KR102171790B1 - the height control system of chair and desk - Google Patents

Abstract

According to the present invention, a height controller for a desk and a chair is capable of reducing costs for component materials through a quick-coupler method in which a socket and a sleeve cap are integrated, and providing convenience in height control through the convenient rotation control of the sleeve cap, preventing the loss and damage of components and random control by locking the sleeve cap with a circular head hexagonal wrench bolt which is hard to control without a special tool, and providing convenience avoiding double-holding for sleeve control thanks to a compression means which is completely separated like the others. In particular, a lock ball, which is provided in a socket corresponding to a height control hole formed on both sides of an upper pole which is a height control target to reduce damage or scratches on upper and lower poles, has excellent deformation resistance in accordance with the tight and compressive provision of an upper protrusion of a sleeve cap, and concerns about noise from operation or an unclad upper pole can be eliminated and durability can be improved.

Description

The height control system of chair and desk}

The present invention relates to an apparatus for adjusting the height of a desk and a stool in which the support of the desk and the stool is separated vertically, and in detail, the upper column fixed to the left and right of the desk top plate or the stool seat plate, the lower column hollow fixed to the floor support in a T-shape In the method of adjusting the height by being inserted into the part, the part is simple and the height control is easy by the quick coupler method, but it is difficult for the students to arbitrarily control the height control device to prevent the loss of the height adjusting device parts. .

In general, in the book chairs for teaching aids used in elementary, middle, and high schools, a variety of height adjustment devices are provided.

However, if the chair is changed only in the new semester, the body shape is different and the height of the chair is arbitrarily adjusted.In the beginning, it is protruded by a bolt nut fastening method that penetrates and assembles from the top of the lower column to the upper column with a large number of adjustment holes. There were many safety accidents that resulted in injury to fasteners, loose fasteners due to loose fasteners, or damage to chairs and chairs due to loss of parts due to student's arbitrary manipulation.

In consideration of the above points, various types of height adjustment devices have been adopted for the recently distributed book chairs. Among them, the "Stool for Height Adjustment" of Korean Utility Model No. 20-0263910, the outer edge of the structural pipe corresponding to the upper column of the chair. Steel ball balls are moved back and forth within the ball holding ball due to the movement of the position of the tapered part that pushes the ball to the up and down movement of the cap by processing the ball fixing tool on the rolling part of the processed ball gripping jaw and the fixing support part for ball support, which is the lower support. A method has been proposed in which the ball support fixing support part is moved and fixed to the rolling part of the ball catching jaw.

However, the height adjustment device increases the processing cost of forming a plurality of ball jamming jaws on the outer periphery of the rolling part, which is the upper support, which is height-adjusted from the lower support, and there is no means of fixing the ball cap, so that several workers are required at the same time for each height adjustment device. There were concerns about inconvenience and easy damage to parts due to external arbitrary manipulation.

In addition, according to the Republic of Korea Patent Publication No. 10-2009-0121953 "Height adjustment device for a desk chair", in the height adjustment device for a book chair that is separated up and down by a lower support and an upper support, a plurality of locking grooves are provided inside the lower support, ,The upper support has a keyway and a key as a pivoting body that penetrates one side of the upper support and extends to the inside as a height adjustment means detachable to the hooking groove, and is coupled to the lower end of the rod that is raised and lowered by the pivoting body to be attached to and detached from the hooking groove. A sieve is included, and the locking body has an inclined portion contacting the guide portion spaced apart from each other at the lower end of the upper support, and a fastening end provided at the lower end of the inclined portion and detached from the locking groove by the lifting rod, and the locking body There is disclosed a method in which a pair of tanji balls is further provided to be detached from the locking groove.

However, the height adjustment device increases the cost of the adjustment device according to a number of configurations such as the additional burden of the inner pipe in which the locking groove is formed in the hollow of the lower support, the key groove and the key, the lifting rod and the locking body and the fastening end, and the tanji ball. , It is expected that the repair burden is large due to the loss of keys.

Another Republic of Korea Patent Registration No. 10-1358077 and an improved invention thereof discloses a "height control device for a desk chair" of Korean Patent No. 10-1862656.

