US2187421A - Doctor blade - Google Patents

Description

Jan. 16, 1940. F GEORGE 2,187,421

DOCTOR BLADE Filed Jan. 5, 1957 2 Sheets-Sheet 1 INVENTOR.

ATTORNEY-w atentecl Jan. 16, 1940 Q UNITED STATES PATENT OFFICE DOCTOR BLADE Fred George, Lakewood, Ohio, assignor, by mesne assignments, to Interchemical Corporation, New York, N. Y., a corporation of Ohio Application January 5, 1937, Serial No. 119,104

13 Claims. (01. 101-469) invention relates to imprlovements in printing plate and-cause no scratches or other doctor blades for gravure printing presses, that injury to the printing surface.

is to say blades for removing excess ink from Another object is the provision e u le intaglio printing plates or cylinders. In such mounting for soft flexible doctor blade material. 5 printing elements the image is commonly pro- Still another object is the provision of a doc- 5 duced on the plate photographically through tor blade of a character such that variations in lined screen and then etched, forming depresthe p e exerted through the blade against sions of uniform area separated from each other the printing Surface Will Cause Variations in the by minute lands, the depressions varying in mou o ink e p the printing Surfacelll depth and in t printing operation carrying Other objects and features of novelty will apmore or less ink, as the high lights and shadows n ar as I p d w th t d ript n f that of the image demand. embodiment of the invention which, for the purln photogravure printing wherein an etched poses of the Present pp I ave lluscylinder carrying the image is partially imed in t accompanying w s, in which 115 mersed in a bath of fluid ink, the excess ink g- 1 is a S elevatienal e r e y eremaining on the cylinder over that required to grammetie, Of a gravllle Printing P s Showing fill the depressions is removed, in the convenonly esse elements thereof, and embodying tional procedure, by causing a metallic blade, the present inventioncalled a doctor blade, to bear against the sur- F 2 s a det l v ew s o n a mod fication 211i face of the rotating cylinder, the doctor blade o e 11001101 bledebeing set at an angle somewhere between 10 Figs. 3, 4 and 5 are sectional views on a greatand 30 from the radial plane passing through y a n fi d Scale Showing the effect of d e the line of contact. In other words, .the doctor ent adjustments of the doctor blade. I blade is arranged at an angle somewhere be Referring to Figis the frame of a at tween 60 and 80 from the tangent at the point We printing press, of which II is the printing of contact. The purpose of such a blade is to cylinder havin an integlio printing Surface o remove completely the ink from the outer surthe usual photogravure character. The cylinder face of the cylinder and leave only that carried II s Carried y Shaft which m y be driven within the depressions; It will be seen therefore y Suitable Dower means 3 is a rlobar-(V- so that the character of the printed image for a reed cyli d a apt to press he eb b in given quality of ink will remain substantially printed against Printing Cylinder, a d constant, and that any desired variations in the is a metallic D roller for meinteiningeenamount of color deposited must be accomplished Stent Pressure between the rubber r0116! i by changes in the quality of the ink or by emand the Printing Cylinder throughout hei ploying a different cylinder having a design enlength. The shafts of rollers I3 and M are car- 35 graved to 'a difierzmt depth.- Metani d t ried in bearing blocks slidably movablein a rablades or other blades of hard material are o en "dial direction w h r s t to yl nd ll, suitto various objections, such as the need for accuable m ans su h as ws fiv e provided for rate regrlnding of the blade due to wear, gradual adjusting the pressure exerted by roller it. The

to wearing off of the design on the cylinder by the w W of p p r x nds halt-Way around roller .40 abrasive action ofthe blade, and a tendency to passes betvveen that ro e and roller l3, scratch the surface of the cylinder; extends half-way ."around roller, l3 and passes According. tothe present invention, a doctor between that rollerandth'e' printingcylinderll,

blade of relatively soft resilient material isproafter which it passesfthrougliany'known and 4,5 vided, together with a method of mounting and suitablenieehanism for drying'theprinted image "4.5

