Patent Description:
Lifting columns comprising a telescopic guide and a box-shaped housing for height-adjustable tables where the telescopic guide appears as a table leg were developed in the late <NUM>. The box-shaped housing, which is usually rectangular, comprises an electric motor, transmission and various electronics. An example of such a lifting column is disclosed in <FIG> of <CIT>. A different type of lifting column is described in <CIT>, where the entire drive unit, i.e. electric motor, transmission and various electronics are integrated in the telescopic guide.

A frame carrying a tabletop for a height-adjustable table, comprises an upper frame, which typically comprises two longitudinal members and two cross members, at least one lifting column and at least one foot. The lifting column can, as described above, be designed with or without a box-shaped housing at the upper end. The longitudinal members are usually constructed as through-going tube profiles, located in parallel with a mutual distance corresponding to the width of the box-shaped housing. At each end of the longitudinal members, a cross member is secured. The longitudinal members and the cross members are usually welded together or must be assembled with screws. A lifting column is mounted at each end by placing the box-shaped housing between the longitudinal members with an end against the respective cross member. The lifting column is secured by means of screws through the two longitudinal members and through the cross member into the box-shaped housing. The same goes for the assembly of the foot to the lifting column. Assembly of the frame is troublesome and time consuming. This is due to the parts of the frame being relatively large and heavy. Furthermore, the assembly of the frame requires several screw operations, which requires that the individual parts are placed correctly relative to each other.

discloses an adjustable table frame, where a connecting member is used to assemble a lifting column to a foot. The connecting member is a tubular element which is to be fastened to the bottom of the lifting column with a screw. Four L-shaped grooves extend at the side of the connecting member and are assessable at the free end of the connecting member. The upper side of the foot comprises an opening with a geometry corresponding to the connecting member and four nuts for engagement with the grooves. When inserted, the foot is turned <NUM> degrees and one of the nuts engage a locking lug preventing the foot from being turned back. This solution will, due to the turning of the foot, scratch the surface of the foot. Moreover, it requires high manufacturing tolerances as even small deviations will cause a loose and unreliable assembly between the foot and lifting column and thus an unstable and a potentially collapsible table frame.

Another solution for assembling a lifting column and a foot is provided in <CIT>. Here the bottom plate of the lifting column has two locking tracks extending approximately a quarter of a circle. The locking tracks are inclined and ends in a locking boss. The foot comprises two locking pins for engagement with the locking tracks. Once the locking pin is inserted into the locking groove, the foot must be turned. Due to the inclination of the locking track, the foot will gradually be forced against the lifting column and locking pin will eventually reach the locking boss. This solution suffers the same drawbacks as the above. Apart from the scratching of the surface of the foot, even small manufacturing tolerances may result in an unreliable assembly of the foot and lifting column. This might be due to the assembly being too loose or too tight. The latter would cause problems for the person assembling as an increased torque will have to be applied to reach the position of the locking boss. There is also a risk that some of the parts would be deformed plastically, leading to instability or an excess stress in some of the parts. A further drawback arises when the lifting column and foot is disassembled. Here, the deformations of the parts could make it difficult or even impossible to reassemble.

<CIT> discloses a further frame for a sit-stand table.

The purpose of the invention is to provide a frame for tables which does not suffer from the drawback mentioned above, and which can be assembled in an intuitive, simple, and easy manner.

This is achieved according to the invention as defined in claim <NUM>. The person assembling the lifting column and the foot just need to insert the bolts and activation pins into their corresponding holes and the fastening mechanism will fix the two together. This self-tightening of the fastening mechanism can therefore take up and absorb the tolerance chain or accumulation of tolerances of the lifting column and the foot. Disassembling the lifting column and the foot will also not be a problem as the fastening mechanism will take up and absorb any changes in tolerances or slack.

In an embodiment of the invention, the clamping sleds is a plate member having a flat portion that engages the inner side of the upper part of the foot. Hereby, it is ensured that the position of the clamping sled inside the foot relative to the bolts is kept.

