KR20100120438A - Backrest rotating and lifting apparatus and chair using the same - Google Patents

Abstract

PURPOSE: A backrest rotating and lifting apparatus, and a chair using thereof are provided to reduce material cost and guarantee the durability by dispersing the opposing power. CONSTITUTION: A backrest rotating and lifting apparatus and a chair using thereof comprise fixed support material(310L) and movable members(350L). The fixed support material comprises a first rotating support, and a first cylindrical body. In the first rotating support, the cylinder piercing hole is formed in the central part. In the first cylindrical body, a plurality of rotation elevation guide grooves having a plurality of helix lifting guide sides guiding the respective rotation elevation is formed in the peripheral part of the first rotating support into upstream. The movable member comprises a second cylindrical body and a second rotating support. In the second cylindrical body, a plurality of rotation elevation projections combined in a plurality of rotation elevation guide grooves to complementary is formed into downward. The second rotating support is inserted into the cylinder piercing hole by expanded from the central part of the cylindrical body to downward.

Description

Backrest rotating and lifting apparatus and chair using the same}

According to the present invention, a pair of backrests supporting the back of the seated seat may rotate to support the waist of the seated seat, thereby giving a massage effect to pull the waist, and the support force is distributed because of a plurality of grooves for the elevated seat. The present invention relates to a backrest lifting device having excellent durability and a chair using the same, even when using a material capable of injection molding.

People who work for a long time sitting in a chair feels pain in the lower back and neck because their back is bent and their neck is bowed forward, rather than their shoulders. In particular, if the sitting position of the seated person is incorrect, the degenerative change of the spine occurs, which causes the sprained disc herniation (椎間 板 脫出 症), which is commonly referred to as' Disk disease (Disk) (椎間 板 脫出 症) and muscles and stretched ligaments. In the case of a neck disc, pain or numbness occurs in the neck, shoulders, arms, and hands, and in the case of a waist disc, the pain in the lower back, buttocks (pelvis), legs, and feet occurs or becomes numb. And if the neck and lumbar disc is severe, the strength may be weakened.

In order for the seated person to sit on the chair in a correct position, a chair suitable for the body type must be selected. The seated chair should be seated in the chair in the correct position, with the hip of the seated seated deep behind the seat so that the back is supported by the backrest, and the shoulders bent backwards. The waist should be straight so that it becomes a normal full curvature posture so that your head does not lean forward. A normal full swing posture refers to a position that is slightly full with the waist slightly forward.

Many documents, such as US Pat. No. 7,040,703, Korean Patent Nos. 0499339 and 0526444, disclose chairs of various structures and shapes so that a person can sit in a comfortable position. Chairs of these documents disclose a height adjustment device that can adjust the height of the seat and an angle adjustment device that can adjust the angle of the backrest.

In addition, Korean Patent Nos. 0499339 and 0526444 disclose a technique for stably supporting a seated person's back by a pair of backrests arranged on left and right sides. Korean Patent No. 0499399 discloses a technology in which the left and right backrests of a seated person can only rotate left and right, and Korean Patent No. 0526444 discloses only a structure in which the backrest rotates with respect to a supporting load by a flexible elastic flow of a spring member. Doing.

On the other hand, Korean Patent No. 0766480 discloses a structure in which a pair of backrests can be adjusted to suit the body of the seated person through a rotary lifting movement.

Hereinafter, a conventional backrest structure will be described with reference to Korean Patent No. 0768480.

Referring to FIG. 1, the rotary lifting movement device 70 of the backrest proposed in Korean Patent No. 0768480 is mounted on the rear surfaces of the backrests 60 and 62 by the rotation of the rotating rods 72. And, the outer surface of the rotating rods 72 is formed with a spiral groove 72a along the longitudinal direction. The spiral groove 72a is formed of an inclined groove inclined along the longitudinal direction with respect to the central axis of the rotating rods 72.

