Patent Description:
In height-adjustable furniture, for example height adjustable tables, the height of the table top can be raised or lowered. These tables have legs in the shape of telescopic columns, each leg having two or more elongated tubes that are arranged in a concentric manner in relation to one another. The table top is arranged on one end of these legs. In connection with the legs, an arrangement for changing the height of the table top is devised, which drives the concentric elongated tubes in the longitudinal direction, out of, or into each other. This arrangement may be a linear actuator positioned inside, and connected to the tubes, while being driven by an electric motor. The concentric elongated tubes can thus be driven in a first direction out of each other, to lengthen the legs, thereby increasing the height of the table, or in an opposite direction so that they are driven into one another, causing the legs to shorten, thereby decreasing the height of the table.

These telescopic columns are usually columns comprising two, three or more tube-shaped telescopic parts. In these designs, in order to lengthen the legs in a stable manner, it becomes necessary that the adjacent tubes of the columns have an overlapping portion when the leg is at its maximum extension.

The two-tube telescopic columns usually have the advantage of a simpler linear actuator, that drives the raising/lowering of the leg. An example of these two-tube column legs is disclosed in <CIT>. Further examples are <CIT>, <CIT> and <CIT>. However, such two-tube designs have a shorter extension height coverage, typically ranging between <NUM> at the most compact position of the leg, and <NUM> at maximum extension. The limited height range is mainly due to stability reasons rooted in an optimal aspect ratio of the telescopic leg at its maximum extension.

In order to increase the extension length of the telescopic leg further, telescopic columns comprising three tubes are utilized. In addition to the inner, and the outer telescopic parts of the two-tube columns, these columns comprise a center telescopic segment. An example of such a three-tube telescopic leg is given in <CIT>. This document discloses a telescopic column for height-adjustable furniture, comprising a linear actuator comprising a first spindle secured to a first end of the column, a tube at least partly enclosing the first spindle and a second spindle at least partly arranged inside the tube and secured to a second end of the column. The telescopic column further comprises an inner telescope part fixedly arranged to a second end of the column, a center telescope part connected to the tube, and an outer telescope part fixedly arranged to the first end of the column. The telescopic column further comprises a device that connects the center telescope part to the tube, the device being arranged to the tube and to the center telescope part in such a way that the center telescope part is movable along the longitudinal axis in relation to the tube.

Three-tube columns can cover a wider range of heights, however the actuator design and operation become much more complex and costly, as a result of the actuator being required to drive the center telescopic segment of the column as well. Therefore, there is a need for a height-adjustable table that has a large adjusting range, but a lower cost compared to state of the art.

The two-tube columns are substantially cheaper as driving them requires less complex, hence more cost efficient means. The inventor has realized that when using only two tube solutions a significant length of the tubes is not participated in accessing the desired maximum height, as this guarantees stability of the table legs. Therefore, in order to reach a larger range of accessible heights with two-tube columns, there is a need to eliminate overlapping of the tubes while simultaneously maintaining stability.

According to a first aspect of the invention, this and other objects are achieved by a telescopic column for height-adjustable furniture, the telescopic column extending along a longitudinal axis from a first end to a second end of the telescopic column, comprising: an outer elongated tube fixedly arranged at the second end of the telescopic column, an inner elongated tube having a top end and bottom end, wherein the top end defines the first end of the telescopic column, and wherein the inner elongated tube is sized and adapted to move into and out of said outer tube, drivable by a driving unit along the longitudinal axis between a maximum height and a minimum height, and an intermediate element having a lower portion being sized and adapted to engage the outer tube from the inside thereof, a middle portion being sized and adapted to be fitted into the inner tube and engage the inner tube from the inside thereof, and an upper portion being sized and adapted to be remain within the inner tube, so as to provide for stability, wherein the intermediate element is passively moved by means of the inner tube when said telescopic column is moved between the maximum height and the minimum height.

It is noted that the term "furniture" should be widely interpreted in the context of this invention, so as to cover any appliance or equipment into which the telescopic column according to this invention may be integrated, such as, but not limited to adjustable workplaces.

In one embodiment, the inner and outer tubes may be concentric.

By passive movement of the intermediate element it is meant that the movement of the intermediate element is not actively controlled by the driving unit. Therefore, unlike the three-tube column solutions wherein movement of at least two members need to be actively controlled separately, and in relation to each other, giving rise to the complexity of these systems, in the solution provided by this invention a simple driving unit may be provided that solely controls one moving member. According to this invention, this member would be the inner tube. This simplifies driving the column within a larger range of heights than previously reachable by two-tube columns, hence substantially reducing the cost, while still allowing for stability.

In one embodiment, the inner tube further comprises an engaging portion, and the intermediate element further comprising a corresponding engaging element adapted to interact with the engaging portion of the inner tube, so as to move the intermediate element during an expansion stroke.

By an expansion stroke it is meant that the telescopic column is being expanded, so to increase its length. The maximum height of the telescopic column will then mark the upper limit of this stroke.

According to this invention, the full expansion stroke is carried out as follows: From the minimum height of the column, the inner tube is driven outwards from the outer tube, when the engaging portion of the inner tube meets the corresponding engaging element on the intermediate element, it will pull the intermediate element with it in the outward direction, only to be stopped when reaching the maximum height.

In one embodiment, the engaging element of the intermediate element defines the onset of the upper portion of the intermediate element.

The engaging element may be arranged in a centeral portion of the intermediate element, so to provide for stability by confining a substantial portion of the intermediate element, that being the upper portion, within the inner tube, and additionally, allowing the intermediate portion to extend into both the inner and outer tube. By arranging the engaging element in a central portion, the portion above the central portion will be placed inside then inner tube and the portion below the central portion will be placed inside the outer tube and thereby maximizing the stability provided by the intermediate element in full extension.

According to the invention the bottom end of the inner tube is adapted to interact with the lower portion of the intermediate element so as to move the intermediate element during a contraction stroke.

The upper, middle, and lower portions of the intermediate element may be continuous portions, only differentiated by their functionality and their positioning. The lower portion may be slightly protruding the periphery of the inner tube (explained more in detail below), while the middle and upper portions have substantially the same shape and dimensions, so as to fit inside the inner tube. The upper portion is confined within the inner tube only by means of interaction of the engagement element with the engaging portion of the inner tube when the column is being expanded.

By a contraction stroke it is meant that the telescopic column is being retracted, so to decrease its length. The minimum height of the telescopic column will therefore mark the lower limit of this stroke.

