Crane Rope Boom Telescopic Hydraulic System and Crane

Abstract

This invention discloses a hydraulic system for the telescopic boom of a crane, comprising a primary telescopic cylinder, a secondary telescopic cylinder, and a control valve assembly. The control valve assembly includes a first electro-proportional pilot-operated pressure reducing valve, a second electro-proportional pilot-operated pressure reducing valve, a first solenoid directional valve, and a second solenoid directional valve. The first electro-proportional pilot-operated pressure reducing valve is controlled to direct oil from the inlet circuit of the first rod chamber to the control terminal of the first balance valve, proportionally controlling the opening of the first balance valve. The second electro-proportional pilot-operated pressure reducing valve is controlled to direct oil from the outlet circuit of the second rod chamber to the control terminal of the second balance valve, proportionally controlling the opening of the second balance valve. This invention also discloses a crane including the aforementioned hydraulic system for the telescopic boom of a crane. This invention solves the problem that the boom retraction speed is greatly affected by the load, improving the smoothness of the boom retraction start-up and deceleration phases.

Description

Technical Field

[0001] This invention relates to the field of crane technology, and in particular to a crane rope-type boom telescopic hydraulic system and a crane. Background Technology

[0002] Currently, multi-section telescopic boom truck cranes typically employ a combination of telescopic cylinders and wire rope pulley systems for boom extension and retraction. For truck cranes with five-section box-type telescopic booms, the boom extension mechanism often uses a configuration of two telescopic cylinders and wire rope pulleys. Due to space constraints within the boom, the hydraulic circuits of the two telescopic cylinders require special design; the hydraulic oil in the rodless and rod-side chambers of the second telescopic cylinder needs to be transferred between the first telescopic cylinder.

[0003] Chinese patents, such as those with publication numbers CN119160784A, CN102838042A, and CN203889961U, all employ a rod-side chamber for hydraulic cylinder retraction speed regulation, with the pressure in the rod-side chamber of the telescopic cylinder controlling the opening of the balance valve. This makes the boom retraction speed highly susceptible to load influence. At the moment of boom retraction startup, the pressure in the small chamber often exceeds the fully open pressure of the balance valve, resulting in a high startup speed, poor speed controllability, and frequent problems such as sudden boom sinking and significant boom vibration. Furthermore, during the boom retraction deceleration phase, the speed cannot be precisely controlled, often requiring the length of the deceleration section to improve telescopic smoothness, leading to a long full boom extension / retraction time; the minimum stable operating speed of the boom is often high, and there is loud noise when stopping.

[0004] Furthermore, in typical rope cranes, the balance valve of the telescopic cylinder only opens in one way. If the balance valve fails to open, the problem is usually solved by replacing the balance valve assembly or its components. However, replacing the balance valve assembly or its components requires the boom to be in a fully retracted state. If the boom is already extended and operating in a confined space, and the boom cannot be retracted, it may be necessary to demolish surrounding buildings or remove the entire crane, making rescue extremely difficult. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a hydraulic system for the telescopic boom of a crane with a rope-driven mechanism. This system solves the problems of boom retraction speed being greatly affected by load, high initial speed, poor speed controllability, and frequent sudden boom sinking and significant boom vibration. This invention also provides a crane.

