Pressing mechanism

Abstract

The utility model relates to a hold-down mechanism which is used for connecting rod expansion breaking equipment and comprises a retaining device and a hold-down assembly, the hold-down assembly is provided with an ejector rod abutting against bolt supporting faces on the two sides of the large end of a connecting rod, the hold-down assembly is provided with a locking part, and the opening direction of the locking part and the force application direction of the hold-down assembly form an angle. The locking part is used for being matched with the retaining device, so that the retaining device has a locking state for limiting the return of the ejector rod when the connecting rod is cracked, the capability of resisting the counter-acting force when the connecting rod is cracked is enhanced, the return of the ejector rod is effectively limited, and the ejector rod can continuously and stably provide the pressing force for the connecting rod in the cracking process of the connecting rod; loosening or displacement of the ejector rod caused by expansion breaking reaction force generated by expansion breaking of the connecting rod to the ejector rod is prevented, then expansion breaking deviation of the connecting rod caused by displacement of the ejector rod is avoided, and the expansion breaking accuracy and the product quality of the connecting rod are greatly improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to connecting rod expansion technology field, especially a kind of pressing mechanism. BACKGROUND

[0002] With the rapid development of automobile industry and the continuous improvement of the performance requirements of engine, expansion processing technology is widely applied and promoted as an important technology in connecting rod processing, and its principle is based on fracture mechanics and stress concentration theory. After rough machining of connecting rod, bolt hole is machined first, and two symmetric prefabricated crack grooves (also known as stress grooves) are artificially machined on the inner side of large hole, forming macroscopic crack notch. Then, using the significant sensitivity of material to notch, high stress concentration is formed at the root of prefabricated crack groove. Then, by pushing the expansion sleeve downward with wedge-shaped iron, pressure is generated in the axial direction of the center line of connecting rod large and small hole, so that prefabricated crack groove is initiated and rapidly expanded, so that the separation of connecting rod body and connecting rod cover is achieved without plastic deformation. This process has the advantages of less machining process, resource saving, high product quality, etc., and is especially suitable for the manufacture of high-performance engine connecting rod. As the core equipment of this technology, the market demand for expansion equipment is also increasing. In order to meet the market demand, expansion equipment manufacturers continuously carry out technical innovation and equipment upgrading to improve the machining precision, production efficiency and intelligence and automation of the equipment.

[0003] The existing expansion equipment adopts pressing mechanism to abut against the bolt support surface on both sides of the large end of connecting rod during expansion process, and the pressing mechanism usually adopts hydraulic system to provide clamping force for the pressing mechanism to ensure the stability of connecting rod during expansion process. However, when the hydraulic system fails or the pressure is insufficient, the clamping mode relying on hydraulic system may cause the clamping force provided by the pressing mechanism to decrease significantly, which may cause displacement of the pressing mechanism during expansion of connecting rod, thereby affecting the expansion effect of connecting rod and product quality. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the utility model is to provide a pressing mechanism, which solves the problem of insufficient pressing force of the existing hydraulic mechanism.

[0005] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0006] A pressing mechanism for connecting rod expansion equipment, comprising a retreat stop device and a pressing assembly, the pressing assembly has a top rod abutting against the bolt support surface on both sides of the large end of connecting rod, the pressing assembly is provided with a locking portion, the opening direction of the locking portion is at an angle with the force applying direction of the pressing assembly, and the locking portion is used to cooperate with the retreat stop device to make the retreat stop device have a locking state of limiting the retreat of the top rod during expansion of connecting rod.

[0007] Further, the locking portion is a groove structure, and the retreat-preventing device penetrates into the locking portion.

[0008] Further, the locking portion is a locking groove penetrating the compression assembly, and the locking groove has only two openings in the penetrating direction.

[0009] Further, the slotting direction of the locking portion is perpendicular to the force applying direction of the compression assembly.

