GB2421216A

GB2421216A - Apparatus for washing a blanket in an offset printing press

Info

Publication number: GB2421216A
Application number: GB0427514A
Authority: GB
Inventors: Alan Broadbent; Raymond Roy Midgley; Daniel Mark Mowbray Rhodes
Original assignee: G A P PRINTING SALES Ltd
Current assignee: G A P PRINTING SALES Ltd
Priority date: 2004-12-16
Filing date: 2004-12-16
Publication date: 2006-06-21
Also published as: EP1671792B1; EP1671792A1; DE602005000227T2; GB0427514D0; DE602005000227D1

Abstract

A blanket cleaning unit is disclosed for use in an offset printing press having a frame carrying a cleaning brush. The frame is mountable on the press for sliding movement towards the blanket cylinder and carries at least one pipe for spraying a liquid onto the brush. In the invention, all the pipes are removable from the frame of the cartridge while the frame remains mounted on the press.

Description

2421216

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APPARATUS FOR WASHING A BLANKET IN AN OFFSET PRINTING PRESS

Field of the invention

5

The present invention relates to offset printing presses and is particularly applicable to sheet fed presses.

Background of the invention

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In the offset lithographic printing process, each colour of ink in applied using three cylinders arranged one above the other. The uppermost is the plate cylinder which carries the image to be printed. As it rotates, the plate 15 cylinder is contacted by rollers which apply ink to the images regions and water to the remaining regions. The ink image thus formed on the plate cylinder is transferred onto a rubber blanket wrapped around the intermediate cylinder and from there the ink image is transferred onto he paper as 20 it passes between the blanket cylinder and the lowermost cylinder, termed the press or impression cylinder.

The rubber blanket in such a press needs to be cleaned at intervals and in many machines the periodic cleaning of 25 the blanket is automated. In some presses, a cleaning unit is arranged next to the blanket cylinder and carries a cleaning brush of the same axial length as the rubber blanket. Two pipes having nozzles drilled into them along their length spray water and a cleaning solution, 30 respectively, onto the brush which is them advanced radially to make contact with the rubber blanket as the blanket cylinder is rotated. The cartridge also has a wiper or squeegee blade to collect the liquid applied to the blanket and return it to a drain.

35

A problem that occurs in such presses is that the pipes spraying water and the cleaning solution onto the cleaning

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brush of the cleaning unit become blocked. Paper dust and other debris can not only clog the discharge nozzles but can pass through the nozzle and clog the inner bores of the pipes.

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Hitherto, the pipes in the blanket cleaning unit could not be serviced because they were integrally formed at both their ends with elbows to which the hoses were coupled using suitable connectors. As the elbows could not be removed from 10 the pipes, it was not possible to clean the interior of the pipes and they needed instead to be replaced.

The replacement of the pipes required removal of the cleaning unit from the press and to permit this operation to 15 be performed the cleaning unit is designed as a cartridge that can be withdrawn from the press. The cartridge is however a heavy and cumbersome item which made its removal a difficult and messy task often requiring three operatives.

20 Once the cleaning unit had been removed from the press,

it needed to be dismantled before one of the pipes could be unbolted from the frame of the cartridge and while the unit was in pieces, it was appropriate to service and clear all the components. The removal and overhauling of the cleaning 25 unit was therefore not only unpleasant but costly on account of the price of the replacement components and the prolonged down time of the press. As this task has to be repeated for each colour of ink being applied, these costs were correspondingly multiplied.

30

Object of the invention

The present invention in its different aspects seeks to simplify and reduce the time and cost of servicing the 35 liquid supply pipes in the blanket cleaning unit of an offset printing press so as to mitigate the foregoing currently experienced disadvantages.

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Summary of the invention accordance with a first aspect of the invention, there is provided a blanket cleaning unit for use in an offset 5 printing press having a frame carrying a cleaning brush, which frame is mountable on the press for sliding movement towards the blanket cylinder and carries at least one pipe for spraying a liquid onto the brush, characterised in that all the pipes are removable from the frame of the cartridge 10 while the frame remains mounted on the press.

