ORTHOPEDIC INSOLE AND METHOD OF ITS MANUFACTURE

Abstract: An orthopedic insert (2) includes a stiffening base part (4) and thereupon a shock-absorbing upper part (8) extending substantially over the entire insert (2). On its underside the insert has regions (14, 16) with material removed under the longitudial and transversal arches of the user's foot to allow a dynamic, natural, shock-absorbing movement of the arches and the foot. At least backwards from a point about 1/3 from the forward edge of it, the shock-absorbing upper part is substantially uniformly thick. The base part (4) is formed with an upstanding wall (6) round the heel portion thereof for keeping the heel cushion in place. A method of manufacturing such an insert is also a subject of the invention.

Description: ORTHOPEDIC INSOLE AND METHOD OF ITS MANUFACTURE TECHNICAL FIELD The invention relates in general to orthopedic insoles and in particular to such an article having improved shock-absorbing properties. The invention also relates to a method of manufacturing the inventive insole. BACKGROUND ART As more and more people take up sports, such as running, and with generally increasing interest in health, the need of orthopedic insoles or inserts in shoes increases, since they reduce the risk of injury, eg. when running, and also usually help to achieve better performance and health. However, the implemen¬ tation of such inserts is of the greatest importance, as a wrong insert is ineffective and may even be a health hazard. Orthopedic shoe inserts are known, where a stiff material, such as ethyl vinyl acetate (EVA) , is used to provide a stiffening function. The drawback with these inserts is that the material is selected either in a too hard quality or density, causing discomfort to the user, or a too soft quality, resulting in deteriorated stiffening function or total lack thereof. Also, known insoles treats the foot as a static unit. Shock-absorbing material, such as HGP or the so-called Grete-Waitz insole have been used to achieve a shock- absorbing insole or insert. In the latter case, the above-mentioned stiffening function is not obtained. The German patent specification DE-A1-35 27 583 (Stu pf) discloses a shoe insole with a base having disposed on it shock-absorbing body giving a damping effect. In the heel region, where loading is greatest, the insole merely comprises the shock-absorbing body. In certain other places the body is thicker, to conform with the underside of the foot. Under the lateral side of the foot, for example, the insole is built up with a wedge of stiffer material. This known shoe insole has several drawbacks. Inter alia, the uneven thickness of the shock-absorbing body results in greater damping in certain areas, which may result in lowered insole performance. In addition, the wedge of stiffer and softer material causes the natural, rolling movement of the foot to be reduced or eliminated, resulting in that the shock-absorbing function of the foot itself is lessened, and this may lead to painfulness and overuse injuries due to strain etc. In the known insoles of the kind in question, heavy shock-absorbing material such as Sorbothane® and Viscolas® are used, with the accompanying disadvantage that they become heavy and clumsy. The US patent E-Re-33648 (Brown) discloses an insert with a cork wedge formed to conform with the user's foot. Cork, being a stiff, "dead" material, inhibits the dynamic movement of the longitudinal arch on the medial side. Therefore, the natural shock-absorbing action of the longitudinal arch of the foot is impaired. The US patent 4 070 770 (Velio) discloses an insole for rock climbing shoes. This insole presents a differen¬ tiated flexibility in a longitudinal direction with a maximum of rigidity in a heel portion and a maximum of flexibility in a toe portion. This type of insole is PCIYSE95/01254 not suitable for use with shoes for other applications, as it is adapted to use with rock climbing shoes. This insole lacks support on the medial side, i.e. there is not enough material to "fill up" under the longitudinal arch region. Also, the insole has a constant thickness in each of its transverse sections, thus preventing yielding of the foot in the longitu¬ dinal arch. OBJECT OF THE INVENTION An object of the present invention is to provide an orthopedic shoe insole or insert, which circumvents the above-mentioned drawbacks and which provides a better shock-absorbing and supporting function than other, known inserts. Another object is to achieve an advantageous method of manufacturing such a shoe insert. BRIEF ACCOUNT OF THE INVENTION The above-mentioned objects are achieved by an ortho¬ pedic insert having a shape formed substantially to the sole of the user's foot. This insert includes a stiffening base part and thereupon a shock - absorbing upper part extending substantially over the entire insert, and is characterised in that the base part (4) comprises a downwardly concave area in the region (12) under the longitudinal arch of the wearer's foot. Preferably, the base part in the area under the forward, transversal arch of the wearer's foot compri¬ ses an essentially circular recess at the underside thereof, said recess having