EP0893252B1 - Apparatus for adjusting web tension after a chilling unit in a printing press - Google Patents

Description

The present invention relates to a Device for regulating the tension of a material web in one Cooling device in a printing machine subsequent area, according to the preamble of claim 1.

In the case of web printing machines, a continuous paper web is passed through the machine guided. The web moves through various components of the press and is guided over driven rollers and free-running rollers, the driven rollers provide the driving force and the free running or guide rollers for the position, guidance and direction of the train.

A web press usually includes a plurality of processing units, such as printing units, a drying unit, a cooling unit and a slitter unit. To produce a color print, each printing unit prints its own color on the Train. In a printing press with four printing units, z. B. a first printing unit Black, a second cyan printing unit, a third magenta printing unit and a fourth Yellow printing unit. The web moves through the nip of each printing unit from one printing unit to another. After the web passes the nip of the last Has left the printing unit, it moves through the pull rollers at the entrance of a subsequent processing unit, e.g. B. a cooling unit.

A pair of traction rollers comprises a pair of cylindrical rollers, which with their axes in the are arranged substantially parallel to each other. The peripheral surfaces of the drawing rollers are in rolling contact with each other and the material web moves between the Pull rollers through on a path that is approximately perpendicular to the plane of the two parallel axes of the rollers. The surface speed of the web is almost identical to the peripheral speed of the drawing rollers.

However, if two pairs of pull rollers rotate in such a way that the Peripheral speed of the first pair is different from that of the second pair, or if there is a slippage between the drawing rollers and the web, this may result lead to an increase or decrease in tension in the web. The train is considered tense or taut when there is a change in web length from 0.1% or more is present. The web is considered sagging or limp when the length of a path section between two points a standard value by z. B. Exceeds 0.1% or more. Of course, other criteria can also be applied to determine if a web is taut or slack. The above The criterion described is based on a 100% safety factor that the The underlying observation is that certain types of paper tear when they have a value stretched beyond 0.2% of their original length.

When a first pair of draw rollers through which the web moves moves at a higher rate Peripheral speed rotates as the following pair of draw rollers, it is possible that a reduction in the web length by z. B. 0.1% occurs, which is in a sag of Railway results. This state of sag in the web is also called a limp web designated.

If, alternatively, the first pair of draw rollers is slower than the next pair turns, then the tension builds up in the web and can slip between the Cause rollers and the web. If the tension is high enough, it can be one Break or break the web. In this case the press must be switched off to remove the torn parts of the web and the web has to go through the Printing machine run, resulting in costly downtime and loss of work leads.

In conventional printing presses, the web moves through the printing units, the Dryer and the cooling unit and then to a slitter. The cooling unit is that first unit in which the web comes into contact with a nip after it has moved out of the machine dryer.

The purpose of the cooling unit is to cool the heated web before it is in the folder the printing press is processed further. The cooling unit includes a variety of Cooling rollers, over which the web is guided to cool the web. The last of the Cooling rollers together with another roller form a pair of pull rollers at the exit the cooling unit. Since the dryer usually does not have a pair of draw rollers, it is one Another purpose of the cooling unit is to pull the web through the drying unit.

A series of fixed guide rolls is usually between the draw rolls at the exit of the cooling unit and the pull rollers at the entrance of the slitter arranged. These guide rollers rotate freely around fixed axes and become driven by the contact of the guide rollers with the web.

A disadvantage of this embodiment is that the guide rollers relax the Only allow the web to slip between the guide rollers and the web. To this In this way, only a limited amount of tension can be released. Another disadvantage is that guide rolls are not suitable to create the sag of a web eliminate.

Various attempts have been made to slack off the slack Eliminate webs or reduce the occurrence of broken webs or to prevent, however, none of these attempts resolved the problem.

An attempt was made to use motor-driven voltage control systems which Maintain tension of the web by changing the motor speed of the web Driven rollers regulate that the feed rate for certain rollers is either increased or decreased. Reducing engine speed reduces feed rate, preventing downstream web sag becomes. Increasing the engine speed reduces the voltage in downstream the web, thereby preventing a web break. Conceptually the solution seems to be good, but in practice it has been shown that the Response time of these motorized control systems is usually too long eliminate the conditions of a sagging web or a broken web, before problems arise. In the same way, the known ones based on a Changing the engine speed does not work web tension control systems to a sag of the web or too high a web tension during the Effectively eliminate the time period of the press start-up during which the Dynamic control requirements are particularly high.

To regulate tension and sag in the web were behind the Infeed unit used by offset printing machines dancer rollers. This regulates it Infeed unit, which is located between the roll stand and the first printing unit, the web is fed into the first printing unit in such a way that the web with the correct Tension enters the first printing unit. There are dancer rolls between that Roll stand and the infeed mechanism provided to keep a constant web tension behind the infeed unit, or there are dancer rollers between the infeed unit and the first printing unit provided to a constant web tension on the first Get printing unit. However, dancer rolls are not usually used in the Cooling unit downstream area of a printing press used because of this negative effects on the cutting register or the length of the in the folder generated signatures are feared. The cutting register regulation concerns the Regulation of the speed and position of the web, especially in relation to the position of the print image to signatures in the unprinted area to cut. A dancer roller causes dynamic changes in the path length of the Train. If a dancer roll is placed downstream of the printing units, then changes the path length of the web on which an image was printed, which in turn increases Difficulty in maintaining the cutting register.

