Abstract:
A method for making an article of footwear is disclosed. The method can include a number of steps where various molds are used to attach or mold a tread element onto a substrate or matrix lining. The tread element can be formed by compressing a rubber block between various molding members to cause the resulting rubber material to flow through at least one injection cavity, which penetrates through holes in the matrix lining, into at least one lug cavity disposed on the side of the matrix lining opposite to the injection cavity. The rubber material eventually enters the lug cavity and becomes attached to the matrix lining.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to articles of footwear, and in particular to a method for creating outsoles. 
     2. Description of Related Art 
     Methods for constructing a tread assembly, which is a set of rubber projections fixed in place to a thin and flexible matrix lining, such as those used for shoe outsoles, have been previously disclosed. 
     Fram (U.S. Pat. No. 6,032,388) discloses a method in which an inelastic sheet material is provided with a pattern of perforations through it, and a plurality of tread elements are created. The sheet material is placed in a molding machine with tread forming cavities below the sheet material. Following this, tread material is injected into tread forming cavities. The tread forming material flows out of the tread forming cavities and through the perforated sheet material into molding cavities which have been secured just under the sheet material. The tread is injected through the perforations in such a manner so that some of the resultant tread elements have anchoring portions extending through the sheet material from an opposite side of the material. 
     Hiraoka (U.S. Pat. No. 6,562,271) discloses a method in which a male and female mold are engaged with each other in order to form a nonslip member, composed of a base fabric and nonslip convexes. The nonslip convex includes a peripheral edge that reinforces anchoring between the nonslip convex and the base fabric. A plate-like material is inserted between the male and female molds, and by engaging these molds a large number of small pieces coincident to a shape of through holes of the female mold are punched out from the plate-like material. These small pieces are then bridged and fixed to the base fabric to serve as the tread of the non-slip member. This method of manufacturing tread elements includes multiple steps. 
     There is currently a need for a method for making a tread assembly that is more efficient, while at the same time, allowing for a great deal of variation or flexibility in terms of the composition of the material that will eventually compose the tread assembly. In particular, a method is needed that can reduce the number of steps used in manufacturing a tread assembly, even complex tread assemblies. 
     SUMMARY OF THE INVENTION 
     The invention discloses a method of making a tread assembly. In one aspect, the invention includes a method of making an article of footwear comprising the steps of: associating a matrix lining with a first side of a central mold, a first surface of the matrix lining confronting the first side of the central mold, the matrix lining also including a second surface disposed opposite the first surface; placing a rubber forming block proximate a second side of the central mold; compressing the rubber forming block and causing a portion of the rubber forming block to become viscous and flow through at least one injection cavity disposed in the central mold; where the portion of the rubber forming block continuing to flowing through a hole disposed in the matrix lining and flowing into a lug cavity; and where the portion of the rubber forming block fills the lug cavity and contacts the second surface of the matrix lining. 
     In another aspect, the step of compressing the rubber forming block includes a step of moving a molding press towards the central mold. 
     In another aspect, the portion of the rubber forming block that fills the lug cavity does not extend beyond the first surface of the matrix lining. 
     In another aspect, the lug cavity is disposed on a molding base. 
     In another aspect, the portion of the rubber forming block becomes a tread element. 
     In another aspect, the matrix lining is attached to an outsole of the article of footwear. 
     In another aspect, the invention includes a method of making an article of footwear comprising the steps of: associating a matrix lining with a first side of a central mold, a first surface of the matrix lining confronting the first side of the central mold, the matrix lining also including a second surface disposed opposite the first surface; placing a first rubber forming block proximate a second side of the central mold; placing a second rubber forming block proximate the second side of the central mold, wherein the second rubber forming block is different than the first rubber forming block; compressing the first rubber forming block and causing a first portion of the first rubber forming block to become viscous and flow through a first injection cavity disposed in the central mold; compressing the second rubber forming block and causing a second portion of the second rubber forming block to become viscous and flow through a second injection cavity disposed in the central mold; where the first portion of the first rubber forming block fills a first lug cavity and contacts the second surface of the matrix lining, and where the second portion of the second rubber forming block fills a second lug cavity and contacts the second surface of the matrix lining. 
     In another aspect, the step of compressing the rubber forming block includes a step of moving a molding press towards the central mold. 
     In another aspect, the first rubber forming block is placed in first central cavity indent and wherein the second rubber forming block is placed in second cavity indent. 
     In another aspect, a first pressing surface disposed on molding press is configured to engage first central cavity indent and wherein a second pressing surface disposed on the molding press is configured to engage second central cavity indent. 
     In another aspect, the first lug cavity is laterally spaced from the second lug cavity. 
     In another aspect, the first and second lug cavities are disposed on a molding base. 
     In another aspect, the matrix lining is attached to an outsole of the article of footwear. 
