Abstract:
A method and apparatus for making a lined waterproof footwear product, and footwear product formed therefrom, are provided. A last, having an exterior surface configured to correspond to the size and shape of the interior surface of the footwear product, is covered with a microcellular lining material. An injection mold comprises shells having a pre-determined configuration to mold an upper portion that attaches to the lining during the molding process. In the finished footwear product, the molded upper portion has a molded foot portion that extends around the wearer&#39;s foot and an upwardly-extending molded portion that covers a part of the lining while leaving another part of the lining uncovered.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention is in the field of footwear and, in particular, pertains to an improved method and apparatus for making waterproof footwear with lining, such as an insulation-type lining in the case of winter footwear, and waterproof footwear formed thereby. 
       BACKGROUND  
       [0002]    Different manufacturing methods are known for making lined (e.g. insulated) waterproof footwear (e.g. winter boots). These include the conventional lasted process, a process for injection molding the main boot and then inserting into it a loose insulating liner, and, for rubber boots, a vulcanization process applied to a lining layer. Each of these known methods involves numerous separate steps which increases costs and impedes efficiency. 
         [0003]    The lasted process is an old, well-known method which uses a last having the shape of the intended boot, the last being a three dimensional model for the intended boot. By this method, the boot materials are formed and fitted onto the last. Hiking boots are typically made in this manner. The selected materials, which may be leather and/or fabrics, including material for a lining layer, are cut into pieces using the last as a model, assembled with a waterproof membrane layer, for example a Gore-Tex membrane, sewn together and then cemented to a rubber sole. 
         [0004]    The vulcanization process is also a well-known method for making rubber boots and uses a last. By this method, a lining material is formed to fit over a last and positioned to cover the last. Unvulcanized (i.e. raw) rubber is cut into pieces according to a pattern and the pieces are laid over and cemented to the lining material covering the last. After the positioning of the pieces has been completed, the assembly is put into a heated oven and subjected to heavy pressure which causes the raw rubber to vulcanize and adhere to the insulating microcellular lining. 
         [0005]    These known methods involve many separate steps or entail multiple sub-processes which increase production costs. Therefore, a simpler method would constitute a desirable improvement. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with the present invention there is provided a method for making a lined waterproof footwear product. A last has an exterior surface configured to correspond to the size and shape of the interior surface of the footwear product. At least a portion of the exterior surface of the last is covered with a microcellular lining material. A first mold is provided for injection molding the footwear product whereby the first mold comprises first and second plates, and first and second shells wherein each shell has a pre-determined configuration to cooperate with the exterior surface of the lining covered last to form: (i) a pre-injection cavity between the shells and the lining covered last when the lining covered last is located between the first and second shells, and between the first and second plates located on opposite sides of the shells, and the plates are closed in position for injection molding; and, (ii) an injection cavity, defining the configuration of the footwear product, between the shells and the lining covered last when the plates have been tightly closed, the lining covered last is between the closed plates and injection material is being injected into the injection cavity whereby the injection pressure causes the microcellular lining material to compress and thereby reconfigure from the pre-injection cavity to the injection cavity. The lining covered last is located between the first and second shells, and between the first and second plates located on opposite sides of the shells. The plates are closed in position for injection molding, thereby forming the pre-injection cavity between the shells and the lining covered last. An injection material is injected under pressure into the pre-injection cavity whereby the pre-injection cavity is reconfigured to the injection cavity, and injecting the injection material until the injection cavity is filled with the injection material. The injection material is hardened in the injection cavity whereby the hardened injection material attaches to the microcellular lining material and forms the footwear product over the last. The first mold is opened to separate the plates and shells and expose the finished footwear product and removing the footwear product from the last. 
         [0007]    The injection material may be a thermoplastic material which is heated prior to the injecting step, is molten when injected, and is hardened by cooling. Preferably, the last is comprised of a hard, durable material selected from a group consisting of hardened aluminum, steel and stainless steel. The covering of the last may comprise positioning a sock lining over the last. 