[0006] The technical solution of the present invention is as follows: a hydraulic system for telescopic boom of a crane with ropes, comprising a primary telescopic cylinder, a secondary telescopic cylinder and a control valve group, wherein the primary telescopic cylinder is provided with a first rod chamber and a first rodless chamber, and the secondary telescopic cylinder is provided with a second rod chamber and a second rodless chamber, wherein the first rod chamber and the second rod chamber are connected. The control valve assembly includes a first electro-proportional pilot pressure reducing valve, a second electro-proportional pilot pressure reducing valve, a first solenoid directional valve, and a second solenoid directional valve. The first rodless chamber's oil circuit is equipped with a first balancing valve. The first solenoid directional valve is controlled to direct oil from the inlet oil circuit of the first rod chamber to the first electro-proportional pilot pressure reducing valve. The first electro-proportional pilot pressure reducing valve is controlled to direct oil from the inlet oil circuit of the first rod chamber to the control terminal of the first balancing valve to proportionally control the opening of the first balancing valve. The second rodless chamber's oil circuit is equipped with a second balancing valve. The second solenoid directional valve is controlled to direct oil from the outlet oil circuit of the second rod chamber to the second electro-proportional pilot pressure reducing valve. The second electro-proportional pilot pressure reducing valve is controlled to direct oil from the outlet oil circuit of the second rod chamber to the control terminal of the second balancing valve to proportionally control the opening of the second balancing valve.

[0007] Furthermore, to avoid malfunctions in the telescopic cylinder caused by electrical control failures due to cable reel damage or controller failure, and to cope with construction scenarios requiring high hoisting efficiency, the control valve group includes a first hydraulic control switch valve, a second hydraulic control switch valve, a first shuttle valve, and a second shuttle valve. The outlet of the first electro-proportional pilot pressure reducing valve is connected to the control terminal of the first hydraulic control switch valve and the first inlet of the first shuttle valve. The first solenoid directional valve by default directs the oil from the inlet oil path of the first rod chamber to the first hydraulic control switch valve. The first hydraulic control switch valve by default is connected to the second inlet of the first shuttle valve, and the outlet of the first shuttle valve is connected to the control terminal of the first balance valve. The outlet of the second electro-proportional pilot pressure reducing valve is connected to the control terminal of the second hydraulic control switch valve and the first inlet of the second shuttle valve. The second solenoid directional valve by default directs the oil from the outlet oil path of the second rod chamber to the second hydraulic control switch valve. The second hydraulic control switch valve by default is connected to the second inlet of the second shuttle valve, and the outlet of the second shuttle valve is connected to the control terminal of the second balance valve.

[0008] This solution, besides utilizing an electro-proportional pilot-operated pressure reducing valve to control the opening of the balance valve in the hydraulic cylinder, which improves the smoothness of the boom retraction start-up and deceleration phases, also allows for the activation of a hydraulically controlled switch valve to control the balance valve in construction scenarios where the electro-proportional pilot-operated pressure reducing valve and solenoid directional valve fail or where high lifting efficiency is required. This not only meets emergency needs but also improves the opening efficiency of the balance valve and reduces acceleration and deceleration time. When the electro-proportional pilot-operated pressure reducing valve and solenoid directional valve are effective, the hydraulically controlled switch valve is controlled to close, preventing the control of the balance valve from being affected by the direct hydraulic control circuit when the electro-proportional pilot-operated pressure reducing valve outputs low oil pressure.

[0009] Furthermore, the oil circuit of the second rodless chamber is connected to the core tube electro-proportional relief valve through the second balance valve. The core tube electro-proportional relief valve is proportionally controlled by the signal of the amplitude angle. By using the core tube electro-proportional relief valve to adapt to the relief pressure required during the retraction of the second boom, the problem of slight extension or retraction of the third, fourth, and fifth boom sections during the retraction of the second boom can be solved.

[0010] Furthermore, an accumulator is provided in the oil line from the second electromagnetic directional valve to the second electro-proportional pilot pressure reducing valve.

[0011] Furthermore, the output oil circuit of the accumulator is equipped with a pressure sensor and an overflow valve.

[0012] Furthermore, the output oil circuit of the accumulator is equipped with a pressure relief ball valve.

