Note: Descriptions are shown in the official language in which they were submitted.
r~
THE FIE~D OF l'HE INVENTION
The invention relates to seating and more particularly
to chairs having one-piece seat-and-~back supports.
BACRGROUND OF THF INVENTION
Chairs having one-piece seat-and-~ack supports are
known. For example, U.S. patent to St. John, 293,813, issued
February l9, 1884, discloses a chair comprising an elongated
seat-and-back support mounted on a floor-engaging base. The
seat-and-back support comprises a lower, rigid, U-shaped seat
support and an upper relatively resilient back support extending
upwardly froli;ih s~ uppcrt. When a rearward and down~ard
force is exerted on the seat-and-back support, the upper back
support deflects backwardly and downwardly.
Although the back support of St. John's seat-and-back
support is flexible, the seat support thereof is not. Thus,
while the back support is designed to deflect downwardly and
backwardly relative to the seat support in response to an
occupant's weight, the seat support is not so constructed. Such
design has been determined to be insufficient in providing the
necessary comfort for users, especially in work environments
where the chairs are occupied for extended periods of time.
It has thus been found desirable to provide a chair one-
piece seat-and-back support comprising a U-shaped seat support
with upper and lower leg portions and an int~rmediate bight
portion, and a back support with a lower bight portion and an
upright back portion, wherein both bight portions are flexible
thereby enabling the seat support and the back support to adjust-
ably respond at different rates of deflection to an occupant's
weight. This chair design has been determined to be most
adequate in providing the necessary comfort to the chair
occupant.
It has also been found desirable to provide a resilient
stiffening means, such a leaf spring, between the upper and lower
leg portions of the seat support to strengthen the same and
increase resistance to relative deflection of the upper leg
portion of ~he seat support.
It should be noted that the use of leaf springs in
~ 72`~
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chairs to resist tilting of seat supports are known, although
such biasing means have not been used in chairs of the preferred
type heretofore described. For example, U.S. patent to Benzing,
3,337,265, issued March 4, 1965, discloses a chair comprising, in
relevant part, a pair of inverted U-shaped sides connected by a
pair of transverse and longitudinal horizontal supports. A pair
of U-shape~ springs are mounted on the transverse supports. A
substantially L-shaped seat-and-back support is mounted on top of
the springs. In this manner, when a rearward and downward force
is exerted on the seat-and-back support, same reclines downwardly
and backwardly against the tension of the springs.
In addition, U.S. patent to Werner, 3,740,792, issued
June 26, 1973, discloses a chair comprises a box-like lower
housiny open d~ ck' and top portions thereof and mounted on top
of a pedestal. An upper seat support is pivotally mounted to the
housing on a horizontal shaft. A number of overlapping leaf
springs surround the shaft and engage the housing and the seat
support. The springs bias the seat support in a horizontal posi-
tion. When a downward force is exerted on the seat support, the
same pivots against the tension of the springs.
Benzing also provides ~or adjustment of the leaf
springs' resistance to deflection of the seat support relative to
the housing. Specifically, the tension of the springs is
adjusted by turning a lever which displaces the springs forwardly
and rearwardly toward and away from the pivotal axis of the seat
support to increase the moment arm of the springs and thus vary
the tension of the same.
In contrast to the leaf spring tension adjustment-means
disclosed by Benzing, it has been found desirable to provide
tension adjustment means in a chair having a one-piece seat-and-
back support, wherein the adjustment means adjustahly engages the
leaf spring along a longitudinal axis thereof to increase and
decrease the effective length of the spring to thereby decrease
and increase, respectively, the spring's resistance to deflection
~5 of the seat support.
SUMM~RY OF THE INVENTION
A chair comprising a seat, a back, a base and an
elongated one-piec~ seat and back support having a substantially
U-shaped seat support and a back support. The seat support
includes a lower leg portion supported by the base, an upper leg
portion supporting the seat an a fir5t bight portion intermediats
the upper and lower leg portions. The back support has a second
2 ~ ~
bight portion extending rearwardly and upwardly from the upper
leg portion and a back support portion extending upwardly from
the second bight portion. The first and second bight portions
are resilient thereby enablin~ the upper leg portion and the back
support portion to deflect downwardly and downwardly and
rearwardly, respectively, in response to forces exerted on the
upper leg portion and the upper back portion.
Preferably, the maximum width of t~e upper leg portion
is enlarged relative to the maximum width of the second bight
portion to provide a relatively broad base of support for the
seat against lateral movement thereof and to facilitate relative
deflection of the second bight portion. The maximum width of the
upper leg portion is preferably equal to at least twice the
maximum width of the se~ond-bi~ portion.
