News

The boom telescopic and hook lifting (driven by the winch motor) of a traditional telescopic boom crane are two independent actions, respectively controlled by two control handles. When the boom is extended and retracted alone, since there is no movement in the winch and the length of the wire rope is fixed, as the boom extends or retracts, the hook will rise and fall accordingly, which may cause the hook to collide with the head of the boom or fall to the ground. For this reason, the hook lifting and lowering operations must be performed at the same time, or the two operations must be performed intermittently. The procedures are complicated and affect the operating efficiency. To this end, the hook lifting compensation technology can be used to only operate the boom to extend or contract, and the hook will automatically perform lowering and raising compensation movements at the same time (that is, the hook will lower or rise accordingly as the boom extends or contracts), so that the distance from the boom head remains unchanged, solving hidden dangers and operational problems. On the contrary, when the hook is raised and lowered alone, the boom does not move and does not affect normal operations. In addition, the function of whether to choose to perform hook compensation movement has been added to the system.

This technology is an improvement on traditional hydraulic systems. As shown in Figure 1, the traditional hydraulic system mainly includes pilot control valve, proportional control valve, telescopic cylinder, and winch motor. The pilot control valve controls the movement of the proportional control valve spool through the pilot oil circuit, thereby controlling the expansion and contraction of the telescopic cylinder and the operation of the hoisting motor. Among them, the hoisting loop and the telescopic loop are independent of each other and do not interfere with each other. After improvement, it evolved into a new hydraulic system, as shown in Figure 2. A proportional pressure reducing valve, switching solenoid valve, pressure relay were added to the new system, and the proportional control valve was improved. Instructions are as follows.

(1) To realize the automatic compensation movement of the hook, first of all, when only the telescopic coupling of the pilot control valve is operated, the telescopic cylinder and the winch must be able to move at the same time. Therefore, a set of switching solenoid valves is added to the pilot control oil line to become the pilot control valve telescopic link, which can control the telescopic control link and the winch control link of the proportional control valve at the same time. The control of the telescopic coupling of the pilot control valve and the hoisting coupling of the proportional control valve and the hoisting coupling is achieved by switching the solenoid valve. The essence is to switch whether the hook performs compensation movement. In order not to affect the normal lifting weight, a set of pressure relays are added to the oil line from the pilot control valve hoisting connection to the proportional control valve hoisting connection to control the switching of the solenoid valve to ensure that the hoisting movement is still prioritized even in the hook compensation state.

(2) The key to solving the hook compensation movement is to solve the problem of speed matching between the telescopic cylinder movement and the hoisting operation, that is, to ensure that the output of the pilot control valve can simultaneously control the pressure of the telescopic coupling of the proportional control valve and the hoisting coupling to a certain ratio. We cooperated with key domestic universities to jointly develop proportional pressure reducing valves that control pressure matching.

　(3) If the proportional control valve flow is not saturated, that is, when the required flow is greater than the flow that the hydraulic pump can provide, according to the principle of fluid dynamics, the flow will preferentially flow to the actuator with lower load pressure, while the actuator with higher load pressure will slow down or even stop moving. To this end, we adopt the internationally leading LUDV (Load Independent Flow Distribution) control technology to control the hydraulic pressure with the highest load pressure of the actuator.The swash plate of the pump also has a pressure compensation function, which is achieved through the pressure compensation located behind the main valve spool. When the flow required by the actuator is greater than the flow provided by the hydraulic pump, the system will proportionally distribute the flow provided by the hydraulic pump to each actuator instead of flowing to the actuator with a lower load pressure. To this end, the original control valve was improved to achieve this function.

The above technical problems are solved, and the choice of whether to compensate for the movement conditions of the hook can be easily realized without affecting the normal lifting weight. That is to say, it solves the original problem of two operating actions that must be performed at intervals or with both hands operating at the same time. After the improvement, just select the hook compensation switch and operate one action to control the two actions at the same time. In addition, since the distance between the hook and the head of the telescopic arm remains unchanged, the following problems are avoided: the arm head pulley may be damaged due to human negligence or poor visibility when extending the arm, or the hoisting wire rope may be too loose due to the failure to raise the hook in time when retracting the arm, causing the hoisting rope to be messed up when lifting again. Especially for medium and small tonnage cranes that are allowed to telescope or travel with load while keeping the height of the heavy object constant, the operating efficiency is greatly improved.

