Sheet transferring machine for printing machine

An apparatus for transferring a sheet between a plurality of printing units is disclosed. A transfer cylinder is provided between the adjacent units and is rotated by a motor. A drive gear mechanically connected to the motor and a driven gear mechanically connected to the transfer cylinder mate with each other. The press on a single surface and on both surfaces of the sheet are selectively performed, and a phase between the gears is adjusted by a phase adjusting mechanism. Stoppers are formed with the drive gear and driven gear respectively, for stopping relative rotation between the gears.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sheet-fed printer employed for an offset 
press, more particularly to a sheet transferring mechanism which transfers 
a sheet between a plurality of printing units so as to perform multiple 
color press on a single surface of the sheet and a single color press on 
both surfaces of the sheets. 
2. Description of the Related Art 
Printed matters such as pamphlets and catalogs are mostly printed using 
offset presses. The offset press is capable of multi-color printing and 
also well suited for mass printing. Sheet-fed printers, to which printing 
paper sheets of the same size are fed one by one to carry out printing, 
are widely employed in such offset press. In a mode where printing is to 
be applied on both surfaces of the sheet (double-side printing) is to be 
carried out in such type of sheet-fed printer, the sheet must be reversed 
and transferred. 
As shown in FIGS. 13(a) and (b), the offset press is provided with a feed 
cylinder 100 and a transfer cylinder 101, with a supply cylinder 102 being 
disposed between and adjacent to these cylinders 100 and 101. The supply 
cylinder 102 has a diameter twice as great as those of the other cylinders 
100,101. The printing sheet Pa subjected to a first printing is forwarded 
from the impression cylinder (not shown) to the feed cylinder 100 with the 
printed surface facing toward the cylinder 100. 
Subsequently, the sheet Pa retained on the transfer cylinder 100 is grasped 
at its front edge by the grippers of the supply cylinder 102 and shifted 
to the outer surface thereof. The sheet Pa is retained on the supply 
cylinder 102 with the printing surface facing outward. 
In a mode where printing is to be applied on a single surface with two 
colors (single-side printing) is to be carried out, as shown in FIG. 
13(a), the front edge of the printing sheet Pa retained on the supply 
cylinder 102 is grasped by a plurality of holders 103 arranged in the 
axial direction of the transfer cylinder 101. The sheet is reversed and 
then fed to the transfer cylinder 101 with the printed surface facing 
inward. Meanwhile, when the printing sheet Pa is to be printed on both 
sides thereof, the rear edge of the printing sheet Pa retained on the 
supply cylinder 102 with the printed surface facing outward is grasped by 
the holders 103 and fed to the transfer cylinder 101 in the same posture, 
as shown in FIG. 13(b). 
Accordingly, when the printing mode is switched from single-side printing 
to the double-side printing, the holders 103 of the transfer cylinder 101 
must grasp the rear edge of the printing sheet Pa. Thus, when another 
printing sheet Pa having a different size is used, the phase of the 
transfer cylinder 101 relative to the supply cylinder 102 must be adjusted 
so as to allow the holders 103 to securely grasp the sheet Pa. 
The phase adjustment of the reversing mechanism at switching between 
single-side printing and double-side printing has conventionally been 
carried out by changing the phase of the input gear 104 and that of the 
output gear 105, which transmit the driving force of the main motor, as 
shown in FIG. 14. Namely, the bolts 106 fastening the input gear 104 are 
loosened to turn the input gear 104 according to the scale. The phase of 
the input gear 104 is adjusted such that the holders 103 of the transfer 
cylinder 101 may securely grasp the rear edge of the printing sheet Pa. 
Since the phase adjustment of the reversing mechanism used to be carried 
out manually as described above, the mode switching from the single-side 
printing to the double-side printing or vice versa incurs a considerable 
loss of time, and further a number of defective prints are liable to occur 
due to mishandling in the switching operation. 
SUMMARY OF THE INVENTION 
The present invention has been accomplished in view of these problems 
inherent in the prior art. 
Accordingly, it is a primary object of the present invention to provide a 
sheet transferring apparatus for the use in a press, in which the time 
required for the printing mode switching can be reduced, and also 
mishandling in the switching operation can be prevented. 
