FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
1 TITLE OF THE INVENTION :
A MOULD SYSTEM FOR CIRCULAR DISC-SHAPED CASTINGS AND A METHOD OF CASTING USING SUCH MOULDS.

2 APPLICANT (S)
Name : Nationality :

STEEL AUTHORITY OF INDIA LIMITED.
A Govt. of India Enterprise;
Bhilai Steel Plant, Bhilai, State of Chattisgarh,India,


3 PREAMBLE TO THE DESCRIPTION
COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.


FIELD OF THE INVENTION
The present invention relates to a method of increasing the yield in non-ferrous castings process. More particularly, the invention is directed to improving the yield of Aluminium bronze castings by modifying the moulding method wherein the riser and the casting are accommodated in the Drag (bottom box) portion of the mould and the Cope (Top box) of the mould is formed just as a plain surface mould. The present method of moulding and casting therefore facilitate producing circular disc shaped castings particularly of Aluminium Bronzes on one hand favour higher yield than convention and on the other hand eliminate excess risering requirement while preventing surface oxidation or dross formation. The method of mould manufacturing for non-ferrous casting and in particular for the aluminium bronze casting would favor generating up to three circular castings in single set of mould box and thereby improving the yield in casting by over 27% over the convention. Thus the present invention is directed to a economic and technologically sound method of generating non-ferrous aluminium bronze castings free of any shrinkage defects, or dross formation and consequent oxide entrapment, with simple moulding technique involving less manpower with increase in productivity/yield and thus favoring wide industrial application in non-ferrous foundry/casting plants.
BACKGROUND ART
It is well known in the field of non-ferrous casting that the pattern and moulding design or the overall methoding process for such castings need extreme care for adequate metal flow by way of risering, prevention of dross formation or oxide entrapments. The complexity and cost involvement vis-a-vis the end quality and yield of the non-ferrous casting process is of critical concern for a methoding engineer engaged in the task. More particularly, for non-ferrous alloy casting like those of Aluminium Bronze alloy castings requires extensive risering in non-ferrous foundry to take care of the shrinkages in conventional methodology of casting circular disk shaped castings. Yield is very moderate in the range of 55%. Moreover, as in the circular section castings the metal is exposed to a wider area chances of oxidation are more. This in turn favors dross formation and subsequently enhancing possibilities of undesired oxide entrapment.
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There has therefore, been a continuing need to develop a method for moulding and casting of non-ferrous metals/alloys, in particular for aluminium bronze alloys in order to achieve higher yield of metal casting with superior casting quality by way of avoiding the dross formation or oxide entrapment or reducing the requirement of excess risering to compensate shrinkage allowance for circular disk shaped castings. The method of the invention shall advantageously generate multiple castings into the same set of boxes in a simple process and would thus favor improving labour productivity and reducing manufacturing cost.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to a method for developing mold system for castings, particularly of circular disk shapes casting using non-ferrous material such as Aluminium Bronze, with improved quality, reduced manpower and higher productivity and lower cost of production.
A further object of the present invention is directed to a method of non-ferrous casting of circular disk shape for aluminium bronze metal alloy whereby the disk pattern with the riser is accommodated in the bottom mould (drag) and the top mould (Cope) is just a flat surface mould thus reducing the complexity and man-hours involved in mould making.
A further object of the present invention is directed to a method of non-ferrous casting of circular disk shaped casting whereby the excess requirement of riser to compensate for the shrinkage loss is avoided, exposure of metal to a wider area is eliminated and thus chances of oxidation is reduced by controlling dross formation and also oxide entrapment.
A further object of the present invention is directed to a method of non-ferrous casting of circular disk shape for aluminium bronze whereby a plurality of circular disk shapes and up to three disks can be cast simultaneously in single set of mould boxes, by adopting casting in vertical position into the mould cavity.
A further object of the present invention is directed to a method of non-ferrous casting of circular disk shape for aluminium bronze metal alloy whereby the method of moulding and casting directs to the saving of metal by use of feeding ability of the casting itself because of the shape of mould cavity created in the drag.
