FR2548591A1 - OFFSET MACHINE - Google Patents

Abstract

OFFSET MACHINE INCLUDING A PLATE HOLDER CYLINDER 1, A PRINTING CYLINDER 2 THAT CAN ROTATE AROUND FIXED CENTERS AND A BLANCHET CYLINDER 3 SUPPORTED AT EACH END BY A RESPECTIVE LEVER 7 CONNECTED BY A SWIVEL MOUNT OF 14 TO A LEP WAY THAT THE MOVEMENT OF THE LEVER 10 DRIVES THE MOVEMENT OF THE BLANCHET CYLINDER BY MOVING IT CLOSER AND AWAY FROM THE PLATE HOLDER CYLINDER AND THAT THE MOVEMENT OF THE LEVER 7 CAUSES THE MOVEMENT OF THE BLANCHET CYLINDER AND BY REACHING IT. AWAY FROM THE PRINTING CYLINDER. EACH LEVER HAS A "PIVOT WITHOUT AXIS" 13, 14 BECAUSE IT IS MADE FROM A SINGLE PIECE WITH A FLEXIBLE AREA AND A CORRESPONDING MOUNTING SQUARE. THE LEVERS AND THE SIDE FRAMES OF THE MACHINE HAVE MOUNTING HOLES 30, 32 WHICH RECEIVE ANCHORS 35 SUITABLE FOR IMMOBILIZING THE LEVERS AND ASSEMBLY MEANS ARE PROVIDED TO IMMOBILIZE THE BLANCHET HOLDER CYLINDER TO CARRY THE LIA. BLANCHET AND LEVERS AND TO ADJUST THE ADJUSTABLE STOP SCREWS ASSOCIATED WITH THE LEVERS.

Description

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OFFSET MACHINE

  The present invention relates to an offset machine and in particular the mounting of the dropping cylinders on the machine namely the plate cylinder, the blanket cylinder and the printing cylinder. An offset machine has the three cylinders designated above arranged so that in the "printing" position the blanket cylinder is in contact with both the printing cylinder and the plate on the cylinder -plaque for an inked image formed by the application of ink on the zones of the oleophilic image of the image (the ink being rejected by the oleophobic zones, that is to say without image, thanks to the action of the aqueous wetting solution applied to the plate) is first transferred to the compressible blanket mounted on the blanket cylinder and then to the copy sheet, for example a sheet of paper pinched between the blanket cylinder

and the printing cylinder.

  There is an intermediate position sometimes referred to as a "preprint" position in which the plate mounted on the surface of the plate cylinder is in contact with the compressible blanket on the blanket cylinder but the printing cylinder is then removed from the blanket cylinder so that there is no printing This position is adopted during the operation of the machine when it is desired to feed the machine unprinted sheets, for example to test the passage of This position is often adopted automatically during start-up at the time of inking the image and progressively transferring the image to the transfer blanket before passing the first sheet between the blanket and the printing cylinder. The third conventional position is the "neutral" position in which the blanket cylinder has been separated from both the plate cylinder and the printing cylinder, the machine then being able to remain at rest with all the cylinders spaced apart from each other. Other and therefore without ink transfer The "neutral" position is adopted at the time of shutdown so as to avoid localized points of fatigue of the blanket where it would remain in pressure contact with the plate cylinder

and the blanket cylinder.

  Pre-determined printing pressures are required to obtain optimal transfer of the image (i) from the blank to the blanket and then (ii) from the blanket to the sheet, and it is this need for effective contact pressure between the blanket and the other two cylinders which firstly result in fatigue of the blanket and secondly disappear momentarily if due to fatigue, a tired area of the blanket came a) in contact with the cliché and b) in contact

with the printing cylinder.

  To some extent, the printing pressures may vary and maximum and minimum values are known for any machine and range of blanket / paper / paper characteristics. However, the envelope of allowable tolerances between these two values may be exceeded if several sheets pass simultaneously or if thinner sheets of paper than the usual sheets are introduced into the machine In the past, this problem has been solved by using spring thrust or gravity pushing to obtain the printing pressures, rather than relying on a fixed mutual positioning of the cylinders in the "printing" position to obtain sufficient compression of the blanket and to obtain the printing pressure The spring loaded or gravity driven machines have the advantage of being compensate for the different thicknesses of paper and / or cliché and to avoid damage to the blanket passing case of a

  "pack" of leaves or more leaves.