The holders 74 are mounted on both sides of the front surface of the back plate 50 and hold the upper and lower ends of the rotating rods 72 to rotate. The guides 76 are mounted to protrude on the front surface of the back plate 50 and are fitted to the spiral grooves 72a of the rotating rods 72 to guide the rotating rods 72 to rotate and lift. In FIG. 1, the guides 76 are formed of a screw 78 that penetrates the back plate 50 and the holders 74 so that the tip thereof is fitted to the spiral groove 72a of the rotating rods 72.

That is, the rotation of the rotating rods 72 is guided by the guides 76 inserted into the spiral grooves 72a, and is raised at the same time as the rotating rods 72 are rotated by the guides of the guides 76. The backrests 60, 62 are rotated together and raised as shown by arrow "B" by the rotation and lift of the rotating rods 72. At this time, each of the backrest (60, 62) is rotated in the opposite direction with respect to each other because the inner end portion of the back end receives a force against the back of the seat, the backrest (60, 62) facing each other Rotate in the direction.

However, the above-described lifting device for rotation of the backrest has a problem in that the operation is not easy because the movement of the guide is moved along the groove of the spiral and the lifting of the backrest is not smooth.

In addition, only the position where the spiral groove is formed can be moved up and down and left and right rotation was not smooth adjustment of the height and left and right rotation of the backrest.

In addition, when the chair is used for a long time, the rotational lifting motion of the backrest should be repeated, resulting in a decrease in durability due to wear of the spiral groove and breakage of the guide.

Accordingly, it is an object of the present invention to provide a backrest lifting device and a chair using the same that can be made smoothly and easily ascending and rotating in the backrest of the backrest.

In addition, another object of the present invention is to include a synthetic resin material capable of injection molding without the use of a metal material is provided by having a plurality of lifting guide surface for inducing a rotary lifting at the time of the rotary lifting of the backrest is distributed without using a metal material The present invention provides a backrest revolving device and a chair using the same that can be manufactured by using the same.

Furthermore, another object of the present invention is to provide a backrest lifting device and a chair using the same that can maintain durability even if the backrest of the backrest is increased by increasing the contact area of the shaft coupling portion.

According to an aspect of the present invention for achieving the above object, it has a first rotating support having a cylindrical through-hole in the center and a plurality of spiral lifting guide surface for guiding the rotary lifting, respectively in the outer peripheral portion of the first rotating support A fixed support member having a first cylindrical body having a plurality of rotary lifting guide grooves formed in an upward direction; And a second cylindrical body having a plurality of rotating lifting protrusions coupled to the plurality of rotating lifting guide grooves in a complementary manner downwardly, and extending downward from a central portion of the cylindrical body to be inserted into the cylindrical through hole. It includes a movable member having a rotation support, the movable member provides a backrest lifting device, characterized in that when the rotational force is applied to the movable member in the direction of forming the lifting guide surface, the lifting member is rotated by the hinge shaft.

According to another aspect of the invention, the base frame is provided with a plurality of legs branched on the lower side; A seat plate fastened to an upper portion of the base frame to support a seated person; And a back support, one end of which is supported at a rear end of the base frame, at a distance between the front of the back support, a front end of which supports a pair of backs for supporting the user's back, the back support and the pair of Is coupled between the backrest and comprises a back plate portion consisting of a pair of backrest lifting device for rotating each of the backrest, the pair of backrest lifting device each of the first rotary support and the cylindrical through hole is formed in the center, and A fixed support member having a first cylindrical body which is formed in a plurality of rotation elevating guide grooves having a plurality of spiral elevating guide surfaces respectively guiding rotation elevating portions on an outer circumferential portion of the first rotary support and fixed to the backrest support; And a plurality of rotating lifting protrusions coupled to the plurality of rotating lifting guide grooves in a complementary manner in a downward direction, the second cylindrical body being fixed to the backrest, and extending downward from a central portion of the cylindrical body. It provides a chair comprising a movable member having a second rotary support inserted into the through hole.

And a release preventing member for limiting the lifting height of the movable member when the movable member is rotated up and down, and preventing it from being separated from the fixed support member. Fixed to the head, and the head of the lower end is made of a bolt set larger than the cylindrical through hole.

