Claims
- 1. An apparatus for abrading a workpiece, the apparatus comprising:
a first plate assembly having a first surface for supporting a workpiece; a second plate assembly having a second surface for engaging the workpiece to abrade a portion thereof; a displacement shaft mounted from movement with respect to said second plate assembly and said first plate assembly and having a first end configured to engage said second plate assembly; and a feedback assembly coupled to a second end of said displacement shaft for moving said displacement shaft to substantially maintain a predetermined load exerted on said displacement shaft by said second plate assembly.
- 2. An apparatus according to claim 1 further comprising a displacement measuring assembly coupled to said feedback assembly for measuring the movement of said displacement shaft with respect to said first plate assembly.
- 3. An apparatus according to claim 2 further comprising a controller coupled to said feedback assembly and to said displacement measuring assembly for monitoring the thickness of the workpiece.
- 4. An apparatus according to claim 3 wherein said controller stores a representation of the position of said first surface and receives from the said displacement measuring assembly a representation of the current position of said second surface to determine the thickness of the workpiece.
- 5. An apparatus according to claim 4 wherein said feedback assembly comprises a pressure sensor coupled to said displacement shaft and to said controller for sensing the load being applied to said displacement shaft by said second plate assembly.
- 6. An apparatus according to claim 5 wherein said feedback assembly comprises a drive mechanism coupled to said displacement shaft and responsive to said controller for moving said displacement shaft when said controller determines that the current load being exerted on said displacement shaft by said second plate assembly is substantially different from said predetermined load.
- 7. An apparatus according to claim 6 wherein said drive mechanism is a first motor having a motor shaft capable of rotation.
- 8. An apparatus according to claim 7 wherein said motor is a stepper motor.
- 9. An apparatus according to claim 8 further comprising a threaded shaft coupled to said displacement shaft and to said stepper motor.
- 10. An apparatus according to claim 9 further comprising a gear assembly coupled to said stepper motor and to said threaded shaft for converting rotary motion of said motor shaft to translational movement of said displacement shaft.
- 11. An apparatus according to claim 10 wherein said threaded shaft is a jack screw.
- 12. An apparatus according to claim 11 wherein each rotation of said motor shaft corresponds to a predetermined amount of translational movement of said displacement shaft.
- 13. An apparatus according to claim 12 wherein said displacement shaft extends through a central portion of said first plate assembly to engage said second plate assembly.
- 14. An apparatus according to claim 13 further comprising a target centrally mounted on said second surface.
- 15. An apparatus according to claim 14 further comprising a pad on the first end of said displacement shaft for engaging said target.
- 16. An apparatus according to claim 15 wherein said first plate assembly is a lower plate assembly, said second plate assembly is an upper plate assembly, and said displacement shaft is configured for vertical movement.
- 17. An apparatus according to claim 16 wherein said upper plate assembly is configured for rotational and vertical movement with respect to said lower plate assembly.
- 18. An apparatus for abrading a workpiece, the apparatus comprising:
a frame; a carriage slidably mounted on said frame; a drive mechanism coupled to said carriage for moving said carriage substantially vertically; a lower plate assembly having an upper working surface for supporting the workpiece; an upper abrading plate assembly having a lower working surface for abradingly engaging the workpiece; a displacement shaft having upper and lower ends and slidingly mounted for vertical movement with respect to said upper plate assembly and said lower plate assembly, said upper end configured to engage said upper plate assembly; a feedback assembly coupled to the lower end of said displacement shaft for sensing the load between said lower plate assembly and said displacement shaft, and in response thereto, moving said displacement shaft to substantially maintain a predetermined load; and a displacement measuring assembly coupled to said feedback assembly for measuring the movement of said displacement shaft.
- 19. An apparatus according to claim 18 wherein said displacement measuring assembly measures the movement of said displacement shaft with respect to said lower plate assembly.
- 20. An apparatus according to claim 19 further comprising a controller coupled to said feedback assembly and to said displacement measuring assembly wherein said controller stores a representation of the position of said upper working surface and receives from said displacement measuring assembly a representation of the current position of said lower working surface to determine the thickness of the workpiece.
- 21. An apparatus according to claim 20 wherein said feedback assembly comprises a pressure sensor coupled to said displacement shaft and to said controller for sensing the load being applied to said displacement shaft by said upper plate assembly.
- 22. An apparatus according to claim 21 wherein said feedback assembly comprises a drive motor coupled to said displacement shaft and responsive to said controller for moving said displacement shaft when said controller determines that the current load being exerted on said displacement shaft by said upper plate assembly is substantially different from said predetermined load.
- 23. An apparatus according to claim 22 wherein said motor is a stepper motor.
- 24. An apparatus according to claim 23 further comprising:
a threaded shaft coupled to said displacement shaft and to said stepper motor; and a gear assembly coupled to said stepper motor and to said threaded shaft for converting rotary motion of said motor shaft to translational movement of said displacement shaft.
- 25. An apparatus according to claim 24 wherein said threaded shaft is a jack screw.
- 26. An apparatus according to claim 25 wherein each rotation of said motor shaft corresponds to a predetermined about of translational movement of said displacement shaft.
- 27. An apparatus according to claim 26 wherein said displacement shaft extends through a central portion of said lower plate assembly to engage said upper abrading plate assembly.
- 28. An apparatus according to claim 27 further comprising a target centrally mounted on said lower working surface.
- 29. An apparatus according to claim 28 further comprising a pad on the first end of said displacement shaft for engaging said target.
- 30. An apparatus according to claim 29 wherein said upper abrading plate assembly is configured for rotation and vertical movement with respect to said lower plate assembly.
- 31. A method for abrading a workpiece to a desired thickness using an abrading apparatus of the type having a vertically stationary lower plate assembly and an upper, vertically moveable and rotatable abrading plate assembly, the method comprising the steps of:
measuring a first position of a displacement shaft in contact with the upper abrading plate assembly when the upper abrading plate assembly is in contact with the lower plate assembly and a substantially predetermined load exists between said displacement shaft and said upper abrading plate assembly; placing the workpiece between the upper abrading plate assembly and the lower plate assembly to abrade the workpiece; sensing increases in load on the displacement shaft as the workpiece is abraded; lowering the displacement shaft to maintain the predetermined load; and terminating the abrading of the workpiece when the displacement shaft has been sufficiently lowered to achieve the desired thickness.
- 32. A method according to claim 31 further comprising:
storing the first position in a controller; and comparing the current position of the displacement shaft with the stored first position to determine the current thickness of the workpiece.
- 33. A method according to claim 32 further comprising:
comparing in the controller the current sensed load exerted between the displacement shaft and the upper abrading plate with the predetermined load; and lowering the displacement shaft if the sensed load is higher than the predetermined load.
- 34. A method according to claim 33 further comprising moving said upper abrading plate assembly from a loading/unloading position to a working position and from the working position to the loading/unloading position.
- 35. A method according to claim 34 wherein the step of lowering comprises activating a stepper motor coupled to the displacement shaft to lower the displacement shaft.
- 36. A method according to claim 35 further comprising:
counting the number of revolutions of the stepper motor shaft; and calculating the translational movement of the displacement shaft from the number of revolutions of the stepper motor.
- 37. A method according to claim 36 further comprising storing in the controller the distance that the displacement shaft moves per revolution of the stepper motor.
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No. 60/450,242, filed Feb. 25, 2003.
Provisional Applications (1)
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Number |
Date |
Country |
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60450242 |
Feb 2003 |
US |