According to this invention, the full contraction stroke is carried out as follows: From the maximum height of the column, the inner tube is driven inwards to the outer tube, when the bottom end of the inner tube meets the lower portion of the intermediate element, it will push the intermediate element with it as it continues its movement within the outer tube, only to be stopped when the minimum height is reached. As explained in later in the text, in tables comprising this telescopic column within their legs, the minimum height may be reached within the bottom of a cavity within the table foot. The cavity bottom will provide a physical barrier to prevent the column being pushed even further (specifically in case the driving unit is malfunctioning).

In one embodiment, the entirety of the middle portion of the intermediate element is arranged inside the inner tube when the telescopic column is in the minimum height.

This is beneficial for achieving a lower minimum height, as the entire length of the intermediate element except the lower portion will be accommodated within the inner tube, therefore not contributing to the total height of the telescopic column. The lower portion may be a significantly small portion such as <NUM>%, <NUM>%, <NUM>%, or only <NUM>,<NUM>% of the entire length of the intermediate element.

In one embodiment, when extended to the maximum height, the inner tube is substantially moved out of said outer tube.

The inner tube may have less than <NUM>% overlap, <NUM>% overlap, <NUM>% overlap, <NUM>% overlap, <NUM>% overlap, or no overlap at all with the outer tube when at maximum height of the column. It is however notable that, in order to have stability, it would be beneficial to have some overlap between the inner and outer tube. Otherwise it could be that depending on the relative thickness of the outer tube and the intermediate element, the column will wobble as a result of the inevitable gap between the latter mentioned members.

In one embodiment, the lower portion of the intermediate element comprises at least one protrusion arranged to protrude from the periphery of the inner tube when the middle portion of the intermediate element is within said inner tube.

This may prevent the intermediate element from going entirely into the inner tube, in the mean while allowing the inner tube to push the intermediate element downwards during the contraction stroke.

In one embodiment, the intermediate element comprises at least one groove on a portion of an outer surface of the middle portion of the intermediate element, the groove positioned between the engaging element and the lower portion, and arranged to accommodate said engaging portion of the inner tube.

This may allow for smooth movement of the engaging portion of the inner tube along said longitudinal direction.

According to another aspect of the present invention, a table is provided comprising at least one leg, each leg comprising a telescopic column according to the first aspect of the invention, wherein the telescopic column is fixedly attached to the table from the top end of the inner tube, and fixedly attached to a foot element at a bottom end of the outer tube.

It may be that only one leg comprises the telescopic column defined by the first aspect that is actively driven by the driving unit, while the other leg(s) are passive legs.

The top end of the inner tube may be attached to the bottom side of the table top.

The bottom end of the outer tube may be fixed onto or within the foot element.

In one embodiment, the bottom end of said outer tube is arranged into a cavity of the foot element, so as to allow the inner tube to enter the foot element when the table is in the minimum height position.

The table foot may be a hollow component, comprising an outer, shape defining body with a certain thickness. In this case the bottom end of the outer tube of the telescopic column will be adjusted within the hollow body of the foot, and attached to an inner side of the outer body. Alternatively, it could be that the foot is not hollow, but comprises a cavity devised to harbor the bottom end of the outer tube. In either case, accommodating the bottom end of the outer tube within the foot element, will increase the accessible height range through further lowering the minimum height by the height of the table foot.

In another aspect of the present invention, a table is provided. The table may comprise a telescopic column according to any of the above-mentioned embodiments of the invention. However, the table does not have to have a telescopic column with the above mentioned features, but may be a standalone table. However, if the table does comprise the telescopic column above, the synergetic effect is that the minimum height of the table is further decreased, as well as that the driving is enabled in a simple and inexpensive manner. The table may comprise: a motor, according to the invention substantially arranged external to the telescopic column, for providing rotary motion to a worm screw extending into the telescopic column, and driving a worm wheel, a hollow bearing sleeve drivably arranged to the worm wheel from the inside thereof, and coupled to a leadscrew so that the leadscrew rotates about the longitudinal axis with the bearing sleeve driven by the motor, a receiving nut with threads for engaging the leadscrew, the receiving nut being coupled to an output shaft, so as to move linearly along the length of the lead screw upon rotation of the lead screw, wherein the output shaft moves the inner elongated tube into and out from said outer elongated tube upon activation of said motor such that a full extraction of the output shaft along the longitudinal axis will render the maximum height of the telescopic column, and a full retraction will render the minimum height of the telescopic column.

According to the invention, the motor being part of the driving unit mentioned earlier in the text, is the driving force providing rotary movement, which ultimately drives the inner tube between the minimum and maximum heights through the other components of the driving unit.

The motor being substantially arranged external to the telescopic column may significantly contribute to accessing a larger range of heights, as neither of its dimensions will add to the ultimate length of the column, making room for a lower minimum of the height range. The motor may, in an embodiment, be attached to the backside of the table top, adjacent to the column, so that the worm screw may reach the relevant components of the column, namely the worm wheel.

The worm wheel may be a hollow structure, devised so to accommodate the bearing sleeve attached within its inner side. Therefore, as the worm screw drives the worm wheel, both the worm wheel and the attached bearing sleeve will be rotated about the longitudinal axis. The sleeve bearing, having a hollow structure. May accommodate the lead screw within its hollow structure. The lead screw may be coupled to the bearing sleeve from a bottom end, and arranged to rotate as the bearing sleeve is rotated. The output shaft, which is in fact the member coupled to, and arranged to move the inner tube in a longitudinal direction, is coupled to the lead screw through the receiving nut from an end. As the lead screw is rotated, the nut will move along the groves of the lead screw, moving the output shaft up or down along the longitudinal axis.

In one embodiment the hollow bearing sleeve is arranged to enable further retraction of the output shaft by accommodating an ending portion of the lead screw and the output shaft when further retracted, within the hollow structure of the bearing sleeve.

This embodiment may allow the minimum height of the column to be lowered even further, giving access to a larger height range.

In one embodiment the bearing sleeve and the worm wheel are situated inside a housing positioned at the first end of the telescopic column, the housing arranged to further accommodate a portion of the lead screw, and the output shaft when output shaft is retracted.

Having these members accommodated within a housing will secure these components together and in place, while providing a better aesthetics. It is notable that, this housing may allow movement of the top end of the inner tube in and out of itself upon the contraction, and expansion strokes of the telescopic column, respectively. In addition, it may permit for accommodating other useful components within itself. Examples of such components are given in the following text.

In one embodiment the housing further comprises at least one axial bearing to decrease rotational friction of the bearing sleeve with rotation of the worm wheel.

