US2355530A - Proofing process - Google Patents

Description

1944- J. FJHAWLEY 2,355,530

PROOFING PROCESS Filed April 4, 1942 Patented Aug. 8, 1944 UNITED STATES PATENT OFFICE PROOFING PROCESS John F. Hawley, Riverside, Ill.

Application April 4, 1942, Serial No. 437,623

3 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. 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 10- cally 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 inefiicient.

It is, therefore, an important object of the present invention to provide proofing apparatus and methods whereby printingplates 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 pro longed idleness of the printing press.

Other and further objects of the present invention will become apparent from the following a rigid, cylindrical inking .roller disposed transversely of the bed and provided with terminal bearing surfaces adapted to rollon the bearing surfaces of the bearers. This arrangement permits the roller to roll lengthwise of the bed. Means are provided for coating the inking roller with ink as the roller rolls over the bed. Racks on the bed and gears on th roller prevent slippage'of the roller over the bed as the roller rolls over the bed. The height of the bearer and the diameter of the roller between its terminal bearing surfaces are so proportioned that the roller surface will always be spaced from the bed surface by 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 plate thickness are made clearly apparent. The plate may be removed, glue or paper or the like may be applied to the reverse side of the plate over relatively thin areas, or relatively thick plate areas may be ground down, and the plate may be washed and again placed on the suction bed 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 preferredexample of an apparatus according to the present invention isdescribed in the appended drawing, wherein:

Figure 1 is a perspective view of a proofing apparatus according to this invention showing a printing plate in position for proofing. Part of the proofing plate is broken away to show the underlying perforated bed portion.

Figure 2 is a transverse, cross-sectional view taken along the line IIII of Figure 1, with parts shown in elevation.

Figure 3 is an obverse view of an inked printing plate of uneven thickness.

Figure 4 is a view of the reverse side of the plate of Figure 4' as built up to compensate for local variations in thickness.

Figure 5 is a longitudinal, cross-sectional view taken along the line V-V of Figure 4.

Figure 6 is a view similar to that of Figure 5 showing the plate of Figure 4 with an adhesive backing.

1 A'sshOwn on the drawing:

ln'Figure 1 the reference numeral l0 indicates generally a proofing apparatus according to the present invention. The apparatus includes a fiat, rectangular bed plate ll supported similarly to a table top at its four corners by four posts or legs l2. A shallow, closed chamber extends immediately beneath the bed plate I l. The side walls of this chamber are formed by elongate longitudinal members l3 and by elongate transverse members l4 depending from the margins of the bed plate. The bottom of the chamber is formed by a plate (not shown) coextensive with the bed plate and attached to the lower margins of the members l3 and M. The roof of the chamber is formed by the bed plate II. The chamber thus defined beneath the bed plate is connected by a duct I5 to a source of vacuum such as a pump or suction fan l6 driven by an electric motor H. The pump, as well as the motor, may be disposedon a shelf l8 supported from the legs l2.

The bed plate 1! includes a middle suction area 20 perforated by circular apertures inch in diameter which occupy about 24% of the suction area.

A rack bar 2| is attached to each upper 1ongitudnal bed plate margin. A bearer 22 is attached to the bed plate inside each rack bar. These bearers provide a pair of elongated flat bearing surfaces 23 extending longitudinally of the bed plate at a level higher than the top of the rack bar.

As shown in Figures 1 and 2, the apparatus further includes a rigid inking roller 25 having terminal bearing surfaces 26 spaced so as to be capable of rolling over the bearing surfaces 23. Outside of these bearing surfaces, the roller 25 carries gears 25 adapted to mesh with the rack The roller 25 is provided with a shaft sions 29 from a trough-like ink box 30'extendingin parallelism with the roller 25 to accommodate an ink distribution roller 31 capable of transferring ink uniformly to the surface of the roller 25. The ink box 30 is supported at its ends by shoes 3| adapted to slide on the bearing surfaces 23, so that the ink box can be pulled or pushed by the roller 25 as the roller moves back and forth over the bed plate II. A film of ink is applied to the roller 25 by the ink distribution roller 3'! when the latter is driven by the rotating inking roller 25. The ink box is so proportioned as to clear the printing plate disposedon the bed plate.

