A multi-stage hydraulic cylinder with sequential extension and retraction

Abstract

This invention discloses a sequentially telescopic multi-stage hydraulic cylinder, comprising: an outer end cap, which fixes a telescopic guide rod and an outer cylinder, and has an oil return port; a telescopic guide rod, which has multiple stages of guide rods that can move relative to each other axially, with the innermost stage guide rod fixed to the outer end cap and having an oil passage communicating with the oil return port; an outer cylinder, which has an oil inlet communicating with the rodless chamber of the outermost piston rod; a multi-stage piston rod unit, with a rear cover at the bottom of each piston rod except the innermost piston rod, and each stage rear cover being fixed to the guide rod of the previous stage; rodless chambers and rod chambers are provided between the rear cover of the first-stage piston rod and the outer cylinder, and between the rear cover of the inner piston rod and the outer piston rod; each rear cover is provided with a one-way sequence valve, and each stage piston rod has an oil hole on its bottom sidewall communicating with the rod chamber of that stage piston rod, and when the next stage piston rod retracts to the starting point of its stroke, the oil hole also connects to the rod chamber of the next stage piston rod. This improves the stability of the sequential action.

Description

Technical Field

[0001] This invention belongs to the field of hydraulic cylinders, and in particular to a multi-stage hydraulic cylinder with sequential extension and retraction. Background Technology

[0002] Multistage hydraulic cylinders are widely used in confined spaces and long-stroke applications, but the problem of disordered piston rod extension and retraction frequently occurs during operation, failing to meet normal working requirements. Currently, most sequential extension and retraction hydraulic cylinders employ a differential area scheme, providing thrust through differences in the force-bearing area. However, this differential area scheme increases device size and economic costs, and is prone to erratic motion, making it unreliable. Therefore, there is an urgent need to propose a reliable sequential extension and retraction multistage hydraulic cylinder to address this issue. Summary of the Invention

[0003] The purpose of this invention is to provide a multi-stage hydraulic cylinder with sequential extension and retraction to solve the problems of uncontrollable piston rod extension and retraction sequence and disordered action in existing hydraulic cylinders, and to improve the stability and reliability of sequential action.

[0004] The technical solution to achieve the purpose of this invention is as follows:

[0005] A multi-stage hydraulic cylinder with sequential extension and retraction, comprising:

[0006] The outer end cap is used to fix the telescopic guide rod and the outer cylinder, and is equipped with an oil return port;

[0007] The telescopic guide rod has a multi-stage guide rod that is nested with each other and can only move relative to each other axially. The innermost guide rod is fixed to the outer end cover and has an oil passage that communicates with the oil return port. The guide rods are sealed to each other.

[0008] The outer cylinder is equipped with an oil inlet for connecting to the rodless chamber of the outermost piston rod, and contains a multi-stage piston rod unit.

[0009] The multi-stage piston rod unit includes multiple nested piston rods from the outside in. Except for the innermost piston rod, each piston rod has a rear cover at its bottom. The outermost piston rod serves as the first-stage piston rod. The rear cover of each stage piston rod is fixed to the bottom of the guide rod of the previous stage. A rodless chamber and a rod chamber are provided between the rear cover of the first-stage piston rod and the outer cylinder, and between the rear cover of the inner piston rod and the outer piston rod. Each rear cover is equipped with a one-way sequence valve, the opening pressure of which is greater than the pressure in the rodless chamber when the piston rod extends to the end of its stroke. Each piston rod has an oil hole on its bottom sidewall that connects to the rod chamber of that stage piston rod. When the next stage piston rod retracts to the beginning of its stroke, the oil hole also connects to the rod chamber of the next stage piston rod. During extension, the sequential opening of the one-way sequence valve controls the sequential extension of the piston rods. During retraction, the sequential retraction of the piston rods is achieved by the sequential connection of the oil hole on the bottom sidewall of each stage piston rod to the rod chamber of the next stage.

[0010] The significant advantages of this invention compared to existing technologies are:

[0011] (1) The sequential telescopic multi-stage hydraulic cylinder provided by the present invention is mainly realized by the one-way sequential valve structure and the sequential connection between the oil hole on the bottom side wall of the piston rod and the next stage rod chamber, which replaces the existing multi-stage cylinder structure and improves the stability and reliability of the telescopic sequence of the multi-stage hydraulic cylinder.

