US3874290A

US3874290A - Master plate feed and discharge device for duplicating apparatus

Info

Publication number: US3874290A
Application number: US368021A
Authority: US
Inventors: Minoru Suzuki
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1972-06-13
Filing date: 1973-06-08
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01
Also published as: JPS4930001U; JPS543761Y2; DE2329757B2; DE2329757A1; GB1432485A

Abstract

In apparatus for producing copies from a master plate, a device comprising a master feed roller for feeding a master plate to a master cylinder, a master discharge roller for discharging the master plate from the master cylinder, and an actuation roller having major diameter portions and minor diameter portions. The feed roller and the discharge roller are disposed in positions spaced apart vertically from each other with the feed roller being disposed above the discharge roller, and the actuation roller is interposed between the feed roller and discharge roller for free vertical movement. When the actuation roller is moved upwardly to bring its major diameter portions into pressing engagement with the feed roller, a master plate feed operation can be performed; when the actuation roller is moved downwardly to bring its minor diameter portions into engagement with the discharge roller, a master plate discharge operation can be performed.

Description

United States Patent 1191 Suzuki Apr. 1, 1975 MASTER PLATE FEED AND DISCHARGE DEVICE FOR DUPLICATING APPARATUS [75] Inventor: Minoru Suzuki, Yokohama, Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: June 8, 1973 [21] Appl. No.: 368,021

[30] Foreign Application Priority Data Primary Examiner-Edgar S. Burr Assistant Examiner-William Pieprz Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Morgan [57] ABSTRACT In apparatus for producing copies from a master plate, a device comprising a master feed roller for feeding a master plate to a master cylinder, a master discharge roller for discharging the master plate from the master cylinder, and an actuation roller having major diameter portions and minor diameter portions. The feed roller and the discharge roller are disposed in posi' tions spaced apart vertically from each other with the feed roller being disposed above the discharge roller, and the actuation roller is interposed between the feed roller and discharge roller for free vertical movement. When the actuation roller is moved upwardly to bring its major diameter portions into pressing engagement with the feed roller, a master plate feed operation can be performed; when the actuation roller is moved downwardly to bring its minor diameter portions into engagement with the discharge roller, a master plate discharge operation can be performed.

3 Claims, 13 Drawing Figures PATEHTEU APR 1 i975 sum u or g FIG.7

MASTER PLATE FEED AND DISCHARGE DEVICE FOR DUPLICATING APPARATUS BACKGROUND OF THE INVENTION This invention relates to a master plate feeding and discharging device for offset duplicating apparatus.

In a known type of offset duplicating apparatus, a master plate is carried on a master cylinder for inking an contact with a blanket cylinder. Ink applied to the master plate is transferred to the blanket cylinder, and thence to a copy sheet advanced between the blanket cylinder and an impression cylinder, to produce a copy of the master. This operation is repeated, with feed of successive copy sheets through the apparatus and successive applications of ink to the master plate, until a desired number of copies have been made. The master plate is then removed and replaced for production of copies from a different master plate. For example, a master plate may be advanced from a feed tray to the master cylinder by means of a master feed roller, and after the requisite number of copies have been made, the plate is advanced from the master cylinder to a discharge tray by means of master discharge rollers.

A master plate feed operation and a master plate discharge operation should be performed for each master plate from which a plurality of printed copies are produced. A master plate can be mounted on and discharged from the master cylinder either manually by interrupting the rotation of the master cylinder or auto- 'matically while the master cylinder is rotating.

In automatically feeding a master plate to the master cylinder and discharging the same therefrom, it has heretofore been customary to rotate the master feed roller (maintained in pressing engagement with the master plate) to a position which corresponds to the position of grip claw means provided on the master cylinder, and to have the leading end portion of the master plate temporarily held between a pair of master delivery rollers. Then the pair of master delivery rollers are rotated in synchronization with the master cylinder so that the leading end portion of the master plate is gripped by the grip claw means. In order to rotate the plate feed roller and the pair of plate delivery rollers at opportune moments, it has heretofore been customary to move a pivotal member in one pivotal movement when the grip claw means moves into a predetermined position. The master feed roller is rotated through a gearing when the pivotal member moves from a first position to a second position and the master discharge roller is rotated through the gearing when the pivotal member returns to the first position from the second position.

