KR100893156B1 - Chair with a movable back support - Google Patents

Abstract

The present invention relates to a chair including a seat part and a backrest, the base frame being coupled to a spaced space on a lower surface of the seat part and having a hollow cylinder protruding from the bottom; A horizontal movement frame coupled to the upper surface of the base frame so as to be movable back and forth, connected to the backrest frame connected to the backrest at left and right ends thereof, and having a driven body provided on the lower surface to receive the force required to move back and forth; A coupling housing coupled to the support and having an upper surface opened to form an empty space therein and having a slide cylinder into which the hollow cylinder is inserted; An elastic body installed between the hollow cylinder and the slide cylinder to move the base frame up and down with respect to the connection enclosure; And a rotational force generating means which is formed inside the connection enclosure to transmit the rotational force generated according to the movement of the base frame to the driven body to move the horizontal movement frame back and forth to contribute to maintaining the correct posture. It is a technology regarding a chair to which the backrest can be moved.

Back, Move, Chair, Horizontal Movement, Weight, Gear, Rotational Force, Spine

Description

Chair with moving back {Chair with a movable back support}

1 is an exploded perspective view of a main part of a chair according to a first embodiment of the present invention;

Figure 2 is a sectional view of the main part in the engaged state.

3 is a sectional view showing a main part of a chair according to the second embodiment;

4 is a schematic side view of a chair according to a third embodiment;

5 is a side view of the connecting shaft;

6 is a state of engagement of the angle adjustment lever.

7 is a front view of the angle adjustment lever.

<Description of Major Symbols Used in Drawings>

100: support 120: piston

200: seat portion 300: backrest

310: back frame 320: connecting shaft

330: angle adjustment lever 340, S: elastic body

400: base frame 450: hollow cylinder

460: Support Bracket

500: horizontal motion frame 510: driven body

700: rotational force generating means 711: rolling part

720: cloud 730: intermediate

820: tilting frame 830: control lever

840: Cam 900: Connecting enclosure

910: Slide Bucket

The present invention relates to a chair including a seat part and a backrest. More specifically, the chair back is automatically controlled by the user's weight even when the user sits on the seat part without the back part of the chair touching the back of the chair. The present invention relates to a chair to which the backrest is moved to support the user's back so as to maintain a correct posture.

In general, the chair has a backrest to support the user's back sitting in the chair to help sit in a comfortable position to relax, and also has the function of protecting the spine by supporting the back of the person sitting on the chair.

Therefore, sitting the hips across the seat is not a correct posture, and the hips are positioned deep behind the seat so that the back portion can be supported by the backrest so that the spine can be prevented from bending and protect the spine.

Accordingly, the back of the chair is designed in consideration of the ergonomic aspects to protect the user's spine.

To this end, in the case of conventional chairs, the backrest can be elastically moved backwards, or the backrest is divided into two to support each back part on both sides of the spine so that the support of the spine is good and the comfort is felt. Various structures have been proposed and are in use, such as employing a bag structure.

However, the conventional chair has the backrest always fixed at the set position regardless of the position where the user sits on the seat, so that the user does not sit in the right position so that the user's hips are placed deeply behind the seat, and sits on the middle or front of the seat. If you do not, the back is away from the backrest because the backrest is unable to support the back, increasing fatigue, such bad posture over a long period of repeated habits to the spine may cause diseases such as discs.

In addition, in the case of the ordinary chair can be stored only when the backrest is up, it takes up a lot of volume during shipping or storage, resulting in many economic losses.

Therefore, the present invention is to solve this problem, regardless of the position where the user is seated on the seat when seated on the chair to support the back of the user at all times to reduce fatigue and maintain a correct posture and prevent spine and musculoskeletal diseases To provide a chair to be moved.

And it is an object of the present invention to provide a chair that can move the backrest can be provided in the structure that can be folded back to provide convenience in storage or delivery and can provide advantages in economical aspect.

