ES2369855T3 - MIXING UNIT FOR CONCRETE PREPARATION SYSTEMS AND ASSOCIATED METHOD. - Google Patents

Abstract

A mixing assembly (100) for systems for preparing concrete, comprising a mixing tank (2) provided with mixing elements (3), at least one loading inlet (4) for introducing binders in powder form, at least one loading inlet (5) for introducing dosage water, a mixing pump (10) for mixing the content of the mixing tank, and a management and control unit which comprises memory means programmed to check the loading and unloading of the concrete components.

Description

Mixing unit for concrete preparation systems and associated method

The present invention relates to a mixing unit for concrete preparation systems and the associated method according to the preamble of claims 1 and 6, respectively. More specifically, the invention relates to a mixing unit for concrete preparation systems and a method that allows concrete to be prepared independently of the relationship between wastewater and binder during the preparation of the cement paste.

Cement conglomerate production systems are known that are transported to construction areas, generally by mixing trucks, for later pouring.

These systems basically consist of independent units in which individual components (water, cement and aggregates) and, optionally, additives, are added and in which they are supplied to a front discharge part in which a mixer truck is placed.

The components are introduced into the mixer truck, where they are mixed according to predefined stoichiometric amounts.

These systems present problems mainly due to dust leaks that occur during the transfer and discharge of cement and, therefore, require the presence of powerful air suction and treatment systems to reduce air pollution in nearby areas.

To avoid these problems, systems are also known which comprise the preliminary preparation of a grout or cement paste inside mixers provided with mixing chambers that are fed with stoichiometric amounts of water, cement and any additive.

Water and cement weighing units are arranged upstream with respect to said mixers and allow the introduction of predefined doses of the different components inside the mixing chamber.

The grout and aggregates are sent separately to the front discharge part, where they are transferred to mixer trucks or the like, inside which they are mixed to form the concrete.

In addition, the operation of these systems is discontinuous; in fact, the mixer's duty cycle is composed of an initial stage of weighing the components to be introduced, a subsequent stage of supply to the chamber and mixing of water, cement and additives, and a final stage of discharge of said camera.

These systems are susceptible to improvements, since they have quite long cycle times and, therefore, only allow a relatively low production rate per hour.

Also known is a system that includes a mixer comprising a weighing unit of the liquid vehicle, the binder material and the slurry, which is included in the mixer itself and which is associated with the load inputs of the mixer.

The method that can be put into practice in the known system types includes an aggregate dosing and moisture detection stage present, a residual water dosing stage that will be sent to the mixer, referring to the expression "residual water" ; to the water established in the concrete preparation formula minus the water contained in the aggregates; a subsequent step of dosing additives in the mixer, the dosage of the binder, the mixing and, finally, the controlled supply of the cement paste to the loading point of the mixing truck.

However, in the operating method described above it is not possible to ensure that it will be possible to mix the cement paste if the relationship between the wastewater (understood as the difference between the water established in the concrete preparation formula and the water contained in the aggregates) and the binder of the formula is less than a certain value, in general, of the order of 0.3. Therefore there is an alarm that allows the user to be notified that, in the presence of a relationship that is lower than the set value, the system cannot carry out the mixing and, therefore, the operator must add the amount of water that it is missing until the predetermined ratio is reached to achieve proper operation of the system under these conditions. Consequently, obviously, the technical characteristics of the resulting concrete would be affected. Alternatively, because it is not possible to pre-mix the water and the binder under such conditions, where the ratio inside the mixer is inadequate, the operator could load the mixer truck in a conventional manner, that is, by sending all the components, aggregates, binder, water and additives directly to the mixer truck.

Document DE-A-1 771 895 describes a method of concrete preparation according to the preamble of the

claim 1 and a concrete preparation system according to the preamble of claim 6. Other examples of concrete preparation units are described in documents JP-A-2003-305714 and JP-A-58 124 526.

The objective of the present invention is to disclose a mixing unit for concrete production systems that allows the production of concrete in an automated manner, with any relation between wastewater and binder established in the concrete preparation formula.

With this objective, a purpose of the present invention is to disclose a mixing unit for concrete preparation systems using recycled water in conjunction with clean water.

Another objective of the present invention is to disclose a method of concrete production that allows the concrete to be obtained from the aforementioned system, regardless of the relationship between wastewater and binder established in the concrete preparation formula.

Another objective of the present invention is to provide a very reliable, relatively simple mixing unit and method with a competitive cost.

These and other objectives, which will be more understandable below, are achieved by a method of concrete preparation according to the invention, which comprises the steps of claim 1.

These and other objectives, which will be more understandable below, are also achieved by a mixing unit for concrete preparation systems according to the invention, which has the characteristics of claim 6.

