|Publication number||US3897074 A|
|Publication date||Jul 29, 1975|
|Filing date||Feb 22, 1974|
|Priority date||Feb 22, 1974|
|Publication number||US 3897074 A, US 3897074A, US-A-3897074, US3897074 A, US3897074A|
|Original Assignee||Karhu Titan Oy|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (14), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1 1 Tiitola 1 July 29, 1975 1 SKI WITH MICROPOROUS BOTTOM SURFACE  Inventor: Antti-JussiTiitoIa,Tampere,
Finland  Assignee: Karhu-Titan 0y, Helsinki, Finland  Filed: Feb. 22, 1974 ] Appl. No.: 444,876
Primary Examiner-Kenneth H. Betts Assistant Examiner David M. Mitchell Attorney, Agent, or FirmSteinberg and Blake  ABSTRACT A ski including an elongated relatively narrow strip having a normally upwardly directed surface to be engaged by a ski boot and a normally downwardly directed opposed surface, the ski including a bottom layer which is fixed to the strip and engages and covers the opposed surface thereof, this bottom layer being composed for the most part of a plastic in which hollow tubular fibers are embedded with some of the fibers being exposed at a surface of the bottom layer which is directed away from the strip to provide the latter surface of the bottom layer with a microporous structure. During manufacture the bottom layer composed for the most part of plastic in which the hollow tubular fibers are embedded is applied to the bottom surface of the strip and while being pressed against the bottom surface of the strip is cured to form a plate fixed to the bottom surface of the strip. The bottom layer is then ground at its surface which is directed away from the strip to expose fibers at the ground surface, thus giving the latter surface a microporous structure.
9 Claims, 4 Drawing Figures PATENTEDJUL29975 Fl G. 1
SKI WITH MICROPOROUS BOTTOM SURFACE BACKGROUND OF THE INVENTION The present invention relates to skis.
In particular, the present invention relates to skis having bottom structures for providing the skis with desired sliding properties, as well as to methods for manufacturing such skis.
It is known to provide for skis different types of synthetic materials situated at the bottom sliding surfaces of the skis. Sliding bottom surfaces of skis have been manufactured from thermosetting as well as thermoplastic materials. Thus, polyethylene is one of the thermoplastic materials most frequently used for this purpose and has indeed been found to be extremely good for alpine skiing. However, the use of a bottom layer of polyethylene for skis intended for cross-country skiing is restricted by reason of the fact that polyethylene has a low coefficient of friction at rest, so that skis provided with polyethylene at the bottom thereof slide very easily and in addition have a poor adherence with wax, so that both from the standpoint of waxing as well as of cross-country skiing polyethylene is undesirable. Other materials having characteristics similar to those of polyethylene have been used, such as Teflon and polypropylene, but there has been no general use of these thermoplastic materials.
Skis with bottom layers consisting exclusively of thermosetting plastic have not been in use unless it is considered that a polyester and epoxy-based varnish forms a thermosetting plastic bottom layer. Such varnishes have been used in order to increase the wear resistance of the bottoms of Wooden skis. These varnishes have been used in the form of thin coats having a thickness of less than 0.1 mm, because thermosetting plastics in thicker layers without fillers have too great a tendency to flake off, particularly along the edges of the ski bottom.
A known ski bottom based on a thermosetting plastic is the so-called plastic wood developed in Finland. This type of construction is believed to be the commonest plastic ski bottom material for skis which at the present time are intended for cross-country skiing. The drawback of plastic wood has proved to be its brittleness, or, in other words, its poor flexural strength. This latter drawback results from the non-uniform fibrous structure of the wood as well as its low ductility across the grain. These factors result in a tendency of skis having plastic wood bottoms to break in two, and such skis are easily scratched, for example by stones.
Another type of known ski bottom includes a combination of thermosetting plastic and a textile fabric having a pile, as disclosed in Finnish Pat. No. 43,401. This ski bottom has an oriented, microscopic pile surface projecting from the ground bottom surface of the ski, and this construction has proved to have a distinct mechanical effect on the sliding and gripping characteristics of the ski. Although such a construction has indeed proved to be highly desirable with regard to its properties, nevertheless due to the high price of such construction, resulting from the difficulty in manufacturing the ski with the special fabric, the use of this type of ski has been restricted only to the most expensive skis.
Also, as a known material for the bottom of the ski paper laminate impregnated with phenolic resin has been tried. However, such a construction has proved to have an excessive tendency for flaking off. In addition this construction has the drawback of poor adherence with ski wax and a poor gliding at low temperatures.
SUMMARY OF THE INVENTION It is accordingly a primary object of the present in vention to provide a ski and a ski-manufacturing method which will avoid the above drawbacks.
Thus, it is an object of the present invention to provide a relatively inexpensive ski having at its bottom a construction which is greatly improved as compared to known skis of similar cost.
