CN217218558U

CN217218558U - Stretching device and movable sofa

Info

Publication number: CN217218558U
Application number: CN202123452713.6U
Authority: CN
Inventors: 冯元峰; 王永梁; 吴林林; 王志禹
Original assignee: Kuka Home Co Ltd
Current assignee: Kuka Home Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-08-19
Anticipated expiration: 2031-12-30

Abstract

The application relates to a stretching device and a movable sofa, the stretching device comprises a base, a seat frame component, a backrest component for mounting a backrest and a foot rest component for mounting a foot pad, the seat frame component comprises a seat frame plate and a supporting rod, the tail part of the supporting rod is connected with the base and can swing relative to the base, and the base or a supporting carrier for supporting the base is provided with a fulcrum for limiting the downward deflection of the supporting rod; the side wall of the supporting rod is riveted with a joint rod, the joint rod is respectively provided with a fixed revolute pair node and a movable revolute pair node at two sides of the riveting position, wherein the fixed revolute pair node is connected with the base, a rear connecting rod is connected between the movable revolute pair node and the seat frame plate, and a front connecting rod is connected between the supporting rod and the seat frame plate; the leg rest component is linked with the head part of the supporting rod and the head part of the seat frame plate, and the back component is linked with the tail part of the seat frame plate and the base. This application has and has adopted a few several parts just to realize pedal and the order adjustment in proper order of back, simple structure, the high effect of travelling comfort.

Description

Stretching device and movable sofa

Technical Field

The application relates to the field of sofas, in particular to a stretching device and a movable sofa.

Background

Along with the improvement of living standard of people, the requirement on furniture is higher and higher. The sofa/rocking chair, the seat and the like in the furniture can be seen everywhere, and some sofas not only can extend the pedals, but also can ascend or descend the backrest.

In the existing movable sofa and seat, an electric or manual mechanical stretching device is usually installed inside the movable sofa and seat, so that the movable sofa and seat can be adjusted in stretching mode, and can be switched between different states.

There are two main types of mechanical stretching devices on the market.

The stretching device has a simple structure, but only has two posture changes, namely sitting posture and lying posture, the stretching device only can stretch the iron frame, and the sequence of controlling leg stretching and backrest overturning is not adjusted, so that leg stretching and backrest overturning can be carried out simultaneously, and user experience is greatly influenced.

The second is that the structure is very complex but can realize three posture changes, namely sitting posture, leisure posture and lying posture, and the sequential order of leg stretching and backrest turning is controlled to be adjusted through the very complex structure. However, the complicated structure also causes problems such as poor stability, easy interference of parts, inconvenience in operation, and high production/installation/maintenance costs.

SUMMERY OF THE UTILITY MODEL

In order to realize sequential adjustment of three postures by using a simple structure, the application provides an extension device and a movable sofa.

In a first aspect, the present application provides an extension apparatus, which adopts the following technical solutions:

an extension device comprises a base, a seat frame assembly, a backrest assembly for mounting a backrest and a foot rest assembly for mounting a foot pad, wherein the seat frame assembly comprises a seat frame plate and a supporting rod, the tail part of the supporting rod is connected with the base and can swing relative to the base, and the base or a supporting carrier for supporting the base is provided with a fulcrum for limiting the downward deflection of the supporting rod; the side wall of the supporting rod is riveted with a joint rod, the joint rod is respectively provided with a fixed revolute pair node and a movable revolute pair node at two sides of the riveting position, wherein the fixed revolute pair node is connected with the base, a rear connecting rod is connected between the movable revolute pair node and the seat frame plate, and a front connecting rod is connected between the supporting rod and the seat frame plate; the leg rest assembly is linked with the head part of the supporting rod and the head part of the seat frame plate and limits the maximum opening angle of the head part of the seat frame plate relative to the head part of the supporting rod; the backrest component is linked with the tail part of the seat frame plate and the base.

