US20110252670A1

US20110252670A1 - Dual-density EVA footwear mid-sole and method for making same

Info

Publication number: US20110252670A1
Application number: US12/802,874
Authority: US
Inventors: Justin R. Smith
Original assignee: Jimlar Corp
Current assignee: Jimlar Corp
Priority date: 2010-04-14
Filing date: 2010-06-15
Publication date: 2011-10-20

Abstract

The method for fabricating a dual-density mid-sole includes the steps of: injection molding EVA material of a first density into a block; placing the first density EVA block and raw EVA material pellets of a second density together in a mold cavity; and applying heat and pressure to the first density EVA block and raw EVA material pellets of a second density in the mold cavity to form a fused component. The fused component is shaped and detailed into the mid-sole in a separate mold cavity. The result is a dual-density mid-sole consisting of one or more blocks of EVA material of a first density fused to EVA material of a second density where the size, shape and location of the different density sections can be accurately controlled and precisely defined. An article of footwear including an upper, the dual-density mid-sole consisting of one or more blocks of EVA material of a first density fused to EVA material of a second density, and an outsole, may be formed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to footwear and to a method for making footwear and more particularly to a dual-density EVA footwear mid-sole and a method for making same.
2. Description of Prior Art Including Information Disclosed under 37 Cfr 1.97 and 1.98
Footwear mid-soles fabricated from ethylene-vinyl acetate (EVA) material are known in the art. Methods of fabricating EVA mid-soles are also known. Such methods normally include heating and applying pressure to raw EVA material in a mold cavity to fuse the material into the desired shape. After the component is removed from the mold and cured, it is shaped further and the exterior is detailed. The mid-sole is then incorporated into the footwear product using conventional fabrication techniques.
Fabrication of the EVA mid-sole in this fashion results in a mid-sole with a substantially uniform hardness throughout. However, for certain applications, it has been found to be desirable to have an EVA mid-sole that is less hard in some areas, such as the forefoot, and harder in other areas, such as the heel.
The conventional method to provide an EVA mid-sole with areas of different hardness is to introduce the two different density raw EVA materials into different locations within the mold cavity and then fuse the different density raw EVA materials together to form the mid-sole in a single step by applying heat and pressure.
For example, raw EVA material of a first (relatively low) density is used in sections of the mid-sole where less hardness is desired and a raw EVA material of second (relatively high) density is used in the sections where greater hardness is required. Each of the different density raw EVA materials is introduced in a mold cavity in the form of pellets that are poured into the respective desired locations in the mold cavity. Heat and pressure is applied to the different density raw EVA materials in the mold cavity. This causes the pellets to fuse and form the mid-sole in a single molding step.
While this single step molding process results in a mid-sole with sections of different hardness due to the different densities of the raw EVA materials, the boundaries of the different density sections are not well defined and are difficult to control. This is because the different density raw EVA pellets tend to mix together to some extent as they are poured into the mold cavity. The result is that the different density sections tend to run into each other. Further, the different density sections are not uniform in size and shape from one mid-sole to another.
It is therefore a prime object of the present invention to provide a method of fabricating dual-density EVA footwear mid-soles with well defined, stable different density sections.
It is another object of the present invention to provide method of fabricating dual-density EVA footwear mid-soles with different density sections of the desired size and shape.
It is another object of the present invention to provide a method of fabricating dual-density EVA footwear mid-soles in which the size, shape and location of the different density sections can be accurately controlled.
It is another object of the present invention to provide a method of fabricating dual-density EVA footwear mid-soles which are uniform in structure.
It is another object of the present invention to provide a method of fabricating dual-density EVA footwear mid-soles using a two-step process where each mid-sole has harder and less hard sections of precisely the desired shape, size and location.
It is another object of the present invention to provide a method for fabricating a footwear mid-sole wherein one or more blocks of EVA material of a first density are formed by injection molding and thereafter the blocks are fused with EVA material of a second density in a separate mold cavity by application of heat and pressure to form the mid-sole.
It is another object of the present invention to provide a dual-density mid-sole including one or more blocks of EVA material of a first density fused to EVA material of a second density.
It is another object of the present invention to provide n article of footwear including an upper, a dual-density mid-sole comprising one or more blocks of EVA material of a first density fused to EVA material of a second density, and an outsole.