[0013] Furthermore, the control valve assembly includes a multi-way valve and a directional valve. The multi-way valve has a first passage and a second passage. The first passage forms the inlet oil passage of the first rod chamber, and the second passage is connected to the directional valve. The first valve position of the multi-way valve is configured such that the first passage forms an inlet oil passage for supplying oil to the first rod chamber, and the second passage forms a return oil passage. The second valve position of the multi-way valve is configured such that the first passage forms a return oil passage for supplying oil to the first rod chamber, and the second passage forms a supply oil passage. The directional valve has a third passage and a fourth passage. The third passage forms the oil passage of the second rodless chamber, and the fourth passage forms the oil passage of the first rodless chamber. The first valve position of the directional valve is configured such that the third passage forms a return oil passage, and the fourth passage is connected to the second passage. The second valve position of the directional valve is configured such that the fourth passage forms a return oil passage, and the third passage is connected to the second passage.

[0014] Furthermore, the multi-way valve and the directional valve are hydraulically controlled valves. The control valve group includes a first pilot directional valve, a second pilot directional valve, and a third pilot directional valve. When the first pilot directional valve is activated, it controls the multi-way valve to be in the first valve position. When the second pilot directional valve is activated, it controls the multi-way valve to be in the second valve position. The third pilot directional valve controls the directional valve to switch valve positions.

[0015] Furthermore, the first passage is provided with a third balancing valve, and the third balancing valve is controlled to operate when the second pilot directional valve is activated.

[0016] Another technical solution of the present invention is as follows: a crane, including the aforementioned crane rope-type boom telescopic hydraulic system.

[0017] Compared with the prior art, the advantages of the technical solution provided by the present invention are as follows: (1) The balance valve of the rodless chamber of the telescopic cylinder is controlled by the first electro-proportional pilot pressure reducing valve and the second electro-proportional pilot pressure reducing valve, so as to avoid the influence of load pressure on the flow area of ​​the balance valve opening, solve the problem that the boom retraction speed is greatly affected by the load, and improve the stability of the boom retraction start and deceleration stages.

[0018] (2) By setting up a hydraulic control switch valve and a shuttle valve, the control of the balance valve of the rodless chamber of the telescopic cylinder can be switched between the control of the first electro-proportional pilot pressure reducing valve and the second electro-proportional pilot pressure reducing valve (normal state) or the direct control of the rod chamber (emergency state), which satisfies both the need for improved stability and the need for emergency response.

[0019] (3) By setting a core tube electro-proportional relief valve, the pressure of the relief valve is controlled according to the amplitude angle ratio, which solves the problem of the extension or retraction of the third, fourth and fifth sections of the boom when the second section is retracted. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the hydraulic system for the telescopic boom of a crane, as illustrated in the embodiment. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading this description, any modifications of this description in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0022] Please combine Figure 1 As shown, the crane involved in this embodiment has a crane rope-type boom telescopic hydraulic system. The hydraulic system includes a primary telescopic cylinder 1, a secondary telescopic cylinder 2, and a control valve group. The primary telescopic cylinder 1 is provided with a first rod chamber 1a and a first rodless chamber 1b. The secondary telescopic cylinder 2 is provided with a second rod chamber 2a and a second rodless chamber 2b. The first rod chamber 1a and the second rod chamber 2a are connected. The oil passage of the outlet oil passage of the second rod chamber 2a and the oil passage of the second rodless chamber 2b of the secondary telescopic cylinder 2 both need to pass through the core tube of the primary telescopic cylinder 1.

[0023] The control valve assembly includes a first electro-proportional pilot pressure reducing valve 3, a second electro-proportional pilot pressure reducing valve 4, a first solenoid directional valve 5, a second solenoid directional valve 6, a first hydraulic control valve 7, a second hydraulic control valve 8, a first shuttle valve 9, a second shuttle valve 10, a multi-way valve 11, and a directional valve 12.