Through adopting above-mentioned technical scheme, seat frame subassembly itself possesses two kinds of change routes:

firstly, the support rod and the connecting rod are fixed, the seat frame plate is limited by the degree of freedom with the front connecting rod and the rear connecting rod as revolute pairs, and the seat frame plate can freely swing and rotate within a limited range; at this time, the leg rest assembly can be set to expand and contract by taking the angle and position change of the seat frame as power input, the main body of the backrest assembly can move together with the seat frame plate or keep not overturning relative to the base, and limitation can be exerted to change the angle and position change of the seat frame into a determined track.

After the leg rest assembly reaches the unfolding limit, the part of the seat frame plate connected with the leg rest assembly does not move or moves in a small range relative to the supporting rod, the connecting rod starts to swing upwards around a fixed point, and the supporting rod is dragged to also start to swing upwards around another fixed point; at the moment, the whole formed by the support rod and the seat frame plate swings upwards by taking the tail part as a fulcrum, and correspondingly, the relative position of the tail part of the seat frame plate and the base changes; meanwhile, the tail part of the seat frame plate is tilted relative to the supporting plate under the limitation of the unfolding limit of the leg rest component, so that the backrest component is forced to generate structural change relative to the base.

Therefore, sequential adjustment of the pedals and the backrest is realized by adopting a few parts, the structure is simple, and the comfort is high.

Optionally, a limit nail is fixed on the side wall of the supporting rod, a limit connecting rod set is movably riveted between the supporting rod and the base, and when the supporting rod is lifted to a set angle, the side wall of the limit pin is abutted against the limit connecting rod set and limits the supporting rod to continue to be lifted.

By adopting the technical scheme, the limiting connecting rod group can be adaptively changed along with the movement and the swing of the seat frame plate, so that the interference on the movement of the seat frame plate is avoided; when the seat frame plate is lifted up and the backrest component is turned down to a certain degree, the limiting connecting rod group can be tightened with the limiting pin to play a limiting role, and the use safety is improved.

Optionally, a pre-tensioning spring for forcing the support rod to descend is connected between the limiting connecting rod group and the base.

By adopting the technical scheme, when the user is used as power input, the effect of limiting the force application threshold value can be achieved. For example, the overall movement adopts: the user leans against the backrest with force, so that the backrest assembly is promoted to generate structural change; the pretension spring can improve the critical value of backrest change in the process, so that the backrest does not change or change in small amplitude when normally leaning against, and the gravity center changes when the backrest is forcefully leaned against or changes into a leaning posture.

Optionally, the middle of the supporting rod is bent, an avoiding space is formed between the bent part and the base, and the linking rod penetrates through the rod avoiding space and can freely rotate in the avoiding space.

Through adopting above-mentioned technical scheme, can provide the sufficient space of swinging of joint pole, make the joint pole can locate initial state's bracing piece top with the connected node of base, and the joint pole locates initial state's bracing piece below and can shift to the top of bracing piece with the connected node of back connecting rod to constitute the structure of lever, make the joint pole can drive the bracing piece lifting.

Optionally, the leg rest assembly includes an input component and a support component driven by the input component to be unfolded, a tension spring is connected between the input component and the seat frame plate, the tension spring reaches a maximum elongation amount in an unfolding process of the leg rest assembly, and the elongation amount of the tension spring in an unfolded state and the elongation amount of the tension spring in a contracted state of the leg rest assembly are both smaller than the maximum elongation amount.

By adopting the technical scheme, on one hand, the function of the bracket is similar to that of a pre-tensioned spring, so that the bracket component can be unfolded only by applying force instead of being unfolded by touching; on the other hand, the tension of the tension spring in the unfolding process of the leg rest assembly is changed from small to large to small, so that the unfolded state of the leg rest assembly can be maintained without continuously applying force to the backrest or the seat frame plate after the user unfolds the leg rest assembly.

Optionally, the input component includes a front footrest connector, a rear footrest connector, a front footrest adapter, and a rear footrest adapter; the front footrest connecting piece and the rear footrest connecting piece are movably riveted on the seat frame plate, the riveting point of the front footrest connecting piece is positioned above the riveting point of the rear footrest connecting piece, different parts of the side wall of the front footrest adapting piece are movably riveted with the supporting rod and the front footrest connecting piece respectively, and different parts of the side wall of the rear footrest adapting piece are movably riveted with the front footrest connecting piece and the rear footrest connecting piece respectively.

