US3022728A

US3022728A - Printing plates and methods and apparatus for forming them

Info

Publication number: US3022728A
Application number: US852260A
Authority: US
Inventors: Heller Franz
Original assignee: American Type Founders Co Inc
Current assignee: American Type Founders Co Inc
Priority date: 1959-11-12
Filing date: 1959-11-12
Publication date: 1962-02-27
Anticipated expiration: 1979-02-27
Also published as: GB910627A

Description

Feb. 27, 1962 F. HELLER 3,0

PRINTING PLATES AND METHODS AND APPARATUS FOR FORMING THEM Filed Nov. 12, 1959 4 SheetsSheet 1 20 PRIOR ART E PRIOR ART ATTORNEYS Feb. 27, 1962 F. HELLER 3,022,728

PRINTING PLATES AND METHODS AND APPARATUS FOR FORMING THEM Filed Nov. 12, 1959 4 Sheets-Sheet 2 ATTORNEYS Feb. 27, 1962 F. HELLER 7 3,022,728

PRINTING PLATES AND METHODS AND APPARATUS FOR FORMING THEM Filed Nov. 12, 1959 4 Sheets-Sheet 5 ATTORNEYS INV EN TOR Feb. 27, 1962 F. HELLER 3,022,728

PRINTING PLATES AND METHODS AND APPARATUS FOR FORMING THEM Filed Nov. 12, 1959 4 Sheets-Sheet 4 ATTORNEY5 ilnited rates Rateat 3,022,728 PRIN'IWG PLATEE AND METHGDS AND APPARA'IUE FUR FQRMING THEM Franz Heller, Mount Vernon, N.Y., assignor to American Type Founders Ce. Inc, Elizabeth, N..I., a corporation of Delaware Filed Nov. 12, 1959, er. No. 852,260 3 Claims. (Cl. Mil-415.1)

This invention relates to certain preparatory steps concerned with the make-ready of a lithographic printing press, for example one of the Web fed offset type, and has as its principal object the provision of a novel plate construction and of novel and improved methods and apparatus for properly forming and applying the printing plates to the plate cylinders of the press.

Workers in the printing industry are aware that the metal printing plates used in high-speed web offset presses must be very accurately applied to the cylinders for quality production, the height or projection of the surface of the plates above the cylinder bearers being measured in thousandths of an inch. To this necessity of accurate packing and securing of the plates must be added the care in insuring that the plates are formed in the bending jig to the exact length appropriate to the circumference of the cylinders. Otherwise the plate is not securely held and continual flexing of the plate during operation of the press will cause the plate to crack, especially during long runs. This is particularly true in the case of aluminum plates.

Research by the applicant has also revealed another contributing factor in this proneness of the plate to crack. This further source of difficulty arises especially where a single reel-rod is employed in the cylinder gap such a reel-rod functioning not only to pull the tail edge of the plate taut but to clamp or wedge the bent portion of the leading edge against an inwardly angled wall of the cylinder gap.

Now the conventional bending of the leading edge of the plate to an acute angled configuration prepares it to fit over the similarly angled portion of the cylinder ad jacent the gap, but no such strong pull is effected at the leading edge as is applied to the tail edge of the plate by the rotation of the reel-rod. As a consequence, it is difficult to insure that the curvature of the plate near its bent or hooked leading edge will conform to the exact radius of the cylinder. Thus there occurs a slight hump in the plate at this point with a minute air space formed between the humped portion of the plate and the cylinder body. Furthermore, the material of which the plate is made is under some stress adjacent the hump or bend, the outer surface of the plate probably being under tension and the inner surface under compression stresses of varying degrees. During the printing operation, as the form rollers and the blanket cylinder pass over this bump, the plate will be alternately depressed and released, and this repeated flexing of the plate will add further stress to the already stressed plate and cause it to crack, with the resulting added costs and inconvenience.

It has been suggested that this difliculty might be overcome by providing reel-rods for both ends of the plate in order to draw the plate more snugly against the cylinder at the forward end in the same manner that the reel rod accomplishes this purpose at the tail end, but these accessories occupy considerable space and increase printing costs, and would necessitate a much wider and uneconomical non-printing cylinder gap.

