US3139709A - Segmented abrasive rim disc and method for making the same - Google Patents

Description

July 7, 1964 R. J. WALTERS 3,139,709

SEGMENTEID ABRASIVE RIM DISC AND METHOD FOR MAKING THE SAME Filed April 15, 1965 INVENTOR Rev J. WALT 5R5 BYJWMW ATTORNEY United States Patent 3,139,709 SEGMENTED ABRASIVE RIM DISC AND METHOD FOR MAKING THE SAME 7 Roy J. Walters, 4985 Voltaire St., San Diego, Calif. Filed Apr. 15, 1963, Ser. No. 272,989 2 Claims. (Cl. 51-195) This invention relates to an improvement in abrasive rim discs for use with edge grinders and to a method of making the same.

In particular this invention is an improvement of the abrasive rim disc and the method of its manufacture disclosed in my co-pending application, Serial No. 16,587, filed on March 21, 1960, now abandoned, which broadly concerns the bonding of an abrasive particle covered ring or rim piece to the peripheral face portion of a plain uncoated fiber backing disc and the method of manufacturing such abrasive rim portions. The method therein disclosed consists of cutting circular rim portions of rings from a sheet of abrasive covered roll stock, or of cutting such circular rim portions from used conventional discs of larger diameter. The advantage of the rim disc of the above mentioned application as well as one of the advantages of the present invention resides in the application of abrasive material only to those portions of the backing disc which are actually used in grinding. The conventional abrasive discs used with edge grinding prior to my invention consisted of a fiber backing disc completely covered with abrasive particles.

The principal object of the present invention is to pro vide an abrassive rim disc having improved flexibility and improved abrasive characteristics and life when it is used on painted and other soft surfaces.

A further object is to provide an improved economical method of manufacture of abrasive rim discs.

These objects are attained by an abrasive rim disc which does not have a uniform abrasive covering over the entire face portion as those generally employed heretofore, but which is made from an abrasive covered strip with transverse slits which is adhered to a backing disc to provide segments of abrasive material separated by generally transverse gaps or grooves. Such grooves provide greater flexibility to the disc at its cutting edge and thus aid in avoiding gouging of the work piece. In addition the discs performance and life, when used on painted or other soft surfaces, is greatly improved because the soft substance does not remain on the abrasive crystals and impairs their cutting ability but is removed by the grinder action and is accumulated in the gaps between the segments.

The novelty of the method of manufacture of the above described abrasive rim disc lies in the fact that the abrasive rim portion is manufactured from a straight strip of abrasive covered material. In View of the fact that generally the same width of abrasive material is required or used on the rim of a disc regardless of its diameter, the same width strip may be employed in the manufacture of a complete line of abrasive rim discs. This method also does not involve any by-product in the form of scrap or trimmings since the entire strip is used in providing the abrasive surface to the disc. In practice it has been found that a one inch wide strip may be used in manufacture of discs ranging from over 8" to 2" in diameter.

The present method is a significant step forward over the method disclosed in the above mentioned co-pending application which contemplated the cutting of concentric rings from a sheet to provide the abrasive rim portions for discs of progressively smaller diameters, since the latter method invariably limits the manufacturer to producing equal number of discs of the various sizes re 3,139,709 Patented July 7, 1964 gardless of the variance in the sales volume or popularity of one size over the other.

Other objects and advantages will be apparent from, or pointed out in, the specification and the appendant claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is a cross sectional side View of a rim disc mounted on a back-up pad connected to a power tool mandrel;

FIG. 2 is a fragmentary top view of a strip of abrasive coated material which is prepared to be bonded to backing disc; and

FIG. 3 is a front view of the abrasive rim disc.

The abrasive rim disc embodying my invention is manufactured by providing a substantially straight strip 10 of abrasive covered material, slitting the same at 12 to provide a plurality of separate equally spaced segments 14 connected by a relatively narrow neck portion 18 along one side of the strip, bending the strip to a flat ring shape, and bonding the same to the peripheral portion of the face of a backing disc 18 with the unitary side of the strip forming the inside of the ring and the segments flaring out to form gaps 20 between the separate segments.

The strip 10 may be cut to the exact finally utilized length from a coil of abrasive coated material equal in width to the required width of the strip, thereby eliminating practically all trimming and other waste of material. The strip material may be abrasive coated paper, cloth or fiber which are well known in the art.

As seen in FIG. 3, the abrasive rim disc manufactured pursuant to the above described method comprises an uncoated fiber backing disc 18 having its peripheral face portion provided with an abrasive rim 22 of a width equal to or slightly larger than that disc portion which is actually used in the use of the disc.

The backing disc 18 has an aperture 21 sized to pass the shank 24 of the head nut 26 and small enough so that the head 28 of nut 26 will not pass through the aperture. Nut 26 has several internal threads 30 sized to receive threaded power tool mandrel 32. The nut is tightened to the mandrel to secure the backing disc 18 to the back-up pad 34 and seats in a counter sunk portion 36 of the pad to prevent the head 28 from contacting the work surface.

There are a number of applications in which it is desirable that the backing disc and its abrasive covered portion flex during sanding. For such uses the back-up pad 34 is of substantially smaller diameter than the abrasive rim disc. Due to its serration the segmented rim disc provides uninhibited flexing of the backing disc 18 and actually exerts more flexing than the conventional coated fiber disc. This free flexing exposes and employs more than the usual number of the abrasive crystals to the surface being sanded which results in a substantially faster cutting action and longer disc life.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. An abrasive rim disc comprising, a flexible backing disc adapted to be attached to and rotated by a power tool, a flat strip bent to a flat ring shaped form and having one of its faces bonded to the peripheral portion of the face of said backing disc and having the other of its faces covered with abrasive material, said strip being unitary on the inner radial side of said disc and forming a plurality of spaced apart segments on the outer radial side of said disc to thereby form a plurality of grooves I 3 each of them defined by two of said segments and said backing disc.

2. A method of manufacturing an abrasive rim disc comprising the steps of: partial transverse slotting of a substantially straight strip of material which has one of its faces coated with abrasive material thereby dividing said strip into a plurality of segments connected by a unitary portion, and bonding the other face of said strip to the peripheral portion of the face of a backing disc in a manner whereby said strip assumes a flat ring shaped form and said unitary portion defines the inner portion of said ring shaped form and the segments spread apart References Cited in the file of this patent UNITED STATES PATENTS 302,952 Smith Aug. 5, 1334 888,129 Tone May 19, 1903 1,216,489 Pfeifier Feb. 20, 1917 10 2,334,642 Moore Nov. 16, 1943 2,677,142 Mundo May 4, 1954

Claims (1)

1. AN ABRASIVE RIM DISC COMPRISING, A FLEXIBLE BACKING DISC ADAPTED TO BE ATTACHED TO AND ROTATED BY A POWER TOOL, A FLAT STRIP BENT TO A FLAT RING SHAPED FORM AND HAVING ONE OF ITS FACES BONDED TO THE PERIPHERAL PORTION OF THE FACE OF SAID BACKING DISC AND HAVING THE OTHER OF ITS FACES COVERED WITH ABRASIVE MATERIAL, SAID STRIP BEING UNITARY ON THE INNER RADIAL SIDE OF SAID DISC AND FORMING A PLURALITY OF SPACED APART SEGMENTS ON THE OUTER RADIAL SIDE OF SAID DISC TO THEREBY FORM A PLURALITY OF GROOVES EACH OF THEM DEFINED BY TWO OF SAID SEGMENTS AND SAID BACKING DISC.

Images