Hand-cranked lifting double-back child learning chair

Abstract

The utility model belongs to the technical field of children's chair, especially relates to a hand -operated lifting double -back children's study chair. The chair back assembly is arranged into double chair back assembly. The chair seat assembly includes seat mechanism, seat pipe and seat depth adjusting mechanism, the armrest is connected with the seat mechanism. The lifting vertical pipe subassembly lower extreme is connected with the chair foot assembly, the lifting vertical pipe subassembly lower extreme is connected with seat pipe, the seat pipe extends along the front -back direction setting, the seat depth adjusting mechanism is connected with the seat mechanism and is connected in the seat pipe with sliding. Through design with armrest assembly's chair seat assembly and design with lifting vertical pipe subassembly's chair foot assembly. Meanwhile, the double chair back assembly with backrest function is also designed, can realize children's sitting posture correction, and prevents small children from appearing "east falls west" accident, simple structure, low in cost, is suitable for the self -regulation of use of students of different height.

Description

Technical Field

[0001] This utility model belongs to the field of children's chair technology, and specifically relates to a hand-cranked height-adjustable double-back children's study chair. Background Technology

[0002] Inappropriate seat height and incorrect sitting posture are among the main causes of myopia in children and teenagers.

[0003] However, existing chairs are difficult to adjust for children's sitting posture. Therefore, it is necessary to design a hand-cranked height-adjustable double-back children's study chair to solve the above problems. Summary of the Invention

[0004] To address the aforementioned problems, this utility model provides a hand-cranked height-adjustable double-back children's study chair, thereby resolving the issues raised in the background section.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a hand-cranked height-adjustable double-back children's study chair, comprising: A seatback assembly, wherein the seatback assembly is configured as a double seatback assembly; A chair seat assembly, comprising a seat mechanism, a seat tube, and a seat depth adjustment mechanism; Armrest assembly, which is connected to the seat mechanism; A chair leg assembly, located below the chair seat assembly; A lifting upright assembly, the lower end of which is connected to the chair leg assembly, the lifting upright assembly is connected to the seat tube, the seat tube extends in the front-to-back direction, and the seat depth adjustment mechanism is connected to the lower end of the chair base plate and is slidably connected to the seat tube in the front-to-back direction.

[0006] Furthermore, the armrest assembly includes: An armrest pivot seat, one end of which is connected to the seat mechanism; A pivot head, which is connected to the other end of the armrest pivot seat in the front-to-back direction; A lifting handrail fixing vertical rod is provided, the lower end of which is connected to the rotating shaft head, and the lower end of the handrail lifting rod is slidably connected to the lifting handrail fixing vertical rod in the up-down direction; The handrail structure is rotatably connected to the upper end of the handrail lifting rod. The handrail lifting and locking handle is connected to the lifting handrail fixing vertical rod.

[0007] Furthermore, the armrest structure includes: The lower armrest panel is rotatably connected to the upper end of the armrest lifting rod in the left-right direction. The handrail surface is connected to the upper end of the lower plate of the handrail surface.

[0008] Furthermore, the chair leg assembly includes: The chair leg body includes a pentagonal metal column, a top cover plate, and a bottom cover plate. The top cover plate is connected to the pentagonal metal column. The top cover plate has an egg-shaped hole, and the lower end of the lifting upright tube assembly passes through the egg-shaped hole. Chair leg tubes, with multiple chair leg tubes circumferentially connected to the pentagonal metal column; A chair wheel brake device is connected to the pentagonal metal column.

[0009] Furthermore, the rising tube assembly includes: The inner tube has three first through holes on its lower end face, and the box bottom plate has three second through holes. The three first through holes and the three second through holes correspond one-to-one. A screw, which passes sequentially through the first through hole and the second through hole; An outer tube is located at the upper end of the inner tube and is slidably connected to the inner tube in the vertical direction. A variable speed transmission handle assembly is disposed inside the outer tube and is used to drive the outer tube to move in the up-down direction.

