DE29508527U1 - Device for mixing a liquid additive into a flowable base - Google Patents

Description

The invention relates to a device for mixing a liquid additive into a flowable base mass/namely a device according to the preamble of claim 1.

The device can be used, for example, for dry or wet spraying of concrete or mortar, for example when cladding tunnel interior walls, in tunnel and mining operations, and for securing slopes and excavations.

Devices for wet spraying concrete or mortar that are known on the market and intended for batch or continuous operation have a hydraulic double-piston pump with two chambers, in each of which a piston is slidably mounted. The two chambers are connected to a filling funnel through which the chambers are alternately filled with flowable concrete. While one chamber is filled with flowable concrete, the piston of the other chamber transports a previously collected batch of concrete into a transport line, which has a spray nozzle at its free end for spraying the concrete.

When processing sprayed concrete or sprayed mortar, flowable additives or additives are often added to the concrete or mortar to be sprayed - hereinafter also referred to as the base material.

Ks/df/18628/Case 3

Additives are added, the latter being added to the base mass using a wet spraying process using a conveyor system and compressed air. When processing sprayed concrete, the base mass normally consists of cement, water and additives such as gravel, sand or crushed rock.

Examples of additives include setting accelerators, which lead to rapid setting of the sprayed mixture, as well as additives which reduce rebound and dust formation during spraying.

These flowable additives mentioned above are preferably added to the concrete or mortar immediately before the spraying process, i.e. in the area of the spray nozzle, and are often solutions that contain chemically aggressive substances, such as setting accelerators based on alkali carbonates or alkali aluminates. However, the flowable additives are often also solid dispersions in liquid media, especially aqueous dispersions, some of which have abrasive properties.

The use of solutions or dispersions with strong alkaline properties or strong abrasive effects usually leads to damage to the conveying equipment very quickly.

This problem, which occurs during the metered delivery of flowable additives for shotcrete or sprayed mortar, has been known for a long time. In order to overcome the aforementioned difficulties, conveying and dosing devices have already been proposed in which the components that define at least one passageway for the flowable additives to be conveyed are made exclusively of elastically deformable or flexible materials.

materials and are also chemically resistant to the flowable additives.

Another problem that occurs with flowable additives that are only added to the shotcrete immediately before the spraying process is that the corresponding additives are dosed in very small quantities and that therefore the exact dosage is very often critical. In addition, especially with such small quantities of additives, it must be ensured that the corresponding additive is nevertheless evenly distributed in the sprayed material so that the required homogeneous properties are achieved both in the sprayed material and in the hardened product.

In addition, it is very often necessary to determine the recipe of the additives, which may consist of at least one component, in advance - before the actual dosing - depending on the composition of the base mass and the properties to be achieved in the finished product.

In this context, however, the known devices have the disadvantage that an additive to be introduced into the aforementioned transport line often cannot be transported at a constant, consistent speed and/or is not always optimally matched to the composition of the base mass, so that, especially in the large-scale use of shotcrete or shotcrete mortar, when larger batches of such are to be processed repeatedly, it cannot be ensured with the known devices and methods that the shotcrete or shotcrete mortar is always applied with consistent physical and chemical properties and that the hardened concrete bodies produced thereby always have the desired properties.

Moreover, if after processing a batch of concrete it is determined that the concrete body or layer formed does not have the desired quality, the known devices often do not allow the cause of the loss of quality to be determined.

The invention is based on the object of creating a device that does not have the disadvantages of the known devices and in particular enables the flowable additives to be mixed quickly and optimally with the base mass mentioned, so that the base mass is homogeneously wetted and the product formed then has a correspondingly homogeneous composition. Furthermore, the device should be able to be used in particular for the preparation of shotcrete and shotcrete mortar.

This object is achieved by a device having the features of claim 1.
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Advantageous embodiments of the device emerge from the dependent claims.

The invention will now be explained using two systems for wet spraying of concrete shown in the drawing. The drawing shows

Figure 1 is a schematic representation of a first system for wet spraying of concrete,
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Figures 2 and 3 each show a schematic representation of a measuring probe for determining the flow velocity and

Figure 4 is a schematic representation of a second system for wet spraying of concrete.

