EP0898514B1 - Reversible printing blanket - Google Patents

Description

The main subject of the present invention is a reversible printing blanket usable in offset printing machines.

Various types of structure have been known for a long time blanket essentially comprising a layer of material compressible, such as for example cellular rubber, which is associated with a lithographic layer susceptible to print on any medium such as than paper for example.

These structures had a number disadvantages among which we must mention the sagging due to loss of resilience, overheating blankets during the printing process and risking to destabilize the balance of the offset process, the paper flow control problems in machines offset presses, and vibration issues on the fast rotary machines.

In addition, the current blankets are too specialized and do not can be used in optimal conditions of quality only in very specific cases, so that, well often as many structures of blanket as types and forms of printing to achieve.

Also, the present invention aims to remedy the disadvantages above by offering a blanket reversible printing whose structural symmetry allows in particular to reduce or even eliminate aforementioned problems, sagging, overheating, paper flow and vibration control.

To this end, the invention relates to a blanket offset printing characterized by at least one layer of compressible material sandwiched between two layers lithographic exterior rendering said blanket reversible.

According to another characteristic of the invention, this blanket includes two layers of compressible material, these two layers being either isotropic or anisotropic, either one is isotropic and the other is anisotropic.

We therefore already understand that such a reversible blanket will allow a blanket printing job on one side or by the other so that two print jobs which may be different and individuals, these two separate works being susceptible to each produce a quality impression on a medium any, such as paper, which will always be better than having a single blanket with a compromise of structural characteristics not giving always satisfied, far from it very often, for perform a print job or another.

According to yet another characteristic, between the two compressible layers of the blanket is interposed a layer unique reinforcement.

This blanket may also include at least one layer of control of flow rate of the paper to be printed, interposed between the layer compressible and one of the two lithographic layers.

The blanket according to this invention is further characterized by a layer of flow control of the paper to be printed, interposed between one of the compressible layers and the associated lithographic layer, and by a second layer of flow control of the paper to be printed, interposed between the other compressible layer and the layer lithographic associated with it.

This blanket is further characterized in that, in the case of a layer of single compressible material, this layer is either a layer of isotropic material having a modulus Young's elasticity of between 0.2 and 50 MPa, i.e. layer of anisotropic material having a modulus of elasticity of Young between 20 and 1000 MPa in a direction parallel to the blanket plane, and between 0.2 and 50 MPa in a direction perpendicular to the plane of said blanket.

Preferably, Young's modulus of elasticity is understood between 1.5 and 15 MPa in the case of a layer of material isotropic, and in the case of a layer of material anisotropic, between 200 and 500 MPa for one direction parallel to the blanket plane and between 1.5 and 15 MPa for a direction perpendicular to the blanket plane.

The blanket according to this invention is further characterized by that at least one of the two layers of material compressible isotropic has a modulus of elasticity of Young between 0.2 and 50 MPa, or at least one two layers of anisotropic compressible material has a Young's modulus of elasticity between 20 and 1000 MPa in a direction parallel to the plane of the blanket, and between 0.2 and 50 MPa in one direction perpendicular to the plane of said blanket.

Preferably, Young's modulus of elasticity is understood between 1.5 and 15 MPa for the one or two layers of material compressible isotropic, and for one or both layers in anisotropic material, between 200 and 500 MPa for a direction parallel to the blanket plane and between 1.5 and 15 MPa for a direction perpendicular to this plane.

We will also specify here that the thickness of the compressible layers is between about 0.2 and 0.8 mm.

The two lithographic layers have a modulus of elasticity Young's identical or different between approximately 1.5 and 50 MPa, while their thickness is identical or different and between approximately 0.05 and 0.4 mm.

As for the aforementioned single reinforcing layer, it has a Young's modulus of elasticity in one direction parallel to the blanket plane between 500 and 10,000 MPa, while its thickness is between about 0.05 and 0.8 mm.

It will also be specified here that the single reinforcing layer mentioned above is constituted either by a textile grid or by a single or multi-layer plastic polymer film.

The blanket of this invention is further characterized in that that the paper flow control layer (s) to print have a Young's modulus of elasticity in a direction parallel to the blanket plane between about 200 and 1000 MPa, while their thickness is between approximately 0.05 and 0.4 mm.

This blanket is further characterized in that the flow control layers of the paper to be printed are made up of an elastomer reinforced with fibers.

