Method of manufacturing midsole for article of footwear

A method of forming includes the steps of: placing a first mold member and a second mold member in contact with one another; injecting a first material into a first recess in the first mold member to form a first portion of a midsole while the first mold member is maintained at a temperature below an ambient temperature; removing the first portion of the midsole from the first recess; positioning the first portion of the midsole in the second recess in the third mold member of the second mold assembly; placing a second material into the second recess in contact with the first portion of the midsole; placing the third mold member and the fourth mold member in contact with one another; and subjecting the second material and the first portion in the second mold assembly to heat and pressure to form a midsole.

FIELD OF THE INVENTION

Aspects of this invention relate generally to a mold assembly for a midsole and a method of manufacture, and, in particular, to a mold assembly for producing a midsole formed of two materials.

BACKGROUND OF THE INVENTION

Conventional articles of athletic footwear include two primary elements, an upper and a sole structure. The upper provides a covering for the foot that comfortably receives and securely positions the foot with respect to the sole structure. In addition, the upper may have a configuration that protects the foot and provides ventilation, thereby cooling the foot and removing perspiration. The sole structure is secured to a lower portion of the upper and is generally positioned between the foot and the ground. In addition to attenuating ground reaction forces, the sole structure may provide traction, control foot motions (e.g., by resisting over pronation), and impart stability, for example. Accordingly, the upper and the sole structure operate cooperatively to provide a comfortable structure that is suited for a wide variety of activities, such as walking and running.

The sole structure generally incorporates multiple layers that are conventionally referred to as an insole, a midsole, and an outsole. The insole is a thin, compressible member located within the upper and adjacent to a plantar (i.e., lower) surface of the foot to enhance footwear comfort. The midsole, which is conventionally secured to the upper along the length of the upper, forms a middle layer of the sole structure and is primarily responsible for attenuating ground reaction forces. The outsole forms the ground-contacting element of footwear and is usually fashioned from a durable, wear-resistant material that includes texturing to improve traction.

The conventional midsole is primarily formed from a resilient, polymer foam material, such as polyurethane or ethylvinylacetate, that extends throughout the length of the footwear, often by way of an injection molding process. The properties of the polymer foam material in the midsole are primarily dependent upon factors that include the dimensional configuration of the midsole and the specific characteristics of the material selected for the polymer foam, including the density of the polymer foam material. By varying these factors throughout the midsole, the relative stiffness and degree of ground reaction force attenuation may be altered to meet the specific demands of the activity for which the footwear is intended to be used. In addition to polymer foam materials, conventional midsoles may include, for example, one or more fluid-filled bladders and moderators.

It would be desirable to provide a mold assembly for a dual density midsole and a method of manufacturing a dual density midsole that reduces or overcomes some or all of the difficulties inherent in prior known devices. Particular objects and advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain embodiments.

SUMMARY

The principles of the invention may be used to advantage to provide a method for producing a midsole for an article of footwear having first and second portions that may have different densities. In accordance with a first aspect, a method of forming a midsole for an article of footwear includes the steps of: placing a first mold member and a second mold member in contact with one another; injecting a first material into a first recess in the first mold member to form a first portion of a midsole while the first mold member is maintained at a temperature below an ambient temperature; removing the first portion of the midsole from the first recess; positioning the first portion of the midsole in the second recess in the third mold member of the second mold assembly; placing a second material into the second recess in contact with the first portion of the midsole; placing the third mold member and the fourth mold member in contact with one another; and subjecting the second material and the first portion in the second mold assembly to heat and pressure to form a midsole

In accordance with another aspect, a method of forming a midsole with a first mold assembly having a first mold member and a second mold member with a first recess formed in the first mold member, and a second mold assembly having a third mold member and a fourth mold member with a second recess formed in the third mold member, includes the steps of placing the first mold member and the second mold member in contact with one another; injecting a first material having a first density into the first recess in the first mold member to form a first portion of a midsole; removing the first portion of the midsole from the first mold member; positioning the first portion of the midsole in the second recess in the third mold member; placing pellets of a second material having a second density that is different from the first density into the second recess in contact with the first portion of the midsole; placing the third mold member and the fourth mold member in contact with one another; and subjecting the second material and the first portion in the second mold assembly to heat and pressure to form a midsole.

