US3540163A - Abrasive disc and method of making it - Google Patents

Description

Nov. 17, 1970 F. O. SHOEMAKER ABRASIVE DISC AND METHOD OF MAKING IT Filed Sept. 28, 1967 FIG. 2

INVENT FRANK O. SHOEM R BYZM HIS ATTORNEY United States Patent 3,540,163 ABRASIVE DISC AND METHOD OF MAKING IT Frank 0. Shoemaker, Palos Park, Ill., assignor to The Bendix Corporation, a corporation of Delaware Filed Sept. 28, 1967, Ser. No. 671,310 Int. Cl. B2411 57/04, 11/00 U.S. Cl. 51209 3 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION The invention relates to grinding wheels of the type in which a flat disc of the abrasive material is secured to a rotatable supporting wheel, and more particularly to reinforced abrasive discs of the nut-inserted type and a method for making.

DESCRIPTION OF THE PRIOR ART Abrasive grinding wheels have been provided with reinforcing members embedded therein to increase the tensile strength and to resist the tendency to rupture under centrifugal force. With face grinding wheels it is also customary to embed securing nuts in the abrasive material which form the anchors engaged by the clamping bolts for securing the abrasive disc to a backing plate. Abrasive discs of the nut-inserted type have been difficult to reinforce, since layers of any reinforcing material in the usable portion of the disc will change the grinding action of the disc as the reinforcing elements are encountered through normal wear.

One prior approach has been to place the reinforcing material on the back side of the disc, next to the supporting wheel. In this area, it does not interfere with the grinding action, but is in the least effective location.

Another approach has been to place the reinforcing material at the junction of the usable abrasive and the non-usable abrasive layer which contains the inserted nuts. First attempts at placing the reinforcing material in this location resulted in a warping or parting of the disc through the reinforcing section. In this location, when the disc is pressed into shape and subsequently cured the internal reinforcement is bent out of its normal plane and thus placed under stress which ultimately results, by reason of internal resiliance and memory in the reinforcing material, in either warping or cracking the abrasive disc. The bending of the reinforcing member out of its normal plane occurs over the inserted nuts during the pressing operation.

Another approach has been to secure the abrasive disc to the supporting wheel by means of screws inserted through the reinforcing member and embedded into the abrasive, but the clamping pressure against the reinforcing material or the abrasive sets up stresses that tend to weaken the disc.

It can be seen that one of the major problems in abrasive disc reinforcing is to place the reinforcing material at the junction of the usable and non-usable layers of abrasive material while eliminating the problems of cracking or warping of the disc due to distortion of the reinforcing material.

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SUMMARY OF THE INVENTION The present invention presents an improved reinforced abrasive disc having a reduced tendency to warp and crack due to internal stresses placed on the reinforcing member during the pressing operations. An apertured reinforcing member is embedded in the disc at the junction between the usable and non-usable layers of the abrasive disc and is entirely independent of the anchor nuts located in the non-usable layer of the disc. The reinforcing member is oriented so that the apertures are maintained in spaced relation over and relative to each of the anchor nuts and in effect floats on the abrasive material independent of the nuts. The pressing steps in the formation thereof will not cause a flexing or distortion of the reinforcing material over the inserted nuts because of the apertures therein.

Thus it is an object of this invention to provide a method for placing a reinforcing member at the junction of the usable and non-usable layers of abrasive material in such manner that it will accommodate itself to the molding pressure and subsequent curing without distortion out of its normal plane.

A further object of this invention is to provide a reinforced abrasive disc in which the reinforcing material is independent of the anchor nuts.

DESCRIPTION OF THE DRAWING In the illustrative embodiment shown,

FIG. 1 is a section through the abrasive disc and the support 'wheel to which it is to be attached,

FIG. 2 is a fragmentary perspective view of the abrasive disc with parts broken away, and

FIG. 3 is a partial section view of the disc and sup porting plate in engagement.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrative embodiment shown in FIG. 1, a reinforced abrasive disc is shown generally at 2 having a usable layer of abrasive material 4 and a non-usable layer of abrasive material 6. It should be noted that the non-usable layer 6 need not be an abrasive mixture but may be of any suitable material which will perform the required function and can be bonded with abrasive layer 4. Attaching elements such as anchor nuts 8 and washers 10 are embedded in the non-usable layer of abrasives. Although a flat type washer is shown, other types such as tapered cup washers have been successfully used. Abrasive disc 2 is clamped to a supporting wheel 12 through the use of bolts 14 which engage nuts 8.

