Cylinder throw-on and throw-off mechanism for printing press

A cylinder throw-on and throw-off mechanism for a printing press having a plate cylinder and a printing cylinder, which are disposed with outer surfaces being separated from each other, and a blanket cylinder disposed therebetween includes a driving unit and a control unit. The driving unit has a motor serving as a driving source and moves the blanket cylinder between an impression-on position where the blanket cylinder is pressed against the plate cylinder and simultaneously pressed against the printing cylinder through a paper sheet and an impression throw-off position where the blanket cylinder is separated from the plate cylinder and the printing cylinder in accordance with a direction of rotation and the number of revolutions of the motor. The control unit sets an operation pattern of the motor, which is defined by the total number of revolutions of the motor and a number of revolutions of said motor on the basis of a printing condition, and drives and controls the motor in accordance with the set operation pattern.

BACKGROUND OF THE INVENTION 
The present invention relates to a cylinder throw-on and throw-off 
mechanism for pressing/separating a blanket cylinder against/from printing 
cylinders such as a blanket cylinder and an impression cylinder and 
adjusting gaps with respect to the printing cylinders in various types of 
printing presses including an offset rotary press and an intaglio printing 
press. 
A cylinder throw-on and throw-off mechanism of this type is disclosed in 
Japanese Utility Model Laid-Open No. 56-26249. In the cylinder throw-on 
and throw-off mechanism disclosed in this prior art, an eccentric bearing 
is pivoted using a motor as a driving source, thereby performing an 
impression-on/impression throw-off operation of a blanket cylinder axially 
supported by the eccentric bearing with respect to a plate cylinder and an 
impression cylinder. With this arrangement, the impression-on/impression 
throw-off operation is performed by driving a single eccentric bearing, 
resulting in a simple arrangement and a decrease in number of components. 
In the above-described conventional cylinder throw-on and throw-off 
mechanism, however, a sheet thickness adjustment mechanism for adjusting a 
gap between the blanket cylinder and the impression cylinder in 
correspondence with the thickness of a paper sheet is not incorporated in 
the motor driving system. Instead, another eccentric bearing is manually 
pivoted. With this arrangement, the impression-on/impression throw-off 
operation cannot be performed in a manner interlocked with sheet thickness 
adjustment, and the sheet thickness adjustment operation is individually 
performed. Therefore, sheet thickness adjustment is troublesome and 
requires a long time, resulting in a complex arrangement. 
Additionally, in the impression-on/impression throw-off operation, the 
phase and timing for pressing/separating the blanket cylinder against/from 
the impression or plate cylinder must be out of the printing range of both 
the cylinders, i.e., within a range where the gaps of the blanket cylinder 
and the impression or plate cylinder oppose each other, so as not to 
adversely affect the thickness of an ink coated on a plate. In the 
above-described conventional mechanism, since the impression-on/impression 
throw-off operation is not preformed while taking the phase between the 
cylinders into consideration, it is difficult to set the timing for the 
impression-of/impression throw-off operation. When the 
impression-on/impression throw-off operation is performed at an 
inappropriate timing, waste sheets are produced. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a cylinder throw-on and 
throw-off mechanism capable of performing sheet thickness adjustment in a 
short time with a simple arrangement. 
It is another object of the present invention to provide a cylinder throw, 
on and throw-off mechanism capable of performing an 
impression-on/impression throw-off operation in association with (in 
consideration of) the phase (rotation phase) between the cylinders. 
In order to achieve the above objects, according to the present invention, 
there is provided a cylinder throw-on and throw-off mechanism for a 
printing press having a plate cylinder and a printing cylinder, which are 
disposed with outer surfaces being separated from each other, and a 
blanket cylinder disposed therebetween, comprising driving means, having a 
motor serving as a driving source, for moving the blanket cylinder between 
an impression-on position where the blanket cylinder is pressed against 
the plate cylinder and simultaneously pressed against the printing 
cylinder through a paper sheet and impression throw-off position where the 
blanket cylinder is separated from the plate cylinder and the printing 
cylinder in accordance with a direction of rotation and a number of 
revolutions of the motor, and control means for setting an operation 
pattern of the motor, which is defined by a total number of revolutions of 
the motor and a number of revolutions of the motor on the basis of a 
printing condition, and driving and controlling the motor in accordance 
with the set operation pattern.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A cylinder throw-on and throw-off mechanism according to an embodiment of 
the present invention will be described below with reference to the 
accompanying drawings. FIGS. 1 to 7 show the first embodiment in which the 
cylinder throw-on and throw-off mechanism according to the present 
invention is applied to an offset rotary press. 
