System for making a non-woven sheet by creating an electrostatic field action

Abstract

A method and apparatus for making a non-woven sheet by providing a slurry of liquid and fibers and forming the slurry into a sheet-like form by flowing said slurry against and between two spaced apart surfaces. An electrostatic field action is provided that acts on the sheet-like form between said two surfaces and causes at least part of the fibers to be arranged into a sheet means adjacent one of the non-conductive surfaces and at least part of the liquid to be arranged adjacent the other surface. The other surface is pervious and the electrostatic field action causes the liquid to be drawn into the pervious surface at a controlled rate. The one surface has needle-like projections projecting at least partially into the sheet-like form to assist the electrostatic field action in forming the sheet means adjacent that one surface.

Description

This invention relates to an improved method and apparatus for making a non-woven sheet and the like.

It is now well known from the U.S. Pat. to Stiles, No. 3,705,847, that a slurry of fluid and papermaking fibers can be passed between parallel adjacent runs of two continuous and looped conductive belt means which are charged to provide a potential differential therebetween and thereby cause the fibers in the slurry to form into a nonpatterned, non-woven fiber mat on one of the belt means by an electrophoretic action while liquid is driven toward the other belt means by electro-osmosis so that the thus formed fiber mat can be transferred from its respective belt means to be further dried to form a dried sheet of paper or the like.

It is well known from the U.S. Pat. to Kalwaites, No. 2,862,251, that a slurry of fluid and natural or synthetic fibers can be formed into a continuous sheet in a conventional paper-making apparatus and before the resulting nonpatterned fiber mat has been dried, jets of liquid can be forced through the fiber mat in combination with unique forming structure to cause the fibers in the fiber mat to be rearranged into a predetermined pattern comprising spaced interconnected packed fibrous portions with less dense or apertured portions therebetween whereby a patterned non-woven sheet is subsequently provided when the rearranged fiber mat is subsequently dried.

It is suggested in the U.S. Pat. to Candor et al., No. 3,757,426, and the various related U.S. patents referred to therein, that a slurry of fluid and paper-making fibers can be formed into a fibrous sheet by utilizing electrostatic means to remove liquid from such slurry during a paper-making operation or the like.

It is a feature of this invention to provide means for making a patterned non-woven sheet similar to the patterned sheets described in the aforementioned patent to Kalwaites by utilizing modified means of the aforementioned U.S. patents to Candor et al and Stiles.

In particular, one embodiment of this invention provides a method and apparatus for making a patterned non-woven sheet by providing a slurry of fluid and fibers and forming that slurry into a sheet-like form. An electrostatic field action is created to act on such sheet-like form and cause the fibers thereof to be arranged into a predetermined pattern whereby a patterned non-woven sheet is provided.

It is another feature of this invention to provide an improved apparatus and method for making a non-woven sheet, whether or not such non-woven sheet is a patterned non-woven sheet or an unpatterned non-woven sheet, by providing improved means of the aforementioned Candor et al and Stiles arrangements.

In particular, one embodiment of this invention provides a method and apparatus for making a non-woven sheet from a slurry of fluid and fibers by passing a sheet-like form of such slurry between insulating faces of a pair of spaced apart-electrode means that provide an electrostatic field action therebetween that acts on the sheet-like form to assist in the making of the non-woven sheet.

Another embodiment of this invention provides a method and apparatus for making a non-woven sheet from a slurry of liquid and fibers by passing a sheet-like form of said slurry between two spaced apart surfaces while creating an electrostatic field action that acts on the sheet-like form between the two surfaces and causes at least part of the fibers to be arranged into a sheet adjacent one of the surfaces and at least part of the liquid to be arranged adjacent the other of the surfaces. Such embodiment of this invention can have means for causing at least part of the liquid to be drawn through the other surface at a controlled rate. Alternately or in addition thereto, such embodiment of this invention can be provided with needle-like projections on the one surface to project at least partially into the sheet-like form disposed between the surfaces and assist the electrostatic field action in forming the sheet adjacent the one surface.

Accordingly, it is an object of this invention to provide an improved method of making a non-woven sheet or the like, the method of this invention having one or more of the novel features set forth above or hereinafter shown or described.

