EP1640061B1

EP1640061B1 - Process for obtaining a compound to be used for making concrete screed and relevant mixing device

Info

Publication number: EP1640061B1
Application number: EP05018510A
Authority: EP
Inventors: Luciano Peron
Original assignee: PERON Srl - Unipersonale
Current assignee: PERON Srl - Unipersonale
Priority date: 2004-09-24
Filing date: 2005-08-25
Publication date: 2010-05-26
Anticipated expiration: 2025-08-25
Also published as: EP1640061A1; DE602005021440D1; ATE468911T1; ITVI20040227A1

Abstract

The invention is a process for obtaining a compound to be used for making concrete screed, comprising the following operations: setting the quantity of compound needed and the proportion of the solid and liquid mixtures that make it up; conveying said solid mixture into a container, and measuring the conveyed volume in order to be able to stop conveying said liquid when the set quantity has been reached; weighing the compound contained in the container in order to calculate the weight of the solid mixture and stop conveying it into the container when the set quantity has been reached. The invention also concerns a mixing device and a corresponding machine.

Description

The invention concerns a process for obtaining a compound to be used for making concrete screed and the relevant mixing device.
It is known that to make concrete screeds a special compound of solid and liquid substances, comprising a mixture of sand, water, binders, etc. is used.
The composition of the compound varies according to the characteristics of the screed to be obtained.
The compound is made on the site where the screed is to be laid, preparing first the suitable quantities of solid elements, including sand, binders, etc, and adding a given percentage of water.
In order to shorten the time necessary to make the compound, the known technique involves the use of preparations, called pre-mixed products, that are constituted by the solid components of the compound.
In particular, said products comprise a solid mixture substantially made up of sand and binders, which is prepared in advance and stored in special containers that are then transported to the site where the compound is going to be laid.
To reduce the time necessary to make the screed and, in particular, its drying time, according to the known technique the product also comprises special additives, also called catalyzers, that are activated when placed in contact with water.
To make said compound, according to the known technique automatic mixing devices are used.
Said devices comprise a container or tank provided with a first duct for conveying said solid elements, a second duct for conveying water and one or more moving blades installed inside the container.
The device also comprises a control unit provided with interface means, suited to control both the opening/closing of the conveying ducts and the rotation of the moving blades.
Practically the operator, once having set the quantity of compound needed and the necessary percentage of water per unit of weight via the interface means, activates the device.
The control unit automatically provides for opening for a preset time the solid mixture conveying duct and the water conveying duct.
The compound is first amalgamated, then uniformly spread on the surface to be treated and finally properly levelled.
Once it has hardened, the operator proceeds to the laying of tiles or similar coverings to obtain the desired floor.
A first drawback posed by the process for obtaining a compound for making concrete screed and the relevant device as described above is constituted by the fact that they do not allow the percentage of components actually introduced in the container to be checked with precision. These quantities, in fact, depend on the capacity of the two conveying ducts that, mainly for the solid mixtures, is not constant due to the natural tendency of the various components to agglomerate.
A further inconvenience connected to the previous one is the fact that the compound obtained by adding water does not feature the optimal characteristics for making a good screed. More precisely, the compound does not contain the required percentage of each component per unit of weight.
This negatively affects both the mechanical characteristics of the screed obtained and the drying time of the screed itself.
A further example of a mixing process and a mixing device according to the prior art is known from document US 2002/09/3875A1
The aim of the present invention is to overcome all the drawbacks described.
In particular, it is a first aim of the invention to propose a process for obtaining a compound for making concrete screed and a relevant mixing device that allow the quantity and the ratio of the components of the compound to be checked more accurately.
It is another aim of the invention to propose a process and a device that make it possible to prepare a compound with shorter drying time than compounds made with processes and devices of known type.
It is another aim of the invention to propose a process and a device that make it possible to prepare a compound that is easier to use and to lay than compounds made with processes and devices of known type.
It is another aim of the invention to propose a process and a device that make it possible to make a screed with higher mechanical resistance than the screeds obtained with processes and devices of known type.
Another aim of the invention is to produce a device that can be easily transported near the laying site.
It is a further aim to produce a device that is easy to use and does not require the intervention of qualified personnel.
It is a further aim of the invention to produce a machine that makes it possible to prepare a compound for making concrete screed directly on the laying site.
It is another, yet not the least aim of the invention to produce a device and a machine, both economic and reliable, that do not require frequent and costly maintenance operations.
The aims described above have been achieved through the implementation of a process for obtaining a compound for making concrete screed, according to claim 1.
The aims described are achieved also by a device constructed according to the contents of claim 6.
The aims described are achieved also by a machine constructed according to the contents of claim 22.
The proposed solution advantageously makes it possible to check more accurately both the quantity of compound prepared and the proportion of the mixtures that make it up.
The aims and advantages described above will be highlighted in greater detail in the descriptions of some preferred embodiments of the invention, given indicatively as examples without limitation, with reference to the enclosed drawings, wherein:

