WO2008110184A1

WO2008110184A1 - Rotation unit

Info

Publication number: WO2008110184A1
Application number: PCT/EP2007/002234
Authority: WO
Inventors: Andreas Geyer
Original assignee: Ab Skf
Priority date: 2007-03-14
Filing date: 2007-03-14
Publication date: 2008-09-18

Abstract

The invention concerns a rotation unit 200 for a mounted display device, which comprises a robust housing 205 to which a mounting bracket 220 is rotatably coupled by means of at least one rotatable coupling. The mounting bracket 220 has suitable attachment means for the direct or indirect attachment of a display device and the rear of the housing is provided with fixation means to fix the unit directly or indirectly to a suitable support structure. To enhance safety, the inventive rotation unit is designed such that when a moment load greater than a predetermined maximum value is exerted on the mounting bracket 220, most of the load is taken up directly by the housing, rather than via the at least one rotatable coupling.

Description

ROTATION UNIT

TECHNICAL FIELD

The invention concerns a rotation unit for supporting a display device and is more particularly directed to a unit that enables a user to adjust the angular position of, for example, a flat screen television, to obtain an optimal viewing angle.

BACKGROUND

Cathode ray television sets are increasingly making way for flat screen televisions based on, for example, LCD or plasma technology. Such technologies allow flat screen televisions to be built only a few inches thick, and more and more consumers are opting for these slim-line screens, for aesthetic and for practical, space-saving reasons.

Flat screen televisions are often mounted flush against a wall or some other flat support surface, and the rest of the furniture in a room is arranged on the basis of viewing the screen from a good vantage point. However, many consumers may wish to arrange their furniture without reference to the TV screen. Moreover, modern homes often incorporate open-plan living space in which sections of the same room are used for different purposes. The ability to continue watching television at an optimal viewing angle from various places is appreciated by many.

Thus there is a need for a unit for adjusting the angular position of, for example, a mounted flat screen television. Such a unit would have to be suitable for use in the home, and safety is therefore a critical consideration, especially in view of the considerable weight of large-size screens. A variety of television screen positioning devices are commercially available, but there is still room for improvement in terms of load carrying capacity, safety and versatility.

SUMMARY An object of the invention is to define a rotation unit that enables adjustment of the angular position of a television screen or some other display device mounted on the unit.

A further object of the invention is to define a compact and robust unit that is capable of rotatably supporting heavy loads.

A further object of the invention is to define a rotation unit that is inherently safe, both in terms of protection from moving parts and the ability to withstand large loads.

A still further object of the invention is to define a unit that is readily incorporable as one module of a complete positioning system.

The aforementioned objects are achieved according to the invention in a rotation unit for a mounted display device, which comprises a robust housing to which a mounting bracket is rotatably coupled by means of at least one rotatable coupling. The mounting bracket has suitable attachment means for the direct or indirect attachment of a display device and the rear of the housing is provided with fixation means to fix the unit directly or indirectly to a suitable support structure. To enhance safety, the inventive rotation unit is designed such that when a moment load greater than a predetermined maximum value is exerted on the mounting bracket, most of the load is taken up directly by the housing, rather than via the at least one rotatable coupling.

More particularly, the aforementioned objects are achieved according to the invention in that the housing of the rotation unit comprises two essentially semicircular sections with a semicylindrical portion in between. The semicylindrical portion is recessed with respect to the radius of the semicircular sections, which creates an upper and a lower ledge of the housing The mounting bracket has a curved portion with a curvature that is designed to fit neatly over the semicylindrical recessed portion, with a small predetermined clearance between the curved portion and the upper and lower ledge. The mounting bracket is further designed such that as it rotates about the axis of rotation, there is a small radial clearance between the housing and the curved portion. A curved geometry of the housing and the mounting bracket are preferred, to facilitate the relative rotation.

The mounting bracket further comprises a first support element. The first support element is a beam-like member that extends from the curved portion of the mounting bracket. The first support element is provided with a connection point in form of a hole, which is located such that the center of the hole coincides with the axis of rotation. The mounting bracket can be coupled to the housing at this connection points by means of, for example, a rolling element bearing. A plain bushing could also be used. A bearing is selected that is capable of rotatably supporting the mounting bracket when an object, like a flat screen television, is mounted on the unit.