SUMMARY OF THE INVENTION This invention has as its object the provision of a master plate feeding and discharging device for duplicating apparatus comprising a master feed roller and a master discharge roller rotating at all times and disposed in positions vertically spaced apart from each other, and an actuation roller interposed between the master feed and master discharge rollers for selective engagement with these two rollers whereby feeding and discharging of a master plate can be effected by these three rollers.

According to the invention, the actuation roller is brought into engagement with the master feed roller in proper timing when a master plate is to be fed to the master cylinder, thereby eliminating the need to provide the pair of delivery rollers, pivotal member, and gearing associated with the pivotal member to rotate the master feed roller, which have heretofore been provided in offset duplicating apparatus. The actuation roller according to the invention comprises major diameter portions adapted to be brought into pressing engagement with the master feed roller and minor diameter portions adapted to be brought into pressing engagement with the master discharge roller. This arrangement is effective to keep the ink stain of the master discharge roller and the minor diameter portions of the actuation roller from being transferred to the nonimage bearing surface of the master plate and the master cylinder.

Further features and advantages of the invention will be apparent from the detailed description hereinbelow set forth, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of an offset duplicating apparatus;

FIG. 2 is a front view of a master plate feeding and discharging device, for offset duplicating apparatus, embodying the present invention in a particular form;

FIG. 3 is a front view of actuation mechanism for ac tuating the master plate feeding and discharging device shown in FIG. 2;

FIG. 4 is a view of a drive system for operating the master feed roller and the master discharge roller of the device of FIG. 2;

FIG. 5 is a fragmentary sectional view of the master cylinder associated with the device of FIG. 2;

FIG. 6 is a view in explanation of the operation of the master feed mechanism shown in FIG. 3;

FIG. 7 is a view in explanation of the operation of the master discharge mechanism shown in FIG. 3;

FIG. 8 is a front view of the master feed cam and the master discharge cam and their followers, in the device of FIG. 2;

FIG. 9 is a view in explanation of the operation of the master feed cam;

FIG. 10 is a sectional side view of the device of FIG. 2, showing the actuation roller and the master feed and discharge rollers;

FIG. 11 is a view in'explanation of the operation of the master discharge cam of the device of FIG. 2;

FIG. 12 is a front view of the actuation roller and the master discharge roller of the device of FIG. 2; and

FIG. 13 is a view in explanation of the operation of the master discharge cam shown in FIG. 11.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 illustrates a generally conventional form of offset duplicating apparatus, to which reference may be made for an understanding of one type of apparatus with which devices embodying the present invention may be used. 1

Functioning of offset duplicating apparatus will first be outlined with reference to FIG. 1. The duplicating machine 1 comprises a master cylinder 2, a blanket cylinder 3 and an impression cylinder 4. A master plate 6 on a master plate feed tray 5 is fed to the master cylinder 2 by means of a master feed roller 7.

An ink-repellent etching liquid is applied by an etching roller 8 to the master plate 6 mounted on the master cylinder 2 so that ink may not adhere to regions other than the image regions. Following the etching trcatment, inking is effected by an ink applying roller 11 of an inking device 9 so as to apply ink to the image regions of the master plate 6. An ink image of the master plate 6 is formed on the blanket cylinder 3, and a copy sheet 12 supplied to the impression cylinder 4 by a copy sheet feed roller 13 and a copy sheet delivery roller 14 is brought into pressing engagement with the blanket cylinder by the impression cylinder 4. Thus the ink image on the blanket cylinder 3 is transferred to the copy sheet 12. The printed copy sheet is ejected onto a printed copy sheet tray 15.

When a predetermined number of copy sheets have been printed from one master plate, the blanket cylinder 3 is cleaned to remove the ink image therefrom and the master plate 6 mounted on the master cylinder 2 is removed therefrom and discharged by master discharge rollers 16 from the master cylinder 2 to a master plate discharge tray 17.

The present invention will now be described with reference to the illustrative specific embodiment shown in FIGS. 2 13. In FIG. 2, a master cylinder 2 is supported by a shaft 21 which in turn is supported by two side plates (not shown) of the duplicating apparatus. The master cylinder 2 is rotated in the direction of an arrow 22 by a drive (not shown). A cutout 23 is formed in the outer periphery of the master cylinder 2 as shown in FIG. 5.

