[0001] This invention relates to a footwear element of rigid or semi-rigid behaviour, in
accordance with the introduction to the main claim.
[0002] As is well known, for certain footwear, and in particular sports footwear, the sole
unit must behave rigidly or at least semi-rigidly. This is for example the case in
mountain shoes or boots, cycle shoes and boots for roller skates (both of traditional
type and with in-line wheels), or in footwear used for certain athletics specialities.
This sole unit behaviour is required in order to achieve better foot support and/or
to enable the user or athlete to transfer the greatest possible force to the ground
or to the vehicle on which he moves (for example a bicycle), in order to achieve improved
performance.
[0003] Usually, to achieve a greater or lesser rigidity of the sole unit (traditionally
of leather or rubber, or of rubber and/or synthetic polymer mixtures), two different
methods are used, namely by inserting into the shoe vamp an insole constructed of
more rigid materials than those used for the sole unit, such as wood, leather, cellulose
conglomerates (such as that known by the commercial name of Texon), or of synthetic
polyurethane resins, polypropylene, nylon or the like, or by metal blade or bar inserts;
or by using rigid materials for the sole unit itself, such as leather, wood or synthetic
resins of the aforesaid type. The first method (insole) is used for example for mountain
shoes or boots, and the second method for example for clogs.
[0004] These solutions only partly achieve the desired object, ie they achieve only a limited
sole or insole rigidity.
[0005] Footwear has recently appeared on the market having the sole unit or insole (and
in particular the whole or part of the sole unit) constructed of composite materials
combining fabrics or fibres of light materials having a high elastic modulus (such
as carbon, aramid, glass or synthetic resin fibres) embedded in a resin acting as
a binder. Such solutions and constructional methods result in components (soles or
insoles) having a considerable rigidity/weight ratio, making them advantageous over
components obtained by the two aforesaid methods. However these components have a
higher cost than that achieved by the other said known methods. This derives from
the high cost of certain fibres (such as carbon fibres) and of the production process,
which is usually slower and more delicate than those involved in the production of
components constructed only of synthetic resins or by the other aforesaid known methods.
[0006] An object of this invention is to provide a footwear element of rigid or semi-rigid
behaviour for use in footwear as a sole unit or part of the sole unit or as an insole
which, although providing the footwear with the required rigidity, is of very low
constructional cost.
[0007] This and further objects which will be apparent to the expert of the art are attained
by a footwear element in accordance with the characterising part of the main claim.
[0008] The invention will be more apparent from the accompanying drawing, which is provided
by way of non-limiting example and on which:
Figure 1 is an exploded view of a mountain boot provided with the element of the invention;
Figure 2 is a section on the line 2-2 of Figure 1;
Figure 3 is a cross-section through a cycling shoe provided with the element of the
invention;
Figure 4 is an exploded view of a different embodiment of the invention;
Figure 5 is a perspective view of a further embodiment of the invention;
Figures 6A, 6B, 6C are sections through that portion of the element of the invention
indicated by K in Figure 4;
Figures 7A, 7B, 7C are sections on the line 7-7 of Figure 4 showing different forms
of the element of the invention;
Figure 8 shows a further embodiment of the invention;
Figures 8A, 8B and 8C are sections on the lines 8A-8A, 8B-8B and 8C-8C of Figure 8
respectively;
Figure 9 shows a further variant of the invention; and
Figures 9A, 9B and 9C are sections on the lines 9A-9A, 9B-9B and 9C-9C of Figure 9
respectively.
[0009] Said figures show an element 1 for footwear such as a mountain boot 2 or a cycle
shoe 3, said element being arranged to stiffen a lower part 4 of said footwear, which
comprises a vamp 7 associated with said part 4. In one embodiment of the footwear,
shown in Figures 1 and 2, this lower part 4 comprises a sole unit 8 of rubber or similar
material, on which the rigid or semi-rigid element 1 is positioned and fixed to act
as an insole. Between the element 1 and sole unit 8 there can be provided a damping
intersole 9 of expanded polyurethane or expanded ethylvinylacetate (EVA). On the element
1 there is placed a usual removable anatomic insole 10. Consequently in these figures,
the element 1 stiffens the part 4, and is fixed to the sole unit by gluing or the
like.
[0010] In contrast, in Figure 3 the element 1 acts as the actual sole unit, and is joined
to the vamp in the usual manner, for example by gluing. The removable insole 10 is
placed on the element 1 as in the footwear embodiment of Figures 1 and 2, added pieces
of rubber 11 (or other like material) possibly being applied externally to the lower
side of said element and fixed to this element in known manner, for example by gluing.
