EP0140985B1

EP0140985B1 - An insole

Info

Publication number: EP0140985B1
Application number: EP19830109926
Authority: EP
Inventors: Toshiro Nakamura
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-10-05
Filing date: 1983-10-05
Publication date: 1988-01-07
Also published as: DE3375062D1; EP0140985A3; EP0140985A2

Description

The invention relates to an improved insole which is used for conservative treatment, for example for bandy legs, knock knees, flat feet, gonarthritis deformans, metatarsalgia, hallux valgus, or the like.
It is known to mold insoles of hard or relatively hard materials such as metal, for example aluminium, hard plastics, leather, cork or the like. Such insoles have to be deeply curved at their brim, to compensate for their bad adhesion to the human sole. As a result, insoles of such type are bulky, and accordingly it is difficult, or rather impossible to insert them into socks. They are not retained in the socks and may damage them. They are not suited to be used even as spacers for slippers or sandals.
When such insoles are inserted in shoes, they prevent the deformation of the shoes (especially of the sole thereof), and cause a feeling of physical disorder, especially during walking or in the standing position of the user, so that it takes a considerable number of days until the user gets accustomed. Further, when using a holder, it is difficult to put on any footwear.
These deficiencies are reduced in case the insole is made of leather or cork. But such insoles meet a hygienic problem.
For the above reasons the users or patients, respectively finish the treatment untimely or interrupt it from time to time.
It is further known to mold an insole of silicone rubber which is mixed with an inorganic filler material (DE-A-29 26 246). The material is injected into an enclosure. Thereafter the design of the insole is molded by pressing the human sole against the soft material so that the insole is accommodated to an individual human sole. Silicone rubber is water-resistant, resistant against pharmaceutical substances and has a thermal and low temperature resistance.
Silicone rubber however is expensive, has a poor tensile strength, and crack resistance due to its weak intermolecular forces and its non-crystal structure. Therefore, it may be damaged by unreasonable or continuous use. Further, a mold of patient's foot must be made or the patient's foot has to mold the insole. This is costly and time consuming. Further, the silicone rubber makes the patient feeling the insole as a cool subject particularly in winter. Finally it is difficult to eliminate the bubbles occurring during the molding process.
It is an object of this invention to provide an insole which is less expensive, easy to manufacture and comfortable for the user. This object is solved by an insole as indicated by claim 1. The insole according to the invention has a small density and is not bulky. It accommodates readily to the movement of the human sole and closely adheres thereto.
The insole according to the invention can be used in connection with usual socks or simple holders. It can be cleaned by washing and gives the user a warm and comfortable feeling. It can be used a long time, and is of light weight and low- price. The insole is well suited for the conservative treatment as mentioned above.
The material used has enough flexibility and toughness, is resistant against breakage, is simple to be treated after molding, and has a good adhesion to the human sole. Further the foamed structure enhances the heat insulation. Owing to these properties, the insole has an effect by which pain of concerned foot portions is reduced.
Therefore, it is unnecessary for the insole to have an extra thickness to achieve the desired strength and form-stability, or to form a largely raised brim to obtain a good fit for the sole.
The invention is further explained here below along drawings.

Fig. 1 is a perspective view showing an example of the insoles according to the invention;
Fig. 2 is a section view along line X-X of Fig. 1;
Fig. 3 is a side view of the insole being loaded by a foot;
Fig. 4(a) is a side view showing an example of the holders for an insole;
Fig. 4(b) is perspective view of the insole loaded by a foot and attached to the foot by a holder;
Fig. 5 is a plan view showing a modification of the insole according to the invention; and
Fig. 6 is a perspective view showing a modification of the holder.
Fig. 7 is a section view along line X-X of Fig. 1 during the molding process:

