US2356866A - Manufacture of abrasive disk materials - Google Patents

Description

1944- R. L. MELToN ET AL MANUFACTURE OF ABRASIV E DISK MATERIALS Filed 061. e, 1941 2 sheets-sheet 1 au ia 1944 R. L. MELTON ETAL MANUFACTURE OF ABRASIVE DISK MATERIALS Filed Oct. 6, 1941 2 Sheets-Sheet 2 Elven-1607's, .ZomzLe dL; Malian, Fd mond 63mm, 1

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Patented Aug. 29, 1944 UNITED "STATES \PAT ENT OFFICE MANUFACTURE OF ABBASIVE DISK TEBIALS Romie L. Melton and Raymond C. Benner, Niagara Falls, N. Y., assignors to The Carborundum Company, Niagara Falls, N. Y.,'a corporation of Delaware Application October 6, 1941, Serial No. 413,788

9 Claims. (Cl. 51-293) felted fibrous web of-the desired thickness is formed-by building up on a moving endless support a plurality of layers of thin carded fibrous dated to produce a disk backing characterized by a radial strength and toughness which is uniformly high in all directions. Such a fibrous disk backing material compares-very favorably with the strength and toughness of vulcanized fiber backings and is much easier and far less expensive to manufacture. The invention further relates to a continuous process of forming such a felted fibrous backing material, adhesively securing abrasive grains to one surface thereof and cutting abrasive diks therefrom.

Heretofore the manufacture'of abrasive disks, having the requisite strength and toughness for heavy duty grinding, has required the use of backing materials of vulcanized fiber. Such vulcanized fiber is expensive to manufacture 'because of the long drawn out chemical treatment required; Furthermore, abrasive disks cut from such materials are not uniform in strength in all directions due to the inherent. characteristic of the fiber to be stronger in its longitudinal. direction and weaker in its transverse direction. Ef-

forts to overcome this difilculty included the application of a reinforcing web or cloth, paper, and other materials to produce a combination of two or more composite layers. Such combination backings have proven successful, even under severe grinding conditions, but are expensive to manufacture due to the number of operations involved.

The present invention provides a much simpli- =fied method of manufacturing abrasive coated disks which greatly reduces the number of steps required to go from the raw materials to the ultimate product and greatly lessens the time required to carry out such manufacture. The present invention further provides an abrasive. disk having a backing which is uniformly tough and strong radially in all directions and will stand up under heavy duty grinding operations. This disk backing also retains the abrasive coating with tenacity and has a highly satisfactory resilience and flexibility as well as being less expensive and easier to make. The present process has a further advantage in that the abrasive disks can be manufactured as a continuous process from raw materials to finished product with a saving of both time andspace.

In accordance with the present invention a membranes to form a loosely felted structure which is then treated with a suitable adhesive binder and consolidated to the desired density. High strength of the web material in all direc- 'tions is obtained by depositing one or 1 more fibrous layers or membranes longitudinally of the movihg conveyor and then depositing the succeeding layers of cahded membranes in a cries-cross direction obliquely transverse to the length of the initially deposited web, with the direction of successively deposited layers changing, whereby'the final web backing has a plurality of carded laps running in all directions. A binder adhesive is then applied into the web and distributed therethrough after which the formed web is consolidated and then subjected to heat and pressure to produce a dense backing ma:

terial of the requisite strength and rigidity.

additional carded fibrous membrane or other woven fibrous material may be applied to the upper surface of the formed web backing immediately prior to the step of maturing the binder adhesive. The top surface of this layer offibrous material will be starved of adhesive andthus provide greater adhesion and improved anchorage for the subsequently applied base coating of adhesive and abrasive granules. The abrasive coated web is then passed to a zone where the adhesive is matured to secure the granules to the backing after which the material is cut up into abrasive disks of desired size.

In order that the invention may be more 7 Figure 3 is a plan view of the. abrasive coated I disc material made by the present process and shows this material in various stages of its mani ufacture so as to better illustrate the body structure of the backing material and the manner in which abrasive discs are cut from the material; and

Figure 4 is a greatly enlarged vertical crossembodying and made in accordance with the teachings of the present invention.