By adopting the technical scheme, the revolute pairs of each point position of the front footrest connecting piece, the rear footrest connecting piece, the front footrest adapter piece and the rear footrest adapter piece are limited mutually, so that the free end of the front footrest connecting piece and the free end of the rear footrest adapter piece are synchronously close to each other in the process of lifting and are separated from each other in the process of descending, and the support component can be turned over while lifting.

Optionally, the lateral wall of back bracket adaptor is equipped with spacing bayonet lock, the lateral wall of preceding bracket connector is equipped with expansion draw-in groove and shrink draw-in groove, spacing bayonet lock inlays in expansion draw-in groove and prevents the bracket subassembly to continue to expand after the bracket subassembly expandes, spacing bayonet lock inlays in shrink draw-in groove and prevents the bracket subassembly to continue to shrink after the bracket subassembly contracts.

Through adopting above-mentioned technical scheme, the cooperation of two draw-in grooves of spacing bayonet lock makes the bracket subassembly possess and expand limit and shrink limit, enables to reach suitable position after the bracket subassembly expandes, forms suitable angle.

Optionally, the support component includes shank connecting rod, preceding footrest, back footrest and front and back connecting piece, the shank connecting rod is along its length direction in proper order with preceding footrest connecting piece, back footrest and preceding footrest activity riveting, the position that back footrest adaptor kept away from back footrest connecting piece is riveted with back footrest activity, the front and back connecting piece is riveted with preceding footrest and back footrest activity respectively.

Through adopting above-mentioned technical scheme, preceding footrest and back footrest constitute the upset platform, make the callus on the sole of installing above can realize the upset at the in-process that goes up and down, be vertical shrink in the lateral wall of sofa if the surface, expand the back and the seatpad parallel and level and keep the level.

In a second aspect, the present application provides a movable sofa, which adopts the following technical scheme:

a movable sofa comprises two stretching devices which are symmetrically arranged, and a cross beam is fixed between bases of the two stretching devices.

By adopting the technical scheme, the state change of the leg rest assembly and the backrest assembly can be realized through the change of the posture of a person, the adjusting critical value can be improved for increasing the safety, and correspondingly, the adjustment is realized in a mode of supporting the handrail by a hand to assist in force application; i.e. normal leaning will not result in a change of state of the leg rest assembly and the backrest assembly.

Optionally, two be connected with the linkage roof beam between the bracket subassembly, it has flexible driving piece to articulate on the crossbeam, the output and the linkage roof beam of flexible driving piece are articulated.

By adopting the technical scheme, the power source can be increased to realize automatic folding and unfolding.

In summary, the present application includes at least one of the following beneficial technical effects:

the seat frame assembly itself has two paths of change: firstly, the support rod and the connecting rod are fixed, the seat frame plate is limited by the degree of freedom with the front connecting rod and the rear connecting rod as revolute pairs, and the seat frame plate can freely swing and rotate within a limited range; at this time, the leg rest assembly can be set to expand and contract by taking the angle and position change of the seat frame as power input, the main body of the backrest assembly can move together with the seat frame plate or keep not overturning relative to the base, and limitation can be exerted to change the angle and position change of the seat frame into a determined track. After the leg rest assembly reaches the unfolding limit, the part of the seat frame plate connected with the leg rest assembly does not move or moves in a small range relative to the supporting rod, the connecting rod starts to swing upwards around a fixed point, and the supporting rod is dragged to also start to swing upwards around another fixed point; at the moment, the whole formed by the support rod and the seat frame plate swings upwards by taking the tail part as a fulcrum, and correspondingly, the relative position of the tail part of the seat frame plate and the base is changed; meanwhile, the tail part of the seat frame plate is tilted relative to the supporting plate under the limitation of the expansion limit of the leg rest component, so that the backrest component is forced to generate structural change relative to the base. Therefore, sequential adjustment of the pedals and the backrest is realized by adopting a few parts, and the chair has a simple structure and high comfort.

