The present invention relates to a brake system for roller skis. The invention also relates to a roller ski including such a brake system.

In addition to being used on roller skis, the invention will also be usable on in-line skates and other types of sporting goods with wheels that allow a user's foot to glide parallel to a supporting surface.

As is known, roller skis constitute items that are used on roads and that, by and large, replace cross-country skis and make it possible to train in summer or under other conditions in which ski tracks in the snow are not available.

Generally, roller skis comprise a pair of elongated bodies which the user places on each of his/her feet with suitable bindings, and which are provided with wheels for movement on the supporting surface in order, thus, to imitate the gliding motion that skis have on snow.

It is a known fact that skis for use on snow, and especially cross-country skis, are usually braked by using the so-called "snowplough" technique, which consists in twisting one or both ankles to place the feet, and therefore also the skis, with converging tips and form a "V" converging in the skier's direction of propulsion. In this way, the skis are incident to each other and to the direction of propulsion, so that the friction of their edges against the snow will brake them.

This technique allows the skier to brake while he/she keeps his/her feet resting on the skis and in such a way that his/her body weight is distributed over the length of the foot, and the skier may thereby maintain good balance and good control of the skis.

When it comes to roller skis, on the other hand, it is not possible to twist the skis in the same way for braking as the high friction between the wheels and the supporting surface does not make this possible without them crossing each other, which would inevitably lead to a fall.

DE102013224611A1 presents a solution with a brake that must be activated by using the hand on a lever at the back of the wheel, and the brake itself works by pressing a friction element down against the wheel rubber of the wheel.

A first drawback presented by said roller skis consists of the fact that, to brake them, it is necessary to use the hands down towards the skis, whereby the main function of the hands, which is to ensure balance, is interrupted.

EP2337613 presents a solution which involves that, to activate the brake, the skier has to twist his/her foot out of its normal position so that the longitudinal direction of the foot is no longer pointing in the longitudinal direction of the ski.

This brake arrangement is encumbered with the drawback of affecting the user's balance and, maybe to an even greater degree, reducing the possibility of controlling the skis optimally in a situation in which this is important to avoid falling or bumping into obstacles.

It is obvious that the drawbacks that are described above are also found with other similar types of sporting goods on wheels, especially with in-line skates, working according to the same principles as roller skis, and, in the main, entailing the same problems regarding braking.

WO1996001672A1 discloses a roller ski with a disc brake braking the rear wheel when the skier pushes off in the diagonal stride to imitate grip. This is not suitable or constructed for braking the propulsion, stopping the ski from rolling forwards, that is.

A known type of in-line skates, as presented in US5704617A among other documents, is provided with a braking device of a static type, consisting, in the main, of a pad which is disposed in the front and/or rear part(s) of the elongated skate body, and which is brought into contact with the supporting surface by bending the foot to achieve a frictional effect.

Clearly, the braking device of the above-mentioned type presents the drawback of affecting the user's balance during braking, and this even more than the brake systems described above that are used for roller skis. A corresponding braking device will also be difficult to use on a roller ski which is substantially longer than an in-line skate.

Rubber has a good friction capacity against other rubber, metal and other friction ele- merits as long as the rubber is dry. In wet conditions, however, it has been shown that the major part of the friction capacity of rubber disappears. This means in turn that the braking effect will be strongly reduced when the friction surface between the friction element (brake pad) and wheel is wet.

Most brake systems for roller skis are encumbered with this problem as they often use the rolling rubber of the wheel as an abutment for the friction element I brake pads.

DE102013224611A1 has a brake that must be preset by adjusting an adjusting screw/arm that sits at the top of the rear wheel. This is not very practical for an active roller skier as, on a downhill slope, the speed cannot be determined without stopping and adjusting the pressure, and the brake is not practical where there is suddenly a situation that requires quick braking. This brake system, too, works directly against the tread rubber of the wheel, with the drawbacks that this has by wet conditions as mentioned above.

US7677600B2 presents a leg-activated arm which, when the foot is pushed forwards, is pressed rearwards, thus transmitting force from the back part of the leg via various brake arms to the rear wheel of the roller ski.

This technique results in only one of the skis being usable for braking at a given time, as long as the other foot must be directed rearwards for balance to be maintained.

The total braking effect is thereby reduced as only one brake can be activated at a given time in relation to a brake system in which both brakes can be activated simultaneously and independently of each other, and in addition, the braking effect of this type will also be reduced when the rubber of the wheel gets wet.

