U.S. patent application number 13/982097 was filed with the patent office on 2013-11-28 for chair backrest device.
This patent application is currently assigned to OKAMURA CORPORATION. The applicant listed for this patent is Yoshinori Isogai, Atsunori Matsumoto, Hiroshi Saotome. Invention is credited to Yoshinori Isogai, Atsunori Matsumoto, Hiroshi Saotome.
Application Number | 20130313884 13/982097 |
Document ID | / |
Family ID | 46580406 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130313884 |
Kind Code |
A1 |
Matsumoto; Atsunori ; et
al. |
November 28, 2013 |
CHAIR BACKREST DEVICE
Abstract
The invention is capable of maintaining the planar view curve
profile of the elastic membranous member of the back-contacting
surface while enabling the maintenance of a stable and comfortable
seated posture. The side frame members (13C) of a backrest frame
(13) are formed substantially as obtuse angles with the bend
towards the front when viewed from the side. The upper frame member
(13A) is formed, in planar view, as an arc that protrudes towards
the back. An elastic membranous member (14) is stretched so that
when viewed from the side, the intermediate position curves gently
towards the front, substantially forming an obtuse angle. Paired
left and right shape-maintaining members (17), each slanting
outward and upward, connect the lower frame member (13B) near the
left and right sides to the bends (13a) in the left and right side
frame members. The lower parts of both the left and right sides of
the elastic membranous member are supported by the
shape-maintaining members.
Inventors: |
Matsumoto; Atsunori;
(Yokohama-shi, JP) ; Saotome; Hiroshi;
(Ryugasaki-shi, JP) ; Isogai; Yoshinori;
(Zushi--shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Matsumoto; Atsunori
Saotome; Hiroshi
Isogai; Yoshinori |
Yokohama-shi
Ryugasaki-shi
Zushi--shi |
|
JP
JP
JP |
|
|
Assignee: |
OKAMURA CORPORATION
Yokohama-shi, Kanagawa-ken
JP
|
Family ID: |
46580406 |
Appl. No.: |
13/982097 |
Filed: |
January 27, 2011 |
PCT Filed: |
January 27, 2011 |
PCT NO: |
PCT/JP2011/051607 |
371 Date: |
August 19, 2013 |
Current U.S.
Class: |
297/452.18 |
Current CPC
Class: |
A47C 7/46 20130101; A47C
7/40 20130101 |
Class at
Publication: |
297/452.18 |
International
Class: |
A47C 7/40 20060101
A47C007/40 |
Claims
1. The backrest of a chair, the backrest comprising a substantially
rectangular backrest frame comprising upper, lower, right-side and
left-side frame members and an elastic membrane stretched in the
backrest frame, wherein the right-side and left-side frame members
of the backrest frame are bent at a bent point so that a middle of
each of the frame members gently projects forward when viewed from
a side, the elastic membrane being stretched so that a middle is
curved at a curved point forward when viewed from the side, the
backrest further comprising a pair of shape-maintaining members
each of which is provided obliquely outward and upward between the
bent portion of each of the right and left side members and part of
the lower frame member close to each of the right and left side
frame members, the elastic membrane being supported at lower ends
of right and left side portions by the shape-maintaining
member.
2. The backrest of claim 1 wherein the curved point of the elastic
membrane is higher than the bent point of the side frame.
3. The backrest of claim 1 wherein the backrest frame is molded
together with the shape-maintaining members and the elastic
membrane.
4. The backrest of claim 1 wherein the upper frame member is formed
like an arc gently projecting backward when viewed from an
above.
5. The backrest of claim 1 wherein the upper frame member is formed
straight when viewed from the above.
6. The backrest of claim 1 wherein the lower frame member is formed
like an arc gently projecting backward when viewed from the above.
Description
TECHNICAL FIELD
[0001] The present invention relates to the backrest of a chair in
which an elastic membrane is stretched over a substantially
rectangular backrest frame to form a back-contacting surface.
BACKGROUND OF THE INVENTION
[0002] The backrest of a chair comprises a substantially
rectangular backrest frame and an elastic membrane knitted or woven
as high-tension elastic mesh that is stretched over the backrest
frame. The backrest in which suitable elasticity is applied to the
back-contacting surface is known in Patent Literatures 1 and 2.
