Limiting mechanism for thread test and tool applying limiting mechanism

Abstract

The utility model relates to a limit mechanism used for thread test and a tool applying the limit mechanism, the limit mechanism comprises an accommodating space used for arranging a connecting piece to be tested and a blocking piece, the blocking piece is provided with an opening for an external thread part to pass through, the limit mechanism is characterized by also comprising a guide piece used for guiding the external thread part, and the guide piece is provided with an opening for the external thread part to pass through. The guiding piece is provided with a first through hole for the external thread part to penetrate through, the guiding piece can be selectively arranged on the opening to be matched with the corresponding to-be-tested connecting piece, and in the state that the matched connecting piece moves upwards, the blocking piece abuts against the to-be-tested connecting piece for limiting. And meanwhile, the hole wall of the first through hole plays a role in guiding the external thread part so as to prevent the axis of the external thread part from offsetting. The limiting mechanism has the advantages that the guide piece of the limiting mechanism can be selectively arranged on the opening so as to be matched with the corresponding connecting piece to be tested; the device can be conveniently adapted to connecting pieces to be tested with thread parts with different diameter specifications, and the precision of the thread test is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to thread tensile test technical field especially, a kind of limiting mechanism for automobile parts thread test and the tooling of application with this limiting mechanism. BACKGROUND

[0002] Threaded connection is one of the most widely used parts in manufacturing industry, for example, on automobile parts, threaded connection almost covers each system and component of automobile, as a kind of basic and key mechanical connection mode, threaded connection bears important functions such as fixing, sealing, load transmission, therefore, testing the thread strength on threaded connection is the key step to ensure its safety and reliability in practical application.

[0003] For the thread strength, tensile test method is usually used, for this, there is threaded strength tensile test tooling in prior art, for example, Chinese patent application No.CN201510879384.3 (publication No.CN106840871A) provides the threaded strength tensile test tooling. One of the outer threaded connection and inner threaded connection used for testing is the connection to be tested, and the other is the matching connection with greater hardness to ensure that the thread of the connection to be tested is damaged first, the above test tooling can be attached to tensile equipment such as universal material testing machine, and includes first limiting piece for clamping nut and the like inner threaded connection and second limiting piece for clamping the head of bolt and the like outer threaded connection, and then the first limiting piece and the second limiting piece are driven by the tensile equipment to make the outer threaded connection and the inner threaded connection away from each other, until the thread of the connection to be tested is broken, and the thread strength can be obtained.

[0004] But the above test tooling and each limiting piece are mostly used for detecting bolt and nut and the like conventional shape threaded connection, when the connection to be tested is workpiece in actual production, there are still the following problems:

[0005] Firstly, the limiting piece of conventional test tooling is only suitable for the connection to be tested with thread part of specific diameter specification, because the limiting piece has through hole for the outer thread part of the connection to be tested or the matching connection to pass through, so that the connection to be tested is stretched along the axial direction of thread, if the diameter of through hole is too large, the inner wall of through hole cannot guide the outer thread part in the test process, the activity space of outer thread part is too large, which will lead to the axial line of the connection to be tested to be offset in the process of stretching, affect the accuracy of test, if the diameter of through hole is too small, the outer thread part cannot pass through. Especially, for example Figure 1The workpiece 2' shown has an internally threaded portion 1', and the workpiece 2' has a larger volume and weight compared with a conventional threaded connector, and needs to be guided during the test process, and when the workpiece 2' with different specifications of the internally threaded portion 1' is faced, the traditional test tool needs to be replaced with the entire limiting piece, and due to the large volume of the workpiece 2', the limiting piece also needs a larger space to accommodate the above-mentioned workpiece 2', which is high in cost and inconvenient to operate.