One end of the shaft 28 is slightly longer than the other end to receive one arm of a crank 32 having a handle 33 for manually rotating the roller 25. When the roller 25 is rotated, the gears 21 meshing with the rack 2| will cause the roller 25 and the ink box 30 associated therewith to movelengthwise of the bed plate A flexible printing plate, such as the plate 34 shown in Figure 3 as having a printing indicium 35, may be mounted on the bed plate I I over the suction area 23 to be held there by suction. Ifthe plate does not cover the suction area 20 completely, the rest of the suction area may be covered with paper 35 or the like. The suction generated in the chamber beneath the bed plate by the pump or blower ll causes the whole reverse faceof the plate to be held against the surface of the bed plate.

The bearing surfaces 23 and 26 are hard. The bearers 22 are of such height and the inking roller 25 is of such diameter that the inking surface of the roller 25 will always be removed from the bedplate surface by a distance equal to the desired height of the printing plate, without any adhesive backing, as measured from the reverse side to the highs of the printing indicium 35.

The inking roller 25, being made of metal or other rigid material, will contact the printing plate 34 without substantial pressure or with a kissing contact, when the highs of the latter reach exactly to the level of the inking roller surface. The racks and gears prevent slippage between the roller and the bearer as the former rolls on the latter. The highs of the printing plate are, therefore, accurately and uniformly coated with ink if of the desired uniform height, but not otherwise.

Figure 3 illustrates the appearance after inking of a-printing plate having areas '40 and 4| of, respectively, pronounced and less pronounced relative local thickness. As shown, the area 40 has received no ink and the area 4| has received less ink than the rest of the printing indicium. As shown in Figures 4 and 5, the areas 40 and 4| may be built up by attaching to each area a make-ready formed, for instance, by adhesive 42 or by paper 43. The correctness of the compensating thickness adjustment may be proofed by again securing the printing plate to the bed plate and inking the plate.

As shown in Figure 6, an adhesive backing 44 may be secured to thereverse side of the printing plate over the make-ready when the plate areas of localized thickness have been built up to make the plate thickness uniform. Of course, the adhesive backing may also be applied after thicker plate areas have been ground down to conform with the thinnestplate area.

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

This invention is not limited to the above deing thereto a printing plate, a rigid inking roller,

and means for effecting a kissing contact between the plate and the inking roller while coating the latter with ink. The plate attaching means may include a bed plate perforated at suitable intervals by apertures of a size such that the plate is not pulled down into the perforations when vacuum is applied to the apertures. This invention further includes proofing methods comprising exposing the highs of a printing plate whose reverse side is adhesively or non-adhesively held against a flat surface to a kissing contact with a'cylindrical surface being covered with a filmof ink having a-color contrasting to that of the printing plate whereby the highs will be uniformly coated with ink if uniformlyv high, but not otherwise. The means and methods of this invention are also applicable to the proofing of flat, non-flexible printing plates. Many details of construction and procedure may be varied within a wide range without departing from the principles of this invention, and it is, therefore, not my purpose to limit the patent granted on this invention otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. 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 fiat surface, kissingly contacting the highs only.

of said plate while the plate is so held with a cylindrical surface covered with a film of ink 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 building up low plate areas until the whole plate area will be inked uniformly by the transfer of ink from said cylindrical surface.

2. A method of proofing a flexible printing plate comprising pressing the reverse face of said plate against a flat surface, kissingly contacting the highs only of said plate while the plate'is so pressed with a cylindrical surface covered with a film 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.

3. A method of proofing a printing plate without the use of a test sheet including holding the reverse face of said plate on a flat surface, kissingly contacting the highs only of said plate while the plate is so held with a cylindrical surface covered with a film of ink colored in contrast to said plate, whereby the high spots, if any, on said plate will be shown by selective transfer of ink from said cylindrical surface to such high spots, and leveling said high spots to insure uniform inking over the entire printing surface of said plate.

JOHN F. HAWLEY.

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