WO2018087221A1

WO2018087221A1 - Method and device for producing a paving stone

Info

Publication number: WO2018087221A1
Application number: PCT/EP2017/078747
Authority: WO
Inventors: Danny Windmolders; Wilfried Blocken
Original assignee: Windmolders Beton N.V.
Priority date: 2016-11-10
Filing date: 2017-11-09
Publication date: 2018-05-17
Also published as: EP3538333A1

Abstract

The method for producing a paving stone starts with a mould filled with a concrete mix (21). The mould has a tray (24) and an upper die (26). The tray (24) has an upper opening which is covered by the upper die (26). The mould is equipped with at least one sensor which detects at least one of the following electrical variables: a) resistance in ohms of a partial area of the concrete mix (21), b) measured value for an ultrasound signal which has passed through at least one partial area of the concrete mix (21). In the method, the mould containing the concrete mix (21) is agitated by means of an agitating device (30) and in at least one agitation step. At least one electrical variable is detected at least during agitation including the progress over time of the change in the electrical variable and the point when the electrical variable achieves a predetermined, stored value is established. Agitation is switched off applying a switch-off delay for the agitating device (30) so that said device comes to a halt when the at least one electrical variable reaches the predetermined, stored value.

Description

Method and device for producing a paving stone

The invention relates to a method and an apparatus for producing a concrete paving stone. Under paving stone handy concrete form stones are understood, which are laid on sidewalks, roads, etc. Such paving stones are known for example from WO 2013/076115 AI.

From DE 196 15 915 C2 a method for monitoring and controlling the strength of concrete blocks in their batchwise production is known. It is described that the degree of compaction of the concrete pulp is influenced by changing the degree of vibration, ie the Rütteins. When shaking, a volume change takes place, which leads to a change in the height of the concrete slurry in the mold. It also describes measuring the intrinsic moisture content of the concrete mix in the mixer.

DE 103 31 758 AI gives general information on concrete for paving stones. It states that a water cement value of 0.4 is considered optimal. According to DE 39 37 698 AI concrete blocks are produced by shaking, while the shaking is limited in time to a minimum. Measuring probes are inserted in the individual concrete masses in order to detect the consistency of the concrete mass and to be able to finish the stamping pressure and the shaking process at a suitable moment.

WO 2006/117173 A2 discloses a system and a method for producing concrete products, in particular paving stones. It explains the individual processes of production. A vibration measuring device is used, with the help of which the applied vibration energy can be measured and checked.

The content of the cited prior publications, including in the following Vorveröffentlichungen, is fully contained in the disclosure of the present application. In the production of concrete paving stones, also called concrete blocks, a multiple mold is generally used, with which a number of paving stones can be formed at the same time. It has a multiplicity of interconnected shells which adjoin one another. Each shell has a common side wall with an adjacent shell, an associated multiple stamp has a corresponding number of punches which are arranged side by side and operated together.

After filling the concrete mixture in at least one shell, an initial shaking is first performed so that the concrete mixture evenly distributed in the individual shell. Thereafter, at least one further shaking operation is carried out with the aim of compacting the concrete mix. In addition, the stamp is pressed onto the concrete mixture, whereby a flat surface for the paving stone is achieved. The shaking is done on a vibrating table. On this the multiple form is brought. When shaking the stamp remains stationary relative to the shell.

The shaking is performed only for a short time, for example 4 ± 2 sec. This refers to a final shaking or main shaking, which may precede a shaking. The duration of the main litter is critical for the quality of the later paving stone. If shaken for a long time, a good compaction is achieved, but shape deviations occur, in particular side surfaces of the paving stone become soft. If shaken too briefly, the stone does not have sufficient strength and shape. The Rüttefzeit is also dependent on the filled concrete pulp, in particular its water content. The distribution of grain, the proportion of fine-grained material, and the proportion of cement in the concrete pulp have an influence on the shaking time.

There is therefore a desire for better control of the process of producing concrete paver bricks. The product produced should be as independent as possible of fluctuations in the concrete mixture used as starting material. This means that the production process must be adapted to the respective starting material. Proceeding from this, the object of the invention is to provide a method and a device, taking into account the previously known methods and devices allow improved control of the manufacturing process so that the quality of the molded brick is more consistent.