Referring further to the drawings, Figures 1 and 2 illustrate one form of apparatus which may be employed in manufacturing abrasive-coated web material suitable for the production of abrading disks in accordance'with the present invention. The particular apparatus shown comprises a carding machine consisting of a carding cylinder 2, a dofl'er roll 3 and a comb I, adapted-to form and deliver an initial carded fibrous membrane or lap 5 to a moving conveyor belt 1. Another carding machine assembly consisting of a similar carding cylinder 2a, dofler roll in, and comb 4a (see Figure 2) is positioned further along the path of travel of the moving conveyor 1 and adapted to deposit a carded fibrous membrane 6 in a criss-cross direction obliquely transverse to the direction of movement of the initially deposited membrane 5/ Either or both of the carding assemblies shown may be supplemented by additional carding mailiary web distributing device.

assessesection through a fragment of an abrasive disk complishing this transverse deposition of carded fibrous membranes is shown in Figure 2 and consists of a conventional carding machine and aux- The carded flbrous membrane 6 is fed onto a moving conveyor l0 which is supported at the opposite ends thereof by the rolls 'H and I2, and driven by suitable means (not shown). The speed of the conveyor belt I0 is synchronized with therate of feed of the fibrous membrane 6 so as to prevent any appreciable strain or pull on the flimsy web. The carded membrane 6 is then fed from the moving belt in onto a camel-back structure, which comprises a pair of moving belts l4 and i5, supmoving conveyor 1 would be extended in length sufficiently to take care of the number of carding machines employed.

The carded membranes or laps are delivered from the carding machines as flimsy webs of independent fibers generally parallel and loosely adhering together. These membranes may consist of any fibrous material capable of being carded into web form orseparable into individualfibers. Such materials include natural fibers,

. such as cotton, wool, jute, flax and asbestos, as

well as the various synthetic fibers, such as glass wool, resinous and rubber-like fibrous substances.

' Any one of these fibrous materials may be used singly or two or more may be mixed in any desired proportion. Cotton fibers are inexpensive and readily available in quantity and have been found to be highly satisfactory in the present process and consequently will be used as a specific example in connection with the detailed description of the apparatus and method of manufacture.

The initial fibrous membrane 5 is deposited upon the conveyor I in the direction of travel of the conveyor to form a continuous bottom layer ported at opposite ends thereof by rolls I6 and I1, and I8 and I9, respectively, and driven by suitable means (not shown). These rolls are supported in turn by-a side frame structure comprising a pair of side frames or arms pivotally mounted at the axis 20 and also pivotally connected at their adjoining ends 2| to permit the camel-back to move back and forth to deposit superimposed layers of the fibrous membrane 6' transversely of the moving conveyor belt I. The

camel-back is provided at its free end with a pair the desired thickness and type of fibrous web to be produced.

After the fibrous web 26 has been built up to the required thickness,- it is ready to be consolidated to a greater density for added strength. At the same time it is usually desirable to incorporate a liquid adhesive within said web to bond the consolidated fibers and produce a web having a strength comparable to vulcanized fiber and the like. The web 26 is initially consolidated and strengthened by passage back and forth through a series of synchronously driven rolls 2'! which may be located near the terminus of the con-'- veyor belt 1., These rolls 2! do not exert any ap-. preciable pressure on the web and are preferably action causes the loose ends of individual fibers of adjacent membranes to become interengaged. Passing from the rolls 21, the web is delivered to the adhesive binder applying rolls 28 and 2!.

The membrane -6 and any additional membranes supplementary thereto, which are deposited by carding machines illustrated in Figure 2,-

are deposited upon the moving conveyor ina cross-cross manner so that this fibrous membrane lies transversely in an oblique direction to the movement of the traveling belt or conveyor 1. The direction of each membrane varies from that of the adjacent membranes so that the composite structure of the built-up fibrous web consists of a plurality of fibrous membranes in which the general fiber direction varies with each individual lap. That part of the apparatus for ac- The liquid adhesive binder is contained in a pan.

transfers a quantityof adhesive binder into'the fibrous web. An adjustable scraper bar '3l provides a means of regulating the amount of adhesive introduced into the web. Passage between the, rolls 28, 29 serves to consolidate the loose fibrous web and causes the binder adhesive to permeate'throughout the web structure. The surfaces of both rolls 28 and'29 are covered with a resilient layer of absorbing material. The adhesive binder applied by rolls 28, 29 herein referred to as the bodybinder, is preferably of a 'heat-hardenable nature, such as thermo-setting phenol-formaldehyde resins, as for example those sold under the trade name Durite 8-2143" and Durite 8-1902, 'or'the like and which will mature with heat to a permanently tough, hard the liquid phenolic resins specified above requires,

a platen temperature of 300 F. for a period of two minutes. Curing time and temperature de: pends upon the thickness of th web and the requirements of the particular adhesive binder v 3 jacketed or heated, as required. Revolving roll 50 is partially immersed in the adhesive and with each revolution transfers a measured amount of adhesive to the web. The adhesive binderapplied may be glue, resin or any other suitable adhesive for the purpose.