Another object of this invention is to provide an improved apparatus for making a non-woven sheet or the like, the apparatus of this invention having one or more of the novel features 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 fragmentary, perspective view illustrating a patterned non-woven sheet that is intended to be made by the method and apparatus of this invention.

FIG. 2 is a schematic view illustrating the improved method and apparatus of this invention believed to be adapted to make the patterned non-woven sheet of FIG. 1 or the like.

FIG. 3 is an enlarged, fragmentary, cross-sectional view taken on line 3--3 of FIG. 2 and illustrates the structure of the upper belt means of the apparatus of FIG. 2, FIG. 3 being turned 180.degree. from the position taken on line 3--3 of FIG. 2.

FIG. 4 is a fragmentary, perspective view illustrating the conductive electrode means of the belt means of FIG. 3.

FIG. 5 is an enlarged, fragmentary, cross-sectional view taken on line 5--5 of FIG. 2 and illustrates a lower belt means of the apparatus of FIG. 2, FIG. 5 being turned 180.degree. from the position taken on line 5--5 of FIG. 2.

FIG. 6 is an enlarged, fragmentary, cross-sectional view taken on line 6--6 of FIG. 2 and illustrates how it is believed that the patterned non-woven sheet can be formed between the adjacent runs of the belt means of FIGS. 3 and 5.

FIG. 7 is an enlarged, fragmentary, cross-sectional view taken on line 7--7 of FIG. 2 and illustrates another lower belt means of the apparatus of FIG. 2, FIGS. 3, 5, and 7 each being turned 180.degree. from the position taken on its respective line of FIG. 2.

FIG. 8 is a fragmentary, perspective view illustrating the conductive member or electrode means of the belt means of FIG. 7.

FIG. 9 is an enlarged, fragmentary, cross-sectional view taken on line 9--9 of FIG. 2 and illustrates how it is believed that the formed non-woven sheet of this invention will pass between the upper belt means of FIG. 3 and the lower belt means of FIG. 7.

FIG. 10 is a fragmentary view similar to FIG. 2 and schematically illustrates another improved method and apparatus of this invention believed to be adapted to make the patterned non-woven sheet of FIG. 1 or the like.

FIG. 11 is an enlarged, fragmentary, cross-sectional view taken on line 11--11 of FIG. 10 and illustrates how it is believed that the patterned non-woven sheet can be formed between the adjacent runs of the belt means of FIG. 10.

FIG. 12 is a view similar to FIG. 10 and schematically illustrates another improved method and apparatus of this invention believed to be adapted to make the patterned non-woven sheet of FIG. 1 or the like.

FIG. 13 is an enlarged, fragmentary, cross-sectional view taken on line 13--13 of FIG. 12 and illustrates how it is believed that the patterned non-woven sheet can be formed between the adjacent runs of the belt means of FIG. 12.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide a non-woven sheet, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide other fibrous structures or the like as desired.

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, a patterned non-woven structure is generally indicated by the reference numeral 10 and can comprise patterned areas 11 of interconnected bundles of fibers surrounding other patterned areas 12, the patterned areas 12 can either by somewhat uniformly arranged apertures passing through the sheet 10 or be substantially uniformly arranged areas of fibers that are less dense than the density of the fibers in the other interconnected patterned areas 11.

As previously stated, the U.S. Pat. to Kalwaites, No. 2,862,251, fully discloses how such patterned sheet means 10 can be formed with the more dense areas 11 and the less dense areas 12 being arranged in various predetermined patterns by forcing jets of fluid through appropriately shaped apertured sheets and then through a non-patterned fiber mat to cause a rearranging of the fibers in such mat to provide the patterned arrangement of more dense areas 11 and less dense areas 12 whereby the resulting patterned sheet has the characteristic feel, hand and drape of conventional textile fabrics for similar uses.

The method and apparatus of this invention that is intended to form the non-woven sheet 10 of FIG. 1 is generally indicated by the reference numeral 14 in FIG. 2 and comprises an upper looped continuous belt means 15 passing around rollers 16 and 17 to define an upper run 18 and a lower run 19 thereof.