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A further object of the present invention is directed to a method of non-ferrous casting of circular disk shape for aluminium bronze metal alloy whereby cast yield is substantially improved by over 27% and thus the productivity improvement is achieved with less labour avoiding requirement of cutting of the bulky risers and also less manpower for mould making.
A further object of the present invention is directed to developing a method of non-ferrous casting of circular disk shape whereby the castings are of superior quality without any defects due to shrinkage or entrapment of oxides avoiding dross formation, at less manpower and cost.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to a mould system for circular disc shaped castings comprising:
a drag portion of the mould comprising a circular disc casting portion formed thereon with a connecting riser formed there through a cut out on its circumferential portion;
a cope portion of the mould comprising a plain surface,
whereby the cope and drag portion together facilitate the self feeding of the casting into the circular disc shaped casting portion of the mould when the same is held standing vertical with the riser open end facing the top.
Another aspect of the present invention directed to said mould system for circular disc shaped castings wherein the riser comprise a gradually tapered entry into the circumferential cut-out of the circular disc shaped portion of the mould.
A still further aspect of the present invention directed to a mould system for circular disc shaped castings comprising a plurality of said circular disc shaped casting portions operatively linked through a riser.
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A stiil further aspect of the mould system for circular disc shaped castings according to the present invention wherein said intermediate risers therebetween two adjacent disc shaped circular casting portions are of lesser height and volume for housing the casting than the riser on top having an open end.
According to yet another aspect of the present invention directed to said mould system for circular disc shaped castings comprising accommodating up to three said circular shaped castings at a time.
Another important aspect of the present invention is directed to a method of casting circular castings using the mould system comprising:
preparing the sand moid by positioning the mold system vertical with the said open riser end facing the top to favour vertical position casting;
allowing the casting metal to enter the mould through gate and allow proper and effective filling of the mould without any turbulence,
effective feeding of castings through self feed in vertical position, without any turbulence.
said vertical position casting adapted to reduce the area of contact of open surface of molten metal only at the riser top to atmosphere reducing the chances of dross formation and oxide entrapment in casting.
According to a still further aspect of the present invention directed to a method wherein said castings comprise circular disk shape and a maximum of three such circular disk shaped of non-ferrous castings are produced at a time.
A still further aspect of said method according to the present invention, wherein the process comprising the steps of
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a. making mold in Drag using composite pattern comprising the shapes of
circular shaped casting as well as the riser by conventional sad molding and
ramming;
b. tilting up the bottom mold box and placing the top mold box over it in a
matched manner and filling with molding sand and compacting;
c. separating the mould boxes and taking out pattern from the bottom box
carefully without any damage to the mold cavity created on bottom box;
d. finishing the mold cavity, painting and drying;
e. assembling the top and the bottom mold boxes and clamped and placed in
vertical position with the riser at top;
f. casting of non-ferrous molten metal/alloy in the mold cavity in vertical
position;
g. finishing of rough casting on solidification and cooling after taking out from
the mould;
According to yet another aspect of the present invention directed to said method of casting, wherein the process ensure the end casting product is free of defects due to shrinkage or oxide entrapments.
According to a further aspect said method of the present invention, wherein said casting material include non-ferrous metal alloys such as Aluminium-Bronze.
The present invention and its objects and advantages are described in greater details with reference to the following non-limiting exemplary figures.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1: is the illustration of the non-ferrous circular shaped casting generated by the conventional moulding process where extensive risering is used to take care of shrinkage losses and thus resulting in poor yield.
Figure 2: is the schematic illustration of the method for circular shaped Al-Bronze casting wherein the riser placement according to the present invention is changed in vertical orientation, so that casting and riser are inside the drag and cope is flat moulded, in order to reduce risering requirement and improve quality and yield.
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Figure 3a & 3b: is the schematic illustration of the Drag portion of mould embodying the casting and the riser and the mould in vertical casting position to favor improved metal feeding and saving of metal.
Figure 4: is the schematic illustration of moulding arrangement vis-a-vis the as cast circular non-ferrous casting generating multiple casting in single set of mould box, following the method of the present invention.
