Piezoelectric pump

An electric pump comprises a housing (22) that encloses a stack of waveplates (18) in which electrically created traveling waves forcefully move fluid (20) from an inlet duct (24) to an outlet duct (26). Each waveplate is made of shear type transducer material that is segmented by film electrodes, the electrode planes lying perpendicular to the direction of fluid flow. Electrode sets are stimulated by a multiphase electrical power source. The pressure at wave crest contacts is electrically controlled to hermetically trap fluid portions between waves, thereby achieving high throughput against high pressure differential. Rubbing is essentially absent throughout the pump, life shortening mechanisms being few and benign. High electromechanical efficiency obtains when waveplates are stimulated by electrically resonant frequencies. Pump variants include variable wavelength, variable wave amplitude, and tapered waveplates for improved effectiveness with compressible fluids. An increasing-wavelength variant is applicable to high specific impulse space propulsion. Other embodiments provide the functions of valves, filters, light modulators, microwave attenuators, fluid flow modulators grinders, x-ray imagers, and emulsifiers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to pumps, and, more particularly, to 
piezoelectric pumps having a multiplicity of waveplates electrically 
undulated by shear transducer action. 
2. Description of Background Art 
The preponderance of known piezoelectric pumps use a stack of piezoelectric 
elements, each element deforming with 2-dimensional extension accompanied 
by a thickness deformation, the latter deformations producing a mechanical 
stroke that is the sum of the minute strokes of each element. Extensions 
and thickness deformations are inseparable. A stack of thickness elements 
is generally bonded to a rigid support means at one end, and is bonded to 
a rigid moving member such as a pump piston at the opposite end. 
Therefore, a bonded stack of thickness elements produces a stroke that is 
less than the stroke produced by a stack that is not rigidly bonded at its 
ends because a portion of the extension stroke is inhibited. The rigid 
bonding also causes internal shear and tensile strains in the stack. 
Thickness stacks used in pumps generally use piezoelectric material of the 
ferroelectric type. The ferroelectric material is polarized in the 
direction of the applied electric field. If a reverse electric field is 
applied, the polarization will be reduced, destroyed, or reversed in 
direction, all of which reduce the performance of the piezoelectric 
elements. Therefore, thickness stacks are usually operated with monopolar 
electric potentials. Electric drive means that provide monopolar electric 
signals are more complicated than bipolar electric drive means because of 
the need for floating power sources. A thickness stack therefore produces 
half the mechanical stroke that would otherwise be available if both 
electric drive potentials and piezoelectric deformation were bipolar. 
Known piezoelectric pumps use a piston or other displacement means to move 
fluid wherein the displacement means generally oscillates while at least 
two valves prevent most of the displaced fluid from moving in a direction 
other than the desired one. Typical of this class of pumps is a 
piezoelectric fuel injector by Takahashi, U.S. Pat. No. 4,803,393 in which 
piezoelectric action is transmitted hydraulically by means of a diaphragm 
or a bellows. The life of known pumps is shortened by rubbing at contacts 
between seals and sliding surfaces, between displacers and cylinders, and 
by fatigue of valves and, if used, of flexible membrane seals. 
Known piezoelectric pumps store a large portion of the circulating energy 
in the form of elastic deformation of the pump body and in the mechanisms 
attaching the displacing means to the piezoelectric actuator stack. 
Additional energy is stored in the piezoelectric elements in the form of 
electric charge. These energies are generally only restored to the pump 
system between portions of the pumping cycles during which useful work is 
performed on the fluid. Energies that are not returned to the pump system 
but are dissipated as mechanical heat of friction or electrical heat of 
resistance operate with reduced electromechanical efficiency, and suffer a 
shorter life because of the accompanying higher operating temperatures. 
The pump drive means of Mitsuyasu, U.S. Pat. No. 4,688,536, charges 
piezoelectric elements in electrical parallel and discharges them in a 
sequence through inductive-capacitive circuits. Pump action is designed to 
be pulsatile and abrupt as required by the application of the invention to 
injecting fuel. 
3. Objects of the Invention 
An object of the present invention is the forceful movement of fluid from 
an inlet to an outlet without wear due to rubbing and with few and benign 
life-shortening mechanisms. 