The axial bearing may be arranged and positioned so to partially surround the worm wheel. It is necessary that, in this embodiment, the axial bearing allows access of the worm screw to the worm wheel from the non-surrounded portion. From the outer side, the axial bearing may be arranged to be fitted within the inner tube. Additionally, it may be arranged to be fitted within the outer tube when the column approaches its minimum height.

In one embodiment the housing further comprises at least one radial bearing, so to radially secure said bearing sleeve, and decrease friction upon rotation of said bearing sleeve relative to said worm wheel.

The radial bearing may be positioned and fixed on either side of the worm wheel along the longitudinal axis, and around the bearing sleeve attached to it from the inside. From the outside the radial bearing may be fitted within the inside of the axial bearing.

An embodiment with two radial bearings is preferable, each positioned on either side of the worm wheel in the longitudinal direction.

In another aspect of the present invention, a foot extension unit is provided. The extension unit may be used in foot for a table according to any of the above embodiments (with or without the telescopic column having an intermediate member). However, the extension unit does not have to be arranged in such a table, but may be a stand-alone component. But if the extension unit is combined with the table as described above, the synergetic effect is that the stroke length (i.e. length between the minimum and maximum height) of such table is further increased, and it is achieved with an inexpensive manner. Regardless of this, the foot comprises an extension unit adapted to be situated within an inner volume of the foot, and manually extendable under the foot parallel to the longitudinal axis, the extension unit comprising: a core shank positioned within the inner volume of the foot, and fixed from one end to the foot, the core shank comprising screw threads on an outer surface, a first extension socket, the first extension socket comprising first grooves on a first portion of an inner surface, the first grooves arranged to engage with the screw threads of the core shank and rotate about an axis parallel to the longitudinal axis, rendering rotatable extension and retraction of the first extension socket out from and into the hollow volume of the foot, respectively, the core shank being hollow, and adapted to receive a tool for exerting a rotation of the core shank relative to the first extension socket so as to adjust the total length extention of the extension unit.

This will provide for an even wider range of accessible heights for the table through increasing the maximum height of the table by the extendable length of the first extension socket.

The core shank preferably may extend for at least <NUM>% of the entire height of the foot, and has grooves along at least <NUM>% of its extension.

The tool accepting part of the core shank may be adapted to receive an allen, or other equivalent tool, in order to exert rotation by manually rotating the allen tool.

In one embodiment, the first extension socket of the extension unit further comprises second grooves on a second portion of the inner surface.

In one embodiment, the first grooves extend along <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the grooved portion of the inner surface of the first extension socket, while the second groves extend along the other <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% of the grooved portion relative to one another.

In one embodiment, the extension unit of the foot further comprises:
a second extension socket, comprising grooves on a portion of an outer surface arranged to engage with the second grooves of the first extension socket and rotate about the longitudinal axis, rendering rotatable extension and retraction of the second extension socket out from and into the first extension socket, respectively.

This may allow for an even further increase of the accessible height range of the table by the extendable length of the second extension socket, and the extendable length of the first extension socket.

In one embodiment, the second grooves of the first extension socket comprise at least one different characteristic from the first grooves of the first extension socket.

The difference could be in the dimensions, such as: groove pitch, groove diameter, groove height, or in their rotational friction, or alternatively any combination of the latter mentioned characteristics.

In one embodiment, the first and second extension sockets have different rotational friction with the threads of the core shank, and the second grooves of the first extension socket, respectively, allowing for sequential activation of the extension sockets.

By this, it may be guaranteed that the extension sockets may be extended outwards in sequential order, rather than at the same time.

The extension socket with the lower relative rotational friction will be activated first upon the manual rotation of the tool, subsequently, when and after that extension socket is extended to its maximum extension, the other extension socket may be rotationally activated through the manual rotation of the tool.

It is notable that, it is not necessary that both extension sockets are extended, and that it is not necessary that they are extended to their maximum length, but the amount of extension may be adjusted by the user in order to obtain the desirable table height.

Further details and aspect of the present invention will become apparent from the following detailed description with reference to accompanying drawings, in which:.

This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the claims.

<FIG> illustrate the different stages of a full expansion and contraction stroke of the telescopic column. In order to help the eye, and put the description in better context, the figures are drawn with reference to a height adjustable table wherein the leg comprises a telescopic column according to the present invention. It should however be noted that, the claims are not limited to the telescopic column with the accompanying table members. Instead, the sought protection is defined by the claims.

<FIG> demonstrates the telescopic column <NUM> at its minimum position <NUM>. Note that the minimum height and minimum position both refer to the same notion, therefore are used interchangeably throughout the rest of the text, unless stated otherwise. Furthermore, the latter notion holds for the maximum height and maximum position as well. Additionally, the minimum <NUM>, and maximum <NUM> heights are defined in relation to a Cartesian coordinate system, where the longitudinal axis of the telescopic column <NUM> corresponds and is parallel to the y-axis of said coordinate system. The point of origin is defined as the minimum position <NUM> of the telescopic column, and the maximum position <NUM> will then be in the first quadrant of the x-y plane of said coordinate system.

<FIG> depicts a portion of a height adjustable table <NUM> at the minimum height <NUM>, wherein the leg is comprised of a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown).

<FIG> and <FIG> show close-up views of the lower part of the telescopic column <NUM> and the foot element <NUM> of the table <NUM>. In <FIG> the outer tube <NUM> of the telescopic column <NUM> can be seen positioned within the cavity <NUM> of the foot element <NUM> of the table <NUM>. An extension unit <NUM> is visible on either sides of the foot element <NUM>. These extension units may assist the user to gain an even wider range of accessible heights of the table <NUM>. The extension unit <NUM> is described in more detail further in the text and in relation to <FIG>.

The bottom of the outer tube <NUM> defines the second end <NUM> of the telescopic column <NUM>. <FIG>, illustrates a view wherein a portion of the outer tube <NUM> is removed, so as to expose the inner tube <NUM>, and the intermediate element <NUM>. As can be seen, at the minimum position <NUM> of the telescopic column <NUM>, the inner tube <NUM>, and consequently the intermediate element <NUM> are sitting at the bottom-most position of the telescopic column, within the cavity <NUM> of the foot element <NUM>. The lower portion <NUM> of the intermediate element <NUM> is protruding from the periphery of the bottom end <NUM> of the inner tube <NUM>. The lower portion <NUM> of the intermediate element is arranged and sized to fit and engage with the inner side of the outer tube <NUM>.

