US 2468853 A
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Description (OCR text may contain errors)
J. A. WILLIAMSON ABRASIVE WEB MATERIAL May 3, 1949.
2 She'ets-Sheet 1 Filed Sept. 15, 1944 AHI May 3, 1949. J. A. WILLIAMSON ABRAsIvEYwB MATERIAL 2 Sheets-Sheet 2 Filed sept. 15, 1944 vPatented May 3, 1949 .UNITED STATES PATENT voF-FlcE 2,468,853 -ABRASIVE WEB MATERIAL John A. Williamson,
to The Carborundum Company,
Niagara Falls, N. Y., asslgnor Niagara Falls,
N. Y., a corporation of Delaware Application September 15, 1944, Serial No. 554,273
11 Claims. (Cl. 51-294) The present product represents an improvement over such articles by reason of the elimination of the backing and may be used for many purposes for which abrasive coated paper is adapted as vwell as in applications for which theI conventional abrasive paper is not suited'. In addition, its fibrous structure lends a strength and durability to the final material not to be expected in a backless product.
Recently it has been proposed to form felted abrasive webs by employing a plurality of carding machines to form a number of membranesv which are interlocked and into which abrasive grains are projected. Firstly, such methods are limited to those fibers which, by reason of their length `and strength, are easily eardable, such as cotton, ramie and the like. Moreover, dry methods of formation are' hampered Vby certain difficulties of inextracting the water or other liquid medium from the web, and further drying and compacting the web to the desired density. The abrasive particles are introduced into the brous structure in an amount sufficient to render the resulting fibrous web highly abrasive in character throughout its thickness.
However, the abrasive grain is not added to such an extent as to interfere with the interlocking and felting action of the fibers in which latter case the resulting sheet material would be appreciably weakened.
An additional feature of the process is the optional preliminary coating of the abrasive grains with a suitable adhesive, which is prefhighly aqueous or fluid condition. That portion of 1 I web structure, and the abrasive of each succeeding corporating the abrasive internally of the web.-
structure and keeping it in position therein until the web has been compacted by the application of pressure and the introduction of adhesive. The process herein disclosed avoids these difficulties and has the further advantage that it employs fibers which 'are cheap and available in quantity,
' thus providing a, new and inexpensive fibrous abrasive material possessing a sof grinding and polishing action.
The present invention provides a method of making felted brous abrasive webs of paper fibers and other relatively short-staple fibers which cannot be readily, if at all, carded and which are not adaptable to being satisfactorily felted by any of the known dry methods. A
In accordance with the present invention felted fibrous webs having abrasive grain incorporated internally of the web are made by first forming a liquid, usually aqueous, suspension of fibrous material, collecting the fibrous lsuspension on a suitable support, introducing abrasive grains with or without an adhesive binder into the brous web while it is in a highly aqueous, or fluid, condition,
erably soluble or softenable in the liquid suspending medium or a, component thereof, to assist in holding the` fibrous abrasive-containing web in compacted form after it has been compressed.
The invention may be practiced in a number of ways. In one such embodiment the fibrous suspension is deposited upon a foraminous support in one step and the abrasive grain is deposited in several increments while the web is still in a abrasive applied first penetrates deepest into the deposition penetrates the web to a lesser degree by reason of the continually decreasing amount of water vpresent and the consequent thickening of the fibrous body. The distribution of abrasive within :the web can thus be controlled by variation of the amounts and places of deposition during the dewatering of the web so as to obtain any desired effect.
