EP0722899A2 - Method and device for compensating the tension forces over the width of a running web - Google Patents

Abstract

The web (3) is drawn over rollers (4, 5, 6) and its tension across its width is equalised. The web (3) is preferably a paper of film track. A tension equalising roller (5) reverses the web (3). The equalising roller (5) is pivoted about a pivot axis (8) which is essentially perpendicular to the roller (5). The equalising roller (5) is pivoted by detecting and regulating a rotary moment exerted on the roller (5) by the web (3). The appts. for carrying out the method has the equalising roller (5) mounted on a shaft (7) to rotate freely about its longitudinal axis. The shaft (7) is supported in a pivot bearing (10) held in a frame (11). The shaft (67) is held either side of the roller (5) and guided in buffers. The shaft (7) is movably held by a toothed gear and supported by roller bearings.

Description

The invention relates to a method and a device for compensating tension forces across the width of a running web according to the type mentioned in the preambles of claims 1 and 5.

Such a device is known from US Pat. No. 2,066,306. It consists of a roller that is freely rotatable on a shaft. The shaft is guided at both ends in scenes and is gripped by a lever linkage. This prevents the two ends of the shaft from moving in the same direction, so that the shaft and with it the roller can only be pivoted about an axis. However, this known device has the disadvantage that sliding movements occur both in the scenes and in the lever linkages when the shaft is pivoted. The associated frictional forces limit the accuracy of the voltage compensation that can be achieved by this device. In particular, tension compensation is not possible if the difference in tension force between the two web sides is less than the considerable static friction forces in the links and lever linkages.

The invention is therefore based on the object of providing a device of the type mentioned at the outset which ensures precise compensation of the tensioning force over the width of the web.

This object is achieved with the method steps of claim 1 and with the features of claim 5.

In this method, a signal proportional to the torque exerted by the web on the tension compensation roller is detected and used as a correction signal for a control. With this control, the torque exerted by the web is regulated to the setpoint zero by swiveling the tension compensation roller. This ensures that the tension forces of both web halves are the same in the steady state of the control. Since the swiveling of the tension compensation roller takes place actively through the control, friction influences and the inertia of the tension compensation roller play only a subordinate role for the tension compensation. They only limit the speed at which a clamping force difference is corrected. The accuracy of the tension compensation is determined exclusively by the precision of the detection of the torque exerted by the web on the tension compensation roller and the quality of the controller.

According to claim 2, it is advantageous to measure the bearing forces of one of the rollers and to calculate their difference. The difference in the bearing forces of both ends of a roller is proportional to the torque that the web exerts on the roller when the web is running in the center. The bearing forces of the roller can be determined particularly easily and precisely by force measuring devices provided in the bearings. The bearing forces are preferably determined on the tension compensation roller. This ensures that the tensioning force of the web is correctly detected without being influenced by the friction of other rolls. In addition, there are time delays between the pivoting of the tension compensation roller and the effect limited to the tension of the web to a minimum. The regulation can therefore more quickly compensate for any tension difference occurring on the web.

According to claim 3, it is favorable to additionally detect the position of the web center and to correct the difference in bearing force. From the difference in the bearing forces of the roller, only a torque related to the center of the roller can be determined. If the path is off-center, however, the torque related to the center of the path must be corrected. This is ensured by calculating the deviation of the difference between the bearing forces caused by the web run and correcting the determined difference in bearing force by this value.

According to claim 4, it is advantageous to compare the torque exerted by the web on the tension compensation roller with a range. Depending on the comparison result, the position of the tension compensation roller is either regulated and thus actively adjusted or kept freely pivotable. A freely pivotable holding has the particular advantage that the tension compensation between the two web halves takes place particularly precisely and independently of the accuracy of the force measurement. The position of the tension compensation roller is only regulated and thus actively adjusted if there are large deviations between the setpoint and actual value. This ensures that a large difference in tension force between the two web halves is corrected very quickly, since the actuators for pivoting the tension compensation roller can exert considerably more force than the web itself. This is particularly important with large rollers which have a correspondingly large moment of inertia . In this case, the pivot bearing of the tension compensation roller is blocked in order to ensure effective power transmission through the control to the tension compensation roller.

