Electrostatic method for treating material

Abstract

In a method for treating material that is disposed in an electrostatic field pattern to be acted upon by the electrostatic field pattern, the improvement of repetitively changing the electrostatic field pattern from a substantially uniform electrostatic field pattern to a substantially non-uniform electrostatic field pattern and then back to the substantially uniform electrostatic field pattern while the field pattern is acting on the material disposed therein, the material being a wet web-like fibrous material, a fluid, etc.

Description

This invention relates to an improved electrostatic method for treating material, such as for electrostatically removing retained liquid from web-like liquid bearing material of the liquid absorbing type.

It is well known from applicant's aforementioned U.S. Pat. No. 3,966,575 and its chain of related patent applications and issued patents that it is believed that liquid in liquid bearing material of the liquid absorbing type can be moved relative to that material when the liquid bearing material is passed through a plurality of non-uniform electrostatic fields with each field having the higher intensity portion thereof substantially oppositely located relative to the higher intensity portion of an adjacent non-uniform field so that the fields at least partially extend through the material to act on at least part of the retained liquid thereof to move at least part of the retained liquid relative to the material.

It is a feature of the aforementioned parent application, Ser. No. 695,068, to illustrate, describe and claim the above liquid moving feature in combination with a conventional method and apparatus of removing retained liquid from web-like liquid bearing material of the liquid absorbing type as the material is being substantially continuously moved therein to improve upon such conventional method and apparatus.

In particular, it is believed that the alternately arranged non-uniform electrostatic fields of this invention will move the moisture particles in the liquid bearing material in such a manner that the liquid particles will be arranged closely adjacent the outer surfaces of the liquid bearing material so that the subsequent engagement of those outer surfaces with the conventional liquid vaporizing equipment will cause a more rapid removal of such liquid particles as the same are concentrated adjacent the outer surfaces thereof rather than dispersed throughout the same as in the conventional methods and apparatus.

Such feature of concentrating the liquid particles adjacent the outer surfaces of the wet web of material is known as the "bonus effect" in the web drying art.

For example, see the December 1974 "Journal of the Technical Association of the Pulp and Paper Industry" volume 5, No. 12, at page 134 wherein an article entitled "An Updated Review of Dielectric Heating in the Paper, Pulp and Board Industry" by T. L. Wilson indicates that the dielectric heating of the liquid particles in a wet web of material causes the center particles to rapidly explode into steam and entrain the other liquid particles to move the same closer to the outer surfaces of the wet web of material so that such moved moisture particles will be more readily subsequently removed by conventional vaporizing equipment and thereby the dielectric heating operation produces the "bonus effect" in a manner similar to the feature of this invention as theorized above.

Accordingly, one embodiment of the invention in the aforementioned parent application, Ser. No. 695,068, provides means for creating a plurality of non-uniform electrostatic fields with each field having the higher intensity portion thereof substantially oppositely located relative to the higher intensity portion of an adjacent non-uniform field and means for passing a continuously moving web-like material through the fields so that the fields at least partially extend through the material to act on at least part of the retained liquid thereof to move at least part of the retained liquid relative to the material, such embodiment of that invention being utilized in a conventional method or apparatus that is utilized for removing retained liquid from web-like liquid bearing material of the liquid absorbing type as the material is being substantially continuously moved.

However, it is a feature of this invention to modify such embodiment to repetitively change the electrostatic field pattern thereof to act not only on wet fibrous material being passed through such changing electrostatic field pattern, but on any desired material, such as gas, liquid, etc., passed through such changing electrostatic fields.

In particular one embodiment of this invention provides a method for treating material that is disposed in an electrostatic field pattern to be acted upon by the electrostatic field pattern and having means for repetitively changing the electrostatic field pattern from a substantially uniform electrostatic field pattern to a substantially non-uniform electrostatic field pattern and then back to the substantially uniform electrostatic field pattern while the field pattern is acting on the material disposed therein, the material being a wet web-like fibrous material, a fluid, etc.

