Running shoe with damping sole element

The invention concerns a shoe with a damping device for use on a hard ground surface such as asphalt. More specifically the invention concerns a running shoe with an outer sole designed to provide good damping also for the front part of the foot.

Background

It is well known that running shoes or sport shoes have good damping of the back part of the foot. The damping can be provided by flexible layers of material, preferably in combination with trapped pockets of air or gas as well as damping gel materials. There are also so-called full-damped shoes with a corresponding, but somewhat less damping under the front part of the foot than under the back part. This type of damping is effective with respect to damping of movements in vertical direction.

For some areas of use, however, there is a significant need for damping of movement in horizontal direction. This is particularly relevant for competition runners which run with high speed on hard surfaces like asphalt and which run in way by which the front part of the foot touches the ground at least as early as the heel of the foot. The problem with landing on the front part of the foot is typically that the horizontal strain on the foot and ankle is very high because the shoes used have soles with high friction that provide an extremely quick retardation each time the foot hits the ground. The problem is not as significant for runners landing on the heel because then a rolling movement is obtained in the direction from the heel to the front part of the foot. For competition purposes the problem is particularly pronounced since a lowest possible weight is desired and therefore the use of damping materials is reduced under the front part as well as the back part of the foot. Some efforts have been made to attempt to alleviate this disadvantage, but none that has provided an optimal solution and particularly not for running shoes designed for competition, i.e. shoes with very low weight.

From DE A1 27 33 605 is known a sporting shoe with a corrugated profile at the sole tip and with elastic ribs across providing a certain flexibility in the length direction. This shoe provides a certain flexibility when the shoe hits the ground, but the extent of damping in the horizontal direction is limited by the height of the ribs and their flexibility. Furthermore the shoe according to this patent does not appear to be suited for competitions.

Objective

It is an object of the present invention to eliminate the mentioned problems by providing a running shoe with particularly good damping in horizontal direction during quick running; i.e.

when the runner hits the ground with the front part of the shoe at least as early as do the heel part of the shoe.

The present invention

The mentioned object is achieved in the form of a running shoe as defined by claim 1. The term "hard ground surfaces" refers to ground surfaces like asphalt, concrete and other compact ground surfaces. The invention will also function, but to a somewhat smaller extent, on softer ground surfaces like different types of synthetic ground surfaces.

Preferred embodiments are disclosed by the dependent claims.

What is particularly obtained when using the running shoe according to the present invention, is a reduced friction between shoe and the ground surface when the runner runs in a manner in which the front part of the shoe hits the ground surface as early as, or earlier than, the heel part of the shoe hits the ground surface. Dependent upon the ground surface, speed and running techniques the shoe will slide a controlled distance for each step, typically 1-3 cm, in some cases 4-5 cm or more, depending upon the speed, surface and inclination. Thereby a smaller load is transmitted to the different joints in the users foot and ankle and an increased step length is obtained which may be used to increase the speed. When the weight is moved forward in the direction of the toes, the friction again increases and during the kick-off for another step the friction is again at its maximum since the plate or the area of reduced friction is no longer in contact with the ground. Even when running in a manner in which the forefoot hits the ground surface early there is a certain rolling of the foot and thereby the sole in the moment after the shoe sole hits the ground surface. The rolling is partly in a forward direction and partly from the lateral side (little toe side) to the medial side (big toe side) of the foot. When the rolling movement is studied in more detail, however, it appears to be more complex than described above, with an early stage of movement backwards before the forward rolling becomes dominant. The present invention does not, however, depend on a scientific understanding of the complete movement pattern for each step. It is on the other hand important that the particular sole element which has a limited friction against the surface, is arranged mainly lateral and therefore obtains contact with the ground surface as early as possible in the landing phase and it is furthermore significant that the medial side of the sole does not have a significant area of such a sole element since this would lead to a poorer grip for kick-off.

In a preferred embodiment the sole element according to the present invention has the form of at least one plate which is adapted to the outer shoe sole. The outer sole will typically comprise at least one recess with mainly the same shape as the plate or plates in question, said plate(s) being permanently or releasably/ replaceably attached to the sole.

Damping, compressible materials of conventional type, which are mainly suitable for damping of vertical retardation, can be arranged under the outer shoe sole and/ pr between said plate and the outer shoe sole.

An alternative to separate plates being attached in recesses of the outer sole is a sole element made as an integral part of the outer shoe sole. This prevents any risk of losing a sole element during use. In addition this allows a gradual change from a certain hardness with corresponding friction coefficient to another hardness with another friction coefficient. On the other hand this type of sole element can not be replaced when worn.

There are different ways of obtaining the desired control of the sole element friction against a surface. One way is to adjust the hardness of a certain material. Generally, the harder the element of a certain material, the lower the friction coefficient will be. Under any circumstance the sole element of the present invention will normally be harder than the other part of the outer sole. The material as such can also influence the friction. It is preferred that the sole element according to the present invention is made in a synthetic material and it does not matter what kind of synthetic material is used as long as a desirable low friction is obtained. From practical and economical reasons a material with a significant wear resistance should be used in order not to wear out the sole element much earlier than the rest of the shoe. In some embodiments it is preferred that the sole element according to the present invention is made in another material than the other parts of the shoe outer sole.

