Classifications

• • A—HUMAN NECESSITIES
  • A43—FOOTWEAR
  • A43B—CHARACTERISTIC FEATURES OF FOOTWEAR; PARTS OF FOOTWEAR
  • A43B1/00—Footwear characterised by the material
  • A43B1/08—Footwear characterised by the material made of metal 
• • A—HUMAN NECESSITIES
  • A43—FOOTWEAR
  • A43B—CHARACTERISTIC FEATURES OF FOOTWEAR; PARTS OF FOOTWEAR
  • A43B23/00—Uppers; Boot legs; Stiffeners; Other single parts of footwear
  • A43B23/02—Uppers; Boot legs
  • A43B23/0205—Uppers; Boot legs characterised by the material
  • A43B23/023—Metal
• • A—HUMAN NECESSITIES
  • A43—FOOTWEAR
  • A43B—CHARACTERISTIC FEATURES OF FOOTWEAR; PARTS OF FOOTWEAR
  • A43B3/00—Footwear characterised by the shape or the use
  • A43B3/12—Sandals; Strap guides thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/006—Resulting in heat recoverable alloys with a memory effect

Definitions

• the present invention relates to a strap shoe with an improved fit, such as a shoe with an ankle strap, with a gladiator strap or with a foot strap.
• the straps can be configured to wrap around the top of the foot, the ankle or even extend along the calf.
• the strap can cause blisters or abrasions as a result of foot movement; conversely, if worn too loosely, it does not allow the shoe to remain properly fastened to the foot, which can lead to unstable situations with consequent falls and/or injury by the user.
• any elastic portions integrated in the strap to increase the wearing comfort thereof tend to quickly lose their initial elastic properties as they are subjected to constant stresses during use.
• the problem underlying the present invention is to overcome the drawbacks of the prior art.
• an aim is to design a strap shoe that is particularly comfortable in use.
• Another aim of the present invention is to make a strap shoe that is effectively adaptable to the conformation of the user's foot, ankle and/or calf.
• Still another aim of the present invention is to make a strap shoe that minimises stresses on the parts of the body with which it comes into contact, preventing any injuries due to rubbing.
• a further aim of the present invention is to design a strap shoe that is particularly resistant to wear and tear and is able to maintain the initial wearing comfort over time.
• Not least of the aims of the present invention is to devise a strap shoe trap that offers the user good stability without sacrificing a comfortable fit.
• the invention therefore relates to a strap shoe comprising an upper, a bottom portion to which the upper is fastened, and a strap connected to the bottom portion and/or to the upper and/or incorporated into at least one thereof, for fastening the shoe to the foot and/or ankle of a user.
• the strap comprises at least one strap portion made of a nickel-titanium alloy, hereinafter also referred to as NiTi or Nitinol alloy, comprising at least two zones with different mechanical properties, in particular bending response mechanical properties.
• NiTi or Nitinol alloy a nickel-titanium alloy
• the Applicant has devised making at least one shoe strap portion in a NiTi alloy with at least two zones behaving differently from a mechanical point of view and, in particular, from the point of view of bending response.
• the invention further relates to a process for making a strap shoe that comprises the steps consisting of:
• strap portion zone is intended to indicate a sub-portion of the strap portion that does not comprise the entire strap portion itself.
• the process for making at least one strap portion of a strap shoe achieves the same advantages as described with reference to a strap shoe according to the present invention.
• FIG. 1 a first preferred embodiment of a strap shoe according to the present invention is illustrated, overall indicated with 10.
• a strap shoe is intended to indicate any type of open or closed shoe provided with a strap for fastening the shoe to the foot or ankle of the user, such as ballerinas with strap, classical women's shoes with strap, sandals with strap, mules with strap, etc.
• a strap shoe comprises three main elements: an upper, a bottom portion to which the upper is fastened and which comprises an insole and a sole, and a strap connected to the upper or incorporated therein, for fastening the shoe to the user's foot and/or ankle.