[0024] The multi-way valve 11 is connected to the output oil circuit of the variable pump 13 and to the oil return circuit connected to the oil tank 29. The interface of the multi-way valve 11 also forms two working passages: a first passage L1 and a second passage L2. The multi-way valve 11 has multiple valve positions. In the default position, the output oil circuit of the variable pump 13 and the second passage L2 are not connected, while the first passage L1 is connected to the oil circuit in use. In the first valve position of the multi-way valve 11, the output oil circuit of the variable pump 13 is connected to the first passage L1 via the multi-way valve 11. The first passage L1, after passing through multiple valves (described later), connects to the first rod chamber 1a of the first-stage telescopic cylinder 1, forming an oil inlet passage for supplying oil to the first rod chamber 1a. Simultaneously, the second passage L2 is connected to the oil return circuit, forming a return oil passage. In the second valve position of the multi-way valve 11, the connection mode of the first passage L1 and the second passage L2 is interchanged, that is, the first passage L1 and the oil passage for oil return are connected to form the oil return passage, and at the same time, the output oil passage of the variable pump 13 is connected to the second passage L2 through the multi-way valve 11, and the second passage L2 forms the oil supply passage.

[0025] In this embodiment, the multi-way valve 11 is a hydraulically controlled valve. The control valve group includes a first pilot directional valve 14 and a second pilot directional valve 15, both of which are controlled by an electrical circuit. The first pilot directional valve 14 is connected to the pilot oil source 16 and the control terminal of the first valve position of the multi-way valve 11. When activated, it uses pilot oil to control the multi-way valve 11 to be in the first valve position. The second pilot directional valve 15 is connected to the pilot oil source 16 and the control terminal of the second valve position of the multi-way valve 11. When activated, it uses pilot oil to control the multi-way valve 11 to be in the second valve position.

[0026] A third balancing valve 17 is provided on the first passage L1 connected to the aforementioned multi-way valve 11. The control end of the third balancing valve 17 is also controlled by the second pilot directional valve 15 through pilot oil.

[0027] The first rodless chamber 1b of the first-stage telescopic cylinder 1 is equipped with a first balance valve 18. A first solenoid directional valve 5 is installed between the third balance valve 17 and the first rod chamber 1a on the first passage L1, and a first relief valve 25 is installed between the third balance valve 17 and the first solenoid directional valve 5. The first solenoid directional valve 5 directs the oil from the first passage L1 (i.e., the inlet oil passage of the first rod chamber 1a) to either a first electro-proportional pilot pressure reducing valve 3 or a first hydraulic control valve 7 through two valve positions. The outlet of the first electro-proportional pilot pressure reducing valve 3 is connected to the first inlet of the first shuttle valve 9 and the control terminal of the first hydraulic control valve 7. The outlet of the first hydraulic control valve 7 is connected to the second inlet of the first shuttle valve 9, and the outlet of the first shuttle valve 9 is connected to the control terminal of the first balance valve 18.

[0028] The second passage L2 of the multi-way valve 11 is connected to the directional control valve 12, which is a hydraulically controlled valve. Its control end is controlled by the third pilot directional control valve 20. When the third pilot directional control valve 20 is electrically activated, it directs pilot oil to the control end of the directional control valve 12 for switching. The directional control valve 12 has a third passage L3 and a fourth passage L4. The third passage L3 passes through the first-stage telescopic cylinder 1 and forms the oil circuit of the second rodless chamber 2b of the second-stage telescopic cylinder 2. The oil circuit of the second rodless chamber 2b is equipped with a second balance valve 19. The third passage L3 is finally connected to the inlet of the second balance valve 19, and the outlet of the second balance valve 19 is then connected to the second rodless chamber 2b. The fourth passage L4 of the directional control valve 12 forms the oil circuit of the first rodless chamber 1b, that is, the fourth passage L4 is connected to the inlet of the first balance valve 18, and the outlet of the first balance valve 18 is then connected to the first rodless chamber 1b. The reversing valve 12 is also connected to a return oil passage, on which a core tube electro-proportional relief valve 21 is connected. The core tube electro-proportional relief valve 21 controls the relief pressure proportionally by the signal of the amplitude angle.

[0029] The directional valve 12 has two valve positions. In the first valve position (default state) of the directional valve 12, the third passage L3 is connected to the return oil passage and the fourth passage L4 is connected to the second passage L2. In the second valve position (the directional valve 12 is controlled to operate), the fourth passage L4 is connected to the return oil passage and the third passage L3 is connected to the second passage L2.

