US 2770928 A
Description (OCR text may contain errors)
w. K. VAN ORMER Erm. 2,770,928
Nov. 20, 195.6
ABRASIVE ARTICLE F'iled June 15, 1951 INVENTOR.
I/VILLAM K. VAN ORME?? JOSEPH B.AUST
ATTORN N0V- 20, 1956 w. K. VAN ORMER ErAL 2,770,928
ABRAsIvE ARTICLE Filed June 15, 195] 3 Sheets-Sheet 2 IN V EN TOR.
WILLIAM K. VAN ORME R JOSEPH B. AUST ATTO E Y NOV- 20, 1956 w. K. VAN ORME-:R ErAL 2,770,928
ABRAsIvE ARTICLE Filed June l5. 1951 5 Sheets-Sheet .'5
GRAMS OF' STOCK REMOVED .PER 3 MINUTE INTERVAL.
l 2124 Z7 30 33 36 39 42 45 46 5l 54- TIME JN MINUTES FIG. 9
INVENTOR. WILLIAM K VAN ORME'R JOSEPH .B.AU.ST
ATTOR E Y United States Patent O ABRASIVE ARTICLE William K. Van Omer and Joseph B. Aust, Niagara Falls, N. Y., assignors to The Carborundum Company, Niagara Falls, N. Y., a corporation of Delaware Application `lune 15, 1951, Serial No. 231,744
9 Claims. (Cl. 51-195) This invention relates to abrasive articles of manufacture such as abrasive discs, belts, bands, wheels and other forms of abrasive articles.
Abrasive products can be usually classified or identified with one or the other of two broad classifications of abrasive products, namely, those belonging in the field of bonded abrasive bodies of the grinding wheel type consisting of a substantial bulk of abrasive grains and bond and those belonging in the field of coated abrasives of the sandpaper type in which a substantially single layer of abrasive grains is adhesively secured to a flexible backing material. Each of these types of abrasive products has certain advantages not possessed by the other type as well as certain limitations.
ln the manufacture of bonded abrasive articles of the grinding wheel type the individual abrasive particles are bonded together by means of an organic or inorganic binder, the desired body being formed by mixing the abrasive grains and bond together to form a molding mixture which is then pressed or otherwise formed into a solid mass of material of the desired shape. The article is then heated or fired to mature the bond and form the desired solidified rigid mass which is then usually dressed to size. The resulting rigid body of abrasive material is either cemented or bolted to a steel backing plate or other support or mounted conventionally on a machine shaft or spindle with appropriate bushings or flanges and operated at relatively high speeds to perform the desired abrading operation.
The strength of the bonded abrasive body is dependent to a great extent upon the strength of the fired or cured bonding material and is controlled within certain limits by the amount by weight and volume of the bonding material in relation to the total weight and volume of the bonded abrasive body. The resultant article is rigid, non-flexible and normally quite brittle and therefore requires careful testing before use. Precautions must be taken in respect to its mounting and use in order to provide the maximum degree of safety during its operation at relatively high speeds. The inherent rigidity, accompanied as it is by a relatively high degree of brittleness or fragility, greatly restricts the scope of application of such articles.
However, products of the grinding wheel type offer the prime advantage of having relatively long operating lives. A further advantage is the relatively high rate of breakdown or expendibility which can be tolerated in view of the availability of a substantial amount of abrasive material in the article, and is often desirable to promote a high rate of cut. The rate of wear-ability or breakdown is dependent largely upon the bond structure of the body which sometimes is rendered porous by the incorporation of filler materials which are volatilized or burned off during the maturing of the bond, particularly in wheels which are designed for fast cutting operations and relatively rapid wheel breakdown is desired. A grinding wheel which cuts fast is referred to as a sof wheel and wears away relatively rapidly. However, pro- 2,770,928 Patented Nov. 20, 1956 ICC motion of the porosity and rate of cut of a Wheel in the above manner has its limitations since it is accompanied by a lowering of wheel strength and life.