Another object of the present invention is pumping of fluid with high 
electromechanical efficiency obtained by electrically resonant activation. 
A further object of the present invention is the pumping of fluid without 
valves. 
Another object of the present invention is higher speed of actuation by the 
direct action of apparatus components on the medium receiving the action, 
without resort to intermediary structural members. Yet another object of 
the invention is the acceleration of fluids to very high speeds for use in 
electromechanical propulsion. 
An additional object of the present invention is controlling any 
combination of fluid flow, inlet pressure, and outlet pressure by a valve 
action, and the maintenance of a valve state without further input of 
electrical power. 
A further object is fluid filtering wherein the upper limit of size of 
passed particles is continuously controllable electrically, and the 
maintenance of a filter state without further input of electrical power. 
Additional objects of the filtering function of the present invention is a 
self-rinsing filtering action and electrically controlled particle 
sorting. 
Still another object of the present invention is emulsification of 
quiescently immiscible fluids such as oil and water, and the disruption of 
agglomerated two-phase fluids such as flocculates and biological cells. 
The object of a variant emulsifier is more efficient action by superposing 
ultrasonic signals on the emulsifying signals. Still yet another object is 
electrical control of short electromagnetic waves. 
Another object is electrical power generation of the pump embodiment by the 
transduction of fluid power to electrical energy. Another object is the 
modulation of an optical beam. 
A further object is the imaging of x-rays by electrically figuring grazing 
incidence mirrors. 
Another object is the application of the present invention to grinding. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings. 
SUMMARY OF THE INVENTION 
The piezoelectric pump forcefully moves fluid in a positive displacement 
fashion. Each of a multiplicity of waveplates is resonantly electrically 
but not necessarily mechanically excited by a multiplicity of electrical 
phases. The electrical phases generate traveling waves. The waveplates are 
arranged to touch at wave crests. The fluid in the volumes between wave 
crests is carried along with the movement of the waves. Contact or 
near-contact between wave crests enhances the positive displacement 
function of the pump but without rubbing friction as all waves, at a given 
instant and location, travel with the same speed. Wave crest contact 
pressure is electrically controlled in accordance with the momentary needs 
of pump pressure differential (head). The moving trapped volume, the 
number of volumes, and the speed of wave motion determine, in the absence 
of leakage, the pumping capacity of the device. Sensors internal to the 
pump allow better control by an electrical controller. The pump operates 
in reverse as an electrical power generator. Pumps operated with slowly 
varying electric signals serve as valves, flow controllers, back-pressure 
regulators and the like. Suitably coated waveplates also function as 
grinders, self cleaning and electrically controllable particle filters, 
emulsifiers, microwave controllers, optical modulators, and imagers of 
x-rays.

DETAILED DESCRIPTION 
Referring to FIG. 1, shown is a fundamental building block of the present 
invention called a dimorph. In this embodiment dimorph 2 comprises a 
piezoelectric body divided into two portions 4a, 4b, by central film 
electrode 8 and external ground film electrodes 6a, 6b. Application of a 
bipolar, preferably symmetric electric waveform to active electrode 8 
creates electric fields E in bodies 4a and 4b. The piezoelectric body 
portion 4a is polarized P antiparallel to that in body portion 4b. 
FIG. 2 is the dimorph of FIG. 1 at an instant when the applied electric 
field, E, is present with polarities indicated by + and -. The shear 
deformation of the dimorph by angle 10 and translation of electrode 6b 
relative to electrode 6a by stroke 12 is the result of the applied 
electric fields E. At another instant of time, the reversal of the 
polarity of the applied electric fields is accompanied by piezoelectric 
deformation angle 10 and translation 12 in directions opposite those shown 
in FIG. 2. The other measures of the size of the dimorph remain constant, 
being independent of the state of shear deformation. Neither the distance 
between ground electrodes, the length measured perpendicular to the plane 
of the figure, nor the height measured in the direction of polarization, 
change during shear deformation. In addition, the volume of the dimorph 
remains essentially independent of the state of deformation. The shear 
dimorph allows operation by a voltage-symmetric electric source without 
depolarizing even ferroelectric materials, thereby affording essentially 
twice the mechanical stroke per unit of applied electric field intensity 
compared to the thickness or extension piezoelectric deformation modes. 