In a, second form of the linvention a fluid fibrous suspension is collected upon a plurality of revolving .ioraminous supports, such as cylinders, which are partially immersed in the fibrous suspension. The thin fibrous membranesf'collected upon the foraminous supports are then successively transferred to a common carrier, usually a moving endless felt blanket or belt, in superimposed -relationship to form a fibrous web structure. Abrasive grain is incorporated into the fibrous web structure by deposition or projection between and into the various individual membranes as they are deposited on the carrier support. This method has the advantage that the fibrous suspension can be varied so that various portions of the web structure can be'varied if desired. Adhesive binders can be incorporated 'in the vfibrous web; regardless of the procedure used,` atvarious stages in the process, such as by inclusion in the fibrous'suspiension, introduction during dewatering of the web, with the abrasive support such as the moving endless felt 8. The
- stock or furnish 9 is maintained at a constant ing a wet fibrous abrasive lap by a cylinder wetpress process, in which a fibrous suspension similar to` that used in the cylinder method above is fed, usually from a single cylinder mold, onto a traveling wet felt carrier belt. The thin fibrous membrane is conveyed over one or more suction boxes to remove a portion of the water and passed between a pair of pressure rolls. As the fibrous ymaterial passes between the pressure rolls it is transferred to the upper pressure roll upon which it is wound in a series of successive layers until the desired thickness of fibrous material is obtained, whereupon the material is removed by- In order that the invention may be more clear-V ly understood, reference is made to the accompanying drawings, in which Figure 1 is a vertical diagrammatic cross- LLI section of an apparatus for making fiexible, abra- 1 sive-included fibrous webs in accordance with one form of the present invention;
Figure 2 is a vertical diagrammatic crosssection taken at right angles to and through the line II-II of Figure 1 and showing in greater detail that part of the apparatus designated in Figure 1 as A and used to apply the abrasive grains;
Figure 3 is a modified form of apparatus to that shown in Figures 1 and 2 for depositing the abrasive grains and is used when it is desired to electrostatically project the abrasive grains into the fibrous structure Figure 4 is an enlarged cross-section ofthe web taken through the line IV-IV of Figure 1;
Figure 5 is a vertical diagrammatic crosssection of an apparatus for carrying out the invention in one of its modified or alternative forms;
Figure 6 is a vertical diagrammatic crosssection of an apparatus for carrying out the invention in still another of its modied or alternative forms; and
Figure '7 is a greatly enlarged vertical crosssection through a portion of a fibrous abrasive web made in accordance with the present invention.
Referring further to the drawings, in Figure 1 is illustrated one form of apparatus which may be employed in manufacturing abrasive webs comprised -of a felted fibrous material with abrasive grains incorporated therein and bonded with a suitable adhesive binder. The particular apparatus shown comprises a `plurality of cylinder machines, suitably spaced apart and consisting of cylinder vats 2, cylinder molds 3 and couch rolls 4 adapted to form and deliver a number of fibrous membranes 5, 6 and 1 to a common carrier suitable means (not shown).
head in each one of the cylinder vats.
The fibrous stock or furnish 9 in the cylinder vats isa thin liquid, usually aqueous, suspension of individually separated fibers, the fiber content being very low and in the neighborhood of .5 to 5% of the suspension. Any of the cellulosic wood fibers commonly used in paper making have been found to be satisfactory for the present process, although it is desirable to select a fiber of suitably high strength which will impart a good durability and lstrength to the final product. Fibers which are used in paper making and which can be used herein include seedhairs, of which cotton and bombax wool are examples, stem-fibers, such as linen, jute, manila, etc., leaf-fibers, such as straw, esparto, palm and the like, fruit fibers such as cocoanut, and any of the well known wood flbers. Other fibers which may be used are any of the synthetic resin or synthetic elastic fibers and normally-cardable fibers such as cotton, provided they are of a fineness and density such that they remain suspended and are of such length that they will felt together on the cylinder mold. Instead of having all the fibers of the same material, one or more of the fibrous suspensions may contain a different fiber than the rest or the suspension may comprise a mixture of different fibers. Although three cylinder machine set-ups are shown in Figure 1, any number of cylinders may be used depending upon the desired thickness and type of web.
