Backrest structure enabling user to obtain dynamic support when switching between different sitting postures

Abstract

A backrest structure enabling a user to obtain dynamic support when switching between different sitting postures. By providing a horizontal movement mechanism (4) and an elastic lifting mechanism (5), the horizontal and vertical movements of the second backrest (2) are controlled, and the combined horizontal and vertical movements can also be performed. The horizontal movement mechanism (4) and the elastic lifting mechanism (5) use the elastic force provided by springs (42, 53) to enable the second backrest (2) to move following the movement of the waist of a user. Regardless of the posture of the user, the second backrest (2) can be ensured to closely fit and support the waist of the user, forming dynamic support, bringing a comfortable use experience to the user, and alleviating waist discomfort such as fatigue caused by prolonged sitting.

Description

A chair back structure that provides dynamic support to users when switching between different sitting positions. Technical Field

[0001] This utility model relates to the field of seating technology, and in particular to a chair back structure that provides dynamic support to users when switching between different sitting postures. Background Technology

[0002] With rapid economic development, people are under high pressure at work. Office workers often need to sit at their desks for long periods of time, which inevitably leads to a series of diseases. Among them, the lack of support and movement in the lower back for extended periods can cause problems such as herniated discs and poor blood circulation, which are extremely harmful. Therefore, it is necessary to set up a suitable structure for the lower back to reduce pressure.

[0003] Currently, most chairs on the market have a lumbar support installed on the backrest that can be slightly adjusted in height and recline angle. The lumbar support provides some support for the lower back, but its function is relatively simple. It requires maintaining a fixed sitting posture and position to provide support, and the lumbar support can only move within a certain angle range. Once the user leaves the operating angle, the lower back will lose the support of the lumbar support. Therefore, its support effect and comfort need to be improved. Technical issues

[0004] In view of the shortcomings of the above-mentioned technologies, such as the lumbar support following the movement of the waist and failing to provide good comfort, this utility model provides a chair back structure that allows users to obtain dynamic support when changing different sitting postures. Technical solutions

[0005] To achieve the above objectives, this utility model provides a chair back structure that provides dynamic support to users when switching between different sitting postures, comprising:

[0006] First chair back;

[0007] A chair back support, wherein the first chair back is fixedly connected to one end of the chair back support, and the other end of the chair back support is movably connected to the chair seat;

[0008] A horizontal movement mechanism is provided, wherein the backrest support is sleeved on one end of the horizontal movement mechanism, and the other end of the horizontal movement mechanism is provided with a spring lifting mechanism. One end of the spring lifting mechanism is fixedly connected to the horizontal movement mechanism, and the other end of the spring lifting mechanism is provided with a second backrest, which is movably connected to the spring lifting mechanism.

[0009] The second chair back undergoes a combined forward and backward and up and down movement simultaneously through the horizontal movement mechanism and the elastic lifting mechanism.

[0010] As an improvement of this utility model, the horizontal movement mechanism includes a sliding cylinder with one open end, a first spring, and an adjusting knob. The chair back support has a fixed cylinder with both open ends, and the chair back support is sleeved on the fixed cylinder. The adjusting knob is movably connected to one end of the fixed cylinder. The end face of the adjusting knob is provided with a positioning post, and the positioning post is sequentially sleeved on the first spring, the sliding cylinder, and the fixed cylinder. The sliding cylinder is slidably engaged with the fixed cylinder, and the end of the sliding cylinder near the elastic lifting mechanism is fixedly connected to the elastic lifting mechanism. One end of the first spring is fixed to the end face of the adjusting knob, and the other end abuts against the inner end face of the sliding cylinder.

[0011] As an improvement of this utility model, the elastic lifting mechanism includes a sliding bracket, a sliding member, and at least one second spring. The second chair back is provided with a first recess, and the sliding bracket is fixedly installed in the first recess. The sliding member is sleeved on the sliding bracket. The sliding bracket is provided with at least two first sliding grooves on one side near the second chair back. The second spring is installed in the first sliding groove. The sliding member is provided with at least two protrusions. One protrusion extends into one of the first sliding grooves, and the other protrusion abuts against one of the second springs. The other side of the sliding bracket is provided with a connecting block. The connecting block is provided with a threaded connecting hole. The end of the sliding cylinder away from the adjustment knob is provided with an installation port. The connecting block is sleeved in the installation port. The wall of the sliding cylinder is provided with a connecting hole. An external bolt passes through the connecting hole and the threaded connecting hole to fix the sliding bracket and the sliding cylinder in a fixed fit.