  Conventional assemblies of self-compensating cylinders employ simple pivoting levers which are actuated by cams or other similar mechanisms. It is also common for machines of this type to move two of the three cylinders relative to each other.

  to the third in order to obtain the gap and the desired contact.

  According to a first aspect of the present invention, there is provided an offset machine in which at least one of the three planetary, plate and printing cylinders is supported at each end by at least one lever so that the lever or each levers comprise a flexible zone which connects it to a corresponding mount, the lever, its flexible zone and its frame

  being made of a single piece.

  A preferred embodiment of the first aspect of the present invention provides a printing machine of this type in which respective cam follower and cam mechanisms cooperate with the first and second levers and wherein the cam and follower mechanism cam associated with the first levers controls the movement of the blanket cylinder by moving it closer to and away from the plate cylinder, and the function of the cam and follower mechanism cooperating with the second levers controls the movement of the cylinder -bleach by bringing it closer and away

of the impression cylinder.

  The invention also provides a method of assembling the preferred embodiment of the first aspect of the offset machine defined above, comprising assembling the first and second levers together, in pairs each comprising a first lever and a second lever supported. by the first; the immobilization of the blanket cylinder by the use of a mechanism which fixes the

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  blanket cylinder relative to the side frames; attaching these pairs of levers to the machine by immobilizing the pivot mounting of each first lever to the side frame of the machine; immobilizing the first and second levers by means of axes introduced into respective pairs of aligned holes, one of which is in one of the levers and the other in a side frame

  partner; attaching said blanket cylinder to said second levers; and then disassembling said 10 axes.

  The following description is intended to do better

  to understand the present invention, with reference to the accompanying drawings, given by way of example and in which: FIG. 1 illustrates the three cylinders in the "printing" position and clearly shows the mounting of the movable blanket cylinder; FIG. 2 shows the same three cylinders but with the blanket cylinder in its displaced position, that is to say in the "neutral" position when the three cylinders are spaced from each other and, FIGS. 3 and 4 are detailed sections indicating the use of the axes and stop axes engaged in the side frames of the machine. FIG. 1 shows the uppermost plate cylinder 1, the lowest printing cylinder 2 and the blanket cylinder 3 between the two. The centers 1a, 2a and 3a of these three cylinders form an angle substantially 135 and the center of the plate cylinder is placed on the vertical passing through the center of the blanket cylinder in the printing position, the center of the printing cylinder being offset on one side and

  below the blanket cylinder.

  It will be readily understood that during normal printing operations, there is a flat printing plate 35 on the outer cylindrical surface of the plate cylinder 1 and a compressible rubber blanket on the cylindrical surface of the blanket cylinder 3 , and that there is a suitable sheet feeding mechanism (not shown) which introduces individual sheets of paper or possibly a

  continuous roll of paper which passes into the space between the blanket cylinder 3 and the impression cylinder 2.

  The blanket cylinder 3 presents at each

  end of a shaft portion 4 journalled in a boss 10 5 forming part of a mounting block 6 attached to a lever 7.

  The lever 7 is effectively able to pivot relative to a one-piece mounting bracket 8 at one end, the mounting bracket being secured by screws (not shown) at locations 9 to a similar lever 10 which includes itself a mounting bracket of a single piece 11 in this case fixed to the frame of the machine by screws (not shown) at the locations 12 of the mounting bracket can be seen mounting bracket 8 located so that the flexible zone 14 is substantially equidistant from the ends of the lever 10 on which is fixed

mounting bracket 8.

  The lever 10 is assembled to its mounting bracket 11 by a zone 13 of substantially flat shape between the fixed mounting bracket 11 having an L-shaped cross-section and the L-shaped cross sectional profile of the lever so that this plane area 13 is able to bend in bending mode to allow the free end of the lever 10 to move exactly

  in the same way as the end of a pivoting lever.

