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BACKGROUND OF THE INVENTION
1. (Field of the Invention)
The present invention relates a piezo-electric vibrator pump in which
suction and discharge of fluid are accomplished by the vibration of a
piezo-electric vibrator formed of a piezo-electric film of a monolayer or
laminate, and more particularly to a piezo-electric vibrator and a
piezo-electric vibrator with an invertor of high efficiency suction
non-return valve can be operated promptly according to the vibration
generated by the frequency voltage produced when it is driven by an
alternate current supply.
2. (Description of the Prior Art)
Referring to the usual piezo-electric vibrator pump shown in FIG. 5, the
usual piezo-electric pump comprises a piezo-electric vibrator 2 mounted in
a casing 1 having a peripheral part secured to casing 1 within casing 1.
The piezo-electric vibrator 2 is formed of two laminated piezo-electric
layers 9, 9 and electrode 3 inserted between the two piezo-electric layers
9, 9, and electrodes 4, 4 laminated on both sides of laminated two
piezo-electric layers 9, 9. Lead wires 11, 12 are connected to the
electrodes 3, 4. The piezo-electric vibrator pump is provided with a
suction non-return valve 5 (check valve) and a discharge non-return valve
6. An alternate current voltage e is applied between the electrodes 3, 4
of said piezo-electric vibrator 2 through lead wires 11, 12 which results
in vibration of said piezo-electric vibrator causing fluid to be sucked
through the suction non-return valve 5 and discharged through the
discharge non-return valve 6 with the vibration of the piezo-electric
vibrator.
However, because of direct attachment of the piezo-electric vibrator 2 to
the casing, the usual pump has many disadvantages. The vibration of the
piezo-electric vibrator 2 is restricted so that the amplitude of the
piezo-electric vibrator 2 becomes smaller, its performance is lower, its
insulation characteristic is inferior, noise occurs due to the vibration
of the piezo-electric vibrator, and in some cases stresses are imposed on
the parts of the piezo-electric vibrator attached to the casing to such an
extent that the piezo-electric vibrator may be broken.
Further, in the usual construction of a piezo-electric vibrator not coated
with an elastic layer, piezo-electric vibrator 2, secured to a pump casing
1, is vibrated as shown in FIG. 5. That is, there is a scarcely displaced
part at the peripheral part of the piezo-electric vibrator so that a dead
space is formed, resulting in lower gas suction-discharge capability and
lower liquid selfsuction. In order to remove such a dead space, it is
conceived to lessen the clearance between the piezo-electric vibrator 2
and an inner surface of the casing 1. However, there is the possibility
that the collision of the piezo-electric vibrator with the casing 1 can
occur resulting in the breakdown of the piezo-electric vibrator.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a
piezo-electric vibrator pump having an improved insulation characteristic
and higher fluid suction-discharge capability to improve the pump
performance, and in which there is no possibility that the piezo-electric
vibrator may be broken prolonging that its service life the problem of
generation of noise is also solved.
The above object of the present invention is attained, according to the
invention, by a piezo-electric vibrator pump in which a piezo-electric
vibrator 2 is mounted in a casing 1 whose peripheral part is secured to
and within the casing 1. The vibrator pump has a suction non-return valve
5 through which fluid is sucked from a suction line, and a discharge
non-return valve 6 through which fluid is discharged to a discharge line
by means of the piezo-electric vibrator 2 vibrated by applying an
alternative current voltage e between electrodes 3, 4 of the
piezo-electric vibrator. The piezo-electric vibrator pump has both sides
of the piezo-electric vibrator 2 coated with an elastic elastomer layer
10.
In the usual piezo-electric vibrator not coated with elastic elastomer,
when suction and discharge of fluid are performed by vibrating the
piezo-electric vibrator 2, the disadvantages are that the amplitude
thereof is small, the performance is inferior, noise occurs, and stresses
are imposed on the fixed part of the vibrator so that the vibrator may be
broken. On the other hand, in a piezo-electric vibrator according to the
present invention which is coated with elastic elastomer layer 10, there
are the advantages of layer amplitude and higher performance because the
elastic elastomer layer coating the vibrator 2 is secured to and within
the casing 1 so that the vibrator is suspended in the elastic elastomer.
Insulation characteristics are excellent because fluid does not come
directly in contact with the piezo-electric vibrator, noise is lower, and
stresses are not directly imposed on the piezo-electric vibrator.