The cylinder molds 3 are large drums with the cylindrical areas covered with a wire screen, usually of 30 to 60 mesh. These are partially immersed in the thin, fibrous suspension and revolved in the direction shown by the arrows. The water level within the cylinder mold is lower than it is in the vat outside the mold and as a result as the mold revolves through the suspension it picks up a thin lm of fibrous material which clings to the foraminous surface of the cylinder mold and is carried up and out of the suspension. This partially formed, highly aqueous fibrous membrane is transferred to the moving carrier support 8 by means of a couch roll 4 which serves to press the carrier belt 8 against the cylinder mold 3. The carrier support is ordinarily a wet woolen felt or blanket and travels around rolls l0, Il, which may be driven by any Roll I6 serves as a stretch roll to remove slack and keep thebelt tight. The highly aqueous fibrous membrane is picked of! the wire mesh of the cylinder mold by the felt 8. to which it adheres with sufcient tenacity to withstand the pull of gravity. As the moving felt passes above the subsequent cylinder molds it similarly picks up additional fibrous membranes which are superimposed lon the initially deposited membrane until a layer oi' fibrous material of the desired thickness has been built up on the belt. The thickness of the individual brous membranes can be controlled by the speed of rotation of the cylinder mold and also by the percentage fiber content of the stock or furnish. The rate of feed of the various brous membranes to the carrier felt must be synchronized with the speed of the moving felt so as to prevent wrinkling and also to prevent any appreciable strain on the flimsy fibrous membranes during their deposition and while they still are in a highly aqueous condition.
After the initial fibrous membrane has been transferred to the carrier belt and while it is in a 2,4es,sss
detail in Figure 2, for projecting the abrasive grain into the fibrous membranes consists of a feed belt 24, supported by end rolls I5, I6 and driven by any suitable means (not shown), an abrasive grain hopper I1, a series of beater bars Iland a container I9 for retrieving any excess.
abrasive grains. The abrasive grain hopper I1 is provided with a feed gate 20 and distributing roll 2I for regulating the flow 'of abrasive grain onto the moving endless feed belt 24 which passes transversely beneath the felt carrier 8. The grain feed belt 24 as it passes beneath lthe Wet fibrous membrane clinging to the under side of the felt,
tromotive force for creating the electrostatic field,
the effective potential ofwhich is 20,080 volts or is subjected to a vibratory. beating action which projects the grain 22 Iupwardly into the fibrous membrane where it becomes lodged within the web structure. The projection of abrasive grain into the membrane is sometimes followed by the application of an adhesive binder which canbe made by means of a suitable series of spray nozzles 23 situated beneath and transversely of the carrier felt.
The above operations are then repeated by the transfer of additional fibrous membranes, such as 6 and 1 of Figure 1, to the carrier felt super` imposed on the initially deposited membrane. Further inclusions of abrasive grain and/or adhesive binder are made between the various membranes in the manner set forth above.
After the web has been finally built up to the desired thickness on the carrier belt 8, it is passed through a pair of squeeze rolls I I, 25 whichserves to further extract water from the brous web. It is thentransferred to a second carrier felt 26 supported by rolls 21, 28, 29, 30 and 3| and maintained relatively taut by means of a stretch roll 32, and passed between rubber-covered squeeze rolls 33, 34 which remove additional water and further compact the web. The lower pressure rolls 25 and 34 may be provided with suction boxes more, is not specifically shown in' the drawing, but is indicated by the positive (-1-) and negative symbols and connected to the electrodes 43 and 4I by the connecting lead wires 43 and 44, l respectively.
The character and construction of the lower electrode 4I is of great importance in the operation of the apparatus the electrode, preferably, being shielded by some poorly conducting material. The material so used should be low enough in conductance that not enough current can flow along or through it to cause arcing between the upper and lower electrodes, yet it should be sumciently conductive to allow a small leakage current to supply electrical charges to the abrasive particles in order that they may be oriented so that their lengthwise axes are normal to the web direction and most suitable for projection into the fibrous structure. Therefore thehigh potential electrode 4I is formed of la poorly conducting material 45 which shields and protects the metallic plate 46 of electrode 4I. The term poorly conducting material is used to distinguish between such materials. as metals and carbon, which are relatively good conductors of' electricity. on the one hand, and highly insulating materials such as hard rubber and varnished cambric which are such good insulators at the voltage used with the present apparatus that thev leakage current which ows through them is insufficient to electrically -charge and project the abrasive particles. Molded 35, if desired, to assist in removal of the water.