  It is, however, significant that the mounting bracket 11 on one side of the flexible zone 13 is integral with the flexible zone and has the same L-shaped cross section as the lever 10 - even placed

  opposite side of the flexible zone 13 This transverse section

  Dirty L gives both the square 11 and the movable lever 10 a certain flexural stiffness compared to the relatively greater flexibility of the flexible flat area 13 The rigidity of the flat area 13 can be controlled by a suitable choice of its width (the dimension measured towards and away from the paper on which FIG. 1 is drawn) as a function of its thickness and the bending strength of the material with which the first lever is constructed Although this is not the case. shown in the drawing, the flexible zone 13 is narrower than the coplanar portions forming the corresponding arm of each mounting bracket 11 and the movable lever 10 so as to ensure that in the flexible zone 13 there is no residue of the fold of the metal blank in which the lever 10, the mounting bracket 1 i and the flexible zone 13 have been stamped In addition, this narrowing is obtained by means of a cutout stamped and curved so that it does not there are no sharp angles in

  which fatigue constraints can be established.

  The lever 7 and its mounting bracket 8 have their own flexible zone 14 in one piece and these three elements are substantially identical to the lever 10, to the square of

  mounting 11 and the corresponding flexible zone 13.

  Remembering that the lever 10 is supported by the frame of the machine and the lever 7 by the lever 10 itself, we go throughout this description designate

  the lever 10 with its flexible zone 13 and its mounting bracket 11 as "the first lever" and the lever 7 with

  its flexible zone 14 and its mounting bracket 8 as the "second lever".

  It will of course be understood that on each side of the machine (i.e. at each end of the laundry cylinder 3) there will be a second pair of levers which are generally similar to the first and second levers shown in the figure. 1, but which are stamped in the opposite direction from identical blanks so as to ensure that the first and second levers on one side are mirror images of the corresponding first and second levers on the other side. side of the machine. The first lever carries a first secondary lever which pivots with respect to the first lever 16 and supports a cam follower 17 which moves on a D-shaped cam 18 having a flat portion 18 'and the remainder 18' being cylindrical A coiled coil spring 19 has its first end fixed to a lug 20 of the frame of the machine and its second end attached to the tip 15a of the first secondary lever 15.

  opposed 15b of the first secondary lever 15 carries an adjustable screw 21 and a lock nut.

  In the same way, the second lever carries at its free end a second secondary lever 22 pushed by a spring in the direction of the arrow 23 of Figure 1 to maintain an adjustable locking screw 24 at the opposite end of the second lever secondary 22 in contact with the arm 7a of the lever 7 while the follower cam follower 25 carried by the second secondary lever 22 is in contact with a rotating cam 2 D-shaped, the

  second secondary lever 22 pivoting with respect to the second lever about the pivot 27.

  It is important to note that the location of the soft zone 14 associated with the second Greyhound is on the line joining the centers 1a and 3a of the platen cylinder and the blanket cylinder, respectively. Turning now to Figure 2, it will be seen that the D-shaped cam 18 acting on the first secondary lever 15 has moved into a position in which its planar portion 18 'is now in contact with the cam follower 17 and in the same way the D-shaped cam 26 acting on the second secondary lever 22 has turned to a position in which its planar portion is in contact with the cam follower roller 25 In this position, the flexible zones 13 and 14 undergo a bending force Under the effect of the rotation of the first mentioned cam 18, the blanket cylinder 3 is lowered away from the plate cylinder 1 and following the rotation of the second In the mentioned cam 26, the blanket cylinder has moved to the right away from the impression cylinder 2. The material and thickness of the blank in which the first lever (including the lever, its mounting bracket 11 and its soft area e 13) has been manufactured are carefully selected so that the flexural stiffness of the flexible zone 13 is sufficient to avoid any undesirable flexing modes in the zone 13 However, the flexible zone 13 must be able to flex that the first lever moves in the appropriate direction as would a pivoting lever. In the same way, the material chosen for the blank in which the second lever (constituted by the lever 7, its mounting bracket 8 and its flexible zone 14) is stamped was chosen from the same considerations. bending deformation to separate the cylinders from the sufficient value (the standard value of this deviation is of the order of 0.5 mm) so that the possibility of a fatigue failure of the zones

flexible 13 and 14 is eliminated.