This object is achieved by a method according to claim 1.

This method has the advantage that the shaking process is only carried out in each case until a desired value for the at least one electrical variable is obtained. The concrete slurry in the mold is detected during the retting by at least one electrical measurement and it is ensured that the finished vibrated paving stone has an electrical size that is indistinguishable from other paving stones of the same batch or another batch.

Specifically, a concrete mix is made in a mixer. At least the water content of this concrete mixture is recorded, preferably also the water cement value. Possibly. Also, other properties of the concrete mixture are detected prior to filling, e.g. the fluidity, the weight and the like.

The concrete mix is now poured into the mold, usually using a multiple mold. The individual compartments of the multiple form each form shells, which are filled with the concrete mixture. In an initial shaking process, which is relatively short and often lasts less than 1 second, the concrete mixture is first spread evenly in the mold. Thereafter, a punch of the mold is moved into the shell and pressed. This is usually followed by an initial shake and a main shake. The stamp remains on the concrete mixture and closes the shell upwards.

At least during the final shaking process, a measurement of the ohmic resistance and / or an ultrasonic signal is now carried out. In each case, a partial area of the concrete mixture in the form is detected. This sub-area may be a superficial area that extends into the interior over only a few millimeters depth from an outer surface of the concrete mix. But it can also be a volume measurement. Both measurements are combined possible. From the recorded during the Rütteins electrical size is now a Signa! derived, which leads to the shutdown of a shaking process. In this case, the time course of a change in the electrical variable is observed and determines when the electrical quantity will take a predetermined, stored value. This predetermined value can be determined, for example, by preliminary tests. In general, it is stored in a value table. There, for different initial values of the concrete mixture, which initial values have already been recorded prior to filling, the time periods respectively determined as optimal for the main shaking are stored.

A vibrator (also called vibration device) works with moving masses. These need a certain amount of time to come to a stop after switching off the drive. This time is called the shutdown delay. If, during the detection of the change in the electrical quantity, it is determined that it will assume the preset, stored value at a time tO and the switch-off delay tA is t, it is switched off at the instant tO-tA. This ensures that the shaking process comes to a standstill at time t0. In the switch-off delay tA is included that the shaking after switching off increasingly weaker. As an approach can be assumed that after switching off the Rütteins on average only half as effective as before. It is also possible to start the shutdown a little later than tO - tA, e.g. At tO - tA / 2. Then the vibrator comes to a stop only after tA, but the shaking is more intense.

After completion of the Rütteins the shaken concrete mixture is demolded, it can now continue to soften.

The period from the filling of the concrete mixture into the mold until demolding is only a few minutes, for example 2 to 3 minutes. During this time, the concrete mix hardens not noticeable. The detection of the at least one electrical variable is therefore due to change during the shaking process by which the concrete mixture is compa keted. By this shaking the electrical resistance changes, it changes the behavior when passing through an ultrasonic signal. An ultrasonic signal runs faster with increasing shaking and with less attenuation through the concrete slurry. Due to the increasingly stronger compaction of the starting slurry during Rütteins the interstices of the concrete mix are increasingly filled better, whereby the sound propagation time increases and the sound attenuation is lower. Preferably In this case, transverse waves can be used because they give better information about material properties, but longitudinal waves can also be used. In the resistance measurement can be used with DC voltage, but it can also be detected resistance with AC voltage. It can be the electrical size, such as the resistance of a surface near area detected, but it can also be measured in a volume range.

The advantage of the method is that the at least one sensor is arranged on the mold itself, so that it can be measured during the rinsing.

In practice, it is sufficient to detect a single shape of the multiple form. You do not have to capture all the individual forms. It is possible to detect one or two other shapes, but it has been found that it is sufficient to equip only one mold with the at least one sensor, but not the others.

The object is further achieved by the device according to claim 5. It is designed for carrying out the method according to claim 1 and ge suitable. A device is used as it is state of the art. This is additionally equipped with at least one sensor, with the associated measuring device and their connection to the control unit of the vibrator. In the measuring device, in the control unit or in a separate component, a table for the optimum Rütteldauer is stored taking into account the parameters of the output mixture. There is also the switch-off delay tA stored, other influencing variables can be stored.

