FR2702706A1 - Printing unit of a rotary offset printing machine. - Google Patents

Abstract

The invention relates to printing machines. The aim here is to reduce the tendency to soiling by ink and paper dust on a cylinder (14) acting only as a back-pressure cylinder, in a printing unit having several double printing units ( 1, 2) arranged one above the other and working in the blanket-blanket principle. For this, the transfer cylinder (14) has an ink repellant lining. Main application: rotary offset printing machines.

Description

The invention relates to a printing unit

  for a rotary offset printing machine, including

  several printer groups arranged one on top of the other and each working according to the blanket-blanket principle, and in which at least

  one of the transfer cylinders does not carry an im-

  awarded and, selectively, no plate cylinder

is associated with him.

  Printing units of this kind are universal.

  are known and speak, for example of a "turn of eight" when four double printer groups are arranged one above the other With such a "turn of eight", a band can be printed in four colors on both For the case where one side of the tape should only be printed in three colors,

  must put a print station at a standstill, that is,

  say stop printing, or the printing group does not have to be put in place However, we need a cylinder that serves as a counter-pressure cylinder for the

  group printing on the other Lace of the band This cylinder

  dre accumulates ink and paper dust from the printing station that precedes it in the direction of unwinding

  of the band (deposit phenomenon).

  In the case of a cylinder belonging to a

  printing machine with double printing units

  placed on top of each other, and who

  only the function of a counterweight cylinder

  the object of the invention is to reduce or completely eliminate the tendency to stain by the ink and the

paper dust.

  According to the invention, this problem is solved by the fact that the transfer cylinder has a filling

which repels the ink.

  Figures in the attached drawing, given only

  by way of example, make it clear how

  vention can be achieved In this drawing,

  Figure 1 shows two printing groups dou-

  placed on top of each other by a schematic side view.

  Figures 2 and 3 represent different

  nitrite for a back-pressure cylinder, by

sectional views.

  In FIG. 1, two printer groups doubly

  1, 2 are arranged one above the other. The double printer units 1, 2 can be considered as parts of a six or eight tower, when one or

  two other double printing units are located

  above these groups The printing group double

  1 includes printer groups 3, 4 which include

  each is a plate cylinder 1, 6 and a transfer cylinder 7, 8; the printing unit 2 comprises the

  printing units 9, 10 which each comprise a cylinder

  plate holder 11, 12 and a transfer cylinder 13, 14.

  A wetting device and a washing device

  16 are associated with the transfer cylinder 14.

  In the represented state of the group tower im-

  In principle, a strip 17 receives a 2/1 print, as indicated diagrammatically by the triangles. The printing unit 10 is at a standstill, that is to say that its transfer cylinder 14 does not carry a printed image. on the strip 17 For this purpose, the plate cylinder 12 is put out of contact with the transfer cylinder

  14 However, the plate cylinder 12, with the disc

  inking unit and the anchoring device not re-

  presented, could be entirely absent.

  The transfer cylinder 14 is lined with a blank

  chet 18 and a metal plate 19 superimposed These

  two elements are preferably stretched by means of

  clamping elements provided in the transfer cylinder 14 for fixing the blanket This may be, for example, a screw tension device not shown For this, the ends of the blanket 18 and the metal plate 19 are clamped in tension bars 20 (Figure 2)

  which are hooked into the screws of the tensioning device

  The blanket 20 may be a flexographic blanket or a compressible or incompressible blanket.

  However, it is also possible to use a supernatural

  simple port of another type The metal plate 19 may be constituted by a steel sheet, a film

  of steel or chromed sheet Thanks to the lipo-

  phobes of these materials, the deposition of ink and paper dust on the transfer cylinder 14 is removed in

  Moreover, this cylinder can be humidified by means of

  wetting agent 15, which reinforces the anti-decay effect

  The cleanliness of the transfer cylinder 14 may still be

  improved by using a washing device 16 which works better, for example, in the case of a

  chromed layer than in that of a rubber blanket

  The implementation of the wetting device or the washing device is not absolutely prescribed by the invention. The metal plate 19 should be

  of a less rigid configuration and consequently

  This metal plate 19 and the blanket 18 can

  vulcanized or glued to one another

  of the metal plate 19, it is also possible to

  a film of plastic material on the blanket 18.

  According to other variants, the transfer cylinder 14 may be lined only with an ink repellent blanket, an ink repellent metal plate or an ink repellent plastic film, which are example, taken in voltage bars as shown in Figure 2 and hung in the

  tension devices of the rubber blanket of the cy-

  The blanket may be composed of rubber

  rubber or an elastic plastic material and be

pressible or incompressible.

  FIG. 3 shows another variant for the ink-repellent lining provided for the transfer cylinder 14. Here, an ink-repellent layer 22, for example, a layer of chromium or nickel is deposited by evaporation on a blanket 21. blanket 21 is

  here also tight in tension bars 23 for ensuring

  tension. The use of the usual blanket tension elements belonging to the transfer cylinder to fix

  the ink repellent pad has the advantage of allowing

  to transform the cylinder for normal function

  blanket printing by very simple operations.

  In this way, it is possible to carry out

  in a very fast and economical way a group of

  printing 10 which was not present in the initial state

  tial. The invention can be applied in many different ways when, in a printing unit comprising a larger number of printer groups

  placed on top of each other, for example

  in the case of a tower of eight, more than one printing station may be shut down or not dismantled. R E V E N D I C A Or I Y N S 1 Printing unit belonging to an offset rotary printing machine, consisting of several double printing units arranged one above the other

  and who work each according to the whiteness-

  blanket and in which at least one of the cylinders of

  report does not postpone the printed image and selectively

  There is no cylinder plate associated with it, which is

  characterized in that the transfer cylinder (14) has

  a pad that repels the ink (18, 19; 21, 22).

  Printing unit according to claim 1, characterized in that the transfer cylinder (14) is

  lined with a blanket repelling the ink.

  Printing unit according to claim 1, characterized in that the transfer cylinder (14) is

  lined with a metal plate repelling the ink.

  Printing unit according to claim 1, characterized in that the transfer cylinder (14) is

  lined with a sheet of plastic material repelling the

  cre. Printing unit according to one of the preceding claims, characterized in that the ink-repellent liner (19) is applied to a blanket (18) and tensioned therewith on the transfer cylinder

(14).

  Printing unit according to claim 1, characterized in that the ink-pushing liner is tensioned on the transfer roll (14) in a state

fixed jointly to a blanket.

  Printing unit according to Claim 1, characterized in that, on the transfer cylinder (14),

  is stretched a blanket (21) on which a layer repouss-

  the ink (22) is deposited by evaporation.

  8 Printing unit according to one of the claims

  prior art, characterized in that a wetting device (15) is associated with the transfer cylinder

(14).

  9 Printing unit according to one of the claims

  previous arrangements, characterized in that a device

  washing (16) is associated with the transfer cylinder (14).