WO2006033490A1

WO2006033490A1 - Chair

Info

Publication number: WO2006033490A1
Application number: PCT/KR2004/002433
Authority: WO
Inventors: Byung-Chul Lee
Original assignee: Byung-Chul Lee
Priority date: 2004-09-22
Filing date: 2004-09-22
Publication date: 2006-03-30
Also published as: CN101060799A

Abstract

Disclosed herein is a chair. According to the present invention, a seat and a backrest are installed on a pair of “<” -shaped support frames in such a way as that the heights of the seat and the backrest can be directly adjusted, thus having a very simple structure, and a load applied to the seat and the backrest is directly transmitted to the support frames, thus more stably bearing a user’s weight. Further the present invention enables the heights of the seat and the backrest to be adjusted in more various manners while avoiding interference of the seat with the backrest.

Description

DESCRIPTION

CHAIR

Technical Field

The present invention relates, in general, to chairs and, more particularly, to a chair in which the heights of a seat and a backrest are capable of being individually adjusted.

Background Art

As is generally known, various types of chairs have been used according to the intended purpose of the chairs.

The chairs are typically classified into a couch and an individual chair. The couch allows several persons to sit together thereon. The individual chair is designed to allow one person to sit thereon. Especially in the case of the individual chair, various functions are provided to the chair so as to allow a user to feel more comfortable.

Generally, the conventional individual chair includes a seat to support a user's buttocks and a backrest to support the user's back. Further, the chair may have a headrest to support the user's head or armrests on which the user's arms are rested. Meanwhile, everyone using a chair has different body sizes. Thus, in order to change the shape of the chair to suit the body size of a person who sits on the chair, various adjusting means, such as a seat height adjusting means and a backrest height adjusting means, are installed on the chair.

Further, a means of adjusting the inclination angle of the backrest may be provided on the chair, thus allowing a user to comfortably sit up straight or lie on his or her back. In the conventional chair, a seat is mounted to a support frame placed on the ground such that the height of the seat is adjusted in a vertical direction, and a backrest is coupled to the seat such that the height thereof may be adjusted in a vertical direction or in a direction inclined relative to the seat. When a user leans with his or her back against the chair, the external force applied to the backrest is indirectly transmitted through the seat to the support frame. Thus, the user's weight is not stably supported, and moments act on respective joints, so that damage to components may result.

Further, the conventional chair is problematic in that the coupling structure of the components is considerably complicated and complex, thus incurring high product costs.

Disclosure Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a chair having a simple structure, of which the heights of a seat and a backrest are capable of easily being adjusted, to suit the body size of a user, thereby safely supporting the user's weight.

In order to accomplish the object, the present invention provides a chair, including a pair of "Z'-shaped support frames each having a bar-shaped support part arranged horizontally and placed on the ground, a guide part disposed to be at a predetermined angle with the support part, with a plurality of locking holes being formed in the guide part in a longitudinal direction thereof, and a coupling member to parallelly couple the support frames to each other; a seat installed on the support part of each of the support frames using seat height adjusting means such that a height of the seat is adjustable; and a backrest installed on the support part of each of the support frames using backrest height adjusting means such that a height of the backrest is adjustable.

According to this invention, the seat height adjusting means and/or the backrest height adjusting means includes a movable block surrounding the support part of each of the support frames, and being secured to the support part in such a way as to be movable in a longitudinal direction thereof; a locking pin movably installed on the movable block, and detachably inserted into a locking hole of the support part; a spring to elastically bias the locking pin in one direction; and a lever rotatably mounted to the movable block, and pushing the locking pin, which is elastically biased in one direction by the spring, into the locking hole.

The seat height adjusting means and/or the backrest height adjusting means includes a housing surrounding the support part of each of the support frames, and secured to the support part in such a way as to be movable in a longitudinal direction thereof; a locking pin movably installed on the housing, and detachably inserted into an associated locking hole of the support part; a spring to bias the locking pin in one direction; and a button mounted to the housing in such a way as to reciprocate, and pushing the locking pin, which is elastically biased in one direction by the spring, into the locking hole.