It is therefore an object of the present invention to provide novel methods and means for eliminating the formation of such a stressed hump in the plate near its leading edge, while at the same time preserving the accuracy of gauging the length of the plate in accordance aaza'zzt Patented Feb. 27, 1952 with the circumference of the curved portion of the plate cylinder.

The invention contemplates the provision of a deliberately pre-formed bend or curvature just inwardly of the bent or hooked leading edge of the plate, this curva plate bending jig by means of which this pre-forming adjacent the leading edge may be accomplished.

Other objects and features of novelty will be apparent from the following specification in which one embodiment of the invention is illustrated by way of example.

In the drawings:

FIGURE 1 is a somewhat diagrammatic View in side elevation of a printing plate in fiat form after it has come out of a bending jig of conventional construction;

FIGURE 1A is a fragmentary diagrammatic view in end elevation of a plate cylinder showing. in somewhat exaggerated style the initial application of the forward acutely bent portion of the plate as it is applied to the cylinder gap;

FIGURE 2 is a similiar view in somewhat exaggerated style the destructive hump formed in the plate bent in the usual way adjacent the cylinder gap;

FIGURE 3 is a view similar to FIGURE 1 showing the pre-formed bend or curvature provided in the plate adjacent its leading edge according to the provisions of the present invention;

FIGURE 4 is a view similar to FIGURE 2 showing the snug application of the plate of such novel configuration to the plate cylinder;

FIGURE 5 is a somewhat diagrammatic view in side elevation of a jig embodying the principles of the invention;

FIGURE 6 is a view in end elevation of the jig as viewed from the left in FIGURE 5;

FIGURE 7 is a fragmentary enlarged view in side elevation of the left-hand end of the jig with certain parts shown in section, as along line 7-7 of FIGURE 6;

FIGURE 8 is a further sectionalized view of the same portion of the jig, for example, as taken on line 88 of FIGURE 6;

FIGURE 9 is a fragmentary sectional view taken on line 9-9 of FIGURE 6;

FIGURE 10 is a detail sectional view taken on line 1ll-l0 of FIGURE 6;

FIGURE 11 is a fragmentary View in side elevation of the right-hand end of the jig as viewed in FIGURE 5;

FIGURE 12 is a plan view of the jig showing certain gauging means for insuring the proper positioning of a plate for bending; said means for the most part having been omitted from the precedin figures for the sake of simplicity and clearness of illustration;

FIGURE 13 is a fragmentary plan view of a portion of the jig including certain optical gauging means;

FIGURE 13A is a fragmentary plan view in perspective of a portion of the upper surface of a plate showing the gauge marks used in positioning'it; and

FIGURE 14 is a fragmentary view in vertical section taken on line 14-14 of FIGURE 12.

In the views illustrative of the prior art set forth in FIGURES 1, 1A, and 2 of the drawings, the conventional printing plate which may be of zinc, copper, aluminum, or other substances familiar in the art, is designated generally by the reference numeral 10 and comprises a flat area 11 constituting the major portion of the plate and carrying the printing areas thereof. At the left-hand end of the plate the leading edge is folded downwardly s eaves In FIGURES 1A and 2 the plate cylinder is given the general designation 2t? and is provided with a gap 21 having a narrowed portion 22 between projecting noselike edges of the body of the cylinder indicated at 23 and,

24. Within the wider inward portion 25 of the gap a reel-rod 26' (FIGURE 2) is positioned for manual adjustment. The conventional plate It) is applied to the periphery of the plate cylinder 26 with the bent'portion 12 of the leading edge hooked around the nose 23 of the cylinder body (see FEGURE 1A), as well as the acute angling of this portion of the plate permits. The extreme bent section 14 of the tail edge is gripped within the cleft 28 of the reel-rod and the circumference of the reel-rod 26 exerts a pull on the tail of' the plate It which due to the obtuse angular disposition of the tail flange 13 not only exerts the tension on the plate in a generally lengthwise direction but also draws it inwardly and quite snugly against the adjacent nose portion 24 f the gap 21.