Therefore the piezo-electric vibrator 2 is difficult to break because the
piezo-electric vibrator 2 is not secured directly to the casing.
Further, the deformation of the elastic elastomer along the pump casing 1
results in a remarkably reduced clearance, preventing the piezo-electric
vibrator from breaking by colliding with the casing. Therefore, the
self-suction ability of the piezo-electric vibrator pump is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 a sectional view showing a first embodiment of a piezo-electric
vibrator pump according to the present invention;
FIGS. 2 and 3 are sectional views of piezo-electric vibrators for second
and the third examples according to the present invention, respectively;
FIG. 4 is a circuit diagram showing one example of an inverter with which a
piezo-electric vibrator pump according to the present invention is
provided; and
FIG. 5 is a sectional view showing one example of a prior art usual pump.
The following example according to the present invention is explained in
connection with the accompanying drawings.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a sectional view showing one example of a piezo-electric vibrator
pump.
In FIG. 1, casing 1 has a piezo-electric vibrator 2 and the peripheral part
of the piezo-electric vibrator 2 fixed to the casing 1. The piezo-electric
vibrator 2 may be a piezo-electric vibrator of the laminate type in which
piezo-electric bodies are laminated on both outer sides of a shim such as
a phosphor bronze, or a piezo-electric vibrator of the monolayer type such
as ceramic, polymer piezo-electric materials, provided with thin film
electrodes 3, 4.
In this example, the piezo-electric vibrator 2 is one of the laminate type
in which two piezo-electric films 9, 9 are laminated and electrodes 4, 4
are laminated on both outer sides of the laminated two piezo-electric film
9, 9 while another electrode 3 is inserted between the two piezo-electric
films 9, 9.
The casing 1 is provided with a suction line 7 and a discharge line 8 on
one side of the casing enclosing piezo-electric vibrator 2. The suction
line 7 and the discharge line 8 are connected with the space within the
casing 1 through a suction non-return valve 5 and a discharge non-return
valve 6, respectively. A non-return valve having a ball moved against a
spring with fluid flowing in one direction so that the valve is opened,
and a non-return valve of umbrella type having an umbrella deformed
against its elastic force with fluid flowing in one direction so that the
valve is opened, or the like can be used as the suction non-return valve 5
and the discharge non-return 6 respectively.
Further the suction line 7 and the discharge line 8 are provided with surge
tanks 13, 14, respectively. The bottom part of the surge tanks 13, 14 are
connected with one suction line 7a and one discharge line 8a,
respectively, while the side walls at the middle height of the surge tanks
13, 14 are connected with another suction line 7b and another discharge
line 8b, respectively.
There are spaces 15, 16 at the upper part in the surge tank 9, 10.
Preferably the surge tanks 13, 14 are arranged as close to the suction
non-return valve 5 and the discharge non-return valve 6 as possible.
Generally the distance between the surge tanks 13, 14 and the non-return
valve 5, 6, is less than 50 mm, preferably less than 30 mm, and more
preferably less than 20 mm.
The surge tanks 13, 14 makes fluid easily to move by vibration of
piezo-electric vibrator 2, which results in exact movement of the
non-return valves, thus increasing the pump discharge ability or the
pumpability.
Further both sides of the piezo-electric vibrator 2, including the part
held in an casing 1, is covered with the elastic elastomer having a
modulus of londitudinal elasticity of less than 5.times.10.sup.8
dyn/cm.sup.2, preferably of less than 2.0.times.10.sup.8 dyn/cm.sup.2, and
more preferably 1.5.times.10.sup.8 dyn/cm.sup.2.
As an elastomer, the elastic material can be silicone rubber, urethane
rubber, natural rubber, SBR (styrenebutadiene rubber), cloroprene rubber,
Neoprene(Trade mark of du Pont for cloroprene rubber), NBR(nitrile
rubber), SBS(styrenebutadienestyrene copolymer), hydrogenated SBR,
fluorosilicone rubber, fluoroelastomer, EPR(ethylene propylene rubber),
ethylene vinylacetate copolymer or the like.