The backrest is rotatably installed on the backrest height adjusting means using backrest rotation angle adjusting means.

The backrest rotation angle adjusting means includes a rotating support shaft, a first end thereof having a gear part and being secured to the backrest, and a second end thereof being rotatably mounted to the housing of the backrest height adjusting means; a button installed on the housing of the backrest height adjusting means in such a way as to reciprocate, and selectively engaging with the gear part; and a spring to elastically bias the button in one direction.

A headrest is installed on an upper portion of the backrest in such a way as to rotate forwards and backwards.

Shoulder parts are provided on the headrest, a neck seat is formed between the shoulder parts to allow a user's neck to be seated in the neck seat, and shoulder seats are provided on a front of the backrest, so that the shoulder parts of the headrest are seated on the shoulder seats of the backrest when the headrest is bent forwards.

A locking protrusion is provided on each of the shoulder parts, and a locking step is provided on each of the shoulder seats, so that the locking protrusion of the shoulder part detachably engages with the locking step of the, shoulder seat.

A headrest coupling pin protrudes upwards from the backrest, and a pin insertion groove is formed on the headrest, so that the headrest is rotatable forwards and backwards about a rotating axis while insertion of the headrest coupling pin into the pin insertion groove is maintained.

The support part of each support frame is provided with front and rear wheels. The chair further includes a brake unit to selectively brake the rear wheel provided on the support part of each of the support frames.

The brake unit includes a serrated part provided on the rear wheel; and a lever rotatably installed on a wheel coupling member of the support part, and selectively engaging with the serrated part.

A handle is provided on the guide part of each of the support frames. The handle is rotatably installed on the support frames using handle rotation control means.

The handle rotation control means includes a first member having a rotating shaft and an uneven part, and secured to an upper end of the guide part of each of the support frames; and a second member having a shaft insertion part and an uneven part, and secured to each of ends of the "U"-shaped handle.

Description of Drawings

FIG. 1 is a perspective view showing a chair, according to the present invention;

FIG. 2 is a perspective view showing a seat height adjusting means of the chair, according to the present invention; FIG. 3 is an enlarged left side view of important parts of FIG. 2;

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is an enlarged front sectional view showing important parts of FIG. 2;

FIG. 6 is an exploded perspective view showing a backrest and a headrest;

FIG. 7 is a sectional view taken along line A-A of FIG. 6; FIG. 8 is a sectional view taken along line B-B of FIG. 7;

FIG. 9 is a view illustrating a backrest rotation angle adjusting means, in which a housing of a backrest height adjusting means is partially broken and seen from a vertical direction of a guide part of a support frame;

FIG. 10 is a right side view showing important parts of the chair, according to the present invention;

FIG. 11 is an enlarged view of important parts of FIG. 10; FIG. 12 is a plan view showing a rear wheel equipped with a brake unit;

FIG. 13 is a sectional view taken along line C-C of FIG. 12;

FIG. 14 is a view corresponding to FIG. 13, illustrating the operation of the brake unit; and FIG. 15 is a partial broken perspective view showing a handle rotation control means.

Best Mode

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

Referring to FIG. 1, a chair according to the present invention includes a pair of "Z'-shaped support frames 10, a seat 20, and a backrest 30. Each of the support frames 10 includes a bar-shaped support part 11 and a guide part 12. The support part 11 is arranged horizontally and placed on the ground. The guide part 12 is obliquely arranged to form a predetermined angle with the support part 11, with a plurality of locking holes 12a formed in a lengthwise direction of the guide part 12. The support frames 10 are coupled via a coupling member 13 in such a way as to be parallel to each other. The seat 20 is mounted to the support parts 11 of the support frames 10 using seat height adjusting means 100 such that the height of the seat 20 is adjustable. The backrest 30 is mounted to the support parts 11 of the support frames 10 using backrest height adjusting means 200 such that the height of the backrest 30 is adjustable.

