Note: Descriptions are shown in the official language in which they were submitted.
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Table, in particular for video workstations
Description:
The invention relates to a table, in particular for
video workstations, having a height-adjustable tabletop with
at least one vertical guide strut, furthermore having a table
frame with at least one table support for the guide strut
which telescopes within it, and having at least one
adjustable spring leg which is arranged between the table
frame or the table support and the height-adjustable table
elements and has a spring on the inside, the adjustable
spring leg being coupled, with its one spring end, in a
positionally fixed manner to the table frame or the table
support and being supported, with its other spring end, in an
adjustable manner against a spring-leg base which varies the
pretension of the spring and is connected to the height-
adjustable spring elements, and it being possible for the
spring-leg base to be locked in positions matched to diffe-
ring loads on the tabletop by means of an attached adjusting
device.
A table of the type of design described at the
beginning has been disclosed by DE 38 17 102 C2. Such a table
can, of course, also be realized with a multiplicity of
tabletops instead of one tabletop. Structures on top of the
tabletop, such as, for example, shelving, cupboard elements
etc. are also conceivable. The tabletop and guide strut (or
guide struts) generally form the height-adjustable table
elements whereas the table frame and table support remain
fixed in position.
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In the case of the known table, which the invention
takes as the starting point, height adjustment is brought
about by the tabletop being kept in suspension by means of
the adjustable spring leg. For this purpose, use is made of
the adjusting device which matches the spring-leg base to
differing loads on the tabletop. In the case of the known
teaching this matching is done in such a way that the
adjusting device for the spring-leg base or the supported
spring end of the adjusting spring leg is designed as a
spindle drive with a handwheel or crank. All in all, a
mounting which is, as it were, suspended is realized for a
height-adjustable table whose tabletop can - because of the
suspended state - be adjusted in height with minimum effort
by a relevant operator. After the desired position of the
tabletop has been reached, the latter is generally fixed via
a (manually operable) locking brake.
The measures described above have proved their
worth per se but, as far as the weight counterbalance or the
reaching of the suspended state are concerned, are in need of
improvement. For one thing, manual adjustment--of the
adjusting spring leg or of the spring-leg base thereof no
longer meets today's requirements for convenience and, for
another thing, inaccuracies are associated with the manual
adjustment and, in particular, flexible and rapid matching to
changing loads on the tabletop is achieved only with a great
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outlay. In addition, if the weight is not completely
counterbalanced and the locking brake is released risks to
the operator cannot be ruled out. This is where the invention
comes in.
The invention is based on the object of developing
a table, in particular for video workstations, of the type
described at the beginning in such a manner that simple,
convenient, safe and flexible matching to changing loads on
the tabletop is made possible.
To achieve this object, in the case of a table of
the generic type, in particular for video workstations, the
invention proposes that a measuring device for determining
the particular load on the tabletop is provided, and that the
adjusting device is correspondingly activated as a function
of load values determined.
Preferably, the measuring device
and adjusting device form a closed control loop for this
purpose. In addition, an open-loop control device for
evaluating the load values supplied by the measuring device
and for the correspondilzg activation of the adjusting device
can be provided. This open-loop control device can, of
course, also be a closed-loop control device. The measuring
device is preferably designed as two or more switches which
are assigned to a rotating rod, the rotating rod being
connected to the guide strut and converting the vertical
movements thereof into rotational movements, and rotations of
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the rotating rod being transmitted to the one switch or the
other switch, depending on the direction of rotation of the
rotating rod, via an attached connecting element, for example
an extension arm.
It should be emphasized that, according to
the teaching of the invention, it is not only possible for
the guide strut to carry out vertical movements in the sense
of telescoping in the associated table support but it is also
possible, of course, within the framework of the invention to
carry out "oblique positions" of the guide strut, on the one
hand, and the table support, on the other hand. In any case,
such linear displacements of the guide strut in the table
support are intercepted via the rotating rod and converted
into corresponding rotational movements. The same is, of
course, also true for another preferred embodiment wherein at
least two guide struts with associated table supports are
realized.