         [0008]    The footwear product may be an upper part of another footwear product, with a sole made by injection molding by a second mold comprising first and second sole plates and first and second sole shells. The sole formed in a sole cavity between the first and second sole shells by injecting injection material into the sole cavity, and attached to the upper to form the other footwear product. The sole may be attached to the upper by injection material during the injection molding and cooling of the upper. A second sole may be injection molded concurrently with the injection molding of the upper. Preferably, an injection port is located on the outside of the first mold. 
         [0009]    The invention further provides apparatus for making a lined waterproof footwear product, wherein a last has an exterior surface configured to correspond to the size and shape of the interior surface of the footwear product. A first mold is provided for injection molding the footwear product whereby the first mold comprises first and second plates, and first and second shells wherein each shell has a pre-determined configuration to cooperate with an exterior surface of a lining covered last to form: (i) a pre-injection cavity between the shells and the lining covered last when the lining covered last is located between the first and second shells, and between the first and second plates located on opposite sides of the shells, and the plates are closed in position for injection molding; and, (ii) an injection cavity between the shells and the lining covered last when the plates have been tightly closed, the lining covered last is between the closed plates and injection material is being injected into the injection cavity whereby the injection pressure causes the microcellular lining material to compress and thereby reconfigure from the pre-injection cavity to the injection cavity; whereby the lining covered last comprises the last with at least a portion of the exterior surface of the last covered with a microcellular lining material and, the configuration of the injection cavity defines the configuration of the footwear product. 
         [0010]    Using the apparatus, the footwear product is formed by injecting under pressure into the pre-injection cavity an injection material thereby causing the pre-injection cavity to reconfigure to the injection cavity, until the injection cavity is filled with the injection material, and hardening the injection material in the injection cavity. The footwear product may be an upper part of another footwear product, with the apparatus further providing a second mold, comprising first and second sole plates and first and second sole shells for injection molding a sole for attachment to the upper. Preferably, an injection port is located on the outside of the first mold. 
         [0011]    The invention further provides a footwear product or upper and other footwear product made by the foregoing steps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention is described in detail below with reference to the following drawings. 
           [0013]      FIG. 1  is a perspective view illustrating a layer of lining material positioned over and covering a last in accordance with the invention. 
           [0014]      FIG. 2  is a sectional plan view of an injection molding machine in accordance with the invention for making a lined, waterproof boot, having an upper mold and two sole molds for cyclically injecting, in each cycle, both a boot upper and a sole and attaching a previously molded sole to the boot upper that is molded during the cycle. A last covered with a sock lining is shown in position between two boot upper mold plates and shells, ready to close the plates around the last and cover the end of the plates with a sole plate containing a previously injection-molded sole. Also shown is a second sole plate that is coupled to the sole plate covering the boot upper mold by a rotatable plate, whereby the second sole plate is closed onto a cover plate when the upper mold is closed and injected with injection material to form a sole during the same injection cycle of injection-molding the boot upper. 
           [0015]      FIG. 3  is a perspective view of a waterproof boot having an interior attached lining made in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The subject invention provides an improved method and apparatus for making lined waterproof footwear, and waterproof footwear formed thereby. The method uses an injection molding process and a last. A predetermined thermoplastic material is selected as appropriate for the application and used as the injection material. As illustrated by  FIGS. 1 and 2 , a last  10  is advantageously used within the injection mold  55  for the upper of the footwear product to position and attach to the upper  130  a lining  20 . The upper mold  55  comprises two shells  70  and two plates  60 . The shells  70  are designed to complement both the configuration of the layer of lining  20  and the dynamic changes the lining configuration undergoes from the pressure applied to it during the course of the injection process so as to create a cavity  80  having a predetermined configuration of the upper  130  of the footwear product (see  FIG. 3 ) to be made by the mold. 
         [0017]    The thermoplastic material, in a fluid state, is injected over the last  10  covered with a lining material (also referred to herein as a sock lining)  20  while the last  10  is located within the upper mold  55  and allowed to set (i.e. harden) within the mold to form a lined waterproof footwear product  120  as illustrated by  FIG. 3 . While in its fluid state after being injected into the upper mold  55 , the thermoplastic material covers the sock lining  20  and attaches to the sock lining  20  as it sets. For the exemplary, illustrated embodiment a winter boot is provided; however, it is to be understood that the invention is not limited to any particular type of boot and also provides other types of lined waterproof footwear including rain boots and shoes. 
