US3822644A

US3822644A - Apparatus for maintaining registry between the plates of a multiple plate cylinder press and sheets supplied thereto

Info

Publication number: US3822644A
Application number: US00302126A
Authority: US
Inventors: L Gazzola; S Amato; I Gazzola; E Gazzola; C Foote
Original assignee: American Bank Note Co
Current assignee: BNY Mellon NA
Priority date: 1972-10-30
Filing date: 1972-10-30
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

Apparatus for supplying sheets to be printed to the plate cylinder of a multiple plate intaglio press, including means for changing the registration of successive sheets with the cylinder to correspond with variations in the positions of successive plates on the cylinder with respect to the sheet feeding means. The sheets move along an inclined feed board as they approach the first sheet transfer cylinder. The motion of each sheet is blocked by a movable stop means as it nears the end of the feed board. While the sheet is stopped, a set of grippers on the first sheet transfer cylinder engage the sheet at a location determined by the position of the stop means. The stop means is then retracted and the first and subsequent transfer cylinders then move the sheet along to the plate cylinder. The registry of the sheet with the plate cylinder is determined by the sheet blocking position of the stop means. The sheet blocking position of the stop means is shiftable and is shifted for successive sheets, to correspond to the differences in position of the successive plates on the plate cylinder. The sheet blocking position is shifted synchronously with the rotation of the plate cylinder, either in response to a pick-up unit which detects a certain angular position of the plate cylinder and operates the stop shifting means, or by a synchronous drive between the plate cylinder and a shaft on the stop shifting means.

Description

United States Patent [191 Gazzola, deceased et al.

[ 1 APPARATUS FOR MAINTAINING REGISTRY BETWEEN THE PLATES OF A MULTIPLE PLATE CYLINDER PRESS AND SHEETS SUPPLIED THERETO [75] Inventors: Ivaldo Gazzola, deceased, late of Lausanne, Switzerland by Eles Gazzola; Lanfranco Gazzola, Lausanne, Switzerland heirs; Salvatore F. D. Amato, Floral Park; Chauncey P. Foote, Jr., Katonah,

both of NY.

[73] Assignee: American Bank Note Company,

New York, NY.

[22] Filed: Oct. 30, 1972 [21] Appl. No.: 302,126

[451 July 9,1974

Primary ExaminerRobert E. Pulfrey Assistant Examiner-William Pieprz Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran 5 7] ABSTRACT Apparatus for supplying sheets to be printed to the plate cylinder of a multiple plate intaglio press, including means for changing the registration of successive sheets with the cylinder to correspond with variations in the positions of successive plates on the cylinder with respect to the sheet feeding means.

The sheets move along an inclined feed board as they approach the first sheet transfer cylinder. The motion of each sheet is blocked by a movable stop means as it nears the end of the feed board. While the sheet is stopped, a set of grippers on the first sheet transfer cylinder engage the sheet at a location determined by the position of the stop means. The stop means is then retracted and the first and subsequent transfer cylinders then move the sheet along to the plate cylinder. The registry of the sheet with the plate cylinder is determined by the sheet blocking position of the stop means.

The sheet blocking position of the stop means is shiftable and is shifted for successive sheets, to

correspond to the differences in position of the 7 Claims, 7 Drawing Figures PAIENTEUJuL 91m 3.822.644

saw 3 or s PAIENTED JUL 91924 SHEU l 0F 5 mmem 91914 3.822.644

SHFU 5 BF 5 APPARATUS FOR MAINTAINING REGISTR BETWEEN THE PLATES OF A MULTIPLE PLATE CYLINDER PRESS AND SHEETS SUPPLIED THERETO CROSS-REFERENCES US. Pat. application Ser. No. 173,555, filed Aug. 20, 1971, by the same inventors, entitled Plate Wiping Mechanism for lntaglio Press, discloses an apparatus which may be used on the same press with the present invention.