On one hand, the leg rest component and the backrest component can be unfolded by force instead of being unfolded once being collided; on the other hand, the tension of the tension spring in the unfolding process of the leg rest assembly is changed from small to large to small, so that the unfolded state of the leg rest assembly can be maintained without continuously applying force to the backrest or the seat frame plate after the user unfolds the leg rest assembly.

The state change of the leg rest component and the backrest component can be realized through the change of the posture of a person, in order to increase the safety, the adjusting critical value can be improved, and correspondingly, the adjustment is realized in a mode that the hand is supported on the handrail to assist in applying force; i.e. normal leaning will not result in a change of state of the leg rest assembly and the backrest assembly.

The power input can be either manual or electric.

Drawings

Fig. 1 is an overall configuration diagram of the stretching device of embodiment 1.

Fig. 2 is a side view of the extension device of embodiment 1 in a sitting position with the base cut away to allow viewing of the structure concealed by the base.

Fig. 3 is a side view of the leisure position of the stretching apparatus of embodiment 1, in which the base is cut away to allow the structure hidden by the base to be seen.

Fig. 4 is a side view of the lying position of the stretcher of embodiment 1 with the base cut away to allow viewing of the structure obscured by the base.

Fig. 5 is a schematic structural view of the movable sofa according to embodiment 2.

Description of the reference numerals: 1. a base; 2. a seat frame assembly; 21. a seat frame plate; 211. a rotation stopping pin; 22. a support bar; 24. a connecting rod; 241. a fixed revolute pair node; 242. a movable revolute pair node; 25. a rear connecting rod; 26. a front link; 27. a limit pin; 28. a limiting connecting rod group; 29. pre-tensioning the spring; 3. a backrest assembly; 31. a backrest insert; 311. a trench; 32. a back support; 4. a leg rest assembly; 401. an input section; 402. a support member; 41. a front leg rest attachment; 411. unfolding the clamping groove; 412. the clamping groove is contracted; 42. a rear leg rest connector; 43. a front leg rest adapter; 431. a limiting clamp pin; 44. a rear leg rest adapter; 45. a leg link; 46. a front footrest; 47. a rear footrest; 48. a front and rear connecting member; 49. a tension spring; 5. a cross beam; 6. a linkage beam; 7. a telescopic driving member; 10. a stretching device.

Detailed Description

The present application is described in further detail below with reference to the attached drawings.

The embodiment of the application discloses stretching device and activity sofa.

Example 1:

referring to fig. 1 and 2, an extension device includes a base 1, a seat frame assembly 2, a back assembly 3 for mounting a back rest, and a foot rest assembly 4 for mounting a foot rest. The base 1 is generally mounted to a bottom support of furniture as a mounting base of the stretching device, and is always kept in a fixed state throughout the change of posture of the stretching device. For convenience of description, the furniture is exemplified by but not limited to a sofa, and the seat cushion of the sofa can be mounted to the seat frame assembly 2 and also can be mounted to the base 1, and the embodiment is exemplified by being mounted to the base 1. The seat frame assembly 2 is positioned in the inner cavity of the sofa, and provides motion transmission for the backrest assembly 3 and the leg rest assembly 4 when the posture of the stretching device is changed, and the motion tracks are mutually limited, so that the position and the angle of the backrest and the leg pad relative to the seat cushion are changed. For convenience of orientation, the side of the extension device attached to the footpad is considered the leading side and the side of the extension device attached to the backrest is considered the trailing side.

The seat frame assembly 2 comprises a seat frame plate 21 and a supporting rod 22, the tail part of the supporting rod 22 is movably riveted with the base 1, and the head part of the supporting rod 22 can swing relative to the base 1. The base 1 or a support carrier for supporting the base 1 is provided with a fulcrum limiting the downward deflection of the support bar 22, such as the bottom support of the furniture described above.