BRIEF SUMMARY OF THE INVENTION

In general, the above objects are achieved by the present invention which includes a method for fabricating a dual-density mid-sole including the steps of: forming EVA material of a first density into a block; placing the first density EVA block and raw EVA material of a second density together; and applying heat and pressure to the block and raw EVA material to form a fused component of dual-density EVA.
Preferably, the raw EVA material of a second density is in the form of pellets when placed together with the first density EVA block.
The step of forming a block of the first density EVA material includes injection molding EVA material of a first density into a block. The block is then trimmed to the desired shape.
The method further includes the step of shaping the fused component into the mid-sole. Thereafter, design details on the exterior surface of the component are created. The steps of shaping and detailing the component may be combined into a single step.
The step of shaping and the step of detailing include the steps of placing the component in a mold cavity and applying heat and pressure to the component.
Preferably, the first density EVA material has a lower density than the second density EVA material.
The raw EVA material of a second density is preferably in the form of pellets.
The method further includes the step of measuring the amount of EVA material of a second density placed together with the first density EVA block. This may be achieved by measuring the amount of raw EVA material of a second density placed in the mold cavity with the bock as a function of the volume of the block.
The step of placing the first density EVA block and the raw EVA material of a second density together includes placing the first density EVA block in a mold cavity and pouring the raw EVA material of a second density into the mold cavity.
The step of applying heat and pressure to the block and raw material includes applying heat and pressure to the block and raw material in the mold cavity.
In accordance with another aspect of the present invention, a method is provided for fabricating a dual-density mid-sole comprising the steps of: injection molding EVA material of a first density into a block; placing the first density EVA block and raw EVA material pellets of a second density together in a cavity; and applying heat and pressure to the first density EVA block and raw EVA material pellets of a second density in the cavity to form a fused component.
The method further includes the step of shaping the fused component into the mid-sole.
In accordance with another aspect of the present invention, a dual-density mid-sole is provided including a block of EVA material of a first density fused to EVA material of a second density.
The EVA block is formed separately, before the EVA block and EVA material are fused together.
In accordance with another aspect of the present invention, a dual-density mid-sole is provided including first and second blocks of EVA material of a first density fused to EVA material of a second density.
The blocks are formed by injection molding, before the EVA material and blocks are fused together.
In accordance with another aspect of the present invention, an article of footwear is provided including an upper, a dual-density mid-sole comprising a block of EVA material of a first density fused to EVA material of a second density, and an outsole.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS

To these and to such other objects that may hereinafter appears, the present invention relates to a dual-density EVA footwear mid-sole and a method for making same as described in detail in the following specification and recited in the annexed claims, taken together with the accompanying drawings, in which like numerals refer to like parts and in which:

FIG. 1 is a perspective with of a footwear product with the dual-density mid-sole of the present invention;

FIG. 2 is a side elevation view of the footwear product of FIG. 1;

FIG. 3 is an exploded view of the footwear product of FIG. 1 showing the components thereof;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 showing an idealized view of the interior of the mid-sole;

FIG. 5 is a cross-sectional view take along line 5-5 of FIG. 4 showing an idealized view of the interior of the mid-sole;

FIG. 6 is an elevation view of the assembly of injection molded EVA blocks;

FIG. 7 is a perspective view of an EVA block of a first size and shape;

FIG. 8 is a perspective view of a an EVA block of a second size and shape;

FIG. 9 is a perspective view of a mold cavity showing the placement of two EVA blocks therein;

FIG. 10 is a perspective view of the mold cavity of FIG. 9 showing the measured amount of raw EVA pellets being introduced into the cavity after placement of the EVA blocks;

FIG. 11 is a perspective view of the mold cavity after the EVA pellets have been introduced and before the application of heat and pressure;