In this aspect of the invention, down time is reduced because the time required to dismantle the pipes from the cartridge is reduced because the cartridge does not need to 15 be removed from the machine.

In the prior art constructions, two separate pipes were provided of which one was positioned on the outside the cartridge and the other in the middle of the cartridge. It 20 is the inner pipe that made it necessary for the cartridge to be dismantled after it was removed from the press.

In a preferred embodiment of the invention, two pipes are welded to each other to form a single sub-assembly which 25 is secured on the outside of the cartridge. In this way,

both pipes can be dismantled by removal of a common set of fixings, such as bolts.

In accordance with a second aspect of the invention, 30 there is provided a blanket cleaning unit for use in an offset printing press having a frame carrying a cleaning brush, which frame is mountable on the press for sliding movement towards the blanket cylinder and carries at least one pipe for spraying a liquid onto the brush, characterised 35 in that each of the pipes is a straight pipe that is blanked off at both ends by means of removable caps to permit a cleaning implement to be passed through the pipe, liquid

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being introduced into the pipe through at least one Injunction arranged between the ends of the pipe.

Preferably, a single T-junction is provided on each 5 pipe near one end of the pipe.

The second aspect of the invention reduces the cost of the servicing of the pipes by allowing them to be cleaned thereby reducing the frequency with which they have to be 10 replaced.

To assist on the occasions when the cartridge needs to be removed from the press, for example for servicing of the cleaning brush, the present invention provides in a third 15 aspect a cleaning unit for the blanket of an offset printing press having at least two elongate handles removably secured to the cartridge by being in threaded engagement with a nut or spigot projecting from a plate secured to the cleaning unit.

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It is not possible to provide handles that permanently project from the cleaning unit because of the limited space available. However, when the cleaning unit has short handles or no handles, there is not sufficient leverage to carry the 25 unit without placing one's hands beneath it and it is this that makes removal of the cleaning unit a messy task requiring several operatives. By providing long removable handles, the third aspect of the invention allows the cleaning unit to be manipulated easily while the handles are 30 in place without their presenting an obstacle when the cleaning unit is fitted to the printing press.

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Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawing, in 5 which :

Figure 1 is a perspective view of a tube assembly for a Heidelberg Speedmaster® cleaning unit, and

Figure 2 shows a removable handle for a cleaning unit.

10 Detailed description of the preferred embodiment

The illustrated pipe assembly is designed to fit the blanket cleaning unit of a Heidelberg Speedmaster® printing press. As such printing presses are well known, it is 15 believed that detailed description of the unit is not necessary within the present context. Essentially the unit comprises a frame that can slide in and out of the press in a compartment adjacent the blanket cylinder. The frame carries a rotary brush that is driven by cogs and onto which 20 water and a cleaning solution are sprayed by two different pipes. In use, the brush is first sprayed with water and the cleaning solution and it is then advanced radially into contact with the rubber blanket at the same time as the blanket cylinder is rotated. The blanket is scrubbed by the 25 brush and a squeegee blade on the cleaning unit collects the surplus liquid so that it can be returned to a drain.

Hitherto, the two pipes could only be removed from the cleaning unit by removing and dismantling the unit. In the 30 present invention, the pipes are instead constructed as a sub-assembly 10 as shown in the accompanying drawing. The two pipes 12 and 14 are straight pipes that are welded to each other and to a rigid backing plate 16 to prevent them from buckling when they come in contact with the bristles of 35 the brush. Fine holes 20 in the pipes 12 and 14 act as spray nozzles to direct water and a cleaning solution onto the brush. Five mounting lugs 18 welded to the backing plate are

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used to allow the sub-assembly 10 to be bolted onto a part of the frame of the cleaning unit that is accessible without dismantling the cleaning unit.

5 Each of the pipes 12 and 14 has a branch pipe 22, 24

near one of its ends, the branch pipes being connected to the pipes at T-junctions to allow the water and cleaning solution to be introduced into the pipes. The ends of the pipes 12 and 14 are fitted with removable blanking plugs 10 which are not shown in the drawing.

