Multi-stage piston jack and jacking system

Abstract

The application relates to a multi-stage piston jack and a jacking system. The multi-stage piston jack comprises a first-stage oil cylinder, a second-stage oil cylinder, a first-stage piston and a second-stage piston; the first-stage oil cylinder is provided with a first oil nozzle on the side wall, the second-stage oil cylinder is coaxially arranged above the first-stage oil cylinder and is provided with a second oil nozzle on the side wall; the first-stage piston is arranged in the first-stage oil cylinder and is provided with a first sealing element, the second-stage piston is connected above the first-stage piston and is provided with a second sealing element, and the cross-sectional areas of the two-stage pistons are equal. The first oil nozzle is used for injecting hydraulic oil into the first-stage oil cylinder to drive the first-stage piston to ascend, and the second oil nozzle is used for injecting hydraulic oil into the second-stage oil cylinder to drive the second-stage piston to ascend. Through the above structure, the jack drives the pistons with equal cross sections by using a parallel type double-oil-way, realizes the superposition and constant output of the jacking force in the whole stroke, and solves the problem that the bearing capacity of the traditional multi-stage jack is attenuated with the stroke due to the step-by-step decrease of the piston area.

Description

Technical Field

[0001] This application relates to the field of jack technology, and in particular to multi-stage piston jacks and lifting systems. Background Technology

[0002] With the continuous development of technologies in fields such as heavy equipment manufacturing, large-scale structure construction, and emergency jacking and rescue, higher demands are being placed on jack equipment: not only is enormous lifting force required, but it also needs to adapt to confined working environments with limited height. To meet this need, multi-stage hydraulic jack technology has emerged. This technology achieves a significantly increased working stroke within a compact height by extending multiple pistons in stages, effectively solving the bottleneck of insufficient stroke of traditional single-stage jacks in low-ceilinged spaces.

[0003] Among related technologies, the most typical approach is to use a multi-stage sleeve-type hydraulic cylinder. This device typically consists of a main cylinder and multiple sequentially nested pistons, driven by a common hydraulic circuit. As the first-stage piston reaches the end of its stroke, the hydraulic pressure pushes the next-stage piston to extend, and so on, until all pistons are fully extended. This design does indeed provide a relatively long stroke within a limited height.

[0004] However, the aforementioned traditional multi-stage sleeve jacks have an inherent and serious drawback: their multi-stage pistons typically employ a progressively decreasing cross-sectional design, meaning the cross-sectional area of ​​the outer piston is larger than that of the inner piston. According to Pascal's principle, under the same hydraulic pressure, the lifting force generated by each piston stage is proportional to its cross-sectional area. Therefore, this "decreasing area" structure causes the jack's load-bearing capacity to decrease progressively with increasing stroke. When the last stage piston, which also has the longest stroke, is working, its lifting capacity is often far lower than that of the first stage. This fails to meet the core requirement of "achieving full-range, high-tonnage lifting in confined spaces," severely limiting its application under heavy-duty conditions. Utility Model Content

[0005] Therefore, it is necessary to address the problem of reduced load-bearing capacity caused by the progressively decreasing piston area in traditional multi-stage jacks by providing a multi-stage piston jack that can maintain a constant large-tonnage lifting capacity throughout its entire stroke.

[0006] A multi-stage piston jack, the multi-stage piston jack comprising:

[0007] The first-stage hydraulic cylinder is equipped with a first oil nozzle;

[0008] The secondary hydraulic cylinder is coaxially mounted above the primary hydraulic cylinder and is equipped with a second oil nozzle.

[0009] A first-stage piston is disposed inside the first-stage cylinder and can slide up and down along the inner wall of the first-stage cylinder. A first sealing element is provided between the first-stage piston and the first-stage cylinder.

[0010] A secondary piston is connected and disposed above the primary piston, and can slide up and down along the inner wall of the secondary cylinder. A second seal is provided between the secondary piston and the secondary cylinder.

