US2951007A - Method and device for regulating the moisture content of endless moving webs of fibrous material - Google Patents

Description

Aug. 30 1960 P. R. LIPPKE 2,951,007

METHOD AND DEVICE FOR REGULATING THE MOISTURE CONTENT OF ENDLESS MOVING WEBS OF FIBROUS MATERIAL Filed .June e, 1957 2 sheets-sheet 1- PAuL e. UPP/ 5 @WJ www l ATTORIJEKSA Aug. 30, 1960 P. R. LIPPKE 2,951,007 METHOD AND 'DEVICE FOR REGULATING THE MOISTURE CONTENT oF ENDLEss MOVING wEBs orFrBRous MATERIAL Filed June 6. 1957 2 Sheets-Sheet 2 INVENTOR FIBEROUS MATER-IAL FEED E m w L e. w. m

ATTORNEYS United tates Paul R. Lippke, R0. Box 163, Augustastrasse 17, Neuwied-Rhine, Germany Filed June 6, 1957, Ser. No. 664,058

14 Claims. (Cl. 162-198) The present invention is to improve the possibilities of equalizing the moisture content in endless moving webs of fibrous material. Y

It is known that such endless webs, as e.g. of paper, pulp or board have not only considerable variations in moisture content in direction of the running web but also across the entire web. These variations partly result from irregularities in the sheet formation being unavoidable on the wire and partly from the fact that the presses and the felts do not work equally and but not least from irregularities within the drying process in so far as the pressure of steam, which is used for the drying process, or the drying ability of the paper, changes. These variations of the moisture content disturb the manufacture of the webs to a high degree, since they prevent an otherwise given possibility, namely to eXsiccate the water only to such a degree that the ready dried web is in hygroscopic balance with the surrounding air in the iinishing room.

The possibilities of modern techniques to improve moisture content of such webs can be realized by the following methods. Firstly by controlling the basis weight of the web, either at the wet part of the drying machine or at the dry end of the machine and that by means of varying the supply or consistency of feed in order to equalize the web. Secondly it is possible to measure the moisture content kat the end of the drying section. According to this measurement a regulator is inuenced which in turn controls the flow of steam to the dryers. Furthermore it has been proposed to utilize the measuring value of the moisture meter for the adjustment of the moistening device so that corresponding with the moisture content 4of the paper more or less water is added tothe paper web. 'The measuring instruments suitable for testing both vbasis weight and moisture content are ot different construction. For the regulating purposes, too, various procedures are known.

-All these measuring instruments and regulators incorporate lone disadvantage which consists in the fact Ythat it is indeed possible to equalize the moisture content in the running direction of the web corresponding to the received measuring value from a certain place of the web but 'not to equalize the variations of the moisture content across the web which is far more disadvantageous in impairing the economic production.

This limitation of the presently known regulating procedures for the moisture content of such webs results in applying the disadvantageous manufacturing method that the entire Web has to be dried down to a very low moistuie content, generally 2-3% H2O, in order 'to be sure -that also the spots which have remained thicker in-the formation process or in the mechanical purification of the web and which are accordingly moisture will dry suiciently. This low moisture content then is kept con- Stant Vby such a regulating procedure. Since it is not possible to deliver the paper with such a low -moisture 'content wateris sprayed on the web subsequently.

VForthis purpose spray devices of various construction are applied. It is evident that this procedure is a very uneconomical one. The hygroscopic balance of diiierent paper types at a climate of 65% relative humidity is about between 7 to 11% H2O. If the paper web has been dried down to 2-3% H2O or sometimes to even a smaller degree it is absolutely necessary to add consider-able amounts of water to the paper. This procedure causes an alteration of the surface of the paper and is very disadvantageous. Moreover in many cases it is not possible to carry out such an intensive moistening of the paper.

The present invention takes care of all these disadvantages and starts from the principle that an over-drying of the paper and the connected horniiication of the fibre must be avoided as well as the excessive consumption of steam and the slow-down of the paper machine speed. At the same time the invention takes care of a far-reaching equalization of the moisture content of the paper being Astill in the drying pro-cess and furthermore allows a subsequent correction of the moisture content of the paper web, as well in the running direction as across the web by subsequent correction of the irregularities which unavoidably remain after the forming and drying of the web.

By means of this invention it is also possible to eliminate the variations of the basis weight which up to now unavoidable in the stage of forming the web and to remove thereby the already described ditiiculties in the later converting process of the paper.