<FIG> <NUM>, shows the telescopic column <NUM> at the minimum height <NUM>, adjusted within the cavity <NUM> of the foot element <NUM> of the table <NUM>, while the table top <NUM> is excluded so to provide a view of the top end <NUM> of the inner tube <NUM> which determines the first end <NUM> of the telescopic column. The table top <NUM> would be positioned above, and attached to the top end <NUM> of the inner tube <NUM>. A motor <NUM> can be seen arranged at the upper portion of the inner tube <NUM>, which is sitting in a housing <NUM>. The motor <NUM> is part of a driving unit <NUM> (not shown), which is utilized for driving the inner tube <NUM> between the minimum <NUM> and maximum <NUM> heights of the column. The driving unit <NUM> is described in extensive detail later in the text. As observed from the figure, the top end of the inner tube <NUM> and the outer tube <NUM> are accommodated within the housing <NUM>.

In the view of <FIG>, the outer tube <NUM>, and the inner tube <NUM> have been partially removed in order to expose the intermediate element <NUM>, and a portion of an output shaft <NUM>, which is part of the driving unit <NUM> (not shown). The intermediate element <NUM>, comprises a lower portion <NUM>, which is sized and adapted to engage the outer tube <NUM> from the inside, a middle portion <NUM> being sized and adapted to be fitted into the inner tube <NUM> and engage the inner tube <NUM> from the inside, and an upper portion <NUM> being sized and adapted to be remain within the inner tube <NUM>, so as to provide for stability. The intermediate element further has an engaging element <NUM> which defines the ending of the middle portion <NUM>, and the beginning of the upper portion <NUM>, and is arranged to engage with the engaging portion <NUM> of the inner tube <NUM> during a second stage of the expansion stroke, i.e. when the inner tube <NUM> is engaged with the intermediate element <NUM>, and is passively moving the intermediate element <NUM> with itself during the expansion stroke of the telescopic column <NUM>. The intermediate element further comprises a groove <NUM> along the length of the middle portion <NUM>, which is devised to accommodate the movement of the engaging portion <NUM> of the inner tube along itself during a first stage of the expansion stroke; i.e. when inner tube <NUM> is moving outwards from the outer tube <NUM>, but is not yet engaged with the intermediate element <NUM>, hence the intermediate element <NUM> is stationary, and a first stage of the contraction stroke of the telescopic column <NUM>, i.e. when the inner tube <NUM> is moving inwards to the outer tube <NUM>, but the bottom end <NUM> of the inner tube <NUM> has not yet reached and engaged the lower portion <NUM> of the intermediate element, so the intermediate element <NUM> is stationary.

<FIG> schematically illustrates the first stage of the expansion stroke. As mentioned above, this stage is defined as when inner tube <NUM> is moving outwards from the outer tube <NUM>, but its engaging element <NUM> is not yet engaged with the engaging portion <NUM> of the intermediate element <NUM>, rendering the intermediate element <NUM> is stationary.

<FIG> depicts a portion of a height adjustable table <NUM> during the first stage of the expansion stroke, wherein the leg comprises a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown). A recess <NUM> is visible on the top end of the outer tube <NUM>, which is devised for accepting a worm screw <NUM> of the driving unit <NUM> (not shown) when the telescopic column <NUM> is at its minimum height <NUM>.

<FIG> and <FIG> show close-up views of the lower part of the telescopic column <NUM> and the foot element <NUM> of the table <NUM>. In the view of <FIG> the outer tube <NUM> is partially removed to expose the inner tube <NUM> and the intermediate element <NUM>. It can be seen that, while the inner tube <NUM> has moved upwards (outwards from the outer tube <NUM>) relative to its position in <FIG>, the intermediate element <NUM> is stationary, and still sitting at the bottom end <NUM> of the telescopic column <NUM>, within the cavity <NUM> of the foot element <NUM>. <FIG> demonstrates a view in which a side wall of the inner tube <NUM> is partially removed so to expose the engaging portion <NUM> of the inner tube <NUM> positioned within the groove <NUM> of the intermediate element <NUM>. The engaging portion <NUM> is devised to move within this groove <NUM> in the first stage of the expansion stroke, so to provide for smooth motion.

<FIG> demonstrates the moment of the expansion stroke of the telescopic column <NUM> in which the engaging portion <NUM> of the inner tube engages with the corresponding engaging element <NUM> of the intermediate element <NUM>. <FIG> shows a close-up view of the lower portion of the table <NUM> where the telescopic column <NUM> and the foot element <NUM> can be partially seen. In the view of <FIG>, the outer tube is partially removed, so to expose the bottom end <NUM> of the inner tube <NUM> and the intermediate element <NUM>. At this moment, while the lower portion <NUM> of the intermediate element still sits at the bottom end <NUM> of the telescopic column <NUM>, and so is stationary, the full length of the middle portion <NUM> resides outside the inner tube <NUM>, since the engaging portion of <NUM> the inner tube <NUM> is now engaged with the engaging element <NUM> of the intermediate element <NUM>. This is better observable from the view provided in <FIG>, in which a side wall of the inner tube <NUM> is removed to provide a perspective of the engagement of the engaging element <NUM> of the intermediate element <NUM>, and the engaging portion <NUM> of the inner tube <NUM>. In <FIG>, the upper portion <NUM> of the intermediate element <NUM> is also partially observable. This upper portion <NUM> will always reside within the inner tube <NUM>, no matter at which stage of the expansion or contraction stroke the telescopic column <NUM> is.

<FIG> illustrates the second stage of the expansion stroke. As mentioned above, this stage is defined as when the inner tube <NUM> is engaged with the engaging element <NUM> of the intermediate element <NUM> through its engaging portion <NUM>, and is passively moving the intermediate element <NUM> with itself during the expansion stroke of the telescopic column <NUM>. <FIG> depicts a portion of a height adjustable table <NUM> during the second stage of the expansion stroke, wherein the leg is comprised of a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown). A recess <NUM> is visible on the top end of the outer tube <NUM>, which is devised for accepting a worm screw <NUM> of the driving unit <NUM> (not shown) when the telescopic column <NUM> is at its minimum height <NUM>. <FIG> demonstrates the same view as in <FIG>, except a side wall of the outer tube <NUM> being removed, so to expose the bottom end <NUM> of the inner tube <NUM>, and the lower <NUM> and middle <NUM> portions of the intermediate element <NUM>. As visible, the intermediate element <NUM> has been passively moved upwards (outwards from the outer tube <NUM>) by the inner tube <NUM>. It can be understood that, during this stage of the expansion stroke, the intermediate element <NUM> is no longer stationary.

