Piezoelectric valve

A piezoelectric valve for controlling fluid flow through valve ports comprises a fluidtight valve body and a diaphragm. The valve body defines valve ports, and the diaphragm includes a plurality of piezoelectric members, the members being adapted to be selectively piezoelectrically deflected in opposite directions in a plane of operation thereof to produce a cumulative excursion to selectively block or unblock the valve ports. The enhanced cumulative excursion enables valve ports of greater cross-sectional area to be employed.

BACKGROUND OF THE INVENTION 
The present invention relates to a piezoelectric valve for controlling 
fluid flow through valve ports and, more particularly, to such a valve 
having a plurality of piezoelectric members. 
Piezoelectric valves offer several advantages relative to comparable 
solenoid valves, a primary advantage being a much lower power consumption 
which renders the piezoelectric valve suitable for applications where the 
power consumption of a solenoid valve renders the latter unsuitable. For 
example, a piezoelectric valve is suitable for battery-powered operation 
in locations where its operation may be activated remotely by radio 
signals. The piezoelectric valve, like the conventional solenoid valve, 
may be used to control fluid flow through one valve port or two valve 
ports, depending upon the desired application. 
The diaphragm of a conventional piezoelectric valve comprises a flexible 
metal substrate to which a piezoelectric material is attached. A single 
piezoelectric diaphragm including a metal substrate approximately 0.005 
inch in thickness and piezoelectric material 0.007 inch in thickness 
provides approximately 0.010 inch of travel or excursion between the 
energized (200 volts D.C.) and de-energized states. Application of higher 
voltages than are appropriate for the piezoelectric material can result in 
piezoelectric material fracture or premature failure of the device. 
Assuming that the single diaphragm is to control two aligned facing valve 
ports, blocking one port in the energized state and the other valve port 
in the de-energized state, the diaphragm would include on each face, 
aligned with an adjacent valve port, a pad of an elastometic material to 
insure the fluidtight nature of the engagements between the diaphragm and 
the respective valve ports. Of the 0.010 inch excursion, approximately 
0.002 inch at the beginning and at the end of the excursion are "lost" or 
used to insure engagement of the elastometic material and the valve 
ports--that is, to insure a fluidtight connection between each pad and its 
respective valve port. As a result, the usable excursion is limited to 
approximately 0.006 inch for the diaphragm (0.006=0.010-(2 .times.0.002)). 
The significance of the usable excursion of the diaphragm arises out of the 
fact that geometrically the maximum usable diameter of the valve port 
cannot exceed four times the effective excursion. More particularly, the 
area through which fluid flow from the valve port can be controlled is 
effectively limited by the surface area of the sidewall of an imaginary 
column created between the open valve port and the adjacent surface of the 
diaphragm (that is, the surface area of an imaginary column having a 
diameter equal to the effective diameter of the valve port through which 
fluid flows and a height equal to the usable excursion of the diaphragm) 
so that 
##EQU1## 
where D is the diameter of the valve port (and imaginary cylinder), and X 
is the excursion (and height of the imaginary cylinder). 
By way of example, a usable excursion of 0.006 inch corresponds to a 
maximum valve port diameter of 0.024 inch. Thus, the aforementioned 
diaphragm having approximately 0.010 inch of total travel is limited to a 
valve port diameter of 0.024 inch, assuming that the diaphragm was 
intended to block one valve port at each end of its excursion. Clearly 
this limitation severely restricts the volume of fluid which can be 
controlled at practical fluid flow rates by a piezoelectric valve, and the 
need remains for a piezoelectric valve which will enable a diaphragm to 
control valve ports of greater cross-sectional area and corresponding flow 
rates than is possible with conventional piezoelectric valves. 
Accordingly, it is an object of the present invention to provide a 
piezoelectric valve in which the effective usable excursion of the 
diaphragm exceeds the usable excursion of a conventional piezoelectric 
valve using a similar diaphragm. 
Another object is to provide such a piezoelectric valve in which the 
effective usable excursion is more than twice the usable excursion of a 
conventional piezoelectric valve using a similar diaphragm. 
A further object is to provide such a piezoelectric valve which is capable 
of controlling a valve port having a cross-sectional area greater than the 
maximum cross-sectional area for a valve port in a conventional 
piezoelectric valve using a similar diaphragm. 
It is also an object to provide such a piezoelectric valve which is of 
compact and sturdy design, inexpensive to manufacture and easy to 
maintain. 
