Ski for cross-country skiing and method for treating the ski

Abstract

The present invention relates to a ski (1) for cross-country skiing, which ski (1) is comprised of an elongated, beam-like structure comprising at least side walls (2), an upper surface (3) and a base (4), the ski (1) being formed to be cambered, wherein the base (4) is made to curve upwards over the length of the ski, the front (41) and rear (43) parts of the base are in contact with the ground, but the middle part (42) of the base is detached from the ground when the ski (1) is placed, with its base (4) against the ground, unweighted on an even horizontal ground. Over at least a part of the distance to the middle part (42) of the base, on the surface layer (40) of the base (4), are formed lamellas (401) by means of slits (400) transverse to the longitudinal direction (L) of the ski (1), tilted backwards with respect to the normal (N) of the base (4) and the longitudinal direction (L) of the ski (1), the lamellas comprising two sides (402, 403), and one side (404) parallel with the base (4), the lamella (401) extending from the surface layer (40) of the base (4) to the inner layer (45), to which the lamella (401) is connected. The invention also relates to a corresponding ski for freestyle cross-country skiing, and a method for treating the ski.

Description

Ski for cross-country skiing and method for treating the skiField of the invention

[0001] The invention relates to a ski for cross-country skiing according to the preambles of claims 1 and 3. In particular, the invention relates to a ski for crosscountry skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls, an upper surface and a base, the ski being formed to be cambered, wherein the base is made to curve upwards over the length of the ski, the front and rear parts of the base are in contact with the ground, but the middle part of the base is detached from the ground when the ski is placed, with its base against the ground, unweighted on an even horizontal ground.

[0002] The invention also relates to a ski for freestyle or classic style crosscountry skiing according to the preamble of claim 4. In particular, the invention relates to a ski for freestyle cross-country skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls, an upper surface and a base, the ski being formed to be cambered, wherein the base is made to curve upwards over the length of the ski, the front and rear parts of the base are in contact with the ground, but the middle part of the base is detached from the ground when the ski is unweighted on the ground.

[0003] The invention also relates to a method for treating a ski according to the preamble of claim 19.Technical background

[0004] The present invention relates, in particular, to skis intended for crosscountry skiing (Nordic skiing) on snowy ground, groomed ski tracks and track bases. The first embodiment of the invention is a ski for the so-called classic skiing style, where a ski track, or two ski track grooves, have been made in the terrain for skis attached to each foot of the skier. To move forward, the skier can use both the strength of their arms and the speed achieved by means of the ski poles as well as their legs, whereupon, during the push-off phase, the camber of the ski is pushed to become even so that the middle part of the base also comes into contact with the ground, that is, the ski track, in the longitudinal direction ofthe ski. For the desired correct functioning of the ski, it is essennai mar rne SKI glides as well as possible when moving forward, but "grips" when the skier pushes forward using their legs or leg. In classic style skiing, the direction of gliding and the direction of pushing are at 180° to each other, which means that the push / kick is aimed directly backwards in the direction of the ski track groove, whereupon the ski should hold, that is, momentarily grip the ground, and not slide backwards. This contrast makes the classic style challenging in terms of the functioning of the ski, as the ski must both glide and grip, and each different snow condition, snow structure, snow humidity, temperature, ice crystal shape, etc. changes this situation.

[0005] The above-described dual requirement on skis to glide and grip in classic style skiing has long been solved by lubricating skis. The front and rear of the base have been lubricated with glide wax and the middle part has been lubricated with grip wax. There is a huge number of such different glide and grip waxes, such as paraffin-based waxes, for a wide variety of snow conditions. In this way, a ski that works well can be achieved by a skilled lubricator, but if the weather conditions change or the lubricator makes a false assessment, the ski may not work properly.

[0006] Another solution that has been used is to make a roughening or pattern in the middle part of the ski base that glides when the ski is moved forward but aims to prevent movement when the ski is moved backwards. Such roughenings or patterns may be made, for example, by roughening the rubberlike material, as in the ski sold under the Fischer Zero brand name, or by coating the base of the ski with very small particles, as is the case with skis sold under Peltonen’s Nanogrip or KSF Oy’s Optigrip brand names. From the prior art in this field of technology are known, among others, the following patent publications: DE7607705U1 , US4118050, US4705290, US4844500 and US10926157B2. In this field, most solutions are also highly dependent on the conditions; a solution may work in one weather condition but not in another. In many solutions, the patterned area also forms a serrated edge in the longitudinal cross-section, that is, when viewed from the side, wherein in the base is a row of wedge-like shapes in the direction of travel. From the prior art is also known US4714266, which discloses a plastic coating for the base of a ski, on which is formed a climbing aid comprising a multiplicity of teeth which are aligned in the longitudinal direction of the ski and terminate towards the rear end of the ski in a pointed end capable ofbeing bent upwards, the said teeth being defined by two series or parallel curs ar a distance from each other, which intersect each other, the individual series of cuts being at an angle of 30°-60° with respect to the longitudinal axis of the ski, the cuts having at least essentially the shape of circular segments and being at an angle of at least 60° and at most 80° to the normal of the base, and that the relative spacing between the cuts is 0.1-1 mm.

[0007] A third solution that is commonly used and has recently been particularly popular with recreational skiers is the so-called skin ski, a grip ski, that is, a ski equipped with a separate skin strip glued to the ski base. When moving forward, the hairs in it are, so to speak, in the same direction as the ski, and during the push-off phase, when the ski tends to move backwards, the hairs stand up, in the opposite direction with respect to the ground. In this field of technology, from the prior art are known, among others, the following patent publications: EP2745886A1 , US4595215. The ease of this solution and its reasonably good performance in all weather conditions are the reasons for its current popularity in recreational use, but for competitive skiing, skin skis are often considered too slow because the hairs that occasionally touch the ground increase friction too much when skiing forward. The most significant problem with these skin skis is the poor glide of the skin zone itself. To provide sufficient glide, the grip zone is short and located at the so-called wax pocket of the ski, an area that does not come into contact with the ski track when the ski is gliding. In order for the ski to grip, the skier must be able to press the middle part of the ski firmly against the track, which is why the stiffness of the ski and the length and location of the grip zone must be precisely dimensioned according to the skier's weight and push-off power. However, on uneven tracks, the middle part of the ski often comes into contact with the snow and causes unpleasant jerking, that is, a braking effect, thus reducing gliding.

[0008] The second embodiment of the invention is a ski for so-called freestyle skiing, where a ski track, that is, an even snow surface for skiing, has been made in the terrain. To move forward, a skier may use both the strength of their arms and push with the poles and their legs to gain speed, whereupon, during the push-off phase, the skis are skated, that is, the skis are glided alternately at a gently opening angle with respect to the direction of travel. In this style of skiing, in the longitudinal direction of the ski, the middle part of the base does not necessarily come into contact with the ground and only glide-increasinglubrication is used on the skis. The faster the skiing speed, the genner me angie at which the ski is pushed outwards with respect to the direction of travel.

