Printing plate attachment arrangement

To secure a thin, flexible printing plate (4) on the circumference of a plate cylinder (2, 20) by inserting the ends of the printing plate into two narrow parallel slits, the printing cylinder has a groove (3, 21) cut therein in which an insert strip (5, 23) is located which has an inner guide portion (6, 24) fitting within the groove, and a projecting engagement or separating wall portion (9, 25) which is narrower than the guide portion, the walls of the engagement or separating wall portion defining, together with the walls of the groove, the respective slits (18, 30) in which the ends of the printing plate can be inserted. The strip can be irremovably adhered to the cylinder in the groove, or can be made axially slidable, for example under control of a worm (27) engaging in the teeth, so that the lateral register of the printing plate wrapped about the circumference of the cylinder can be adjusted, the printing plate engaging suitable abutment strips or pins (13, 31) formed on the insert strip.

The present invention relates to an arrangement to attach a thin, flexible 
printing plate on the plate cylinder of a printing machine. 
BACKGROUND 
It has previously been proposed to cut two narrow slots, parallel to the 
axis of a plate cylinder, into its circumference. The slots extend at an 
angle with respect to the tangent of the outer circumference of the plate 
cylinder, at the point of intersection of the slot with the surface. The 
slots are arranged to receive respective ends of the printing plate. 
German Utility Model Publication DE-GM No. 16 11 416 describes an 
arrangement to secure a metal foil on the cylinder of a duplicating 
machine. The structure is characterized by its simplicity--which, however, 
is not the case with respect to its manufacture. Forming two parallel 
slits, of very small width dimension, is difficult. The slits must be 
narrow so that the ends of the metal foil can be reliably secured. 
Manufacture of such slits must be done with material removing tools, in 
which the cut must be made at an inclination to the surface of the 
cylinder. The cut must be made accurately, since the slits must be 
precisely parallel to the axis of the cylinder. 
While it is possible to make slits of this type in cylinders of the limited 
length used in copy machines, or duplicating machines, it is practically 
impossible to make slits of this type in the much larger and substantially 
longer cylinders used in printing machines which, for example, are 
employed in newspaper printing and the like. The cost of making such 
slits, of the small width required, which extend precisely parallel to the 
axis of the cylinder, is excessive. 
THE INVENTION 
It is an object to provide an attachment arrangement for a flexible 
printing plate to place the printing plate about a printing cylinder, in 
which the cost of making narrow slits in the printing cylinder, which 
extend precisely parallel to the axis of the cylinder, is substantially 
reduced over that if methods used in connection with making small, 
duplicating or copy machine cylinders, are used. 
Briefly, a groove is formed in the circumference of the plate cylinder at 
the required angle which, however, is substantially larger, that is, 
substantially wider, and also deeper than the desired slits. The width of 
the groove must be larger than twice the thickness of the printing plate; 
in actual practice, it is substantially larger. An insert strip is then 
placed in the groove, and retained therein, the insert strip having a 
guide portion located at the root or bottom of the groove, engaging the 
walls of the groove. The strip is reduced in thickness in the region of 
the slits, leaving a free space between the strip and the walls of the 
groove which then form the narrow slits. 
The strip can be retained in the groove by adhesion or by other well known 
elements, such as screws, holding clips or the like. 
The arrangement has the advantage that register or locating projections, 
pins or other elements which, preferably, are positioned within the slits, 
can readily be formed on the strip, before its insertion, so that such 
register arrangements can be easily introduced--whereas, if a slit is to 
be cut into a cylinder, placement of such register elements within cut 
narrow slits is practically impossible. By making the slit axially 
movable, for example under control of a worm gear engaging projections or 
teeth formed on the inner side of the strip, it is possible to adjust the 
axial register of a printing plate placed on the cylinder even after its 
insertion.