WO-A 90/15715 describes a web-fed rotary printing press in which one Web tension control in the area after the chill roll level by using a acting as a pull roll cooling roll, the rotational speed is dependent is increased or decreased accordingly by the web tension. The web tension is measured on a further roller, which is subordinate to the cooling roll serving as the drawing roll.

US-A 3,556,510 describes a web-fed rotary printing press in which the over a Printing roller web guided by a roller with a pull roller cooperating slitter in a variety of individual web strands is divided, each of which has an associated dancer roller and one Subordinate pull roller arrangement for controlling the cutting register is performed.

DE-A 39 06 043 describes a method with an arrangement for building up the Web tension before starting in a web-fed rotary printing press, in which the Substrate is guided over a dancer roller before being fed to the printing units, which is mounted on a lever arm which can be pivoted at one end supported on the frame of the printing press.

According to the invention the object is to be achieved during a sag of the web to avoid starting up the printing press.

This object is achieved by the features of claim 1. Further Features of the invention are contained in the subclaims.

According to the present invention, a device for regulating the voltage comprises a Web in a printing press an adjustable positionable dancer roller with a Air cylinder is connected and the web downstream of the drawing rollers at the exit of the Cooling unit and in front of a next pair of draw rollers, e.g. B. the pull rollers at the entrance of Slitter, contacted. The air cylinder applies a pressure to the dancer roller constant force while a control device that with the air cylinder and the connected next pair of pull rollers, monitors the position of the dancer roller. In In response to a movement of the dancer roller indicating a sag in the web, the speed of the next pair of draw rollers is determined by the control device increased to eliminate the slack. Conversely, in response to movement the dancer roller, which shows a reduction in the length of the web between the pull rollers Exit of the cooling unit and the drawing rollers before the next processing unit of the Printing press indicates by the control device the speed of the next Pull roller pair reduced. Thus the tension in the web between the Pull rollers at the exit of the cooling unit and the next (downstream) Pull roller pair kept essentially constant. It should be noted that the same Principle, albeit in the opposite sense depending on the speed increase or - Reduction can be applied to a control system in which the position of the Dancer roller the speed of the pull rollers at the exit of the cooling unit instead of Speed of the drawing rollers of the next unit is regulated. Because the web are kept in a taut state and the position of the dancer roller is checked sagging or slack webs, especially when starting up Avoided printing press and maintained the regulation of the cutting register.

According to a first embodiment of the present invention, the Dancer roll along an arc with a radius that is essentially two parallel lever arms is determined, with at each end of the axis of rotation Dancer roller is a lever arm with one end rotatably attached. The other The end of each lever arm is rotatably connected to the machine frame. Two in substantially parallel air cylinders are rotatably connected to the dancer roll, and an air cylinder with one end at each end of the axis of rotation Dancer roll. The other end of each air cylinder is at a different location on the Frame rotatably attached. One embodiment sees a 90 ° angle between that Lever arm and the air cylinder, under which both with the axis of rotation of the Dancer roller are connected. There are also other relative angles between the Lever arms and the air cylinders can be realized. Regardless of the size of the Relative angle this embodiment provides that the dancer roller along a Arc moves, the radius of which is the lever arm, while the air cylinder in response apart on the forces exerted by the web on the dancer roller and be brought together. Another advantageous embodiment provides that the arc on which the dancer roll moves is in a substantially horizontal Level lies. Such a construction also contributes to minimizing the Effect of gravity on the mass of the dancer roller.

According to a second embodiment of the present invention, the Dancer roller essentially straight or linear. The linear path is two in given essentially parallel air cylinders, with at each end of the An air cylinder is attached with one end to the dancer roller. The other end of the respective air cylinder is attached to the machine frame so that the air cylinder can't turn. This will essentially force the rod of the air cylinder straight forward and backward, resulting in a linear movement of the Dancer roll results. The dancer roller can also be used on both ends Frame fixed movable supports to be mounted to their linear movement facilitate. It is also conceivable that using movable supports for Guiding the linear movement of the dancer roller different arrangements with one or more air cylinders are possible to move the dancer roller influence. According to the present invention, the air cylinder and the Dancer roller in a neutral position when the speed of the out Cooling unit emerging part of the web at the speed of in the Longitudinal cutter entering part of the web matches. However, if one Speed difference between the web part emerging from the cooling unit and The air cylinder becomes the part of the web entering the slitter extended or retracted as needed to position the dancer roller change and maintain a constant tension in the web. The change in Position of the dancer roll is detected by the control unit, the speed of the traction rollers arranged at the entrance of the slitter are increased accordingly or reduced. Changing the speed of the pull rollers at the entrance of the Longitudinal cutter brings the dancer roller back into its neutral position. If the The dancer roller remains in its neutral position, the speed of out of the right Cooling unit emerging web part essentially at the speed of in the Longitudinal cutter entering web part. The changes in position of the Find the dancer roller and the resulting speed adjustments of the pull rollers particularly when the press is ramping up while an essentially constant tension is maintained in the web. The cutting register can continue after reaching a correct speed if necessary be readjusted.