Further, the coefficient of transduction for shear, d.sub.15, and the 
electromechanical coupling factor are generally higher than for other 
deformation modes, thereby further enhancing performance. The advantages 
of the properties of shear dimorphs will become apparent with additional 
detailed description. 
FIG. 3 shows a six-phase set of electric potentials V1 . . . V6 of 
amplitude A plotted as functions of time t. FIGS. 4 and 5 illustrate the 
effect on a sheet of dimorphs joined by common ground electrodes, 
hereinafter called a waveplate, said dimorphs respectively connected 
modulo-six to the potentials of FIG. 3. 
FIG. 4 is an animated sequence t1 . . . t9 of the positions of dimorphs D1 
. . . D12 of the modulo-six waveplate of FIG. 5. The heavy trace is the 
locus of dimorphs edges (for example, edge 4 of FIG. 1), each trace 
segment having a slope that is proportional to the product of the 
instantaneous electric potential and the shear piezoelectric constant 
d.sub.15. 
FIG. 5 is a cross section view of a stack of waveplates A immersed in fluid 
20. Each wave plate comprises many dimorphs 2 joined by common ground 
electrodes 8. Waveplates are arranged to alternate with polarization 
directions up and down. At the instant of time of the figure, potential V1 
obtains in dimorph D1, V2 in D2, and so forth. Dimorphs are connected 
modulo-six in the example of the figure, giving a wave period 16. 
Electrical connections are omitted for clarity. Since the volume of an 
isolated dimorph does not change with varying applied electric potential, 
an isolated dimorph cannot affect the fluid other than to rearrange it. 
However, when dimorphs are joined into waveplates as shown, the shear 
deformation of one dimorph translates the attached adjacent dimorphs 
vertically in the figure. The net vertical displacement of the adjacent 
dimorphs result in a net fluid displacement. In other words, waveplates in 
contact or near contact at their wave crests enclose segments of the 
immersing fluid. By dint of the electrical phases of FIG. 3 and the 
traveling of waves in direction 14 of FIG. 4, the segments of fluid 20 are 
translated in the direction indicated by the arrows. The entrapped volume 
of each fluid segment remains essentially constant during the movement of 
shear waves as depicted in FIG. 4. 
Each waveplate has a constructed thickness 18, but waveplates are arranged 
equally spaced by a distance greater than thickness 18 to include the 
peak-to-peak amplitude of the waves. The wave amplitude is the sum of the 
shear strokes taken over half of the period 16 and is electrically 
controlled by unison variation of the amplitudes A of potentials V1 . . . 
V6 of FIG. 3. 
FIG. 6 is a partially phantomed cutaway perspective view of an embodiment 
of the piezoelectric pump comprising waveplate stack 18 in housing 22. 
Fluid inlet and outlet 24, 26 permit the passage of fluid 20 through the 
pump. In accordance with the illustrated coordinate system, dimorph 
electrodes (omitted from the figure for clarity) lie parallel to y-z 
planes, fluid flows in direction x, and wave crest contact forces are 
controlled in direction z. 
FIG. 7 is a simplified schematic system control diagram for the 
piezoelectric pump, comprising pump 18, controller 34, resonator 
components 30, source of electrical power 36, and a source of external 
operating commands 38. Controller 34 distributes electrical power 44 and 
control signals 42 to resonating components 30 in accordance with 
operating instructions 38. In a preferred embodiment, each set of active 
electrodes of dimorphs that lie in a vertical y-z plane (FIG. 6) are 
connected together and are connected to a corresponding resonating 
component 30. Each said set is stimulated to electrical but not 
necessarily electromechanical resonance with a predetermined phase and 
amplitude. Controller 34 maintains the wave propagation in waveplate stack 
18. Optionally, state sensors internal to the waveplate stack 18 or its 
housing provide state signals 40 to controller 34 in order to better match 
the performance of the pump with the requirements of the operating 
instructions 36. Such state sensors include but are not limited to 
temperature sensors, pressure sensors, flow sensors, contact pressure 
sensors, fluid velocity sensors and the like. A preferred sensor comprises 
one or more dimorphs of a waveplate that are independently electrically 
connected to controller 34. Since dimorphs are electromechanically 
reciprocal, the electrical signal on the sensor dimorph is a measure of 
the state of stress on that dimorph, said state being easily related to 
one or more pump performance parameters that are used by the controller. A 
variant of the dimorph sensor is a sensor using only a portion of a 
dimorph, the active electrode being bifurcated at a predetermined 
location, and thereby allowing a prescribed portion of the dimorph to 
participate in fluid pumping. 
