Width-adjustable row frame

Abstract

The utility model relates to furniture technical field, specifically disclose a width adjustable row skeleton, including first frame body, second frame body and adjustable telescopic mechanism, first frame body and second frame body are along the bed width direction sliding connection, adjustable telescopic mechanism includes: adjusting slot, set up in first frame body, along the bed width direction, the interval is equipped with a plurality of locking slots on adjusting slot, movable pulley assembly, movable setting in second frame body, movable pulley assembly has first state and second state: when being in first state, movable pulley assembly has the tendency of swinging to first direction, to card into any locking slot, the sliding of first frame body and second frame body in the direction of mutual approach is locked, when being in second state, the posture of movable pulley assembly is fixed and is located locking slot outside, first frame body and second frame body between arbitrary sliding to realize the telescoping of row skeleton in the bed width direction. The width adjustable row skeleton can solve the universality problem of row skeleton.

Description

Technical Field

[0001] This utility model relates to the field of furniture technology, and in particular to a slatted frame with adjustable width. Background Technology

[0002] In existing furniture technology, conventional bed frames typically employ a fixed-size, integral structure, with the outer frame made of rectangular tubing or other profiles welded or fixedly connected. The length and width dimensions of this type of frame are predetermined at the factory, and a single frame size can usually only fit a bed frame with a specific inner diameter.

[0003] When users need to replace their beds or when bed size standards change, the original fixed-size slatted frame often cannot match the new bed, resulting in idle and wasted resources. Manufacturers also need to produce and stock various specifications of slatted frames for beds of different sizes to meet the differentiated needs of the market, which not only increases the complexity of production management but also occupies a lot of storage space. Utility Model Content

[0004] The purpose of this invention is to provide a width-adjustable slat frame to solve the problem of slat frame versatility.

[0005] This utility model provides a width-adjustable slatted bed frame, which includes a first frame, a second frame, and an adjustable telescopic mechanism. The first frame and the second frame are slidably connected along the width direction of the bed. The adjustable telescopic mechanism includes:

[0006] An adjustment slot extends along the width of the bed and is provided on the first frame. Along the width of the bed, the adjustment slot is provided with a plurality of locking slots at intervals.

[0007] The movable pulley assembly is movably mounted on the second frame, and the movable pulley assembly has a first state and a second state:

[0008] When in the first state, the movable pulley assembly has a tendency to swing in the first direction to engage with any of the locking slots, and the sliding of the first frame and the second frame in the direction of mutual approach is locked.

[0009] When in the second state, the movable pulley assembly is fixed in posture and located outside the locking slot, and the first frame and the second frame can slide arbitrarily to realize the extension and retraction of the slatted frame in the bed width direction.

[0010] As an optional technical solution, the locking groove includes a limiting wall and a guide wall. The limiting wall is located on the side of the locking groove away from the second frame, and the guide wall is located on the side of the locking groove close to the second frame. The limiting wall is arranged vertically, or the limiting wall is inclined towards the side close to the second frame, and the guide wall is inclined towards the side close to the second frame. When the movable pulley assembly is in the first state, the movable pulley assembly can slide along the guide wall to disengage from the locking groove.

[0011] As an optional technical solution, the movable pulley assembly includes a movable pulley and a limiting unit, wherein the limiting unit includes:

[0012] A connecting plate is rotatably mounted on the second frame. The movable pulley is connected to the connecting plate. As the connecting plate rotates, the movable pulley can selectively engage with the locking groove. The periphery of the connecting plate is provided with a first ratchet portion and a second ratchet portion that are spaced apart along its circumference.

[0013] The fixing bar is rotatably connected to the second frame at one end and has a hook at the other end;

[0014] When the pawl engages with the first ratchet, the limit position of the connecting plate's rotation along the first direction is limited, and the connecting plate can rotate within a preset angle so that the movable pulley swings up and down within a preset range, thereby selectively engaging with the locking groove.

