A clamping mechanism for screwing the tube cap of a test tube

Abstract

The present invention provides a clamping mechanism for screwing a test tube cap, which includes a clamping mechanism body connected to a guide shaft assembly of a cap screwing device body. The clamping mechanism body includes a plurality of cap jaws for clamping the cap of the test tube, an elastic member connected to the cap jaws, and a guide member. Among them, the elastic member drives the relative opening between the plurality of cap jaws to completely or partially wrap the cap; the guide member drives the relatively opened plurality of cap jaws to approach each other to clamp the cap; the plurality of cap jaws rotate under the drive of the guide shaft assembly and move along the axis direction of the cap at the same time to screw the cap. The structure is simple, easy to control, occupies a small space, and when gripping the cap to screw it, the cap is not easy to slide in the jaws, which is beneficial to screwing the cap and has high screwing efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and particularly to a clamping mechanism for screwing a test tube cap. Background Art

[0002] In medical clinical examinations, test tubes are needed to collect blood, body fluids, etc. as test samples. After collecting the blood, subsequent analysis is carried out. In this series of processes, the process of capping or uncapping the test tube cap is inevitably involved. In the market, the common test tube cap and the test tube itself are combined by a threaded tightening method. In this way, the isolation effect between the inside and outside of the test tube is good, and it is not easy to cause pollution to the collected blood, body fluids, etc. At present, some are manually operated to cap or uncapp the test tube, which is inefficient, costly, and also easy to cause the operator to be infected with bacteria, posing a hazard to the health of the operator. In addition, some automated inspection devices have emerged on the market, equipped with a test tube capping and uncapping mechanism. These capping and uncapping mechanisms clamp the cap through a clamping jaw. In order to achieve clamping and subsequent coordinated capping and uncapping actions, the entire capping and uncapping gripper mechanism has a complex structure and requires multiple driving components. In order to clamp the cap, some existing ones install a spring on the clamping jaw and rotate the spring to clamp the cap, which is difficult to operate and inefficient. In addition, during the capping and uncapping process, the relative sliding of the cap in the clamping jaw is also a technical problem. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, an object of the present invention is to provide a clamping mechanism for screwing a test tube cap, which makes several cap claws relatively open by an elastic member to completely or partially wrap the cap, drives the relatively open several cap claws to approach each other by the guiding member to clamp the cap, and under the drive of the guiding shaft assembly, several of the cap claws screw the cap, with a simple structure, easy to control, and small occupied space.

[0004] In order to achieve the above object, the present invention is realized through the following technical solutions.

[0005] The present invention provides a clamping mechanism for screwing a test tube cap, including a clamping mechanism body connected to the guiding shaft assembly of the capping and uncapping device body. The clamping mechanism body includes several cap claws for clamping the cap of the test tube, an elastic member connected to the cap claws, and a guiding member; wherein,

[0006] The elastic member drives the relative opening between several cap claws to completely or partially wrap the cap; the guiding member drives the relatively open several cap claws to approach each other to clamp the cap; several of the cap claws rotate and move along the axis direction of the cap under the drive of the guiding shaft assembly to screw the cap.

[0007] Preferably, the number of the cap clamping jaws is two, the elastic member includes a torsion spring, and the torsion spring abuts against the two cap clamping jaws respectively. The elastic force of the torsion spring causes the two cap clamping jaws to open to form a first cavity for clamping the cap.

[0008] Preferably, one end of each cap clamping jaw is provided with a first through hole, and the two cap clamping jaws are rotationally connected by a rotating shaft rod passing through the first through hole.

[0009] Preferably, further included is a first connecting block connected to one end of the cap clamping jaw. A convex block is provided on the first connecting block, and a second through hole is provided on the convex block. The two cap clamping jaws are rotationally connected by a rotating shaft rod passing through the second through hole.

[0010] Preferably, the torsion spring is sleeved outside the rotating shaft rod and located between the two cap clamping jaws; when the two cap clamping jaws clamp the cap, the inner surface of the cap clamping jaw fits with part or all of the outer surface of the cap.

[0011] Preferably, the first connecting block is in the shape of a triangular prism, the included angle between the two side surfaces of the first connecting block is 90°, and the convex block is provided on one bottom surface of the first connecting block; the cap clamping jaw includes two finger claws, and the two finger claws are respectively connected to the two side surfaces with an included angle of 90° of the first connecting block; the finger claw is in the shape of a cuboid, and one end surface of the finger claw is flush with the bottom surface of the first connecting block where the convex block is provided.

