EP0479992A1

EP0479992A1 - Cloth guide with proportional roller pressure control.

Info

Publication number: EP0479992A1
Application number: EP91907813A
Authority: EP
Inventors: Herbert Oberstaller; Wolfgang Krauth
Original assignee: Erhardt and Leimer GmbH
Current assignee: Erhardt and Leimer GmbH
Priority date: 1990-04-19
Filing date: 1991-04-18
Publication date: 1992-04-15
Anticipated expiration: 2011-04-18
Also published as: DE4190843T; DE4012488A1; BR9105712A; DE59106018D1; WO1991016258A1; EP0479992B1; DE4012488C2; DE4190843D2

Abstract

Un dispositif de guidage et de tension d'une étoffe comprend au moins un guide-étoffe oblique par rapport au sens de déplacement de l'étoffe. Le guide-étoffe comprend un rouleau rotatif de réglage (1) et un contre-rouleau rotatif (2) à peu près parallèle au premier, définissant entre les deux une région marginale (K1, K2). Un générateur de force (3) qui agit sur le rouleau de réglage sollicite le rouleau de réglage sur le contre-rouleau. Un dispositif de balayage génère un signal de correction proportionnel à la position marginale. Un dispositif de réglage susceptible d'être influencé par les signaux de correction ajuste le générateur de force afin de corriger un déport de l'étoffe. Le générateur de force (3) est réglable en continu par modification de la force de serrage, sans que le rouleau de réglage ne soit entièrement soulevé, jusqu'à une valeur limite de longueur (Q) de contact des rouleaux encore admissible pour obtenir une correction du déport de l'étoffe. Ce n'est que lorsque le générateur de force (3) descend au-dessous de la valeur limite (Q) de longueur de contact qu'il peut être réglé jusqu'à annulation de la force de serrage.A fabric guiding and tensioning device includes at least one fabric guide oblique with respect to the direction of movement of the fabric. The fabric guide comprises an adjusting rotary roller (1) and a rotary counter roller (2) approximately parallel to the first, defining between the two a marginal region (K1, K2). A force generator (3) which acts on the adjustment roller urges the adjustment roller on the back roller. A scanner generates a correction signal proportional to the marginal position. An adjuster capable of being influenced by the correction signals adjusts the force generator to correct for an offset in the fabric. The force generator (3) is infinitely adjustable by modifying the clamping force, without the adjusting roller being fully lifted, up to a limit value for the length (Q) of contact of the rollers which is still admissible to obtain a correction of the offset of the fabric. Only when the force generator (3) drops below the contact length limit value (Q) can it be adjusted until the clamping force is canceled.

Description

Web guide with proportional increase in roller pressure

description

The invention relates to a device of the type specified in the preamble of claim 1 and a method according to the preamble of claim 16.

In a web guiding device known from practice with control and counter-rollers lying at an angle to the web, the guiding effect is based on the clamping force between the control roller and the counter-roller which, because of the inclined position, generates a web offset correction force acting transversely to the web running direction. Signals generated when the edge positions are scanned control the force transmitter for the control roller. If the scanned edge moves outwards, the clamping force is released and the control roller is lifted off. If, on the other hand, the edge strives inwards, the control roller is pressed against the counter roller with the set clamping force. The opposite web guide works accordingly. The control roller is either pressed with the set clamping force or completely relieved. In this open / close mode of operation, the web of material tends to jump or flutter because the clamping force starts and stops immediately and suddenly. When the clamping force is suddenly applied, an undesirable pressure marking occurs in the edge area. Furthermore, when the clamping force is suddenly inserted and released, the web is pulled apart in cycles and then left to itself and narrower, which makes edge scanning difficult. Permanent keeping of the web of goods is not possible. Rather, when the web guide is opened, the web runs to the side, so that it has to be stopped and first re-threaded for a new start.

