Method of manufacturing sole assembly formed of multiple preforms

1. A method of forming a sole assembly, comprising the steps of:

positioning a plurality of polymer foam preforms together to form a unitary sole assembly preform, at least one of the plurality of polymer foam preforms having a color that is different than a color of another one of the plurality of polymer foam preforms, wherein the plurality of polymer foam preforms includes a first polymer foam preform, a second polymer foam preform, and a third polymer foam preform, and wherein in the unitary sole assembly preform:

(i) the first polymer foam preform includes: (a) a first interior recess having a lower surface, wherein an outer periphery of the first interior recess is surrounded by a rib formed as part of the first polymer foam preform and (b) a shoulder extending about at least a portion of the rib and located on an opposite side of the rib from the first interior recess,

(ii) the second polymer foam preform is received the first interior recess and is completely surrounded by the rib, and

(iii) the third polymer foam preform includes an aperture into which the rib of the first polymer foam preform is received and an interior lip that is seated on the shoulder of the first polymer foam preform;

placing the unitary sole assembly preform in a recess in a first portion of a heated mold assembly at one time in a single step, the first portion of the mold assembly being pre-heated to at least a melting temperature of the unitary sole assembly preform such that all of the plurality of polymer foam preforms of the unitary sole assembly preform start to melt at the same time upon insertion into the first portion of the mold assembly;

closing the mold assembly such that a second portion of the mold assembly is above and in contact with the first portion;

subjecting the unitary sole assembly preform to heat such that the plurality of polymer foam preforms bond to one another to form a sole assembly;

opening the mold assembly; and

removing the sole assembly from the mold assembly.

2. The method of claim 1 , wherein at least one of the plurality of polymer foam preforms has a performance characteristic that is different than a performance characteristic of at least one other polymer foam preform.

3. The method of claim 1 , wherein the first polymer foam preform is formed in a first preform mold assembly.

4. The method of claim 3 , wherein a bottom surface of a recess of the first preform mold assembly includes at least one surface irregularity.

5. The method of claim 4 , wherein said at least one surface irregularity comprises one of a projection and a recess.

6. The method of claim 1 , wherein the second polymer foam preform and the third polymer foam preform are formed in a second preform mold assembly.

7. The method of claim 6 , wherein the second polymer foam preform and the third polymer foam preform each has a color that is different than the other.

8. The method of claim 6 , wherein bottom surfaces of each of a first recess and a second recess of the second preform mold assembly include at least one surface irregularity.

9. The method of claim 8 , wherein said at least one surface irregularity on the bottom surface of each of the first recess and the second recess comprises one of a projection and a recess.

10. A method of forming a sole assembly, comprising the steps of:

positioning a first polymer foam preform having a first color, a second polymer foam preform having a second color, and a third polymer foam preform having a third color together to form a unitary sole assembly preform, wherein in the unitary sole assembly preform:

(i) the first polymer foam preform includes: (a) a first interior recess having a lower surface, wherein an outer periphery of the first interior recess is surrounded by a rib formed as part of the first polymer foam preform and (b) a shoulder extending about at least a portion of the rib and located on an opposite side of the rib from the first interior recess,

(ii) the second polymer foam preform is received the first interior recess and is completely surrounded by the rib, and

(iii) the third polymer foam preform includes an aperture into which the rib of the first polymer foam preform is received and an interior lip that is seated on the shoulder of the first polymer foam preform;

placing the unitary sole assembly preform in a recess in a first portion of a heated mold assembly at one time in a single step, the first portion of the heated mold assembly being pre-heated to at least a melting temperature of the unitary sole assembly preform such that the first polymer foam preform, the second polymer foam preform, and the third polymer foam preform of the unitary sole assembly preform start to melt at the same time upon insertion into the first portion of the mold assembly;

closing the mold assembly such that a second portion of the mold assembly is above and in contact with the first portion;

subjecting the unitary sole assembly preform to heat such that the first polymer foam preform, the second polymer foam preform, and the third polymer foam preform bond to one another to form a sole assembly;

opening the mold assembly; and

removing the sole assembly from the mold assembly.

11. The method of claim 10 , wherein a plurality of second polymer foam preforms having the second color are used to form the unitary sole assembly preform.

12. The method of claim 10 , wherein the first polymer foam preform is formed in a first preform mold assembly.

13. The method of claim 10 , wherein the second polymer foam preform and the third polymer foam preform are formed in a second preform mold assembly.

14. A method of forming a sole assembly, comprising the steps of:

forming a first polymer foam preform having a first color in a recess of a first mold assembly, wherein the step of forming the first polymer foam preform includes forming the first polymer foam preform to include: (a) a first interior recess having a lower surface, wherein an outer periphery of the first interior recess is surrounded by a rib formed as part of the first polymer foam preform and (b) a shoulder extending about at least a portion of the rib and located on an opposite side of the rib from the first interior recess;

forming a plurality of second polymer foam preforms having a second color in first recesses of a second mold assembly;

forming a third polymer foam preform having a third color in a second recess of the second mold assembly, wherein the step of forming the third polymer foam preform includes forming an aperture and an interior lip in the third polymer foam preform;

positioning the second polymer foam preform in the first interior recess of the first polymer foam preform, and positioning the third polymer foam preform with respect to the first polymer foam preform such that the interior lip of the third polymer foam preform is seated on the shoulder of the first polymer foam preform and a side surface of the aperture of the third polymer foam preform abuts an outer periphery of the rib of the first foam polymer preform, wherein the positioning steps place the first polymer foam preform, the second polymer foam preform, and the third polymer foam preform together to form a unitary sole assembly preform;

placing the unitary sole assembly preform in a recess in a first portion of a third mold assembly at one time in a single step, the first portion of the third mold assembly being pre-heated to at least a melting temperature of the unitary sole assembly preform;

closing the third mold assembly such that a second portion of the third mold assembly is above and in contact with the first portion;

subjecting the unitary sole assembly preform in the third mold assembly to heat such that the first polymer foam preform, the second polymer foam preform, and the third polymer foam preform bond to one another to form a sole assembly;

opening the third mold assembly;

removing the sole assembly from the third mold assembly;

allowing the sole assembly to cool; and

trimming the sole assembly.

15. The method of claim 14 , wherein the step of forming the first polymer foam preform further includes forming the first polymer foam preform to include a second interior recess having a lower surface, wherein an outer periphery of the second interior recess is surrounded by the rib formed as part of the first polymer foam preform, and

wherein the positioning steps further include positioning an additional polymer foam preform in the second interior recess of the first polymer foam preform, wherein the additional polymer foam preform is included in the unitary sole assembly preform in the placing step.

16. The method of claim 14 , wherein the step of forming the first polymer foam preform further includes forming the first polymer foam preform to include a second interior recess having a lower surface and a third interior recess having a lower surface, wherein an outer periphery of the second interior recess is surrounded by the rib formed as part of the first polymer foam preform and an outer periphery of the third interior recess is surrounded by the rib formed as part of the first polymer foam preform, and

wherein the positioning steps further include positioning a first additional polymer foam preform in the second interior recess of the first polymer foam preform and positioning a second additional polymer foam preform in the third interior recess of the first polymer foam preform, wherein the first additional polymer foam preform and the second additional polymer foam preform are included in the unitary sole assembly preform in the placing step.

17. The method of claim 16 , wherein in the positioning steps, the first polymer foam preform, the second polymer foam preform, the third polymer foam preform, the first additional polymer foam preform, and the second additional polymer foam preform are positioned so as to form a portion of an exterior bottom surface of the sole assembly.