The investigations being performed on occasion of this invention have shown that the peaks and irregularities alongV and across the paper web, which are of disadvantageous influence to an economic drying, exclusively result from variations of the basis weight, with the understanding that the steam for the drying process is supplied constantly. According to this invention the irregularities of the iibrous web shall be eliminated by the following procedure: by the periodic movement of the measuring feeler of a moisture meter which is to be installed at or behind the dry end of the paper machine, the moisture content of every part of the web which corresponds with the breadth of the measuring feeler, is measured. In relation to these measuring values a plurality of partial elements of the fibrous material inlet slit is adjusted by means of a continuous regulating device, which will be described later on. Just so Ia plurality of partial elements of a spray device are adjusted, also in a manner, which will be described later on. By these procedures rstly .the basis weight variations-will be eliminated and secondly, by means of a more or less intensive moistening, the remaining variations ofthe moisture content will be equalized so that a paper of most equal basis weight and moisture content will be obtained inally. The invention eX- tends to the'application of the therein described procedure and to the performance of the equipment being necessary for the execution of the proced-ure.

In order to illustrate the performance of the invention an `example is represented. Fig. 1 shows a moisture prole of `a paper web under diierent drying conditions. Fig. 2 illustrates in a total scheme the arrangement of the single parts at a paper -machine and the construction of the regulator. Fig. 3 represents in a scheme the arrangement of the water spray nozzles with air pressure diffusion. Fig. 4 shows an example of the performance of the adjusting device for the variation of the ow inlet. Fig. 5 shows the example of an adjusting device for the partial alteration of the eiectiveness of [a brush-or spray damper for the moistening of the paper web. Y

The execution of the invention is described v,in the following example:

The moisturemeterlwhichtraverses the web period- .,ieally is arranged at the end of the drying-section. The

measuring values are recorded on the recording strip 2, whereat the recording strip is only moving when the measuring feeler of the -moisture meter from the front Iside' Vto the driving sideiwhilst theV transport ofthe recording strip is stopped during the returnmovement. This is necessary in order to have the possibility to compare the recording diagrams right next t-o each other. The Vmeasuring value of the moisture meter is fed' at the same time to the regulator 3 which may work in any way. The steering mechanism of the regulator, in this example an'electromotor 4, acts the arm 5 which inuences by means of the groove, which is formed by the two control surfaces 6,`via the roll 7 the needle valve 8.

i Imagine the arm 5 being pushed forward so far that the Vroll 7 is placed between the control surfaces 6 it becomes Yevident that the needle valve 8 will beopened more for the case in which the moisture meter inds out a lower moisture content or less if a spot of higher moisture content has been tested. A spray nozzle of the moistening 'apparatus 9 whichbelongs to this needle valve accordingly would add more or less water to the paper. The regulator 3 has a desired value adjustment 10 by means of -which the nominal value of the moisture content of the paper web can be xed. The difference value between the moisture meter 1 and the desired value adjustment 10Yeffects the regulatingprocess and by means of the needle valve the amount of water is sprayed on the place concerned of the web. This amount of water and the already existing moisture content in the web yield together the desired value.

Therewith the function of the regulating process would be described for the single nozzle. But since it is necessary, to alter the eiciency continuously not only from one nozzle, but from a plurality of nozzles and since it would be uneconomical to provide a plurality of such regulators, the arm 5 being the actual steering mechanism is passed along the needles which belong to the nozzles concerned, synchronized with the movement of the measuring feeler across the web, so that those nozzles are `actuated which lie at the same place of the breadth of the paper web where the measuring feeler stays.

It is possible to arrange all needle valves in one line and to move the arm 5 by means of the motor straight alongside these needle valves. But it is even more advantageous to arrange all the needle valves in a circle 'round the swivel axle of thearm 5 and to turn the arm, which is xed on the drive shaft, corresponding with the movement of the measuring feeler to and fro. Now the purpose of the control surfaces 6 is to be understood from the following. They are so dimensioned that they have at the beginning a distance which corresponds to the entire regulating lift of the valve rod and having a distance at the middle, which corresponds exactly with the diame- Ater ofthe roll 7.

