NZ517037A - A casting process and cast product - Google Patents

Abstract

Here is disclosed a process for forming a cast stator or rotor component, which includes a number of radially extending vanes or blades, comprising supporting preformed inserts, each of which in the cast stator or rotor component will form a leading portion of a vane or blade of the rotor or stator component, in association with a mould part or parts which define(s) passages between the vanes or blades during the casting process, surrounding the mould part(s) with one or more other mould parts which define the balance of the stator or rotor component shape, filling the mould with molten material, and allowing the molten material to cool and removing the mould parts to leave the cast stator or rotor component with each preformed insert cast in situ as an integral leading portion of a vane or blade with a trailing portion of the vane or blade being formed of the material from which the balance of the stator or rotor component is cast, the preformed inserts being formed of a stronger or more wear-resistant material than the material from which the balance of the product is cast.

Description

517037 NEW ZEALAND PATENTS ACT 1953 No: 517037 Date: 5 February 2002 COMPLETE SPECIFICATION A CASTING PROCESS AND CAST PRODUCT We, C W F HAMILTON & CO LTD, a New Zealand company of Lunns Road, Middleton, Christchurch 4, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: Jt YljA. PROPERTY -H,- M y^ 7 red MJ3 • ■/ r D INTELLECTUAL PROPERTY OFFICE OF N.Z.

U 7 FEB 2003 received 1 22603-1 FIELD OF INVENTION The invention comprises a casting process for forming a cast stator or rotor from one material incorporating pre-formed inserts of another material, and a cast stator or rotor incorporating inserts within the cast stator or rotor of a different material which are integral in the finished product.

BACKGROUND Casting processes such as sand casting are well known and commonly used in industry for forming a wide range of products and product components for numerous applications. Without intending to be limiting, many of the components of water jet propulsions systems for watercraft are produced by casting, typically from aluminium or an aluminium alloy.

SUMMARY OF INVENTION In a first aspect the invention comprises a process for forming a cast stator or rotor component, which includes a number of radially extending vanes or blades, comprising supporting preformed inserts, each of which in the cast stator or rotor component will form a leading portion of a vane or blade of the rotor or stator component, in association with a mould part or parts which defme(s) passages between the vanes or blades during the casting process, surrounding the mould part(s) with one or more other mould parts which define the balance of the stator or rotor component shape, filling the mould with molten material, and allowing the molten material to cool and removing the mould parts to leave the cast stator or rotor component with each preformed insert cast in situ as an integral leading portion of a vane or blade with a trailing portion of the vane or blade being formed of the material from which the balance of the stator or rotor component is cast, said preformed inserts being formed of a stronger or more wear-resistant material than the material from which the balance of the product is cast. 2 INTELLECTUAL property office of n.z. 1 0 AUG 2004 received 22603-1 In broad terms in another aspect the invention comprises a stator or rotor including a number of radially extending vanes or blades, the leading portions of which are formed by preformed inserts about which a trailing portion of each of the vanes or blades and the balance of stator or rotor have been cast, the preformed inserts being formed of a stronger or more wear-resistant material than the material from which the trailing portions of vanes or blades and balance of the stator or rotor has been cast.

Preferably, the preformed inserts are formed from stainless steel while the balance of the stator or rotor is cast from aluminum or an aluminium alloy (or any other material such as magnesium or a magnesium alloy for example).

BRIEF DESCRIPTION OF THE DRAWINGS The process and a product of the invention are described with reference to the accompanying drawings, by way of example and without intending to be limiting, in which: Fig 1 is a side view of a stator component, Fig 2 is a view from one end of a conventionally cast stator component, in the direction of arrow A in Fig 1, Fig 3 is a view similar to Fig 2 but of a stator component of the invention, Figs 4a to d are views from different angles of one of the preferred form stainless steel inserts, which are preformed and incorporated into the stator of Fig 3 during casting, Figs 5 to 10 show mould parts and illustrate the casting process of the invention, Fig 11 is a view of a cast stator component with a single mould core insert part unremoved, Fig 12 is a view of the cast stator component similar to Fig 11 but with all of the mould core insert parts unremoved, and INTELLECTUAL PROPERTY OFFICE OF N.Z.