[0009] The problem with the solutions disclosed above is that most of the solutions disclosed above are suitable for specific conditions, such as snow conditions, snow structure, snow humidity, temperature, ice crystal shape, track hardness, etc., but may not work well in other conditions. For example, some well-known solutions are known to work well in temperatures above 0 Celsius, that is, when the snow contains water in an aqueous phase between the snow crystals, but when the snow becomes dry due to frost, such dry snow freezes tightly to the base of the ski, almost completely preventing forward gliding.Description of the invention

[0010] The purpose of the invention is to improve the state of the art in the field by providing a ski for cross-country skiing that minimizes the problems of the prior art. The aim is to develop a solution that works in a wider range of snow conditions than previous solutions and provides good gliding properties combined with good grip properties, that is, a ski that glides better than current skis, but still has grip. One aim of the invention is to provide a solution that combines the ease of a skin ski, the gliding properties of a lubricated ski, and the grip of a patterned base. On the one hand, the aim of the invention is to make the ski work in a wider range of snow conditions than known solutions. On the other hand, the aim is to provide a ski that is successful in extremely tough competitions, for which it is possible to carefully select the parameters that work best for the narrower snow conditions in question from the versatile parameters that affect glide and grip that are now available with the invention. One of the aims is, therefore, to provide a ski that competes with the best solutions in the industry, also in the area of competitive skiing, when fighting for those last seconds.

[0011] The aim of the invention is also to provide a method by which a ski according to the invention can be manufactured in an efficient and simple manner.

[0012] The aims of the invention are achieved mainly as disclosed in greater detail in independent claims 1 , 3, 4 and 19, as well as in the other claims. Other additional features characteristic of the invention appear from the appendedclaims and the following description as well as the description or me embodiments shown in the figures.

[0013] One embodiment of the invention is a ski for cross-country skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls, an upper surface and a base, the ski being formed to be cambered, wherein the base is made to curve upwards over the length of the ski, the front and rear parts of the base are in contact with the ground, but the middle part of the base is detached from the ground when the ski is placed, with its base against the ground, unweighted on an even horizontal ground; wherein over at least a part of the distance to the middle part of the base, on the surface layer of the base, are formed lamellas by means of slits transverse to the longitudinal direction of the ski, tilted backwards with respect to the normal of the base and the longitudinal direction of the ski, the lamellas comprising two sides, and one side parallel with the base at the gliding phase, the lamella extending from the surface layer of the base to the inner layer, to which the lamella is connected, wherein the space between the slits is 0.04-0.35 mm in the longitudinal direction of the ski, wherein the ratio d:s between the depth of and the space between the slits that form the lamella is within the range 1: 1-12: 1, preferably within the range 1.8: 1-7.5: 1. In this way are formed lamellas that are tilted backwards in the gliding direction, the side of which parallel with the base forms a smooth gliding surface, enabling good gliding, and which lamellas return to their original position as accurately as possible when the ski is in the gliding phase. During the gliding phase, the ski is weighted by the skier's relatively evenly distributed mass, but the ski is not actually pushed in the same way as during the thrust or push- off phase. The push-off causes the ski to lose its camber, making the ski substantially flat in the longitudinal direction and the slits between the lamellas open, causing the grip edge of the lamella to grip the surface. The skier's push- off creates a backward force, which, for its part, also causes the lamellas to deform, the lamellas bending in the direction of the normal of the base, forming a surface that grips the snow. The change between these two positions, the glide and the grip, must take place with little force and quickly, especially when changing from grip back to the gliding / sliding position. One embodiment of the invention is, therefore, a ski for cross-country skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls, an upper surface and a base, the ski being formed to be cambered, wherein the base is made tocurve upwards over the length of the ski, the front and rear pares or tne case are in contact with the ground, but the middle part of the base is detached from the ground when the ski is placed, with its base against the ground, unweighted on an even horizontal ground; over at least a part of the distance to the middle part of the base, on the surface layer of the base, are formed lamellas by means of slits transverse to the longitudinal direction of the ski, tilted backwards with respect to the normal of the base and the longitudinal direction of the ski, each lamella comprising a foot, two sides, and one base side, wherein in the gliding phase, the base side is arranged to be substantially parallel with the base, defining an substantially even gliding surface, wherein in the push-off phase, when a backwards pushing force is exerted on the ski, at least some of the lamellas are deformed in the direction of the normal of the base, while in general retaining their shape from the foot, creating a contact surface for increased friction. The contact surface for increased friction is formed by the inclination of the lower surface of at least some of the lamellas and / or of the offset of the lower sides of at least some of the lamellas with respect to each other.

[0014] Without further committing to any theory of how a ski works, studies have found that a significant difference to prior art solutions is achieved when the lamella bends from the foot as a unit that substantially retains its shape. In this case, the angle of the backwards-directed tip of the lamella that forms the grip is maintained, and the grip does not take place only from the tip of the lamella or the like, as is the case with almost all prior art solutions. However, for example, US4714266 works in a very different way in principle; in it, too, the deformation is specifically directed at the thin and flexible tip area of the tooth. This may be the reason why this solution has never achieved any notable success in racing tracks or commercially. In the solution according to the basic idea of the invention, when the ski changes its shape from a cambered shape to an substantially flat shape during the push-off phase, at least some of the lamellas bend while substantially maintaining their shape and the tip area of the lamella cannot bend in the wrong direction, sideways or backwards due to a local load when the ski impacts an object on an uneven track, a piece of ice, a lump of snow or a similar bump. This allows for good skiing efficiency, good grip and at the same time good glide. When the angle (which can be called the attack angle) and shape of the lamella's grip edge remain correct, this allows the sharp edge of the lamella to penetrate the very thin layer of water between the surface of the track and the base of the ski and to bite into the ground, enabling good grip. Thiswater layer and its effect are a very significant factor in skiing, coin in a posiuve sense in terms of gliding and in a negative sense in terms of grip formation, since in practically all conditions, from extremely cold weather to a track soaked by rain, there is almost invariably a thin film of water in the ice or snow crystal. The friction caused by the ski's movement also melts some of the individual ice or snow crystals on the surface of the ski track and adds a layer of water to the interface. A water film is needed for a ski to glide well, but at the same time, if the lamellas do not penetrate the water film during the grip phase, the grip will be weaker.

