FOOTWEAR STRUCTURE WITH IMPROVED WATERPROOF PROPERTIES AND METHOD OF ITS MAGNIFACTURE

Abstract: Footwear structure comprising an outer shaft (11), an inner shaft or lining (12), made of a material which is impermeable to water, but permeable to water vapour, an inner sole (13), an outer sole (14), made of a plastic material which is injection-moulded in situ from its liquid state, and at least a continuous rigid member (15) arranged between at least a portion of said inner sole (13) and the ground-treading base (14b) of said outer sole (14). The continuous rigid member (15) is substantially embedded in the plastic material of the outer sole (14), whose peripheral end (14a) extends upwards above at least a sewing seam (17) that joins together the lower ends (11a, 12a) of the outer shaft (1) and the inner lining (12), respectively, to each other. ADVANTAGES: footwear actually is waterproof, simple and of low-cost construction.

Description: FOOTWEAR STRUCTURE WITH IMPROVED WATERPROOF PROPERTIES AND METHOD OF ITS MANUFACTURE DESCRIPTION The present invention refers to a kind of footwear having waterproof properties as recited in the preamble of the appended claim 1. In the last few years, a number of solutions have been proposed in view of remedying the age-old water seepage problem that most especially troubles footwear made under heavy utilization of synthetic materials, both in the form of cut-to-measure pieces of cloth or parts that are injection-moulded in-situ. It is in fact largely known that, owing mainly to the kind of comfort that they offer to the users and their relatively reduced cost, these footwear enjoy an ever increasing acceptance on the marketplace. Figure 1, which accompanies this description, reproduces, albeit with different reference numerals, Figure 4 accompanying the patent publication US-A-6 088 935, which is a schematical cross-sectional view of a footwear structure that can be considered as constituting a particularly interesting example of the current state of the art. Said footwear structure comprises, further to an outer outer shaft 1, an inner shaft or lining 2, an inner sole or arch-support 3 and an injection-moulded outer sole 4, also two sealing strips 5, 6. The inner lining 2 is constituted by at least a functional layer that is impermeable to water, but permeable to water vapour, as well as at least a layer of lining material on the inner side of the footwear, whereas the inner sole 3 is made more or less integrally of a waterproof material. The same applies to the strips 5, 6, which are also made of a waterprof material. The lower end 2a of the inner lining is enclosed between the two strips 5, 6, which on one side are glued in a waterproof manner to said end 2a and, on the other side, are glued together. The lower end la of the outer shaft 1 is in turn joined to the strip 5 by means of a first Strobel sewing seam 7 (which is called in this way owing to its being carried out with a sewing machine manufactured by the homonymous firm that makes a sewing seam following a zigzag pattern), while both strips 5 and 6, in correspondence of the zone where they are glued to each other, are joined to the inner sole 3 by means of a second Strobel sewing seam 8. Quite obviously, the outer side end 4a of the injection- moulded sole 4 extends upwards beyond the strips 5, 6. Such a footwear structure performs quite satisfactorily, but requires a rather complex manufacturing cycle, especially as far as to the positioning of the strips and to the need for both gluing and sewing techniques to be used, and this does of course considerably affect the manufacturing costs on the whole. Furthermore, owing to the fact that, with a Strobel machine, the perforations of the needle reach only up to 5 to 6 millimetres from the end of the outer shaft, an integral embedding of the sewing seams 7 and 8 in the injected plastic material of the sole 4 can not be ensured It therefore is a main purpose of the present invention to provide a footwear structure featuring an excellent resistance to water seepage and capable of being manufactured in a simple and economic manner. As a result, also consumers with a medium-to-low purchasing power can afford to buy footwear made in this way. The features of the present invention form the subject of the appended claims and will be more readily understood, along with the advantages of the present invention, from the description that is given below of a preferred, although not sole embodiment thereof. In this connection, reference should be made also to the accompanying drawings, in which: — Figure 1 is a schematical view of a footwear structure representing the state of the art which is considered by the Applicant as being the most relevant, and which has been already discussed earlier in the present description; - Figure 2 is a view of a footwear structure according to the present invention, as represented again in a schematical form from a section on a transversal plane, ie. a plane that is perpendicular to the median longitudinal plane of the foot. As shown in Figure 2, a footwear structure according to the present invention comprises, further to an outer shaft 11 and an inner shaft or lining 12, also a continuous rigid member 15 arranged in an intermediate position between an inner sole or arch- support 13 and the ground-treading base 14b of an outer sole 14. As this is the case in the prior art, the inner lining 12 is made of a material (such as the ones that are currently marketed under the trade-names of SYMPATEX™ and GORE- TEX™) that is constituted by at least a functional layer, which is impermeable to water, but permeable to water vapour, and by at least a layer of lining material on the inner side of the footwear, whereas the outer sole 14 is manufactured out of a plastic material, such as a polyurethane, which is injection-moulded in situ from its liquid state. The inner sole 13 is in turn manufactured out of a wide-mesh net-like fabric capable of being penetrated, during the injection-moulding operation, by the liquid-state material of the outer sole 14, and is interrupted at a short distance, which may be situated anywhere between approx. 