Method and device for regulating the moisture content of endless moving webs of fibrous material

Aug. 30, 1960 p _R lippke 2 951 007

METHOD AND DEVICE FOR REGULATING THE MOISTURE CONTENT * „._{Ί J} , ' ENDLESS MOVING WEBS OF FIBROUS MATERIAL

Filed June 6, 1957 ₂

Filed June 6, 1957

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INVENTOR

PAUL R. LIPPKE BY

ATTORNEYS

Aug. 30, 1960 p, r. lippke 2 951 007

METHOD AND DEVICE FOR REGULATING THE MOISTURE CONTENT * nc — _{M0VING WEBS QF FIBROUS MATERIAL}

Sheets-Sheet 2

Filed June

6,

OF ENDLESS 1957

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INVENTOR

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PAUL R. UPPKE

ATTORNEYS

United States Patent Office

2,951,007

Patented Aug. 30, 1960

2,951,007

METHOD AND DEVICE FOR REGULATING THE MOISTURE CONTENT OF ENDLESS MOVING WEBS OF FIBROUS MATERIAL

Paul R. Lippke, P.O. Box 163, Augustastrasse 17, Neuwied-Rhine, Germany

Filed June 6,1957, Ser. No. 664,058

Claims. (CI. 162—198)

The present invention is to improve the possibilities of equalizing the moisture content in endless moving webs of fibrous material.

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 finishing room.

The possibilities of modem 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 at the end of the drying section. According to this measurement a regulator is influenced 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 of the paper more or less water is added to the paper web. The measuring instruments suitable for testing both basis weight and moisture content are of different construction. For the regulating purposes, too, various procedures are known.

All these measuring instruments and regulators incorporate one disadvantage which consists in the fact that 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 moisture 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 sufficiently. This low moisture content then is kept constant by such a regulating procedure. Since it is not possible to deliver the paper with such a low moisture content water is sprayed on the web subsequently.

For this purpose spray devices of various construction are applied. It is evident that this procedure is a very uneconomical one. The hygroscopic balance of different paper types at a climate of 65% relative humidity is about between 7 to 11 % H₂O. If the paper web has been 5 dried down to 2-3 % H₂O or sometimes to even a smaller degree it is absolutely necessary to add considerable 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 IQ 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 homification of the fibre must be avoided as well as the excessive consumption of 25 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 still in the drying process and furthermore allows a subsequent correction of the moisture content of the 20 P^aP^er 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 elim25 inate 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 difficulties in the later converting process of the paper.

The investigations being performed on occasion of this 3θ invention have shown that the peaks and irregularities along 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 35 constantly. According to this invention the irregularities of the fibrous 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 mois4θ ture 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 45 described later on. Just so a plurality of partial elements of a spray device are adjusted, also in a manner, which will be described later on. By these procedures firstly the basis weight variations will be eliminated and secondly, by means of a more or less intensive moistening, the re50 maining variations of the moisture content will be equalized so that a paper of most equal basis weight and moisture content will be obtained finally. The invention extends to the application of the therein described procedure and to the performance of the equipment being 55 necessary for the execution of the procedure.

In order to illustrate the performance of the invention an example is represented. Fig. 1 shows a moisture profile of a paper web under different drying conditions. Fig. 2 illustrates in a total scheme the arrangement of 0Q 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 ₆₅ flow inlet. Fig. 5 shows the example of an adjusting device for the partial alteration of the effectiveness of a brush or spray damper for the moistening of the paper web.

The execution of the invention is described in the fol₇q lowing example:

The moisture meter 1 which traverses the web periodically is arranged at the end of the drying section. The

2,961,007 stant value and since the water pressure is constant in front of the needle valves 8 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 fibrous 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. This 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 15 order to obtain a self-acting control of the passage cross section of the fibrous material feed inlet the nut of the hand-wheel 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 of the lip 14 of 20 the fibrous material feed inlet.

In relation to every nozzle of the 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 connected by the common water pipe line.

Every variation in this pipe line, which is caused by the needle valve 8 thus effects at the same time a change of the moistening as well as a change of the position of the fibrous material feed inlet lip 14. Consequently, the partial variations of the basis weight and the uneven mois30 ture content of the web resulting therefrom will be elimi^; nated at the same time.

Indeed, it is possible to realize the one and the other regulating procedure, e.g. the control of the moistening and fibrous material feed inlet, either operating together 35 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 40 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 45 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 will—under the 50 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 55 the desired value, which has been adjusted at the regulator. This pressure 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 difference between the two moisture values 60 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 with an impinging plate the same 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 web being in this case also dependent on the 70 difference-value between moisture reading of the moisture meter and adjustment of the desired value at the regulator.

Since the two last-mentioned moistening procedures do not offer the exactness which is necessary for a useful moistening and the distribution of the water to single 75 sections of the web these procedures shall be mentioned 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 side to the driving side whilst the transport of the recording strip is stopped during the return movement. This is necessary in order to have the possibility to compare the recording diagrams right next to each other. Tne measuring 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 ₁₀example an electromotor 4, acts the arm 5 whicn influences by means of the groove, which is formed by the two control surfaces 6, via the roll 7 the needle valve 8.

• Imagine the arm 5 being pushed forward so far that the roll 7 is placed between the control surfaces 6 it becomes evident that the needle valve 8 will be opened more for the case in which the moisture meter finds 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 which belongs 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 fixed. The difference value between the moisture meter 1 and the “desired value adjustment 10 effects the regulating process 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 efficiency 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 the arm 5 and to turn the arm, which is fixed 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 diameter of the roll 7.

Arm 5 together with the control surfaces 6 can now occupy 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 meet 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 altered by the respective needle valve 8. Thereby it can be achieved that for every amount of water which is to be atomized an absolutely equal diffusion and a constant cone of dispersion can be guaranteed.

With the same arrangement it will be possible to control the fibrous, material feed inlet, too. Since the hydraulical resistance of the atomized nozzle is of a con2,961,007

K 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 to 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 web 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 notales, is installed—as shown in Fig. 2—within the drying section, and that at a place, where the paper web is not yet so far overdried that hornification 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 i of the following drying cylinders is reduced to the actual JI measure of the other parts of the cylinder surface.

The entire arrangements can remain the same as described.