On longer downslopes, there will often be a need to change course along the way. By braking on only one foot, the body and the skis will turn in the direction where the braking ski is, and it will therefore be necessary to correct the course by stopping the braking and correcting the diction by moving the skis. In this way, the braking will happen in jerks and cause imbalance with an increased risk of falling.

The brake that is made on the basis of US7677600B2 also gives a considerable weight increase in the roller skis as the brake arms are long and normally made of metal to have sufficient strength and rigidity, which in itself is both undesired and may, with time, lead to wear in knee joints and the like.

In the above-mentioned patent and in EP2337613 and most other brake systems, the brake, more often than not, has one or more arms or callipers that are attached to the ski/brake and that have one or more articulated connections for activation of the brake. Most of them also have spring systems for keeping the brake arm and friction element away from the wheel when the brake is not activated.

WO2015110167 Al presents a brake system for roller skis. The brake system comprises brake discs that are placed on both sides of a wheel on the roller ski. Two brake pads are placed on the inside of the fork of the roller-ski shaft and are activated with a button on the user's ski pole.

The present invention has for its object to overcome one or more drawbacks of the known techniques as described above, or at least provide an alternative to known solutions. The invention also has for its object to simplify manufacturing production, simplify maintenance and in such a way that the safety is ensured both by the skis enabling braking independently of each other and by the system having a built-in warning indicator for when the disc brake should be replaced.

The present invention is also arranged in such a way that the brake system should allow easy retrofitting to existing roller skis or mounting on new skis.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.

In the present invention, disc brakes are used instead of using the rubber or PU tread of the wheel as the abutment point for the friction element. This makes the risk of friction loss on a wet supporting surface be considerably reduced.

The present invention does not have any of the drawbacks associated with the brake on one foot, either, as the braking can be controlled from an activating device, which may, for example, be connected to or integrated with the brake lever on the pole corresponding to that used on bicycles. A brake cable runs down beside the skier's body, down to the brake of the roller ski which usually sits on the rear wheel. If desired, the brake may be electronically activated. By pressing a brake lever, if the embodiment uses a brake cable, on the poles, the cable is tightened and the brake arms of the brake of the roller ski are pulled towards each other so that the braking begins.

With this technique it is possible to brake on the right and left feet completely independently of each other and by adjusting the braking effect in a continuously variable manner between the two skis so that there will be an even and planned "steering" down the slope and without having to correct the course by letting up on the brake and lifting the skis into a new position.

In a first aspect, the invention relates to a brake system for roller skis, the brake system comprising:

- two brake arms arranged to be attached to the roller ski on separate sides of a wheel of the roller ski,

- a friction element attached to an inside of each of the brake arms; and

- a tightening mechanism arranged to be activated by a user of the roller ski so that the brake arms are pressed towards each other, whereby the friction elements are arranged to be brought into contact with brake discs on the wheels of the roller ski.

In a second aspect, the invention relates to a roller ski including a brake system in accordance with the first aspect of the invention, the roller ski including a wheel with a brake disc on either side, the brake arms being attached to the roller ski in such a way that the friction elements can be brought into contact with the brake discs when a user activates the tightening mechanism.

In a third aspect, the invention relates to a roller-ski system comprising a roller ski in accordance with the second aspect of the invention and an activating device for activating the tightening mechanism.

In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings, in which:

Figure 1 shows the rearmost part of a standard roller ski 1 with a wheel 20 with a rubber-coated tread 22, to which a new brake system has been fitted, the brake system being mounted directly on the ski. In this figure, a friction element 2 that has been removed from the brake arm is shown as well.

Figure 2 shows the rearmost part of a standard roller ski 1 with a wheel 20 with a rubber-coated tread 22, on which a new brake system has been mounted by means of a bracket 13. This figure also shows a lower, cut part of a brake cable 12 with a brake-cable sleeve 16. Figure 3 shows a new type of wheel rim 4 that has recesses 7 on both sides of the circumference of the rim. The figure also shows the spokes 23 of the rim and the attachment hole 9 where the setscrew 8 of the brake disc 3 is attached, see figures 1 and 2. The rubber tread 22 and wheel bearings 6 of the wheel, figures 1, 2 and 5, have been removed in order to see the recesses 7 better.

Figure 4 shows the brake disc 3, with cooling slots 25, draining slots 26, a hole 21 for the setscrew 8 and the "ears" 5 of the brake disc which are adapted for allowing insertion thereof into the recesses 7 of the rim.

