GRINDING SYSTEM

TECHNICAL FIELD.

The invention refers to a grinding system, suitable for grinding raw materials for producing ceramic products. STATE OF THE ART.

The grinding of raw materials, such as, e.g., stone materials for the production of ceramic products, is currently done using two procedures: a first procedure comprises the discontinuous grinding of the materials and a second procedure comprises their continuous grinding. According to the first procedure, the materials to be ground are introduced into grinding apparatuses which are loaded after being stopped and, after the completion of the grinding operating cycle, they are again stopped to be unloaded and again loaded with another quantity. According to the second procedure, the materials are introduced continuously into the grinding apparatuses through loading openings obtained at one end, without these having to be stopped, and the ground materials are unloaded, again continuously, from an unloading opening opposite that of loading, and obtained at one opposite end with respect to the previous one. For the sake of clarity, it should be remembered that a known grinding apparatus is composed of a substantially cylindrical body which is supported by a frame with its longitudinal axis substantially horizontal.

Inside some cylindrical bodies, some grinding bodies are also arranged composed essentially of balls of very hard material of different diameters and which grind the materials first of all with very coarse grain size and then more and more finely, as the materials move closer to the unloading opening, from where they exit by overflowing. The cylindrical body has rotary movement around its own longitudinal axis and inside defines one or more grinding chambers having on the walls ribs that are shaped so as to increase the lifting and falling angle of the grinding bodies during the rotation of the cylindrical body, if necessary also making a selection of the grain size of the ground materials.

To obtain materials of desired grain size, systems have been made that have several

grinding chambers placed in series and, alternatively, joined together or separate, depending on whether their rotation is joint or independent the one from the other.

In each chamber, besides water, the grinding bodies are also inserted which have preset dimensions, according to the grain size to be obtained and according to the grinding times required to obtain these grain sizes.

The grinding chambers can also have different diameters the one from the other and can rotate with different angular speeds, because the grinding is also function of the angular speeds with which the grinding chambers rotate.

A continuous grinding system comprising two adjacent grinding chambers of different diameter and which are linked together is known by the Italian patent no.

RE2000U000002, deposited in the name of the Company I.F.C. INDUSTRIE CIBEC

S.P.A..

According to this system, the material to be ground is introduced through an introductory opening provided at one end of a first grinding chamber that turns continuously and which is of smaller diameter, in which are also introduced some grinding bodies of large dimensions, provided to obtain a first coarse grinding of the raw materials.

Due to the rotation, to the gradual reduction of the dimensions and to the mixing with water, the materials gradually move towards the second grinding chamber adjacent to the first and separated from this by a transversal diaphragm which, nevertheless, has a connecting opening between the two grinding chambers.

The materials to be ground, after undergoing a first coarse grinding, enter the second grinding chamber with a diameter greater than that of the first chamber and, consequently, also a higher tip speed at the same rotation speed. Into this second chamber, grinding bodies are introduced that have considerably smaller dimensions than those of the first chamber and which allow obtaining considerably finer grinding.

Due to the rotation of the grinding chambers and to the constant introduction of further materials into the first grinding chamber, the materials continue to move in an axial direction towards the unloading opening from which they exit outside by overflow.

This known system does have some drawbacks.

A first drawback is that it is not possible to equip the grinding chambers with rotation speeds independent from each other.

Another drawback is that in the case of a fault, e.g., to a motor driving the rotation of the grinding chambers, the system is completely unusable and the production cycle stops.

Another drawback is that this type of system has considerable longitudinal overall dimensions and its positioning inside companies engaged in supplying ground materials can become difficult. Another drawback is that this system cannot be extended or reduced according to specific requirements and therefore has high purchase costs that cannot be dilated over time.

Another drawback is that this type of system also has high maintenance costs due to its complex structure, the dimensions of the machines that make it up and of the relative component parts.

A continuous grinding system that comprises two separate grinding chambers each with independent motorisation is known by Italian patent no. RE2003A000013, registered in the name of the company Sacmi - Cooperativa Meccanici Imola - Soc.

Coop a R.L. According to this patent, two grinding chambers are provided placed one after the other, coaxial to each other and connected by means of a duct through which the materials transit from one first chamber towards a second downstream chamber.

The two chambers have independent motorisations that allow each of these to turn at a different rotation speed. Furthermore, the first chamber has a feed opening through which the materials to be ground are continuously introduced during the rotation, while the second chamber has an opposite unloading opening through which the ground materials are unloaded by overflowing.

As has been said, between the first and the second chamber, a duct is provided, through which the materials ground in the first grinding chamber pass into the second grinding chamber without the rotary movement of either stopping.

