Height-adjustable caster

Abstract

The utility model discloses an adjustable height's trundle, including mounting plate, center axle seat, support and gyro wheel, mounting plate is through the center screw hole screw joint installation on the threaded outer surface of center axle seat, and the support includes the top plate and two corresponding solidly installed arm plate in the top plate lower end surface front and back two sides, and the center axle seat lower end rotation is installed on the top plate upper end surface of support, and the gyro wheel is rotationally installed in the lower end inside of two arm plates through the wheel shaft subassembly, and the lifting adjustment control mechanism with two kinds of states of unlocking and locking is equipped between mounting plate and center axle seat two, when unlocking state, the center screw hole on mounting plate and the threaded outer surface on center axle seat can relatively rotate and move to adjust the height of trundle, when locking state, mounting plate and center axle seat are locked together. When adjusting the height of trundle, the operation step is simple and convenient, and the whole structure design is ingenious and simple, and the preparation implementation difficulty is small, and the manufacturing cost is low, and the whole stability controllability is high, and it is favorable to ensuring the stability when walking.

Description

Technical Field

[0001] This utility model relates to the field of caster technology, specifically to a height-adjustable caster. Background Technology

[0002] Casters are a general term, typically including swivel casters and fixed casters. Swivel casters, also known as universal casters, allow 360° rotation; fixed casters, also known as directional casters, lack a rotating structure and cannot turn. Lifting machines require casters for movement, and due to variations in the height of the object being lifted and the specific lifting requirements, the casters need to be height-adjustable. Existing lifting machine casters generally lack height adjustment functionality; the few that do have this function are mostly complex in structure, have high manufacturing costs, and exhibit poor stability during movement. Therefore, this invention proposes a height-adjustable caster to address the aforementioned technical problems. Summary of the Invention

[0003] The purpose of this utility model is to overcome the defects in the existing technology and provide an adjustable height caster. This is achieved by screwing a mounting plate onto the threaded outer surface of a central axle seat, and providing a lifting adjustment control mechanism between the mounting plate and the central axle seat. When the caster height needs to be adjusted, the lifting adjustment control mechanism is unlocked. After the caster is adjusted to the appropriate height, the lifting adjustment control mechanism is readjusted to the locked state. The operation is simple and convenient. The overall structure is ingeniously and simply designed, easy to manufacture and implement, has low manufacturing costs, and offers high overall stability and controllability, which helps ensure good stability during walking.

[0004] To achieve the above objectives, the technical solution of this utility model is to design an adjustable height caster, including a mounting plate, a central bearing, a bracket, and rollers. The mounting plate has a central screw hole, and the outer peripheral side of the central bearing has a threaded outer surface. The mounting plate is screwed onto the threaded outer surface of the central bearing through the central screw hole. The bracket includes a top plate and two arm plates correspondingly fixed to the front and rear sides of the lower end of the top plate. The lower end of the central bearing is rotatably mounted on the upper surface of the top plate of the bracket. The rollers are rotatably mounted on the lower inner sides of the two arm plates through a wheel and axle assembly. A lifting adjustment control mechanism is provided between the mounting plate and the central bearing. The lifting adjustment control mechanism has two states: unlocked and locked. In the unlocked state, the central screw hole on the mounting plate and the threaded outer surface on the central bearing can rotate relative to each other to adjust the height of the caster. In the locked state, the mounting plate and the central bearing are locked together.

[0005] This utility model discloses an adjustable height caster. A mounting plate is screwed onto the threaded outer surface of a central axle seat, and a lifting adjustment control mechanism is provided between the mounting plate and the central axle seat. When the caster height needs to be adjusted, the lifting adjustment control mechanism is unlocked. After the caster is adjusted to the appropriate height, the lifting adjustment control mechanism is readjusted to the locked state. The operation is simple and convenient. The overall structure is ingeniously and simply designed, easy to manufacture and implement, has low manufacturing costs, and offers high overall stability and controllability, which helps ensure good stability during walking.