         [0018]    As illustrated by  FIG. 1 , the last  10  functions as a three dimensional model or pattern which is used to size and fit the sock lining  20 . The last  10  is made of a hard metal, usually of hardened aluminum or steel for high durability. The exterior surface of the last  10  is configured to mirror (i.e. correspond to) the size and shape of the interior surface of the item of footwear that is to be made by the upper mold  55 . A predetermined relatively thick, microcellular lining material is sized, cut and sewn to match the size, shape and configuration of the exterior surface of the last  10  and fit tightly over the last  10  to form the sock lining  20 . The sock lining  20  may, for example, be chosen to provide insulation to a winter boot such as that shown by  FIG. 3 . When the lining pieces have been sewn together  30 , the resulting sock lining  20  is positioned over the last  10  to cover it as shown in  FIGS. 1 and 2 . 
         [0019]    By “microcellular” it is meant that the material is comprised of a large number of cells and having a compression—expansion property so that the lining material is caused to compress during the process of injecting the injection material into the mold cavity, under pressure, and then expand after the molded boot has been removed from the mold and taken off the last. 
         [0020]    In the example of the illustrated embodiment a neoprene microcellular material manufactured by Nam Liong Enterprises Co. Ltd. of Tainan, Taiwan, grade WS-2H comprising 30% polychloroprene rubber and 70% styrene butadiene rubber, is selected for use for the lining material. This is a foamed synthetic rubber product (i.e. containing gas cells) and is selected for the illustrated application of a winter boot because of its relatively good insulation characteristic. Examples of other suitable microcellular materials are foam blends such as polyurethane or EVA (ethylene vinyl acetate)—based blends. For the illustrated example, the selected lining material has a relatively large thickness of 3 mm but it will be understood by the skilled reader that the thickness to be chosen will vary from application to application according to design choices for the particular footwear product to be formed and the particular mold materials to be used. 
         [0021]    To mold the boot upper  130 , the last  10  with sock lining  20  is attached to the upper mold  55  using the last holder  40  whereby it is positioned in the cavity  80  between the two sets of plates  60  and shells  70  of the upper mold  55  as illustrated by  FIG. 2 . The plates  60  and shells  70  are comprised of a hard metal such has hardened aluminum or steel for high durability. The shells  70  are precision measured to take into consideration the thickness of the sock lining  20  when it is compressed during the injection molding process. A key criteria for the design of the upper mold  55  is to provide a cavity  80 , referred to as the pre-injection cavity, between the interior surfaces of the mold  55  and the sock lining  20  having a configuration which accounts for a non-uniform compression of the sock lining  20  when it is, subsequently, subjected to pressure from an injection of thermoplastic material into the cavity  80 . This is because it is the final configuration of the cavity, referred to as the injection cavity, after the injection of the thermoplastic material with its attendant pressure applied to the sock lining  20 , that becomes occupied by thermoplastic material and defines the configuration of the footwear product made by the process. Therefore, the upper mold  55 , the sock lining  20  and the cavity  80  together must be designed to account for a non-uniform compression factor of the sock lining  20  over the area of the sock lining  20 . Thus, the combination of the last  10  with sock lining  20  in position with the mold shells  70  and plates  60  closed there over, together operate in a novel manner to form the cavity that is required to make the intended item of footwear in like manner to a conventional mold core having no lining material. 
         [0022]    For the injection process, the plates  60 ,  105  of the upper and sole molds  55 ,  115  are tightly closed and sealed whereby the last  10  with sock lining  20  is positioned between upper plates  60  and shells  70  to form an upper cavity  80  into which the molten thermoplastic injection material is injected in conventional manner by the injection molding machine  50 . As is the case for the conventional injection molding process, the upper mold  55  includes two shells  70  and two plates  60  which, when closed, provide the upper cavity  80  into which heated, molten injection material is injected under pressure. The mold  55  also includes a channel (not illustrated) extending from an opening to the cavity  80  for passage of the pressure-injected injection material into the cavity  80  to completely fill it, whereby the thermoplastic material adheres to the sock lining  20 . 
