Plastic article or earthenware shaping or treating: apparatus – Press forming apparatus having opposed press members – Male shaping member and female mold
Reexamination Certificate
1999-11-29
2001-10-30
Nguyen, Nam (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Press forming apparatus having opposed press members
Male shaping member and female mold
C425S421000, C425S432000
Reexamination Certificate
active
06309206
ABSTRACT:
BACKGROUND OF THE INVENTION
Ceramic tiles are commonly formed by pressing material in powder form, of between 1% and 10% moisture content, within a mould.
This forming method is commonly known as dry forming.
The soft material is loaded into the mould by known means.
After the mould has been closed by punches operated by pressing members, the powder undergoes initial light pressing, with consequent volume reduction, facilitating powder deaeration.
The initial light pressing, also known as a first pressing, is followed by the deaeration stage, during which pressing is interrupted and the mould is sometimes reopened to allow the air to escape.
This is followed by the main pressing to a pressure of about 400 kg/cm
2
, which ensures perfect powder compaction.
The main pressing generally takes place in several successive steps, with the powder in the mould cavity being subjected to increasing compacting pressure up to the maximum compacting pressure permitted by the press capacity.
The thrust exerted by the upper cross-member of the press is distributed over the total surface of the tiles pressed during each cycle.
The largest currently available presses have a capacity (pressing force) of 4000 tonnes, and during each cycle are able to press a surface area of not exceeding 10,000 cm
2
. Thus, for example, they can operate a die having three impressions of 54 cm×54 cm.
Tiles of large and ever larger dimensions, having sides exceeding one meter, have not been able to be formed so far by known dry processes because the capacity (pressing force) of the press required to compact the pressure would involves a structure of such dimensions as to be difficult to construct.
Large-dimension tiles having sides of the order of one meter or more are currently manufactured either by extrusion processes or by wet forming processes within hygroscopic moulds similar to those used for sanitary appliances.
Apart from the low cost effectiveness of such processes, the subsequent drying and high-temperature firing of the material creates important problems due to the excessive or poorly distributed moisture contained in the material.
SUMMARY OF THE INVENTION
The object of the present invention is to achieve dry-forming of ceramic tiles by powder compaction which are particularly but not exclusively of large dimensions, having for example a side dimension of the order of 100 cm, using currently available pressing forces, ie presses of currently available capacity.
In particular the method of the present invention enables very high compacting pressures to be obtained with pressing forces which are not in themselves high.
The method of the present invention comprises dividing the tile surface into two or more portions, preferably of equal surface area, and pressing these portions not simultaneously, but one at a time in succession.
It is immediately apparent that by dividing the surface to be pressed into two portions having the same area, the press capacity is halved.
To implement the method the mould punch must itself be divided into adjacent portions, preferably having the same surface area.
For example such punch portions can conveniently be concentric.
The pressing cycle according to the present invention comprises the following operations.
The powder is loaded into the mould in a conventional manner, i.e., having expelled the tile the movable carriage grid carries the powder into the mould die.
A cross-member carrying an upper punch divided into portions is then lowered to close the mould. An initial light compaction, or first pressing, follows.
The first pressing can be done by moving the various (for example two) portions of the punch as if the punch were in one piece. This is because the compacting pressure of the first pressing multiplied by the total tile area certainly does not exceed the pressing force which can be exerted by the press.
Considering a punch divided into two portions of equal surface area, as the maximum pressing force exertable by the press is achieved by pressing simultaneously with the two punch portions, part of the pressing force is applied in succession, for example firstly to a first punch portion, and then to a second punch portion, applying increments of force until the entire press, pressing force is applied firstly to one portion and then to the other.
The entire press force can also be applied from the beginning, firstly to one punch portion and then to the other.
The divided punch can be the upper punch or the lower punch, or a combination of both.
To obtain a degree of powder compaction which is as homogeneous as possible, according to the present invention, at least one of the two portions into which the punch is divided operates isostatically, as will be apparent hereinafter.
With presses having a capacity of up to 4000 tons compacting pressures of up to 500 bar can be achieved on the powder in the mould cavity, even for large-dimension tiles.
REFERENCES:
patent: 2618833 (1952-11-01), Adams
patent: 3671618 (1972-06-01), Huber et al.
patent: 3717693 (1973-02-01), Kohl et al.
patent: 3767351 (1973-10-01), Blaser
patent: 3795464 (1974-03-01), Backman et al.
patent: 3813527 (1974-05-01), Langston
patent: 3816052 (1974-06-01), Schoppee et al.
patent: 4418671 (1983-12-01), Kelso et al.
patent: 4561251 (1985-12-01), Moret et al.
patent: 4649818 (1987-03-01), Switall et al.
patent: 4666389 (1987-05-01), Relis et al.
patent: 4725220 (1988-02-01), Percinel et al.
patent: 4726221 (1988-02-01), Tavlarides et al.
patent: 5198240 (1993-03-01), Baxi
patent: 5242641 (1993-09-01), Horner et al.
patent: 5330346 (1994-07-01), Scardovi
patent: 5401153 (1995-03-01), Katagiri et al.
patent: 5472334 (1995-12-01), Takahashi
patent: 5478225 (1995-12-01), Takeuchi et al.
patent: 5494426 (1996-02-01), Ibar
patent: 5498147 (1996-03-01), Katagiri et al.
patent: 5551856 (1996-09-01), Katagiri
patent: 5599566 (1997-02-01), Casolari
patent: 5786003 (1998-07-01), Debbia
patent: 4320203A (1994-12-01), None
patent: 0556163 (1993-08-01), None
patent: 2662381A (1991-11-01), None
patent: 1257658B (1996-02-01), None
Luk Emmanuel S.
Nguyen Nam
Sacmi-Cooperativa Meccanici Imola-Soc Coop. A.R.L.
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