U.S. patent application number 12/734978 was filed with the patent office on 2010-09-30 for chair.
Invention is credited to Nobuyuki Ueda.
Application Number | 20100244521 12/734978 |
Document ID | / |
Family ID | 42315619 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100244521 |
Kind Code |
A1 |
Ueda; Nobuyuki |
September 30, 2010 |
CHAIR
Abstract
A chair includes a seat 5 for sinking backward as a backrest 7
mainly made up of an elastically deformable back shell 71 tilts
back, wherein a back support post 6 which is pivoted at its lower
end portion on a support base portion 3 disposed below the seat 5
and which supports the back shell 71 includes an upper back frame
61 for supporting a portion of the back shell 71 above a lumbar
support portion 71L of the back shell 71 capable of supporting a
lumbar part of a seated person and a lower back frame 62 for
supporting a portion near a lower end portion of the back shell 71,
the back frames (the upper back frame 61 and the lower back frame
62) are pivoted on each other and the pivot point (third support
shaft X3) is set behind the lower end portion of the back shell 71,
and the whole back shell 71 is curved and deformed to protrude the
lumbar support portion 71L relatively forward as the upper back
frame 61 tilts back about the pivot point (third support shaft X3)
with respect to the lower back frame 62.
Inventors: |
Ueda; Nobuyuki; (Osaka,
JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY LAW GROUP, PLLC
8321 OLD COURTHOUSE ROAD, SUITE 200
VIENNA
VA
22182-3817
US
|
Family ID: |
42315619 |
Appl. No.: |
12/734978 |
Filed: |
August 5, 2008 |
PCT Filed: |
August 5, 2008 |
PCT NO: |
PCT/JP2008/064032 |
371 Date: |
June 7, 2010 |
Current U.S.
Class: |
297/298 |
Current CPC
Class: |
A47C 1/03272 20130101;
A47C 1/03279 20180801; A47C 1/03255 20130101; A47C 1/03294
20130101; A47C 1/03266 20130101 |
Class at
Publication: |
297/298 |
International
Class: |
A47C 7/46 20060101
A47C007/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2008 |
JP |
2008-007398 |
Claims
1. A chair including a seat for moving in synchronization with
backward tilting operation of a backrest mainly made up of an
elastically deformable back shell, wherein a back support post
which is pivoted at its lower end portion or its portion near the
lower end portion on a support base portion disposed below the seat
and which supports the back shell includes an upper back frame for
supporting a portion of the back shell above a lumbar support
portion of the back shell capable of supporting a lumbar part of a
seated person and a lower back frame for supporting a lower end
portion or a portion near the lower end portion of the back shell,
the back frames are pivoted on each other, the pivot point is set
behind the lower end portion of the back shell, and the whole back
shell is curved and deformed to protrude the lumbar support portion
relatively forward as the upper back frame tilts back about the
pivot point with respect to the lower back frame.
2. The chair according to claim 1, wherein either one of the upper
back frame and the lower back frame has an overhanging portion
extending in a predetermined direction from the pivot point and a
resilient body for generating a reaction force as the upper back
frame tilts back is disposed between the overhanging portion and
the other back frame.
3. The chair according to claim 1, wherein a space is formed
between the upper back frame and the lumbar support portion of the
back shell.
4. The chair according to claim 1, wherein at least one of the
upper back frame and the lower back frame supports the back shell
while engaged with the back shell for sliding movements in a height
direction.
5. The chair according to claim 1, wherein the one back support
post including the upper back frame and the lower back frame is
disposed at a substantially central portion in a lateral width
direction of the back shell.
6. The chair according to claim 1, wherein a deformation trigger
means which is more likely to be deformed than portions adjacent to
the lumbar support portion is provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
7. The chair according to claim 6, wherein the deformation trigger
means comprises one or a plurality of slit(s) extending in the
lateral width direction of the back shell.
8. The chair according to claim 2, wherein a space is formed
between the upper back frame and the lumbar support portion of the
back shell.
9. The chair according to claim 2, wherein at least one of the
upper back frame and the lower back frame supports the back shell
while engaged with the back shell for sliding movements in a height
direction.
10. The chair according to claim 3, wherein at least one of the
upper back frame and the lower back frame supports the back shell
while engaged with the back shell for sliding movements in a height
direction.
11. The chair according to claim 2, wherein the one back support
post including the upper back frame and the lower back frame is
disposed at a substantially central portion in a lateral width
direction of the back shell.
12. The chair according to claim 3, wherein the one back support
post including the upper back frame and the lower back frame is
disposed at a substantially central portion in a lateral width
direction of the back shell.
13. The chair according to claim 4, wherein the one back support
post including the upper back frame and the lower back frame is
disposed at a substantially central portion in a lateral width
direction of the back shell.
14. The chair according to claim 2, wherein a deformation trigger
means which is more likely to be deformed than portions adjacent to
the lumbar support portion is provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
15. The chair according to claim 3, wherein a deformation trigger
means which is more likely to be deformed than portions adjacent to
the lumbar support portion is provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
16. The chair according to claim 4, wherein a deformation trigger
means which is more likely to be deformed than portions adjacent to
the lumbar support portion is provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
17. The chair according to claim 5, wherein a deformation trigger
means which is more likely to be deformed than portions adjacent to
the lumbar support portion is provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
Description
TECHNICAL FIELD
[0001] The present invention relates to a chair suitable for use in
an office or the like.
BACKGROUND TECHNIQUE
[0002] Conventionally, as a chair suitable for use in an office or
the like, there is a known chair having a synchronous rocking
function for enabling a seat to slide in a direction of sinking
backward as a backrest tilts back.
[0003] As an example of such a chair, there is one in which a back
shell is supported by a back support post, a lower end portion of
the back support post extends forward, and the extending end is
pivoted on a support base portion provided to an upper portion of a
leg body for turning about a horizontal axis, and the back shell is
curved and deformed so that a lumbar support portion of the back
shell capable of supporting a lumbar part of a seated person
protrudes forward as the back support post tilts back according to
a load applied on the back shell (see Patent Document 1 described
below, for example).
