GB2166387A - Inking device - Google Patents

Abstract

A device suitable for use in supplying ink in a printing machine, which comprises a first roller 7 for contacting an image-bearing surface 1A, the roller 7 being provided with at least one axially reciprocating roller 16 in peripheral engagement therewith, and a means for supplying ink to the first roller, the arrangement being such that a supply of ink provided to a portion of the first roller is contacted by at least one axially reciprocating roller before being supplied to the image-bearing surface. Preferably, ink supply is from duct 17 and messenger roller 18 to a further roller 8 also provided with axially reciprocating distributor rollers. The printing machine may be lithographic, with cylinder 1 carrying plate 1A over less than half its periphery and the inking roller, being lifted clear of the cylinder surface when not opposite the plate. <IMAGE>

Description

SPECIFICATION Inking device This invention relates to the application of a coating material, especially a printing ink, to a surface, especially a stereo surface or a lithographic plate which is mounted on a continuously rotating cylinder. More especially, it relates to the inking of plates on dual cylinders. These are cylinders on which the plate or stereo occupies less than half of the circumference, the remainder comprising a counter-pressure surface which is at the same radius but which is to be kept free of ink.

When printing, it is generally accepted, there should be as many rollers as possible between the ink source and the "form" rollers which apply the ink to the plate. This is to achieve as uniform a layer as possible on the form rollers, bearing in mind that at each revolution the plate takes ink from some parts of the roller and not others. Another requirement in conventional printing is that there should be as many form rollers as possible, to ensure complete and uniform application of ink to the plate.

Hitherto, these requirements have hindered the development of dual cylinder systems, in which the form rollers must be lifted clear of the cylinder for half of each cylinder revolution. If large numbers of intermediate rollers are employed, they must all be lifted together, requiring a powerful, cumbersome and potentially inaccurate lifting means. If there is more than one form roller, the problem is compounded. Further difficulties arise from the need to apply a continuous axial oscillating movement to several of the rollers.

It is therefore the object of the invention to provide a form roller which is of such efficiency that it may if desired suffice alone, and which is mounted in such a way that it may be lifted easily at each revolution without perturbation of the ink flow, as well as being able, if desired by the same means, to be lifted completely clear for maintenance purposes. A further object of the invention is to provide a system of intermediate oscillating rollers which is no encumbrance to maintenance or adjustment of the form roller and which will work efficiently in either direction. It is a further object of the invention to provide a means that allows the cylinder to be run clockwise or anti-clockwise at will, without loss of inking performance on either direction.

The present invention provides a device suitable for use in supplying ink in a printing machine, which comprises a first roller for contacting an image-bearing surface, the roller being provided with at least one axially oscillatable roller in peripheral engagement therewith, and a means for supplying ink to the first roller, the arrangement being such that a supply of ink provided to a portion of the first roller is contacted by at least one axially oscillatable roller before being supplied to the imagebearing surface.

Advantageously, the means for supplying ink to the first roller comprises a second roller in peripheral engagement therewith, the second roller being provided with a primary source for supplying ink thereto. The second roller is advantageously, like the first roller, provided with at least one axially oscillatable roller in peripheral engagement therewith, the arrangement being such that a supply of ink provided by the primary source is contacted by at least one axially oscillatable roller before being transferred to the first roller. The primary source advantageously comprises a "vibrator" roller.

Advantageously, at least two, and preferably four, axially oscillatable rollers are provided on the second roller, at least one, and preferably two, on each side of the primary source. By this means, the device operates equally well in both directions.

The first roller is advantageously carried on a support pivotally mounted about the axis of the second roller, the support preferably also carrying a cam follower. Normally, the image bearing surface is borne by a cylinder, and this advantageously also carries a cam upon which the cam follower rests. By this means, the first roller may be periodically lifted out of contact with the cylinder at a desired stage in the cycle.

In a preferred embodiment of the present invention, the first roller is the sole form roller and it has a circumference slightly greater than the length of the longest image which will be printed. This roller is mounted between relatively long arms which are free to pivot about a fixed tube. Surrounding this tube is a second roller of diameter equal or similar to that of the form roller and in peripheral contact with it. Both are driven at a peripheral speed equal to that of the dual cylinder. Within the tube is an axially oscillating shaft. A number of small diameter rollers rest on the peripheries of the form roller and second roller and are connected to the oscillating shaft so that they all slide axially to and fro while the machine is running. The system is completed by a conventional ink duct and "vibrator" roller which cyclically applies ink to the second roller.The small rollers resting on the second roller are equally disposed on either side of this point of ink application. The small rollers may, though less desirably, be replaced by other means of distributing the ink on the roller surfaces, e.g., by pads, preferably oscillatable in the same sense as the small rollers.