[0012] (2) The present invention adopts an oil circuit layout inside the cylinder to avoid oil circuit sagging, reduce safety hazards, and make the appearance of the device neater.

[0013] (3) The present invention adopts a multi-stage piston rod nesting structure with a total of four stages of piston rods. The device has a compact structure, occupies little space, and is more conducive to widespread use. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of the hydraulic cylinder in its fully retracted state in this invention;

[0015] Figure 2 This is a fracture cross-sectional view of the hydraulic cylinder in the extended state of the first stage in this invention;

[0016] Figure 3 This is a fracture cross-sectional view of the hydraulic cylinder in the second-stage extended state in this invention;

[0017] Figure 4 This is a fracture cross-sectional view of the hydraulic cylinder in the third-stage extended state in this invention;

[0018] Figure 5 This is a cross-sectional view of the hydraulic cylinder in its fully extended state in this invention.

[0019] Figure 6 This is a fracture cross-sectional view of the hydraulic cylinder in the fourth stage of retraction in this invention.

[0020] Figure 7 This is a fracture cross-sectional view of the hydraulic cylinder in the third stage of retraction in this invention.

[0021] Figure 8 This is a fracture cross-sectional view of the second-stage retracted state of the hydraulic cylinder in this invention;

[0022] Explanation of some markings in the image:

[0023] 1-Outer cylinder, 2-First piston rod, 3-Second piston rod, 4-Third piston rod, 5-Fourth piston rod, 6-First guide sleeve, 7-Second guide sleeve, 8-Third guide sleeve, 9-Fourth guide sleeve, 42-First guide rod, 43-Second guide rod, 44-Third guide rod, 45-Fourth guide rod, 10-Third one-way sequence valve, 11-Second one-way sequence valve, 12-First one-way sequence valve, 19-Fourth gland, 20-Third rear cover, 22-Third gland, 23 - Third screw cap, 24- Second rear cover, 26- Second pressure cap, 27- Second screw cap, 28- First rear cover, 31- First pressure cap, 29- First screw cap, 33- Outer end cap, A- Oil inlet, B- Oil outlet, 37- First oil hole, 38- Second oil hole, 13- Third oil hole, 14- Fourth oil hole, 15- Fifth oil hole, 16- Sixth oil hole, Y1- First oil passage, Y2- Second oil passage, Y3- Third oil passage, Y4- Fourth oil passage, Y5- Fifth oil passage. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1As shown, the present invention provides a multi-stage telescopic hydraulic cylinder controlled by a one-way sequence valve, which includes an outer cylinder 1 and a multi-stage piston rod unit. The multi-stage piston rod unit includes a first piston rod 2, a second piston rod 3, a third piston rod 4, a fourth piston rod 5, a first guide sleeve 6, a second guide sleeve 7, a third guide sleeve 8, a fourth guide sleeve 9, a first guide rod 42, a second guide rod 43, a third guide rod 44, a fourth guide rod 45, a first one-way sequence valve 12, a second one-way sequence valve 11, and a third one-way sequence valve 10. The fourth piston rod 5 is disposed inside the third piston rod 4, the third piston rod 4 is disposed inside the second piston rod 3, the second piston rod 3 is disposed inside the first piston rod 2, and the first piston rod 2 is disposed inside the outer cylinder 1. A first piston rod is disposed between the front end of the outer cylinder 1 and the first piston rod 2. Guide sleeve 6; a second guide sleeve 7 is provided between the front ends of the first piston rod 2 and the second piston rod 3; a third guide sleeve 8 is provided between the front ends of the second piston rod 3 and the third piston rod 4; a fourth guide sleeve 9 is provided between the front ends of the third piston rod 4 and the fourth piston rod 5; a first guide rod 42 is located inside the second guide rod 43 and its bottom is fixed to the outer cylinder 1 by a cylindrical pin; a second guide rod 43 is located inside the third guide rod 44 and its bottom is fixed to the first rear cover 28 by a key; a third guide rod 44 is located inside the fourth guide rod 45 and its bottom is fixed to the second rear cover by a key; a fourth guide rod 45 extends into the fourth piston rod 4 and its bottom is fixed to the third rear cover 20 by a key. Each guide rod can only slide axially and has no rotational relationship, and can extend or retract with each rear cover and piston rod.

