Concrete pump at home and abroad is a modern building construction commonly used in concrete pump tools. At present, the leading domestic form of concrete pump is a single-action double-row hydraulic push piston . In the concrete pumping too thin, always through a certain control, to ensure that the two hydraulic cylinders can automatically alternate work, so that concrete cylinder can alternately suction, spit concrete material, to achieve concrete pumping. In this paper, several typical typical automatic reversing control loop, the corresponding characteristics of a comparative analysis.
A mechanical hydraulic synergistic control method
Figure 1 represents the control method of liquid-control circuit diagram. When the main cylinder T2 into the oil run to the end of the stroke, the tapered surface of the piston, hit the two-valve 1 ejector rod (machine), to change direction, by damping to reduce the control of the main oil hydraulic pressure, so that four Valve 6 commutated to the upper work, and by the mechanical body drop spool lock main. Then the pressure oil into the distribution cylinder F2, pushing the distribution valve at the same time, the control oil from the distribution line through the valve 7 to promote the four-way valve 3, began to provide oil to the master cylinder T1. When the T1 push to the end of the stroke, the cone on the piston hit the top of the two-valve valve 2 to commutation, control the oil pressure in turn makes the four-way valve 6 to the lower position, and by the mechanical system down spool lock live. Similarly, the pressure oil into the distribution cylinder F1, pushing the distribution valve, the control oil from the distribution line through the valve 7 to promote the four-way valve 3, the master cylinder T2 oil, start the next cycle of concrete push.
The circuit shock of this control mode is relatively small because the impact when the master cylinder is pushed in place is relieved by the four check valves on the master cylinder. The specific process is to control the main hydraulic circuit 3-way valve for the action of the pressure oil to pass through the orifice. In this way, the four-way valve 3 lags behind the four-way valve 6, and the distribution cylinder preferentially performs the switching action in a short time (0.2-0.3 seconds) to prevent the backflow of the concrete. The main hydraulic cylinder is operated before the distribution hydraulic cylinder reaches the position (0.03 ~ 0.05s), and the main pump is shunted to supply oil, thereby reducing the impact when the distribution is sent to the place. The accumulator in the system can absorb the instantaneous peak impact in the oil circuit. This control mode reversing action is very reliable, components from external interference, but the control circuit repair is relatively complicated.
2 hydraulic control mode
This control method is based on the control of oil source and reverse delivery mode of operation is divided into manual and electric reverse delivery two.
Figure 2 shows the manual reverse control mode of liquid-control circuit diagram, when the T1 cylinder into the oil push in place, T2 cylinder also retracted to the end, T1 cylinder into the oil push in place, T2 cylinder also retracted to the end, T1 medium and high pressure oil through the valve 1.2 into the T2 cylinder, then the valve 2.1 A, B mouth there is a pressure difference, the valve 2.1 X port open, the control oil to promote four-way valve 5 for work, the pressure oil into the distribution of hydraulic cylinder F2, to promote the distribution valve in place. At the same time, the control oil from the distribution oil circuit drives the four-way valve 4 to change position and starts to supply oil to the master cylinder T2. The high pressure of the T2 rodless chamber high pressure oil passes through the damping between the B and X ports of the valve 2.1 to ensure the upper position of the valve 5 jobs. When the T2 push in place, T1 cylinder also retracted to the end. At this point, the valve 2.2 A, B port there is a pressure difference, then the valve X2 port opened, the control oil to promote the four-way valve 5 for the next bit of work, then the pressure oil into the oil distribution control circuit to promote four-way valve 4 Host work began to give main hydraulic cylinder T1, T2 rod cavity high pressure oil through the valve orifice B, B, X between the orifice to ensure that the lower valve 5 work to complete a work cycle. Followed by a complete cycle.
This control mode circuit impact is small, the distribution of circuit shock by the control mode. The specific process is as follows: the four-way valve 4 of the main oil line is reversed by the orifice, the four-way valve 4 reverses and lags behind the four-way valve 5, the distribution hydraulic cylinder preferentially performs the switching action within a short time (0.2~0.3 s) Anti-concrete backflow; and the main hydraulic cylinder in place before the allocation of hydraulic cylinder (0.03 ~ 0.05s) action, shunt the main pump fuel supply, so that the distribution valve in place to reduce the impact. The accumulator in the system can absorb the instantaneous peak impact in the main circuit, and the relief valve 7 can relieve the continuous impact. This control method reversing action is reliable, but the control circuit repair more complicated.
Figure 3 shows the reverse flow control electronic control circuit diagram of liquid-level control. The principle and the control method shown in Figure 2 similar, but the manual valve 3 and 4 in Figure 2 to electronic control.
This control loop is characterized by: automatic reversal of reliable, the main hydraulic cylinder in place after the allocation of action, the allocation of action in place, the main cylinder began to push. Commutation impact than Figure 1, Figure 2 shows the control method. However, the throttle valve 7 and the accumulator can well relieve the impact of the distribution oil passage.
3 electro-hydraulic coordinated control
Electro-hydraulic synergistic control of the more common cartridge valve with electro-hydraulic valve control.
(1) cartridge valve with electro-hydraulic commutation automatic commutation
Figure 4 shows the cartridge valve with electro-hydraulic directional control schematic diagram. After the main pump is operated, the valve 2 cuts off the main pump overflow, the solenoid valve 9 is in the left position, the valve 8 is in the left position and the cylinder F2 is in action; the right end of the solenoid valve 1 lags behind the solenoid valve 9 (0.15 ~ 0.2s). Control oil through port A of valve 1 to maintain pressure oil at port X of valve 4 and valve 6. A, B port closed, valve 3 and valve X port unloading oil, A, B port conduction, T1 cylinder retracted to the end, the collision stroke switch, so that the solenoid valve 9 is working in the right position, the valve 8 is in the right work , The cylinder F1 action in place; solenoid valve 1 lag behind the solenoid valve 9 (0.1 ~ 0.15s) have electricity. Control the right valve through the B port of the valve 3 and valve 5 X into the oil. Port A and B are closed, ports X and X of valve 4 and valve 5 are unloaded. Ports A and B are conducting, port T2 has oil in the rod chamber, and oil in the rod chamber of T1 has been pushed.
(2) electro-hydraulic valve control automatically commutation
Figure 5 shows the electro-hydraulic directional control valve schematic. After the solenoid valve B of valve 1 is energized, the main pump overflows and cuts off. Valve 3 right work F1 cylinder rodless chamber into the oil action in place; valve 2 lag valve 3 (0.1s ~ 0.15s) right work, T1 rod chamber into the oil retraction, T2 push concrete. T1 retracts to the end collision limit switch. Valve 3 right work, F2 cylinder rodless chamber into the oil action in place. Valve 2 lag valve 3 (0.1s ~ 0.15s) left bit work, T2 rod cavity into the oil retraction, T1 push concrete, in turn cycle.
4 Conclusion
Reverse control of the above control automatic transmission and reverse the opposite. Figure 3 way is to use two four-way solenoid valve to achieve. Figure 1, 2 through the manual two-way valve to achieve the commutation. The reverse transport of Figures 4 and 5 is achieved through the logical transformation of the electrical system. Currently in electro-hydraulic synergetic control, are generally used programmable logic controller PLC, used to reduce the impact of the environment on the components.
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