The present invention relates to a height adjustable support for display means such as a projector screen or a display. More specifically the present invention relates to a support comprising a support structure to be arranged on a wall and a movable structure which is height adjustable in relation to the support structure and which comprises counterbalancing means arranged to apply a force upwards on the movable structure in relation to the support structure.

Description of the prior art

When presenting information stored in a computer it is possible to show the information on a display means such as a display by connecting the computer to the display or a projector screen by connecting the computer to a projector which projects the information on the projector screen. In recent years so called "short- throw-projectors" have entered the market. Short throw projectors are sometimes referred to as "ultra short throw projectors". Such projectors can be placed at a short distance from the screen on which the images from the projector are projected. Such projectors are normally arranged on an arm which extends from the screen so that the projector and screen are arranged fixed in relation to each other. In order to facilitate the display of information, the display means in the form of the display or the screen and the projector may be arranged on a height adjustable support so that the screen may be positioned at different heights.

The height adjustability may be provided in one of many ways. The US application US 2009/0015798 A1 describes a display system incorporating a display surface and a short throw projector arranged to project an image onto the display surface. The display surface and the short throw projector are height adjustable by means of two elongated actuators, which may be controlled mechanically or electrically, for example by remote control.

WO 2005072504 A2 describes an interactive display system including a support frame having a vertical positioning element that counterbalance the weight of an attached interactive display. The vertical positioning element includes hydraulic or pneumatic devices such as pistons and gas springs. US 3,822,848 describes a picture screen holder of the wall mounted bracket type and provides for manual adjustment of the screen in a vertical direction.

PCT application WO 2012/008897 A1 describes a projector screen support comprising a support structure with at least one guide means defining a length axis which is to be arranged essentially vertically and a screen holding support for holding a projector screen. The screen holding support is arranged movable along the length axis, defined by said at least one guide means. The projector screen support also comprises counterbalancing means arranged to apply a force directed upwards on the screen holding support in relation to the support structure. The counterbalancing means comprises at least two constant force springs each producing a predetermined force, wherein the springs are attachable/detachable in at least one end without using any tools, so that the total force from the counterbalancing means may be easily varied by attaching or detaching springs.

Summary of the invention

An object of the present invention is to provide a height adjustable support for a display means, which is an alternative to the supports according to the prior art.

Another object of the present invention is to provide a height adjustable support for a display means, which comprises counterbalancing means for balancing the weight of the display means, which support is more easy to operate than supports according to the prior art.

A further object of the present invention is to provide a height adjustable support for a display means, which comprises counterbalancing means for balancing the weight of the display means, which support requires less force for height adjustment than the supports according to the prior art, while still providing a stable positioning of the display means.

At least one of the above objects are fulfilled with a projector screen support according to claim 1 .

Further advantages of the invention are provided with the features of the

dependent claims. According to a first aspect of the invention a support for a display means is provided. The support comprises a support structure with a fastening surface and a height axis, which support structure is arranged to be fastened on a wall with the fastening surface facing against the wall and the height axis arranged essentially vertically. The support also comprises a movable structure on which the display means is to be arranged and which is arranged movable along the height axis in relation to the support structure, and counterbalancing means arranged to apply a force directed upwards on the movable structure in relation to the support structure. The counterbalancing means comprises at least two constant force springs in the form of rolled ribbons of spring steel, which each produces a predetermined force, has a roll axis arranged perpendicular to the height axis and is attachable/detachable in at least one end, so that the total force from the counter- balancing means may be easily varied by attaching or detaching springs. The support is characterized in that it comprises at least one first locking means arranged on one of the support structure and the movable structure, at least one second locking means which is arranged on the other of the support structure and the movable structure and which may interact with the first locking means in order to lock the position of the movable structure in relation to the support structure, and at least one control means arranged for controlling said at least one second locking means.

With a support according to the invention the force from the counterbalancing means may be adapted to different weights on the projector screen. Constant force springs in the form of rolled ribbons of spring steel are readily available and provide an essentially constant force independently of their extension. Such springs are in the form of a roll with one free end that may be extended from the roll in a straight line. As it is not possible to perfectly match the strength of the springs to the weight of the support and the display means the supports according to the prior art has had to rely on a sufficient friction in the movement between the support structure and the movable structure in order for the movable structure to be still after positioning in a new position. This friction has made the operation of prior art supports unnecessarily heavy. With at least one array of first locking means and at least one second locking means the movable structure may be locked in a number of different positions regardless of the friction between the movable structure and the support structure. With a support according to the invention the friction may be made as low as possible. This will make operation of the support easier as the operator will only have to overcome the difference between the gravity on the movable structure with display means and the force of the constant force springs. The first locking means may be implemented in a number of different ways such as, e.g., a surface on which the second locking means pushes similarly to a brake on a bike.

