Note: Descriptions are shown in the official language in which they were submitted.
377
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The present invention relates to a liquid ink
supply system in an ink jet system printer of the charge-
amplitude controlling type and, more particularly, to a
pump system in an ink jet system printer for supplying
liquid ink to a nozzle included in the ink jet system
printer.
An ink jet system printer of the charge-
amplitude controlling type requires a small amount,
constant flow rate pump system in order to ensure stable
printing operation when ambient conditions vary.
The conventional liquid in supply system of an
ink jet system printer of the charge-amplitude controlling
type includes a mechanical plunger pump of the constant
flow rate type. However, mechanical plunger pumps do not
lo ensure a stable, constant flow rate supply when supply of
only a small amount is required. Also, mechanical plunger
pumps are relatively large in size.
feature of the present invention is the
provision of a novel pump system suited for a liquid ink
supply system in an ink jet system printer of the charge-
amplitude controlling type.
An aspect of the present invention is the
provision of a pump system which ensures a constant flow
rate when supply in only a small amount is desired.
The present invention provides an ink liquid
supply system for supplying ink liquid from an ink liquid
reservoir to a printer head in an ink jet system printer
of the charge amplitude controlling type, comprising, a
pump system disposed between the ink liquid reservoir and
the printer head, the pump system comprising, a pump
chamber, and a pus element secured to the pump chamber
for varying the volume of the pump chamber in response to
a drive signal applied thereto.
also, in accordance with the present invention
the vibration pipe is made of hard vinyl chloride resin sheet having a thickness of about I mm.
Other features and aspects of the present
invention will become apparent from the detailed
y
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description of one embodiment given hereinafter. It
should be understood, however, that the detailed
description of this specific embodiment is included by way
of illustration only, since various changes and
modifications within the spirit and scope of the invention
will become apparent to those skilled in the art from this
detailed description. The detailed description makes
reference to the accompanying drawings which are included
by way of illustration only, and in which:
FIGURE 1 is a block diagram of a liquid ink
supply system in an ink jet system printer of the charge-
amplitude controlling type, and which includes an
embodiment of a pump system of the present invention;
FIGURE 2 is a front view (partially in section)
lo of the pump system included in the liquid ink supply
system of FIGURE l; and
FIGURE 3 is a schematic perspective view of a
pus vibrator included in the pump system of FIGURE 2.
Referring to FIGURE 1, a liquid ink supply
system of an ink jet system printer of the charge-
amplitude controlling type includes a cartridge tank 1,
removably secured to the liquid ink supply system. The
liquid ink supply system includes an ink outlet needle 2
for discharging the ink liquid from the cartridge tank 1,
and an ink inlet needle 3 for introducing the ink liquid
into the cartridge tank 1. The ink outlet needle 2 and
the ink inlet needle 3 are inserted into the cartridge
tank 1 when the cartridge tank 1 is secured to the liquid
'SKI
ink supply system.
The ink liquid discharged from the cartridge
tank 1 is introduced into a main tank 4. A pump system
6 of the present invention is connected to introduce the
ink liquid from the main tank 4 via an ink inlet valve
5. The pump system 6 provides -liquid ink at a constant
flow rate to an accumulator 8 through an ink outlet valve
7. The accumulator 8 functions to stabilize the static
pressure of the ink liquid supplied from the pump system
6.
The thus stabilized ink liquid is supplied from
the accumulator to a printer head 10 via an electron
magnetic cross valve 9. us is well known in the art, the
printer head 10 includes a nozzle to which an electron
mechanical transducer (pus vibrator) is attached in order to emit ink droplets at a given frequency. The printer
head 10 further includes a charging tunnel for charging
the ink droplets in accordance with a print information
signal. The charged ink droplets are deflected when
they pass between a pair of deflection electrodes which
are also included in the printer head 10. Ink droplets
not contributing to the actual printing operation are
not charged nor deflected, and are directed to a beam
gutter 11. The liquid ink collected by the beam gutter
11 is returned to the cartridge tank 1 via a return
conduit 15.