In addition, the chair comprises a stabilizer means
connected to and between the upper leg portion and the back
support portion for providing lateral stability to the back
support during relative deflection of the back support portion.
The stabilizer means comprises elongated substantially V-shaped
armrests mounted to and between the seat and the back on opposite
lateral sides of the chair, each of the armrests being flexible
along a portion thereof to accommodate relative deflection of the
upper leg portion and the back support.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to
the accompanying drawings in which:
FIG. 1 is a front perspective view of a chair in
accordance with the invention;
FIG. 2 is a rear perspective view of the chair shown in
FIG. l;
FIG. 3 is a side elevational view of the chair shown in
FIG. l;
FIG. 4 is a side elevational view of the chair shown in
FIG. 1 illustrating the chair tilting capabilit~;
FIG. 5 is a perspective view of a support means of the
chair and certain elements of a stabilizer means and one
embodiment of a tension control means;
FIG. 6 is a detailed side elev~tional YieW of a seat-
and-back support of the chair;
FIG. 7 is a bottom view of the seat-and-back support;
FIG. 8 is a fragmented perspective view of a seat
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support of the seat-and-back support illustrating the stabilizer
means and the tension control means;
FIG. 9 is an exploded view of the stabilizer means;
FIG. 10 is a perspective view of a stiffening means of
the chair mounted to a cradle of the tension control means;
FIG. 11 is a front elevational view of the stiffening
means and the cradle shown in FIG. 10;
FIG. 12 is a side elevational view of a second
embodiment of the tension control means;
FIG. 13 is a side elevational view of a third embodiment
of the tension control means;
FIG. 14 is an exploded view of an armrest mounting means
of the chair; and
FIG. 15 is a perspective view o~ th~ ~e_~ir:d embodiment
of the tension control means illustrated in FIG. 12.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring generally to the drawings, there is shown a
chair 10 comprising a castered base 12, a vertically adjustable
pedestal 14 mounted to base 12 and an elongated one-piece seat-
and-back support 16 mounted to the pedestal. The seat-and-back
support is adapted to deflect downwardly and backwardly against
the weight of an occupant. A resilient stiffening means 18 is
provided for increasing the seat-and-back support's resistance to
deflection. A tension control means 20 is provided for adjusting
the tension of the stiffening means 18.
Referring now specifically to Figures 1-5, the chair
base 12 comprises a plurality of equidistantly spaced arms 22
having mounted at outer ends 24 thereof floor engaging casters
26. Inner ends 28 of the arms 22 are connected by a central web
30 having a central socket 32 extending therethrough. The base
12 is preferably a one-piece member made of cast aluminum or
Zytel (a glass reinforced nylon). Although the base 12 is
illustrated as having five arms 22, any other number of arms can
be used to provide the necessary support for the chair 10. The
illustrated chair base 12 is of a similar type used in connection
with a chair manuEactured and sold under the trademark EQUA by
Herman Miller, Inc., of Zeeland, Michigan, Applicant's assignee
of record. However, other suitable chair bases known in the art
may be substituted for the illustrated base 120
The pedestal 14 comprises a lower tube 34 securely
received within the web socket 32 of the base 12 and an upper
tube 36 above the lower tube and securely rotatably mounting at
.
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an upper end 38 thereof a support means 40 preferably made of die
cast aluminum. ~ pneumatic air spring 42 is positioned between
and partially received within the upper and lower tubes 34, 36
and comprises a piston (not shown) securely mounted to the web 30
5 and a cylinder 44 secured to the support means 40. The air
spring 42 includes an adjustment pin 46 projecting upwardly from
the upper axial end (not shown) of the cylinder 44 and through a
vertical bore (not shown) in the support means 40. The pin 46 is
adapted to move between an upper position, where the cylinder and
piston of the air spring 42 are helcl stationary in locked
engagement, and a lower position, where the cylinder and piston
are released for movement relative to each other to extend or
contract the air spring longitudinally. The adjustment pin 46 is
normally biased in the upper, locked position. ~ height
lS adjustment lever 50 is pivotally mounted to the support means 40,
engages at an inside end 52 of the lever the adjustment pin 46
and extends outwardly from the casting at the lever outside end
54 at lateral side 56 of the chair 10. When the lever 50 is
actuated by lifting upwardly on the outside end of the same, the
lever inside end 52 forces the pin 46 to the lower position,
thereby releasing the piston (not shown) relative to the cylinder
44 and thus allowing the pedestal 14 to extend or contract to
raise or lower the chair upper portion 58. When the lever 50 is
released, the pin moves to the upper position and the pedestal 14
becomes locked in the adjusted position. A hand knob 60 is
provided at the lever outside end 54 to facilitate manual pivotal
actuation of the lever 50.
