US20170332729A1

US20170332729A1 - Footwear

Info

Publication number: US20170332729A1
Application number: US15/521,181
Authority: US
Inventors: Francesco Milianti
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-10-23
Filing date: 2015-10-15
Publication date: 2017-11-23
Also published as: WO2016063178A1

Abstract

A footwear comprises a sole constituted by at least an outer sole and a inner sole, it is of the type without heel, capable of support the foot substantially parallel to the ground or with the ground contacting surface of the heel raised of not more than 20 mm compared to the metatarsal ground contacting surface, and has a configuration such as to form a bending at the metatarsal-phalangeal joint, with the phalangeal portion elastically deformable downwards.

Description

TECHNICAL FIELD

The present invention fits in the technical field of footwear.
More specifically, the invention relates to a shoe having a peculiar conformation of the sole with a front portion bent upwards.

BACKGROUND ART

In the footwear industry it is widely known the need to design footwear which will allow and help the correct execution of the stepping activity and in general the maintenance of a correct posture. It is common knowledge the fact that footwear with soles too stiff, or with heel too high can give rise with long use to postural problems since, in fact, do not allow the correct execution of the step which, as well known, must be characterized from a correct succession of ground contacts and oscillations of the limbs that allow the correct transfer of loads from a limb.
In general, sport footwear are those in which greater attention is paid, at the design stage, to the respect of the needs described above with the result of producing footwear with ergonomic insoles, cushioning ability and differentiated flexibility, the outer sole being shaped so as promote the proper oscillatory movement of the foot. In particular, especially in shoes so-called ‘running’, the lower profile of the sole presents very often a suitable upward bending of the front portion, from approximately the metatarsal area forward, in order to facilitate the loading on the front area of the foot (metatarsal and fingers) in the last part of the ground contacting phase. As is obvious from the above, the sole of the shoe is the most important part of the shoe to achieve the purposes described above regarding the proper execution of the step, however, also the uppers associated with it has an important function as it must ensure the proper and stable positioning of the foot on the sole.
In addition, they are also known footwear and devices with unique characteristics suitable to promote proper posture. For example, in the published application WO0115560A1 it is described a device wherein to a closed upper of conventional type it is associated a sole with distinctive features which allows a correct oscillation of the foot during the whole phase of contact with the ground. The sole is composed of an inner sole, a midsole and an outer sole, each having certain characteristics of rigidity and elasticity, and wherein the outer sole and the midsole have the lower portion suitably curved in a convex shape, in particular with the front portion upwardly bent. Although the described sole has obvious advantages in facilitating the correct setting of the step, however, is rather bulky and heavy, thus requiring to be associated to an upper that ensures a stable positioning of the foot on the sole along its whole extension. In addition, also the production costs of a sole like that described in WO0115560A1 are quite relevant.
In addition, in footwear with open upper, such as sandals or slippers, it is particularly difficult to study soles, suitable to favour the correct execution of the stepping activity since, even for aesthetic reasons, the sole is usually of rather reduced thickness and the upper is of little help in maintaining a correct positioning of the foot on the sole. In fact, in this type of footwear there is the problem of keeping the foot correctly positioned on the sole and bound to it during all phases of the step.
A sole suitable especially for open summer footwear such as sandals or slippers, which tries to solve the problem of providing an aid to take a correct posture during walking and running is proposed by the United States patent application no. US 2012/0060390. It is described herein a shoe in which, inter alia, the sole provides for a bending in correspondence with the metatarsal zone and it is resilient so as to be bent with a certain angle of inclination between the front portion and the rear portion when unstressed, while relaxing completely in a configuration with the two portions (front and rear) substantially aligned when it is compressed by the weight of the foot. The main object of the aforesaid patent application is to propose a sole that improve comfort during walking, especially with open shoes, avoiding the detachment of the rear part of the sole from the heel of the foot during the phase of flexion of the foot and subsequent detachment from the ground, and yet must be sufficiently flexible to allow the sole to flatten out completely when there is the pressure of the foot above it. To achieve the above purposes the elastic return force must be limited. To obtain the desired elasticity the sole can be realized in various ways and in various materials as the elastic characteristics that must have the sole are not very stringent. In fact, in the patent application in question are cited a list of materials rather broad and vague for the sole, or for an insert inserted inside the sole. Thanks to the low elastic return force assured by the elastic material of the sole or the insert, when the foot and therefore the weight of the body are supported on the sole this exerts a very limited resistance to bending, therefore it flattens completely. The footwear described, although it is able to increase the comfort of use of footwear with open upper, as it facilitates the maintenance of a contact between the rear of the sole and the heel during all stages of the stepping activity, it does not solve the problem of providing a real assistance to the stepping activity since, because of the low coefficients of bending elasticity of the sole, the entity of the forces exerted by this on the sole of the foot, which are responsible for providing the activity of the path, are substantially irrelevant. The solution to the problem of increasing the elastic response of the sole to the stresses which are due to the support of the foot can not be limited to selecting a suitable material as the increase of rigidity of the sole tends to cause problems of comfort and stability of support of the foot, whose solution must be sought.