In addition it is an object of the present invention to provide a ski and ski-manufacturing method according to which it is possible to take into consideration the desired use of the ski so that in accordance with the invention it is possible to provide skis having extremely good slidability to be used in ski contests, while if desired it is also possible to design the ski to have maximum wear resistance for alpine skiing, or it is also possible to provide a ski which has the best possible properties for cross-country skiing.
In addition it is an object of the invention to provide a ski with a bottom layer having a relatively low thermal conductivity to improve the gliding of the ski on extremely cold snow.
In accordance with the invention the ski includes an elongated ski strip having a normally upwardly directed surface to be engaged by a ski boot and a normally downwardly directed surface which is engaged and covered by a bottom layer which is fixed to the ski strip. This bottom layer in accordance with the present invention is composed for the most part of a plastic in which hollow tubular fibers are embedded. These fibers have internal capillary passages, and some of the fibers are exposed and flush with a bottom surface of the bottom layer which is directed downwardly away from the ski strip, so that in this way this latter bottom surface has a microporous construction. According to the method of the invention the plastic with the tubular fibers embedded therein is applied to the bottom surface of the ski strip while being pressed against the ski strip during curing so as to form a plate which is fixed to the ski strip, and thereafter the bottom surface of this cured layer which is directed away from the ski strip is ground so as to expose fibers at the bottom surface of the bottom layer.
BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:
FIG. 1 is a schematic side elevation of a ski according to the invention;
FIG. 2 is a fragmentary longitudinal sectional elevation of part of the ski of FIG. 1 at the region of its lower surface, illustrating schematically the construction of the ski at an enlarged scale;
FIG. 3 is a fragmentary longitudinal sectional eleva tion of the ski at the region of its lower surface shown at a scale which is much larger than that of FIG. 2 so as to illustrate in detail the construction of the ski; and
FIG. 4 is a fragmentary bottom plan view of the ski of FIG. 1 showing schematically at an enlarged scale the microporous structure of the bottom surface of the ski.
DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with the invention the ski has a bottom layer which is designed to slide and which is composed for the most part of a thermosetting plastic and a fibrous material in the form of hollow tubular fibers which are embedded in the thermosetting plastic, this plastic with the fibers therein being cured to form a plate which is attached to the bottom of the ski. After curing is completed the exposed bottom surface of the layer of plastic with the tubular fibers embedded therein is machined, as by being ground, so that the capillary passages in those fibers which become exposed by grinding at the bottom surface of the bottom layer are opened to provide the bottom surface of the ski with a microporous construction.
Referring to FIG. 1, there is shown therein in a schematic side elevation a ski strip in the form of an elongated narrow strip of wood, for example, having a normally upwardly directed surface 12 to be engaged by a ski boot. Thus, FIG. 1 schematically illustrates the structure 14 for releasably holding a ski boot. As may be seen from FIG. 1, the strip 10 has fixed thereto a bottom layer 16 which is constructed in accordance with the present invention, the thickness of the bottom layer 16 being exaggerated with respect to the illustrated thickness of the strip 10 in FIG. 1 for the sake of clarity.
Referring to FIG. 2 it will be seen that the strip 10 has fixed thereto the bottom layer 16 which is composed of a synthetic plastic material 18 in which hollow tubular fibers 20 are embedded, as schematically illustrated. Preferably the plastic 18 is a thermosetting plastic and the fibers 20 are cellulose fibers. The layer 16 which is composed of the most part of the thermosetting plastic 18 and the tubular fibers 20 is applied to the bottom surface of the strip 10 and is cured under pressure so that the layer 16 forms a plate which is fixed to the bottom surface of the strip 10. Then the bottom surface 22 of the layer 16 is machined as by grinding so as to expose a number of the fibers 20 which are flush with the bottom surface 22, thus opening the capillary passages of the fibers 20.
Referring to FIG. 3, which shows this construction at a greatly enlarged scale, it will be seen that one of the fibers 20 has its capillary passage 24 open at the bottom surface 22 of the plastic material 18.
Referring to FIG. 4 which also shows the construction at an enlarged scale for the sake of clarity, this structure of the invention provides the bottom surface 22 of the ski with a multiplicity of tiny openings 26 which give the bottom surface a highly desirable microporous construction.
Thus, with the present invention the bottom layer of the ski will eliminate all of the drawbacks which have been encountered with plastic wood while at the same time preserving properties which are important with respect to good gliding of the ski and the capability of waxing the bottom thereof. By selecting for the material to be impregnated with the thermosetting plastic 18, instead of wood, hollow tubular fibers 20 which preferably are cellulose fibers or other equivalent tubular hollow fibers, a completely uniform construction capable of being technically controlled is achieved with the fibers in the plastic 18 either being haphazardly arranged or oriented in a preselected manner. The hollow cellulose structure of the cellulose fiber or other equivalent fiber is significant from the viewpoint of the present invention in that it provides the exposed bottom surface 22 of the ski with a microporous characteristic which aids in the adherence of wax. When the hollow fibers are impregnated with the synthetic resin which is then cured to form a plate which is fixed to the bottom surface of the strip 10, with pressure being applied usually simultaneously with the curing, a sliding bottom ski surface is achieved where this latter surface has a combination of different materials with the proportions of the fibers and resin being capable of exact determination as, for example, by adjusting the pressure applied during the simultaneous pressing and curing of the layer 16.