[0006] A preferred technical solution is that the upper end face of the central shaft seat has an upward-opening groove, and an arc-shaped groove communicating with the interior of the groove is formed on the side wall of the groove. A threaded through hole is formed on the outer peripheral wall of the groove, longitudinally penetrating the upper and lower ends of the central shaft seat. The threaded through hole also penetrates the arc-shaped groove. A screw is screwed into the threaded through hole. The arc-shaped groove, the groove, the threaded through hole, and the screw constitute the lifting adjustment control mechanism: in the unlocked state, the screw is screwed into the portion of the threaded through hole located on the upper or lower side of the arc-shaped groove; in the locked state, the screw pulls the portions of the groove side wall located on the upper and lower sides of the arc-shaped groove together, causing the outer surface of the thread to deform and abut against the central screw hole on the mounting plate. The lifting adjustment control mechanism has a clever and reasonable structural design. By rotating the adjusting screw to adjust its position inside the threaded through hole, the lifting adjustment control mechanism can be easily switched between the unlocked and locked states. This also ensures that the overall structure of the caster of this invention is simple to design and highly feasible to manufacture and implement.

[0007] A further preferred technical solution is that the arc-shaped groove is located in the horizontal direction, and its length accounts for 1 / 3 to 1 / 2 of the circumference of the outer surface of the thread. The threaded through hole passes through the middle of the arc-shaped groove. The arc-shaped groove's length accounting for 1 / 3 to 1 / 2 of the circumference of the outer surface of the thread ensures good overall stability of the outer periphery of the groove, and also ensures that the portion of the outer periphery of the groove located on the upper and lower sides of the arc-shaped groove has good relative elastic deformation capability. This ensures that the screw can effectively tighten and connect the portion of the groove's sidewall located on the upper and lower sides of the arc-shaped groove together, thus ensuring good stability and firmness when the mounting plate and the central shaft seat are in the locked state.

[0008] A further preferred technical solution is that the groove has a "D"-shaped structure, and the threaded through hole is located in the middle of the straight side of the groove. This gives the straight side of the outer peripheral wall of the groove a large thickness, thereby helping to ensure that the location of the threaded through hole has good structural strength.

[0009] A further preferred technical solution is that the upper end of the threaded through hole is provided with a countersunk groove structure, and the screw passes through the threaded through hole from top to bottom. This ensures the ease of operation of the lifting adjustment control mechanism when switching between the unlocked and locked states, and the screw nut is embedded in the countersunk groove structure at the upper end of the threaded through hole, so it will not interfere with the normal installation and use of the caster.

[0010] A further preferred technical solution is that the bottom of the groove is provided with a hexagonal countersunk groove corresponding to the axial centerline of the central shaft seat. When adjusting the height of the casters, a hexagonal wrench can be inserted into the hexagonal countersunk groove on the upper surface of the central shaft seat, which improves the convenience of adjusting the height of the casters.

[0011] A further preferred technical solution includes a downwardly extending internally threaded sleeve at the lower end of the mounting plate. The upper end of the internally threaded sleeve is coaxially connected to the lower end of the central threaded hole. The central threaded hole is screwed onto the upper end of the threaded outer surface of the central bearing, and the internally threaded sleeve is screwed onto the lower end of the threaded outer surface of the central bearing. The internally threaded sleeve effectively extends the axial length of the central threaded hole, thereby increasing the effective contact area between the mounting plate and the central bearing, further improving the overall stability of the caster of this invention.

[0012] A further preferred technical solution includes a shaft extending downwards from the center of the lower end face of the central bearing seat; an annular groove one on the outer periphery of the lower end face of the central bearing seat; an annular groove two coaxially located on the outer periphery of the upper end of the central hole on the upper end face of the top plate of the bracket; an annular groove three communicating with the lower end of the central hole on the lower end face of the top plate; the lower end of the shaft passing through the central hole of the top plate and extending to its lower side; a nut screwed onto the threaded section at the lower end of the shaft; the lower end face of the central bearing seat and the upper end face of the top plate being rotatably connected by thrust ball bearings embedded in the annular groove one and annular groove two; and the lower end face of the top plate being rotatably connected to the shaft by a tapered roller bearing embedded in the annular groove three. The lower end of the central bearing seat is rotatably connected to the top plate of the bracket via components such as the shaft, bearings, and nut, resulting in a simple connection method that ensures the smooth manufacture and implementation of the caster of this utility model.

