Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02714758 2010-09-13
Seat mechanism for an item of seating furniture, in
particular office swivel chair
The invention relates to a seat mechanism, in
particular for a chair, according to the preamble of
patent claim 1.
A seat mechanism of this type is disclosed, for
example, in DE 198 23 632 Cl. In said known chair, the
force accumulator is designed in the form of a tension
spring which is prestressed upon loading of the seat,
and therefore said prestressing is dependent on the
weight of the seated person. Since the backrest carrier
and therefore the backrest are inclined counter to the
action of the force accumulator, the resetting force
for the backrest is therefore likewise dependent on the
weight.
On the other hand, the weight is not utilized
effectively in the known device since, in said device,
the force accumulator is loaded via the front region of
the seat, i.e. the thigh region of the seated person.
By contrast, the invention is based on the object of
specifying a seat mechanism with a we-ight -dependent
resetting force for the backrest, which seat mechanism
is distinguished by simple construction and with which
the weight can be utilized efficiently.
This object is achieved by the features of patent claim
1; the dependent claims relate to advantageous
refinements of the invention.
According to the invention, a deviation is made from
the known principle of prestressing the force
accumulator by means of the weight of the seated
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Person, and it is accordingly proposed to convert an
inclination movement of the backrest and therefore of
the backrest carrier into a lifting movement for the
seat. Therefore, upon inclination of the backrest, the
entire seat with the person seated thereon is raised,
and therefore all of the weight can be utilized to
apply the resetting force for the backrest.
In this case, the conversion can take place, for
example, via a lever mechanism or via a slotted guide
mechanism of the seat or of the seat carrier.
A space-saving construction is produced in particular
by using helical springs as the force accumulator.
Dynamic seating can be assisted if the seat is of
flexible design and has a web in the central region.
The rear region of the seat is preferably designed such
that it can be lowered. In order to permit the lowering
in the rear region of the seat, a flexible seat cushion
carrier can have, in the side region, slots which run
from the edges toward the center, wherein the slots are
preferably arranged in the center to rear region of the
seat cushion carrier, and the slots preferably become
shorter in length with increasing distance from the
rear edge of the seat cushion carrier.
The flexibility of the seat cushion carrier can be
increased by, for example, perforations being provided
in the region of the ischial tuberosities, wherein the
perforations are formed by slots which run parallel to
the rear edge of the seat cushion carrier, and/or slots
which run parallel to the side edges.
In particular in the case of heavy/light people, the
resetting force, which is purely weight-dependent, may
be perceived to be too great/small. According to the
invention, the use of a second force accumulator is
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therefore proposed and this, when the need arises,
assists/obstructs the lifting movement such that the
resetting force is reduced/increased.
For this purpose, the second force accumulator is
preferably adjustable.
In a preferred embodiment, the force accumulator is
mounted pivotably and can be prestressed when the
backrest is pivoted or moved.
In particular when working at computer screens, it is
considered comfortable if the seat of the item of
seating furniture can be lowered forward. The inventors
have discovered that, when leaning back in the inclined
position of the seat, an unpleasant sensation of
"sliding" out of the seat may arise. According to the
invention, it is therefore proposed to provide a
resetting device which inevitably cancels the lowering
upon a lifting movement of the seat carrier, wherein
the resetting device preferably has a lever mechanism.
Depending on the specific configuration, the force
accumulators used may be, for example, tension springs,
compression springs, gas-filled compression elements,
torsion springs, leg springs, etc.
An exemplary embodiment of the invention is explained
with reference to the attached drawings, in which
figure 1 shows an exploded illustration of the
basic elements of a seat mechanism,
figure 2 shows a perspective top view of the
assembled seat mechanism,
figures 3-6 show various side and side section
illustrations,
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figure 7 shows a central section of the office
swivel chair,
figure 8 shows a side illustration of the office
swivel chair without a seat cushion,
figure 9 shows a perspective illustration of the
frame construction of the office swivel
chair, and
figure 10 shows a top view of the frame
construction.
In the above text, the definitions of "forward",
"rearward", "at the top" etc. arise from the normal
position of the chair.