The present invention for achieving the object as described above in the chair comprising a support and a seat portion and the backrest is installed on the support,

A base frame coupled to a spaced space on a lower surface of the seat part, the base frame having a hollow cylinder protruding from the bottom surface thereof; A horizontal movement frame coupled to the upper surface of the base frame so as to be movable back and forth, connected to the backrest frame connected to the backrest at left and right ends thereof, and having a driven body provided on the lower surface to receive the force required to move back and forth; A coupling housing coupled to the support and having an upper surface opened to form an empty space therein and having a slide cylinder into which the hollow cylinder is inserted; An elastic body installed between the hollow cylinder and the slide cylinder to move the base frame up and down with respect to the connection enclosure; A chair for moving the backrest, comprising: a rotational force generating means formed in the connection enclosure to transmit the rotational force generated according to the movement of the base frame to the driven body to move the horizontal movement frame back and forth. It is about.

Preferably the rotational force generating means in the chair that the backrest is moved according to the present invention is fixed to the connection enclosure and the cloud portion formed with a rack gear in a vertical direction on the outer surface; A rolling body installed on a support bracket projecting vertically downward while being connected to the base frame between the hollow cylinders and rotating in contact with the rolling part; It is suitable that the intermediate body is connected to the rolling body and the driven body to rotate the horizontal motion frame linear movement.

Preferably, the chair is moved backrest according to the present invention is provided with a locking groove forming a concave-convex shape bent so that one side end of the base frame is directed downward, and positioned upwards as wrapping the horizontal motion frame and corresponds to the locking groove It is provided with a tilting frame is formed with a protruding engaging piece at one end to the side, and installed to rotate through the side of the horizontal frame and the tilting frame and comprises an adjustment lever to which the eccentric cam is attached to the rotation of the adjustment lever Accordingly, the cam pushes the tilting frame upwards so that the engaging groove and the engaging piece are coupled to restrict the movement of the horizontal frame.

Preferably the connection housing is connected to the support via a connecting bracket coupled to the support in the chair is moved backrest according to the present invention, the connecting housing is connected to the connecting bracket to be rotated and the angle adjusting elastic body is coupled to the connecting bracket And the connection enclosure are constrained so that the connection enclosure is inclined backward within a certain range.

Preferably, in the chair in which the backrest is moved, the backrest is rotatably coupled to the left and right sides of the backrest frame, and a plurality of fixing parts are formed at the end of the connection shaft protruding to one side of the backrest frame. The angle adjusting lever is coupled to move in the axial direction, and is selectively engaged with a fixing pin provided in the back frame to adjust the inclination angle of the backrest. An elastic body is connected to the rear of the lower end of the backrest, and the elastic body is a backrest. It is suitable to restrain with the rear side of the frame.

Preferably, the elastic body is variable, the end of the guide ring is moved along the guide rod is fixedly installed on the backrest and the other end is screwed with the control rod detachable with respect to the opening groove formed in the back frame frame back side variable It is also suitable to be connected to the rod.

More preferably, the opening groove is open toward the upper surface of the back frame, and when the control rod fitted to the opening groove is pushed out of the opening groove, the back support pivots forwardly about the connecting shaft.

Hereinafter, a preferred embodiment of the present invention will be described in more detail, and reference will be made to related drawings for the convenience of understanding. However, the accompanying drawings are embodied as an example of the technical idea according to the present invention, the scope of the present invention is not limited to the drawings themselves.

Figure 1 is an exploded perspective view of the main part of the chair according to the first embodiment of the present invention, Figure 2 is a cross-sectional view of the main part in the engaged state.

The chair according to the first embodiment includes a base frame 400, a horizontal frame 500, a connecting enclosure 900, an elastic body (S) and the rotational force generating means 700 as a main component, in particular the connection As the base frame 400 is moved up and down with respect to the enclosure 900, a driving force for moving the horizontal frame 500 is formed.

The base frame 400 is coupled to form a space that can be formed in the lower surface of the seat portion 200, the bottom surface is provided with two hollow cylinders 450 protruding. In addition, a region between the hollow cylinders is partially opened in the base frame 400 in which the hollow cylinders 450 are provided. In addition, more preferably, the support bracket 460 required for installation of the rotational force generating means 700 to be described later is formed to face left and right. That is, the support bracket 460 is formed in the opening portion formed between the hollow cylinder 450 and is configured by bending a portion of the base frame 400 or by combining a separate plate material in a manner such as welding with the base frame. can do.