• the upper of the strap shoe can comprise side parts, a heel part and a toe part.
• the upper of the shoe is often formed by a plurality of material elements (e.g. fabrics, layers of polymer sheets, foamed or otherwise, leather, synthetic leather) that are sewn or glued together to delimit a space within the shoe configured to comfortably and securely accommodate a foot.
• the upper forms a structure that can extend over one or more of the following areas of the foot: instep, toe, lateral sides, medial side and heel.
• the shoe comprises an opening for the entry and removal of the foot from the space defined inside the upper, which extends from the heel portion of the upper.
• the shoe 10 in Figure 1 comprises a bottom 11 and an upper 12 attached to the bottom of the shoe.
• the upper 12 comprises a toe part 122 and a heel part 123 joined or connected to each other by lateral portions 121 to form a peripherally closed structure.
• the parts of the upper 12 define, in a position opposite the bottom 11, an opening 13 for the entry and exit of the foot.
• the upper 12 and the bottom 11 define a housing configured to accommodate a user's foot.
• a strap 14 is fastened to the upper 12, which in the embodiment of Figure 1 , is connected thereto by means of a loop 124 made at the heel part 123.
• a heel 15 is applied to the bottom 11.
• the strap 14 comprises at least one strap portion made of a nickel-titanium alloy, hereinafter also referred to as NiTi or Nitinol alloy, having a percentage weight composition (%) of the alloy between Ni(46%)Ti(54%) (w:w) and Ni(55%)Ti(45%); preferably, Ni(51%)Ti(49%) (w:w) and Ni(50.8%)Ti(49.2%) (w:w).
• NiTi or Nitinol alloy having a percentage weight composition (%) of the alloy between Ni(46%)Ti(54%) (w:w) and Ni(55%)Ti(45%); preferably, Ni(51%)Ti(49%) (w:w) and Ni(50.8%)Ti(49.2%) (w:w).
• the at least one strap portion comprises at least two zones 14a,14b with different mechanical properties, in particular bending response mechanical properties.
• the strap 14 of the shoe in Figure 1 is made entirely of NiTi alloy and comprises at least two zones 14a,14b with different bending response mechanical properties.
• the strap 14 can have at least one portion made of a NiTi alloy with at least two zones 14a,14b with different bending response mechanical properties, or comprise a core 141 (shown diagrammatically in Fig. 4 ) of which at least one portion is made of such a NiTi alloy with at least two zones 14a,14b with different bending response mechanical properties.
• a NiTi alloy can have either a bending response mechanical behaviour characterised by a sharply flag-shaped bending response curve, indicative of a substantially pure pseudo-elastic mechanical behaviour, or a quasi-linear behaviour with hysteresis, i.e. an intermediate or combined behaviour between a perfectly linear behaviour, typical for example of steel, and a substantially pure pseudo-elastic behaviour.
• bending response mechanical properties with quasi-linear behaviour with hysteresis is intended to indicate mechanical properties characterised by a bending response curve having a non-zero slope plateau and in any case less than a characteristic elastic deformation slope of steel, hereinafter also only “characteristic slope”, e.g. greater than at least 10% and less than 85% of the characteristic slope.
• bending response mechanical properties with essentially pure pseudo-elastic behaviour is intended to indicate mechanical properties characterised by a bending response curve with an essentially zero slope plateau, e.g. below 10% of the characteristic slope.
• plateau is intended to indicate a curve section with a lower slope with respect to a previous section, for example a first section with a slope reduced by at least 10% with respect to a slope of a second previous section.
• the at least two zones 14a,14b with different bending response mechanical properties both have a quasi-linear behaviour with hysteresis, albeit different from one zone to the other.
• Figure 2 shows the bending response curves 20 of a strap portion 14 comprising two zones 14a,14b with different mechanical properties according to the first variant, characterised through a temperature-controlled single cantilever bending test with reference to the ASTM F2516
• the strap portion made of NiTi alloy comprises at least a first zone 14a with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, so as to ensure the hold between the shoe and the foot, and at least a second zone 14b with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour, so as to give the second zone sufficient deformation softness to facilitate the operations necessary to put the shoe on and not hinder the movement of the foot and the ankle.
