying the second layer comprises a dipping process. In yet another alternative the second layer is less than about 1 mm thick.  
         [0022]     In another alternative, the method further comprises applying a third layer of material as the first surface of the first material layer remote from the second material layer. The third material layer is qualitatively different from the second material layer. In addition, the third material layer is selected to have a high degree of adhesion to the upper portion of the article of footwear and is no greater than 1 mm thick. The second material layer is selected to have a greater coefficient of friction than the third material layer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a side sectional view of one embodiment of the outsole of the present invention  
         [0024]      FIG. 2  is a bottom view of one embodiment of the outsole of the present invention.  
         [0025]      FIG. 3  is a side sectional view of another embodiment of the outsole of the present invention.  
         [0026]      FIG. 4  is a shoe employing an outsole in accordance with aspects of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0027]     Referring to the figures,  FIG. 1  is a side sectional view of outsole  10  in accordance with an aspect of the present invention. Outsole  10  is preferably formed from a natural or synthetic rubber, with the outsole  10  divided into at least two distinct material areas or regions. The distinct material areas are desirably part of the same physical structure and are not manufactured as two physically separate components that are later adhered together. In contrast, these material areas are preferably integrally formed or otherwise fabricated as a unitary structure absent of intermediary bonding agents or materials. In a preferred embodiment, one region is an inner surface  20 , and another is an outer surface  30 .  
         [0028]     The inner surface  20  is prepared from a first material and the outer surface or tread area  30  is prepared from a second material. The first material can be the same or different from the second material. Suitable materials of fabrication include rubber, both the natural and synthetic varieties, polyvinylchloride, polyurethane, and other synthetic elastomeric materials. While the first and second materials can be the same, the materials desirably have different qualitative characteristics, such as stiffness, hardness, or roughness. Other qualitative characteristics include performance characteristics such as durability, traction, wear resistance, abrasion or scuff resistance, heat dissipation, adhesion or bonding to other materials, cushioning, stability, liquid repellant or impermeability, and the like. By way of example only, liquid repellant and impermeability traits include resistance to chemicals, fuels, lubricants, human or animal fluids, degreasing agents, etc. Materials may be selected based on one or more characteristics, including any combination of same. Materials may also be selected in view of other considerations such as cost, ease of manufacturing, inventory availability, etc. The materials may have the same or different colors. However, as color is not a material attribute as far as the physical properties or characteristics of the outsole are concerned; color is not a qualitative characteristic in accordance with the present invention.  
         [0029]     Inner surface  20  is depicted containing a first material that is designed to be attached to the shoe upper materials, such as by bonding well to the shoe upper materials, and preferably selected to be less expensive than the second material, such as a lower grade material than the second material.  
         [0030]     The outer surface  30  provides the shoe/ground contact surface, and this surface is made from a second material. The second material is preferably selected based on its performance characteristics, such as traction and abrasion. The traction coefficient of the second material of the outer surface  30  is preferably greater than the traction coefficient of the first material of the inner surface  20 . As used herein, the term “ground” is intended to mean a surface which contacts the outer surface of the outsole, and includes, without limitation, pavement, soil, wood, concrete, asphalt, grass, rock, mixed terrain, carpeting, tile and the like.  
         [0031]     The inner surface  20  need not be as thick as the outer surface  30 . In a preferred example, the inner surface  20  is less than about 2 mm thick. More preferably, the inner surface  20  is on the order of 1 mm thick or less, for example between 0.25 mm and 0.85 mm. The inner surface  20  can be thinner than the outer surface  30  because the inner surface  20  is not subject to the same wear and tear due to contact with the ground. The outer surface  30  may be, for example, at least 2 mm thick. In many cases, the outer surface  30  may be on the order of 4 mm or thicker.  
         [0032]      FIG. 2  is a bottom view of an outsole  40  in accordance with another aspect of the present invention. The figure shows the outsole outer surface. The major portion of the outsole outer surface which contacts the ground comprises a first material  60 . This material is selected primarily based on cost and its ability to withstand the rigors of the outsole manufacturing process. At least one second material  50  is strategically placed within the outsole outer surface. The second material  50  is selected based on one or more performance factors such as traction, abrasion, cushioning properties, fuel resistance, electrostatic discharge, and the like. By way of example only, the second material  50  has a greater traction coefficient than the first material  60 . The second material  50  preferably directly connects to the first material  60  without any intervening bonding agents or materials. In a preferred embodiment, at least one region of second material  50  is completely surrounded by the first material  60 . The identified specialized materials or areas  50  within the outsole outer surface are designed to have the most interaction with the ground, and, therefore, present the best opportunity for improving shoe/ground performance by optimizing traction, cushioning, stability, etc. By using a heterogeneous approach to material placement, increased performance can be achieved without large cost increases. This heterogeneous approach is preferably part of a single manufacturing process forming the outsole. Benefits such as cost savings, time savings, structural stability, etc. can be achieved in such a manufacturing process, in contrast with multiple processes for fabricating each material layer or area separately and subsequently gluing the components together in the outsole.  