In an embodiment of the invention, the guides of the clamping sleds extend at an angle relative to the plane parallel to the flat portion of the spring biased spacer. This serves to pull the bolts and thereby move the lifting column and the foot into a forced and tight engagement.

In an embodiment of the invention, the open ends of the guides are closest to the upper part and from where the guides extend at an angle towards the lower part. When the fastening mechanism is released, the bolts will be pulled in a direction toward the lower part.

In an embodiment of the invention, the open end of the guides is coincident with the plane parallel to the flat portion of the spring biased spacer. Once the clamping sleds and the tension springs enter the retracted state, this position of the open end ensures a reliable engagement with the bolts.

In an embodiment, the bolts comprise a shank divided in three portions: a first portion and second portion having a diameter close to but not equal to the diameter of the holes in the upper part of the foot and the spring biased spacer, and a third portion between the first portion and second portion. The third portion having a diameter which is less than the diameter of the first portion and the second portion. Hereby, faces between the different portions are created and helps to better guide the clamping sleds into engagement with the bolt.

In an embodiment, the diameter of the third portion of the bolts is smaller than the width of the guides of the clamping sleds such that the third portion of the bolts can be accommodated in the guides, including engagement with the face between the second portion and the third portion of the bolts. This maximizes the area of the faces engaging the guides of the clamping sleds which again ensures the required transfer of forces.

In an embodiment, the profile of the lifting column to be assembled with the foot comprises a bottom plate at the lower end of the profile to which the bolts are fixed. The bolts extend in a direction parallel to the longitudinal axis of the profile. The bottom plate serves to transfer force applied by the fastening mechanism to and from the foot and the lifting column.

In an embodiment, the activation pins are arranged between the bolts such that they extend in a direction parallel to the longitudinal axis of the profile. An even, i.e. parallel, movement of the spring biased spacer can thereby be achieved.

In an embodiment, the open end of the guides of the clamping sleds face each other. This mirrored position results in applying an even force to pull the clamping sleds towards each other, keeping the forced engagement between the lifting column and the foot approximately equal.

The invention relates a further embodiment to a height-adjustable table comprising a frame according to one or more of the above-mentioned embodiments.

An embodiment of the invention will be described more fully below with reference to the accompanying drawing, in which:.

<FIG> shows a perspective view of a height-adjustable table <NUM> comprising a tabletop <NUM>. At each side of the height-adjustable table <NUM>, a linear actuator in the form of a lifting column <NUM> is mounted in a carrying frame (not shown) onto which the tabletop <NUM> is mounted. The other end of each lifting column <NUM> is fixed to a foot <NUM> on which the height-adjustable table <NUM> stands. The lifting columns <NUM> comprise a drive unit (not shown) and two or three mutually telescopically arranged profiles <NUM>,<NUM>,<NUM>. One profile <NUM> is fixed to the foot <NUM> and one profile <NUM> is mounted to the carrying frame of the table <NUM>. Depending on the type of lifting column <NUM>, the profile <NUM> can be directly mounted to the frame of the table or via a motor housing at the top of the profile <NUM>. Each lifting column <NUM> is driven by means of an electric motor, which drives a spindle through a gear. The spindle is furnished with a spindle nut secured to the telescopically movable profile(s) <NUM>,<NUM>,<NUM>. The height-adjustment of the tabletop <NUM> is thus performed by the lifting columns <NUM>. The adjustment is achieved by activating the operating panel <NUM>. The number of telescopically arranged profiles in a lifting column can vary from at least two and up. Also, the length of the profiles and the stroke length of the lifting column can be configured as needed.

<FIG> illustrate a side view of the height-adjustable table <NUM> in a sitting position <NUM> and a standing position <NUM>, respectively. Since the length of the lifting columns <NUM> can be adjusted, the sitting position <NUM> and standing position <NUM> can be set to accommodate the physical characteristics and personal preferences of each individual user of the height-adjustable table <NUM>.

