Patent Description:
Shower heads can be fixed to a wall using a slide rail system. The shower head is held in a holder that allows the shower head to be swivelled, tilted, removed and replaced. The holder is part of a chassis that is fixed to a rail that extends vertically along the wall. The chassis is able to move up and down the rail, and can be secured in place, to allow the height of the shower head to be set.

It is known to secure the chassis using a clamp mechanism that can be tightened and loosened using a rotatable handle, allowing repositioning of the shower head. This arrangement requires the user to adjust the position of the shower head with both hands, one to operate the clamp mechanism and the other to move the chassis along the rail. This can make adjustment difficult for some users with limited dexterity.

Document <CIT> discloses a sliding rail consisting of two standards reciprocally defining a slotting wherein there is housed a shower support, into which there is obtained a recess intended to partly house a block forming a sliding guide for the support on the slotting, said sliding being allowed by the horizontal pivoting of the support relative to the block and by the consequent insertion or removal of the teeth provided on the support.

Document <CIT> discloses a shower head adjustment assembly consisting of a guide and a slide fastened to the shower head support and comprising a cam element rigidly connected to the shower head support, and a catch element hinged to the cam element. Specifically, the cam element and the catch element are arranged on opposite sides of a sliding wall of the guide and define a reversible locking position of the slide by compressing the sliding wall from opposite sides.

According to the invention as defined by claim <NUM>, there is provided a slide rail mechanism having a chassis for holding a shower head, wherein the chassis is slideable along a slide rail, and includes a holding means for holding the chassis at a position along the slide rail wherein the holding means is actuated by movement of the chassis.

Embodiments of the invention will now be discussed, by way of example only, with reference to the accompanying drawings, in which:.

<FIG> illustrates a shower rail system <NUM> that can be used for supporting a shower head (not shown), which may, for example, be over a bath or shower tray (not shown). The system <NUM> includes a slide rail <NUM>, which is fixed vertically along a wall (not shown) and a slider assembly <NUM> for holding the shower head. As will be discussed below in more detail, the slider assembly <NUM> is slideable along the slide rail <NUM>, to set the height of the shower head.

<FIG> only shows a section of the slide rail <NUM>, and it will be appreciated that the slide rail <NUM> may extend for any length, and be fixed to the wall in any suitable manner, as is known in the art. In one example, the slide rail <NUM> may have a length of <NUM> metre or <NUM> metre. The slide rail <NUM> may include stops (not shown) to prevent the slider assembly <NUM> being slid off the ends of the slide rail <NUM>.

In the example shown in <FIG>, the slider assembly <NUM> includes a chassis <NUM> having a first chassis member <NUM>, which is slidably attached to the slide rail <NUM>, and a second chassis member <NUM>, including a grip <NUM>. The grip <NUM> is formed of a partially open cylinder, and is sized for holding the shower head by friction or mechanical fit. The shower head may comprise a handset connected to a source of water (not shown) by a flexible hose (not shown). The water source may be, for example, a mixer valve or an instantaneous electric water heater. The water source may provide a supply of temperature controlled water to the shower head. The shower head may be detachable from the grip <NUM>.

The grip <NUM> is connected to the second chassis member <NUM> by a first pivot <NUM>, such that the shower head can be tilted around a horizontal axis (as shown by arrow A). The second chassis member <NUM> is in turn connected to the first chassis member <NUM> by a second pivot <NUM>, so that the shower head may be rotated around a second axis, parallel to the slide rail <NUM>, and perpendicular to the first axis (as shown by arrow B).

<FIG> shows the slide rail <NUM> in more detail. As can be seen from <FIG>, the slide rail <NUM> is of substantially hollow cross section, with a substantially flat front face <NUM>, and curved edges 19a, 19b. The rear face <NUM> is formed with a pair of projections <NUM> that can be used for fixing the slide rail <NUM> to the wall. In this example, the slide rail <NUM> is fixed to the wall along its length.

<FIG> show the first chassis member <NUM> in more detail. The first chassis member <NUM> is formed of a vertically extending wall <NUM> that is shaped to fit around the brake saddle <NUM> and slide rail <NUM> The rear face <NUM> of the first chassis member <NUM> is open to accommodate the projections <NUM> for attaching the slide rail <NUM> to the wall. A pair of horizontal arms <NUM> extend from the front face <NUM> for connection to the second chassis member <NUM>. The second chassis member <NUM> is received between the arms <NUM>, and then connected by a pin <NUM> (<FIG>) passing through openings <NUM> in the arms <NUM> and second chassis member <NUM> to form the second pivot <NUM>.