In contrast to abrasive products of the grinding wheel type which are extremely hard, rigid and inflexible in character and have relatively long operating life, abrasive articles of the coated type consist of a substantially single layer of abrasive grits adhesively secured to a exible backing and, as a result of the relatively small amount of abrasive particles available in the article, the products have a relatively short life with a very high rate of stock removal. Consequently, the cost of various backing materials in such products must be kept to a minimum in order that the overall cost of the product does not become so great as to nullify the advantages gained from the flexibility and versatility of the products derived therefrom. Attempts to extend or prolong the life of coated abrasive products by the use of heavier coatings of abrasive material in conjunction with the use of extra heavy or more durable backings have never proven satisfactory since such products have tended to become dull and glazed regardless of coating thickness and often break down excessively due to the premature separation of the abrasive coating from the backing.
It is an object of the present invention to provide abrasive articles which combine to a large extent the long operating life and durability of abrasive articles of the grinding wheel type with certain elements of versatility and flexibility previously found only in abrasive articles of the coated abrasive or sandpaper type.
It is a further object to provide a type of abrasive article which can be made with any desired degree of rigidity or flexibility.
lt is a further object to provide abrasive products having a relatively substantial mass of abrasive material embodied in the article without total loss of flexibility characteristics.
It is a still further object to provide an abrasive product in which a substantial mass of bonded abrasive material is embodied in the article and secured to a supporting structure in such a manner that the abrasive mass is substantially fully expendable without premature disruption or dislocation from its support.
These and other objects and advantages accruing from the present invention will become apparent as the description proceeds.
In order that the invention may be more fully understood, reference is made to the drawings which are offered by Way of illustration only, are not intended to restrict the invention in any way to the specific articles shown, and in which,
Figure l is a top plan view of an abrasive disc made in accordance with the present invention,
Figure 2 is a vertical, diametrical cross-sectional view through the line 2--2 of Figure l,
Figure 3 is a vertical, sectional view through an endless abrasive belt made in accordance with the present invention,
Figure 4 is a vertical, diametrical sectional view through a cup-shaped abrasive wheel made in accordance with and embodying various features of the present in vention,
Figure 5 is a view similar to that of Figure 2 of a modified form of abrasive disc embodying features of the present invention,
Figure 6, likewise similar to Figure 2 in view, shows a still further modification of the invention,
Figure 7 shows certain structural details of the textile anchoring 'layer and vertical pile members embodied in the disc structure shown in Figure 2 and the belt structure shown in Figure 3,
Figure 8 shows a top plz-1n view of a modified form of abrasive disc; and
Figure 9 is a graph showing graphically the grinding results obtained with products of the present invention as compared to conventionally prepared coated abrasive articles and bonded articles heretofore used for the same purpose.
We have found that abrasive articles such as abrasive discs, wheels, belts, bands and other shapes can be made in accordance with and embodying various features of the present invention so as to combine the long life and durability characteristics in many respects found in abrasive articles of the grinding wheel type with that lexibili-ty and dependent versatility of application heretofore found only in coated abrasive products. The inventiort is not intended to be limited to the specific articles illustrated in the various figures of the drawing since it is applicable to the construction of numerous forms of abrasive articles commonly known and used in the art including such articles as:
l. Abrasive bands and belts for operating over either drums or pulleys and back-up plates,
2. Abrasive discs for use with or without auxiliary backup supports,
. Cup wheels,
. Annular type snagging wheels,
. Ring and recessed wheels of various types and sizes,
. Flexible polishing wheels; and
. Blocks and shapes adapted for use on expanding chucks such as those shown in U. S. Patents Nos. 2,207,439 and 2,264,589.