Supported by portions of two

side walls

2a and 2b of the master cylinder 2 (side wall 2a is shown in FIG. and side wall 2b is shown in FIG. 2) which are disposed in the cutout 23 is a shaft 24 extending parallel to the axis of the master cylinder 2. Master plate grip claw means 25 and a stop 26 are secured to this shaft 24 at their bases by screws 27.

Master plate pushout means 28 has a free end 28a which is disposed below a free end of grip claw means 25. The free ends of claw means 25 and pushout means 28 are maintained in pressing engagement with one end of the outer periphery of master cylinder 2 by the biasing force ofa spring (not shown). The pushout means 28 is secured at its base to a support plate 29 which is formed therein with a slot 29a for loosely receivinga pin 31 fixedly projecting from the cylinder side wall 2a, and which has an end portion pivotally supported by a shaft 32 secured to one end of an arm 33. The arm 33 is secured at its base to a shaft 34 pivotally supported at opposite ends by the two side walls 2a and 2h. A follower 35 for master plate discharge (shown in FIG. 2), adapted to be actuated when a master plate discharge operation is performed, is secured to an end portion of the shaft 34 extending outwardly of the side wall 2!).

A claw opening and closing member 36 is secured to one end portion of the shaft 24 to which the master plate grip claws are secured as aforementioned. The member 36 supports at one end portion a roller 37 which is maintained in contact with a free end a of the follower 35, and is formed at the other end portion with a bent portion 36a which is maintained in light pressing engagement with a roller 39 supported by a free end of a follower 38 for master plate feed. The follower 38 is pivotally supported at its base by the shaft 34, and is adapted to be actuated (when a master plate feed operation is performed) to move clockwise about the shaft 34 so as to move the grip claw means 25 (see FIG. 5) to an open position. The follower 38 is normally urged by the biasing force of a spring (not shown) to move counterclockwise about the shaft-34.

The follower 38 for master plate feed has a roller 41 mounted on a shaft supported by an intermediate portion of the follower 38 and adapted to cooperate with a cam edge 42a of a master feed cam 42. The master feed cam 42 is supported at its base by a shaft 43 which in turn is supported by the main side plate (not shown) and urged to move clockwise about the shaft 43 by the biasing force of a spring 44 (see FIG. 8) connected at one end to the cam 42 andv at the other end to an immovable member (not shown), so that one side edge 42a of its free end portion is maintained in pressing engagement with an immovable pin 45.

Referring to FIG. 2 again, a pin 46 is mounted on the free end portion of the master feed cam 42. A lock member 47 having a locking offset portion 47a is pivotally supported at its base by an immovable shaft 48 and maintained at its lower edge in pressing engagement with the pin 46 by gravity.

The follower 35 for master plate discharge has a roller 49 mounted on a shaft supported by one end of the follower 35 for cooperation with a cam edge 51a of a master discharge cam 51. The master discharge cam 51 is pivotally supported at its base by a shaft 52 connected to an immovable member (not shown) and has a lower side edge 51c which is maintained in pressing engagement with a pin 53 mounted on one end of arelease member 54 pivotally supported at its base by an immovable shaft 55. The release member 54 is normally urged to move counterclockwise about the shaft base to one end portion of the shaft 52 supporting the master discharge cam 51 as aforementioned, so that the actuation member 57 is substantially integral with the master discharge cam 51. The actuation member 57 has a free end to which is connected one end of a spring 7 58 connected at the other end to an actuator 59a of a master plate discharge initiation solenoid 59. The actuation member 57 is normally urged to move counterclockwise about the shaft 52 by the biasing force of a spring 61 connected at one end to the member 57 and at the other end to an immovable member (not shown), so thatthe master discharge cam 51 is maintained at its lower side in pressing engagement with the shaft 55. A stop 62 shown in FIG. 3 is disposed below'the actuation member 57 to limit the range of movement of the actu-" ation member 57.

Disposed rightwardly of the master cylinder 2 in FIG. 2 are strip claw means 63 for picking off the leading end of the master plate from the master cylinder 2 when the master plate is to be discharged, a master feed roller 64 and a master discharge roller 65.'The master feed roller 64 and master discharge roller 65 each'comprise a plurality of roller members and are secured to

V shafts

66 and 67 respectively for rotation in directions indicated by arrows in FIG. 2.

