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Title:
A DEVICE FOR PRESSING CERAMIC POWDERS
Document Type and Number:
WIPO Patent Application WO/2019/092628
Kind Code:
A1
Abstract:
A pressing device for material in powder or granular form, comprising: a press; a conveyor plane (2), movable in advancement along a longitudinal direction (X); at least one hopper (3), arranged above the conveyor plane (2) and provided with a discharge opening (4), positioned at a predetermined height above the conveyor plane (2); a leveller (5), arranged downstream of the discharge opening (4) in the advancement direction of the conveyor plane (2), which is positioned above the conveyor plane (2) at a levelling height (H) which is lower than the height of the discharge opening (4).

Inventors:
STEFANI, Franco (VIALE GIACOBAZZI 25, SASSUOLO, 41049, IT)
GHIRELLI, Ivan (VIA BARCAROLI 3, CASTELLARANO, 42014, IT)
GOZZI, Franco (VIA DON LUIGI STURZO 33, FORMIGINE, 41043, IT)
Application Number:
IB2018/058775
Publication Date:
May 16, 2019
Filing Date:
November 08, 2018
Export Citation:
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Assignee:
SYSTEM S.P.A. (VIA GHIAROLA VECCHIA 73, FIORANO MODENESE, 41042, IT)
International Classes:
B28B13/02; B28B3/12; B28B5/02; B30B15/30
Foreign References:
EP0793565B12003-03-19
DE69738589T22009-04-23
JPH11105020A1999-04-20
GB2389527A2003-12-17
US20040251582A12004-12-16
US1702730A1929-02-19
US6702966B12004-03-09
EP0429330A11991-05-29
Attorney, Agent or Firm:
CASADEI, Giovanni (Bugnion S.P.A, Via Vellani Marchi 20, Modena, 41124, IT)
Download PDF:
Claims:
CLAIMS

1) A device for pressing ceramic powders, comprising:

a press, provided with an upper punch (1 10) and a lower punch (1 1 1 ); a device for spreading a layer of material in powder or granule form, comprising: a conveyor plane (2), movable in advancement along a longitudinal direction (X); at least one hopper (3), arranged above the conveyor plane (2) and provided with a discharge opening (4), positioned at a predetermined height above the conveyor plane (2), in order to deposit a layer (L) of material in powder or granule form on the conveyor plane (2);

a supply plane, which comprises the conveyor plane (2) and is movable along a path that, at least for one section, is arranged between the punches (1 10, 1 1 1 ) of the press;

characterised in that:

the spreading device comprises a leveller (5), arranged downstream of the discharge opening (4) in the advancement direction of the conveyor plane (2), which is positioned above the conveyor plane (2) at a levelling height (H) that is lower than the height of the discharge opening (4);

the leveller (5) is arranged for removing a surface layer of a predetermined thickness from the layer (L).

2) The device according to claim 1 , wherein the leveller (5) is placed at an operating distance (C) from the discharge opening (4), and wherein the operating distance (C) is such that an accumulation (A) of material which forms in contact with the leveller (5) interferes with a discharge flow (B) of material coming from the discharge opening (4).

3) The device according to claim 1 , wherein the leveller (5) comprises a lower edge (51 ), positioned at the levelling height (H) above the conveyor plane (2).

4) The device according to claim 1 , wherein the leveller (5) is movable at least in a direction perpendicular to the conveyor plane (2), for enabling regulation of the levelling height (H).

5) The device according to claim 1 , wherein the leveller (5) is equipped with vibrating means.

6) The device according to claim 1 , wherein the leveller (5) comprises a doctor blade (50) provided with a lower edge (51 ), positioned at the levelling height (H) above the conveyor plane (2).

7) The device according to claim 6, wherein the doctor blade (50) lies on a plane whose inclination is adjustable with respect to a plane that is perpendicular to the conveyor plane (2).