The sub-assembly 10 can be removed from the cleaning unit after the unit has been slid out of the press without removing it entirely. The sub-assembly is mounted on the 15 underside of the unit and is removed by loosening the bolts passing through the lugs 18 and disconnecting the hoses connected to the branch pipes 22 and 24. It is desirable to replace two of the bolts by threaded alignment spigots so that the sub-assembly can be positioned on the cleaning unit 20 more easily when it is reassembled.

After the sub-assembly has been removed, a replacement is mounted on the cleaning unit and the latter is pushed back into position in the press. By having a replacement 25 ready for substitution, the down time of the press is minimised.

The removed sub-assembly can be serviced by removing the blanking plugs and passing a cleaning implement along 30 the entire length of each pipe 12, 14. Because the pipes are straight and open at both ends, this can be performed in a straightforward manner. The cleaning implement may be designed as a drill or a wire brush or it may comprise a tube aiming a high pressure jet onto the inner walls of the 35 pipes. The individual nozzle holes 20 can also be cleaned using a stiff wire. Once any blockages have been removed,

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the sub-assembly can be re-used and it need only be replaced when it ceases to be serviceable.

Even in a multi-colour press, it is only necessary to 5 retain one spare sub-assembly as the cleaning units of the different colours can be serviced one at a time because of the small down time required for each colour. The press need not be out of action while each sub-assembly is being cleaned and the cleaning of each sub-assembly is itself fast 10 because there is not need to dismantle and overhaul the entire cleaning unit. Of course, it is alternatively possible to retain as many spare sub-assemblies as there are colours, in which case all the cleaning units can be serviced at the same time.

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On occasions, it will still be necessary to remove the entire cleaning unit and to assist in the task two mounting plates 30 (see Figure 2) are bolted on the cleaning unit which have holes 32 aligned with existing bolt holes in the 20 cleaning unit, represented by dotted lines. The plates 30 have welded onto them an internally threaded nut 34 or an externally threaded spigot for receiving a mating thread 38 on the end of handle 36 designed as an elongate tube. It is important to note that no part of the handle 36 nor its 25 mounting plates 30 can intrude into cleaning unit as it could interfere with the rotating parts within the cleaning unit.

When the handles 36 are not in place, the mounting 30 plates 30 do not present any obstruction to personnel but when the handles 36 are fitted to the mounting plates 30 they offer sufficient leverage and purchase to allow the cleaning unit to be withdrawn from the press without coming into contact with any part of it. The length of the handles 35 36 allows an operative to hold a handle with two hands and, with one operative carrying the cleaning unit at each end,

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it can easily be lifted out of the press and carried away for dismantling and servicing on a suitable work bench.

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Claims

1. A blanket cleaning unit for use in an offset printing press having a frame carrying a cleaning brush,

5 which frame is mountable on the press for sliding movement towards the blanket cylinder and carries at least one pipe for spraying a liquid onto the brush, characterised in that all the pipes are removable from the frame of the cartridge while the frame remains mounted on the press.

10

2. A blanket cleaning unit as claimed in claim 1, wherein two pipes are welded to each other to form a single sub-assembly which is secured on the outside of the cartridge.

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3. A blanket cleaning unit for use in an offset printing press having a frame carrying a cleaning brush, which frame is mountable on the press for sliding movement towards the blanket cylinder and carries at least one pipe

20 for spraying a liquid onto the brush, characterised in that each of the pipes is a straight pipe that is blanked off at both ends by means of removable caps to permit a cleaning implement to be passed through the pipe, liquid being introduced into the pipe through at least one T-junction

25 arranged between the ends of the pipe.

4. A blanket cleaning unit as claimed in claim 3, wherein a single T-junction is provided on each pipe near one end of the pipe.

30

5. A cleaning unit for a blanket of an offset printing press having at least two elongate handles removably secured to the cartridge by being in threaded engagement with a nut or spigot projecting from a plate

35 secured to the cleaning unit.

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6. A blanket cleaning unit for an offset printing press, constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.