[0010] Further, the retreat-preventing device has a first abutting surface, the locking portion has a second abutting surface, the first abutting surface can abut the second abutting surface and apply a force to the second abutting surface which is parallel and same as the force applying direction of the ejector rod.

[0011] Further, the first abutting surface and the second abutting surface are both inclined surfaces.

[0012] Further, the retreat-preventing device has a third abutting surface, the third abutting surface and the first abutting surface are respectively located on two sides of the retreat-preventing device in the force applying direction of the ejector rod; the compression assembly further comprises a fourth abutting surface, the fourth abutting surface is located in the penetrating direction of the locking portion,

[0013] The retreat-preventing device can penetrate out of the locking portion, the third abutting surface on the penetrating-out portion abuts the fourth abutting surface and applies a force to the fourth abutting surface which is parallel and opposite to the force applying direction of the ejector rod.

[0014] Further, the compression assembly further comprises a supporting portion and a movable portion, the movable portion is fixedly connected with the ejector rod and drives the ejector rod to move in the force applying direction; the locking portion is located on the movable portion;

[0015] The supporting portion has a first through groove and a second through groove which are in communication with each other, the slotting direction of the first through groove is perpendicular to the slotting direction of the second through groove and same as the force applying direction of the retreat-preventing device, and the movable portion moves in the first through groove;

[0016] Part of the retreat-preventing device moves in the second through groove to cooperate with the locking portion on the movable portion to limit the retreat of the ejector rod when the connecting rod is broken.

[0017] Further, the pressing assembly further comprises a first sleeve and a second sleeve fixedly arranged at two sides of the second through groove located at two sides of the first through groove, the retreat-stopping device comprises a retreat-stopping rod, the retreat-stopping rod is in sliding fit with the first sleeve, and the retreat-stopping rod is capable of being in sliding fit with the second sleeve through a part of the retreat-stopping rod penetrating through the locking portion, the third abutting surface and the first abutting surface are located at two sides of the retreat-stopping rod in the jacking direction of the jacking rod respectively, and the fourth abutting surface is arranged on an inner wall of the second sleeve.

[0018] The retreat-stopping rod further has a fifth abutting surface, and an inner wall of the first sleeve has a sixth abutting surface, the fifth abutting surface and the sixth abutting surface are in circumferential fit.

[0019] Further, the movable portion comprises two movable rods, the jacking rod and the locking portion are both two, the movable rods are fixedly connected with the jacking rods in one-to-one correspondence, and each movable rod is provided with a locking portion; and / or

[0020] The retreat-stopping device further comprises a driving portion, the driving portion is fixed on the supporting portion, and a movable end of the driving portion is fixed with the retreat-stopping rod to drive the retreat-stopping rod to move in the second through groove.

[0021] Compared with the prior art, the utility model has at least the following beneficial effects:

[0022] The utility model relates to a kind of pressing mechanisms for connecting rod expansion breaking equipment, comprising retreat-stopping device and pressing assembly, pressing assembly has with the jacking rod of the two sides bolt support surface of connecting rod big head end abutting, pressing assembly is equipped with locking portion, the opening direction of locking portion is angle with the force direction of pressing assembly, and locking portion is used to cooperate with retreat-stopping device, to make retreat-stopping device have the locking state of limiting jacking rod back when connecting rod is expanded and broken, it is changed from original single hydraulic jacking to hydraulic jacking and mechanical locking cooperation, ensure that jacking rod can continuously and stably provide pressing force to connecting rod during connecting rod expansion, prevent the expansion reaction force of jacking rod due to connecting rod in expansion from causing jacking rod loosening or displacement, to further avoid the expansion deviation of connecting rod due to jacking rod displacement, greatly improve the precision and product quality of connecting rod expansion. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the specific embodiment of the utility model or the technical scheme in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiment or the prior art description, and obviously, the drawings in the following description are some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creating labor.

[0024] Figure 1The compression mechanism is applied to the installation schematic view of the connecting rod expansion and breaking equipment.

