GB2191608A

GB2191608A - Web position adjusting means

Info

Publication number: GB2191608A
Application number: GB08712580A
Authority: GB
Inventors: Dietrich Hank; Friedrich Richter
Original assignee: Polygraph Leipzig Kombinat Veb
Current assignee: Polygraph Leipzig Kombinat Veb
Priority date: 1986-06-09
Filing date: 1987-05-28
Publication date: 1987-12-16
Anticipated expiration: 2007-05-28
Also published as: DE3716562A1; GB8712580D0; DD249898A1; GB2191608B; FR2599728A1

Description

1 GB 2 191 608 A 1 SPECIFICATION tional deviation of the web in falsified

manner, since the pivoted outlet guide rollerturns the material web Web position adjusting means and the sensor detects only its projection.

Known equipmentforthe guiding of a moved web The present invention relates to web position adjust- 70 avoid this disadvantage (cf. DE-AS 22 12 212 and DE ing means, especiallyfor a continuously moved mat- OS 23 05 689) by arranging forthe sensor, on pivota eriai web in a rotary roller printing machine in which tion of the outlet guide roller, to trackthe plane of the the web to be printed on must be moved true to regi- issuing turned web by a special tracking device while ster. maintaining a fixed spacing from a reference linefor Known web position control systems comprise re- 75 the edge of the running web in orderto keep spacing gulation of a basic kind. The regulation is a control and direction substantially constant relativetothe with continuous feedback of the controlled magni- outlet plane of the web. Asignificant disadvantage of tude,the regulation magnitude. The regulation path this equipment isthat accurate and costlytracking and regulating equipmentform a regulating circuit equipment is required.

and a sensorforthe detection of theweb position 80 There isthus a need for meansforthe control of deviation is arranged,with respectto the running the position of a continuously moved material web in direction of the web, behind a setting memberfor such a manner as to substantially eliminate, without influencing the position of the web (cf., for example, delay, the effect of disturbances on the web position.

D. Hank and T. Niesgoda: "Bahnkantenregelungen According to the present invention there is prov- an Rollendruckmaschinen, Papier und Druck 27 85 ided web position adjusting means comprising a (1 978)l " part Trinting and processing" pages 1 to sensorforthe detection of deviation of the position 7). of a material web and arranged in running direction The arrangement of the sensor behind the setting in front of a setting memberforthe influencing of the member, however, has a substantial disadvantage. position of theweb, and control means connected at The regulation path, which starts atthe setting 90 its inputtothe sensor and having a transferchar member and comprisesthe web conveying and acteristicwhich is approximately equal to thetrans guiding equipment up to the location of the sensor, fer characteristic of web conveying and guiding equi represents a transfer member in the sense of regula- pment in theweb portion between the sensor and tion technique. In general, a path with proportional the setting member, the output of the control means behaviour and time delay of first order, a PT, 95 being connected with the setting member byway of member, is concerned. The time constantTof the a setting drive with proportional behaviourand the path obeysthe equation T = Uv, wherein L istheweb time constant of the transfer function of the control travel length between the setting member and the means being controllable bythe machine cycle prop sensorand v isthe web speed. Compensation for ortionallyto the machine cycietime. It is realised disturbances orsetting action atthe location of the 100 through the proportionality factorthat the time con setting member is terminated atthe location of the stant of the control means is, in terms of amount, sensor only after elapsing of the compensating time approximately equal to the time constant of the web T,,, which is approximately equal to 3.Uv. conveying and guiding equipment in the web por- If a disturbance appears atthe input of the path, tion between the sensor and the setting member.

then the regulating equipment, its input member 105 In a preferred embodiment, on the occurrence of a being the sensor, "notices" only a part of the disturb- deviation in web position clueto disturbance ance effect during the compensating time Ta and dis- apparent atthe location of the sensorthe deviation is places the setting member onlyto that extent. The detected bythesensorand converted into an analog regulating equipment receivesthe full disturbance signal, by which the control means isacted on. Ifthe effect only after elapsing of the compensating time 110 web isdeflected bya disturbance, for example atthe Ta and displaces the setting memberasfaras isnec- location of the sensor, then the compensating pro essaryforthe elimination of the effect of the disturb- cess isterminated atthe location of thesetting ance. However, the setting memberaction becomes member only after the time T,, 3.Uv, wherein Lis fully effective only after the compensating time Ta thewebtravel length between sensor and setting haselapsed approximately once again, so that the 115 member and v is the web speed. The time constant of effect of the disturbance is completely eliminated the control means is so controlled bythe machine only afterthe time 2.T, cycle proportionallyto the machine cycletimethat In orderto minimisethis delay, the sensor is, in the temporal course of the control signal,with which known web position regulating systems, arranged in the setting drive is acted on, is approximately equal running direction of the web closely afterthe firstfix- 120 to the temporal course of the web position deviation edly arranged guide rollerfollowing the setting at the input of the setting member. The setting drive member. The positional accuracythus attained is acting proportionally so sets the setting memberthat not, however, sufficientfor quality printing. a position adjustment compensating forthe web Afurther shortening of the web travel between set- position deviation comes into being.