A horizontal motion frame 500 that is horizontally moved above the base frame 400 is formed. The horizontal motion frame 500 has a form in which a left and right side is provided by bending a plate and is linearly moved along the base frame 400. Proper guide means (G) are to be placed. Since the guide means (G) can be applied to a variety of known, a detailed description thereof will be omitted. A lower surface of the horizontal frame 500 is coupled to the driven body 510, the rotational force generated by the rotating force generating means 700 to be described later through the driven body 510 is transmitted to the horizontal frame 500 This is a straight line movement horizontally. On the other hand, the driven member 510 is preferably a straight rack gear. The backrest frame 310 is connected to both left and right ends of the horizontal frame 500. The backrest frame 310 may be coupled to the horizontal motion frame upper surface portion by crossing the horizontal motion frame 500 from side to side. As will be described later, when the tilting frame 820 is further provided on the horizontal motion frame 500, the backrest frame should be connected to the tilting frame.

A connection enclosure 900 is provided below the base frame 400, and the base frame 400 is coupled to the connection enclosure 900. As shown in the connection housing 900, the upper surface is opened, an empty space is formed therein, and slide cylinders 910 are provided at left and right sides thereof. A hollow cylinder 450 constituting the base frame 400 is inserted into the slide cylinder 910, and an elastic body S is installed between the hollow cylinder 450 and the slide cylinder 910. The elastic body (S) may utilize a common coil spring and the elastic body (S) is inserted into the hollow cylinder 450, but the length thereof is longer than the hollow cylinder 450, the lower end of the elastic cylinder slide 910 It is installed in contact with the floor. The connection box 900 is connected to the support part 100 in a fixed state, and the base frame 400 moves upward and downward with respect to the connection box 900.

The horizontal motion frame 500 is moved by the rotational force generating means 700 which is operated in association with the vertical movement of the base frame 400. The rotational force generating means is installed in the connection housing 900. Looking at the configuration of the more specific rotational force generating means 700 will include a cloud portion 711, a cloud body 720, the intermediate body 730. The cloud portion 711 is fixed to the inner bottom surface of the connection enclosure 900 in contact with the cloud body 720 to be described later to induce the cloud body to rotate. Preferably, the cloud portion 711 is preferably a rack gear formed in the vertical direction.

Inside the connection enclosure 900 is further provided with a cloud body 720 in contact with the cloud portion 711, the installation of the cloud body 720 is extended from the base frame 400 is formed vertically downward To use the support bracket (460). As shown in the figure, a hole is formed at the bottom end of the support bracket 460 to fix the cloud body 720 by using a horizontal axis, and the cloud body 720 is coupled using a bearing or the like so as to be rotated about the horizontal axis. do. The rolling body is preferably geared and can be rotated by engagement with the rolling part.

The rotational force formed in the cloud 720 is transmitted to the driven body 510 via the intermediate body 730, and the intermediate body 730 is connected to the cloud body 720 to rotate together. In this example, an arc gear is used as the intermediate body 730. The arc gear may be directly or indirectly connected to a cloud body. The arc-shaped gear as the intermediate body 730 is engaged with the driven body 510. When the intermediate body rotates, the force is transmitted to the driven body 510 so that the horizontal frame 500 moves linearly in the horizontal direction. And the arc-shaped gear which is the intermediate body 730 protrudes through the opening part formed in the base frame 400, and comes into contact with the driven body.

When the user sits on the seat unit 200 in a coupling relationship as described above, the base frame 400 itself including the seat unit is lowered downward with respect to the fixed connection enclosure 900, and accordingly, the cloud body 720 is clouded. 711 is rotated and lowered to rotate the intermediate body 730 and the intermediate body 730 transmits a force to the driven body 510 to move the horizontal frame 500 to be in close contact with the user's back. do.

In configuring the chair to which the backrest is moved according to the first embodiment of the present invention, it is more preferable to provide a braking means for fixing the horizontal frame 500 to a desired point.

In order to constitute such a braking means, one side end portion of the base frame 400 is bent to face downward, and a plurality of locking grooves 811 are formed to form an uneven shape. The horizontal frame 500 is installed on an upper surface of the base frame 400, and a tilting frame 820 is further installed on the horizontal frame 500. The tilting frame 820 is disposed to surround the horizontal motion frame 500, and a locking piece 822 corresponding to the locking groove 811 is formed at one end of the tilting frame 820. An adjustment lever 830 is installed to rotate through the side surfaces of the horizontal frame 500 and the tilting frame 820, and an eccentric cam 840 is attached to the adjustment lever 830.

