Flexible sequential telescopic oil cylinder and multi-stage oil cylinder combination

Abstract

A flexible sequential telescopic oil cylinder and multi-stage oil cylinder combination belongs to the technical field of engineering machinery, and is characterized in that a rear valve body is fixedly mounted at the tail part of a cylinder body; the rear valve element is installed on the rear valve body. The rear valve element is sleeved with the rear valve sleeve in a sliding mode. The reset spring is arranged between the rear valve sleeve and the cylinder body; one end of the central pipe is fixedly connected with the rear valve sleeve, and the other end penetrates through the piston and the piston rod; a variable cross-section valve port of which the through-flow area continuously changes when the rear valve sleeve axially moves is formed between the rear valve core and the rear valve sleeve; an inlet of the variable cross-section valve port is communicated with a cylinder body large cavity oil port, and an outlet is communicated with a central oil duct of the central pipe and used for being communicated with a next-stage oil cylinder large cavity; when the stage of oil cylinder extends to the tail section of the stroke, the piston drives the rear valve sleeve through the central pipe to overcome the pretightening force of the reset spring to move axially, so that the through-flow area of the variable cross-section valve port is gradually increased along with displacement, the flow entering the next stage of oil cylinder is correspondingly and gradually increased, and flexible sequential extension of the next stage of oil cylinder is achieved.

Description

Technical Field

[0001] This invention relates to a flexible sequential telescopic hydraulic cylinder and a multi-stage hydraulic cylinder combination, belonging to the field of engineering machinery technology. Background Technology

[0002] The sequential extension and retraction control of multi-stage booms of cranes involves improving the lifting capacity of the boom, reducing the stress on the overall structure, and perfecting the force-limited anti-tipping algorithm for safety control. It is one of the core technologies of boom cranes, and this function is mainly achieved by the sequential extension and retraction control of the hydraulic cylinders of each stage of the boom.

[0003] In existing technologies, the sequential extension and retraction of multi-stage hydraulic cylinders on a boom is often achieved by installing sequence valves between each stage of the cylinders. This method suffers from problems such as large pressure loss, difficulty in adjustment, and high cost. Furthermore, existing sequential extension and retraction cylinders generally exhibit large system impacts and severe boom swaying during operation, seriously affecting the stability and reliability of boom movement. Summary of the Invention

[0004] To address the shortcomings of existing multi-stage boom cylinder sequential telescopic control technology for cranes, this invention provides a flexible sequential telescopic cylinder and a multi-stage cylinder combination, which has a simple structure, stable operation, and high reliability.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a flexible sequential telescopic hydraulic cylinder, including a cylinder body, a piston, a piston rod, and a piston rod head, characterized in that it further includes:

[0007] The rear valve body, as an independent unit, is fixedly installed at the tail of the cylinder body;

[0008] The rear valve core is fixedly installed on the rear valve body;

[0009] A rear valve sleeve is axially slidably sleeved outside the rear valve core;

[0010] A return spring is disposed between the rear valve sleeve and the tail of the cylinder body, and is used to provide a preload force to press the rear valve sleeve toward the rear valve core;

[0011] A central tube has a central oil passage in its middle; one end of the central tube is fixedly connected to the rear valve sleeve, and the other end slides axially through the piston and piston rod, and the end of the central tube forms a transmission engagement with the piston in the axial direction;

[0012] Between the outer wall of the rear valve core and the inner wall of the rear valve sleeve, a combined groove structure with a cross-sectional area that varies axially is provided to form a variable cross-section valve port with a continuously changing flow area when the rear valve sleeve moves axially.

[0013] The inlet of the variable cross-section valve port is connected to the large cavity oil port on the cylinder body, and its outlet is connected to the central oil passage of the central tube. It is also connected to the large cavity of the next stage oil cylinder through the oil port on the piston rod head.

[0014] When the cylinder extends to the end of its stroke, the piston drives the rear valve sleeve through the central tube to move axially against the preload of the return spring, so that the flow area of ​​the variable cross-section valve port gradually increases with the displacement, and the flow rate into the next cylinder gradually increases accordingly, thus realizing the flexible sequential extension of the next cylinder.

[0015] Furthermore, the cross-sectional area of ​​the combined groove structure varies continuously along the axial direction, such that the flow area S(Δx) of the variable cross-section valve port and the axial displacement Δx of the rear valve sleeve satisfy the following relationship:

[0016] S(Δx) = k·Δx (1)

[0017] Where k is a constant.

[0018] Furthermore, the return spring causes the rear valve sleeve to fit tightly onto the rear valve core, so that the sealing cone surfaces of the rear valve sleeve and the rear valve core tend to form a sealing fit.

[0019] Furthermore, the combined groove structure consists of multiple U-shaped combined grooves distributed along the circumferential direction of the rear valve core, each U-shaped combined groove being formed by sequentially connecting multiple U-shaped grooves with varying widths and / or depths along the axial direction.

[0020] Furthermore, each U-shaped combination groove is formed by connecting four U-shaped grooves d1, m1, e1, and n1 with varying widths and depths along the axial direction. The width and depth of the U-shaped grooves d1, m1, e1, and n1 gradually increase from the rear valve core toward the cylinder body.

[0021] Furthermore, the rear valve core is provided with a central blind hole b1, and the side wall of the rear valve core is provided with a uniformly distributed hole a1 and a through hole h1. The uniformly distributed hole a1 is connected to the root of the central blind hole b1, and the through hole h1 is located in the U-shaped combination groove (preferably at the U-shaped groove n1) and is connected to the central blind hole b1.

[0022] Furthermore, the rear valve body is provided with a central through hole, and the tail end face of the cylinder is provided with a limiting protrusion. The limiting protrusion is inserted into the central through hole of the rear valve body, and a sealing structure is provided between the two. The central through hole of the rear valve body includes a valve core mounting cavity and a valve sleeve mounting cavity along the axial direction.

[0023] Furthermore, the rear valve core is threadedly fixed to the valve core mounting cavity, and the inner wall of the valve core mounting cavity bulges radially outward at the position corresponding to the uniformly distributed holes a1 of the rear valve core, forming an oil cavity o; the valve sleeve mounting cavity and the rear valve sleeve form a space for mounting a return spring, i.e., forming a spring cavity a.

[0024] Furthermore, the central hole of the rear valve sleeve is provided with a radially concave annular stop block, which divides the central hole of the rear valve sleeve into two parts for assembly with the central tube and the rear valve core, respectively; an oil cavity b is formed between the rear valve core and the annular stop block.

[0025] Furthermore, as the axial displacement of the central tube changes, the different positions of the U-shaped combination groove of the rear valve core and the inner wall of the rear valve sleeve can form a flow-through variable cross-section structure from left to right (from the rear valve core towards the cylinder body) and from small to large spring cavity a to oil cavity b, that is, a variable cross-section valve port is formed.

