DESCRIPTION OF THE INVENTION

The subject of the present invention is an adjustable nozzle, of the type used for liquid or slurry atomization systems, in which the liquid fluid is transformed by the nozzle into a jet or bundle of drops that are introduced countercurrent into a flow of hot air so as to interfer with it and produce a drying of the drops with consequent generation of solid particles with a low moisture content. This type of use is carried out in the ceramic industry, in particular for the manufacture of ceramic tiles, which is carried out starting from a process of forming the product by pressing ceramic powders consisting of powder materials better defined as atomized material. This well-known technique involves in fact that the fluid, or slurry, to be atomized, in the specific application called slip, is injected into the chamber of the atomizer by means of nozzles that form a spray which is injected, in countercurrent, in a flow of hot air with the result of forming a final product consisting of an atomized material formed by tiny solid particles with a low moisture content.

In common practice, nozzles have a fixed calibrated size and sprayers are operated at the highest possible flow rate. Therefore, to modify the characteristics of the particle size curve of the particles so obtained, the method used in the known technique provides for changing the type of nozzle. This way of working, besides presenting the drawback of necessarily requiring a shutdown of the atomisation plant or in any case a reduction in the production capacity, does not allow, while keeping other parameters at the same values, a "fine" adjustment of the jet or bundle of drops generated by the nozzle, nor adjustments during a production process that is running.

The known technique therefore configures a system that is very rigid and that does not allow the process to be kept under control with sufficient continuity over time, in order to adjust characteristics and performance to the entire tile production process.

In this regard, it should be noted that the use of the known technique as described above, generally adopted for the indicated industrial application, owes its adoption essentially to the characteristics of high abrasiveness of the solid component that forms the fluid, or slurry, to be sprayed through the nozzle in suspension in the liquid.

The high abrasiveness has the consequence of producing a not negligible wear of the calibrated hole through which the fluid is fired out of the nozzle to produce the spray over time, with the inevitable consequence of altering, after a certain time of operation, the proper operation of the nozzle. It is in fact essential, for the constant and proper operation of the nozzle, that the configuration and the initial dimensional characteristics of the calibrated hole be constantly maintained. Also making said calibrated hole in the centre of a disc, made of hard materials, such as tungsten carbide and the like, which are used, for example, for making cutting tools, such disc being called a pad and being coupled exactly inside a special cavity obtained inside the nozzle head, cannot solve the problem. The method illustrated hereintofore, however, only offers the positive aspect that the only pad can be replaced instead of the entire nozzle, but always requires disassembly and reassembly of the latter, and therefore shutdown of the atomization plant or anyway a reduction in production capacity.

The main object of the present invention is to overcome the limitations of the known technique by providing a system that allows an effective regulation of the operation of the sprayer nozzles without the need of interventions that involve disassembly and reassembly with consequent downtime or reduction of productivity. Another object of this invention is to allow an adjustment of the spray jet generated by the single nozzle during the production process, and therefore both to recover the wear, bringing the operating characteristics back to the initial ones, and to allow an adjustment of the characteristics of the granulometric curve of the atomised product through an adjustment action carried out on the adjustable nozzle.

Among other advantages, we must mention the achievement of a benefit in terms of productivity, consistent production quality, and also a reduction in waste resulting from deformation and breakage caused by pressing.

These and other objects and advantages are obtained by the present invention as described, illustrated in the enclosed drawings and claimed hereinafter.

The characteristics of the present invention will become more evident from the following description of some of its preferred embodiments illustrated by way of not limiting example with the help of the enclosed figures, in which:

-figures 1 and 2 show two exploded perspective views of two nozzles of the known technique;

-figure 3 shows a schematic perspective exploded view of a first embodiment of the invention;

-figure 4 shows a schematic side view from the right of the exploded view of Figure 3:

-figure 4a shows part of a schematic section executed according to the tracing line l-l of Figure 4;

- figure 5 shows a detail of a section taken along the tracing line I l-l I of figure 4a represented in two different operating positions;

-figure 6 shows a schematic perspective exploded view of a second embodiment of the invention;

-figure 7 shows a schematic side view from the right of the exploded view of Figure 6:

-figure 7a shows part of a schematic section executed according to the tracing line l-l of Figure 7;

-figure 8 shows a schematic perspective exploded view of a third embodiment of the invention;

-figure 9 shows a schematic side view from the right of the exploded view of Figure 8:

