Method and means for forming ceramic tiles

Abstract: A machine (30) for forming ceramic tiles by pressing in a mould, comprising a fixed lower base (31) acting as a reaction base during pressing and having a horizontal bearing surface, a vertically movable member (33), and an upper die (32) carried by the movable member (33) to define the upper surface of the mould forming cavity, includes a flat lower element (11) of sufficiently compression-resistant material resting on the bearing surface and movable on it to act as the lower surface of the mould cavity, a mould die plate (35) positioned above said flat element (11) to define the side walls of the mould cavity and movable vertically between a lower position in contact with the flat lower element (11) and an upper position in which it is raised from the flat element (11) to enable the formed tiles (9) to pass below it, after each pressing operation said flat lower element (11) being moved horizontally in combination with the raising of the die plate (35), to remove the formed tile (9).

Description: METHOD AND MEANS FOR FORMING CERAMIC TILES This invention relates to a new and original method, machine and plant for forming ceramic tiles. The WO 96/15888 A discloses a method for compacting powders starting from a layer of powders formed on a belt conveyor, isolating a portion of said layer inside a die plate having a cavity upperwardly and downwardly open, and compacting said portion of powder inside the mould cavity defined by the die plate and the underlying belt of the conveyor. This document further discloses also a machine for carrying out the method. A further document disclosing the production of plate-like products is DE 2 242 168 A, in which a mould cavity is filled with powder and then removed after the pressing stage has been carried out. Compaction is made at a first pressure and must be subjected to a final compaction of about 250-400 kg./cm 2 . The method of the invention comprises the following operations: depositing a succession of downwardly orientated single or compound decorative layers on a relatively thin endless belt defining the belt of a belt conveyor, driving the conveyor belt in such a manner as to bring each decorative layer at a time below a lowerly-open mould die plate, and positioning the die plate on the conveyor belt such that the upper surface of this latter defines the lower surface of the mould cavity, loading the tile-forming material into the mould cavity, then forming a downwardly orientated tile by pressing the material above the decorative layer located on the conveyor belt. The invention also comprises a plant for implementing the aforesaid method, comprising: a conveyor with a conveyor belt of sufficiently compression-resistant material having an upper branch working on a horizontal bearing surface, at least one decorating machine positioned at the upstream end of the conveyor belt to spread a succession of decorative layers on the upper surface of the belt, a machine for forming tiles by pressing, comprising: a fixed lower base acting as a reaction base during pressing and having a horizontal bearing surface on which the conveyor belt is supported during its travel, an upper die carried by a vertically movable member to define the upper surface of the mould forming cavity, and a mould die plate defining the side walls of the mould cavity and movable vertically between a lower position in contact with the upper surface of said conveyor belt and an upper position in which it is raised from the conveyor belt to enable the formed tiles to pass below it, the conveyor belt being driven with intermittent stepwise movement, and after each pressing operation being advanced in combination with the raising of the die plate, to remove the formed tile. Finally, according to the invention a forming machine is provided suitable both for forming decorated tiles by the aforesaid method and for forming tiles not by said method. Said machine comprises a fixed lower base having a horizontal bearing surface acting as a reaction base during pressing, a vertically movable member, and an upper die carried by the movable member to define the upper surface of the mould forming cavity. The machine is characterised by comprising a flat lower element of sufficiently compression-resistant material resting on the bearing surface and movable on it to act as the lower surface of the mould cavity, and further comprising a mould die plate positioned above said flat element to define the side walls of the mould cavity and movable vertically between a lower position in contact with the flat lower element and an upper position in which it is raised from the flat element to enable the formed tiles to pass below it. After each pressing operation, said flat lower element is moved horizontally in combination with the raising of the die plate, to remove the formed tile. The plant and machine of the invention are of particularly simple and economical construction. They are also intrinsically suitable for operation at a very high rate. The plant is also particularly short and compact in plan view. These and further advantages are attained by the invention as characterised in the claims. The invention is described in detail hereinafter with the aid of the accompanying figures, which illustrate a non-exclusive embodiment thereof. Figure 1 is a general schematic side view of the entire plant Figure 2 is a section through the downstream part of Figure 1, taken on the plane II-II. Figure 3 is a section on the plane III-III of Figure 1. Figures 4A, 4B, 4C represent three different operating stages, shown in section on the plane IV-IV of Figure 2. The plant of the invention comprises a conveyor 10 with its conveyor belt 11 of material sufficiently rigid against compression. In particular, the belt 11 is an endless relatively thin steel belt passing about at least two end rollers, to define the belt of a belt conveyor. Advantageously the belt 11 is provided with two sets of regularly distributed holes 12 extending along the two longitudinal edges of the belt, to engage corresponding teeth provided on the four end rollers 13 about which the belt passes. The holes 12 and the corresponding teeth on the rollers 13 totally prevent belt slippage on the rollers, to hence achieve perfect synchronization between the movement of the belt and the operation of the other machines which operate on it. The conveyor 10 has a horizontal upper branch working on a horizontal bearing surface which in its upstream part is defined by a support means 14 having an upper surface on which the belt 11 bears. In this upstream part there are positioned a plurality (three in the embodiment shown in the figures) of decorating machines 20A, 208 and 20C, each arranged to spread a succession of decorative layers 21 on the upper surface of the belt. The machines 20A, 20B and 20C (shown only schematically in the figures) are identical to the usual known machines for spreading a layer of decorative material on tiles. In particular, they are silk-screen machines arranged to spread a layer of silk-screen ink by means of a flat or cylindrical screen. According to the invention, these machines operate by