USRE24161E

USRE24161E - Doctor blade and mounting for rotogravure printing machines

Info

Publication number: USRE24161E
Authority: US
Publication date: 1956-06-05

Description

June 5, 1956 E, A. ROGGE EI'AL Re. 24,161

DOCTOR BLADE'AND MOUNTING FOR ROTOGRAVURE PRINTING MACHINES Original Filed Aug. 24, 1953 I INVENTORS [Mu/4M 4.POEHM EDMUND 4. P0665 "4., Z 3/ nrroeuer madeIyrel-ne.

\ United States Patent Oflice Re. 24,161 Reissues! June 5, 1956 24,1: nocron sums AND MouN'riNc non ao'ro- GRAVURE rnnsrnsc mcnmrs EdmnndA.R IacksonHetghmandWllllamA.

mdfi'hmcm Own! No. 2,704,026, dated March 15, 1955, Serial No. 3 6,0, Augud 24 1953. A llcatlon for. rel-us February :1, 1956, a. No. 5 ,144

, 5 Claims. (Cl. 101-157) Mattsrenclosedlnheavybracketsljlapearslnthe patent but forms no of thls reLue cltlmatter printed it lndlcates the ad tlons This invention relates to rotogravure or intaglio printing and is directed more particularly to a novel doctor blade and mounting therefor.

Rotogravure web printing, ever since its inception, has had diillculty with streaking" and similar defects in the impression on the web. Streaking, in particular, has constituted a major problem in this industry that has never been satisfactorily overcome. It is generally manifested by false printing impressions in the form of lines entirely foreign to the intaglio recesses of the printing cylinder.

This phenomenon of streaking has been attributed to a wide variety of causes, the most common of which is the presence of extraneous matter which may be in the ink when received from the supplier or which accumulates in the ink during a printing run. For example, lint from the raw web stock printed upon, hardened ink particles, as well as metal particles which may be freed from the doctor blade or from the copper or chromium plating of I with the result that in some cases they act as minute cut- As a result of protracted research, experimentation and tests, we have found that many of the causes of streaking may be entirely eliminated through a radical departure from prior practice in the removal of excea ink from the cylinder by the doctor blade. We have been able to accomplish this result by entirely changing the relation between the doctor blade and the cylinder. Whereas the doctor blade has heretofore invariably been inclined in the direction of rotation of the cylinder, the present invention, reverses this relation and so mounts the doctor blade that its cylinder contacting edge faces in a direction contrary to the direction of rotation of the cylinder. Thus while prior practice was such that the doctor blade had a wiping action on the cylinder surface, the doctor blade of the present invention has a r shearing action with respect. to the ink on said surface. In other words, the angle of approach of the doctor blade the cylinder, are carried along with the ink to the doctor blade and, as the surplus ink is wiped from the cylinder, these particles cause scratches in the cylinder, nick me blade or produce uneven wiping of the'cylinder surface. Various expedients have been resorted to in an attempt to free the ink from these impurities and foreign matter prior to its passage to the doctor blade. Screens, magnetic devices, and other expedients have been employed in this connection and while streaking has been lessened, it has not been eliminated by any means and continues to be the source of much annoyance and expense in the in- During many years of experience with gravure print- I ing, we have studied the phenomenon of streaking and cylinder wear and we have concluded that one of the factors which causes the same is inherent in the present practice of removing the surplus ink from the cylinder through the wiping action of the doctor blade upon the cylinder. As invariably constructed, rotogravure machines are so constituted that the doctor blade bears against the surface of the cylinder in an inclined direction, wherein the cylinder contacting edge of the blade faces in the direction of rotation of the cylinder. The bodyofthebladebackofitswipingedgeisthus arranged at an acute angle to the surface of the cylinder and forms therewifltataperingrecesswhichtheinkuponthecylinder enters in advance of the wiping edge.

As a result of'this arrangement, the ink is literally squeezed, in an uncontrolled manner, from the surface of the cylinder, out of the angular recess below the wiping edge and laterally beyond the ends of the doctor blade. Experience has convinced us that extraneous matter in the ink, particularly hard-particles, such as metalllcparticleacannotbeeflectuallysqueenedinaretrogradeirection. Onthecontrary',theybecomewedged in the dtarp anglebetween theblade and the cylinder,

to the surface of the cylinder is contra to the direction of rotation of the cylinder.

As a result, the ink is actually cut or sheared from the surface of the cylinder in such manner that there is no entrapment of extraneous matter which may be contained in the ink and no pressing of such extraneous matter against the surface of the cylinder as heretofore. In contradistinction, the surplus ink and all impurities thereinare freed from the surface of the cylinder by a shearing edge which enters beneath these particles and the surplus ink and actually lifts them free from the surface of the placing said ink under compression as heretofore. Consequently ink slinging" (the squirting of the ink laterally beyond the ends of the blade), so common to prior practice is entirely eliminated through the use of our blade.