It is another object of the present invention to provide a sheet 
transferring apparatus having an improved mechanism for registration of 
sheet reference position. In the improved mechanism, the registration of 
reference position in single-side printing can automatically and 
accurately be carried out to give printed matters with improved quality. 
In order to attain the intended objects described above, a sheet 
transferring apparatus of the present invention is proposed. According to 
the present invention, a sheet is transferred between a plurality of 
printing units by a transfer cylinder which is rotatively provided between 
the adjacent units. This apparatus is for the use in an offset press which 
performs operations on a single surface and on both surfaces of the sheet 
selectively. The press has a power source for actuating the transfer 
cylinder, a first rotating member mechanically connected to the power 
source and a second rotating member mechanically connected to the transfer 
cylinder. The second rotating member is driven by the first rotating 
member. The press includes a phase adjusting mechanism for adjusting a 
phase between the first rotating member and the second rotating member and 
stopping means formed with the first and the second rotating members 
respectively, for stopping relative rotation between the first and the 
second rotating members.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will be described hereinafter 
referring to the drawings. 
The offset press shown in FIG. 1 is provided with first and second printing 
units 1, 2. A feeder 3 is disposed adjacent to the first printing unit 1, 
while a delivery device 4 is disposed beside the second printing unit 2. 
In each printing unit 1, 2, an ink is fed to a plate cylinder 6 via ink 
distribution rollers 5, and water is also fed to the plate cylinder 6 via 
water distribution rollers 7. The ink and water are mixed on the plate 
cylinder 6. The mixture is transferred to a blanket cylinder 8a or 8b. A 
printing sheet Pa is fed from the feeder 3 via a sheet feeder 9 to an 
impression cylinder 10a. 
Motions of the respective cylinders in single-side two-color printing are 
shown in FIG. 2. A printing sheet Pa, which is retained on the 
circumference of a right impression cylinder 10a, is brought into contact 
with the circumference of the right blanket cylinder 8a to be subjected to 
a first color printing. The blanket cylinder 8a is revolved as the 
impression cylinder 10a revolves to apply printing on the entire surface 
of the sheet Pa. The thus printed sheet Pa is fed via a feed cylinder 11 
to a supply cylinder 12 with the printed surface facing outward. The sheet 
Pa is then grasped at the front edge thereof by a plurality of holders 14 
arranged in the axial direction of the transfer cylinder 13. The sheet Pa 
is fed to the transfer cylinder 13 with the printed surface facing inward. 
The sheet Pa is then retained on the left impression cylinder 10b with the 
printed surface facing outward again to be subjected to a second color 
printing by a left blanket cylinder 8b. These cylinders are revolved by a 
main motor 15. 
Meanwhile, in the case of double-side single-color printing, the printing 
sheet Pa is likewise printed on one surface thereof by the blanket 
cylinder 8a and then forwarded to the supply cylinder 12 via the feed 
cylinder 11 with the printed surface facing outward, as shown in FIG. 
3(a). In this process, the front edge of the sheet Pa is grasped by 
grippers 16 of the supply cylinder 12 and retained on the circumference of 
the supply cylinder 12. After the supply cylinder 12 assuming such state 
is turned by a predetermined amount, the holders 14 grasp the rear edge of 
the sheet Pa. Subsequently, the holders 14 of the transfer cylinder 13 
pivot counterclockwise so as not to crease the sheet Pa. As shown in FIG. 
3(b), the rear edge of the sheet Pa is retained by the suction head 17 of 
the supply cylinder 12. The supply cylinder 12 consists of a front and a 
rear segments 12a, 12b. The segments 12a, 12b are designed to change the 
angle formed therebetween for accurately holding the rear edge of the 
sheet Pa by the suction head. After the front edge of the printing sheet 
Pa retained on the supply cylinder 12 passes the contact point between the 
cylinders 12 and 13, the rear edge of the sheet Pa is grasped by the 
holders 14 of the transfer cylinder 13. Further, as shown in FIG. 3(c), 
the sheet Pa is fed to the transfer cylinder 13 with the printed surface 
facing outward, and then retained on the left impression cylinder 106 
shown in FIG. 1 with the printed surface facing inward to be subjected to 
printing on the rear surface by the left blanket cylinder 8b. The thus 
printed sheet Pb is forwarded to the delivery device 4 to complete 
printing. 
