Crystal selector pattern

• US 20020005265A1
• Filed: 06/25/2001
• Published: 01/17/2002
• Est. Priority Date: 06/27/2000
• Status: Abandoned Application

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Ford, David A.
• Application Number:
  US09/887,053
• Publication Number:
  US 20020005265A1
• Time in Patent Office: Days
• US Class Current: 164/122.2
• CPC Class Codes: B22C 7/02 Lost patterns
• CPC Class Codes: B22C 9/04 Use of lost patterns
• CPC Class Codes: C30B 11/14 characterised by the seed, e.g. its crystallographic orientation

Abstract

A crystal selector pattern for use in forming a mould in an investment casting process, which is formed from a water-soluble organic composition which, in a preferred embodiment, comprises 80% urea.

Claims

1. A crystal selector pattern for forming a crystal selector in an investment casting mould, the crystal selector pattern being formed from a water-soluble organic composition.

2. A crystal selector pattern as claimed in claim 1, in which the water-soluble organic composition is thermoplastic.

3. A crystal selector pattern as claimed in claim 1, which is formed in an injection moulding process.

4. A crystal selector pattern as claimed in claim 1, in which the solubility of the water-soluble organic composition is not less than 500 g/l.

5. A crystal selector pattern as claimed in claim 4, in which the solubility of the water-soluble organic composition is not less than 900 g/l.

6. A crystal selector pattern as claimed in claim 1, in which the water-soluble organic composition comprises hydroxypropylcellulose.

7. A crystal selector pattern as claimed in claim 1, in which the water-soluble organic composition comprises urea.

8. A crystal selector pattern as claimed in claim 1, in which the water-soluble organic composition comprises polyvinyl acetate.

9. A crystal selector pattern as claimed in claim 1, in which the water-soluble organic composition comprises stearic acid.

10. A crystal selector pattern for forming a crystal selector in an investment casting mould, the crystal selector pattern being formed from a water-soluble organic composition which contains urea.

11. A crystal selector pattern as claimed in claim 10, in which urea is present in the water-soluble organic composition in a proportion not less than 50%.

12. A crystal selector pattern as claimed in claim 11, in which the urea is present in the water-soluble organic composition in a proportion not less than 70%.

13. A crystal selector pattern as claimed in claim 10, in which the water-soluble organic composition comprises polyvinyl acetate.

14. A crystal selector pattern as claimed in claim 13, in which the polyvinyl acetate is present in the water-soluble organic composition in a proportion not less than 10%.

15. A crystal selector pattern as claimed in claim 14, in which the polyvinyl acetate is present in the water-soluble organic composition in a proportion not less than 15%.

16. A crystal selector pattern as claimed in claim 10, in which the water-soluble organic composition comprises stearic acid.

17. A crystal selector pattern as claimed in claim 16, in which the stearic acid is present in the water-soluble organic composition in a proportion not less than 1.

18. A crystal selector pattern for forming a crystal selector in an investment casting mould, the crystal selector pattern being formed from a water-soluble organic composition which comprises:

70 to 90% urea,

10-25% polyvinyl acetate, and

1 to 5% stearic acid.

19. A crystal selector pattern in accordance with claim 18, in which the water-soluble organic composition comprises:

80% urea,

18% polyvinyl acetate, and

2% stearic acids.

20. An investment casting process comprising:

making a pattern corresponding to the shape of a desired mould cavity, which mould cavity includes a crystal selector region;

investing the pattern with a hardenable coating of a ceramic material thereby to form a mould cavity about the pattern;

hardening the coating;

removing the pattern from the mould cavity; and

casting an article in the mould cavity,

wherein the pattern corresponding to the crystal selector region is made form a water-soluble organic composition, and wherein the step of removing the pattern corresponding to the crystal selector region comprises steam autoclaving the moulding cavity.

21. An investment casting process as claimed in claim 20, wherein the water-soluble organic composition contains urea.

22. An investment casting process as claimed in claim 20, wherein the water-soluble organic composition comprises:

70 to 90% urea,

10-25% polyvinyl acetate, and

1 to 5% stearic acid.

23. An investment casting process as claimed in claim 20, wherein the water-soluble organic composition comprises:

80% urea,

18% polyvinyl acetate, and

2% stearic acid.