[0004] The Patent Document 1 discloses a structure in which an
upper portion of the backrest (back shell) is supported for turning
on a shaft provided to an upper portion of the back support post,
guide chips having cam grooves in shapes of L in side views are
secured to lower portions of back faces of left and right opposite
side portions of the backrest, and an operation lever is operated
to move tilting chips integrally provided to the operation lever in
the cam grooves to thereby adjust an amount of forward protrusion
of the lumbar support portion.
[0005] Patent Document 1: Japanese Patent Application Laid-Open No.
2004-49719
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] However, the above-described prior-art chair requires a
special mechanism for protruding the lumbar support portion
forward, which complicates the structure, requires special
operation of the seated person (user), takes the user time to get
used to how to use, and makes the chair less practical.
[0007] Moreover, the chair described above has the synchronous
rocking function for moving the seat in synchronization with the
backward tilting operation of the backrest but does not have a back
tilting function for curving and deforming the back shell to
thereby tilt back only the backrest. Even if the above-described
structure is combined with a chair having the back tilting
function, the chair is still not practical because it requires the
special mechanism for protruding the lumbar support portion forward
and requires the special operation of the seated person (user).
[0008] The present invention has been made while focusing on such
problems and it is a main object to provide a chair that has not
only a synchronous rocking function but also a back tilting
function and is practical because it does not require a special
mechanism for protruding a lumbar support portion forward when the
chair shifts from a normal state in which no load is applied on a
backrest to a back tilt state in which only the backrest is tilted
back, has a simplified structure, and does not require a special
operation for protruding the lumbar support portion forward of a
seated person.
Approach for Solving the Problems
[0009] In other words, a chair according to the invention includes
a seat for moving in synchronization with backward tilting
operation of a backrest mainly made up of an elastically deformable
back shell, wherein a back support post which is pivoted at its
lower end portion or its portion near the lower end portion on a
support base portion disposed below the seat and which supports the
back shell includes an upper back frame for supporting a portion of
the back shell above a lumbar support portion of the back shell
capable of supporting a lumbar part of a seated person and a lower
back frame for supporting a lower end portion or a portion near the
lower end portion of the back shell, the back frames are pivoted on
each other, the pivot point is set behind the lower end portion of
the back shell, and the whole back shell is curved and deformed to
protrude the lumbar support portion relatively forward as the upper
back frame tilts back about the pivot point with respect to the
lower back frame.
[0010] With this structure, the chair has both the synchronous
rocking function for moving the seat in synchronization with the
backward tilting operation of the backrest and the back tilting
function for tilting back only the backrest by curving and
deforming the back shell. A pivot point between the upper back
frame for supporting the portion of the back shell above the lumbar
support portion of the back shell, i.e., the upper portion of the
back shell and the lower back frame for supporting the lower end
portion or the portion near the lower end portion of the back shell
is set behind the lower end portion of the back shell. Therefore,
when the seated person purposely puts his/her weight on the upper
portion of the back shell, the upper back frame tilts back about
the pivot point to cause the upper portion of the back shell to
lean back. As a result, an area between the upper portion and the
lower portion of the back shell and specifically the lumbar support
portion is naturally curved and deformed in such a direction as to
protrude forward to provide the seated person with a comfortable
feeling of support of his/her lumbar part. Moreover, an amount of
forward protrusion of the lumbar support portion changes according
to a degree to which the seated person puts his/her weight on the
upper portion of the back shell. Therefore, the seated person can
set the amount of protrusion of the lumbar support portion to such
an amount as to obtain a desired feeling of support of the lumbar
part by changing the manner in which he/she puts his/her weight
without separately operating a special operation portion, which
simplifies the structure without impairing practicality of the
chair at all.
[0011] As described above, because a special mechanism for
protruding the lumbar support portion forward is unnecessary, it is
possible to effectively simplify the structure. Moreover, because
special operation for protruding the lumbar support portion forward
or special operation for adjusting the amount of protrusion of the
lumbar support portion are not required, the chair is usable for
the seated person.
[0012] Especially, if either one of the upper back frame and the
lower back frame has an overhanging portion extending in a
predetermined direction from the pivot point and a resilient body
for generating a reaction force as the upper back frame tilts back
is disposed between the overhanging portion and the other back
frame, it is possible to make the reaction force mechanism compact,
the mechanism being especially for the back tilting operation which
is the tilting back of only the upper back frame with respect to
the lower back frame.
[0013] To prevent suppression of the forward protruding deformation
of the lumbar support portion due to interference of the lumbar
support portion with the upper back frame, a space for allowing
curving and deformation of the shell in the backward tilting
operation of the backrest may be formed between the upper back
frame and the lumbar support portion of the back shell.
[0014] Moreover, at least one of the upper back frame and the lower
back frame may support the back shell while engaged with the back
shell for sliding movements in the height direction. In this way,
when the seated person puts his/her weight on the upper portion of
the back shell and the upper back frame tilts back about the pivot
point, the back shell slides in the height direction with respect
to at least one of the upper back frame and the lower back frame to
thereby allow smooth curving and deformation of the whole back
shell with respect to the back support post.
[0015] Because the one back support post including the upper back
frame and the lower back frame is disposed at a substantially
central portion in the lateral width direction of the back shell,
opposite side end portions of the back shell become free and can be
warped flexibly and greatly according to a load when the load is
applied on the left and right opposite end portions of the back
shell even if the back shell which is a resin plate-shaped member
has enough strength to support a load of a back of the seated
person. As described above, torsional deformation of the back shell
is allowed and three-dimensional deformation of the back shell
according to the manner in which the seated person puts his/her
weight and movements of the back of the seated person is
possible.