In the basic invention of the disclosed height adjustment device, a first height adjustment hole is inserted into the upper outer periphery of the lower support member formed through the upper end and fixedly coupled, and a plurality of second heights at the end sliding into the hollow part of the lower support member An upper support member having multiple adjustment holes, and a bolt sequentially penetrating through the first and second height adjustment holes, a fastening nut and a protruding piece thereof are formed on the outer peripheral surfaces of both sides of the fixing member, and are slidingly coupled to the outer surface of the upper support member. By lowering the closing cap, a method of supporting the locking jaw inside the closing cap caught on the bottom of the fixing member has been disclosed.

However, in the basic invention, it is inconvenient by applying a predetermined force to remove the finishing cap from the locking jaw, loosening the bolt nut, aligning the first and second height adjustment holes, and adjusting the height. There is a problem that requires attention due to loosening of the bolt nut or loss of damage.

In the improved invention for this, the support member has a first locking protrusion formed on one side of the inner circumference so as to be coupled to the first fitting groove of the upper outer circumference of the lower support member, and a shake preventing part provided with a bolt hole on the reinforcing piece of the outer circumference of the rear side; The anti-shake part and the stepped jaw are divided into an integral part of the upper part with a coupling part formed with a second locking protrusion on one side, and one side is opened by force-fitting on the outer circumferential surface of the upper pipe in which a number of height adjustment holes are formed. A method of incorporating a fixture provided with a fixing pin on an inner circumferential surface, and then coupling a closing cap having a second coupling groove formed on one edge thereof to be coupled to the second locking projection of the fixture insertion portion is disclosed.

Even with the improved invention, when the second locking protrusion of the closing cap is pressed with a flat tool, it is easily separated and, contrary to the intention, the fixing tool frequently loses hands, and the fixing pin protrudes toward one side of the inner circumferential surface. On the other side, a new problem arises that a gap phenomenon occurs.

In the invention disclosed in the following Republic of Korea Patent Registration No. 10-1974490 "Desktop Leg Height Adjustment Device", the bookrest leg is a support member that is forcibly coupled to the upper outer circumferential surface of the lower leg that is divided into upper and lower parts, and the upper leg with a height adjustment hole, etc. A hollow ring-shaped sleeve fitted in the longitudinal direction at the periphery, and an elastic body corresponding to both sides of the sleeve, and in the elastic body, a hemispherical protrusion plate is bent in a'U' shape with a gap in the center direction of the sleeve. It is arranged spaced apart and fitted into the upper outer periphery of the support member, and the inner periphery of the support member has a screw-assembled adjustment member provided with a contact piece for compressing the sleeve elastic protrusion plate, and the height adjustment is performed in the height adjustment hole at the adjustment position. The fitted sleeve is a method of assembling the adjusting member to the supporting member so that the elastic protrusion plate is pressed with a close contact piece in the supporting member.

However, the fixing method of the support member and the lower leg has a weak coupling force due to the force-fitting method, so there is a high risk of separation when lifting the chair and moving it. Also, there is a slight gap in the center direction of both sides of the attached sleeve. The clearance with the left and right sleeves is large, and there is always a discomfort requiring attention to the protrusion from the height adjustment hole in the process where the contact plate of the adjustment member is inserted into the sleeve elastic body in the support member at the height adjustment point, and the upper and lower ends are'U' type. The inner wear of the adherend by the elastic body that is bent and spaced apart from it leads to a reduction in adherence, and there is no stopping means for the adjusting member, resulting in the inconvenience of having to double grip when operating the sleeve, and there is no external arbitrary operation prevention means.

[Document 1] KR 20-0263910 (Y1) 2002.01.29 [Document 2] KR 10-2009-0121953 (A) 2009.11.26 [Document 3] KR 10-1358077 (B1) 2014.01.22 [Document 4] KR 10-1862656 (B1) 2018.05.24 [Document 5] KR 10-1974490 (B1) 2019.04.25

The present invention is to solve the above problems, in the apparatus for adjusting the height of the stool according to the present invention, the upper posts fixed to the left and right of the desk top plate or the stool seat are inserted into a hollow portion of the lower post fixed in a T-shape to the floor support. Regarding the height adjustment method, a quick coupler method makes parts simple and easy to manipulate the height, but it is difficult for students to arbitrarily operate, and it relates to a height adjustment device for a chair and a chair to prevent loss of parts of the height adjustment device.