a diameter of about 1-4 cm, and the base part comprises a protrusion essentially over the circular recess. In accordance with another aspect of the invention a method is provided for manufacturing an insert, including making a plaster cast of an unstressed foot, allowing said cast to set, manufacturing a base of stiff material, which, by utilizing said plaster cast is in conformity with the sole of the foot, coating an upper part of shock-absorbing material with contact glue previous to applying it to the base part, and pressing together the upper part and base part in an apparatus using vacuum technique, for the time the glue takes to set characterised by the step of removing material to form an arch at the medial or inner side of the base. Remaining distinguishing features are disclosed in the depending claims. BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in more detail in the form of an example, and with reference to the accompanying drawing, where: Fig. 1 is a view from above of the inventive insert. Fig. 2 is a section through the insert of Fig. 1 along the lines A-A. Fig. 3 is a cross section through the insert of Fig. 1 along the lines B-B. Fig. 4 is a cross section through the insert of Fig. 1 along the lines C-C. Fig. 5 is a cross section through the insert of Fig. 1 along the lines D-D. Fig. 6 is a cross section through the insert of Fig. 1 along the lines E-E. PREFERRED EMBODIMENTS An insert in accordance with the invention in a preferred embodiment will be described below, together with a preferred method of manufacturing such an insert. As will be seen from Fig. 1, the inventive insert 2 has a shape fitting ordinary shoes. Fig. 2, which is a section through the insert in Fig. 1, illustrates how it is built up. The lower part or base 4 extends over the entire length of the insert and has a profile adjusted to the shape of the sole of the user's foot. The base 4 also includes an upstanding side wall 6 round its heel portion, giving this portion a basin¬ like configuration, which keeps the fat pad under the heel bone together, thus increasing shockabsorbing capacity. The wall 6 has a height of 1-5 cm. In the preferred embodiment the base 4 is made from ethyl vinyl acetate (EVA) , which has been shaped to fit the foot sole. On top of the base there is provided an upper part 8, of shock-absorbing material, eg. HGP or an insole marketed under the trade name "Grete Waitz Insole". Rearwards, starting at a point at least about 1/3 of the total length of the insert from the forward edge thereof and denoted by a dashed line in fig. 1, the upper part has a substantially uniform thickness, preferably of about 6 mm. On its underside, the upper part tapers off forwards from said point, starting at the dashed line indicated in Fig. 1 and situated at least about 1/3 of the total length of the insert from the forward edge thereof, to become about 1-2 mm at said forward edge, where the shock-absorbing requirement is less than that more rearwards. The insert is thus very thin at its forward portion, which enables its use in most shoes. The upper part is thus given its greatest thickness where loading is greatest, since there is not the same need to absorb shocks in the forward part of the foot. Completing the orthopedic insert or insole, there is a covering 10 made from some tough material, eg. galloon or P.V.C. coated fabric, over the whole of the upper side of the insert, which prevents friction between foot and insert as well as increasing the life of the latter. In Fig. 2 an arch 14 is indicated by crosses. In this region the insert is pared away on the medial or inner side of the insert in the area 12 in Fig. 1. This is also shown in the cross-section of Fig. 4. There is also a support in this area under the longitudinal arch. The portion pared away will allow a resilient spring action of this support and thus of the longitu- dinal arch of the foot when this is working dynamical¬ ly, e.g. during walking, running etc. By this implemen¬ tation the foot can yield in the longitudinal arch, so that the natural shock-absorbing action of the foot is maintained. For practical reasons, also the outer side of the insert can be pared away to a lesser extent in this area. With reference to figs. 1,2 and 5, there is a recess or depression pared away from under the bottom part of base 4 in the area 16 under the forward or transverse (metatarsal) arch. The recess, which is essentially circular, has a diameter of about 2 cm, but can have a diameter in the range from 1-4 cm, depending on the size of the insole, the weight of the user etc. The function of this recess is to allow a "pad" or a support 17 for the transverse arch on the upper side of the insole above the recess 16 a resilient spring action when pressure is put on the forward part of the foot, to allow the transversal arch to "flatten out" when the forefoot is working dynamically, e.g. in midstance of the gait, when the stress is largest. In this way, discomfort and possible injury to the user can be avoided. This support usually has a diameter of about twice the diameter of the recess 16, and is preferably wider towards the front of the insert, to conform with the form of the transversal