FIG. 8 is a plot of a traveling wave in the piezoelectric pump having 
constant amplitude 50, travel direction 20, and wavelength that changes 
progressively in direction 20 such that fluid segment volume, hereinafter 
called cell displacement, at 52 is greater than at 54. The quotient of 
cell displacement 52 and cell displacement 54 is referred to as the 
compression ratio. The pump has a fixed compression ratio when the 
connections of FIG. 7 are made to dimorphs groups, each group connecting a 
progressively fewer number of dimorphs in direction 20. 
The variant of the system controller of FIG. 7 having a matrix switch 
allows instantaneous reconnection of dimorphs into a variety of resonating 
phase groups, thereby allowing electrical control of the compression ratio 
and shape of the pressure gradient in the pump. Variable cell displacement 
allows the pump to maintain a predetermined cell pressure despite leakage 
when incompressible fluid is pumped. When compressible fluids such as gas 
are pumped, the progressive compression ratio allows control of the rate 
of compression, the initial, and the final pump operating pressures. 
Constant wave amplitude 50, also electrically controlled, allows a fixed 
housing dimension in the z direction (FIG. 6). 
FIG. 9 is a plot of a traveling wave in the piezoelectric pump having a 
constant period 58, and a linear taper of amplitude from a large amplitude 
56 to a small amplitude at 60. The crest envelope of each waveplate thus 
excited is a wedge shape, therefore requiring a housing 22 that tapers in 
z from inlet 24 to outlet 26 (FIG. 6). The taper is fixed once made, but 
is not restricted to a linear taper. The taper of amplitude affects a 
compression of fluid similar to the arrangement of FIG. 8. 
FIG. 10 combines amplitude taper from 62 to 68 and period taper from 64 to 
66 to achieve a greater compression ratio than otherwise available using 
either taper alone. 
An alternate embodiment of the pump employs a y housing taper from inlet to 
outlet to alter compression ratio. Other embodiments use any combination 
of the foredescribed tapers to provide a predetermined fluid compression 
and rate of compression. 
It is to be understood that reversing the sign of the electrical phases, or 
equivalently, reversing the order of the phases, reverses the direction of 
fluid pumping. 
The advantage of operating each y-z-plane set of dimorphs at resonance is 
reduced controller operating voltage, and greater operating efficiency. In 
a preferred transformer embodiment of the resonating component 30 (FIG. 
7), the low-voltage primary winding of the transformer is driven by solid 
state circuitry that operates with greater efficiency and reliability at 
low voltage and relatively high currents. The secondary of the transformer 
is connected in a loop with the essentially completely capacitive 
reactance of the dimorph set. The loop is tuned to electrical but not 
necessarily electromechanical resonance. At or near resonance, relatively 
high oscillating potentials are stimulated in the waveplates. Accompanying 
the high peak potentials are relatively large circulating reactive 
currents. The large circulating currents, temporarily stored in the 
dimorphs, are largely returned to and reused by the system each cycle. The 
loop resistance in preferred practice is made small in order to restrict 
the resistive dissipation of electrical power to a value below a desired 
level. 
It is clearly shown in FIG. 5 that the use of sine electrical waves and the 
resulting straight line segment approximation of sine curves made by the 
dimorphs of the waveplates does not provide the greatest possible pump 
throughput. A waveplate waveform such as a trapezoid would increase the 
cell displacement over that available when sine waves prevail. A variant 
of controller FIG. 7 replaces the previously described resonating 
components 30 with switch matrices. The switches, operated by controller 
34, rearrange connections between dimorphs or dimorph groups and separate 
sources of a variety of fixed-value potentials. A predetermined 
arrangement of switch states provides essentially any waveplate waveform 
allowed by the shear deformation capabilities of the constituent dimorphs. 