The support is intended for use with a display means. The display means may be a display such as a LED or LCD display or plasma display. The display means may also be a projector screen, possibly in combination with a short throw projector. To this end the screen holding support may also comprise an arm extending essentially perpendicularly to the length axis defined by said at least one guide means. The arm may be arranged for the arrangement of a short throw projector.

According to a second aspect of the present invention a support for a display means is provide. The support comprises a support structure comprising a fastening surface and a height axis, wherein the support structure is arranged to be fastened on a wall with the fastening surface facing the wall and with the height axis essentially vertical, a movable structure on which the display means is to be arranged and which is arranged movable along the height axis in relation to the support structure, and counterbalancing means arranged to apply a force directed upwards on the movable structure in relation to the support structure. The counterbalancing means comprises at least two constant force springs in the form of rolled ribbons of spring steel, which each produces a predetermined force, has a roll axis arranged perpendicular to the height axis and is attachable/detachable in at least one end, so that the total force from the counterbalancing means may be easily varied by attaching or detaching springs. The support is characterized in that it comprises at least one array of first locking means arranged in different positions along the height axis, on the movable structure, at least one second locking means which is arranged on the support structure and which is arranged to interact with any one of the first locking means in the array in order to lock the position of the movable structure in relation to the support structure, and at least one control means arranged for controlling said at least one second locking means, wherein the control means comprises a spring, which is arranged to apply a force on the second locking means to be in engagement with one of the first locking means, and a pulling means connected to the second locking means. The pulling means is arranged for pulling the second locking means out of engagement with the first locking means against the force of the spring, wherein the pulling means comprises a control handle attached to the movable support and a Bowden wire of which one end is connected to the control handle and the other end is connected to one of said at least one bolt.

Such a support is favourable in many ways. With the support it is possible to make the support structure small as it only has to accommodate the second locking means which may be made small. The array of first locking means which is arranged on the movable structure may take up considerably more space as the movable structure may be larger. It is favourable to have the movable structure larger than the support structure as the movable structure may then be made to cover the support structure for all positions of the movable structure in relation to the support structure. Such an arrangement of the support structure in relation to the movable structure eliminates the risk for an operator of the support to get pinched between the movable structure and the support structure. Furthermore, the support provides for easy operation as an operator may operate the pulling means and the movement of the movable structure with one hand. The positioning of the control handle and the second locking means is made possible with the Bowden wire used in the support.

The roll axes of the constant force springs may be arranged essentially parallel to each other. By such an arrangement it is possible to arrange all constant force springs on a common axle.

The movable structure may be arranged on the support structure by means of guiding means comprising two rods attached to one of the support structure and the movable structure and at least one bearing, preferably two bearings, for each rod, which bearings are attached to the other one of the support structure and the movable structure, wherein the movement of the movable structure is defined by the rods and the bearings. Such rods and bearings may be made with very little friction which is favourable for facilitating the operation of the support. The surface of the rods may also function as the first locking means.

The rods may be attached to the movable structure and the bearings may be attached to the support structure. This is a favourable arrangement as it makes it easy to hide the rods behind the display means for all positions of the movable structure in relation to the support structure.

The bearings may be linear ball bearings. Linear ball bearings are usually arranged as a sleeve with balls which is to be arranged around a rod with circular cross section. Linear ball bearings may provide a very low friction between the ball bearing and the rod.

The support according to the first aspect may comprise at least one array of first locking means arranged in different positions along the height axis, wherein the second locking means is arranged to interact with any one of the first locking means in the array. By having an array of first locking means the locking means may be made to provide a better locking without the need to push as hard as is necessary when the first locking means is a surface on which the second locking means pushes.

One array of first locking means may be arranged on the movable structure and a second locking means may be arranged on the support structure in a support according to the first aspect of the invention. Such an arrangement of the array of first locking means is easier to implement when using rods arranged in the movable structure.

The movable structure may comprise a frame with two side frame members, a top frame member and a bottom frame member, wherein at least one array of first locking means is arranged on each one of the side frame members and a second locking means is arranged for each one of said at least one array of first locking means. Such arrangement of frame members does not intrude on the space for the constant force springs and will contribute to the possibility of minimising the depth of the support. Preferably the at least one array of first locking means is arranged on the side of one of the side frame members facing the other side frame member.

