EP0548500A1 - Device for cleaning the cylinders of a rotary printing machine - Google Patents

Abstract

A device for cleaning the cylinders of a rotary printing machine has an uncoilable cleaning cloth (4) and an engagement body (5). The cleaning which is otherwise carried out at fixed intervals and for which specifically dimensioned cloth sections can be provided is changed to a measure which proceeds with alternating pressing-on of the engagement body (5) and virtually continuous cloth feed (w). The cloth (4) is gripped directly in the pressing-on zone and pulled. An oscillating mechanism which is preferably of pneumatic design is provided for the alternating pressing-on. <IMAGE>

Description

The innovation relates to a device for cleaning cylinders of a rotary printing press according to the generic features specified in the protection claim.

Such a design is known in cleaning devices in which a cleaning cloth is used to hold the dirt adhering to the respective cylinder. The cloth is brought into contact with the surface of the cylinder with an adjusting body, the force exerted to generate a frictional force being generated by an activatable drive.

The contact force must result in the required surface pressure at which a satisfactory cleaning result is achieved. The cleaning effect is based on softening or dissolving the adhering dirt particles from paint residues and paper dust with the help of solvents with simultaneous abrasion of the particles.

Dirt and solvent are removed by the cleaning cloth used, which is pressed against the cylinder in the axially extending contact zone. The absorption capacity of dirt is limited by the structure of the cloth. That is why new, clean strips are periodically fed into the cleaning zone. For this purpose, a cloth feeder winds the cloth from a supply roll onto a dirt roll. With the dirt roller, the dirt absorbed by the cloth can be found as a wrapped layer. As long as a strip of the cleaning cloth is pressed, the rubbed off dirt collects and accumulates.

Shear forces occur in the gap of the accumulating dirt, through which the dirt immediately dodges when relaxation occurs. If the cylinder channel runs through the pressure zone, dirt will penetrate into the channel recess. The "back pressure" exerted in the dirt gap also does not allow proper cloth application and abrasion.

The task is to improve the handling of the dirt jam in the gap between the cylinder to be cleaned and the employed dirt-absorbing part.

The solution is designed by the features specified in the characterizing part of protection claim 1.

It is based on the distribution of the dirt on a larger piece of cleaning cloth. The cloth strip in engagement is enlarged. Because the cloth movement and the high pressing forces necessary for cleaning, which brake the cloth, are excluded, an increased cloth surface area on the nominal surface area of the cylinder to be cleaned, calculated in partial circumferences or cylinder revolutions, is solved in a kinematic manner.

For this purpose, a contact pressure change is applied in quasi-continuous operation. The contact pressure change is based on the drive of the dirt-receiving part. Does the pressure device run e.g. with a cam or crank drive back and forth, maximum and minimum contact pressures are created synchronously.

When this alternating application is carried out by means of a pressurized medium which acts on a membrane as a pressure element, the alternating application is generated by corresponding pressure changes.

The relationship between the normal pressure force generated by the pressing device and the frictional force which is decisive for the cloth movement allows a coupling between the alternating application of the pressing force and the cloth movement.

A cloth under tension is preferably brought into a decreasing and increasing feed movement in accordance with increasing and decreasing contact pressure.

Moving the cloth forward results in the cloth sliding on the pressure element. There is a considerable speed difference between the rotating cylinder surface and the cloth feed movement. To reduce the stress that occurs when the cloth slides on the pressure element, it is possible to move the pressure element partly tangentially with the cloth.

The pull to be applied to the cloth results in a constriction in the loaded zone of the cloth, which means that the width of the cloth in the cleaning zone is smaller than the unloaded nominal width of the cloth. This constriction is countered by keeping the stretch of the cleaning cloth as short as possible. For this purpose, a cloth clamping point is formed as close as possible to the cleaning strip of the cleaning cloth. The main tensile force is not introduced at the winding spindle, but at this clamping point. The clamping point which locks the cleaning cloth and moves with the cloth is reset outside the operating cycle of the cleaning device.