The direct current matrix switch control method proffers relatively great 
operational flexibility, but does not achieve the high efficiency as does 
the method of multi-phased resonance stimulation previously described 
because electrical charge is not stored and reused in as effective a 
manner. 
It is also to be understood than the pressure of contact between crests of 
waves of proximate waveplates is electrically adjustable. When the pump 
operates against a difference between outlet and inlet pressures, the 
pressure internal to the pump tends to force the crest contacts apart, 
thereby increasing leakage and retrograde flow. The controller, using 
pressure sensors, increases the electrical amplitude, but not necessarily 
the stroke amplitude of the wave crests in order to maintain retrograde 
fluid flow to a level lower than a prescribed amount. The energy consumed 
by the pump during operation is therefore somewhat dependent on the 
pumping conditions, the advantage being the use of less energy when 
pumping conditions are less demanding. 
The practice of the present invention entails the use of waveplate edge 
seals, lead insulation, and electrically insulating coatings for the 
waveplates. Encapsulation of waveplate edges comprises elastomers when the 
pumped fluids are compatible therewith. Only enough elastomer is used to 
provide shear compliance between waveplates and the housing wall. The 
elastomer seal also encapsulates and protects electrical leads. More 
chemically active fluids are handled by labyrinth or honed proximate 
waveplate edge surfaces. Low viscosity fluids require relatively small 
waveplate edge clearances that are maintained by selecting housing 
materials that match the linear thermal expansion properties of the 
waveplates. Insulating layers are applied to all surfaces of waveplates 
that operate immersed in electrically conductive, corrosive, or otherwise 
ionically active fluids. 
An advantage of connecting dimorphs in y-z planes (FIG. 6), wherein 
waveplate polarization directions alternate waveplate to waveplate, is 
that active dimorph electrodes, particularly those electrodes at or near 
wave crest contacts, remain at essentially the same electrical potential 
even though the magnitude of the potential may be relatively high. 
Proximate active electrodes, having the same potential, have essentially 
no tendency to initiate dielectric breakdown in the pumped fluid, or, if 
used, in the electrically insulating coatings on the waveplates. Another 
advantage of the aforedescribed dimrph connections is, given a 
predetermined uniformity of dimorph electromechanical response, that no 
rubbing occurs at wave crest contacts. Therefore, the use of elastomer or 
controlled-clearance waveplate edge seals, in combination with 
frictionless wave crest contacts, virtually precludes frictional wear as a 
life shortening mechanism. It appears in the figures that sharp edges are 
in contact at wave crests. This is due to the relative coarseness of 
waveplate electrical segmentation used to provide clarity of the figures. 
In practice, tens to hundreds of dimorphs operate in each moving fluid 
cell of the pump, thereby providing a sufficiently accurate approximation 
of a smoothly curved surface that sharp edge contact is avoided. 
As an example, an embodiment of a liquid pump having constant wave 
amplitude and constant wavelength, uses ferroelectric piezoelectric 
material with a shear coefficient d.sub.15 of 2.0 nm/volt and a maximum 
applied electric field intensity E of 20 kV per [cm]. Piezoelectric layers 
are 0.10 mm thick, making dimorphs 0.20 mm in size in the flow direction 
(x, FIG. 6). Waveplates are 0.76 mm thick (z direction), 140 of which are 
contained in a housing 110 mm square (y, z) by 61 mm (x). One hundred 
dimorphs are connected to 100 corresponding resonant stimulating circuits 
having phases differing by 2.pi./100 radians. Each wave has a length of 20 
mm, allowing three cells along the x flow direction. The displacement 
(volume delivered per pump cycle) of the pump is 0.057 cu.cm (volume of 
140 cells in a y-z plane). Waveplates are arranged on 0.79 mm centers, a 
distance that accommodates the 0.76 mm waveplate thickness and 0.025 mm 
wave p--p amplitude when excited to a peak voltage of 200 volts. This 
example pump passes approximately 3780 liters per minute when the 
resonance frequency is 8 kHz (disregarding crestcontact leakage). This 
example pump uses elastomer edge seals. Internal to the elastomer are 
cavities that fill with the pumped fluid via connecting conduits (not 
shown in figures) in order to balance the hydrostatic pressure in the area 
of the seals. The weight of this example pump, not including the weight of 
the electrical drive means, is approximately 12 kgr, comprising 5.5 kgr of 
waveplates and 6.5 kgr of housing. It is to be understood that this 
example uses a well known piezoelectric material (PZT-5H) evincing 
altogether ordinary electromechanical responsivity, and that substantially 
greater performance is expected when advantageous materials are 
substituted. 
