Note: Descriptions are shown in the official language in which they were submitted.
CA 02004002 1999-02-22
IMPROVEMENTS IN OR RELATING TO CHAIRS
The present invention relates to chairs and more
particularly to chairs designed to be able to support the body
of a human being (the user) at one or more heights.
Chairs are normally designed to support a user in a
sitting position even though the height at which the user sits
can be adjusted to suit users of different heights. Known
adjustment systems comprise spring loaded central support
columns or gas filled cylinder systems controlled by a lever
adjacent the chair seat.
It is an object of the present invention to provide
a chair with a seat which. can support a user in a sitting or a
semi-standing position.
According to th.e present invention there is provided
a chair for supporting a user in a sitting or semi-standing
position including a seat, the seat providing a substantially
horizontal uppermost surface for the user irrespective of the
angle at which the seat is set. If cushioned the actual upper
surface may be curved when not in use.
In particular, according to the present invention
there is provided a chair comprising: a seat; a base
structure supporting said seat; and means for adjusting said
seat between two different positions in which it is held
respectively at relativel.y lower and higher levels and at
different inclinations suited to use in sitting and semi-
standing postures; said seat being shaped to provide
20195-384
CA 02004002 1999-02-22
respectively different transversely extending, substantially
horizontal portions of its upper surface for supporting the
weight of a user at said positions; and in which said portions
are each, when in their respective weight supporting
positions, the highest position of the seat upper surface and
are disposed in a vertical plane passing through said base
structure.
20195-384
Preferably the horizontal surface comprises at lea~t
a thin line running transversely on -the seat surface
forming the highest portion of the seat, this line lying
in a vertical plane passing through a base structure of
the chair. When the seat angle is adjusted this line,
in a preferred embodiment, remains substantially in the
same vertical plane relative to the base of the chair.
Embodiments of the present invention will now be
described, by way of example with reference to the
accompanying drawings, in which:-
Figure 1 shows schematically a chair according tothe present invention;
Figure 2 shows a perspective view of a first seat
according to the present invention suitable for the chair
of Figure 1;
Figure 3 shows a plan view of one half of the seat
of Figure 2;
Figure ~ shows a cross-section of the seat of Figure
3 on line A-A;
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Figure 5 shows a first cross-sectional front
elevation of the seat of Figure 2;
Figure 6 shows diagrammatically the design of a
second seat according to the present invention suitable
for the chair of Figure 1;
Figure 7 shows diagrammatically the design of a
third seat according to the present invention suitable
for the chair of Figure 1;
Figure 8 shows a suitable adjustment mechanism for
use with the chair of Figure 1 to provide an automatic
tilting action for the seat;
Figure 9 shows in elevational partial cross section
a practical embodiment of a chair incorporating a seat
according to the present invention;
Figure 1~ shows a cross sectional view along line A-
A of Figure 9; and
Figure 11 shows a cross sectional view along line B-
B of Figure 9.
With reference now to Figure 1, a chair 10 is shown
diagrammatically. The chair comprises three basis
component parts, a base 20, a seat 30 and a backrest 40
(if provided). The base 20 may be of the star or similar
known type providing a stable base providing that the
weight on the chair is within the area of the base. The
backrest 40 (if fitted) may be attached to the seat in
~nown manner.
The seat 30 has an upper curved surface 32 and may
be adjusted or set at a number of angles as shown by
dotted lines 321, 322. Dotted line 321 is suitable for a
higher position of the chair corresponding to a stand
position for the user and dotted line 322 is suitable for
a lower for the chair corresponding to a sitting position
for the user.
In the present invention the highest "point" on the
surface of the seat shown diagrammatically at 323 is
sho~-n on the vertical dotted line 324. As the seat 30 is
adjusted into the positions shown at 321 and 322 the
highest "point" of the seat will in the seat desi~n
according to the present invention still remain
substantially on the line 324.
o~
Ln a practical seat design in three dimensions as
opposed to the dia~rammatic representation shown in Figure
1 the line 324 is in fact a plane and the point on the seat
comprises a horizontal line across the seat as indicated
by line X-X in Figure 2 to which reference is now made.
The seats shown in Figures 2 to 7 are specifically
designed such tha-t there is always an uppermost horizontal
portion of the seat X-X to be sat on by the user for
support at all heights within the designed height range.
The shape of seat 30 is shown in Figures 2 to 5 and with
reference to Figure 4 the seat is contoured to provide an
upper surface 31 the shape of which is dictated by three
arcs of radii R1, R2 and R3 as shown. The seat is shaped to
be narrower at t~e front as indicated by the cross-
sectional shapes A'-A', B'-B' and C'-C' shown in Figure 5
and by the plan view of Fi~ure 3. With reference to
figure 5, the seat shape could, however, be of the more
conventional substantially rectangular shape as indicated
by the dotted lines.
- With respect to the cross-sections the upper surface
31 of the seat need not necessarily be flat to form a
completely horizon-tal surface but could be contoured by
suitable upholstery to provide for e~ample a domed shape
which may be more comfortable or a seat contoured to
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accommodate the shape of the upper legs or thighs. The
seat may be provided for example with a tensioned net or
canvas sling stretched over a suitable frame.
In a particular embodiment the dimensions of the
radii R1, R2 and R3 are as follows:-
R1 - 140 mm
R2 - 280 mm
R3 - 350 mm
These dimensions are given only by way of e~ample
and may be varied to suit specific requirements.