[0016] To allow the back shell to reliably protrude the lumbar
support portion forward while the whole back shell is curved and
deformed when the seated person puts his/her weight on the upper
portion of the back shell and the upper back frame tilts back about
the pivot point, a deformation trigger means which is a portion of
the lumbar support portion and more likely to be deformed than
portions around it is preferably provided to the lumbar support
portion of the back shell in order to direct a deformation
characteristic of the back shell.
[0017] A preferable example of the deformation trigger means is a
deformation trigger means made up of one or a plurality of slits
extending in the lateral width direction of the back shell.
EFFECTS OF THE INVENTION
[0018] As described above, according to the invention, it is
possible to provide the chair having not only the synchronous
rocking function but also the back tilting function. The chair does
not require the special mechanism for protruding the lumbar support
portion forward when the chair is shifted from the normal state in
which no load is applied on the backrest to the back tilt state in
which only the backrest is tilted back, the structure of the chair
can be simplified, and the chair is excellent in practicality,
because it does not require special operation for protruding the
lumbar support portion forward of the seated person.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] [FIG. 1] A general view from a diagonally front side of a
chair according to an embodiment of the present invention.
[0020] [FIG. 2] A general view from a diagonally back side of the
chair according to the embodiment.
[0021] [FIG. 3] A side view of the chair in a normal state in the
embodiment.
[0022] [FIG. 4] A back view of the chair in the normal state in the
embodiment.
[0023] [FIG. 5] An operation explanatory view showing FIG. 3 while
omitting part of it.
[0024] [FIG. 6] A view from a direction of an arrow X in FIG.
5.
[0025] [FIG. 7] A vertical sectional view schematically showing
part of FIG. 5, i.e., only a back shell and taken at a center in a
lateral width direction.
[0026] [FIG. 8] A drawing schematically showing a manner in which
the back shell and a back support post are mounted to each other in
an area Y in FIG. 5.
[0027] [FIG. 9] A drawing showing the chair in a synchronous
rocking state in the embodiment and corresponding to FIG. 3.
[0028] [FIG. 10] A drawing showing the chair in the synchronous
rocking state in the embodiment and corresponding to FIG. 5.
[0029] [FIG. 11] A drawing showing the chair in a back tilt state
in the embodiment and corresponding to FIG. 3.
[0030] [FIG. 12] A drawing showing the chair in the back tilt state
in the embodiment and corresponding to FIG. 5.
[0031] [FIG. 13] Drawings schematically showing a variation of a
slide engagement mechanism in the embodiment and corresponding to
FIGS. 5 and 12.
EXPLANATION OF REFERENCE NUMERALS
[0032] 1 . . . chair [0033] 3 . . . support base portion [0034] 5 .
. . seat [0035] 6 . . . back support post [0036] 61 . . . upper
back frame [0037] 612 . . . overhanging portion [0038] 62 . . .
lower back frame [0039] 63 . . . resilient body (second coil
spring) [0040] 7 . . . backrest [0041] 71 . . . back shell [0042]
713 . . . deformation trigger means [0043] 713a . . . slit [0044]
71L . . . lumbar support portion [0045] X3 . . . pivot point (third
support shaft)
BEST MODE FOR CARRYING OUT THE INVENTION
[0046] An embodiment of the present invention will be described
below with reference to the drawings.
[0047] As shown in FIGS. 1 to 5, a chair 1 according to the present
embodiment is what is called a rotary chair including a leg 2, a
support base portion 3 mounted on an upper end side of the leg 2 to
be able to turn horizontally, a seat receiver 4 supported at its
front portion on the support base portion 3, a seat 5 mounted on
the seat receiver 4, a back support post 6 pivoted at its lower end
portion on the support base portion 3 and supporting a back portion
of the seat receiver 4, and a backrest 7 mounted to the back
support post 6.
[0048] The leg 2 is made up of a plurality of (five in the example
in the drawings) leg blades 21 each having a caster at a tip end
thereof and a leg stay 22 rising from a portion where base end
portions of the respective leg blades 21 gather.
[0049] As shown in FIG. 6, which shows a state viewed from a
direction of an arrow X in FIG. 5, the support base portion 3 is a
member made of metal, for example, and including an upper wall
portion 31, a pair of hanging side wall portions 32 respectively
hanging integrally from opposite side edges of the upper wall
portion 31 by bending, and a pair of partition walls 33 and 34
provided between front end portions of the pair of hanging side
wall portions 32 and serving as reinforcing ribs and the support
base portion 3 is supported on the leg stay 22 by mounting an upper
end portion of the leg stay 22 to a rear end portion of the upper
wall portion 31. The partition wall 33 on a relatively back side
out of the pair of partition walls 33 and 34 is provided with a
retainer guide portion 33a formed in a wall thickness direction to
guide a retainer 912b inserted through the retainer guide portion
33a for moving forward and backward in a compressive
forward/backward moving direction of a coil spring 911 described
later. A first support shaft X1 for axially supporting the back
support post 6 for turning is laterally supported like a bridge
between portions of the support base portion 3 slightly displaced
backward from substantially central portions of the left and right
hanging side wall portions 32. Furthermore, elongated holes 32a for
supporting a front frame (not shown) of the seat receiver 4
(described later) are respectively formed in a wall thickness
direction at front end portions of the left and right hanging side
wall portions 32. The support base portion 3 is covered with a
support base portion cover body 3c from below so that it cannot be
seen directly from outside (see FIG. 3).
[0050] The seat receiver 4 is located above the support base
portion 3 and supported on the support base portion 3 with the
rod-shaped front frame (not shown) provide at a front end portion
of the seat receiver 4 inserted through the elongated holes 32a of
the support base portion 3. The chair 1 in the embodiment has
armrests 8 respectively extending upward from portions near left
and right opposite side edge portions of the seat receiver 4.
