WO2004107917A1

WO2004107917A1 - Chair having automatically adjustable backrest

Info

Publication number: WO2004107917A1
Application number: PCT/KR2004/001201
Authority: WO
Inventors: Jong-Ho Lee
Original assignee: Manplus Co., Ltd.
Priority date: 2003-05-23
Filing date: 2004-05-20
Publication date: 2004-12-16
Also published as: DE602004018920D1; JP4477011B2; WO2004107917A8; JP2006528048A; US7401858B2; EP1635673A1; US20070069564A1; EP1635673B1; ATE419766T1

Abstract

The present invention relates to a chair having an automatically adjustable backrest for thereby preventing various backbone-related diseases, and in particular to a chair having an automatically adjustable backrest for thereby preventing various backbone-related diseases in which a user’s backbone is safely protected in such a manner that a chair backrest is automatically adjusted based on a user’s weight, and a user’s back is safely supported, so that a user can sit in an upright posture even when a user sits in a seat in a state that a user’s back is not properly supported by a backrest of a chair wherein a user uses various kinds of chairs including a seat that has four legs supported by the floor or that is adjustable in a forward or backward direction in a vehicle.

Description

Title: CHAIR HAVING AUTOMATICALLY

ADJUSTABLE BACKREST

Technical Field

The present invention relates to a chair having an automatically

adjustable backrest for thereby preventing various backbone-related diseases,

and in particular to a chair having an automatically adjustable backrest for

thereby preventing various backbone-related diseases in which a user's

backbone is safely protected in such a manner that a chair backrest is

automatically adjusted based on a user's weight, and a user's back is safely

supported, so that a user can sit in an upright posture even when a user sits in

a seat in a state that a user's back is not properly supported by a backrest of a

chair wherein a user uses various kinds of chairs including a seat that has four

legs supported by the floor or that is adjustable in a forward or backward

direction in a vehicle.

Background Art

All people study or work for a business using a desk or a table in an

office and conference room of a school, academy institute or public organs or

various industrial fields, sitting on chair. In this case, almost chairs have

backrests for safely supporting a user's back. Generally, since a chair backrest supports a back of a user sitting on a

chair, the user can take a rest in comfortable posture. In addition, the user's

back can be protected in such a manner that a user's back is properly

supported. When sitting on a chair, it is needed to sit on a chair in an upright

posture in such a manner that a hip part of a user is closely contacted with a

rear side of a seat, and a user's back is contacted with a backrest.

Therefore, the backrest of a chair is basically designed to safely protect

a user's back based on a human body mechanic system.

The conventional chair has a structure that a backrest is elastically

supported in a backward direction, and a dual-back structure that a backrest is

divided into two parts for thereby effectively supporting both sides of a

backbone of a user.

In the conventional chair, since a backrest of a chair is fixed at a set

position irrespective of a position that a user sits, a user must move his hip to a

deep corner of a seat in order to sit in upright posture and a user's back must

be supported by a backrest, so that a user can sit on a chair in an upright

posture. In the case that a user sits on a chair in a manner that a hip part of a

user is positioned at an intermediate portion of a seat or is positioned at a front

side of a seat, the backside of a user cannot be properly supported by a

backrest of a chair. If the user works for a long time in a state that the user did

not sit on a chair in an upright posture, a user's back may receive over load, so

that a user may feel fatigue within a short time period. In addition, an abnormal phenomenon may occur in a backbone. Namely, the user may have a certain

disease such as a back disc, etc.

A student studying on a chair or a worker working on a chair may sit at

a rear side of a seat with his hip portion being positioned at a rear side of a sear,

without sitting on a chair in an upright posture. If the user works in the above

posture for a long time, since the user's upper body is not safely supported by a

backrest of a chair, the user may feel fatigue faster. In more serious case, an

over load may be applied to a user's back, so that a certain disease such as a

back disc may occur in a user's back.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide a chair

having an automatically adjustable backrest for thereby preventing various

backbone-related diseases capable of overcoming the problems encountered in

a conventional art.

It is another object of the present invention to provide a chair having an

automatically adjustable backrest for thereby preventing various backbone-

related diseases in which a backrest of a chair is automatically adjusted to

closely contact with a user's back so that a user sits on a chair in an upright

posture for thereby protecting a user's back without an artificial operation even

when a user sits on a chair in such a manner that a user's hip portion is

positioned at an intermediate portion or a front side of a seat, not in a proper manner that a user's hip portion is closely contacted with a back side of a seat

when sitting on a chair. In addition, in a state that a backrest of a chair is closely

contacted with a user's back as a backrest is forwardly moved in the above

manner, when a user adjusts his sitting posture to a forward direction, the

backrest is automatically further moved in a forward direction. Even when a

user tilts his back backwardly, sitting on a chair, the backrest is not backwardly

moved for thereby safely supporting a user's back. Therefore, the user can

always sit on a chair in an upright posture when sitting on a chair.

