Stepless lifting tablet chair tube frame device and corresponding stepless lifting tablet chair

Abstract

The utility model provides a stepless lifting tablet chair tube frame device and a corresponding stepless lifting tablet chair. The stepless lifting tablet chair tube frame device comprises a tablet chair upper tube frame, a tablet chair lower tube frame, two hand cranking lifters, a linkage rod and a hand cranking handle. The tablet chair upper pipe frame comprises two upper vertical pipes; the lower tube frame of the tablet chair comprises two lower vertical tubes; a hand-cranking lifter is arranged between each upper vertical pipe and each lower vertical pipe; the two ends of the linkage rod are connected to driving holes of the two hand cranking lifters respectively. The hand crank is detachably connected to a driving hole. When the height of the tablet chair needs to be adjusted, a hand crank is connected to a driving hole, one of the hand cranking lifters is driven through the hand crank, the two hand cranking lifters can synchronously ascend and descend through a linkage rod, the two upper vertical pipes can synchronously ascend and descend, and therefore it is guaranteed that the relative position between the tablet chair upper pipe frame and the tablet chair lower pipe frame is stably adjusted; the overall height of the stepless lifting tablet chair tube frame device is adjusted conveniently, and stable lifting of the left side and the right side is effectively guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of school chairs, and in particular to a stepless height-adjustable school chair frame device and a corresponding stepless height-adjustable school chair. Background Technology

[0002] Students vary in height, and their height changes as they grow. To ensure proper posture and comfort, school chairs are typically designed with a continuously adjustable height. However, current technology requires individual height adjustment for each support point, which is inconvenient and can cause uneven seat surfaces, affecting usability. Utility Model Content

[0003] This utility model provides a stepless height-adjustable chair frame device and a corresponding stepless height-adjustable chair, which is convenient to adjust and effectively ensures smooth height adjustment.

[0004] This utility model provides a stepless lifting chair tube frame device, including an upper chair tube frame, a lower chair tube frame, two hand-cranked lifting devices, a linkage rod, and a hand crank;

[0005] The chair frame is used to install the seat and backrest, and includes two upper uprights;

[0006] The lower frame of the chair includes two lower uprights; the bottoms of the two upper uprights are respectively inserted into the two lower uprights, and a hand-cranked lifting device is provided between each upper upright and each lower upright; each hand-cranked lifting device has a drive hole.

[0007] The two ends of the linkage are respectively connected to the two drive holes;

[0008] The hand crank is detachably connected to one of the drive holes so as to drive the two hand cranks to rise and fall synchronously through the drive hole and the linkage rod.

[0009] The chair frame includes a seat frame and a backrest frame. The seat frame is fixed to the top of the two upper uprights and has a seat mounting hole for mounting the seat. The backrest frame is connected to the back of the seat frame and has a backrest mounting hole for mounting the backrest.

[0010] The seat plate frame includes two longitudinal tubes and two transverse tubes, which are connected to form a square frame. The two longitudinal tubes are arranged in the left-right direction and are fixedly connected to the top of the two upper upright tubes respectively. The two transverse tubes are arranged in the front-back direction.

[0011] The backrest tube frame includes a top tube and two back tubes. The bottoms of the two back tubes are respectively connected to the two ends of the two horizontal tubes. The tops of the two back tubes are close to each other and bent, and are fixedly connected by the top tube.

[0012] Among them, an inner insertion hole is provided on the pipe wall of the two lower upright pipes at the position corresponding to the driving hole. The linkage rod passes through the inner insertion hole and is inserted into one end of the driving hole, and the linkage rod is circumferentially positioned with the driving hole.

[0013] One of the lower tubes has an external insertion hole on its wall, which is corresponding to the other end of the drive hole. The hand crank passes through the external insertion hole and is detachably inserted into the other end of the drive hole.

[0014] The lower frame of the chair also includes a lower horizontal connecting pipe, the two ends of which are fixedly connected to the two lower vertical pipes respectively, and the linkage rod is sleeved in the lower horizontal connecting pipe;

[0015] Both ends of the lower horizontal connecting pipe are provided with notches; the linkage rod is sleeved in the lower horizontal connecting pipe; a pin hole is provided at one end of the linkage rod near the outer insertion hole, and a positioning pin is inserted into the pin hole. The pin hole is provided in accordance with the notch so that the positioning pin is exposed through the notch.