• the strap portion comprising at least two zones 14a,14b with different bending response mechanical properties is characterised by a bending response represented by a curve 20 with at least two curve sections 21,22 with different trends, each representing the points at which bending is concentrated.
• each section 21,22 of the bending response curve given by the strap portion 14 has a nearly linear behaviour with hysteresis, each characterised by a different plateau slope.
• the plateau slope of each curve section 21,22 is between 85%-10% of the characteristic slope of an elastic deformation, such as the characteristic deformation of steel, which always has a linear trend, without any kind of plateau.
• the trend of each section 21,22 of the bending response curve given by the strap portion 14 according to the first variant corresponds to deformation with martensite induction.
• a first curve section 21 representative of the first zone 14a with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a linear behaviour has a plateau slope lower than the characteristic slope, but still more than 50% of such characteristic slope, more preferably between 60%-85% of the characteristic slope, more preferably between 65%-80% of the characteristic slope.
• a second curve section 22 representative of the second zone 14b with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a pseudo-elastic behaviour has a plateau slope between 20%-50% of the characteristic slope, preferably between 25%-45% of the characteristic slope, more preferably between 30%-40% of the characteristic slope.
• thermoforming process of a NiTi alloy semi-finished product which comprises the following steps:
• the starting NiTi alloy semi-finished product is a wire.
• the wire can be purchased already in the desired work-hardened state (Cold Worked or As Drawn) or be subjected to the above-mentioned work-hardened phase after a short heat treatment (Straight Annealed).
• the wire is a wire with a round cross-section with a thickness (diameter) between 0.10 mm and 30 mm; between 0.10 mm and 10 mm; between 0.20 mm and 9 mm; between 0.30 mm and 8 mm; between 0.40 mm and 7 mm; between 0.50 mm and 6 mm; between 0.60 mm and 5 mm; between 0.70 mm and 4 mm; between 0.80 mm and 3 mm; other values not specifically comprised in the above list are however freely possible depending on processing requirements and, of course, also form part of the present invention.
• the wire is a wire with a square cross-section with sides between 0.10 mm x 0.10 mm and 5 mm x 5 mm; preferably, between 0.20 mm x 0.20 mm and 2 mm x 2 mm.
• the wire is a wire with rectangular cross-section with sides between 0.10 mm x 0.15 mm and 0.15 mm x 30 mm.
• the possible lengths they are freely variable and/or selectable depending on the final shape of the desired strap portion.
• a direct electric current is then passed through the wire (thermal pre-treatment step) applying a voltage averaging between 3 volt and 180 volt; between 10 volt and 150 volt; between 20 volt and 100 volt; preferably, between 30 volt and 90 volt; more preferably, between 40 volt and 80 volt.
• the intensity of the applied electric current depends on the dimensions of the semi-finished product, e.g. preferably the length of the wire.
• a direct current between 0.2 ampere and 15 ampere; between 0.3 and 10 ampere; between 0.4 ampere and 5 ampere; between 0.4 ampere and 4 ampere; preferably between 0.4 ampere and 3 ampere; even more preferably between 0.5 ampere and 2 ampere, applying it for a time between 3 and 10 seconds, preferably between 4 and 9 seconds, more preferably between 5 and 8 seconds, or between 5 and 10 seconds, depending on the thickness and length of the wire.
• a voltage between 40 V and 80 V and a current intensity from 0.5 to 3 ampere is applied for times of 5-10 sec.
• the first thermal treatment step can also be carried out alternating with traditional treatment phases, such as rolling and/or drawing, in order to optimise the microstructure, eliminating work hardening defects and the possibility of breaking the material.