To this end, in the present invention, the upper post 10 fixed to the left and right of the desk top plate or the stool seat plate is inserted into the hollow part of the lower post 20 fixed in a T-shape to the floor support to adjust the height. The post 10 is formed with a plurality of height adjustment holes 10a at a predetermined height on both outer circumferential surfaces in the longitudinal direction, and a rectangular hooking groove 20a is formed at the upper outer periphery of the lower post 20, and the rectangular hooking groove ( A socket 310 that is assembled to correspond to the lower post 20 on which 20a) is formed; It is intended to provide a height adjustment device 30 including a sleeve cap 320 that is closely assembled in a shape corresponding to the outer periphery of the upper end of the socket 310,

The lower end of the socket 310 of the height adjustment device 30 has an upper side at right angles to the corresponding positions of the rectangular engaging grooves 20a, so that the lower end of the lower post 20 is forcibly fitted in a shape corresponding to the inner periphery, An inclined stepped step 310a having an inclined lower side is formed, and a lower strut upper limit 310b is provided on the inner periphery as a limit for force fitting, and a locking bolt tapped hole is provided under the outer step 310c at the front center of the lower end of the socket 310 (310d) is formed, a male screw part 310h is formed at the lower edge of the locking bolt tapped hole 310d, and the upper end of the socket 310 on the outer stepped 310c is formed on the inner circumferential surface. A hollow part is provided so as to be fitted in a corresponding shape to slide up and down, and a snap ring groove 310f is formed on the upper outer circumference of the socket 310, and both lower ends of the round outer circumferential surface adjacent to the snap ring groove 310f are less than the outer hole. It is configured to form a lock ball hole (310g) with an inner hole formed to embed the lock ball (310e),

The sleeve cap 320 has a bottom opening portion fitted from the upper end of the socket 310 to the outer periphery of the lower end, and the upper edge of the opening of the sleeve cap 320 of the standard in close contact with the outer periphery of the upper end of the socket 310 Is a slope having a certain depth and an inner diameter, and the bottom is formed with a sleeve cap upper stepped step 320a formed at a right angle to be blocked by the outer stepped step 310c of the socket 310, and the locking bolt tapped hole at the bottom of the socket 310 The sleeve cap 320 of the portion corresponding to (310d) has a locking bolt hole (320b) formed in the front portion, and has a round head-specific wrench bolt (320c), corresponding to the male screw portion (310h) at the bottom of the socket (310) The lower inner periphery of the sleeve cap 320 of the portion that is to be provided with a female screw portion (320e) is to provide a height adjustment device of the chair, characterized in that it is provided.

The height adjustment device of the chair according to the present invention is a quick coupler method in which the socket and the sleeve cap are assembled as an integral module, which reduces the cost of parts and materials, provides convenience of simple operation of the sleeve cap, and is difficult to operate without special tools. The sleeve cap is locked with a wrench bolt for each head to prevent arbitrary manipulation and loss of parts, and in particular, in order to reduce scratches or damage of the upper and lower braces, a lock ball provided in the socket corresponding to the height adjustment hole of the upper column to be adjusted It is to provide a height adjustment device with improved durability that provides excellent compression support and release structure of the upper step of the sleeve cap to eliminate concerns such as peeling off the cover of the upper support.

In addition, when the socket part assembled on the lower post and the upper post are fixed, the crimping means is completely separated like any other, so that it does not double grip when operating the sleeve, thereby providing loss of loss of parts or convenience of operation when adjusting the height.

1 to 2 are exemplary views of a book chair to which a height adjustment device for a book chair according to the present invention is applied.
3 to 4 are perspective and plan views of the adjusting device according to the present invention.
Figure 5 is an exploded perspective view of the adjusting device according to the present invention.
6 to 7 are cross-sectional views taken along lines A-A' and B-B' of FIG. 4;
Figure 8 is an exploded perspective view of the adjustment device including the upper and lower holdings of the chair according to the present invention.
Figure 9 is an excerpt of the front before and after the operation of the adjustment device including the upper and lower holders of the chair according to the present invention.
Figure 10 is a longitudinal sectional view of Figure 9;
Figure 11 is a side excerpt before and after the operation of the adjustment device including the upper and lower holdings of the chair according to the present invention.
12 is a longitudinal sectional view of FIG. 11;

Hereinafter, the adjustment device according to the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, in the method in which the upper posts fixed to the left and right of the desk top plate or the stool seat plate are inserted into the hollow portion of the lower post fixed in a T-shape to the floor support to adjust the height, the quick coupler method makes the parts simple and easy to operate. In addition, it relates to a height adjustment device for a chair and a stool that prevents the loss of parts of the height adjustment device because random manipulation is difficult for students.