The present invention is more preferred in the following description Embodiments in connection with the attached, explained below Drawings explained in more detail.

Fig. 1

eine Ansicht einer herkömmlichen Druckmaschine;

Fig. 2

eine Seitenansicht eines der Kühleinrichtung nachfolgenden Bereichs der Druckmaschine, der eine Anordnung mit einer Tänzerwalze gemäß einer ersten Ausführungsform der vorliegenden Erfindung aufweist;

Fig. 3

eine Seitenansicht des der Kühleinrichtung nachfolgenden Bereichs der Druckmaschine, der eine Anordnung mit einer Tänzerwalze gemäß einer zweiten Ausführungsform der vorliegenden Erfindung aufweist;

Fig. 4

eine perspektivische Ansicht einer Tänzerwalze, die in linearen Schienen gehalten wird, welche am Rahmen der Druckmaschine befestigt sind;

Fig. 5

eine Seitenansicht des der Kühleinrichtung nachfolgenden Bereichs einer Druckmaschine, der eine Anordnung mit einer Tänzerwalze gemäß einer dritten Ausführungsform der vorliegenden Erfindung aufweist.

Show it:

Fig. 1

a view of a conventional printing press;

Fig. 2

a side view of a region of the printing press following the cooling device, which has an arrangement with a dancer roller according to a first embodiment of the present invention;

Fig. 3

a side view of the area of the printing press following the cooling device, which has an arrangement with a dancer roller according to a second embodiment of the present invention;

Fig. 4

a perspective view of a dancer roller, which is held in linear rails which are attached to the frame of the printing press;

Fig. 5

a side view of the area of the printing machine following the cooling device, which has an arrangement with a dancer roller according to a third embodiment of the present invention.

The present invention relates to a device for controlling the voltage in the web running through a printing press.

1 shows a conventional printing press with a roll stand 100, a Feed mechanism 200; a first printing unit 300, a second printing unit 400, a third printing unit 500, a fourth printing unit 600, a drying unit 700, a Cooling roll stand 800 and a folder 900. A paper roll 110, of which the Web 120 is withdrawn, is in the roll stand 100. The web 120 moves from the roller stand 100 to the feed unit 200, from where they continue through one Inlet nip and moved around a dancer roller, not shown. From there the web 120 moves into the first printing unit 300, which e.g. B. the color black the web prints, and on to the second printing unit (which prints cyan), the third Printing unit 500 (which prints magenta) and into the fourth printing unit 600 (the yellow printed).

After leaving the fourth printing unit 600, the web 120 enters the Drying unit 700, wherein it is dried by supplying heat. Since the Web 120 stretches or shrinks in length due to heating and moisture loses, the tension of the web after exiting dryer 700 and Change 800 before entering the chill roll stand. The chill roll stand 800 includes a plurality of chill rolls that pull the web out of dryer 700 and cool at the same time as the web passes between the chill rolls emotional. The individual cooling rollers are driven simultaneously, which z. B. by a Belt drive system is done. Should the web 120 yield or give due to a imprecise absorption by the cooling rollers can be longer, so the dryer can Blow excess web into an arcuate path and thus the correct one Maintain tension in the web. Because the web tends to move through shrinking the cooling rolls, the tension in the web can also change again.

In the systems of the prior art, the web moves after leaving the Pull rollers at the exit of the cooling unit by a variety of guide and control rollers, before moving between the pull rollers at the entrance of the slitter in Folder 900 moved through. The guide and control rollers can, for. B. used to steer the web, apply silicone to the web or that To control the cutting register or the cutting length. As mentioned above, guide rollers can do not fix the condition of a limp web and offer only very limited Opportunities when it comes to reducing web tension.

According to the present invention is between the drawing rollers at the exit of the cooling unit and the dancer rollers at the entrance to the slitter intended. The dancer roller device includes a dancer roller with respect to the printing unit is mounted in such a way that it is moved relative to the printing unit can, and furthermore has a force compensation element, for example an air cylinder, which exerts an essentially constant, position-dependent force through which the Dancer roller is kept in contact with the web.

Fig. 2 shows a side view of a cooling unit of the printing press downstream Area with a dancer roller device according to a first embodiment of the The present invention. The web 120 moves around a series of driven ones Cooling rolls 2, 3, 4, 5 and 6 which cool the web 120. Lane 120 joins the Cooling roller 2 into the cooling unit and moves around rollers 3, 4 and 5 and between the nip formed by the cooling roller 6 and the pull roller 7 on Cooling unit exit through. Then the web 120 passes a guide roller 8, one Dancer roll 20 and a guide roll 50 before moving into a downstream Processing unit in the nip 9 at the entrance of the slitter emotional.

The dancer roller 20 is with its axis on the air cylinder 30 and on one Lever arm 40 attached. The air cylinder 30 is at its first end with the Dancer roller 20 and with its second end rotatable with the machine frame connected. The lever arm 40 is at its first end with the dancer roller 20 and its second end rotatably connected to the machine frame. This Configuration ensures that the dancer roller 20 along with an arc a radius that corresponds to the length of the lever arm and at which the Center or the fulcrum at a point where the lever arm with the Frame is connected.