[0030] A second solenoid directional valve 6 is installed in the outlet oil circuit of the second rod chamber 2a of the secondary telescopic cylinder 2. The second solenoid directional valve 6 guides the oil from the outlet oil circuit of the second rod chamber 2a to the second electro-proportional pilot pressure reducing valve 4 or the second hydraulic control valve 8 through two valve positions. The outlet of the second electro-proportional pilot pressure reducing valve 4 is connected to the first inlet of the second shuttle valve 10 and the control terminal of the second hydraulic control valve 8. The outlet of the second hydraulic control valve 8 is connected to the second inlet of the second shuttle valve 10, and the outlet of the second shuttle valve 10 is connected to the control terminal of the second balance valve 19. A check valve 22 and an accumulator 23 are provided in the oil circuit from the second solenoid directional valve 6 to the second electro-proportional pilot pressure reducing valve 4. The output oil circuit of the accumulator 23 is equipped with a pressure sensor 24, a second relief valve 26, and a pressure relief ball valve 27. Both the second relief valve 26 and the pressure relief ball valve 27 can release the oil from the accumulator 23 back to the oil tank 29. An electrically controlled switching valve 28 is also installed on the passage from the accumulator 23 to the second electro-proportional pilot pressure reducing valve 4.

[0031] The working principle of this crane's rope-type boom telescopic hydraulic system is as follows: the balance valve, which is originally directly controlled by the hydraulic fluid in the rod chamber, is controlled by an electro-proportional pilot pressure reducing valve, which then controls the hydraulic fluid pressure to open the balance valve. In emergency situations, the hydraulic fluid can also be directly used to control the opening of the balance valve. The specific process is as follows: Arm retraction control In normal mode, the retraction motion of the third, fourth, and fifth arm segments: After receiving the signal that the handle has moved backward, the controller energizes the first pilot directional valve 14, causing the pilot oil to flow to the control end of the multi-way valve 11, thus reversing its direction (to the first valve position). The oil flows from the multi-way valve 11 through the third balance valve 17 to the first rod chamber 1a of the first-stage telescopic cylinder 1, and finally to the second rod chamber 2a of the second-stage telescopic cylinder 2. Simultaneously, the third pilot directional valve 20 is energized and reversed, allowing the pilot oil to flow through it to the control end of the directional valve 12, thus reversing its direction (to the second valve position). After the handle is moved backward, the second solenoid directional valve 6, the solenoid switch valve 28, and the second electro-proportional pilot pressure reducing valve 4 are successively energized. Pilot oil flows through the second solenoid directional valve 6, the check valve 22, the solenoid switch valve 28, the second electro-proportional pilot pressure reducing valve 4, and the second shuttle valve 10, finally flowing to the control end of the second balance valve 19 and the control end of the second hydraulic control switch valve 8, causing them to switch directions. Part of the oil is stored in the accumulator 23 for the switching of the second balance valve 19. At the same time, the second hydraulic control switch valve 8 switches and cuts off the oil circuit from the second solenoid directional valve 6 to the second shuttle valve 10. After the second balance valve 19 switches directions, the oil in the second rodless chamber 2b of the second-stage telescopic cylinder 2 flows through the second balance valve 19 to the core tube in the first-stage telescopic cylinder 1, and finally flows back to the oil tank 29 through the directional valve 12 and the multi-way valve 11. In maintenance mode, when it is necessary to replace components such as accumulator 23, electrically controlled switching valve 28, or check valve 22, ball valve 27 opens to release the high-pressure oil in accumulator 23. When the pressure in accumulator 23 exceeds the set value, it overflows through the second relief valve 26. The pressure in accumulator 23 is constantly monitored by pressure sensor 24.