Abrasive articles of the present invention, regardless of their specific form or shape, are provided with a layer of bonded abrasive material of substantial thickness and are further characterized by having a multitude of spaced pile members extending through the mass of bonded abrasive substantially to the grinding surface with the lower ends of the pile members anchored in the base layer of the article in any one of a variety of ways. The article is further characterized in that the bonded abrasive mass provides a substantially continuous or solid grinding surface with no deep, irregular depressions` between the spaced pile members contained therein. The. reinforcing pile members can be of any material of organic or inorganic nature and can be single or multiple strands, either straight, crimped or looped members, and either lamentary or fibrous in character. For example, the spaced pile members can be composed of various textile fiber cord materials, such as corded cotton fibers, corded wool fibers or other animal or vegetable fibers, or lilamentary materials. The pile members can also be composed of any of the numerous synthetic organic materials now available in either fibrous or lamentary form, such as the polyamide fibers or filaments known and sold by E. I. du Pont de Nemours and Company of Wilmington, Delaware, under the generic trade name of nylon, the vinylidine chloride polymers in fibrous or filamentary form such as those known and sold by Dow Chemical Company of Midland, Michigan, under the trade name of Saran fibers or filaments, or by Firestone Plastic Company of Pottstown, Pennsylvania, under the trademark name of Velon fibers or filaments, the zein protein fibers known under the trademark name of Vicara fibers and sold by the Virginia-Carolina Chemical Corporation, Fiber Division of Taftville, Connecticut, the viscose rayon fibers sold by E. I. du Pont de Nemours and Company under the trade name of Cordura fibers, or the polyacrylonitrile fibers sold by the same company under the trade name of Orlon" fibers. or other organic resinous fibrous or tilamentary materials. The pile members can also consist of an inorganic filament or ber such as a cord or rope composed of glass or rock wool fibers or filaments such as those known and sold by Owens-Corning Fiberglas Corporation of Toledo, Ohio as Fiberglas products.
These pile members which extend through thc mass of granular abrasive material and are an essential feature of articles made in accordance with the present invention are anchored at their lower ends in any one of a variety of ways. For example, the pile members can be secured in the base of the bonded abrasive layer by being set or anchored in a solidified layer of adhesive or binder which is preferably of the permanently liexible or resilient type such as a rubber base adhesive or a coagulated latex adhesive composition. Also various resinous binders of a naturally and permanently flexible type, or a resinous bond which retains its strength under and after mechanical flexing, can be used. The anchoring layer of the article instead of consisting of a layer of adhesive or binder may be, and preferably is, constructed of one or more courses of interwoven warp or braid strands of textile fibrous material which is in turn reinforced and held together by being impregnated with a suitable adhesive, usually of the resilient type, such as a latex or rubber base adhesive composition. Where reference is made to the use of a latex or rubber base adhesive in the anchoring layer it is intended to include` not only natural rubber latex or natural rubber base adhesives, but also those various synthetic latices or rubber compositions available such as the butadiene type synthetic rubbers, polychloroprene, and the like. When a layer of textile material is used in the anchoring layer the vertical pile members are anchored therein, such as by being looped through one or more of the courses of warp strands with the free ends of the vertical pile members extending or protruding above the fia-t surface of the anchoring layer into the bonded abrasive mass which is superimposed thereon. Another mannel: of providing a plurality of spaced, vertical pile members anchored in a warp or braid strand heading or base is by interweaving a. continuous cord or strand through one or more courses of the base layer with loose loops of the cord or strand` pulled up and projecting in a loo-p above thev upper face of the` base layer at selected intervals. This anchoring layer is usually, although not necessarily, backedup or supported by a further backing layer of flexible nature such as a rubber or latex impregnated sisal fiber backing, a thin sheet oli spring steel, vulcanized fiber backing, or the like.
A further and specific modification of the present invention consists in the provision of an article of the above-described type in which a combination of vegetable or anirnai pile members with pile members of a more heat resistant character, such as pile members of synthetic resinous material such as nylon" or "Saran" are incorporated within the bonded abrasive layer. Also, combina-tions of any organic fiber can bc used in conjunction with inorganic glass or mineral fibers. The ratio of animal or vegetable fibers or other organic fiber pile members of low heat resistance to Velom "nylon, glass or other more heat-resistant pile members can range all the way from 5% to 95% of one to 95% to 5% of the other, or any intermediate combination o1 tw'o or more fibrous or flamentary materials. During thel cure of' an article embodying a combination of two or more materials as pile members the less heat resistant pile members disintegrate to provide relatively weak areas iir the' bonded abrasive mass whereby those arcas of the. overall structure tend to break dcwn more rapidly than adjoining areas. The remaining fibers et more heat resistant character break` down later during the grinding` operation without interfering. with the cutting ability of the article although at the same time they would remain in the body of the abrasive mass as a reinforcing and strengthening element. By the use of such composite mixtures of vertical pile members it is possible to provide a wide range of different desirable cutting characteristics depending upon the type and condition of use to which the article is to be put.