According to the present invention, the seat 20 and the backrest 30 are mounted to the support frames 10 each having the "Zl shape in such a way as to enable direct adjustment of the heights of the seat and the backrest. Thus, the chair's structure is very simple. Further, load applied to the seat 20 and the backrest 30 is directly transmitted through the guide parts 12 of the support frames 10 to the support parts 11 of the support frames 10, so that a user's weight is more stably supported.

Moreover, since the seat 20 and the backrest 30 are individually installed on the support frames 10, the heights of the seat 20 and the backrest 30 may be adjusted variously without causing interference of the seat 20 with the backrest 30.

As shown in FIGS. 2 through 5, each seat height adjusting means 100 includes a movable block 110, a locking pin 120, a spring 130, and a lever 140. The movable block 110 surrounds the support part 11 of each support frame 10 in such a way as to be movable in a lengthwise direction thereof. The locking pin 120 is movably installed to the movable block 110, and is detachably inserted into a locking hole 12a of each support part 11. The spring 130 biases the locking pin 120 in one direction. The lever 140 is rotatably installed on the movable block 110, and pushes the locking pin 120, which is biased in one direction by the spring 130, to the locking hole 12a. The lever 140 includes a pushing part 141 and a grip part 142. The pushing part 141 pushes the locking pin 120, which is biased in one direction by the spring 130, to the locking hole 12a. The grip part 142 allows a user to easily grasp the seat height adjusting means. The outer circumferential surface of the pushing part 141 is shaped so that the pushing part 41 gradually moves in a direction of a rotating shaft Hl. Meanwhile, both ends of the seat 20 are firmly secured to seat height adjusting means 100 which are arranged to be opposite to each other. Here, reference numeral "Bl" denotes a fastening member, such as a bolt, which prevents the lever 140 from being removed from the rotating shaft Hl.

The operation of each seat height adjusting means will be described below. In the state shown in FIGS. 2 to 5, a user grasps the grip part 142 and bends the seat height adjusting means upwards. At this time, the lever 140 rotates forwards about the rotating shaft Hl, so that the locking pin 120 is smoothly dislodged from the locking hole 12a of the guide part 12 by the restoring force of the spring 130. In such a state, the height of the seat 20 is adjusted, and then the grip part 142 is bent downwards. At this time, the lever 140 rotates backwards about the rotating shaft Hl, thus pressing the spring 130. Thereby, the locking pin 120 is forcibly fitted into an associated locking hole 12a of the guide part 12.

As shown in FIGS. 6 to 8, each backrest height adjusting means 200 includes a housing 210, a locking pin 220, a spring 230, and a button 240. The housing 210 is secured to the support part 11 of each support frame 10 in such a way as to move in a lengthwise direction thereof, and surrounds the support part 11. The locking pin 220 is movably installed on the housing 210, and is detachably inserted into the locking hole 12a of the support part 11. The spring 230 biases the locking pin 220 in one direction. The button 240 is installed on the housing 210 in such a way as to reciprocate, and pushes the locking pin 220, which is biased by the spring 230 in one direction, to the locking hole 12a. The button 240 includes a pushing part 241 and a press part 142. The pushing part 241 pushes the locking pin 220 which is elastically biased in one direction by the spring 130 to the locking hole 12a. The press part 142 allows a user to easily manipulate the backrest height adjusting means. The pushing part 241 has a fork shape, and the surface of the pushing part 241 contacting the locking pin 120 is formed so as to be inclined.

The operation of each backrest height adjusting means will be described below. In the state shown in FIGS. 6 to 8, when a user holds the housing 210 with his or her hand and presses the press part 242, the button 240 is thrust into the housing 210, thus pushing the locking pin 220 in one direction. Thus, the spring 230 is compressed, and the locking pin 220 is forcibly dislodged from the locking hole 12a of the guide part 12. In such a state, when the height of the backrest 30 is adjusted and, thereafter, the press part 242 is released, the locking pin 220 is naturally fitted into an associated locking hole 12a of the guide part 12 by the restoring force of the spring 230. Thereby, the lever 140 returns to its original position. The seat height adjusting means 100 and the backrest height adjusting means 200 may be variously modified without being limited to the preferred embodiment of the present invention. For example, the height adjusting means shown in FIGS. 2 to 5 may be used as the backrest height adjusting means 200. Further, the height adjusting means shown in FIGS. 6 to 8 may be used as the seat height adjusting means 100. As long as it is possible to adjust the height of the seat 20 or the backrest 30 along the guide part 12 of each support frame 10, any one may be used as the seat height adjusting means 100 or the backrest height adjusting means 200.