Figure 5: is the illustration of the flow chart showing the sequential process steps for the moulding and casting process for the non-ferrous Al-Bronze circular shaped castings according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
The present invention relates to a method of developing mould system and a method of casting of Al-Bronze non-ferrous circular shaped casting directed to eliminating problems associated with excess of risering for compensating shrinkage of metal, wider contact area and thereby increased tendency of dross formation and surface oxidation and thereby risks of oxide entrapment. The invention is further directed to improve utilization of resources, higher productivity and yield, reduced labour involvement in moulding and casting/finishing and superior casting quality and hence resultant lower cost of production.
Reference is first invited to the accompanying Figure 1, that illustrate the conventional method of casting circular disk shaped castings from Aluminium Bronze that requires extensive risering in non-ferrous foundry to take care of the shrinkages in such conventional methodology.. It is deariy apparent that both the part to be cast and the riser are circular in cross-section having substantial area. As a consequence of this the metal is exposed to a wider area and chances of oxidation is more. Yield of metal in such conventional method is in the moderate range of about 55 %. The moulding method clearly indicates a distribution of casting in the Drag and the riser in the Cope box. Under this arrangement, the molten metal cast is more prone to dross formation and subsequent chances of oxide entrapment.
Reference is now invited to the accompanying Figure 2 that illustrates the riser replacement and rearrangement of the casting and the riser in vertical orientation such
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that the circular disk shaped casting and also the riser are accommodated in the bottom box (Drag) of the mould and the top box (Cope) is just a plain surface mould. This riser replacement configuration in mold design not only save risering requirement and thus leading to higher yield of metal but also reduce chances and risks of oxidation and dross formation or any defect due to shrinkage on solidification of molten metal. Advantageously, the mold design and casting in vertical position according to the method of the invention is, in particular, providing the metal feeding ability by the casting itself because of the shape and thus resulting in a saving in metal and consistently good quality of casting free of any oxide entrapment is also ensured.
Reference is next invited to the accompanying Figure 3a that illustrates the Drag portion of mould showing the formation of mould cavity using a predetermined commensurate shape of pattern and by simple sand moulding, said cavity comprising accommodating room for non-ferrous circular casting and also the risering in the bottom box (Drag) itself. The riser is having a gradual tapered link from open end to mold cavity. The accompanying Figure 3b also shows the complete assembly of the top and bottom mould boxes or the Cope and the Drag, wherein the Cope portion is a plain flat surface mould. The combination of the top and bottom mould clamped together is placed in vertical position with riser on the top so as to favor casting of molten nonferrous alloy such as Al-Bronze, in the vertical position of the mold. This unique configuration according to the embodiment of the present invention is capable of ensuring saving of metal by use of 'feeding ability' of the casting itself, because of the shape. The same principle is further illustrated in the accompanying Figure 4, wherein an alternative embodiment of the present method of casting of non-ferrous circular shaped castings have been demonstrated, that is adapted to generate two such circular castings in a row which can be cast in a single set of mould box and this configuration may work up to three castings in numbers. Such advantageous aspect of the method of casting according to the present invention enable achieving a simple and cost-effective way of producing non-ferrous castings such as the Al-Bronze castings, with increase in yield by over 27%, from conventional level of approx. 55%, and improved productivity accompanied with less manpower involvement in cutting of heavier riser and making of mould, ensuring consistently good quality free of shrinkage related defects or oxide entrapment, at reasonably lower cost of production.
The reference is now invited to the accompanying Figure 5 that illustrates the total flow process chart comprising various sequential steps for mould making and casting of non-ferrous metal/alloy such as Al-Bronze of circular shaped castings according to the present
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invention, as described in the preceding paragraphs. It is clearly apparent from said process flow diagram that first a preformed pattern and riser are placed in the bottom Mould box (Drag), the box filled with molding sand and rammed to form the compacted mould cavity according to the outer profile of the pattern. The bottom mold box is then tilted/overturned and then the upper mold box is placed over the bottom and filled with molding sand and packed. Thereafter the two boxes are safely separated and the pattern carefully shaken out to release without damaging the mold cavity. The mold is then finished and painted and dried up and two boxes are assembled to form desired mold cavity ready for casting molten metal. However, the finished and clamped complete set of mold boxes (Cope & Drag) is placed in vertical position and casting carried out in vertical position so as to ensure 'feeding ability' of the casting itself, because of the shape and thus ensuring saving in metal and resultant improvements in yield of metal, better utilization of resources and improved productivity with less manpower and lower cost of production.