[0011] The cross-sectional areas of the first-stage piston and the second-stage piston are equal;

[0012] The first nozzle is used to inject hydraulic oil into the first-stage cylinder to drive the first-stage piston to rise, and the second nozzle is used to inject hydraulic oil into the second-stage cylinder to drive the second-stage piston to rise to the top position.

[0013] In one embodiment, the multi-stage piston jack further includes:

[0014] A sealing assembly is disposed between the secondary piston and the secondary cylinder;

[0015] A locking assembly is disposed above the secondary cylinder and connected to the secondary piston, used to lock the secondary piston when the secondary piston is in the top-lifted position.

[0016] In one embodiment, a third seal is provided between the secondary piston and the secondary cylinder.

[0017] In one embodiment, the secondary piston is connected to the primary piston via a connecting boss.

[0018] In one embodiment, the connecting boss is coaxially connected to the top surface of the first-stage piston.

[0019] In one embodiment, the sealing assembly is threadedly connected to the secondary piston, and a fourth seal is provided between the sealing assembly and the secondary piston.

[0020] In one embodiment, the locking assembly includes a locking nut, and the secondary piston is threadedly connected to the locking nut.

[0021] In one embodiment, the bottom of the primary cylinder is provided with a base, and the base is provided with an anti-slip structure.

[0022] In one embodiment, the primary cylinder and the secondary cylinder are made of alloy steel.

[0023] A lifting system includes the aforementioned multi-stage piston jack and a hydraulic device, wherein the hydraulic device is connected to the multi-stage piston jack via a first oil nozzle and / or a second oil nozzle.

[0024] The aforementioned multi-stage piston jack, by employing first-stage and second-stage pistons with equal cross-sectional areas and configuring independent oil inlet circuits, enables each stage of pistons to generate equal lifting force under the same oil pressure. Its total lifting force is the sum of the thrust of each stage of pistons. This fundamentally overcomes the defect of traditional multi-stage jacks where the load-bearing capacity decreases with increasing stroke due to the progressively decreasing piston area. It achieves the beneficial effect of providing stable, high-tonnage lifting force throughout the entire working stroke. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a multi-stage piston jack provided in an embodiment of this application.

[0026] Figure 2 This is a cross-sectional view of a multi-stage piston jack provided in an embodiment of this application.

[0027] Figure 3 This is a cross-sectional view of a multi-stage piston jack in operation, provided in an embodiment of this application.

[0028] Figure 4 A cross-sectional view of a multi-stage piston jack in its working state, provided for another embodiment of this application.

[0029] The reference numerals in the detailed embodiments are as follows:

[0030] 100. Multi-stage piston jack;

[0031] 10. Primary hydraulic cylinder; 20. Secondary hydraulic cylinder; 30. Primary piston; 40. Secondary piston; 50. Sealing assembly; 60. Locking assembly; 70. Hydraulic oil;

[0032] 11. First grease fitting; 21. Second grease fitting;

[0033] 31. First seal; 41. Second seal; 42. Third seal; 51. Fourth seal;

[0034] 43. Connect the boss. Detailed Implementation

[0035] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0036] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0037] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0039] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0040] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0041] See Figure 1 , Figure 1 A schematic diagram of a multi-stage piston jack 100 according to an embodiment of this application is shown. The multi-stage piston jack 100 provided in this embodiment includes a primary cylinder 10, a secondary cylinder 20, a primary piston 30, and a secondary piston 40. The primary cylinder 10 is provided with a first nozzle 11; the secondary cylinder 20 is coaxially disposed above the primary cylinder 10 and is provided with a second nozzle 21. The primary piston 30 is disposed inside the primary cylinder 10 and can slide up and down along the inner wall of the primary cylinder 10; a first seal 31 is provided between the primary piston 30 and the primary cylinder 10. The secondary piston 40 is connected and disposed above the primary piston 30 and can slide up and down along the inner wall of the secondary cylinder 20; a second seal 41 is provided between the secondary piston 40 and the secondary cylinder 20. It should be noted that the cross-sectional areas of the first-stage piston 30 and the second-stage piston 40 are equal; the first nozzle 11 is used to inject hydraulic oil 70 into the first-stage cylinder 10 to drive the first-stage piston 30 to rise, and the second nozzle 21 is used to inject hydraulic oil 70 into the second-stage cylinder 20 to drive the second-stage piston 40 to rise to the top position.