Meanwhile, the backrest 30 may be firmly secured to the backrest height adjusting means 200. However, as in this embodiment, it is preferable that the backrest 30 be rotatably installed to the backrest height adjusting means 200 via backrest rotation angle adjusting means 300.

As shown in FIGS. 9 to 11, each backrest rotation angle adjusting means 300 includes a rotating support shaft 310, a button 330, and a spring 320. One end of the rotating support shaft 310 having a gear part 311 is secured to the backrest 30, and the other end of the rotating support shaft 310 is rotatably secured to the housing 210 of each backrest height adjusting means 200. The button 330 is installed on the housing 210 of the backrest height adjusting means 200 in such a way as to be reciprocable, and selectively engages with the gear part 311. The spring 320 elastically biases the button 330 in one direction. The button 330 includes a locking part 331 and a press part 142. The locking part 331 includes a guide groove 331a in which the rotating support shaft 310 is inserted, a gear part 331b which selectively engages with the gear part 311 of the rotating support shaft 310, and a locking protrusion 331c which supports both ends of the spring 320. The press part 142 allows a user to easily manipulate the button, and is secured to the housing 210 of each backrest height adjusting means 200 in such a way as to reciprocate. In this case, reference numeral "211" denotes a shaft seat which is provided on the housing 210 so that the rotating support shaft 310 is rotatably seated in the shaft seat.

The operation of the backrest rotation angle adjusting means will be described below. In the state shown in FIGS. 9 to 11, a user presses the press part 332 which protrudes out from the housing 210. At this time, the button 330 is thrust into the housing 210, so that the spring 320 is compressed and the gear part 331b of the button locking part 331 is separated from the gear part 311 of the rotating support shaft 310. Thereby, the engagement of the gear parts is released. In such a state, when the inclination angle of the backrest 30 is adjusted and the press part 332 is released, the button 330 is moved outwards from the housing 210 by the restoring force of the spring 320. Thereby, the gear part 331b of the button locking part 331 engages with the gear part 311 of the rotating support shaft 310.

Further, according to this embodiment, as shown in FIGS. 1, 6, and 10, the headrest 40 is installed on the upper portion of the backrest 30 in such a way as to rotate forwards or backwards. However, the headrest may be variously installed without being limited to this embodiment. For example, the headrest may be integrally provided on the upper portion of the backrest 30. After the headrest is separately manufactured, the headrest may be firmly secured to the upper portion of the backrest 30 via a fastening member, such as a bolt or screw. Further, a headrest which is separately manufactured may be provided on the upper portion of the backrest 30 in such a way that the height thereof is adjustable. Of course, all conventional headrests may be used in this invention.

Referring to FIGS. 1, 6, and 10, shoulder parts 41 are provided on the headrest 40, with a neck seat 42 formed between the shoulder parts 41 so that a user's neck is seated in the neck seat 42. Shoulder seats 31 are provided on the front of the backrest 30. Thereby, when the headrest 40 is rotated forwards, the shoulder parts 41 of the headrest 40 are seated on the shoulder seats 31 of the backrest 30 to support the back of the headrest 40. According to this embodiment, headrest coupling pins 32 protrude upwards from the backrest 30, and pin insertion grooves 43 are formed on the headrest 40. Thereby, the headrest 40 may rotate forwards or backwards about a rotating axis H while the coupling pins 32 are inserted into the pin grooves 43. In this case, the parts coupling the backrest 30 with the headrest 40 are embedded in the headrest 40, thus preventing the ability the headrest 40 to rotate from being deteriorated due to the entry of foreign materials, such as dust, and providing a good appearance. Further, locking protrusions 41a are provided on the shoulder parts 41, and locking steps 31a are provided on the shoulder seats 31, so that the locking protrusions 41a of the shoulder parts 41 detachably engage with the corresponding locking steps 31a of the shoulder seats 31. In this case, the shoulder parts 41 of the headrest 40 are stably seated on the shoulder seats 31 of the backrest 30, thus preventing the headrest 40 from being undesirably bent backwards.

