This invention relates to a cleaning method and means particularly applicable to the cleaning of a damping roller used in offset printing machinery (this is also known as a dampener roller).

A dampener roller is used to apply a film of water to an offset plate during the printing process.

During such an application, the roller itself picks up ink and because of its character having a number of fibres, it is necessary if the colour of ink being used on the printing press is changed, to clean this particular roller.

Typically, the time required for this cleaning process is about twenty minutes and it requires substantive effort and by reason of the time is relatively expensive to clean.

According to this invention, we have discovered a technique for cleaning rollers of this type which firstly can be achieved almost without manual effort, and secondly very much quicker than has hitherto been the case using manual cleaning methods.

Perhaps best of all finally, the method can be very simply and economically applied and will therefore be of very significant benefit to all offset printers.

According to this invention there is proposed a method of cleaning printing ink from a dampener roller which comprises the steps of supporting the dampener roller for rotation about its elongate central axis and then directing a jet of cleaning fluid so that at least some of the cleaning fluid is directed to effect a rotational pressure to the roller and such that the jet of cleaning fluid is continued to be directed to maintain the rotation about its elongate central axis dampener roller while being subjected to the jet of cleaning fluid.

In a further form of this invention this can be said to reside in a dampener roller cleaning apparatus comprising a cradle to hold for rotation about it elongate central axis a dampener roller of a type used for dampener offset printing plates in offset printing, and at least one cleansing fluid outlet supported and adapted to direct a cleansing jet of fluid at pressure such as to affect a rotation at high speed of the roller about it central elongated axis.

In preference the cleansing fluid is a fluid Which is immiscible with ink. The method is effective because the cleansing fluid usually water itself is immiscible with the ink. This has the significant advantage of avoiding the use of chemicals which may be environmentally harmful apart from the advantage that the method is very fast. Further the water left on the roller is compatible with the subsequent use of the dampener roller which has not been the case with previous cleaning techniques where the solvent has to be totally removed before the roller can again be used.

In preference, the roller is adapted to be supported by roller bearings which are conventionally incorporated at each end of a dampener roller.

In preference, there are means to change the position of the jet of cleansing fluid so that this can be aimed at a selected angle relative to the dampener roller to assist with a more effective direction for achieving a best cleaning affect.

In preference, the means to effect and direct the jet of cleansing fluid are supported so as to be movable during the issuing of the jet of cleansing fluid, such movement being in a direction parallel to the central axis about which the dampener roller will rotate.

In preference, the cleansing fluid is simply water and this is directed from either a single jet or a number of jets extending laterally along the length of the dampener roller and each of these is directed so that a high speed stream of water as in a fan impinges in more or less continuous manner an edge of the roller. Because the liquid is first caused to impinge and be directed relatively deeply into the mesh and fibre of the dampener roller and then with that continued inertia and momentum to be directed out, and this together with centrifugal force, there seems to be an extremely powerful cleansing action at work.

An advantage of the arrangement is that the dampener roller has often attached at each end, roller bearings so that when this is removed from the printing press, the roller bearings are still on the shaft supporting the dampener roller.

There only needs therefore to be a bracket support for the external ring of the roller bearings and the damper roller then is free to rotate about its own axis very freely.

The invention might be better understood when referred to a preferred embodiment which shall now be described with the assistance of drawings in which

FIG 1 is a side elevation illustrating the manner in which the spray of water is directed more or less tangentially to the radius of the dampener roller;

FIG 2 is a view in plan of a schematic arrangement of the embodiment as shown in FIG 1 a surrounding containing chamber being shown simply in dotted outline;

FIG 3 is a side elevation illustrating the manner in which the spray water in a second embodiment is directed in an approximately tangential direction to the radius of the dampener roller;

FIG 4 is a plan view of a schematic arrangement of the second embodiment as shown in FIG 3 with a surrounding chamber shown simply as a dotted outline;

FIG 5 is a perspective view of a third embodiment;

FIG 6 is a front view with part cut away, of the third embodiment as shown in FIG 5;

FIG 7 is a cross sectional view of the third embodiment as shown in FIGS 5 and 6 with a jet in position to effect the cleansing action;

FIG 8 is the same view as in FIG 7 of the third embodiment except that a front part of the cover shield supporting the jet is pivoted outwardly to enable access to within the cover shield for positioning of a dampener roller;

FIG 9 is a perspective view of that part of the third embodiment whereby the dampener roller is supported, the view showing in perspective the dampener roller supported for rotational rotation about its central axis of rotation.

Referring in detail to FIGS 1 , 2, 3 and 4 of the drawings, a dampener roller 1 has an external blanket 2 with appropriate fibres to hold and apply for purposes in conventional manner water to an offset plate of a printer.