As shown in Figures 3,4, and 6, the one-piece seat-and-
back support 16 is mounted to the pedestal 14 and is bent so as
to form a lower generally U-shaped seat support 62 open toward
the chair back portion 64 and an upper, somewhat S-shaped back
support 66. The seat support 62 comprises upper and lower leg
portions 68, 70 and a first bight portion 69 intermediate the leg
portions. The back support 66 comprises a second bight portion
73 extending rearwardly and upwardly from the upper leg 68 and an
upper back support portion 75 extending upwardly from the second
bight portion. The first and second bight portions 69, 73 are
resilient and the upper and lower legs 68, 70 and the upper back
support portion 75 are somewhat stiff.
The chair seat 72 is mounted on the upper leg portion 68
of the seat support 62. The chair back 74 is mounted on the
upper back support portion 75 of the back support 66.
2 ~ ~ 7 ~
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As illustrated in Flgures 5-8, the lower leg 70 of the
U-shaped seat support 62 forms a downwardly oriented cover 76 at
a rear end 71 of the leg. The cover 76 has a rearwardly and
downwardly sloping U-shaped side wall 78 and a top wall 80. The
cover 76 is complementary to, slidably received on and mounted to
the support means 40. Mounting of t:he cover 76 and thus the
seat-and-back support 16 to the support means 40 can be achieved
by any suitable mechanical means, such as by plurality of bolts
82 in registry with a number of aligned holes 84 and threaded
bores 86 of the cover and support casting, respectively. The
cover 76 functions to protect elements of the height-adjustable
pedestal 14 described above. Elements of the tension control
means 20 are similarly protected by the cover 76 as will be
described below.
As shown in Figures 3 and 4, when the weight of an
occupant is exerted on the seat-and-back support 16, the first
and second portions 69, 73 resiliently respond to deflect and
move the seat-and-back support downwardly and backwardly between
three general degrees of flex: a full upright "work intensive"
position, a partially flexed "relaxed" position, and a "full
tilt" position.
In the work intensive position, an occupant exerts
minimal force on the back support 66 to impart limited deflection
thereof. In the work intensive position, an occupant's weight is
exerted downwardly on the chair seat 72, with some deflection of
the seat support upper leg 68 relative to the lower leg 70.
In the relaxed position, an occupant is leaned slightly
rearwardly exerting some degree of force on the back support 66.
By leaning backwardly, an occupant shifts his/her center of
gravity rearwardly away from a pivot point A. Displacement of
the center of gravity increases the moment arm about pivot point
A, thereby enabling the seat-and-back support 16 to flex
rearwardly and downwardl~. The flexing motion causes the
S-shaped back support 66 to flatten slightly, thereby increasing
the angle formed between the upper leg 68 of the seat support 62
and the back support 66.
Substantially maximum flex of the seat-and-back support
16 is achieved in the full tilt position obtained when an
occupant exerts additional pressure on the back support 66. In
this position, the outer angle between the seat support upper leg
68 and the back support 66 is maximized by the further downward
and rearward seat-and-back support 16 deflection. In the full
tilt position, a significant portion of an occupant's upper body
weight is shifted to the chair back 74.
There~ore, the elongated one-piece seat-and-back
support 16 is adapted to resiliently respond to shifts in an
occupant's weight by smoothly flexing at the first and second
bight portions 69, 73 thereof from an upright work intensive
position to a partially relaxed position to a full tilt position
as an occupant shifts his/her weight rearwardly against the back
support 66. The novel design of the elongated one-piece flexible
seat-and-back support 16 is such that the same is directly
responsive to shifts in an occupant's weight to smoothly bend
among the various degrees of flex heretofore described, with the
upper leg 68 of the seat support 62 deflecting at a rate
different from the rate of deflection of the back support 66.
This different deflection rate is due to the differing downward-
and rearward load distributions exerted on the seat-and-back
support when an occupant sits in the chair. To attain the
desired resiliency, the seat-and-back support 16 is preferably
made of a glass reinforced nylon resin, a suitable example of
which is marketed by the DuPont Company under the trademark
Zytel. The seat-and-back support is preferably injection molded
from such material. A polyester resin by DuPont sold under the
trademark Rynite may also be used.
