US2355529A - Proofing apparatus and process - Google Patents

Description

Aug. 8, 1944.

J. F. HAwLEY PROOFING APPARATUS AND PROCESS Filed May 1s. 1941 ses Patented Aug. 8, 1944 UNITED STATES PATENT OFFICE PROOFING APPARATUS AND PROCESS John F. Hawley, Riverside, Ill.

Application May 16, 1941, Serial No. 393,716

(o1. 1in-401.3)

9 Claims.

This invention relates to proofing apparatus and methods for flexible printing plates.

Printing plates formed of rubber or like flexible or resilient material are conventionally mounted on printing rollers by means of adhesive compositions.v Since such printing plates as a rule show small but significant local variations in thickness, as measured from the highs of the printing indicia to the reverse face of the plate, and since these variations in thickness cause locally faint and hence imperfect impressions, it has heretofore been customary to compensate for such local variations in thickness by a method including adhesively mounting a plate on a printing roller, taking proof impressions on paper, removing the plate, building up depressed areas by painting the same with an adhesive composition or by attaching a piece of paper thereto, taking a second proof impression, and repeating this procedure until satisfactory imprints are obtained. This method is quite laborious and consumes time wherein the printing press could otherwise be kept operating productively. In view of the fact that a printing press that may cost many thousands of dollars is thus kept for practical purposes idle for a long time whenever new plates are being mounted therein, the prior art method must be characterized as costly and inelcient.

It is therefore an important object of the present invention to provide proofing apparatus and methods whereby printing plates may quickly and easily be adjusted to uniform thickness apart from the printing press wherein the plates are to be used so that the plates may thereafter be attached to the printing rollers of the press in one operation with no further interruption of productive operation and without causing prolonged idleness of the printing press.

Other and further objects of the present invention will become apparent from the following description and appended drawing.

The present invention provides a proofing apparatus including a tubular perforated terminally flanged roller on which a flexible printing plate may be held by suction. The anges of the roller are of such a height as to maintain between the middle portion of the roller and a rigid inking roller combined therewith a distance corresponding to the desired uniform height of the plate which will give satisfactory impressions in the printing press. When the plate is inked by the rigid inking roller, for instance, with a white non-drying ink, any local variations in thickness are made clearly ap'- parent. The plate may be removed, glue or paper or the like may be applied to the reverse side thereof over relatively thin areas, or relatively thick areas may be ground down, and the plate may be washed and again placed on the suction roller and inked. The plate may thus easily and quickly be proofed and adjusted `to the desired uniform thickness, without consuming printing press time and without even resorting to proof impressions.

A preferred example of an apparatus-accord-i ing to the present invention is described in' the appended drawing, wherein:

Figure 1 isa side elevational view of a proofing apparatus embodying the principles of this invention.

Figure 2 is a plan view of the same;

Figure 3 is an enlarged fragmentary transverse cross-sectional View through theprinting roller, printing plate and grinding wheel ofthe apparatus of Figures land 2. 1

Figure 4 is a view of the obverse side of an inked printing plate of uneven thickness.

Figure 5 is a View of the reverse side of the plate of Figure 4 as built up to compensate forlocal variations in thickness.

As shown on the drawing:

In Figures l and 2 the Vreference numeral I indicates generally a proong apparatus according to the present invention. This apparatus includes a frame II carrying bearings I2 for a printing roller I3 and an inking roller Ill. Ends `of the two rollers are provided with meshing gears I5 whereby force transmitted from the driving shat IB to the printing roller I3 directly drives the inking roller I4 without relative slippage between the rollers.

The printing roller I3 is tubular and has walls pierced by numerous perforations 20, as shown in Figure 3, the ends of the roller being closed. A pipe 2l for vacuum opens into the interior of the roller I3 at the center of one closed side.

, The apparatus further includes two rollers 22 for transferring ink Vfrom ink boxes 23 to thev inking roller I4. The rollers 22 may be journalled in the ink boxes which in turn may be supported from the inking roller side of the frame II by brackets 24. i

A roller 26 formed of emery or other abrasive material is journalled in a carriage 2l slidable over a bed formed by an extension 28 from the printing ink roller side of the frame so as to be movable into engagement with the printing roller. The exact spacing of the abrasive roller 26 from the printing roller I3 may be adjusted by means of a set screw 29 and by means of adjustable stops 50 piercing a flange 5I on the frame Il and held there by nuts 52. An idler gear 30 meshing with the gear I5 for the printing roller is rotatably mounted from the frame II so as to be capable of operatively engaging a gear 3I alxed to a shaft 3| for the roller 26, whereby the latter is positively driven from the printing roller gear I5.