The device according to claim 5 has a pivotally held tension compensation roller. This is freely rotatable on a shaft, the ends of which are supported in a swivel bearing. This ensures that the space around the tension balancing roller is free so that the running of the web is in no way disturbed is. The swivel bearing of the shaft is realized by toothed gears provided on both sides of the tension compensation roller. If the web exerts a torque on the tension compensation roller, this tries to push the tension compensation roller on the side of the higher tensioning force away in the direction of the force. The toothed gear converts this movement of the tension compensation roller into a rotary movement of the shaft. This is in turn converted by the opposing toothed gear into an opposing adjustment movement of the opposite end of the shaft. This mechanism ensures that the tension compensation roller is only pivoted about an axis and cannot be moved as a whole. This in turn causes the tension compensating roller not to reach any of its end stops when the total tension force of the web varies. The tension compensation across the width of the web is therefore ensured under all operating conditions. The use of toothed gears for pivotably holding the shaft results in particularly low frictional forces, since the teeth of the toothed gears roll against one another without sliding against one another. The shaft ends are supported in the scenes via roller bearings that roll on the scenes. In this way, frictional forces emanating from the scenes are largely suppressed. The force required to pivot the tension compensating roller is therefore very low, so that the tension compensation of the web can also take place without the active adjustment of the tension compensation roller solely by the torque transmitted by the web. The desired clamping force compensation is therefore achieved in a particularly cost-effective manner using the simplest of means. In addition, the device can be constructed very compactly, so that even existing systems can be converted without problems by simply changing a roller.

According to claim 6, ball or roller bearings have proven themselves as rolling bearings. These have very favorable running properties, in particular the frictional force, which is damaging for an exact tension compensation, is negligible. The ball or roller bearing is only on one side of a rail or column as a counter bearing and rolls on it. This counter bearing limits the freedom of movement of the tension compensation roller to one level. This prevents pivoting of the Tension compensation roller around an axis perpendicular to the desired swivel axis, which would result in a lateral path. In addition, the counter bearing ensures the correct position of the parts of the toothed gear so that its teeth always interlock correctly.

According to claim 7, it is advantageous to form the toothed gear from a rack and a gear. Preferably, the gear meshes directly with the rack, which minimizes the friction losses of the pivot bearing. Since the toothed rack is fixed, the toothed wheel must roll on the tension compensating roller when it is adjusted, the toothed wheel being rotated together with the shaft. The racks are preferably provided on both ends of the shaft on diagonally opposite sides of the shaft axis. This means that the adjustment of the shaft ends is synchronized in opposite directions to each other. The tension compensation roller can therefore only be pivoted about a fixed, predetermined pivot axis, which runs through the center of gravity of the tension compensation roller when the gear meshing with the rack. Alternatively, the racks could also be provided on the same side of the shaft axis. In this case, one of the toothed gears should have an intermediate gear which reverses the rotational movement of this side. In order to minimize the frictional forces between the gearwheel and the toothed rack, it is favorable to equip them with involute or cycloid teeth.

According to claim 8, it is favorable to provide an intermediate gear between the rack and the shaft. This allows the pivot axis of the tension compensation roller to be displaced in a simple manner. The height of this pivot axis with respect to the tension compensation roller is determined by the axes of the intermediate gears meshing with the rack.

Particularly in the case of printing machines, it is desirable that the center line of the web does not undergo any change in length due to the tension compensation roller. This is achieved according to claim 9 in that the pivot axis of the tension compensation roller is shifted to its jacket. The pivot axis affects the Tension compensation roller in the area in which it is wrapped in the web, so side and longitudinal registers remain unaffected.

If the rack is designed as a threaded spindle or worm, the tension compensating roller can be adjusted very simply by rotating the threaded spindle or worm in its height.

If the threaded spindles or screws are connected to actuators according to claim 11, then the pivoting of the tension compensation roller can be carried out actively by the actuators. In order to prevent the tension compensation roller from pivoting freely under the pressure of the web, the shaft is blocked against rotation about its longitudinal axis. The pivoting of the tension compensation roller by means of actuators offers the advantage that its inertia can be overcome more easily than if the web itself had to exert the actuating force.

According to claim 12, it is favorable to connect the actuators to a control device. The control device receives its actual value from force measuring devices which are provided in the bearings of a roller. The measured force values are subtracted from each other via a subtractor, the output value of which is proportional to the torque exerted by the web on the tension compensation roller. This value is regulated by the control device to the nominal value of zero, so that the tensioning forces of the web in both web halves are equal to one another in the steady state of the control device.

