Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to chairs of
the type which are used in offices, such as for secre-
tarial or managerial use wherein a person occupies the
chair for extended periods of time and the chair should --
be designed to provide not only sustained comfort to
the occupant but to facilitate the performance of a
large variety of tasks and a large number of positions
and movements. More specifically, the present invention
relates to an office chair in which the seat of the chair
is vertically adjustable by means of a pneumatic cylinder
and the backrest is independently adjustable for postural
attitude. The postural attitude adjustment is also
achieved with a pneumatic cylinder. Both cylinders are
actuated by the same cam which is mounted to a shaft
which extends laterally outwardly beneath the seat and
includes a handle to facilitate rotation of the cam shaft
by the occupant to the various operating positions.
When the cam shaft is rotated in one direction,
a first surface of the cam unlocks a vertically oriented
pneumatic cylinder orming a pedestal o the chair so
that the seat may be adjusted in height. The vertical
pneumatic cylinder is biased in such a way as to offset
the weight of the seat, frame and backrest such that when
the chair is unoccupied, these elements will rise as a
unit. Height adjustment is accomplished by the occupant's
using his or her weight to overcome the upward bias on
the vertical cylinder. When the seat is in the desired
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adjusted position, the cam is rotated to the neutral
position to lock the vertical cylinder.
The backrest assembly includes a support
channel which is pivotally mounted to the rear of the
base of the seat near the sacral region of the occ~pan~.
The lower end of the back suppor~ member is pivotally
connected to the back adjusting pneumatic cylinder, and
the backrest assembly is mounted to the upper end of
the back support member. By rotating the cam shaft in
a direction opposite to that which unlocked the height-
adjusting vertical pneumatic cylinder, a second cam
surface unlocks the back adjusting cylinder to permit
the occupant to adjust the backrest in postural attitude
about the pivotal connection of the back support member
to the rear of the seat base.
This second cam surface which unlocks the back-
rest adjusting cylinder also includes a detent which may
be stably positioned on the valve actuator of the adjust-
ing cylinder for the backrest for continuously actuating
or unlocking the backrest adjusting cylinder to provide
a floating support or dynamic cushioning to the back of
the occupant.
The backrest cushion assembly is mounted to its
support by means of a pair of laterally spaced cushion
mounts which provide lesser resistance to body motion in
a fore-and-aft direction and greater support to reaching
motions of the occupant in a lateral or rearward direction
where such support is desired.
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Other features and advantages of ~he present
invention will be apparent to persons skilled in the
art from the following detailed description of a pre~
ferred embodiment accompanied by the attached drawing
wherein iden~ical reference numerals refer to like parts
in the various views.
The Drawing
FIG. 1 is a side elevational view of a chair
incorporating the present invention;
FIG. 2 is a fragmentary rear elevational view
of the chair of FIG. 1 showing the backrest support and
adjusting mechanism;
FIG. 3 is a fragmentary upper perspective view
showing the backrest adjusting cylinder and actuating
mechanism;
FIG. 4 is a right side elevational view of the
structural framework for the seat and backrest oE the
chair of FIG. l;
FIG. S is a fragmentary front view of the lower
portion of FIG. 4 showing the seat assembly support
structure; and
FIGS. 6A-6D are diagrammatic side views illus-
trating the various positions of the actuating cam in
relation to the adjusting gas cylinders for illustrating
the various operating modes of ~he chair of FIG. 1.
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General Des_r~tion
Referring first to FIG. 1 J an office chair is
seen to include a base generally designated 10 and
provided with casters 11. Preferably the base 10 includes
five outwardly extending support arms for greater stability.
Above ~he base 10 is a pneumatic cylindrical unit 12 having
its cylinder end press fit into a tapered seat (No. 3 -.
Morris taper) formed in the center of base 10. A rod 15
extends vertically above the unit 12 and is similarly
(i.e. No. 3 Morris taper) attached to a seat support
frame 18. A sculptured cover or panel 16 houses the seat
support structure and a control mechanism generally dPsig-
nated 19.