Therefore, it is an object of this invention to provide an improved electrostatic method for treating material, the method of this invention having one or more of the novel features of this invention as set forth above or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is a schematic view illustrating the improved method and apparatus of this invention.

FIG. 2 is an enlarged, fragmentary, cross-sectional view taken on line 2--2 of FIG. 1.

FIG. 3 is an enlarged, fragmentary, cross-sectional view taken on line 3--3 of FIG. 1.

FIG. 4 is a fragmentary view similar to FIG. 1 and illustrates another embodiment of the method and apparatus of this invention.

FIGS. 5 and 6 are respectively fragmentary views similar to FIG. 1 and illustrate other embodiments of the method and apparatus of this invention.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide means for removing liquid from wet fibrous material, it is to be understood that the various features of this invention may be utilized singly or in any combination thereof to remove liquid from and/or act on other types of material, such as to act on a gas, liquid, etc. to remove and/or separate particles etc. therefrom.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, the improved method and apparatus of this invention is generally indicated by the reference numeral 10 and comprises a conventional paper making apparatus wherein a wet fibrous sheet 11 is formed in a conventional web-forming section 12 commonly known as a wet forming section.

The wet fibrous web 11 emerges from the wet forming section 12 and is normally passed through a press section 13 which tends to mechanically squeeze as much moisture from the wet web 11 as possible without adversely crushing the same whereby the wet web 11 of material emerging from the press section 13 still retains a relatively large amount of liquid therein which must be subsequently removed.

For example, see FIG. 2 wherein the web of material 11 is schematically illustrated in cross-section as having a plurality of liquid particles 14 dispersed throughout the same between the top surface 15 and bottom surface 16 thereof.

Normally, the wet web of material 11 passing from the press section 13 is directed to a liquid vaporizing drying section 33 which can comprise a plurality of heated cylindrical drums or "cans" around part of the periphery of which the wet web of material 11 is directed to have the moisture particles 14 thereof evaporated through the heating thereof by such steam heated "cans". Also, such drying section 33 could comprise a hot air impingement drying section wherein heated air is impinged against the opposed surfaces 15 and 16 of the wet web of material 11 to tend to vaporize the moisture particles 14 therein through the heating thereof by the heated air.

In any event, it is believed, according to the teachings of this invention, that if the web web of material 11, between the press section 13 and the drying section 33, is passed through a plurality of alternately arranged non-uniform electrostatic fields such electrostatic field action will act on the moisture particles 14 in the wet web of material 11 to tend to move the same from the center area thereof to areas closely adjacent the outer surfaces 15 and 16 thereof as illustrated in FIG. 3 so that when the web of material 11 enters the drying section 33, the moisture particles 14 can more readily be evaporated from the web of material 11 whereby a "bonus effect" will be produced by the non-uniform electrostatic field action of this invention.

For example, the wet web of material 11 between the press section 13 and the conventional drying section 33 can be passed by guide rollers 17 and 18 against the outer peripheral portion 19 of a rotatable drum means 20 so that the web of material 11 will be carried by the drum 20 through an arcuate path as illustrated.

A plurality of pairs 21 of large 22 and small 23 electrodes are disposed in the arcuate arrangement illustrated in FIG. 1 so that an inner row 24 of alternating large and small electrodes 22 and 23 is disposed inside the non-conductive outer periphery 19 of the drum 20 laterally across the width of the web 11 being carried thereon and an outer row 25 of cooperating and alternating small and large electrodes 23 and 22 are disposed exterior to the peripheral surface 19 of the drum 20 laterally across the width of the web 11 in the arcuate arrangement illustrated so that each pair 21 of cooperating small and large electrodes 22 and 23 define a non-uniform electrostatic field 26 therebetween when the electrodes 22 and 23 of each pair are charged with opposite potentials or with a potential differential therebetween by one of the electrodes having a greater potential than the other electrode, such as by having the other electrode grounded or with a like but lesser charge thereon.

In any case, the electrodes in the outer row 25 have a different potential than the electrodes in the inner row 24 so that a plurality of alternating non-uniform electrostatic fields 26 are arranged in an arcuate path and extend through the material 11 as the same is moved by the rotating drum 20.