[0012] As an improvement of this utility model, at least one limiting groove is provided on one side of the sliding member, and a first slot hole is provided on the groove wall opposite to the limiting groove of the first recess. A limiting adjustment rod and a fixing member are provided on the second chair back. The fixing member is fixedly installed in the first slot hole, and the limiting adjustment rod is sleeved in the cavity of the fixing member. The limiting adjustment rod is movably connected to the fixing member, and one end of the limiting adjustment rod is engaged with the limiting groove through the first slot hole.

[0013] As an improvement of this utility model, the wall surface of the sliding cylinder is provided with at least one limiting through hole, the outer wall surface of the positioning cylinder forms a first connecting cylinder with one open end, the opening end of the first connecting cylinder is fitted with a limiting knob, the limiting knob is movably connected to the first connecting cylinder, the wall surface of the first connecting cylinder connected to the sliding cylinder is provided with a first through hole, the limiting knob is fixedly connected to one end of the limiting post, and the other end of the limiting post is engaged with the limiting through hole through the first through hole.

[0014] As an improvement of this utility model, at least one sliding wheel is symmetrically provided on the outer wall surface of the sliding cylinder, and the sliding wheel is fixedly connected to the sliding cylinder; at least one guide post is provided on the inner wall surface of the fixed cylinder, the guide post is integrally formed with the fixed cylinder, the guide post is provided with a guide groove, the two guide posts are arranged opposite each other with the side having the guide groove, and at least one sliding wheel is embedded between the two guide grooves.

[0015] As an improvement of this utility model, the first connecting cylinder is provided with a first connecting post with openings at both ends. Two opposing external threads are symmetrically provided on the outer wall of the first connecting post. The end face of the limiting knob connected to the limiting post is also provided with a second connecting cylinder with one end opening. At least two second connecting posts are symmetrically provided on the inner wall of the second connecting cylinder. The two second connecting posts clamp the first connecting post, and the second connecting posts are in contact with the external threads. Beneficial effects

[0016] The beneficial effects of this utility model are as follows: Compared with the prior art, this utility model provides a chair back structure that allows users to obtain dynamic support when switching between different sitting postures. By setting a horizontal movement mechanism and an elastic lifting mechanism to control the horizontal and vertical movement of the second chair back, it can also perform compound horizontal and vertical movements simultaneously. The horizontal movement mechanism and the elastic lifting mechanism, through the elastic force given by the spring, enable the second chair back to move with the user's waist. No matter what posture the user is in, it can ensure that the second chair back is close to and supports the user's waist. Moreover, it can form dynamic support when the user's waist moves. The lumbar support has a very high degree of freedom of movement, bringing a comfortable user experience and relieving the problem of waist fatigue and other discomforts caused by prolonged sitting. Attached Figure Description

[0017] Figure 1 is a left view of this utility model;

[0018] Figure 2 is an exploded view of the horizontal motion mechanism of this utility model;

[0019] Figure 3 is a bottom view of the sliding cylinder of this utility model;

[0020] Figure 4 is a schematic diagram of the first settling tank of this utility model;

[0021] Figure 5 is a rear view of the second chair of this utility model;

[0022] Figure 6 is a schematic diagram of the fixing cylinder of this utility model;

[0023] Figure 7 is an exploded view of the elastic lifting mechanism of this utility model;

[0024] Figure 8 is a schematic diagram of the sliding bracket of this utility model;

[0025] Figure 9 is a perspective view of this utility model;

[0026] Figure 10 is a cross-sectional view of this utility model;

[0027] Figure 11 is a schematic diagram of the sliding cylinder and sliding bracket of this utility model;

[0028] Figure 12 is a schematic diagram of the limiting knob and the first connecting cylinder of this utility model;

[0029] Figure 13 is a schematic diagram of the first connecting cylinder of this utility model;

[0030] Figure 14 is a cross-sectional view of the first connecting cylinder of this utility model.