An apertured reinforcing member 16 is embedded in the abrasive disc at the junction between the usable layer 4 and non-usable layer 6 of the abrasive material with the cut out apertures or openings opposite each nut 8. The reinforcing member is thus independent of nuts 8 and is not attached thereto.

The reinforcing member 16 may be an open wire mesh or other equivalent material, as for instance a fiber glass mesh. In the illustrative embodiment shown in FIG. 2 an open wire mesh material is embedded in the abrasive disc and makes a strong reinforcement by providing many interlocking surfaces for holding the abrasive body in place.

In a known manner, nuts 8 and washers 10 are attached in a predetermined arrangement upon a molding plate (not shown) upon which the abrasive disc is to be formed. A first layer of abrasive mixture is placed in the molding plate to completely surround and overlay anchor nuts 8. Holes of greater diameter than the corresponding anchor nuts are cut in the reinforcing memher so as to correspond to the predetermined arrangement of the anchor nuts. This apertured reinforcing member is then placed over the first layer of abrasive material and oriented so that the apertures are maintained in a spaced relation over and relative to the anchor nuts. The apertures thus allow the reinforcing member to essentially float Without distortion about the anchor nuts as the abrasive disc is compressed. A second layer of abrasive material is then added over the reinforcing member to a desired or predetermined height. The disc is then pressed with a press plate (not shown) to the required formulated density. Because the reinforcing member 16 is not secured to nuts 8 it is free to locate itself in the abrasive material without distortion during the pressing operation.

The abrasive disc thus formed is hardened by curing in any known or suitable operation.

As a consequence, the abrasive disc has a reinforcing member placed at the junction of the usable and nonusable layers of abrasive material which is freefrom internal stress and not likely to warp or crack the disc.

It will, therefore, be appreciated that the anchor nuts 8 are independent of the reinforcing member 16 and hence they cannot transmit any clamping stress to the reinforcing or wire mesh.

It will be observed that the abrasive body may be worn away down to the reinforcing member since there are no obstructive members or securing devices above the reinforcing member which can interfere with the grinding operation. This gives a maximum use of the abrasive for a given thickness of the usable layer 4.

While the preferred form of the invention and mode of production has been illustrated and described by way of example, the scope of the invention is believed to be subject to minor changes and variations in materials, proportions, and minor details of manufacture without departing from the scope of the invention as defined in the following claims.

What I claim is:

1. A reinforced abrasive disc adapted to be attached to a rotatable supporting wheel comprising:

a first layer of material,

a second layer of abrasive material,

attachment means embedded in said first layer adapted to attach said abrasive disc to a supporting wheel, and

a reinforcing member independent of said attachment means at the junction of said first and second layers of material, said reinforcing member having apertures larger than said attachment means and disposed so that an aperture registers with each attachment means, the periphery of said reinforcing member at' each registering aperture being held by abrasive material.

2. The method of claim 1 in which said forming of said first layer comprises the steps of:

placing a plurality of anchor means in a pre-determined arrangement on a molding plate, and

spreading a layer of material around and above said anchor means;

said reinforcing member is placed adjacent said first layer and registered with said attachment means by:

placing an apertured reinforcing member over said first layer of material, and

orienting said reinforcing member whereby said apertures are aligned with and maintained in a spaced relation relative to each of said anchor means; and

said second layer is bonded to said reinforcing member and said non-usable layer by:

adding a layer of abrasive material over said apertured reinforcing member,

compressing said abrasive disc to the required formulated density, and

curing said reinforced abrasive disc.

3. A method of making a reinforced abrasive disc comprising the steps of:

forming a first layer of material having a plurality of attachment means embedded therein:

placing a reinforcing member having apertures larger than said attachment means adjacent said first layer so that said reinforcing member is independent of said attachment means and an aperture registers with said attachment means;

bonding a second layer of abrasive material to said apertured reinforcing member and said first layer.

References Cited UNITED STATES PATENTS 1,812,076 6/1931 Beebe 51-209 2,279,278 4/ 1942 Shue 51-209 2,624,986 1/1953 Loofboro 51-209 2,926,469 3/ 1960 Kubsh 51 209 3,250,045 5/ 1966 Caserta 51-209 FOREIGN PATENTS 388,034 2/1933 Great Britain.

ROBERT C. RIORDON, Primary Examiner DONALD G. KELLY, Assistant Examiner US. Cl. X.R. 51-297

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