The operation of the method and apparatus 10 of this invention will now be described.

It is believed that as the wet web of material 11 moves in a clockwise direction from the guide roller 17 to the guide roller 18 on the outer periphery 19 of the drum 20, the action of the non-uniform electrostatic fields 26 causes the moisture particles 14 in the web of material 11 to be moved toward the higher intensity portions thereof which are disposed adjacent the smaller electrodes 23 for the reasons advanced in the aforementioned Patent No. 3,966,575 whereby the moisture particles 14 in the web 11 on the side 15 of the center line or at the center line thereof are driven toward the side 15 and the moisture particles 14 at and on the side 16 of the center line thereof are driven toward the side 16 thereof by the theory of dielectrophoresis.

Further, it is believed that as a moisture particle 14 in the web 11 is being repetitively moved through an intense portion of a non-uniform electrostatic field 26 and then through an untense portion of the next adjacent field 26, a pulsating pumping action is being imposed on such moisture particle 14 as it is rapidly being moved through all of the non-uniform fields 26 because the intense portion of a field 26 pulls or pushes the particle 14 outwardly toward one side of the web 11 with a greater force than the force of an untense portion of a field 26. Thus, by providing a large number of alternately arranged non-uniform fields 26 and with the normal speed of a paper making machine, such as 3,000 to 5,000 feet per minute, it can be seen that each liquid particle 14 will be subjected to a rapid outward pumping action by the fields 26 as the particle 14 moves through the circular array of fields 26 from the inlet guide roller 17 to the outlet guide roller 18.

However, as set forth in the aforementioned article, the wet web of material 11 normally has the outer layers of material thereof formed substantially denser and harder than the inner layers of material thereof so that the moved moisture particles 14 would tend to be trapped in the outer denser layers. Thus, the force of the electrostatic fields 26 may not be sufficient to actually remove the moisture particles 14 from the wet web of material 11 but it is believed that the force will cause the same to move to and gather near the outer denser surfaces 15 and 16 thereof as set forth in the aforementioned article wherein the liquid particles are driven outwardly by exploding steam within the center of the wet web of material, the steam being caused by dielectric heating of the material in contrast to this invention which causes the moisture particles to be moved solely by an electrostatic non-uniform field action.

Thus, it is believed that when the wet web of material 11 leaves the drum 20, the same will have the moisture particles 14 arranged in the manner illustrated in FIG. 3 so that the same will be more readily evaporated when the same reaches the drying section 33 than if the drum 20 and non-uniform field arrangement 26 of this invention were not utilized whereby a "bonus effect" is produced by this invention to improve upon the conventional drying methods and apparatus.

Also, it is believed that since no actual current flow occurs between the electrodes 22 and 23 in each cooperating pair 21 thereof as each non-uniform field 26 is produced by a capacitance arrangement, this "bonus effect" of this invention is believed to be most efficient as the only work required is the movement of the web 11 through the fields 26 in much the same manner that a wire is moved in a permanent magnet field to create a current flow in the wire.

While the drum 20 of this invention is illustrated and described as being located between the sections 13 and 33, it is to be understood that the same could be located anywhere in the line, as desired. For example, the drum 20 could be located in the middle of the "can" drying section 33. Also, the outer peripheral part 19 of the drum 20 could be heated to assist the electrostatic field forces in moving the liquid particles 14 relative to the material 11. For example, steam could be injected into the drum 20 to heat its outer peripheral part 19, if desired, whereby such heated drum 20 could be considered one of the "cans" of the drying section 33.

In addition, it is believed that the liquid particles 14 can be water or any other suitable conductive or non-conductive liquid or combination of liquids, as desired. Also, the non-uniform fields 26 can be created by suitably interconnecting the electrodes 23 and/or 22 to a direct current source or alternating current source of any suitable voltage.