[0042] Combination Figure 3 , Figure 3 A cross-sectional view of the multi-stage piston jack 100 provided in an embodiment of this application is shown in its working state. The first oil nozzle 11 and the second oil nozzle 21 serve as independent hydraulic interfaces, their core function being to establish controllable oil inlet channels for the first-stage cylinder 10 and the second-stage cylinder 20, respectively. Through an external hydraulic station, the operator can inject hydraulic oil 70 into the first-stage cylinder 10 via the first oil nozzle 11, thereby driving the first-stage piston 30 to rise; similarly, injecting hydraulic oil 70 into the second-stage cylinder 20 via the second oil nozzle 21 can drive the second-stage piston 40 to rise. Furthermore, the dual-oil-circuit design of this application allows both cylinders to receive hydraulic oil 70 from the same pressure oil source, achieving synchronous drive of the two pistons.

[0043] The functions of the first seal 31 and the second seal 41 are to ensure the static and dynamic sealing integrity of their respective cavities, thereby maintaining the working pressure required by the jack and ensuring the reliability and efficiency of the lifting process. The first seal 31 is disposed between the inner wall of the first-stage piston 30 and the first-stage cylinder 10. Its primary function is to seal the annular gap between the inner wall of the first-stage cylinder 10 and the first-stage piston 30, preventing the hydraulic oil 70 injected from the first nozzle 11 from leaking through this gap, ensuring that the pressure is effectively applied to the bottom bearing surface of the first-stage piston 30, pushing it upwards sufficiently. Similarly, the second seal 41 is disposed between the inner wall of the second-stage piston 40 and the second-stage cylinder 20, used to seal the annular gap between the inner wall of the second-stage cylinder 20 and the second-stage piston 40. Its function is to ensure that the hydraulic oil 70 injected from the second nozzle 21 is sealed in the space below the second-stage cylinder 20, effectively driving the second-stage piston 40 upwards, and preventing the hydraulic oil 70 from leaking into the upper cavity or the outside during piston movement. The two work together to form the basis for maintaining the independent, efficient and stable operation of the two-stage hydraulic circuits, and are an indispensable structure for realizing the independent and controllable drive of the two oil circuits and the superposition of lifting force.

[0044] In this application, point A represents the cross-section of the first-stage piston 30, and point B represents the cross-section of the second-stage piston 40. This design breaks the limitation of the traditional multi-stage jack's "gradually decreasing area." By designing the first-stage piston 30 and the second-stage piston 40 to have equal cross-sectional areas and equipping them with independent first and second oil nozzles 11 and 21, the two-stage pistons are no longer in a sequential series relationship, but rather in a parallel relationship that can be driven synchronously. This means that under the same oil pressure, the two-stage pistons can generate equal lifting forces. Therefore, the total output lifting force of the jack achieves a simple superposition effect, that is, the total lifting force is the sum of the thrust generated by the two-stage pistons. This structure ensures that the lifting capacity provided by the jack remains constant throughout the entire stroke, as long as pressure is continuously supplied, thus solving the technical problem that the load-bearing capacity of traditional multi-stage jacks decreases sharply with the increase of stroke. It is particularly suitable for stable lifting operations with large tonnage and long strokes in working conditions where space and height are limited.