Figure 1 shows a schematic view of a mixing device carried out according to the invention;
Figure 2 shows a side view of a machine for preparing compounds for making concrete screeds that is also the subject of the invention.

The process subject of the invention and the examples of embodiment of a relevant mixing device described are particularly suited to obtain a compound for making concrete screed from a mixture or product of the type called "pre-mixed" P comprising sand, binders and additives.
In this case the compound is obtained by mixing the solid mixture with a liquid mixture comprising, for example, water.
It is clear that the solution proposed can be applied also to make different compounds, used preferably in the building sector, like, for example, clay-based insulating compounds, polystyrene, pearlite, etc.
According to the invention, a process for obtaining a compound to be used for making concrete screed comprises the following operations set out in claim 1.
Always according to the invention, the compound contained in the container is mixed and the weight of the solid mixture is calculated in order to be able to stop conveying it into the container when the set quantity has been reached.
The weighing and the measurement of the liquid volume are carried out at the same time, in order to calculate the weight of the solid mixture present in the container.
The weight of the solid mixture present in the container is calculated by deducting the weight of the liquid mixture, which is given by its volume multiplied by its specific weight, from the weight of the compound contained in the container.
This makes it possible to check continuously and precisely both the quantity of compound that is being made and its composition, with no risk to meet the inconveniences described above.
The calculated weight coincides, in fact, with the weight of the solid mixture actually present in the container.
The compound is then properly stirred in order to obtain a substantially homogeneous compound that is successively spread onto the surface to be treated. A device for mixing compounds for making concrete screed that implements the method described is represented in Figure 1, where it is indicated as a whole by 1. It comprises first means 2 for conveying a solid mixture P in container means, indicated as a whole by 4, and second means 3 for conveying a liquid mixture L in the same container means 4.
Measuring means, indicated as a whole by 5, constantly measure the volume of liquid mixture L conveyed into the container means 4 comprising, in the case in question, a container 41.
According to the invention, the device 1 also comprises weighing means 6 suited to weigh the compound contained in the container means 4 to obtain the weight of the solid mixture P and check its flow into the container means 4.
In the case in question, the device also comprises a control unit 7 cooperating with the measuring means 5 and with the weighing means 6, suited to automatically stop the flow of the solid mixture P into the container means 4 when the weight of the solid mixture P is substantially equal to a weight calculated according to the quantity of compound needed and to the desired proportion of the mixtures P and L.
A different embodiment of the device subject of the invention is differentiated from the previous ones due to the fact that the flow of the mixtures P and L can be stopped even manually by the operator. In this case the operator receives a signal, for example an acoustic signal, that indicates that the quantity of mixture conveyed is as desired.
The control unit 7 also comprises interface means 8 comprising a keyboard 81 and a display 82 that allow the operator to set the parameters regarding the weight of the compound to be obtained and the percentage of its various components.
In the example given, the control unit 7 comprises a microprocessor unit and a memory unit.
As regards the first conveying means 2 of the solid mixture P, they comprise a duct 9 fed by a tank 10 of mixture P, provided at its outlet 11 with an on-off throttle valve 12 controlled by the control unit 7. In the case in question, the duct 9 is fed by means of a rotary auger/screw 13, also controlled by the control unit 7, that transports the mixture P from the tank 10 to the container 4. In the example of embodiment described, therefore, the mixture P is conveyed by gravity.
As regards the second means 3 for conveying the liquid mixture L, they comprise a duct 15 that can be fed by a tank containing the liquid mixture L, provided with an on-off throttle valve 17 controlled by the control unit 7.
As regards the means 5 for measuring the volume of liquid mixture L conveyed into the container 4, they comprise a flow meter 51 cooperating with the control unit 7. In the case in question, the flow meter is of the type called turbine flow meter, but in other embodiments it may be of a different type, for example a piston or Venturi flow meter, etc.
The device also comprises mixing means, indicated as a whole by 18, positioned inside the container 4 and suited to stir the mixtures P, L to obtain a substantially homogeneous compound.