The slider assembly <NUM> further includes a brake saddle <NUM> and a brake shoe <NUM>. <FIG> shows the brake saddle <NUM>, and <FIG> show the brake shoe <NUM>. As best shown in <FIG>, the brake saddle <NUM> and brake shoe <NUM> are received inside the first chassis member <NUM>, between the first chassis member <NUM> and the slide rail <NUM>. These components co-operate to grip the slide rail <NUM>, to hold the slider assembly <NUM> (and hence the shower head) at a chosen height.

As with the first chassis member <NUM>, the brake saddle <NUM> is formed to fit around the slide rail <NUM>, with an opening <NUM> in the rear face <NUM> to accommodate the projections <NUM> for fitting the slide rail <NUM> to the wall.

The brake saddle <NUM> also includes an opening <NUM> in its front face <NUM>. The opening <NUM> includes a narrow rectangular top section 51a and a wider rectangular base section 51b, such that it is substantially T-shaped. The opening <NUM> is divided into two by a rectangular wall projection <NUM> (which may also be described as a bridge <NUM>, as it straddles the opening <NUM> in the embodiment shown) that is formed above the wider base section 51b. The wall projection <NUM> is spaced from the front face <NUM> of saddle <NUM>, and is sized to fit into a recess <NUM> in the inner face <NUM> of the first chassis member <NUM> (<FIG>). At the top of the opening <NUM>, a pair of projections <NUM> are provided with cylindrical through holes <NUM>. Recesses <NUM> (one only shown) in the front face <NUM> of the brake saddle <NUM> align with the through holes <NUM>.

The brake shoe <NUM> is generally of the form of an elongate body <NUM> having a rear face <NUM> (see <FIG>) arranged to face the front face <NUM> of the slide rail <NUM>, and an opposing front face <NUM> (see <FIG>) arranged to face the inner face <NUM> of the first chassis member <NUM>.

The top of the brake shoe <NUM> includes a cylindrical hinge pin <NUM> mounted on a hinge mount <NUM>, such that the hinge pin <NUM> projects from both sides of the brake shoe <NUM>. The hinge pin <NUM> is sized to be received in the through holes <NUM> in the projections <NUM> on the brake saddle <NUM> and the recesses <NUM> to form a pivot connection at the top of the brake shoe <NUM>.

The body <NUM> of the brake shoe <NUM> includes a substantially rectangular portion <NUM> towards the top, and a shaped cam region <NUM> at the base. The shaped cam region <NUM> is formed of a pair of cam surface 77a, 77b that are angled such that, when the shower rail system <NUM> is assembled, the cam surfaces 77a, 77b extend obliquely to the slide rail <NUM>.

The cam surfaces 77a, 77b form a space <NUM> on the rear face <NUM> of the brake shoe <NUM>, and an outward facing projection <NUM> on the front face <NUM>, with an apex <NUM>. The maximum spacing between the cam surfaces 77a, 77b and the slide rail <NUM> is at the apex. In the unclaimed embodiment being described, the cam region <NUM> is symmetrical about the apex <NUM>. In alternative unclaimed embodiments, the cam region <NUM> may not be symmetrical about the apex <NUM>.

Immediately above the cam region <NUM>, the body <NUM> of the brake shoe <NUM> includes a recess <NUM> on the front face <NUM>. A resiliently deformable spring member <NUM> is mounted in the recess <NUM>. Above this, the body <NUM> of the brake shoe <NUM> includes a recess on the rear face <NUM>. A brake pad <NUM>, formed of rubber, EPDM or other high friction material is mounted in the recess. The brake pad <NUM> is adjacent the hinge mount <NUM>.

<FIG> show the slider assembly <NUM> mounted on the slide rail <NUM>.

The brake shoe <NUM> and brake saddle <NUM> are arranged such that when the brake shoe <NUM> is mounted on the brake saddle <NUM> through the hinge connection, the region of the front face <NUM> of the shoe <NUM> opposite the brake pad <NUM> is positioned within the top section 51a of the opening <NUM> in the brake saddle <NUM>, and the projection <NUM> on the base part of the shoe brake <NUM> projects through the lower section 51b of the opening <NUM>.

The spring member <NUM> seats against the wall projection <NUM> of the brake saddle <NUM> and biases the brake shoe <NUM> towards the front face <NUM> of the slide rail <NUM>.