  It is particularly significant that both (i) the lever 10 and its mounting bracket 11 are in one piece with the adjacent flexible zone 13 and (ii) the other lever and its mounting bracket 8 are of one single piece with the associated flexible zone 14 so that it is not necessary to connect a prefabricated flexible piece 35 to a lever and a prefabricated mounting bracket

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  separately with the possible consequences of a link defect There are known disclosures of the use of flexible zones instead of pivots under conditions where repeated reversals of effort occur but o small efforts are made. exert on flat springs; For example, the text presented by Earl Masterson at the Spring Joint Computer Conference held in Boston, USA, April 26-28, 1966. which are shown in Figures 2 and 3 are springs

  separated tight between the mounting pieces.

  The advantage of using the flexible zones 13 and 14 to obtain the pivoting movement of the first and second levers is that there is no possibility of undesirable wear likely to occur during use of the machine. print which would require a new adjustment of the machine or the replacement of any pivot bearing during the life of the machine It is surprising that the use of these flexible parts 13 and 14 In Figures 1 and 2 of the present application does not reduce the duration of the offset machine, despite the fact that it is expected that the flexible zone 14 withstands a longitudinal stress while undergoing a bending stress which should not interfere to a large extent with the pressure on

  the blanket cylinder space / impression cylinder.

  A typical cycle of operation of the machine will now be described beginning with position 30 of FIG. 2 or "neutral position".

  When the three cylinders 1, 2 and 3 are thus separated from one another, the blanket of the blanket cylinder having been cleaned to eliminate the previous image and a plate placed on the plate cylinder 1

  having already received an activation solution that makes

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  In the hydrophilic non-image areas, the plate cylinder 1 is rotated by bringing the plate into contact with the first inking system roll (not shown) to form an inked image on the hydrophobic but oleophilic areas of the image This rotation can be performed for several turns before the blanket is brought into contact with the plate by a rotation of the cam 18 which moves its flat portion 18 'of the follower cam follower 17 which raises the follower 10 cam 17 to pivot the first pivot clockwise by returning its flexible zone 13 to the rest position, or this rise of the blanket cylinder 13 can occur immediately

  after the start so that the inked image refers to the blanket at the same time as it is formed on the plate.

  After the desired number of turns of the platen cylinder 1 to ink the image properly, the machine is ready to print and the paper feed system is put into operation When the first sheet 20 passes in front of the paper detection system, the cam 26 rotates to the position it occupies in FIG. 1 thereby pivoting the second lever clockwise and causing its associated flexible zone 14 to relax when the blanket cylinder 13 is fed to the left in the direction of the impression cylinder 2 This movement occurs as the conventional flat areas (not shown) of the blanket cylinder 3 and the impression cylinder 2 receiving the blanket fastening clamps for the blanket cylinder and the printing cylinder paper clamps are facing each other Therefore, there is no noisy contact and the cylinders 2 and 3 gradually come into contact with each other. contact only when the

  flat parts are no longer facing each other A succession of sheets of paper passes between the cylinder

  blanket 3 and the impression cylinder 2 in synchronism with the passage of the image areas of the blanket 3 so that the image of the blanket is carried on the sheets

of paper.

  When the desired number of copies has been printed, the cam 26 returns to the position it occupies in FIG. 2 to return the machine to the pre-printing position and the tension of the spring 28 (FIG. 2) then deforms the flexible zone. 14 In the same way, if at any stage of printing a paper feed defect occurs and no sheet of paper enters the space between the cylinder blanket 3 and the impression cylinder 2, the paper detection system (not shown) will rotate the cams 18 and 26 to the position of FIG. 2 so that the arrival of their flat portions in contact with the cam follower rollers pulls the springs 19 (Fig. 1) and 28 (Fig. 2) by rotating the second levers 15 and 22 counter-clockwise and effectively separates the slatted cylinder 3 from both the impression cylinder 2 and plate on the plate cylinder 1 in order to avoid unwanted inking of

  the cylindrical surface of the impression cylinder 2.