Another looped continuous belt means 20 of this invention is looped around rollers 21 and 22 to define an upper run 23 and a lower run 24 thereof whereby the upper run 23 of the lower belt 20 is disposed adjacent, but spaced from the lower run 19 of the upper belt means 15 to run substantially parallel therewith and be maintained uniformly spaced therefrom and have the side edges thereof sealed in the same manner as similar belt means in the aforementioned U.S. Pat. to Stiles, No. 3,705,847.

A slurry of the desired fluid and fibers, such as a liquid and paper making fibers, can be fed from a supply means 25 through a trough 26 to be fed in a continuous or intermitten sheet-like form between the adjacent runs 19 and 23 of the belt means 15 and 20 with such sheet-like form of slurry being somewhat uniformly provided by having the trough 26 vibrated in a suitable manner as provided in the aforementioned patent to Stiles.

The upper belt means 15 of this invention can be formed from flexible electrically insulating material 27, such as plastic material, having a flexible conductive sheet or electrode 28 embedded therein and being formed into a desired pattern such as by having a plurality of apertures 29 passing completely therethrough in a patterned arrangement as illustrated in FIG. 4 for a purpose hereinafter described.

The conductive sheet 28 of the belt means 15 is thus electrically insulated from the opposed faces 30 and 31 thereof and can be appropriately charged at the side edges of the belt means 15 in any suitable manner, such side edge charging of the belt means 15 being provided by the lead means 32 schematically illustrated in FIG. 6 and charging the conductive sheet 28 with a positive charge for a purpose hereinafter described.

While one form of a patterned conductive sheet 28 for the belt means 15 is illustrated in FIG. 4, as well as in FIGS. 11 and 13, it is to be understood that other forms of patterned conductive sheets can be utilized in any of the embodiments of this invention to provide a patterned non-woven sheet in the manner hereinafter described. For example, such patterned conductive sheet can actually comprise a wire screen, grill, etc., as the particular shape of the patterned areas 11 and 12 of the non-woven sheet 10 do not form the novel features of this invention as one of the novel features of this invention is to provide a non-woven sheet with any desired patterned areas.

The lower belt means 20 of this invention is best illustrated in FIG. 5 and also comprises a flexible sheet of electrically insulating material 33 also having a conductive sheet or electrode 34 embedded therein so as to be electrically insulated from opposed faces 35 and 36 of the belt means 20 while being adapted to be provided with a charge at the side edges thereof as illustrated schematically in FIG. 6 wherein a lead means 37 is illustrated as charging the conductive sheet 34 with a negative charge for a purpose hereinafter described.

While the conductive sheet 34 of the lower belt means 20 is illustrated as being continuous throughout and non-patterned, as well as in FIGS. 11 and 13, it is to be understood that the conductive sheet 34 could be also patterned in the same manner or in any desired different manner than the conductive sheet 28 of the upper belt means 15 in order to produce a desired electrostatic field action therewith which will produce a patterned non-woven sheet of the desired pattern as hereinafter described.

In any event, it can be seen that when the upper belt 15 is driven in a counterclockwise direction and the lower belt 20 is driven in a clockwise direction so that the adjacent runs 19 and 23 thereof continuously move from left to right in FIG. 2 at substantially the same speed, the slurry of fluid and fibers being fed from the supply means 25 through the trough 26 to the adjacent runs 19 and 23 of the belts 15 and 20 enters the same in a sheet-like form in a continuous manner and it is believed that the electrostatic field generated between the oppositely charged conductive sheets 28 and 34 of the belt means 15 and 20 will cause the fibers in the slurry between the runs 19 and 23 of the belt means 15 and 20 to form into a patterned non-woven mat against the surface 30 of the upper belt means 15 while the liquid in the slurry will be driven downwardly toward the surface 35 of the lower belt means 20 by the combined electrophoretic and electro-osmotic action of the electrostatic field on the slurry between the oppositely charged conductive sheets 28 and 34 which causes the fibers to move upwardly and the liquid to move downwardly as fully described in the aforementioned U.S. patent to Stiles.

