US2292261A - Abrasive disk and method of making the same - Google Patents

Description

1942- F. 0. ALBVEIIQTSON 2,292,261

ABRASIVE DISK AND METHOD OF MAKING THE SAME Filed Feb. 19, 1940 jz adezzzziz". flan/E UsierzaflZierZsma M Jaw $76 g Patented Aug. 4, 1942 UNITED STATES anansrvn msx AND METHOD OF MAKING THE SAME Frank Osbcrn Albertson, Sioux City, Iowa, as-- signor to Albertson 8; Company, Inc., Sioux City, Iowa, a corporation of Iowa Application February 19, 1940, Serial No. 319,639

4 Claims.

in which the curling of the backing is eliminated l and the disk is adapted to maintain its flat or plane condition throughout its effective life.

Another object of the invention is the provision of improved abrasive disks of the type described,

which are adapted to withstand action of water,

oil, or other solvents usually encountered in sanding or grinding work, and which are adapted to hav a particularly fast and effective cutting action.

Another object of the invention i the provision of an improved backing for abrasive disks of the class described which is adapted to be impregnated more thoroughly than the backings of the prior art, and which is therefore adapted to be used for making flexible, non-curling abrasive disks,

Another object of the invention is the provision of an improved abrasive disk which is 50 constructed as to eliminate loading or filling of the interstices between the abrasive particles, and

which is fast cutting, durable, and capable of long service under the most arduous conditions.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawing, in which similar characters of reference indicate similar parts throughout th several views.

Referring to the single sheet of drawings,

Fig. 1 is a plan view of the'working face of the abrasive disk constructed according to the 40 invention;

Fig. 2 is anal! size fragmentary elevational view of the face of the disk;

Fig. 3 is a half size fragmentary vreareleva- 5 tional view of the disk;

Fig. 4 is a greatly enlarged fragmentary sectional view, taken on the plane Of the lin 4-4 of Fig. 2, looking in the direction of the arrows.

One of the main difficulties in the manufacture of abrasive disks is the provision of a suitable backing which can be so impregnated with resin that the moisture condition of the disk may be stabilized and curling of the disk eliminated.

It is very dimcult ona commercial basis to backings of the type that can be bought upon the open market, and according to th present method of manufacture of. abrasive disks, the use of a new type of fiber backing is contemplated.

The fibers utilized in this backing are preferably of sisal. The sisal is first treated or soaked in a suitable resin, or the sisal may be sprayed with the resin, which is brought to a suitable liquid condition by th addition of a volatile solvent.

A relatively thin sheet of indurated fiber or kraft paper, such as, for example, a sheet of flve-thousandths of an inch thickness, is laid on a layer of the impregnated sisal, and th assembly is placed under a hydraulic press, where a predetermined high pressure is applied at the same time as the application of a curing temperature. The pressure, for example, may be approximately 1500 pounds per square inch, and the curing temperature approximately 266 degrees F., when a phenolic condensation resin is used with a solvent, such as alcohol.

The layer of indurated fiber or kraft paper provides the resulting backing with a greater strength and flexibility and a proper surface for adhesion of the binder which holds the abrasive particles. The fiber or kraft paper layer is also adapted to absorb the sprayed binder coat, which impregnates this layer and penetrates to such an extent that the binder and abrasive particles are securely anchored to the backing in a way that could not be accomplished by direct application of the binder to a hard cured resin surface which would not absorb sprayed resin.

The next step in the manufacture of the abrasive disk is the spraying of binder in the form of a thick coat of a suitable resin, such as a phenolic condensation resin, thinned with'a suitable solvent, such as alcohol. Thereafter, while the binder coat is in a tacky condition, an excess of abrasive particles is applied to the front surface of the disk, which is coated with binder, and the particles are embedded in the binder. I

- The excess abrasive particles not embedded or adhering to the binder may then be shaken ofi 'by impact of the edge of the disc by or against some instrument or support, and thereafter, while the binder coat is still uncured, the abrasive surface of the disc is suitably shaped by the application of pressure dies. These pressure dies are preferably formed with a plurality of ridges, the ridges being formed in two series at right secure adequate impregnation with resin of fiber 55 an es to ea h o h r nd f rmi v dicated by the horizontal lines in and the vertical lines II in the disk I! of Fig. 1.

These grooves and ridges on the die in the abrasive surface are preferably substantially rectangular in cross section so that the grooves ll of Fig. 4 are rectangular in cross section, and the ridges l3 in Fig. 4 are likewise rectangular in cross section. The ridges l3 are, however, cut up transversely, as shown in Fig. 2, leaving a plurality of substantially rectangular islands H spaced from each other by the grooves I and II.

It should be noted that the binder coat and application of abrasive particles is sufliciently thick so that there is an abrasive surface at the base of every groove II, as well as at the face of every island 14, and on the sides of each island. This gives the abrasive disk a very effective quick cutting action, due-to the high contact pressure of the relaitvely small island areas; but when the island areas H are worn down, the disk is still adapted to have a long cutting life by virtue of the abrasive particles which still project below the initial island surface and at the base of the grooves I0.

Referring to Figs. 1 and 3, every disk is preferably provided with a centrally located non-circular aperture I5 for engagement with the arbor or threaded securing member which secures the disk to a pad.

The disks are preferably manufactured in circular shape from the beginning so as to eliminate the wastage of the finished backing, and any waste, except that involved in the cutting of the thin indurated fiber layer or kraft paper layer into disks.

Referring to Fig. 4, 25 indicates the main body layer of sisal, its fibers extending in random directions, with various curvatures, and being thoroughly soaked and impregnated with a suitable resin which holds the fibers together when subjected to hydraulic pressure and heat curing.