[0026] Furthermore, the combined groove structure adopts another variable cross-section form, which is a combined groove with a broken line change in axial cross-section.

[0027] That is, the combined groove with a broken line change in axial cross section is formed by connecting multiple annular slopes with gradually increasing slopes (from the rear valve core towards the cylinder body) sequentially along the axial direction, and its axial cross section is a broken line. By using broken line one and broken line two, or more broken line segments, at different positions that are concentrically matched with the inner wall of the rear valve sleeve, the effect of changing cross section of the flow channel valve port is achieved.

[0028] Furthermore, the rear valve body also includes:

[0029] One-way valve 1 is installed on the channel connecting the inlet of the variable cross-section valve port and the large chamber of the oil cylinder, and is used to supply oil to the large chamber of the oil cylinder in one direction.

[0030] The second check valve has its inlet connected to the central oil passage of the central tube through the oil passage in the rear valve body, and its outlet connected to the large cavity oil port of the oil cylinder, for guiding the oil flowing back from the large cavity of the lower-level oil cylinder through the central oil passage of the central tube.

[0031] Furthermore, the cylinder body is provided with a large cavity oil port d and a small cavity oil port g, and the spring cavity a is connected to the large cavity oil port d at the tail of the cylinder body through the channel c on the rear valve body;

[0032] Furthermore, the spring chamber a is connected to the large chamber x of the oil cylinder through the channel j on the rear valve body, the one-way valve one and the channel z on the rear valve body, and the channel y at the tail of the cylinder body;

[0033] Spring cavity a is also connected to oil cavity o through channel j on the rear valve body, check valve 2, and channel i on the rear valve body. With the help of four evenly distributed holes a1 and central blind hole b1 on the rear valve core, oil cavity o is connected to oil cavity b and the central oil passage e of the central tube.

[0034] Furthermore, a central tube sleeve, a piston rod sleeve, and a piston rod are sequentially fitted outside the central tube, and the central tube sleeve, piston rod sleeve, and piston rod are respectively fixedly connected to the piston;

[0035] The central tube is axially connected to the piston via a guide ring, which is fixedly connected to the end of the central tube and has a sliding fit with the inner wall of the central tube sleeve.

[0036] Furthermore, the piston rod end is fixedly connected to the piston rod head, and the piston rod head is provided with channel k and channel p. Channel k is provided with an oil port m connected to the oil port of the small chamber of the next stage oil cylinder, and channel p is provided with an oil port n connected to the oil port of the large chamber of the next stage oil cylinder.

[0037] An annular oil passage t is formed between the central tube and the central tube sleeve. A small hole f is provided on the wall of the central tube, and the central tube connects the central oil passage e and the annular oil passage t through the small hole f. An annular oil passage l is formed between the central tube sleeve and the piston rod sleeve, and an annular oil passage u is formed between the piston rod sleeve and the piston rod.

[0038] Furthermore, it also includes a stroke valve installed on the piston rod head, the two oil ports of which are respectively connected to the large chamber of the oil cylinder and the large chamber of the next stage oil cylinder, for conducting the return oil path of the large chamber of the oil cylinder when triggered.

[0039] Furthermore, the stroke valve is provided with a stroke valve stem for conduction, the stroke valve stem extending outside the piston rod head, for cooperating with a stop block on an adjacent cylinder to trigger the stroke valve to conduct.

[0040] The stroke valve has two working positions. When the stroke valve stem is not pressed by the stop block, the channel q on the stroke valve is disconnected from the channel p on the piston rod head. Otherwise, when the stroke valve stem is pressed, the stroke valve switches to a position where the channel q and the channel p are connected.

[0041] Furthermore, the large chamber x of the hydraulic cylinder is connected to one port of the stroke valve through the channel w on the piston, the annular channel l, and the channel q on the stroke valve; the other port of the stroke valve is connected to the channel p on the piston rod head and the large chamber port of the next stage hydraulic cylinder.

[0042] Furthermore, the oil chamber b is connected to the channel p on the piston rod head and the oil port of the next stage oil cylinder through the central oil passage e of the central tube and the central oil passage r of the central tube sleeve.

[0043] The piston rod (hollow structure) has a small hole v on its side wall. The small cavity oil port g of the cylinder body is connected to the small cavity s of the cylinder through the oil port h. The small cavity s of the cylinder is connected to the channel k on the piston rod head and the small cavity oil port of the next stage cylinder through the small hole v and the annular oil passage u.

[0044] Furthermore, a differential pressure reducing valve is connected in series on the inlet oil line of the variable cross-section valve port to maintain a constant pressure difference before and after the variable cross-section valve port.

[0045] The differential pressure reducing valve, as a pressure compensation valve for the variable cross-section valve port, is located in channel c on the rear valve body, which allows the large cavity oil port d to supply oil to the spring cavity a of the rear valve body through the differential pressure reducing valve. The control oil passage c1 of the differential pressure reducing valve is connected to the spring cavity a of the rear valve body, and the spring cavity oil passage c2 of the differential pressure reducing valve is connected to the oil cavity o.

[0046] On the other hand, the present invention provides a multi-stage hydraulic cylinder assembly, including at least two stages of hydraulic cylinders connected in sequence, wherein each stage of hydraulic cylinders other than the last stage is a flexible sequential telescopic hydraulic cylinder as described above.

[0047] Furthermore, the final stage cylinder is the flexible sequential telescopic cylinder described above, and the stroke valve on its piston rod head is normally open. A cover plate connecting oil passage q and oil passage p is installed on the piston rod head of the final stage cylinder. Alternatively, the final stage cylinder can be a conventional cylinder.

[0048] Furthermore, taking a three-stage hydraulic cylinder assembly as an example, its flexible sequential extension and retraction principle is as follows:

[0049] 1) The sequential extension process is as follows:

[0050] ① The first-stage sequential telescopic cylinder extends:

[0051] The oil flows from the large chamber port d of the first-stage cylinder through channel c, spring chamber a, channel j, one-way valve one, channel z and channel y, into the large chamber x of the first-stage cylinder, pushing the cylinder piston and the piston rod fixed to it to extend outward; the oil in the small chamber s of the first-stage cylinder returns through port h and small chamber port g, thereby realizing the extension action of the first-stage cylinder.

[0052] Although the oil in the large chamber x of the first-stage cylinder also reaches the first port of the stroke valve through channel w, annular oil passage l, and channel q, the stroke valve is in the open state at this time, and the oil is sealed there. On the other hand, in the spring chamber a of the rear valve body, the rear valve sleeve is tightly fitted to the sealing cone surface of the rear valve core under the action of the return spring. The oil cannot enter the oil chamber b from the spring chamber a and supply oil to the large chambers of the second and third-stage cylinders through the central oil passage e, central oil passage r, channel q, and port n. Therefore, the second and third-stage cylinders will remain non-extended.

