Typewriting machines – Typing by other than type-face or type-die – Character formation by impact
Reexamination Certificate
2001-04-02
2004-03-02
Hirshfeld, Andrew H. (Department: 2854)
Typewriting machines
Typing by other than type-face or type-die
Character formation by impact
C400S124010, C400S124040, C400S279000
Reexamination Certificate
active
06698955
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for adjusting the print positions of a dot line printer.
A method and an apparatus for adjusting the print positions of a dot line printer in the prior art will be described in detail with reference to the drawings.
FIG. 1
is a perspective view for explaining a first prior-art example (refer to, for example, Japanese Unexamined Patent Publication (JP-A) No. 244282/1996).
The dot line printer is constructed of a hammer bank
2
in which a large number of printing hammers
1
are arrayed in one row, a shuttle mechanism
8
which vibrates the hammer bank
2
laterally at a predetermined amplitude, a sheet feed mechanism
12
, and so forth.
In the shuffle mechanism
8
, the hammer bank
2
supported by right and left parallel flat springs
7
is connected to an eccentric cam
6
of a shuttle drive motor
5
through a connecting rod
4
. When the shuttle drive motor
5
is rotated, the hammer bank
2
is vibrated in an approximate sinusoidal wave rightwards and leftwards. The sheet feed mechanism
12
is constituted by a platen
9
for transporting a printing sheet
13
, and a sheet feed motor
11
for driving the platen
9
through a belt
10
, thereby to transport the sheet
13
every dot line very exactly. While the hammer bank
2
is vibrated, the respective printing hammers
1
are operated to print dots at predetermined intervals, so that one row of dots is formed by the one-way operation (forward printing) Subsequently, when the hammer bank
2
is turned back (for reverse printing), the sheet
13
is transported the interval of one dot line, and the next dot line is printed. Further, the sheet
13
is transported one dot line immediately before forward printing. Characters are printed by repeating such operations. Incidentally, numeral
3
designates an inking ribbon.
FIG. 2
is a waveform diagram showing the printing timing signals of the prior-art dot line printer. A hammer bank leftmost-end signal
30
and a hammer bank rightmost-end signal
31
indicating the arrivals of the hammer bank
2
at the leftmost end and rightmost end thereof start a forward printing timing signal
32
for executing the forward printing and a reverse printing timing signal
33
for executing the reverse printing, respectively. Both the forward printing timing signal
32
and the reverse printing timing signal
33
are generated substantially at the time when hammer bank speed
36
is a set value. Since the printing is performed by reciprocally moving the hammer bank
2
by means of the shuttle mechanism
8
, the printing of the identical printing hammer
1
must not allow a misalignment or shear between the lateral printing of the forward printing mode and that of the reverse printing mode. It is difficult, however, to avoid the lateral print shear of the identical printing hammer
1
between the forward and reverse printing modes merely by keeping the mechanical balance of the shuttle mechanism
8
which reciprocally moves the hammer bank
2
. In the prior-art dot line printer, therefore, a reverse printing timing signal
35
as shown in
FIG. 2
is generated after a delay of a time period after the transmission of the pulse of the hammer bank rightmost-end signal
31
. The printing of the identical printing hammer
1
can be freed from the lateral print shear between in the forward printing mode and in the reverse printing mode by adjusting the time period t.
Besides, the line feed of the dot line of the sheet
13
is started by the final pulse of both the forward printing timing signal
34
and the reverse printing timing signal
35
.
With the method for adjusting the print positions of the dot line printer in the first prior-art example, it is intended to compensate for the lateral print shear of the identical printing hammer
1
by shifting the reverse printing timing signal
35
in the reciprocal motion. On the other hand, the sheet line feed operation is started by the final pulse of both the forward printing timing signal
34
and the reverse printing timing signal
35
, so that decrease or increase in the time period of the line feed is incurred. Accordingly, the sheet
13
does not cease moving before the start of the printing as shown by the sheet line feed speed
37
in
FIG. 2
, and hence, print dot positions become disordered to degrade print quality.
FIG. 3
is a waveform diagram showing a second prior-art example. Here in the second prior-art example, a dot line printer itself is supposed the same as shown in
FIG. 1. A
hammer bank leftmost-end signal
20
and a hammer bank rightmost-end signal
21
indicating the arrivals of the hammer bank
2
at the leftmost end and rightmost end thereof start a forward printing timing signal
22
for executing the forward printing and a reverse printing timing signal
23
for executing the reverse printing, respectively. Both the forward printing timing signal
22
and the reverse printing timing signal
23
are substantially generated at times when hammer bank speed
26
is a predetermined value.
Since the printing is performed by reciprocally moving the hammer bank
2
by means of the shuttle mechanism
8
, in the printing of the identical printing hammer
1
shear or misalignment between the lateral print of the forward printing mode and that of the reverse printing mode is not allowable. It is difficult, however, to avoid the lateral print shear of the identical printing hammer
1
between in the forward printing mode and in the reverse printing mode merely by keeping the mechanical balance of the shuttle mechanism
8
which reciprocally moves the hammer bank
2
.
Therefore, a forward printing timing signal
24
as shown in
FIG. 3
is generated after a delay of a time period t
1
following generation of the pulse of the hammer bank leftmost-end signal
20
.
Subsequently, a reverse printing timing signal
25
as shown in
FIG. 3
is generated after a delay of a time period t
2
following generation of the pulse of the hammer bank rightmost-end signal
21
. The printing of the identical printing hammer
1
can be freed from the lateral print shear between the forward printing mode and the reverse printing mode by adjusting the time periods t
1
and t
2
.
The line feed of the dot line of the sheet
13
is started by the final pulse of both the forward printing timing signal
24
and the reverse printing timing signal
25
. In this embodiment, the forward printing timing signal
24
and the reverse printing timing signal
25
are both adjusted by the predetermined adjustment time periods t
1
and t
2
relatively to the hammer bank leftmost-end signal
20
and the hammer bank rightmost-end signal
21
, respectively. As shown by a sheet line feed speed
27
in
FIG. 3
, therefore, decrease or increase in the time period of the line feed is not incurred, to eliminate the drawback that the sheet
13
does not come to a stop before the start of the printing, causing print dot positions to become disordered to degrade print quality. Further, the adjustment can be facilitated more by equalizing the adjustment time periods t
1
and t
2
.
With the method and apparatus for adjusting the print positions of the dot line printer in the second prior-art example, only one printing element assembly is concerned, and hence, the print shear can be avoided by adjusting the forward and reverse printing timing signals. However, in a case where a dot line printer includes a plurality of printing element assemblies and where the relative positions of the printing element assemblies in the extending direction thereof (in the line direction of a printing sheet) are not exactly in alignment, the relative positions of the print dots of the printing element assemblies cannot be corrected merely by the pair of printing timing signals in the forward and reverse modes.
Further, even in case of a known dot line printer whose printing mechanism module has a plurality of printing element assemblies, only one drive circuit is included, and only one printing timing signal is generated by
Chu Minh H.
Hirshfeld Andrew H.
McGinn & Gibb PLLC
NEC Corporation
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