Concrete mixer trucks, vehicles specifically designed for transporting concrete, are ingeniously constructed by integrating a truck chassis with specialized concrete mixing and transport equipment. In China, the chassis for these vehicles typically utilizes Class II universal chassis provided by vehicle manufacturers, ensuring dual advantages in performance and compatibility. Its core specialized mechanisms encompass the power take-off unit, front and rear mixing drum supports, reduction gearbox, hydraulic system, mixing drum, control mechanism, and cleaning system-each component playing an indispensable role. Its operating principle is as follows: Power is efficiently extracted from the truck chassis via the power take-off device, driving the hydraulic system's variable displacement pump. This ingeniously converts mechanical energy into hydraulic energy, which is then transmitted to the fixed displacement motor. The motor then drives the reduction gearbox, which in turn powers the mixing mechanism to achieve thorough and uniform concrete mixing.
Domestic Standards for Mixer Trucks
Model Maximum Gross Weight/kg Mixing Drum Capacity/m³ Mixing Drum Geometric Capacity/m³
Two-axle mixer truck 16000 ≤4 ≤7.7
Three-axle mixer truck 25000 ≤6 ≤11.6
Four-axle mixer truck 31000 ≤8 ≤15.5
Single-axle semi-trailer mixer truck 18000 ≤6 ≤11.6
Two-axle semi-trailer mixer truck 35000 ≤12 ≤23.3
Three-axle semi-trailer mixer truck 40000 ≤14 ≤27.2
Additionally, a series of standards related to mixer truck performance and safety exist, such as mixing drum rotation speed, speed limits, feed rate, and discharge rate. Simultaneously, the water supply system and hydraulic system have explicit technical requirements to ensure the stability and safety of mixer trucks.
Classification of Mixer Trucks
Mixer trucks can be categorized based on different criteria. By mixing material, they are divided into dry mix and wet mix types; by discharge method, they are classified as front-discharge and rear-discharge models, with rear-discharge being the predominant type in the domestic market. Additionally, drive configuration and drum mixing capacity are key classification factors.
Basic Structure of Mixer Trucks
The fundamental structure comprises a truck chassis and specialized concrete mixing and transport equipment. Core components include the power take-off unit, front and rear mixing drum supports, gear reducers, and hydraulic systems. These elements collaborate to achieve thorough and uniform concrete mixing. The discharge chute design accommodates diverse unloading positions and height requirements, ensuring operational flexibility and practicality.
Concrete mixer trucks are meticulously constructed from two main components: the chassis and the superstructure. Specifically, they can be divided into ten key sections: the chassis system, hydraulic transmission system, mixing drum, discharge system, cleaning system, subframe, control system, support wheel system, feeding system, and electrical system. The structural diagram of the mixing apparatus is detailed on the following page.
Detailed Explanation of the Mixing Drum's Internal Structure
The mixing drum is the core component of the concrete mixer truck, featuring a complex and intricate internal structure. The structural diagram clearly illustrates the layout and function of each part. These components include the loading hopper, annular raceway, drum shell, connecting flange, reducer, frame, support rollers, adjustment mechanism, movable discharge chute, and fixed discharge chute. They work together to ensure efficient and uniform concrete mixing.
Detailed Explanation of Feeding and Discharging Devices
Within the mixing drum's internal structure, the feeding and discharging devices play a crucial role. They ensure concrete flows smoothly into the drum and is efficiently discharged after mixing. These devices include the feed chute, roller track, and support rollers, whose design and layout directly impact the drum's operational efficiency. Additionally, the manhole provides convenient access for maintenance and inspection.
Feed Hopper
Fixed Discharge Chute
Gantry Frame
Adjustable Chute Rotation Disc
Adjustable Chute Control Arm
Movable Discharge Chute
Mixing Drum
Next, we will detail each component. First, the feed hopper is the device used to add concrete into the mixing drum. Its rational design directly affects mixing efficiency. The fixed discharge chute ensures smooth concrete discharge upon mixing completion. The gantry frame provides stable support for the movable chute, while the ingenious design of the movable chute adjustment turntable and adjustment arm enables flexible positioning of the movable discharge chute to accommodate varying discharge requirements. Finally, the mixing drum serves as the core component of the entire unit. Its complex and precise internal structure critically influences the quality of concrete mixing. Simultaneously, the application of hydraulic systems enables these components to work in concert, ensuring the efficient and stable operation of the mixing drum.
Engine;
Fuel Tank;
Oil Pump;
Hydraulic Motor;
Reducer;
Mixing Drum
Control Lever
Next, we will delve into the working principle of the mixer truck. The truck's mixing function relies on power transmission from the engine. The power take-off unit transmits engine power to the small drive shaft, which in turn drives the rotation of the hydraulic pump and hydraulic motor. After reduction through the gearbox, this power ultimately drives the mixing drum to rotate. During concrete transportation, the mixing drum must maintain a low rotational speed of 1-3 revolutions per minute to ensure concrete homogeneity and prevent segregation-a process known as agitation or mixing.
Additionally, the mixer truck features loading, unloading, and cleaning functions. During loading, the mixing drum's speed increases to 6-10 rpm to facilitate concrete flow through the loading system into the drum, guided by the spiral blades toward the middle and lower sections. For unloading, engine power is transmitted through the PTO, hydraulic pump, and reduction gear to rotate the drum at 3-14 rpm. Concrete is then propelled toward the discharge opening by the spiral motion of the blades and expelled through the discharge chute. It is important to note that the drum's rotation direction during discharge is opposite to that during loading.
Finally, the mixer truck's cleaning function is achieved by pressurizing the water tank using the air reservoir from the braking system. The pressurized water flow cleans the mixing drum system, loading port, and discharge system, thereby completing the truck's cleaning process.
