US 3109368 A
Description (OCR text may contain errors)
Nov. 5, 1963 LUTTRELL 3,109,368
PRINTING PLATES Filed Sept. 11, 1962 Fag-4: Inventor Raven D. Luttre H 13 and-.DM/
. Hz-ko rn e 1443 United States Patent 3,109,368 PRINTING PLATES Ravon D. Luttrell, 30 W. Chicago Ave., Chicago, Ill. Filed Sept. 11, 1962, Ser. No. 222,804 1 Claim. (Cl. 101-376) This invention relates to printing plates, and in particular to printing plates of the kind adapted to produce impressions on corrugated cardboard or the like that present an irregular surface.
Printing on corrugated cardboard presents a special problem inasmuch as the surface presented is quite irregular. The variance can be of the order of 0.010" to 0.030". In view of this, it has been heretofore proposed to utilize printing plates presenting type faces of relatively soft rubber. Resultantly, the type faces of the plate when pressed against the irregular surface incidental to producing an impression thereon will assume a state of compression conforming to the irregularity of the surface being printed, which is to say that the soft type faces will seek out the low spots on the surface being imprinted, or will be compressed by high spots. Thus, the type face may be squashed or flattened producing an imperfect print, and the primary object of the present invention is to overcome this problem by providing a rubber printing plate, for printing irregular surfaces, with a relatively soft rubber backing supporting relief type characters having relatively hard rubber printing faces. As a consequence, the hard rubber on the faces of the printing characters that will be inked will not squash or distort because of variant pressure due to surface irregularities, but rather will remain undistorted, whereas the soft backing associated with the type characters will permit such compliance with surface irregularity as may be necessary to enable the type characters to seek out the valleys or low spots presented by the surface being printed. Thus, the soft rubber backing becomes a cushion or pliant support for the hard rubber type faces which are non-distorting under the printing pressures involved.
Another object of the present invention is to further assure uniformity in prints by providing the more narrow or sharp characters with relatively thick hard rubber faces, in comparison to broad characters having thinner hard rubber faces, whereby ideal hardness is obtained for each printing area.
Other and further objects of the present invention will be apparent from the following description and claim and are illustrated in the accompanying drawing which, by way of illustration, shows a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claim.
In the drawings:
FIG. 1 is a perspective view of a typical printing plate constructed in accordance with the present invention;
FIG. 2 is a sectional view illustrating a typical printing plate of the prior art;
FIG. 3 is a sectional view illustrating the character of the printing plate of the present invention; and
FIG. 4 is a sectional view showing mold features characterizing the present invention.
A printing plate composed in accordance with the present invention is illustrated in FIG. 1 as inclusive of a backing 11 of relatively soft rubber presenting relief type characters 12 on the printing side thereof. The type characters 12 are faced with a harder rubber 13, FIGS, and the hand rubber is vulcanized to the soft rubber as hereinafter described.
The printing plate 10 is specifically adapted to print irregular surfaces such as corrugated cardboard =14, the plate being supported on a printing cylinder '15. An advantage of this is that a rubber plate as 10' does not tend to crush the cardboard under the printing pressures involved, and the soft rubber relief type characters 12' will conform to such surface irregularities as may be presented by the body being printed.
However, at the same time, a type character such as 12" (FIG. 2) which encounters a high area on the surface being printed, will be squashed or flattened, manifesting a distortion in the imprint. The result appears to be a cheap print, and one that approaches illegibility.
In accordance with the present invention, the printing plate 10, FIG. 3, is provided with a backing '11 of soft rubber having a durometer hardness of the order of 10 to 20, and the relief portions 11R thereof, which in part afford the type characters 12, are faced with hard rubber 13 as has been noted, whereby distortion of the type faces is substantially overcome. Thus, with the plate 10 secured to the cylinder 15 in the usual fashion, in the event a type character 20, FIG. 3, should encounter a high spot on the cardboard surface 14 being printed, the relief backing 11R will yield as a cushion or pliant support therefor, whereas the inked type face of the character 20 is substantially unaffected and will retain its original geometry, reproducing the precise font design originally embodied therein. Advantageously, the type characters are faced with hard rubber having a hardness of the order of 40 to 60 on the durometer scale.
The wider type characters of course display more resistance to squashing or distorting than do the more narrow characters. Referring to FIG. 1, the word PRINT to be printed by the plate 10 includes wide characters WC and narrow characters NC. Under and in accordance with the present invention the narrow characters NC, FIG. 3, have hard rubber facings of maximum thickness, and the widest characters WC have the thinnest hard rub ber facings. Resultantly, the narrowest characters that are likely to be distorted the greatest amount are the most resistant to distortion by virtue of the thicker hard rubber facings.
Printing plates of the present invention are produced in a matrix or mold 25, FIG. 4. The matrix 25, in view of the relief plate involved, is produced with precision intaglio depressions 26 representing the data to be eventually imprinted, and these depressions, representing the printing faces of the ultimate printing plate, are lined with the hard rubber material 13. In compliance with the inverse order of hard rubber thickness, as related to the width of the type characters above noted, the depressions in the matrix corresponding to the most narrow characters NC are provided with hard rubber material 113 of maximum thickness.
After the intaglio depressions in the mold have thus been filled with hard rubber material 13 in the desired thickness relationship, the soft rubber backing 11 is then provided, whereafter the backing 11 and facing 12 are vulcanized to afford the unitary plate.
It will be realized from the foregoing that the rubber printing plate of the present invention, for printing on irregular surfaces, is characterized by relief type faced with rubber of a given hardness having a thickness which varies inversely with the Width of the characters, and this hard rubber facing is backed by a pliant cushion of significantly softer rubber. The order of rubber hardness has been specified above, but it will be appreciated that this amounts to a general proposition which can be varied appreciably for different circumstances, without departing from the principle of the present invention. Likewise, while synthetic rubber is the preferred material for the plate, in view of the need to have an oil-resistant material because of -the oil-base inks that might be used, circumstances may permit utilization of other materials of various pliant compositions, and hence the term rubber as used herein embraces what other pliable materials may prove to be useful.
I have referred herein to the soft rubber material as a backing, and this term is used in reference to the hard rubber facing. In actual practice, plates of the kind here involved are provided with a canvas or similar attaching means which is used to secure the plate to the cylinder and which prevents stretching of the plate, but this, manifestly, is not material to an understanding of the present invention and hence has not been illustrated.
Hence, whileI have illustrated and described a preferred embodiment of my invention, it is to be understood that this is capable of variation and modification, and I therefore do not Wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claim.
A printing plate for printing on corrugated cardboard and the like and comprising a backing, said backing supporting type characters of rubber of a given softness to conform to irregularities in the surface to be printed and said type characters having printing faces of appreciably harder rubber which is substantially non-distortable under the printing pressures involved whereby the softer rubber of the type characters will yield when a high spot is encountered during printing while the face of the corresponding character remains substantially unaltered, the thickness of the hard rubber facing of the type characters extending toward the backing :less than the entire height of the character, and wherein the thickness of the hard rubber facing of the type characters varies inversely with the width of the characters.
References Cited in the file of this patent UNITED STATES PATENTS 336,481 Hall Feb. 16, 1886 2,101,838 Cochran Dec. 14, 1937 FOREIGN PATENTS 388,482 Great Britain Mar. 2, 1933 662,179 Great Britain Dec. 5, 1951