U.S. patent application number 10/477801 was filed with the patent office on 2004-07-22 for cushion structure.
Invention is credited to Fujita, Etsunori, Kawasaki, Seiji, Kikusui, Miho, Ogura, Yumi, Ueno, Yoshiyuki.
Application Number | 20040142619 10/477801 |
Document ID | / |
Family ID | 18991632 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040142619 |
Kind Code |
A1 |
Ueno, Yoshiyuki ; et
al. |
July 22, 2004 |
Cushion structure
Abstract
A cushioning structure effective to alleviate a blood stream
trouble and loads on muscles and to prevent an outbreak of trouble
caused by them such as economy-class syndrome and the like is
provided. The structure includes an upper elastic member 11
composed of a three-dimensional net member formed by connecting a
pair of ground knitted fabrics disposed apart from each other using
connecting yarn, and a spring constant in the range of initial load
during a pressurizing process is set in the range of 0.1 to 20 N/mm
and, at the same time, during a restoring process, a spring
constant after restoring to an amount of displacement of 20 mm or
less, at the latest, to 2 mm, is set to be lower than the spring
constant in the range of initial load during the aforementioned
pressurizing process. As a result, when a person comes into contact
with a cushioning member by a sitting movement or a standing
movement, temporal set in fatigue (stroke) of about several
millimeters to about ten and several millimeters is created,
thereby improving a feeling of fitting (compatibility) which makes
a person feel comfortable, and effectively alleviate a blood stream
trouble and loads on muscles.
Inventors: |
Ueno, Yoshiyuki;
(Ichihara-shi, JP) ; Fujita, Etsunori;
(Hiroshima-shi, JP) ; Kawasaki, Seiji;
(Hiroshima-shi, JP) ; Ogura, Yumi; (Hiroshima-shi,
JP) ; Kikusui, Miho; (Hiroshima-shi, JP) |
Correspondence
Address: |
STEINBERG & RASKIN, P.C.
1140 AVENUE OF THE AMERICAS, 15th FLOOR
NEW YORK
NY
10036-5803
US
|
Family ID: |
18991632 |
Appl. No.: |
10/477801 |
Filed: |
November 14, 2003 |
PCT Filed: |
May 14, 2002 |
PCT NO: |
PCT/JP02/04653 |
Current U.S.
Class: |
442/306 ; 442/2;
442/304 |
Current CPC
Class: |
D10B 2505/08 20130101;
D10B 2403/0221 20130101; A47C 27/122 20130101; Y10T 442/413
20150401; Y10T 442/40 20150401; D04B 21/12 20130101; Y10T 442/102
20150401 |
Class at
Publication: |
442/306 ;
442/002; 442/304 |
International
Class: |
D04B 001/18; D04B
021/14; D04B 011/12; D04B 009/00; D04H 001/00; D03D 019/00; D04G
001/00; D04B 001/00; D04C 001/00; D03D 009/00; D04B 021/00; D04B
007/00; D04B 011/00; D04B 007/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2001 |
JP |
2001-145896 |
Claims
1. A cushioning structure including an elastic member composed of a
three-dimensional net member formed by connecting a pair of ground
knitted fabrics disposed apart from each other using connecting
yarn, wherein, as a load bearing characteristic of the cushioning
structure, a spring constant during a pressurizing process is set
in the range of 0.1 to 10 N/mm and, at the same time, during a
restoring process, a spring constant after restoring to an amount
of displacement of 20 mm or less, at the latest, to 2 mm, is set to
be lower than the spring constant in the aforementioned
pressurizing process.
2. The cushioning structure according to claim 1, wherein the
spring constant in the aforementioned pressurizing process is set
in the range of 0.1 to 5 N/mm.
3. The cushioning structure according to claims 1 or 2, wherein the
amount of hysteresis loss between the pressurizing process and the
restoring process in the load bearing characteristic is in the
range of 40 N or less.
4. The cushioning structure according to any one of claim 1 to
claim 3, wherein the elastic member composed of the
three-dimensional net member is configured to have a small reaction
force such that as a load bearing characteristic during the
pressurizing process the three-dimensional net member with a board
for press of 30 mm in diameter alone, a spring constant after
restoring to an amount of displacement of 20 mm or less, at the
latest, to 1 mm during the restoring process is lower than the
spring constant during the pressurizing process in the whole load
bearing characteristic.
5. The cushioning structure according to claim 4, wherein said
three-dimensional net member formed in a structure having a small
reaction force has a thickness in the range of 5 to 30 mm.
6. The cushioning structure according to claim 4 or claim 5,
wherein said three-dimensional net member formed in a structure
having a small reaction force is provided with concave and convex
portions at least on one surface, and the elasticity of the concave
portion and that of the convex portion are different from each
other.
7 The cushioning structure according to claim 6, wherein said
three-dimensional net member formed in a structure having a small
reaction force has a structure in which the convex portion is
formed substantially in an arch shaped cross section between
adjacent concave portions, and the elasticity in a bending
direction of the convex portion having the substantially arch
shaped cross section and the damping caused by friction
accompanying sliding of the connecting yarn disposed in the concave
portions can be utilized.
8. The cushioning structure according to any one of claims 4 to 7,
wherein another elastic member serving as a function to prevent the
cushion from bottom touch during the pressurizing process is
provided below an elastic member composed of said three-dimensional
net member formed in a structure with a small reaction force.
9 The cushioning structure according to claim 8, wherein
aforementioned another elastic member serving as a function to
prevent the cushion from bottom touch is a net type elastic member,
a sheet type elastic member, or a net or sheet type elastic member
supported via metal springs.
10. The cushioning structure according to claim 8 or claim 9,
wherein aforementioned another elastic member serving as a function
to prevent bottom touch is disposed at a predetermined interval to
the elastic member composed of a three-dimensional net member
formed in a structure with a small reaction force.
11. The cushioning structure according to any one of claim 4 to
claim 9, wherein still another elastic member higher in surface
stiffness than the elastic member composed of the three-dimensional
net member formed in a structure with a small reaction force is
layered, in addition to the elastic member composed of said
three-dimensional net member formed in a structure with a small
reaction force and aforementioned another elastic member serving to
prevent bottom touch.
12. The cushioning structure according to claim 11, wherein an
elastic member composed of the three-dimensional net member formed
in a structure with a small reaction force is laminated on the
upper portion of still another elastic member described above, and
another elastic member described above serving as a function to
prevent bottom touch is arranged on the lower portion of still
another elastic member described above at a predetermined
interval.
13. The cushioning structure according to any one of claim 1 to
claim 12, wherein the cushioning structure is applied to various
seat structures including a vehicle seat and a furniture chair or a
mat for furniture or for seating.
14. The cushioning structure according to claim 13, wherein the
cushioning structure is applied to a seat structure for an
aircraft.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cushioning structure
including a three-dimensional net member, and especially to a
cushioning structure suitable for manufacturing a seat structure
and the like which reduces blood stream trouble or loads on
muscles.
BACKGROUND ART
[0002] In recent years, a cushioning structure using a thin net
member (three-dimensional net member) which is of a
three-dimensional solid structure, can display high cushioning
property, has a large number of pores, and is excellent in
breathability has been known. Such a three-dimensional net member
is built up its three-dimensional structure by connecting a pair of
ground knitted fabrics disposed apart from each other with a plenty
of connecting yarns, and excellent in breathability, body pressure
dispersing property, and rebounding property.
[0003] In general, when the load bearing characteristic of a
cushioning member is higher than the load bearing characteristic of
the muscle, and a difference in shape between the cushioning member
and the muscle is large, the muscle is much deformed by a reaction
force from the cushioning member (mainly a force in the normal line
direction in a case of rather hard cushioning member, and mainly a
force in a shear direction in case of a cushion harder than the
muscle but totally the hardness being on a soft side), thereby
causing the muscle to be deformed largely, and pressed, which
results in bias flow of blood or increase of loads on muscles. On
the contrary, when the load bearing characteristic of a cushioning
member is remarkably low compared with the load bearing
characteristic of the muscle, the deformation of the muscle is
restrained. However, though the amount of deformation of the
cushioning member is large, since the amount of depression of the
cushioning member is also large, mainly shear stress serves in
play, which rather increases the loads on muscles. For instance,
when soft polyurethane slab foam and viscoelastic polyurethane foam
are used in piles, though considerably soft load bearing
characteristic can be obtained, compared with the case of using
other materials, since the amount of deformation as a cushioning
member is large, it has a problem of increase of loads on muscles
due to shear stress, as described above.
[0004] In recent years, especially in an aircraft, outbreak
instances of a trouble so-called economy-class syndrome have been
reported. A blood stream trouble caused by taking the same posture
for a long time in sitting on a chair having a structure of
supporting the femoral region strongly to prevent backside slipping
is thought to contribute to this syndrome. The aircraft industry
are looking forward to a proposal of a seat structure which can
reduce the outbreak of such an economy-class syndrome.
