EP4299170A1 - Mixing method and mixer - Google Patents

Abstract

The present invention relates to a mixing method for mixing mixture components, the mixing being carried out by introducing mechanical power into the mixture components, the power being provided by a drive, the mixing being carried out at least partially with controlled power and/or that a mixing quality of the mixture components is determined. The invention also relates to a mixer.

Description

The present invention relates to a mixing method for mixing mixture components, the mixing being carried out by introducing mechanical power into the mixture components, the power being provided by a drive.

In known mixing processes from the prior art, it is common to operate the drive of the mixer at a constant speed. At a constant mixer speed, the drive power fluctuates during the mixing process. This is due to changes in the homogeneity or consistency of the mix.

During loading, the mixing performance increases because the addition of material requires a higher mixing torque. The power required is highest when the materials are added. The drive power is therefore designed for this point.

During the course of mixing, the mixing performance usually decreases again as homogeneous properties of the mix are established and the mixing torque decreases. During the rest of the mixing process, the mixing performance is therefore lower than during feeding. As a result, the mixer is oversized for large areas of the mixing process.

By emptying the mix, the mixing performance decreases further because there is less material in the mixer.

This can be seen from the mixing performance curve in the diagram Fig. 2 where the time is plotted on the abscissa of the diagram and the mixing power is plotted on the ordinate of the diagram. The three phases “loading”, “mixing” and “emptying” are also included Fig. 2 drawn.

The point in time at which the mix is sufficiently mixed, i.e. the desired mixing quality is present or the final quality of the mix is reached, is usually estimated according to the state of the art. For this purpose, the mix can be assessed visually, for example using a camera.

At the end of the mixing process, the mixing performance curve turns into an asymptote, like this Fig. 2 emerges. It can be assumed that if the mixing performance is approximately horizontal, there will no longer be any change in consistency or change in the mixing quality. This point in time is currently estimated by the mixing master, for example, and is therefore dependent on the mixing master's personal experience and is therefore not reproducible.

The average power of the drive PA is usually far below the nominal power of the drive PN, as shown Fig. 2 shows where the two services PA and PN are represented by horizontal lines. If the drive speed is constant, the required mixing power is directly proportional to the required mixing torque. The relationship between power, torque and speed can be seen in the following equation: $$\mathrm{Performance}=2\mathrm{\pi }\times \mathrm{Torque}\times \mathrm{number\; of\; revolutions}\mathrm{.}$$

If the drive speed is constant during the mixing process, the nominal power of the drive is therefore not optimally utilized.

Against this background, the present invention is based on the object of providing a mixing process in which the installed nominal power of the drive is better utilized.

This task is solved by the method with the features of independent claim 1. Advantageous developments of the invention are the subject of the dependent claims.

Accordingly, it is provided according to the invention that the mixing takes place at least partially at controlled power and/or that a mixing quality of the mixture components is determined.

The mixture components preferably produce the mixture.

From a process engineering perspective, a performance-controlled mixing process is preferably provided to shorten the mixing time and maintain constant machine utilization. Likewise, a defined and reproducible method for determining the required homogeneity of the mixture or for determining the point in time at which the required final quality of the mixture is achieved and the mixer can be emptied is preferably provided.

With the method according to the invention, the output of a stationary mixing system is preferably increased by optimally utilizing the installed engine power. In addition, the point in time at which the final quality of the mixture is achieved is preferably determined by a defined measuring method.

The speed of the drive is preferably adjusted during the mixing process so that the motor power, i.e. the drive power, is constantly regulated to an optimal value.

As a result, there is preferably a higher average mixing speed during the mixing process. The required mixing time is reduced and the output is increased. The constantly regulated motor power prevents the drive from overheating and mechanical components are protected.

Reducing the mixing time has the further advantage that the mixer can be made smaller in order to achieve the same output.

It is preferably provided that the mixture components comprise a liquid, such as water, a binder, such as cement, and an aggregate, such as aggregate, and in the mixed state include or are concrete.

It can be provided that the power is introduced by moving or rotating a mixing tool and/or by moving or rotating a mixing container.

It is conceivable that power is regulated to the nominal power of the drive.

It is preferably provided that the drive is a rotating drive and is only operated up to a maximum speed.

There is preferably the possibility of variable adjustment of the mixer speed. This means that an optimal speed can preferably be set.

The method according to the invention advantageously reduces energy consumption.

In an advantageous embodiment it is provided that the mixing quality is determined by the change in the force or torque of the drive and a desired mixing quality is considered to have been achieved when the change in the force or torque remains below a defined value for a defined time. It can be provided that the mixture components are emptied after the desired mixing quality has been achieved.

The defined value is preferably zero. The change, i.e. the derivative, of the force or torque is then preferably negative, which means that the force or torque decreases.

With the method according to the invention, the condition of the mixture, i.e. the quality of the mixture, is preferably assessed based on the derivation of the torque signal. Mixing too long or too short is preferably excluded and consistent quality is preferably guaranteed.

It is conceivable that there is no user intervention during mixing.

It is preferably provided that the mixing takes place between loading a mixing container with the mixture components and emptying the mixture components from the mixing container, the mass of the mixture components that are emptied from the mixing container being over 90%, preferably over 95 or 98%. corresponds to the mass of the mixture components with which the mixing container was charged.

A high speed when emptying preferably results in less residual material remaining in the mixer. This ensures the purity of subsequent mixtures.

The invention also relates to a mixer which has means which are designed to carry out a mixing method according to the invention and/or a frequency converter and/or a programmable controller.

In terms of mechanical engineering, the mixer is preferably operated with a frequency converter in combination with a programmable control.