[0045] The multi-stage piston jack 100 of this application operates on the principle of Pascal's principle, achieving superposition of lifting forces through parallel dual-oil circuit drive and a piston structure with equal cross-sections. Specifically, during operation, hydraulic oil 70 enters the cavities of the first-stage cylinder 10 and the second-stage cylinder 20 via independent first nozzle 11 and second nozzle 21, respectively, causing the first-stage piston 30 and the second-stage piston 40 to rise upwards. Under the same oil pressure, since the cross-sectional areas of the first-stage piston 30 and the second-stage piston 40 are equal, they will generate the same lifting force.

[0046] Continue reading Figure 1 and Figure 2The multi-stage piston jack 100 of this application also includes a sealing assembly 50 and a locking assembly 60. The sealing assembly 50 is disposed between the secondary piston 40 and the secondary cylinder 20; the locking assembly 60 is disposed above the secondary cylinder 20 and connected to the secondary piston 40, and is used to lock the secondary piston 40 when the secondary piston 40 is in the raised position.

[0047] The sealing assembly 50 further enhances the static sealing reliability between the secondary piston 40 and the secondary cylinder 20. Especially under high pressure or long-term pressure holding conditions, it, together with the second seal 41, forms multiple sealing defenses, significantly reducing the risk of internal leakage of hydraulic oil 70 and ensuring the sealing integrity of the pressure chamber of the secondary cylinder 20, thereby maintaining a stable output of lifting force.

[0048] The locking assembly 60 provides mechanical safety. Once the secondary piston 40 has risen to the target height, tightening the locking assembly 60 ensures a tight fit between it and the upper surface of the secondary cylinder 20, reliably locking the secondary piston 40 and its load in the current position. Figure 4 , Figure 4 This is a sectional view of the multi-stage piston jack 100 in its working state. Figure 4 In this state, the locking assembly 60 is already locked, tightened, and in contact with the upper end face of the secondary cylinder 20. At this time, the load transmission path of the heavy object has changed. The load is no longer borne solely by the pressure of the hydraulic oil 70, but is directly transmitted to the locking assembly 60 connected to it through the raised secondary piston 40, and then the locking assembly 60 transmits the force to the top of the secondary cylinder 20. Figure 4 The jack is in a mechanically self-locking state, meaning that even if the external hydraulic device is completely depressurized or an accidental leak occurs, the load can still be safely and reliably supported at the predetermined height, completely eliminating the risk of jack retraction due to oil leakage. This provides a safety guarantee for equipment maintenance, component replacement, or lifting operations requiring long-term pressure maintenance, expanding the application range of jacks in safety-critical working conditions.

[0049] According to some embodiments of this application, a third seal 42 is further provided between the secondary piston 40 and the secondary cylinder 20. The addition of this third seal 42 further improves the sealing redundancy during the movement of the secondary piston 40, especially under high pressure or long-term pressure holding conditions, it can more effectively suppress the micro-leakage of hydraulic oil 70 and ensure the long-term stability of the lifting force.

[0050] However, it should be noted that the third seal 42 is an optimized enhancement design, not a necessary technical feature. With proper machining accuracy and clearance control of the secondary piston 40, the second seal 41 alone is sufficient to meet the sealing requirements of most operating conditions. The precise clearance fit between the piston and the cylinder already creates a certain hydraulic resistance effect, which can suppress leakage to some extent. Therefore, the addition of the third seal 42 is mainly for applications with extremely high requirements for sealing reliability; its presence or absence does not affect the realization of the core function of this application. Those skilled in the art can flexibly decide whether to adopt this design based on specific performance indicators and cost considerations.

[0051] In one embodiment, the secondary piston 40 is connected to the primary piston 30 via a connecting boss 43. Preferably, the connecting boss 43 is coaxially connected to the top surface of the primary piston 30. The connecting boss 43 can smoothly transmit the thrust generated when the primary piston 30 is lifted upward to the secondary piston 40, enabling the two pistons to move as a whole. Connecting the connecting boss 43 to the middle area of ​​the top surface of the primary piston 30 ensures that the point of application of the thrust is located at the geometric center of the primary piston 30, thereby avoiding additional bending moments or deflection moments caused by off-center loading. This center-aligned force transmission method ensures that the primary piston 30 and the secondary piston 40 always bear axial pressure in their respective cylinders, maintaining smooth, unhindered linear motion and greatly reducing abnormal wear between the piston and the cylinder wall.