Experience with this invention has shown that the best results are obtained when the blade is made relatively thin and of resilient material, such as spring steel and when the blade is placed under transverse stress. A thin resilient blade thus stressed will automatically adapt its shearing edge to the surface of the cylinder and, as it is reciprocated axially of the cylinder, as is common, the contact which it makes with the cylinder will be uniform throughout and the shearing action to which we have referred will result. Furthermore, through the use of a relatively light, thin and resilient doctor blade, we have found that the pressure of its shearing edge may be much less than is required under prior practice. Consequently both the blade and the cylinder are subjected to less wear and consequently will last longer than former gravure printing assemblies. Moreover, when a stiff blade is used, as heretofore, it must be pressed very tightly against the cylinder and there is the ever present tendcy thereof to crush the side walls of the intaglio recesses. That cannot occur with the thin blade of this invention, functioning in the manner slated.

cylinderandzaeooperating impression roll. longltudinallyofthe cylinderandis atitaoppositeendsinclamps4formingpart oftheapparatuswhichsupportsthedoctorbladeand longitudimllyreciproatesthelatterduringtheoperation ofthemachine'. The

To insure proper relation between the blade and the cylinder, each of the brackets 8 is provided with a stop pin 18 (Fig. 3) adapted to cooperate with a limiting pin 19 carried by an adjustable collar 20 on the shaft 3. This collar may be circumferentially adjusted by rotating it on the shaft and locking, it in adjusting position by a set screw 21. By this means, the position of the blade holder will be accurately regulated to yield the best performance.\ :i.

It is to be noted that, when the blade is set up as shown in the, drawings, its free end 100 will face in a direction contra to the direction of rotation of the cylinder. In any event, it will exert a shearing action upon 1 the ink carried by the cylinder during the operative rotation of the latter and experience has shown that it will longitudinally adapt itself to the cylinder surface and produce. substantially uniform pressure throughout its length. lnsteadofwipingtheinkfromthesurfaceas cppositeendsoftheshaftliary flttedintocircularholesinthe clampslandtheseclamps asesplitaaahownatl. Screwsservetotightenthe'" clampsaothattheywill griptheshaft3andlockitagainst rotation. Whenthescrewsareloosenedtheahaftmay s v m ofths hereinaftermorefullydeacribed. The lisintheformofanelongatedbarextotheaxisofthecylinderandprovided wgbracketsiflxedtothebar EEEEES' i i'zgg saidtigure.

iii #5 portion of the width of a doctor blade 10. This blade is by a clamping strip 11, by spaced apart bolts 12 passing alined perforations in the strip, bladeand holder 13 for convenience of manipulation.

from relatively thin resilient maso as to have both longitusizeofthemachineinwhichitis optimumthicknessformedium is betweenfiandlothousandths Ablade fthisthickness will'possess the strengthandatthesametimethedesiredresilisnip may be extended to function as a this is not essential to the proper operation of our invention. Thebladeisforced againstthe surface of'the cylinder one of which is associated with is coiled about the shaft 3 extending into a hole in an the shaft 3, while the other end the spring extends into a hole 1 in the correspond- I. These springs so bias the holder as to impel the free edge of the doctor blade against the surface of the cylinder 1. The force thus exerted by the yberegulatedbyturningthecollarslson 3, while set screws 17 are loose, and then said set screws when the desired pressure of blade against the cylinder has'been obtained.

any event that pressure should be suflicient to hold firmly against the cylinder and the curvature is preferably such that it will approach tansurface of thecylinder but not be exactly Pig. 2 diows a very satisfactory relationship installation.

holder 7 is-of arcuate referred to. Its thickness may vary Abackingblademaybeassociated therewith or,

r tudinal reciprocatory movement of the blade.

has heretofore been the practice, the blade of this invention will actually shear .it from \the surface and this shearing action will be facilitated by the normal longi- Consequently there will be no entrapment of extraneous matter which may be carried by the cylinder into engagement with the blade. There is no acute angle nor reentrant recess in which hard or soft particles or dirt can lodge. The ink and its impurities will be sheared cleanly from the surface of the cylinder leaving in such surface only such ink as is contained in the intaglio recesses of the etched cylinder. As the surplus ink is sheared or shaved from the drum, it will flow back along the surface of the drum or follow the under surface of the-blade to tlaiien blade holder and from there gravitate into the foun- 86 Contact between the blade and die cylinder will main- .tain the free edge of the blade sharp because of the blade honing action between these parts and said edge of the blade will conform to the surface of the cylinder so that a highly satisfactory knife edge for shearing purposes 60' will result.

