The present invention relates to an underframe for height-adjustable
tables and comprising at least a pair of lifting columns having a four-sided or
substantially four-sided cross-section and a cross member, said cross member being
connected with the lifting columns by a bracket comprising a first part (called
column bracket below) secured to the lifting column.
Underframes having a single lifting column at each side, where the
columns have a rectangular cross-section, are known, cf. e.g. EP 1 079 511 to Linak,
in which a table with lifting columns DESKLINE®DL1 of the make Linak A/S is
indicated. The lifting columns typically have a lower stationary member and one
or two members telescoping in it. The columns may be adjusted manually, as the
weight is typically balanced by gas/torsion springs, or electrically with an electric
motor driving a spindle unit WO 01/78556 to Okin, DE 199 20 672 to Baumeister.
Also known is a novel construction, where the drive unit comprises an endless chain
driven by an electric motor PCT/DK02/00467 to Linak. The lower end of the lifting
columns is secured in an elongated foot, while a tabletop may be mounted on top
of the columns. The stationary member of the lifting columns is connected at the
top with a cross member, typically a profile of rectangular cross-section. The
cross member is secured to a wide side of the column. A narrow plate member having
two threaded holes is welded on the wide side, and a similar plate member is welded
on the end of the cross member and extends vertically past the cross member. The
two flaps, which thereby extend upwards and downwards, respectively, from the cross
member, are formed with holes for securing the cross member with machine screws
in the threaded holes in the column bracket. The construction has a good stability
as far as it goes, but, on the other hand, there is a wish for a greater rigidity
of the construction.
Another aspect in this connection is that if the side wall of the
column is deformed by a local load because of the narrow bracket on the side wall,
this may affect the function of the column, in particular when the wall curves
inwards and gets into contact with the internal members.
The object of the invention is to provide a joint of greater rigidity
between column and cross member, it being required at the same time that the construction
is simple and easy to manufacture. In addition, it is an absolute requirement
that columns and cross member may be transported separately. Since height-adjustable
tables are now becoming increasingly popular also in dwellings, it is moreover
desirable that the joint between column and cross member may be made easy to perform.
The sale to private persons typically takes place as do it yourself furniture.
The object is achieved according to the invention in that the column
bracket per se is rigid and constructed so as to extend out to or substantially
out to two adjacent corner edges on the column. This provides an extremely rigid
joint between cross member and column, as the joint utilizes the corner region
rigidity in the column. The bracket may be secured inwards on the side of the
column, and the bracket is then supported by the rigid corner regions, but the
rigidity is increased if the attachment is also performed in the corner region.
The column bracket may be formed as an integrated part of the cross member, e.g.
by construction and bending of flaps thereon, but it is preferred to use a separate
and more rigid cross member bracket which is secured to the cross member.
In an embodiment where the lifting column has a rectangular or a substantially
rectangular cross-section, the column bracket is secured on a narrow side of the
column, which results in a bracket with smaller dimensions compared to securing
on the wide side and also gives a greater rigidity.
The shape of the cross member, in cross-section as well as in longitudinal
section, may be adapted as desired, of course, as long as its stability is in
order. A cross member of four-sided or substantially four-sided cross-section is
particularly simple and advantageous for securing. Thus, a cross member bracket
which per se is rigid and constructed so as to extend out to or substantially out
to two adjacent, horizontal corner edges of the cross member, gives a particularly
good stability. When the cross member bracket is secured on the side of the cross
member, it may be positioned such that it faces away from the user of the table,
which increases the leg-room. In the traditional structures where the cross member
is secured between the lifting column sides facing toward each other, it has been
necessary to make a curve on the cross member in order to create sufficient leg-room.
The wish for an easy-to-mount joint may be met by a wedge bracket,
allowing the cross member to be mounted without the use of tools. If locking of
the cross member in the mounted state is desired, this may take place with a locking
screw, e.g. a pointed screw which is screwed from the cross member into the column.
A particular embodiment of the wedge bracket is defined in claim 10, said embodiment
being attractive in that it is rigid and may be formed with a thickness of only
three thicknesses of material, so that it is not very conspicuous in the end product.
The invention will be explained more fully below with reference to
the embodiment shown in the accompanying drawing. In the drawing:
- Fig. 1 shows an underframe for a height-adjustable table, said underframe being
shown without feet,
- fig. 2 shows a perspective view of a column bracket, seen inwards toward the
- fig. 3 shows a perspective view of a cross member bracket, seen inwards toward
the cross member,
- fig. 4 shows a lifting column in the fully extended position, and
- fig. 5 shows an end of the cross member having the cross member bracket mounted
The underframe shown in fig. 1 for a height-adjustable table comprises
two electrically driven lifting columns 1a, 1b having an essentially rectangular
cross-section with a pair of wide sides 2a, 2b and a pair of narrow sides 3a,
3b. The columns are interconnected by a cross member 4 consisting of a profile
having a rectangular cross-section closed at both ends.
The lifting columns 1a, 1b have a stationary member 5 at the bottom
and either one or two extensible members 6. The lower end of the stationary member
5 is secured in a foot (not shown). This foot may be elongated and extend out from
the narrow sides of the column.
It is noted for the sake of good order that the lifting columns are
connected by cables 7a, 7b to a control box with control equipment and a power
supply, which may optionally be separate. In addition, a control panel is provided,
arranged expediently for the user for moving the table up and down.
The lifting columns and the cross member are interconnected by a wedge
bracket, where the column bracket 8a is shown in fig. 2, while the cross member
bracket 8b is shown in fig. 3.
As will appear from fig. 4, the column bracket 8a is welded at its
side edges 9a, 9b in two adjacent corner regions 10a, 10b of the outer profile
5 of the column. In fig. 4, the column is shown in its fully extended position.
As will appear from fig. 5, the cross member bracket 8b is welded
with its upper and lower edges 11a, 11b to two adjacent longitudinal corner regions
12a, 12b of the cross member 4.
In the mounting, the two side flaps 13a, 13b of the cross member bracket
are moved down into the pocket 14 of the column bracket. The pocket is formed
by the bent side edges 15a, 15b of the column bracket and receives the side flaps
13a, 13b. The bracket is wedge-shaped downwards, i.e. widest at the top and narrowest
at the bottom. Pressure on the cross member causes the cross member bracket to
be wedged in the column bracket, thereby securing columns and cross member to each
The invention thus provides a rigid joint, as the rigidity at the
corner regions is utilized, and at the same time the joint is easy to perform is
it may take place without the use of tools.
A beam-shaped cross member is shown here, but it will be appreciated
that the cross member may have other shapes, just as it may be provided with cover
plates which close the opening between the two lifting columns.