-figure 9a shows part of a schematic section taken along the tracing line IV-IV of Figure 9;

-figure 10 shows a schematic perspective exploded view of a fourth embodiment of the invention;

figure 1 1 shows a schematic side view from the right of the exploded view of Figure 10:

-figure 11a shows part of a schematic section taken along the tracing line V-V of Figure 11 ;

- figure 12 shows a detail of a section taken along the tracing line VI-VI of figure 11a represented in two different operating positions; -figure 13 shows a schematic perspective exploded view of a fifth embodiment of the invention;

-figure 14 shows a schematic side view from the right of the exploded view of figure 13:

-figure 14a shows part of a schematic section taken along the tracing line VII-VII of figure 14;

- figure 15 shows a schematic perspective exploded view of a sixth embodiment of the invention;

- figure 16 shows a schematic side view from the right of the exploded view of figure 15:

- figure 16a shows part of a schematic section taken along the tracing line VIII-VIII of Figure 16.

Figures 1 and 2 above show two different solutions of the known technique for nozzles commonly used in atomizing devices. The fluid is conveyed into the nozzles under pressure, so as to generate the spray stream coming out from holes 1 and 6 of heads 2 and 7.

In the first nozzle shown in figure 1 , the fluid enters into a nut 3 which has four holes that provide a rotary motion coaxial with the fluid. A distributor 4 has the shape of a converging truncated cone aimed at accelerating the fluid, moved with a rotary motion component, towards the calibrated hole 5a, that is made in a perforated pad 5 of hard material, such as tungsten carbide or similar, and which is exactly housed in a special cavity of the head 2.

In the second nozzle shown in figure 2, a different system is used to give a rotary motion to the fluid, and includes a distributor 8, having the task of moving the fluid into a circular crown far away from the axis of the nozzle, and a three-way nut 9 which has spiral grooves converging towards the center, that is towards the calibrated hole 10a of a perforated pad 10 also made of hard material and housed with a precise fit in a special cavity of the head 7.

In both cases, the rotation component of the motion imparted to the fluid determines an opening of the angle at the centre of the spray jet. In fact, the greater the rotation component imparted to the fluid, the greater the opening angle at the center of the spray.

In both cases, all other factors being kept at the same value, the characteristics of the spray and the particle size distribution of the atomised product depend on the calibrated holes provided in the pads.

In the figures following figures 1 and 2 there are shown some embodiments of the invention.

The subject of the invention is a nozzle, of the type used for liquid or slurry atomization systems, in which the liquid fluid is transformed by the nozzle into a jet or bundle of drops that are introduced countercurrent in a flow of hot air, so as to interfer with it and produce a drying of the drops with consequent generation of solid particles with a low moisture content which nozzle has the peculiar characteristic of being adjustable. In fact, the nozzle includes adjustment means operated on command from the outside in order to change the characteristics of the nebulized jet or stream of drops emitted by the same nozzle during orpetaion.

More specifically, these adjustment means include devices that allow the geometry of the passage section for the fluid to be modified in a controlled manner.

These adjustment means include control devices capable of intercepting, upon command, the flow rate of the fluid in the nozzle so as to partialize the same flow rate.

Each of these devices includes a first diaphragm device, which is composed of a fixed plate 11 onto which a rotating plate 12 is coupled and which is controlled so as to rotate, thus varying its angular position, by a driving motor or actuator 18.

The fixed plate 11 and the rotating plate 12 are individually provided with respective through-holes 19 and 20. The through-hole 20 is shaped in such a way as to be able to suitably limit the passage of the fluid through the fixed hole 19, by varying its position with respect to the hole 19. This can be achieved by turning the plate 12.

the calibrated through-holes 19 and 20 preferably have a circular profile and the calibrated through-hole 20 is arranged eccentrically with respect to the axis of rotation of the mobile plate 12 in order to face the calibrated through-hole 19 of the fixed plate 11 , in this way limiting (partializing) the passage of the fluid or overlapping it perfectly, so as to open the passage completely. Preferably, the through hole 19 of the fixed plate 11 and the through hole 20 of the movable plate 12 have the same dimensions and are located at the same distance from the rotation axis of the movable plate (12). In the present case, the through-hole 19 of the fixed plate 11 is permanently positioned in axis with the hole 17 on the head 15 of the nozzle 16.