The middle part of the support rod 22 is bent, and an avoiding space is formed between the bent part and the base 1. The side wall of the support rod 22 is riveted with a joint rod 24, and the joint rod 24 penetrates through the rod avoiding space and can freely rotate in the avoiding space. The connecting rod 24 is respectively provided with a fixed revolute pair node 241 and a movable revolute pair node 242 at two sides of the riveting position with the support rod 22, wherein the fixed revolute pair node 241 is connected with the base 1, and when the support rod 22 is laid flat, the fixed revolute pair node 241 is located above the support rod 22 and is closer to the head of the support rod 22 relative to the movable revolute pair node 242. A rear connecting rod 25 is connected between the movable revolute pair node 242 and the seat frame plate 21, and the rear connecting rod 25 is L-shaped. A front connecting rod 26 is connected between the head part of the supporting rod 22 and the seat frame plate 21.

At this time, the seat frame plate 21 can be regarded as having a two-stage change path with respect to the base 1: in the first stage, the support rod 22 and the connecting rod 24 are not moved, and the seat frame plate 21 is limited by the degree of freedom with the front link 26 and the rear link 25 as revolute pairs, thereby realizing free swing and rotation of the seat frame plate 21 within the limited range. Referring to fig. 3 and 4, in the second stage, the support rod 22 is lifted, and the seat frame plate 21 makes corresponding movement in the state that the support rod 22 is lifted. Both movements will be limited by the backrest module 3 and the leg rest module 4 to form a specific movement track, wherein the first stage movement will drive the extension and contraction of the leg rest module 4, and the second stage movement will drive the extension and contraction of the backrest module 3.

Referring to fig. 2 and 3, leg rest assembly 4 includes an input member 401 and a support member 402 that is deployed by input member 401.

The input member 401 comprises a front foot-rest connector 41, a rear foot-rest connector 42, a front foot-rest adaptor 43 and a rear foot-rest adaptor 44. The front footrest connector 41 and the rear footrest connector 42 are both movably riveted to the seat frame plate 21, and the riveting point of the front footrest connector 41 is located above the riveting point of the rear footrest connector 42. The side walls at the two ends of the front footrest adapter 43 are respectively in movable riveting with the support rod 22 and the front footrest connector 41, and the side wall corresponding to one end of the rear footrest adapter 44 is in movable riveting with the side wall at the end of the rear footrest connector 42. The rear footrest adapter 44 and the front footrest connector 41 are staggered with each other and are movably riveted with each other at the staggered positions. The free ends of the rear leg rest adapter 44 and the front leg rest attachment 41 are connected to the support member 402.

The support member 402 includes a leg link 45, a front footrest 46, a rear footrest 47, and front and rear connectors 48, the leg link 45 is movably riveted to the front footrest connector 41, the rear footrest 47, and the front footrest 46 in this order along the length direction thereof, one end of the rear footrest adapter 44 remote from the rear footrest connector 42 is movably riveted to the rear footrest 47, and both ends of the front and rear connectors 48 are movably riveted to the front footrest 46 and the rear footrest 47, respectively.

In the case of the unfolding motion of the leg rest unit 4, the rivet point between the head portion of the seat frame plate 21 and the front link 26 moves to the tail portion of the support rod 22 around the rivet point between the front link 26 and the support rod 22, and the head portion of the seat frame plate 21 also moves correspondingly and slightly swings. In this process, the front footrest connector 41, the rear footrest connector 42, and the front footrest adapter 43 are all swung upward, the support member 402 is swung upward as a whole, and the planes of the front footrest 46 and the rear footrest 47 are turned to the horizontal. With the orientation in this state as a reference, the upper sidewall of the front leg rest connector 41 is provided with an expansion slot 411 and a contraction slot 412, the sidewall of the rear leg rest adapter 44 is provided with a limit latch 431, and at this time, the limit latch 431 is embedded in the expansion slot 411 and prevents the leg rest assembly 4 from continuing to expand. If the leg rest assembly 4 is in the retracted state, the limiting bayonet 431 is embedded in the retracting bayonet 412 and prevents the leg rest assembly 4 from being retracted continuously.

After the leg rest assembly 4 is extended to the limit, the seat frame assembly 2 can be moved in a second stage to adjust the backrest assembly 3.