To achieve the above objects, in a chair having a seat, a backrest and

support legs, there is provided a chair having an automatically adjustable

backrest for thereby preventing various backbone-related diseases, comprising

upper, intermediate and lower plates that are installed between the seat and the

support legs at a certain interval therebetween in upper and lower directions; a

hydraulic pressure-applying unit that is installed between the intermediate plate

and the lower plate in such a manner that an elastic operation is achieved in the

upper and lower directions, and includes a hydraulic pressure-applying cylinder

operating in such a manner that when a user sits on a chair, the intermediate

plate is elastically compressed by the weight of the user, and a hydraulic

pressure is applied to a reciprocation operation cylinder installed between the

upper plate and intermediate plate, and when the user gets up from the seat,

the compressed state of the intermediate plate is recovered to its original state,

so that the hydraulic pressure supplied to the cylinder is collected; a guide box that is installed between the upper plate and the intermediate plate and is

horizontally installed on an upper surface of the intermediate plate in the

forward and backward directions; a backrest moving unit including a

reciprocation operation cylinder that is horizontally installed in the interior of the

guide box, and the piston rod is appeared as the hydraulic pressure is inputted

when the hydraulic pressure is discharged from the hydraulic pressure-applying

cylinder of the hydraulic pressure-applying unit, and when the hydraulic

pressure-applying cylinder collects the hydraulic pressure, the hydraulic

pressure is discharged for thereby disappearing the piston rod; and a main

operation member that is horizontally installed and passes through a movement

elongated hole formed at both sides of the guide box in a direction

perpendicular to the guide box and is connected with a front end of the piston

rod of the reciprocation operation cylinder and is forwardly and backwardly

moved within a moving range of the movement elongated hole of the guide box

based on the forward and backward movements of the piston rod; a backrest

frame that is connected with both ends of the main operation member of the

backrest moving unit and is forwardly and backwardly moved together with the

main operation member; and an assistant operation member that is movably

installed at a rear side between the upper plate and the intermediate plate and

is forwardly and backwardly moved together with the backrest frame in a state

that both ends of the same are connected with the backrest frame.

In the hydraulic pressure-applying unit, a certain fluid selected between oil or gas is injected into the hydraulic pressure-applying cylinder, and the

hydraulic pressure-applying cylinder is connected in such a manner that a

hydraulic pressure is supplied to the reciprocation operation cylinder of the

backrest moving unit through the hydraulic pressure line and is collected, and a

hydraulic pressure control valve is connected with the hydraulic pressure line for

controlling the flow of hydraulic pressure by opening and closing the pressure

adjusting valve capable of adjusting the discharge amount of the hydraulic

pressure and the hydraulic pressure line.

The backrest moving unit includes a shaft support member fixed to both

sides near the movement elongated hole of left and right sides with respect to

the guide box; an operation shaft that passes through the movement elongated

hole of the guide box, wherein both ends of the same are rotatably installed at

the shaft support member through the movement elongated hole of the guide

box; a stopper that is installed in the interior of the guide box in a state that it is

fixed to the operation shaft; a pair of roller support members fixed to both sides

of the main operation member; and a guide roller that is rotatably installed at the

roller support member and supports a protruded guide rail at both lower sides of

the upper plate in parallel and rolls along the guide rail as the main operation

member is moved.

In the stopper of the backrest moving unit, a moving roller is rotatably

installed in the operation shaft in a roller installation hole and forwardly and

backwardly moves along a moving path formed at a lower center portion of the guide box, and backward and forward movement prevention driving gears are

installed at an upper surface of the forward side of the stopper and at a lower

surface of the backward side of the same in a slanted state for thereby stopping

the stopper.

The backward and forward movement prevention fixing gears engaged

with the backward and forward movement prevention driving gears formed in

the stopper are formed in the upper and lower surface of the inner side of the

guide box for thereby stopping the stopper.

A rotary shaft is installed at a portion higher than the seat as a lower

side of the backrest frame wherein both ends of the same are rotatable with

respect to the backrest frame; and a detection lower backrest is provided

separately from the backrest in the rotary shaft that is rotated in a state that it is

protruded in the direction of the seat in the case that the user is not sited on the

chair or a certain space is formed between the user's hip portion and the

backrest, and when the user sits on the chair, the backrest frame is moved in

the forward direction, so that the backrest first contacts with the user's hip

portion before the backrest contacts with the back portion of the user for thereby

being rotated as if it is pushed in the backward direction, thus rotating the rotary

shaft; and a stopper operation wire connects an end of one side of the rotary

shaft and one end of the operation shaft of the main operation member and

transfers a rotational force when the rotary shaft is rotated, so that the stopper

performs a movement prevention operation and movement release operation. A rotary shaft is installed at a portion higher than the seat as a lower

side of the backrest frame wherein both ends of the same are rotatable with

respect to the backrest frame; and a detection lower backrest is provided

chair or a certain space is formed between the user's hip portion and the

backrest, and when the user sits on the chair, the backrest frame is moved in

the forward direction, so that the backrest first contacts with the user's hip

shaft; and a hydraulic pressure control wire connects an end of , one side of the

rotary shaft and a hydraulic pressure control valve installed in the hydraulic

pressure line for thereby opening and closing the hydraulic pressure control

valve.

Brief Description of Drawings

The present invention will become better understood with reference to

the accompanying drawings which are given only by way of illustration and thus

are not limitative of the present invention, wherein;

Figures 1 and 2 are views illustrating a front and lateral side of a chair

according to the present invention;

Figure 3 is a cross sectional view taken along line A-A of Figure 1 ; Figure 4 is a partially separated perspective view illustrating a major part

for describing the present invention;

Figure 5 is a plane view illustrating an arrangement state of elements

provided in an intermediate plate frame by separating a seat and an upper plate

frame and a connection state with a backrest frame for describing the present

invention;

Figure 6 is a cross sectional view taken along line B-B of Figure 3;

Figures 7 through 9 are cross sectional views of an operation state of a

backrest according to the present invention, of which:

Figure 7 is a view illustrating a state before a user sits on a chair;

Figure 8 is a view illustrating a state that a backrest frame is moved

when a user sits on a chair; and

Figure 9 is a view illustrating an operation state of a lower backrest for a

control when a backrest framer is moved; and

Figure 10 is a cross sectional view illustrating a chair according to

another embodiment of the present invention.