The system for wet spraying concrete shown in Figure 1 and designated as a whole by 1 has feed means to add the flowable additives to the concrete base mass. These feed means have a storage container 2 for flowable additives and a controllable conveyor device with, for example, a speed-controlled gear. The storage container 2 is provided with an outlet through which the flowable additives to be conveyed pass when the device is in operation and reach the conveyor device 3 via a feed line 4. For this purpose, the additives are sucked in by the conveyor device 3, for example, or are otherwise fed into the conveyor device 3. A rotary peristaltic pump can be used as the conveyor device, for example. Peristaltic pumps are used in laboratory technology for the metered conveyance of small and large quantities. It is known that peristaltic pumps can also be used to meter thick, highly viscous and aggressive media.

However, other types of positive displacement pumps can also be used to pump flowable additives. For example, gear pumps, screw pumps or eccentric screw pumps are also suitable. Eccentric screw pumps and hose squeeze pumps have the advantage over other pumps that they are less sensitive to abrasive additives.

The system 1 also has a double piston pump 12, of which only the most important components are shown in Figure 1. This is preferably an oil-hydraulically driven double piston pump, for example the

Double piston pump manufactured by MEYCO AG in Winterthur, which is contained in the concrete spraying machine sold under the trade name SUPREMA. This double piston pump is already the subject of Swiss patent application no.

When pumping flowable or liquid concrete or mortar, it is important that the concrete or mortar flow is pumped continuously, with little or no fluctuation. This requirement is essentially met - as can be seen from the aforementioned Swiss patent application - by the double piston pump from MEYCO AG.

The double piston pump 12 has two cylindrical chambers 13 and 14, each of which opens via an opening 15 (only one of which is visible in Figure 1) into a filling funnel 16 intended for receiving the concrete. Two pistons 17 and 18 are also movably guided in the chambers 13 and 14. Finally, within the filling funnel 16 there is a curved pipe section 20 attached to a rotating joint 19, which is connected with its outlet in a fixed position to a material line 21, referred to below as the concrete delivery line. In the illustrated embodiment, the pipe section 20 is designed and attached to the joint 19 in such a way that it can be rotated with its inlet selectively in front of one of the two openings 15.

At the free end section of the concrete delivery line 21 there is a spray nozzle 22 for spraying the concrete, which in turn has a passage 22a through which the flowable base mass, i.e. the shotcrete, can be passed. The above-mentioned additive supply line 11 and also a gas line 23 now open into this nozzle 22. The latter is connected to a pressure

air source 25, which for example has at least one compressor and a storage container in order to generate a compressed gas, namely compressed air.

The additive supply line 11 and the concrete delivery line 21 also each have a flow measuring probe 26 or 27, respectively, in order to measure the flow rate, i.e. the amount of additive or concrete passed through the corresponding line per unit of time.

At this point, it should be noted that, within the scope of the invention, the system 1 can also have only one flow measuring probe, in particular only the measuring probe 26 arranged in the additive supply line 11.

For example, an electromagnetic or inductive measuring cell known in its function can be used as the flow measuring probe 26 or 27. In Figure 3, the flow measuring probe 26 arranged in the line 11 is shown schematically as a representative of both flow measuring probes. This has a U-shaped electromagnet 28 which surrounds a line section 11a of the supply line 11 and generates a homogeneous magnetic field perpendicular to the line axis 11b. The line section 11a is provided with insulation 29 on the inside of the pipe and has two electrodes 30 in its wall which are arranged perpendicular to the magnetic field and perpendicular to the pipe axis 11b and from which the voltage induced in the liquid, which is proportional to the flow, can be tapped. As a result of the fact that the magnetic field strength cannot be chosen arbitrarily, the voltage generated may not be very high, so that the measuring signals recorded by the measuring probe 2 6 are first amplified in a control and measuring circuit designated 31 in Figures 1 and 3.

must be transmitted to the central control system 32 shown in Figure 1.

Electromagnetic flow measurement is practically independent of interference that can occur in conventional flow measuring devices due to bends or constrictions in the measuring area of the passages intended to accommodate the fluid. Likewise, the viscosity and density of the liquid have no influence on the measurement accuracy, which is particularly advantageous for viscous dispersions and the like.

The central control system 32 includes a control circuit (not shown) with electrical and/or electronic components for measuring, controlling and regulating. The control circuit is connected with electrical connections indicated by arrows to the motors of the conveyor device 3 and the piston pump 12 and, if necessary, to the controllable compressed air valve 24. The control circuit also has measuring and control means to register the signals measured by the flow measuring probes 26 and 27 and amplified by the control and measuring circuit 31 and to control the subsequent injection process in a manner explained in more detail below depending on these signals or the measured values determined from them. The control circuit can, for example, have analogue computing amplifiers, comparison circuits and the like and/or an analogue/digital converter for converting the measurement signals into digital signals and a digital computer.