The first chassis member <NUM> fits over the assembled brake saddle <NUM> and brake shoe <NUM> and is aligned by spacers <NUM> (<FIG>) on the inner front face <NUM> of the first chassis member <NUM>. The inner front face <NUM> of the first chassis member <NUM> includes a tab <NUM> projecting perpendicular to the face <NUM>, into the volume defined by the first chassis member <NUM>. The tab <NUM> is adjacent the cam region <NUM> and includes a cam pin <NUM> projecting perpendicular to the tab <NUM> into the concave space <NUM> defined by the cam surfaces 77a, 77b.

In normal use, the cam pin <NUM> rests at the apex <NUM> formed between the two cam surfaces 77a, 77b. In this position, the brake pad <NUM> engages with the front face <NUM> of the slide rail <NUM> under the biasing of the spring <NUM> and prevents movement of the slider assembly <NUM> relative to the slide rail <NUM>. In this way the position of the shower head is fixed.

If a user wants to move the shower head higher or lower, they push or pull the chassis <NUM> up or down the slide rail <NUM>. This causes the cam pin <NUM> to move up the first cam surface 77a or down the second cam surface 77b. This causes the brake shoe <NUM> to rotate around the hinged connection, lifting the brake pad <NUM> away from the front face <NUM> of the slide rail <NUM> against the biasing of the spring <NUM>, and allowing the whole slider assembly <NUM> to be moved up or down. When the user releases the chassis <NUM>, the spring <NUM> causes the pin <NUM> to return to the apex <NUM>, and the brake pad fully reengages the rail <NUM> to secure the slider assembly <NUM> at the selected position along the length of the slide rail <NUM>.

The brake pad <NUM> holds the slider assembly <NUM> in place by providing a constant frictional force. The friction should be sufficient that it is not overcome by the weight of the slider assembly <NUM> and shower head. Therefore, the user must provide a force over a threshold, determined by the spring <NUM>, before the cam pin <NUM>, and hence slider assembly <NUM> are moved. The force may be applied by the user pushing or pulling a part of the chassis <NUM> directly or indirectly, for example through the shower head or through a water supply hose connected to the shower head.

In the unclaimed embodiment being described, when the slider assembly <NUM> passes along any section of the slide rail <NUM> which needs a higher or lower amount of force as compared to the expected value (e.g. due to higher friction resulting from a scratched rail surface), the cam regulates friction of the brake shoe <NUM> accordingly to compensate for the difference. Such unclaimed embodiments may be described as "self-regulating" or "constant force" systems as the friction is adjusted to maintain an at least substantially constant level of force requirement.

In the unclaimed embodiment being described, the cam pin <NUM> regulates friction of the brake shoe <NUM> because the extent to which the cam pin <NUM> moves along the cam surface 77a, 77b increases with increased friction, and decreases with decreasing friction. As such, if the friction between the brake pad and the slide rail <NUM> increases for any reason then the brake pad <NUM> will 'drag' more and the slider assembly <NUM> will move accordingly to reduce the spring pressure, balancing the force. Conversely, if the friction between the brake pad <NUM> and the slide rail <NUM> reduces, then the cam <NUM>, <NUM> will operate proportionally to increase spring pressure.

For example, if the slider assembly <NUM> encounters a stiffer section of the slide rail <NUM> (for example due to dirt or other reside on the slide rail, or a lack of a lubricant such as water or soap present on another part of the slide rail) then the brake pad <NUM> tends to 'slow down' on at this point on the rail <NUM>. Continued upward or downward force from the user causes the chassis <NUM> to continue moving relative to the brake shoe <NUM> and cam surfaces 77a, 77b. This continued movement forces the tab <NUM> and cam pin <NUM> (part of the chassis <NUM>) to move relative to the cam surfaces 77a, 77b (part of the brake shoe <NUM>), moving the shoe <NUM> either in or out and thus adjusting the force relatively until the stiff section is traversed. At this point, the lesser force on the brake shoe <NUM> reverses the process and reapplies the relevant pressure.

<FIG> illustrate an alternative shower rail system <NUM>. As with the first example discussed above, the shower rail system includes a slide rail <NUM>, and a slider assembly <NUM> mounted on the slide rail <NUM>. The slider assembly <NUM> includes a chassis <NUM> having a first chassis member <NUM> and a second chassis member <NUM>, in a similar manner as discussed above, although in this example, the arms <NUM> are formed in the second chassis member <NUM>, and fit around a projection extending from the first chassis member <NUM>. It will be appreciated that this could be applied to the first example and vice versa.