[0012] Preferably, further included is a second connecting block. Both ends of the rotating shaft rod are connected to one end of the second connecting block, and the other end of the second connecting block is connected to the guide shaft assembly; the guiding member is a limiting sleeve, and the limiting sleeve is provided with a third through hole. The guide shaft assembly drives the two cap clamping jaws to extend into or away from the third through hole, so that the two cap clamping jaws clamp or release the cap under the resilience of the elastic member.

[0013] Preferably, one end of the second connecting block is connected to the guide shaft assembly through a limiting block, and the limiting block is located on the other side of the limiting sleeve relative to the cap clamping jaw to limit the maximum distance of the cap clamping jaw away from the limiting sleeve.

[0014] Preferably, a guiding inclined surface is provided on the outer wall of the finger claw near one end of the limiting sleeve; when the limiting block abuts against the limiting sleeve, the guiding inclined surface wholly or partially extends into the third through hole, and the limiting sleeve cooperates with the elastic member to enable the two relatively open cap clamping jaws to exactly completely wrap the cap; the two cap clamping jaws clamping the cap can completely pass through the third through hole and the outer contour when inside the third through hole fits with the inner wall of the third through hole.

[0015] Preferably, the finger claws are provided with a first protrusion and a second protrusion. The distance between the first protrusion and the second protrusion is slightly greater than the height of the tube cap. The third through hole makes the size of the first cavity slightly smaller than the outer contour size of the tube cap when the two tube cap claws are close to clamp the tube cap. The stiffness of the tube cap claws and the limit sleeve is much greater than that of the tube cap; wherein,

[0016] When the limit block abuts against the limit sleeve, the two tube cap claws open so that one outer wall of the tube cap abuts against the first protrusion. The guide shaft assembly drives the two tube cap claws to extend into the third through hole. When the two tube cap claws approach each other to clamp the tube cap, the other outer wall of the tube cap claws relative to the limit sleeve abuts against the second protrusion, and the guide shaft assembly drives the two tube cap claws to rotate for screwing the cap.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) An object of the present invention is to provide a clamping mechanism for screwing the tube cap of a test tube. Through the elastic member, several tube caps are relatively opened to completely or partially wrap the tube cap. Through the guide member, several relatively opened tube cap claws are driven to approach each other to clamp the tube cap. Driven by the guide shaft assembly, several tube cap claws screw the tube cap. The structure is simple, easy to control, and occupies a small space.

[0019] (2) In a preferred embodiment of the present invention, two tube cap claws are rotationally connected through two first connecting blocks, a rotating shaft rod, and a torsion spring. The relatively opened two tube cap claws are close to each other through the limit sleeve. The structure is simple and the manufacturing cost is low.

[0020] (3) In a preferred embodiment of the present invention, through the guiding inclined surface, the limit block, and the first protrusion and the second protrusion are provided on the finger claws. When the limit block abuts against the limit sleeve, the guiding inclined surface entirely or partially extends into the third through hole. The relative opening amplitude of the two tube cap claws just completely wraps the tube cap, that is, clamping can start when the limit block abuts against the limit sleeve; when the limit block is away from the limit sleeve, that is, when the two tube cap claws continue to extend into the third through hole, the two tube cap claws clamp the tube cap, and at this time, the size of the first cavity formed by the two tube cap claws is slightly smaller than the outer contour size of the tube cap, so that the tube cap will not slide within the two tube cap claws when screwing the cap.

[0021] (4) In a preferred embodiment of the present invention, the first connecting block is in the shape of a triangular prism, and the included angle between the sides respectively connected to the two finger claws is 90°, so that the four finger claws are evenly distributed on the circumference of the tube cap, and the tube cap is evenly stressed.