[0005] The present invention is achieved in view of the
above-described points, and the object thereof is to provide a
cushioning structure effective to reduce blood stream trouble,
loads on muscles, and to prevent the outbreak of the economy-class
syndrome and the like including the outbreak of troubles owing
thereto.
DISCLOSURE OF THE INVENTION
[0006] As a result of assiduous studies to solve the
above-described problems, the present inventor paid attention that
when the load bearing characteristic of a cushioning member
(elastic member) which comes in contact with the muscles directly
or indirectly is made close to the load bearing characteristic of
people's muscle, the cushioning member deforms according to the
shape of the muscle, which helps to restrain large deformation of
the muscle without setting the load bearing characteristic of the
cushioning member softer than necessary, and is effective to
prevent blood stream trouble and the like. The present inventor
also paid attention that deformation of muscles at a portion
protruded by the bone is also reduced in the deformation, which is
effective to prevent the blood stream trouble locally. The present
inventor also paid attention that amount of the deformation can be
reduced, as mentioned above, by using a three-dimensional net
member which can display high cushioning property even if it is
thin as a cushioning member (elastic member), and increase of loads
on muscles due to a shear stress created by a large deformation
when a soft cushioning member is used, and in an area of small
displacement, a reaction force inputted from the cushioning member
into the muscle can be made small by setting the load bearing
characteristic to a further softer load bearing characteristic than
that during the pressurizing process.
[0007] From these aforementioned points of view, the present
inventor thought that not only a three-dimensional net member is
used as a cushioning member (elastic member), but also by utilizing
the hysteresis loss of its load bearing characteristic, the
characteristic is made close to the load bearing characteristic of
a person in the pressurizing process (go-process), and made to be a
softer load bearing characteristic with a small reaction force
after the amount of displacement reaches a predetermined point
during the restoring process (return process), thereby movement of
the body can be induced. The present inventor has accomplished the
present invention by thinking that through this setting of the load
bearing characteristic, when the cushioning member is touched at
the time of a sitting movement or a standing movement, temporal set
in fatigue (stroke) under loads in the range of about several
millimeters to about ten and several millimeters is generated, and
when a portion of a small area protruded by the bone among the
haunches portion and the like which come into contact with the
cushioning member contacts with the cushioning member, the
cushioning member fits quickly with little sensing of the reaction
force owing to this temporal set in fatigue under loads so that a
feeling of fitting (compatibility) which makes a person comfortable
can be improved, thereby, the blood stream trouble and the loads on
muscles can be effectively reduced.
[0008] At the same time, the present inventor has also paid
attention that when the amount of stroke is made small, and the
load bearing characteristic in a small load area and a small
displacement area until arriving at an equilibrium point of the
load is set to be soft to make the above-described temporal set in
fatigue (stroke) under loads in the range of several millimeters to
ten and several millimeters, though it is effective to prevent
blood stream trouble as described above, when a load more than
predetermined is applied and the contact angle is increased, this
temporal set in fatigue under loads is felt to be bottom touch.
Accordingly, in the present invention, in order to prevent such a
feeling of bottom touch, another elastic member which is high in
linearity and high in a feeling of a spring is arranged in two
tiers or in multi-tiers in series, or is arranged to be combined in
parallel.
[0009] That is, the present invention described in claim 1 is to
provide a cushioning structure including an elastic member composed
of a three-dimensional net member formed by connecting a pair of
ground knitted fabrics disposed apart from each other using
connecting yarn, wherein, as a load bearing characteristic of the
cushioning structure, a spring constant during a pressurizing
process is set in the range of 0.1 to 10 N/mm and, at the same
time, during a restoring process, a spring constant after restoring
to an amount of displacement of 20 mm or less, at the latest, to 2
mm, is set to be lower than the spring constant in the
aforementioned pressurizing process.
[0010] The present invention described in claim 2 is to provide the
cushioning structure according to claim 1, wherein the spring
constant in the aforementioned pressurizing process is set in the
range of 0.1 to 5 N/mm.
[0011] The present invention described in claim 3 is to provide the
cushioning structure according to claims 1 or 2, wherein the amount
of hysteresis loss between the pressurizing process and the
restoring process in the load bearing characteristic is in the
range of 40 N or less.
[0012] The present invention described in claim 4 is to provide the
cushioning structure according to any one of claim 1 to claim 3,
wherein the elastic member composed of the three-dimensional net
member is configured to have a small reaction force such that as a
load bearing characteristic during the pressurizing process the
three-dimensional net member with a board for press of 30 mm in
diameter alone, a spring constant after restoring to an amount of
displacement of 20 mm or less, at the latest, to 1 mm during the
restoring process is lower than the spring constant during the
pressurizing process in the aforementioned whole load bearing
characteristic.
[0013] The present invention described in claim 5 is to provide the
cushioning structure according to claim 4, wherein the
aforementioned three-dimensional net member formed in a structure
having a small reaction force has a thickness in the range of 5 to
30 mm.
[0014] The present invention described in claim 6 is to provide the
cushioning structure according to claim 4 or claim 5, wherein the
aforementioned three-dimensional net member formed in a structure
having a small reaction force is provided with concave and convex
portions at least on one surface, and the elasticity of the concave
portion and that of the convex portion are different from each
other.
[0015] The present invention described in claim 7 is to provide the
cushioning structure according to claim 6, wherein the
aforementioned three-dimensional net member formed in a structure
having a small reaction force has a structure in which the
aforementioned convex portion is formed substantially in an arch
shaped cross section between adjacent concave portions, and the
elasticity in a bending direction of the convex portion having the
substantially arch shaped cross section and the damping caused by
friction accompanying sliding of the connecting yarn disposed in
the concave portions can be utilized.
[0016] The present invention described in claim 8 is to provide the
cushioning structure according to any one of claim 4 to claim 7,
wherein another elastic member serving as a function to prevent the
cushion from bottom touch during the pressurizing process is
provided below an elastic member composed of the three-dimensional
net member formed in a structure with a small reaction force.
[0017] The present invention described in claim 9 is to provide the
cushioning structure according to claim 8, wherein the
aforementioned another elastic member serving as a function to
prevent the cushion from bottom touch is a net type elastic member,
a sheet type elastic member, or a net or sheet type elastic member
supported via metal springs.
[0018] The present invention described in claim 10 is to provide
the cushioning structure according to claim 8 or claim 9, wherein
the aforementioned another elastic member serving as a function to
prevent bottom touch is disposed at a predetermined interval to the
elastic member composed of a three-dimensional net member formed in
a structure with a small reaction force.
[0019] The present invention described in claim 11 is to provide
the cushioning structure according to any one of claim 4 to claim
9, wherein still another elastic member higher in surface stiffness
than the elastic member composed of the three-dimensional net
member formed in a structure with a small reaction force is
layered, in addition to the elastic member composed of the
three-dimensional net member formed in a structure with a small
reaction force and aforementioned another elastic member serving to
prevent bottom touch.
[0020] The present invention described in claim 12 is to provide
the cushioning structure according to claim 11, wherein an elastic
member composed of the three-dimensional net member formed in a
structure with a small reaction force is laminated on the upper
portion of still another elastic member described above, and
another elastic member described above serving as a function to
prevent bottom touch is arranged on the lower portion of still
another elastic member described above at a predetermined
interval.
[0021] The present invention described in claim 13 is to provide
the cushioning structure according to any one of claim 1 to claim
12, wherein the cushioning structure is applied to various seat
structures including a vehicle seat and a furniture chair or a mat
for furniture or for seating.
[0022] The present invention described in claim 14 is to provide
the cushioning structure according to claim 13, wherein the
cushioning structure is applied to a seat structure for an
aircraft.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a view schematically showing the structure of a
cushioning structure relating to a first embodiment of the present
invention;
[0024] FIG. 2 is a view schematically showing the structure of a
cushioning structure relating to a second embodiment of the present
invention;
[0025] FIG. 3 is a view schematically showing the structure of a
cushioning structure relating to a third embodiment of the present
invention;
[0026] FIG. 4 is a view schematically showing the structure of a
cushioning structure relating to a fourth embodiment of the present
invention;
[0027] FIG. 5 is a view schematically showing the structure of a
cushioning structure relating to a fifth embodiment of the present
invention;
[0028] FIG. 6 is a cross sectional view showing the structure of an
example of a three-dimensional net member usable in the
above-described respective embodiments;
[0029] FIG. 7 is a view showing an example of one grand knitted
fabric;
[0030] FIG. 8 is a view showing an example of the other grand
knitted fabric;
[0031] FIG. 9A to FIG. 9E are explanatory views showing the way of
various arrangement of connecting yarn;
[0032] FIG. 10 is a perspective view showing a three-dimensional
net member provided with a concave and convex portion usable as an
upper elastic member in the above-described respective
embodiments;
[0033] FIG. 11 is a cross sectional view of the three-dimensional
net member shown in FIG. 10;
[0034] FIG. 12 is a view for explaining a function of substantially
arch-shaped spring elements formed in the three-dimensional net
member shown in FIG. 10;
[0035] FIG. 13 is a view for explaining the function of
substantially arch-shaped spring elements formed in the
three-dimensional net member shown in FIG. 10;
[0036] FIG. 14 is a perspective view of another three-dimensional
net member with no concave and convex portion usable as an upper
elastic member in the above-described respective embodiments, which
is used in test example 1;
[0037] FIG. 15 is a graph showing a relation of load to
displacement characteristic of three-dimensional net members alone
in experiments 1 to 4.
