BACKGROUND OF THE INVENTION The prior art is replete with abrasive devices made out of some substrate and having abrasive particles or grit secured thereto. See for example: United States Letters Patent Nos.: 3,963, 458 (Gladstone et al.), 3,997, 302 (Supkis), and 4,027, 435 (alloy). One of the most common abrasive devices comprises a paper or plastic sheet or disk on which a plurality of abrasive particles are adhesively secured. Other types of abrasive devices comprise fabrics or non-wovens having a filament structure on which abrasive particles are adhesively secured. See for example, United States Letters Patent No.: 6,287, 353 (Celikkaya) which discloses an open lofty polymer, e. g. , polyester, polyamide, and polyaramid, non-woven filament or fiber structure having abrasive grains distributed throughout the structure and adherently bonded therein by an organic binder.

United States Letters Patent No. 3,947, 169 discloses abrasive-filled plastic rods or tubes as a man-made alternative to natural abrasive filaments. The apparatus of that patent is in the form of extrusion cylinders which are arranged for receiving plastic molding pellets. The pellets may be thermoplastic or thermosetting, are rendered to a semi-liquid state in the apparatus and then a filler, grit, is introduced into the plastic so that the liquid or semi-liquid state of the plastic envelops the filler.

Other arrangements for applying an abrasive coating on fibers or filaments are shown in the following United States Letters Patent Nos.: 4,715, 150 (Takeuchi,

et al.) ; 5,491, 025 (Pihl, et al.) ; 5,571, 296 (Barber, Jr. , et al.) ; 5,591, 239 (Larson, et al.) ; 5,616, 411 (Barber, et al.) ; and 5, 863, 305 (Beardsley, et al.).

While the prior art abrasive devices making use of abrasive fibers and apparatus and methods for producing them are generally suitable for their intended purposes, they still leave much to be desired from one or more of various standpoints, e. g. , ease of manufacture, ease of incorporation into other abrasive products, fineness of abrasiveness, ease and effectiveness of use, etc.

SUMMARY OF THE INVENTION One aspect of this invention is an abrasive filament or fiber that is suitable for use by itself or for incorporation into other structures for abrasive applications.

Another aspect of the invention constitutes methods of making the abrasive filament and the abrasive structures incorporating it.

The abrasive filament has an outer surface to which plural, small size particles of an abrasive material are secured. The filament is formed from a mass of a molten polymer material that has been extruded through a small diameter opening to form a hot elongated filamentary body. The abrasive particles are exposed from the outer surface, e. g. , they are applied as a cloud or spray onto the outer surface of the hot elongated filamentary body, whereupon the abrasive particles adhere to that surface and remain permanently secured thereto when the filamentary body cools to form the filament.

The abrasive filament can be made into abrasive cloths, fabrics or non-woven in accordance with another aspect of this invention. Further still, the abrasive cloths, fabrics or non-wovens can themselves be incorporated into other abrasive devices, e. g. , abrasive cloths can be secured to a surface of a substrate, such as a disk, to form a sanding or polishing disk.

DESCRIPTION OF THE DRAWING Fig. 1 is a schematic diagram of a system constructed in accordance with one aspect of this invention for producing an abrasive filament constructed in accordance with another aspect of this invention; Fig. 2A is a greatly enlarged isometric view of one exemplary embodiment of the abrasive filament produced by the system of Fig. 1;

Fig. 2B is an isometric view, similar to Fig. 2A, but showing another exemplary embodiment of the abrasive filament produced by the system of Fig. 1; Fig. 3 is an isometric view showing a portion of an abrasive cloth or fabric constructed in accordance with another aspect of this invention and utilizing the filament of Fig. 2B (or any other filament constructed in accordance with this invention); and Fig. 4 is a reduced plan view of an abrasive disk constructed in accordance with another aspect of this invention and utilizing the cloth of Fig. 3 (or any other woven, knitted or non-woven fabric constructed in accordance with this invention).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. 1 there is shown at 10 a system for forming an abrasive filament, thread or fiber 20 constructed in accordance with this invention. The abrasive filament 20 is best seen in Figs. 2A and 2B and basically comprises a thin, elongated filamentary member or body 22 that may be in the form of a single fiber <BR> <BR> (e. g. , a mono-filament) or plural fibers or filaments. A plurality of abrasive particles 24 are secured to the filamentary body 22 so that portions of the particles are exposed, e. g. , extend beyond the surface of the filamentary body.

The details of the filamentary body 22 and the particles 24, will be described <BR> <BR> later. Suffice it for now to state that the particles are hard members, e. g. , grit, and can be irregularly shaped or regularly shaped, so long as they exhibit sharp corners and/or edges so that when secured to the filamentary body they provide an abrasive exposed surface. In order to ensure that the particles 24 are securely affixed to the filamentary body, as will be described later in accordance with one exemplary aspect of this invention, they are applied to the filamentary body during its formation, e. g., while it is hot, so that a portion of each particle 24 adheres to the surface of the filamentary body 22 or else is partially embedded therein. This offers various advantages over prior art techniques involving securing abrasive particles to the outer surface of a fiber or filament by means of an adhesive or polymer layer.

The particles 24 can be any type of material used for abrasive applications, e. g. , iron oxide, emery, silicon carbide, aluminum oxide, zirconia alumina and ceramic alumina. The size of the particles 24 used is dependent upon the diameter of the filamentary body 22 and the amount of abrasiveness desired for the resulting

filament 20. In accordance with one exemplary aspect of this invention the particles 24 are quite small, e. g., approximately 10 micrometers or less in diameter. Such particles, when secured to a fine filamentary body, e. g. , a body on the order of approximately 400 denier, enable one to produce abrasive devices that are <BR> <BR> particularly suitable for fine finishing or polishing applications, e. g. , fine finishing of automobile paint. It should, of course, be apparent to those skilled in the art that other sizes of particles and other sizes of filaments can be used in lieu of the above described examples, depending upon the desired abrasiveness and the application to which the abrasive filament will be utilized.