DISCLOSURE OF INVENTION

Summary of the Invention

The object of the present invention is to propose a shoe provided with a peculiar sole that favours the correct execution of the stepping activity.
More specifically, an object of the present invention is to propose a shoe with an upper which has a bending at the metatarsal axis able to elastically react to the forces applied by the body weight through the foot so as to provide assistance during the execution of the step, without reducing the comfort.
Another object is to propose a shoe provided with a sole that is both lightweight and has low manufacturing costs compared to that of other footwear adapted to facilitate the proper execution of the step.
Another object of the present invention is to propose in particular a shoe with open upper, such as a sandal or a slipper, which is improved in allowing the correct execution of step compared to conventional sandals or slippers.
Another object of the present invention is to propose a sandal that present laces or other wraparound fastening elements of the foot located only in correspondence of the proximal portion of the foot and at the same time ensures an optimum and stable positioning of the foot on the sole during all phases of the step.
The foregoing objects are achieved by means of a shoe as described in Claim 1.
A conventional type of shoe is constituted by an upper and a sole comprising at least an outer sole and an inner sole.
According to a characteristic feature of the present invention the sole of the shoe presents a bending line in correspondence of the metatarsal-phalangeal joint, with a phalangeal portion of the sole suitably connected to a metatarsal portion of the same, and wherein between the phalangeal portion and the metatarsal portion of the inner sole there is an angle in the longitudinal direction of between 25° and 60°, and the sole has bending elasticity and elastic bending limit at least at the bending such as to enable the elastic deflection downwards of the phalangeal portion of the sole up at least the alignment of the phalangeal portion with the metatarsal portion. Moreover, the elastic bending return force of the sole is such that when the entire sole of the foot is resting on the latter exerts on the front portion of the foot a force that maintains the portion of the fingers bent upwards of a certain angle.
The inner sole of the shoe of the invention has a shape such as to tend to maintain the phalangeal portion of the foot upwardly bent with respect to the rest of the foot, which is the natural position at least in the final part of the contact with the ground during the execution of the step. During all other phases of the contact with the ground and during the phases of the oscillation the phalangeal portion of the foot tends to push down the phalangeal portion of the sole so bending it elastically and creating an elastic reaction force of the phalangeal portion of the sole upwards. This elastic reaction force on the one hand tends to maintain the phalangeal portion of the sole well adherent to the bottom of the foot, even in the absence of elements of the upper which act as a constraint in the upper zone of the phalangeal portion and the metatarsal portion of the foot, and on the other tends to cause a counterclockwise rotation of the ankle, thus favouring the correct positioning with the heel in the terminal phase of the oscillation. In addition, the upward force exerted on the front portion of the foot, in particular on the fingers, is particularly helpful for all those people who tend physiologically and unknowingly to maintain tension on the fingers in a kind of attempt to anchor themselves to the ground.
Advantageously, the inner sole has raised peripheral edge of height not less than 0.5 cm at least at the heel and the phalangeal and metatarsal area.
The raised peripheral edge allows the side containment of the foot and, together with the upward force exerted upon the phalangeal portion of the foot caused by peculiar bending and the elasticity of the sole allow a perfect adherence of the foot to the sole at all stages of the step also in presence of open uppers having fastening elements of the foot only in correspondence of the proximal area.
Still advantageously the outer sole is hard and elastic, preferably made of EVA or like material for outer soles, inner soles is soft and elastic, preferably with cork core, and between them is interposed a sheet-like midsole element, preferably made of harmonic steel material or fiber-reinforced polymer matrix, comprising a phalangeal portion and a metatarsal portion in correspondence with a suitably rounded bending located at the metatarsal-phalangeal joint, wherein said midsole element has elasticity and limit of bending elasticity such as to constitute a torsion spring with appropriate elastic coefficient.
The presence of a midsole element as defined above allows to provide a sole of very thin substantially constant thickness and having the peculiar characteristics of shape and elasticity outlined above.

