DE2128826A1 - Laminated plastic ski - with lightweight polymethylacrylimide foam core and high tensile plastic surface layers - Google Patents

Abstract

The bonding surfaces between the foam core and its upper and lower surface layers are effectively increased in surface area by a rib and groove profiling, the longitudinal components of the ribs and grooves being greater than the components running perpendicularly to the ski. Pref. the ribs on the surface layer projecting into complementary grooves on the core are spaced further apart than the width of the rib. The high tensile layers are fibreglass reinforced plastic.

Description

Ski with a foam core The invention relates to a ski with a lightweight foam core with an upper and a lower layer made of at least in the longitudinal direction of the ski opposite the core and any cover layers that may be present Much more tensile material is firmly bonded.

When a foam core is mentioned here and below, such a core does not have to consist exclusively of foam. He can too Deposits and Have reinforcements made of other materials, e.g.

those made of metal or glass fiber reinforced plastic that increase are used for strength, or those made of elastomers such as rubber, for example to increase can be used for elasticity or internal damping.

If above and below from a layer opposite the core and any cover layers that may be present are spoken of substantially more tensile material is, so it should be essentially over the entire top or bottom of the ski extending layer, for example made of metal, preferably made of glass fiber reinforced Plastic. The layer may be if it is constructive or for other reasons it is necessary to be composed of several strips.

The entirety of these strips should then be practically the whole Cover the top or bottom of the core. The layer should also correspond to its essence have a substantial compressive strength that goes beyond that of the foam core, because the two-n layers of more tensile material together with the core after the Principle of sandwich construction are connected.

With a material connection there is a connection here and below meant, in which the fabrics adhere directly to one another. Such a connection can like this is also preferred by direct gluing a plastic layer reinforced with glass fibers, applied in a liquid state or such a layer temporarily brought into a liquid state the core. However, an indirect adhesive connection can also be provided in which a separate adhesive bonds the layer of tensile strength material with the Core connects.

In the case of skis of the type mentioned at the outset, the core is essentially formed from a polyurethane foam. Many such ski cores have cheap ones Features including light weight.

The invention aims to create a ski that is also able to withstand these even light skis are characterized by their even lower weight. To this end the invention proposes a particularly light foam, namely a polymethacrylimide foam to be used for the ski core, as e.g. from the company Röhm GmbH in Darmstadt under under the name 'ROHACELL ". The apparent specific gravity of the Foam, which is at least closed-cell for use according to the invention is advantageously between 0.10 and 0.35, preferably between 0.13 and 0.21. Such weights are significantly below those of wood comparable Strength and also below that of corresponding polyurethane foams. Will Skis with a core made of such a foam have been used for a while, so However, it was found that the foam immediately at the interface between Foam and high tensile layer overloaded by the constant deformation of the ski becomes and breaks. A useful ski of the type outlined above with a Creating a core from a polymethacrylimide foam must therefore also have this deficiency be eliminated, which according to the invention by a special shape of the connecting surfaces between the foam and the tensile strength layers is achieved.

Accordingly, the ski according to the invention is characterized in that the connecting surfaces between the one made of a polymethacrylimide foam formed core and the tensile layers by a rib-groove profile are enlarged, the component of the direction running in the length of the ski the ribs and grooves is larger than the perpendicular to the longitudinal direction of the ski Component. By shaping the connecting surfaces in this way, in which the layers of high tensile strength material and the core are interlocked with one another, so to speak there is a sharp transition from the core material of low strength to the material the shift high strength replaced by a more gradual transition.

This gives the ski the indispensable fatigue strength, albeit the rib and groove profile is basically oblique to the longitudinal direction of the ski can run, it is preferred that the ribs and grooves exactly in the longitudinal direction of the ski get lost. That's not just in terms of manufacturing but also in terms of the strength is an advantage.