[0038] FIG. 16 is a graph showing a relation of load to
displacement characteristic of cushioning structures relating to
respective embodiments;
[0039] FIG. 17 is a graph showing a relation of load to
displacement characteristic of the three-dimensional net member
having the concave and convex portion when pressurized with a board
for press of 30 mm in diameter;
[0040] FIG. 18 is a graph showing a relation of load to
displacement characteristic of the three-dimensional net member
having the concave and convex portion when pressurized with a board
for press of 98 mm in diameter;
[0041] FIG. 19 is a graph showing a relation of load to
displacement characteristic of the three-dimensional net member
having the concave and convex portion when pressurized with a board
for press of 200 mm in diameter;
[0042] FIG. 20 is a view for explaining a function of a seat
cushion portion applied with the cushioning structure of the
present invention;
[0043] FIG. 21 is a view for explaining a function of a seat
cushion portion applied with the cushioning structure of the
present invention;
[0044] FIG. 22A and FIG. 22B are views for explaining a function of
a seat back portion applied with the cushioning structure of the
present invention;
[0045] FIG. 23 is a view for explaining a function of the seat back
portion applied with the cushioning structure of the present
invention;
[0046] FIG. 24A and FIG. 24B are views for explaining
characteristics of a seat applied with the cushioning structure of
the present invention;
[0047] FIG. 25 is a graph showing a relation of load to
displacement characteristic of the seat cushion portion applied
with the cushioning structure of the present invention;
[0048] FIG. 26 is a graph showing a relation of load to
displacement characteristic of the seat back portion applied with
the cushioning structure of the present invention; and
[0049] FIG. 27 is a graph showing a vibration characteristic of a
seat applied with the cushioning structure of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0050] Hereinafter, the present invention will be explained in
further detail based on embodiments shown in the drawings. FIG. 1
is a view showing a cushioning structure 10 relating to a first
embodiment. The cushioning structure 10 relating to the first
embodiment is formed by disposing two elastic members 11 and 12
vertically. Between them, an upper elastic member 11 is composed of
a three-dimensional net member with a concave and convex portion
formed therein. For instance, when it is employed as a seat cushion
of a seat structure, it is spread over and strained between
confronting side frames (not shown) constituting the seat structure
with a predetermined elongation percentage. It should be noted that
in order to ensure that the characteristics belonging to the
three-dimensional net member itself are displayed sufficiently, and
to make its load bearing characteristic close to the load bearing
characteristic of the muscle in a small load area during the
pressurizing process and to make its reaction force small in a
small displacement area during the restoring process by elastic
deformation in the vertical direction and in the horizontal
direction at the time of straining, it is not recommended that it
be strained with a high tension but with an elongation percentage
of 5% or less.
[0051] An lower elastic member 12 is formed of a net type elastic
member such as Plumaflex or a sheet type elastic member. When the
cushioning structure 10 is employed, for instance, in a seat
structure as described above, it is supported by engaging with one
end of a metal spring 15 through the metal spring 15 engaging at
the other end thereof with side frames (not shown) which strains
the upper elastic member 11 or with a frame member and the like
disposed at a lower portion of the side frame. It is preferable
that the spring characteristic created by the lower elastic member
12 and the metal spring 15 be high in linearity than that of the
upper elastic member 11 composed of a three-dimensional net member,
and a spring constant of 35 N to 100 N by a board for press of 98
mm in diameter when combined with the upper elastic member 11 is
close to the spring constant of the muscle of the haunches. On the
other hand, though the upper elastic member 11 is high in surface
stiffness against pressure over a large area at a force of 20 N or
less, the partial spring constant measured by pressing the concave
portion and in the vicinity of the convex portions on both sides of
the concave portion with a board for press of about 30 mm in
diameter to about 20 mm in diameter is set to be smaller than the
spring constant created by the lower elastic member 12 and the
metal spring 15 because of its shape being provided with a ridge
composed of concave and convex portions. Through this
configuration, it creates temporal set in fatigue under loads as
described above, when a protruding portion of the body comes into
contact with the seat, it becomes easy to settle partially (refer
to FIG. 13), and a feeling of fitting is improved.
[0052] As will be described later, the upper elastic member 11
composed of a three-dimensional net member has a thickness of about
5 mm to about 30 mm, the amount of displacement stroke in the
vertical direction is small, and the load bearing characteristic in
a small displacement area is extremely small and has little
reaction force. Accordingly, when an applied load meets or exceeds
a predetermined value, a person sitting on the cushion may feel the
bottom touch. Therefore, a restoring force of the upper elastic
member 11 is made up by the lower elastic member 12 having a spring
characteristic high in linearity and the metal spring 15 so that
the feeling of bottom touch is prevented by the elastic force in a
load area where the predetermined load is exceeded.
[0053] It should be noted that it is possible to structure in a
manner that the spring characteristic created by the above
described lower elastic member 12 and the metal spring 15 is
possessed by the lower elastic member alone composed of a net type
elastic member or sheet type elastic member having surface
stiffness. In other words, it is possible to use the lower elastic
member alone which has a spring characteristic including the spring
characteristic of the metal spring together with high surface
stiffness. Needless to say, in this case, the lower elastic member
is directly strained over the side frames.
[0054] Though the upper elastic member 11 and the lower elastic
member 12 can be disposed to come into contact with each other when
no load is applied, it is preferable to dispose them a little apart
from each other when the cushion structure is employed in the seat
cushion of a seat structure for instance. Through this arrangement,
since the upper elastic member 11 itself has a predetermined amount
of stroke till it touches the lower elastic member 12, a feeling of
fitting in a small load area and a small displacement area due to
deformation in the vertical direction and elongation in the
horizontal direction of the upper elastic member 11 can be further
improved.
[0055] FIG. 2 is a view showing one example of a cushioning
structure 20 relating to a second embodiment of the present
invention. In the second embodiment, the cushioning structure is
formed of three layers composed of an upper elastic member 21, a
lower elastic member 22 and a middle elastic member 23 disposed in
the middle of both the upper and lower elastic members. The upper
elastic member 21 is composed of a three-dimensional net member
having concave and convex portions, and has a same function as the
upper elastic member 11 relating to the above-described first
embodiment. The lower elastic member 22 is composed of a net type
elastic member such as Plumaflex or the like which is formed by
putting, metal wires together for instance, or a sheet type elastic
member such as a three-dimensional net member or the like, disposed
to an appropriate frame members or the like forming, for instance,
a seat structure via a metal spring 25, so that the similar
function to the lower elastic member 12 relating to the
above-described first embodiment is provided.
[0056] The middle elastic member 23 is composed of a
three-dimensional net member, and disposed to be layered under the
upper elastic member 21 between side frames of the seat cushion
which forms a seat structure, for instance. The middle elastic
member 23 is higher in surface stiffness than the upper elastic
member 21 which is provided to display a soft load bearing
characteristic as described above in a small load area, when the
load area becomes a predetermined area or more, and is provided to
prevent depression more than necessary, to increase a feeling of
stability at the time of being seated or lying owing to a feeling
of the stiffness, and at the same time, to restrain a feeling of
bottom touch of the upper elastic member 21 similarly to the lower
elastic member 22. Moreover, it is provided to reduce a feeling of
something foreign caused by the metal spring 25 or the side frames.
It should be noted that a reaction force against a seated person
can be drastically reduced by disposing either the upper elastic
member 21 or the middle elastic member 23, or preferably both of
them so that respective side portions become free ends. This is
because at the time of being seated or the like, respective side
portions move upwards in the drawing (in the direction of normal
line) as if to roll in the direction of rotation by the deformation
accompanied by the input load, and a force in the shear direction
is not generated so much, which helps to disperse the input load.
Accordingly, in order to display such a function, the
three-dimensional net member composing the middle elastic member 23
is disposed with a tension higher than that of the upper elastic
member 21, or in order to increase tolerance in deformation (degree
of freedom) and to reduce a reaction force against a person, the
three-dimensional net member for the middle elastic member 23 is
arranged so that the respective side portions become rotation-free
ends. Further, a three-dimensional net member having the load
bearing characteristic in the thickness direction is higher than
that of the upper elastic member 21 or having a large deflection
amount is adopted so as to feel like a spring rich in
elasticity.
