US2309305A - Abrasive article - Google Patents

Description

Jan. 26, 1943.

E. PQDAHLSTROM ET AL ABRASIVE ARTICLE Filed March 10, 1941 INVENTORS. ERIC. PJDAHLS'TROM EDGAR HORNE ATTORNEY Patented Jan. 26, 1943 amusrvn ARTIC E Eric P. Dahlstrom, Niagara. Falls, N. Y., and Edgar Horne, Niagara Falls, Ontario, Canada, assignors to The Carborundum Company, Niagara Falls, N. Y., a corporation of Delaware.

Application March 10, 1941, Serial No. 382,520

6 Claims. (Cl. 51-188) This invention relates to endless abrasive belts formed from strips of flexible, abrasive coated,

web material. More particularly the invention is concerned with methods of joining the ends of the abrasive strips together and to the product resulting from such methods.

Heretofore abrasive belts have been formed by splicing, i. e., by overlapping and joining, the ends of a strip of coated abrasive with a suitable adhesive between the laps. Usually the abrasive coating is removed from one end of the strip by grinding-an operation referred to in the art as skiving--- and the opposite end of the strip placed upon and adhered. to the skived area. Such splices are thicker than the abrasive strip and as a result undesirable effects are brought out by thisthicker portion as the belt is used. For example, there is a pounding action which separates the work momentarily from the abr'ading surface at each revolution of the belt and reduces the contact time and cutting efficiency; furthermore, the pounding of the thicker splice portion is objectionable as it causes difliculty in generating flat surfaces at the boundaries of the work piece, and the excessive thickness encourages premature belt breakage at the splice.

Belts of uniform thickness have been made by butt-joining the ends of an abrasive strip and at the same time adhering this strip to an inner, non-abrasive strip or liner, but this construction the use of a full length of liner material plus the quantity of adhesive necessary to join the liner and the abrasive strip. 7

a is more expensive than a plain belt as it involves I It is therefore included in the objects of this invention to provide a belt splice which is inexpensive, of the same thickness as the belt proper, and of sufficient strength and flexibility to function for all the purposes for which the belt' is intended. These requirements are more difllcult of attainment because modern industrial uses demand larger belts than heretofore; many belts from 28" to wide, and from 6 to'22 feet long are supplied. These large belts are used extensively in the polishing and surfacing of stainless steel. There are, nevertheless, important uses for smaller sized belts-approximately 4" wide-as in wet sanding automobile bodies and fenders wherein there must be a perfect splice in order not to streak or otherwise mar the work.

The present invention .provides a superior splice for joining-the ends of flexible coated abrasive strips toiform abrasive belts and discloses in adequate detail methods of manufacture enabling those skilled in the art to practice the invention.

Referring to the drawing:

Fig. 1 shows an enlarged longitudinal crosssection of a strip of abrasive coated web with the abrasive removed for a, small distance back from the end; directly over this abrasive-bared portion is a cross sectional view of an abrasive wheel used for skiving off the abrasive.

Fig. 2 is a fragmentary diagrammatic plan view of an end portion of a coated abrasive strip in position for beveling the abrasive-cleared end area, and the abrasive wheel to be used for beveling.

Fig. 3 is longitudinal, similarly enlarged crosssection of the abrasive strip shown in Fig. 1 after having been beveled by an abrasive wheel a fragmentary cross-section of which is shown above the beveled end of the strip.

Fig. 4 is a longitudinal enlarged cross-section of the beveled end of the opposite end of the abrasive-coated strip shown in Figs. 1 and 3; theabrasive wheel for beveling is shown in fragmentary cross-section directly below the beveled. end of the strip.

Fig. 5 is a longitudinal, enlarged cross-section of the mating beveled ends of a belt, with adhesive coating, but prior to final splicing. I

Fig. 6 is a longitudinal, enlarged cross-section of a completed splice.

Fig. '1 is a top plan view of the completed splice shown in Fig. 6.

Fig. 8 is a vertical section of belt in position on a curved splice-drying support.

As an illustrative embodiment of this invention, the preparation of a spliced abrasive belt in accordance therewith and the necessary materials, adjustments, process steps, etc., are described below.

The coated abrasive web material is prepared by any desired process. The more common form would be that of adhesively securing abrasive granules such as flint, garnet, silicon carbide, fused alumina or other natural or manufactured abrasive to one surface of a sheet of strong rope or manila paper althoughother felted fabrics or woven cloth can be used. In the majority of cases the fibrous web contains a sizing material for additionally bonding the fibres or for imparting either firmness or flexibility, or for waterproofing purposes. The adhesive bonding agent may be glue, silicate, synthetic resin, varnish, lacquer, etc., the choice depending upon such factors as intended use, cheapness, strength, flexibility, resistance to cooling liquids and so direction.

abrasive web material described above. diiferent figures, like numerals refer .to and on.. The coated abrasive material is dried to set the adhesive bond and in many cases heat and forced air circulation are used to facilitate the process. 'With a glue bond it is usually con- 7 ceded that a superior cutting product is obtained after the freshly dried material has aged for a number of weeks, and that certain processing steps such as splicing are scarcelyfeasible to attempt with non-aged material. This invention, however, makes it possible to splice quite freshly made coated abrasive, at least as early as ten days after its manufacture.

