US3040807A - Moisture balance correction system - Google Patents

Description

June 26, 1962 w. E. CHOPE MOISTURE BALANCE CORRECTION SYSTEM Filed Nov. 4, 1959 INVENTOR mwhnmsau ow wow now 0m ture across the width or profile of the paper. v

ence of these wet streaks imposes a further limitation on United States Patent ()flice 3,040,807 Patented June 26, 1962 3,040,807 MOISTURE BALANCE CORRECTION SYSTEM Wilbert E. Chope, Columbus, Ohio, assignor to Industrial Nucleonics Corporation, a corporation of Ohio Filed Nov. 4, 1959, Ser. No. 850,933 6 Claims. (Cl. 162-252) This invention relates to measuring and controlling system utilized in process manufacturing and particularly to method and means for correcting the moisture profile in the manufacture of fibrous materials.

In a typical industrial process, such as a paper making machine, the three essential steps are the preparation of the pulp material in a form which will permit the formation of a continuous sheet of material; the formation of the sheet, such as, on a screen or Wire; and drying the resulting sheet of fibrous material.

In the drying of the sheet formed a considerable volume of water is removed from the sheet by the action of gravity. This causes free water to pass through the supporting means used at the point of sheet formation. Water is next removed by the application of suction by means of vacuum pumps as the wet sheet'passes over a roll fitted with openings into which the aspirated water may pass. Absorbing and/ or pressing the moisture out is also commonly done by a press felt on the paper making machines. driving out of the remaining moisture by means of heat applied to the moving sheet.

The capacity of most paper making machines is limited by the ability of the dryer section to remove the required amount of water from the sheet. This has the effect of determining the maximum speed at which the paper making machine may be operated. If the machine is operated at speeds in excess of the time rate of moisture removal capacity of the dryer section to reduce the fin.- ished moisture content of the paper to its specification value, then the paper is finished at an excessive moisture content. Economic penalties result from the production of such material. Conversely, if the machine is operated at speeds less than the time rate of moisture removal capacity its inefiiciency is readily apparent.

A further limitation in the speed of paper making machines is the occurrence of wet streaks at locations across the width of the moving sheet of paper. These wet streaks occur because of an uneven distribution of mois-.

The presthe dryer section because of the need for the machine speed to be adjusted such that the, dryer section has enough capacity to dry the wettest region of the sheet. This mode of operation of the dryer section results in the majority of the dryer section having excess capacity beyond that needed to dry the greater portion of the entire width of the moving sheet, and only a small portion of the sheet is demanding the full capacity.

The present invention teaches the addition of another method of drying the sheet to those mentioned above. This added section is operative in combination with the dryer section of the paper machine in such a way that the capacity of the dryer section, and consequently the speed of the paper making process is matched for the moisture condition existing in the majority of the material produced. The drying means of the present invention is selectively applied at that portion of the width of the paper being produced which as a moisture content greater than the average moisture content acrossthe entire width of the sheet.

It is accordingly a primary object of the present invention to provide a new and improved method and means The final step in the drying process is the 2. of controlling'the moisture drying process in the formation of fibrous material.

It is another object of the present invention to control the moisture drying process in the formation of fibrous material that is most economical to the process.

It is a furtherobject of the present invention to provide method and means of controlling the moisture drying process in the formation of fibrous material that is simple in operation and readily adaptable to present day. processes with only a minimum of modification.

Other objects and features will become apparent to those skilled in the art from the following, detailed description of a typical embodiment of the present invention illustrated in the single FIGURE as being adapted to a paper making process.

Referring now to the figure, in the paper making process a sheet of material 10 emerges from a dryer section comprising the frames 15 and 1 6,-and the steam heated drums 17 and 18. The paper passes under a frame 14 mounting local heating devices 31a, 31b, 31c, 31d, and

' 31a, spaced laterally across the width of the sheet 10 emerging from the dryer section. The sheet further passesthrough a measuring apparatus 11 comprising moisture responsive elements 12 and 13. The measuring apparatus 11 is so disposed relative to the moving sheet of mate-. rial that it may be traversed laterally to obtain information on the relative moisture content at all points across, the Width of the sheet of moving material. -A number of devices are suitable for this detector. One of these is a beta radiation absorption gauging system. In this instance, the variations in indicating the mass per unit area across the width of the sheet of paper aregrossly interpreted to be the result of moisture content variations. Another means of performing this measurement is a dielectric measuring apparatus which is responsive to changes in the capacitance of the measured material as it is traversed across its Width. In this instance the variations in the resulting signal from the measuring device are again interpreted to result from variations in the moisture content at various points across the width of the sheet of material. This interpretation is based on the fact that variations in moisture content contribute of the order of 40 times as much variational signal to the detector output as would corresponding variations in the amount of pulp material in the sheet. Numerous other detecting devices could be adapted for this use; among them, those depending on infrared reflectance and absorptivity. It is to be emphasized here that the output of the moisture responsive device does not have to be of any particular accuracy with regard to absolute readings of the value of moisture existing at any one region of the sheet. Rather, all that. is required is that the detecting device be able to signal what regions of the sheet have more moisture content than others. Thus, only a relative signal is required and an absolute value is not required. However, a moisture gauge especially adaptable for use in a preferred embodiment is the two' radio frequency signal system shown in the copending applications of Allen R. Davidson, Serial No. 642,525, and Gordon William Walls, Serial No. 608,095. r

A readout of the indications of the moisture responsive detector is shown in the recorder apparatus 19 which contains the scale 20 on which the .width of the sheet of paper has been arbitrarily divided into the regions 20a, 20b, 20c, 20d, and 20s. The marking device 21 which may be the recording pen of a self-balancing XY potentiometer traces the indication of the profile data developed by the measuring device 11. The trace 22 is represented to occur at a later time than the trace 23. Traces 22 and 23 represent sequential recordings of the output of the moisture responsive detector in its sequenfore, to regions of the sheet a, 10b, 10c, 10d, and 10.