Arm 5 together with the control surfaces l6 can now oc cupy another position opposite to the rolls 7 of the various nozzles for every situation in the rotating movement being equivalent to the position of the measuring feeler on the web, and the adjustment of the needle valves will be altered according to the actual moisture reading of the moisture meter. It is planned to install a spray damper for water at which the necessary air atomizer-nozzles 12 are arranged, as shown in Figure 3, together on a pipe in such a distance of the web that their cones of dispersion Ymeet exactly on the surface of the sheet. In order to keep the cones of dispersion and the output of the nozzles constant, air with a constant pressure is fed to the common main pipe. Then the output of each nozzle is a1- tered by the respective needle valve 8. Thereby it can be achieved that for every amount of Water which is to be atomized yan absolutely equal dilfusion and a kconstant cone of dispersion can be guaranteed.

Withthe same arrangement it will be possible toicontrol thertibrousl material feed inlet, too. Since the hydraulical resistance of the atomized nozzleis of av constant value and since the water pressure is constant in front of the needle valves S it can be understood that a pressure change will take place in the pipes behind the needle valves 8, which corresponds to the amount of water which is fed to every nozzle. This pressure change is used at the same time for an'alteration of the passage cross section of the brous material feed inlet device. The performance of the necessary equipment is shown under Figure 4. The lip 14 of the fibrous material feed inlet must, as already described before, be changed according to the measuring values of the moisture meter. 'I'his is to be done as usual by means of the spindle 15 with the handwheel 16.

The nut of the handwheel 16 is firmly imbedded. In order to obtain a self-acting control of the passage cross section of the fibrous material feed inlet the nut of the handwheel 16 is imbedded in the turnable lever arm 17 'which influences via the pressure cylinder 18 with its piston 19 and counterspring 20 the position ofthe lip 14 of the fibrous material feed inlet.

In relation to every nozzle ofthe spray damper at the same place on the respective lip of the fibrous material feed inlet such a pressure cylinder is arranged. Both parts are connectedV by the common water pipe line. Every variation in this pipe line, which iscaused by the needle valve 8 thus effects at the same time achange of the moistening as well as a change-of the position ofthe fibrous material feed inlet lip 14. Consequently, the partial variations of the basis weight and the uneven moisture content of the web resulting therefrom will be eliminated at the same time. 1

Indeed, it is possible to realize the one and the other regulating procedure, eg. the control of the moistening and fibrous material feed inlet, either operating together or separately.

The moistening procedure by means of atomizernozzles for water, especially such nozzles, which operate with compressed air, will be in any case the most advantageous because of its possibility to limit the effect of the moistening exactly; but it will be also possible to control other sorts of moistening apparatuses in their efficiency across the web.

In Fig. 5 such a possibility is illustrated. The needle valves 8 are connected with the pressure cylinders 21 which are distributed along the entire breadth of the brush damper in the same number as lips are at the fibrous material feed inlet. If an arbitrary leak is fed into the connecting line between the needle valve 8 and the respective pressure cylinder 21, there willunder the supposition of constant water pressure in front' of the needle'valve and constant amount of water in front of the leak-occur a corresponding pressure which corresponds to the difference between the actual moisture content-which is represented by the moisture meter--and the desired value, which has been adjusted at the regulator. This Ypressure causes by means of the piston 22 and the counter spring a corresponding variation of the position of the impinging plate 24.

At a great diiference between the two moisture values the impinging plate is pushed towards the bristles of the brush so that more Water sprays on the web. Whilst at a smaller difference between the two moisture values the impinging plate is not pushed so far towards the brush and less water is sprayed on the web.

When using atomizer nozzles working withV an impinging plate the sameV device can be applied. The water spray which streams out of the nozzle 25 can be atomized by means of the impinging plate more or less, the moistening of the Vweb being in this case also dependent on the difference-,value between moisture reading of the moisture meter and adjustment of the desired value at the regulator.

Since thetwo Ylast-mentioned moistening procedures do not olfer the exactness which is necessary for a useful moisteningA and the distribution of the'water to single sections of the Web these procedures shall be mentioned only in order to complete the description on the possibilities of the application of the invention. Naturally, it will be possible to connect the control of the moistening device with that of the fibrous material feed inlet when applicating such a moistening device, too, and t produce the same effect as under application of a moistening by means of air-pressure atomizing.

It has been explained in the present description of the application and the idea of the invention that it is not only possible to obtain by means of this invention a subsequent moistening which treats the single parts of the paper Vweb differently but furthermore to bring about that the excessive drying of single parts of the web will be avoided.

