The invention relates to a mobile concrete dispenser with weight control. More specifically, the mobile concrete dispenser according to the invention is a vehicle provided with a mixer suitable for producing concrete by mixing a plurality of ingredients, in which the ingredients are mixed at the same site at which the concrete has to be dispensed. The mobile dispenser according to the invention operates in a continuous manner, that is to say, it mixes the ingredients, produces the concrete and dispenses the concrete continuously during the entire period of time in which the concrete is to be cast.

Mobile concrete dispensers are known in the prior art comprising a volumetric mixer mounted on a truck. The mobile dispenser comprises a plurality of separate containers, each of which is suitable for containing a respective ingredient necessary for producing the concrete, that is to say, gravel, sand and water. The individual ingredients intended to produce the concrete are mixed together at the time of the casting, that is to say, when the concrete must be dispensed in order to perform a building work. For this purpose, the individual ingredients of the concrete are picked up from the respective containers and sent towards a mixing screw, which has the purpose of mixing suitable quantities of all the components to obtain the concrete. In an end zone of the mixing screw there is a chute through which the concrete just prepared can be dispensed at a desired point.

The mobile concrete dispensers of the type described above are therefore intended to be loaded with large quantities of sand, gravel, cement and water and can travel also for many kilometres before reaching a delivery site where the concrete has to be used. The concrete is produced, by mixing the various ingredients, only after the dispensing site has been reached. Immediately after its production, the concrete is dispensed in the delivery site.

In the prior art mobile dispensers, below the sand container and the gravel container respective conveyor belts are provided, the conveyor belts being suitable for receiving respectively sand and gravel from the overlying containers, and for conveying the ingredients towards the mixing screw. The sand and gravel are dosed on the respective conveyor belt in a volumetric manner, that is to say, based on the volume of sand or, respectively, gravel, which leaves the respective container per unit time. For this purpose, a stationary element is provided, the stationary element being positioned at a predetermined height above each conveyor belt, the stationary element having the funciont of letting pass a predetermined thickness of sand or gravel, respectively, on the conveyor belt towards the mixing screw. Consequently, for a predetermined speed of the conveyor belt, the volume of sand or gravel which, in the unit of time, leaves the respective container to be conveyed towards the mixing screw (i.e. the volumetric flow rate of the sand or gravel) is predetermined.

If the density of the sand or gravel is known, the weight of the sand or gravel which, in the unit of time, enters into the mixing screw can be determined from the volumetric flow rate

A drawback of the prior art mobile dispensers is that dosing the components intended to form the concrete on the basis of the respective volume which, in the unit of time, is conveyed towards the mixing screw, may be quite imprecise.

In effect, the density of the sand, of the gravel and, even more so, of the cement, considered when the materials are arranged in the form of a pile, as occurs in the respective containers, is affected by the content of air between the grains of material and is therefore different from the theoretical density which sand, gravel or cement would have if the grains were perfectly compacted. Moreover, the density of the sand, gravel and cement inside the respective containers can vary during operation of the mobile dispenser, for example because the dispenser has moved and the degree of compaction of sand and/or gravel and/or cement inside the respective container has varied, or because the quantity of material present in the container has reduced, with a consequent reduction in weight which, from the top, presses the relative ingredient at the outlet towards the conveyor belt. Moreover, the density of the solid ingredients of the concrete, in particular sand and gravel, is also influenced by the moisture content, that is to say, it varies with the variation of the quantity of water contained inside them.

It can therefore happen that, even if there is an initial calibration to determine the relationship between weight and volume of an ingredient, this relationship varies over time, due to variations in density of the ingredient considered. If this occurs, the quantity of that ingredient which is actually introduced into the mixing screw is different from the expected quantity. This may have negative consequences since, in order to ensure that the concrete produced has a high quality (and can therefore be certified), each ingredient has to be present in a precise quantity by weight, which the prior art mobile dispensers are not always able to comply with.