[0057] Further, as the middle elastic member 23, any members can be
adopted provided that it can prevent unnecessarily large depression
of the upper elastic member 21 and has an elastic force capable of
displaying a predetermined feel of stiffness. Accordingly, it is
not limited to a three-dimensional net member. For instance, a felt
formed in a predetermined thickness can be used as a third
embodiment shown in FIG. 3, as a middle elastic member 33. It
should be noted that the structure of an upper elastic member 31
and the structure of a lower elastic member 32 supported via a
metal spring 35 in a cushion structure 30 of the third embodiment
shown in FIG. 3 are the same as those in the second embodiment.
[0058] FIG. 4 is a view showing a cushioning structure 40 relating
to a fourth embodiment of the present invention. The cushioning
structure 40 has a configuration specially suitable for using as a
mat for bedding or the like and is composed of an upper elastic
member 41, a middle elastic member 43, and a lower elastic member
42 piled vertically. Further, as explained in the above-described
embodiments, it is preferable to dispose respective elastic members
41 to 43 without connecting respective end portions thereof, but
making them as free ends, thereby enabling input load to disperse
so that the reaction force against a person can be reduced.
However, even in the case of connecting these respective elastic
member 41 to 43 by sewing or the like, if the end portions of
respective elastic member 41 to 43 are connected in a state to
leave a room capable of creating similar deformation to that when
they are made free ends, it becomes possible to bring a similar
effect to the above-described effect due to the elasticity
possessed by respective elastic members. It is needless to say that
an effect of making a reaction force against a person small in
quest of dispersing an input load, by making ends of respective
elastic members free ends, or by connecting respective elastic
member leaving a deformable room (or space), as described above, is
not limited to the present embodiment but also similar to other
embodiments.
[0059] The upper elastic member 41, the middle elastic member 43,
and the lower elastic member 42 are all composed of a
three-dimensional net member, and in this embodiment, and are
structured in layer without connecting respective members to each
other, which have different load bearing characteristic from each
other.
[0060] The upper elastic member 41 is, similarly to the upper
elastic member 11 of the first embodiment, the upper elastic member
21 of the second embodiment, and the upper elastic member 31 of the
third embodiment, disposed to let the cushioning structure 40
provide a function to set its load bearing characteristic to come
close to the load bearing characteristic of muscle in a
pressurizing process, and to make the reaction force small in a
small displacement area in a restoring process. Accordingly, the
upper elastic member 41 is set to have a soft load bearing
characteristic with a low spring constant. However, in FIG. 4,
there is no concave and convex portion, different from those shown
in FIG. 1 to FIG. 3. When a concave and convex portion is formed,
since a convex portion is formed in a substantially arch-shaped
cross section between adjacent concave portions, the connecting
yarn between ground knitted fabrics are disposed with an
inclination, the convex portion serves to form an arch-shaped
spring, and the elasticity in the bending direction and the
horizontal direction can be utilized. Accordingly, in a structure
forming concave and convex portions, a soft spring constant that is
close to the load bearing characteristic of a person, and has
temporal set in fatigue characteristic under loads in which the
reaction force is decreased in a fixed deformation can be easily
set up.
[0061] On the other hand, in the case of no concave and convex
portion being formed, when compared with the case of forming
concave and convex portions, the connecting yarn is disposed
between confronting ground knitted fabrics without so much
inclination, and the load bearing characteristic is determined
mainly by buckling strength of the connecting yarn. Therefore, when
a soft load bearing characteristic like the above-mentioned first
to third embodiments is given without forming a concave and convex
portion, a three-dimensional net member having a feeling of a soft
spring can be obtained by designing the connecting yarn to be
disposed at a predetermined inclination in advance at the time of
formation, or by selecting thickness and length of the connecting
yarn appropriately. It should be noted that when a
three-dimensional net member is set to have a soft structure with a
feeling of a spring by arranging the formation structure, it can be
adjusted by either any one element or a combination of any two or
more elements among such an element as density of the connecting
yarn arrangement, material of the connecting yarn, a stitch shape
of the ground knitted fabric, a stitch size of the ground knitted
fabric, material of the ground yarn composing the ground knitted
fabric, a knot fixing power at a joint portion between the
connecting yarn and the ground knitted fabric as well as the
thickness and length of the above-described connecting yarn.
Needless to say, in the case of a three-dimensional net member
forming concave and convex portions, by adjusting similar elements,
it is possible to obtain a structure having a feeling of various
springs even the width of a concave and convex portion is similar
to each other.
[0062] When a load area becomes more than a predetermined area, the
middle elastic member 43 is, similar to the middle elastic members
23 and 33 relating to the above-described second and third
embodiment, provided to prevent unnecessary depression of the upper
elastic member 41 disposed to display a soft load bearing
characteristic in a small load area, to increase a feeling of
stability at the time of being seated and lying by displacement
created by the free ends and by a feeling of stiffness which the
elastic member itself possesses, and at the same time, to restrain
a feeling of bottom touch of the upper elastic member 41 together
with the lower elastic member 42. For instance, a three-dimensional
net member formed to have a feeling of a spring harder than the
upper elastic member 41.
[0063] The lower elastic member 42 is, similar to the lower elastic
member 12, 22 and 32 of the above-described first to third
embodiments, disposed to prevent a feeling of bottom touch due to
its elastic force, and a three-dimensional net member provided with
a spring characteristic high in linearity than that of the upper
elastic member 41 is adopted.
[0064] It should be noted that as the middle elastic member 43 and
the lower elastic member 42 in the fourth embodiment, it is not
limited to a three-dimensional net member but it is possible to
substitute them with other members having the above-described
predetermined characteristics such as, for instance, felt,
polyurethane foam, or the like.
[0065] FIG. 5 is a view showing a cushioning structure 50 relating
to a fifth embodiment. The cushioning structure 50 has a
configuration suitable for using as a mat for bedding or the like
similar to the fourth embodiment, and six elastic members 51 to 56
consisting of a three-dimensional net members are structured in a
vertical multilayer.
[0066] In the present embodiment, a first elastic member 51
disposed on the top portion and a sixth elastic member 56 disposed
on the lowermost portion are formed of a three-dimensional net
member having concave and convex portions, similarly to the upper
elastic member 11 and the like of the above-described first
embodiment, and has a function to set its load bearing
characteristic to come close to the load bearing characteristic of
muscle in a small area in the pressurizing process, and to make the
reaction force small in a small displacement area in the restoring
process, and a partial spring constant by a board for press of 30
mm in diameter is set to be low so as to have a soft load bearing
characteristic though a feel of stiffness in a wide area is
high.
[0067] Among four layers of elastic members disposed between the
above-described first elastic member 51 and the sixth elastic
member 56, a second elastic member 52 which is the second from the
top in FIG. 5, and a fourth elastic member 54 which is the fourth
from the top in FIG. 5, are provided with a function corresponding
to the middle elastic member 23 in the above-described second
embodiment and the like. When a load area becomes more than a
predetermined area, the second elastic member 52 and the fourth
elastic member 54 are provided to prevent unnecessary sink-in of
the first and sixth elastic members 51 and 56 provided to display a
soft load bearing characteristic in a small load area, to increase
a feeling of stability at the time of being seated and lying by its
feeling of stiffness, and at the same time, to restrain a reaction
force to a person or a feeling of bottom touch by dispersion of the
load.
[0068] On the other hand, a third elastic member 53 and a fifth
elastic member 55 are provided with a spring characteristic similar
to the spring characteristic created by the lower elastic member 12
and the metal spring 15 of the above-described first embodiment,
and the load bearing characteristic by a board for press of 98 mm
in diameter is close to the load bearing characteristic of muscles
of the haunches in the area of 35 N to 100 N. It should be noted
that the second to fifth elastic member 52, 53, 54 and 55 disposed
between the first elastic member 51 and the sixth elastic member 56
are acceptable so far as any of them can mainly supply a feeling of
stiffness and others can display mainly a high feeling of spring,
so that its order of layer or the number of layers are not limited.
Further, in the present embodiment, in order to enhance a load
dispersion function, it is preferable to make the end portions free
similarly to the fourth embodiment.
[0069] Next, a structure of a three-dimensional net member 100 used
as the upper elastic member 11 in the first embodiment, the upper
elastic member 21 or the middle elastic member 23 in the second
embodiment, the upper elastic member 31 in the third embodiment,
the upper elastic member 41, the middle elastic member 43 or the
lower elastic member 42 in the fourth embodiment, and the first to
sixth elastic member 51 to 56 in the fifth embodiment will be
explained referring to FIG. 6 to FIG. 9. As shown in FIG. 6, the
three-dimensional net member 100 is structured of a solid
three-dimensional structure including a pair of ground knitted
fabrics 110 and 120 disposed apart from each other and a lot of
connecting yarn 130 running between the pair of ground knitted
fabrics 110 and 120 to connect both.