[0052] According to some embodiments of this application, the sealing assembly 50 is threadedly connected to the secondary piston 40, and a fourth seal 51 is provided between the sealing assembly 50 and the secondary piston 40. The threaded connection provides a stable and reliable installation and fixing method for the sealing assembly 50, ensuring that the assembly can maintain its preset position and posture under long-term vibration or pressure fluctuations, and avoiding the sealing effect due to loosening. The fourth seal 51, which is provided at the connection interface, plays a crucial role in forming a static sealing barrier. It can effectively fill the microscopic gaps that may exist in the threaded connection, completely block the path of hydraulic oil 70 leaking upward along the surface of the secondary piston 40, and prevent oil from entering the threaded joint or even seeping out of the cylinder body.

[0053] In one embodiment, the locking assembly 60 includes a locking nut, and the secondary piston 40 is threadedly connected to the locking nut. When the secondary piston 40 is raised to the target height, the locking nut is rotated downwards until it is tightly fitted against the upper surface of the secondary cylinder 20. At this point, the enormous downward pressure generated by the heavy load is directly transmitted to the locking nut through the secondary piston 40, and then from the locking nut to the cylinder body of the secondary cylinder 20, thus forming a rigid mechanical force transmission path independent of the hydraulic system. By transforming traditional hydraulic support into reliable mechanical support, even if the jack experiences internal leakage due to prolonged pressure holding or suffers pressure loss due to unexpected malfunction, the heavy object can be safely and reliably locked in its current position, eliminating the risk of settlement. The locking nut, as a mechanically self-locking actuator, has a simple structure, is easy to operate, and has extremely high reliability, providing a safety guarantee for jacks in long-term support conditions with extremely high safety requirements, such as equipment maintenance and bridge bearing replacement.

[0054] In one embodiment, the bottom of the primary hydraulic cylinder 10 is equipped with a base, on which an anti-slip structure is provided. The base is designed primarily to increase the contact area between the jack and the ground or supporting foundation. By dispersing the force, the base can effectively reduce the pressure on soft ground, preventing the jack from sinking or tilting under load, thus providing a stable and reliable foundation for the entire lifting operation. The anti-slip structure on the lower surface of the base, such as intersecting grid grooves, protruding teeth, or anti-slip rubber pads, is designed to increase the static friction between the base and the contact surface. This design can effectively resist the slight tendency of horizontal slippage that may occur during the lifting process. The synergistic effect of the base and the anti-slip structure ensures the stability of the jack under huge vertical loads, fundamentally eliminating the risk of equipment overturning or heavy objects falling due to foundation slippage, and improving the safety and controllability of the lifting process.

[0055] In one embodiment, the primary cylinder 10 and the secondary cylinder 20 are made of alloy steel, and the inner walls of both cylinders are polished and / or coated. The selection of high-strength alloy steel as the base material for the cylinders primarily ensures that the entire pressure-bearing structure can withstand the extremely high internal hydraulic stress generated when lifting large tonnage objects, effectively preventing the risk of expansion, deformation, or bursting of the cylinders under high pressure, thus providing a fundamental material guarantee for the safe and reliable operation of the equipment. Fine polishing of the cylinder inner walls significantly reduces their surface roughness, thereby greatly reducing the frictional resistance and wear between the piston and the cylinder wall during reciprocating motion, making the piston movement smoother.