Each of the arms carrying the form roller also carries a cam follower roller. These rollers normally rest on identical cams disposed at either side of the dual cylinder. Where required, the cams lift the arms and with them the form roller and the associated small rollers. Alternatively, the same assembly may be lifted manually and swung away to give clear access to both itself and the cylinder.

The arms may also be fitted with double-acting air cylinders which will perform this lift as well as providing a means of pressing the followers against the cams, should the weight of the assembly prove insufficient. Alternative means for lifting the form roller from the dual cylinder at appropriate stages during the cycle may of course be used.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing.

A dual cylinder 1 carries a lithographic plate 1A.

Mounted on the ends of cylinder 1 are two cams 2 (the other is behind the cylinder) on which rest follower rollers 3 carried on two arms 4. The arms are pivotably mounted on the tube which projects from the main machine casing 6. The arms carry between them the form roller 7 which is brought into correct contact with the plate 1A by fine posiional adjustment of rollers 3. The second roller 8 is pivotably mounted on tube 5 and is in peripheral contact with form roller 7. The two rollers are geared together by gears (not shown) whose pitch circles coincide with the roller peripheries. Roller 8 is connected to the main drive of the machine so that it and form roller 7 and the cylinder 1 are all synchronised.

Mounted astride the arms and rollers are two carriages comprising end plates 9 and 10 and spacer bars 11. The carriages are free to slide axially but not to rotate. Plate 10 is connected to oscillating shaft 12 within tube 5, as is plate 9 by way of rocker arm 13. Thus when the machine is running, the two carriages perform a continuous oscillating motion. Plates 9 and 10 contain slots 14 which receive the end bearings 15 of four or more small rollers 16. The bearings are retained by spring clips (not shown) which urge the rollers radially inwards so that they rest on the surfaces of rollers 7 and 8 while the carriages cause them to oscillate axially across those surfaces.

Ink is administered to the system by means of a conventional duct 17 and dabber roller 18. If the cylinder is rotating anti-clockwise, the roller 8 does the same; so the ink strips from the dabber roller passes under the roller 8 and is spread by the oscillating rollers 16. The ink then passes over the form roller 7 and is further smoothed by the four (or more) rollers oscillated by the plates 9. Thus by the time the ink reaches the plate 1A it has passed under at least six oscillating rollers.

If the cylinder is rotating clockwise, the ink stripe passes over the roller 8 and under roller 7. It does not meet the plate here because delivery of the stripe has been timed so that it passes under roller 7 while the latter is raised by cams 2 and followers 3, i.e. when the plate is at the opposite side of the cylinder. So the stripe passes around roller 7 anticlockwise, passes under the remaining oscillating rollers and is applied to the plate after 1 114 revolutions of roller 7.

The followers are maintained in contact with cam 2 by the weight of the arms and rollers. While the machine is stopped, the assembly can be swung over-centre to position 19 to allow access to all the parts.

The load on the cam followers can be supplemented by springs or by one or more double-acting cylinders which will also serve to raise the assembly to the position 19, saving effort on the part of the operator.

Claims (11)

1. A device suitable for use in supplying ink in a printing machine, which comprises a first roller for contacting an image-bearing surface, the roller being provided with at least one axially oscillatable roller in peripheral engagement therewith, and a means for supplying ink to the first roller, the arrangement being such that a supply of ink provided to a portion of the first roller is contacted by at least one axially oscillatable roller before being supplied to the image-bearing surface.

2. A device as claimed in claim 1, wherein the means for supplying ink to the first roller comprises a second roller in peripheral engagement therewith, the second roller being provided with a primary source for supplying ink thereto.

3. A device as claimed in claim 2, wherein the second roller is provided with at least one axially oscillatable roller in peripheral engagement therewith, the arrangement being such that a supply of ink provided by the primary source is contacted by at least one axially oscillatable roller before being transferred to the first roller.

4. A device as claimed in claim 2 or claim 3, wherein the primary source comprises a vibrator roller.

5. A device as claimed in any one of claims 2 to 4, wherein at least two axially oscillatable rollers are provided on the second roller, at least one being on each side of the primary source.

6. A device as claimed in any one of claims 2 to 5, wherein the first roller is carried on a support pivotally mounted about the axis of the second roller.

7. A device as claimed in claim 6, wherein the support also carries a cam follower.

8. A device as claimed in claim 7, wherein the image-bearing surface is borne by a cylinder that also carries a cam upon which the cam follower rests.

9. A device as claimed in claim 1, substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

10. A printing machine comprising a device as claimed in any one of claims 1 to 9.

11. A new feature hereinbefore described or any new combination of hereinbefore described features.