[0006] Secondly, the workpiece 2' includes a main body 10' provided with an internal thread 1' and a thin-walled portion 3' located at the periphery of the main body 10', and the limiting piece limits the workpiece 2' by abutting against the end face of the workpiece 2', but Figure 2 As shown, one side of the thin-walled portion 3' of the workpiece 2' protrudes axially beyond the main body 10', so that during the test process, the protruding side of the thin-walled portion 3' will first contact the limiting piece, resulting in the axis of the connector to be tested being offset during the stretching process, affecting the accuracy of the test and even directly damaging the workpiece 2' and being difficult to test. Utility model content

[0007] The first technical problem to be solved by the utility model is to provide a limiting mechanism that can adapt to a connector to be tested with different diameter specifications of threaded portions.

[0008] The second technical problem to be solved by the utility model is to provide a limiting mechanism that can avoid the negative impact of a thin-walled portion and other structures on threaded tests.

[0009] The third technical problem to be solved by the utility model is to provide a tool for threaded tests that applies the above-mentioned limiting mechanism.

[0010] The technical solution adopted by the utility model to solve the first technical problem is that the limiting mechanism for threaded tests includes a containing space for containing a connector to be tested, a blocking piece is arranged above the containing space, and the blocking piece is provided with an opening through which an external threaded portion of the connector to be tested or a mating connector passes, so that the connector to be tested and the mating connector are screwed together.

[0011] The application is characterized in that: the guiding member is further provided with a first through hole for guiding the external thread part, the limiting mechanism comprises a plurality of guiding members with the first through hole corresponding to the specification, the guiding member can be selectively arranged on the opening to adapt to the corresponding connecting piece to be tested, and in the state that the connecting piece is moved upward away from the connecting piece to be tested, the blocking member abuts against the connecting piece to be tested, so that the connecting piece to be tested cannot be moved toward the connecting piece, and the hole wall of the first through hole guides the external thread part to avoid the axis of the external thread part from being offset.

[0012] In order to solve the second technical problem, preferably, the connecting piece to be tested comprises a main body for setting the thread structure and a thin-walled part located at the periphery of the main body, the periphery of the first through hole of the guiding member is at least partially formed with a convex part protruding toward the connecting piece to be tested, and in the state that the connecting piece is moved upward away from the connecting piece to be tested, the convex part abuts against the main body of the connecting piece to be tested, so that the main body keeps a preset distance between the end face of the main body and the blocking member, and the preset distance is greater than the distance between the end face of the main body and the end part of the thin-walled part, thereby avoiding the thin-walled part of the connecting piece to be tested from contacting the blocking member. Such design is made in consideration of the fact that the side of the thin-walled part protruding axially beyond the main body sometimes exists on the connecting piece to be tested, so that the side of the thin-walled part protruding will first contact the blocking member in the test process, resulting in the axis of the connecting piece to be tested being offset in the stretching process. Due to the principle of force decomposition, the thread strength obtained in the final test will be less than the actual thread strength. In order to avoid the interference of the thin-walled part on the test result, the convex part of the guiding member is arranged to abut between the blocking member and the main body, so that the main body keeps a preset distance from the blocking member. The guiding member has the functions of guiding and avoiding the interference of the thin-walled part on the test result, and has the effect of one thing serving two purposes.

[0013] In order to facilitate the replacement of the guiding member on the blocking member, preferably, the guiding member further comprises a connecting part for being screwed with the opening, the first through hole extends downward from the upper end of the connecting part and penetrates through the connecting part, correspondingly, the lower end of the connecting part is at least partially outwardly protruding to form a flange, the flange constitutes the convex part, and the distance between the end face of the flange and the blocking member is the preset distance. The guiding member is arranged to be screwed on the opening of the blocking member through the connecting part, so that the replacement of the guiding member can be realized in a relatively simple structure, and the preset distance can be adjusted in a certain range through the screwing manner.