Next, phase adjustment of the transfer cylinder 13 in the above-described 
switching between "single-side two-color printing" and "double-side 
single-color printing" will be described. While such adjustment is 
performed by a control unit shown in FIG. 8, the details of the control 
unit will be described later. 
As shown in FIGS. 4 and 5, a main shaft 24 is rotatably supported between 
frames 20, 21 by way of a pair of bearings 22, 23. A pair of side plates 
25a, 25b constitute the diaphragms of the transfer cylinder 13. The 
diaphragms is fixed on the main shaft 24 at the positions inner than the 
frames 25a, 25b, respectively. A plurality of guide pieces 26 are fixed 
onto the main shaft 24 at equal intervals between these side walls 25a, 
25b. The circumferential surfaces of these guide pieces 26 guide the sheet 
Pa. A cylinder groove is defined in the respective guide pieces 26. 
Further, a support member 56 is secured on the outer side of the frame 20 
by way of a bracket 59. 
A driven gear 27 is provided at one end portion of the main shaft 24 to be 
rotatable integrally therewith. A drive gear 28 is attached to the driven 
gear 27 via Harmonic Differential Unit (a trademark; Harmonic Differential 
Co.) as a decelerator 29. The drive gear 28 is rotatably supported via a 
bearing 61 on the support member 56. The driving force of the main motor 
15 is transmitted via a gear (not shown) to the drive gear 28. The driving 
force is further transmitted from the drive gear 28 through the driven 
gear 27 to the rollers 5 of the second printing unit 2. 
The phase adjusting shaft 30 of the decelerator 29 protrudes from the outer 
surface of the support member 56. The phases of the gears 27, 28 are 
adjusted by turning the phase adjusting shaft 30. The adjusting shaft 30 
is immobilized, so that transmission of the rotation of the drive gear 28 
to the driven gear 27 is achieved at the ratio of 1:1. 
A couple of gears 31, 32 is secured on the outer end portion of the 
adjusting shaft 30. The gear 31 is fixed to the adjusting shaft 30 at an 
outer position. The gear 32 is arranged next to the gear 31 and fixed by 
means of bolts 33 on the drive gear 28. 
A locking electromagnetic clutch 35 is secured on the outer surface of the 
support member 56 by way of a bracket 60. A gear 36 is fixed to the shaft 
37 of the clutch 35 together with a gear 34. The gear 34 is engaged with 
the gear 31 and connected to the shaft 37 of the gear 36 by way of the 
clutch 35. The gear 36 is engaged with the gear 32 so as to prevent 
relative rotation between the gear 34 and the gear 36 while the clutch 35 
is actuated. The adjusting shaft 30 is retained as locked against the 
drive gear 28. 
A phase control motor 41 drives the gear 31 connected to a shaft 42 of the 
motor 41 by way of gears 38, 39 and an electromagnetic clutch 40. A gear 
43 is fixed onto the shaft 42. An encoder 45 is fixed to the member 56. A 
gear 44 mounted on the shaft of the encoder 45 is engaged with the gear 
43. The revolution of the motor 41 is detected by this encoder 45. The 
phases of two gear 27, 28 are detected in accordance with the revolution 
of the motor 41. 
An electromagnetic brake 47 is secured to a bracket 46 extending from the 
frame 21, as illustrated in FIG. 5. The brake 47 functions as the braking 
means for the transfer cylinder. The electromagnetic brake 47 is fitted on 
the main shaft 24 for holding the shaft 24 unrotatable upon actuation of 
the brake 47. A timing detector (resolver) 50 is mounted on the bracket 
46. The resolver 50 has a gear 49 and detects the actuating timing of the 
second unit. The main shaft 24 is connected at its end to the timing 
detector 50 by way of a gear 48 mating the gear 49. The reference position 
of the second unit 2 is detected by the timing detector 50. 