When the adjustment lever 830 is rotated, the cam 840 is exposed on the upper surface of the horizontal motion frame 500 and comes into contact with the tilting frame 820 to push up the tilting frame upwards, thereby the locking piece 822. ) Is fitted into the locking groove 811, the movement of the horizontal frame 500 is inhibited. That is, the user can secure the backrest in a desired position, and if the cam lever and the tilting frame 820 are prevented from contacting by further rotating the control lever 830, the locking piece 822 inserted into the locking groove 811 is The horizontal motion frame 500 is shifted to the movable state. When the tilting frame 820 is placed, the backrest frame has a coupling structure that is directly connected to the tilting frame.

Next, a second embodiment of the present invention will be described, and FIG. 3 is a cross-sectional view showing main parts and shows a difference before and after a change.

To configure a chair having the same basic structure as in the second embodiment, but using the connecting bracket 1000 as an additional element in connecting the connecting box 900 with the support 100. The connection bracket 1000 is positioned below the connection enclosure 900, the connection bracket is fixedly installed on the support 100, and the connection enclosure 900 is connected in a structure that can be rotated with respect to the connection bracket 1000. . In addition, the connection bracket 1000 is provided with an angle adjusting elastic body 1100 and forms a structure in which the connection housing is connected to the angle adjusting elastic body. As shown in the drawing, the connection enclosure can be inclined at a certain angle to the rear with respect to the connection bracket and is very useful when the user takes a break.

Next, a chair according to a third embodiment of the present invention will be described. FIG. 4 shows a schematic side view of the chair according to the present invention, FIG. 5 shows a side view of the connecting shaft, and FIG. 6 shows a coupling state diagram of the angle adjustment lever. Shows. 7 corresponds to a front view of the angle adjustment lever.

As shown in the third embodiment, the backrest 300 is moved in the horizontal direction together with the horizontal motion frame 500, and the backrest 300 itself is rotated to adjust the angle.

The backrest 300 is coupled between the left and right sides of the backrest frame 310 connected to the horizontal motion frame 500 or the tilting frame 820 by the connecting shaft 320 to form a structure that can be rotated and the connecting shaft 320 This is the turning point. Chair in the present invention is formed higher than the upper surface of the seat portion 200 so that the backrest frame 310 connected to the horizontal movement frame 500 can be an armrest from the bottom of the seat portion 200 to the upper side, Accordingly, the connecting shaft 320 is connected to the backrest at a position higher than the lowest end of the backrest 300. In the case of a general chair, the pivoting point of the backrest or the inclined backrest 300 becomes the lower part of the backrest. In this case, there is a problem that causes a disease by causing a separation space between the backrest and the user's back part and the hip part. .

On the contrary, by making the pivot point of the backrest 300 correspond to the distance from the shoulder to the elbow which is higher than the lower part of the backrest as in the present invention, the backrest of the portion below the pivot point moves forward even when the backrest 300 is inclined. It is in close contact with the user's back and hips can be solved the problem described above.

The connecting shaft 320 is inserted from the outside of the backrest frame 310 is inserted into the backrest 300 and the angle adjustment lever on the connecting shaft 320 protruding to either side or both sides of the backrest frame 310. 330 to be combined. The angle adjusting lever 330 may be moved in the axial direction with respect to the connecting shaft 320 and a plurality of recessed or perforated fixing parts 331 are provided near the edge. In the present embodiment, the fixed portion 331 is recessed in a form in which a plurality of circles overlap each other along the edge of the angle adjustment lever 330.

On the other hand, in response to the fixing part 331, the back support frame 310 is provided with a fixing pin 311 of a protruding form so that the fixing pin 311 can be coupled to the fixing part 331. The angle adjusting lever 330 may be moved in the axial direction with respect to the connecting shaft 320. When the angle adjusting lever 330 is pulled out, the fixing portion 331 is separated from the fixing pin 311. When the backrest 300 is configured to be rotated, on the contrary, when the angle adjustment lever 330 is pushed toward the backrest frame 310, the backrest 300 is no longer coupled to the fixing pin 311. It cannot be rotated.