[0013] A further preferred technical solution is that a washer is fitted onto the lower end of the shaft body, located between the lower end face of the inner ring of the tapered roller bearing and the nut. This effectively improves the clamping stability of the nut on the inner ring of the tapered roller bearing, thereby ensuring good embedding stability of the tapered roller bearing within the annular groove on the lower end face of the top plate.

[0014] A further preferred technical solution is that a threaded through hole two is provided at the bottom of the groove, and an oil injection nozzle is screwed to the upper end of the threaded through hole two, with the lower end communicating with the annular groove one. Lubricating oil can be periodically added to the thrust ball bearing through the oil injection nozzle to ensure good rotational flexibility of the caster of this invention.

[0015] The advantages and beneficial effects of this utility model are as follows:

[0016] 1. This utility model discloses an adjustable height caster, which is installed by screwing a mounting plate onto the threaded outer surface of a central axle seat. A lifting adjustment control mechanism is provided between the mounting plate and the central axle seat. When the height of the caster needs to be adjusted, the lifting adjustment control mechanism is adjusted to the unlocked state. After the caster is adjusted to the appropriate height position, the lifting adjustment control mechanism is readjusted to the locked state. The operation steps are simple and convenient. The overall structure is ingenious and simple, easy to manufacture and implement, low in manufacturing cost, and has high overall stability and controllability, which helps to ensure good stability when walking.

[0017] 2. The lifting adjustment control mechanism has a clever and reasonable structural design. By rotating the adjusting screw to the position inside the threaded through hole, the lifting adjustment control mechanism can be easily switched between the unlocked and locked states. This also ensures that the overall structure of the caster of this utility model is simple and has high feasibility for manufacture and implementation.

[0018] 3. The length of the arc-shaped groove is 1 / 3 to 1 / 2 of the circumference of the outer surface of the thread. On the one hand, it ensures the overall firmness of the outer circumference sidewall of the groove, and on the other hand, it ensures that the part of the outer circumference sidewall of the groove located on the upper and lower sides of the arc-shaped groove has good relative elastic deformation ability. This ensures that the screw can effectively pull the part of the groove sidewall located on the upper and lower sides of the arc-shaped groove together, that is, it ensures that the mounting plate and the central shaft seat have good stability and firmness when they are locked.

[0019] 4. The groove has a "D" shaped structure, and the threaded through hole is located in the middle of the straight side of the groove. This gives the straight side of the outer perimeter of the groove a large thickness, which helps to ensure good structural strength at the location of the threaded through hole.

[0020] 5. The upper end of the threaded through hole is provided with a countersunk groove structure, and the screw passes through the threaded through hole from top to bottom. This ensures the ease of operation of the lifting adjustment control mechanism when switching between the unlocked and locked states, and the screw nut is embedded in the countersunk groove structure at the upper end of the threaded through hole, so it will not interfere with the normal installation and use of the caster.

[0021] 6. The mounting plate has a downwardly extending internally threaded sleeve at its lower end. The upper end of the internally threaded sleeve is coaxially connected to the lower end of the central threaded hole. The central threaded hole is screwed onto the upper end of the threaded outer surface of the central shaft seat, and the internally threaded sleeve is screwed onto the lower end of the threaded outer surface of the central shaft seat. The internally threaded sleeve effectively extends the axial length of the central threaded hole, thereby increasing the effective contact area between the mounting plate and the central shaft seat, further improving the overall stability of the caster of this utility model.

[0022] 7. A threaded through hole two is provided at the bottom of the groove. An oil injection nozzle is screwed onto the upper end of the threaded through hole two, and the lower end communicates with the annular groove one. Lubricating oil can be periodically added to the thrust ball bearing through the oil injection nozzle to ensure good rotational flexibility of the caster of this utility model. Attached Figure Description

[0023] Figure 1 This is a perspective view of the right front side of an adjustable height caster according to this utility model;

[0024] Figure 2 This is a longitudinal sectional view of an adjustable height caster according to the present invention;

[0025] Figure 3 yes Figure 2 A magnified view of a section at point S in the middle;

[0026] Figure 4 This is a top-down 3D view of the mounting plate;

[0027] Figure 5 It is a top-down perspective view of the central axis.