Below the running shoe according to the present invention is described with reference to some embodiments which are illustrated by drawings, where:

Fig. 1 is a top view of a shoe sole of a running shoe according to the present invention, Fig. 2 shows principally the same as Fig. 1 bur with a slightly different localization of the sole element according to the invention,

Fig. 3 shows an embodiment of the present invention having two separate sole elements, Fig. 4 shows a variant of the version shown in Fig. 3 in which the two sole elements partly overlap one another; Fig. 5a and 5b show a side sectional view of the shoe sole shown in Fig. 1 along the line V-V and an enlarged detail from Fig. 5a respectively.

Figure 1 shows a shoe sole of a running shoe according to the present invention from below. The sole has a toe portion 2, a heel portion 3, a lateral side 4 and a medial side 5. The characterizing part of the shoe sole is a particular sole element 6 that provides reduced friction, arranged substantially lateral under the front part of the foot. A stapled line across the sole's longitudinal extension indicates where the user's transverse foot arch

is highest. The front part of the foot should be interpreted as the part of the foot in front said stapled line.

In Fig. 2 another variant of the shoe sole according to the present invention is illustrated. According to this variant the particular sole element 6' extends from lateral side and somewhat over to the medial side of the foot, but has its main area at the lateral side.

In Fig. 3 yet a variant of the shoe sole according to the present invention is shown. In this case there are two separate sole elements 6a and 6b, arranged mainly laterally in the front part of the shoe sole. The elements are separate but in close proximity with one another.

Fig. 4 shows a variant of a shoe sole shown in Fig. 3, in which the two sole elements 6a' and 6b' appear to partly overlap one another. It might be a cut out in the sole element 6a' that corresponds to the part of sole element 6b' "overlapping sole element" 6a'. It might also be more than two sole elements (not shown) according to the present invention, hereunder at least one sole element with reduced friction localized at the medial side of the front foot as long as the size of such element is not predominant. The sole element 6a and 6b in Fig. 3 can have mutually different properties. The can for example have different hardness and provide different friction against e.g. asphalt, e.g. such that the sole element 6a which will normally hit the ground surface first, can have a friction against asphalt which is lower than that of sole element 6b, which has a higher friction than sole element 6a but a lower friction than the other part of the shoe sole. The same is to be said about sole elements 6a' and 6b' in Figure 4.

In Fig. 5a a side sectional view of the shoe sole of Fig. 1 is shown, the section being put along the line V-V in Fig. 1. The sole thickness of the drawing is exaggerated in proportion to the other dimensions of the sole. In Fig. 5b an enlarged section (encircled) from Fig. 5a is shown. By Fig. 5b is apparent that the sole element 6 protrudes from the sole as such as illustrated by the δ (delta). Such a height difference in not mandatory but it is preferred with a height difference in the range 0.5 to 5 mm. Thereby the probability that the particular sole elements hits the ground surface first will increase, even when the surface is not quite smooth or when the users foot has a reduced pronation (pronative) movement.

Figures 5a and 5b provide an illustration of a sole element having a longitudinal flange along a part of or its entire circumference in order to support or hold the sole element fixed to the sole 1. This is not a mandatory feature of the invention and will normally not constitute a sufficient method of attachment for the sole element 6 which preferably will be attached to the sole 1 over the entire or a substantial area in which the sole elements are in contact with the sole 1. Suitable attachment mechanisms comprise gluing and vulcanization. In a layer 8 between the sole 1 and the sole element 6 a particular damping element or damping material for the sole element 6 can be arranged in addition to the

damping element or elements which will normally be located above the sole 1 , covering part of or all of the area of the sole. The damping material 8 will be resilient and its thickness can in some embodiments be at least the magnitude of the protrusion "δ" or the height difference between the sole element and the other part of the sole 1 , so that the sole element for each step is compressed to about the level of the other parts of the sole. The damping material 8 will, if present, contribute to damping both in vertical and horizontal direction.

The sole element is typically made in a synthetic material which is highly wear resistant and which have a hardness or particularly a surface hardness that provides a friction against a ground surface like asphalt, concrete, paving stones and the like which is lower than the friction the sole 1 has against such surfaces. The sole element can also be provided with fibres or particles to further accommodate its properties with respect to strength and friction coefficient.

It is preferred that the sole element provides a friction coefficient against (dry) asphalt and (dry) concrete which is lower than 0.8, more preferred a friction coefficient in the range from 0.1 to 0.6 and even more preferred in the range 0.2 to 0.4.

It is still further preferred that the sole element 6 has an area that constitute at least 15 % of the area of the part of the shoe sole situated under the front part of the foot , i.e. which is in front of the traverse stapled line in the figures 1-4. If there are more than one sole element as shown in Figure 3, it is the sum of the areas of said sole elements that should have the mentioned relative size.

Furthermore the sole element according to the present invention is situated mainly laterally under the sole; i.e. that the largest part of, or the entire sole element, will lie laterally of an imaginary centre line along the shoe sole 1. More preferred at least 75 % of the area of the sole element is typically situated at the lateral side of such an imaginary, longitudinal centre line along the sole.

In the figures only the sole of a right shoe is shown. It should be understood that the same principle applies for both shoes of a pair, the meaning of "lateral" and "medial" implying that drawings of the sole for a left shoe will appear as mirror images of the figures 1-4.