AUG 2004 22403-1 received Figures 13 to 16 show forming of a core insert mould part carrying a preformed stainless steel insert.

DETAILED DESCRIPTION OF PREFERRED FORM The casting process of the invention is described in detail with reference to the casting of a stator component as shown in the drawings, by way of example only and the process of the invention may be used to form a wide range of cast stator or rotor components.

Referring to Figures 1 to 3, and also Figures 11 and 12, the stator component comprises a generally tapered cylindrical body having external wall 1 and a center part 2 which are joined by a series of radial vanes 3. Passages 5 pass through the stator between the angled vanes 3. Conventionally the stator component is entirely formed by casting from a material such as aluminium or aluminium alloy for example.

Figure 3 shows a product of the invention, which is a stator similar to that of Figure 2 except that the leading edge of each vane 3 is formed from stainless steel. Each stator vane 4 is formed partly by a stainless steel insert 6, which is preformed and incorporated in the product during the casting process so as to be an integral part of the final product.

A single preformed insert 6 is shown in more detail in Figs 4a to 4d. The insert forms the leading edge of a vane 4. The forward edge 6a of the insert 6 forms the tip of the leading edge of the stator vane, and a rear edge 6b abuts so as to be flush and integral with the balance of the vane which is formed from aluminium alloy during the casting process. In the preferred form the particular preformed leading edge vane insert shown has a base 7 incorporating protrusion 7a, which is surrounded by cast material during the casting process so that the top surface of the base 7 is flush with the interior surface of the stator. At its other end the preformed insert has grooves 8 to assist in fixing the other end of the preformed component in the cast material. The preformed insert is shown by way of example only and could be of any desired shape depending on the shape of the stator or rotor. Where a preformed insert has height as shown, at its either end it may comprise a base 7 and optionally a protrusion 7a, ribs or depressions 8, or any other irregularity or means for fixing the preformed component so that in the finished cast product the preformed insert is an integral part of the product. 4 INTiLLfCTUAL PROPERTY ^ , OFFICE OF N.Z. 2*03'1 ;10 AUG 2004 ;In relation to water jet propulsion systems it is well known that the leading edges of the vanes of the tail pipe stator are prone to damage from cavitation, abrasion, and galvanic corrosion, and that it is necessary to inspect, repair, and if necessary replace the tail pipe stators of water jet propulsion systems periodically. A tail pipe stator of the invention formed as described with stainless steel inserts will have substantially greater life due to the increased wear resistance and resistance to galvanic corrosion of the stainless steel leading edges of the stator vanes. Similar advantages are likely to be obtained with product or components for other applications which are cast by the process of the invention, with an insert or inserts formed of a different material having different wear characteristics or other desirable properties for the particular application, relative to the material from which the balance of the component is cast. ;The casting process of the invention as applied to forming the stator of Fig 3 is illustrated by Figs 5 to 12. As is conventional, the stator component is cast using a number of mould components which define the external and internal shapes including internal passages of the stator component, which are formed of sand in a sand casting process. Figure 5 shows a base mould part 10. Portions 10b and 10c of the mould base part 10 define the shape of the center 2 of the stator. A number of core insert mould parts 11, one of which is shown in Fig 7, and which are formed from sand if the product is to be formed using sand casting, are assembled together on the base component as shown in Figures 6, 8 and 9. Each of the core insert part 11 defines the passage space between two vanes during the casting process. A number of the core insert parts 11 are mounted on the mould base 10 in assembly of the mould - Figure 6 shows a first core insert part 11 in position on the mould base 10, Figure 8 shows three core insert parts 11 in position, and Figure 9 shows all of the core inserts in position on the mould base part. The way in which the core insert parts define the passages between the vanes in the finished stator product is illustrated by Figure 11 which shows a cast stator with a single core insert part unremoved (before breaking out of the final core insert part), and Figure 12 which shows a cast stator with all of the core insert parts in situ, before breaking out of the core inserts. ;When the mould is assembled before filling the mould with molten material to carry out the casting process, one of the preformed stainless steel inserts 6 is carried by each core ;5 I INTELLECTUAL PROPERT*431 I OFFICE OF N.Z. I I 10 AUG ?nn& I insert part 11, as shown, so that each core insert part 11 holds a preformed stainless steel insert 6 in the correct position during casting, when the cavities between the mould base mould top 13 - see Figure 10, and core insert part 11 of the mould are filled with molten material. It is apparent from Figures 8 and 9 how the core insert parts 11 when assembled together each carry a preformed insert 6 in the correct position around the mould from the center of the mould, so that in the finished cast product the preformed inserts will form the leading edges of the radiating stator vanes. Referring to Figures 8 and 9, the shaped spaces 14 between each two adjacent mould insert parts 11 form the stator vanes, with the preformed stainless steel inserts as the leading edges thereof.