8) The device according to claim 6, wherein: the leveller (5) comprises two or more doctor blades (50), each provided with a lower edge (51 ), positioned at a levelling height (H) above the conveyor plane (2); the doctor blades (50) are arranged in succession downstream of the discharge opening (4); the levelling height (H) of each lower edge (51 ) is lower with respect to the levelling height (H) of the preceding lower edge (51 ).

9) The device according to claim 1 , wherein the leveller (5) comprises a roller (R) rotating in an opposite direction with respect to the advancement direction of the conveyor plane (2).

10) The device according to claim 1 , comprising an abutting member (7), arranged below and in contact with the conveyor plane (2), at the position of the leveller (5).

11) The device according to claim 10, wherein the abutting member (7) comprises an aspirating device, arranged for attracting the conveyor plane (2) into contact with a reference plane (A).

Description:
A device for pressing ceramic powders

DESCRIPTION

The present invention relates to a device for pressing materials in powder or granule form, for example ceramic powders.

The invention relates in particular to systems for pressing ceramic slabs of large dimensions. These systems substantially envisage the pressing of a layer of soft material previously spread on a conveyor plane that, for at least a section of its path, passes through a press.

The spreading of the layer of soft material to be pressed is performed by spreading devices that comprise one or more hoppers, positioned above the conveyor plane, from which the soft material is discharged by force of gravity on the underlying plane, while the latter is in motion. Each hopper is equipped with a closure device that cyclically interrupts and resumes the discharge of the material for forming a succession of layers that, one after the other, are supplied to the press or by the same conveyor plane on which they have been deposited, or by a subsequent conveyor plane on which they are transferred.

In faster systems, the material discharged from the hopper or hoppers present is deposited directly on the underlying conveyor plane without any element that affects or interferes how the soft material is deposited onto the conveyor plane. This free spreading is very fast, and makes it possible to maintain the conveyor plane moving at a relatively high speed. It also makes it possible to use multiple hoppers, arranged consecutively one next to the other, for depositing successive superimposed layers between them.

The free spreading of the material does not however ensure a constant thickness of the deposited layer. In order for the thickness of the deposited layer to be constant, the advancement speed of the plane and the flow rate of the material discharged from the hopper must be adjusted with precision. In any case, even the more precise adjustment does not make it possible to avoid marks and depressions on the surface of the deposited layer.

The aim of the present invention is to offer a device for pressing ceramic powders that makes it possible to overcome the limits and drawbacks of the known devices.

An advantage of the device according to the present invention is that it allows the deposition of a layer of constant and predetermined thickness, irrespective of the advancement speed of the conveyor plane and the flow rate of the material discharged from the hopper or hoppers present.

Another advantage of the device according to the present invention is that it produces a layer whose surface is free of irregularities.

Further features and advantages of the present invention will become more apparent in the following detailed description of an embodiment of the present invention, illustrated by way of non-limiting example in the attached figures, wherein:

- figure 1 shows a schematic view of a pressing device according to the present invention;

- figure 2 shows an enlargement of figure 1 ;

- figure 2a shows an alternative embodiment of the device shown in figure 2;

- figure 3 shows an alternative embodiment of a component of the device visible in figure 2;

- figure 4 shows a diagram of a further embodiment of the device according to the present invention;

- figure 5 shows an enlargement of figure 4;

- figure 6 shows a further embodiment of the spreading device according to the present invention.

The spreading device according to the present invention comprises a conveyor plane (2), movable in advancement along a longitudinal direction (X). In a preferred, non-exclusive embodiment, the conveyor plane (2) comprises a belt which is slidable along a predetermined path that has a main section parallel to the longitudinal direction (X).

The device further comprises at least one hopper (3), arranged above the conveyor plane (2) and provided with a discharge opening (4), positioned at a predetermined height above the conveyor plane (2). The hopper (3) contains the soft material, in powder or granule form, intended to be spread on the conveyor plane, to be supplied to a press. The discharge opening (4) is structured to allow the descent by gravity and the fall of a discharge flow (B) of the material on the conveyor plane (2). A closure device is associated with the hopper (3) to allow the controlled opening and closing of the discharge opening (4). The hopper (3) will not be described in further detail, as it is a known device in the field.