[0025] Figure 2 The cross section enlarged schematic view of the compression mechanism is provided in an embodiment of the utility model.

[0026] Figure 3 The cross section schematic view of the compression mechanism is provided in an embodiment of the utility model.

[0027] Mark explanation:

[0028] 1, retreat stop device;11, retreat stop rod;12, driving part;

[0029] 2, compression assembly;21, ejector rod;22, locking part;23, support part;231, first through slot;232, second through slot;24, first sleeve;25, second sleeve;26, movable part;

[0030] 31, first abutting surface;32, second abutting surface;33, third abutting surface;34, fourth abutting surface;35, fifth abutting surface;36, sixth abutting surface;

[0031] 4, connecting rod. Specific implementation

[0032] The technical scheme of the utility model will be described clearly and completely in combination with the drawings, obviously, the described embodiment is a part of the embodiment of the utility model, instead of all the embodiment. Based on the embodiment in the utility model, all other embodiments obtained by the ordinary skill in the art without making creative labor belong to the scope of protection of the utility model.

[0033] In the description of the utility model, it is necessary to explain that the orientation or position relation indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" is based on the orientation or position relation shown in the drawing, only for the convenience of describing the utility model and simplifying the description, and is not indicated or implied that the indicated device or element must have a particular orientation, a particular orientation and operation, therefore, it cannot be understood as the limitation of the utility model. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0034] In the description of the utility model, it needs to explain, unless another explicit provision and limitation, the term "installation", "connection", "connection" should do the broad sense understanding, for example, can be fixed connection, can be detachable connection, or integrally connected;Can be mechanical connection, can be electrical connection;Can be directly connected, can be indirectly connected through the intermediate medium, can be the communication inside two elements.For the ordinary skill in the art, the specific meaning of the above-mentioned terms in the utility model can be understood according to the specific circumstances.

[0035] As shown in the accompanying Figure 1 and the accompanying Figure 2 A pressing mechanism for connecting rod expansion equipment, comprising a retreat stop device 1 and a pressing assembly 2, the pressing assembly 2 has a top rod 21 abutting with the bolt support surface on both sides of the large end of the connecting rod 4, the pressing assembly 2 is provided with a locking portion 22, the opening direction of the locking portion 22 is at an angle with the force direction of the pressing assembly 2, through the cooperation of the locking portion 22 and the retreat stop device 1, the top rod 21 can enter the locking state through the retreat stop device 1 when the large end of the connecting rod 4 is expanded. Specifically, in some embodiments, the main structure of the pressing assembly 2 is only the top rod 21 and the driving device for driving the top rod 21, and the locking portion 22 is arranged on each top rod 21;In other embodiments, the main structure of the pressing assembly 2 is to integrate the top rods 21 on both sides into a common frame, flat plate or shell, etc., through a total rod capable of pushing the integrated body to ensure that the two top rods 21 act synchronously, the driving device is connected to the total rod for pushing the top rod 21, and the locking portion 22 is arranged on the total rod. Further, the retreat stop device 1 can include a pin, a plunger or other structures capable of cooperating with the locking portion 22.

[0036] When the pressing assembly 2 pushes the top rod 21 to the predetermined position of the connecting rod 4, the retreat stop device 1 is moved by the driving device and cooperates with the locking portion 22, so that the top rod 21 is switched to the locking state, and during the expansion of the connecting rod 4, the top rod 21 is ensured to provide stable pressing force to the connecting rod 4 in a self-locking manner, solving the problem of insufficient pressing force provided by the hydraulic system to the pressing mechanism. Further, since the original single hydraulic pressing has become hydraulic pressing and mechanical locking cooperation in the present application, the top rod 21 can always remain stationary during the expansion of the connecting rod, and the retreat of the pressing mechanism caused by the reverse expansion force generated during the expansion of the connecting rod will not occur, thereby further avoiding the expansion deviation of the connecting rod 4 caused by the displacement of the top rod 21, effectively ensuring the size consistency of each connecting rod 4 during expansion, and significantly improving the precision of the expansion of the connecting rod 4 and the overall quality of the product.

