EP0499768A1

EP0499768A1 - A rapid-drying apparatus, in particular for unfired ceramic tiles

Info

Publication number: EP0499768A1
Application number: EP91830570A
Authority: EP
Inventors: Graziano Monterumici
Original assignee: Poppi SpA
Current assignee: Poppi SpA
Priority date: 1991-02-18
Filing date: 1991-12-17
Publication date: 1992-08-26
Also published as: ITMO910020A0; ITMO910020A1; IT1246024B

Abstract

The invention relates to a rapid-drying apparatus, in particular for unfired ceramic tiles. According to the invention, the surfaces of the said tiles (2), which are transported on a conveyor plane (1), are subjected to the uniformly-distributed action of special blowing and aspirating devices (3) and (13). Said blowing and aspirating devices (3) and (13) are formed by a plurality of blowing nozzles (6), uniformly distributed and arranged alternately side-by-side with intake ports (7) also uniformly distributed, together with the said nozzles (6), on a surface which is virtually parallel to the tile (2) surfaces. The nozzles 6 are fed with air at a water-column discharge pressure of about 120-160mm and at a temperature of about 120-200248C. The distance between the nozzles (6) and the tiles (2) is not normally superior to 5-7 times the diameter of the same nozzles (6).

Description

The invention relates to a rapid-drying apparatus, in particular for unfired ceramic tiles.
The necessity and convenience of proceeding to a drying phase of unfired ceramic products after forming derives from considerations of a technical and economical nature. In fact, during the successive firing operation good drying permits, apart from a considerable energy saving, of obtaining improved technical characteristics, principally in relation to the regularity of the shrinking phenomenon of the product.
The prior art realisations all present various drawbacks and lacks, characterised by rather long operative cycles, especially if rapid firing cycle times are taken into consideration, which the tiles must subsequently undergo. Furthermore, the modalities with which the drying process is realised necessitate, in some cases, complex structuring of the driers in order to realise a pre-ordered movement of the tiles with the aim of performing, with the greatest efficiency possible, the heat exchange operations of the drying cycle. In such systems the material to be dried is brought into contact more or less regularly with hot air currents which brush more or less tangentially the surfaces of the said material.
The result of the operation is very often characterised by irregularities and lack of uniformity which are the origin of internal defects only revealed after firing.
The prior art also embraces systems in which the tiles, in transit on a normal motorised roller transport plane, are brought into contact with hot air currents which are directed orthogonally against the surfaces of the tiles. The blown air is always evacuated, and therefore made to circulate, tangentially to the tiles and is collected by appropriate manifolds situated by the side of the roller conveyor plane. Also in this case, although with different intensity, there is the drawback of a relatively poor uniformity in drying for every single tile, which can be the origin of defects such as small cracks or cuts around the edges of the said tiles, only sufficiently clearly revealed after firing.
The present invention, as it is characterised in, the claims, proposes to overcome the lacks and drawbacks in the prior art, by providing a rapid drying apparatus, in particular for unfired ceramic tiles, which is functionally simple and suitable to be introduced directly to the work line.
Further characteristics of the present invention will better emerge from the description which follows, of a preferred but not exclusive embodiment of the invention illustrated it, a purely non-limiting example in the enclosed drawings, in which:

Figure 1 shows a schematic longitudinal median section;
Figure 2 shows in enlarged scale a particular of figure 1;
Figures 3 and 4 show two schematic sections along planes III-III and IV-IV of figure 1.

