The invention has been especially developed in connection with the need for the raising and lowering of tabletops within a height range of 62-122 cm, reckoned from a floor surface. A height adjustment range of this kind is requirement in an EU standard for computer tables. The height adjustment allows the table to be ergonomically adjusted to the individual user.

There are several known suggestions for providing a telescopic support column which is sufficiently low in its lowest position and which reaches a sufficient height in its highest position. For example, the applicant's Norwegian Patent Application No. 974725 describes an embodiment provided with an actuator that lifts tubes and takes with it the innermost tube by means of a double action wire system. There are also previously known telescopic air or oil hydraulic cylinders for taking large lifts, and which therefore have large diameters so as to be able to take side loads at the same time. On the market there are also support columns that take large side loads, and which have several internal actuators in order to-manage sufficiently high lifts for telescopic support columns.

Common to these known embodiments is that the lifting device is of large dimensions in order to also be able to take large side loads.

It is an object of the present invention to provide a height-adjustable or telescopic support column where the actual lifting device (the actuator) has relatively small dimensions, and where there is a separate telescopic column for taking up the side loads.

Another object of the invention is to provide a product in the form of a height-adjustable support column that is simple, inexpensive and reliable, and has a clean design.

Yet another object of the invention is to provide a height-adjustable support column where the actuator is a double-action actuator, i. e., that it has two directions of force (up and down), or can"run"either way. This prevents a jerky movement that easily occurs as a result of, for instance, an uneven distribution of turning moment and the ensuing

uneven distribution of friction when using single-action actuators, where the force of gravity alone is typically responsible for the lowering movement.

A particular object of the invention is to provide a height-adjustable support column having slide elements that are very readily adjustable and that act between pairs of telescoping tubes in a telescoping tubular column. Adjustable slide elements are advantageous, in particular because they allow a reduction in the precision of the tubular sections of which the telescoping tubes are made.

According to one inventive aspect there is proposed a height-adjustable support column, comprising a telescoping screw actuator which acts between an underlying surface and a tabletop that is to be raised and lowered, which screw actuator comprises a first hollow cylinder having a first threaded internal portion, a second hollow cylinder having external threads in engagement with said internal threaded portion and having a second internal threaded portion, and a cylindrical body having external threads in engagement with said second internal threaded portion.

It is especially advantageous if the first and second internal threaded portions are made on a respective sleeve body that is mounted in the respective hollow cylinder.

Advantageously, the cylindrical body can be designed for connection to a drive means, which may be a pulley in a pulley-and-cord drive or a direct-action electric motor.

According to a second inventive aspect, there is proposed a height-adjustable support column comprising an actuator which acts between an underlying surface and a tabletop that is to be raised and lowered, and a sideways stabilised telescoping tubular column having a tube axis and constructed of intertelescoping tubes, and slide elements spaced apart around the circumference in the tubular column and which are mounted in one of the two respective, interacting telescoping tubes and have sliding contact with a slide face on the other of the two said tubes, wherein of a set of slide elements preferably arranged essentially in the same cross-sectional plane through the tubular column, one is adjustably mounted and is eccentrically arranged relative to the tube axis so that on an adjusting movement against the slide face there is obtained a rotational movement of the two tubes about a longitudinal axis in the tubular column, whereby the other slide elements in the unit are caused to tighten or slacken relative to their respective slide face.

It is especially advantageous to allow the slide elements to have sliding contact with the inside of said second tube.

In one telescopic position of the tubes, it is advantageous to have coinciding openings in the two interacting telescoping tubes immediately opposite a respective adjustable slide element.