During the operation of the device, through the discharge opening (4) the hopper (3), lets a certain flow of soft material fall toward the underlying conveyor plane (2) in motion. The soft material is arranged in a continuous layer (L) whose initial thickness (S) depends on the advancement speed of the conveyor plane (2) and the flow rate that is discharged from the discharge opening (4). The layer (L) also has a width, i.e. a linear dimension perpendicular to the longitudinal direction (X), which substantially depends on the width of the discharge opening (4). The width of the discharge opening (4) can be adjusted by means of suitable adjustment means, that can be combined with the closure device of the hopper (3) described above.

The spreading device according to the present invention comprises a leveller (5), arranged downstream of the discharge opening (4) in the advancement direction of the conveyor plane (2), which is positioned above the conveyor plane (2) at a levelling height (H) that is lower than the height of the discharge opening (4). The levelling height (H) of the leveller (5) is substantially equal to the thickness that is desired in the layer (L) on the conveyor plane (2), for the subsequent pressing. In other words, the levelling height (H) of the leveller (5) is lower than the initial thickness (S) of the layer (L) which is determined downstream of the discharge opening, due to the combined effect of the advancement speed of the conveyor plane (2) and the flow rate of material coming from the discharge opening (4). The leveller (5) removes a surface thickness from the layer (L), substantially equal to the difference between the initial thickness (S) of the layer (L) and the levelling height (H) of the leveller (5). This makes it possible to obtain, downstream of the leveller (5), a constant thickness of the layer (L), and a flat and uniform surface. The surface material removed from the leveller (5) is retained by the latter while the underlying material continues to advance on the conveyor plane (2). Moreover, the material retained in contact by the leveller (5) forms an accumulation (A) which makes it possible to compensate and regularize any discontinuities or variations in the flow rate of the material discharged from the hopper (3). In the case of an increase in the flow rate of the discharge flow (B), the accumulation (A) tends to increase, while in the case of a loss of flow, the accumulation tends to decrease, while still making it possible to maintain the thickness of the layer downstream of the leveller (5) constant.

In a particularly advantageous embodiment, shown in figure 6, the leveller (5) is positioned at an operating distance (C) from the discharge opening (4). The operating distance (C) is such that the accumulation (A) of material which forms in contact with the leveller (5) interferes with the discharge flow (B) of material coming from the discharge opening (4). In other words, the operating distance (C) is predefined in such a way that the discharge flow (B) is directed, in whole or in part, on the accumulation (A).

The operating distance (C) is substantially adjusted as a function of the flow rate of the discharge flow (B). To this end, the hopper (3) and/or the leveller (5) are provided with the possibility to translate, one with respect to the another, in a direction parallel to the longitudinal direction (X), through means known to those skilled in the art. The operating distance (C), adjusted as described above in the solution of figure 6, produces the following advantageous effects.

The accumulation (A) helps to regulate the flow rate of the discharge flow (B) coming from the discharge opening (4). In substance, the accumulation (A) helps to stabilize the flow rate of the discharge flow (B), making it uniform and constant. Moreover, the interference with the discharge flow (B) contributes to making the accumulation (A) stable and constant. In practice, the mutual interference makes both the discharge flow (B) and the accumulation (A) stable and constant over time. This makes it possible to obtain the spreading of material, i.e. a layer (L), of uniform and constant thickness, even in the presence of constructive defects or imperfections of the discharge opening (4) and/or of the hopper (3). Any unevenness in the grain size of the material, or any lumps of material, are cancelled by the turbulence that is created in the area of interference between the discharge flow (B) and the accumulation (A).

In a possible embodiment, the leveller (5) comprises a lower edge (51 ), positioned at the levelling height (H) above the conveyor plane (2). The lower edge (51 ) is therefore positioned at a height from the conveyor plane (2) which is lower than the initial thickness (S) of the layer (L), so as to be able to remove a surface layer of a determined thickness.

