Pressurizing loop for pushing jack of end hydraulic support

Abstract

An end hydraulic support advancing jack pressurizing loop belongs to the technical field of hydraulic pressure and is provided with two electro-hydraulic reversing valve groups, and each electro-hydraulic reversing valve group is provided with two two-position three-way reversing valves. And the first two-position three-way reversing valve is connected with a first one-way sequence valve and a second one-way lock through a liquid path. The second one-way lock is connected with the first one-way lock and a piston rod cavity of the pushing jack through a liquid path. And a piston cavity liquid path of the advancing jack and the second one-way lock are jointly connected with the second two-position three-way reversing valve. The first one-way sequence valve is connected with a piston cavity of the pressurizing jack and a right side lock pressure cavity of the two-way lock through a liquid path. A piston rod cavity of the pressurizing jack is connected with a left side locking pressure cavity of the two-way lock and the second one-way sequence valve through a liquid path. The second one-way sequence valve is in liquid path connection with the first one-way lock. And liquid is supplied to the two stand columns. The pressurization loop is compact and reasonable in pipeline layout, convenient to overhaul and maintain and low in failure rate. The invested transformation cost is low, the income economic benefit is high, and the safety is higher.

Description

Technical Field

[0001] The utility model belongs to the field of hydraulic technology, in particular to a pressure-increasing circuit of a terminal hydraulic support pushing jack. Background Art

[0002] After many years of use in Tiefa Energy Company, the coal planer has good safety performance, high block rate, high heat generation, high degree of automation and good use effect. However, with the increase of service years, some functions can no longer meet the requirements of high-yield and high-efficiency development of coal mines. For example, the end hydraulic support is a supporting equipment matched with the middle support of the working face. It mainly supports the top plate at the end of the working face to ensure the smooth flow of the upper and lower exits of the working face and sufficient ventilation section. It overlaps with the scraper conveyor of the working face to provide thrust for the forward movement of the scraper conveyor and the transfer machine, which is an important guarantee for the normal production of the working face. Under normal circumstances, the push jack can push the scraper conveyor and the transfer machine forward, but due to the uneven floor under the machine body, there are many rocks, and the coal wall of the head section of the working face is hard, etc., the push resistance increases. When the ZT6200 / 18 / 32 end hydraulic support is used in the W3-1501 working face of Xiaoqing Mine, the thrust of the push jack is insufficient, and three single pillars 25 are required to assist in pushing. Not only is it time-consuming, labor-intensive and inefficient, but each single pillar weighs about 150 pounds and sometimes shifts, falls over or even bounces up, posing a great safety hazard to workers and seriously affecting the normal advance of the working face. Therefore, the hydraulic circuit of the push jack needs to be improved to meet the needs of the development of automatic control of the coal-cutting working face. Utility Model Content

[0003] Aiming at the problem of insufficient thrust of the pushing jack of the hydraulic support at the end of the coal planing working face, the utility model designs a new boost control circuit, improves the thrust of the pushing jack, and improves the working efficiency and safe operability of the hydraulic support at the end.

[0004] The technical solution adopted is:

[0005] The end hydraulic support push jack booster circuit includes a first electro-hydraulic reversing valve group and a second electro-hydraulic reversing valve group, wherein the first electro-hydraulic reversing valve group includes a first two-position three-way reversing valve and a second two-position three-way reversing valve. The second electro-hydraulic reversing valve group includes a third two-position three-way reversing valve and a first two-position three-way reversing valve.

[0006] The first two-position three-way reversing valve fluid path is connected to the first one-way sequence valve and the second one-way lock.

[0007] The second one-way lock fluid path connects the first one-way lock and the piston rod chamber of the push jack.

[0008] The piston chamber fluid path of the push jack and the second one-way lock are connected to the second two-position three-way reversing valve.

[0009] The first one-way sequence valve fluid path connects the piston chamber of the booster jack and the right side lock pressure chamber of the two-way lock. The right side lock pressure chamber liquid return port of the two-way lock is used for liquid return.

[0010] The piston rod chamber fluid path of the booster jack is connected to the left lock pressure chamber of the two-way lock and the second one-way sequence valve.

[0011] The second one-way sequence valve fluid path is connected to the first one-way lock.

[0012] The third two-position three-way reversing valve fluid path connects the left lock pressure chamber of the two-way lock and the piston chambers of the two columns.

[0013] The fourth two-position three-way reversing valve has a fluid path connecting the piston rod chambers of the two columns.