[0070] One of the ground knitted fabrics 110 is formed with a flat
knitted fabric structure (small mesh) structured with yarns made of
twisted monofilaments continuous to any directions in both wale
direction and course direction as shown in FIG. 7, for instance. On
the other hand, the other ground knitted fabric 120 is formed in a
larger stitch structure than that of the ground knitted fabric 110
including a honeycomb-like (hexagon) mesh made of twisted short
filaments, as shown in FIG. 8 for instance. Needless to say, this
knitted fabric structure is just an example, and it is possible to
adopt knitted fabric structures other than the small mesh structure
or the honey comb structure. The connecting yarns 130 are knitted
between the pair of ground knitted fabrics 110 and 120 to keep a
predetermined distance between one of the ground knitted fabrics
110 and the other ground knitted fabric 120 so that a predetermined
stiffness is given to the three-dimensional net member 100 which is
a solid mesh knitting.
[0071] The thickness or the like of the ground yarn forming the
ground knitted fabrics 110 and 120 is not limited particularly, but
selected from that which can provide firmness in structure required
for a solid knitted fabric and being in the range not to give
difficulty in a formation work. As a ground yarn, a monofilament
can be used, but it is preferable to use a multifilament or a spun
yarn from the point of view such as feeling, softness in surface
touch and so on.
[0072] It is preferable to use a monofilament as a connecting yarn
130, and it is suitable to use the one having a thickness in the
range of 167 to 1100 decitex. This is because a cushioning property
having a favorable restoring force cannot be given by the
multifilament, and when the thickness becomes lower than 167
decitex, it becomes difficult to obtain suitable firmness in
structure. When it becomes more than 1100 decitex, it becomes too
hard to obtain a suitable spring property (cushioning property). In
other words, adoption of the monofilament having the
above-described range as a connecting yarn 130 makes it possible to
support the load of a seated person by deformation of the stitch
structure composing respective ground knitted fabrics 110 and 120,
and by falling down and buckling characteristic of the connecting
yarn 130, and by restoring force of adjacent connecting yarn 130
giving a spring characteristic to the buckling characteristic, in
other words, is possible to support by the buckling characteristic
having a restoring force, so that a soft structure having a soft
spring characteristic without occurring of stress concentration can
be realized. It should be noted that in the case of forming concave
and convex portions, since a spring element having a cross section
of substantially arch shape can be formed as will be described
later, it is possible to give a further softer spring
characteristic.
[0073] As a material for the ground yarn or the connection fiber
130, it is not limited to some special material and, for instance,
synthetic fiber or regenerated fiber such as polypropylene,
polyester, polyamide, polyacrylonitrile, rayon and so on, or
natural fiber such as wool, silk, cotton and so on can be cited.
The above material can be used alone or can be used as any
combination thereof. It is preferable to use thermoplastic
polyester fibers such as polyethylene terephthalate (PET), and
polybutylene terephthalate (PBT), polyamide fibers such as nylon 6
and nylon 66, polyolefine fibers such as polyethylene and
polypropylene, or a combination of two or more kinds of these
fibers. Incidentally, polyester fibers is suitable because of its
regeneration property. It should be noted that the shape of fibers
used for the ground yarn or the connecting yarn 130 is not limited,
and a round cross sectional fiber, a modified cross sectional fiber
and so on can be used.
[0074] As for the manner of arranging the connecting yarn 130 (pile
structure), when the connecting yarns 130 connecting respective
ground knitted fabrics 110 and 120 are expressed from states seen
from the side, more concretely, they are classified in the types
shown in FIG. 9A to FIG. 9E. FIG. 9A and FIG. 9B are a straight
type in which the connecting yarns 130 are knitted almost
vertically between the ground knitted fabrics 110 and 120, and
between the two, FIG. 9A is the one knitted straight in the shape
of the letter 8, and FIG. 9B is the one knitted simply straight.
FIG. 9C to FIG. 9E are cross types in which the connecting yarns
130 are knitted to cross each other on the way between the ground
knitted fabrics 110 and 120. Among these, FIG. 9C is the one
knitted to cross the fibers in the shape of the letter of 8, FIG.
9D is the one knitted in a cross simply, and FIG. 9E is the one
knitted two fibers together in cross (double cross). It should be
noted that, as shown in FIG. 9C to FIG. 9E, when the connecting
yarn 130 are disposed slantwise in a cross with each other, it is
possible to give a soft spring characteristic having large
compressibility while keeping a sufficient restoring force due to
buckling strength of respective connecting yarn 130 compared with
the pattern in which the connecting yarn 130 are disposed almost
vertically between the ground knitted fabrics 110 and 120 (refer to
FIG. 9A and FIG. 9B).
[0075] Here, when the above-described three-dimensional net member
100 is used as the upper elastic members 11, 21, 31 of the
above-described first to third embodiments, and the first and sixth
elastic members 51, 56 of the fifth embodiment, it is processed
into a structure having concave portions 150 and convex portions
160, as shown in FIG. 10 and FIG. 11. More concretely, the
three-dimensional net member 100 is processed so that the pair of
ground knitted fabrics 110 and 120 which are disposed apart from
each other at predetermined intervals along the course direction
come close in the three-dimensional net member 100 to form concave
portions 150, thereby forming convex portions 160 between adjacent
concave portions 150 and 150.
[0076] Though the concave portion 150 can be formed from one side
alone out of the pair of ground knitted fabrics 110 and 120, it can
be formed from both sides as shown in FIG. 10 and FIG. 11. As a
means for forming the concave portion 150 by allowing the ground
knitted fabrics 110 and 120 to come close to each other, a sewing
means by sewing on a machine, or further such as interposing fusion
fiber between the ground knitted fabrics 110 and 120 to bond them
by melting the fusion fiber, as well as by welding, or by bonding.
It is preferable to use a vibration welding means among these means
described above. It is because this means can prevent the welded
portion to become stiff, and at the same time, the bonding strength
is very high.
[0077] As above, by forming the concave portions 150, at the
portions where the concave portions 150 are formed, the connecting
yarns 130 disposed in those area are tend to incline or bend, and
further some connecting yarns 130 move to the areas of adjacent
convex portions 160 via the concave portions 150 so as to be
unevenly distributed. Accordingly, in these areas, nearby
connecting yarns 130 are confounded with each other when being
bonded. As a result of confoundly bonding as described above, both
sides of the connecting yarn 130 putting the confounded portion
130a inbetween can serve as respective independent spring elements
(deforming elements) for the ground knitted fabric 110 or the
ground knitted fabric 120 which are respective bonding objects of
both sides. Therefore, as schematically shown in FIG. 12, the area
from a confounded portion 130a where the connecting yarns 130 are
confounded in a concave portion 150 to another confounded portion
130a where the connecting yarns are confounded in a neighboring
concave portion 150, formed is a structure taken to be serving as a
spring element having substantially an arch shaped cross section
and a damping element due to friction between yarns including the
ground knitting fabric 110 and the connecting yarns 130 disposed in
this area.
[0078] As a result, in the three-dimensional net member having
concave and convex portions, the modulus of elasticity at the
concave portion 150 is different from that at the convex portion
160. When the convex portion 160 is compression-deformed due to an
applied load, the buckling strength of the connecting yarn 130
becomes relatively small so that the buckling characteristic
becomes hard to exhibit compared with the case of using the
three-dimensional net member 100 without forming a concave and
convex portion, and as shown by an imaginary line in FIG. 12, an
elastic function in the bending direction of the spring element
having a cross section in a substantially arch shape including the
confounded connecting yarn 130 becomes relatively large. In other
words, in the spring characteristic of the convex portion 160
compared with a three-dimensional net member formed in the same
condition except not forming a concave and convex portion, the
spring constant is small and becomes easy to start deforming from a
very small load area, so that its buckling characteristic is hard
to exhibit. As a result, a three-dimensional net member with a
concave and convex portion becomes small in a maximum value in the
amount of hysteresis loss and becomes high in linearity compared
with the case without a concave and convex portion. However, in its
load bearing characteristic, an ordinary three-dimensional net
member shows a characteristic similar to a viscoelastic material of
which restoring movement is delayed due to the hysteresis even the
load becomes zero at the time of restoring, because of friction
between the connecting yarns at the time of restoring of the
connecting yarn 13, and in a three-dimensional net member having a
concave and convex portion, the friction between yarns acts on the
above-described bending elasticity to cause further increase in the
friction between yarns at a concave portion. As a consequence,
direction of the deformation and the like change according to an
input, which allows the spring element and the damping element
corresponding to the input to work.
[0079] Further, in the three-dimensional net member forming concave
and convex portions, elasticity expanding and contracting in
substantially perpendicular to a formation line of the concave
portion 150 is given by confoundly bonding the connecting yarns 130
at the concave portion 150. Accordingly, when it is strained over
seat frames or the like of a seat structure, in addition to a
spring property in the bending direction by a spring element having
a substantially arch-shaped cross section generated in the
thickness direction, elasticity (spring property) generated in the
surface direction substantially perpendicular to the bending
direction comes is added by the connecting yarn forming a spring
element having a substantially arch-shaped cross section, and this
elongation further contributes to reduction of the spring constant.