SUMMARY OF THE INVENTION 
It has now been found that the above and related objects of the present 
invention are obtained in a piezoelectric valve for controlling fluid flow 
through a valve port. The piezoelectric valve comprises a fluidtight valve 
body defining a valve port. A diaphragm disposed within the valve body 
includes a plurality of piezoelectric members, the members being adapted 
to be selectively piezoelectrically deflected in opposite directions in a 
plane of operation thereof to produce a cumulative excursion to 
selectively block or unblock the valve port. Electrical means are 
operatively connected to the members for piezoelectrically deflecting the 
same. Preferably the members are adapted to be selectively 
piezoelectrically deflected between a first orientation wherein the 
members are bowed apart and a second orientation wherein the members are 
generally parallel, the members assuming the first orientation when the 
electrical means are energized to piezoelectrically deflect the members 
and the second orientation when the electrical means are de-energized so 
said members are not piezoelectrically deflected. The members may be 
substantially planar when not piezoelectrically deflected and 
substantially curved when piezoelectrically deflected. 
In a preferred embodiment, the piezoelectric valve controls fluid flow 
through the valve port and a second valve port. The valve body further 
defines a second valve port aligned with the valve port, and the valve 
port is an inlet port and the second valve port is an exhaust port. 
Piezoelectric deflection of the members to selectively block or unblock 
the valve port also selectively unblocks or blocks the second valve port. 
Where there are only a pair of the members, the valve port extends through 
one of the members, and the other of the members has a first face for 
selectively blocking or unblocking the valve port and an opposed second 
face for selectively blocking or unblocking the second valve port. 
Preferably the one member has a central annular portion fixed to the valve 
body about the valve port to thereby substantially double the effective 
excursion of the other member. An annular element with opposed faces has 
one face secured to the central annular portion of the one member and the 
opposite face secured to the valve body about the valve port. Means are 
provided for biasing the members towards the valve port. 
In a preferred embodiment, the valve body additionally defines a third 
valve port, the third valve port being an inlet/outlet port in fluid 
communication with an unblocked one of the valve port and the second valve 
port. The diaphragm additionally includes flow channel means disposed 
intermediate the members to space the members apart and enable the flow of 
fluid intermediate the members between the center thereof and the 
periphery thereof. The flow channel means is annular in configuration and 
preferably a convoluted washer. The valve port extends through the central 
annular portion of the one member. An unblocked valve port communicates 
with the end of the flow channel means adjacent the center of the members, 
an unblocked second valve port communicates with the third valve port 
directly, and the third valve port communicates with the end of the flow 
channel means adjacent the periphery of the members, thereby providing 
communication between the third valve port and alternately an unblocked 
one of the valve port and the second valve port. The valve body limits the 
excursion of one of the members and blocks such excursion in a given 
direction and thereby substantially doubles the effective excursion of the 
other of the members in the opposite direction and substantially more than 
doubles its usable effective excursion. Means are provided for biasing the 
members in the given direction. 
The electrical means are functionally electrically connected to a common 
electrical circuit for simultaneous piezoelectric deflection of the 
plurality of members.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawing, and in particular to FIG. I thereof, therein 
illustrated is a piezoelectric valve, generally designated by the 
reference numeral 10, according to the present invention. The valve 10 is 
a 3-way valve adapted to control fluid flow among a first valve port 12, 
an aligned and opposed second valve port 14, (see FIGS. 2-3 and 5) and a 
transverse third valve port 16. The first valve port 12, when unblocked, 
acts as an inlet port and is in fluid communication with the third valve 
port 16. The second valve port 14, when unblocked, acts as an exhaust port 
and is in fluid communication with the third valve port 16. The third 
valve port 16 acts as an inlet/outlet port (that is, at times it acts as 
an inlet port and at times it acts as an outlet port) and is never 
blocked. By way of contrast with the third port 16, as will become clear 
hereinafter, one or the other of the first and second ports 12, 14 is 
blocked at any given instant, assuming instantaneous deflections and 
returns by the deflecting valve members. 