Best Mode for Carrying Out the Invention

The preferred embodiment of the present invention will be described

with reference to the accompanying drawings.

Figures 1 and 2 are views illustrating a front and lateral side of a chair

according to the present invention; Figure 3 is a cross sectional view taken along line A-A of Figure 1 ; Figure 4 is a partially separated perspective view

illustrating a major part for describing the present invention; Figure 5 is a plane

view illustrating an arrangement state of elements provided in an intermediate

plate frame by separating a seat and an upper plate frame and a connection

state with a backrest frame for describing the present invention; Figure 6 is a

cross sectional view taken along line B-B of Figure 3; Figures 7 through 9 are

cross sectional views of an operation state of a backrest according to the

present invention, of which Figure 7 is a view illustrating a state before a user

sits on a chair; Figure 8 is a view illustrating a state that a backrest frame is

moved when a user sits on a chair; and Figure 9 is a view illustrating an

operation state of a lower backrest for a control when a backrest framer is

moved; and Figure 10 is a cross sectional view illustrating a chair according to

another embodiment of the present invention.

In the drawing, reference numeral 1 represents a chair. The chair 1

includes a seat 11 on which a user sits, a backrest 12 for supporting a user's

back, and support legs 13 for supporting the seat. The support legs 13 include a

height-adjusting cylinder and wheels supported by the floor. As shown in Figure

2, an armrest is provided at both sides of the seat 11.

The seat 11 of the chair 1 is designed in order for the user to comfortably

sit thereon like a conventional chair. The support legs 13 are capable of

adjusting the height of the chair line a conventional chair and have wheels by

which the chair is movable in a state that a user sits on the chair. In the present invention, there is provided a backrest frame 3 between

the seat 11 and the support legs 13. A backrest 12 is attached to a backrest

frame 3 using an upper plate 2a, an intermediate plate 2b and a lower plate 2c

that are installed at a certain interval in the upper and lower directions. Even

when a user sits on a chair in a state that his hip portion is not closely contacted

with a backrest, the backrest 12 is automatically forwardly moved until it

contacts with a user's back without an additional operation. In addition, in the

case that the user tilts his upper body without moving his hip portion in a state

that the user sits on a chair without an additional operation, the backrest 12 is

not moved. When the user gets up from the seat 11, the backrest 12 is

automatically backwardly moved and is returned to its original position.

The constructions of each element for implementing the above operation

will be described.

A hydraulic pressure-applying unit 4 is installed between the intermediate

plate 2b and the lower plate 2c. Here, in the hydraulic pressure-applying unit 4,

a cylinder body is attached to a lower side of the intermediate piate 2b, and a

front end of a piston rod is formed of a hydraulic pressure-applying cylinder 41

attached to an upper surface of the lower plate 2c. The hydraulic pressure-

applying cylinder outputs a hydraulic pressure through a hydraulic pressure line

42 based on a weight of a user (more than 15kg) and performs a compression

operation when the user sits on the seat 11 as a hydraulic pressure is filled

thereinto. In addition, when the user gets up from the seat 11 and the weight applied to the hydraulic pressure-applying cylinder is removed, the hydraulic

pressure discharged during the compression is sucked, and it is returned to its

original state. The fluid filled in the hydraulic pressure-applying cylinder 41 may

be selected between oil or gas or a combination of oil and gas.

In addition, a return spring 43 is elastically installed in the interior of the

cylinder body for thereby achieving a faster compression and returning

operation of the hydraulic pressure-applying cylinder 41. The hydraulic pressure

line 42 is provided to transfer the hydraulic pressure discharged when the

hydraulic pressure-applying cylinder 41 performs a compression operation to a

reciprocation cylinder 52 of a transfer unit 5. A hydraulic pressure control valve

45 is installed in the hydraulic pressure line 42 for controlling the flow of

hydraulic pressure by opening and closing the pressure adjusting valve 44 and

the hydraulic pressure line 42.

The hydraulic pressure control valve 45 is basically provided to open and

close the hydraulic pressure line 42. It may have a mechanical structure like a

ball valve or an electrical structure such as a solenoid valve.

In addition, the intermediate plate 2b and the lower plate 2c are

supported by upper and lower support pipes 47a and 47b having a spring 46

therein. Here, the upper end of the upper support pipe 47a is attached to a

lower side of the intermediate plate 2b, and the lower side of the same

surrounds the lower support pipe 47b attached to an upper surface of the lower

plate 2c. It is elastically operated in the upper and lower directions by the spring 46. The upper and lower support pipes 47a and 47b elastically support the

intermediate plate 2b together with the hydraulic pressure-applying cylinder 41.

A backrest-moving unit 5 is installed between the upper plate 2a and the

intermediate plate 2b.

The backrest-moving unit 5 includes a guide box 51 fixed in a straight

line shape in the forward and backward directions from the center of the

intermediate plate 2b, a reciprocation cylinder 52 that is installed in an inner

side of the guide box for reciprocating a piston rod (forward^' and backward

movements), and a main operation member 53 that is horizontally formed in

such a manner that a movement elongated hole 511 formed in the forward

direction from the left and right intermediate portions of the guide box 51 passes

through therein, wherein it is connected with a front end of the piston rod of the

reciprocation cylinder and reciprocates within a set range of the movement

elongated hole 511.