[0032] Emergency mode arm retraction movements (sections 3, 4, and 5): When the handle moves backward, if the cable reel is damaged or the controller malfunctions, the telescopic system is in emergency mode. The second electro-proportional pilot pressure reducing valve 4 on the secondary telescopic cylinder 2 cannot receive signals and therefore cannot perform a reversing action. In emergency mode, the oil inlet to the second rod chamber 2a of the secondary telescopic cylinder 2 remains unchanged. However, because the second solenoid directional valve 6 and the solenoid switch valve 28 cannot be reversed, the pilot oil flows directly through the second solenoid directional valve 6, the second hydraulic switch valve 8, and the second shuttle valve 10 to the control end of the second balance valve 19 of the secondary telescopic cylinder 2, causing it to reverse. After the second balance valve 19 of the secondary telescopic cylinder 2 reverses, the oil in the second rodless chamber 2b of the secondary telescopic cylinder 2 flows through the second balance valve 19 to the core tube in the primary telescopic cylinder 1, and finally flows back to the oil tank 29 through the directional valve 12 and the multi-way valve 11.

[0033] Normal mode two-segment arm retraction motion: After pressing the two-section arm switch and receiving a signal that the handle is in the backward position, the first pilot directional valve 14 is energized, and the pilot oil flows to the control end of the multi-way valve 11, causing it to switch (to the first valve position). The oil flows from the multi-way valve 11 to the first rod chamber 1a of the first-stage telescopic cylinder 1. The first solenoid directional valve 5 and the first electro-proportional pilot pressure reducing valve 3 are energized, and the pilot oil flows through the first solenoid directional valve 5, the first electro-proportional pilot pressure reducing valve 3, and the first shuttle valve 9 to the control end of the first balance valve 18 of the first-stage telescopic cylinder 1, causing it to switch. Simultaneously, the pilot oil flows through the first solenoid directional valve 5 and the first electro-proportional pilot pressure reducing valve 3 to the control end of the first hydraulic control valve 7, causing it to switch, thus cutting off the passage from the first solenoid directional valve 5 to the first shuttle valve 9. After the first balance valve 18 of the first-stage telescopic cylinder 1 switches, the oil in the rodless chamber of the first-stage telescopic cylinder 1 flows to the oil tank 29 through the first balance valve 18, the directional valve 12, and the multi-way valve 11.

[0034] Emergency mode two-section arm retraction action: When the handle is moved backward, in emergency mode, the first electro-proportional pilot pressure reducing valve 3 on the first-stage telescopic cylinder 1 cannot receive signals and therefore cannot perform a reversing action. In emergency mode, the oil inlet to the first rod chamber 1a of the first-stage telescopic cylinder 1 remains unchanged. However, since the first solenoid directional valve 5 and the first hydraulic control valve 7 cannot be reversed, the pilot oil can directly flow through the first solenoid directional valve 5 and the first hydraulic control valve 7 (i.e., the first shuttle valve 9) to the control end of the first balance valve 18 of the first-stage telescopic cylinder 1, causing it to reverse. After the first balance valve 18 of the first-stage telescopic cylinder 1 reverses, the oil in the first rodless chamber 1b of the first-stage telescopic cylinder 1 flows to the oil tank 29 after passing through the first balance valve 18, the directional valve 12, and the multi-way valve 11.

[0035] Arm extension control Extend the third, fourth, and fifth arm segments: After the controller receives the signal for the handle to move forward, the second pilot directional valve 15 is energized. Pilot oil flows through the second pilot directional valve 15 to the control end of the multi-way valve 11 and the control end of the third balance valve 17, causing them to switch (to the second valve position). At the same time, the third balance valve 17 opens. After the multi-way valve 11 switches, the oil in the second rod chamber 2a of the secondary telescopic cylinder 2 flows to the first rod chamber 1a of the primary telescopic cylinder 1, and returns to the oil tank 29 through the third balance valve 17 and the multi-way valve 11. After the handle moves forward, the third pilot directional valve 20 is energized and switches. Pilot oil flows through the third pilot directional valve 20 to the control end of the directional valve 12, causing it to switch. The oil is pumped out by the variable pump 13, passes through the multi-way valve 11 and the directional valve 12, flows through the core tube in the primary telescopic cylinder 1 to the second balance valve 19, and then enters the second rodless chamber 2b of the secondary telescopic cylinder 2, causing the third, fourth, and fifth sections of the boom to extend.