In practicing the invention, any of the abrasive materials in common use may be employed, such as granular silicon carbide, diamonds, boron carbide, fused aluminum oxide, flint, corundum, emery, rouge and similar substances. Another specific, and relatively new, product which can be used as the abrasive material in articles of the present invention is a foam, or cellular, glass in granulated form. Regardless of the kind of abrasive used, the size of the abrasive particles may vary from the finest polishing or buffing powders to the coarser grit sizes used in grind- The abrasive particles can be bonded with any suitable bond which can be matured at temperatures which will not destroy the vertical pile members which are to remain in the finished article as a permanent part thereof and which function to preserve the integrity of the article over its intended life or until the abrasive layer has been usefully expended. Very satisfactory results have been obtained usefully expended. Very satisfactory results have been obtained with the use of thermosetting phenolic condensation product resins, including those specifically set forth later herein in connection with the various examples. However, other organic binding materials, all of which can be modified by the inclusion of suitable catalysts or vulcanizers, inert and reactive fillers, and other modifying agents as desired, can be used.
Among the organic resins which can be used are melamine-formaldehyde resins and analogs thereof, ureaformaldehyde resins and analogs thereof, thiourea-formaldehyde resins and analogs thereof, furane resins, anilineformaldehyde resins, thermosetting alkyd resins, thermosetting polyesters such as diallyl phthalates, diallyl carbonates, styrene and maleic anhydride-glycol adducts, and the like, and thermosetting bisphenol-epichlorohydrin resins and analogs thereof. The thermosetting bisphenolepichlorohydrin resins are especially useful where it is desired to form a bonded abrasive mass in which the bond will set to a hardened condition at room temperature without the application of heat.
Other substances which can be used as the bond for the abrasive particles include shellac, natural rubber and the various synthetic rubbers, such as butadiene-styrene copolymers, butadieneacrylic nitrile copolymers, polychloroprene and the like. An inorganic bond which can be used is an air-setting hydraulic cement such as magnesium oxychloride.
The various materials set forth above as bonding substances for the abrasive particles can be used in the form of suitable liquids, solutions, emulsions, or dispersons, depending upon the form in which the bonding material is most economically available.
Referring further to various figures of the drawing, Figures 1 and 2 depict an abrasive disc consisting of a layer 8 of bonded granular abrasive material of substantial thickness, as for example in the order of magnitude of M3" in thickness, adhesively secured to a textile anchoring layer 9 which in turn is adhesively bonded to a backing 10 of latex-impregnated sisal fiber. The bonded abrasive layer 8, as shown in Figure l, has a plain continuous flat upper grinding surface 12. However, the disc can be modified, when desired, by pressing the abrasive layer with a top plunger having a gridded surface whereby the upper grinding surface 12 of the abrasive layer S is provided with a plurality of shallow annular grooves 13 and a plurality of radial grooves 24, such a modified form of disc being illustrated in Figure 8.