With reference to the figures, 1 indicates a motorised roller conveyor plane on which the tiles 2 are transported. Above the conveyor plane 1 a blowing and aspirating device 3 is located, which device 3 comprises a plurality of pressurised hot-air alimentation conduits 4 arranged transversally to the direction of the advancement direction of the conveyor plane 1, all of said conduits 4 being placed at the same distance from the said conveyor plane 1. The conduits 4 are parallel to and uniformly distanced from each other along the advancement direction of the tiles 2. The conduits 4 are in their turn connected to feed manifolds 5 which feed them with hot air. The conduits 4 are equipped with nozzles 6 which nozzles 6 are located at a distance from the tiles 2, which tiles 2 are placed on and in transit on the said conveyor plane 1; said distance is never superior to 5-7 times the diameter of the said nozzles 6. The said nozzles 6 are distributed uniformly on the plane generated by the conduits 4 and parallel to the conveyor plane 1 and thus parallel to the surface of the tiles 2. Intake ports 7 are arranged alternated side-by-side with the nozzles 6, which intake ports 7, in the preferred embodiment, are constituted by spaces between the conduits 4. In this way the said intake ports 7 are uniformly distributed on the level of the nozzles 6 and are alternated with said nozzles 6. The distribution and location of the intake ports 7 with respect to the nozzles 6 has an essential function, that of picking up (ideally one port for each nozzle) the whole volume of fluid sent out from the nozzles 6 immediately after the fluid has brushed the surface of the tiles 2. Located above the conduits 4 is a suction manifold 8 which has the function of collecting the air evacuated through the intake ports 7 in an opposite direction to the outflow direction of the nozzles 6, thus directed away from the tiles 2. The aspirated hot and humid air is sent via the suction manifold 8 to a recycling and/or expulsion plant through which it is, at least in part, re-utilised and sent, by means of the feed manifold 5, to the nozzles 6 together with "new" air. In the illustrated embodiment, another blowing and aspiration device 13, completely analogous to the device 3, is located below the said conveyor plane 3. The structure of devices 3 and 13 covers the entire width of the conveyor plane and the length to a pre-established degree. The distance of the nozzles 6 from the tiles 2 located on the conveyor plane is established according to the criterion previously indicated, considering however the presence of the motorised rollers which form the same conveyor plane. The nozzles 6 have diameters of about 2-5mm.
The hot air with which the nozzles 6 are fed has the following characteristics: water column discharge pressure 120-160mm; temperature 120-200°C. The configuration and geometrical structure of devices 3 and 13 and their location at the said distance from the surfaces of the tiles 2 permits of the realisation of a hot air flow indicated schematically by arrows 9 and 10. This flow, in combination with the speed at which the jets expelled from the nozzles 6 hit virtually normally the surfaces of the tiles 2 and with the temperature of the said jets, creates a uniform situation of conditions for each tile 2. Furthermore, the heat exchange velocities and thus the drying velocity are extremely fast.
The invention, thanks to its characteristics as described above; permits of drying:

a) making the unit (tile) dimensional variations uniform;
b) reducing to a minimum the said variations.

The obtaining of such results is made possible by the particular functional "structuring" of the invention which permits of locally taking in the whole volume of fluid sent out by the nozzles 6 immediately after said fluid has covered the surface of the tile 2.

Claims

Rapid drying apparatus, in particular for unfired ceramic tiles, comprising:
- a conveyor plane 1 on which the tiles 2 are transported;

- at least one blowing and aspirating device 3 comprising a plurality of nozzles 6 located at a pre-established distance from said conveyor plane 1, which nozzles 6 aim at the said tiles 2 in a virtually orthogonal direction, a plurality of air jets at pre-established temperature, humidity and pressure; being envisaged that the said nozzles 6 are distributed uniformly on at least one side of the said conveyor plane 1 in such a way as to cover a pre-established portion of said plane 1; a plurality of intake ports 7 arranged alternately with the said nozzles 6 and like these last, uniformly distributed, in such a way as to take up locally the entire volume of fluid sent out by each single said nozzle 6 immediately after said fluid has brushed over the surfaces of the said tiles 2; at least one suction manifold 8 to collect the air evacuated through the said intake ports 7 and to send it to a recycling and/or expulsion plant; being also envisaged that each said nozzle 6 is located at a distance from the surface of the tiles 2 not superior to 5-7 times the diameter of the same nozzle 6; being furthermore envisaged that the air with which the nozzles are fed has the following discharge characteristics: water-column discharge pressure 120-160mm; temperature 120-200°C.
Apparatus as in claim 1, wherein said nozzles 6 have diameters variable from about 2 to 5 mm.
Apparatus as in claim 1, wherein said nozzles 6 are arranged on a plurality of feed conduits 4 which conduits 4 are located transversally to the movement direction and on a single plane parallel to the conveyor plane 1; said conduits 4 being parallel between themselves and uniformly distanced one from the other along the direction of the said movement direction.
Apparatus as in claim 1, wherein said conveyor plane comprises one motorised roller conveyor plane; at least one first said blowing and aspirating device 3 and at least one second blowing ans aspirating device 13 being envisaged, located opposite one another, one being above and one below the said conveyor plane 1.