In addition, a shaft support member 531 is installed near the movement

elongated hole 511 with respect to the guide box 51 , respectively, in the main

operation member 53. A pair of roller support members 532 are fixed at a

portion distanced from the movement elongated hole 511 of both sides. The

both ends of the operation shaft 54 are connected with the shaft support

member 531 by nuts wherein the operation shaft 54 is horizontallv installed and

passes through the movement elongated hole 511. A guide roller 55 is rotatably

installed in the roller support members 532 provided in pair. The guide rollers 55 of both sides are moved along a guide rail 21 protruded from the lower side of

the upper plate 2a in parallel.

A stopper 56 is installed at an intermediate portion of the operation shaft

54 positioned in the interior of the guide box 51 and rotates together with the

operation shaft 54. A movement roller 562 rotatably installed in the operation

shaft 54 is installed in a roller installation hole 561 passing through the stopper

56. The movement roller is forwardly and backwardly movable along a

movement path 512 formed in the lower surface of the guide box 51 in the

forward direction in a shape of groove.

In addition, a tooth-shaped fixing gear 513 for a backward movement

prevention control and a tooth-shaped fixing gear 514 for a forward movement

prevention control are formed on the upper and lower surfaces of the guide box

51. A driving gear 563 for a backward movement prevention control and a

driving gear 564 for a forward movement prevention control are provided on the

forward upper surface and backward lower surface of the stopper 56 and are

engaged and disengaged with the fixing gear 513 for the backward movement

prevention control and the fixing gear 514 for the forward movement prevention

control. Here, the fixing gear and the driving gear are disengaged for thereby

permitting the forward and backward movements of the stopper when the

stopper 56 stops and moves in the horizontal state. When the stopper 56 is

rotated in the clockwise direction, the driving gears formed in the forward upper

surface and backward lower surface are engaged with the fixing gears formed on the upper and lower surfaces of the guide box 51. When the driving gear of

the stopper 56 is engaged with the fixing gear of the guide box, the stopper 56

cannot move forwardly and backwardly, namely, it is fixed. Therefore, the main

operation member 53 having the operation shaft 54 that supports the stopper 56

cannot move forwardly and backwardly. When the stopper 56 and the main

operation member 53 are stopped, the movement unit 5 is stopped.

A return spring 521 is elastically installed in the interior of the

reciprocation cylinder 52 for returning the piston to its original position.

In addition, an assistant operation member 6 that is moved together with

the main operation member is installed in the rear side of the main operation

member 53.

Here, the assistant operation member is installed in parallel with the main

operation member 53 at the height slightly higher than the height of the guide

box 51 in the rear side of the intermediate plate 2b. The support roller 62

rotatably attached to a bracket 61 fixed to both sides of the lower portion of the

assistant operation member 6 rolls in the forward and backward directions in a

state that it is supported by the support rail 63 fixed to the rear upper surface of

the intermediate plate 2b.

The upper plate 2a and the intermediate plate 2b are engaged in a state

that the upper and lower portions are fixed. A plurality of cylindrical spacers 57

are installed between the upper plate 2a and the intermediate plate 2b. Here,

the upper plate and the intermediate plate are fixedly engaged by engaging an engaging bolt 58 passing through the center of the space 57 using a nut. In

addition, a support member is installed on an upper surface of the guide box 51

installed on the upper surface of the intermediate plate 2b for supporting the

intermediate portion of the upper plate 2a. Therefore, it is possible to prevent

the upper plate 2a from being sunk by the weight of the user.

The backrest frame 3 will be described.

The upper side of the backrest frame 3 is upwardly protruded for thereby

supporting the back portions of the user sitting on the chair. The lower side of

the same is extended in the left and right sides of the chair 1 and is concurrently

connected with both sides of the main operation member 53 and the assistant

operation member 6 using an assembling member such as bolt, etc.

Therefore, as the main operation member 53 of the movement unit 5 is

forwardly and backwardly moved, the backrest frame 3 is moved together, and

the assistant operation member 6 is moved when the backrest frame 3 is

moved.

A detection lower backrest 7 is installed just below the backrest 12

formed in the backrest frame 3. It is installed at the portion slightly higher than

the upper surface of the rear side of the seat 11 and is installed in a rotary shaft

rotatably and horizontally installed in a lower side of the backrest frame 3. The

detection lower backrest 7 is rotatable together with the rotary shaft 71.

When the user does not use the chair, the detection lower backrest 7

maintains slanted forwardly. Namely, the rotary shaft 71 passes through the rear end of the lower side of the detection lower backrest 7 in a state that the

detection lower backrest 7 is more forwardly protruded as compared to the

backrest 12 (namely, in a state that the rotation operation is ready in the rear

direction as the detection lower backrest contacts with the hip portion of the

user when the backrest frame of forwardly moved when the user sits on the

chair). Therefore, when the user does not sit on the chair, the detection lower

backrest 7 is forwardly rotated by the self-weight with respect to the rotary shaft

71 as a rotation center and maintains a slanted state in such a manner that the

upper side of the detection lower backrest 7 is protruded in the forward direction.

A torsion spring 72 is installed at one end or both ends of the rotary shaft

71 for assisting an operation that the detection lower backrest 7 is tilted in the

forward direction when the user sits and gets up from the chair.

In addition, one end of the rotary shaft 71 and one end of the operation

sensor 541 installed in the operation shaft 51 of the backrest moving unit 5 are

connected by a stopper operation member 8a. In a state that the operation wire

541 is rotatably wound on one side of the operation shaft 54, ,one end of the

same is connected with a stopper operation wire 8a, and the other end of the

same is inserted into a hole formed in a front end of the stopper 56. Therefore,

when the stopper operation wire 8a pulls one end of the operation wire 8a, the

other end of the same rotates the stopper 56 in the clockwise direction. In

addition, the other end of the rotary shaft 71 and the hydraulic pressure control

valve 45 of the hydraulic pressure generation unit 4 are connected by the hydraulic pressure control wire 8b.

