INSOLE

The invention relates to an insole for a shoe, which extends at least over the front foot region, preferably the entire foot region, of the sole, comprising a spring steel plate which is rigid in the transverse direction of the sole, in particular in the rolling region of the sole, but is vertically flexible in the longitudinal direction of the sole and resiliently returns after loading, the spring steel plate having a transverse profile which preferably extends perpendicularly to the longitudinal direction of the sole substantially over the entire sole region, and comprising a plastics layer in which the spring steel plate is arranged.

Insoles of this kind are known from EP 373 336 A1 and EP 1 189 527 A1.

Said insoles provide comfort during wear for the wearer of a shoe since, on account of their stability, the insoles provide the sole of a shoe with greater stability than conventional soles. Furthermore, the high spring tension of the spring steel of the insole provides an improved walking sensation since the spring and return properties of the metal material have a beneficial effect on the walking comfort of the wearer.

The disadvantage of a spring steel material is, however, the limited shock absorption properties thereof, i.e. the energy applied to the spring steel material by a falling weight component is absorbed only to a limited extent by a metal plate of this kind, the remaining energy being passed to the rebounding weight component by the resilience of the metal plate.

Transferring to an insole of this kind in a shoe means, for the wearer of the shoe, that the shoe springs back during walking, the rebound energy released being introduced into the wearer's foot and having to be absorbed there.

If a shock absorption test is carried out following ASTM F 1976, it is found that, for a spring steel sole according to EP373336, depending on the shock being measured in the ball or heel region, approximately 61% and 60% respectively of the energy exerted on the metal material is absorbed, while the remaining energy is returned to the rebounding weight component.

An improved insole having increased shock absorption properties compared with the metallic spring material insole described in EP 373 336 A1 is therefore desirable.

In order to improve the shock absorption capacity, shoe inserts made of gel have already been proposed as shoe insoles. Shoe insoles of this kind are shown for example in the German publication “Kunststoffe” Heft 8 [“Plastics materials” Book 8] (2005), pages 56-58. Further shoe insoles produced from a gel are described in DE 20 2005 005011U1, US 2012/0023776A1 or WO 2007/092091A2.

Gel materials have the property that, unlike plastics foams, they are not only pressed together when pressure is exerted, but rather also yield laterally and thus elastically deform in all three spatial dimensions and return again after the load is removed, in the manner of the memory effect. Specifically, portions of the gel molecules are quasi-fluid and can flow within the remainder of the gel matrix. Said molecules are in part chemically bound, in part physically held to the matrix in a highly complex equilibrium process and are deformed by deformation of the matrix when a compressive load is applied. This deformation occurs substantially in a reversible manner and thus leads, when load is applied, to the transferred kinetic energy of the impacting body being received and absorbed.

A similar test, as described above, has now shown that the shock absorption quality of an insole produced from gel material alone does not have any substantially improved absorption behaviour compared with the metal sole alone. Thus, a gel sole absorbs, in the ball/heel region, approximately 65% and 63% respectively of the input energy in accordance with the above-described test.

The object of the invention is therefore that of providing an insole of the type mentioned at the outset, which has improved shock absorption behaviour.

The object is achieved by means of the characterising features of claim 1.

Surprisingly, it was found, according to the invention, that embedding a spring steel sole in a gel layer, the gel completely enveloping the metal layer, surprisingly raises the shock absorption properties of this combination sole to 73.8% in the ball region and 76.1% in the heel region.

This fact was not to be expected by a person skilled in the art, who would have anticipated, in the case of this combination, a value of at best 61-63% in the ball region/heel region.

In order to produce pliable solid gels, polyurethane components can be used, such as are described in EP 57 838 A1 and EP 511 570 A1. In this case, two components, specifically an isocyanate component and a polyol component can be used, which are usually mixed in the one-shot method and then processed during the pot life.

Advantageously, the polyurethane gel is produced from prepolymers, in which the product of the isocyanate functionality and the functionality of the polyol component is at least 5.2, preferably at least 6.5. Based on the weight ratio, this ratio is advantageously 1:6.5-1:8. In a particularly preferred embodiment, the polyol component for producing the gel consists of a mixture of

a) one or more polyols having hydroxyl numbers of less than 112, and
b) one or more polyols having hydroxyl numbers in the range of from 112-600, the weight ratio of component a to component b being between 90:10 and 10:90, the isocyanate index of the reaction mixture being in the range of from 15-59.81, and the product of the isocyanate functionality and the functionality of the polyol component being at least 6.15.