The central control system 32 also has analog and/or digital display means 33 for displaying operating states and the like. These can be designed to continuously display the measured values determined during the measuring phase.

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Furthermore, manually operable control elements 34 such as push-button switches and the like are provided with which, for example, the conveying speed of the concrete or additive can be regulated manually, preferably continuously. 5

The control system 32 is therefore designed in such a way that the sequence of the method for spraying concrete described below can be controlled either by manually operating control elements, at least partially by a person, or completely automatically by the control system 32. However, when processing shotcrete or sprayed mortar on a large scale, the spraying process described below is to be controlled automatically as much as possible and the method is to be controlled "manually" by a person only temporarily.

When the system 1 is in operation, a base mass consisting essentially of water, cement and additives is fed into the filling funnel 16 of the double piston pump 12 and conveyed with it through the concrete delivery line 21. In the spray nozzle 22, the base mass, i.e. the flowable concrete, is then additionally mixed with the additive required for the specific purpose and subjected to the pressure required to spray the concrete via the compressed air line 23.

If, for example, a shotcrete layer is to be applied to a tunnel face that is to be secured using the system 1, the speed of the additive flowing through the line 11 is measured, recorded and compared with a predetermined target value, in particular using the measuring probe 26, either continuously or at short, successive time intervals. As soon as the flow rate of the

If the flow rate of the additive changes, the motor of the conveyor device 3 is driven or regulated by the central control system 32 in such a way that the preset target value for the flow rate of the additive is restored. If necessary, the control valve 24 of the compressed air supply line 23 can also be regulated by the control system 32. The target value mentioned is preferably set before the system 1 is put into operation and depends on the desired properties of the concrete body or concrete layer to be formed, i.e. in particular on the base mass used, which is made up of sand, water and aggregates, and on the additive or additive mixture to be added to this base mass.

With the method, using the device according to the invention, a constant and consistent delivery of the additive and thus also a constant and consistent dosage of the additive in the mixture can be easily maintained, so that an optimal shotcrete quality is achieved. In addition, the device according to the invention can be used to virtually completely automate the spraying work, which is particularly important for larger construction projects. The occupational safety and general working conditions of the staff are also significantly improved. For example, the automatic dosage of the additives can prevent unintentional dust formation when there is insufficient liquid added. Furthermore, if necessary, the cause of a loss of quality identified after the formation of a concrete body can be subsequently determined using the recording and storage means of the central control system 32.

With the control system 32 of the system 1 according to the invention, the additive flow rate can also be controlled.

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speed depending on a possibly fixed concrete delivery rate, which is advantageous for consistent product quality with large delivery quantities.

However, controlling the additive flow rate depending on the delivery rate requires that the concrete or mortar flow is pumped continuously, or if necessary only with little or as little fluctuation as possible. This requirement is - as already mentioned - essentially met by the double piston pump 12 from Meyco AG.

The measuring probe 27 shown in Figure 1 can also be used to measure the speed of the shotcrete conveyed through the concrete delivery line 21, so that the concrete delivery rate can then also be regulated by the control system 32 in analogy to the regulation of the additional flow rate described above. To this end, the speed of the shotcrete conveyed through the concrete delivery line 21 is measured continuously or at short, successive time intervals, recorded and compared with a target value that is also set in advance. As soon as the flow rate of the concrete changes, the motor of the double-piston pump 12 is driven or regulated by the central control system 32 in such a way that the target value for the flow rate of the concrete that was set in advance is restored.

Because the concrete delivery rate can also be controlled and regulated in the illustrated example, the additive flow rate, which may be dependent on the delivery rate, can then be optimally adjusted to the concrete flow.

Finally, the system 1 and in particular the central control system 32 can also be designed in such a way that the recipe of the additives, which may be made up of at least one component, is calculated automatically depending on the composition of the concrete base mass, namely according to a predetermined calculation rule, so that an optimal product quality can be achieved.

It should be noted at this point that the system 1 described with reference to Figures 1 and 2 and the method that can be carried out with this system represent only a selection of possible embodiments of the invention and can be modified in various respects.

Figure 3 shows another embodiment of a flow measuring probe that can be used for the purpose according to the invention, namely a vane wheel flow meter 40. This has a chamber 41 that is circular in longitudinal section and has a star-shaped counter wheel 42 that can rotate therein. In the wall of the chamber 41 there is also an optical or magnetic - for example electromagnetic - sensor 43 that functionally interacts with the measuring sensors 44 of the counter wheel 42.