Referring to FIGS. 1, 2, and 7, the seat support upper
leg portion 68 is enlarged or relatively wide with respect to
other portions of the seat and back support 16, namely, the first
bight portion 69 and the lower leg portion 70 of the seat support
62 and the second bight portion 73 and the upper back support
portion 75 of the back support 66. Specifically, the back
support portion 75 and the second bight portion 73 of the back
support 66 are relatively narrow and each preferably has a width
of approximately four inches along substantially the full length
thereof. The upper leq portion 68 of the seat support 62 is
approximately 10.5 inches in width at a central transverse axis
thereof. The upper leg portion tapers as it extends forwardly to
the first bight portion 69 which tapers along its length to the
lower leg portion 70, the first bight portion having a maximum
width of approximately 9.5 inches and an average width of
approxima~ely 8.125 inches. The lower leg portion 70 of the seat
support also tapers along the length thereof continuing from the
first bight portion 69 and has a maximum width of 6.75 inches and
an average width of approximately 6 inches.
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With respect to the thickness of relevant portions of
the seat-and-back support 16, preferably the second bight portion
73 is approximately 0.500 inches in thickness and the upper leg
portion 68 has a thickness less than the thickness of the second
bight portion. The average thickness of the upper leg portion 68
is approximately .250 inches. The thickness gradient between the
second bight portion and the upper leg portion is gradual. In
addition, the first bight portion 69 and the lower leg portion
also preferably have a thickness of .250 inches.
Given the above-discussed prefered material composition
of the seat-and-back support 16, the forgoing dimensions thereof
provide the same with sufficient flexibility at the first and
second bight portions 69, 73 to achieve desired relative
defiection of the upper leg portion 68 and the back support
portion 75.
As illustrated in Figures 5, and 7-9, the chair 10
further includes a bridle 88 (hereinafter, sometimes referred to
as the "stabilizer means") mounted to and between the upper and
lower legs 68, 70 of the seat support 62 and for providing
stability to the same during deflection of the seat-and-back
support 16. Specifically, the bridle 88 comprises an upper
bracket ~0 mounted to the seat support upper leg 68 and a U-
shaped stabilizer bracket 92 secured to and between the upper
bracket and the support means 40.
The bracket 90 comprises an upper plate 94 and a pair of
spaced bilateral flanges 96 preferably formed integral with the
plate. The plate 94 is positioned above and mattingly engages
the seat support upper leg 68 by a plurality of bolts 98 in
registry with aligned holes 100 in the overlapping plate and seat
support upper leg. The flanges 96 of the bracket 90 depend
downwardly therefrom and are in registry with a pair of spaced
slots 102 extending through the seat support upper leg 68.
The U-shaped stabilizer bracket 92 is pivotally mounted
to the bracket 90 at upper ends 104 of spaced arms 106 of the
stabilizer. To this end, each flange 96 of the bracket go
includes a slot 108 forming a pair of spaced legs 110 having a
pair of aligned openings 112 extending therethrough. The upper
ends 104 of the arms 106 are received in the slots 108 and
include holes 114 aligned with the aligned openings 112. A pair
of pins 116 extencl through the aligned openings 112 and holes 114
to pivotally mount the stabilizer arms 106 to the bracket 90.
The U-shaped stabilizer bracket 92 is also pivotally mounted
- 9 -
at a lower bight portion 118 thereof to the support means 40 in
sandwiched relationship between the same and the seat support
lower leg 70. To this end, the support means 40 has formed
therein a front transverse channel 120 in which a U-shaped, in
5 cross section, shoe 122 complementary to the front transverse
channel is received. The bight portion 118 of the stabilizer
bracket 92 rotatably engages the shoe 122 and is fully received
within the channel 120 such that there is sufficient clearance
between the seat support lower leg 70 and the bight portion 118
to permit free rotation of the same with respect to the support
means 40. Lower portions 124 of the stabilizer arms 106 are in
slidable registry with a pair of`spaced elongated slots 126
extending through the seat support lower leg.