  From the pre-printing position, the printing can be resumed by rotating the cam 26 again to the position of FIG. 1 to return the machine to the printing position, but at the end of a printing cycle, the cam 18 will rotate to the position of Figure 2 in which the traction exerted by the spring 19 on the free end of the first secondary lever 15 will rotate the first lever in the opposite direction of the needles a watch to constrain the flexible zone 13 in bending mode and lower the blanket cylinder 3 away from the cylinder

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  plate holder 1 (while keeping it off contact with

the impression cylinder 2).

  After disassembling or automatically ejecting the cylinder 1 image, the image on the blanket 3 can be removed by a blanket cleaning system (not shown) during the continuous rotation of the cylinders and then a new photograph can be placed on the blank.

clutch cylinder 1.

  The cams 18 and 26 rotate under the effect of any suitable positive circuit, for example by means of levers driven by solenoids which can be actuated electrically by signals controlled by a microprocessor or by any other device. In fact, the use of solenoids is not essential to the present invention. The cams 18 on both sides of the machine are supported by a first common drive shaft. and the two cams

  26 are supported by a second shaft.

  The stop screws 21 and 24 have functions that will

now be defined.

  The printing pressure between the blanket and the plate is obtained by the fact that at the moment when the cam follower rollers 17 of the first secondary levers 15 are on the cylindrical portions of the respective D-shaped cams 18 the cylinder The blanket is held upward against the plate cylinder 1 in a position sufficient for the blanket sg to compress sufficiently to apply the desired printing pressure against the plate. For this, the stop screws 21 are adjusted so that the tips other screws just come into contact with the wings 10 has levers 10 when using the cliche and the blanket

the thinnest.

  It will of course be understood that if each pebble is

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  The cam lever 17 was supported by the respective lever itself, which naturally has a rigid construction, the soft zones 13 would be damaged in case a plate of different thickness would be attached to the plate cylinder 1, or in case of replacement. a thinned blanket thinned on the blanket cylinder 3 by a blanket which has been reconstituted and thickened by the use of one of the known blanket reconstitution products. To avoid this risk, the first secondary levers 15 pivot in 16 relative to the lever 10 and are held in a substantially fixed position with respect to the lever 10 under the effect of the tension springs 19 which rotate each first secondary lever 15 counterclockwise around 15 of the axis of the cam follower follower corresponding 17, in

  thus maintaining the abutment screw ends 21 near or in contact with the wings O 10 has levers 10.

  In the event of a blanket change or a change of the plate, the blanket cylinder 3 can descend and therefore, although the cam follower rollers have a fixed position imposed by the radius of the cylindrical surface 18 "of each cam 18, the descent of the blanket cylinder 3 is enabled by the spacing of the ends of the abutment screws 20 relative to the wings 10a and the slight rotation of each first secondary lever 15 about the axis of the cam follower roller corresponding 17 at the time of the extension of the spring 19 This "floating" of the first secondary lever 15 results in a substantially constant cliché / blanket pressure (due to the small extension of the spring 19) imposed by the tension of the

spring 19.

  The precise position of the blanket cylinder 3 by

  relative to the plate cylinder 1 when the tip of the stop screw 21 is again in contact with the wing 35 a is, as already indicated above, deter-

  by the appropriate adjustment of the stop screw 21 which can be retracted or out of the threaded hole of the end 15b of the first secondary lever 15 In the unlikely case that an even thinner plate or blanket 5 would be used, the blanket cylinder 3 will not move so that the pressure between blanket and plate will decrease when the compressible blanket goes

slightly relax.

  Similarly, the accidental passage of several sheets of paper between the blanket cylinder 3 and the impression cylinder 2 will cause a movement towards

  the right of the blanket cylinder 3 which will naturally be allowed by the spacing of the ends of the stop screws 24 relative to the flanges 7 has levers 7 and the slight corresponding extension of the spring 28 (Figure 2).

  As in the case of the stop screws 21, the adjustment of the stop screws 24 makes it possible to accurately position the blanket cylinder 3, and thus makes it possible to adjust the compression of the blanket 3 in the space separating the cylinder blanket 3 of the impression cylinder 2 when the follower follower 25 of the second secondary levers 22 are on the cylindrical surfaces of the cams 26 and the ends of the screws 24 in contact with the

wings 7 a.

