A special hydraulic jack for step-by-step cushioning jacking equipment

Abstract

This utility model discloses a special hydraulic jack for a step-by-step lifting device, relating to the technical field of stacking lifting equipment, and applicable to heavy-duty synchronous lifting systems. It includes a cylinder assembly comprising a coaxially arranged lifting cylinder body, lifting cylinder piston, and lifting cylinder piston rod. The upper and lower ends of the lifting cylinder are respectively provided with a cylinder head and a bottom cover. The cylinder assembly adopts an inverted structure, with the cylinder body flange fixedly connected to the lifting platform, and the piston rod connected to the equipment base via a mounting flange, achieving vertical lifting and lowering of the platform. The jack integrates a built-in displacement sensing unit, providing non-contact stroke detection, improving measurement accuracy and environmental adaptability, and offering excellent mechanical protection. The cylinder head, bottom cover, and piston are all equipped with multiple sealing components and guide ring structures, effectively enhancing sealing performance and suppressing off-center wear, ensuring high reliability and long-term stable operation.

Description

Technical Field

[0001] This utility model relates to the field of stacked lifting equipment technology, specifically to a special hydraulic jack for step-by-step lifting equipment, which is particularly suitable for high-tonnage precision lifting applications in heavy-duty synchronous lifting systems. Background Technology

[0002] Stacked jacking technology is widely used in engineering fields such as bridge jacking and heavy equipment installation. Its core hydraulic actuators must meet the requirements of large tonnage load-bearing capacity, high-precision synchronous control, and long-term environmental adaptability. While existing hydraulic jacks can achieve basic jacking functions, they still have significant shortcomings in heavy-duty stacked jacking scenarios:

[0003] For example, the prior art CN203624948U discloses an ultra-thin jack that adopts a forward mounting structure, with the cylinder body fixed to the base and the piston rod extending upward to connect to the load. This structure causes the piston rod to be exposed to the external environment for a long time, making it susceptible to dust and rainwater corrosion, accelerating the aging of seals (such as the failure of dust seals), and thus causing hydraulic oil leakage. In heavy engineering projects, this may induce safety accidents, and the structure has insufficient reliability.

[0004] The system employs a forward mounting configuration with a fixed cylinder and an upward-lifting piston rod. This structure exposes two major problems under heavy loads: Firstly, due to the unique action of the superimposed lifting equipment, the piston rod acts as a cantilever beam bearing the entire load bending moment. This cantilevered force on the piston rod leads to stress concentration at its root, easily causing fatigue cracks. Secondly, the piston rod extends upwards to connect with the load, resulting in a sharp drop in reliability under heavy-load lifting conditions. Thirdly, the piston rod is constantly exposed to the external environment, making it susceptible to dust and rain corrosion, accelerating the aging of seals (such as dust seal failure), and potentially causing hydraulic oil leaks. This could lead to safety accidents in heavy engineering projects, indicating insufficient structural reliability.

[0005] Furthermore, existing stroke detection systems mostly rely on external displacement sensors (such as wire-type or grating-type sensors), which need to be independently installed outside the piston rod. These sensors have significant drawbacks: the sensor signal lines are easily interfered with in strong electromagnetic fields (such as near hydraulic stations), causing synchronization control inaccuracies and exhibiting weak anti-interference capabilities; exposed sensors face risks of collision damage and oil penetration in construction site environments, with a sharp increase in failure rate in dusty and oily environments, and insufficient mechanical protection.

[0006] In addition, under high load conditions, the existing hydraulic cylinders have a simple guide and sealing system design. The piston and cylinder rely on only a single-stage sealing ring. When the load is off-center, the radial force imbalance can easily cause wear between the piston rod and the inner wall of the cylinder (commonly known as "cylinder scoring"). This can lead to uneven distribution of sealing pressure and local leakage when the load is off-center. At the same time, the lack of multi-stage guide ring support and restraint causes the piston to swing when it is not perpendicular to the load, which aggravates abnormal wear of the seals and shortens the equipment life. As a result, the sealing and guiding system has insufficient resistance to off-center loads. Utility Model Content

[0007] The problems to be solved by this utility model are the instability defects caused by the forward installation structure of existing jacks, the inherent drawbacks of external displacement detection systems, and the insufficient resistance to eccentric loads of the sealing and guiding systems. It provides a special hydraulic jack for step-by-step lifting equipment, which integrates an inverted cylinder structure, high-efficiency sealing, multi-stage guidance and high-precision detection, and can work stably and reliably in large-tonnage, high-precision and harsh environments such as bridge lifting and heavy equipment installation.