In operation of the one-piece seat-and-back support 16, when
an occupant's weight is exerted on the seat support 62, the upper
leg 68 thereof deflects downwardly causing the arms 106 of the
stabilizer bracket 92 to pivot about their mounting to the
flanges 96, the arm lower ends 124 to register to a greater
extent with the elongated slots 126 of the seat support lower leg
70 and the stabilizer bracket bight portion 118 to rotate within
the front transverse channel 120 of the support means 40. In
this manner, the bridle 88 accommodates relative movement of the
upper and lower legs 68, 70 of the seat support 62 while at the
same time performing its primary functions of resisting
separation of the upper and lower legs 68, 70 when the chair 10
is not occupied and providing lateral stability to the U-shaped
seat support 62 during flex of the same between the work
intensive and full tilt positions.
To adjust the resistance to deflection of the seat-and
back support 16 to accommodate occupants differing in weight, the
chair 10 is provided with the resilient stiffening means 18 and
the tension control means 20. As generally illustrated in
Figures 3-5 and 8, the stiffening means 18 comprises an elongated
strap-like leaf spring mounted to and between the upper and lower
legs 68, 70 of the seat support 62. The geometry of the leaf
spring will be hereinafter described in detail. The leaf spring
resists downward relative movement of the seat support upper leg
68 when an occupallt's weight i~ exerted thereon. The leaf spring
is preferably made of a composite material such as unidirectional
S-glass with an epoxy resin (i.e., glass-reinforced epoxy). The
tension control means adjusts the leaf spring's resistance to
deflection of the seat-and-back support 16. To this end, the
--10--
tension control means 20 is adapted to adjustably engage the leaf
spring along a longitudinal axis thereof to decrease and increase
the effective length of the leaf spring to increase and decrease,
respectively, the spring~s resistance to relative deflection of
5 the seat-and-back support.
The tension control means 20 generally comprises an engaging
means 123 for ad~ustably engaging the leaf spring, a mounting
means 125 for movably mounting the engaging means to the support
means 40 for movement between front and rear positions relative
lo to the leaf spring and an actuating means 127 operably connected
to the mounting means for actuating movement of the engaging
means between the front and rear positions. In this manner,
movement of the engaging means 123 toward the rear position
decreases the effective moment arm length between the leaf spring
and the force exerted on the rear portion of the seat support by
the occupant, thereby increasing the spring's resistance to
deflection of the upper leg 70. Movement of the engaging means
toward the front position increases the effective moment arm
length to thereby decrease the spring's resistance to deflection
of the upper leg. In this manner, the resiliency or resistance
to deflection of the seat-and-back support 16 can be adjusted to
comfortably accommodate occupants varying in weight. It may be
surmised that a relatively heavy occupant would adjust the
tension control means 20 to a position adjacent the rear position
to increase resistance to deflection of the seat-and-back support
16, while an occupant of relatively light weight would set the
tension control means closer to the front position to decrease
the leaf springls resistance to deflection of the seat-and-back
support.
In one embodiment of the invention, illustrated in
Figures 5 and 7-11, the resilient stiffening means 18 comprises a
substantially bow-shaped leaf spring 128, having upper front and
rear portions 130, 132 and a central portion 134. The spring
front and rear portions 130, 132 reverse in curvature, the apexes
of the curves freely slidably engaging front and back bottom
surfaces 136, 138 of the seat support upper leg 68. In addition,
the leaf spring 128 is slidably engaged with, at the central
portion 13~ thereof, the tension control means 20. The tension
control means is slidably mounted to the support means 40 through
an elongated opening 140 in the seat support lower leg 70 for
movement between the front and rear positions heretofore
described.
Referring now specifically to Figures 8 and 10-11 for a
detailed discussion of the tension control means 20, the engaging
means 123 thereof comprises a cradle 142 slidably mounted to the
support means 40 for movement between the front and rear
positions heretofore describe~ through the elongated opening 140
in the seat support lower leg 70. The cradle 142 is positioned
between the spaced stabili~er arms 106 of the bridle 88 and
comprises a substantial U-shaped member having a pair of
sidewalls 146, a bottom wall 148 and a transverse pin 150 mounted
to and between the sidewalls in spaced relationship to the bottom
wall. The bottom wall 148 has depending downwardly therefrom a
pair of tangs 152 fixedly secured to the mounting means 125 of
the tension control means 20. The leaf spring central portion
134 is captured between the transverse pin 15Q and the cradle
bottom wall 148. The cradle transverse pin 150 is preferably
fitted with a rubber sleeve 154 and the cradle bottom wall 148 is
preferably covered with a rubber sheet 156. The sleeve 154 and
the sheet 156 function to eliminate noise otherwise caused by
direct movable engagement of the spring center portion 134 with
the cradle 142 during operation of the tension control-means and
caused by the variable deflection of the spring 128 during usage
of the chair 10.
