US2768579A - Lock-up device for flexible printing plates - Google Patents

Description

Oct. 30, 1956 E. E. Flr-:s

Loox-UF nEvIcE FoR FLEXIBLE PRINTING PLATES Filed July 26. 1952 3 Sheets-Sheet l Il lllll vallwll l lIIIHl/ifnllllflinlll I l' Oct. 30, 1956 E. E. Fles 2,768,579

LUCK-UP DEVICE FOR FLEXIBLE PRINTING PLATES Filed July 26, 1952 3 Sheets-Shawl'I 2 3 sneetssheet 5 E. E. Fn-:s

LOCK-UP DEVICE FOR FLEXIBLE PRINTING PLATES Filed July 2e, 1952 Oct. 30, 1956 LOCK-UP DEVICE FOR FLEXIBLE PRINTING PLATES Emerson E. Fies, Hendersonville, N. C., assignor to Tribune Company, Chicago, Ill., a corporation of Illinois Application July 26, 1952, Serial No. 301,119

Claims. (Cl. IUI-415.1)

This invention relates to a device for locking up flexible printing plates, such, for example, as those used in dry offset printing, on a printing cylinder of the type used in rotary presses, preparatory to commencement of a printing operation.

One of the objects of the invention is to provide a lock-up device of this character by which the plate may be tightened and held tight on the cylinder at all points in the printing area of the plate. Y

Another object is to provide such a device in which this result is accomplished by means of members to which the plate is attachable and which are carried by the cylinder but which are movable relative thereto by simple manipulation of operating elements that are readily accessible to the pressmen.

A further object is the provision, in combination with such -a lock-up device, of convenient and easily-operated means for adjusting the position of the plate on the cylinder to provide for proper registration of successive impressions in color printing.

A more specific object is to provide in a device of this character screw-operated cam elements for actuating the tightening members and holding them positively in the locked-up position during the printing operation.

Another specific object is to provide screw-operated registration adjusting devices by which accurate registration can be obtained by slight turning motion of the screws when the plate is loose on the cylinder.

Other objects and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawings, in which:

Fig. 1 is a top plan view of a printing cylinder equipped with the lock-up device of my invention, with the outline of two semi-circular printing plates shown on the cylinder, one of such plates being partially broken away for convenience in illustration;

Fig. 2 is a transverse sectional view taken substantially 01.1 the Section line 2 2 in Fig. 1;

Fig. 3 is a partial longitudinal sectional view taken substantially on the section line 3 3 in Fig. 1;

Fig. 4 is an enlarged sectional view of a portion of the cylinder showing one of the two cut-outs that are provided therein and two lock-up members pivotally mounted in said cut-out, such members being shown in their position prior to the tightening of the plates on the cylinder; and

Fig. 5 is a similar view showing said lock-up members in the position assumed thereby after they have been operated to tighten the plates upon the cylinder.

In said drawings I have shown, as an illustrative embodiment of the invention, a structure comprising a cylinder 11 mounted on a drive shaft 12 on which there is a hub 13, a gear 14, and a bearer 15, the cylinder having a recesed portion 16 for providing access to operating screws to be hereinafter described, two semicircular printing plates, marked 17 and 18, respectively, being shown on the cylinder with the edges thereof en- 2,768,579 Patented Oct. 30, 1956 gaged with lock-up and registration adjusting devices l0- c'ated in the cylinder, as also hereinafter described.

As above noted, said plates are of the type suitable for use in dry offset printing and, while they are referred to herein as iiexible, which of course they are and must be to some degree, they have considerably more rigidity than do the plates that are used in regular offset or lithographic printing. A suitable thickness for dry offset printing plates has been found to be about .032" and, while some variation from this thickness is possible, it must be substantially greater than that of the plates used lin ordinary offset printing. ln the latter the printing and non-printing 'areas are in the same plane and the plate is flat `before it is a attached to the cylinder. In dry offset printing plates the non-printing areas are etched away and the plate if of such gauge that it must be curved on a bending machine to very nearly the curvature of the cylinder before it is applied.

The difference between the printing and non-printing areas of a dry offset printing plate is only a few thousandths of an inch. Therefore, if the plate does not lie tightly on the cylinder throughout its area some of the non-printing yareas may be inked in :and the ink in such areas transferred to the paper. Accordingly, there is a very special problem in applying and tightening such plates upon the cylinder, requiring a degree of exactness and uniformity that is not involved in applying other types of plates or in 'applying blankets or other surface elements to printing or other cylinders.

