U.S. patent application number 10/315838 was filed with the patent office on 2003-07-10 for chair with lumbar support and conforming back.
Invention is credited to Deimen, Michael L., Hasenour, Joseph G., Hatcher, Stephen D., Schweikarth, Derek.
Application Number | 20030127896 10/315838 |
Document ID | / |
Family ID | 23334458 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030127896 |
Kind Code |
A1 |
Deimen, Michael L. ; et
al. |
July 10, 2003 |
Chair with lumbar support and conforming back
Abstract
A task chair including a seat support structure, a backrest
frame attached to the seat support structure, and a backrest
supported by the backrest frame. The backrest includes a back
support surface which may ergonomically conform to a seated user
when the user shifts positions while sitting in the chair. The back
support surface includes rigid and flexible portions connected to
one another, the flexible portions allowing resilient flexing of
the back support surface to create conformance zones which
dynamically support the back of a seated user in an ergonomic
manner.
Inventors: |
Deimen, Michael L.;
(Holland, IN) ; Schweikarth, Derek; (Jasper,
IN) ; Hatcher, Stephen D.; (Jasper, IN) ;
Hasenour, Joseph G.; (St. Anthony, IN) |
Correspondence
Address: |
BAKER & DANIELS
111 E. WAYNE STREET
SUITE 800
FORT WAYNE
IN
46802
|
Family ID: |
23334458 |
Appl. No.: |
10/315838 |
Filed: |
December 10, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60340673 |
Dec 14, 2001 |
|
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Current U.S.
Class: |
297/301.1 |
Current CPC
Class: |
A47C 7/46 20130101; A47C
7/14 20130101; A47C 7/448 20130101 |
Class at
Publication: |
297/301.1 |
International
Class: |
A47C 003/00 |
Claims
What is claimed is:
1. A chair, comprising: seat support structure; a backrest frame
connected to said seat support structure; and a backrest formed of
a flexible portion having at least one rigid member embedded
therein, said backrest frame connected to said at least one rigid
member at at least one flex point, said backrest resiliently
movable about said at least one flex point to conform to a seated
user.
2. The chair of claim 1, wherein said flexible portion is formed
from one of a flexible urethane material and a flexible silicone
material.
3. The chair of claim 1, wherein said at least one rigid member is
made from one of wood, metal, and a plastic material.
4. The chair of claim 1, wherein said backrest includes at least
two of said rigid members respectively disposed along opposite
sides of said backrest, said backrest frame having opposite ends
respectively connected to said rigid members at said flex
points.
5. The chair of claim 1, wherein each said rigid member includes a
spring member extending therefrom, each said spring member embedded
within said flexible portion.
6. The chair of claim 1, wherein each said flex point includes a
flexible bushing member disposed between said backrest frame and
said backrest rigid member, said bushing member providing a return
force against movement of said backrest at said flex points.
7. The chair of claim 1, wherein said backrest includes a flexible
upper portion, said upper portion resiliently moveable about said
flex points between a substantially upright position and a reclined
position responsive to movement of a seated user.
8. The chair of claim 1, wherein said backrest includes a lumbar
support portion projecting outwardly from said backrest in the area
of the lumbar region of the back of a seated user, said lumbar
support portion resiliently moveable about said flex points
responsive to movement of a seated user.
9. A chair, comprising: seat support structure; a backrest frame
connected to said seat support structure; and a backrest including
a flexible body portion surrounding at least two rigid portions,
said at least two rigid portions pivotally attached to said
backrest frame at respective joints which are disposed proximate
opposite sides of said backrest.
10. The chair of claim 9, wherein each said rigid portion is made
from one of metal, plastic, and wood, each said rigid portion
embedded within said flexible portion.
11. The chair of claim 9, wherein said rigid portions are
respectively disposed along opposite sides of said backrest, said
backrest frame having opposite ends respectively connected at said
joints to said rigid portions.
12. The chair of claim 9, wherein said flexible portion is formed
from one of a flexible urethane material and a flexible silicone
material.
13. The chair of claim 9, wherein each said joint includes a
flexible bushing member disposed between said backrest frame and
said backrest rigid portion, said bushing members providing a
return force against pivoting of said backrest at said joints.
14. The chair of claim 9, wherein each said rigid portion further
comprises a spring member extending therefrom, said spring member
embedded within said flexible portion.
15. The chair of claim 9, wherein said backrest includes a flexible
upper portion, said upper portion moveable about said joints
between a substantially upright position and a reclined position
responsive to movement of a seated user.