An object of the invention is to improve the mobile concrete dispensers suitable for operating in a continuous manner, particularly conformed as vehicles comprising a mixer for preparing the concrete at a site where the concrete must be dispensed.

A further object is to provide a mobile concrete dispenser, suitable for operating continuously, which is able to produce good quality concrete, in which the ratio of the quantities of the ingredients of the concrete are complied with, with relatively small tolerances.

Another object is to provide a mobile concrete dispenser, suitable for operating continuously, in which variations over time of the quantity of main ingredients of the concrete are reduced, or even eliminated.

Still another object is to provide a mobile concrete dispenser, suitable for operating in a continuous manner, which is not excessively affected by variations of density of the solid ingredients of the concrete, more specifically sand, gravel and cement.

According to the invention, there is provided a vehicle for producing concrete comprising a supporting frame which supports at least one gravel container suitable for containing gravel, at least one sand container suitable for containing sand and at least one cement container suitable for containing cement, the vehicle being further provided with a mixer for mixing a plurality of ingredients so as to obtain the concrete, characterised in that it comprises a first screw conveyor for collecting gravel from the gravel container and conveying the gravel towards the mixer, a second screw conveyor for collecting sand from the sand conveyor and conveying the sand towards the mixer, a third screw conveyor for collecting cement from the cement conveyor and conveying the cement towards the mixer, a measurement system for determining the weight of the gravel, sand and cement coming from, respectively, the gravel container, the sand container and the cement container and directed towards the mixer, a feedback control system for modifying an operating parameter of the first screw conveyor and/or of the second screw conveyor and/or of the third screw conveyor if the weight of the gravel and/or of the sand and/or of the cement determined by the measurement system differs from a corresponding theoretical value by an error greater than a predetermined threshold value.

Owing to the invention, it is possible to dose the solid ingredients of the concrete, that is to say, the sand, gravel and cement, with a good level of precision, even if the density of the sand, gravel and cement contained in the respective containers changes over time. In fact, the measurement system is not of volumetric type, as was the case with the prior art, but it is of the weighing type, that is to say, based on a measurement of the weight of the solid ingredients of the concrete. Consequently, the measurement system of the vehicle according to the invention promptly measures any variations in the density of the sand and/or gravel and/or cement, which the prior art mobile dispensers were not able to detect because their operation was based on the volume of sand, gravel and cement coming from the respective containers. Indeed, any variations in density of the solid ingredients of the concrete determine a variation in the weight which the measurement system detects.

Moreover, the feedback control system makes possible to act on the first screw conveyor and/or on the second screw conveyor and/or on the third screw conveyor for varying the amount of gravel and/or sand directed towards the mixer, as a function of the weight values detected by the measurement system. If, for example, the measurement system detects that the quantity of sand which the respective screw conveyor collects from the sand container is less than the expected quantity, the feedback control system can intervene on the screw conveyor intended to convey the sand to increase the quantity of sand sent towards the mixer. The opposite occurs if it is detected that the quantity of sand sent towards the mixer is greater than the expected quantity. Similar operating modes are provided with regard to the gravel and cement.

Lastly, the first screw conveyor, the second screw conveyor and the third screw conveyor allow the quantity of the respective ingredients of the concrete sent to the mixer to be adjusted in a simple and reliable manner. In an embodiment, the operating parameter of the first screw conveyor and/or of the second screw conveyor and/or of the third screw conveyor which the feedback control system is configured to vary is the speed of the first screw conveyor and/or of the second screw conveyor and/or of the third screw conveyor.

By increasing the speed of a screw conveyor it is in fact possible to increase the quantity of the relative ingredient conveyed towards the mixer. The opposite occurs if the speed of a screw conveyor is reduced.