However, according to the teachings of this invention, no electrical current flow takes place between the conductive layers 28 and 34 of the belt means 15 and 20 as the same are respectively insulated from the slurry disposed therebetween and it is believed that the electrostatic field action still functions in the same manner as in the patent to Stiles to drive the fibers upwardly and the liquid downwardly, so that a fiber mat is formed against the lower surface 30 of the lower run 19 of the upper belt means 15.

However, because the conductive sheet 28 of the upper belt means 15 of this invention is formed in a predetermined pattern, it is believed that such patterned conductive sheet 28 will cooperate with the lower conductive sheet 34 of the lower belt means 23 to create a plurality of non-uniform electrostatic fields that are generally indicated by the reference numeral 38 in FIG. 6 to cause the fibers to be formed against the surface 30 of the upper belt means 15 in a patterned arrangement of more dense interconnected fiber bundles 11 adjacent the non-perforated portions of the conductive sheet 28 while the fibers of the slurry will form adjacent the perforated parts 29 of the conductor sheet 28 with a pattern either of areas 12 of no fibers or of fibers less dense than the fibers in its interconnected areas 11 since it is well known that the more intense portion of a non-uniform field is stronger than a less intense portion of the non-uniform field so that the fibers will tend to form into the more dense bundles 11 adjacent the more intense portions of the fields 38 which are adjacent the unperforated parts of the conductive sheet 28 as illustrated in FIG. 6.

It is also believed that the liquid in the slurry between the runs 19 and 28 of the belts 15 and 20 will be driven downwardly even though it is toward the less intense portions of the non-uniform fields 38 because of the attraction of liquid for a negative charge which is on the conductive sheet 34. Also, the paper-making fibers have a tendency to be negatively charged and therefore tend to normally move toward the positively charged upper conductive sheet 28.

However, it is believed that there are times when there will be neutral fiber particles and the like in the slurry whereby the non-uniform fields will move such neutral particles toward the upper belt 15 through the action of the more intense parts of the non-uniform fields 38 tending to move neutral particles upwardly through the action of dieelectrophoresis whereby it is believed that all of the particles and fibers in the slurry will be utilized in forming the patterned mat against the belt 15.

Of course, if the lower belt means 20 has its conductive sheet 34 also provided with a pattern of conductive parts and non-conductive parts in a like manner or a different manner than the upper patterned conductive sheet 28, it is believed that the fibers will merely move upwardly where field actions are provided between the conductive parts of the upper and lower sheets 28 and 34, whether or not such fields are non-uniform or uniform, and will not move to any great extent into areas where no field action is taking place therebetween whereby it is believed that the resulting fiber mat against the upper belt 15 can be provided with the desired pattern through the patterned arrangement of either one or both of the upper and lower electrode means 28 and 34.

Therefore, it is believed that by the time the fiber mat passes beyond the upper run 23 of the lower belt 20 in the apparatus 14 illustrated in FIG. 2, the same has been formed into a sufficiently self-adhering patterned non-woven sheet form that is indicated by the reference numeral 39 in FIG. 2 to be further dried in its fiber arranged form in any suitable manner, the liquid from the slurry that has been removed from the fiber mat 39 by the electro-osmotic action of the fields 38 will flow off of the upper run 23 of the lower belt 20 as the same passes around the right-hand roller 22 to be received in a suitable reservoir 40 in the manner fully described in the aforementioned U.S. patent to Stiles, with such liquid being relatively free of fibers, etc., to be reused in processing more fibers for forming the slurry for the source 25.

Thus, the patterned non-woven mat 39 as it leaves the lower belt means 20 can be subsequently treated and dried in any desired manner, such as the manners set forth in the aforementioned U.S. patents to Kalwaites, Stiles and Candor et al.

However, if desired, the patterned non-woven sheet 39 can have at least some of the remaining liquid therein removed by another belt means of this invention that is generally indicated by the reference numeral 41 in FIGS. 2 and 7 and cooperates with the upper belt means 14 in a manner hereinafter described.