Other features and advantages of the invention will be more understandable from the following detailed description of a preferred, but not exclusive, embodiment of the mixing unit according to the present invention and the corresponding method, shown only by way of non-limiting example in the accompanying drawings, in which:

Figure 1 is a side elevational view of the mixing unit for concrete production systems according to the present invention;

Figure 2 is a top plan view of the mixing unit shown in Figure 1;

Figure 3 is a flow chart of the concrete preparation method according to the present invention;

Figure 3a is a flow chart of the continuation of the method shown in Figure 3;

Figure 4 is a top plan view of a concrete production system using a mixing unit according to the present invention.

Referring to the figures, a mixing unit for concrete preparation systems according to the present invention, indicated generally by reference number 100, comprises a mixing tank 2 which is provided with mixing elements 3 arranged inside of the deposit to mix the components introduced in said deposit in order to obtain cement paste or grout. The mixing tank is provided with at least a first inlet 4 to introduce cement, at least a second inlet 5 for clean water from a clean water reservoir 6 and, optionally, a third inlet 7 to introduce recycled water.

The tank is adequately supported in load cells 8 and 9 that allow the weight of the material contained inside the tank to be detected, taking into account the weight of the tank itself.

A mixing pump 10 is arranged to mix the contents of the tank and, suitably, the pump is of the variable speed type; The speed of rotation of the pump is selected for each type of concrete preparation formula that can be chosen.

Reference number 11 indicates a wash water discharge valve at the end of the work cycle, that is, after the tank has been washed after preparing the cement paste.

The cement paste prepared in this way is sent to a loading hopper 12 of a mixing truck, not shown.

Then, the cement paste is sent via line 13 to the loading hopper 12 of the mixing truck, and can be returned to the mixing tank 2 via line 14 in case of jamming or suspension of the loading process, after opening an open / close return valve 15.

The reference number 16 indicates a proportional valve for unloading the cement paste in the hopper 12. Consequently, the cement paste is discharged proportionally and, in case of jamming or suspension of the loading process, the valve 15 opens and the valve 16 is closed to allow the cement paste to return to the mixing tank 2 via line 14.

Reference numbers 17 and 18 indicate two accordion sleeves, arranged on line 13 and line 14, respectively, to make the weighing system formed by load cells 8 and 9 independent, weighing the mixing tank 2, with respect to the amount of cement paste present in lines 13 and 14 and with respect to the weight of the lines themselves.

The reference number 20 indicates the motor of the mixing pump 10 and the reference number 21 indicates a washing system of the mixing tank 2.

Advantageously, the mixing unit 100 can be installed in an existing concrete preparation system or in a new one.

In any case, as shown schematically in Figure 4, the system, indicated generally by reference number 300, comprises a first aggregate storage unit 301, provided with a weighing system of the amount of aggregates discharged in a collection tank, and a first unit 302 for supplying the aggregates discharged to a front discharge part 303, which is arranged at the loading inlet of a mixer truck, not shown, since it is of known type. The collection tank for unloaded and heavy aggregates is generally equipped with conventional detectors to detect residual moisture.

The system 300 also has a second powder binder storage unit 304 (cement), a second powder binder supply unit 305 to the front discharge part 302, along which a weighing unit 306, such as a balance, and a third binder supply unit 307 to the first inlet 4 of the mixing unit 100. In an alternative embodiment, the first part 305a of the second supply unit, disposed between the second storage unit and the balance, and the third supply unit 307 may be integrated.

Advantageously, the mixing unit 100 is provided with a management and control unit comprising memory means programmed to perform the steps of the method described below. Such a management and control unit, typically of an electronic type, is not shown in the figures, since it is of the traditional type.

Next, the method of use of the mixing unit and, more specifically, the system in which the mixing unit is installed according to the present invention is described.

The method comprises a cycle start stage 200, which is followed by a step 201 for selecting the desired concrete formula and the necessary components. It is followed by a step 202 which checks if the volume of necessary components is less than a minimum volume of necessary components. If the answer is yes, then a stage 203 is followed in which the cycle is declared non-executable by the mixing unit according to the invention (indicated by the acronym CHTT in the figures) and, therefore, the intervention of the operator to cancel or change the necessary components or to continue the execution without automatic mixing by means of the mixing unit according to the invention.

If the answer is negative, the process moves from step 202 to step 204 to calculate the amounts of aggregates, powder binders, liquid additives and total water.

Next, a step 205 of dosing the aggregates follows, which is followed by a step 206 for detecting moisture in the aggregates.

This step is followed by a step 207 to calculate the amount of water available in the mixing tank 2, obtained by subtracting from the total amount of water the sum of the water present in the aggregates and the wash water, that is, the water that It is preserved and reintroduced during unloading in the cement paste.