The rotation of the rotating plate 12 can be obtained because the latter is bound, with respect to rotation, to an external toothed crown 13 with which an external pinion 14 engages, which is in turn controlled into rotation by a driving motor or actuator 18.

A second embodiment comprises a second type of diaphragm device, which consists of a needle-type shutter 21 or adjusting needle adapted to operate coaxially with a calibrated through seat 22 facing hole 23 of the head (24) of a nozzle 25. This calibrated seat 22 is preferably made of a hard material pad 29. Coaxial displacement of the needle shutter (21 ) with respect to the axis of the calibrated seat 22 is controlled by an external linear actuator 26. The external linear actuator 26 controls axial displacement in both directions of an axially mobile means, which is coupled smoothly and tightly in the body 27 of the nozzle 25 and supports the needle shutter 21 at one end.

Said axially mobile means has a conduit (28) and channels for the supply of fluid to the head 24, both coaxially arranged internally therein.

A third device with variable section 31 consists of a deformable tubular member which is placed coaxially at the hole 32 provided inside the head 34 of a nozzle 37, and is tightly housed inside an annular chamber 35 provided to house a hydraulic control fluid which is fed directly therein through a conduit 36. A function of acting on and deforming the deformable tubular member is entrusted to the hydraulic fluid being supplied, on command, by means of the duct 36, in order to vary the diameter of the lumen through which the fluid is sent under pressure to the hole 32 of the head 34. The possibility to realize a continuous variation of the fluid outflow lumen from the nozzle can be easily understood upon consideration of the structure of the device itself, by virtue of its structural characteristics.

In devices with control devices capable of intercepting the fluid flow rate in the nozzle, on command, by partializing it, the control system can be suitably operated to obtain an intermittent atomised jet, i.e. a spray characterised by a flow rate pulsating over time.

The modification of the characteristics of the atomised jet or stream of drops emitted by the nozzle is possible by means of adjustment devices, which could be defined as dynamic, and which are capable of regulating the rotary motion of the fluid within the nozzle.

A first device of this type, called a vortex or swirl partializer 41 , consists of a fixed part consisting of a sort of fixed nut 42 which is set coaxially with respect to the calibrated 38 hole, preferably obtained in a pad 40 of hard material facing the hole 43 of a head 44 of the nozzle 39. Facing the inner side of the fixed nut 42 is operating a mobile disc partializer 45. The latter is equipped with spiral channels and placed in direct communication with the chamber into which the fluid is sent under pressure. Furthermore, the mobile disc partializer is coaxially connected to an external actuator 47 by means of a rod 46 that can be rotated on command, the external actuator carrying out a positioning in the desired relative position between the movable partializing disc 45 and the fixed nut 42, so as to geometrically determine the fluid passage area. Also in this case the calibrated hole 38 is made in a pad 40 of hard material and faces the hole 43 of the 44 head of the 39 nozzle. Figure 12 shows situations corresponding to three different relative positions that determine three different areas of passage.

A second partializer device in which the fluid is subjected to a rotary motion is equipped with a rotor 48, having a set of radial vanes 49, which is housed inside a chamber, obtained in the body 54 of the nozzle 50 and is driven in rotation by external motor means 57. A distributor disc 51 is located "downstream" of the rotor 48 and is entrusted with the task of conveying the fluid to a calibrated hole 56 preferably obtained in a pad 55 of hard material and facing the hole 53 of the head 52.

A further embodiment includes a third device 61 which is equipped with a rotating member 62 equipped with radial blades 63 and which is mobile in rotation inside a chamber, obtained in the body 64 of a nozzle 65. The rotating member 62, which is driven in rotation by external motor means, includes a needle type shutter 67 or adjustment needle firmly fastened at its end and facing the head 66 of the nozzle 65. The shutter is so set as to operate coaxially with a calibrated through seat that is in turn located in coaxial relation with the calibrated hole 72, which is preferably obtained in a pad 71 of hard material facing the hole 68 of a head 66. The coaxial displacement along the axis of the calibrated through seat, this one obtained in a hard metal pad 71 too, performed by the needle shutter 67, which is firmly supported by the rotating member 62, is controlled by an external linear actuator 70 that controls the axial displacement in both directions of the entire rotating member (62).

In addition to the ceramic industry, the invention can also find application in atomisation plants for pharmaceuticals, paints, food products, such as milk, fertilizers, pesticides, detergents, etc.