[0010] Furthermore, the variable speed transmission crank assembly includes: A transmission seat, which is connected to the outer tube; A large gear, which is located at the upper end of the transmission base and rotatably connected to the transmission base; The small gear is located at the upper end of the transmission seat and meshes with the large gear; A lead screw, the upper end of which is connected to the pinion; A transmission cover, which is located above and connected to the transmission seat, and a locking groove is provided on the top of the transmission cover; A crank assembly, one end of which is connected to the large gear, and the other end of which is used to be inserted into the locking groove; Inner and outer sleeves are connected to the upper end of the inner tube and are connected to the screw drive.

[0011] Furthermore, the seat depth adjustment mechanism includes: U-shaped slide rail plate, the U-shaped slide rail plate is connected to the seat mechanism and is slidably connected to the seat tube in the front-back direction; A telescopic positioning angle iron is provided, which is connected to the base tube and has an elongated through hole. The U-shaped seat has its top end fastened to the U-shaped slide rail plate, a transverse through hole in the middle of the U-shaped seat, and a protruding post at the bottom of the U-shaped seat. The positioning handle has at least one cylinder at its front end, a transverse through hole in its middle, and a handle at its end. A protruding post is provided at the lower middle part of the positioning handle. The middle part of the positioning handle is rotatably connected to the transverse through hole via a rotating shaft. The cylinder is used for plugging and unplugging the elongated through hole. A cylindrical spring, wherein the cylindrical spring is located between the two protruding pillars; A linear bearing assembly is provided, wherein two linear bearing assemblies are provided, both of which are connected to the U-shaped slide rail plate, and the seat tube is located between the two linear bearing assemblies.

[0012] Furthermore, the linear bearing assembly includes: An open bearing housing, wherein the open bearing housing is connected to the U-shaped slide rail plate; An open bearing, wherein the open bearing is disposed within the open bearing housing; An optical axis, which passes through the open bearing housing and the open bearing; An optical axis support frame, with optical axis support frames connected to both ends, and the optical axis support frame connected to the base tube.

[0013] The technical effects and advantages of this utility model are as follows: 1. By designing a seat assembly with armrests and a leg assembly with lifting uprights, a double backrest assembly with back support function is also designed. This can correct children's sitting posture and prevent young children from falling over. The structure is simple, low-cost, and suitable for students of different heights to adjust themselves.

[0014] The chair seat assembly includes a seat mechanism, a seat tube, and a seat depth adjustment mechanism. It can adjust the front-to-back distance between the seat mechanism and the lifting upright assembly, thereby adjusting the distance between the child and the table to help the child maintain a correct sitting posture.

[0015] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the structures pointed out in the description and drawings. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the structure of the hand-cranked height-adjustable double-back children's learning chair according to an embodiment of the present invention is shown; Figure 2 A schematic diagram of the chair seat assembly according to an embodiment of the present invention is shown; Figure 3 A schematic diagram of the chair leg assembly according to an embodiment of the present invention is shown; Figure 4 A schematic diagram of the handrail assembly according to an embodiment of the present invention is shown; Figure 5 An exploded view of the handrail assembly according to an embodiment of the present invention is shown; Figure 6 A schematic diagram of the structure of the pentagonal metal column according to an embodiment of the present invention is shown; Figure 7 A schematic diagram of the structure of the top plate of the box cover according to an embodiment of the present invention is shown; Figure 8 A schematic diagram of the structure of the box bottom plate according to an embodiment of the present invention is shown; Figure 9 An exploded view of the lifting riser assembly according to an embodiment of the present invention is shown. Figure 10 A schematic diagram of the structure of the variable speed transmission handle assembly according to an embodiment of the present invention is shown; Figure 11 A schematic diagram of the seat depth adjustment mechanism according to an embodiment of the present invention is shown; Figure 12 A schematic diagram of the linear bearing assembly according to an embodiment of the present invention is shown.