Figure 5 shows a rim 4 on which the brake disc has been mounted, and a partially unscrewed setscrew 8 and an imaginary wheel bearing 6. The rubber tread of the wheel has been removed.

Figure 6 shows a rim 4 with the rubber tread of the wheel fitted. The rest is as shown in figure 5.

Figure 7 shows a wheel in which the brake disc 3 has been removed on one side so that the wheel bearing 6, the spokes 23 of the wheel and the attachment hole 9 for a setscrew 8 is shown.

Figure 8 shows the contour of the brake arms 11 and the mounting 10 before the brake body has been bent into its final shape as shown in figures 1, 2 and 9, and the slots 18 into which the cable is placed when being fitted and the recess 24 where the friction element 2 is to lie.

Figure 9 shows the brake system after it has been bent into its final shape. Here, the recess 19 in one brake arm is shown as well, which is used for the cable sleeve 16 or cable attachment 17, see figures 1 and 2.

Figure 10 shows the rearmost part of a standard roller ski with a wheel with a rubber- coated tread which has been fitted with a new brake system in which the brake arms are attached directly to the wheel axle 27. Holes 28 can be used for a setscrew.

Figure 11 shows the brake arm and the mounting before the cut-out has been bent into its original shape as shown in figure 10. 28 - holes for setscrew, 10 - mounting arms, 11 - brake arms, 18 - holes for brake cable, 29 - holes for wheel axle.

Figure 12 shows the brake system with two short brake arms 11 set vertically, which are attached by means of the axle of the wheel. The brake arms can be locked in their vertical position in different ways or they may be pushed forward towards the ski and locked into position by means of, for example, setscrews not shown.

Figure 13 shows the brake system with two long brake arms 11 that are attached to the ski and to each other by means of two, as shown in the Figure, or more screws that lie over and under the ski. The position of the brake arm can be locked by means of a setscrew 28 to prevent rotation of the brake arm during braking.

Figure 14 shows an alternative embodiment of a brake system in accordance with the invention, the brake system being arranged to be activated electronically.

Figure 15 shows a first embodiment of a combined rim and brake disc; and

Figure 16 shows a second embodiment of a combined rim and brake disc.

Like reference numerals indicate like or corresponding elements in the figures. In the figures, which are shown somewhat schematic and simplified, the elements are not necessarily all shown to scale.

General drawings of the present invention are shown in figures 1, 2, 10, 12, 13 and 14. In the attached figures, only the rear part of the roller ski is shown as this is normally where the brake device is mounted.

In the present invention, the brake system roughly consists of a few parts: Two brake arms 11, one on either side of the wheel, which are connected to each other either via a transverse mounting 10, and attached to the ski 1 with screws 14, as shown in figure 1, or via a bracket 13, as shown in figure 2. Alternatively, the brake arms may be formed as in figure 10 where they are connected to the ski via the axle of the wheel. Alternatively, the two brake arms may be separate and attached to the ski as shown in figures 12 and 13.

Further, two friction elements 2 are used, which are attached on the inside of each of the arms 11 of the brake.

- Two brake discs that are attached on either side of the rim 4 of the wheel, as shown in figures 1, 2, 10, 12, 13 and 14.

- A brake cable, a hydraulic brake line which is attached to the rear parts of the brake arm 11 is connected to a brake lever, corresponding to that on a bicycle, attached to the grip of the ski pole. The brake cable I hydraulic line could be replaced by an electronic device that will pull the arms towards each other. In what follows, for the sake of convenience, these devices are called "the brake cable or the cable", but it will be understood that this does not exclude a wire- less, electronic variant.

Unlike a conventional brake-disc system used, for example, on bicycles and cars that usually have just one brake disc for each wheel, there is, in this invention, only one friction element on each brake disc, but, on the other hand, two brake discs for each wheel. As the wheels, and thereby also the brake discs, on a roller ski are small, the frictional heat that develops during braking will, in this invention, be distributed on two brake discs so that the temperature is thereby reduced.

In this invention the tightening of the cable 12 and the resilience and rigidity of the brake arms 11 will replace the conventional calliper, which both simplifies the production, reduces the number of parts and, not least, makes the manufacturing cheaper.

In this way, there will be no need for springs to keep the friction elements clear of the brake discs or articulated connections to transmit the force from the brake lever to the friction element and brake disc.