This duct is placed coaxially to both the chambers and has a much smaller diameter than these, so as to create an entry and an exit threshold substantially close to the centres of the two chambers.

The ground materials pass into the duct by overflowing from the first grinding chamber and fall inside the second grinding chamber.

According to the patent, the latter also has a separate loading device which also permits introducing further grinding bodies or additive substances that favour the grinding of the latter parallel to the connection duct connecting the two chambers and which allows the materials to pass from the first chamber into the second chamber. This type of grinding system also has some drawbacks.

A first drawback is that if a fault occurs in the first grinding chamber, the grinding cycle must be completely interrupted because the second grinding chamber can only be fed with the already-ground materials coming from the first chamber.

Another drawback is that the two grinding chambers must be arranged one after the other and this arrangement restricts the possibility of the grinding system adapting to small spaces which could, alternatively, require the two grinding chambers to be arranged side by side.

Another drawback is that it is not possible, even though required by the product production cycle, to completely or partially remove the materials from the first grinding chamber without first having them pass into the second grinding chamber and therefore through the unloading opening of the latter.

OBJECTS OF THE INVENTION.

One object of the invention is to improve the state of the art.

Another object of the invention is to make a grinding system, in the specific case a continuous grinding system, that allows being arranged according to various space requirements.

A further object of the invention is to make a grinding system that also allows taking ground materials between one grinding chamber and the next.

Another object of the invention is to make a grinding system that can continue to operate even if a part of this is faulty, maintaining in any case a production of ground raw materials, albeit in reduced quantities.

A further object of the invention is to make a grinding system that can be extended or reduced according to requirements.

Another object of the invention is to make a grinding system that allows curbing initial purchase costs and which can be extended at a later time in accordance with growing quantities of work to be done.

A further object of the invention is to make a grinding system with low purchase and maintenance costs.

According to one aspect of the invention, a grinding system is provided comprising: at least a first and a second grinding chambers arranged in operating succession separate and independent the one from the other and a feeding device of materials to be ground in at least said first grinding chamber, characterized by the fact that between said first and said second grinding chambers is positioned a collection device for collecting the ground materials in said first grinding chamber. According to another aspect of the invention, a continuous grinding method is provided comprising: grinding quantities of materials to be ground in a first grinding chamber obtaining first grinding materials; extracting said quantities of first grinding materials from said first grinding chamber; sending said quantities of first grinding materials towards other processing and/or utilisation stations, characterized by the fact that between said extracting and said sending is comprised to collect said quantities of first grinding materials in collection means.

The grinding system and grinding method permit obtaining the following advantages:

- arrangement of the grinding chambers according to specific space requirements;

- possibility of picking up quantities of ground materials or materials being ground between one grinding chamber and the next, without interrupting the grinding cycle;

- possibility of alternating the grinding chambers in case of a fault in one of them;

- adapting the dimensions of the grinding system according to requirements, by adding or eliminating grinding chambers including after installation of the grinding system;

- low cost of making each grinding chamber;

- low maintenance cost of each grinding chamber;

- reduction in the amount of money needed for the initial purchase of a grinding system with just a few grinding chambers, but which can be extended later on according to operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will appear more evident from the detailed description of an embodiment of a grinding system, illustrated indicatively by way of non limiting example, in the attached drawings wherein: Figure 1 is a side schematic view of a grinding system in a simplified embodiment; Figure 2 is a view on an enlarged scale of a grinding apparatus comprised in the system of Figure 1 ;

Figure 3 is a possible embodiment of a grinding system having three separate grinding chambers, which might also be higher in number, placed in sequence substantially coaxial between them;

Figure 4 is a possible alternative embodiment of the system of Figure 3 with three grinding chambers arranged side by side with parallel longitudinal axis.

EMBODIMENTS OF THE INVENTION. With reference to the Figure 1, by 1 is indicated a grinding system comprising a first grinding apparatus 2 and a second grinding apparatus 3 which are arranged one after the other, substantially coaxial, and which have rotating motorisation units 4 and 5, the one independent from the other.

Each of the grinding apparatuses 1 or 2 comprises a drum 6 or 7 with rotation axis "A" either horizontal or substantially horizontal which is supported by its own support frame 8 and 9.

Inside each first drum 6 or second drum 7 a grinding chamber is defined, a first grinding chamber 10 and a second grinding chamber 11 respectively. As can be seen by means of the broken lines of Figure 2, the inner chamber of each drum, in this case e.g. the first chamber 10 of the first drum 6, has on the inner wall a series of ribs in relief 13 which, normally, have a helical pattern, or substantially such, and which while the first drum 6 (or 7) rotates, carries the loose material, partially or

completely ground, contained in the grinding chamber 10 from an entry end of this, marked 106, to an opposite exit end, marked 206, close to which is a threshold diaphragm 306.