Step 207 leads to a step 208 for checking the ratio of available water with respect to the binders in powder form, in order to check if the ratio is less than the minimum limit established in the formula, said variable limit may be depending on the formula

If the answer is yes, then a step 209 follows to calculate the amount of binder in powder form that will be dosed in the balance 306 of the cement, without sending it to the mixing unit 100, and the same is followed by a step 210 of dosing of the excess amount of binders in powder form in the cement scale.

In case of a negative response to step 208, the process continues, in the same way as following step 210, with a water dosing stage 211 in the mixing tank 2.

Simultaneously, a step 212 branches from step 210 to recalculate the amount of aggregates based on the water content detected by the moisture detectors disposed in the aggregate collection tank; the same being followed by a step 213 of completion of the dosage of the aggregates.

Step 211 leads to a step 214 for dosing and introducing liquid additives, to a step 215 for dosing powdered binders in the mixing tank and, finally, to a step 216 for mixing the cement paste in the mixing tank 2.

At this point, the cement paste is ready to be loaded into the mixer truck, in step 217, which is followed by the start-up stage 218 of the mixer truck.

This loading stage occurs with a stage 219 for loading aggregates by means of conveyor belts, following a step 220 for checking jams or emergencies which, in case of affirmative response, leads to a stopping stage 221, which returns from this mode to step 219.

If the answer is negative, the process continues with a stage 221a of completion of loading the aggregates.

At the same time, a stage 222 for loading cement paste from the mixing tank 2 into the mixing truck and a stage 223 for jamming or emergency checking is performed; In this last stage, after a positive response, a stop stage 224 is carried out which returns to stage 222 (which acts to open the valve 15 and close the valve 16).

If the answer is negative, the process continues with a step 225 of checking for irregular reduction of the aggregates and of the binders in powder form. An affirmative response to this stage is followed by a step 226 of adjusting the speed of delivery of the cement paste, which returns to step 222.

If the answer is negative, the process continues with a step 227 that asks if an intermediate wash is necessary. If the answer is yes, then a step 228 of performing an intermediate wash cycle follows, which returns to step 222.

If the answer is negative, proceed with a step 229 for checking the completion of the loading of the cement paste. If the response is negative, the process returns to step 222, while a positive response leads to a final washing stage 230 of the mixing tank and then to a final stage 231 of the cycle, which is also reached from stage 221a.

Advantageously, a proportional load of aggregates and cement paste in the mixing truck is ensured, so that the components are mixed uniformly to obtain a concrete having high-level chemical and physical properties.

The mixing truck can also be loaded in stages or by varying the dosage rate of the powder binder when dosed in the cement dosing unit, provided with a spindle feeder, in step 232. This stage is followed by a stage 233 for jamming or emergency checking which, in case of a positive response, is followed by a stopping stage 234 that returns to stage 232.

If the response is negative, the process has a step 235 for checking the completion of the powder binder charge which, in case of a negative response, is followed by a return to step 232 and, if the response is positive, It is followed by a continuation of the cycle towards step 231 of the end of the cycle.

Substantially, the method according to the invention discloses a step of introducing a residual water / hydraulic binder ratio for each concrete preparation formula in order to obtain a suitable mixture in the mixing tank.

In addition, the residual water is checked to determine if the amount of said water is less than the minimum residual water / binder ratio initially established in the concrete formula; At this point a dosage of wastewater and a dosage of binder is carried out that meets the residual water / binder ratio established in the formula, ensuring this relationship the proper functioning of the system, as mentioned.

The cement paste obtained through the system is sent to the mixer truck simultaneously with the aggregates and, if there is an amount of binder powder that has been sent to the balance, the latter amount of powder is also sent in stages to the loading of the mixer truck to obtain, also in this case, a perfect distribution of the cement powder (or other powders) in the total mass of the aggregates and in the cement paste.

In practice, it has been found that the system and method according to the invention fully meet the intended objectives and purposes, since they allow the residual / binder water relationship to be independent of a specific formula and to introduce a relationship for each formula It is suitable for obtaining a good mixture in the mixing tank.

In addition, the system according to the invention allows varying the speed of rotation of the mixing pump depending on the type of formula used at a specific time to prepare the cement paste.

Therefore, the system and method described are susceptible of numerous modifications and variations, all within the scope of the appended claims; In addition, all the details can be replaced by other technically equivalent elements.

5 In practice, the materials used, as well as the related shapes and dimensions, can be any according to the needs and state of the art.

The description of the Italian patent application number MO2006A000177, of which the present application claims priority, is available in the published patent IT13693748.

The reference signs used to indicate the technical characteristics mentioned in any claim are

10 have included the sole purpose of improving the understanding of the claims and, consequently, such reference signs have no limiting effect on the interpretation of each element identified by way of example by said reference signs.