It is vcustomary to provide, in addition to the felt carrier belt 26 shown in `Figure 1, an additional top felt so that as the wet fibrous web passes between the rolls 33 and 34 it is held between two felts which serve to hold the web in position and, due to the absorbency of the felt carriers, assist in removing the large amount of water necessarily initially present. Additional press rolls tov those shown may be included, after which the fibrous web, which still contains a large per-` centage of water, is passed over guide roll 31 to a series of steam-heated dryer rolls 38, from which the web is conducted to a wind-up reel 39.
The abrasive grain may be included in the fibrous membranes as described above or by the more recently developed electrostatic or magnetic methods of grain projection. Briefly, projection of the grain by electrostatic forces is accomplished lby replacing the apparatus for projecting the grain shown at A of Figure 1 by that shown schematically in Figure y3, in which the felt carrier belt 8 with its attached fibrous membrane 5 is passed into the electrostatic field created between the two electrodes and 4I. Simultaneously,
abrasive grains are fed from a hopper and conveyed by means of a moving endless belt 42 into the same electrostatic eld where they receive an electrostatic charge and are projected upwardly into the fibrous membrane. The source of elecmaterials, such as those sold under the trade names of Micarta" and Bakelite, have been found to be most satisfactory although other-materials such as dry, knot-free wood can also be used. While these materials are so poorly conducting that they will not carry enough current to permit spark-over or arcing between the upper and lower electrodes, they are suiilciently conductive at the voltages employed to allow enough leakage current to pass and supply the small amount of electrostatic charges required. Ordinarily the upper electrode 40 is at ground potential and thus does not need to be encased by a poorly conducting sheath. l
Figure 4, taken along the line IV-IV of Figure 1, shows in enlarged detail the structure of a partially formed brous web in the process of being loaded with abrasive grain during its travel on the felt carrier support 8. The initially deposited membrane 5`has been charged with abrasive grains which are lodged among the fibers 5I, while the newly laid fibrous membrane 6 is without grain but is uncompacted and receptive to the ready. inclusion of abrasive grain similar to that already included in the first portion of the web. As can be seen from the detail of Figure 4, any one or morev of the brous layers can be deposited without inclusion of abrasive therein. This provides a desirable control over the location of the abrasive within the nal productdepending upon the use to which it is to be put. V
Figure 5 depicts in schematic cross-section another form of apparatus which may be used for carrying out the present invention. The thin aqueous suspension or stock 53, which is of the same generalconsistency'as that used in` the apparatus of Figures 1 and 2, i. e., betweenl0.5 and 5.0% ber content, is maintained at a constant head in a owor head box 54 from which it is forced by its own weight or under controlled pressure out through the slice onto the endless wire rolls 62.
Massa k 7 wire screen 58. The rate of flow off-the thin fibrous stock is governed by the consistency of the stock, the extent of head maintained, and by valve regulators 51 and 58 which control the degree of opening of the slice 55. The wire screen B is drivert/:by the couch roll 59 and supported by the breast roll 80, table rolls 6| and web is continually being removed, first by the series of table rolls 6|, and then by the suction' boxes 63 and suction couch roll 59 and coacting top pressure roll 84.