For safety reasons, the rotation unit needs to be able to support up to five times the moment load exerted on the mounting bracket by the object. When the object in question is a large flat-screen television, such an overload might damage the rotatable coupling or reduce its service life. Consequently, the inventive rotation unit is designed such that when a predetermined maximum moment load is applied, the load is carried by the housing directly. This is attained by means of the first support element, which is designed to have a predetermined stiffness. When the predetermined maximum moment load is applied on the mounting bracket, the stiffness of the first support element is such that the support element deflects by an amount that is at least equal to the predetermined clearance between the lower ledge of the housing and the curved portion of the support bracket. Consequently, at this predetermined moment load, the mounting bracket rests on the lower ledge of the housing. This means that the load is also transferred to the support structure, to which the rotation unit is connected, directly via the housing, rather than via first rotatable coupling.

In a preferred embodiment of the invention, the mounting bracket is coupled to the housing by a first and a second rotatable coupling and suitably comprises a first and second support element. The second rotatable coupling could also be a rolling element bearing or a plain bushing. In the preferred embodiment of the invention, the first and second support elements are designed such that at the predetermined maximum moment load, the load transfer occurs directly via the housing as described above. The predetermined maximum moment load is preferably set at a value somewhat in excess of the moment load that would be exerted on the mounting bracket by a large-size flat-screen display device for which the unit is designed.

For safety reasons, the one or more rotatable couplings are preferably located inside the housing. The housing must therefore comprise at least one opening, to enable the insertion of the one or more support elements and allow the mounting bracket to rotate relative to the housing. The opening is preferably symmetrical about a radial centerline of the housing. Starting from a 'zero' position, where the centerline of the one or more support elements coincides with that of the housing, the mounting bracket can suitably rotate through a certain maximum angle α in a first and a second direction of travel. The radial size of the opening that is needed to enable the mounting bracket to rotate through the angle α, starting from the zero position, also depends on a radial width of the one or more support elements. The radial widths are preferably equal. The radial size of the opening needs to be equal to the radial distance that corresponds to 2α plus the radial width of the one or more support elements. In the preferred embodiment with a first and second rotatable coupling, the housing could comprise one opening to accommodate the first and second support elements. To enhance the strength and stiffness of the housing, however, a corresponding first and second opening are preferable.

A further key safety feature of the inventive rotation unit is that the one or more openings in the housing remain covered, regardless of the orientation of the mounting bracket. Starting from the zero position, the mounting bracket can travel a maximum distance x in the first direction of travel before the one or more support elements make contact with a first edge of the opening. The curved portion of the mounting bracket has a first extension, which extension defined by the radial distance between a second edge of the opening and a first extreme edge of the curved portion. To ensure that the opening always remains covered when the mounting bracket moves in the first direction travel, the first extension is of greater radial distance than the maximum distance x. To ensure that the opening remains closed in the second direction of travel, the curved portion of the mounting bracket has a corresponding second extension.

If the one or more openings in the housing are covered by the curved portion, regardless of the orientation of the mounting bracket, the radial size of the opening partly determines the geometry of the housing. In one embodiment of the invention, the housing further comprises straight sections that extend from the semicylindrical portion. In this embodiment, the maximum opening is approximately thirty degrees either side of the radial centerline. Embodiments are envisioned with a greater radial opening that would enable a greater angle of rotation. The housing would then need to comprise curved sections extending from the semicylindrical portion, to accommodate the curvature of the extension of the mounting bracket that would be needed to keep the opening in the housing covered. For this reason, it is advantageous to make the housing from material that can be readily cast. Aluminium is preferred, given that it is a lightweight material, but steel or a suitable composite material could also be used. A further safety feature of the rotation unit according to the invention is that there is a minimum distance between a rear edge of the housing and a leading edge of the curved portion of the mounting bracket in either of its extreme positions. This minimum distance is sufficiently large to prevent a person's finger from becoming trapped. For applications of the rotation unit in the home, this is an important feature.

The inventive rotation unit is further designed to enable motorized rotation of the mounting bracket. There is sufficient space inside the housing to mount a motor. One of the first or second support elements then further comprises an opening with a toothed portion on a radially outward side. The toothed portion is adapted to mesh with a gear that is driven by the motor. To enable manual override positioning of, for example, a flat screen television mounted on the unit, the motor preferably has an integrated friction clutch. The integrated friction clutch also protects the gears of the motor if an obstruction is encountered during motorized rotation.

In an advantageous further development of the rotation unit according to the invention, the rotation unit is further provided with a friction element in a threaded hole of the mounting bracket. This friction element has spring- loaded tip that bears against a suitable counterface of the housing and applies a predetermined friction torque when the unit is in motion. This friction torque dampens backlash in the gears and reduces noise.