Referring to FIG. 1, the offset rotary press comprises a plate cylinder 2 
mounted with a plate, an impression cylinder 4 serving as a printing 
cylinder arranged to be parallelly separated from the plate cylinder 2 by 
a predetermined interval, and a blanket cylinder 3 mounted with a blanket 
on its outer surface and brought into contact with the plate cylinder 2 
and the impression cylinder 4 during a printing operation. Each shaft of 
the plate cylinder 2 and the impression cylinder 4 is rotatably and 
axially supported at its two ends by left and right frame is 6 provided to 
a printing unit 5, through a pair of bearings (not shown). A shaft 7 of 
the blanket cylinder 3 is rotatably and axially supported at its two ends 
by a pair of eccentric bearings (to be described later) fitted in the left 
and right frames 6. 
A bracket 10 is supported by a stud 9 projecting outward from one of the 
frames 6 to be close to the shaft of the impression cylinder 4. A stepping 
motor 11 serving as a driving unit is fixed to the bracket 10 while 
vertically standing a driving rod 12. When a nut 11a is rotated upon 
rotation of the stepping motor 11, the driving rod 12 having a screw 
portion threadably engaged with the nut 11a is moved. A lever 13 axially 
supported by the left and right frames 6 at its two end portions is 
arranged near the distal end of the driving rod 12. A coupling lever 14 
having an L-shaped section, as shown in FIG. 2, is axially mounted on a 
projecting portion 13a of the lever shaft 13 projecting from one of the 
frames 6. A coupling lever 15 is axially mounted on another projecting 
portion 13b of the lever shaft 13. 
The pair of left and right eccentric bearings 8 for axially supporting the 
shaft 7 of the blanket cylinder 3 are rotatably supported by housings 16 
which are fitted in bearing holes 6a of the frames 6 and fixed with bolts 
through needle rollers 17, respectively. The eccentric bearing 8 is 
constituted by an outer ring 18 fitted in the housing 16 through the 
needle roller 17, and an inner ring 20 rotatably fitted in the outer ring 
18 through tapered rollers 19. Bearing levers 21 on the left and right 
sides, which are fixed to the outer rings 18 of the eccentric bearings 8, 
are respectively coupled with the above-described coupling levers 14 and 
15 through rods 22. When the driving rod 12 is moved upon rotation of the 
stepping motor 11, the eccentric bearings 8 on both the sides are pivoted 
through the coupling levers 14 and 14, the rods 22, and the bearing levers 
21 while rolling the needle rollers 17. 
In FIG. 2, reference symbol B denotes an axis of the inner surface of the 
inner ring 20 constituting the eccentric bearing 8, i.e., the axis of the 
blanket cylinder 3 in an impression-on state. Reference symbol F denotes 
an axis of the outer surface of the outer ring 18 of the eccentric bearing 
8 (to be referred to as the axis of the eccentric bearing 8 hereinafter). 
The axes B and F are offset from each other by a predetermined size. A 
control unit 36 (to be described later) is connected to the cylinder 
throw-on and throw-off mechanism of this embodiment so as to operate each 
portion at a predetermined timing. 
Referring to FIG. 3 showing an impression-on state, an axis P of the plate 
cylinder 2 is separated from the axis B of the blanket cylinder 3 by an 
interaxial distance for applying an appropriate printing pressure to the 
contact portion between the outer surfaces of the two cylinders. Taking a 
thickness t of a printing paper sheet 25 into consideration, the axis B of 
the blanket cylinder 3 is separated from an axis I of the impression 
cylinder 4 by an interaxial distance for applying an appropriate printing 
pressure to the contact portion between the outer surfaces of the two 
cylinders. 