[0014] Its advantages are:

[0015] Through careful analysis of the problem of insufficient thrust of the push jack, careful calculation and bold design, new ideas are provided for coal mine users in dealing with hydraulic failure problems.

[0016] The designed fluid circuit meets the requirements for on-site use in coal mines, is simple and practical, and is suitable for the use of automated hydraulic supports.

[0017] Reasonable use is made of the narrow space inside the end hydraulic support to ensure the normal operation of the booster system without affecting the normal work and maintenance space under the support.

[0018] The boost circuit piping layout is compact and reasonable, easy to inspect and maintain, and has a low failure rate.

[0019] The investment in transformation is low and the economic benefits of generating income are high.

[0020] The hydraulic system realizes fully automated operation, reduces the risk of personnel entering under the frame, has high safety performance, and improves work efficiency.

[0021] With the continuous application of mechanized, automated and intelligent coal mining technologies, we can solve and transform unreasonable designs in actual work, ensure efficient production of equipment, meet usage requirements, improve labor productivity, reduce employee labor intensity, improve harsh working environments, and reduce the rate of personal accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the end hydraulic support.

[0023] Figure 2 Schematic diagram of the trigonometric functions of the push jack and the long push frame.

[0024] Figure 3 This is the original hydraulic control diagram of the push jack.

[0025] Figure 4This is the working principle diagram of the boost system.

[0026] Figure 5 This is the hydraulic circuit diagram of the utility model.

[0027] Figure 6 This is a schematic diagram of the booster jack installation position.

[0028] Scraper conveyor base 1, long pushing frame 2, base gantry 3, pushing jack 4, base 5, original one-way lock 6, original electro-hydraulic reversing valve group 7, booster jack 8, one-way sequence valve 9.

[0029] The column 10 , the first one-way sequence valve 11 , the second one-way sequence valve 12 , the first one-way lock 13 , the second one-way lock 14 , the two-way lock 15 , the first electro-hydraulic reversing valve group 16 , and the second electro-hydraulic reversing valve group 17 .

[0030] A first two-position three-way directional valve 18 , a second two-position three-way directional valve 19 , a third two-position three-way directional valve 20 , and a fourth two-position three-way directional valve 21 .

[0031] Bottom support plate 22 , booster jack seat 23 , front connecting rod 24 , and single body support 25 . DETAILED DESCRIPTION

[0032] 1. The end hydraulic support is a supporting and shielding hydraulic support. Its push jack 4 is installed on the gantry on the base 5. It is inverted and used with a long push frame. Figure 1 As shown:

[0033] A base gantry 3 is arranged on the base 5, a cylinder of a push jack 4 is hinged on the base gantry 3, a piston rod of the push jack 4 is hinged on the right end of a long push frame 2, and a left end of the long push frame 2 is connected to the scraper conveyor base 1 and the transfer machine.

[0034] When pushing the scraper conveyor, the piston rod of the push jack 4 retracts to drive the long push frame 2 to extend to the left (front). When pulling the frame, the piston rod of the push jack 4 extends to push the long push frame 2 to the right, thereby driving the scraper conveyor base 1 to move in the reverse direction to pull the frame. Since the push jack 4 and the long push frame 2 are inverted, the thrust is small when pushing the scraper conveyor to the left, and the pulling force is large when pulling the frame to the right, and there is a certain angle between the push jack 4 and the long push frame 2, which is 10°.

[0035] The inner diameter of the piston chamber of the push jack 4 is D = 200mm, the diameter of the piston rod of the push jack 4 is d = 130mm, and the hydraulic pressure of the pump station is P = 31.5MPa. The thrust of the push jack 4 on the long push frame 2 is calculated according to the cosine function in the trigonometric function, as follows: Figure 2AB is the push jack 4, AC is the long push frame 2, ∠A=10 0 , calculate the thrust F of AC.

[0036] Then, F = 40·(D 2 -d 2 )·P·cos10 0

[0037] =(W / 40)×(20 2 -13 2 )×31.5×cos10 0

[0038] =560KN

[0039] 2. The original hydraulic control circuit of the end hydraulic support push jack 4 is analyzed below. Figure 3 As shown:

[0040] When the first two-position three-way reversing valve of the original electro-hydraulic reversing valve group 7 is placed in the left position, the high-pressure liquid pushes open the original one-way lock 6 and supplies liquid to the piston rod chamber of the push jack 4. The piston rod of the push jack 4 retracts to the left, and the liquid returns from the piston chamber of the push jack 4, while driving the long push frame 2 to push the scraper conveyor to the left.

