EP1366874B1

EP1366874B1 - A device for forming a soft load of ceramic powders

Info

Publication number: EP1366874B1
Application number: EP03425301A
Authority: EP
Inventors: Giuliano Spadoni
Original assignee: Cerservice Srl
Current assignee: Cerservice Srl
Priority date: 2002-05-31
Filing date: 2003-05-12
Publication date: 2008-12-17
Anticipated expiration: 2023-05-12
Also published as: ITMO20020150A0; ES2316712T3; ATE417716T1; DE60325296D1; EP1366874A3; ITMO20020150A1; EP1366874A2

Abstract

The device comprises: a mobile conveyor plane (2) moving in an advancement direction (A); means (3) for depositing a layer of ceramic powders (4) on the mobile conveyor plane (2); a mobile upper surface (5) commandable to move in a vertical direction, arranged superiorly to the mobile conveyor plane (2) and located downstream with respect to advancement direction (A) of the means (3) for depositing a layer of ceramic powders (4); a barrier (8) developing peripherally of the mobile upper surface (5) for delimiting a forming die (9) for a soft load of ceramic powders, which forming die (9) is inferiorly closed by the mobile conveyor plane (2); the barrier (8) comprising a wall (10) which is vertically mobile, for opening and closing a side of the forming die (9) which is located upstream with respect to the advancement direction (A) of the barrier (8). <IMAGE>

Description

In the production of die-forming ceramic tiles from powders, a soft load, i.e. a layer of loose powders for forming a tile after pressing, is formed by pouring a predetermined quantity of the powders directly into a pressing die of a press.
The die is inferiorly delimited by a bottom die and laterally by a closed-periphery matrix. The soft load is poured onto the bottom die in a quantity which exceeds the capacity of the die. The excess is removed by a scraper operating above the die.
The development of tile types having a dishomogeneous composition, obtained by using variously-composed powders of different colours with the aim of achieving special aesthetic effects, has made traditional forming processes unsuitable for soft-powder tile forming. In particular, the scraping operation, which is necessary for the definition of the thickness of the soft load and therefore the final tile thickness, can be incompatible with compositions of powders which reproduce special multi-coloured patterns, which would be altered or destroyed by a surface mechanical action.
Document US-A-5,862,612 discloses a system and a method wherein water content, which is bound by capillarity in fiber cells of carboniferous materials, is reduced by a thermomechanical dewatering process. In the process, the carboniferous materials are conveyed by a dispersion box into a pressure chamber including upper and lower plates. The pressure chamber is surrounded by two lateral walls and two mobile vertical front and rear barriers which, in a lower position, do not come into contact with the bottom wall of the chamber. Steam is applied to the materials introduced into the pressure chamber from both the upper and lower plates to heat the materials up to about 125 DEG C. and to release the water which is bound by capillarity in the fiber cells. Initially, the pressure within the chamber is maintained at no greater than the steam pressure. Subsequently, the pressure chamber is sealed gastight and the carboniferous materials in the pressure chamber are pressed using the upper and lower plates.
Document WO-A-96/15888 discloses a device for forming a soft load of ceramic powders, according to the pre-amble of claim 1.
The main aim of the present invention is to provide a device for forming a soft load of ceramic powders, which device enables a precise definition of the thickness of a soft load.
A further aim of the present invention is to provide a device for forming a soft load in which the surface characteristics of the load are left intact.
These aims and advantages and more besides are all attained by the invention, as it is characterised in the appended claims.
Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, of a preferred but not exclusive embodiment thereof, illustrated purely by way of example in the accompanying figures of the drawings, in which:

figure 1 is a first overall view of the device of the invention;
figure 2 is a detail of a first operative configuration of the device;
figure 3 is a detail of a second operative configuration of the device;
figure 4 is a second overall view of the device of the invention;
figure 5 is a further embodiment of the device of the invention.