The wire screen carrying the wet fibrous web passes beneath a series of abrasive grain hoppers 65 which are providedwith adjustable feed gates 86 and distributing rolls 61 for regulating the fiow of abrasive grain into the fibrous web. The abrasive grain from the first hopper of the series is vdeposited while the web is still in a highly ponded condition, in other words, the water content is sufficiently high that many of the fibers are still separate and floating, whereupon The water content of the fibrous the high density of the abrasive grain causes-it to sink through a large part of the material and penetrate to the lower part where it becomes embedded in the lower fibers. As the web and supporting wire screen proceed along over the table rolls, the web continues to lose water and gradually loses its ponded condition and becomes felted. While this felting action is taking place, additional abrasive grain is deposited from grain hoppers and becomes lodged in successively higher portions of the web. Theamount of abrasive grain incorporated in the various portions of the web is governed by the position of the abrasive grain hoppers along the path of travel uof the screen and the amount of abrasive grain fed into the web from the various hoppers. S'ufiicient abrasive grain is incorporated within the fibrous structure to impart an efficient and effective abrasive character to the final sheet material, although the amount of abrasive grain must be retained within certain upper limits, above which the felting action of the fibers is interfered with so as to weaken the fibrous structure. As the water is extracted from the web the fibers become felted about the abrasive grains and interlocked to form a strongly felted body having abrasive grainsecurely included therein. Suitable adhesive can be applied, as by means of a, series of spray nozzles 88 positioned above the wire screen or by prellminarily coating the abrasive grains, or by inclusion in the suspension, to provide additional strength and to assist in maintaining the web in its final compacted form.
The fibrous abrasive-included web is transferred from the wire screen to a pressing felt 1li, which is usually an endless woolen blanket, and passes between the top and bottom pressure rolls 1|, 12, where more water is removed and the sheet further compacted. If desired, the bottom roll may be provided with a suction box to promote the extraction of water. The felt 10 is supported and maintained taut by the felt rolls 13 and stretch roll 14. Additional pressing felts may be provided, if desired; also a top felt may be used to operate in conjunction with the bottom felt so as to retain the fibrous web between two felts as it is being pressed and to provide additional support in its earlier stages. After the fibrous abrasive web leaves the pressing feltsit still contains a large amount of water and is passed over a series of steam-heated dryer rolls 15 which remove additional water, follow- 8 ing which the web is rolled onto s, reel 18 for storage or'conveyance to machines for cutting into sheets, strips, discs and the like suitable for use.
Figure 6 depicts in schematic cross-section another form of apparatus which may be used for carrying out the present invention. The particular apparatus shown is of the cylinder wet-press type and comprises a single cylinder machine consisting of a cylinder vat 80, cylinder mold 8| and couch roll 82 adapted to form and deliver a fibrous membrane 83 to a carrier support such as the moving endless felt 84. The stock or furnish is maintained at a constant head.
The thin aqueous suspension or stock 85, which is of the same general consistency as that used in the apparatus of Figures 1 and 5, i. e., between 0.5 and 5.0% fiber, content is fed into the vat-through the inlet 86. The cylinder mold 8| is a large drum with the cylindrical surface covered with a wire screen, usually of 80 to 80 mesh, partially immersed in the thin, fibrous suspension and revolved ln the direction shown by the arrow. The water level within the cylinder mold and the white-water discharge box 81 is lower than it is in the vat outside the mold andv discharge box and as a lresult as the mold revolves through the suspension it picks up a thin film of fibrous material which clings to the foraminous surface of the cylinder mold and is carried up and out 'of the suspension. The white-water filtrate through the foraminous surface of the cylinder mold is continually dis-4 88 so as to maintain a constant differential of liquid levels'outside and inside the cylinder mold.
The partially formed, highly aqueous fibrous membrane 83 which is withdrawn from the aqueous suspension onto the cylinder mold is transferred to the moving carrier support 84 by means of the couch roll 82 which presses the felt carrier belt against the cylinder mold. 'I'he carrier support is ordinarily a wet woolen felt or blanket and is supported and guided by rolls 90, 9|, which may be driven by any suitable means (not shown). Roll 9| serves also as a stretch roll to remove slack and keep the belt tight. The felt carrier 84 passes around the couch roll 82 carrying on its outside surface the thin fibrous membrane. The fibrous membrane and supporting felt is then passed over the suction box 92 where additional water is withdrawn so that when the press rolls 93, 94 are reached the fibrous sheet is dry enough to stand the pressure exerted by the rolls. Prior to the passage of the fibrous membrane and supporting felt between the pressure rolls 93, 94, abrasive grain is projected into the fibrous membrane so as to incorporate the abrasive particles within the fibrous structure. The abrasive grain can be fed onto the membrane either as shown just as the fibrous membrane is entering the rolls or it can be deposited ahead of the suction box. As shown. the abrasive Igrain is fed from a hopper 95 .through an adjustable feed gate l96 and distributing roll 91 onto a vibrating plate 98 from which it is shaken onto the fibrous membrane.