As can be seen in the Figure 1, the first drum 6 turns at a rotation speed "O ₁ " while the second drum 7 turns at a rotation speed "ω ₂ " which is normally different from the previous one.

Inside the first and the second grinding chambers 10 and 11 are grinding elements comprising ball-shaped, or round-shaped bodies, 14, 15, 16 having gradually decreasing diameters passing from the entry end 106 to the exit end 206. The ends of each first drum 6 or second drum 7 are closed by side walls that have, at the centre, coaxial openings 17 and 18 through which the materials can be introduced into the grinding chamber 10 (or 11) and exit from this by overflowing when the level of these materials inside the grinding chamber 10 (or 11) exceeds the threshold of the diaphragm 306 located near the opening 18. Between a first drum 6 and a second drum 7 a container 19 is arranged that is designed to collect the materials that exit from the first grinding chamber 10 after undergoing a first grinding operation.

As is shown in the Figure 1, the container 19 is connected to the exit opening 18 of the first drum 6 by means of a segment of pipe 20 while a further segment of pipe 21 connects the container 19 to the entry opening 17 of the second drum 7; on this second segment of pipe 21 is also fitted a pump 22 that allows conveying the material collected in the container 19 and which has already undergone a first grinding operation inside the second grinding chamber 11. The container 19 permits accessing the material that has undergone a first grinding operation before this is introduced into the second grinding chamber, so as to send it, when required by the product production cycles, in this case ceramic tiles, to other processing or utilisation stations that are different to the second grinding chamber 11. The material to be ground is introduced into the first grinding chamber 10 through the opening 17 into which runs an unloading end of a conveyor 23 into which unloads a hopper 24 for storing this material.

Also running into the conveyor 23 are two feeding pipes 25 and 26, supplying

additive substances that prevent material agglomeration and water for mixing with the ground materials and forming a mix usable for the production of ceramic products respectively.

With reference to the figure 3, it will be seen that the grinding system 1 comprises a third grinding apparatus 27 completely identical to the first grinding apparatus 2 and to the second grinding apparatus 3.

Consequently, the third grinding apparatus 27 comprises a third drum 28 supported rotating by its own support frame 29 and which is driven in rotation independently from the others by means of its own motorisation unit 30. Between the second drum 7 and the third drum 28 a further container 31 is provided to collect the materials that have undergone a second grinding operation in the second grinding chamber 11 and which is connected with the exit opening 18 of the second drum 7 by means of a pipe segment 32 while the third drum 28 is connected to the further container 31 by means of a pipe segment 33 on which a pump 34 is fitted to pump the material collected in the further container 31 inside the third drum 28 to undergo a third grinding operation.

It should be noted that in this embodiment of the grinding system 1 each drum can, if necessary, be disengaged from operation without this completely interrupting the grinding cycle. In fact, if e.g. a fault occurs in the second drum 7, either the first drum 6 can be directly connected to the further container 31 or, alternatively, the third drum 28 can be directly connected to the container 19 by means of the respective pipe segments suitably extended, maintaining grinding operations active for all the time required to repair the second drum 7. With reference to the Figure 4, it will be seen that the grinding system 1 comprises another three grinding apparatuses which have been described previously, but which are arranged with the rotation axes "Al" of the first drum 6, "A2" of the second drum 7 and "A3" of the third drum 28 parallel instead of coaxial. Furthermore, it will be seen that the hopper 24 unloads the material to be ground onto a conveyor belt 35 which has conveying directions reversible according to need and which can unload the conveyed materials both onto the conveyor 23 and onto a further

conveyor 123 fitted, e.g., at the entry opening 17 of the second drum 7 or onto the same conveyor 23 moved from the entry opening 17 of the first drum 6 to the corresponding entry opening 17 of the second drum 7.

This way, the hopper 24 can indifferently supply, in a direct way, both the first drum 6 and the second drum 7.

The person skilled in the field will easily appreciate that by extending the conveyor 35 it is also possible to directly supply the third drum 28 instead of the second drum 7.

This is useful when a fault occurs to one of the drums, to prevent having to interrupt the continuous grinding of the materials to be ground. If a fault occurs in the third drum 28, the grinding can continue with just the first drum

6 and the second drum 7 while if a fault occurs in the second drum 7, the grinding can continue with the first drum 6 and the third drum 28 by connecting the latter to the container 19, extending the segment of pipe 21 as shown in the Figure 4 with the broken lines 121. If a fault occurs in the first drum 6, the conveyor directly supplies the second drum 7 and this continues grinding together with the third drum 28.