According to the invention there is therefore proposed a height-adjustable support column comprising a telescoping screw actuator that acts between an underlying surface and a tabletop that is to be raised and lowered; a sideways stabilised telescoping tubular column encasing the support column, having a tube axis and constructed of mutually telescoping tubes; and slide elements spaced apart around the circumference in the tubular column and mounted in one of two respective, interacting telescoping tubes and having sliding contact with a slide face on the other of the said two tubes, wherein of a set of slide elements preferably arranged essentially in the same cross-sectional plane through the tubular column, one is adjustably mounted and is eccentrically arranged relative to the tubular axis so that on an adjusting movement against the slide face there is obtained a mutual rotational movement of the two tubes about a longitudinal axis in the tubular column, whereby the other slide elements in the set are caused to be tensioned or slackened relative to their respective slide face.

In a height-adjustable support column of this kind it is the telescoping screw actuator that is the height-adjusting element. The surrounding telescoping tubular column provides necessary sideways stabilisation, the individual telescoping tubes being mutually slide-supported by the said slide elements.

In previously known telescopic tubular columns where slide elements are arranged between the individual tubes for mutual control of the tubes, at least some of the slide elements are capable of adjustment towards/from an abutting slide face on a tube, so that the control can be tightened/retightened. As a rule, in columns having a polygonal cross-section, two slide elements are used on each side of the cross-section, and the slide elements on one of two opposite sides must be capable of being tightened, i. e., adjusted inwards against the abutting tube-slide face, so that the slide elements on the opposite side are also actuated. Thus, it is necessary to have several adjustable slide elements in a cross-sectional plane. For example, in a square column, two slide

elements must be used on each side of the square, i. e., a total of eight (plus eight more in another cross-sectional plane), and at least four must be adjustable.

In a height-adjustable support column according to the invention, the number of adjustable slide elements in the same cross-sectional plane is reduced, preferably so that it is sufficient to have one adjustable slide element in a set of slide elements located in a cross-sectional plane.

It is particularly advantageous to allow the slide elements to have sliding contact with the inside of the respective said second tube.

In a design of this kind the slide faces will not be visible from the outside of the support column, which helps to improve the aesthetic appearance of the support column, because any worn or damaged slide faces are not exposed.

In order to be able to adjust the adjustable slide element in a simple and convenient manner, it is advantageous to have in one telescopic position of the tubes coinciding openings in two interacting telescoping tubes immediately opposite a respective adjustable slide element.

The telescoping screw actuator may advantageously be a screw actuator that includes a first hollow cylinder having a first internal threaded portion ; a second hollow cylinder having external threads in engagement with said internal threaded portion and having a second internal threaded portion ; and a cylindrical body having external threads in engagement with said second internal threaded portion.

A screw actuator of this kind can be made in a simple manner and can easily be dimensioned so that it gives the desired, preferred lifting range of between 62 and 122 cm relative to a floor surface on which the screw actuator rests.

It is especially advantageous to allow the first and second threaded portions to be formed on a respective sleeve body that is mounted in the respective hollow cylinder.

The cylindrical body in the screw actuator can advantageously be made for connection to a drive means.

The drive means may include a pulley in a pulley-and-cord drive.

The drive means may also be a motor.

A relatively small and simple motor, specifically a single-phase motor, can be used for the preferred application, i. e., the raising and lowering of computer tables.

The invention will now be explained in more detail with reference to the drawings, wherein: Fig. 1 is a partially cut-away view of a height-adjustable support column according to the invention, in its lowest position; Fig. 2 shows a vertical section through the height-adjustable support column in its highest, i. e., fully extended position; Fig. 3 shows a longitudinal section through the actuator, in its lowest position as in Fig.

1 ; Fig. 4 is a perspective view of the height-adjustable support column in extended, i. e., highest position; Fig. 5 shows the height-adjustable support column in Fig. 4, seen from the other side and without a base; Fig. 6 is a perspective view of the upper tube in the telescoping tubular column; Fig. 7 is also a perspective view of the upper tube in the telescoping column, seen from the other side than in Fig. 6; Fig. 8 is a perspective view of the intermediate tube in the telescoping tubular column; Fig. 9 is a perspective view of the lowermost tube in the telescoping tubular column; Fig. 10 shows different cross-sections of the height-adjustable support column, brought together in the paper plane; and Fig. 11 shows a cross-section through a height-adjustable support column as in the preceding figures, but with the slide elements in contact with the external slide faces on the respective tubes in the tubular column.