Although the armrests 8 shown in FIG. 1 and the like are not
height-adjustable, it is possible to employ height-adjustable
armrests in place of the armrests 8. Alternatively, the chair may
not have armrests.
[0051] The seat 5 includes a seat shell 51 performing a function as
a structural member for uniformly supporting a load applied on the
seat 5, a seat cushion (not shown) provided above the seat shell
51, and a seat cushion cover 52 covering the seat cushion.
[0052] The backrest 7 includes a back shell 71 serving as a
structural member for uniformly supporting a load applied on the
backrest 7 and supported on the back support post 6, a back cushion
(not shown) provided in front of the back shell 71, and a back
cushion cover 72 covering the back cushion.
[0053] The back shell 71 is mainly made up of an elastic
plate-shaped body made of resin and has a three-dimensional shape
with an upper portion and a lower portion protruding further
backward than its central portion in a height direction and left
and right opposite side edge portions protruding further forward
than its central portion in the lateral width direction. An area of
the back shell 71 above a lumbar support portion 71L capable of
supporting a lumbar part of a seated person and more specifically
an area of the back shell 71 above its central portion in the
height direction is provided with a large number of apertures 711
so that an aperture ratio which is a ratio of the apertures 711 to
a predetermined area of the back shell 71 gradually increases
toward an upper edge portion and the opposite side edge portions of
the back shell 71. In the following description, the whole area
provided with the apertures 711 out of the back shell 71 will be
referred to as "a back shell upper portion 71T". In other words, as
shown in FIG. 4 and the like, the back shell 71 integrally includes
the back shell upper portion 71T, a back shell central portion 71S
which is the central portion of the back shell 71 in the height
direction, the lumbar support portion 71L positioned slightly below
the back shell central portion 71S, and a back shell lower portion
71U which is an area below the lumbar support portion 71L. The back
shell central portion 71S, the lumbar support portion 71L, and the
back shell lower portion 71U have the same curvature of curved
faces in a plan view and the curvature is set to a magnitude
greater than a curvature of a curved face of the back shell upper
portion 71T in the plan view. As shown in FIG. 7 (which is a
vertical sectional view corresponding to FIG. 5, schematically
showing only the back shell 71, and taken at the center in the
lateral width direction), the back shell central portion 71S, the
lumbar support portion 71L, and the back shell lower portion 71U
having the relatively greater curvature are curved and arched to be
continuous with each other while the back shell upper portion 71T
having the relatively smaller curvature is in a substantially
straight shape along the height direction. The back shell central
portion 71S and the back shell upper portion 71T are continuous
with each other at a discontinuous line 712 as a border
therebetween.
[0054] The lumbar support portion 71L of the back shell 71 is
provided with a deformation trigger means 713 which is more likely
to be deformed than portions of the lumbar support portion 71L
around it. In the embodiment, slits 713a extending in the lateral
width direction are employed as the deformation trigger means 713.
A single slit 713a or a plurality of slits 713a may be provided and
the pair of upper and lower slits 713a with a predetermined
interval therebetween in the height direction is provided in the
embodiment.
[0055] As shown in FIG. 8 (which is a drawing schematically showing
a state before mounting of the back shell upper portion 71T to the
back support post 6 in order to show a manner of mounting of the
back shell 71 and the back support post 6 to each other in an area
Y in FIG. 5), the back shell upper portion 71T is integrally or
substantially integrally provided with an engagement portion 714
protruding backward and capable of being engaged in a slide
engagement hole 611 formed in an upper end portion of an upper back
frame 61 (described later). In FIG. 8, the apertures 711 in the
back shell upper portion 71T are not shown. The engagement portion
714 is substantially in a block shape and integrally has a flange
portion 714a at a tip end portion (an end portion on a side away
from a back face of the back shell 71).
[0056] As shown in FIG. 5 and the like, the back shell lower
portion 71U is integrally or substantially integrally provided with
supported portions 715 protruding backward and supported on an
upper end portion of a lower frame (described later). In the
embodiment, the pair of left and right thin plate-shaped supported
portions 715 is provided at a lower end portion of the back shell
lower portion 71U, i.e., a lower end portion of the back shell
71.
[0057] As shown in FIG. 5 and the like, the back support post 6 for
supporting the back shell 71 includes the upper back frame 61 for
supporting a portion of the back shell 71 above the lumbar support
portion 71L supporting the lumbar part of the seated person and
specifically the back shell upper portion 71T and a lower back
frame 62 for supporting the back shell lower portion 71U. A pivot
point (a third support shaft X3 that will be described later)
between the upper back frame 61 and the lower back frame 62 is set
behind a lower end portion of the back shell 71 so that the upper
back frame 61 can tilt about the pivot point with respect to the
lower back frame 62 (tilting operation). As shown in FIG. 2, the
upper back frame 61 and the lower back frame 62 are covered with an
upper back frame cover body 61c and a lower back frame cover body
62c from behind and below, respectively, and cannot be directly
seen from outside.
[0058] As shown in FIGS. 5, 6, and the like, the lower back frame
62 includes a pair of left and right lower back frame main bodies
621 disposed on outer sides of opposite side faces of the support
base portion 3 and a rigid connection shaft 622 for rigidly
connecting lower end portions of the pair of lower back frame main
bodies 621 and disposed below a lower face of the support base
portion 3.
[0059] The respective lower back frame main bodies 621 are
substantially in plate shapes and are in shapes, in a side view,
gradually extending diagonally backward from their lower end
portions toward their portions near their upper end portions and
bent diagonally forward at their portions near their upper end
portions.
[0060] The rigid connection shaft 622 is in a rod shape and is laid
and fixed like a bridge between the lower end portions of the lower
back frame main bodies 621 by appropriate means such as
welding.