The master discharge roller 65 is maintained in thereto. The actuation roller 68, as shown in FIG. 12..

comprises major diameter portions 68a in addition to the minor diameter portions 68b, the major diameter po' tions 68a and minor diameter portions 68b being disposed alternately at regular intervals. The major diameter portions 68a are normally spaced apart from the master feed roller 64 as shown in FIG. 2.

interposed between the actuation roller 68 and master feed roller 64 is a master plate feed tray 5 which is formed with an offset portion 5a and an opening 5)) in a portion of the tray 5 which is disposed near the two

rollers

64 and 68. The offset portion 5a is for correctly positioning the leading end of a master plate 6 on the tray 5, and the major diameter portions 680 extend through the opening 5b when the actuation roller 68 is moved into engagement with the master feed roller 64 as subsequently to be described.

As shown in FIG. 10, the actuation roller 68 is rotatabIy supported by a shaft 69 connected to a free end of an arm 71 pivotally supported at its base by a shaft 72 supported by the opposite side plates. A follower 73 is secured at its base to an end portion of the shaft 72 which extends out of one of the side plates. The follower 73 supports at its free end through a shaft a roller 74 which is positioned against a cam 70 secured to the shaft 21 supporting the master cylinder 2 as shown in FIG. 3. The follower 73 is urged to move clockwise about'the shaft 72 by the biasing force of a spring 75 connected at one end to the follower 73 and at the other end to an immovable member (not shown), so that a bent portion 73a formed at one end of its short arm is maintained in pressing engagement with an engaging portion 76a of a master feed actuation member The actuation member 76 is pivotally supported by a shaft 77 connected to an immovable member (not shown), and a spring 79 is connected at one end to a free end of the follower 76 and at the other end to an actuator 78a of a plate feed initiation solenoid 78. A return spring 81 is connected at one end to an immovable member (not shown) and at the other end to the member 76.

A drive gear 81a and a sprocket 82 substantially integral with the gear 81a are rotatably supported by the shaft 72 supporting the follower 73 as shown in FIG. 4.

Pinions

83 and 84 maintained in meshing engagement with the gear 81a are secured to ends of the

shafts

66 and 67 supporting the master feed roller 64 and master discharge roller 65 (see FIG. 2) respectively.

A chain 86 is trained over the sprocket 82 and over another sprocket 85 secured to the shaft 21 supporting the master cylinder 2. When the master cylinder 2 rotates in the direction of the arrow 22, the

pinions

83 and 8 4 and the plate feed roller 64 and plate discharge roller 65 substantially integral with the

pinions

83 and 84 respectively rotate in the directions indicated by arrows in FIG. 4.

In operation, the master feed initiation solenoid 78 shown in FIG. 3 is energized when an instruction to start master feed is given thereto. The master feed actuation member 76 is pulled by the spring 79 and moves clockwise about the shaft 77, thereby releasing the follower 73. Upon being released, the follower 73 moves clockwise about the shaft 72 as the roller 74 is brought into engagement with a minor diameter portion 70a of the cam 70 as shown in FIG. 6. When the follower 73 moves clockwise as aforementioned, the arm 71 (see FIG. 2) substantially integral with the follower 73 also moves clockwise about the shaft 72. This brings the supported by the arm 71 into pressing engagement with the master feed roller 64. As the major diameter portions 68a are brought into pressing engagement with the master feed roller 64, the free end portion of the master plate 6 disposed on the master plate feed tray 5 is gripped between the master feed roller 64 and the major diameter portions 68a of the actuation roller 68, and is moved thereby toward the master cylinder 2 as shown in FIG. 10.

The above-described clockwise movement of the ac tuation member 76 also moves the master feed cam 42 from an inoperative position shown in FIG. 8 to an operative position shown in FIG. 9 by suitable means, and the pin 46 at the free end of the cam 42 is brought into locking engagement with the offset portion 47a of the lock member 47. The master cylinder 2 rotates in the direction of the arrow 22, so that the roller 41 is pushed and moved by the cam edge 42a of the master feed cam 42 toward the shaft 21, and the follower 38 for master feed moves counterclockwise about the shaft 34.