16. The chair of claim 9, wherein said backrest includes a lumbar
support portion projecting outwardly from said backrest in the area
of the lumbar region of the back of a seated user, said lumbar
support portion moveable about said joints responsive to movement
of a seated user.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn. 119(e) of U.S. Provisional Patent Application Serial No.
60/340,673, entitled CHAIR WITH LUMBAR SUPPORT AND CONFORMING BACK,
filed on Dec. 14, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention.
[0003] The present invention relates to chairs, and in particular,
to a task chair for supporting the back of a seated user in an
ergonomic manner.
[0004] 2. Description of the Related Art.
[0005] Task chairs are commonly used by persons while working in a
seated position in offices or other occupational environments.
Typically, such chairs include a caster wheel assembly supporting
the chair for rolling movement over a floor surface, as well as a
number of manual adjustment features to allow the user to adjust
the shape or movement characteristics of the chair to a desired
configuration.
[0006] Many task chairs include a rigid back pan having a layer of
foam padding thereon which is covered by a decorative upholstery
material, and may also include an adjustable lumbar support
mechanism built into the backrest. Such backrests typically allow
only a very limited degree of adjustment, in terms of both the
movement of the lumbar support and the reclining of the backrest.
Further, adjustment of the backrest is typically performed by
manual operation of controls which may be difficult to locate and
manipulate.
[0007] What is needed is a task chair having a backrest which
conformingly and comfortably supports a seated user, and which is
an improvement over the foregoing.
SUMMARY OF THE INVENTION
[0008] The present invention provides a task chair including a seat
support structure, a backrest frame attached to the seat support
structure, and a backrest supported by the backrest frame. The
backrest includes a back support surface which ergonomically
conforms to a seated user when the seated user shifts positions
while sitting in the chair. The back support surface includes rigid
and flexible portions connected to one another, the flexible
portions allowing resilient flexing of the back support surface to
create conformance zones which dynamically support the back of a
seated user in an ergonomic manner.
[0009] The rigid portions of the backrest may be formed of wood,
metal, or a rigid plastic, and the flexible portions may be formed
of a pliable urethane or a silicone material, for example. The
rigid and flexible portions are connected to one another by insert
molding the flexible portions to the rigid portions, or by
mechanically or adhesively joining the flexible portions to the
rigid portions. The particular shape, size, and relative
configurations of the rigid portions and the flexible portions may
be selectively varied to provide a backrest surface having desired
conformance and support characteristics for supporting the back of
a seated user in the chair.
[0010] The backrest is connected to the seat support structure by a
backrest frame, which may include one or more support arms which
may be moveably mounted to the seat support structure. The support
arms additionally include support portions extending therefrom
which are in abutment with the rigid portions of the backrest to
define substantially rigid flex points about which the back support
surface may flex to conform to the back of a seated user. In
addition, the backrest may be connected to the backrest frame at
one or more flex joints which facilitate flexing of the lumbar
portion of the backrest outwardly or forwardly to support the
lumbar area of the back of a seated user when the user leans
backwardly against an upper portion of the backrest. The flex
joints may flex together or may flex independently from one
another, and additionally, the flex joints may flex to a varying
extent with respect to one another.
[0011] A slide plate may connect the backrest frame to a rigid
portion of the backrest. The slide plate is slidable with respect
to the backrest frame to adjust the height position of the backrest
with respect to the backrest frame.
[0012] Additionally, the flexible portion of the backrest may
include a lumbar support portion which bows outwardly from the
backrest to define a flexible lumbar support. The backrest frame
may additionally include a pair of slide plates slidably attached
thereto, the slide plates slidable with respect to the backrest
frame in response to forces exerted on the lumbar support portion
of the backrest. A force mechanism may be operably associated with
the slide plates to bias same to a position in which the lumbar
support portion of the backrest is forced to bow outwardly, thus
providing a firm, yet flexible, support to the lumbar region of a
seated user.
[0013] Advantageously, the present task chair in one form thereof
includes a back support surface having rigid portions which may be
configured to provide a relatively firm support to the lumbar
region or another region of the back of a seated user, and flexible
portions which facilitate resilient flexing movement of the
backrest and which provide a relatively cushioning support to
certain areas of the back of a seated user in selected zones of the
back support surface. The upper portion of the backrest and the
lumbar portion of the backrest may flex about flex points provided
by the backrest frame to dynamically conform to the upper and
lumbar regions of the back of a seated user as the seated user
shifts positions while sitting in the chair.