The air cylinder 30 stretches and retracts like this from the application of force the web 120 is determined on the dancer roller 20. The air cylinder 30 is with a constant pressure (P) applied to a certain force or load generates the same as the pressure (P) multiplied by the working area (A) of the cylinder is. This specific force (PA) compensates for that from the web 120 on the Dancer roller 20 exerted force, so that the dancer roller 20 in a neutral position is held when the web is not under tension or slack. There are not any resulting forces on the dancer roll, d. that is, the forces are balanced are and therefore no acceleration of the dancer roller occurs. If that on the Dancer roller 20 acting load of the web 120 decreases, the air cylinder 30 moves in such a way that a corresponding movement of the dancer roller 20 sags the web 120 eliminated and the web load increased again to the predetermined level. If if the web load increases, the air cylinder moves in the opposite direction, so that a corresponding movement of the dancer roll 20 the web load on certain measure reduced.

A position sensor 60 is connected to the lever arm 40 and a control unit 90. The control unit 90 controls based on the position of the lever arm 40 the speed of the pull rollers 9 at the entrance of the slitter.

When the part of the web 120 leaving the cooling roller unit 2-6 (position 80) at the same speed as that in the nip 9 at the entrance of the Longitudinal cutter entering part of web 120 (position 85) moves, takes Dancer roller 20 a neutral starting position, as shown in Fig. 3. If the path speed at position 80 is higher than the path speed at Is position 85, the air cylinder 30 is extended and moves the Dancer roll 20 to eliminate slack in the web. If the Web tension at position 80 is lower than the web tension at position 85 the air cylinder 30 collapses to prevent the tension in the Lane 120 exceeds a threshold.

The position sensor 60 attached to the lever arm 40 detects any deviation of the Dancer roller 20 from the neutral position and sends a deviation value 95 to the Control unit 90. The position sensor 60 can e.g. B. be designed so that it Deviation values between 0.0 and -10.0 for a corresponding incremental Moving the air cylinder between, for example, approx. 0 to -5 cm (0 to -2 inches) or about 0 to -10 cm (0 to -4 inches); and that he has deviation values between 0.0 and +10.0 when the air cylinder moves apart incrementally between, for example, about 0 to 5 cm (0 to 2 inches) or about 0 to 10 cm (0 to 4 inches) returns. Of course, these values are only given as examples and the real ones Movement of the dancer roller 20 depends on the physical dimensions of the Device related to the system applied to it. It can be a Transducer (LVDT) is provided to convert a linear voltage into a distance to be the deviation value 95 based on the position of the dancer roller 20 deliver. However, other sensors can of course also be used for this purpose be used. As is known from the prior art, the Deviation value 95 can be any suitable control signal, such as. B. an analog Voltage, an impedance, a digital value or other signals which the Control unit 90 can be supplied with or without additional signal conditioning. Depending on the deviation value 95 output by the position sensor 60 the control unit 90 increases or decreases the speed of the pull rollers 9 am Input of the slitter at a speed that is necessary to get the To move dancer roll 20 back to its neutral position. This can Cutting register in the downstream cross cutter, especially during startup the printing press are essentially maintained.

Alternatively, the control unit 90 can adjust the speed of the pull rollers 6, 7 am Increase or decrease the cooling unit output to achieve a similar result, d. H. to move the dancer roll 20 back to its neutral or home position. According to a second alternative, the control unit 90 can control the speed of a or both pull rollers 6, 7 at the exit of the cooling unit or the pull rollers at Increase or decrease the input of the slitter to get the dancer roller 20 back in to move their neutral position.

In general, the position of the dancer roller 20 is determined by the equilibrium of forces acting on the dancer roller 20, which can be expressed as T ₁ + T ₂ = PA, (here is a 180 ° turn around the dancer roller 20 with neglected friction and one not considered mass)), where T ₁ the tension in the web 120 when entering the dancer roll 20, T ₂ the tension in the web 120 when the web leaves the dancer roll 20, P the pressure in the air cylinder 30 and A the working surface of the Air cylinder 30 is. The position of the dancer roller 20 is related to the amount of paper moved through the nips over a period of time.

If the nip 6, 7 at the exit of the cooling unit moves a quantity of paper dl ₁ in a period of time dt and the nip 9 at the entrance of the slitter moves a quantity of paper dl ₂ in the same period of time, the difference integrated over time results in a value Δ1 which is different from the Dancer roll must be included to maintain web tension. The value Δ1 results from the following equation: Δ1 = ∫ 0 t (dl 2 / dt - dl 1 / dt) dt or Δ1 = (l 2 - l 1 ) at time t

If the speeds in the nip of the drawing rollers 6, 7 at the outlet of the cooling unit and the drawing rollers 9 at the entrance of the slitter are substantially the same, e.g. B. have a value such that the elongation caused by the tensile load on the web is less than 0.01% of the web span (the slip is neglected and the radii are assumed to be constant): dl 1 = d 1 r 1 and dl 2 = d 2 r 2 and Δ1 = ∫ 0 t [(D 2 / Dt) r 2 - (d 1 / dt) r 1 ] German or Δ1 =  2 r 2 -  1 r 1 at time t. However, if there is slip, as is often the case, then equation (5) is not an accurate representation and equation (1) must be used.