The height-adjustable support column 1 shown in Fig. 1 comprises a telescoping screw actuator 2 and a telescoping tubular column 3.

The support column 1 is placed on a base 4, intended for contact with a non-illustrated floor surface. The support column 1 supports a tabletop 5 that is merely indicated.

As can be seen in particular from Figs. 1 and 2, the tubular column 3 encases the screw actuator 2.

The screw actuator 2, which is the height-adjusting and supporting element in the support column 1, consists of (see in particular Fig. 3) a first hollow cylinder 6 having a first internal threaded portion 7, a second hollow cylinder 8 having external threads 9 in engagement with the said first internal threaded portion 7 and having a second internal threaded portion 10, and a cylindrical body 11 equipped with external threads 12 in engagement with said second internal threaded portion 10 in the second hollow cylinder 8.

As shown in Fig. 3, the first 7 and the second 10 internal threaded portions are formed on a respective sleeve body 13,14, that is mounted in the respective hollow cylinder 6, 8.

The advantage of having two sleeve bodies 13,14 is that it is easier to form the respective internal threaded portion 7,10 in these short sleeves instead of in the respective hollow cylinder 6,8.

The first hollow cylinder 6, which is the outer hollow cylinder in the screw actuator 2, rests against and is attache to the base or foot 4. The actual attachment is not shown in Fig. 3. The hollow cylinder 6 may, for example, have a lower end flange which is connected to the foot 4 using screws, or it may be welded in place.

The inner cylindrical body 11 is attached to the tabletop 5 and supports it. It is advantageous to allow the cylindrical body 11 to be pivotally supported in the tabletop 5 in a manner not shown in detail, and thus have a pivot extension 15 that can be connected to a separate drive means, for example, a non-illustrated pulley in a pulley- and-cord drive, or an electric motor, directly or via a suitable transmission.

When the cylindrical body 11 is turned it will screw its way out of the second, intermediate hollow cylinder 8 as a result of the threaded interaction between the external threaded portion 12 on the cylindrical body 11 and the internal threads 10 in the sleeve body 14. When the cylindrical body 11 has reached its uppermost position in the intermediate hollow cylinder 8, the threads 7 and 9 will as a consequence of their interaction cause the intermediate hollow cylinder 8 to move up. In this way there is

achieved a double length of stroke in relation to the length of the working stroke of the cylindrical body 11.

The design of the screw actuator 2 is such that the cylindrical body 11 does not need to screw its ways to the top before the intermediate hollow cylinder 8 begins to rotate.

Both the cylindrical body 11 and the hollow cylinder 8 can go around simultaneously, controlled, inter alia, by the friction between the threads. Provided that both thread systems have the same thread pitch, the lifting speed will nevertheless be constant.

Loss of thread pitch motion in one of the thread systems will be countered by gain in the other thread system, and it is thus unimportant for the function where rotation takes place. As will be appreciated, the screw actuator will be double-acting. Lowering takes place by changing the direction of rotation of the cylindrical body 11.

As already mentioned, the screw actuator 2 in Fig. 1 is shown in its lowest and highest position respectively. The threads on the hollow cylinder 8 and the cylindrical body 11 are not shown in Figs. 1 and 2.

In Figs. 1 and 2 at the top by the tabletop 5 there is indicated a bearing housing 16 for pivotal support of the cylindrical body 11. Two wheels or pulleys 17,18 are also indicated and these constitute elements in a transmission in a drive means that is not show in any detail. For example, the wheel or pulley 18 can be driven by a belt drive from a motor, whilst the wheel or pulley 17 is an element of a transmission to another height-adjustable table leg.