     In another aspect, the invention includes a method of making an article of footwear comprising the steps of: placing a first rubber forming block proximate a second side of the central mold and placing a second rubber forming block proximate the second side of the central mold, wherein the second rubber forming block is different than the first rubber forming block; compressing both the first rubber forming block and the second rubber forming block simultaneously; thereby causing a first portion of the first rubber forming block to become viscous and flow through the matrix lining and also causing a second portion of the second rubber forming block to become viscous and flow through the matrix lining. 
     In another aspect, the first portion of the first rubber forming block flows through a first injection cavity after the compression step. 
     In another aspect, the second portion of the second rubber forming block flows through a second injection cavity after the compression step. 
     In another aspect, the first rubber forming block is harder than the second rubber forming block. 
     In another aspect, the first rubber forming block has a different color than the second rubber forming block. 
     In another aspect, the first rubber forming block has a different composition than the second rubber forming block. 
     In another aspect, the matrix lining is attached to an outsole of an article of footwear. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the invention, and be protected by the following claims 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a schematic diagram of a preferred embodiment of a molding system; 
         FIG. 2  is a schematic diagram of a preferred embodiment of a molding system with matrix lining attached; 
         FIG. 3  is a schematic diagram of a preferred embodiment of a molding system with molding base compressed against central mold; 
         FIG. 4  is a schematic diagram a preferred embodiment of the compression of molding press with central mold; 
         FIG. 5  is a schematic diagram a preferred embodiment of a tread assembly; 
         FIG. 6  is a preferred embodiment of a shoe with tread assembly displayed as an outsole; 
         FIG. 7  is a schematic diagram of a preferred embodiment of a molding system; 
         FIG. 8  is a schematic diagram of a preferred embodiment of a molding system with matrix lining attached; 
         FIG. 9  is a schematic diagram of a preferred embodiment of a molding system with molding base compressed against central mold; 
         FIG. 10  is a schematic diagram of a preferred embodiment of the compression of molding press with central mold; 
         FIG. 11  is a schematic diagram of a preferred embodiment of a tread assembly; 
         FIG. 12  is a preferred embodiment of a shoe with tread assembly displayed as an outsole; 
         FIG. 13  is a schematic diagram of a preferred embodiment of a molding system with matrix lining attached; 
         FIG. 14  is a schematic diagram of a preferred embodiment of the compression of the molding press with the central mold; and 
         FIG. 15  is a schematic diagram of a preferred embodiment of a tread assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A method for creating a tread assembly is disclosed. In particular, this tread assembly may be used as an outsole for an article of footwear. The tread assembly is made of a matrix lining that is joined to rubber projections to provide lightweight grip and support. In some embodiments, the matrix lining may be a synthetic fabric, for example. In many cases, it will be important that the matrix lining be thin, flexible, durable, and lightweight. The tread elements may be convex in shape, but any three dimensional shape is possible. This tread assembly could be used in any kind of footwear. This tread assembly is certainly not limited to shoe outsoles, as it may be used to form elements that provide extra grip in gloves in some embodiments. 
       FIG. 1  is a schematic diagram of a preferred embodiment of a manufacturing system  100  that can be used to create a tread assembly. Molding press  102  is disposed adjacent to central mold  104 . Molding press  102  includes press extension  103 . Press extension  103  includes a pressing surface  199  that extends towards central mold  104 . Press extension  103  is formed by first extension wall  120  and second extension wall  122 . Press extension  103  can also include other extension walls as well. In particular, press extension  103  may include a forward and rear wall, not seen in this schematic diagram of molding press  100 . Press extension  103  corresponds to a central cavity  106  disposed in central mold  104 . In a preferred embodiment, central cavity  106  is disposed on the second side  190  of central mold  104 . Central cavity  106  includes first central cavity wall  124  and second central cavity wall  126  along with central cavity floor  128 . Central cavity  106  may also include a forward wall and rear wall that are not shown in this schematic diagram of molding system  100 . Molding press  102  may move independently of central mold  104 . 
     On a first side  191  of central mold  104 , molding base  108  is disposed near central mold  104 , forming gap  110 . The distance between molding base  108  and central mold  104  can be varied. In particular, both molding press  102  and molding base  108  can be moved closer to central mold  104 , in some cases molding press  102  and molding base  108  can be moved to contact central mold  104 . In some embodiments, the items comprising manufacturing system  100  can be made of a metallic material. 
     Central mold  104  includes first injection cavity  112  and second injection cavity  113 . First injection cavity  112  includes first injection tip  187 , which protrudes from central mold  104 . Second injection cavity  113  includes second injection tip  188 , which protrudes from central mold  104 . Preferably, first injection cavity  112  is in fluid communication with central cavity  106  via first upper orifice  136 . First injection cavity  112  is also in fluid communication with gap  110  via first lower orifice  130 . This arrangement allows a liquid or viscous substance to pass between central cavity  106  and gap  110 , through first injection cavity  112 . Likewise, second injection cavity  113  is preferably in fluid communication with central cavity  106  by way of second upper orifice  138 . Second injection cavity  113  is also in fluid communication with gap  110  by way of second lower orifice  132 . This arrangement allows a liquid or viscous substance to pass between central cavity  106  and gap  110 , through second injection cavity  113 . 