[0014] In one form thereof, the present invention provides a chair,
including seat support structure; a backrest frame connected to the
seat support structure; and a backrest formed of a flexible portion
having at least one rigid member embedded therein, the backrest
frame connected to the at least one rigid member at at least one
flex point, the backrest resiliently movable about the at least one
flex point to conform to a seated user.
[0015] In another form thereof, the present invention provides a
chair, including seat support structure; a backrest frame connected
to the seat support structure; and a backrest including a flexible
body portion surrounding at least two rigid portions, the at least
two rigid portions pivotally attached to the backrest frame at
respective joints which are disposed proximate opposite sides of
the backrest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0017] FIG. 1 is a side elevational view of a task chair in
accordance with the present invention;
[0018] FIG. 2 is an additional side elevational view of the task
chair of FIG. 1, schematically showing a user seated therein;
[0019] FIG. 3 is a rear elevational view of the task chair of FIG.
1;
[0020] FIG. 4 is a rear perspective view of one embodiment of a
backrest in accordance with the present invention, including a
backrest frame having a pair of support arms moveably connected to
the seat support structure of a chair, and supporting a backrest
which includes rigid and flexible portions defining a back support
surface which is flexible between a first position shown in solid
lines and a second position shown in dashed lines;
[0021] FIG. 5 is a rear perspective view of a second embodiment of
a backrest in accordance with the present invention, including a
backrest frame having a support arm moveably connected to the seat
support structure of a chair, and supporting a backrest including
rigid and flexible portions defining a back support surface which
is flexible between a first position shown in solid lines and a
second position shown in dashed lines;
[0022] FIG. 6A is a rear perspective view of a third embodiment of
a backrest in accordance with the present invention, including a
backrest frame having a support arm supporting a backrest at a pair
of flex joints positioned proximate sides of the backrest, the
backrest flexing at both flex joints between a first position shown
in solid lines and a second position shown in dashed lines;
[0023] FIG. 6B is a side elevational view of the embodiment of FIG.
6A;
[0024] FIG. 6C is a second side elevational view of the embodiment
of FIG. 6A, showing the backrest flexing about the flex joints;
[0025] FIG. 6D is a second rear perspective view of the embodiment
of FIG. 6A, the backrest flexing at one flex joint between a first
position shown in solid lines and a second position shown in dashed
lines;
[0026] FIG. 6E is an enlarged fragmentary view of a portion of FIG.
6C;
[0027] FIG. 7 is a rear perspective view of a fourth embodiment of
a backrest in accordance with the present invention, including a
backrest frame moveably connected to the seat support structure of
a chair, and a slide plate secured to a rigid portion of the
backrest, and slidably connected to the backrest frame for
adjustment of the height position of the backrest with respect to
the backrest frame; and
[0028] FIG. 8 is a rear perspective view of a fifth embodiment of a
backrest in accordance with the present invention, including a
backrest frame moveably connected to the seat support structure of
a chair, and a pair of slide plates secured to respective rigid
portions of the chair, the slide plates slidable within the
backrest frame in response to forces exerted on a flexible lumbar
support portion of the backrest which bows outwardly from the
backrest.
[0029] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate preferred embodiments of the invention, and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0030] Task chair 20 is shown in FIGS. 1-3, and generally includes
seat portion 22, backrest portion 24, and seat support structure
26. Seat support structure 26 includes caster wheel assembly 32
having a plurality of arms 34 projecting radially outwardly of
central hub 36, the terminal ends of arms 34 having caster wheels
38 pivotally mounted thereon. Supported within central hub 36 of
caster wheel assembly 32 is a height-adjustable pneumatic cylinder
40. Cylinder 40 includes piston 42 slidably disposed therein, an
upper end of which is attached to chair support beam 44 by a press
fit or in another suitable manner.
[0031] A plurality of links 46 (only two of which are shown in
FIGS. 1 and 2 for clarity) each include first ends 48 pivotally
attached to chair support beam 44 and second ends 50 pivotally .
attached to seat support member 52. Referring to FIG. 3, seat
support member 52 is connected to U-shaped arm support 54 having
upper ends 56 to which a pair of adjustable or fixed armrests 58
are connected. Armrests 58 may include moveable armrest pads 60,
which may be adjusted as desired by a user. Also attached to upper
ends 56 of U-shaped arm support 54 are a pair of L-shaped brackets
62 including lower ends 64 supporting chair seat 70, and upper ends
66 pivotally attached to U-shaped arm support 54. Backrest frame 68
extends between and is moveably mounted to upper ends 66 of the two
L-shaped brackets 62 and arm support 54. Backrest frame 68 is
connected to and supports backrest 72 as described below.