The invention has for its object to provide a device and a method of the type mentioned with which a gentle, jump and flutter-free guiding and holding a running web is made possible, and with which one standing web can be kept wide.

The object is achieved according to the invention with the features specified in the characterizing part of claim 1 or with the method steps according to claim 16.

With this configuration of the device and with the application of the method, no edge area is practically completely cleared in a web guide until the roll engagement length limit value still permissible for a web offset correction is reached. A minimal clamping force is always maintained in the edge area, so that with two web guides, the web remains stretched in its width even at a standstill. The respectively acting clamping force is continuously modulated in the web guide as it is required to correct a web offset. Since the clamping force is continuously changed, pressure marks by the rollers are omitted. Fluttering or hitting the web is excluded. The scanning of the edge positions is also easier because the web is never left to itself. There is no tendency to commute when regulating. This practically prevents loss of the web, even at a standstill. The web is guided gently and with a smooth run. This gentle, yet sensitive, modulable treatment of the web takes place within a web offset area in which it is ensured that the web offset is actually also corrected.

According to claim 2, however, the device is also expediently designed such that, in a limit case of the web offset when the roll engagement length limit is undershot for one web guide, the clamping force on the opposite web guide is completely eliminated in order to make it easier for the web guide to correct the web misalignment. However, the undesired pressure markings are omitted, because when the clamping force is reinstated, it is gradually increased and there is no sudden pressing of the rollers. If the length limit is reached, at which the rollers of this web guide are only partially in engagement with the web, then under certain circumstances even the full clamping force may no longer be sufficient to overcome the counter-pull of the other web guide, which acts with minimal clamping force. However, as soon as the clamping force on the opposite and fully engaged web guide is released, the slight intervention of one web guide with full clamping force is usually sufficient to correct the web offset.

In the embodiment according to claim 3, there is a very clean web correction with a continuous spreading effect, because the clamping force in one edge area is changed in the opposite way to the other edge area, provided that the web is not offset to the limit area.

Alternatively, it is also possible to adjust the clamping force on one side asynchronously to the change in the clamping force on the other side and in opposite directions. This suppresses a correction effect that is too rapid and a tendency to oscillate.

Alternatively, it is expedient, according to claim 5, to continuously adjust only one of the two force transmitters while the other maintains the clamping force just present or - if the length limit value is undershot - does not apply any clamping force.

Particularly advantageous is the embodiment according to claim 6, which has two web guides. The falling below the roll engagement length limit value can easily be determined by the scanning devices. The control devices react and adjust the force transmitter towards zero, the web operator of which is still fully engaged. The other web guide alone corrects the web offset. It is easily possible for the force transmitter to be adjustable continuously or in several predetermined steps until a minimum length and maximum force value is reached for a web train operator until the permissible roller engagement length limit is reached. With continuous adjustment, the cross elasticity of the web is optimally used. If, on the other hand, adjustment is made in several predetermined stages, this means a simplification in terms of control technology with a reliable Bah offset correction.

It is also expedient to proceed according to claim 7. Within an engagement range of 100% to 60% or 70%, the correction force generated by the rollers is still sufficient to eliminate the web offset. In addition, it may be difficult to correct the web misalignment if the other web guide works with minimal clamping force. However, the engagement areas can also be changed if a roller covering with a different grip is selected or the quality of the goods is different or even the angular position of the rollers is oriented differently.

The embodiment according to claim 8 is expedient because a broadband proportional sensor has a large active proportional range and generates clear signals that can be converted into unambiguous control signals for the force transmitters.

In the embodiment according to claim 9, a closed control loop is achieved via the goods path.

The embodiment according to claim 10 is particularly advantageous. Proportional magnets can be obtained inexpensively with exactly known and constant characteristics. They are functionally reliable and precisely adjustable. Such proportional magnets are characterized in that the magnetic force generated is directly proportional to the current applied, so that the proportional magnet fulfills the function of a spring which is adjustable in its spring hardness without changing the characteristic curve. Proportional magnets can be easily Control via a current regulator.