[0053] ② The second-stage sequential telescopic cylinder extends:

[0054] When the first-stage cylinder extends to the end of its stroke, its piston will drive the guide ring to move outward together, and drive the rear valve sleeve, which is fixed to the other end of the central tube, to disengage from the sealing cone surface of the rear valve core. At this time, the rear valve sleeve and the rear valve core will form a flow channel with variable cross-section from the spring cavity a to the oil cavity b through the circumferentially evenly distributed combination groove structure and the central blind hole b1 of the rear valve core. As the rear valve sleeve is lifted to the right by the piston of the cylinder and the central tube, the distance the rear valve sleeve moves from left to right relative to the rear valve core is... The increase in cross-sectional area of ​​the variable cross-section valve port The oil supply will gradually increase from small to large, through this valve port from spring chamber a to oil chamber b, central oil passage e, central oil passage r, channel p, and the large chamber oil port of the second-stage oil cylinder. The supply of fuel will also gradually increase accordingly. The calculation is as follows:

[0055] (2)

[0056] In the formula: For flow coefficient, For the cross-sectional area of ​​the flow path, This refers to the valve port pressure difference (i.e., the pressure difference between spring chamber a and oil chamber b). This represents the density of the oil.

[0057] In this way, at the end of the extension stroke, the first-stage hydraulic cylinder will supply oil to the large-cavity oil port d on the cylinder body of the second-stage hydraulic cylinder through the oil port n on the piston rod head. Consistent with the extension principle of the first-stage hydraulic cylinder, the piston of the second-stage hydraulic cylinder and the piston rod fixed to it will begin to extend. The oil in the small cavity s of the second-stage hydraulic cylinder will return through the oil port h and the small cavity oil port g of the second-stage hydraulic cylinder, return to the oil port m on the piston rod head of the first-stage hydraulic cylinder, and return to the small cavity s of the first-stage hydraulic cylinder through the channel k and the annular oil passage u of the first-stage hydraulic cylinder, and then return through the oil port h and the small cavity oil port g of the first-stage hydraulic cylinder, thereby realizing the sequential extension of the second-stage hydraulic cylinder.

[0058] ③ The third-stage sequential telescopic cylinder extends:

[0059] Similar to the description of the sequential extension process of the second-stage cylinder, when the second-stage cylinder extends to the end of its stroke, the piston of the second-stage cylinder will drive the guide ring to move outward together, and drive the rear valve sleeve, which is fixed to its central tube. The rear valve sleeve disengages from the sealing cone surface of the rear valve core, and supplies oil to the large chamber oil port d of the third-stage cylinder. The oil supply amount is also... The amount of oil supplied also varies with the distance the rear valve sleeve of the second-stage cylinder moves from left to right relative to the rear valve core. The increase in cross-sectional area of ​​the flow path and fuel supply The oil in the small chamber s of the third-stage oil cylinder gradually increases in size. The oil returns through the oil port h and the small chamber oil port g of the third-stage oil cylinder to the oil port m of the piston rod head of the second-stage oil cylinder. It then returns to the small chamber s of the second-stage oil cylinder through the channel k and the annular oil passage u. The oil returns from the second-stage oil cylinder to the oil port g of the first-stage oil cylinder on a similar operating principle.

[0060] 2) The process of sequential contraction is as follows:

[0061] ① Third-stage hydraulic cylinder retraction:

[0062] When the hydraulic cylinder retracts, oil is supplied from the small cavity port g of the first-stage hydraulic cylinder. The oil port h, small cavity s, small hole v, annular channel u, channel k, and oil port m of the first-stage hydraulic cylinder are identical to those of the second and third-stage hydraulic cylinders, all possessing high-pressure oil. All three cylinders exhibit a tendency to retract. However, the oil in the large cavity x of the third-stage hydraulic cylinder enters through the channel w on the piston of the third-stage hydraulic cylinder, the annular oil passage l, the channel q on the stroke valve, and the channel on the stroke valve cover plate, entering the channel p on the stroke valve of the third-stage hydraulic cylinder, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, the oil cavity b, the oil cavity o, the channel i on the rear valve body, and the one-way valve. Oil flows back to the oil port n of the piston rod head of the second-stage cylinder through the channel j on the rear valve body, the spring chamber a, the channel c on the rear valve body, and the large chamber oil port d. It then flows through the channel p on the piston rod head of the second-stage cylinder, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, the oil chamber b, the oil chamber o, the channel i on the rear valve body, the one-way valve II, the channel j on the rear valve body, the spring chamber a, the channel c on the rear valve body, and the large chamber oil port d, and then back to the oil port n of the piston rod head of the first-stage cylinder. Following the same operating principle, the oil in the large chamber x of the third-stage cylinder eventually returns to the large chamber x of the first-stage cylinder, and then returns through the oil port h of the first-stage cylinder and the small chamber oil port g, thus realizing the retraction of the third-stage cylinder.

[0063] At this time, since the stroke valve rods on the first and second stage cylinders do not touch the stop, the stroke valves of the first and second stage cylinders are both in the open state. The oil in the large chamber of the first and second stage cylinders is sealed and cannot flow back due to the action of the check valve and the stroke valve. Therefore, neither the first nor the second stage cylinders can retract.

[0064] ② Second-stage hydraulic cylinder retraction:

[0065] When the piston rod of the third-stage cylinder retracts to its position, the stop block fixed to the third-stage cylinder will push against the stroke valve rod of the second-stage cylinder's stroke valve, causing the second-stage cylinder's stroke valve to switch from the disconnected state to the connected state, connecting channel q with channel p. Thus, the oil in the large chamber x of the second-stage cylinder, which was previously sealed, will flow through channel w on the piston, annular oil passage l, stroke valve q, channel p, central oil passage r of the central tube sleeve, central oil passage e of the central tube, oil chamber b, oil chamber o, channel i on the rear valve body, check valve two, channel j on the rear valve body, spring chamber a, and channel c of the rear valve body to the large chamber oil port d on the second-stage cylinder body. It will then return to the oil port n on the piston rod head of the first-stage cylinder and the central oil passage r of the central tube sleeve of the second-stage cylinder. The subsequent oil flow process is similar to that of the second-stage cylinder. Finally, the oil in the large chamber x of the second-stage cylinder returns to the large chamber oil port d of the first-stage cylinder body, achieving oil return and thus realizing the retraction of the second-stage cylinder.

[0066] At this point, the first-stage cylinder cannot retract because the stroke valve on the piston rod head is still in the open position.