         [0033]     As depicted in  FIG. 2 , more than two materials can be advantageously used to construct the shoe outsole according to the present invention. A first material can be used as the base material  20 , forming the shoe/upper interface, a second material  60  can be used to form the base of the shoe/ground interface, and a third material  50  can be strategically placed in certain areas of the shoe/ground interface. One or more regions of the third material  50  may be partly or completely surrounded by the second material  60 . Alternatively, the third material  50  may form part of or the entire perimeter of the outsole  10 , and may partly or substantially surround the second material  60 .  
         [0034]      FIG. 3  is a side view section of outsole  80  in accordance with yet another aspect of the present invention.  FIG. 3  is similar to  FIG. 1 , except that  FIG. 3  depicts an outsole with heterogeneous layers of material  90  and  110  applied by using a painting, dipping, or skim coating process to each of the surfaces of the outsole. The outer layers of material  90  and  110  can be advantageously less than 1 mm or no greater than 4 mm in thickness, for example. In a preferred example, one or both of the layers  90 ,  110  are less than about 0.85 mm. In this example, one or both of the layers  90 ,  110  are desirably between 0.25 mm and 0.75 mm. The application of these thin layers  90 ,  110  can be optimized to adhere to the surface of the outsole  80 .  
         [0035]     The portion  90  of the outsole that is in contact with the shoe upper can be made from materials designed to increase bonding strength between the outsole  80  and the upper. The layer applied to the outsole surface that interfaces with ground  110  can be designed to enhance the frictional coefficient between the shoe and ground surface, and therefore, improve traction. Alternatively, layer  110  can also comprise a material very similar to the remainder of the outsole  80 , but the application of this layer can differ in texture, and therefore provide improved traction by enabling in effect a mechanical interlock between the textured outsole outer surface and the ground. The outsole outer surface  110  can also be fabricated from a material designed to provide protection against chemicals or other substances that would damage the remainder of the outsole  80 .  
         [0036]     Outsoles of the present invention can be fabricated in numerous ways. By way of example only, techniques including compression molding, injection molding, open pouring, painting, dipping and/or skim coating may be utilized. Numerous materials are suitable when forming the outsole layers and/or regions of the present invention. For instance, natural or synthetic rubbers, PVC, and/or PU may be used.  
         [0037]     Once the outsole is fabricated, it may be joined or otherwise affixed to the shoe&#39;s upper by a suitable bonding agent, e.g., cement.  FIG. 4  illustrates a shoe  200  including the outsole  10  affixed to upper  210 . As shown, region  220  connects the outsole  10  to the upper  210 . The region  220  may be integral with the upper  210 , or may comprise a separate midsole, a lasting board, etc. Alternatively, the outsole  10  may directly connect to the upper  210 .  
         [0038]     The material on the inner surface  20  of the outsole  10  can be matched to the performance necessary to meet specific needs of the shoe  200 . Such needs may be based on performance, cost, ease of manufacture, etc. In most cases, a less expensive material, such as an inexpensive or lesser grade of rubber, can be used on the inner surface  20  of the outsole  10 . This less expensive material should have the ability to adhere well to typical shoe upper, midsole or lasting board materials, such as leather, fabric and synthetic leather.  
         [0039]     While this invention has been particularly shown and described with reference to certain preferred embodiments thereof, these particular embodiments are illustrative, and it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.  
         [0040]     The features of any of the embodiments disclosed herein may be utilized with any of the features of other embodiments of the invention. By way of example only, the outer surface  30  may have one or more areas of the first material  60  and one or more materials of the second material  50  therein. Each material may be selected to have one or more different qualitative characteristics, such as stiffness, hardness, roughness, durability, cushioning, stability, traction, wear resistance, abrasion or scuff resistance, heat dissipation, adhesion or bonding to other materials, cushioning, stability, liquid repellant or impermeability, etc. One material may be selected from a group consisting of a first set of qualitative characteristics, and another material may be selected from a group consisting of a second set of qualitative characteristics. The sets may overlap or have no overlap of members.