초록 ▼

The invention relates to a high pressure casting method for producing articles of sanitaryware and to a machine implementing the method. The method of type “A” comprises the steps of forming the thickness of the sanitaryware article, emptying the excess slip out of the mould and consol

The invention relates to a high pressure casting method for producing articles of sanitaryware and to a machine implementing the method. The method of type “A” comprises the steps of forming the thickness of the sanitaryware article, emptying the excess slip out of the mould and consolidating the article, all these steps being performed at a constant pressure equal in value to the maximum pressure of the step in which the thickness of the article is formed. In the method of type “B”, the steps of emptying out the excess slip and consolidating the sanitaryware article (14) are performed at a pressure equal to 75% of the maximum pressure of thickness formation. The casting machine comprises a discharge device for draining out the excess slip through a calibrated valve that enables the slip to be discharged without decreasing the pressure in the mould. Compared to prior art casting methods, the moulds and the sanitaryware articles are therefore subjected to less stress and strain and the time required to complete a casting cycle is significantly reduced.

대표청구항 ▼

The invention claimed is: 1. A high pressure casting method in a machine for producing an article of sanitaryware using a ceramic mixture or slip, the machine being equipped with at least one mould comprising at least two parts, the method comprising in sequence the steps of: closing the mould; fil

The invention claimed is: 1. A high pressure casting method in a machine for producing an article of sanitaryware using a ceramic mixture or slip, the machine being equipped with at least one mould comprising at least two parts, the method comprising in sequence the steps of: closing the mould; filling the mould with slip; first thickness formation of the sanitaryware article by increasing the pressure in the mould; second thickness formation of the sanitaryware article by providing pressure in the mould effective to force water in the slip out through the mould; emptying non-solidified excess slip out of the mould; after the emptying step, consolidating the sanitaryware article in the mould by providing pressure in the mould greater than atmospheric pressure for a time sufficient to effectively complete consolidation of the sanitaryware article; decompressing the mould until the pressure in the mould is substantially equal to atmospheric pressure; opening the mould; and demoulding the sanitaryware article thus formed, wherein pressure in the mould is not increased after the second thickness formation step and up through the consolidating step. 2. The method of claim 1, wherein during the step of second thickness formation, a maximum pressure is reached and said maximum pressure is thereafter maintained substantially constant in said mould through the remainder of the second thickness formation step, through the emptying step and through the consolidating step. 3. The method of claim 2, wherein said maximum pressure is between 12 bar and 35 bar. 4. The method of claim 2, wherein said maximum pressure is between 12 bar and 13 bar. 5. The method of claim 1, wherein the pressure in the mould during the emptying step is between 9 bar and 13 bar. 6. The method of claim 1, wherein a maximum pressure in the mould is used during the second thickness formation step, and wherein the emptying step and the consolidating step occur at one or more pressures below the maximum pressure used during the second thickness formation step. 7. The method of claim 6, wherein a maximum pressure in the mould is used during the emptying and consolidating steps, and wherein the maximum pressure in the mould during the emptying and consolidating steps is about 75% of the maximum pressure in the mould during the second thickness formation step. 8. The method of claim 6, wherein the pressure in the mould during the emptying and consolidating steps is between 9 bar and 13 bar. 9. The method of claim 6, wherein the maximum pressure in the mould during the emptying and consolidating steps is between 9 bar and 27 bar. 10. The method of claim 1, wherein, after a maximum pressure in the mould is reached during the second thickness formation step, the pressure in the mould thereafter, through the step of decompressing the mould, is decreased or maintained but not increased. 11. The method of claim 1, wherein, after a maximum pressure in the mould is reached during the second thickness formation step, the pressure in the mould thereafter, through the consolidating step, is decreased or maintained but not increased. 12. The method of claim 1, wherein during the step of second thickness formation a maximum pressure is reached, said maximum pressure being between 12 bar and 35 bar. 13. The method of claim 1, wherein during the step of second thickness formation a maximum pressure is reached, said maximum pressure being between 12 bar and 13 bar. 14. The method of claim 1, wherein pressure in the mould is maintained at a constant level during the emptying and consolidating steps. 15. A high pressure casting machine for producing an article of sanitaryware through steps including first thickness formation of the article, second thickness formation of the article, emptying non-solidified excess slip out of mould, consolidating the article, and opening the mould, the machine comprising: at least one mould comprising at least two parts, wherein the mould comprises a cavity within which the sanitaryware article may be formed, the cavity being connected through a first pipe to a source of compressed air and through a second pipe to a source of slip equipped with a pump, the second pipe being connected to a discharge device and to a pressurizing device, said pressurizing device being distinct from the source of slip, wherein the discharge device comprises a first, full opening valve and a second, calibrated valve provided along distinct respective pipes for passage of the excess slip, a third valve being provided along the second pipe between the mould and the pressurizing device, said third valve being distinct from said first, full opening valve and from said second, calibrated valve, wherein said second, calibrated valve is configured to control drainage of the excess slip so that pressure in the mould is not increased after the second thickness formation step and up through the consolidating step. 16. The casting machine of claim 15, wherein the first, full opening valve and the second, calibrated valve are each connected to a respective tank, both tanks being distinct from the source of slip. 17. The casting machine of claim 15, wherein the second, calibrated valve comprises a pipe with a section of length “L” whose diameter is “D”, “L” and “D” being selected to permit pressure in the mould to be maintained or decreased but not increased after the second thickness formation step and up through the consolidating step. 18. The casting machine of claim 17, wherein the length “L” and the diameter “D” have a ratio L/D of between 10 and 20. 19. The casting machine of claim 17, wherein said section is replaceable. 20. The casting machine of claim 19, wherein said section is made of elastomeric material. 21. The casting machine of claim 15, wherein the second, calibrated valve is also configured so that pressure in the mould is not decreased after the second thickness formation step and up through the consolidating step.