[0008] To address the aforementioned problems, this utility model provides a special hydraulic jack for a step-by-step lifting device, comprising a cylinder assembly including a lifting cylinder body, a lifting cylinder piston, and a lifting cylinder piston rod coaxially arranged. The upper and lower ends of the lifting cylinder body are respectively provided with a lifting cylinder cover and a lifting cylinder bottom cover. The cylinder assembly adopts an inverted structure. The lifting cylinder body flange is fixedly disposed on the lower outer edge of the lifting cylinder body and connected to the lifting platform of the stacking lifting device. The piston rod mounting flange is disposed at the lower end of the lifting cylinder body. The bottom end of the lifting cylinder piston rod is fixedly connected to the piston rod mounting flange and connected to the base of the stacking lifting device through the piston rod mounting flange. This converts the extension and retraction motion of the lifting cylinder piston rod into the vertical lifting motion of the lifting platform, thereby realizing the lifting action of the lifting platform.

[0009] The lifting cylinder body integrates a built-in displacement sensing unit. The lifting cylinder cover, lifting cylinder bottom cover and lifting cylinder piston are equipped with multiple sealing components and guide ring structures to improve sealing performance and prevent contact wear between the piston rod and the cylinder body due to off-center load.

[0010] Preferably, the lifting cylinder sealing flange is located between the lifting cylinder bottom cover and the lifting cylinder piston rod. The built-in displacement sensing unit includes a built-in displacement sensor inside the cavity of the lifting cylinder sealing flange and a sensor magnetic ring mounting seat fixed to the end of the lifting cylinder piston rod. The sensor magnetic ring is positioned in the stroke path of the lifting cylinder piston rod and moves synchronously with the piston rod, achieving stroke detection through magnetic induction, thus forming a non-contact stroke sensing. This improves measurement accuracy and environmental adaptability, and eliminates maintenance. Furthermore, integrating the displacement sensor into the cavity of the sealing flange and using the magnetic ring to achieve non-contact magnetic induction detection completely isolates the sensing element from external media and mechanical damage, eliminating the need for external wires or optical guides, significantly improving resistance to contamination, oil, and electromagnetic interference; it also eliminates the need for periodic calibration and maintenance of traditional external sensors, ensuring high-precision and long-term stable stroke feedback.

[0011] Preferably, the guide ring structure includes: a piston guide ring disposed at the outer end of the piston of the lifting cylinder, a piston rod guide ring disposed on the outer side of the piston rod, and a lifting cylinder guide ring installed on the upper end of the cylinder head of the lifting cylinder, with the piston rod of the lifting cylinder sleeved on its inner end.

[0012] Guide rings are installed at the outer end of the piston, the outer side of the piston rod, and the cylinder head to form three distributed radial supports. When the load is uneven, each guide ring works together to share the radial force, preventing the piston rod from contacting and wearing the inner wall of the cylinder, suppressing component wear caused by uneven load, and significantly improving the smoothness of movement and component life under uneven load conditions.

[0013] Preferably, the multi-seal assembly includes:

[0014] The O-ring and the retaining ring that fits therewith are both located between the lifting cylinder body and the lifting cylinder sealing flange.

[0015] The second O-ring and the second retaining ring that fits therewith are both located between the piston of the lifting cylinder and the piston rod of the lifting cylinder.

[0016] A square ring is used for the hole, which is located between the cylinder body of the lifting cylinder and the piston of the lifting cylinder.

[0017] The piston rod seal ring is located between the guide ring of the lifting cylinder and the piston rod of the lifting cylinder.