[0031] The symbols for the main components are explained below:

[0032] 1. First chair back; 2. Second chair back; 21. First recessed groove; 3. Chair back support; 31. Fixed cylinder; 311. Guide post; 312. Guide groove; 4. Horizontal movement mechanism; 41. Sliding cylinder; 411. Limiting through hole; 42. First spring; 43. Adjustment knob; 44. Positioning post; 45. Sliding wheel; 5. Elastic lifting mechanism; 51. Sliding bracket; 511. First sliding groove; 512. Connecting block; 52. Sliding part; 521. Protrusion; 522. Limiting groove; 53. Second spring; 6. First connecting cylinder; 61. First connecting post; 611. External thread; 612. Slot; 7. Limiting knob; 71. Limiting post; 72. Second connecting cylinder; 73. Second connecting post; 8. Connecting hole; 9. Threaded connecting hole. The best embodiment of the present invention

[0033] To more clearly illustrate this utility model, the following description, in conjunction with the accompanying drawings, will provide a further picture.

[0034] In the following description, specific examples are given to provide a more in-depth understanding of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of them. It should be understood that the specific embodiments described are only used to explain the present invention and are not intended to limit the present invention.

[0035] It should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the said feature, integral, step, operation, element, or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, or combinations thereof.

[0036] Please refer to Figures 1-14. This utility model discloses a chair back structure that provides dynamic support to the user when switching between different sitting positions, comprising:

[0037] First chair back 1;

[0038] The chair back support 3 is fixedly connected to one end of the first chair back 1 and the other end of the chair back support 3 is movably connected to the chair seat.

[0039] A horizontal motion mechanism 4 is provided, and a chair back support 3 is fitted on one end of the horizontal motion mechanism 4. A spring lifting mechanism 5 is provided at the other end of the horizontal motion mechanism 4. One end of the spring lifting mechanism 5 is fixedly connected to the horizontal motion mechanism 4, and the other end is provided with a second chair back 2. The second chair back 2 is movably connected to the spring lifting mechanism 5.

[0040] The second chair back 2 undergoes a combined forward and backward and up and down movement simultaneously through the horizontal movement mechanism 4 and the elastic lifting mechanism 5.

[0041] The first backrest 1 is positioned above the second backrest 2, fitting snugly against the user's back and waist. The second backrest 2 is connected in sequence to the elastic lifting mechanism 5 and the horizontal movement mechanism 4. The elastic lifting mechanism 5 and the horizontal movement mechanism 4 can adjust the height and position of the second backrest 2, and can also perform combined vertical and horizontal movements simultaneously, keeping the position of the user's waist relative to the second backrest 2 dynamically constant. The user controls the position of the second backrest 2 through the frictional resistance between their waist and the second backrest 2, ensuring that the user receives lumbar support from the second backrest 2 in different sitting postures. This effectively alleviates symptoms such as soreness or fatigue caused by prolonged sitting due to lack of lumbar support, providing the user with excellent comfort. Embodiments of the present invention

[0042] The working principle of this utility model is as follows:

[0043] The second backrest 2 is movably connected to the elastic lifting mechanism 5. When the user's waist rests on the second backrest 2, the sliding member 52 in the elastic lifting mechanism 5, which is slidably engaged with the sliding bracket, moves with the user's movement. A second spring 53 is installed in the first sliding groove 511 of the sliding bracket. The protrusion 521 on the sliding member 52 abuts against the second spring 53. When the user leans back or presses down on the second backrest 2, the protrusion 521 squeezes the second spring 53. The second spring 53 generates elastic force after being squeezed. This elastic force returns the second backrest 2 to its original height position when the user leaves the second backrest 2. In the horizontal movement mechanism 4, the horizontal sliding of the second backrest 2 is achieved through the cooperation of the sliding wheel 45 on the sliding cylinder 41 and the guide groove 33 on the fixed cylinder 31. The first spring 42, sleeved on the positioning post 44 inside the sliding cylinder 41, is fixedly connected to the adjustment knob 43. When the sliding cylinder 41 slides, it squeezes the first spring 42. Similarly, the first spring 42 causes... The second chair back 2 is reset to the horizontal starting position. The second chair back 2, through the first spring 42 and the second spring 53, can move with the user's waist and can simultaneously perform horizontal and vertical reset movements with a high degree of freedom. Since the first spring 42 is also fixedly connected to the adjustment knob 43, the tension of the first spring 42 can be adjusted by rotating the adjustment knob 43, which indirectly adjusts the magnitude of the rebound force and support force of the second chair back 2. Furthermore, both the elastic lifting mechanism 5 and the horizontal movement mechanism 4 are equipped with lockable structures, such as the limit knob on the horizontal movement mechanism 4 and the limit through hole 411 on the sliding cylinder 41. When the user wants to keep it fixed in a suitable position, the limit knob can be inserted or removed to fix the horizontal position of the second chair back 2. Similarly, the limit adjustment rod set on the second chair back 2 is fitted and connected to the limit groove 522 on the sliding member 52. By adjusting the limit adjustment rod to fit into the limit groove 522 at different positions, the second chair back 2 at different heights can be fixed.