Now in the case of the prior art plate illustrated diagrammatically in FIGURE I, the head end portion of thev plate adjacent the frontor head flangev 12 tends to retain its acute angularity and the exposed portion of the plate to remain in a somewhat straight line, suggested at a, tangent to the circumference of, the cylinder. This results from the lack of' a direct inward pull as applied to the tail flange by a reel rod. Then when the leading flange 12 is wedged against the inner wall surface 29 of the cylinder gap, along with the tail flange 13, the wedging and frictional efifect applied by the reel rod exerts a pull along this wall 29, and not by way of the obtuse angle by which the tail flanges are drawn by the reel rod. This results in the formation of a curved or humped portion in the plate adjacent the apex of the bend of the flange 12 as shown in FIGURE 2 of the drawings in somewhat exaggerated form, an air space 31 being left beneath this portion of the plate. Also, the plate adjacent this raised, humped, or curved area is under stress, and it is understandable that the humped area will have additional stresses applied to it in rapid alternation during the continual high speed rotation of the plate cylinder in contact with the blanket cylinder and the associated inking system, and this, especially in-long runs, will cause the plate to crack adjacent the hump and the leading flange- The application of a plate such as indicated at 10 and formed in a conventional jig in accordance with present practices invariably results in the formation of a hump portion indicated at 30 in FIGURE 2 of the drawings, an air space 31 being left beneath this portion of the plate as shown. It will be very obvious that the continual high speed rotation of the plate cylinder in contact with the blanket cylinder and the inking system will result in such a flexing which, especially in long runs, will cause the plate to crack adjacent the hump portion.

So much for the existing situation with respect to conventional devices of this nature. Now, referring particu larly to FEGURES 3 and 4 of the drawings,- it will be seen that the novel plate conformation provided'by the present invention and indicated generally by the reference numeral t? comprises a similar level portion 51 before it is applied to the cylinder, but toward the leading edge of the plate this major portion of the plate is given a definite downward curvature as shown at 55 The downwardly curved portion 55 terminates in the usual hook portion 52 at the leading edge of the plate. The plate at its tail end terminates in the double bend 53 and 54 as in the earlier described structure FIGURE 4 merely shows the novel plate structnre 50 applied to the plate cylinder 20 the major intelligence bearing portion 51 being wrapped around the cylinder in the usual way with the leading edge flange. or hook pot.-

tion 52 clamped in the gap 21 by means of the reel-rod 26 which grips the tail' areas 53 and 5d and holds both ends of the plate firmly gripped within the gap. It will be noted that at the additional inwardly bent area 55 the plate hugs the cylinder surface snugly and the hump such as shown atBtl in FIGURE 2 is completely eliminated.

Bearing in mind that the aim of the provision of the curvature or bend 55is to cause the plate at this point to hug the underlying surface of the cylinder more closely in spite of the sharpness of the angularity of the flange 52, it will be readily understood that the degree of prebending at 55 will vary somewhat depending upon the size of the cylinder, the thickness of the plate, and the material of which it is formed, as Well as the temper or hardness of the plate material. Furthermore, the curvature of the bend, that is the radius indicated air in FIG- URE 3, is not critical and becomes even less so as the diameters of the cylinders increase. However, it might be mentioned that the radius r will in most cases beless than the radius of the cylinder itself since in the case of a plate of more than usual resilience, a slight overbending may be necessary to compensate for any sprin back which might occur. Thus, it may be stated broadly. that the radius r maybe anywhere from that of the cylinder down to a value considerably less than the radius Of the, cylinder.

Theprocess thus, described may be carriedout by. means of the novel plate bending jig which is given the general designation 64 as ilustrated in the remaining fig ures of drawing. In the somewhat diagrammatic view comprising FIGURE 5, it will be seen that the body of the jig 66 comprises two base blocks 61 and 62, these plate to conform to the circumference of the particular plate cyiinder, a space 64 being left between the

blocks

61 and 62 for this purpose.