The stopper operation wire 8a and the hydraulic pressure control wire 8b

are formed of a wire cable that is easily bent and is not twisted for thereby well

transferring a pulling force. One end of the stopper operation wire 8a is

connected with a first protrusion 711 protruded from one end of the rotary shaft

71 , and the other end of the same is connected with one end of the operation

wire 541 rotatably wound on the operation shaft 54. One end of the hydraulic

pressure control wire 8b is connected with a second protrusion 712 formed at

the other end of the rotary shaft 71 , and the other end of the same is connected

with an opening and closing member of the hydraulic pressure control valve 45.

The hydraulic pressure control valve 45 may be formed- of any type of

valve capable of connecting or disconnecting the supply of the hydraulic

pressure from the hydraulic pressure-applying cylinder 41 to. the reciprocation

operation cylinder 52.

In the case of the stopper operation wire 8a, the rotary shaft 71 and the

operation wire 541 are connected in such a manner that the stopper operation

wire 8a is extended from one end of the rotary shaft 71 installed in the backrest

frame 3 through the guide hole formed in two guide members 713 and 714

attached to the upper surface of one side of the main operation member 53 of

the backrest moving unit 5 and is bent in a certain direction. In addition, the

hydraulic pressure control wire 8b is extended and bent between the end of the

rotary shaft 71 and the opening and closing member of the hydraulic pressure control valve 45 for thereby connecting the rotary shaft 71 and the opening and

closing member of the hydraulic pressure control valve 45.

Here, the operation member 541 is formed of a metallic wire and is

rotatable with respect to the operation shaft 54.

When the rotary shaft 71 is rotated, the operation wire 541 and the

hydraulic pressure control valve 45 are rotated. Namely, as the detection lower

backrest 7 is rotatably moved in the rear direction, when the rotary shaft 71 is

rotated in the clockwise direction, as shown in Figure 9, in the case of the

stopper operation wire 8a, the operation wire 541 of the backrest moving unit 5

rotates the stopper 56 in the clockwise direction, so that the backward and

forward movement prevention driving gears 563 and 564 of the stopper m56 are

engaged with the backward and forward movement prevention fixing gears 513

and 514. In the case of the hydraulic pressure control wire 8b, it opens and

closes the opening and closing member of the hydraulic pressure control valve

45.

In addition, the upper plate 2a, intermediate plate 2b and lower plate 2c

supporting the seat 11 of the chair 1 are covered with a protection casing in all

directions. The protection casing allows the upper plate and intermediate plate

to move upwardly and downwardly and supports the upper and lower plates. As

the user sits on the chair or gets up from the same, even when the upper plate

and intermediate plate are elastically compressed or recovered, the protection

casing always maintains a state of covering the upper, intermediate and lower plates.

The operation that the backrest is automatically adjusted as the user

uses the chair will be described.

Figures 3 and 7 are cross sectional views when the chair 1 is not used.

The detection lower backrest 7 installed below the backrest 12 is rotated in a

state that it is tilted in the forward direction with respect to the roiation shaft 71

by the self weight, and the upper end of the same is more protruded in the

forward direction as compared with the backrest 12. In addition; the lower side

of the same does not contact with the seat 11 with a certain distance. A rotation

control shaft 73 is installed in a lower side of the backrest frame 3 for controlling

an angle that the detection lower backrest 7 is rotated in the forward direction.

Therefore, the detection lower backrest 7 is moved without contacting with the

seat 11 when the backrest frame 3 is forwardly or backwardly moved.

Figure 8 is a cross sectional view of an operation state when a user uses

a chair according to the present invention. The user generally sits on a chair

with his hip portion being positioned at an intermediate portion of the seat 11,

not positioned at a rear end of the seat. When the user sits on the seat in the

above manner, the weight of the user is applied to the seat 11. At this time,

since the upper plate 2a and the intermediate plate 2b are fixed by the spacer

57 and the engaging bolt 58, even when the user sits on the seat 11 , the

distance between the upper plate 2a and the intermediate plate 2b is not

changed. Namely, since the intermediate plate 2b is supported by the hydraulic pressure-applying cylinder 41 and the upper and lower support pipes 47a and

47b that may be elastically compressed with respect to the lower plate 2c, the

hydraulic pressure-applying cylinder 41 and the upper support pipes 47a that

support the intermediate plate 2b are elastically compressed by the weight of

the user sitting on the seat 11. When the hydraulic pressure-applying cylinder

41 of the hydraulic pressure-applying unit 4 is elastically compressed, the

hydraulic pressure filled therein is discharged through the hydraulic pressure

line 42 and is supplied to the reciprocation operation cylinder 52 of the backrest

moving unit 5. The hydraulic pressure supplied to the reciprocation operation

cylinder 52 is higher than the elastic force of the return spring; 521 elastically

supporting the piston head, so that the piston rod of the reciprocation operation

cylinder 52 is forwardly moved in the forward direction of the chair, whereby the

main operation member 53 is forwardly moved. As the main operation member

53 is forwardly moved, the stopper 56 movably installed in the interior of the

guide box 51 is moved in the forward direction.

