Head wiping arrangement for ink jet printer

Details Head wiping arrangement for ink jet printer Head wiping arrangement for ink jet printer

1998-05-01

2001-06-12

Beatty, Robert (Department: 2852)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S022000

Reexamination Certificate

active

06244685

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to systems for cleaning an ink jet print head. More particularly, the present invention concerns a system for wiping ink from an ink jet print head before, during, or after a print job.
2. Description of the Related Art
Conventional ink jet printers utilize ink jet print heads to print images upon a recording medium. Ink jet print heads contain ink jet nozzles which eject ink droplets onto the recording medium through nozzle openings. Over time, ink collects on the print head nearby the nozzle openings, thereby tending to obstruct the openings.
Due to the foregoing, many conventional ink jet printers provide systems for cleaning ink from an ink jet print head before, during, or after printing using the ink jet print head. One such system is a wiping system, in which an element is moved across a nozzle-containing surface of a print head so as to wipe ink from the print head. More specifically, conventional wiping systems operate by dragging a flexible wiping element across an ink jet print head through relative motion between the wiping element and the print head.
However, conventional wiping systems have proved to be inadequate. In particular, conventional wiping systems, even when used in conjunction with other nozzle cleaning systems such as purging or sucking systems, leave an unsatisfactory amount of residual ink on the print head after wiping. Moreover, the amount of residual ink left behind after wiping increases with subsequent wiping.
Accordingly, what is needed is a system for effectively wiping ink away from a nozzle surface of an ink jet print head in which wiping effectiveness does not degrade significantly with use.
Special problems arise during wiping of “engraved” ink jet print heads. In this regard,
FIG. 1
a
shows representative engraved print head
1000
. As shown, nozzles
1001
are disposed linearly within nozzle surface
1002
of print head
1000
. However, as shown in
FIG. 1
b
, nozzles
1001
are disposed in groove
1004
within nozzle surface
1002
. Accordingly, the openings of nozzles
1001
are not coplanar with the area of nozzle surface
1002
outside of groove
1004
. In contrast, non-engraved print heads include nozzle openings which are generally coplanar with the surface of the print head. As can be understood from the foregoing, effective wiping of an engraved print head is difficult due to variations in the features of the print head along a nozzle surface.
Conventional systems have attempted to address this problem by utilizing two or more wipers of varying dimensions in order to wipe different areas of an engraved print head.
FIG. 2
illustrates such a conventional scheme. As shown in
FIG. 2
, wiper blade
1006
is longer than groove
1004
, while wiper blade
1007
is shorter than groove
1004
. Accordingly, as illustrated in
FIG. 2
, wiper blade
1006
is used to wipe regions of nozzle surface
1002
which do not include groove
1004
. On the other hand, wiper blade
1007
is used primarily to wipe groove
1004
. Such multiple wiping systems, however, present mechanical problems due to the need to coordinate wiping using both wiper blades. Moreover, in a case that wiper blade
1007
initially passes over groove
1004
, followed by wiper blade
1006
, wiper blade
1006
tends to transfer ink from ledge
1011
into groove
1004
.
Conversely, in a case that wiper blade
1006
is moved first across nozzle surface
1002
, followed by wiper blade
1007
, wiper blade
1006
gathers ink within groove
1004
, and wiper blade
1007
proceeds to push the gathered ink onto ledges
1009
and
1010
.
Another conventional attempt to address the foregoing difficulties in wiping an engraved print head utilizes a specially-shaped non-planar wiper intended to contact all of nozzle surface
1002
, including groove
1004
, during wiping. However, such wipers, as currently used, fail to adequately wipe either one or both regions.
Accordingly, what is also needed is a system for effectively wiping ink away from a nozzle surface of an ink jet print head which is capable of effectively wiping engraved ink jet print heads.
SUMMARY OF THE INVENTION
In view of the foregoing, the present Applicants have discovered that buildup of ink upon a wiping element contributes significantly to degradation of wiping effectiveness over time. In this regard,
FIG. 3
a
illustrates a conventional wiping system. As shown in
FIG. 3
a
, wiper blade
1015
moves relatively across ink jet nozzles
1016
of ink jet print head
1017
. After wiping, ink wiped from print head
1017
is deposited as nodule
1019
upon wiper blade
1015
. Applicants have discovered that because conventional systems allow nodule
1019
to dry, subsequent wipings fail to remove adequate amounts of nodule
1019
from wiper blade
1015
, even despite scraping of nodule
1019
with wiper cleaner
1018
during subsequent wipings. Accordingly, wiper blade
1015
gradually collects solid ink deposits, as shown in
FIG. 3
b
. These deposits reduce the effectiveness of wiping by presenting an uneven wiping surface to print head
1017
during wiping.
The present invention address the foregoing by wiping an ink jet print head having a wiper cleaner two consecutive times during a wiping sequence. By wiping an ink jet recording head twice, ink is not allowed to significantly harden upon a wiping element and is more effectively removed from the wiping element than with conventional wiping systems. As a result, the wiping element presents a more uniform surface to a print head during wiping and resulting wiping is more effective.
Therefore, in one aspect, the present invention is a system to perform a wiping operation upon an ink jet print head including a first motion of the ink jet print head in a first direction to wipe the ink jet print head against a wiping element, and a second motion of the ink jet print head in the first direction to wipe the ink jet print head against the wiping element.
By virtue of the foregoing aspect, wiping effectiveness increases. Moreover, a wiping element remains more free of ink than those of conventional systems, thereby providing more effective wiping over time.
Preferably, the system also includes a third motion of the ink jet print head in a second direction opposite to the first direction the third motion between the first and second motions to wipe the ink jet print head against the wiping element.
The foregoing preferred aspect also has the object of effectively wiping ink from an exceptionally wet print head, for example, after a purging operation.
Applicants have also discovered that wiping effectiveness is increased if ink located on a print head as well as on a wiping element is in a liquid state. The present invention utilizes this discovery by wetting an ink jet print head and a wiping element during a wiping process so as to more effectively wipe ink from the ink jet print head.
Therefore, in one aspect, the present invention is a system to wipe an ink jet print head including a first motion of the ink jet print head in a first direction against a wiping element to wipe the ink jet print head, and ejection of ink toward the wiping element during the first motion. In one preferred arrangement, ink ejected toward the wiping element deflects off of the wiping element and collects on the ink jet print head. The system also preferably includes control of the ejection based upon a shape of the wiping element during the first motion.
In a related aspect, the present invention also includes ejection of ink toward a top edge and a trailing surface of the wiper element during the first motion, and/or a second motion of the ink jet print head in a second direction opposite to the first direction to wipe the ink jet print head against the wiping element.
It should be noted that various combinations of the above aspects can be used during printer operation in order to ensure fast and effective wiping. In this regard, the present invention also relates to a system to wipe an ink jet print head in a p

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