For example, as shown in figures 2, 2a and 6, the leveller (5) comprises a doctor blade (50) provided with a lower edge (51 ), positioned at the levelling height (H) above the conveyor plane (2). The doctor blade (50) substantially defines a barrier that retains a surface layer of the layer (L), forming the accumulation (A) and leaving the part located at a height lower than the levelling height (H) to transit. Downstream of the lower edge (51 ), the layer of soft material has a constant thickness and a flat surface free of irregularities. In this embodiment, the material retained by the doctor blade (50) forms the accumulation (A) in contact with the doctor blade itself, producing the advantages already described previously. In the embodiment of figure 6, the doctor blade (50) is positioned at an operating distance (C) from the discharge opening (4).

Preferably, but not necessarily, the doctor blade (50) lies on a plane whose inclination is adjustable with respect to a plane that is perpendicular to the conveyor plane (2). In other words, the doctor blade (50) can be tilted forward or backwards with respect to the advancement direction of the conveyor plane (2). The possibility to adjust the inclination of the doctor blade (50) makes it possible to adapt its action in relation to materials with different compositions and grain sizes, and/or to variations in the speed of the conveyor plane (2).

On one possible embodiment, the leveller (5) comprises two or more doctor blades (50), each provided with a lower edge (51 ), positioned at a levelling height (H) above the conveyor plane (2); The doctor blades (50) are arranged in succession downstream of the discharge opening (4), so that the levelling height (H) of each lower edge (51 ) is lower than the levelling height (H) of the preceding lower edge (51 ). In other words, the levelling height (H) of the different doctor blades (50) decreases away from the hopper (3). Each doctor blade (50) removes a surface thickness from the layer (L) below, which is retained in contact with the doctor blade itself as already described. The use of two or more doctor blades (50) makes it possible to split into two or more steps the removal of the planned surface thickness of the layer in motion on the conveyor plane (2). This makes is possible to split in as many parts the total accumulation of material in contact with each doctor blade, further increasing the uniformity of the surface and the thickness of the layer (L) in motion on the conveyor plane (2).

In a further possible embodiment, the leveller (5) comprises a roller (R) rotating in an opposite direction with respect to the advancement direction of the conveyor plane (2). The roller (R) is positioned above the transport plane (2), so that a lower portion (R) of the roller itself can come into contact with the layer (L), with an opposite peripheral velocity with respect to the speed of the conveyor plane (2). The roller (R) retains a surface thickness of the layer (L), substantially in the same manner as already described in relation to the preceding embodiments of the spreading device. Rotating, the roller (R) produces a continuous and favourable remixing of the accumulation, which assumes a uniform distribution along the entire width of the layer (L). This makes it possible to further improve the uniformity of the thickness of the layer (L).

In all the embodiments described, the leveller (5) can be moved in a direction perpendicular to the conveyor plane (2), to allow the adjustment of the levelling height (H). Flow rate adjustment means can be used by a person skilled in the art to allow the displacement of the leveller (5) in a direction perpendicular to the conveyor plane (2).

The leveller (5) can be further equipped with vibrating means. The use of vibrating means makes it possible to avoid the material adhering to the leveller (5), remaining fluid and uniformly distributed. In particular, in the embodiment comprising the doctor blade (50), it is possible to arrange the vibrating means which act on the doctor blade (50) itself. This makes it possible to uniformly distribute the accumulation of material along the entire width of the layer (L).

In order to facilitate the action of the leveller (5), the spreading device according to the present invention can be provided with an abutting member (7), arranged below and in contact with the conveyor plane (2), at the position of the leveller (5). The abutting member (7) can for example be in the form of a plate, positioned in contact with the conveyor plane (2) so as to exert pressure on the latter. This pressure tends to stretch the conveyor plane (2), especially in the embodiment comprising a conveyor belt. The abutting member (7) can be positioned below the leveller (5). In one possible embodiment, not shown in that it is within the reach of a person skilled in the art, the abutting member (7) can be provided with an aspirating device, arranged to attract the conveyor plane (2) in contact with a reference plane (A), for example horizontal.

