mixer truck is a special truck used to transport concrete for construction; due to its appearance, it is often called a field screw truck and an olive truck. Trucks like are equipped with cylindrical mixing drums to carry mixed concrete. During transportation, the mixing drum will always be kept rotating to ensure that the concrete carried will not solidify. After transporting the concrete, the inside of the mixing drum is usually rinsed with water to prevent the residual concrete from hardening and occupying space, so that the volume of the mixing drum is less and less.
Recently, many car friends are consulting about the relevant knowledge of mixing truck tank bodies. When I checked the information, the editor found that the knowledge of mixing truck tank bodies and internal structures is very important. Today, I will explain the mixing truck tank in detail for you. Knowledge of body structure.
Concrete mixing truck mixing drum is shown in the figure, generally consisting of three sections: front cone, middle cone and rear cone. has two spiral blades symmetrically welded on the cylinder wall with 180° intervals. These two spiral lines form a spiral channel with the cylinder wall. The concrete completes feeding, stirring and unloading along these spiral channels, etc. Work. Generally, the front and rear cones use conical logarithmic spiral sheets with the same equi-rise angle, while the middle cylinder is generally a cylinder, and cylindrical spiral blades with different equi-rise angles are generally used.
stirring working principle
The mixing drum of the stirring truck relies on the rotating cylinder to drive two spiral blades to stir and unload the concrete. When is working, the mixing drum rotates about its axis, causing the concrete to move along the spiral line of the mixing blade. The spiral curve prompts the concrete to move to the end and top layer in the opposite direction, which is the main movement during concrete mixing. At the same time, due to the friction between the concrete and the cylinder wall and the blade and its internal adhesion, during the rotation of the cylinder, after the concrete reaches a certain height, it must overcome the above friction and cohesion and go downward under its own weight under the action of its own weight. Flip and slip. Secondly, at the bottom of the blade, since the shape of the blade is curved, the concrete produces rotating agitation under the action of external forces. Since the mixing drum is rotating continuously, the concrete does a composite motion of three kinds of movements, that is, three-dimensional stirring motion. This allows the concrete to be stirred evenly to ensure its uniformity.
analysis of the tank body of the mixer truck
The following figure is a sectional view of the tank body. It can be seen that the inside of the tank body is mainly divided into eight parts, divided into sealed tubes, blades, mixing leaves, head plates, and mixing drum shell. Mixer raceway, connecting flange, and inspection hole.
Sealing tube A is funnel-shaped and has a large diameter, which can ensure smooth feeding and prevent concrete from overflowing.
B is curved, which helps the discharge performance of low slump concrete.
Mixed leaf C has good stirring performance, which is conducive to maintaining the quality of ready-mixed concrete.
Head plate D is a high-strength steel plate integrally rolled, and has a reliable steel degree after welding with the head reinforcement plate.
Mixing drum shell E and various blades are made of high-strength wear-resistant steel plate for mixer trucks, which has extremely high wear resistance.
mixing drum raceway F integral rolling has good wear resistance. The raceway is used to support the mixing drum on pallet .
connection flange G is connected to the gearbox and supports the mixing drum on the rack.
maintenance hole H is used for emergency maintenance.
Can structure design principles
mixing drum structure should be simple, compact and light to minimize the weight of the vehicle, which is conducive to improving the effective loading capacity of the mixing transport truck and relatively reducing the power consumption of the vehicle.At the same time, the structure should be arranged to adapt to the narrow and long body shape and height limitation of the chassis. The height and center of gravity of the mixing drum and the mixing transport vehicle should be reduced as much as possible to ensure the stability and passability of the mixing transport vehicle. It should also be effective enough The loading capacity meets the specified mixing and loading and unloading performance, and is structurally adapted to the characteristics of the carrier chassis and stirring work. The appearance of the mixing drum is relatively complex, and the cross-sectional diameter along the axis direction varies. The middle part has the largest diameter and gradually shrinks on both sides. A large-capacity mixing drum adds a cylinder between the two truncated cones to expand the loading capacity and avoid excessive size in the middle of the mixing drum.
Usually, the parameters of the front cone, middle cone and back cone length of the mixing drum are selected as follows:
Usually, the maximum diameter is between 2100 and 2300mm. If the maximum diameter is between 2400mm, the mixing transport truck will turn If there is a phenomenon of floating, it may cause an accident.
