Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1997-07-08
2001-11-06
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S323020
Reexamination Certificate
active
06313566
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to piezoelectric motors, and more particularly, to a piezoelectric motor capable of storing energy which may be used to propel the motor.
In piezoelectric motors, an electro-active material is used to convert electric potential directly into mechanical strain. Piezoelectric motors rely on friction to convert micro strain to macro motion.
Piezoelectric motors are useful in precision actuators and effectors, such as robotic manipulators. They typically offer advantages over conventional motors (i.e., those that rely on electromagnetic coupling in air gaps) in precision control applications in which light weight, compact size, low energy use, or the ability to operate under cryogenic or other extreme environmental conditions is desired.
Conventional piezoelectric motors generally involve a series of mechanical steps. The motors do not store energy.
The components of conventional piezoelectric motors are small relative to the stepwise displacement. It may be difficult or expensive to manufacture such motors that are capable of maintaining acceptable tolerances using conventional equipment and methods. They also are susceptible to failure if wear exceeds these tolerances.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a piezoelectric motor capable of motion by successively inducing small amounts of strain in a substrate, and particularly a piezoelectric motor suitable for use in applications that require compact, large power-density, long stroke precision actuators.
It is another object of the present invention to provide a piezoelectric motor capable of storing energy from the motion of a leg, which energy may be released to cause the motor to move relative to a substrate, and that is capable of holding a constant force while consuming no power.
It is yet another object of the invention to provide a piezoelectric motor having a compliant surface that tends to urge the motor into engagement with the substrate, thereby avoiding the tolerance and wear problems encountered in the prior art.
It is a further object of the invention to provide a piezoelectric motor having a sufficient number of substrate-engaging legs to provide an acceptable level of redundancy to minimize single point failures.
The foregoing objectives are achieved in a piezoelectric motor including a motor body, a compliant layer in communication with the motor body, and a predetermined number of legs in communication with the compliant layer that urges the legs into engagement with a substrate. Each of the legs includes a piezoelectric wafer, which preferably is operated in the shear mode. The actuation of a piezoelectric wafer causes the corresponding leg to be displaced relative to a substrate. This displacement results in the transfer of strain energy to the compliant layer. The energy stored in the compliant layer may be released, causing the motor to advance along the substrate.
The legs may be capable of moving independently from one another; they also may be capable of moving sequentially or in a predetermined groups or units. In one preferred embodiment, the legs are arranged in pairs with the leg pairs being capable of simultaneous actuation. The piezoelectric wafers in the legs may be actuated by an analog voltage source arranged in parallel with the leg pairs.
In another preferred embodiment, the piezoelectric motor may include a motor body and a predetermined number of legs connected to the body through a compliant interface that urges the legs into engagement with a substrate. Each leg includes at least one electro-active element, which preferably is a piezoelectric wafer operated in the shear mode.
The piezoelectric motor of another preferred embodiment comprises a motor body, a compliant layer capable of storing strain energy in communication with the motor body and a predetermined number of legs in communication with the compliant layer, which maintains the legs in engagement with a substrate. Each leg includes a piezoelectric element. Actuation of a piezoelectric element causes displacement of the corresponding leg. The discharge of the piezoelectric element transfers strain energy to the compliant layer. The release of the energy stored in the compliant layer causes the motor to advance along a substrate. The motor is capable of maintaining a high holding force in the absence of a power input.
These and further objects of the invention will become apparent from the following detailed description.
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Cunningham John
Garcia Ephrahim
Newton David V.
Budd Mark O.
Porter Wright Morris & Arthur
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