GB1560287A - Offset printing machines provided with alternative water and water-alcohol mixture wetting systems - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE OFFSET PRINTING MACHINES PROVIDED WITH ALTERNATIVE WATER AND WATER-ALCOHOL MIXTURE WETTING SYSTEMS (71) We, O.M.C.S.A. OFFICINE MEC CANINE CIGARDI, Body Corporate organised under the Laws of Italy, of 45, Via Manzoni, 20021 Bollate, Milano, Italy, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be described in and by the following statement: The present invention relates to offset printing machine having an improved wetting device, based on a water and wateralcohol mixture.

As it is known, the offset type of printing machines are broadly known and used and due to this reason a detailed description thereof is deemed not necessary.

It should however be pointed out, in order to obtain a complete understanding of the invention, that in the offset lithographic system, being the "form" (or "plate") completely flat, (i.e. not in relief), the inking is carried out by exploiting a well determined physical-chemical process.

This process, which is at the base of the offset photographic inking, causes a repulsion between the fat substances (which in the instant case consist of the printing inks) and the water (or, more generally, the wetting liquid).

In particular, the surface of the plates (made of zinc, aluminium or of multiple different metals), on which has been previously formed the drawing and/or pattern to be printed, has to be moistened, before the linking operation, in order to assure the necessary repulsion of the ink from the not engraved or etched portions.

Accordingly, each printing unit of the offset printing machines is provided with a "wetting or moistening device", which acts to moisten or wet the plate as wound onto the "cylinder-plate", and an independent "inking device".

These wetting devices comprise a plurality of counterwatating rollers, (in part driven and in part friction-moved by the adjacent rollers), including at least a so-called"drawing" roller, which is partially immersed in the wetting liquid, and at least a so-called "wetting" roller.

This latter tangentially contacts the cylinder-plate and another intermediate roller which, through a further roller receives, by tangential contact, the wetting liquid from the drawing roller.

The wetting roller (or rollers) is generally coated by rubber and, if necessary in order to assure an optimal supplying of the liquid, by a braiding or textile covering.

One of the intermediate rollers is provided with a reciprocating axial movement, in order to aid a homogenous distributing of the wetting liquid, which is received and carried by surface adhesion.

Due to this reason and on the analogy of the rollers provided with this type of movement, which are present in the inking assemblies, it is called "vibrating" roller.

It is also known that in the offset printing it is essential to maintain an equilibrium between the water and ink and that the ideal equilibrium is obtained as it is possible to reduce to a minimum the water amount sup plied to the plate, and adjust the ink under these conditions of minimum wetting.

The metering of the wetting liquid, transferred to the plate, is obtained in different ways: for example, one of the intermediate rollers, in particular that called "ductor" roller, which is located adjacent to the drawing rollers, is supported in such a way as to be shiftable, parallely to itself, and it is cyclically moved or driven, in such a way as to move away and rest again periodically onto said drawing roller.

Due to this movement, the liquid amount transferred onto the plate, is a function of the ratio of the operation effective time of the printing unit and the sum of the inter mittent contact times of the ductor and drawing rollers.

It should furthermore be pointed out that are used additional members in order to aid the metering of the wetting liquid and an even distribution of the liquid film onto the transversal dimension of the system, i.e. in the direction of the roller axes.

These members may, possibly, carry out a selective distribution of the liquid, with prevalence at the centre or sides of the rollers, depending on the printing requirements.

In particular, is used an auxiliary roller, the so called paring-metering roller, which tangentially contacts, with an adjustable pressure, the first roller (or drawing roller) of the roller series starting with the drawing roller and ending with the wetting roller (or rollers), and supported in an orientable way onto the tangency plane, perpendicular to the plane of the axes of said rollers.

Furthermore, in some machines, has been adopted a technical solution according to which the wetting roller or one of the wetting rollers also provides the function of the end inking roller of the system or of one of the inking systems or assemblies, thereby carrying out the supplying, onto the plate, of a liquid film formed by a mixture or emulsion of ink and wetting liquid.