[0036] Two-section arm extended: After the two-section boom switch is pressed, the controller receives the signal from the pressed switch and the handle moving forward. The second pilot directional valve 15 is energized, and pilot oil flows through it to the control terminals of the multi-way valve 11 and the third balance valve 17, causing them to switch (to the second valve position). Simultaneously, the third balance valve 17 opens. After the multi-way valve 11 switches, the oil in the first rod chamber 1a of the first-stage telescopic cylinder 1 returns to the oil tank 29 via the third balance valve 17 and the multi-way valve 11. The oil is then pumped out by the variable pump 13, passes through the multi-way valve 11 and the directional valve 12, and flows to the first rodless chamber 1b of the first-stage telescopic cylinder 1.

[0037] During the above control process, the pressure of the core tube electro-proportional relief valve 21 is controlled according to the amplitude angle ratio to solve the problem of extension or retraction of the third, fourth, and fifth boom sections when the second boom section is retracted. Specifically: When the second-section boom retracts, the cavity inside the first-stage telescopic cylinder 1 decreases, and excess oil flows back to the oil tank 29 through the reversing valve 12 and the core tube electro-proportional relief valve 21. In common dual-cylinder rope-type telescopic systems, the second-stage telescopic cylinder 2 uses core tube oil supply, which may lead to a slight extension and retraction of the third, fourth, and fifth sections of the boom simultaneously during the second-section boom retraction. During the second-section boom retraction, if the pressure of the core tube electro-proportional relief valve 21 is too high, the third, fourth, and fifth sections of the boom may slightly extend; conversely, a slight retraction will occur. By proportionally controlling the pressure of the core tube electro-proportional relief valve 21 according to the amplitude angle signal to match the required relief pressure, the problem of slight extension or retraction of the third, fourth, and fifth sections of the boom during the second-section boom retraction can be solved.

[0038] In this embodiment, under normal mode, the opening area of ​​the balance valve is unaffected by the boom load or pressure fluctuations in the small chamber of the telescopic cylinder during boom retraction, thus solving the problem of boom retraction speed being greatly affected by load and improving the smoothness of boom retraction start-up and deceleration phases. In construction scenarios requiring high lifting efficiency, such as cable reel damage, controller malfunction, or other issues, the emergency mode can be activated. This mode improves the opening efficiency of the balance valve and reduces acceleration / deceleration time, thereby enhancing overall telescopic efficiency.

Claims

1. A hydraulic system for telescopic boom extension of a crane, characterized in that, It includes a primary telescopic cylinder, a secondary telescopic cylinder, and a control valve assembly. The primary telescopic cylinder has a first rod chamber and a first rodless chamber, and the secondary telescopic cylinder has a second rod chamber and a second rodless chamber. The first rod chamber and the second rod chamber are connected. The control valve assembly includes a first electro-proportional pilot pressure reducing valve, a second electro-proportional pilot pressure reducing valve, a first solenoid directional valve, and a second solenoid directional valve. The first rodless chamber's oil circuit is equipped with a first balancing valve. The first solenoid directional valve is controlled to direct oil from the inlet oil circuit of the first rod chamber to the first electro-proportional pilot pressure reducing valve. The first electro-proportional pilot pressure reducing valve is controlled to direct oil from the inlet oil circuit of the first rod chamber to the control terminal of the first balancing valve to proportionally control the opening of the first balancing valve. The second rodless chamber's oil circuit is equipped with a second balancing valve. The second solenoid directional valve is controlled to direct oil from the outlet oil circuit of the second rod chamber to the second electro-proportional pilot pressure reducing valve. The second electro-proportional pilot pressure reducing valve is controlled to direct oil from the outlet oil circuit of the second rod chamber to the control terminal of the second balancing valve to proportionally control the opening of the second balancing valve.