[0061] To mount the lower back frame 62 to the support base portion
3, the pair of left and right lower back frame main bodies 621 is
put from behind on the support base portion 3 in such a manner as
to sandwich the support base portion 3 between the portions near
the lower end portions of the respective lower back frame main
bodies 621 after rigidly connecting the lower back frame main
bodies 621 by the rigid connection shaft 622 and the first support
shaft X1 is inserted through insertion holes 621a formed at the
portions near the lower end portions of the respective lower back
frame main bodies 621 and through holes (not shown) formed at the
opposite hanging side wall portions 32 of the support base portion
3 after making the insertion holes communicating with each other.
In this way, the lower back frame 62 and eventually the back
support post 6 becomes able to turn about the first support shaft
X1 with respect to the support base portion 3. In the embodiment,
extending portions 621b extending further forward than other
portions are integrally provided to the portions near the lower end
portions of the respective lower back frame main bodies 621 and the
insertion holes 621a are formed in the respective extending
portions 621b. The first support shaft X1 is disposed on an upper
back side with respect to the rigid connection shaft 622.
[0062] In a state in which the lower back frame 62 is mounted to
the support base portion 3 in the chair 1 according to the
embodiment, the rigid connection shaft 622 of the lower back frame
62 is located below the lower face of the support base portion 3
(specifically, lower faces of the hanging side wall portions 32)
and the coil spring 911 for generating a reaction force as the back
support post 6 tilts back is disposed between the rigid connection
shaft 622 and the support base portion 3. When the lower back frame
62 tilts back about the first support shaft X1, the rigid
connection shaft 622 biases the coil spring 911 in such a direction
as to accumulate resilience.
[0063] To put it concretely, as shown in FIG. 6, the rigid
connection shaft 622 supports a coil spring receiving portion 911x
provided on one end side of the coil spring 911 (described later)
at its central portion in a longitudinal direction. The coil spring
911 and the coil spring receiving portion 911x form a tilting
reaction force adjusting device 9 for adjusting the reaction force
in tilting back the back support post 6.
[0064] As shown in FIGS. 5 and 6, at least part of the tilting
reaction force adjusting device 9 is housed in the support base
portion 3 and the tilting reaction force adjusting device 9
includes a reaction force generating portion 91 for generating the
reaction force in tilting back the back support post 6
independently of the seat receiver 4 and a reaction force adjusting
operation portion 92 provided on a front end side of a side edge of
the seat 5 for adjusting operation of strength of the reaction
force of the reaction force generating portion 91.
[0065] To put it more concretely, the reaction force generating
portion 91 includes the coil spring 911 and a compressing and
expanding portion 912 provided on one end side of the coil spring
911 to compress or expand the coil spring 911 in synchronization
with the adjusting operation applied to the reaction force
adjusting operation portion 92. The compressing and expanding
portion 912 is made up of a slider 912a in a trapezoidal shape in a
plan view and for moving forward and backward in a direction
orthogonal to a direction of compression and expansion of the coil
spring 911 in synchronization with the adjusting operation applied
to the reaction force adjusting operation portion 92, a retainer
912b in a trapezoidal shape in a plan view and for moving forward
and backward in the direction of the compression and expansion
while sliding against the slider 912a and supporting the coil
spring 911, and the retainer guide portion 33a for guiding the
forward and backward movements of the retainer 912b in the
direction of the compression and expansion. As described above, the
retainer guide portion 33a is formed on the partition wall 33 of
the support base portion 3 for supporting the seat receiver 4.
[0066] The reaction force adjusting operation portion 92 includes a
rod 921 extending in the lateral width direction while passing
through one of the hanging side wall portions 32 of the support
base portion 3 and an operation grip 922 provided to a tip end
portion of the rod 921 to rotate the rod 921 about an axis.
[0067] Getting back to description of the lower back frame 62, the
respective lower back frame main bodies 621 of the lower back frame
62 are integrally provided with second extending portions 621c
extending further forward than portions around them at portions
slightly below central portions in the height direction and a
second support shaft X2 laid and fixed like a bridge between the
second extending portions 621c supports a rear end side of the seat
receiver 4. Furthermore, the supported portions 715 of the back
shell 71 are fixed to portions near the upper end portions of the
respective lower back frame main bodies 621 by appropriate means
such as screws so that relative angles cannot be changed.
[0068] As shown in FIG. 5, the upper back frame 61 pivoted on the
upper end portion of the lower back frame 62 having the
above-described structure has such width as to be sandwiched
between the pair of left and right lower back frame main bodies 621
and is substantially in a shape of < in a side view with its
upper end portion and lower end portion protruding further backward
than its central portion in the height direction. As shown in FIG.
8, the slide engagement hole 611 in which the engagement portion
714 provided to the back shell upper portion 71T can be engaged by
sliding is formed in the upper end portion of the upper back frame
61. The slide engagement hole 611 is made up of a large hole
portion 611a in and from which the flange portion 714a of the
engagement portion 714 can be inserted and withdrawn and a small
hole portion 611b formed continuously with an upper side of the
large hole portion 611a and allowing a relative sliding movement of
the engagement portion 714 while prohibiting withdrawal of the
flange portion 714a that has been inserted from the large hole
portion 611a. The small hole portion 611b is greater than the large
hole portion 611a in height so as to secure a margin for relative
sliding movements of the slide engagement hole 611 and the
engagement portion 714.
[0069] An insertion hole (not shown) is formed to pass through a
lower end portion of the upper back frame 61 in the lateral width
direction and the third support shaft X3 is inserted through the
insertion hole and insertion holes 621d formed in the upper end
portions of the respective lower back frame main bodies 621 after
making the insertion holes communicating with each other to thereby
enable the upper back frame 61 to tilt back about the third support
shaft X3 (corresponding to "the pivot point" in the invention). In
the embodiment, the third support shaft X3 is located behind the
lower end portion of the back shell 71. The upper back frame 61
includes an overhanging portion 612 extending downward from the
pivot point (third support shaft X3) and a second coil spring 63
which is a resilient body in the invention and which generates a
reaction force as the upper back frame 61 tilts back is disposed
between the overhanging portion 612 and the lower back frame 62. In
the embodiment, a fourth support shaft X4 is laid and fixed like a
bridge between portions of the pair of left and right lower back
frame main bodies 621 of the lower back frame 62 slightly below the
bent portions near the upper end portions, one end portion of the
second coil spring 63 is supported on the fourth support shaft X4,
and the other end portion of the second coil spring 63 is supported
on the overhanging portion 612 of the upper back frame 61.