The adhesively coated web is then moved over idler rolls 52, 53 and under a grain hopper 55 where a layer of abrasive granules is deposited onto the freshly coated adhesive surface. The

hopper 55 is provided with an adjustable feed employed. Also, partial cures can be carried out at this stage of the process with the final or complete cure being effected later in the process at the time of maturing the base adhesive coating. The continuously curing apparatus for so treating the web comprises two flexible endless, metal belt platens 3'2, 33 mounted on end pulleys 34, and 36, 31 respectively, and driven bymeans (not shown) at a speed synchronized withthat of the moving web 26a. The belt platensare arranged with their adjacent outside faces substantially parallel and spaced apart by an amount approximately equivalent to or very slightly less thanthe thickness of-the traveling web to be treated. Directly in back of equalportlonsof both adjacent faces of the traveling platem 32, 33 are fiat, plate shape fluid pressure transmitting members 38, 39 equipped with pressure cylinders 40, 4|. These fiat members 38, 33 are heatedby steam ducts 42 and are positioned so that when steam or other fluid pressure is introduced to the pressure cylinders fill, H the traveling platens will be thrust toward each other to exert a uniform heat and pressure against the traveling web to mature the included adhesive binder and permanently consolidate the and hard as otherwise might occur and therefore presents a bettersurface for the anchorage of a top coating of abrasive grain and adhesive binder. In other words, the application of an additional fibrous layer following the introduction of adhesive into the web serves to give a top surface which is simulative in effect to the use of a top cloth or fabric layer in the ordinary manufacture of combination backings but without the expense involved therewith. -However, a cloth or fabric layer may be used at this point. in the present process insteadof the fibrous membrane if desired. i

Passing from the curing apparatus the web is carried around idler -rolls45, ISJI-and 43 to adhesive-applying rolls 43, 50 for applying a surface or base coating of adhesive. The liquid adhesive is gate 56 and grain distributing rolls 51 which permits a uniform shower of grain of desired density to be deposited. The abrasive coated web is then passed over'supporting rolls 59, Ell, 6|

, and suction drum 6-2 to a chamber where the adhesive is matured. This chamber may contain a festooning device 83 for festooning the coated material on to supporting sticks carried by the moving rack 64.

After a preliminary'set or cure has been imparted to the base adhesive coating,-a second or sizing layer of adhesive may be applied over the abrasive layer to more firmly anchor the individual granules in position. Such a sizing coating may be applied by the conventional adhesive rolls and further details are not deemed necessary. The coated web is then passed toa final heating chamber or rack where it is fully matured. When the cured web is removed from the final curing chamber it is either cut into abrasive disks by dieing out the blanks with a punch press or the coated material rolled up and stored for future use as a disk material.

Figure 3 illustrates an abrasive coated fibrous disk material made according to the present invention and shows the material in various stages of its manufacture in order to bring out certain features of its structure. The obliquely transverse positioning of the fibrous membrane 6 is clearly shown as it' is deposited on the'initially deposited lengthwise web 5. The transverse arrangement of the membrane or membranes 6 serve to .increase the cross-ways strength of the final web so that when abrasive disks cut from the areas 66 areobtained they will have a uniformly high tensile strength in all directions across the disk.

Figure 4 is a greatly enlarged vertical section through a fragment of coated abrasive disk material. This view shows clearly the initial longitudinally deposited carded fibrous layer 5 and the transversely deposited membranes 6- forming the body structure of the backing. The fibrous top layer 44, applied after the base has been adabrasive grain adherence, is also shown. The

. abrasive granules 63 are held in place, by the base adhesive binder 53, which has penetrated the fibrous structure to the limited degree per-.

mitted by use of the adhesive-starved fibrous top layer 44, but which is sufiicient to firmly grip the backing so as not to be dislodged therefrom in use. The lesser amount of adhesive in the fibrous layer 44 is shown by the lightness of the upper portions of the diagonal lines Ill representing the impregnating body adhesive. A further sizing 5 coat ll of adhesive further anchors th abracontained in a pan" 5|, which may be water- 3 sive grain in place.

Abrasive coated disks as herein. made exhibit numerous advantages accruing from the method of manufacture and the structure resulting thereparable to the strength of vulcanized fiber backings but the strength will be substantially uniformly high in all directions because of the plurality of directions in which the various fibrous layers have been deposited. Furthermore, the provision ofan adhesive-starved top fibrous layer produces a slightly roughened top surface promoting astrong adherence of surface grain and adhesive thereto without the .necessity of resorting to use of woven cloth fabrics. The economic savingobtained by being able to make the finished product directly from the raw materials, which in themselves are relatively cheap as compared to the vulcanized fiber backings heretofore used, is of considerable value. Other advantages and benefits accruing from the present invention are apparent and obvious from the above description and explanation.

In practicing the invention any of the abrasive materials in common use may be employed, such as silicon carbide, fused aluminum oxide, flint, corundum, emery and similar substances. The size of the abrasive particles may vary depending upon the type of grinding operation to which the disk material is to be put.