The interaction of the backrest 30 and the headrest 40 will be described below with reference to FIGS. 1, 6 and 10.

In the state of FIG. 1, when an external force acts on the upper end of the headrest 40, so that the headrest 40 is bent backwards, the engagement of the locking protrusions 41a of the shoulder parts with the locking steps 31 of the shoulder seats is forcibly released. Thereby, as shown in FIGS. 6 and 10, the headrest 40 rotates about the rotating axis H2, so that it is bent backwards. In such a state, a user places his or her neck in the neck seat 42 provided between the shoulder parts 41. Afterwards, when his or her head is rested on the headrest 40, the shoulder parts 41 naturally cover the user's shoulders. In this state, when one desires to use the chair according to this invention for a general purpose, friction between the rotation parts coupling the headrest 40 with the backrest 30 is set to be high so that the rotation of the headrest 40 is slightly impeded. This sufficiently supports a user's head while keeping the headrest 40 rotatable. Meanwhile, when one desires to use the chair according to this invention as a shampooing chair, the friction of the rotating parts coupling the headrest 40 and the backrest 30 is set to be low to ensure smooth rotation of the headrest 40. Thereby, the upper end of the headrest 40 can be placed on a washstand (not shown) . This sufficiently supports a user's head while the headrest 40 is maintained on the washstand.

In such a state, the user raises his or her head and bends his or her body forwards so that his or her neck is removed from the neck seat 42 of the headrest 40. Thereafter, the headrest 40 is bent forwards. At this time, the headrest 40 rotates forwards about the rotating axis H, as shown in FIG. 4, so that the shoulder parts 41 of the headrest are seated on the shoulder seats 31 of the backrest. Thereby, while the back of each shoulder part 41 is supported, the locking protrusions 41a of the shoulder parts engage with the locking steps 31a of the shoulder seats, thus maintaining the state of FIG. 1. In such a state, the backrest 30 supports the lower region of the user's back, and the headrest 40 supports the upper region of his or her back. That is, the headrest 40 is used as an auxiliary backrest.

According to this embodiment, when the headrest 40 is rotated away from the backrest 30, the headrest 40 serves to support a user's head. Meanwhile, when the headrest 40 is rotated over the backrest 30, the headrest 40 serves as an auxiliary backrest. Thus, such a construction considerably enhances the usefulness and convenience of the chair. Further, the shoulder parts 41 of the headrest- 40 are seated on the shoulder seats 31 of the backrest 30 to support the back of each shoulder part. Thus, while the height of the headrest 40 is appropriately maintained, each shoulder part 41 may be enlarged to sufficiently cover a user's shoulder. Therefore, in the case where the present invention is used as a shampooing chair, the user is protected from splashes.

In order to afford convenient movement of the chair, as shown in FIG. 1, it is preferable that front and rear wheels 14 and 15 be installed on the support part 11 of each support frame 10. More preferably, the front wheel 14 is installed on the corresponding support part 11 in such a way as to rotate about a coupling shaft. Thus, it is convenient to manipulate the chair so as to move the chair to another place.