     The diameters of first lower orifice  130  and second lower orifice  132  are constrained by two competing factors. The first factor relates to the amount of flow between first injection cavity  112  and gap  110 . The larger the diameter, the better the flow. However, a second factor must also be considered. In order to obtain an aesthetically pleasing tread element, one that has a minimal amount of excess material or obvious signs of first lower orifice  130 , the diameter should be kept as small as possible. In some embodiments, first lower orifice  130  and second lower orifice  132  may comprise diameters less than 3 mm. In a preferred embodiment, first lower orifice  130  and second lower orifice  132  may comprise diameters between 0.5 mm and 1.5 mm. In the embodiment shown here, the diameter of first lower orifice  130  and second lower orifice  132  is 1 mm. Throughout the rest of this specification, any orifice that allows for fluid communication between an injection cavity and a gap, disposed between a central cavity and a molding base, comprises a diameter of 1 mm. 
     Molding base  108  includes first lug cavity  114  and second lug cavity  115 . First lug cavity  114  and the second lug cavity  115  are exposed to gap  110  via first lug opening  197  and second lug opening  198 . In the embodiment shown in  FIG. 1 , first lug cavity  114  and second lug cavity  115  are rectangular, however these cavities can assume any shape including but not limited to typical shapes found on the outsoles of many shoes. In addition, molding base  108  is equipped with first lining recess  116 , second lining recess  117  and third lining recess  119 . 
     In  FIG. 1 , only two injection and lug cavities are shown, however in some embodiments many more injection and lug cavities may be included. In particular, first injection cavity  112  and first lug cavity  114  may be associated with a set of injection and lug cavities which may extend in the direction perpendicular to molding system  100  as seen in  FIG. 1 . 
     Referring to  FIG. 2 , a preferred embodiment of a step for making a tread assembly is shown. First, a matrix lining  202  is associated with central mold  104 . In particular, a first side  220  of matrix lining  202  is disposed against first side  191  of central mold  104 . A second surface  222  of matrix lining  202  is disposed to face gap  100 . The placement of matrix lining  202  against central mold  104  can be achieved by sliding matrix lining  202  into place through gap  110 , or by first moving molding base  108  away from central mold  104  and then returning molding base  108  after matrix lining  202  has been added. It may be preferable to fix matrix lining  202  in place to assure proper alignment with first lug cavity  114  and second lug cavity  115 . In some embodiments, matrix lining  202  may be clamped to central mold  104  or held in place with an adhesive. 
     In some embodiments, matrix lining  202  can include holes. In some embodiments, these holes in matrix lining  202  can be associated or aligned with a corresponding injection tip disposed on central mold  104 . 
     Matrix lining  202  represents any suitable material. In some embodiments, matrix lining  202  may be composed of any of the following materials, either singularly or as a composition of two or more of the following materials: un-buffered textile, leather, synthetic material, suede, or an open mesh. In general, matrix lining  202  may be composed of any type of material used in manufacturing uppers. In a preferred embodiment, matrix lining  202  is composed of a buffered textile. Throughout the specification other matrix linings may also be composed of these materials. 
     Referring to  FIG. 2 , first injection tip  197  may be inserted through first lining hole  206 . Second injection tip  198  may also be inserted into through second lining hole  204 . This allows for liquefied rubber to pass through matrix lining  202  into first lug cavity  114  and second lug cavity  115 . 
       FIG. 3  is a schematic diagram of a preferred embodiment of another step, where the movement of central mold  104  towards molding base  108  is accomplished. During this movement, portions of matrix lining  202  fill first lining recess  116 , second lining recess  117 , and third lining recess  119 . In some embodiments, portions of central mold  104  will be in contact with molding base  108  after this movement step. Preferably molding base  108  will be positioned with respect to central mold  104  in such a way that matrix lining  202  is exposed to first lug cavity  114  and second lug cavity  115 . 
     At this point, a rubber forming block  302  is preferably placed in central cavity  106 . Rubber forming block  302  may rest on central cavity floor  128 . This rubber forming block  302  may be any type of solid material that can enter first injection cavity  112  and second injection cavity  113  under the designed heat and pressure exerted by manufacturing system  100 . 
     Rubber forming block is generally composed of the kinds of rubber that are normally used to form the outsoles of shoes and other articles of footwear. In one embodiment, rubber forming block  302  is composed of Duralon©, which is a blown rubber having a specific gravity less than one. In other embodiments, other types of rubber may be used, including rubber compositions with a specific gravity greater than one. In some embodiments, rubber forming block  302  may be substituted with a block of any material that can flow and cure. That is, the block used to create tread elements need not be rubber. In general, materials with very high expansion rates and very high shrinkage rates are not suitable for this process. Therefore, any material with low expansion rates and low shrinkage rates, that can also flow and cure, are suitable. Throughout the specification, other rubber forming blocks that are disclosed may be composed of similar suitable materials. 