In order to achieve the above object, as shown in Figs. 1 to 2, the height adjustment device of the book stool according to the exemplary view of the book stool to which the device for adjusting the height of the stool according to the present invention is applied is fixed to the left and right of the desk top or stool seat. In the height adjustment device (30) of a book chair to adjust the height of the lower post (20) is inserted into the hollow portion of the upper post (10) is fixed to the bottom support in a T-shape, the upper post (10) is a certain height on the outer circumferential surface A plurality of height adjustment holes (10a) are formed, and a rectangular engaging groove (20a) is formed in the upper outer periphery of the lower column (20).

Next, the height adjustment device 30 according to the present invention is largely composed of a socket 310 and a sleeve cap 320.

3 and 5 to 8, the lower end of the socket 310 is forcibly fitted in a shape corresponding to the lower post 20 to the inner periphery, and the upper side of the rectangular engaging groove 20a is at each corresponding position. An inclined stepped jaw 310a having a right angle and an inclined lower side is formed, and a lower support upper limit 310b is provided on the inner periphery as a limit for force fitting, and the lower side of the outer step 310c at the front center of the lower end of the socket 310 A locking bolt tapping hole 310d is formed, a male threaded portion 310h is formed at a lower edge of the locking bolt tapping hole 310d, and the upper end of the socket 310 on the outer stepped 310c is on the inner circumferential surface. 10) is fitted in a corresponding shape and provided with a hollow portion so as to slide up and down, and a snap ring groove 310f is formed on the upper outer circumference of the socket 310, and both lower ends of the round outer circumferential surface adjacent to the snap ring groove 310f are outer It is to form a lock ball hole 310g having an inner hole smaller than that of the hole to embed the lock ball 310e.

On the other hand, referring to FIGS. 3 and 5 to 8, the sleeve cap 320 has a bottom opening portion fitted from the upper end of the socket 310 to the outer periphery of the lower end, and the shape corresponding to the outer periphery of the upper end of the socket 310 The sleeve cap 320 of the standard close to the opening edge is a slope having a certain depth and an inner diameter, and the bottom is formed with a sleeve cap upper stepped step 320a formed at a right angle to the outer stepped step 310c of the socket 310 The sleeve cap 320 at a portion corresponding to the locking bolt tapping hole 310d at the bottom of the socket 310 is provided with a locking bolt hole 320b to form a round head wrench bolt 320c, and the A female threaded portion 320e is provided at the lower inner periphery of the sleeve cap 320 at a portion corresponding to the male threaded portion 310h at the lower end of the socket 310.

The height adjustment device 30 provided with the socket 310 and the sleeve cap 320 configured as described above as a single module includes the sleeve cap 320 at the upper end of the socket 310 and the bottom opening of the sleeve cap 320 inserted into the upper end of the socket 310, The snap ring of the upper end of the socket 310 protruding above the sleeve cap upper step 320a by rotating the sleeve cap 320 to the limit that the lower end of the sleeve cap upper step 320a is blocked by the outer step 310c of the socket 310 By fastening the snap ring 320d to the groove 310f, it is combined into one module.

In the above, the snap ring (320d) is a stainless steel material for a spring having a Rockswell hardness (HRC) of 44 to 52, and adopts a snap ring (320d) of 1.5 mm thick or 1.5 mm thick wire or plate, more preferably preventing arbitrary manipulation. In order to do so, it is to adopt a sheet-shaped snap ring (320d) close to the incision gap, which has good hardness and durability compared to the wire rod.

An example of adjusting the height of the chair according to the height adjusting device 30 of the present invention configured as described above will be described in detail through the accompanying drawings.

As shown in Figures 1 and 2, a height adjustment device 30 provided with a sleeve cap 320 and a socket 310 in one module on the lower support 20 of a desk or stool, each formed with a rectangular hanging groove 20a at the top When the socket 310 is inserted into the lower opening of the socket 310 and is poured to the lower columnar upper limit 310b at the limit of force fitting, the inclined stepped jaws 310a of the socket 310 are at respective corresponding positions of the rectangular engaging grooves 20a of the lower column 30 It is tightly bound and bound.