[0015] When the pawl engages with the second ratchet, the rotational freedom of the connecting disc is restricted, so that the movable pulley remains outside the locking groove.

[0016] As an optional technical solution, multiple locking slots are provided at the bottom of the adjustment slot hole, and the movable pulley assembly has a tendency to swing in the first direction under the action of gravity;

[0017] When the connecting plate rotates in the first direction, the movable pulley rotates downward;

[0018] When the connecting plate rotates in the second direction, the movable pulley rotates upward.

[0019] As an optional technical solution, the adjustment slot is provided with a first limiting section at one end near the second frame, and a first adjusting wall is provided at the bottom of the first limiting section. The first adjusting wall is inclined upward along the bed width direction near the second frame.

[0020] When the movable pulley assembly slides to the first limit section, the first adjusting wall abuts against the movable pulley and gradually lifts the movable pulley, while simultaneously pushing the connecting plate to rotate in the second direction until the hook engages with the second ratchet portion, and the movable pulley assembly switches to the second state.

[0021] As an optional technical solution, the end of the adjustment slot away from the second frame is provided with a second limiting section, and the top of the second limiting section is provided with a second adjusting wall. Along the bed width direction away from the second frame, the second adjusting wall is inclined downward.

[0022] When the movable pulley assembly slides to the second limit section, the second adjusting wall abuts against the movable pulley and gradually presses down on the movable pulley, while simultaneously pushing the connecting plate to rotate in the second direction until the pawl disengages from the second ratchet portion, and the movable pulley assembly switches to the first state.

[0023] As an optional technical solution, the connecting plate includes a main plate, a connecting rod, and a collar. The two ends of the connecting rod are respectively connected to the main plate and the collar. The main plate is rotatably mounted on the second frame. The first ratchet and the second ratchet are both located on the periphery of the main plate. The movable pulley is installed through the collar.

[0024] As an optional technical solution, the limiting unit further includes:

[0025] The elastic retainer has one end connected to the second frame and the other end abutting or connected to the fixing strip. The elastic retainer has a tendency to push the fixing strip toward the connecting disc to keep the pawl engaged with the first ratchet or the second ratchet.

[0026] As an optional technical solution, the movable pulley assembly includes two limiting units, which are symmetrically arranged along the length of the bed. The movable pulley is configured as a roller-shaped structure, and the two connecting discs are respectively connected to both ends of the movable pulley.

[0027] As an optional technical solution, the first frame is provided in the middle of the first frame, which is arranged along the width of the bed. The first frame is configured as a hollow structure, and the adjustment slot is opened in the first frame.

[0028] The second frame has a second frame strip in the middle part along the width of the bed. The second frame strip passes through the first frame strip, and the movable pulley assembly is installed on the second frame strip near one end of the first frame.

[0029] The adjustable width slat frame provided by this utility model has at least the following beneficial effects:

[0030] The width-adjustable slat frame includes a sliding and telescopic first frame and a second frame. Telescopic adjustment is achieved through an adjustable telescopic mechanism, which includes an adjustment slot and a movable pulley assembly. The adjustment slot is located on the first frame and has multiple locking slots spaced apart. The movable pulley assembly is movably mounted on the second frame and has two states: In the first state, the movable pulley assembly can engage with any locking slot, locking the sliding of the first and second frames in the direction of approach. The user can still pull the first and second frames outwards to increase the width of the slat frame. In the second state, the movable pulley assembly is fixed in position and outside the locking slot, allowing the first and second frames to slide freely to achieve telescopic movement of the slat frame in the bed width direction. In summary, the width-adjustable slat frame provided by this invention can adjust its width to adapt to different specifications of bed frames, offering greater versatility, avoiding resource idleness and waste, and meeting differentiated market demands without increasing the complexity of production management or consuming more storage space. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the adjustable-width slat frame in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the first frame bar and the adjusting slot in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the structure of the second frame bar and the movable pulley assembly in an embodiment of this utility model;

[0034] Figure 4 This is a schematic diagram of the movable pulley assembly in its first state in an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of the movable pulley assembly in the second state in an embodiment of this utility model.