The coated abrasive material is slit into appropriate widths and then cut .to length. This cut is usually made at an acute angle .to the lengthwise direction of the strip as shown in Figs. 2 and '7, but this is not a limiting condition as the out could be made'normal .to the lengthwise Reference is made to the drawing for a better understanding of the method of preparing and forming the splice or joint by which endless abrasive belts are formed from the strips of coated In the the strip passed beneath the wheel. The skived or abrasive-cleared area 3 is conveniently made about one-half an inch-wide for an average belt. A 40 grit vitrified bonded fused alumina wheel of a medium hardness grade is well adapted to perform this operation. The grinding face 6 of the abrasive wheel is dressed parallel to the axis of rotation.

Figure 2 presents a plan view of the method of carrying out the beveling operation and Figure 3 shows aside view of the beveling operation with the beveling wheel slightly raised from its position in grinding, and further shows a crosssection of the finished, beveled area, which has -'been slightly enlarged to more clearly show the slope of the newly beveled surface I. This illustrates the effect of traversing the skived area 3 of Figure 1 with a bevel-faced abrasive wheel 8. Assume for illustration that supporting web I is 0.010" thick and the distance AB is approximately one-half inch. Since there is a finite yet 1 very small thickness of web at the end B after the beveling operation this thickness has been taken as 0.001"; micrometer measurements indicatethis to be reasonably'accurate. The thickness -of the web at A after bev'eling is about 0.009", hence the included angle in this specific instance is 0 55'. Entirely contrary .to the normal expectation it has been discovered that the wheel edge 9 of the abrasive wheel 8 in Figs. 2 and 3 must be dressed to an angle of bevel slightly greater than, the desired angle C to be produced on the surface-3 of the abrasive coated strip. For example, the abrasive wheel 8 has had its grinding edge 9 dressed to make an angle 1 23' out of parallel with the axis of wheel totation. It has been found that a single passage and return of such a wheel edge will produce the desired angle C of the bevel. A wheel which has been found to perform this operation-successfully on supporting webs for coated abrasives is made of sharply angular white fused alumina grit, compacted to a very open porous structure, and vitrified bonded with a very low percentage of bond to yield an exceedingLv soft grade hardness. The wheel is rotatedat about 5000 surface feet per minute and traversed across the work surface at a rate of 3 inches per second. This rate can be modified within reasonable limits, for example, as slow'as one and one-half inches per second, or as fast as four and onehalf inches per second. Any considerable departure from these limits causes glazing and burning,if too slow, or tearing, if too fast.

The opposit end of the abrasive strip 4 is now beveled as illustrated in Fig. 4 to form the same angle C as shown in Fig. 3. In this operation it has been found essential to perform the abrading with the same wheel edge angle as used to provide the beveled surface I of Figure 3; in practice it is customary to use the identical wheel for the process.

While Figures 1 to 4 have shown the preferred method of preparing the end portions for splicing it is not desired to limit the invention to the precise operations so depicted in detail. For example, without departing from the scope of the invention the skiving operation of Figure 1 may be combined with the beveling operation of Figures 2 and 3. Also, instead of using an abrasive wheel such as that shown in Figures 2 and 3 having a beveled grinding edge 8 it is permissible to support the abrasive strip 4 upon a table H or other suitable support which by adjustable means may be inclined slightly so as to present the narrow abrasive-cleared area to the grinding wheel at an inclination sufficient to give a satisfactory bevel, in which case a standard abrasive wheel such as shown in Figure 1 can be used. Alternatively the abrasive wheel itself can be tilted to give a beveling action. when the skiving and beveling actions are combined it is found that the angle of inclination of the grinding edge of the wheel, although always greater than the angle of inclination of the bevel, will vary depending upon the grit size of the abrasive grain to be removed from the area 3. Generally, the larger the grit size, the greater the angle of inclination of the grinding edge.

Fig. 5 shows the two ends of .the abrasive strip 4 which have been beveled as described above; one of the ends carries an adhesive layer I! which may be any suitable material, glue, synthetic resin, rubber compound, etc, that can be set by pressure with or without heat. One example of a strong flexible cement which makes a satisfactory splice is that sold as Graton and Knight Cement dissolved in water to a solution density of 16 Twaddell at -'150 F.