In Figs. 1 and 2, there is shown an embodiment of an insole (1). This insole (1) is exclusively for left feet and used for the conservative treatment of the baker leg or the like. The upper face of the insole (1) is made in the undulating form of a human sole part (31) (Fig. 3), and the whole of the insole has the form of a wedge being thicker toward the left side (11) for obtaining the expected therapeutic effect. The insole (1) is formed of foamed silicone rubber which develops the gum-like elasticity under normal temperatures. Incidentally, reference number (2) indicates small holes for air permeation which extend through from the upper face to the lower face. (5) indicates the small porous foam, which are equally distributed in whole of the insole (1).
As can be seen in Fig. 3, the insole (1) is not bulky relative to the foot (3) but is rather compact. The insole (1) has an extremely good accommodation to the sole and generates a comfortable feeling; it is further skidproof, and can satisfactorily follow the movement of the sole (31). Consequently, the load on the insole (1) is reduced and the stability of the foot is improved.
The insole (1) may be applied to the sole (3) by use of a holder (4) as shown in Fig. 4(a). This holder (4) is constructed, for example, in such a manner that band portions (43) (43) are attached to both sides of a pocket body (42) which has an opening portion (41) for putting in and removing the insole (1), and that coupling means (44) (44) are provided on both ends of those band portions (43) (43). In making use of the holder (4), the pocket body (42) is applied to the sole in the state where the insole (1) is received within the pocket body (42), and then the band portions (43) (43) are coupled above the instep of the foot. Materials for the pocket body (42) and the band portions (43) (43) are preferably of good adhesion to the sole (3) and of fine air permeability. To this end, they are normally made of cloth, for example, stretchy yarn, spandex, and the like, or knitted goods. For the coupling means (44) (44) shown in the figure, face fasteners are used, but in addition to that or alternatively buttons, snaps, hooks, strings and others could be used.
As for the position and form of the opening portion (41) of the holder (4), this may be modified. While the band portions (43) (43) are separated into two portions in Fig. 4a they may be formed as a single continuous arch-shaped band, both ends of which being fixed to the pocket body (42). It is also possible to manufacture the insole with a simple holder (6) by molding the band portions (43) integrally with the insole as shown in Fig. 5.
If using a holder (4) the insole (1) can be put on the sole (31) very simple and stably irrespective of indoor and outdoor use and irrespective of what kind of footwear is used. The whole of the insole (1) follows the movement of the sole (31), thereby the desired therapeutic effect is enhanced. A sock can be drawn over the applied insole 1 because the holder does not exaggerate. Further, the holder (4) has a good air permeability since it is made of cloth or knitted goods, and it is also hygienic because it is washable.
As already mentioned the insole is provided with small holes (2), as shown in Fig. 3, which are never filled with dampness due to perspiration, thereby the cleanliness of the foot (3) is preserved and the unpleasant sensation of somehow offensive smell is eliminated to a large degree. The holes (2) might be about 0.5-2 mm in diameter and about 10-50 in number. The curvature of the insole (1) described above is relatively small except the insole, shown in Fig. 6, which can be manufactured for the purpose of using it for shoes.
The description will be now directed to the materials used.
The insole (1) is molded of a silicone compound which has a gum-like elasticity in the vicinity of the normal temperature.
The silicone rubber material used is a mixture of both ,inorganic filler and hydrous silicate powder with heat-vulcanized silicone rubber. If only calcium carbonate as a filler is mixed with silicone rubber, the fluidity is kept and the material has a good workability. A positive effect on the swell in volume is not achieved neither a lowering of the production costs. On the other hand, where only hydrous silicate powder is mixed to silicon rubber it is difficult to disperse it in the silicone rubber. However it leads to a foam-formation. On the other hand the fluidity is lowered remarkably, thus the workability is reduced. Therefore good results are obtained by mixing and dispersing both components: calcium carbonate and hydrous silicate powder into silicone rubber at a certain ratio.
As inorganic fillers can be used various sorts and grain sizes of calcium carbonate, magnesium carbonate, talc, aluminium hydroxide, magnesium hydroxide, calcium sulfate, calcium silicate, ground silica, clay, mica, glass beads, microballoon (hollow spherical glass powder), silica balloon, and others. Preferred are those which have a low in oil absorption value so that the fluidity may be hard to drop at the time of mixing silicone rubber, and which allow a surface treatment such as a silane treatment with a view to increase the strength of the product, especially the tensile strength, cracking resistance, and so on. Most preferred is surface-reactive calcium carbonate the grain surface thereof being activated by silane coupling agent. And micro-balloon is one of the most preferable filler. Further preferred is a filler which specific gravity is as low as possible.
As for hydrous silicate powder, it fulfills its function such that it is resulting in high strength and in the reduction of production cost, and further it generates small uniform bubbles by the action of water contained therein (water of crystallization), playing an important role in making the product light-weight. In this way, it does not need any particular foaming agent belonging to an organic group. In practice, there is used for instance white carbon which is one of the non- crystal hydrous silicate powder. To say in addition, any pigment and other additives can be freely mixed so far as it is possible to obtain a product having the expected object properties.
The preferable mixture ratio of these components is 5-75 parts (by weight: herein the same) of an inorganic filler and 5-30 parts of hydrous silicate powder together with 100 parts of heat-vulcanized silicone rubber and 10 parts (be changed in compliance with the kind of silicone rubber or vulcanizing agent) of vulcanizing agent. When mixing more than 75 parts of the inorganic filler, the fluidity drops and the workability becomes bad, and when less than 5 parts are used, small bubbles are not obtained in the foam-formation, so that blow-off holes occur. Especially preferred are 10-50 parts. When mixing more than 30 parts of hydrous silicate powder, the fluidity drops considerably, and when less 5 parts are used, the foam-formation is not satisfactory. Especially preferred are 10-20 parts.
By way of a preferred example, as a start 10 parts of the vulcanizing agent are mixed and stirred thoroughly with 100 parts of the heat-vulcanized silicone rubber (a colorless, transparent liquid). Next, when commingling 25 parts of calcium carbonate being previously surface- treated by silane coupling agent, and 15 parts of white carbon which is noncrystal hydrous silicate powder of high purity, there can be obtained an abundantly fluid slurry. After being poured into a mold, the slurry is heated at about 100°C in a thermostatic oven for about one hour to harden it. The object which is removed from the mold is a hardened body which is light-weight and contains many small bubbles distributed uniformly in the whole surface, as shown in Fig. 1 and Fig. 2. The hardened body is the insole (1) described above.
The product obtained can be subjected to work afterwards. Accordingly, it can be cut and grounded to fit the patient's foot. For this the insole can be selected out of a plurality of insoles which are manufactured in advance.
By shaping the upper part (12) of the insole (1) it is only formed in an arc, and the bottom part (13) has a flat shape, as shown in Fig. 7. The semi- product (14) can be finished by cutting and/or grinding the bottom part (13) to fit the patient's foot.

Claims

1. Insole molded of a mixture of a silicone rubber and an inorganic filler material, characterized by a mixture which comprises 5-75 parts (by weight) of the inorganic filler, 5-30 parts (by weight) of a hydrous silicate powder and a vulcanizing agent per 100 parts (by weight) of silicone rubber and by a permeable structure thereof.

2. The insole as set forth in claim 1, characterized by a plurality of small holes (2) for air permeation.

3. The insole as set forth in the claims 1 and 2, characterized in that band portions (43) are integrally molded with the insole.

4. The insole as set forth in the claims 1 to 3, characterized in that it is colored, especially by a skin color.

5. The insole as set forth in one of the claims 1 to 4, characterized in that it is cut out of a molded piece and/or ground after molding.