[0037] In some embodiments of the utility model, as shown in the accompanying Figure 2As shown, the locking portion 22 is a groove structure, and the retreat-stop device 1 is at least inserted into the locking portion 22. Specifically, in some embodiments, the locking portion 22 is an embedded groove structure, and the retreat-stop device 1 is completely or partially embedded in the locking portion 22 to prevent the displacement of the connecting rod 4 when the ejector rod 21 is expanded; in other embodiments, the locking portion 22 is one or more groove structures arranged on the outer edge of the pressing assembly 2, and the retreat-stop device 1 is at least partially embedded in the groove structure to mechanically block the pressing assembly 2 to prevent the displacement of the connecting rod 4 when the ejector rod 21 is expanded. The locking portion 22 can be several, preferably symmetrically designed. Further, the groove structure can be linear, arc-shaped or other shapes, which are selected according to the actual product use requirements, and are not limited here.

[0038] In some embodiments of the present utility model, as shown in the accompanying drawings Figure 2 As shown, in order to make the connection of the retreat-stop device 1 and the pressing assembly 2 more secure and to limit the displacement of the pressing assembly 2 as a whole, the locking portion 22 is a locking groove penetrating the pressing assembly 2, and the locking groove has only two openings in the penetrating direction to form a penetrating channel. The locking groove is limited in the straight line direction determined by the two openings, which can provide a guide path for the retreat-stop device 1, so that the retreat-stop device 1 can only move along the penetrating direction of the locking groove, limiting the displacement of the retreat-stop device 1 in other directions. When the expansion force of the connecting rod 4 is applied to the ejector rod 21 and the ejector rod 21 has a tendency to move along the expansion force, the retreat-stop device 1 will contact the groove wall in the locking groove and exert a restraining reaction force on the pressing assembly 2, thereby limiting the displacement of the pressing assembly 2 and ensuring the stability and reliability of the pressing assembly 2 during the working process.

[0039] In some embodiments of the present utility model, as shown in the accompanying drawings Figure 2 As shown, the slotting direction of the locking portion 22 is perpendicular to the force applying direction of the pressing assembly 2, so that external vibrations cannot generate a force to make the retreat-stop device 1 separate from the locking portion 22, preventing the retreat-stop device 1 from being separated from the locking portion 22 due to vibrations and other forces, making the connection of the entire pressing mechanism more stable. Furthermore, when the slotting direction of the locking portion 22 is not perpendicular to the force applying direction of the pressing assembly 2, a large expansion force may generate a shearing force on the locking portion 22 when the connecting rod 4 is expanded. After the pressing mechanism operates for a long time, this repeated shearing force will cause wear or deformation of the locking portion 22, affecting its service life. Further, the retreat-stop device 1 can move along the slotting direction of the locking portion 22, so that when the retreat-stop device 1 is perpendicular to the locking portion 22, the retreat-stop device 1 can bear the main pressure from the expansion of the connecting rod 4 and transmit and disperse the pressure, effectively reducing the adverse effects of the shearing force on the locking portion 22.

[0040] In some embodiments of the present utility model, as shown in the accompanying drawings Figure 2 and the accompanying drawingsFigure 3 As shown in the drawings, the retreat-stop device 1 has a first abutting surface 31, the locking portion 22 has a second abutting surface 32, the first abutting surface 31 and the second abutting surface 32 are two mutually matched surfaces, when switched to the locked state, the first abutting surface 31 and the second abutting surface 32 are in close contact with each other, the retreat-stop device 1 transmits a force parallel and identical to the force direction of the ejector rod 21 to the second abutting surface 32 of the locking portion 22 through the first abutting surface 31, so that the retreat-stop device 1 can more effectively resist the displacement tendency of the ejector rod 21 when the connecting rod 4 is broken. Preferably, the roughness of the first abutting surface 31 and the second abutting surface 32 is not greater than Ra1.6.