[0018] Reference numerals: 1. Backrest assembly; 2. Seat assembly; 3. Armrest assembly; 4. Leg assembly; 5. Height adjustment upright assembly; 6. Seat plate; 7. Seat pad; 8. Locking screw; 9. Seat post; 10. Seat depth adjustment mechanism; 11. Leg body; 12. Long leg tube; 13. Wheel brake device; 14. Short leg tube; 15. Armrest pivot seat; 16. Pivot head; 17. Height adjustment armrest fixing rod; 18. Armrest lifting rod; 19. Armrest structure; 20. Armrest lifting locking handle; 21. Lower armrest surface plate; 22. Armrest surface; 23. Long slot; 2 4. Pentagonal metal column; 25. Top plate of box cover; 26. Bottom plate of box; 27. Egg-shaped hole; 28. Inner tube; 29. ​​Outer tube; 30. Second through hole; 31. Transmission seat; 32. Large gear; 33. Small gear; 34. Lead screw; 35. Transmission cover; 36. Crank handle assembly; 37. Inner and outer tube sleeves; 38. Locking groove; 39. U-shaped slide rail plate; 40. Telescopic positioning angle iron; 41. U-shaped seat; 42. Positioning handle; 43. Columnar spring; 44. Linear bearing assembly; 45. Open bearing seat; 46. Open bearing; 47. Optical axis; 48. Optical axis support frame. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0020] The positive X-axis points forward, and the negative X-axis points backward; the positive Y-axis points left, and the negative Y-axis points right; the positive Z-axis points upward, and the negative Z-axis points downward.

[0021] like Figure 1 As shown in the figure, a hand-cranked height-adjustable double-back children's learning chair according to an embodiment of the present invention includes a backrest assembly 1, a seat assembly 2, an armrest assembly 3, a leg assembly 4, and a height-adjustable upright tube assembly 5. The backrest assembly 1 is configured as a double-backrest assembly 1. The seat assembly 2 includes a seat mechanism, a seat tube 9, and a seat depth adjustment mechanism 10. The armrest assembly 3 is mechanically connected to the seat plate 6. The lower end of the height-adjustable upright tube assembly 5 is connected to the leg assembly 4, and the seat tube 9 is connected to the height-adjustable upright tube assembly 5. The seat tube 9 extends in the front-to-back direction, and the seat depth adjustment mechanism 10 is connected to the lower end of the seat base plate and slidably connected to the seat tube 9 in the front-to-back direction.

[0022] Specifically, the design incorporates a seat assembly 2 with armrests 3 and a leg assembly 4 with lifting uprights 5. Additionally, a double backrest assembly 1 with back support function is designed to correct children's posture and prevent young children from slouching. The design is simple, low-cost, and suitable for students of different heights to adjust themselves.

[0023] Secondly, when children use chairs for learning, they are usually placed next to the table. Children of different ages require different seat depths. The chair seat assembly 2 includes a chair seat mechanism, a seat tube 9, and a seat depth adjustment mechanism 10. The distance between the chair seat mechanism and the lifting upright tube assembly 5 can be adjusted, which can adjust the distance between the child and the table so that the child can maintain the correct sitting posture.

[0024] In this embodiment, as Figure 2 As shown, the chair seat assembly 2 includes a seat plate 6, an inner seat plate, seat cushion 7, locking screws 8, a seat tube 9, and a seat depth adjustment mechanism 10. The inner seat plate is located on the upper end of the seat plate 6 and is connected to it by the locking screws 8. The upper end of the inner seat plate is connected to the seat cushion 7, and the armrests are connected to the seat plate 6. By configuring the chair seat assembly 2 with a structure including the seat plate 6, inner seat plate, seat cushion 7, and locking screws 8, the seat cushion 7 can ensure the comfort of children when sitting, while the seat plate 6 and inner seat plate can be connected by the locking screws 8 to achieve quick assembly.

[0025] like Figure 4 and Figure 5 As shown, optionally, the armrest assembly 3 includes an armrest pivot seat 15, a pivot head 16, a lifting armrest fixing vertical rod 17, an armrest lifting rod 18, an armrest structure 19, and an armrest lifting locking handle 20. One end of the armrest pivot seat 15 is connected to the seat plate 6. The pivot head 16 is rotatably connected to the other end of the armrest pivot seat 15 in the front-back direction. The lower end of the lifting armrest fixing vertical rod 17 is connected to the pivot head 16, and the lower end of the armrest lifting rod 18 is slidably connected to the lifting armrest fixing vertical rod 17 in the up-down direction. The armrest structure 19 is connected to the upper end of the armrest lifting rod 18. The armrest lifting locking handle 20 is connected to the lifting armrest fixing vertical rod 17.

