Patent Description:
The use of automatic opening and closing of sliding doors is commonly known to facilitate access to buildings, rooms and other areas. Conventional sliding doors are driven by a drive unit mounted at the door frame for driving a wagon along a rail via a driving belt. The wagon, in turn, is attached to the sliding door leaf, whereby the sliding door leaf is driven by the drive unit.

The driving belt has to be kept at a high tension at all times since loss of belt tension causes effect loss or in worst case that no torque can be transferred via the driving belt altogether.

Belt tension is strongly correlated to temperature since the belt and the support structure onto which the driven belt wheel is mounted has different temperature expansion properties. Thus, changes in temperature will quickly cause loss in belt tension.

In order for service personnel to adjust the belt tension, sliding door system are often equipped with a spring tensioned bolt tightened to a level indicated on a tension wheel device. However, the tensioning is time consuming and requires a trained professional in order to achieve the correct tensioning in a safe manner.

The inventors has realized that there is a need for improvement in this field. <CIT> discloses an example of a belt tensioning system.

An object of the present invention is therefore to provide a solution to the above-mentioned problem, reducing the disadvantages of prior art solutions.

According to an aspect, a belt tensioning system for tensioning of a belt drive system for transferring from a drive unit of a door operating system to a sliding door leaf of a sliding door assembly is provided.

The belt tensioning system comprises a belt wheel connectable to the belt for torque transfer between said belt wheel and an additional belt wheel of the belt drive system and a belt wheel guiding arrangement. The belt wheel is movably connected to said belt wheel guiding arrangement.

The belt tensioning system further comprises a belt tensioning arrangement operatively connecting the belt wheel and the belt wheel guiding arrangement for adjusting the position of the belt wheel relative the belt wheel guiding arrangement.

The belt tensioning arrangement comprises an engagement member and a tensioning member. The engagement member comprises an eccentric cam structure and the tensioning member is arranged to engage said eccentric cam structure of the tensioning member. The engagement member and the tensioning member is adjustable relative each other to adjust the position of the belt wheel relative the belt wheel guiding arrangement.

According to an aspect, a belt drive system is provided. The belt drive system comprises the belt tensioning system according to the above, a belt and an additional belt wheel. The belt wheel is connected to the additional belt wheel by means of the belt.

According to an aspect, a door operating system is provided. The door operating system comprises a drive unit <NUM> and a belt drive system according to the above for transferring torque from the drive unit to a sliding door of a sliding door assembly.

According to an aspect, a sliding door assembly is provided. The sliding door assembly comprises at least one sliding door leaf and a door operating system according to the above adapted to operate said at least one sliding door leaf.

Embodiments of the invention will be described in the following; reference being made appended drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

An example of a door operating system <NUM> and a sliding door assembly <NUM> will be described in the following. With reference to <FIG>, a sliding door assembly comprises a sliding door leaf <NUM>, sliding door rail <NUM>, and a door operating system <NUM> for operating the sliding door leaf <NUM>. The door operating system <NUM> comprises a drive unit <NUM> for driving the sliding door leaf <NUM>. The sliding door leaf <NUM> is driven by the drive unit <NUM> along the sliding door rail <NUM> which is fixed relative a door frame <NUM>.

The sliding door leaf <NUM> is slidingly connected to the sliding door rail <NUM> for example by means of at least one wagon <NUM>. The wagon <NUM> is preferably engaging with the sliding door rail <NUM> via at least one low friction wheel allowing the sliding door leaf <NUM> to move into a closed and open position along the horizontal sliding door rail <NUM>.

Further referring to <FIG>, the door operating system <NUM> may comprise the drive unit <NUM>, which may be of any conventional type. Typically, the drive unit <NUM> comprises an electric motor and a reduction gearing providing the necessary torque to move the sliding door leaf <NUM> between the open and closed position. According to the present example, a belt drive arrangement connects the drive unit <NUM> with the wagon <NUM>, which works as a drive member. Advantageously, the drive unit <NUM> is adapted to be connected to the door frame <NUM> of the sliding door assembly, or even mounted within the interior of the upper part of the door frame <NUM>. The door operating system <NUM> may thus be mounted to a support structure <NUM> of the sliding door assembly <NUM>.