The two sleeve bodies 13 and 14 are secured in a suitable manner in the hollow cylinder 6 and the hollow cylinder 8 respectively, for example by press fitting, and can, if required, be prevented from turning by set screws in a way that is known per se. In the bottom position, as shown in Fig. 3, the cylindrical body 11 rests against a bottom part 19 that is fastened in the bottom of the intermediate hollow cylinder 8. The intermediate hollow cylinder 8 rests with its bottom body 20 against a bottom plate 21 in the outer hollow cylinder 6.

As mentioned, the screw actuator 2 is encased by a telescoping tubular column 3, see in particular Figs. 2,4 and 5.

The tubular column 3 consists of a lower tube 22, that is fastened in the base 4 in a suitable manner, for example, by using screws or a welded connection, an intermediate

tube 23 and an outer or upper tube 24, which at the top is fastened to the tabletop 5 in a suitable manner, for example, with the aid of a flange that is screwed to the tabletop.

An attempt has been made to provide the tubular column 3 with an aesthetically pleasing appearance by giving the individual tubes 22,23 24 a special cross-sectional shape and smooth, attractive outer surfaces. The tubular column can advantageously be made of a suitable aluminium alloy.

As will be appreciated, the middle tube 23 in the tubular column 3 will be freely suspended; lugs or the like are provided, which on contact ensure that the intermediate tube 23 is taken upwards by the upper tube 24.

In Fig. 4 the tubular column 1 is seen from one side whilst in Fig. 5 it is seen from the opposite side, so as to show certain details that will be explained in detail below.

The upper or outer tube 24 in the tubular column is shown in more detail in perspective in Figs. 6 and 7.

As the starting material for the tube 24, as for the tubes 22 and 23, there is used a string- pressed tube having a desired cross-sectional profile, in this case a hexagonal form with extended corners 25 having through-going drilled holes. Fixing screws 16 can be fastened, uppermost in these drilled holes see Fig. 4, for fastening to the superjacent tabletop 5 directly by means of the screw 26, or for example, with the aid of a flanged plate that is screwed to the tube 24 by the screws 26 and then with the aid of screws is fastened to the tabletop 5.

A stud screw 28 is screwed in at the bottom of one of the walls 27 of the tube 24. In the wider wall 29, hidden from view in Fig. 6, two through holes 30,31 have been made as shown in Fig. 7.

Fig. 8 is a perspective view of the intermediate tube 23. This tube 23 is also cut from a string-pressed tube having a hexagonal profile.

In this intermediate tube 23, in the upper area that interacts with the upper or outer tube 24, two sets of slide elements are provided. Thus, four slide elements 32 to 35 are arranged at the top and further down the tube 23 another set of slide elements 36 to 38 (the fourth slide element is not visible) is provided. The slide elements 35 and 38 are

mounted in the tube wall in an adjustable manner, i. e., they can be moved towards and away from the opposite inner wall or slide face in the surrounding outer tube 24. The other slide elements are fixed. Opposite the upper adjustable slide element 35 in tube wall 39 a hole 40 has been made, and similarly, opposite the adjustable slide element 38 a non-illustrated hole has been made in the wall 39. Through-going stud screws 41,42 are provided in the tube wall in the upper area of the tube wall, and at the bottom a through-going stud screw 43 is provided. As shown in Fig. 8, two through holes 44,45 have been made in the lower region of the tube 23. The purpose of the stud screws and the holes will be explained in detail below.

Fig. 9 is a perspective view of the lower tube 22 in the tubular column 3. This tube is also made from a string-pressed tube having a hexagonal profile. In its upper part, the tube 22 has two sets of slide elements 46 to 49 and 50 to 52, corresponding to the slide elements in the intermediate tube 23 (Fig. 8). A through-going stud screw 53 is provided in one tube wall, and, as shown, two holes 54 and 55 have also been made in the upper region of the tube 22, i. e., the region of the tube 22 that will at any given time be inside the intermediate tube 8.

Fig. 10 shows cross-sections taken through the tubular column 3 at several different levels, the cross-sections being brought together in the common paper plane.

