A method and system for protecting the differential lifting cylinder of a front crane from cracks

Abstract

The present invention provides a method and system for crack protection of a reach stacker's differential lift cylinder. The method comprises the following steps: when operating in a differential mode, with P1 = P2, determining the maximum safe operating pressure of the lift cylinder's rod chamber, monitoring the boom extension length, determining the boom extension length corresponding to the maximum safe operating pressure of the lift cylinder's rod chamber as the maximum boom extension length based on the relationship between the boom extension length and the pressure in the lift cylinder's rodless chamber, and canceling the differential mode and restoring normal operating conditions when the boom extension length approaches the maximum boom extension length. The system implements the method. Using the method of the present invention, the reach stacker's differential lift cylinder's rod chamber cylinder body will no longer crack.

Description

Technical Field

[0001] The invention relates to a crack protection method and a protection system for a differential lifting oil cylinder of a front loader. Background Art

[0002] To stack, retrieve, load, and unload containers, a reach stacker requires the lifting cylinder to rise and lower, and the telescopic boom to extend and retract. The lifting cylinder requires significant oil pressure to achieve this, and when the boom is extended, the lever action multiplies the oil pressure.

[0003] The oil outlet at the upper end of the rod cavity of the front lifting cylinder was welded, and welds and cracks appeared on the welding part, causing the cylinder to be scrapped.

[0004] The normal lifting principle of the reach stacker is as follows Figure 1 As shown: Pressurized oil P enters from VA and, through the pressure of VA (dashed line), turns the lifting valve K1 to the left, allowing the pressurized oil to pass through the valve and reach the C+ position. Then, it enters the rodless chamber T1 of the lifting cylinder, pushing the piston upward (the piston is connected to the piston rod, supporting the boom and the load). The pressurized oil in the rod chamber T2 of the lifting cylinder exits through the welded oil pipe at the oil outlet at the top end of the cylinder barrel, reaches the C- port downward, and then reaches the lowering valve K2. The lowering valve oil pressure (dashed line) turns the valve to the right, allowing the lowering oil to pass through the valve body to the T position and then return to the tank.

[0005] At this point, the oil pressure in the rodless chamber T1 is high (the greater the load, the higher the oil pressure), and the piston rod supporting the load needs to be lifted upward. The pressure in the rod chamber T2 is low, so simply open the rightmost valve that controls the oil return (down valve K2).

[0006] The principle is the same as normal lifting, but in the opposite direction. Due to the self-generated gravity of the load, the hydraulic oil pressure in the lifting bar chamber T2 and the rodless chamber T1 is very low.

[0007] When the reach stacker is in three working conditions: empty, 20-foot empty container, and 40-foot empty container, the lifting system is designed with a differential system. Figure 2 As shown, the differential control solenoid valve K3 activates, redirecting the hydraulic flow (see red arrow in the red line) so that the hydraulic oil in the rod chamber T2 returns from the tank to the cylinder's oil inlet (the rodless chamber). This increases lifting flow, speeds up lifting, and improves operating efficiency. While this efficiency is enhanced, the hydraulic pressure in the rodless chamber, a characteristic of hydraulics, suddenly increases from its original low level (only requiring about 25 bar of valve opening) to equal the oil inlet pressure due to the interconnected hydraulic inlet and return ports. When this pressure exceeds the weld's tolerance, the weld cracks, which then propagate to the cylinder body, rendering the cylinder useless.

[0008] During differential operation, the pressure at the oil outlet is often greater than the pressure in the rodless chamber P1 during normal lifting. The oil outlet welding reduces the weld's ability to withstand pressure. When P1 exceeds the weld's ability to withstand pressure, the weld cracks, and eventually the cylinder body cracks, causing the cylinder to become scrapped. Summary of the Invention

[0009] The present invention provides a method for protecting the differential lifting cylinder of a front crane from cracks, aiming at the problem that the lifting cylinder body of the front crane may crack and become scrapped due to the increase in oil outlet pressure when the lifting cylinder of the front crane is in differential working condition. The method can prevent the lifting cylinder body from cracking.