Such a 3-way valve finds utility in a great many applications. For example, 
such a valve may be used to control the passage of air or other fluid into 
a pneumatic cylinder (not shown) and the expulsion of fluid from the 
cylinder in response to the restorative force of a spring or similar 
restoring means. In such an application the third or inlet/outlet port 16 
is connected to the pneumatic cylinder. With the valve in one functional 
orientation air or fluid entering the first or inlet port 12 is introduced 
into the cylinder via the inlet/outlet port 16, the second or exhaust port 
14 being blocked, while with the valve in the alternative orientation 
fluids are expelled from the cylinder into the inlet/outlet port 16 via 
the exhaust port 14, the inlet port 12 being blocked. The 3 way valve of 
the present invention is obviously useful in a variety of other 
applications and two valves may be used in tandem to provide 4-way 
operation wherein, for example, when one valve is actuated a pneumatic 
cylinder is caused to extend and when the other valve is actuated the 
cylinder is caused to retract by the force exerted by air or another fluid 
(rather than by a spring). Furthermore, the principles of the present 
invention are equally applicable to 2-way valves. 
The valve 10 of the present invention includes a fluidtight valve body or 
housing generally designated 20 and composed of an inlet section 22 
defining inlet port 12 and an exhaust section 24 defining exhaust port 14. 
While the size of the housing 20 will vary with particular applications 
the housing may be, for example, on the order of 1 5/8.times.1 5/8.times.1 
inches. In each corner of the housing 20 a screw 26 extends through the 
inlet section 22 and into the exhaust section 24 to maintain the inlet and 
exhaust sections 22, 24 in close proximity. Alternatively, the two 
sections may be joined by welding, adhesives, or other techniques for 
sealing a fluidtight housing appropriate to the material, the fluids, the 
pressures involved, etc. 
Referring now as well to FIGS. 2-5, each of the adjacent faces of the inlet 
and exhaust sections 22, 24 defines a recess 28, 30, respectively. The two 
recesses 28, 30 together define a single chamber 32. An 0-ring or other 
sealant 34 is disposed within the chamber 32 to insure a fluidtight 
connection therebetween about the periphery of the chamber 32. 
The first and second ports 12, 14 are internally threaded and adapted to 
receive therein externally threaded ferrules 40, 42, respectively. Each 
ferrule 40, 42 defines a hollow cylindrical central core 44 having an 
outer end 46 (remote from the chamber 32) and an inner end 48 (adjacent 
the chamber 32). The outer end 46 of each ferrule 40, 42 is slotted to 
receive a screwdriver or other adjusting tool (not shown) so that the 
externally threaded ferrule 40, 42 may be rotated relative to the 
internally threaded valve port 12, 14 to control the positioning of the 
inner end 48 along the port axis, within either the valve port 12, 14 or 
the chamber 32. As illustrated in FIGS. 2 and 3, the inner end 48 of the 
inlet ferrule 40 (that is, the ferrule 40 within the inlet port 12) is 
well within the chamber 32, while the inner end 48 of the exhaust ferrule 
42 (that is, the ferrule 42 within the exhaust port 14) is still 
substantially within the exhaust port 14. It will be appreciated that the 
effective diameters of the valve ports 12, 14 are the inner diameters of 
the cores 44 of the ferrules 40, 42 as the fluids traverse the-valve pots 
12, 14 only through such cores 44. 
The ferrules 40, 42, like the housing sections 22, 24, may be made of metal 
or other rigid material (such as particular plastics), depending upon the 
particular application intended and, in particular, the fluids to be 
encountered. For example, corrosive fluids will require the deployment of 
non-corrosible material for the housing sections 22, 24, the ferrules 40, 
42, and such other portions of the valve 10 as are exposed to the 
corrosive fluid. 
Unlike the inlet and exhaust ports 12, 14, the inlet/outlet port 16 
contains no ferrule. As this port 16 is never blocked, there is no need to 
provide an adjustable effective disposition. Nonetheless, the inlet/outlet 
port 16 may be internally threaded to facilitate the engagement therein of 
externally threaded members for connecting it with a remote device such as 
a pneumatic cylinder. As illustrated, the inlet/outlet port 16 extends 
transverse to the aligned inlet and exhaust ports 12, 14, but alternate 
orientations are equally useful. 