[0011] The element 1 is of layered type and comprises (see Figures 6A, 6B and 6C) three
layers mutually superposed to form a one-piece sandwich. The outer layers 13 and 14
are of a material having greater rigidity than the inner layer 15, the thickness of
this latter being however greater than the individual layers 13 and 14. Preferably
the layers 13 and 14 (connected together laterally, at the edges or side walls 26
and 27 of the element 1, so as to enclose the layer 15 within them), are constructed
of the same material, and in particular of artificial plastic or synthetic resin,
or of nylon, polyurethane or polypropylene, or of composite material comprising synthetic
resins and fabrics or fibres of carbon aramid, glass or other synthetic resins. The
layer 15, acting as the core of the layered structure 1A of the element 1, is constructed
of a lighter material than the constituent material of the layers 13 and 14, such
as artificial plastic foam or expanded resin (shown in Figure 6C), cellular materials
of natural origin (such as light wood, shown in Figure 6A), or cavity-containing materials
(Figure 6B) formed from touching cylindrical plastic elements 17 of equal or different
circular cross-sections or of elliptical or polygonal cross-sections. The elements
17 can be solid or hollow and define a honeycomb structure.
[0012] As stated, the various layers 13, 14 and 15 are joined together to form a one-piece
structure 1A which cannot be separated into its various components. The various components
(layers) of the structure 1A are integrated in various ways: for example by polymerizing
the epoxy resin with which the layers 13 and 14 have been preimpregnated, if thermoplastic
materials are used; by softening the resin defining the core (Figure 6C) until fusion,
if thermoplastic materials are used for the layers 13 and 14; or by gluing the various
layers together, this method being suitable whether the layers 13 and 14 are of thermosetting
or thermoplastic materials.
[0013] A stiffening element 1 obtained in accordance with the invention is of lower cost
than a known equal-thickness similar element obtained from composite materials, however
its rigidity is comparable to these. The element 1 is very light in weight compared
with analogous known elements, while having at least a comparable rigidity to these
layer. It is preferably used along the entire extent of the lower part 4 of the footwear
2 or 3 (ie along the entire foot of the user) and can comprise a plurality of portions
of constant or variable cross-section 20, 21, 22 (Figure 5 but again in layer form)
with different flexibilities on the basis of their position relative to the user's
foot (for example with greater flexibility at the forefoot). This different flexibility
can also be obtained by constructing the element 1 in one piece (but again of layer
form) with different thicknesses, decreasing towards the front end 23 of the element
1 (with reference to the foot shape of the user wearing the footwear 2 or 3), as shown
in Figures 4 and 5. Alternatively, the thickness of the element 1 can be greater in
the forefoot portion or region 20 and decrease towards the heel region 22, or be constant
along its entire longitudinal axis A, as shown in Figure 1. Furthermore, the cross-section
of the element 1 can be constant (Figure 7A), variable (Figure 7B) and decreasing
towards its lateral edges 26 and 27, or comprise ribs 28 (Figure 7C) for further stiffening.
[0014] Alternatively, to achieve differential rigidity for the element 1, it can comprise
differently ribbed portions (as in the embodiment of Figure 8 to 8C). For example
the front portion or forefoot 20 can comprise at least one pair of lower parallel
ribs 33, with no ribs on the arch portion, and with the heel or ankle portion 22 comprising
only one central rib 34.
[0015] In a further variant of the invention (see Figures 9 to 9C), at least the lower part
(with reference to the figures under examination) can be clad with a film 36 of thermoplastic
material (such as that known by the commercial name of PEBAX) able to protect that
element. As shown in Figure 9, the film 36 can also cover at least a portion of the
upper part of the insert, in its forefoot region 20, and in that case also wrap the
lateral part of the corresponding element 1 (see Figure 9A). This film is associated
with the element 1 for example during the polymerization of the aforedescribed resin,
or otherwise during the assembly (moulding) of the various portions of said element.
During this stage, a layer 44 of fibrous material, such as felt or non-woven fabric,
can also be associated with the underside of the element 1 (see Figures 9 to 9C).
This facilitates the subsequent fixing of this element into the sole unit or onto
the intersole (or equivalent element) when this element is finally positioned, as
a foot support, within the relative footwear (for example the boot 2).
[0016] Other variants of the invention can be devised in the light of the aforegoing description,
and are to be considered as falling within the scope of this document.