In the preferred form the mould base 10 includes recesses 10a into which protrusions 1 lb on the bottom end 1 la of the core inserts 11 fit to assist in retaining the core insert parts 11 in position on the mould base 10. After all of the core inserts have been put in position as shown in Fig 9, the top part 13 of the mould is placed over the mould base and core inserts, as shown in Fig 10. Beneath the mould top part 13 and exterior surfaces of the assembled core insert part 11 is defined the cavity which forms the outer tapered circular wall section 1 of the stator.

The mould is then filled with molten material, through port 15 for example, the molten material is allowed to cool, and the mould is disassembled, in a sand casting process by breaking the mould components away from around the cooled stator product formed by the casting process. The core inserts parts 11 are removed, and in the finished cast product the preformed inserts 6 will form the leading edges of the stator vanes 3 as shown in Fig 3.

Figs 13 to 16 show how, in the preferred form, the sand core insert mould parts 11 are formed around the preformed stainless steel inserts 6 so as to carry the inserts during the moulding process, until the sand core inserts 11 are broken away from around the cooled stator product formed by the casting process. Each sand core insert mould part 11 is formed in a mould 16 having an internal cavity 17, which generally comprises a base surface 16 and side walls 17 and 19. In the preferred form, in forming the core insert 11 a preformed stainless steel insert 6 is first inserted into the mould 16, as shown in Fig 14.The end of the insert 6 opposite the base 7 engages into a complementary shaped slot 21 in the base surface 16 of the insert mould to hold the preformed insert 6 , INTELLECTUAL PROPERTY 1 6 OFFICE OF N.Z. f603-' 1 0 AUG 2004 I in position while the mould 16 is filled with sand and binder to form the core insert, and the base 7 of the insert 6 similarly engages into the underside of the top 21 of the mould. The top 21 which has a suitably shaped undersurface to complete the interior surfaces of the mould cavity, is placed on the mould 16 as shown and the mould is filled with sand and binder.. Fig 16 shows a core insert 11 in the mould 16 after removal of the mould top 21 and prior to removal of the core insert 11 from the mould. Referring to the description of the casting process of the invention as applied to forming a stator as described above, prior to assembly of the stator mould parts the required number of sand core inserts 11 are formed as described immediately above with reference to Figs 13 to 16.

Because the core insert parts 11 are formed around the stainless steel preformed inserts 6, they hold the preformed inserts in the correct position and securely during the casting process. Subsequently in disassembly of the mould the core insert parts 11 are broken away from within the cast product, leaving the stainless steel inserts, now an integral part of the cast product, behind. In an alternative arrangement, it is possible that the preformed inserts 6 may simply be slotted or placed into mould parts which hold the preformed parts during the casting process, rather than the mould parts (such as the core inserts 11) being first formed around the preformed inserts (stainless steel inserts 6) as described.