Each array of first locking means may be holes and each second locking means may be a bolt which may engage with one of the holes. This is a favourable realisation of the locking means as it is easy to implement.

It is possible to arrange the first locking means as indentations, notches or any other suitable means. It is within the scope of the invention to have the second locking means in the form of two or more bolts which interact with different holes. The bolts are preferably operated by the same pulling means. It is for example possible to have the bolts arranged to interact with adjacent holes. Such an arrangement improves the mechanical strength of the support.

It is of course also possible to arrange the first locking means as protrusions with which the second locking means is arranged to engage.

The control means may comprise a spring, which is arranged to apply a force on the bolt to be in engagement with one of the holes, and a pulling means connected to the second locking means, which pulling means is arranged for pulling the bolt out of engagement with said hole against the force of the spring. By the

arrangement of such a spring engagement of the second locking means with one of the first locking means is realised when no force is applied be the pulling means. The pulling means may be realised in a number of different ways. It is possible to have an electric pulling means, a hydraulic pulling means or a mechanical pulling means.

The pulling means may comprise a control handle attached to the movable support and a Bowden wire of which one end is connected to the control handle and the other end is connected to one of said at least one bolt. It is possible to implement a mechanical coupling between the control handle and the bolt in other ways than by using Bowden wires. However, Bowden wires are cheap and easy to install and functions well when the ends of the wire is on different parts that move in relation to each other. The control handle may comprise a fixed bracket which in one end is fixed to the movable support, a fixed handle part which is attached in the other end of the fixed bracket, a lever means which is rotatably arranged in the fixed bracket around an axis of rotation, which is arranged between the fixed handle part and the movable support, and a movable handle part which is attached to the outer part of the lever means most distant from the movable support. The Bowden wire is attached to the inner part of the lever means closest to the movable support, and the lever means and the handle parts are arranged so that movement of the movable handle part towards the fixed handle part pulls the bolt out of engagement with the holes. Such an implementation of the handle provides a control handle that is easy to use for an operator with one hand as he may push the two handle parts together with the same hand as is later used to move the movable structure.

The support may comprise a first locking means and a second locking means on each side, wherein both second locking means are connected to the same control handle. This facilitates the operation of the support at the same time as the stability of the fixed position is made more stable.

The constant force springs may be attachable/detachable in at least one end without using any tools. This facilitates easy adjustment of the total force from the constant force springs. The outer end of at least one of the constant force springs may be provided with a hole having a decreasing width towards the outer end of the constant force spring. The hole is to be in engagement with a knob having a length axis and a form at the outer end of the knob so that when the outer end of the hole is in engagement with the knob the outer end of the spring is prevented from moving along the length axis of the knob out of engagement with the knob. With such a hole the spring may be easily attached by pulling out the spring until the knob may be inserted through the hole. When the pulling force on the spring is released the spring retracts so that the knob enters the outer end of the hole. In that position the spring may not be pulled out from the knob in a direction along the length axis of the knob. In order to detach the spring from the knob the spring first has to be pulled down so that the knob then may exit through the part of the hole with the largest width. The hole may preferably have a form resembling the form of a keyhole.

The knob may have one of many different forms as long as the knob fulfils the requirement to lock the spring in position at the outer end of the hole, into which end the knob is forced due to the force from the spring. The knob may be a screw with a screw head.

With the knob having the form of a screw with a screw head the attached spring may be secured by tightening the screw. When the spring is to be detached it is first unsecured by rotation of the screw in the opposite direction. A plate may be arranged attached to the outer end of the constant force spring, in which plate the hole is formed. Such a spring is easier to manufacture as the material in the plate may be chosen freely to be easily machinable.

The outer part of the plate may be formed with a gripping part. The gripping part may for example be formed by bending the outermost part of the plate in an angle to the rest of the plate.

The constant force springs may comprise springs of at least two different strengths, i.e., which produce forces of at least two different magnitudes. This increases the possibility of matching the force of the constant force springs to the weight of the movable support and display means as the force from the

counterbalancing means may be altered in finer steps. Constant force springs in the form of rolled ribbons of spring steel may also be called roll formed coil springs.