As seen in Figure 5, the mounting means 125 comprises a
scissor mechanism 144 slidably mounted to the support means 40 in
substantially flush relationship to a top surface 158 thereof and
beneath the seat support lower leg 70. The actuating means 127
comprises an adjustment rod 164 rotatably mounted to the support
means 40 in substantially flush relationship to th~ same's top
surface 58. To this end, the support means 40 has formed in the
~0 top surface 158 thereof rear transverse and longitudinal channels
160, 162. The transverse channel 160 is positioned rearwardly of
the front transverse channel 120 associated with the bridle 88.
The adjustment rod 164 is rotatably received within the
support means rear transverse channel 160 at an inner end 172 of
the rod, the rod outer end 174 extending laterally outwardly from
the support means 40 at chair lateral side 176 opposite the
height adjustment lever 50. The rod 164 is mounted in rotatable
registry with the transverse channel 160 by brackets 178 secured
to the support means 40 by any suitable mechanical means, such as
by screws 180 in registry with aligned holes (not shown) in the
brackets and threaded bores (not shown) in the support means.
The scissor mechanism 144 comprises a block 166, a pair of plates
L !~ ~J) ~j ~
168 and a pair of arms 170. The block 166 is slidably received
within the longitudinal channel 162 of the support means 40 and
includes a pair of shoes 182 in which the tangs 152 of the cradle
142 are securely received. The plates 168 include threaded
portions (not shown) operatively engaging the threaded ad~ustment
rod 164. Because the plate threaded portions (not shown) and
their respective rod threaded portions 184, 186 are oppositely
directed, rotation of the adjustment rod in one direction or the
other causes the plates to move toward or away from each other.
The arms 170 are pivotally mounted at front and rear ends 188,
190 thereof to and between the plates 168 and the block 166,
respectively.
In this manner, when ths adjustment rod 164 is rotated
in one direction, the plates 168 move toward each other causil~
the scissor arms 170 to pivot and force the block 166 toward the
rear position of the tension control means 20. Rearward movement
of the block 166 forces the cradle 142 and leaf spring 128
rearwardly, thereby decreasing the effective moment arm length
between the spring and the force exerted by the occupant on the
rear portion of the seat support upper leg 68 to increase the
spring's resistance to deflection of the seat-and-back support
16. When the rod 164 is rotated in the opposite direction, the
plates 168 move away from each other causing the scissor arms 170
to pivot and force the block 166 forwardly. Forward movement of
the block 166 forces the cradle 142 and spring 128 forwardly,
thereby increasing the effective moment arm length and thereby
decreasing the spring's resistance to deflection of the seat-
and-back support 16.
To facilitate manual rotation of the adjustment rod 164,
the same is provided on the outer end 174 thereof with a hand
knob 194. The hand knob 194 preferably differs in geometry from
the height adjustment knob 60 so that the knobs can be easily
differentiated by an occupant.
As indicated above, certain elements of the tension
control means 20 are enclosed by the seat support lower leg cover
76 and are thus protected from damage and accumulation of dust
which can affect operation of the tension control means.
In a second embodiment of the invention, illustrated in
Figures 12 and 15, the tension control means 20 further comprises
a retainer 196 securely mounted to the seat support lower leg 70
and having an open rear portion 198 providing access to the
interior of the retainer. The retainer 196 can be formed
2 ~
-13-
integrally with the seat support lower leg 70 or be separate
therefrom but mounted to the seat support by any suitable
mechanical means. The stiffening means 18 comprises a
substantially S-shaped leaf spring 200 having an upper curved end
201 freely engaging the seat support upper leg rear part at an
apex 202 of the curved end, and a lower substantially straight
end 204 received within the retainer 196 through the open rear
portion 198 thereof. In this embodiment of the invention, the
elements of the tension control means 20 are substantially
identical to those of the above-described embodiment except that
in the embodiment of Figure 12, a fulcrum pad 206 is mounted to
the block 166 rather than the cradle 142. Like the cradle 142,
however, the fulcrum pad 206 is set in slidable registry with the
elongated opening 140 of the seat support lower leg 70 and
includes tangs 152 engaging the shoes 182 of the block 166. The.
pad 206 is set in slidable engagement with a bottom sur.face 208
of the leaf spring straight end 204. In addition, like the
cradle 142, the fulcrum pad 206 is adapted to move between the
front and rear positions heretofore described to alter the
effective length of the leaf spring and-thereby adjust the same's
resistance to deflection of the seat-and-back support 16.