DESCRIPTION OF DRAWINGS

These and other features and advantages of the invention will be more easily understood from the following description of preferred embodiments, given as nonlimiting examples, according to with what reported in the claims and with reference to the accompanying drawings in which:

FIG. 1 shows a side view of a shoe, specifically a sandal, according to the present invention;

FIG. 2 shows a top view of the sole of the shoe of FIG. 1;

FIG. 3 shows, in a view similar to that of FIG. 1, an alternative embodiment of a shoe, specifically a sandal, according to the present invention;

FIG. 4 shows a midsole element comprised in the footwear of FIGS. 1, 2, and 3: FIG. 4a shows a side view, FIG. 4b shows a top view of it;

FIG. 5 shows a top view of an alternative embodiment of a midsole element comprised in a shoe according to the invention;

FIG. 6 shows in side view a sequence of four sub-stages of ground contacting phase of the step activity of a right foot wearing a shoe according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2 it is shown as a whole with 10 a shoe according to the present invention. In the embodiment represented in particular the footwear is a sandal comprising a sole, 20, and an open upper, 30. More precisely, the upper 30 is constituted by an elongated element anchored at two binding ends, 31, to the sole 20, and forming a front strap, 32, suitable to bind the foot in correspondence of the upper surface next to the ankle, in particular in correspondence of the scaphoid bone, wedge or the proximal portion of the metatarsals, and a back strap, 33, suitable to bind the foot in correspondence of the rear surface of the calcaneus. The front strap 32 and the back strap 33 are represented as continuous elements but can also be constituted by two semi-laces provided with constraint members such as buckles, Velcro fasteners or more.
Compared to a conventional open upper sandals, the upper described above completely lacks laces or other elements suitable to contain and constrain the distal portion of the foot, ie a distal metatarsals area and the phalangeal area.
The sole 20 has a rear portion 24, and a front portion 25, identified by a bending line, ‘a’, oriented transversely in correspondence with the metatarsal-phalangeal joint. By virtue of the bending, the rear portion 24 and the front portion 25 form between them a bending angle, #, between 25° and 60°, more specifically approximately 40° in the embodiment depicted, with the front portion 25 that is bent upwards with respect to the rear portion 24 which is substantially horizontal. In the specific embodiment, the sole 20 has a substantially constant height, that is to say the distance from the tread of the heel is substantially equal to the distance from the tread of the remaining parts of bottom of the foot, mainly the metatarsal area and the phalangeal area. In this type of footwear, substantially without heel and without difference in height between the heel and the front of the foot, the internal bending angle # existing internally between the rear portion 24 and front portion 25 is virtually equal to the outer bending angle existing between the same rear portion and the front portion at the height of the tread. The rear portion 24 and front portion 25 are suitably rounded to one another and of course the radius of curvature in correspondence of the upper surface is smaller than the radius of curvature in correspondence of the tread. The radius of curvature of the round portion is such as to allow the upper surface to follow as closely as possible the natural curvature of the metatarsal arc. The above feature is particularly important in a sole according to the invention as it greatly improves the quality of the support of the entire sole of the foot that otherwise would tend to rest exclusively on the area of the heel and the tip of the fingers, creating a tendency to detachment of the metatarsal portion.
The sole 20 includes an outsole 21, and an inner sole, 22. The outer sole 21, comprising the lower external surface acting as the tread, has a constant thickness and is made advantageously in EVA (ethylene vinyl acetate), polymeric material which has excellent characteristics of flexibility, softness, lightness and strength. Also the inner sole 22 has thickness substantially constant in the longitudinal direction and it is provided, however, with a raised edge, 23, of suitable height extending along the entire perimeter of the footwear. The height of the edge 23 is variable and presents its maximum height in correspondence of the internal side of the plantar arch, as in inner soles or insoles of the conventional type. The edge 23 has a minimum height of 0.5 cm in the front, ie in the phalangeal portion 25 or in any case from the metatarsal area forward, and preferably has a height in this area of about 1 cm. Similarly, at the rear end of the heel, edge 23 has a minimum height of 0.5 cm and advantageously about 1 cm. In the embodiment depicted the upper surface of the inner sole 22 is, apart from the edge 23, substantially flat, and yet could also have an anatomical conformation with protrusions, in particular in correspondence of the plantar arch and at the metatarsal-phalangeal joint, as in many soles for sandals of conventional type. The raised edge 23 has a great importance, especially in a shoe with open upper according to the present invention. In fact, while in footwear with open upper of conventional type a raised edge mainly has the function of providing a lateral protection for the foot, in the present invention it is an important element of containment and stabilization of the foot on the sole, which otherwise due to the elastic return force of the sole would tend to make the front area of the foot, and in particular the fingers, slide on the surface of the sole causing the detachment of the foot from the sole that would tend naturally to resume its bending angle remaining in contact with the foot only in at the front end and the rear end.