Furthermore, since dry offset printing plates must be etched below the surface there is a limit to the size of a plate that a photo er1-graver can handle, the maximum size being about a newspaper page size. Also, such plates have to be attached to or removed from the cylinder very quickly, this being particularly necessary in color printing where a great deal of proving has to be done, often requiring attachment and removal of the plate several times before printing can begin. Therefore the lock-up devices for such plates must be adaptable to unusual space limitations and lend themselves to exceptionally fast attaching and detaching operations.

Continuing with the description of the mechanism shown in the drawings, the gear 14 intermeshes with a mating gear 19 on a co-acting impression cylinder 21, and the bearer 15 engages a mating bearer 22 on said cylinder 21 in the customary manner.

The cylinder 11 is formed with cut- outs 23 and 24, respectively, on opposite sides thereof for receiving parts of the lock-up 'and registration devices (see Figs. 2 and 3). The mechanism on each side of the cylinder is the same and it is duplicated (except for a reverse arrangement) in each of the wells or cut-outs in the cylinder, so a detailed description of but one of the four mechanisms will suffice for an understanding of the construction.

Referring to the mechanism at the left in the cut-out 23 (viewing Figs. 4 and 5, for example), a rocker bar 25 is pivotally secured to a rod 26 which is supported in brackets 27 iixedly attached by screws 28 to the cylinder block at the bottom lof said :cut-out 23. The outer side of said bar 25 has cam elements in the form of risers 2@ thereon, the latter being secured in place by screws 31. The opposite side of the bar 25 has a row of pins or hooks 32 thereon by means of which an end 33 of the flexible printing plate 17 may be secured to said rocker bar 25. Said end 33 of the printing plate is provided with :apertures 35 through which said pins 32, which are inclined inwardly of the cylinder, may extend, the printing plate thus being adapted to be hooked onto said pins preparatory to the locking up of the plate on the cylinder.

A recessed bar 36 is mounted adjacent the outer side of the bar 25 and is provided with a series of rollers 37 arranged to bear upon the risers 29 on said bar 25. Said rollers 37 are rotatably mounted in recesses 38 in the bar 36 by means of pins or shafts 39.

' Said bar 36 carries another series of rollers, identified by the numeral 41, which ride in a groove 42 in a frame and supporting member 43 positioned in the cut-out 23 and secured to the cylinder bleek by means of screws 44.

At the left-hand end of the bar 36 there is an operating member which, in the embodiment shown, is a screw 5 (see Figs. l and 3) having an inner threaded end 46 which has screw-threaded engagement with the said lefthand end of the bar 326. Said screw 45 has a square or hexagonal head 47 on the outer end thereof located in the recess 16 in the cylinder and being thus accessible to the pressmen who may apply a wrench thereto for rotating said operating member to effect endwise movement of the bar 36.

When said bar 36 is moved to the right (viewing Figs. l and 3) the rollers 37, acting on the risers 29 on the member 25, will pivot said member on the rod or shaft 26 and will move said member from the position shown in Fig. 4 to that shown in Fig. 5, thus tightening the flexible plate 17 on the cylinder and locking the same in operative position thereon with all points in the printing area of the plate held tightly to the cylinder. Prior to this lock-up operation the plate 17 is loose on the cylinder as shown in Figs. 2 and 4, and after the lock-up it is taut thereon as shown in Fig. 5, with a part 53 thereof, near the end of the plate and without printing matter thereon, extending across the space between the end of the member 25 and the adjacent part of the support 43, as shown in said Fig. 5. Reverse rotation of the operating member 45 will move the bar 36 in the opposite direction, thus causing the rollers 37 to ride downwardly on the inclined risers 29 and permitting the rocker bar 25 to be returned to the position shown in Fig. 4. This return movement is caused by a torsion spring 50 mounted on the rod or shaft 26 and having one end connected to one of the brackets 27 and the other end to one of several lugs or ears 51 (through which the rod 26 extends) on the bottom of said rocker plate 25.

