The concrete automatic loading mixer is a kind of concrete mixing truck which is suitable for small-scale engineering construction and integrates automatic feeding, mixing, transportation and automatic unloading. It is composed of high-power diesel engine, hydraulic torque converter, front and rear four-wheel drive axle, feeding device, feeding hopper, unloading hopper, lengthened discharge hopper, frame, mixing tank, planetary reducer for mixing, hydraulic system, electric control system, automatic water feeding system, etc. Automatic feeding mixer has many advantages, which can greatly improve the efficiency of production. Now we will introduce in detail the characteristics and working principle of the automatic feeding mixer.
1、 Characteristics of automatic feeding mixer
1. The walking system from the engine through the hydraulic torque converter, front and rear transmission shaft to the front and rear axle. The hydraulic steering four-wheel drive is adopted to greatly reduce the turning radius, which is more suitable for working on the construction site, especially in the narrow space. The hydraulic torque converter is used to reduce the impact on the engine and prolong the service life of the engine. Stepless variable speed electric control valve is used for walking, which is convenient to control.
2. The constant power variable piston pump is used in the hydraulic system to reduce the power loss of the engine.
3. The rotation of the mixing tank is driven by the hydraulic motor through a special planetary reducer. The output shaft of the planetary reducer can swing at a certain angle to meet the beating of the mixing tank under bad road conditions. The mixing tank of the mixer is equipped with a speed control valve, which can accurately control the mixing speed of the mixing tank.
4. Dry material loading, according to the designed proportion, the shovel arm, boom cylinder, bucket shovel, electronic weighing, automatic feeding. The feeding hopper is inclined to ensure smooth feeding. The discharge chute for discharging can be rotated and fixed in proper position by locking mechanism. The extended chute for lengthening the length of the discharge chute can be folded and placed in its fixed position, and is fixed on the discharge chute with a hook.
5. The water inlet system is equipped with quantitative self-priming pump and quantitative controller setting to realize automatic quantitative water inflow.
6. The mixing tank is fixed and supported on the underframe through three points, and the front end is connected with the gearbox output flange fixed on the underframe. The flange can change the tilt angle. The mixing tank is supported on two rollers with tapered bearings through welded rails. The feeding, mixing and discharging are completed by pressing blade system. The forward rotation of the mixing tank is for feeding and concrete mixing; for reverse rotation, the concrete is discharged from the discharge outlet under the push of spiral blades.
2、 Working principle of automatic feeding mixer
The mixer is determined by many parameters. It is impossible to describe a mixer with any single parameter. Shaft power (P), blade discharge (q), head (H), blade diameter (d) and stirring speed (n) are the five basic parameters to describe a mixer. The discharge volume of the blade is directly proportional to the flow standard of the blade itself, the first power of the blade speed and the third power of the blade diameter. The shaft power consumed by stirring is directly proportional to the specific gravity of the fluid, the power criterion of the blade itself, the third power of the rotating speed and the fifth power of the blade diameter. Under the condition of certain power and blade form, the discharge volume (q) and head (H) can be adjusted by changing the matching of diameter (d) and speed (n) of blades, that is, large diameter blades with low speed (ensuring the same shaft power) produce higher flow effect and lower head, while small diameter blades with high speed produce higher head and lower head Mobility. In a stirred tank, the only way to make the pellets collide with each other is to provide sufficient shear rate.
From the view of mixer mechanism, it is the existence of fluid velocity difference that makes the fluid layers mix with each other. Therefore, the shear rate of fluid is always involved in the mixing process. Shear stress is a kind of force, which is the real cause of bubble dispersion and droplet breakup in stirring applications. It must be pointed out that the shear rate of fluid in the whole stirred tank is not the same.
The results show that there are at least four kinds of shear rate values in a stirred tank. They are: the experimental results show that the maximum shear rate and the average shear rate increase with the increase of the rotating speed, regardless of the size of the impeller. However, when the rotating speed is constant, the relationship between the maximum shear rate and the average shear rate and the blade diameter is related to the pulp shape. When the rotating speed is constant, the maximum shear rate of radial blade increases with the increase of blade diameter, but the average shear rate has nothing to do with the blade diameter.
These concepts about the shear rate in the blade zone need to be taken care of in the design of the mixer. Compared with the large tank, the small tank mixer often has the characteristics of high speed (n), small blade diameter (d) and low blade tip speed (nd), while the large tank mixer often has the characteristics of low speed (n), large blade diameter (d) and high blade tip speed (nd).