         [0023]    For the illustrated embodiment, the sole  140  of the footwear product is also injection molded by the injection molding machine  50  during the same injection cycle. The sole mold  115  includes a shell  100  and two plates  105 ,  110  as shown in  FIG. 2 . To provide processing efficiency, the illustrated exemplary injection molding machine  50  includes two sole mold shells  100  which are both attached to a rotatable plate  105 . After each injection cycle of the injection molding machine  50  the plate  105  is rotated 180 degrees whereby an empty shell  100  is positioned opposite a cover plate  110  attached to a table  90  of the injection molding machine and the other shell  100 , for which a sole injection has just been completed, is moved away from the cover plate  110  and in-line with the upper mold  70 . This enables the injection molding machine  50  to mold both a boot upper  130  and a boot sole  140  during one injection cycle and attach to a boot upper  130  molded during the same injection cycle a boot sole  140  that was molded during the previous cycle. Since the liquid injection material would flow between sole and upper if both were to be molded and attached at the same time, a previously molded sole is attached to an upper during the molding of the upper, and another sole is molded at the same time so it is ready for attachment to the next-molded upper. 
         [0024]    With reference to  FIG. 2 , when the upper plates  60  are closed the sole shell  100  opposite the cover plate  110  is tightly closed onto the cover plate  110  to form a cavity (not illustrated) between them into which an injection material for the sole is injected during the same injection cycle that the upper cavity  80  is injected with the injection material for the upper. At the same time, the other sole shell  100 , which is filled with a molded sole made during the previous injection cycle, is tightly closed onto the end of the upper mold  55  in-line with the bottom of the sock lining  20 . That previously made molded sole attaches to the upper while the upper is molded. 
         [0025]    After injection of the thermoplastic material into the upper cavity  80  and sole cavity formed between the sole shell  100  and cover plate  110 , it is cooled and hardens, thereby forming the molded boot. When sufficiently cooled, the plates  60 ,  105 ,  110  of the molds are opened (separated) and an operator of the injection molding machine  50  removes the finished waterproof boot having an attached lining  120  from the last  10  while the last holder  40  remains attached to the upper mold  55 . 
         [0026]    The upper mold  55  is designed to provide full coverage of the injection material into the cavity  80 . To do so, the design is crafted to take into consideration the non-uniform reaction of the microcellular material of the sock lining  20  as and when it is exposed to high pressure, high temperature and high stress during the injection molding process. For example, the exemplary 3 mm thick sock lining  20  will compress 0.075 mm more at the edges, where the mold closes, than in the middle of the mold. The surfaces of the shells  70  are designed to account for the dynamic compression changes which the sock lining  20  will undergo during the injection molding process, by allowing more (or less) space to form for the cavity  80  in relation to the compression factor of the sock lining  20  at the adjacent surfaces of the shells  70 . 
         [0027]    Injection ports of the mold (not illustrated) are provided for the passage of the molten injection material from an injector (not illustrated) of the injection molding machine  50 . For the illustrated embodiment, the injection ports are unconventionally placed on the outside of an upper shell  70 , rather than being hidden on the sole mold  115  as in the conventional injection molding process, to allow for a better flow of the injection material and filling of the upper mold cavity  80 . If, instead, the upper mold  55  is injected in conventional manner, the top of the toe area of the boot will have a joint line and, depending upon the application, this may not be desirable for aesthetic reasons. It may also decrease durability because a joint line may be more prone to crack when the boot is worn. 
         [0028]    As for conventional molds, the particular positioning and configuration (i.e. size and shape) to be selected for the injection ports also affects the timing of the contact of the injection material with the sock lining. If there is insufficient spacing for the injection material to flow and reach the extremities of the cavity, within seconds at the very high pressures and temperatures applied by the injection molding process, the injection material will become obstructed and the delay in flow will cause it to harden too early, not fill the cavity and clog the injector of the injection molding machine. Also, the upper mold  55  is designed so as to produce no overspill of the injection material which occurs when the edges of the mold plates are not sufficiently sealed together after the mold is closed. 
         [0029]    The details of the illustrated embodiment may be varied as considered expedient to a person skilled in the art and are not to be considered essential to the invention by reason only of inclusion in the preferred embodiment. Rather, the invention is defined by the appended claims.