For purposes of lateral registration adjustment, the rocker bar 25, with the printing plate 17 hooked thereon, may be moved lengthwise of the cylinder slightly in one direction or the other as may be required for aecurate registration of the image on the printing plate with a previous impression or impressions on the web made by a plate or plates on one or more other printing cylinders in color printing. This adjustment is accomplished by means of a screw member 48 having an inner threaded end 49 which has screw-threaded engagement with the left-hand lug 51 (viewing Fig. 3) on the lower side of the rocker bar 25. The outer end of the member 48 has a wrench-receiving head 52 similar to the head 47 on the member 45 and is also located in the recess 16 in the cylinder. It will be evident that rotation of the operating member 48 slightly in one direction or the other will move the rocker member 25 correspondingly to effect desired correction of the registration of the printing plate connected to the latter member. It will be understood of course that the printing plates are loose on the cylinder when such registration adjustment is made, the initial adjustment being made, if necessary, prior to the original lock-up of such plates on the cylinders, and the plates being loosened when later adjustment is required and retightened after proper registration has been effected.

Circumferential adjustment of the plates on the cylinder for purposes of correcting the registration around the cylinder may be accomplished by suitable manipulation of the rocker members 25 to which opposite ends of the plate 17 or the plate 18 are connected. This will be best understood from viewing Fig. 2 in which the plate are loose on the cylinder and can be moved one way or the other circumferentially by suitable differential movement of members 25 at opposite ends of a plate 17 or 18. For example, if it is desired to move the plate 17 in clockwise direction around the segment of the cylinder on which it is positioned, the member 25 to which the right-hand end of said plate 17 is connected (viewing said Fig. 2) may be moved in the lock-up operation a little farther than the member 25 to which the left-hand end of said plate is connected. If the required adljustinent is in the opposite direction the differential movement of said two members would of course be the reverse of that just described.

Thus, either plate 17 or 18 may be moved either circumferentially or laterally in either direction to effect the required adjustment for correct registration.

While, as above noted, one only of the four substantially identical lock-up and registration adjustment mechanisms has been described in detail, it will be understood that the description applies in the same way (except as to variations for rightor left-hand positions) to the other three mechanisms and corresponding reference numerals have accordingly been applied to each of the mechanisms.

While but one illustrative embodiment of the invention has been shown and described, it is to be understood that various modiications may be made without departing from the spirit or scope of the invention as defined in the claims.

I claim:

l. A lock-up device for attaching dry-offset printing plates to the printing cylinder of a rotary printing press comprising, at each end of the plate, a pivoted bar positioned in a recess in the cylinder and extending across o the width of the plate, said bar having an outer pointed edge normally liush with the peripheryI of the cylinder in position to engage in a right angle bend in the plate by which an edge portion of the plate is turned into said recess; a plurality of pins on said bar positioned inwardly from said edge thereof and in closely spaced relationship across the bar, said pins being engageable in apertures in said inturned edge portion of the plate to hold the latter upon said bar, said bar, upon pivoting, exerting a tightening strain on said plate through said right angle bend in a plane tangential to the periphery of the cylinder; actuating means for said bar including pressure-exerting elements arranged to act upon the bar at a plurality of closely spaced points across the Width thereof whereby actuating pressure is applied to the bar, and tightening strain is in turn applied by said bar to the plate, Vwith exact uniformity throughout the width of said bar and said plate; and means for restoring said bar to normal position upon release of the actuating pressure on said bar.

2. A lock-up device for attaching dry-offset printing plates to the printing cylinder of a rotary printing press comprising, at each end of the plate, a pivoted bar positioned in a recess in the cylinder and extending across the width of the plate, said bar having an outer pointed edge normally Hush with the periphery of -the cylinder in position to engage in a right angle bend in the plate by which an edge portion of the plate is turned into said recess; a plurality of inwardly inclined pins on said bar positioned inwardly from said edge thereof and in closely spaced relationship across the bar, said pins being engageable in apertures in said inturned edge portion of the plate to hold the latter upon said bar, said bar, upon pivoting, exerting a tightening strain on said plate through said right angle bend in a plane tangential to the periphery of the cylinder: actuating means for said bar including pressure-exerting elements arranged to act upon the bar at a plurality of closely spaced points across the width thereof whereby actuating pressure is applied to the bar, and tightening strain is in turn applied by said bar to the plate, with exact uniformity throughout the width of said bar and said plate; and means for restoring said bar to normal position upon release of the actuating pressure on said bar.