The abutting member (7) allows the leveller (5) to operate on a perfectly flat section of the conveyor plane (2), so that, downstream of the leveller (5), the layer (L) has a uniform thickness. The use of an abutting member (7) of the type described is particularly advantageous in the embodiments of the spreading device in which the conveyor plane (2) also passes under the press. In such cases, the conveyor plane (2) can undergo substantial deformations which can compromise its planarity. The presence of the abutting member (7) makes it possible to restore the planarity of the conveyor plane (2).

The spreading device according to the present invention is particularly suited to be used in a system for pressing ceramic tiles or slabs, also of large format.

This system, known in the field from the publication EP150048, comprises a press to which ceramic material to be pressed is supplied. Through the spreading device according to the present invention, a layer (L) of ceramic material is spread on the conveyor plane (2) which, at least for one section, passes between the two half-moulds of a press.

The pressing of the layer of ceramic material takes place directly on the conveyor plane (2) during a stopping step whose duration depends on the time required by the press for performing its work cycle. In this case, the conveyor plane (2) is preferably in the form of a flexible belt.

With reference to figure 1 , the pressing device according to the present invention comprises a lower punch (100), provided with a pressing surface (100a) facing upwards, and an upper punch (1 10) provided with a pressing surface (1 10a) facing downwards. The two punches are part of a press, not illustrated in detail, by which press they are activated to reciprocally approach and distance so as to carry out the pressing of a layer (L) of ceramic material. By way of example, the upper punch (1 10) might be rigidly constrained to the press, while the lower punch (100) might be movable by action of an oil-dynamic cylinder.

The layer (L) can be conducted and extracted from the punches (100,1 10) by means of a movable supply plane. This supply plane is movable along a path that, at least for a section thereof, is arranged between the two punches (1 10,1 1 1 ). The supply plane comprises the conveyor plane (2). In one possible embodiment, at least a section of the conveyor plane (2) is arranged between the upper punch (1 1 ) and the lower punch (10). The layer (L) to be pressed is deposited by means of the spreading device according to the present invention, upstream of the two punches. The conveyor plane (2) is activated by means of rollers (R) arranged in relation to the path to be followed, in a known way in the art. The rollers have been only schematically represented in the figures. In one alternative embodiment not shown, the layer (L) is deposited on the conveyor plane (2) and from this is transferred to a subsequent conveyor plane, not shown, which passes between the two punches (10,1 1 ).

The pressing device preferably comprises a second movable belt (1 1 1 ) provided with at least one section arranged between the first conveyor plane (2) and the upper punch (1 10). In particular, the second movable belt (1 1 1 ) slides along a ring-shaped path around the upper punch (1 10). Along the section arranged at the punches (100,1 10), and partially upstream and downstream thereof, the conveyor plane (2) and the second belt (1 1 1 ) are both parallel to the longitudinal direction (X). The second belt (1 1 1 ) is also activated by means of rollers (R) arranged in relation to the path to be followed, in a known way in the art. The rollers have been only schematically represented in the figures.

During the supplying of a layer (L) to the press, the movable belts (2,1 1 1 ) move at a controlled speed. The movable belts (2,1 1 1 ) preferably move in a synchronized way and at the same speed. A control device known to a person skilled in the art can be predisposed for the correct relative positioning of the movable belts (2,1 1 1 ). During the supply of the layer (L), the punches (100,1 10) and the movable belts (2,1 1 1 ) are separated by a greater distance to allow the entrance of the layer (L) into the space comprised between the same punches. Once the layer (L) has been correctly positioned between the punches, the pressing step is actuated. At the end of the pressing step the second belt (1 1 1 ) is advanced so as to distance the part which previously entered into contact with the layer (L), so that it can be cleaned. At the same time a consecutive portion of the second belt (1 1 1 ), which has already undergone the cleaning operations, takes the place of the preceding portion.