Figure 4 shows a side illustration of a seat mechanism
with a seat carrier 1 on which a seat (not illustrated)
is mounted, with a panel 10, wherein a backrest carrier
3 is mounted pivotably on the seat carrier 1 via a
coupling spindle 7. The backrest carrier 3 carries a
backrest (not illustrated), wherein, in the
illustration of figure 4, the seat mechanism is in the
normal position, i.e. the backrest is upright.
Figure 1 shows a perspective exploded illustration and,
in addition to the backrest- carrier 3 and the seat
carrier 1, shows a main carrier 9 and a front link and
a central link 17. -
The main carrier 9 carries the entire seat mechanism
and is connected to a chair pillar in a manner known
per se via a bore 11.
In the assembled state, the seat carrier 1 is connected
to the main carrier 9 via the front link 15,
specifically via bearing bores 19, which are aligned
with bearing bores 21 on the main carrier, and via
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bearing bores 23 which are aligned with corresponding
bearings (not illustrated) on the seat carrier.
Furthermore, in the assembled state, the backrest
carrier 3 is fastened pivotably to the main carrier 9,
5 specifically via bearing bores 25 which are aligned
with bearing bores 27 on the main carrier, wherein said
bearing bores define a main axis 13 (compare figure 4).
Furthermore, the backrest carrier 3 is fastened to the
seat carrier via bearing eyes 26 on corresponding
bearings such that the backrest carrier is pivotable
with respect to the seat carrier. The bearing eyes 26
are offset with respect to the bearing bores 25 such
that the backrest carrier 3 itself forms a rear link.
Figure 2 shows the seat carrier 1 and the backrest
carrier 3 in the assembled state. Helical springs 33
are additionally illustrated, said helical springs
being mounted in the backrest carrier 3 and the legs of
said helical springs being supported in an abutment 35
of the backrest carrier 3, wherein the legs at the
other end of the helical springs are supported on the
main carrier (not illustrated).
Spring assemblies 37 are accommodated pivotably in the
seat carrier 1, wherein the spring assemblies act at
one end on a displaceable spindle 39 and at the other
end on an abutment 43 of the main carrier 9 (figure 6).
The displaceable spindle 39 is mounted at both ends on
curved tracks 47 and can be displaced on the curved
track via an actuating lever 41. The curved track 47
runs at different distances with respect to the
abutment 43, and therefore the spring assemblies 37 are
loaded differently in different positions, for example
in three positions, i.e. without loading in a first
position, with average loading in a second position and
with high loading in a third position. The spring
assemblies here act as tension springs, and, under
loading, tension forces act between the seat carrier
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and the main carrier. It should also be mentioned in
this respect that the spring assemblies 37 are designed
in terms of internal construction in such a manner that
spring elements in the form of compression springs are
formed, since a higher load-bearing capacity and longer
service life can be achieved with this design.
As already explained, figure 4 shows the seat mechanism
in the normal state, i.e. with the backrest upright. By
contrast, figure 6 shows the position of the seat
mechanism with the backrest inclined at maximum to the
rear, wherein the seat carrier 1 is raised parallel in
relation to figure 4, specifically in the rear region
via the rear link, as is evident from the position of
the axis 13 and spindle 7, and in the front region via
the front link 15, as is evident from the position of
the latter. In this case, the helical springs 35 are
loaded and subject the backrest carrier 3 to a
resetting force which is additionally reinforced via
the front and the rear links by the weight acting on
the seat, wherein, as mentioned, the resetting force
can be changed via the spring assemblies 37.
As is apparent in particular from figure 5, which shows
the same position of the seat mechanism as figure 6,
the front link 15 is mounted in elongated holes 49 on
the seat carrier. In the normal position according to
figure 4 and in positions in which the seat carrier 1
is raised, the position of the link 15 in the elongated
holes 49 is locked in the lower position of the
elongated holes. In the normal position of figure 4,
said locking can be canceled, and the seat carrier can
be inclined forward, as illustrated in figure 3. Said
seating position is suitable particularly for people
working at computer screens, etc. Since said position
of the seat carrier is unfavorable when the backrest is
inclined rearwards, according to the invention the seat
carrier is inevitably displaced into the horizontal
position when the backrest carrier is pivoted. For this
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purpose, levers 51 are provided, said levers acting at
one end on the main carrier 9 and at the other end on
the seat carrier 1 and causing the front edge of the
seat carrier to be inevitably raised. In this case, the
front link can be locked in the lower region of the
elongated holes 49.