US. Pat. application Ser. No. 188,195, filed Oct. 12, 1971, by the same inventors, entitled Printing Press with Sheet Inspection Station," discloses another apparatus which may be used on the same press with the present invention.

US. Pat. application Ser. No. 195,364, filed Nov. 3, 1971, by the same inventors, entitled Apparatus for Delivering Sheets Onto a Moving Strip of Material, discloses another apparatus which may be used on the same press with the present invention.

US. Pat. application Ser. No. 298,443, filed Oct. 17, 1972, by the same inventors, entitled Printing Pressure Control Apparatus for lntaglio Press, discloses another apparatus which may be used on the same press with the present invention.

US. Pat. application Ser. No. 298,444, filed Oct. 17, 1972, by the same inventors, entitled Paper Feed Mechanism for Cylinder Press, discloses another apparatus which may be used on the same press as the present invention.

BRIEF SUMMARY OF THE INVENTION The present invention is useful in connection with presses, having a plurality of saddles on the plate cylinder, each adapted to support a printing plate. Such presses commonly employ a single sheet supply means for supplying sheets to all the plates on the cylinder. Conventionally, all sheets are supplied with their leading edges in the same positions relative to the sheet supply means and consequently, relative to the leading edges of the saddles on which the plates are mounted. lntaglio presses are almost the only multiple plate cylinder presses in current use.

In operating a multiple plate cylinder press, it is necessary either to have each of the several plates on the cylinder in perfect registry with one another or to provide some mechanism for changing the registry of the successive sheets with respect to the cylinder, so that the positions of the successive sheets correspond with the different positions of the successive plates on the cylinder. If no registry changing mechanism is used, then the mounting of the first plate on the cylinder establishes the registry, to which all subsequently mounted plates must conform. It is necessary to be very careful in fixing the position of the second plate on the cylinder. The problem of mounting the plates accurately becomes even more difficult with four plates on the cylinder.

In accordance with the present invention, it is not necessary to establish within fine limits of accuracy, the positions of each of the several plates on the cylinder, but the tolerance of variation in the plate position is fairly wide.

Registry of the successive sheets with the successive plates on the cylinder is achieved by changing the blocking position of a stop means by which each successive sheet is stopped as it approaches the first sheet transfer cylinder in the transfer chain which moves the sheets from the feed board to the impression cylinder. The first sheet transfer cylinder may be operated through a cycle which involves stopping the cylinder, opening the grippers thereon, reversing the cylinder for a short distance so that the grippers overlap the edges of the stopped sheet, closing the grippers, withdrawing the stop means, and then accelerating the first transfer cylinder so that by the time the leading edge of the sheet reaches the point of tangency with the second transfer cylinder, the first cylinder has been accelerated so that it is running at the same speed as the second cylinder, which receives the sheet at that point without substantial acceleration or deceleration of the sheet.

DRAWINGS FIG. 1 is a fragmentary elevational view, somewhat diagrammatically showing an intaglio press embodying the invention, with certain parts broken away.

FIG. 2 is a diagrammatic view, showing the first sheet transfer cylinder and the control apparatus associated with the sheet stop mechanism in accordance with one embodiment of the invention.

FIG. 3 is a fragmentary perspective view, showing the sheet stop mechanism.

FIG. 4 is a fragmentary view, similar to a part of FIG. 2 but on a larger scale, showing additional details of the sheet stop mechanism.

FIG. 5 is a view similar to FIG. 2, illustrating a different embodiment of the invention.

FIG. 6 is a sectional view on the line 6-6 of FIG. 3.

FIG. 7 is a fragmentary diagrammatic view showing the gripper fingers on the impression cylinder.