each depositing a succession of respective layers of decorative material on the surface of the underlying belt 11. If a complex decoration is to be formed on the tile, consisting of a compound decorative layer 21 formed from different superposed layers, that layer which is to form the upper layer on the tile is firstly deposited, then on this (while on the belt 11) are deposited the other layers, from the upper to the lower in turn, ie the layers are deposited on the belt 11 in the reverse order to that followed in the traditional method, in which firstly the lower layer is deposited, then the upper layers are deposited on this in turn. Consequently, the most upstream-positioned machine 20A deposits on the belt 11 that decorative layer which is to form the most outer layer on the tile, the machine 20B positioned downstream of the first deposits on each layer deposited by the preceding machine that decorative layer which is to form the intermediate layer on the tile, and finally the most downstream machine 20C deposits on those layers deposited by the preceding machines that decorative layer which is to form the lower layer on the tile. The decorating machines are coordinated with each other and with the movement of the belt 11, in such a manner as to form said decorative layers on each other with precision. Downstream of the decorating machine there is a machine 30 for forming tiles by pressing in a mould, the machine comprising a fixed lower base 31 acting as the reaction base during pressing and having a horizontal bearing surface on which the conveyor belt 11 bears during its travel. The machine 30 also comprises a usual upper die 32 which defines the upper surface of the mould forming cavity and is carried by a vertically movable member 33 guided by lateral vertical columns 34. The member 33 is operated by suitable known means (for example a large hydraulic cylinder-piston unit, not shown in the figures) able to provide the necessary thrust for pressing the tile within the mould die plate. The machine 30 also comprises a usual die plate 35 defining the lateral walls of the mould cavity. For simplicity of description, the text will refer to the formation of a single tile per pressing operation. However (as shown in the figures), the mould can be of multiple type, ie able to form several tiles simultaneously with one pressing operation. In this case the upper die 32 will be of multiple type comprising several dies, and likewise the die plate 35 will comprise several cavities. Likewise the decorative layers deposited by the machines 20A, 20B and 20C will be multiple layers (as shown in the figures). The die plate 35 is movable vertically between a lower position in contact with the upper surface of the conveyor belt 11 and an upper position in which it is raised from the belt 11 to enable those tiles which have just been formed to pass below it. The die plate 35 is driven for example by four vertical cylinder-piston units 36, of which the casings are fixed to the sides of the base 32 and the rods are fixed to the die plate itself. The tile-forming material is loaded into the mould cavity by usual loading means, for example by a traditional loading carriage 41 provided with a grid for homogeneous material distribution and moving with reciprocating movement along a fixed horizontal travel surface 45. The carriage 41 is driven by a motor 42 with a crank 43, and is fed by a usual loading hopper 44. According to the invention, the travel surface 45 is positioned in line with and adjacent to the upper surface of the die plate 35 when this rests on the belt 11. The surface 45 is defined by the upper surface of a thin fixed horizontal panel 46 positioned transversely above the belt 11 in the region immediately upstream of the machine 30, and spaced from the belt and from the decorative layers lying on it. The described plant implements the following method. The conveyor belt 11 is driven with intermittent motion. The machines 20A, 20B and 20C firstly deposit a succession of single or compound decorative layers. In the latter case the layers are orientated downwards, as already stated, with that layer to appear as the upper layer on the tile being positioned below the others, and so on for the other layers. The decorative layers are deposited directly onto the upper surface of the conveyor belt 11. To prevent said layers remaining adhering to the belt 11, the belt upper surface can be coated with a non-adhesion material, such as a fluoroethylene (TEFLON R ). Said decorative layers can be deposited on the belt 11 while this is in movement if the machines 20A, 20B and 20C operate with a cylindrical screen, otherwise if the machines operate with a flat screen the belt 11 must be at rest. Each single or compound decorative layer 21 (see Figure 2) is then carried by the belt 11 to below the die plate 35 of the machine 30, where it stops. During this stoppage a tile (possibly multiple) is formed. When the belt 11 carries a decorative layer to below the die plate 35, this latter is raised from the belt 11 and the die 32 is raised (see Figure 4C). The die plate 35 is then lowered onto the belt 11, the upper surface of this latter (which carries the decorative layer) then defining the lower surface of the mould cavity. At this point the described loading means load the material into the mould cavity above the decorative layer (see Figure 3). Immediately afterwards, the upper die 32 is lowered into the die plate cavity and the material is pressed onto the belt 11 together with the decorative layer, with the pressure necessary to obtain a tile 9 with the required degree of compaction (see Figure 4A). The result is a tile 9 (possibly multiple) already provided with the decorative layer, and with its exposed face orientated downwards. This exposed face is shaped by the upper surface of the belt 11. Immediately afterwards, the die plate 35 and the upper die 32 are raised into their initial position to enable the tile which has just been formed to pass below the die plate. Specifically, to achieve correct extraction of the tile 9 from the die plate 35, the die plate is firstly raised while the die 32 remains at rest, to press the tile 9 against the belt 11 (see Figure 48), with the result that the tile is urged and guided out of the die plate 35. The die plate 35 is then further withdrawn from the belt 11, and the belt 11 is driven one step forwards to move the just formed tile 9 out of the machine 30 (see Figure 4C). The machine of the invention is particularly suitable for implementing the described method by which decorated tiles (unfired) are formed. However the machine is also suitable for other methods, for example for forming undecorated tiles. Moreover, instead of the described flexible steel belt 11, the machine can comprise a different flat element of a sufficiently compression-resistant material which rests on the bearing surface of the lower base 31 and is movable along it, to act as the lower surface of the mould cavity (as a substitute for the belt 11). Numerous modifications of a practical and applicational nature can be made to the invention, but without leaving the scope of the inventive idea as claimed below.