[0003] An elastic membrane is molded by suitable tension together
with a backrest frame with a die, which is known in Patent
Literature 3.
[0004] However, in the chair in each of the Patent Literatures,
elasticity of the back-contact surface of the backrest is applied
by elasticity of the elastic membrane itself and by tension for
stretching the elastic membrane over the backrest frame. So the
back-contacting surface is flat and a back position of the user is
not stable when he/she sits.
[0005] As described in Patent Literature 2, in order to stabilize
the back of the user when he/she sits, the middle of the
back-contacting surface projects backward when viewed from the
above, and right and left side frames are bent to project forward
in the middle so that the back of the user may be fitted.
[0006] However, when viewed from the above, upper and lower frame
members of the backrest frame are rounded backward, and right and
left side frame members are bent to project forward in the middle
when viewed from the side. Upper and lower edges of the elastic
membrane are stretched over the backrest frame, and right and left
side edges are stretched to the right and left side frame members
for the backrest frame. By tension that applies to the elastic
membrane over the whole circumference, restoration force acts so
that the back-contact surface becomes planar in the vicinity of the
bent portion of the side frame members.
[0007] In order to maintain the back-contact surface in the shape
when viewed from the above and side, it is necessary to provide
separate complicated holding means. It is disadvantageous that the
shape of the elastic membrane cannot be kept for a long time.
PRIOR ART
Patent Literature
[0008] Patent Literature 1: Japanese Patent No. 3993375
[0009] Patent Literature 2: Japanese Design No. 1199426
[0010] Patent Literature 3: Japanese Patent No. 3200409
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] In view of the disadvantages, it is an object of the present
invention to provide a backrest of a chair in which an arc of an
elastic membrane is kept for long time, whereby a stable sitting
posture of a user can be maintained.
Means for Solving the Problems
[0012] The foregoing problems are solved by the following invention
as claimed.
[0013] (1) In the backrest of a chair, the backrest comprising a
substantially rectangular backrest frame comprising upper, lower,
right-side and left-side frame members and an elastic membrane
stretched in the backrest frame, the right-side and left-side frame
members of the backrest frame are bent at a bent point so that a
middle of each of the frame members gently projects forward when
viewed from a side, the elastic membrane being stretched so that a
middle is curved at a curved point forward when viewed from the
side, the backrest further comprising a pair of shape-maintaining
members each of which is provided obliquely outward and upward
between the bent portion of each of the right and left side members
and part of the lower frame member close to each of the right and
left side frame members, the elastic membrane being supported at
lower ends of right and left side portions by the shape-maintaining
member.
[0014] (2) In the item (1), the curved point of the elastic
membrane is higher than the bent point of the side frame.
[0015] (3) In the item (1) or (2), the backrest frame is molded
together with the shape-maintaining members and the elastic
membrane.
[0016] (4) In any one of the items (1) to (3), the upper frame
member is formed like an arc gently projecting backward when viewed
from an above.
[0017] (5) In any one of the items (1) to (4), the upper frame
member is formed straight when viewed from the above.
[0018] (6) In any one of the items (1) to (5), the lower frame
member is formed like an arc gently projecting backward when viewed
from the above.
Advantages of the Invention
[0019] According to claim 1, the side frame member of the backrest
frame is bent at the bent point to project in the middle forward
when viewed from the side and the elastic membrane is stretched
over the backrest frame to curve forward at the curved point in the
middle. The shape-maintaining member is provided between is
provided between the bent point of each of the right and left side
frame members and part of the lower frame member near the side
frame member. The lower part of the elastic membrane is supported
by shape-maintaining member. The shape-maintaining member creates
restraining force for restraining a returning force for elastically
returning the elastic membrane to a flat face. Thus, the curve of
the elastic membrane of the back-contacting surface can be
maintained for a long time.
[0020] The shape-maintaining member is provided obliquely outward
and upward between the bent point of the side frame member and part
of the lower frame member near the side frame member. When a user
sits on the chair, he/she can take stable and comfortable sitting
posture without giving discomfort that the shape-maintaining member
comes in contact with the back bone of the user,
[0021] According to claim 2, the curved point of the elastic
membrane is higher than the bent point of the side frame member
close to the back bone of the user. When the user sits, the curved
point of the elastic membrane presses the lumbar of the user,
he/she can keep stable sitting posture with a straight back.