The layer or layers of compressible material are cellular rubber containing oriented fibers preferably in a direction parallel to the plane blanket, in the case of anisotropic layers.

La figure 1 est une vue partielle et an coupe transversale d'un blanchet, conforme au principe de l'invention.

La figure 2 est une vue partielle et en coupe d'un autre mode de réalisation de blanchet selon cette invention.

La figure 3 est une vue similaire aux précédentes mais montrant une autre variante de blanchet selon cette invention.

La figure 4 est encore une vue similaire aux précédentes mais montrant un autre mode de réalisation de blanchet conforme à cette invention.

La figure 5 est une vue schématique et en perspective d'un blanchet à plat pour illustrer ses deux directions principales d'élasticité, à savoir une direction sensiblement parallèle au plan du blanchet, et une direction sensiblement perpendiculaire à ce plan.

However, other characteristics and advantages of the invention will appear better in the detailed description which follows and refers to the appended drawings, given solely by way of example, and in which:

Figure 1 is a partial view in cross section of a blanket, according to the principle of the invention.

Figure 2 is a partial sectional view of another embodiment of the blanket according to this invention.

Figure 3 is a view similar to the previous but showing another blanket variant according to this invention.

Figure 4 is still a view similar to the previous but showing another embodiment of the blanket according to this invention.

Figure 5 is a schematic perspective view of a blanket flat to illustrate its two main directions of elasticity, namely a direction substantially parallel to the plane of the blanket, and a direction substantially perpendicular to this plane.

According to an exemplary embodiment, and with reference to the Figure 1, we see that a blanket B conforms to the principle of the invention comprises a layer 1 of compressible material in cellular rubber for example, which is taken into sandwich between two exterior lithographic layers 2 and 3.

Thus blanket B intended for coating for example a offset printing cylinder (not shown) is reversible, i.e. can make prints on a support (not shown) such as for example paper, by one or other of its two faces made up respectively by the lithographic layer 2 and by the lithographic layer 3. This means that with the same blanket such as B, we can have two surfaces having different transfer properties for printing under different conditions which will of course depend on the nature, modulus of elasticity and thickness that we adopt for layers 1, 2 and 3. In other words, we can for example, with this same blanket B print glossy or blotting paper.

The compressible layer 1 can be made of an isotropic material or anisotropic. By isotropic material is meant a material which exhibits the same behavior, i.e. the same elastic modulus in the three geometric axes x, y and z. Thus, in this case, layer 1 could be consisting of a single layer of cellular rubber, i.e. with a multiplicity of voids, such as identified in 11, according to a number and a distribution any.

On the other hand, the term “anisotropic compressible material” means a material with different elastic moduli in the three axes x, y and z. So the layer compressible 1 could, in this case, consist of cellular rubber containing fibers (not shown) preferably oriented along a direction x parallel to the blanket plane B, like this clearly appears in Figure 5.

In the case where the layer of compressible material 1 is isotropic, it will have a Young's elastic modulus included between about 0.2 and 50 MPa, preferably between 1.5 and 15 MPa.

In the case where layer 1 is a layer of material compressible anisotropic, it will have a module Young's elasticity between 20 and 1000 MPa, preferably between 200 and 500 MPa, in the direction x parallel to the plane of blanket B, and between 0.2 and 50 MPa, preferably between 1.5 and 15 MPa in a direction y (see Figure 5) perpendicular to the plane of the blanket B.

The thickness of the layer of isotropic compressible material or anisotropic 1 will be between approximately 0.2 and 0.8 mm.

The two lithographic layers or surfaces 2 and 3 will have an identical or different Young's modulus of elasticity. This elastic modulus will be between about 1.5 and 50 MPa.

The thickness of the lithographic layers 2 and 3 may be identical or different, as we can see on the Figure 1 where layer 2 has a thickness greater than that of layer 3, which, as explained above, give blanket B printing qualities different depending for example on the nature of the support to be printed. The thickness of lithographic layers 2 and 3 may be between approximately 0.05 and 0.4 mm.

In the embodiment shown in Figure 2, we sees that the layer of compressible material consists of two separate layers 1a and 1b between which is interposed a single reinforcement layer identified in 4.

The two layers of compressible material 1a, 1b are both isotropic or anisotropic, or one of layers is isotropic material and the other layer is made of an anisotropic material. Young's modulus of elasticity of these two layers 1a and 1b is included in the value intervals given above about the mode of embodiment of FIG. 1 comprising a single layer 1 in isotropic or anisotropic compressible material. Onne therefore will not repeat these values here.