The more conventionally and usually used wetting liquid is water which however presents the drawback of the instability of the water-ink optimal-equilibrium, the obtaining and maintaining of which are indispensable conditions for a quality production This equilibrium is more and more difficult to be obtained as, in order to provide a proper tonality colour, the water amount has to be reduced.

In relatively recent years, has been introduced the use of water-alcohol suitably metered or dosed mixtures, which provided the advantages well known to those skilled in the art.

However, the use of alcohol requires the adoption of particular expedients of preparation or setting and especially skilled operators.

Furthermore, this use may be difficult, or even impossible, - under some environmental conditions such as, for example, in the tropical climates.

In relatively recent years, has been attempted to solve this problem in the generality thereof, by providing machines which, as suitably adapted, may be predisposed or set to operate both with the conventional water wetting and the alcohol wetting (as a matter of fact a water-alcohol mixture).

These latter types of machines. however, are until now effected by remarkable drawbacks.

In the light of the above reasons, it is an object of the present invention to provide offset printing machines improved in such a way as to be able of alternatively and selectively operating at will either with the conventional type of water wetting or with a water-alcohol mixture wetting, of high yield and qualitative level, without carrying out other operations in addition to the substituting of the ductor and wetting rollers, and which machines are not affected by the drawbacks of the known machines.

In particular, the improvement relates essentially to the wetting assembly, completely separated, with respect to the inking assembly.

Thus, according to the invention there is provided an offset printing machine including a plate cylinder and independent wetting and inking devices for respectively applying wetting fluid and ink to the plate cylinder, wherein the wetting assembly comprises: (i) a tray for containing wetting fluid; (ii) a drawing roller for immersing in wetting fluid in the wetting fluid tray; (iil) a ductor roller in tangential rolling contact with the drawing roller; (iv) an axially reciprocable roller in tangential rolling contact with the ductor roller; (v) at least one wetting roller in tangential rolling contact with the axially reciprocable roller and with the plate cylinder; and (vi) a paring-metering roller in tangential contact with the drawing roller, upstream of the ductor roller, for metering the quantity of wetting fluid collected by the drawing roller.

These and other characteristics, of functional and constructional nature of the wetting improved assembly, effective to be applied onto offset printing machines, according to the present invention, will become more apparent from the accompanying drawing which is a schematic view of the improved wetting assembly according to the invention.

Referring particular to the numeral references of the accompanying drawing, the improved wetting assembly according to the present invention comprises, in the order corresponding to the direction according to which the wetting liquid, contained in the tray (V) is transferred and distributed onto the surface of the cylinder-plate (L), a drawing roller (1), a ductor roller (2), a vibrating roller (3) and at least one wetting roller (49), possibly but not critically associated with a second wetting roller (4").

This wetting device comprises, furthermore, a metering-paring roller (5), tangentially contacting only the drawing roller (1), located upstream, with respect to the rotation direction (and hence to the transportaion direction) of the liquid, of the contacting point between said drawing roller and said ductor roller.

Of the aforesaid rollers, the drawing roller (1) has a plated metal surface, and it is driven by a motor-reducing assembly provided with a speed variator, in order to obtain the metering of the wetting liquid.

The ductor roller (2), which is covered by rubber (and, in the use with water wetting, by a textile braiding) is driven by the vibrating roller (3) and mounted in such a way as to be adjustable in order to obtain, by modifying the pressure, a transferring of the proper amount of wetting liquid.

The aforesaid vibrating roller (3), having a plated metal surface and driven by the cylinder-plate (L) is provided with an axial reciprocating movement The wetting rollers (4') and (4"), which are covered by rubber (and, in the water wetting use, by a textile braiding) are driven by friction by the vibrating roller (3) and are supported in such a way as to allow for the contact pressure thereof, both onto the cylinder-plate (L) and onto the vibrating roller (3) to be adjusted.

The metering-paring roller (5), which is rubber covered, is driven by the drawing roller (1) and it is mounted, in an adjustable way, in order to allow for, by changing the pressure, a precise adjusting of the scraping and removing action thereof onto the excess liquid collected and transported by said drawing roller, said excess liquid being returned to the underlying tray (V).