A second pneumatic cylinder 22 is also located
within the seat panel 16 and ac~uated by the control mechanism
19. The butt end of the cylinder 22 is pivotally connected
by a pin 23 to the lower end of a backrest support channel
gcnerall.y designated 24 which is pivotal.ly mounted at 25
to the seat support frame 18, and extends above the seat
cushion 17 Eor supporting the backrest assembly generally
designated 28 which includes a backrest cushion 29.
The backrPst assembly 28 is m~unted to the
support member 24 by means of a pair of cushion mounts
shown at 31, 32 in FIG. 2, and to be described further below~
Before describing the structure of the chair
in more detail, it may be helpful to understand the overall
unctioning of the major componen~s just described. The
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control mechanism lg includes a cam shown in dotted line
at 35 in FIG. 1, and it is mounted ~o a cam shaft 36
which extends outwardly through the seat support frame 18
and is connected to a shank 37 fitted at i~s outboard
end with a handle 38 (see FIG. 2). The handle 38 is
located just heneath the side of the seat cushion 17
toward the center (in a fore-and-aft direction) of the
seat so that an occupant may conveniently reach down and
turn it.
By turning the handle 38 in one direction
(clockwise in FIG. 1~ the cam 35 is rotated to a first
actuating position in which it unlocks the pneumatic
cylinder 13 to permit the chair to be adjusted in height.
Each of the pneumatic cylinders 13, 22 is similar in
structure and operation. These cylinders 13, 22 is
similar in structure and operation. These cylinders are
commercially available and known in the art. Cylinders
othis type are sometimes referred to as "gas cy'linders".
These pne~natic cylinders include pressurized gas which
is trapped within the cylinder and may be communicated
between the chamber partially'defined by the working face
of the piston (that is, the butt end o:E the cylinder) and
the chamber partially defined by the rod surface of the
piston (or rod end of the cylinder) by means of a valve
, located in the piston. The valve is actuated by 2 stem
such as that designated 39 in FIG. 1 for the cylinder 13
which extends through the rod 15 of the cylinder for
engagement by the cam 35. When the valve stem ls depressed,
the valve is opened to communicate the two cylinder
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chambers with each other. Because the area of the
working surface of the piston is larger and the internal
pressure is equalized when the valve is open, there is
a tendency to extend the rod 15 vertica'lly and thereby
elevate the seat assembly, backrest assembly and backrest
support structure as a unit. The occupant of the chair
may offset this upward force by applying his or her own
weight in a seating action if it is desired to lower the
seat.
By rotating the handle 38 in the opposite
direction (counterclockwise in FIG. 1), the cam 35 actuat~s
the bdckres~ adjusting cylinder 22 to vary the postural
attitude of the backrest. This cylinder is biased to
urge the backrest assembly 28 to a forward poSitiQn. At
least part of the unbalanced force on the gas cylinders
may be offset by a spring if desired. When the backrest
adjusting cylinder 22 is thus unlocked, the backrest will
have a natural tend~ncy to go forward~ and again, this
may be offset by the occupant in a normal seated position
by ~imply leaning rearwardly to place the backrest assembly
in the desired adjusted position and then lock lt in that
position by releasing the actua~ing mechanism. It is
considered an advantage of the invention that the pivotal
mounting of the backrest suppor~ member 24, namely the
connectlon 25 is located behind the sacral area of the
occupant so that the backrest cushion provides suppor~
to the same general area of the occupant for all adjusted
positions. It will also be appreciated that both the
height of the seat and the postural attitude of the
backrest may be adjusted over a continuous range, rather
than in discrete steps.
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The cam 35 is also provided with a recess or
detent to couple Lo the valve stem of the backrest
adjusting cylinder 22 in a stable position so that the
two remain engaged when the operator releases the handle
38. This permits the backrest to "free float" to provide
a dynamic cushioning support to the back of the occupant.