The door operating system <NUM> may comprise a belt drive system <NUM>. The belt drive system comprises a belt wheel <NUM>, an additional belt wheel <NUM> and a belt <NUM>. The belt <NUM> connects the belt wheel <NUM> and the additional belt wheel <NUM> for torque transfer between said belt wheel <NUM> and the additional belt wheel <NUM>. The belt drive system <NUM> is configured to be driven by the drive unit <NUM>. The belt <NUM> may be defined as a first belt wheel, whereby the additional belt wheel <NUM> may be defined as a second belt wheel <NUM>.

The wagon <NUM> is connected to the belt <NUM> for transfer of torque from the belt drive system <NUM> to the sliding door leaf <NUM>. Hence, the belt <NUM> is configured to be mounted to the sliding door leaf <NUM>.

The belt <NUM> is preferably a synchronous endless drive belt extending between the belt wheel <NUM> and the additional belt wheel <NUM>. In one embodiment, the additional belt wheel <NUM> is directly driven by the drive member <NUM> and the second belt wheel <NUM> is rotationally supported by a console <NUM> being fixed to the door frame <NUM>. The belt wheel <NUM> and the additional belt wheel <NUM> may be cogged wheels. The drive belt <NUM> may accordingly be a cogged belt.

Typically, the door frame <NUM> comprises the support structure <NUM>. The support structure <NUM> may be a top beam. The top beam may extend above the sliding door leaf <NUM>. The belt tensioning system <NUM> as well as the door operating system <NUM> may be mounted to said top beam <NUM>.

Accordingly, the belt wheel <NUM> and the additional belt wheel <NUM> are rotatably coupled to the top beam <NUM>. In most cases, the top beam <NUM> and the belt <NUM> are made of different materials. For example, the top beam <NUM> may be in aluminum and the belt <NUM> is often in a material at least comprising steel, i.e. a steel-reinforced material. Thus, if the sliding door assembly is subjected to changes in temperature, the difference in thermal expansion properties between the top beam <NUM> and the belt <NUM> will cause the belt <NUM> to loose tension due to the top beam <NUM> and the belt <NUM> expanding differently.

According to the invention, this may be addressed by means of having the belt wheel <NUM> comprised in a belt tensioning system, which will be further described with reference to <FIG>.

<FIG> depicts a front view of the belt tensioning system <NUM> for tensioning the belt <NUM> of the belt drive system described with reference to <FIG>.

The belt tensioning system <NUM> comprises the belt wheel <NUM>. The belt wheel <NUM> is connectable to the belt and the additional belt wheel of belt drive system described with reference to <FIG>.

The belt tensioning system <NUM> comprises a belt wheel guiding arrangement <NUM>. The belt wheel <NUM> is movably connected to the belt wheel guiding arrangement <NUM>. Hence, the belt wheel guiding arrangement <NUM> is arranged to accommodate adjustment of the position of the belt wheel <NUM> relative said belt wheel guiding arrangement <NUM>. Worded differently, the belt wheel guiding arrangement <NUM> is arranged to accommodate adjustment of the belt wheel <NUM> relative the additional belt wheel <NUM>.

Further, the belt tensioning system <NUM> comprises a belt tension arrangement <NUM> for adjusting the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM> (and the additional belt wheel <NUM>). The belt tension arrangement <NUM> operatively connects the belt wheel <NUM> and the belt wheel guiding arrangement <NUM>. Accordingly, the belt tensioning arrangement <NUM> is arranged between the belt wheel <NUM> and the belt wheel guiding arrangement <NUM>.

The belt tensioning arrangement comprises an engagement member <NUM> and a tensioning member <NUM>. The engagement member <NUM> comprises an eccentric cam structure <NUM>. The tensioning member <NUM> is arranged to engage said eccentric cam structure <NUM> of the engagement member <NUM>. Thus, the tensioning member <NUM> is arranged to be in contact with said eccentric cam structure <NUM>.

The engagement member <NUM> and the tensioning member <NUM> are adjustable relative to each other to adjust the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM>. Thus, the point(s) of engagement between the engagement member <NUM> and the tensioning member <NUM> on the eccentric cam structure <NUM> is adjustable such that relative adjusting of the tensioning member <NUM> and the engagement member <NUM> causes adjustment of the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM>. Accordingly, the engagement member <NUM> and the tensioning member <NUM> may be selectively movable relative to each other.

