Horizontally supported planar surfaces – Vertically adjustable – With force-multiplying means
Reexamination Certificate
2000-05-05
2002-07-02
Chen, Jose V. (Department: 3636)
Horizontally supported planar surfaces
Vertically adjustable
With force-multiplying means
Reexamination Certificate
active
06412427
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for adjusting the height of pieces of furniture, and more particularly, to a device for adjusting the height of lift tables.
In order to adjust the height of office furniture, in particular of desks, use has hitherto been made of standing feet having tubes which can be pushed one into another telescopically, the standing feet each being provided with a spindle drive whose actuation causes the telescopic tubes to be displaced with respect to one another. The spindle units are synchronized via a connecting shaft, so that a synchronization results without the piece of furniture tilting. On account of the high forces which act on these spindle drives in the interior of the telescopic tubes, the said spindle drives conventionally have a very small pitch. The result is a comparatively slow height adjustment requiring, for example in the case of current lift tables of the prior art, between about 15 and 35 seconds for adjustment between the end positions for a lift of 500 mm.
German utility model 84 11 361 has disclosed a height-adjustable desk in which a cable-pull guide is routed in each case from the lower end of a telescopic inner tube via a deflecting pulley into the interior of the connecting frame between two standing feet. The cable pull is routed via two further deflecting pulleys into the opposite standing leg and is fastened there to the upper framework of the table, which is connected to the work-top. The two cable pulls which are arranged symmetrically with respect to each other result in a synchronization during the height adjustment, the said synchronization avoiding tilting of the inner tubes of the two telescopic feet. As a drive for the height adjustment a spindle drive is provided in the interior of the frame, which is provided as a transverse connection, between the two standing feet. This firstly requires a cable-pull guide which does not come into contact with the spindle drive. Secondly, this type of height adjustment still has the disadvantage referred to above of it only being possible for a very slow height adjustment to be carried out because of the spindle drive.
Furthermore, German utility model 298 22 188 has disclosed a height-adjustable desk in which the inner tubes of two standing feet are of height-displaceable design mounted on rollers on a traction cable fastened to the outer tube. The traction cables are routed via deflecting pulleys into the interior of a transversely situated connection frame. Two cable reels are arranged there one directly behind the other on the rotational axis of a driving motor, the said cable reels in each case jointly winding up or unwinding two traction cables of the left and of the right standing leg. The windings here are positioned in such a manner that the corresponding cable pulls are unwound on the one cable reel if winding up takes place on the other cable reel, and vice versa.
With one cable reel onto which two traction cables are wound simultaneously, mutual obstruction of the traction cables may occur. However, this has to be avoided in order to insure that the retracted cable length of the one cable reel corresponds exactly to the discharged cable length from the other cable reel.
The object of the invention, therefore, is to propose a device for adjusting the height of pieces of furniture, the device enabling rapid height adjustment with precise synchronization of the two telescopic feet.
Starting from a prior art item of the type mentioned in the introduction, this object is achieved by a device for adjusting the height of pieces of furniture, in particular lift tables, having two spaced apart standing feet, each of which has an inner tube which can be displaced telescopically in an outer tube, a connecting frame between the standing feet, a drive which includes a driving source for at least part of the lifting force, the drive including a device for deflecting the lifting force from the lifting direction (H) into a direction along the connecting frame, the driving source being arranged in the region of the connecting frame, and at least two rotatable driving elements which are situated with their axes transverse to the connecting frame being provided, wherein each of the two rotatable driving elements is connected to the upper end region of an inner tube of a standing foot and to the lower end region of an inner tube of a standing foot in a tensionally fixed manner.
Therefore, the advantageous designs and developments of the present invention are possible.
Accordingly, the invention proceeds from the height adjustment of a piece of furniture with two standing feet and a connecting frame connecting the standing area, a deflecting device being provided for deflecting the essentially vertical lifting force, which is required for displacing the two telescopic tubes, into the transverse direction along the connecting frame, the driving source for the drive being arranged in the region of the connecting frame, and at least two rotatable driving elements which are situated with their axes transverse with respect to the connecting frame being provided.
The drive of the invention is characterized in that each of the two rotatable driving elements is connected to the upper end region of an inner tube of a standing foot and to the lower end region of an inner tube of a standing foot in a tensionally fixed manner.
This results in the advantage that in every rotatable driving element, the length of run of the corresponding traction element which, for example when lowering the table, has to be retracted at the upper end region of an inner tube is simultaneously discharged again at the lower end region of an inner tube. This avoids it being possible for two traction elements, for example two cable pulls, to mutually obstruct each other when being retracted together on a driving element. A fluctuation when retracting or when discharging the corresponding length of the traction element, which could result due to traction elements winding over one another, is therefore reliably avoided in the case of a device according to the invention. Accordingly, a precise synchronization between the two telescopic standing feet cap be achieved, with rapid height adjustment being retained, as before.
In a particular embodiment of the invention, a cable pull for deflecting the lifting force and therefore for transferring the force from the rotatable driving element to the inner tube is provided. The deflection of the lifting force can be brought about in a particularly simple manner with a cable pull.
In one specific development of this embodiment, the driving element is connected both to the upper and the lower end region of the same inner tube. The driving element is designed in such a manner that the length, required in the lower region of the inner tube when pushing in the inner tube, of the corresponding traction element is released from the driving element, and the length, which becomes free in the upper region of the same inner tube, of the corresponding traction element is retracted. The equalizing of the length when extending the inner tube is carried out in a corresponding manner in the reverse direction. A precise synchronization is possible here even without a direct, diagonal connection between the two standing feet, for example of the upper end of the inner tube of one standing foot to the lower end of the inner tube of the other standing foot, by means of a coupling between the two driving elements. This coupling is preferably realized mechanically, for example via a gear mechanism or by installing the two driving elements on a common driving axle.
In another embodiment, however, a continuous, torsionally fixed connection of the lower end region of the inner tube of one standing foot to the upper end region of the inner tube of the other standing foot may also be provided.
Since the length of run between the two fastening points on the two inner tubes to be raised simultaneously does not vary during the height adjustment of the piece of furniture, in this arrangem
Chen José V.
Konrad Merkt GmbH
Morgan & Lewis & Bockius, LLP
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