A particularly expedient embodiment is further evident from claim 11. The window comparator monitors the position of the web for the proportional control of the two proportional magnets. The first timing element is used to switch off the current regulator of the proportional magnet, in whose web guide there is still full engagement when the roller engagement length limit value is reached in the other web guide. The timer is activated as soon as the window comparator detects this critical web offset. If the web offset remains for the period of time set on the first timing element, the current controller is switched off in order to enable the web guide to make the correction with the lesser roller intervention.

Furthermore, the embodiment according to claim 12 is advantageous because the components provided here help to avoid damage to the web or the device. If, in spite of the currentless current regulator, the web guide operating with little intervention is not able to correct the web offset, for which the first time element provides him with time, then the second time element actuates a warning signal after the set time period has elapsed , which indicates an error to the machine operator or even a switch that stops the web.

It is advantageous if the force transmitter used is a pneumatic diaphragm cylinder with an actuating force proportional to the compressed air supply for the control roller or a prestressed spring element which is adjustable in the prestress. Pneumatic membrane cylinders, which are particularly useful in potentially explosive atmospheres or in the case of wet material webs, can be adjusted very sensitively by modulating the application pressure or by means of an inlet or outlet regulator. Although a change in the characteristic curve can hardly be avoided in the case of a spring element when the pretension is changed, it is nevertheless a continuous adjustment of the clamping force in a simple manner, for example. by means of a spindle or lever drive which adjusts the spring preload.

In the method emphasized in claim 13, a desirable proportionality between the positions of the edge areas and the clamping forces effective in the edge areas is achieved. The web is never completely released at normal offset, but is tensioned in the transverse direction - even when it is at a standstill. If the web is pulled to this side by increasing the clamping force on one side, then the clamping force, which is still effective, but possibly reduced, on the opposite side brings about a restraining effect which dampens the correction movement of the web and ensures that the web is kept in place. Only when the roll engagement becomes so small in one edge area that a correct correction becomes questionable is the opposite edge area completely released in order to make the correction easier for the web guide who works with reduced roll intervention. When the previously exposed clamping force is reinserted, the clamping force is gradually increased in order to avoid undesired pressure markings. Very slight tension fluctuations in the transverse direction of the material web are achieved with certainty in a method variant if the clamping force at one edge area is changed in inverse proportion to the clamping force at the other edge area until the roller engagement length limit value is reached for a web guide.

Alternatively, it can also be expedient, according to claim 14, to change the clamping force more in one edge area than in the other edge area. A change in tension in the transverse direction is indeed made in this way. With regard to a smooth web run and a sensitive correction, however, this method variant can be advantageous. It would also be advantageous, especially with a slight offset and full engagement of both web guides, to keep the clamping force at a fixed area at an edge area and change at the other edge area.

The method variant according to claim 15 is also advantageous because the two proportional magnets generate their magnetic forces in strict dependence on the position of the web in the scanning area. The current supply that is preferably specified is intended for a customary size of a web guide. With a considerable change in the size and the actuation mechanism, the range of suitable current application changes.

The method variant according to claim 16 is particularly advantageous because the guiding and spreading of the web is carried out with high security against damage. No edge area is completely released within a normal web offset area. The clamping force on the other web guide is released after a predetermined first period of time only after falling below the roller engagement in one web guide in order to increase the corrective effect. If, nevertheless, the web offset is not corrected, a warning signal is generated after a further second period of time or the web is stopped in order to avoid serious damage.

An embodiment of the device and the method according to the invention are described with reference to the drawing.

Show it:

Figure 1 is a schematic plan view of a device for guiding and spreading a web and

Figure 2 shows a specific embodiment of a web guide in and 3 two mutually associated views.