The inner sole 22 advantageously has a core made of cork or cork based, between two layers of fabric and lined at the top by a leather layer or other material for insoles. The thicknesses and the materials of the inner sole 22 are such that the inner sole 22 is very soft and flexible.
Between the outer sole 21 and the insole 22 is interposed an midsole element, 40, shown in FIGS. 4a and 4b , of thin constant thickness, smaller than the plan size of the sole and, as in the outer sole 21 and the inner sole 22, a rear portion, 41, and a front portion, 42, can be defined that are separated by a rounded portion, 44, in correspondence with the bending line. As previously described, the rounded portion 44 has a radius of curvature and extension such as to allow the upper surface to follow as closely as possible the natural curvature of the metatarsal arc. The midsole element 40 is made up of a sheet of harmonic steel of a thickness equal to about 1 mm, and both the rear portion 41 of the midsole element and the front portion 42 of the midsole element are planar. The midsole element 40 has stiffness much greater than the outer sole 21 and the inner sole 22 and has a elastic bending limit very high. The midsole element 40 gives the sole the peculiar characteristics of elasticity and resilience that allow the sole to exert a elastic return force on the fingers of the foot such that, when the entire bottom of the foot is resting on the sole, the latter keeps in any case the fingers bent upward at a predetermined angle. Obviously, the elastic deformation limit is in any case sufficient to allow the front portion and rear portion of the sole at least to flatten as a result of stress of greater entity. Given the large difference between the modulus of elasticity of the material of which the midsole element 40 is made, which is at least three orders of magnitude higher than that of the materials forming the outer sole 21 and the inner sole 22, the overall elasticity of the sole 20 is substantially corresponding to that of the midsole 40. When the fingers are pressing on the front portion 25, an elastic deformation of the front portion occurs that causes the elastic reaction forces. On a macroscopic level the said elastic deformation can be seen as a rotation around the bending line ‘a’ and the sole 20 behaves as if it were present a torsion resilient element located at the bending line ‘a’, which exerts a reaction torque, indicated by M in FIG. 4a , which tends to rotate upwards the fingers about the metatarsal-phalangeal joint. The choice of a midsole element composed of a sheet of harmonic steel of a thickness of about 1 mm allows to have characteristics of elasticity of the sole such that during the normal execution of the step the force exerted by the fingers on the front portion of the sole 25 is balanced by the elastic reaction of the sole as a result of a rotation of a few degrees, on average, between 10 and 15°, of the front portion 25 with respect to the rear portion 24, and simultaneously the limit of elasticity is such as to allow high elastic deformation at least to reach a substantial alignment of the front portion 25 with the rear portion 24.
The midsole element 40 has a plurality of through holes, 43, distributed over the entire surface, which lighten the overall weight of the midsole element, improve the breathability of the sole, regulate the resilience and elasticity of the midsole element itself and promote the correct gluing of the three elements forming sole, that is to say the outer sole 21, the inner sole 22 and the midsole element 40.
As shown in FIG. 6 during the execution of the step the peculiar characteristics described above of the shoe of the invention are very advantageous. During a preground contacting phase (a) fingers which are pushing downwards cause a force of elastic reaction of the front portion 25 which tends to rotate upwards not only the fingers around the metatarsal-phalangeal joint but also the entire foot about the ankle joint. This promotes proper ground contacting at the heel. During step (b) the large bending angle existing between the rear portion 24 and front portion 25 of the sole promotes proper rotation of the foot in order to properly set the thrust phase (c). During the foot oscillation phase, the natural pressure of the fingers, which tend to realign the metatarsal portion, on the front portion of the sole 25 gives rise to a reaction torque which maintains the front portion 25 adhering to the fingers themselves even in the absence of parts of the upper which are able to bind the front of the foot and in particular the phalangeal portion. Moreover, the presence of the edge 23 of the inner sole prevents forward or lateral sliding of the fingers thus helping to maintain the front portion 25 of the sole perfectly adherent to the foot.