Finally, it is advantageous according to claim 13 to detect the position of both web edges by means of an edge sensor when the web is off-center and to link this value with the measured bearing forces. This enables the bearing force difference caused by the web run to be calculated and corrected so that a signal is fed to the controller which is proportional to the torque of the web related to the center of the web.

The method according to the invention and preferred embodiments of the subject matter of the invention are described by way of example with reference to the drawing, without restricting the scope of protection.

Figur 1

eine perspektivische Darstellung einer Vorrichtung zum Ausgleich von Spannkräften einer Bahn,

Figur 2

eine perspektivische Darstellung einer Seite einer Schwenklagerung,

Figur 3

die Schwenklagerung gemäß Figur 2 ohne Zahnrad,

Figur 4

eine Schnittdarstellung einer alternativen Ausführungsform einer Seite eines Schwenklagers mit verschobener Schwenkachse und

Figur 5

eine Vorrichtung zum Ausgleich von Spannkräften einer Bahn mit aktiver Regelung.

It shows:

Figure 1

1 shows a perspective view of a device for compensating tension forces of a web,

Figure 2

a perspective view of one side of a pivot bearing,

Figure 3

the pivot bearing according to Figure 2 without gear,

Figure 4

a sectional view of an alternative embodiment of a side of a pivot bearing with shifted pivot axis and

Figure 5

a device for compensating tension forces of a web with active control.

FIG. 1 shows a device 1 for compensating tension forces across the width of a web 3 running in the direction of arrow 2. This web 3 is deflected on rollers 4, 5, 6 held in bearings 12, the central roller 5 being designed as a tension compensation roller is. The tension compensation roller 5 is freely rotatably mounted on a shaft 7 which is held pivotably about a pivot axis 8 running through its center of gravity S. Both ends 9 of the shaft 7 are supported in bearings 10 which are held on a frame 11 and together form a pivot bearing for the shaft 7.

The structure and function of the bearing 10 is described in more detail with reference to FIGS. 2 and 3. Figure 2 shows the bearing 10 consisting of a housing block 15, the cover is removed. In the housing block 15 there is a stationary threaded spindle 16. This meshes with a gear 17, the toothing 18 of which is only indicated. The gear 17 is connected to the shaft 7 in a rotationally fixed manner.

In practice, the web 3 presses the shaft 7 with a force F and tries to move it in this direction. Since the gear 17 meshes with the threaded spindle 16, it must roll on the threaded spindle 16 during this displacement, so that it is simultaneously rotated in the direction 19. In the bearing 10 provided at the opposite end 9, the shaft 7 is held in mirror image for the illustration according to FIG. This has the effect that the described rotation 19 of the gear 17 and thus the shaft 7 at its opposite end 9 causes a displacement directed against the force F. The movements of the ends 9 of the shaft 7 are therefore synchronized in opposite directions to one another, so that the shaft 7 and thus the tension compensation roller 5 can only be pivoted about the pivot axis 8 indicated in FIG.

FIG. 3 shows the bearing 10 according to FIG. 2, the gearwheel 17 with the shaft 7 being removed in order to be able to see the parts underneath. In the housing block 15 two columns 20 are defined at a distance e, which form a link guide for the shaft 7. For this purpose, the shaft 7 carries a roller bearing 21, which is shown alone and only with its receiving opening 22. The roller bearing 21 runs between the columns 20, the spacing e of which is slightly larger than the outer diameter D of the roller bearing. It is thereby achieved that the roller bearing 21 rests only on one of the two columns 20 and rolls on it without sliding. The backdrop guide means that the shaft 7 can only move within one plane ε. This ensures that the axis 23 of the shaft 7 is always at the same distance from the threaded spindle 16, so that the teeth 19 of the threaded spindle 16 and the gear 17 mesh correctly with one another. This is important so that the teeth of the gear 17 roll on those of the threaded spindle 16 without sliding.

In the housing block 15 21 through holes 24 are provided in the plane of movement of the rolling bearing, in which stops, not shown, are provided to limit the travel of the shaft 7 on both sides. In addition, a shock absorber could be provided in one of the through bores 24, which dampens vibratory movements of the shaft 7.

