Classifications

• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
  • E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
  • E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
  • E01C19/1059—Controlling the operations; Devices solely for supplying or proportioning the ingredients
  • E01C19/1068—Supplying or proportioning the ingredients
  • E01C19/1072—Supplying or proportioning the ingredients the solid ingredients

Definitions

• the present invention relates to a method and a tower for batching the aggregates for producing bituminous concretes, and to a plant for asphalt production.
• asphalts are substantially formed of several different components, such as gravel, sand, filler, binder (generally bitumen) and other substances (cork, cellulose, rubber latex, resins, etc.) adapted to give the base product its main features or to enhance said features.
• binder generally bitumen
• cork cork, cellulose, rubber latex, resins, etc.
• asphalts having physical features that are quite different from each other but that, once they have been formulated and established by a designer, must be compulsorily complied with during the production step.
• this feature is the particle-size curve, i.e.
• some vertically-set areas from top to bottom, can be identified for discharge of each area into the subsequent one by gravity, i.e. the hot-aggregate selecting area, the area of the waiting hoppers, the weighing area, the mixing area and, finally, the area for discharge of the finished product.
• the area of the waiting hoppers consists of a sheet metal body, in the form of a parallelepiped, internally divided by partitions so as to form as many funnel-shaped sectors as there are aggregate fractions to be distinguished.
• the automatic system simultaneously operates all the pre-batchers necessary to compose the formulation, so that the aggregates are mixed and on coming out of the drier they must be regraded. To this aim, the aggregates are conveyed to a vibrating screen disposed in the selecting area on top of the mixing tower.
• each feeder is provided to contain an already well defined particle-size class that can be used for several formulations. Drying of the aggregates and conveyance of same to the mixing tower takes place individually for each particle size necessary for a particular formulation and in the selecting area on top of the tower there is only a distributor sequentially starting the different particle sizes in the preestablished waiting sector to avoid earlier mixing of said particle sizes. Therefore production of the concrete can only start when the waiting sectors have been all filled.
• Both types of plants have advantages and disadvantages. For instance, in known plants of the first type, to keep the screen bulkiness and complexity within reasonable limits, the standard number of selections is usually four, while the maximum number is generally no more than seven and only for the most sophisticated plants .
• a hopper for weighing the aggregates a hopper is used that is positioned on the vertical of the mixer and under the discharging mouths of the waiting silos. During the mixing period (about 30 seconds) the waiting silo mouths open and close, one at a time and in succession, so that each of them introduces the amount of aggregates provided by the formulation into the underlying hopper.
• the control system closes the discharge shutter of this aggregate from the corresponding section of the waiting silo.
• a space is necessarily present that, upon closure of the upper shutter, still contains an undefined amount of falling aggregates that have not yet been weighed. This involves an unavoidable batching in excess.
• the present invention it is a general aim of the present invention to obviate the above mentioned drawbacks by providing a method, a tower and a plant enabling high accuracy in making a formulation, while being of easy and cheap accomplishment. It is a further aim to solve the problem concerning the non- standardization of the waiting silos.
• the method, tower and plant in accordance with the invention not only enable the weighing problems typical of known aggregate-weighing systems to be solved, but they also reach the further purpose of solving the problems present in known plants due to the impossibility of precise level indicators being provided and to the requirement of outflow channels discharging the hot aggregates to the ground, which will bring about an important energy waste (note that more than 90% of the thermal and electric energy consumed by the plant is used for heating/drying the aggregates) .
• a further problem in known plants for producing bituminous concretes resides in that, in order to avoid an excessive and unacceptable extension in height of the mixing tower, the space (and therefore the available volume) between the weighing hopper sized for receiving the discharged materials from all waiting silos and the underlying mixer, is limited in height.
• the direct admission to the mixer of wet milled asphalt to be recycled that in this manner comes into contact with the overheated aggregates already present in the mixer, causes a sudden and uncontrollable formation of vapor. This phenomenon gives rise to a vapor "explosion" in the mixer and, as a result, to an anomalous escape of dusty gases from the hopper case and entrainment of even coarse powders towards the surrounding metal walls.
• Another aim of the present invention is to solve these problems as well, enabling creation of a suitable free volume for gas expansion over the mixer, without at the same time greatly increasing the tower height or reducing the useful sizes of the different tower components.
• a method has been devised of batching the aggregates to be introduced into a mixer in a plant for producing bituminous concretes, which comprises the steps of, for each aggregate to be batched, filling a weighing hopper with the aggregate to be batched and operating discharge of the hopper into the mixer in a batching cycle, through a computerized control system, until the hopper weight that is detected by the computerized control system has decreased by a value that has been previously established to correspond to the aggregate amount to be introduced into the mixer.
• a tower for mixing the ingredients of a production formulation for a plant producing bituminous concretes which comprises a mixer and means for batching the aggregates to be introduced into the mixer in accordance with the formulation, characterized in that the batching means for each aggregate of the formulation comprises a hopper provided with weighing means and fed with the aggregate to be batched, and a computerized control system that in a batching cycle operates discharge of the hopper into the mixer until the hopper weight that is detected by the computerized control system through the weighing means has decreased by a value that has been previously established to correspond to the amount of that aggregate to be introduced into the mixer.