[0028] Figure 6 It is a three-dimensional view of the central axis from an upward angle;

[0029] Figure 7 This is a top-down 3D view of the right front side of the bracket;

[0030] Figure 8 This is a three-dimensional view of the support frame from an upward angle.

[0031] In the diagram: 1. Mounting plate; 2. Central bearing; 3. Bracket; 4. Roller; 5. Screw; 6. Oil nozzle; 7. Thrust ball bearing; 8. Tapered roller bearing; 9. Washer; 10. Nut; 11. Wheel and axle assembly; 1-1. Central threaded hole; 1-2. Mounting hole; 1-3. Internal threaded sleeve; 2-1. Threaded outer surface; 2-2. Arc-shaped groove; 2-3. Groove; 2-3a. Hexagonal countersunk groove; 2-4. Shaft; 2-5. Threaded through hole one; 2-5a. Countersunk groove structure; 2-6. Threaded through hole two; 2-7. Annular groove one; 3-1. Top plate; 3-1a. Annular groove two; 3-1b. Annular groove three; 3-2. Arm plate. Detailed Implementation

[0032] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0033] Example

[0034] like Figures 1-8 As shown, an adjustable height caster includes a mounting plate 1, a central bearing 2, a bracket 3, and rollers 4. The mounting plate 1 has a central screw hole 1-1, and the outer peripheral side of the central bearing 2 has a threaded outer surface 2-1. The mounting plate 1 is screwed onto the threaded outer surface 2-1 of the central bearing 2 through the central screw hole 1-1. The bracket 3 includes a top plate 3-1 and two arm plates 3-2 correspondingly fixed to the front and rear sides of the lower end of the top plate 3-1. The lower end of the central bearing 2 is rotatably mounted on the bracket 3. On the upper surface of the top plate 3-1, the roller 4 is rotatably mounted on the inner lower end of the two arm plates 3-2 via a wheel and axle assembly 11. A lifting adjustment control mechanism is provided between the mounting plate 1 and the central shaft seat 2. The lifting adjustment control mechanism has two states: unlocked and locked. When unlocked, the central screw hole 1-1 on the mounting plate 1 and the threaded outer surface 2-1 on the central shaft seat 2 can rotate relative to each other to adjust the height of the caster. When locked, the mounting plate 1 and the central shaft seat 2 are locked together. Specifically, the mounting plate 1 is a flange plate structure, and its outer periphery is provided with several mounting holes 1-2 spaced circumferentially.

[0035] Preferably, the upper end face of the central shaft seat 2 has an upward-opening groove 2-3. An arc-shaped groove 2-2 is provided on the side wall of the groove 2-3, which is connected to the interior of the groove. A threaded through hole 2-5 is provided on the outer peripheral wall of the groove 2-3, which is longitudinally connected to the upper and lower end faces of the central shaft seat 2. The threaded through hole 2-5 also connects to the arc-shaped groove 2-2. A screw 5 is screwed into the threaded through hole 2-5. The arc-shaped groove 2-2, the groove 2-3, the threaded through hole 2-5 and the screw 5 constitute the lifting adjustment control mechanism: when in the unlocked state, the screw 5 is screwed into the part of the threaded through hole 2-5 located on the upper or lower side of the arc-shaped groove 2-2; when in the locked state, the screw 5 pulls the part of the side wall of the groove 2-3 located on the upper and lower sides of the arc-shaped groove 2-2 together, so that the threaded outer surface 2-1 is deformed and abuts against the central screw hole 1-1 on the mounting plate 1.

[0036] More preferably, the arc-shaped groove 2-2 is located in the horizontal direction, and its length accounts for 1 / 3 to 1 / 2 of the circumference of the outer surface 2-1 of the thread, and the threaded through hole 2-5 passes through the middle of the arc-shaped groove 2-2.

[0037] More preferably, the groove 2-3 has a "D" shaped structure, and the threaded through hole 2-5 is located in the middle of the straight side of the groove 2-3.

[0038] More preferably, the upper end of the threaded through hole 2-5 is provided as a countersunk groove structure 2-5a, and the screw 5 is inserted into the inside of the threaded through hole 2-5 from top to bottom.

[0039] More preferably, the bottom of the groove 2-3 is provided with a hexagonal countersunk groove 2-3a corresponding to the position of the axial center line of the central shaft seat 2.