The pump of the present invention encompasses a diverse class of pumping 
devices in which construction and operational parameters are varied to 
suit particular applications. It is to be understood that the detailed 
description is couched in terms of piezoelectric shear transducer material 
by way of example, whereas the use of any transducer material that 
produces an electromechanical action equivalent to that of the 
hereindescribed piezoelectric shear transducer material is considered to 
be within the scope of the present invention. 
Practice of the invention requires the use of grillages or porous members 
(omitted from figures) to support the inlet and outlet edges of waveplates 
against the forces of pumping, while allowing unrestricted fluid flow. 
Edge support includes elastic compliance sufficient to allow essentially 
unconstrained waveplate motion. Despite appearances, the relatively thin 
waveplates exert a relatively high fluid pressure during pumping without 
failure due to excess stress because wave amplitudes are relatively small 
and because pumping pressures are essentially completely canceled internal 
to the pump. Small wave amplitudes, typically a few per cent of the 
thickness of the waveplates, maintain the waveplates in a nearly flat 
condition. Nearly flat waveplates bear an edge-on hydrostatic pressure of 
pumping by placing the entire waveplate in compression. Of all physical 
strength properties of the brittle ceramics typically used for 
piezoelectric transducers, the compressive strength is by far the 
greatest. 
Pump embodiments of the present invention operate as bidirectional pumps, 
the flow direction being reversed with the sign of each electrical phase 
is reversed, or equivalently, when the order of phase application is 
reversed. 
Variants of the pump having progressively greater cell lengths and 
progressively smaller cell volumes use tenuous fluids for propulsion in 
deep space. The pump of the present invention is a positive displacement 
pump in the sense that a trapped volume of fluid is confined and propelled 
by the trapped fluid volumes, independent of changes of speed and 
pressure. Progressively greater cell lengths are conveniently made by 
progressively increasing the number of dimorphs that operate from the same 
electrical stimulus. As is well known, very high group velocities are 
achieved with commonly used frequencies when wavelengths are increased to 
relatively large values. Neglecting aerodynamic drag and boundary layer 
effects, packets of gas may be mechanically accelerated to very high 
velocities using the present invention. 
The last few groups of dimorphs near the exit end of a propulsion 
embodiment may have a direct current superimposed on the alternating 
current drive signal. The direct current component causes a net departure 
of the exit portion of the pump from straight. The transverse deflection 
of the exiting fluid path affects steering by electrical thrust vector 
control. A transition duct with a quarter turn about the x axis (FIG. 6) 
may direct a portion of the exiting fluid to a second outlet, thereby 
affording two-axis thrust vectoring. In addition to maintaining the 
passage of the thrust vector through the center of mass of a space 
vehicle, higher frequency components are added to the vectored thrust to 
cancel thrust-generated vibrations in the vehicle's structure. 
The electrical power generator embodiment of the present invention does not 
require modification of the device itself. A combination of kinetic and 
potential energy borne by a fluid passing through the device is converted 
to useful electrical power when the fluid accentuates the amplitudes of 
waveplate undulations. The controlling means maintains resonance and phase 
coordination of waveplates, while extracting all electrical energy that 
exceeds the input from the controller. Electrical power generation is 
particularly effective when waveplates are constructed of essentially 
completely electromechanically reciprocal transducer materials, such a 
piezoelectric shear dimorphs. Complete reciprocity, accompanied by 
negligible electrical and mechanical losses permit conversion of 
fluid-borne energy to electrical power with relatively high efficiency. As 
in the case of the pump embodiment of the present invention, the generator 
embodiment does not cause wave crests to rub, thereby providing a 
generator life that is shortened by few and benign mechanisms. 
The present invention also functions as an electrically controlled valve. 