In an embodiment, the measurement system comprises first weight sensor means associated with the gravel container, second weight sensor means associated with the sand container and third weight sensors associated with the cement container for measuring the weight, respectively, of the gravel container and the contents thereof, the sand container and the contents thereof, and the cement container and the contents thereof. By measuring the weight of the gravel container and/or sand container and/or cement container, it is possible to determine how much gravel and/or sand and/or cement is extracted from the respective containers to be conveyed to the mixer. This makes possible to know the quantity of gravel and/or sand and/or cement which, at a predetermined instant in time or in a predetermined time interval, is sent towards the mixer.

The first weight sensor means associated with the gravel container can comprise at least one load cell.

The second weight sensor means associated with the sand container can comprise at least one load cell.

The third weight sensor means associated with the cement container can comprise at least one load cell.

Owing to the load cells, it is possible to determine the weight of an ingredient of the concrete taken out from the respective container in a simple and effective manner.

In an embodiment, moisture sensor means are provided for measuring the moisture content of the sand and possibly of the gravel, which from the respective containers are intended to reach the mixer.

The moisture sensor means allow the moisture content of the sand and possibly of the gravel to be taken into account in order to correct the theoretical quantity of sand and possibly of gravel to be sent into the mixer.

This allows a further improvement in the precision in dosing the ingredients of the concrete.

In an embodiment, the supporting frame supports at least one tank suitable for containing water, the tank being in fluid communication with the mixer so that the water can reach the mixer.

In an embodiment, the measurement system further comprises a detector, particularly a flow meter, for measuring the quantity of water sent from the tank towards the mixer.

In an embodiment, the feedback control system is configured to modify the quantity of water sent towards the mixer if the quantity of water measured by the detector differs from a respective theoretical value by an error of greater than an acceptable threshold value.

This allows the precise dosing of another ingredient of the concrete, that is to say, the water.

The invention can be better understood and implemented with reference to the accompanying drawings which illustrate a non-limiting example embodiment thereof, wherein:

Figure 1 is a perspective view of a vehicle for producing concrete;

Figure 2 is a perspective view of the vehicle of Figure 1 , from a different angle;

Figure 3 is a perspective view from above of the vehicle of Figure 1 , in which some parts have been removed;

Figure 4 is a block diagram showing the operation of a measurement system of the vehicle of Figure 1.

Figures 1 and 2 show a vehicle 1 for producing concrete starting from a certain number of ingredients, which typically comprise a coarse aggregate, i.e. gravel, a fine aggregate, i.e. sand, cement and water.

The vehicle 1 is intendet to produce concrete at the point at which the concrete is intended to be cast, i.e. at the point where the concrete has to be dispensed in order to perform a building work. The vehicle 1 is configured to produce, in a continuous manner, the quantity of concrete required for making the building work in question. This means that, once the point at which the concrete has to be cast has been reached, the respective ingredients are mixed and the concrete is dispensed in a continuous manner, until the ingredients conveyed by the vehicle 1 are used up or up to the moment in which the quantity of concrete dispensed is equal to that desired at the location where the building works are to be performed.

The vehicle 1 comprises a supporting frame 2 suitable for supporting a plurality of components which will be described below. The vehicle 1 further comprises movement elements 3 for moving the vehicle 1 along a desired path. In the example shown, the movement elements 3 are conformed as wheels. In an embodiment that is not shown, the movement elements 3 could be conformed as tracks.

A motor, not illustrated, and a transmission system are provided for driving the movement elements 3, which allow the vehicle 1 to be moved along a road, either unpaved or paved, in a construction site, in a field or in another place.

The vehicle 1 further comprises a cab 4, positioned in a front zone of the vehicle 1 , and intended to house an operator. The operator has the task of driving the vehicle 1 and, when the vehicle 1 has reached a predetermined point and has stopped, the operator has the taks of starting the process of continuously producing and discharging the concrete. The operator subsequently controls this process and ends it when the desired quantity of concrete has been discharged or when the ingredients of the concrete conveyed by the vehicle 1 are used up.

The vehicle 1 can in particular be conformed as a truck.