<FIG> illustrates the telescopic column <NUM> at its maximum position <NUM>. <FIG> depict a portion of a height adjustable table <NUM> at the maximum height <NUM>, wherein the leg is comprised of a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown). The bottom end of the outer tube <NUM> is defining the second end of the telescopic column <NUM> can be seen positioned within the cavity <NUM> of the foot element <NUM>. The worm screw <NUM> (not shown) accepting recess <NUM> of the outer tube <NUM> is also visible in <FIG>. In <FIG> a side wall of the outer tube <NUM> is removed, so to expose the bottom end <NUM> of the inner tube <NUM>, and the intermediate element <NUM>. <FIG> shows a close-up view of the boxed portion of the telescopic column <NUM> of <FIG>. as seen from <FIG> and <FIG>, the entire length of the middle portion <NUM> of the intermediate element <NUM> resides outside he inner tube <NUM>. As observable, the overlap p<NUM> of the inner <NUM> and outer tubes <NUM> at this stage is very small relative to the total length L of the telescopic column <NUM>. As the length of the overlap increases the length of the telescopic column in its minimum height, and/or, decreases the length of the telescopic column in its maximum height, it is desirable to have as small overlap P1 as possible, preferably less than <NUM>% of the length, <NUM>% of the length, <NUM>% of the length <NUM>% of the length or as little as <NUM>% of the length or less.

<FIG> shows the telescopic column <NUM> at the maximum height <NUM>, adjusted within the cavity <NUM> of the foot element <NUM> of the table <NUM>, while the table top <NUM> is excluded so to provide a view of the top end <NUM> of the inner tube <NUM> which determines the first end <NUM> of the telescopic column. The table top <NUM> would be positioned above, and attached to the top end <NUM> of the inner tube <NUM>. The motor <NUM> can be seen arranged at the upper portion of the inner tube <NUM>, which is sitting in the housing <NUM>. In the view of <FIG>, a side wall of the outer tube <NUM> and a portion of the inner tube <NUM> have been removed so to give a perspective of the entire intermediate element <NUM>, the output shaft <NUM>, and a portion of a lead screw <NUM>. The lead screw <NUM> is also a component of the driving unit <NUM>, and will be explained in better detail in further in the text. As observed in this figure, the engaging portion <NUM> of the inner tube <NUM> and the engaging element <NUM> of the intermediate element <NUM> are engaged, and are positioned at the top-most portion of the interior of the outer tube <NUM>, and the bottom-most portion of the interior of the inner tube <NUM>. The upper portion <NUM> of the intermediate element <NUM> as mentioned earlier, will always reside within the inner tube <NUM> to provide for stability. Also, the lower portion <NUM>, which is sized and adapted to engage the outer tube <NUM> from the inside, is frictionally engaged with the inner walls of the outer tube <NUM>.

<FIG> schematically demonstrates the first stage of the contraction stroke of the telescopic column <NUM>. As mentioned above, this stage is defined as when the inner tube <NUM> is moving inwards to the outer tube <NUM>, but the bottom end <NUM> of the inner tube <NUM> has not yet reached, nor engaged the lower portion <NUM> of the intermediate element <NUM>, rendering the intermediate element <NUM> stationary. During the first stage of the contraction stroke the lower portion <NUM> of the intermediate element <NUM> is maintained stationary by frictional engagement with the inner walls of the outer tube <NUM>.

<FIG> depicts a portion of a height adjustable table <NUM> during the first stage of the contraction stroke, wherein the leg is comprised of a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown), and the bottom end of the outer tube <NUM>, which defines the second end <NUM> of the telescopic column <NUM> is within the cavity <NUM> of the foot element <NUM>. <FIG> is a close-up view of the boxed portion of the telescopic column <NUM> marked in <FIG>. A side wall of the outer tube is removed in both <FIG>, so to expose the bottom end <NUM> of the inner tube <NUM>, the intermediate element <NUM>, and a portion of the output shaft <NUM>. As visible from these figures, and as a result of the inner tube <NUM> moving downwards (inwards into the outer tube <NUM>), the overlap p<NUM> of the inner <NUM>, and outer tubes <NUM> is larger in comparison to the overlap p<NUM> of the latter mentioned members at the maximum height <NUM> of the telescopic column <NUM>, shown in <FIG>. A smaller portion of the middle portion <NUM> of the intermediate element <NUM> is remains exterior to the inner tube <NUM> compared to that at the maximum position <NUM> of the telescopic column <NUM> due to the downwards movement of the inner tube <NUM>, over the middle portion <NUM> of the intermediate element <NUM>. The engaging portion <NUM> of the inner tube <NUM> will move within the groove <NUM> of the intermediate element <NUM> during the first stage of the contraction stroke.

<FIG> depicts the final stage of the movement of the telescopic column <NUM>, namely the second stage of the contraction stroke. This stage is defined as when the inner tube <NUM> is moving inwards to the outer tube <NUM>, and is engaged with the lower portion <NUM> of the intermediate element <NUM> through its bottom end <NUM>, and is passively moving the intermediate element <NUM> with itself during the contraction stroke of the telescopic column <NUM>.

<FIG> depicts a portion of a height adjustable table <NUM> during the second stage of the contraction stroke, wherein the leg is comprised of a telescopic column <NUM> according to the present invention. The telescopic column is attached to the under-side of the table top <NUM> from the top end <NUM> of the inner tube <NUM> (not shown). A portion of the outer tube <NUM> is removed in the view of <FIG>, so to show the portion of the inner tube <NUM> that resides within the outer tube <NUM> at this stage, the lower portion <NUM> of the intermediate element <NUM> located under, and protruding from the periphery of the bottom end <NUM> of the inner tube <NUM>, and a portion of the output shaft <NUM>. As observable form this figure, an upper portion of the inner tube <NUM> remains exterior to the outer tube, as the telescopic column <NUM> is yet to reach its minimum height <NUM> at the end of the contraction stroke.

<FIG> shows a close-up view of the lower part of the telescopic column <NUM> and the foot element <NUM> of the table <NUM>. In the view of <FIG> the outer tube <NUM> is partially removed to expose the inner tube <NUM> and the intermediate element <NUM>.

<FIG> schematically shows a cross sectional perspective view of the intermediate element <NUM>. As observed, the interior of the intermediate element <NUM> is hollow, comprising two sections; namely the first interior hollow <NUM>, and the second interior hollow <NUM> of the intermediate element <NUM>. The hollow structure of the intermediate element <NUM>, is devised to accommodate the output shaft <NUM> and/or the lead screw <NUM>. The first interior hollow <NUM> has a cross sectional diameter D<NUM>, which is larger than the cross sectional diameter D<NUM> of the second interior hollow <NUM>. The onset of the second interior hollow <NUM> from the first <NUM> is defined by the top edge <NUM> of the second interior hollow <NUM>. This top edge <NUM> serves the purpose of an end stop for the intermediate element <NUM>, similar to a physical barrier, so to hinder the intermediate element from moving further out in the expansion stroke. Hence forth, the top edge <NUM> will be referred to as the physical barrier. The stopping mechanism of the physical barrier <NUM> is explained with respect to <FIG> as follows.