[0010] The technical solution of the present invention is: a method for protecting a differential lifting cylinder of a front loader from cracks, comprising the following steps:

[0011] Step 1: In differential working condition, P1=P2, determine the following mechanical model:

[0012]

[0013] Where:

[0014] α is the angle between the lifting cylinder and the ground;

[0015] L1 is the extended length of the upper arm;

[0016] L2 is the total length of the upper arm;

[0017] P1 is the rodless chamber pressure of the lifting cylinder;

[0018] S1 is the rodless piston area of ​​the lifting cylinder;

[0019] P2 is the rod chamber pressure of the lifting cylinder;

[0020] S2 is the piston area of ​​the rod chamber of the lifting cylinder;

[0021] β is the angle between the boom telescopic cylinder and the ground;

[0022] G is the weight of the container;

[0023] Step 2: Determine the maximum safe working pressure of the rod chamber of the lifting cylinder, monitor the extension length of the boom, and based on the relationship between the extension length of the boom and the pressure of the rodless chamber of the lifting cylinder, determine that the extension length of the boom corresponding to the maximum safe working pressure of the rod chamber of the lifting cylinder is the maximum extension length of the boom. When the extension length of the boom is close to the maximum extension length of the boom, cancel the differential working condition and restore the normal working condition.

[0024] Furthermore, in the above-mentioned front loaders differential lifting cylinder crack protection method: in the above-mentioned step 2, a telescopic arm length sensor and an angle sensor with a CANOPEN function are additionally installed to measure the boom extension length L1, the angle α between the lifting cylinder and the ground, and the angle β between the boom telescopic cylinder and the ground in real time;

[0025] The data of the telescopic arm length sensor and angle sensor are transmitted to the controller of the reach stacker.

[0026] Furthermore, the above-mentioned method for protecting the differential lifting cylinder of a front crane from cracks also includes the step of repairing cracks in the oil outlet of the rodless cavity of the lifting cylinder. In this step, the oil outlet at the upper end of the rod cavity of the front crane lifting cylinder is welded, and welds and cracks in the welding part appear.

[0027] Furthermore, the above-mentioned method for crack protection of the differential lifting cylinder of a front loader also includes the step of determining the maximum safe working pressure of the rod cavity of the lifting cylinder by testing the pressure resistance of the welded cylinder.

[0028] Furthermore, in the above-mentioned crack protection method for the differential lifting cylinder of the front loader: the maximum safe working pressure of the rod chamber of the lifting cylinder is 100 BAR.

[0029] The present invention also provides a front loaders differential lifting oil cylinder crack protection system, which exits the differential working condition when the rod chamber of the lifting oil cylinder approaches the maximum safe working pressure in the front loaders differential working condition; the system comprises: a telescopic arm length sensor and an angle sensor with a CANOPEN function, and an intelligent controller; the intelligent controller calculates according to the following formula

[0030]

[0031] Where:

[0032] α is the angle between the lifting cylinder and the ground;

[0033] L1 is the extended length of the upper arm;

[0034] L2 is the total length of the upper arm;

[0035] S1 is the rodless piston area of ​​the lifting cylinder;

[0036] P2 is the rod chamber pressure of the lifting cylinder;

[0037] S2 is the piston area of ​​the rod chamber of the lifting cylinder;

[0038] β is the angle between the boom telescopic cylinder and the ground;

[0039] G is the weight of the container.

[0040] By adopting the method of the present invention, the rod cavity cylinder body of the differential lifting oil cylinder of the front loader will no longer crack.

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Attachment Figure 1 This is the hydraulic principle diagram of the normal lifting system of the reach stacker;

[0043] Attachment Figure 2 This is the hydraulic system diagram for the differential lifting of the reach stacker;

[0044] Attachment Figure 3 It is the mechanical model of the reach stacker. DETAILED DESCRIPTION

[0045] In Example 1, the reach stacker's differential lift cylinder consists of a cylinder barrel, a piston and piston rod, and a cylinder barrel end cap, forming a pressure-tight chamber. The piston and piston rod divide the cylinder barrel into a rod chamber (T2) (with a piston rod) and a rodless chamber (T1) (without a piston rod). Excessive oil pressure in the cylinder barrel can cause cracks.