The fixed support member is supported by a fixed structure, that is, the backrest support, and the movable member is supported by the movable member, that is, the backrest.

A first flange portion extending from the first cylindrical body in the axial direction in a vertical direction and fixed to the backrest support; and a pair of second flange portions extending in the horizontal direction of the second cylindrical body and fixed to the backrest; do.

The plurality of rotary lifting guide grooves each include a lifting guide surface for guiding the rotary lifting of the movable member and a stopper surface for limiting the lowering position when the movable member is rotated, and the movable member rotates between the lifting guide surface and the stopper surface. The lower surface of the lifting projection further includes a seating surface is seated.

It is coupled to the back of the back support, and made of a guide groove having a guide rail that penetrates the back support further comprises a white supporter adjustable spacing of the backrest.

The fixed support member and the movable member are made of synthetic resin.

Accordingly, the present invention provides a plurality of rotary lifting guide grooves for inducing a linear movement (rising movement) simultaneously with the rotational movement of the movable member as a rotational force is applied between the fixed support member connected to the backrest support and the movable member connected to the backrest. Since the counter force acting between the fixed support member and the spiral elevating guide surface of the movable member is distributed to a plurality of rotary elevating guide grooves during the rotary elevating movement of the movable member, the rotary elevating operation of the movable member is easily and smoothly performed. According to the dispersion of the counter force, even if manufactured using the synthetic resin material can ensure the durability, and as a result can reduce the material cost.

In addition, when the seated person sits on a chair and leans on the backrest, the backrest is raised to comfortably support the back and waist of the seated person, as well as to pull the waist to give a massage effect along with the traction treatment effect.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2a is a perspective view showing a chair according to an embodiment of the present invention, Figure 2b is a rear view showing a chair according to an embodiment of the present invention, Figure 2c is an exploded perspective view showing a chair according to an embodiment of the present invention 2d is a partially enlarged view of a chair according to an embodiment of the present invention.

2a to 2c, the chair 1000 according to an embodiment of the present invention is a seat plate 100 having a plurality of rollers 110 in the center to support the thighs and buttocks of the seated occupant, the amount of seated persons A pair of armrests (200a, 200b) having a height adjustment button 201 to support the arm and to adjust the height, a pair of backrests (302R, 302L) and the back support 301 for supporting the seat of the seat It includes a back plate 300, a head support 400 for supporting the head of the seated person, and a leg 500 for supporting the seat plate 100 with respect to the floor.

The pair of armrests 200a and 200b are provided with height adjustment buttons 201a and 201b, respectively, so that the heights of the armrests 200a and 200b can be adjusted according to the height of the seated person by pressing the height adjustment buttons 201a and 201b. Do.

The rear of the back support 301 is coupled to the white supporter 410, the groove between the white supporter 410 and the back support 301 is inserted into the head connection portion 430 to move the head support 400 up and down Support as much as possible. Therefore, it is possible to comfortably support the head of the seated person by adjusting the height of the head restraint 400 to suit the head position of the seated person so as to be positioned at an appropriate position.

The base frame 600 has a lower leg 500 and a sliding rail 602 is provided on both sides thereof, and a pair of armrests 200a and 200b are slidably fixed to each other. In addition, one side of the base frame 600, the back support frame 601 is formed to protrude to the top is inserted into the coupling groove 303 of the back part 300 is coupled to.

Hereinafter, the supporting structure and the mutual coupling structure of the backrest revolving device according to the present invention will be described with reference to FIGS. 2C to 5.

A pair of fixing bolts 415L and 415R for fastening the pair of backrest lifting devices (see 304L and 304R in FIG. 2C) to the backrest support 301 are fastened to the left and right extensions of the white supporter 410. .

In addition, a pair of backrests 302L and 302R are fixed to the backrest support 301 by a pair of backrest lifting devices 304L and 304R.

That is, the right backrest lifting device 304R has one side fastened with the right backrest 302R and the other side fastened to the right side of the backrest support 301. In addition, the right back rotation lifting device (304R) is composed of the fixed support member 310R and the movable member 350R is fitted, the fixed support member 310R is fixed to the bolt 415R outside the white supporter 401 as described above ), The movable member 350R is coupled to the backrest 302R by having a fixing hole 351R on the left and right sides thereof.

