1. Working principle and structural characteristics

The concrete mixer truck is composed of two major assemblies: the chassis and the upper part of zhi. The upper part is composed of mixing drum, auxiliary frame, feeding and discharging device, control system, hydraulic system, electrical system, water supply system and guardrail.

The specific structure is shown in the figure below:

(1) Working principle

The built-in blades are used to constantly force the concrete to stir, so that it will not solidify within a certain period of time (maximum 90 minutes), so that the mixer truck can meet the requirements of use after it reaches the construction site.

(2) Structural characteristics

Mixing drum

The mixing drum is a key component of the entire mixer truck. As a container for storing concrete, it plays a decisive role in preventing its solidification and segregation. It is composed of mixing drum, supporting wheel and so on.

The cylinder body is formed by group welding of the front cone section, the rear cone section, the cylindrical section, the head, the blade, the feeding cone, and the raceway. The front end is connected with the reducer, and the rear part is supported on the auxiliary frame through the supporting wheel. The supporting wheel plays the role of supporting the drum body, and is composed of a support, a bearing seat, a shaft, a bearing and the like.

The mixing cylinder is made of high-strength steel plate and the blade is made of high-strength fine-grain alloy steel (its wear resistance is 1.6 times that of Q345), which has higher wear resistance. The head is integrally spin-formed once, and has sufficient rigidity and strength after being welded to the reinforcing plate.

The feeding cone directly affects the feeding speed of the whole vehicle. If the speed is too fast, segregation will occur, and if the feeding speed is too slow, it will affect the work efficiency. Therefore, the design of the feeding cone is funnel-shaped, large diameter, and the feeding speed is maintained at 3.2m3/min, which can ensure smooth feeding and prevent concrete overflow.

The raceway is a forging, which is forged as a whole. After the entire cylinder is welded, the outer ring is processed to ensure the coaxiality requirements.

The optimized design of the mixing drum has reliable structural rigidity, good wear resistance, smooth in and out of the material, and a very low residual amount, which can mix the concrete and agitate and transport the pre-mixed concrete, and there is no discharge segregation phenomenon. Ensure the homogeneous performance of concrete.

2.The subframe of the concrete self-loading truck

The subframe of the concrete self-loading truck is the main load-bearing part. The load during operation is almost supported by it. In addition, the impact load caused by the bumps of the road and the acceleration and deceleration during exercise are all related to the structure of the subframe. Make very high demands.

The entire subframe is composed of the main beam, the front support frame, and the back support frame.

The main beam adopts an integral box structure beam, which fundamentally enhances its torsional, flexural and tensile properties, ensuring the rigidity requirements. An auxiliary cross beam is added between the two main beams to adjust the rigidity of each section of the main beam To allow the load to be more evenly distributed over the entire length of the subframe.

During the exercise, it is inevitable that special braking will be encountered and emergency braking will be taken. The inertial force caused by this is very large. In addition, the mixing drum itself has a certain inclination, so the load on the front of the subframe is relatively It is much larger, and this part of the load is mainly added to the six bolts connecting the reducer and the front support seat. To prevent the bolts from being cut and causing an accident, a thrust stopper is added to the front support table to make the bolts It is not affected by the shearing force, ensuring the safety of the vehicle during operation.

In order to meet the filling rate of concrete self-loading trucks, the mixing drum must also meet certain inclination requirements. After the assembly, the mixing drum, the speed reducer and the front support frame have been fixed together. Due to manufacturing errors, it is possible that the back support frame cannot meet the requirements of the inclination angle after assembly, and cannot effectively support the mixing barrel. At this time, the entire structure is equivalent to a cantilever beam. This will produce a large torsional moment for the reducer. In order to prevent the harm caused to the reducer by this, the installation position of the supporting roller on the background support frame can be adjusted. Moreover, after the assembly and commissioning are completed, a fixed stopper is added to prevent the deviation of the roller due to loose bolts.