<FIG> demonstrates the telescopic column <NUM>, and the relative positions of the intermediate element with respect to the output shaft <NUM> and the lead screw <NUM>. <FIG> shows a view in which a side wall of the outer tube <NUM>, and the inner tube <NUM> are removed so to expose the intermediate element <NUM>, the output shaft <NUM>, and the lead screw <NUM>. The mechanisms of the driving unit are described in detail later in the text, but in brief, the lead screw <NUM> translates rotational movement to longitudinal movement of the output shaft <NUM>. The output shaft <NUM> in turn is coupled to the inner tube <NUM>, and drives the inner tube <NUM> outwards from, and inwards to the outer tube <NUM> during the expansion and contraction strokes of the telescopic column <NUM>, respectively.

In <FIG> the opening of the first interior hollow <NUM> of the intermediate element <NUM> can be seen throw which the lead screw <NUM> is penetrating. The output shaft <NUM> exits the intermediate element <NUM> from an opening of the second hollow <NUM> (not shown), from the other end. <FIG> shows the same view as <FIG>, except that the intermediate element <NUM> is partially removed so to expose the portions of the output shaft <NUM>, and the lead screw <NUM> that are within the intermediate element <NUM>. On the top of the output shaft <NUM>, and coupling it to the lead screw <NUM>, a receiving nut <NUM> is situated. <FIG> shows a close-up view of a portion of the telescopic column in <FIG>, wherein the entire length of the intermediate element, and portions of the output shaft <NUM> and lead screw <NUM> are visible. In addition, in <FIG>, the outer tube <NUM> and the inner tube <NUM> are completely removed from the picture. Focusing on the inner side of the intermediate element <NUM>, the first interior hollow <NUM>, the second interior hollow <NUM>, and the physical barrier <NUM> is visible. While the lead screw <NUM> is within the first interior hollow <NUM>, the output shaft <NUM> is well within the first interior hollow <NUM>, tailing into the second interior hollow <NUM> of the intermediate element <NUM>. This is due to the column being somewhere midway between its minimum <NUM> and maximum <NUM> heights, as indicated by the positioning of the inner tube <NUM> relative to the outer tube <NUM> in <FIG>. Furthermore, from <FIG>, it can be seen that the receiving nut <NUM> of the output shaft <NUM> comprises a lower protrusion <NUM> with a slightly larger cross sectional diameter than that of the output shaft <NUM>. The diameter of this protrusion <NUM> is larger than the diameter D<NUM> of the second interior hollow <NUM> of the intermediate element <NUM>. This is so that when in the expansion stroke, the protrusion <NUM> will hit against the physical barrier <NUM> of the intermediate element <NUM>, thus hindering the intermediate element <NUM> from moving further out in the telescopic column <NUM>. This situation is depicted in <FIG>, where a cross sectional perspective close-up view of the telescopic column <NUM> is given. It is notable that, as observed in this figure, a portion <NUM> of the lead screw <NUM> well extends within the output shaft <NUM>. However, one must note that, this portion of the lead screw <NUM> may never exit the output shaft <NUM>, as <FIG> demonstrates the maximum height <NUM> of the telescopic column <NUM>. Thus, when it is said that "the lead screw does not extend inside the second hollow <NUM> of the intermediate element <NUM>", it is only meant to refer to that portion of the lead screw <NUM>, excluding portion <NUM>.

In <FIG> and <FIG> the mechanism of the driving unit <NUM> will be extensively explained. Note that, in all these figures, as better seen in <FIG>, an upside-down view of the table <NUM>, and thus the telescopic column <NUM>, and the driving unit <NUM>, is given.

<FIG> displays the telescopic column <NUM>, and the driving unit <NUM> when the telescopic column <NUM> is somewhere midway between its minimum <NUM> and maximum <NUM> heights. This is visible from the relative positioning of the outer <NUM> and inner <NUM> tubes, also the receiving nut <NUM> of the output shaft <NUM> (more explanation given below). As observable in <FIG>, the table <NUM> is upside down, displaying underneath the table top <NUM>. A breadth fastening bar <NUM>, and two length fastening bars <NUM> help fasten the telescopic column <NUM> and the driving unit <NUM> to the under-side of the table top <NUM>, through the housing <NUM>. In <FIG>, a portion of the outer tube <NUM> and inner tube, as well as the entirety of the intermediate element <NUM> have been removed so to provide a better view of the output shaft <NUM> and the lead screw <NUM>. It is observed that, the lead screw <NUM> is penetrated within a bearing sleeve <NUM>, into the housing <NUM>. The receiving nut <NUM> of the output shaft <NUM> is well outside the bearing sleeve <NUM>, which is an indication of the telescopic column <NUM> not being at its minimum height <NUM>.

<FIG> illustrates a close-up view of the top portion of the telescopic column <NUM>, wherein a portion of the outer tube <NUM>, inner tube <NUM>, and the housing <NUM> are removed to give a better view of the components of the driving unit <NUM> situated within the housing <NUM>, additional to the lead screw <NUM>, and the output shaft <NUM>. <FIG> demonstrates a view of the driving unit <NUM> while excluding the housing <NUM>, and the outer <NUM> and inner tubes <NUM>. From <FIG> it can be understood that, the worm screw <NUM> is attached from one end to the motor <NUM>, the housing <NUM>, the inner holder <NUM> of the housing <NUM>, inner tube <NUM>, and in the case of approximately minimum height <NUM> of the telescopic column, the outer tube <NUM>, from a recess (<NUM>, <NUM>-not shown, <NUM>- not shown) devised the receive the other end of the worm screw <NUM>. Depending on whether the column <NUM> is desired to expand or contract, the worm screw <NUM> is configured to rotate in either rotary direction driven by the motor <NUM>. The worm wheel <NUM> will then transfer this rotary movement to a worm wheel <NUM>, arranged and attached around the bearing sleeve <NUM>. As the worm wheel <NUM> rotates about the longitudinal axis, it will rotate the bearing sleeve <NUM> about the longitudinal axis together with itself. From <FIG> it is observable that the lead screw <NUM> is attached from an end <NUM> to the bearing sleeve <NUM>. The lead screw <NUM> is rotatable along the longitudinal axis, and as the bearing sleeve <NUM> rotates, it will rotate the lead screw <NUM> together with itself. The lead screw <NUM> in turn, is coupled with the output shaft <NUM> through the receiving nut <NUM>. The output shaft <NUM> is fixed to the second end <NUM> of the telescopic column from the other end by a fixation <NUM>. Note that, this fixation <NUM> keeps the output shaft <NUM> rigidly attached to the second end <NUM> of the column <NUM>, not allowing for any separation of movement. As the lead screw <NUM> rotates, the inner threads (not shown) of the receiving nut <NUM> interact with the grooves on the lead screw <NUM>. By this, the rotary movement of the lead screw <NUM> is translated to longitudinal movement of the output shaft <NUM> along the longitudinal axis, allowing for height adjustment of the table <NUM> comprising a telescopic column <NUM> according to the present invention.