FIG. 12 is perspective view of the mold cavity and contents as heat and pressure are being applied to fuse the EVA, including a cut-out portion showing the EVA material;

FIG. 13 is a perspective view of the fused EVA component as it is removed from the mold;

FIG. 14 is a perspective view of the fused EVA component shaping and detailing mold; and

FIG. 15 is a perspective view of the completed dual-density EVA mid-sole.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 illustrate a typical footwear product, generally designated A, incorporating the dual-density EVA mid-sole of the present invention, generally designated B. The mid-sole B of the present invention can be formed in whatever shape and size that may be appropriate for footwear product A and with whatever exterior contours and surface features desired. Accordingly, the particular mid-sole design and footwear product style shown in the drawings should not be considered in any way as a limitation on the scope of the present invention but instead simply as a means of illustrating a typical mid-sole B resulting from the fabrication process of the present invention and a typical footwear product A that might incorporate such a mid-sole.
FIG. 3 shows the components of footwear product A in exploded form. Product A consists of an upper 10, an insole 12, mid-sole B and an outsole 14. Upper 10, insole 12 and outsole 14 are all standard components manufactured by any one of a number of well known fabrication methods and assembled with mid-sole B to form product A using conventional techniques.
In order to achieve the dual density mid-sole B of the present invention, as illustrated in the figures, a two step process is employed. First, the blocks 16, 18 of one density EVA material are forming by injection molding. The EVA material from which the blocks 16, 18 are formed is selected for example to form blocks that will be softer and more resilient than the EVA material that will eventually form the remainder of the mid-sole.
The term “block” as used herein is meant to be broadly construed to include any mass of material (such as the relatively low density EVA as described in the preferred embodiment) having definite, well-defined boundaries which is formed (for example by injection molding) prior to and separately from the molding process that fuses the block with a material of different density (such as the higher density EVA pellets of the preferred embodiment) to form a component.
FIG. 6 illustrates the assembly of blocks 16, 18 after it has cooled and has been removed from the injection molding machine. Blocks 16, 18 are still connected together by the plastic stem 20 produced by the channels in the injection mold through which the molten EVA flows.
After blocks 16, 18 are severed from stem 20 and trimmed as needed; they appear as seen in FIGS. 7 and 8. Two different size and shaped blocks 16, 18 are shown to illustrate that the blocks may be of any appropriated size and shape. Further, more than one block may be incorporated into a single mid-sole, as shown in FIG. 9.
As seen in FIG. 9, one or more of the soft EVA blocks 16, 18 are placed in the mold cavity 22 of a forming/pressing machine 24. The blocks can be positioned at any location within the cavity. As shown in FIG. 10, after the soft blocks are placed in cavity 22, a measured amount of raw EVA material pellets 26 is the poured into the cavity. The mold cavity then appears as shown in FIG. 11.
The raw EVA pellets 26 introduced into the mold cavity are of a different density than the EVA material used to form the blocks. In this example, the EVA pellets 26 are made of less dense EVA material than the EVA material from which blocks 16, 18 are formed. Accordingly, the raw EVA pellets will form a harder, less resilient end product than the blocks. The amount of pellets introduced into the cavity is carefully measured in accordance with the volume of the cavity, using a set formula, such that the fused component, called a “cup” because of its shape, will be approximately the size and shape of the desired mid-sole.
As illustrated in FIG. 12, after the mold is closed, heat and pressure is applied to fuse the EVA pellets 26 and the blocks 16, 18 into a single component or cup 28, see FIG. 13. Cup 28 is roughly the size and shape of the mid-sole but requires some finishing. The cup is then shaped and detailed in a second forming/pressing step which is performed in a different mold 30 to complete the dual-density mid-sole of the present invention, illustrated in FIG. 15.
FIGS. 4 and 5 are idealized illustrations of the internal structure of the mid-sole of the present invention. FIG. 4 is a longitudinal cross-section of the mid-sole showing the locations of blocks 16 and 18 within the mid-sole. FIG. 5 is a lateral cross-section take through the front portion of the mid-sole showing block 18.
These figures show that the blocks 16, 18, made of the softer, less dense EVA material, are precisely located within the mid-sole and substantially maintain their original shape and size through the fusing process. The blocks are completely surrounded by the harder EVA material formed from the more dense raw EVA pellets. The result is more cushioning for the foot in areas where the softer blocks are located and more support for the foot in the areas where the harder EVA is located.
Although somewhat idealized because some melting of the exterior of the blocks may occur, FIGS. 4 and 5 show that the boundaries between the different density EVA materials in the fused component are much more well defined than would be possible in a single step molding process where raw EVA pellets of both densities are poured into different areas of a mold cavity and melted together.
It will now be appreciated that using the fabrication method of the present invention, the contours of two different densities of EVA material in the mid-sole will match perfectly and the location of each of the different density EVA materials within the mid-sole can be accurately controlled to form a stable fused component with softer and harder sections of size, shape and location precisely as desired.
While only a single preferred embodiment of the present invention has been disclosed for purposes of illustration, it is obvious that many modifications and variations could be made thereto. It is intended to cover all of those modifications and variations which fall within the scope of the present invention, as defined by the following claims.