[0026] Specifically, by rotatably connecting the pivot head 16 to the armrest pivot seat 15, and connecting the armrest pivot seat 15 to the seat plate 6, the armrest structure 19 can swing back and forth relative to the seat assembly 2. Secondly, by sliding the armrest lifting rod 18 vertically to the lifting armrest fixing rod 17, the armrest structure 19 can move vertically. The armrest lifting locking handle 20 is provided to lock the armrest lifting rod 18, thus limiting the height of the armrest structure 19. For example, multiple limiting holes can be sequentially distributed vertically on the armrest lifting rod 18, and one end of the armrest lifting locking handle 20 can be inserted into the corresponding limiting hole to limit the armrest structure 19.

[0027] In this embodiment, the axial direction of the pivot head 16 is oriented to the left and right. Next, the lower end of the lifting armrest fixing rod 17 is fastened to the pivot head 16 at a 90-degree angle, and the shaft column at one end of the pivot head 16 is inserted laterally into the shaft hole of the armrest pivot seat 15. The armrest pivot seat 15 is fixed to the seat plate 6 by a screw. The pivot head 16 can then rotate 120 degrees clockwise and counterclockwise in the shaft hole of the armrest pivot seat 15. Two stop blocks are provided in the shaft hole to restrict 360-degree rotation.

[0028] like Figure 5 As shown, optionally, the handrail structure 19 includes a lower handrail plate 21 and a handrail surface 22. The lower handrail plate 21 is rotatably connected to the handrail lifting rod 18 in the left-right direction, and an elongated hole 23 is provided on the lower handrail plate 21. The handrail surface 22 is connected to the upper end of the lower handrail plate 21 and is slidably connected to the elongated hole 23 in the front-back direction.

[0029] Specifically, by rotating the lower armrest panel 21 to the armrest lifting rod 18 in the left-right direction, the armrest structure 19 can swing relative to the seat assembly 2 in the left-right direction. Secondly, the armrest surface 22 is connected to the upper end of the lower armrest panel 21 and slidably connected to the elongated hole 23 in the front-back direction, which allows the position of the armrest surface 22 in the front-back direction to be adjusted.

[0030] In this embodiment, a cylindrical ring is provided below the lower plate 21 of the handrail surface, and the cylindrical ring is longitudinally fitted into the upper end of the tubular handrail lifting rod 18. Furthermore, the handrail structure 19 also includes a handrail pressure strip, which is connected to the handrail surface 22.

[0031] like Figure 3 , Figures 6 to 8As shown, optionally, the chair leg assembly 4 includes a chair leg body 11, chair leg tubes, and a chair wheel brake device 13. The chair leg body 11 includes a pentagonal metal column 24, a top cover plate 25, and a bottom cover plate 26. The top cover plate 25 is connected to the pentagonal metal column 24, and the top cover plate 25 has an egg-shaped hole 27 through which the lower end of the lifting upright tube assembly 5 passes. Multiple chair leg tubes are circumferentially connected to the pentagonal metal column 24. The chair wheel brake device 13 is connected to the pentagonal metal column 24.

[0032] Specifically, the chair legs include long chair legs 12 and short chair legs 14. An egg-shaped hole 27 is provided above the top plate 25 of the pentagonal metal column 24. Two 300-450mm long chair legs 12 are provided within a 70-90 degree range on the front side of the pentagonal metal column 24, with one end of the leg perpendicularly attached to the two front sides of the pentagon and securely connected, ensuring that children will not lean forward while on the chair. At least two 150-300mm short chair legs 14 are provided within a 90-120 degree range on the rear side of the pentagonal metal column 24, with their ends attached to the two rear sides of the pentagon and securely connected. This design shifts the center of gravity backward, preventing the chair from tipping over.

[0033] In this embodiment, the chair leg body 11 includes an arc-shaped outer shell, and a pentagonal metal column 24 is located inside the outer shell. Furthermore, the chair wheel braking device 13 includes suction cups that adhere to the ground to secure the chair leg.