FIG. 6 shows a cross section taken along Y--Y line in FIG. 7. The drive 
gear 28 and the driven gear 27 have stoppers 51, 52, as the reference 
position registering mechanism, fastened by bolts 53, respectively. The 
driven gear 27 is fixed to the main shaft 24. The stoppers 51, 52 are 
arranged to be equally spaced from the axis of the main shaft 24 in such a 
way that the end faces of the stoppers 51, 52 may be abutted against each 
other at the reference position when the drive gear 28 is turned by the 
motor 41. 
Since the stoppers 51, 52 are provided on the opposing surfaces of these 
gears 27, 28, the reference position registering mechanism can be 
constructed compactly. This compact mechanism can be disposed in the press 
without interfering with other members. Further, as shown in FIG. 7, the 
stoppers 51, 52 are abutted against each other at the reference position 
(the stopper 52 as indicated by a fantom line). Accordingly, and when the 
drive gear 28 is turned, the driven gear 27 is pushed by the stoppers 
51,52 to turn together with the drive gear 28. 
A scale 54 for "single-side printing" and a paper size scale 55 for 
"double-side printing" are secured on the other surface of the gear 28. 
Two scales 54, 55 have an arc shape and extend along the periphery of the 
gear 28 As shown in FIGS. 4 and 7, a reference position sensor 57 is 
attached via a bracket 58 to a free end of the support member 56 extended 
from the frame 20. The sensor 57 detects the reference position of the 
gears 27, 28, where the abutment of two stoppers 51, 52 is taken place. 
While a proximity sensor is employed as the reference position sensor 57 
in the preferred embodiment, other sensors can be also employed. 
The sensor 57 is disposed to oppose to the center or therearound of the for 
the "single-side printing" scale 54 when the drive gear 28 is at the 
reference position. When the drive gear 28 is turned to reset to the 
reference position from the "double-side printing position", the sensor 57 
detects the "single-side printing" scale 54 and outputs a signal 
immediately before the gear 28 reaches the reference position. 
As illustrated in FIG. 8, the control unit which performs mode switching 
and phase adjustment, is provided with two CPU (central processing units) 
70, 71. A display unit 72 is connected to the first CPU 70 for display. 
The display unit 72 is provided with control switches or an input section 
including sheet size setter etc. 
The control switches are arranged in the form of a touch panel. The 
smallest necessary number of switches on the screen is selected and 
operated. The sheet size setter consists of ten keys provided on the 
display unit 72 and is used for inputting data indicative of the 
longitudinal size of the sheet Pa. Further, the display unit 72 has a 
function of a real-time-display relating to the progress of operation. In 
addition the display unit 72 has an alarm function for displaying 
malfunction such as failure. 
The second CPU 71 is for use of controlling the electric members in the 
press. To the CPU 71 are connected a ROM (read only memory) 73 and a RAM 
(random access memory) 74. A program for controlling the motions of the 
press is stored in the ROM 73. The RAM 74 stores temporarily data in the 
course of computing operation etc. Further, an input/output unit (I/O) 75 
is connected to the second CPU 71. 
The phase control motor 41 is connected to the I/O unit 75 by way of a 
magnet 76, so that the revolution direction of the motor 41 is controlled. 
A first unit timing detector 77 and a transfer cylinder maximum position 
sensor 78 are connected to the I/O unit 75. The maximum position sensor 78 
detects the transfer cylinder 13 to be at the maximum phase position where 
the phase between the reference position and current position of the 
cylinder 13 is maximum. Meanwhile, the electromagnetic brake 47, the 
electromagnetic clutch 40 and the locking electromagnetic clutch 35 are 
connected to the I/O unit 75. The encoder 45 is also connected to the 
second CPU 71 via a counter 79. 
In order to adjust the phase between two gears 27, 28 through the motor 41 
by CPU 71, a signal is transmitted from the CPU 71 via the I/O unit 75 to 
the brake 47 and the clutch 40. More specifically, the main shaft 24 is 
free from locking of the brake 47. The clutch 40 allows the motor shaft 42 
to mate the gear 39. Subsequently, a signal is transmitted from the CPU 71 
via the I/O unit 75 to the motor 41. 