The inner end of each constant force spring is preferably arranged around an axle. The arrangement of the constant force spring around an axle provides a

construction with a longer lifetime and also with a potentially lower friction. The friction between the projector screen support and the support structure may then be adjusted by other means. Preferably the axle is journalled in the support structure. The axle may be journalled in slide bearings. Slide bearings provide a cost efficient solution for the projector screen support. It is, however, possible to use roller bearings in case an even lower friction is required. The support structure may be arranged to be attached to a wall. To this end the support structure may have an attachment surface and be arranged to be attached to a wall with the attachment surface against the wall.

Alternatively the support structure may be arranged to be attached on a base for placement on a floor or the support structure may be integral with a base for placement on a floor.

Preferably, the constant force springs are arranged so that they are released by moving the outer end of the coil spring away from the attachment surface, i.e., the coil springs are arranged on the side of the support structure facing away from the attachment surface. In this way space for the movement of the springs is easy to achieve without having to make the support structure unnecessarily thick. By removing the projector screen from the projector screen support space for the movement is readily provided. In the following preferred embodiments of the invention will be described with reference to the appended drawings.

Short description of the drawings

Fig 1 is a front perspective view of a support according to an embodiment of the present invention.

Fig 2 is a front view of the support shown in Fig 1 . Fig 3 is a cross sectional view along A-A in Fig 1 . Fig 4 is an enlargement of detail B in Fig 2. Fig 5 is a cross sectional view along C-C in Fig 4. Fig 6 is a cross sectional view along D-D in Fig 3. Fig 7 is an enlargement of detail E in Fig 6. Fig 8 is a front view of the support shown in Fig 1 . Fig 9 is an enlargement of detail F in Fig 8.

Fig 10 is a cross sectional view along G-G in Fig 9.

Description of preferred embodiments of the invention

In the following description of preferred embodiments of the invention similar elements or features in different figures will be denoted with the same reference numeral. It is to be noted that the drawings are not drawn to scale.

Fig 1 is a front perspective view of a support 1 for a display means (not shown) according to an embodiment of the present invention. Fig 2 is a front view of the support shown in Fig 1 . Fig 3 is a cross sectional view along A-A in Fig 1 . The support 1 comprises a support structure 2 with a height axis 3. The support structure 2 is to be arranged with the height axis 3 essentially vertical. The support 1 also comprises a movable structure 4 on which the display means is to be arranged and which is arranged movable along the height axis 3 in relation to the support structure 2, and counterbalancing means arranged to apply a force directed upwards on the movable structure 4 in relation to the support structure 2, wherein the counterbalancing means comprises at least two constant force springs 5 in the form of rolled ribbons of spring steel, which each produces a predetermined force, has a roll axis 6 arranged perpendicular to the height axis 3 and is attachable/detachable in at least one end, preferably without using any tools, so that the total force from the counterbalancing means may be easily varied by attaching or detaching springs 5. The support comprises an axle 7 which is journalled in the support structure 2. The inner end of the constant force springs 5 is arranged around the axle 7 so that the roll axes of the springs 5 are parallel to each other as they are arranged on a common axis 6. The outer end of at least one of the constant force springs may be provided with a hole 35 (Fig 8) having a decreasing width towards the outer end of the constant force spring, which hole is to be in engagement with a knob 36 (Fig 8) having a length axis and a form at the outer end of the knob so that when the outer end of the hole is in engagement with the knob the outer end of the spring is prevented from moving along the length axis of the knob out of engagement with the knob.

The movable structure comprises a frame with two side frame members 8, 9, a top frame member 10 and a bottom frame member 1 1 . The movable structure 4 is arranged on the support structure 2 by means of guiding means comprising a first rod 12, and a second rod 13, attached to the movable structure 4 between the top frame member 10 and the bottom frame member 1 1 close to each of the two side frame members 8, 9. The guiding means also comprises a first top bearing 14, a first bottom bearing 15, a second top bearing 16 and a second bottom bearing 17 attached to the support structure. The first rod 12 is guided by the first top bearing 14, and the first bottom bearing 15, while the second rod is guided by on the second top bearing 16 and the second bottom bearing 17. Thus, the movement of the movable structure is defined by the rods and the bearings. Preferably the bearings are linear ball bearings.