"으로 형성됨이 억지끼움 조립시 마모방지를 위해 바람직한 구성이다.In the above, the preferred shape of the inclined stepped step 310a of the socket 310 according to the present invention is that the boundary between the upper side of the right angle and the lower side of the slope is in the shape of a plane rather than a line.

Formed with "is a desirable configuration for preventing wear during assembly.

On the other hand, as an example of the height adjustment operation according to the height adjustment device 30 installed on the lower post 20 of the book chair, referring to the accompanying drawings 6 to 12 as follows.

The assembly of the upper column 10 of the height adjustment device 30 installed on the lower column 20 for adjusting the height of the chair is preferentially provided on the sleeve cap 320 of the height adjustment device 30 formed on the left and right sides of the book chair. It is necessary to release the constrained sleeve cap 320 by loosening the rounded head star wrench bolt 320c with a separate accessory, a star wrench (not shown).

The above round head wrench bolt (320c) is in the form of a round head after tightening the height adjustment, and cannot be operated with a hand, straight or cross screwdriver, and a separate wrench stored by a separate manager is used to avoid loss of parts of the height adjustment device. It was made useful to prevent.

In this way, even if the restraints of the sleeve caps 320 are released on the left and right sides of the shelf, the sleeve cap 320 has the protrusion of the upper end of the sleeve cap 320a formed on the upper frame in the snap ring groove 310f at the upper end of the socket 310. Since the lock ball 310e embedded in the adjacent lock ball hole 310g protrudes inward, which is the upper inner diameter of the socket 310 to maintain a compression support state, the upper post 10 is not inserted as it is.

Therefore, as shown in Figs. 9 to 12, when the sleeve cap 320 is rotated 2 to 3 pitches by screw rotation and moved downward to the outer step 310c of the socket 310 to the lower side of the maximum socket 310, the sleeve cap 320 ) While the inner hole of the lock ball hole 310g of the socket 310 is matched with the inner diameter space of the sleeve cap upper step 320a having a certain depth and slope formed on the upper edge of the opening, a certain spherical surface inside the inner diameter of the upper end of the socket 310 The protruding and compression-supported lock ball 310e is released from the compression toward the lock ball hole 310g of the outer portion having the same diameter.

Therefore, even if the upper column 10 is inserted or removed through the hollow portion of the upper end of the socket 310, the height adjustment is easy while the lock ball 310e is free from restraint, and phenomena such as noise or peeling of the upper column are not generated. Does not.

On the other hand, the operation of fixing the upper column 10 from the lower column 20 at the height desired by the user is the opposite operation to the position of the lock ball 310e of the upper rock ball hole 310g of the socket 310. , The upper column 10 is pulled up or down from the upper hollow portion of the socket 310 to a desired adjustment height, and at a position corresponding to the height adjustment hole 10a formed in the upper column 10, the lower portion of the socket 310 The sleeve cap 320 assembled with the male and female screw is rotated by 2 to 3 pitches of the screw, so that the upper step of the sleeve cap 320a makes the lock ball 310e of the lock ball hole 310g formed on both sides of the upper column 10 By pressing and supporting toward the control hole (10a), the upper column (10) was maintained in a fixed state in the upper hollow portion of the socket (310).

The present invention is quiet compared to the existing bolt or pin fastening type, and the parts are simple and convenient in a one-touch method.When a large impact is applied to the top or seat of a chair or an excessive weight is carried, it is common in the contact type of elastic protrusions on the hemispherical surface. The resulting elastic protrusion is more than locked in the height adjustment hole 10a by the deformation force of the elastic protrusion, so that the durability that does not lead to scratches or damage of the upper adjustment member of the height adjustment hole 10a of the upper post 10 is strong.

On the other hand, a supplementary description of the means by which the arbitrary operation of the students described above with respect to the height adjustment device 30 according to the present invention is provided is as follows.

After the height adjustment of the chair according to the present invention is completed, through the locking bolt hole 320b formed on the front of the sleeve cap 320 so that the sleeve cap 320 according to the present invention is not arbitrarily operated and maintains a constrained state, When the provided round head wrench bolt (320c) is inserted and firmly coupled through the locking bolt tapping hole (310d) at the corresponding position at the bottom of the socket 310, a hand or a straight or cross in the shape of the round head wrench bolt (320c) It prevents arbitrary manipulation in a state in which the sleeve cap 320 cannot be slid downward from the socket 310 because it cannot be operated with a driver, and prevents loss of parts of the height adjustment device by using only a separate wrench stored by a separate manager. It is a useful invention.