[0014] In order to facilitate the replacement of the guide and the setting of the to-be-tested connector, preferably, a frame is further arranged below the blocking member, the blocking member and the frame jointly form the accommodating space, the blocking member further comprises at least two end portions for connecting with the frame, and the end portions of the blocking member are detachably connected with the frame. The design is made in consideration of the fact that the conventional blocking member can be provided with a notch for the insertion of the externally threaded portion, but since the connecting portion is screwed with the opening, it is difficult to provide the notch on the blocking member for the purpose of ensuring the strength, and even though the accommodating space is correspondingly larger in order to adapt to the to-be-tested connector with a larger size, it is still possible that the worker cannot directly put his hand into the accommodating space for the replacement of the guide or the setting of the to-be-tested connector. By arranging the limiting mechanism in the form of the detachable connection between the blocking member and the frame, the guide can be firstly installed on the blocking member or the to-be-tested connector is firstly set on the blocking member, and then the blocking member is connected with the frame so that the to-be-tested connector enters the accommodating space. The above-mentioned scheme is more convenient in operation.

[0015] In order to jointly form the accommodating space by the blocking member and the frame, preferably, the frame comprises a bottom plate, both ends of the bottom plate along the length direction at least partially extend towards the blocking member to form side walls connected with the blocking member, and the blocking member, the bottom plate and the two side walls jointly form the accommodating space. The upper part of the accommodating space is the blocking member, and the lower part is the bottom plate. The blocking member can be used for limiting the to-be-tested connector, and the bottom plate can be attached to the stretching device.

[0016] In order to realize the connection between the blocking member and the frame, preferably, the two side walls comprise a first side wall and a second side wall, the blocking member has a first end portion extending towards the first side wall and a second end portion extending towards the second side wall, and correspondingly, the upper end of the first side wall is at least partially recessed in the center to form a first recess for the insertion of the first end portion, and the upper end of the second side wall is at least partially recessed in the center to form a second recess for the insertion of the second end portion.

[0017] In order to realize the detachable connection of the blocking piece and the frame body, preferably, a first pin for connecting the first side wall and the first end portion and a second pin for connecting the second side wall and the second end portion are further included, the first side wall and the first end portion are provided with a second through hole for the first pin to pass through, the second through hole penetrates the first side wall and the first end portion in a direction perpendicular to the extension direction of the blocking piece, and correspondingly, the second side wall and the second end portion are provided with a third through hole for the second pin to pass through, the third through hole penetrates the second side wall and the second end portion in a direction perpendicular to the extension direction of the blocking piece. After the first end portion is inserted into the first recess, the connection can be realized by the first pin passing through the second through hole of the first end portion and the second recess, and the connection between the second end portion and the second recess is realized in the same way. The connection structure is simple and reliable, and is more flexible and convenient to disassemble and reassemble.

[0018] In order to solve the third technical problem, the utility model provides a tool for being attached to a stretching device and carrying out a thread test on a to-be-tested connecting piece, comprising a seat body for arranging a matched connecting piece, characterized in that: the seat body further comprises a limiting mechanism as described above, the seat body is used for being attached to a first clamp of the stretching device, and correspondingly, the limiting mechanism is used for being attached to a second clamp of the stretching device, so that the seat body and the limiting mechanism can move towards each other or away from each other. The first clamp and the second clamp of the stretching device can move towards each other or away from each other, so that the seat body and the limiting mechanism can move away from each other, and then the matched connecting piece and the to-be-tested connecting piece screwed together move away from each other, and finally the thread is damaged, so that the thread strength of the to-be-tested connecting piece is obtained.