[0041] In some embodiments of the utility model, as shown in the drawings, Figure 2 and the drawings, Figure 3 As shown in the drawings, the first abutting surface 31 and the second abutting surface 32 are both inclined surfaces, and preferably the part of the retreat-stop device 1 extending into the locking portion 22 is a wedge-shaped structure. This is because there are tolerances in the length of the bolt hole of the connecting rod 4, and when the ejector rod 21 abuts against the bolt support surface on both sides of the large-end end of the connecting rod 4, the position of the ejector rod 21 will always change due to these tolerances, becoming a variable that cannot be accurately predicted. The uncertainty of the position of the ejector rod 21 causes the position of the retreat-stop device 1 to be slightly deviated after being tightened against the connecting rod 4. When the first abutting surface 31 and the second abutting surface 32 are inclined surfaces, the relative sliding and adjustment between the inclined surfaces can automatically adapt to this change, and the retreat-stop device 1 and the locking portion 22 can be re-stabilized through the relative displacement of the first abutting surface 31 and the second abutting surface 32, ensuring that the locking effect is not affected by the position variable of the ejector rod 21, so as to achieve a stable locked state. Preferably, the angle of the first abutting surface 31 and the second abutting surface 32 is 5-7°.

[0042] In some embodiments of the utility model, as shown in the drawings, Figure 3 As shown in the drawings, the retreat-stop device 1 has a third abutting surface 33, the third abutting surface 33 and the first abutting surface 31 are located on the two sides of the retreat-stop device 1 in the force direction of the ejector rod 21; the pressing assembly 2 further comprises a fourth abutting surface 34, the fourth abutting surface 34 is located in the penetrating direction of the locking portion 22; the retreat-stop device 1 can pass through the locking portion 22, the third abutting surface 33 on the passing-through part is in close contact with the fourth abutting surface 34 and applies a force parallel and opposite to the force direction of the ejector rod 21 to the fourth abutting surface 34, which can form a balanced system with the force between the first abutting surface 31 and the second abutting surface 32, preventing the locking portion 22 from deforming due to unilateral force, and further enhancing the stability of the entire structure. Preferably, the third abutting surface 33 and the fourth abutting surface 34 are circular arc surfaces, so as to better close.

[0043] In some embodiments of the utility model, as shown in the drawings, Figure 2 and the drawings, Figure 3As shown, the pressing assembly 2 further comprises a support part 23 and a movable part 26, the movable part 26 is fixedly connected with the top rod 21 and drives the top rod 21 to move along the force applying direction; the locking part 22 is located on the movable part 26; the support part 23 has a first through groove 231 and a second through groove 232 which are communicated with each other, the slotting direction of the first through groove 231 is perpendicular to the slotting direction of the second through groove 232 and is the same as the force applying direction of the stop device 1, and the movable part 26 moves in the first through groove 231; the partial stop device 1 moves in the second through groove 232, the first through groove 231 and the second through groove 232 play the roles of guiding and limiting on the one hand, that is, the first through groove 231 provides a specific moving path for the movable part 26 and the top rod 21 connected therewith, so that the movable part 26 and the top rod 21 can only move along the slotting direction of the first through groove 231 and the same direction as the force applying direction of the stop device 1, avoiding the deviation of the force applying direction, and the second through groove 232 limits the moving track of the partial stop device 1, so that the partial stop device 1 can only move on the specific path perpendicular to the slotting direction of the first through groove 231; on the other hand, the fourth abutting surface 34 is located on the second through groove 232 and the locking part 22, when the stop device 1 is switched to the locked state, the third abutting surface 33 is attached to the fourth abutting surface 34, which can more stably switch the stop device 1 to the locked state, ensuring the stability of the entire structure during the force applying of the top rod 21 and the locking of the stop device 1 and the like. Specifically, before the expansion and breaking of the connecting rod 4, the top rod 21 moves along the force applying direction under the action of the movable part 26, in this process, the movable part 26 moves in the first through groove 231, ensuring the accuracy of the force applying direction and position of the top rod 21, then the stop device 1 moves in the second through groove 232, so that the first abutting surface 31 and the second abutting surface 32 are attached, and the third abutting surface 33 and the fourth abutting surface 34 are attached, thereby switching the stop device 1 to the locked state and more stably limiting the back-off of the top rod 21.