[0015] A significant advantage is also achieved by the fact that the lamella is wide in the transverse direction of the ski; in practice, the width of the lamella is at least 3-5 times the thickness of the lamella. A wider lamella grip edge is much more durable as the lamella can only bend in one direction. The spike-like teeth known from the prior art bend in many directions depending on the load. The wider lamella of the ski according to the invention bends and moves at the same pace and also supports the adjacent lamellas across the entire width, even if a local load impacts the base of the ski. When all the lamellas move at the same pace, the ski is more sensitive. Therefore, the ski is faster when the majority of the lamellas achieve sufficient grip at the same time and the ski cannot move backwards when the lamellas bite and the ski stops. Also in the gliding phase, when the lamellas close, the wide lamellas work well with better efficiency. In this case, lamellas that are curved in the transverse direction can also be used as the appropriate curvature provides the right amount of spring force, allowing the lamellas to work better in pace and to close faster. Especially top-level competitive skiers have found, when blind testing the skis according to the invention, that this ski can be pushed forward faster and slightly further than the reference skis. When pushing forward, it is particularly important that the ski and the lamellas do not brake, because the relative speed of the ski with respect to the snow is significantly greater than when pushing backwards, that is, in the grip phase, where the skier's entire weight is used to push the ski downwards into the snow and the ski stops. In this case, it is important that the lamellas bite into the snow quickly and simultaneously so that the ski does not move backwards unnecessarily. Thus, a wider lamella will most often improve stride length at both ends of the ski stroke and the speed increases. It has also been found in tests that because wide lamellas move better in pace and retain their shape, snow and ice flakes fall off better compared to cross-cut diamond-shaped toothed lamellas.Therefore, when the snow is not trapped between the lamellas, me lameiias ciose and return to their original position, and the ski glides. A large number of prior art skis use slanted or heavily diamond-shaped lamellas. Studies relating to the present invention have shown that these are extremely vulnerable to ice accumulation, so the present invention is for its part solving this problem. When the cross-cut or diamond-shaped lamellas according to the prior art are not used but the lamellas are at an angle of almost 90 degrees to the longitudinal direction of the ski, the direction of the frictional force vector of the kick is almost entirely directly in the direction of travel of the ski, whereupon no lateral forces are generated and, therefore, the efficiency of skiing is significantly improved.

[0016] According to one embodiment of the invention, the lamellas are formed by means of slits, most preferably a slit between the lamellas is formed in such a way that at the foot of the lamella is formed a cavity, at which the lamella is thinner than the rest of the lamella. This cavity allows the flexural stiffness of the lamella to be changed and ensures that the lamella bends while substantially maintaining its shape and the angle of the grip edge but is still sensitive enough to allow the lamellas to bend into the gliding and grip phase with even less energy, without braking, and at the same time increasing efficiency.

[0017] Unlike in a traditional skin ski base, where the cross-section of an individual hair is round, in this structure the cross-section of the lamella is angular, usually resembling a diamond when viewed from the side. Thus, the slit provides a significant advantage in gliding as the lamellas can fit tightly against each other, whereupon, when viewed in the transverse direction of the ski, the geometry of the lamella is very close to the shape of a completely flat base in the gliding phase. In theory, such gliding surface formed in the grip zone in the middle part of the ski is as smooth and gliding as the gliding part of the ski, wherein the side of the lamella parallel with the base behaves against the ground like the front part and rear part of the ski where there are no lamellas. Therefore, even if the middle part of the base should at some point also grip the ground, it would, however, not cause braking. In addition, in the base may be used, throughout its entire length, both in the front, middle and rear parts, a known ground pattern that has been found necessary for the particular conditions. Grinding is a well- known technique by means of which the base of a ski is ground to best suit the desired conditions. Furthermore, when considering the situation in the longitudinal direction of the ski, transverse slits prevent significant longitudinalgrooving unsuitable for the purpose, which occurs, for exampie, in oiamono- shaped lamellas or in a skin ski when hundreds or thousands of individual round hairs are adjacent to each other in the transverse direction of the ski, which under certain conditions accumulates snow and ice crystals. This longitudinal grooving, which differs from the ground grooving, may be a contributory cause of why a skin ski seems to glide less well if the skin part impacts the ground during the gliding phase.

[0018] According to one embodiment of the invention, the slit between the lamellas is made substantially by means of a non-removing material processing method, but nevertheless in such a way that a cavity or passage parallel with the slit is formed in the foot area of the lamella. According to another embodiment, the cavity is formed in a material-removing manner, but the slit is made in a non- material-removing manner. This feature allows the lamellas to overlap each other accurately during the gliding phase. Especially during the gliding phase, it is important that the lamellas fit very tightly against each other, thereby rendering the base of the ski flat. On the other hand, during push-off, the lamellas must open easily so that the ski grips and does not slip. The lamellas must not "stick" to each other, because then they will not have time to open during push-off, and the ski will slip. An excessively tight, closing gap between the lamellas may begin to accumulate material such as freezing water, ice crystals or other impurities from the ground. As a result of the accumulation, deformation may occur, that is, a situation where the geometry of the lamellas may begin to change towards the geometry of the push-off phase, that is, a situation where the friction between the lamellas and the ground is as high as possible. The cavity may facilitate the escape of water or air from between the lamellas, allowing the lamellas to work faster than without the cavity. Suitable non-removing material processing methods include, for example, cutting with a sharp, smooth and thin blade, the tip of which has a shape that forms a cavity at the bottom of the slit by moulding. In forming the cavity, it is advantageous to treat the base material by stretch forming, wherein the material surrounding the cavity is stretched in forming the cavity. In this case, the stretched section becomes more sensitive to movement than the unstretched section and at the same time more durable; the stretched area, where the plastic molecules are arranged in a suitable manner, withstands a significantly greater number of loading cycles than the unstretched structure. Durability is much better than in known solutions. The surface roughness of the blade used for cutting is a factor that affects material removal. An excessivelyrough blade may cause some kind of unwanted material aorasion. i ne SIR between the lamellas is preferably made substantially by means of a nonremoving material processing method, wherein in the method is used a cutting blade, the cutting area of which is polished to a surface roughness of 2.0 pm Ra or less. The opposite of the non-removing material processing method presented above is a material-removing method, such as sawing or grinding, which leaves a clear gap between the lamellas.

[0019] According to one embodiment, the slit is straight, bent or curved in the depth direction of the base. This feature can be used to affect the flexural stiffness of the lamellas in the push-off phase and in returning to the gliding phase. In the basic embodiment, when the slit is straight, the lamella begins to bend at the bottom of the slit. By means of a bent slit can be created another bending point, a so-called pivot point, at a desired point in the depth direction of the lamella. For example, if the angle with respect to the normal of the base increases at a deeper point, a thinner section is formed at this point of bending, where the lamella bends. Correspondingly, if the angle is greater compared to the normal on the surface, such a lamella will taper towards the tip, whereupon the tip of the lamella, that is, the part near the surface bends more easily than a part at a deeper point. However, the range of use of the lamella with a bending tip is highly limited and it is mainly suited for certain special snow conditions and if very high durability is not required. By means of a curved slit can in practice be achieved the same effect as with a bent slit. In practice, this is just a matter of the radius of curvature of the bend. In this way, it is also possible to affect the angle of the grip edge (attack angle). The cavity described above can be combined with the embodiment provided by means of the curved slit. In this case, also according to this embodiment, at least some of the lamellas deform in the direction of the normal of the base, generally retaining their shape from the foot, when the ski changes its shape from the cambered shape to an substantially flat shape in the push-off phase.