[0067] ③ First-stage hydraulic cylinder retraction:

[0068] When the piston rod of the second-stage cylinder retracts to its position, the stop block fixed to the second-stage cylinder will push against the stroke valve rod of the first-stage cylinder stroke valve, causing the first-stage cylinder stroke valve to switch from the disconnected state to the connected state. Channel q will then connect with p. In this way, the oil in the large chamber x of the first-stage cylinder, which is closed, will pass through channel w on the piston, annular oil passage l, stroke valve q, channel p, central oil passage r of the central tube sleeve, central oil passage e of the central tube, oil chamber b, oil chamber o, channel i on the rear valve body, check valve II, channel j on the rear valve body, spring chamber a, and channel c on the rear valve body to reach the large chamber oil port d on the first-stage cylinder body, thereby realizing the retraction of the first-stage cylinder.

[0069] Furthermore, the flexible action principle of the flexible sequential telescopic hydraulic cylinder is as follows:

[0070] When the hydraulic cylinder extends to the end of its stroke and pulls open its rear valve sleeve, the variable cross-section valve port flow area between the rear valve sleeve and the rear valve core... The displacement of the valve opening (That is, the distance by which its rear valve sleeve is pulled apart by its central tube) is proportional: Its oil supply to the large chamber x of the next stage hydraulic cylinder for:

[0071]

[0072] (3)

[0073] The current stage hydraulic cylinder x large chamber piston area is At that time, see , If the velocity is constant, then the piston rod velocity of the next stage cylinder is... :

[0074]

[0075] (4)

[0076] Assume the combined equivalent mass of the piston rod of the next-stage hydraulic cylinder and its load is: Then the acceleration of the next stage hydraulic cylinder for:

[0077] (5)

[0078] At this moment, the piston rod of the hydraulic cylinder experiences a thrust generated by the oil pressure in the large chamber. :

[0079] (6)

[0080] When the pressure difference at the valve port When the change is small and tends to a constant value, the above formula can be simplified to:

[0081] (7)

[0082] That is: the force on the piston The size and the distance the valve sleeve is pulled apart by the central tube Directly related, and If the cylinders are pulled apart from smallest to largest, the piston rod of the next stage cylinder will experience a force. It also changes from small to large, thereby achieving flexible movement of the next stage hydraulic cylinder.

[0083] Conversely, if the oil supply to the next stage cylinder is at the end of the stroke of this stage cylinder... If there is no gradual change from small to large, but instead a jump from 0 to the maximum, then: middle, tending to the minimum As it approaches its maximum, the hydraulic pressure in the large chamber x of the next stage hydraulic cylinder... It also tends to be extremely large, thus causing system pressure. The impact was significant, and the structure was subjected to stress. The impact was significant.

[0084] Furthermore, a differential pressure reducing valve is used to supply oil to the valve port. The control oil passage c1 of the differential pressure reducing valve is connected to the spring chamber a, and the spring chamber oil passage c2 of the differential pressure reducing valve is connected to oil chamber o and oil chamber b. The function of this differential pressure reducing valve is to maintain a constant pressure difference across the variable cross-section valve port (equal to the pre-pressure value generated by the spring pressure of the differential pressure reducing valve), that is... Maintaining a constant value, under such conditions, as can be seen from the above analysis:

[0085] Oil supply to the large chamber x of the next stage hydraulic cylinder The size will be proportional to the flow area of ​​the valve orifice. And flow area Furthermore, the structure of the combined groove is directly proportional to the distance the rear valve sleeve is pulled by the central tube. Therefore, the oil supply Proportional to distance The speed of the piston rod movement in the next stage hydraulic cylinder This is proportional to the distance the rear valve sleeve is pulled by the central tube. , The change from 0 to a large value, then It also strictly changes from 0 to large, thus actually forming a valve pre-compensation proportional valve control device, and the movement of the next stage oil cylinder has a more obvious impact-free and flexible effect.

[0086] This invention utilizes a combined groove structure between the rear valve core and the rear valve sleeve to alter the flow area of ​​the variable cross-section valve port formed by their interaction, thereby achieving a flexible sequential extension function of the hydraulic cylinder. Furthermore, this sequential extension device avoids the through-hole design commonly used in related technologies in the industry, improving the operational reliability of the hydraulic cylinder.

[0087] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0088] 1. Flexible extension: Through the variable cross-section valve port structure, the flow rate into the next stage cylinder gradually increases with the displacement of the subsequent valve sleeve, realizing a flexible transition of sequential extension and avoiding system impact and boom swaying;

[0089] 2. Simple structure: No need for complex sequence valves in series, low pressure loss, convenient adjustment, and low cost;

[0090] 3. High reliability: The combination of check valve and stroke valve enables reliable control of sequential retraction, avoiding damage from ultra-high pressure and disordered operation. Attached Figure Description

[0091] Figure 1 This is a schematic diagram of the flexible sequential telescopic cylinder of the present invention (fully retracted state).

[0092] Figure 2 This is a schematic diagram of the rear valve core structure of the present invention (using a U-shaped combined groove);

[0093] Figure 3 for Figure 2 The main view;

[0094] Figure 4 for Figure 3 Sectional view along line AA;

[0095] Figure 5 This is a schematic diagram of the flexible sequential telescopic hydraulic cylinder of the present invention (fully extended state).

[0096] Figure 6 This is a schematic diagram of the flexible sequential telescopic cylinder of the present invention (with a differential pressure reducing valve).

[0097] Figure 7 This is a schematic diagram of the rear-mounted valve core of the present invention (using a combination groove with a broken line change in axial cross section);

[0098] Figure 8 for Figure 7 The main view;

[0099] Figure 9 for Figure 8 Sectional view along the BB direction;

[0100] Figure 10 for Figure 7 The rear view;

[0101] Figure 11 for Figure 10 C-axis sectional view;

[0102] Figure 12 This is a schematic diagram of the multi-stage hydraulic cylinder assembly of the present invention;

[0103] In the diagram: 1. Rear valve core, 1-1 sealing cone, 2. Rear valve body, 2-1 valve core mounting cavity, 2-2 valve sleeve mounting cavity, 3. Position spring, 4. Rear valve sleeve, 5. Piston, 6. Cylinder body, 6-1 limiting protrusion, 7. Central tube, 8. Piston rod sleeve, 9. Central tube sleeve, 10. Piston rod head, 11. Stroke valve stem, 12. Stroke valve, 13. Guide ring, 14. Check valve one, 15. Check valve two, 16. Combined groove structure, 17. Fold line one, 17-1, 17-2, differential pressure reducing valve, 18. Stop block, 19. Cover plate, 20. Detailed Implementation

[0104] Example 1

[0105] A flexible sequential telescopic hydraulic cylinder, such as Figure 1 As shown, it includes a cylinder body 6, a piston 5, a central tube 7, a piston rod 10 and a piston rod head 11, a rear valve, etc. The rear valve includes: a rear valve core 1, a rear valve body 2, a return spring 3, a rear valve sleeve 4, etc.