The effective orifice of the valve is easily varied from wide open when 
excitation voltage is zero, to completely closed when crests of waveplates 
are pressed together at maximum voltage. Valves tolerant of a small amount 
of leakage are made with at least one closable pair of wave crests. Valves 
with relatively complete sealing are made with enough wave crests pressed 
together to constitute a labyrinth seal. A wave crest may consist of one 
or more pairs of broad surfaces of proximate dimorphs in forceful contact, 
the planar contact offering advantageously greater resistance to fluid 
leakage than an edge-to-plane contact. 
Wave crests are coated with malleable metal or resilient material in 
embodiments requiring a complete seal. The malleable metal sealing coating 
facilitates sealing in high vacuum valves. An advantage of the embodiment 
of the present invention using piezoelectric shear dimorphs and slowly 
varying direct current activation is that the shape of waveplates, once 
established by the placement of a prescribed amount of electric charge, 
remains until the quantity of charge is intentionally changed, or until 
the charge autodischarges through the known high but finite electrical 
resistivity of the piezoelectric material. Even allowing for 
autodischarge, the electrical energy requirements for a valve that is 
adjusted at a leisurely pace are essentially insignificant. 
An alternate function of the piezoelectric pump is use as a pressure, flow, 
and mass flow controller. The previously described electrical control of 
wave crest contact pressure is used to control crest clearance. When zero 
potential remains, each waveplate assumes its quiescent planar shape, 
thereby offering the least resistance to the passage of fluid, namely, a 
wide-open state. Any flow area from wide open to zero area is therefore 
electrically controllable. Sensors allow the controller to maintain a 
variety of states such as predetermined upstream pressure, prescribed 
downstream pressure, a desired flow velocity, and a useful mass flow of 
fluid. Flow and pressure control may also be used in any combination with 
the other actions of the present invention. 
The present invention operates as a filter wherein the sizes of the fluid 
passages between waveplates are adjustable electrically. The range of 
particle sizes trapped by the filter is adjusted from essentially zero 
diameter at maximum voltage to maximum diameter when zero voltage is 
applied. Trapped particles are easily released when the applied voltage is 
momentarily made zero. A variant of the filter embodiment sorts particles 
by connecting a valve embodiment in the fluid stream line and another 
valve in a fluid branch between the line valve and the filter. For 
example, after collecting particles of a certain size for a predetermined 
time interval, the line valve is closed and the branch valve is opened, 
after which the filter is self-cleaned by momentarily setting its voltage 
to zero (or eliciting pumping action). The batch of filtered particles is 
then passed from the filter to the branch, thereby affecting a first step 
in the method of sorting particles by size. Other configurations of the 
present invention incorporate valve, flow regulator, and filter functions 
into the same device by adding valved ports, also called fluid taps, at 
prescribed intervals along the flow path, constituting analogs to certain 
biological fluid functions such as those found in the mammalian kidney. 
The present invention functions as an emulsifier when wave crests are 
separated by a prescribed distance, and the wave propagation directions in 
even numbered waveplates are opposite to the propagation directions in odd 
numbered waveplates. Waves traveling in opposite directions impose an 
electrically controlled amount of fluid shear in each displacing cell. 
Fluid between waveplates is not trapped in the sense of trapping in the 
positive displacement pump embodiment, but fluid is sufficiently confined 
to render the fluid shearing action adequate to emulsify many combinations 
of quiescently immiscible fluids such as oil and water. When the wave 
propagation speed of one waveplate set differs from the other set, the 
emulsifier combines the action of pumping previously described with the 
action of emulsifying. The emulsifying action of the present invention is 
also applicable to the disruption of biological tissue and agglomerates. A 
variant of the electric drive means of the emulsifier superposes a high 
frequency signal on the normal drive signals to add an ultrasonic 
component to the wave motion. The ultrasonic component, at least in 
piezoelectric shear dimorphs, is efficiently transduced into the passing 
fluid, thereby enhancing the emulsifying and disbursing action of the 
waveplates. 