[0019] In order to realize that the seat body can limit the matched connecting piece, preferably, the seat body is columnar, and the outer wall of the seat body is recessed along a direction perpendicular to the outer thread part of the to-be-tested connecting piece or the matched connecting piece to form a T-shaped slot, the vertical end of the slot forms a channel for the outer thread part to pass through, and the horizontal end of the slot is used for arranging the head of the matched connecting piece, so that the matched connecting piece is resisted by the end face of the channel to limit the movement of the matched connecting piece in the direction of approaching the to-be-tested connecting piece. Since the to-be-tested connecting piece and the matched connecting piece need to move away from each other during the test, and the to-be-tested connecting piece is limited by the limiting mechanism, in order to avoid that the matched connecting piece approaches the to-be-tested connecting piece in the axial direction, the T-shaped slot is arranged on the seat body, and the matched connecting piece is resisted by the end face of the channel to realize the limiting action of the seat body on the matched connecting piece.

[0020] In order to realize that the seat body and the limiting mechanism can be attached to the stretching device, preferably, the first clamp and the second clamp of the stretching device are cylindrical, the seat body further comprises a first connecting portion for being inserted into the first clamp, the limiting mechanism comprises a second connecting portion for being inserted into the second clamp, and the first connecting portion and the second connecting portion are connected with the respective corresponding clamps through pin connection structures.

[0021] Compared with the prior art, the limiting mechanism for thread test has the advantages that the opening through which the outer thread part of the to-be-tested connecting piece or the matched connecting piece passes is arranged on the blocking piece, the guiding piece for guiding the outer thread part is further arranged, the guiding piece can be selectively arranged on the opening to adapt to the corresponding to-be-tested connecting piece, the axis of the outer thread part can be prevented from being offset, the to-be-tested connecting piece with the thread part of different diameter specifications can be conveniently adapted, and the precision of the thread test is improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structure schematic view of a workpiece in the background technology of the utility model;

[0023] Figure 2 It is a sectional structure schematic view of a workpiece in the background technology of the utility model;

[0024] Figure 3 It is a structure schematic view of a to-be-tested connecting piece in the embodiment of the utility model;

[0025] Figure 4 It is a structure schematic view of a stretching device and a tooling in the embodiment of the utility model;

[0026] Figure 5 It is a local enlarged structure schematic view of the tooling in the embodiment of the utility model;

[0027] Figure 6 It is a structure schematic view of a to-be-tested connecting piece and a blocking piece in the embodiment of the utility model;

[0028] Figure 7 It is an explosion structure schematic view of the tooling in the embodiment of the utility model;

[0029] Figure 8 It is an explosion structure schematic view of the limiting mechanism in the embodiment of the utility model;

[0030] Figure 9 It is a structure schematic view of a seat body and a matched connecting piece in the embodiment of the utility model;

[0031] Figure 10 It is a state schematic view of the stretching device and the tooling in the first state in the embodiment of the utility model;

[0032] Figure 11 Figure 8 is a state diagram of the stretching device and tool in the second state according to an embodiment of the present application;

[0033] Figure 12 Figure 9 is a state diagram of the stretching device and tool in the third state according to an embodiment of the present application;

[0034] Figure 13 Figure 10 is a state diagram of the stretching device and tool in the fourth state according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below with reference to specific embodiments.