- The present invention has been described as a continuous process in which the abrasive coating is preferably applied to the fibrous backing at the time that the backing is formed. However, it is within the scope of the present invention that a felted fibrous disk backing may be formed in the which comprises feeding plurality of layers of carded fibrous membranes, the fibers of 'whichr un manner described or may be obtained in substantially similar felted form by any suitable but substantially equivalent procedure and the abrasive coating adhesively applied and secured to the backing as a later and separate operation.

While the preferred 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.

-We claim:

1. The method of making flexible abrasive disks which comprises dry-forming a felted fibrous disk backing material, applying an adhesive binder thereto and consolidating said backing, applying a fibrous layer to the upper surface of the consolidated backing after the application of the adhesive binder to the mainfibrous body struc-. ture, combining the backing and top fibrous layer lengthwise thereof. onto a moving conveyor in a direction transverse to the direction of travel of the said conveyor whereby the superimposed layers of fibrous material lie in a plurality of directions throughout the body of the structure obliquely transverse to the lengthwise direction of the resulting fibrous'web so as to'impart a-varied fiber disposition whereby a high strength in all directions in said web is produced, introducing an adhesive into the fibrous web so made and con-' solidating the same, maturing said adhesive,-coating a surface of the fibrous web so formed with a layer of adhesive, applying abrasive grain totl e adhesively coated surface, setting the adhesive to, secure the abrasive grain, and cutting abrasive disks therefrom.

4. The method of making flexible abrasive disks which comprises feeding longitudinally upon a traveling conveyor a'base layer of fibrous material, feeding thereon a plurality of layers of a carded fibrous sheet material, the fibers of which run lengthwise thereof, in a directiontransverse to the direction of travel of the said conveyor whereby the superimposed layers of fibrous material lie in a plurality'of directions throughout the body of the structure obliquely transverse to the lengthwise direction of the resultin fibrous web so as to impart a variedfiber disposition whereby a high strength in all directions in said web is produced, introducing an adhesive binder into the fibrous web so made andconsolidating the same, maturing said adhesive binder, coating the surface of the fibrous web so formed with additional adhesive binder, applying abrasive grain to .the

adhesively coated surface, setting the adhesive to secure the abrasive grain, and cutting abrasive disks therefrom. i

5. The method of making flexible abrasive disks in accordance with claim 3 in which a fibrous layer is applied to the upper surface of the compacted web backing after the introduction of the adhesive binder into the web backing. I

6. The method of making flexible abrasive disks in accordance with claim 3 in which a layer of fabric is applied to the upper surface of the compacted web backing after the introduction of theadhesive binder into the web backing.

and setting the adhesive to provide a backing having the upper surface starved of adhesive and therefore receptive to a strong adhesive attach- 2. The method of making flexible abrasive disks which comprises dry-forming a felted fibrous backing, introducing an adhesive binder into said fibrous body to render it strong and dense, applying 'a top facing of fibrous material to the backing after the application of the adhesive binder to the main fibrous body structure but while the adhesive binder remains uncured, maturing the adhesive binder to provide a backing having the upper surface starved of adhesive and therefore receptive to a strong adhesive attachment of abrasive grains thereto, applying a surface layer of abrasive grains and'adhesive binder therefor, setting the adhesive to secure the abrasive grain and cutting abrasive disks therefrom.

3. The method of making flexible abrasive disks 7. A flexible abrasive disk comprising a; felted fibrous backing formed from a plurality of heter-v ogeneously arranged fibrous layers, the general directional disposition of the fibers of each layer throughout the body of the abrasive disk being different from that of adjacent layers, said layers being adhesively consolidated by presence of an adhesive therein to form a dense structure and an upper surface layer of partially felted fibers having a lower content of consolidating adhesive for reception of abrasive granules, said backing having a surface layer of abrasive grain adhesively S84lll8d to the fabric coated face of said backing.

8. abrasive disk comprising a backing having a layer of abrasive grains adhesively attached to a surface thereof, said backing comprising a plurality of membranes formed of cardable fibers, the major proportion of the fibers of each of said membranes having their longitudinal axes lying generally parallel and lengthwise thereof whereby each of the said membranes is .stronger in the lengthwise direction than in the crosswise direction, and the membranes being so positioned with respect to eachother that the longitudinal axes of the major proportion of the fibers of any membrane form an angle with the longitudinal axes of the major proportion-oi the fibers of adjacent membranes whereby the-backing is substantially uniform in strength in all directions.

9. An abrasive coated article adapted for the manufacture of flexible abrasive disks, said article comprising a backing having a layer of abrasive grains adhesively attached to a surface thereof, said backing comprising a plurality of membranes formed of cardable fibers, the major-proportion of the fibers of each of said membranes having their 10 longitudinal axes lying generally parallel and lengthwise thereof whereby each of the said membranes is stronger in the lengthwise direction than in the crosswise direction, and the membranes 'being so positioned with respect to each other

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