Patent Application
20080163519
The present invention relates to a reinforced toe-cap for safety footwear according to the characteristics set forth in the preamble to the main claim. It is also directed towards a kit for the production of a reinforced toe-cap.
In the technical field to which the invention relates, reinforcing toe-caps to be inserted so as to fit in toe regions of safety footwear are known.
Since these toe-caps are intended to protect the ends of the feet, they have to be able to withstand the impact of predetermined falling loads without breaking and without undergoing significant deformation in accordance with standard tests for evaluating the strength of these items. In order to offer the mechanical properties that are necessary to pass the required strength tests, it is known to make the toe-caps of metal or plastics material or even of composite material.
However, each of the above-mentioned types has some disadvantages. In fact metal toe-caps are generally heavy and are also unsuitable for some uses including use in locations in which there may be metal-sensitive apparatus (for example, metal detectors) or in locations in which there is a need to withstand very high or very low temperatures, given the high thermal conductivity of metals. As far as toe-caps made of plastics materials are concerned, they generally have to have considerable thicknesses in order to offer the required mechanical strength, to the detriment of the dimensions and comfort of the footwear in which they are fitted. Finally, the use of reinforcing toe-caps made of composite material is limited by the relatively high production cost.
Reinforcing toe-caps having particular shapes, for example, with variable thickness along the cross-section of the toe-cap, are also known.
The problem underlying the present invention is that of providing a reinforcing toe-cap for safety footwear that is designed structurally and functionally to overcome the limitations set out above with reference to the prior art mentioned.
This problem is achieved by the present invention by means of a reinforcing toe-cap formed in accordance with the appended claims.
The characteristics and the advantages of the invention will become clearer from the detailed description of some preferred embodiments thereof which are described by way of non-limiting example with reference to the appended drawings, in which:
With reference initially to
The toe-cap 1 is intended to be connected, by conventional techniques, to a sole and/or to the upper of a safety shoe or boot, not shown.
The toe-cap 1 comprises a body 2 which is generally in the shape of a half-shell that is open on one side in the region of an opening 3 through which the user's foot is inserted; the half-shell is closed at the opposite end by a front region 4 of the toe-cap.
A top region 5 extends and is defined between the opening 3 and the front region 4 which is intended to face the end of the foot in use; the top region 5 is connected to the front region 4 and is intended to face the upper surface of the foot in use.
A terminal portion 2a of soft material such as, for example, rubber preferably also extends from the opening 3 of the body 2 to improve the comfort of the footwear.
According to a first aspect of the invention, a protuberance 6 is formed on the body 2, the protuberance projecting from the natural profile defined by the curvature of the toe-cap. For clarity, the natural profile of the toe-cap is indicated by a broken line in the section of
In this context, the term “protuberance” therefore adopts the generally accepted meaning which, in an attempt to give it a greater geometrical connotation, could be defined as a surface portion which comprises a maximum of curvature and is joined at least to a portion of the surrounding surface by a concave connecting region, or by a region of discontinuity of curvature.
The protuberance 6 is preferably formed on the top region 5 at a distance S of between 10 and 35 mm from the end of the front region 4, but it may also usefully be formed on the front region, as explained further below.
The body 2 is preferably produced by the technique of injection and moulding of a plastics material such as, for example, polycarbonate, polyamide, polypropylene, polyethylene or other polyolefins. However, it may also advantageously be made of other materials that are conventionally used in the field in question, such as metals or composite materials. The latter are preferably of the type with woven or non-woven long fibres impregnated with a thermosetting or thermoplastic resin matrix.
In the first embodiment of the invention described herein, the protuberance 6 is produced integrally with the body 2 and preferably has a lenticular shape with a generally elliptical base plan and with the following dimensions: height H relative to the profile of the top region of between 1 and 5 mm; both longitudinal and transverse dimensions L of the base of between 10 and 40 mm.
The protuberance 6 may, however, be circular in plan or may have other shapes more complex than that shown in the appended drawings. For example, it may extend longitudinally along the top region 5 possibly also extending over the front region 4, it may extend longitudinally in a central position or in an offset position, or it may have an arcuate base plan or a flatter profile, for example, with a trapezoidal cross-section.
Moreover, two or more protuberances may also be provided, extending on the top region 5 and/or the front region 4 parallel to one another or intersecting one another.
To compare the properties of toe-caps formed in accordance with the present invention with those produced conventionally, that is, without protuberances on the top region, the Applicant has carried out a series of tests to demonstrate their impact strength.
A test typically used to check the impact strength consists in dropping a metal gravity body having a predefined weight (normally 20 kg), on edge, from a predetermined height (normally 1 metre), onto the toe-cap to be tested (ISO standard 20345/2003).
The test is considered to be passed if the maximum deformation caused in the toe-cap by the impact with the gravity body is below a predetermined threshold and the toe-cap does not have significant cracks. In this case the toe-cap would in fact be able to perform the function of protecting the user's foot in a positive manner.
Naturally, the toe-caps of both types were produced by the injection and moulding of the same plastics material, in the specific case, polycarbonate.
The results of the tests showed that the presence of the protuberance 6 conferred on the toe-cap 1 a greater ability to withstand impacts by falling gravity bodies which was quantifiable as an increase of about 10%-15%.