[0026] A first rear cover 28 is provided at the rear end of the first piston rod 2, a second rear cover 24 is provided at the rear end of the second piston rod 3, a third rear cover 20 is provided at the rear end of the third piston rod 4, and a fourth pressure cap 19 is provided at the rear end of the fourth piston rod 5. A first one-way sequence valve 12 and a first pressure cap 31 are respectively provided inside the first rear cover 28 and at the bottom center. The first pressure cap 31 is connected to the first rear cover 28 by screws and is used to guide the first guide rod 42 and seal the second guide rod 43. A second one-way sequence valve 11 and a second pressure cap 26 are respectively provided inside the second rear cover 24 and at the bottom center. The second pressure cap 26 is connected to the second rear cover 24 by screws and is used to guide the first guide rod 42 and seal the second guide rod 43. The second guide rod 43 is guided and the third guide rod 44 is sealed. The third rear cover 20 is provided with a third one-way sequence valve 10 and a third pressure cover 22 at its interior and bottom center, respectively. The third pressure cover 22 is connected to the third rear cover 20 by screws and is used to guide the third guide rod 44 and seal the fourth guide rod 45. The fourth pressure cover 19 is connected to the fourth piston rod 5 by screws and serves as a seal. The rear end of the first rear cover 28 is provided with a first screw cap 29 to fasten the first rear cover 28. The rear end of the second rear cover 24 is provided with a second screw cap 27. The rear end of the third rear cover 20 is provided with a third screw cap 23. Each screw cap is connected to the rear cover by screws and serves as a fastener.

[0027] The outer cylinder 1 is provided with an outer end cover 33 at the bottom. The bottom of the outer end cover 33 is provided with an oil port B and a first guide rod 42. The first rear cover 28 is provided with a second guide rod 43. The second rear cover 24 is provided with a third guide rod 44. The third rear cover 20 is provided with a fourth guide rod 45. The first guide rod 42 is located inside the second guide rod 43. The second guide rod is located inside the third guide rod 44. The third guide rod is located inside the fourth guide rod 45. The fourth guide rod 45 is sealed with the third guide rod 44. The third guide rod is sealed with the second guide rod. The second guide rod is sealed with the first guide rod.

[0028] The outer cylinder 1 has a first oil passage Y1 on its side wall, a second oil passage Y2 on its first rear cover 28, a third oil passage Y3 on its second rear cover 24, a fourth oil passage Y4 on its third rear cover 20, a fifth oil passage Y5 inside its first guide rod 42, a first oil hole 37 and an oil inlet A on its side wall, the first oil hole 37 and the oil inlet A are connected through the first oil passage Y1, the bottom of the outer cylinder 1 has a second oil hole 38 as an oil return port B, the bottom side wall of the first piston rod 2 has a ring of third oil holes 13, the bottom side wall of the second piston rod 3 has a ring of fourth oil holes 14, the bottom side wall of the third piston rod 4 has a ring of fifth oil holes 15, the bottom side wall of the fourth piston rod 5 has a ring of sixth oil holes 16, the oil inlet A is connected to the first oil hole 37 through the first oil passage Y1, and the first oil hole 37 is connected to the first rodless chamber;

[0029] A first rodless chamber is provided between the first rear cover 28 and the bottom of the outer cylinder 1, and a first rod chamber is provided between the outer wall of the first piston rod 2 and the inner wall of the outer cylinder 1. A first one-way sequence valve 12 is installed on the second oil passage Y2 and controls the opening and closing of the second oil passage Y2. The opening pressure of the first one-way sequence valve 12 is greater than the pressure of the first rodless chamber when the first piston rod 2 reaches the end of its stroke. When the first piston rod 2 leaves the starting point of its stroke, the first one-way sequence valve 12 has not reached the opening pressure and is in the closed state. The second oil passage Y2 is not open. At this time, only the first rodless chamber has high-pressure oil to ensure that the other piston rods extend together with the first piston rod. When the first piston rod 2 reaches the end of its stroke, the first rodless chamber continues to increase pressure until it reaches the opening pressure of the first one-way sequence valve 12. The first one-way sequence valve 12 opens and the second oil passage Y2 is connected.