[0036] As shown in Figures 1-9 , the preferred embodiment of the present application is shown. As shown in Figure 3 , the test connector A in the embodiment includes a main body 1a for setting a threaded structure and a thin-walled part 2a located at the periphery of the main body 1a, and one side of the thin-walled part 2a protrudes axially beyond the main body 1a, wherein the threaded structure provided on the main body 1a is an internal thread, and therefore the mating connector B adapted to the test connector A is a bolt. As shown in Figure 4 , Figure 5 , the limiting mechanism 72 for thread testing in the embodiment includes a receiving space 1 for accommodating the test connector A, and a blocking piece 2 located above the test connector A is provided on the receiving space 1, and the blocking piece 2 is provided with an opening for the outer threaded part C of the test connector A or the mating connector B to pass through, so that the test connector A and the mating connector B are screwed together. As shown in Figure 7 , Figure 8 , the limiting mechanism 72 for setting the test connector A further includes a guide piece 3 for guiding the outer threaded part C, and the guide piece 3 is provided with a first through hole 31 for the outer threaded part C to pass through. The limiting mechanism 72 includes a plurality of guide pieces 3 with respective corresponding specifications of the first through hole 31, and the guide piece 3 can be selectively provided on the opening 21 to adapt to the corresponding test connector A. In the state where the mating connector B moves upward away from the test connector A, the blocking piece 2 abuts against the test connector A, so that the test connector A cannot move towards the mating connector B, and the hole wall of the first through hole 31 guides the outer threaded part C to avoid the axis of the outer threaded part C from being offset. Considering that one side of the thin-walled part 2a protrudes axially beyond the main body 1a, if the thin-walled part 2a contacts the blocking piece 2 first, it will cause the axis of the test connector A to be offset, reducing the precision of the thread testing. Therefore, as shown in Figure 6As shown, the periphery of the first through hole 31 of the guide 3 in the embodiment is formed with a protrusion 32 at least partially protruding towards the connector A to be tested, and in the state that the mating connector B moves upwards away from the connector A to be tested, the protrusion 32 abuts against the main body 1a of the connector A to be tested, so that the end face of the main body 1a adjacent to the blocking member 2 keeps a preset distance H from the blocking member 2, and the preset distance H is greater than the distance between the end face of the main body 1a and the end of the thin wall part 2a, thereby avoiding the thin wall part 2a of the connector A to be tested from contacting the blocking member 2. If the protrusion 32 is not provided, the side of the thin wall part 2a of the connector A to be tested protruding first will contact the blocking member 2, which will cause the axis of the connector A to be tested to be offset during the stretching, and according to the principle of force decomposition, the thread strength obtained by the final test will be less than the actual thread strength. By abutting the protrusion 32 of the guide 3 between the blocking member 2 and the main body 1a, the main body 1a keeps a preset distance H from the blocking member 2, and the guide 3 has the functions of "guiding" and "avoiding the thin wall part 2a from interfering with the test results", thereby achieving the effect of one thing serving two purposes.

[0037] As to other structural aspects of the limiting mechanism 72, the replacement of the guide piece 3 and the arrangement of the to-be-tested connecting piece A need to be considered. Firstly, the guide piece 3 further comprises a connecting portion 33 for being screwed with the opening 21, the first through hole 31 extends downward from the upper end of the connecting portion 33 and penetrates the connecting portion 33, and the lower end of the connecting portion 33 at least partially protrudes outward to form a flange, which constitutes the protruding portion 32, and the distance between the end face of the flange and the blocking piece 2 is the preset distance H. Arranging the guide piece 3 to be screwed on the opening 21 of the blocking piece 2 can achieve the replacement of the guide piece 3 in a relatively simple structure, and the preset distance H can also be adjusted in a certain range in a screwed manner. Secondly, in combination with the above-mentioned replacement of the guide piece 3 and in order to facilitate the arrangement of the to-be-tested connecting piece A, the limiting mechanism 72 further comprises a frame 4 located below the blocking piece 2, the blocking piece 2 and the frame 4 jointly enclose the accommodation space 1, and the blocking piece 2 further comprises at least two end portions for being connected with the frame 4, and the end portions of the blocking piece 2 are detachably connected with the frame 4. Such design is considered that although the accommodation space 1 is also relatively large in order to adapt to the to-be-tested connecting piece A with a large volume, it may still be insufficient for the operating personnel to directly reach in to replace the guide piece 3 or arrange the to-be-tested connecting piece A, and arranging the limiting mechanism 72 in the above-mentioned form of detachable connection between the blocking piece 2 and the frame 4 can firstly install the guide piece 3 on the blocking piece 2 or arrange the to-be-tested connecting piece A on the blocking piece 2, and then connect the blocking piece 2 with the frame 4 to make the to-be-tested connecting piece A enter the accommodation space 1, and the above-mentioned scheme is more convenient in operation. Specifically, the above-mentioned frame 4 comprises a bottom plate 41, both ends of the bottom plate 41 along the length direction at least partially extend toward the blocking piece 2 to form side walls connected with the blocking piece 2, and the blocking piece 2, the bottom plate 41 and the two side walls jointly enclose the accommodation space 1. The two side walls comprise a first side wall 42 and a second side wall 43, the blocking piece 2 has a first end portion 22 extending toward the first side wall 42 and a second end portion 23 extending toward the second side wall 43, and correspondingly, a first recess 421 for the first end portion 22 to insert is at least partially recessed in the center of the upper end of the first side wall 42, and a second recess 431 for the second end portion 23 to insert is at least partially recessed in the center of the upper end of the second side wall 43. The limiting mechanism 72 further comprises a first pin 51 for connecting the first side wall 42 and the first end portion 22 and a second pin 52 for connecting the second side wall 43 and the second end portion 23, the first side wall 42 and the first end portion 22 are provided with a second through hole 61 for the first pin 51 to pass through, the second through hole 61 penetrates the first side wall 42 and the first end portion 22 along a direction perpendicular to the extension direction of the blocking piece 2, and correspondingly, the second side wall 43 and the second end portion 23 are provided with a third through hole 62 for the second pin 52 to pass through, the third through hole 62 penetrates the second side wall 43 and the second end portion 23 along a direction perpendicular to the extension direction of the blocking piece 2.After the first end portion 22 is inserted into the first recess portion 421, the connection between the first end portion 22 and the first recess portion 421 can be achieved by the first pin member 51 passing through the second through hole 61, and the connection between the second end portion 23 and the second recess portion 431 is achieved in the same way. The connection structure is simple, reliable, flexible, and convenient to disassemble and reassemble.

