Note: Descriptions are shown in the official language in which they were submitted.
~' 2~9~398
A CHAIR, IN PARTICULAR AN OFFICE CHAIR
TECHNICAL DOMAIN
The present invention relates to a chair, in particular an office
chair, as described in the preamble to patent Claim 1.
PRIOR ART
Various designs for chairs of this kind have been known for some
time. However, the known chairs of this kind do not take into
account the ergonomic demands that have to be satisfied in order
to provide dynamic seating. The chair must permit a series of
movements that correspond as closely as possible to the natural
body movements of the user. When this is done, the chair must
maintain its supporting function whilst providing the greatest
possible freedom of movement on the part of the user.
The user's movements are determined, in the first instance, by
the shape and arrangement of the joints, which determine the
direction and angle of rotation of the movement, as well as by
the pivoting radius that results from the length of the limbs
that are moved about a joint in the body.
Thus, centres of rotation that permit pivoting movements through
different angles exist on or in the human body. In order to
achieve a symbiosis of the movements of the user and of the
chair, the pivoting movements and the points of rotation of the
user must agree to the greatest extent possible with those of the
chair mechanism.
In the designs that have been known up to now, the centres of
rotation have been integrated into the framework of the chair in
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the form of materiel axes. However, the central problem lies in
the fact that in order to achieve optimal movement sequences, the
important centres of rotation have to be located outside the
framework of the chair. For this reason, the anatomically
correct centre of rotation cannot be achieved by designs that
integrate the axes into the framework of the chair. For this
reason, in thè case of known chairs, the sequences of movements
that can be carried out can only approximate human movements to
an inadequate degree.
In principle, it i5 possible to dispense with designs that
involve axes if one considers the fact that in chairs of this
type a range of angles of pivot of at most 25 is sufficient.
This makes it possible to use a pivoting mechanism that permits
pivoting that is effected about a virtual axis located outside
the structure of the chair. This virtual axis coincides with the
important moving joints of the human body.
For the movement of the seating surface, what i.5 relevant is that
for movement of the body in a relaxed position, the ankle becomes
a centre of rotation. The lower leg pivots about this centre of
rotation or pivot point at the same angle as the seating surface
tilts to the rear. Because of this tilting, the distance between
the floor and the lower leg is reduced. If it is intended that
the chair moves freely and completely in compliance with this
movement, the following demand will be imposed on the movement of
the seating surface: if the seat is loaded in the rear area, then
the seating surface must move downward and backward about the
ankle joint. Thus, the reference system for the movement of the
seating surface lies in the ankle joint and not--as is usually
the case--in the front underneath area of the seating surface.
By displacing the axis of pivot of the chair into the area of the
ankle, in keeping with this demand, it is ensured that the feet
remain in contact with the floor in all pivoted positions and
that during the pivoting process, no different and additional
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pressure is applied to the underneath area of the thigh by the
front edge of the seat.
The following considerations are relevant with respect to an
anatomically correct configuration of the change in the position
of the backrest:
If the user is in an upright attitude on a seat and maintains the
position between the third and fourth lumbar vertebrae, and if
the user inclines his back by an additional 20 to 30 to the rear
and one can see that the two lumbar vertebrae pivot downwards
around the hip joint. This means that the contour of the back
grows increasingly shorter as the angle of pivot of this backward
inclination grows larger. This means that the following will
apply for developing a chair that is as ergonomically perfect as
possible: if one wishes to synchronize the movements of the back
and the backrest, then the backrest must pivot about the axis of
the hips and thus grow shorter, as it were. In contrast to this,
in conventional designs the lumbar support provided by the
baskrest moves upwards and thus loses its supporting function.
In addition, when this happens, the "shirt-tail pull out" effect
is seen.
Taking this information into consideration, the point of rotation
for the structural configuration of the backrest is to be
established in the hip joint. Consequently, this means
decoupling the movements of the seating surface and the backrest.
The sequences of movement that are initially independent of each
other are accordingly related to each other in a natural manner
since the chair and the body move synchronously. No other
control need be imposed since control of the movement of the
chair is effected exclusively by body movement, and specifically
by the shift in weight.
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THE INVENTION
Proceeding from the prior art discussed above, it is the task of
the present invention to create a chair that permits dynamic
seating whilst observing the important ergonomic considerations
to the greatest extent possible.
This problem has been solved with the distinguishing features set
out in the descriptive section of Claim 1.
Preferred and additional configurations of the present invention
are set out in the secondary claims.
The chair according to the present invention corresponds
completely, or at least almost completely, to the ergonomic
necessities that result from the conditions described above. The
desired and ergonomically favourable movement sequences can be
converted at comparatively little outlay into the design
configuration of chairs.