<FIG> shows the profile <NUM> attached to the foot <NUM> and <FIG> shows the profile <NUM> detached from the foot <NUM>. The upper side <NUM> of the foot <NUM> comprises two holes <NUM>,<NUM> through which the bolts <NUM>,<NUM> can be inserted for attachment of the profile <NUM> of the lifting column <NUM> to the foot <NUM>.

As shown in <FIG>, one end of the bolts <NUM>,<NUM> are fixed in the bottom plate <NUM> at the lower end of the profile <NUM> and extends in a direction parallel to the longitudinal axis of the profile <NUM>. An activation element <NUM> having two pins <NUM>,<NUM> is arranged between the two bolts <NUM>,<NUM>. The pins <NUM>,<NUM> extend in the same direction as the bolts <NUM>,<NUM> and can be inserted in the holes <NUM>,<NUM> when the profile <NUM> of the lifting column <NUM> is to be attached to the foot <NUM>. When the pins <NUM>, <NUM> and the bolts <NUM>,<NUM> are inserted into the holes <NUM>,<NUM> and the bolt holes <NUM>,<NUM> respectively, they engage different parts of a fastening mechanism <NUM>, which will be explained in the following.

The fastening mechanism <NUM> comprises two clamping sleds <NUM>, <NUM>, two tension springs <NUM>, <NUM>, and a spring biased spacer <NUM>. The fastening mechanism is arranged inside the foot <NUM> which comprises a lower part <NUM> and an upper part <NUM>. In the embodiment of the foot <NUM> in <FIG>, the lower part <NUM> has a U-shaped cross section relative to the longitudinal axis of the foot <NUM>. The upper part <NUM> is an elongated plate member fixed to the lower part <NUM> such that it covers the opening of the U and thus forms an oblong cavity or channel with open ends. These ends are closed by bended end sections of the upper part <NUM>, which extends towards the bottom of the U of the lower part <NUM>. The fastening mechanism <NUM> is arranged such that it can extend and retract along the longitudinal axis of the foot <NUM>. The lower part <NUM> has two holes <NUM>,<NUM> aligned with the holes <NUM>,<NUM> of the upper part <NUM>.

In this embodiment, the spring biased spacer <NUM> is formed as an oblong plate member having two holes <NUM>,<NUM> which are aligned with the holes <NUM>,<NUM>,<NUM>,<NUM> of the upper part <NUM> and the lower part <NUM>, respectively. To ensure that the spring biased spacer <NUM> is not unintentionally displaced along the longitudinal axis inside foot <NUM>, a spacer fastener <NUM> is attached to the spring biased spacer <NUM> from the outside of the foot <NUM> through an opening <NUM> in the lower part <NUM>.

The spacer fastener <NUM> has a squared part <NUM> and two snap legs <NUM>,<NUM> extending perpendicular to the plane of the squared part <NUM>. With the legs <NUM>,<NUM>, the spacer fastener <NUM> is inserted in the opening <NUM>. The legs <NUM>,<NUM> are then led through the slots <NUM>,<NUM> in the spring biased spacer <NUM>. Once through, snap locking means 37a,38a engage the spring biased spacer <NUM>, fastening the two together. The legs <NUM>,<NUM> extend further into the slots <NUM>,<NUM> in the upper part <NUM> of the foot <NUM>. The squared part <NUM> of the spacer fastener <NUM> can abut the sides of the opening <NUM> in the lower part <NUM>, and the legs <NUM>,<NUM> can abut the sides of the slots <NUM>,<NUM> in upper part <NUM>. This allows a displacement of the spring biased spacer <NUM> along an axis parallel or coaxial with the longitudinal axis of the profiles <NUM>,<NUM>,<NUM> of the lifting column <NUM> when attached to the foot <NUM>, but, at the same time, a displacement of the spring biased spacer <NUM> along the longitudinal axis of foot <NUM> is prohibited.