  Ansi, not only the two sets of adjustable stop screws allow the blanket cylinder 3 to deviate from a space in which there is a large thickness of unexpected cliché or blanket or paper, these two games also allow the setting of the precise position of the blanket cylinder which, of course, establishes the necessary printing pressures between, firstly, the blanket and the plate and, second, the blanket and the sheet in the printing space.

  when using very thin materials.

  It follows from the description above that the zones

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  The flexible members 13 and 14 undergo bending mode stresses when the cylinders are separated (as a result of "reprocessing" the cams 18 and 19 when their planar portions come into contact with the cam follower rollers 17 and 25 which allows the cam assemblies and secondary lever 7, 22 and 10, respectively to "lock" so that the low tension of the springs 19 and 28 is amplified by the lever action to apply a sufficient bending moment on the flexible zones 13 and 14 to overcome the flexural rigidity of the flexible zones 13 and 14); conversely, when the blanket cylinder 3 is in the printing position shown in FIG. 1, the flexible zones 13 and 14 are relaxed. It can thus be seen that the bending of the zones 13 and 14 does not generate the On the other hand, it simply raises the levers 7 and 10 so that they operate as "pivotless" pivoting levers to allow the displacement of the cam follower rollers 17 and 25 induced by the rotation of the cams 18 and 26 to rotate the first and second levers during the movement

  between the positions "separate rollers" and "rollers in contact".

  To enable assembly of the printing machine according to the present invention, the first and second levers and 7 respectively have mounting holes 30 and 31 which align with the corresponding mounting holes 32 (FIG. sides of the frame 34, of the machine so that common dowels 35 (Figure 3) can be introduced into these pairs of aligned mounting holes so that the mounting or marking positions of the first and second levers already connected are respectively maintained Suitable supports for mounting the bosses of the bearing 5 and the fastening blocks 6 of the carrier cylinder are also provided to support the carrier cylinder 3 in the desired register position corresponding to the reference positions.

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  First and second levers When the various components are thus maintained in their mounting position, the blanket cylinder can be attached to the lever 7 and the mounting bracket integral with the first lever 10 can be attached to the associated side frame 34 of the machine to allow assembly of the device Optionally, the stop screws 21 and 24 can now be adjusted to the correct position which corresponds to the correct printing pressures on the finest materials that can be expected . When the components are thus connected, the pegs 33 and 35 can be removed and replaced by other pegs 36 (FIG. 4) (in the holes 15 and 32), the difference between these other pegs 36 and the pegs 35 being that if both types of pins and 36 can be securely fastened in the hole 32 or 33 of the frame, the adjustment of the pins 36 in the holes 30 or 31 of the flexible part is loose and thus allows the necessary rotation of the lever 10 or lever 7 respectively while providing protection against excessive rotation which would naturally damage the

flexible zones 13 or 14 associated.

  It is considered important that the offset machine illustrated by the drawings only use the movement of the blanket cylinder 3 to take or leave its printing position, and that this movement is possible so that, if the cylinder axis The blanket holder 3 deviates from the axis of the plate cylinder (eg if a blanket or plate is thicker), the printing pressure between the blanket and the printing cylinder remains unchanged, and the same way, if the blanket cylinder 3 still deviates from the surface of the printing cylinder (for example in the event of a paper feed defect or in the case of the use of different sheets

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  thicknesses) this has no noticeable effect on the

  printing pressure between blanket and cliché.

  This has so far required the movement of two

  cylinders relative to the third.