The roller 1 is held within a confining chamber 3 and there is a water pipe 4 which has a number of outlet jets 5. Each of the jets has an outlet 6 from

which there issues a stream of water 7 arranged to hit the roller 1 at an angle such that it is more or less tangential such as at 8. Accordingly the water is directed into the body of the blanket 2 but thereafter forced by the centrifugal force of the very rapidly rotating roller 1 , is flung therefrom carrying self- evidently any subsequently attracted ink.

It is this combination of high pressure water being directed strongly into the blanket but then being rapidly cleared that apparently causes this very effective cleansing step.

The dampener roller 1 has end roller bearings 9 which simply rest on the shaped bracket which is not shown at each end but such that the roller is allowed to rotate very freely about its own cylindrical axis.

Now referring to the second embodiment as shown in FIGS 3 and 4 the difference here being rather than as shown in FIG 1 and 2 there is a single jet the position of which varied so as to change the direction of the output jet of water effecting the cleansing method, and there are shown means by which the jet can be supported so as to be movable in a direction parallel to the dampener roller elongate axis.

Accordingly, there is shown the dampener roller 10 with the nozzle 11 supported by a first rotatable knuckle 12 and a second rotatable knuckle 13 such that both the relative position of the nozzle 11 and its direction can be relatively varied in respect of the roller 10.

In this way, the position of the jet can be optimised for a respective diameter of dampener roller 10.

As shown in FIG 4, the dampener roller 10 is supported by its own bearings at 14 and 15 which are inturn supported by cradle 16 and 17 the position of cradle 17 being able to be varied along track 18 to accommodate different lengths of dampener roller 10.

There is a flexible hose connected to the nozzle 11 and there is also slide support arms 19 and 20 whereby the nozzle 11 together with its knuckles 12 and 13 can be changed in position in the respective directions as shown by arrows 21 and 22.

In use, the cleansing fluid is found in most cases to be effectively water and this is issued at a pressure conventionally available from a normal domestic

water supply which can be typically 30 psi, the higher the pressure the quicker the cleansing action being affected.

It is found by being supported on rollers, the rotational speed about the central axis of the dampener roller 10 can be very high indeed and this provides centrifugal force which combined with the pressure of the water being directed into the fibres and then being flung seems to have a very effective cleansing action indeed.

In tests conducted, an adequate cleansing of a dampener roller which has hitherto taken 20 to 25 minutes with conventional cleaning techniques has taken 1 to 2 minutes using this alternate technique.

Further, the technique is essentially non-damaging or non-wearing as far as the fibres of the dampener roller are concerned leading therefore to a longer life of dampener roller.

Now referring to the third embodiment as illustrated in FIGS 5 through 9, the dampener roller cleaning apparatus 23 includes a cover shield 24 which is comprised of two parts which are a top part 25 and a front part 26.

The top part 25 has end caps 27 and 28 by which parallel tubes 29 and 30 are supported at each respective end the parallel tubes 29 and 30 acting as parallel guides to support and locate roller support brackets 31 and 32.

Each of the roller support brackets 31 and 32 has secured at a bottom thereof a bifurcate spring bracket 33 in the one case and 34 in the other. This spring bracket has two legs one of which shown at 35 is shaped so as to match the convex shape of the side of the pipe 29 and under resilient pressure engage against this and to resiliently interlock thereby, and the other leg 36 likewise has a concave shape matching the convex shape so that this again resiliently interlocks so that the two together press outwardly and thereby hold the bracket 31 in position between the parallel rods 29 and 30. Likewise for the bracket 32, the bifurcate spring bracket 34 has legs 37 and 38 that match with resiliently interlocking shapes the inside faces of the tubes 29 and 30.

In this manner, both brackets 31 and 32 can be positioned in an appropriate location any where along the length of the parallel tubes 29 and 30 and therefore can be positioned so that they can provide rotational support at a convenient location for a roller 39. Each bracket 31 and 32 includes a right angle metal member 40 in the one case and 41 in the other the vertical part of

which supports for relative rotation about their own axis rotatable bearings 42 and 43 in the one case and 44 and 45 in the other.

Each roller shown generally at 39 is of a conventional type which is used to dampen plates for the off set printing process.

Such a roller has an outermost fabric surface and has in a typical case (but not always) at each end a bearing shown at 46 in the one case and 47 at the other.

These bearings are in place as a matter of course and provide in the first instance relatively low friction rotational freedom for the roller 39 when resting on the outer casing of the respective bearing 46 and 47.

However, the bearings 42 and 43 and 44 and 45 also act together to provide further rotational freedom so that even if for some reason, the bearing such as at 46 and 47 were not operating especially freely, this would be compensated in that the other bearings would rotate because of the nesting position of these between the two bearings for instance as is shown in FIG 9 where bearing 46 sits between the two spaced apart bearings 42 and 43 and it is of course the same on the other end.