DETAILED DESCRIPTION The press illustrated includes front and rear vertical frame members 1 and 2 (FIGS. 1 and 3), only the front vertical frame member 1 being visible in FIG. I. Between the frame members, and journaled therein, are a plate carrying cylinder 3 and an impression cylinder 4. Sheets of paper to be printed may be supplied by a conventional sheet feeding mechanism along a feed board 11 to a train of

sheet feeding rolls

5, 6, 7, from which they are transferred to the impression cylinder 4, and pass through the nip between the impression cylinder and the plate carrying cylinder 3, as is common in the art, being shown, for example, in the US. Pat. to

-Schunemann, No. 2,831,425, and in FIGS. l4-l7 of our copending application Ser. No. 298,443, mentioned above. The printed sheets are then removed by a conveyor 9, running over a sprocket 8.

The press illustrated is a multicolor press. The ink applying mechanism includes a carriage 10 partially shown in FIG. 1, including ink conveying roller trains l5, l6 and 17 leading to

rollers

20, 21 and 22, which transfer the ink to the plates on the cylinder 3. The

rollers

20, 21 and 22 are contoured, so that each contacts a portion only of the surface of the cylinder 3. Typically, only one color of ink will be applied to any given portion of the surface of the plate, although it may be arranged that colors overlap, if desired.

The plate carrying cylinder 3 turns clockwise, as viewed in FIG. I. A wiping roll 25 is rotatably mounted so that it runs with its periphery in contact with the plate cylinder 3, and also becomes immersed in a suitable solvent in a tank 26. The wiping roll 25 removes the ink from the surface of the plate on the printing cylinder, between the lines on the plate, so that as the plate approaches the nip of the cylinders 3 and 4, the only ink remaining on the plate is in the recessed lines.

The plate cylinder 3 is driven by a motor 27 through a multiple V-belt drive 28 and a suitable gear train (not shown). Conveyor 9 is driven from the plate cylinder through a bevel pass shown at 29 in FIG. 1. The wiping roll is driven by a motor 30, which may be controlled as described in our copending application Ser. No. 173,555, mentioned above.

FIGS. 2, 3, 4 AND 6 The plate cylinder 3 in this figure has two saddles 3a and 3b separated by recesses 3c and 3d. Within the recesses 3c and 3d are located a first pair of clamps 31 for engaging the leading edges of the respective plates and a second pair of clamps 32 for engaging the trailing edges of the respective plates. The plates on the cylinder 3 are indicated at 33 and 34, respectively.

The cylinder 3 is mounted on a rotatable shaft 39, having a hub which carries a magnetic armature 35, which is fixed in position with respect to the leading edge clamps 31. The armature 35 cooperates with a pair of

stationary coils

37, 38, in which electrical pulses are generated by the passage of the armature as the cylinder 3 rotates. The

coils

37 and 38 are connected through a selector switch 40 to the input ofan amplifier 4! whose output is connected to a solenoid 42 controlling a valve 43 which regulates the flow of hydraulic fluid from a suitable source to two hydraulic cylinders 44 (only one of which is shown in FIG. 2). Each cylinder 44 is pivotally mounted on a bracket 46 (FIG. 2) which is attached to a suitable fixed part of the press, and operates a piston connected by a piston rod 47 to an arm 51 fixed on a hub 52 journaled in a

frame member

1 or 2 of the press. The hubs 52 eccentrically support a shaft which carries a plurality of blocks 53. On each block 53 is clamped a stop finger 54. A bar 55 engages the finger 54 and clamps it against the block 53, being held in place by a screw 56, which passes through a slot in the finger 54. One end of the finger 54 is turned over at 54a and threadedly receives another screw 57 which adjusts the position of stop finger 54 and its extension 54b of finger 54, with respect to block 53. The clamp screw 56 must, of course, be loosened before the screw 57 may be adjusted.

The shaft 50 carries at one end a bell crank lever 81 fixed at its center to the shaft 50. One arm of the bell crank lever 8ll carries a follower 82 cooperating with a cam 83 driven synchronously with the press cylinders 3 and 4. A spring 86 biases the follower 82 into engagement with cam 83. When the low portion 83a of cam 83 is engaging follower 82, then the bell crank lever 81 is rotated counterclockwise from the position shown in the drawings, thereby turning the shaft 50 through a small angle and lifting the stop fingers 54 from the position shown in the drawings in full lines to a retracted position shown in chain line in FIG. 4, wherein a sheet 27 on the feed board 11 is free to be removed by the gripper fingers 62 on the sheet transfer cylinder 5.