In addition, <FIG> demonstrate two radial bearings <NUM> fitted and attached to the bearing sleeve <NUM>, and surrounding either sides of the worm wheel <NUM>. The radial bearings <NUM> serve the purpose of radially securing the bearing sleeve <NUM>, and decreasing rotational friction upon rotation of the bearing sleeve <NUM> relative to the worm wheel <NUM>. Furthermore, in <FIG> an inner holder <NUM> is also visible attached to the inner side of the housing <NUM>, and fitted to surround the radial bearings <NUM>, and the worm wheel <NUM>. Additionally, an axial bearing <NUM> is attachably fitted between the housing <NUM> and a radial bearing <NUM>. The axial bearing is meant to decrease rotational friction of the bearing sleeve <NUM> with rotation of the worm wheel. It is necessary that, in this embodiment, the inner holder <NUM> of the housing <NUM> allows access of the worm screw <NUM> to the worm wheel <NUM> from the non-surrounded portion. From the outer side, the inner holder <NUM> is arranged to be fitted within the inner tube <NUM>, and additionally the outer tube <NUM> when the column <NUM> approaches its minimum height <NUM>.

As mentioned earlier, in the illustrations of <FIG>, the telescopic column <NUM> is not at its minimum height <NUM>. This is observable from the location of the receiving nut <NUM> of the output shaft <NUM> on the lead screw <NUM>. In the embodiment demonstrated here, for increasing the range of accessible heights of the telescopic column <NUM> even further, the bearing sleeve <NUM>, is configured to have a hollow structure, so as to be able to accommodate the receiving nut <NUM>, and a portion of the output shaft <NUM> within its hollow <NUM>. This is to facilitate decreasing the height of the telescopic column <NUM> even further, therefore allowing for lower minimum heights to be achieved.

The latter situation is schematically demonstrated in <FIG>, where the telescopic column <NUM> and the driving unit <NUM> are shown at the minimum height <NUM> of the telescopic column <NUM>. In <FIG> the first end <NUM> of the telescopic column <NUM> is shown wherein the housing <NUM>, the inner tube <NUM>, the outer tube <NUM>, and the inner holder <NUM> are partially removed so to expose the worm screw <NUM>, the worm wheel <NUM>, the radial bearings <NUM>, a portion of the bearing sleeve <NUM>, and the output shaft <NUM>. The receiving nut <NUM>, nor the lead screw <NUM> is visible in this position, as they are fully immersed in the hollow <NUM> of the bearing sleeve <NUM>. This is better seen in the view given in <FIG>, where in addition to the above, the bearing sleeve <NUM>, the worm screw <NUM>, the worm wheel <NUM>, and the radial bearings <NUM> are also partially removed so to show the hollow <NUM> of the bearing sleeve <NUM>. As observable from these two figures, the outer tube <NUM> is situated fully within the housing <NUM>, indicating the column <NUM> is at minimum height <NUM>. <FIG> shows a scheme of the driving unit <NUM> in which the housing <NUM>, inner holder <NUM>, and the inner <NUM> and outer <NUM> tubes are fully removed. From <FIG> and <FIG> it is observed that, the receiving nut <NUM> is sitting at the lowest end of the bearing sleeve <NUM>, such that the lead screw <NUM> is barely visible at its attaching end <NUM> to the bearing sleeve <NUM>. By this, the height of the telescopic column <NUM> may be further reduced by the axial length x of the bearing sleeve <NUM>.

<FIG> depict different states and/or embodiments of an extension unit <NUM> arranged on the foot element <NUM> of the height adjustable table <NUM> according to the second aspect of the invention. The extension unit <NUM> allows accessing an even wider range of heights of the table <NUM> by increasing the maximum height of the table <NUM> even further.

<FIG> shows an extension unit <NUM> with a single extension socket <NUM> arranged on the foot element <NUM> of a height adjustable table <NUM>. Note that, the extension unit <NUM> may be arranged to be fully retracted within the body <NUM> of the foot element <NUM> when further maximizing the height of the table <NUM> is not necessary. This situation is demonstrated in <FIG>, where a cross sectional view of the foot element <NUM> is given, exposing a first extension socket <NUM> fully retracted within the body <NUM> of the foot element <NUM>. <FIG> illustrates the same state as <FIG> with the cross sectional cut going through the extension unit <NUM> so to expose the elements there within. A core shank <NUM> is visible, being fixedly attached to the foot element <NUM> from one end <NUM>. The core shank <NUM> is hollow, so to enable receiving a tool at the tool accepting end <NUM> of the first extension socket <NUM>, to provide manual rotation from a tool accepting portion <NUM>. The core shank <NUM> has screw threads <NUM> on its outer surface, and is arranged to be within the first extension socket <NUM> upon full retraction of the extension unit <NUM>. The first extension socket <NUM> comprises a set of first grooves <NUM> on the inner side, configured to engage with the screw threads <NUM> on the core shank <NUM> upon rotation of the first extension socket <NUM>. As the tool (not shown) is rotated, the first extension socket <NUM>, engages with the threads <NUM> of the core shank <NUM> through the first set of grooves <NUM>, and consequently, the first extension socket will move along an axis parallel to the longitudinal axis, extending outwards from underneath the foot element <NUM>.

<FIG> shows the latter mentioned embodiment of the extension unit <NUM> at its maximum extension. In <FIG>, the first extension socket <NUM> is seen extending underneath the foot element <NUM>. Note that an insignificant portion <NUM> of the first extension socket <NUM> remains within the body <NUM> of the foot element <NUM> even upon full extension. This is to ensure stability. The screw threads <NUM> of the core shank <NUM> are left visibly bare. <FIG>, illustrates the same state of <FIG>, wherein the extension unit <NUM> comprising one extension socket <NUM> is at its maximum extension, such that the line cute of the cross section goes through the extension unit <NUM>. The interior view of the non-extended portion <NUM> of the first extension unit reveals that the grooves <NUM> of the first extension unit <NUM> are still engaged with the screw threads <NUM> of the core shank in that portion <NUM>.