The backrest 300 and the angle adjustment lever 330 coupled to the connection shaft 320 are rotated in the same direction at the same time as the backrest is inclined. That is, the angle adjustment lever 330 can be moved only a predetermined distance in the axial direction with respect to the connecting shaft 320, the rotation is made with the connecting shaft when rotating. In order to implement the axial movement of the angle adjustment lever 330 with respect to the connecting shaft 320, as shown in Figure 5 to have two guide grooves 321 on the outer surface near the end of the connecting shaft 320 and corresponding angle A plurality of balls 332 as shown in the adjustment lever 330 is supported by the spring 333 so that the ball 332 is located in the guide groove 321. Therefore, the angle adjustment lever 330 is moved in the axial direction with respect to the connecting shaft 320 by the user push or pull to move between the two guide grooves (321).

The angle that the fixing portion 331 is formed with respect to the connecting shaft 320 will be the maximum angle that the backrest 300 can be rotated during the use of the chair, in the case of not using the chair in the fixing pin 311 The back part 300 may be completely folded by allowing the fixing part 331 to be separated.

More preferably, one end of the elastic body 340 is connected to the rear of the lower end of the backrest 300, and the other end of the elastic body 340 is connected to the rear side of the backrest frame 310. Various kinds of known ones may be applied to the type of the elastic body 340, and this case corresponds to the case of using the coil spring. When the backrest 300 and the backrest frame 310 are connected by the elastic body 340, when the user pushes the backrest 300 to the rear, the elastic body is stretched and the restoring force is applied to the backrest to return to the original position.

In installing the elastic body 340, it is also possible to directly connect both ends of the elastic body to the backrest 300 and the backrest frame 310, respectively, but more preferably, the structure described below is preferable.

Coil springs are used as the elastic body 340, and for connecting the backrest 300 to the backrest frame 310, a guide rod 341, a guide ring 342, a control rod 343, and a variable rod 344 are used. Install more elements. That is, the guide rod 341 is installed at the center of the rear surface of the lower end of the backrest 300, and the guide rod 341 is coupled to the guide ring 342 so as to slide and the elastic body 340 of the guide ring 342. It forms a structure where one end is connected.

A control rod 343 and a variable rod 344 are used as a means for connecting the other end of the elastic body 340 to the backrest frame 310, and the control rod 343 is located at the rear side of the backrest frame 310. It is coupled to a position corresponding to the same vertical surface 341, the variable rod 344 is screwed to the control rod 343 and the other end of the elastic body 340 is connected to the variable rod 344. The control rod 343 is rotated in a state coupled to the opening groove 312 formed in the backrest frame 310 and the position of the variable rod 344 is changed according to the rotation of the control rod 343 elastic body 340 The initial elastic force of can be adjusted.

In particular, in the present invention, as the elastic body 340 is inclined backward, the guide ring 342 connected to the elastic body 340 gradually moves along the guide rod 341 as the backrest 300 is inclined backward. There is a technical feature in that. Compared to the fixed position of the one end of the elastic body 340 connected to the backrest 300, when the position is changed, the force that the user should apply to the backrest 300 does not increase sharply when tilted by the same angle, so that less force There is an advantage that can be changed the angle of the backrest.

In installing the control rods 343 using the opening grooves 312 formed in the backrest frame 310, the control rods 343 may be coupled by simply opening a hole in the backrest frame 310 with the opening grooves 312. In this embodiment, however, the control rod 343 is to be freely separated from the backrest frame 310 so that the backrest 300 itself can be rotated forward and left in a horizontal state. Since the backrest 300 is formed to the upper side of the seat portion 200, there is a lot of inconvenience and unnecessary waste due to the height occupied by the backrest 300 when moving or when storing or storing goods. However, when the backrest can be freely rotated as in the present invention, it is expected to reduce storage costs and logistics costs.

To this end, the opening groove 312 is opened to the upper side of the back frame 310 and the specific shape of the opening groove can be variously changed. However, it is suitable to insert a suitable stopper (not shown) in the backrest frame 310 to prevent the control rod from being stepped off after the control rod is inserted into the opening groove.

In the case of using a chair, the control rod 343 is inserted into the opening groove 312 so that the backrest of the backrest is limited within the range controlled by the user using the angle adjustment lever 330 or within the limited range according to the elastic modulus of the elastic body. The angle of rotation can be adjusted. However, during delivery or moving, if the control rod 343 is pushed upward from the opening groove 312 to be separated from the opening groove 312, the backrest 300 is tilted forward with respect to the connecting shaft 320 to 90 degrees or more. The angle can be adjusted so that the front part of the backrest comes into contact with the upper surface of the seat part 200.