The revolution of the motor 41 is transmitted via the gears 39, 38, 31 to 
the adjusting shaft 30. Since the electromagnetic clutch 35 is deactuated 
at this moment, the gears 31, 32 can rotate relative to each other. In 
accordance with this rotation, the phase of two gears 27, 28 are adjusted. 
The revolution of the motor 41 is constantly detected by the encoder 45, 
and the signals from the encoder 45 are transmitted via the counter 79 to 
the CPU 71. 
When the phase adjustment between two gears 27, 28 is not carried out, the 
clutch 40 is deactuated and the clutch 35 is actuated. If the main motor 
15 is revolved in this state, the adjusting shaft 30 of the decelerator 29 
receives a force to be rotated with respect to the drive gear 28 due to 
the load applied to the driven gear 27. However, since the electromagnetic 
clutch 35 is actuated, relative rotation of the gears 31, 32 is inhibited 
thereby, so that the shaft 30 is kept immobilized on the gear 28. In other 
words, the drive gear 28 is immobilized to the driven gear 27 to prevent 
induction of out-of-phase due to the load. It should be noted here that 
the electromagnetic clutch 40 is deactuated, so that the extra load is not 
applied to the rotation of the gear 31 but the gears 38, 39 engaged with 
the gear 31 merely rotate. 
In the thus constituted offset press, phase adjustment of the gears 27, 28, 
namely transfer cylinder 13 will be described referring to the flow chart. 
The proceeding of the flow chart is subject to the control of the second 
CPU 71 in accordance with the program in the ROM 73. 
When the control switch for mode switching is turned on (Step 1) as shown 
in FIG. 9, the CPU 71 calls a program for switching the printing mode 
(Step 2). The CPU 71 determines the current printing mode (Step 3). 
Namely, when the current mode of the press is "the single-side two-color 
printing mode", the mode is switched to the "double-side single-color 
printing mode" (A). When the current mode is the "double-side single-color 
printing mode", the CPU 71 further determines whether the sheet size 
should be changed (Step 4). When the sheet size is to be changed, the mode 
is switched to the sheet size change mode (B), whereas when the sheet size 
is not to be changed, the "double-side single-color printing mode" is 
changed to the "single-side two-color printing mode" (C). 
Phase adjustment of the transfer cylinder 13 is performed when the 
"single-side two-color printing mode" is changed to the "double-side 
single-color printing mode". This adjustment process represented by (A) 
will be described referring to the flow chart shown in FIG. 10. 
When the data indicative of the sheet size is input using the ten keys of 
the display unit 72 (Step 5), the angle between the front and rear 
segments 12a, 12b of the supply cylinder 12 is adjusted in accordance with 
the sheet size (Step 6). The main motor 15 is then driven (Step 7). The 
transfer cylinder 13 is turned to a predetermined position based on the 
signal of the second unit timing detector 50 (Step 8). The electromagnetic 
brake 47 is actuated upon stopping of the main motor 15 to lock the 
transfer cylinder 13 (Step 9). In this state, the electromagnetic clutch 
40 for adjusting phase is deactuated and the other electromagnetic clutch 
35 for locking is actuated. Subsequently, the clutch 40 is actuated and 
the clutch 35 is deactuated. Subsequently, the motor 41 is driven (Step 
10). The driving operation of the motor 41 opens the transfer cylinder 13 
to the maximum phase position where the position sensor 78 outputs a 
signal. The transfer cylinder 13 is kept in such state (Step 11). 
Further, the phase control motor 41 is driven (Step 12). The phase of the 
transfer cylinder 13 is adjusted to conform to the desired sheet size 
based on the signal transmitted from the encoder 45 (Step 13). Since the 
electromagnetic brake 47 is actuated to lock the transfer cylinder 13, the 
rotation of the respective cylinders in the second printing unit is 
prevented, enabling accurate phase adjustment of the transfer cylinder 13. 
Next, phase adjustment of the transfer cylinder 13 in the sheet size 
changing mode (B) will be described referring to the flow chart of FIG. 
11. 