During the counterclockwise movement of the follower 38, the roller 39 pushes and moves the bent portion 36a of the claw opening and closing member 36, so that the latter moves counterclockwise about the shaft 24 from a position shown in FIG. 8 to a position shown in FIG. 9. Counterclockwise rotation of the shaft 24 mounting the claw opening and closing member 36 results in the grip claw means 25 (see FIG. 5) moving in the same direction into an open position. The leading end portion of the master plate 6, moving toward the master cylinder 2 as aforementioned, is received by the grip claw means 25 in the open position. Further rotation of the master cylinder 2 releases the roller 41 from engagement with the cam edge 42a and restores the claw opening and closing member 36 to its original position, so that the grip claw means 25 is restored to the closed position and grips the leading end portion of the master plate 6. At the same time, the free end of the lock member 47 is flipped by the roller 41 to release the pin 46 from locking engagement with the lock member 47. This restores the master feed cam 42 to the inoperative position shown in FIG. 8.

The master discharge solenoid 59 shown in FIG. 3 is energized when an instruction to remove the master plate 6 from the master cylinder 2 is given. Energization of the solenoid 59 causes the actuation member 57 to be pulled by the spring 58 and move clockwise about the shaft 52. The master discharge cam 51 (see FIG. 2) substantially integral with the master discharge actuation member 57 also moves in the same direction, and is maintained in an operative position as the pin 53 on the release member 54 is brought into engagement with the offset portion 51b as shown in FIG. 11.

As shown in FIG. 11, a lever 92 supporting at its free end a hold-down roller 91 through a shaft is secured at its base to the shaft 55 supporting the release member 54. As the release member 54 moves counterclockwise and locks the master discharge cam 51, the hold-down roller 91 also moves in the same direction to force the master plate 6 tightly over the master cylinder2.

Rotation of the master cylinder 2 at this time results in the roller 49 being pushed and moved by the cam edge 51a of the master discharge cam 51 toward the shaft 21, so that the follower 35 moves clockwise about the shaft 34. As the follower 35 moves clockwise as aforementioned, its free end 35a pushes and moves the roller 37 and moves the claw opening and closing member 36 counterclockwise to a position shown in FIG. 11. As a result, the shaft 24 and the grip claw means 25 (see FIG. mounted thereon move counterclockwise, so that the leading end portion 6a of the master plate is released from the grip claw means 25. At the same time, the arm 33 substantially integral with the follower 35 moves clockwise in FIG. 5 about the shaft 34 and moves the pushout means 28 in the direction of an arrow 93. Thus the pushout means 28 pushes out at its free end 28a the leading end portion 6a of the master plate 6 as shown in FIG. II.

The master plate 6 pushed out in this way is picked off from the periphery of the master cylinder by pickoff claws 63 as shown in FIG. 13 and gripped by the master discharge charge roller 65 rotating at all times and the minor diameter portions 68b of the actuation roller 68 to be conveyed in the direction of an arrow 94 in FIG. 13 until it is ejected onto the master plate discharge tray 17 (see FIG. 1).

When the master plate 6 is discharged from the master cylinder 2, the master discharge roller 65 and the minor diameter portions 68b of the actuation roller 68 are soiled by the ink on the upper surface of the master plate. However, since the minor diameter portions 681? are not brought into contact with the lower surface of the master plate when the latter is fed to the master cylinder, staining of the master plate and the periphery of the master cylinder 2 on which the master plate 6 is mounted can be precluded. When the master plate discharge operation is performed, the master plate 6 is brought into engagement with the major and

minor diameter portions

68a and 68b of the actuation roller 68 as shown in FIG. 12, so that discharge of the master plate can be facilitated.

After being released from engagement with the cam edge 5111, the roller 49 supported by the follower 35 flips the free end 54a of the release member 54 and causes the same to move clockwise about the shaft 55, so that the pin 53 is released from engagement with the offset portion 51b and the master discharge cam 51 is released. As a result, the master discharge cam 51 and the actuation member 57 (see FIG. 3) substantially integral with the master discharge cam 51 are restored to their original positions by the biasing force of the return spring 61.

It is to be understood that the invention is not limited to the features and embodiments hereinabove specifically set forth, but may be carried out in other ways without departure from its spirit.