Referring to Figure 7 for further details of the textile layer 9 it can be seen that this element of the article which can be referred to as the anchoring layer or heading comprises a single course 11 of interwoven warp or braid strands of textile fibrous material such as cotton strands which are spirally wound and impregnated With a latex adhesive composition to form an annular resilient supporting surface for the bonded abrasive layer and also as a means for mechanically anchoring the vertical pile members 14 which, as shown in Figure 7, are looped through the layer of interwoven textile warp strands with the free ends 15 extending vertically above the anchoring layer of warp strands a distance substantially equal in thickness to the thickness of the bonded abrasive layer` As clearly pointed out these vertical pile members can consist of any organic or inorganic fibrous or filamentary material, or combinations of one or more organic fibrous or filamentary materials with one another or with inorganic fibrous or filamentary materials. The central or arbor portion of the abrasive disc shown is further reinforced by a centrally positioned disc 16 which is also of latex-impregnated compressed sisal fibers. The abrasive disc is provided with a mounting arbor hole 17 of suitable diameter for mounting upon the driving spindle or shaft of the machine upon which the abrasive disc is to be used. The vertical pile members 14 not only strengthen and reinforce the bonded abrasive layer of the article throughout its thickness but, anchored as they are in the textile base layer 9 of the article, they also serve to prevent disruption or dislocation of the bonded abrasive layer from its supporting base or anchoring layer during the use of the article. The inherently flexible and resilient character of the backing 10 and the anchoring layer 9 provide in the finished product a degree of flexibility and resilience utterly lacking in a conventional abrasive article of the grinding wheel type while at the same time the substantial thickness of bonded abrasive material provided in the article provides a useful life far exceeding that to be found in similar abrasive articles of the conventional coated abrasive type.
Figure 3 shows an endless abrasive belt consisting of a licxible backing 18 to which is bonded a textile anchoring layer 19, which latter layer comprises a single course of interwoven textile warp or braid strands similar to the warp strand course embodied in the anchoring layer of the disc of Figures l and 2. This warp strand anchoring layer is impregnated with a latex base adhesive which secures the anchoring layer to the backing 18 and also provides additional strength and resilience to the anchoring layer itself. A multitude of spaced vertical pile members 20 of twisted nylon cords are looped through the warp strands in a manner such as that shown in Figure 7 and extend above the top surface of the anchoring layer. The space between the vertical pile members 20 is filled with a thick layer 21 of bonded abrasive material such as a mixture of abrasive branules and phenolic resin bond. Before use the belt is fiexed over a small diameter steel rod or bar to fracture the coating of abrasive material 21 transversely of the belt in a plurality of places 22 so that the abrasive belt can be rotated upon a drum or set of pulleys although at the same time the belt presents a substantially continuous grinding surface 23 to the work to be abraded. Each fragment of the belt however contains a number of vertical pile members which act as a reinforcement for the abrasive material and also as a means of securing the separate fragments of the abrasive coating against shearing away from the anchoring layer.
`Figure 4 shows a cup wheel which is composed of a bonded abrasive body 25 reinforced by a multitude of spaced vertical pile members 26 which are anchored in a textile anchoring layer 27 which is in turn cemented to the mounting hub 28. The mounting hub, which can be of aluminum or other metal, a molded resin body, or other suitable structural material, is provided with a screw threaded arbor hole 29 suitable for mounting the abrading device upon a spindle or shaft. The textile anchoring 'layer 27 is composed of a single course of interwoven warp or braid strands similar .to the structure shown for the anchoring layer of the abrasive belt pictured in Figure 3. However, it may consist of one or more courses of a coarsely woven textile fabric such as glass `fiber fabric, burlap, canvas, or the like, through 7 which the pile members 26 are needled or looped to anchor them in the tex-tile layer.
Figure 5 shows a modified form of abrasive disc in which the bonded abrasive body 31 extends over the entire upper face of the disc, and in which the spaced vertical pile members 312 are anchored in an anchoring layer 33 of a rubber base adhesive by which the bonded abrasive body is adhesively secured to the backing or support 34.
Figure 6 shows a still further modification of the invention in the form of an abrasive disc in which the abrasive body 36 is reinforced by vertical pile members 37 which are anchored in a base layer 38 of latex-impregnated interwoven textile warp strands similar to those described for Figures l and 2. This particular modification of the invention is for use in conjunction with a separately provided back-up pad or plate and therefore is not provided with a backing support as a permanent part ofthe article.
Abrasive articles of the above-illustrated type, as for example the abrasive disc shown in Figures l and 2 have been made in the following manner.