In practical operation, the mold rests on a vibrating plate so that access from below is difficult. The measurement of the electrical variable therefore preferably takes place on a side surface of the mold and / or in the stamp. In a multiple mold with a plurality of shells, an outer wall of an outer shell can be used. It can also be durchschal lt by ultrasound a variety of individual trays. It has proved to be advantageous to arrange the sensors on an externally accessible wall of a tub and / or the stamp. For resistance measurement, small electrodes are preferably used. You have to example 0.5-2 cm ² area. At least one Electrode is isolated and in direct contact with the concrete pulp. Also, the shell, if it is made of metal, can be used as an electrode, the same applies to the stamp. The ultrasound measurement can be carried out through the wall of the tub and / or the punch, in this case, the wall serves as a flow path. It is also possible to bring ultrasonic sensors into direct contact with the concrete pulp. One can also exploit a reflection of the ultrasonic waves on a wall of the shell and thus capture a longer path. In preliminary tests, it has been shown that individual surface areas of the vibrated paving stones have higher humidity than others. The invention relates to paving blocks which consist of a uniform mixture and to paving blocks, which are essentially made of a simpler concrete and a superficial layer of a header. Here are two filling operations in succession. During the retting, the intent and the ground substance usually behave differently under the intent. It is therefore advantageous to detect at least one electrical variable of the attachment and at least one electrical variable to the ground substance.

The detection of the at least one electrical variable can already begin before the shaking process. It can begin as soon as the shell has been filled and, if necessary, the stamp has been put on, if a sensor is provided in it. However, only during the Rütteins a noticeable change in at least one electrical variable is measurable. The electrical variable is preferably designed and selected such that it is influenced in particular by the shaking process.

It is known that ultrasound can be used to investigate the curing of concrete, see, for example, DE 198 56 259 B4. This is the curing process itself and not a measurement before and during a retting. Further advantages and features of the invention will become apparent from the other claims and the following description of several, non-limiting embodiments of the invention, which are explained in more detail with reference to the drawings. In this drawing show:

Fig. 1: a simplified representation of some parts of the apparatus for producing a paving stone, namely a concrete mixer, a filling device and a mold, a schematic representation similar to FIG. 1, but now for a closed, filled with concrete slurry form, based on a vibrating table a vibrator device, the mold is equipped with two sensors, each connected to a measuring device, which is connected to a control unit and to a memory, a perspective view of a partially cut tray with a total of three sensors, a plan view of a multiple mold, a Shell is equipped with two sensors, a perspective view of a stamp of a form, the Un terfläche is equipped with three sensors, a representation of the time course of the amplitude of an ultrasonic signal, and a diagram of the time course of measurements to Errei chen a predetermined W ertes.

The description uses a right-handed xyz coordinate system. The xy-plane lies in the horizontal, the z-axis goes vertically upwards. FIG. 1 schematically shows a concrete mixer 20, which may also be designed as a transport container. In it is a concrete slurry 21, too Called concrete mix. About a filling device 22, this concrete slurry 21 is filled in a shell 24. The shell 24 belongs together with a stamp 26 to a shape. FIG. 1 shows that the shell 24 is located below the device 22. The shell 24 has an upper opening, which is covered in the further course by the punch 26, this is shown in FIG. 2,

In Figure 2, the punch 26 has already been pressed onto the concrete slurry 21, it has previously been an initial shaking. The now closed mold is located on a vibrating table 28 of a vibrating device 30. It is assigned a control unit CON 32.

In two opposite side walls of the shell 24 and opposite each other, a first sensor 32 and a second sensor 34 are embedded in the wall so that their front surfaces have direct contact with the concrete slurry 21. The two sensors 32, 34 are ultrasonic oscillators, specifically an ultrasonic transmitter 32 and an ultrasonic receiver 34. These are designed for a frequency of 2 MHz and have a resonator diameter of about 25 mm. They are connected via a specially helical lead 40 with an M ES 42 measuring device. About the special leads 40, the shaking motion is intercepted. It typically takes place at a frequency of 50 Hz with an amplitude of 2 to 20 mm. The measuring device 42 is designed here as an ultrasonic measuring device, it generates a transmission pulse (see FIG. 6) for the sensor 32 and prepares the signals received by the sensor 34. The ultrasound passes once through the concrete slurry in the direct line between the two sensors 32, 34. It can be the sound propagation time and the Schailschwächung be measured.