One of the important features of the present invention resides in the fact that the bottom surface 22 is ground or otherwise machined so that the sealed surface which results from the pressing is broken up to create the microporous surface where the passages 24 of the fibers 20 flush with the surface 22 are open at the surface 22.
As a further feature of the present invention it is preferred to provide a bottom layer 16 which has a thickness on the order of 0.5-1 mm, so as to achieve the additional advantage of eliminating scratches or other damage to the bottom surface by an equalizing grinding operation applied to the bottom surface 22 after it has become excessively scratched or otherwise damaged during use. Inasmuch as the entire bottom layer 16 is of a homogeneous construction throughout its thickness, any machined surface 22 provided even subsequent to extensive use of the ski will have the abovedescribed characteristics of the invention.
It is possible to regulate the characteristics of the surface 22, in accordance with the invention, by varying the quantitative proportions of fibers and resin as well as the hardness of the resin so as to achieve the best possible wear, sliding and waxing properties for different conditions. It becomes possible, therefore, to produce for different intended uses particular sliding bottom surfaces 22 which are most appropriate for the intended purposes. For example a surface 22 which has optimum sliding properties will be provided for skis to be used in contests, while maximum wear resistance will be provided for alpine skiing.
In addition, the hollow tubular fibers 20 have the effect of lowering the thermal conductivity of the layer 16. This property is of great significance because a low thermal conductivity improves the ease with which the surface 22 glides on extremely cold snow.
One example of the composition of the layer 16 which has proved to be highly successful for the bottom layer of a ski according to the invention is the follow- The plastic 18 is an epoxy resin while the fibers are cellulose fibers, and the cellulose fibers constitute 50% by volume while the epoxy resin 18 constitutes 45% by volume of the layer 16. The remaining 5% by volume of the layer 16 is made up of fillers and pigments.
What is claimed is:
1. In a ski, an elongated narrow strip having one surface which is normally directed upwardly to be engaged by a ski boot and an opposed surface which is normally directed downwardly toward the ground, and a bottom layer fixed to said strip and engaging and covering said opposed surface thereof, said bottom layer being comprised for the most part of a plastic material in which short tubular fibers are embedded with random orientations, said tubular fibers having internal capillary passages and including at a surface of said bottom layer which is normally directed downwardly away from said strip a number of fibers which are flush with and have their passages exposed at said surface of said bottom layer to provide the latter surface with a microporous structure.
2. The combination of claim 1 and wherein said plastic is a thermosetting plastic.
3. The combination of claim 2 and wherein said fibers are cellulose fibers.
4. The combination of claim 3 and wherein said plastic is an epoxy resin.
5. The combination of claim 4 and wherein said cellulose fibers and epoxy resin respectively form 50% and 45% by volume of said bottom layer while the remainder thereof includes 5% by volume of fillers and pigments.
6. The combination of claim 5 and wherein said bottom layer has a thickness on the order of 0.5-1 mm.
7. The combination of claim 1 and wherein said bottom layer has a thickness on the order of 0.5-1 mm.
8. In a method of manufacturing a ski, the steps of applying to a normally downwardly directed bottom surface of a ski strip a layer comprised for the most part of plastic with short hollow tubular fibers embedded with random orientations therein, pressing said layer against said strip with a given pressure while curing said layer to form therefrom a plate which is fixed to said bottom surface of said strip, and then grinding a surface of said layer which is normally directed downwardly away from said strip to expose the hollow interior of some of the fibers at the ground surface of said layer so as to provide the latter surface thereof with a microporous structure.
9. In a method as recited in claim 8 and including the step of regulating the pressure applied to said layer during curing thereof for controlling the proportions by volume of said plastic and fibers with respect to each other.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|US20100102533 *||May 4, 2009||Apr 29, 2010||Edmunds Louis R||Snotz snow skis|
|DE10130392A1 *||Jun 23, 2001||Jan 9, 2003||Bernd Spaeth||Body contacting media has surfaces with micrometric- or nanometric structuring, adapted to the respective media|
|DE10130392C2 *||Jun 23, 2001||Jun 26, 2003||Bernd Spaeth||Gleitelemente, beispielsweise Schneegleitelemente, mit verbesserten Eigenschaften|
|EP0086939A2 *||Jan 13, 1983||Aug 31, 1983||Karhu-Titan Oy||Coating material and coating for a ski for varying snow conditions, and method of making the same|
|EP0086939A3 *||Jan 13, 1983||Apr 11, 1984||Karhu-Titan Oy||Coating material and coating for a ski for varying snow conditions, and method of making the same|
|WO2005065790A1 *||Jan 6, 2005||Jul 21, 2005||The University Of Sheffield||Ski and snowboard lubrication system|
|International Classification||A63C5/00, A63C5/056, A63C5/04|