An alternative embodiment of the bearing 10 is shown in FIG. It consists of the housing block 15, on which a cover 30 is fixed. The cover 30 has an opening 31 penetrated by the shaft 7. The shaft 7 is supported on the pillars 20 by means of the roller bearing 21 and is connected to the gear 17 in a rotationally fixed manner. The gear 17 meshes with an intermediate gear 32, the shaft 33 of which is also supported on the columns 20 via a further roller bearing 34. The shafts 7, 33 are supported by roller bearings 35 on a cage 36 which keeps the mutual distance M between the shaft axis 23 and the shaft axis 37 constant. The two roller bearings 21, 34 allow the cage 36 to move up and down in the direction of the force F. However, they prevent the cage 36 from moving sideways and pivoting. In order to hold the shaft 33 in the longitudinal direction, there is a stop in the cover 30 38 provided, which presses against the shaft 33. The ball 39 is preferably held resiliently. The stop 38 limits the movement of the cage 36 only in one direction, but at the opposite end 9 of the shaft 7 there is another bearing diagonally opposite the bearing 10, which limits the movement of the cage 36 provided there in the opposite direction. Since both cages 36 are connected to the shaft 7, movement of the shaft 7 in the direction of its longitudinal axis 23 is excluded.

In order to place the pivot axis 8 tangentially on the jacket 40 of the tension compensation roller 5, where the web 3 also contacts the compensation roller 5, an intermediate gear 32 is provided in mesh with the threaded spindle 16 and the gear 17, the axis 37 of which is aligned with the jacket 40 . The gears 17, 32 are dimensioned accordingly in their diameter.

In order to be able to pivot the tension compensation roller 5 also by means of active regulation by means of actuators, the threaded spindle 16 penetrates the housing block 15 at its lower end. In this way, the threaded spindle 16 can be connected to an actuator, for example an electric motor or a hydraulic motor, which turning them. This rotation of the threaded spindle 16 is transmitted to the shaft 7 via the gear wheels 32 and 17. The bearing 10 located at the opposite end 9 of the shaft 7 then also has an actuator. Both actuators are coupled in opposite directions, so that a bearing 10 causes an upward movement of the shaft end 9 and the opposite bearing 10 causes a downward movement of the shaft end 9. So that the rotation of the threaded spindle 16 is converted into an adjustment of the cage 36 and not only causes a rotation of the shaft 7, a braking device 41 is provided on the slide 36. It acts against the shaft 7 and prevents it from rotating relative to the cage 36 in the tightened position. In the released position, the braking device 41 is spaced from the shaft 7, so that the tension compensation roller 5 can pivot freely.

FIG. 5 shows an alternative embodiment of the device 1 with active adjustment of the tension compensation roller 5. The basic structure corresponds to the device 1 according to FIG. 1, the shaft 7 being blocked against rotation about its longitudinal axis 23. The threaded spindles 16 of the bearings 10 are connected to actuators 50. These can be, for example, electric motors with flanged gears or hydraulic motors. The actuators 50 set the threaded spindles 16 in rotation and in this way cause the ends 9 of the shaft 7 to be adjusted in height. The actuators 50 are operatively connected to displacement sensors 51 which detect the adjustment path of the threaded spindle 16. Since the rotational movement of the threaded spindle 16 is coupled to the shaft 7 via the toothed wheel 17, the signal obtained from the displacement sensor 51 is also proportional to the displacement of the end 9 of the shaft 7. Force measuring devices 52 are provided between the bearings 10 and the frame 11, which from the tension compensating roller 5 and the web 3 exert bearing forces F. Edge sensors 54 are provided on both web edges 53 for continuous detection of the web position.