Although it is not desired to be bound to a particular theory, the favourable results obtained might be explained by the fact that, for a given material and thickness, the impact is absorbed better by a structure having a more marked curvature in comparison with a flatter structure, since a significant component of the forces discharged onto the toe-cap by the impact with the gravity body is discharged towards the side walls of the toe-cap and by the side walls to the sole. With the low-curvature surface of conventional toe-caps, on the other hand, the component of the force which has to be absorbed by the region of the toe-cap corresponding to the impact is much greater and this consequently causes the greater deformation of the material.
Moreover, it should be noted that, in conventional toe-caps, the region of lesser curvature is often precisely the top region where the likelihood of an impact by a load falling from above is greatest and therefore where the protective function of the toe-cap is most important.
The impact strength of the top region can thus be increased without increasing the thickness of the layer of plastics material.
In the above-mentioned case in which the protuberance is formed in the front region 4, the toe-cap naturally adopts a greater impact strength in that region. This may be useful when the footwear in which the toe-cap is to be fitted is required to offer a particular impact strength in that specific region. This is the case, for example, in footwear used by firemen which have to be capable of being used to kick down obstacles (for example, a door).
The toe-cap 100 comprises a protuberance 106 which is produced by being moulded onto the previously-produced body 2.
The protuberance 106 can thus advantageously be moulded on with a plastics material different from that used to produce the body 2, thus permitting greater freedom in the selection of the materials to be used in accordance with appropriate considerations of economy, type of application, and efficiency of performance. For example, the protuberance may advantageously be made of polycarbonate or of polyamide and the body 2 of less expensive polypropylene.
In the toe-cap 200, the protuberance is produced by connecting a supplementary piece 206 to the body 2. These elements are produced separately and independently and can be connected, for example, by gluing.
The supplementary piece 206 may advantageously be made of any material that is considered suitable, including plastics material, for example, those mentioned above, a metal, a composite material, etc.
In this embodiment, a closed chamber 207 is defined between the supplementary piece 206 and the body 2. This structure is generally stronger, given that the overall impact strength in the region of the protuberance is determined both by the presence of the supplementary piece 206 and by the presence of the body 2.
According to a first variant of the invention, a material having viscoelastic or elastomeric properties, such as, for example, silicone or thermoplastic, vulcanized or even expanded rubbers, may be provided in the closed chamber 207.
According to a second variant of the invention, a layer of tear-resistant and substantially inextensible material, for example, an aramidic-fibre fabric such as the material known by the trade name of Kevlar®, is interposed between the supplementary piece 206 and the body 2.
These measures further improve the impact strength of the toe-cap 100.
In fact, tests carried out by the Applicant have shown that the interposition of a viscoelastic or elastomeric layer or of an aramidic-fibre fabric increases the impact strength of the toe-caps by a fraction quantifiable as between 15% and 20%.
As well as providing finished toe-caps in which the body and the toe-cap are already connected to one another, this latter embodiment of the invention advantageously permits the production of safety toe-caps from separate elements which are made of different materials and which can be combined with one another in various ways to produce toe-caps that are individualized according to the specific field of application of the safety footwear in which they are to be fitted.
The body 2 will generally be produced by injection and moulding of plastics material, whereas the supplementary piece 206 that can be connected to the body 2 will be available in plastics material with better mechanical characteristics (polycarbonate, polyamides, ABS, and other techno-polymers), or in metal, or even in composite material.
It is thus possible to provide kits suitable for the production of a reinforced toe-cap for safety footwear and comprising a body made of plastics material and one or more supplementary pieces made of different materials each arranged to be connected to the body 2. This operation can be performed by the safety footwear manufacturer who may in general be other than the manufacturer of the toe-caps. In this latter case, moreover, the capability is provided for a supplementary piece that has been damaged as a result of an impact to be replaced-by another supplementary piece without replacing the entire shoe or boot.
According to a variant of the present invention which is applicable in the same manner to all of the embodiments described above, a layer of tear-resistant and substantially inextensible material such as an aramidic-fibre fabric, for example, Kevlar® may be applied firmly on top of the protuberance 6, 106, and 206. The toe-caps thus obtained have clear improvements, at least of the order of 10%-20%, in terms of impact strength.
This advantageous effect can reasonably be attributed to the fact that, by virtue of the presence of the aramidic-fibre fabric, the stresses resulting from the impact, which is extremely localized, are distributed over a much larger area. In fact it is pointed out that a localized deformation of the body 2 translates into a tensile load on the fabric between the deformed region and the non-deformed (or less deformed) region and into a shearing stress between the fabric and the surface of the body that is in contact with the fabric. However, these loads are resisted by the properties of tensile strength and very low percentage extension which characterize aramidic fibres and by the adhesion force between the fabric and the body.
The aramidic-fibre fabric may also be wrapped around the body 2 so as to be closed in a loop around the body without breaks in continuity. Greater lateral limitation of deformation of the toe-cap is thus achieved, resulting in a further increase in impact strength.
The present invention thus solves the problem discussed with reference to the prior art mentioned, at the same time offering many further advantages.
| Number | Date | Country | Kind |
|---|---|---|---|
| PD2005A000084 | Mar 2005 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/000942 | 2/3/2006 | WO | 00 | 9/6/2007 |