As shown from <FIG>, the slide rail <NUM> and slider assembly <NUM> are of a different construction to that of the first example discussed above.

<FIG> and <FIG> show the slide rail <NUM> of the second example. As can be seen, the slide rail <NUM> is of hollow construction, and includes a front face <NUM> with a substantially flat central portion, and curved edges 119a, 119b. However, the rear face <NUM> of the slide rail <NUM> is open. A pair of projections <NUM> extend from the front face <NUM>, through the hollow centre, and out of the rear face <NUM>. A pair of flat cross members <NUM> extend from the curved edges 119a, 119b to the projections <NUM>, in the hollow centre of the slide rail <NUM>. A brace <NUM>, having a face parallel to the flat cross members <NUM> of the slide rail <NUM>, extends vertically from the projections <NUM>. The brace <NUM> is used for spacing the slide rail <NUM> from the wall (not shown).

In this example, the first chassis member <NUM> is formed of a wall <NUM> having an at least substantially flat front face <NUM>, and edges shaped to fit around the slide rail <NUM>. The wall <NUM> may be fully curved to fit in other embodiments. The wall <NUM> has an opening <NUM> formed in the back of the first chassis member <NUM> to accommodate the projections <NUM> and brace <NUM> of the slide rail <NUM>. On each edge of the opening <NUM>, a vertical wall <NUM> extends vertically, at a right angle to the rear face <NUM> of the slide rail <NUM>, into the centre of the slide rail <NUM>. At or near the top of each wall <NUM>, a first brake stop <NUM> projects at a right angle to the wall <NUM>, further into the opening on the rear face <NUM>. At or near the bottom of each vertical wall <NUM>, a second brake stop <NUM> projects at a right angle to the wall <NUM>, further into the opening on the rear face <NUM>. The brake stops <NUM>, <NUM> only extend a short distance vertically, and still provide sufficient opening for the projections <NUM> when the first chassis member <NUM> is fitted to the slide rail <NUM>.

At or near the centre of each wall <NUM> (vertically and horizontally) a brake pivot <NUM> is provided. A brake arm <NUM> is mounted on one of the brake pivots <NUM>, extending vertically along the wall <NUM>. The brake arm <NUM> is mounted on the pivot <NUM> such that it can rotate about an axis through the centre of the pivot <NUM>, perpendicular to the slide rail <NUM>, and the wall <NUM>.

At a first end of the brake arm <NUM>, a first brake end 151a is formed. At a second end of the brake arm <NUM>, a second brake end 151b is formed. The brake arm <NUM> includes an annular hub <NUM> arranged around the brake pivot <NUM>. A first arm section <NUM> extends between the hub <NUM> and the first brake end 151a, and a second arm section <NUM> extends from the hub <NUM> to the second brake end 151b.

The first arm section <NUM> is connected to the hub <NUM> on one side of the pivot <NUM>, towards the front face <NUM> of the slider <NUM>. The first arm section <NUM> is curved so that the first brake end 151a is positioned on the side of the first brake stop <NUM> facing the brace <NUM> of slide rail <NUM>.

The second arm section <NUM> is connected to the opposite side of the hub <NUM> to the first arm section <NUM>. The second arm section <NUM> is curved such that the second brake end 151b is positioned on the side of the second brake stop <NUM> facing the cross member <NUM> of slide rail <NUM>.

The brake arm <NUM> is biased by a spring 1100b acting between first brake stop <NUM> and brake end 151a so that the brake end 151a engages the brace <NUM> and the brake end 151b engages the cross member <NUM> with a force sufficient to hold the slider assembly <NUM> in any selected position along the length of the slide rail <NUM>.

A pin <NUM> is fitted to the lower part of the vertical wall <NUM>, adjacent the brake arm <NUM>. The pin <NUM> extends out of the wall, parallel to the brake stops <NUM>, <NUM>, and engages the second arm section <NUM>. The pin <NUM> is formed with a cam projection <NUM>. A manual mechanism <NUM>, fitted in an aperture <NUM> in the rear face <NUM> of the first chassis member <NUM>, adjacent the pin <NUM> is provided to rotate the cam projection to adjust the position of the brake ends 151a, 151b relative to the brake stops <NUM>, <NUM>.