SpecificalIy, upon rotation of the adjustment rod 164 in one
direction, the fulcrum pad 206 moves rearwardly to shorten the
effective moment arm length between the spring and occupant
downward force and thereby increase the spring's resistance to
relative downward movement of the seat support upper leg 68.
When the fulcrum pad 206 is moved toward the front position of
the tension control means, the moment arm is increased, thereby
decreasing the springls resistance to downward relative movement
of the seat support upper leg 6~. Consequently, when a
relatively light occupant uses the chair, the fulcrum pad 206 is
positioned adjacent the front position of the tension control
means 20. Alternatively, when a heavy occupant uses the chair
10, the fulcrum pad 206 is positioned closer to the rear posi-
tion of the~ tension control means 20.
In a third embodiment of the invention, illustrated inFigure 13, the stiffening means 20 comprises a substantially
straight leaf spring 210 having the lower front end 212 thereof
fixedly secured to the seat support lower leg front part 21~ by
any suitable mechanical means, such as by a plurality of bolts
216 in registry with an equal number of pairs of aligned holes
(not shown) extending through the spring front end 212 and the
?, .~ ~
-14-
lo~er leg front part 214. An upper rear end 220 of the leaf
spring 210 is bent along a gradual curve, the apex 222 of which
freely mattingly engages the seat support upper leg rear part
138.
In the tension control means 20 of the embodiment
illustrated in Figure 13 the engaging means 123 comprises a cam
pad 224 mounted about a horizontal axis of rotation on a pin 226
forming the mounting means 125 and rotatably secured transversely
to and between opposing sidewalls 78 of the seat support lower
leg cover 76. The cam pad 224 is set in registry with an
enlarged opening 228 extending throuyh the seat support lower leg
70 and an enlarged channel 229 within and the support means 40.
The cam pad 224 engages a bottom surface 230 of the leaf spring
210 at a rear part 232 of the pad. The cam pad 224 is somewhat
triangular in shape, with the rear end 232 thereof being enlarged
relative to a front end 234 of the pad. Due to this geometry,
rotation of the same in one direction causes the pad to move
rearwardly and upwardly and to engage the spring lower front
portion 212 to a greater extent to thereby shorten the effective
moment arm length between the spring and the force exerted on the
seat by the occupant and thereby increase the spring's resistance
to deflection of the seat support upper leg 68. Rotation of the
pad 224 in the other direction moves the same forwardly and
downwardly to thereby increase the moment arm length and reduce
the spring's resistence to deflection.
The actuating means 127 comprises an adjustment shaft 26
threada~ly mounted to the support means 40 through a vertical
threaded bore (not shown) of the same, and has a lower end 238
extending downwardly from the support means and mounting a
handwheel 240 and an upper end 242 above the casting and in
abutting engagement with the cam pad rear end 232.
In operation, rotation of the handwheel 240 in one
direction threads the adjustment shaft 236 upwardly to force the
cam pad 224 about its pivot axis and rearwardly and upwardly
against the leaf spring lower front end 212. The effective
length of the leaf spring 210 is thereby decreased to therefore
increase the spring's resistance to deflection of the seat
support upper leg 68. Conversely, upon rotation of the handwheel
240 in the other direction, the shaft 236 is adjusted downwardly
to lower the rear portion 232 of the cam pad 224 to thereby
increase the effective length of the spring 210 and decrease the
same's resistance to deflection of the upper leg 68.
?~
Referring now to Figures 1-3 and 7, the chair seat 72
comprises an inner shell (not shown) and an outer structural
shell (not shown) and is mounted to and above the seat support
upper leg 68 by any suitable mechanical means, such as by a
plurality of screws (not shown) in registry with aligned holes
246 extending through the seat outer shell and the seat support
upper leg. The shape of the seat 72 is complementary to that of
the seat support 62, but enlarged with respect thereto to provide
the necessary comfort and support to the occupant. In addition,
the seat front portion 248 is rolled over to comfortably
accommodate an occupant's legs. A cushion 250 is molded to the
top of the inner shell. The inner shell is removably fastened by
any suitable snap means to the outer shell. By this me~hod, the
seat cushion 250 can be replaced as necessary. The seat 72 is
preferably made of Zytel or polypropylene, compositions which
provide some degree of flexibility to the seat during flex of the
seat-and-back support 16.