In a further advantageous embodiment, the raw materials for producing the gel consist of

a) one or more polyisocyanates
b) a polyol component consisting of one or more polyols (b1) having hydroxyl numbers of less than 112, and one or more polyols (b2) having hydroxyl numbers in the range of from 12-600, and
c) optionally a catalyst for the reaction between the isocyanate groups and hydroxyl groups, and
d) optionally fillers and/or additives known from polyurethane chemistry per se, the weight ratio of the component (b1) to the component (b2) being between 90:10 and 10:90, the isocyanate index of the reaction mixture being in the range of from 15-59.81, and the product of the isocyanate functionality and the functionality of the polyol component being at least 6.15.

In a further embodiment, the polyol component consists of one or more polyols having a molecular weight of between 1,000 and 12,000 and an OH-value of between 20 and 112, the product of the functionalities of the polyurethane-forming components being at least 5.2 and the isocyanate index being between 15 and 60.

For producing the gel, preferably isocyanates of the formula Q(NCO)n can be used, the letter n standing for from 2 to 4 and Q being an aliphatic hydrocarbon radical having 8-18 C-atoms, a cycloaliphatic hydrocarbon radical having 4-15 C-atoms, or an aromatic hydrocarbon radical having 8-15 C-atoms. The isocyanates can be present either in pure form or as modified isocyanate.

Gel compounds can in addition contain fillers and/or additives known from polyurethane chemistry in an amount of up to 50 wt.% in total, based on the total weight of the gel compound.

As already mentioned above, in a preferred embodiment the weight ratio of the polyisocyanate component to the polyol component is from 1:6.5 to 1:8. This leads, with an increasing weight ratio, to an increasingly pliable resilient solid gel. Thus, as the weight ratio increases, the Shore Hardness 00 (measured in accordance with ASTM D 2240) decreases from approximately 80 to approximately 35 at room temperature.

The Shore Hardness 00 values according to the invention are in a range of from 45-70, in particular 52-64, at room temperature and are determined in accordance with ASTM D 2240.

In the method for manufacturing the gel according to the invention, the isocyanate component and the polyol component are mixed together in the one-shot method, in which the obtained mixture must be processed within the pot life (usually 5-15 minutes) and poured into a mould.

The selection of the mixing ratio of the polyisocyanate component and the polyol component depends on the desired hardness of the gel, it being necessary to take account of the specific structure of the materials used and, if applicable, an added catalyst, the effect of which leads to an increased hardness value of the gel. Finally, a person skilled in the art empirically determines the mixing ratio and the mixing parameters in order to achieve the desired hardness value of the gel.

The integrated sole, produced from gel and metal plate, is manufactured in a conventional casting method using a conventional mould, as are used in gel manufacturing for example. The composite material formed in the sole according to the invention has spring and absorption properties which are improved when compared with those of the individual materials, which results in an improvement in the shock absorption properties of the sole according to the invention.

Advantageously the sole, consisting of gel and metal plate, has an outer covering layer on at least one side, which is impermeable to the polyurethane gel.

A covering layer of this kind may consist of a film, leather, imitation leather or a textiles material, for example a microfibre material which is impermeable to the PU gel. Preferably leather or an imitation-leather plastics material is used as the covering material. In this case, the purpose of the covering layer is not only to aid the comfort of the shoe user, but much rather also to aid the stabilisation of the gel surface upon action of the underside of the foot in the use state.

The method according to the invention for manufacturing the integrated gel and metal plate sole comprises a casting method in which, in a first embodiment, the following steps are carried out:

a) During the pot life, a first portion of the liquid, not yet fully hardened gel compound is poured into a mould, forming a first gel layer, the upper side of which has the conventional adhesive properties.
b) The metal plate is laid on the first gel layer and pressed into the gel layer using gentle pressure.
c) After the metal plate has been laid on, a second gel layer is applied to the metal plate in the mould.
d) Optionally, a covering layer is laid on the still sticky second gel layer or, in a second embodiment, the covering layer is inserted into the mould before the first gel layer is introduced, whereupon the gel compound for the first gel layer is introduced into the mould.

In a further embodiment of the manufacturing method, the metal plate is arranged in a mould in such a way that both a gel upper layer and a gel lower layer can be formed. After the metal plate has been arranged in the mould, the gel is then continuously introduced into the entire mould under air displacement, or introduced into a mould which has been freed of air by evacuation, such that the moulding is formed in situ.

The insole according to the invention comprises a sole produced substantially from spring steel and gel, which sole is usually inserted in the shoe as a separate support sole. Alternatively, however, this insole can also be used as an inner sole when the edges are appropriately formed.

The spring steel sole, which is used as an inlay inside the gel bed, is flexible in the longitudinal direction and rigid in the transverse direction, and typically cushions the foot in the ball region thereof. In addition, a transverse or wave profile supports the rolling of the foot.