• FIG. 1 is a diagrammatic view of a plant for producing bituminous concretes, made in accordance with the invention
• Fig. 1 shows a diagram of a plant, generally denoted at 10, for producing bituminous concretes.
• Plant 10 comprises an area 11 for preparation of the aggregates and an area or tower 12 for measuring or batching and mixing the formulation components .
• the area 11 for example comprises feeders 13 receiving the aggregates of different particle sizes (picked up by a bucket from storage heaps 22) and sending them to a known drier 14.
• the hot aggregates coming out of the drier are lifted by a known elevator 15 (a bucket elevator, for example) for reaching the top of the mixing tower in the area 12.
• a known elevator 15 a bucket elevator, for example
• the number of silos 16 will be at least the same as the number of the aggregate components that are wished to be kept separate.
• Each silo 17 has a discharge opening provided with a shutter at the lower part thereof for carrying out discharging, upon command, into an underlying weighing hopper 18 of its own. All hoppers in turn have discharge shutters operated for pouring the aggregates into the underlying known mixer 19. In other words, each particle-size fraction of aggregates is provided with two waiting silos 17, 18 vertically superposed on each other.
• the other components of the formulation reach the mixer through batching systems 20 (generally weight measuring systems), that are known by themselves and are not herein further described as they can be easily envisaged by a person skilled in the art.
• batching systems will be designed to add components such as bitumen, filler and several additives provided by the formulation, into the mixer .
• the mixer has an outlet 21 for ensilage, upon command, of the finished product that will be sent to the use yard. Except for the operation of charging the aggregates from the storage heaps 22 (which operation is typically carried out manually) operation of the plant is managed by a known and proper electronic control system 23 with a suitably programmed command computer 24.
• Fig. 2 Shown in greater detail in Fig. 2 is that portion of the mixing tower 12 that is designed to batch the aggregates.
• one silo alone 17 is fully shown with the related weighing hopper 18 associated therewith.
• all pairs of silos 17 with the underlying hopper 18 are identical although it is not excluded that they may have features different from each other, and the description of only one of them is sufficient for full understanding of the invention.
• All hoppers 18 of the different silos 17 discharge into a conveying funnel 25 carrying the aggregates into the underlying mixer 19.
• the distributor device 16 fills each silo 17 with the assigned aggregate.
• each silo 17 is suspended on a weighing system 26 (a loading cell, for example) that, after subtracting the tare, gives the net weight of the aggregate contained in the silo and therefore the level reached by the aggregate contained therein.
• a weighing system 26 a loading cell, for example
• Each silo 17 is provided with a mechanism of its own 27 operated for discharge of the silo contents to the associated hopper 18 of a lower capacity.
• the weighing hopper 18 under the silo is in turn provided with a weighing system of its own 28 (a loading cell as well, for example) and with a mechanism 29 operated for discharge of the contents to funnel 25. Both weighing systems and discharge mechanisms of each pair are connected to the control system 23, 24.
• each silo 17 filled by the distributor device 16 is operated by the control system to feed the respective lower hopper.
• the weighing system 28 allows the control system to stop feeding of silo 17 when the lower hopper 18 reaches a weight corresponding to a preestablished filling condition (maximum load) . In this step it is not important whether after closure of shutter 27 an excess weight is obtained due to the fact that some material was still falling when closure of shutter 27 was operated.
• the control system can open the discharge shutter (or shutters) 29 and measure the amount of aggregates discharged into the mixer as the weight difference from the starting weight. In this way, when the aggregate weight provided by the particular execution formulation is reached, the control system will close shutter (or shutters) 29 and the tolerance from the provided weight practically will only depend on the driving speed for closing shutter. Thus, the tolerance can be reduced to a minimum.
• the weighing system 26 of each silo 17 enables the computerized control system 23, 24 to stop introduction of material into the silo when a maximum filling level is reached and to maintain the amount of aggregate in the silo within a preestablished minimum and maximum interval.
• a detection by weight enables an indication of the silo contents instant by instant, which will allow systems of proportional feedback control to be implemented for treatment of the aggregates disposed upstream and for carrying out filling of the silo.
• shapes and sizes of the different elements can change depending on specific requirements, as well as the stages for treating the aggregates and the other different components in the formulation.
• the towers 12 and therefore the different elements 16, 17, 18, 19 can be enclosed in an environment separated from the outside by means of panels that can be insulated and in any case adapted to create a big environment where gas expansion can be allowed.
• This environment can be constantly maintained under a vacuum by known systems, such as an exhaust fan, and the gases can be conveyed to filtering systems.

Landscapes

• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Preparation Of Clay, And Manufacture Of Mixtures Containing Clay Or Cement (AREA)
• Working-Up Tar And Pitch (AREA)
• Road Paving Machines (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

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Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (2)

Citations (4)

• 2004
  • 2004-03-22 IT IT000547A patent/ITMI20040547A1/it unknown
• 2005
  • 2005-03-16 CN CN200580000299.XA patent/CN1774544A/zh active Pending
  • 2005-03-16 RU RU2006137287/03A patent/RU2006137287A/ru not_active Application Discontinuation
  • 2005-03-16 WO PCT/EP2005/002797 patent/WO2005093159A1/en active Application Filing
  • 2005-03-16 EP EP05716116A patent/EP1727939B1/de not_active Not-in-force
  • 2005-03-16 DE DE602005014454T patent/DE602005014454D1/de not_active Expired - Fee Related
  • 2005-03-16 AT AT05716116T patent/ATE431461T1/de not_active IP Right Cessation

Patent Citations (4)

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