[0016] The hand-cranked lifting device includes a gearbox, an active bevel gear, a transmission bevel gear, a lead screw, a gear sleeve, and a limiting guide block. The gearbox is fixed in the lower vertical tube. The active bevel gear meshes with the transmission bevel gear, and both are rotatably disposed in the gearbox. The rotation axis of the active bevel gear is the centerline axis of the linkage rod. The driving hole is disposed in the active bevel gear and passes through the active bevel gear along its rotation axis. The transmission bevel gear is fixedly connected to the bottom end of the lead screw to drive the lead screw to rotate around its central axis. The gear sleeve is threadedly connected to the lead screw and is fixed in the upper vertical tube. The limiting guide block is slidably disposed in the upper vertical tube along its axial direction, and the top end of the lead screw is rotatably connected to the limiting guide block.

[0017] The hand crank includes a drive rod, a crank body, and a handle; the drive rod is fixedly connected to one end of the crank body, and the drive rod is made of metal and is used to insert into the drive hole; the crank body is made of plastic; the drive rod and the crank body are manufactured by in-mold injection molding; a rocker arm is fixed to the other end of the crank body, and the handle is a hollow structure that is sleeved on the rocker arm and rotatably connected to the rocker arm.

[0018] The drive rod has a hexagonal cross-section, the drive hole has a hexagonal hole, and the linkage rod has a hexagonal cross-section.

[0019] The continuously adjustable chair frame device further includes a connecting sleeve; the top inner side of the lower upright tube is provided with a buckle hole, the outer side of the connecting sleeve is provided with a buckle, the bottom of the connecting sleeve is inserted into the inner cavity of the lower upright tube, and the buckle is engaged in the buckle hole; the top of the connecting sleeve protrudes from the lower upright tube; the upper upright tube is inserted into the inner hole of the connecting sleeve and slides up and down in the inner hole of the connecting sleeve.

[0020] This utility model also provides a continuously adjustable school chair, including a seat board, a backrest, and the aforementioned continuously adjustable school chair frame device; the seat board and the backrest are both installed on the upper frame of the continuously adjustable school chair frame device.

[0021] The continuously adjustable chair frame device and corresponding continuously adjustable chair provided by this utility model allow for the adjustment of chair height by connecting a hand crank to the drive hole of a hand crank lifter. The hand crank drives one of the hand crank lifters, and the linkage rod enables both hand crank lifters to rise and fall synchronously. The two upper uprights can also rise and fall synchronously, thus ensuring a smooth adjustment of the relative position between the upper and lower uprights of the chair. This achieves the overall height adjustment of the continuously adjustable chair frame device, which is convenient and effectively ensures smooth rise and fall on both sides. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the stepless lifting chair frame device provided in a preferred embodiment of this utility model;

[0023] Figure 2 yes Figure 1 A structural schematic diagram of the stepless height-adjustable chair frame device from another angle;

[0024] Figure 3 yes Figure 2 A structural schematic diagram of the stepless height-adjustable school chair frame device from another angle;

[0025] Figure 4 yes Figure 2 Exploded view of the frame device for a continuously adjustable school chair;

[0026] Figure 5 yes Figure 3 Enlarged view of point A in the image;

[0027] Figure 6 yes Figure 4 A schematic diagram of the hand-cranked lifting mechanism of the stepless height-adjustable school chair frame device;

[0028] Figure 7 yes Figure 6 Exploded view of the hand-cranked lifting mechanism;

[0029] Figure 8 yes Figure 4 A schematic diagram of the hand crank of the stepless height-adjustable chair frame device. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0031] In the diagram, units with similar structures are represented by the same labels.

[0032] A preferred embodiment of this utility model provides a continuously adjustable chair, including a seat, a backrest, and a continuously adjustable chair frame device 100. Both the seat and backrest are mounted on the continuously adjustable chair frame device 100, which allows for adjustment of their heights.

[0033] like Figure 1 , Figure 2 and Figure 3 As shown, the continuously adjustable chair frame device 100 includes an upper chair frame 1, a lower chair frame 2, two hand-cranked lifters 3, a linkage rod 4, and a hand crank 5. The upper chair frame 1 and the lower chair frame 2 are connected by the two hand-cranked lifters 3. The linkage rod 4 connects the two hand-cranked lifters 3, and the hand crank 5 is used to drive the lifting action of the hand-cranked lifters 3.