There are generally two operating modes or modes of operation with dancer rollers. at In the first operating mode, the web is taut and therefore the web tension over one Period constant. In the second mode, the web is loose or limp. at In this mode of operation the web tension is reduced and the web is called sagging Track called.

In mode 1, a lightweight, fast-acting air cylinder 30 eliminates any cyclic voltage change below a preselected cutoff frequency. The clipping frequency is determined by the physical properties of the Dancer roller device, such as the spring constant and the damping constant of Air cylinder 30 and the mass of the dancer roller determined. For example, are suitable an air cylinder 30 and a dancer roller 20 with a natural frequency of 10 Hertz, Record deviations in the web tension in the range of 10 Hertz. Depending on the physical and dynamic properties of the printing press can be higher or lower natural frequency of the dancer roller device may be required. in the Operating mode 1 does not result in any significant movement of the position of the dancer roller 20 detected. In operating mode 2, a still movable dancer roller 20 is required to absorb the changes in length Δ1 generated in the path 120. If the Tension in the path is constant, Δ1 represents the cumulative deviation of the two speeds of the rolls, as shown in Equation 4.

In operating mode 1, the voltage is normally stabilized by balancing the forces acting on the dancer roller 20. However, e.g. B. during the machine start-up times the dancer roller 20 show a transition behavior, the mass must be accelerated and the tension is not stable. During these operating periods, the speed of the pull rollers 6, 7 at the exit of the cooling unit does not optimally match the speed of the pull rollers 9 at the input of the slitter with regard to the web tension, with the result that the dancer roller 20 moves considerably. The web tension control functions primarily due to the ability of the dancer roll 20 to maintain positive contact with the web 120 and to produce a tight, ie non-sagging web. In transitional periods, only the transport difference,  ₂ r ₂ -  ₁ r _{1, is} important and the tensile load on the web 120 contributes very little to the position of the dancer roller 20.

According to the present invention, a change in the position of the dancer roller 20 used to increase the speed of the drawing rollers 9 at the entrance of the slitter control, whereby the dancer roller 20 is held in operating mode 1. If the Deviation of the dancer roller 20 from its initial or neutral position as an error the integral can be defined via the error for resetting the dancer roller 20 be used in their home or neutral position so that Δ1 goes to 0. Suitable control algorithms for this purpose are in the following the example of further embodiments of the invention explained in detail.

3 shows a side view of the region of the cooling unit following Printing machine with a dancer roller device according to a second Embodiment of the present invention. 3, web 120 moves around a dancer roller 20 attached to an air cylinder 30. The air cylinder 30 is firmly attached in the machine frame so that the rod of the air cylinder in can be extended and retracted substantially in a straight line around the dancer roller 20 to follow an essentially linear path.

In this second embodiment, the air cylinder 30 travels in response to the the web tension exerted forces and thus reduces the tension to prevent this from increasing to a level that will lead to a web break can. The control unit 90 which the deviation signal, the position of the Dancer roller 20 represents, receives as input, reduces the speed of rotation Pull rollers 9 at the entrance of the slitter to the dancer roller 20 in its neutral Bring position back.

The air cylinder 30 contracts along its linear path when the Tension in the web 120 below a predetermined load value of the Air cylinder 30 falls. This pulling back or pulling together becomes one maintain positive tension in the web and slack in the web to effective Way eliminated. The control unit 90, which is the retracted position of the Dancer roller 20 used as input increases the speed of rotation of the pull rollers 9 at the entrance of the slitter to the dancer roller 20 in its neutral position return.

As shown in FIG. 4, the dancer roller 20 can be provided with a guide frame 36 be connected. The guide frame 36 includes air cylinders 30 attached thereto provide an urging force that the dancer roller 20 contacts the web 120 holds. The guide frame 36 is constructed so that it is in linear rails 35th can move to facilitate the linear movement of the dancer roller 20.

5 shows a side view of the region of the cooling unit following Printing machine with a dancer roller device according to a third embodiment of the present invention. In Fig. 5, the dancer roll 20 is at the free end of a Air cylinder 30 attached. As in the second embodiment, the Air cylinder 30 attached to the frame of the printing press in such a way that the rod the air cylinder is retracted and extended substantially in a straight line to the To guide the dancer roller on its linear path. The linear ones shown in Fig. 4 Rails 35 and the guide frame 36 can advantageously also on the Construction of Fig. 5 can be applied. However, the air cylinder 30 in the Contrary to the second embodiment in response to a decrease in Web tension extended to a positive tension in web 120 and to prevent sagging in the web. The Air cylinder 30 contracts in response to an increase in web tension causing an increase in voltage to a point where a web break breaks fear is prevented. The control unit 90 increases the rotational speed of the Pull rollers at the entrance to the slitter in response to the extension of the Air cylinder 30 and reduces the speed of rotation of the drawing rollers 9 at the entrance of the slitter in response to the retraction or contraction of the Air cylinder 30.