As the felt carrier leaves lthe pressure rolls 93, 94 the initial sheet of fibers adheres to the surface of the top pressure roll 93 and continues to follow it around, thus causing the roll to be covered with successive layers Vwhich are compacted into a homogeneous sheet. After the top roll has received the initial layer of fibrous mahand wheel |03. The supporting framework and structure of the depicted apparatus is not shown, l except the fragment |04, as it would interfere with a clear understanding of the operations involved.
The fibrous abrasive-included sheet or layer is removed from the pressure roll 93, when the fibrous layer reaches the -desired thickness, by
cutting it byv hand with a sharp knife, or by means of a suitable doctor bladesuspended over the roll. The sheet falls on the table |05 froml which it is removed for cutting to the desired shape and size for various abrasive uses.
As the carrier felt leaves the pressure rolls it is passed over rolls 90, 9| back to the cylinder vat for receiving another fibrous membrane. The felt may be cleaned while the machine is in operation as by the use of a shower of water and the whipper |06; the revolving blades of the whipper come into contact with the water soaked felt, knock ofi any fibers that adhere to it, and keep the felt in proper condition to receive another fibrous membrane.
Any suitable adhesive binder can be incorporated in the fibrous material at various stages during its fabrication. For example, the adhesive can be included in the fibrous suspension 85 as it exists in the cylinder -vat or it can be introduced into the membrane byv means of a series of suitable spray nozzles |01 positioned above the carrier belt 84. Likewise, it can be incorporated into the fibrous structure as a powdered ingredient separately or with the abrasive particles or as a coating thereof, or it can be incorporated as a roll coating operation using the top pressure roll as the recipient roll.
As an alternative to ythe use of a powdered or liquid adhesive separately introduced into the brous structure, the requisite strength of the compacted web can be obtained by the yinclusion i in the fibrous suspension of a sufficient number of thermoplastic fibers such as cellulose acetate fibers, vinyl chloride-vinyl acetate copolymers, polyamide bers and the like synthetic fibers, which `are distributed throughout the material as the web or sheet is formed, and later under the application of heat and/or pressure can be caused to coa'lesce with and serve as a binder or strengthening means for the other fibers.
Figure 7 shows a greatly enlarged cross-section through a portion of a finished web made in accordance with the present invention and shows how the` abrasive grains 50.are included internally throughout the web 4structure and are `held in place-by the felted fibers. 5|. In the particular embodiment shown the abrasive is uniformly distributed throughout the entire web, whereas the web can be made, as is evident from consideration of the methods given above, so that the abrasive grain is concentrated -in -any desired portions of the web where it Will be` most effective, depending upon the use to which the final product is to be put.
The present process provides Aa product in which the abrasive grain content can be increased to such 4proportion ofthe final product that the polishing and cutting action of the abra- 'sive is effective while the fibrous structure provides a softness of abrasive action and freedom from harshness not otherwise found. The products are strong enough to withstand the stresses and strains to which .the material is subjected in use and yet they possess a pliant flexibility much t0 be desired in such products.
The amount of abrasive grain included in lthe web can be readily controlled, and, in caseswhere the entire structure of the web is charged with abrasive, it has been found that where fused alumina is used most satisfactory results are obtained when the nished products contain from 70% to 8,5% by weight of abrasive material. An example of an abrasive sheet material which has Ibeen loaded throughout its entire fibrous structure with abrasive grain and was found highly satisfactory for effective and eicient polishing and cutting operations when placed in form for use is one comprising' wet felted paper-stock fibers containing by final analysis approximately 80% by weight of 80 grit fused alumin-um oxide abrasive grain. Where other kinds of abrasive materials are used the weight percentage of abrasive grain is adjusted to allow for the difference in density of the abrasive.
