Printing – Press part or attachment
Reexamination Certificate
2000-08-18
2002-01-08
Colilla, Daniel J. (Department: 2854)
Printing
Press part or attachment
C101S366000, C417S326000, C417S415000
Reexamination Certificate
active
06336405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pump for a printing machine for supplying ink while a plunger is rotated and reciprocated by a motor in an offset printing machine.
2. Description of the Background Art
There are conventionally many known examples of a pump for an offset printing machine. For example, Japanese Patent No. 286447 (prior art) discloses an ink pump for a printing machine for supplying ink by repeatedly reciprocating a plunger within a cylinder once while the plunger is rotated once by using a variable speed motor.
In the pump for a printing machine of the prior art, as shown in
FIG. 7
, a cylinder
102
has a suction hole
121
and a discharge hole
122
opened in positions in which a main hole
120
closed on one side thereof is shifted by 180 degrees in phase. This cylinder
102
is fixed to one side of a base
101
through the space of a hollow portion thereof. A plunger
103
is fitted and inserted into the main hole
120
of the cylinder
102
on the other side thereof so as to be rotated and reciprocated. The cylinder
102
is closed by the plunger
103
. One portion of a fitting circumferential face of the plunger
103
to the cylinder
102
is notched until its end tip and one end of the plunger
103
is projected from the other side of the main hole
120
to the hollow portion of the base
101
such that either the suction hole
121
or the discharge hole
122
can be communicated with the main hole
120
by rotating the plunger
103
.
A variable speed motor
104
is attached to the base
101
in accordance with the plunger
103
. An output shaft
140
of the variable speed motor
104
is projected to the hollow portion of the base
101
. A rotating central line of the output shaft
140
is set to cross a rotating central line of the plunger
103
by a predetermined angle. Further, an arm
160
is attached to the output shaft
140
so as to project to the hollow portion. A spherical bearing
162
arranged at the other end of the arm
160
and an end portion side of the plunger
103
are connected to each other by a connection member
161
so that a crossing angle between the rotating central line of the output shaft
140
and an axis of the connection member
161
can be changed.
The crossing angle between the rotating central line of the output shaft
140
and the axis of the connection member
161
becomes maximum at the final stage of a sucking stroke and becomes minimum at the final stage of a discharging stroke at the time of a rotating phase in which the plunger
103
simultaneously closes the suction hole
121
and the discharge hole
122
every half rotating phase of the plunger
103
.
FIGS. 8
a
to
8
f
are partial sectional perspective explanatory views showing an operating mode of the plunger
103
of the prior art, showing an operating mode where the plunger
103
is reciprocated once while the plunger
103
is fitted into the main hole
120
of the cylinder
102
and is rotated once in the direction of an arrow X.
FIG. 8
a
shows a terminating state of the sucking stroke in which the plunger
103
is located at an upper dead point and closes the suction hole
121
and the discharge hole
122
.
FIGS. 8
b
and
8
c
show states of the discharging stroke. In these states, while the suction hole
121
is closed, the plunger
103
is moved in an inserting direction of the main hole
120
while the plunger
103
is rotated in the direction of the arrow X. Then, ink is discharged from the discharge hole
122
.
FIG. 8
d
shows a terminating state of the discharging stroke in which the plunger
103
is located at a lower dead point and closes the suction hole
121
and the discharge hole
122
.
FIGS. 8
e
and
8
f
show states of the sucking stroke. In these states, while the discharge hole
122
is closed, the plunger
103
is moved in a direction pulled out of the main hole
120
while the plunger
103
is rotated in the direction of the arrow X. The ink is then sucked from the suction hole
121
.
In the pump P of the prior art, ink piping is connected between a fluid passage on an ink discharging side and an ink rail to discharge the ink sucked from an external ink tank.
When the variable speed motor
104
for operating the plunger
103
is a stepping motor
104
shown in an embodiment mode of the prior art, rotation of this stepping motor is controlled by a pulse signal. When it is not necessary to discharge the ink, or when the stepping motor is intermittently driven to adjust a discharging amount of the ink, the rotation of a rotor of the stepping motor
104
corresponding to the plunger
103
is stopped in accordance with necessity. Further, an exciting current flows through the stepping motor to self-hold a stopping position of this stepping motor
104
, or the electric current flowing through the stepping motor
104
corresponding to the plunger
103
is interrupted in accordance with necessity so that an unmagnetizing state is set. Thus, the operation of the plunger
103
is ceased or is temporarily stopped.
The above prior art has several problems to be solved. For example, in the pump P of the prior art, the internal pressure of the ink pipe on the discharging side is increased by a discharging pressure of the ink at the discharging stroke of the ink so that force for pushing back the plunger
103
is caused. Further, at the discharging stroke of the ink, the crossing angle between the rotating central line of the output shaft
140
and the axis of the connection member
161
is gradually changed from a maximum angle to a minimum angle. Accordingly, the force for pushing back the plunger
103
is applied such that the arm
160
is angularly displaced in a reverse direction through the connection member
161
and the spherical bearing
162
. Thus, the output shaft
140
begins to be angularly displaced in the reverse direction.
In rotating control using the stepping motor
104
, a method for performing a magnetizing operation by flowing an electric current through winding of the stepping motor
104
is adopted to give self holding force to the output shaft
140
such that the output shaft
140
is not rotated by an external force during stoppage of the stepping motor. The stepping motor
104
is heated by this magnetizing electric current. There is a case in which the surface temperature of the stepping motor
104
is increased to 60 degrees centigrade or more in accordance with an operating condition of the pump P.
When the printing machine is operated at a relatively low speed, or the number of image lines of a printing plate is small, an ink supplying amount per unit time is small so that a stopping time of the pump P is lengthened. Therefore, the exciting current flows through the stepping motor during the stoppage of the pump P so that the stepping motor is heated. Accordingly, there is a case in which the stepping motor abnormally rises in temperature.
The temperature due to these heatings is transmitted to the base
101
and the cylinder
102
is heated so that the temperature of the ink rises and ink viscosity is reduced and the ink supplying amount becomes unstable and has a bad influence on printing quality. Further, when the electric current flowing through the stepping motor
104
is interrupted at the time of a pump stopping state during the operation of the printing machine to avoid this heating and no magnetizing operation is performed to restrain the heating, the plunger
103
is pushed back by the internal pressure of the ink piping on the discharging side caused by the ink discharging stroke. Displacement of the plunger
103
is transmitted to the arm
160
through the connection member
161
and the spherical bearing
162
so that the output shaft
140
is angularly displaced in a reverse direction. As a result, pulse signals are again transmitted by the next control amount from an unillustrated control means with a returning position of the plunger
103
as a starting point so that the stepping motor
104
is angularly displaced. Accordingly, the discharging amount of th
Kawata Tomoshi
Nobuta Yosuke
Colilla Daniel J.
Foley & Lardner
Kabushiki Kaisha Tokyo Kikai Seisakusho
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