The actuators 50, the displacement sensors 51, the edge measuring devices 52 and the edge sensors 54 are operatively connected to a control device 55. This control device 55 has the task of compensating for differences in tension force in both web halves by adjusting the tension compensation roller 5. A totalizer 56 is operatively connected on the input side to the force measuring devices 52 and calculates the difference in the measured bearing forces, which is proportional to that of the web 3 on the Tension compensation roller 5 is exerted torque. The output signal of the summer 56 is fed via a further summer 57 to a controller 58, which preferably has a P, PI or PID behavior. The correction signal obtained by the controller 58 is fed to a non-inverting input 59 and an inverting input 60 from summers 61, 62 which are operatively connected to the actuators 50 via power amplifiers (not shown). In the event of a difference in bearing force between the ends 9 of the shaft 7, this control loop causes the shaft 7 to be adjusted in the opposite direction, that is to say it is pivoted. In order to keep the position of the pivot axis 8 of the shaft 7 constant, the mean value of the adjustment paths from the ends 9 of the tension compensation roller 5 is also regulated. For this purpose, the displacement sensors 51 are connected to a further summer 63, the output signal of which is proportional to the average of the adjustment paths of both ends 9 of the shaft 7. This signal is regulated in a further controller 64 to a constant setpoint. The controller 64 also preferably has a P, PI or PID behavior. The correction signal obtained from the controller 64 reaches non-inverting inputs 65, 66 of the summers 61, 62 and therefore causes both ends 9 of the shaft 7 to be adjusted in the same direction. This control loop determines the central position of the voltage compensation roller 5 and thus the position of its pivot axis 8 recorded.

wobei a, b den horizontalen Abständen der Bahnkanten 53 von den Kraftmeßvorrichtungen 52 und L dem Abstand beider Kraftmeßvorrichtungen 52 entspricht.The above-described control loops presuppose that the web 3 runs centrally over the tension compensation roller 5, so that, in the case of the same tension forces in both web halves, both bearing forces F are equal and the difference is zero. Should the web 3 exceptionally run eccentrically over the tension compensation roller 5, then this eccentric run causes a torque and thus different bearing forces F at both ends 9 even with balanced tensioning forces of both web halves Correction device 67 is provided. This has a circuit block 68 which is operatively connected to the edge sensors 54 on the input side. Circuit block 68 calculates the expression from the signals obtained from edge sensors 54 $$\mathit{\text{f =}}\text{2}\frac{\mathit{\text{L}}\text{(}\mathit{\text{a - b}}\text{) +}{\mathit{\text{b}}}^{\text{2nd}}{\mathit{\text{- a}}}^{\text{2nd}}}{\mathit{\text{L}}\text{(}\mathit{\text{L -}}\mathit{\text{a - b}}\text{)}}\text{,}$$

where a , b corresponds to the horizontal distances of the web edges 53 from the force measuring devices 52 and L to the distance between the two force measuring devices 52.

The signal f calculated by the circuit block 68 is multiplied in a multiplier 69 by a signal which corresponds to the total force exerted by the web 3 on the tension compensation roller 5. This signal is obtained from a summer 70 which is operatively connected to the force measuring devices 52 on the input side. Via an inverting input 71, the summer 70 is connected to a coefficient element 72, with the aid of which the weight of the tension compensation roller 5 is subtracted from the values measured by the force measuring devices 52. The multiplier 69 calculates that difference in force at both ends of the shaft 7 which is caused by the off-center web travel. This value is fed to an inverting input 73 of the summer 57, so that a signal proportional to the tension force difference between the two web halves is present at the output 74 of the summer 57.

A window comparator 75 is connected to the output 74 of the summer 57 and compares the control deviation with two fixed limit values. A zero level is present at a digital output 76 of the window comparator 75 if the control deviation is within the range between the limit values. The digital output 76 is operatively connected to a hold input 77 of the controller 58, which becomes inactive in the event of a zero level. This is important so that integrators in controller 58 do not assume undefined output values. In addition, the output 76 is operatively connected to a braking device of the bearing 10, which, when a level is present, blocks the shaft 7 against rotation about its longitudinal axis, so that the actuators 50 can adjust the tension compensation roller 5. This special arrangement ensures that in the event of a large control deviation Shaft 7 is blocked, and the actuators 50 actively adjust the tension compensation roller 5 via the threaded spindles 16. This adjustment takes place very quickly since the actuators 50 can exert relatively large forces on the tension compensation roller 5. If the tension forces of both web halves are almost equalized, that is, the control deviation at the output 74 within the range defined by the window comparator 75, the controller 58 is switched off via the holding input 77 and the blocking of the shaft 7 is released. Thus, the tension compensation roller 5 is freely pivotable again and sets itself automatically under the action of the tension force of the web 3.

The control device 55 can be implemented by analog or digital computing circuits. In particular, implementation using a microcomputer is advantageous, since in this case additional functions and changes in the control algorithms can easily be taken into account by adapting the program.