       FIG. 4  is a schematic diagram of a preferred embodiment of the compression of molding press  102  with central mold  104 . This compression, along with a heating process, liquefies rubber forming block  302 . This liquid is then pressed through first injection cavity  112  and second injection cavity  113 . Some of the liquid entering first injection cavity  112  eventually enters first lug cavity  114 , passing through first lining hole  206 , via first lower orifice  130 . Likewise, some of the liquid entering second injection cavity  113  eventually enters second lug cavity  115 , passing through second lining hole  204 , via second lower orifice  132 . Simultaneously, excess liquid can be gathered in first molding recess  118  and second molding recess  121 . In embodiments including first spring  181  and second spring  183 , these springs may be depressed during this step of compression. Preferably, enough liquid or viscous substance is supplied to fill first lug cavity  114  and second lug cavity  115  in such a manner that the liquid or viscous substance is in contact with portions of second side  222  of matrix lining  202 . 
     In a preferred embodiment of molding system  100 , first lug cavity rim  402 , which preferably extends around the entire periphery of first lug cavity  114 , is preferably in contact with matrix lining  202  under enough pressure so that no liquefied rubber escapes the region enclosed by first lug cavity rim  402 . In a similar manner, second lug cavity rim  404 , which preferably extends around the entire outer periphery of second lug cavity  115 , is preferably in contact with matrix lining  202  under enough pressure so that no liquefied rubber escapes the region enclosed by second lug cavity rim  404 . 
     Preferably, manufacturing system  100  includes provisions that provide a pressure relief or pressure imbalance so that excess pressure does not cause manufacturing defects. Some embodiments include first molding recess  118  and second molding recess  121 . These recesses can be used to collect excess molding material, for example liquefied rubber if rubber is used. First and second molding recesses  118  and  121  help to prevent excess rubber from seeping between any of the lug cavities and matrix lining  202 . 
     In other embodiments, first molding recess  118  and second molding recess  121  are replaced with springs. In a preferred embodiment, manufacturing system  100  may include a first molding spring  181  and a second molding spring  183 . First molding spring  181  may be disposed outward of first molding recess  118  or first molding spring  181  may replace first molding recess  118 . Second molding spring  183  may be disposed outward of second molding recess  121  or second molding spring  183  may replace second molding recess  121 . First molding spring  181  and second molding spring  183  are each preferably attached to central mold  104 . These molding springs  181  and  183 , preferably engage molding press  102  when molding press  102  is moved closer to central mold  104 . These springs  181  and  183  preferably act to create a pressure imbalance that creates narrow gaps between molding press  102  and central mold  104 . This allows excess liquid to escape through these narrow regions, as opposed to seeping between the lug cavities and matrix lining  202 . Throughout this specification, molding recesses may be replaced by a molding spring, thus providing the pressure imbalance function described here. 
     As the rubber material cools, it attaches to second side  222  of matrix lining  802 . After the cooling of the rubber material is complete, central mold  104  can be separated from molding base  108 , yielding tread assembly  502 , seen in  FIG. 5 . This separation can be performed by either lowering molding base  108  or raising central mold  104 . What remains is tread assembly  502 , which includes is matrix lining  202  adjoined with first tread element  504  and second tread element  506 . First tread element base  510  of first tread element  504  is no larger than the width of first lug cavity rim  402 , and second tread element base  512  of second tread element  506  is no larger than the width of second lug cavity rim  404 . 
     As some additional rubber material may be attached from rubber material which has solidified in first injection cavity  112  and second injection cavity  113 , some means of removing this excess material may be desired. It is unlikely however that such excess material will interfere with the performance of tread assembly  502 . In this particular embodiment, first rubber projection  504  and second rubber projection  506  are rectangular in shape but any shape can be made using first lug cavity  114  and second lug cavity  115 . Such shapes may include tetrahedrons, cylinders, or rectangles. Irregular shapes may also be used. Since the composition of rubber forming block  302  may be modified, the composition of first rubber projection  504  and second rubber projection  506  can likewise be modified. This is a useful attribute since some tread assemblies may require the use of more durable rubber, while others may require the use of more flexible material. 
     The size of lug cavities is also unrestricted in this method. Although first lug cavity  114  and second lug cavity  115  are identical in size and shape, this need not be true in other embodiments. Some embodiments may have lug cavities in a variety of shapes and sizes and lug cavities that are different from one another. 
     Tread assembly  502 , as seen in  FIG. 5 , includes only two tread elements. In other embodiments, tread assembly  502  may comprise a matrix lining with multiple tread elements. These tread elements could be simultaneously formed and joined to a matrix lining by modification of central mold  104  to include multiple injection cavities and lug cavities. 
       FIG. 6  is a preferred embodiment of an article of footwear  600 . Here, tread assembly  502  has been attached to article of footwear  600  to form a portion of tread pattern  602  of article of footwear  600 . Tread assembly  502  includes tread elements  504  and  506 . Tread assembly  502  is joined to article of footwear  600  by matrix lining  202 . Tread elements  504  and  506  are seen to be rectangular in this embodiment. Tread pattern  602  of article of footwear  600  can any design, including various shapes and sizes of tread elements. 