If, for example, a flowable additive is passed through the chamber 41, the counter wheel 42 is rotated in the direction of arrow 45, whereupon a signal proportional to the flow can be measured with the sensor 43.

Figure 4 shows a second system for wet spraying of concrete. This system, designated as a whole by 101, is essentially the same as system 1 and has a double piston pump 112, a nozzle 122 connected to the outlet of the double piston pump 112.

concrete conveying line 121, a conveying device 103, an additive supply line 111, and a compressed air line 123 with a control valve 124. The lines 111 and 121 also each have a flow measuring probe 126 or 127 of the type described above. With regard to the flow measuring probe 126, it should also be mentioned that this can also be arranged downstream of the conveying device 103 with respect to the additional flow direction, especially if the latter sucks in the additive to be conveyed from a storage container.

In the illustrated embodiment, however, the compressed air line 123 also has a flow divider 150, which divides the compressed air between the two compressed air lines 123a and 123b when the system is operating. As can be seen from Figure 4, the additive supply line 111 flows into the compressed air line 123b. The latter then guides the additive pressurized with compressed air into the spray nozzle 122 when the system 101 is operating. The line 123a, which only carries compressed air, also flows into the spray nozzle 122. This can - in relation to the flow direction of the concrete - either flow into the spray nozzle 122 before or after the compressed air line 123b.

Like system 1, system 101 also has a control and measuring circuit 131 and a central control system

132. Plant 101 essentially works in exactly the same way as plant 1, but differs from it in terms of the supply of the additive. Plant 101 is particularly suitable for the use of silicate-based additives.

Furthermore, instead of the flow measuring probes shown in Figures 2 and 3, other flow measuring devices can also be used, such as volumetric measuring devices or mass flow meters, such as turbine flow meters.

or oval gear meters"k"preferred are flow meters, which do not have any cross-sectional constrictions or bends in the additive passage in the measuring range.

Claims (9)

■fÄTHSTANS PRÜCHE 1. Device for mixing at least one flowable additive into a base mass flowing through a transport line (21, 121), with feed means for adding the at least one additive to the base mass flowing through the transport line (21, 121), characterized in that the feed means have at least one flow measuring element for determining a measurement variable which provides a measure for the amount of the at least one additive introduced into the transport line (21, 121) per unit of time, and that a control system (32, 132) connected to the at least one flow measuring element and the feed means is present in order to control the feed means and thereby the amount of additive introduced into the transport line (21, 121) per unit of time during operation of the device depending on the said measurement variable. 2. Device according to claim 1, characterized in that said flow measuring element is an electromagnetic flow measuring probe (26, 126), or a vane flow meter (40), or a turbine flow meter, or an oval gear meter . 3. Device according to claim 1 or 2, characterized in that the supply means comprises at least one storage container (2) for the at least one flowable additive and a conveying device (3, 103) fluidly connected to the storage container (2) with a controllable drive, wherein the conveying device (3, 103) is connected to an additive supply line (11, 111) which opens into the said transport line (21, 121), and that the flow measuring element (26, 126) is arranged upstream of the conveying device (3, 103) with respect to the additive flow direction. 4. Device according to claim 3, characterized in that the conveying device (3, 103) is a rotary hose pump, or a spindle pump, or an eccentric screw pump or a gear pump; 5. Device according to one of claims 1 to 4, wherein a pump device is provided in order to convey the said base mass through the transport line (21, 121), characterized in that the pump device is connected to the control system (32, 132) in such a way that the amount of additive introduced into the transport line (21, 121) per unit of time during operation of the device can be controlled as a function of the concrete delivery rate. 6. Device according to one of claims 1 to 5, wherein a pump device is provided to convey said base mass through the transport line (21, 121), characterized in that the transport line (21, 121) has at least one flow measuring element to determine a measurement variable which provides a measure for the amount of base mass passed through the transport line (21, 121) per unit of time, and that this flow measuring element and said pump device are connected to the control system (32, 132) in such a way that the pump device and thus the amount of base mass passed through the transport line (21, 121) per unit of time can also be controlled during operation of the device depending on the above-mentioned measurement variable. 7. Device according to claim 5 or 6, characterized in that the said flow measuring element is an electromagnetic flow measuring probe (27, 127). 8. Device according to one of claims 1 to 7, characterized in that a recording device is provided to continuously record all measurement variables. 9. Plant for processing sprayed mortar or sprayed concrete, characterized by a device according to one of claims 1 to 8.