25 and 35 mm, from the end portion of the heel to the purpose of allowing for the insertion of a continuous rigid member 15. Such a continuous rigid member, that forms one of the main features of the present invention, has a uniform thickness in the order of 4 to 5 millimetres and is made of either a natural material (eg. leather) or a synthetic material (eg. polypropylene homopolymer) which remains grafted, ie. clinging to the injected material of the outer sole 14, but, unlike the inner sole 13, is not penetrated by the same material. According to another basic feature of the present invention, the peripheral end 13a of the inner-sole 13 is bent downwards in such a manner as to be capable of being joined to the lower ends 11a and 12a of the outer shaft 11 and the inner lining 12, respectively, by means of a kind of straight-line sewing seam 17 running close to the terminal end, which, in a per se known manner, is preferably carried out with the use of a monofilament. It should be recalled here that a straight-hne sewing seam of such a kind is a continuous seam (rather than a zigzag one like a typical Strobel sewing seam) and this offers the practical advantage that the perforations of the needle reach up to as far as 2 millimetres from the end of the outer shaft 11 (whereas, as this has been pointed out earlier in this description the perforations of the needle reach up to only 5 to 6 millimetres from the end of the outer shaft in a Strobel sewing seam). As this may be noticed in Figure 2, the thickness of the continuous rigid member 15 is more or less equal to the height of the afore cited ends 11a, 12a, 13a which are joined to each other by the straight-line sewing seam 17. The manufacturing cycle for a footwear structure according to the present invention substantially consists of the following steps, which come downstream of the production of the individual component parts that are not made or obtained in situ: a) joining of the peripheral end 13a of the inner sole 13 to the lower ends 11a and 12a of the outer shaft 11 and the inner lining 12, respectively, by means of the afore cited straight- line sewing seam 17; b) rotation by 180° (practically, an overturning) of the first sub-assembly, ie. the one obtained in the preceding phase a); c) arrangement of the continuous rigid member 15 on the portion 13b of the inner sole 13 that is inside the peripheral end 13 a, in such a manner as to obtain a second sub-assembly constituted by the combination of said first sub-assembly with said member 15. In this connection, the fact should be duly emphasized that the "clearance", as indicated with X in Figure 2, between the end 15a of the member 15 and the end 13a of the inner sole 13 is actually quite narrow, typically 4 to 5 mm. d) arrangement of the second sub-assembly, ie. the one obtained in the preceding phase c), in a traditional mould formed by a plunger or male portion and, of course, a corresponding female portion whose pattern reproduces the ground-treading surface 14b of the footwear. Such a mould does not require a more detailed illustration or explanation, since it is largely known to all those skilled in the art; e) closing of the mould and injection of the liquid plastic material for moulding the outer sole 14 in situ, in such a manner as to enable the peripheral end 14a thereof to come to lie clearly above the straight-line sewing seam 17, as this is already per se known. As already mentioned earlier in this description, during its injection the liquid plastic material penetrates through the meshes of the net-like fabric used to make the inner lining 13, but is unable to penetrate the continuous rigid member 15. The advantages deriving from a footwear structure made in the above illustrated manner can be summarized as follows : - thanks to the penetration through the wide meshes of the net-like fabric used in the manufacture of the inner sole 13, and thanks to said inner sole being interrupted at a short distance from the end of the heel, both the continuous rigid member 15 and the straight- line sewing seams 17 between the afore cited ends 13 a, 11a, 12a of the inner sole or arch- support 13, the outer shaft 11 and the inner lining 12, respectively, are entirely embedded in the plastic material used in the manufacture of the outer sole 14. As a result, the footwear actually assumes a structure that might be defined as "monolithic" and, as such, is therefore very effective in ensuring both mechanical strength and robustness and resistance against water infiltrations along the surfaces of the outer shaft 11 and the inner lining 12; — the continuous rigid member 15 being so centered with respect to the outer shaft 11 and the inner lining 12 ensures a constant quality even in the case of mass-production in very large quantities; — the use of a monofilament for the straight-line sewing seams 17 is effective in further reducing the risk of seepage (water penetration). Although the above description refers to a preferred embodiment of the present invention, it will be appreciated that the footwear structure may be implemented according to other embodiments, without of course departing from the scope of the present invention as defined by the appended claims.