[0020] According to one embodiment, lamellas are formed in the surface layer of the base of the ski by means of transverse, mutually parallel slits in the longitudinal direction of the ski, each slit being transversely straight or curved with respect to the longitudinal axis of the ski, the transversal angle being ± 0° -<30° with respect to the longitudinal axis of the ski. Transverseness, therefore, means a 90° angle relative to the longitudinal axis of the ski, and theaforementioned transversal angle describes the change wun respecr ro me longitudinal axis of the ski (90° ± B). Studies have found that the lamellas do not have to bend exactly parallel with the longitudinal axis of the ski to provide the desired effect, but if there are slits at two different angles, whereupon the lamellas form extremely narrow spikes, as taught, among others, by US4714266, this type of solution seems to have a tendency to accumulate snow and ice, causing the ski to practically stop gliding completely. Durability is also worse when the tip of the lamella can bend strongly in many directions. According to a further embodiment, the slits are transverse to the longitudinal axis of the ski at one transversal angle or curved around one centre line of rotation. By means of the longitudinal grooves or slits in the ski, which are here referred to as longitudinal slits, the lamellas can be made into cut lamellas having a smaller width than the ski, whereupon their flexural stiffness is lower than that of a solid wide lamella. The width of a cut lamella can be, for example, 1 / 3-1 / 20 of the width of the ski. If the track is uneven and a lot of localised forces are exerted on the base of the ski, the lamellas that are “cut” in the lateral direction, that is, the cut lamellas, work more sensitively. The longitudinal slits may be parallel with the normal of the base. On the other hand, the longitudinal slits may be tilted with respect to the normal of the base. In this case, the cut lamella opens in a different direction with respect to the longitudinal direction of the ski, which may, for example, improve keeping the gaps between the lamellas clean, that is, prevent ice crystals or other solid materials from accumulating in the gaps.

[0021] Today, HDPE plastic is typically used as the base material of factory- made skis, and the properties disclosed below should be taken into account when forming the lamellas. HDPE is a fairly rigid plastic, but its molecular chains are not strongly linked to each other. HDPE consists of long polyethylene chains that do not form a strong, regular crystal structure. When HDPE is subjected to bending force, it stretches or deforms relatively easily, but it does not return to its original shape. HDPE has a low modulus of elasticity, which means that it does not withstand stretching or bending well without permanently changing its shape. When the plastic is bent, the molecular chains slide past each other and are trapped in the new shape, causing permanent deformation. Thus, HDPE is a very tough and malleable material, which makes it excellent at withstanding impacts and stretching without breaking, but its ability to return to its original shape (elasticity) is limited. Based on research work now carried out, it can be assumed that known solutions with a thin lamella tip would have insufficient durability whenimplemented on an HDPE base due to the properties of HDPE. A mm, narrow up overbends easily and so strongly that permanent deformation occurs, after which the ski no longer functions as intended. This has also been shown by durability tests, and, at the same time, it has also been found that a wide grip edge of a lamella, which does not bend in many directions, is many times more durable than a sharp, spike-like tip.

[0022] The behaviour of the lamellas under different conditions can be influenced by dimensioning the lamellas. Dimensioning is to some extent also dependent on the ski base material used, its density, stiffness, elasticity, etc., but the dimensioning values disclosed herein have been found to work with the standard HDPE base material used by most ski manufacturers. According to one embodiment, a slit extends to a depth of 0.3-0.9 mm from the base, although a slit extending to a depth of only 0.1 mm may be used in some cases. Smaller depth values seem to work particularly well in conjunction with a cavity-forming slit. The depth of the slit may be variable, for example, deeper in the lateral direction in the middle of the ski than on the edge or vice versa. Since the ratio between the depth of the slit to the space between the slits affects the stiffness of the lamella, and thus its suitability for different weather and ski track conditions, the depth of the slit can be made to vary to some extent over the width of the ski, thereby expanding the range of use of the ski. On the other hand, the maximum efficiency will then decrease. According to one embodiment, the distance between the slits is 0.04-0.35 mm in the longitudinal direction of the ski. The ratio of the depth of the slits to the distance between the slits is 1 :1 or more, for example 4:1 or 5:1 , with 12:1 being considered the extreme value. According to a further embodiment, the slit at the base-side end is at an angle of tilt of 25-70° with respect to the normal of the base, according to another embodiment, the slit at the base-side end is at an angle of tilt a = 15-<60° with respect to the normal of the base. Similarly, the radius of curvature and direction of the slit (smiling profile or depressed profile) can affect the stiffness of the lamella. The radius of curvature can also affect the lamella’s bending sensitivity. A smaller radius of curvature produces a stiffer lamella and a larger radius of curvature, a more flexible lamella; in practice, it is a matter of the bending spring force. When the lamella bends, a compressive or tensile force is generated, which is used to adjust the sensitivity and speed of the lamellas between the grip and gliding phases. These forces can be used to adjust the stiffness of the lamella so that other parameters, such as the depth and thickness of the lamella, can be adaptedto the properties for which they are needed. The radius of curvarure ano wiorn or the lamella’s curve are selected so that the lamella can be returned from the grip phase to the unweighted state by means of the energy bound to the base material during the push-off phase. This energy is charged as deformation energy for the lamella during the push-off phase. In this way, the ski is ready for the gliding phase more quickly, requires less energy and the ski brakes less when pushing forward. According to a further embodiment, the transversal angle of the slits can be changed so that the distance between the slits changes over the course of one lamella, for example within the disclosed limit values or by 10-50%. In this case, the lamella is thus thicker at one end than at the other, when viewed in the direction of the normal of the base. It has been found that when operating within the limit values presented above, the ski generally becomes functional. When building a ski that is extremely high-performance and functions in a variety of conditions, the parameter combination disclosed above must be specified to a narrower range than the mentioned limit values, depending on the material used.

