Footwear construction and method

Abstract

An article of footwear having a rubber outsole, a polyurethane midsole bonded to the rubber outsole by polyurethane (PU) adhesive, and a polyurethane upper bonded to the midsole and the rubber outsole by injection molding. The invention also relates to a method of manufacturing an article of footwear comprising the steps of applying a layer of primer to a selected portion of a rubber outsole and allowing the layer of primer to dry; applying a first layer of PU adhesive over the primed portion of the outsole and allowing said first layer of PU adhesive to dry; applying a second layer of PU adhesive over the dried first layer of PU adhesive and allowing the second layer of PU adhesive to dry; forming, separately, a polyurethane upper by injection molding; setting the outsole and the upper in a mold; and, forming, via injection molding, a polyurethane midsole and activating the PU adhesive to bond the outsole to the midsole and to the upper, thereby forming the article of footwear.

1 . An article of footwear, comprising:
 a) a rubber outsole   b) a polyurethane midsole bonded to the rubber outsole by polyurethane (PU) adhesive and by injection molding of the midsole; and   c) a polyurethane upper bonded to the polyurethane midsole by said injection molding of the midsole.   
   
   
       2 . The article of footwear according to  claim 1 , further comprising a polyurethane shaft integrally formed with said upper such that the article of footwear is a boot. 
   
   
       3 . The article of footwear according to  claim 2 , further comprising a removable insole which is insertable into the article of footwear and rests upon said midsole. 
   
   
       4 . The article of footwear according to  claim 3 , further comprising one or both of a reinforced toe plate integrated into the polyurethane upper and a sole plate integrated into the polyurethane midsole. 
   
   
       5 . The article of footwear according to  claim 1 , wherein the polyurethane midsole is formed from polyurethane of a density different from that of polyurethane used to form the polyurethane upper. 
   
   
       6 . The article of footwear according to  claim 5 , wherein the polyurethane midsole is formed from a foamed polyurethane with a density higher than that of the polyurethane used to form the polyurethane upper. 
   
   
       7 . A method of manufacturing an article of footwear, comprising:
 a) applying a layer of primer to a selected portion of a rubber outsole and allowing said layer of primer to dry;   b) applying a first layer of polyurethane (PU) adhesive over the primed portion of the rubber outsole and allowing said first layer of PU adhesive to dry;   c) applying a second layer of PU adhesive over the dried first layer of PU adhesive and allowing said second layer of PU adhesive to dry;   d) forming, separately, a polyurethane upper by injection molding;   e) setting the rubber outsole and the polyurethane upper in a mold; and,   f) forming, via injection molding, a polyurethane midsole between said polyurethane upper and said rubber outsole, said injection molding bonding the polyurethane upper to the polyurethane midsole and activating said polyurethane adhesive to bond the polyurethane midsole to the rubber outsole, thereby forming the article of footwear.   
   
   
       8 . The method of  claim 7 , further including a step of inserting an insole into the footwear after the step of forming the polyurethane midsole. 
   
   
       9 . The method of  claim 8  wherein said primer drying step takes place at a temperature from 50° C. to 55° C. 
   
   
       10 . The method of  claim 9 , wherein said PU adhesive drying steps take place at a temperature from 50° C. to 55° C. 
   
   
       11 . The method of  claim 10 , further including inserting a removable insole into the article of footwear after completion of said forming step. 
   
   
       12 . The method of  claim 7 , further including a step of inserting one or both of a reinforced toe plate and reinforced sole plate into the mold with the rubber outsole and polyurethane upper, such that the toe plate and the sole plate, when present, are integrated into the polyurethane upper and the polyurethane midsole, respectively. 
   
   
       13 . The method of  claim 7 , wherein, a polyurethane shaft is formed in addition to the polyurethane upper as part of said step of forming the polyurethane upper, such that the article of footwear is a boot. 
   
   
       14 . The method of  claim 7 , further including a step of cleaning and buffing the rubber outsole prior to said step of applying the layer of primer. 
   
   
       15 . The method of  claim 7 , wherein the polyurethane midsole is formed from polyurethane of a density different from that of polyurethane used to form the polyurethane upper. 
   
   
       16 . The method of  claim 15 , wherein the polyurethane midsole is formed from a foamed polyurethane with a density higher than that of the polyurethane used to form the polyurethane upper.