The belt tensioning system according to the above may thus be operated in a user friendly manner simply by adjusting the belt tensioning arrangement compared to a conventional belt tensioning system where the user has to use particular tools and follow a hard to interpret scale in order to set the correct tension by means of incremental turning of multiple adjustment screws. The tensioning system according to the invention may simplify this process by enabling usage of a suitable eccentric cam structure guiding the user to the correct tension.

The tensioning of the belt <NUM> may be achieved by rotation of the engagement member <NUM> due to the tensioning member engaging the eccentric cam structure <NUM>. The rotation of the engagement member <NUM> causes the belt wheel <NUM> to move relative the belt wheel guiding arrangement <NUM>. Hence, the engagement member <NUM> is adjustable relative the tensioning member <NUM> by means of rotation of said engagement member <NUM>. In one embodiment, the eccentric cam structure <NUM> is formed by an eccentric disc <NUM>. In one embodiment, the engagement member <NUM> is adjustable relative the tensioning member <NUM> by means of rotation of said eccentric disc <NUM>.

As is recognizable by the skilled person, the positioning of the engagement member and the tensioning member may be possible to alter. According to the invention, the engagement member <NUM> is operatively connected to the belt wheel <NUM> and the tensioning member <NUM> is operatively connected to the belt wheel guiding arrangement <NUM>. Thus, the engagement member <NUM> is mounted to the belt wheel <NUM>. The belt wheel <NUM> is rotatable relative said engagement member <NUM>. This allows for a less complex and more intuitive to use belt tensioning system. However, in an alternative embodiment, which is not part of the invention, the tensioning member <NUM> may be operatively connected to the belt wheel <NUM> while the engagement member is operatively connected to the belt wheel guiding arrangement <NUM>.

The belt tension system <NUM> may comprise a mounting portion <NUM>. The mounting portion <NUM> is arranged to be mounted to a support structure <NUM> of the sliding door assembly <NUM> (shown in <FIG>). The mounting portion <NUM> may be arranged to be mounted to the support structure by means of fastening elements <NUM>.

The belt wheel guiding arrangement <NUM> is fix relative a support structure of the sliding door assembly. The belt wheel guiding arrangement <NUM> may be connected to, e.g. fix to, the mounting portion <NUM>. Thus, the belt wheel guiding arrangement <NUM> may be arranged to be mounted to the support structure <NUM> by means of the mounting portion <NUM>.

The belt wheel guiding arrangement <NUM> is arranged to allow movement of the belt wheel <NUM> along a tensioning axis A. The tensioning axis A extends parallel with the belt.

In one embodiment, the belt tensioning system comprises a first plate element <NUM>. The first plate element is connected to the mounting portion <NUM>. The first plate element <NUM> extends along the tensioning axis A. The first plate element <NUM> may comprise the belt wheel guiding arrangement <NUM>.

In one embodiment, the belt tensioning system <NUM> may further comprise a fixating member <NUM>. The fixating member <NUM> is adapted to releasably fixate the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM>. Thus, once the position of the belt wheel <NUM> has been adjusted, the belt wheel <NUM> may be fixated in the adjusted position relative the belt wheel guiding arrangement <NUM>. In order to allow for adjustment, the fixating member may be released. Releasable may herein refer to disengagable, i.e. arranged to be in an engaged position and a disengaged position.

The fixating member <NUM> may be arranged to releasably fixate the engagement member <NUM> relative the tensioning member <NUM>. Thus, the fixation of the position of the engagement member and the securing of the position of the belt wheel may be performed in one operation, allowing for a more user-friendly and time efficient belt tensioning system. In one embodiment, the fixating member <NUM> may be arranged to releasably fixate the engagement member <NUM> to belt wheel guiding arrangement <NUM>.

The fixating member <NUM> will later be further described with reference to <FIG>.

Further referencing <FIG>, the tensioning member <NUM> may be biased against the engagement member <NUM>. This ensures that the engagement between the engagement member and the tensioning member is maintained. Further, it allows for adjusting of the tension in the belt without manually setting up the tensioning member relative the engagement member each time. Accordingly, the tensioning member <NUM> is adjustable relative the engagement member <NUM> at least by means of being biased against said engagement member <NUM>.

Biased against herein refers to the tensioning member <NUM> being spring-loaded to exert a contact force onto the eccentric cam surface <NUM> of the engagement member <NUM>.

The tensioning member <NUM> may comprise a tensioning element <NUM>. The tensioning element <NUM> may be an elongated element such as a screw.