[0032] Chair support structure 26 and chair seat 70 may be of the
type described in U.S. Provisional Patent Application Serial No.
60/340,570, entitled CHAIR WITH CONFORMING SEAT, filed on Dec. 14,
2001, assigned to the assignee of the present invention, the
disclosure of which is expressly incorporated herein by
reference.
[0033] Referring to FIG. 4, a first embodiment of backrest 72 is
shown. Backrest 72a includes backrest frame 68 having a pair of
support arms 82 with first ends 84 moveably connected to upper ends
66 of L-shaped brackets 62. Support arms 82 each include second
ends 86 opposite first ends 84 which include support portions 88
projecting upwardly therefrom. Support portions 88 of support arms
82 are attached to rigid portion 80a of backrest 72a in a suitable
manner, with rubber bushings 92 therebetween. Support portions 88
of lumbar support arms 82 and rubber bushings 92 provide
substantially rigid flex points which, in cooperation with the
flexible portions of backrest 72, allow backrest 72 to
ergonomically conform to a seated user, as described in further
detail below.
[0034] Backrest 72a includes back support surface 94a defined by
rigid portion 80a and flexible portion 90a. Rigid portion 80a has a
generally inverted T-shape, including base section 96a and a single
arm section 98a projecting upwardly therefrom and disposed
centrally within backrest 72a. Flexible portion 90a is disposed
around the periphery of rigid portion 80a and on either side of arm
section 98a thereof.
[0035] Suitable materials for the rigid portions of the backrests
disclosed herein include, for example, a 9-ply, gumwood, upholstery
grade plywood or a rotary cut maple veneer shell. Alternatively,
the rigid portions may be made from metal or a suitable rigid or
semi-rigid plastic material. The flexible portions of the backrests
may be made from an elastomeric material, such as a urethane or a
silicone material, for example. Such material may have one or more
of a shore hardness ranging from 37.+-.7A to 82.+-.7A, a tensile
strength ranging from 505 PSI to 2200 PSI as determined by ASTM
D-412, and an elongation of 320% to 340% as determined by ASTM
D-368. Suitable urethane materials for the flexible portion include
Vantico brand polyurethanes, available from Ciba Specialty
Chemicals, such as RP6400-1, RP6401-1, RP 6402-1, and RP 6410-1
polyurethanes. The thickness of the flexible portion may be uniform
throughout the backrest, or alternatively, the thickness of the
flexible portion may be varied as desired. The flexibility of the
flexible portion generally decreases with increasing material
thickness. Conversely, the flexibility of the flexible portion
generally increases with decreasing material thickness.
[0036] In each of the embodiments of the backrests disclosed
herein, the flexible portion of the backrest is resiliently
flexible, such that the flexible portion may flex or bend to change
shape in response to a force or load exerted thereon, followed by
return of the flexible portion to its original shape or position
when the force or load is removed. The material of the flexible
portion may also exhibit elasticity, wherein the material may
stretch as necessary responsive to forces exerted thereon, followed
by return to its original shape and position. Further, the flexible
portion may optionally include a series of perforations, a series
of ridges and valleys, scoring, or other features therein which
facilitate flexing movement in designated areas of the flexible
portion.
[0037] The flexible portion of the backrest may be attached to one
or more rigid portions thereof by insert molding, wherein the rigid
portion is placed in a mold, and the flexible portion is molded
therearound such that, upon curing, the flexible portion surrounds
the periphery of the rigid portion and is securely adhered to the
rigid portion. For example, if the rigid portion is made of wood or
another porous or semi-porous material having roughened surfaces,
the flexible portion may penetrate within the interstices of the
rigid portion and, upon curing, form a tight bond with same.
[0038] Another molding process which may be used to form the
backrest is performed according to a two-step molding procedure,
sometimes referred to in the art as a "two-shot" molding process.
First, the rigid portions are formed from a first plastic material
which is substantially rigid upon curing. The first material is
injected into one or more molds which correspond to the shape of
the rigid portions of the backrest. Then, before the material of
the rigid portions is fully cured, the flexible material is
injected around the rigid portions into a mold which corresponds to
the shape of the backrest. The flexible material forms a chemical
bond with the partially cured rigid material to provide a very
strong connection between the rigid and flexible portions of the
chair. After the flexible and rigid materials cure, the mold is
removed to provide the backrest.