The foregoing describes the process of the invention in the application of forming a cast stator component, in which the preformed inserts form the leading edges of the stator vanes, by way of example only and as previously indicated the process of the invention may be used to form a wide range of stator or rotor components in which it is desired to provide inserts of a different material having different properties for any desired reason such as to obtain increased resistance to wear, corrosion, or similar for part of the cast product.

The foregoing describes the invention including a preferred form thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated in the scope thereof as defined in the accompanying claims.

INTELLECTUAL PROPERTY OFFICE OF N.Z. 1 0 AUG 2004 22 >03-

Claims (15)

CLAIMS:

1. A process for forming a cast stator or rotor component, which includes a number of radially extending vanes or blades, comprising supporting preformed inserts, each of which in the cast stator or rotor component will form a leading portion of a vane or blade of the rotor or stator component, in association with a mould part or parts which define(s) passages between the vanes or blades during the casting process, surrounding the mould part(s) with one or more other mould parts which define the balance of the stator or rotor component shape, filling the mould with molten material, and allowing the molten material to cool and removing the mould parts to leave the cast stator or rotor component with each preformed insert cast in situ as an integral leading portion of a vane or blade with a trailing portion of the vane or blade being formed of the material from which the balance of the stator or rotor component is cast, said preformed inserts being formed of a stronger or more wear-resistant material than the material from which the balance of the product is cast.

2. A process according to claim 1 wherein at least some of said mould parts are formed of sand by sand casting.

3. A process according to either one of claims 1 to 2 wherein the preformed inserts are formed from stainless steel.

4. A process according to any one of claims 1 to 3 wherein the balance of the stator or rotor is cast from aluminium or an aluminium alloy or magnesium or a magnesium alloy.

5. A process according to any one of claims 1 to 4 wherein the stator or rotor component is a stator component which comprises a centre part, a generally cylindrical body around the centre part, and a series of said vanes spaced around the centre part and extending radially from the centre part to the cylindrical body.

6. A process according to claim 5 wherein the preformed inserts extend the length of the vanes (in the radial direction) and include an enlarged end at either end of the preformed inserts, which enlarged ends are surrounded by the material of the balance of the stator during casting of the product. INTELIKtlML PROPERTY OFFICE OF N.Z. 10 AUG 2004 received 22603-1

7. A process according to any one of claims 1 to 6 including the steps of positioning the preformed inserts in a mould base, positioning one or more core insert parts of the mould in association with the mould base and so as to hold or assist in holding the preformed inserts in position, and fitting a mould top part to the mould.

8. A process according to claim 7 including positioning the preformed inserts in the mould base by fitting the preformed inserts into one or more recesses in the mould base.

9. A stator or rotor including a number of radially extending vanes or blades, the leading portions of which are formed by preformed inserts about which a trailing portion of each of the vanes or blades and the balance of stator or rotor have been cast, the preformed inserts being formed of a stronger or more wear-resistant material than the material from which the trailing portions of vanes or blades and balance of the stator or rotor has been cast.

10. A stator or rotor according to claim 9 wherein the preformed inserts are formed from stainless steel.

11. A stator or rotor according to either one of claims 9 and 10 wherein the balance of the stator or rotor is cast from aluminium or an aluminium alloy or magnesium or a magnesium alloy.

12. A stator according to any one of claims 9 to 11 which comprises a centre part, a generally cylindrical body around the centre part, and a series of said vanes spaced around the centre part and extending radially from the centre part to the cylindrical body.

13. A stator according to claim 12 wherein the preformed inserts extend the length of the vanes (in the radial direction) and include an enlarged end at either end of the preformed inserts which enlarged ends are surrounded by the material of the balance of the stator during casting of the product.

14. A process for forming a cast product or component substantially as herein described with reference to Figures 5 to 10 of the accompanying drawings.

15. A product or component substantially as herein described with reference to Figures 3 and 4 of the accompanying drawings. INTELLECTUAL PROPERTY OFFICE OF N.Z. 10 AUG 2004 21603-1 RECEIVED