Pumps – Expansible chamber type – Pumping member position controlled port
Reexamination Certificate
2002-06-04
2004-04-13
Yu, Justine R. (Department: 3746)
Pumps
Expansible chamber type
Pumping member position controlled port
C417S498000, C418S206400, C101S366000
Reexamination Certificate
active
06719542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pump for a printing press which is configured so as to axially reciprocate a plunger, while rotating the same, by means of a motor, to thereby supply ink to an inking unit of the printing press.
2. Description of the Related Art
A conventional pump for an offset printing press is disclosed in, for example, Japanese Patent No. 2864447. In the disclosed pump, a plunger accommodated within a main bore is reciprocated and rotated by a variable-speed motor in such a manner that the plunger undergoes a single cycle of reciprocating motion for each turn; and such operation is repeated in order to supply ink to an inking unit.
As shown in
FIG. 8
, the conventional pump consists of a body
101
, a cylinder
102
, a plunger
103
, a variable-speed motor
104
, and a transmission mechanism
105
. The body
101
is formed by a block portion
111
and a hollow housing portion
112
connected to the block portion
111
. The cylinder
102
is fitted into a through hole
113
of the block portion
111
in such a manner that its outer end projects from the outer side surface of the block portion
111
, and its inner end reaches a hollow space
112
a
formed inside the hollow housing portion
112
. The plunger
103
is accommodated within a main bore
120
of the cylinder
102
to be rotatable and receiprocatable along the axial direction. A base end portion of the plunger
103
projects into the hollow space
112
a
of the hollow housing portion
112
. The variable-speed motor
104
is attached to an outer wall
112
b
of the hollow housing portion
112
in such a manner that an output shaft
140
of the variable-speed motor
104
projects into the hollow space
112
a
of the hollow housing portion
112
. The transmission mechanism
105
is disposed in the hollow space
112
a
in order to connect the output shaft
104
to the plunger
103
, to thereby transmit rotation of the output shaft
140
to the plunger
103
while converting the rotational motion of the output shaft
140
to rotation and reciprocative motion of the plunger
103
.
The through hole
113
of the block portion
111
for receiving the cylinder
102
is formed to extend from the side of the hollow housing portion
112
toward the outer side surface of the block portion
111
, while inclining downward at a certain inclination angle. Accordingly, the cylinder
102
also inclines downward at the same inclination angle. An outer-end opening portion of the main bore
120
of the cylinder
102
is closed by means of a plug. At an axial position which is a predetermined distance away from the outer end of the cylinder
102
, an intake hole
121
and a discharge hole
122
are provided in the cylinder
102
at diametrically opposite positions such that the intake hole
121
and the discharge hole
122
penetrate the cylinder
102
upward and downward, respectively, along a common center axis. In other words, the intake hole
121
and the discharge hole
122
are opened to the main bore
120
with a phase difference of 180° therebetween.
A distal-end portion of the plunger
103
, which is accommodated within the main bore
120
to be rotatable and receiprocatable along the axial direction, has a cutaway portion
131
. The cutaway portion
131
is formed through removal of a portion having a substantially semicircular cross section and extends axially over a predetermined distance from the distal end surface.
Specifically, the cutaway portion
131
has a length such that the base end of the cutaway portion
131
is located on the side toward the open end of the main bore
120
with respect to the intake hole
121
and the discharge hole
122
, when the plunger
103
is moved to the deepest point within the main bore
120
, as will be described later.
More specifically, the cutaway portion
131
is formed in such a manner that, when the plunger
103
is moved to the deepest point within the main bore
120
in the course of its reciprocating movement, the base end of the cutaway portion
131
is located at a position which is offset toward the open end of the main bore
120
with respect to axial positions at which the intake hole
121
and the discharge hole
122
communicate with the main bore
120
, respectively, and a cylindrical surface of the cutaway portion
131
can close the intake hole
121
and the discharge hole
122
simultaneously, and that the distal end of the plunger
103
is located between the plugged end of the main bore
120
and the points at which the intake hole
121
and the discharge hole
122
communicate with the main bore
120
, respectively. Therefore, upon rotation of the plunger
103
, the intake hole
121
and the discharge hole
122
are closed simultaneously by the cutaway portion
131
at phase angles having an angular difference of 180° therebetween, and only one of the intake hole
121
and the discharge hole
122
is closed by the cutaway portion
131
at other phase angles.
The rotational axis of the plunger
103
and the rotational axis of the output shaft
140
form an angle therebetween; and a tip end portion of the output shaft
140
is connected to the base end portion of the plunger
103
by means of the transmission mechanism
105
.
Moreover, fluid passages
114
and
115
communicating with the intake hole
121
and the discharge hole
122
, respectively, of the cylinder
102
are formed in the block portion
111
.
The fluid passage
114
is connected to an unillustrated ink supply source. The fluid passage
115
is connected to an inking unit of a printing press. Therefore, ink is supplied to the main bore
120
of the cylinder
102
via the intake hole
121
; and ink pressurized to a predetermined pressure is fed from the main bore
120
to the inking unit via the discharge hole
122
.
The transmission mechanism
105
, which connects the output shaft
140
of the variable-speed motor
104
to the plunger
103
, includes a connection member
151
and an arm
150
. The connection member
151
projects radially from the base end portion of the plunger
103
, which projects into the hollow space
112
a
. The arm
150
is attached to the output shaft
140
and has a protrusion which projects toward the plunger
103
at an eccentric position with respect to the rotational axis of the output shaft
140
. A spherical bearing
152
is attached to the tip end of the projection of the arm
150
, and the tip end portion of the connection member
151
attached to the plunger
103
is fitted into the inner ring of the bearing
152
to be movable along the axis thereof.
The above-described conventional pump for a printing press involves the following problems.
Since the variable-speed motor (hereinafter referred to as the “motor”)
104
is disposed in such a manner that the rotational axis of the output shaft
140
of the motor
104
intersects the rotational axis of the plunger
103
at a predetermined intersecting angle, when the output shaft
140
of the motor
104
rotates 180° (a half turn) during a single rotation, the plunger
103
rotates 180° and moves toward the open end of the main bore
120
to thereby take in ink.
When the output shaft
140
rotates a further 180° (the remaining half turn), the plunger
103
rotates another 180° and moves toward the closed end of the main bore
120
to thereby discharge ink. The relationship between angular displacement of the output shaft
140
of the motor
104
and that of the plunger
103
is maintained constant at all times; and the angular displacement of the output shaft
140
for the intake stage of the operation cycle of the plunger
103
is identical with that for the discharge stage of the operation cycle. Therefore, intake and discharge of ink are performed alternately over respective periods of equal length.
Therefore, when the plunger
103
is in the intake stage, supply of ink to the inking unit stops even when a paper surface undergoing printing requires ink. When the plunger
103
enters the discharge stage, an increased amount of ink is discharged in
Liu Hai L.
Tokyo Kikai Seisakusho Ltd.
Westerman Hattori Daniels & Adrian LLP
Yu Justine R.
LandOfFree
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