[0022] The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and be able to implement it according to the content of the specification, the following will be described in detail with some embodiments. The specific implementation manners of the present invention are given in detail by the following embodiments. Brief Description of the Drawings

[0023] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 is an exploded view of the structure of the cap-tightening gripper mechanism in an embodiment of the present invention;

[0025] Figure 2 is a three-dimensional structure diagram of the cap-tightening gripper mechanism in an embodiment of the present invention;

[0026] Figure 3 is a sectional view of the structure of the cap-tightening gripper mechanism in an embodiment of the present invention;

[0027] Figure 4 is a structure diagram when the two cap jaws of the cap-tightening gripper mechanism clamp the cap in an embodiment of the present invention;

[0028] Figure 5 is a structure diagram of the connection between the finger claw and the first connection block in an embodiment of the present invention;

[0029] Figure 6 is a three-dimensional structure diagram of the first connection block in an embodiment of the present invention;

[0030] Figure 7 is a three-dimensional structure diagram of the finger claw in an embodiment of the present invention Figure 1 ;

[0031] Figure 8 is a three-dimensional structure diagram of the finger claw in an embodiment of the present invention Figure 2 ;

[0032] In the figure:

[0033] 400, test tube; 410, tube cap;

[0034] 510, clamping mechanism body; 511, cap jaw; 5111, finger claw; 5111a, guiding inclined surface; 5111b, first protrusion; 5111c, second protrusion; 512, rotating shaft rod; 513, first connection block; 5131, convex block; 5131a, second through hole; 514, torsion spring; 515, second connection block; 516, limiting sleeve; 5161, third through hole; 517, limiting block;

[0035] 520. Guide shaft assembly. Detailed implementation

[0036] The following further elaborates on the present invention in conjunction with the accompanying drawings. The foregoing and other objects, features, aspects, and advantages of the present invention will become more apparent, enabling those skilled in the art to implement it based on the description in the specification. In the drawings, for clarity, the shapes and dimensions may be enlarged, and the same reference numerals will be used throughout all the figures to indicate the same or similar components. In the following description, terms such as center, thickness, height, length, front, back, rear, left, right, top, bottom, upper, lower, etc. are based on the orientation or positional relationship shown in the drawings. Specifically, "height" corresponds to the dimension from the top to the bottom, "width" corresponds to the dimension from the left to the right, and "depth" corresponds to the dimension from the front to the back. These relative terms are for convenience of description and generally do not intend to require a specific orientation. Terms related to attachment, connection, etc. (e.g., "connect" and "attach") refer to the relationship in which these structures are directly or indirectly fixed or attached to each other through an intermediate structure, as well as a movable or rigid attachment or relationship, unless otherwise explicitly stated.

[0037] Next, in conjunction with the accompanying drawings and specific implementation manners, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0038] Embodiment 1

[0039] As Figures 1 to 8 shown, the present invention provides a clamping mechanism for screwing a test tube cap, including a clamping mechanism body 510 connected to the guide shaft assembly 520 of the cap-screwing device body. The clamping mechanism body 510 includes a plurality of cap claws 511 for clamping the cap 410 of the test tube 400, an elastic member connected to the cap claws 511, and a guiding member. Among them,

[0040] the elastic member drives the relative opening between the plurality of cap claws 511 to completely or partially wrap the cap 410; the guiding member drives the relatively opened plurality of cap claws 511 to approach each other to clamp the cap 410. Under the drive of the guide shaft assembly, while the plurality of cap claws 511 rotate, they move along the axis direction of the cap 410 to screw the cap 410.

[0041] The number of the cap claws 511 is two. The elastic member includes a torsion spring 514. The torsion spring 514 abuts against the two cap claws 511 respectively, and the two cap claws 511 are opened at a certain angle by the elastic force of the torsion spring 514 itself to form a first cavity for clamping the cap 410.

[0042] In one embodiment, one end of the cap gripper 511 is provided with a first through hole. The two cap grippers 511 are rotationally connected by a rotating shaft rod 512 passing through the first through hole. The torsion spring 514 is sleeved outside the rotating shaft rod 512 and is located between the two cap grippers 511. One end of the rotating shaft rod 512 is fixed by a retaining ring (not shown in the figure). The elastic force of the torsion spring 514 itself causes the two cap grippers 511 to open, and the cap 410 is wrapped in the first cavity. Driven by the guiding member, the two cap grippers 511 approach each other until the two cap grippers 511 clamp the cap 410. At this time, the inner surface of the cap gripper 511 fits with part or all of the outer surface of the cap 410, so that the contact surface between the cap gripper 511 and the cap 410 is larger, and the clamping force is improved.