Although the dancer roll 20 was previously described as being attached to an air cylinder 30 other mechanisms for applying force to the web can also be used become. So z. B. springs or depending on the radii of rollers Masses to generate a dynamically changing range of Positions acting force can be used to act on the dancer roller.

The control unit 90 controls the rotational speed of the one forming an inlet gap Pull rolls or the pull rolls forming an outlet nip to the tension in the Regulate and close the web, in particular while the printing press is starting up ensure that the web sags in this operating condition with certainty is excluded. An algorithm to control the sag of the web takes into account e.g. B. a web span of a length ℓ between an inlet gap and an outlet gap. The outlet gap has z. B. an outflow increase of 0.5%. The track section has a maximum tensile load of 0.1%, a speed v, and a certain amount of unstretched paper s (0).

At every point in time t after t = 0, the length of the incoming paper is given by multiplying the web speed (v) by the time (t), or vxt. The length of the paper running out of the outlet gap with 0.5% increase is 1.005 vx t. The amount of unstretched paper s (t) jammed at time t is equal to the original amount of slack paper, s (0), plus the amount of paper received minus the amount of paper leaked, as shown in the following equation: s (t) = s (0) + vt - 1.005 vt or s (t) = s (0) - 0.005 vt

The time to remove all of the jammed paper s (0) from the web span (the time in which the amount of paper stored is reduced to zero or the time in which slack is removed) results from the following equation: t s = 0 = s (0) / (0.005 v)

A web span length ℓ of approximately 8 m (25 feet) and a web speed v of approximately 457 m / min are used only for the purpose of discussion and not to limit the invention. (1500 fpm) or 7.6 m / sec. (25 feet / sec.) Assumed. Under these circumstances it may seem that the time in which a tensile load of 0.001 develops is given by the following linear relationship: t (0.001) = ℓ * 0.001 / (0.005 * v) or t (0.001) = 0.2 (ℓ / v) = 0.2 sec.

However, this is incorrect because every time there is a tensile load in the Web span developed by the increase in the outlet gap, an element of the material with the new web span tensile load is removed from the outlet gap while a new, unstretched part of the material enters the inlet gap. Thus the The above linear method has an incorrect result.

If the nonlinear factors are taken into account, this leads to a first order differential equation with an exponential solution as follows: s (t) = s (∞) (1-e - (v / 1) (t) ) where s (∞) is the final tensile load value. Since ℓ / v is 1 second here, the tensile load only increases up to 63.2% of its final value after 1 second. It takes almost 3 seconds for the tensile load to increase to 95% of the final value. Since this solution is an exponential function, the final value is theoretically never reached. If, in accordance with a preferred embodiment of the invention, the increase in the nip is increased to five times the value which is required to maintain the final tensile load, the process for achieving the increase in the slip nip which occurs during normal printing operation of the printing press becomes accelerated to about 0.22 seconds.

Thus the time for the creation of "nominal running strain" is 0.1% (at maximum tensile load) 0.22 seconds for an "unstretched web" (i.e. one incoming web with zero tensile load), which moves at 457 m / min. (1500 fpm) or 7.6 m / sec. (25 feet / sec.) Over a span of 7.6 m (25 feet) with an increase of 0.5% moved. Although the incorrect linear method mentioned above is a result of 0.2 seconds, this is just random. Would, for example, be the run-out increase to 0.1%, then the time would reach 95% Increase for 3 seconds. The linear method incorrectly sees a response time of 1 second before if an increase of 0.1% is assumed.

That for a tensile load of 0.1% in a web span of 7.6 m (25 feet) too developing strain would be 0.001 by 7.6 m (25 feet) or 0.0076 m (0.025 feet) or Is 7.6 mm (0.3 inches). If at the time a 7.6 mm (0.3 inch) Elongation occurs, the increase in the outlet gap is reduced to the level at which the stretch is maintained, the tensile load remains at 0.1%. This increase would be a value of 0.001. However, if the web 120 is correct Tensile load enters the inlet gap 6, 7 and the tensile load of the web span 0.001, then the speed at the outlet gap 9 with the speed in Inlet gap 6, 7 match, so that no additional tensile load develops. In addition, if the train has an additional load higher than the tensile load of the Web span of 0.1% enter the inlet gap 6, 7, then the increase in Outlet gap must be reduced below 0.001 in order to achieve a tensile load of 0.1%. This rather complex process is usually caused by this in web presses copes with the fact that between the pull roller with high growth (in this case the Nip 9) and the web 120 slip at the load value to be maintained is allowed. If separate drives are used on the nips, the "transition increases" must be set with care, since the "natural, non-linear" Transition to slip may or may not exist. This can Confusing when trying to respond to the drive controller response to optimize.

t(0) = 1/12/v/Zuwachs

t(0) = 1/12/25/0.005

t(0) = 0.667 sec/inch (sec./2,5 cm)

ergibt.In summary, the time taken to remove 2.5 cm (1 inch) of stored unstretched web from an arbitrarily long web span is a nominal speed of 25 feet / sec (7.6 m / sec) at one exit -The nip has an excess speed of 0.5%, too

t (0) = 1/12 / v / increase

t (0) = 1/12/25 / 0.005

t (0) = 0.667 sec / inch (sec./2.5 cm)

results.