[0106] The rear valve body 2 is an independent unit installed at the tail of the cylinder body 6. The rear valve body 2 has a central through hole, and the tail end face of the cylinder body has a limiting protrusion 6-1. The limiting protrusion 6-1 is inserted into the central through hole of the rear valve body 2, and a sealing structure is provided between the two. The central through hole of the rear valve body 2 includes a valve core mounting cavity 2-1 and a valve sleeve mounting cavity 2-2 along the axial direction. The rear valve core 1 is threadedly installed in the valve core mounting cavity 2-1 of the rear valve body 2. The rear valve sleeve 4 is axially slidably sleeved outside the rear valve core 1 and located in the valve sleeve mounting cavity 2-2 of the rear valve body 2. The valve sleeve mounting cavity and the rear valve sleeve form a space for the installation of the return spring, that is, a spring cavity a.

[0107] The return spring 3 is located between the rear valve sleeve 4 and the tail of the cylinder 6. The return spring makes the rear valve sleeve 4 fit tightly on the rear valve core 1, so that the sealing cone surfaces of the rear valve sleeve 4 and the rear valve core 1 tend to form a sealing fit.

[0108] The central tube 7 has a central oil passage e in the middle. One end of the central tube 7 is fixedly connected to the rear valve sleeve 4, and the other end slides axially through the piston and piston rod. This end and the piston form a transmission engagement in the axial direction.

[0109] The rear valve sleeve 4 has a radially concave annular stop in its central hole. The annular stop divides the central hole of the rear valve sleeve 4 into two parts, which are respectively assembled with the central tube 7 and the rear valve core 1. An oil cavity b is formed between the rear valve core 1 and the annular stop.

[0110] Between the outer wall of the rear valve core 1 and the inner wall of the rear valve sleeve 4, a combination groove structure 17 with a cross-sectional area varying axially is provided to form a variable cross-section valve port with a continuously changing flow area when the rear valve sleeve moves axially. That is, as the axial displacement of the central tube changes, the different positions of the U-shaped combination groove of the rear valve core 1 and the inner wall of the rear valve sleeve 4 concentrically fit together can form a flow-variable cross-section structure from left to right (from the rear valve core 1 toward the cylinder 6) from small to large spring cavity a to oil cavity b.

[0111] The inlet of the variable cross-section valve port is connected to the large cavity oil port d on the cylinder body, and its outlet is connected to the central oil passage e of the central tube. It is also connected to the large cavity of the next stage oil cylinder through the oil port n on the piston rod head 11.

[0112] When the cylinder extends to the end of its stroke, the piston drives the rear valve sleeve through the central tube to overcome the preload of the return spring and move axially. This causes the flow area of ​​the variable cross-section valve port to gradually increase with the displacement, and the flow rate into the next cylinder gradually increases accordingly, thus realizing the flexible sequential extension of the next cylinder.

[0113] The cross-sectional area of ​​the combined groove structure changes continuously along the axial direction, such that the flow area S(Δx) of the variable cross-section valve port and the axial displacement Δx of the rear valve sleeve satisfy the following relationship:

[0114] S(Δx) = k·Δx (1)

[0115] Where k is a constant.

[0116] In one embodiment of the present invention, such as Figures 1 to 4 As shown, the combined groove structure 17 adopts four U-shaped combined grooves evenly distributed along the circumference of the rear valve core. Each U-shaped combined groove is formed by connecting four U-shaped grooves d1, m1, e1 and n1 with varying width and depth along the axial direction. The dimensions of the width and depth of the U-shaped grooves d1, m1, e1 and n1 gradually increase from the rear valve core 1 toward the cylinder 6.

[0117] The rear valve core 1 has a central blind hole b1. The side wall of the rear valve core has evenly distributed holes a1 and a through hole h1. The evenly distributed holes a1 communicate with the root of the central blind hole b1. The through hole h1 is located within the U-shaped combination groove (preferably at the U-shaped groove n1) and communicates with the central blind hole b1. The inner wall of the valve core mounting cavity bulges radially outward at the location corresponding to the evenly distributed holes a1 of the rear valve core, forming an oil cavity o.

[0118] In one embodiment of the present invention, such as Figures 7 to 9 As shown, the combined groove structure 17 adopts another variable cross-section form, which is a combined groove with a broken line change in axial cross-section. The combined groove with a broken line change in axial cross-section is formed by connecting multiple annular slopes with gradually increasing slopes (from the rear valve core towards the cylinder body) sequentially along the axial direction, and its axial cross-section is a broken line. By using broken line 17-1 and broken line 17-2, or more broken line segments, at different positions that are concentrically matched with the inner wall of the rear valve sleeve, the effect of variable cross-section of the flow channel valve port is achieved.

[0119] In one embodiment of the present invention, the rear valve body is further provided with a first check valve 15 and a second check valve 16. The first check valve 15 is disposed on the channel connecting the inlet of the variable cross-section valve port and the large chamber x of the cylinder, for unidirectional oil supply to the large chamber x of the cylinder; the inlet of the second check valve 16 is connected to the central oil passage e of the central pipe through an oil passage within the rear valve body, and its outlet is connected to the large chamber oil port d of the cylinder, for guiding the oil returning from the large chamber of the lower-level cylinder through the central oil passage e of the central pipe. Specifically:

[0120] The cylinder body 6 is provided with a large cavity oil port d and a small cavity oil port g. The spring cavity a is connected to the large cavity oil port d at the tail of the cylinder body through the channel c on the rear valve body. The spring cavity a is also connected to the large cavity x of the oil cylinder through the channel j on the rear valve body, the one-way valve 15, the channel z on the rear valve body 2, and the channel y at the tail of the cylinder body 6. The spring cavity a is also connected to the oil cavity o through the channel j on the rear valve body 2, the one-way valve 16, and the channel i on the rear valve body 2. With the help of the four evenly distributed holes a1 on the rear valve core and the central blind hole b1, the oil cavity o is connected to the oil cavity b and the central oil passage e of the central tube.

[0121] In one embodiment of the present invention, a central tube sleeve 9, a piston rod sleeve 8, and a piston rod 10 are sequentially sleeved outside the central tube 7. The central tube sleeve 9, the piston rod sleeve 8, and the piston rod 10 are respectively fixedly connected to the piston 5. The central tube 7 forms a transmission fit with the piston 5 in the axial direction through a guide ring 14. The guide ring 14 is fixedly connected to the end of the central tube 7 and forms a sliding fit with the inner wall of the central tube sleeve 9.