[0034] The upper frame 1 of the chair is used to install the seat and backrest, and includes two upper uprights 11. The lower frame 2 of the chair includes two lower uprights 21. The bottoms of the two upper uprights 11 are respectively inserted into the two lower uprights 21. The two upper uprights 11 and the two lower uprights 21 can be connected to form the two legs of the chair, which are respectively located on the left and right sides of the chair. A hand-cranked lifting device 3 is provided between each upper upright 11 and each lower upright 21. The two hand-cranked lifting devices 3 are used to adjust the position between the two upper uprights 11 and the two lower uprights 21. By changing the position of the upper uprights 11, the height of the two legs can be changed, thereby adjusting the height of the entire continuously adjustable chair frame device 100.

[0035] Each hand-cranked lifting device 3 has a drive hole 30. By rotating the drive hole 30, the hand-cranked lifting device 3 can be raised or lowered.

[0036] The two ends of the linkage rod 4 are respectively connected to the drive holes 30 of the two hand-cranked lifting devices 3, and the linkage rod 4 enables the two hand-cranked lifting devices 3 to rise and fall synchronously. The hand crank 5 is detachably connected to a drive hole 30, so as to drive the two hand-cranked lifting devices 3 to rise and fall synchronously through the drive hole 30 and the linkage rod 4, thereby enabling the two upper uprights 11 to rise and fall synchronously.

[0037] When the height of the chair needs to be adjusted, the hand crank 5 is connected to a hand crank lifter 3. The hand crank 5 drives one of the hand crank lifters 3, and the linkage rod 4 enables the two hand crank lifters 3 to rise and fall synchronously. The two upper uprights 11 can also rise and fall synchronously, thereby ensuring the smooth adjustment of the relative position between the upper upright frame 1 and the lower upright frame 2 of the chair. This achieves the adjustment of the overall height of the stepless height adjustment chair upright device 100, which is convenient and effectively ensures the smooth rise and fall of the left and right sides of the seat.

[0038] The seat and backrest are both mounted on the upper frame 1 of the school chair, more specifically, in conjunction with... Figure 1 and Figure 2 As shown, the upper frame 1 of the chair also includes a seat frame 12 and a backrest frame 13. The seat frame 12 is fixed to the top of the two upper uprights, so that the upper frame 1 of the chair forms an integral structure, improving structural strength. The seat frame 12 is provided with seat mounting holes 120 for installing the chair seat. The bottom of the backrest frame 13 is connected to the back side of the seat frame 12, and it is provided with backrest mounting holes 130 for installing the chair back. Through the seat mounting holes 120 and the backrest mounting holes 130, chair seats and backrests of different shapes, materials, and sizes can be installed with screws.

[0039] like Figure 2 , Figure 3 As shown, the seat plate support 12 includes two longitudinal tubes 121 and two transverse tubes 122, which are connected in a rectangular shape. The two longitudinal tubes 121 are arranged in the left-right direction and are fixedly connected to the top ends of the two upper upright tubes 11 respectively. Seat plate mounting holes 120 can be provided on the two longitudinal tubes 121 and / or the transverse tubes 122. The two transverse tubes 122 are arranged in the front-back direction. Utilizing the rectangular seat plate support 12 can improve structural strength and ensure support reliability.

[0040] The backrest support frame 13 includes a top tube 132 and two back tubes 131. The bottoms of the two back tubes 131 are respectively connected to the two ends of two horizontal tubes 122. The tops of the two back tubes 131 are close to each other and bent, and are fixedly connected by the top tube 132. Backrest mounting holes 130 can be provided on the two back tubes 131. The top tube 132 can be used to connect the two back tubes 131 into a single structure. The bent shape of the tops of the two back tubes 131 reduces the length of the top tube 132, facilitating the fixed connection between the two.

[0041] Combination Figure 4 and Figure 6 As shown, the hand-cranked lifting device 3 has a drive hole 30. On the opposing walls of the two lower vertical tubes 21, corresponding to the drive hole 30, there are inner insertion holes 211. The linkage rod 4 passes through the inner insertion hole 211 and is inserted into one end of the drive hole 30, with the linkage rod 4 circumferentially positioned with the drive hole 30. The inner insertion hole 211 exposes the drive hole 30, facilitating the connection between the linkage rod 4 and the drive hole 30.

[0042] Combination Figure 2 , Figure 4 As shown, one of the lower risers 21 has an external insertion hole 212 on its wall, which corresponds to the other end of the drive hole 30. The hand crank 5 passes through the external insertion hole 212 and is detachably inserted into the other end of the drive hole 30 to drive the hand crank lift 3 to rise and fall through the drive hole 30. The other end of the drive hole 30 is exposed through the external insertion hole 212, making it easy to insert the hand crank 5 into the drive hole 30.