The clamping point of the cloth in the pull section on this side between the cleaning strip and winding roll can be supplemented by a parallel clamping point on the other side between the cloth processing, supply roll and cleaning strip.

The first and the second clamping point are steered together. They form a tenter frame enclosing the cleaning strip.

In order to make the sliding of the cloth on the pressure element wear-resistant for the stressed sliding surface of the pressure element, it is possible to arrange an intermediate layer between the cleaning cloth and the pressure element. This intermediate layer, which can be made from a film of low-friction material, can either firmly cover the sliding surface of the cloth on the side of the pressure element or can be moved by appropriate fastening at the clamping points mentioned.

The advantage here is that there is no friction and scraping effect between the cleaning cloth and the pressure element.

The underlying process for cleaning cylinders of a rotary printing press is as follows: the cloth extending across a contact zone on a cylinder is pressed, the cloth is pulled through the contact zone, the contact pressure is applied alternately, the cloth movement is coupled with the changing contact pressure, so that increasing / decreasing lengths of cloth are moved through the pressure zone. The radial movement applied to the pressure element or the cyclically applied pressure is coupled with the change course of the cloth movement. The cloth is moved under the influence of the variable value of the friction. The claimed unwinding length of the blanket in the pressure zone is made as short as possible by intermediate clamping.

In the ideal case, the sequence of the movement or the pressure of the pressure element and the sequence of the cloth movement are continuous, here constantly changing. In practical operation, however, discontinuous, jerky movements can also appear.

Technically and objectively, the innovation offers several advantages, with improved dirt removal, more even use of the cleaning cloth with more even loading of the cloth with dirt, lower rubber blanket load with the resulting longer service life of the rubber blanket, lower amounts of in the channel or in the pit of the cylinder accumulated dirt can be achieved.

There follows an exemplary embodiment of the invention which is explained with reference to drawings.

Fig. 1:

Anstellkonturen einer Anpreßeinrichtung bei einer Vorrichtung zum Reinigen von Druckmaschinenzylindern;

Fig. 2:

Schematisierter Zusammenhang zwischen der Tuchreibung R (Normalkraft/Anpreßdruck N) und dem Tuchvorschub w;

Fig. 3:

Wechselantrieb für die Anpreßeinrichtung,

• a) pneumatisch
• b) mechanisch;

Fig. 4:

Drehantrieb für die Tuchaufwickelrolle,

• a) E-motorisch,
• b) direkter Tuchantrieb (Servozylinder, Traktor, Stachelwalze)
• c) Torsionsantrieb;

Fig. 5:

bewegter Spannrahmen mit Tuchabschnitt.

The figures show:

Fig. 1:

Contour contours of a pressing device in a device for cleaning printing press cylinders;

Fig. 2:

Schematic relationship between the cloth friction R (normal force / contact pressure N) and the cloth feed w;

Fig. 3:

Change drive for the pressure device,

• a) pneumatic
• b) mechanical;

Fig. 4:

Rotary drive for the cloth winding roll,

• a) electric motor,
• b) direct cloth drive (servo cylinder, tractor, spiked roller)
• c) torsion drive;

Fig. 5:

moving stenter with cloth section.

Compared to the cylinder 1 of a printing unit of a printing press, for. B. a web β printing blanket cylinder of a web-fed offset printing machine, a cleaning device 3 is arranged, which is used for cleaning the outer surface of the cylinder 1 from time to time. The cylinder 1 covered with a rubber blanket has a tensioning channel 2 which has dirt-absorbing edges even when a filler is used.

The cleaning device 3 consists of an adjusting body 5, in front of which a cleaning cloth 4 runs opposite the cylinder 1, the handling of which from a supply roll 7 to a winding roll 6 is ensured by a cloth drive 8. For the purpose of cleaning, the adjusting element 5 provided with a pressure element 9 moves from a rest position H into the engagement position E pressing the cloth 4 against the cylinder 1. The contact with the engagement position E, which presupposes the cloth 4, takes place under the effect of variable contact pressure or variable, pressing normal force N, on which the friction force R depends.