The continuous belt means 41 of this invention is looped around rollers 42 and 43 so as to provide an upper run 44 and a lower run 45 with the upper run 44 being disposed substantially parallel to but spaced from the lower run 19 of the upper belt 14 so that when the lower belt means 41 is driven in a clockwise direction in FIG. 2 so as to have the upper run 44 running at substantially the same speed as the lower run 19 of the upper belt 14, the fiber mat 39 leaving the other lower belt means 20 will enter between the adjacent runs 44 and 19 of the belt means 41 and 15 to be carried from left to right therewith and have at least some of the liquid thereof removed by an electro-osmotic action as hereinafter described.

The belt means 41 is best illustrated in FIG. 7 and comprises a layer 46 of felt or other porous absorbing material attached to a flexible electrically insulating sheet 47 having a conductive sheet or electrode 48 embedded therein whereby the conductive sheet 48 is electrically insulated by the sheet 47 from the opposed faces 49 and 50 of the belt means 41 as well as from the felt layer 46.

The electrode 48 can take any desired configuration and in the embodiment of this invention illustrated in the drawings, the conductive sheet 48 comprises a continuous conductive sheet having a plurality of conductive points 51 projecting upwardly therefrom toward the felt layer 46 with the points 51 being disposed in any desired pattern that will be cooperable with the unperforated portion of the conductive sheet 28 of the upper belt 15 to provide a plurality of non-uniform electrostatic fields that are generally indicated by the reference numeral 52 of FIG. 9 when the conductive sheet 48 is charged with a negative charge by a lead means 53 that is schematically illustrated in FIG. 9 so that the more intense portions of the non-uniform fields 52 will be directed downwardly into the felt layer 46 of the belt means 41 and thereby drive at least some of the retained moisture in the fibrous mat 39 downwardly into the belt layer 46 to be carried away by the felt layer 46 in the manner set forth in the aforementioned U.S. patents to Stiles and Candor et al.

The retained moisture that is now driven into the felt layer 46 of the belt 41 can be subsequently removed therefrom by having the lower run 45 of the belt 41 pass over a suction box means 54, FIG. 2, or any other suitable liquid-removing means.

The pattern of the points 51 of the conductive sheet 48 of the belt 41 can be so arranged relative to the unperforated portions of the conductive sheet 28 of the upper belt 15 that when the mat 39 passes between the adjacent runs 44 and 19 thereof in the manner illustrated in FIG. 9, a plurality of non-uniform fields will be extended through the more dense portions 11 of the mat 39 than the less dense portions 12 thereof for believed to be a better moisture removal operation.

Therefore, it can be seen that the method and apparatus 14 of this invention is readily adapted to take a slurry of fluid and fibers in sheet-like form and through the cooperation of the conductive layers 28 and 34 of the adjacent runs 19 and 23 of the belt means 15 and 20 to arrange the fibers into a predetermined pattern by an electrophoretic action while removing some of the liquid therefrom by an electro-osmotic action so that a patterned fibrous mat 39 will be formed therefrom which can further have the retained moisture therein removed electro-osmotically by passing through the electrostatic field means 52 created between the conductive sheet 28 of the lower run 19 of the upper belt 15 and the conductive sheet 48 of the upper run 44 of the lower belt means 41 so that a more dried patterned non-woven mat 39 can be removed from the right-hand end of the belt means 15 by suitable take-off belt means 55 in the same manner as set forth in the aforementioned U.S. patent to Stiles for further treating and/or drying of the mat 39 by other electro-osmotic means or conventional drying means, as desired.

While the non-uniform fields 38 being provided between the belt means 15 and 20 of this invention are illustrated as each having its more intense portion directed upwardly, it is to be understood that the conductive layers 28 and 34 could be so constructed and arranged that the more intense portions could point downwardly or could be in any desired pattern of pointing upwardly and downwardly for the desired purposes. Likewise, the electrostatic fields 52 between the belt means 15 and 41 of this invention could through the proper arrangement of the conductive sheets 28 and 48 be provided with the more intense portions thereof pointing upwardly rather than downwardly as illustrated or any combination of patterns that point up and down for the desired purpose.

Further, while the belt means 15, 20 and 41 have been illustrated as having the conductive parts forming a part thereof, it is to be understood that stationary electrodes could be disposed inside the runs of the respective belt means 15, 20 and 41 to create a field action across the space defined between the cooperating runs thereof as fully provided in the aforementioned patent to Candor et al.