[0044] In some embodiments of the present application, as shown in the accompanying drawings Figure 2 and the accompanying drawings Figure 3As shown, since the support part 23 needs to be connected with other parts of the connecting rod expansion device, threaded holes need to be opened on the surface of the support part 23, and the machining requirement of opening the threaded holes limits the heat treatment process of the support part 23, so that the heat treatment hardness of the support part 23 cannot be particularly high, which leads to poor wear resistance of the support part 23, and in the long-term use process, the support part 23 is easy to be worn due to the friction of the third abutting surface 33 of the retreat stop device 1, and the support part 23 is usually a relatively complex integral part in the whole structure, and once worn, it is difficult to realize quick replacement, which affects the maintenance efficiency and use cost of the equipment. Therefore, the pressing assembly 2 further comprises a first sleeve 24 and a second sleeve 25 fixedly arranged on the second through groove 232 located on both sides of the first through groove 231, and the first sleeve 24 and the second sleeve 25 have high hardness. The retreat stop device 1 comprises a retreat stop rod 11, the retreat stop rod 11 is in sliding fit with the first sleeve 24, and the part of the retreat stop rod 11 penetrating through the locking part 22 can be in sliding fit with the second sleeve 25. The retreat stop device 1 is no longer in direct contact with the support part 23 during movement, but in contact with the first sleeve 24 and the second sleeve 25 with high hardness, thereby avoiding the direct wear of the support part 23 by the retreat stop device 1, effectively prolonging the service life of the support part 23, and further increasing the service life of the whole pressing mechanism.

[0045] Further, as shown in Figs. 1 and 2, Figure 2 and Figs. 3 and 4, Figure 3 As shown, the third abutting surface 33 and the first abutting surface 31 are located on both sides of the retreat stop rod 11 in the force application direction of the jacking rod 21, the fourth abutting surface 34 is arranged on the inner wall of the second sleeve 25, and the retreat stop rod 11 further has a fifth abutting surface 35, the inner wall of the first sleeve 24 has a sixth abutting surface 36, the fifth abutting surface 35 and the sixth abutting surface 36 are circumferentially matched, that is, when the retreat stop rod 11 is switched to the locked state, the third abutting surface 33 and the fourth abutting surface 34 are matched with each other, and the fifth abutting surface 35 and the sixth abutting surface 36 are matched with each other, thereby supporting the retreat stop rod 11 from two dimensions of axial and circumferential directions, and enabling the retreat stop rod 11 to bear high-strength force and effectively prevent the jacking rod 21 from being retracted when the connecting rod 4 is expanded.

[0046] In some embodiments of the utility model, the movable part 26 comprises two movable rods, the jacking rod 21 and the locking part 22 are both two, the movable rod is fixedly connected with the jacking rod 21 one by one, and each movable rod is provided with a locking part 22. Compared with a single structure, support and force can be provided at multiple positions, so that the whole pressing mechanism is more stable during work.

[0047] In some embodiments of the utility model, as shown in Figs. 1 and 2, Figure 2As shown, the retreat-stop device 1 further comprises a driving part 12 fixed on the supporting part 23, and the movable end of the driving part 12 is fixed with the retreat-stop rod 11 to drive the retreat-stop rod 11 to move in the second through groove 232. Preferably, the driving part 12 is a retreat-stop motor or an oil cylinder, which is not limited here.

