COMPLETE AFTER PROVISIONAL
LEFT ON 27/9/06

FORM 2

THE PATENTS ACT, 1970 (39 OF 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
[SECTION 10; RULE 13]
"AN IMPROVED METHOD FOR MANUFACTURING ISOSTATIC PUNCH AND THE PUNCH PREPARED THEREFROM"
H & R JOHNSON (INDIA) LTD., AN INDIAN COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, HAVING ITS OFFICE AT "WINDSOR", 7TH FLOOR, C.S.T. ROAD, KALINA, SANTACRUZ (E), MUMBAI - 400098, MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IS TO BE PERFORMED:
27 SEP 2006

FIELD OF INVENTION:
The present invention relates to a method of manufacturing an isostatic punch and the isostatic punch manufactured therefrom.
BACKGROUND OF THE INVENTION:
The tile manufacturing process involves the step of filling powder / dust in the cavity of the tile mould. Normally the powder/dust is randomly spread in the said cavity and it is not filled uniformly in the said cavity. A flat punch is normally used to press the said powder/dust so spread into the tile mould. Since the powder/dust is not filled uniformly, the tile so formed after pressing by the flat punch has large variations in the density of the powder/dust in the obtained tile. In order to control and minimize the density variations, isostatic punches are used in the prior art. An isostatic punch comprises of a base metal plate having a floatable rubber layer.
In the method known in the prior art for making an isostatic punches the cavities with the channels that connect them together, called as the 'cavity network' are machined to the required dimensions on the surface of a metal block called as the 'base metal plate'. Oil port/s are drilled at the bottom of the said base metal plate leading to some of the aforesaid
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cavities so that oil can be filled through the said oil port/s. Externally prepared, rubber grid of nearly equal dimensions as of the cavity network and made of rubber is placed in the cavity network so that the said rubber grid can tight-fit into the cavity network. Thereafter, another rubber sheet is placed upon the aforesaid base metal plate with the rubber grid assembled in the said cavity network, and is pressed with the finishing master to form the finished punch. Oil is then filled through oil ports to create an oil layer below the said rubber grid, to produce an 'isostatic' effect. The isostatic effect is essential to ensure that the said rubber grid floats in the same plane and when the said rubber grid comes in contact with the powder/dust having differing densities at different cross sections when filled into the said cavity of the tile mould, the presence of oil underneath the said rubber grid helps in the easy distribution or compensation of density of powder/dust, over the entire area of the said cavity of the tile mould, uniformly.
However it is found that the use of externally prepared rubber grid causes a mismatch between the said cavity network and the said rubber grid, mainly because of improper finishing in machining the cavity network and the said rubber grid.
Further, the punches prepared by the aforesaid known method can be checked only after the complete finishing of the whole process, as
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quality check of the punches manufactured in this way cannot be done during the continuance of the said process, thereby increasing the chances of rejection of the punch so prepared.
The present invention obviates the aforesaid drawbacks by providing an improved method of manufacturing an isostatic punch and the isostatic punch manufactured therefrom.
SUMMARY OF THE INVENTION:
This invention proposes a method of manufacturing an isostatic punch comprising of preparing an inbuilt rubber grid tight-fitting in the cavity / cavities of a metal base having opening/s to fill in a viscous liquid at the base of the said inbuilt rubber grid and further rubberizing it with layer/s of rubber. Further, a mould spray is applied over the said metal base having the cavity / cavities before the stage of rubberizing the cavity / cavities making the inbuilt rubber grid. Still further, valve/s are provided in the cavities having opening/s at their base, to prevent blocking of the said opening/s. The said valve/s adhere to the said inbuilt rubber grid to maintain bi-directional flow, of the viscous liquid. The thickness of the said valve/s is between 0.5 mm to 1 mm. The ratio of cavity area to non-cavity area of the said metal base is between 35:65 and 40:60. This
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invention further proposes an isostatic punch prepared by the above method and having the abovementioned novel features.
DETAILED DESCRIPTION OF THE INVENTION:
The present invention will now be described with reference to the figures accompanying this complete specification, however the said figures only illustrate the invention and in no way limit the said invention.
In the said figures same numerals are used to denote the same parts.