     In another embodiment, the tread assemblies can be varied in a number of ways. In some embodiments, different colored rubber forming blocks can be used simultaneously to create multi-colored tread elements. In other embodiments, several rubber blocks with different material composition can be used simultaneously. The resulting tread elements will likewise have varying colors and/or compositions within the same tread assembly. 
     This may be useful in designing outsoles where regions of tread that will be in contact with the ground most often must be made of a more durable rubber composition, while other regions that receive less wear can be designed with a more flexible rubber composition. Also, with aesthetics of particular importance in designing footwear, the ability to create a multi-colored tread in one step allows for more decorative patterns without a decrease in the production efficiency. 
       FIG. 7  is a schematic diagram of a preferred embodiment of a manufacturing system  700  used to create a tread assembly. Molding press  702  is disposed adjacent to central mold  704 . Molding press  702  preferably includes press extension  706 . Press extension  706  includes a first pressing surface  708  and a second pressing surface  710 , each extending towards central mold  704 . Press extension  706  is formed by first extension wall  712  and second extension wall  714 . Press extension  706  is preferably also composed of a forward and rear wall, not shown in the schematic diagram of this embodiment of manufacturing system  700 . Press extension  706  can also include other extension walls as well. Press extension  706  corresponds with a central cavity  716  disposed in central mold  104 . In a preferred embodiment, central cavity  716  is disposed on second side  780  of central mold  704 . Central cavity  716  includes first central cavity wall  718  and second central cavity wall  720  along with first central cavity indent  722  and second central cavity indent  724 . Central cavity  716  also preferably includes a forward and rear wall not shown in this schematic view of this embodiment of manufacturing system  700 . Molding press  702  may move independently of central mold  704 , and in some cases first pressing surface  708  and second pressing surface  710  may contact first central cavity indent  722  and second central cavity indent  724 . 
     On first side  781  of central mold  704 , a molding base  726  is disposed near central mold  704 , forming gap  728 . The distance between molding base  726  and central mold  704  can be varied. In particular, both molding press  702  and molding base  726  can be moved closer to central mold  704 , in some cases molding press  702  and molding base  726  can be moved to contact central mold  704 . In some embodiments the items comprising manufacturing system  700  can be made of a metallic material. 
     Central mold  704  includes first injection cavity  730  and second injection cavity  732 . First injection cavity  730  includes first injection tip  787 , which protrudes from central mold  704 . Second injection cavity  732  includes second injection tip  788 , which protrudes from central mold  704 . Preferably, first injection cavity  730  is in fluid communication with central cavity  706  via first upper orifice  790 . First injection cavity  730  is also in fluid communication with gap  728  via first lower orifice  794 . This arrangement allows a liquid or viscous substance to pass between central cavity  706  and gap  728 , through first injection cavity  730 . Likewise, second injection cavity  732  is preferably in fluid communication with central cavity  706  by way of second upper orifice  790 . Second injection cavity  732  is also in fluid communication with gap  728  by way of second lower orifice  796 . This arrangement allows a liquid or viscous substance to pass between central cavity  706  and gap  728 , through second injection cavity  732 . 
     Molding base  726  includes first lug cavity  734  and second lug cavity  736 . First lug cavity  734  is laterally spaced from second lug cavity  736 . First lug cavity  734  and second lug cavity  736  are exposed to gap  728  via first lug opening  776  and second lug opening  777 . In the embodiment shown in  FIG. 7 , first lug cavity  734  and second lug cavity  736  are rectangular, however these cavities can assume any shape including but not limited to typical shapes found on the outsoles of many shoes. In addition, molding base  726  is equipped with first lining recess  740 , second lining recess  742  and third lining recess  744 . Central mold  704  additionally includes first molding recess  746  and second molding recess  748 . Some embodiments additionally include first spring  701  and second spring  703 . 
     In  FIG. 7 , only two injection and lug cavities are shown, however in some embodiments many more injection and lug cavities may be included. In particular, first injection cavity  730  and first lug cavity  734  may be associated with a set of injection and lug cavities which may extend in the direction perpendicular to molding system  700  as seen in  FIG. 7 . 
     Referring to  FIG. 8 , a preferred embodiment of a step for making a tread assembly is shown. First, a matrix lining  802  is associated with central mold  704 . In particular, a first side  820  of matrix lining  802  is disposed against first side  781  of central mold  704 . A second surface  822  of matrix lining  802  is disposed to face gap  728 . The placement of matrix lining  802  against central mold  704  can be achieved by sliding matrix lining  802  into place through gap  728 , or by first moving molding base  726  away from central mold  704  and then returning molding base  726  after matrix lining  802  has been added. It may be preferable to fix matrix lining  802  in place to assure proper alignment with first lug cavity  734  and second lug cavity  736 . In some embodiments, matrix lining  802  may be clamped to central mold  704  or held in place with an adhesive. 