[0048] The above-mentioned embodiments are only the preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and replacements made by those skilled in the art on the basis of the present application shall fall within the scope of protection of the present application.

Claims

1. A compacting mechanism for a connecting rod stretch breaking apparatus, characterized by, The device comprises a retreat-preventing device and a pressing assembly, the pressing assembly has a top rod abutting with the bolt supporting surface on both sides of the big end of the connecting rod, the pressing assembly is provided with a locking part, the opening direction of the locking part is at an angle with the force applying direction of the pressing assembly, and the locking part is used for cooperating with the retreat-preventing device to make the retreat-preventing device have a locking state of limiting the back-off of the top rod when the connecting rod is broken.

2. The holdback mechanism of claim 1 wherein, The locking part is a groove structure, and the retreat-preventing device at least penetrates into the locking part.

3. The holdback mechanism of claim 2 wherein, The locking part is a locking groove penetrating through the pressing assembly, and the locking groove only has two openings in the penetrating direction.

4. The holdback mechanism of claim 2 wherein, The opening direction of the locking part is perpendicular to the force applying direction of the pressing assembly.

5. The holdback mechanism of claim 2 wherein, The retreat-preventing device has a first abutting surface, the locking part has a second abutting surface, the first abutting surface can be attached to the second abutting surface and apply a force to the second abutting surface, the force is parallel and same to the force applying direction of the top rod.

6. The holdback mechanism of claim 5 wherein, The first abutting surface and the second abutting surface are both inclined surfaces.

7. The holdback mechanism of claim 5 wherein, The retreat-preventing device has a third abutting surface, the third abutting surface and the first abutting surface are respectively located on both sides of the retreat-preventing device in the force applying direction of the top rod; the pressing assembly further comprises a fourth abutting surface, the fourth abutting surface is located in the penetrating direction of the locking part; The retreat-preventing device can penetrate out of the locking part, the third abutting surface on the penetrating-out part is attached to the fourth abutting surface and applies a force to the fourth abutting surface, the force is parallel and opposite to the force applying direction of the top rod.

8. The holdback mechanism of claim 7 wherein, The pressing assembly further comprises a supporting part and a movable part, the movable part is fixedly connected with the top rod and drives the top rod to move along the force applying direction; the locking part is located on the movable part; The supporting part has a first through groove and a second through groove which are communicated with each other, the opening direction of the first through groove is perpendicular to the opening direction of the second through groove and same to the force applying direction of the retreat-preventing device, and the movable part moves in the first through groove; Part of the retreat-preventing device moves in the second through groove to cooperate with the locking part on the movable part to limit the back-off of the top rod when the connecting rod is broken.

9. The holdback mechanism of claim 8 wherein, The pressing assembly further comprises a first sleeve and a second sleeve which are fixedly arranged on both sides of the second through groove located on both sides of the first through groove; The retreat-preventing device comprises a retreat-preventing rod, the retreat-preventing rod is in sliding cooperation with the first sleeve, and the part of the retreat-preventing rod penetrating through the locking part can be in sliding cooperation with the second sleeve, the third abutting surface and the first abutting surface are respectively located on both sides of the retreat-preventing rod in the force applying direction of the top rod, The fourth abutting surface is arranged on the inner wall of the second sleeve; The retreat-preventing rod further has a fifth abutting surface, the inner wall of the first sleeve has a sixth abutting surface, and the fifth abutting surface and the sixth abutting surface are circumferentially cooperated.

10. The holdback mechanism of claim 9 wherein, The movable part comprises two movable rods, the top rod and the locking part are both two, the movable rods are fixedly connected with the top rods one by one, each movable rod is provided with one locking part; and / or The retreat-preventing device further comprises a driving part, the driving part is fixed on the supporting part, the movable end of the driving part is fixed with the retreat-preventing rod to drive the retreat-preventing rod to move in the second through groove.

Images