The left-hand base block 61 is formed at its extremity with a projecting ledge or nose portion 65 which is most clearlyshown in FIGURES 7 and 8 of the drawings. The angularity of this projecting ledge may of course vary somewhat and a suggested angle useful for most purposes is approximately 35. The extreme apex or point 66 of the ledge 65 is slightly rounded, preferably on a radius of approximately 0.05 of an inch, taken on the center of the pintle 76.

However, the most radical feature of the bending ledge 65 is the provision of the curvature near the extreme edge thereof in the area designated 79. This curvature is provided in order to form the preliminary bend 55 in the plate 59 adjacent the leading edge.

Extending from each side of the left-hand edge of the base block 61 are a pair of brackets 72, theserather fiat brackets being secured to the respective sides of the base 60 as by means of the screws 73. These brackets 72 have projecting ears provided with registered threaded openings 75. Pintles 76 are threaded into the openings 75, each of these pintles having an inwardly projecting attenuated unthreaded portion 77 terminating in a rounded tip 78. Fixed to the outer ends of the spindles 76 are the hand wheels or knobs 79.

A bending bar 80 extends transversely across the jig just off of the nose or ledge portion 65 and is provided at each of its ends with a hinge bracket plate 81, these plates being provided with openings 82 to receive the cylindrical portion 77 of the pintle or spindle members 76. Thus, the bending bar 80 is mounted with one of the lower corners thereof substantially coinciding with the apex or ultimate edge 66 of the bending ledge 65. Extending outwardly from the bar'80 is the bracing and supporting fr mework 85 surmounted by the handle por- Each of the brackets 72 tending vertically downwardly therethrough and adapted to fixedly secure the lower ends of the pins or posts indicated at 88. These openings occur just beneath the curved portion 70 of the bending ledge 65, and immediately above this curved portion is positioned the preliminary bending and clamping bar 90 which has a bottom surface 91 conforming to the curvature of the portion 70 of the block 61 and of the desired preliminary bend to be impressed upon the plate 50 adjacent its leading edge. The clamp bar 90 is provided at its left-hand end as viewed in FIGURE 6 with a notch or kerf 92 extending in the longitudinal direction, and at its righthand end with a transversely extending notch or kerf 94. The end notch 92 virtually comprises a fork which is made to straddle the intermediate portion of the threaded post 88 at that end of the device, the lower end of the cylindrical wheeled head 95 threaded upon the spindle bearing downwardly upon the upper surface of that end of the clamping bar 90 adjacent the kerf 92. The right-hand end of the clamp bar 90 may be swung into position beneath the wheeled head 96 applied to the post 88 at that end of the clamp bar so that the notch or kerf 94 embraces the stem of the spindle as most clearly shown in FIGURE 9 of the drawings. The head 96 threaded onto the post 88 at this end of the device bears downwardly upon the upper surface of the clamp ing bar 90 as in the case of the left-hand end.

The clamping bar 90 is provided with a bowed truss element 98 to insure its rigidity.

In order to facilitate the installation of the bending bar 80 upon the spindles 76, a pair of rests or supporting brackets 100 are secured to the bending bar 80 and have portions 101 which overlie the clamp bar' 90 and are allowed to rest upon the clamp bar in order to support the weight of the bending bar during the time that the spindles 76 are threaded through the openings 75 in the hanger brackets 72.

At the tail end of the jig, as indicated in FIGURES 5 and 11, there is provided a clamp bar 110 which in most respects is the counterpart of the clamp bar 90 at the leading end, except that the bottom surface 111 is perfectly flat and not provided with a curve such as characterizes the leading edge of the arrangement. Stiffening and bracing superstructure 112 is provided for the clamping bar and the bar 110 is brought to bear downwardly upon the plate as by means of the hand wheels or knobs 95' and 96.