As illustrated in Figures 1-3 the chair back 74 is
substantially half oval in shape and has an enlarged U-shaped
channel 252 within a central relief portion 254 formed on a rear
surface 256 of the back. The back 74 comprises an inner and an
outer shell (not shown), the outer shell being securely fastened
to the back support 66, with the same received within the chan
nel 252 and flush with respect to the relief portion 254 by any
suitable mechanical means, such as by a plurality of screws (not
shown) extending through aligned orifices (not shown) in the back
and the back support. Like the chair seat 72, the back 74 is
preferably made of a material such as Zytel or polypropylene to
provide flexibility of the back. The chair back 74 is enlarged
with respect to the back support and in this manner functions to
distribute the weight transferred from the occupant to the chair
seat and back support as the occupant leans rearwardly in the
same between the upright and full tilt positions. A cushion 262
is molded to the inner shell, the same being removably fastened
by any suitable snap means to the outer shell. By this method,
the back cushion 262 can be replaced as necessary.
As illustrated in Figures 1-3, the chair can be provided
with a pair of op~ional armrests 264 mounted on opposite lateral
sides 56, 176 of the chair 10. Specifically, each armrest 264 is
a substantially V-shaped flexible member having, with reference
to the work intensive position of the seat-and-back support 16, a
substantially horizontal leg 266 and a diagonal leg 26~, free
1 f '.~
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ends of the horizontal and diagonal legs being ro-tatably mounted
to the back 74 and the seat 72, respectively, at a lateral side
56 or 176 of the chair. The horizontal leg 266 provides support
for an occupant's arm. In this manner, as the seat-and-back
support 16 flexes downwardly and backwardly in response to a
shift in an occupant's weight, the armrests 264 likewise flex
thereby accommodating the changing geometry of the seat-and-back
support. Flex of the V-shaped armrests generally occurs at the
vertices 270 of the Vs, due to the rotatable connection be-tween
the armrests and the seat 72 and back 74. Each armrest 264 is
substantially rectangular, in cross section, with the thickness
thereo~ tapering substantially at the vertex 270 of the V. A
reduction of thickness at the vertex facilitates the resiliency
of the armrest 264.
As stated above, the armrests 264 are rotatably mounted
to the chair back 74 and the chair seat 72 at lateral sides 56,
176 of the chair 10. To this end, the free ends 272, 274 of the
horizontal and diagonal legs 266, 268, respectively, have formed
thereon sockets 276. In addition, an attachment means 278 is
provided for mounting the armrests 264 to the seat 72 and the
back 74.
As best seen in Figure 14, the armrest attachment means
278 comprises a pair of U-shaped brackets 280, each having a web
portion 282 and a pair of side portions 28~. Each side portion
284 includes a hole 286 extending therethrough. One bracket 280
is securely mounted to and between the chair back shells, with
the web portion 282 sandwiched therebetween and the side portions
284 extending rearwardly of the chair. A recess in the inner
chair back shell (not shown~ accommodates the bracket web. The
other bracket 280 is mounted to and between the chair seat
shells, the web portion 282 sandwiched therebetween and the side
portions 284 extending downwardly from the chair seat 72. A
recess in the inner chair s at shell (not shown) accommodates the
bracket web.
The attachment means 278 further comprises a hollow
tubular spacer 288 partially received within each armrest socket
276, the spacer being aligned with a respective hole 286 in the
U--shaped bracket 280. Bolts 290 extend through the aligned
sockets 276, spacers 288 and holes 286 to securely mount the
armrest 264 to the brackets 280. Hemispherical protective caps
292 can be placed over the bolts 290.
As stated above, the chair 10 comprises the first
2~ 7~
-17-
stabilizer means or bridle 88 pivotally mounted to and between
the upper and lower leg portions 68, 70 of the seat support 62
for providing stability to the same during deflection of the
upper leg 68 relative to the lower leg by virtue of the resilient
first bight portion 69 intermediate the same.
In a similar manner, the armrests 264 also function as
stabilizer means for the seat and back support 16, but not with
respect to the upper and lower legs 68, 70 thereof. Rather, by
virtue of the pivotal connection of the armrests 264 to and
between the seat 70 and the back 74, on opposite lateral sides
56, 76 of the chair, the armrests provide lateral stability to
the seat and back support 16 between the upper leg portion 68 and
the upper back support portion 75 during relative deflection
thereof by virtue of the resilient second bight portion 73.
While the invention has been described in connection
with a preferred embodiment, it will be understood that I do not
intend to limit the invention to that embodiment. To the
contrary, I intend to cover all alternative modifications and
equivalents as may be included within the spirit and scope of the
invention as defined by the appended claims.