Fig. 1 shows the top view of the base metal plate with the cavity network and the oil ports present at the base of pre-selected cavities.
Fig. 2 shows the sectional front view of the base metal plate shown in fig. 1 along the line A-A.
Fig. 3 shows the top view of the base metal plate with the cavity network and the valves in the cavities having oil ports.
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Fig. 4 shows the sectional front view of the base metal plate shown in fig. 3 along the line B-B.
Fig. 5 shows an exploded open view of the assembly of the base metal plate with rubber sheet and the master during the pressing operation of the method of preparing an inbuilt rubber grid.
Fig. 6 shows the top perspective view of the base metal plate with the inbuilt rubber grid with excess rubber formed on the surface of the base metal plate immediately after the pressing operation as shown in fig. 5.
Fig. 7 shows the top perspective view of the base metal plate as shown in fig .6 after the excess rubber has been removed.
Fig. 8 shows an exploded open view of the assembly of the base metal plate with inbuilt rubber grid, rubber sheet and the master during the final pressing operation.
Fig. 9 shows the top perspective view of the final isostatic punch, resulting from the pressing operation in fig. 8.
Fig. 10 shows the sectional front view of the final isostatic punch as shown in fig. 9 along the line C-C.
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Referring to the aforesaid figures 1 to 4 a base metal plate (1) has cavities (2)-(2) connected by channels (3)-(3) together forming the cavity network. The said base metal plate (1) is provided with oil ports (4)-(4) connected to the base of pre-selected cavities. Valves (5)-(5) are placed inside the cavities having oil ports (4)-(4). An adhesive is applied on the top surface of valves (5)-(5).
In fig. 5 is shown the 1st stage rubberizing process. In the said figure rubber sheet (6) is placed over the base metal plate (1) and then the pre-rubberising master (7) presses the rubber sheet (6) placed over the base metal plate (1) resulting into the base metal plate (1) with the inbuilt rubber grid (8) as in fig. 7. However, after the pressing operation excess rubber (9) spreads over the base metal plate (1) as shown in fig. 6, which is removed to produce a base metal plate with the inbuilt rubber grid (10), as shown in fig. 7.
In fig. 8 is shown the 2nd or final stage rubberizing process. In the said figure a rubber sheet (11) is placed upon the base metal plate with the inbuilt rubber grid (10) and then the finishing master (12) presses the rubber sheet (11) to produce the final isostatic punch (13) as shown in fig. 9. When oil is filled through oil ports (4)-(4) a layer of oil (14) is formed below the inbuilt rubber grid (8) as shown in fig. 10.
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WORKING OF THE INVENTION
As shown in fig. 1 and 2, the surface of the base metal plate (1) is machined to the desired dimensions to obtain the cavities (2)-(2), the channels (3)-(3) and openings (oil ports) (4)-(4), together forming the cavity network. In a preferable embodiment, the approximate ratio of the cavity area to the non-cavity area is within the range of 35:65 to 40:60, in order to have adequate area to sustain the working pressure and oil leakage during tile pressing. Thereafter the entire surface of the base metal plate (1) including the said cavity network is shot blasted. Then a mould spray which is a semi permanent releasant in a chlorofloro carbon (CFC) free solvent system, such as Monocoat or Lubrolene is applied over the entire face of the base metal plate (1) including the said cavity network, to avoid adhesion of the rubber sheet (6) with the base metal plate (1) during the 1st stage rubberising process.
As shown in fig. 3 and 4 metal discs acting as non-return valves (5)-(5) preferably having a shape and dimension nearly equal to those of cavities (2)-(2) and thickness preferably ranging from 0.5mm to 1mm, are placed at the base of only those cavities which have at their base the oil ports (4)-(4). The said non-return valves (5)-(5) prevent the rubber from entering and thereby blocking the oil ports (4)-(4). Adhesive is applied over the top surface of the valves (5)-(5) so that the inbuilt
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rubber grid (8) sticks to the valves (5)-(5), so as to ensure that the passage of oil is bi-directional.
As shown in fig. 5, 1st stage rubberization of the cavity network is done by pressing the rubber sheet (6) with the help of the pre-rubberizing master (7). The rubber used in rubber sheet (6) should preferably have hardness ranging between 90 and 95 shore to maintain adequate flexibility and achieve the isostatic effect.