It should be observed that the region 2% of the profile trace 23 is seen to have a different value and greater value of moisture content thanthe average. Alternatively, the recording system illustrated in U.S. Patent No. 2,909,660 to Frank Alexander may be adapted to indicate moisture reading with profile position.

The output of the recorder 19 is fed to a computer 33 whereas in turn the output of the computer 33 is applied to the heater controller 35. This controller selectively actuates one or more of the auxiliary heating devices mounted on the frame 14, and shown as 31a, 31b, 31c, 31d, and 31a, mounted transversely to the process.

In operation the moisture responsive device- 11 gencrates profile information such as that'represented by trace 23. Assuming that the moisture content of region 101) of the sheet is greater than the average moisture content of the sheet, the computer 33 determines that the deviation from the average is of sufiicient degree and/or duration to require correctivelocalized heating. The signal from the computer 33 actuates heat lamp 311) through the heater controller 35 to apply the proper degree and duration of local heat to region 101) of the moving sheet of paper. In this instance 31b is ignited for a duration equal to the moisture deviation. The heating devices 31a-31e may be infrared lamps, dielectric heating devices, or any other device which allows heating to be applied selectively at particular points across the width of the paper making machine. Alternatively a lesser number of heating devices may be employed by movably mounting the same to permit their traversing the sheet to the area of greatest moisture. The heating lamps 31a-31n are preferably the high intensity, quick response infrared lamp manufactured by the Fostoria Corporation.

- The computer 33 may be'one conventionally available or may simply comprise circuitry capable of signal comparison and operative to produce a voltage for a duration dependent upon the degree of moisture deviation. Controller' 35 also is conventionally known and Would preferably be of the proportional type such as that disclosed and utilized in the U.S. Patent to Don E. Varner, No. 2,895,888.

The use of the above cited localized heating of regions across the profile of the moving sheet produces significantly economic benefits in the manufacture of the materials in which one of the operations required is the removal of moisture from the material while it is in a sheet form. Even though the B.t,u. cost of the local heating is higher than the B.t.u. cost of the dryer section, this increased cost is greatly ofiset by the increased machine-speed. 7

Although certain and specific illustrations are given, it

will be apparent to those skilled in the art that modifications may be had Without departing from thetrue spirit and scope of the invention.

I claim: 2 7 I l. The combination, with a manufacturing machine for continuously processing a laterally extended length of a fibrous material, and wherein said machine includes a material feed action, material forming section and a 4.- means for moisture gauging said material, means for mounting said gauging means on the processed material output side of said machine, traversing means associated with said mounting means for causing said gauging means to cyclically scan said processed material to and fro across said width thereof, computer means connected to said gauging-means for generating an error signal indicative of the deviation of said moisture condition from a desired value thereof at the traversing point of measurement, a

. said auxiliary drying means for connecting said generated error signalto each of said actuators in sequence to actuate an auxiliary drying means corresponding to that portion of the width having a moisture deviation and for a duration and intensity dependent on said moisture deviation.

2. A fibrous material manufacturing machine including 7 in sequential operation a material forming section, a sheet forming section, a moisture removal section, and an auxiliary drying section comprising a plurality of selective drying means positioned across thewidth of said sheet to affect the moisture content of a corresponding portion of said sheet, means for determining the moisture variations of said sheet after said sheet has left said drying section, and means; for actuating one of said selective drying means relative to the moisture variations in said selective area.

3. In a fibrous material manufacturing machine having a material forming section, a sheet forming section and a drying section, an auxiliary drying section comprising a plurality of selective drying means spaced across the width of said sheet, each of said selective means corresponding to a given area of said sheet; moisture determining means for determining the moisture deviation of each of said areas from that of a given standard, actuating means connected to said moisture determiningmeans for actuating one or more of said selective drying means upon the moisture deviation of a corresponding area of said sheet, said actuating means responsive to control said drying mems for a period and intensity equal to the degree of moisture deviation. p

4. The subcombination of claim 3 which further includes a computer connecting said gauging means to said ture determining means includes traversing means for cyclically scanning said sheet to and fro.

6. A paper making machine comprising a material forming section, a sheet forming section, a drying section, and a plurality of auxiliary drying means positioned across the width of said sheet at the output thereof, selective means for selectively controlling each of said auxiliary drying means in accordance with the profile moisture content of said sheet, and means responsive to the profile moisture content of said sheet to actuate said selective means.

drying-section, comprising a series of auxiliary drying means spaced across the width of said processed material, each of said means affectingthe moisture condition of said material at a portion of said width, said portion being substantially less than the total extent of said width,

Q References :Cited inthe file of this patent UNITEDSTATES PATENTS 2,479,031 Tait Aug. 16, 1949 2,797,171 Fralish June 25, 1957 2,922,475 Alexander Jan. 26, 1960 3,000,438 Alexander Sept. 19, 1961

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