Claims: CLAIMS 1. Footwear structure comprising: - an outer shaft (11), made using one or more materials, - an inner shaft or lining (12), made of a material that is constituted by at least a functional layer, which is impermeable to water, but permeable to water vapour, and, on the inner side of the footwear, by at least a layer of lining material, - an inner sole (13), - an outer sole (14), made of a plastic material that is injection-moulded in-situ from its liquid state, whose peripheral end (14a) extends upwards above at least a sewing seam (17) that joins the lower ends (11a, 12a) of the outer outer outer shaft (11) and the inner lining (12), respectively, to each other, characterized in that it further comprises at least a continuous rigid member (15) arranged between at least a portion of said inner sole (13) and the ground-treading surface (14b) of said outer sole (14). 2. Footwear structure according to claim 1, characterized in that said continuous rigid member (15) is made of such materials, either natural or synthetic, as to enable it to cling to the injected material of the outer sole (14), while preventing penetration by the same material. 3. Footwear structure according to claim 1 or 2, characterized in that said inner sole (13) is made of a wide-mesh net-like or similar fabric capable of being penetrated, during the injection-moulding operation, by the liquid-state material of the outer sole (14). 4. Footwear structure according to any of the preceding claims, characterized in that the peripheral end (13a) of the inner sole (13) is bent downwards and spaced from the peripheral end (15a) of said continuous rigid member (15). 5. Footwear structure according to the preceding claims, characterized in that even the at least one sewing seam (17) is of the continuous type and capable at the same time of also ensuring the downward-bent peripheral end (13a) of the inner sole (13) to be joined to said lower ends (11a, 12a) of the outer shaft (11) and the inner lining (12), respectively. 6. Footwear structure according to any of the preceding claims, characterized in that said at least one sewing seam (17) is carried out using a monofilament. 7. Method for manufacturing a footwear structure comprising, according to any of the preceding claims : - an outer shaft (11), made using one or more materials, - an inner shaft or lining (12), made of a material that is constituted by at least a functional layer, which is impermeable to water, but permeable to water vapour, and, on the inner side of the footwear, by at least a layer of lining material, - an inner sole (13), - an outer sole (14), made of a plastic material that is injection-moulded in-situ from its liquid state, whose peripheral end (14a) extends upwards above at least a sewing seam (17) that joins the lower ends (11a, 12a) of the outer outer outer shaft (11) and the inner lining (12), respectively, to each other, - at least a continuous rigid member (15), characterized in that it comprises the steps of: - joining of the peripheral end (13a) of the inner sole (13) to the lower ends (11a, 12a) of the outer shaft (11) and the inner lining (12), respectively, by means of a same continuous sewing seam (17), so as to thereby obtain a first subassembly; - rotation of said first subassembly by 180° so as to overturn it; - arrangement of the continuous rigid member (15) on the portion (13b) of the inner sole (13) that is inside the peripheral end (13a) thereof, in such a manner as to obtain a second subassembly; - arrangement of said second sub-assembly in a traditional mould for the injection of the plastic material of the outer sole (14), in such a manner as to enable said continuous sewing seam (17) and said continuous rigid member (15) to be substantially embedded in the same plastic material of the outer sole (14).

Inventors: MUGNAINI SERGIO, MUGNAINI, SERGIO
Applicants: CALZATURIFICIO SKANDIA SRL, MUGNAINI SERGIO, MUGNAINI, SERGIO
Application year: 2001
Main classification: A43B7
IPC codes: A43B7, A43B9, B29D31