BRIEF DESCRIPTION OF THE ILLUSTRATIONS
Preferred embodiments of the present invention are des~ribed in
greater detail below on the basis of the drawings appended
hereto. These drawings show the following: ~ -
igure 1: a diagrammatic illustration of the body attitude in two
different user situations;
Figure 2: a diagrammatic and perspective illustration of a seat
and backrest frame with a lower frame shown in part, in
an embodiment without arm rests;
Figure 3: an illustration analogous to Figure 2, of an embodiment
with arm rests;
Figure 4: a side view of the complete chair as in Figure 2 in an
unloaded starting position;
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igure 5: the chair as in Figure 4, with the backrest pivoted
back;
Figure 6: the chair as in Figure ~, with the seat pivoted
downward;
Figure 7: the chair as in Figure 4, with the seat pivoted
downward and the backrest pivoted back;
Figure 8: a side view of the complete chair as in Figure 3, with
the arm rests in position ready for use;
Figure 9: an illustration as in Figure 8, with the arm rests
pivoted upward and backward.
THE BEST MODE TO IMPLEMENT THE INVENTION
Figure 1 shows two different user attitudes. In the initial
position, in which the lower leg is essentially perpendicular to
the floor, the user is shown with an upright spinal column as
indicated by the black shape. The continuous lines showing the
chair with its arm rests, which is only indicated in the
drawings, correspond to this position; in a second position,
which is tilted back, only the outline of the user is shown, and
the outlines of the chair are indicated by dashed lines.
The important joint for the arcs that are followed by the
movement of the seat is the ankle joint, which is indicated here
as K. This joint through the ankle is simultaneously the first
axis of the chair. The position of the knee joint when the user
is in an upright position i5 indicated by G and the hip joint in
the upright position is indicated by H. The hip joint
simultaneously represents the second axis of the chair, about
which the lower area of the backrest of the chair is tilted back
when inclined.
It is clear from Figure 1 that the position of the first axis K
is always unchanged, whereas the knee joint G moves into the
position G' and the hip joint H moves into the position H'.
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Figure 2 shows the basic construction of a chair without arm
rests. The perspective drawing shown in Figure 2 shows the
complete chair although this does not show the seat and backrest
upholstery or the cruciform base that continues in the stand pipe
3. A seat carrier 6 is attached to the stand pipe 3. The seat
support 5 fits into the seat carrier receptacle 6. The seat
carrier 5 is secured centrally to the seat frame la. The
backrest frame 2a can be pivoted relative to the seat frame la.
The construction of the chair shown in Figure 3 is similar.
However, what differs here is the connection between the backrest
frame 2a and the seat frame la. In Figure 3, the curved areas
lla of the arm rests 11 are slid into the rear ends lc of the
seat frame la that are curved upward. The double arrow 12
indicates the pivoting mobility of the arm rests 11. ;
Parts that are identical or correspond to each other all bear -
identical reference numbers in the different drawings.
In the embodiments that are shown in Figures 4 to 7, the overall
seat is numbered 1, and this consists of the seat frame la and
seat upholstery lb. The seat frame la consists of rectangular
tubes, although other materials having other cross-sections can
also be used. The two rectangular side tubes of the seat frame
la are curved upwards in their rear area through a radius r2.
The radius r2 corresponds to the distance between the second axis
H, which coincides with the hip joint, and the midline 14 of the
curved area lc. A similarly curved or bent area 2c of the
backrest, which bears the overall number 2, fits into the curved
area lc. The backrest 2 consists essentially of a backrest frame
2a and backrest upholstery 2b. The midline 14 of the curved area
lc of the seat and of the curved area 2c of the backrest frame 2a
coincide. The areas lc and 2c that are curved at an equal radius
r2 are connected to each other, so as to be able to slide,
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through curved bearings, for example, curved longitudinal ball
bearings.
The height of the stand pipe 3 can be adjusted relative to the
cruciform base 4 that is provided with casters. The seat carrier
receptacle 6 is installed on ~he stand pipe 3 and the seat
support 5 fits into this. The seat support 5 and the seat
support receptacle 6 have a joint common line 13 that is curved
at radius r1 about the first axis K, which passes through the
ankle of the user. The curved seat support 5 is guided so as to
be able to slide in the curved seat support receptacle 6 with the
help of longitudinal ball bearings that are only indicated
diagrammatically herein. All other types of slide guides can be
used, particularly plastic guides.
Between the seat support 5 and the seat support receptacle 6
there is a spring element 9 and this grows shorter when under
load. This spring element is an energy accumulator that can be
in the form of a conventional compressed gas spring. Between the
backrest frame 2a and the curved area lc of the seat frame there
is a corresponding spring element 10 that grows shorter when the
backrest is tilted to the rear, as can be seen, for example, by
comparing Figure 4 with Figure 5.
In the embodiment that is shown in Figures 8 and 9, which
corresponds to the diagrammatic representation shown in Figure 3,
the fundamental construction of the stool remains the same.
However, the version shown in Figures 8 and 9 has an arm rest 11
that consists of a surface llb and an arm rest lower tube llc.
The arm rest lower tube is curved in its rear area, this being
done at the same radius as the rear curved piece lc of the seat
frame. Figure 8 shows the arm rest ready for use. Figure 9
shows the arm rest tilted upward in which the tube llc forms an
extension of the contour of the backrest frame 2a.