[0039] The rigid portion is at least partially embedded within the
flexible portion such that the flexible portion surrounds the outer
periphery of the rigid portion. The top and bottom surfaces of the
rigid portion may be exposed, or alternatively, the rigid portion
may be completely embedded or encapsulated within the flexible
portion such that the flexible portion encompasses all sides of the
rigid portion. Alternatively, the flexible portion may be
pre-molded, wherein after curing thereof, the flexible portion is
mechanically or adhesively joined to the rigid portion by a
suitable adhesive or by suitable fasteners, for example.
[0040] As discussed below, the shapes and relative configurations
of the rigid and flexible portions of the backrests of the present
invention may be varied substantially in order to selectively
modify the nature of the support provided by the rigid portions and
the flexible portions, as well as the dynamics of the flexing of
the back support surfaces of the backrests. The embodiments of
FIGS. 4-8 illustrate some possible shapes and relative
configurations of the rigid and flexible portions, although one of
ordinary skill in the art may develop others based upon the
teachings herein.
[0041] Referring again to FIG. 4, it may be seen that backrest 72a
is supported by support arms 82 of backrest frame 68, which are
movably connected to seat support structure 26 of chair 20 by joint
mechanism 100. Joint mechanism 100 includes an energy source (not
shown), such as a torsion spring or other torsion element such as a
stiff rubber bushing, which allows the positioning of support arms
82 and backrest 72a to be varied in response to the weight of a
user seated in chair 20. For example, support arms 82 and backrest
72a are shown in a first, more upright position in solid lines in
FIG. 4, and in a second, more reclined position in dashed lines in
FIG. 4. Joint mechanism 100 may include a tension adjustment
member, such as lever 102, for example, for varying the pre-tension
of the energy source of joint mechanism 100 to provide selectively
more or less resistance to movement of support arms 82.
[0042] When a user is seated in chair 20, the upper back and
shoulder blades of the user abut the upper sections of flexible
portion 90a which are disposed in either side of arm section 98a of
rigid portion 80a. As a seated user shifts positions while seated
in chair 20, for example by leaning backward and to one side, or by
twisting about the user's trunk, the upper sections of flexible
portion 90a may flex about arm section 98a of rigid portion 80a,
and rigid portion 80a may flex about the pair of substantially
rigid flex points which are defined by the attachment of support
portions 88 of support arms 82 to rigid portion 80a of backrest 72a
by rubber bushings 92. In other words, such flex points provide
substantially rigid fulcrum points about which back support surface
94a of backrest 72a may flex. Further, as described in more detail
below with respect to the embodiment of FIGS. 6A-D, the flex points
which are defined by the attachment of support portions 88 of
support arms 82 to rigid portion 80a of backrest 72a by rubber
bushings 92 may further include flex joints which facilitate
forward or outward flexing of the lumbar portion of backrest 72a
when a user leans backward against the upper portion of backrest
72a.
[0043] A second embodiment of backrest 72, backrest 72b, is shown
in FIG. 5, and is somewhat similar to backrest 72a. Backrest 72b
includes back support surface 94b defined by rigid portion 80b and
flexible portion 90b. Rigid portion 80b is generally U-shaped,
including base section 96b and a pair of arm sections 98b
projecting upwardly therefrom. Flexible portion 90b is disposed
around the periphery of rigid portion 80b and in between rigid
portions 90b. Backrest 72b is supported by backrest frame 68
including a single support arm 106, having first ends 108 movably
attached to upper ends 66 of L-shaped brackets 62. Joint mechanism
100 operates similar to the joint mechanism 100 described above
with respect to backrest 72a. Joint mechanism 100 of backrest 72b
may also include tension adjustment lever 102, which is provided
for adjusting the pre-tension of the energy source of joint
mechanism 100, which supports support arm 106 and backrest 72b and
allows movement of same between the more upright position shown in
solid lines and the more reclined position shown in dashed lines in
FIG. 5 in response to weight of a seated user. Support arm 106 also
includes support portions 110 secured to arm sections 98b of rigid
portion 80b, with rubber bushings 92 disposed therebetween.