[0122] In one embodiment of the present invention, the end of the piston rod 10 is fixedly connected to the piston rod head 11. The piston rod head 11 is provided with a channel k and a channel p. Channel k is provided with an oil port m connected to the small chamber oil port of the next stage oil cylinder, and channel p is provided with an oil port n connected to the large chamber oil port of the next stage oil cylinder. An annular oil passage t is formed between the central tube and the central tube sleeve. A small hole f is provided on the wall of the central tube, and the central tube connects to the central oil passage e and the annular oil passage t through the small hole f. An annular oil passage l is formed between the central tube sleeve and the piston rod sleeve, and an annular oil passage u is formed between the piston rod sleeve and the piston rod.

[0123] In one embodiment of the present invention, a stroke valve 13 is provided on the piston rod head. The stroke valve is a two-position two-way valve, with two oil ports respectively connected to the large chamber of the hydraulic cylinder x and the large chamber of the next-stage hydraulic cylinder, for opening the return oil path of the large chamber of the hydraulic cylinder when triggered. The stroke valve 13 is provided with a stroke valve rod 12 for opening, which extends outside the piston rod head 11 and is used to cooperate with a stop block on the adjacent hydraulic cylinder to trigger the stroke valve to open.

[0124] The stroke valve has two operating positions. When the stroke valve stem 12 is not pressed by the stop block, the passage q on the stroke valve is disconnected from the passage p on the piston rod head. Otherwise, under pressure on the stroke valve stem, the stroke valve switches to a position where passage q and passage p are connected. The large chamber x of the hydraulic cylinder is connected to one port of the stroke valve through the passage w on the piston, the annular passage l, and the passage q on the stroke valve. The other port of the stroke valve is connected to the passage p on the piston rod head and the port n of the large chamber of the next stage hydraulic cylinder.

[0125] Oil chamber b is connected to the large chamber oil port of the next stage oil cylinder through the central oil passage e of the central tube, the central oil passage r of the central tube sleeve, the channel p on the piston rod head, and the oil port n; the piston rod 10 (hollow structure) has a small hole v on its side wall, and the small chamber oil port g of the cylinder body 6 is connected to the small chamber s of the oil cylinder through the oil port h. The small chamber s of the oil cylinder is connected to the channel k on the piston rod head and the small chamber oil port m of the next stage oil cylinder through the small hole v and the annular oil passage u.

[0126] In one embodiment of the present invention, such as Figure 6 As shown, the differential pressure reducing valve 18 serves as a pressure compensation valve for the variable cross-section valve port. The channel c on the rear valve body allows the large cavity oil port d to supply oil to the spring cavity a of the rear valve body through the differential pressure reducing valve. The control oil passage c1 of the differential pressure reducing valve is connected to the spring cavity a of the rear valve body, and the spring cavity oil passage c2 of the differential pressure reducing valve is connected to the oil cavity o.

[0127] Example 2

[0128] A multi-stage hydraulic cylinder assembly, such as Figure 12 As shown, the system includes three sequentially connected hydraulic cylinders. The first and second stage cylinders are the flexible sequential telescopic cylinders of Embodiment 1. The third stage cylinder can be a regular hydraulic cylinder. Alternatively, the third stage cylinder can be the flexible sequential telescopic cylinder of Embodiment 1, with a cover plate 20 connecting oil passage q and oil passage p installed on its piston rod head, so that the stroke valve is in a normally open state.

[0129] Example 3

[0130] The flexible sequential telescopic principle of the three-stage hydraulic cylinder assembly in Example 2 is shown in Figure 12:

[0131] 1) The sequential extension process is as follows:

[0132] ① The first-stage sequential telescopic cylinder extends:

[0133] The oil flows from the large chamber port d of the first-stage cylinder through channel c, spring chamber a, channel j, one-way valve 15, channel z and channel y, into the large chamber x of the first-stage cylinder, pushing the cylinder piston 5 and the piston rod 10 fixed to it to extend outward; the oil in the small chamber s of the first-stage cylinder returns through port h and small chamber port g, thereby realizing the extension action of the first-stage cylinder.

[0134] Although the oil in the large chamber x of the first-stage cylinder also reaches the first port of the stroke valve 13 through the channel w, the annular oil passage l, and the channel q, the stroke valve 13 is in the open state at this time, and the oil is sealed there; on the other hand, in the spring chamber a inside the rear valve body 1, the rear valve sleeve 4 is tightly fitted to the sealing cone surface 1-1 of the rear valve core 1 under the action of the return spring 3, and the oil cannot enter the oil chamber b from the spring chamber a and supply oil to the large chambers of the second and third-stage cylinders through the central oil passage e, the central oil passage r, the channel q, and the port n, so the second and third-stage cylinders will remain non-extended.

[0135] ② The second-stage sequential telescopic cylinder extends:

[0136] like Figure 5 As shown, when the first-stage cylinder extends to the end of its stroke, its piston 5 will drive the guide ring 14 to move outward together, and drive the rear valve sleeve 4, which is fixed to the other end of the central tube 7, to disengage from the sealing cone surface 1-1 of the rear valve core 1. At this time, the rear valve sleeve 4 and the rear valve core 1 will form a flow channel with variable cross-section from the spring cavity a to the oil cavity b through the circumferentially evenly distributed combination groove structure 17 and the central blind hole b1 of the rear valve core. As the rear valve sleeve 4 is lifted to the right by the cylinder piston 5 and the central tube 7, the distance the rear valve sleeve 4 moves from left to right relative to the rear valve core 1 is... The increase in cross-sectional area of ​​the variable cross-section valve port The oil supply will gradually increase from small to large, flowing through the valve port from spring chamber a to oil chamber b, central oil passage e, central oil passage r, channel p, oil port n, and the large chamber oil port of the second-stage cylinder. The supply of fuel will also gradually increase accordingly. The calculation is as follows:

[0137] (2)

[0138] In the formula: For flow coefficient, For the cross-sectional area of ​​the flow path, This refers to the valve port pressure difference (i.e., the pressure difference between spring chamber a and oil chamber b). This represents the density of the oil.

[0139] Thus, as Figure 12 As shown in the pipeline connection, at the end of the extension stroke, the first-stage hydraulic cylinder will supply oil to the large-cavity oil port d on the body of the second-stage hydraulic cylinder 6 through the oil port n on the piston rod head. This is consistent with the extension principle of the first-stage hydraulic cylinder. The piston 5 of the second-stage hydraulic cylinder and the piston rod 10 fixed to it will begin to extend. The oil in the small cavity s of the second-stage hydraulic cylinder will return through the oil port h and the small cavity oil port g of the second-stage hydraulic cylinder, returning to the oil port m of the piston rod head 11 of the first-stage hydraulic cylinder. It will then return to the small cavity s of the first-stage hydraulic cylinder through the channel k and the annular oil passage u of the first-stage hydraulic cylinder, and then return through the oil port h and the small cavity oil port g of the first-stage hydraulic cylinder, thereby realizing the sequential extension of the second-stage hydraulic cylinder.