arch. The function of this combination of the pad 17 and the recess 16 is very much the same as that of the arch 14, i.e., to allow a dynamic movement of the foot. The transversal arch is situated right behind the metatarsal heads, and the pad 17 thus supports this transversal arch in a resilient way. A preferred method of manufacturing the inventive insert will now be described. Initially, a plaster cast of the foot is made, the prospective user lying face down during this procedure to ensure that the foot is not stressed. The cast is subsequently removed and allowed to set hard. There is, thus, obtained a mould corresponding to the sole of the foot. The mould is then utilised to manufacture the base 4 of the insert and in the preferred embodiment the latter comprises ethyl vinyl acetate. This material may be obtained in different shores (densities) , and one of 55 shore zero is suitable in this case. It is heated to make it soft, and then pressed against the mould to provide the base 4, which is subsequently tapered off at the medial or inner side such as to correspond to the arches of a foot, thus obtaining its final shape. The upper part 8 has the general configuration of an insole, and is about 6 mm thick to start with. From a distance of about 1/3 of the length of the part away from its forward end it is tapered down towards this end to a thickness of about 1-2 mm. The part is then coated with contact glue, applied to the base and pinned in place. The combination of upper part 8 and base 4 is now placed in an apparatus using vacuum to press the upper part against the base, and left there for some minutes. This affords a very tight joint between the two parts, and accordingly there is obtained an insert that has an upper side conforming to the foot sole, even with the upper part added. The insert 2 is finally dressed, this process including the removal of an arch 14 on the medial or inner side of it, corresponding to the longitudinal arch of the foot, removal of a recess 16 essentially under the transversal arch of the foot, as well as adjusting its shape to the shoe or shoes with which it is to be used. Preferably a protective material 10 such as galloon or PVC coated fabric is glued on top of the upper part 8. The manufacturing method in accordance with the invention thus ensures a pliable insert, since the latter is tapered and consequently thinner. The insert also allows for a dynamic movement of the arches and the rest of the foot, which promotes the natural, shock-absorbing movements thereof. Only a preferred embodiment of the invention has been described above, and it can have further variants within the scope of the claims. For example, the entire upper part 8 can have an uniform thickness.

Claims: CLAIMS 1. An orthopedic insole or insert (2) of a shape substantially adjusted to the sole of the user, said insert including a stiffening base part (4) on top of which there is disposed a shock-absorbing upper part (8) extending substantially over the entire insert, c h a r a c t e r i s e d i n that the base part (4) comprises a downwardly concave area in the region (12) under the longitudinal arch of the wearer's foot. 2. An insole as claimed in claim 1, wherein the base part (4) in the area (16) under the forward, trans¬ versal arch of the wearer's foot comprises an essen- tially circular recess (16) at the underside thereof, said recess having a diameter of about 1-4 cm, and wherein the base part (4) comprises a protrusion (17) essentially over the circular recess (16) . 3. An insole as claimed in claim 2, wherein the protrusion (17) is slightly wider at the front part. 4. An insole as claimed in any of claims 1-3, wherein the upper part (8), at least backwards from a point about 1/3 from the forward edge thereof, is substan¬ tially uniformly, and preferably about 6 mm thick. 5. An insole as claimed in claim 4, wherein the thickness of the upper part (8) decreases forwardly from a point about 1/3 from the forward edge thereof. 6. An insole as claimed in any of claims 1-5, wherein the base part (4) includes an upstanding wall (6) around the heel portion of the insert. 7. An insole as claimed in any of claims 1-6, wherein the upper part (8) is made from HGP. 8. A method of manufacturing an orthopedic insole or insert, said method including: Making a plaster cast of an unstressed foot, allowing said cast to set, manufacturing a base part of stiff material, which, by utilizing said plaster cast is in conformity with the sole of the foot, coating an upper part of shock- absorbing material with contact glue previous to applying it to the base part, and pressing together the upper part and base part in an apparatus using vacuum technique, for the time the glue takes to set, c h a r a c t e r i s e d b y the step of removing material to form an arch at the medial or inner side on the underside of the base part. 9. A method as claimed in claim 8, including the step of removing material on the underside of the base part under the transversal arch of the foot.

Inventors: HEDSTROEM PETER, HEDSTROEM, PETER
Applicants: HEDSTROEM PETER, ORTOLAB AB, HEDSTROEM, PETER
Application year: 1995
Main classification: A43B17
IPC codes: A43B7, A43B13, A43B17