[0044] When a user is seated in chair 20 having backrest 72b, the
upper back and shoulder blades of the user abut arm sections 98b of
rigid portion 80b, and the spine of the seated user is cushioned by
the area of flexible portion 90b which is disposed between arm
sections 98b of rigid portion 80b. As a seated user shifts
positions while seated in chair 20, for example by leaning backward
and to one side, or by twisting about the user's trunk, rigid
portions 90b may flex about flexible portion 90b disposed
therebetween, and about the pair of substantially rigid flex points
which are defined by the attachment of support portions 110 of
support arm 106 to rigid portion 80b by rubber bushings 92. In
other words, such flex points provide substantially rigid fulcrum
points about which the back support surface 94b of backrest 72b may
flex. Further, as described in more detail below with respect to
the embodiment of FIGS. 6A-D, the flex points which are defined by
the attachment of support portions 110 of support arm 106 to rigid
portion 80b of backrest 72b by rubber bushings 92 may each further
include a flex joint which facilitates forward or outward flexing
of the lumbar portion of backrest 72b when a user leans backward
against the upper portion of backrest 72b.
[0045] A third embodiment of backrest 72 is shown in FIGS. 6A-6D.
Backrest 72c includes back support surface 94c defined by a pair of
rigid portions 80c which are disposed along respective sides of
backrest 72c, and flexible portion 90c which is disposed around the
peripheries of rigid portions 80c and which defines the remainder
of backrest 72c. Backrest 72c is supported by backrest frame 150
having central portion 152 and end portions 154 attached to the
upper ends 56 of U-shaped arm support 54. Support arm 156 includes
central portion 158 attached to central portion 152 of backrest
frame 150, and also includes end portions 160 attached to rigid
portions 80c of backrest 72c at flex joints 162, as described
below. The attachment of central portion 158 of support arm 156 to
central portion 152 of backrest frame 150 may be a fixed
connection, or alternatively, may be an adjustable connection which
provides vertical height adjustment of support arm 156 and backrest
72c with respect to backrest frame 150.
[0046] Rigid portions 80c may optionally further include spring
members 155, which are made from a suitable semi-rigid, yet
resilient material such as spring steel or a semi-rigid plastic.
Spring members 155 are shown in FIGS. 6A and 6D extending upwardly
from rigid portions 80c. Spring members 155 may comprise separate
components attached to rigid portions 80c, or alternatively, spring
members 155 may be integrally formed with rigid portions 80c as
extensions of rigid portions 80c. Spring members 155 are shown
encapsulated within flexible portion 90c, but may alternatively be
disposed in line or flush with the front or rear outer surfaces of
flexible portion 90c of backrest 72c. Spring members 155 are
generally more flexible than rigid portions 80c, yet are more stiff
than flexible portion 90c, and may be selectively located in areas
of backrest 72c in which additional support to flexible portion 90c
is desired without the more rigid support which would otherwise be
provided by rigid portions 80c. In the embodiment of FIGS. 6A-6D,
spring members 155 provide resilient support within flexible
portion 90c in the area of upper portion 172 of backrest 72c to
support the area around the upper back of a seated user.
[0047] Flex joints 162 are generally configured to allow flexible,
elastic movement of backrest 72c with respect to support arm 156 in
response to movement of a seated user, and are shown in further
detail in FIGS. 6B, 6C, and 6E. Flex joints 162 each include plate
164 attached to rigid portion 80c of backrest 72c, or
alternatively, plates 164 may be integrally formed as a feature of
rigid portions 80c. A rubber bushing 92 is disposed between each
plate 164 and a corresponding end portion 160 of support arm 156.
Pivot members 166, which may comprise axles or bolts, for example,
are disposed through cooperating apertures in plates 164, rubber
bushings 92, and end portions 160 of support arm 156 to pivotally
attach backrest 72c to each end portion 160 of support arm 156 with
rubber bushings 92 therebetween. Further, pivot members 166 define
substantially horizontal pivot axes about which backrest 72c may
pivot with respect to support arm 156. Although flex joints 162 are
shown as pivots including pivot members 166, the particular
construction of flex joints 162 may vary. For example, flex joints
162 may optionally be formed as ball-and-socket joints or as hinge
joints. Also, flex joints 162 may rely solely on the resilient
flexing properties of rubber bushings 92, which may be attached
with adhesive or via suitable fasteners directly to each of rigid
portions 80c and end portions 160 of support arm 156. Flex joints
162 may include metal springs, such as leaf springs, or coil
springs disposed about pivot members 166, for example, instead of
rubber bushings 92.