[0041] When the second two-position three-way control valve of the original electro-hydraulic reversing valve group 7 is placed in the right position, the high-pressure liquid opens the original one-way lock 6 and supplies liquid to the piston chamber of the push jack 4. At the same time, the high-pressure liquid in the piston rod chamber of the push jack 4 returns after passing through the original one-way lock 6, and the piston rod of the push jack 4 extends out, driving the long push frame 2 to pull the frame.

[0042] The push jack 4 of the end hydraulic support provides thrust for the scraper conveyor and the transfer machine to move forward. The weight of the transfer machine is 130T, and the weight of the head of the scraper conveyor is 20T. There are three groups of end hydraulic supports, and the total thrust generated is F=560×3=1680KN. 1680KN is about 168T. The overall thrust of the three groups of end hydraulic supports is 168T>130T+20T. Under normal circumstances, the scraper conveyor and the transfer machine can be pushed forward. However, due to the uneven floor under the transfer machine body with many rocks and the hard rock of the coal wall in the head section of the working face, the push resistance increases. Through analysis, it can be seen that the push jack 4 of the ZT6200 / 18 / 32 end hydraulic support does have the problem of insufficient thrust.

[0043] Problem Solved:

[0044] According to the above situation, it is decided to redesign a boost control circuit to increase the thrust of the push jack 4. First, the working principle of the boost system is explained. Figure 4 As shown:

[0045] The booster jack 8 is also called a supercharger. It does not act as a hydraulic actuator, but rather increases the pressure of the liquid. The low-pressure liquid is input into the piston chamber of the booster jack 8, and the output thrust is F1 = 40·D. 2 ·P1, because there is a one-way sequence valve 9 (as an external load and also as a pressure switch) behind the piston rod chamber of the booster jack 8, the piston rod chamber of the booster jack 8 cannot return liquid, and the piston rod of the booster jack 8 cannot extend to the left. As the pressure P1 gradually increases, the thrust F1 continues to increase. When the pressure P2 acting on the inner chamber of the piston rod of the booster jack 8 reaches the opening pressure of the one-way sequence valve 9 (external load), the liquid pressure in the piston rod chamber of the booster jack 8 is P2, and the liquid returns through the one-way sequence valve 9, and the piston rod of the booster jack 8 extends to the left. At this time, the thrust F2 acting on the piston rod chamber of the booster jack 8 = F1. The two-chamber thrust balance equation of the booster jack 8 is:

[0046] F2 = 40·(D 2 -d 2 )·P2

[0047] Wu / 40·D 2 ·P1=W / 40·(D 2 -d 2 )·P2

[0048] D 2 ·P1=(D 2 -d 2 )·P2

[0049] Where P1 is the input pressure of the booster jack 8

[0050] P2 is the output pressure of the booster jack 8

[0051] D is the piston diameter of the booster jack 8

[0052] d is the piston rod diameter of the booster jack 8

[0053] From the above analysis, it can be seen that when the boosting jack 8 is working, the thrusts at both ends are equal, and the piston chamber area of ​​the boosting jack 8 is larger than the piston rod chamber of the boosting jack 8. Therefore, when a lower-pressure liquid is input into the piston chamber of the boosting jack 8, a higher-pressure liquid will be output from the piston rod chamber of the boosting jack 8. The boosting ratio is determined by the ratio of the cross-sectional area of ​​the piston chamber of the boosting jack 8 to the cross-sectional area of ​​the piston rod chamber of the boosting jack 8.

[0054] The boost control circuit of this technical solution is as follows: Figure 5 Shown:

[0055] The end hydraulic support push jack boosting circuit includes a first electro-hydraulic reversing valve group 16, a second electro-hydraulic reversing valve group 17, two columns 10, a boosting jack 8, a push jack 4, a first one-way sequence valve 11, a second one-way sequence valve 12, a first one-way lock 13, a second one-way lock 14 and a two-way lock 15.

[0056] The first electro-hydraulic directional valve group 16 includes two two-position three-way directional valves, a first two-position three-way directional valve 18 and a second two-position three-way directional valve 19 .

[0057] The second electro-hydraulic directional valve group 17 includes two two-position three-way directional valves, a third two-position three-way directional valve 20 and a fourth two-position three-way directional valve 21 .

[0058] The first two-position three-way reversing valve 18 of the first electro-hydraulic reversing valve group 16 is connected in a hydraulic circuit to the first one-way sequence valve 11 and the second one-way lock 14 .