2. The crane rope-type boom telescopic hydraulic system according to claim 1, characterized in that, The control valve assembly includes a first hydraulic control valve, a second hydraulic control valve, a first shuttle valve, and a second shuttle valve. The outlet of the first electro-proportional pilot pressure reducing valve is connected to the control terminal of the first hydraulic control valve and the first inlet of the first shuttle valve. The first solenoid directional valve by default directs the oil in the inlet oil path of the first rod chamber to the first hydraulic control valve. The first hydraulic control valve by default is connected to the second inlet of the first shuttle valve, and the outlet of the first shuttle valve is connected to the control terminal of the first balance valve. The outlet of the second electro-proportional pilot pressure reducing valve is connected to the control terminal of the second hydraulic control valve and the first inlet of the second shuttle valve. The second solenoid directional valve by default directs the oil in the outlet oil path of the second rod chamber to the second hydraulic control valve. The second hydraulic control valve by default is connected to the second inlet of the second shuttle valve, and the outlet of the second shuttle valve is connected to the control terminal of the second balance valve.

3. The crane rope-type boom telescopic hydraulic system according to claim 1, characterized in that, The oil circuit of the second rodless chamber is connected to the core tube electro-proportional relief valve through the second balance valve. The relief pressure of the core tube electro-proportional relief valve is proportionally controlled by the signal of the amplitude angle.

4. The crane rope-type boom telescopic hydraulic system according to claim 1, characterized in that, An accumulator is provided in the oil line from the second solenoid directional valve to the second electro-proportional pilot pressure reducing valve.

5. The crane rope-type boom telescopic hydraulic system according to claim 4, characterized in that, The accumulator's output oil circuit is equipped with a pressure sensor and an overflow valve.

6. The crane rope-type boom telescopic hydraulic system according to claim 4, characterized in that, The accumulator's output oil circuit is equipped with a pressure relief ball valve.

7. The crane rope-type boom telescopic hydraulic system according to claim 1, characterized in that, The control valve assembly includes a multi-way valve and a directional valve. The multi-way valve has a first passage and a second passage. The first passage forms the inlet oil passage of the first rod chamber, and the second passage is connected to the directional valve. The first valve position of the multi-way valve is configured such that the first passage forms an inlet oil passage for supplying oil to the first rod chamber, and the second passage forms a return oil passage. The second valve position of the multi-way valve is configured such that the first passage forms a return oil passage for supplying oil to the first rod chamber, and the second passage forms a supply oil passage. The directional valve has a third passage and a fourth passage. The third passage forms the oil passage of the second rodless chamber, and the fourth passage forms the oil passage of the first rodless chamber. The first valve position of the directional valve is configured such that the third passage forms a return oil passage, and the fourth passage is connected to the second passage. The second valve position of the directional valve is configured such that the fourth passage forms a return oil passage, and the third passage is connected to the second passage.

8. The crane rope-type boom telescopic hydraulic system according to claim 7, characterized in that, The multi-way valve and the directional valve are hydraulically controlled valves. The control valve group includes a first pilot directional valve, a second pilot directional valve, and a third pilot directional valve. When the first pilot directional valve is activated, it controls the multi-way valve to be in the first valve position. When the second pilot directional valve is activated, it controls the multi-way valve to be in the second valve position. The third pilot directional valve controls the directional valve to switch valve positions.

9. The crane rope-type boom telescopic hydraulic system according to claim 8, characterized in that, The first passage is equipped with a third balancing valve, and the third balancing valve is controlled to operate when the second pilot directional valve is activated.

10. A crane, characterized in that, The crane rope-type boom telescopic hydraulic system includes any one of claims 1 to 9.

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