A flexible printing plate such as the plate 34 of Figures 4 and 5 may be mounted on the printing roller I3 and held there by suction by covering the rest of the roller I3 with a sheet 35 of paper or the like. reverse face of the plate to be held against the surface of the printing roller. provided with terminal flanges 36 presenting annular hard surfaces 31 at a height H equal to the desired height of the printing plate, without any adhesive backing, as measured from the reverse face to the highs of the printing indicia 38. The hard surfaces 31 bear against like hard terminal surfaces 40 on the printing roller I4 which is perfectly cylindrical except for circumferential grooves 4I separating the surfaces 40 from the rest of the roller to prevent the transfer of ink to the hardened annular end surfaces. The inking roller I4 is made of metal or other rigid material and contacts the printing plate 34, when the highs of the latter reach exactly to the level of the hardened flange surfaces 31, without substantial pressure or with a. kissing contact. The highs of the printing plate are therefore accurately and uniformly coated with ink if of the desired uniform height, but not otherwise,

Figure 4 illustrates the appearance after inking of a printing plate having areas 43 and 44 of, respectively, pronounced and less pronounced relative local thinness. As shown, the area 43 has received no ink and the area 44 has received less ink than the rest of the printing indicium. As shown in Figure 5, the area 43 may be painted with adhesive 45 and paper 46 may be secured to the area 44, to compensate for the relative local thinness of these areas. The correctness of the compensating thickness adjustment may be proofed by again securing the printing plate to the roller and inking the same. If a printing plate should be too thick, as the plate 34 shown in Figure 3 mounted, reverse side out, on the printing roller I3, then the reverse face of the plate may be ground down by means of the abrasive wheel 26 to any degree, as shown. y

Uniform thickness of plates may be obtained, besides by building up areas of relative local thinness or by grinding down areas of relative local thickness, by fabricating plates that are too thick over their whole areas and thereafter grinding down the whole reverse face of the plates to effect the desired thickness, which will then be uniform all over the plate, for the abrasive wheel can be made to grind with an exceedingly high accuracy. Building up' or grinding down may be resorted to indifferently to compensate for local variations in thickness, for if the plate as awhole be too thin, although uniformly thin, this fact can be compensated for by painting von one or more uniformly thick layers of adhesive until the desired thickness has been effected.

Obviously a vacuum need not be used to hold the reverse face of the printing plate against the roller. It is suicient to close the vacuum pipe' The Aroller I3 is 'I'he suction causes the whole plate and paper against the printing roller, effecting a superatmospheric pressure in the room wherein the proong apparatus is operated. Whether this method be resorted to or vacuum is used, the printing plate is pressed against the printing roller surface by the pressure of the atmosphere outside the roller. It is also possible to hold the printing plate on the roller surface by means of a pressure sensitive adhesive or by means of suitable clamps.

Printing plates proofed and adjusted according to the present invention are suitably mounted on Vprinting rollers having terminal flanges for coaction with rigid form inking rollers kissingly contactingthe printing plates, as described in my copending application Serial No. 393,717, entitled Printing press assembly and method.

" The height H of the ange 36 may therefore suitably be made equal to the height of the terminal flanges of the printing roller into which the printing plates are to be secured adhesively minus the thickness of the adhesive layer.

This invention is not limited to the above described preferred examples but includes generally proofing apparatus comprising a printing roll (so called because it carries the printing plate, not because any imprinting is actually done therewith), means for non-adhesively attaching thereto a printing plate together with a rigid inking roll, and means for effecting a kissing contact between the plate and the inking roll as well as means for varying the thickness of the printing plate. This invention further includes proofing methods comprising exposing the highs of a printing plate whose reverse side is non-adhesively held against a cylindrical surface to a kissing contact with a cylindrical surface covered with a film ofV ink having a color contrasting to' that of the printing plate whereby the highs will be uniformly coated with ink if uniformly high, but not otherwise. Further, the means and methods of this application may be employed to hold printing plates on flat surfaces as well as on cylindrical surfaces. In this case, too, holding by suction instead of by adhesives is highlyV advantageous, for rubber plates are liable to become distorted and stretched after having been mounted on and taken oif a few times from a sticky cylinder or flat bed. It is therefore not my intention to limit the patent granted on this invention otherwise than necessitated by the scope ofthe appended claims.

