Typewriting machines – Control of print position along print-line by signal...
Reexamination Certificate
1998-12-04
2001-05-15
Hilten, John S. (Department: 2854)
Typewriting machines
Control of print position along print-line by signal...
C400S283000
Reexamination Certificate
active
06231250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a print device wherein a hammer bank forms an image on a recording medium while reciprocally transported by a shuttle mechanism. The present invention more particularly relates to such a print device including a reversing urging means for reversing a transporting direction of the hammer bank and to a method of controlling reciprocal movement of the hammer bank.
2. Description of Related Art
There has been known a print device including a hammer bank for forming an image on a recording medium, such as a sheet of paper, while reciprocally transported. Dot line printers and shuttle printers are representative examples of such print devices. Several types of shuttle mechanisms are known for reciprocally transporting the hammer bank. For example, one type of mechanism is provided with a cam or a link mechanism for converting rotational drive of a drive motor into a linear movement. Another type of mechanism reverses a transport direction of the hammer bank by changing rotational direction of a drive motor. There is also known a direct drive type mechanism including a linear motor. The direct drive type mechanism requires no transmission mechanism for transmitting drive of the linear motor to the hammer bank.
In order to provide a print unit wherein printing is performed in a improved speed, there has been proposed a shuttle mechanism provided with urging means, such as a spring. The urging means facilitates acceleration of transport speed of the hammer bank when its transport direction is reversed.
FIG. 1
shows an example of printing unit of a print device. The print unit includes such a shuttle mechanism provided with springs. Specifically, as shown in
FIG. 1
, the printing unit
1
includes a shuttle mechanism
2
, a hammer bank
3
, a sensor
4
, and a shuttle drive mechanism. The shuttle mechanism
2
includes a guide shaft
11
, direct drive bearings
12
, a linear motor
20
, an inversion mechanism
30
, and springs
40
. The shuttle drive mechanism includes a controller
50
, a shuttle control circuit
60
, and a shuttle drive circuit
70
. The guide shaft
11
extends leftward and rightward as viewed in FIG.
1
. The direct drive bearings
12
are reciprocally movably mounted on the guide shaft
11
. The hammer bank
3
is supported on the direct drive bearings
12
, and so reciprocally movable with the direct drive bearings
12
. Although not shown in the drawings, the hammer bank
3
is provided with a plurality of printing hammers for forming a dot pattern on a recording medium based on print data received from an external device. The linear motor
20
is provided with a coil
21
and magnets (not shown), and driven in a well known manner. Although not shown in the drawings, the coil
21
includes a reverse coil and a constant velocity coil. The inversion mechanism
30
has a pair of timing pulleys
32
and a timing belt
31
wound around the timing pulleys
32
. The coil
21
is connected to the direct drive bearings
12
via the inversion mechanism
30
. With this configuration, the drive force of the linear motor
20
is transmitted to the direct drive bearings
12
so as to reciprocally transport the direct drive bearings
12
. The coil
21
is also reciprocally transported in synchronization with the direct drive bearings
12
, but always in a direction opposite to the direction in which the direct drive bearings
12
are transported. In this way, the coil
21
serves as a counter balance. That is, when the direct drive bearings
12
with the hammer bank
3
mounted thereon are reciprocally transported, such a reciprocal movement of the coil
21
, which has a fixed weight, achieves leftward and rightward weight balance of the print device, thereby reducing vibration generated on the print device due to the transport of the direct drive bearings
12
.
As shown in
FIG. 1
, the springs
40
are disposed at each end of the guide shaft
11
and the coil
21
for supplying repulsive force to the hammer bank
3
, via the direct drive bearings
12
, and the coil
21
when their transport directions are changed during reciprocal transport. The sensor
4
is provided near a movable portion, which in the present example is on the hammer bank side, for detecting a position of the hammer bank
3
. The shuttle drive circuit
70
energizes the coil
21
by supplying an electric current, and the shuttle control circuit
60
controls the amount of electric current supplied to the coil
21
. Based on positional information supplied by detection by the sensor
4
, the controller
50
controls the shuttle control circuit
60
and the shuttle drive circuit
70
to move the hammer bank
3
in a predetermined shuttle speed pattern which is graphically shown in FIG.
3
. The controller
50
also receives a variety of commands from an external device (not shown).
FIG. 2
shows a sheet transport mechanism
80
. A platen
81
is rotatably supported on a printer frame (now shown). A pair of left and right pin tractors
82
are provided for transporting a sheet S on the platen
81
in a direction perpendicular to the reciprocal movement direction of the hammer bank
3
. The platen
81
and the pin tractor
82
are driven by a sheet feed motor
83
. An ink ribbon
84
is provided for supplying ink.
As shown in
FIGS. 3 and 4
, the hammer bank
3
is reciprocally moved in a transport region defined by a pair of predetermined reversing positions P
0
. The transport region is divided into a constant velocity region and two reverse regions. The constant velocity coil and the reverse coil are energized in the constant velocity region and in the reverse regions, respectively. In the constant velocity region, the hammer bank
3
is transported at a constant speed. On the other hand, in the reverse regions, the hammer bank
3
abuts against the spring
40
and influenced by the repulsive force of the spring
40
. That is, in the reverse regions, the repulsive force is generated, and deceleration and acceleration of the shuttle are performed.
More specifically, when the hammer bank
3
enters the reverse region from the constant velocity region, the hammer bank
3
is decelerated by pressing against the spring
40
. Then, the velocity of the hammer bank
3
drops to zero at the reverse point P
0
wherein the spring
40
is maximally compressed. At this point, the repulsive force of the spring
40
increases to its maximum, and the transport direction of the hammer bank
3
is reversed. Next, the repulsive force of the spring
40
starts accelerating the hammer bank
3
in the reverse direction.
In the above-described print unit
1
, there is a need to perform initialization operations when the print unit
1
is first started. The initialization operations mean repeating reciprocal transport, that is, shuttle operations, of the hammer bank
3
not associative with printing operations until a predetermined shuttle speed is achieved. More specifically, when the printing unit
1
is driven, the shuttle operations are started. However, the predetermined shuttle speed cannot be reached immediately. Therefore, the shuttle speed is gradually increased by repeating shuttle operations using the repulsive force of the spring
40
. As the hammer bank
3
accelerates, the amount that the hammer bank
3
compresses the spring
40
increases. Printing is started once the hammer bank
3
compresses the spring
40
by a predetermined amount and the shuttle speed reaches a predetermined shuttle speed.
The initialization operations are also performed when shuttle operations are restarted after shuttle operations are temporarily stopped during printing.
As shown in
FIG. 4
, the shuttle operations during printing are repeated at a substantially fixed cycle. Normally, sheet feed operations are performed while the hammer bank
3
is in one of the reverse regions. That is, after a single row's worth of printing is completed at a position P
1
, sheet feed operations are performed for a single line's distance and completed by the
Mamiya Hideaki
Matsumoto Yoshikane
Ohmura Yuji
Tobita Satoru
Hilten John S.
Hitachi Koki Co,. Ltd.
McGuireWoods LLP
Nolan, Jr. Charles H.
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