<FIG> is a schematic illustration of another embodiment of the extension unit <NUM>, namely the double extension socket, at its fully retracted state. This embodiment comprises a second extension socket <NUM>, in addition to the first extension socket <NUM>. The first extension socket <NUM> is configured to engulf the second extension socket <NUM> within a portion <NUM> of itself, when extension unit <NUM> is in full retraction. From the remaining portion <NUM>, the first extension socket <NUM> is adjacent the core shank <NUM>, at this state. Again, similar to the previous embodiment, the core shank <NUM> is hollow, so to enable receiving a tool from the tool accepting portion <NUM> to be received at the tool accepting end <NUM> of the second extension socket <NUM>. The first extension socket comprises a set of first grooves on the portion <NUM> adjacent to the core shank <NUM>, configured to engage it upon rotation of the tool (not shown), and additionally comprises a set of second grooves <NUM>, configured to engage the second extension socket <NUM>. The first <NUM> and second <NUM> grooves of the first extension unit may be different in their dimensions. In the particular embodiment demonstrated in <FIG> and <FIG>, they vary in their diameter, and thread pitch. The second extension socket <NUM> comprises exterior grooves <NUM> configured to engage the first extension socket <NUM> through the second grooves <NUM> of the first extension socket <NUM>.

The first <NUM> and second <NUM> extension sockets have different rotational friction with the threads <NUM> of the core shank <NUM>, and the second grooves <NUM> of the first extension socket <NUM> respectively, allowing for sequential activation of the extension sockets <NUM>, <NUM>.

By this, it may be guaranteed that the extension <NUM>, <NUM> sockets may be extended outwards in sequential order, rather than at the same time.

The extension socket with the lower relative rotational friction will be activated first upon the rotation of the second extension socket <NUM> by the manual rotation of a tool (not shown) engaged to the tool accepting end <NUM> of the second extension tool <NUM>, subsequently, when and after that extension socket is extended to its maximum extension, the other extension socket may be rotationally activated through the manual rotation of the tool.

<FIG> depict the double extension socket embodiment of the extension unit <NUM> in its fully extracted state. As can be seen, a portion <NUM> of the first extension socket <NUM> remains within the body <NUM> of the foot element <NUM>, while a portion <NUM> of the second extension socket <NUM> remains within the interior of the first extension socket <NUM>. These overlapping portions <NUM>, <NUM> guarantee stability of the extension unit <NUM> upon full extension.

<FIG> and <FIG> respectively show the retracted and extracted state of an embodiment of the extension unit <NUM> where the extension socket <NUM> has a quadratic cross section. In this embodiment comprises only a first extension socket <NUM>. In <FIG>, the extension socket has been removed so to expose the core shank <NUM>, and the screw threads <NUM>. It the view of <FIG>, the recess <NUM> in the foot element <NUM> through with the extension unit <NUM> will extend beneath the foot element <NUM>. <FIG> demonstrates the extension unit <NUM> with the quadratic single extension socket <NUM> in the retracted state.

<FIG> demonstrates the extension unit <NUM> with a quadratic single extension socket <NUM> in the fully extracted position, extending beneath the foot element <NUM>. The core shank <NUM> and its screw threads <NUM> are visible in the view given in <FIG> demonstrates the extension unit <NUM> with a quadratic single extension socket <NUM> in the fully extracted state, with a line cut through the elements of the extension unit <NUM> so to expose the inner elements there within. The inner grooves <NUM> of the quadratic extension socket <NUM> are visible. In this embodiment, unlike the previous ones wherein the extension sockets <NUM>, <NUM> have a circular cross section, enabling their rotation around an axis parallel to the longitudinal axis, the quadratic extension socket <NUM> cannot rotate. Instead, unlike the previous embodiments, where the core shank <NUM> is fixedly attached, and is not meant to rotate, in the embodiments for <FIG> and <FIG> the core shank <NUM> is made to rotate about the axis parallel to the longitudinal axis. It is noted that, the core shank <NUM> is only allowed rotational movement, and is otherwise static in the longitudinal and lateral directions. The core shank <NUM> of this embodiment accepts a tool (not shown) into the hollow of its body through the tool accepting portion <NUM>. When the tool is rotated, the core shank <NUM> is rotated together with the tool. Through this, the inner grooves <NUM> of the quadratic extension socket <NUM> engage with the screw threads <NUM> of the core shank, enabling the axial movement of the extension socket <NUM>.

It is noted that, the extension socket may have any geometrical cross section, and/or the extension unit may comprise any number of extension sockets.

Claim 1:
A telescopic column (<NUM>) for height-adjustable furniture, said telescopic column extending along a longitudinal axis from a first end (<NUM>) to a second end (<NUM>) of said telescopic column (<NUM>), comprising:
- an outer elongated tube (<NUM>) fixedly arranged at said second end (<NUM>) of said telescopic column (<NUM>),
- an inner elongated tube (<NUM>) having a top end (<NUM>) and bottom end (<NUM>), wherein said top end (<NUM>) defines said first end (<NUM>) of the telescopic column (<NUM>), and wherein the inner elongated tube (<NUM>) is sized and adapted to move into and out of said outer tube (<NUM>), drivable by a driving unit (<NUM>) along said longitudinal axis between a maximum height (<NUM>) and a minimum height (<NUM>),
- and an intermediate element (<NUM>)having a lower portion (<NUM>) being sized and adapted to engage the outer tube (<NUM>) from the inside thereof, a middle portion (<NUM>) being sized and adapted to be fitted into the inner tube (<NUM>) and engage the inner tube (<NUM>) from the inside thereof, and an upper portion (<NUM>) being sized and adapted to be remain within the inner tube (<NUM>), so as to provide for stability,
wherein said intermediate element (<NUM>) is passively moved by means of the inner tube (<NUM>) when said telescopic column (<NUM>) is moved between said maximum height (<NUM>) and said minimum height (<NUM>),
wherein the telescopic column further comprises
a housing (<NUM>) adapted to be fastened to a table top (<NUM>), wherein a top end of the inner elongated tube (<NUM>) and a top end of the outer elongated tube (<NUM>) are accommodatable within the housing (<NUM>), and
characterized in that said housing is further adapted to allow a worm screw (<NUM>) to enter the housing while being driven from a motor (<NUM>) positioned substantially external to the housing, and in that
said bottom end of the inner tube is adapted to interact with the lower portion of the intermediate element so as to move the intermediate element during a contraction stroke.