When the follower 82 is engaging the high portion of the cam, as shown at 83b in FIG. 3, the stop fingers 54 v are blocking the advance of any sheet which appears on the feed board 11. The particular position along the feed board in which a sheet 27 is stopped is determined by the operation of the cylinders 44, operating arms 51. When the arms 51 are in the full line positions shown in FIGS. 2 and 4, then the center of the shaft 50 is at the position shown at 84 in FIG. 4. When the arms 51 are moved to their dotted line positions in FIGS. 2 and 4, then the shaft 50 is moved to its dotted line position in FIG. 4 and its center is moved to the location shown at 85 in that figure. This movement of the shaft 50 between its full line and dotted line positions in FIG. 4 results in the movement of the stop fingers 54 between the full line and dotted line positions shown in that figure and thereby changes the stopping position of the advancing sheet by a distance which may be adjusted by setting the dotted line position 51a of the arm 51. This is done by means of a pair of adjustable stop screws 60, which are threaded into the front and

rear frame members

1 and 2 of the press, and which may be locked in position by means of lock nuts 61. The arm of the bell crank lever 81 opposite the follower 82 is received in a hollow frame 87 operated by hydraulic cylinder 88, and controlled, through conventional means not shown, by a pair of sensors which detect the presence or absence of a sheet against the stop fingers 54. If no sheet is there to be engaged by the grippers of the sheet transfer cylinder 5, or if the sheet is skewed so that it is not present under one of the sensors 90, then a signal from the one or more sensors 90 where the sheet is missing is effective to supply fluid to the hydraulic cylinder 88 and pull the frame 87 down, thereby holding the bell crank lever 8ll in a position corresponding to its position when follower 82 is engaging the high portion 83b of cam 83. The stop fingers 54 remain in the path of any advancing sheet, and are effective to prevent it from being fed into the press. A corresponding signal is supplied to the mechanism for operating the grippers on the transfer cylinder, thereby preventing them from closing on the skewed sheet.

Appropriate controls may be provided to relieve the printing pressure between the press cylinders when a sheet is absent at the sensors 90, for example, as disclosed in our copending application, Ser. No. 298,443, entitled Printing Pressure Control Apparatus for Intaglio Press mentioned above.

Thus, the fingers 54b serve to stop the incoming sheets in desired positions so that each sheet will be in registry with either

plate

33 and 34, when it reaches the plate cylinder 3. The feed board 11 is provided with slots 11a (FIG. 2) in which the finger extensions 54b move.

The hubs 52 are mounted in the

frame members

1 and 2 by means of universally movable bearings 89, as best seen in cross-sectional view in FIG. 6. These universal bearings permit the shaft 50 to be skewed slightly with respect to the axis of the plate cylinder 3, so that by introducing different adjustments for the screws 60 on the opposite sides of the press, a correction may be made for a slightly skewed position of a plate on the plate cylinder 3. The stop fingers 54 on the opposite ends of the shaft 50 would then be in slightly different positions because of the skewed position of the shaft and would stop the sheet 27 in a skewed position corresponding to the skewed position of the printing plate on the plate cylinder 3. The sheet 27 would thereafter be fed past the plate cylinder 3 in registry with the skewed plate.

In operating the apparatus of FIG. 2, the position of the finger extensions 54b, when the piston 45 is in the position shown, is determined by setting the adjusting screw 57 so that sheets picked up by the grippers 62 on the first sheet transfer cylinder 5 from that blocking position will reach one particular set of gripper fingers 58 (FIG. 7) on the impression cylinder 4 so as to be in registry with the

plate

33 or 34.