[0030] A second rodless chamber is provided between the second rear cover 24 and the first rear cover 28. A second rod chamber is provided between the outer wall of the second piston rod 3 and the inner wall of the first piston rod 2. A second one-way sequence valve 11 is installed on the third oil passage Y3 and controls the opening and closing of the third oil passage Y3. The opening pressure of the second one-way sequence valve 11 is greater than the pressure of the second rodless chamber when the second piston rod 3 reaches the end of its stroke. When the second piston rod 3 leaves the starting point of its stroke, the second one-way sequence valve 11 has not reached the opening pressure and is in the closed state. The third oil passage Y3 is not open. At this time, only the first rodless chamber and the second rodless chamber have high-pressure oil, ensuring that the third piston rod 4 and the fourth piston rod 5 extend together with the second piston rod 3. When the second piston rod 3 reaches the end of its stroke, the second rodless chamber continues to increase pressure until it reaches the opening pressure of the second one-way sequence valve. The second one-way sequence valve opens and the third oil passage Y3 is connected.

[0031] A third rodless chamber is provided between the third rear cover 20 and the second rear cover 24; a third rod-type chamber is provided between the outer wall of the third piston rod 4 and the inner wall of the second piston rod 3; a fourth rodless chamber is provided between the fourth pressure cap 19 and the third rear cover 20; and a fourth rod-type chamber is provided between the outer wall of the fourth piston rod 5 and the inner wall of the third piston rod 4, thus dividing the fourth piston rod 5 into a fourth rodless chamber and a fourth rod-type chamber; a third one-way sequence valve 10 is installed on the fourth oil passage Y4 and controls the opening and closing of the fourth oil passage Y4; the opening pressure of the third one-way sequence valve 10 is greater than that of the third piston rod 4. When the third piston rod 4 leaves the starting point of the stroke, the pressure in the third rodless chamber is such that the third one-way sequence valve 10 has not reached the opening pressure and is in the closed state, and the fourth oil passage Y4 is not open. At this time, there is no high-pressure oil in the fourth rodless chamber, ensuring that the fourth piston rod 5 extends together with the third piston rod 4. When the third piston rod 4 reaches the end of the stroke, the pressure in the third rodless chamber continues to rise until it reaches the opening pressure of the third one-way sequence valve. The third one-way sequence valve 10 opens, the fourth oil passage Y4 is connected, and high-pressure oil enters the fourth rodless chamber, causing the fourth piston rod 5 to extend.

[0032] The sixth oil hole 16 is connected to the interior of the fourth piston rod 5 and the fourth rod chamber on both sides, respectively. The fifth oil hole 15 is connected to the third rod chamber, the fourth oil hole 14 is connected to the second rod chamber, the third oil hole 13 is connected to the first rod chamber, the second oil hole 38 is connected to the oil return port B, and the first oil hole 37 is connected to the oil inlet A. When the fourth piston rod 5 returns to the end point, the fifth oil hole 15 is connected to the fourth rod chamber. When the third piston rod 4 returns to the end point, the fourth oil hole 14 is connected to the third rod chamber. When the second piston rod 3 returns to the end point, the third oil hole 13 is connected to the first rod chamber.

[0033] When the piston rod needs to extend, high-pressure oil is injected into the outer cylinder 1 through oil port A, first oil passage Y1, and first oil hole 37. High-pressure oil enters the first rodless chamber, while low-pressure oil from the first rod chamber returns to the oil tank through third oil hole 13, fourth oil hole 14, fifth oil hole 15, sixth oil hole 16, and second oil hole 38, passing through the second rod chamber, third rod chamber, fourth rod chamber, fifth oil passage Y5, and oil port B. The first piston rod 2 extends. Because the opening pressure of the first one-way sequence valve 12 is greater than the pressure in the first rodless chamber when the first piston rod 2 reaches the end of its stroke, the first one-way sequence valve 12 is closed, the second oil passage Y2 is blocked, and the remaining piston rods remain stationary inside the first piston rod 2, extending along with it. Figure 2 As shown.