A device V for guiding and spreading a web B running in the direction of an arrow 8 consists of two web guides W _a. and W ₂ , which act on the edge regions K _x and K-. The two web guides W _1} W ₂ are inclined at an angle α against the right angle to the web direction 8. Each web guide W _1} W ₂ includes a control device S _{1 5} S ₂ , which are expediently combined in a common control device R, which also contains an amplifier A. Furthermore, a window comparator F is provided in the control unit R, which is connected to the current regulator SR _a , SR ₂ . Each current regulator SR _1} SR ₂ can be switched off via a first, preferably adjustable, timer Z_ which can be activated by the window comparator F. With a second timer Z ₂ , which is connected to the window comparator F like the first timer Z _x , a warning signal generator G can be actuated, or a main switch (not shown) for the web run can be activated.

Each web guide W _1} W ₂ has (Figures 2 and 3) a lower control roller 1 and an approximately parallel upper counter roller 2. The rollers 1, 2 enclose the respective edge area K _a , K _{2 of} the web B between them. A scanning device 4 is arranged in the web running direction 8 behind the rollers 1, 2. The control roller 1 is movably mounted on a power transmitter 3 relative to the counter roller 2. Both rollers 1, 2 are either freely rotatable or can be driven to rotate at the speed of the web B by means of an additional drive (not shown). Each force generator 3 of a control roller 1 is continuously adjustable in such a way that the clamping force between the two rollers 1, 2 can be continuously changed without releasing the web. The force generator 3, for example. a proportional magnet 14 is connected via a line 5 to the control device S _a or Sz, as are the scanning devices 4 via lines 6. A line 7 links the two control devices S _α , S ₂ . In the direction of travel behind the web guides Wi, W ₂ , the web B is guided over a deflection roller 9.

While the web B is running, both web guides Wi, W ₂ apply a clamping force to their edge areas K_ K ₂ . The goods- Railway B is being spread out. If the material web B runs to the right in the running direction 8 in FIG. 1, for example, the scanning device 4 generates a signal corresponding to the edge position. The force transmitter 3 is adjusted to a lower force value, so that, thanks to the clamping force in the web guide W _2, the web B is pulled to the other side and the web run is thus corrected again. With a course in the reverse direction, these processes take place in reverse. The clamping forces in both edge areas K_ K ₂ can be changed synchronously in opposite directions. However, it is also conceivable to change the one clamping force in a different way from the other clamping force or to change only one clamping force at all. It is important in any case that a clamping force is applied to an edge area K _1} K ₂ at all times. The clamping forces can still be maintained even when the web B is stationary in order to keep the web tensioned.

1, 2 and 3, a proportional magnet 14 is provided as the force generator 3, the magnetic force of which is proportional to that of the current regulator SRa. or SR ₂ controlled current strength changed continuously. Instead of a proportional magnet 14, however, a pneumatic diaphragm cylinder could also be provided, the actuating force of which for the control roller 1 can be directly varied in proportion to the pressurization. It is also conceivable for a force element 3 to be a spring element, for example. to use a helical spring, the pretension of which is changed continuously and in stages or continuously. Electric motors or similar proportionally adjustable power transmitters could also be used.

According to FIGS. 2 and 3, the two rollers 1, 2 are mounted approximately parallel to one another in a holder 13. The control roller 1, which must be adjustable, is seated on a support part 12 on which the force generator 3 acts. In the embodiment shown, the scanning device 4 is a broadband proportional sensor with a lower part 10 and an upper part 16, which are likewise fastened to the holder 13. In the direction of web travel in front of rolls 1, 2 there is a securing device 11 attached. The bracket 13 can be fixed by means of a support 15 in the desired inclined position (angle α) relative to the track on a frame, not shown. The control device can be attached directly to one of the two web guide or integrated and connected to the other web guide via appropriate cable connections.