[0056] In addition, a hard coating (such as chrome plating) can be selectively applied to the inner wall to further enhance its surface hardness, wear resistance, and corrosion resistance. The coating acts as a robust barrier, effectively resisting the erosion of trace amounts of moisture or contaminants that may be present in the hydraulic oil 70, and reducing scratch damage that may occur during long-term use, ensuring the smoothness and dimensional stability of the cylinder's inner wall over extended periods of use.

[0057] This application also provides a lifting system, including the aforementioned multi-stage piston jack 100 and a hydraulic device, wherein the hydraulic device is connected to the multi-stage piston jack 100 via a first oil nozzle 11 and / or a second oil nozzle 21. Figure 4 When the lifting operation is complete and the jack needs to be retracted, the operator first fully unlocks and loosens the locking assembly 60, releasing its mechanical constraint on the secondary piston 40. Then, the return valve of the hydraulic system is opened, and the load weight at the top of the jack becomes the natural retraction force, acting on the primary piston 30 and the secondary piston 40, forcing them to move downwards to return to their starting position. Figure 2 In this process, the piston pushes the hydraulic oil 70 in the cavity back into the oil tank of the hydraulic device through the first oil nozzle 11 and the second oil nozzle 21. Under the combined action of gravity and piston thrust, the hydraulic oil 70 is smoothly discharged, and the pistons of each stage descend smoothly and finally return to the bottom of the cylinder. The equipment is restored to its initial state, which is convenient for transportation and the next use.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A multi-stage piston jack characterised in that, The multi-stage piston jack comprises: a first-stage oil cylinder provided with a first oil nozzle; a second-stage oil cylinder coaxially arranged above the first-stage oil cylinder and provided with a second oil nozzle; a first-stage piston arranged in the first-stage oil cylinder and capable of sliding up and down along the inner wall of the first-stage oil cylinder, the first-stage piston being provided with a first sealing element between the first-stage piston and the first-stage oil cylinder; a second-stage piston connected to the first-stage piston and arranged above the first-stage piston and capable of sliding up and down along the inner wall of the second-stage oil cylinder, the second-stage piston being provided with a second sealing element between the second-stage piston and the second-stage oil cylinder; the cross-sectional area of the first-stage piston is equal to that of the second-stage piston; the first oil nozzle is used to inject hydraulic oil into the first-stage oil cylinder to drive the first-stage piston to rise, and the second oil nozzle is used to inject hydraulic oil into the second-stage oil cylinder to drive the second-stage piston to rise to a jacking position.

2. The multi-stage piston jack of claim 1, wherein, The multi-stage piston jack further comprises: a sealing assembly arranged between the second-stage piston and the second-stage oil cylinder; a locking assembly arranged above the second-stage oil cylinder and connected to the second-stage piston to lock the second-stage piston when the second-stage piston is at the jacking position.

3. The multi-stage piston jack of claim 1, wherein, The second-stage piston is further provided with a third sealing element between the second-stage piston and the second-stage oil cylinder.

4. The multi-stage piston jack of claim 1, wherein, The second-stage piston is connected to the first-stage piston through a connecting boss.

5. The multi-stage piston jack of claim 4, wherein, The connecting boss is coaxially connected to the top surface of the first-stage piston.

6. The multi-stage piston jack of claim 2, wherein, The sealing assembly is threadedly connected to the second-stage piston, and the sealing assembly is provided with a fourth sealing element between the sealing assembly and the second-stage piston.

7. The multi-stage piston jack of claim 2, wherein, The locking assembly comprises a locking nut, and the second-stage piston is threadedly connected to the locking nut.

8. The multi-stage piston jack of claim 1, wherein, The bottom of the first-stage oil cylinder is provided with a base, and the base is provided with an anti-skid structure.

9. The multi-stage piston jack of claim 1, wherein, The first-stage oil cylinder and the second-stage oil cylinder are made of alloy steel.

10. A jacking system, characterized by The multi-stage piston jack according to any one of claims 1-9 and a hydraulic device are provided, the hydraulic device being connected to the multi-stage piston jack through the first oil nozzle and / or the second oil nozzle.

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