The chair of the present invention according to the configuration as described above is automatically adjusted so that the backrest always comes in close contact with the user's back despite the user's physical condition or bad sitting posture, so it is very likely that the chair is actually applied and used in the industry as a new concept chair. It will be called a high technology.

In addition, the chair of the present invention has the additional advantage that the backrest is folded in the horizontal direction so as to minimize the volume of storage or movement as well as convenience in use, and will be referred to as a technology of higher availability.

On the other hand, the chair that the backrest of the present invention is moved has the advantage that it can be applied to all ranges used for seating of a person, such as a car chair, an aircraft chair or a sofa as well as a home, office chair.

The chair is moved backrest according to the present invention even if the user is sitting at any position of the seat portion is moving forward backrest to support the back of the human body strongly so that you sit on the chair in the state of standing back naturally to protect the correct posture and spine It is effective in preventing diseases related to the spine and preventing diseases related to the musculoskeletal system.

And compared to the prior art there is also an effect that provides a lot of convenience and cost savings when storing or moving the chair.

Claims (7)

In the chair comprising a support and a seat portion and a backrest installed on the support above, A base frame coupled to a spaced space on a lower surface of the seat part, the base frame having a hollow cylinder protruding from the bottom surface thereof; A horizontal movement frame coupled to the upper surface of the base frame so as to be movable back and forth, connected to the backrest frame connected to the backrest at left and right ends thereof, and having a driven body provided on the lower surface to receive the force required to move back and forth; A coupling housing coupled to the support and having an upper surface opened to form an empty space therein and having a slide cylinder into which the hollow cylinder is inserted; An elastic body installed between the hollow cylinder and the slide cylinder to move the base frame up and down with respect to the connection enclosure;  A chair for moving the backrest, comprising: a rotational force generating means formed in the connection enclosure to transmit the rotational force generated according to the movement of the base frame to the driven body to move the horizontal movement frame back and forth. . The method of claim 1, The rotational force generating means, A cloud unit fixed to the connection box and having a rack gear formed in a vertical direction on an outer surface thereof; A rolling body installed on a support bracket projecting vertically downward while being connected to the base frame between the hollow cylinders and rotating in contact with the rolling part; And an intermediate body which is connected to the rolling body and the driven body and rotates so that the horizontal movement frame is linearly moved. The method according to claim 1 or 2, The chair to which the backrest is moved, One side end of the base frame is bent downward to have a locking groove forming a concave-convex shape, the tilting frame which is positioned upwards as if surrounding the horizontal motion frame and protruding a locking piece formed at one end corresponding to the locking groove Is provided, is installed to rotate through the sides of the horizontal frame and the tilting frame and comprises an adjustment lever is attached to the eccentric cam is configured to push the cam upwards tilting frame according to the rotation of the control lever The chair is moved backrest is characterized in that the engaging groove and the engaging piece is coupled to limit the movement of the horizontal movement frame. The method according to claim 1 or 2, The chair to which the backrest is moved, The connection box is connected to the support through a connection bracket coupled to the support, and the connection box is connected to the connection bracket so as to be rotatable, and the connection housing is constrained by the angle adjusting elastic body coupled to the connection bracket. The chair is moved backrest, characterized in that inclined backward in a certain range. The method according to claim 1 or 2, The backrest, An angle adjustment lever formed with a plurality of fixing parts is coupled to the back frame so as to be rotatably coupled to the connecting shaft rotatably with respect to the left and right sides of the back frame, and an end of the connecting shaft protruding to one side of the back frame. It is selectively fastened with a fixing pin provided to adjust the inclination angle of the backrest, and an elastic body is connected to the rear of the lower end of the backrest, but the backrest is characterized in that the elastic body is constrained with the rear side of the backrest frame. Chair moved. The method of claim 5, The elastic body, The guide ring which is moved along the guide rod fixedly installed on the backrest is coupled to one end and the other end is connected to a variable rod which is screwed with a control rod detachably attached to the opening groove formed at the rear side of the backrest frame. The chair is moved backrest characterized in that. The method of claim 6, The opening groove, The chair is open toward the upper side of the back frame and the backrest is moved, characterized in that the backrest is rotated forward and lying on the connecting shaft when the control rod fitted in the opening groove is removed from the opening groove.

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