The supporting frame 2 supports a plurality of containers, suitable for containing the ingredients of the concrete which are conveyed by the vehicle 1 . More specifically, the supporting frame 1 supports a gravel container 5 suitable for containing the coarse aggregate or gravel and a sand container 6 suitable for containing the fine aggregate or sand. The gravel container 5 and the sand container 6 can be conformed as hoppers or tanks provided with an upper opening through which the gravel or, respectively, the sand can be loaded on the vehicle 1 . In the example shown, the sand container 6 is located in a position closer to the cab 4 than the gravel container 5. In other words, the sand container 6 is interposed between the gravel container 5 and the cab 4. This condition is not however necessary and other arrangements of the gravel container 5 and of the sand container 6 are possible.

A cement container 7 is further provided, the cement container 7 being suitable for containing the cement. Also the cement container 7 can be conformed as a hopper or tank and is provided with an upper opening for loading the cement on the vehicle 1 . The upper opening is closed by a cover 80 to prevent the cement contained in the cement container 7 from being dispersed into the environment due to its small grain size.

The cement container 7 can be located in a rear position on the vehicle 1 , that is to say, in a position furthest away from the cab 4. In particular, in the example shown, the gravel container 5 is interposed between the sand container 6 and the cement container 7.

The supporting frame 2 can further support one or more water tanks 8 suitable for containing the water which allows the concrete to be mixed. In the example shown, the water tanks 8 are located alongside the sand container 6, even though other arrangements are possible.

The vehicle 1 further comprises a mixer 9 suitable for mixing a plurality of ingredients, in particular sand, gravel, cement and water, to obtain the concrete. The mixer 9 can comprise a mixing screw, not visible in the drawings, which can be rotated inside a casing 10. The mixer 9 is configured to operate continuously. In other words, the mixing screw provided inside the mixer 9 is configured to rotate without interruptions until the desired quantity of concrete has been produced and dispensed where the building works are being performed.

The mixer 9 has an inlet end 1 1 , in which the ingredients of the concrete enter, and a discharge end 12, opposite the inlet end 1 1 , from which the concrete can be discharged. The mixing screw extends along a longitudinal axis, which, in the example illustrated, is tilted upwards. In other words, the discharge end 12 is at a higher level than the inlet end 1 1.

At the discharge end 12 a chute 13 can be provided for allowing the concrete coming out of the discharge end 12 to be dispensed in the desired point in a guided manner.

The vehicle 1 further comprises a first screw conveyor 14, visible in Figure 3, suitable for collecting the gravel from the gravel container 5 and conveying the gravel towards the mixer 9. The first screw conveyor 14 is positioned on the bottom of the gravel container 5 so that the gravel contained in the gravel container 5 is positioned, when falling by gravity, in the spaces provided between one turn and the other of the first screw conveyor 14. The first screw conveyor 14 can comprise a shaft 15 which extends along a longitudinal direction of the vehicle 1 , that is to say, parallelly to a centre line of the vehicle 1 which from the cab 4 runs towards the mixer 9. The shaft 15 is visible in Figure 3 and a rear end thereof is also shown in Figure 1 . The shaft 15 extends from one end of the gravel container 5 adjacent to the sand container 6, up to a rear area of the vehicle 1 close to the mixer 9. A protection element 16 may be provided for partially covering the first screw conveyor 14 at least on a portion of the length of the shaft 15, in such a way as to prevent an excessive quantity of gravel from falling between the turns of the first screw conveyor 14. As shown in Figure 3, the protection element 16 can be absent in an initial portion of the shaft 15, that is to say, in a zone of the first screw conveyor 14 in which it is useful for a relatively large quantity of gravel to fall between the turns of the first screw conveyor 14.

