EP1279496A1 - Offset press with bearing mounting - Google Patents

Abstract

The offset press comprises a frame, at least one plate cylinder, a press cylinder, and a blanket cylinder interposed between the plate cylinder and the press cylinder, together with bearing assemblies carried by the frame and receiving the longitudinal ends of the cylinders so that each cylinder is rotatable relative to the frame about a respective longitudinal central axis. Each of the longitudinal ends of at least a first cylinder are received in a first bearing assembly and a second bearing assembly, the second bearing assembly being spaced apart from the first bearing assembly along the longitudinal axis of the first cylinder.

Description

The present invention relates to an offset press of the type comprising a frame, at least one plate cylinder, a pressure cylinder and a blanket cylinder interposed between the plate and pressure cylinders, and bearings carried by the frame and receiving the longitudinal ends of the cylinders so that each cylinder can rotate relative to the frame around a respective longitudinal central axis.

In such a press, each end of the cylinder is mounted by means of a rotary bearing on the frame. Drive means ensure the rotation of the cylinders.

In operation, the plate carried by the plate cylinder is moistened and then inked. The plate transfers the ink from its printing regions onto the blanket carried by the blanket cylinder. The blanket then transfers the ink onto the printing paper which passes between the blanket cylinder and the pressure cylinder.

To be able to transfer the ink on the one hand from the plate to the blanket, and on the other hand from the blanket to the paper, the plate, blanket and pressure cylinders must, in operation, be tackled against each other. The cylinders then exert on each other radial bending forces.

To prevent the cylinders from bending too much under the action of these forces, which could adversely affect the proper functioning of the press, care is taken to ensure that the ratio between the length of each cylinder between its two end bearings and the diameter of the cylinder remains relatively small and generally less than about 6.

Thus, the diameters of the cylinders of a press of the aforementioned type are relatively large, which induces a large mass and relatively high production and installation costs.

This poses an additional problem for the plate cylinder which, because of its large circumference, requires either the use of very long plates and whose assembly is complex, or the mounting of two plates each corresponding to a half-circumference, this which also involves significant costs due to the greater number of plates to be used for a given print run and the difficulties of installing two plates simultaneously on a plate cylinder.

An object of the invention is to solve these problems by providing a press of the aforementioned type which makes it possible to reduce the diameter of at least one cylinder and thus the costs associated with this press.

To this end, the subject of the invention is an offset press of the aforementioned type, characterized in that the longitudinal ends of at least one first cylinder are each received in a first bearing and a second bearing, the second bearing being spaced from the first bearing along the longitudinal axis of the first cylinder.

• la presse comprend, pour chaque extrémité du premier cylindre, des moyens d'excentration du premier palier par rapport au deuxième palier ;
• le premier palier est mobile par rapport au bâti entre une première position d'excentration plus faible ou nulle et une deuxième position d'excentration plus importante par rapport au deuxième palier, et les moyens d'excentration comprennent des moyens de déplacement du premier palier entre sa première et sa deuxième position ;
• le premier palier est pivotant par rapport au bâti autour d'un axe sensiblement parallèle à l'axe du deuxième palier ;
• les moyens de déplacement comprennent un vérin s'étendant entre le bâti et le premier palier ;
• pour chaque extrémité du premier cylindre, les moyens de déplacement sont réglables pour permettre d'amener le premier palier dans une position intermédiaire entre sa première et sa deuxième position ;
• le premier cylindre est le cylindre porte-plaque ; et
• le cylindre porte-plaque a un diamètre inférieur à celui du cylindre porte-blanchet.

According to particular embodiments, the offset press can include one or more of the following characteristics, taken alone or in any technically possible combination:

• the press comprises, for each end of the first cylinder, means of eccentricity of the first bearing relative to the second bearing;
• the first bearing is movable relative to the frame between a lower or zero first eccentric position and a second greater eccentric position relative to the second bearing, and the eccentric means comprise means for moving the first bearing between its first and second positions;
• the first bearing is pivotable relative to the frame about an axis substantially parallel to the axis of the second bearing;
• the displacement means comprise a jack extending between the frame and the first bearing;
• for each end of the first cylinder, the displacement means are adjustable to allow the first bearing to be brought into an intermediate position between its first and its second position;
• the first cylinder is the plate cylinder; and
• the plate cylinder has a smaller diameter than that of the blanket cylinder.