When the data representing of the sheet size is input using the ten keys of 
the display unit 72 (Step 14), the angle between the front and rear 
segments 12a, 12b of the supply cylinder 12 is adjusted so as to conform 
to the sheet size, and these segments 12a, 12b are locked by a segment 
lock pin which is not shown (Step 15). The main motor 15 is then started 
(Step 16). When the transfer cylinder 13 is turned to the reference 
position of the second unit based on the signals from the timing detector 
50 (Step 17), the brake 47 is actuated upon stopping of the main motor 15 
to lock the transfer cylinder 13 (Step 18). 
Subsequently, the clutch 40 for adjusting the phase is actuated, and the 
clutch 35 for locking operation is deactuated. After the phase control 
motor 41 is driven (step 19), the transfer cylinder 13 is opened to the 
maximum phase position. According to the signal transmitted from the 
position sensor 78, the CPU 71 determines the cylinder 13 is fully opened 
and keep the cylinder 13 is in this state (Step 20). Further, the control 
motor 41 is driven (Step 21). Therefore, the phase of the cylinder 13 is 
adjusted to conform to the desired sheet size in accordance with the 
signal from the encoder 45 (Step 22). 
Phase adjustment of the transfer cylinder 13 when the "double-side 
single-color printing mode" is changed to the "single-side two-color 
printing" (C) will be hereinafter explained referring to the flow chart of 
FIG. 12. The angle between the front and rear segments 12a, 12b of the 
supply cylinder 12 is adjusted to the maximum position to conform the 
maximum sheet size (Step 23). After completion of the adjustment in the 
supply cylinder 12, the main motor 15 is driven (Step 24). When the 
transfer cylinder 13 is turned to the reference position of the second 
unit (Step 25), the brake 47 is actuated upon stopping of the main motor 
15 to lock the transfer cylinder 13 (Step 26). In this state, the clutch 
40 for adjusting phase is deactuated, and the other clutch 35 for locking 
operation is actuated. 
At the phase adjustment, the electromagnetic clutch 40 is first actuated, 
and the locking electromagnetic clutch 35 is deactuated. When the control 
motor 41 is driven (Step 27), the transfer cylinder 13 is turned close to 
the reference position in "single-side printing". When the reference 
position sensor 57 transmits a ON signal (Step 28), the motor 41 is 
stopped (Step 29). 
Subsequently, following the deactuation of the phase-adjusting clutch 40 
and the brake 47 for unlocking the transfer cylinder 13, the main motor 15 
is slowly revolved (Step 30). This causes the drive gear 28 to start to 
rotate alone. The stopper 51 of the drive gear 28 abuts against the 
stopper 52 of the driven gear 27, resulting in the driven gear 27 to 
rotate together with the drive gear 28. Accordingly, the transfer cylinder 
13 begins to rotate. After the transfer cylinder 13 is rotated for a 
predetermined time (Step 31), the locking clutch 35 is actuated to 
immobilize the phase between the gears 27, 28 (step 32). The state where 
the stopper 51 of the gear 28 abuts against the stopper 52 of the gear 27 
corresponds to the reference position in "single-side printing", and the 
switching operation is completed by the series of procedures described 
above. 
As described above, the two stoppers 51, 52 abut against each other at the 
reference position in the offset press according to the embodiment. 
Therefore, the registration accuracy of the reference position can be 
improved. 
Further, following the stop motion of the drive gear 28 prior to reaching 
the reference position, the drive gear 28 is turned slowly. This may 
weaken the impact when the stoppers 51, 52 abut against each other, 
preventing reduction in deformation of the stoppers 51, 52. Accordingly, 
the accurate registration of the reference position may be carried out. 
It should be understood that the present invention is not limited to the 
embodiment described herein, but the constitution thereof may partly be 
modified without departing from the spirit of the invention. For instance: 
(1) While an electromagnetic brake 47 is employed for applying a braking 
force so as to stop rotation of the transfer cylinder, a recess may be 
formed on the transfer cylinder in which a pin is inserted from the frame 
side instead of using the electromagnetic brake. 
(2) While the stoppers 51,52 are fastened with bolts in this embodiment, 
they may be formed integrally with the drive gear and the driven gear 
respectively.