In accordance with a further aspect, a method of forming a midsole with a first mold assembly having a first mold member and a second mold member with a first recess formed in the first mold member, and a second mold assembly having a third mold member, an intermediate mold member, and a fourth mold member with a second recess formed in the third mold member, includes the steps of placing the first mold member and the second mold member in contact with one another; injecting a first material into the first recess in the first mold member to form a first portion of a midsole while the first mold member is maintained at a temperature below an ambient temperature; removing the first portion of the midsole from the first recess; placing the third mold member and the intermediate mold member in contact with one another; injecting a second material into the second recess in the second mold member to form a second portion of a midsole while the first mold member is maintained at a temperature below an ambient temperature; removing the intermediate mold member from the third mold member; positioning the second portion and the first portion of the midsole in contact with one another in the second recess in the third mold member of the second mold assembly; placing the third mold member and the fourth mold member in contact with one another; and subjecting the second portion and the first portion in the second mold assembly to heat and pressure to form a midsole.

Substantial advantage is achieved by providing a method of forming a midsole having two different portions. In particular, certain embodiments provide the ability to provide portions of the midsole with materials of different densities and/or hardnesses, thereby providing different performance characteristics for the different portions of the midsole

These and additional features and advantages disclosed here will be further understood from the following detailed disclosure of certain embodiments.

The figures referred to above are not drawn necessarily to scale, should be understood to provide a representation of particular embodiments of the invention, and are merely conceptual in nature and illustrative of the principles involved. Some features of the mold assembly for a midsole depicted in the drawings have been enlarged or distorted relative to others to facilitate explanation and understanding. The same reference numbers are used in the drawings for similar or identical components and features shown in various alternative embodiments. Mold assemblies for a midsole and methods of manufacture for such a midsole as disclosed herein would have configurations and components determined, in part, by the intended application and environment in which they are used.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

An illustrative embodiment of a first mold assembly10for use in forming a first portion of a midsole for an article of footwear is shown inFIG. 1. First mold assembly10includes a first mold member12and a second mold member13. A first recess14is formed in a surface of first mold member12. A channel16is formed in a surface of first mold member12and extends from an exterior of first mold member12to first recess14such that first recess14is in fluid communication with an exterior of first mold member12by way of channel16when first mold member12and second mold member13are in contact with one another. First mold member12is configured to form a first portion18of a midsole, as seen inFIG. 3.

In the illustrated embodiment, there are two first recesses14formed in first mold member12, one of which serves to form a first portion18of a left midsole of an article of footwear, and the other which serves to form a first portion18of a right midsole of an article of footwear. It is to be appreciated that first mold member12may include only one first recess14, or more than two first recesses. That is, any number of first recesses14may be provided in first mold member12, thereby providing for the simultaneous formation of any number of midsole first portions18.

A method of forming a midsole is initiated by placing first mold member12and second mold member13in contact with one another, as seen inFIG. 2. A first material19is then injected into first mold assembly10from an injection assembly20by way of channel16.

First mold assembly10is maintained at a temperature below ambient, in a process known as cold molding, and produces first portion18. In certain embodiments, first mold assembly10maintained at a temperature between approximately 48° C. and approximately 52° C. for between approximately 40 seconds and approximately 60 seconds. In certain embodiments, first material19is maintained at a pressure of between approximately 80 kg and approximately 100 kg.

First mold assembly10is then disassembled, that is, first and second portions12,13are separated from one another, and each first portion18, as seen inFIG. 3, is removed from first mold assembly10. In the illustrated embodiment, first portion18is a first heel portion18of a midsole. It is to be appreciated that first portion18can be any portion of a midsole, as illustrated and described in greater detail below.