The measuring device 42 is connected to a memory MEM 44. It contains a value table which contains the best values for the duration of the main lump as a function of several influencing variables, for example the moisture content of the concrete slurry 21 in the concrete mixer 20, the mechanical deformability of this concrete pulp, for example measured by an indenter or toughness , the grain distribution in the concrete pulp and the specific gravity. Thus, the value for the period of the main rinsing is present as a predetermined value V in the measuring device 42. The measuring device 42 determines an electrical variable from the ultrasound signals (see FIG. 6), see Figure 7. This changes constantly during the shaking process, as Figure 7 shows. Figure 7 shows only a few individual measuring points, in reality much more measuring points are obtained. It is possible to carry out a continuous measurement or measurement at specific time intervals, for example milliseconds. In Figure 7, the decrease of the switching attenuation S is exemplified over the time t. It can be seen that with increasing time the ultrasound passes faster through the tub. At a time tO - tA and taking into account the previous course, it is foreseeable at the latest that the predefined value V will be reached at the time t0. At the time tO-tA, therefore, the measuring device 42 sends a signal to the control unit 32, which switches off the drive of the vibrator device 30. This then comes to a standstill at time t0.

In the exemplary embodiment according to FIG. 3, the shell 24 is provided with two directly adjacent sensors 36, 37, which are suitable for a resistance measurement. They are identical. You have a distance from each other, for example, between 1 and 10 cm. They each have a central electrode 46 and around it an insulating body 48. this insulates the electrode with respect to the shell 24. The electrode 46 is in each case connected to a corresponding measuring device 42. The two electrodes 46 are in contact with the concrete slurry. The resistance of a surface area of the concrete slurry can be determined via the two electrodes 46. Furthermore, the resistance of a volume region of the concrete slurry can be measured via at least one of the two electrodes and the entire metallic shell as counterelectrode. Here, too, values are obtained, as shown similarly in FIG. The resistance changes during the course of the cooking and a time can be calculated at which the predetermined value V is reached. It then run from the described operations. In addition, in the shell 24 according to Figure 3, a sensor 38 is still arranged in a side wall, which is an ultrasonic transceiver. It is connected to a corresponding measuring device 42. About him a measurement signal is obtained. He first sends out a transmission pulse, as shown in Figure 6, this passes through the concrete slurry. A wall reflects the sound signal, the reflected signal goes back to the transceiver, which is now in the receiving operation is. Also in this way ultrasonic measurements can be achieved, as described above.

In the embodiment of Figure 4 is a multiple form is shown, of which only a small portion is shown, Shown is a complete shell 24, which is located in a corner area and therefore easily accessible. It is adjacent to three other, only partially shown shells 24, the shells 24 a multiple shell are identical. The fully illustrated shell 24 is provided on an outer wall with two sensors 38, 39. The sensor 38 corresponds to the ultrasonic sensor as described above for FIG. The sensor 39 is placed from the outside on the outer wall of the mold, it is also designed as a transceiver. His pulse first radiates through the metallic wall, then passes through the concrete porridge, is reflected on the opposite partition and returns to the sensor 39 back. This sensor is evaluated like the sensor according to FIG. 3. In the arrangement according to FIG. 4, the sensors 38, 39 can also cooperate. Thus, the transmission pulse of the sensor 38 can also be received by the sensor 39 in the reception mode and vice versa. It is also possible to irradiate a whole series of shells 24. If a transceiver is used, reflected signals of further partitions of the multiple form are also received. In this way, the double path of the form shown completely in FIG. 4 and the second form adjacent to the right is detected, later in time the echo signal of the third form adjoining it in the x-direction arrives, etc. The use of a transmitter 32 is advantageous instead of the sensor 38 in Figure 4 and a receiver 34 on the opposite in the x-direction outer wall of the multiple mold.