The system is constructed in such a way that both friction elements 2 and brake discs 3 should be easily replaceable, and also in such a way that it is easy to disconnect the cable 12, when present, from the roller ski 1 itself by a simple grip and without the use of a tool, by pressing the arms carefully towards each other and then lifting the brake cable off.

The integrated brake system as shown in figures 1, 2 and 10 comprising the mounting 10 and the two brake arms 11 shows two out of many different shapes that may be produced in one piece by: milling, laser-cutting, flame-cutting or sawing out a suitable shape as shown in the examples in figures 8 and 11 from a suitable piece of sheet made of metal, for example aluminium, or some other suitable material, for example polycarbonate, which may then be bent into a final shape as shown in the examples in figures 1, 2, 9 and 10 by means of, or without using, heat,

- or milling, laser-cutting, flame-cutting or sawing out a square or U-shaped beam of a suitable material so that the desired shape, as mentioned above, is achieved.

- The final shape as shown in figures 1, 2, 9, 10, 12, 13 and 14, may also be produced by moulding of, for example, various types of plastic, metal, such as aluminium, or some other suitable material.

As an alternative to having the two brake arms integrated into one and the same part as described above, two independent brake arms may be used, which are either at- tached to the skis, for example as shown in figure 13, or attached directly to the axle of the wheel, as shown in figure 12. The brake arms may then preferably be secured against being pushed forwards or rearwards by, for example, locking the position with setscrews, not shown, in holes 28 as shown in figure 13.

The material that is used must have the necessary strength and rigidity so that the arms with the friction elements 2 can be pushed in against the brake discs 3 of the wheel with sufficient force for an effective braking while, at the same time, the rigidity and elasticity of the material help the brake arms with brake pads to return automatically to their starting points when the brake is deactivated. Thereby there is no need to use spring systems to keep the brake arms free from the brake disc.

The main part of the brake system, which comprises the mounting 10 and the brake arms 11, may be attached either directly to the skis with screws 14 as shown in figure 2, or be attached to a bracket 13 which is clamped around the roller ski and attached with screws running transversely under the ski as shown in figure 2. Drilling in the ski itself is thereby avoided.

A corresponding solution may also be used by using two separate arms as illustrated in figure 13.

Another alternative is to attach the brake arms to the wheel axle 27 itself, as shown in figures 10 and 12. This increases the flexibility with respect to using the system on as many types of skis as possible; there is no need to drill in the skis and there is no need to make different types/sizes of mounting brackets for different types of skis. A setscrew can be screwed into the hole 28 to prevent the brake arm from rotating backwards or forwards if the brake is activated while the ski is rolling backwards. The mounting 10 connecting the two brake arms 11 will prevent the brake system from rotating during normal braking.

The present invention will utilize brake discs 3 that are attached directly to either side of the rim 4 of the wheel, which in its turn is attached to the ski by means of the axle 27 that runs through ball or roller bearings 6 attached in the centre of the rim 4, see figures 1 and 2. When the axle 27 has been removed and the wheel has come loose from the sports item I roller ski, the brake disc 3 can easily be fitted to I removed from the rim 4 of the wheel. The disc brake 3 is to be easily replaceable when worn.

The present invention uses a common friction element 2, which may have different forms and which may have a rubber coating, an aluminium coating or other wearresistant coating, corresponding to that used on, for example, disc brakes for bicycles. The friction element 2 may be attached with a screw 15 as shown in figures 1 and 2 or glued or attached in some other way to the inside of each of the two brake arms 11. To prevent the friction element 2 from being pushed out of position during braking, a recessed area 24 fitting the shape of the friction element may have been made on the inside of the brake arm 11, the side facing the wheel 20 that is, as shown in figures 8 and 9. A corresponding recessed area may be used on any design chosen for brake arms.

On the wheel 20 itself, a brake discs 3 is fitted on each side. It may be recessed into the rim of the wheel and possibly also into parts of the rubber tread (rubber, PU or other suitable material) of the wheel, so that the thickness of the wheel remains unchanged or just increases minimally after the brake discs have been fitted, and so that the diameter of the brake disc can be increased as much as possible in order thereby to reduce the force requirement during braking.

The wheel rim 4 itself, see fig. 3, may be formed in such a way that the protruding "ears" 5 of the disc, see figure 4, can be pressed into the recesses 7 belonging to the wheel rim and be rotated in such a way that the "ears" 5 of the brake disc 3 will lie wedged in the recesses 7 of the rim, see figure 5.