It is thus possible by way of the present invention to develop a method for casting of non-ferrous metal/alloys such as the aluminium bronze to generate circular disk shaped castings wherein the placement of riser in a selective manner so that both the circular casting and the riser is accommodated in the bottom mold and the top mold is a plain surface sand mold, co-operatively creating a mold cavity with riser arrangement of lighter section and favoring casting in vertical position. The casting so achieved is free of any defects due to shrinkage or oxide entrapments and having lesser tendencies to dross formation during pouring having effectively less contact area for atmospheric surface oxidation. The mold making is simplified requiring less manhours for production and finishing operations. Moreover, the favored gravity feeding of molten metal in vertical position of mold, also favor generating up to three circular shaped castings from a single set of assembled mold box, ensuring soundness of casting and consistent good quality at substantially higher yield and reasonably lower cost and thus having potential for wide industrial application in non-ferrous foundry/casting operations.
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We Claim:
1. A mould system for circular disc shaped castings comprising:
a drag portion of the mould comprising a circular disc casting portion formed thereon with a connecting riser formed there through a cut out on its circumferential portion;
a cope portion of the mould comprising a plain surface,
whereby the cope and drag portion together facilitate the self feeding of the casting into the circular disc shaped casting portion of the mould when the same is held standing vertical with the riser open end facing the top.
2. A mould system for circular disc shaped castings as claimed in claim 1 wherein the riser comprise a gradually tapered entry into the circumferential cut-out of the circular disc shaped portion of the mould.
3. A mould system for circular disc shaped castings as claimed in anyone of claims 1 or 2 comprising a plurality of said circular disc shaped casting portions operatively linked through a riser.
4. A mould system for circular disc shaped castings as claimed in claim 3 wherein said intermediate risers therebetween two adjacent disc shaped circular casting portions are of lesser height and volume for housing the casting than the riser on top having an open end.
5. A mould system for circular disc shaped castings as claimed in claim 4 comprising accommodating upto three said circular shaped castings at a time.
6. A method of casting circular castings using the mould system as claimed in anyone of claims 1 to 5 comprising:
preparing the sand mold by positioning the mold system vertical with the said open riser end facing the top to favour vertical position casting;
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allowing the casting metal to enter the mould through gate without any turbulence and allow proper and effective filling of the mould through self feed in vertical position;
said vertical position casting adapted to reduce the area of contact of open surface of molten metal only at the riser top to atmosphere reducing the chances of dross formation and oxide entrapment in casting.
7. A method as claimed in claim 6 wherein said castings comprise circular disc shaped and a maximum of three such circular disc shaped of non-ferrous castings are produced at a time.
8. A method as claimed in anyone of claims 6 or claim 7, wherein the process comprising the steps of
a. making mold in Drag using composite pattern comprising the shapes of
circular shaped casting as well as the riser by conventional sad molding and
ramming;
b. tilting up the bottom mold box and placing the top mold box over it in a
matched manner and filling with molding sand and compacting;
c. separating the mould boxes and taking out pattern from the bottom box
carefully without any damage to the mold cavity created on bottom box;
d. finishing the mold cavity, painting and drying;
e. assembling the top and the bottom mold boxes and clamped and placed in
vertical position with the riser at top;
f. casting of non-ferrous molten metal/alloy in the mold cavity in vertical
position;
g. finishing of rough casting on solidification and cooling after taking out from
the mould;
9. A method as claimed in any one of claims 6 to 8, wherein the process ensure the end casting product is free of defects due to shrinkage or oxide entrapments.
10. A method as claimed in any one of claims 6 to 9, wherein said casting material include non-ferrous metal alloys such as Aluminium-Bronze.
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11. A method for improving yield in non-ferrous circular disc shaped castings adapted to produce multiple castings into the same set of boxes with improved casting quality and reduced riser volume adapted to ensure high productivity and improved quality at lower cost as here in described with reference to the accompanying drawings.

Dated this 30th day of August, 2008. Anjan Sen
of Anjan Sen & Associates (Applicants Agent)
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