Method of forming a shoe insert
This application is a division of application Ser. No. 566,186, filed Dec. 28, 1983 now U.S. Pat. No. 4,586,273. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates in general to a shoe insert and pertains, more particularly, to a shoe insert that is adapted to provide improved arch support, shock attenuation, and shock absorption. Also, the present invention is concerned with the associated method of manufacture of the shoe insert. 
     Shoe inserts that are presently in use do not adequately withstand impact, particularly as might occur when the shoe or sneaker is used in a sporting event. For example, in connection with basketball or football playing, the player may well be subjected to severe shock impact in the foot area. 
     Accordingly, it is an object of the present invention to provide an improved shoe insert construction that provides proper foot, and in particular, arch support. 
     Another object of the present invention is to provide an improved shoe insert construction that provides for substantial shock attenuation and shock absorption. 
     Still another object of the present invention is to provide an improved shoe insert that is lightweight, relatively simple to manufacture, relatively inexpensive in construction, and which can withstand impacts that occur particularly in connection with sporting events. 
     A further object of the present invention is to provide an improved shoe insert that maintains its functionality even over long periods of wear and further maintains its desired shape even after long hours of use. 
     SUMMARY OF THE INVENTION 
     To accomplish the foregoing and other objects, features and advantages of the invention, there is provided a shoe insert which is comprised of a base layer of a relatively resilient material, a foam layer disposed over the base layer, a fabric disposed over the foam layer and means for integrally forming the base layer, foam layer, and fabric into a sheet tri-laminate. A support layer is disposed at the heel area of the insert and is of a rigid material of a higher density than that of the tri-laminate. This rigid support layer is attached to and formed with the tri-laminate layer. The base layer and support layer are preferably both of a urethane foam. The fabric may be of cotton, polyester or polypropylene knit. The base layer is preferably of a cross-linked polyethylene. 
     The method in accordance with the invention comprises the steps of providing a foam layer, providing a fabric layer, heating the foam layer, joining the foam and fabric layers, and providing a base layer. One of the base layer and foam layer are heated so as to join the base layer with the foam layer to form a tri-laminate. There is provided a pre-formed heel member and adhesive is applied between the heel member and the tri-laminate with the adhesive being heat and pressure reactivatable. Finally, the heel member and tri-laminate are molded under pressure causing shaping thereof and formation into an integral one-piece shoe insert. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Numerous other objects, features and advantages of the invention should now become apparent upon a reading of the following detailed description taken in conjunction with the accompanying drawing, in which: 
     FIG. 1 is a longitudinal cross-sectional view of a shoe insert as constructed in accordance with the present invention; 
     FIG. 2 is a top plan view of the insert of FIG. 1; 
     FIG. 3 is a bottom view of the insert of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 2 in the ball area of the insert; 
     FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 2; 
     FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 2 in the heel area of the insert; and 
     FIG. 7 is a schematic perspective view illustrating one of the steps in the sequence of manufacture of the insert of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1-6 illustrate the details of the shoe insert construction of the present invention. FIG. 7 is a schematic perspective view illustrating one of the steps in the sequence of the method of the invention. With regard to the construction of the insert, as illustrated in FIGS. 1-7, the insert comprises a base layer 12, a support layer 13, a foam layer 11, and a fabric layer 14. The layers 11, 12, and 14 are relatively resilient and conform in shape to the desired shoe size. The support layer 13 is rigid and as noted in FIG. 1 is principally at the heel area of the shoe insert. 
     The foam layer 11 as well as the support layer 13 is preferably constructed of a polyurethane foam material. The support layer 13 is of a denser foam thus making the support layer more rigid. The layer 11 preferably has a density of 5 lbs. per cubic ft. and it is preferred that this density be in the range of 4-6 lbs. per cubic ft. The layer 11 has a preferred thickness of 1/8&#34;+or-5% and is preferably in a range of thickness of 3/32&#34;-5/32&#34;. The material used for layer 11 as well as layer 13 may be made by Crestfoam Company. 
     The layer 12 preferably also has a density in a range of 4-6 lbs. per cubic ft. The base layer 12 is preferably of cross-linked polyethylene. The thickness of the base layer 12 is preferably on the order of 5/16&#34;+or-10%. The thickness of the base layer 12 may actually extend through a range of 1/4&#34; to 7/16&#34; in thickness. The material of the base layer 12 may be made by Dynamet Nobel Company. 
     With regard to the support layer 13, which is formed primarily at the heel area of the insert, this is also made of a polyurethane foam. However, this is made by being compressed so that the final density is on the order of 22-23 lbs. per cubic ft. The fabric layer 14 may be constructed of, for example, cotton, polyester, or a polypropylene knit. 