A grinding embodiment of the present invention uses the electrically 
controlled and undulated clearance between waveplates to crush large 
particles into smaller fragments, for example, as is commonly done with 
pigments. The peristaltic action of the waveplates provides a grinding 
action similar to a gyratory crusher, an action that is distinguished from 
that of the sliding of a grinding member past another proximate grinding 
member. Grinding embodiments may have an abrasion resistant coating 
applied to waveplates and other surface portions in contact with the 
ground medium. Grinders may have fineness stages within an integral 
waveplate structure, and alternatively may have fineness stages in 
separately housed waveplate sets in any combination of main stream and 
branch stream valves of the present invention. It will be noted that 
filtering, valving, and pumping action are inherent in the grinder and are 
used in any combination prescribed by a particular application. 
An embodiment of the present invention having electrically conducting 
coatings on waveplates (insulation internal thereto) functions as an 
electrically activated control means for the passage of high frequency 
electromagnetic waves, such as microwaves. For example, the waveplate 
edges at a waveguide branch may serve as a power divider wherein a portion 
of the incoming wave passes to a branch and the remainder of the wave 
passes between the waveplates. The magnitude of the divided portion is 
controlled by varying the spacing between wave crests. In addition, the 
waveplate edges on which the microwaves first impinge, a relatively 
responsive area, may be arranged in a desired pattern by predetermined 
changes of potentials applied to the waveplates. A closed end variant of 
the present invention is appended to a resonant electromagnetic cavity, 
allowing remote electrical tuning. 
An attenuating variant of the microwave controller has waveplates coated 
with material having a prescribed dielectric constant and absorptivity. By 
remote control, waveplate edges and wave crest spacing are electrically 
rearranged to alter microwave transmission and reflection properties. 
Advantageously, microwave electrical properties may be affected in 
approximately one tenth of the time required by an equivalent 
electromagnetic (solenoid and plunger) actuator, and in even less time 
when electrical energy temporarily stored as charge in the wave plates is 
suddenly released or mutually annihilated. 
A variant of the present invention having waveplate surfaces coated with 
optical materials provides the functions of collimation, attenuation, and 
spatial information encoding. The collimation function is provided when 
the optical coating is reflective, and the spaces between waveplates serve 
as optical wave guides analogous to optical fibers. Application of a 
prescribed set of voltages to the waveplates causes each waveplate to 
approximate a smooth curve, allowing the waveplates to collectively 
constitute a cylindrical lens. Metal coated waveplates may be arranged 
into a nested set of parabolic single or multiple grazing incidence 
mirrors for x-ray imaging. Two sets of waveplates, one following the 
second and rotated about the optical axis by one quarter turn, approximate 
a circular lens for full imaging capability. Two more sets of waveplates, 
electrically curved to approximate hyperbolas, further refine the focused 
image from the parabolic waveplates, a combination known to achieve 
greater image resolution than either one used separately. 
Light modulators with relatively fast response are constructed with thin 
waveplates. Such modulators require waveplates to exert no force other 
than that arising from the inertial force of reaction to accelerating 
during rearrangement from one optical transmission level to another. 
WAveplates may have predetermined incidence edge treatment to reduce 
reflection and absorption, for example, during Q-switching of a high power 
laser. In addition, waveplates may be cooled by passing fluid through 
internal ducts. 
A method of assembly of dimorphs into waveplates is the use of diffusion 
bonding of common metal ground electrodes. When true piezoelectric 
materials (intrinsically polarized) are used, diffusion bonding is 
generally affected at relatively high temperatures. With the 
lower-coercive-force ferroelectric materials, elements are shear polarized 
with temporary electrodes, metallized, then diffusion bonded at relatively 
low temperatures but with correspondingly longer bonding times and higher 
pressures. The preferred method is the alternating tenous deposition of 
metal electrodes and deposition-polarized transducer material, followed by 
slicing into waveplates. 
It is also clear that a single waveplate may be joined to another similar 
waveplate in order to enhance the pumping and general forcing capability 
of such joined, said performance being greater than either waveplate used 
alone. Two waveplates bonded with wave directions perpendicular constitute 
a deformable mirror, the forces in which are predominantly shear, all 
other forces being of such low influence as to be virtually negligible. 
Obviously, many modifications and variations of the present invention are 
possible in light of the above teachings. It is therefore to be understood 
that, within the scope of the appended claims, the invention may be 
practiced otherwise than as specifically described.