[0043] The lower frame 2 of the chair also includes a lower horizontal connecting pipe 22, the two ends of which are fixedly connected to two lower upright pipes 21, so that the lower frame 2 of the chair forms an integral structure and improves the structural strength. The linkage rod 4 is sleeved in the lower horizontal connecting pipe 22. The lower horizontal connecting pipe 22 can protect the linkage rod 4, prevent the rotation of the linkage rod 4 from being disturbed by external factors, and ensure the reliability of rotation.

[0044] like Figure 4 and Figure 5 As shown, notches 220 are provided on the lower sides of both ends of the lower horizontal connecting pipe 22. The notches 220 can be used for observation and installation of the linkage rod 4.

[0045] A pin hole (not shown in the figure) is provided at one end of the linkage rod 4 near the external insertion hole 212. A positioning pin 221 is inserted into the pin hole. The pin hole and the notch 220 are correspondingly arranged so that the positioning pin 221 is exposed through the notch 220 to facilitate the installation and removal of the positioning pin 221. After the linkage rod 4 is assembled in place, the positioning pin 221 is inserted into the pin hole to prevent the linkage rod 4 from coming out of the drive hole 30 and the external insertion hole 212. Only one positioning pin 221 needs to be installed to achieve the positioning connection of the linkage rod 4, which is convenient and quick to install.

[0046] After the hand-cranked lifting device 3 is installed into the lower upright pipe 21 with the external insertion hole 212, both ends of the drive hole 30 of the hand-cranked lifting device 3 are exposed. When installing the linkage rod 4, the linkage rod 4 can pass through the external insertion hole 212, the drive hole 30 and the internal insertion hole 211 in sequence. One end of the linkage rod 4 further passes through the lower horizontal connecting pipe 22 and is inserted into the drive hole 30 of the other hand-cranked lifting device 3. In this way, both ends of the linkage pipe can be installed at one end of the two drive holes 30 respectively, so as to facilitate the assembly of the linkage rod 4. Since the other lower upright pipe 21 only has an internal insertion hole 211, the other end of the drive hole 30 of the other hand-cranked lifting device 3 will not be exposed, thus restricting the linkage rod from coming out of the other drive hole 30. Finally, the positioning pin 221 is installed into the pin hole to complete the assembly of the linkage rod 4. The positioning pin 221 can prevent the linkage rod 4 from moving towards the external insertion hole 212, so that both ends of the linkage rod are positioned in the two drive holes 30 respectively.

[0047] Combination Figure 7 and Figure 8 As shown, the hand-cranked lifting device 3 includes a gearbox 31, an active bevel gear 32, a transmission bevel gear 33, a lead screw 34, a gear sleeve 35, and a limiting guide block 36. The gearbox 31 houses the active bevel gear 32 and the transmission bevel gear 33 to ensure transmission stability. The lead screw 34 is fixedly connected to the transmission bevel gear 33. When the lead screw 34 rotates around its own axis, the gear sleeve 35 can move along the axis of the lead screw 34, and the gear sleeve 35 can drive the upper riser 11 to move up and down. The limiting guide block 36 is disposed in the upper riser 11 to ensure the rotational stability of the lead screw 34.

[0048] The gearbox 31 is fixed in the lower riser tube 21 to connect the hand-cranked lifting device 3 to the lower riser tube 21. The gearbox 31 includes two gearbox shells 311, which are arranged side by side and connected. The active bevel gear 32 and the drive bevel gear 33 are both located between the two gearbox shells 311. The two gearbox shells 311 facilitate the assembly and connection between the active bevel gear 32, the drive bevel gear 33 and the gearbox 31.

[0049] Combination Figure 4 , Figure 5 As shown, the lower riser 21 is provided with a through hole 213, and a bolt 2131 for fixing the gearbox 31 is inserted into the through hole 213 to fix the gearbox 31 to the lower riser 21. Here, the gearbox 31 can also be fixed to the lower riser 21 by welding, riveting or other methods.

[0050] like Figure 8As shown, the active bevel gear 32 meshes with the transmission bevel gear 33, and both are rotatably mounted in the gearbox 31. The direction of rotation can be changed through their meshing. The rotation axis of the active bevel gear 32 is the centerline axis of the linkage rod 4. The drive hole 30 is located in the active bevel gear 32 and passes through the active bevel gear 32 along its rotation axis to facilitate the insertion and engagement of the drive hole 30 with the linkage rod 4 and the hand crank 5.