1. An element of rigid or at least semi-rigid behaviour for stiffening a lower part or
portion (4) of footwear (2, 3), and suitable for use as the sole unit or as an insole
or internal foot support for the footwear, this latter comprising a vamp (7) associated
with the lower portion (4) of the footwear, characterised in that said element (1)
presents a layered body (1A) comprising at least three mutually associated superposed
portions (13, 14, 15) defining a sandwich structure, the outer portions (13, 14) having
greater rigidity than the inner portion (15), these portions being stably joined together
to form a single body (1A).
2. A stiffening element as claimed in claim 1, characterised by being positioned on a
sole unit (8) and acting as an assembly foot support.
3. A stiffening element as claimed in claim 1, characterised by being positioned on the
outside of the footwear (3) to act as a sole unit.
4. A stiffening element as claimed in claim 1, characterised by being positioned along
the entire plantar arch by the user who wears the footwear.
5. A stiffening element as claimed in claim 1, characterised by comprising portions of
differential flexibility, preferably with greater flexibility at its front end (23).
6. A stiffening element as claimed in claim 5, characterised in that said portions are
well defined parts (20, 21, 22) of its body (1A).
7. A stiffening element as claimed in claim 5, characterised in that said portions are
defined by a variation in the thickness of the body (1A) of the element (1), this
thickness decreasing at the front end (23) of said body.
8. A stiffening element as claimed in claim 1, characterised by being of constant cross-section.
9. A stiffening element as claimed in claim 5, characterised in that the thickness of
the portions (20, 21, 22) of its body (1A) decrease along the longitudinal axis (A)
of said body in passing from the forefoot portion (20) to the heel portion (21).
10. A stiffening element as claimed in claim 1, characterised by a tapered cross-section
in correspondence with its lateral edges (25, 27).
11. A stiffening element as claimed in claim 1, characterised by comprising surface projections
(28) extending from a free face thereof.
12. A stiffening element as claimed in claim 1, characterised by comprising at least one
stiffening rib (33, 34) along at least a part of that surface facing the lower part
of the footwear (2, 3) with which it is associated.
13. A stiffening element as claimed in claim 1, characterised in that the outer portions
or layers (13, 14) of its layered body (1A) are joined together at the lateral edges
(26, 27) of said body, said portions enclosing the central portion or core (15).
14. A stiffening element as claimed in claim 13, characterised in that the outer portions
(13, 14) of its layered body (1A) are of an artificial plastic material of at least
relatively high rigidity.
15. A stiffening element as claimed in claim 14, characterised in that the outer portions
(13, 14) are of polyurethane.
16. A stiffening element as claimed in claim 14, characterised in that the outer portions
(13, 14) are of polypropylene.
17. A stiffening element as claimed in claim 14, characterised in that the outer portions
(13, 14) are of nylon.
18. A stiffening element as claimed in claim 14, characterised in that the outer portions
(13, 14) are of composite material.
19. A stiffening element as claimed in claim 18, characterised in that the composite material
comprises a carbon, aramid, glass or similar fibre fabric.
20. A stiffening element as claimed in claim 18, characterised in that the composite material
comprises carbon, aramid, glass or similar fibres.
21. A stiffening element as claimed in claim 1, characterised in that the inner portion
or core (15) is of plastic foam or expanded resin.
22. A stiffening element as claimed in claim 1, characterised in that the inner portion
or core (15) is of cellular material of natural origin.
23. A stiffening element as claimed in claim 1, characterised in that the inner portion
or core (15) is of honeycomb material.
24. A stiffening element as claimed in claim 1, characterised in that the inner portion
(15) comprises cylindrical elements positioned between the outer layers (13, 14).
25. A stiffening element as claimed in claim 1, characterised by being clad, at least
on one of its faces, with a protection film (36).
26. A stiffening element as claimed in claim 25, characterised in that the protection
film (36) is of thermoplastic material.
27. A stiffening element as claimed in claim 1, characterised by being clad, at least
on one of its faces, with a fibrous material layer (44).
28. A stiffening element as claimed in claim 1, characterised in that the various portions
(13, 14, 15) of the layered body are joined together by gluing.
29. A stiffening element as claimed in claim 1, characterised in that the various portions
(13, 14, 15) of the layered body (1A) are joined together by polymerizing the resinous
material defining the outer layers of said body.
30. A stiffening element as claimed in claim 1, characterised in that the various portions
(13, 14, 15) of the layered body (1A) are joined together by fusing the inner layer
(15).