The fastening mechanism <NUM> can either be in an extended state or a retracted state. The extended state is a where the fastening mechanism <NUM> is ready for receiving the bolts <NUM>,<NUM> and pins <NUM>,<NUM> of the profile <NUM> of the lifting column <NUM>. In the other words, this is the state prior to the assembly of the lifting column <NUM> with the foot <NUM>. The retracted state is where the bolts <NUM>,<NUM> are clamped in the fastening mechanism <NUM>, i.e. the state where lifting column <NUM> is assembled to the foot <NUM>. The extended state of the fastening mechanism <NUM>, which is illustrated in <FIG> and <FIG>, and the retracted state, which is illustrated in <FIG>, of the fastening mechanism <NUM> will now be explained.

In this present embodiment, the spring biased spacer <NUM> comprises a spring <NUM> which abuts the bottom inner side <NUM> of the lower part <NUM>. The spring <NUM> has two legs which abut the inner side <NUM> of the lower part <NUM> at each side of the holes <NUM>,<NUM>. The spring <NUM> is connected to the spring biased spacer <NUM> such that it also abuts an area between the two holes <NUM>,<NUM>. The spring <NUM> is pre-tensioned and slightly compressed when arranged inside the foot <NUM>, such that the accumulated potential energy presses the spring biased spacer <NUM> towards a forced engagement with the inner side <NUM> of the upper part <NUM>. Further compression of the spring <NUM> will allow displacement of the spring biased spacer <NUM> in a direction parallel to the center axis of the holes <NUM>, <NUM>. The spring <NUM> could be made of for example spring steel or another material with similar characteristics. In an alternative embodiment, the spring <NUM> could be substituted by two coil springs encircling or surrounding the pathway created by the two holes <NUM>,<NUM> for the spring biased space <NUM> and the two holes <NUM>,<NUM> of the lower part <NUM>.

The clamping sleds <NUM>,<NUM> are alike and are arranged in a mirrored manner at each end of the spring biased spacer <NUM> opposite the holes <NUM>,<NUM>. In the present embodiment, the clamping sled <NUM>,<NUM> is a plate member having a flat portion which can engage the inner side <NUM> of the upper part <NUM> of the foot <NUM>. The flat portion comprises several bent portions which extend approximately perpendicular relative to the plane of the flat portion. The free ends of the bent portions face and can engage the inner side <NUM> of the lower part <NUM> of the foot <NUM>. Parts of the sides or edges of the flat portion of the clamping sleds <NUM>,<NUM> face and can engage the inner side <NUM> of the lower part <NUM>, which in the present embodiment would be the inner side of the arms in the U-shaped cross section of the lower part <NUM>. This embodiment of the clamping sleds <NUM>,<NUM> allow them to be displaced and guided inside the foot <NUM> along the longitudinal axis of the same.

The clamping sleds <NUM>,<NUM> each have a guide or tracks <NUM>,<NUM> with an open end <NUM>,<NUM> facing the holes <NUM>,<NUM>. The guides <NUM>,<NUM> extends in a direction approximately parallel to the longitudinal axis of the foot <NUM>. The width of the guides <NUM>,<NUM>, i.e. the distance between the parallel sides of the guides <NUM>,<NUM>, is smaller than the diameter of the holes <NUM>,<NUM> and adapted to engage a portion of the bolts <NUM>,<NUM>. The guides <NUM>,<NUM> are wedge-shaped relative to the flat portion of the clamping sleds <NUM>,<NUM> or a plane parallel to the spring biased spacer <NUM>. The open ends <NUM>,<NUM> of the guides or tracks <NUM>,<NUM> are closest to the upper part <NUM>, such that the plane of the guides or tracks <NUM>,<NUM> extend in an angle towards the lower part <NUM> and ends a distance into the flat portion of the clamping sled <NUM>,<NUM>. The clamping sleds <NUM>,<NUM> are connected to each other via two tension springs <NUM>,<NUM>, which in parallel extends along and on each side of the spring biased spacer <NUM>. In this embodiment, the connection points <NUM> for the tension springs <NUM>,<NUM> are at an end of the clamping sleds <NUM>,<NUM> opposite the open end <NUM>,<NUM> of the guides <NUM>,<NUM>.