Instead of the variable surface pressure that occurs, several engagement positions E ', E' ', E' '' are drawn in contour to illustrate "hard" and "soft" positions. At E 'there is extreme pressure on the cloth 4. At E '' the contact pressure is reduced and the cloth 4 is easier to move with respect to the position E 'when the pull is applied. In position E '' 'there is still a touch, but the cloth 4 is easily movable. With further spacing of the adjusting body 5 with the cloth 4 away from the cylinder 2, the rest position H is assumed.

The development of the cloth 4 and the direction of rotation of the cylinder 1 are preferably in opposite directions. Coincidence is also possible. The in the inlet gap 10 between the cylinder 1 and the cloth 4 collecting dirt tries to escape through the pressure gap. When the tensioning channel 2 runs past, a partial relaxation occurs, so that the dirt penetrates into the depression provided.

The amount of dirt sitting in the inlet gap 10 is limited when a part of it is removed via the cloth 4 in the intended direction of development of the cloth 4. If the engagement position E is moved from E 'to the "softer" positions E' ', E' '', the fabric unwinding changes to an increasing feed rate w.

Figure 2 shows the relationship between the cloth feed w and the frictional force R (N), the frictional force R representing the total surface pressure. The point I on the y-axis means that with friction force R = 0 e.g. in the rest position H of the cleaning device 3, any feed speeds w can be controlled for removal of the soiled strip of cloth. Point II on the x-axis indicates the application of extreme frictional force at a practical cloth feed speed w = 0. Between points I; II runs the feed curve. (This feed curve can also progressively increase from approximately w = 0; R = 0, but the operation, which is favorable in itself, would be connected with excessive feed with maximum pressure and excessive cloth constriction. Depending on the characteristic curve of the cloth drive 8, characteristic curves w (R) set up that are constant or hyperbolic as shown in dashed lines.)

The contact of the cloth 4 on the cylinder 1 between the fixed pressure and the position out of contact from E, E ', E'',E''' to H is generated by the adjusting drive 11. The back and forth movement of the adjusting body 5 of the cleaning device 3 takes place by means of a control curve 24 which controls the deflection of the pressure element 9 in time or in phase (FIG. 3b).

According to FIG. 3a, the adjusting body 5 is coupled to a cam drive or to a crank drive which acts on the back and forth movement. During the periodic rotary movement of the cam or crank operation, the surface pressure of the cloth 4 changes from minimal to maximum.

In the case of a construction of the cleaning device 3 as a cleaning bar with an elastic pressure element 9, which is brought into the rest position H by pressure or by inflow into the engagement position E, correspondingly by relaxation or outflow of the fluid, there is a line system for supplying the fluid. To achieve changing internal pressure in the pressure element 9 is supplied with a constant pre-pressure. The interior of the pressure element 9 is connected to an overpressure valve 12 which is adjustable in terms of the release value and the opening characteristic. Inflow of the fluid with increasing pressure on the cloth 4, opening of the pressure relief valve 12 with accompanying relaxation of the internal pressure, again closing of the pressure relief valve 12 with renewed pressure build-up change with one another.

Instead of a constant supply of the pressure element 9 with a supply line led via a reducing valve, a buffer 13 can be set up which alternately feeds and reduces the pressure due to its volume change. To compensate for pressure loss, the closed, corresponding volume connecting the buffer volume and the interior of the pressure element 9 is provided with a fluid supply. The consumption of e.g. However, compressed air is low compared to the structure that works with a leak through the pressure relief valve 12.

For increasing and decreasing pressure as the pressure element 9 moves back and forth, a two-way valve 16 can be placed in the supply line 14, through the rotation of which compressed air flows periodically and flows out of the interior of the pressure element 9 via the vent 15.