[0043] In one embodiment, it further includes a first connecting block 513 connected to one end of the cap gripper 511. The first connecting block 513 is in the shape of a triangular prism. A convex block 5131 is provided on one bottom surface of the first connecting block 513. A second through hole 5131a is provided on the convex block 5131. The two cap grippers 511 are rotationally connected by a rotating shaft rod 512 passing through the second through hole 5131a. The torsion spring 514 is sleeved outside the rotating shaft rod 512 and is located between the two cap grippers 511. One end of the rotating shaft rod 512 is fixed by a retaining ring (not shown in the figure). The cap gripper 511 includes two finger claws 5111, and the two finger claws 5111 are respectively connected to two side surfaces of the first connecting block 513. The first connecting block 513 forms an angle of 90° with the two side surfaces of the two finger claws 5111 respectively, so that the four finger claws 5111 of the two cap grippers 511 are evenly distributed on the periphery of the cap 410, and the cap 410 is stressed evenly. The finger claw 5111 is in the shape of a cuboid, and one end surface of the finger claw 5111 is flush with the bottom surface of the first connecting block 513 where the convex block 5131 is provided. In one embodiment, when the two cap grippers 511 clamp the cap 410, the two first connecting blocks 513 do not contact each other, so as not to affect the screwing of the two cap grippers 511 after clamping the cap 410.

[0044] The size of the first connecting block 513 should not be too large, so that the two cap grippers 511 can clamp the cap 410 under the limiting action of the limiting sleeve 516, and the distance required for the two cap grippers 511 to move along the axis direction of the cap 410 from the time when the two cap grippers 511 are relatively opened to just completely wrap the cap 410 to the time when the two cap grippers 511 approach each other to clamp the cap 410 is not too large, reducing the required space for movement. The size of the first connecting block 513 also affects the relative opening amplitude of the two cap grippers 511 and affects the spacing between the arrangements of several test tubes 400.

[0045] It further includes a second connecting block 515. The second connecting block 515 has a hollow structure. The first connecting block 513 is located within the second connecting block 515. Both ends of the rotating shaft rod 512 penetrate and are connected to one end of the second connecting block 515. The other end of the second connecting block 515 is connected to the guide shaft assembly 520.

[0046] The guiding member is a limiting sleeve 516. The limiting sleeve 516 is provided with a third through hole 5161. The size of the second connecting block 515 is smaller than the size of the third through hole 5161, so that the second connecting block 515 can move within the third through hole 5161. The guide shaft assembly 520 drives the second connecting block 515 to move along the axial direction of the pipe cap 410, driving the first connecting block 513 connected to the second connecting block 515 and the two pipe cap claws 511 to move along the axial direction of the pipe cap 410, extending into or away from the third through hole 5161. When the two pipe cap claws 511 gradually extend into the third through hole 5161, the two pipe cap claws 511 approach each other until they clamp the pipe cap 410; when the two pipe cap claws 511 are separated from the third through hole 5161, the two pipe cap claws 511 loosen the clamped pipe cap 410 under the elastic return force of the elastic member, that is, the two pipe cap claws 511 clamp or loosen the pipe cap 410 under the elastic return force of the elastic member. The limiting sleeve 516 is fixedly installed on the surface of an object, so that the limiting sleeve 516 will not move along with the movement of the two pipe cap claws 511 driven by the guide shaft assembly 520.

[0047] One end of the second connecting block 515 is connected to the guide shaft assembly 520 through a limiting block 517. The limiting block 517 has a hollow structure. One end is connected within the second connecting block 515, and the size of the opposite end is larger than the size of the third through hole 5161. The limiting block 517 is located on the other side of the limiting sleeve 516 relative to the pipe cap claws 511 to limit the maximum distance that the pipe cap claws 511 can move away from the limiting sleeve 516 under the drive of the guide shaft assembly 520.

[0048] On the outer wall of the finger claw 5111 near one end of the limit sleeve 516, there is a guiding inclined surface 5111a; the guiding inclined surfaces 5111a of the four finger claws 5111 make the end surface of one end of the two cap claws 511 facing the limit sleeve 516 have a structure that gradually decreases from large to small. When the limit block 517 abuts against the limit sleeve 516, all or part of the guiding inclined surface 5111a extends into the third through hole 5161. Further, when the limit block 517 abuts against the limit sleeve 516, the guiding inclined surface 5111a just completely extends into the third through hole 5161. The inclination angle of the guiding inclined surface 5111a is such that when the guiding inclined surface 5111a just completely extends into the third through hole 5161, the first cavity formed by the relative opening of the two cap claws 511 under the restoring force of the elastic member and the limiting action of the limit sleeve 516 can exactly and completely wrap the cap 410 therein. When the cap claws 511 continue to extend into the third through hole 5161 under the driving action of the guiding shaft assembly 520, the opening angle of the two cap claws 511 gradually becomes smaller until the cap 410 is clamped. At this time, the two cap claws 511 can completely pass through the third through hole 5161 and the outer contour when in the third through hole 5161 fits the inner wall of the third through hole 5161.