The vehicle 1 further comprises a second screw conveyor 17 for collecting sand from the sand container 6 and conveying the sand towards the mixer 9. The second screw conveyor 1 7 is positioned on the bottom of the sand container 6 and comprises a spiral which is wound on a shaft 18. The shaft 18 extends in a longitudinal direction of the vehicle 1 , that is to say, parallelly to a centre line of the vehicle 1 . In particular, the shaft 18 extends from one end of the sand container 6 adjacent to the cab 4 up to a rear zone of the vehicle 1 , close to the mixer 9. The second screw conveyor 1 7 passes beneath a side wall 19 of the gravel container 5, so that the sand, after being collected from the sand container 6, is conveyed below the gravel container 5 until reaching the mixer 9.

The first screw conveyor 14 and the second conveyor 17 are positioned one at a side of the other and can be at the same level, that is to say, at the same height with respect to the ground.

The first screw conveyor 14 and the second screw conveyor 17 can be positioned on opposite sides of the centre line of the vehicle 1 , for reasons connected with their respective overall dimensions.

The side walls 19 of the gravel container 5, that is to say, the walls which delimit two opposite sides of the gravel container 5 converging towards the first screw conveyor 14 are, in the example illustrated, arranged at different angles relative to each other. In other words, the side walls 19 converge from the top towards the first screw conveyor 14 with different slopes from each other.

Similarly, the sand container 6 can be provided with respective side walls 20, located on opposite sides of the second screw conveyor 17 which converge from the top towards the second screw conveyor 17 with different slopes from each other.

A third conveyor screw conveyor, not illustrated, is associated with the cement container 7. The third screw conveyor is provided with a shaft 21 shown in Figure 1 . The third screw conveyor is configured to collect the cement contained in the cement container 7 and convey it towards the mixer 9. The third screw conveyor is positioned on the bottom of the cement container 7. The third screw conveyor is arranged in an intermediate position, in plan view, between the first screw conveyor 14 and the second screw conveyor 17 and it can be at a higher level than the first screw conveyor 14 and the second screw conveyor 17.

In the example shown, the second screw conveyor 17 is longer than the first screw conveyor 14, which in turn is longer than the third screw conveyor.

In order to introduce the gravel, sand and cement in the mixer 9, a transfer element 23 can be provided, for example shaped like a funnel, which receives gravel, sand and cement, respectively, from the first conveyor screw conveyor 14, from the second screw conveyor 17 and from the third screw conveyor and transfers them all together into the mixer 9.

The at least one water tank 8 is in fluid communication with the mixer 9 through at least one conduit (not illustrated). A pump 22 allows water to be sent from the at least one water tank 8 towards the mixer 9.

A hydraulic power system 24, shown in Figure 2, is further provided for hydraulically driving a number of components of the vehicle 1 , in particular the first, the second and the third screw conveyors, as well as the mixer 9. The vehicle 1 comprises a measurement system to determine the weight of the gravel, sand and cement coming, respectively, from the gravel container 5, the sand container 6 and the cement container 7 and directed to the mixer 9.

The measurement system comprises first weight sensor means for determining the weight of the gravel which leaves the gravel container 5 and is sent towards the mixer 9. For this purpose, the first weight sensor means can be configured to measure the weight of the gravel container 5, so as to obtain, by difference, the weight of the quantity of gravel which, in a predetermined period of time, or at a predetermined instant, is sent to the mixer 9. The first weight sensor means can comprise at least one load cell 25 for detecting the weight of the gravel container 5, including the contents thereof. In the example shown, a plurality of load cells 25 associated with the gravel container 5 is provided.

The measurement system further comprises second weight sensor means for determining the weight of the sand which leaves the sand container 6 and is sent towards the mixer 9. The second weight sensor means can be configured to measure the weight of the sand container 6, so as to obtain, by difference, the weight of the quantity of sand which, in a predetermined period of time, or at a predetermined instant, is sent to the mixer 9. The second weight sensor means can comprise one or more load cells, not shown, for detecting the weight of the sand container of 6, comprising the contents thereof.