When the main operation member 53 of the backrest moving unit 5 is

moved in the forward direction, the backrest frame 3 is moved. At this time, the

backrest 12 and the detection lower backrest 7 are forwardly moved in the

direction of the user's back sitting on the seat 11. Since the detection lower

backrest 7 is protruded in a forwardly tilted state, when the backrest frame 3 is

forwardly moved, the detection lower backrest 7 first contacts with the user's hip

before the backrest 12 contacts with the user's back. The backrest frame 3 continuously forwardly moved from when the protruded portion of the detection

lower backrest 7 contacts with the user's hip portion to when the rotation in the

backward direction is stopped. When the backrest 12 contacts with the user's

back and cannot move anymore, the detection lower backrest 7 completes the

rotation in the backward direction (clockwise direction). At the same time, the

rotary shaft 71 is rotated in the same direction of the detection lower backrest 7.

When the rotary shaft 71 is rotated, the stopper operation wire 8a and the

hydraulic pressure control wire 8b connected with both ends of the same are

operated for thereby stopping the backrest frame 3. The above operation will be

described in more detail with reference to Figure 9.

As shown in Figure 9, the backrest 12 is forwardly moved until it contacts

with the back of the user sitting on the seat, and its forward movement is

stopped. The detection lower backrest 7 is rotated in the backward direction

with respect to the rotary shaft 71. When the detection lower backrest 7 is

rotated in the backward direction, the rotary shaft 71 is rotated. Therefore, the

first protrusion 711 formed at one end of the rotary shaft 71 pulls the stopper

operation wire 8a, and the operation wire 541 installed in the operation shaft 54

of the backrest moving unit 5 is rotated in the clockwise direction, and the

stopper 56 is rotated in the same direction. The backward movement and

forward movement driving gears 563 provided in the upper surface of the

forward side and lower surface of the backward side of the stopper are engaged

with the backward and forward movement prevention fixing gears 513 and 514 formed on the upper and lower surfaces of the guide box 51. When the forward

and backward driving gears of the stopper 56 are engaged with the upper and

lower side fixing gears of the guide box 51 , the backrest frame 3 is not moved in

the forward and backward directions. At this time, the backrest 12 is supported

by the user's back. The detection lower backrest 7 is fully rotated in the

backward direction, and the backrest 12 is contacted with the user's back, and

the detection lower backrest 7 is closely contacted with the user's hip portion.

Therefore, the user can sit on the chair 1 in a leaned state to the backrest 12.

The first protrusion 711 of one end of the rotary shaft 71. pulls the stopper

operation wire 8a, and the second protrusion 712 of the other end of the rotary

shaft 71 pulls the hydraulic pressure control wire 8b. The hydraulic pressure

control wire 8b changes the opened state to the closed state of the hydraulic

pressure control valve 45 by a pulling operation of the second protrusion 712.

When the hydraulic pressure control valve 45 is changed to the closed state,

and the hydraulic pressure line 42 is closed, the supply and collecting

operations of the hydraulic pressure to the hydraulic pressure-applying cylinder

41 and the reciprocation operation cylinder 52 are stopped. At this time, since

the hydraulic pressure supplied to the reciprocation operation cylinder 52 is not

moved in the direction of the hydraulic pressure-applying cylinder 41, the main

operation member 53 is forwardly moved by a certain distance and then stops.

As the hydraulic pressure control wire 8b closes the hydraulic pressure

control valve 45, the main operation member 53 of the backrest moving unit 5 is forwardly moved and stops. Therefore, the backrest frame 3 stops in a state that

the backrest 12 is closely contacted with the back of the user sitting on the seat

11.

In the above structure, two stopper operation wire 8a and hydraulic

pressure control wire 8b are connected with both ends of the rotary shaft 71 of

the detection lower backrest 7. The stopper 56 and the hydraulic pressure

control valve 45 are concurrently operated, so that the backrest 12 stops in a

state that it is closely contacted with the user's back. Even when one of two

wires 8a and 8b is selected and installed in the rotary shaft 71 , the backrest 12

is closely contacted with the back of the user sitting in the seat 11 and is

stopped. Therefore, the user can sit on the chair in a state that the user's back

is leaned to the backrest 12.

When the user sits in the above manner, the backrest 12 is moved and

stops in a state that it is closely contacted with the user's back In the above

state, the user sits on the chair in an upright posture. Even when the user

backwardly tilts his upper body in a state that he leaned to the backrest 12,

sitting on the chair in an upright posture, the backrest frame 3 is not backwardly

moved. Therefore, the user can safely lean to the backrest 12. Even when the

user tilts his upper body forwardly without moving his hip portion, the backrest

frame 3 is not forwardly moved. In the above state, when the user tilts his upper

body in a state that he sits on a chair in an upright posture and returns to the

original position, the user can lean to the backrest 12 in an upright posture. When the user gets up from the seat 11 of the chair 1 , the weight of the

user applied to the seat 11 disappears, and at the same time the force applied

to support the detection lower backrest 7 is removed, so that the backrest 12 is

returned to the original state, namely, the non-use state. The above operation

will be described in detail. First, the detection lower backrest 7 is rotated in the

forward direction (counterclockwise direction) with respect to the rotary shaft 71

based on the elastic recovery force and self-weight of the torsion spring 72.

When the detection lower backrest 7 is rotated in the forward direction (refer to

Figure 3), the rotary shaft 71 is rotated together. Therefore, the stopper

operation wire 8a and the hydraulic pressure control wire 8b connected with

both ends of the rotary shaft 71 operate the operation wire 541 and the

hydraulic pressure control valve 45 in the manner reverse to the earlier

described manner. Namely, the stopper operation wire 8a rotates the operation

wire 541 in the counterclockwise direction, and the driving gears 563 and 564 of

the stopper 56 are released from the upper and lower side fixing gears 513 and

514 of the guide box 51. The hydraulic pressure control wire 8b changes the

closed state to the opened state of the hydraulic control valve 45. The hydraulic

pressure line 42 connecting the hydraulic pressure-applying cylinder 41 and the

reciprocation operation cylinder 52 is opened, and the hydraulic pressure

supplied to the reciprocation operation cylinder 52 is collected by the hydraulic

pressure-applying cylinder 41.