[0140] ③ The third-stage sequential telescopic cylinder extends:

[0141] Similar to the description of the sequential extension process of the second-stage cylinder, when the second-stage cylinder extends to the end of its stroke, the piston 5 of the second-stage cylinder will drive the guide ring 14 to move outward together, and drive the rear valve sleeve 4, which is fixed to its central tube 7, to disengage from the sealing cone surface 1-1 of the rear valve core, and supply oil to the large chamber oil port d of the third-stage cylinder. The oil supply amount is also... The amount of oil supplied also varies with the distance the rear valve sleeve 4 of the second-stage cylinder moves from left to right relative to the rear valve core 1. The increase in cross-sectional area of ​​the flow path and fuel supply The oil in the small chamber s of the third-stage oil cylinder gradually increases from small to large. The oil returns through the oil port h and the small chamber oil port g of the third-stage oil cylinder, and returns to the oil port m of the piston rod head 11 of the second-stage oil cylinder. It then returns to the small chamber s of the second-stage oil cylinder through the channel k and the annular oil passage u. The oil returns from the second-stage oil cylinder to the small chamber oil port g of the first-stage oil cylinder.

[0142] 2) The process of sequential contraction is as follows:

[0143] ① Third-stage hydraulic cylinder retraction:

[0144] like Figure 12 As shown, when the hydraulic cylinder retracts, oil is supplied from the small cavity port g of the first-stage hydraulic cylinder. The oil port h, small cavity s, small hole v, annular channel u, channel k, and oil port m of the first-stage hydraulic cylinder are identical to those of the second and third-stage hydraulic cylinders, all containing high-pressure oil. All three cylinders exhibit a tendency to retract. However, the oil in the large cavity x of the third-stage hydraulic cylinder enters through the channel w on the piston of the third-stage hydraulic cylinder, the annular oil passage l, the channel q on the stroke valve, and the channel on the stroke valve cover plate, then enters through the channel p on the stroke valve of the third-stage hydraulic cylinder, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, the oil cavity b, the oil cavity o, the channel i on the rear valve body, and the one-way valve. Oil flows back to the oil port n of the piston rod head of the second-stage cylinder through the channels j on the rear valve body, spring chamber a, channel c on the rear valve body 2, and large chamber oil port d. It then flows through the channels p on the piston rod head of the second-stage cylinder, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, oil chamber b, oil chamber o, channel i on the rear valve body, check valve 2, channel j on the rear valve body, spring chamber a, channel c on the rear valve body, and large chamber oil port d, and then back to the oil port n of the piston rod head of the first-stage cylinder. Following the same operating principle, the oil in the large chamber x of the third-stage cylinder eventually returns to the large chamber x of the first-stage cylinder, and then returns through the oil port h of the first-stage cylinder and the small chamber oil port g, thus realizing the retraction of the third-stage cylinder.

[0145] At this time, since the stroke valve stems 12 on the first and second stage cylinders do not touch the corresponding stops 19, the stroke valves 13 of the first and second stage cylinders are both in the open state. The oil in the large chambers x of the first and second stage cylinders is sealed and cannot flow back due to the action of the check valve 15 and the stroke valve 13. Therefore, neither the first nor the second stage cylinders can retract.

[0146] ② Second-stage hydraulic cylinder retraction:

[0147] When the piston rod of the third-stage cylinder retracts to its position, the stop block 19, which is fixed to the third-stage cylinder, will push against the stroke valve rod 12 of the second-stage cylinder stroke valve 13, causing the second-stage cylinder stroke valve 13 to switch from the disconnected state to the connected state, so that channel q will connect with channel p. In this way, the oil that was closed in the large chamber x of the second-stage cylinder will pass through the channel w on the piston, the annular oil passage l, the stroke valve q, channel p, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, oil chamber b, oil chamber o, and the rear... The oil flows through the channel i on the valve body, the one-way valve 16, the channel j on the rear valve body, the spring chamber a, and the channel c on the rear valve body to the large cavity oil port d on the second-stage cylinder body. Then it returns to the oil port n on the piston rod head of the first-stage cylinder and the central oil passage r of the central tube sleeve of the second-stage cylinder. The subsequent oil flow process is similar to that of the second-stage cylinder. The oil in the large cavity x of the second-stage cylinder eventually returns to the large cavity oil port d of the first-stage cylinder body to achieve oil return, thereby realizing the retraction of the second-stage cylinder.

[0148] At this time, the first-stage cylinder cannot retract because the stroke valve 13 on the piston rod head 11 of the first-stage cylinder is still in the open position.

[0149] ③ First-stage hydraulic cylinder retraction:

[0150] When the piston rod of the second-stage cylinder retracts to its position, the stop block 19, which is fixed to the second-stage cylinder, will push against the stroke valve rod 12 of the first-stage cylinder stroke valve, causing the first-stage cylinder stroke valve to switch from the disconnected state to the connected state. The channel q will then connect with p. In this way, the oil in the large chamber x of the first-stage cylinder, which is closed, will pass through the channel w on the piston, the annular oil passage l, the q of the stroke valve, the channel p, the central oil passage r of the central tube sleeve, the central oil passage e of the central tube, the oil chamber b, the oil chamber o, the channel i on the rear valve body, the check valve 16, the channel j on the rear valve body, the spring chamber a, and the channel c on the rear valve body to reach the large chamber oil port d on the first-stage cylinder body, thereby realizing the retraction of the first-stage cylinder.

[0151] The flexible action principle of the flexible sequential telescopic hydraulic cylinder is as follows:

[0152] When the hydraulic cylinder extends to the end of its stroke and pulls open its rear valve sleeve 4, the variable cross-section valve port flow area between the rear valve sleeve 4 and the rear valve core 2... The displacement of the valve opening (That is, the distance by which its rear valve sleeve is pulled apart by its central tube) is proportional: Its oil supply to the large chamber x of the next stage hydraulic cylinder for:

[0153] (3)

[0154]

[0155] The current stage hydraulic cylinder x large chamber piston area is At that time, see , If the velocity is constant, then the piston rod velocity of the next stage cylinder is... :

[0156] (4)

[0157]

[0158] Assume the combined equivalent mass of the piston rod of the next-stage hydraulic cylinder and its load is: Then the acceleration of the next stage hydraulic cylinder for:

[0159] (5)

[0160] At this moment, the piston rod of the hydraulic cylinder experiences a thrust generated by the oil pressure in the large chamber. :

[0161] (6)

[0162] When the pressure difference at the valve port When the change is small and tends to a constant value, the above formula can be simplified to:

[0163] (7)

[0164] That is: the force on the piston The size and the distance the valve sleeve is pulled apart by the central tube Directly related, and If the cylinders are pulled apart from smallest to largest, the piston rod of the next stage cylinder will experience a force. It also changes from small to large, thereby achieving flexible movement of the next stage hydraulic cylinder.