A first end <NUM> of said tensioning element may be arranged to engage the engagement member <NUM>.

The belt tensioning system <NUM> may further comprise a tensioning guide arrangement <NUM>. The tensioning guide arrangement <NUM> is adapted to guide movement of the tensioning element <NUM> relative the engagement member <NUM>.

The tensioning guide arrangement may be fix relative the mounting portion <NUM>. In an alternative embodiment, said tensioning guide arrangement may be arranged to be directly fixated to the support structure of the sliding door assembly.

In one embodiment, the tensioning element <NUM> may be connected to the tensioning guide arrangement <NUM> by means of a spring <NUM>. Said spring <NUM> being arranged to bias the tensioning element <NUM> against the engagement member <NUM>. A first end of the spring <NUM> may be connected to the first end <NUM> of the tensioning element <NUM>. A second end of the spring <NUM> may be connected to the tensioning guide arrangement <NUM>.

The tensioning element <NUM> may extend along the tensioning axis A. The tensioning element <NUM> may be movable along said tensioning axis A. The spring <NUM> may be coaxial to said tensioning element <NUM>. The tensioning axis A may be aligned with the eccentric cam structure <NUM> of the engagement member <NUM> such that the tensioning element <NUM> engages the eccentric cam structure <NUM>. Accordingly, the eccentric outer surface of the eccentric cam structure <NUM> may extend orthogonally to the tensioning axis A.

The tensioning element <NUM> may comprise a second end <NUM>. Said second end <NUM> is opposite to the first end <NUM>. The second end <NUM> may be a guided by means of the tensioning guide arrangement <NUM>. The second end <NUM> may be a free end of the tensioning element <NUM>.

As depicted in <FIG>, the belt tensioning system <NUM> may further comprise a tensioning indicating arrangement <NUM>. The tensioning indicating arrangement <NUM> is intended for providing an indication on the tension of the belt to a user.

Accordingly, the tension indicating arrangement <NUM> is arranged to indicate at least one predefined position of a reference point <NUM> of the tensioning element <NUM> relative the engagement member <NUM>. Each of the at least one predefined position is associated with a corresponding position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM>.

The reference point may be the second end <NUM> or an arbitrary chosen point along the tensioning element <NUM>. By using the tension indicating arrangement, the service personnel is directly informed regarding suitable positions of the belt wheel. Said suitable positions may be chosen to accommodate for different tensions of the belt. The service personnel may thus adjust the engagement member and the tensioning member according to a predefined position of the reference point of the tensioning element indicated by the tensioning indicating arrangement.

The tensioning indicating arrangement may comprise a set of indicators of predefined positions along the tensioning axis A. Said set of indicators may comprise a scale with markings <NUM>, <NUM>, <NUM> indicating said predefined positions.

The tensioning indicating arrangement may be positioned proximal to the tensioning element <NUM>. In one embodiment, the tensioning indicating arrangement is positioned on the tensioning guide arrangement <NUM> or the mounting portion <NUM>. Preferably however, the tensioning indicating arrangement <NUM> is positioned on the first plate element <NUM>, preferably proximal to the tensioning member <NUM>.

The tensioning member <NUM> may comprise an adjustment element <NUM> adapted to adjust the biasing of said tensioning member <NUM>, i.e. adjusting tension of the spring <NUM>. Thus, the force which the tensioning member is engaging the engagement member may be adjusted by means of said adjustment element. This allows for a more robust and reliable belt tensioning system less susceptible to wear or failure due to the engagement member and the tensioning member coming out of engagement.

The adjustment element <NUM> may be arranged adjacent to an adjustment flange <NUM> of the tensioning guide arrangement. The adjustment flange <NUM> comprises an aperture for movably receiving the tensioning element <NUM>.

In one embodiment, the spring <NUM> is mounted to the adjustment flange <NUM> and the first end <NUM> of the tensioning element <NUM>. In one embodiment, the tensioning element <NUM> comprises a threaded portion, whereby the adjustment element <NUM> is mounted to said threaded portion for adjusting the tension of the spring <NUM> relative the adjustment flange <NUM>. The adjustment element <NUM> may be a nut.

The tensioning element <NUM> may comprise a head portion. The first end <NUM> may be said head portion. The head portion may protrude radially from the tensioning axis A relative an intermediate portion of the tensioning member <NUM> to prevent passage of the first end through the aperture of the adjustment flange <NUM>.