The transversal distributing or spreading of the wetting liquid onto said drawing roller, is adjustable and determined by the slanting of the metering-paring roller with respect to said drawing roller.

It should moreover be pointed out that the instant wetting assembly (B) is completely separated from the inking assembly (1) formed by the roller assemblies (1') and (1") supplied by the tray (C).

From the above description and the ob servation of the drawing it may be seen that the improved wetting device according to the invention is characterized in that it comprises five roller assemblies, a part of which forms the connection between the adjacent assemblies, which assemblies, from the operation point of view, may be considered as independent, although they are interconnected and strictly cooperating and more specifically: a) a wetting roller assembly comprising the one or more wetting rollers (4) and possibly (4s") which provides the wetting of the surface of the plate (L); b) a vibrating roller assembly formed by those same wetting rollers (43 and possibly (4"), by the ductor roller (2) and a vibrating roller (3) cooperating with the first rollers. and assuring an even transferring of the wetting liquid from the ductor roller to the wetting rollers; c) a continuous supplying roller assembly, including that same ductor roller (2) and the drawing roller (1), which takes up the wetting liquid from the tray (V) and transfers said wetting liquid to the rollers of the wetting assembly, more precisely to the vibrating roller (3); and d) a metering and paring roller assembly formed by that same drawing roller (1) and by the metering-paring roller (5), cooperating with the first, which allows for the liquid continuously supplied by the supplying assembly to be metered and transversely pared.

This allows for the wetting liquid to circulate through the overall wetting assembly, even during the printing stops and hence to begin the printing operation without difficulties and under optimal conditions, both in the conventional water wetting and in the water-alcohol wettig.

It has been determined that the roller quality, the surface finishing, the combination, cooperative organization, movements and related controls, as thereinabove listed and described, allow for the instant improved wetting device according to the invention to be used alternatively and selectively both with water and water-alcohol, thereby obtaining, in both cases high quality and even printings.

WHAT WE CLAIM IS: 1. An offset printing machine including a plate cylinder and independet wetting and inking devices for respectively applying wetting fluid and ink to the plate cylinder, wherein the wetting assembly comprises: (i) a tray for containing wetting fluid; (ii) a drawing roller for immersing in wetting fluid in the wetting fluid tray; (iii) a ductor roller in tangential rolling contact with the drawing roller; (iv) an axially reciprocable roller in tangential rolling contact with the ductor roller; (v) at least one wetting roller in tangential rolling contact with the axially reciprocable roller and with the plate cylin der; and (vi) a paring-metering roller in tangential contact with the drawing roller, upstream of the ductor roller, for metering the quantity of wetting fluid collected by the drawing roller.

2. An offset printing machine as claimed in Claim 1, wherein two said wetting rollers are provided, one of which is removable.

3. An offset printing machine as claimed in Claim 1 or 2, wherein the or each wetting roller is coated in rubber.

4. An offset printing machine as claimed in Claim 3, wherein the or each wetting

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   ductor roller.

   Of the aforesaid rollers, the drawing roller (1) has a plated metal surface, and it is driven by a motor-reducing assembly provided with a speed variator, in order to obtain the metering of the wetting liquid.

   The ductor roller (2), which is covered by rubber (and, in the use with water wetting, by a textile braiding) is driven by the vibrating roller (3) and mounted in such a way as to be adjustable in order to obtain, by modifying the pressure, a transferring of the proper amount of wetting liquid.

   The aforesaid vibrating roller (3), having a plated metal surface and driven by the cylinder-plate (L) is provided with an axial reciprocating movement The wetting rollers (4') and (4"), which are covered by rubber (and, in the water wetting use, by a textile braiding) are driven by friction by the vibrating roller (3) and are supported in such a way as to allow for the contact pressure thereof, both onto the cylinder-plate (L) and onto the vibrating roller (3) to be adjusted.

