Apparatus for washing a blanket in an offset printing press

Abstract

 A blanket cleaning unit (10) for use in an offset printing press comprises a frame (12) to be mounted on the press for sliding movement towards the blanket cylinder (50) of the press. A brush (14) is rotatably supported in the frame (12) for scrubbing the blanket when the frame is advanced into a position to bring the brush (14) into contact with the blanket cylinder (50). Two pipes (160,162) are mounted on the frame (12) for spraying water and a cleaning agent, respectively, onto the brush (14). In the invention, the two pipes (160,162) are combined to form a single sub-assembly (100) secured to the exterior surface of the frame (12).

Description

Field of the invention

[0001] The present invention relates to offset printing presses and is particularly applicable to sheet fed presses.

Background of the invention

[0002] In the offset lithographic printing process, each colour of ink is 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 cylinder is contacted by rollers which apply ink to the image 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 the paper as it passes between the blanket cylinder and the lowermost cylinder, termed the press or impression cylinder.

[0003] The rubber blanket in such a press needs to be cleaned at intervals and in many machines the periodic cleaning of the blanket is automated. In the Heidelberg Speedmaster® SM102 printing press, a cleaning unit is arranged next to the blanket cylinder and carries a rotating cleaning brush of the same axial length as the rubber blanket. Two separate pipes having spray nozzles drilled into them along their length spray water and a cleaning reagent, respectively, onto the brush. The cleaning unit is mounted on rollers so that it can be advanced to make contact with the rubber blanket as the blanket cylinder is rotated. The cleaning unit also has a wiper or squeegee blade to collect the liquid applied to the blanket and return it to a drain.

[0004] A problem that occurs in such presses is that the pipes spraying water and the cleaning reagent onto the rotating brush of the cleaning unit become blocked. Paper dust and other debris not only clogs the spray nozzles but can pass through the nozzles and clog the inner bores of the pipes.

[0005] 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 the pipes, it was not possible to clean the interior of the pipes and they needed instead to be replaced.

[0006] The replacement of the pipes required removal of the cleaning unit from the press, this being facilitated by the cleaning unit being constructed as a cartridge that can be withdrawn from the press. The cartridge is however a heavy and cumbersome item which makes its removal a difficult and messy task often requiring two or more operatives.

[0007] Once the cleaning unit had been removed from the press, it needed to be dismantled before one of the pipes could be removed from the frame of the cartridge and, while the unit was in separate pieces, it was appropriate to service and clear all the components. The removal and overhauling of the cleaning unit was therefore not only difficult 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.

Object of the invention

[0008] The present invention seeks therefore to simplify and reduce the time and cost of servicing the liquid supply pipes in the blanket cleaning unit of a press, in particular one of the type used in the Heidelberg Speedmaster® SM102

Summary of the invention

[0009] In accordance with the present invention, there is provided a blanket cleaning unit for use in an offset printing press comprising a frame to be mounted on the press for sliding movement towards the blanket cylinder of the press, a brush rotatably supported in the frame for scrubbing the blanket when the frame is advanced into a position to bring the brush into contact with the blanket cylinders and two pipes mounted on the frame for spraying water and a cleaning agent, respectively, onto the brush, characterised in that the two pipes are combined to form a single sub-assembly secured to the exterior surface of the frame.

[0010] By exterior surface, it is meant a surface that is accessible while the frame of the cleaning unit remains fully assembled. This therefore permits the pipes to be removed without the need to dismantle the frame. Furthermore, by combining the two pipes into a single sub-assembly, the invention allows both pipes to be removed by unfastening a common set of fixings, such as bolts, thereby considerably speeding the process.

[0011] It is preferred to mount the sub-assembly in such a manner as to enable the sub-assembly to be removed from the cleaning unit without the need to remove the entire cleaning unit from the press. In this case, the down time needed for servicing and replacement of the pipes is reduced significantly. Furthermore, by avoiding the need to carry the heavy and cumbersome cleaning unit away from the press, the preferred embodiment of the invention allows the task of replacing the pipe sub-assembly to be performed by an unassisted person.

[0012] It is further preferred for each of the pipes to be a straight pipe that is blanked off at both ends by means of removable end caps to permit an implement to be passed down the length of the pipe, liquid being introduced into the pipe through at least one T-junction arranged between the ends of the pipe. It is only necessary to provide a single T-junction on each pipe near one end of the pipe.

[0013] Forming the pipes in this manner reduces the cost of servicing the pipes by allowing them to be cleaned and thus reduces the frequency with which they have to be replaced.

[0014] The two pipes are preferably welded to one another and/or to a back plate. Such reinforcement of the pipes prevents then from bending during use and thereby makes it possible to pass a servicing implement such as a wire brush or a high pressure water jet down the length of each pipe.

[0015] To assist on the occasions when a cleaning unit does need to be removed from the press, for example for servicing of the cleaning brush, it is further preferred to secure sockets to the frame for receiving removable handles by which the cleaning unit may be carried.