In this case, the moistening apparatus, preferably a device with air pressure atomizer nozzles, is installedas shown in Fig. Z-Within the drying section, and that at a place, where the paper web is not yet so far overdried that hornication takes place at the surface.

As already described, more water is added now to the drier parts of the paper so that the paper becomes moister.

By the increased evaporation power Which becomes necessary at this place of the web the surface temperature of the following drying cylinders is reduced to the actual measure of the other parts of the cylinder surface.

The entire arrangements can remain the same as described.

I claim:

1. The method of making a web of material and regulating the liquid content and basis weight thereof which comprises forming a liquid slurry of the material into a sheet by passing slurry thereof through an elongated slit, passing the sheet along an elongated course, evaporating liquid from the sheet as it traverses said course, successively sensing liquid content of the web at points disposed along a path extending across said course and depending upon the amount of liquid sensed at said points simultaneously applying liquid in varying amounts across the width of the web and varying opening size along said slit to improve uniformity of the web with respect to liquid content and basis weight, the slit opening and amount of liquid applied when a liquid deficiency is sensed, each simultaneously being increased at corresponding points along the slit and across the web, respectively and when a liquid excess is sensed each simultaneously being decreased at corresponding points along the slit and across the web, respectively, to realize said improved uniformity.

2. The method of regulating the liquid content of a Web of material which comprises passing the web along an elongated course, evaporating liquid from the web as it traverses said course, successively sensing liquid content of the web at points disposed along a path extending across said course, and depending upon the amount of liquid sensed at said points, applying liquid in varying amounts across the width of the web to improve uniformity of the web with respect to moisture content.

3. The method of making a web of material and regulating the basis weight thereof which comprises forming a liquid slurry of the material into a sheet by passing slurry through an elongated slit, passing the sheet along an elongated course, successively sensing liquid content of the web at points disposed along a path extending across said course, and depending upon the amount of liquid sensed at said points, varying opening size along said slit to improve uniformity of the web with respect to the basis weight thereof.

4. Apparatus for making a web of material and regulating the liquid content and basis weight thereof, which comprises means for forming a liquid slurry of the material into a sheet by passing slurry through an elongated slit, means for passing the sheet along an elongated course, means for evaporating liquid from the .sheet as it traverses said course, sensing means for successively sensing liquid content of the web at points disposed along a path extending across said course, lirst and second lreactive" rnens responsive to the sensing means depending on the amount of liquid sensed by the sensing means, the first reactive means being for applying liquid in varying amounts across the width of the web and the second reactive means being for varying opening size along said slit, said first and second reactive means being effective tov improve uniformity of the web with respect to moisture content and basis weight.

5. Apparatus according to claim 4, the first reactive means comprising a plurality of valved liquid lines disposed at spaced intervals transversely of the Web course for discharge of liquid to the web, the sensing means comprising a liquid meter for sensing liquid of the web, means for moving the liquid meter back and forth across the web, transmitter means operatively connected to the liquid meter, and valve control means responsive to the transmitter means arid effective to control the valves of said valved liquid lines, the transmitter means being effective to actuate the said valves for valve response to travel of the liquid meter in one direction only across said web, the second reactive means comprising a plurality of slit opening size changing means for controlling the slit opening size at places along the slit and slit control means for the slit opening size changing means for actuating said changing means, said slit control means being arranged for response to pressure drop associated with the said valved liquid line. c

6. Apparatus according to claim 5, said valved liquid lines being provided with atomizer discharge nozzles, the atomizer nozzles being connected to a constant pressure compressed air source, whereby compressed air can be discharged with liquid to provide improved liquid distribution to the web.

7. Apparatus according to claim 6, said valve control means comprising a control surface, the valve in each valved line having means for cooperation with said control surface and operating the valve, and means for moving the control surface so that it operatively engages a plurality of the means for cooperating with the valve control surface.

8. Apparatus according to claim 5, each valved line having a discharge nozzle, an impingement baffle Ifor each valved liquid line disposed adjacent the line nozzle discharge, baffle positioning means for each baille whereby the baffle can be positioned relative to its nozzle and delivery of liquid to the web can thereby be controlled, each baffle positioning means comprising a spring biased pistoncylinder arrangement, conduit means for communicating the piston-cylinder arrangement with pressure in front of its valve and a leak in said conduit means whereby actuation of a valve causes a pressure change in the Valves conduit means and actuates the valves piston-cylinder arrangement and in turn the valves impingement baffle.