On the other hand, the left back lifting device 304L is fastened to one side of the left backrest 302L and the other side is fastened to the left side of the backrest support (301).

Referring to the enlarged partial view of Figure 3, the left back rotary lifting device (304L) is a cylindrical lifting support guide 310L for providing a plurality of rotary lifting guide grooves during the rotary lifting and rotary lifting guide grooves during the rotary lifting It consists of a movable member (350L) moving along.

In this state of fastening, the backrest lifting devices 304L and 304R are supported by the backrest support 301 and the backrests 302L and 302R with both ends fixed, and a pair of backrests 302L and 302R are rotated. Make sure that it is in close contact with the seated person's back.

As shown in the partially enlarged view of FIGS. 2C and 2D, each of the backrests 302L and 302R is guided inside the guide grooves 305L and 305R to which the backrest lifting devices 304L and 304R are fastened according to the user's body shape. Left and right adjustable along the rail 306R, at this time, by loosening the pair of fixing bolts (415L, 415R) shown in Figure 2b by moving the backrest lifting device (304L, 304R) left and right each back ( Left and right movement adjustment of 302L, 302R is also possible. Here, the guide rails 306L and 306R inside the guide grooves 305L and 305R are connected through the back support 301 and the white supporter 401 to the guide grooves 305L and 305R of the back support 301. Inserted backrest lifting device (304L, 304R) is fixed by fixing bolts (415L, 415R) outside the white supporter (401).

Figure 3 is a side view showing a fastening state of the backrest lifting device according to an embodiment of the present invention.

3 is a side view of the pair of backrest lifting devices 304L and 304R fastened between the backrest support 301 and the pair of backrests 302L and 302R, showing the side of the left backrest lifting device 304L. .

The cylindrical fixed support member 310L and the movable member 350L are fitted to rotate and lift. The fixed support member 310L forms a first fixing hole 314L (see FIG. 4) and is fastened to the fixing bolt 415L through the back support 301 and the white supporter 410, and the eastern member 350L is Fastening bolts (not shown) are fastened to the backrest 302L through the fixing holes 351L.

In order to explain the structure of the backrest lift device, the backrest lift devices 304L and 304R will be described in more detail with reference to the following drawings.

Referring to Figures 4 and 5, the backrest lifting device (304L, 304R) is a fixed support member (310L, 310R) to support during rotational lifting and movable members (350L, 350R) to move during rotation lifting prevent separation The members 330L and 330R are sandwiched between the members 330L and 330R, and are configured to be rotatable up and down.

The backrest rotation lifting device 304L, 304R configured as described above supports a seated person's back by rotating as the seated person sits in a chair and the back member comes into contact with the backrest 302L while the movable member 350L is separated from the fixed support member 310L. Done.

Here, the fixed support members 310L and 310R have a first cylindrical body 317L and 317R and a first cylindrical body 317L and 317R having a pair of rotating lifting guide grooves 311L, 312L; 311R and 312R facing each other. The first flange support portion 313L, 313R having a through hole into the inner side of the slit, and the first flange portion 315L having a first fixing hole 314L, 314R extending on one side of the first cylindrical body 317L, 317R. , 315R). Each of the rotary lifting guide grooves 311L, 312L; 311R, 312R has a first stopper surface A and a first stopper surface for preventing the reverse rotation of the movable members 350L, 350R by more than a predetermined angle when the movable members 350L, 350R are lowered. It is composed of a first lifting guide surface (C) made of a spiral curve for rotating ascending and facing (A), and a first seating surface (B) for seating the movable members (350L, 350R). The first lifting guide surface C is formed to have a gentle inclination angle along the outer circumferential surfaces of the fixed support members 310L and 310R to guide the rotation lifting movement of the backrests 302L and 302R. That is, the first elevating guide surface (C) is formed spirally with respect to the central axis of the first cylindrical body (317L), so that when the seated person is pushed against the backrest (302L, 302R) against the backrest (302L, 302R) The backrests 302L and 302R are caused to rotate while being raised.