[0016] It is not possible to provide handles that permanently project from the cleaning unit because of the limited space available. On the other hand, with a cleaning unit having short handles or no handles, there is not sufficient leverage to carry the 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. Allowing long handles to be removably secured to the cleaning unit, enables the cleaning unit to be manipulated easily while the handles are in place without the handles presenting an obstacle when the cleaning unit is fitted to the printing press.

Brief description of the drawings

[0017] The invention will now be described further, by way of example, with reference to the accompanying drawing, in which :

Figure 1 is a perspective view of a blanket cleaning unit of the type to which the present invention relates,

Figure 2 is a schematic section through a conventional cleaning unit,

Figure 3 is a section similar to that of Figure 2 showing an embodiment of the present invention,

Figure 4 is a perspective view of the tube sub-assembly used in the cleaning unit of Figure 3, and

Figure 5 shows a detail of a removable handle for a cleaning unit.

Detailed description of the preferred embodiment

[0018] The cleaning unit 10 shown in perspective in Figure 1 comprises a frame 12 rotatably supporting a cleaning brush 14. The frame 12 is composed of two end plates 16 and 18 in which the brush 14 is journalled. The end of the brush 14 projecting from the end plate 16 is driven by means of a cog 20 meshing with an idler gear 22. The end plates carry rollers 24 and 26 to allow the cleaning unit to slide along guides provided in the press, to enable the cleaning unit to be advanced towards a blanket cylinder. As can be seen from the schematic section of Figure 2, the end plates 16 and 18 are connected to one another by means of transversely extending bars 30 and 32 and the entire frame is surrounded by means of a casing 34 having a opening through which the brush 14 projects.

[0019] In operation, the cleaning unit is advanced until the brush 14 makes contact with the blanket cylinder, which is designated 50 in Figure 2. Bearings 52 carried by the ends plates 16 and 18 serve to determine when the cleaning unit 10 has been advanced to its end position. While the cylinder 50 and the brush 14 rotate to scrub the surface of the blanket, water and a cleaning reagent are sprayed onto the brush 14 by means of small holes in pipes 60 and 62, which act as spray jets.

[0020] In the prior art construction shown in Figure 2, the pipe 60 is welded on to the transverse bar 32, and the pipe 62 is mounted by means of brackets 64 on the underside of the cleaning unit and is held in place by bolts 66 that pass through the brackets 64 into threaded holes in the transverse bar 32. Each of the pipes 60 and 62 is formed at both its ends with elbows to allow the relevant liquid to enter the pipe from both ends. This is done to ensure that there is no pressure drop along the pipe. The presence of elbows at both ends does however make it impossible for the pipes to be cleaned internally.

[0021] During use, paper dust tends to collect in the spray jets drilled into the pipes 60 and 62 causing them to block and dirt can also penetrate into the pipes to prevent liquid from reaching the spray jets. When this occurs in the case of a prior art unit as shown in Figure 2, a repair can only be carried out by removing the cleaning unit 10 from the printing press and dismantling it completely to replace the pipe 60 and the transverse bar 32 to which it is welded. Furthermore because the ends of the pipe 62 are made inaccessible by the elbow joints, that pipe cannot easily be cleaned and often has to be replaced. As the removal of the transverse bar 32 requires the entire frame to be dismantled, one normally takes advantage of the inevitable down time to service other items such as the bearings 52 and the rollers 24 and 26.

[0022] To mitigate these problems, the preferred embodiment of the present invention modifies the cleaning unit 10 of Figure 2 in the manner best shown in the equivalent section of Figure 3. In place of the pipe 60 mounted within the interior of the cleaning unit 10, a sub-assembly 100 is formed of two pipes 160 and 162 which is bolted in place of the pipe 62.

[0023] A pipe sub-assembly 100 designed to fit the blanket cleaning unit of a Heidelberg Speedmaster® printing press is shown in Figure 4. The pipes 160 and 162 are straight pipes that are welded to each other and to a rigid back plate 165 to prevent them from buckling when they come in contact with the bristles of the brush. Fine holes 180 in the pipes 160 and 162 act as the spray nozzles which direct water and a cleaning reagent onto the brush. Five mounting lugs 164 welded to the back plate 165 are used to allow the sub-assembly 10 to be bolted onto the outer surface of transverse bar 32 this being a part of the frame of the cleaning unit that is accessible without dismantling the cleaning unit.

[0024] Each of the pipes 160, 162 has a branch pipe 170, 172 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 160, 162. The ends of the pipes 160, 162 are fitted with removable blanking plugs which are not shown in the drawing.

[0025] The sub-assembly 100 can be removed from the cleaning unit after the unit has been slid out of the press without removing it entirely from the press. The sub-assembly 100 is mounted on the underside of the unit and is removed by loosening the bolts passing through the lugs 164 and disconnecting the hoses connected to the branch pipes 170 and 172. 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 more easily when it is reassembled.