In the example represented, the mixing means 18 comprise several moving blades 19 fixed to a revolving shaft 20 controlled by the control unit 7.
As regards the weighing means 6, they comprise, in the embodiment, load cells 61 connected to the control unit 7. In other embodiments also different weighing systems may be provided.
The device 1 also comprises means for extracting the compound from the container 41, comprising, in the case in question, a pump provided with a suction mouth 21 and positioned on the bottom of the container 41.
In other embodiments the container 41 is tight and the compound is extracted by pressurizing the container 41 itself with a compressor unit that pushes the compound towards an outlet duct positioned on the bottom of the container 41.
A machine for preparing a product for making concrete screed that is also subject of the invention is represented in Figure 2, where it is indicated as a whole by 500.
It comprises a motor-driven vehicle 501 on which a compound mixing device 502 of the type described above is installed.
The machine 500 also comprises means 503 suitable for storing and transporting a pre-mixed preparation or product. Said means are suited to stir the preparation or product in order to maintain and guarantee its homogeneity during both storage and transport to the laying site.
To prepare the compound, the operator proceeds by setting, via the interface means 8, the weight of the compound needed and the proportion of the solid and liquid mixtures P and L that make it up.
For example, the operator introduces, according to the solid mixture or pre-mixed product P available, the percentage of water per kg of solid mixture that is necessary to obtain the best performance in term of both compound drying time and hardness of the screed obtained.
At the end of the setting phase, whose parameters can also be stored and successively recalled in the control unit 7, the operator starts the process.
The control unit 7 activates the first conveying means 2 that convey the mixture P into the container 4 and then the second means 3 that convey the liquid mixture L.
This serves to avoid, in the case in question, the outflow of the liquid L from the container through the outlet mouth 20.
At the same time, the load cells 61 and the measuring means 5 communicate to the control unit 7 the weight of the mixtures P, L present in the container 41 and the volume of the liquid L conveyed into the same container 41, respectively. The control unit 7 calculates first the weight of the liquid L and then the weight of the solid mixture P, deducting the calculated weight of the liquid from the value measured for the load cells.
In this regard it should be observed that the weight of the liquid L is calculated by the processing unit by multiplying the volume of liquid L measured from the flow meter by the specific weight of the liquid L itself, which can also be set in advance by the operator via the above mentioned interface means 8.
The control unit 7 then compares the weight of the two mixtures with the desired weights as indicated by the data set in advance by the operator.
When the weight of the mixtures contained in the container is equal to the desired weight, the unit 7 stops the flow of the corresponding mixture by means of the corresponding on-off valve 12 or 17.
At the end of these operations, the control unit activates the mixing means 18 for a lapse of time that can be set, until a substantially homogeneous compound is obtained.
Finally, the operator starts the means for extracting the compound that, through the outlet duct 20, discharge the compound onto the surface on which the screed must be laid.
It should be observed that the mixing means 18 can be activated also while the mixtures P, L are conveyed into the container, thus reducing the time necessary to prepare the compound.
The above clearly shows that the process and the device proposed allow the drawbacks described to be overcome and the goals set to be achieved.
Even though the invention has been described making reference to the attached drawings, upon implementation changes can me made that shall all be considered protected by the present patent, provided that they are within the scope of the inventive concept expressed in the following claims.

Claims

Process for obtaining a compound for making concrete screed, comprising the following operations:
- setting the quantity of compound needed and the proportion of the solid (P) and liquid mixtures (L) that make it up;

- conveying said solid mixture into container means (4);

- conveying said liquid mixture (L) into said container means (4), measuring the volume of said liquid mixture conveyed into said container means in order to be able to stop conveying said liquid when the set quantity has been reached;

- weighing the compound contained in said container;

- mixing the compound contained in the container means (4);
characterized in that it further comprises:
- calculating the weight of said liquid mixture conveyed into said container means;