[0044] In another embodiment, all the technical features of the above embodiments are included. The horizontal movement mechanism 4 includes a sliding cylinder 41 with one end open, a first spring 42, and an adjusting knob 43. The backrest support 3 is provided with a fixed cylinder 31 with both ends open, and the backrest support 3 is sleeved on the fixed cylinder 31. The adjusting knob 43 is movably connected to one end of the fixed cylinder 31. The end face of the adjusting knob 43 is provided with a positioning post 44, and the positioning post 44 is sequentially sleeved on the first spring 42, the sliding cylinder 41, and the fixed cylinder 31. The sliding cylinder 41 is slidably engaged with the fixed cylinder 31, and the end of the sliding cylinder 41 near the elastic lifting mechanism 5 is fixedly connected to the elastic lifting mechanism 5. One end of the first spring 42 is fixed to the end face of the adjusting knob 43, and the other end abuts against the elastic lifting mechanism 5. The second chair back 2 moves horizontally through the sliding engagement of the sliding cylinder 41 and the fixed cylinder 31. The first spring 42 inside the sliding cylinder 41 is connected to the elastic lifting mechanism 5 and the adjusting knob 43 respectively. When the second chair back 2 moves horizontally, the first spring 42 is compressed and relaxed as the second chair back 2 moves. The first spring 42 can also be tightened and relaxed by rotating the adjusting knob 43 to control the tension of the first spring 42, thereby controlling the elastic support force of the horizontal movement mechanism 4 on the second chair back 2.

[0045] Furthermore, it also includes a spring-loaded lifting mechanism 5 for controlling the height of the second chair back 2, including a sliding bracket 51, a sliding member 52, and a second spring 53. The second chair back 2 is provided with a first recess 21, and the sliding bracket 51 is fixedly installed in the first recess 21. The sliding member 52 is sleeved on the sliding bracket 51. The side of the sliding bracket 51 near the second chair back 2 is provided with two first sliding grooves 511, and the second spring 53 is installed in the first sliding grooves 511. The sliding member 52 is provided with at least two protrusions 521, which are arranged opposite to each other in the first sliding grooves 511. The other side of the sliding bracket 51 is provided with a connecting block 512, which is provided with a threaded connection hole 9. The end of the sliding cylinder 41 away from the adjustment knob 43 is provided with an installation port, and the connecting block 512 is sleeved on it. Inside the mounting port, the wall of the sliding cylinder 41 is provided with a connecting hole 8. External bolts pass through the connecting hole 8 and the threaded connecting hole 9 to fix the sliding bracket 51 to the sliding cylinder 41. When the sliding member 52 drives the second backrest 2 to slide downward, the protrusion 521 squeezes the second spring 53 to generate elastic force. After the second spring 53 is released, the second backrest 2 returns to its original position. With the cooperation of the horizontal movement mechanism 4, the user can adjust the position at any position in the horizontal and vertical directions. The spring can provide elastic support for the second backrest 2, so that when the second backrest 2 moves relative to the user's waist, it can ensure that the second backrest 2 closely follows the user's waist. The user only needs to use the frictional resistance when the waist moves to drive the movement of the second backrest 2, without having to deliberately adjust the second backrest 2 in other ways.