While an arcuate path of non-uniform fields 26 and a cylindrical carrier drum 20 therefor has been illustrated and described, it is to be understood that the nonuniform field path could be straight or any other desired configuration with the web 11 being carried on any suitable carrier or being passed through such non-uniform field path without a carrier, as desired. Further, while only one drum 20 is illustrated, a plurality of drums 20 could be utilized with such drums 20 being in series or alternating with nonelectrostatic "cans" as desired.

Also, it is to be understood that while the rows 24 and 25 of electrodes 22 and 23 are illustrated in FIG. 1 as being spaced from the opposed sides of the web 11 a considerable distance, one or both of the rows 24 and 25 of electrodes 22 and 23 could be disposed closer or farther away from the web 11 than as illustrated as desired. Further, the length of each electrode 22 or 23 could be shorter or longer than as illustrated. In fact, the smaller electrodes 23 could each be a fine wire disposed laterally to moving web 11. Thus, it can be seen that the non-uniform fields 26 could be uniform in the appearance thereof from inlet roller 17 to the outlet roller 18 or could be any arrangement of large, small etc. as they extend around the periphery of the drum 20 with some or all of the electrodes 22 and 23 being spaced from the web 11 different distances, as desired.

Thus, it can be seen that the rows 24 and 25 of electrodes 22 and 23, in effect, define a passage means having an inlet adjacent the guide roller 17 and an outlet adjacent the guide roller 18 so that the web 11 is passed through the inlet of such passage defining means to have the electrostatic action of the alternating non-uniform electrostatic fields act thereon whereby it is believed that by the time the web 11 reaches the outlet at least some of the liquid particles 14 will be removed from the web 11 and/or at least some of the liquid particles 14 will be moved relative to the web as illustrated in FIG. 3 to provide a "bonus effect" which will improve upon the efficiency of the conventional drying section 33 in removing the liquid 14 from the material 11.

While the method and apparatus 10 has been previously described as operating with the inner row 24 of large and small electrodes 22 and 23 being stationary during the rotation of the drum 20, it is to be understood that the inner row 24 of electrodes 22 and 23 could rotate in unison with the drum 20 by forming part of the outer periphery 19 thereof or rotate independently of the movement of the drum 20 in either a clockwise or counterclockwise direction as desired by being carried on a drum separate from the drum 20.

In this manner, the electrostatic field pattern being created between the outer stationary row 25 of electrodes 22 and 23 and the moving inner row 24 of electrodes 22 and 23 would repetitively change from the non-uniform configurations 26 illustrated in FIG. 1 to the uniform field configurations 26' of FIG. 5 and then back to the non-uniform field arrangements 26 of FIG. 1 so that there would constantly be a nonuniform field arrangement 26 of FIG. 1 changing infinitely to the uniform field arrangement 26' of FIG. 5 and then changing infinitely back to the non-uniform field arrangement 26 of FIG. 1.

It might be found that the changing electrostatic field pattern between the non-uniform field arrangement 26 of FIG. 1 and the uniform field arrangement 26' of FIG. 5 has a greater effect for moving the moisture particles 14 toward the outer surfaces 15 and 16 of the web fibrous material 11 than just when the constant action of the nonuniform fields 26 is imposed thereon as previously described in connection with the operation of FIG. 1.

While the arrangement of FIG. 5 shows the electrostatic fields being formed uniform through the movement of the inner row 24 of electrodes 22 and 23 relative to the outer row 25 of electrodes 22 and 23, it is to be understood that the outer row 25 of electrodes 22 and 23 could be moved relative to the inner row 24, whether or not the inner row 24 is also movable or stationary as desired, whereby the resulting effect would still be a repetitively changing electrostatic field pattern between non-uniform fields and uniform fields for the reasons previously set forth.

While the method and apparatus 10 of this invention has been previously described as having all of the electrodes 22 and 23 in the inner row 24 provided with one like charge thereon and all of the electrodes 22 and 23 in the outer row 25 being provided with a like charge opposite to the charge on the inner row 24, it is to be understood that the nonuniform fields 26 could be provided by having all of the small electrodes 23 in both of the rows 24 and 25 of a like charge and all of the large electrodes 22 in the inner and outer rows 24 and 25 with a like and opposite charge as illustrated in FIG. 4. With such an arrangement, it might only perhaps be necessary to provide electrically insulating barriers 27 between adjacent electrodes 22 and 23 in each row 24 and 25 as illustrated in FIG. 4 to prevent adverse field action between adjacent electrodes 22 and 23 in the same row 24 or 25 thereof.