Example I A disc shaped base was provided consisting of an anchoring layer or heading of a single interwoven, spinally laid course of cotton warp strands which is impregnated with latex and thereby cemented to a l/s" thick lateximpregnated sisal fiber backing. The anchoring layer had a plurality of spaced vertical pile members consisting of 50% twisted cotton fiber cording and 50% twisted Saran ber cording looped through the interwoven strands of the warp or braid strand course and spaced approximately 1A from one another circumferentially and `about 1,56" from one another radially of the disc, although any other desired degree of spacing of the pile members, either more open or closer together, may be employed, if desired. The vertical pile members extended approximately Ida above the upper face of the warp strands. thus provided was dip-sized with a low-viscosity, phenol formaldehyde liquid resin containing 1/i% of a wetting agent. One suitable phenol formaldehyde liquid resin found suitable for sizing was that known and sold by the Bakelite Corporation of Bloomfield, New Jersey, under the trademark designation of Bakelite No. BR10190 resin. A suitable wetting agent is that known and sold under the trademark name of Span 20 by Atlas Powder Company of Wilmington, Delaware. Span 20 is otherwise identified as sorbitan monolaurate. disc was then placed in a die mold and an abrasive mixture of the following composition applied to the top surface of the disc in suicient quantity to till the space between the spaced vertical pile members and levelled off iiush with the tops of the vertical pile members:
Grams LowLv-iseosity, phenol formaldehyde liquid resin A surface coating of loose abrasive grain of the same grit size and character was applied to the top surface of the abrasive coated disc after which the disc was placed under light pressure sufficient to seat the entire abrasive mass trmly. The disc wasthen placed in an oven and subjected to the following heat treatment to mature the resinY bond: 2'4 hours at 135 F., 2 hours at 150 F., 18 hours at 175 F., 2 hours at 185 F., 18 hours at 200 F., 2 hours at 225 F., l2 hours at 250 F., 3*/2 hours at 275"V F., and 4' minutes at 375 F. The oven The upper surface of the anchoring layer as The sized was then allowed to cool to room temperature and the `abrasive disc removed ready for use.
Example II Abrasive discs of the type shown in Figures l and 2 have been made as follows: A disc shaped base of the type described in Example I was provided, the sole difference being that the spaced vertical pile members consisted entirely of twisted cottonl cording, although the pile members were spaced the same as those in Example l. The upper or piled surface of the heading was first dip-sized with a low viscosity, phenol formaldehyde liquid resin such as that used for the same purpose in Example I. The sized disc was then placed in a mold `and an abrasive mixture of the following composition applied to the top surface of the disc and rolled into the spaces or recesses between the pile members in increments until the pile members were covered with suicient abrasive-bond mixture to bring the top surface of the mass, when levelled off, flush with the tops of the vertical pile members.
Grams Low viscosity, phenol formaldehyde liquid resin (such as that known and sold under the name Bakelite BR10190) 341 Calcium carbonate 426.4 Ethylene glycol 76.7 Sorbitan monolaura'te (such as that known and sold as Span 20) a 3.8 24 grit size, fused aluminum oxide abrasive grain-- 935 The disc was pressed at 4000 pounds per square inch and pla-ced in an oven and subjected to the following heat treatment to mature the resin bond: 6 hours at 130 F., l5 hours at 150 F., 6 hours at 170 F., 2% hours at 185 F., 18 hours at 200 F., 12 hours at 225 F., 6 hours at 250 F., and 3% hours at 275 F. Temperature taken to 350 F. after which the oven was allowed to cool to room temperature immediately and the discs removed ready for use.
The resulting abrasive disc made as above-described was used to grind welds from metal surfaces with the following results. The disc was operated for a total grinding time of 69 minutes during which time a typical abrasive disc removed a total of 4345 grams of metal with a disc weight loss of 335.9 grams. This can be cornpared to the results obtained with a conventional 24 grit size resin bonded sander disc made by prior art methods in which the disc was operated for a total time of 21 minutes before failure with a total metal stock removal of 715 grams. A cup wheel removed 3392 grams of metal in 54 minutes at a rate of 62.7 grams per minute and a wheel loss of 906.5 grams at 5400 R. P. M. The grinding results obtained with an abrasive disc made according' to Example II as compared to the grinding results ob tained with a conventional resin bonded abrasive coated disc of the same abrasive grit size and a resin bonded cup wheel are shown in Figure 9. As the graph shows, the life of the sander disc (see curve A of graph) is inordinately short as compared to the period of usefulness shown by an abrasive disc made according to the present invention (see curve B of graph) and even compares favorably with the long life of the rigid bonded cup wheel (see curve C of graph). The actual cutting rate of the abrasive disc as herein made is also noted as being remarkably high, averaging 63 grams of metal removed per minute over the entire 69 minutes grinding period of the test. The remarkably longer life and durability of discs made in accordance with the present invention as compared to conventional abrasive coated discs heretofore used for the same purpose is outstanding.