- calculating the weight of said solid mixture by deducting the calculated weight of said volume of liquid mixture conveyed into said container means from the weight of the compound contained in said container and stop conveying it into said container when the set quantity has been reached.
Process according to claim 1, characterized in that the weight of said volume of liquid mixture conveyed into said container means is calculated multiplying the volume of liquid mixture conveyed into said container means by the specific weight of said liquid mixture itself.
Process according to one of claims 1 and 2, characterized in that said liquid mixture comprises water.
Process according to one of claims 1 to 3, characterized in that said solid mixture comprise sand and/or binders and/or additives.
Process according to one of claims 1 to 4, characterized in that said weighing and volume-measuring operations are carried out at the same time.
Device (1) for mixing compounds for making concrete screed, comprising:
- first (2) and second (3) conveying means and container means (4), said first and second conveying means being adapted to convey at least one solid mixture (P) and one liquid mixture (L), respectively, which make up said compound, into said container means (4);

- measuring means (5) adapted to measure the volume of said liquid mixture (L) conveyed into said container means (4);

- weighing means (6) adapted to weigh the compound contained in said container means (4);

- mixing means (18) positioned inside the container means (4) and suited to stir said mixtures;
characterized in that it further comprises:
- means adapted to calculate the weight of said volume of liquid mixture conveyed into said container means (4), and means adapted to calculate the weight of said solid mixture (P) by deducting the calculated weight of said volume of liquid mixture conveyed into said container means (4) from the weight of the compound contained in said container means (4) and check its flow into said container means (4).
Device according to claim 6, characterized in that said device further comprises means adapted to calculate the weight of said volume of liquid mixture conveyed into said container means (4) by multiplying the volume of liquid mixture conveyed into said container means (4) by the specific weight of said liquid mixture itself.
Device (1) according to claim one of claims 6 and 7, characterized in that said device (1) also comprise signalling means cooperating with said weighing means (6) and adapted to send out a signal at least when the quantity of said solid mixture (P) in said container means (4) is substantially equal to the quantity of mixture that is desired and/ or that can be set.
Device (1) according to one of claims 6 to 8, characterized in that said device (1) also comprises a control unit (7) cooperating with said measuring means (5) and said weighing means (6) and adapted to automatically stop the flow of said solid mixture (P) into said container means (4) when the weight of said solid mixture (P) in said container means (4) is substantially equal to the quantity that is desired and/or that can be set.
Device (1) according to one of claims 6 to 9, characterized in that said control unit (7) is adapted to automatically stop the flow of said liquid mixture (L) when the measured quantity is substantially equal to the quantity that is desired and/or that can be set.
Device (1) according to one of claims 9 and 10, characterized in that said control unit (7) comprises interface means (8) for setting at least the quantity of compound needed and the proportion of the solid and liquid mixtures making up said compound.
Device according to one of claims 9 to 11, characterized in that said one control unit (7) comprises a processing unit suited to calculate the quantity of solid mixture (P) to be conveyed into said container means (4), according to the quantities of compound that are desired and/or that can be set and to the proportions of said mixtures (P, L).
Device (1) according to one of claims 6 to 12, characterized in that said first conveying means (2) comprise at least one duct (9) provided with at least one on-off valve (12).
Device (1) according to one of the claims 6 to 13, characterized in that said second conveying means (3) comprise at least a second duct (5) provided with at least one on-off valve (17).
Device (1) according to one of claims 13 and 14 when appended to claim 10, characterized in that said on-off valve (12, 17) is controlled by said control unit (7).
Device (1) according to one of claims 6 to 15, characterized in that said mixing means (18) comprise at least one moving blade (19).
Device (1) according to one of claims 6 to 16, characterized in that said device (1) comprises means for extracting said compound from said container means (4).
Device (1) according to claim 17, characterized in that said means for extracting said compound comprise at least one pump.
Device (1) according to claim 17, characterized in that said means for extracting said compound comprise a compressor unit.
Device (1) according to claim 19, characterized in that said container means (4) comprise a pressurized container (41) cooperating with said extracting means.
Device (1) according to one of claims 6 to 20, characterized in that said weighing means (6) comprise at least one load cell (61).
Machine (500) for preparing compounds for making concrete screed, comprising a vehicle (501), a device (502) for mixing compounds for making concrete screed, characterized in that said machine comprises a device (1) for mixing compounds for making concrete screed, as claimed in one of claims 7 to 21.