[0038] As shown in Figure 4 , the tool can be attached to the stretching device M and includes a seat body 71 for arranging the mating connector B and the above-mentioned limiting mechanism 72 for arranging the connector A to be tested. The seat body 71 is used to be attached to the first clamp 1m of the stretching device M, and correspondingly, the limiting mechanism 72 is used to be attached to the second clamp 2m of the stretching device M, so that the seat body 71 and the limiting mechanism 72 can move towards each other or away from each other. The first clamp 1m and the second clamp 2m of the stretching device M can move towards each other or away from each other, so that the seat body 71 and the limiting mechanism 72 can move away from each other, and then the mating connector B and the connector A to be tested screwed together move away from each other, and finally the threads are damaged, so as to obtain the thread strength of the connector A to be tested. Specifically, as shown in Figure 9 , the seat body 71 is columnar, and the outer wall of the seat body 71 is recessed along the vertical direction of the outer threaded portion C of the mating connector B to form a T-shaped slot 711, the vertical end of the slot 711 forms a passage 712 for the outer threaded portion C to pass through, and the horizontal end of the slot 711 is used to arrange the head of the mating connector B, so that the mating connector B is resisted by the end face of the passage 712 to limit the movement of the mating connector B towards the connector A to be tested. Since the connector A to be tested and the mating connector B need to move away from each other during the test, and the connector A to be tested is limited by the limiting mechanism 72, in order to avoid the mating connector B moving towards the connector A to be tested along the axial direction, the T-shaped slot 711 is arranged on the seat body 71, and the mating connector B is resisted by the end face of the passage 712 to achieve the limiting action of the seat body 71 on the mating connector B. The first clamp 1m and the second clamp 2m of the stretching device M are cylindrical, the seat body 71 further includes a first connecting portion 713 for being inserted into the first clamp 1m, and correspondingly, the limiting mechanism 72 includes a second connecting portion 721 for being inserted into the second clamp 2m, and the first connecting portion 713 and the second connecting portion 721 are both connected to the respective clamps by pin connection structure.

