Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-12-08
2001-04-17
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06217164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recorder. In particular, the invention relates to an ink jet recorder with an ink supply system including an ink tank and a recording head which are connected by a supply tube.
2. Description of Related Art
A conventional ink jet recorder such as an ink jet printer includes an ink tank and a recording head, which are connected by a supply tube and a return tube. The recorder also includes a pump for circulating ink between the tank and the head.
FIGS. 27-29
of the accompanying drawings schematically show a known ink supply system. With reference to
FIG. 27
, an ink jet printer
100
includes a sub tank
4
a
and a head unit, which includes a print head
5
a
. The tank
4
a
and the head
5
a
are connected by two supply tubes
21
a
and two return tubes
22
a
. The upstream supply tube
21
a
is fitted with a circulating pump. The upstream supply tube
21
a
and the downstream return tube
22
a
are connected to the downstream supply tube
21
a
and the upstream return tube
22
a
, respectively, by a joint
40
. The joint
40
has two passages formed through it, one of which communicates with the supply tubes
21
a
, and the other passage communicates with the return tubes
22
a.
Each of the passages is fitted with a filter
32
for removing foreign substances etc. from ink. The head unit is mounted on a carriage, and can reciprocate at high speed over a printing medium. The reciprocating unit is followed by the upstream supply tube
21
a
and the downstream return tube
22
a
, which are connected to it. While these tubes
21
a
and
22
a
are reciprocating at high speed, waves are generated in the ink in the tubes. If the waves propagate to the head
5
a
, they affect the characteristics of ink ejection. The filters
32
for the passages also function to prevent the waves from propagating to the head
5
a
. The filters
32
are positioned horizontally so that ink can flow vertically through them. The ink flowing between the supply tubes
21
a
moves downward through the associated filter
32
. The ink flowing between there turn tubes
22
a
moves upward through the other filter
32
.
Otherwise, the joint
40
and the filters
32
might be positioned in such a manner that ink could flow horizontally through the filters.
Very small air bubbles may be contained in the ink supplied from the sub tank
4
a
to the recording head
5
a
. If some of the bubbles are trapped on the filter
32
in the supply line, the trapped bubbles tend to move up buoyantly, and can hardly pass through this filter. Therefore, the trapped bubbles are liable to stay or be retained on the filter
42
. The staying bubbles reduces the contact or touch area between the filter
42
and ink, and therefore reduces the effective area of this filter. This prevents a sufficient amount of ink from flowing to the head
5
a
, and therefore defective recording may occur. The staying bubbles act as dampers, which may hinder or impede the intended normal ink flow when the circulating pump is driven.
As shown in
FIGS. 28 and 29
, the joint
40
includes a double connector
151
, a seal member
152
and a holder
153
, which engages with the connector. The double connector
151
includes integral twin connectors, each of which is connected to one of the upstream supply tube
21
a
and the downstream return tube
22
a
. Each of the twin connectors is fitted with one of the filters
32
on its bottom. The seal member
152
surrounds bottom portions of the twin connectors. The holder
153
includes integral twin connectors, each of which is connected to one of the downstream supply tube
21
a
and the upstream return tube
22
a
. The double connector
151
also includes lock pawls
151
a
. The holder
153
also includes lock pawls
153
a
for each engaging with one of the pawls
151
a
to keep it and the double connector
151
connected. The holder
153
further includes a ridge
153
b
formed on its top for engaging with the seal member
152
to seal the junctions between the holder
153
and the connector
151
. The ridge
153
b
is positioned away from the passages in the joint
40
and the filters
32
. Therefore, gaps are liable to be formed between the ridge
153
b
and each of the passages and the filters
32
. Air bubbles may stay in the gaps. If the bubbles grow larger, they narrow the passages. This makes it impossible to secure the necessary amount of ink flow.
Because the joint
40
includes a number of parts, its production costs are high.
Another conventional ink jet recorder of the foregoing type includes a carriage, on which a head holder can be mounted. The head holder is fitted with a connector. The system also includes an ink tank, which is connected to a supply tube and a return tube. When the head holder is mounted on the carriage, the connector is connected to the tubes. The mounting involves positioning the head holder with high accuracy to align the connector with the tubes.
U.S. Pat. No. 5,359,357, which corresponds to Japanese Patent Application Laid-Open No. 5-318761, discloses an ink jet recorder including a carriage, a head unit, an ink supply tube and an ink return tube. Each of the tubes is connected to a connector. The elasticity of the seal rubber of the connector absorbs the displacement or misalignment of the connector from the associated tube when the head unit is mounted on the carriage. Because the amount of deformation of the seal rubber is limited, however, it is not possible to absorb a large amount of displacement.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the invention to provide an ink supply system for an ink jet recorder in which, when ink flows through the filter in the ink passage, the air trap at the filter is reduced to increase the substantially effective area of the filter.
It is another object of the invention to provide an ink supply system for an ink jet recorder in which common parts are used for the joint connecting the ink supply tubes and for the joint connecting the ink return tubes so that the number of parts and the production costs for the joints can be reduced, and in which no air bubbles stay in the joints so that good recording results can be produced.
It is still another object of the invention to provide an ink supply system for an ink jet recorder which includes small joints in the ink supply lines, the joints being able to be assembled out of parts by a simple process, and in which few air bubbles are liable to stay at the junctions between parts of the joints so that ink can be supplied always normally.
It is a further object of the invention to provide an ink supply system for an ink jet recorder in which, when the recording head is mounted on the carriage, it is possible to simply align the upstream and downstream supply tubes with each other.
In accordance with a first aspect of the invention, an ink jet recorder is provided which comprises:
a tank for storing ink;
an ink jet head for ejecting the ink onto a recording medium;
an ink tube for connecting the tank and the head, a part of the ink tube being formed such that the ink can flow upward; and
an ink filter for removing foreign substances from the ink, the ink filter being fitted in the part of the ink tube.
The ink filter of this recorder is fitted in the part of the ink tube where ink can flow upward. Consequently, the air bubbles flowing with ink from the tank or the air bubbles produced in the ink pass easily with buoyancy through the filter, and are therefore restrained from being trapped by the filter. This prevents the bubbles from staying at the filter, and can therefore increase the effective area of the filter.
In general, an ink jet recorder carries out cleaning or maintenance by ejecting ink forcedly out of the ink jet head to prevent the head from clogging. The maintenance involves discharging air bubbles together with ink from the head, or recovering air bubbles into the tank.
The recorder according to the first aspect may include a pump for circ
Brother Kogyo Kabushiki Kaisha
Le N.
Oliff & Berridg,e PLC
Vo Anh T. N.
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