The window comparator F is used for proportional control of the proportional magnets 14 of the two web guides W _x and W ₂ via the current regulators SR _X , SR ₂ . If a normal web offset occurs, in which the rollers 1, 2 of the web guide are in engagement with the edge region at least up to 60 or 70% of their length L, the clamping force on a web guide is never completely eliminated, but rather the Clamping forces changed proportionally to the web position. However, if there is a web offset at which a roller engagement length limit value Q (FIG. 3) is reached, that is to say that the rollers 1, 2 of this web guide W _1} W _{2 are} only engaged by 60 or 70% there is the danger that this web guide W _{1 (} W _z with reduced roller engagement even with maximum magnetic current (approx. 500 mA) will no longer be able to generate a sufficient correction force because the other web guide W ₂ , W _α itself also Magnet¬ low current (about 150 mA) but prefers maximum rolling engagement too strong. this critical offset, the window F fixed by means of the signals of the sensing devices. 4 He activates the first Zeit¬ membered Z _α. Within by the first timer Z _α The time period set is waited to see whether a correction of the path offset occurs. If this is the case, the timer Z _x is switched off again. If this is not the case, however, the timer Z _Λ switches after lapse Chen the period of time, the current regulator SR _α or SR _{2 of} the proportional magnet 14, in whose rollers 1, 2 there is full engagement. The clamping force is completely eliminated there, if necessary the control roller 1 is lifted off completely. At the same time, the second timer Z ₂ is then activated. The window comparator F monitors over the period of the second timer Z ₂ whether the material web B is corrected properly and in the positive case then turns off the second timing element Z ₂ and the previously switched off current regulator SR _α , SR ₂ again to the minimum current value (150 mA). If there is no correction of the web offset, then after the time period of the second timer Z _{2 has} elapsed, the signal generator G is actuated to warn the machine operator or the main switch is actuated to stop the web B and prevent further damage. The complete removal of the clamping force on both web guides W _1} W ₂ can also be set arbitrarily for threading the web B when starting up or after a shutdown. In normal operation with a normal web offset, the method described at the outset is used.

In Figure 1, the device is designed so that it serves to guide the center of the web B and has two web guides Wi, W ₂ . However, applications are also conceivable where only one web guide is provided in an edge area. Furthermore, it is expedient if the control roller 1 is pivotally mounted on its support part 12, so that it is able to apply exactly parallel to the counter roller 2. In addition, with this position of the control roller 1 it is achieved that when the clamping force is increased, it is initially highest near the free edge and lower toward the center.

Claims

1. Device for guiding and holding a web, with at least one web guide arranged at an angle to the web running direction, which has a rotatable control roller and a rotatable counter-roller approximately parallel thereto, which receive an edge region of the web between them, with one on the Power sensor acting on the control roller for pressing the control roller onto the counter-roller, with a scanning device generating correction signals proportional to the edge position and with a control device influenced by the correction signals for adjusting the power transmitter in order to correct a web replacement, characterized in that the power transmitter ( 3) can be continuously adjusted at least up to a roller engagement length limit value (Q) which is just permissible for a web offset correction by varying the clamping force without completely lifting the control roller (1).

2. Device according to claim 1, characterized in that the length limit value (Q) is continuously adjusted up to the roller engagement. bare force transducers (3) can only be adjusted from falling below the roll engagement length limit value (Q) until the clamping force is eliminated.

3. Apparatus according to claim 1, wherein a web guide is arranged on both edge regions, characterized in that the control devices (S _a , S ₂ ) for both power transmitters (3) are linked such that the two power transmitters (3) to the still admissible ¬ other roll intervention length limit value (Q) in a web guide (Wi or W ₂ ) are synchronously adjustable in opposite directions.

4. The device according to claim 1, wherein a web guide is arranged on both edge regions, characterized in that the control devices (Sj, S _a ) for both power sensors (3) are linked such that the two power sensors (3) up to the permissible roller engagement. Length limit value (Q) can be asynchronously adjusted in opposite directions in the case of a web guide (W _α , W ₂ ).