In a further preferred embodiment, the extension arm
can be attached to the rotating rod by means of a sliding bearing
and, when the rotating rod is rotated, can strike against the
switches, which act as stops, with either the one switch or
the other switch being struck, depending on the direction of
rotation. This enables the simple and, at the same time,
height-independent measurement of the particular load on the
tabletop. This is because as long as the rotating rod strikes
against a switch with its extension arm, it can be
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ascertained via this switch actuation that the tabletop is
moved up or down by the guide strut. In order to ensure a
corresponding weight counterbalance it is now - after the
switch has been actuated - merely necessary additionally to
activate the adjusting device in such a manner that the
adjusting spring leg or a spring-leg base thereof is suitably
positioned. For~eXample, in the case of an upward movement of
the tabletop by the guide strut it is to be assumed that the
weight of the tabletop and any objects lying on it is
overcompensated, with the result that the pretension of the
spring has to be reduced by means of the adjusting device and
the spring-leg base which can be varied thereby. This takes
place until the extension arm strikes against the other
switch and consequently the weight is (under)compensated and
the extension arm alternately abuts or strikes against both
switches.
In the event of the tabletop being moved downward
by the guide strut in the preferred embodiment, the procedure is
carried out in a correspondingly opposing manner, i.e. the
pretension of the adjustable spring leg is increased in order to
counterbalance the weight undercompensation which is present
here. It is always ensured that a (vertical) movement of the
tabletop - with the locking brake released - corresponds to
corresponding variations of the spring-leg base so that the
weight is counterbalanced in a simple, convenient and flexible
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manner. This is of particular importance nowadays since the
service life of tables, in particular video workstation
tables or else CAD tables, generally far exceeds the useful
life of corresponding electronic (computer) components.
Moreover, additional pieces of equipment are often required,
and thus flexible matching to the weight ratios prevailing in
each case on the tabletop is possible. In addition,
particular emphasis must be given to the fact that
operational safety can clearly be increased compared to the
prior art. In actual fact, in the case of the known table and
an insufficient weight counterbalance and also a released
locking brake there is the risk of the tabletop - acted upon
by the adjustable spring leg - leaping up and in the worst
scenario being able to injure the operator. In any. case, such
risks no longer need to be feared with the preferred embodiment,
since leaping up of the tabletop is preferably automatically
retarded or suppressed because such a vertical adjustment
registers via the two switches and corresponding countermeasures
in the form of changing -the pretension of the spring are taken.
The same is, of course, also true for the case in which the
weight counterbalance has not been sufficient and the tabletop -
without the measures according to the invention - would strike
against the table support or the table frame. An automatic weight
counterbalance is always achieved - without complex, manual
adjusting operations.
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Further measures which are preferred for the inven-
tion are given below. The spring-leg base is generally
designed as a curved rail and the adjusting device is preferably
designed as a spindle drive with an electric motor, the
curved rail and the spindle drive being pivotably attached to
a common coupling point, the spindle drive furthermore having
a displaceable slide which can be moved by means of the
electric motor and is intended for the adjustable spring end,
and the curved rail being attached to the height-adjustable
guide strut or the tabletop counter to the force of the
spring by means of a flexible tensile means which can be
coiled up and uncoiled on a driving roller: Of course, other
driving concepts for the spindle drive or the displaceable
slide, for example a hydraulic drive, are also conceivable
within the framework of the invention.
The curved rail is preferably designed in the shape
of a mirror-inverted L with a vertical limb and horizontal
limb, the common coupling point of the curved rail and
spindle drive~being arranged on the head side of the vertical
limb, and the tensile means being attached on the foot-edge
side of the horizontal limb. The concept of vertical limb and
horizontal limb also, of course, includes limbs in an oblique
position, which limbs are not perpendicular to one another.
According to a particularly preferred embodiment of
the invention two or more spring legs are provided, the one
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spring leg being arranged in the guide strut and being
supported between the guide strut or tabletop and table
support or table frame, and being adjusted for counter-
balancing the weight of the tabletop (with the guide strut),
and the other spring leg being designed as the adjustable
spring leg and being coupled centrally to a horizontal
crossbeam. This permits a particularly sensitive
counterbalancing of the weight over an extraordinarily large
area. This is initially ensured by the spring leg which is
arranged in the spring strut and ensures the counterbal-
ancing of the weight of the tabletop (with the guide strut).