[0036] In the picture:

[0037] 100. First frame; 101. First frame strip; 102. Third frame strip; 200. Second frame; 201. Second frame strip; 202. Fourth frame strip;

[0038] 10. Adjusting slot; 11. Locking slot; 12. Limiting wall; 13. Guide wall; 14. First limiting section; 15. First adjusting wall; 16. Second limiting section; 17. Second adjusting wall;

[0039] 20. Movable pulley assembly; 21. Movable pulley; 22. Connecting plate; 1. First ratchet part; 2. Second ratchet part; 221. Main plate part; 222. Connecting rod part; 223. Collar part; 23. Fixing bar; 231. Claw; 24. Elastic retaining element; 25. First pivot; 26. Second pivot; 27. Fixing pin. Detailed Implementation

[0040] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0041] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Moreover, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0043] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0044] like Figures 1 to 5 As shown, this embodiment provides a width-adjustable slatted bed frame, which includes a first frame 100 and a second frame 200, which are slidably connected along the bed width direction. Specifically, the first frame 100 has a first frame strip 101 arranged along the bed width direction in its middle, and the first frame strip 101 is a hollow structure. The second frame 200 has a second frame strip 201 arranged along the bed width direction in its middle, and the second frame strip 201 passes through the first frame strip 101. The first frame 100 has a third frame strip 102 arranged along the bed width direction at the head and foot of the bed, and the third frame strip 102 is a hollow structure. The second frame 200 has a fourth frame strip 202 arranged along the bed width direction at the head and foot of the bed, respectively. Through the sliding connection between the above frame strips, the extension and contraction in the bed width direction and the limiting in the bed length direction are realized.

[0045] Furthermore, such as Figures 1 to 5 As shown, the slatted frame includes an adjustable telescopic mechanism, which includes an adjustment slot 10 and a movable pulley assembly 20. The adjustment slot 10 extends along the bed width direction and is disposed on the first frame bar 101 of the first frame 100. Along the bed width direction, the adjustment slot 10 is provided with multiple locking slots 11 spaced apart. The movable pulley assembly 20 is movably disposed on the second frame bar 201 of the second frame 200, specifically installed on the second frame bar 201 near the end of the first frame 100. The movable pulley assembly 20 has a first state and a second state.

[0046] When in the first state, the movable pulley assembly 20 has a tendency to swing in the first direction to engage with any locking slot 11. The sliding of the first frame 100 and the second frame 200 in the direction of approaching each other is locked. At this time, the user can still pull the first frame 100 and the second frame 200 outward to increase the width of the frame.

[0047] When in the second state, the movable pulley assembly 20 is fixed in posture and located outside the locking groove 11, and the first frame 100 and the second frame 200 can slide arbitrarily to realize the extension and retraction of the slatted frame in the width direction of the bed.

[0048] In summary, the adjustable-width slat frame provided in this embodiment can adjust its width to adapt to different specifications of bed frames, thus increasing its versatility, avoiding idle and wasteful resources, and meeting the differentiated needs of the market without increasing the complexity of production management or the storage space occupied.

[0049] For example, such as Figure 4 and Figure 5As shown, the locking groove 11 includes a limiting wall 12 and a guide wall 13. The limiting wall 12 is located on the side of the locking groove 11 away from the second frame 200, and the guide wall 13 is located on the side of the locking groove 11 close to the second frame 200. The limiting wall 12 is arranged vertically, or the limiting wall 12 is inclined towards the side close to the second frame 200, and the guide wall 13 is inclined towards the side close to the second frame 200. When the movable pulley assembly 20 is in the first state, the movable pulley assembly 20 can slide along the guide wall 13 to disengage from the locking groove 11. In this embodiment, the limiting wall 12 is arranged vertically.