     Reference may now be made to FIG. 7 which shows one of the steps in the method of construction of the shoe insert of this invention. The shoe insert is formed by first joining the foam layer 11 with the fabric layer 14. The layers 11 and 14 are laminated together by a flame lamination technique which employs an open flame which is directed to the foam layer 11. The open flame generates sufficient heat on the surface to cause melting of the flat sheet layer 11. Once melted, the fabric layer 14 is joined therewith and the two sandwiched together layers are preferably run between chilled rollers and sufficient pressure is applied between the rollers so that the layers 11 and 14 are joined together. At this point in the process, these layers are still maintained in a flat sheet form. 
     The integrated layers 11 and 14 are then next joined also by flame lamination to the base layer 12. This step in the method of manufacture may also be carried out by the use of an open flame directed to either layer 11 or layer 12 to cause melting thereof. The previously integrated layers 11 and 14 are then joined to layer 12 and the laminated layers are then run betweeen chilled rollers. At this stage of the process, the layers are still in flat sheet form. 
     The layers thus laminated to this point are then ready for molding. This requires a neating of the laminated layers to a molding temperature of approximately 250° F. for a period of about 225 seconds. This heats the previously laminated layers sufficiently to permit them to be inserted into the mold. 
     Reference may now be made to FIG. 7 which shows the mold in the schematic manner as comprised of mold pieces 20 and 21. The mold may be made of aluminum. FIG. 7 also shows the tri-laminate 22 which is comprised of layers 11, 12, and 14. The tri-laminate 22 is shown as still in flat sheet form in FIG. 7 and disposed adjacent the pre-formed support layer or cup 13. Reference is made hereinafter to the manner in which the compressed foam cup 13 is formed. 
     The pre-formed heel layer or cup 13 is placed in the mold comprised of mold pieces 20 and 21 and an adhesive is applied to the inside of the layer 13. The tri-laminate 22 is appropriately positioned and the mold is closed. The adhesive is preferably a chlorinated rubber base adhesive which is heat and pressure reactivatable. One adhesive that is used is made by Jetco. Thus, during this molding step, it is seen that the adhesive is activated at substantially the same time that the shaping of the tri-laminate 22 along with the heel layer 13 occurs. This shaping is accomplished of course, by means of the mold press. The molding occurs under a pressure, preferably of 85 lbs. psi. The mold is illustrated in FIG. 7 in a schematic fashion and is preferably a water cooled mold. The mold may be cooled by passage of water therethrough so as to maintain the temperature at approximately 40° F. The mold is maintained in its press-mold state for approximately 50-65 seconds. Thus, the material inserted into the mold which includes the tri-laminate 22 and the layer 13, essentially is inserted into the mold in a hot condition, recalling that at least the tri-laminate 22 is heated to proper molding temperatures, and is then brought to a colder temperature by virtue of the cooling of the mold. Also, at the same time that this molding occurs, the adhesive is activated by virtue of contact with the preheated tri-laminate 22 along with the activation of the adhesive by means of the pressure applied during the molding operation. 
     Thus, the molding step schematically illustrated in FIG. 7 causes the simultaneous shaping of the insert. It also causes the affixing of the cup or heel layer 13 to the previously formed tri-laminate 22. 
     Now, with regard to the technique for forming the cup or heel 13, it is noted that previously it has been indicated that this member is constructed of a polyurethane foam that has been compressed to a density on the order of 22-23 lbs. per cubic ft. In its compressed state, the layer 13 may have a thickness of 1/16&#34;-1/8&#34;. However, initially, before being compressed, the polyurethane has a thickness of 1.5&#34; and is constructed of a urethane product that has characteristics of being clickable and reticulated. The urethane is preferably clickable so that when it is cut with, for example, a scissors, there will not be a pinching on the ends. The reticulated form of the urethane means that the cell membranes have been removed electrically or chemically. Ideally, the reticulation is on the order of 80-90 pores/inch, although, a preferred range is 50-90 pores/inch of reticulated foam. In this regard, the higher the cell or pore count, the more cosmetically acceptable is the material because the cells are smaller and thus have a more pleasing aesthetic appearance. 
     The 1.5&#34; thick urethane is compressed by means of a steel or brass tool. The compressing tool preferably has a high heat conductivity and in this regard, brass is preferred. The tool is heated, preferably to a temperature of 450° F. and this causes the foam to be uniformly softened whereby it is caused to be compressed by the tool. Once compressed, it is set into this compressed state and it maintains the compressed state. The tool is similar in form to a mold and operates at say, 86 psi. for 90 seconds. The heat, as mentioned previously, is preferably at 450° F. It is preferred that this temperature be maintained during the compressing phase and that the heat not be allowed to drop substantially from that temperature. 
     Once the cup layer 13 has been preformed, then it is employed in the mold illustrated in FIG. 7 with the adhesive being coated inside of the cavitated heel layer 13. 
     Having now described one form of the present invention, it should now be apparent to those skilled in the art that numerous other embodiments and modifications thereof are contemplated as falling within the scope of this invention.