It can be provided that the mixer is a stationary or mobile concrete mixer, a concrete mixing plant or a truck mixer or a component of one of these machines.

At this point it should be noted that the terms “a” and “an” do not necessarily refer to exactly one of the elements, although this represents a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular and, conversely, the singular also includes several of the elements in question. Furthermore, all of the features of the invention described herein can be combined with one another as desired or claimed in isolation from one another.

Fig. 1:

fünf Diagramme mit Mischparameterkurven.

Fig. 2:

ein Diagramm mit einer Mischleistungskurve eines Mischverfahrens aus dem Stand der Technik.

Further advantages, features and effects of the present invention result from the following description of preferred exemplary embodiments with reference to the figures, in which the same or similar components are designated by the same reference numerals. Show here:

Fig. 1:

five diagrams with mixing parameter curves.

Fig. 2:

a diagram with a mixing performance curve of a mixing process from the prior art.

For example, a stationary mixer is provided with at least one mixing tool rotating in a mixing container. The mixing tool is driven by an electric motor.

In Figure 1 Five diagrams with mixing parameter curves for mixing with the exemplary mixer can be seen, with the time being plotted on the abscissa of the respective diagram and the mixing parameters being plotted on the ordinate of the respective diagram.

The top left diagram shows the mixing performance at constant speed as the mixing parameter and the bottom left diagram shows the speed at constant speed as the mixing parameter.

The upper right diagram shows the mixing performance with controlled mixing performance as a mixing parameter. The right middle diagram shows the speed with controlled mixing power as the mixing parameter and the bottom right diagram shows the derivation of the mixing torque as the mixing parameter.

T _{mixed const} denoted in Fig. 1 the mixing time that an uncontrolled mixing process with constant speed requires to achieve the desired mixing quality or final quality.

T _{mixed regulated} denoted in Fig. 1 the mixing time that the controlled mixing process requires to achieve the desired mixing quality.

n _const denotes in Fig. 1 the constant speed that is set in a mixing process according to the prior art.

n _max denotes in Fig. 1 the maximum speed that should not be exceeded.

t _{M const} denotes in Fig. 1 the time in which the derivative of the torque should be within the predefined limits so that the desired mixing quality is considered to have been achieved.

Ṁ _min denotes in Fig. 1 the area in which the derivative of the torque should be over a defined period of time so that the desired mixing quality is considered to have been achieved.

In order to be able to adjust the speed, for example of the mixing tools during mixing, the use of a frequency converter is necessary. Included Different parameters have to be implemented and defined in the control.

P _target is the motor power that is controlled during the mixing process. To ensure that the speed does not increase extremely at a low mixing torque, such as during dosing or emptying, a maximum speed (n _max ) is defined to protect the mechanical components of the drive train, which should not be exceeded.

The percentage reduction in mixing time Δt _% , which results from an average higher mixer speed, can be determined as follows: $${\mathit{\Delta t}}_{\%}=\frac{T_{\mathit{Mix}\mathit{const}.}-T_{\mathit{Mix}\mathit{regulated}}}{T_{\mathit{Mix}\mathit{const}.}}$$

In an electric motor, the torque is directly proportional to the motor current and can therefore be measured via the motor current.

The torque that the drive must generate in order to rotate the mixing tools at a certain speed changes during the mixing process.

This is due to the fact that the consistency changes when mixing suspensions and the coefficients of friction when mixing dry substances. After the mixing process is complete, the consistency or friction values no longer change. The torque for rotating the mixing tools remains constant. The mixture has reached its final state.

An assessment criterion for the condition of the mixture is the change over time, i.e. the derivative or the differential quotient, of the torque signal. If the derivative of the torque signal at the end of the mixing process falls below a certain value, such as Ṁ _min in Fig. 1 the mixture has reached its final state and the mixing process is complete.

In addition, the parameter t _{M const} is implemented in terms of control technology. This indicates how long the derivative of the torque Ṁ _Min must be undershot before it is ensured that the final quality of the mixture has been achieved.

Claims (10)

Mixing method for mixing mixture components, wherein the mixing takes place by introducing mechanical power into the mixture components, the power being provided by a drive, characterized in that the mixing takes place at least partially with controlled power and/or that a mixing quality of the mixture components is determined . Mixing method according to claim 1, characterized in that the mixture components comprise a liquid, such as water, a binder, such as cement and an aggregate, such as aggregate, and in the mixed state comprise concrete. Mixing method according to claim 1 or 2, characterized in that the power is introduced by moving or rotating a mixing tool and / or by moving or rotating a mixing container. Mixing method according to one of the preceding claims, characterized in that power is regulated to the nominal power of the drive. Mixing method according to one of the preceding claims, characterized in that the drive is a rotating drive and is only operated up to a maximum speed. Mixing method according to one of the preceding claims, characterized in that the mixing quality is determined by the change in the force or torque of the drive and a desired mixing quality is considered to have been achieved if the change in force or torque is below a defined value for a defined time remains. Mixing method according to one of the preceding claims, characterized in that there is no user intervention during mixing. Mixing method according to one of the preceding claims, characterized in that the mixing takes place between loading a mixing container with the mixture components and emptying the mixture components from the mixing container, the mass of the mixture components that are emptied from the mixing container being over 90%, preferably corresponds to over 95 or 98% of the mass of the mixture components with which the mixing container was charged. Mixer, the means which are designed to carry out a mixing process according to one of the preceding claims and/or has a frequency converter and/or a programmable controller. Mixer according to claim 9, characterized in that the mixer is a stationary or mobile concrete mixer, a concrete mixing plant or a truck mixer or a component of one of these machines.

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