This spring leg serves, as it were, to counterbalance the
"minimum weight" of the tabletop to be kept in suspension. Of
course, this minimum weight can also include fixedly
installed structures etc. This enables flexible matching to
the particular installation and working conditions. The
additional adjustable spring leg then ensures the so-called
"fine counterbalancing of weight", i.e. that additional loads
on the tabletop due to pieces of equipment, video display
units etc. which have been placed on it can be
counterbalanced.
The guide strut is preferably of E-shaped design in
cross section with two semicircular arches and a web con-
necting the semicircular arches. In contrast, the table
support is generally essentially of rectangular design in
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cross section with indentations which are complementary to
the semicircular arches for guide roller disks which are in
each case arranged between the semicircular arches and
indentations and are intended for vertically guiding the
guide strut. This not only achieves a simple and precise and
also smooth-running guiding of the guide strut in the table
support but corresponding guide rails for the guide roller
disks can be omitted since the respective external or
internal profile of the guide strut or table support acts as
appropriate designs of rails.
The invention is explained in more detail in the
following with reference to a drawing which merely represents
one exemplary embodiment; in the drawing:
Fig. 1 shows a table according to the invention in a side
view,
Fig. 2 shows a section through the table according to
Fig. 1 in the region of a horizontal crossbeam,
Fig. 3 shows a view from the direction Z in Fig. 2 of the
adjustable spxing-leg base,
Fig. 4 shows a section through Fig. 1 in the-region of the
locking brake,
Fig. 5 shows a side view of Fig. 4 from the direction X,
Fig. 6 shows a view from the direction Y in Fig. 5, and
Fig. 7 shows a section through Fig. 5 in the region of the
locking brake.
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The figures show a table, in particular for video
workstations and/or CAD workstations. In its basic design
this table has a tabletop 1 with at least one vertical guide
strut 2, a table frame 3 with at least one table support 4
for the guide strut 2 which telescopes within it, and also at
least one adjustable spring leg 5 which is arranged between
the table frame 3 or the table support 4 and the height-
adjustable table elements 1, 2 and has a spring, in the
exemplary embodiment a gas-filled spring. According to the
exemplary embodiment two guide struts 2 and, accordingly, two
associated table supports 4 are provided. The adjustable
spring strut 5 is coupled, with its one spring end 6, in a
positionally fixed manner to the table frame 3 or the table
support 4. The adjustable spring leg 5 is supported, with its
other spring end 7, in an adjustable manner against a spring-
leg base 8 which varies the pretension of the spring and is
connected to the height-adjustable spring elements 1, 2. The
spring-leg base 8 can be locked in positions matched to
differing loads on the tabletop 1 by means of an attached
adjusting device 9.
The adjusting device 9 is a spindle drive 9 with an
attached electric motor 10. The spring-leg base 8 is designed
as a curved rail, the curved rail 8 and the spindle drive 9
being pivotably attached to a common coupling point. This
coupling point is designed as a pivot bearing 11 and, at the
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same time, as an actuating shaft for the attached electric
motor 10. By means of the electric motor 10, which is
attached to the pivot bearing 11, the spindle drive 9, or a
displaceable slide 13 which can be moved longitudinally on
said spindle drive 9, can be adjusted via two bevel gear-
wheels 12 which interengage essentially at right angles. This
displaceable slide 13 is connected to the adjustable spring
end 7 (cf. in particular Figs. 2 and 3). Should the electric
motor 10 break down, manual adjustment via a crank is of
course also conceivable, as indicated in Fig. 1.
Fig. 2 reveals that, when the electric motor 10 is
activated, the displaceable slide 13 can be moved up and down
along the spindle drive 9, guided by the curved rail 8. The
shape of the curve 8' over which the displaceable slide 13
passes is selected in such a manner that in every position of
the supported or adjustable spring end 7 the vertical force
components which are effective in the guide strut 2 are at
least essentially of equal size in both end positions of the
tabletop 1. The result here is a procedure comparable to that
described in DE 38 17 lb2 C2, to which reference is expressly
made, in particular to the vector diagram in it of Fig. 3. In
any case, with the adjustable spring end 7 being adjusted via
the displaceable slide 13 it is ultimately possible to vary
the pretension of the spring leg 5 or of the (gas-filled)
spring, specifically in such a manner that, with the piston
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Sb of the spring leg 5 entering to an increased extent into a
cylinder 5a, growing spring forces have to be overcome, the
pretension consequently increases and therefore a
corresponding weight on the tabletop 1 can be
counterbalanced. According to the exemplary embodiment the
curve 8' can be depicted by two circular arcs with differing
radii R1) Rz, R1 being approximately 300 mm and RZ
approximately 200 mm.