As shown in fig. 7, the final inbuilt rubber grid (8) is obtained by machining/scrapping the excess rubber (9), so that the inbuilt rubber grid (8) tight fits in the cavity network, thereby avoiding any mismatch.
Thereafter the base metal plate with the inbuilt rubber grid (10) is shot blasted.
In a preferable embodiment adhesive like Chemlok-218 diluted with Toluene-DlOl in an appropriate proportion of 6:4 is applied over the top surface of the base metal plate with inbuilt rubber grid (10) that helps in binding the top layer rubber sheet (11) with the base metal plate having the inbuilt rubber grid (10), during the 2nd or final stage rubberizing process, as shown in fig. 8.
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In the 2nd or final stage rubberisation process, the rubber sheet (11) of hardness ranging between 85 and 90 shores is placed over the base metal plate with the in built rubber grid (10) and is pressed with the help of finishing master (12).
As shown in fig. 10, oil is filled through the oil ports (4)-(4) at a pressure ranging from 0.5bar to lbar, thus forming an oil layer (14) under the surface of the inbuilt rubber grid (8), thereby enhancing the isostatic effect.
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WE CLAIM:
1) A method of manufacturing an isostatic punch comprising of preparing an
inbuilt rubber grid tight-fitting in cavity / cavities of a metal base having
opening/s to fill in a viscous liquid at the base of the said inbuilt rubber grid
and further rubberizing it with layer/s of rubber.
2) A method claimed in claim 1 wherein, a mould release spray is applied over the said metal base with the cavity / cavities, before the stage rubberizing the said cavity / cavities making the said inbuilt rubber grid.
3) A method claimed in claim 1 wherein, valve/s are provided in the cavities having opening/s used to fill in viscous liquid at their base, to prevent blocking of the said opening/s.
4) A method claimed in claim 3 wherein, the valves are adhered to the said inbuilt rubber grid to maintain bi-directional flow, of the viscous liquid.
5) A method claimed in claim 3 wherein, the thickness of the said valves is between 0.5 mm and 1 mm.
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6) A method claimed in claim 1 wherein, the ratio of cavity area to non-cavity area of the said metal base is between 35:65 and 40:60.
7) A method claimed in claim 1 wherein, the said inbuilt rubber grid has hardness between 90 and 95 shores.
8) A method as claimed in claim 1 wherein, adhesive is applied over the metal base prior to subsequent rubberizing process/es.
9) A method of manufacturing an isostatic punch substantially as herein described.

10) An isostatic punch made by a method claimed in any of the claims 1 to 8.
11) An isostatic punch, comprising of an inbuilt floating rubber grid tight-fitting in one or more cavities of a metal base having opening/s to fill in viscous liquid at the base of the said inbuilt rubber grid and further rubberized with layer/s of rubber.
12) An isostatic punch as claimed in claim 11 wherein, valve/s are
provided in the cavities of the said metal base having opening/s at their
base to fill in a viscous liquid, to prevent blocking of the said opening/s.
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3) An isostatic punch as claimed in claim 12 wherein, the valve/s are dhering to the said inbuilt rubber grid to maintain bi-directional flow, of the viscous liquid.
14) An isostatic punch as claimed in claim 12 wherein, the thickness of
the said valve/s is between 0.5 mm and 1 mm.
15) An isostatic punch as claimed in claim 11 wherein, the ratio of
cavity area to non-cavity area of the said metal base is between 35:65
and 40:60.
16) An isostatic punch as claimed in claim 11 wherein, the inbuilt floating rubber grid has hardness between 90 and 95 shores.
17) An isostatic punch substantially as herein described with reference to the drawings accompanying the complete specification.
Dated this 26th day of Sept' 2006.
Himanshu W. Kane Applicants' Patent Agent
To,
The Controller of Patents, Patent Office,
Mumbai.
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ABSTRACT
This invention proposes an improved method of manufacturing an isostatic punch comprising of preparing an inbuilt rubber grid tight-fitting in the cavity / cavities of a metal base having opening/s to fill in a viscous liquid at the base of the said inbuilt rubber grid and further rubberizing it with layer/s of rubber, and the punch prepared therefrom.