For the purpose of diagrammatic illustration, in Fig. 4 there is shown an external impregnating or sealing layer of the same resin on the sisal base, indicated at l6, while I! indicates a similar sealing and adhesive layer of the same resin between the thin indurated fiber or kraft paper layer l8 and the sisal. Similarly, l9 indicates a layer of the same resin external to the sisal, at the edges of the sisal and at the edges of the indurated fiber or kraft paper I8, so that the body of the abrasive disk or backing is completely sealed with the resin.

As a matter of fact, in the manufacture of the abrasive disks, these are not layers separately applied, but by reason of the impregnation of the sisal fibers with the resin, it is a fact that there is resin on all sides of all of the sisal fibers and at the edges of the disk, and a part of the resin, which impregnates and covers the sisal fibers, produces the sealing effect which is diagrammatically illustrated at l6, l1 and i9; that is, the impregnated sisal fiber may use its own resin for effecting a seal of/the fibers in the backing and for adhesively securing the kraft paper layer to the impregnated sisal fiber backing. There is an excess of resin which acts as adhesive to secure the kraft paper to the sisal fiber backing and to seal the sisal fiber within the backing, and that is diagrammatically illustrated by the layers which are clearly shown at Figs. 16, 1'7, and 19 in the drawing, but which do not appear as separate, visible layers in the structure of the-abrasive disc.

material secured to invention,

As all of the resins employed in the disk are preferably of the same material in different conditions of viscosity, the abrasive disk is practically an integral member of the resin with the thin indurated fiber or kraft paper layer, and the sisal fiber enclosed in the resin to give it the desired strength, flexibility and resilientcharacteristics.

After the surface of the abrasive disk has been suitably shaped, as shown in Figs. 2 and 4, the abrasive surface is then again sprayed with a thin binder or anchoring coat of the same resin of a thinner consistency, and the disks are then subjected to a heat curing by passage through an oven or a drying heated atmosphere, which removes the solvent and renderes the resin hard and insoluble to water, oil, and the usual solvents to which an abrasive disk may be subjected.

The disk may be subjected to a relatively quick evaporation of the solvent at, for example, a temperature of degrees F. for a period of, for example, twelve hours, and thereafter to a longer heat curing at a subsequent higher temperature of, for example, 230 degrees F. for ten hours.

During this evaporation of the solvent and the curing, the abrasive disks are preferably held in a substantially plane condition, so that they will be set, cured, and hardened in a plane condition.

Various types of the fibrous material may be employed, but the sisal is preferred, as its strength is not affected by the application of the resin. As distinguished from sisal, it has been found that ordinary cloth and paper becomes brittle when it is impregnated with resin; and backings of indurated fiber, which are actually made up of laminations, tend to split at the edge, causing the abrasive disk to weaken at the edge, where most of the work is done.

The specific pressure and heat applied and the period of application will vary for different types of resins, and various types of resins may be employed, the phenolic condensation resin and solvent mentioned being merely exemplary of one type of materials. The resin should be one which is not affected after curing by heat or moisture, and which is strong, not brittle, and adapted to hold its shape. The resin should be tough and bendable and flexible, and yet relatively still when combined with the sisal fiber in the form of an abrasive disk.

The sisal fiber acts in the same way as a reinforcing for the resin, and the resin forms the real body of the backing for the abrasive disk. Such abrasive disks are adapted to have a long life and to maintain their plane condition, although they are adapted to bend or flex during the application of the disk to the work.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A backing for abrasive disks comprising a disk of resin reinforced with sisal fibers extending in random directions throughout said disk, said disk being cured to resilient flexible condition by the application of heat and pressure, and said disk having a facing of absorbent paper the resin before curing, and

adapted to receive a binder for abrasive particles.

2. The method of making abrasive disks comprising soaking sisal fibers in a resin adapted to be rendered insoluble by the application of heat and pressure, forming a disk of the fibers impregnated with resin, applying an absorbent sheet to one face of the assembly of fiber and resin, curing the resulting disk by application of heat and pressure, spraying the absorbent face with binder resin of similar characteristics to the resin of the disk, applying an excess of abrasive particles, removing the abrasive particles not secured or embedded in the binder, shaping the semi-plastic mass of abrasive particles and binder on the face of the disk to provide a multiplicity of ridges and grooves, all formed with abrasive surfaces, spraying an anchoring coat on the abrasive surface, and subjecting the abrasive disk to curing by heat while holding the disk in plane condition.

3. A backing for abrasive disks comprising a disk of resin reinforced with fibers extending in random directions, said disk being cured from a single felted mass of resin impregnated fibers to resilient flexible condition by the application of heat and pressure, said disk having an integrally formed resin seal on all sides of said fibers and at the edges of said disk.

4.- An abrasive disk comprising a resilient, yet flexible, resin disk reenforced with fibers extending in random directions through the body of said disk, said resin being cured to an insoluble condition by the application of heat and pressure and abrasive particles applied to the outer face of said layer of paper material, the surface of said abrasive disk being formed with a multiplicity of grooves and ridges, the ridges being substantially rectangular in outline, and the grooves terminating in the edge of said disk for the discharge of cuttings from the disk, the bases of said grooves being also covered with abrasive particles for insuring a long life of the abrasive surface.

FRANK O-SBERN ALBERTSON.

DISCLAIMER 2,292,261.Frank Osbem Albertson, Sioux City, Iowa. ABRABIYE Drsc AND METHOD OF MAKING THE SAME. Patent dated August 4, 1942. Disclaimer filed September 16, 1943, by the assignee, Albertson (f: Company, In'c. Hereby enters this disclaimer to claim 3 in said patent.

[Ofiicial Gazette October 19, 1.948.]

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