In this manner, all of the non-uniform fields 26 will have the intense portions thereof adjacent the smaller electrodes 23 of a like charge so that if the moisture particles 14 in the web of wet fibrous material 11 are more readily attracted toward the negative charges as illustrated in FIG. 4, then the movement of the moisture particles 14 toward the outer surfaces 15 and 16 of the web of material 11 would be greater by having the small electrodes 23 in both rows 24 and 25 provided with the desired negative charge thereon as illustrated rather than having the small electrodes 23 in either row 24 or 25 of FIG. 1 with positive charges thereon.

Of course, the arrangement of FIG. 4 could have the electrodes 22 and 23 being charged by alternating current rather than direct current so that all of the small electrodes 22 would first have a positive charge thereon and then have a negative charge thereon in a repetitive manner as provided by alternating current.

In fact, it may be found that when utilizing alternating current for any of the electrode arrangements of this invention, the same could be alternated with a high enough frequency that would place the same into a dielectric heating range for the dual benefit of attracting the particles 14 outwardly by electrostatic field forces as well as causing the particles 14 to be blown outwardly by the exploding steam created in the center section of the wet web of material 11 through the dielectric heating of the center moisture particles 14 thereof as fully disclosed in the aforementioned U.S. Pat. No. 3,966,575.

Also, it is to be understood that uniform electrostatic fields 26' of any desired length or combination of lengths could be disposed intermediate the non-uniform electrostatic fields 26 as illustrated in FIG. 6 to produce a desired pulling or pushing effect on the particles 14 in the web 11 as the same is passed therethrough in a manner similar to the embodiment of FIG. 5 as previously described.

While it is believed that the thickness of the material 11 could range anywhere between relatively thick ceiling tile sheets of fibrous material 11 down to paper thickness, it is to be understood that the web fibrous material 11 could be thicker than ceiling tile or thinner than paper, as desired.

Also, while the various electrostatic arrangements have been previously described as operating on wet web-like fibrous material, it is to be understood that the same could operate on other material, such as fluid, etc., as desired.

Accordingly, it can be seen that this invention provides an improved method for removing liquid from liquid bearing material.

While the methods of this invention now preferred have been described and illustrated as required by the Patent Statute, it is to be understood that other method steps can be utilized and still fall within the scope of the appended claims.

Claims

1. A method of treating liquid bearing material comprising the steps of creating a plurality of non-uniform electrostatic fields in an arrangement so that each field has the higher intensity portion thereof substantially oppositely located relative to the higher intensity portion of an adjacent non-uniform field, disposing said material in said arrangement so that said non-uniform fields at least partially extend through said material to act on at least part of the liquid thereof to move at least part of said liquid relative to said material, and repetitively changing said fields from said non-uniform arrangement thereof to substantially all be uniform and then back to said non-uniform arrangement thereof to tend to pulse said movement of said liquid relative to said material while said material is disposed in said arrangement.

2. A method as set forth in claim 1 and including the step of causing relative movement of said material and said arrangement of electrostatic fields.

3. A method as set forth in claim 1 wherein said step of creating said electrostatic fields comprises the step of providing two spaced apart rows of electrodes with each row having a repeating pattern of a large electrode and a small electrode adjacent thereto whereby each said nonuniform electrostatic field is defined between a small electrode of one row and a cooperating large electrode of the other row.

4. A method as set forth in claim 3 wherein said step of disposing said material comprises the step of disposing said material between said rows of electrodes.

5. A method as set forth in claim 3 wherein said step of repetitively changing said fields comprises the step of causing relative movement between said rows of electrodes so that said small and large electrodes of one row will tend to cooperate with said small and large electrodes of the other row and thereby produce said uniform electrostatic fields therebetween.