In order to throw the double bend into the tail end of the plate as represented by the parts 53 and 54 a bending bar 125 is provided, this bending bar being provided at each end with the hinge plate 126 which is adapted to be connected by a pintle 127 with the corresponding hinge plate 128 secured to the tail end of the base block 62 of the jig. Obviously, the pintle 127 is centered upon the edge or corner 129 of the block 62. The end of the block 62 is provided with a sloping surface 130 which merges at 131 with the downwardly and inwardly inclined surface 132. The bending bar 125 has a fiat lower surface 136 and a supplemental bar 140 is secured to the side of the bending bar 125, this supplemental bar being provided with an inclined surface 142.

The bending bar 125 is provided with a stiffening superstructure 145 surmounted by an operating handle 146 as in the case of the bending bar 80 at the other end of the ig.

Referring now more particularly to FIGURES 12 to 14 of the drawings, certain gauge devices for properly positioning the plate on the jig will be described. Midway along each side of the body of the jig 60, bridging the gap 64 between the

blocks

61 and 62, are the fixed plates or inserts 150. These small plates have inscribed thereon, with a great degree of accuracy, the rectilinear gauge markings 151. These gauge marks project slightly beyond the end margins of the printing plate P indicated is provided with openings exby the lines 152. Similar register marks 151' are inscribed on the printing plate and these are brought into exact alignment with the gauge marks 151 on the insert Other and somewhat more accurate gauging and aligning means are provided by the optical devices commonly called scopes and indicated at 155, 156, 157 and 158 in FIGURE 12 of the drawings. Two of these scopes, dessignated 155 and 156, are carried by

brackets

160 and 161, which are disposed at an angle with respect to the margin of the plate P to be bent, and the

scopes

157 and 158 are carried in the rectilinearly disposed brackets 162 and 163. The scope 158 and its bracket 163 are shown to advantage upon an enlarged scale in FIGURES 13 and 14 of the drawings.

Directly beneath the position which the scope158 will occupy, the base block 61 is drilled to provide a recess or pocket 165 and fixed Within the recess is a cylindrical block 166 preferably made of brass and inscribed upon its upper surface with cross lines as at 167. There are four of these blocks 166, one beneath each of the scopes adjacent to the four corners of the plate, and the linear and transverse measurements between the crosshairs of adjacent scopes are very accurately predetermined.

The bracket 163 as shown in FIGURES 13 and 14, has its'shank end drilled at three places to receive the bolt 168 and the dowel pins 169. Bolt 168 is threaded into the base block 61 as at 1761 and the dowel pins 169 are fitted closely in hardened steel bushings 172 which are pressed into the recess 173 in the block.

The forward end of the bracket 163 is bifurcated as at 175 and adapted to receive the optical scope 158 which is of cylindrical configuration and may be provided with any suitable system of lenses, suggested at 176, and with crosshairs 177 which are brought into exact register with the cross marks 167 on the brassblock 166 for a preliminary setting. The bifurcated end 175 of the bracket 163 may be brought into close gripping contact with the scope 158 by means of the bolt 179. It will be noted that the forward end of the bracket 163 is indicated to provide a slot 181) for the reception of the edge of the plate P. The plate P, as shown in FIGURE 13, is provided with cross gauge marks 187 which will be brought into alignment with the crosshairs 177 of the scope 158 when the plate is in properly located position.

The scope and bracket installation 1157, 162 will be identical with the one just described in connection with FIGURES 13 and 14 of the drawings, except in reversed position. The scopes 155 and 156 (160 and 161) are similarly formed, equipped, and fastened, except that they are disposed 'at a 45 angle with the edges 152 of plate P, and the undercut or notched portion 181} is V-shaped at its inner extremity as clearly shown in the upper portions of FIGURE 12. I

The operation of the device in forming the novel plate configurations will be readily understood from the following description: The clamping bars and as well as the bending bars 80 and are removed from the jig and the plate P is placed on the jig and lined up, according to one method, by bringing the inscribed lines or register marks 151 on the plate P into alignment with the inscribed gauge marks 151 on the insert at either side of the jig. The register marks 151' are placed on the plate by the plate maker in accurate relation to the image on the plate. This will locate the plate quite accurately in the jig. Then the clamp bars are replaced into position, the plate securely clamped adjacent its ends, the bending bars installed, and then swung downwardly to throw the bends into the respective ends of the plate.