[0059] The second one-way lock 14 is connected by a fluid path to the first one-way lock 13 and the piston rod chamber of the push jack 4 .

[0060] The piston chamber fluid path of the push jack 4 and the second one-way lock 14 are connected together to the second two-position three-way reversing valve 19 of the first electro-hydraulic reversing valve group 16 .

[0061] The first one-way sequence valve 11 is connected in a liquid path to the piston chamber of the booster jack 8 and the right side locking pressure chamber of the two-way lock 15. The right side locking pressure chamber liquid return port of the two-way lock 15 is used for liquid return.

[0062] The piston rod chamber fluid path of the booster jack 8 is connected to the left locking pressure chamber of the two-way lock 15 and the second one-way sequence valve 12 .

[0063] The second one-way sequence valve 12 is fluidly connected to the first one-way lock 13 .

[0064] The third two-position three-way directional valve 20 of the second electro-hydraulic directional valve group 17 is connected to the left locking pressure chamber of the two-way lock 15 through a fluid path.

[0065] The fourth two-position three-way directional valve 21 of the second electro-hydraulic directional valve group 17 is connected to the piston rod chambers of the two columns 10 through a fluid path.

[0066] The third two-position three-way directional valve 20 of the second electro-hydraulic directional valve group 17 is connected to the piston chambers of the two columns 10 through a fluid path.

[0067] The working principle is:

[0068] When the two two-position three-way reversing valves of the first electro-hydraulic reversing valve group 16 of the push jack 4 are placed in the left position, one control fluid circuit is divided into two circuits, and one control fluid circuit enters before the first one-way sequence valve 11. Since the pressure of the first one-way sequence valve 11 is set to 25MPa, it is in a closed state; after the other control fluid circuit pushes the second one-way lock 14 open, it is divided into two circuits, one control fluid circuit enters the lock pressure chamber of the first one-way lock 13, and is in a closed state, and the other fluid circuit supplies fluid to the piston rod chamber of the push jack 4, the piston rod of the push jack 4 retracts, and the fluid returns from the piston chamber of the push jack 4, the push jack 4 retracts, and drives the long push frame 2 to extend to the left.

[0069] As the push resistance increases, when the control pressure rises to 25MPa, the high-pressure control liquid opens the first one-way sequence valve 11 and is divided into two liquid paths. One control liquid path goes to the right side locking pressure chamber of the two-way lock 15 and is in a closed state; the other control liquid path enters the piston chamber of the booster jack 8, and the thrust generated by the 25MPa pressure liquid is input into the piston chamber of the booster jack 8. From the thrust balance equation at both ends of the booster jack 8, it can be seen that when the liquid pressure in the piston rod chamber of the booster jack 8 reaches the set pressure of 32MPa of the second one-way sequence valve 12, the piston rod of the booster jack 8 is pushed forward. The 32MPa high-pressure liquid in the piston rod chamber of the booster jack 8 is divided into two paths, one of which enters the left side locking pressure chamber of the two-way lock 15 and is in a closed state. One high-pressure liquid opens the second one-way sequence valve 12 and enters the first one-way lock 13, pushing the first one-way lock 13 open, and the 32MPa high-pressure liquid enters the piston rod chamber of the push jack 4. Since the 32MPa pressure is greater than the pressure in the piston rod chamber of the push jack 4, the second one-way lock 14 that controls the piston rod chamber of the push jack 4 is closed, thereby continuing to supply high-pressure liquid to the piston rod chamber of the push jack 4. When the push resistance increases, the input pressure of the booster jack 8 increases, and the input pressure of the booster jack 8 to the push jack 4 also increases. The piston rod of the push jack 4 continues to retract, and the liquid returns from the piston chamber of the push jack 4, driving the long push frame 2 to continue to extend to the left until the piston rod of the push jack 4 has no working stroke. The work of the push scraper conveyor head is completed.

[0070] The two two-position three-way directional valves of the second electro-hydraulic directional valve group 17 operating the two columns 10 are placed in the right position to lower the columns.

[0071] When the two two-way three-way directional control valves of the first electro-hydraulic directional control valve group 16 for operating the push jack 4 are placed in the right position, the high-pressure control fluid is divided into two paths. One path of the control fluid enters the second one-way lock 14 to open the second one-way lock 14. The other path of the control fluid enters the piston chamber of the push jack 4 to push the piston rod of the push jack 4 to move to the right. The high-pressure fluid in the piston rod chamber of the push jack 4 returns to the first two-way three-way directional control valve 18 through the second one-way lock 14. The piston rod of the push jack 4 extends to the right, driving the long push frame 2 to complete the work of pulling the support.