   The metering-paring roller (5), which is rubber covered, is driven by the drawing roller (1) and it is mounted, in an adjustable way, in order to allow for, by changing the pressure, a precise adjusting of the scraping and removing action thereof onto the excess liquid collected and transported by said drawing roller, said excess liquid being returned to the underlying tray (V).

   The transversal distributing or spreading of the wetting liquid onto said drawing roller, is adjustable and determined by the slanting of the metering-paring roller with respect to said drawing roller.

   It should moreover be pointed out that the instant wetting assembly (B) is completely separated from the inking assembly (1) formed by the roller assemblies (1') and (1") supplied by the tray (C).

   From the above description and the ob servation of the drawing it may be seen that the improved wetting device according to the invention is characterized in that it comprises five roller assemblies, a part of which forms the connection between the adjacent assemblies, which assemblies, from the operation point of view, may be considered as independent, although they are interconnected and strictly cooperating and more specifically: a) a wetting roller assembly comprising the one or more wetting rollers (4) and possibly (4s") which provides the wetting of the surface of the plate (L); b) a vibrating roller assembly formed by those same wetting rollers (43 and possibly (4"), by the ductor roller (2) and a vibrating roller (3) cooperating with the first rollers. and assuring an even transferring of the wetting liquid from the ductor roller to the wetting rollers;

   c) a continuous supplying roller assembly, including that same ductor roller (2) and the drawing roller (1), which takes up the wetting liquid from the tray (V) and transfers said wetting liquid to the rollers of the wetting assembly, more precisely to the vibrating roller (3); and d) a metering and paring roller assembly formed by that same drawing roller (1) and by the metering-paring roller (5), cooperating with the first, which allows for the liquid continuously supplied by the supplying assembly to be metered and transversely pared.

   This allows for the wetting liquid to circulate through the overall wetting assembly, even during the printing stops and hence to begin the printing operation without difficulties and under optimal conditions, both in the conventional water wetting and in the water-alcohol wettig.

   It has been determined that the roller quality, the surface finishing, the combination, cooperative organization, movements and related controls, as thereinabove listed and described, allow for the instant improved wetting device according to the invention to be used alternatively and selectively both with water and water-alcohol, thereby obtaining, in both cases high quality and even printings.

   WHAT WE CLAIM IS: 1. An offset printing machine including a plate cylinder and independet wetting and inking devices for respectively applying wetting fluid and ink to the plate cylinder, wherein the wetting assembly comprises: (i) a tray for containing wetting fluid; (ii) a drawing roller for immersing in wetting fluid in the wetting fluid tray; (iii) a ductor roller in tangential rolling contact with the drawing roller; (iv) an axially reciprocable roller in tangential rolling contact with the ductor roller; (v) at least one wetting roller in tangential rolling contact with the axially reciprocable roller and with the plate cylin der; and (vi) a paring-metering roller in tangential contact with the drawing roller, upstream of the ductor roller, for metering the quantity of wetting fluid collected by the drawing roller.
2. 2. An offset printing machine as claimed in Claim 1, wherein two said wetting rollers are provided, one of which is removable.
3. 3. An offset printing machine as claimed in Claim 1 or 2, wherein the or each wetting roller is coated in rubber.
4. 4. An offset printing machine as claimed in Claim 3, wherein the or each wetting

   roller is overcoated with a textile sheath.
5. 5. An offset printing machine as claimed in any one of Claims 1 to 4, wherein the or each wetting roller is adjustable in position towards and away from the reciprocable roller and towards and away from the plate cylinder to adjust the pressure of the or each wetting roller with respect to the reciprocable roller and the plate cylinder.
6. 6. An offset printing machine as claimed in any one of Claims 1 to 5, wherein the paring-metering roller is adjustable towards and away from and obliquely with respect to the drawing roller.
7. 7. An offset printing machine as claimed in any one of Claims 1 to 6, wherein the ductor roller is adjustable towards and away from the reciprocable roller and towards and away from the drawing roller to adjust the pressure of the ductor roller with respect thereto.
8. 8. An offset printing machine as claimed in Claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.