With the rapid development of concrete production and construction technology, some countries have gradually adopted the method of concentrated concrete mixing and commercial supply. The concrete is provided by a special concrete mixing station and then transported to various construction sites by concrete mixer trucks.
Concrete mixer structure principle
The concrete mixer truck consists of a special device for the car chassis and concrete mixing and transportation. The chassis of the concrete mixer truck produced in China mostly adopts the second-class universal chassis provided by the whole vehicle manufacturer. Its special mechanism mainly includes power take-off, front and rear brackets of the mixing drum, reducer, hydraulic system, mixing drum, operating mechanism, cleaning system and so on. The working principle: the power of the automobile chassis is taken out by the force taking device, and the variable pump of the hydraulic system is driven, the mechanical energy is converted into the hydraulic energy and transmitted to the quantitative motor, the motor drives the speed reducer, and the stirring device drives the stirring device to carry out the concrete. Stir.
(1) Power take-off device
The domestic concrete mixer truck adopts the main vehicle engine power take-off method. The function of the power take-off device is to take out the engine power by manipulating the power take-off switch, and drive the mixing drum through the hydraulic system. The stirring drum rotates forward during the feeding and transportation process to facilitate the feeding and stirring of the concrete. Reverse rotation, cutting off the power connection with the engine after the end of the work.
(2) Hydraulic system
The engine power taken out by the power take-off is converted into hydraulic energy (displacement and pressure), and then the motor output is mechanical energy (speed and torque) to power the mixing drum.
The speed of the motor output in the hydraulic system is decelerated and transmitted to the mixer drum.
(4) Operating mechanism
a. The direction of rotation of the mixing drum is controlled so that it rotates in the forward direction during feeding and transportation, and rotates in reverse when discharging.
b. Control the speed of the mixing drum.
(5) Stirring device
It consists mainly of a mixing drum and its auxiliary support components. The mixing drum is a concrete loading container. It is made of high-quality wear-resistant steel sheet. In order to automatically load and unload concrete, the inner wall is welded with special-shaped spiral blades. The concrete moves in the direction of the spiral of the blade as it rotates and is mixed and agitated during constant lifting and turning. During the feeding and transportation process, the mixing drum rotates forward and the concrete moves inward along the blades. When discharging, the mixing drum reverses and the concrete is discharged outward along the blades. The rotation of the mixing drum is ensured by a hydraulic drive.
The concrete mixer truck with a load of 3-6 cubic meters is generally driven by a car engine through a power output shaft to drive the hydraulic pump, and then the high-pressure oil pushes the hydraulic motor to drive the mixing drum. When the load is 9-12 cubic meters, it is driven by the vehicle-assisted diesel engine. The hydraulic pump drives the hydraulic motor. The blades are the main components in the agitator, and damage or severe wear can result in uneven mixing of the concrete. In addition, if the angle of the blade is not reasonable, it will cause the concrete to segregate.
(6) Cleaning system
The main function of the cleaning system is to clean the mixing drum and sometimes to dry the material during transportation. The cleaning system also cools the hydraulic system.
Concrete mixer maintenance
As a transportation vehicle, the concrete mixer truck must perform the maintenance and repair system of “regular inspection, mandatory maintenance, and condition-based repair” in accordance with the provisions of the Ministry of Communications Decree No. 13 of 1990. Under this premise, combined with the actual situation of the concrete mixer truck, maintenance and repair should be done. In terms of daily maintenance, in addition to the maintenance of the automobile engine and chassis, the concrete mixer truck must also perform the following maintenance work.
(1) Cleaning the concrete storage tank (mixing drum) and the inlet and outlet
Since concrete will solidify into hard blocks in a short time and it is corrosive to steel and paint, it is necessary to clean the concrete adhered to the concrete storage tank and the inlet and outlet after each use of the concrete storage tank. Serious work. These include:
a. Rinse the feed port with water before each charge to keep the feed port moist during filling;
b. Filling the washing water tank that is included with the vehicle with water at the same time as loading;
c. Rinse the feed port after charging, and wash the concrete remaining near the feed port;
d. After unloading at the construction site, rinse the discharge trough, and then add 30-40 L of cleaning water to the concrete storage tank; keep the concrete storage tank rotating slowly while the vehicle is returning;
e. Remember to let go of the sewage in the concrete storage tank before the next loading;
f. Thoroughly clean the concrete storage tank and the inlet and outlet around the work every day to ensure that no cement and concrete agglomerates.
As long as the above work is not carried out seriously, it will bring a lot of trouble to future work.
(2) Maintenance drive
The driving device is used to drive the rotation of the concrete storage tank. It consists of a power take-off, a universal joint shaft, a hydraulic pump, a hydraulic motor, a control valve, a hydraulic oil tank and a cooling device. If this part stops working due to failure, the concrete storage tank will not be able to rotate, which will cause the concrete in the vehicle to be scrapped, and even the whole tank concrete will be condensed in the tank, causing the concrete mixer truck to be scrapped. Therefore, whether the drive device is reliable or not is a problem that must be highly valued in use. In order to ensure that the drive is in good condition, the following maintenance work should be done:
a. The universal rotating part is the faulty part. The grease should be filled on time, and the wear condition should be checked frequently and repaired and replaced in time. The fleet should have an alternate cardan shaft assembly to ensure that it can recover in a matter of minutes if a failure occurs.
b. Keep the hydraulic oil clean. The working environment of the concrete mixer truck is bad, and it is necessary to prevent the dirty cement sand from entering the hydraulic system. Hydraulic oil should be replaced regularly as required by the manual. Once the inspection reveals that water or sand is mixed into the hydraulic oil, it is necessary to immediately stop the hydraulic system and replace the hydraulic oil.
c. Ensure that the hydraulic oil cooling device is effective. It is necessary to regularly clean the hydraulic oil radiator to avoid the radiator being blocked by the cement, check whether the radiator electric fan is running normally, and prevent the hydraulic oil temperature from exceeding the standard. As long as the hydraulic part ensures that the hydraulic oil is clean, there are generally few faults; however, the manufacturer has different service life.