[0072] Place the two-way three-way directional control valve of the second electro-hydraulic directional control valve group 17 for operating the support column 10 in the left position. The high-pressure control fluid is divided into two paths. One path supplies fluid to the piston chamber of the support column 10 to raise the support column 10. The other path of the control fluid enters the two-way lock 15. As the pressure increases, the second one-way lock 14 is opened, and at the same time, the two-way lock 15 is pushed open, dividing into two fluid paths. One path goes to the front of the second one-way sequence valve 12. Since the set pressure of the second one-way sequence valve 12 is 32 MPa and it cannot be opened, it is in the closed state. The other path supplies fluid to the piston rod chamber of the booster jack 8. The piston rod of the booster jack 8 moves to the right. Since the right one-way lock of the two-way lock 15 has been opened, the high-pressure fluid in the piston chamber of the booster jack 8 is divided into two paths to return. One path goes to the front of the first one-way sequence valve 11. Since the first one-way sequence valve 11 locks the pressure chamber and is in the closed state; the other path of the high-pressure fluid passes through the right one-way lock of the two-way lock 15 and returns from the return port of the two-way three-way directional control valve. Until the piston rod of the booster jack 8 is fully retracted, and at the same time, the piston chamber of the booster jack 8 is filled with high-pressure fluid, preparing for the next boosting work. The support column 10 has completed raising the column, completing one working cycle.

[0073] Complete one working cycle through the end hydraulic support: the pump station pressure pushes the head of the scraper conveyor and the transfer machine, the booster jack 8 boosts to push the head of the scraper conveyor and the transfer machine, lower the support, pull the support, raise the column while retracting the booster jack 8 and filling it with high-pressure fluid to prepare for the next boosting, and the column raising is completed.

[0074] It can be seen that the entire boosting operation process is completely automatically completed without manual assistance.

[0075] In the newly designed boosting control circuit, the booster jack 8 uses the same type and specification as the original push jack 4 to meet the requirements of boosting and capacity.

[0076] If the inner diameter of the piston chamber of the booster jack 8 is D = 200 mm and the pump station supply pressure is P = 31.5 MPa, then the thrust generated by the piston chamber of the booster jack 8:

[0077] F = π / 40 · D 2 · P

[0078] =(π / 40)×20 2×31.5

[0079] =989KN

[0080] Since the piston rod diameter of the booster jack 8 is d=110 mm, the pressure generated by the piston rod chamber of the booster jack 8 is:

[0081] F = 40·(D 2 -d 2 )·P

[0082] P = F / {(W / 40) × (D 2 -d 2 )}

[0083] P = 989 ÷ {(W / 40) × (20 2 -11 2 )}

[0084] =45MPa

[0085] The thrust of the supercharged push jack 4 on the long push frame 2 is:

[0086] F = 40·(D 2 -d 2 )·P·cos10 0

[0087] =(W / 40)×(20 2 -13 2 )×45×cos10 0

[0088] =800KN

[0089] After the push jack 4 is pressurized, the three sets of end hydraulic supports can generate a total thrust of F=800×3=2400KN. The total thrust of the original three sets of end hydraulic supports is 1680KN, and the increased thrust is: 2400-1680=720KN, which is the same as the thrust generated by the three single pillars 25, and can replace the three single pillars 25.

[0090] To ensure safe operation, the pressure-resistant values ​​of various valves used in this boost control circuit are all 50MPa, and the pressure-resistant values ​​of high-pressure hoses are all up to 70MPa.

[0091] The installation position of the boost jack 8 is as follows Figure 6 :

[0092] The base 5 is originally provided with a column 10 and a front connecting rod 24 , and a bottom support plate 22 of 1400 mm×300 mm is fixed on the base 5 between the column 10 and the front connecting rod 24 .

[0093] A booster jack seat, a one-way lock frame and a two-way lock frame are welded on the bottom support plate 22 .

[0094] Place the boost jack 8 Figure 6 The booster jack seat is installed in the direction shown. The booster jack seat is 300mm high and is supported and welded on the bottom support plate 22 with M30 steel plate, and connected to the booster jack 8 with a φ30mm cross pin. After the booster jack 8 is installed, the lowest point of the cylinder of the booster jack 8 is 200mm away from the bottom support plate.

[0095] The installation positions of the one-way lock frame and the two-way lock frame are on the base 5 in front of the piston rod of the booster jack 8.