The boom telescopic and hook lifting (driven by the winch motor) of a traditional telescopic boom crane are two independent actions, respectively controlled by two control handles. When the boom is extended and retracted alone, since there is no movement in the winch and the length of the wire rope is fixed, as the boom extends or retracts, the hook will rise and fall accordingly, which may cause the hook to collide with the head of the boom or fall to the ground. For this reason, the hook lifting and lowering operations must be performed at the same time, or the two operations must be performed intermittently. The procedures are complicated and affect the operating efficiency. To this end, the hook lifting compensation technology can be used to only operate the boom to extend or contract, and the hook will automatically perform lowering and raising compensation movements at the same time (that is, the hook will lower or rise accordingly as the boom extends or contracts), so that the distance from the boom head remains unchanged, solving hidden dangers and operational problems. On the contrary, when the hook is raised and lowered alone, the boom does not move and does not affect normal operations. In addition, the function of whether to choose to perform hook compensation movement has been added to the system.

This technology is an improvement on traditional hydraulic systems. As shown in Figure 1, the traditional hydraulic system mainly includes pilot control valve, proportional control valve, telescopic cylinder, and winch motor. The pilot control valve controls the movement of the proportional control valve spool through the pilot oil circuit, thereby controlling the expansion and contraction of the telescopic cylinder and the operation of the hoisting motor. Among them, the hoisting loop and the telescopic loop are independent of each other and do not interfere with each other. After improvement, it evolved into a new hydraulic system, as shown in Figure 2. A proportional pressure reducing valve, switching solenoid valve, pressure relay were added to the new system, and the proportional control valve was improved. Instructions are as follows.

(1) To realize the automatic compensation movement of the hook, first of all, when only the telescopic coupling of the pilot control valve is operated, the telescopic cylinder and the winch must be able to move at the same time. Therefore, a set of switching solenoid valves is added to the pilot control oil line to become the pilot control valve telescopic link, which can control the telescopic control link and the winch control link of the proportional control valve at the same time. The control of the telescopic coupling of the pilot control valve and the hoisting coupling of the proportional control valve and the hoisting coupling is achieved by switching the solenoid valve. The essence is to switch whether the hook performs compensation movement. In order not to affect the normal lifting weight, a set of pressure relays are added to the oil line from the pilot control valve hoisting connection to the proportional control valve hoisting connection to control the switching of the solenoid valve to ensure that the hoisting movement is still prioritized even in the hook compensation state.

(2) The key to solving the hook compensation movement is to solve the problem of speed matching between the telescopic cylinder movement and the hoisting operation, that is, to ensure that the output of the pilot control valve can simultaneously control the pressure of the telescopic coupling of the proportional control valve and the hoisting coupling to a certain ratio. We cooperated with key domestic universities to jointly develop proportional pressure reducing valves that control pressure matching.

　(3) If the proportional control valve flow is not saturated, that is, when the required flow is greater than the flow that the hydraulic pump can provide, according to the principle of fluid dynamics, the flow will preferentially flow to the actuator with lower load pressure, while the actuator with higher load pressure will slow down or even stop moving. To this end, we adopt the internationally leading LUDV (Load Independent Flow Distribution) control technology to control the hydraulic pressure with the highest load pressure of the actuator.The swash plate of the pump also has a pressure compensation function, which is achieved through the pressure compensation located behind the main valve spool. When the flow required by the actuator is greater than the flow provided by the hydraulic pump, the system will proportionally distribute the flow provided by the hydraulic pump to each actuator instead of flowing to the actuator with a lower load pressure. To this end, the original control valve was improved to achieve this function.

The above technical problems are solved, and the choice of whether to compensate for the movement conditions of the hook can be easily realized without affecting the normal lifting weight. That is to say, it solves the original problem of two operating actions that must be performed at intervals or with both hands operating at the same time. After the improvement, just select the hook compensation switch and operate one action to control the two actions at the same time. In addition, since the distance between the hook and the head of the telescopic arm remains unchanged, the following problems are avoided: the arm head pulley may be damaged due to human negligence or poor visibility when extending the arm, or the hoisting wire rope may be too loose due to the failure to raise the hook in time when retracting the arm, causing the hoisting rope to be messed up when lifting again. Especially for medium and small tonnage cranes that are allowed to telescope or travel with load while keeping the height of the heavy object constant, the operating efficiency is greatly improved.