[0050] For example, such as Figure 4 and Figure 5 As shown, the guide wall 13 extends along an arc-shaped path to reduce the sliding resistance of the guide wall 13 on the movable pulley assembly 20, making the movement of the movable pulley assembly 20 out of the locking groove 11 smoother and improving the user experience.

[0051] For example, such as Figures 3-5 As shown, the movable pulley assembly 20 includes a movable pulley 21 and a limiting unit. The limiting unit includes a connecting plate 22 and a fixing bar 23. The connecting plate 22 is rotatably mounted on the second frame 200 via a first rotating shaft 25. The movable pulley 21 is connected to the connecting plate 22. As the connecting plate 22 rotates, the movable pulley 21 can selectively engage with the locking groove 11. The periphery of the connecting plate 22 is provided with a first ratchet portion 1 and a second ratchet portion 2 spaced apart along its circumference. One end of the fixing bar 23 is rotatably mounted on the second frame 200 via a second rotating shaft 26, and the other end of the fixing bar 23 is provided with... There is a pawl 231; when the pawl 231 is engaged with the first ratchet part 1, the limit position of the connecting plate 22 rotating in the first direction is limited, and the connecting plate 22 can reciprocate within a preset angle so that the movable pulley 21 swings up and down within a preset range, thereby selectively engaging with the locking groove 11. At this time, the movable pulley assembly 20 is in the first state; when the pawl 231 is engaged with the second ratchet part 2, the rotational freedom of the connecting plate 22 is restricted by the fixing bar 23 so that the movable pulley 21 is kept outside the locking groove 11. At this time, the movable pulley assembly 20 is in the second state.

[0052] For example, such as Figure 2 As shown, multiple locking slots 11 are located at the bottom of the adjusting slot 10. The movable pulley assembly 20 tends to swing in a first direction under the influence of gravity. When the connecting plate 22 rotates in the first direction, the movable pulley 21 rotates downwards; when the connecting plate 22 rotates in a second direction, the movable pulley 21 rotates upwards. It should be noted that the first direction is... Figures 3 to 5 The counterclockwise direction shown is the second direction. Figures 3 to 5The clockwise direction is shown. In some embodiments, an elastic element such as a torsion spring can be provided on the first rotating shaft 25 to push the movable pulley 21 to rotate toward the locking groove 11 by elastic force.

[0053] For example, in order to switch the state of the active pulley assembly 20, such as Figure 2 , Figure 4 and Figure 5 As shown, the adjusting slot 10 is provided with a first limiting section 14 at one end near the second frame 200. The bottom of the first limiting section 14 is provided with a first adjusting wall 15. Along the bed width direction near the second frame 200, the first adjusting wall 15 is inclined upward. When the movable pulley assembly 20 slides to the first limiting section 14, the first adjusting wall 15 abuts against the movable pulley 21 and gradually lifts the movable pulley 21. At the same time, it pushes the connecting plate 22 to rotate in the second direction until the hook 231 is engaged with the second ratchet part 2, and the movable pulley assembly 20 switches to the second state.

[0054] At the end 200 meters away from the second frame, such as Figure 2 As shown, the adjusting slot 10 is provided with a second limiting section 16, and a second adjusting wall 17 is provided at the top of the second limiting section 16. The second adjusting wall 17 is inclined downward along the bed width direction away from the second frame 200. When the movable pulley assembly 20 slides to the second limiting section 16, the second adjusting wall 17 abuts against the movable pulley 21 and gradually presses down on the movable pulley 21, while pushing the connecting plate 22 to rotate in the second direction until the hook 231 disengages from the second ratchet portion 2, and the movable pulley assembly 20 switches to the first state. It should be noted that the second ratchet portion 2 is set as a V-shaped groove structure. When a pushing force is applied to the connecting plate 22 to drive the connecting plate 22 to rotate, the hook 231 can disengage from the second ratchet portion 2 along the inclined groove wall of the second ratchet portion 2, thereby unlocking the connecting plate 22.