Also, while the fields 38 and 52 have been illustrated and described as being non-uniform fields, it is to be understood that the same could be uniform fields, if desired. Such uniform fields would then produce a non-pattern non-woven sheet in the above manner.

Therefore, it can be seen that this invention not only provides an improved method and apparatus for forming a patterned non-woven sheet, but also this invention provides improved methods and apparatus for making an unpatterned non-woven sheet, or the like.

However, while the apparatus and method 14 has been previously described as forming the non-woven mat 39 by originally arranging the fibers in the predetermined patterns 11 and 12, it is believed that the method and apparatus 14 could act on an already formed mat wherein the fibers are nonpatterned and not permanently secured together to rearrange the fibers thereof into the patterned areas 11 and 12 as the same passes between the belts 15 and 24 through the action of the fields 38 and the moisture of such rearranged mat would be removed therefrom by the electro-osmotic action of the fields 38 and the fields 52 as the rearranged mat passes between the belts 15 and 41. Thus, it is believed that by appropriately charging certain already existing structure disclosed in the aforementioned patent to Kalwaites and similar patents of Kalwaites, the fibers of the material disclosed therein could be rearranged electrostatically with or without the rearranging fluid jets disclosed in such patent or patents.

Also, if it is found that it is desirable to have the conductive parts 28 and 34 of the upper and lower belts 15 and 20 in electrical contact with the slurry therebetween as in the patent to Stiles, the conductive sheet 28 could have the openings 29 thereof filled with insulating material so that the fibers would only be attracted to the unperforated parts thereof to produce the patterned mat 39 previously described.

It is to be understood that all of the above-described variations of the method and apparatus 14 of FIG. 2 from that illustrated in FIGS. 2-9 could equally apply to the other embodiments of this invention that are illustrated in FIGS. 10 and 12 where such variations are appropriate.

While the liquid being driven from the sheet-like form in the apparatus 14 of FIG. 2 by electro-osmosis is carried on the upper run 23 of the belt 20 to run all of the same into the reservoir 40 at the roller 22, it is a feature of another embodiment of this invention to have such belt means 20 be provided with a pervious surface means which will draw the removed liquid therein at a controlled rate as the liquid and fiber means are being separated between the adjacent runs of the upper and lower belts 15 and 20.

In particular, another embodiment of this invention is generally indicated by the reference numeral 14A in FIG. 10 and parts thereof similar to the method and apparatus 14 previously described are indicated by like reference numerals followed by the reference letter A.

As illustrated in FIGS. 10 and 11, the upper belt 15A is substantially identical to the belt 15 previously described and the lower belt 20A is substantially identical to the belt 20 previously described except that the belt 20A has an additional moisture pervious layer 60 thereon that is adapted to receive liquid therein at a controlled rate as will be apparent hereinafter, the pervious layer 60 being on the outer surface of the belt 20A so as to be disposed spaced from the belt 15A as the slurry is formed in the sheet-like form therebetween.

Also, the rollers 21A and 22A for the belt 20A are so arranged that the upper run 23A of the belt 20A is angled relative to the lower run 19A of the upper belt 15A for a purpose hereinafter described, the gap between the runs 19A and 20A narrowing as the same moves from the left to right in the drawings.

Further, a pair of squeezing rollers 61 and 62 are provided for cooperating together to act on the lower run 24A of the lower belt 20A to squeeze moisture from the pervious layer 60 thereof as will be apparent hereinafter whereby the removed moisture from the squeezed run 24A of the belt 20A can flow off the lower squeezing roller 62 into a reservoir 63 for reuse thereof as desired.

The operation of the method and apparatus 14A of this invention will now be described.

As the slurry of liquid and fiber from the supply 25A enters the space between the adjacent runs 19A and 23A of the belts 15A and 20A, the same is acted on by the electrostatic field created between the conductor means 28A and 34A of the belts 15A and 20A in the manner previously described whereby the fibers form into the interconnected bundles 11A adjacent the run 19A of the belt 15A while the liquid is driven downwardly toward the run 23A of the belt 20A against the top surface 64 of the pervious layer 60.