When the impression throw-off operation is performed upon completion of the 
printing operation, the axis B of the blanket cylinder 3 pivots 
counterclockwise about the axis F of the eccentric bearing 8 to move to a 
position B.sub.2 in FIG. 3. As a result, the interaxial distance between 
the axis P of the plate cylinder 2 and the axis B.sub.2 of the blanket 
cylinder 3 increases to form a gap S.sub.1 between the outer surfaces of 
the two cylinders. Similarly, the interaxial distance between the axis 
B.sub.2 of the blanket cylinder 3 and the axis I of the impression 
cylinder 4 also increases to form a gap S between the outer surfaces, 
thereby setting an impression throw-off state. To restart the printing 
operation, the axis B.sub.2 of the blanket cylinder 3 pivots clockwise 
about the axis F of the eccentric bearing 8 in FIG. 3 to move to the 
position of the axis B, thereby setting an impression-on state. 
When the thickness of the paper sheet changes upon exchanging the printing 
paper sheet 25, the axis of the blanket cylinder 3 moves from the position 
B to a position B.sub.1 such that an appropriate printing pressure is 
applied on the basis of sheet thickness data from a sheet thickness data 
input unit (to be described later). As a result, a gap t.sub.1 shown in 
FIG. 3 is formed between the blanket cylinder 3 and the impression 
cylinder 4, thereby obtaining a printing pressure corresponding to the 
changed sheet thickness. Upon completion of the printing operation, the 
axis of the blanket cylinder 3 moves from the position B.sub.1 to the 
above-described position B.sub.2, thereby setting an impression throw-off 
state. 
The stepping motor 11 is driven in accordance with an operation pattern set 
by the control unit 36. More specifically, referring to FIG. 4, reference 
numeral 30 denotes a speed/rotation phase detection sensor for detecting 
the operation speed and rotation phase of the printing press by using a 
known conventional sensor such as a rotary encoder for generating at one 
or more pulses for a predetermined phase every time the cylinder rotates 
by one revolution. Reference numeral 32 denotes a sheet thickness data 
input unit for inputting sheet thickness data by the operator. The sheet 
thickness data input unit 32 may be a unit for automatically measuring a 
sheet thickness instead of inputting data by the operator. Reference 
numeral 33 denotes an emergency impression throw-off switch used to 
perform the impression throw-off operation in case of abnormality of the 
printing press during the printing operation. The emergency impression 
throw-off switch may be an abnormality detection sensor for detecting the 
abnormality of the printing press and outputting an abnormality signal. 
Reference numeral 34 denotes a plate exchange switch for performing an 
operation of bringing the blanket cylinder 3 into contact with the plate 
cylinder 2 to bring a plate into tight contact with the outer surface of 
the plate cylinder in mounting the plate on the plate cylinder of the 
printing press. 
Reference numeral 35 denotes a printing paper sheet detection sensor using 
a known conventional sensor, which is arranged on a printing paper sheet 
conveyance path between a feeder for supplying printing paper sheets and 
the printing unit. The printing paper sheet detection sensor 35 issues an 
impression-on command when the printing paper sheets supplied from the 
feeder are detected in an impression throw-off state, and issues an 
impression throw-off command when the printing paper sheets supplied from 
the feeder are not detected in an impression-on state. The control unit 36 
determines the operation pattern of the stepping motor 11 in accordance 
with signals supplied from the speed/rotation phase detection sensor 30, 
the sheet thickness data input unit 32, the emergency impression throw-off 
switch 33, and the plate exchange switch 34 and outputs a drive control 
signal to a driving unit 37. The driving unit 37 outputs an operation 
signal, an operation speed signal, or a stop signal on the basis of the 
drive control signal output from the control unit 36, thereby driving the 
stepping motor 11. Reference numeral 38 denotes a unit for displaying a 
sheet thickness input by the sheet thickness data input unit 32. The 
operator confirms the thickness of sheets used in the current printing 
operation by the display unit 38. 
The impression-on operation will be described below. Referring to FIGS. 1 
and 2, when the stepping motor 11 rotates by the number of revolutions or 
steps, which is calculated and determined by the control unit 36, the 
driving rod 12 moves to pivotally move both the eccentric bearings 8 along 
a circular arc about the axis F of the eccentric bearings 8 through the 
coupling levers 14 and 15, the rods 22, and the bearing levers 21 while 
rolling the needle rollers 17. With this operation, the axis of the 
blanket cylinder 3 moves from the position B.sub.2 to the position B in 
FIG. 3. The blanket cylinder 3 at the impression throw-off position is 
brought into contact with the plate cylinder 2 and subsequently moved to a 
position corresponding to the sheet thickness to set an impression-on 
state with respect to the impression cylinder 4. 