     In some embodiments, matrix lining  202  can include holes. In some embodiments, these holes in matrix lining  202  can be associated or aligned with a corresponding injection tip disposed on central mold  104 . 
     As seen in  FIG. 8 , first injection tip  787  may be inserted through first lining hole  804 . Second injection tip  788  may also be inserted into through second lining hole  806 . This allows for liquefied rubber to pass through matrix lining  802  into first lug cavity  734  and second lug cavity  736 . Matrix lining  202  may be a synthetic fiber, or any material which is lightweight and flexible. 
       FIG. 9  is a schematic diagram of a preferred embodiment of another step where the movement of central mold  704  towards molding base  726  is accomplished. During this movement, portions of matrix lining  802  fill first lining recess  740 , second lining recess  742 , and third lining recess  744 . [why?] In some embodiments, portions of central mold  704  will be in contact with molding base  726  after this compression step. Preferably, molding base  726  will be positioned with respect to central mold  704  in such a way that matrix lining  802  is exposed to first lug cavity  734  and second lug cavity  736 . 
     At this point a first rubber forming block  902  is preferably placed in first central cavity indent  722  and a second rubber forming block  904  is preferably placed in second central cavity indent  724 . First rubber forming block  902  and second rubber forming block  904  may be made of similar material and color. In some embodiments, first rubber forming block  902  and second rubber forming block  904  may be made of different materials or colors. In some embodiments, first rubber forming block  902  is harder than second rubber forming block  904 . In some embodiments, first rubber forming block  902  has a different color than second rubber forming block  904 . In some embodiments, first rubber block  902  is made of a different material than second rubber forming block  904 . 
       FIG. 10  is a schematic diagram of a preferred embodiment of the compression of molding press  702  with central mold  704 . This compression, along with a heating process, liquefies first rubber forming block  902  and second rubber forming block  904 . This liquid is then pressed through first injection cavity  730  and second injection cavity  732  into first lug cavity  734  and second lug cavity  736 . Some of the liquid entering first injection cavity  730  enters first lug cavity  734 , passing through first lining hole  804 , via first lower orifice  794 . Likewise, some of the liquid entering second injection cavity  732  eventually enters second lug cavity  736 , passing through second lining hole  806 , via second lower orifice  796 . Simultaneously, excess material can be gathered in first molding recess  746  and second molding recess  748 . In embodiments including first spring  701  and second spring  703 , these springs may be depressed during this step of compression. In some embodiments first pressing surface  708  fits within first central cavity indent  722 . Also second pressing surface  710  fits within second central cavity indent  724 . In some embodiments first central cavity wall  718  is in contact with first extension wall  712 . Also second central cavity wall  720  is in contact with second extension wall  714 . Preferably, enough liquid or viscous substance is supplied to fill first lug cavity  734  and second lug cavity  736  in such a manner that the liquid or viscous substance is in contact with portions of second side  822  of matrix lining  802 . 
     In a preferred embodiment of molding system  700 , first lug cavity rim  1002 , which preferably extends around the entire periphery of first lug cavity  734 , is preferably in contact with matrix lining  802  under enough pressure so that no liquefied rubber escapes the region enclosed by first lug cavity rim  1002 . In a similar manner, second lug cavity rim  1004 , which preferably extends around the entire outer periphery of second lug cavity  736 , is preferably in contact with matrix lining  802  under enough pressure so that no liquefied rubber escapes the region enclosed by second lug cavity rim  1004 . 
     As the rubber material cools, it attaches to second side  822  of matrix lining  802 . After the cooling of the rubber material is complete, central mold  704  can be separated from molding base  726 , yielding tread assembly  1102 , seen in  FIG. 11 . This separation can be performed by either lowering molding base  726  or raising central mold  704 . What remains is tread assembly  502 , which includes matrix lining  802  adjoined with first tread element  1104  and second tread element  1106 . First tread element base  1110  of first tread element  1104  is no larger than the width of first lug cavity rim  1002  and second tread element base  1112  of second tread element  1106  is no larger than the width of second lug cavity rim  1004 . 
     As some additional rubber material may be attached from rubber material which has solidified in first injection cavity  730  and second injection cavity  732 , some means of removing this excess material may be desired. It is unlikely however that such excess material will interfere with the performance of tread assembly  1102 . In this particular embodiment, first rubber projection  1104  and second rubber projection  1106  are rectangular in shape but any shape can be made using modified first lug cavity  734  and second lug cavity  736 . Such shapes may include tetrahedrons, cylinders, or rectangles. Irregular shapes may also be used. Since the composition of first rubber forming block  902  and second rubber forming block  904  may be modified, the composition of first rubber projection  1104  and second rubber projection  1106  can likewise be modified. This is a useful attribute since some tread assemblies may require the use of more durable rubber, while others may require the use of more flexible material. 