The rotation unit according to the invention has further advantages. For example, there is a space between the curved portion of the mounting bracket and a plate-like section of the bracket on which an object is mounted. This space could be used to accommodate a tilt actuator. The inventive rotation unit could therefore be integrated in an extremely compact, tilt and rotation unit. The rotation unit is designed to be mounted directly or indirectly on a support structure. This could be a wall or a pedestal that comprises a lift actuator. Thus, the rotation unit according to the invention is incorporable in a complete positioning system, to lift, tilt and rotate a mounted object.

One envisaged application of the inventive rotation unit is as a rotatable support for a flat screen television. Other display devices, like a projector or a beamer, could also be mounted on the unit. In principle, the mounting bracket of the rotation unit could be adapted for the mounting of a wide range of objects.

In summary, the rotation unit according to the invention has the following advantages:

It is a robust device capable of rotatably supporting large weights. It is a safe device, designed to withstand overloads. Safety is further enhanced in that the moving parts of the rotation unit are either covered or are designed such that they cannot cause injury.

It is a versatile device that can be mounted on a wall, or incorporates as a rotation module in a complete positioning system

Other advantages of this invention will become apparent from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail for explanatory, and in no sense limiting, purposes, with reference to the following figures, in which

Fig. 1 illustrates an application of a rotation unit according to the invention,

Fig. 2a illustrates a front view of a rotation unit according to the invention,

Fig. 2b -2c illustrate sectional views of a preferred mounting bracket of the rotation unit of Fig. 1 , from a non-driven and a driven side,

Fig. 2d illustrates a side view of a rotation unit according to the invention,

Fig. 3 illustrates a cross-sectional view of a rotation unit according to a preferred embodiment of the invention.

DETAILED DESCRIPTION

In order to clarify the rotation unit according to the invention, some examples of its use will now be described in connection with Figures 1 to 3.

Fig. 1 illustrates a flat screen television 100 mounted on a freestanding pedestal that comprises a pillar 1 10 and a base 120. Such televisions can also be mounted on a support structure like a wall. In order to obtain an optimal viewing angle, it is advantageous to be able to adjust the angular position of the screen. One way of doing this is by connecting the screen to the support structure via a rotation unit according to the invention.

Fig. 2a illustrates a front view of a rotation unit according to the invention. The unit 200 comprises a robust, preferably single-piece housing 205 that has an essentially semicircular first section 207 and an identically shaped second section 210, with a semicylindrical portion therebetween which is recessed with respect to the outer circumference of the first 207 and second section 210 of the housing 205. This creates a first ledge 212 and a corresponding second ledge of the housing 205. The unit 200 further comprises a mounting bracket 220 that has a mounting plate 225 provided with at least one fixation hole 227 or some other suitable fixation means for the direct or indirect attachment of, for example, a display device. The mounting bracket 220 further comprises a curved portion 230 with a curvature that is designed to fit precisely over the semicylindrical recessed portion and rotate about an axis of rotation 235. The curved portion 230 is further designed such that when mounted against the recessed semicylindrical portion, there is a small, predetermined clearance with respect to the first ledge 212 and the second ledge. The mounting bracket 220 is further designed such that as it rotates about the axis of rotation, there is a small radial clearance between the housing 205 and the curved portion 230. A rear side of the housing 205, being the side opposite from the mounting bracket side, is provided with suitable fixation means to mount the unit 200 directly or indirectly to a suitable support structure.

The mounting bracket 220 is coupled to the housing 205 by at least one support element, such as shown in Fig. 2b. Fig. 2b illustrates a sectional view of the mounting bracket 220 and a part of the housing 205 at a non- driven side. As can be seen from this figure, the mounting bracket 220 further comprises a first support element 240 that extends from the center of the curved portion 230 and is provided with a connection point 242 in the form of a hole. The hole is located such that its center coincides with the axis of rotation 235. The mounting bracket can thus be rotatably coupled to the housing 205 at the point 242 with the aid of, for example, a first bearing.