With reference now to Figure 6 a simpler contour for
the seat is shown comprisin~ two arcs of radii R4 and R5
as shown. Radius R4 is the shorter and is used as
indicated by the solid line to form the bac~ of the seat
and R5 is the longer and is used to form the front of the
seat as shown by -the solid line. The dotted continuation
lines of arc are only shown to illustrate the differences
in -the radii. The seat is pivoted about point P to
achieve the desired property of maintaining an uppermost
horizontal line ~-~ to sit on at all angles of pivot of
the seat.
- ~0~)40~
A modification of the sea-t con-tour of Figure 6 is
shown in Fi~ure 7, the radius R5 being replaced by a
tangential shape as indicated by the straight line R,
radius R5 being shown dotted ~or comparison.
In a practical embodiment R4 = 140 mm and R5 =
200 mm.
The seat shapes shown may be set at fixed angles for
various types of seat and they will always provide an
uppermost substantially horizontal line X-X for the user
to sit on. In practise this line will, in an upholstered
or padded seat provide a generally horizontal platform
sloping at its extremities both to the back and the front
of the seat. Thus the user will not be unbalanced on the
seat since there there will be no tendency to slide to
the front or back of the seat. This is particularly
advantageous since any such tendency is always resisted
by a user causing strain. The seat desi~n according to
the present invention is therefore comfortable to sit on
at all heights at which is it set. Thus for example for
laboratory stools the seat can be set for a high level
use and for typing chairs it can be set at a low lever.
2~ )2
g
If it is required to provide an automatic adjustment
of the angle of the seat the embodiment of Figure 8 may
be used. In Figure 8 -the upper part of a chair is shown
and comprises the seat 30 pivoted on a pivot 35 attached
to a main support member 25.
A first height adjustment is provided by for example
a gas filled cylinder 200. This is used to adjust the
seat for the height of the user ~or example at the lowest
or sitting position by altering the height of ram 202.
Once set for a particular user this cylinder 200 would
not be further altered.
A further cylinder 204 is positioned within ram 202
to provide further vertical movement of seat 30. To
further alter the height of seat 30 cylinder 204 is
activated by means of for example of a lever in known
manner to allow main support member 25 to move upwardly
under the force of the cylinder or downwardly under the
weight of the user on the seat 30. As member 25 moves
into or out of cylinder 204 so seat 30 is moved by an arm
36 connected in a pivotal manner between ram 202 and the
front of the seat a-t pivot points 37, 38. The seat 30
will therefore move as indicated by dotted outline 30'.
1ine X-X (as indicated by the arrow X) will as shown
always be at the highest point on the seat and in -this
X00~i~S)2
embodiment this line is vertically above the main support
member 25 providing the most suitable condition for the
seat.
As an alternative to -the automatic adjustment
provided by arm 36 a manual adjustment could be provided
by a suitable screw clamp on pivot 35 allowing the seat
to be rotated to suit the user. Line X-~ will however
always be the highest portion of the seat.
With reference now to Figures 9 to 11 a practical
embodiment of a chair incorporating a seat according to
the present invention is shown.
The chair 100 comprises a base 1200 which may be of
the conventional three or five star configuration. In
the drawing only two feet 1202, 1204 are shown for
simplicity of drawin~. A first main support member 1206
is fixed; for example by welding into the base 1200 and a
second main support member 1208 is slidably mounted over
the first member 1206 as shown. Pre~erably each support
member 1206, 1208 comprises a steel tube of circular
cross section.
20~ )2
Support member l208 is movable vertically relative
to support member 1206 by means of a spring 1210 (which
in a practical chair would be provided with a cover 1212
shown as a dotted line).
The two members are normally locked together by a
lockin~ arrangemen-t 1214, 1216 which operates in known
manner to allow relative movement between the members on
compression of a spring 1~18. This is achieved by a
downward movement of operating rod 1220 by downward
operation of a lever 1222 which is situa-ted under the
front of seat 30 (Figure 1). This movement is well known
in such chair desi~ns and will not therefore be described
in any greater detail. The lift provided for the chair
seat by this arrangement is in the chair shown 120 mm
~approx. 5 inches) which accomodates for the sitting
position height range. It is noted here that the angle
of the seat 30 does not change due -to opera-tion of lever
1222.
The seat 30 is pivotally supported on a pin 1224 and
tilting of the seat is accomplished by the pivotal
connection of the front of the seat to a lever 1226 on a
pivot pin 1228. The seat is supported on a platform 1230
which is mounted on a bearing 1232 which enables the seat
to be revolved.
Z0~4~C~2
11
The seat 30 may be raisecl by opera-tion o~ a lever
1234 into the position shown partially at 301 and 12261.
The lever 1234 operates when depressed to release the
piston 1236 and allow the seat to rise (in known manner)
under the pressure provided by either a pneumatic
pressure or by a further spring (not shown). The seat
may be lowered by operating the lever 1234 and pressin~
down on the top of the seat.
The operation of the seat may be clearly seen by the
two posi-tions 30, 1226 and 301, 12261. As the piston
1236 rises the upper portion 1240 of the platform 1230
rises relative to the base portion 1242 to which the
opposite end of lever 1226 is pivotally connected at
pivot point 1244. Thus as the seat rises the angle of
the seat is tilted gradually, the seat always having a
horizontal portion to support the user.
A backrest 1246, 124~ is also attached to the upper
part 1240 of the platform 1230 so that -the backrest rises
with the seat,