As is apparent in particular from figure 1, the central
link 17 has one lever 51 in each case. The central link
17 is mounted in fastening tabs 31 which are fastened
to the seat carrier. At the end facing away from the
fastening tabs 31, the levers 51 each bear bearing pins
29, which are mounted in the main carrier.
The seat mechanism illustrated here is suitable in
particular for office swivel chairs but may also be
used in other items of seating furniture, such as 4-
legged chairs, armchairs, sofas and the like.
According to figure 7, an office chair comprises the
seat mechanism described, a seat 61 with a seat cushion
carrier 65 and a seat cushion 63, and a backrest frame
67. The seat 61 is mounted on the seat carrier 1 such
that it can be displaced forward or rearward, wherein
the backrest frame 67 is connected via the backrest
carrier to the main carrier 9, which is fastened to a
chair pillar 73.
A lower backrest frame 77 is mounted pivotably on the
backrest frame 67, said lower backrest frame being
connected at the lower end thereof to the rear edge of
the seat 61. Furthermore, a lumbar support 75 is
provided, said lumbar support being mounted on a lumbar
support carrier consisting of a transverse carrier 81
and a longitudinal carrier 83.
The arrangement of the last-mentioned elements is
apparent in particular from the perspective
illustration of figure 9, which shows the frame
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construction of the chair without a seat cushion. It is
apparent from said illustration that the transverse
carrier 81 extends between two struts of the backrest
frame 67. The longitudinal carrier 83, which extends as
far as a traversely running strut of the lower backrest
frame 77, is fastened in the center of the transverse
carrier 81. Furthermore, the longitudinal carrier 89
has a telescopic connection 85.
The backrest frame 77, for its part, is connected to
the backrest frame 67 via an articulated connection 89
consisting of lamellas.
Figure 9 furthermore shows that the seat cushion
carrier 65 is designed as a plate which is manufactured
from flexible material and has a web 91 extending from
the front rearward in the center. The web 91 rests on
the seat carrier 1 (figure 7) but may also be connected
to the latter and to the seat mechanism 79. The resting
action and the flexibility promote dynamic seating when
the right/left loading changes.
In the region of the ischial tuberosities, the seat
cushion carrier is provided with slots 95 which extend
parallel to the side edges of the seat cushion carrier,
and with slots 97 which extend parallel to the rear
edge of said seat cushion carrier, in order to further
increase the flexibility.
In the region of the side edges, the seat cushion
carrier 65 is provided with slots 99 which extend from
the side edge toward the web 91. The length of said
slots 99 increases the closer said slots are arranged
to the rear edge of the seat cushion carrier 65.
As illustrated by the double arrow in figure 8, which
shows the chair without a seat cushion, the seat
cushion carrier 65 is mounted displaceably in the depth
direction of the chair. In this case, the lower
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backrest frame 77 follows a movement of the seat
cushion carrier 65 such that a horizontal gap cannot be
produced. Figure 8 shows the seat cushion carrier 5 in
a central position.
In this regard, it should also be noted that, in the
use state of the chair, the backrest carrier is
provided with a fabric covering, upholstery or the
like.
The seat cushion carrier 65 is mounted displaceably on
the seat mechanism on lateral guides 105 (figure 1),
wherein, in the normal position, i.e. with the backrest
not inclined, the web 91 rests on the seat mechanism
79.
It is apparent in particular from figure 9 that the
seat cushion carrier 65 is not designed as a flat plate
but rather as a curved plate, wherein in particular the
side regions of the seat cushion carrier 65 are curved
upward in the normal position. If the seat cushion
carrier is raised by the seat mechanism 79, the web 91
is raised from the surface of the seat mechanism 79,
and the regions of curvature are pressed downward, and
therefore compensated for, in dependence on the
bodyweight of the seated person. This is assisted by
the arrangement of the slots 99 and the shaping thereof
such that the compensation takes place in particular in
the rear region of the seat, and therefore the seat
surface is lowered in particular in the rear region, as
a result of which the seating comfort is increased when
the seated person leans back.