[0023] One embodiment of the invention is a ski for freestyle cross-country skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls, an upper surface and a base, the ski being formed to be cambered, wherein the base is made to curve upwards in the longitudinal direction of the ski, the front and rear parts of the base are in contact with the ground, but the middle part of the base is detached from the ground, when the ski is unweighted on the ground, wherein in the front and rear parts of the base are formed lamellas by means of slits transverse to the longitudinal direction of the ski, tilted backwards with respect to the normal of the base and the longitudinal direction of the ski, the lamellas comprising two sides, and one side parallel with the base at the gliding phase, the lamella being connected to the inner layer of the base, wherein the space between the slits is 0.04-0.35 mm in the longitudinal direction of the ski, wherein the ratio d:s between the depth of and the space between the slits that form the lamella is within the range 1 :1-12:1 , preferably within the range 1 .8: 1-7.5: 1 . This type of freestyle ski differs from the classic style ski in that no grip-increasing wax or grip skin, etc. is used in a freestyle ski. The aim is that the ski moves constantly only forwards and the push- off takes place partly sideways as a skating kick. As the skating kick approaches the extreme position, the skier performs a weight shift to one leg and begins to push off with this other leg. This type of ski does not require a grip part at all, but it has been shown in practice that the ski now presented, which includes lamellas,glides so well that it could also be used in the gliding part, that is, in me rrom ano rear parts of the ski, when the lamellas are lubricated with gliding wax to close them. In this case, the hot glide wax, in practice paraffin, is impregnated deep into the part of the ski comprising lamellas, which means that the paraffin does not wear off even during a long skiing trip. The paraffin in the slits between the lamellas works as a source of wax in the depth direction, from which new wax is dispensed during use on the base of the ski moving forward on the ground. Furthermore, all the features described above in paragraphs

[0014] —

[0018] are also applicable to this embodiment, only the location of the lamellas is different from that described previously in connection with the classic style ski. As another possible modification, the depth of the lamella can be reduced to a depth of 0.1 mm if the intention is to use the slits as a source of wax. In practice, this ski according to the invention for classic style cross-country skiing and the ski according to the invention for freestyle cross-country skiing can be combined and implemented in the same ski, wherein the lamellas can be implemented over the entire length of the ski or almost the entire length of the ski base. In this case, there are slits over the entire length of the ski base.

[0024] The invention also relates to a method for manufacturing the skis described above. This is a method for treating the base of a ski, wherein, in the method, on the base of the ski are formed lamellas by means of slits transverse to the longitudinal direction of the ski, tilted backwards with respect to normal of the base and the longitudinal direction of the ski, the lamellas comprising two sides, and one side parallel with the base in the gliding phase, the lamella being in contact with the inner layer of the base or substrate. The slits are formed on the base of the ski with a machine tool suitable for the purpose. In practice, the base material is shaped during machining in such a way that the lamellas remain slightly open when the ski is in an unweighted state. However, the lamellas close with very little force when the ski is weighted at the beginning of the gliding phase, allowing the ski to glide easily. In turn, when the skier pushes forward, the lamellas return and open into the gripping position, wherein the sharp edge of the lamella bites into the ski track. The mutual dimensioning and repeatability of the slits, that is, the machining accuracy, are significant here, thus the end result would probably not be as desired if worked on by hand. The machine tool preferably has a means for moving the ski longitudinally, while the cutting blade is reciprocated or the cutting blade is rotated by means of a blade holder attached to a rotating spindle. The slit is most preferably made with a rotating blade,wherein the speed of rotation of the blade and the longuuoinai speeo or movement of the ski are adjusted to be such that the desired lamella thickness is achieved in the longitudinal direction of the ski. The geometry of the lamella is largely determined by the shape of the blade used. According to a preferred embodiment, the slit between the lamellas is made substantially by means of a non-removing material processing method, wherein, in the method, a cutting blade is used, the cutting area of which is polished to a surface roughness of 2.0 pm Ra or below. With a chosen working method can be created a ski, where the slits forming the lamella are parallel or change in certain sections. At the baseside end, the slit may be at an angle of tilt a = 15-<60° with respect to the normal of the base and the angle of tilt a varies by section, wherein one section comprises 2-1000 slits, and within the section the angle of tilt a varies between 0.5-45°. According to another embodiment, the space between the slits varies by section, wherein the space between the slits is 0.04-0.35 mm in the longitudinal direction of the ski and one section comprises 2-1000 slits. This means that some of the lamellas can be made stiffer than others. This can also be accomplished by adjusting the rotational speed or the speed of the ski, or by running multiple blades in succession, or by passing the ski several times through the machine tool. This can be done, for example, by means of a rotating blade so that the blade comprises several cutting blades arranged circumferentially relative to each other. This could be, for example, a multi-blade blade holder that makes two or more slits per blade rotation. This allows for a significant increase in production rate, as well as a geometry which varies by section, by means of which the depth of the slit, the angle of tilt, the shape of the slits (straight, curved, oblique), the tilt of the grip edge, the space between the slits, the dimensions of the cavity or the like can be varied by section. For example, by changing the angle of tilt can be made a block of lamellas that opens in a fan-like manner. The range of use of the ski can be expanded in this way. In this way, it is also possible to change the bending of the lamellas and, if necessary, in some circumstances use the thinnest lamellas to achieve sensitivity, but at the same time use thicker support lamellas to prevent the lamellas from overbending and causing permanent deformation. The angle of the grip edge can also be changed between different lamellas if so desired. In general, the lamellas may be formed in sections on the base of the ski, wherein one section comprises 2-1000 slits, the said section beginning and / or ending with a support lamella which is of a different shape, has a different angle of tilt a, a different space between the slits, or a different flexural stiffness compared to the other lamellas.List of drawings

[0025] The invention and its functioning are described in the following with reference to the accompanying schematic drawings, in whichFigure 1 shows schematically an embodiment of the ski according to the invention,Figure 2 shows schematically an embodiment of the ski of Figure 1 , as seen from below,Figure 3 shows schematically an embodiment of the lamellas according to the invention, as seen from the side,Figure 4 shows schematically an embodiment of the lamellas according to the invention, as seen from the side,Figure 5 shows schematically an embodiment of the lamellas according to the invention, as seen from the side,Figure 6 shows schematically an embodiment of the lamellas according to the invention, as seen from the side,Figure 7 shows schematically an embodiment of the lamellas according to the invention, as seen from the side,Figure 8A shows schematically an embodiment of the application of the method according to the invention for treating the base of the ski,Figure 8B shows schematically an embodiment of the lamella according to the invention in sections, as seen from the side,Figure 9 shows schematically an embodiment of the cross-section of the ski.Description of the drawings

[0026] Figure 1 shows schematically an embodiment of the ski 1 according to the invention for cross-country skiing, which ski is comprised of an elongated, beam-like structure comprising at least side walls 2, an upper surface 3 and a base 4, the ski being formed by means of longitudinal stiffness to be cambered, wherein the base 4 is made to curve upwards over the length of the ski. In this case, the front part 41 and rear part 43 of the base are in contact with the ground, but the middle part 42 of the base is detached from the ground when the ski 1 is placed, with its base 4 against the ground, unweighted on an even horizontalground. In Figure 1 (and in the next Figure 2) are shown vemcai lines A ano D which illustrate the areas of the base 4 of the ski 1 ; to the left of line A is the front part 41 of the ski base, between lines A and B is the middle part 42 of the base and to the right of line B is the rear part 43 of the base. For the sake of illustration, Figure 1 also shows a binding 8 and a ski boot 9, by means of which the skier can attach the ski 1 to the foot. In Figure 1 can be seen how the shape of the ski is curved upwards, that is, the ski is cambered. This camber can be adjusted by selecting the ski according to the weight, strength and push-off technique of the user, that is, the skier, so that when using and pushing off a correctly selected ski, the user can also make the middle part 42 of the base contact the ground. In the context of this invention, the longitudinal stiffness (flexural stiffness) of the ski 1 means that the arch-like shape, or camber, of the ski resists deformation when the ski 1 rests on the base 4, freely on the ground, and the ski 1 is weighted downwards from the top of the ski, in the middle part 42 area, by means of vertical force. The structure of the side walls 2 of the ski and the core (not shown in the Figure) of the ski 1 play a significant role in achieving this stiffness but so do also the structure of the upper surface 3 and the base 4 to a lesser extent. In generally sold skis, the base 4 is typically a one to a few millimetres thick HDPE or similar plastic sheet (thickness b in Figure 3).

