Analysis of Hydraulic Control System of Concrete Conveying Pump Automatic Commutation (Part Ⅰ)

Concrete pump is commonly used in modern construction at home and abroad 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. 1 mechanical and hydraulic synergistic control mode Figure 1 represents the control mode of hydraulic 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 of oil through the valve 7 to promote the four-way valve 3, began to supply 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 transport 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.