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Claims  |
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I claim:
1. A piezoelectric valve for controlling fluid flow through a valve port,
comprising:
(A) a fluid-tight valve body defining a pair of valve ports;
(B) a diaphragm disposed within said valve body and including a plurality
of piezoelectric members, said members being selectively piezoelectrically
deflectable in opposite directions in a plane of operation thereof in
response to voltages applied thereto to produce a cumulative excursion to
selectively assume one of two functionally opposite positions relative to
one of said valve ports, said members in one of said positions operatively
blocking said one valve port and in the other of said positions unblocking
said one valve port, at least one of said members being disposed
intermediate said pair of valve ports; and
(C) electrical means operatively connected to said members for
piezoelectrically deflecting the same to one of said positions.
2. The piezoelectric valve of claim 1 wherein said members are adapted to
be selectively piezoelectrically deflected between a first orientation
wherein said members are bowed apart and a second orientation wherein said
members are generally parallel, said members assuming said first
orientation when said electrical means are energized to piezoelectrically
deflect said members and said second orientation when said electrical
means are de-energized so said members are not piezoelectrically
deflected.
3. The piezoelectric valve of claim 1 for controlling a fluid flow through
said valve port and a second valve port, wherein said valve body further
defines a second valve port aligned with said valve port, said valve port
is an inlet port and said second valve port is an exhaust port, said valve
port and second valve port are said pair of valve ports, and at least one
of said members is disposed intermediate said valve port and second valve
port.
4. The piezoelectric valve of claim 3 wherein piezoelectric deflection of
said members to selectively block or unblock said valve port also
selectively unblocks or blocks said second valve port.
5. The piezoelectric valve of claim 1 for providing 3-way valve action for
controlling a fluid flow among said valve port and second and third valve
ports, wherein said valve body further defines second and third valve
ports.
6. The piezoelectric valve of claim 1 wherein said valve body limits the
excursion of one of said members.
7. The piezoelectric valve of claim 6 wherein said valve body blocks the
excursion of one of said members in a given direction and thereby
substantially doubles the effective excursion of the other of said members
in the opposite direction.
8. The piezoelectric valve of claim 7 wherein said valve body blocks the
excursion of said one member in a given direction and thereby
substantially more than doubles the effective usable excursion of said
other member in the opposite direction.
9. The piezoelectric valve of claim 7 additionally comprising means for
biasing said members in the given direction.
10. The piezoelectric valve of claim 1 wherein said electrical means are
functionally electrically connected to a common electrical circuit for
simultaneous piezoelectric deflection of said plurality of members.
11. The piezoelectric valve of claim 1 wherein said members are
substantially planar when not piezoelectrically deflected and
substantially curved when piezoelectrically deflected.
12. The piezoelectric valve of claim 1 wherein said valve ports are in
spaced and generally opposite disposition to each other.
13. A piezoelectric valve for controlling fluid flow through a valve port
and a second valve port, comprising:
(A) a fluid-tight valve body defining a valve port and a second valve port
aligned with said valve port, said valve port being an inlet port and said
second valve port being an exhaust port;
(B) a diaphragm disposed within said valve body and including at least a
pair of piezoelectric members, said members being selectively
piezoelectrically deflectable in opposite directions in a plane of
operation thereof in response to voltages applied thereto to produce a
cumulative excursion to selectively assume one of two functionally
opposite positions relative to said valve port and said second valve port,
said members in one of said positions operatively blocking said valve port
and operatively unblocking said second valve port and in the other of said
positions operatively unblocking said valve port and operatively blocking
said second valve port, said valve port extending through one of said pair
of said members, and the other of said pair of said members having a first
face for selectively blocking or unblocking said valve port and an opposed
second face for selectively blocking or unblocking said second valve port;
and
(C) electrical means operatively connected to said members for
piezoelectrically deflecting the same to one of said positions.
14. The piezoelectric valve of claim 13 wherein said one member has a
central annular portion fixed to said valve body about said valve port to
thereby substantially double the effective excursion of said other member.
15. The piezoelectric valve of claim 14 additionally including an annular
element having opposed faces, one face being secured to said central
annular portion of said one member and the opposite face being secured to
said valve body about said valve port.
16. The piezoelectric valve of claim 14 additionally comprising means for
biasing said members towards said valve port.
17. The piezoelectric valve of claim 14 providing 3-way valve action for
controlling a fluid flow among said valve port, said second valve port and
a third valve port, wherein said valve body additionally defines said
third valve port, said third valve port being an inlet/outlet port, said
third valve port being in fluid communication with an unblocked one of
said valve port and said second valve port.
18. The piezoelectric valve of claim 17 wherein said diaphragm additionally
includes flow channel means disposed intermediate said members to space
the members apart and enable the flow of fluid intermediate said members
between the center thereof and the periphery thereof.