Claims

1. A method for fabricating a dual-density mid-sole comprising the steps of:

forming EVA material of a first density into a block;

placing the first density EVA block and raw EVA material of a second density together; and

applying heat and pressure to the first density EVA block and raw EVA material of a second density to form a fused component.

2. The method of claim 1 wherein the raw EVA material of a second density is in the form of pellets when placed together with the first density EVA block.

3. The method of claim 1 wherein the step of forming a block comprises injection molding EVA material of a first density into a block.

4. The method of claim 1 further comprising the step of trimming the block.

5. The method of claim 1 further comprising the step of shaping the fused component into the mid-sole.

6. The method of claim 1 further comprising the step of creating design details on the exterior surface of the fused component.

7. The method of claim 6 further comprising the step of shaping the fused component into the mid-sole.

8. The method of claim 7 wherein the step of shaping and the step of detailing are combined into a single step.

9. The method of claim 7 wherein the step of shaping and the step of detailing comprise the steps of placing the fused component in a mold cavity and applying heat and pressure to the fused component.

10. The method of claim 1 wherein the first density EVA material has a lower density than the second density EVA material.

11. The method of claim 1 wherein the raw EVA material of a second density has a higher density than the first density EVA material.

12. The method of claim 1 further comprising the step of measuring the amount of EVA material of a second density placed together with the first density EVA block.

13. The method of claim 12 wherein the step of measuring comprises the step of measuring the amount of raw EVA material of a second density placed in the mold cavity with the bock as a function of the volume of the block.

14. The method of claim 1 wherein the step of placing the first density EVA block and the raw EVA material of a second density together comprises the step of placing the first density EVA block in a mold cavity and pouring the raw EVA material of a second density into the mold cavity.

15. The method of claim 14 wherein the step of applying heat and pressure to the block and raw material comprises the step of applying heat and pressure to the block and raw material in the mold cavity.

16. The method of claim 1 further comprising the step of introducing a second first density block prior to applying heat and pressure to fuse the component.

17. A method for fabricating a dual-density mid-sole comprising the steps of:

injection molding EVA material of a first density into a block;

placing the first density EVA block and raw EVA material pellets of a second density together in a cavity; and

applying heat and pressure to the first density EVA block and raw EVA material pellets of a second density in the cavity to form a fused component.

18. The method of claim 17 further comprising the step of shaping the fused component into the mid-sole.

19. A dual-density mid-sole comprising a block of EVA material of a first density fused to EVA material of a second density.

20. The mid-sole of claim 19 wherein the EVA block is formed separately, before the EVA block and EVA material are fused together.

21. A dual-density mid-sole comprising first and second blocks of EVA material of a first density fused to EVA material of a second density.

22. The mid-sole of claim 21 wherein the blocks are formed by injection molding, before the EVA material and blocks are fused together.

23. An article of footwear comprising an upper, a dual-density mid-sole comprising a block of EVA material of a first density fused to EVA material of a second density, and an outsole.