The advantages described above are also present in different embodiments of the invention or in the presence of modifications or variations to the above described.
For example, in FIG. 3 it is shown an embodiment, 10′, of a shoe according to the invention in which the outer sole, 21′, has a thickness progressively decreasing from the rear forward, so that the heel is raised approximately 20 mm compared to the metatarsal portion. In this case the upper surface of the inner sole, 22, is slightly inclined downwards, of about 10°, from the heel toward the front and the angle # between the rear portion 24 and front portion 25 of the shoe 10′ is measured at the upper surface (the surface supporting the foot) which is different from the angle measured at the lower surface. The upper 30 has only the front strap 32 that, thanks to the peculiarities of the sole according to the invention, is sufficient to ensure the maintenance of the correct positioning of the foot on the sole in all phases of the step.
The embodiment 10′ is further advantageous in the proper execution of the step due to the slight difference in height between the heel and the forefoot and thanks to the shaping, 27, of the heel.
In FIG. 5 is shown a different embodiment, 40′, of the midsole element that has a longitudinal extension shorter than the overall length of the shoe. In particular, the front portion 42′ and the round portion 44′ are substantially the same as those of the embodiment 40 described above, while the rear portion 41′ is much shorter since it does not extend to the heel area. The alternative embodiment 40′ provides elastic properties in correspondence with the metatarsal-phalangeal joint similar to those of the previous embodiment and able to create the above-described effect of a torsion spring located at the metatarsal-phalangeal joint, and at the same time it lightens significantly the structure of the sole. Obviously, the alternative embodiment 40′ of the midsole element can be used where the outer sole 21 and the inner sole 22 provide a foot support without let a wearer perceive the discontinuity between the rear portion 24 in which the midsole element 40′ is not present and the front portion 25 in which the foot is supported also by the midsole element 40′.
In different embodiments of a shoe according to the invention, the peculiar bending properties of the phalangeal portion and elasticity of the same, conferred by the harmonic steel sheet which forms the midsole element 40 or 40′, are obtained by different means. For example, a variant provides a midsole element 40 made of a fiber-reinforced polymer matrix material chosen for having mechanical characteristics, at least in the longitudinal direction, as similar as possible to those of the harmonic steel. Obviously, materials may be used having modulus of bending elasticity, at least in the longitudinal direction, also much lower and the thickness of the midsole could be increased so as to obtain in any case the desired elastic properties. In still other embodiments, the midsole element may not be provided, in the case that the outsole itself is made of a material able to furnish the desired elastic properties at least of the metatarsal and the phalangeal portions. More specifically, the outer sole could be made of a polymeric material by injection moulding such as PU, TPU, TR, TPR, PVC, a combination of these, or other similar moldable material for shoe soles, in which the peculiar shape with bending line at the metatarsal joint is given directly during moulding.
The bending line ‘a’, advantageously rectilinear and oriented in the transverse direction, is particularly advantageous since the inner sole 22 and the outer sole 21 can be manufactured in a flat configuration and then attached together with the interposition of the midsole element 40 which determines such bending angle. Differently, when the various components of the sole, the inner sole 22, the outer sole 21 and midsole element 40 are obtained by moulding directly in the bent configuration, the bending line could be oriented differently or even be non-rectilinear, so as to follow with greater accuracy the line of the metatarsal-phalangeal joint. In FIG. 2 are shown with dotted line and indicated with ‘b’ and ‘c’ two alternatives bending lines.
In the description of the present invention it has been spoken of inner sole and the outer sole to mean respectively an upper part of the sole which includes the contact surface of the foot and a lower part of the sole which includes the tread surface. However, the distinction between the inside and the outside of the sole in many embodiments may not be materially evident.
Finally, although the advantages of the invention are particularly evident in sandals or other footwear with open upper, a sole as described may be associated to a closed upper of any type.
It is however understood that the above description has value of non limiting example, therefore any alternative embodiments and/or modifications of detail are considered from now falling within the same protective scope defined by the following claims.