5. The device according to claim 1, wherein a web guide is provided on both edge regions, characterized in that the control devices (S _{1 (} S ₂ ) for both power transmitters (3) are linked such that until reaching the permissible roller intervention - length limit value (Q) in the case of a web guide (W _a , W ₂ ) only one of the two force transmitters (3) is continuously adjustable.

6. Device according to claims 2 to 5, wherein a web guide is provided on both edge regions, characterized ge indicates that the control devices (S _a , S ₂ ) for both power transmitters (3) are linked together such that from falling below the roller engagement length limit value (Q) in the case of a web guide (W _1} W ₂ ) of the force transmitter (3) for the control roller (1) of the opposite web guide (W ₂ , W _A ) until the clamping force is completely removed, if necessary is adjustable until the control roller (1) is lifted off the web (B).

7. Device according to claims 1 to 6, characterized gekennzeich¬ net that the roll engagement length limit (Q) is about 60 to 70% of the roll length still covered by the web (L).

8. The device according to claim 1, characterized in that the scanning device (4) has a broadband proportional sensor (10, 16), and that in the control device (S _{1 5} S ₂ ) an amplifier (A) is provided.

9. Device according to one of claims 1 to 8, characterized ge indicates that the linked control devices (S _1} S ₂ ) are combined in a control device (R) to which the scanning devices (4) and the force transmitter (3 ) are connected.

10. Device according to one of claims 1 to 9, characterized ge indicates that the force transmitter (3) is a proportional magnet (14) with a magnetic force proportional to the current applied, and that in the control device (S _{X i} S ₂ ) an adjustable current ¬ controller (SR _X , SR ₂ ) is provided for the current application.

11. The device according to claim 10, characterized in that the current controller (SR _α , SR ₂ ) of the proportional magnet (14) via a window comparator (F) for monitoring the edge position and at least a first timer (Z_) can be switched off as soon as one by Roller engagement length limit value (Q) represents inadmissible deviation of the material web (B) from the central position over a period of time that can be set by the first timer (Z _a ).

12. The apparatus according to claim 11, characterized in that parallel to the first timer (Zi), a second, to an extension of the duration of the first timer (Z _a ) or to a longer period of time timer (Z ₂ ) is provided, with a Warning signal generator (G) or a web run switch can be actuated, as soon as the current controller is switched off the inadmissible deviation the web (B) is maintained.

13. A method for guiding and spreading a running web of material with web guides arranged obliquely to the web at both edge regions, in each of which a control roller can be pressed against a counter roller by means of a force sensor by clamping an edge region, the position of the edges being achieved by signal-generating scanning devices scanned and the force transmitters actuated as a function of the signals are characterized in that the clamping force at each edge area up to a roller engagement length limit value (Q) which is just still permissible for a web offset correction without complete release of the web (B ) is increased or decreased in proportion to the signals, and that the clamping force is completely eliminated when the roll engagement length limit (Q) is undershot for one edge area (W _a , W ₂ ) in the opposite edge area (K ₂ , K _a ) becomes.

14. The method according to claim 13, characterized in that the clamping force at one edge region (K _a , K ₂ ) is changed more than the clamping force at the other edge region (K ₂ , K _a ).

15. The method according to any one of claims 13 or 14, characterized ge indicates that both force transmitters (3) are proportional magnets (14) with magnetic force that can be changed as a function of the current applied, and that the current applied to the proportional magnets (14) via current regulators to achieve a just permissible roller engagement length limit value (Q) depending on the positions of the edges in the scanning devices, preferably between 500 mA and 150 mA.

16. The method according to claims 13 to 15, characterized gekenn¬ characterized in that upon reaching the roller engagement length limit (Q) in a web guide (W _a , W ₂ ), the current application of the proportional magnet (14) of the other web guide (W ₂ , W _a ) is switched off after a predetermined first period of time, and that after the current supply has been switched off, a warning signal is generated after a second predetermined period of time or the web (B) is shut down if an inadmissible web offset is maintained.