Claims: A machine for forming ceramic tiles by pressing in a mould, comprising a fixed lower base (31) acting as a reaction base during pressing and having a horizontal bearing surface, a vertically movable member (33), and an upper die (32) carried by the movable member (33) to define the upper surface of the mould forming cavity, characterised by comprising: a flat lower element (11) of sufficiently compression-resistant material supported by the reaction bearing base (31) and movable on it to act as the lower surface of the mould cavity, a mould die plate (35) lowerly open that can be positioned above and in contact with said flat element to define the side walls of the mould cavity, loading means (41) to load the tile-forming material directly into the mould cavity while the mould die plate is resting on the flat lower element (11), said mould die plate (35) being movable vertically between a lower position in contact with the flat lower element (11) and an upper position in which it is raised from the flat element (11) to enable the formed tiles to pass below it, after each pressing operation, said flat lower element (11) being moved horizontally in combination with the raising of the die plate (35), to remove the formed tile from the area underlying the upper die, further comprising at least one decorating means (20A, 20B, 20C) positioned at the upstream end of the flat lower element (11) to spread a succession of decorative layers on the upper surface thereof. A machine for forming ceramic tiles as claimed in claim 1, characterised in that said flat lower element is defined by a relatively thin endless belt (11) passing about at least two end rollers, to define the belt of a belt conveyor. A machine for forming ceramic tiles as claimed in claim 2, characterised in that the belt (11) is provided with at least one set of regularly distributed holes (12) extending along one of the longitudinal edges of the belt to engage corresponding teeth on the rollers (13). A machine for forming ceramic tiles as daimed in claim 2, characterised in that upper surface of the belt (11) is coated with a non adhesion material A machine for forming ceramic tiles as claimed in claim 1, characterised in that said loading means are a loading carriage (41) provided with a grid for homogeneous material distribution and moving with reciprocating movement along a fixed horizontal travel surface (45). A method for forming decorated tiles, characterised by comprising the following operations: depositing a succession of downwardly orientated decorative layers on portions of a flat lower element (11) positioned upstream to the region where said portions reach a die plate; providing a mold cavity comprising a mould die plate (35) lowerly open resting on said flat lower element (11) of sufficiently compression-resistant material supported by a bearing surface (31) and movable step by step on it; depositing tile-forming material into said mould cavity; subjecting the tile-forming material to a pressing operation; rising the die plate (35) and moving the flat lower element of a further step to remove the tile from the area underlying the die plate (35); driving the flat lower element (11) in such a manner as to bring one portion of said flat lower element (11) corresponding to an advancement step at a time below the lowerly-open mould die plate (35); lowering the lowerly-open mould die plate (35) into contact with the flat lower element to define the mould cavity for the next operation. A method as claimed in claim 6, characterised in that to form on the tile complex decorations, several superposed layers are deposited, one layer is firstly deposited on the flat lower element (11), then on this layer are deposited those decorative layers which are to lie therebelow on the tile, in decreasing order. A method as claimed in claim 6, characterised in that to extract the tile from the die plate, the die plate (35) is firstly raised while the die remains at rest pressing on the tile, which is hence urged and guided out of the die plate (35).

Inventors: MIOTTO SERGIO, MIOTTO, SERGIO
Applicants: MIOTTO SERGIO, SERTAM SOCIETA A RESPONSABILIT, MIOTTO, SERGIO, SERTAM SOCIETA A RESPONSABILITA LIMITATA
Application year: 1999
Main classification: B28B7
IPC codes: B28B3, B28B13, B28B7