10: upper support 10a: height adjustment hole
20: lower support 20a: rectangular groove
30: height adjustment device
310: socket 310a: inclined stepped jaw
310b: upper limit of lower column 310c: external step
310d: locking bolt tapping hole 310e: locking ball
310f: Snap ring groove 310g: Lock ball hole
310h: Male thread
320: sleeve cap 320a: upper step chin of sleeve cap
320b: Locking bolt hole 320c: Round head wrench bolt
320d: snap ring 320e: female thread

Claims (4)

The upper post 10 fixed to the left and right of the desk top plate or the stool seat is inserted into the hollow part of the lower post 20 fixed in a T-shape to the floor support to adjust the height. The upper post 10 is A plurality of height adjustment holes (10a) are formed at a predetermined height on both outer circumferential surfaces in the longitudinal direction, and a rectangular engaging groove (20a) is formed at the upper end of the outer circumference of the lower column (20), and the lower part is formed with the rectangular engaging groove (20a). A socket 310 that is assembled to correspond to the holding 20; In the height adjustment device 30 including a sleeve cap 320 assembled in a shape corresponding to the outer periphery of the upper end of the socket 310,
The lower end of the socket 310 of the height adjustment device 30 is forcibly fitted to the inner circumference of the lower post 20 in a corresponding shape, and the upper side is perpendicular to each corresponding position of the rectangular engaging grooves 20a, and the lower side An inclined stepped step 310a, which is the slope, is formed, and a lower strut upper limit 310b is provided on the inner periphery as a limit of force fitting, and a locking bolt tapping hole is provided under the outer step 310c at the front center of the lower end of the socket 310. 310d) is formed, and a male screw part 310h is formed at the lower edge of the locking bolt tapped hole 310d, and the upper post 10 corresponds to the upper end of the socket 310 on the outer stepped 310c. A hollow part is provided so as to be inserted into a shape to slide up and down, and a snap ring groove 310f is formed at the upper outer circumference of the socket 310, and both lower ends of the round outer circumferential surface adjacent to the snap ring groove 310f are inside less than the outer hole. It is configured to form a rock ball hole (310g) with a hole formed to internally lock the ball (310e),
The sleeve cap 320 has a bottom opening portion fitted from the upper end of the socket 310 to the outer periphery of the lower end, and the upper edge of the opening of the sleeve cap 320 of the standard in close contact with the outer periphery of the upper end of the socket 310 Is a slope having a certain depth and an inner diameter, and the bottom is formed with a sleeve cap upper stepped step 320a formed at a right angle to be blocked by the outer stepped step 310c of the socket 310, and the locking bolt tapped hole at the bottom of the socket 310 The sleeve cap 320 of the portion corresponding to (310d) has a locking bolt hole (320b) formed in the front portion, and has a round head-specific wrench bolt (320c), corresponding to the male screw portion (310h) at the bottom of the socket (310) The height adjustment device of the book chair, characterized in that the female screw portion (320e) is provided in the lower inner periphery of the sleeve cap (320) of the portion. According to claim 1, The socket 310 and the sleeve cap 320 is provided in one module, the height adjustment device 30 is inserted into the upper end of the socket 310, the sleeve cap 320, the bottom opening of the socket 310 , By rotating the sleeve cap 320 to the limit that the lower end of the sleeve cap upper stepped portion 320a is blocked by the outer stepped step 310c of the socket 310, the upper end of the socket 310 protruding above the sleeve cap upper stepped step 320a The height adjustment device of the book chair, characterized in that the snap ring (320d) is fastened to the snap ring groove (310f) and combined into one module. The book chair according to claim 2, wherein the snap ring (320d) is a stainless steel material for a spring having a Rockswell hardness (HRC) of 44 to 52, and a retaining ring (320d) of either a wire or a plate of 1.5 mm thick or thick is adopted. Height adjustment device. According to claim 1, The inclined stepped step 310a of the socket 310 is a plane that is not a line, but a boundary between the upper side and the lower side of the slope.

The height adjustment device of the chair, characterized in that it is formed of ".

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