Method for securing a mounting bar at one end of a printing blanket and resulting printing blanket

A method for securing a mounting bar at one end of a blanket including a lithographic layer and a support layer and, interposed between those two layers, at least one reinforcing woven layer. The end of the blanket, where the bar is to be fixed, is stripped until the main or single reinforcement of the blanket is exposed and the bar is fixed at least on the stripped part on the end of the blanket. The invention is applicable to printing machines.

FIELD OF THE INVENTION

The invention relates to a process for securing a mounting bar to one end of a printing blanket which has a lithographic layer and a compressible layer, and at least one woven reinforcing layer between the lithographic layer and the compressible layer, and the invention relates to a blanket thus obtained.

BACKGROUND

The blankets of the prior art, as described in the document EP 0 742 760, for example, are gripped at both ends in a mounting bar that bears on the free surfaces of the two exterior layers.

It is known that the mechanical performance of the mounting bars is of prime importance in printing machines. In effect, loss of the bar by possible unseating of it can have very serious consequences, with possible breaking of the printing cylinders and loss of production for the user.

SUMMARY OF THE INVENTION

The present invention proposes a process for securing a mounting bar to a blanket that increases the mechanical performance of the mounting bars and eliminates the above-mentioned risk.

In order to attain this aim, in the process according to the invention, the end of the blanket on which a mounting bar is to be secured is stripped until the main reinforcement or sole reinforcement of the blanket is free, and the mounting bar is secured to the reinforcement.

According to one characteristic of the invention, the mounting bar is secured to the reinforcement by gluing.

According to one characteristic of the invention, both surfaces of the beam are stripped, and the mounting bar is secured by gluing to the two exposed surfaces of the beam.

A printing blanket according to the invention has at least one surface of the reinforcement stripped, and the mounting bar is secured by gluing to this surface.

According to another characteristic of the invention, the mounting bar has the shape of a flat strip.

According to yet another characteristic of the invention, the mounting bar has an L-shaped profile wherein one limb is glued onto the exposed beam portion.

According to yet another characteristic of the invention, the mounting bar has a U-shaped profile wherein one limb is glued on one exposed surface of a beam.

According to yet another characteristic of the invention, the two surfaces of the beam are stripped, and each limb of the mounting bar is glued on one of the two exposed surfaces of the beam.

DETAILED DESCRIPTION

FIG. 1shows one end of blanket1onto which mounting bar2is mounted by gluing, the bar having a general U shape in which end3of the blanket is engaged. This blanket inFIG. 1has three layers, namely exterior lithographic layer5, exterior base layer6, and, inserted between these two layers, reinforcing layer7which comprises a main or sole reinforcement, such as beam8. In the part of end3of the blanket that is taken between the two limbs of rod2, layer6is removed at9in order to expose beam8, as will be described in detail further on. The glue indicated at4and which is used as a means of securing the mounting bar to end3of the blanket is arranged directly on the beam in zone9. Thus, a part of upper limb11of the mounting bar is secured, by means of a layer of glue, at its front part to the exterior surface and at its end part to the beam8, while the other limb13of the mounting bar is secured to the exterior surface of lithographic layer5.

Blanket1represented inFIG. 2could in reality have a structure such as is illustrated inFIG. 2or FIG.3. In the example ofFIG. 2, between lithographic layer5and opposite exterior layer6, which is a slightly compressible polymer layer, the blanket has stabilizing fabric layer15, compressible layer16into which beam8is integrated, and compact polymer layer17, the beam being arranged inside layer16on the layer17side. The blanket according toFIG. 3is distinguished from the blanket represented inFIG. 2by the fact that compact polymer layer17has been eliminated. Consequently, the blanket ofFIG. 3can have a smaller thickness of 1.1 mm in comparison with the 1.2 mm of the blanket according to FIG.2. Of course, the invention applies also to blankets of standard thickness, generally between 1.35 and 2.35 mm.

FIGS. 2 and 3show the blanket after beam8has been stripped at part9, the original contour of end3being represented by a broken line.

FIGS. 4to6show three steps of the process for mounting of bar2onto end3of blanket1. In a first steps, represented inFIG. 4, a part of the thickness of the blanket is delaminated over an appropriate width in order to expose the wires which provide the stretch resistance of the blanket, that is to say, in general the aramid beam8. Advantageously, the exposed surface as well as the rest of the surface which is to be glued can be prepared for gluing or for molding by washing with solvents or by mechanical brushing or the equivalent. Then, in a second operation, the beam thus exposed is coated with glue as illustrated in FIG.5. After spreading the glue, one proceeds to mount bar2on end3of the blanket.FIG. 6shows the mounting bar in its position before the effective gluing. Then, by application of a force in the direction of arrow F, limb11of the bar is forced towards the exterior surface to the position shown in FIG.1. After hardening of the glue, a high degree of resistance to pull-out is obtained, which is necessary for mounting the blanket on an offset printing cylinder.

As an example, the blanket can be stripped for a distance of, for example, 1 to 20 mm, and the blanket can be grasped by mounting bars with a length, width or depth of between 5 and 30 mm.

It should be noted that a number of modifications can be made to the embodiment described and represented. Thus, the blanket can be stripped on both surfaces simultaneously until freeing of the wires which provide the stretch resistance of the blanket. It is also possible to use a simple bar, for example, a bar in the form of a flat rod or a bar with an L-shaped profile, which will then be secured to the exposed, glue-covered surface of the strengthening wires. As a variant, the bar can be molded onto the stripped blanket. The bar can be made of metal but also of composite material, of thermoplastic reinforced, or not, by fibers or by a metallic mesh.

The invention can be used for blankets with a single reinforcement, blankets with two lithographic layers, blankets with a polymer backing, and blankets with thinned ends, as described, for example, in the document FR 9900828.

The above-mentioned single reinforcement can consist of an aramid beam, a beam produced with other fibers with a high modulus and high strength, a known fabric with different weaves, or else a mesh or a plastic film.

The invention also applies to a blanket of more conventional design and which, if necessary, has more than one reinforcement in its body.