The adhesive binder used to permeate and assist in maintaining the consolidated condition of the web is preferably one of a flexible or resil, ient nature, such as latex, fiexibilized animal or vegetable glue, plasticized vinyl resin, plasticized urea aldehyde resins, and the like. Such flexible adhesives permit the retention of the natural pliable character of the interlocked felted fibrous structure. As stated the adhesive binder may be included at any stage in the production of the web depending upon the specific procedure employed and the type of web material being made. For example, the adhesive may be incorporated in the aqueous suspension as a separate adhesive substance or in the form of a thermoplastic fiber before it is flowed into web form, it may be deposited or applied with the abrasive grains, at any stage during the building up of the fibrous web, during the dewatering operations, or after the web has been dewatered and lprior or subsequent to the pressing and compacting of the web. Also, in practicing the invention any of the abrasive materials in common use, or combinations thereof may be employed, such as silicon carbide, fused aluminum oxide, flint, corundum, emery, rouge and similar substances. The size of the abrasive particles may vary from the finest polishing or bufling powders to the coarser grit sizes used in grinding.
While certain embodiments of the invention have been specifically illustrated and described, it is to be understood that the invention may be otherwise embodied and practiced within the scope of the appended claims.
1. A method of making flexible fibrous abrasive webs whichcomprises forming a thin aqueous suspension of fibrous material, the fibers of which are of wet-feltable length, depositing said suspension on a foraminous support as a highly aqueous fibrous web, introducing a sufficient amount of abrasive particles and an adhesive binder into the interior of said web while said web ison said foraminous support and While said web is highly aqueous and uncompacted to provide an abrasive particle content of 'l0-85% by weight based on the dry weight of the fibrous web, said abrasive particles being distributed incompacted, extracting water from the highly aqueous web to felt the fibers about the abrasive particles, and drying and compacting the felted web to the desired density.
2. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of paper-stock fibers, depositing said suspension on a foraminous supportas a highly aqueous fibrous web, introducing a suiiicient amount of abrasive particles and an adhesive binder into the interior of said web while said web is on said foraminous support and while said web is highly aqueous and uncompacted to provide an abrasive particle content of 'l0-85% by weight based on the dry weight of the fibrous web, said abrasive particles being distributed internally throughout the thickness of the web structure as a result of being applied to the web while the latter is stillvhighly aqueous and uncompacted, extracting water from the highly aqueous web to felt the fibers about the abrasive particles, and drying and compacting the felted web to thevdesired density.
3. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of paper-stock fibers, depositing said suspension on a foraminous support as a highly aqueous fibrous web, introducing a suiiicient amount of abrasive Aparticles and an adhesive binder into the interior of said web while said web is on said foraminous support and while said web is highly aqueous and uncompacted to provide an abrasive particle content of approximately 80% by weight based on the dry weight of the fibrous web, said abrasive particles being distributed internally throughout the thickness of the web structure as a result of being applied to the web while the latter is still highly aqueous and uncompacted, extracting water from the highly aqueous web to felt the fibers about the abrasive particles, and drying and compacting the felted web to the desired density/ 4. A method of making iiexible fibrous abrasive webs which comprises forming a thin aqueous suspension of fibrous material, the flbers of which are of wet-feltable length, including an adhesive binder therein, depositing said suspension on a foraminous support as a highly aqueous fibrous web, introducing a suiiicient amount of abrasive particles into the interior of said web while said web is on said foraminous support and while said web is highly aqueous and uncompacted to provide an abrasive grain content of 'I0-85% by weight based on the `,dry weight of the fibrous web, said abrasive particles being distributed internally throughout `the thickness of the web structure as a result of being applied to the web while the latter is still highly -aqueous and uncompacted, extracting water from the highly aqueous web to felt the fibers about the abrasive particles, and drying and compacting the felted web to the desired density.
