JPS6213818Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a blanket for an offset printing machine,
In particular, the present invention relates to an improvement in a blanket for an offset printing press, which has two sections of images transferred onto its peripheral surface and which prints the images onto paper.

FIG. 3 schematically shows an example of a typical structure of a conventionally used offset printing press. In the figure, P is a plate cylinder to which a printing plate is attached, B is a blanket cylinder to which a blanket is attached, and I is an impression cylinder, and between the impression cylinder I and the blanket cylinder B, the paper is pressed against the surface of the blanket to form an image. is transferred.

By the way, as shown in FIG. 3, some of the blanket cylinders B have diameters formed at a ratio of 1:1 to those of the plate cylinder P and impression cylinder I, and others whose diameters are formed at a ratio of 2:1. Something is being formed.
In the former case, one section of the image is transferred onto the circumferential surface of the cylinder B, but in the latter case, two sections of the image are transferred onto the circumferential surface.

On the other hand, to attach the printing plate to the circumferential surface of the printing cylinder P, as shown in FIG. This is done by fixing in the groove G. Therefore, the recess R to be formed between the two ends
In addition to collecting ink inside the blanket during use, since the recess R contacts the exact middle of the circumference of the blanket, the ink in the recess R is transferred to the surface of the blanket at the point mentioned above, and the ink is transferred to the surface of the blanket. The surface of the printing paper is stained.

Therefore, the object of the present invention is to provide a blanket for offset printing presses that eliminates the above-mentioned drawbacks. It has a structure in which the surface rubber is shaved off very shallowly in the width direction.

As illustrated in FIG. 1 or 2, the blanket to which the present invention can be applied consists of a plurality of base fabric layers made of rubberized woven fabric and a surface rubber layer spread and adhered to the surface thereof. (Fig. 1), or a structure in which a porous compressible layer formed by a known method such as mixing foam material or destructible microcapsules is interposed between the base fabric layers. (Figure 2) may also be used. In either structure,
In the surface rubber layer, the outermost rubber is removed linearly along the width direction of the blanket at a position approximately 1/2 of its circumference. The depth of the rubber to be scraped off is
The thickness is approximately 0.1 mm or more and is within the total thickness of the surface rubber layer. By the way, the thickness of the entire blanket is usually 1.5 to 2.5 mm, and the thickness of the surface rubber layer is 0.2 to 0.8 mm.
It is. Note that if the surface rubber layer is scraped too deeply, the fibers of the underlying base fabric layer will be exposed, and there is a risk that the fibers will swell and deteriorate due to ink or solvent.
It is preferable that the depth is less than or equal to the above-mentioned depth.

According to the above configuration, the part of the blanket where the rubber is shaved off linearly at a position of about 1/2 of its circumference always faces the fixed end part of the printing plate on the printing cylinder. The ink accumulated in the end portion is not transferred, and therefore,
It also prevents the printing paper from getting dirty.

According to another preferred embodiment of the present invention, the surface rubber layer has a two-layer structure colored in different colors to facilitate accurate scraping of the surface rubber layer to a predetermined depth as described above. Let the thickness of the surface layer correspond to the depth to be scraped off. With this structure, the surface rubber can be scraped off by a predetermined thickness without excess or deficiency, as long as the surface rubber layer is scraped off until the underlying different-colored layer is exposed.

Examples of the present invention will be described below. FIG. 1 is a partial sectional view showing an embodiment of the present invention.
The blanket 1 of this example is composed of a plurality of base fabric layers 2, . . . made of rubberized cotton cloth, and a surface rubber layer 3 made of acrylonitrile-butadiene copolymer rubber.

The surface rubber layer 3 has a circumferential length L of the blanket 1.
At the 1/2L position, an extremely shallow groove 4 is formed by cutting to a depth of 0.1 mm in the width direction.

The blanket 1 of this example can effectively prevent stains on the printed paper surface by forming the grooves 4 described above.

FIG. 2 shows a first embodiment of a blanket according to another embodiment.
It is a partial sectional view similar to the figure. The blanket 1 of this example includes a plurality of base fabric layers 2, . It consists of a compressible layer 5 and a two-layer surface rubber layer 3 integrally formed on the upper surface of the base fabric layer 2.

The surface rubber layer 3 consists of a lower layer 3a colored black by blending carbon black and an upper layer 3b colored green, and the thickness of the upper layer 3b is 0.1 mm. Incidentally, the thickness d of the surface rubber layer 3 is 0.3 mm.

The surface rubber layer 3 having the above structure is extremely convenient in processing because it is only necessary to scrape off the upper rubber layer 3b until the lower black rubber layer 3a is exposed.

As described above, the present invention provides a blanket suitable for a printing machine that transfers two sections of images onto the surface of one blanket and then transfers and prints the images onto printing paper.

[Brief explanation of the drawing]

1 and 2 are partial sectional views of a blanket showing an embodiment of the present invention, FIG. 3 is a schematic diagram showing an example of a typical structure of a known printing press, and FIG. 4 is a diagram showing the apparatus shown in FIG. FIG. 3 is an enlarged cross-sectional view of the plate cylinder of FIG. 1: blanket, 2: base fabric layer, 3: surface rubber layer, 3a: lower layer of 3, 3b: upper layer of 3, 4: groove,
5: Porous compressible layer, B: Blanket body, I:
Impression cylinder, P: plate cylinder.

Claims (1)

[Claims for Utility Model Registration] (1) A plurality of base fabric layers made of rubberized woven fabric, a surface rubber layer, and optionally between the base fabric layers, or between the surface rubber layer and the base fabric layer. and a porous compressible layer interposed between the surface rubber layer and the surface rubber layer, the outermost surface of which is approximately 0.1 mm thick at a position of approximately 1/2 of the circumference of the blanket body. 1. A blanket for an offset printing machine, characterized in that it is scraped in the width direction to a depth of at least mm and within the total thickness of the surface rubber layer. (2) The blanket according to claim (1) of the utility model registration, wherein the surface rubber layer has a different color rubber layer having a thickness corresponding to the depth to be scraped off on the outermost surface thereof.