[0027] Figure 2 shows in a simplified manner that over at least a part of the distance to the middle part 42 of the base, on the surface layer 40 (see Figure 3) of the base 4, are formed lamellas 401 by means of slits 400 (in this embodiment parallel with each other) transverse to the longitudinal direction of the ski 1. Figure 2 shows a solution according to the first embodiment of the invention, where the slits and the lamellas 401 formed by them are transverse, that is, at a 90° angle to the longitudinal direction L of the ski 1. In this case, the transversal angle B = 0° (see Figure 8, where the transversal angle B is illustrated).

[0028] Figure 3 shows an embodiment, a longitudinal cross-section of the ski from the base 4 of the ski, where the customary forward skiing direction of the ski is shown by arrow F. Lamellas 401 are formed by means of slits 400 tilted (angle of tilt (a)) backwards with respect to the normal N of the base 4 and the longitudinal direction of the ski 1 , wherein each lamella 401 comprises a foot 405, two sides 402, 403, and one side 404 parallel with the base 4 at the gliding phase, the lamella 401 extending from the surface layer 40 of the base 4 to the inner layer 45, to which the lamella 401 is connected. Here, connection refers toattachment or the continuation of the material such that the lameiia is rormeo or a part of the base 4 material. At the depth b of the base, the surface layer 40 and the inner layer 45 may be of the same material or different materials, or they may have similar or different properties, for example, the inner layer 45 may be more elastic than the surface layer 40. The space between the slits parallel with each other is shown in the Figure by arrow s, the space between the slits preferably being 0.04-0.35 mm in the longitudinal direction of the ski. If so desired, from this can be calculated the thickness of the lamella, t = s * cos(a), which t is in different embodiments of the angle of tilt roughly between 0.01-0.3 mm.

[0029] The thickness of the base is shown in Figure 3 by the letter b, and the depth of the slit by the letter d, the slit preferably extending to a depth of 0.3- 0.9 mm from the base 4, or more precisely from the surface 404 of the base. In some embodiments, even a slit depth of 0.1 mm may be used, for example, when making a lamella in the gliding area in the front part 41 of the base or the rear part 43 of the base. At the base-side end, the slit is preferably at an angle of tilt a = 25-70° with respect to the normal N of the base 4. According to another embodiment, the slit 400 is at the base-side end at an angle of tilt (a) = 15-<60° with respect to the normal (N) of the base (4). In this case, the trailing edge of the lamella 401 , that is, the grip edge angle (attack angle) between side 402 and the side 404 parallel with the base, becomes sharp (meaning an angle <90°), biting efficiently into the ground during push-off. These parameters presented above, the angle of tilt a, the transversal angle B, the space s between the slits and the slit depth d, are applicable to all embodiments according to Figures 3, 4, 5, 6 and 7, although they will not be described again in connection with the embodiments disclosed below. According to one embodiment (not shown in Figure 3), the slit 400 is at the base-side end at the angle of tilt a = 15-<60° with respect to the normal N of the base 4 and the angle of tilt a changes by section, wherein one section comprises 2-1000 slits 400, and within which section the angle of tilt a varies between 0.5-45°.

[0030] Figure 4 shows an embodiment as shown in Figure 3, a longitudinal cross-section of the ski from the base of the ski, where the slit 400 between the lamellas 401 is formed such that at the foot 405 of the lamella 401 is formed a cavity 4001 , at which the lamella 401 is thinner than the rest of the lamella 401. In Figure 4, this is illustrated so that the thickness of the lamella is t2 < t1 , that is, at the thinnest point the thickness of the lamella is t2 and in the remaining part ofthe lamella the thickness is t1 . This forms a natural hinge poinr (or pivor poinr; in the lamella 401 , where the lamella 401 bends when weighted. Thus, the slit 400 between the lamellas 401 is made substantially by means of a non-removing material processing method, but nevertheless in such a way that in the foot area of the lamella 401 is formed a cavity 4001 or passage 4001 in the longitudinal direction of the slit 400, that is, transverse to the longitudinal direction of the ski, which cavity 4001 , for example, can be made by a material-forming method, by forming with a cutting blade. This feature allows the lamellas 401 to overlap against each other accurately during the gliding phase, but to open easily. Especially at the gliding phase, it is important that the lamellas 401 fit very tightly against each other, thereby making the base 4 of the ski 1 flat. On the other hand, it is equally important that the lamellas 401 open easily when pushing off, so that the ski will grip and does not slip. The lamellas must not "stick" to each other, because then they will not open in time during push-off, and the ski will slip.

[0031] Figure 5 shows an embodiment, where the direction of travel of the ski base 4 is indicated by arrow F and where the slit 400 is bent in the depth direction of the base. The lamella 401 then becomes variable in thickness, the lamella 401 is thinner at the foot than closer to the surface, t2 is smaller than t1. Figure 5 also illustrates how the lamellas behave in different situations. Starting from the left, the first three lamellas 401 are depicted in a situation where, when pushing off, the side 404 of the lamella parallel with the base is strongly bent and the rear corner of the lamella 401 bites into the ground, preventing movement backwards. Next, the next four lamellas 401 in the middle depict the lamellas 401 in the transition phase (when moving from grip to glide or vice versa) and the four lamellas 401 on the right are as they would be when the ski is gliding forward in direction F.

[0032] Figures 6 and 7 show embodiments, where the direction of travel of the ski base 4 is indicated by arrow F and where the slit 400 is curved in the depth direction of the base. In Figure 6, the curvature is forward-curving and in Figure 7, backwards-curving. This direction of curvature can be used to affect the thickness profile of the lamella in the depth direction; in the forward-curving embodiment of Figure 6, the lamella 401 is thicker near the surface and thinner at the foot, in the embodiment of Figure 7, vice versa. In Figure 6, one of the lamellas 401 is shown to be in the grip position, its side 404 parallel with the base being lower than the other lamellas 401. Especially the embodiment according toFigure 7 can be modified by thermoforming to become suuaoie ror specinc conditions. In addition, the cavity 4001 (not shown in Figure 7) previously described in connection with Figure 4 can be combined with the embodiment according to Figure 7. In this case, also according to this embodiment, at least some of the lamellas deform in the direction of the normal of the base, generally retaining their shape starting from the foot, when the ski changes its shape from a cambered shape to a substantially flat shape during the push-off phase.