Disposed within the chamber 32 of valve body 20 is a diaphragm, generally 
designated 50. The diaphragm 50 includes a plurality of piezoelectric 
members generally designated 52, 54. Generally a pair of piezoelectric 
members suffices but, where additional excursion is required, a greater 
number of piezoelectric members may be used, the members being arranged so 
that, for an end piezoelectric member, the excursions of each 
piezoelectric member are cumulative. As is conventional in a piezoelectric 
valve, each piezoelectric member 52, 54 is composed of a thin, 
electrically conductive substrate 56, such as a metal, having disposed 
thereon on one side in a thin layer a piezoelectric material 58. Both the 
substrate 56 and the piezoelectric material 58 have the configuration of a 
disc in the illustrated embodiment, although other configurations may be 
used as well. The piezoelectric material 58 preferably does not extend as 
far as the periphery of the substrate 56. The piezoelectric material 58 of 
each member 52, 54 face each other --that is, they are on the inner 
surfaces of the piezoelectric members 52, 54, while the substrates 56 face 
the valve ports 12, 14--that is, they are on the outer surfaces of the 
members 52, 54. When appropriately energized (for example, by the 
application of a 200 volt dc potential), each piezoelectric material 58 
contracts and causes its substrate 56 to bow outwardly and assume a convex 
configuration. Clearly the nature of the connection between the 
piezoelectric material 58 and the substrate 56 must be flexible in order 
to accommodate the desired deflection. 
It is a critical feature of the present invention that adjacent 
piezoelectric members 52, 54 are so arranged in the diaphragm 50 that they 
are adapted to be selectively piezoelectrically deflected in opposite 
directions in a plane of operation thereof to produce a cumulative 
excursion, thereby to selectively block or unblock a valve port 12, 14. 
More particularly, in the diaphragm 50 the piezoelectric members 52, 54 
are adapted to be selectively piezoelectrically deflected between a first 
orientation wherein the members 52, 54 are substantially curved and bowed 
apart, as shown in FIG. 3, and a second orientation wherein the members 
52, 54 are substantially planar and generally parallel, as shown in FIG. 
2. The members 52, 54 assume the first orientation when they are energized 
for piezoelectric deflection and the second orientation when they are not 
energized and thus not piezoelectrically deflected. 
The diaphragm 50 is of lesser diameter than the chamber 32 and slightly 
spaced radially inwardly from the surrounding surface of the housing 20 
(and in particular the inlet section 22) so that the chamber 32 defines a 
travel path for at least a portion of the diaphragm 50, that is, the 
portion of the diaphragm 50 which is not fixedly secured to the housing 20 
in the manner described immediately below. 
Inlet piezoelectric member 52 (that is, the member 52 adjacent the inlet 
port 12) defines a central aperture 60 therethrough to enable passage of 
the core 44 of inlet ferrule 40 to pass therethrough. A thin, flat, 
centrally apertured annular member 62, such as a washer, annular spacer, 
annular piece of tape, or an adhesive, is disposed intermediate a margin 
of the inner surface of the inlet section 22 about the inlet port 12 and a 
margin of the outer surface of the substrate 56 of the inlet piezoelectric 
member 52 about the aperture 60. The annular element 62 fixedly secures 
the inlet piezoelectric member 52 to the inlet section 22 and may 
conveniently be formed with adhesive on each face thereof for this 
purpose. Securing the inlet piezoelectric member 52 to the inlet section 
22 in this manner insures a continued alignment of the inlet port 12 and 
the inlet piezoelectric member aperture 60, this alignment being more 
tenuous when the diaphragm 50 is allowed to float freely in the chamber 32 
without being securely anchored to the housing 20. While the annular 
element 62 provides one means for securing the diaphragm 50 to the inlet 
section 22 to insure continued alignment of inlet port 12 and aperture 60, 
yet providing sufficient flexibility and freedom of movement to allow the 
piezoelectric member 52 to deflect; clearly other means may be used to 
this end. 
Secured by adhesives or the like to opposite faces of exhaust piezoelectric 
member 54 (that is, the piezoelectric member 54 adjacent the exhaust port 
14) for movement therewith are an elastometic inlet pad 72, secured to 
piezoelectric material 58 facing the inlet port 12 and aligned with the 
inner core end 48 of inlet ferrule 40, and an elastometic exhaust pad 74, 
secured to substrate 56 facing the exhaust port 14 and aligned with the 
inner core end 48 of exhaust ferrule 42. The pads 72, 74 act as valve 
seats for the ferrules 40, 42. While the use of separate inlet and exhaust 
pads 72, 74 is preferred, clearly alternative arrangements may be 
employed. For example, the exhaust piezoelectric member 54 may be 
apertured and a single elastometic element may extend through the aperture 
so that its ends act as the inlet and exhaust pads 72, 74 of elastometic 
material secured to the piezoelectric material 58 and substrate 56, 
respectively. It will be appreciated that, while the central portion of 
the inlet piezoelectric member 52 is fixedly secured to the housing inlet 
section 22, the central portion (that is, the elastometic pads 72, 74) of 
the exhaust piezoelectric member 54 is free to move in both directions 
along the axis defined by the inlet and exhaust ferrule cores 44. 