[0018] Dust seals are installed between the cylinder head and piston rod of the lifting cylinder to achieve a multi-stage sealing effect and prevent hydraulic oil leakage. O-rings, square rings, dust seals, and matching retaining rings are arranged at key locations such as the cylinder body-sealing flange, piston-piston rod, cylinder body-piston, and cylinder head-piston rod, forming a cascaded sealing structure with stepped bearings. This not only maintains excellent sealing performance under high-pressure operation but also effectively prevents oil leakage and premature seal failure in long-term cyclic and vibration environments.

[0019] Preferably, the lifting cylinder has a hydraulic medium channel extending through its side wall, which connects to the internal oil chamber. The hydraulic medium channel includes an oil port located on the side wall of the cylinder and a removable plug. The oil port with the removable plug extending through the side wall of the cylinder facilitates the connection of oil pipes and the injection of hydraulic medium, simplifying the equipment installation and commissioning process. At the same time, it integrates internal sensing and sealing components, reducing external accessories and lowering maintenance costs.

[0020] Preferably, the bottom end of the piston rod of the lifting cylinder is fixedly connected to the piston rod mounting flange by an internal hexagon head screw.

[0021] Preferably, the lifting cylinder sealing flange and the lifting cylinder piston are fixedly connected by an internal hexagonal tapered set screw.

[0022] Compared with the prior art, the present invention achieves the following beneficial technical effects:

[0023] This utility model adopts an inverted cylinder assembly. The cylinder body flange is connected to the lifting platform to fix the cylinder body to the lifting platform, and the piston rod flange is fixed to the base to connect the piston rod to the equipment base, so that the piston rod is always under pressure, avoiding cantilever bending and root stress concentration, and completely eliminating the cantilever stress problem of traditional forward-mounted piston rods. The load bending moment is borne by the entire cylinder body, which greatly improves the structural strength and service life under heavy load conditions. The inverted shape forms a closed structure, which completely isolates the piston rod, sensors and other core components from the external environment, avoiding sealing failure caused by dust and rainwater corrosion, and preventing hydraulic oil leakage.

[0024] This invention integrates a displacement sensor into the cavity of a sealed flange and uses a sensor magnetic ring to achieve non-contact magnetic induction detection. This completely isolates the sensor from mud and oil, eliminates the need for regular calibration and maintenance, and significantly improves measurement accuracy and environmental adaptability.

[0025] This invention employs a multi-stage sealing system to effectively prevent hydraulic oil leakage. O-rings, square rings, dust rings, and matching retaining rings are arranged at the cylinder head, bottom cover, and piston, forming a cascaded protection system. This not only maintains excellent sealing performance under high pressure but also effectively prevents seal failure and oil leakage during long-term cyclic operation. A multi-guide ring design suppresses off-center wear. Guide rings are installed at the piston end, piston rod, and cylinder head. When an off-center load occurs, the guide rings work together to share the radial force, forming distributed support and preventing contact damage between the piston rod and the cylinder wall. This ensures the smoothness and synchronization of piston movement and significantly extends the service life of components. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the hydraulic jack for the step-by-step lifting equipment of this utility model.

[0027] Figure 2 This is a top-down schematic diagram of the hydraulic jack used in the step-by-step lifting equipment of this utility model.

[0028] Figure 3 for Figure 2 A schematic diagram of the cross-sectional structure of section AA.

[0029] In the diagram: 1-Lifting cylinder body; 2-Lifting cylinder head; 3-Lifting cylinder piston; 4-Lifting cylinder bottom cover; 5-Lifting cylinder guide ring; 6-Piston rod mounting flange; 7-Lifting cylinder sealing flange; 8-Lifting cylinder body flange; 9-Lifting cylinder piston rod; 10-Sensor magnetic ring mounting seat; 11-Built-in displacement sensor; 12-Dustproof ring; 13-Piston rod guide ring; 14-Piston rod sealing ring; 15-O-ring one; 16-Retaining ring one; 17-Piston guide ring; 18-Square ring for hole; 19-O-ring two; 20-Retaining ring two; 21-Hex socket head cap screw; 22-Hex socket head cap screw; 23-Hex socket head cap tapered set screw. Detailed Implementation

[0030] The present invention will be further explained below with reference to the accompanying drawings and embodiments.