• la figure 1 est une vue schématique latérale d'une presse selon l'invention,
• la figure 2 est une vue schématique, partielle, agrandie et en coupe prise suivant la ligne II-II de la figure 1, cette figure illustrant les paliers de montage d'une extrémité du cylindre porte-plaque sur le bâti de la presse de la figure 1
• la figure 3 est une vue schématique, latérale et agrandie illustrant les paliers de la figure 2 dans une première position relative,
• la figure 4 est une vue analogue à la figure 3 illustrant une deuxième position relative des paliers.

The invention will be better understood on reading the description which follows, given only by way of example, and made with reference to the appended drawings, in which:

• FIG. 1 is a schematic side view of a press according to the invention,
• Figure 2 is a schematic, partial view, enlarged and in section taken along line II-II of Figure 1, this figure illustrating the mounting bearings of one end of the plate cylinder on the frame of the press of the figure 1
• FIG. 3 is a diagrammatic, side and enlarged view illustrating the bearings of FIG. 2 in a first relative position,
• Figure 4 is a view similar to Figure 3 illustrating a second relative position of the bearings.

There is shown schematically in FIG. 1 an offset press 1 which essentially comprises a frame 2, a plate cylinder 3, a blanket cylinder 4 and a pressure cylinder 5.

The blanket 4 and pressure 5 cylinders have identical diameters double that of the plate cylinder 3.

The frame 2 essentially comprises two lateral uprights 6 in the form of vertical panels and only one of which is visible in FIG. 1. These uprights 6 are arranged on either side of the cylinders 3 to 5.

The cylinders 3 to 5 are rotatably mounted by each of their ends on the uprights 6, as will be described later, in order to be able to rotate each around a respective longitudinal central axis A3, A4 and A5.

More specifically, and as illustrated by FIGS. 1 or 2, each longitudinal end 31 of the plate cylinder 3 is rotatably mounted on the corresponding upright 6 by means of a first bearing 32 laterally on the outside and of a second bearing 33 laterally inside.

The press 1 being substantially symmetrical with respect to a median vertical plane, only the connection of one end 31 to the frame 2 will be described later.

The bearings 32 and 33 are spaced from each other by a non-zero distance d along the longitudinal axis A3 of the plate cylinder 3.

The bearings 32 and 33 each comprise a bearing 34. The bearing 34 of the bearing 32 is supported on a first region 35 of the end 31 considered. The bearing 34 of the bearing 33 is supported on a second region 36 of the end 31 considered.

The bearings 34 have central geometric axes which constitute those of the bearings 32 and 33 respectively. These axes, which are tangent to the axis A3 in regions 35 and 36, will be referenced A32 and A33.

Note that the bearings 34 have not been shown in Figure 1 to facilitate the representation.

As illustrated in FIG. 2, the second bearing 33 comprises a sheath 331 flanged by a laterally external flange 332 at the corresponding upright 6. The second bearing 33 is therefore fixed relative to the frame 2.

A stepped bore 333 is formed in the sleeve 331.

This bore 333 comprises a laterally inner section 334 centered on the axis A3, an intermediate section 335 also centered on the axis A3 but of smaller diameter than the section 334, and a laterally outer section 336 of larger diameter than the section intermediate 335 and offset from the A3 axis. The section 336 is centered on an axis P3 situated in the same vertical plane as the axis A3 above the latter. Typically, the distance separating the axis A3 and the axis P3 is 3 mm.

The bearing 34 of the second bearing 33 is arranged in the inner section 334 of the bore 333.

The first bearing 32 comprises a movable support 321. The support 321 has the general shape of a circular flat plate centered on the axis P3 and extended upwards by a drive arm 322.