With reference to the figures of the drawings, the device of the present invention is indicated in its entirety by 1.
The device 1 comprises: a mobile conveyor plane 2 moving in an advancement direction A; the plane 2 can be a conveyor belt. Means 3 for depositing a layer of ceramic powders 4 on the conveyor plane 2 are associated thereto. The means 3 for depositing can be a hopper with a downwards-facing opening to enable the powders contained therein to fall downwards.
The invention further comprises a mobile upper surface 5, mobile on command in a vertical direction, arranged above the conveyor plane 2 and downstream (with reference to advancement direction A) of means for depositing a layer of ceramic powders 4. The surface 5 is mobile in a vertical direction between an inactive upper position and a lower active position on an underlying layer of ceramic powders 4. The following are associated to the surface 5: at least one pressor 6, operatively connected to the mobile upper surface 5, and one or more gauging elements 7, located above the mobile upper surface 5 and contacting the mobile upper surface 5 to define the upper position of the surface. The pressor 6 can for example be represented by a pneumatic or hydraulic double-acting cylinder, a retracting run of which is superiorly limited by the gauging elements 7. The position of the gauging instruments 7 has a precise function which will be better described herein below.
A barrier 8 is operatively associated to the mobile upper surface 5, which barrier 8 develops peripherally about the mobile upper surface 5 to delimit a forming die 9 for a soft load, which die 9 is inferiorly delimited and closed by the conveyor plane 2. The barrier 8 comprises a vertically-mobile wall 10, for opening and closing the side located upstream of the barrier 8 with respect to the advancement direction A.
The barrier 8 is a rectangular wall, closed on one side by the wall 10. The barrier 8 in its entirety creates a perimeter wall around the mobile upper surface 5. When the wall 10 is lowered, the forming die 9, comprised between the mobile upper surface 5, the mobile conveyor plane 2 and the barrier 8, constitutes a closed chamber.
The operation of the device is as follows.
The ceramic powders inside the means 3 for depositing are dropped onto the conveyor plane 2. The ceramic powders thus deposited form the layer 4, which is less thick than the distance between the mobile conveyor plane 2 and the upper position of the mobile upper surface 5, which is drawn in the direction of the barrier 8.
In at least an initial stage, the wall 10 is raised and the mobile upper surface 5 is in the upper position (figure 2), enabling the ceramic powders to enter the forming die 9. The layer of ceramic powders 4 meets a barrier to advancement thereof, namely the side of the barrier 8 opposite to the wall 10. In this situation the ceramic powders progressively fill the forming die 9. A sensor 11, located upstream of the wall 10 with respect to the advancement direction A, detects the filling of the forming die 9. The sensor 11 can for example measure the thickness of the layer of ceramic powders 4 in an immediately-upstream section of the wall 10. When the thickness reaches a predetermined amount, i.e. when the ceramic powders fill the forming die 9 up to the height of the surface 5, the wall 10 is brought down by means of special means, thus closing the forming die 9 which is now full of ceramic powders (see figure 3). The upper position of the mobile upper surface 5 can be defined by means of the gauging elements 7, in order to obtain a soft load of a thickness which is correctly correlated to the desired thickness of the finished tile after the pressing cycle.
Following the lowering of the wall 10, the mobile conveyor plane 2 is commanded to stop and the depositing of the ceramic powders stopped. At this point the mobile upper surface 5 can be lowered towards the lower position and the soft load can be formed (see figure 3). The lower position of the surface 5 can advantageously be set on the basis of the pressure load that which is to be exerted on the soft load. For example, an advantageous solution might be a load which gives the soft load a level of consistency which permits other manipulations to be made thereon.
Once the forming has been completed, for example at a position indicated by C in figure 1, the system constituted by the barrier 8 and the mobile upper surface 5 is transferred, by special means for such, to the die 14 of a press 15, which position is indicated by D in figure 4 ; at this point the final tile is formed. The formed soft load is deposited in the die 14 and is subject to a final pressing, while the system consisting of the barrier 8 and the mobile upper surface 5 is repositioned on the mobile conveyor plane 2, in position C, to start the forming process of another soft load. In a case where the forming is carried out with a sufficient pressure load to give the soft powders a fairly strong resultant consistency, it will not be necessary to move the barrier 8 and the mobile upper surface 5 in order to transfer the pressed powders to the die; the wall 10, for example, can be used as a pushing device, moving the tile in a parallel direction to the mobile conveyor plane 2.
The invention can also be usefully applied in cases where the real pressing of the tile is performed directly on the mobile conveyor plane 2. Advantageously in this case the mobile upper surface 5 is a bottom surface 12 of a die 13 of a pressing device. In this embodiment the die 9 is inferiorly delimited by the mobile conveyor plane 2, superiorly by the lower surface 12 and laterally by the barrier 8.
The invention proposes considerable advantages.
Firstly, it precisely defines the thickness of the soft load, on which the thickness of the final tile fully depends. It should be noted that any lack of uniformity in the thickness of the soft load will lead to surface imperfections in the final tile, as well as internal tensions which might well result in hairline fractures.
A further important advantage is managing to maintain any multi-coloured patterns resulting from the use of powders with differently-coloured tones in the conveyor-plane depositing stage. The mobile upper surface of the layer of ceramic powders 4 simply contacts with the mobile upper surface 5, with no further movements which might in some way change its appearance.

Claims

A device for forming a soft load of ceramic powders, comprising:
a mobile conveyor plane (2) moving in an advancement direction (A);

means (3) for depositing a layer of ceramic powders (4) on the mobile conveyor plane (2);

a mobile upper surface (5) commandable to move in a vertical direction, arranged superiorly to the mobile conveyor plane (2) and located downstream with respect to advancement direction (A) of the means (3) for depositing a layer of ceramic powders (4); characterised in that it further comprises:
a barrier (8) developing peripherally of the mobile upper surface (5) for delimiting a forming die (9) for a soft load of ceramic powders, which forming die (9) is inferiorly closed by the mobile conveyor plane (2);

the barrier (8) comprising a wall (10) which is vertically mobile, for opening and closing a side of the forming die (9) which is located upstream with respect to the advancement direction (A) of the barrier (8) ; said forming die (9), when the wall (10) is lowered, constituting a closed chamber.
The device of claim 1, characterised in that it comprises at least one sensor (11) arranged upstream with respect to the advancement direction (A) of the wall (10), for detecting that the forming die (9) has been filled with the ceramic powders.
The device of claim 2, characterised in that the mobile upper surface (5) is mobile in a vertical direction between an inactive upper position and an active lower position on an underlying layer of ceramic powders, and comprises:
a pressor element (6) which is operatively connected to the mobile upper surface (5);

one or more gauging elements (7) which are located above the mobile upper surface (5) and which strike against the mobile upper surface (5) in order to define an upper position of the mobile upper surface (5).
The device of claim 2, characterised in that the mobile upper surface (5) is defined by the lower surface (12) of a die (13) of a pressing device.