[0165] Conversely, if the oil supply to the next stage cylinder is at the end of the stroke of this stage cylinder... If there is no gradual change from small to large, but instead a jump from 0 to the maximum, then: middle, tending to the minimum As it approaches its maximum, the hydraulic pressure in the large chamber x of the next stage hydraulic cylinder... It also tends to be extremely large, thus causing system pressure. The impact was significant, and the structure was subjected to stress. The impact was significant.

[0166] like Figure 6As shown, a differential pressure reducing valve 18 supplies oil to the valve port. The control oil passage c1 of the differential pressure reducing valve is connected to the spring chamber a, and the spring chamber oil passage c2 of the differential pressure reducing valve is connected to oil chamber o and oil chamber b. The function of this differential pressure reducing valve is to maintain a constant pressure difference across the variable cross-section valve port (equal to the pre-pressure value generated by the spring pressure of the differential pressure reducing valve), i.e. Maintaining a constant value, under such conditions, as can be seen from the above analysis:

[0167] Oil supply to the large chamber x of the next stage hydraulic cylinder The size will be proportional to the flow area of ​​the valve orifice. And flow area And because Figure 2 The structure of the combined groove is directly proportional to the distance the rear valve sleeve is pulled by the central tube. Therefore, the oil supply Proportional to distance The speed of the piston rod movement in the next stage hydraulic cylinder This is proportional to the distance the rear valve sleeve is pulled by the central tube. , The change from 0 to a large value, then It also strictly changes from 0 to large, thus actually forming a valve pre-compensation proportional valve control device, and the movement of the next stage oil cylinder has a more obvious impact-free and flexible effect.

Claims

1. A flexible sequential telescopic hydraulic cylinder, comprising a cylinder body (6), a piston (5), a piston rod (10), and a piston rod head (11), characterized in that, Also includes: The rear valve body (2) is fixedly installed at the tail of the cylinder body (6); The rear valve core (1) is fixedly installed on the rear valve body (2); The rear valve sleeve (4) is axially slidably sleeved outside the rear valve core (1); A reset spring (3) is provided between the rear valve sleeve (4) and the tail of the cylinder (6) to provide a preload force that presses the rear valve sleeve (4) toward the rear valve core (1); The central tube (7) has a central oil passage in its middle part; one end of the central tube (7) is fixedly connected to the rear valve sleeve (4), and the other end slides axially through the piston (5) and piston rod (10), and the end of the piston (5) forms a transmission fit with the piston (5) in the axial direction; Between the outer wall of the rear valve core (1) and the inner wall of the rear valve sleeve (4), a combined groove structure with a cross-sectional area that varies axially is provided to form a variable cross-section valve port with a continuously changing flow area when the rear valve sleeve (4) moves axially. The inlet of the variable cross-section valve port is connected to the large cavity oil port on the cylinder body (6), and its outlet is connected to the central oil passage of the central pipe (7), and is used to connect to the large cavity of the next stage oil cylinder through the oil port on the piston rod head (11). When the cylinder extends to the end of its stroke, the piston (5) drives the rear valve sleeve (4) to move axially through the central tube (7) to overcome the preload of the return spring (3), so that the flow area of ​​the variable cross-section valve port gradually increases with the displacement, and the flow rate into the next cylinder gradually increases accordingly, thus realizing the flexible sequential extension of the next cylinder.

2. The flexible sequential telescopic hydraulic cylinder according to claim 1, characterized in that, The cross-sectional area of ​​the combined groove structure changes continuously along the axial direction, so that the flow area S(Δx) of the variable cross-section valve port and the axial displacement Δx of the rear valve sleeve (4) satisfy: S(Δx) = k·Δx, where k is a constant.

3. The flexible sequential telescopic cylinder according to claim 2, characterized in that, The combined groove structure consists of multiple U-shaped combined grooves distributed along the circumference of the rear valve core (1), each U-shaped combined groove being formed by connecting multiple U-shaped grooves with varying widths and / or depths along the axial direction.

4. The flexible sequential telescopic cylinder according to claim 2, characterized in that, The combined groove structure is a combined groove with a broken line change in axial cross section.

5. The flexible sequential telescopic hydraulic cylinder according to claim 1, characterized in that, The rear valve body (2) is also provided with: One-way valve (15) is installed on the channel connecting the inlet of the variable cross-section valve port and the large chamber of the oil cylinder, and is used to supply oil to the large chamber of the oil cylinder in one direction; One-way valve 2 (16) has its inlet connected to the central oil passage of the central pipe (7) through the oil passage in the rear valve body (2), and its outlet connected to the large cavity oil port of the oil cylinder, for guiding the oil flowing back from the large cavity of the lower oil cylinder through the central oil passage of the central pipe (7).

6. The flexible sequential telescopic cylinder according to claim 1, characterized in that, A differential pressure reducing valve (17) is connected in series on the inlet oil line of the variable cross-section valve port to maintain a constant pressure difference before and after the variable cross-section valve port.

7. The flexible sequential telescopic cylinder according to claim 1, characterized in that, It also includes a stroke valve (13) installed on the piston rod head (11), the oil port of the stroke valve (13) being connected to the oil port of the large chamber of the oil cylinder and the large chamber of the next stage oil cylinder, respectively, for conducting the return oil path of the large chamber of the oil cylinder when triggered.

8. The flexible sequential telescopic hydraulic cylinder according to claim 7, characterized in that, The stroke valve (13) is provided with a stroke valve stem (12) for conduction. The stroke valve stem (12) extends outside the piston rod head (11) and is used to cooperate with the stop block (20) on the adjacent cylinder to trigger the stroke valve (13) to conduct.

9. A multi-stage hydraulic cylinder assembly, comprising at least two stages of hydraulic cylinders connected in sequence, characterized in that, All cylinders except the last stage are flexible sequential telescopic cylinders as described in any one of claims 1 to 8.

10. The multi-stage hydraulic cylinder assembly according to claim 9, characterized in that, The final stage cylinder is a flexible sequential telescopic cylinder as described in any one of claims 1 to 8, and the stroke valve on its piston rod head is normally open.

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