19. The piezoelectric valve of claim 18 wherein said valve port extends
through said central annular portion of said one member, and an unblocked
valve port communicates with the end of said flow channel means adjacent
the center of said members, an unblocked second valve port communicates
with said third valve port directly, and said third valve port
communicates with the end of said flow channel means adjacent the
periphery of said members, thereby providing fluid communication between
said third valve port and alternately an unblocked one of said valve port
and said second valve port.
20. The piezoelectric valve of claim 18 wherein said flow channel means is
annular in configuration.
21. The piezoelectric valve of claim 20 wherein said flow channel means is
a convoluted washer.
22. A piezoelectric valve for controlling fluid flow through a valve port,
comprising:
(A) a fluid-tight valve body defining a pair of spaced and generally
opposed valve ports;
(B) a diaphragm including at least a pair of piezoelectric members and a
flow channel means disposed between and spacing said members apart, said
members being selectively piezoelectrically deflectable in opposite
directions in a plane of operation thereof in response to voltages applied
thereto to produce a cumulative excursion to selectively assume one of two
functionally opposite positions relative to one of said valve ports, said
members in one of said positions operatively blocking said one valve port
and in the other of said positions operatively unblocking said one valve
port, said valve body precluding the excursion of one of said members in a
given direction and thereby substantially doubling the effective excursion
of the other of said members in the opposite direction, at least one of
said members being physically disposed intermediate said pair of valve
ports; and
(C) electrical means operatively connected to said members for
piezoelectrically deflecting the same to one of said positions, said
electrical means being functionally electrically connected to a common
electrical circuit for simultaneous piezoelectric deflection of both of
said members, said members being substantially planar when not
piezoelectrically deflected and substantially curved when
piezoelectircally deflected.
23. A piezoelectric valve for providing three-way valve action for
controlling a fluid flow among first, second and third valve ports,
comprising:
(A) a fluid-tight valve body defining first, second and third valve ports;
(B) a diaphragm disposed within said valve body and including at least a
pair of piezoelectric members, said members being selectively
piezoelectrically deflectable in opposite directions in a plane of
operation thereof in response to voltages applied thereto to produce a
cumulative excursion to selectively assume one of two functionally
opposite positions relative to first said valve port and said second valve
port, said members in one of said positions operatively blocking said
first valve port and operatively unblocking said second valve port and in
the other of said positions operatively unblocking said first vale port
and operatively blocking said second valve port, said first valve port
being an inlet port extending through a central portion of said one
member, said second valve port being an exhaust port aligned with said
first valve port, and said third valve port being an inlet/outlet port in
fluid communication with the periphery of said members and with one of
said first and second valve ports when the same is unblocked, said other
member having a first face for selectively blocking or unblocking said
first valve port and an opposed second face for selectively unblocking or
blocking said second valve port;
(C) electrical means operatively connected to said members for
piezoelectrically deflecting the same, said electrical means being
functionally electrically connected to a common electrical circuit for
simultaneous piezoelectric deflection of both of said members, said
members being substantially planar when not piezoelectrically deflected
and substantially curved when piezoelectrically deflected;
(D) means for biasing said members towards said first valve port
(E) means for securing a central annular portion of said one member to said
valve body about said first valve port to preclude excursion of said one
member in a given direction and thereby to substantially double the
effective excursion of said other member in the opposite direction; and
(F) flow channel means disposed between and spacing said members apart
comprising a convoluted washer disposed in said diaphragm intermediate
said members to enable the flow of fluid intermediate said members between
the center thereof and the periphery thereof;
said valve thereby providing fluid communication between said third valve
port and an unblocked one of said first valve port and said second valve
port. |
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Claims |
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Description |
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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.
BRIEF DESCRIPTION OF THE DRAWING
The above brief description, as well as further objects and features of the
present invention, will be more fully understood by reference to the
following detailed description of the presently preferred, albeit
illustrative, embodiments of the present invention when taken in
conjunction with the accompanying drawing wherein:
FIG. 1 is an isometric view of a piezoelectric valve according to the
present invention;
FIG. 2 is a fragmentary sectional view taken along the line 2--2 of FIG. 1
and in the direction of the arrows, but to an enlarged scale, showing the
piezoelectric members in a de-energized state;
FIG. 3 is a view similar to FIG. 2, but showing the piezoelectric members
in an energized state;
FIG. 4 is a sectional view taken along the line 4--4 of FIG. 2 and in the
direction of the arrows, but to a reduced scale, with portions thereof
being cut away to reveal details of internal construction; and
FIG. 5 is a sectional view taken along the line 5--5 of FIG. 2 and in the
direction of the arrows, but to a reduced scale.
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 | | |