In use, the first chassis member <NUM> is fitted over the slide rail <NUM>. The first brake stop <NUM> rests against the cross member <NUM>, and the first brake end 151a rests against the brace <NUM> under the biasing of the spring 1100b. The second brake stop <NUM> rests against the brace <NUM>, and the second brake end 151b rests against the cross member <NUM> under the biasing of the spring 1100a. In alternative or additional embodiments, a single spring, or more than two springs, may be used.

Without input from the user, the biasing of the brake arm <NUM> provides a constant friction force holding the first chassis member <NUM> in place.

When a user applies a force to move the slider assembly <NUM> up the rail <NUM>, for example by pushing the first chassis member <NUM>, the force tends to cause the brake stops <NUM>, <NUM> to lift away from the slide rail <NUM> in the embodiment shown (in some embodiments it is possible for these stops to remain in contact with the slide rail <NUM>, but with a very low, and preferably at least substantially zero Newtons (0N) force therebetween). As a result, the frictional force is reduced and the slider assembly <NUM> can move up the slide rail <NUM>.

When the user applies an upward force to the arm projection <NUM> this generates a moment of rotation which relaxes pressure on the fixed brake stops <NUM> and <NUM> so that only the brake ends 151a, 151b (which in this case take the form of sprung pads) remain in contact with the rail <NUM> under the biasing spring force and so resist the upward force. The slider assembly <NUM> can then move up the slide rail <NUM>.

Thus, the brake arms <NUM> generally do not rotate - rather the chassis <NUM> rotates with respect to the brake arm <NUM>. The chassis rotation is generally only slight, but sufficient that pressure is taken off the brake stops <NUM> and <NUM>.

Once the user stops moving the slider assembly <NUM> the brake arm <NUM> applies sufficient frictional force to hold the slider assembly <NUM> in position. More particularly, in the embodiment being described, the brake stops <NUM>, <NUM> return to contact with the slide rail <NUM>, so applying a sufficient frictional force to hold the slider assembly <NUM> in position.

In the embodiment being described, when the system <NUM> is at rest, the brake pads and brake ends provide (for example) <NUM> Newtons of force to the slide rail <NUM>, in this case as a result of the biasing springs 1100a, 1100b. The user then applies an upward force to the second chassis member <NUM> which provides a rotational moment. This moment may not be sufficient for the chassis <NUM> to rotate. In this example, the chassis <NUM> will only rotate when the rotational moment exceeds 10N. Before it reaches this point, however, the rotational moment causes a decrease in pressure on the brake pads and brake ends. Thus, a pressure can be applied which will not (or at least only negligibly) rotate the chassis <NUM>, but will nonetheless reduce the brake pad force to a point where the chassis <NUM> can slide on the rail <NUM>.

The skilled person will appreciate that the mechanism also has an effect on downwards forces applied by a user.

When a user applies a force to move the slider assembly <NUM> down the slide rail <NUM>, for example by pulling the first chassis member directly or indirectly via the hose, the force tends to cause the chassis <NUM> to rotate to increase the frictional force on the brake pads <NUM>, <NUM> so that it is harder to move the slider assembly down the slide rail <NUM> than to push it up the slide rail <NUM>. Once the user stops moving the slider assembly <NUM> the brake arm <NUM> applies sufficient frictional force to hold the slider assembly <NUM> in position.

Most users generally pull the chassis <NUM> down the slide rail <NUM> by pulling on the hose of a mounted showerhead (not shown). Other users pull down on the second chassis member <NUM>. The downwards pull tends to create a rotational moment which has the opposite effect of the situation above - i.e. the fixed brake stops <NUM> and <NUM> are pressed even more firmly against the slide rail <NUM>. Thus, to pull the chassis assembly <NUM> down the rail <NUM> a user must overcome this additional pressure on the brake pads <NUM> and <NUM>, as well as the pressure from the brake ends 151a, 151b. However, it is still the chassis <NUM> which rotates slightly to provide this moment.

The frictional force holding the slider assembly <NUM> in place should be sufficient that it is not overcome by the weight of the slider assembly <NUM> and shower head. Furthermore, the user must provide a force over a threshold in order to move the slider assembly <NUM> up or down the slide rail <NUM>. In this example the force to move the slider assembly <NUM> up the slide rail <NUM> is lower than the force to move the slider assembly <NUM> down the slide rail <NUM>.

From the above, the skilled person will appreciate that the change in force which results from the mechanism being moved up or down the rail is a result of change in pressure between the brake pads <NUM> and <NUM> and brake ends 151a, 151b and the slide rail <NUM>. This change in force is achieved by rotation of the chassis <NUM>.