[0055] For example, the specific structure of the connecting disk 22 is as follows: Figure 3 As shown, the connecting plate 22 includes a main plate portion 221, a connecting rod portion 222, and a collar portion 223. The two ends of the connecting rod portion 222 are respectively connected to the main plate portion 221 and the collar portion 223. The main plate portion 221 is rotatably mounted on the second frame 200 via a first rotating shaft 25. The first ratchet portion 1 and the second ratchet portion 2 are both located on the periphery of the main plate portion 221. The movable pulley 21 is installed through the collar portion 223.

[0056] For example, such as Figure 3As shown, the limiting unit also includes an elastic retainer 24. One end of the elastic retainer 24 is connected and fixed to the second frame 200 via a fixing pin 27, and the other end of the elastic retainer 24 abuts against or connects to the fixing strip 23. The elastic retainer 24 has a tendency to push the fixing strip 23 toward the connecting disc 22 to keep the hook 231 in abutting against the periphery of the connecting disc 22, and to keep it engaged with the first ratchet portion 1 or the second ratchet portion 2, preventing the hook 231 from disengaging from the connecting disc 22. In this embodiment, the elastic retainer 24 is a compression spring. In some embodiments, the elastic retainer 24 may also be a tension spring or other elastic element.

[0057] For example, such as Figure 3 As shown, the movable pulley assembly 20 includes two limiting units, which are symmetrically arranged on the two side walls of the second frame bar 201 along the length of the bed. The movable pulley 21 is configured as a roller-shaped structure, and two connecting discs 22 are respectively connected to the two ends of the movable pulley 21 to improve the reliability of the installation structure.

[0058] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A width-adjustable slat frame, characterized in that, The bed includes a first frame (100), a second frame (200), and an adjustable telescopic mechanism. The first frame (100) and the second frame (200) are slidably connected along the width of the bed. The adjustable telescopic mechanism includes: An adjustment slot (10) extends along the width of the bed and is provided on the first frame (100). Along the width of the bed, the adjustment slot (10) is provided with a plurality of locking slots (11) at intervals. A movable pulley assembly (20) is movably mounted on the second frame (200), and the movable pulley assembly (20) has a first state and a second state: When in the first state, the movable pulley assembly (20) has a tendency to swing in the first direction to engage with any of the locking slots (11), and the sliding of the first frame (100) and the second frame (200) in the direction of mutual approach is locked; When in the second state, the movable pulley assembly (20) is fixed in posture and located outside the locking groove (11), and the first frame (100) and the second frame (200) can slide arbitrarily to realize the extension and retraction of the slatted frame in the bed width direction.

2. The adjustable-width slat frame according to claim 1, characterized in that, The locking groove (11) includes a limiting wall (12) and a guide wall (13). The limiting wall (12) is located on the side of the locking groove (11) away from the second frame (200), and the guide wall (13) is located on the side of the locking groove (11) close to the second frame (200). The limiting wall (12) is arranged vertically, or the limiting wall (12) is inclined toward the side close to the second frame (200), and the guide wall (13) is inclined toward the side close to the second frame (200). When the movable pulley assembly (20) is in the first state, the movable pulley assembly (20) can slide along the guide wall (13) to disengage from the locking groove (11).