When A C voltage e is applied between electrodes 3, 4 the piezo-electric
vibrator 2 is vibrated in a direction perpendicular to the surfaces of the
piezo-electric vibrator 2, that is up and down as shown in FIG. 1. When
the piezo-electric vibrator 2 bends downwards, the pressure on the inside
of the piezo-electric vibrator pump is reduced to the negative pressure by
which discharge non-return valves 6 is closed while the suction non-return
valve 5 is opened so that fluid is sucked into the piezo-electric vibrator
pump through the suction non-return valve 5. On the other hand, when the
piezo-electric vibrator 2 bends upwards, the pressure on the inside of the
piezo-electric vibrator pump is increased to a positive pressure closing
suction non-return valve 5 and, discharge non-return valve 6 opens so that
fluid is sucked in and discharged from the piezo-electric vibrator pump
through the discharge non-return valve 6. Further the suction and
discharge of fluid is performed with the vibration of the piezo-electric
vibrator 2.
Under the condition that the suction and discharge of fluid is performed
with the vibration of the piezo-electric vibrator 2 to which A C voltage e
is applied, coating the piezo-electric vibrator 2 with the elastic
elastomer 10 results in an improvement of the lifetime and performance of
the pump and an increase of uses for the pump.
When the piezo-electric vibrator 2 not covered with elastic elastomer 10,
the disadvantages that insulation characteristics are worse, because of
the small amplitude the pump performance is lower, and because the
piezo-electric vibrator 2 is fixed direcly to the casing 1, stresses are
imposed on the supported part of the piezo-electric vibrator so that the
piezo-electric vibrator 2 may break easily and noise is made.
However, when the piezo-electric vibrator is coated with the elastic
elastomer 10, insulation characteristics improve, and the amplitude of the
piezo-electric vibrator increases because the piezo-electric vibrator 2 is
suspended in the elastic elastomer 10. Thus pump performance is improved.
According to the invention, the piezo-electric vibrator 2 is not fixed
directry to casing 1, but elastic elastomer 10 is fixed to the casing 1,
stresses being difficult to impose on the supported part of the elastomer
10 by the casing 1. Therefore, the piezo-electric vibrator will be not
broken, and noise will be difficult to make.
Further, it becomes possible to flow many sorts of fluid, by laminating
many types of plastic films on the elastic elastomer 10 with which the
piezo-electric vibrator 2 is covered.
In order to demonstrate the effect of the pump according to the invention
experiments were made comparing an example of the piezo-electric vibrator
coated with the elastomer according to the invention with a comparison of
the piezo-electric vibrator which is conventionally not coated, under the
same conditions with respect to self-suction ability, pressure, and flow.
The results are shown in the following table.
______________________________________
Self-suction
Pressure
ability(mm)
(kg/cm) Flow (ml/min)
liquid
gas liquid gas liquid
gas
______________________________________
Comparison
50 -- 0.05 0.02 80 500
Example 900 -- 0.20 0.11 400 1000
______________________________________
From the results of the experiment, it is obvious that pump performance is
improved by covering the piezo-electric vibrator 2 with elastomer.
As above-mentioned, the pump according to the invention has advantages of
improved insulation characteristics, improved suction and discharge
ability of fluid so that pump performance is improved. There is no danger
of the piezo-electric vibrator being broken because stress is difficult to
impose on the supported part of the piezo-electric vibrator by the casing,
the lifetime can be lengthend, and also the problem of noise can be almost
dissolved.
According to the invention, plural piezo-electric vibrators of monolayer
type or laminate type may be used and insulating elastomer film(s) may be
inserted between the plural piezo-electric vibrators.
FIGS. 2 and 3 are sectional views respectively showing two piezo-electric
vibrators in which an elastic elastomer film 17 is inserted between the
laminated piezo-electric vibrators, and a laminate of three piezo-electric
vibrators in which two elastic vibrators, with electrodes 3, 4 of
respective laminates of piezo-electric vibrators 2 being connected in
parallel with lead wires. Liquid-impermeable film 18 is laminated on the
surface of the elastomer 10 with which the piezo-electric vibrator 2 is
covered, and connecting part 19 is for connecting electrodes 4, 4 of the
respective piezo-electric vibrator 2.
As elastomer films 17, elastic materials such as elastic rubbers, plastics,
metals or the like. Preferably an elastic material with a coefficient of
thermal conductivity as high as possible is applied as elastomer films 17
with a view to facilitating cooling of the piezo-electric vibrator 2.
