ADAPTIVE DESIGN OF FIXTURE FOR THIN-WALLED SHELL/CYLINDRICAL COMPONENTS

• US 20140283368A1
• Filed: 03/24/2014
• Published: 09/25/2014
• Est. Priority Date: 03/06/2007
• Status: Abandoned Application

• Current Assignee: University of Sheffield
• Original Assignee: University of Sheffield
• Inventors: GENG, Zunmin
• Application Number:
  US14/223,076
• Publication Number:
  US 20140283368A1
• Time in Patent Office: Days
• US Class Current: 29/559
• CPC Class Codes: B23B 2215/64 Thin walled components
• CPC Class Codes: B23B 31/305 the gripping means is a deformable sleeve
• CPC Class Codes: B23Q 17/0976 Detection or control of chatter B23Q15/12 takes precedence
• CPC Class Codes: B23Q 3/06 Work-clamping means
• CPC Class Codes: B25B 1/20 Vices for clamping work of special profile, e.g. pipes
• CPC Class Codes: B25B 5/065 involving the use of flexible pressure bags or diaphragms
• CPC Class Codes: G01M 7/022 Vibration control arrangements, e.g. for generating random vibrations
• CPC Class Codes: Y10T 279/1024 Directly expanding jaws
• CPC Class Codes: Y10T 279/1029 Jaw is expansible chamber; i.e., bladder type
• CPC Class Codes: Y10T 279/1087 Resilient
• CPC Class Codes: Y10T 279/1216 Jaw is expansible chamber; i.e., bladder type
• CPC Class Codes: Y10T 279/1283 Fluid pressure directly moves jaws
• CPC Class Codes: Y10T 29/49998 Work holding

Abstract

A group of fixtures for thin-walled shell/cylindrical components (10) while they are being machined internally and externally, has a mounting base (1) having mounting holes, positioning pins and clamps to locate one end of the thin-walled component. A supporting arbour or cylinder (5) is fixed in the base. A circular lid (12) is fixed to the supporting arbour or cylinder and has a wedged step to locate the other end of the cylindrical component for internal and external machining, or the major open end of shell component for internal machining. A pair of modified vehicle wheel inner tubes (8) are disposed around the supporting arbour or cylinder. A multi-layered sacrificial liner (7) surrounds the pressure element and is adapted to fit between it and the thin-walled components. When properly inflated according to the design and validation procedure, the fixture adaptively holds the thin-walled components for machining, with sufficient supporting rigidity and dynamic stability, so as to maintain the machining precision and surface finish to an acceptable engineering standard. Furthermore, a reasonable and practical design and validation procedure is supplied, easily adapted to different sized thin-walled shell/cylindrical components.

Claims

1. A fixture for supporting a cylindrical component for machining comprising:

a base for mounting the component;

a column fixed to the base;

an endless tubular inflatable elastomeric pressure element, disposed on the base between the column and, when in use, the component; and

a sacrificial liner adapted to fit between the pressure element and the component for preventing penetration of the pressure element by tool movements through the component during a machining operation,

wherein the pressure element is capable of pneumatic inflation up to five times its flat diameter.

2. A fixture as claimed in claim 1, in which the fixture further comprises a lid to be fixed to the column.

4. A fixture as claimed in claim 1, in which the liner has a total thickness between 10 mm and 20 mm.

5. A fixture as claimed in claim 1, in which the liner is a multi-layered material, the layers being adhered or otherwise bonded together.

6. A fixture as claimed in claim 5, in which there are between 4 and 7 sheets of material in the liner.

7. A fixture as claimed in claim 1, in which regional enhancements of the liner are provided in areas where minor openings of the component are to be situated, the enhancements comprising a curled nylon sheet between the liner and the component.

8. A fixture as claimed in claim 1, wherein the pressure element is pneumatically inflatable to an inflating pressure up to 4 Bar.

9. A fixture as claimed in claim 1, wherein the component comprises one of a rocket shell or an airplane jet engine casing.

10. A fixture as claimed in claim 1, wherein the column is hollow.

11. A fixture as claimed in claim 1, wherein the pressure element comprises a vehicle wheel inner tube.

12. A fixture as claimed in claim 11, wherein an inflation valve of the inner tube protrudes though an aperture in the column.

13. A fixture as claimed in claim 11, wherein two or more of the inner tubes are employed one on top of the other.

14. A fixture as claimed in claim 1, wherein the sacrificial liner comprises a rectangular sheet of nylon.

18. A combination of a fixture as claimed in claim 1 and a cylindrical component secured in the fixture.

19. A combination as claimed in claim 18, in which the component is thin-walled.

20. A combination as claimed in claim 19, in which the component is an airplane jet engine casing or a rocket nose cone.

21. A fixture as claimed in claim 1, wherein the base has a first location means to locate and clamp one end of the component.

22. A fixture as claimed in claim 21, in which the first location means comprises positioning pins and clamps.

23. A fixture as claimed in claim 21, wherein the base has a second location means to locate and clamp one end of the component.

24. A fixture as claimed in claim 23, in which the second location means comprises positioning pins and clamps.

3. (canceled)

15. A method for validating a fixture for a cylindrical component, the fixture comprising:

a base for mounting the component;

a column fixed to the base;

an endless tubular inflatable elastomeric pressure element, disposed on the base between the column and, when in use, the component; and

a sacrificial liner adapted to fit between the pressure element and the component for preventing penetration of the pressure element by tool movements through the component during a machining operation,

wherein the pressure element is capable of pneumatic inflation up to five times its flat diameter, in which

the inflation pressure for the pressure element is regulated within a range up to 4 Bar;

a FRF ensemble test is performed with shaker excitation; and

the Vibration-Amplitude-Ratio is in the range of R_H≦

2.5, with obvious sparseness of vibration modes observed within the frequency range around 1000 Hz.

16-17. -17. (canceled)