[0070] In a state in which the back shell upper portion 71T and the
back shell lower portion 71U are supported on the upper end portion
of the upper back frame 61 and the upper end portion of the lower
back frame 62, respectively, a space is formed between the back
shell 71 and the back support post 6 (specifically, the upper back
frame 61).
[0071] Next, usage and operation of the chair 1 according to the
embodiment and made up of the above-described respective members
will be described.
[0072] The chair 1 according to the embodiment can be brought into
at least a normal state (S) in which the backrest 7 is in a
standing attitude as shown in FIGS. 1 to 5, asynchronous rocking
(synchronous tilt) state (R) in which the seat 5 slides in such a
direction as to sink backward in synchronization with the backward
tilting operation of the backrest 7 as shown in FIGS. 9 and 10, and
a back tilt state (T) in which the upper back frame 61 tilts back
about the third support shaft X3 (the pivot point in the invention)
when the seated person purposely puts his/her weight on an upper
portion of the backrest 7 in the normal state (S) and, as a result,
the whole back shell 71 is curved and arched in the side view as
shown in FIGS. 11 and 12.
[0073] In the normal state (S), the back shell 71 that is mainly
made up of the elastic plate-shaped body is in an arched and curved
shape in the side view against its elasticity.
[0074] If the seated person leans at his/her entire back against
the backrest 7 of the chair 1 in this normal state (S), the back
support post 6 tilts back about the first support shaft X1 while
keeping the relative angle between the upper back frame 61 and the
lower back frame 62 and the back shell 71 tilts back as well as
shown in FIG. 10. At this time, because the weight of the seated
person is applied substantially uniformly on the whole backrest 7
and therefore the back shell 71 tilts back while maintained in
substantially the same shape as in the normal state (S) without
tilting back of the upper back frame 61 with respect to the lower
back frame 62, i.e., without changing the relative angle between
the upper back frame 61 and the lower back frame 62. Then, the seat
receiver 4 with its rear end side supported by the second support
shaft X2 of the lower back frame 62 slides in such a direction as
to sink backward while moving the front frame (not shown) provided
on its front end portion in the elongated holes 32a as a result of
the backward tilting operation of the back support post 6. As a
result, the whole seat 5 supported on the seat receiver 4 slides in
the same direction as the seat receiver 4, i.e., in such a
direction as to sink backward (see FIG. 9) to thereby bring the
chair 1 into the synchronous rocking state (R).
[0075] In the synchronous rocking state (R), the rigid connection
shaft 622 of the lower back frame 62 presses the coil spring 911 in
such a direction as to accumulate the resilience. Therefore, if the
seated person moves his/her back away from the backrest 7, i.e.,
sits up, the whole back support post 6 naturally returns into a
normal attitude before titling back due to the resilience of the
coil spring 911. In the embodiment, it is possible to adjust the
reaction force in tilting back the backrest 7 by using the tilting
reaction force adjusting device 9. To put it concretely, if the
operation grip 922 is rotated in one of clockwise and
counterclockwise directions (e.g., in the clockwise direction), the
slider 912a moves in such a direction as to approach the operation
grip 922 in synchronization with the rotation and the slider 912a
presses the retainer 912b. Then, the retainer 912b pressed by the
slider 912a moves in such a direction as to compress the coil
spring 911 to thereby increase the reaction force in tilting back
the backrest 7. On the other hand, if the operation grip 922 is
rotated in the reverse direction (e.g., in the counterclockwise
direction), it is possible to reduce the reaction force in tilting
back the backrest 7.
[0076] On the other hand, if the seated person purposely puts
his/her weight on the back shell upper portion 71T in the normal
state (S), the upper back frame 61 of the back support post 6 tilts
back about the third support shaft X3 with respect to the lower
back frame 62 as shown in FIG. 12. As the upper back frame 61 tilts
back, a force for leaning back is applied to the back shell upper
portion 71T of the back shell 71 supported on the upper back frame
61 while the lower end portion of the back shell 71 supported on
the lower back frame 62 tries to stay in its position in the normal
state (S) due to the lower back frame 62 which does not tilt back.
Therefore, the back shell 71 is arched and curved to protrude its
portion between the back shell upper portion 71T and the back shell
lower portion 71U further forward. In the embodiment, because the
lumbar support portion 71L of the back shell 71 is provided with
the deformation trigger means 713 which is specifically the slits
713a, the lumbar support portion 71L is deformed in such a
direction as to reduce height of the openings of the slits 713a
when the whole back shell 71 is arched and curved and, as a result,
the lumbar support portion 71L protrudes further forward than in
the normal state (S). In the embodiment, the back shell upper
portion 71T is engaged and supported in the upper back frame 61 so
that it can relatively slide in the height direction. By relatively
sliding the engagement portion 714 provided to the back shell upper
portion 71T in the height direction in the slide engagement hole
611 formed in the upper end portion of the upper back frame 61 in
such a range as not to be disengaged from the slide engagement hole
611 in the tilting back of the upper back frame 61, the whole back
shell 71 can be curved to follow the backward tilting operation of
the upper back frame 61. In the chair 1 in the embodiment, because
the curvature of the curved face of the back shell 71 in the plan
view is smaller than that of the other portion and the upper end
portion of the upper back frame 61 relatively slides against the
back shell upper portion 71T in a substantially straight line shape
along the height direction, it is possible to achieve the smooth
sliding movement in the stable state.