[0034] like Figure 8 and Figure 9 As shown, optionally, the lifting riser assembly 5 includes an inner tube 28, a screw, an outer tube 29, and a variable speed transmission handle assembly. The lower end face of the inner tube 28 has three first through holes, and the bottom plate 26 has three second through holes 30, with each of the three first through holes corresponding to one of the three second through holes 30. The screw passes through the first through holes and the second through holes 30 sequentially. The outer tube 29 is located at the upper end of the inner tube 28 and is connected to the seat tube 9. The outer tube 29 is slidably connected to the inner tube 28 in the vertical direction. The variable speed transmission handle assembly is disposed inside the outer tube 29 and is used to drive the outer tube 29 to move in the vertical direction.

[0035] Specifically, to ensure the stability of the study chair, the inner tube 28 of the height-adjustable upright tube assembly 5 obliquely passes through the egg-shaped hole 27 and is inserted into the bottom surface of the pentagonal metal column 24. The end face of the inner tube 28 has a first through hole in a triangular configuration, and the bottom plate 26 has a second through hole 30 in a triangular configuration. These are secured with screws, resulting in a relatively stable connection. Furthermore, by setting up a variable-speed transmission crank assembly, the outer tube 29 can be driven to move up and down relative to the inner tube 28. The outer tube 29, connected to the seat tube 9 to support the seat plate 6, allows for adjustment of the height of the seat assembly 2.

[0036] like Figure 10 As shown, optionally, the variable speed transmission crank assembly includes a transmission base 31, a large gear 32, a small gear 33, a lead screw 34, a transmission cover 35, a crank assembly 36, and inner and outer sleeves 37. The transmission base 31 is connected to the outer tube 29. The large gear 32 is located at the upper end of the transmission base 31 and is rotatably connected to the transmission base 31. The small gear 33 is located at the upper end of the transmission base 31 and meshes with the large gear 32. The upper end of the lead screw 34 is connected to the small gear 33. The transmission cover 35 is located above the transmission base 31 and is connected to the transmission base 31, and a locking groove 38 is formed on the top of the transmission cover 35. One end of the crank assembly 36 is connected to the large gear 32, and the other end is used to insert into the locking groove 38. The inner and outer sleeves 37 are connected to the upper end of the inner tube 28, and the inner and outer sleeves 37 are helically connected to the lead screw 34.

[0037] Specifically, the crank assembly 36 rotates to drive the large gear 32, which in turn meshes with the small gear 33 to drive the small gear 33 to rotate. The small gear 33 is connected to the lead screw 34, which in turn drives the lead screw 34 to rotate. The inner and outer sleeves 37 are connected to the inner tube 28, and the inner and outer sleeves 37 are connected to the lead screw 34 via a helical drive. Thus, during the rotation of the lead screw 34, the outer tube 29 can be driven to move vertically relative to the inner tube 28.

[0038] Secondly, a locking groove 38 is provided on the top of the transmission cover 35. By inserting one end of the crank assembly 36 into the locking groove 38, the crank assembly 36 can be limited, thereby locking the height of the outer tube 29 relative to the inner tube 28.

[0039] In this embodiment, the outer tube 29, the inner tube 28, and the lead screw 34 are all coaxially distributed. Furthermore, the crank assembly 36 consists of at least a hexagonal rod and a crank handle. A hexagonal hole is formed on the large gear 32, one end of the hexagonal rod is connected to the crank handle, and the other end is inserted into the hexagonal hole.

[0040] like Figure 11As shown, optionally, the seat depth adjustment mechanism 10 includes a U-shaped slide rail 39, a telescopic positioning angle iron 40, a U-shaped seat 41, a positioning handle 42, a cylindrical spring 43, and a linear bearing assembly 44. The U-shaped slide rail 39 is connected to the seat plate 6 and is slidably connected to the seat tube 9 in the front-back direction. The telescopic positioning angle iron 40 is connected to the seat tube 9 and has an elongated through hole. The top of the U-shaped seat 41 is fastened to the U-shaped slide rail 39, the middle of the U-shaped seat 41 has a transverse through hole, and the bottom of the U-shaped seat 41 has a protruding post. The positioning handle 42 has at least one cylinder at its front end, a transverse through hole in its middle, and a handle at its end. A protruding post is located below the middle of the positioning handle 42, and the middle of the positioning handle 42 is rotatably connected to the transverse through hole via a rotating shaft. The cylinder is used for insertion and removal connection to the elongated through hole. The cylindrical spring 43 is located between two of the protruding posts. Two linear bearing assemblies 44 are provided, and both linear bearing assemblies 44 are connected to the U-shaped slide rail plate 39. The seat tube 9 is located between the two linear bearing assemblies 44.