     The size of lug cavities is also unrestricted in this method. Although first lug cavity  734  and second lug cavity  736  are identical in size and shape, this need not be true in other embodiments. Some embodiments may have lug cavities in a variety of shapes and sizes and lug cavities that are different from one another. 
     Tread assembly  1102 , as seen in  FIG. 11 , includes only two tread elements. In other embodiments, tread assembly  1102  may comprise a matrix lining with multiple tread elements. These tread elements could be simultaneously formed by modification of central mold  704  to include multiple injection cavities and lug cavities. 
       FIG. 12  is a preferred embodiment of an article of footwear  1200 . Here, tread assembly  1102  has been attached to article of footwear  1200  to form tread pattern  1202  of footwear  1200 . Tread assembly  1102  includes first tread element  1104  and second tread element  1106 . In this embodiment, matrix lining  802  has been attached directly to the bottom of article of footwear  1200 . First tread element  1104  may be different in appearance and/or composition from second tread element  1106 . Tread pattern  1202  of article of footwear  1200  can be any design, including various shapes and sizes of tread elements. As previously discussed, each tread element in article of footwear  1200  may comprise any color or material. 
       FIG. 13  is a schematic diagram of a possible embodiment of a manufacturing system  2500  used to create a tread assembly. In this embodiment, rubber blocks that form the starting material in other embodiments are replaced with liquefied material that is directly injected into a lug cavity. Manufacturing system  2500  includes upper mold  2502  and molding base  2504 . A first side  2506  of upper mold  2502  is preferably disposed adjacent to a first side  2508  of molding base  2504 . 
     Upper mold  2502  preferably includes injection channel  2510 . Upper mold  2502  also preferably includes first injection cavity  2512 , second injection cavity  2514 , and third injection cavity  2516 . In a preferred embodiment, first injection cavity  2512  is in fluid communication with injection channel  2510  via first upper orifice  2518 . Likewise, second injection cavity  2514  is preferably in fluid communication with injection channel  2510  via second upper orifice  2520 . Likewise, third injection cavity  2516  is preferably in fluid communication with injection channel  2510  via third upper orifice  2522 . 
     Manufacturing system  2500  also preferably includes provisions to accommodate or receive a matrix lining  2554 . Matrix lining  2554  is preferably placed on upper mold  2502 . Matrix lining  2554  may be attached to upper mold  2502  by sliding matrix lining  2554  into place, through gap  2524 , or by first moving molding base  2504  away from upper mold  2502  and then returning molding base  2504  after matrix lining  2554  has been added. It may be preferable to fix matrix lining  2554  in place to assure proper alignment with first injection cavity  2512 , second injection cavity  2514 , and third injection cavity  2516 . In some embodiments, matrix lining  2554  may be clamped to upper mold  2502  or fixed with an adhesive. Additionally, matrix lining  2506  preferably includes first hole  2590 , second hole  2592 , and third hole  2594 . 
     Molding base  2504  preferably includes first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530 . First lug cavity  2526 , second lug cavity  2528  and third lug cavity  2530  are all preferably exposed to gap  2524  via first lug opening  2538 , second lug opening  2540 , and third lug opening  2542 . 
     Manufacturing system  2500  preferably includes screw injection machine  2550 . Screw injection machine  2550  is preferably capable of pumping or moving liquefied material through injection channel  2510 . In some embodiments, screw injection machine  2550  may include provisions to heat its liquefied contents. To move liquefied material to the various lug cavities, screw injection machine  2550  is preferably in fluid communication with injection channel  2510  via intermediate channel  2552 . 
     The distance between molding base  2504  and upper mold  2502  may be varied. In particular, molding base  2504  and upper mold  2502  may be moved closer together or farther away. In some embodiments, molding base  2504  may be moved to contact upper mold  2402 . In some embodiments, the items comprising manufacturing system  2500  may be made of a metallic material. 
     In the embodiment shown in  FIG. 13  only three injection and lug cavities are shown, however in some embodiments many more injection and lug cavities may be included. In particular, first injection cavity  2512 , second injection cavity  2514 , and third injection cavity  2516  may be associated with a set of injection that may extend in the direction perpendicular to molding system  2500  as seen in  FIG. 13 . Likewise, first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530  may be associated with a set of lug cavities that may extend in the direction perpendicular to molding system  2500  as seen in  FIG. 13 . 
     In the embodiment shown in  FIG. 13 , first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530  are rectangular, however these cavities can assume any shape including, but not limited to, typical shapes found on the outsoles of articles of footwear. 
       FIG. 14  is a preferred embodiment of another step in the manufacturing process, where the movement of upper mold  2502  towards molding base  2504  is accomplished. In some embodiments, portions of upper mold  2502  will be in contact with molding base  2504  after this movement step. Preferably, molding base  2504  will be positioned with respect to upper mold  2502  in such a way that matrix lining  2554  is exposed to first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530 . 