adjusting theapressure of: the, blade against the and rewindingthe weblf Thecylindrf-ll" upon cylinder, whereby abrasive action between the whichthe printing designis'formed (Jr-mounted is blade and thecylinder isareduced and variations V partially immersed in the inlt iii ca ie'd in thecharacter of the printing are obtainable ink pe by means pfrsimple adjusgmentgog t doctor The ink clinging toa ie sul'iace otcylinderylM501 1 blade, ,in excess of that required to-wfll-lthel depressions One of thetobjects of theinventionis-to proof the design is removedx bytmeans;ofaia doctor vide a doctor blade for gravure printing ma ,,blade which is shown inii ig d;asaconsistin'g of chines, the;active portions of which shall prothree parts-athin sot strip; l8 .ofqqresilientamaa duce no appreciable w ion thecylinder or terial such assoftru er; the end-oi .the,;.'strip,-55

being cut square, a thicker strip Is also resilient and somewhat soft or yielding although less resilient and less soft than strip l8, and a hard backing strip 20 which is preferably metallic. All three of these strips are clamped firmly together by means of bars 2| and 22 and bolts 23, the bars running the full length of the doctor blade. To the bar 22 are fastened brackets 24, one at each end, which are secured to a shaft 25 that is journaled in the sideframes of the press. To each end of shaft 25 outside of the frame of the press there is attached an arm 28, and upon these arms weights 2'! of selected size may be hung in order to exert forces of different strength producing varying pressures of the doctor blade against the surface of the printing cylinder ll.

As illustrated in the drawings my doctor blade is mounted nearly but not quite tangent to the cylinder, which mounting is in sharp contradistinction to the mounting of the conventional hard blade which ispositioned nearly at right angles to the tangent. This is an important feature of the invention. In practice; have found that for average conditions the most desirable angle of the blade with reference to the tangent at the line of contact is 13 or thereabouts. This angle may be varied advantageously to some extent to suit different conditions, such as changes in the speed of rotation of the printing cylinder, changes in the ink used, and changes in the pressure of the blade against the cylinder. In no case however should the angle exceed I have found that soft rubber, either natural or synthetic, is a suitable material for the strip l8, but it will be understood that other flexible soft materials having more or less similar characteristics of softness and resiliency may be substituted with good results. The two strips l8 and ll! of Fig. 2 may be Joined together by cement or otherwise, or they may be joined together by vulcanization.

For certain purposes one thickness only of rubber or the like may be required. Such an arrangement is shown in Fig. 2, in which the soft flexible portion 28 of the blade is backed up by a more or less stiif metallic strip 29 and mounted in the way previously described. A single strip of rubber may also be composed of layers or zones of difierent resiliency and softness graded progressively from the backing to the engaging surface.

In Figs. 3, 4 and 5 I have illustrated on a magnified scale a small section of the etched plate or cylinder with the soft doctor blade wiping off the ink, Fig. 3 showing the average or normal pressure adjustment for removing all ink from the surface or lands while leaving the depressions filled. The depressions are indicated at 30 and the lands at 3|. It will be noted that the bottom and end surfaces of the strip l8 of the doctor blade are at right angles to each other, but that the pressure exerted through this strip has deformed the engaging edge to some extent. In other words instead of a true line contact between the blade and the cylinder we have contact over a very narrow surface conforming to the curvature of the cylinder.

In Fig. 4 the pressure exerted is less than in Fig. 3, and the deformation of the active edge of the'strip II is less. with this adjustment the depressions 30 are left filled as before, but in addition there is left upon the lands 3| a 1 thin film 'of ink. when a print is taken from a plate inked in this manner the whole image is darkened slightly over what it would be if printed from the same plate inked in the manner indicated in Fig. 3.

In Fig. 5 the pressure induced by the weights 21 or the like is increased above normal and to such an extent that the active edge of the blade strip I8 is forced into the depressions 30 and wipes some of the ink out of these depressions as well as removing all ink from the outer printing surfaces. By thus removing a quantity of ink from all of the depressions throughout the extent of the printing surface the tone of the print taken from the surface is of course lightened or weakened.

It will be apparent therefore that the operator of a press equipped with my novel doctor blade may, by merely varying the pressure exerted on the doctor blade, and without changing the speed of the press or the character of the ink used, produce prints that vary in tone or depth over a considerable range. The ink carried up by the cylinder and held back by the doctor blade forms a wedge-shaped reservoir 32, as shown in Figs. 3, 4 and 5', which because of the rotation of the cylinder is under a pressure tending to force it past the blade. This effect combined with the resilience of the rubber blade permits accurate regulation by pressure changes of the amount of ink allowed to pass the blade, as in Fig. 4. In so far as the condition illustrated in Fig. 4 is concerned, speeding up the cylinder has the same effect as decreasing the pressure on the blade.