• the thermal pre-treatment step is followed by the thermoforming step for achieving the desired final "shape-setting", for example, by carrying out a thermal treatment in an electric oven with the use of suitable jigs or moulds, to give the semi-finished product obtained in the thermal pre-treatment step the shape/form of the desired strap portion to be made.
• the thermoforming step is carried out in an electric metal-forming oven with a refractory material mouth at a temperature between 200 °C and 650 °C, preferably between 470 °C and 530 °C, depending on the size of the mould and the thickness and length of the wire, for a period of time between 5 to 120 minutes, preferably between 15 to 40 minutes.
• thermoforming step is followed by a further thermal treatment (post-treatment), carried out through heating by Joule effect generated by a direct electric current that is applied to specific zones of such a semi-finished product.
• post-treatment carried out through heating by Joule effect generated by a direct electric current that is applied to specific zones of such a semi-finished product.
• the further thermal treatment is carried out by passing a direct current with a voltage from 40 V to 80 V (current intensity from 0.5 to 3 ampere) for times of 5-10 sec in a first zone of the strap portion to obtain the at least one zone 14a with bending response mechanical properties with near-linear behaviour with hysteresis close to a linear behaviour.
• a direct current with a voltage from 40 V to 80 V (current intensity from 0.5 to 3 ampere) for times of 5-10 sec in a first zone of the strap portion to obtain the at least one zone 14a with bending response mechanical properties with near-linear behaviour with hysteresis close to a linear behaviour.
• Such a step is carried out by applying the electrodes of a voltage generator to the ends of the first zone.
• the further thermal treatment is carried out by passing a direct current with a voltage from 40 V to 80 V (current intensity from 0.5 to 3 ampere) for times of 15-20 sec in a second zone of the strap portion to obtain the at least a second zone 14b with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a pseudo-elastic behaviour.
• a direct current with a voltage from 40 V to 80 V (current intensity from 0.5 to 3 ampere) for times of 15-20 sec in a second zone of the strap portion to obtain the at least a second zone 14b with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a pseudo-elastic behaviour.
• Such a step is carried out by applying the electrodes of a voltage generator to the ends of the second zone.
• the further thermal treatment is carried out only at one or more given zones of the already thermoformed semi-finished product to form the strap 14 or a portion thereof so that the strap portion has different bending response mechanical properties in different zones 14a,14b, i.e. a modular elasticity.
• a strap that has at least locally a pseudo-elasticity and deformation softness particularly suitable for the specific use to fasten a shoe to a user's foot or ankle without impeding the movement thereof and reducing abrasion in use, while at the same time guaranteeing an excellent hold of the strap on the shoe.
• the strap at least part of which is made of NiTi alloy obtained by the combined process described above, can express mechanical properties that vary depending on the geometry, but can also be modulated within the geometry itself, providing the mechanical response required for use as a shoe strap.
• the strap thus obtained has a very soft embrace, but at the same time offers a very firm hold on the shoe.
• the strap 14 is made entirely of a NiTi alloy in accordance with the first variant described above, having a first zone 14a close to the loop 124, preferably fastened thereto, with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, and a second zone 14b configured to rest against a part of the user's body, with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour.
• Figure 3 shows a second embodiment of a shoe 10 according to the invention with a strap 14 made in accordance with the first variant which differs from the first embodiment in that it has a plurality of straps 14.
• a first strap 14 is configured to fasten the shoe to the user's ankle, while the remaining straps are configured to rest against the user's instep.
• Each strap 14 of the plurality of straps 14 is made with a liner 142 in which a core 141 is housed made of a NiTi alloy configured to give the strap 14 both elasticity properties and at the same time a high deformation softness.
• the straps 14 are particularly comfortable, facilitating the movement of the ankle and foot without substantially stressing or rubbing against the parts of the body with which they interact.
• the straps 14 comprise at least a first zone 14a bordering with and fastened to the upper 12 of the shoe which has bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, and at least a second zone 14b configured to rest against a part of the user's body, with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour.
