Line ink jet head and a printer using the same

Details Line ink jet head and a printer using the same Line ink jet head and a printer using the same

2000-04-04

2001-11-13

Nguyen, Thinh (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S013000, C347S049000

Reexamination Certificate

active

06315390

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a line ink jet head used as an ink jet head in a line printer. More particularly, the present invention relates to an on-demand type line ink jet head comprising an arrangement of a plurality of identically structured ink jet head units.
BACKGROUND
An ink jet device comprising a line ink jet head of this type is taught, for example, in Japanese Examined Patent Application (kokoku) 3-58917. An ink jet device as taught in the cited application comprises a line ink jet head having a plurality of ink jet head units, each having a plurality of ink nozzles, arranged in series in line with the ink nozzle arrangement (that is, in the line printing direction).
The ink jet head units
10
(n) (where n is an integer of one or more with only ink jet head units
10
(
1
) and
10
(
2
) shown in
FIG. 13
) are arranged in line as shown in FIG.
13
and bonded together end to end. The ink nozzles
11
(m) (where m is an integer of one or more) arrayed in line in the line printing direction must be spaced with the same pitch p between every nozzle. The last and first (i.e., endmost) ink nozzles
11
(
128
) and
11
(
1
) in adjacent ink jet head units
10
(
1
) and
10
(
2
) must also be placed at this same pitch p. This means that the thickness of the wall separating the ink chambers communicating with the ink nozzles
11
(
1
) and
11
(
128
) at the ends of each ink jet head unit, that is, the adjacent end walls
12
(
1
) and
12
(
128
) of the ink jet head units, must be half the thickness of the wall separating the ink chambers communicating with the other ink nozzles.
Changing the wall thickness, however, means that the rigidity of the end walls is less than the rigidity of the other internal ink chamber dividers, and the ink discharge characteristic of the ink nozzles associated with these end ink chambers differs from the discharge characteristic of the other internal ink nozzles. This is undesirable because a difference in ink discharge characteristics lowers print quality.
Furthermore, as noted above the ink jet head units are bonded together at the outside of these end walls. This means that the end walls must be finished with good precision. This, however, makes manufacturing that much more difficult, and is thus undesirable.
These problems can be resolved by arranging the ink nozzles of the ink jet head units in a staggered pattern as taught in Japanese Unexamined Patent Application (kokai) 8-127137.
A problem with a staggered arrangement of ink nozzles in the ink jet head units is that positioning the inkjet head units to each other becomes more difficult. Imprecise alignment of the ink jet head units results in lower print quality, and is thus obviously undesirable. In addition, no method for precisely and easily aligning ink jet head units to each other has yet been proposed.
When using a staggered ink nozzle arrangement it is also necessary to adjust the ink nozzle drive timing between ink jet head units so that the ink drops ejected from different ink nozzles are placed on the same line on the print medium. Therefore, when the line ink jet head comprises a plurality of ink jet head units with a staggered ink nozzle array, the circuitry needed to adjust the drive timing is more complex compared with the drive circuitry of a line ink jet head having the ink nozzles in a straight line.
SUMMARY
In general, in one aspect, the invention features a line ink jet head having a plurality of ink jet head units, each having a plurality of ink nozzles formed in a line, arranged in the direction of the ink nozzle line, includes a head unit mounting layer, a head unit mounting surface formed on at least one side of this head unit mounting layer, a plurality of the ink jet head units affixed in a staggered pattern in the direction of the ink nozzle line on the head unit mounting surface, and a common ink supply path formed in the head unit mounting layer for supplying ink to each ink jet head unit. Each ink jet head unit includes an ink nozzle surface in which the ink nozzles are formed; and a mounting reference surface for affixing the ink jet head unit to the head unit mounting surface, the mounting reference surface being orthogonal to the ink nozzle surface and parallel to the direction of the ink nozzle line.
The ink jet head units can be precisely aligned to each other in staggered rows by means of simply bonding the mounting reference surface of each ink jet head unit to a head unit mounting surface formed on the head unit mounting layer.
In an implementation, the head unit mounting surface is first and second head unit mounting surfaces parallel to each other with a specific interval therebetween and formed on different surfaces of the head unit mounting layer. An odd numbered inkjet head unit is bonded to each first head unit mounting surface, and an even numbered ink jet head unit is bonded to each second head unit mounting surface.
In another implementation, the first and second head unit mounting surfaces can be formed on the same side of the head unit mounting layer
2
. The first head unit mounting surfaces are formed at a specific interval on this surface of the head unit mounting layer. Between first head unit mounting surfaces is a protrusion protruding a specific distance from the surface of the head unit mounting layer. The second head unit mounting surfaces are then formed on these protrusions.
In an implementation, the inkjet head is an electrostatic drive type. An electrostatic drive type ink jet head unit comprises an ink pressure chamber communicating with an ink nozzle, and an electrostatic drive mechanism for changing the volume of the ink pressure chamber using electrostatic force to discharge ink drops from the ink nozzles as a result of this volume change.
To further downsize this electrostatic drive type ink jet head unit, the ink jet head unit preferably has laminated first, second, and third substrates bonded to each other. A common ink chamber communicating with the common ink path is formed in the first substrate. The ink nozzles and ink pressure chamber are formed between the first and second substrates. The electrostatic drive mechanism is preferably formed between the second and third substrates.
In another implementation, the side of the first substrate opposite the side thereof to which the second substrate is bonded, or the side of the third substrate opposite the side thereof to which the second substrate is bonded, is the mounting reference surface.
To avoid requiring complex circuitry for adjusting the drive timing of the staggered ink jet head units in a line ink jet head according to the present invention, the distance between offset ink nozzle lines in the staggered ink jet head units is an integer multiple of the base resolution of a printed image.
In another aspect, the invention features a printer having a line ink jet head, a form transportation mechanism for transporting a print medium; and an ink supply mechanism for supplying ink to the line ink jet head. The line ink jet head is disposed covering a printing area of a print medium transported by the form transportation mechanism.
By printing to a print medium by means of the line ink jet head while transporting thereby a print medium, a printer according to the invention can print at high speed without requiring a complex drive circuit, and is simple to manufacture.
An advantage of the present invention is to provide a line ink jet head whereby ink jet head units having a staggered ink nozzle array can be positioned to each other easily with good precision.
A further advantage of the present invention is to provide a line ink jet head in which the drive timing of the ink jet head units having a staggered ink nozzle array can be adjusted without making the drive circuitry complex.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.


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