Each first heel portion18is then placed in a second recess22formed in a third mold member24of a second mold assembly26, as seen inFIG. 4. Second mold assembly26also includes a fourth mold member28. In the illustrated embodiment, there are two second recesses22formed in third mold member24of second mold assembly26, one of which receives a first heel portion18of a left midsole of an article of footwear, and the other which receives a first heel portion18of a right midsole of an article of footwear. It is to be appreciated that third mold member24may include only one second recess22, or more than two second recesses22. That is, any number of second recesses22may be provided in third mold member24, thereby providing for the simultaneous formation of any number of midsoles for an article of footwear.

After each first heel portion18is placed in a corresponding second recess22in third mold member24of second mold assembly26, a second material30is placed in each second recess22. In certain embodiments, second material30is formed of a plurality of pellets36. Pellets36may be spherical, cylindrical, or any other desired shape. In certain embodiments pellets36are substantially cylindrical extruded members with a diameter of between approximately 3.4 mm and approximately 4.0 mm.

After the desired number of pellets of second material30is placed in each second recess22, third mold member24and fourth mold member28of second mold assembly26are then placed in contact with one another, as seen inFIG. 5. Second mold assembly26is then subjected to heat and pressure for a desired amount of time, thereby producing a second forefoot and midfoot portion32that is bonded to first heel portion18, thereby forming a midsole34, which is seen inFIG. 6after being removed from second mold assembly26.

In certain embodiments, second mold assembly26is maintained at a temperature between approximately 165° C. and approximately 169° C. for between approximately 590 seconds and approximately 610 seconds.

In certain embodiments, first material19may have a first hardness and second material30may have a second hardness that is different than the first hardness. In certain embodiments, first material19has a first hardness between approximately 34 Asker C and approximately 36 Asker C, while second material30has a second hardness between approximately 39 Asker C and approximately 42 Asker C.

By providing first material19with a different density or hardness than second material30, midsole34can be modified to achieve particular performance characteristics. Particular regions of midsole34can easily be engineered and constructed to have performance characteristics that are different from other regions of midsole34.

First material19and second material30can be formed of any desired material. Suitable first and second materials include rubber, polyurethane foam, microcellular elastomeric foams, or phylon (Ethylene Vinyl Acetate (‘EVA’) foam). In certain embodiments, second material30is injection phylon. Other suitable first and second materials will become readily apparent to those skilled in the art, given the benefit of this disclosure.

Another embodiment of a first mold assembly40having a first mold member42with first recesses44and a channel46, and a second mold member43, and a method of forming a midsole having two portions, is illustrated inFIGS. 7-12. To form a midsole41, first mold member42and second mold member43of first mold assembly40are placed in contact with one another, as seen inFIG. 8. First material19is then injected into first recesses44of first mold assembly40from injection assembly20by way of channel46.

First mold assembly40is maintained at a temperature below ambient, in a cold molding process, and produces first portions48of midsole41. In certain embodiments, first mold assembly40maintained at a temperature between approximately 48° C. and approximately 52° C. for between approximately 40 seconds and approximately 60 seconds. In certain embodiments, first material19is maintained at a pressure of between approximately 80 kg and approximately 100 kg.

First mold assembly40is then disassembled, that is, first and second portions42,43are separated from one another, and each first portion48, as seen inFIG. 9, is removed from first mold assembly40. In the illustrated embodiment, first portion48is a first forefoot and midfoot portion48of midsole41.

Each first portion48is then placed in a second recess52formed in a third mold member54of a second mold assembly56, as seen inFIG. 10. Second mold assembly56also includes a fourth mold member58. In the illustrated embodiment, there are two second recesses52formed in third mold member54of second mold assembly56, one of which receives a first forefoot and midfoot portion48of a left midsole of an article of footwear, and the other which receives a first forefoot and midfoot portion48of a right midsole of an article of footwear. It is to be appreciated that third mold member54may include only one second recess52, or more than two second recesses52. That is, any number of second recesses52may be provided in third mold member54, thereby providing for the simultaneous formation of any number of midsoles for an article of footwear.