Referring to fig. 3 and 4, the backrest module 3 includes a backrest insertion sheet 31 and a backrest support 32, and both ends of the backrest support 32 are movably riveted with the middle portions of the base 1 and the backrest insertion sheet 31, respectively. One end of the backrest insertion sheet 31 is hook-shaped and is formed with a groove 311, and the middle part of the hook-shaped structure is movably riveted with the tail part of the seat frame plate 21. The rotation stopping pin 211 is welded on the side wall of the seat frame plate 21, and when the backrest inserting sheet 31 is turned downwards to a set turning-downwards position, the rotation stopping pin 211 is abutted against the side wall of the groove 311; when the back plate 31 is turned up to the set home position, the rotation stop pin 211 abuts against the other part of the side wall of the groove 311. The downward-turning position and the return position can be set according to actual requirements, for example, the backrest corresponding to the backrest inserting piece 31 is used as a reference, the downward-turning position is a position where the surface of the backrest is horizontal, and the return position is a position where the surface of the backrest is vertical.

Referring to fig. 1, 3 and 4, when the second stage of movement is performed, the support rod 22 is turned up, the end of the backrest insertion piece 31 away from the seat frame plate 21 is turned down, and the riveted point between the seat frame plate 21 and the backrest insertion piece 31 is turned up. When the backrest is turned flat, the backrest is not suitable to be turned down any more, correspondingly, a limit nail 27 is fixed on the side wall of the support rod 22, a limit connecting rod group 28 is movably riveted between the support rod 22 and the base 1, and the limit connecting rod group 28 consists of two connecting rods. When the backrest is turned over, the support rod 22 is also lifted to a set angle, and at this time, the side wall of the limit pin is abutted against the limit linkage 28 and limits the support rod 22 to be continuously lifted. In addition, in this embodiment, the limit pin 27 and the fulcrum are the same component, and when the support rod 22 is in a horizontal state, the limit pin 27 abuts against the top of the base 1.

For the power source of the posture change of the stretcher, it is possible to push the seat frame plate 21 or the backrest backward.

Referring to fig. 1, in order to prevent the leg rest assembly 4 from extending or the backrest assembly 3 from turning backwards when a person leans against the backrest normally, a pre-tension spring 29 for forcing the support rod 22 to descend is connected between the limit linkage 28 and the base 1, and a tension spring 49 is connected between the input component 401 and the seat frame 21. Wherein, the tension spring 49 reaches the maximum elongation in the unfolding process of the leg rest assembly 4, and the elongation of the tension spring 49 in the unfolding state and the elongation of the tension spring 49 in the contraction state of the leg rest assembly 4 are both smaller than the maximum elongation. In this way, after the footrest assembly 4 is forcibly unfolded, the unfolded state of the footrest assembly 4 can be maintained without continuously applying a force to the backrest or the seat frame plate 21.

Example 2:

referring to fig. 5, the movable sofa comprises two stretching devices 10 of embodiment 1, the two stretching devices 10 are symmetrically arranged, a cross beam 5 is fixed between bases 1 of the two stretching devices 10, and a telescopic driving member 7 is hinged on the cross beam 5. A linkage beam 6 is connected between the two leg rest assemblies 4, and specifically, the linkage beam 6 is hinged with a front leg rest connecting piece 41 of the leg rest assembly 4. The output end of the telescopic driving piece 7 is hinged with the linkage beam 6. The telescopic drive 7 of this embodiment is an electric cylinder.

When the adjustment is needed, the electric cylinder is used as a power source for adjustment.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. A stretching device comprises a base (1), a seat frame component (2), a backrest component (3) for mounting a backrest and a foot rest component (4) for mounting a foot pad, and is characterized in that: the seat frame assembly (2) comprises a seat frame plate (21) and a supporting rod (22), the tail part of the supporting rod (22) is connected with the base (1) and can swing relative to the base (1), and the base (1) or a supporting carrier for supporting the base (1) is provided with a fulcrum for limiting the downward deflection of the supporting rod (22); the side wall of the supporting rod (22) is riveted with a joint rod (24), two sides of the riveting position of the joint rod (24) are respectively provided with a fixed revolute pair node (241) and a movable revolute pair node (242), wherein the fixed revolute pair node (241) is connected with the base (1), a rear connecting rod (25) is connected between the movable revolute pair node (242) and the seat frame plate (21), and a front connecting rod (26) is connected between the supporting rod (22) and the seat frame plate (21); the leg rest component (4) is linked with the head part of the support rod (22) and the head part of the seat frame plate (21) and limits the maximum opening angle of the head part of the seat frame plate (21) relative to the head part of the support rod (22); the backrest component (3) is linked with the tail part of the seat frame plate (21) and the base (1).