Timings and positional (phase) relationships between the cylinders in the 
impression-on operation and will be described below with reference to 
FIGS. 5A and 5B. The timing for bringing the blanket cylinder 3 into 
contact with the plate cylinder 2 must be out of the printing range of the 
two cylinders, i.e., within a range of an angle .theta..sub.1 where a gap 
P of the plate cylinder 2 and a gap B of the blanket cylinder 3 oppose 
each other, as shown in FIG. 5A, so as not to adversely affect the 
thickness of an ink coated on the plate. Similarly, the timing for 
bringing the blanket cylinder 3 into contact with the impression cylinder 
4 must be within a range of an angle .theta..sub.1 where the gap B of the 
blanket cylinder 3 and a gap I of the impression cylinder 4 oppose each 
other, as shown in FIG. 5B. 
After the paper sheet is supplied, the printing paper sheet detection 
sensor 35 detects the paper sheet, and the impression-on operation is 
performed immediately before the paper sheet passes between the blanket 
cylinder and the impression cylinder. An image transferred from the plate 
on the plate cylinder 2 to the blanket on the blanket cylinder 3 is 
transferred to the paper sheet 25 passing between the blanket cylinder 3 
and the impression cylinder 4, thereby performing printing. Upon 
completion of the printing operation, the impression cylinder 4 is 
separated from the blanket cylinder 3 at the same timing as in the 
above-described impression-on operation, i.e., within the range of the 
angle .theta..sub.2 where the gaps B and I oppose each other. Similarly, 
the stepping motor 11 is reversely rotated at a timing for separating the 
blanket cylinder 3 from the plate cylinder 2, i.e., within the range of 
the angle .theta..sub.1 where the gaps P and B oppose each other. With 
this operation, the axis of the blanket cylinder 3 is pivotally moved from 
the position B to the position B.sub.2, thereby performing an impression 
throw-off operation. 
The operation patterns of the impression-on/impression throw-off operation 
will be described below with reference to FIGS. 6 and 7. Referring to 
FIGS. 6 and 7, the mechanical rotation phase of the printing press is 
plotted along the abscissa, and the stroke (reciprocal amount) of the 
driving rod 12 according to rotation of the stepping motor 11 is plotted 
along the ordinate. The lowermost point represents an impression throw-off 
position while the uppermost point represents an impression-on position at 
a minimum sheet thickness. A portion .alpha. indicated by a central blank 
portion represents mechanical rotation phases within a range allowing the 
impression-on/impression throw-off operation as the above-described timing 
for the impression-on/impression throw-off operation. The operation 
pattern of the driving rod 12 must be set within the portion .alpha.. 
The portion .alpha. changes depending on, e.g., the arrangement or 
diameters of the plate cylinder 2, the blanket cylinder 3, and the 
impression cylinder 4. It also changes depending on the sheet thickness. 
At a minimum sheet thickness I, the boundary is indicated by a solid line. 
At an intermediate sheet thickness II, the boundary is indicated by a 
broken line. At a maximum sheet thickness III, the boundary is indicated 
by a chain double-dashed line. A portion .beta. indicated by hatching 
represents a printing enable range excluding the gaps P, B., and I. The 
impression-on operation must be avoided in the portion .beta. because it 
is not preferable. 
Curves A, B, and C in FIG. 6 represent operation patterns of the stepping 
motor 11 in the impression-on operation, which respectively correspond to 
the sheet thicknesses I, II, and III. A curve D represents an operation 
pattern for a plate exchanging operation Curves A', B', and C', in FIG. 7 
represent operation patterns of the Stepping motor 11 in the impression 
throw-off operation, which respectively correspond to the sheet 
thicknesses I, II, and III. A curve E represents an operation pattern for 
an emergency impression throw-off operation. 
The operation of the stepping motor 11 corresponding to each operation 
pattern will be described below. Prior to the operation of the printing 
press, sheet thickness data is input from the sheet thickness data input 
unit 32 to the control unit 36. The control unit 36 sets the total number 
of revolutions of the stepping motor 11, which corresponds to the 
operation stroke length of the driving rod 12, and the 
acceleration/deceleration rate of the stepping motor 11, i.e., the 
inclination of the curve A. 