5. A method of,y making iiexible fibrous abrasive webs which comprises forming a thin aqueous suspension of fibrous material the fibers of which are of wet-feltable length, depositing said suspension on a foraminous support as a highly aqueous fibrous web, introducing abrasive particles internally of the web while said web is on said foraminous support and while said web is still highly aqueous and uncompacted whereby said abrasive particles are distributed throughout the thickness of the web, extractingwater therefrom to felt the iibers about the abrasive particles, and drying and `compacting the web to the desired density.
6. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of fibrous material the bers of which are of wet-feltable length, depositing said suspension on a foraminous support as a highly aqueous fibrous ^.web, introducing abrasive particles and an adhesive binder into the interior of the web while said web is on said foraminous support and while said web is highly aqueous and uncompacted whereby said abrasive particles are distributed throughout the thickness of the web, extracting water therefrom to felt the fibers about the abrasive particles, and drying and compacting the felted web to the desired density.
7. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of fibrous material the fibers of which are of wet-feltable length, including an adhesive binder therein, collecting said suspension on a foraminous support as a highly aqueous fibrous web, introducing abrasive particles internally of the web while said web is on said foraminous support and while said web is still highly aqueous and uncompacted whereby said abrasive particles are uniformly distributed throughout the thickness of the web, extracting water therefrom to felt the fibers about the abrasive particles, and drying and compacting the felted web to the desired density.
8. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of fibrous material the fibers of which are of wet-feltable length, depositing said suspension on a foraminous support as a highly aqueous fibrous web, introducing abrasive particles into the interior Vof the web while said web is on said foraminous support and while said web is highly aqueous and uncompacted whereby said abrasive particles are distributed throughout the thickness of the web, extracting water therefrom and adding additional abrasive particles thereto at successive intervals during the removal of water therefrom so as to distribute the abrasive particles throughout the interior of the brous web with the bers feltedl about the abrasive particles, applying adhesive to the abrasive-laden web, and drying and compacting the web to the desired density.
Q 9. A method of making flexible fibrous abrasive webs which comprises forming a thin aqueous suspension of iibrous material, the fibers of which are of wet-feltablelength, depositing said suspension upon a foraminous support as a thin felted fibrous membrane, transferring said thin fibrous membrane to a suitable carrier support, similarly forming additional felted fibrous membranes, superimposing said additional membranes upon the initially depoisted membrane,
Yintroducing abrasive particles between the sevsuspension on a foraminous support as a highly 13 aqueous fibrous web, introducing abrasive particles into the interior of the web while said web is on said foramnous support and' while said web is still highly aqueous and uncompacted whereby said abrasive particles are uniformly distributed throughout the thickness of the web, extracting water therefrom to felt the bers about the abrasive particles, and drying and compacting the web to the desired density.
1l. A method of making flexible brous abrasive webs which comprises forming a'thin aquejous suspension of brous material the bers of which are of wet-feltable length', depositing said suspension on a foraminous support as a highly aqueous fibrous web, coating abrasive particles with an adhesive binder, introducing said adhesive-coated abrasive particles into the interior of the brous web While said web is on said foraminous support and while said web is still highly aqueous and uncompacted whereby said abrasive particles are distributed throughout the thickness of the web, extracting water therefrom to felt the bers about the abrasive particles, and drying and compacting the web to the desired density. i"
. JOHN A. WILLIAMSON.l
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 105,320 Eaton July 12, 1870 296,463 Rupp Apr. 8, 1884 305,139 Boynton et al Sept. 16, 1884 305,210 Manseld et al Sept. 16, 18,84
1,463,611- Clapp July 31, 1923 2,027,090 Carter Jan. 7, 1936 2,284,715 Benner-et al June 2, 1942 2,284,716 Bennet et a1 June 2, 1942 2,284,739 Hurst June 2, 1942