Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-02-04
2004-01-27
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S040000
Reexamination Certificate
active
06682171
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ink jet head unit for performing color printing by using a plurality of ink nozzle arrays each for use in printing one line, the plurality of ink nozzle arrays corresponding to a plurality of basic colors, and an ink jet printing apparatus incorporating the head unit.
2. Prior Art
Conventionally, an ink jet head unit of this kind was proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 10-95114. In this ink jet head unit, ink nozzle arrays each for use in printing one line are divided with respect to the direction along the line (by cutting each line in a direction crosswise to the direction along the line) into a plurality of divisional ink nozzle arrays, and ink jet heads are constituted by the divisional ink nozzle arrays, respectively. The plural ink jet heads formed as above are arranged in a manner staggered from each other on a support base, and each of them is fixed to the support base by two screws.
In the conventional ink jet head unit, since the ink nozzle arrays each for printing one line are divided to form the ink jet heads, the yield of the ink jet head unit can be improved. However, it is required to fix each of the plural ink jet heads onto the support base with precision, which makes it difficult to ensure positional accuracy between the ink jet heads.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ink jet head unit which is capable of incorporating a large number of ink jet heads with ease and precision, and an ink jet printing apparatus incorporating the ink jet head unit.
To attain the above object, according to a first aspect of the invention, there is provided an ink jet head unit for performing color printing by using a plurality of ink nozzle arrays each for use in printing one line, the plurality of ink nozzle arrays corresponding to a plurality of basic colors.
The ink jet head unit according to the first aspect of the invention is characterized by comprising:
a plurality of head groups each formed by a plurality of ink jet heads, and having the plurality of ink nozzle arrays arranged therein such that the plurality of ink nozzle arrays are divided among the plurality of head groups;
a plurality of sub-carriages having respective ones of the plurality of head groups mounted thereon; and
a unitizing carriage having the plurality of sub-carriages mounted thereon.
According to this ink jet head unit, a plurality of ink jet heads constituting each head group are mounted on a sub-carriages, and hence it is possible to mount the ink jet heads on the sub-carriage with relatively high accuracy. Further, a plurality of sub-carriages thus constructed are mounted on a unitizing carriage. This makes it possible to mount all the ink jet heads on the unitizing carriage with relatively high accuracy. In short, by ensuring positional accuracy between each individual ink jet head and a corresponding one of the sub-carriages as well as between each sub-carriage and the unitizing carriage, it is possible to ensure a high mounting accuracy between each ink jet head and the unitizing carriage. Therefore, it is possible to mount a large number of ink jet heads on the unitizing carriage with precision, without any need to directly consider positional accuracy between the individual ink jet heads and the unitizing carriage.
It should be noted that the term “one line” mentioned above means “a line of dots corresponding to a sequence of ink nozzles on the head unit substantially corresponding to a printing width in a sub scanning direction”. The term is intended to include a line of dots corresponding to a combination of divisional ink nozzle arrays, referred to hereinafter, and further, a line of dots in the case where the combination of divisional ink nozzle arrays are arranged in the sub scanning direction in an overlapping fashion. However, it is not intended to mean the width of a print medium.
Preferably, the plurality of ink nozzle arrays are each divided into a plurality of divisional ink nozzle arrays with respect to a direction along the one line, and are grouped into a plurality of divisional ink nozzle array groups each formed of corresponding ones of the plurality of divisional ink nozzle arrays, and the plurality of ink jet heads of each of the plurality of head groups have the plurality of divisional ink nozzle arrays of a corresponding one of the plurality of divisional ink nozzle array groups arranged therein such that the plurality of divisional ink nozzle arrays are divided among the plurality of ink jet heads.
According to this preferred embodiment, each divisional ink nozzle array group is formed by a plurality of ink jet heads and mounted on an associated sub-carriage. Therefore, it is possible to intensively arrange the (divisional) ink nozzle arrays of the basic colors. This makes printing, especially, color matching printing less susceptible to the accuracy or inaccuracy of the moving position of the head unit in the main scanning direction, so that it is possible to prevent degradation of print quality due to displacement of dots.
Alternatively, the head groups may be constructed such that each of them has ink nozzle arrays of a corresponding one of the basic colors.
Preferably, the plurality of sub-carriages are arranged in a manner staggered from each other on the unitizing carriage.
According to this preferred embodiment, the plurality of sub-carriages can be more intensively arranged on the unitizing carriage. Therefore, the unitizing carriage can be made compact in size, and a large number of ink jet heads can be intensively arranged.
More preferably, each of the ink jet heads comprises a head base plate, and a head body arranged in one substantial half of the head base plate toward one longitudinal side, the head body having a corresponding portion of the plurality of ink nozzle arrays arranged therein, and in each two of the plurality of head groups, adjacent to each other with respect to a direction along the line, the head body of each of the plurality of ink jet heads of one of the two head groups and the head body of each of the plurality of ink jet heads of another of the two head groups are arranged opposed to each other in a back-to-back fashion.
According to this preferred embodiment, the ink jet heads can be arranged further intensively.
Preferably, the plurality of ink jet heads are bonded to a corresponding one of the plurality of sub-carriages in a positioned state.
According to this preferred embodiment, each ink jet head is positioned on a corresponding one of the sub-carriages e.g. by using a jig and then fixedly bonded to the same. Therefore, differently from the case of fixing the ink jet heads by screws or the like, it is possible to effectively prevent positional displacement of the ink jet head. Moreover, this facilitates the work of fixing each ink jet head onto a sub-carriage.
Preferably, the unitizing carriage has a plurality of positioning pin groups provided on a surface thereof, for enabling each of the plurality of sub-carriages to be mounted in a positioned state, and each of the positioning pin groups positions a corresponding one of the plurality of sub-carriages on the unitizing carriage, with reference to a reference position set to a position of an outermost ink nozzle of an arbitrary one of the plurality of ink jet heads mounted on the corresponding one of the plurality of sub-carriages.
According to this preferred embodiment, in positioning each sub-carriage on the unitizing carriage, the position of the outermost ink nozzle of an ink jet head is set to a reference position for positioning the sub-carriage. Therefore, it is possible to minimize influence of positioning error between the sub-carriages and the unitizing carriage. Further, since the sub-carriages are each removable from the unitizing carriage, replacement of the sub-carriages is facilitated.
More preferably, the each of the positioning pin groups comprises a reference pin arranged in a manner corresponding to the reference p
Hogan & Hartson LLP
Nguyen Lamson
Seiko Epson Corporation
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