[0096] The one-way lock frame is provided with a first one-way lock 13, a second one-way lock 14, a first one-way sequence valve 11 and a second one-way sequence valve 12, and the two-way lock frame is provided with a two-way lock 15, the highest point of which is 150 mm away from the bottom support plate.

[0097] When the booster jack 8 is working, the piston rod of the booster jack 8 can freely extend and retract on the two one-way locks, the two one-way sequence valves and the two-way lock without being disturbed by space.

[0098] The newly designed boost control circuit of the push jack 4 fundamentally solves the problem of insufficient thrust of the push jack 4 .

[0099] Application effect and economic benefits

[0100] The boost control fluid circuits of the three groups of end hydraulic support push jacks 4 of the W3-1501 working face of Xiaoqing Mine have all been improved in accordance with the above-mentioned plan. According to feedback from field tests, the effect is very ideal. The push and slide movement of each hydraulic support is normal, and there has been no shortage of thrust. The unsafe operation of using three single pillars 25 as auxiliary supports to increase thrust has been completely solved.

[0101] Labor cost saving: According to the calculation that the W3-1501 working face can be mined for 1,500 meters, the front end head push step is 0.6 meters, and the front end head needs to be pushed 2,500 times. It takes 4 employees 1.5 hours to push the front end head once. After using the booster liquid line, it takes 2 employees to work for 1 hour. The labor cost is 40 yuan per hour. After the booster liquid line is modified, the mine can save:

[0102] Before using the booster fluid circuit, 2500×4×1.5×40=600,000 yuan

[0103] After using the booster fluid circuit, 2500×2×1×40=200,000 yuan

[0104] 600,000-200,000=400,000 yuan

[0105] Material saving: Before the use of the booster fluid circuit, the W3-1501 working face front end needs to replace 25 single pillars every month. Based on 24 months of mining, the cost of each single pillar is 530 yuan, which can save the mine:

[0106] 5×24×530=63,600 yuan

[0107] Renovation cost:

[0108] Invest in 3 hydraulic cylinders, calculated at 1,500 yuan each:

[0109] 3×1500=4500 yuan

[0110] A total of 15,000 yuan was invested in 3 one-way locks, 6 one-way sequence valves, 3 two-way locks, 18 DN10 high-pressure hoses, etc.

[0111] Other expenses (including labor costs) about 1,000 yuan

[0112] The total cost is: 4500+15000+1000=20500 yuan

[0113] Creating economic value

[0114] Creating economic value = labor savings + material savings - transformation costs

[0115] =400000+63600-20500

[0116] =443,100 yuan

[0117] Safety value after transformation

[0118] After the boost control circuit is used, the end workers do not need to lift the single support 25 weighing more than 150 pounds to push the scraper conveyor head every day, which truly reduces the labor intensity of the workers. At the same time, it avoids the safety hazard of the single support leaning and popping out to injure people, thus fundamentally ensuring the personal safety of the employees.

Claims

1. A booster circuit for a hydraulic support push jack, comprising a first electro-hydraulic reversing valve group (16) and a second electro-hydraulic reversing valve group (17), wherein the first electro-hydraulic reversing valve group (16) comprises a first two-position three-way reversing valve (18) and a second two-position three-way reversing valve (19); and the second electro-hydraulic reversing valve group (17) comprises a third two-position three-way reversing valve (20) and a fourth two-position three-way reversing valve (21); characterized in that: The first two-position three-way reversing valve (18) is connected in a fluid circuit to the first one-way sequence valve (11) and the second one-way lock (14); The second one-way lock (14) has a fluid path connecting the first one-way lock (13) and the piston rod chamber of the push jack (4); The piston chamber fluid path of the push jack (4) and the second one-way lock (14) are connected to the second two-position three-way reversing valve (19); The first one-way sequence valve (11) has a fluid path connecting the piston chamber of the booster jack (8) and the right side locking pressure chamber of the two-way lock (15); the right side locking pressure chamber of the two-way lock (15) has a fluid return port for returning fluid; The piston rod chamber fluid path of the booster jack (8) is connected to the left locking pressure chamber of the two-way lock (15) and the second one-way sequence valve (12); The second one-way sequence valve (12) is fluidly connected to the first one-way lock (13); The third two-position three-way reversing valve (20) has a fluid path connecting the left locking pressure chamber of the two-way lock (15) and the piston chambers of the two columns (10); The fourth two-position three-way reversing valve (21) has a fluid path connected to the piston rod chambers of the two columns (10).

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