An experimental miniature peristaltic pump exploits piezoelectrically excited flexural waves that travel around a ring: A fluid is carried in the containers formed in the valleys between the peaks of the flexural waves (see Figure 1). The basic action of this pump is similar to that described in "Piezoelectric Flexural- Traveling- Wave Pumps" (NPO-19737), NASA Tech Briefs, Vol. 21, No. 4 (April 1997), page 66.
What sets the present pump apart from other pumps that exploit piezoelectrically excited flexural waves is the ring shape, which makes it possible to take advantage of some of the desirable characteristics of previously developed piezoelectric rotary motors. A major advantage of the circular (in contradistinction to a straight-line) wave path is that the flexural waves do not come to a stop and, instead, keep propagating around the ring. Hence, a significant portion of the excitation energy supplied during each cycle is reused during the next cycle, with the result that the pump operates more effectively than it otherwise would.
The principal components of this pump (see Figure 2) include a cover and segmented-ring piezoelectric actuator bonded to one face of a brass ring. The other face of the brass ring is pressed against the cover and against silicone rubber seals that protrude slightly from grooves in the cover. The protrusion is sufficient to maintain sealing at the maximum flexural-wave amplitude expected to occur during operation of the pump. The pattern of grooves and seals is chosen, in conjunction with the pattern of inlet and outlet holes in the cover, to eliminate the need for conventional valve mechanisms, sliding seals, and other moving parts that would be highly susceptible to wear. Moreover, when the pump is turned off (that is, in the absence of piezoelectrically actuated flexural waves), the loading of the brass ring against the cover effects a tight seal equivalent to that of a closed valve.
The polarities and phases of the voltages applied to the piezoelectric ring segments are chosen to excite a desired flexural-traveling-wave mode. For maximum pumping effectiveness, the excitation frequency should equal the resonance frequency of the desired wave mode.
This work was done by Yoseph Bar-Cohen, Zensheu Chang, Xiaoqi Bao, and Shyh-Shiuh Lih of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Machinery/Automation category.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Intellectual Assets Office
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109
Refer to NPO-30415, volume and number of this NASA Tech Briefs issue, and the page number.
This Brief includes a Technical Support Package (TSP).
Miniature Ring-Shaped Peristaltic Pump
(reference NPO30415) is currently available for download from the TSP library.
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