[0046] In another embodiment, all the technical features of the above embodiments are included. The sliding member 52 has at least one limiting groove 522 on one side. The first recess 21 has a first slot hole on its groove wall opposite to the limiting groove 522. The second chair back 2 has a limiting adjustment rod and a fixing member. The fixing member is fixedly installed in the first slot hole, and the limiting adjustment rod is sleeved in the cavity of the fixing member. The limiting adjustment rod is movably connected to the fixing member. One end of the limiting adjustment rod is engaged with the limiting groove 522 through the first slot hole. The position of the elastic lifting mechanism 5 can be locked and fixed to the height desired by the user through the limiting adjustment rod. Similarly, on the horizontal movement mechanism 4, the horizontal position of the second chair back 2 can be fixed by the cooperation of the limiting post on the limiting knob and the first through hole 311 on the sliding cylinder 41. Through the limiting adjustment rod and the limiting knob, the user can freely adjust to the most comfortable position and keep it unchanged.

[0047] In another embodiment, all the technical features of the above embodiments are included. At least one sliding wheel 45 is symmetrically provided on the outer wall surface of the sliding cylinder 41, and the sliding wheel 45 is fixedly connected to the sliding cylinder 41. At least one guide post 32 is provided on the inner wall surface of the fixed cylinder 31. The guide post 32 is integrally formed with the fixed cylinder 31, and a guide groove 33 is provided on the guide post 32. The sides of the two guide posts 32 with the guide groove 33 are arranged opposite to each other. At least one sliding wheel 45 is embedded between the two guide grooves 33. Through the cooperation between the sliding wheel 45 and the guide groove 33, the sliding cylinder 41 can slide more smoothly. The sliding mechanism is smooth. The sliding wheel 45 can be configured as a rotatable roller, with two sets on each side of the sliding cylinder 41. Unlike the prior art where sliding is achieved through surface friction between the slider track, this application sets the motion structure as a sphere, configuring the friction between surfaces as friction between points and surfaces. This reduces the friction generated between the sliding wheel 45 and the guide groove 33, solving the problem of the second chair back 2 not sliding smoothly due to the large friction between surfaces. Therefore, the sliding of the rollers allows the extension and retraction of the second chair back 2 to be more natural and easy, thereby improving the user experience.

[0048] In another embodiment, all the technical features of the above embodiments are included. At least one limiting through hole 411 is provided on the wall of the sliding cylinder 41. A first connecting cylinder 6 with one open end is formed on the outer wall of the positioning cylinder. A limiting knob 7 is sleeved on the open end of the first connecting cylinder 6. The limiting knob 7 is movably connected to the first connecting cylinder 6. A first through hole is provided on the wall connecting the first connecting cylinder 6 and the sliding cylinder 41. One end of the limiting knob 7 is fixedly connected to one end of the limiting post 71. The other end of the limiting post 71 is fitted into the limiting through hole 411 through the first through hole. A first connecting post 61 with openings at both ends is provided inside the first connecting cylinder 6. Two opposing external threads are symmetrically provided on the outer wall of the first connecting post 61. The end face of the limit knob 7 connected to the limit post 71 is also provided with a second connecting cylinder 72 with one end open. At least two second connecting posts 73 are symmetrically provided on the inner wall of the second connecting cylinder 72. The two second connecting posts 73 clamp the first connecting post 61 and fit the external thread 611. By rotating the limit knob 7, the second connecting post 73 rotates along the thread diameter of the external thread 611, extending the limit post 71 into or out of the limit through hole 411. The user can freely change the forward and backward movement position of the sliding cylinder within a certain range. Combined with the limit adjustment rod on the second chair back that fixes the elastic lifting mechanism, the user can freely adjust and fix the horizontal and height positions of the second chair back. Industrial applicability

[0049] The advantages of this utility model are:

[0050] 1) The second chair back provides dynamic support for the user's waist through a horizontal motion mechanism and an elastic lifting mechanism. It can provide dynamic support for the waist when the user changes any sitting posture, adaptively tracks the waist, and has a high degree of freedom of movement, which improves the user's comfortable experience and relieves the fatigue and soreness of the waist caused by prolonged sitting.

Claims

1. A chair back structure that provides dynamic support to users when switching between different sitting postures, characterized in that, include: First chair back; A chair back support, wherein the first chair back is fixedly connected to one end of the chair back support, and the other end of the chair back support is movably connected to the chair seat; A horizontal movement mechanism is provided, wherein the backrest support is sleeved on one end of the horizontal movement mechanism, and the other end of the horizontal movement mechanism is provided with a spring lifting mechanism. One end of the spring lifting mechanism is fixedly connected to the horizontal movement mechanism, and the other end of the spring lifting mechanism is provided with a second backrest, which is movably connected to the spring lifting mechanism. During operation, the second chair back undergoes a combined forward and backward and up and down movement simultaneously through the horizontal movement mechanism and the elastic lifting mechanism.