[0051] The transmission bevel gear 33 is fixedly connected to the bottom end of the lead screw 34 to drive the lead screw 34 to rotate around its central axis; the toothed sleeve 35 is threadedly connected to the lead screw 34 and is fixed inside the upper riser 11. When the lead screw 34 rotates around its own axis, the threaded engagement between the toothed sleeve 35 and the lead screw 34 causes the toothed sleeve 35 to move up and down along the central axis of the lead screw 34, thereby moving the upper riser 11 and causing it to rise and fall.

[0052] like Figure 4 As shown, the upper riser 11 is provided with a screw through hole 1135 for fixing the toothed sleeve 35 with a screw, so that the toothed sleeve 35 is fixed in the upper riser 11. Figure 7 As shown, the toothed fitting 35 includes two semi-circular toothed fittings 351, which are joined together to clamp the lead screw 34 between them. The upper riser 11 has two screw through holes 1135, which are used to fix the two semi-circular toothed fittings 351 by two screws respectively.

[0053] The limiting guide block 36 is slidably disposed within the upper riser 11 along the axial direction, and the top end of the lead screw 34 is rotatably connected to the limiting guide block 36. The limiting guide block 36 ensures the stability of the top end of the lead screw 34 during rotation and prevents the lead screw 34 from shaking.

[0054] like Figure 8 As shown, the hand crank 5 includes a drive rod 51, a crank body 52, and a handle 53. The drive rod 51 is made of metal and is used to insert into the drive hole 30. The crank body 52 is made of plastic. The drive rod 51 and the crank body 52 are manufactured by in-mold injection molding to form an integral structure, thereby improving the connection strength between the two. The drive rod 51 is located at one end of the crank body 52, and a rocker arm 521 is fixed to the other end of the crank body 52. ​​The handle 53 is a hollow structure, fitted over the rocker arm 521, and rotatably connected to the rocker arm 521, so that the handle 53 can rotate automatically on the crank body 52 without loosening, facilitating the rotation of the drive rod 51. Furthermore, the handle 53 is riveted to the rocker arm 521 to facilitate the assembly and connection between the handle 53 and the rocker arm 521.

[0055] Furthermore, the drive rod 51 has a hexagonal cross-section, the drive hole 30 is a hexagonal hole, and the linkage rod 4 has a hexagonal cross-section. The drive hole 30, linkage rod 4, and drive rod 51 are all hexagonal to facilitate their processing and fabrication. Of course, in this embodiment, the drive hole 30, linkage rod 4, and drive rod 51 can also be other shapes such as quadrilaterals, triangles, or crosses.

[0056] like Figure 4 As shown, the continuously adjustable school chair frame device 100 also includes a connecting sleeve 6. A snap-fit ​​hole 216 is provided on the inner top side of the lower upright tube 21, and a snap-fit ​​61 is provided on the outer side of the connecting sleeve 6. The bottom of the connecting sleeve 6 is inserted into the inner cavity of the lower upright tube 21, and the snap-fit ​​61 is engaged in the snap-fit ​​hole 216. The top of the connecting sleeve 6 protrudes from the lower upright tube 21, and the upper upright tube 11 is inserted into the inner hole of the connecting sleeve 6 and slides up and down within the inner hole of the connecting sleeve 6. The connecting sleeve 6 can seal the gap between the upper upright tube 11 and the lower upright tube 21, preventing foreign objects from entering and avoiding friction between the upper upright tube 11 and the lower upright tube 21, reducing wear and increasing service life.

[0057] like Figure 4 As shown, each lower support tube 21 has a base tube 23 fixed to its bottom. The base tube 23 is arranged in the front-to-back direction, and foot pads 7 are provided at both ends of the base tube 23. The base tube 23 is used to maintain the stability of the two legs of the school chair.

[0058] In summary, although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A stepless height-adjustable school chair frame device, characterized in that, Includes upper and lower tube frames for the chairs, two hand-cranked lifting mechanisms, a linkage rod, and a hand crank; The chair frame is used to install the seat and backrest, and includes two upper uprights; The lower frame of the chair includes two lower uprights; the bottoms of the two upper uprights are respectively inserted into the two lower uprights, and a hand-cranked lifting device is provided between each upper upright and each lower upright; each hand-cranked lifting device has a drive hole. The two ends of the linkage are respectively connected to the two drive holes; The hand crank is detachably connected to one of the drive holes so as to drive the two hand cranks to rise and fall synchronously through the drive hole and the linkage rod.