To briefly describe the action of the cushion
mounts 31, 32 of FIG. 2, they may be bent about a horizon-
tal transverse axis exten~ling perpendicular to the axes
of the cushion supports themselves, as when the occupant
leans direc~ly backward. In this type of support, such
as when the occupant is relaxing, a lesser resistance
is glven by the mounts 31, 32 because they are placed in
a bending mode of deflection. However, if the occupant
were, Eor example, to lean to the right and rear, as in
reaching for a telephone or o~herwise, he or she will want
to return to the upright position. In this mode, the
cushion supports are placed in shear (that is, deformed
in such a manner that ~he top of ~he support is laterally
displ.aced from, but remains parallel to the bottom of the
cushion member); and in this situation, the cushion
mounts, acting in unison, provide a greater resistance to
deflection and thereby a greater support to the occupan~,
and at least some return force.
Referring now to FIGS. ~ and 3, the seat support
frame 18 includes first and second side channels 43, 44
which extend beneath the seat cushion assem~ly and, toward
the rear of it, curv~ upwardly (see the portion designated
45 for the side channels 43 in FIG. 4). The support
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member 24 is pivotally mounted to the rear, upper portions
of opposing inner flanges of these channels by means of a
pin 25, as best seen in FIG. 2.
Returning to FIG. 3, a pair of plates 47, 48
are welded respectively to the channels 43, 44 and
extend inwardly toward each other and thence downwardly,
the downwardly extending portions being designated 47A
and 4$A respectively and seen best in FIG. 5. This
structure is braced by forward and rear plates 51, 52
which are welded to the depending portions 47A, 47B and
also to the opposing inner flanges of the channels 43, 44
(see FIGS. 4 and 5).
A collar 54 is welded to the opposing inner
surfaces o the portions 47A, 48A, and it includes a tapered
central bore 55 which receives the upper portion of the
rod lS of the pneumatic cylinder 13 in a press fit while
permitting the valve stem or actuator 39 to protrude above
the top of the collar 54 for engagement by cam 35, as best
seen in FIGS. 1 and 2.
Returning to FIG. 3, the downwardly depending
portions 47A, 48A of the plates 47, 48 are stamped to
provide vertical slots designated 57, 58 respectively
for receiving an anchor block 60. The anchor block 60
has a threaded bore at 61 for threadedly receiving the
rod 62 of the pnet~atic cylinder 22 while permitting
the valve actuator 65 to extend through the anchor block 60
for actuation by the cam 35~ The butt end of the cylinder
22 is seen to be pivotally connected by the pin 23 to the
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lower portion of the support 24 for the backrest assembly.
The support 24 is in ~he form of a channel, as best seen
in FIG. 2.
As also seen in FIG. 3, the cam 35 is received
on the cam shaft 36 and connected to by a flat (see 36A
in FIG. 6A). The shaft extends through the right channel
frame member 43 and is connected to the shank 37 of the
handle 38 by suitable means to transmit torsional Eorces
from the handle to the cam.
Referring now to FIGS. 2 and 4, the upper portion
of the backrest support channel 24 is formed into a flange
designated 70. An angle member 71 ls fastened to the
rear panel 73 of the backrest assembly (see FIG. 1) by
threaded fasteners 74. The angle bracket 71 includes
a lower horizontal flange 75 spaced above the 1ange 70
of the channel support 24. Each o the cushion mounts
31, 32 is similar so that only one need be described in
detàil. The cushion mount 31 includes a cylindrica].
body 80 of natural rubber complying with SAE specificatior
No. J200-3BA625-B13C1221. It is integrally molded with
oppositely extended threaded studs 81, 82. Stud 81 is
secured to flange 70 by means of a threaded aperture,
and stud 82 is secured to flange 70 by a nut 84. Each
of the threaded studs has an enlarged or disc-shaped
base embedded in the rubber during the molding process
so that they do not tear loose from the rubber body during
use.