In Figs. 2A and 2B there is shown two exemplary embodiments of filaments constructed in accordance with this invention, the difference being in the diameter of their respective filamentary bodies 22.

The system 10 for carrying out the method of fabricating the filament entails the use of an extrusion device or extruder 11 along with an abrasive particle applicator 12. The extruder 11 is a conventional device that is arranged to receive a polymer, e. g., nylon, for forming the filamentary body 22. Other polymers than nylon can be used. Irrespective of the type of polymer used, it is typically introduced into the extruder in the form of small pellets or other small media particles or granules.

The polymer media is heated in the extruder 11 to cause it to melt, and the molten polymer is drawn out of the extruder through a very small diameter outlet nozzle 13 <BR> <BR> to form an elongated, e. g. , continuous, filamentary body 22. The filamentary body 22 exiting the extruder nozzle 13 is hot and its outer surface is still somewhat molten or at least tacky.

The hot elongated filamentary body 22 exiting the nozzle 13 enters into the abrasive particle applicator 12. In accordance with one preferred aspect of this invention the particle applicator comprises a device having an interior chamber 14 through which the filamentary body 22 is drawn. A conduit 15 is provided to carry a plurality of very small or fine abrasive particles 24 from some remote source (not shown) to the chamber 14. In particular, the fine particles are introduced, e. g., pumped, via the conduit 15 to a spray port 16 in communication with the interior of the chamber 14, whereupon the particles 24 form a dispersed cloud or spray 16 in the chamber 14. Since the outer surface of the elongated filamentary body 22 being

drawn through the chamber 14 is still hot and thus either molten or tacky, the fine particles 24 of the cloud that make contact with that surface adhere to it. In fact, some portions of the of adhering particles may actually be slightly embedded in the hot elongated filamentary body, depending upon the degree to which its surface is molten at the time of adherence. In any case, as best seen in Figs. 2A and 2B portions of the particles 24 project upward from the outer surface of the elongated filamentary body 22. Those projecting portions include sharp corners or edges, thereby producing an abrasive exterior surface. The filamentary body 22 with the adhered abrasive particles 24 exits the applicator chamber 14 and is allowed to cool to ensure that the particles 24 are permanently secured thereto. The resulting abrasive filament 20 can then be reeled up into a reel 17 for subsequent use.

To that end, the filament 20 can be used by itself for extremely fine abrasive applications, e. g. , applications requiring an fine abrasive filament to be pulled through a very small diameter opening or crevice to smooth or polish the contiguous surfaces. A more likely and common application of the filament 20 is for use in forming a woven, knitted or non-woven fabric or cloth exhibiting abrasive properties.

Fig. 3 shows one such application for the abrasive fiber 20 of this invention. In particular, as can be seen therein one or more abrasive filaments or fibers 20 of this <BR> <BR> invention are formed, e. g. , woven, into a flexible fabric 30. The filaments/fibers 20 making up the fabric 30 can be of any diameter desired and can make use of any size abrasive particles desired for the particular application. For fine finishing applications, such as the heretofore mentioned fine finishing of automobile paint, the cloth is formed of nylon fibers of approximately 400 denier and the particles are of approximately 5-10 micrometers. For such applications, the filaments are woven so that relatively large interstitial spaces 32 exist between adjacent fibers 20 to render the fabric 30 breathable, e. g., enable air to pass freely therethrough, and resistant to clogging. These open interstitial spaces 32 enable the abrasive fabric 30 to be able to temporarily hold debris or dust produced by the use of the fabric, without clogging or otherwise detracting from the abrasion/polishing application.

Moreover, any debris that finds its way into the interstitial spaces, can be readily removed by either shaking the fabric or by vacuuming it, thereby enabling long term use of the abrasive fabric. Further still, as will be appreciated by those skilled in the

art, breathable abrasive fabrics 30 constructed in accordance with this invention are particularly suitable for wet sanding applications, such as finishing coats on automobiles or other hard surfaces that need a very high end finish, since water will be held within the interstitial spaces as the fabric is used.

It must be pointed out at this juncture that the woven fabric 30 as described above is merely exemplary. Thus, abrasive fibers of this invention can be woven into tighter fabrics than that shown and described above. Moreover, such fabrics need not be woven, but can be knitted or otherwise formed of intersecting or interconnected fibers, such as by knitting. In fact, the fabric may be in the form of a non-woven, constructed of short sections of abrasive fibers that are entangled with one another to form a flexible sheet.

Irrespective of the make-up of the fabric 30, the fabric itself may be incorporated into an abrasive device or structure. For example, as shown in Fig. 4, a sanding or polishing disk 40 may be constructed in accordance with this invention by providing a disk like substrate, e. g. , a plastic disk having a foam surface (not shown), to which a circular section of a cloth 30 constructed in accordance with this invention is adhesively secured.

It should be pointed out at this juncture that while the filaments or fibers 20 of this invention are preferably formed by extruding a polymer into a filamental body and applying abrasive particles or grit to the surface of that body while it is still hot, that process is not exclusive. Thus, the subject invention contemplates mixing or introducing the abrasive particles into the mass of molten polymer so that the particles are in situ when the filament is extruded. In such an application, portion of the particles contiguous with the surface of the filament will be exposed to produce the desired abrasive surface.

Without further elaboration the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, adopt the same for use under various conditions of service.