DETAILED DESCRIPTION 
A plate cylinder 1 has a groove 3 cut at an angle with respect to the 
cylindrical surface 2 of the plate cylinder. The groove 3 extends parallel 
to the axis of the plate cylinder and extends over the entire width of a 
printing plate 4 to be secured to the circumference of the plate cylinder 
1. The groove 3 has a width a which is wider than twice the thickness b of 
the printing plate. Preferably, it is substantially wider, for example 
about 8 to 10 times as wide as the thickness of the printing plate; in one 
illustrative example, the printing plate has a thickness b of about 0.25 
mm; for such a printing plate, the groove 3 has a width a of about 2 mm. 
The narrow slits to receive the printing plate are defined by an insert 
strip 5 which extends over the entire length of the groove 3. The groove 3 
may extend in the printing cylinder essentially from end to end. The 
insert strip 5 has a guide portion 6 which engages the lower region 7 of 
the side walls which define the groove 3 as well as the root or bottom 8 
of the groove; thus, the guide portion 6 is located within the inner end 
of the groove. The insert strip 5 further includes a separating wall 9 
which extends up to just about the upper end of the groove 3. The two side 
walls 10 of the upper end portion 9 extend parallel to the upper region 11 
of the side walls which define the groove 3. The separating portion or 
separating wall 9 is slightly narrower than the width of the groove, 
leaving between the side walls 10 and 11 the narrow slit 12 into which the 
respective ends of the printing plate 4 can be inserted. 
The insert strip 5 can be positioned in the groove 3 in various ways, for 
example by adhesion, with a suitable adhesive such as epoxy or the like, 
bonding the guide element 6 to the inner region 7 of the groove and to the 
bottom 8 thereof. Other connections may be used, for example attachment by 
screws or the like. 
Two pins 13--of which only one is shown in FIG. 1--pass through the 
separating wall portion 9 of the insert strip 5. The pins are securely 
connected to the wall 9, and the length of the pins 13 is slightly less 
than the width a of the groove. The pins 13 can be readily inserted into 
the groove 3 together with the insert strip 5. The pins 13 are used to 
maintain lateral register of the printing plate 4, and to insure 
maintenance of this register. The printing plate 4--see FIG. 3--is formed 
at the front and rear end portions with notches 15 in the edge 14 thereof. 
The width c of the notches corresponds to the diameter of the pins 13. 
In some machines, the plate cylinder may rotate in either direction, which 
then will require locating the printing plate such that its angle of 
inclination, at the exit of the groove, extends, selectively, towards the 
right or the left. FIG. 1 illustrates, in abbreviated form, a second 
groove 16 which can be the mirror image of groove 3. Groove 16 has a 
further insert strip 17 secured therein which defines two slits 18 with 
the inner walls of the groove. The arrangement is mirror-image identical 
to that described in connection with the right side of FIG. 1. 
In accordance with a feature of the invention, the lateral register of the 
printing plate 4 can be adjusted if the embodiment of FIG. 2 is used. A 
plate cylinder 20 has a groove 21, corresponding to the groove 3 cut 
therein, which is formed at its inner end with an enlarged portion 22. The 
groove 21 has an insert strip 23 inserted therein which, as before, 
includes a guide portion 24 and a separating or engagement portion 25. The 
guide portion 24 is enlarged at its inner end, as seen at 26, and formed, 
interiorly of the cylinder, with projections, typically teeth, which 
engage a worm wheel 27. The worm 27 is shown only schematically, and may 
be of any suitable construction, engaging the teeth of the enlarged 
portion 26. Upon rotation of the worm 27--which is restrained against 
axial shifting--the insert strip 23 will be moved axially with respect to 
the cylinder to thereby permit axial register adjustment of a printing 
plate secured to the circumference thereof--not shown in FIG. 2. 
The lateral sides 28 of the separating wall or projection 25, together with 
the upper regions 29 of the side walls of the groove 21, define respective 
slits 30 to receive the ends of a printing plate. The separating wall 25 
includes two longitudinal strips 31 which form register abutments and, 
together with the notches 15 in the printing plate, insure lateral 
register thereof. 
The insert strip 25 can be shifted parallel with respect to the axis of the 
plate cylinder 20 within the groove 21. The guide element 24 engages the 
side walls of the groove 21 in the inner region 32 of the groove. By 
rotation of the worm 27, the insert strip 23 can be shifted parallel to 
the axis of the cylinder 20 within the groove 21. Since the lateral 
abutment strips 31 follow with the insert strip 23, a plate secured to the 
circumference of cylinder 20 and located between the abutment strips 31 
will be shifted axially. 
The insert strip 23 can be held in position by any suitable means, not 
shown, such as, for example, a loop or the like surrounding a cylindrical 
portion or cylindrical portions of the worm 27, besides being guided by 
the enlargement 26 fitting against the shoulder 22 in the interior of the 
groove 21. 
Various changes and modifications may be made, and any features described 
herein may be used with any of the others within the scope of the 
inventive concept. 
The width a of the grooves 3, 21 is, preferably, between about 5 to 10 
times the thickness b of the printing plate, preferably at least 6 times 
this thickness; the maximum dimension will be governed by availability of 
cutting tools and the accuracy with which a groove can be made on existing 
machinery which is precisely parallel to the axis of the printing cylinder 
2, 20, respectively. If the groove is made wider, more material will be 
required for the respective insert strips and, of course, more machining 
time and energy will be required to make the groove; thus, a suitable 
engineering compromise between ease of manufacture and assembly will 
readily determine the upper limit of the width of the groove.