The diaphragm 50 further includes flow channel means 80 disposed 
intermediate the piezoelectric members 52, 54 (and in particular 
intermediate the facing surfaces of substrates 56) to enable the flow of 
fluid intermediate the members 52, 54 between the center thereof and the 
periphery thereof. The flow channel means 80 may be adhesively or 
otherwise secured to both piezoelectric members 52, 54 to define a 
subassembly for movement as a unit. The flow channel means 80 defines a 
path intermediate the piezoelectric members 52, 54 from adjacent the 
center thereof, where fluid is discharged from the inlet ferrule inner end 
48, to adjacent the periphery thereof, where fluid is received by the 
chamber 32. A preferred flow channel means 80 is a convoluted washer 
member, the radially inner surface of which is preferably at least 
slightly spaced radially outwardly beyond the radially outer surface of 
the piezoelectric material 58 and the convolutions 81 of which are 
effective to permit fluid flow from a center point (aligned with the inlet 
ferrule core end 48) outwardly past the periphery of the piezoelectric 
members 52, 54 into the chamber 32 and ultimately, in or out inlet/outlet 
port 16. The diaphragm 50 is of lesser diameter than the chamber 32 and 
slightly spaced radially inwardly from the surrounding surface of the 
inlet section 22 so that fluid discharged at the periphery of the 
diaphragm 50 enters the chamber 32 and hence can flow into the 
inlet/outlet port 16. Accordingly, inlet/outlet port 16 is in fluid 
communication alternately with an unblocked one of the inlet port 12 and 
the exhaust port 14. The fluid communication between the inlet/outlet port 
16 and the exhaust port 14 is direct via chamber 32, whereas the fluid 
communication between the inlet/outlet port 16 and the inlet port 12 is 
indirect, via the flow channel means 80 and chamber 32. Alternatively, the 
flow channel means can be a series of apertures formed in the exhaust 
piezoelectric member 54, radially outwardly beyond the elastometic pads 
72, 74, or any other means by which fluid can flow past the exhaust 
piezoelectric member 54. 
A spiral compression spring 84 has its large base seated in a groove of the 
output section 24 surrounding the exhaust port 14 and its small end 
bearing on the substrate 56 of the exhaust piezoelectric member 54 about 
the elastometic pad 74 thereon (but spaced sufficiently from the pad 74 so 
as not to interfere with its functioning). The spring 84 biases the 
diaphragm 50 towards the inlet valve port 12 so as to unblock the exhaust 
port 14 and block the -inlet port 12 when the piezoelectric members 52, 54 
are not energized (see FIG. 2). The surface of the inlet section 22 about 
inlet port 12 (in conjunction with annular member 62) acts on the central 
portion of the inlet piezoelectric member 52, limiting movement of the 
member 52 towards the inlet port 12. 
Each of the piezoelectric members 52, 54 is connected to an annular power 
supply 90 disposed in the external face of the inlet section 22 by a wire 
92 engaging the substrate 56 and a wire 94 engaging the piezoelectric 
material 58. To insure simultaneous energization of both piezoelectric 
members 52, 54, the two wires 94 are connected to the power supply 90 by a 
single common wire 96 and the two wires 92 are connected to the power 
supply 90 by a single common wire 98. In order to enable passage of the 
wires 96, 98 from the chamber 32 to the power supply 90, a small hole 100 
is provided in the wall of inlet section 22 separating the power supply 90 
and the chamber 32. The hole 100 may be sealed about the wires 96, 98 or, 
alternatively, the power supply 90 may be used to block the hole 100 to 
prevent fluid egress. 
The voltage and AC/DC nature of power supply 90 may vary with the 
particular application and the particular diaphragm 50 employed in the 
valve. The power supply 90 is fed by a power source (not shown). The power 
supply 90 may be activated and de-activated remotely by radio signals. For 
example, upon receipt of the appropriate input signals, the power supply 
90 may deliver an output signal of appropriate potential across each of 
the piezoelectric members 52, 54 via the appropriate wires 92, 94, 96, 98. 