There are many options for creating ribs and grooves. The tensile strength layers can be ribbed at intervals that are much larger are wider than the ribs, protrude into complementary shaped grooves of the core. In this case, the ribs of the tensile strength layers are preferably much higher than wide. The ribs can also be in the form of thin layers of a tensile strength Extending one layer to the other, the thin layers are advantageous in this case in a small thickness of one to several tenths of a millimeter from a tensile strength Layer to the other. They can be made from the same material as the tensile layers exist.

In all cases, the ribs are preferably at the base of the tensile strength Layers widened. That gives one particularly favorable frictional connection at the transition from the tensile layers to the core. The easiest and most related In many cases, the construction is particularly favorable to the strength, if a uniform zigzag profile is selected as the rib and groove profile.

The tensile layers can be made of fiber-reinforced plastic » as it is often used for such layers in ski construction. You can However, they are also made of metal. In the latter case, the tensile strength layers are advantageously formed from folded sheet metal strips. The sheet metal strips can for example be folded into a zigzag profile. Another possibility consists in that protruding ribs from the sheet metal strips by doubling the Sheet are formed.

Rei a particularly favorable embodiment of the invention are the the layers forming the ribs are preferably connected to the tensile strength layers Slats made of wood, fiber-reinforced, running perpendicular to the tensile layers Plastic or phenolic hard paper, of course, should also be taken care of here that the lamellas at their end faces with which they are attached to the tensile strength layers butt, are well glued to the latter, there are also more for the slats Plastics in question, which are not reinforced with glass fibers, if they have a sufficient one strength exhibit. Such a construction connects in optimally the high quality properties of a ski with a wood core with the. low weight of a ski with a core made of polymethacrylimide foam.

Preferably the two outermost lamellae are in the latter The construction is considerably thicker than the lamellas further inside.

In the following, the one in the drawings in the form of several becomes more preferred AusfUhrungsbeispielSe illustrated subject matter of the invention with reference to these drawings explained in more detail.

1 to 4 show each in the same schematic representation Cross-sections through skis according to the invention.

Fig. 5 shows a half cross section through a further ski according to Invention.

FIG. 6 shows, on an enlarged scale, part of the section according to FIG. 5.

7 shows a cross section through a further ski according to the invention.

FIG. 8 shows a partial cross section through a further ski according to FIG Invention.

Fig. 9 shows an enlarged part of the section according to Fig. 8, Fig.10 shows an enlarged partial section through a further ski according to the invention.

11 shows a cross section through a further ski according to the invention, In the following, the polymethacrylimide foam is merely used for the sake of simplicity referred to as foam.

The ski shown in Fig. 1 has a core 1, an upper one with tensile strength Layer 2 made of glass fiber reinforced epoxy resin, a lower tensile strength layer 3 from the same material, side protection strips 4 made of butadiene and acrylonitrile modified polystyrene (ABS) an upper cover layer 5 made of ABS, an outsole 6, for example made of PolySthylen, an intermediate layer 7, depending on the intended use of the ski can be made of different materials, such as polyethylene or an elastomer such as rubber or also made of a glass fiber reinforced plastic. Finally, the ski also has the usual steel edges 8.

According to the invention, the connecting surfaces run between the more tensile ones Layers 2 and 3 and the foam core 1 longitudinally profiled. As from the drawing visible are the ribs and grooves of both the core and the more tensile one Layers in the same way provided with a zigzag profile in which the ribs have the same profile as the groove cut out between two ribs. The more pointed the profile, the more favorable the strength values. However, perfect production is all the more difficult.

You will therefore usually get by with a profile in which the The tip angle of the ribs or the opening angle of the grooves 600 are not significant falls below.

In the manufacture of a ski according to the invention, the core is first 1 provide the desired profiling on the top and bottom. this can for example be done by cutting by milling. However, it can also through Press-in done. The latter can be done with warming. However, it is essential that the profiled surface before the connection with the more tensile layers has been properly cleaned to ensure a good bond with the more tensile layers comes about.