The observant reader will understand that in a particular position of the upper tube 24 in relation to the intermediate tube 23, the holes 30,31 in the upper tube 24 will be aligned with the two holes 40 (only one is shown in Fig. 8) in the intermediate tube 23, as shown in Fig. 10. Similarly, the intermediate tube 23 and the lower or inner tube 22 can be brought into an interposition of this kind so that the holes 44,45 are made to lie over the holes 54,55, as shown in Fig. 10.

This means that when the holes are aligned with one another it is possible to introduce a suitable tool through the holes 30,40 and 31,40 (the second non-illustrated hole) respectively, for example a hexagon key that can be brought into engagement with a respective adjustable slide element 35, 38 for the adjustment thereof.

Each of the two adjustable slide elements 35,38 consist of a slide pad 56, intended for sliding contact with the inner wall of the outer tube 24, and a threaded set screw 57 that is screwed into a threaded drilled hole in the intermediate tube 23. Advantageously, the

threaded set screw 57 may have a hexagonal hole in the end for interaction with a hexagon key that is passed in through the aligned holes 30,31,40.

Similarly, in the lower or inner tube 22 there are arranged two adjustable slide elements 46,50. These two slide elements 46,50 are made in the same way as the slide elements 35, 38 and are screwed into threaded drilled holes in the lower tube 22. They can be adjusted by using a hexagon key that is passed in through the aligned holes 44,45,54, 55. Thus, the slide elements 46,50 can be adjusted relative to the inner wall of the surrounding tube 23.

As can be seen from Fig. 10, the adjustable slide elements 35, 38 are arranged eccentrically relative to the tube axis 56 so that when the slide elements 35,38 are adjusted, for example, pushed against the opposite slide face, i. e., the inner wall of the outer tube 24, both the outer tube 24 and the inner tube 23 will make a small rotational movement, whereby the slide elements 33,32,36 and 34,37 are pressed against their respective opposite slide face on the inside of the tube 24. The same applies on an actuation of the adjustable slide elements 46,50, wherein there is obtained a relative rotational movement between the inner tube and the intermediate tube 23, whereby the slide elements 48,51,49,52,47 are tightened or slackened relative to their opposite slide face, i. e., the inner wall of the intermediate tube 23.

The advantage of internal slide faces is that they are invisible, even when the tubular column is fully extended or in its highest/longest state, so that there will always be a clean, aesthetically pleasing outer surface on the tubular column.

The non-adjustable slide elements are fastened to the wall of the respective inner tube of a pair of tubes in a manner not shown in detail. The adjustable slide elements are as mentioned screwed into the respective tube wall, so that by using a suitable tool inserted through the aligned openings, it is possible to gain access to the slide element for screw actuation thereof, towards and away from the opposite slide face.

Of course, the same simple means of adjustment for the slide elements and thus the sideways stabilisation of the tubular column can be achieved by allowing the slide elements to act on respective outer sides of the tubes, as shown in Fig. 11, where there is shown a cross-section through a modified tubular column having a lower, inner tube 57, an intermediate tube 58 and an upper, outer tube 59 in functions corresponding to the tubes 22,23,24 described above. In the wall of the outer tube 59 there is shown an

adjustable slide element 60, and in the wall of the intermediate tube 58 there is shown an adjustable slide element 61. Furthermore, there are shown slide elements 62,63,64 and 65,66 between the inner tube 57 and the intermediate tube 58 and the intermediate tube 58 and the outer tube 59 respectively. By adjusting the adjustable slide elements 60,61, that are accessible from the outside of the respective tube, it will be possible to obtain the same twist adjustment as shown and described in connection with Fig. 10.

The stud screw 43 will move towards the stud screw 53 and stop the upward movement of the tube 23 relative to the lower tube 22.

The stud screw 28 will move towards the stud screw 41 and stop the upward movement of the upper tube 24.

The stud screw 42 will move towards the upper edge of the lower tube 22 and stop downward movement.