A circular bore 323 is formed in the support 321. This bore 323 is eccentric relative to the axis P3, the center of the bore 323 being located substantially opposite the axis P3 relative to the arm 322.

The support 321 is extended laterally inwards by a sleeve 324 received in the laterally outer section 336 of the bore 333 of the sleeve 331, so that the support 321 can pivot in the sleeve 331 around the axis P3.

The bearing 34 of the first bearing 32 is received in the bore 323 of the support 321. The bearing 32 is therefore pivotable relative to the frame 2.

The offset press 1 further comprises for each end 31 of the plate cylinder 3 an adjustable displacement cylinder 37 connected by a first end to the corresponding upright 6 and by the other end to the arm 322 of the support 321 of the first bearing 32. The jack 37 is typically a pneumatic jack.

This jack 37 makes it possible to move the support 321, and therefore the first bearing 32, between two positions illustrated respectively in FIGS. 1 to 3 and in FIG. 4.

In the position of FIGS. 1 to 3 or first position, the axis A32 of the first bearing 32, and the axis A33 of the second bearing 33 are merged.

The first bearing 32 therefore has zero offset relative to the second bearing A33.

The longitudinal axis A3 of the plate cylinder 3 is therefore straight and the plate cylinder 3 is not subjected to any bending stress.

In the position of Figure 4 or second position, the cylinder 37 has caused the pivoting of the support 321 relative to the frame 2 around the pivot axis P3 clockwise.

Thus, the axis A32 of the first bearing 32 has pivoted around the axis P3 and is therefore no longer coincident with the axis A33 of the second bearing 33.

The axis A32 is then offset radially relative to the axis A33 substantially in the direction and in the direction of the bending force F exerted by the blanket cylinder 4 on the plate cylinder 3 when the press 1 is operating.

The longitudinal axis A3 of the plate cylinder 3 is then bent to be tangent to the axes A32 and A33 in the corresponding regions 35 and 36 of the ends 31 of the cylinder 3.

Thus, the plate cylinder 3 is prestressed in bending opposite to the force F. The first and second positions of the bearing 32 are end positions.

Note that in Figures 3 and 4 the pivot angle of the support 321 between its two positions and the distances between the axes P3, A33 and A32 have been exaggerated to facilitate the representation.

Note also that the bearings 34 of the bearings 32 and 33 have not been shown in Figures 3 and 4 to simplify the representation.

As can be seen in FIG. 1, each longitudinal end 41 of the blanket cylinder 4 is mounted, as in the prior art, on the corresponding upright 6 by virtue of a single bearing 42 movable relative to the upright 6. This bearing 42 has a structure similar to that of a bearing 32 and thus comprises a support 421 pivotally mounted on the corresponding upright 6 around an axis P4. The support 421 is extended by a drive arm 422. The support 421 has a bore 423 of axis A42 eccentric with respect to the axis P4 and receiving the end 41 considered of the blanket cylinder 4. An adjustable cylinder of displacement 47 is connected to the upright 6 and to the arm 422 to drive the support 421 in rotation about the axis P4 and therefore move the axis A4 of the cylinder 4 to bring it closer or away from the plate cylinder 3.

Each longitudinal end 51 of the pressure cylinder 5 is mounted, as in the prior art, on the corresponding upright 6 by virtue of a single bearing 52 movable relative to the upright 6. This bearing 52 has a structure similar to that of a bearing 32 and thus comprises a support 521 pivotally mounted on the corresponding upright about an axis P5. The support 521 is extended by a drive arm 522. The support 521 has a bore 523 of axis A52 eccentric with respect to the axis P5 and receiving the end 51 considered of the pressure cylinder 5. An adjustable displacement cylinder 57 is connected to the upright 6 and to the arm 522 to drive the support 521 in rotation about the axis P5 and therefore move the axis A5 of the cylinder 5 to bring it closer or away from the blanket cylinder 4.

Finally, the press 1 comprises conventional means, not shown, for driving the cylinders 3 to 5 in rotation about their axes A3 to A5.