The skilled person will appreciate that, in additional or alternative embodiments, the configuration may be adjusted so as to require a greater force to push the slider <NUM> up as opposed to down, or the forces required may be equal.

In this example, the brake arm <NUM> is made of the same material as the brake ends 151a, 151b such that the brake arm and ends may be formed as a single part. In alternative embodiments, the brake arm <NUM> may be made of a different material from the brake ends 151a, 151b. For example, a material with lower friction may be chosen for the brake ends 151a, 151b so as to facilitate the slider assembly <NUM> moving up or down the slide rail <NUM> when the user applies sufficient force, or a higher friction material may be chosen to increase grip.

In the discussion above of the second example, a single brake arm <NUM> is provided on one of the pivots <NUM>. It will be appreciated that the brake arm <NUM> may be provided on either pivot <NUM>. Alternatively, two brake arms <NUM> may be provided, one on each pivot <NUM>.

In the first and second examples discussed above, the slide rail <NUM>, <NUM> may be formed of any suitable material, such as moulded or extruded plastics, or metal such as stainless steel. The slider assembly <NUM>, <NUM> may also be formed of any suitable material, such as moulded or extruded plastics.

In the first and second examples discussed above, the holding mechanism is engaged and released automatically. There is no manual locking or unlocking of the holding mechanism, instead the holding mechanism is released when the slider assembly <NUM>, <NUM> is moved relative the rail <NUM>, <NUM> by the user rather than by an active releasing action prior to moving the slider assembly <NUM>, <NUM>, and is re-engaged to hold the slider assembly <NUM>, <NUM> in position when the slider assembly <NUM>, <NUM> is released.

It will be appreciated that any suitable automatic holding means may be used, instead of the ones discussed above.

The shape and construction of the slide rail <NUM>, <NUM> and slider assembly <NUM>, <NUM> discussed above are given by way of example. The slide rail <NUM>, <NUM>, and slider assembly <NUM>, <NUM> may be any suitable shape and construction.

For example, the slide rail <NUM>, <NUM>, may have circular or other shaped cross section, and, where it is not necessary for components of the system to project into the centre of the slide rail <NUM>, <NUM>, the slide rail <NUM>, <NUM> may be solid rather than hollow.

Furthermore, the slide rail <NUM>, <NUM> may be fixed to the wall at separate fixing points, or all along its length. Alternatively, the slide rail <NUM>, <NUM> may be fixed to the wall in any other suitable way.

The slider assembly <NUM>, <NUM> may have any shape that accommodates the holding mechanism.

The construction of the slider assembly <NUM>, <NUM> discussed above is by way of example only, particularly with reference to how the shower head is held, tilted and rotated. Any suitable chassis <NUM>, <NUM> may be used with the slider assembly <NUM>, <NUM>, as is known in the art.

The slider assembly <NUM>, <NUM> can be used to hold a shower head at a fixed height, and allow the height to be adjusted. The slider assembly <NUM>, <NUM> with the slide rail <NUM>, <NUM>, provides the slide rail system <NUM>, <NUM>.

Claim 1:
A slide rail mechanism having a chassis (<NUM>) for holding a shower head, wherein the chassis (<NUM>) is slideable along a slide rail (<NUM>), and includes a holding means for holding the chassis (<NUM>) at a position along the slide rail (<NUM>), wherein the holding means is actuated by movement of the chassis (<NUM>); the holding means includes a braking element (151a, b) arranged to engage the slide rail (<NUM>) to prevent movement of the chassis (<NUM>) relative to the rail (<NUM>); the braking element (151a, b) being arranged on a brake carrier (<NUM>); and the brake carrier (<NUM>) is mounted pivotally with respect to a body of the chassis (<NUM>); the brake carrier (<NUM>) is pivoted at the centre of the brake carrier (<NUM>), and wherein the rotational position of the chassis (<NUM>) is controlling the level of frictional force;the brake carrier (<NUM>) includes a projection forming the braking element (151a, b) at one end, arranged to engage with the slide rail (<NUM>), and apply the frictional force when the chassis (<NUM>) is sufficiently rotated; the brake carrier (<NUM>) is biased by a spring (1100a, b) to engage the slide rail (<NUM>); and wherein movement of the chassis relative to the slide rail (<NUM>) in a first linear direction causes rotation of the chassis (<NUM>) in a first rotational direction to reduce the frictional force applied to the slide rail (<NUM>).