• Figure 5 shows a third embodiment of a shoe 10 with a strap 14 according to the present invention which differs from the first embodiment in that the strap 14 is configured to fasten the shoe to the user's heel. Also in this case, the strap 14 is made with a liner 142 in which a core 141 is housed made of a NiTi alloy configured to give the strap 14 both elasticity properties and at the same time a high deformation softness.
• the strap 14 comprises at least a first zone 14a bordering with and fastened to the upper 12 of the shoe which has bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, and at least a second zone 14b configured to rest against a part of the user's body, with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour.
• Figure 6 shows a fourth embodiment of a shoe 10 with a strap 14 according to the present invention which, similarly to the embodiment of Figure 3 , has a plurality of straps 14 of which, a first sub-assembly is configured to fasten the shoe to the user's ankle, while a second sub-assembly of the plurality of straps 14 is configured to rest against the user's instep.
• the at least one strap 14 of the plurality of straps comprises at least one portion made of a NiTi alloy, preferably configured to give the strap 14 both elasticity properties and at the same time high deformation softness.
• the straps 14 comprise at least a first zone 14a bordering with and fastened to the upper 12 or to the bottom 11 of the shoe, which has bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, and at least a second zone 14b configured to rest against a part of the user's body, with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour.
• three zones 14a, 14b, 14c are provided with different bending response mechanical properties.
• the strap portion made of NiTi alloy comprises a first zone 14a with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a linear behaviour, a second zone 14b with bending response mechanical properties with quasi-linear behaviour with hysteresis closer to a pseudo-elastic behaviour, and a third zone 14c with bending response mechanical properties with substantially pure pseudo-elastic behaviour.
• the third zone 14c is represented by a third curve section (not illustrated) with a plateau slope trend less than 20% of the characteristic slope, preferably less than 15% of the characteristic slope, more preferably less than 10% of the characteristic slope.
• a plateau slope trend less than 20% of the characteristic slope, preferably less than 15% of the characteristic slope, more preferably less than 10% of the characteristic slope.
• thermoforming process of a semi-finished product made of a NiTi alloy requires that a direct current with a voltage of 40 V to 80 V (current intensity of 0.5 to 3 ampere) is passed through a zone of the strap portion for times of 21-25 sec during the thermal post-treatment step in order to obtain the third zone 14c with bending response mechanical properties with substantially pure pseudo-elastic behaviour.
• a direct current with a voltage of 40 V to 80 V current intensity of 0.5 to 3 ampere
• Such a step is carried out by applying the electrodes of a voltage generator to the ends of the third zone.
• Figure 7 shows a fifth embodiment of a shoe 10 with a strap 14 according to the present invention using a strap having at least one portion obtained in accordance with the second variant.
• the shoe 10 according to the fifth embodiment differs from the first embodiment in that the strap is fastened to the bottom 11 of the shoe 10, in particular to the heel 15 applied to the bottom 11.
• the strap 14 is configured to fasten the shoe to the user's ankle and has a liner 142 in which a core 141 made of a NiTi alloy is housed.
• the strap 14 used in the shoe of the fifth embodiment comprises:
• the third strap portion 14c makes it suitable for wrapping around the ankle and calf of the user, ensuring a high level of wearing comfort
• the first portion 14a can be tightened around the heel 15, which has an invariable shape and size, locking in place.
• the strap 14 can be made of the type that can be removed from the shoe 10.
• the at least two zones 14a,14b,14c with different mechanical properties can comprise any combination between a first zone with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a linear behaviour, a second zone with bending response mechanical properties with quasi-linear behaviour with hysteresis close to a pseudo-elastic behaviour and a third zone with response mechanical properties with substantially pure pseudo-elastic behaviour.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Footwear And Its Accessory, Manufacturing Method And Apparatuses (AREA)

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Citations (3)

• 2025
  • 2025-04-03 EP EP25168308.2A patent/EP4631381A1/fr active Pending

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Non-Patent Citations (1)

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