Data as a basis for an operation pattern representing the relationship 
between the mechanical rotation phase and the operation stroke of the 
driving rod 12, e.g., an operation pattern represented by the curve A in 
FIG. 6 at the sheet thickness I is set. 
After the preparation, the printing press is operated, and printing paper 
sheets are supplied from the feeder. A Signal is output from the printing 
paper sheet detection sensor 35 to the control unit 36. The speed/rotation 
phase detection sensor 30 outputs a speed signal and a phase signal. At 
this time, the control unit 36 calculates the speed of the stepping motor 
11 on the basis of the speed signal and data serving as a basis for an 
operation pattern and outputs an impression-on operation signal to the 
stepping motor 11 through the driving unit 37 at a predetermined timing on 
the basis of the phase signal. With this operation, the stepping motor 11 
rotates in accordance with the calculated and predetermined speed and the 
predetermined total number of revolutions, i.e, the operation pattern A, 
thereby performing the impression-on operation of the blanket cylinder 3 
to a predetermined position. 
Upon completion of the printing operation, supply of printing paper sheets 
from the feeder is stopped. The printing paper sheet detection sensor 35 
detects the absence of printing paper sheets to output a signal to the 
control unit 36, and the speed/rotation phase sensor 30 outputs a speed 
signal and a phase signal. At this time, the control unit 36 outputs an 
impression throw-off operation signal to the stepping motor 11 through the 
driving unit 37 at a predetermined timing on the basis of this phase 
signal. With this operation, the stepping motor 11 rotates in a direction 
reverse to that in the impression-on operation at a speed calculated by 
the control unit 36 on the basis of the speed signal and data serving as a 
basis of an operation pattern, e.g., in accordance with the operation 
pattern A', thereby performing the impression throw-off operation. 
If thin paper sheets are replaced with thick paper sheets, new sheet 
thickness data, e.g., the sheet thickness II is input to the sheet 
thickness data input unit 32. The control unit 36 sets the total number of 
revolutions of the stepping motor 11 and a new operation pattern, e.g., 
the operation pattern B defined by the relationship between the mechanical 
rotation phase and the operation stroke. In accordance with the operation 
pattern B, an impression-on operation corresponding to the sheet thickness 
II is performed. 
When the plate is to be exchanged before a printing operation is newly 
started, the plate exchange switch 34 is operated to output a plate 
exchange signal to the control unit 36. At this time, an impression-on 
operation signal according to the operation pattern D shown in FIG. 6 is 
output to the driving unit 37 regardless of the phase of the printing 
press. The stepping motor 11 rotates on the basis of the total number of 
revolutions, which is calculated by the control unit 36 in advance, to 
bring the blanket cylinder 3 into contact with the plate cylinder 2. With 
this operation, the plate gripped by a gripper-side plate lockup device is 
brought into tight contact with the outer surface of the plate cylinder 2, 
thereby improving the plate mounting precision. 
If some abnormality occurs during the printing operation, and the printing 
press must be stopped, the emergency impression throw-off switch 33 is 
operated to output an emergency impression throw-off signal to the control 
unit 36. At this time, an impression throw-off signal according to the 
operation pattern E shown in FIG. 7 is output to the driving unit 37 
regardless of the phase of the printing press. The stepping motor 11 
reversely rotates to perform the impression throw-off operation of the 
blanket cylinder 3. If an abnormality detection sensor for detecting 
abnormality of the printing press is arranged, an emergency impression 
throw-off signal is automatically output to the control unit 36 upon 
detection of abnormality by the abnormality detection sensor. 
As described above, the operation patterns of the stepping motor 11 for 
performing the impression-on/impression throw-off operation by the control 
unit 36 include not only the operations patterns A to C and A' to C' based 
on the sheet thickness data according to input signals from the 
speed/rotation phase detection sensor 30 and the sheet thickness data 
input unit 32 but also the operation patterns D and E according to the 
operations of the plate exchange switch 34 and the emergency impression 
throw-off switch 33. 
FIGS. 8 and 9 show the second embodiment of the present invention. The same 
reference numerals as in the first embodiment denote the same parts in the 
second embodiment, and a detailed description thereof will be omitted. The 
second embodiment is characterized in that an outer rotor type direct 
driving system is used in place of the stepping motor 11 serving as a 
driving source in the first embodiment. More specifically, an outer rotor 
type direct drive motor 40 has a stator 41 at its center, which is fixed 
to a frame 6. A rotating outer rotor 42 is arranged around the stator 41. 