[0046] This embodiment is a method for protecting a differential lifting cylinder of a reach stacker from cracks, comprising the following steps:

[0047] Step 1: In differential working condition, P1=P2, determine the following mechanical model: Figure 3 As shown:

[0048] F×sin(α)×L1=(P1×S1-P2×S2)×sin(α)×L1=G×L2×cos(β)

[0049] Normal lifting: P2 = 25 (BAR), that is, the oil outlet pressure of the rod chamber;

[0050]

[0051] When differential: P2 = P1;

[0052] It can be seen that the oil outlet pressure P2 not only increases from zero to P2, but also increases significantly due to the reduction of the force area (S1-S2). When the boom cylinder is extended, due to the lengthening of L2 and the effect of the lever, P2 will also increase significantly.

[0053]

[0054] Where:

[0055] α is the angle between the lifting cylinder and the ground;

[0056] L1 is the extended length of the upper arm;

[0057] L2 is the total length of the upper arm;

[0058] P1 is the rodless chamber pressure of the lifting cylinder;

[0059] S1 is the rodless piston area of ​​the lifting cylinder;

[0060] P2 is the rod chamber pressure of the lifting cylinder;

[0061] S2 is the piston area of ​​the rod chamber of the lifting cylinder;

[0062] β is the angle between the boom telescopic cylinder and the ground;

[0063] G is the weight of the container.

[0064] Step 2: Determine the maximum safe working pressure of the rod chamber of the lifting cylinder, monitor the extension length of the boom, and based on the relationship between the extension length of the boom and the pressure of the rodless chamber of the lifting cylinder, determine that the extension length of the boom corresponding to the maximum safe working pressure of the rod chamber of the lifting cylinder is the maximum extension length of the boom. When the extension length of the boom is close to the maximum extension length of the boom, cancel the differential working condition and restore the normal working condition.

[0065] It can be seen that the pressure P2 of the rod chamber of the lifting cylinder not only increases from zero to the pressure P1 of the rodless chamber of the lifting cylinder, but also increases significantly due to the reduction of the force area (S1-S2) in the two chambers. When the boom cylinder is extended, due to the lengthening of L2 and the effect of the lever, P2 will also increase significantly.

[0066] During differential operation, the pressure at the oil outlet is often greater than the pressure in the rodless chamber P1 during normal lifting. The oil outlet welding reduces the weld's ability to withstand pressure. When P1 exceeds the weld's ability to withstand pressure, the weld cracks, and eventually the cylinder body cracks, causing the cylinder to become scrapped.

[0067] In this embodiment, a telescopic arm length sensor and an angle sensor with a CANOPEN function are also installed to measure the arm extension length L1, the angle α between the lifting cylinder and the ground, and the angle β between the arm telescopic cylinder and the ground in real time;

[0068] The data of the telescopic arm length sensor and angle sensor are transmitted to the controller of the reach stacker.

[0069] According to tests, the hydraulic pressure at the oil outlet jumps from near zero to a certain high pressure during differential operation. However, when the boom is extended or the load reaches a certain level, the hydraulic pressure continues to rise, even exceeding the normal range of the weld. Therefore, it is necessary to clearly understand the relationship between the horizontal extension position of the telescopic boom and the oil outlet pressure (P2) when the lifting load is constant (i.e., under a certain differential operating condition). The relationship between the boom extension length and P2 was tested under three operating conditions.

[0070] In this embodiment, a maximum pressure limit for P2 is established. When P2 exceeds the limit, the differential function is canceled, and the pressure at P2 port returns to the normal lifting pressure state (approximately 25 bar). This maximizes the differential function, ensures efficient operation of the equipment, and protects the hydraulic cylinder from cracks and losses.