Claims

1.-9. (canceled)

10. Footwear having an upper and a sole, comprising:

an outer sole and an inner sole, wherein the sole is configured to have a bending line corresponding to a wearer's metatarsal-phalangeal joint; and

a phalangeal portion connected to a metatarsal portion, the phalangeal portion and the metatarsal portion of the inner sole being provided at an angle in a longitudinal direction of between 25° and 60°, the sole having a bending elasticity and an elastic bending limit at least at the bending so as to enable an elastic deflection downwardly of the phalangeal portion at least up to an alignment of the phalangeal portion with the metatarsal portion, an elastic bending return force of the sole being configured such that when an entire sole of a wearer's foot is resting on the sole, the latter keeps the phalangeal portion bent upwardly at a predetermined angle.

11. The footwear according to claim 10, wherein the bending elasticity of the sole is such that during a normal execution of a step, the force exerted by fingers on the phalangeal portion of the sole is balanced by the elastic return force of the sole as a result of a rotation in a range of 1° to 15° of the phalangeal portion with respect to the metatarsal portion.

12. The footwear according to claim 10, wherein the inner sole has a peripheral edge raised at a height of not less than 0.5 cm at least at a heel portion and at the phalangeal portion.

13. The footwear according to claim 10, wherein the outer sole is hard and elastic, the inner sole is soft and elastic, between them being interposed a sheet-like midsole element comprising a phalangeal portion and a metatarsal portion jointed at a rounded bending joint located at the metatarsal-phalangeal joint, and a midsole element having bending elasticity and a bending elastic limit such as to constitute a torsion spring.

14. The footwear according to claim 13, wherein the midsole element is made of a harmonic steel sheet.

15. The footwear according to claim 13, wherein the midsole element is made of a fiber-reinforced polymer.

16. The footwear according to claim 13, wherein the midsole element is provided with holes to allow a passage of bonding material for connecting the inner sole with the outer sole.

17. The footwear according to claim 13, wherein the midsole element has a longitudinal length shorter than an overall length of a shoe, wherein a rear portion of the midsole element does not extend to a heel area.

18. The footwear according to claim 10, wherein the footwear is a sandal, the upper being formed by laces or bands configured to bind the wearer's foot only at a region of the wearer's scaphoid bone, cuneiform and proximal metatarsal or a rear portion of the wearer's heel.