[0077] As the chair 1 shifts from the normal state (S) into the
back tilt state (T), the overhanging portion 612 of the upper back
frame 61 presses the second coil spring 63 disposed between the
overhanging portion 612 and the lower back frame 62 in such a
direction as to accumulate the resilience. Therefore, if the seated
person moves his/her back away from the backrest 7, i.e., sits up,
the upper back frame 61 naturally returns into its normal attitude
before the tilting back of the upper back frame 61 due to the
resilience of the second coil spring 63 and the chair 1 returns
from the back tilt state (T) to the normal state (S). Moreover,
when the chair 1 shifts from the normal state (S) to the back tilt
state (T), an elastic recovering force of the back shell 71 which
has been further arched and curved than in the normal state (S)
acts as a force for biasing the upper back frame 61 in such a
direction as to pull the upper back frame 61 back forward.
Therefore, if the seated person purposely puts his/her weight on
the lumbar support portion 71L when the chair 1 is in the back tilt
state (T), the biasing force further increases; the biasing force
and the resilience of the second coil spring 63 combine with each
other, and, when the seated person moves his/her back away from the
backrest 7, i.e., sits up, the upper back frame 61 follows the
operation and quickly and automatically returns to its normal
attitude before the tilting back.
[0078] If the seated person puts his/her weight on the whole
backrest 7 after the chair 1 is shifted from the normal state (S)
into the back tilt state (T), the lower back frame 62 tilts back
about the first support shaft X1 while maintaining the upper back
frame 61 in the backward tilted attitude with respect to the lower
back frame 62. As a result, the chair 1 is brought into a most
reclined state (not shown) which is a combination of the back tilt
state (T) and the synchronous rocking state (R). Substantially
similarly, if the seated person purposely puts his/her weight on
the upper back frame 61 after the chair 1 is shifted from the
normal state (S) into the synchronous rocking state (R), the upper
back frame 61 tilts back about the third support shaft X3 with
respect to the lower back frame 62 and the chair 1 is brought into
the most reclined state (not shown) which is the combination of the
synchronous rocking state (R) and the back tilt state (T).
[0079] In other words, the chair 1 according to the embodiment is
brought into the normal state (S), the synchronous rocking state
(R), the back tilt state (T), the most, reclined state, or an
intermediate state between two of them (e.g., an intermediate state
between the normal state (S) and the synchronous rocking state (R)
and an intermediate state between the normal state (S) and the back
tilt state (T) (not shown)) depending on how the seated person sits
and more specifically how the seated person puts his/her weight on
the chair 1.
[0080] The chair 1 in the embodiment includes a tilting braking
device A provided between the back support post 6 and the support
base portion 3 to selectively enable the tilting operation of the
backrest 7. A lower end portion of the tilting braking device A is
supported for swinging on a rear end side of the support base
portion 3 and an upper end portion of the tilting braking device A
is supported for swinging on the fourth support shaft X4 of the
lower back frame 62. As shown in FIG. 6, employed as the tilting
braking device A in the embodiment is a known gas spring which has
a substantially cylindrical gas spring main body A1 and a piston
rod portion (not shown) for moving forward and backward so that
substantially the whole piston rod portion is housed in the gas
spring main body A1 and which functions as a tilting braking
portion and the tilting braking device A will not be described in
detail.
[0081] As described above, the chair 1 according to the embodiment
is the chair 1 that can be brought into the synchronous rocking
state (R) in which the seat 5 moves in synchronization with the
backward tilting operation of the backrest 7 and the back tilt
state (T) in which the back shell 71 is curved and deformed and
only the backrest 7 is tilted back. The pivot point (third support
shaft X3) between the upper back frame 61 for supporting the
portion of the back shell 71 above the lumbar support portion 71L
and specifically the back shell upper portion 71T and the lower
back frame 62 for supporting the lower end portion of the back
shell 71 is set behind the lower end portion of the back shell 71.
Therefore, when the seated person purposely puts his/her weight on
the upper portion of the back shell 71, the upper back frame 61
tilts back about the pivot point (third support shaft X3) to cause
the upper portion of the back shell 71 to lean back. As a result,
an area between the upper portion and the lower portion of the back
shell 71 and specifically the lumbar support portion 71L is
naturally curved and deformed in such a direction as to protrude
forward to provide the seated person with a comfortable feeling of
support of his/her lumbar part. Moreover, an amount of forward
protrusion of the lumbar support portion 71L changes according to a
degree to which the seated person puts his/her weight on the upper
portion of the back shell 71. Therefore, the seated person can set
the amount of protrusion of the lumbar support portion 71L to such
an amount as to obtain a desired feeling of support of the lumbar
part by changing the manner in which he/she puts his/her weight
without separately operating a special operation portion, which
simplifies the structure without impairing practicality of the
chair at all.
[0082] Especially because the upper back frame 61 has the
overhanging portion 612 extending below the pivot point (third
support shaft X3) and the resilient body (second coil spring 63)
for generating the reaction force as the upper back frame 61 tilts
back is disposed between the overhanging portion 612 and the lower
back frame 62, it is possible to make the reaction force mechanism
for the back tilting compact to effectively prevent the structure
from increasing in size and becoming complex.
[0083] Moreover, because the space is formed between the upper back
frame 61 and the lumbar support portion 71L of the back shell 71,
it is possible to reliably prevent suppression of the forward
protruding deformation of the lumbar support portion 71L due to
interference of the lumbar support portion 71L with the upper back
frame 61.
[0084] The upper back frame 61 supports the back shell 71 while
engaged with the back shell 71 for sliding movements in the height
direction. Therefore, when the seated person purposely puts his/her
weight on the upper portion of the back shell 71 and the upper back
frame 61 tilts back about the pivot point (third support shaft X3),
the back shell 71 slides in the height direction with respect to
the upper back frame 61 to thereby allow the leaning back of the
back shell upper portion 71T and smooth deformation of the whole
back shell 71 in the arched shape.