The springs 14, which hold the blade in cooperative relation with the cylinder, have several advantages. For example, should it be desired at any time to stone the edge of the blade, these springs will permit the blade 45 holder, with the blade attached, to be moved away from the cylinder in a clockwise direction, as the parts appear in-Pig. 2, so that the blade can be stoned without removing it from its holder or without destroying the adjustment of theparts. Furthermore, should the blade engage 50 with extraneous matter on the cylinder which the blade isnot able to properly shear therefrom, the springs 14 will permit retraction of the blade under the force applied thereto by such matter without damage to the blade. Also, when a press is stopped for any reason and the 55 stoppage is of suflcient duration to permit drying of the ink on the cylinder in advance of the blade, this ink becomes hard and extremely diflicult to remove. If the press is subsequently started,the force required to remove the dried ink would tend to buckle the blade and damage 00 the cylinder. Should such a condition exist, the springs permit retraction of the blade as stated without harm to either the blade or to the cylinder.

As shown in the drawing, the line of contact between the edge of the blade and the cylinder is spaced from- 7 hard obstruction on the surface of the cylinder which the blade is unable to readily shear of, will cause the blade to travel with the obstruction and be automatically retracted or backed away from the cylinder against the tension of the springs which normally maintain it in 16 engagementwithsaidmrfaceand'sopermittheobstrucsane! 5 tiontopasswithoutdamagetoeitherthebladeorthe of the cylinder.

Anotheradvantageofusingaresilientbladeisthas increaaeordecreaseinspeedofthecylinderdoesnot require corresponding manual adjustment .of the spring tension. 'Ifthespeedoi the cylinderisincreased,the surplus ink must be more rapidly removed and consequently the blade should apply correspondingly more pressure to the cylinder surface. The springs 14 are placed under somewhat more tension than is required for ordinary speeds while the limiting pin 19 maintains proper cooperation between the blade and the cylinder, so that the blade will not unduly press against the cylinder surface. There is litus sulflcient energy stored in the springs to hold the blade firmly against the cylinder even when the press is speeded up, with the result that this speedmp lnay cause a slight flexure or bowing of the blade beyond its normal curvature, so that the blade will press more firmly against the cylinder and be able to efleotually remove the increased amount of ink fed thereto. 'If the press is later slowed down, the blade will assume its normal curvature for the particular speed of press operation. The blade thus autogeneously adlusts itself to the cylinder speed and will give satisfactory 7 results under a wide range of speeds of press operation.

flnedshearingoperatiom-theinkisatnotimeplacedunpressure beneath the blade and consequently slinganaItisparallel-totheaxisofthecylinder,athinresilient' blade carried by said blade holder and bearing against the surface of the cylinder with the cylinder engaging edge of the blade facing in a direction oppositely to the direction of rotation of the cylinder and [contacting with the cylinder above] in the directtbn of the plane which includes the axes of both the cylinder and the blade holder, and means for retractably maintaining said edge of the blade in contact with the cylinder.

2. An assembly accordingtoclaim 1, wherein the means for retractably maintaining the edge of the resilient blade in contact with the cylinder comprises a spring.

3. An assembly according to claim 1, wherein the resilient blade is of bowed shape with its concave side facing the axis of the blade holder.

4. An assembly of the character described comprising: an intaglio printing cylinder mounted to rotate on [its] a horizontal axis, a blade holder mounted for bodily movement toward and away from the cylinder in a direction substantially normal to-the surface of the cylinder, a thin resilient blade carried by the blade holder and movable therewith t'n'a direction transversely of the width of the blade and bearing against the surface of the cylinder with the cylinder engaging edge of the blade above the axis of the cylinder and facing in a downward direction oppositely to the direction of rotation of the cylinder, and means for yieldably and retractably maintaining the blade holder with the edge of the blade in contact with the cylinder.

5. An assembly of the character described comprising: an intaglio printing cylinder mounted to rotate on its axis, a blade holder, a thin resilient blade carried by the blade holder and bearing against the surface of the cylinder with the cylinder engaging edge of the blade facing in a direction oppositely to the direction of rotation of the cylinder, means for mounting the blade holder for bodily movement toward and away from the cylinder in a direction transversely of the width of the blade, and means for yieldably and retractably forcing said blade holder in the direction of the cylinder to maintain the blade holder '40 in engagement with the cylinder with the blade under transverse stress.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS 1,252,431 Gubelman Ian. 8, 1918 1,631,169 Weiss June 7, 1927 1,837,672 Pirie Dec. 22, 1931 2,106,029 Horton Jan. 18, 1938 FOREIGN PATENTS 282,885 Germany Dec. 29, 1927