However, the time in which a tensile load of 0.001 in a web span is a length corresponding to the pure numerical value of the web speed (e.g. 7.6 m at 7.6 m / s), 0.22 or more seconds, which is due to the time constant, ℓ / v and the increase is determined.

According to the invention, there are thus two mechanisms which regulate the acceptance of the paper. The first mechanism is based on the difference between infeed web speed and outfeed web speed under constant web tension. The second mechanism is an exponential change in tensile load change due to a change in the tensile load of the incoming web and the tensile load the expiring web.

If you also consider the placement of a "perfect" dancer roller device in the Railway path to a low positive tension without sag of the railway such a facility should, if possible, be very low Have mass, a very small diameter and very low inertia and be equipped with a force component that slightly counteracts the path to just make contact between the dancer roller and the web.

If such a dancer roll device were added to the web span to the Path path to enlarge "sagging s" (0), and when the Wrap angle of the dancer roller would be approximately 180 °, then the Move the dancer roller half of the sag to close the sag to save.

To maintain a straight path, the control unit must be in such a System in which the web wraps around the dancer roller by 180 °, the movement of the Grab the dancer roll and multiply by two to get s. Instructs however Slip gap has a slip of 0.5% and the goal is only that Take up slack, then the control unit need not be active.

The integrated increment removes 2.5 cm (1 inch) per 0.667 seconds (at "0" Tensile load) and then sets the tensile load to 0.1% after another 0.22 seconds. Thus, after about 0.7 seconds, this weightless dancer roller would return to its zero position returned, the train path would be straight and exactly 7.6 m (25 feet) and would not trap the dancer roll and the tensile load would begin to level up to develop to their final value of 0.1%. Unfortunately, one could Dancer roll device, however, an excessive tensile load, i. H. a tensile load greater than 0.1%, do not correct as there is no way to get paper straight Eliminate path. Only the slip gap can take over this function.

Since there is no such "perfect" dancer roller and the slip gap is subject to uncontrolled behavior and fluctuations in the tensile load of the incoming web, the dancer roller and the outlet part of the system must be compensated for in order to achieve the desired behavior. A limitation of the maximum possible growth of the system to small values, e.g. B. to twice the normal slip value, ensures low acceleration and kinetic energy (½ mv ² ) in the movement of the dancer roller. The kinetic energy of the dancer roller must be converted into potential energy (½ kx ² ) stored in the path if the dancer roller is to stop and no damping takes place. To illustrate, let us assume that a dancer roll with a weight of approx. 45 kg moves at approx. 1.5 cm per second. This provides a kinetic energy of approx. 0.1 J. If a spring constant of approx. 227 kg per 2.5 cm (500 lbs per inch) is also assumed (e.g. approx. 68 kg (150 lbs) cause a stretch of approximately 0.8 cm (0.3 inches) in a path approximately 127 cm (50 inches) wide over a span of 7.6 m (25 feet), then is the amount by which the web 120 must stretch to absorb the kinetic energy (2 * 0.0039 / 500 * 144) ^0.5 = 0.047 inch (about 1.2 mm) web stretch. This is about 16% of the normal path stretch mentioned above. Since there is a certain amount of damping, this is a maximum possible value. The dancer roller 20 only moves half of this distance or about 60 mm due to the wrapping of the roller. So the actual value would be lower.

The natural frequency of the vibration for this simple spring-mass system is about 7 Hz. Thus, for the occurrence of a complete vibration 0.14 seconds required.

If the dancer roller had the ability to meet all the conditions of movement, would be nothing more than to create the necessary space for the movement. However is this is not practical even with the simplest dancer roller systems, because some Means for moving the dancer roller back into a predetermined working position always required. A control unit according to the invention can be used for this purpose be designed so that the average position is fixed and that the dancer roller for can move a reasonable distance for short periods.

The control unit according to the invention preferably controls only that Difference between the inlet nip and the outlet nip to slowly move the dancer roller 20 back to its zero position. However, this is slow speed higher than the one set by the spout increase of 0.5% lower limit, i.e. H. not less than about 2.5 cm (1 inch) in 0.75 seconds. The Speed must therefore be high enough to prevent the dancer roller 20 reaches its maximum movement point. For the sake of simplicity and if it is allow low dynamic requirements (e.g. a movement of approx. 3.8 cm / sec. (1.5 inch / sec.) The control unit regulates the increase in such a way that it increases in Range is from + 0.5% to -0.5%, so that in combination with an integrated mechanical increase of 0.5% with low web tension or with no tension According to the invention, a doubling of the total growth (integrated mechanical growth plus growth of the control unit) occurs, the z. B. in the area can be from 0.0 to 1.0%.

The following shows an exemplary calculation method for executing the desired control, in which the change in the surface speed of the controlled drawing roller is given as delta v:

In a more robust design, the inlet roller nip and the outlet roller nip can be used be matched to the same nominal speed, d. that is, the Outlet has no integrated growth. In the control algorithm, a Amount that holds the dancer roller in the neutral or neutral position on average be added to or subtracted from the nominal speed. This would z. B. be referred to as an integral controller. Because the extent of the movement of the Dancer roller is a sign of the error size of the existing tensile load can the increase can be regulated in order to increase the correction factor accordingly.