In using the scopes, the operator will locate the plate approximately on the bending jig, then place the clamp bars in position and snug down the plate on the jig.

He will then takeflthet four; optiealscopes as they,.are mer nte d, on their supporting brackets and pliCfi. the" seniblyintoposition over theiplaite? new i j nm ye; the plate until the four -register 'rn'arks' inscribed 'on' the; plate coincide with the crosshairs in the fou r scopes; Finally he willfclarnp the; plate tightly andfrnalie the l nd v .i J t At any time during the life oi the bending jig the operatoii'can check the accuracy ofithe seopes against the cros shair s which areperrnanently loeated'on .th'e'jigsf on the plngslfi, l

In thebending operation, the movement of the leading edge bending bar se is'elearly shoxvnin FIGURES of the drawings, the initial position'beingindicated in solidi lines and the dotted line position showing the .trltiniafe' end of the swinging movement where the' heel; portion of the plate has been swung downwardly and inwardly against the underside of the" ledge 65. At the tail: end of the device the downwardly swinging r'novernentof the bending

bar

125, 140 from the solid line position tofthe dotted line position effects the double bend in that endof the plate. i i

Upward swinging return movement of the bending bars and the releasing of theyclampingbars frees'the' plate for removal and application to the plate cylinder of the press. v

It is understood, that Various changes and modifications rnay beir nade in the illusti ative embodiment of the invention set forth herein without departing" front the" seopeof the invention as definedx by'thel following clainisi Having thus described the invention, vvhat is claimed as new and desired to be secured by Letters Patent. isz' l. A printing plate for application to the printing cylinder of a lithographic oflset printing press, said plate: being (if-conventional substantiallyuniform thickness and having a tail edge portion bent away from the irnprsf sion face of the plate to form the inwardly. directed flanged edge portions for seizure by gripping means in; the cylinder gap, a hook flange formed on the leading" edge. of the plate for anchoring engagement with the similarly angled edge of the cylinder gap, and an arcuate portion immediately adjacent the hook flange at the eading edge, said arcuate portion impressed upon the plate to curve it uniformly and without variation, in the,

H .t i. l

' to the plate'fcylin'der of an eff set printing press ture being oonvex upon the iiiipres'sion s'ide of the plate and of a "radius somewhat less thanjth'at of plate elditqe i at wax m ineir pr g office f aiep a mg; edge, isle id "a'rcuate portion impressed upon' the plate sof'the'plat'e in adireetion' aviay from the ir'npfre s'sion faqe' offthepl'at e, and upon a radius sometha'ii that of tlie plate cylinderto Which the less plate is' to" he'fapplied 3i The"met h6tl of preparing a lithographic plate of conventionalsubstantially uniform thickness for appliea jcomprises the steps'gof' bending flange: at the tail edge of the plate as'forengagenient by' gripping means ga ofth'e plate cylinderfbending a hook flange a't'the leading'e'dge of tliejla'te for; engagement with a ponding'angled edgefof the plat yli1ider' gap,

and inipress ng uponfthe plate a'curva'tltire' throughout a "s'rnall 'a'r'cua te egit'e'ntirninediatelfadjaeent s aid hook the #9 aee iaei i a e a e -Re ferenc es Cited in the file of this patent UNIIED. TA S EA NT 1 55 05 Me se et a M r 1 32 2,192,924 Maher'et al. Mar. 12, 1940 2,285,1l v; Grgupe June 4 23115 852, Durh arn Dee. 22 19.42 ,609 142 ett wj i se a 63i l is Amen De i 1 5 2,619,279, 'Sehgva rtz et al, May 25, i954. 9,Q Q i i g V p printing i press; said plate a u 'ddnventional substantiallf'nniform thickness aiid havin'gata il edge portion heiit'away'fronl the irri-f' the inwardly directedv r t. 3 3N53 l' i aa n he an e an: r -6 n r d on} h a n edge off't h'e platefiof'anchorihg engagement with the si'rnil'arl'y angled edgeoi the Cylinder gap; andan arcuate funifornily' and without variation, in the gen