When the user gets up from the chair, in the hydraulic pressure-applying cylinder 41 elastically compressed by the weight of the user and the upper

support pipes 47a, the intermediate plate 2b and the upper plate 2a are fast

returned to the original state by the elastic recovery force of the spring. At this

time, a certain suction force is generated in the interior of the hydraulic

pressure-applying cylinder returned to the original state the elastic recovering

force of the return spring 43 elastically compressed in the interior of the

hydraulic pressure-applying cylinder 41 for thereby sucking the hydraulic

pressure supplied to the reciprocation operation cylinder 52 through the

hydraulic pressure line 42. In addition, the piston rod is moved into the interior

of the cylinder by the elastic recovering force of the return spring 43 elastically

compressed in the interior of the reciprocation operation cylinder 52 for thereby

pushing the hydraulic pressure, so that the main operation member 53 is moved

in the backward direction of the chair. Therefore, the backrest frame 3 is

backwardly moved, and the backrest 12 is fully moved in the backward direction

of the seat 11 and standbys for the next forward movement.

Figure 10 is a cross sectional view of another embodiment of the present

invention. In this embodiment, there is provided an assistant hydraulic pressure

applying cylinder 9 capable of pressurizing and operating the piεton rod of the

hydraulic pressure-applying cylinder 41 of the hydraulic pressure-applying

cylinder 4 for allowing the backrest 12 to move in the forward direction in

maximum for thereby supporting the user's back when the user sits at a front

side of the seat 11. The above assistant hydraulic pressure-applying unit 9 includes an

assistant support shaft 91 fixedly installed at a front side of the upper surface of

the lower plate 2c, and a seesaw operation member (front side in the drawing)

is connected to a lower surface of the intermediate plate 2b, and the other end

(rear end in the drawing) is connected to the piston rod of the hydraulic

pressure-applying cylinder 41.

In addition, in the above embodiment of the present invention, the piston

rod of the hydraulic pressure-applying cylinder 41 may not be fixed to the lower

plate 2c, but may be movable in the direction of the cylinder body.

Therefore, when the user sits at a front side of the seat 11 , the weight of

the user is intensively applied at the front side of the chair. In this case, the

upper plate 2a and the intermediate plate 2b are supported by a plurality of

spacers 57 and are engaged with the engaging bolt 58. Since the intermediate

plate 2b and the lower plate 2c are supported by the upper and lower support

plates 47a and 47b in which the spring 46 is elastically installed, the

intermediate plate 2b is not horizontally compressed, but compressed in a

forwardly tilted state. At this time, the front end of the seesaw operation member

92 connected to the lower side of the intermediate plate 2b is downwardly

moved with respect to the upper end of the assistant support shaft 91, and the

rear end of the same raises the piston rod of the hydraulic pressure-applying

cylinder 41. As a result, the seesaw operation member 92 elastically supports

the front side of the intermediate plate 2b based on a repulsive force caused as the piston rod of the hydraulic pressure-applying cylinder 41 is raised and

compressed, so that an over tilting of the intermediate plate 2b js prevented. In

addition, the seesaw operation member 92 further compresses the hydraulic

pressure of the hydraulic pressure-applying cylinder 41. The hydraulic pressure

of the hydraulic pressure-applying cylinder 41 is achieved based on the weight

of the user and the compression operation of the seesaw operation member 91.

The hydraulic pressure applied to the reciprocation operation cylinder 52 is

increased. The backrest frame 3 is forwardly moved in maximum for thereby

effectively supporting the back of the user sitting at the front side of the seat.

In addition, the front end of the seesaw operation member 92 of the

assistant hydraulic pressure-applying unit 9 is divided into two parts that are

widened in the left and right directions for thereby stably supporting the both

sides of the lower side of the intermediate plate 2b.

Industrial Applicability

As described above, in the present invention, when the backrest

according to the present invention is adapted to all chairs, even when the user

sits at an intermediate portion of the seat, the backrest is automatically moved

in the forward direction for thereby supporting the user's back. Therefore, the

user can naturally sit on the chair in the upright posture. In the present invention,

even when the user sits at a certain portion of the seat of the chair, the user can

always sit on the seat in the upright posture in a state that the user leans to the backrest. Therefore, the user can study or work for long time, sitting on the chair,

for thereby protecting a user's backbone and helping a user's health. In

particular, when the chair according to the present invention is adapted to

children in growing age, young persons and adults as well as weak persons or

patients, it is possible to effectively protect the backbone of the users.

As the present invention may be embodied in several forms without

departing from the spirit or essential characteristics thereof, it should also be

understood that the above-described examples are not limited by any of the

details of the foregoing description, unless otherwise specified, but rather

should be construed broadly within its spirit and scope as defined in the

appended claims, and therefore all changes and modifications that fall within

the meets and bounds of the claims, or equivalences of such meets and bounds

are therefore intended to be embraced by the appended claims.