[0026] After the sub-assembly 100 has been removed, a replacement is mounted on the cleaning unit 10 and the latter is pushed back into position in the press. By having a replacement ready for substitution, the down time of the press is minimised.

[0027] The removed sub-assembly can be serviced by removing the blanking plugs and passing a cleaning implement along the entire length of each pipe 160, 162. 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 pipes. The individual nozzle holes 180 can also be cleaned using a stiff wire. Once any blockages have been removed, the sub-assembly can be re-used and it need only be replaced when it ceases to be serviceable.

[0028] Even in a multi-colour press, it is only necessary to retain one spare sub-assembly 100 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 100 is being cleaned and the cleaning of each sub-assembly is itself fast because there is no need to dismantle and overhaul the entire cleaning unit. Of course, it is alternatively possible to retain as many spare subassemblies as there are colours, in which case all the cleaning units can be serviced at the same time.

[0029] On occasions, it will still be necessary to remove the entire cleaning unit and to assist in the task two mounting plates 130 (see Figures 2 and 5) are bolted on the cleaning unit which have holes 132 aligned with existing bolt holes in the cleaning unit 10. The plates 130 have welded onto them an internally threaded socket 34 or an externally threaded spigot for receiving a mating thread 138 on the end of handle 136 designed as an elongate tube. It is important to note that no part of the handle 136 nor its mounting plates 130 can intrude into cleaning unit as it could interfere with the rotating parts within the cleaning unit.

[0030] When the handles 136 are not in place, the mounting plates 130 do not present any obstruction to personnel but when the handles 136 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 136 allows an operative to hold a handle with two hands and, with one operative carrying the cleaning unit at each end, it can easily be lifted out of the press and carried away for dismantling and servicing on a suitable work bench.

Claims

1. A blanket cleaning unit (10) for use in an offset printing press comprising a frame (12) to be mounted on the press for sliding movement towards the blanket cylinder (50) of the press, a brush (14) rotatably supported in the frame (12) for scrubbing the blanket when the frame is advanced into a position to bring the brush (14) into contact with the blanket cylinder (50) and two pipes (160,162) mounted on the frame (12) for spraying water and a cleaning agent, respectively, onto the brush (14), characterised in that the two pipes (160,162) are combined to form a single sub-assembly (100) secured to the exterior surface of the frame.

2. A cleaning unit as claimed in claim 1, wherein the sub-assembly (100) is mounted in such a manner as to enable the sub-assembly (100) to be removed from the cleaning unit (10) without the need to remove the entire cleaning unit from the press.

3. A cleaning unit as claimed in claim 1 or 2, wherein each of the pipes (160,162) is straight pipe that is blanked off at both ends by means of removable end caps.

4. A cleaning unit as claimed in claim 3, each pipe (160,162) is provided with a connector at a T-junction (170,172) to permit liquid to be introduced into the pipe.

5. A cleaning unit as claimed in any preceding claim, wherein the two pipes (160,162) are welded to one another.

6. A cleaning unit as claimed in any preceding claim, wherein the two pipes (160,162) are welded to a back plate (165).

7. A cleaning unit as claimed in any preceding claim, wherein sockets (134) are secured to the frame (12) for receiving removable handles (136) by which the cleaning unit (10) may be carried.

Amended claims

Amended claims in accordance with Rule 86(2) EPC.

1. A blanket cleaning unit (10) for use in an offset printing press comprising a frame (12) to be mounted on the press for sliding movement towards the blanket cylinder (50) of the press, a brush (14) rotatably supported in the frame (12) for scrubbing the blanket when the frame is advanced into a position to bring the brush (14) into contact with the blanket cylinder (50) and two pipes (160,162) mounted on the frame (12) for spraying water and a cleaning agent, respectively, onto the brush (14), the two pipes (160,162) being combined to form a single sub-assembly (100) secured to a surface of the frame that is accessible without the need to dismantle the cleaning unit, characterised in that each of the pipes (160,162) comprises a straight section that is blanked off at both ends by means of respective removable blanking plugs and a branch pipe (170,172) connected to the straight section of the pipe at a T-junction located between the opposite ends of the pipe (160,162) to permit liquid to be introduced into the pipe.

2. A cleaning unit as claimed in claim 1, wherein the sub-assembly (100) is mounted on a part of the cleaning unit that is accessible when the cleaning unit is mounted on the press, so as to enable the sub-assembly (100) to be removed from the cleaning unit (10) without the need to remove the entire cleaning unit from the press.

3. A cleaning unit as claimed in claim 1 or 2, wherein the two pipes (160,162) are welded to one another.

4. A cleaning unit as claimed in claim 1 or 2, wherein the two pipes (160,162) are welded to a back plate (165).

5. A cleaning unit as claimed in any preceding claim, wherein sockets (134) are secured to the frame (12) for receiving removable handles (136) by which the cleaning unit (10) may be carried.

Drawing