After each first forefoot and midfoot portion48is placed in a corresponding second recess52in third mold member54of second mold assembly56, second material30is placed in each second recess52. In certain embodiments, second material30is placed in second recess52in pellet form.

After the desired number of pellets of second material30is placed in each second recess52, third mold member54and fourth mold member58of second mold assembly56are then placed in contact with one another, as seen inFIG. 11. Second mold assembly56is then subjected to heat and pressure for a desired amount of time, thereby producing a second heel portion62that is bonded to first forefoot and midfoot portion48, thereby forming midsole41, which is seen inFIG. 12after being removed from second mold assembly56.

It is to be appreciated that the first portion of a midsole formed using the first and second mold assemblies can be any portion of the midsole, and that the second portion of the midsole can be any complimentary portion of the midsole.

Yet another embodiment of a first mold assembly60having a first mold member62with first recesses64and a channel66, and a second mold member63, and a method of forming a midsole having two portions, is illustrated inFIGS. 13-18. In the illustrated embodiment, there are two first recesses64formed in first mold, member62of first mold assembly60. It is to be appreciated that first mold member62may include only one first recess64, or more than two first recesses64. That is, any number of first recesses64may be provided in first mold member62, thereby providing for the simultaneous formation of any number of midsoles for an article of footwear.

To form a first portion of a midsole, first mold member62and second mold member63of first mold assembly60are placed in contact with one another, as seen inFIG. 14. First material19is then injected into first mold assembly60by way of channel66from an injection assembly (not visible in this view). First mold assembly60is maintained at a temperature below ambient, in a cold molding process, and produces first portion68of a midsole. In certain embodiments, during the cold molding process, first mold assembly60is maintained at a temperature between approximately 48° C. and approximately 52° C. for between approximately 40 seconds and approximately 60 seconds. In certain embodiments, first material19is maintained at a pressure of between approximately 80 kg and approximately 100 kg.

In the embodiment illustrated inFIGS. 13-18, first portion68is a central portion of a midsole. It is to be appreciated that first portion68can be any desired portion of a midsole.

A second recess72in a third mold member74of a second mold assembly76, seen inFIGS. 15-16, is used to form a second portion of a midsole. Second mold assembly76also includes an intermediate mold member78. In the illustrated embodiment, there are two second recesses72formed in third mold member74of second mold assembly76. It is to be appreciated that third mold member74may include only one second recess72, or more than two second recesses72. That is, any number of second recesses72may be provided in third mold member74, thereby providing for the simultaneous formation of any number of midsoles for an article of footwear.

Intermediate mold member78is placed in contact with third mold member74, as seen inFIG. 16. Second material30is then injected into second recess72of second mold assembly76by way of channel80from an injection assembly (not visible in this view). Second mold assembly76is maintained at a temperature below ambient, in a cold molding process, and produces second portion84of a midsole. In the illustrated embodiment, second portion84is a peripheral portion that surrounds the central first portion68. It is to be appreciated that second portion84can be formed as any portion of the midsole.

In certain embodiments, during the cold molding process, second mold assembly76is maintained at a temperature between approximately 165° C. and approximately 169° C. for between approximately 590 seconds and approximately 610 seconds.

Intermediate mold member78is then separated from third mold member74and, as illustrated inFIGS. 17-18, first portion68is positioned within and in contact with second portion84. A fourth mold member86of second mold assembly76is then placed in contact with third mold member74. Second mold assembly76is then subjected to heat and pressure for a desired amount of time, thereby bonding first portion68and second portion84together to form a midsole, such as those seen inFIGS. 6 and 12above.

Thus, while there have been shown, described, and pointed out fundamental novel features of various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. For example, it is expressly intended that all combinations of those elements and/or steps which perform substantially the same function, in substantially the same way, to achieve the same results are within the scope of the invention. Substitutions of elements from one described embodiment to another are also fully intended and contemplated. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.