Hard wired signals may also be used as input to control operation of the 
power supply 90. The power supply may, among other functions, convert the 
input signal to an appropriate output voltage for energizing the 
piezoelectric members, typically in the range of 200 volts dc. While other 
voltages may be employed, the voltage must be high enough to effect 
deflection of the piezoelectric members 52, 54, but low enough not to 
overstress them so that they do not return to their original orientation 
or develop cracks. 
To initialize the valve 10 prior to use, the ferrules 40, 42 are rotated by 
means of the slotted outer core ends 46 so that the inner core ends 48 are 
positioned such that in the deenergized state flow through inlet port 12 
is completely blocked and in the energized state flow through exhaust port 
14 is entirely blocked. Inlet/exhaust port 16 is secured to the desired 
external device, such as a pneumatic cylinder. Where desired, an 
appropriate fluid inlet source (not shown) may be connected to the outer 
portion of inlet port 12, and an appropriate exhaust receptacle (not 
shown) may be secured to the outer portion of exhaust port 14. 
Alternatively, any one or more of the ports 12, 14, 16 may communicate 
directly with the ambient atmosphere. 
Referring now in particular to FIG. 2, when the valve 10 is in the 
deenergized state so that the-power supply 90 is not energizing the 
piezoelectric members 52, 54, the piezoelectric members 52, 54 are 
substantially planar and parallel. The natural or at rest (i.e., 
deenergized) configuration of the exhaust piezoelectric member 54, secured 
to the housing 20 by annular member 62 and assisted by the bias exerted 
thereon by spring 84, causes the elastometic pad 72 to block the inlet 
ferrule inner end 48 to preclude fluid flow through inlet port 12. At the 
same time, exhaust gases discharged in the direction of arrow 102 into the 
inlet/outlet port 16 (here acting as an inlet port) enter the chamber 32 
and subsequently exhaust ferrule inner end 48 for discharge through 
exhaust port 14 in the direction of arrow 104. 
Referring now in particular to FIG. 3, when the valve 10 is in the 
energized state so that the piezoelectric members 52, 54 are energized by 
power supply 90, the piezoelectric members 52, 54 are substantially curved 
and bow outwardly, the inlet piezoelectric member 52 towards the inlet 
port 12 and the exhaust piezoelectric member 54 towards the exhaust port 
14. The inlet piezoelectric member 52 is actually fixed to the inlet 
section 22 about the inlet port 12 by means of the annular member 62 so 
that its outward bowing results in deflection of the transverse centerline 
of the diaphragm 50 (the transverse centerline being perpendicular to the 
axis of the inlet and exhaust ports 12, 14) towards the exhaust port 14. 
Cumulative or additive to this excursion of the inlet piezoelectric member 
52 is the outward bowing of the exhaust piezoelectric member 54 against 
the bias of the compression spring 84. The cumulative effect is to space 
the inlet-side elastometic pad 72 from the inlet ferrule inner end 48 and 
to cause the exhaust-side elastometic pad 74 to block the exhaust ferrule 
inner end 48 and thereby terminate fluid flow through the exhaust port 14. 
Fluid emerging from the inlet ferrule inner end 48 in the direction of 
arrow 106 is discharged intermediate the piezoelectric members 52, 54 at 
the center thereof, eventually passes along the various convolutions 81 of 
the involuted flow channel means 80 to the periphery of the piezoelectric 
members 52, 54 and ultimately discharges into the chamber 32. As the 
exhaust port 14 is blocked, the fluid flows out of the inlet/outlet port 
16 to the external pneumatic cylinder in the direction of arrow 108. 
Once the power supply 90 ceases to energize the piezoelectric material 58 
of the piezoelectric members 52, 54, the piezoelectric members return to 
their original configuration, assisted by the urging bias of spring 84, 
with the transverse centerline of the entire diaphragm 50 returning to its 
original position. 