3. Feeding and discharging device

The feeding and discharging device is composed of a feeding hopper, a discharging hopper, a main discharge chute, an auxiliary discharge chute, a bracket, a locking frame, etc. It is an important part of the concrete self-loading truck, which directly affects the speed and quality of the feed and discharge.

The inlet and outlet hoppers are connected to the background support frame of the sub-frame through a bracket. Lining plates are added in the discharge hopper and the main discharge tank. The lining plates are made of high-strength fine-grain alloy steel, and their wear resistance is 1.6 times that of Q345A (formerly 16Mn)

Greatly improve the wear resistance.

The main discharge chute can discharge concrete in the required direction, and the auxiliary discharge chute plays the role of extending the length of the main discharge chute. When it is necessary to connect the auxiliary discharge tank to the long discharge, it is only necessary to install the auxiliary discharge tank on the main discharge tank, which is very convenient.

The lock frame device locks the main discharge chute when the discharge chute is not working. How to use: When the discharge chute is not working, push it inwards and it will automatically lock. Lift the lock handle to pull out the discharge chute.

The control lever of the unloading chute plays a role of supporting the unloading chute and adjusting the vertical displacement of the notch of the unloading chute. The shoulder-type telescopic sleeve is used to adjust the inclination of the main chute during unloading. The positioning is accurate and the connection is reliable. The operation is convenient and labor-saving.

The locking lever locks the discharge chute to any position. How to use: Lift the handle to release the lock.

4. Control system

The operating system is composed of a controller, a linkage shaft, a flexible shaft and a linkage mechanism, which mainly controls the rotation speed and rotation direction of the mixing drum. A set of controllers are arranged on both sides of the rear of the concrete self-loading truck. The left and right controllers can be linked. There is only one joystick on the controller. The output end is connected to the variable pump through the link mechanism, and the control is changed by changing the pump. The angle of the handle adjusts the flow of the oil pump to achieve the control of the direction and speed of rotation of the cylinder, which can be controlled by moving left and right; at the same time, the outlet is connected to the throttle of the engine through a flexible shaft, which can be manipulated up and down when the speed is required to increase To control the joystick to increase the speed of the cylinder.

5. Hydraulic drive system

The hydraulic system is a closed circuit composed of a reducer, variable plunger pump, and motor. The schematic diagram is as follows:

The reducer, plunger pump and hydraulic motor are made of concrete and concrete self-loading products produced by companies such as Italy, which can provide excellent output performance and long service life.

The hydraulic oil brands used by the system are: Mobile (Mobil)-DTE26, Shell (Tellus)-Tellus 68 hydraulic oil, Mobile should be used in low temperature environments.

The lubricating oil filled in the reducer is heavy-duty vehicle gear oil, 

Viscosity grade 85W/90; Shell Spirax ASX lubricant should be used in low temperature environment.

In order to meet the minimum starting temperature (minimum limit temperature) requirements, please use a preheating system when necessary. When the ambient temperature is below -5℃, no matter what lubricating oil grade is used, preheat for at least 10 minutes.

The system has an automatic temperature protection device. When the operating temperature exceeds 65°C, the temperature control switch automatically turns on and the cooler starts to work. When the working temperature is below 60°C, the temperature control switch automatically turns off and the cooler stops working.

6. Electrical system

The electrical system of the concrete self-loading truck is mainly the cooling fan control part.

The start and stop of the cooling fan is automatically controlled by the temperature switch. The fan starts when the temperature is higher than 65 degrees, and stops when the temperature is lower than 60 degrees. The temperature switch is located on the cooler, and the relay and fuse are in the power supply relay box next to the battery.

7. Water supply system

The water supply system is composed of pressure water tank, water gun, water pipe and valve. The volume of the water tank is about 550 liters, and it is supplied by air pressure. The main function is to flush the hopper after loading the material and flush the mixing drum and discharge tank after the material is discharged to prevent the concrete from sticking. When the temperature is below zero degrees Celsius, after the flushing is completed, the water in the water tank and water pipe should be drained to prevent freezing.