Now they are impregnated with a hardenable epoxy resin Fiberglass strands, which were previously brought into the appropriate shape, on the top and bottom of the core and inserted into the grooves formed there. Here must be special care must be taken to ensure that the fiberglass strands fill the grooves perfectly. For this purpose it can be advantageous that the glass fiber strands (rovings) do not be laid flat, but first at one point and then for example onto the core surface by means of a roller that is continuously moved over the core and pressed into the groove.

After that, the curing of layers 2 and 3 and the final Shaping the same take place in the usual way. The other components of the Skis can be applied in the usual way. It has to be based on it, however care should be taken that the temperatures used are not those which lead to a lead to substantial softening of the foam core. Thermal treatments should therefore do not exceed temperatures of around 1500C. Deviations are a matter of course possible if the thermal treatment is very brief.

As a rule, it is sufficient if in the exemplary embodiment shown the rib and groove profile has a height of 1 to 2 mm.

In the embodiment shown in Fig. 2 also extend on the top and bottom of the core 11 tensile strength layers 12 and 13 from one glass fiber reinforced epoxy resin. However, the two layers 12 and 13 are on both Sides connected to a hollow box profile by corresponding webs. Even with this one Construction is an upper cover layer 15 provided with side cover layers 14, however, is connected to a circumferential U-profile box. This ski too has steel edges 18 and an outsole 16. In this embodiment are relatively large and wide grooves 19 are provided on the top and bottom of the core 11, in which corresponding ribs of the glass fiber reinforced epoxy resin layers 12 and 13 protrude. The grooves 19 have here on the top and trapezoidal profile Underside triangular profile. This difference is only used to indicate different To show possibilities. Usually you will be on the top of a ski and underside choose the same profile for the ribs and grooves.

The ski shown in Fig. 3 has a core 21, an upper one with tensile strength Layer 22 and a lower tensile strength layer 23, an upper cover layer 25, to which Adjoining lateral cover layers 24, steel edges 28 and an outsole 29. He differs from the ski according to Figure 2 essentially in that the with glass fiber reinforced Epoxy resin filled grooves on the top and bottom Underside of the core 21 are much deeper than in the construction according to FIG. 2. In this way, of course, a particularly good connection is achieved that weight is however increased. To get by with a low weight here, you have to either the lateral distances between the grooves 27 in the core 21 are relative large or keep the width of these grooves relatively small. Another Difference from the construction according to FIG. 2 is that the upper and lower cover layer on the sides not connected to one another by continuous webs are.

In the case of the ski shown in FIG. 4, the core also consists of three parts 31, 32 and 33. It is similar on both the top and the bottom the core of FIG. 1 is grooved. A major difference from this core is, however, in the three-part division, which is through continuous webs 34 made of glass fiber reinforced Plastic is effected. Here, too, cause lateral webs 35 and 36 that the three-part Core surrounded by a closed box profile made of glass fiber reinforced epoxy resin is. This ski also has an upper cover layer 37, lateral cover layers 38, steel edges 39 and an outsole 40.

It goes without saying that all of the exemplary embodiments shown the possibility of assembling the core from individual lamellas as well, like this is common practice for skis with wooden cores.

For the side and top cover layers is suitable for all Models such as ABS. There are of course other common materials used here in question.

The ski according to FIG. 4 can be manufactured as follows.

The foam parts 31, 32 and 33 are manufactured separately.

The middle foam part 32 is initially given a glass fiber epoxy coating, is then placed in the center of the mold so that the parts 31 and 33 are exactly symmetrical come to rest on both sides of part 32. The GRP laminate layer 35 and 36 sheathed de core parts 31, 32 and 33 completely, while a thermoplastic film 38 U-shaped the side walls of the ski and the top of the ski covered. The film 38 can also be made with glass chips, Carbon fibers or other reinforcing materials can be provided. The conclusion after below forms the outsole 40 preferably made of low-pressure polyethylene, which is of the Steel edges 39 is bordered.

