A BLANKET FOR LINING THE CYLINDERS OF A PRINTING SYSTEM

Abstract: The blanket (2) comprises a base (3), an elastomeric layer (4), and an outer film (10) applied over the elastomeric layer (4); the film (10) has low affinity to printing ink and is formed from PVC, polyester, polyethylene, PTFE, or PVF, preferably from PVF.

Description: A blanket for lining the cylinders of a printing sys tem DESCRIPTION Tec ni p ca_l_Fτ_eJ.d Thi s i nventi on re lates to a b lanket for li ni ng the cy li nders of a pri nt i ng system, compri si ng a base and an e lastomeri c layer . ______2_______ Printing machines usually include a large number of cylinders performing a variety of functions. In particular, many cylinders are arranged to act in direct contact with the paper, to either transfer ink thereto (impression cylinders) or perform some other functions, typically such as paper conveyance or feed-in functions (transport cylinders) and counteracting the pressure from the impression cylinders (pressure cylinders). Even though the aforesaid cylinders are to perform different functions, they may be lined with the same blanket type, comprising a base and an elastomeric layer. This blanket, which has been specifically developed to fit. the requirements of the impression cylinders, is frequently employed on the pressure and transport cylinders as well, in order to provide similar mechanical and dynamic characteristics (specifically, deformabi Lity and peripheral velocity) for all the cylinder pairs acting on the paper and ensure, therefore, the highest possible paper handling and printing accuracy. This option clashes, however, with the productivity of the system, due to the frequent stops necessary to clean the pressure and transport rolls, which pick up from the freshly printed paper large amounts of ink and paper fiber particles. £i__i2§_.E_._2l________2_ The problem underlying this invention is to provide a lining blanket which is not easily fouled, and in any case, can be readily washed clean when used on pressure and transport cylinders without impairing the printing accuracy. This problem is solved, according to the invention, by a blanket for lining the cylinders of a printing system, which comprises a base and an elastomeric layer and is characterized in that it further comprises an outer film on " its elastomeric layer side, said film having low affinity to printing ink. The film does not affect the elastic characteristics of the blanket, which depend on the base . and the elastomer layer, but reduces drastically the chances of ink particles and paper fibrous matter becoming stuck to the blanket. Said film can be formed from a suitable polymeric material, to be selected preferably from polyvinyl chloride (PVC), polyester, polyethylene, polyvinyl fluoride (PVF), and polytetrafluoroethylene (PTFE). It has been found that PVF yields excellent results. Advantageously, the film is applied to the elastomeric layer by a cold rolling process before subjecting the elastomeric layer to vulcanization. In this way, perfect adhesion of the film on the underlying elastomeric layer can be achieved. Alternatively, the f lm may be structurally independent of the elastomeric layer/base, assembly and be simply combined therewith during the cylinder preparation/assembly stage. Further features and advantages of a blanket according to the invention will become apparent from the following detailed •• description of a preferred embodiment thereof, given with reference to the accompanyi ng drawi ngs . ____________E__2Q_2______i___ In the drawings: Figures 1 and 2 are fragmentary perspective views showing schematically two printing systems which employ rolls lined with the blanket of this invention; and Figure 3 is a sectional view through a blanket according to the invention. ______2____2___________2_____________i2_ Shown schematically in Figure 1 is a detail view of a printing system S, in particular a roto-offset printing system comprising a unit S1 for printing in four colors on a side A of paper C, and a unit S2 for printing in a single color on the other side B of the paper C. Each unit, S1 and S2, comprises impression cylinders R and pressure cylinders P lined with a blanket 2 in accordance with this invention. Figure 2 is instead a detail view of a different printing system S', in particular a flexographic printing system, comprising a unit S' for printing in a single color on the two sides A' and B' of paper C*, and a unit S2' for printing in four colors on just the side A". Each unit, S1', S2' comprises impression cylinders R' and pressure cylinders P 1 lined with the blanket 2. The blanket 2 comprises a base 3 and an elastomeric layer 4; the base 3 consists, in turn, of a plurality of plies 5 interleaved with layers 6 of an elastomeric material. One of the layers 6 may be a so-called compressible layer comprising a microporous structure with closed or open cells. The blanket 2 further comprises an outer film 10, applied onto the elastomericLayer 4 and formed from polyvinyl fluoride (PVF). For making the blanket 2, use is made, at an initial stage, of a conventional method whereby the base 3 and overlying elastomer That method includes sequential steps for coating the plies with elastomeric material, and the coupling of further plies together by a cold rolling process. Prior to subjecting the base 3 with the layer 4 to vulcanization in order to stabi lize -the elastomeric layer 4, the film 10 is cold rolled thereon. Thereafter, the green blanket 2 is subjected to vulcanization, thereby accomplishing at one time stabilization of the elastomeric layer 4 and the anchoring of the film 10 thereon. The blanket 2 so obtained has an outward surface which has an extremely low affinity to printing ink and can be readily washed clean. In addition, the film 10 provides excellent resistance to surface abrasion, as well as excellent chemical resistance to the action of the solvents usually employed with printing systems.

Claims: CLAIMS 1. A blanket for lining the cylinders of a printing system, comprising a base (3) and an elastomeric layer (4), characterized in that it further comprises an outer film (10) on its elastomeric Layer (4) side, said film (10) having low affinity to printing ink. 2. A blanket according to Claim 1, characterized in that said film (10) is made of a material selected from a group including polyvinyl chloride (PVC), polyester, polyethylene, polyvinyl fluoride (PVF), and polytetrafLuoroethylene (PTFE). 3. A blanket according to Claim 2, characterized in that said material is PVF. 4. A blanket according to the preceding claims, characterized in that it is formed by cold rolling said film (10) over the elastomeric layer (4) prior to subjecting the elastomeric layer (4) to vulcanization. 5. A blanket according to the preceding claims, characterized in that the film (10) is structurally independent of the elastomeric layer (4)/ base (3) assembly and simply combined therewith during the cylinder making/assembling stage.

Inventors: CASTELLI FRANCESCO, INVERNIZZI GIAMPIETRO, CASTELLI, FRANCESCO, INVERNIZZI, GIAMPIETRO
Applicants: REEVES SPA, REEVES S.P.A.
Application year: 1990
Main classification: B41N10
IPC codes: B41F30, B41N10