[0031] Reference Figures 1 to 3 As shown, this utility model provides a special hydraulic jack for a step-by-step lifting equipment, including a cylinder assembly, which includes a lifting cylinder body 1, a lifting cylinder piston 3, and a lifting cylinder piston rod 9 arranged coaxially. The upper and lower ends of the lifting cylinder body 1 are respectively provided with a lifting cylinder cover 2 and a lifting cylinder bottom cover 4. The cylinder assembly adopts an inverted structure. The lifting cylinder body flange 8 is fixedly set on the lower outer edge of the lifting cylinder body 1 and connected to the lifting platform of the stacking lifting equipment. The piston rod mounting flange 6 is set on the lower end of the lifting cylinder body 1. The bottom end of the lifting cylinder piston rod 9 is fixedly connected to the piston rod mounting flange 6 and connected to the base of the stacking lifting equipment through the piston rod mounting flange 6. The extension and retraction movement of the lifting cylinder piston rod 9 is converted into the vertical lifting and lowering movement of the lifting platform to realize the lifting and lowering movement of the lifting platform.

[0032] The lifting cylinder body 1 integrates a built-in displacement sensing unit. The lifting cylinder cover 2, the lifting cylinder bottom cover 4, and the lifting cylinder piston 3 are equipped with multiple sealing components and guide ring structures to improve sealing performance and prevent contact wear between the piston rod and the cylinder body due to off-center load.

[0033] The lifting cylinder sealing flange 7 is located between the lifting cylinder bottom cover 4 and the lifting cylinder piston rod 9. The built-in displacement sensing unit includes a built-in displacement sensor 11 embedded in the cavity of the lifting cylinder sealing flange 7 and a sensor magnetic ring mounting seat 10 fixed to the end of the lifting cylinder piston rod 9. The sensor magnetic ring is positioned in the stroke path of the lifting cylinder piston rod 9 and moves synchronously with the piston rod, achieving stroke detection through magnetic induction, thus forming a non-contact stroke sensing. This improves measurement accuracy and environmental adaptability, and eliminates maintenance. Furthermore, by integrating the displacement sensor into the sealing flange cavity and using the magnetic ring to achieve non-contact magnetic induction detection, the sensing element is completely isolated from external media and mechanical damage, eliminating the need for external wires or optical guides, significantly improving resistance to contamination, oil, and electromagnetic interference; it also eliminates the need for periodic calibration and maintenance of traditional external sensors, ensuring high-precision and long-term stable stroke feedback.

[0034] The guide ring structure includes: a piston guide ring 17 disposed at the outer end of the lifting cylinder piston 3 and a piston rod guide ring 13 disposed on the outer side of the piston rod, and a lifting cylinder guide ring 5 installed on the upper end of the lifting cylinder cylinder head 2, with the lifting cylinder piston rod 9 sleeved on its inner end.

[0035] Guide rings are installed at the outer end of the piston, the outer side of the piston rod, and the cylinder head to form three distributed radial supports. When the load is uneven, each guide ring works together to share the radial force, preventing the piston rod from contacting and wearing the inner wall of the cylinder, suppressing component wear caused by uneven load, and significantly improving the smoothness of movement and component life under uneven load conditions.

[0036] The multi-seal assembly includes:

[0037] O-ring 15 and retaining ring 16 that fits therewith are both located between the lifting cylinder body 1 and the lifting cylinder sealing flange 7.

[0038] O-ring 219 and retaining ring 20 that fits therewith are both located between lifting cylinder piston 3 and lifting cylinder piston rod 9.

[0039] A square ring 18 is used for the hole, which is set between the cylinder body 1 of the lifting cylinder and the piston 3 of the lifting cylinder.