Claims

Claims:

1. In a chair having a seat, a backrest and support legs, a chair having an

automatically adjustable backrest for thereby preventing various backbone-

related diseases, comprising:

upper, intermediate and lower plates that are installed between the seat

and the support legs at a certain interval therebetween in upper and lower

directions;

a hydraulic pressure-applying means that is installed between the

intermediate plate and the lower plate in such a manner that an elastic

operation is achieved in the upper and lower directions, and includes a

hydraulic pressure-applying cylinder operating in such a manner that when a

user sits on a chair, the intermediate plate is elastically compressed by the

weight of the user, and a hydraulic pressure is applied to a reciprocation

operation cylinder installed between the upper plate and intermediate plate, and

when the user gets up from the seat, the compressed state of the intermediate

plate is recovered to its original state, so that the hydraulic pressure supplied to

the cylinder is collected;

a guide box that is installed between the upper plate and the

intermediate plate and is horizontally installed on an upper surface of the

intermediate plate in the forward and backward directions;

a backrest moving means including:

a reciprocation operation cylinder that is horizontally installed in the interior of the guide box, and the piston rod is appeared as the hydraulic

pressure is inputted when the hydraulic pressure is discharged from the

hydraulic pressure-applying cylinder of the hydraulic pressure,-applying means,

and when the hydraulic pressure-applying cylinder collects the hydraulic

pressure, the hydraulic pressure is discharged for thereby disappearing the

piston rod; and

a main operation member that is horizontally installed and

passes through a movement elongated hole formed at both sides of the guide

box in a direction perpendicular to the guide box and is connected with a front

end of the piston rod of the reciprocation operation cylinder and is forwardly and

backwardly moved within a moving range of the movement elongated hole of

the guide box based on the forward and backward movements of the piston rod;

a backrest frame that is connected with both ends of the main operation

member of the backrest moving means and is forwardly and backwardly moved

together with the main operation member; and

an assistant operation member that is movably installed at a rear side

between the upper plate and the intermediate plate and is forwardly and

backwardly moved together with the backrest frame in a state that both ends of

the same are connected with the backrest frame.

2. The chair of claim 1 , wherein in said hydraulic pressure-applying means,

a certain fluid selected between oil or gas is injected into the hydraulic pressure- applying cylinder, and the hydraulic pressure-applying cylinder is connected in

such a manner that a hydraulic pressure is supplied to the reciprocation

operation cylinder of the backrest moving means through the hydraulic pressure

line and is collected, and a hydraulic pressure control valve is connected with

the hydraulic pressure line for controlling the flow of hydraulic pressure by

opening and closing the pressure adjusting valve capable of adjusting the

discharge amount of the hydraulic pressure and the hydraulic pressure line.

3. The chair of claim 1 , wherein said backrest moving means includes:

a shaft support member fixed to both sides near the movement

elongated hole of left and right sides with respect to the guide box;

an operation shaft that passes through the movement elongated hole of

the guide box, wherein both ends of the same are rotatably installed at the shaft

support member through the movement elongated hole of the guide box;

a stopper that is installed in the interior of the guide box in a state that it

is fixed to the operation shaft;

a pair of roller support members fixed to both sides of the main

operation member; and

a guide roller that is rotatably installed at the roller support member and

supports a protruded guide rail at both lower sides of the upper plate in parallel

and rolls along the guide rail as the main operation member is moved.

4. The chair of either claim 1 or claim 3, wherein in said stopper of the

backrest moving means, a moving roller is rotatably installed in the operation

shaft in a roller installation hole and forwardly and backwardly moves along a

moving path formed at a lower center portion of the guide box, and backward

and forward movement prevention driving gears are installed at an upper

surface of the forward side of the stopper and at a lower surface of the

backward side of the same in a slanted state for thereby stopping the stopper.

5. The chair of one selected among claim 1 , 3 or 4, wherein backward and

forward movement prevention fixing gears engaged with the backward and

forward movement prevention driving gears formed in the stopper are formed in

the upper and lower surface of the inner side of the guide box for thereby

stopping the stopper.

6. The chair of claim 1, wherein a rotary shaft is installed at a portion

higher than the seat as a lower side of the backrest frame wherein both ends of

the same are rotatable with respect to the backrest frame; and a detection lower

backrest is provided separately from the backrest in the rotary shaft that is

rotated in a state that it is protruded in the direction of the seat in the case that

the user is not sited on the chair or a certain space is formed between the

user's hip portion and the backrest, and when the user sits on the chair, the

backrest frame is moved in the forward direction, so that the backrest first contacts with the user's hip portion before the backrest contacts with the back

portion of the user for thereby being rotated as if it is pushed in the backward

direction, thus rotating the rotary shaft; and a stopper operation wire connects

an end of one side of the rotary shaft and one end of the operation shaft of the

main operation member and transfers a rotational force when the rotary shaft is

rotated, so that the stopper performs a movement prevention operation and

movement release operation.

7. The chair of claim 1, wherein a rotary shaft is installed at a portion

higher than the seat as a lower side of the backrest frame wherein both ends of

backrest is provided separately from the backrest in the rotary shaft that is

the user is not sited on the chair or a certain space is formed between the

user's hip portion and the backrest, and when the user sits on the chair, the

backrest frame is moved in the forward direction, so that the backrest first

contacts with the user's hip portion before the backrest contacts with the back

direction, thus rotating the rotary shaft; and a hydraulic pressure control wire

connects an end of one side of the rotary shaft and a hydraulic pressure control

valve installed in the hydraulic pressure line for thereby opening and closing the

hydraulic pressure control valve.

8. The chair of claim 1, further comprising an assistant support shaft

vertically fixed to an upper surface of the lower plate, and an assistant hydraulic

pressure applying means that is provided between the intermediate plate and

the lower plate and includes a seesaw operation member being rotatably

attached to an upper end of the assistant support shaft wherein a front end of

the same is connected with a lower surface of the front side of the intermediate

plate, and the rear end of the same is connected with a piston rod of the

hydraulic pressure applying cylinder.