When -the actual printing operation is terminated,
the pump system 6 is disabled, and the electromagnetic
cross valve 9 is switched to connect the printer head
10 to return conduit lo. The ink liquid disposed between
the electromagnetic cross valve 9 and the printer head
10 is forced to flow into the return conduit 15 due to
the negative pressure created in return conduit 15. That
is, when the printing operation is not conducted, ink
liquid does not remain in the nozzle portion of
printer head 10.
Ink liquid introduced into return conduit 15
v
is returned to the cartridge tank 1 by means of a suction
pump 13. Valves 12 and 14 are associated with the suction
pump 13.
The pump system 6 and the accumulator 8 are
constructed as shown in FIGURE 2. In FIGURE 2, like
elements corresponding to those of FIGURE 1 are indicated
by like reference numerals.
The pump system 6 includes a pump chamber 20
surrounded by a cylindrically-shaped vibration pipe 22.
At the bottom end of pump chamber 20, a valve seat 25 is
provided. An ink inlet pesky 35 is formed through the
valve seat 25, and the ink inlet valve 5 is secured to
the valve seat 25 through the use of a valve cap I
At the top end of pump chamber 20, another valve seat
21 is provided. An ink outlet passage 36 is formed
through the valve seat 21, and the ink outlet valve 7
is secured to valve seat 21 through the use of a valve
cap 26. A block housing 37 is secured to valve seat
21 in order to form the accumulator 8. O-shaped rings
30, 31 and 32 are disposed between the valve seat 25
and the vibration pipe 22, between valve sea-t 21 and
the vibration pipe 22, and between valve seat 21 and
the block housing 37, respectively, for sealing purposes.
A pus element 23 is attached to the cylindrically-shaped
vibration pipe 22 through the use of an adhesive. The vibration pipe 22
preferably has a thickness of about 0.2 mm. Accordingly, when a pulse
drive signal is applied to the pus en 23, the volume of pump
chamber 20 is varied to perfc~ the pump operation.
Referring to Figure 3, assume that the pus
element 23 has a radius R and a length Q as shown. When
a pulse drive signal is applied to the pus element 23,
the pus element 23 expands in the directions shown
by the arrows in FIGURE 3. When the pulse drive signal
is not applied to the pus element 23, the volume "v"
defined by the pus element 2:3 is expressed as follows:
v = ~R2Q
When the pulse signal is applied to the pus element 23,
the radius R and the length Q become R' and Q',
I
-5-
respectively.
R' = Al K V )
Q' = Al + K V 3
t
Accordingly, the volume v is changed to (v TV).
V -I TV = 1rR2Q[l -I TV ) 3
t
~R2Q(l + OK V )
t
where:
K : strain constant
R : radius of the pus element 23
Q : length of the pus eliminate 23
V : voltage level of the pulse drive signal
t : thickness of the pus element 23
TV : volume variation
The small amount ink liquid supply is conducted
by -the volume variation TV applied to pump chamber 20.
TV = (v + TV) - v = TRUCK t
In a specific example, cylindrically-shaped
vibration pipe 22 was made of hard vinyl chloride resin,
and had a thickness of 0.2 mm. The pus element 23
had a thickness (t) of 1.5 mm, a length (Q) of 40 mm, and
a radius I of 13 mm, and was attached to the hard vinyl
chloride resin pipe 22 through the use of an epoxy base
adhesive. The strain constant K was 300 x 10 12 m/V.
When a pulse drive signal having 700 Up p level was
applied to the pus element 2:3, the volume variation
A was 8.8 mm3. In a preferred form, the pulse drive
signal applied to the pus element 23 has a frequency
of 122 Liz.
The invention having been described, it will
be apparent that the same may be varied in many ways. Such
35 variations are not to be regrade as departing from the spirit
and scope of the invention, and such modifications are in-
tended to be included within the scope of the following
claims. Jo
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