[0049] The outer contour of the cap 410 of the test tube commonly used in the market is cylindrical, the third through hole 5161 is cylindrical, the side surfaces of the first connecting block 513 connected to the two finger claws 5111 respectively are of the same size, and the outer contour when the two cap claws 511 clamp the cap 410 can be circumscribed by a cylinder, and the shape and size of this cylinder are the same as those of the third through hole 5161. The inner surfaces of the two cap claws 511 are uniformly attached to the outer wall of the cap 410. In the extremely rare case where the outer contour of the cap 410 is irregular, the inner contour of the two cap claws 511 matches the outer contour of the cap 410, and the outer contour of the two cap claws 511 can still be circumscribed by a cylinder, and the shape and size of this cylinder are the same as those of the third through hole 5161, so that while the two cap claws 511 can be pressed by the limit sleeve 561 for clamping, the two cap claws 511 can rotate in the third through hole 5161.

[0050] The finger claw 5111 is provided with a first protrusion 5111b and a second protrusion 5111c. The first cavity is the space formed between the inner surfaces of the two cap grippers 511, the first protrusion 5111b, and the second protrusion 5111c. The distance between the first protrusion 5111b and the second protrusion 5111c is slightly greater than the height of the cap 410. When the two cap grippers 511 clamp the cap 410 under the pressing action of the limiting sleeve 516, the cap 410 is located in the first cavity formed between the inner surfaces of the two cap grippers 511, the first protrusion 5111b, and the second protrusion 5111c, and the cap 410 is in contact with the inner surfaces of the two cap grippers 511. The third through hole 5161 makes the size of the first cavity formed by the two cap grippers 511 close to each other for clamping slightly smaller than the outer contour size of the cap 410. The rigidity of the cap grippers 511 and the limiting sleeve 516 is much greater than the rigidity of the cap 410, that is, the elastic deformation performance of the cap 410 is better than that of the cap grippers 511 and the limiting sleeve 516. Under the pressing and limiting action of the inner wall of the third through hole 5161 of the limiting sleeve 516, the two cap grippers 511 clamp the cap 410, and under the elastic deformation of the cap 410 itself, the two cap grippers 511 continue to approach each other until the cap 410 is clamped for screwing the cap. When screwing the cap, the cap 410 will not slide relative to the cap grippers 511. Among them,

[0051] When the limiting block 517 abuts against the limiting sleeve 516, the two cap grippers 511 open so that an outer wall of the cap 410 abuts against the first protrusion 5111b. The guide shaft assembly 520 drives the two cap grippers 511 to extend into the third through hole 5161. When the two cap grippers 511 approach each other to clamp the cap 410, the cap grippers 511 abut against the second protrusion 5111c relative to the other outer wall of the limiting sleeve 516, and the guide shaft assembly 520 drives the two cap grippers 511 to rotate for screwing the cap.

[0052] In one embodiment, the cap grippers 511 and the limiting sleeve 516 are made of a metal material with surface oxidation to improve the surface wear resistance; the cap 410 is made of plastic.

[0053] In one embodiment, a rubber layer (not shown in the figure) is provided on the inner surface of the cap grippers 511 for clamping the cap 410 to increase the clamping force on the cap 410.

[0054] It should be understood that the guide shaft assembly 520 (simplified representation in the attached drawing) in this embodiment can be any existing structure that can realize the movement and / or rotational movement of the gripper along the axis direction of the cap, and will not be elaborated here.

[0055] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those skilled in the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the embodiments shown herein.