A setscrew 8 is passed through a hole 21, figure 4, in the brake disc 3 and screwed into a pre-threaded hole 9 in the spokes of the wheel rim 4, figure 3, until the outermost part of the setscrew 8 lies at a predefined distance below the outer surface of the brake disc when this is fitted on the rim 4, figure 5.

By placing the setscrew 8 in the wear path of the friction element 2 on the brake disc 3, which will arise after repeated braking, and adjusting the length of the setscrew 8 to the depth of the screw hole 9 in the wheel rim 4, it is possible to predefine how much wear should be allowed on the brake disc 3 before the friction element 2 begins wearing the head of the setscrew 8. When the brake disc 3 has been worn down so much that the friction element 2 begins wearing the head of the setscrew 8, it is time for the brake disc 3 to be replaced.

The setscrew 8 may also prevent the brake disc 3 from unintendedly rotating back so that the "ears" 5 of the brake disc may slip out of the recesses 7 of the rim 4 when the brake is not activated, so that the brake disc comes 3 loose.

Alternatively, the brake discs may be attached with screws directly in, for example, the spokes of the wheel or be attached in some other suitable way to the rim of the wheel. A roller ski 1 with an alternative activating device is shown in figure 14. Instead of a brake cable, an electric motor 31 is used here, which is shown only schematically in the figure. The motor 31, which is connected to a receiver not shown, is activated wirelessly or via a wire from a transmitter not shown, which may be connected to or integrated with the user's pole. On activation, the motor 31, via an angular gear not shown, rotates a double screw 30 pressing the two brake arms 11 evenly together in a manner corresponding to that of the cable solution shown in figure 2, for example. When the brake activation ceases, the rotation of the motor is reversed and the brake arms "jump" back into their starting positions when the rotation of the motor ceases.

In an alternative embodiment, as shown in figure 15, the brake discs may be included in the rim 32. This rim 32 thus extends more or less through the entire width of the wheel, and thereby there is no need for brake discs to be used on the sides of the wheel. The number of parts is reduced. In addition, the installation becomes easier. By optimizing the cooling ribs/slots 25, the weight on the wheel will also be kept under control. As the rim will have the same width all around, the need for machining will be considerably reduced.

A further variant of a rim 35 that also functions as a brake disc is shown in figure 16, where the rim is formed with a number of holes 37 extending through the thickness of the rim. The holes 37 function as both drainage and cooling slots/openings while, at the same time, they reduce the weight of the combined rim-and-brake-disc solution. In the embodiment shown, the diameter of the holes decreases from the periphery of the rim 35 in towards the centre. It will also be possible to achieve a corresponding weight reduction, draining and cooling by other types of hole configurations. This wheel rim 35 needs little or no machining after extrusion has been done. In a manner corresponding to that of the embodiment of figure 15, there is no need to install brake discs on both sides, which simplifies installation and maintenance. The weight will be equivalent to, or even somewhat lower than, that of a conventional rim plus separate brake discs.

Draining holes 26 have been made along the periphery of the brake disc 3 as well, see figures 1, 2 and 4, so that water penetrating between the brake discs lying on either side of the wheel will drain out again. The number and shape of the draining holes 26 and cooling slots 25 may vary.

The brake cable 12 is attached in such a way that the sleeve 16 of the cable, see figure 2, rests against the outer side of one brake arm 11 whereas the brake cable 12 itself is attached 17 to the brake arm 11 of the opposite side. In both brake arms, there is a small slot 18 from the upper edge of the arm 11 down to where, respectively, the brake sleeve 16 and the attachment 17 of the cable are placed, Figure.

On the outer side of both brake arms 11, at the bottom of the cable slot 18, there is a recess 19, see figure 1, in the brake arm 11 so that a cable sleeve 16 and the cable attachment 17, see figure 2, on the opposite arm 11 each lie in a respective recess. When the brake cable 12 is correctly tightened, the resilience of the brake arms 11 will maintain enough tension on the cable all the time so that it does not come loose from the brake arms.

The cable 12 can easily be removed from the brake arms 11 by pressing these slightly towards each other while simultaneously lifting the cable out of the recesses 19 and up and out of the slots 18.

By using the above-mentioned solutions, the design of the brake can easily be changed and adapted for various types of sporting goods, for example skis, in-line skates, and wheel forms/sizes, which increases the range of application and reduces costs in production. Easy retrofitting of brakes will then also be possible on most used roller skis.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.