In the motor 40, the stator 41 is fixed to a pin 43 standing from the 
frame 6 and supported by the frame 6, and a lever 44 pivotally supported 
by the pin 43 and having its free end portion connected to a rod 22 
through a pin is fixed to the outer rotor 42. 
With the above arrangement, when the motor 40 is operated by a control unit 
36 through a driving unit 37 on the basis of a predetermined operation 
pattern, the outer rotor 42 pivots to swing the lever 44. Upon swing of 
the lever 44, an eccentric bearing 8 pivots through the rod 22 and a 
bearing lever 21 to move a blanket cylinder 3, thereby performing an 
impression-on/impression throw-off operation of the blanket cylinder 3. 
The rod 22 is directly swung by rotating the outer rotor 42 of the motor 
40. Therefore, the number of components can be decreased, and the 
mechanism can be simplified, thereby achieving size reduction of the 
mechanism. 
Although the curve A is set as an operation pattern, the operation pattern 
is not necessarily limited to the inclination of the curve A. To further 
soften the shock in the impression-on operation, a curve for further 
decelerating the final speed of the stepping motor 11 may be set as far as 
the curve does not extend from the portion .alpha. in FIGS. 6 and 7. 
In addition, a speed sensor and a rotation phase sensor may be individually 
arranged in place of the speed/rotation phase detection sensor 30. In this 
case, a tachogenerator or the like may be used as a means for detecting 
the printing speed, and a proximity sensor or the like may be used as a 
means for detecting the rotation phase. Various changes and modifications 
can be made. 
The operation pattern of the stepping motor 11 is set in accordance with 
the total number of revolutions of the stepping motor 11 and a 
relationship between the mechanical rotation phase and the number of 
revolutions of the stepping motor 11. However, the operation pattern may 
be set only in accordance with the total number of revolutions of the 
stepping motor 11 without using the relationship between the mechanical 
rotation angle and the number of revolutions of the stepping motor 11. In 
this case, acceleration/deceleration of the stepping motor 11 is not 
controlled. The operation pattern is indicated by a straight line in FIGS. 
6 and 7. When acceleration/deceleration is not controlled, the 
acceleration/deceleration characteristics of the stepping motor 11 itself, 
e.g., the deceleration characteristics by inertial rotation after driving 
is stopped may be used. 
As has been described above, according to the present invention, there is 
provided a cylinder throw mechanism having a plate cylinder and a printing 
cylinder, which are disposed with outer surfaces being separated from each 
other, and a blanket cylinder disposed therebetween, and a driving unit 
for moving the blanket cylinder between an impression-on position where 
the blanket cylinder is pressed against the plate cylinder and 
simultaneously pressed against the plate cylinder and the printing 
cylinder through a paper sheet and an impression throw-off position where 
the blanket cylinder is separated from the plate cylinder and the printing 
cylinder, wherein a motor is used as the driving source of the driving 
unit, and a control unit for freely setting the operation pattern of the 
motor. With the control unit, various types of operation patterns of the 
impression-on/impression throw-off operation can be automatically executed 
without requiring an operator. Therefore, the operation is facilitated, 
thereby decreasing the operation time and labor. 
According to the present invention, since rotation of the motor is 
converted into a linear movement by a rod, the printing cylinder can be 
precisely moved. 
According to the present invention, since an outer rotor type direct drive 
motor is used, the number of components can be decreased, and the 
mechanism can be simplified, thereby achieving size reduction of the 
mechanism. 
According to the present invention, since the moving amount of the plate 
cylinder is controlled in accordance with the number of revolutions of a 
stepping motor, the moving amount can be accurately controlled, and the 
control system can be simplified. 
According to the present invention, the control unit can change the 
operation pattern of the motor on the basis of sheets thickness data, and 
the impression-on/impression throw-off operation can be automatically 
executed in accordance with various sheet thicknesses without requiring an 
operator. For this reason, the operation is facilitated, thereby 
decreasing the operation time. 
According to the present invention, operation patterns such as an 
impression-on/impression throw-off operation according to a rotation phase 
and an emergency impression-on/impression throw-off operation can be 
selected. For this reason, the mechanism can cope with various types of 
operation patterns, thereby improving convenience in use.