The measurement system can further comprise third weight sensor means for determining the weight of the cement leaving from the cement container 7 and sent towards the mixer 9. The third weight sensor means can be configured to measure the weight of the cement container 7, so as to obtain, by difference, the weight of the quantity of cement which, in a predetermined period of time, or at a predetermined instant, is sent to the mixer 9. The third weight sensor means can comprise one or more further load cells 26 for detecting the weight of the cement container 7, including the contents thereof.

The measurement system can further comprise a detector, for example a flow meter, arranged for measuring the quantity of water, for example the flow rate, sent from the at least one tank 8 towards the mixer 9.

The flow meter, which is not shown in the drawings, can be, for example, located along the conduit which carries the water into the mixer 9.

A feedback control system is further provided for modifying an operating parameter at least of the first screw conveyor 14 and/or of the second screw conveyor 17 and/or of the third screw conveyor in the case of excessive deviations of the weight of the gravel and/or sand and/or cement which, from the respective containers, are sent towards the mixer 9, with respect to corresponding theoretical values. The operating parameter which the feedback control system makes it possible to modify can be the speed of the first screw conveyor 14 and/or of the second screw conveyor 17 and/or of the third screw conveyor, more specifically the speed of rotation of the respective screws.

The feedback control system can be configured also to modify the quantity of water sent from the at least one tank 8 towards the mixer 9, if the quantity of water measured by the flow meter differs from an expected value by an error greater than an acceptable threshold value. If it is determined that the quantity of water must be modified, the feedback control system can act on the flow rate of water sent by the pump 22.

Figure 4 schematically shows how the feedback control system operates for any ingredient selected between gravel, sand, cement and water. Consequently, Figure 4 will be schematically described below with reference to a generic ingredient which can be gravel, sand, cement or water.

As shown in Figure 4, the operational diagram of the feedback control system comprises two feedback cycles, that is, a fast feedback cycle 1 00 and a slow feedback cycle 200, which differ, amongst other things, by the respective execution times. In particular, the fast feedback cycle 100 is performed at shorter time intervals than the slow feedback cycle 200.

The fast feedback cycle 100 makes it possible to detect whether the single quantity of an ingredient of the concrete sent towards the mixer 9, measured after a predetermined period of time from the previous measurement, differs excessively from a theoretical value. The slow reaction cycle 200 is, on the other hand, based on a cumulative evaluation of the quantity of each ingredient of the concrete discharged from the corresponding container. This cumulative evaluation takes into consideration several consecutive measurements of the quantity of the particular ingredient considered. This is to be sure that the total quantity of that ingredient is not too great or small, as a result of the accumulation of errors (which were acceptable if taken individually) in the quantities discharged in the single predetermined periods of time.

“S” indicates the start of the method for operation of the feedback control system. This method is implemented in a control unit of the vehicle 1 . According to this method, it is firstly checked whether a time t longer than a control time period tci has passed since the previous measurement, so as to determine whether the fast feedback cycle 100 is to be started, or if, on the other hand, it is necessary to wait further. The speed feedback cycle 100 only starts if the current value of the time t is greater than the control time period tci .

If the condition t > tci is verified, an evaluation step 101 starts, in which the quantity of the ingredient that has been taken from the corresponding container is evaluated. This evaluation is performed by the control unit on the basis of the signals received from the load cells 25 associated with the gravel container 5, or on the basis of the signals received from the load cells associated with the sand container 6, or on the basis of the signals received from the further load cells 26 associated with the cement container 7, or on the basis of the signals received from the flow meter associated with the conduit in which the water flows, depending on the ingredient considered.

The evaluation performed in the evaluation step 1 01 allows the error Ei to be determined, that is to say, the difference between the quantity of the ingredient considered which was effectively discharged from the relative container in the control time period tci and the theoretical quantity expected.

In a subsequent comparison step 1 02, the error Ei is compared with a first maximum value Emax which can be accepted for the error Ei .

