Created on:2021-09-24 14:44

Construction machinery_ Construction and construction machinery_ Improvement of hydraulic system of concrete pump

Construction machinery_ Construction and construction machinery_ Improvement of hydraulic system of concrete pump

(1) Raising questions

Due to structural reasons, it is necessary to return the piston of the master cylinder first whether it is to maintain the concrete pump or replace the piston. Even if the piston rod of the master cylinder retracts into the master cylinder and enters the water washing tank, especially when it is necessary to replace the concrete pump delivery cylinder, master cylinder, piston rods, pistons and seals of two master cylinders, only one piston is returned, which is still inconvenient for maintenance, Both master cylinder pistons need to be retracted at the same time. At present, most of the newer concrete pumps have the function of returning a single master cylinder piston, but they do not have the function of returning two master cylinder pistons at the same time, which brings great inconvenience to the overhaul of the concrete pump and seriously affects the maintenance efficiency.

(2) Analysis of hydraulic working principle of concrete pump

The hydraulic system principle of hbt60c Ⅲ concrete pump is shown in Figure V (a). As can be seen from figure V (a), when the concrete pump works normally, as long as the left electromagnet of electromagnetic overflow unloading valve 6 and electromagnetic reversing valve 16 is energized and the other electromagnets are not energized, the concrete pump works under the condition of low pressure and large displacement. In this process, only valves 23, 24 and 28 of the six cartridge valves are opened and the rest are closed. As can be seen from figure V (a) and Figure w, if you want to return any cylinder of master cylinders 29 and 30 in Figure V (a) to the water washing tank, it can be realized as long as the concrete pump is in the working state and the electromagnetic iron of 26 is energized. However, if you want to return master cylinders 29 and 30 at the same time, it is impossible, because the two concrete pumps always move in the opposite direction and cannot move in the same direction, Otherwise, concrete cannot be pumped.

W.jpg

It can be seen that the above purpose can be achieved as long as the concrete pump adds a function to make the master cylinders 29 and 30 move in the same direction and at different times from the normal pumping. As can be seen from figure V (a), when only the left solenoid of electromagnetic overflow unloading valve 6 and electromagnetic directional valve 16 is energized and the other electromagnets are not energized, if valves 22, 24, 27 and 28 of the six cartridge valves are opened and the rest are closed, the pressure oil of main pump 3 in the concrete pump can reach cartridge valve 24 through the right position of hydraulic valve 8. After that, one path of hydraulic oil enters the rod cavity of master cylinder 29, and the oil without rod cavity of master cylinder 29 returns to the oil tank through valve 22 and valve 8, so as to return master cylinder 29; At the same time, the other hydraulic oil enters the rod cavity of master cylinder 30 through cartridge valve 27. The hydraulic oil without rod cavity of master cylinder 30 passes through valve 28, then returns to hydraulic valve 8 through valve 22, and finally returns to the oil tank to complete the return of master cylinder 30, so as to realize double cylinder return. At this time, as long as the solenoid iron of the electromagnetic directional valve 26 is energized, the two master cylinders 29 and 30 can be retreated to the water washing tank at the same time to meet the maintenance requirements.

V.jpg

(3) Improvement scheme

Based on the above analysis and consideration of cost reduction and easy realization, the method of improving the control oil circuit of the high and low pressure reversing system of the concrete pump is adopted. The schematic diagram of the main hydraulic system of the improved concrete pump is shown in Figure V (b). When the concrete pump is pumping normally, follow the oil circuit shown in Figure V (a). If you want to return the master cylinders 29 and 30 at the same time, just disconnect the original control signals of cartridge valves 22, 23 and 27, change the control signal of cartridge valve 22 to ef oil pressure, change the control signal of valve 27 to CD oil pressure, change the control signal of valve 23 to ab oil pressure, and the rest remains unchanged, that is, as shown in Figure V (b). Therefore, when it is necessary to return the master cylinders 29 and 30 at the same time, first remove the valve covers of cartridge valves 22, 23 and 27 and replace them with the pre modified cartridge valve covers. The specific operations are as follows.

During the reconstruction, block the X oil ports of three valve covers with the same model as the cartridge valve cover on the concrete pump, remove the plug y on its side (see figure x), install the reconstructed valve covers one by one with the four mounting screws that remove the valve cover, then connect the Y ports of cartridge valves 22 and 27 to the oil tank with the prepared oil pipe, and connect the Y port of cartridge valve 23 to the control oil, This control oil can be supplied by the constant pressure pump 2 shown in Figure V (a). Incidentally, when manufacturing the concrete pump, as long as the pressure control oil passage and return oil passage are drilled on the hydraulic manifold of the concrete pump where the cartridge valves 22, 23 and 27 are located at the same time, and the valve cover is improved so that the X port is connected with the control oil passage and isolated from the return oil port in one installation direction. When it is installed by rotating 90 ° or 180 °, If port x is connected to the oil return passage and isolated from the control pressure oil passage, when the main pump of the concrete pump is returned at the same time, it can be realized as long as the installation direction of the valve covers of cartridge valves 22, 23 and 27 is changed, which greatly simplifies the maintenance work and reduces the maintenance cost.

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