6. A method as set forth in claim 1 wherein said step of repetitively changing said fields causes said liquid in said material to be dielectrically heated.

7. A method as set forth in claim 1 wherein said steps of disposing said material and changing said fields to cause said fields to move at least part of said retained liquid relative to said material causes part of said moved liquid to move toward one side of said material and part of said moved liquid to substantially simultaneously move toward the other side of said material whereby said moved liquid provides a "bonus effect" for said material.

8. A method of treating liquid bearing material comprising the steps of providing two spaced apart rows of electrodes with each row having a repeating pattern of a large electrode and a small electrode adjacent thereto, disposing said material between said rows, charging at least some of said electrodes so that electrostatic fields will be created between cooperating pairs of electrodes with each pair comprising an electrode from one row and an electrode from the other row and will have its field extend through said material if disposed therein, and causing relative movement between said rows of electrodes so that each field repetitively changes between a non-uniform electrostatic field caused by a pair of cooperating large and small electrodes and a uniform electrostatic field caused by a pair of cooperating large electrodes or small electrodes and will tend to move at least part of the liquid in the material disposed in that field relative to said material.

9. A method as set forth in claim 8 and including the step of causing relative movement between said material and said rows of electrodes so that said material is, in effect, passed through the space between said rows of electrodes.

10. A method as set forth in claim 9 and including the step of moving said material and one of said rows of electrodes together in one direction relative to the other row of electrodes to provide said step of causing relative movement between said rows of electrodes as well as said step of causing relative movement between said material and said rows of electrodes.

11. A method as set forth in claim 10 and including the step of carrying said material on the outer periphery of a rotatable drum that has said outer periphery thereof rotating relative to said other row of electrodes, and carrying said one row of electrodes on said drum and inboard of said outer periphery thereof.

12. A method as set forth in claim 9 wherein said step of causing relative movement between said material and said rows of electrodes comprises the step of moving said material in one direction relative to one of said rows of electrodes, said step of causing relative movement between said rows of electrodes comprising the step of moving the other row of electrodes relative to said one row of electrodes in a direction opposite to said one direction of movement of said material.

13. A method as set forth in claim 12 and including the step of carrying said material on the outer periphery of a rotatable drum that rotates said outer periphery thereof relative to said one row of electrodes in said one direction, said step of moving said other row of electrodes comprising the step of rotating said other row of electrodes inside said drum and inboard of said outer periphery thereof in said opposite direction to the direction of rotation of said drum.

14. A method as set forth in claim 8 wherein said step of causing relative movement to cause said fields to move at least part of said retained liquid relative to said material causes part of said moved liquid to move toward one side of said material and part of said moved liquid to substantially simultaneously move toward the other side of said material whereby said moved liquid provides a "bonus effect" for said material.

15. A method of treating liquid bearing material comprising the steps of creating an electrostatic field pattern that comprises a plurality of electrostatic fields that are serially arranged in a repeating serial pattern of a non-uniform field then a uniform field with said nonuniform fields each having the higher intensity portion thereof substantially oppositely located relative to the higher intensity portion of an adjacent non-uniform field, and causing relative movement between said material and said electrostatic field pattern so that said fields extend at least partially through said material to act on at least part of said liquid thereof in such a manner that said nonuniform fields move at least part of said liquid relative to said material and said uniform fields tend to cause a pause in said movement of said liquid relative to said material to thereby tend to pulse said movement of said liquid relative to said material.

16. A method as set forth in claim 15 wherein said step of creating said electrostatic field pattern comprises the step of creating said fields so that the same define an arcuate path through which said material must, in effect, be passed by said step of causing relative movement between said material and said electrostatic field pattern.

17. A method as set forth in claim 15 wherein said step of causing relative movement to cause said fields to move at least part of said retained liquid relative to said material causes part of said moved liquid to move toward one side of said material and part of said moved liquid to substantially simultaneously move toward the other side of said material whereby said moved liquid provides a "bonus effect" for said material.