In one embodiment, the tensioning guide arrangement <NUM> may comprise a stop flange <NUM>. Said stop flange <NUM> may comprise an aperture for movably receiving the tensioning member <NUM>. The stop flange <NUM> is arranged along the tensioning axis A distant from the engagement member <NUM> relative the adjustment flange <NUM>. The tensioning member <NUM> may comprise a stop element <NUM>. The stop element <NUM> may protrude radially from the tensioning axis A relative the tensioning member <NUM> to prevent passage of the tensioning member <NUM> through the aperture of the stop flange <NUM> beyond said stop element <NUM>.

In one embodiment, the stop element <NUM> is mounted to the threaded portion of the tensioning element <NUM> for adjusting the position of the stop element <NUM> relative the tensioning element <NUM> along the tensioning axis A. The stop element <NUM> may be a nut.

In one embodiment, the first plate element <NUM> may comprise the tensioning guide arrangement <NUM>. The stop flange <NUM> and/or the adjustment flange <NUM> may accordingly form protruding portions of said first plate element <NUM>.

Thus, the tensioning member <NUM> is movably connected to said first plate element <NUM>. Further, the belt wheel <NUM> the belt wheel <NUM> may be rotatably and movably connected to said first plate element <NUM> by means of the belt wheel guiding arrangement <NUM>.

As depicted in <FIG>, the belt wheel guiding arrangement <NUM> comprises an elongated recess <NUM> for receiving a guiding member connected to the belt wheel <NUM> for guiding the belt wheel <NUM>. The elongated recess may extend along the tensioning axis A. The guiding member may thus extend orthogonally to the tensioning axis A and through the elongated recess <NUM>. The belt wheel <NUM> is thus movably connected to the elongated recess <NUM> by means of said guiding member. The first plate element <NUM> may comprise the belt wheel guiding arrangement and said elongated recess <NUM>.

The skilled person realizes that the belt wheel guiding arrangement <NUM> may be arranged in different manners allowing for guided movement of the belt wheel <NUM>. In alternative embodiment, the belt wheel <NUM> may be mounted to a movable console slidably connected to a track forming the guide arrangement.

Turning to <FIG>, a cross-section view of a part of the belt tensioning system is depicted. The belt wheel <NUM> is rotatable about a belt wheel axis B. The belt wheel axis B extends orthogonally to the tensioning axis A described with reference to <FIG>.

As seen in said <FIG>, the fixating member <NUM> comprises a fixating element <NUM>, such as a screw member. The fixating element <NUM> may be rotatably coupled to the belt wheel <NUM>. The fixating element <NUM> may extend through the belt wheel guiding arrangement <NUM> and the engagement member <NUM>. Upon tightening of the fixating element <NUM>, the engagement member <NUM> is locked into position and the position of the belt wheel <NUM> is fixated relative the belt wheel guiding arrangement <NUM>. Upon loosening of the fixating element <NUM> the engagement member is rotatable relative the fixating element <NUM> and the belt wheel <NUM> is movable relative the belt wheel guiding arrangement <NUM>.

This allows for a less complex tensioning, since the fixating element allows may secure or enable the positioning of both the belt wheel and the engagement member only by one action.

The fixating element <NUM> may constitute the guide member guided in the elongated recess <NUM>. The elongated recess <NUM> may thus be adapted to receive a portion of the fixating element <NUM> for guiding the belt wheel <NUM>.

The engagement member <NUM> may thus comprise a through-hole for receiving the fixating element <NUM>. The through-hole may be aligned with the belt wheel axis B.

The fixating element <NUM> may extend along the belt wheel axis B. The fixating element <NUM> may be rotatably coupled to the belt wheel <NUM> by means of a bearing <NUM> comprising bearing mounting <NUM> adapted to receive said fixating element <NUM>. The fixating element <NUM> is fixedly connected to the bearing mounting and the bearing <NUM> is adapted to allow relative rotation between the fixating element <NUM> and the belt wheel <NUM>.

The fixating element <NUM> may extend through the first plate element <NUM> by means of extending through the elongated recess <NUM> of the belt wheel guiding arrangement <NUM> of said first plate element <NUM>. Thus, fixation of the fixating member <NUM> fixates the engagement member <NUM> to the first plate element <NUM> and fixates the positon of the belt wheel <NUM> relative the first plate element <NUM>.