[0034] When the first piston rod 2 reaches the end of its stroke, the first rodless chamber continues to pressurize until it reaches the opening pressure of the first one-way sequence valve 12. The first one-way sequence valve 12 opens, the second oil passage Y2 is connected, and high-pressure oil enters the second rodless chamber. The low-pressure oil in the second rod chamber returns to the oil tank through the fourth oil hole 14, the fifth oil hole 15, the sixth oil hole 16, the second oil hole 38, the third rod chamber, the fourth rod chamber, the fifth oil passage Y5, and the oil port B. The second piston rod 3 extends. Since the opening pressure of the second one-way sequence valve 11 is greater than the pressure in the second rodless chamber when the second piston rod 3 reaches the end of its stroke, the second one-way sequence valve 11 is closed at this time. The third oil passage Y3 is blocked, and the third piston rod 4 and the fourth piston rod 5 remain stationary inside the second piston rod 3 and extend together with the second piston rod 3. Figure 3 As shown.

[0035] When the second piston rod 3 reaches the end of its stroke, the second rodless chamber continues to pressurize until it reaches the opening pressure of the second one-way sequence valve 11. The second one-way sequence valve 11 opens, the third oil passage Y3 is connected, and high-pressure oil enters the third rodless chamber. The low-pressure oil in the third rod chamber returns to the oil tank through the fifth oil hole 15, the sixth oil hole 16, the second oil hole 38, the fourth rod chamber, the fifth oil passage Y5, and the oil port B. The third piston rod 4 extends. Since the opening pressure of the third one-way sequence valve 10 is greater than the pressure in the third rodless chamber when the third piston rod 4 reaches the end of its stroke, the third one-way sequence valve 10 is closed at this time. The fourth oil passage Y4 is blocked, and the fourth piston rod 5 remains stationary inside the third piston rod 4, extending out together with the third piston rod 4. Figure 4 As shown.

[0036] When the third piston rod 4 reaches the end of its stroke, the third rodless chamber continues to pressurize until it reaches the opening pressure of the third one-way sequence valve 10. The third one-way sequence valve 10 opens, the fourth oil passage Y4 is connected, and high-pressure oil enters the fourth rodless chamber. The low-pressure oil in the fourth rod chamber returns to the oil tank through the sixth oil hole 16, the second oil hole 38, the fifth oil passage Y5, and the oil port B. The fourth piston rod 5 begins to extend until the end of its stroke, and the sequential extension is complete. Figure 5 As shown.

[0037] When the piston rod needs to retract, high-pressure oil is injected through port B. The high-pressure oil flows through the second oil hole 38, the fifth oil passage Y5, the fourth rod chamber, and the sixth oil hole 16 into the fourth rod chamber. Since the one-way valve portion of the one-way sequence valve can pass normally in reverse, the low-pressure oil in the fourth rodless chamber flows through the one-way valve portion of the third one-way sequence valve 10, the third rodless chamber, the one-way valve portion of the second one-way sequence valve 11, the second rodless chamber, the one-way valve portion of the first one-way sequence valve 12, the first rodless chamber, the first oil hole 37, the first oil passage Y1, and port A back to the oil tank. The fourth piston rod 5 then begins to retract. Figure 6 As shown, at this time, the oil holes on the other piston rods are not connected to the rod chamber of the previous stage and remain stationary.

[0038] When the fourth piston rod 5 retracts to the beginning of its stroke, the fifth oil port 15 connects to the fourth rod chamber. After the fourth rod chamber is filled with high-pressure oil, the high-pressure oil flows through the fifth oil port 15 to the third rod chamber. Since the one-way valve part of the one-way sequence valve can pass normally in reverse, the low-pressure oil in the third rodless chamber returns to the oil tank through the one-way valve part of the second one-way sequence valve 11, the second rodless chamber, the one-way valve part of the first one-way sequence valve 10, the first rodless chamber, the first oil port 37, the first oil passage Y1, and the oil port A. The third piston rod 4 then begins to retract. Figure 7 As shown, at this time, the oil holes on the first piston rod 2 and the second piston rod 3 are not connected to the rod chamber of the previous stage and remain stationary.

[0039] When the third piston rod 4 retracts to the beginning of its stroke, the fourth oil port 14 connects to the third rod chamber. After the third rod chamber is filled with high-pressure oil, the high-pressure oil flows through the fourth oil port 14 to the second rod chamber. Since the one-way valve part of the one-way sequence valve can pass normally in reverse, the low-pressure oil in the second rodless chamber returns to the oil tank through the one-way valve part of the first one-way sequence valve 12, the first rodless chamber, the first oil port 37, the first oil passage Y1, and the oil port A. The second piston rod 3 then begins to retract. Figure 8 As shown, at this time, the third oil hole 13 on the first piston rod 2 is not connected to the second rodless chamber and remains stationary.