It is believed that the pervious layer 60 could have the capillaries and pores thereof so constructed and arranged that the same will only permit the liquid to enter into the layer 60 at a controlled rate even though the electrostatic field action is tending to move the liquid downwardly toward the conductive layer 34A of the belt 20A whereby only the separated out liquid of the slurry sheet-like form would be entering into the layer 60 as the belt 20A moves from left to right in FIG. 10 so that by the time the particular section of the belt 20A reaches the roller 22A, there is only the collected fibers being disposed between the runs 19A and 23A of the belts 15A and 20A as the layer 60 is of sufficient thickness to absorb all of the separated liquid by the time it reaches the pulley 22A.

In this manner, it is believed that as the liquid is being absorbed into the layer 60 of the lower belt 20A, as the sheet-like form moves from left to right in FIG. 10, the unseparated liquid and fibers are being moved closer to the lower run 19A of the upper belt 15A to increase the action of the electrostatic field action thereon to separate the same as the conductors 28A and 34A of the belts 15A and 20A are being moved closer together as the same move from left to right in FIG. 10 and thereby decreases the amount of time for forming the mat 39A as previously described.

The moisture now retained in the layer 60 of the belt 20A is squeezed therefrom by the cooperating rollers 61 and 62 as illustrated in FIG. 10 so that the layer 60, when the same returns to be adjacent the belt 15A, the layer 60 can reabsorb additional moisture therein in the manner previously described.

Another method and apparatus of this invention is generally indicated by the reference numeral 14B in FIG. 12 and parts thereof similar to the method and apparatus 14 previously described are indicated by like reference numerals followed by the reference letter B.

As illustrated in FIGS. 12 and 13, the upper and lower belts 15B and 20B of the method and apparatus 14B are substantially identical to the belts 15 and 20 previously described except that the upper belt 15B has a plurality of projections 65 extending outwardly therefrom with such projections 65 comprising needle-like conductive members 66 extending from the conductive layer 28B thereof and beyond the outer surface 30B thereof so as to project into the space between the adjacent runs 19B and 23B of the belts 15B and 20B as illustrated in FIGS. 12 and 13. The projecting parts of the needle-like members 66 are still insulated by the insulating layer 30B so as to maintain the needle-like conductors 66 out of electrical contact with the sheet-like form being disposed between the belt 15B and 20B by the reservoir 25B in the manner previously described.

While the projections 65 are illustrated as only partially extending across the gap between the belts 15B and 20B, it is to be understood that the projections 65 could extend completely across the gap between the belts 15B and 20B or to just to the extent that the fiber bundles 11B are being formed or actually extend out of the fiber bundles 11B as desired.

In any event, it can be seen that as the sheet-like form of fibers and liquid moves from left to right in the apparatus 14B of FIG. 12, the previously described electrostatic field action causes the fibers to form the interconnected fiber bundles 11B adjacent the lower run 19B of the belt 15B while the liquid is driven downwardly toward the upper run 23B of the lower belt 20B as previously described. However, it is believed that the needle-like projections 65 assist such electrostatic field action in driving the fibers upwardly toward the belt 15A and/or drive the liquid downwardly toward the belt 20B through the non-uniform field action created by the needle-like members 65 themselves.

Also, it may be found that such needle-like members 65 should be on the lower belt 20B in lieu of or in addition to the needle-like members 65 on the upper belt 15B, such combination of needle-like members 65 on both belts 15B or 20B being arranged so as to be directed toward each other, or staggered, or overlapping, etc., as desired, and with all or some of the needle-like members of one or both belts 15B and 20B extending completely and/or partially through the sheet-like form of slurry that is disposed therebetween.

Also, the improved belt 15B of FIG. 12 could be utilized with the improved belt 20A of FIG. 10 or the improved belts 15B and 20A can be utilized by themselves in the manner illustrated on the drawings as desired.

In any event, the upper belt 15A and 15B can be utilized to cooperate with belts similar to the belt 41 previously described to further drive the moisture out of the mats 39A and 39B in the manner previously described.

