Multi-head printer

Details Multi-head printer Multi-head printer

1998-06-23

2001-09-25

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S041000, C347S042000

Reexamination Certificate

active

06293651

ABSTRACT:

BACKGROUND OF INVENTION
The present invention relates to a printer which prints data at high speed through use of a multi-head having a plurality of printing heads placed thereon, wherein the printing heads form a plurality of printing elements. More particularly, the present invention relates to an ink-jet printer, a laser printer, an LED printer, or a thermal recording printer.
The dominant existing printer for recording a color image is an inexpensive color printer having a simple structure. In order to enable a common ink-jet serial printer such as that shown in
FIG. 4
to print a high-quality monochrome or color image at high speed, the resolution of nozzles must be increased by increasing the density of nozzles of a printing element
101
, the element recording an image on recording paper
102
wrapped around a platen
103
, as well as to increase the printing speed of the printing element
101
by increasing its length in the secondary scanning direction and increasing the number of nozzles. As a result of a reduction in the particle weight of a droplet to be squirted from the nozzle and an increase in the number of nozzles, an inexpensive ink-jet printer having a resolution of about 720 dpi has recently been realized.
However, a further increase in the density of printing elements involves an increase in the precision of a mechanism including the printing elements, thus adding to the cost. To prevent an increase in the cost, there is employed an interlaced driving method which uses a plurality of comb-shaped heads arranged in the primary scanning direction and offset from one another in the secondary scanning direction.
FIG. 5
shows nozzles of a conventional interlaced printing apparatus. Reference numeral
301
designates a nozzle for squirting recording ink (hereinafter may be referred to simply as “ink”);
302
to
305
designate ink squirting elements;
307
designates a retaining section; and
308
designates printing signal cables and ink feed pipes. The plurality of nozzles
301
are arranged in a line at given intervals, and one head is wholly formed from a plurality of nozzle lines. At the time of a primary scanning operation, data corresponding to print positions are supplied to the squirting elements
302
by way of the cables
308
, so that ink is squirted from the nozzles
301
to thus record the data on the paper.
However, in the conventional interlaced printing apparatus, the number (N) of nozzles
301
constituting a multi-nozzle is
15
, and the nozzles
301
are formed at a pitch (K) of 4 or so. Accordingly, the resolution of the nozzles is 720 dpi or less. If an attempt is made to increase the density of printing elements in order to increase resolution to 1000 dpi or more, which allows printing of halftone dots, the apparatus suffers a problem of a drop in print speed.
If an attempt is made to increase the print speed by increasing the number of nozzles, manufacturing yields of a print head are deteriorated, adding to cost.
SUMMARY OF INVENTION
To solve the foregoing problems, the object of the present invention is to provide a high-resolution, inexpensive multi-head printer which enables even a print head having a smaller number of nozzles to print data at high speed.
To accomplish the foregoing object, according to a first aspect of the present invention, there is provided a multi-head printer for printing an image on a medium, comprising: a plurality of printing heads, each head having a plurality of printing elements formed thereon at given pitches; and a multi-head to which the printing heads are fixed in one line at equal pitches.
According to a second aspect of the invention, there is provided the multi-head printer of the first aspect, wherein an interlaced printing operation is performed a plurality of times through use of the multi-head.
According to a third aspect of the invention there is provided the multi-head printer described above, further comprising: a drum having an outer periphery around which the medium is wrapped so as to face the multi-head, wherein the interlaced printing operation is carried out in the primary scanning direction through rotation of the drum.
With the foregoing configurations, a print data item is recorded on the recording paper wrapped around the outer periphery of the platen drum, by actuation of the multi-head having the printing elements provided in one line thereon in the primary scanning direction while the platen drum is rotated in the primary scanning direction, thus enabling simple interlaced recording of a print data item.
According to a fourth aspect of the invention, there is provided the multi-head printer described above, wherein the interlaced printing operation is carried out in the primary scanning direction by back-and-forth actuation of the multi-head.
According to a fifth aspect of the invention, there is provided the multi-head printer described above, wherein taking a pitch at which the printing elements are moved in the secondary scanning direction, or in the direction in which the printing elements are arranged, as “p,” and “j” as a natural number, and a pitch between the printing heads as “Q,” a relationship between the printing heads and their movement in the secondary scanning direction is defined so as to satisfy a relationship Q=j×p. As a result, a scanned area can be precisely filled without clearance or an overlapped portion through scanning operations carried out a plurality of times (“j” times).
Prefarably, the printing elements for each head are arranged to satisfy following equations: p=Nd, and N=kn+1, where N represents the number of printing elements effectively used in an actual printing operation, d represents the pitch of the printing elements, k represents a natural number, and n represents the number of divisions between the adjacent printing elements.


REFERENCES:
patent: Re. 28219 (1974-10-01), Taylor
patent: 3560641 (1971-02-01), Taylor
patent: 5057854 (1991-10-01), Pond et al.
patent: 5583550 (1996-12-01), Hickman et al.
patent: 5587730 (1996-12-01), Karz
patent: 5677719 (1997-10-01), Granzow
patent: 5710582 (1998-01-01), Hawkins et al.
patent: 0023433 (1981-05-01), None

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