[0041] Specifically, by connecting the U-shaped slide rail 39 to the seat plate 6 and sliding it to the seat tube 9, the seat plate 6 can move relative to the seat tube 9 in the front-back direction, thereby driving the seat assembly 2 to move in the front-back direction. Secondly, under the action of the cylindrical spring 43, the cylinder on the positioning handle 42 is inserted into the elongated through hole of the telescopic positioning angle iron 40. The positioning handle 42 is connected to the U-shaped slide rail 39 via the U-shaped seat 41, and the telescopic positioning angle iron 40 is connected to the seat tube 9, thus limiting the U-shaped slide rail 39 and the seat tube 9. When it is necessary to drive the U-shaped slide rail 39 to slide relative to the seat tube 9, the end handle of the positioning handle 42 is turned, causing the middle part of the positioning handle 42 to rotate around the pivot in the transverse through hole, causing the cylinder to disengage from the elongated through hole of the telescopic positioning angle iron 40, releasing the limitation between the U-shaped slide rail 39 and the seat tube 9, thereby facilitating the sliding of the U-shaped slide rail 39 relative to the seat tube 9.

[0042] Secondly, by setting two linear bearing assemblies 44, the U-shaped slide rail 39 can be guided to ensure that the U-shaped slide rail 39 moves smoothly back and forth along the seat tube 9.

[0043] like Figure 12 As shown, optionally, the linear bearing assembly 44 includes an open bearing seat 45, an open bearing 46, an optical axis 47, and an optical axis support frame 48. The open bearing seat 45 is connected to the U-shaped slide rail plate 39. The open bearing 46 is disposed within the open bearing seat 45. The optical axis 47 passes through the open bearing seat 45 and the open bearing 46. Both ends of the optical axis support frame 48 are connected to the optical axis support frame 48, and the optical axis support frame 48 is connected to the seat tube 9.

[0044] Specifically, the open bearing 46 is fitted between two open bearing seats 45, and the two open bearing seats 45 are securely connected to the sides of the U-shaped slide rail plate 39. The optical shaft 47 passes through the open bearing 46 and the open bearing seats 45, and its front and rear ends are supported and secured to the optical shaft support frames 48 on both sides. Thus, when the seat depth adjustment mechanism 10 moves back and forth along the seat tube 9, the optical shaft 47 moves linearly relative to the open bearing 46, thereby ensuring smooth movement of the seat depth adjustment mechanism 10.

[0045] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hand-cranked, height-adjustable, double-back children's study chair, characterized in that, include: The chair back assembly (1) is configured as a double chair back assembly (1); the chair seat assembly (2) includes a chair seat mechanism, a seat tube (9) and a seat depth adjustment mechanism (10); the armrest assembly (3) is connected to the chair seat mechanism; the chair leg assembly (4) is located below the chair seat assembly (2); the lifting upright tube assembly (5) is connected at its lower end to the chair leg assembly (4), the lifting upright tube assembly (5) is connected to the seat tube (9), the seat tube (9) extends in the front-back direction, and the seat depth adjustment mechanism (10) is connected to the lower end of the chair seat base plate and is slidably connected to the seat tube (9) in the front-back direction.

2. The hand-cranked height-adjustable double-back children's study chair according to claim 1, characterized in that, The armrest assembly (3) includes: an armrest pivot seat (15), one end of which is connected to the seat mechanism; a pivot head (16), which is connected to the other end of the armrest pivot seat (15) in the front-back direction; a lifting armrest fixing rod (17), the lower end of which is connected to the pivot head (16); an armrest lifting rod (18), the lower end of which is slidably connected to the lifting armrest fixing rod (17) in the up-down direction; an armrest structure (19), which is rotatably connected to the upper end of the armrest lifting rod (18); and an armrest lifting locking handle (20), which is connected to the lifting armrest fixing rod (17).