In one embodiment, the belt tensioning system may further comprise a distance element <NUM> arranged between engagement member <NUM> and the first plate element <NUM> along the belt wheel axis B. This ensures proper alignment between the tensioning member and the engagement member. The fixating element <NUM> may extend through said distance element <NUM>. The distance element <NUM> may be an annular distance element.

Referencing <FIG>, a top view of the belt tensioning system is depicted. The belt tensioning system <NUM> may further comprise a retention heel <NUM>. The retention heel <NUM> may protrude from the mounting portion <NUM>. The retention heel <NUM> is arranged to engage a corresponding surface of the sliding door assembly <NUM>. This allows for a more stable mounting of the belt tensioning system.

The belt tensioning system may further comprise a second plate element <NUM>. The second plate element <NUM> may interconnect the first plate element <NUM> and the mounting portion <NUM>. The second plate element <NUM> may extend along the tensioning axis A.

In one embodiment, the second plate element <NUM> may be orthogonal to the first plate element <NUM> and the mounting portion <NUM>. The mounting portion <NUM> and the first plate element <NUM> may be parallel. Preferably, the mounting portion <NUM> and the first plate element <NUM> are arranged to be parallel to the at least one sliding door leaf of the sliding door assembly.

In one embodiment, the first and second plate element and the mounting portion may be in aluminum.

According to an aspect, a belt drive system <NUM> is provided. The belt drive system <NUM> comprises the belt tensioning system <NUM> according to any of the previously described embodiments, the belt <NUM> and the additional belt wheel <NUM>. The belt wheel <NUM> of the belt tensioning system <NUM> is connected to the additional belt wheel <NUM> by means of the belt <NUM>.

According to an aspect, a door operating system <NUM> is provided. The door operating system <NUM> comprises the drive unit <NUM>. The door operating system <NUM> comprises the belt drive system <NUM> for transferring torque from the drive unit <NUM> of said door operating system <NUM> to a sliding door leaf <NUM> of the sliding door assembly <NUM>.

According to an aspect, a sliding door assembly <NUM> is provided. The sliding door assembly comprises the at least one sliding door leaf <NUM> and the door operating system <NUM>. The door operating system is adapted to operate said at least one sliding door leaf <NUM>.

According to an aspect, a method for adjusting the tension of the belt in a belt drive system <NUM> according to the above is provided. The method comprises adjusting the engagement member <NUM> and the tensioning member <NUM> relative each other to adjust the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM>.

The method may further comprise fixating the position of the belt wheel <NUM> relative the belt wheel guiding arrangement <NUM> by means of the fixating member <NUM>.

The method may further comprise fixating the engagement member <NUM> relative the tensioning member <NUM> by means of the fixating member <NUM>.

Claim 1:
A belt tensioning system (<NUM>) for tensioning a belt (<NUM>) of a belt drive system (<NUM>) for transferring torque from a drive unit (<NUM>) of a door operating system (<NUM>) to a sliding door leaf (<NUM>) of a sliding door assembly (<NUM>), the belt tensioning system comprising:
a belt wheel (<NUM>) connectable to the belt (<NUM>) for torque transfer between said belt wheel (<NUM>) and an additional belt wheel (<NUM>) of the belt drive system (<NUM>);
a belt wheel guiding arrangement (<NUM>), the belt wheel (<NUM>) being movably connected to said belt wheel guiding arrangement (<NUM>); and
a belt tensioning arrangement (<NUM>) operatively connecting the belt wheel (<NUM>) and the belt wheel guiding arrangement (<NUM>) for adjusting the position of the belt wheel (<NUM>) relative the belt wheel guiding arrangement (<NUM>),
wherein the belt tensioning arrangement (<NUM>) comprises an engagement member (<NUM>) and a tensioning member (<NUM>), whereby the engagement member (<NUM>) comprises an eccentric cam structure (<NUM>) and the tensioning member (<NUM>) is arranged to engage said eccentric cam structure (<NUM>) of the engagement member (<NUM>), the engagement member (<NUM>) and the tensioning member (<NUM>) being adjustable relative each other to adjust the position of the belt wheel (<NUM>) relative the belt wheel guiding arrangement (<NUM>), characterized in that the engagement member (<NUM>) is mounted to the belt wheel (<NUM>) and the belt wheel (<NUM>) is rotatable relative said engagement member (<NUM>).