Referring now to FIG. 6A, the cam 35 i.s seen
in a neu~ral position. It includes a firs~ cam surface
35A and a second cam surface 35B. A recess or detent
35C is formed adjacent the second cam sur~ace 35.
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In the position shown in FIG. 6A, the cam 35
does not actuate either valve stem 39 of the vertical
adjustment pneumatic cylinder or the valve s~em 65
of the postural attitude adjusting cylinder 22.
If the cam 35 is rota~ed counterclockwise by
the handle 38 from the position of FIG. 6A to ~hat of
FIG. 6B~ the cam surface 35B depresses the valve actuator
65 because the rod 62 is secured in position by the
anchor block 63, as described above. In this mannerS
the postural attitude adjusting cyli.nder 22 is unlocked
so that the backrest support channel 24 may be pivoted
about the pin 25 for adjustment purposes. As explained
previously, the bias of the cylinder 22 is such that
when it is unlocked,it has a tendency to force the
backrest assembly to a forward position, and the occupant
can then set it at will by applying pressure agains~ it
with his back, while holding the handle 38 in the
actuated position shown in FIG. 6B.
By rotating the cam still further counterclockwise
to the position shown in FIG. 6C, the detent 35C of the
cam 3S couples to the valve actuator 65 in a stable
position. Thus, the handle need not be continuously
held for the cam in this position to continuously actuate
the cylinder 22. In this position, ~he occupant of the
chair may continue to work and the backrest will supply
a floating support or dynamic cushioning.
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With the cam 35 in the positions illustra~.ed
in FIGS. 6A, 6B ~nd 6C, the height adjusting cylinder 12
is not ac~uated. By turning the cam 35 clockwise to the
position shown in FIG. 6D, the cam surface 35A depresses
the valve actuator 39 to unlock the cylinder 12 for
hei~,ht adjus~ment. Again, the rod 15 is biased in an
upward direction ~o raise the seat frame and backrest
frame as a unit, and height adjustment is accomplished
by holding the cam 35 in the position of FI&. 5D while
the occupant uses his or her weight to ofset the normal
upward force of the pneumatic cylinder until the seat is
located in the desired vertical position. The handle i5
then released, and the vertical adjusting cylinder is
locked.
Referring back to FIGS 1 and 2, by locating
the pivot pin 25 for the backrest support at a location
behind the sacral area of the occupant, as the postural
attitude of the backrest assembly is adjusted by means
of the cylinder 22, the bac.krest cushion nevertheless
remains in substantially the same position for support
of the back o~ ~he occupant. For all such pos~ural
attitudes, the cushion mounts 31, 32 have the same
operation. That is, as the occupant leans directly
backward, the cushîon members are deflected in a bending
mode, and in this mode, they offer little resistance ~o
deflection. The backrest is prevented rom being tilted
backwardly beyond a limit position by means of a limit
position element generally designated by reference
numeral 90 in FIG. 2 and including a chain 91 secured by
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means of a fastener 92 to a tab 94 stamped from the
channel support member 24 and bent rearwardly thereof
(see FIG. 1), and having its other end fast~ned at 98
to the panel 73 of the backrest assembly.
On the other hand, if the occupant leans toward
the rear and side, the cushion mounts 31, 32 have their
associated flexure members placed in a shear mode of
de1ection which provides greater resistance, and ~here-
fore some restoring force to assist the occupant in
re-assuming a normal occupancy position.
Having thus disclosed in detail a preferred
embodiment of the invention, persons skilled in the
art will be able to modify certain of the structure which
has been illustrated and to substitute equivalent elements
for those disclosed while continuing to practice the
principle o~ the invention; and it is, therefore, intended
that all such modifications and substitutions be covered
as they are embraced within the spirit and scope of the
appended claitns.
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