If the absolute value of the error Ei is greater than Emax, it means that a malfunction has occurred which caused an error such that it cannot be recovered by feedback on the screw conveyors or on the water pump 22. For this reason, the error condition is reported in a signalling step 103 and the production of concrete is stopped in the stop step 104.

If, on the other hand, the absolute value of the error Ei is less than Emax, a further comparison step 1 05 is carried out in which the absolute value of the error Ei is compared with a first predetermined threshold value ETI , in order to determine whether the feedback control system has to be activated or not.

In particular, if the absolute value of the error Ei is greater than ETI , a correction step 106 is provided in order to correct the rotation speed of the screw whose purpose it is to convey the ingredient considered, or the flow rate of water sent by the pump 22, so as to correct the extraction speed of the ingredient at issue from the corresponding container. In particular, if the control unit detects that the quantity of the ingredient considered which is extracted from the corresponding container is too low, the speed of rotation of the corresponding screw is increased, or the speed of the pump 22 which conveys the water is increased. If, on the other hand, the control unit detects that the quantity of the ingredient considered which is extracted from the container is excessive, the speed of rotation of the screw of the corresponding container is reduced, or the speed of the pump 22 is reduced. The concrete production can now continue normally.

If, on the other hand, the absolute value of the error Ei is less than the first predetermined threshold value ETI , production of concrete continues without any feedback corrections of the speed of the screw conveyors or the pump 22.

Subsequently, an assessment is made to determine whether to start the slow feedback cycle 200.

The slow feedback cycle 200 is only carried out if a time t has passed which is greater than a control time interval tc2, that is to say, if a predetermined period of time has passed since the previous control.

If this condition is met, the control unit starts an evaluation step 201 in which the cumulative quantity of the ingredient considered is evaluated. This is done in order to determine whether the weight errors (either positive or negative) of the single ingredient which are accumulated in a period of time corresponding to the control time interval tc2 have given rise to a error E2 whose absolute value is greater than a second predetermined threshold value ET2.

If, in fact, during a subsequent comparison step 202, it is determined that the absolute value of the error E2 is greater than the second predetermined threshold value ET2, a correction step 203 is performed in which the speed of extraction of the ingredient considered from the corresponding container is corrected, by acting in a feedback on the rotation speed of the screw of the screw conveyor in question, or on the speed of the pump 22.

If, on the other hand, during the comparison step 202, the control unit determines that the absolute value of the error E2 is less than the second predetermined threshold value ET2, the cycle continues. At this point, a decision step 204 can be activated in which the control unit decides whether to stop the production of concrete passing to the stop step 1 04, or whether to continue the production of concrete returning to the start of the method schematically illustrated in Figure 4.

The vehicle 1 can further comprise a moisture sensor for measuring the quantity of water present in the sand. The moisture sensor can be positioned in an outfeed zone of the second screw conveyor 17 and can be configured to calculate, in a predetermined period of time Tu, the weight quantity of sand and water conveyed by the second screw conveyor 1 7. The quantity of sand and water thus determined will be subsequently used to correct the theoretical value of sand and water provided in the concrete recipe.

A further moisture sensor can further be provided for measuring the quantity of water present in the gravel. The further moisture sensor can be positioned in an outfeed zone of the first screw conveyor 14 and can operate in a similar manner to that described above with reference to the moisture sensor arranged for measuring the moisture content of the sand. The vehicle 1 , after being loaded with sand, gravel, water and cement which are introduced in the respective containers, is sent to the site where the concrete has to be dispensed. The vehicle 1 stops here and continuous concrete production is activated, sending the ingredients into the mixer 9. The quantity of the ingredients of concrete is controlled and, if necessary, modified in feedback according to the diagram in Figure 4, which ensures that the concrete recipe is complied with, with good precision, even in the case of variation of the density of the sand, and/or gravel, and/or the cement, and/or the water. In this way, the vehicle 1 allows high-quality concrete production.