This may hinder the chair from being held at a predetermined position. However, as shown in FIGS. 1, 12, and 13, if a brake unit 400 is installed on the support part 11 of each support frame 10 to selectively brake each rear wheel 15, the above-mentioned problem is easily solved. Any conventional brake unit may be applied to this invention. However, according to this embodiment, the brake unit includes a serrated part 410 which is provided on the rear wheel 15, and a lever 420 which is rotatably installed on a wheel coupling member 11a of the support part 11 and selectively engages with the serrated part 410. The lever 420 includes a manipulating part 421 to allow a user to easily manipulate the brake unit, and a locking part 422 having a locking protrusion 422a that engages with the serrated part 410. In this case, the serrated part 410 may be separately manufactured, and installed on the corresponding rear wheel 15 via a fastening member, such as a bolt or a screw. Alternatively, the serrated part 410 may be integrated with the rear wheel 15. Meanwhile, reference numeral "11a" denotes the wheel coupling member which is secured to an end of each support part 11 via a fastening pin lib. Reference numeral "H3" denotes a rotating shaft which rotatably couples each rear wheel 15 to the corresponding wheel coupling member 11a, and reference numeral "H4" denotes a rotating shaft which rotatably couples each lever 420 to the wheel coupling member 11a. The rotating shaft H4 is spaced apart from the rotating shaft H3 by a predetermined distance.

The operation of each brake unit 400 will be described below with reference to FIGS. 13 and 14.

In the state shown in FIG. 13, when a user raises each manipulating part 421 using his or her foot or hand, the lever 420 rotates about the rotating shaft H4. Thereby, the locking protrusion 422a of the locking part 422 is disengaged from the serrated part 410, so that the locked state of each rear wheel 15 is released, as shown in FIG. 14. In such a state, the chair is moved to a desired position, and then each manipulating part 421 is pressed downwards. At this time, the lever 420 rotates backwards about the rotating shaft H4, so that the locking protrusion 422a of the locking part 422 engages with the serrated part 410. Thus, as shown in FIG. 13, each rear wheel 15 is locked, so that rotation of the rear wheel 15 is impossible. In this case, the friction of the rotating part coupling the lever 420, with the wheel coupling member 11a is increased, so that the rotation of the lever 420 is restricted. Thereby, the lever 420 is sufficiently secured to a predetermined position, as long as no external force is applied to the lever. In order to allow the chair to be easily moved to another place, as shown in FIGS. 1 and 15, it is preferable that a handle 60 be installed on the guide parts 12 of the support frames 10. According to this embodiment, the handle 60 may be rotatably installed on each support frame 10 via a handle rotation control means 500. However, the installation of the handle may be variously modified without being limited to the above-mentioned embodiment. For example, a handle 60 that is separately manufactured may be firmly installed on the support frames 10. The shape of the handle 60 may be variously changed.

Referring to FIG. 15, the handle rotation control means 500 includes a first member 510 and a second member 520. The first member 510 has a rotating shaft 511 and an uneven part 512, and is secured to an upper end of the guide part 12 of each support frame. The second member 520 has a shaft insertion part 521 and an uneven part 522. The second member 520 is secured to each end of the "U"-shaped handle 60. In this case, reference numeral "B2" denotes a bolt which is inserted into the shaft insertion part 521 and secured to the rotating shaft 511. The bolt functions to prevent the removal of the second member 510. As long as it is possible to control the rotation angle of the handle 60, all conventional devices may be used as the handle rotation control means 500 without being limited to this embodiment. The operation of each handle rotation control means 500 will be schematically described below with reference to FIG. 15.

When a user pushes the "U"-shaped handle 60 forwards or pulls it backwards, it is supported by the engaging uneven parts 512 and 522 of the first and second members 510 and

520. Thus, the chair may be pushed forwards or pulled backwards.

Conversely, when the handle 60 is bent upwards or downwards, the uneven part 522 of the second member 520 disengages from the uneven part 512 of the first member 510, and the second members 520 provided on both sides approach each other by the elasticity of the handle 60. Thus, the handle 60 rotates about the rotating shaft 511 of the first member 510 while generating a clicking sound. When the handle 60 is rotated by a predetermined angle and then no additional external force is applied to the handle 60, the second members 520 are moved away from each other by the restoring force of the handle 60. The engagement of the uneven part 522 of each second member with the uneven part 512 of an associated first member is maintained.

Industrial Applicability

As described above, the present invention provides a chair, in which a seat and a backrest are installed on a pair of " Z'-shaped support frames in such a way as that the heights of the seat and the backrest can be directly adjusted, thus having a very simple structure, and a load applied to the seat and the backrest is directly transmitted to the support frames, thus more stably bearing a user's weight.