According to the first embodiment thereof, the support sole covers merely the front ball region, but in a second embodiment covers the entire foot, including the front region and heel region. In this case, said sole is anatomically adapted according to the shape of the shoe or the shape of the foot, i.e. is available in sizes corresponding to the various shoe sizes. The transverse profiling can extend over both the front foot region and the heel region. In this case, the transverse profile advantageously extends in the manner of a sine wave, the magnitude of the overall height being of 0.5-2 mm, advantageously of approximately 1.3-1.6 mm. The wavelength of the wave is advantageously of 3-5 mm, preferably of 7-12 mm, in particular of approximately 10 mm.

The transverse profiling itself preferably extends, at least in the front foot region, at a specified first angle to the longitudinal direction of the sole, in particular of between 70°-90°, advantageously of between 75° and 80°. The transverse profiling can extend at these angles in the heel region too.

In order to support a natural roll movement, the waves can also extend, in the back or hind foot region (heel region), at a second angle which differs from the first angle and is preferably of between 90° and 110°.

According to a further preferred embodiment, the angle in both regions (front foot and rear foot region) is approximately 90°.

The hard resilient plate material, consisting of spring steel, has a uniform thickness of 0.1-0.6 mm, preferably of approximately 0.2 mm-0.4 mm, in particular of 0.25 mm-0.35 mm.

According to a further embodiment, the transverse and/or longitudinal profiling can also have a different shape in cross section, for example that of a channel, furrow, rib, groove, corrugation or crease.

In the composite plate material according to the invention, the respective wave troughs of the transverse profiling are completely filled with the PU gel, the thickness of the gel layer being additionally greater than the overall height of the transverse profile. Advantageously, the thickness of the gel layer is uniform, such that the composite sole has a flat and smooth surface on both the upper side and the lower side thereof, having a completely smooth structure.

The overall height of the transverse profiling of the spring steel plate itself is of between 0.5 and 2.5 mm, preferably of 1-2 mm, in particular of approximately 1.5 mm.

Furthermore, the thickness of the gel layer is 1.5-4 times, in particular 1.8-3.5 times, more preferably approximately 2.5-3 times, with respect to the overall height of the transverse profiling.

Regarding the term “overall height”, it should be noted that this is the height of a profile of any kind which extends from the plane.

In a particularly preferred embodiment, the overall height of the profile including the plate thickness is of approximately 1.5 mm and the overall thickness of the gel is of approximately 4 mm, wherein the thickness of the spring steel plate being of approximately 0.3 mm.

Whereas, according to a first embodiment, the spring steel plate is arranged in the gel layer having its respective wave crests at equal distances from the upper and lower outer surfaces of the PU layer, i.e. the gel layer protrudes by the same amount d1 and d2 on the upper and lower side respectively of the profile, according to a second embodiment, the magnitude of the protruding layers d1 and d2 can also be different. In each case, d1 and d2 of the gel layers and the overall height H of the profile are measured. In this case, the ratio of d1:H and/or d2:H can assume a value of from 0.5:1 to 1.5:1, preferably of 0.8:1 to 1.2:1.

According to a further preferred embodiment, the solid plate-shaped material is completely encompassed by a gel border, which thus substantially annularly surrounds the side edges of the plate material. As a result, complete covering of the plate-shaped material is achieved, and thus a further stabilisation of said composite arrangement is achieved. On account of the adhesive ability thereof during the polymerisation phase, the hardened gel has a strong adhesion to the plate-shaped material and can be released from the spring steel plate only if the entire arrangement is destroyed. If the plate-shaped material is deformed in the longitudinal direction during walking, the gel layer is compressed on the upper side of the plate and stretched on the underside, with the result that the ability of the plate-shaped material to return from the deformed state into the initial state is improved. In this case, the gel layer does not become detached when the metal surface is either compressed or stretched, and remains bonded thereto.

Any kind of shoe can be used with the insole according to the invention, not only shoes being intended here, but also boots, high-heeled shoes and the like. The sole itself supports and protects the arch of the foot and provides protection in the ball region, the foot becoming less tired on account of the improved ability for shock absorption of the loading pressure.

Moreover, the sole according to the invention can be used for normal shoes, for example street shoes and running shoes, in particular sports shoes. Said sole has the effect of improving performance and protecting health. Likewise, the solid plate structure guards against the risk of injury to feet, in particular in the working region.

Further features and advantages of the invention form the subject matter of the following description and the illustrative representation of embodiments.

In the figures:

FIG. 1 is a plan view of the lower side of an insole having a front foot region and a heel region,

FIG. 2 is a further plan view of the lower side of an insole for the front foot region, and

FIG. 3 is an enlarged cross section along the line A-A through the insole according to FIG. 1.