In a preferred embodiment of rotation unit according to the invention, the mounting bracket 220 is coupled to the housing 205 at a second connection point. The mounting bracket can suitably further comprise a second support element. Fig. 2c illustrates a sectional view of the mounting bracket 220 and a part of the housing 205 at a driven side. The second support element 255 likewise extends from the center of the curved portion 230 of the mounting bracket and is provided with a connection point 260 in the form of a hole. The hole is located such that its center coincides with the axis of rotation 235. A second bearing 262 is suitably mounted in the second connection point 260, to facilitate a rotatable connection with the housing 205. In a preferred embodiment of the rotation unit according to the invention, the second support element 255 further comprises a second opening located between the connection point 260 and the curved portion 230 of the mounting bracket. Preferably, a radially outward side of the opening is provided with a toothed portion 265 to enable the mounting bracket (and a mounted display device) to be drivingly rotated by a gear 270 coupled to a motor (not shown). When only one rotatable coupling is used, the first support element can be designed with similar provisions.

The rotation unit 200 is designed such that when, for example, a display device is mounted on the mounting bracket 220, the load can be supported by the one or more bearings, to enable easy rotation of the display device. These bearings can be a ball bearing, a needle roller bearing, a plain bushing or some other suitable type of bearing. Different types of bearing could also be used for the first and second rotatable coupling. For safety reasons, the rotation unit needs to be able to withstand up to five times the moment load exerted by the mounted display device. Such a load might very well damage the first of the one or more bearings or reduce its service life. Consequently, it is a feature of the inventive rotation unit that when subjected to an overload, the load is mainly carried by the housing directly.

The one or more support elements are designed such that when a moment load in excess of a predetermined maximum safe value is applied on the mounting bracket 220, the first support element 240 deflects by a certain magnitude. This magnitude must be at least equal to the predetermined clearance between the underside of the curved portion 230 and the first ledge 212 of the housing 205. The magnitude of deflection that occurs at the predetermined maximum moment load is primarily defined by the stiffness of the first support element 240, which can therefore be designed with an appropriate stiffness. At a moment load greater than the predetermined maximum value, the underside of the curved portion 230 comes to rest on the first ledge 212. Thus, when subjected to an overload, the load transfer to the support structure, to which the rotation unit 200 is connected, mainly occurs via the housing directly, thereby reducing the load on the one or more bearings. This is a key design feature of the rotation unit according to the invention, both in terms of increasing the service life of the unit and in terms of safety.

To enhance safety even further, the one or more bearings are located inside the housing 205. The housing must therefore be provided with a suitable opening, to allow for the insertion of the one or more support elements and enable the mounting bracket 220 to rotate through an angle α in a first 247 and a second direction of travel 250, starting from a position where a centerline of the first support element coincides with a radial centerline. Such an opening in the housing can be seen in Fig 2b. The radial size of the opening must also take account of a radial width t of the first support element 240. Suitably, the size of the radial opening is equal to the radial width t plus twice the radial distance that corresponds to the angle α.

Again for reasons of safety, the curved portion 230 of the mounting bracket is preferably dimensioned such that the opening is covered, regardless of the orientation of the mounting bracket 220. Consequently, the curved portion 230 has a predetermined extension y, where y is a radial distance between a first extreme edge of the curved portion 230 and a proximal extreme edge of the opening in the housing. The extension y needs to be larger than a radial distance x. The radial distance x is the maximum distance that the support element 240 can travel in the first direction travel 247, when starting from the position in which the centerline of the support element coincides with the radial centerline 245. The opening and the curved portion are preferably symmetrical with reference to the radial centerline 245, and consequently the opening remains covered in the second direction travel 250.

When the mounting bracket 220 is coupled to the housing 205 by a second support element 255, the housing 205 can comprise one opening to accommodate both support elements 240, 255. To improve the stiffness of the housing 205, however, the housing preferably further comprises a second opening to enable the insertion and rotatable coupling of the second support element 255 of the mounting bracket. The radial size of the second opening is preferably equal to that of the first opening. As described above for the first opening in the housing, the second opening therefore remains covered by the curved portion 230 of the mounting bracket, regardless of the angular position of the mounting bracket 220.

The rotation unit according to the invention has further advantages. For example, it can be seen from Fig. 2b that there is space between the curved portion 230 and the mounting plate of the mounting bracket at both sides, with reference to the radial centerline 245. This space could be utilized for a tilt actuator, for example, enabling the rotation unit according to the invention to be integrated in an extremely compact combined tilt and rotation unit.

A further safety feature of the rotation unit according to the invention will be explained with reference to Fig. 2d, which illustrates a side view of the rotation unit when the mounting bracket is at its extreme angular position in the first direction of travel. The recessed semicylindrical portion of the housing has a recessed extension in the direction towards the rear of the unit. This means that there is a distance d between a leading edge 275 of the curved portion of the mounting bracket and an edge 280 of the housing, where the recess begins. Preferably, the distance d is large enough to prevent a person's finger getting trapped. The same safety feature applies when the mounting bracket is at its extreme position in the second direction of travel.