[0039] The specific use process of the tool and the limiting mechanism 72 in the embodiment is as follows:

[0040] As shown in Figure 10As shown, the seat body 71 is inserted and pinned on the first clamp 1m of the stretching device M through the first connecting part 713, and the limiting mechanism 72 is inserted and pinned on the second clamp 2m of the stretching device M through the second connecting part 721 connected with the bottom plate 41. In the state that the blocking piece 2 has not been installed to the frame body 4, the guide piece 3 can be selectively selected to be matched with the current connector A to be tested, and then the guide piece 3 is screwed on the opening 21 of the blocking piece 2 from bottom to top through the connecting part 33, and the dashed line in the figure represents the moving direction of the guide piece 3; then referring to Figure 11 the matching connector B is inserted into the slot 711 of the seat body 71, the outer threaded part C is screwed with the connector A to be tested through the opening of the blocking piece 2 and the first through hole 31 of the guide piece 3, and then the stretching device M drives the first clamp 1m to move downward in the direction shown by the dashed line in the figure; as shown in Figure 12 at this time, the first end part 22 of the blocking piece 2 is inserted into the first recess part 421 of the first side wall 42 and is pinned through the first pin 51, and the second end part 23 is inserted into the second recess part 431 of the second side wall 43 and is pinned through the second pin 52; finally as shown in Figure 13 the first clamp 1m of the stretching device M moves upward together with the connector A to be tested as shown by the dashed line in the figure, at this time, the main body 1a of the connector A to be tested is in contact with the recess part 32 of the guide piece 3, so that a predetermined distance H is kept between the main body 1a and the blocking piece 2, and at the same time, the hole wall of the first through hole 31 of the guide piece 3 plays a guiding role for the outer threaded part C, so as to ensure that the outer threaded part C is subjected to axial force, and finally the inner thread of the connector A to be tested is damaged, and the thread strength is obtained and recorded.

Claims

1. A limiting mechanism for thread testing, comprising a receiving space (1) for receiving a connecting piece (A) to be tested, a blocking piece (2) being arranged above the connecting piece (A) to be tested, and the blocking piece (2) being provided with an opening (21) for the outer threaded portion (C) of the connecting piece (A) to be tested or a mating connecting piece (B) to pass through, so that the connecting piece (A) to be tested and the mating connecting piece (B) are screwed together; a guide piece (3) for guiding the outer threaded portion (C) is further included, and the guide piece (3) is provided with a first through hole (31) for the outer threaded portion (C) to pass through, the limiting mechanism comprises a plurality of guide pieces (3) with the first through hole (31) of respective corresponding specifications, and the guide piece (3) can be selectively arranged on the opening (21) to adapt to the corresponding connecting piece (A) to be tested; in the state that the mating connecting piece (B) moves upward away from the connecting piece (A) to be tested, the blocking piece (2) abuts against the connecting piece (A) to be tested, so that the connecting piece (A) to be tested cannot move toward the mating connecting piece (B), and at the same time, the hole wall of the first through hole (31) guides the outer threaded portion (C) to avoid the axis of the outer threaded portion (C) from being offset. characterized in that The connecting piece (A) to be tested comprises a main body (1a) for arranging a threaded structure and a thin-walled portion (2a) at the periphery of the main body (1a), and the periphery of the first through hole (31) of the guide piece (3) is at least partially formed with a convex portion (32) protruding toward the connecting piece (A) to be tested; in the state that the mating connecting piece (B) moves upward away from the connecting piece (A) to be tested, the convex portion (32) abuts against the main body (1a) of the connecting piece (A) to be tested, so that the main body (1a) maintains a predetermined distance (H) between the end face of the main body (1a) and the blocking piece (2), and the predetermined distance (H) is greater than the distance between the end face of the main body (1a) and the end portion of the thin-walled portion (2a), thereby avoiding the thin-walled portion (2a) of the connecting piece (A) to be tested from contacting the blocking piece (2).