  It will be appreciated that the cams 18 and 26 and their cam followers 17 and 25 may be replaced by any other suitable drive means; for example a rocking mechanism which can increase the mechanical advantage of the cylinder moving means. 10

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Claims (9)

  An offset machine in which at least one of the blanket, plate-holder and printing cylinders is supported at each end by at least one lever, characterized in that the or each lever (7) comprises a flexible zone. (14) which connects it to a respective mount (8) and by the fact that this lever, its zone   flexible and its mount are formed of a single piece.   2 Machine offset according to claim 1, characterized in that said lever (7) placed at each end of that of the cylinders associated therewith (3) is rotated between a first printing position in which the cylinder supported (3) is in contact with another one of said cylinders (2) and a second position in which the supported cylinder is out of contact with said other one of these cylinders, the driving action being controlled by a cam and follower system camming (25, 26) cooperating with the levers (7) of this pair.   3 Machine offset according to claim 2, characterized in that the assembly is such that the movement of the lever (7) to the second position applies a bending stress to the associated flexible zone (14) while   that the movement of this lever to its first position coincides with the bending relaxation of the flexible zone.   4 offset machine according to one of claims 2   and 3, characterized in that the blanket cylinder (3) is that which is supported by said levers (7); at each end of the blanket cylinder (3) a first lever (10) is attached to the frame of the machine and a second lever (7) is supported by said first levers; and at each end of the blanket cylinder (3) said second lever (7) is oriented substantially perpendicular to the first lever (10), the blanket cylinder being supported by said second levers (7).   Offset machine according to claims 2 and 4,   considered as a whole, characterized in that it comprises respective cam and cam follower mechanisms (17, 18 and 25, 26) which cooperate with the first levers (10) and the second levers (7) and by the fact that the cam and follower mechanism (17, 18) associated with the first levers (10) controls the movement of the blanket cylinder (3) by moving it closer to and away from the plate cylinder (1 ) and that the operation of the cam and cam follower mechanism   (25, 28) cooperating with the second levers (7) causes the movement of the blanket cylinder (3) by bringing it closer and away from the impression cylinder (2).   6 machine offset according to claim 5, characterized in that the axis about which pivot said second levers (7) is substantially in the plane joining the axes of rotation (3 a and la) of the cylinders blanket and plate holder.   An offset machine according to any one of claims 2 to 6, characterized in that each   said levers (7 and 10) are constructed in two parts constituting a same lever (7 and 10) and a corresponding secondary lever (22 or 15) pivoting at the free end of the first; the secondary lever (22 or 15) is in contact with a movement mechanism (25, 26 or 17, 18) for causing movement of the blanket cylinder (3); that the secondary lever (22 or 15) can still come into contact at a first end of the opposite side of its pivot (27 or 16) with the body of the main lever (7 or 10) via a stop mechanism adjustable (24 or 21), and that the free end of said second lever (22 or 25) is pushed (23 or 19) in a certain direction to maintain the first end of said secondary lever in contact with   the body of the main lever (7 or 10).   8 machine offset according to claim 7, characterized in that said adjustable stop mechanisms each comprise an adjustable stop screw (21 or 24) between each secondary lever (15 or 22) and the associated main lever (10 or 7) on which it is installed, said stop screws (21 and 24) being each adjustable to control the positioning of said supported cylinder   (3) in the first position of the first and second levers (10 and 7) associated therewith.   9 method for assembling an offset machine according to claim 5, characterized by the assembly of said first and second levers (10 and 7), in pairs each comprising a first lever (10) and a second lever (7) 15 supported by the first; immobilization of the cylinder   blanket carrier (3) by the use of mounting means for.   attaching the blanket cylinder (3) relative to the side frames (34) of the printing machine; attaching said pairs of levers (10, 7) to the machine by installing the pivot mounting (11) of each first lever (10) to the side frame (34) of the machine; immobilizing the first and second levers (10, 7) by pins (35) introduced into the respective pairs of aligned holes, the first hole (30 or 31) of which is in one of the respective levers and the other (32) in the associated side frame (34); attaching said blanket cylinder (3) to said second levers (7); and then the dismantling of pegs (35).   The method of claim 9, further comprising the step of introducing immobilizing pins (36) into said pairs of aligned holes (30, 32) to allow limited pivotal movement of said pins levers (7 and 10) during movement of the blanket cylinder (3) toward and away from both the plate cylinder (1) and the impression cylinder (2).   Method according to claim 9, characterized in that the offset machine is according to claim 7, and further characterized by the step of adjusting said adjustable stop means (21, 24) associated with both the first levers (10) and with the second levers (7) to compensate for inadvertent movement while the pins (35) are in place after the cylinder blanket (3) has been fixed to the second levers (7). 10