Here, the first lifting guide surface (C) is such that the backrest (302L, 302R) can be rotated up without a great force when the seated person is leaning against the backrest (302L, 302R) and pushed against the backrest (302L, 302R) Can be adjusted appropriately within the angle.

In addition, the first stopper surface A prevents the backrests 302L and 302R from rotating downward by a predetermined angle, and in particular, the inclination angle is set to prevent the backrests 302L and 302R from rotating toward the outside of the seated person. Preferably, the movable member 350L, 350R is stopped by the first stopper surface (A) and the first seating surface (B) the rotation lowering movement.

The movable members 350L and 350R are provided with rotating lifting projections 353L, 354L; 353R, 354R facing each other so as to complementarily engage with the rotary lifting guide grooves 311L, 312L; 311R, 312R of the fixed support member. It extends on both sides of the two cylindrical bodies 355L, 355R, the second cylindrical supports 352L, 352R having a hollow inside the second cylindrical bodies 355L, 355R, and the second cylindrical bodies 355L, 355R. It is composed of second flange portions 356L and 356R having a pair of second fixing holes 351L and 351R. Here, the outer diameter of the second rotary support (352L, 352R) is formed slightly smaller than the inner diameter of the first rotary support (313L, 313R) is set to prevent the rotational movement is disturbed.

The rotary lifting projections 353L and 354L; 353R and 354R have a second stopper surface a contacting each of the rotary lifting guide grooves 311L, 312L; 311R and 312R of the fixed support members 310L and 310R, and a second stopper. A second lifting guide surface (c) and a second seating surface (b) for rotating ascending and facing the surface (a) are provided.

The separation prevention members 330L and 330R may use bolts formed of polygonal heads 333L and 333R and threads formed with threads 331L and 331R on the outer circumference thereof, and the through holes of the second rotation support members 352L and 352R. Screwed together.

In addition, the heads 333L and 333R of the release preventing members 330L and 330R prevent the second rotating supports 352L and 352R from being separated upward from the first rotating supports 313L and 313R, and the second rotating supports. Depending on the degree of coupling to the (352L, 352R) serves to limit the rotational rise distance of the movable members (350L, 350R).

As described above, the fixed support members 310L and 310R are positioned below the movable members 350L and 350R, the fixed support members 310L and 310R are fixed, and the movable members 350L and 350R are rotated up and down. Although the present invention is not limited thereto, the fixed support members 310L and 310R are positioned on the movable members 350L and 350R, and the movable members 350L and 350R are fixed and the fixed support members 310L, 310R) may rotate up and down.

In addition, the fixed support members 310L and 310R are fixed to the backrest support 301, and the movable members 350L and 350R are shown to be fixed to the backrests 302L and 302R, but the present invention is limited thereto. Instead, the fixed support members 310L and 310R may be fixed to the backrests 302L and 302R, and the movable members 350L and 350R may be fixed to the backrest support 301.

The operation of the backrest lift device configured as described above will be described with reference to the following drawings.

6A, 6B, 7A, and 7B, the gentle inclination angles of the first lifting guide surface C and the second lifting guide surface c may be given a force that the seated person leans against the backrests 302L and 302R. At this time, the movable members 350L and 350R rotate up and down along the gentle inclination angles of the first lifting guide surface C and the second lifting guide surface c so that the backrests 302L and 302R rotate and rise within an appropriate angle. When the rotational increase continues, when the second rotation support members 352L and 352R reach the lower ends of the fixed support members 310L and 310R, the heads 333L and 333R of the separation prevention members 330L and 330R reach the lower surfaces. The upward motion is stopped (see Figs. 6B and 7B).

In addition, in the state where the rotation lifting is completed, if the seat occupant's leaning force on the backrests 302L and 302R disappears, the weight of the first lifting guide surface C and the second lifting guide surface c by the weight of the backrests 302L and 302R will be reduced. The movable members 350L and 350R rotate downward along the gentle inclination angle. At this time, since the first stopper surface A and the second stopper surface a are formed substantially vertically, the backrests 302L and 302R have a predetermined angle. Abnormal rotation lowering can be prevented, the first seating surface (B) and the second seating surface (b) abuts to stop the rotation lowering motion to return the backrest (302L, 302R) to its original position (Fig. 6a and 7a).