FIG. 1 shows an insole 10 from below, comprising a front foot region 12, a central foot region 14 and a heel region 16, and a longitudinal axis L-L.

The insole 10 comprises a PU gel layer 18 as the first component, the edge 20 of which forms the outer limit of the insole 10.

The PU gel layer 18 is substantially transparent, meaning that the spring steel inlay 22 together with its contour line 24 which forms the outer limit of the spring steel inlay 22, is visible. The spring steel inlay 22 extends substantially in parallel with the edge 20 of the PU gel layer 18, a PU gel inter-edge region 26 being formed between the contour line 24 and the edge 20.

On account of the transparent structure of the PU gel, first transverse profiles 28 can be seen in the front foot region 12 and second transverse profiles 30 can be seen in the heel region 16.

The profiles 28/30 extend at an angle a to the longitudinal axis L-L.

FIG. 2 shows a second insole 40 which covers only the front foot region 12. Consequently, the same reference numerals are used as in FIG. 1.

Merely the edge 44 extends only in the front foot region 12.

Likewise, the second spring steel inlay 42 extends only in the front foot region.

In FIG. 3 an enlarged sectional view through the insole 10 according to FIG. 1 is shown. The spring steel inlay is denoted by 50, which inlay has, as a profile 55, a wave-like structure having wave crests 52 and wave troughs 54. The distance H of the wave crests from the wave troughs corresponds to the height of the profile 55.

Likewise, the length of a wave corresponds to the distance W.

The spring steel inlay 50 is embedded in a PU gel layer 56 which has a thickness S. Said layer extends on the lower side by the thickness d1 beyond the wave trough 54 of the spring steel inlay 50 on the lower side. Likewise, the protrusion of the PU gel layer 56 above the wave crest 52 of the spring steel inlay 50 has the thickness d2.

Consequently, the overall thickness S of the PU gel layer 50 therefore amounts to H plus d1 plus d2.

In the example according to FIG. 3, d2 is greater than d1.

Furthermore, the insole 10 according to FIG. 3 has, on the upper side thereof, a covering layer 58 which is rigidly connected to the PU gel layer 56 and consists of leather or a plastics layer such as a microfiber layer.

The following testing methods are used when measuring physical parameters.

In the shock absorption (impact test), tests are carried out in the heel and ball region, with reference to ASTM F 1976. In this case, the impact of the human foot on the ground is simulated using a free-falling mass of 7.5 kg. The impact of the free-falling mass on the testing object occurs at a precisely specified speed of 0.5 m/s. During the deformation of the material, the speed of the falling mass reduces. In this case, the speed change per unit of time is a measure of the braking effect of the material.

When carrying out the test, the maximum acceleration of the mass upon contact with the test body is measured and at the same time the penetration depth and the rebound height are determined. Furthermore, the energy taken up, the emitted and absorbed energy are measured. Finally, inter alia the percentage absorption ratio and the spring constant are calculated.

A spring steel sole, a gel sole and a combination sole made of gel in which the spring steel sole is embedded were used.

The spring steel sole has a thickness of 0.285 mm and a profiling which extends over both the front foot region and the rear foot region, having an overall profile height of 1.5 mm and a wavelength of 1 cm.

The gel sole itself is 4 mm thick.

In the combination gel sole comprising the spring steel inlay, the spring steel sole is inserted in a uniform manner, having a peripheral edge of approximately 5 mm, the gel extending above the overall height of the profile by approximately 1.25 mm on both sides.

When measuring the shock absorption, the following absorption ratio was found for the front ball region:

- spring steel sole 61.23%
- gel sole 64.99%
- gel sole comprising integrated spring steel sole 72.84%.
- In the heel region, the following shock absorption values were obtained:
- spring steel sole 59.85%
- gel sole 63.33%
- gel sole comprising integrated steel sole 76.12%.
- The spring constant is measured in N/mm. The following values were found for the ball region/heel region:
- spring steel sole 2959.56/3792.82
- gel sole 2008.97/2042.34.
- gel sole comprising integrated steel sole 2483.38/2909.34.
- Furthermore, for the gel soles comprising the integrated spring steel sole, the flexural strength was tested according to DIN EN 12568/DIN EN ISO 20344/DIN EN ISO 20345.
- After 5 million bends, no damage could be identified on the samples.

LIST OF REFERENCE NUMERALS

10 Insole

12 Front foot region

14 Central foot region

16 Heel region

18 PU gel layer

20 Edge

22 Spring steel inlay

24 Contour line

26 Inter-edge region

28 first profile

30 second profile

40 Insole

42 Spring steel inlay

44 Edge

50 Spring steel inlay

52 Wave crest

54 Wave trough

55 Profile

56 PU gel layer

58 Covering layer

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