2. The limit mechanism of claim 1, wherein: The guide piece (3) further comprises a connecting portion (33) for being screwed with the opening (21), and the first through hole (31) extends downward from the upper end of the connecting portion (33) and penetrates through the connecting portion (33), and correspondingly, the lower end of the connecting portion (33) is at least partially outwardly protruded to form a flange, the flange constitutes the convex portion (32), and the distance between the end face of the flange and the blocking piece (2) is the predetermined distance (H).

3. The limit mechanism of claim 2, wherein: A frame (4) is further included below the blocking piece (2), and the blocking piece (2) and the frame (4) jointly enclose the receiving space (1), and the blocking piece (2) further comprises at least two end portions (22; 23) for being connected with the frame (4), and the end portions (22; 23) of the blocking piece (2) are detachably connected with the frame (4).

4. The limit mechanism of claim 3, wherein: ​ 5. The limit mechanism of claim 4, wherein: The frame (4) comprises a bottom plate (41) extending at least partially towards the blocking member (2) at both ends in the length direction, forming side walls (42; 43) connected with the blocking member (2), and the blocking member (2), the bottom plate (41) and the two side walls (42; 43) together enclose the accommodation space (1).

6. The limit mechanism of claim 5, wherein: The two side walls (42; 43) comprise a first side wall (42) and a second side wall (43), the blocking member (2) has a first end portion (22) extending towards the first side wall (42) and a second end portion (23) extending towards the second side wall (43), and correspondingly, the first side wall (42) is at least partially recessed in the center of the upper end to form a first recess (421) for inserting the first end portion (22), and the second side wall (43) is at least partially recessed in the center of the upper end to form a second recess (431) for inserting the second end portion (23).

7. The limit mechanism of claim 6, wherein: Further comprising a first pin member (51) for connecting the first side wall (42) and the first end portion (22), and a second pin member (52) for connecting the second side wall (43) and the second end portion (23), the first side wall (42) and the first end portion (22) are provided with a second through hole (61) for the first pin member (51) to pass through, the second through hole (61) penetrates the first side wall (42) and the first end portion (22) in a direction perpendicular to the extension direction of the blocking member (2), and correspondingly, the second side wall (43) and the second end portion (23) are provided with a third through hole (62) for the second pin member (52) to pass through, the third through hole (62) penetrates the second side wall (43) and the second end portion (23) in a direction perpendicular to the extension direction of the blocking member (2).

8. A tool for attachment to a tensile device (M) and for performing a thread test on a connection (A) to be tested, comprising a seat (71) for setting a mating connection (B), characterized in that: Further comprising a limiting mechanism (72) according to any one of claims 1-7, the seat body (71) is used to be attached to the first clamp (1m) of the stretching device (M), and correspondingly, the limiting mechanism (72) is used to be attached to the second clamp (2m) of the stretching device (M), so that the seat body (71) and the limiting mechanism (72) can move towards each other or away from each other.

9. The tooling of claim 8, wherein: The seat body (71) is columnar, and the outer wall of the seat body (71) is recessed to form a T-shaped slot (711) perpendicular to the outer threaded portion of the to-be-tested connector (A) or the mating connector (B), the vertical end of the slot (711) forms a passage (712) for the outer threaded portion to pass through, and the horizontal end of the slot (711) is used to set the head of the mating connector (B), so that the mating connector (B) is resisted by the end face of the passage (712) to limit the movement of the mating connector (B) towards the to-be-tested connector (A).

10. The tooling of claim 9, wherein: The first clamp (1m) and the second clamp (2m) of the stretching device (M) are in a cylindrical shape, the seat body (71) further comprises a first connecting portion (713) for being inserted into the first clamp (1m), correspondingly, the limiting mechanism (72) comprises a second connecting portion (721) for being inserted into the second clamp (2m), and the first connecting portion (713) and the second connecting portion (721) are both in a pin connection structure with the respective corresponding clamp (1m; 2m).

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