6A and 6B, when the seated person is seated on a chair and leans back to the backrests 302L and 302R, the left backrest lifting device 304L rotates to the right to the right (first screw direction). And second stopper surfaces A, a and first and second lifting guide surfaces C, c.

In addition, referring to FIGS. 7A and 7B, when the seated person is seated on a chair and leans back against the backrests 302L and 302R, the right backrest lifting device 304R is rotated upward to the left (left screw direction). The first and second stopper surfaces A, a and the first and second lifting guide surfaces C, c are the first and second stopper surfaces A, a and the first and second lifting surfaces of FIGS. 6A and 6B. It is arranged opposite to the guide surfaces C and c.

As such, when the seated person leans back to the backrests 302L and 302R, the backrests 302L and 302R wrap around and support the seated person's back to give a comfortable and comfortable feeling, and the backrests 302L and 302R face each other and rise in rotation. By supporting the seater's back and waist with a sense of stability, it can give a massage effect to pull back.

In addition, the backrest rotary lifting device (304L, 304R) of the present invention is provided with a plurality of rotary lifting guide grooves (311L, 312L; 311R, 312R), the fixed support member (310L, 310R) and the movable member during the rotary lifting movement The counter force acting on each other between the 350L and 350R is distributed to the plurality of rotary lifting guide grooves 311L and 312L; 311R and 312R, so that the rotatable movement of the movable members 350L and 350R is made easy and smooth. Depending on the dispersion, durability can be guaranteed even if manufactured using synthetic resin materials.

Furthermore, in the present invention, the shaft coupling portion between the fixed support members 310L and 310R and the movable members 350L and 350R, which are axially coupled, that is, the first rotary support and the second rotary support, and the first rotary support 313L, As the contact area between 313R and the rotary lifting projections 353L and 354L; 353R and 354R is increased, durability can be maintained even if the rotary lifting operations of the backrests 302L and 302R are repeated.

The chair of the present invention can be used in various fields such as office, medical, etc. as a chair that reinforces the comfort and comfort of the backrest, and is excellent in low cost and durable at mass production due to material cost reduction.

1 is a partial cross-sectional view for explaining a backrest lifting device in a conventional chair,

Figure 2a is a perspective view of a chair according to an embodiment of the present invention,

Figure 2b is a rear view showing a chair according to an embodiment of the present invention,

Figure 2c is an exploded perspective view showing a chair according to an embodiment of the present invention,

2d is a partially enlarged view of a chair according to an embodiment of the present invention;

Figure 3 is a side view of a part of the chair showing a fastening state of the backrest lifting device according to the invention,

Figure 4 is an exploded perspective view showing the left back lifting device according to the invention,

5 is an exploded perspective view showing a right back rotation lifting device according to the present invention,

6a and 6b is a perspective view showing the operating state of the left back lifting device;

7A and 7B are perspective views illustrating an operating state of the right back lifting device.

DESCRIPTION OF THE REFERENCE NUMERALS

100: seat 200: armrest

300: back 400: headrest

500: leg 110: roller

302L, 302R: Backrest 304L, 304R: Backrest lifting device

310L, 310R: Fixed support member 350L, 350R: Movable member

330L, 330R: Release prevention member

311L, 312L, 311R, 312R: Rotating lifting guide groove

353L, 354L, 353R, 354R: Rotating lifting projection

Claims (18)