     First lug cavity  2526  is preferably in fluid communication with first injection cavity  2612  via first lower orifice  2532 . In particular, first lower orifice  2532  is preferably aligned with first hole  2590 , while first hole  2590  is disposed adjacent to first lug cavity  2526 . This arrangement allows a liquid or viscous substance to pass between first injection cavity  2512  and first lug cavity  2526 , through first hole  2590 . Second lug cavity  2528  is preferably in fluid communication with second injection cavity  2520  via second lower orifice  2534 . In particular, second lower orifice  2534  is preferably aligned with second hole  2592 , while second hole  2592  is disposed adjacent to second lug cavity  2528 . This arrangement allows a liquid or viscous substance to pass between second injection cavity  2514  and second lug cavity  2528 , through second hole  2592 . Third lug cavity  2530  is preferably in fluid communication with third injection cavity  2522  via third lower orifice  2536 . In particular, third lower orifice  2536  is preferably aligned with third hole  2594 , while third hole  2594  is disposed adjacent to third lug cavity  2530 . This arrangement allows a liquid or viscous substance to pass between third injection cavity  2516  and third lug cavity  2530 , through third hole  2594 . In addition, first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530  are all preferably exposed to portions of matrix lining  2554  via first lug opening  2538 , second lug opening  2540 , and third lug opening  2542  respectively. 
     During this step, a viscous material  2602  flows from screw injection machine  2550 , through intermediate channel  2552 , into injection channel  2510 . From injection channel  2510 , viscous material  2602  flows into first injection cavity  2512 , second injection cavity  2514 , and third injection cavity  2516 . Viscous material  2602  then flows into first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530 . It is also possible to pre-position viscous material  2602  so that viscous material  2602  is near or in the injection cavities  2512 ,  2514  and  2516 . To prevent the premature curing of viscous material  2602 , upper mold  2502  may include provisions to heat viscous material  2602 . 
     Viscous material  2602  may comprise Duralon©, or any blown rubber. Viscous material  2602  may also comprise other kinds of rubber. In general, viscous material  2602  may comprise any material that can flow and cure. 
     In a preferred embodiment of manufacturing system  2500 , first lug cavity rim  2604 , which preferably extends around the entire outer periphery of first lug cavity  2526 , is preferably in contact with matrix lining  2554  under enough pressure so that no viscous material escapes the region enclosed by first lug cavity rim  2604 . In a similar manner, second lug cavity rim  2606 , which preferably extends around the entire outer periphery of second lug cavity  2528 , is preferably in contact with matrix lining  2554  under enough pressure so that no viscous material escapes the region enclosed by second lug cavity rim  2606 . In a similar manner, third lug cavity rim  2608 , which preferably extends around the entire outer periphery of third lug cavity  2530 , is preferably in contact with matrix lining  2554  under enough pressure so that no viscous material escapes the region enclosed by third lug cavity rim  2608 . 
     Once viscous material  2602  has cooled, upper mold  2502  can be separated from molding base  2504 , yielding tread assembly  2702 , seen in  FIG. 15 . This separation can be performed by either lowering molding base  2504  or raising upper mold  2502 . What remains is tread assembly  2702 , which includes matrix lining  2554  adjoined with first tread element  2704 , second tread element  2706 , and third tread element  2708 . First tread element base  2710  of first tread element  2704  is preferably no larger than the width of first lug cavity rim  2604 . Second tread element base  2712  of second tread element  2706  is preferably no larger than the width of second lug cavity rim  2606 . Third tread element base  2714  of third tread element  2708  is preferably no larger than the width of third lug cavity rim  2608 . 
     As some additional rubber material may be attached from viscous material that has solidified in first injection cavity  2512 , second injection cavity  2514 , and third injection cavity  2616 , some means of removing this excess material may be provided. It is unlikely however that such excess material will interfere with the performance of tread assembly  2702 . In this particular embodiment, first tread element  2704 , second tread element  2706 , and third tread element  2708  are rectangular in shape but any shape can be made using first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530 . Such shapes may include tetrahedrons, cylinders, or rectangles. Irregular shapes may also be used. 
     The size of lug cavities is also unrestricted in this method. Although first lug cavity  2526 , second lug cavity  2528 , and third lug cavity  2530  are identical in size and shape, this need not be true in other embodiments. Some embodiments may have lug cavities in a variety of shapes and sizes and lug cavities that are different from one another. 
     Tread assembly  2702 , as seen in  FIG. 15 , includes only two tread elements. In other embodiments, tread assembly  2702  may comprise a matrix lining with multiple tread elements. These tread elements could be simultaneously formed and joined to a matrix lining by modification of upper mold  2502  to include multiple injection cavities and lug cavities. Tread assembly  2702  may be attached to the outsole of an article of footwear in an identical manner as has been shown in previous embodiments. 
     Using this manufacturing process  2500 , precise amounts of viscous material  2602  can be dispensed and waste of viscous material  2602  can be dramatically reduced. This manufacturing process  2500  also can increase the speed of production by eliminating the step of placing a rubber forming block. 
     While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.