Variations from the described structure may be employed. Accordingly I desire it to be understood that the scope of the invention is to be regarded as defined exclusively by the appended claims rather than by the foregoing description or the accompanying illustration.

Having thus described my invention, I claim:

1. A doctor blade for a printing element of the intaglio surface type, said blade comprising a plurality of layers of resilient material, the foremost layer being of such softness as to require external support, said foremost layer being adapted in operative position to contact said printing surface, and substantially rigid supporting means adapted to prevent deflection of said layers.

2. A doctor blade for a printing element of the intaglio surface type, said blade comprising a resilient surface contacting portion of such softness as to require external support,.and a plurality of layers of material of increasingly greater stifiness for supporting said surface contacting portion in operative position.

3. A doctor blade for a printing element of the intaglio surface type, said blade comprising a plurality of strips of resilient material of different degrees of stiffness, said strips being arranged with the softest strip in contact with the printing surface to remove ink therefrom, and a backing strip of material harder than the first mentioned strips.

4. In a gravure printing press, an intaglio printing cylinder having a screened, etched, surface, a cooperating impression cylinder, and a doctor blade operatively associated with said printing cylinder and having a soft resilient ink removing edge.

5. In a gravure printing press, an intaglio printing cylinder having a screened, etched, surface, a cooperating impression cylinder, a doctor 7. A gravure printing press, comprising an intaglio printing cylinder having a printing surface of the usual photogravure character; an impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing cylinder; and a doctor blade having a soft resilient wiping edge operatively arranged at an angle of less than 30 with respect to the tangent at the line of contact of said doctor blade with said printing cylinder.

8. A gravure printing press, comprising an intaglio printing cylinder having a printing surface of the usual photogravure character; an impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing, cylinder; and a doctor blade having a wiping edge of such softness as to be deformed in the region of said edge by the pressure of the blade against said printing cylinder.

9. A gravure printing press, comprising an intagllo printing cylinder having a printing surface of theusual photogravure character; an impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing cylinder; a doctor blade having a Wiping edge of such softness as to be deformed in the region of said edge by the pressure of the blade against said printing cylinder; and means for varying the pressure of said doctor blade against the cylinder in order to control the tone effect of, the prints produced.

10. A gravure printing press comprising an intaglio printing cylinder having a printing sur face of the usual photogravure character; an

impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing cylinder; and a doctor blade comprising a strip of material having the softness andv resiliency characteristics of soft rubber, a backing therefor, and means for exerting pressure through said backing to cause said strip to bear against the printing cylinder for removing marking material therefrom.

'11. A gravure printing press comprising an intaglio printing cylinder having a printing surface of the usual photogravure character; an impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing cylinder; anda doctor blade comprising a strip of material having the softness and resiliency characteristics of soft rubber, arranged to bear against the printing cylinder for removing marking material therefrom, the cylinder contact g portion of the strip being formed of two fa es substantially at right angles to one another. I

12. A gravure printing press comprising an intaglio printing cylinder having a printing surface of the usual photogravure character; an impression cylinder cooperating with said printing cylinder; means for applying marking material to said printing cylinder; and a doctor blade comprising a printing cylinder contacting portion having the softness and resiliency characteristics of soft rubber, means for supporting said portion throughout the length thereof, and means for exerting varying amounts of pressure against said supporting means in a direction toward said printing cylinder in order to control the tone effect of the prints produced.

13. A gravure printing press comprising an intaglio printing cylinder having a printing surface ofthe usual photogravure character; an

impression cylinder cooperating with said printing cylinder; means for applying marking ma terial to said printing cylinder; and a doctor blade comprising a strip of material having the softness and resiliency characteristics of soft rubber, a backing therefor, and means for exerting pressure through said backing to cause said strip to bear against the printing cylinder in such a manner that a thin film of marking material will be left upon the surface of said printing cylinder.

FRED GEORGE.

Images