The ski shown in Fig. 5 has a foam core 41, which on the top and bottom has longitudinal grooves, the profile of which is equal to the profile of the there are ~ ribs left between the grooves. The profile is V-shaped. On this Profile is a correspondingly folded strip 42 on the top and a similar one Strip 43 on the underside by means of a suitable adhesive such as, for example an epoxy resin or a polyester resin. In Fig. 6 is the glue indicated at 44. A cover layer 45 extends on the top of the ski, which is profiled accordingly and thus the outer grooves of the upper tensile sheet metal layer 42 covers. The cover layer 45 can, for example, be applied with thermal heating and be bonded to the outside of the sheet metal by adhesion. On the side of the ski extends a side protection strip 46, for example made of ABS.-The ski has also an outsole 47. The space between the outsole 47 and the The lower sheet metal layer 43 is made of a suitable plastic that is attached to both the outsole as well as adheres well to the sheet metal, for example an epoxy resin 48 filled. Of the Finally, the ski has steel edges 49. With this construction, the Usually a sheet thickness of 0.2 to 0.3 mm.

In the embodiment shown in FIG. 7 there is the Core of the ski made of foam lamellas 51 running in the longitudinal direction of the ski this type of construction is known from skis with wooden cores. On the top A glass fiber reinforced epoxy resin layer extends 52. On the underside A glass fiber reinforced epoxy resin layer 5S runs along the core. The two epoxy resin layers are connected by webs made of epoxy resin, which here are in the core protruding ribs of the more tensile layers 52 and 53 form. With this construction it is not necessary that the epoxy resin layers 54 also be glass fiber reinforced. This way the core can be glued first with epoxy and then with the top and lower tensile strength layers 52 and 53 are provided. The thickness of the webs 54 can be minor. Thus, in many cases, a thickness of these webs is of the order of magnitude 0.1 mm is sufficient.

The thickness of the webs 54 need not be uniform everywhere. It is best to be thicker near the roots on the more tensile layers 52 and 53 and decreases towards the center of the core. Such a technically particularly advantageous one However, training is expensive to manufacture.

This ski is also box-shaped on the surface and sides Cover layer 56 made of ABS surrounded.

It has steel edges 57 and a polyethylene outsole 58. Of the The ski shown in FIGS. 8 and 9 differs from the ski according to FIG. 7 only in that the lamellas forming the core have Trapezprof'il, whereby the upper and lower tensile strength layer compared to the upper and lower edges of the Foam slats 61 can be kept very thin at 62 because relatively Interstices between the beveled upper and lower surfaces of the lamellae 61 and the upper cover layer or the outsole 67 remain free, whereby the tensile strength Layers get the required cross-sectional size. Instead of the trapezoidal profile the lamellas 61 can also be beveled evenly on both sides. That has Advantage that that shown in FIG. 8, in relation to the plane of symmetry of the ski symmetrical arrangement of the lamellas is omitted due to the equality of the lamellas. Even this ski finally has steel edges 68 and in one piece with the upper one Cover layer 66 formed side protection tires 69, which materially with the Ski core or the tensile layers 63 and 64 are connected.

In all of the embodiments shown, the connections are between the various elements of material connection, basically it is natural also possible, for example, to connect the steel edges to the ski in a fora-locking manner. Given the current state of the art, a material connection is generally to be preferred.

The ski shown in Fig. 10 has a foam core 71, which on its upper and lower side grooves 72 from that shown in the drawing Has shape. These grooves have substantially parallel walls and are approximately semicircular rounded base, so that it is separated from the upper and lower layers with more tensile strength forming sheet metal strips 73 and 74 are fully filled.

Of course, the grooves are made with such an oversize that that the sheet metal strips 73 and 74 are sandwiched by a correspondingly thin layer of adhesive, For example, such a -Epoiyharzes, in the grooves can be glued. The sheets 73 and 74 are bent in the manner shown in the drawing. The parts on which the sheets are doubled to form ribs protruding into the core 71, can be connected by means of an appropriate metal adhesive. In this case the metal adhesive expediently also fills those created by the bending of the sheet metal small grooves 75 on the outside of the sheets 73 and 74 so that the folded Sheets get a certain lateral tensile strength.