Furthermore, owing to the characteristic similar to a viscoelastic
material created by the increase of the friction between yarns, the
damping characteristic also gets large. Accordingly, by disposing
the upper elastic member 11, the middle elastic members 23 and 33
above respective lower elastic members 12, 22, and 32 shown in the
above-described first to third embodiments at respectively
predetermined distances of intervals, elongation in lateral
directions of respective upper elastic members 11, 21, and 31
composed of three-dimensional net members having concave and convex
portions work effectively, delay characteristic of the restoring
movement are revealed more remarkably, and the damping ratio also
gets large.
[0080] Further, as shown in FIG. 13, when a portion protruded by a
bone of the human body (corresponding nearly to a board for press
having a diameter of 30 mm) comes in contact with a
three-dimensional net member, the convex portions 160 on both sides
of the concave portion 150 sandwiched therebetween are depressively
deformed as if running away toward outside and partial temporal set
in fatigue under loads is created. Then, when the portion is
further applied with a load and pressed in a large area, the whole
three-dimensional net member comes to support the load, and since
deformation as shown in FIG. 13 appears due to the existence of
such concave and convex portions, a feeling of fitting is improved
in a small displacement area.
[0081] The upper elastic members 11, 21, 31 and 41 of the
above-described respective embodiments and the first and sixth
elastic members 51 and 56 of the fifth embodiment are provided with
a soft spring characteristic, and a reaction force in the range of
predetermined amount of displacement or less is made small.
However, when the amounts of the upper elastic members 11, 21, 31,
41 and so on are large, shear stress starts to serve on the
muscles, which leads to increase in a load on the muscles instead.
Therefore, it is preferable to form respective upper elastic
members 11, 21, 31, 41 and so on to have a thickness including a
pair of ground knitted fabrics (the thickness of the convex portion
when concave and convex portions are formed) in the range of 5 to
30 mm, lest the maximum amount of deformation should be so
large.
TEST EXAMPLE
[0082] The load characteristics of individual three-dimensional net
members (test example 1 to 4) usable for the upper elastic member
11 of the first embodiment shown in FIG. 1, the upper elastic
member 21 of the second embodiment shown in FIG. 2, the upper
elastic member 31 of the third embodiment shown in FIG. 3, the
upper elastic member 41 of the fourth embodiment shown in FIG. 4,
the first and sixth elastic members 51 and 56 of the fifth
embodiment shown in FIG. 5 are measured. The measurement is carried
out by pressing a circular board for press of 200 mm in diameter at
a speed of 50 mm/minute. The results are shown in FIG. 15.
[0083] The conditions of manufacturing the three-dimensional net
members used in test examples 1 to 4 are as follows. The
three-dimensional net member used in test example 1 has no concave
and convex portion, and is structured, as shown in FIG. 14, that
space portions 210 are formed between ridge portions (band-shaped
portion) 200 formed at intervals of one wale or a plurality of
wales. In the space portion 210, connecting portions 220 are formed
over the range of 1 to several courses so as to bridge between the
adjacent ridge portions 200. All of the test examples 2 to 4 are
formed with concave and convex portions as shown in FIG. 10 and
FIG. 11. A manufacturing condition for a comparison example is the
same as that for the test example 4 except that concave portions
are not formed by vibration welding, and the compressibility is
13.2%, the compression modulus of elasticity is 98.1%.
Test Example 1
[0084] knitting machine: Double Raschel knitting machine (9
guage/2.54 cm, bed gap distance 15 mm)
[0085] wale density: 10 wale/2.54 cm
[0086] course density: 14 course/2.54 cm
[0087] finished thickness (distance between surfaces of a pair of
ground knitted fabrics): 11.5 mm
[0088] ground yarn used in one ground knitted fabric: 1170
decitex/96f polyester.multidot.BCF multifilament (crimped yarn)
[0089] ground yarn used in the other ground knitted fabric: 660
decitex/192f polyester.multidot.BCF multifilament (crimped
yarn)
[0090] connecting yarn: 660 decitex/1f polyester
[0091] structure of one ground knitted fabric: derivative stitch of
2 course mesh
[0092] structure of the other ground knitted fabric: queen's
cord
[0093] total thickness of a stitch formed with ground yarn in one
ground knitted fabric and connecting yarn: 1830 decitex, (partially
3000 decitex)
[0094] total thickness of a stitch formed with ground yarn in the
other ground knitted fabric and connecting yarn: 1980 decitex
[0095] compressibility of ridge portion: 49.5%
[0096] compression modulus of elasticity of ridge portion:
98.8%
[0097] difference in compressibility between ridge portion and
other portions: 5.2%
[0098] width of ridge portion: 6 wales
[0099] width of space portion: 1 wale
Test Example 2
[0100] knitting machine: Double Raschel knitting machine (9
guage/2.54 cm, bed gap distance 15 mm)
[0101] wale density: 10 wale/2.54 cm
[0102] course density: 14 course/2.54 cm
[0103] finished thickness (distance between surfaces of a pair of
ground knitted fabrics): 11.5 mm
[0104] ground yarn used in one ground knitted fabric: 1170
decitex/96f polyester.fwdarw.BCF multifilament (crimped yarn)
[0105] ground yarn used in the other ground knitted fabric: 660
decitex/192f polyester.fwdarw.BCF multifilament (crimped yarn)
[0106] connecting yarn: 660 decitex/1f polyester
[0107] structure of one ground knitted fabric: derivative stitch of
2 course mesh
[0108] structure of the other ground knitted fabric: queen's
cord
[0109] total thickness of a stitch formed with ground yarn in one
ground knitted fabric and connecting yarn: 1830 decitex, (partially
3000 decitex)
[0110] total thickness of a stitch formed with ground yarn in the
other ground knitted fabric and connecting yarn: 1980 decitex
[0111] compressibility of convex portion: 57.9%
[0112] compression modulus of elasticity of convex portion:
98.8%
[0113] difference in compressibility between convex portion and
concave portion: 57.8%
[0114] vibration welding condition of concave portion: applied
pressure 18.2 kgf/m.sup.2, amplitude 1.0 mm, time period 1.2
sec
[0115] width of convex portion: 5 wales
[0116] width of concave portion: 2 wales
Test Example 3
[0117] knitting machine: Double Raschel knitting machine (9
guage/2.54 cm,
[0118] bed gap distance 15 mm)
[0119] wale density: 9.8 wale/2.54 cm
[0120] course density: 12.8 course/2.54 cm
[0121] finished thickness (distance between surfaces of a pair of
ground knitted fabrics): 12.05 mm
[0122] ground yarn used in one ground knitted fabric: 1170
decitex/384f
[0123] ground yarn used in the other ground knitted fabric: 560
decitex/70f
[0124] connecting yarn: 560 decitex/1f
[0125] structure of one ground knitted fabric: 1 repeat 2 course
mesh
[0126] structure of the other ground knitted fabric: queen's
cord
[0127] total thickness of a stitch formed with ground yarn in one
ground knitted fabric and connecting yarn: 1730 decitex
[0128] total thickness of a stitch formed with ground yarn in the
other ground knitted fabric and connecting yarn: 1120 decitex
[0129] compressibility of convex portion 89.1%
[0130] compression modulus of elasticity of convex portion:
100%
[0131] difference in compressibility between convex portion and
concave portion: 89.0%
[0132] vibration welding condition of concave portion: applied
pressure 21.7 kgf/m.sup.2, amplitude 1.0 mm, time period 1.0
sec
[0133] width of convex portion: 6 wales
[0134] width of concave portion: 2 wales
Test Example 4
[0135] knitting machine: Double Raschel knitting machine (9
guage/2.54 cm, bed gap distance 15 mm)
[0136] wale density: 9 wale/2.54 cm
[0137] course density: 13.5 course/2.54 cm
[0138] finished thickness (distance between surfaces of a pair of
ground knitted fabrics): 11.5 mm
[0139] ground yarn used in one ground knitted fabric: 1170
decitex/96f
[0140] ground yarn used in the other ground knitted fabric: 660
decitex/192f
[0141] connecting yarn: 660 decitex/1f
[0142] structure of one ground knitted fabric: convex
portion.fwdarw.1 repeat 4 course mesh, concave
portion.fwdarw.modified W atlas
[0143] structure of the other ground knitted fabric: queen's
cord
[0144] total thickness of a stitch formed with ground yarn in one
ground knitted fabric and connecting yarn: 2050 decitex (partially
3220 decitex)
[0145] total thickness of a stitch formed with ground yarn in the
other ground knitted fabric and connecting yarn: 1540 decitex
[0146] compressibility of convex portion: 20.0%
[0147] compression modulus of elasticity of convex portion:
94.3%
[0148] difference in compressibility between convex portion and
concave portion 310: 6.8%
[0149] vibration welding condition of concave portion: applied
pressure 18.2 kgf/m.sup.2, amplitude 1.0 mm, time period 1.2
sec
[0150] width of convex portion: 9 wales
[0151] width of concave portion: 3 wales
[0152] Incidentally, the compressibility and the compression
modulus of elasticity are measured according to a test method based
on JASO Standard M404-84 "Compressibility and Compression modulus
of elasticity". More concretely, three sheets of samples in the
size of 50 mm.times.50 mm are prepared, and respective thickness
are measured after an initial pressure of 3.5 g/cm.sup.2 (0.343
kPa) is applied on each of the samples in the thickness direction
for 30 seconds. Then, the thickness of the samples are measured at
the time of keeping them for 10 minutes under the pressure of 200
g/cm.sup.2 (19.6 kPa). Then, after keeping the samples for 10
minutes with the loads being removed, a pressure of 3.5 g/cm.sup.2
(0.343 kPa) is applied again for 30 seconds and the thickness is
measured. The compressibility and the compression modulus of
elasticity are calculated based on the following equations and
expressed in an average value of three samples respectively.