[0033] Figure 8A shows a method for treating the base of a ski. In the method, on the base 4 of the ski 1 are formed lamellas 401 by means of slits 400 transverse to the longitudinal direction L of the ski 1 , tilted backwards with respect to the normal N of the base and the longitudinal direction L of the ski, the lamellas comprising two sides 402, 403, and one side 404 parallel with the base at the gliding phase, the lamella 401 being in contact with the inner layer 45 of the base 4 (see the shapes of the lamella 401 and other details from Figures 3-7). The slit 400 may be transversely straight or curved with respect to the longitudinal direction of the ski, the transversal angle B being ± 0°-< 30° with respect to the longitudinal axis L of the ski. The slit 400 is preferably made with a rotating blade, wherein the speed of rotation of the blade and the longitudinal velocity of the ski in the machine tool are adjusted to be such that the desired space s between the slits (or thickness t, t1 , t2 of the lamella 401) in the longitudinal direction L of the ski is achieved. The radius of curvature R of the slit can be made as desired by selecting the diameter of the rotating blade as desired. By this choice of the radius of curvature R can be affected the flexural stiffness of the lamella, that is, the bending spring force. The slit can also be made variable in depth d, for example by tilting the axis of rotation of the rotating blade in a direction other than the normal N of the base. The slits 400 can also be made using a tool that performs a reciprocating linear or curved motion.

[0034] Figure 8B shows a side view of an embodiment of the base 4 of the ski, where the lamellas 401 are made on the base 4 of the ski 1 in sections, wherein each section comprises 2-1000 slits 400, the said section beginning with and / or ending in a support lamella 4010 which is of a different shape (such as a transverse ridge or other part without lamellas), has a different angle of tilt a (for example a negative tilt compared to the angle of tilt a), the space s between the slits 400 is different or has a different flexural stiffness compared to the lamellas 401. At the base-side end, the slit 400 may be at an angle of tilt a = 15-<60° withrespect to the normal N of the base 4 and the angle of tilt a may vary oy secnon, wherein one section comprises 2-1000 slits 400 and within which section the angle of tilt a varies between 0.5-45°. For the sake of illustration, Figure 8B shows a simplified embodiment, where the section comprises five slits, within which section the angle of tilt a varies. The space s between the slits (or the thickness t of the lamella 401) may also vary by section, wherein the space s between the slits 400 is 0.04-0.35 mm in the longitudinal direction L of the ski 1 , and one section comprises 2-1000 slits 400.

[0035] Figure 9 shows a cross-section of a ski 1 , as seen in the longitudinal direction of the ski, wherein in the beam-like structure of the ski 1 can be seen the base 4 of the ski, the side walls 2 and the upper surface 3 of the ski. On the base 4 of the ski are formed longitudinal slits 408, wherein the lamellas can be formed into cut lamellas which have a smaller width w than the ski, the width w of a cut lamella being, for example, 1 / 3-1 / 20 of the width of the ski, however, at least 3-5 times the thickness t of the lamella. The longitudinal slits 408 may be parallel with the normal N of the base. On the other hand, the longitudinal slits 408 may be tilted at an angle y with respect to the normal N of the base. In this case, the lamella opens in a different direction compared to the longitudinal direction of the ski, which may, for example, help keep the gaps between the lamellas clean, that is, prevent ice crystals or other solid materials from accumulating in the gaps.

[0036] It should be noted that only a few of the most advantageous embodiments of the invention are disclosed above. It is, therefore, obvious that the invention is not limited to the foregoing embodiments but can be applied in many ways within the scope defined by the accompanying claims. The features presented in connection with the different embodiments may also be used in connection with other embodiments within the basic idea of the invention and / or the features presented may be combined into various entities if so desired and if the technical possibilities for doing so exist.List of reference numerals:1 skiL longitudinal direction (L) of the ski2 side walls3 upper surface4 baseN normal (N) of the base40 surface layer (40) of the base400 slit a angle of tilt of the slitB transversal angle with respect to the longitudinal axis (L) of the skiY angle of tilt of the longitudinal slit r centre line of rotationR radius of curvature d depth of the slit s space (s) between the slits (in the longitudinal direction (L) of the ski w width of the lamella (width of the cut lamella) 4001 cavity401 lamella4010 support lamella402 side of a lamella (rear side)403 side of a lamella (front side)404 side parallel with the base of the lamella405 foot of the lamella408 longitudinal slit t thickness of the lamella t1 thick point of the lamella t2 thin point of the lamella41 front part of the base42 middle part of the base43 rear part of the baseA dividing line, front / middle partB dividing line, middle / rear part8 binding9 ski boot

Claims

Claims1. A ski (1) for cross-country skiing, which ski (1) is comprised of an elongated, beam-like structure comprising at least side walls (2), an upper surface (3) and a base (4), the ski (1) being formed to be cambered, wherein the base (4) is made to curve upwards over the length of the ski, the front (41) and rear (43) parts of the base are in contact with the ground, but the middle part (42) of the base is detached from the ground when the ski (1) is placed, with its base (4) against the ground, unweighted on an even horizontal ground, over at least a part of the distance to the middle part (42) of the base, on the surface layer (40) of the base (4), are formed lamellas (401) by means of slits (400) substantially transverse to the longitudinal direction (L) of the ski (1), tilted backwards with respect to the normal (N) of the base (4) and the longitudinal direction (L) of the ski (1), each lamella (401) comprising a foot (405), two sides (402, 403), and one base side (404), wherein, at the gliding phase, the base side (404) is arranged to be parallel with the base (4), defining an substantially even glide surface, characterised in that at the push-off phase, when a backwards pushing force is applied to the ski (1), at least some of the lamellas (401) deform in the direction of the normal (N) of the base (4), generally retaining their shape starting from the foot (405), forming a contact surface of increased friction.

2. A ski (1) according to claim 1 , characterised in that the contact surface of increased friction is formed by the tilt of the lower surface (404) of at least some of the lamellas (401) and / or the offset of the lower sides (404) of at least some of the lamellas (401) with respect to each other.

