US 1999733 A
Description (OCR text may contain errors)
April 30, 1935. H 1 LUEHRS 1,999,733
PRINTING BLANKET Filed Aug. 16, 1953 F/G. I
HAA/.S J. L UEHRJNVENTOR.
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Patented Apr. 30, 1935 UNITED STATES PAT-ENT OFFICE i v v 1 ,999,733
rmNTNG BLANKET Hans J; Luehrs, `Wsterly, RgI; Application August 16, 933","s ria1 No. '685325 6 Claims.
The objects of my invention are to provide a printing blanket with a desirable hard impression surface having improved ink-repellent qualities and a more permanent resistance against deformation combined with the necessary resiliency in order to enable the blanket surface to conform tothe typehigh variation of the printing plate and whereby to avoid the embedding of the types into the impression surface, preventing the rounding off of the type edges and affcrd an easier slippage of the paper web, thereby reducing 'the known paper breaks.
The features of my invention are more fully set forth in the accompanying drawing, forming a part of this specification, in which:
Fig. 1 is a cross-sectional View of a printing blanket embodying my invention comprising an outer impression member and an inner or supporting resilient member.
Fig. 2 is a similar View showing a modification.
Fig. 3 shows a still further modification including a resilient member of non-uniform compressibility.
Fig. 4 is a modification of the blanket shown in Fig. 3.
In Fig. 1 the printing blanket consists of a layer of soft rubber or other resilient material 3 as a base, and a printing surface 2 in the form of a thin fiexible steel sheet or' other hard but fiexible material of a high elastic moduus. The blanket is attached to the-impression cylinder in the usual manner either in individual layers or as an integral manufactured unit. Fig. 2 represents a printing blanket consisting of a base layer of soft rubber or other resilient material 3, a thin flexible steel sheet or metal screen of a high elastic modulus or other hard but fiexible material 4 as a reinforcement to' provide sufricient hardness and a thin outer layer of rubber, paper or other suitable material 5 as a printing surface. Fig. 3 shows a blanket comprising a base layer 6 of rubber or like material of nonuniform compressibility in which the meeting edge portions 1, 'I are of greater compressibility graduating towards the middle 'of the blanket then the central portion 8 thereof.
Fig. 4 shows a blanket in which the base resilient member 9 has its lower or cylinder contacting surface shaped in the form of a suitable parabolic curve.
One of the features or objeots of my invention is to provide a printing blanket adapted to be mounted on the cylinder in initially preloaded condition which may be defined as a condition under which a definitely predetermined load or compression is put upon the resilient base of the blanket whereby shifting and non-uniformity is avoided. If the base layer of the blanket is of the same size as the outer con- 5 tact layer or is merely compressed when the blanket is put on the cylinder without definite provision having been made against casual or uneven compression, a true circular printing surface cannot be obtained, or is at least very diffi- 10 cult to attain. The object of mounting the printing blanket in predetermined initialiy preloaded condition may be accomplished by making the resilient member in Figures 1 and 2 oversize. Or as disclosed in Figure 3 the re- 15 -si1ient member may be of non-uniform compressibility circumferentially or as shown in Figure 4 the lower surface of the resilient member may be shaped in the form of a parabolic curve.
When a blanket is clamped down on the cy1- inder, the greatest compression occurs of course at the meeting edges of the blanket. Hence an uneven compression or load is created and the desired true cylindrical form of the printing surface cannot be had. If however, the resilient layer is prepared so as to have greater compressibility, inherent in the composition as in Figure 3 or by reason of the form as in Figure 4, an even load all around is obtained and the printing surface member may be mounted in the 30 form of a true circle. This object may be accomplished by making the resilient member oversize in all the forms shown, in order to obtain a compressed condition of the supporting member while the blanket is clamped down to the proper printing pitch diameter. Another object of my invention is to provide a blanket of such form that when mounted, the preloaded printing surface remains parallel to the surface of the impression cylinder.
It will be obvious that my blanket provides effective ink repellence to avoid oifsets, conforms easier to plate or cylinder Variation and provides a better possibility of maintaining a correct printing pitch. My blanket also eliminates the em- 45 bedding of the types on account of the hard but resilient impression surface and therefore avoids the undesirable wear of the type edges which is a well' known disadvantage with softer blankets. The elimination of the embedding of the types is also desirable as it permits easy slippage of the paper web and therefore will diminish paper breaks.
Although I have illustrated and described my invention' in its preferred form, modifications may latter having its lower surface shaped to form a parabolic curve.
3. A printing blanket comprisng an impres'sion member and a, resilient inner supporting member therefore, the latter having its lower surface shaped in the form of a parabolic curve;
4. A printing blanket comprising an outer impression member and a. compressible inner supporting member therefore, the latter having greater compressibility at its meeting edges than at its central portion.
5. A printing blanket comprising a resilient compressible supporting member having greater compressibility at its'meeting edges than at its central portion, a. thin outer impression member and a. reinforcing metal member interposed between the said. two other members.
i 6. A printing blanket comprising an outer impression member and an inner resilient com'- pressible supporting member having a predetermined greater degree of compressibility at the meeting edges of said blanket than at the inside area thereof whereby to mount said blanket in a predetermined initially loaded condition.
HANS J. LUEHRS.