Compressibility (%)={(t.sub.0-t.sub.1)/t.sub.0}.times.100 Equation
1
Compression modulus of elasticity
(%)={(t.sub.0-t.sub.1)/(t.sub.0t.sub.1)}- .times.100 Equation 2
[0153] Here, to indicates a thickness (mm) of the sample when a
pressure of 3.5 g/cm.sup.2 (0.343 kPa) is applied, t.sub.1
indicates a thickness (mm) of the sample when a pressure of 200
g/cm.sup.2 (19.6 kPa) and t'.sub.0 indicates a thickness (mm) of
the sample when a pressure of 3.5 g/cm.sup.2 (0.343 kPa) is applied
again.
[0154] As is clear from FIG. 15, when the load bearing
characteristic in the go-process (pressurizing process) till the
upper initial load range of 200 N (about 20 kg) while using a board
for press of 200 mm in diameter is observed, it is found that the
spring constant in each test example is lower than that in the
comparison example having low compressibility and high compression
modulus of elasticity. Further, when the test example 1 which forms
no concave and convex portion and the test example 2 which forms
concave and convex portions are compared, the test example 2 which
forms concave and convex portions shows a lower spring constant and
a softer load bearing characteristic. This is because by utilizing
mainly the spring property in a bending direction owing to a spring
element having a substantially arch-shaped cross section, the
hysteresis loss becomes small and the linearity becomes high
compared with an ordinary three-dimensional net member having a
high friction coefficient owing to its buckling characteristic and
knot fixing strength.
[0155] In the return process (restoring process), though both are
found to have spring constants lower than those in the pressurizing
process due to the hysteresis loss, in the case of the comparison
example, the spring constant in the restoring process even in the
displacement range of 2 to 1 mm is still about 40 N/mm, and the
reaction force remains till the displacement amount becomes nearly
0 mm. On the other hand, in the case of test examples 1 to 4, after
the displacement amount comes to 1 mm at the latest in the
restoring process, the structure is found to have a very small
reaction force such that the spring constant becomes much lower
than the spring constant in the pressurizing process of all the
cushioning structure in each embodiment which will be described
later, and becomes nearly zero. This load bearing characteristic is
measured by pressing with a board for press of 200 mm in diameter
at a speed of 50 mm/min. In the load bearing characteristic of a
three-dimensional net member alone, it is required as described
above to have a function to improve a feeling of fitting in a small
displacement area by a partial displacement. Therefore, a
characteristic of a spring characteristic to become nearly zero
after the displacement amount of 20 mm or less comes to 1 mm in the
above-described restoring process can preferably exhibit at the
time of being pressed with a board for press of 30 mm in diameter
at a speed of 50 mm/min (refer to FIG. 13).
[0156] (Embodiments 1 to 5)
[0157] Load bearing characteristics are measured for the whole
cushioning structures relating to the first embodiment shown in
FIG. 1 (embodiment 1), the second embodiment shown in FIG. 2
(embodiment 2), the third embodiment shown in FIG. 3 (embodiment
3), the fourth embodiment shown in FIG. 4 (embodiment 4), and the
fifth embodiment shown in FIG. 5 (embodiment 5). It should be noted
that the three-dimensional net member used for the upper elastic
members 11, 21, and 31 in the embodiment 1 to 3, and the first and
sixth elastic members 51 and 56 in the embodiment 5 is used in the
above-described test example 2 which is strained at the elongation
percentage of zero and the longitudinal direction of the convex
portion is along the direction of gap between the side frames. In
the embodiment 4, the elastic member adopted in the above-described
test example 1 is used as the upper elastic member 41. The
measurement is carried out by pressing a circular board for press
of 98 mm in diameter from a surface of the three-dimensional net
member to 100 N at a speed of 50 mm/minute. The result is shown in
FIG. 16. Further, for the muscles of haunches of a person, the load
bearing characteristic is measured similarly by pressing with a
circular board for press of 98 mm in diameter and the result is
shown in the same figure.
[0158] In all of respective lower elastic members 12, 22, and 32 in
embodiments 1 to 3, the same Plumaflex is strained by 4 pieces of
metal springs on the right and left respectively. The adopted metal
spring is a coil spring having 2.6 mm in wire diameter, 54.6 mm in
coil length, 16.1 mm in coil average diameter, 20 in winding
number, and 0.55 N/mm in spring constant.
[0159] As is clear from FIG. 16, spring constants of the load
bearing characteristic in the go-process (pressurizing process) are
all in the range of 0.1 to 10 N/mm, and at the same time, the
amounts of hysteresis loss are in the range of 10 to 20 N, and
especially in the area of 35 to 100 N which is over the load
equilibrium point, it shows a low spring constant close to the
spring characteristic of muscles. Incidentally, a preferable spring
constant is in the range of 0.1 to 5 N which is closer to the
spring constant of muscles. The amount of hysteresis loss is
preferably in the range of 10 to 20 N as a characteristic when
measurement is carried out by pressing with a board for press of 98
mm in diameter as described above, but the range below 40 N is
acceptable.
[0160] On the other hand, in a return process (restoring process)
of the load bearing characteristic, embodiment 1, embodiment 2, and
embodiment 4 show the spring constants after the displacement
amounts come to about 3 to 5 mm which is before the displacement
amount comes to zero or the tested samples are completely restored,
becomes substantially zero which is lower than the spring constant
of muscles. Further in embodiment 3 and embodiment 5, when the
displacement amounts come to about 15 to 18 mm before it becomes
zero or the tested samples are completely restored, the spring
constant thereafter becomes substantially zero. In other words, in
the load bearing characteristic of the three-dimensional net member
alone in the above-described test example 2, the spring constant
comes to near zero at the time of the displacement amount to be
about 2 mm. However, by making it into a layered cushioning
structure as in the embodiments, it is found that the range to get
near zero of the spring constant is widened.
[0161] From the above, by disposing to a three-dimensional net
member another elastic member to prevent bottom touch in layers,
and if necessary, by arranging still another elastic member such as
a metal spring, Plumaflex, or the like which is high in surface
stiffness, capable of preventing a feeling of something foreign in
layers, it is found that a spring constant which does not allow a
seated person to feel a reaction force can be provided in an area
below the predetermined displacement amount, more concretely, in an
area from the displacement amount of 20 mm to 2 mm at the latest
considering the data in the above-described embodiments, for
instance, after the displacement amount comes to about 15 mm or
less in embodiment 3. Through this arrangement, in the range of
displacement from several millimeters to ten and several
millimeters or so, the structure tends to bend under a small load
due to the spring constant of 0.1 to 10 N/mm or less, which is
close to muscles during pressurizing process, but since it causes
only temporal set in fatigue due to the load with almost no
inputting of the reaction force thereof, the cushioning structures
in respective embodiments only give the seated person a feeling of
light touch on a small contact area as in the case of coming in
contact with a portion protruded by a bone of the human body, and
there is no reaction force which causes a blood stream trouble or
loads on muscles. Therefore, a feeling of seating with a feeling of
being safe can be obtained.
[0162] (Embodiment 6)
[0163] A three-dimensional net member (embodiment 6) with concave
and convex portions as shown in FIG. 10 and FIG. 11 is mounted on a
plane board, and the load bearing characteristic is measured while
changing the size (diameter) of a board for press. The results are
shown in FIG. 17 to FIG. 19. FIG. 17 shows the case of pressurizing
to 100 N with a board for press of 30 mm in diameter, FIG. 18 shows
the case of pressurizing to 100 N with a board for press of 98 mm
in diameter, and FIG. 19 shows the case of pressurizing to 1000 N
with a board for press of 200 mm in diameter. It should be noted
that all of the speed of the board for press are 50 mm/minute.
Further, in all cases, similar measurement is carried out for a
three-dimensional net member (for comparison) with no concave and
convex portion prepared under completely the same condition as in
embodiment 6 except no formation of concave and convex portion by
vibration welding.