Such an arrangement allows for simple location and removal of the roller 39 and it allows for very quick readjustment of the position of the brackets 31 and 32 in the case of a longer roller and of course the diameter of the roller is of negligible consequence within reason with the arrangement shown.

The front part 26 of the cover shield 24 is shaped to provide a shield 48 which is positioned so as to have a top inner lip 49 which is positioned so that water being flung from the rotating roller will generally be intersected by the underneath surface of this as it is flung from the roller or the remaining water will otherwise be directed so that at the least most will be caught by the underneath surface at 50 of the top part 25.

This means that water as it is flung off the roller will not be directed through gap 51 so that an operator standing in front of the apparatus can see through this gap onto the rotating roller 39 and of course can see what is happening as a result of the positioning of the jet 52 which is issuing a jet at high pressure of cleansing water against the surface of the roller 39.

The position of the jet 52 is controlled by three means these being bracket 53 which is resiliently retained by engagement of the spring bracket 54 with parallel rods 55 and 56, the relative position of the bracket 53 along the length of the tubes 55 and 56, and finally the height which is governed by screw 57.

The screw 57 has an engaging cone 58 fitting into a corresponding shape 59 in cover 60.

The cover 60 is pivotally secured at 61 to a sump 62 so that all of the assembly comprising the front part 26 can be swung outwardly as is shown in FIG 8 which allows for open access to the interior 62 and of course allows for replacement of the roller 39 and maintenance purposes which includes filter replacement.

Screwing through handle 63 will relatively raise the remainder of the front part 26 or lower this and thereby the location of the jet outlet at 52 so that this can be adjusted to be most appropriate for the method of cleansing.

Any cleansing fluid which is of course water in this case which is flung from the rapidly rotating roller 39, will be captured within the cover shield 24 and otherwise be directed back into the sump 62 where there is provided an appropriate filtering to intersect ink according to standard techniques and the water is then directed through outlet tube 64 into pump 65 from whence it is redirected through tube 66 to issue through the jet 52.

The filter material is shown at 67 in FIG 6.

The filter material 67 can be removed from time to time and cleaned and returned to a filtering position.

The apparatus as a whole is arranged to be supported either by rear brackets which are not shown or a ground supporting frame 68.

In use, the electrically driven pump 65 is arranged to drive water at a high pressure through the outlet jet 52.

The operator will grasp bracket 53 and locate the issuing jet stream of water onto the fabric at one end of the roller and then as it appears to fully clean shift this slowly along to the other end of the roller 39.

Some adjustments may have to be made with respect to the relative height of the jet so that the cleaning effect is optimised but this is best achieved by trial and error.

What has been discovered is that the roller can be caused to rotate at a very high speed indeed (estimated to be in the vicinity of 2000 rpm in one typical case) and that because the water is being directed again at a high speed as a narrow jet into the fabric it appears that there are two quite violent effects namely the force with which the water hits the fabric in the first instance and therefore probably acts to assist in freeing ink particles and then almost immediately be thrown out from the fabric with whatever ink has been impinged by the forceful flow.

It is this forceful flow that seems to have this very effective cleaning action.

It has been found that by providing the cover shield shape so as to allow a slot which extends along the parallel direction of the axis of the roller 39 that is at 51 , that this avoids having such devices as say a transparent plastic window which would doubtless be covered with ink and not be able to be seen through.

The advantage of the bifurcate brackets is that they can allow for very economic manufacture while allowing for easy fitting and removal of the elements that is the spring brackets as appropriate and they also allow for a reasonable differential tolerance of positions of the respective parallel tubes.

It has been found preferable to provide for hand positioning of the outlet jet as this allows for the cleansing process to be guided by the operator as the roller is seen to be cleaned and this which will vary to some extent on each occasion will allow for a most efficient selection of the speed of lateral movement along the parallel guides.

The front part 26 of the cover shield is kept in position relative to the cover 60 with the assistance of two adjustably located springs one at each end shown at 69 and 70.

The method of the invention then is to effect a support of the dampener roller so that it can be caused to rotate under the influence of water at a very high speed indeed and this seems to give the joint effect of allowing the water to penetrate deeply and be flung out.

In trials now with equipment of the type shown and with reasonable water pressures, cleansing times of standard rollers have been in the order of 20 to 30 seconds.

This compares with previous times of 20 to 25 minutes that have been necessary with previous equipment and other methods which have used other chemical or other solvents.

Further the process enables the rollers to be cleaned merely using water rather than chemicals, detergents or other solvents which has been used hitherto.

The preferred form is to have the dampener roller free of such separate rotational means and to rely upon the jet of cleansing fluid immiscible to the ink to effect such rotation.