[0040] The piston rod sealing ring 14 is disposed between the lifting cylinder guide ring 5 and the lifting cylinder piston rod 9;

[0041] Dust seal 12 is installed between the cylinder head 2 and the piston rod 9 of the lifting cylinder to achieve a multi-stage sealing effect and prevent hydraulic oil leakage. O-rings, square rings, dust seals, and matching retaining rings are arranged at key locations such as the cylinder body-sealing flange, piston-piston rod, cylinder body-piston, and cylinder head-piston rod, forming a cascaded sealing structure with gradient bearings. This not only maintains excellent sealing performance under high-pressure operation but also effectively prevents oil leakage and premature seal failure in long-term cyclic and vibration environments.

[0042] A hydraulic medium channel is provided through the side wall of the lifting cylinder body 1, which connects to the internal oil chamber. The hydraulic medium channel includes an oil port and a removable screw plug 21 located on the side wall of the cylinder body 1. The oil port with the removable screw plug through the side wall of the cylinder body facilitates the connection of oil pipes and the injection of hydraulic medium, simplifying the equipment installation and commissioning process. At the same time, the internal integrated sensing and sealing components reduce external accessories and lower maintenance costs.

[0043] The bottom end of the piston rod 9 of the lifting cylinder is fixedly connected to the piston rod mounting flange 6 by a hexagon socket head cap screw 22. The sealing flange 7 of the lifting cylinder is fixedly connected to the piston 3 of the lifting cylinder by a hexagon socket head cap set screw 23.

[0044] To facilitate understanding of the above technical solutions of this utility model, the following detailed description of the above technical solutions of this utility model is provided through specific usage methods.

[0045] The specific working process is as follows: During actual lifting, hydraulic oil is injected into the cylinder oil chamber through the oil port on the side wall of the lifting cylinder body 1 (the internal hexagonal plug 21 is in the disassembled state). The piston rod 9 of the lifting cylinder is rigidly fixed to the equipment base through the piston rod mounting flange 6. At this time, the lifting cylinder body 1 is in the lowest position. Next, the hydraulic station outputs pressurized oil, which enters the lower chamber of the inverted lifting cylinder body 1 through the oil port, pushing the lifting cylinder piston 3 to move upward. When the lifting cylinder piston 3 moves upward, because the lifting cylinder piston rod 9 is fixed, the reaction force drives the lifting cylinder body 1 to move upward synchronously. The lifting cylinder body flange 8 drives the lifting platform to rise vertically, realizing the inverted movement of the piston rod being stationary and the cylinder body being actively lifted. The sensor magnetic ring mounting seat 10 moves upward with the lifting cylinder piston 3, and the distance between it and the built-in displacement sensor 11 in the lifting cylinder sealing flange 7 decreases. The built-in displacement sensor 11 calculates the displacement signal through the change of magnetic flux and transmits it to the synchronous control system. When the load center of gravity shifts, the three-stage guide rings work together to resist the deviation: the piston guide ring 17 bears the lateral force of the lifting cylinder piston 3; the piston rod guide ring 13 constrains the swing of the lifting cylinder piston rod 9; the cylinder head guide ring 5 suppresses the radial displacement at the cylinder port; the sealing pressure is adaptive: the square ring 18 of the hole deforms under radial compression to compensate for the gap; the piston rod sealing ring 14 has a gradient pressure distribution to avoid local leakage. During pressure holding in the hydraulic system, five sealing components form a cascaded sealing barrier: In the high-pressure zone, a square ring 18 blocks the main leakage path in the piston chamber; in the medium-pressure zone, an O-ring 19 prevents oil from seeping into the piston rod 9 cavity; in the low-pressure zone, a dustproof ring 12 blocks external dust intrusion, and a piston rod sealing ring 14 provides bidirectional oil locking. During descent, the hydraulic station depressurizes, and the lifting platform's own weight drives cylinder 1 to move downwards; oil in the lower chamber of the lifting cylinder 1 returns to the oil tank through the oil port; a built-in displacement sensor 11 monitors the cylinder position in real time, ensuring synchronization of multiple cylinders.

[0046] In the description of this utility model, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model 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 utility model. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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 connection of two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0047] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0048] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the present invention.