One array 18 of first locking means in the form of holes (Fig 6 and 7) arranged in different positions along the height axis is arranged on each one of the side frame members 8, 9, and a second locking means in the form of a bolt (Fig 6 and 7) is arranged for each one of the arrays 18 of first locking means. The second locking means which are arranged on the support structure may interact with any one of the holes in the respective array 18 of first locking means in order to lock the position of the movable structure in relation to the support structure 4. The support 1 also comprises a control means arranged for controlling said at least one second locking means. The control means comprises a spring 38 (Fig 6 and 7), which is arranged to apply a force on the bolt to be in engagement with one of the holes 24 (Fig 5, 6 and 7). The control means also comprises a pulling means comprising a control handle 19 attached to the movable support 4 and a first Bowden wire 20 and a second Bowden wire 21 . Each one of the Bowden wires 20, 21 , is in one end connected to the control handle 19 and in the other end connected to a respective bolt. By use of the control handle 19 the Bowden wires may be controlled for pulling the bolts out of engagement with their respective holes against the force of the spring.

The support also comprises two mounting brackets 22, 23, arranged between the top frame member 10 and the bottom frame member 1 1 , on which mounting brackets the display means may be arranged. In the shown embodiment the counterbalancing means comprises nine constant force springs 5 of at least two different strengths, i.e. which produce forces of at least two different magnitudes.

The outer ends of the constant force springs 13 are provided with plates 36 (Fig 8) each having a key hole formed hole 35. Knobs in the form of screws 37 are arranged in the movable structure 4. When the springs 5 are to be attached to the screws 37 they are pulled down to the screws 37 so that they may be inserted through the wide parts of the holes 35. When the pulling force is released the springs 5 are drawn upwards by the spring force so that the screws are positioned in the narrow part of the holes 35. The screws 37 may then be tightened to secure the plates 36 to the movable structure 4.

The support structure 5 may be arranged to be attached to a wall. Alternatively the support structure may be arranged to be attached to a base to be placed on the floor or form part of a base to be placed on the floor. As is shown in Fig 3 the support structure 2 comprises a fastening surface 24. The support structure 2 is arranged to be fastened on a wall or a base with the fastening surface 24 facing the wall or the base. Fig 1 shows fastening holes 25 arranged in the support 2. The fastening holes 25 may be used to attach the support to a wall. Fig 4 is an enlargement of detail B in Fig 2 while Fig 5 is a cross sectional view along C-C in Fig 4. In Fig 5 it is clearly seen how the balls 39 of the second top bearing 16 are arranged against the second rod 13. In Fig 5 it is shown how the hole 24 is arranged closer than the second rod 13 to the fastening surface 24.

Fig 6 is a cross sectional view along D-D in Fig 3, while Fig 7 is an enlargement of detail E in Fig 6. Fig 6 shows a bracket 26 in which one end of the first Bowden wire 20 is arranged. The moving part of the Bowden wire 20 is attached via a ring 27 to the bolt 28. In Fig 6 and 7 the bolt is partly in engagement with one of the holes 24. Fig 7 shows a tube 29 attached to the support structure 2, the bolt 28 arranged in the tube 29 and a spring 38 arranged between the tube and the bolt 28 forcing the bolt 28 into engagement with a hole 24 in the array 18 of second locking means. By operating the control handle 19 the Bowden wires 20, 21 , pulls the bolts 28 out of engagement with the holes 24 so that the movable structure may be moved along the height axis 3.

Fig 8 is a front view of the support shown in Fig 1 . Fig 9 is an enlargement of detail F in Fig 8 while Fig 10 is a cross sectional view along G-G in Fig 9. Fig 9 and 10 shows the control handle in more detail. The control handle 19 comprises a fixed bracket 30 which in one end is fixed to the movable support 4, a fixed handle part 31 which is attached in the other end of the fixed bracket 30, a lever means 32 which is rotatably arranged in the fixed bracket 30 around an axis of rotation 33, which is arranged between the fixed handle part 31 and the movable support 4. The control handle 19 also comprises a movable handle part 34 which is attached to the outer part of the lever means 32 most distant from the movable support 4, wherein the Bowden wires 20, 21 , are attached to the inner part of the lever means 32 closest to the movable support 4. The lever means and the handle parts are arranged so that movement of the movable handle part 34 towards the fixed handle part 31 pulls the bolts 28 out of engagement with the holes 24.

The described embodiments may be modified in many ways without departing from the spirit and scope of the present invention which is limited only by the appended claims. In the shown embodiments the axes of the constant force springs are arranged parallel to the projector screen. It is, however, possible to arrange the axes of the constant force springs perpendicular to the projector screen.

It is not necessary to have the array of first locking means in the form of holes. Alternatively they may be made in the form of indentations or notches.