[0040] When the second piston rod 3 retracts to the beginning of its stroke, the third oil hole 13 connects to the second rod chamber. After the second rod chamber is filled with high-pressure oil, the high-pressure oil flows through the third oil hole 13 to the first rod chamber. The low-pressure oil in the first rodless chamber returns to the oil tank through the first oil hole 37, the first oil passage Y1, and the oil port A. The first piston rod 2 then begins to retract until the end of its stroke. The sequential retraction is then complete. Figure 1 As shown.

[0041] The sequential telescopic multi-stage hydraulic cylinder provided by this invention solves the problem of disordered piston rod extension and retraction sequence in existing multi-stage cylinders, improves the stability and reliability of the extension and retraction sequence of multi-stage hydraulic cylinders, and has a compact structure, occupies little space, and is more conducive to widespread use.

[0042] In summary, this invention utilizes three one-way sequence valves with progressively increasing set pressures to control the extension sequence of four piston rods. The set pressure of the one-way sequence valves is determined by the load, enabling the piston rods to extend in the order of first, second, third, and fourth. Oil holes are installed at designated positions on each piston rod, and the sequential retraction of the piston rods (fourth, third, second, and first) is achieved by controlling the opening and closing of these holes. This solves the problem of disordered extension and retraction sequence in existing multi-stage cylinders, improving the stability and reliability of the extension and retraction sequence in multi-stage hydraulic cylinders.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection defined by the claims of the present invention.

Claims

1. A multi-stage hydraulic cylinder with sequential telescopic movement, characterized in that, include: The outer end cap is used to fix the telescopic guide rod and the outer cylinder, and is equipped with an oil return port; The telescopic guide rod has a multi-stage guide rod that is nested with each other and can only move relative to each other axially. The innermost guide rod is fixed to the outer end cover and has an oil passage that communicates with the oil return port. The guide rods are sealed to each other. The outer cylinder is equipped with an oil inlet for connecting to the rodless chamber of the outermost piston rod, and contains a multi-stage piston rod unit. The multi-stage piston rod unit includes multiple nested piston rods from the outside in. Except for the innermost piston rod, each piston rod has a rear cover at its bottom. The outermost piston rod serves as the first-stage piston rod. The rear cover of each stage piston rod is fixed to the bottom of the guide rod of the previous stage. A rodless cavity is provided between the rear cover of the first-stage piston rod and the outer cylinder, and between the rear covers of every two inner stages of the piston rod. A rod-type cavity is provided between the outer wall of the first-stage piston rod and the inner wall of the outer cylinder, and between the outer wall of the inner piston rod and the inner wall of the adjacent outer piston rod. Each rear cover has a unidirectional sequential... The valve has a one-way sequence valve on each piston rod that opens at a pressure greater than the pressure in the rodless chamber when the piston rod extends to the end of its stroke. Each piston rod has an oil hole on its bottom sidewall that connects to the rod chamber of that piston rod. When the next piston rod retracts to the beginning of its stroke, the oil hole also connects to the rod chamber of the next piston rod. During extension, the sequential opening of the one-way sequence valve controls the sequential extension of the piston rod. During retraction, the sequential retraction of the piston rod is achieved by connecting the oil hole on the bottom sidewall of each piston rod to the rod chamber of the next piston rod.

2. The multi-stage hydraulic cylinder with sequential telescopic movement according to claim 1, characterized in that, The guide rods at each level can only slide axially, with no rotational relationship.

3. The multi-stage hydraulic cylinder with sequential telescopic movement according to claim 1, characterized in that, Guide sleeves are provided between the outer cylinder and the first-stage piston rod, and between adjacent-stage piston rods.

4. The multi-stage hydraulic cylinder with sequential telescopic movement according to claim 1, characterized in that, Each piston rod has a pressure cap at the bottom center for sealing with the guide rod of the previous stage.

5. The multi-stage hydraulic cylinder with sequential telescopic movement according to claim 1, characterized in that, Each back cover has a screw cap at the rear.

6. The multi-stage hydraulic cylinder with sequential telescopic movement according to claim 1, characterized in that, Each piston rod is secured to its corresponding rear cover via a locking mechanism.

Images