What is claimed is:

l. A master plate feed and discharge device for duplieating apparatus, comprising a. a master plate feed tray for holding a master plate;

b. a master feed roller for feeding a master plate to a master cylinder from said feed tray;

0. means provided on the master cylinder for automatically gripping a leading end portion ofa master plate fed to the master cylinder;

d. a master discharge roller disposed below the master feed roller;

0. an actuation roller interposed between said master feed roller and said master discharge roller and adapted selectively to cooperate with the two rollers; and

f. means for moving the actuation roller to a position in which it cooperates with the master feed roller when a master feed operation is performed and to a position in which it cooperates with the master discharge roller when a master discharge operation is performed;

g. said actuation roller comprising a plurality of major diameter portions and minor diameter portions arranged alternately on the same axis, said major diameter portions being disposed for cooperation with the master feed roller and said minor diameter portions being disposed for cooperation with the master discharge roller.

2. In duplicating apparatus, in combination,

a. a rotatable master cylinder including means for releasably gripping a master plate to hold the plate on the cylinder;

b. means for supporting a master plate in position for advance to said cylinder;

c. a driven plate feed roller for engaging and advancing a plate to the cylinder from said supporting means;

. a driven plate discharge roller for engaging and advancing a plate away from the cylinder, said feed and discharge rollers being disposed in spaced, axially parallel relation adjacent said cylinder;

e. a third roller disposed intermediate said feed and discharge rollers in axially parallel relation thereto;

f. means mounting said third roller for movement between positions in which said third roller respectively cooperates only with said feed roller, and only with said discharge roller, for advance of a plate therebetween; and

g. means for moving said third roller between the aforesaid positions for selectively effecting feed of a plate to, and discharge of a plate from, said cylinder;

h. said third roller comprising a plurality of first portions of equal diameter and a plurality of second portions of equal diameter smaller than the diameter of said first portions, said second portions being disposed in alternating relation with said first portions along a common axis;

i. said feed roller comprising a plurality of coaxial roller segments spaced apart for register with said first portions of said third roller to grip a plate therebetween; and

j. said discharge roller comprising a plurality of coaxial roller segments spaced apart for register with said second portions of said third roller to grip a plate therebetween.

3. Apparatus as defined in claim 2, wherein said supporting means comprises a tray interposed between said feed roller and said third roller, for supporting a plate in position to be gripped between said feed and third rollers, and having an opening in register with said last-mentioned rollers for permitting the rollers to grip the plate.

Claims

1. A master plate feed and discharge device for duplicating apparatus, comprising a. a master plate feed tray for holding a master plate; b. a master feed roller for feeding a master plate to a master cylinder from said feed tray; c. means provided on the master cylinder for automatically gripping a leading end portion of a master plate fed to the master cylinder; d. a master discharge roller disposed below the master feed roller; e. an actuation roller interposed between said master feed roller and said master discharge roller and adapted selectively to cooperate with the two rollers; and f. means for moving the actuation roller to a position in which it cooperates with the master feed roller when a master feed operation is performed and to a position in which it cooperates with the master discharge roller when a master discharge operation is performed; g. said actuation roller comprising a plurality of major diameter portions and minor diameter portions arranged alternately on the same axis, said major diameter portions being disposed for cooperation with the master feed roller and said minor diameter portions being disposed for cooperation with the master discharge roller.

2. In duplicating apparatus, in combination, a. a rotatable master cylinder including means for releasably gripping a master plate to hold the plate on the cylinder; b. means for supporting a master plate in position for advance to said cylinder; c. a driven plate feed roller for engaging and advancing a plate to the cylinder from said supporting means; d. a driven plate discharge roller for engaging and advancing a plate away from the cylinder, said feed and discharge rollers being disposed in spaced, axially parallel relation adjacent said cylinder; e. a third roller disposed intermediate said feed and discharge rollers in axially parallel relation thereto; f. means mounting said third roller for movement between positions in which said third roller respectively cooperates only with said feed roller, and only with said discharge roller, for advance of a plate therebetween; and g. means for moving said third roller between the aforesaid positions for selectively effecting feed of a plate to, and discharge of a plate from, said cylinder; h. said third roller comprising a plurality of first portions of equal diameter and a plurality of second portions of equal diameter smaller than the diameter of said first portions, said second portions being disposed in alternating relation with said first portions along a common axis; i. said feed roller comprising a plurality of coaxial roller segments spaced apart for register with said first portions of said third roller to grip a plate therebetween; and j. said discharge roller comprising a plurality of coaxial roller segments spaced Apart for register with said second portions of said third roller to grip a plate therebetween.