inasmuch as the term braided is sometimes narrowly construed to refer to a type of cording made up from a plurality of intertwined strands, it is to be pointed out that where the term braided" is used herein it is intended to refer not only to cording made up from a plurality of intertwined strands, but also to cording made up from a single strand interlockcd with itself in such a manner as to form a cording of braided appearance, such as that shown in Figure 7.
Having described the invention it is desired to claim:
1. An abrasive disc comprising a backing and a substantially continuous layer of bonded abrasive material secured thereto, said backing comprising a base layer, a textile ber layer comprising at least one spirally wound braided strand forming an anchoring laycr upon said base layer and adhesively bonded thereto, and a multitude ot spaced vertical reinforcing pile members passing through said braided strand and extending into the aforesaid layer of bonded abrasive material.
2. An abrasive disc comprising a backing and a substantially continuous layer of bonded abrasive material secured thereto, said backing comprising a base layer of latex-impregnated sisal fiber, a textile ber layer comprising at least one spirally wound braided strand forming an anchoring layer upon said base layer and adhesively bonded thereto by means of a latex base adhesive, and a multitude of spaced vertical reinforcing pile members passing through said braided strand and extending into the aforesaid layer of bonded abrasive material.
3. An abrasive article comprising (a) a backing, (b) an anchoring layer comprising at least one course of textile iber braided strand adhesively impregnated and bonded to said backing by means of a ilexible rubber base adhesive and containing a plurality of vertically extending spaced textile ber reinforcing pile members secured therein with the free ends projecting above the top surface of said anchoring layer, and (c) a layer of resin-bonded abrasive material imposed upon said anchoring layer and filling the space between said spaced pile members so as to form a substantially continuous grinding face.
4. An abrasive article comprising a composite back ing comprising a exible sheet backing material and an anchorng layer of textile braided strand impregnated with a resilient latex base adhesive, said anchoring layer having a plurality of spaced reinforcing pile members anchored therein with the free ends extending vertically therefrom, `and a substantially continuous layer of phenolic resin-bonded granular abrasive material bonded to said anchoring layer and of a thickness at least coextensivc` with the height of said pile members.
5. An abrasive article comprising a composite backing comprising a flexible sheet backing material and an anchoring layer of interwoven textile material impregnated with a resilient latex base adhesive, said anchoring layer having a plurality of spaced reinforcing pile members anchored therein with the free ends extending vertically therefrom, and a substantially continuous layer of resinbonded granular abrasive material bonded t-o said anchoring layer and of a thickness at least coextensive with the height of said pile members.
6. An abrasive article according to claim 5 in which the vertical reinforcing pile members are nylon cords and the textile material is a cotton fabric.
7. An abrasive article according to claim 4 in which 5% to 95% of said pile members are of heat resistant organic thermoplastic material and to 5% of said pile members are of natural organic fibrous material.
8. An abrasive disc comprising a backing, a substantially continuous layer of bonded abrasive material secured thereto, and a multitude of spaced vertical reinforcing pile members extending into the layer of bonded abrasive material, said backing comprising a single spirally wound braided strand, said pile members passing through said braided strand.
9. An abrasive disc comprising a backing, a substantially continuous layer of bonded abrasive material secured thereto, and a multitude of vertical reinforcing pile members extending into the layer of bonded abrasive material, said backing comprising at least one spirally wound braided strand, said pile members being spaced approximately 1A inch from one another circumferentially and about 1,46 inch from one another radially of the disc and passing through said strand.
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