3. A lock-up device for attaching dry-offset printing plates to the printing cylinder of a rotary printing press comprising, at each endof the plate, a pivoted bar positioned in a recess in the cylinder and extending across the width of the plate, said bar having an outer pointed edge normally flush with the periphery of the cylinder in position to engage in a right angle bend in the plate by which an edge portion of the plate is turned into said recess; a plurality of pins on said bar positioned inwardly from said edge thereof and in closely spaced relationship across the bar, said pins being engageable in apertures in said inturned edge portion of the plate to hold the latter upon said bar, said bar, upon pivoting, exerting a tightening strain on said plate through said right angle bend in a plane tangential to the periphery of the cylinder; actuating means for said bar including a plurality of cams on the side of said bar opposite the side on which said pins are located, a member movable lengthwise of the cylinder, a set of rollers carried by said member corresponding in number to the number of said cams and arranged to act thereon, respectively, to pivot said bar in plate-tightening direction when said member is moved in one direction and means for moving said member lengthwise of the cylinder in said direction to so tighten the plate upon the cylinder and in the opposite direction to loosen the same thereon; and means for restoring said bar to normal position upon release of the actuating pressure on said bar.

4. A lock-up device for attaching dry-offset printing plates to the printing cylinder of a rotary printing press comprising, at each end of the plate, a pivoted bar positioned in a recess in the cylinder and extending across the width of the plate, said bar having an outer pointed edge normally flush with the periphery of the cylinder in position to engage in a right angle bend in the plate by which an edge portion of the plate is turned into said recess; a plurality of pins on said bar positioned inwardly from said edge thereof and in closely spaced relationship across the bar, said pins being engageable in apertures in said inturned edge portion of the plate to hold the latter upon said bar, said bar, upon pivoting, exerting a tightening strain on said plate through said right angle bend in a plane tangential to the periphery of the cylinder; actuating means for said bar including a plurality of cams on the side of said bar opposite the side on which said pins are located, a member movable lengthwise of the cylinder, a set of rollers carried by said member corresponding in number to the number of said cams and arranged to act thereon, respectively, to pivot said bar in plate-tightening direction when said member is moved in one direction, a second set of rollers carried by said member constituting guide rollers, means providing a xed guideway within the cylinder in which said guide rollers are disposed for lengthwise travel, and means for moving said member lengthwise of the cylinder in said direction to so tighten the plate upon the cylinder and in the opposite direction to loosen the same thereon; and means for restoring said bar to normal position upon release of the actuating pressure on said bar.

5. A lock-up device for attaching dry-oiset printing plates to the printing cylinder of a rotary printing press comprising, at each end of the plate, a pivoted bar positioned in a recess in the cylinder and extending across the width of the plate, said bar having an outer pointed edge normally flush with the periphery of the cylinder in position to engage in a right angle bend in the plate by which an edge portion of the plate is turned into said recess; a plurality of pins on said bar positioned inwardly from said edge thereof and in closely spaced relationship Vacross the bar, said pins being engageable in apertures in said inturned edge portion of the plate to hold the latter upon said bar, said bar, upon pivoting, exerting a tightening strain on said plate through said right angle bend in a plane tangential to the periphery of the cylinder; actuating means for said bar including pressure-exerting elements arranged to act upon the bar at a plurality of closely spaced points across the width thereof whereby actuating pressure is applied to the bar, and tightening strain is in turn applied by said bar to the plate, with exact uniformity throughout the Width of said bar and platte; means for restoring said bar to normal position upon release of the actuating pressure on said bar; and means for moving said bar lengthwise of the cylinder to adjust said plate for margin correction, said last mentioned means comprising a threaded adjusting shaft and a tapped hole in said bar interengaged with the threaded portion of said shaft.

References Cited in the le of this patent UNITED STATES PATENTS 416,801 Osborn et al Dec. 10, 1889 680,302 White Aug. 13, 1901 786,031 Henderson Mar. 28, 1905 1,074,775 Cornwall Oct. 7, 1913 1,090,664 Wait Mar. 17, 1914 1,531,124 Murray Mar. 24, 1925 1,827,300 Prichard et al Oct. 13, 1931 2,047,364 Foster July 14, 1936 2,579,517 Rowell et al. Dec. 25, 1951

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