Concrete mixing truck mixing drum is usually equipped with a pair of strip-shaped spiral blades, which are installed at 180° in the wrong phase and use left-handed blades. When the mixing drum rotates, the two spiral blades are driven to move around the agitation axis to realize the feeding, stirring and unloading operations of concrete. The mixing drum can be divided into 2 sections according to its function. The tail cone outlet section is the unloading guidance section. The cylindrical part and the front cone part are mainly used to agitate the concrete during transportation to prevent solidification and separation. When unloading, it will The bottom concrete is pushed out.
You think there are two spiral lines in the mixing truck cylinder. In fact, there are 9 spiral lines in the cylinder, namely the spiral line of the blade root of the front cone part (spiral line 1) and the spiral line of the blade top (spiral line 4), and the column Some blade root spiral lines (spiral line 2) and leaf top spiral lines (spiral line 5), tail cone part spiral lines (spiral line 3), middle spiral lines (spiral line 6 and spiral lines 8), leaf The top spiral line (helical line 7 and helical line 9), wherein the spiral line 8 and helical line 9 are transition spiral lines between the cylindrical part and the tail cone part.
The root and top type and spiral angle of these stirring drum spiral lines determine the intensity of concrete moving axially or tangentially in the mixing drum, and therefore also affects the performance of stirring and unloading, which is the key to the design of the mixing drum.
stirring drum spiral blade design principles
stirring blade design generally rotates clockwise as feed and stir, and rotates counterclockwise as discharge. The stirring drum rotates faster when feeding, in order to save working time, and the stirring drum rotates slowly when stirring, in order to reduce moisture evaporation too quickly and reduce separation. However, during transportation, the mixing drum must be operated at a constant speed in order to prevent the concrete from solidifying and deteriorating. During the rotation of the cylinder, the concrete is continuously pushed to the front of the mixing drum by the blades. The concrete that reaches the front end must be reversed back by the end wall of the mixing drum, so that the concrete will roll before and after ; The continuous rotation of blades drives the continuous rotation of concrete, and the concrete at the same position changes continuously through this movement, thereby playing a stirring role; in addition, the change in the shape curve of the blade can make the concrete at its root and cylinder wall Small cycles are formed between them, which also plays a certain role in stirring concrete. When the concrete is transported to the working site, the mixing drum will rotate counterclockwise. At this time, the rotation direction of the blade is also opposite. The concrete will be guided by the blade to move towards the mixing drum port until it is unloaded from the barrel port.
Effect of spiral blades on stirring quality
Before, when the concrete tank manufacturer did not use optimization technology during the installation of spiral blades, it did not first spray powder on the sheet and then cut the rolling circle, and then followed the rolling circle. The spiral blade busbar formed on the tank is installed, but is completely welded and installed based on the worker's production experience. causes unreasonable spiral blades with spiral lines as the busbar after installation, and the tank body is formed with relatively high dimensional accuracy. The poor results in the inlet and discharge speed, making the discharge rate low.
Now, by parameterizing and optimizing the design of the tank spiral line, the blank can be optimized, and the precise discharge of CNC can be used to complete the cone forming of the tank body using a cone mold, and finally the entire tank body is completed by CO2 gas protection welding Welding to the blades completes the formation of the tank body. tested and experimented on the tank formed after optimization process. The results showed that the dimensional accuracy of the tank body was significantly improved and met the requirements, and the discharge rate of the tank body was also significantly improved, which complyed with national standards.
other influencing factors of the mixing truck tank body design principles
Although the oblique angle of the mixing drum is not a geometric parameter of the mixing drum itself, it affects the effective loading capacity and stirring performance of the mixing drum. Unloading performance, load uniformity, etc., so it also restricts the geometric parameters of the mixing drum, and the mutual influence is shown in the table. During design, the geometric parameters of the mixing drum must be considered in connection with its oblique angle. When the oblique angle changes, in order to meet the design requirements, it is often necessary to increase the length or diameter of the cylinder.
At present, the angle between the axis of the stirring drum and the chassis plane is between 10° and 20°, depending on the load capacity of the stirring drum, the above-mentioned influencing factors and the selected chassis length. The general relationship between the angle of the mixing drum and the effective loading capacity is shown in the table.
is a question that has been under investigation. According to relevant experimental data, it is believed that the middle part of the pear-shaped cylinder has a large diameter, and the front cone is short, making the shape of the middle and lower part of the mixing drum close to the shape of the sphere. At this time, not only is the stirring effect good, but the stirring efficiency high, but it is also Because the center of gravity of the mixing drum is appropriate to move, it is beneficial to reasonably allocate the load of the front and rear axles of the transport chassis and improve the loading capacity of the mixing transport truck. However, the maximum diameter in the middle of the mixing drum is limited by the width of the carrier chassis and is also limited by the influence of the height of the center of gravity of the mixing drum on the stability of the vehicle. It is also necessary to consider the relevant provisions of national transportation and transportation regulations on vehicle passage. In addition, this size directly involves the working performance and loading capacity of the mixing drum, so when determining this maximum diameter, the above factors must be considered comprehensively.