However, in the laminate of two piezo-electric vibrators (FIG. 2), the
radiation of the piezo-electric vibrator 2 can be neglected as one side of
the piezo-electric vibrator 2 is in contact with the elastomer 10.
The thickness of the elastomer film is about 0.1-5 mm, and preferably about
0.3-2 mm.
The phases of A C voltage e applied between electrodes 3, 4 of the
respective piezo-electric vibrators are the same as the electrodes 3, 4 of
the respective vibrators are connected in parallel with lead wires so that
the function and the effect of the pump can be attained in the same manner
as in the above mentioned first example. However, when laminates of
piezo-electric vibrators 2 over two layers are used, higher pump
performance can be attained.
It is preferable to use conductive material as the elastomer film 17,
because film 17 serves both as the elastic material and as the electric
connection between respective piezo-electric vibrators 2.
When the laminate of plural piezo-electric vibrators 2 are laminated with
interposed elastomer film(s) they are oscillated up and down in the
direction perpendicular to the surface of the respective piezo-electric
vibrator 2. In this case, it is necessary to freely bend elastomer(s)
interposed between each respective piezo-electric vibrator 2 and adhered
to each respective piezo-electric vibrators 2 in such a way that the
elastomer film(s) 17 can not prevent the piezo-electric vibrator 2 from
bending. Further, it is necessary to avoid deforming the elastomer film(s)
in the direction of the thickness in order to effectively take out the
displacement and the forces generated in respective piezo-electric
vibrator 2 to the outer areas of the elements.
For this purpose, it is desirable that the both sides of the elastomer(s)
17 are provided with many ribs which intersect either lengthwise or
crosswise.
Further, it is possible to make the elastomer film(s) serve both as the
transmitting means of stress generated in respective elastomer film(s) and
as the electric connection between electrodes of the piezo-electric
vibrators, by giving conductivity to the elastomer film(s) by mixing metal
powder such as aluminum, or conductive carbon black with the elastomer
material.
The pump according to the invention can be driven with commercial electric
source. When the commercial electric source is used the pump driving force
can be controlled to control the discharge of fluid by controlling the
voltage of the electric source through a transformer or variable
resistance.
Further, the pump according to the invention can be driven by a D C
electric source as occasion demands. For example when the pump according
to the invention is applied to a portable apparatus the pump according to
the invention can be driven with the following inverter.
FIG. 4 is a circuit diagram showing an example of an inverter driving the
pump according to the invention. Constant-voltage circuit 26 for
transforming the voltage V.sub.1 of the D C electric source input to the
constant-voltage circuit into constant-voltage (3 terminal regulator), can
be omitted. Oscillation circuit 27 to which D C voltage V is output with
oscillations according to the time constant of capacitor Cx and resistor
(CR=VRx+Rx) with the following frequency:
##EQU1##
In the example shown in FIG. 4, a triangular wave is oscillated and
triangular wave voltage V.DELTA. is output. The oscillation circuit 27
comprises a square wave generating division circuit including a comparator
IC element IC.sub.1 and resistors R.sub.3, R.sub.4, a triangular wave
genarating division circuit including a capacitor Cx transforming square
wave voltage output from square wave generating division circuit into a
triangular wave voltage, a resistor R, and a comparator IC element
IC.sub.2. The triangular wave generating division circuit is called a
Miller integrating circuit. In this example, the triangular wave
generating division is designed so that oscillation frequency f can be
altered by changing the resistance value of a variable resistor VRx.
Resistors R.sub.1, R.sub.2 are for dividing D C voltage V.sub.1.
The potential dividing point (connecting point) of resistor R.sub.1,
R.sub.2 is connected to a negative terminal of the comparator IC element
IC.sub.1 and the positive terminal of the comparator IC element IC.sub.2.
The resistor R.sub.4 is connected between the positive terminal of and the
output terminal of the comparator IC element IC.sub.1, while the resistor
R.sub.3 is connected between the positive terminal and the output terminal
of the comparator IC element IC.sub.2.
The series circuits of the variable resistor VRx and the resistor Rx are
connected between the output terminal of the IC element IC.sub.1 and the
negative terminal of the IC element IC.sub.2, while the capacitor Cx is
connected between the negative terminal and the output of the IC element
IC.sub.2.