[0022] According to claim 3, the backrest frame is molded together
with the shape-maintaining member and elastic membrane, thereby
increasing support strength of the elastic membrane by the backrest
frame and shape-maintaining member and restraining
elastic-returning force of the elastic membrane.
[0023] According to claim 4, the upper frame member is formed like
an arc projecting backward when viewed from the above. Thus, the
back surface of the elastic membrane is supported by the
shape-maintaining member to press forward. A restraining force is
applied against the direction of elastic returning force. Thus, the
elastic membrane which acts as back-contacting surface can stably
be maintained like an arc which curves backward when viewed from
the above.
[0024] According to claim 5, the upper frame member is straight
when viewed from the above. A restraining force for pushing the
elastic membrane forward is applied by the shape-maintaining member
against a returning force which pushes backward to have the
back-contacting surface of the elastic membrane come closer to a
flat surface.
[0025] According to claim 6, the lower frame member is formed like
an arc which projects backward. The lower edge of the elastic
membrane can be maintained like an arc. In addition to the effect
by claim 4, the shape of the elastic membrane forming a
back-contacting surface can be maintained for a long time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a perspective view of one embodiment of a chair
comprising the backrest according to the present invention;
[0027] FIG. 2 is a back elevational view of the chair;
[0028] FIG. 3 is a central vertical sectional view taken along the
line III-III in FIG. 2 to illustrate that a user sits on the
chair;
[0029] FIG. 4 is an exploded perspective view of the chair.
[0030] FIG. 5 is an enlarged vertical sectional view of the seat
taken along the line V-V in FIG. 4;
[0031] FIG. 6 is an enlarged vertical sectional view of the seat
taken along the line VI-VI in FIG. 4;
[0032] FIG. 7 is an enlarged vertical sectional view of the seat
taken along the line VII-VII in FIG. 4;
[0033] FIG. 8 is an enlarged vertical sectional view of the seat
taken along the line VIII-VIII in FIG. 4.
[0034] FIG. 9 is an enlarged horizontal sectional view of the
backrest taken along the line IX-IX in FIG. 4;
[0035] FIG. 10 is an enlarged horizontal sectional view taken along
the line X-X in FIG. 4; and
[0036] FIG. 11 is an enlarged vertical sectional view taken along
the line XI-XI in FIG. 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0037] One embodiment of the present invention will be described
with respect to the appended drawings.
[0038] FIG. 1 is a perspective view of one embodiment of a chair
comprising the backrest according to the present invention; FIG. 2
is a back elevational view of the chair; FIG. 3 is a central
vertical sectional view taken along the line III-III in FIG. 2 to
illustrate that a user sits on the chair; and FIG. 4 is an exploded
perspective view of the chair.
[0039] In FIGS. 1 to 4, in the chair according to the present
invention, a leg unit 2 comprises a pair of side legs 3,3 to which
metal pipe is bent like a rectangle, and a pair of cross rails 4,5
for connecting the upper ends of the side legs 3,3 to each other. A
seat 6 is attached over the leg unit 2 and a backrest 7 is attached
to the back end of the seat 6.
[0040] In the seat 6, a synthetic-resin seat frame 8 such as
polypropylene comprises front and back frame members 8A,8B and
right and left frame members 8C,8C like a rectangle. The
circumferential edge of an elastic membrane 9 into which polyamide
or polypropylene fiber is knitted or woven like a mesh is stretched
by one-piece molding.
[0041] FIG. 5 is an enlarged vertical sectional view of the seat
taken along the line V-V in FIG. 4; FIG. 6 is an enlarged vertical
sectional view of the seat taken along the line VI-VI in FIG. 4;
FIG. 7 is an enlarged vertical sectional view of the seat taken
along the line VII-VII in FIG. 4; and FIG. 8 is an enlarged
vertical sectional view of the seat taken along the line VIII-VIII
in FIG. 4.
[0042] In FIGS. 5-8, in the elastic membrane 9, a front edge 9a is
supported by the inner circumferential surface of the front frame
member 8A of the seat frame 8; a back edge 9b is supported by the
inner circumferential surface of the back frame member 8B of the
seat frame 8; and right and left side edges 9c,9c are supported by
the inner circumferential surfaces of the side frame members 8C,8C
of the seat frame 8.
[0043] In FIGS. 6 and 7, an arcuate front tongue 10 is formed to
extend backward and upward, and the front part of the elastic
membrane 9 is held on the upper surface of the front tongue 10.
[0044] In FIG. 7, the front tongue 10 has two arcs projecting
downward between the center of the width and the side frame members
8c,8c. The rear end 10a of the front tongue 10 is curved downward
not to come in contact with the lower surface of the elastic
membrane 9.
[0045] Hence, in FIG. 3, the buttock of the user goes down in a
recess 12 and the right and left thighs bends down with the elastic
membrane 9 to come in contact with the right and left recesses of
the front tongue 10, so that the front tongue 10 plays a role in
cushioning against the weight of the user.
[0046] The back frame member 8B is an arc which slightly projects
backward when viewed from the above and an arc which slightly
projects downward when viewed from the back. The back frame member
9B has a rear tongue 11 in a trapezoid in which a front side is
shorter than a back side when viewed from the above.
[0047] The rear tongue 11 has a front end 11a which is an arc which
slightly projects backward when viewed from the above and curves
forward and downward to be lower than the upper surface of the back
frame member 8B.
[0048] The middle of the back edge 9b of the elastic membrane 9 is
supported by the front end of the rear tongue 11 so that the middle
of the elastic membrane 9 gently projects downward in FIG. 8.
[0049] Thus, in FIG. 5, the elastic membrane 9 is stretched so as
to form a gentle curve from the highest point P in the middle of
the front tongue 10 formed as an arc backward and upward from the
front frame member 8A, to the lowest point Q at which the elastic
membrane 9 is supported by the front end 11a of the rear tongue 11
curved downward, thereby forming the recess 12 which gradually
lowers from the back end 10a of the front tongue 10 in the middle
of the seating surface of the seat 6 to the front end 11a of the
rear tongue 11 of the back frame member 8B. The recess 12 ensures
that the user's buttock and thighs are held with the front
sectional shape of the front tongue 10 to not deviate
laterally.
[0050] In FIG. 6, the side frame member 8C is formed from the
highest point R of the front part which curves backward and upward,
to the middle part which curves backward and downward and the
lowest point of the back part, and curves backward and upward. The
lowest point Q at the back end of the elastic membrane 9 supported
by the front end 11a of the rear tongue 11 is rearward of and lower
than the lowest point S of the back part of the side frame member
8C supporting the side edges of the elastic membrane 9.
[0051] Hence, the highest point R of the side frame member 8C is
higher than the middle of the front tongue 10, and the front part
of the seat 6 becomes lower toward the middle. The lowest point Q
at the back end of the elastic membrane 9 supported by the front
end 11a of the rear tongue 11 is positioned at the back of the
lowest point S of the back part of the side frame member 8C. The
seat 6 lowers without spreading backward from the highest point R
to the lowest point S of the side frame member 8, and the seat 6
gradually shrinks and lowers toward the front end 11a of the rear
tongue 11 at the lowest point Q at the back end of the elastic
membrane 9 from the lowest point S of the side frame member 8c, so
that the buttocks of the user can be held more suitably and he/she
can take more stable sitting posture.
[0052] In the side frame member 8C, the front part is tilted
backward and upward, and the middle part is tilted backward and
downward from the highest point R. The side frame member 8C is
gently tilted backward and upward from the lowest point A of the
rear part, thereby improving the appearance of the seat.
[0053] Furthermore, the lowest point Q is lower than the lowest
point S of the side frame member 8C by which the elastic membrane 9
is supported. Thus, even if the transversely middle part of the
elastic membrane 9 is returned to horizontal flat surface by
tension, more shaping force than longitudinally shaping force of
the side frame member 8C can be applied, thereby making the shape
of the recess 12 more stable.
[0054] The side edges of the elastic membrane is positioned at the
back of the lowest point S of the side frame member 8C. Hence, the
recess 12 curves gradually backward from the back part of the side
frame member 8C when viewed from the above to enable it to fit the
top and side shapes of the back frame member 8C.