In the extended state, the clamping sleds <NUM>,<NUM> are, by applying a force to extend the tension springs <NUM>,<NUM>, pulled away from each other and positioned such that they rest against a projecting edge <NUM> at the ends of the oblong plate member of the spring biased spacer <NUM>. The potential energy accumulated in the tension springs <NUM>,<NUM> as they are extended will exert a pull force between the clamping sleds <NUM>,<NUM>. This pull force is kept unreleased as along as the clamping sleds <NUM>,<NUM> rest against the projecting edge <NUM> of the spring biased spacer <NUM> which, as explained above, is in forced engagement with the inner side <NUM> of the upper part <NUM>.

When the lifting column <NUM> is to be assembled with the foot <NUM>, the bolts <NUM>,<NUM> and the pins <NUM>,<NUM> of the lifting column <NUM> are led into the respective holes <NUM>,<NUM> and <NUM>,<NUM>, from the upper side <NUM> of the upper part <NUM> of the foot <NUM>. As the holes <NUM>,<NUM> of the upper part <NUM>, the holes <NUM>,<NUM> of the lower part <NUM>, and the holes <NUM>,<NUM> of the spring biased spacer <NUM> are all aligned, the bolts <NUM>,<NUM> can be led into these until the lower end of profile <NUM> abuts and engages the upper side <NUM> of the foot. The pins <NUM>,<NUM> inserted into holes <NUM>,<NUM> will, once through, move towards and eventually engage the spring biased spacer <NUM>. Moving the pins <NUM>,<NUM> further will displace the spring biased spacer <NUM> towards the bottom inner side <NUM> of the lower part <NUM> and thus away from its forced engagement with inner side <NUM> of the upper part <NUM>. Hereby, the fastening mechanism will enter the retracted state, as this will cause a disengagement between the projecting edge <NUM> of the spring biased spacer <NUM> and the clamping sleds <NUM>,<NUM>. The potential energy accumulated in the tension springs <NUM>,<NUM> will then be released and pull the clamping sleds <NUM>,<NUM> against each other, initiating engagement between the bolts <NUM>,<NUM> and the guides <NUM>,<NUM>.

The bolts <NUM>,<NUM> have a threaded portion <NUM> fixed to a corresponding thread in the bottom plate <NUM> of the lower end profile <NUM> of the lifting column <NUM>. The remaining part of the bolts <NUM>,<NUM> is a shank divided in three portions: a first portion <NUM> and a second portion <NUM>, the first portion <NUM> being closest to the bottom plate <NUM>. The first portion <NUM> and second portion <NUM> have a diameter smaller than the diameter of the holes <NUM>,<NUM>;<NUM>,<NUM>;<NUM>,<NUM>. A third portion <NUM> extending between the first portion <NUM> and the second portion <NUM> has a reduced shank diameter relative to the first and second portions <NUM>,<NUM>. The faces between the third portion <NUM> and the first and second portions <NUM>,<NUM> are approximately perpendicular to the longitudinal axis of the bolts <NUM>,<NUM>. Moreover, the shank diameter of the third portion <NUM> is smaller than the width of the guides <NUM>,<NUM> and can be accommodated in the guides <NUM>,<NUM>. This will allow the guides <NUM>,<NUM> to engage only the third portion <NUM> of the bolts <NUM>,<NUM> including the face <NUM> between the second portion <NUM> and the third portion <NUM>. The released potential energy of the tension springs <NUM>,<NUM> will, as mentioned, pull the clamping sleds <NUM>,<NUM> towards each other moving the point engagement with the bolts <NUM>,<NUM> further into guides <NUM>,<NUM>. Since the guides <NUM>,<NUM> are wedge-shaped or extend in an angle, the bolts <NUM>,<NUM> are pulled in a direction away from the upper part <NUM> of the foot <NUM>, which brings the lower end of the profile <NUM> into a forced engagement with the upper side <NUM> of the upper part of the foot <NUM>. This forced engagement is so tight that the lifting column <NUM> is immovably or almost immovably assembled to the foot <NUM>. Even in the retracted state of the fastening mechanism <NUM>, the tension springs <NUM>,<NUM> will never be fully contracted and thereby still hold a certain potential energy, which exerts a constant pull force between the clamping sleds <NUM>,<NUM>. Over time, dynamic loads exerted on the assembled lifting column <NUM> and foot <NUM> would cause the clamping sleds <NUM>,<NUM> to move further towards each other and thereby further tightening the forced engagement between them.