FIG. 5 shows how sensors 36, 37 and 38 are arranged in the stamp 26 on the lower surface. The sensors 36, 37 correspond to the sensors 36, 37 according to FIG. 3 and are evaluated accordingly. However, it is also possible to provide in an interaction of the sensors of the shell, for example those of Figure 3, and the punch 26 of Figure 5 additional measuring distances for resistance measurements and ultrasonic measurements, namely z. B. resistance measurements between one or the other electrode 46 in the punch 26 and the one and / or the other electrode 46 in the shell 24 or the shell 24 in total as a counter electrode. In addition, Figure 5 shows a sensor 38 of the ultrasonic type, which is directed in the beam direction to the bottom of the shell 24. The ultrasonic pulse is reflected there and returns to the sensor 38 back. The three sensors 36-38 of the punch 26 may be used to determine at least one electrical size of a header of the concrete block. In contrast, the sensors of the shell 24, for example according to Figure 3, can be used to detect the ground substance. In this way, two-layer concrete blocks can be detected technically. FIG. 6 shows the typical sequence of an ultrasonic measuring process. At a time 50, a transmission pulse 60 is radiated into the concrete pulp. This passes through the concrete slurry and arrives at a receiver, possibly after one or more reflections, at time 52. Another ultrasonic signal arrives at time 54, a third signal at time 56, etc. Normally, the longitudinal waves are faster and the signal 52 is thus the signal of a longitudinal wave. The other signals can be assigned accordingly, typically at time 54, the signal of the transverse wave has arrived. By measuring the time interval from the time 50 to the individual times 52, 54, 56, the transit time is determined, from which the speed of sound can be determined. This changes during the shaking process. In addition, the amplitude of the signals can be detected. As FIG. 6 shows, the amplitude of the signals generally decreases progressively. The amplitude, ie the height of the signals, changes during the retting. If it grows larger during the retting, this means less attenuation of the ultrasonic signal in the concrete pulp.

FIG. 7 shows an example of the procedure. Initially, for example, at the beginning of the main rinse, an electrical quantity M with the value 70 is obtained. This can be achieved, for example, via a single measurement, for example only of the resistance, or via an evaluation of several measurements obtained by resistance measurement and ultrasound measurement. A short time later, and thus a small period of Rütte later a second value 72 is obtained, which is different from the 1st. This continues with a third value 74, etc. After having a series of such values, it is possible to estimate by known mathematical methods, for example, to be extrapolated when the given value V will be reached. Then it is also possible to determine when the teleinrichtung 30 must be switched off so that at the end of the shaking the final value 80 is reached. For the purpose of explanation, it is assumed that the mathematical method initially does not consider the decay process that takes place during the turn-off delay. Rather, it is initially assumed that the shaking process continues undisturbed.

When the shaking process is completed, the values M no longer change. The time of shutdown can be adapted in a further development to the decay process of Rütteins. Since shaking becomes progressively weaker after the shaker device is switched off, but the abovementioned mathematical method initially assumes that the shaking continues unaltered, the decay process must either be additionally taken into account in the mathematical method or the shutdown process must be considered at a time tO-tA + tx, which lies between tO - tA and tO. Then, however, the vibrator 30 comes only a little later, namely at time tO + tx to a standstill. For example, the time period tx can be determined such that in the time period between tO-tA and tO + tx, a total energy of the product is achieved, as it exists without switching off in the time period from tO-tA to tO. The time span between tO - tA and tO is the switch-off delay. The duration of the delayed delay is tA.

In the mathematical method, the switch-off ^delay can be taken into account. For example, in a first approximation tx = Vz (tO - tA) can be selected. The method for producing a paving stone proceeds from a concrete mixture 21 filled into a mold. The mold has a shell 24 and a stamp 26. The shell 24 has an upper opening which covers the punch 26 from ^¬ . The mold is equipped with at least one sensor that detects at least one of the following electrical variables: a) ohmic resistance of a portion of the concrete mixture 21, b) measured value of an ultrasound signal that has passed through at least a portion of the concrete mixture 21. In the method, a shaking of the mold located therein with Betonmi ^¬ Research 21 by means of a vibrating device 30 and in at least one Rüttelschritt occurs. At least one electrical variable is detected at least during the shaking, including the time course of the change in the electrical quantity, and it is determined when the electrical variable reaches a predetermined level. stored value will take. The shaking is switched off, taking into account a switch-off delay of the vibrator 30, so that it comes to a standstill when the at least one electrical variable assumes the predetermined, stored value.