An example of a calculation method according to the invention for executing the control described above, the pull roller speed and the position of the dancer roller, in particular when the printing machine is started up, is described below.

A constant force developing device, e.g. B. a pair of Air cylinders 30 on either side of the dancer roller 20 can be used at almost any time Place the dancer roller on the web 120. The only time when the Dancer roller 20 is not employed on the web 120 can occur if the dynamic vibrations of the dancer roller 20 z. B. during a role change Would loosen the tensile load of the web completely, so that the web no longer on the Dancer roller is applied. Regarding the physical parameters in the described For example, vibrations of approximately 0.127 cm (0.05 inch) could result cause. However, the high damping rate of the cylinders and the occurring Friction in the rotating components ensures that this does not happen.

LIST OF REFERENCES

2 - 5

chill rolls

6

Cooling roller / pull roller (inlet nip)

7

Draw roller (nip point)

8th

guide roll

9

Nip / pair of draw rollers (outlet nip)

20

dancer roll

30

air cylinder

35

linear rails

36

guide frame

40

lever arm

50

guide roll

60

position sensor

80

Position / part of lane 120

85

Position / part of lane 120

90

control unit

95

deviation value

100

roll stand

110

paper roll

120

train

200

feeding

300

first printing unit

400

second printing unit

500

third printing unit

600

fourth printing unit

700

drying unit

800

Chill stand

900

folding

Claims (11)

1. Device for controlling the tension in the web of a printing press having a chill unit and a slitter unit, the device comprising nip rollers (6, 7) forming an exit nip at the exit of the chill unit (2-6),
   characterized by
   a dancer roller device arranged between the nip rollers (6, 7) forming an exit nip at the exit of the chill unit (2-6) and nip rollers (9) forming an infeed nip at the entrance of the slitter unit, the web (120) contacting a dancer roller (20) of the dancer roller device; and
   a control unit (90) connected to the dancer roller (20) for sensing a position change of the dancer roller (20) and for controlling the rotational speed of one of the nip rollers (9) at the entrance of the slitter unit based on the sensed position change of the dancer roller (20) in order to maintain a substantially constant tension in the web (120).
2. Device according to claim 1,
   characterized in that the device comprises a position sensor (60) transmitting a deviation signal to the control unit (90), the deviation signal indicating the distance between the current position and the neutral position of the dancer roller (20), and that, based on the deviation signal, the control unit (90) controls the rotational speed of at least one of the nip rollers (9) of the infeed nip and of at least one of the nip rollers (6, 7) of the exit nip.
3. Device according to claim 1 or 2,
   characterized in that the device comprises a force compensation element in the form of an air cylinder (30), which applies a force to the dancer roller (20), in order to keep the dancer roller (20) in contact with the web (120), the force acting against a force applied to the dancer roller (20) by the web (120).
4. Device according to one of the preceding claims,
   characterized in that the dancer roller device further comprises a lever arm (40) having a first end rotatably connected to the frame of the printing press and a second end connected to the dancer roller (20), and that the lever arm (40) determines the arc of motion of the dancer roller (20), the arc of motion having a radius substantially corresponding to the length of the lever arm (40).
5. Device according to one of the preceding claims 1 to 3,
   characterized in that a plurality of rails (35) is provided, which are attached to the press frame of the printing press, which are substantially parallel and in which the dancer roller (20) is guided.
6. Device according to claim 5,
   characterized in that the plurality of substantially parallel rails (35) are substantially linear rails.
7. Device according to claim 5 or 6,
   characterized in that a guide frame (36) connected to the dancer roller (20) and the force compensation element (30) is provided, the guide frame being movably received in the rails (35) so that the guide frame (36) and the dancer roller (20) move along the path determined by the rails (35).
8. Device according to one of the preceding claims,
   characterized in that the control unit (90) controls the rotational speed of at least one of the nip rollers (9) of the infeed nip and of at least one of the nip rollers (6, 7) of the exit nip based on an error signal defined by the relationship Δ1 = ₂r₂ - ₁r₁, wherein Δ1 is the difference between the length of the web moving through the infeed nip and the length of the web moving through the exit nip, ₂r₂ is the length of the web portion moving through the exit nip (6, 7) and ₁r₁ is the length of the web portion moving through the infeed nip (9).
9. Device according to one of the preceding claims,
   characterized in that the control unit (90) comprises means for determining the gain difference between the infeed nip and the exit nip and that the control unit (90) controls the rotational speed of at least one of the nip rollers (9) of the infeed nip and of one of the nip rollers (6, 7) of the exit nip based on the gain difference between the infeed nip and the exit nip in such a way that the dancer roller (20) is kept in a substantially neutral position.
10. Device according to one of the preceding claims,
    characterized in that the dancer roller device further comprises a first idler roller (8) rotatably attached to the frame of the printing press between the infeed nip (9) and the dancer roller (20).
11. Device according to one of the preceding claims,
    characterized in that the dancer roller device further comprises a second idler roller (50) rotatably attached to the frame of the printing press between the dancer roller (20) and the exit nip.

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