[0071] Specifically, in this embodiment:

[0072] First, we developed a comprehensive welding repair process to repair the cylinder and ensure that the safe working pressure of the rod cavity (weld end) of the hydraulic cylinder is less than or equal to 100 bar.

[0073] The CANOPEN length and angle sensor is then used to measure the angle and length of the telescopic arm, transmit the data to the controller, and then calculate the horizontal length of the telescopic arm.

[0074] Finally, three differential working conditions are determined by the rack signal: A, empty rack working condition; B, 20-foot empty container working condition; C, 40-foot empty container working condition; D, full container working condition (A / B / C working conditions have differential functions).

[0075]

[0076] Based on the test results: optimize the differential working conditions, transform the pressure relationship of the three working conditions into the length relationship of the corresponding telescopic arm extension, so that when the three working conditions are working differentially, the P2 port pressure is less than or equal to 100BAR, ensuring that the cylinder works at a safe pressure.

Claims

1. A method for protecting a differential lifting cylinder of a reach stacker from cracks, characterized by: The following steps are involved: Step 1: In differential working condition, P1=P2, determine the following mechanical model: Where: α is the angle between the lifting cylinder and the ground; L1 is the extended length of the upper arm; L2 is the total length of the upper arm; P1 is the rodless chamber pressure of the lifting cylinder; S1 is the rodless piston area of ​​the lifting cylinder; P2 is the rod chamber pressure of the lifting cylinder; S2 is the piston area of ​​the rod chamber of the lifting cylinder; β is the angle between the boom telescopic cylinder and the ground; G is the weight of the container; Step 2: Determine the maximum safe working pressure of the rod chamber of the lifting cylinder, monitor the extension length of the boom, and based on the relationship between the extension length of the boom and the pressure of the rodless chamber of the lifting cylinder, determine that the extension length of the boom corresponding to the maximum safe working pressure of the rod chamber of the lifting cylinder is the maximum extension length of the boom. When the extension length of the boom is close to the maximum extension length of the boom, cancel the differential working condition and restore the normal working condition.

2. The method for protecting the differential lifting cylinder of a reach stacker from cracks according to claim 1, characterized in that: In step 2, a telescopic arm length sensor and an angle sensor with a CANOPEN function are also installed to measure the arm extension length L1, the angle α between the lifting cylinder and the ground, and the angle β between the arm telescopic cylinder and the ground in real time; The data of the telescopic arm length sensor and angle sensor are transmitted to the controller of the reach stacker.

3. The method for protecting the differential lifting cylinder of a reach stacker from cracks according to claim 1, characterized in that: It also includes the step of repairing cracks in the oil outlet of the rodless cavity of the lifting cylinder. In this step, the oil outlet at the upper end of the rod cavity of the front lifting cylinder is welded, and welds and cracks appear at the welding points.

4. The method for protecting the differential lifting cylinder of a reach stacker from cracks according to claim 3, characterized in that: It also includes the steps of determining the maximum safe working pressure of the rod chamber of the lifting cylinder by testing the pressure resistance of the welding repair cylinder.

5. The method for protecting a differential lifting cylinder of a reach stacker from cracks according to claim 1, 2, 3 or 4, wherein: The maximum safe working pressure of the rod chamber of the lifting cylinder is 100BAR.

6. A crack protection system for differential lifting cylinders of a reach stacker, characterized by: In the differential working condition of the front loader, when the rod chamber of the lifting cylinder approaches the maximum safe working pressure, the differential working condition is exited; including: installing a telescopic arm length sensor and angle sensor with CANOPEN function and an intelligent controller; the intelligent controller calculates according to the following formula Where: α is the angle between the lifting cylinder and the ground; L1 is the extended length of the upper arm; L2 is the total length of the upper arm; S1 is the rodless piston area of ​​the lifting cylinder; P2 is the rod chamber pressure of the lifting cylinder; S2 is the piston area of ​​the rod chamber of the lifting cylinder; β is the angle between the boom telescopic cylinder and the ground; G is the weight of the container.

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