The curved rail 8 is attached to the height-
adjustable guide strut 2 (on the left-hand side in the
exemplary embodiment) or to the tabletop 1 counter to the
direction of force of the spring of the spring leg 5 by means
of a flexible tensile means 15 which can be coiled up and
uncoiled on a driving roller 14. In addition, a deflecting
roller 16 is realized, which deflecting roller is fastened to
the left guide support 4 or to the table frame 3 and ensures
that vertical movements of the left guide strut 2 are
converted into corresponding, horizontal extensions or
contractions of the tensile means 15 via the driving roller
14, which extensions or contractions correspond to corre-
sponding pivoting movements of the curved rail 8 (and, of
course, also of the spindle drive 9) about the pivot bearing
11 (cf. the arrow in Fig. 2). That is to say, in the event of
the tabletop 1 moving downward, the deflecting roller 16
rotates anticlockwise (as can be seen in Fig. 1), which has
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the consequence that the driving roller 14 according to
Fig. 2 moves clockwise and, via a coupling point 17 on the
curved rail 8, results in the latter pivoting in the clock-
wise direction. Accordingly, the piston 5b enters to a
greater extent into the cylinder 5a. In consequence, to
counterbalance the weight during this type of movement of the
tabletop 1, a corresponding pretension has to be ensured by
means of the piston 5b entering to a greater depth into the
cylinder 5a.
The driving roller 14 is coupled via extension arms
18 to a horizontal crossbeam 19 and to a U-shaped frame 19a.
This horizontal crossbeam 19 serves to connect the table
supports 4 and to accommodate the adjustable spring leg 5
which is attached to it via the U-shaped frame 19a. The
driving wheel 14 is a twin roller with two different roller
cores 14a and 14b which have different diameters. Altogether,
the adjustable spring leg 5, the driving wheel 14, the curved
rail 8 and the adjusting device 9 form a constructional unit
and are combined in a U-shaped or box-shaped housing 20 with
the driving wheel 14 lying on the outside or with the roller
core 14b lying on the outside. The tensile means 15 is an
endless steel cable 15. This steel cable 15 is, as it were,
split in two and wound, on the one hand, onto the roller core
14a and, on the other hand, onto the roller core 14b.
In addition to the adjustable spring leg 5 which is
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shown, according to the exemplary embodiment four further
spring legs 21 are realized, which spring legs are in each
case arranged in the guide strut 2 and are supported between
the guide strut 2 or tabletop 1 and the table support 4 or
table frame 3. They are adjusted for counterbalancing the
weight of the tabletop 1 with the guide strut 2. The guide
strut 2 is of E-shaped design in cross section with two
semicircular arches 22 and a web 23 connecting the semicir-
cular arches 22. The four semicircular arches 22 enclose the
spring legs 21 which have already been mentioned. It can be
seen from Fig. 4, in particular, that the table support 4 is
essentially of rectangular design in cross section with
indentations 22' which are complementary to the semicircular
arches 22 for guide roller disks 24 which in each case are
arranged between the semicircular arches 22 and indentations
22' and are intended for the vertical guiding of the spring
struts 2. The curved rail 8 has a twin rail design in the
shape of a mirror-inverted L, the common coupling point 11 of
the curved rail 8 and spindle drive 9 being arranged on the
head side of the vertical limb 8a, and the tensile means 15
being attached in the coupling point 17 on the foot-edge side
of the horizontal limb 8b. Grooved disks 13' are provided for
guiding the displaceable slide 13 on the twin-rail curved
rail 8 (cf. Fig. 3).
