Pumps – Expansible chamber type – Elongated flexible chamber wall progressively deformed
Reexamination Certificate
2002-08-19
2004-05-11
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Elongated flexible chamber wall progressively deformed
C417S477800, C347S085000
Reexamination Certificate
active
06733255
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a tube pump using deformation of a tube for generating pressure and an ink jet recording apparatus comprising recovery device of an ink ejection capability for discharging ink from a recording head using negative pressure generated by the tube pump.
An ink jet recording apparatus produces comparatively small noise at the printing time and moreover can form small dots at a high density and thus nowadays is widely used for print centering on color print.
Such an ink jet recording apparatus comprises an ink jet recording head for receiving ink supplied from an ink cartridge and paper feed device for relatively moving record paper to the recording head.
While the recording head is moved in response to a print signal, ink droplets are ejected onto record paper for forming dots, thereby recording. In this case, a recording head capable of ejecting black ink, yellow ink, cyan ink, and magenta ink, for example, is mounted on a carriage and the ink ejection percentage is changed, thereby making full color print possible.
Since such an ink jet recording apparatus ejects ink onto record paper as ink droplets through nozzle openings for printing, it involves the following problem: clogging occurs in the nozzle openings due to a rise in ink viscosity caused by evaporation of an ink solvent from the nozzle openings, ink solidification on the nozzle formation face, or deposition of dust and further air bubbles are mixed into the recording head, causing a print failure to occur.
Thus, in addition to the recording head and the paper feed device, the ink jet recording apparatus comprises capping device for sealing the nozzle formation face of the recording head in a non-print mode, a suction pump for sucking and discharging ink into the capping device, and wiping device for cleaning the nozzle formation face of the recording head after ink is sucked and discharged by the suction pump.
To prevent clogging from occurring in the nozzle openings and air bubbles from being mixed into the recording head, ink is forcibly sucked and discharged from the recording head into the capping device by the suction pump (ink ejection capability recovery processing) and then the nozzle formation face of the recording head is wiped by the wiping device.
The forcible discharge processing of ink performed to remove clogging of the recording head or if air bubbles remain in the recording head is called cleaning operation. The cleaning operation is performed when print is restarted after the recording apparatus is in a nonoperating mode for a long time or when the user recognizes a print quality failure of faint print, etc., and presses a cleaning switch.
To perform the cleaning operation, the recording head is sealed with the capping device and a negative pressure is made to act on the inside of the capping device.
Used as a device for feeding a negative pressure into the capping device is a tube pump which has a comparatively simple structure, can be easily miniaturized, and moreover does not cause pollution in the mechanical portion for sucking and discharging ink.
The tube pump has a configuration, for example, as shown in
FIGS. 7 and 8
.
FIG. 7
shows a pump operation state as the pump is driven in a forward direction and
FIG. 8
shows a release operation state as the pump is driven in a reverse direction.
The tube pump shown in
FIGS. 7 and 8
comprises a pump frame
44
having a tube support face
52
for guiding the outer shape of a flexible tube
51
to be a circular-arc manner, a pump wheel
42
rotated by a paper feed motor, for example, and rollers
43
a
and
43
b
having roller shafts
43
A and
43
B moving along roller support grooves
42
a
and
42
b
opened to an end face of the pump wheel
42
.
The pump frame
44
is formed with L-shaped retention grooves
44
a
and
44
b
opposed to the tube support face
52
and guide members
53
a
and
53
b
made of elastic material projecting in the center direction of the pump wheel
42
are retained in the retention grooves
44
a
and
44
b.
In such a tube pump, if the pump wheel
42
is rotated in the normal direction (arrow A direction) as shown in
FIG. 7
, the rollers
43
a
and
43
b
move in the outer peripheral direction of the roller support grooves
42
a
and
42
b
and are rotated and rolled while pressing the flexible tube
51
in the arrow A direction. Accordingly, a pressure is generated in the flexible tube
51
for feeding a negative pressure into the capping device. Ink is forcibly discharged from the recording head by the negative pressure and further the ink discharged into the capping device is sucked and is sent to a waste ink tank.
If the pump wheel
42
is rotated in the reverse direction (arrow B direction) as shown in
FIG. 8
, the rollers
43
a
and
43
b
move in the inner peripheral direction of the roller support grooves
42
a
and
42
b
and are rotated and rolled in the arrow B direction while keeping the flexible tube
51
in the release operation state in which the rollers
43
a
and
43
b
come in contact with the flexible tube
51
only a little. Accordingly, failure occurrence of the roller
43
a
,
43
b
sticking to the flexible tube
51
or the like is prevented.
In this case, the guide members
53
a
and
53
b
act so as to guide the rollers
43
a
and
43
b
in the wheel rotation backward direction of the roller support grooves
42
a
and
42
b
as the pump wheel
42
is rotated.
However, in this kind of tube pump, when the pump operation state is switched to the release operation state, the rollers
43
a
and
43
b
rotate and roll with the pump wheel
42
while pressing the flexible tube
51
, and thus the following problem is involved. That is, just after the pump operation state is switched to the release operation state, the rollers
43
a
and
43
b
receive such a force displacing in the wheel rotation direction with the rollers
43
a
and
43
b
pressed into contact with the flexible tube
51
from the groove walls of the roller support grooves
42
a
and
42
b
and thus fluids of ink, air, etc. which are sucked into the flexible tube
51
flow back and the reliability on the pump quality is degraded.
On the other hand, to use the tube pump with the ink jet recording apparatus, ink bubbles are produced in the capping device because of flowback of ink, etc. which is sucked from the recording head and some of the ink bubbles may be exposed to the outside of the capping device.
If the ink bubbles are thus exposed to the outside of the capping device, when the recording head is next sealed with the capping device, as they come in contact with each other the ink bubbles are broken and this action may cause instantaneous air pressure change to occur in the nozzle openings of the recording head, destroying meniscuses of ink formed in the nozzle openings.
Consequently, the normal ejection operation of ink droplets through the nozzle openings cannot be accomplished, causing a print fault called missing dots to occur, leading to degradation of the reliability on cleaning; this is a problem.
It is therefore an object of the invention to provide a tube pump for making it possible to enhance reliability on pump quality, simplify the whole structure, and reduce costs and an ink jet recording apparatus using the tube pump to make it possible to enhance reliability on cleaning.
To this end, according to the invention, there is provided a tube pump comprising:
a pump frame having a tube support face for guiding a curve of a flexible tube in a circular-arc manner;
a pump wheel rotatably disposed in the pump frame and having a roller support groove; and
a roller having a roller shaft, disposed rotatably and rollably on the pump wheel and relatively displaceable between a pump operation position and a release operation position in the roller support groove, the roller being configured to deform the flexible tube by a press contact so as to generate a pressure in the tube pump;
the roller shaft being guided by a groove wall in contact therewith;
wherein the groove wall of the r
Koase Takashi
Ota Mitsugu
Freay Charles G.
Seiko Epson Corporation
Sughrue & Mion, PLLC
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