3. A ski (1) for cross-country skiing, which ski (1) is comprised of an elongated, beam-like structure comprising at least side walls (2), an upper surface (3) and a base (4), the ski (1) being formed to be cambered, wherein the base (4) is made to curve upwards over the length of the ski, the front (41) and rear (43) parts of the base are in contact with the ground, but the middle part (42) of the base is detached from the ground when the ski (1) is placed, with its base (4) against the ground, unweighted, on an even horizontal ground, over at least a part of the distance to the middle part (42) of the base, on the surface layer (40) of the base (4), are formed lamellas (401) by means of slits (400) transverse to the longitudinal direction (L) of the ski (1), tilted backwards with respect to the normal (N) of the base (4) and the longitudinal direction (L) of the ski (1),characterised in that the lamellas (401) comprise two sides (^uz, ■ U ;, ano one side (404) parallel with the base (4) at the gliding phase, the lamella (401) extending from the surface layer (40) of the base (4) to the inner layer (45), to which the lamella (401) is connected, wherein the space (s) between the slits (400) is 0.04-0.35 mm in the longitudinal direction (L) of the ski (1), wherein the ratio (d):(s) between the depth (d) of and the space (s) between the slits that form the lamella is within the range 1 :1-12:1 , preferably within the range 1.8:1-7.5:1.

4. A ski (1) for freestyle or classic style cross-country skiing, which ski (1) is comprised of an elongated, beam-like structure comprising at least side walls (2), an upper surface (3) and a base (4), the ski (1) being formed by means of longitudinal (L) stiffness to be cambered, wherein the base (4) is made to curve upwards over the length of the ski (1), the front (41) and rear (43) parts of the base are in contact with the ground, but the middle part of (42) of the base is detached from the ground when the ski is unweighted on the ground, in the front (41) and rear (43) parts of the base are formed lamellas (401) by means of slits (400) transverse to the longitudinal direction of the ski, tilted backwards with respect to the normal (N) of the base and the longitudinal direction (L) of the ski, characterised in that the lamellas (401) comprise two sides (402, 403), and one side (404) parallel with the base at the gliding phase, the lamella (401) extending from the surface layer (40) of the base (4) to the inner layer (45), to which the lamella (401) is connected, wherein the space (s) between the slits (400) is 0.04- 0.35 mm in the longitudinal direction (L) of the ski (1), wherein the ratio (d):(s) between the depth (d) of and the space (s) between the slits that form the lamella is within the range 1 :1-12:1 , preferably within the range 1.8:1-7.5:1.

5. A ski (1) according to any of the preceding claims, characterised in that the slit (400) between the lamellas (401) is made by forming, at the foot (405) of the lamella (401), a cavity (4001) at which the lamella (401) is thinner than the rest of the lamella (401).

6. A ski (1) according to any of the preceding claims, characterised in that the slit (400) is straight, bent or curved in the depth direction of the base (4).

7. A ski (1) according to any of the preceding claims, characterised in that the slit (400) is transversely straight or curved with respect to the longitudinalaxis (L) of the ski, the transversal angle (B) being ± 0°— < 30° wnn respecr io me longitudinal axis (L) of the ski.

8. A ski (1) according to any of the preceding claims, characterised in that the radius of curvature (R) and width (w) of the curve of the lamella (401) are selected so that the lamella (401) can be returned from the grip phase to the unweighted state by means of the energy bound in the base (4) material at the push-off phase.

9. A ski (1) according to any of the preceding claims, characterised in that the slit (400) extends to a depth (d) of 0.1-0.9 mm, preferably 0.3-0.9 mm, from the base (4).

10. A ski (1) according to any of the preceding claims, characterised in that, at the base-side end, the slit (400) is at an angle of tilt (a) = 25-70° with respect to the normal (N) of the base (4).

11. A ski (1 ) according to any of the preceding claims, characterised in that, at the base-side end, the slit (400) is at an angle of tilt (a) = 15-<60° with respect to the normal (N) of the base (4).

12. A ski (1) according to any of the preceding claims, characterised in that the lamellas (401) are formed on the base (4) of the ski (1) in sections, wherein each section comprises 2-1000 slits (400), the said section beginning with and / or ending in a support lamella (4010) which is of a different shape, has a different angle of tilt (a), the space (s) between the slits (400) is different or has a different flexural stiffness compared to the lamellas (401).

13. A ski (1) according to any of the preceding claims, characterised in that, at the base-side end, the slit (400) is at an angle of tilt (a) = 15-<60° with respect to the normal (N) of the base (4) and that the angle of tilt (a) varies by section, wherein one section comprises 2-1000 slits (400), and within the section the angle of tilt (a) varies between 0.5-45°.

14. A ski (1) according to any of the preceding claims, characterised in that the space (s) between the slits varies by section, wherein the space (s)between the slits (400) is 0.04-0.35 mm in the longitudinal direction ( LJ or me SKI (1) and one section comprises 2-1000 slits (400).

15. A ski (1) according to any of the preceding claims, characterised in that on the base (4) are formed longitudinal slits (408), wherein the lamellas (401) can be formed into cut lamellas which have a smaller width (w) than the ski, the width (w) of a cut lamella being, for example, 1 / 3-1 / 20 of the width of the ski.

16. A ski (1) according to claim 12, characterised in that on the base (4) are formed longitudinal slits (408) which are parallel with the normal (N) of the base or tilted (y) with respect to the normal (N) of the base.

17. A ski (1) according to any of the preceding claims, characterised in that there are slits (400) over the entire length of the base (4) of the ski (1).

18. A ski (1) according to any of the preceding claims, characterised in that the lamella (401) is wide in the transverse direction of the ski (1), in practice the width (w) of the lamella is at least 3-5 times the thickness (t) of the lamella (401).

19. A method for treating the base (4) of a ski (1), characterised in that, in the method, on the base (4) of the ski (1) are formed lamellas (401) by means of slits (400) transverse to the longitudinal direction (L) of the ski (1), tilted backwards with respect to normal (N) of the base and the longitudinal direction (L) of the ski, the lamellas comprising two sides (402, 403), and one side (404) parallel with the base, the lamella (401) being in contact with the inner layer (45) of the base (4) by the foot (405) of the lamella, wherein the space (s) between the slits (400) is 0.04-0.35 mm in the longitudinal direction (L) of the ski (1), wherein the ratio (d):(s) between the depth (d) of and the space (s) between the slits that form the lamella is within the range 1 :1-12:1 , preferably within the range 1.8:1-7.5:1.

20. A method according to claim 19, characterized in that the slits are formed on the base of the ski with a machine tool suitable for the purpose, which comprises a means for moving the ski longitudinally, while the cutting blade is reciprocated, or the cutting blade is rotated by means of a blade holder attached to a rotating spindle21. A method according to claim 19 or 20, characterised in that the slit (400) is made with a rotating blade, wherein the speed of rotation of the blade and the longitudinal (L) velocity of the ski (1) or substrate (10) is adjusted to be such that the desired thickness (t, t1 , t2) of the lamella (401) in the longitudinal direction (L) of the ski is achieved.

22. A method according to any of the claims 19 to 21 , characterised in that the slit (400) between the lamellas (401) is made substantially by means of a non-removing material processing method, wherein, in the method, a cutting blade is used, the cutting area of which is polished to a surface roughness of 2.0 pm Ra or below.

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