Claims

1. A clamping mechanism for screwing a test tube cap, comprising a clamping mechanism body (510) connected to a guide shaft assembly (520) of a cap screwing device body, characterized in that, The clamping mechanism body (510) includes cap jaws (511) for clamping the cap (410) of the test tube (400), an elastic member connected to the cap jaws (511), and a guiding member; wherein, the elastic member drives the relative opening between several cap jaws (511) to completely or partially wrap the cap (410); the guiding member drives the relatively opened several cap jaws (511) to approach each other to clamp the cap (410); several of the cap jaws (511) rotate under the drive of the guiding shaft assembly and move along the axis direction of the cap (410) to screw the cap (410); the number of the cap jaws (511) is two, the elastic member includes a torsion spring (514), the torsion spring (514) abuts against the two cap jaws (511) respectively, and the elastic force of the torsion spring (514) causes the two cap jaws (511) to open to form a first cavity for clamping the cap (410); further includes a first connection block (513) connected to one end of the cap jaw (511), a convex block (5131) is provided on the first connection block (513), a second through hole (5131a) is provided on the convex block (5131), and the two cap jaws (511) are rotatably connected by a rotating shaft rod (512) passing through the second through hole (5131a); the first connection block (513) is in the shape of a triangular prism, the included angle between the two side surfaces of the first connection block (513) is 90°, and the convex block (5131) is provided on a bottom surface of the first connection block (513); the cap jaw (511) includes two finger claws (5111), and the two finger claws (5111) are respectively connected to the two side surfaces of the first connection block (513) with an included angle of 90°; the finger claw (5111) is in the shape of a cuboid, and one end surface of the finger claw (5111) is flush with the bottom surface of the first connection block (513) where the convex block (5131) is provided.

2. The clamping mechanism for screwing a test tube cap according to claim 1, characterized in that, One end of the cap jaw (511) is provided with a first through hole, and the two cap jaws (511) are rotatably connected by a rotating shaft rod (512) passing through the first through hole.

3. The clamping mechanism for screwing the test tube cap according to claim 1 or 2, characterized in that, The torsion spring (514) is sleeved outside the rotating shaft rod (512) and is located between the two cap jaws (511); when the two cap jaws (511) clamp the cap (410), the inner surface of the cap jaw (511) fits with part or all of the outer surface of the cap (410).

4. The clamping mechanism for screwing the test tube cap according to claim 3, characterized in that, Further includes a second connection block (515), both ends of the rotating shaft rod (512) are connected to one end of the second connection block (515), and the other end of the second connection block (515) is connected to the guiding shaft assembly (520); the guiding member is a limiting sleeve (516), the limiting sleeve (516) is provided with a third through hole (5161), and the guiding shaft assembly (520) drives the two cap jaws (511) to extend into or away from the third through hole (5161) so that the two cap jaws (511) clamp or loosen the cap (410) under the resilience of the elastic member.

5. The clamping mechanism for screwing a test tube cap according to claim 4, characterized in that, One end of the second connecting block (515) is connected to the guiding shaft assembly (520) through a limiting block (517). The limiting block (517) is located on the other side of the limiting sleeve (516) relative to the cap gripper (511) to limit the maximum distance of the cap gripper (511) away from the limiting sleeve (516).

6. The clamping mechanism for screwing the test tube cap according to claim 5, wherein, A guiding inclined surface (5111a) is provided on the outer wall of one end of the finger claw (5111) close to the limiting sleeve (516). When the limiting block (517) abuts against the limiting sleeve (516), the guiding inclined surface (5111a) wholly or partially extends into the third through hole (5161). The limiting sleeve (516) cooperates with the elastic member so that the two relatively opened cap grippers (511) exactly and completely wrap the cap (410). The two cap grippers (511) clamping the cap (410) can completely pass through the third through hole (5161), and the outer contour when inside the third through hole (5161) fits with the inner wall of the third through hole (5161).

7. The clamping mechanism for screwing the test tube cap according to claim 5, characterized in that, The finger claw (5111) is provided with a first protrusion (5111b) and a second protrusion (5111c). The distance between the first protrusion (5111b) and the second protrusion (5111c) is slightly larger than the height of the cap (410). The third through hole (5161) makes the size of the first cavity formed when the two cap grippers (511) approach to clamp the cap (410) slightly smaller than the outer contour size of the cap (410). Wherein, When the limiting block (517) abuts against the limiting sleeve (516), the two cap grippers (511) open so that an outer wall of the cap (410) abuts against the first protrusion (5111b). The guiding shaft assembly (520) drives the two cap grippers (511) to extend into the third through hole (5161). When the two cap grippers (511) approach each other to clamp the cap (410), the other outer wall of the cap gripper (511) relative to the limiting sleeve (516) abuts against the second protrusion (5111c), and the guiding shaft assembly (520) drives the two cap grippers (511) to rotate for screwing the cap.

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