With the existing coupling of the cloth feed w with the changing surface pressure by the pressure element 9, the rotary movement of the two-way valve 16 is coupled with the cloth drive 8. According to FIG. 2, in the venting phase there is an increasing, in the pumping-up phase decreasing, towards zero cloth advance.

The cloth winder with the take-up reel 6 applies the tension necessary for the movement of the cloth 4 in a spaced-apart position and in a pressed-against position against the cylinder 1 against the frictional force R. The winding spindle 17 is connected on both sides to electric motors driving via worm drives 18. Electric motors as 4-wire asynchronous motors or as DC shunt motors have a relatively small size and are suitable for space-saving installation of the cloth drive 8.

The planned movement of the cloth 4 is in the peeling direction, counter to the direction of rotation of the cylinder 1. The cloth 4 is thus automatically tightened against the pull caused by the cloth drive 8. To ensure that the cloth 4 is handled more tightly, the supply roll 7 is provided with an adjustable friction brake, as indicated in FIG.

The rotational movement of the electric motors, ie the cloth drive 8, can be controlled in terms of torque and speed by means of a pressure sensor attached to the pressure element 9, so that the characteristic curves according to FIG. 2 can be fulfilled. For the characteristic curve with, for example, a constant course of the feed w over the frictional force R, the torque of a small amount with the spaced position of the pressure element 9 changes to high torque with strong pressure.

According to another embodiment for the rotary drive of the winding 6, a torsion bar 19 is provided inside the winding roller 6. The principle of the torsion drive shows a firm clamping of the torsion bar 19 within the take-up reel 6 and a rotatable bearing provided with an actuating lever 20 on the other side of the torsion bar 19. A cloth drive 8 designed as a linear servo drive 8.1 acts on the actuating lever 20. The clamping point of the actuating lever 20 on the torsion bar 19 runs for moving the actuating lever 20 relative to the winding roller 6 to be rotated via a freewheel or ratchet drive with a pawl. During operation of the servo drive 8.1, the torsion bar 19 is prestressed, the take-up roll 6 remains in a manner suitable for processing.

To advance the cloth, the take-up roll 6 is released by means of a clutch or a ratchet wheel 20.1, with which the take-up roll 6 moves in the biasing direction of the torsion bar 19 until it is again locked by means of the clutch 21.

The torsion drive has the advantage of simple mechanical construction and simple operation. When using a two-sided pawl for the clutch 20.1 - two-sided in such a way that a locking element is disengaged and disengaged as in the unrest of a watch - very small feed cycles of the cloth 4 can be achieved. The spring element in the form of the torsion bar 19 can also by another spring element, for. B. can be replaced or supplemented by a linear spring between the servo drive 8.1 and the actuating lever 20.

If the feed movement of the cloth 4 is to take place without a constant pull caused by a spring element, the servo drive 8.1 transmits the servomotor movement directly to the take-up reel 6 in short, fast cycles (FIG. 4b).

The introduction of the tensile force for the cloth feed on the winding spindle 17 is relatively indirect because of the winding positions of the cloth 4, because the piece of cloth 4 that is actually to be advanced is limited only to the section in front of the pressing element 9. For the direct introduction of the pull with respect to this section Arranged to the left and right of the adjusting body 5 is a cloth tractor 21 formed from a barbed loop. The driven barbed endless loop only captures the relevant section of the cloth 4 in the area of the pressure element 9.

To advance the pulling engagement from the winding spindle 17 closer to the pressing element 9, it is also possible to place a driven spiked roller 21.1 with cloth engagement over the entire width of the cloth directly parallel to the pressing element 9 to the winding side (FIG. 4b).