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As shown in Figs. 4 to 6, a measuring device 25 for
determining the particular load on the tabletop 1 is
provided. The adjusting device 9 is correspondingly activated
as a function of load values determined. The measuring device
25 according to the exemplary embodiment comprises two
switches 25a, 25b which are assigned to a rotating rod 26,
the rotating rod 26 being connected to the guide strut 2 and
converting the vertical movements thereof into rotational
movements. According to the exemplary embodiment, the
rotating rod 26 is arranged in a parallel horizontal plane
below the horizontal crossbeam 19 (cf. Fig. 1). In this case,
rotations of the rotating rod 26 are transmitted via~~an
attached connecting element, according to the exemplary
embodiment an extension arm 27, to the switches 25a, 25b,
specifically to the one switch 25a or the other switch 25b
depending on the direction of rotation of the rotating rod 26
(cf. Fig. 6). The measuring device 25 and the adjusting
device 9 form a closed control loop, an open-loop control
device (or closed-loop control device) 28 for evaluating the
load values supplied by the measuring device -25- and for the
corresponding activation of the adjusting device 9 being
provided.
The rotating rod 26 according to the exemplary
embodiment is a rod of the type which has a locking brake 29
on its end side. According to the exemplary embodiment, this
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locking brake 29 consists of a coupling gearwheel 29a which
is connected to the rotating rod 26 and has end-side teeth 30
(cf. Figs. 4 and S) which engage into corresponding recesses
30' in a plastic, positionally fixed coupling bush 29b (cf.
Fig. 7) when the coupling gearwheel 29a and coupling bush 29b
are brought into engagement. This can take place by coupling
or uncoupling the coupling bush 29b (cf. the arrow in Fig.
4). When the coupling gearwheel 29a is engaged into the
coupling bush 29b, the tabletop 1 is secured because the
rotating rod 26 engages, via an end-side gearwheel 31, into a
rack pinion 32 in the left guide strut 2. Consequently,
corresponding vertical movements of the guide struts 2 via
the rack pinion 32 result in corresponding rotational
movements of the rotating rod 26 via the gearwheel 31. With
the aid of a linear adjusting device attached to the rotating
rod 26 the coupling gearwheel 29a and coupling bush 29b can
be moved apart from one another and toward one another and
thus locked (cf. Fig. 4) .
The-extension_arm 27 according to the exemplary
embodiment is a retaining frame 27 which is U-shaped in
longitudinal section and is intended for the locking brake
29, which frame is attached, by means of sliding bearings 33
in its two U-limbs, to the rotating rod 26 (cf. Figs. 1 and
6). In any case, rotation of the rotating rod 26 results in
the extension arm or retaining frame 27 pivoting into the
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positions shown by dashed-dotted lines in Fig. 6 (the
position indicated by solid lines shows the rest position).
The extension arm 27 is "carried along" in accordance with
the rotational movements of the rotating rod 26, specifically
via the friction between the sliding bearing 33 and
rotational rod 26. This results - depending on the direction
of rotation of the rotating rod 26 - in the extension arm 27
striking against the one switch 25a or the other switch 25b
(cf. Fig. 6). This allows the conclusion that the tabletop l
is either over- or undercompensated in terms of weight. The
corresponding measured values or the positions of the
switches 25a and 25b are evaluated in the open-loop control
device 28 and converted into adjusting signals for the
adjusting device 9 so that the pretension of the adjustable
spring leg 5 is correspondingly changed.
It should be emphasized that the constructional
unit comprising the adjustable spring leg 5, driving wheel
14, curved rail 8, adjusting device 9 and, if appropriate,
housing 20 can generally be used in any tables having an
adjustable tabletop l.~In particular, it is conceivable to
install the above-mentioned component complex as a
retrofitted part or replacement part or to provide it and run
it as an adjustable module. This also applies in conjunction
with the measuring device 25, the rotating rod 26, the
extension arm 27 and also the open-loop or closed-loop
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control device 28 in conjunction with the electric motor 10.
The only further requirement is a corresponding connection or
a matching of the tensile means 15 and, if appropriate, of
the rotating rod 26 to the structural conditions. In any
case, this inventive complex can be realized independently
and used in general in any tables having an adjustable
tabletop 1. It can even be envisaged using it in adjustable
cupboards, chairs, table-like desks or high desks etc.
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