Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Utility Patent
1998-07-22
2001-01-02
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000, C310S330000
Utility Patent
active
06169355
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Reference is made to commonly assigned U.S. Patent Application Ser. No. 09/071,485, filed May 1, 1998, entitled “Controlled Composition and Crystallographic Changes in Forming Functionally Gradient Piezoelectric Transducers” by Chatterjee et al, U.S. patent application Ser. No. 09/071,486 filed May 1, 1998, entitled “Functionally Gradient Piezoelectric Transducers” by Furlani et al, and U.S. patent application Ser. No. 09/093,268 filed Jun. 8, 1998, entitled “Using Morphological Changes to Make Piezoelectric Transducers”, by Chatterjee et al, the disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates generally to the field of ink jet printing and, more particularly, to an ink jet head that utilizes a functionally gradient piezoelectric element.
BACKGROUND OF THE INVENTION
Piezoelectric ink jet elements are used in a wide range of micro-fluidic printing devices. Conventional ink jet elements utilize piezoelectric transducers that comprise one or more uniformly polarized piezoelectric elements with attached surface electrodes. The three most common transducer configurations are multilayer ceramic, mono-morph or bi-morphs, and flex-tensional composite transducers. To activate a transducer, a voltage is applied across its electrodes thereby creating an electric field throughout the piezoelectric elements. This field induces a change in the geometry of the piezoelectric elements resulting in elongation, contraction, shear or combinations thereof. The induced geometric distortion of the elements can be used to implement motion or perform work. In particular, piezoelectric bimorph transducers that produce a bending motion, are commonly used in micro-pumping devices. However, a drawback of the conventional piezoelectric bimorph transducer is that two bonded piezoelectric elements are needed to implement the bending. These bimorph transducers are typically difficult and costly to manufacture for micro-pumping applications (in this application, the word micro means that the dimensions of the element range from 100 microns to 10 mm). Also, when multiple bonded elements are used, stress induced in the elements due to their constrained motion can damage or fracture an element due to abrupt changes in material properties and strain at material interfaces.
Therefore, a need persists for an ink jet head that overcomes the aforementioned problems associated with conventional ink jet apparatus.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an ink jet head actuated by a functionally gradient piezoelectric actuating element.
It is a feature of the invention that a functionally gradient piezoelectric transducer integral to an ink jet head actuates the flow of ink from an ink compartment where droplets of ink are emitted from the ink jet head.
To accomplish these and other objects of the invention, there is provided an ink jet head having a body, a base attached to the body, the body having a plurality of independent ink compartments each having an inlet and outlet orifice and a piezoelectric actuating element associated therewith. The actuating element enables the ink jet head to receive ink from an ink reservoir in fluid communications with the inlet orifices of the independent ink compartments and then eject droplets of the ink onto a receiver to form an image. The piezoelectric actuating element includes a substantially planar piezoelectric transducer comprising a slab of piezoelectric material. According to the invention, the slab has a first surface and an opposing second surface. A plurality of spatially separated first electrodes are arranged on the first surface of the slab. A second electrode extends substantially lengthwise along the opposed second surface. Piezoelectric material of the invention has a functionally gradient d-coefficient selected so that the slab changes geometry in response to an applied voltage which produces an electric field in the slab. The plurality of first electrodes and second electrode are arranged so that voltage applied to any one of the plurality of first electrodes and second electrode induces an electric field in a portion of the slab between the select one of the plurality of first electrodes and the second electrode. Further, a source of power operably associated with each one of the plurality of first electrodes and to the second electrode of the piezoelectric transducer for enabling fluid flow through the ink compartment. When the piezoelectric transducer is energized to pump fluid from the ink storage chamber, the source of power provides a negative voltage to the first terminal and a positive voltage to the second terminal. On the other hand, when the piezoelectric transducer is energized to pump fluid into the ink compartment, the source of power provides a positive voltage to the first terminal and a negative voltage to the second terminal.
REFERENCES:
patent: 4115789 (1978-09-01), Fischbeck
patent: 4356424 (1982-10-01), Marcus
patent: 4375042 (1983-02-01), Marcus
patent: 4700203 (1987-10-01), Yamamuro et al.
patent: 5589725 (1996-12-01), Haertling
Chatterjee Dilip K.
Furlani Edward P.
Ghosh Syamal K.
Bailey, Sr. Clyde E.
Budd Mark O.
Eastman Kodak Company
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