Another construction with restriction of the loading zone essentially to the pressed-on section of the cloth 4 consists of a tensioning frame 22 which extends in a window shape in front of the pressure element 9. The tensioning frame 22 shows, seen in the direction of development of the cloth 4, a clamping strip 23 a upstream of the pressing element 9 and a clamping strip 23 b downstream of the pressing element 9. The terminal strips 23 a; 23 b form clamping points for a clamping section T extending therebetween. During a feed period, the cloth 4 moves from the beginning of the clamping section T to the end of the clamping section T. In the end position of the tensioning frame 22 towards the winding roller 6, the clamping strips 23 a; 23 b the cloth free, whereupon the tensioning frame 22 is moved back into the starting position. In the initial position, the terminal strips 23 a; 23 b the cloth 4 is clamped again (FIG. 5).

The movement of the tensioning frame 22 takes place either linearly, specifically tangentially to the pressure element 9, or by means of a pivoting movement which relates to a pivoting of the tensioning frame 22 over an angular range.

The displacement of the tensioning frame 22 towards the supply roll 7 is coupled with a loosening of the clamping points 23 a; 23 b in an automatic manner based on the belt buckle principle. If the cloth 4 is pulled, the clamping is reinforced automatically by a clamping wedge or by stronger, higher friction wrap. When the tension on the cloth 4 subsides, the clamping connection loosens and the tensioning frame 22 can be moved back relative to the cloth stretch held between the winding roll 6 and the supply roll 7.

When using the tenter frame 22, the essential fabric feed forces are applied by the tenter frame 22. The power of the drive for the tenter frame 22 is decisive for overcoming the frictional forces prevailing when the cloth 4 is pressed on. The drive power is therefore essential in the design of the characteristic curves according to FIG. 2. If the drive power is low, the cloth 4 can only be moved when contact with the cylinder 1 decreases. With high drive power, the feed movement of the cloth 4 is possible without hindrance even with strong pressure, strong contact with overcoming the frictional force R.

Claims (9)

Device for cleaning cylinders of a rotary printing machine with a development of a cleaning cloth, which can be pressed against the lateral surface temporarily with the aid of a normal body exerting a normal force on the lateral surface of the cylinder and can be forcibly moved for the purpose of exchanging fresh for dirty cloth when the position of the connecting body is from an engaged position alternately extends into a rest position spaced apart from the lateral surface of the cylinder,
characterized in that the engagement position is made finely adjustable to a plurality of closely adjacent positions (E ', E'',E''') by variable application of the pressing force (N) within a value-defined working range and that the movement of the cloth (4th ) depending on the positions (E ', E'',E''') can be controlled by a cloth drive (8) guided by the value of the contact pressure (N). Device according to claim 1,
characterized in that for the engagement positions (E ', E'',E''', H) there is provided an adjusting drive (11) which alternately displaces the adjusting body (5) by means of a control cam (24). Device according to claim 1,
characterized in that a pressure element (9) is membrane-like, that the positions (E ', E'',E''', H) can be generated pneumatically and fluidic means (12-15) are provided for pressure build-up and pressure reduction. Device according to claim 3,
characterized in that the pneumatic adjusting drive (11) is provided with an alternately draining, closing pressure relief valve (12). Device according to claim 3,
characterized in that the pneumatic actuator (11) is provided with an alternating pressure on the pressure element (9) leading multi-way valve (16). Device according to claim 1,
characterized in that there is an electric motor which can be operated at variable speed for the cloth drive (8). Device according to claim 1,
characterized in that the fabric winding can be pretensioned with a spring element (19) and can be released depending on the pressing force (N) by means of a stepping mechanism (Maltese cross) or a clutch (20.1). Device according to claim 1,
characterized in that the tensile force for the winding of the cloth in the pressing area of the cloth (4) in front of the pressing element (9) can be introduced by means of a cloth tractor (21) or a spiked roller (21.1) or an advanced clamping frame (22) with clamping strips (23a, 23b) . Method for operating a cleaning device for cylinders of a rotary printing press with an unwinder of a cleaning cloth and an adjusting body which can be set against the cylinder,
characterized in that the adjusting body is oscillated back and forth in a spacing area which comprises the touch of the cloth on the cylinder between low and strong and, accordingly, the pressure between high and low value, and the cloth is simultaneously moved forward with changing transport speed.

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