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

Claims

1. A method of making a non-woven sheet comprising the steps of providing a slurry of liquid and fibers, forming said slurry into sheet-like form by flowing said slurry against and between two spaced apart first and second surfaces, creating an electrostatic field action that acts on said sheet-like form between said two surfaces and causes at least part of said fibers to be arranged into a sheet adjacent said first surface and at least part of said liquid to be arranged adjacent said second surface, and causing needle-like projections of one of said surfaces to project at least partially into said sheet-like form and assist said electrostatic field action in forming said sheet adjacent said first surface.

2. A method as set forth in claim 1 and including the step of charging said needle-like projections of said one surface with one electrical potential to provide at least part of said electrostatic field action.

3. A method as set forth in claim 2 and including the step of electrically insulating said needle-like projections from said sheet-like form.

4. A method as set forth in claim 2 and including the step of also chargingg said one surface with the same potential as said needle-like projections thereof.

5. A method as set forth in claim 4 and including the step of electrically insulating said one surface and said needle-like projections thereof from said sheet-like form.

6. An apparatus for making a non-woven sheet comprising means for supplying a slurry of liquid and fibers, a pair of spaced apart first and second surfaces, means for flowing said slurry against and between said pair of surfaces to form said slurry into a sheet-like form between said surfaces, and means for creating an electrostatic field to act on said sheet-like form and cause at least part of said fibers thereof to be arranged into a sheet adjacent said first surface and at least part of said liquid to be arranged adjacent said second surface, one of said surfaces having needle-like projections projecting at least partially into said sheet-like form for assisting said electrostatic field action in forming said sheet adjacent said first surface.

7. Apparatus as set forth in claim 6 and including means for charging said needle-like projections of said one surface with one electrical potential to provide at least part of said electrostatic field action.

8. Apparatus as set forth in claim 7 wherein said needle-like projections are electrically insulated from said sheet-like form.

9. Apparatus as set forth in claim 8 and including means for also charging said one surface with the same potential as said needle-like projections thereof.

10. Apparatus as set forth in claim 9 wherein said one surface and said needle-like projections thereof are electrically insulated from said sheet-like form.

11. A method of making a non-woven sheet comprising the steps of providing a slurry of liquid and fibers, forming said slurry into sheet-like form by flowing said slurry against and between two spaced apart surfaces, creating an electrostatic field action that acts on said sheet-like form between said two surfaces and causes at least part of said fibers to be arranged into a sheet adjacent one of said surfaces and at least part of said liquid to be arranged adjacent the other of said surfaces, and causing needle-like projections of said one surface to project at least partially into said sheet-like form and assist said electrostatic field action in forming said sheet adjacent said one surface.

12. A method as set forth in claim 11 and including the step of charging said needle-like projections of said one surface with one electrical potential to provide at least part of said electrostatic field action.

13. A method as set forth in claim 12 and including the step of electrically insulating said needle-like projections from said sheet-like form.

14. A method as set forth in claim 12 and including the step of also charging said one surface with the same potential as said needle-like projections thereof.

15. A method as set forth in claim 14 and including the step of electrically insulating said one surface and said needle-like projections thereof from said sheet-like form.

16. An apparatus for making a non-woven sheet comprising means for applying a slurry of liquid and fibers, a pair of spaced apart surfaces, means for flowing said slurry against and between said pair of surfaces to form said slurry into a sheet-like form between said surfaces, and means for creating an electrostatic field to act on said sheet-like form and cause at least part of said fibers thereof to be arranged into a sheet adjacent one of said surfaces and at least part of said liquid to be arranged adjacent the other of said surfaces, said one surface having needle-like projections projecting at least partially into said sheet-like form for assisting said electrostatic field action in forming said sheet adjacent said one surface.

17. Apparatus as set forth in claim 16 and including means for charging said needle-like projections of said one surface with one electrical potential to provide at least part of said electrostatic field action.

18. Apparatus as set forth in claim 17 wherein said needle-like projections are electrically insulated from said sheet-like form.

19. Apparatus as set forth in claim 17 and including means for also charging said one surface with the same potential as said needle-like projections thereof.

20. Apparatus as set forth in claim 19 wherein said one surface and said needle-like projection thereof are electrically insulated from said sheet-like form.