I claim as my invention:

1. A method of proofing a flexible printing plate comprising pressing the reverse face of said plate against a cylindrical surface, kissingly contacting the highs only of said plate, While the plate is so pressed, with a cylindrical surface covered with a lm of ink colored in contrast to said plate to effect a selective transfer of ink exclusively to the highs of said plate, and changing the thickness of said plate in accordance with the extent of ink transfer from said second surface to said highs.

2. An apparatus for proofing a flexible printing plate including a rigid body having a cylindrical surface, means for pressing the reverse face of said plate against said cylindrical surface, another rigid body having a cylindrical surface adapted to be covered with a film of ink colored in contrast to said plate, means for kissingly contacting said latter surface with the highs of said plate when said plate is pressed against said rst cylindrical surface, and means for changing the 5: thickness of said plate, while said plate is held against the cylindrical surface of said first rigid body in accordance with the extent `of ink transfer from said second surface to said highs.

3. An apparatus for proofing a, flexible printing plate including a perforated tubular roller, means connecting the interior of said roller with a sour-ce of vacuum, a rigid inking roller, means for kissingly contacting the highs of said printing plate when the plate is held with the reverse side against said tubular roller said kissing contact being effected uniformly over all said highs when, and only when, all said highs are equidistant from the reverse side of said face, and an abrasive roller for grinding said plate when held against said tubular roller to effect equidistance of all said highs to the reverse face of said plate.

4. An apparatus for proofing a flexible printing plate including a perforated tubular roller having raised hardened terminal annular bearing surfaces and closed ends, means connecting an end of said tubular roller with a source of vacuum, a rigid inking roller having terminal hardened annular bearing surfaces separated from the intermediate roller section by circumferential grooves, said latter bearing surfaces bearing directly against the bearing surfaces of said tubular roller, N

an abrasive roller, means for adjusting the spacing between said tubular roller and said abrasive roller including a carriage and a set-screw, a gear carried by said tubular roller, gears for driving said inking roller and said ab-rasive roller from said first gear, a frame for supporting said rollers, gears and carriage and an adjustable stop on said frame for said carriage.

5. A method of proofing a flexible printing plate comprising pressing the reverse face of said plate against a surface, kissingly contacting the highs of said plate, while the plate is so pressed, with a surface covered with a film of ink colored in contrast to said plate, and changing the thickness of said plate in accordance with the extent of ink transfer from said second surface to said highs.

6. A method of proofing a flexible printing plate without the use of a test sheet including holding the reverse face of said plate against a backing surface, kissingly contacting the highs only 0f said plate while the plate is so held with a cylindrical surface covered with an ink iilm colored in contrast to said plate, whereby the high spots, if any, will be shown by selective transfer of ink from said cylindrical surface to such high spots, and then changing the thickness of the plate to eliminate local differences in plate thickness as indicated by said selective ink transfer.

7. A method of proofing a printing plate Without the use of a test sheet, including holding the reverse face of said plate on a backing surface, kissingly contacting the highs only of said plate while the plate is so held with a surface covered with an ink lm colored in contrast to said plate, whereby the high spots, if any, will be shown by selective transfer of ink from said surface to said high spots, and then leveling said high spots to eliminate local differences in plate thickness as indicated by said selective ink transfer.

8. An apparatus for proong a printing plate without the use of a test sheet, including a rigid body having a backing surface on which said printing plate may be held, another rigid body having a surface adapted tov be covered with an ink film colored in contrast to said plate, means for effecting a kissing ink-transferring contact of said latter surface with the highs only of said plate when the reverse side of said plate is held on said backing member whereby the extent of ink transfer on local high spots on the face is revealed by selective transfer of ink on said highs and means for leveling said high spots to insure uniform inking over the entire printing surface of said plate.

9. |An apparatus for proofing a, printing plate without the use of a test sheet, including a rigid body having a backing surface on which said printing plate may be held, another rigid body 'having a cylindrical surface adapted to be covered with an ink film colored in contrast to said plate, means for effecting a kissing ink-transferring contact of said cylindrical surface with the highs only of said plate when the reverse side of said plate is held on said backing surface, whereby the extent of local high spots on the plate is revealed by selective transfer of ink to said high spots, and ineans for changing the thickness of said plate in accordance with the extent of ink transfer from said second surface to said highs to insure uniform inking over the entire printing surface of said plate.

JOHN F. HAWLEY.

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