The present invention relates to a surface element for formation of a gliding surface, comprising a substantially transverse frame unit with at least attaching means for attaching the surface element to the base, a gliding unit with several substantially transverse and flexible gliding means attached to the joining point of the frame unit, such as fibres, strings, threads or the like, and a supporting unit with a supporting surface which is in connection with the frame unit and supports the gliding unit of at least one surface element substantially in the longitu- dinal direction.

Gliding elements forming a gliding surface have been used for a long time, most usually in down-slopes of ski jumping hills and at the sides of in-run ski tracks uphill. Gliding elements of relatively small size have been arranged side by side and one' after another in a way that the abutments of the gliding are overlapped to achieve an integrated gliding surface formed by the gliding parts. The gliding properties of the gliding surface correspond very well to the properties of snow, which is important for ski jumping corresponding to winter conditions also in the summer.

The gliding elements are attached to a framework, such as a metal net, mounted in the slope and thus placed directly below the gliding surface. Consequent¬ ly, there is the risk if the ski-jumper falls that the fibres forming the gliding unit turn away and the ski-jumper hurt himself when falling onto the metal net exposed.

For eliminating this problem, an improved gliding unit is presented in the Patent Publication FI-71065.

The solution presented in the publication is charac¬ terized in that a bottom plate, either uniform or formed of separate strips, corresponding substan¬ tially to the size of the gliding element is attached to the same abutment below a plastic mat. As an advantageous embodiment, also a profile bottom plate is presented in the publication. With the profile form, an attempt has been made to make the gliding element flexible in order to avoid the need of using an additional flexible layer, usually of cellular plastic, commonly used underneath the metal net. In spite of its advantageous principle, the said solution has obviously not convinced the users, because its appli¬ cation in practice has remained insignificant.

Particularly when equipped with a uniform bottom plate, the embodiment described above might, in principle, function in a reasonable way. Neverthe¬ less, this embodiment still has the disadvantage typical of conventional gliding elements that the length of the gliding unit of the gliding element substantially corresponds to the total length of the gliding element. However, relatively long fibres do not function satisfactorily, because in practice they are placed and returned into the longitudinal direction at random. Consequently, e.g. after the previous jump, the coating may have openings with uncovered metal net or bottom plate.

The problem described above can be naturally relieved by placing several gliding elements on top of each other in a way that there are several layers of gliding units. In the embodiment presented in the Finnish Patent Publication mentioned above, it is naturally possible to make the total length of the gliding element correspondingly shorter. However, such arrange¬ ments are not economically advantageous, because the

covering must thus be formed of a relatively too large number of gliding elements.

Further, the profile bottom plate used in the embodi¬ ment of the said patent publication is not particularly advantageous, because it has a corrugated form in the transverse direction which produces a "nubbly" coating and thus may hamper the return of the fibres into the longitudinal direction.

It is an aim of the surface element of the present invention to achieve a decisive improvement of the disadvantages presented above and thus to improve the state of knowledge in the field. For achieving this aim, the surface element of the invention is primarily characterized in that the supporting unit of the surface element is arranged in connection with the frame unit in a way that in the coating formed of several successive surface elements in the longitudinal direction, the supporting unit of the next surface element forms the supporting surface supporting the gliding unit of at least one preceding surface element.

The most important advantages of the surface element of the invention include simplicity and reliability, which are essential prerequisites for improving safety, particularly in the demanding use in question. The surface element of the invention is inexpensive with regard to both its manufacture and installation, whereby also the total costs of the coating made thereof are clearly less in comparison with the present solutions. The improvement in reliability is based on the fact that a substantially shorter fibrous unit can be used with regard to the present solutions. Thus the fibrous unit can be made stiffer, whereby it returns better into its longitudinal direction. Naturally, the fibrous units also have a better guiding effect in the coating.

Advantageous embodiments of the surface element of the invention are presented in the other dependent claims.

In the following description, the invention is il¬ lustrated in detail with reference to the appended drawings. In the drawings,

Fig. 1 shows an advantageous surface element of the invention,

Fig. 2 shows a corresponding surface element as seen from below, and

Fig. 3 shows the coating of a gliding surface formed of several surface elements.