[0040] More preferably, the lower end of the mounting plate 1 has a downwardly extending internal threaded sleeve 1-3, the upper end of the internal threaded sleeve 1-3 is coaxially connected to the lower end of the central screw hole 1-1, the central screw hole 1-1 is screwed to the upper end of the threaded outer surface 2-1 of the central shaft seat 2, and the internal threaded sleeve 1-3 is screwed to the lower end of the threaded outer surface 2-1 of the central shaft seat 2.

[0041] More preferably, the lower end face of the central shaft seat 2 has a shaft 2-4 extending downward, and the outer periphery of the lower end face of the central shaft seat 2 has an annular groove 2-7. The upper end face of the top plate 3-1 of the bracket 3 has an annular groove 3-1a coaxially located on the outer periphery of the upper end of its central hole. The lower end face of the top plate 3-1 has an annular groove 3-1b communicating with the lower end of its central hole. The lower end of the shaft 2-4 passes through the central hole of the top plate 3-1 and extends to its lower side. A nut 10 is screwed onto the threaded section at the lower end of the shaft 2-4. The lower end face of the central shaft seat 2 and the upper end face of the top plate 3-1 are rotatably connected by a thrust ball bearing 7 embedded in the annular groove 2-7 and the annular groove 3-1a. The lower end face of the top plate 3-1 is rotatably connected to the shaft 2-4 by a tapered roller bearing 8 embedded in the annular groove 3-1b.

[0042] More preferably, a washer 9 is fitted onto the lower end of the shaft 2-4 between the lower end face of the inner ring of the tapered roller bearing 8 and the nut 10.

[0043] More preferably, the bottom of the groove 2-3 is provided with a threaded through hole 2-6, the upper end of which is screwed with an oil injection nozzle 6, and the lower end is connected to the annular groove 2-7.

[0044] The working principle of this utility model is as follows:

[0045] Several casters are fixedly installed at designated positions on the bottom of the mobile machinery (e.g., a lift) using bolt assemblies that pass through the mounting holes 1-2 on the mounting plate 1. When the machinery is moving, the lifting adjustment control mechanisms on each caster are in the locked state, that is, the mounting plate 1 and the central shaft seat 2 on each caster are locked together. When it is necessary to adjust the height of the casters, first adjust the lifting adjustment control mechanism on the casters to the unlocked state, rotate the central shaft seat 2 to adjust the mounting plate 1 to a suitable position on the threaded outer surface 2-1 of the central shaft seat 2, then readjust the lifting adjustment control mechanism on the casters to the locked state, and adjust all casters to the appropriate height position in sequence.

[0046] This utility model discloses an adjustable height caster. A mounting plate is screwed onto the threaded outer surface of a central axle seat, and a lifting adjustment control mechanism is provided between the mounting plate and the central axle seat. When the caster height needs to be adjusted, the lifting adjustment control mechanism is unlocked. After the caster is adjusted to the appropriate height, the lifting adjustment control mechanism is readjusted to the locked state. The operation is simple and convenient. The overall structure is ingeniously and simply designed, easy to manufacture and implement, has low manufacturing costs, and offers high overall stability and controllability, which helps ensure good stability during walking.

[0047] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A height-adjustable caster, characterized in that, The system includes a mounting plate (1), a central bearing (2), a bracket (3), and rollers (4). The mounting plate (1) has a central screw hole (1-1), and the outer peripheral side of the central bearing (2) has a threaded outer surface (2-1). The mounting plate (1) is screwed onto the threaded outer surface (2-1) of the central bearing (2) through the central screw hole (1-1). The bracket (3) includes a top plate (3-1) and two arm plates (3-2) correspondingly fixed on the front and rear sides of the lower end of the top plate (3-1). The lower end of the central bearing (2) is rotatably mounted on the bracket (3). On the upper surface of the top plate (3-1), the roller (4) is rotatably mounted on the inner side of the lower end of the two arm plates (3-2) via the wheel axle assembly (11). A lifting adjustment control mechanism is provided between the mounting plate (1) and the central shaft seat (2). The lifting adjustment control mechanism has two states: unlocked and locked. When it is in the unlocked state, the central screw hole (1-1) on the mounting plate (1) and the threaded outer surface (2-1) on the central shaft seat (2) can rotate relative to each other to adjust the height of the caster. When it is in the locked state, the mounting plate (1) and the central shaft seat (2) are locked together.