2. An extension device according to claim 1, wherein: bracing piece (22) lateral wall is fixed with spacing nail (27), the activity riveting has spacing linkage (28) between bracing piece (22) and base (1), and when bracing piece (22) lifting to the angle of settlement, the lateral wall and the spacing linkage (28) of spacer pin contradict and restrict bracing piece (22) and continue the lifting.

3. An extension device according to claim 2, wherein: a pretension spring (29) for forcing the support rod (22) to descend is connected between the limiting connecting rod group (28) and the base (1).

4. An extension device according to claim 1, wherein: the middle of the supporting rod (22) is bent, an avoiding space is formed between the bent part and the base (1), and the connecting rod (24) penetrates through the rod avoiding space and can freely rotate in the avoiding space.

5. An extension device as claimed in claim 1, wherein: the leg rest assembly (4) comprises an input component (401) and a supporting component (402) driven by the input component (401) to unfold, a tension spring (49) is connected between the input component (401) and the seat frame plate (21), the tension spring (49) reaches the maximum extension amount in the unfolding process of the leg rest assembly (4), and the extension amount of the tension spring (49) in the unfolding state and the extension amount of the tension spring (49) in the contraction state of the leg rest assembly (4) are both smaller than the maximum extension amount.

6. An extension device according to claim 5, wherein: the input component (401) comprises a front footrest connector (41), a rear footrest connector (42), a front footrest adapter (43) and a rear footrest adapter (44); preceding bracket connecting piece (41) and back bracket connecting piece (42) all activity riveting in pedestal board (21), and this riveting point of preceding bracket connecting piece (41) is located the top of the riveting point of back bracket connecting piece (42), the different positions of preceding bracket adaptor (43) lateral wall respectively with bracing piece (22) and preceding bracket connecting piece (41) activity riveting, the different positions of back bracket adaptor side wall respectively with preceding bracket connecting piece (41) and back bracket connecting piece (42) activity riveting.

7. An extension device according to claim 6, wherein: the lateral wall of back bracket adaptor (44) is equipped with spacing bayonet lock (431), the lateral wall of preceding bracket connector (41) is equipped with expansion draw-in groove (411) and shrink draw-in groove (412), inlay in expansion draw-in groove (411) and prevent bracket subassembly (4) to continue to expand after bracket subassembly (4) expand spacing bayonet lock (431), inlay in shrink draw-in groove (412) and prevent bracket subassembly (4) to continue to contract after bracket subassembly (4) shrink spacing bayonet lock (431).

8. An extension device according to claim 6, wherein: the support component (402) comprises a leg connecting rod (45), a front footrest (46), a rear footrest (47) and front and rear connecting pieces (48), wherein the leg connecting rod (45) is movably riveted with the front footrest connecting piece (41), the rear footrest (47) and the front footrest (46) along the length direction of the leg connecting rod in sequence, the part of the rear footrest connecting piece (44) far away from the rear footrest connecting piece (42) is movably riveted with the rear footrest (47), and the front and rear connecting pieces (48) are movably riveted with the front footrest (46) and the rear footrest (47) respectively.

9. A movable sofa is characterized in that: comprising two stretching devices (10) according to any one of claims 1 to 8, the two stretching devices (10) being arranged symmetrically, and a cross beam (5) being fixed between the bases (1) of the two stretching devices (10).

10. The movable sofa of claim 9, wherein: two be connected with linkage roof beam (6) between bracket subassembly (4), it has flexible driving piece (7) to articulate on crossbeam (5), the output of flexible driving piece (7) is articulated with linkage roof beam (6).