In a preferred embodiment of the invention, the rotation unit is further equipped with means to enable motorized rotation of the unit. A cross section through such a preferred embodiment is illustrated in Fig. 3a.

A bi-directional geared motor 305 is mounted on a platform 307 in the housing, which platform 307 is preferably integrally formed with the housing. For power consumption reasons, the geared motor 305 is preferably a low current motor. Furthermore, the gearbox of the motor should have a high gear ratio, in order to generate sufficient torque to rotate a heavy display device mounted on the rotation unit 300 via the mounting bracket 310. An output shaft 312 of the motor 305 drives a gear 312, which gear meshes with a corresponding toothed portion 317 on the second support element 320 of the mounting bracket. (The gear and toothed portion are shown in greater detail on Fig. 2c, and are referenced by the numerals 270 and 265 respectively.) Thus, as the gear 315 is driven by the motor 305, the second support element 320 of the mounting bracket is made to rotate relative to the housing, given that the second support element 320 is rotatably coupled to the housing by means of a second bearing 322. To dampen gear backlash and reduce noise, the unit is preferably fitted with a friction element 324, to generate a friction torque when the mounting bracket 310 is rotating. The friction element 324 comprises a threaded shank and is inserted into a correspondingly threaded hole in the mounting bracket. The friction element 324 further comprises a spring-loaded tip. The spring-loaded tip is preferably covered with a plastic cap and bears against a suitable counterface of the housing. The tip is therefore in sliding contact with the housing. If wear occurs, the spring loading of the tip means that friction torque continues to be applied. Preferably, the position of the mounting bracket is controlled via a potentiometer 325. The potentiometer 325 has a head, which fits into a slot in a spindle 327. The spindle 327 centers the first bearing 330 and acts as a pivot point about which the first, non-driven support element 332 rotates. Thus, the head of the potentiometer 325 rotates as the first support element 332 rotates, meaning that the potentiometer 325 can measure the angular position of the first support element by means of a corresponding resistance. The potentiometer 325 is connected to a PCB (not shown), which allows an end position in both directions of rotation to be programmed. The motor 305 is also connected to the PCB. To protect the motor, the preprogrammed end stops should be reached slightly before mechanical end stops. The mechanical end stops can be the extreme edges of the one or more openings in the housing, through which the first support element 332 and second support element 320 are inserted. The mounting of the head of the potentiometer 325 in the slot of the spindle 327 also means that the head remains perpendicular to the first support element 332, which is beneficial for the accuracy of the angular measurement.

To enable manual override adjustment of the angular position of a display device mounted on the unit 300, the motor preferably has an integrated friction clutch. The integrated friction clutch is also beneficial for safety reasons, to stop the rotation of the output shaft 312 of the motor 305 if the mounting bracket 310 encounters an obstacle during motorized rotation. The integrated friction clutch also protects the gears of the geared motor 305. To enable remote control, the rotation unit is preferably further provided with an IR receiver 335

Thus, a motorized rotation unit according to the invention can be achieved that is capable of being remote controlled. The invention is not restricted to the above-described embodiments, but may be varied within the scope of the claims.

Fig. 1 - illustrates an application of a rotation unit according to the invention, 100 flat-screen television,

105 pillar,

110 base.

Fig. 2a - 2d - illustrate views of a rotation unit according to the invention and sectional views of a preferred mounting bracket of the rotation unit,

200 rotation unit,

205 housing,

207 first section,

210 second section, 212 first ledge,

220 mounting bracket,

225 mounting plate,

227 fixation holes,

230 curved portion, 235 axis of rotation,

240 first support element,

242 first connection point,

245 radial centerline,

247, 250 direction of travel 255 second support element,

260 second connection point,

262 bearing,

265 toothed portion,

270 gear, 275 leading edge of curved portion,

280 rear edge, α maximum angle of rotation, x maximum distance of travel, y extension of curved portion, t radial width of support element, d safe distance.