The selector switch 40 is closed in one direction or the other so as to place either coil 37 or coil 38 in control of the solenoid 42. the selection is made so that the other one of the two

plates

33 and 34, whose sheet registry is not controlled alone by the screws 57, is controlled by the stop screws 60 in conjunction with screws 57. The finger extension 54b is shifted to accommodate the actual position of the

other plate

33 or 34 on cylinder 3 by the generation of a signal in the selected

coil

37 or 38 due to the passage of armature 35. When such a signal is generated, it actuates the solenoid 42 and the valve 43 is operated to supply hydraulic fluid to the cylinder 44 and drive piston 45 to the left as shown in FIG. 2, forcing the arm against the stop screws 60 and establishing the finger extensions 54b in a new blocking position for the approaching sheet 27. This new blocking position may be adjusted by changing the setting of screw 60 so that the sheet is delivered to one set of grippers 58 (FIG. 7) on the impression cylinder 4 in proper registry with the

plate

33 or 34.

The valve 43 is biased to the position shown in the drawing, so that the hydraulic cylinders 44 always operate the arms 51 to the full line position illustrated in the absence of a signal from one of the pick-up coils.

It may be seen that one set of alternate sheets 27 arriving at the stop finger extensions 54b are stopped with the extensions 54b in the full line position, which may correspond to either

sheet

33 or 34, depending upon the operation of the selector switch 40, and that the other set of alternate sheets will be stopped by the extensions 54b in their dotted line positions, which will correspond to a position of registry with the other one of the two

plates

33 and 34. Thus, by operation of the selector switch 40, the press operator may determine which of the two plates has its sheet registry adjusted by the screws 57 alone, and which by the screws 60 in conjunction with screws 57.

FIG. 5

In this figure, those parts which are counterparts, corresponding in structure and in function, to parts shown in FIG. 2, have been given the same reference numerals and will not be further described.

The principal parts which differ from those in FIG. 2 are the plate cylinder 63, which is adapted to carry four printing plates rather than two, and the adjustable stop mechanism 64 for the arm 61.

The plate cylinder 63 has four

saddles

63a, 63b, 63c and 63d for accommodating four printing plates. The cylinder 63' also has four

recesses

63e, 63f, 63g'and 6311 for accommodating four sets of leading edge clamps 31 and trailing edge clamps 32.

The stop mechanism 64 is fixed on a shaft 65, driven in synchronism with a shaft 66 which supports the plate cylinders 63. The shaft 65 carries four adjusting

screws

64a, 64b, 64c and 64d, each provided with a lock nut.

The shaft 66 carries a hub 67 on which are formed four cam projections 67a which operate a contact 71 controlling an obvious circuit for supplying a signal to the input of amplifier 41. The arm 61 is reciprocated by the hydraulic cylinder 44 each time that a

plate

72, 73, 74 or 75 passes the nip of the plate cylinder and its cooperating impression cylinder. During the interval when a sheet is being picked up by the grippers 62 on the first sheet transfer cylinder 5, the arm 51 is engaging one of the adjusting screws 640 on the shaft 64, and the position of the stop finger extension 54b is then determined by one of the adjusting

screws

64a, 64b, 64c and 64d. Thus, the registry of each of the four

plates

72, 73, 74, 75 on the plate cylinder 63 may be different from the others, and the registry of each set of four successive sheets 27 with respect to the sheet feeding mechanism may be adjusted to accommodate the different registers of the four printing plates.

It is necessary that the arm 51 be reciprocated in synchronism with the plate cylinder 53, these being four reciprocations of the arm 51 to each rotation of the cylinder. Instead of using the cams 67a, contact 71, amplifier 41, solenoid 42, valve 43 and hydraulic cylinder 44, a mechanical drive between plate cylinder 53 and arm 51 may be substituted. In such a mechanical drive, some strain relief means must be provided to absorb the strain occurring when the arm 51 engages a stop. In the apparatus disclosed, the strain relief function is performed by the hydraulic cylinder 44.

