Fluid sprinkling – spraying – and diffusing – With means to vibrate or jiggle discharge – By electric transducer
Reexamination Certificate
2002-11-07
2004-03-09
Tapolcai, William E. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
With means to vibrate or jiggle discharge
By electric transducer
C239S102100
Reexamination Certificate
active
06702196
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit for driving a liquid drop spraying apparatus used for a variety of machines, the liquid drop spraying apparatus treating a liquid or operating by spraying the liquid as a small amount of liquid drops.
2. Description of Prior Art
A liquid drop spraying apparatus is generally composed as shown in a longitudinal cross section of
FIG. 7
, including a piezoelectric or electrostrictive element
1
(piezoelectric/electrostrictive element) as a pressurizing means for spraying liquid. The piezoelectric/electrostrictive element
1
is provided on a wall face of a pressurizing chamber
2
for pressurizing liquid to be sprayed, a liquid drop spraying nozzle
3
is provided at the tip end of the pressurizing chamber, and an introducing hole
5
for supplying liquid to the pressurizing chamber
2
is formed at its proximal end, thereby entirely constituting a liquid drop spraying unit
6
. This liquid drop spraying unit
6
is concurrently formed in plurality, and an introducing hole
5
for a plurality of the adjacent liquid drop spraying units
6
,
6
, . . . is coupled with a common liquid supply path
7
.
A drive circuit for driving a liquid drop spraying apparatus deforms the wall of the pressurizing chamber
2
by applying a predetermined voltage signal to the piezoelectric/electrostrictive element
1
and charging the element. In this manner, the drive circuit generates a pressure at the pressurizing chamber
2
, and causes the liquid supplied to the pressurizing chamber from the liquid drop spraying nozzle
3
. In addition, the drive circuit causes power discharge and release deformation, thereby restoring the deformation of the pressurizing chamber
2
, and causes liquid to flow from the introducing hole
5
to the pressurizing chamber.
In the meantime, in the liquid drop spraying apparatus, a large amount of liquid must be supplied for certain uses. In order to cope with such uses, the apertures of the nozzle and introducing hole have been increased in size.
If the aperture of the liquid drop spraying nozzle
3
is too large, however, only a small amount of liquid can be sprayed. The introducing hole
5
is not a mere path through which liquid is supplied to the pressurizing chamber
2
, but serves to prevent back flow even if pressurization is performed so as to spray a small amount of liquid drops from the liquid spraying nozzle
3
. Thus, the aperture cannot be widened infinitely.
Therefore, it is considered that if the time interval for applying a predetermined voltage signal to the piezoelectric/electrostrictive element
1
is shortened, the number of signal applications per unit time is increased, and the number of supplies to the liquid drop spraying apparatus is increased. In that case, if the time interval for applying the voltage is shortened, there occurs a new problem, in that a delay in liquid supply from the introducing hole
5
to the pressurizing chamber
2
occurs, and a large amount of liquid cannot be constantly supplied.
In addition, the piezoelectric/electrostrictive element acts as a capacitor. Charging/discharging is repeated when the spraying operation is repeated. Thus, when an operating period is shortened, power consumption is further increased, and the calorific value is increased.
A technique to cope with the above increased power consumption is described in Japanese Patent Application Laid-open No. 10-107335 or Japanese Patent No. 2909150. A technique for shortening the application period of a voltage signal per unit time is disclosed in Japanese Patent Application Laid-open No. 8-300646. In Japanese Patent Application Laid-open No. 10-107335, there is disclosed an arrangement in which an external capacitor is provided for power recollection, a coil that is an inductance is interposed in a charge/discharge circuit, and part of a discharge of the piezoelectric/electrostrictive element is effectively stored in the external capacitor and utilized for the next charge, thereby ensuring power saving. In Japanese Patent No. 2909150, there is disclosed an arrangement in which piezoelectric elements to be driven at different timings are mutually utilized as power recollecting means, thereby reducing power consumption without additionally providing an external circuit.
However, in all of these arrangements, although there is provided an advantageous effect on saving power consumption, a technique for constantly spraying a large amount of liquid is not described. Thus, the delay in liquid supply from the introducing hole to the pressurizing chamber is not solved.
In addition, in Japanese Patent Application Laid-open No. 8-300646, there is disclosed an arrangement in which the rise of a drive voltage wavelength is divided into two stages and/or three stages, whereby the stability of meniscus is improved and the occurrence of satellite drops is suppressed. As a result of reducing a constant during discharge when the waveform is divided into three stages, the printing speed is increased, thereby making it possible to increase an ink discharge quantity. However, discharge start characteristics are not smooth at the respective stages. Thus, the printing speed cannot be significantly increased, and the discharge quantity cannot be significantly increased.
In view of the foregoing problems, even in the case where a large amount of liquid is sprayed, it is an object of the present invention to provide a circuit for driving a liquid drop spraying apparatus capable of smoothly supplying liquid to the pressurizing chamber.
SUMMARY OF THE INVENTION
In order to solve the foregoing problems, according to a first aspect of the present invention, the following is provided. A liquid drop spraying apparatus comprises a plurality of units for spraying a small amount of liquid drops, wherein each unit comprises a liquid drop spraying nozzle, a pressurizing chamber for pressurizing liquid to be sprayed from the nozzle, an introducing hole for supplying liquid to the pressurizing chamber, and a piezoelectric/electrostrictive element for operating the pressurizing chamber to be pressurized. The liquid introducing holes of the plurality of the adjacent liquid drop spraying units are coupled with a common liquid supply path, and there is provided a liquid drop spraying apparatus driving circuit for applying a predetermined voltage signal to the piezoelectric/electrostrictive element, thereby deforming the wall of the pressurizing chamber, and discharging from the nozzle the liquid to be supplied to the pressurizing chamber by a pressure produced in the pressurizing chamber. The ratio between the introducing hole diameter and the nozzle hole diameter (introducing hole diameter
ozzle hole diameter) is in a range of 0.6 to 1.6, and the ratio between the nozzle hole diameter and nozzle thickness (nozzle hole diameter
ozzle thickness) is in a range of 0.2 to 4. An applied voltage signal supplies a current to the piezoelectric/electrostrictive element to charge the element, and then holds the final charge voltage for a predetermined time after applying the current. Discharging with two or more time constants during discharge is then performed sequentially. The time constant during the first discharging is greater than the time constant during the second discharging, and the second discharging is started at a voltage that is 35% to 70% of a voltage difference between the charging start voltage and the final charge voltage when the charging start voltage is defined as a reference. An inductance and a resistor are interposed in at least one discharge circuit in series with respect to the piezoelectric/electrostrictive element.
With this arrangement, when liquid drops are sprayed during the charging of the piezoelectric/electrostrictive element, when a charge is discharged, the time constant during discharging of the first discharge circuit is large, and thus, the piezoelectric/electrostrictive element can start deformation gently. In the case where liquid drops are sprayed simultaneously from a p
Hirota Toshikazu
Ohnishi Takao
Ohwada Iwao
Ali Mohammad M.
Burr & Brown
NGK Insulators Ltd.
Tapolcai William E.
LandOfFree
Circuit for driving liquid drop spraying apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit for driving liquid drop spraying apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit for driving liquid drop spraying apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3276796