[0055] As shown in the seat 6, in the backrest 7, a synthetic resin
backrest frame 13 such as polypropylene comprises an upper frame
member 13A and a lower frame member 13B, and right and left frame
members 13C,13C like a rectangle. The circumferential edges of an
elastic membrane 14 to which polyamide fibers or polypropylene
fibers are knitted or woven as mesh are supported and stretched on
the inner circumferential surface of the frame members 13A-13C.
[0056] In FIG. 4, support rods 16,16 which project from the upper
ends of the rear legs 3a,3b of the right and left side legs 3 of
the leg unit 2 are inserted into holes 15 in the lower end of the
right and left frame members 13C,13C of the backrest frame 13, so
that the backrest 7 is mounted to stand on the back part of the
seat 6.
[0057] In FIGS. 1 and 2, the upper frame member 13A and lower frame
member 13B of the backrest frame 13 curve backward when viewed from
the above. In FIG. 3, the right and left side frame members 13C
each bends to project forward in the middle when viewed from the
side.
[0058] In FIGS. 1, 2 and 4, a pair of shape-maintaining members
17,17 is symmetrically disposed between the lower frame member 13B
close to the side and a bent portion 13a of the right and left side
frame members 13C,13C, and the lower sides of the elastic membrane
14 are supported by the shape-maintaining member 17.
[0059] The shape-maintaining member 17 is molded together with the
backrest frame 13 and elastic membrane 14 when the backrest 7 is
molded.
[0060] FIG. 9 is an enlarged horizontal sectional view of the
backrest taken along the line IX-IX in FIG. 4; FIG. 10 is an
enlarged horizontal sectional view taken along the line X-X in FIG.
4; and FIG. 11 is an enlarged vertical sectional view taken along
the line XI-XI in FIG. 4.
[0061] In FIGS. 9-11, in the elastic membrane 14 stretched over the
backrest frame 13, an upper edge 14a is held on the inner
circumferential surface of the upper frame member 13A; and a lower
edge 14b is held on the inner circumferential surface of the lower
frame member 13C of the side frame member 13C. When viewed from the
side, the elastic membrane 14 is curved to project forward in the
middle in FIG. 11 and like an arc which projects backward in FIG. 9
when viewed from the above
[0062] In the backrest 7, the elastic membrane 14 is stretched and
supported on the lower part to the shape-maintaining member 17
provided between the part of the lower frame member 13B close to
the bent portion 13a of the right and left side frame members
13C,13C in FIG. 10, causing a forward elastic returning force
obtained at the elastic membrane 14 close to the bent portion 13a
of the right and left side frame members 13C, or a restraining
force as shown by an arrow in FIG. 11 restraining tension for
getting near a flat surface forward by forming an arc projecting
backward when viewed from the above.
[0063] Specifically, the shape-maintaining member 17 supports the
back surface of the elastic membrane 14 to press forward thereby
applying restraining force against a direction of elastic returning
force of the elastic membrane 14.
[0064] Thus, when viewed from the side, the curve of the elastic
membrane 14 close to the bent portion 13a of the right and left
side frame member 13C can be maintained for a long time.
[0065] The lower side parts of the elastic membrane 14 are
supported by the shape-maintaining member 17. As shown by broken
lines in FIG. 11, a curving point C is higher than a bending point
C0 of the side frame member 13C. When the user sits in FIG. 3, the
curving point C is higher than the bending point C0 of the side
frame member 13C in a position close to the lower part of a back
bone of the user to press lumbar of the user, so that the user can
be held in more stable straight sitting posture.
[0066] In the foregoing embodiment, the upper frame member 13A is
formed like an arc that projects backward. By stretching the
elastic membrane 14, forward elastic returning force is produced
close to the bent portion 13a. When the upper frame member 13A is
straight when viewed from the above, forward elastic returning
force is not produced, but the back surface of the elastic membrane
comes closer to the flat surface to cause restoration force for
pushing back. Against this force, restraining force for pushing the
elastic membrane forward is applied by the right and left
shape-maintaining member 17 enabling the vertical curve of the
elastic membrane 14 to be kept for a long time.
* * * * *