As another example of a mechanical drive for the arm 51 and shaft 65, the shaft may be intermittently driven in synchronism with the plate cylinder, i.e., with the same period of rotation, so that the shaft 65 dwells for an interval, each time one of the

screws

64a, 64b, 64c and 64d comes opposite the end of the arm 51. A cam surface may then be provided between the screws about the periphery of the shaft 65 and the arm 51 may be spring loaded to ride against the four screws and the cam surfaces. The cam follower should then be contoured suitably to slide smoothly on the screws and the cam surfaces, or perhaps be provided with a roller. It may be desirable to provide a stop for the arm 51 to keep it from following the recessed contours of the cam between the heads of the screws.

Similar arrangements may be provided in the mechanism of FIG. 2. In other words, the apparatus shown in FIG. 5 and its equivalents are not limited to use on a four plate press but could be used on a two plate press, like that illustrated in FIG. 2.

We claim:

1. A printing press, including:

a. a rotatable plate cylinder having a plurality of spaced plate supporting peripheral portions;

b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board;

c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means;

d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheetsinto printing contact with I the plates on the plate cylinder;

e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates;

f. reciprocating means for operating said position changing means;

g. means to set the limit of travel of said reciprocating means at least at one end of its reciprocating stroke;

h. a crank arm operated by said reciprocating means;

and

i. eccentric means operated by said crank arm and connected to said stop shifting means.

2. A printing press as in claim 1, in which said limit setting means is in the path of the crank arm, and is adjustable relative to the frame of the press.

3. A printing press as in claim l, including:

a. a plurality of limit setting means equal in number to said plurality of plate supporting portions on the plate cylinder;

b. a shaft rotatable about an axis transverse to the path of the crank arm;

0. each said limit setting means comprising a screw adjustably threaded in said shaft and aligned with said crank arm, said screws being located at a plurality of angular positions on the rotating shaft corresponding in number to the plate supporting portions on the plate cylinder; and

d. means for driving said shaft with the same period of rotation as the plate cylinder.

4. A printing press, including:

(1. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder;

e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates, said position changing means comprising a hydraulic cylinder and piston;

f. means adjustable to set the limit of travel of the piston at one end of its stroke; and

g. control means responsive to rotation of the plate cylinder to drive the piston to said one end of its stroke as alternate sheets approach said movable stop means and to the opposite end of its stroke as the sheets intervening between said alternate sheets approach said movable stop means.

5. A printing press, comprising:

e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates, said blocking position changing means comprising:

1. reciprocating means;

2. a plurality of settable means to adjust the travel limit of the reciprocating means at one end only of its stroke, said travel limit adjusting means being equal in number to the number of plates on the cylinder; Y

3. means to drive the reciprocating means to said one end of its stroke as each sheet approaches the stop means, and to return said reciprocating means to the opposite end of its stroke after a sheet is removed from the stop means;

4. a movable support for all said settable means;

and

5. means for driving said movable support cyclicaliy with a period equal to the period of rotation of said plate cylinder to bring said settable means successively into a position where they are effective to establish said travel limit.

6. A printing press, including:

d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder;

f. said movable stop means including separate stop means at the opposite sides of the feed board;

g. said means for changing the sheet blocking position of the stop means for successive sheets including separate means for changing the sheet blocking positions of the stop means on opposite sides of the feed board, so that sheets may be stopped in skewed position corresponding to the position of a skewed plate on the plate cylinder, said separate means comprising, for each side of the press:

1. reciprocating means;

' 2. means to set the limit of travel of said reciprocating means at one end of its stroke, a crank arm operated by said reciprocating means, an eccentric operated by said crank arm; and

3. a universal bearing mounted in the frame of the press and supporting said eccentric; and

h. said sheet blocking position changing means further comprising:

1. a shaft fixed in both eccentrics at the opposite sides of the press and extending across the press; and

2. a plurality of stop means spaced along said shaft and shiftable by angular movement thereof, said means for shifting the stop means being operable to produce angular movements of the shaft.