[0048] As shown in FIG. 6B, backrest 72c is disposed in an unflexed
or neutral position for supporting the back of a user seated in
chair 20. Backrest 72c includes lumbar portion 170, which is curved
outwardly or forwardly from backrest 72c in the area of the lumbar
region of the back of a seated user to thereby support the lumbar
region of the seated user's back. Vertical plane P.sub.1-P.sub.1
defines the outwardmost or forwardmost extent of lumbar portion 170
of backrest 72c in the position shown in FIG. 6B. Upper portion 172
of backrest 72c is disposed in a first, substantially upright
position in FIG. 6B.
[0049] As shown in FIGS. 6C and 6E, when a seated user leans
backwardly against upper portion 172 of backrest 72c along the
direction of arrow 174, backrest 72c pivots about member 166 of
flex joint 162. Movement of backrest 72c as shown in FIGS. 6C and
6E causes the upper portion of plates 164 of flex joints 162 to
press against and compress the upper portions 92a of rubber
bushings 92, while the lower portions 92b of rubber bushings 92 are
allowed to expand as necessary. In this manner, the rubber bushings
92 provide a compressive force against pivoting of backrest 72c
from the position shown in FIG. 6B. Notably, this compressive force
also operates to return backrest 72c to the position shown in FIG.
6B when the seated user leans forward away from upper portion 172
of backrest 72c in a direction opposite arrow 174. Further,
movement of backrest 72c about member 166 of flex joint 162 as
shown in FIG. 6C causes lumbar portion 170 to concurrently move
outwardly or forwardly from vertical plane P.sub.1-P.sub.1 toward
vertical plane P.sub.2-P.sub.2 along the direction of arrow 176 to
increase the support provided by lumbar portion 170 to the lumbar
region of the back of a seated user. Typically, lumbar portion 170
may move through a horizontal distance of up to two inches (5.08
cm) between planes P.sub.1-P.sub.1 and P.sub.2-P.sub.2.
[0050] As shown in FIGS. 6A and 6D, backrest 72c may pivot to the
same extent at both flex joints 162, or flex joints 162 may pivot
independently of one another, depending on the position of a user
seated in chair 20. Further, the relative extent to which each flex
joint 162 pivots with respect to the other flex joint may also
vary, depending upon the position of a user seated in chair 20 and
the relative distribution of the user's weight against various
areas of backrest 72c. Referring to FIG. 6A, when a seated user
leans backwardly and evenly against upper portion 172 of backrest
72c along the direction of arrow 174, such as when a seated user
presses both shoulder blades against upper portion 172 of backrest
72c, backrest 72c pivots to a similar extent at both flex joints
162a and 162b which are disposed at the left and right sides of
backrest 72c, respectively. As described above, upper portion 172
of backrest 72c reclines from a substantially upright position,
shown in solid lines in FIG. 6A, to a reclined position, shown in
dashed lines in FIG. 6A. Concurrently, lumbar portion 170 flexes
from a first position, shown in solid lines in FIG. 6A, to a more
outwardly or forwardly projecting position, shown in dashed lines
in FIG. 6A, to support the lumbar region of the back of the seated
user along substantially the entire width of backrest 72c.
[0051] Referring to FIG. 6D, when a seated user leans backwardly
and to one side of upper portion 172 of backrest 72c along arrow
178, such as when a seated user turns about the user's trunk and
presses only one shoulder blade against the left side of upper
portion 172 of backrest 72c, backrest 72c pivots primarily at flex
joint 162a and pivots only minimally, or not at all, at flex joint
162b. The left side of upper portion 172 of backrest 72c reclines
from a substantially upright position, shown in solid lines in FIG.
6D, to a reclined position, shown in dashed lines in FIG. 6D.
Concurrently, the left side of lumbar portion 170 flexes from a
first position, shown in solid lines in FIG. 6D, to a more
outwardly or forwardly projecting position, shown in dashed lines
in FIG. 6D, to support the left area of the lumbar region of the
seated user's back. Of course, when a seated user leans backwardly
to the opposite side of upper portion 172 of backrest 72c, such as
when a seated user turns about the user's trunk and presses only
one shoulder blade against the right side of upper portion 172 of
backrest 72c, backrest 72c pivots primarily at flex joint 162b, and
pivots only minimally, or not at all, at flex joint 162a. In this
manner, flex joints 162a and 162b may pivot concurrently or
independently of one another as needed to accommodate and support
the movement of a user seated in chair 20.
[0052] Referring to FIG. 7, a fourth embodiment of backrest 72 is
shown. Backrest 72d includes back support surface 94d defined by
rigid portion 80d and flexible portion 90d disposed around the
periphery of rigid portion 80d. Backrest 72d is supported by
backrest frame 112, having first ends 114 attached to upper ends 66
of L-shaped brackets 62. Backrest frame 112 includes central
portion 116 with slide plate 118 slidably connected thereto. Slide
plate 118 is secured to rigid portion 80d of backrest 72d, with
rubber bushings 92 therebetween. The connection points between
slide plate 118 and rigid portion 80d of backrest 72d provide
substantially rigid flex points about which rigid portion 80d of
backrest 72d may flex, similar to the manner described above with
respect to backrests 72a-72c. Thus, as a seated user shifts
positions while seated in chair 20, for example by leaning backward
and to one side, or by twisting about the user's trunk, rigid
portion 80d may flex about such flex points, and flexible portion
90d may also flex with respect to both rigid portion 80d and such
flex points.
[0053] Additionally, slide plate 118 may slide upwardly and
downwardly with respect to central portion 116 of backrest frame
112, as indicated by arrow 113 in FIG. 7, to adjust the height
position of backrest 72d with respect to backrest frame 112. The
position of slide plate 118 with respect to central portion 116 of
backrest frame 112 may be fixed in a selected position by a
friction fit, or by a suitable locking or detent mechanism, for
example.
[0054] A fourth embodiment of backrest 72 is shown in FIG. 8.
Backrest 72e includes back support surface 94e defined by upper
rigid portion 80e, lower rigid portion 80e', and flexible portion
90e. Upper rigid portion 80e is generally U-shaped, including base
section 96e and a pair of arm sections 98e projecting upwardly
therefrom. Lower rigid portion 80e' has a generally elongated oval
shape. Flexible portion 90e is disposed around the peripheries of
upper and lower rigid portions 80e and 80e' and therebetween, and
also in between arm section 98e of upper rigid portion 80e.
Additionally, flexible portion 90e includes a lumbar support
portion 130 intermediate upper rigid portion 80e and lower rigid
portion 80e'.
[0055] Backrest 72e is supported by backrest frame 122, having ends
123 moveably attached to upper ends 66 of L-shaped brackets 62. An
adjustment mechanism, similar to those shown above with respect to
backrests 72a, and 72b, may be provided for tension adjustment of
backrest frame 122 with respect to the seat support structure of
the chair. Backrest frame 122 includes central portion 124 with
upper slide plate 126 and lower slide plate 128 slidably connected
thereto. Upper and lower slide plates 126, 128 are secured to upper
and lower rigid portions 80e and 80e' of backrest 72e,
respectively, with rubber bushings 92 therebetween. The connection
points between upper slide plate 126 and rigid portion 80e of
backrest 72e provide substantially rigid flex points about which
chair support surface 94e of backrest 72e may flex, similar to the
manner described above with respect to backrests 72a-72d.
[0056] A force mechanism (not shown), such as a spring disposed
within central portion 124 of backrest frame 122, biases each of
upper and lower slide plates 126, 128 inwardly toward backrest
frame 122. This spring mechanism, as well as the inherent flex
tension in lumbar support portion 130, cause lumbar support portion
130 to bow outwardly from back support surface 94e in the area of
the lumbar region of a seated user to define a flexible lumbar
support, as shown in dashed lines in FIG. 8. Forces exerted upon
lumbar support portion 130 from the abutment of a user's back
thereagainst move lumbar support portion 130 and slide plates 126,
128 to the positions shown in solid lines in FIG. 8, and such
forces are resisted by the flex tension of lumbar support portion
130, and by the force mechanism within central portion 124 of
backrest frame 122 which biases upper and lower slide plates 126,
128 inwardly, to provide a firm lumbar support to the seated user.
When the user exits the chair, or leans forwardly away from
backrest 72d, the flex tension of lumbar support portion 130 and
the spring mechanism within central portion 124 of backrest frame
122 return lumbar support portion 130 to its more prominent forward
position, shown in dashed lines in FIG. 8. The foregoing movement
of lumbar support portion 130 and slide plates 126, 128 is
illustrated by arrows 127 in FIG. 8.
[0057] While this invention has been described as having preferred
designs, the present invention can be further modified within the
spirit and scope of this disclosure. This application is therefore
intended to cover any variations, uses, or adaptations of the
invention using its general principles. Further, this application
is intended to cover such departures from the present disclosure as
come within known or customary practice in the art to which this
invention pertains and which fall within the limits of the appended
claims.
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