Claims

1. A hydraulic jack for a step-by-step lifting device, comprising a cylinder assembly, including a lifting cylinder body (1), a lifting cylinder piston (3), and a lifting cylinder piston rod (9) coaxially arranged, wherein the upper and lower ends of the lifting cylinder body (1) are respectively provided with a lifting cylinder cover (2) and a lifting cylinder bottom cover (4), characterized in that, The cylinder assembly adopts an inverted structure. The lifting cylinder body flange (8) is fixedly set on the lower outer edge of the lifting cylinder body (1) and connected to the lifting platform of the stacked lifting equipment. The piston rod mounting flange (6) is set at the lower end of the lifting cylinder body (1). The bottom end of the lifting cylinder piston rod (9) is fixedly connected to the piston rod mounting flange (6) and connected to the base of the stacked lifting equipment through the piston rod mounting flange (6). The extension and retraction movement of the lifting cylinder piston rod (9) is converted into the vertical lifting action of the lifting platform to realize the lifting action of the lifting platform. The lifting cylinder body (1) integrates a built-in displacement sensing unit, and the lifting cylinder cover (2), the lifting cylinder bottom cover (4) and the lifting cylinder piston (3) are provided with multiple sealing components and guide ring structures.

2. The hydraulic jack for the step-by-step lifting equipment according to claim 1, characterized in that, The lifting cylinder sealing flange (7) is located between the lifting cylinder bottom cover (4) and the lifting cylinder piston rod (9). The built-in displacement sensing unit includes a built-in displacement sensor (11) built into the cavity of the lifting cylinder sealing flange (7) and a sensor magnetic ring mounting seat (10) fixed to the end of the lifting cylinder piston rod (9). The sensor magnetic ring is located in the stroke path of the lifting cylinder piston rod (9). The sensor magnetic ring moves synchronously with the piston rod and achieves stroke detection through magnetic induction, forming a non-contact stroke sensing.

3. The hydraulic jack for the step-by-step lifting equipment according to claim 1, characterized in that, The guide ring structure includes: The piston guide ring (17) is set on the outer end of the piston (3) of the lifting cylinder, and the piston rod guide ring (13) is set on the outer side of the piston rod, and the lifting cylinder guide ring (5) is installed on the upper end of the cylinder head (2) of the lifting cylinder. The piston rod (9) of the lifting cylinder is sleeved on its inner end to suppress the wear of the components caused by the off-center load and improve the stability of the piston movement.

4. The hydraulic jack for the step-by-step lifting equipment according to claim 3, characterized in that, The multi-seal assembly includes: O-ring 1 (15) and retaining ring 1 (16) that fits therewith are both located between the lifting cylinder body (1) and the lifting cylinder sealing flange (7); The second O-ring (19) and the second retaining ring (20) that fits therewith are both located between the piston (3) of the lifting cylinder and the piston rod (9) of the lifting cylinder; A square ring (18) is used to set between the cylinder body (1) of the lifting cylinder and the piston (3) of the lifting cylinder; The piston rod seal ring (14) is located between the lifting cylinder guide ring (5) and the lifting cylinder piston rod (9); A dust seal (12) is installed between the cylinder head (2) of the lifting cylinder and the piston rod (9) of the lifting cylinder to achieve multi-stage sealing.

5. The hydraulic jack for the step-by-step lifting equipment according to claim 1, characterized in that, The lifting cylinder body (1) has a hydraulic medium channel through the side wall, which connects to the internal oil chamber. The hydraulic medium channel includes an oil port and a removable screw plug (21) located on the side wall of the cylinder body (1).

6. The hydraulic jack for step-by-step elevation and lifting equipment according to claim 1, characterized in that, The bottom end of the piston rod (9) of the lifting cylinder is fixedly connected to the piston rod mounting flange (6) by an internal hexagonal head screw (22).

7. The hydraulic jack for a step-by-step lifting device according to claim 2, characterized in that, The lifting cylinder sealing flange (7) and the lifting cylinder piston (3) are fixedly connected by an internal hexagonal tapered set screw (23).

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