Are the sheets 73 and 74 very thin, for example with a Thickness of 0.1 or 0.2 mm running, 8o can be between these and the top cover layer 66 or the lower intermediate layer 77 provided in the exemplary embodiment glued in another thin metal layer from the same or a different sheet metal be. Such Sheet metal layers are in the embodiment of For the sake of clarity, however, not shown. The ski shown here also has Side protection strips 78, standard steel edges 79 and an outsole 80.

The ski shown in FIG. 11 represents a particularly advantageous construction In this ski, the ribs of sipes 84 are made of wood, such as ash wood educated. The lamellas 84 are on their end faces with the tensile strength layers 82 and 83, which in the exemplary embodiment are closed by side wall parts 89 Box are connected, firmly glued. The two outermost lamellae 85 differentiate differs from the lamellae 81 only in that they are much wider. While the lamellae 84, for example, advantageously have a width of 3 mm, the the outermost lamellae 85 have a width of, for example, 3, depending on the circumstances to 15 mm, a width of 15 mm being preferred over a width of 3 mm will. Between the lamellae 82 and 83 extend the SahaùmstoPP core forming Polymethacrylimide foam strips 81.

The outsole is located under the lower tensile strength layer 83 87 made of PolySthylen, to which two steel edge strips 88 connect on the outside. the The high tensile strength layer is preferably made of synthetic peat on the outside ABS provided.

Instead of the wooden slats, slats can also be used, for example the end Glass fiber reinforced plastic or phenolic hard paper strips or ABS are provided be. Such slats can be kept thinner than wooden slats.

With these, a width of about 1 mm is usually sufficient this last-described construction according to FIG. 11, the polymethacrylimide foam can be chosen even more easily than with the constructions described above. Depending on the requirements, up to the density of the foam, for example 0.07 go down. Here, too, the more solid the construction, the better the bond between foam, slats and tensile layers is.

Claims (12)

Claims: Skis with a lightweight foam core that has a top and a lower layer of at least in the longitudinal direction of the ski opposite the core and optionally Existing cover layers are firmly bonded to a material that is substantially more tensile is, characterized in that the connecting surfaces between the made of a polymethacrylimide foam formed core and the tensile layers by a rib-groove profile are enlarged, the component of the direction running in the longitudinal direction of the ski the ribs and grooves is larger than the perpendicular to the longitudinal direction of the ski Component. 2. Ski according to claim 1, characterized in that the ribs and Grooves run in the longitudinal direction of the ski. 3. Ski according to claim 1 or 2, characterized in that of the tensile layers of ribs at intervals that are much larger than the ribs are wide, protrude into complementary grooves in the core. 4. Ski according to claim 3, characterized in that the ribs of the tensile layers are much higher than they are wide. 5. Ski according to one of claims 1 to 4, characterized in that the ribs move in the form of thin layers from one high-tensile layer to the other extend. 6. Ski according to one of claims 1 to 5, characterized in that the ribs are widened at the approach to the tensile layers. 7. Ski according to claim 1 or 2, characterized in that the rib-groove profile is a uniform zigzag profile. 8. Ski according to one of claims 1 to 6, characterized in that the tensile layers are made of fiber-reinforced plastic. 9. Ski according to one of the = claims 3 to 6, characterized in that the tensile layers consist of folded metal strips. 10. Ski according to claim 9, characterized in that of the sheet metal strips protruding ribs are formed by doubling the sheet metal. 11. Ski according to claim 5, characterized in that the ribs forming layers of preferably perpendicularly connected to the tensile strength layers to the Zug-EschPnhol z. solid layers running lamellas made of wood fiber reinforced Plastic or phenolic hard paper and the like. 12. Ski according to claim 11, characterized in that the two outermost Lamellae are significantly thickened compared to the lamellae located further inside.