Further, the seat and the backrest are individually installed on the support frames, thus enabling the heights of the seat and the backrest to be adjusted in more various manners while avoiding intereference of the seat with the backrest.

Claims

1. A chair, comprising: a pair of "Z'-shaped support frames each having: a bar-shaped support part arranged horizontally and placed on the ground; a guide part disposed to be at a predetermined angle with the support part, with a plurality of locking holes being formed in the guide part in a longitudinal direction thereof; and a coupling member to parallelly couple the support frames to each other; a seat installed on the support part of each of the support frames using seat height adjusting means such that a height of the seat is adjustable; and a backrest installed on the support part of each of the support frames using backrest height adjusting means such that a height of the backrest is adjustable.

2. The chair according to claim 1, wherein the seat height adjusting means and/or the backrest height adjusting means comprises: a movable block surrounding the support part of each of the support frames, and being secured to the support part in such a way as to be movable in a longitudinal direction thereof; a locking pin movably installed on the movable block, and detachably inserted into a locking hole of the support part; a spring to elastically bias the locking pin in one direction; and a lever rotatably mounted to the movable block, and pushing the locking pin, which is elastically biased in one direction by the spring, into the locking hole.

3. The chair according to claim 1, wherein the seat height adjusting means and/or the backrest height adjusting means comprises: a housing surrounding the support part of each of the support frames, and secured to the support part in such a way as to be movable in a longitudinal direction thereof; a locking pin movably installed on the housing, and detachably inserted into an associated locking hole of the support part; a spring to bias the locking pin in one direction; and a button mounted to the housing in such a way as to reciprocate, and pushing the locking pin, which is elastically biased in one direction by the spring, into the locking hole.

4. The chair according to claim 1, wherein the backrest is rotatably installed on the backrest height adjusting means using backrest rotation angle adjusting means.

5. The chair according to claim 4, wherein the backrest rotation angle adjusting means comprises: a rotating support shaft, a first end thereof having a gear part and being secured to the backrest, and a second end thereof being rotatably mounted to the housing of the backrest height adjusting means; a button installed on the housing of the backrest height adjusting means in such a way as to reciprocate, and selectively engaging with the gear part; and a spring to elastically bias the button in one direction.

6. The chair according to claim 4, wherein a headrest is installed on an upper portion of the backrest in such a way as to rotate forwards and backwards.

7. The chair according to claim 6, wherein shoulder parts are provided on the headrest, a neck seat is formed between the shoulder parts to allow a user's neck to be seated in the neck seat, and shoulder seats are provided on a front of the backrest, so that the shoulder parts of the headrest are seated on the shoulder seats of the backrest when the headrest is bent forwards.

8. The chair according to claim 7, wherein a locking protrusion is provided on each of the shoulder parts, and a locking step is provided on each of the shoulder seats, so that the locking protrusion of the shoulder part detachably engages with the locking step of the shoulder seat.

9. The chair according to claim 7, wherein a headrest coupling pin protrudes upwards from the backrest, and a pin insertion groove is formed on the headrest, so that the headrest is rotatable forwards and backwards about a rotating axis while insertion of the headrest coupling pin into the pin insertion groove is maintained.

10. The chair according to any one of claims 1 to 9, wherein the support part of each support frame is provided with front and rear wheels.

11. The chair according to claim 10, further comprising: a brake unit to selectively brake the rear wheel provided on the support part of each of the support frames.

12. The chair according to claim 11, wherein the brake unit comprises: a serrated part provided on the rear wheel; and a lever rotatably installed on a wheel coupling member of the support part, and selectively engaging with the serrated part.

13. The chair according to any one of claims 1 to 9, wherein a handle is provided on the guide part of each of the support frames.

14. The chair according to claim 13, wherein the handle is rotatably installed on the support frames using handle rotation control means.

15. The chair according to claim 14, wherein the handle rotation control means comprises: a first member having a rotating shaft and an uneven part, and secured to an upper end of the guide part of each of the support frames; and a second member having a shaft insertion part and an uneven part, and secured to each of ends of the "U"-shaped handle.