List of Reference Concrete mixer

concrete mix

filling

Bowl

stamp

shaking table

shaker

Control unit CON

first sensor

second sensor

third sensor

fourth sensor

fifth sensor

sixth sensor

supply

measuring device

Storage

electrode

insulator

, 52,54,56 times transmit pulse

1. received pulse

2. received pulse

3. received pulse

1. Value of electrical quantity 2. Value of electrical quantity 3, value of electrical quantity n-th value of electrical quantity

Claims

claims

1. A process for the production of a paving stone with the following process steps

- producing a concrete mixture (21)

- filling the concrete mixture (21) into a mold having a shell (24) and a punch (26), wherein the shell (24) has an upper opening which covers the punch (26), the mold is at least one Equipped sensor that detects at least one of the following electrical variables; a) ohmic resistance of a portion of the concrete mixture (21), b) measured value of an ultrasonic signal that has passed through at least a portion of the concrete mixture (21),

Shaking the mold with concrete mixture (21) contained therein by means of a vibrator (30) and in at least one shaking step,

Detecting the at least one electrical variable at least during the cooking, including detecting the time course of the change in the at least one electrical variable and determining when the at least one electrical variable will assume a predetermined, stored value,

Switching off the Rütteins taking into account a switch-off delay of the vibrator (30) so that it comes to a standstill when the at least one electrical variable assumes the predetermined, stored value, and

Demolding the vibrated concrete mixture (21) from the shell (24) and

- Allow the shaken concrete mixture (21) to harden.

2. The method according to claim 1, characterized in that before filling at least one property of the concrete mixture (21), including the water content, is determined and that the measurement result thus obtained is taken into account to set the predetermined, stored value.

3. The method according to any one of the preceding claims, characterized in that the detection of the at least one electrical variable begins before shaking.

4. The method according to any one of the preceding claims, characterized in that the electrical size of a surface area and / or a volume range of the concrete mixture (21) is detected.

5. Apparatus for producing a paving stone having

a concrete mixer (20) for producing a concrete mixture (21) and a filling device (22),

- A mold, which is at least temporarily under the filling device (22) and which has a shell (24) and a punch (26), wherein the shell (24) has an upper opening which covers the punch (26) which Form is equipped with at least one sensor (32) which detects at least one of the following electrical variables: a) Resistivity of a portion of the concrete mix (21), b) Measured value of an ultrasonic signal passing through at least a portion of the concrete mix (21) .

a measuring device which is electrically connected to the at least one sensor (32), the signal of which is conditioned and has at least one output,

a vibrator (30) with a control unit, the vibrator

(30) has a receiving area for the mold, the control unit is electrically connected to the output of the measuring device (42),

- means for demolding the vibrated concrete mixture (21) from the shell (24),

Device according to claim 5, characterized in that the sensor (32) comprises at least two electrodes (46) which are in contact with the concrete mixture (21) and in each case electrically connected to the measuring device (42) which determines the ohmic resistance between the two Electrodes (46) are detected, connected.

7. Apparatus according to claim 5 or 6, characterized in that the measuring device (42) comprises either at least one ultrasonic transmitter and an ultrasonic receiver or at least one transceiver for ultrasound, each of which is electrically connected to the measuring device (42), which at least one ultrasound Measured value recorded, wherein detection of the propagation time of the ultrasound signal, detection of the attenuation of the ultrasound signal are possible ultrasound measured values,, Device according to one of claims 5-7, characterized in that the plunger (26) at least one sensor (32) and / or that at least one side wall the shell (24) has at least one sensor (32). , Device according to one of claims 5-8, characterized in that the punch (26) and the shell (24) made of a metal, in particular iron or steel, is made.