The length of the cylinder along the axis direction should refer to the load weight. The geometric parameters such as the maximum diameter of the middle and the top angle of the cone determined by the calculation auxiliary design or manual drawing method are obtained. However, this The size is limited by the length of the selected car chassis and should be adjusted according to the layout and support points of each component of the agitator (such as water tanks, special engines, etc.). The mutual influence of the length of the axis direction and its main influencing factors are shown in the table.
mixer truck volume introduction
mixer truck geometric volume: mixer bucket actual geometric volume refers to the geometric volume calculated by mathematical method when designing mixing tank .
stirring volume: the amount of ready-mixed concrete that the mixer truck can transport (based on the volume after tamping). It can be seen as the amount of concrete that the mixer truck can unload when it arrives at the project site. The premixed concrete capacity is calculated as 2400kg/m3.
Agitation volume: mixing truck is placed in a horizontal position. The mixing barrel can accommodate the largest unmixed concrete material (including water) and can be stirred out of the amount transported to concrete (based on the volume after tamping). The relationship between
should be: mixer truck geometric volume> stirring volume> stirring volume . The volume often mentioned by users should refer to the stirring volume, so when purchasing a mixer truck, you should pay attention to distinguishing the stirring of the vehicle. Volume.
New car mixer truck purchase tips
There is a lot of knowledge to buy a mixer truck. It not only depends on the brand awareness, but also on the product quality of the parts and reliable after-sales service.
There are many options for cement mixer truck chassis, such as Dongfeng, Jiefang, Fotian , Heavy Truck, etc. These are large and well-known chassis manufacturers, and you can choose according to your preferences Choose a solid and reliable chassis.
2. Look at the roller parameters
The drum should pay special attention to the process and materials, and look at its smoothness and wall thickness, as well as the process and materials of the mixing blades. The drum process determines the residual rate of the concrete.
If you have the conditions, you can choose the three major hydraulics of imported quality, which are stable and durable than the three major hydraulics of domestic products. Of course, with the continuous maturity of technology in recent years, the three major hydraulics in China are also good, and the price is much cheaper than that in foreign countries.
4. Reliable after-sales service
Concrete mixer truck is a special heavy-duty vehicle with small holdings and few sources of accessories. Compared with general general vehicles, it depends on the manufacturer's after-sales service. Therefore, can the manufacturer provide convenient and reliable After-sales service is an important factor that must be considered when selecting a model.
second-hand mixer truck purchase tips
second-hand mixer truck In addition to the above purchase precautions, you should also refer to the following content.
If you are not familiar with the used car trading market and have an urgent desire to buy a car, the easiest way is to invite an expert who knows how to go with you. After all, he has a deeper understanding of mixer trucks. Understand and understand the price of the mixer truck.
2. Don’t judge the car by its appearance
The appearance of a car is the easiest to change, which is also a routine used by second-hand car dealers. Don’t judge the quality of a vehicle from the appearance, and focus on key factors that reflect the performance and driving conditions of the vehicle.Mainly check the engine, chassis, mixing drum, etc. of the mixer truck. These are important components of the mixer truck. You must ensure that it is correct before you can proceed to the next step.
Before purchasing a car, be sure to check whether the vehicle source is legal, so as to avoid buying cars with illegal sources or forging vehicle procedures, and causing trouble for yourself.
Carefully verify the authenticity of the vehicle certificate, as well as whether the vehicle certificate matches the car seller, and whether the car seller has the qualification to sell the car, so as to avoid causing major economic disputes to yourself or bearing other civil liability .
Car mileage is an important criterion for measuring the value of a car. Some unscrupulous merchants often tamper with the odometer in order to buy a good price for cars, and consumers should be more careful about this.
When purchasing a car, you must sign a formal contract and make clear agreements on the model of the vehicle, the transaction price, the transfer time, the warranty and maintenance. Once a dispute occurs, there is a basis for protecting your rights.
Some buyers can get impatient after traveling to two or three stores. They don’t want to see a few more stores, but they compare the several stores they have seen. In fact, there are not many of them in this way. Comparing the data of the market, it is not clear about the market conditions and is easily slaughtered.
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