If the lifting column <NUM> and the foot <NUM> are to be disassembled, the fastening mechanism <NUM> can be moved from the retracted state to the extracted state. This is done by accessing each of the clamping sleds <NUM>,<NUM> through openings <NUM>,<NUM> in the lower part <NUM> of the foot <NUM> and pull them away from each other either by hand or using a suitable tool. When the distance between the clamping sleds <NUM>,<NUM> exceeds the distance between the projecting edges <NUM> of the spring biased spacer <NUM> engaging each of the clamping sleds <NUM>,<NUM>, the accumulated potential energy of the spring <NUM> will be released and push the the spring biased spacer <NUM> into the open space between the clamping sleds <NUM>,<NUM>. Allowing the clamping sleds <NUM>,<NUM> to move towards each other, they will again engage the projecting edge <NUM> of the spring biased spacer <NUM>, bringing the fastening mechanism <NUM> into its extracted state.

Claim 1:
A frame for a sit-stand-table comprising
a height-adjustable lifting column (<NUM>) with at least two telescopically arranged profiles (<NUM>,<NUM>,<NUM>), two bolts (<NUM>,<NUM>) and two activation pins (<NUM>,<NUM>),
a foot (<NUM>) comprising an upper part (<NUM>) having holes (<NUM>,<NUM>) for the bolts (<NUM>,<NUM>) and holes (<NUM>,<NUM>) for the activation pins (<NUM>,<NUM>),
a fastening mechanism (<NUM>) arranged inside the foot (<NUM>) accessible through the two holes (<NUM>,<NUM>) for the bolts (<NUM>,<NUM>) and the two holes (<NUM>,<NUM>) for the activation pins (<NUM>,<NUM>), and where the fastening mechanism (<NUM>) further comprises
a spring biased spacer (<NUM>) having
a spring (<NUM>),
two holes (<NUM>,<NUM>) aligned with the two holes (<NUM>,<NUM>) for the bolts (<NUM>,<NUM>),
two tensions springs (<NUM>,<NUM>), and
two clamping sleds (<NUM>,<NUM>) each having a guide (<NUM>,<NUM>) with an open end (<NUM>,<NUM>) and where the clamping sleds (<NUM>,<NUM>) are connected by the two tension springs (<NUM>,<NUM>),
and where the spring biased spacer (<NUM>) is configured to set in either
<NUM>) An inactive state where the spring biased spacer (<NUM>) is in forced engagement with an inner side (<NUM>) of the upper part (<NUM>) of the foot (<NUM>),
<NUM>) An active state where the two activation pins (<NUM>,<NUM>) are moved to displace the spring biased spacer (<NUM>) out of engagement with the inner side (<NUM>) of the upper part (<NUM>) of the foot (<NUM>),
and where the clamping sleds (<NUM>,<NUM>) and the tension springs (<NUM>,<NUM>) are configured to set in either
<NUM>) An extracted state where the clamping sleds (<NUM>,<NUM>) are in forced engagement with opposite sides of the spring biased spacer (<NUM>) when the spring biased spacer (<NUM>) is in the inactive state,
<NUM>) A retracted state where clamping sleds (<NUM>,<NUM>) are pulled towards each other by the two tensions springs (<NUM>,<NUM>) such that the guides (<NUM>,<NUM>) engage with bolts (<NUM>,<NUM>) when the spring biased spacer (<NUM>) is in the active state.