Therefore the square wave generating division of the oscillating circuit 27
is operated with the voltage of capacitor Cx, thereby the square wave
voltage is output from the output terminal of IC element IC.sub.1, the
square wave voltage is input to the triangular wave generating division
circuit so that triangular wave voltages are integrated, and the
triangular wave voltage V.DELTA. is output from the output terminal of the
IC element IC.sub.2.
Numeral 28 designates a driving circuit receiving the output of the
oscillating circuit 17 and from which after the quiescent period t.sub.1,
two operating signals Vd.sub.1, Vd.sub.2 with operating times different
from each other are output. The driving circuit comprises a comparator IC
element IC.sub.3, which operates during the period of a positive wave of
the triangular wave voltage V.DELTA., a comparator IC element IC.sub.4
which operates during the period of negative wave of the triangular wave
wave voltage V, resistors R.sub.5, R.sub.6, a variable resistor VR for
adjusting the pulse quiescent period and diodes D.sub.1, D.sub.2.
The series circuit of the resistor R.sub.5, the variable resistor VR.sub.1
and the resistor R.sub.6 is connected between the DC voltage line and the
earth line. The connecting point of the resistor R.sub.5 and the resistor
R.sub.4 is connected to the positive terminal of the IC element IC.sub.4.
The positive terminal of the IC element IC.sub.3 and the negative terminal
of the IC element IC.sub.4 are connected with each other and are connected
to the output terminal of the IC element IC.sub.2 of the triangular wave
oscilating circuit 17. Diodes D.sub.1, D.sub.2 anode side is connected to
the output terminals of the IC elements IC.sub.3, IC.sub.4, respectively.
Pulse generating circuit 29 receives the output from IC elements IC.sub.3,
IC.sub.4 to convert DC voltage V.sub.2 into positive and negative pulse
voltages .+-.Vp. The pulse generating circuit 29 comprises the bridge
circuit 30 including npn, pnp transistors Tr.sub.1, Tr.sub.2 respectively
on oposing lines and npn, pnp transistors Tr.sub.3, Tr.sub.4 on other
opposing lines. Transistors Tr.sub.1, Tr.sub.2 and transistors Tr.sub.3,
Tr.sub.4 are alternately switched on and off, respectively. The bridge
circuit 30 is designed, as hereinafter described in detail so that
positive and negative pulse voltages .+-.Vp having a quiescent period
t.sub.1 can be alternately obtained between the output terminals of the
bridge circuit 30 by applying DC voltage V.sub.2 between the voltage
terminals of the bridge circuit 30.
That is, resistors R.sub.14, R.sub.15 are connected between the base and
emitter of npn transistor Tr.sub.1 on one line of the opposing lines, and
between the base and emitter of npn transistor Tr.sub.3 on one line of the
other opposing lines, respectively. The respective emitters are connected
to earth. Resistors R.sub.8, R.sub.7 are connected between the bases of
the respective transistors Tr.sub.1, Tr.sub.2 and the diodes D.sub.1,
D.sub.2, while diodes D.sub.5, D.sub.6 are connected between the
collectors and the emitters of transistors Tr.sub.3 and Tr.sub.1.
Resistors R.sub.11, R.sub.12 are connected between base and emitter of the
npn transistor Tr.sub.2 on the other line of the opposing lines and
between base and emitter of the pnp transistor Tr.sub.4 on the other line
of yet another opposing lines, respectively. The respective bases are
connected to voltage terminal V.sub.2 through resistors R.sub.11,
R.sub.12. Resistors R.sub.9, R.sub.10 are connected between the respective
bases and the collectors of the npn transistors Tr.sub.1, Tr.sub.3, while
diodes D.sub.3, D.sub.4 are connected between the respective collectors
and the respective voltage terminals V.sub.2.
Further, the collector of the npn transistor Tr.sub.1 on one of the
opposing lines is connected to the collector of the other pnp transistor
Tr.sub.4, and the collector of the npn transistor Tr.sub.3 of one line of
another opposing two lines is connected to the collector of the other pnp
transistor Tr.sub.2.