ting member and sensorthrough the arrangement of 125 The setting member may atthe sametime be part the sensor between the output guide roller and the of a regulating circuitfor regulation of the web posi setting member and the firstfixedly arranged guide tion by a sensorjorthe detection of theweb position rollerfollowing the setting memberand neartothe deviation, arranged downstream of the setting outlet guide roller has the disadvantage thatthe member. The control chain of the equipment forthe sensor arranged to be locally fixed detects the posi- 130 control of the web position and the regulating circuit 2 GB 2 191 608 A 2 for the regulation of the web position thus have a web 2 is, for example, deflected at the location of the commonplace of action at the setting member. This sensor 1, then the compensating process at the loca embodiment represents a regulation superimposed tion of the setting member3 isterminated only after on a forward control. However, onlythe elimination thetimeTa 3.LIv, wherein L is thewebtravel length of a compensating errorof the control chain is still 70 between the sensor 1 and setting member3 and v is incumbent on the regulating circuit. the web speed. The time constant of the control de A particular advantage achieved by adjusting vice 4 is so controlled bythe machine cycle prop means embodying the invention is that on the ortionallyto the machine cycletime thatthe tem occurrence of periodic disturbances, i.e. oscillations poral course of the control signal, bywhich the of the web, the amplitude is reduced just as well as 75 setting drive 7 is acted on, is approximately equal to on the occurrence of step-shaped disturbances. A the temporal course of the web position deviation at further advantage is thatweb position control is gen- the entry of the setting member 3. The setting drive 7 erally simpler in function and construction and there- acting proportionally so resets the setting member3 fore cheaperthan web position regulation. that an adjustment compensating forthe web posi The embodiment in which regulation is superim- 80 tion deviation is produced.

posed on a forward control affordsthe particular A residual web position deviation,which is advantage of a high stationary regulating factor traceable backto a compensating error of the device attainable by relatively simple means. It is also forthe control of the web position, is reduced, how advantageous thatthe sensor downstream of the ever, with delay bythe web position regulating cir setting member can be arranged almost as far as de- 85 cuit consisting of the sensor 8, the regulator 9,the sired behind the setting member and as a compo- setting drive 7 and the setting member 3.

nent of a known web position regulation forthe re- Adjusting means embodying the present inven moval of stationary web position deviation. tion as hereinbefore described has a simple build-up An embodimentof the present invention will now and high reliabilityand contributes substantiallyto be more particularly described byway of example 90 securing the quality of the printed productsthrough with referencetothe accompanying drawing,the web guidancetrueto register.

single Figure of which is a schematic diagram of

Claims

adjusting means embodying the invention. CLAIMS

Referring nowto the drawing,there is shown web position adjusting means comprising a sensor 1 for 95 1. Web position adjusting means comprising dis the detection of the spacing of the edge of the web 2 placing means operable to displace a longitudinally of material to be printed on from a reference line, the moved material web transversely to the direction of sensor being arranged, in running direction of the movement thereof, the displacing means having a web, upstream of a setting member3 for inf luencing porportional transfer characteristic, detecting means of the web position and being connected to the input 100 arranged upstream of the displacing means with re of a control device 4. The control device 4 has a trans- spectto said direction to detect lateral deviation of fer characteristic which is approximately equal to the the web from a predetermined longitudinal position transfer characteristic of web conveying and guiding and to provide a signal indicative of any such detec equipment in the web portion between the sensor 1 ted deviation, and control means responsiveto such and the setting membef---3. Disposed in this web por- 105 signal to provide a control signal for use in con tion isjor example, a cooling roller unit 5 placed be- trolling operation of the displacing means,the con hind a hot air drier. Theweb portion betweenthe trol means having a transfer characteristic substanti sensor 1 and the setting member 3 represents, in the ally equal to the transfer characteristic of the web sense of regulation technique, a PT, member. Acconveying between the detecting means and the dis cordingly,the control device 4 also has a PT, be- 110 placing means and having a time constant con haviour. The time constant of the transferfunction of trollable proportionally to the cycle time of cyclically the control device 4 is controllable from the machine operable means influencing the speed of the web cycle proportionally to the machine cycle time. The movement.

chosen proportionality factor realises thatthe time
2. Web position adjusting means as claimed in constant.of the control device 4 is, in terms of 115 claim 1, comprising further detecting means arran amount, approximately equal to the time constant of ged downstream of the displacing means with re the web portion between the sensor 1 and the setting spectto said direction to detect lateral deviation of member
3. The output of the control device 4 is con- the web from a predetermined longitudinal position nected with the setting member 3 by way of a mixing and to provide a signal indicative of any such detec device 6 and a setting drive 7 with proportional be- 120 ted deviation, and further control means responsive haviour. to such signal of the further detecting means to pro Afurther sensor 8forthe detection of the spacing vide a further control signal for use in controlling op of the edge of the web 2 from a reference line is eration of the displacing means.

arranged downstream of the setting member 3 and is 3. Web position regulating means substantially connected byway of a proportionally acting regula- 125 as hereinbefore described with reference to the ac torgto a further input of the mixing point& companying drawings.

On the occurrence of a web position deviation in consequence of a disturbance detected at the sensor Printed for Her Majesty's Stationery Office by 1,the detected deviation is represented by an analog Croydon Printing Company (UK) Ltd, 10187, D8991685.

Published by The Patent Office, 25 Southampton Buildings, London, signal which is applied to the control device
4. If the WC2A lAYfrom which copies maybe obtained.