Fig. 3 - illustrates a cross section of a preferred embodiment of the invention,

300 rotation unit,

305 motor,

307 platform,

310 mounting bracket,

312 output shaft of motor,

315 gear,

317 toothed portion,

320 second support element,

322 second bearing,

324 friction element,

325 potentiometer,

327 spindle,

330 first bearing,

332 first support element,

335 IR receiver.

Claims

1. A rotation unit (200, 300) comprising a mounting bracket (220, 310) and a housing (205), where the mounting bracket (220, 310) is rotatably coupled to the housing (205) about an axis of rotation (235) by means of a first rotatable coupling (330), and where the mounting bracket (220, 310) is suitably adapted for the direct or indirect mounting of an object and the housing (205) is suitably adapted for attaching the rotation unit (200, 300) directly or indirectly to a support structure, and where the load exerted on the mounting bracket (220, 310) by the object mounted on the mounting bracket (220, 310) is transferred to the housing (205), and thereby to the support structure, via the first rotatable coupling (330), up to a predetermined maximum moment load, characterized in that when the mounting bracket (220, 310) is subjected to a load greater than the predetermined maximum moment load, the load is additionally transferred directly from the mounting bracket (220, 310) to the housing (205).

2. A rotation unit according to claim 1 , characterized in that the mounting bracket (220, 310) comprises a first support element (240, 332) with a connection point (242) at which the mounting bracket (220, 310) is rotatably coupled to the housing (205).

3. A rotation unit according to claim 2, characterized in that the mounting bracket (220, 310) further comprises a load-transfer element that has a predetermined clearance with respect to a load-receiving portion of the housing (205).

4. A rotation unit according to claim 3, characterized in that the first support element (240, 332) is designed with a stiffness such when the predetermined maximum moment load is applied on the mounting bracket (220, 310), the first support element (240, 332) deflects by an amount that is at least equal to the predetermined clearance between the load-transfer element of the mounting bracket (220, 310) and the load-receiving portion of the housing (205).

5. A rotation unit according to claim 3 or 4, characterized in that the load receiving portion of the housing (205) is a ledge (212) created by a semicylindrical recessed portion between a first (207) and a second section (210) of the housing.

6. A rotation unit according to any of claims 3 to 5, characterized in that the load-transfer element is a curved portion (230) of the mounting bracket (220, 310) with a curvature adapted to fit over the semicylindrical recessed portion of the housing (205).

7. A rotation unit according to any of the preceding claims, characterized in that the first rotatable coupling (330) is located inside the housing (205).

8. A rotation unit according to claim 7, characterized in that the housing (205) comprises at least one opening with a radial size that is equal to a radial width (t) of the first support support element (240, 322) plus twice the radial distance that corresponds to an angle (α), where the angle (α) is the maximum angle of rotation of the first support element (240,322) in a first (247) and second direction of travel (250, starting from a position in which a centerline of the first support element coincides with a radial centerline (245).

9. A rotation unit according to claim 8, characterized in that the curved portion (230) of the mounting bracket (220, 310) comprises a first extension (y), which first extension (y) is a radial distance between a first extreme edge of the mounting bracket and a proximal extreme edge of the at least one opening in the housing, where the first extension (y) is greater than the maximum distance of travel (x) of the first support element (240, 322), starting from the position in which the centerline of the first support element coincides with the radial centerline (245).

10. A rotation unit according to any of the preceding claims, characterized in that a distance (d) between a leading edge (275) of the mounting bracket (220, 310) in a first and second extreme position and a rear edge (280) of the housing (205) has a predetermined minimum value.

11. A rotation unit according to any of the preceding claims, the mounting bracket (220, 310) is coupled to the housing (205) by means of a second rotatable coupling (262, 322).

12. A rotation unit according to claim 11 , characterized in that the mounting bracket (220, 310) comprises a second support element (255, 320) with a connection point (260) at which the mounting bracket (220, 310) is rotatably coupled to the housing (205)

13. A rotation unit according to any of claims 2 to 13, characterized in that the rotation unit (200, 300) is provided with a motor (305) to drivingly rotate the mounting bracket (220, 310) in the first (247) and the second direction of travel (250).

14. A rotation unit according to claim 13, characterized in that one of the first and second support elements further comprises an opening with a toothed portion (265, 317) on a radially outward side, which toothed portion (265, 317) is adapted to mesh with a gear (270, 315) that is driven by the motor (305).

15. A rotation unit according to claims 13 or 14 characterized in that the motor (305) is provided with an integrated friction clutch.

16. A rotation unit according to any of claims 13 to 15, characterized in that the rotation unit (200, 300) is further provided with a friction element (324) in a threaded hole of the mounting bracket (220, 310), which friction screw (324) has a spring-loaded tip that bears against a counterface of the housing (205).

17. A positioning system comprising a rotation unit according to any of the preceding claims characterized in that the positioning system further comprises a tilt actuator and a lift actuator.