Also, the lithographic layers or surfaces 2 and 3 have the same or different thickness, as explained in about FIG. 1, this thickness being included, as previously indicated, between approximately 0.05 and 0.4 mm.

Likewise, the thickness of the compressible layers 1a and 1b will be between about 0.2 and 0.8 mm, as it was case of the layer of compressible material 1 of the visible in Figure 1.

The single reinforcing layer 4 interposed between the layers compressible 1a and 1b has a modulus of elasticity of Young in x direction (see figure 5) parallel to the plane blanket B between approximately 500 and 10,000 MPa. This reinforcing layer 4 may consist of a textile grid or by a plastic polymer film such as a polyester or polycarbonate film, consisting in one or more layers. Its thickness will between approximately 0.05 and 0.8 mm.

Such a single reinforcement layer 4 will allow advantageously reductions in the thickness of the blanket as well as cutting them in two directions, this which will maximize the blanket distribution yield rolled up. Indeed the blankets are provided to the distributor in the form of rolls intended to be cut to the format of offset machines, format which is very variable and disparate.

In the blanket variant visible in Figure 3, we sees that said blanket is similar to that of FIG. 2, with the addition that it includes a first layer 5 for controlling the flow of the paper to be printed (not shown) interposed between the compressible layer 1a and the layer lithographic 2, while a second layer 6 of flow control of the paper to be printed is interposed between the other compressible layer 1b and the other layer lithographic 3.

These two layers 5 and 6 of paper flow control have a Young's modulus of elasticity in a direction x parallel to the blanket plane B between about 200 and 1000 MPa.

The thickness of these two layers may be between about 0.05 and 0.4 mm. We will also specify that these two layers 5 and 6 may consist of an elastomer suitable fiber-reinforced.

Thanks to layers 5 and 6, the flow control of the paper to printing will be improved due to reversibility or blanket B can be turned over in order to adjust the linear speed of the output paper flow for a given and constant speed of rotation of the printing machine.

A single layer of paper flow control from a single side of the single reinforcing layer 4, such as the layer 5 or layer 6, could perfectly be provided in the embodiment of Figure 3, without departing from the scope of the invention as defined in the claims.

If we now refer to the blanket variant B visible in Figure 4, we see that this variant is similar to the embodiment of Figure 1, with in addition the fact that a layer 7 of paper flow control at print is interposed between the material layer compressible single 1 and one 2 of the two layers or opposite lithographic surfaces 2, 3.

This layer 7 both with regard to its module of elasticity that its thickness and its constitution, is as defined above with reference to the realization of Figure 3.

The different intervals given in the description of the realization of figure 1 and concerning the module of elasticity and thickness of layer 1 of material compressible isotropic or anisotropic, apply to achievements of Figures 2, 3 and 4 with regard to the same type of layers that they understand, it being understood that for the embodiments of FIGS. 2 and 3, the two layers compressible 1a and 1b can be identical or different, as previously explained.

It will also be observed that the flow control layers paper 5, 6, 7 are made of any polymer material possibly reinforced by fibers or by sheets textiles.

If we still refer to the embodiments of FIGS. 2 and 3, it is understood that by varying the rate of compressibility of layers 1a and 1b as well that possibly their thickness and / or even the thickness lithographic layers 2 and 3, we will obtain advantageously surface properties for the layers which are different and which will be by respectively suitable for printing media in paper or other material that is different, and that with a single blanket B.

A blanket was therefore produced according to the invention reversible with two work surfaces allowing produce high quality prints on media different, which was not possible with the blankets of the prior art having only one layer lithographic.

In addition, such a blanket, due to its kind symmetry resulting from the presence of two layers opposite lithographic advantageously solves sagging problems due to loss of resilience, significant heating problems on the machine and which could disrupt the offset printing process, as well that the problems with paper flow control and vibrations on rotary machines.

Finally, the blanket according to this invention avoids advantageously to have the printers bear the cost of several blankets for printing different or on different supports, it being understood again that the compromise of features which could be found in a blanket that does only one lithographic layer in order to be able to print with the same print quality of different supports, cannot claim to be satisfactory to obtain the desired print quality on different media.

Of course, the invention is in no way limited to the modes described and illustrated that have not been given as an example.