3. The hand-cranked height-adjustable double-back children's study chair according to claim 2, characterized in that, The handrail structure (19) includes: a lower handrail plate (21), which is rotatably connected to the upper end of the handrail lifting rod (18) in the left and right direction; and a handrail surface (22), which is connected to the upper end of the lower handrail plate (21).

4. The hand-cranked height-adjustable double-back children's study chair according to claim 3, characterized in that, The chair leg assembly (4) includes: a chair leg body (11), which includes a pentagonal metal column (24), a box cover top plate (25), and a box bottom plate (26). The box cover top plate (25) is connected to the pentagonal metal column (24), and the box cover top plate (25) has an egg-shaped hole (27). The lower end of the lifting tube assembly (5) passes through the egg-shaped hole (27); chair leg tubes, which are circumferentially connected to the pentagonal metal column (24); and a chair wheel brake device (13), which is connected to the pentagonal metal column (24).

5. The hand-cranked height-adjustable double-back children's study chair according to claim 4, characterized in that, The lifting riser assembly (5) includes: an inner tube (28), the lower end face of which has three first through holes and the bottom plate (26) of the box has three second through holes, the three first through holes and the three second through holes corresponding one-to-one; a screw, the screw passing through the first through holes and the second through holes in sequence; an outer tube (29), the outer tube (29) located at the upper end of the inner tube (28), the outer tube (29) being slidably connected to the inner tube (28) in the vertical direction; and a speed transmission crank assembly, the speed transmission crank assembly being disposed inside the outer tube (29) and used to drive the outer tube (29) to move in the vertical direction.

6. The hand-cranked height-adjustable double-back children's study chair according to claim 5, characterized in that, The speed transmission handle assembly includes: a transmission base (31) connected to the outer tube (29); a large gear (32) located on the upper end of the transmission base (31) and rotatably connected to the transmission base (31); a small gear (33) located on the upper end of the transmission base (31) and meshing with the large gear (32); a lead screw (34) connected at its upper end to the small gear (33); and a transmission cover. (35), the transmission cover (35) is located above the transmission seat (31) and connected to the transmission seat (31), and the top of the transmission cover (35) is provided with a locking groove (38); the crank assembly (36), one end of the crank assembly (36) is connected to the large gear (32), and the other end is used to insert into the locking groove (38); the inner and outer tube sleeves (37), the inner and outer tube sleeves (37) are connected to the upper end of the inner tube (28), and the inner and outer tube sleeves (37) are connected to the lead screw (34) in a helical transmission.

7. The hand-cranked height-adjustable double-back children's study chair according to claim 1, characterized in that, The seat depth adjustment mechanism (10) includes: a U-shaped slide rail plate (39), which is connected to the chair seat mechanism and is slidably connected to the seat tube (9) in the front-back direction; a telescopic positioning angle iron (40), which is connected to the seat tube (9) and has an elongated through hole; a U-shaped seat (41), the top of which is fastened to the U-shaped slide rail plate (39), the middle of which has a transverse through hole, and the bottom of which has a protruding post; and a positioning handle (42), which is a positioning handle (43) that is fastened to the U-shaped slide rail plate (39). 2) At least one cylinder is provided at the front end, a transverse through hole is provided in the middle, and a handle is provided at the end. A protruding post is provided below the middle part of the positioning handle (42). The middle part of the positioning handle (42) is rotatably connected to the transverse through hole through a rotating shaft. The cylinder is used for plugging and unplugging connection of the long through hole. A columnar spring (43) is located between the two protruding posts. A linear bearing assembly (44) is provided in two. Both linear bearing assemblies (44) are connected to the U-shaped slide rail plate (39). The seat tube (9) is located between the two linear bearing assemblies (44).

8. The hand-cranked height-adjustable double-back children's study chair according to claim 7, characterized in that, The linear bearing assembly (44) includes: an open bearing seat (45) connected to the U-shaped slide rail plate (39); an open bearing (46) disposed inside the open bearing seat (45); an optical axis (47) passing through the open bearing seat (45) and the open bearing (46); and an optical axis support frame (48) with optical axis support frames (48) connected to both ends, and the optical axis support frame (48) connected to the seat tube (9).

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