The lap ends as shown in Figure 5 are placed one directly over the other in a press with appropriately shaped presser feet and a pressure example, one method is to suspend the belt as shown in Fig. 8 with the splice l4 uppermost over asoasos ii. The curvature of the support in conjunction with the weight of the belt causes the inner portion of the splice to be under a slight compressive tress while the outer portion is under a slight tensile stress. The foregoing procedure is conveniently applicable to belts to feet long. Longer belts are similarly placed over curved supports with the splices placed upon the top of the support and the remainder of the belt coiled or resting without strain upon the joint.

While the type of beveled splice or joint herein disclosed is particularly applicable to abrasive coated'belts in which the backing is composed of paper or similar fibrous material it can also be applied to the making of belts in which the backing is composed of one or more layers of fabric such as cloth and the like either alone or combined with paper, fibre layers and so on. However, when the backing contains a cloth layer or other laminated materials and it is desired to prepare a splice in accordance with the practice.

of the present invention satisfactory results can be obtained by an embrittling treatment of the splicing portions of the strip, such as impregnation with a resinous material, as for example, a phenol-formaldehyde resin of'brittle character.

Belts incorporating the present splice are found to run more smoothly and efficiently than the older type overlapping splice, and to be considerably less expensive and easier to fabricate than the butt-joint splice used with a liner. The unexpected superiority in strength of the present splice in spite of its simplicity is undoubtedly due to no single factor in its fabrication but to the proper development and combination of steps taken in its manufacture. For example, care in selection of the proper abrasive wheel for skiving and beveling whereby a clean, even removal is obtained without damaging or weakening the remaining fibrous structure is essential for a strong joint. "Similarly the suspension of the newlyformed Joint over a curved support tends to provide a splice free of wrinkles and inclined to be of uniformly strong cross-section. Likewise. other advantages and improvements accrue from the procedure of making belt joints such as herein described. I 7

Having set forth the invention in full detail, it is desired to claim:

1. The method of making endless abrasive belts from strips of abrasive coated web material which comprises cutting a strip of the abrasive web material of the desired width and length with the ends of the strip obliquely disposed with respect to the sides-of the strip, skiving the abrasive from a narrow area along one end of the abrasive strip, impregnating the skived area with an embrittling agent, beveling the surface of said abrasive cleared, embrittled area, similarly beveling the under surface of a similar area disposed at the opposite end of said abrasive web, applying a suitable adhesive to the beveled surfaces, bringing the beveled surfaces together in superposed relation and, applying pressure to complete the p ice.

2. The method of making endless abrasive belts from strips of abrasive coated web material which comprises cutting a strip of the abrasive web material of the desired width and length with the ends of the strip obliquely disposed with respect to the sides of the strip, skiving the abrasive from a narrow area along one end of the abrasive strip,

beveling the surface of said abrasive-cleared area, similarly beveling the under surface of a similar area disposed at the opposite end of said abrasive web, applying a suitable adhesive to the beveled surfaces, bringing the beveled surfaces together in superposed relation, applying pressure to complete the splice and suspending said newlyformed splice upon a curved support whereby the Y coated .web material comprised of a'fibrous backi newly-formed splice and the adhesive therein is allowed to set while the joined portions are in curved conformation.

3. The endless abrasive belt of flexible, abrasive ing and abrasive grains adhesively secured thereto, and having a joint formed by two superposed, cemented end portions of gradually decreasing thicknesses, the fibers of .said backing being impregnated with an embrittling agent in the vicinity of said joint to render the backing tear-resistant, said joint traversing the belt in a. diagonal direction.

4. An endless abrasive beltof flexible, abrasive coated web material comprised of a fabric backing and abrasive grains adhesively secured thereto, and having a joint formed by two superposed, cemented end portions of gradually decreasing thicknesses, the fabric backing being impregnated with an embrittling agent in the vicinity of said joint to render the backing tear-resistant,

said joint traversing the belt in a diagonal direction.

5. An endless abrasive belt comprised of a layer of abrasive grains adhesively secured to a laminated backing material one of the laminations of which is a fabric material, said abrasive belt having a joint formed by two superposed, cemented end portions of gradually decreasing thicknesses, thefabrlc layer of said backing being impregnated with an embrittling agent in the vicinity of said joint, said joint traversing the belt in a diagonal direction.

6. In the manufacture of endless abrasive belts from strips of abrasive coated web material the steps which comprise cutting a strip of the abrasive web material of the desired width and length with the ends of the strip obliquely disposed with respect to the sides of the strip, impregnating the ends of the strip with an embrittling agent, skiving the abrasive from a narrow area along one end of the abrasive strip, beveling the surface of said abrasive-cleared embrittled area, similarly beveling the under surface of a similar area disposed at the opposite end of said abrasive web, applying a suitable adhesive to the beveled surfaces, bringing the beveled surfaces together in superposed relation and .applying pressure to complete the splice,

ERIC P. min-smear. I EDGAR mm.

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