To use the press 1, the respective longitudinal axes A4 and A5 of the cylinders 4 and 5 are moved, thanks to the movable bearings 42 and 52, in order to position them relative to the axis A3 in a manner allowing satisfactory transfer of the ink from the plate carried by the cylinder 3 towards the blanket carried by the cylinder 4 and towards the paper to be printed passing between the cylinders 4 and 5.

Such relative positioning is perfectly conventional for those skilled in the art and will therefore not be described in more detail.

Prior to this positioning, the first bearings 32 of the plate cylinder 3 have been moved from their first position to their second position or to an intermediate position under the action of the jacks 37.

The cylinder 3 is then bent as described above. Thus, when the blanket cylinder 4 is applied against the plate cylinder 3 to ensure satisfactory transfer of the ink, the bending force F applied by the blanket cylinder 4 on the plate cylinder 3 is compensated by the prestressing of the plate cylinder 3 created by the eccentricity of the first bearings 32 relative to the second bearings 33.

Thus, the overall deformation of the cylinder 3 when the offset press 1 is operating, measured for example by the deflection of the deformation of the cylinder 3, is particularly small. However, the diameter of the cylinder 3, and therefore its mass and associated costs, are reduced.

Thanks to the use of adjustable jacks 37, the preload applied to the cylinder 3 can be fixed at an acceptable value by placing the bearings 32 in intermediate positions between their first and second positions.

In reality, the bending of the plate cylinder 3 is limited on the one hand due to the presence for each end 31 of the plate cylinder 3 of two bearings 32 and 33 spaced apart longitudinally from each other, and d 'other part of the relative eccentricity of these two bearings 32 and 33 when the press 1 operates.

It should be noted that the first of this characteristic can be used alone to limit the flexing of the plate cylinder 3.

It has thus been found that under identical operating conditions, the use of two fixed end bearings spaced longitudinally from one another makes it possible to reduce the deflection deflection of the plate cylinder 3 by two.

More generally, the above principles can be applied separately or not to each of the cylinders 3, 4 and 5 of the offset press 1 to reduce their respective diameters, although they are of particular interest for the plate cylinder 3 since they avoid the problems associated with mounting large plates or simultaneously mounting two plates.

Thus, the diameters of cylinders 4 and 5 can also be reduced independently or not of that of cylinder 3.

Claims (8)

Offset press (1) of the type comprising a frame (2), at least one plate cylinder (3), a pressure cylinder (5) and a blanket cylinder (4) interposed between the plate cylinders and pressure, and bearings (32, 33, 42, 52) carried by the frame and receiving the longitudinal ends (31, 41, 51) of the cylinders so that each cylinder can rotate relative to the frame around a respective longitudinal central axis (A3, A4, A5), characterized in that the longitudinal ends (31) of at least one first cylinder (3) are each received in a first bearing (32) and a second bearing (33), the second bearing ( 33) being spaced from the first bearing along the longitudinal axis (A3) of the first cylinder (3). Press according to claim 1, characterized in that it comprises, for each end (31) of the first cylinder, means (37, 321, 322) for eccentricity of the first bearing (32) relative to the second bearing (33) . Press according to claim 2, characterized in that the first bearing (32) is movable relative to the frame (2) between a first weaker or zero eccentric position (Figure 3) and a second larger eccentric position ( Figure 4) relative to the second bearing (33), and in that the eccentricity means comprise means (37) for moving the first bearing (32) between its first and its second position. Press according to claim 3, characterized in that the first bearing (32) is pivotable relative to the frame around an axis (P3) substantially parallel to the axis (A33) of the second bearing (33). Press according to claim 3 or 4, characterized in that the displacement means comprise a jack (37) extending between the frame and the first bearing. Press according to one from claims 3 to 5, characterized in that , for each end (31) of the first cylinder (3), the displacement means (37) are adjustable to allow the first bearing (32) to be brought into an intermediate position between its first and its second position. Press according to one of the preceding claims, characterized in that the first cylinder is the plate cylinder (3). Press according to claim 7, characterized in that the plate cylinder (3) has a diameter smaller than that of the blanket cylinder (4).

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