Shape Memory Polymer Footwear Last

Abstract

A dynamic footwear last constructed from a shape memory polymer (SMP) material is disclosed. A single dynamic SMP footwear last may be repeatedly adapted to change into any size and shape with accuracy and reliability thereby dramatically reducing the total inventory of footwear lasts required at a particular footwear manufacturing facility.

1 . A shape memory polymer footwear last system comprising
 a dynamic shape memory polymer (SMP) footwear last pre-form of a first size, the pre-form comprising:
 (1) an interior surface and an exterior surface; 
 (2) an internal volume defined by the interior surface; 
 (3) an opening passing from the exterior surface to the internal volume; 
   a heat source for heating the dynamic SMP footwear last pre-form above a threshold temperature;   a first mold comprising a first cavity, the first cavity having a second size corresponding to a first footwear last, wherein the first size of the dynamic SMP footwear last pre-form less than the second size of the first footwear last; and   a cooling source for cooling the first footwear last.   
     
     
         2 . The shape memory polymer footwear last system of  claim 1 , wherein the heat source comprises one of a conventional oven, an induction system, and a microwave oven. 
     
     
         3 . The shape memory polymer footwear last system of  claim 1 , further comprising a compressed fluid source. 
     
     
         4 . The shape memory polymer of footwear last system of  claim 3 , wherein the system further comprises a connection valve for connecting the fluid source to the opening of the dynamic SMP footwear last pre-form. 
     
     
         5 . The shape memory polymer footwear last system of  claim 4 , wherein the connection valve provides a pressure tight fit between the dynamic SMP footwear last pre-form and the fluid source to allow the fluid from the fluid source to travel from the fluid source to the internal volume of the dynamic SMP footwear last-pre-form at a controllable rate and pressure. 
     
     
         6 . The shape memory polymer footwear last system of  claim 1 , wherein the cooling source is one selected from a fluid cooling system and a gas cooling system. 
     
     
         7 . The shape memory polymer footwear last system of  claim 1 , wherein the dynamic SMP footwear last pre-form is flexible when heated above the threshold temperature and substantially rigid below the threshold temperature. 
     
     
         8 . The shape memory polymer footwear last system of  claim 1 , wherein the dynamic SMP footwear last pre-form is re-shapeable a plurality of times. 
     
     
         9 . The shape memory polymer footwear last system of  claim 1 , wherein the system further comprises a pressurized fluid source in fluid communication with the internal volume of the dynamic SMP footwear last pre-form, and wherein the first mold comprises an opening for the fluid source to remain in fluid communication with the footwear last pre-form while the footwear last pre-form is inside the first mold. 
     
     
         10 . The shape memory polymer footwear last system of  claim 1 , wherein the first mold comprises one material selected from a metal material and a polymer material. 
     
     
         11 . The shape memory polymer footwear last system of  claim 1 , wherein the dynamic SMP footwear last pre-form can be formed into a plurality of footwear lasts ranging in size from US sizes 1-16. 
     
     
         12 . The shape memory polymer footwear last system of  claim 1 , wherein the first size of the SMP footwear last pre-form is smaller than a smallest footwear last for which a mold is included in the last system. 
     
     
         13 . A method for forming a footwear last form a shape memory polymer (SMP) footwear last pre-form, the method comprising:
 providing the SMP footwear last pre-form having a first size and shape;   heating the SMP footwear last pre-form above a threshold temperature;   placing the SMP footwear last pre-form into a first molding cavity of a first footwear last mold for producing a first footwear last having a second size and a second shape;   expanding the SMP footwear last pre-form inside the first molding cavity of the first footwear last mold to produce the first footwear last;   cooling the first footwear last; and   removing the first footwear last from the first footwear last mold.   
     
     
         14 . The method of  claim 13 , wherein the threshold temperature is at least 75° C. 
     
     
         15 . The method of  claim 13 , wherein the threshold temperature is between 50° C. and 80° C. 
     
     
         16 . The method of  claim 13 , wherein the heating of the SMP footwear last pre-form is performed after the SMP footwear last pre-form has been placed into the first molding cavity of the first footwear last mold. 
     
     
         17 . The method of  claim 14 , wherein the heating of the SMP footwear last pre-form is performed before the SMP footwear last pre-form is placed into the first molding cavity of the first footwear last mold. 
     
     
         18 . The method of  claim 13 , wherein the first footwear last is cooled with one of a fluid cooling system or a gas cooling system. 
     
     
         19 . A method for using a single shape memory polymer (SMP) footwear last pre-form in the production of footwear of different shapes and sizes, the method comprising:
 providing the SMP footwear last pre-form;   heating the SMP footwear last pre-form above a threshold temperature;   placing the heated SMP footwear last pre-form into a first molding cavity of a first mold for producing a first footwear last having a first size and a first shape;   expanding the SMP footwear last pre-form inside the first molding cavity of the first mold to form the first footwear last;   cooling the first footwear last;   removing the first footwear last from the first molding cavity of the first mold; and   using the first footwear last in a first footwear production process of a first plurality of footwear having the first size and the first shape.   
     
     
         20 . The method of  claim 19  further comprising:
 placing the first footwear last into a second molding cavity of a second mold for producing a second footwear last having a second size and a second shape; 
 heating the first footwear last above the threshold temperature inside the second molding cavity of the second mold; 
 expanding the first footwear last inside the second molding cavity of the second mold to form the second footwear last; 
 cooling the second footwear last; 
 removing the second footwear last from the second molding cavity of the second mold; and 
 using the second footwear last in a second footwear production process of a second plurality of footwear having the second size and the second shape. 
 
     
     
         21 . The method of  claim 20 , wherein the first size of the first footwear last is less than the second size of the second footwear last. 
     
     
         22 . The method of  claim 19  further comprising:
 heating the first footwear last above the threshold temperature, wherein once heated, the first footwear last returns to the SMP footwear last pre-form; 
 heating the SMP footwear last pre-form above the threshold temperature; 
 placing the SMP footwear last pre-form into a second molding cavity of a second mold for producing a second footwear last having a second size and a second shape; 
 expanding the SMP footwear last pre-form inside the second molding cavity of the second mold to form the second footwear last; 
 cooling the second footwear last; 
 removing the second footwear last from the second molding cavity of the second mold; and 
 using the second footwear last in a second footwear production process of a second plurality of footwear having the second size and the second shape;