The primary advantage of the piezoelectric valve of the present invention 
relative to the conventional piezoelectric valve using a similar diaphragm 
will become apparent from the following discussion. It will be recalled 
from the previous discussion that in a conventional piezoelectric valve 
having a diaphragm of a single piezoelectric member with an excursion of 
0.010 inch the usable excursion was only 0.006 inch due to the need to 
allow a "lost" excursion of 0.002 inch at each end for engagement of the 
piezoelectric member with a valve port (or, more particularly, the 
engagement of the elastometic pad of the piezoelectric member with the 
ferrule core inner ends). By way of contrast, in a valve according to the 
present invention, the total excursion of an end piezoelectric member of a 
diaphragm composed of N piezoelectric members (similar to those specified 
in previous discussion) would be N.times.0.010 inch. For a valve according 
to the present invention having two such piezoelectric members, the total 
excursion is 2.times.0.010 or 0.020 inch. As there are still only two 
elastometic pads to engage the two ferrule inner ends, the "lost" 
excursion remains 2.times.0.002 or 0.004 inch. Accordingly, the maximum 
usable excursion of the valve is 0.020-0.004 or 0.016 inch, substantially 
more than double the maximum usable excursion of a conventional 
piezoelectric valve with a single piezoelectric member of the same 
configuration (that is, substantially more than 2.times.0.006 or 0.012 
inch). Significantly, the increase in excursion permits a substantial 
increase in the diameter of the valve port. In the example given here, 
when there are two piezoelectric members, the maximum usable valve port 
diameter is 0.064 inch instead of the 0.024 inch when a single 
piezoelectric member is used. 
As a result of the enhanced maximum usable excursion, the piezoelectric 
valve of the present invention may be used to control valve ports (i.e., 
ferrule inner ends) of substantially greater cross-section than a 
conventional piezoelectric valve using a single comparable piezoelectric 
member and a comparable applied voltage, and to do so while consuming only 
a fraction of the power of a solenoid valve. In fact, since fluid flow 
through the valve is proportional to the area of the valve port, an 
increase in diameter of the valve port to 0.064 inch from 0.024 inch 
results in an increase in fluid flow of in excess of 7 times. 
Alternatively, the present invention enables the use of a lower voltage 
applied to the piezoelectric members, thus reducing the total travel of 
each piezoelectric member and thereby enhancing its fatigue life. 
It will be apparent that many modifications may be made in the valve 
without departing from the principles of the present invention. For 
example, diaphragm 50 may be turned around 180.degree. such that the 
apertured piezoelectric member 52 is secured to the exhaust section 24 
about the exhaust port 14 and the disposition of the ferrules 
appropriately adjusted so that the diaphragm in the deenergized 
orientation blocks the exhaust port rather than the inlet port and in the 
energized orientation blocks the inlet port rather than the exhaust port. 
Or the diaphragm may contain more than two piezoelectric members 52, 54, 
the piezoelectric members preferably being arranged with adjacent members 
bowing in opposite directions when energized so that the cumulative 
excursion of one end member of the diaphragm is substantially equal to the 
sum of the individual excursions of the several piezoelectric members. 
To summarize, the present invention provides a piezoelectric valve in which 
the effective usable excursion of the diaphragm exceeds the usable 
excursion of a conventional piezoelectric valve using a similar diaphragm, 
providing at least twice the usable excursion and enabling use of the 
valve to control a valve port having a greater cross-sectional area than 
the a valve port in a conventional piezoelectric valve using a similar 
diaphragm, and hence a greater flow rate through the valve, or to enhance 
fatigue life without sacrificing flow. The piezoelectric valve is of 
compact and sturdy design, inexpensive to manufacture and easy to 
maintain. 
It will be appreciated that the drawings are not to scale and that the 
separation between the piezoelectric members and the size of the flow 
channel means have been greatly exaggerated for illustrative purposes. 
For the purposes of clarity of explanation and illustration, the 
piezoelectric members 52, 54 have been described throughout the 
specification and claims as being substantially or generally planar and 
substantially or generally parallel in their non-energized state and shown 
as planar and parallel in their non-energized state in FIG. 2. This will 
normally be the case where the piezoelectric member 54 is stiff relative 
to the force of compression spring 84 bearing thereon. However it will be 
understood that where the force of compression spring 84 is high relative 
to the stiffness of piezoelectric member 54, the compression spring 84 
will cause the central portion of piezoelectric member 54 to bow slightly 
towards the opposed central portion of piezoelectric member 52. A 
reference to the piezoelectric members 52, 54 being substantially or 
generally planar and substantially or generally parallel, as these terms 
are used herein, encompasses such a slight bowing. 
Now that the preferred embodiments of the present invention have been shown 
and described in detail, various modifications and improvements thereon 
will become readily apparent to those skilled in the art. Accordingly, the 
appended claims are to be construed broadly and in a manner consistent 
with the spirit and scope of the present invention.