Reference list

1

contraption

2nd

Web direction

3rd

train

4th

roller

5

Tension compensation roller

6

roller

7

wave

8th

Swivel axis

9

The End

10th

camp

11

frame

12th

camp

15

Housing block

16

Threaded spindle

17th

gear

18th

Gearing

19th

Direction of rotation

20th

pillar

21

roller bearing

22

opening

23

axis

24th

Through hole

30th

cover

31

opening

32

Idler gear

33

wave

34, 35

roller bearing

36

Cage

37

axis

38

attack

40

Lateral surface

41

Braking device

50

Actuator

51

Displacement sensor

52

Force measuring device

53

Web edge

54

Edge sensor

55

Control device

56, 57

Totalizer

58

Regulator

59

non-inverting input

60

inverting input

61, 62, 63

Totalizer

64

Regulator

65, 66

non-inverting input

67

Correction device

68

Circuit block

69

Multiplier

70

Totalizer

71

inverting input

72

Coefficient term

73

inverting input

74

exit

75

Window comparator

76

Digital output

77

Stop entrance

a, b

Distance of the web edge from the force measuring devices

D

outer diameter

e

Distance of the columns

F

force

L

distance

S

main emphasis

ε

level

Claims (13)

Method for compensating tension forces across the width of a web (3), preferably a paper or film web, which is pulled over rollers (4, 5, 6), in which a tension-compensating roller (5) deflecting the web (3) by approximately is pivoted perpendicular to it pivot axis (8), characterized in that the pivoting of the tension compensation roller (5) is carried out by detecting and regulating a torque exerted by the web (3) on the tension compensation roller (5). Method according to claim 1, characterized in that the detection of the torque of the web (3) exerted on the tension compensation roller (5) by measuring both bearing forces (F) of one of the rollers (4, 5, 6), preferably the tension compensation roller (5), and their difference is calculated. Method according to Claim 2, characterized in that the position of the web is detected by palpating its edge edges (53) and the difference between the bearing forces (F) determined is corrected by the deviation caused by the web run. Method according to Claim 1 or 2, characterized in that the torque exerted by the web (3) on the tension compensation roller (5) is compared with a range lying between two limit values, the tension compensation roller (5) at torques within the Area is freely pivoted and otherwise its position is regulated. Device for compensating tensioning forces across the width of a web (3) drawn over rollers (4, 5, 6), preferably a paper or film web with a freely rotatable web (3) that deflects the web (3), on one about its longitudinal axis (23) rotatable shaft (7) mounted tension compensation roller (5), the shaft (7) being supported in a pivot bearing (10) which is held in a frame (11), and the shaft (7) on both sides of the tension compensation roller ( 5) the movement of their two The ends are held in opposite directions and are guided in links (20), characterized in that the shaft (7) is movably held on both sides of the tension compensation roller (5) by toothed gears (16, 17, 32) and in the links (20) via roller bearings (21) is supported. Apparatus according to claim 5, characterized in that the roller bearing (21) is a ball or roller bearing fixed on the shaft (7), which is supported on a rail or column (20) as a counter bearing. Apparatus according to claim 5, characterized in that the toothed gear (16, 17, 32) is formed by a toothed rack (16) which is operatively connected to a toothed wheel (17) non-rotatably connected to the shaft (7). Apparatus according to claim 7, characterized in that an intermediate gear (32) is provided as an operative connection between the rack (16) and the gear (17) of the shaft (7). Apparatus according to claim 8, characterized in that the axis (37) of the intermediate gear (32) is flush with the outer surface (40) of the tension compensation roller (5). Device according to at least one of claims 7 to 9, characterized in that the toothed rack (16) is designed as a threaded spindle or worm. Device according to at least one of claims 5 to 10, characterized in that actuators (50) coupled in opposite directions to one another act on both threaded spindles (16) or screws, and the shaft (7) is blocked against rotation about its longitudinal axis (23). Apparatus according to claim 11, characterized in that the actuators (50) are operatively connected to a control device (55) which at least from on the bearings (12) of one of the rollers (4, 5, 6), preferably the tension compensation roller (5), provided force measuring devices (52) is influenced. Apparatus according to claim 12, characterized in that the control device (55) is influenced by at least one edge sensor (54) which detects the position of the web edge (53).

Images