2. The chair back structure according to claim 1, which provides dynamic support to the user when switching between different sitting postures, is characterized in that... The horizontal movement mechanism includes a sliding cylinder with one open end, a first spring, and an adjustment knob. The chair back support has a fixed cylinder with both open ends, and the chair back support is sleeved on the fixed cylinder. The adjustment knob is movably connected to one end of the fixed cylinder. The end face of the adjustment knob is provided with a positioning post, and the positioning post is sequentially sleeved on the first spring, the sliding cylinder, and the fixed cylinder. The sliding cylinder is slidably engaged with the fixed cylinder, and the end of the sliding cylinder near the elastic lifting mechanism is fixedly connected to the elastic lifting mechanism. One end of the first spring is fixed to the end face of the adjustment knob, and the other end abuts against the inner end face of the sliding cylinder.

3. A chair back structure according to claim 2 that provides dynamic support to the user when switching between different sitting postures, characterized in that, The elastic lifting mechanism includes a sliding bracket, a sliding member, and at least one second spring. The second chair back has a first recessed groove, and the sliding bracket is fixedly installed within the first recessed groove. The sliding member is sleeved on the sliding bracket. The sliding bracket has at least two first sliding grooves on one side near the second chair back, and the second spring is installed within each of the first sliding grooves. The sliding member has at least two protrusions, one protrusion extending into one of the first sliding grooves and the other protrusion abutting against one of the second springs. The other side of the sliding bracket has a connecting block with a threaded connection hole. The end of the sliding cylinder away from the adjustment knob has an installation port, and the connecting block is sleeved within the installation port. The wall of the sliding cylinder has a connecting hole, and an external bolt passes through the connecting hole and the threaded connection hole to fix the sliding bracket and the sliding cylinder together.

4. A chair back structure according to claim 3, providing dynamic support to the user when switching between different sitting postures, characterized in that, The sliding member has at least one limiting groove on one side. The first groove has a first slot hole on the groove wall opposite to the limiting groove. The second chair back has a limiting adjustment rod and a fixing member. The fixing member is fixedly installed in the first slot hole. The limiting adjustment rod is sleeved in the cavity of the fixing member. The limiting adjustment rod is movably connected to the fixing member. One end of the limiting adjustment rod is engaged with the limiting groove through the first slot hole.

5. A chair back structure according to claim 2 that provides dynamic support to the user when switching between different sitting postures, characterized in that, The sliding cylinder has at least one limiting through hole on its wall surface. The outer wall surface of the positioning cylinder forms a first connecting cylinder with one open end. A limiting knob is sleeved on the open end of the first connecting cylinder. The limiting knob is movably connected to the first connecting cylinder. A first through hole is provided on the wall surface where the first connecting cylinder connects to the sliding cylinder. The limiting knob is fixedly connected to one end of the limiting post. The other end of the limiting post is engaged with the limiting through hole through the first through hole.

6. A chair back structure according to claim 2 that provides dynamic support to the user when switching between different sitting postures, characterized in that, At least one sliding wheel is symmetrically arranged on the outer wall surface of the sliding cylinder, and the sliding wheel is fixedly connected to the sliding cylinder; at least one guide post is provided on the inner wall surface of the fixed cylinder, the guide post is integrally formed with the fixed cylinder, the guide post is provided with a guide groove, the two guide posts are arranged opposite each other with the guide groove, and at least one sliding wheel is embedded between the two guide grooves.

7. A chair back structure according to claim 5, providing dynamic support to the user when switching between different sitting postures, characterized in that, The first connecting cylinder is provided with a first connecting post with openings at both ends. Two opposing external threads are symmetrically provided on the outer wall of the first connecting post. The end face of the limiting knob connected to the limiting post is also provided with a second connecting cylinder with one end opening. At least two second connecting posts are symmetrically provided on the inner wall of the second connecting cylinder. The two second connecting posts clamp the first connecting post and the second connecting posts are in contact with the external threads.

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