A first cylindrical body having a first rotating support having a cylindrical through-hole in the center portion and a plurality of rotating lifting guide grooves having a plurality of spiral lifting guide grooves for guiding the rotating lifting respectively at the outer circumferential portion of the first rotating support. Fixed support member having a; And A second cylindrical body having a plurality of rotating lifting protrusions coupled to the plurality of rotating lifting guide grooves in a complementary manner in a downward direction, and a second rotation extending downward from a central portion of the cylindrical body and inserted into the cylindrical through hole; A movable member having a support, The movable member is a backrest lifting device, characterized in that when the rotating force is applied to the movable member in the direction of forming the lifting guide surface, the lifting member is rotated by the hinge shaft of the fixed support member. 2. The backrest lifting device according to claim 1, further comprising a release preventing member for limiting the lifting height of the movable member when the movable member rotates up and down, and at the same time preventing the departure from the fixed support member. . 3. The backrest lifting device of claim 2, wherein the detachment preventing member is formed of a bolt having a tip end fixed to a rotational support of the movable member, and a head of a lower end set larger than the cylindrical through hole. The backrest lifting device of claim 1, wherein the fixed support member is supported by a fixed structure, and the movable member is supported by a movable member. 2. The backrest lifting device according to claim 1, wherein the fixed support member is fixed to the backrest support, and the movable member is fixed to the backrest. According to claim 1, The first flange portion extending from the first cylindrical body in the axial direction in the vertical direction and fixed to the backrest support, A pair of first extending in the horizontal direction of the second cylindrical body fixed to the backrest Backrest lifting device characterized in that it further comprises a flange portion. According to claim 1, The plurality of rotary lifting guide grooves, respectively, the lifting guide surface for guiding the lifting and lowering of the movable member and a stopper surface for limiting the lowering position when the movable member is rotated down Device. 8. The backrest rotation elevating apparatus according to claim 7, further comprising a seating surface on which a lower end surface of the rotary lifting projection of the movable member is seated between the elevating guide surface and the stopper surface. The backrest lifting device according to claim 1, wherein the fixed support member and the movable member are made of synthetic resin. A base frame having a plurality of legs branched to the lower side; A seat plate fastened to an upper portion of the base frame to support a seated person; And One end of the back support is supported at the rear end of the base frame, the back support is disposed at intervals in front of the back support, a pair of back support for supporting the back of the user, the back support and the pair of backrest It is coupled between the backrest comprises a pair consisting of a pair of backrest lifting device for rotating lifting each of the backrest, The pair of backrest lifting devices are respectively A plurality of rotating lifting guide grooves having a first rotating support having a cylindrical through hole formed in a central portion thereof and a plurality of spiral lifting guide surfaces respectively guiding rotating lifting of an outer peripheral portion of the first rotating support are formed upwards. A fixed support member having a first cylindrical body fixed to the first support member; And A second cylindrical body which is coupled to the plurality of rotary lifting guide recesses in a complementary manner, is formed in a downward direction and is fixed to the backrest; and extends downward from a central portion of the cylindrical body to extend the cylindrical through hole. And a movable member having a second rotary support inserted into the chair. 11. The chair according to claim 10, further comprising a release preventing member for limiting the lifting height of the movable member when the movable member rotates up and down, and at the same time preventing the deviation from the fixed support member. 12. The chair according to claim 11, wherein the detachment preventing member is formed of a bolt having a tip end fixed to a rotational support of the movable member and a head of a lower end set larger than the cylindrical through hole. The chair of claim 10, wherein the fixed support member is fixed to the backrest support, and the movable member is fixed to the backrest. 11. The apparatus of claim 10, further comprising: a first flange portion extending from the first cylindrical body in the axial direction in the axial direction and fixed to the backrest support; and a pair of first extensions extending in the horizontal direction of the second cylindrical body and fixed to the backrest. The chair further comprises two flanges. The chair according to claim 10, wherein the plurality of rotary lifting guide recesses each include a lifting guide surface for guiding the lifting and lowering of the movable member and a stopper surface for limiting the lowering position when the movable member is rotated. The chair according to claim 15, further comprising a seating surface on which a lower end surface of the rotary lifting projection of the movable member is seated between the lifting guide surface and the stopper surface. 11. The chair of claim 10, further comprising a white supporter coupled to the back of the back support, the back support being made of a guide groove having a guide rail penetrating the back support. 11. The chair as claimed in claim 10, wherein the fixed support member and the movable member are made of synthetic resin.

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