The inventions described below relate to the field inflatable liners for shoes and boots, and their method of manufacture. More specifically, the invention relates to unique removable snowboard boot liners made from Ethyl Vinyl Acetate (EVA) containing an air bladder and their method of manufacture.
While removable liners present many advantages, one major disadvantage associated with removable liners is that the foot of an athlete wearing a snowboard boot with a removable liner has a tendency to slip and move within the boot. This slipping may be caused by the athlete""s foot moving within the liner, by the lliner moving within the boot, or by a combination of these two phenomena. The most common result of this slipping is that the heal of the athlete lifts up from the bed of the boot. This slipping and lifting makes it more difficult for the athlete to control the snowboard, results in blisters and increases the likelihood of more serious injuries to the athlete.
This slipping problem has been found in the context of ski boots. Multiple solutions to this problem in the field of ski boots have been presented including several variations on the theme of using an air bladder positioned at various locations between the foot of the athlete and the exterior of the boot. Air bladders also have been used in other types of footwear for various purposes.
This invention is specifically concerned with snowboard boot liners made of EVA having an inflatable air bladder incorporated therein and the mass production of such liners.
Holstine, U.S. Pat. No. 5,692,321 discloses an athletic boot such as a snowboard boot having a bladder system consisting of an upper and lower bladder in communication with each other disposed between the wearer""s foot and the exterior of the boot. The upper and lower bladder system is a closed system. Thus, the overall inflation level of the bladder system is fixed and may not be readily adjusted. The system disclosed in Holstine is designed to give increased support to the ankle of a wearer when downward forces compress the lower bladder causing a corresponding inflation of the upper bladder. Holstine stresses that the disclosed boot provides the athlete with increased flexibility and range of motion of the athlete""s foot when impact or operational forces are removed from the boot. Holstine does not disclose how his boot is to be produced.
Potter, et al., U.S. Pat. No. 5,765,298 discloses an athletic shoe with an inflatable bladder present in the ankle collar The bladder has weld fines or other means incorporated therein to prevent the formation of restrictive vertical columns of pressurized gas in the medial and lateral section of the bladder. This allows increased flexibility and mobility of the wearer""s ankle. Potter, et al. do not disclose how their product is to be produced.
Nishimura U.S. Pat. Nos. 3,744,159 and 3,758,964 disclose sports shoes containing an inflatable air bladder. The majority of Nishimura""s disclosures focus on ski boots containing inflatable air bladders. Nishimura does not disclose the methods used to manufacture his products. Nor does Nishimura disclose the use of EVA as a liner material.
None of the foregoing prior art have suggested snowboard boot liners made of EVA having an inflatable air bladder incorporated therein and the mass production of such liners.
The present invention is directed to snowboard boot liners made of EVA having an inflatable air bladder incorporated therein and the mass production of such liners.
The steps involved in making a conventional snowboard boot liner from EVA are as follows:
1. The pattern of the liner must be cut from a flat sheet of EVA;
2. The EVA is then folded and stitched together to approximate the shape of the final liner;
3. The stitched EVA is placed on a last;
4. The stitched EVA on the last is heated to allow the EVA to be molded to its final shape; and
5. The heated EVA is molded to its final shape.
The method outlined above is well known to those in the art. The length of time and temperature used to heat the EVA in step 4 is well known to those ordinarily skilled in the art of making snowboard boot liners from EVA. However, for purposes of illustrative example, the heating may be accomplished in a tunnel oven set at about 100xc2x0 C. The total residence time in the tunnel oven may be approximately five minutes. The exact methods used to accomplish the molding of the EVA to its final shape in step 5 are well known to those of ordinary skill in the art of making snowboard boot liners from EVA. However, for purposes of illustrative example, neoprene socks may be used.
Air bladders in shoes generally are made by placing one sheet of suitable material on top of a second sheet of suitable material, cutting out the material in the appropriate pattern and securing the sheets together to form the boundary of the bladder and any desired internal contours such as uninflated spaces to accommodate the ankle bones. Frequently the two sheets are attached together by melting both sheets together wherever a seam is desired.
The method of the invention allows the air bladder to be stitched into place on the EVA liner before the EVA is stitched and molded. This allows the air bladder to be stitched when the liner is still a flat sheet of EVA. It would be extremely difficult, if not impossible, to attach the air bladder by machine stitching once the EVA has been folded, stitched, heated and molded. Prior to the invention of the method described in this patent, it was not possible to attach an air bladder made from typical materials known in the art of footwear air bladders prior to the heating and molding of the EVA. This is because the two sheets that make up the air bladder would melt together when the bladder went through the heating and molding process with the EVA-Thus, the bladder could not be inflated and would be useless. This made the mass production of EVA snowboard boot liners with inflatable bladders impractical.
The present method solves this problem by introducing a substance between the two sheets that make up the air bladder prior to the sealing of the seams of the bladder and partially inflating the air bladder prior to the heating and molding of the EVA liner. The introduction of this substance and partial inflation of the bladder keep the two sheets that make up the bladder separated during the heating and molding of the EVA. In addition, the disclosed design and installation of the bladder minimizes the amount of slipping of the athlete""s foot within the liner and minimizes the amount of lifting of the athlete""s heal from the bed of the boot.