Claims (10)

1. Concrete preparation method, which includes the steps of: dosing (205) aggregates in a collection tank of an aggregate storage unit (301) with an aggregate weighing system and detecting (206) the humidity present in said aggregates by means of humidity detectors, characterized by the stages of verify (207, 208) the amount of wastewater to check if the amount of wastewater is less than the minimum residual water / binder ratio initially established in the concrete preparation formula, said amount of wastewater being determined by the established water in a concrete preparation formula minus the water contained in said aggregates detected in the moisture detection step (206); dosing (208, 211) the wastewater that will be sent to a mixing tank (2) of a mixing unit (100, CHTT) of a concrete preparation system (300); dose (214) and introduce liquid additives into said mixing tank (2); dosing (215) binders in said mixing tank (2), dosing (215) of the binders in said mixing tank (2) being carried out until the residual water / binder ratio established in the concrete preparation formula is met; introducing (211) into the mixing tank (2), for each concrete preparation formula, a residual water / binder ratio to achieve a correct mixture in the mixing tank (2); mix (216) the binders, water and additives introduced into the mixing tank (2) to obtain a cement paste; send (219, 222) in a controlled manner the resulting cement paste and the aggregate to a loading point (303) of a mixer truck; dosing (210, 209) any residual binder directly into a binder weighing unit (306) with which the concrete production system (300) is provided; Y send (232) a quantity of binder powder to the binder weighing unit (306), said quantity of binder powder being sent in stages or at a variable rate to the loading point (303) of the mixer truck to obtain an optimal distribution of the powder binder in the whole mass of aggregates and cement paste.

2.

Method according to claim 1, wherein said step (222) of sending the cement paste to the loading point of a mixing truck is followed by a stage (220) of jamming or emergency checking which, in case of response Yes, it leads to a stage (221) of stopping the load that returns to the stage (219) of loading the aggregates, and that, if the answer is negative, continues the loading with a stage (221a) of termination of loading of the aggregates.

3.

Method according to claim 2, which comprises, in addition to the step (222) of loading cement paste, a step (223) for checking jams or emergency; wherein, following a positive response from said test stage (223), a stop stage (224) is performed that returns to stage (222), which acts to open a return valve (15) to return cement paste to the mixing tank (2) and close a proportional valve (16) to discharge the cement paste into the mixer truck; and in which, if the response of the check step (223) is negative, a check step (225) of unequal reduction of the aggregates and of the binders in powder form is carried out, so that an affirmative response to said uneven reduction check stage (225) is followed by a step (226) of adjusting the cement paste supply speed, which returns to said cement paste loading stage (222).

Four.

 Method according to claim 3, further comprising, in case of a negative response to said uneven distribution check stage (225), to carry out a step (227) of requesting if an intermediate wash is necessary, so that if the response to said request stage (227) is affirmative, a step (228) of performing an intermediate washing cycle is carried out, which returns to the step (222) of loading cement paste.

5.

Method according to claim 4, further comprising, in the case of a negative response to the request stage (227), to carry out a stage (229) for checking the completion of the loading of the cement paste, and in which, if the response to said loading completion stage (229) is negative, a return to the cement paste loading stage (222) is carried out, while, with a positive response to said testing stage (229) at the end of loading, a final washing stage (230) of the mixing tank (2) is performed and then an end-of-cycle stage (231), which is also reached from said final stage (221a) of load of aggregates.

6.

Concrete preparation system comprising a mixing unit having a mixing tank (2) provided with mixing elements (3), at least one loading hole (4) for introducing binder in powder form, at least one inlet (5, 7) loading to introduce dosed water, an aggregate storage unit (301) and a management and control unit, a mixing pump (10) to mix the contents of said

5 mixing tank (2) and an aggregate weighing system and which detects the humidity by means of humidity detectors arranged in said aggregate storage unit (301), characterized in that said management and control unit comprises memory means programmed to perform the steps of the method according to one or more of claims 1 to 5. 7. Mixing unit according to claim 6, characterized in that said mixing pump (10) is a mixing pump with a variable and controllable rotation speed.

8.

Mixing unit according to claim 6 or 7, characterized in that it comprises at least one inlet (7) of recycled water that is suitable for dosing inside said mixing tank (2).

9.

Mixing unit according to one of claims 6 to 8, characterized in that it comprises load cells that are suitable to allow the weighing of the contents of said mixing tank.

10. Mixing unit according to one of claims 6 to 9, characterized in that it comprises a washing system (21) for said mixing tank (2). 11. Mixing unit according to one of claims 6 to 10, characterized in that it comprises a tank (6) of clean water that is suitable for dosing (211) at said inlet (5) of clean water of said tank (2) of mixture. 12. Concrete preparation system (300), characterized in that it comprises at least one mixing unit (100, CHTT) according to one or more of claims 6 to 11.