[0164] As is clear from FIG. 17, when pressurized with a board for
press of 30 mm in diameter, embodiment 6 is found to be low as a
whole in a load value against a displacement amount compared with
the comparison example, and a displacement amount in which the
spring constant during the restoring process comes to zero is found
to be increased. Accordingly, it is found that it tends to displace
partially, and when a protruded portion comes in contact, the
reaction force at that time is small. As shown in FIG. 18, when
pressurized with a board of 98 mm in diameter (corresponding to the
one side size of human haunches), a load value against a
displacement amount is lowered as a whole similarly, compared with
the comparison example. The spring constants both in the
pressurizing process and the restoring process are lowered and when
compared with the comparison example, the reaction force is found
to be small. However, the linearity gets higher compared with the
case of pressurizing with the board of 30 mm in diameter in FIG.
17, which shows that the surface stiffness becomes high by
increment of pressurized area. In the case of pressurizing with the
board for press of 200 mm in diameter in FIG. 19, the linearity is
similarly enhanced and the surface stiffness is increased compared
with the case of the comparison example.
[0165] As above, it can be said that it becomes clear from the
experiment result that by making a structure including concave and
convex portions as in embodiment 6, in the case of a small contact
area, the structure gives only a seated person a feeling of light
contact, and creates no reaction force which may cause a blood
stream trouble or loads on muscles, and in the case of a large
contact area, the structure can exhibit a sufficient surface
stiffness, absorbs physique differences between seated persons to
give a feeling of seating with a feeling of being safe.
[0166] Here, in a case that a cushioning structure according to the
present invention is applied to a sitting seat, it is preferable
that at a portion coming into contact with haunches, namely at a
seat cushion portion, when a portion protruded by a bone is
abutted, it can create temporal set in fatigue under loads while
being partially bent as shown in FIG. 20, and as shown in FIG. 21,
when a load is further applied, it has a structure that can support
the load with a wider area according to the size of the inputted
figure (shape and size of the haunches). This is because that since
there is little difference of physique in shape and size of the
haunches, when a load more than predetermined is applied, it
enhances its vibration absorbability by serving the spring property
sufficiently. Therefore, in a seat cushion portion, similarly to
each embodiment described above, it is preferable to use such a
structure that on an elastic member having a small reaction force
such as a three-dimensional net member with concave and convex
portions, another elastic member (such as Plumaflex, a metal
spring, or the like) having a spring property is disposed, or if
necessary, still another elastic member having a high surface
stiffness is disposed.
[0167] On the other hand, in a seat back portion, a difference in
physique is exhibited more clearly than the haunches due to a
skeletal structure, and a difference in a position protruded by
bones is larger compared with the haunches. Accordingly, it is
preferable for a cushioning structure to form a seat back portion
to put emphasis on a function to absorb a difference in physique.
From this point of view, the conventional cushioning structure of
using a polyurethane foam is insufficient in respect of a physique
difference absorbing function, because, as shown in a imaginary
line in FIG. 22B, the whole cushion is bent backwards around a
substantially central portion of the seat back potion so that both
sides are drawn nearly to the central portion. On the contrary,
when the three-dimensional net members explained in the
above-described respective embodiments are used and strained at an
elongation percentage of less than 5%, a structure can be obtained
in which, as shown in FIG. 23, it can create a partial temporal set
in fatigue under loads in a small load range and displacement area,
and, as shown in FIG. 22A, even when a further load is applied on
it, it can follow the skeletal structure to absorb the difference
in physique, and deform while fitting to the body by a damping
characteristic due to friction between yarns. Therefore, in a
cushioning structure composing a seat back portion, it is
recommendable to make a structure to use, for instance, a
three-dimensional net member with concave and convex portions
explained in the above-described respective embodiment as an
elastic member and only strain it, but not to dispose other elastic
members.
[0168] Through this formation, in a seat cushion portion, as shown
in FIG. 24A and FIG. 24B, a cushioning structure putting emphasis
mainly on a spring element can be formed, and in a seat back
portion, a cushioning structure putting emphasis mainly on a
damping element can be formed. Therefore, the present invention has
a merit of realizing a sitting seat structure provided with such
ideal functions by selecting a combination of cushioning structures
easily and at low costs.
[0169] According to FIGS. 24A and 24B, for a seat cushion portion,
a cushioning structure of the present invention in which Plumaflex
is supported with right and left total 8 pieces of metal springs
(coil spring) and a three-dimensional net member with concave and
convex portions is arranged thereon is adopted (refer to FIG. 1),
and for a seat back portion, only a three-dimensional net member
with concave and convex portions is adopted as a cushioning
structure of the present invention, to prepare a car seat and
respective load bearing characteristics are measured. It should be
noted that the three-dimensional net members are supported at an
elongation percentage of zero.
[0170] FIG. 25 shows load bearing characteristics of the cushioning
structure adopted for the seat cushion portion, in which a broken
line shows a load bearing characteristic combined both of the metal
springs and Plumaflex, a thin solid line shows a load bearing
characteristic of the whole cushioning structure layered with
three-dimensional net members, and a bold solid line shows a spring
constant (k) of the whole cushioning structure. As is clear from
the drawing, it is found that linearity is high and the spring
characteristic contributes to a high degree because the metal
springs and Plumaflex are arranged to the three-dimensional net
member in layers. Incidentally, after about 8 to about 10 mm in the
restoring process, the spring constant comes to nearly zero, and
temporal set in fatigue under loads is generated in a small
displacement area.
[0171] FIG. 26 shows a load bearing characteristic of the
cushioning structure adopted for the seat back portion, namely the
cushioning structure consisting of only a three-dimensional net
member with concave and convex portions. Incidentally, a bold solid
line shows a load bearing characteristic of the haunches. From this
result, it is found that in the cushioning structure adopted for
the seat back portion, hysteresis loss becomes large compared with
that in the seat cushion portion, showing large contribution of the
damping element. Further, it is also found that the load bearing
characteristic of this cushioning structure is almost parallel to
the load bearing characteristic of the haunches, and has a
characteristic close to the load bearing characteristic of the
muscle. Incidentally, after the displacement amount of about 20 mm
in the restoring process, the spring constant is nearly zero.
[0172] Then, a person of JM96 (cushion share load: 85 kg) is seated
on the above-described seats, a vibrator platform is disposed below
the seat cushion portion, and acceleration transmittance against
frequency (G/G) is measured. The result is shown by a broken line
in FIG. 27. For comparison, a vibration characteristic of a seat
using polyurethane foam is shown by a thin solid line, and a
vibration characteristic of a seat using an ordinary
three-dimensional net member without concave and convex portion
(provided that other conditions except no concave and convex
portion are the same as that for the seat of the present invention)
is shown by a bold solid line.
[0173] Although if the acceleration transmittance (G/G) exceeds
2.0, it gives a bad effect to a feeling of riding comfort, but as
for this point they are all restrained to a low vibration
transmittance. However, compared with a seat using polyurethane
foam, all of the seat using a three-dimensional net member has a
slightly lower vibration transmittance, and shows a favorable
characteristic.
[0174] It has been known that a factor affecting a riding comfort
largely is vibration of 2 Hz or less and 5 Hz which shakes a
skeletal structure itself by vibration. Accordingly, it is
desirable that the resonance peak should keep away from these
ranges and the acceleration transmittance of 6 to 8 Hz which makes
resonance with the internal organs should be lowered. As for this
point of view, when the cushioning structure of the present
invention is used, the resonance peak is set between 2 Hz and 5 Hz,
and the frequency is set to be lower than those of other two
cushioning structures. Accordingly, the acceleration transmittance
in the range of 6 Hz to 8 Hz at which the internal organ resonates
is set to be remarkably lower than those of other two cushioning
structures. Therefore, it is found that when the cushioning
structure of the present invention is used, it is also very
excellent in a point of vibration absorbency.
INDUSTRIAL AVAILABILITY
[0175] The cushioning structure of the present invention includes
an elastic member composed of a three-dimensional net member formed
by connecting a pair of ground knitted fabrics disposed apart from
each other using connecting yarn, and a spring constant during a
pressurizing process is set in the range of 0.1 to 10 N/mm and, at
the same time, during a restoring process, a spring constant after
restoring to an amount of displacement of 20 mm or less, at the
latest, to 2 mm, is set to be lower than the spring constant during
the aforementioned pressurizing process. As a result, when a person
comes into contact with a cushioning member by a sitting movement
or a standing movement, temporal set in fatigue under loads
(stroke) of about several millimeters to about ten and several
millimeters is created, thereby improving a feeling of fitting
(compatibility) which makes a person feel comfortable, and
effectively alleviate a blood stream trouble and loads on muscles.
Therefore, when the cushioning structure of the present invention
is applied especially to a seat structure of aircraft, it is
effective to prevent a trouble so-called an economy-class syndrome
which is caused by blood stream trouble or loads on muscles.
* * * * *