This is how all the layers of the various blankets described and illustrated are adhered to each other by any suitable means and not shown, such as diapers additional adhesive bonding for example.

The invention therefore includes all technical equivalents means described as well as their combinations if these fall within the scope of the claims which follow.

Claims (16)

1. Offset printing blanket, characterised by at least one layer of a compressible material (1,1a,1b) sandwiched between two external lithographic layers rendering said blanket (B) reversible.
2. Blanket according to claim 1, characterised in that it includes two layers (1a, 1b) of a compressible material, these two layers being either isotropic, anisotropic, or one is isotropic and the other anisotropic.
3. Blanket according to claim 2, characterised in that a sole reinforcement layer (4) is inserted between said compressible layers (1a, 1b).
4. Blanket according to claim 1, characterised by at least one layer (7) for controlling the flow of the paper to be printed inserted between the compressible layer (1) and one (2) of the two lithographic layers (2, 3).
5. Blanket according to claim 2 or 3, characterised by a layer (5) for controlling the flow of the paper to be printed inserted between one (1a) of the compressible layers and the lithographic layer (2) associated with it, and by a second layer (6) for controlling the flow of the paper to be printed inserted between the other compressible layer (1b) and the lithographic layer (3) associated with it.
6. Printing blanket according to claim 1, characterised in that said layer (1) of a compressible material is either an isotropic material layer having a Young modulus of elasticity of between 0.2 and 50 MPa, or an anisotropic material layer having a Young modulus of elasticity of between 20 and 1000 MPa along a direction (x) parallel to the plane of the blanket (B) and between 0.2 and 50 MPa along a direction (y) perpendicular to the plane of the blanket (B).
7. Printing blanket according to claim 6, characterised in that the Young modulus of elasticity is between 1.5 and 15 MPa for an isotropic material layer (1) and for an anisotropic material layer (1) is between 200 and 500 MPa for a direction (x) parallel to the plane of the blanket (B) and between 1.5 and 15 MPa for a direction (y) perpendicular to the plane of said blanket.
8. Printing blanket according to claim 2,3 and 5, characterised in that at least one of the two layers (1a, 1b) is either made of an isotropic compressible material having a Young modulus of elasticity between 0.2 and 50 MPa, or of an anisotropic compressible material having a Young modulus of elasticity of between 20 and 1000 MPa along a direction (x) parallel to the plane of the blanket (B) and between 0.2 and 50 MPa along a direction (y) perpendicular to the plane of the blanket (B).
9. Printing blanket according to claim 8, characterised in that the Young modulus of elasticity is between 1.5 and 15 MPa for the two isotropic compressible material layers (1a, 1b) and for one or both anisotropic material layers (1a, 1b) is between 200 and 500 MPa for a direction (x) parallel to the plane of the blanket (B) and between 1.5 and 15 MPa for a direction (y) perpendicular to this plane.
10. Printing blanket according to one of the preceding claims, characterised in that the thickness of the compressible layer(s) (1, 1a, 1b) is between about 0.2 and 0.8 mm.
11. Printing blanket according to claim 1, 4 or 5, characterised in that the two lithographic layers (2,3) have an identical or different Young modulus of elasticity of between about 1.5 and 50 MPa, whereas their thickness is identical or different and is between about 0.05 and 0.4 mm.
12. Printing blanket according to claim 3, characterised in that said sole reinforcement layer (4) has a Young modulus of elasticity in a direction (x) parallel to the plane of the blanket (B) between about 500 and 10000 MPa, whereas its thickness is between about 0.05 and 0.8 mm.
13. Printing blanket according to claim 12, characterised in that said sole reinforcement layer (4) is made up of either a textile grille or a mono or multilayer plastic polymer film.
14. Printing blanket according to claim 4 or 5, characterised in that the layer(s) (5, 6, 7) for controlling the flow of paper to be printed has/have a Young modulus of elasticity in a direction (x) parallel to the plane of the blanket (B) of between about 200 and 1000MPa, whereas their thickness is between approximately 0.05 and 0.4 mm.
15. Printing blanket according to claim 14, characterised in that the layer(s) (5, 6, 7) for controlling the flow of paper to be printed are constituted by an elastomer reinforced by fibres.
16. Printing blanket according to one of claims 1 to 10, characterised in that the compressible layer(s) (1, 1a, 1b) are made of cellular rubber containing fibres preferably orientated along a direction (x) parallel to the plane of the blanket (B) when said layers are anisotropic.

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