Electrical generator or motor structure – Non-dynamoelectric – Charge accumulating
Reexamination Certificate
2001-01-05
2001-12-25
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Charge accumulating
C310S400000
Reexamination Certificate
active
06333584
ABSTRACT:
SCOPE OF THE INVENTION
The present invention relates generally to electrostatic actuators and more particularly to rotary electrostatic microactuators with comb drive assemblies.
BACKGROUND
Many early rotating electrostatic motors used a central bearing with various arrangements of electrostatic stators around the motors to effect rotation. Unfortunately, these motors tended to have problems with friction at the central bearing and have had lifetime issues related to wear of the bearing. The motors typically acted as stepper motors where the rotor rotates with an incremental motion as the stator elements are attracted. Thus it was difficult to precisely adjust a plate to a particular angle with such motors.
Other angular motors have been described which use flexural elements to support a rotating element. Comb drive fingers are arranged in concentric arcs around a central flexural pivot, so that small angular motion is provided around the pivot. See, for example, D. A. Horsley, et al., “Angular Micropositioner for Disk Drives”, Proceedings of the Tenth International Workshop on Micro Electro Mechanical Systems, 1997, pp 454-458; L.-S. Fan, et al., “Batch-Fabricated Area-Efficient Milli-Actuators”, Proceedings 1994 Solid State Sensor and Actuator Workshop, Hilton Head, pp 38-42; T. Juneau, et al., “Dual Axis Operation of a Micromachined Rate Gyroscope”, Proceedings 1997 International Conference on Solid State Sensors and Actuators, V.2, pp 883-890; E. H. Klaassen, et al., “Silicon Fusion Bonding and Deep Reactive Ion Etching; A New Technology for Microstructures”, The 8th International Conference on Solid-State Sensors and Actuators, and Eurosensors IX, Stockholm, Sweden, Jun. 25-29, 1995, pp 556-559; W. C. Tang, et al., “Laterally Driven Polysilicon Resonant Microstructures”, Sensors Actuators 20, 1989, pp 25-31 (IEEE reprint pp. 53-59) and U.S. Pat. No. 5,025,346 to Tang et al. Unfortunately, all of these devices provide a limited angular range of motion.
Other electrostatic microactuators with improved angular range of motion have been provided for rotating devices such as optical components. See, for example, International Publication No. WO 00/36740 to Jerman et al. It has been found, however, that such components may require additional positional adjustments during use due to initial placement errors or subsequent misalignments resulting from temperature changes or other environmental factors.
In general, it is an object of the present invention to provide a rotary electrostatic microactuator having a movable member that can be adjusted during use in a direction other than its primary direction of angular motion.
Another object of the invention is to provide a rotary electrostatic microactuator of the above character in which the movable member can be tilted about an axis extending substantially parallel to the substrate of the microactuator.
Another object of the invention is to provide a rotary electrostatic microactuator of the above character in which the movable member can be tilted relative to the movable comb drives of the microactuator.
SUMMARY OF THE INVENTION
The present invention provides a tiltable electrostatic microactuator comprising a substantially planar substrate and a rotatable member overlying the substrate for rotation about an axis of rotation extending perpendicular to the planar substrate. A plurality of comb drive assemblies are provided and each has a first comb drive member mounted on the substrate and a second comb drive member coupled to the rotatable member. Each of the first and second comb drive members is provided with comb drive fingers. First and second spaced-apart springs are included in the microactuator and each has a first end portion coupled to the substrate and a second end portion coupled to at least one of the second comb drive members for suspending the second comb drive members and the rotatable member over the substrate. The second comb drive members are movable in a direction of travel about the axis of rotation between a first position in which the comb drive fingers of the first and second comb drive members are not substantially fully interdigitated and a second position in which the comb drive fingers of the first and second comb drive members are substantially fully interdigitated. A controller is electrically coupled to the second comb drive members and the substrate for tilting the rotatable member relative to the substrate about a pivot axis extending parallel to the planar substrate. A method for using the microactuator is provided.
REFERENCES:
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L.A. Field, et al., “Micromachined 1×2 Optical-fiber Switch”, Sensors and Actuators A 53, 1996 Elsevier Science S.A., pp. 311-315.
V.R. Dhuler, et al.; “A Novel Two Axis Actuator for High Speed Large Angular Rotation”, Transducers '97, 1997 International Conference on Solid-State Sensors and Actuators, Chicago, Jun. 16-19, 1997 IEEE, pp. 327-330.
E.H. Klaassen, et al.; “Silicon Fusion Bonding and Deep Reactive Ion Etching; A New Technology for Microstructures”, Transducers '95—Eurosensors, International Conference on Solid-State Sensors and Actuators, and Eurosensors IX, Stockholm, Sweden, Jun. 25-29, 1995, pp. 556-569.
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Grade John D.
Jerman John H.
Flehr Hohbach Test Albritton & Herbert LLC
Iolon, Inc.
Waks Joseph
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