[0085] Because the one back support post 6 including the upper back
frame 61 and the lower back frame 62 is disposed at a substantially
central portion in the lateral width direction of the back shell
71, opposite side end portions of the back shell 71 are open to
allow torsional deformation of the back shell 71 and
three-dimensional bending deformation of the back shell 71
according to the manner in which the seated person applies his/her
weight. In the embodiment, the plurality of apertures 711 are
formed in the back shell upper portion 71T and greatly contribute
to achievement of the smooth torsional deformation of the back
shell upper portion 71T for supporting parts around shoulders of
the seated person. Additionally, the fact that the aperture ratio
which is the ratio of the apertures 711 to the predetermined area
gradually increases toward the upper edge portion and the opposite
side edge portions of the back shell 71 contributes to achievement
of the smooth torsional deformation of the back shell upper portion
71T as well.
[0086] Because the deformation trigger means 713 which is the
portion of the lumbar support portion 71L and more likely to be
deformed than portions around it is provided to the lumbar support
portion 71L of the back shell 71 in order to direct a deformation
characteristic of the back shell 71, the back shell 71 can reliably
protrude the lumbar support portion 71L forward while the whole
back shell 71 is curved and deformed when the upper back frame 61
tilts back about the pivot point (third support shaft X3).
Especially because the deformation trigger means 713 is made up of
the plurality of slits 713a extending in the lateral width
direction of the back shell 71 in the embodiment, it is possible to
achieve the deformation trigger means 713 by an extremely easy
method.
[0087] The invention is not limited to the embodiment described
above in detail.
[0088] For example, although the upper back frame 61 has the
overhanging portion 612 extending in the predetermined direction
from the pivot point (third support shaft X3) and the resilient
body (second coil spring 63) for generating the reaction force as
the upper back frame 61 tilts back is provided between the
overhanging portion 612 and the lower back frame 62 in the
embodiment, the lower back frame may have an overhanging portion
further extending in a predetermined direction (e.g., upward) from
the pivot point between the upper back frame and itself and a
resilient body for generating a reaction force as the upper back
frame tilts back may be disposed between the overhanging portion
and the upper back frame.
[0089] As the resilient body for generating the reaction force as
the upper back frame tilts back, it is possible to use what is
called a coil spring with its axial direction substantially aligned
with the lateral width direction of the chair and its opposite end
portions extending away from each other from an axial center or
rubber. Furthermore, the overhanging portion provided to either one
of the upper back frame and the lower back frame may pull the
resilient body disposed between the overhanging portion and the
other frame in such a direction as to accumulate the resilience as
the upper back frame tilts back.
[0090] The upper back frame 61 supports the back shell upper
portion 71T while engaged with the back shell upper portion 71T for
sliding movements in the height direction in the example shown in
the embodiment. Instead, the lower back frame may support the lower
portion of the back shell while engaged with the lower portion for
sliding movements in the height direction or the both the upper
back frame and the lower back frame support the back shell while
engaged with the back shell for sliding movements in the height
direction. In other words, the slide engagement mechanism for
allowing relative sliding movements of the back shell and the back
support post may be provided only between the upper back frame and
the back shell, only between the lower back frame and the back
shell, or between each of the back frames and the back shell.
Furthermore, a distance of sliding may be changed appropriately
according to specifications and the like. Although the engagement
portion is engaged in the engagement hole in the example shown in
the embodiment, an engagement groove may be employed in place of
the engagement hole. Moreover, as the slide engagement mechanism,
an engagement recessed portion such as an engagement hole and an
engagement groove may be integrally provided to the back shell and
an engagement protruding portion that can be engaged in the
engagement recessed portion by sliding may be provided to the back
frame. For example, as shown in FIG. 13, a pocket-shaped engagement
recessed portion 714' open downward is integrally provided to a
back face of the back shell 71 (back shell upper portion) and an
upward engagement protruding portion 611' which is in an L shape in
the side view and which can be inserted into the engagement
recessed portion 714' from below is provided to the back support
post (upper back frame 61). As the upper back frame 61 tilts back,
an amount of covering of the engagement protruding portion 611'
with the engagement recessed portion 714' is reduced in such a
range as not to disengage the engagement protruding portion 611'
and the engagement recessed portion 714' from each other. In this
way, the back shell 71 can slide in the height direction with
respect to the back support post (upper back frame 61). In this
case, it is possible to engage the engagement recessed portion and
the engagement protruding portion with each other by slipping the
back shell over the back support post from above, which facilitates
an assembly operation.
[0091] The back support post made up of the upper back frame and
the lower back frame may be provided to each of the opposite side
edge portions of the back shell or portions near the opposite side
edge portions of the back shell. In other words, the chair may
include a plurality of (including three or more) back support posts
each made up of the upper back frame and the lower back frame.
[0092] In place of the slits extending in the lateral width
direction of the back shell as the deformation trigger means,
thin-walled portions (thin-walled hinges), notch portions formed by
notching the opposite side edges of the back shell in the lateral
width direction toward the center, or a plurality of holes formed
at equal intervals or intermittently along the lateral width
direction of the back shell may be employed.
[0093] Moreover, the lower back frame may support a portion of the
back shell near the lower end portion instead of the lower end
portion.
[0094] The specific structures of the respective portions are not
limited to those in the above-descried embodiment but can be
changed in various ways without departing from the gist of the
invention.
INDUSTRIAL APPLICABILITY
[0095] As described above, according to the invention, it is
possible to provide the chair having not only the synchronous
rocking function but also the back tilting function. The chair does
not require a special mechanism for protruding the lumbar support
portion forward when the chair is shifted from the normal state in
which no load is applied on the backrest to the back tilt state in
which only the backrest is tilted back, the structure of the chair
can be simplified, and the chair is excellent in practicality,
because it does not require special operation for protruding the
lumbar support portion forward of the seated person.
* * * * *