The surface element shown as an advantageous embodiment in Figs. 1-3 is intended for formation of a gliding surface e.g. in a down-slope or the like. The surface element e comprises a substantially transverse frame unit l, a gliding unit 3 and a supporting unit 4. The frame unit 1 is equipped with attaching means 2 for attaching the surface element e into a base A. The gliding unit 3 comprises several flexible gliding means 3a attached to the joining point L of the frame unit 1, such as fibres, strings, threads or the like. The supporting unit 4 comprises a supporting surface 4a connected with the frame unit 1 and continuously supporting the gliding unit 3 of at least one surface element substantially in the longitudinal direction s. The supporting unit 4 of the surface element e is arranged in connection with the frame unit 1 in a way that in the coating formed of several successive surface elements el, e2, e3 in the longitudinal direction s, the supporting unit 4 of the next surface element e2, e3 forms the supporting surface 4a support-

ing the gliding unit 3 of at least one preceding surface element el, e2.

Further in an advantageous embodiment according to Fig. 2, the frame unit 1 of the surface element 1 extends in the longitudinal direction s in a way that the holes 2 acting as the attaching means, whereby the surface element is attached e.g. with a binding to a framework 6 on the base A, are arranged at one end and the joining point L at the other end of the frame unit l. Thus the said supporting unit 4 is formed of the upper surface 4a of the frame unit 1. Further, the supporting surface 4a of the surface element is arranged to be planar, thus enabling the return of fibres 3a into the longitudinal direction s as well as possible.

As shown in Figs. 1 and 3, the height of the first end of the frame unit 1 of the surface element e is substantially lower than that of the other end, whereby the upper surface 4a of the frame unit 1 of the 'surface element is placed in an inclined position with regard to the base A. Thus, an advantageous gliding surface is achieved which is as continuous as possible in the longitudinal direction s.

In an advantageous embodiment, the part la of the frame unit 1 joining the joining point L is formed of a plate with an even thickness, equipped with placement means 5 for achieving the inclined position of the upper surface 4a of the frame unit 1. In the shown embodiment, the placement means 5 are formed by four protruding parts 5a with a width corresponding to that of the frame unit 1 and a small thickness in the longitudinal direction s in the middle part of the lower surface lb. Further, in the height direction, the protruding parts 5a have a shape widening towards the lower surface lb of the frame unit 1. By the

constructions presented above, the use of the material for the frame unit 1, preferably polypropylene, is minimized and an advantageous flexible structure is achieved in the frame unit 1.

In a further advantageous embodiment, the length xl of the frame unit 1 of the surface element e cor¬ responds substantially to the length x2 of the gliding unit 3. Thus a minimum material saving of 20% is obtained for the gliding unit. In addition, the length of the gliding unit can be arranged to be e.g. 50% shorter than in the present constructions, whereby the gliding unit can be made stiffer. Consequently, the guiding effect of the the gliding unit is em- phasized, whereby it is also returned more securely to the longitudinal position.

It is obvious that the invention is not limited to the embodiment presented above but it can be modified within the basic idea even to a great extent. The supporting unit can naturally be arranged in accordance with the principle described above also e.g. as a flexible plate separating from the frame unit, or as a plate attached to the frame unit in a flexible way. For security reasons it is thus essential that the supporting unit in connection with each surface element extends as an integrated surface substantially above the frame unit and the joining point included therein. It is obvious that the frame unit can also be arranged in principle as a separate plate or the like which is placed in the above-mentioned way partially above the frame unit of the surface element. In practice, however, a solution of this kind is firstly not competitive with regard to manufacturing or installing techniques, because it requires that the frame unit and the supporting surface are manufactured separately, whereby separate attaching means must be arranged in both parts. The installation thus requires a double

workload in comparison with the installation of e.g. an integrated surface element shown in Fig. 1. Most important, a solution of the type described above is not sufficiently secure either, because the supporting surface to be placed separately above the frame unit can, for reasons of manufacturing techniques or impurities, stones etc. conveyed between the frame unit and the supporting surface during operation, be loose at some sections of the frame unit supporting it, at which points the framework is thus almost directly exposed. This problem can be avoided by using the said integrated frame element. In a cor¬ responding manner, the frame unit can be formed to have an even thickness throughout, or e.g. to be integral and have a thickness being gradually reduced. The lower surface and/or the supporting unit of the frame unit can naturally be arranged to be corrugated in the longitudinal or transverse direction. The surface element of the invention can be manufactured of a large variety of materials by applying a variety of different manufacturing techniques.