2. The stepless height-adjustable chair frame device according to claim 1, characterized in that, The upper tube frame of the chair also includes a seat tube frame and a backrest tube frame. The seat tube frame is fixed to the top of the two upper uprights and has a seat mounting hole for mounting the chair seat. The bottom of the backrest tube frame is connected to the back side of the seat tube frame and has a backrest mounting hole for mounting the chair back.

3. The stepless height adjustment chair frame device according to claim 2, characterized in that, The seat plate frame includes two longitudinal tubes and two transverse tubes, which are connected to form a square frame. The two longitudinal tubes are arranged in the left-right direction and are fixedly connected to the top of the two upper upright tubes respectively. The two transverse tubes are arranged in the front-back direction. The backrest tube frame includes a top tube and two back tubes. The bottoms of the two back tubes are respectively connected to the two ends of the two horizontal tubes. The tops of the two back tubes are close to each other and bent, and are fixedly connected by the top tube.

4. The stepless height adjustment chair frame device according to claim 1, characterized in that, An inner insertion hole is provided on the pipe wall of each of the two lower upright pipes at the position corresponding to the drive hole. The linkage rod passes through the inner insertion hole and is inserted into one end of the drive hole, and the linkage rod is circumferentially positioned with the drive hole. One of the lower tubes has an external insertion hole on its wall, which is corresponding to the other end of the drive hole. The hand crank passes through the external insertion hole and is detachably inserted into the other end of the drive hole.

5. The stepless height adjustment chair frame device according to claim 4, characterized in that, The lower frame of the chair also includes a lower horizontal connecting pipe, the two ends of which are respectively fixedly connected to the two lower vertical pipes, and the linkage rod is sleeved in the lower horizontal connecting pipe; Both ends of the lower horizontal connecting pipe are provided with notches; the linkage rod is sleeved in the lower horizontal connecting pipe; a pin hole is provided at one end of the linkage rod near the outer insertion hole, and a positioning pin is inserted into the pin hole. The pin hole is provided in accordance with the notch so that the positioning pin is exposed through the notch.

6. The stepless height adjustment chair frame device according to claim 1, characterized in that, The hand-cranked lifting device includes a gearbox, an active bevel gear, a transmission bevel gear, a lead screw, a gear sleeve, and a limiting guide block. The gearbox is fixed in the lower vertical tube. The active bevel gear meshes with the transmission bevel gear, and both are rotatably disposed in the gearbox. The rotation axis of the active bevel gear is the centerline axis of the linkage rod. The driving hole is disposed in the active bevel gear and passes through the active bevel gear along its rotation axis. The transmission bevel gear is fixedly connected to the bottom end of the lead screw to drive the lead screw to rotate around its central axis. The gear sleeve is threadedly connected to the lead screw and is fixed in the upper vertical tube. The limiting guide block is slidably disposed in the upper vertical tube along its axial direction, and the top end of the lead screw is rotatably connected to the limiting guide block.

7. The stepless height adjustment chair frame device according to any one of claims 1-6, characterized in that, The hand crank includes a drive rod, a crank body, and a handle; the drive rod is fixedly connected to one end of the crank body, and the drive rod is made of metal and is used to insert into the drive hole; the crank body is made of plastic; the drive rod and the crank body are manufactured by in-mold injection molding; a rocker arm is fixed to the other end of the crank body, and the handle is a hollow structure that is sleeved on the rocker arm and rotatably connected to the rocker arm.

8. The stepless height adjustment chair frame device according to claim 7, characterized in that, The drive rod has a hexagonal cross-section, the drive hole has a hexagonal hole, and the linkage rod has a hexagonal cross-section.

9. The stepless height adjustment chair frame device according to any one of claims 1-6, characterized in that, The continuously adjustable chair frame device also includes a connecting sleeve; the top inner side of the lower upright tube is provided with a buckle hole, the outer side of the connecting sleeve is provided with a buckle, the bottom of the connecting sleeve is inserted into the inner cavity of the lower upright tube, and the buckle is engaged in the buckle hole; the top of the connecting sleeve protrudes from the lower upright tube; the upper upright tube is inserted into the inner hole of the connecting sleeve and slides up and down in the inner hole of the connecting sleeve.

10. A continuously adjustable height school chair, characterized in that, The chair includes a seat, a backrest, and a continuously adjustable chair frame as described in any one of claims 1 to 9; the seat and backrest are both mounted on the upper frame of the continuously adjustable chair frame.

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