3. The adjustable-width slat frame according to claim 1, characterized in that, The movable pulley assembly (20) includes a movable pulley (21) and a limiting unit, the limiting unit comprising: The connecting plate (22) is rotatably mounted on the second frame (200). The movable pulley (21) is connected to the connecting plate (22). As the connecting plate (22) rotates, the movable pulley (21) can selectively engage with the locking groove (11). The periphery of the connecting plate (22) is provided with a first ratchet portion (1) and a second ratchet portion (2) spaced apart along its circumference. A fixing bar (23) is rotatably connected to the second frame (200) at one end and has a hook (231) at the other end. When the pawl (231) engages with the first ratchet (1), the limit position of the connecting plate (22) rotating in the first direction is limited, and the connecting plate (22) can rotate within a preset angle so that the movable pulley (21) swings up and down within a preset range, thereby selectively engaging with the locking groove (11). When the pawl (231) engages with the second ratchet (2), the rotational freedom of the connecting disc (22) is restricted so that the movable pulley (21) remains outside the locking groove (11).

4. The adjustable-width slat frame according to claim 3, characterized in that, Multiple locking slots (11) are provided at the bottom of the adjustment slot (10), and the movable pulley assembly (20) has a tendency to swing in the first direction under the action of gravity; When the connecting disc (22) rotates in the first direction, the movable pulley (21) rotates downward; When the connecting disc (22) rotates in the second direction, the movable pulley (21) rotates upward.

5. The adjustable-width slat frame according to claim 4, characterized in that, The adjustment slot (10) is provided with a first limiting section (14) at one end near the second frame (200), and a first adjusting wall (15) is provided at the bottom of the first limiting section (14). The first adjusting wall (15) is inclined upward along the bed width direction near the second frame (200). When the movable pulley assembly (20) slides to the first limiting section (14), the first adjusting wall (15) abuts against the movable pulley (21) and gradually lifts the movable pulley (21), while pushing the connecting plate (22) to rotate in the second direction until the hook (231) engages with the second ratchet part (2), and the movable pulley assembly (20) switches to the second state.

6. The adjustable-width slat frame according to claim 4, characterized in that, The adjustment slot (10) is provided with a second limiting section (16) at one end away from the second frame (200), and a second adjusting wall (17) is provided at the top of the second limiting section (16). The second adjusting wall (17) is inclined downward along the bed width direction away from the second frame (200). When the movable pulley assembly (20) slides to the second limiting section (16), the second adjusting wall (17) abuts against the movable pulley (21) and gradually presses down the movable pulley (21), while pushing the connecting plate (22) to rotate in the second direction until the hook (231) disengages from the second ratchet part (2), and the movable pulley assembly (20) switches to the first state.

7. The adjustable-width slat frame according to claim 3, characterized in that, The connecting plate (22) includes a main plate (221), a connecting rod (222) and a collar (223). The two ends of the connecting rod (222) are respectively connected to the main plate (221) and the collar (223). The main plate (221) is rotatably mounted on the second frame (200). The first ratchet (1) and the second ratchet (2) are both provided on the periphery of the main plate (221). The movable pulley (21) is installed through the collar (223).

8. The adjustable width slat frame according to claim 3, characterized in that, The limiting unit further includes: The elastic retainer (24) is connected at one end to the second frame (200) and at the other end to abut or connect to the fixing strip (23). The elastic retainer (24) has a tendency to push the fixing strip (23) toward the connecting disc (22) to keep the claw (231) engaged with the first ratchet part (1) or the second ratchet part (2).

9. The width-adjustable slat frame according to claim 3, characterized in that, The movable pulley assembly (20) includes two limiting units, which are symmetrically arranged along the length of the bed. The movable pulley (21) is configured as a roller-shaped structure, and the two connecting discs (22) are respectively connected to the two ends of the movable pulley (21).

10. The width-adjustable slat frame according to any one of claims 1-9, characterized in that, The first frame (100) has a first frame strip (101) in the middle part along the width of the bed. The first frame strip (101) is a hollow structure, and the adjustment slot (10) is opened in the first frame strip (101). The second frame (200) has a second frame strip (201) arranged along the width of the bed in the middle. The second frame strip (201) passes through the first frame strip (101). The movable pulley assembly (20) is installed on the second frame strip (201) at one end near the first frame (100).

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