9. Apparatus for making a web of material and regulating the liquid content thereof, which comprises means for passing the web along an elongated course, means for evaporating liquid from the web as it traverses said course, sensing means for successively sensing liquid content of the Web at points disposed along a path extending across said course, reactive means responsive to the sensing means depending on the amount of liquid sensed by the sensing means, the reactive means being for applying liquid in varying amounts across the width of the web, said reactive means being effective to improve uniformity of the web with respect to moisture content.

10. Apparatus according to claim 9, the reactive means comprising a plurality of valved liquid lines disposed at spaced intervals transversely of the web course for discharge of liquid into the web, the sensing means cornprising a liquid meter for sensing liquid of the web, means for moving the liquid meter back and forth across the web, transmitter means operatively connected to the liquid meter, and valve control means responsive to the transmitter means and effective to control the valves of Vsaid valved liquid lines', the transmitter meansbeing Veiective to actuate the said valves for valve response to travel of the liquid meter in one direction only across said Web.4

11. Apparatus according to claim 9, said valved liquid lines being provided with atomizer discharge nozzles, the atomizer nozzles being connected to a constant pressure compressed air source, whereby compressed air can be discharged with liquid to provide improved liquid disltribution to the web.

12. Apparatus according to claim 9, said valve control means comprising a control surface, -the valve in each valved line having means for cooperation with said control surface and operating the valve, and means for moving the control surface so that it operatively engages a plurality of the means for cooperating with the valve control surface.

13.v Apparatus according -to claim 9, each valve line having a discharge nozzle, and impingement bame for each valved liquid line disposed adjacent the line nozzle discharge, baie positioning means for each baille where- Vby the baffle can be positioned relative to its nozzle and delivery of liquid to the web can thereby be controlled, each bafe positioning means comprising aspring biased "piston-cylinder arrangement, conduit means for communicating the piston-cylinder arrangement with pressure in front of its valve and a leak in said conduit means whereby actuation of a valve causes apressure change in the valves conduit means and actuates the valves piston- Acylinder arrangement andAinmturnthe valves impinge ment baille, Y Y

14. Apparatus for making a web of material and regu- -lating thebasis weight thereof, which comprises means for forming a liquid slurry of the material into a sheet by passing slurry through fan elongated slit, means for pass- Vving the sheet along an elongated course, sensing means for successively sensing liquid content of the web at points disposed along a path extending across said course, reactive means responsive to the sensing means depending on the amount of liquid sensed by the sensing means, the reactive means being for varying opening size along said slit, said reactive means being effective to improve uniformityof the web with respect to basis weight.

References Cited in the le of this patent UNITED STATES PATENTS 423,435 Great Britain J an. 28,

Claims (1)

1. THE METHOD OF MAKING A WEB OF MATERIAL AND REGULATING THE LIQUID CONTENT AND BASIS WEIGHT THEREOF WHICH COMPRISES FORMING A LIQUID SLURRY OF THE MATERIAL INTO A SHEET BY PASSING SLURRY THEREOF THROUGH AN ELONGATED SLIT, PASSING THE SHEET ALONG AN ELONGATED COURSE, EVAPORATING LIQUID FROM THE SHEET AS IT TRAVERSES SAID COURSE, SUCCESSIVELY SENSING LIQUID CONTENT OF THE WEB AT POINTS DISPOSED ALONG A PATH EXTENDING ACROSS SAID COURSE AND DEPENDING UPON THE AMOUNT OF LIQUID SENSED AT SAID POINTS SIMULTANEOUSLY APPLYING LIQUID IN VARYING AMOUNTS ACROSS THE WIDTH OF THE WEB AND VARYING OPENING SIZE ALONG SAID SLIT TO IMPROVE UNIFORMITY OF THE WEB WITH RESPECT TO LIQUID CONTENT AND BASIS WEIGHT, THE SLIT OPENING AND AMOUNT OF LIQUID APPLIED WHEN A LIQUID DEFICIENCY IS SENSED, EACH SIMULTANEOUSLY BEING INCREASED AT CORRESPONDING POINTS ALONG THE SLIT AND ACROSS THE WEB, RESPECTIVELY AND WHEN A LIQUID EXCESS IS SENSED EACH SIMULTANEOUSLY BEING DECREASED AT CORRESPONDING POINTS ALONG THE SLIT AND ACROSS THE WEB, RESPECTIVELY, TO REALIZE SAID IMPROVED UNIFORMITY.

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