2. The height-adjustable caster as described in claim 1, characterized in that, The upper end face of the central shaft seat (2) has an upward-opening groove (2-3). An arc-shaped groove (2-2) is provided on the side wall of the groove (2-3) and communicates with its interior. A threaded through hole (2-5) is provided on the outer peripheral wall of the groove (2-3) and runs longitudinally through the upper and lower end faces of the central shaft seat (2). The threaded through hole (2-5) also passes through the arc-shaped groove (2-2). A screw (5) is screwed into the threaded through hole (2-5). The arc-shaped groove (2-2) and the groove (2-3) are connected in series. The threaded through hole (2-5) and the screw (5) constitute the lifting adjustment control mechanism: when in the unlocked state, the screw (5) is screwed into the part of the threaded through hole (2-5) located on the upper or lower side of the arc-shaped groove (2-2); when in the locked state, the screw (5) pulls the part of the side wall of the groove (2-3) located on the upper and lower sides of the arc-shaped groove (2-2) together, so that the outer surface of the thread (2-1) is deformed and abuts against the center screw hole (1-1) on the mounting plate (1).

3. The height-adjustable caster as described in claim 2, characterized in that, The arc-shaped groove (2-2) is located in the horizontal direction, and its length accounts for 1 / 3 to 1 / 2 of the circumference of the outer surface (2-1) of the thread. The threaded through hole (2-5) passes through the middle of the arc-shaped groove (2-2).

4. The height-adjustable caster as described in claim 3, characterized in that, The groove (2-3) is a "D" shaped structure, and the threaded through hole (2-5) is located in the middle of the straight side of the groove (2-3).

5. The height-adjustable caster as described in claim 4, characterized in that, The upper end of the threaded through hole (2-5) is provided with a countersunk groove structure (2-5a), and the screw (5) is inserted into the inside of the threaded through hole (2-5) from top to bottom.

6. The height-adjustable caster as described in claim 5, characterized in that, The bottom of the groove (2-3) is provided with a hexagonal countersunk groove (2-3a) corresponding to the axial center line of the central shaft seat (2).

7. The height-adjustable caster as described in claim 6, characterized in that, The mounting plate (1) has a downwardly extending internal threaded sleeve (1-3) at its lower end. The upper end of the internal threaded sleeve (1-3) is coaxially connected to the lower end of the central threaded hole (1-1). The central threaded hole (1-1) is screwed to the upper end of the threaded outer surface (2-1) of the central shaft seat (2). The internal threaded sleeve (1-3) is screwed to the lower end of the threaded outer surface (2-1) of the central shaft seat (2).

8. The height-adjustable caster as described in any one of claims 1 to 7, characterized in that, The central bearing (2) has a shaft (2-4) extending downward from the center of its lower end face. The outer periphery of the lower end face of the central bearing (2) has an annular groove (2-7). The upper end face of the top plate (3-1) of the bracket (3) has an annular groove (3-1a) coaxially located on the outer periphery of the upper end of its central hole. The lower end face of the top plate (3-1) has an annular groove (3-1b) communicating with the lower end of its central hole. The lower end of the shaft (2-4) passes through the center of the top plate (3-1). The core hole extends to its lower side, and a nut (10) is screwed onto the threaded section at the lower end of the shaft (2-4). The lower end face of the central shaft seat (2) and the upper end face of the top plate (3-1) are rotatably connected by thrust ball bearings (7) embedded in the first annular groove (2-7) and the second annular groove (3-1a). The lower end face of the top plate (3-1) is rotatably connected to the shaft (2-4) by tapered roller bearings (8) embedded in the third annular groove (3-1b).

9. The height-adjustable caster as described in claim 8, characterized in that, The lower end of the shaft (2-4) is fitted with a washer (9) located between the lower end face of the inner ring of the tapered roller bearing (8) and the nut (10).

10. The height-adjustable caster as described in claim 9, characterized in that, The bottom of the groove (2-3) is provided with a threaded through hole two (2-6), and an oil injection nozzle (6) is screwed on the upper end of the threaded through hole two (2-6), and the lower end is connected to the annular groove one (2-7).

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