Therefore, in pulse generating circuits 29, during a positive slope of
triangular voltage V.DELTA. the comparator IC element IC.sub.3 functive to
produce signal Vd.sub.1 which is sent to earth (ground) through the diode
D.sub.1, the resistor R.sub.8, and the resistor R.sub.14, the npn
transistor Tr.sub.1 change to an on-state with the signal on resistor
R.sub.14, thus electric current is sent from voltage terminal V.sub.2 to
earth through the resistors R.sub.11, R.sub.9 and the collector of the npn
transistor Tr.sub.1, changing the pnp transistor Tr.sub.2 to an on-state
by the voltage on the resistor R.sub.11. Thereby, positive pulse voltage
+Vp is obtained from the output terminals 0 which is connected to the
collector of the pnp transistor Tr.sub.2.
Further, during the negative slope of thee triangular wave voltage V.DELTA.
the comparator IC element IC.sub.4 functive to produce signal Vd.sub.2
which is sent to the earth through the diode D.sub.2, the resistor
R.sub.7, and R.sub.13. The npn transistor Tr.sub.3 is changed to an
on-state, thereby electric current is sent from the voltage terminal
V.sub.2 to the earth through the resistors R.sub.12, and R.sub.10, and the
collector and the emitter of npn transistor Tr.sub.3. The pnp transistor
Tr.sub.4 is changed to an on-state by the voltage on the resistor
R.sub.12. Thereby, negative pulse voltage-Vp can be obtained at the output
terminals 0 connected to the collector of the pnp transistor Tr.sub.4.
The positive and negative pulse voltage .+-.Vp can be freely changed by
changing the DC voltage V.sub.1. Thus, by connecting the output terminal
to the piezo-electric vibrator pump as shown in FIGS. 1 to 3, it is
possible to work the pump with the positive and negative pulse voltage
.+-.Vp with voltage values adjusted to the pump. It is not necessary to
elaborate but the positive and negative pulse voltage .+-.Vp can be held
constant by holding the input constant.
The oscillation frequency of the triangular wave voltage V.DELTA. can be
freely changed by changing the value of the variable resistor VRx. Further
the triangular wave voltage V.DELTA. can be converted into a sine wave
voltage by passing the positive and negative pulse voltages .+-.Vp
generated at the output terminals of the pulse generating circuit 29
through a filter.
It being obvious from the hereinabove description, the following is
possible, according to the invention:
(1) the positive and negative pulse voltage DC output voltages .+-.Vp can
be freely changed by changing the voltage of the DC power source (DC input
voltage) V.sub.1, thus the piezo-electric vibrator pump can be operated:
(2) the positive and negative pulse voltages .+-.Vp can be held constant by
stabilizing the DC power source, thus the operation of the piezo-electric
vibrator pump can be stabilized;
(3) the output frequency adjusted for the piezo-electric vibrator pump can
be set by changing the time constant and the oscillation frequency,
therefore the frequency adjustment for the piezo-electric vibrator pump
can be made so that maximum efficiency is achieved.
(4) the piezo-electric vibrator pump can be operated with maximum electric
power rather than with a conventional sine wave output voltage as positive
and negative pulse voltages .+-.Vp can be obtained;
(5) the invertor can be simple and smaller and of low-cost construction as
a switching element with a gate is not used;
(6) the power consumption can be reduced and accidents almost eliminated as
compared with the conventional device in which an output voltage is
changed as the positive and negative pulse voltages .+-.Vp are changed by
changing the DC input voltage V.sub.1 ; and
(7) on-off states of the npn transistors and pnp transistors Tr.sub.1,
Tr.sub.2, Tr.sub.3, and Tr.sub.4 can be positively switched on and off
even if the frequency and switching speed becomes higher with the two
output operation signals Vd.sub.1, Vd.sub.2 with the pulse quiescent
period t.sub.1 of the driving circuit 28 to which the output triangular
wave voltage V.DELTA. of the triangular wave oscilation circuit 27 is
input and from which two operation signal Vd.sub.1, Vd.sub.2 whose
operating points are different from each other are output after the
quiescent period t.sub.1. Therefore, the four transistors are not at all,
if transiently, short-circuited and there is no possibility of overheating
damage, and also the pump can be operated with alternately output positive
and negative pulse voltages .+-.Vp with a pulse quiescent period t.sub.1
from the output terminal.
From the hereinabove recited reason, the above-mentioned invertor is
suitable for driving an electric power source for a piezo-electric
vibrator pump, and therefore, the piezo-electric vibrator pump itself with
the invertor according to the invention.
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