7. A printing press, including:

a. a rotatable plate cylinder having only two spaced plate supporting peripheral portions;

e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates; and

f. means for operating said position changing means,

including:

1. reciprocating means;

2. means settable when the reciprocating means is at one end of its stroke to adjust the sheet blocking position of the stop means;

3. means to set the limit of travel of said reciprocating means at the other of its reciprocating stroke; and

4. control means responsive to rotation of the plate cylinder to drive the reciprocating means to alternate ends of its stroke as alternate sheets approach said movable stop means.

Claims

1. A printing press, including: a. a rotatable plate cylinder having a plurality of spaced plate supporting peripheral portions; b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board; c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means; d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder; e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates; f. reciprocating means for operating said position changing means; g. means to set the limit of travel of said reciprocating means at least at one end of its reciprocating stroke; h. a crank arm operated by said reciprocating means; and i. eccentric means operated by said crank arm and connected to said stop shifting means.

2. a plurality of settable means to adjust the travel limit of the reciprocating means at one end only of its stroke, said travel limit adjusting means being equal in number to the number of plates on the cylinder;

2. means to set the limit of travel of said reciprocating means at one end of its stroke, a crank arm operated by said reciprocating means, an eccentric operated by said crank arm; and

3. a universal bearing mounted in the frame of the press and supporting said eccentric; and h. said sheet blocking position changing means further comprising:

3. A printing press as in claim 1, including: a. a plurality of limit setting means equal in number to said plurality of plate supporting portions on the plate cylinder; b. a shaft rotatable about an axis transverse to the path of the crank arm; c. each said limit setting means comprising a screw adjustably threaded in said shaft and aligned with said crank arm, said screws being located at a plurality of angular positionS on the rotating shaft corresponding in number to the plate supporting portions on the plate cylinder; and d. means for driving said shaft with the same period of rotation as the plate cylinder.

4. a movable support for all said settable means; and

4. A printing press, including: a. a rotatable plate cylinder having a plurality of spaced plate supporting peripheral portions; b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board; c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means; d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder; e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates, said position changing means comprising a hydraulic cylinder and piston; f. means adjustable to set the limit of travel of the piston at one end of its stroke; and g. control means responsive to rotation of the plate cylinder to drive the piston to said one end of its stroke as alternate sheets approach said movable stop means and to the opposite end of its stroke as the sheets intervening between said alternate sheets approach said movable stop means.

5. A printing press, comprising: a. a rotatable plate cylinder having a plurality of spaced plate supporting peripheral portions; b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board; c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means; d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder; e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates, said blocking position changing means comprising:

5. means for driving said movable support cyclically with a period equal to the period of rotation of said plate cylinder to bring said settable means successively into a position where they are effective to establish said travel limit.

6. A printing press, including: a. a rotatable plate cylinder having a plurality of spaced plate supporting peripheral portions; b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board; c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means; d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder; e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates; f. said movable stop means including separate stop means at the opposite sides of the feed board; g. said means for changing the sheet blocking position of the stop means for successive sheets including separate means for changing the sheet blocking positions of the stop means on opposite sides of the feed board, so that sheets may be stopped in skewed position corresponding to the position of a skewed plate on the plate cylinder, said separate means comprising, for each side of the press:

7. A printing press, including: a. a rotatable plate cylinder having only two spaced plate supporting peripheral portions; b. sheet feeding apparatus, including a feed board and movable stop means for holding a sheet advancing along the feed board; c. means for shifting the stop means alternately between a sheet blocking position adjacent the feed board in which it stops an advancing sheet and a retracted position in which the sheet is free to move beyond the stop means; d. sheet transfer apparatus for gripping sheets engaging the stop means and, after retraction of the stop means, moving the sheets into printing contact with the plates on the plate cylinder; e. means for changing the sheet blocking position of the stop means for successive sheets, to correspond with the positions of successive plates on the cylinder, so as to maintain registry between the successive sheets and the successive plates; and f. means for operating said position changing means, including: